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Background and Rationale. miRNAs are small non-coding RNAs that regulate gene expression by acting on the epigenetic machinery and are themselves controlled by epigenetic mechanisms. The expression of miRNAs is linked to cancer development and miRNA profiles are studied as new prognostic factors or therapeutic new perspectives (Jiang X et al. Nat Commun 2016). High-risk MDS are now treated with hypomethylating agents, like Azacitidine (AZA), alone or in combination with other drugs, such as Lenalidomide (LEN). Recent data showed that the concurrent acquisition of specific point mutations on PI3KCD, PLCG2 and AKT3 genes is associated with loss of response to AZA+LEN therapy (Follo MY et al. Leukemia 2019). Inositide signalling regulated by Phospholipase C (PLC) and PI3K/AKT is indeed involved in epigenetic processes and in MDS progression to AML, through the regulation of proliferation, differentiation and apoptosis. Patients and Methods. This study included 26 high-risk MDS patients treated with AZA (75 mg/m2/day, days 1-5, sc) and LEN (10 mg/day, days 1-21 or 8-21, orally) every 4 weeks. Patients showing complete remission (CR), partial remission (PR), any hematologic improvement (HI) or marrow CR+HI following IWG response criteria were considered as responders, while patients showing stable disease or disease progression were considered as non-responders. miRNAs expression was assessed using an Affymetrix miRNA 4.0 array on patients' cells extracted at baseline and during the therapy, at the 4th (T4) and 8th (T8) cycle of therapy. Results were then validated by Real-Time PCR and miRNA targets were studied by dual Luciferase assay. Real-Time PCR was also used to examine the expression of PLC genes. Results. All patients included in this study were considered evaluable for response. According to the revised IWG criteria (14), the overall response rate (ORR) was 76.9% (20/26 cases): CR (5/26, 19.2%), PR (1/26, 3.8%), marrow CR (mCR, 2/26, 7.7%), HI (6/26, 23.1%), mCR+HI (6/26, 23.1%), whereas 6/26 patients (23.1%) had a stable disease. For our analyses, we considered 10 patients as responders (R, showing response within T4 and maintaining it at T8), 10 losing response (LR, showing response within T4 and losing it at T8) and 6 non-responders (NR, never showing a response). Paired analysis between R and NR patients showed a statistically significant up-regulation of miR-192-5p and miR-21-5p between T0 and T4, as well as a down-regulation of miR-224-5p between T4 and T8, hinting at a relevant role for these miRNAs during AZA+LEN response. Real-Time PCR analyses confirmed the modulation of miR-192-5p and an altered expression of PLC genes during AZA+LEN therapy in all patients' subgroups, as well as an involvement of BCL-2 (possible target of miR-192-5p) that was also proven in vitro by dual Luciferase assays. Furthermore, as miR-192-5p expression seemed to be correlated with response, we performed Kaplan-Meier analyses and found out an association between high levels of miR-192-5p at T4 and OS (p=0.08) or LFS (p=0.04) in our MDS cases. More interestingly, this correlation was stronger (p=0.03) in R, as compared with LR and NR. Conclusions. This study shows that AZA+LEN therapy in MDS affects the expression of miR-192-5p, whose high level at T4 is associated with higher OS and LFS in responder patients. Moreover, we showed that miR-192-5p specifically targets and inhibits BCL-2, hinting at a regulation of MDS proliferation and apoptosis. Additional studies, to be performed in a larger cohort of MDS patients, are needed to confirm these data, as well as better understand the molecular mechanisms and the prognostic relevance of miR-192-5p in AZA+LEN therapy. Disclosures Cavo: AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Consultancy, Honoraria; Novartis: Honoraria; GlaxoSmithKline: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Accommodations, Speakers Bureau; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bristol-Myers Squib: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Finelli: Celgene BMS: Consultancy, Research Funding, Speakers Bureau; Takeda: Consultancy; Novartis: Consultancy, Speakers Bureau.

Background and Rationale. Inositide signalling regulated by Phospholipase C (PLC) and AKT is involved in epigenetic processes and in MDS progression to AML. miRNAs are small non-coding RNAs that regulate gene expression by acting on the epigenetic machinery and are themselves controlled by epigenetic mechanisms. The expression of miRNAs has been definitively linked to cancer development and miRNA profiles are studied as new prognostic factors or therapeutic new perspectives (Jiang X et al. Nat Commun 2016). Azacitidine (AZA) is a standard first-line therapy in high-risk MDS. Its combination with Lenalidomide (LEN) has been tested, but its molecular effect is still under investigation, although the concurrent acquisition of specific point mutations on PI3KCD, PLCG2 and AKT3 genes has recently been associated with loss of response to this combination therapy (Follo MY et al. Leukemia 2019). Here we further analyzed the effect of AZA+LEN therapy on epigenetic processes and inositide regulation, focusing on miRNA expression in MDS patients. Patients and Methods. This study included 12 high-risk MDS patients treated with AZA (75 mg/m2/day, days 1-5, sc) and LEN (10 mg/day, days 1-21, orally) every 4 weeks. Patients showing complete remission (CR), partial remission (PR) or any hematologic improvement were considered as responders, while patients showing stable disease or disease progression were considered as non responders. miRNAs expression was assessed using an Affymetrix miRNA 4.0 array on patients' cells extracted at baseline and during the therapy, at the 4th (T4) and 8th (T8) cycle of therapy. Results. All patients included in this study were considered evaluable for response. 2 patients never responded, while 10 patients showed a positive response within T4: 9 of them maintained it at T8, whereas the remaining patient lost response at T8. These clinical results do not mirror the expected clinical outcomes, but this is due to our small population. However, our analyses could be relevant to test the molecular effect of the therapy in a time course, as well as comparing different phases (baseline vs T4; baseline vs T8; T4 vs T8). Paired analysis within the same patients during treatment course showed 61 miRNAs up- or down-regulated (p Conclusions. This preliminary study shows that AZA+LEN therapy affects the expression of specific clusters of miRNAs that target the PI3K signalling and, more specifically, three inositide genes that are mutated and associated with loss of response to this combination therapy, i.e. PI3KCD, AKT3 and PLCG2. Additional studies are warranted to confirm these data and to further analyze the role of these clusters, especially to test their pathogenetic or therapeutic relevance in MDS. Disclosures Cavo: AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel accomodations, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel accomodations, Speakers Bureau; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; GlaxoSmithKline: Honoraria, Speakers Bureau; Karyopharm: Honoraria. Finelli:Janssen: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Chronic myeloid leukemia (CML) treatment is based on company-sponsored and academic trials testing different tyrosine kinase inhibitors (TKIs) as first-line therapy. These studies included patients selected according to many inclusion-exclusion criteria, particularly age and comorbidities, with specific treatment obligations. In daily clinical practice (real-life), inclusion-exclusion criteria do not exist, and the treatment outcome does not only depend on the choice of first-line TKI but also on second- and third-line TKIs. To investigate in a real-life setting the response and the outcome on first-line imatinib, with switch to second generation TKIs in case of unsatisfying response or intolerance, we analyzed all newly diagnosed patients (N = 236), living in two Italian regions, registered in a prospective study according to population-based criteria and treated front-line with imatinib. A switch from imatinib to second-generation TKIs was reported in 14% of patients for side effects and in 24% for failure or suboptimal response, with an improvement of molecular response in 57% of them. The 5-year overall survival (OS) and leukemia-related survival (LRS) were 85% and 93%, respectively; the 4-year rates of MR3.0 and MR4.0 were 75% and 48%, respectively. Cardiovascular complications were reported in 4% of patients treated with imatinib alone and in 6% of patients receiving nilotinib as second-line. Older age (≥70 years) affected OS, but not LRS. These data provide an unbiased reference on the CML management and on the results of TKI treatment in real-life, according to ELN recommendations, using imatinib as first-line treatment and second-generation TKIs as second-line therapy. Am. J. Hematol. 92:82-87, 2017. © 2016 Wiley Periodicals, Inc.

Introduction. The association of Azacitidine (AZA) and Lenalidomide (LEN), either administered concurrently or sequentially, has proven effective in Myelodysplastic Syndromes (MDS), however the optimum dose and schedule remains unknown. The aim of this study was to evaluate the efficacy and safety of the combination vs the sequential use of AZA and LEN in higher-risk MDS pts. Primary endpoint: ORR, defined as the Rate of Complete Remission (CR), Partial Remission (PR), Marrow Complete Remission (mCR), and Hematological Improvement (HI), following the IWG criteria (Cheson, 2006). Moreover, the aim of this analysisis is to enucleate the clinical and biological features of pts who showed long-lasting (≥ 20 cycles) responses. Methods. This is a randomized, phase II, multicenter, open label study, including pts with MDS with IPSS risk High or Intermediate-2, without previous treatment with AZA or LEN. ARM 1 (combined treatment): AZA: 75 mg/m2/day (days 1-5) I.C. + LEN: 10 mg/day (days 1-21), orally, every 4 weeks. ARM 2 (sequential treatment): AZA: 75 mg/m2/day (days 1-5) I.C. + LEN: 10 mg/day (days 6-21), orally, every 4 weeks. The induction treatment was planned for 8 cycles. For responder pts the same treatment was continued until disease progression or unacceptable toxicity. Results. From March 2013, 44 pts (27 males), median age: 72 (48-83 yrs) were enrolled, from 13 hematologic Centers. 21 pts were randomly assigned to ARM 1, and 23 pts to ARM 2. Treatment was given for a median of 8.5 (1-68) cycles; in ARM 1: 9 (1-68) cycles; in ARM 2: 8 (1-63) cycles, respectively. Median follow-up: 15 (2-77) months. 10/44 pts (22.7%) did not complete at least 6 cycles of treatment for causes other than disease progression, and were not considered evaluable for response. Among the 34/44 pts (77.3%) evaluable for response, 26/34 pts (ORR: 76.5 %) showed a favourable response to treatment. Intention-to-treat (ITT) analysis: ORR: 59.1%. First response was observed after a median of 2 (1-8) cycles. The Best Response achieved was: CR: 8 pts (23.5%) (ITT: 18.1%), PR: 1 pt (2.9%) (ITT: 2.2%), mCR: 3 pts (8.8%) (ITT: 6.8%), HI: 8 pts (23.5%) (ITT: 18.1%), mCR+HI: 6 pts (17.6%) (ITT: 13.6%). Median duration of hematologic response: 10.5 months. 37 pts (84.1%) died , and 20 pts (45.4%) showed progression to AML. Grade >2 non haematological toxicity: 54.5%. Median OS: 15 months. OS was significantly longer in responder pts as compared to the other pts (28 vs 7 months, p2 non haematological toxicity (ARM 1: 66.7%; ARM 2: 43.5%), AML incidence (ARM 1: 33.3%; ARM 2: 56.5%; p=0.2150) and OS (ARM 1: 14 months; ARM 2: 16 months). However, among responder pts, sequential treatment showed a longer clinical benefit, as compared to combined treatment. Responder pts of ARM 2 showed a significantly longer median duration of response (18 vs 6 months, p=0.0481), a longer median duration of therapy (28 vs 10 months, p=0.0870; 20 vs 10 cycles, p=0.1181), more long-lasting (≥ 20 cycles) responses (34.8% vs 9.5%, p=0.1017) and a longer OS (35 vs 26 months, p=0.3868), as compared to responder pts of ARM 1. Overall, 10/44 long-responder pts (22.7%) received ≥ 20 cycles; 5/10 pts (50%) achieved CR. IPSS risk: Intermediate-2 (8 pts); High (2 pts); IPSS-R risk: Intermediate (2 pts); High (6 pts); Very High (2 pts); IPSS cytogenetic risk: Good (5 pts); Intermediate (3 pts); Poor (2 pts); IPSS-R cytogenetic risk: Good (5 pts); Intermediate (4 pts); Very Poor (1 pt); 4/6 patients with altered karyotype achieved cytogenetic remission; it is noteworthy that the only 3 pts of the entire series who showed no gene mutations at baseline are included in this subset of long-responders pts, while 5/10 pts showed at baseline ≥ 1 prognostically unfavorable gene mutations (none with TP53 mutations), with variable VAFs during treatment. Moreover all long-responder pts showed a common gene mutation on SOD2 gene, and mutations on PLCG2 gene. Conclusions. Our results confirm the efficacy of both AZA+LEN treatment regimens in higher-risk MDS pts, in terms of ORR and OS, although sequential treatment was associated with a longer clinical benefit among responder pts. A subset of pts (22,7 %) with less unfavorable cytogenetic and molecular characteristics showed a long-lasting response to treatment. Disclosures Finelli: Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees. Crugnola:BMS: Honoraria; Janssen: Honoraria; Celgene: Honoraria; Novartis: Honoraria. Rigolin:Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Cavo:Jannsen, BMS, Celgene, Sanofi, GlaxoSmithKline, Takeda, Amgen, Oncopeptides, AbbVie, Karyopharm, Adaptive: Consultancy, Honoraria.

Monitoring of BCR-ABL1 levels by quantitative PCR (qPCR) is essential for the management of CML patients treated with TKIs. Because of intrinsic limits, qPCR does not appear to be an optimal assay to select the best candidates to TKIs discontinuation. Up to 40% of CML patients treated with TKIs can achieve a Deep Molecular Response (DMR), but only 50% maintain a stable Treatment Free Remission (TFR) after therapy discontinuation. Digital PCR (dPCR), giving an absolute quantification of BCR-ABL1, is expected to be more sensitive and accurate than qPCR in the assessment of molecular MRD. dPCR performed on a QuantStudio 3D Digital PCR System (Life Technologies) by using a TaqMan-MGB probes targeting the BCR-ABL1 transcript was used to comparatively analyse 102 CML patients with Major (MR3.0 = 31 cases) or Deep (MR4.0= 33 cases; MR4.5 = 24 cases and MR5.0 = 14 cases) molecular response. Preliminary results showed that: a) ≥77% of deep responders (MR4.0, MR4.5 and MR5.0) fell under the value of 0.468 BCR-ABL1 copies/▢l indicated by the ROC analysis as the value below which the patients with lower levels of MRD might be dissected (spec.=71%, sens.=77%; AUC=0,79); b) BCR-ABL1 transcript levels were detectable by dPCR also in cases resulted undetectable by qPCR. In this study, we analysed the BCR-ABL1 transcript levels by dPCR in 207 samples related to 102 CML patients. Fourteen (14%) out of 102 CML patients discontinued the TKIs therapy. Among them, 3 patients (21%) lost DMR and all of them showed dPCR values > 0.468 BCR-ABL1 copies/▢l (previously described as cut-off for a deep MRD), while 11 (79%) maintained a stable DMR and 9 of them (82%) fell under the value of 0.468 BCR-ABL1 copies/▢l. These latter patients stratified in different DMR classes by qPCR and all had undetectable level of BCR-ABL1 by qPCR. In 149 out of 207, qPCR revealed DMR. They were: MR4.0= 59 samples; MR4.5= 61 cases; MR5.0 = 29 cases. One hundred twenty-five (84%) fell under the value of 0.468 BCR-ABL1 copies/▢l. A linear regression analysis in these samples did not show any correlation between BCR-ABL1 copies/▢l detected by qPCR with the ones detected by dPCR (R2 < 0.01). On the basis of our preliminary results, TFR seems to be correlated to the maintenance of dPCR values < 0.468 BCR-ABL1 copies/▢l. The concordance between qPCR and dPCR quantification in patients with DMR and with BCR-ABL1 copies/▢l value < 0.468 was poor. Patients with dPCR values < 0.468 BCR-ABL1 copies/▢l may have 75% of probability to maintain TFR status. These results suggest that dPCR may be more sensitive to detect the MRD and could be more useful for DMR monitoring and for dissecting the best candidate to discontinuation of therapy with TKIs. Disclosures Tiribelli: Ariad Pharmaceuticals: Consultancy, Speakers Bureau; Bristol-Myers Squibb: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau. Castagnetti:Bristol-Myers Squibb: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; ARIAD Pharmaceuticals: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria. Soverini:Novartis: Consultancy; Ariad: Consultancy; Bristol-Myers Squibb: Consultancy. Rosti:Pfizer: Honoraria, Research Funding, Speakers Bureau; Roche: Honoraria, Research Funding, Speakers Bureau; BMS: Honoraria, Research Funding, Speakers Bureau; Incyte: Honoraria, Research Funding, Speakers Bureau; Novartis: Honoraria, Research Funding, Speakers Bureau. Martinelli:Roche: Consultancy; ARIAD: Consultancy; Pfizer: Consultancy, Speakers Bureau; Genentech: Consultancy; Amgen: Consultancy; MSD: Consultancy; Roche: Consultancy; ARIAD: Consultancy; Pfizer: Consultancy, Speakers Bureau; BMS: Speakers Bureau; Genentech: Consultancy; Amgen: Consultancy; Novartis: Speakers Bureau; MSD: Consultancy.

Interferon a (IFNa) prolongs survival of CML patients achieving CCyR and potentially synergizes with TKIs. We report on the molecular status and long term outcome of 121 patients who were treated in Italy between 1986 and 2000 with IFNa based therapy and who obtained CCyR. After a median follow up of 16.5 years, 74 (61%) patients were switched to standard imatinib: 48 (65%) lost the CCyR on IFNa, and 36 (75%) are alive and in CCyR; 26 (35%) were switched to imatinib when they were still in CCyR on IFNa, and all 26 are alive and in CCyR. Forty-seven patients (39%) were never switched to imatinib: 24 (51%) continued and 23 (49%) discontinued IFNa, respectively, and 39/47 (83%) are alive and in CCyR. At last follow-up, the BCR-ABL transcripts level was available in 96/101 living patients (95%) The BCR-ABL:ABL ratio was between 0.1 and 0.01% (MR 3.0 ) in 17%, and less than 0.01% (MR 4.0 ) in 81% of patients. No patient was completely molecular negative (MR 4.5 or MR 5.0 ). The OS at 10 and 20 years is 92 and 84%, respectively. This study confirms that CCyR achieved with IFNa and maintained with or without imatinib or any other therapy significantly correlates with long term survival in CML patients who mostly have MR 4.0 . Complete molecular response (MR 4.5 or MR 5.0 ) seems to be unnecessary for such a long survival. This study further supports development of studies testing the clinical effect of the combinations of TKIs with IFNa. Am. J. Hematol. 89:119–124, 2014. V C 2013 Wiley Periodicals, Inc.

Background and Rationale. Azacitidine (AZA) is a standard first-line therapy in high-risk MDS. Also its combination with Lenalidomide (LEN) has been tested, but its molecular effect is still under investigation. Here we analyzed the effect of AZA+LEN therapy on gene mutations and microRNA expression in MDS patients. Patients and Methods. This study included 44 high-risk MDS patients treated with AZA (75 mg/m2/day, days 1-5, sc) and LEN (10 mg/day, days 1-21, orally) every 4 weeks. Patients showing complete remission (CR), partial remission (PR) or any hematologic improvement were considered as responders, while patients showing stable disease or disease progression were considered as non responders. Molecular analyses were performed at baseline and during the therapy. Gene mutations were studied by an Illumina Cancer Myeloid Panel and an Ion Torrent specific panel, whereas microRNAs expression was assessed using an Affymetrix miRNA 4.0 array. Results. 34/44 patients were considered evaluable for response, with an overall response rate of 76.25% (26/34 cases). 13 patients showed a positive response within the 4th cycle (T4) and maintained it at T8; 9 patients showed a positive response within T4 and lost response at T8; 4 patients responded after T4 and maintained the response at T8; 8 patients never responded. Molecular analyses were performed on serial samples (baseline, T4 and T8) available for 30 patients. Results from the Illumina analysis on cancer myeloid genes showed that 3/30 cases had no mutations at all, all other cases showed mutations both at baseline and during the therapy. The most frequently mutated genes were ASXL1 (14 cases = 47%), TET2 (11 cases = 37%), RUNX1 (8 cases = 27%) and SRSF2 (5 cases = 17%). All samples with a decreasing variant allele frequency (VAF) had a favourable response at T8 (CR, marrow CR or PR), while none of the non responders showed a decreasing VAF. Ion Torrent analysis of 24 inositide-specific genes showed that all patients had mutations both at baseline and during the therapy. Interestingly, all patients responding at T4 and losing response at T8, as well as cases that did not respond, acquired the same 3 point mutations at T8, affecting respectively PIK3CD (D133E), AKT3 (D280G) and PLCG2 (Q548R) genes. Patients responding at T4 and losing response at T8 showed these mutations even at T4. Kaplan-Meier analyses revealed that the presence of these mutations was significantly associated with a decreased duration of therapy (39.5 vs 8.5 months; p As for microRNA profiling, paired analysis between responders and non responders showed specific clusters of up- or down-regulated microRNAs. Interestingly, unpaired analysis on patients responding at T4 and losing response at T8 showed 18 up- and 11 down-regulated microRNAs, like miR-3613-3p and miR-6757-5p, whose predicted targets are our 3 genes among the others. Also in patients never responding to the therapy there was a specific cluster of 3 up- and 12 down-regulated microRNAs and, interestingly, 7 of these microRNAs, like miR-4786-5p or miR-6853-3p, targeting our 3-gene cluster among the others, were altered also in patients losing response. Conclusions. Our results show that the presence of a common cluster of point mutations affecting 3 inositide-specific genes (PI3KCD, AKT3, PLCG2, all regulating cell proliferation), is significantly associated with loss of response to AZA+LEN therapy. Moreover, also a cluster of 7 microRNAs, targeting our 3 genes among the others, is associated with unfavourable outcome. Further studies are warranted to confirm these data, to further analyze the role of this 3-gene cluster and to identify the specific targets for the dysregulated microRNAs identified. Disclosures Gobbi: Janssen: Consultancy; Amgen: Consultancy; Ariad: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy; Celgene: Membership on an entity's Board of Directors or advisory committees; Pfister: Membership on an entity's Board of Directors or advisory committees. Cavo:Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees. Finelli:Janssen: Consultancy, Speakers Bureau; Celgene: Research Funding, Speakers Bureau; Novartis: Consultancy, Speakers Bureau.

Introduction. The association of Azacitidine (AZA) and Lenalidomide (LEN), either administered concurrently (Sekeres, 2010; 2012; 2017), or sequentially (Platzbecker, 2013; Di Nardo 2015; Mittelman 2016; Narayan 2016) has proven effective in Myelodysplastic Syndromes (MDS), however the optimum dose and schedule remains unknown. The aim of this study was to evaluate the efficacy and safety of the combination vs the sequential use of AZA and LEN in higher-risk MDS pts. Primary endpoint: ORR, defined as the Rate of Complete Remission (CR), Partial Remission (PR), Marrow Complete Remission (mCR), and Hematological Improvement (HI), following the IWG criteria (Cheson, 2006). Secondary endpoints: a) rate of CR; b) duration of responses; c) overall survival (OS). Methods. This is a randomized, phase II, multicenter, open label study, including pts with MDS with IPSS risk High or Intermediate-2, without previous treatment with AZA or LEN. ARM 1 (combined treatment): AZA: 75 mg/m2/day (days 1-5) I.C. + LEN: 10 mg/day (days 1-21), orally, every 4 weeks. ARM 2 (sequential treatment): AZA: 75 mg/m2/day (days 1-5) I.C. + LEN: 10 mg/day (days 6-21), orally, every 4 weeks. The induction treatment was planned for 8 cycles. For responder patients the same treatment was continued until disease progression or unacceptable toxicity. Results. From March 2013, 44 pts (27 males), median age: 72 (48-83 yrs) were enrolled, from 13 hematologic Centers. At baseline, IPSS risk was: Intermediate-2: 31 pts; High: 9 pts; not determined (N.D.) (because of lack of cytogenetic data): 2 pts. (all with RAEB-2). In 2 pts IPSS risk was Intermediate-1, but they were enrolled because of severe thrombocytopenia and neutropenia, respectively. IPSS-R risk was: intermediate: 8 pts; High: 16 pts; Very-High: 18 pts; N.D.: 2 pts. In 5 pts (11.4%) del(5q) was present (additional cytogenetic alterations: 1 in 1 pt, and > 1 in 4 pts , respectively). 21 pts were randomly assigned to ARM 1, and 23 pts to ARM 2. Treatment was given for a median of 8.5 (1-52) cycles; in ARM 1: 9 (1-51) cycles; in ARM 2: 8 (1-52) cycles, respectively. Median follow-up: 15 (2-54) months; 47 (37-54) months for survivors. 10/44 pts (22.7%) did not complete at least 6 cycles of treatment for causes other than disease progression (6 pts for adverse events, 2 pts for consent withdrawal and 2 pts for medical decision), and were not considered evaluable for response. Among the 34/44 pts (77.3%) evaluable for response, 26/34 pts (ORR: 76.5 %) showed a favourable response to treatment. Intention-to-treat (ITT) analysis: ORR: 59.1%. First response was observed after a median of 2 (1-8) cycles. The Best Response achieved was: CR: 8 pts (23.5%) (ITT: 18.1%), PR: 1 pt (2.9%) (ITT: 2.2%), mCR: 3 pts (8.8%) (ITT: 6.8%), HI: 8 pts (23.5%) (ITT: 18.1%), mCR+HI: 6 pts (17.6%) (ITT: 13.6%). The remaining 8 pts showed either Stable Disease (SD) (6 pts, 17.6%) or Disease Progression (DP) (2 pts, 5.9%). Among the 27 pts (21 evaluable for response) with an abnormal karyotype at baseline, ORR was 66.7% (ITT: 51.8%) and 4 pts achieved complete cytogenetic response. Median duration of hematologic response: 10.5 months. 34 pts (77,3%) died , and 17 pts (38.6%) showed progression to AML. Grade >2 non haematological toxicity: 54.5%. Median OS: 15 months. No significant differences between the 2 arms were observed, in terms of ORR (ARM 1: 76.5%, ITT: 61.9%; ARM 2: 76.5%, ITT: 56.5%), CR rate (ARM 1: 17.6%, ITT: 14.3%; ARM 2: 29.4%, ITT: 21.7%), grade >2 non haematological toxicity (ARM 1: 66.7%; ARM 2: 43.5%), AML incidence (ARM 1: 28.6%; ARM 2: 47.8%) and OS (ARM 1: 14 months; ARM 2: 16 months), but the median response duration was significantly longer in ARM 2 (18 months) as compared to ARM 1 (6 months) (p=0.0459). At the time of last analysis, 5/44 (11.4%) patients, 1/21 (4.8%) in ARM 1, and 4/23 (17.4%) in ARM 2, were still maintaining the haematological response, and were still in treatment, after 54, 54, 52, 51 and 37 months, and after 52, 51, 33, 48 and 35 cycles of therapy, respectively. The changes observed during treatment in mutational status of inositide-specific genes and microRNA expression profiling were related to clinical outcome, predicting a negative response to therapy. Conclusions. Our results confirm the efficacy of both AZA+LEN treatment regimens in higher-risk MDS pts, in terms of ORR and OS, although pts treated with the sequential regimen showed a significantly longer duration of haematological response. Disclosures Finelli: Celgene: Other: speaker fees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: speaker fees; Janssen: Membership on an entity's Board of Directors or advisory committees, Other: speaker fees. Candoni:Janssen: Honoraria, Speakers Bureau; Celgene: Honoraria, Speakers Bureau; Gilead: Honoraria, Speakers Bureau; Pfizer: Honoraria, Speakers Bureau; Merck SD: Honoraria, Speakers Bureau. Gobbi:Novartis: Consultancy; Janssen: Consultancy; Ariad: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy; Pfister: Membership on an entity's Board of Directors or advisory committees. Rigolin:Gilead: Research Funding. Cavo:GlaxoSmithKline: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Background. Chronic myeloid leukemia (CML) treatment is based on company-sponsored and academic trials testing different tyrosine kinase inhibitors (TKIs) as first-line therapies. However these clinical trials included patients selected according to different inclusion and exclusion criteria, particularly age and comorbidities, and with specific treatment obligations. In daily clinical practice (real life), no inclusion and exclusion criteria do exist, and treatment outcomes depend not only on choice of the first-line TKI, but also on doctor- and patient-choice of second- and third-line TKIs. Aims. To investigate the response and the outcome on first-line imatinib, with switch to 2nd generation TKIs in case of failure or toxicity, in BCR-ABL1+ CML patients enrolled in a population-based registry (real-life setting). Methods. We report here the results from a prospective study, enrolling all newly diagnosed patients (N = 236, median age 60 years) living in two Italian regions, that were registered according to population-based criteria and treated front-line with imatinib. The decision to switch to second-line treatment was up to the Local Investigator (no predefined criteria) Definitions: major molecular response (MMR or MR3.0): BCR-ABL1IS ratio 10,000 ABL1 copies; failure and suboptimal response: according to 2009 European LeukemiaNet (ELN) criteria; progression: transformation to advanced phases according to ELN criteria; leukemia-related death (LRD): death after progression. Results. Median age was 60 years at diagnosis and 64 years at last contact, with a median follow up of 48 months (range 2-86 months). High risk patients according to Sokal score and new EUTOS long-term survival (ELTS) score were 23% and 18%, respectively. A switch from imatinib to a second generation TKI was reported in 14% of patients for side-effects, and in 24% for failure or suboptimal response, with an improvement of molecular response in 57% of them. The median time to switch was 8 months for toxicity and 20 months for failure. At 12 months, 55% of all evaluable patients were in MR3.0 or better. At last contact, 75% of all evaluable patients were in MR3.0 or better and 48% were in MR4.0 or better. The molecular response of patients switching for failure or suboptimal response was evaluable in 61/63 patients: improved in 57%, not modified in 38%, worsened by at least 1 log in 5% of patients. Overall, the treatment switch was associated with a remarkable increase of MR3.0 rate: from 10% at the time of switching to 52% at last qPCR. Overall, 33% achieved a stable MR4.0, of whom 22% with imatinib alone, and 11% after switching to a second generation TKI (Table 1). The 5-year overall survival (OS) and leukemia-related survival (LRS) were 85% and 93%, respectively. Twenty-seven patients (11%) died, of whom 13 (6%) of leukemia, after disease progression and 14 (6%) of "other" causes, without any evidence of progression. Cardiovascular complications were reported in 4% of patients treated with imatinib alone and in 6% of patients who received nilotinib in second-line. OS was not affected by age in the interval between 18 and 69 years (5-year OS 92%, ranging from 89% to 95 % in the different decades), but 5-year OS probabilities of elderly (70-79 years) and very elderly patients (≥ 80 years) were significantly lower (78%, P = 0.003, and 34%, P < 0.0001, respectively). The probability of LRS was not affected by age. The Sokal score predicted OS, but not LRS. The ELTS score clearly separated low, intermediate, and high risk patients for OS and also for LRS. Conclusions. The results of this prospective population-based study emphasize the importance of second-line treatment in the clinical practice: the CML management with the 3 available TKIs in the period 2008-2012, according to current treatment recommendations for switching and without any predefined obligation, resulted in response rates and outcomes, that are in the high range of prospective interventional studies investigating the efficacy and the safety of a single TKI in selected patients. This study provides a robust dataset on the results of CML treatment with TKI in clinical practice, that will be important for interpreting and evaluating the results of the next prospective studies, arguably limited to selected patients. Disclosures Castagnetti: Bristol-Myers Squibb: Consultancy, Honoraria; ARIAD Pharmaceuticals: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Gugliotta:Bristol Myers Squibb: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Marasca:Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria; Roche: Honoraria. Soverini:Novartis: Consultancy; Bristol-Myers Squibb: Consultancy; Ariad: Consultancy. Martinelli:Genentech: Consultancy; ARIAD: Consultancy; Roche: Consultancy; Bristol-Myers Squibb: Speakers Bureau; Novartis: Speakers Bureau; MSD: Consultancy; Pfizer: Consultancy, Speakers Bureau; Amgen: Consultancy. Cavo:Bristol-Myers Squibb: Honoraria; Amgen: Honoraria; Takeda: Honoraria; Celgene: Honoraria, Research Funding; Janssen: Honoraria, Research Funding. Rosti:Novartis: Honoraria, Research Funding, Speakers Bureau; Pfizer: Honoraria, Research Funding, Speakers Bureau; Roche: Honoraria, Research Funding, Speakers Bureau; Incyte: Honoraria, Research Funding, Speakers Bureau; BMS: Honoraria, Research Funding, Speakers Bureau. Baccarani:Ariad: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; BMS: Consultancy, Honoraria, Speakers Bureau; Pfizer: Consultancy, Honoraria, Speakers Bureau.

Background/aim Controversial experimental observations suggest that granulocyte colony stimulating-factor may promote hepatic regeneration after hepatectomy and chemical injury either by directly stimulating adult liver cells or facilitating the mobilization of bone marrow cells and their homing to the liver. We investigated whether different schedules of granulocyte colony stimulating-factor administration protect against experimental acute liver injury. Methods Acute liver injury was induced in Sprague-Dawley fed rats by injecting a single intraperitoneal dose of carbon tetrachloride. Recombinant human granulocyte colony stimulating-factor or vehicle was given daily after intoxication (4 days) or before (7 days) and after carbon tetrachloride administration. Liver injury and regeneration were assessed 2 and 4 days after damage. Bone marrow cells mobilization was evaluated by the white blood cell count and the assessment of circulating clonogenic haematopoietic progenitors (colony forming unit-cells). Results In this experimental model, although granulocyte colony stimulating-factor induced the significant mobilization of colony forming unit-cells, the study cytokine had no effect on liver injury (serum alanine amino transaminase level and necrotic index) and liver regeneration (mitotic index and bromodeoxyuridine incorporation), regardless of the administration schedule. Conclusions This study does not support the conclusion that: (1) granulocyte colony stimulating-factor exerts a protective effect against toxic-induced, non-lethal acute liver injury and (2) promotes hepatocyte regeneration.

Abstract 2601 Background: Tyrosine Kinase Inhibitors (TKI) have been shown to be very effective for the treatment of Acute Lymphoblastic Leukemia (ALL), with a Complete Hematologic Remission (CHR) rate close to 100%, and a high rate of Complete Cytogenetic and Molecular responses (CCgR and CMR). However, when they are used alone, as single agents, most patients relapse, so that they are currently used in combination with chemotherapy and as a preparation to allogeneic stem cell transplantation (SCT). Since Ph+ ALL is more frequent in the elderly, many patients cannot tolerate intensive chemotherapy and are not eligible for SCT. We have explored if the administration of two TKIs, Nilotinib (NIL) and Imatinib (IM) can improve the results without increasing the toxicity. Aims: To evaluate the response and the outcome of Ph+ ALL patients treated with the sequential administration of NIL and IM, to investigate the type and number of BCR-ABL kinase domain mutations developing during and after the study. Methods: We have designed a study (ClinicalTrials.gov. NCT01025505) in which patients more than 60 years old or unfit for intensive chemotherapy and SCT where treated with two TKIs, NIL 400 mg twice daily, and IM 300 mg twice daily, alternating for 6 weeks for a minimum of 24 weeks (study core) and indefinitely in case of response. The 6-weeks rotation schedule was respected, irrespectively of temporary discontinuations. The primary end-point was the rate of Disease Free Survival (DFS) at 24 weeks (4 courses of treatment); the secondary end points included the evaluation of CHR, CCgR and CMR rates. Mutation analysis was performed by nested RT-PCR amplification of the ABL kinase domain of the BCR-ABL transcript (codons 206 through 421). Amplified products were screened by denaturing-high performance liquid chromatography (D-HPLC). Samples scored positive for the presence of sequence variations were then subjected to direct automatic sequencing to characterize the mutation. Results: 39 patients have been enrolled in 15 Italian hematologic Centers (median age 66 years, range 28–84). Among these, 8 patients were unfit for standard chemotherapy or SCT (median age 50 years, range 28–59). 27 patients were p190, 5 were p210 and 7 were p190/p210. After 6 weeks of treatment, 36 patients were evaluable for response: 34 were in CHR (94%) and 2 in PHR (6%). 23 patients have already completed the study core (24 weeks), 87% were in CHR and 17 are currently continuing therapy in the protocol extension phase. Thus, the OS at 1 year is 79%, and 64% at 2 years. Overall, 1 patient was primarily resistant and 13 patients have relapsed, with a median time to relapse of 7.6 months (range 0.8–16.1 months), for a DFS of 51.3% at 12 months (Figure 1). Mutations detected were T315I in 2 cases, Y253H in 3 cases, T315I and Y253H in 1 case, E255K in 1 case, T315I and E255K in 1 case, E255V and Y253H in 1 case. Two patients were WT. A detailed kinetics of Molecular responses is shown in Table 1. Data on mutational analysis are reported in Table 2. Further details about Cytogenetic and Molecular responses, and about Adverse Events will be provided on site. Conclusions: In this small cohort of Ph+ ALL elderly/unfit patients, the rates of relapse and progression were not likely to be different from the rates observed with Imatinib alone (Vignetti et al, Blood 2007, May 1;109(9):3676-8) and Dasatinib alone (Foà, Blood 2011, Dec 15;118(25):6521-8). It's important to notice that the mutations that occurred at the time of relapse were sensitive to other TKIs (Dasatinib and Ponatinib). Acknowledgments: COFIN, Bologna University, BolognAIL, PRIN, Fondazione del Monte di Bologna e Ravenna, INPDAP. Disclosures: Pizzolo: Hoffmann-La Roche: Consultancy, Honoraria. Luppi:CELGENE CORPORATION: Research Funding. Vallisa:CELGENE CORPORATION: Research Funding. Martinelli:NOVARTIS: Consultancy, Honoraria, Speakers Bureau; BMS: Consultancy, Honoraria, Speakers Bureau; PFIZER: Consultancy; ARIAD: Consultancy. Baccarani:ARIAD, Novartis, Bristol Myers-Squibb, and Pfizer: Consultancy, Honoraria, Speakers Bureau.

The aim of this study was to investigate the effects of a non-standard, intermittent imatinib treatment in elderly patients with Philadelphia-positive chronic myeloid leukaemia and to answer the question on which dose should be used once a stable optimal response has been achieved. Seventy-six patients aged ⩾65 years in optimal and stable response with ⩾2 years of standard imatinib treatment were enrolled in a study testing a regimen of intermittent imatinib (INTERIM; 1-month on and 1-month off). With a minimum follow-up of 6 years, 16/76 patients (21%) have lost complete cytogenetic response (CCyR) and major molecular response (MMR), and 16 patients (21%) have lost MMR only. All these patients were given imatinib again, the same dose, on the standard schedule and achieved again CCyR and MMR or an even deeper molecular response. The probability of remaining on INTERIM at 6 years was 48% (95% confidence interval 35–59%). Nine patients died in remission. No progressions were recorded. Side effects of continuous treatment were reduced by 50%. In optimal and stable responders, a policy of intermittent imatinib treatment is feasible, is successful in about 50% of patients and is safe, as all the patients who relapsed could be brought back to optimal response.

BACKGROUND: The incidence of chronic myeloid leukemia (CML) increases with age, but it is unclear how the characteristics of the disease vary with age. In children, where CML is very rare, it presents with more aggressive features, including huge splenomegaly, higher cell count and higher blast cell percentage. PATIENTS AND METHODS: To investigate if after childhood the disease maintains or loses these characteristics of aggressiveness, we analyzed 2784 adult patients, at least 18 years old, registered by GIMEMA CML WP over a 40-year period. RESULTS: Young adults (YAs: 18-29 years old) significantly differed from adults (30-59 years old) and elderly patients (at least 60 years old) particularly for the frequency of splenomegaly (71%, 63% and 55%, P < 0.001), and the greater spleen size (median value: 4.5, 3.0 and 1.0 cm, P < 0.001). According to the EUTOS score, that is age-independent, high-risk patients were more frequent among YAs, than among adult and elderly patients (18%, 9% and 6%, P < 0.001). In tyrosine kinase inhibitors-treated patients, the rates of complete cytogenetic and major molecular response were lower in YAs, and the probability of transformation was higher (16%, 5% and 7%, P = 0.011). CONCLUSIONS: The characteristics of CML or the host response to leukemia differ with age. The knowledge of these differences and of their causes may help to refine the treatment and to improve the outcome. CLINICAL TRIAL NUMBERS: NCT00510926, NCT00514488, NCT00769327, NCT00481052. © The Author 2014. Published by Oxford University Press on behalf of the European Society for Medical Oncology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Exploration of the immunomodulatory activities of the multifunctional cytokine interleukin-11 (IL-11) has prompted several therapeutic applications. The immunomodulatory effects of IL-11 on human antigen-presenting cells and on T cells were investigated. IL-11 inhibited IL-12 production by activated CD14+ monocytes, but not by mature dendritic cells (DCs) stimulated via CD40 ligation. Moreover, IL-11 did not affect either DC maturation, as demonstrated by phenotypic analysis and evaluation of cytokine production, or DC generation from progenitor cells in the presence of specific growth factors. Molecular analysis demonstrated the expression of IL-11 receptor messenger RNA in highly purified CD14+ monocytes, CD19+ B cells, CD8+, and CD4+T cells, and CD4+CD45RA+ naive T lymphocytes. In keeping with this finding, IL-11 directly prevented Th1 polarization of highly purified CD4+CD45RA+naive T cells stimulated with anti-CD3/CD28 antibodies, as demonstrated by significant increases of IL-4 and IL-5, by significantly decreased interferon-γ production and by flow cytometry intracellular staining of cytokines. Coincubation of naive T cells with DCs, the most potent stimulators of Th1 differentiation, did not revert IL-11–mediated Th2 polarization. Furthermore, parallel experiments demonstrated that the activity of IL-11 was comparable with that induced by IL-4, the most effective Th2-polarizing cytokine. Taken together, these findings show that IL-11 inhibits Th1 polarization by exerting a direct effect on human T lymphocytes and by reducing IL-12 production by macrophages. Conversely, IL-11 does not exert any activity on DCs. This suggests that IL-11 could have therapeutic potential for diseases where Th1 responses play a dominant pathogenic role.

Immunotoxins specific for the CD80 and CD86 antigens were prepared by linking three type 1 ribosome-inactivating proteins (RIPs), namely bouganin, gelonin and saporin-S6, to the monoclonal antibodies M24 (anti-CD80) and 1G10 (anti-CD86). These immunotoxins showed a specific cytotoxicity for the CD80/CD86-expressing cell lines Raji and L428. The immunotoxins inhibited protein synthesis by target cells with IC50s (concentration causing 50% inhibition) ranging from 0.25 to 192 pmol/l as RIPs. The anti-CD80 immunotoxins appeared 1-2 log more toxic for target cells than the anti-CD86 ones. Immunotoxins containing saporin and bouganin induced apoptosis of target cells. The toxicity for bone marrow haemopoietic progenitors of these conjugates was also evaluated. Bouganin and related immunotoxins at concentrations up to 100 nmol/l did not significantly affect the recovery of committed progenitors or of more primitive cells. The saporin-containing immunotoxins at concentrations >/= 1 nmol/l showed some toxicity on colony-forming unit cells (CFU-C). The expression of the CD80 and CD86 molecules is prevalently restricted to antigen-presenting cells and is also strong on Hodgkin and Reed-Sternberg cells in Hodgkin's disease. Present results suggest that immunotoxins targeting type 1 ribosome-inactivating proteins to these antigens could be considered and further studied for the therapy of Hodgkin's disease or other CD80/CD86-expressing tumours.

The c-mpl ligand, thrombopoietin (TPO), is a physiologic regulator of platelet and megakaryocytic production, acting synergistically on thrombopoiesis with the growth factors interleukin 11 (IL-11), stem cell factor, interleukin 3 (IL-3), interleukin 6 (IL-6), and granulocyte-macrophage colony-stimulating factor. Because some of these growth factors, especially TPO and IL-11, are now being evaluated clinically to reduce chemotherapy-associated thrombocytopenia in cancer patients, we evaluated 25 acute myeloid leukemia (AML) samples to test whether TPO, IL-11, and other early-acting megakaryocyte growth factors can affect leukemic cell proliferation, cell cycle activation, and programmed cell death (PCD) protection. TPO induced proliferation in the majority of AML samples from an overall mean proportion of S-phase cells of 7.8% +/-1.5% to 14.5% +/- 2.1% (p = 0.0006). Concurrent G0 cell depletion was found in 47.3% of AML samples. TPO-supported leukemic cell precursor (CFU-L) proliferation was reported in 5 of 17 (29.4%) of the samples with a mean colony number of 21.4 +/- 9.6 x 10(5) cells plated. In 13 of 19 samples, a significant protection from PCD (from an overall mean value of 13% +/-0.7% to 8.8% +/- 1.8%;p = 0.05) was detected after TPO exposure. Conversely, IL-11-induced cell cycle changes (recruitment from G0 to S phase) were detected in only 2 of 14 samples (14.2%). In addition, IL-11 showed little, if any, effect on CFU-L growth (mean colony number = 17.5 9.5) or apoptosis. Combination of TPO with IL-11 resulted in only a slight increase in the number of CFU-L, whereas IL-3 and stem cell factor significantly raised the mean colony numbers up to 119.2 +/- 68.3 and 52.9 +/- 22.1 x 10(5) cells plated, respectively. We conclude that TPO induces cell cycle activation in a significant proportion of cases and generally protects the majority of AML blast cells from PCD. On the other hand, IL-11 has little effect on the cell cycle or PCD. Combination of both TPO and IL-11 is rarely synergistic in stimulating AML clonogenic growth. These findings may be useful for designing clinical studies aimed at reducing chemotherapy-associated thrombocytopenia in AML patients.

CD34+ and CD34+ DR− cells from the bone marrow (BM) of chronic-phase chronic myelogenous leukaemia (CML) patients at diagnosis were tested for their colony-forming ability in response to early and intermediate-late colony stimulating factors (CSFs). Molecular analysis revealed that 55.6 ± 9% SD of CD34+DR− colonies, in which actin and ABL mRNA were detectable, expressed the product of the BCR-ABL gene. The percentage and the clonogenic efficiency of CML DR− cells were significantly lower than those of comparable DR− cells from normal donors. However, clonogenic assays using recombinant human CSFs demonstrated a remarkable proliferation of CML cells when stimulated by SCF, IL-11 and IL-3, used as single factors in the presence of erythropoietin (EPO) and was almost entirely due to erythroid progenitors. Conversely, optimal stimulation of CD34+DR− cells from normal donors required co-incubation with three or more CSFs. Stroma-noncontact long-term cultures were then established in the presence of exogenous CSFs and human irradiated allogeneic stromal layers or the murine stromal cell line M2-10B4, engineered to produce G-CSF and IL-3. In these cultures the combination of SCF and IL-3 induced a 25.4 ± 5 SD, 40 ± 6 SD and 20.5 ± 6 SD fold increase of colony-forming unit cells (CFU-C), at weeks 2, 4 and 5, respectively. At the same time-points the number of primitive long-term culture initiating cells (LTC-IC) showed a 4 ± 2 SD, 3.3 ± 1.5 SD and 2.3 ± 1 SD fold increase compared to baseline values. BCR-ABL mRNA analysis of single colonies demonstrated that 27 ± 9% SD and 7 ± 3% SD CFU-C at weeks 4 and 5, respectively, expressed the fusion gene, whereas leukaemic LTC-IC disappeared from the culture by week 2. These results suggest that leukaemic CD34+DR− cells have a different pattern of response to CSFs than normal cells. In addition, we established culture conditions which allow selective expansion of benign haemopoietic cells coexisting with leukaemic progenitors.

BACKGROUND: The INTERIM study (ClinicalTrials.gov NCT 00858806) showed that in elderly (> 65 years) Ph+ CML patients selected for a stable complete cytogenetic response (CCgR) lasting > 2 years, the policy of intermittent imatinib treatment (one month on/one month off) may affect the markers of residual disease (CCgR and major molecular response, MMR or MR3.0), but not the clinical outcomes (overall survival and progression-free survival) (Russo D et al, Blood 2013; 121(26):5138-44). AIMS: To update the results of the INTERIM Study, with a follow up ≥ 5 years. METHODS: After 4 years of follow up, patients continouing INTERIM treatment were monitored with peripheral blood RT-Q-PCR every 3 months according to the ELN-2013 guidelines. RESULTS: At 48thmonth, out of 76 patients enrolled in the INTERIM study, 13 (17%) had lost CCgR and MMR, 14 (18%) had lost MMR only and 50 patients (75%) continued INTERIM. The patients who had lost CCgR and/or MMR resumed imatinib continuously and all of them regained the CCgR and the MMR, within 3 to 12 months. No patient progressed to accelerated or blastic phase, or developed clonal chromosomal abnormalities in Ph+ cells, or BCR-ABL mutations. No patient complained of new or more severe side effects during the months “on”. After a follow up ≥ 5 years, 45/76 (59%) enrolled patients are on INTERIM, with a probability of maintaining intermittent administration of 59% (95% CI: 46-69). No patient lost the CCgR and only 9 additional patients lost the MMR while on intermittent treatment. All these patients resumed continuous imatinib treatment and regained the MMR. Thus, at ≥ 5 years, the probability of maintaing CCgR is 80% (95% CI 68-87) and the probability of maintaining the MMR is 61% (95% CI: 48-71). From start of INTERIM, 6 patients died but no deaths were related to CML progression (3 cases of other non haematological neoplasms, 1 stroke, 1 myocardial infarction, 1 chronic obstructive pulmonary disease).The PFS at ≥ 5 years is 94% (95% CI: 89-100) CONCLUSIONS: In summary, with a follow up ≥ 5 years, intermittent imatinib administration (INTERIM) confirmed to be safe, to produce a reversible increase of residual molecular disease in about one third of patients, but not to affect the long-term outcome. Aknowledgments: This work was supported in part by EuropeanLeukemiaNet (contract LSHC-CT-2004-503216) through the European Treatment and Outcome Study (EUTOS), supported by Novartis Oncology Europe, and COFIN 2009 Disclosures Russo: Celgene: Research Funding; Gilead: Research Funding; Novartis: Consultancy. Martinelli:Novartis: Speakers Bureau; Bristol-Meyers and Squibb: Speakers Bureau; Pfizer: Speakers Bureau. Soverini:Novartis: Consultancy, Honoraria; Bristol-Meyers Squibb: Consultancy, Honoraria; Ariad: Consultancy, Speakers Bureau. Turri:Novartis: Consultancy, Honoraria; Bristol-Meyers Squibb: Consultancy, Honoraria. Castagnetti:Novartis: Consultancy, Honoraria; Bristol-Meyers Squibb: Consultancy, Honoraria. Breccia:novartis: Consultancy; BMS: Consultancy; Celgene: Consultancy. Abruzzese:Novartis: Consultancy. Tiribelli:Novartis: Consultancy, Honoraria; Bristol-Meyers and Squibb: Consultancy, Honoraria. Rosti:Consultant: Consultancy, Speakers Bureau; Bristol-Meiers Squibb: Consultancy, Speakers Bureau; Ariad: Consultancy, Speakers Bureau.

In this study, we assessed the functional and kinetic characteristics of highly purified hematopoietic CD34+ cells from the apheresis products of 16 normal donors undergoing glycosylated granulocyte colony-stimulating factor (G-CSF ) treatment for peripheral blood stem cells (PBSC) mobilization and transplantation in allogeneic recipients. Mobilized CD34+ cells were evaluated for their colony-forming capacity and trilineage proliferative response to selected recombinant human (rh) CSF in vitro and the content of very primitive long-term culture initiating cells (LTC-IC). In addition, the cycling status of circulating CD34+ cells, including committed clonogenic progenitor cells and the more immature LTC-IC, was determined by the cytosine arabinoside (Ara-C) suicide test and the acridine orange flow cytometric technique. By comparison, bone marrow (BM) CD34+ cells from the same individuals were studied under steady-state conditions and during G-CSF administration. Clonogenic assays in methylcellulose showed the same frequency of colony-forming unit cells (CFU-C) when PB-primed CD34+ cells and BM cells were stimulated with phytohemagglutinin–lymphocyte-conditioned medium (PHA-LCM). However, mobilized CD34+ cells were significantly more responsive than their steady-state BM counterparts to interleukin-3 (IL-3) and stem cell factor (SCF ) combined with G-CSF or IL-3 in presence of erythropoietin (Epo). In cultures added with SCF, IL-3, and Epo, we found a mean increase of 1.5- ± 1-fold (standard error of the mean [SEM]) of PB CFU–granulocyte-macrophage and erythroid progenitors (burst-forming units-erythroid) as compared with BM CD34+ cells (P < .05). Conversely, circulating and BM megakaryocyte precursors (CFU-megakaryocyte) showed the same clonogenic efficiency in response to IL-3, granulocyte-macrophage–CSF and IL-3, IL-6, and Epo. After 5 weeks of liquid culture supported by the engineered murine stromal cell line M2-10B4 to produce G-CSF and IL-3, we reported 48.2 ± 35 (SEM) and 62.5 ± 54 (SEM) LTC-IC per 104 CD34+ cells in PB and steady-state BM, respectively (P = not significant). The Ara-C suicide assay showed that 4% ± 5% (standard deviation [SD]) of committed precursors and 1% ± 3% (SEM) of LTC-IC in PB are in S-phase as compared with 25.5% ± 12% (SD) and 21% ± 8% (SEM) of baseline BM, respectively (P < .001). However, longer incubation with Ara-C (16 to 18 hours), in the presence of SCF, IL-3 and G-CSF, or IL-6, showed that more than 60% of LTC-IC are actually cycling, with no difference being found with BM cells. Furthermore, studies of cell-cycle distribution on PB and BM CD34+ cells confirmed the low number of circulating progenitor cells in S- and G2M-phase, whereas simultaneous DNA/RNA analysis showed that the majority of PB CD34+ cells are not quiescent (ie, in G0-phase), being in G1-phase with a significant difference with baseline and G-CSF–treated BM (80% ± 5% [SEM] v 61.9% ± 6% [SEM] and 48% ± 4% [SEM], respectively; P < .05). Moreover, G-CSF administration prevented apoptosis in a small but significant proportion of mobilized CD34+ cells. Thus, our results indicate that mobilized and BM CD34+ cells can be considered equivalent for the frequency of both committed and more immature hematopoietic progenitor cells, although they show different kinetic and functional profiles. In contrast with previous reports, we found that PB CD34+ cells, including very primitive LTC-IC, are cycling and ready to progress into S-phase under CSF stimulation. This finding should be taken into account for a better understanding of PBSC transplantation.

The median age at diagnosis of chronic myeloid leukemia (CML) is between 60 and 65 years in most epidemiologic registries. Rather than age per se, a comprehensive evaluation of comorbidities may describe more properly the general clinical status of a patient. Tyrosine-kinase inhibitors (TKIs) have a different tolerability profile, and some adverse events (AEs) are peculiar of each drug, in particular, in presence of predisposing factors (comorbidities, concomitant medications). This article will review the impact of comorbidities in the safety and outcome of CML patients treated with TKIs. We will explore how the comorbidity status may be considered, together with CML-related factors, in the selection of the TKI in order to optimize treatment.

Abstract 860 Background: Elderly CML patients treated with Imatinib (IM) in early chronic phase (CP) have similar cytogenetic response and survival compared with younger patients, but they show a lower compliance to standard IM therapy (400 mg/day). Aims: The aim of the study is to investigate if CCgR that has been achieved with standard (daily administration) IM therapy can be maintained with the same dose of IM given intermittently (INTERIM). Methods: The study population is represented by elderly patients (≥ 65 years old) with Ph+ CML and with stable CCgR after at least 2 years of standard IM therapy (daily administration). IM is given at the same dose that was given at the time of enrollment by the following intermittent schedule: 1 week on / 1 week off for the 1st month; 2 weeks on / 2 weeks off for the 2nd and 3rd month; 1 month on / 1 month off from the 4th month thereafter. In cases of loss of CCgR INTERIM was stopped and standard therapy (daily administration) was resumed. After 12 months, the patients who are in continuous CCgR are advised to continue the intermittent study schedule and to be followed indefinitely. The CgR status was evaluated at baseline (by conventional cytogenetics on bone marrow and FISH on peripheral-blood) and every 3 months during the study (only by FISH on peripheral-blood). If FISH (% of Ph+ cells) increased more than 1% in two consecutive examinations, evaluation of marrow cells metaphases was performed to confirm the loss of CCgR and to check for additional cytogenetic abnormalities. Quantitative molecular assessment of BCR-ABL transcript by RQ-PCR on peripheral blood was due at baseline and every 3 months during the study and mutational analysis of ABL was performed in case of loss of CCgR. Results: One-hundred and fourteen patients have been considered eligible, but 17 (15%) refused to enter into the protocol. Out of 97 enrolled patients, 87 started INTERIM, 5 patients (5%) went off the study for major protocol violation before the 3rd month and, at present, 82 patients are ongoing. Of these 82 patients, 52, 30 and 11 completed the 3rd, 6th and 9th month, respectively. The preliminary results of the first 6 months are here reported. The distribution of patients according to FISH results is shown in Fig. 1. Only 1/68 pts (at 6th month) showed an increased >1% in Ph+ cells by FISH but he maintained a CCgR when checked by conventional cytogenetic. As showed in Fig. 2, 96 to 87% of patients maintained a major molecular response MMR (≤0,1) according to International Scale (IS). Conclusions: This study is trying to test the minimum effective dose of Imatinib to maintain the CCgR in elderly CML patients with stable CCgR. The preliminary results at 6 months do not show negative trends both for cytogenetic and molecular response. Therefore, the study is ongoing and all patients are expected to complete the trial time (12 months). Disclosures: No relevant conflicts of interest to declare.

We show the molecular and functional characterization of a novel population of lineage-negative CD34-negative (Lin−CD34−) hematopoietic stem cells from chronic myelogenous leukemia (CML) patients at diagnosis. Molecular karyotyping and quantitative analysis of BCR-ABL transcript demonstrated that approximately one-third of CD34− cells are leukemic. CML Lin−CD34− cells showed kinetic quiescence and limited clonogenic capacity. However, stroma-dependent cultures induced CD34 expression on some cells and cell cycling, and increased clonogenic activity and expression of BCR-ABL transcript. Lin−CD34− cells showed hematopoietic cell engraftment rate in 2 immunodeficient mouse strains similar to Lin-CD34+ cells, whereas endothelial cell engraftment was significantly higher. Gene expression profiling revealed the down-regulation of cell-cycle arrest genes and genes involved in antigen presentation and processing, while the expression of genes related to tumor progression, such as angiogenic factors, was strongly up-regulated compared with normal counterparts. Phenotypic analysis confirmed the significant down-regulation of HLA class I and II molecules in CML Lin−CD34− cells. Imatinib mesylate did not reduce fusion transcript levels, BCR-ABL kinase activity, and clonogenic efficiency of CML Lin−CD34− cells in vitro. Moreover, leukemic CD34− cells survived exposure to BCR-ABL inhibitors in vivo. Thus, we identified a novel CD34− leukemic stem cell subset in CML with peculiar molecular and functional characteristics.

Standard therapy with Imatinib (i.e. daily administration) significantly prolongs the survival of Ph+ CML patients who obtain a complete cytogenetic response (CCgR). Elderly patients (i.e. > 65 yrs) have similar cytogenetic responses and survival, but they usually show a low compliance. This prospective multicenter trial addresses the issue of intermittent administration of Imatinib (INTERIM) in Ph+ CML patients older than 65 years with stable complete cytogenetic response (CCgR) after at least 2 years of standard therapy with IM. Lower doses of IM could be sufficient to maintain the CCgR, to improve the tolerance and to reduce the costs of therapy. For this purpose, IM will be given at the same dose that was given at the time of enrollment by the following intermittent schedule: 1 week on/1 week off for the 1st month (weeks 1–4); 2 weeks on/2 weeks off for the 2nd and 3rd month (weeks 5–12); 1 month on/1 month off from the 4th month thereafter (weeks 13 on). The primary objective of the study is to evaluate the proportion of patients who remain in CCgR with INTERIM. The cytogenetic response (CgR) status will be evaluated at baseline (by conventional cytogenetics on bone marrow and FISH on peripheral-blood) and every 3 months during the study (only by FISH on peripheral-blood). If FISH documents a variation of the baseline value of more than 1% in two consecutive examinations, evaluation of marrow cells metaphases will be performed to confirm the loss of CCgR and to check for additional cytogenetic abnormalities (ACA). In case of loss of CCgR INTERIM will be stopped and standard therapy (daily administration) will be resumed. Quantitative molecular assessment of BCR-ABL transcript by RQ-PCR on peripheral blood is due at baseline and every 3 months during the study and mutational analysis of ABL will be performed in case of loss of CCgR. After 12 months, the patients who are in continuous CCgR are advised to continue the intermittent study schedule and to be followed indefinitely. The study started in May 2008 and, at present, 18 patients have been enrolled. Preliminary data on the first six months will be presented.

Homing and engraftment of hematopoietic stem cells (HSCs) to the bone marrow (BM) involve a complex interplay between chemokines, cytokines, and nonpeptide molecules. Extracellular nucleotides and their cognate P2 receptors are emerging as key factors of inflammation and related chemotactic responses. In this study, we investigated the activity of extracellular adenosine triphosphate (ATP) and uridine triphosphate (UTP) on CXCL12-stimulated CD34+ HSC chemotaxis. In vitro, UTP significantly improved HSC migration, inhibited cell membrane CXCR4 down-regulation by migrating CD34+ cells, and increased cell adhesion to fibronectin. In vivo, preincubation with UTP significantly enhanced the BM homing efficiency of human CD34+ cells in immunodeficient mice. Pertussis toxin blocked CXCL12- and UTP-dependent chemotactic responses, suggesting that G-protein alpha-subunits (Gαi) may provide a converging signal for CXCR4- and P2Y-activated transduction pathways. In addition, gene expression profiling of UTP- and CXCL12-treated CD34+ cells and in vitro inhibition assays demonstrated that Rho guanosine 5′-triphosphatase (GTPase) Rac2 and downstream effectors Rho GTPase–activated kinases 1 and 2 (ROCK1/2) are involved in UTP-promoted/CXCL12-dependent HSC migration. Our data suggest that UTP may physiologically modulate the homing of HSCs to the BM, in concert with CXCL12, via the activation of converging signaling pathways between CXCR4 and P2Y receptors, involving Gαi proteins and RhoGTPases.

In animals, the bone marrow (BM) is a source of liver-repopulating cells with therapeutic potential in case of tissue damage. However, the early response of human BM-derived stem cells (SC) to liver injury is still unknown. Here, we studied 24 patients undergoing orthotopic liver transplantation (OLT) for end-stage liver disease or hepatocellularcarcinoma, and 13 patients submitted to liver resection. The concentration of circulating BM-derived SC was determined by phenotypic analysis and clonogenic assays. Moreover, we assessed the serum level of inflammatory and tissue-specific cytokines. Reverse transcriptase-polymerase chain reaction and fluorescence-in situ hybridization were also used to characterize mobilized SC. At baseline, patients showed a significant lower concentration of circulating CD133(+), CD34(+) SC and clonogenic progenitors (colony-forming unit cells) than healthy controls. However, the time-course evaluation of peripheral blood cells after OLT demonstrated the significant early mobilization of multiple subsets of hematopoietic and endothelial stem/progenitor cells. Cytogenetic and molecular analyses of CD34(+) cells showed the host origin of mobilized SC and the expression of transcripts for GATA-4, cytokeratin 19, and alpha-fetoprotein hepatocyte markers. In contrast with OLT, only total circulating CD34(+) cells significantly increased after liver resection. Mobilization of BM cells after OLT or liver surgery was associated with increased serum levels of granulocyte-colony stimulating factor, interleukin-6, stem cell factor, hepatocyte growth factor, and vascular endothelial growth factor. In summary, we demonstrate that tissue damage after OLT and liver resection induces increased serum levels of multiple cytokines but only ischemia/reperfusion injury associated with OLT results in the remarkable mobilization of BM stem/progenitor cells.

Viral-based techniques are the most efficient systems to deliver DNA into stem cells because they show high gene transduction and transgene expression in many cellular models. However, the use of viral vectors has several disadvantages mainly involving safety risks. Conversely, nonviral methods are rather inefficient for most primary cells. The Nucleofector technology, a new nonviral electroporation-based gene transfer technique, has proved to be an efficient tool for transfecting hard-to-transfect cell lines and primary cells. However, little is known about the capacity of this technique to transfect adult stem cells. In this study, we applied the Nucleofector technology to engineer human bone marrow– derived mesenchymal stem cells (hMSCs). Using a green fluorescent protein reporter vector, we demonstrated a high transgene expression level using U-23 and C-17 pulsing programs: 73.7% ± 2.9% and 42.5% ± 3.4%, respectively. Cell recoveries and viabilities were 38.7% ± 2.9%, 44.5% ± 3.9% and 91.4% ± 1.3%, 94.31% ± 0.9% for U-23 and C-17, respectively. Overall, the transfection efficiencies were 27.4% ± 2.9% (U-23) and 16.6% ± 1.4% (C-17) compared with 3.6% ± 2.4% and 5.4% ± 3.4% of other nonviral transfection systems, such as FUGENE6 and DOTAP, respectively (p < .005 for all comparisons). Nucleofection did not affect the immunophenotype of hM-SCs, their normal differentiation potential, or ability to inhibit T-cell alloreactivity. Moreover, the interleukin-12 gene could be successfully transfected into hMSCs, and the immunomodulatory cytokine was produced in great amount for at least 3 weeks without impairment of its biological activity. In conclusion, nucleofection is an efficient nonviral transfection technique for hMSCs, which then may be used as cellular vehicles for the delivery of biological agents.

Although extracellular nucleotides support a wide range of biologic responses of mature blood cells, little is known about their effect on blood cell progenitor cells. In this study, we assessed whether receptors for extracellular nucleotides (P2 receptors [P2Rs]) are expressed on human hematopoietic stem cells (HSCs), and whether activation by their natural ligands, adenosine triphosphate (ATP) and uridine triphosphate (UTP), induces HSC proliferation in vitro and in vivo. Our results demonstrated that CD34+ HSCs express functional P2XRs and P2YRs of several subtypes. Furthermore, stimulation of CD34+ cells with extracellular nucleotides caused a fast release of Ca2+ from intracellular stores and an increase in ion fluxes across the plasma membrane. Functionally, ATP and, to a higher extent, UTP acted as potent early acting growth factors for HSCs, in vitro, because they strongly enhanced the stimulatory activity of several cytokines on clonogenic CD34+ and lineage-negative CD34- progenitors and expanded more primitive CD34+-derived long-term culture-initiating cells. Furthermore, xenogenic transplantation studies showed that short-term preincubation with UTP significantly expanded the number of marrow-repopulating HSCs in nonobese diabetic/severe combined immunodeficiency mice. Our data suggest that extracellular nucleotides may provide a novel and powerful tool to modulate HSC functions. (Blood. 2004;104:1662-1670)

Circulating monocytes from multiple myeloma patients enrolled in a clinical study of anti-idiotype vaccination were labelled with clinical-grade anti-CD14 microbeads and positively selected with the CliniMACS instrument. Cells were then grown, according to good manufacturing practice guidelines, in fetal-calf-serum-free medium in cell culture bags and differentiated to dendritic cells (DC) with granulocyte-macrophage colony stimulating factor plus interleukin 4 (IL-4), followed by either tumour necrosis factor-alpha (TNF-alpha) or a cocktail of IL-1beta, IL-6, TNF-alpha and prostaglandin-E2. The CD14+ cell yield was increased from 17.6 +/- 6.5% to 93.8 +/- 6.3% (recovery 64.4 +/- 15.4%, viability97%). After cell culture, phenotypic analysis showed that 86.7 +/- 6.8% of the cells were DC: 2.27 +/- 0.9 x 108 DC/leukapheresis were obtained, which represented 20.7 +/- 4.6% of the initial number of CD14+ cells. Notably, the cytokine cocktail induced a significantly higher percentage and yield (28.6 +/- 3% of initial CD14+ cells) of DC than TNF-alpha alone, with secretion of larger amounts of IL-12, potent stimulatory activity on allogeneic T cells and efficient presentation of tumour idiotype to autologous T cells. Storage in liquid nitrogen did not modify the phenotype or functional characteristics of preloaded DC. The recovery of thawed, viable DC was 78 +/- 10%. Finally, interferon-alpha-2b was at least as efficient as IL-4 in inducing the differentiation of mature, functional DC from monocytes.

Objectives To generate mature and fully functional CD83 + dendritic cells derived from circulating CD14 + cells highly purified from the leukapheresis products of multiple myeloma patients. Materials and Methods CD14 + monocytes were selected by high-gradient magnetic separation and differentiated to immature dendritic cells with granulocyte-macrophage colony-stimulating factor and interleukin-4 for 6–7 days and then induced to terminal maturation by the addition of tumor necrosis factor-α or stimulation with CD40 ligand. Dendritic cells were characterized by immunophenotyping, evaluation of soluble antigens uptake, cytokine secretion, capacity of stimulating allogeneic T cells, and ability of presenting nominal antigens, including tumor idiotype, to autologous T lymphocytes. Results Phenotypic analysis showed that 90% ± 6% of cells recovered after granulocyte-macrophage colony-stimulating factor and interleukin-4 stimulation expressed all surface markers typical of immature dendritic cells and demonstrated a high capacity of uptaking soluble antigens as shown by the FITC-dextran assay. Subsequent exposure to maturation stimuli induced the downregulation of CD1a and upregulation of CD83, HLA-DR, costimulatory molecules and induced the secretion of large amounts of interleukin-12. Mature CD83 + cells showed a diminished ability of antigen uptake whereas they proved to be potent stimulators of allogeneic T cells in a mixed lymphocyte reaction. Monocyte-derived dendritic cells, pulsed before the addition of maturation stimuli, were capable of presenting soluble proteins such as keyhole limpet hemocyanin and tetanus toxoid to autologous T cells for primary and secondary immune response, respectively. Conversely, pulsing of mature (CD83 + ) dendritic cells was less efficient for the induction of T-cell proliferation. More importantly, CD14 + cells-derived dendritic cells stimulated autologous T-cell proliferation in response to a tumor antigen such as the patient-specific idiotype. Moreover, idiotype-pulsed dendritic cells induced the secretion of interleukin-2 and γ -interferon by purified CD4 + cells. T-cell activation was better achieved when Fab immunoglobulin fragments were used as compared with the whole protein. When dendritic cells derived from CD14 + cells from healthy volunteers were analyzed, we did not find any difference with samples from myeloma patients as for cell yield, phenotypic profile, and functional characteristics. Conclusion These studies demonstrate that mobilized purified CD14 + cells represent the optimal source for the production of a homogeneous cell population of mature CD83 + dendritic cells suitable for clinical trials in multiple myeloma.

Objective Transforming growth factor β 3 (TGF-β 3 ) is a potent suppressor of human hematopoietic progenitor cells. In this article, we compare the activity of TGF-β 3 on highly purified CD34 + cells and more immature CD34 + DR − cells from chronic myelogenous leukemia (CML) patients in chronic phase and normal donors. Materials and Methods Primitive hematopoietic progenitors were stimulated in liquid cultures and clonogenic assays by early-acting growth factors such as stem cell factor (SCF) and interleukin 11 (IL-11) and the intermediate-late–acting stimulating factors IL-3, granulocyte-macrophage colony-stimulating factor, and erythropoietin. Molecular analysis of bcr/abl mRNA was performed on single CML colonies by nested reverse transcriptase polymerase chain reaction. Moreover, cell cycle analysis and assessment of apoptosis of normal and leukemic CD34 + cells were performed by propidium iodide (PI) alone and simultaneous staining with annexin V and PI, respectively. Results The colony-forming efficiency of CML CD34 + cells was generally inhibited by more than 90% regardless of whether the colony-stimulating factors were used alone or combined. When compared to normal CD34 + cells, leukemic cells were significantly more suppressed in 6 of 8 culture conditions. The inhibitory effect of TGF-β 3 on CD34 + cells was exerted within the first 24 hours of incubation as demonstrated by short-term preincubation followed by IL-3– and SCF-stimulated colony assays. Evaluation of bcr/abl transcript on residual CML colonies incubated with TGF-β 3 demonstrated a small subset of neoplastic CD34 + cells unresponsive to the inhibitory effect of the study cytokine. TGF-β 3 demonstrated a greater inhibitory activity on primitive CD34 + DR − cells than on more mature CD34 + cells. Again, CML CD34 + DR − cells were significantly more inhibited by TGF-β 3 than their normal counterparts in 3 of 8 culture conditions. Kinetic analysis performed on CD34 + cells showed that TGF-β induces cell cycle arrest in G 1 phase. However, this mechanism of action is shared by normal and leukemic cells. Conversely, TGF-β 3 preferentially triggered the programmed cell death of CML CD34 + cells without increasing the proportion of leukemic cells coexpressing CD95 (Fas receptor), and this effect was not reversed by functional blockade of Fas receptor. Conclusion We demonstrate that TGF-β 3 exerts a potent suppressive effect on CML cells that is partly mediated by Fas-independent apoptosis.

CD40 antigen is a costimulatory molecule highly expressed on dendritic cells (DC) and activated B cells, which induces T-cell proliferation through the binding with CD40L receptor. In this study, we evaluated CD40 expression on normal CD34(+) blood cells and functionally characterized CD34(+)CD40(+) and CD34(+)CD40(-) cell subsets. CD40, CD80, and CD86 antigens were constitutively expressed on 3.2% +/- 4.5%, 0%, and 1.8% +/- 1.2% CD34(+) blood cells, respectively. However, after 24 hours in liquid culture with medium alone, or with tumor-necrosis-factor-alpha (TNF-alpha), or with allogeneic mononuclear cells 10.8% +/- 3.8%, 75.3% +/- 15.0% and 53. 7% +/- 17.0% CD34(+) blood cells, respectively, became CD40(+). After incubation for 24 hours with TNF-alpha CD34(+)CD40(+) blood cells expressed only myeloid markers and contained less than 5% CD86(+) and CD80(+) cells. Also, a 24-hour priming with TNF-alpha or ligation of CD40 significantly increased the CD34(+) blood cells alloantigen presenting function. Finally, purified CD34(+)CD40(+) blood cells stimulated an alloreactive T-cell response in MLC, were enriched in granulocytic, monocytic, and dendritic precursors, and generated high numbers of DC in 11-14 d liquid cultures with GM-CSF, SCF, TNF-alpha and FLT-3L. In contrast, CD34(+)CD40(-) cells were poorly immunogenic, contained committed granulocytic and erythroid precursors and early progenitors, and differentiated poorly toward the DC lineage. In conclusion, a short incubation with TNF-alpha allows the selection of CD40(+) blood progenitors, which may be a useful source of DC precursors for antitumor vaccine studies, and also a CD34(+)CD40(-) blood cell fraction that could be exploited in innovative strategies of allogeneic transplantation across HLA barriers.

Dendritic cells (DCs) are the most powerful professional antigen-presenting cells (APC), specializing in capturing antigens and stimulating T-cell-dependent immunity. In this study we report the generation and characterization of functional DCs derived from both steady-state bone marrow (BM) and circulating haemopoietic CD34+ cells from 14 individuals undergoing granulocyte colony-stimulating factor (G-CSF) treatment for peripheral blood stem cells (PBSC) mobilization and transplantation. Clonogenic assays in methylcellulose showed an increased frequency and proliferation of colony-forming unit-dendritic cells (CFU-DC) in circulating CD34+ cells, compared to that of BM CD34+ precursors in response to GM-CSF and TNF-alpha with or without SCF and FLT-3L. Moreover, peripheral blood (PB) CD34+ cells generated a significantly higher number of fully functional DCs, as determined by conventional mixed lymphocyte reactions (MLR), than their BM counterparts upon different culture conditions. DCs derived from mobilized stem cells were also capable of processing and presenting soluble antigens to autologous T cells for both primary and secondary immune response. Replacement of the early-acting growth factors SCF and FLT-3L with IL-4 at day 7 of culture of PB CD34+ cells enhanced both the percentage of total CD1a+ cells and CD1a+ CD14- cells and the yield of DCs after 14 d of incubation. In addition, the alloreactivity of IL-4-stimulated DCs was significantly higher than those generated in the absence of IL-4. Furthermore, autologous serum collected during G-CSF treatment was more efficient than fetal calf serum (FCS) or two different serum-free media for large-scale production of DCs. Thus, our comparative studies indicate that G-CSF mobilizes CD34+ DC precursors into PB and circulating CD34+ cells represent the optimal source for the massive generation of DCs. The sequential use of early-acting and intermediatelate-acting colony-stimulating factors (CSFs) as well as the use of autologous serum greatly enhanced the growth of DCs. These data may provide new insights for manipulating immunocompetent cells for cancer therapy.

Human interleukin-9 (IL-9) stimulates the proliferation of primitive hematopoietic erythroid and pluripotent progenitor cells, as well as the growth of selected colony-stimulating factor (CSF)-dependent myeloid cell lines. To further address the role of IL-9 in the development of acute leukemia, we evaluated the proliferative response of three leukemic cell lines and 32 primary samples from acute myeloblastic leukemia (AML) patients to recombinant human (rh)-IL-9 alone and combined with rh-IL-3, granulocyte-macrophage CSF (GM-CSF), and stem cell factor ([SCF] c-kit ligand). The colony-forming ability of HL60, K562, and KG1 cells and fresh AML cell populations upon IL-9 stimulation was assessed by a clonogenic assay in methylcellulose, whereas the cell-cycle characteristics of leukemic samples were determined by the acridine-orange flow cytometric technique and the bromodeoxyuridine (BRDU) incorporation assay. In addition, the terminal deoxynucleotidyl transferase assay (TDTA) and standard analysis of DNA cleavage by gel electrophoresis were used to evaluate induction of prevention of apoptosis by IL-9. Il-9, as a single cytokine, at various concentrations stimulated the colony formation of the three myeloid cell lines under serum-containing and serum-free conditions, and this effect was completely abrogated by anti-IL-9 monoclonal antibodies (MoAbs). When tested on fresh AML samples, optimal concentrations of IL- 9 resulted in an increase of blast colony formation in all the cases studied (mean +/- SEM: 19 +/- 10 colony-forming unit-leukemic [CFU- L]/10(5) cells plated in control cultures v 107 +/- 32 in IL-9- supplemented dishes, P < .02). IL-9 stimulated 36.8% of CFU-L induced by phytohemagglutinin-lymphocyte-conditioned medium (PHA-LCM), and it was the most effective CSF for promoting leukemic cell growth among those tested in this study (i.e., SCF, IL-3, and GM-CSF). The proliferative activity of IL-9 was also observed when T-cell-depleted AML specimens were incubated with increasing concentrations of the cytokine. Addition of SCF to IL-9 had an additive or synergistic effect of the two cytokines in five of eight AML cases tested for CFU-L growth (187 +/- 79 colonies v 107 +/- 32 CFU-L, P = .05). Positive interaction was also observed when IL-9 was combined with IL-3 and GM-CSF. Studies of cell-cycle distribution of AML samples demonstrated that IL-9 alone significantly augmented the number of leukemic cells in S-phase in the majority of cases evaluated. IL-9 and SCF in combination resulted in a remarkable decrease of the G0 cell fraction (38.2% +/- 24% v 58.6% +/- 22% of control cultures, P < .05) and induced an increase of G1- and S- phase cells. Conversely, neither IL-9 alone nor the combination of IL-9 and SCF had any effect on induction or prevention of apoptosis of leukemic cells. In summary, our results indicate that IL-9 may play a role in the development of AML by stimulating leukemic cells to enter the S-phase rather than preventing cell death. Moreover, IL-9 acts synergistically with SCF for recruiting quiescent leukemic cells in cell cycle.

We studied the kinetic response and concentration of bone marrow (BM) progenitor cells of patients with lymphoid malignancies submitted to autologous bone marrow transplantation (ABMT), treated with a granulocyte-colony-stimulating factor (G-CSF)/interleukin-3 (IL-3) combination. The results were compared with those of lymphoma patients receiving the same pretransplant conditioning regimen followed by G-CSF alone. Recombinant human (rh)G-CSF was administered as a single subcutaneous (s.c.) injection at the dose of 5 micrograms/kg/day from day + 1 after reinfusion of autologous stem cells, while rhIL-3 was added from day +6 at the dose of 10 micrograms/kg/day s.c. (overlapping schedule). In both groups (i.e. G-CSF- and G-CSF/IL-3-treated patients), cytokine administration was discontinued when the absolute neutrophil count was0.5 x 10(9)/l of peripheral blood for 3 consecutive days. Following treatment with the CSF combination, the percentage of marrow CFU-GM and erythroid progenitors (BFU-E) in the S phase of the cell cycle increased from 9.3 +/- 2 to 33.3 +/- 12% and from 14.6 +/- 3 to 35 +/- 6%, respectively (p0.05). The number of actively cycling megakaryocyte progenitors (CFU-MK and BFU-MK) also increased. Conversely, G-CSF augmented the proliferative rate of CFU-GM (22.6 +/- 6% compared to a baseline value of 11.5 +/- 3%; p0.05) but not of BFU-E, CFU-MK or BFU-MK, and the increase in S-phase CFU-GM was significantly lower than that observed in the posttreatment samples of patients receiving IL-3 in addition to G-CSF. The absolute number of both CFU-GM and BFU-E/ml of BM was significantly augmented after treatment with G-CSF/IL-3 but not G-CSF alone. Similarly, administration of the cytokine combination resulted in a higher number of CD34+ cells and their concentration was significantly greater than that observed in the posttreatment samples of G-CSF patients. We also investigated the responsiveness to CSFs, in vitro, of highly enriched CD34+ cells, collected after priming with G-CSF in vivo (i.e. after 5 days of G-CSF administration). Our results demonstrated that pretreatment with G-CSF modified the response of BM cells to subsequent stimulation with additional CSFs. When the hematological reconstitution of patients treated with G-CSF/ IL-3 was compared to that of individuals receiving G-CSF alone, the addition of IL-3 resulted in a significant improvement in granulocyte and platelet recovery, a lower transfusion requirement and shorted hospitalization. In conclusion, our results indicate that in vivo administration of two cytokines increases the proliferative our results indicate that in vivo administration of two cytokines increase the proliferative our results rate and concentration of BM progenitor cells better than G-CSF alone and support a role for growth factor combinations for accelerating hematopoietic recovery after high-dose chemotherapy.

Interleukin-11 is a stromal cells derived cytokine which stimulates the proliferation of primitive haemopoietic progenitor cells. For this paper we have studied the constitutive expression of IL-11 mRNA in a panel of wellknown leukaemic cell lines and samples from AML patients at diagnosis. Moreover, the same cellular populations were evaluated for their proliferative response to recombinant-human-(r-hu). IL-11 alone and combined with r-hu-IL-3, granulocyte-macrophage colony stimulating factor (GM-CSF) and stem cell factor (SCF, c-kit ligand). The colony-forming ability of HL60, K562, KG1 cells and eight fresh AML cell populations was assessed by a clonogenic assay in methylcellulose. In eight additional AML cases the number of S-phase leukaemic cells induced by IL-11 was determined by the bromodeoxyuridine (BRDU) incorporation assay after 3d of liquid culture. IL-11, as single cytokine, did not stimulate the colony formation of the three myeloid cell lines under serum-containing and serum-free conditions. In contrast, the proliferation of the leukaemic cells in response to IL-3, GM-CSF and SCF was enhanced by co-incubation with IL-11, and this effect was reversed in blocking experiments by the anti-IL-11 Moab. When tested on primary AML samples, IL-11 alone showed little, if any, proliferative activity. However, it increased the IL-3-dependent blast colony formation in eight out of eight cases and GM-CSF in seven cases. IL-11 also augmented synergistically the number of CFU-L stimulated by SCF in seven cases. A combination of three factors (IL-11, SCF and IL-3) yielded optimal colony formation. The BRDU studies showed the significant increase of AML cells in S-phase when IL-11 was combined with SCF, whereas the two CSF had no activity on their own. Positive interaction was also observed when IL-11 was added to IL-3 supplemented cultures in five out of eight cases tested. Reverse transcriptase-polymerase chain reaction amplification (RT-PCR) demonstrated the constitutive expression of IL-11 mRNA in all the cell lines and 11/12 AML samples studied at diagnosis. These results indicate that IL-11 is expressed in leukaemic myeloid cells and that their proliferation is regulated by the cytokine which acts as a synergistic factor.

In this study we investigated the proliferation of three well-documented MM lines and 10 bone marrow samples from myeloma patients in response to rh-SCF alone and combined with Interleukin-6 (IL-6), IL-3 and IL-3/GM-CSF fusion protein PIXY 321. Neoplastic plasma cells were highly purified (> 90%) by immunomagnetic depletion of T, myeloid, monocytoid and NK cells. The number of S-phase cells was evaluated after 3 and 7 d of liquid culture by the bromodeoxyuridine (BRDU) incorporation assay. The proliferation of RPMI 8226 and U266 cell lines was also assessed by a clonogenic assay. All the experiments were performed in serum-free conditions. RPMI 8226 cell line was not stimulated by SCF which also did not augment the proliferative activity of IL-6, IL-3 and PIXY-321. Conversely, SCF addition resulted in 2.4-fold increase of the number of U266 colonies and in a higher number of U266 and MT3 cells in S-phase (24.5 +/- 2% SEM v 14.5 +/- 1% SEM and 32 +/- 3% SEM v 21 +/- 4% SEM, respectively; P < 0.05). The c-kit ligand also enhanced the proliferation of MT3 and U266 cells mediated by the other cytokines. Anti-SCF polyclonal antibodies completely abrogated the proliferative response of MT3 cells to exogenous SCF and markedly reduced the spontaneous growth of the same cell line. Reverse transcriptase-polymerase chain reaction amplification (RT-PCR) did detect SCF mRNA in MT3 and RPMI 8226 cells. Moreover, secreted SCF was found, in a biologically active form, in the supernatant of the two cell lines by the MO7e proliferation assay. When tested on fresh myeloma samples, SCF increased the number of S-phase plasma cells (4.7 +/- 1.6% v 3.4 +/- 1.3% in control cultures: P = 0.02). Significant proliferation was also induced by IL-6 (7 +/- 2.3% of BRDU+ cells; P = 0.006), IL-3 (5.3 +/- 1.3%; P = 0.01) and PIXY-321 (5.4 +/- 1.6%; P = 0.02). The addition of SCF significantly enhanced the proliferation of myeloma cells responsive to IL-6. In summary, our results indicate that SCF is expressed in MM cells and stimulates the proliferation of neoplastic plasma cells.

Abstract 786 Interferon alpha (INFα) either alone or in combination with Ara-C was the frontline therapy of Ph+ chronic myeloid leukaemia (Ph+ CML) between 1980 and 2000. INFα prolonged survival as compared to conventional chemotherapy and it was the first drug able to induce complete cytogenetic responses (CCgRs). Patients achieving a CCgR by INFα ± Ara C were less than 10–15%, but they represent fascinating elite of patients who are the most likely candidates for prolonged survival and possibly for cure. The last update of the largest European cohort of 317 CML patients who had obtained a CCgR on IFNα was reported in 2001 (Bonifazi et al., Blood, 2001). Briefly, the median time to first CCgR was 19 months, the 10 year survival rate from first CCgR was 72% and the survival probability for patients with low Sokal risk was 84%. In this study, the contribution of the Italian Cooperative Study Group on CML was of 119 cases. Although INFα was used more than 20 years ago, obtaining information on this selected category of CCgR–INFα responding patients in the Imatinib era may be interesting both from the biological and clinical point of view. We report here the preliminary results of an observational study aimed to update the overall survival (OS), the progression free survival (PFS) to accelerated-blastic phase (ABP) and the CCgR duration in 92 Ph+ CML patients who were treated in Italy with an INFα based therapy between 1986 and 2001 and who obtained a CCgR at least once. In this selected cohort of patients, the median time to first CCgR was 24 months (range, 3–143), and the median duration of the first CCgR was 87 months (3-252). The overall survival (OS) calculated from diagnosis, from start of IFNα and from the time of the first CCgR was 185 months (range, 74–334), 179 months (range, 74–287) and 154 months (range, 51–274), respectively. This is the longest follow-up of Ph+ CML patients who obtained a CCgR with an IFNα-based therapy. Out of 92 patients in CCgR, 71 (77%) cases stopped IFNα and 21 (23%) continued to be treated with IFNα. Out of the 71 cases who stopped IFNα, 38 (53%) cases lost CCgR and 3 (4%) cases died because of progression to ABP; 15 (21%) maintained CCgR without any other therapy and 18 (25%) maintained CCgR but shifted to Imatinib. Among the latter 33 patients maintaining the CCgR, 4 cases died because of CML unrelated causes. Out of the 21 cases who continued to be treated with IFNα, 18 (86%) currently maintain the CCgR and are alive and well, while 3 lost CCgR and died (2 cases for ABP). These data show that there are at least 33/92 (36%) patients who are alive and well and are maintaining a CCgR, either with continued IFNa treament (18 cases) or after IFNα treatment discontinuation (15 cases) but who have never been treated with Imatinib or any other tyrosine kinase inhibitor (TKI). We are now analyzing molecular data and we are collecting peripheral blood and bone marrow samples for correlative biological studies aimed to characterize the peculiar genetic and epigenetic features of these patients Work supported by European LeukemiaNet and Cofin 2009 Disclosures: Castagnetti: Bristol Myers Squibb: Honoraria; Novartis: Honoraria. Rosti:Novartis: Consultancy; Bristol Myers Squibb: Consultancy; Novartis: Research Funding; Novartis: Honoraria; Bristol Myers Squibb: Honoraria. Baccarani:Novartis: Consultancy; Bristol Myers Squibb: Consultancy; Novartis: Honoraria; Bristol Myers Squibb: Honoraria; Pfizer: Honoraria; Ariad: Honoraria.

Abstract 1682 Background: The introduction of Imatinib has significantly improved the outcome for patients with Ph+ CML. The complete cytogenetic response (CCgR) is a strong and confirmed predictor of improved long-term outcome. According to current recommendations, Imatinib (IM) should be continued indefinitely. However, optimal responders can be eligible for investigational trials of treatment discontinuation. AIMS: This study (ClinicalTrials.gov NCT 00858806) describes the effects of a policy of intermittent Imatinib (INTERIM) treatment (one month on/one month off) on cytogenetic and molecular responses in a selected population of patients ≥ 65 years old who were receiving treatment with Imatinib for > 2 years and were in stable complete cytogenetic response (CCgR). The primary endpoint of the study was the proportion of patients who maintained CCgR after 1 year of INTERIM. The secondary endpoint was the level of BCR-ABL transcripts during INTERIM METHODS: Cytogenetic and molecular responses were monitored by FISH and RT-Q-PCR every 3 months. The definition of CCgR, and of CCgR loss was based on CBA of marrow metaphases which was performed at baseline and in all the patients who became FISH positive (BCR-ABL–positive nuclei > 1%). Major molecular response (MMR), corresponding to a 3-log reduction in BCR-ABL transcript level from the standardized baseline, was defined as BCR-ABL ≤0.1%IS and was indicated as MR3.0. For the purposes of this study, complete molecular response (CMR) was defined as a 4-log reduction in BCR-ABL transcript level ( RESULTS: Seventy-six patients have been enrolled. Six patients (8%) lost CCgR (CBA positive), and 3 other patients became FISH positive while remaining CBA negative. At 12 months, the probability of maintaining CBA negativity was 92% (95% CI 86–98%), while the probability of maintaining FISH negativity was 87% (95% CI 79–94%). None of the factors that were examined by univariate and multivariate analysis were found to be associated with an higher probability of either loosing the CCgR (CBA) or showing a FISH positivity (> 1%), with the exception of the duration of imatinib therapy (HR = 0.23, 95% CI 0.008–0.73, P =.01). Among patients with prior Imatinib treatment longer or shorter than 48 months, the probability of maintaining FISH negativity was 94% (95% CI 88–100%) vs 71% (95% CI 53–89%), respectively, HR = 0.23 (P =.007). All the 6 patients who lost CCgR regained the CCgR with daily Imatinib, at the same dose, defined by FISH negativity after 3 to 9 months (4/6 also CBA negative, 2 patients refused bone marrow aspiration). At baseline, all but one patient (99%) were in MMR (MR3.0, BCR-ABL ≤0.1%IS), and 63 patients (83%) were in MR4.0 ( CONCLUSIONS: The intermittent use of imatinib in older patients in stable CCgR after continuous imatinib treatment results in the transient loss of the CCgR in a minority (8%) of the patients. However, the disease burden at the molecular level significantly increased. A policy of intermittent treatment may be an alternative both to chronic continuous treatment and to treatment discontinuation, particularly in the elderly. However, a longer follow up is required before drawing final conclusions. Acknowledgments: This work was supported in part by EuropeanLeukemiaNet through the European Treatment and Outcome Study (EUTOS) and by Cofin 2009. Disclosures: Baccarani: Novartis: Consultancy; Bristol Myers Squibb: Consultancy; Novartis: Honoraria; Bristol Myers Squibb: Honoraria; Pfizer: Honoraria; Ariad: Honoraria. Castagnetti:Novartis: Honoraria; Bristol Myers Squibb: Honoraria. Di Raimondo:celgene: Honoraria. Rosti:Novartis: Consultancy; Bristol Myers Squibb: Consultancy; Novartis: Research Funding; Novartis: Honoraria; Bristol Myers Squibb: Honoraria.

The introduction of hematopoietic growth factors into the management of leukemia can influence the outcome of treatment in several ways, depending on the sensitivity and the response of normal and leukemic cells. In this paper we report on the effects of the administration of Escherichia coli-produced, human recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) in 15 adult patients with acute nonlymphocytic leukemia (ANLL) resistant to first-line treatment or in relapse. GM-CSF was given at a dose of 5-10 micrograms/kg/day as a 6-h i.v. infusion, prior to chemotherapy (CHT) (for 7 days) and after CHT (until evidence of failure or of remission). In the pre-CHT period there was a clear trend towards an increase of circulating neutrophils (PMN) and/or blast cell count (median 0.3 vs. 1.0 x 10(9)/l for PMN, and 0.5 vs. 2.3 for blast cells). After chemotherapy, in the patients who achieved complete remission (CR), the median time to a PMN count greater than 0.5 x 10(9)/l and greater than 1 x 10(9)/l was 16 days (range 13-27) and 19 days (range 13-42) respectively. The outcome of treatment was CR for 8/15 (53%), death during induction for 3/15 (20%), and failure for 4/15 (27%). All failures occurred in patients with an increase of blast cell count during pre-CHT GM-CSF administration. Toxicity and side effects were minor, apart from an acute respiratory syndrome that developed twice in the same patient, at doses of 10 and 3 micrograms/kg/day. These data suggest that investigation of GM-CSF in the treatment of ANLL is worth pursuing, with special attention to GM-CSF effects prior to chemotherapy.

We show the molecular and functional characterization of a novel population of lineage-negative CD34-negative (Lin−CD34−) hematopoietic stem cells from chronic myelogenous leukemia (CML) patients at diagnosis. Molecular caryotyping and quantitative analysis of BCR-ABL transcript demonstrated that about one third of CD34− cells are leukemic. CML Lin−CD34− cells showed kinetic quiescence and limited clonogenic capacity. However, stroma-dependent cultures induced CD34 expression on some cells, cell cycling, acquisition of clonogenic activity and increased expression of BCR-ABL transcript. Lin−CD34− cells showed hematopoietic cell engraftment rate in immunodeficient mice similar to Lin-CD34+ cells whereas endothelial cell engraftment was significantly higher. Gene expression profiling revealed the down-regulation of cell cycle arrest genes, genes involved in antigen presentation and processing, while the expression of genes related to tumor progression, such as angiogenic factors, was strongly up-regulated when compared to normal counterparts. Flow cytometry analysis confirmed the significant down-regulation of HLA class I and II molecules in CML Lin−CD34−cells. Imatinib mesilate did not reduce fusion transcript levels, BCR-ABL kinase activity and clonogenic efficiency of CML Lin− CD34− cells in vitro. Moreover, leukemic CD34− cells survived to BCR-ABL inhibitors in vivo. Thus, we identified a novel CD34− leukemic stem cell subset in CML with peculiar molecular and functional characteristics.

We analyzed the kinetics of hematological recovery after autologous bone marrow transplantation in 13 patients with acute nonlymphoid leukemias (ANLL). A comparison was made with 31 patients with non-Hodgkin's lymphoma (NHL) whose bone marrow was harvested and cryopreserved, either at diagnosis or after intensive chemotherapy. Hematological recovery of ANLL patients was similar to that of pretreated NHL patients and significantly slower than that of untreated NHL patients. We suggest that chemotherapy before harvest (more than the possible decreased stem cell marrow potentiality resulting from the underlying disease) appears to be the main factor responsible for delayed recovery after autologous bone marrow transplantation in ANLL.