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We studied telomere length in 32 CML patients who discontinued imatinib after achieving complete molecular remission and 32 age-sex-matched controls. The relative telomere length (RTL) was determined by q-PCR as the telomere to single copy gene (36B4) ratio normalized to a reference sample (K-562 DNA). Age-corrected RTL (acRTL) was also obtained. The 36-month probability of treatment-free remission (TFR) was 59.4 %. TFR patients showed shorter acRTL compared to relapsed (mean ± SD = 0.01 ± 0.14 vs 0.20 ± 0.21; p = 0.01). TFR was significantly higher in CML patients with acRTL ≤0.09 (78.9 vs 30.8 %, p = 0.002). CML stem cells harboring longer telomeres possibly maintain a proliferative potential after treatment discontinuation. Electronic supplementary material The online version of this article (doi:10.1186/s13045-016-0293-y) contains supplementary material, which is available to authorized users.

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Several factors are predictive of treatment-free remission (TFR) in chronic myeloid leukemia (CML), but few data exist on the role of natural killer (NK) cells and their killer-cell immunoglobulin-like receptors (KIRs). KIR and human leukocyte antigen (HLA) genotypes were investigated in 36 CML patients who discontinued tyrosine kinase inhibitor (TKI) treatment after achieving deep molecular response (MR 4.5 ). Cumulative TFR was significantly higher in patients homozygous for KIR A haplotype (85.7% vs. 45.5%; p = 0.029). Younger age, Bx haplotype, and the combination KIR3DS1/KIR3DL1 present/HLA-Bw4 present were significantly associated with relapse. KIR genotypes could prove useful in identifying patients that are likely to maintain MR 4.5 after discontinuing TKI treatment.

BACKGROUD: Nilotinib, a potent 2nd generation tyrosin kinase inhibitor, is efficacious in the treatment of chronic myelogenous leukemia (CML). Impaired glucose metabolism represents one of the most frequently observed adverse events and several clinical trials, reported a high diabetes incidence during treatment with this drug. The mechanism of this side effect is poorly understood, but recently has been hypothesized an increased postreceptorial insulin resistence. Moreover, "in vitro"results indicated that c-ABL is involved in the insulin receptor signaling pathway. A large number of genetic variants associated with Type 2 diabetes (T2D) are implicated in beta-cell function but the role of common genetic variants associated with insulin resistance in the etiology of T2D, remains poorly documented. Scott R. and al. (Diabetes 2014) recently identified 10 multiple single nucleotide polymorphisms (SNPs) associated with insulin resistance and created a genetic risk scores (uGRS) as complementary tool to for insulin resistance. AIM of the study was to identify whether this uGRS could be a valid prognostic tool in identifying patients developing diabetes during Nilotinib therapy PATIENTS AND METHODS:45 patients (19 males) were included in the study. Twenty-four were treated with Nilotinib in first-line and 21 as second line (10 for resistance, 8 intolerance and 3 for other reasons). None of the subjects studied had abnormal blood glucose or took any antidiabetic drug before Nilotinib treatment. We genotyped all patients with the GRS created by Scott R. including those in, or near, the IRS1, GRB14, ARL15, PPARG, PEPD, ANKRD55/MAP3K1, PDGFC, LYPLAL1, RSPO3, and FAM13A1 genes that have primary effects on subcutaneous adipocyte function. Also we added 2 new variants, one for TCF7L2 gene, associated with insulin secretion and another in FTO gene, whose effect on insulin levels is mediated by BMI. The uGRS was calculated, as previously reported, by summing the number of risk alleles across the 12 variants (0 for risk allele absent, 1 for heterozygosity and 2 for homozygosity for risk allele). A cut-off point for uGRS, maximizing predictivity and sensitivity of the score was calculated using Youden's index. Diabetes and impaired fasting Glycaemia were defined using the American Diabetes association (ADA) criteria. Data were reported as median and range, RESULTS:Age at diagnosis was 45(18-82) years, the Sokal was low in 16 (42%), intermediate in 12 (26%) and high in 17 (32%) patients. During treatment and subsequent follow up of 45(7-127) months, 28 patients remained euglycemic, 5 (2 treated in the first line) developed diabetes after 14(1-32) months and 12 (6 treated as first line) developed IFG in 6 (1-12) months. No IFG patients developed an overt diabetes in the subsequent follow-up of 60.3 (33-102) months. We calculated a cut-off point of 12 for uGRS. When the 28 euglycemic patient were compared with 5 patients becoming diabetics after Nilotinib, uGRS showed a sensibility of 100% and a specificity of 46% in predicting diabetes. Consequently, the positive predictive valuewas 25% where the negative predictive values 100%. When the 28 euglycemic patients were compared with the 12 patients developing IFG after Nilotinib, the sensibility and specificity of uGRS was low: 50% and 46% respectively. CONCLUSIONS: A Genetic risk score for insulin resistance showed high specificity and a strong negative predictive values when used to identify CML patients treated with Nilotinib developing an overt diabetes. Further studies in lager populations are needed to confirm this predictivity that can be used in clinical practice to tailor the best anti TKI therapy. Disclosures No relevant conflicts of interest to declare.

Background: Diagnosis of a prefibrotic state (MF0) presents histological diagnostic difficulties. MF0 has a worst prognostic impact than Essential Thrombocythemia (TE) as regard the thrombotic risk and a higher risk towards Idiopathic Myelofibrosis (MI) and acute leukemia evolution. For this reason it is very useful to identify this group of patients. Aims: The aim of this study was to evaluate clinical and hematological impact of the mutational status in patients with an MF0 diagnosis. Methods: A retrospective chart review was performed from January 2010 to July 2015 in a single center in 317 patients affected by Ph negative chronic myeloproliferative neoplasms. Polycythemia vera cases were excluded. Thirty-three patients have been classified as MF0 on the base of the bone marrow histological examination. Onset features include cytogenetics, blood counts, peripheral CD34-positive cells, spleen and liver size, thrombotic events (prior to and post-diagnosis) and thrombotic risk. Fragment analysis was performed to study exon 9 CALR mutation, Real-time PCR was applied for exon 14 JAK2 V617F mutation and Sanger sequencing was used to identify exon 10 MPL mutations for 505 and 515 codons. According to genetic results, patients were identified into four groups according to a positivity for JAK2, MPL, CALR and for triple negativity. Results: The 33 patients with MF0 were: 11 (33%) JAK2 positive, 10 (30%) CALR positive, (10) 30% triple negative and 2 (7%) MPL positive. The latter group was not further considered for analysis due to the low number of cases. Eighty percent of CALR positive patients had a deletion on the exon 9 of the gene (8 del52bp and 2 del46bp), while 20% had the type 2 mutation (ins5bp). The average of JAK2 allelic burden was 20%. The 3 groups of patients were comparable for age, white blood counts and hemoglobin values. There was a female prevalence (23 vs 10 males). Platelet count was higher (median 875.500 103 µl, interquartile range 303.000 103 µl , p = 0.008) in CALR positive patients compared to JAK2 positive (median 569.000 103 µl, interquartile range 433.000 103 µl) and to triple negative patients (median PLT count 629.500 103 µl, interquartile range 378.250 103 µl). Noteworthy, bone marrow cytogenetic exam was normal in all patients. JAK2 positive patients had a larger spleen compared to the other two groups. Pre-diagnosis thrombotic events were exclusive for JAK2 positive patients and absent in the other groups. Triple negative patients do not have a negative prognostic impact for the thrombotic risk. Conclusions: CALR deletion could be considered as an MF0 marker and should be included in diagnostic work-up. JAK2 positivity in MF0 is associated with a high thrombotic risk. Disclosures No relevant conflicts of interest to declare.

Background: According to recent findings, the management of myeloproliferative neoplasms (MPNs) is highly dependent on presence or absence of thrombotic events. The JAK2 mutation has been identified as a marker of MPNs. It is also an occult marker in several patients with splanchnic venous thrombosis (SVT), but its contribution as an additional thrombotic risk factor in MPNs is still under discussion. Moreover, a pro-thrombotic risk factor, either inherited or acquired (Factor V Leiden mutation, deficiencies in protein C, protein S and Prothrombin mutation 20210) can be identified in these patients. Recently, another milestone in the molecular diagnosis of MPNs, somatic mutations in the CALR gene, has been reported. A total of 36 types of frame-shifting insertions and deletions were detected in the exon 9 of CALR gene, which encodes a Ca2+ binding protein in endoplasmic reticulum called calreticulin. Type-1, 52-bp deletion (p.L367fs*46), and type-2, 5-bp TTGTC insertion (p.K385fs*47) variants constitute more than 80% of these mutations These mutations were reported to have a incidence of over 60% to 80% in JAK2 and MPLmutation-negative Essential Thrombocythemia (ET) and Primary Myelofibrosis (PMF) patients. Compared to those with JAK2 mutation, CALR-mutated ET patients are younger and have a lower leukocyte count and higher platelet count. CARL mutations have been also reported as a favorable prognostic factor on thrombosis-free survival (TFS) for ET patients. Aims: In this study, we evaluated the incidence of SVT, JAK2 and CALR mutations, and prothrombotic risk factors in patients with MPNs observed in our center from January 2000 to January 2014. Methods: We performed a retrospective review of clinical charts of 466 Ph1 negative MPN patients followed in our center, classified according to the WHO 2008 classification. Patient and disease characteristics, including JAK2V617F, MPL and CALR mutations and thrombotic risk factors were recorded. Results: The median age of patients with diagnosis of MPN was 43 years. Fourteen patients (13 females, 1 male; 3%) of median age 46 years presented a SVT. Three had a Budd Chiari syndrome and 11 a portal venous thrombosis. According to a histological review, these patients were classified as follows: ET, 2 cases, PMF, 3 cases, Polycythemia Vera (PV) 1 case, Myelofibrosis in a prefibrotic phase (MF0) 8 cases. Classification of 11 cases with Myelofibrosis according to the IPSS identified 7 as INT1, 1 as INT2 and 3 as low risk. Among all 14 patients diagnosed with SVT, 12 were JAK2V617F positive with a median allelic burden of 30%, 1 patient was MPL positive, and 1 patient was triple-negative. CALR mutation was not observed in any of the patients. Two cases were diagnosed with MPN 30 months after SVT, 3 patients experienced SVT after a median follow-up of 108 months from MPN diagnosis while in 9 patients the diagnosis of MPN was concomitant to SVT. In the latter patients, median Hb levels were 12.4 g/dL , WBC 8260 /µL, HCT 36.3%, PLT 337.000/ µL and a modest hepatomegaly and splenomegaly were documented. Prothrombotic risk factors were found in 9 of 13 patients. Two patients experienced a thrombotic episode prior to the diagnosis of SVT and two subsequently during the follow-up. Interestingly, 9 (70%) of MPN patients with SVT exhibited at least one prothromobtic risk factor, such as factor V Leiden, Protein C deficiency, hyperhomocystinemia and 50% had two or more associated defects. Thirteen of the 14 patients are currently being treated as follows hydroxyurea (9), interferon (1), and ruxolitinib (3). All patients received oral anticoagulant treatment except for three who are on antiplatelet therapy. MPN patients without SVT had a lower prevalence of prothrombotic risk factors and developed venous thrombosis in different anatomical sites: in these cases WBC count, platelet values and the presence of JAK2V617F mutation correlated with the development of the thrombotic event. Conclusions: Although SVT has a low incidence in MPN patients, a potential benefit of testing for mutations in CALR gene and for additional prothrombotic risk factors is suggested in the whole MPN population for the prevention and treatment of this complication. Disclosures No relevant conflicts of interest to declare.