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Donor cell leukaemia (DCL) is a rare complication of allogeneic haematopoietic cell transplantation (HCT). We have investigated the prevalence and outcome of donor cell haematology malignancies within centres registered with the European Society of Blood and Marrow transplantation (EBMT). We have sought to identify risk factors to shed light on the pathogenesis of DCL as a model for leukaemogenesis. DCL cases were identified by questionnaire and a follow-up questionnaire requested detailed data. Control subjects from the EBMT registry who had not developed DCL were used for a matched pair analysis to identify risk factors. We identified 38 patients with DCL; the estimated prevalence was 80.5/100,000 transplants. Patients were predominantly treated for haematological malignancy. A clone was retrospectively identified in 7/25 (28%) donors for whom data was available. Overall survival was poor with 29/38 patients dead a median of 11 (range 0-91) months after DCL diagnosis. Matched case-pair analysis identified three factors on multivariate analysis as significantly associated with an increased risk for DCL: use of growth factors within the first 100 days after transplantation, in vivo T-cell depletion and multiple allografts. The risk factors identified, support reduced immune surveillance and replicative stress as pathogenic in the development of DCL.

Myelodysplastic syndromes (MDS) are characterized by abnormal growth of committed progenitors in clonogenic assay, with reduced number of colonies and decreased colony/cluster ratio. It has been suggested that excessive apoptosis is the cause of marrow failure in MDS. We studied the expression of caspase-1 (interleukin-1beta-converting enzyme, ICE) and caspase-3 (CPP32/apopain) in marrow mononuclear cells, and the growth pattern of committed progenitors in a series of 83 MDS cases. The percentage of apoptotic cells as detected by TUNEL technique, and the percentage of caspase-3-positive cells were significantly higher in refractory anemia (RA) and RA with ringed sideroblasts (RAS) than in chronic myelomonocytic leukemia (CMML), refractory anemia with excess of blasts (RAEB) and RAEB in transformation (RAEB-T). Spontaneous growth of CFU-GM was associated with a higher percentage of blasts, and with a lower expression of caspase-3 and caspase-1. The yield of CFU-E, BFU-E, and CFU-GM (in the presence of growth factors) was decreased by comparison to normal marrow, but large individual differences were observed in all cytological categories. Inhibition of caspase-1 and caspase-3 activities by specific inhibitors resulted in a significant increase of the production of all types of colonies (up to 50-fold of control). In the presence of caspase-3 inhibitor, the number of BFU-E and CFU-E was in the range of normal values in most cases of RA and RAS. In addition, caspase-1 and -3 protease activities were detectable by fluorogenic assay in all cases studied. Western blot analysis confirmed the expression of caspase-3, including the cleaved (activated)-p17 form in most cases of RA/RAS analyzed. It is concluded that caspase-3 is implicated in the increased apoptosis observed in MDS and that inhibition of its activity can restore at least partially the growth of committed progenitors.

Increased caspase-3 activity in refractory anemias: lack of evidence for Fas pathway implication

Allogeneic peripheral blood stem cell transplantation (PBSCT) has emerged as an alternative to bone marrow transplantation. PBSCT can be associated with a higher incidence of chronic graft-versus-host disease (cGVHD). In this study, we investigated whether there was a correlation between the composition of PBSC grafts (CD34+ and CD3+ cells) and hematological recovery, GVHD, relapse, and relapse-free survival (RFS) after myeloablative HLA-identical sibling PBSCT. The evolution of 100 acute or chronic leukemia patients was analyzed. Neither hematological recovery, acute or cGVHD, nor relapse, was significantly associated with CD3+ cell dose. Increasing CD34+ stem cells was associated with faster neutrophil (P=0.03) and platelet (P=0.007) recovery. Moreover, 47 of the 78 patients evaluable for cGVHD (60%; 95% CI, 49-71%) developed extensive cGVHD. The probability of extensive cGVHD at 4 years was 34% (95% CI, 21-47%) in patients receiving a 'low' CD34+ cell dose (8.3 x 10(6)/kg), as compared to 62% (95% CI, 48-76%) in patients receiving a 'high' CD34+ cell dose (8.3 x 10(6)/kg) (P=0.01). At a median follow-up of 59 months, this has not translated into a difference in relapse. In patients evaluable for cGVHD, RFS was significantly higher in patients receiving a 'low' CD34+ cell dose as compared to those receiving a 'high' CD34+ cell dose (P=0.04). This difference was mainly because of a significantly higher cGVHD-associated mortality (P=0.01). Efforts to accelerate engraftment by increasing CD34+ cell dose must be counterbalanced with the risk of detrimental cGVHD.

Cytarabine ocfosfate (YNK01) is a prodrug analogue of cytarabine which is resistant to systemic deamination after oral administration. Following initial studies indicating significant anti-tumour activity of YNK01 a phase II trial was initiated in order to assess the tolerability and efficacy of a combination of this agent with interferon alpha-2b (IFN-alpha2b) in recently diagnosed chronic phase CML patients (n = 98). The treatment was subdivided into cycles consisting of 4 weeks of continuous administration of IFN-alpha-2b (3 MU/m(2)/day 1st week and then 5 MU/m(2)/day) and 14 days of oral YNK01 (600 mg/day 1st cycle). At the end of each cycle the dose of YNK01 was adjusted according to the blood count observed during the previous 4 weeks. The median time from diagnosis to inclusion in the trial was 2 months (range 6 days to 7.5 months). At 12 weeks, 62 patients (63%; 95% CI, 54-73) achieved a complete hematological response. At 24 weeks, of 98 patients, two achieved a complete cytogenetic response, 14 a partial response (16% major cytogenetic response rate; 95% CI, 9-24) and 34 a minor response; 19 patients were not evaluable for cytogenetic response. During the trial, 20 patients progressed to accelerated (6) or blastic phases (14). The median time to progression was 15 months (range 2-38 months). At 3 years the overall survival was 79% (95% CI, 70-88). Although the complete hematological response rate compared favorably with the 40% response rate previously obtained with the subcutaneous formulation of Ara-c, the cytogenetic response rate was less than expected. Most of the patients experienced side-effects and all permanently stopped YNK01. Although the combination seems attractive the initial dose of 600 mg per day is probably too high and should be reconsidered in further trials.

In chronic myelogenous leukemia (CML), autologous stem cell transplantation could be a promising new approach for patients with no cytogenetic response after interferon alpha (IFN-alpha) therapy. We report data on 28 CML patients autotransplanted in chronic phase with peripheral blood progenitor cells mobilized with G-CSF (5 microg/kg/day x 5 days) given subcutaneously while continuing IFN-alpha therapy. At mobilization, 23 patients (82%) were in complete hematological remission (CHR), 16 (57%) achieved a minor cytogenetic response (mcr). We obtained, after stimulation, a median of 37.4 x 10(9)/l (6.9-108) white blood cells, 7.2 x 10(8)/kg (2.2-16.6) mononuclear cells, 39 x 10(4)/kg (4.8-403.5) CFU-GM and 4.2 x 10(6)/kg (0-58.6) CD34+ cells. Six patients received GM-CSF after transplantation. All patients engrafted, with no significant influence stemming from the Sokal index score and pretransplantation IFN-alpha therapy duration. The first cytogenetic evaluation after transplantation showed 11 (39%) major cytogenetic response (Mcr), and nine (32%) mcr with no significant correlation between these responses, the Sokal index score, and pretransplantation IFN-alpha therapy duration, although there was a significant impact from GM-CSF administration (P=0.01). After transplantation, 26 patients received IFN-alpha alone or associated with hydroxyurea. The median follow-up was 12 months after transplantation and 57 months after diagnosis. At the time of follow-up, nine patients were in CHR, six remained stable in chronic phase, three presented an mcr and one remained in Mcr. At the last follow-up, 22 patients were alive. We conclude that the results of this strategy are encouraging in poor IFN-alpha responders but that other prospective studies that try to maintain the cytogenetic responses obtained immediately after transplantation are needed.

Philadelphia (Ph) or BCR/ABL-negative cells with immature phenotype (CD34-positive, DR-negative) can be recovered from patients with chronic myeloid leukemia (CML) in chronic phase. We used the technique described by Berardi et al (Science 1995; 267: 104-108) to select stem cells from marrow or blood of CML patients at diagnosis or during treatment with alpha-interferon. Mononuclear cells (MNC), and in some experiments CD34+ cells, were maintained for 7 days in the presence of 5-fluorouracil (5-FU), stem cell factor and interleukin-3. The number of viable cells recovered after culture was between 7.4 and 70.2 for 10(6) cells plated. These cells exhibited the following phenotype: CD34+, CD117+, CD38-, lineage-, and were able to generate cobblestone areas and secondary colonies in long-term culture (LTC), with a frequency similar to that of cells selected from normal marrow. Study by fluorescence in situ hybridization of LTC cells or secondary colonies showed no evidence of BCR/ABL rearrangement. Reverse transcriptase polymerase chain reaction studies on pooled LTC cells or secondary colonies were also negative. By contrast, LTC cells or secondary colonies obtained from CML CD34+ cells without culture in the presence of 5-FU were always positive for BCR/ABL rearrangement. Finally, 5-FU selected cells were able to engraft NOD/SCID mouse, as human cells were detected in blood and marrow 10 weeks post transplantation, which were BCR/ABL negative by RT-PCR. This method of culture makes it possible to select constantly BCR/ABL-negative cells with capacities of development in LTC assay and of NOD/SCID mouse engraftment.