Platelet Dense Bodies Loaded with Mepacrine Study in Chronic Idiopathic Thrombocytopenic Purpura (ITP)

In 22 cases of chronic ITP, the platelet 5-HT storage organelles were counted by examination of platelets loaded with mepacrine and correlated with the size and volume of the platelets. Statistical analysis showed that the mean volume and the number of granules increased in ITP without increase in the mean number of granules per unit volume. A strong correlation was found between platelet long diameter and number of dense bodies in controls (44 healthy subjects) (r = 0.94; y = 2.826 × – 0.699) and in ITP (r = 0.92; y = 2.587 × + 0.06). This study demonstrated in chronic ITP the presence both of platelets without granules and others rich in granules. These anomalies were present no matter what the count of platelets and did not change the mean values for granules and for ADP in most cases. Most platelets remain morphologically normal.

p62/SQSTM1 upregulation constitutes a survival mechanism that occurs during granulocytic differentiation of acute myeloid leukemia cells

The p62/SQSTM1 adapter protein has an important role in the regulation of several key signaling pathways and helps transport ubiquitinated proteins to the autophagosomes and proteasome for degradation. Here, we investigate the regulation and roles of p62/SQSTM1 during acute myeloid leukemia (AML) cell maturation into granulocytes. Levels of p62/SQSTM1 mRNA and protein were both significantly increased during all-trans retinoic acid (ATRA)-induced differentiation of AML cells through a mechanism that depends on NF-κB activation. We show that this response constitutes a survival mechanism that prolongs the life span of mature AML cells and mitigates the effects of accumulation of aggregated proteins that occurs during granulocytic differentiation. Interestingly, ATRA-induced p62/SQSTM1 upregulation was impaired in maturation-resistant AML cells but was reactivated when differentiation was restored in these cells. Primary blast cells of AML patients and CD34(+) progenitors exhibited significantly lower p62/SQSTM1 mRNA levels than did mature granulocytes from healthy donors. Our results demonstrate that p62/SQSTM1 expression is upregulated in mature compared with immature myeloid cells and reveal a pro-survival function of the NF-κB/SQSTM1 signaling axis during granulocytic differentiation of AML cells. These findings may help our understanding of neutrophil/granulocyte development and will guide the development of novel therapeutic strategies for refractory and relapsed AML patients with previous exposure to ATRA.

First evaluation of the French cancer clinical research projects funding program (PHRC)

6601

Background: Data on success and failure rates of clinical studies are cruelly missing, especially for public funded programs. The French Cancer Plan 2003–2007 has launched such program as a specific extension of the wider ‘Programme Hospitalier de Recherche Clinique‘ (PHRC). Grant applications are submitted yearly. Funding is competitively based, projects being selected by a national committee supported by independent experts. A substantial financial support for the recruitment of clinical research associates (CRA) was launched simultaneously.We performed a preliminary analysis of the projects’ outcome 5 years after their funding. Methods: We carried out a survey of the projects funded in 2003 and 2004. A questionnaire was sent to the principal investigator. Data on project status, number of patients recruited per project, reasons for delay or failure, and publication results were collected. Projects were classified as failure (not started or closed for lack of inclusions) or success (ongoing or completed). Results: Of 257 projects submitted, 85 (33%) were selected. Of them, 24 failed (28%). Higher failure rates were observed for breast (5/11, 45%), gastrointestinal tract (6/16, 38%), genitourinary tract (4/11, 36%), and immune or cell therapy (8/15, 53%) projects. In contrast, haematological malignancies projects showed a low failure rate (3/20, 15%) as well as studies associated with translational research (6/34, 18%) or led by cooperative groups. The main reason for trials delay or failure was recruitment difficulties, due to overestimation of recruitment potential or restrictive inclusion criteria. Very few (< 5%) mentioned difficulty raised by the evolution of the scientific question or competing studies. No financial issue was reported. With 4-year of follow-up, 25% and 52% of projects have been respectively published in a peer-reviewed journal or presented at scientific meetings. Conclusions: In this first set of trials funded by the French Cancer Plan 2003–2007, more than a quarter failed despite apparent adequate funding. Main cause was a discrepancy between inclusion potential announced and real accrual. Application processes should evaluate more carefully this issue in order to improve the effectiveness of public health funding interventions in the future.

No significant financial relationships to disclose.

Persistence of complete molecular remission in chronic myeloid leukemia after imatinib discontinuation: Interim analysis of the STIM trial

7084

Background: Imatinib (IM) has greatly improved survival in chronic myeloid leukemia (CML). However, IM must be continued for an indefinite period of time. A multicenter trial “Stop Imatinib” (STIM) was initiated in July 2007, in order to evaluate the persistence of complete molecular remission (CMR) after stopping IM and determine factors associated with CMR persistence. Methods: Inclusion criteria were IM treatment duration ≥3 years and sustained CMR, defined as BCR-ABL transcripts below a detection threshold of a 5-log reduction (undetectable by RQ-PCR) for ≥2 years. Molecular relapse was defined as RQ-PCR positivity confirmed on 2 successive occasions. In case of relapse, pts were rechallenged with IM at 400 mg daily. Molecular monitoring was performed according to international recommendations. Results: Sixty-nine pts were recruited among which 60 with a follow-up >1 month, including 22 males and 38 females. Median age was 62 (29–80), 31 pts had been treated with IFN prior to IM and 29 with IM frontline (de novo). Median follow-up was 5 months (1–16). Relapse occurred in 37 pts within 6 months of IM discontinuation. Only 1 pt relapsed after 6 months (M7). All patients in molecular relapse were sensitive to IM reintroduction. At last follow-up in December 2008, CMR was sustained in 8 pts at M14 and 3 pts at M16. No differences in terms of demography, duration of IM treatment and CMR duration were found between pts who relapsed and those who did not. At M9, the probability of persistent CMR was 46% (95% CI: 32–59%), 53% (95% CI: 33–69%) for previously IFN-treated pts and 39% (95% CI: 20–58%) for de novo pts (p = 0.54). A trend for a lower probability of relapse in low Sokal score pts was observed. Conclusions: Our data confirm that CMR can be long-lasting after discontinuation of IM. Using stringent criteria, it is possible to stop IM in patients with sustained CMR, even in those treated with IM as a single agent. Updated follow-up will be presented.

No significant financial relationships to disclose.

[Management of 315neutropenic febrile episodes in a cancer center]

Management of febrile neutropenic patients is described in guidelines. Each cancer center can adapt these according to its local bacterial ecology. We present a retrospective study made in a cancer center from 2001 to 2003.

METHOD

Three hundred and fifteen febrile neutropenic episodes after chemotherapy (66% for solid tumor) were analysed.

RESULTS

For 279 episodes, no antibiotic therapy was given before admission. Clinical or radiological manifestations occurred in 46%; microbiologically documented infections by hemocultures in 28% (Gram positive: 42%; Gram negative: 51%) and by puncture in 14% (Gram negative: 58%). The length of pyrexia was inferior to 7 days in 88% and neutropenia inferior 7 days in 80.8%. 79.7% of episodes were treated with one of the three antibiotic therapy recommended by the center (ceftriaxone+tobramycin; ceftriaxone+ciprofloxacin; ceftriaxone+ofloxacin); 13.3% were treated with an other therapy; 7% received no antibiotic therapy. 68.5% of patients treated with one of the three antibiotic therapies, became afebrile without changing the antibiotic protocol.

CONCLUSION

In our study, there were a majority of Gram negative bacteria except for Pseudomonas aeruginosa. The three antibiotic therapy recommended by the center (third generation cephalosporin+aminoglycosides or fluoroquinolones) were effective and glycopeptide was not necessary in first intention treatment.

Trough plasma imatinib concentrations are associated with responses to standard-dose imatinib in chronic myeloid leukemia and could improve its clinical management

7027

Background: Variable responses to imatinib in the treatment of myelogenous leukemia (CML) are incompletely understood. Previous studies focused on cellular mechanisms of resistance to imatinib. Another hypothesis for variable response lies in pharmacokinetic variability that may reduce drug exposure in patients receiving imatinib. Methods: Using high- performance liquid chromatography-tandem mass spectrometry, we assessed trough plasma imatinib concentrations at steady state (Cmin) in more than 150 CML patients. Major molecular response (MMR) was defined as a 3 logarithm reduction of BCR-ABL transcripts, quantified from peripheral blood using Q-RTPCR. In addition, suboptimal response criteria defined by the European Leukemianet were used to increase doses of imatinib. Results: i) we assessed Cmin in 85 CML patients and demonstated a correlation with imatinib doses (median values 813, 1,135, 1,709 ng/ml for respectively 300,400, 600 mg/day). ii) for 68 patients after at least one year's treatment mean Cmin were significantly higher in the group with MMR (34 patients) than in the group without (1,452.1±649.1 ng per milliliter vs. 869.3±427.5 ng per milliliter, P<0.001) whereas there was no difference in the imatinib daily dose. For Cmin and their discrimination potential for MMR, the area under receiver-operating characteristic curve was 0.775, with best sensitivity (76.5 percent) and specificity (70.6 percent) at a plasma threshold of 1,002 ng per milliliter. iii) dose escalation of imatinid, 400mg up to 600mg was proposed in 8 patients in suboptimal response (3 according to cytogenetic criteria and 5 according to molecular criteria). The median Cmin increase from 573 ng/ml [181–1,376] to 1,139 ng/ml [733–2,262] and 5 patients had a cytogenetic (n=3) or a molecular (n=2) response. Conclusions: Monitoring of imatinib plasma levels could be very useful for the management of CML patients, or should at least be checked in the case of treatment failure or suboptimal response or in patients nonadherent with imatinib or with a drug-drug interaction suspicion.

No significant financial relationships to disclose.

Progress in allogeneic bone marrow and peripheral blood stem cell transplantation for multiple myeloma: a comparison between transplants performed 1983-93 and 1994-98 at European Group for Blood and Marrow Transplantation centres

Out of 690 allogeneic matched sibling donor transplants for multiple myeloma reported to the European Group for Blood and Marrow Transplantation (EBMT) registry, 334 were performed during the period 1983-93 (all with bone marrow) and 356 during 1994-98 [223 with bone marrow and 133 with peripheral blood stem cells (PBSCs)]. The median overall survival was 10 months for patients transplanted during the earlier time period and 50 months for patients transplanted with hone marrow during the later period. The use of PBSCs was associated with earlier engraftment but no significant survival benefit compared to bone marrow transplants during the same time period. The improvement in survival since 1994 with the result of a significant reduction in transplant-related mortality, which was 38%, 21% and 25% at 6 months and 46%, 30% and 37% at 2 years during the earlier period, and the later period with bone marrow and PBSCs respectively. Reasons for the reduced transplant-related mortality appeared to be fewer deaths owing to bacterial and fungal infections and interstitial pneumonitis, in turn a result of earlier transplantation and less prior chemotherapy. Better supportive treatment and more frequent use of cytokines may also play a role. The improvement in survival was not directly related to the increased use of PBSCs.

Reassessing autotransplantation for acute myeloid leukaemia in first remission – a matched pair analysis of autologous marrow vs peripheral blood stem cells

The role of autologous stem cell transplantation in adult patients with acute myeloid leukaemia (AML) in first remission is unclear, yet it has become standard treatment for myeloma and this paper explores whether the source of transplanted stem cells may explain this paradox. In total, 57 patients from the Royal Marsden Hospital who received an unpurged bone marrow transplant (ABMT) were matched with 114 patients from the EBMT registry who had undergone peripheral blood stem cell transplantation (PBSCT). Patients were matched for karyotype, FAB type, remission-autograft interval and age. In the PBSCT group, haematopoietic recovery was significantly faster and nonrelapse mortality at 4 years was significantly lower (13 vs 1%, P=0.04). The relapse rate and overall survival at 4 years (20 vs 31% and 77 vs 63%) were also better with PBSCT, although the differences were not statistically significant. Autografting should be reassessed in a randomised trial for first remission AML patients using peripheral blood as a source of stem cells rather than bone marrow.

Risk assessment in adult acute lymphoblastic leukaemia before early haemopoietic stem cell transplantation with a geno-identical donor: an easy clinical prognostic score to identify patients who benefit most from allogeneic haemopoietic stem cell transplantation

In 1402 patients allografted in Europe during the period 1990-2000 with an HLA-identical sibling in first remission (CR1), the median interval from CR1 to allotransplant (96 days) was a major prognostic factor, patients transplanted earlier having a worse outcome. We studied in depth the 414 fully evaluable patients transplanted less than 96 days after achieving CR1; in these patients, only three factors predicted for the outcome by multivariate analysis: patient age, CR1 achievement with one or more induction courses and the recipient/donor sex combination. These three factors overcame the information from cytogenetics and source of stem cells. Three prognostic groups could be identified in relation to the outcome, using a prognostic score affecting 1 to each poor risk factor (total from 0 to 3): Group 1 (good prognosis) includes patients <35 years old, achieving CR1 with one induction course and to be transplanted with any other sex combination than female to male (score 0); group 2 (intermediate) with one adverse factor (score 1); and group 3 (bad prognosis) with two or three adverse criteria (scores 2 and 3). In these three groups, the 3-year leukaemia-free survival was 56+/-5%, 48+/-4% and 29+/-4% and the overall survival was 65+/-5, 53+/-4 and 29+/-5%, respectively. Therefore, adult patients with ALL and a score of 0 or 1 are good candidates for an early transplant if they have an identical sibling donor. Patient age, response to induction and the sex of the HLA-identical family donor (if existing) are the strongest easy predictors of the outcome for an early transplant in an adult patient with ALL. No additional information is mandatory.

Higher doses of CD34+ peripheral blood stem cells are associated with increased mortality from chronic graft-versus-host disease after allogeneic HLA-identical sibling transplantation

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.

Resistance to daunorubicin-induced apoptosis is not completely reversed in CML blast cells by STI571

The leukemogenic property of BCR-ABL in chronic myeloid leukemia (CML) is critically dependent on its protein tyrosine kinase activity. STI571 inhibits the BCR-ABL kinase activity, the growth and the viability of BCR-ABL expressing cells. In this study, we report the apoptotic effect of STI571 in combination with daunorubicin (DNR) on peripheral blood mononuclear cells from 11 CML patients and four BCR-ABL-positive cell lines: AR230, LAMA84, K562 and KCL22. Primary blast cells were identified by flow cytometry on the basis of their low CD45 expression. Nucleus fragmentation, exposure of phosphatidylserines and decrease in mitochondrial membrane potential were measured using acridine orange, FITC-annexin V and DiOC6(3), respectively, to evaluate apoptosis. On cell lines, the effect of DNR was negligible, whereas STI571 induced 10 to 35% of apoptosis in 18 h. STI571 sensitized AR230, LAMA84 and K562 cells to DNR when apoptosis was measured at the mitochondrial and membrane but not the nuclear levels. On CML blast cells, phosphatidyl serine exposure was significantly induced by both DNR and STI571 and was higher when these drugs were used in combination (P < 0.0003). However, the effects of this drug combination were only additive and no sensitization of blast cells to DNR by STI571 was observed. Interestingly, sensitization was evidenced in CML but not normal lymphocytes. These results suggest that other mechanisms additional to Bcr-Abl tyrosine kinase activity could be responsible for DNR resistance, and further investigations are needed to understand its origin.

Results of a phase II trial of a combination of oral cytarabine ocfosfate (YNK01) and interferon alpha-2b for the treatment of chronic myelogenous leukemia patients in chronic phase

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.

Nitric oxide induces the apoptosis of human BCR-ABL-positive myeloid leukemia cells: evidence for the chelation of intracellular iron

Anti-leukemia activity of human macrophages involves the generation of nitric oxide (NO) derivatives. However, leukemic transformation may involve mechanisms that rescue cells from NO-mediated apoptosis. In the present work, we analyzed the effects of exogenous NO on the proliferation of BCR-ABL(+) chronic myelogenous leukemia (CML) cells. As normal leukocytes, the proliferation of leukemia cells was inhibited by SNAP (S-nitroso-N-acetyl-penicillamine), GEA (Oxatriazolium amino-chloride), and SIN-1 (Morpholino-sydnonimine), whereas SNP (sodium nitroprusside) had no effect on leukemia cell growth. SIN-1 induced higher anti-proliferation activity in BCR-ABL(+) cells, compared to normal hemopoietic cells. Inhibition of leukemia cell proliferation correlated with increased apoptosis and DEVDase activity. The simultaneous addition of exogenous iron reversed NO-mediated inhibition of cell growth, caspase activation and apoptosis in all BCR-ABL(+) cells tested. The quantification of intracellular iron levels in leukemia cells indicated that NO induced an early, dose-dependent decrease in ferric iron levels. Accordingly, elevation of intracellular iron protected leukemia cells from NO-mediated apoptosis. Together, the present work reveals the presence of an iron-dependant mechanism for leukemia cell rescue from NO-induced growth inhibition and apoptosis.

Follow-up of complete cytogenetic remission in patients with chronic myeloid leukemia after cessation of interferon alfa

PURPOSE

A small proportion of patients with chronic myeloid leukemia (CML) achieve a complete cytogenetic response (CCR), defined as the disappearance of Philadelphia (Ph) chromosome-positive metaphases, after treatment with interferon alfa (IFN). In this population of patients, the question of whether treatment should then be withdrawn is not yet resolved.

PATIENTS AND METHODS

In the present study, we followed 15 patients who stopped IFN after achieving CCR. In nine patients IFN was stopped in view of adverse reactions (n = 8) or patient's choice (n = 1). For the remaining six patients, the treatment was stopped because no BCR/ABL rearrangement could be detected by reverse transcriptase polymerase chain reaction (RT-PCR) in four successive analyses using peripheral-blood samples.

RESULTS

Loss of CCR and survival were not statistically different (P =.48; P =.7) for the 15 patients who stopped IFN compared with 41 other CCR patients who continued IFN therapy in our institution. The median follow-up after discontinuation of IFN treatment was 36 months (range, 6 to 108 months). Seven patients (47%) (females, or CCR > 24 months and RT-PCR negative before IFN cessation; P <.0001) did not relapse. Eight other patients (53%) relapsed (lost CCR) within 3 to 33 months of treatment discontinuation. One of them relapsed in major cytogenetic remission (MCR) and was still in MCR 87 months after stopping therapy without any treatment.

CONCLUSION

It is possible to stop IFN treatment at least in some patients with CML who achieve a prolonged period of CCR. This study also illustrates the hypothesis that persistence of low numbers of Ph-positive cells does not necessarily imply hematologic relapse.

Prior treatment with alpha interferon does not adversely affect the outcome of allogeneic transplantation for chronic myeloid leukaemia

The timing of transplantation in chronic myeloid leukaemia is still debated and previous treatment with interferon (IFN) alpha has been reported to be deleterious. We have analysed the outcome of 438 allogeneic transplants performed between 1984 and 1995 and reported to the Société Française de Greffe de Moelle (SFGM) registry. One hundred and two patients (group I) received IFN for more than 6 weeks (median = 9 months) before transplant. Their outcome was compared with 336 other patients (group II) not pretreated with IFN. There were no significant differences between the groups for engraftment and chronic graft-versus-host disease (GVHD) incidence. However, other significant differences included the incidence of acute GVHD > or = 2 at 3 months which was higher in group I (65 +/- 10%) than in group II (38 +/- 5%; P = 0.01). Moreover, disease-free survival (DFS) and overall survival (OS) at 5 years were significantly shorter for group I than for group II (33 +/- 10% vs. 41 +/- 6%; P = 0.005)(95% CI) and (41 +/- 10% vs. 55 +/- 6%; P = 0.002)(95% CI) respectively. After adjustment for patient and transplant covariables in a multivariate analysis, prior IFN was not found to adversely affect transplant outcome.

Chronic myeloid leukemia and interferon-alpha: a study of complete cytogenetic responders

Achieving a complete cytogenetic response (CCgR) is a major target in the treatment of chronic myeloid leukemia (CML) with interferon-alpha (IFN-alpha), but CCgRs are rare. The mean CCgR rate is 13%, in a range of 5% to 33%. A collaborative study of 9 European Union countries has led to the collection of data on 317 patients who were first seen between 1983 and 1997 and achieved CCgRs with IFN-alpha alone or in combination with hydroxyurea. The median time to first CCgR was 19 months (95% CI, 17-21; range, 3-84 months). At last contact, 212 patients were still alive and in continuous CCgR; 105 patients had lost CCgR, but 53% of them were still alive and in chronic phase. IFN-alpha treatment was discontinued permanently in 23 cases for response loss, in 36 cases for chronic toxicity (15 are still in unmaintained continuous CCgR), and in 8 cases because it was believed that treatment was no longer necessary (7 of these 8 patients are still in unmaintained continuous CCgR). The 10-year survival rate from first CCgR is 72% (95% CI, 62%-82%) and is related to the risk profile. High-risk patients lost CCgR more frequently and more rapidly and none survived more than 10 years. Low-risk patients survived much longer (10-year survival probability 89% for Sokal low risk and 81% for Euro low risk). These data point out that a substantial long-term survival in CCgRs is restricted mainly to low-risk and possibly intermediate-risk patients and occurs significantly less often in high-risk patients.

[Interphase FISH analysis of frozen or fixed tissues for the detection of t(11;14) (q13;q32) in mantle cell lymphoma]

Cytogenetic analyses have revealed that mantle cell lymphomas (MCL) are closely associated with the t(11;14)(q13;q32). This translocation juxtaposes the immunoglobulin heavy chain gene (IGH) sequences with the BCL-1 locus, leading to up-regulation of the CCND1 gene and consequently to an overexpression of cyclin D1 protein. We studied 27 MCL with characteristic morphological and immunological (CD5+, CD10-, CD20+, CD23-) features and 2 controls (reactionnal lymphadenitis) to evaluate the feasibility and the interest of FISH analysis on interphase cells from frozen or paraffin-embedded tissues. Sections (CC) and touch preparations (EC) of frozen tissues and sections of paraffin-embedded tissues (CF) were successfully hybridized with the Vysis LSI IgH/CCND1 dual color dual fusion translocation probe. The touch preparations presented a lower cellularity than sections, therefore allowing an easier analysis. Hybridization spots intensities were found stronger in CC and EC than in CF. The percentages of t(11;14) positive cells were similar in CC, EC and CF from a same patient. The percentage of non hybridized cells, analogous in CC and EC, was higher in CF. However, the CF were directly analysed on microscope without the need of any numerical picture treatment. The t(11;14) was detected in all the cases (27/27) and positive cells percentages were always higher than the probe cut-off (5%). The FISH analysis on interphase cells appears a performing and rapid technique to detect t(11;14) in MCL on both frozen and paraffin-embedded tissue, thus extending its practical and diagnostic use.

A randomized prospective multicentre trial of cefpirome versus piperacillin-tazobactam in febrile neutropenia

Fever is frequently the only clinical sign of infection in patients with chemo-induced neutropenia. In this setting, empirical administration of broad spectrum antibiotics must be rapid. The aim of this work was to compare, for the first time, cefpirome (CPO) and piperacillin-tazobactam (PT) in a large randomized trial. Two hundred-eight febrile neutropenic episodes (FNE) (> or = 38.5 degrees C and ANC < or = 0.5 giga/l) were treated by randomization, as first line therapy, using either CPO 2 g x 2/day (105 cases) or PT 4 g x 3/day (103 cases), alone (CPO: 15/PT: 15), or plus aminoglycoside (165 cases, CPO: 82/PT: 83) or quinolone (CPO: 2/PT: 2). There were 131 men and 77 women aged between 17 and 83 years (median: 49) who received chemotherapy (n = 160) or allogeneic (n = 10) or autologous (n = 38) stem cell transplantations. Underlying diseases were: acute leukemia (n = 131), lymphoma (n = 33), myeloma (n = 16), solid tumor (n = 8), myeloproliferative disorder (n = 9), chronic lymphoid leukemia (n = 5), aplastic anemia (n = 3), myelodysplasia (n = 3). Distribution of age, neutropenia duration (median: 17 days), underlying disease, and protocol therapy duration (median: 11 days) was comparable in both arms. A microbiologically documented infection (MDI) was evidenced in 57 cases (27%). Bacteria were isolated from blood cultures in 54 cases (Gram positive: 32 cases). Their in vitro susceptibility rates to CPO and PT were not different. Two days after antibiotics initiation, clinical (fever disappearance) and microbiological (culture negativation) success rates (SR) were 62% for CPO versus 61% for PT and 50% versus 55% respectively in case of MDI (p = 0.89). Two deaths and 77 failures were registered. At the end of protocol, SR (no antibiotic change/absence of superinfection) was 59% with CPO versus 50% with PT (p = 0.27) and 53% versus 40% respectively in the 151 cases with neutropenia > or = 10 days (p = 0.17). The occurrence of side effects was similar in both arms. In our hands, the efficacy of CPO and PT was comparable for treating FNE.

Role of iron in tumor cell protection from the pro-apoptotic effect of nitric oxide

F2The host defense against tumor cells is in part based upon the production of nitric oxide (NO) by activated macrophages. However, carcinogenesis may involve mechanisms that protect tumor cells from NO-mediated apoptosis. In the present study, we have assessed the effects of exogenous NO on the proliferation and survival of human liver (AKN-1), lung (A549), skin (HaCat), and pancreatic (Capan-2) tumor cell lines, compared with normal skin-derived epithelial cell cultures. Except to the HaCat cell line, all of the other human epithelioid cells were sensitive to the antiproliferation effect of S-nitroso-N-acetyl-penicillamine or Deta NONOate, whereas tumor cells had low if any response to sodium nitroprusside. Growth inhibition with exogenous NO correlated with increased apoptosis, but was not mediated by cyclic GMP, peroxynitrite generation, or poly(ADP-ribose) polymerase modulation, all of which involved in NO-mediated growth inhibition of normal skin-derived epithelial cell cultures. The simultaneous addition of iron-containing compounds protected tumor cells from NO-mediated growth inhibition and apoptosis. Intracellular iron quantification indicated that, as deferoxamine, exogenous NO significantly decreased intracellular ferric iron levels in tumor cells. Together, the current study reveals that intracellular iron elevation rescues tumor cells from NO-mediated iron depletion and subsequent growth inhibition and apoptosis.

[Molecular mechanisms controlling the cell cycle: fundamental aspects and implications for oncology]

INTRODUCTION

Comprehension of cell cycle regulation mechanisms has progressed very quickly these past few years and regulators of the cell cycle have gained widespread importance in cancer. This review first summarizes major advances in the understanding of the control of cell cycle mechanisms. Examples of how this control is altered in tumoral cells are then described.

CURRENT KNOWLEDGE AND KEY POINTS

The typical mammalian cell cycle consists of four distinct phases occurring in a well-defined order, each of which should be completed successfully before the next begins. Progression of eukaryotic cells through major cell cycle transitions is mediated by sequential assembly and activation of a family of serine-threonine protein kinases, the cyclin dependent kinases (CDK). The timing of their activation is determined by their post-translational modifications (phosphorylations/dephosphorylations), and by the association of a protein called cyclin, which is the regulatory subunit of the kinase complex. The cyclin family is divided into two main classes. The 'G1 cyclins' include cyclins C, D1-3, and E, and their accumulation is rate-limiting for progression from the G1 to S phase. The 'mitotic or G2 cyclins', which include cyclin A and cyclin B, are involved in the control of G2/M transition and mitosis. The cyclins bind to and activate the CDK, which leads to phosphorylation (and then inhibition) of the tumor suppressor protein, pRb. pRb controls commitment to progress from the G1 to S phase, at least in part by repressing the activity of the E2F transcription factors known to promote cell proliferation. Both the D-type cyclins and their partner kinases CDK4/6 have proto-oncogenic properties, and their activity is carefully regulated at multiple levels including negative control by two families of CDK inhibitors. While members of the INK4 family (p16INK4A, p15INK4B, p18INK4C, p19INK4D) interact specifically with CDK4 and CDK6, the CIP/KIP inhibitors p21CIP1/WAF1, p27KIP1 and p57KIP2 inhibit a broader spectrum of CDK. The interplay between p16INK4A, cyclin D/CDK, and pRb/E2F together constitute a functional unit collectively known as the 'pRb pathway'. Each of the major components of this mechanism may become deregulated in cancer, and accumulating evidence points to the 'pRb pathway' as a candidate obligatory target in multistep oncogenesis of possibly all human tumor types.

FUTURE PROSPECTS AND PROJECTS

Major advances in the understanding of cell cycle regulation mechanisms provided a better knowledge of the molecular interactions involved in human cancer. This progress has led to the promotion of new therapeutic agents presently in clinical trials or under development. Moreover, the components of the cell cycle are probably involved in other non-cancerous diseases and their role must be defined.

Outcome of adult patients with acute myeloid leukemia who failed to achieve complete remission after one course of induction chemotherapy: a report from the BGMT Study Group

Between 50 and 75% of adult patients with de novo acute myeloid leukemia achieve complete remission (CR) but 25 to 40% of them require more than one course of induction chemotherapy to achieve CR. In order to investigate the impact of this situation on the overall outcome of patients we conducted a retrospective analysis of 130 patients, resistant to a single induction course from among three consecutive protocols, using the same induction regimen employed by the BGMT study group. This group of patients has a particularly poor prognosis with relapse and survival rates of 70% and 14% respectively at 5 years. For these patients, being in CR after two induction courses appears to be a major prognostic factor for outcome, since the 5-year Kaplan-Meier survival probability is significantly better (29%, range 17-46) than of those patients with resistant disease (5%, range 2-13). However, results are worse than when complete remission is obtained after a single course. Thus, post remission treatment should have a powerful anti-leukemic effect in preventing relapse. Allogeneic bone marrow transplantation is a preferential strategy in this setting but to be effective this should be performed as early as possible. Furthermore, these results indicate that allogeneic bone marrow transplantation from an alternative donor should be considered in the absence of HLA identical sibling.

Expression of interferon-α (IFN-α) receptor 2c at diagnosis is associated with cytogenetic response in IFN-α–treated chronic myeloid leukemia

For the management of chronic myeloid leukemia (CML), prediction or early determination of the response to interferon-alpha (IFN-α) treatment is important for identifying nonresponder patients to whom alternative therapy may be proposed. In this study, the levels of expression of both BCR-ABL and subunit 2c of IFN-α receptor (IFN-αR2c) genes were analyzed at diagnosis in 74 patients with chronic phase CML treated with an IFN-α monotherapy. By using blood samples, real-time quantitative polymerase chain reaction was performed to quantify BCR-ABL, IFN-αR2c, and G6PDH mRNA as external control. The results were compared with hematologic and cytogenetic responses to IFN-α. A wide variation in the BCR-ABL/G6PDH ratio was observed at diagnosis (median, 6.68%; range, 0.18%-41.31%), but no significant association with response to IFN-α was observed. In contrast, the variation of IFN-αR2c/G6PDH ratio at diagnosis was significantly associated with the achievement of major cytogenetic response (MCR; 34% or lower Ph+metaphases). Median values of IFN-αR2c/G6PDH ratio for patients achieving MCR and for those who did not achieve it were 110.75% (range, 9.47%-612.30%) and 64.42% (range, 5.96%-425.40%), respectively (P = .037). In addition, this novel molecular factor, combined with the achievement of complete hematologic response at 3 months, makes it possible to predict MCR achievement with high probability by Kaplan-Meier analysis (91% ± 17% at 24 months; P = .0001).

Primary Digestive Richter's Syndrome

The clinical and morphologic transformation of 3 to 5% of chronic lymphocytic leukemia (CLL) to diffuse large-cell lymphoma (DLCL) is commonly referred to as Richter's syndrome. Richter's syndrome occurs mostly in lymph nodes and may represent a second neoplasm or a transformation from the same clonal population. Clinical features in six patients with digestive Richter's syndrome were recorded. Paired samples of CLL and DLCL were investigated by immunohistological analysis (n = 6) and by polymerase chain reaction (PCR) for immunoglobulin heavy-chain gene rearrangement (n = 4). Histological examination revealed the involvement of the gastrointestinal tract by DLCL of B-cell phenotype (n = 6). The same monoclonal rearrangement between CLL and DLCL was demonstrated by PCR and sequencing analyses in two patients. The monoclonal rearrangement was different between CLL and DLCL in only one case. Median survival was 22 months for five patients receiving chemotherapy, suggesting that digestive Richter's syndrome has a better prognosis than nodal Richter's syndrome. Indeed, appropriate surgical resection combined with chemotherapy led to partial or complete remission in four patients.

Allogeneic transplantation for patients with advanced acute leukemia: a single center retrospective study of 92 patients

Allogeneic transplantation is a well recognized treatment strategy of leukemia. However, its use in advanced leukemia patients is a subject of some debate especially when donors are not HLA-identical siblings because of the toxicity and cost of the procedure. We reviewed retrospectively the outcome of patients (pts) who received allogeneic transplantation for advanced acute leukemia in our center between 09/86 and 11/97. Thirty-six pts (study group) who lacked a matched sibling donor received partially matched related donor (n=14: PMRD group) or matched unrelated donor transplantation (n=22: MUD group). Fifteen pts had AML and 21 ALL. Seventeen pts (47%) were in CR>1, 13 pts (36%) had refractory disease and six pts (17.7%) were in untreated relapse. The outcome was compared to that of 56 patients (AML: 45.5 %, ALL: 55.5 %, CR>1: 49.9 %, refractory disease: 37.5 %, untreated relapse 19.6 %) who received allogeneic transplantation from a matched sibling donor (control group). Various conditioning regimens and GVHD prophylaxis were used. The actuarial incidence of grade II to IV acute GVHD was significantly higher in the study group (57%) than in the control group (34%) (p=0.047). The actuarial risk of relapse at three years was 21% +/- 22% in the study group versus 65% +/- 16% in the control group (p= 0.04). The actuarial probability of transplant-related mortality at 3 years is 64 +/- 16% for the study group and 25 +/- 11% for the control group (p=0.001). The leading cause of death in the study group was infection (30%) followed by acute GVHD and relapse. Relapse was the major cause of death in the control group (54%), followed by infection, interstitial pneumonia, veno-occlusive disease and GVHD. The OS and probability of leukemia-free survival at 3 years were 28 % +/- 15% (95% CI) and 27% +/- 15% (95% CI) in the study group. The overall survival and probability of LFS at 3 years were respectively 28 +/- 12% (95% CI) and 23 +/- 12% (95% CI) in the control group (p = 0.08 and p=0.11 respectively). In multivariate analysis, transplant-related mortality was higher in the study group (p=0.04) and lower if both donor and recipient were seronegative for CMV (p=0.007). OS was significantly higher for seronegative couples (p=0.0001), and when CR was achieved before BMT (p=0.0022). These results suggest that all efforts in this field should be directed on lowering the transplant related mortality for non geno-identical transplants and the relapse rate in geno-identical transplants.

A comparison of toxicity following two different doses of cyclophosphamide for mobilization of peripheral blood progenitor cells in 116 multiple myeloma patients

High-dose cyclophosphamide (HDC) has been shown to be an effective regimen for collecting PBPC in multiple myeloma (MM) patients, but the optimal dose to be used remains controversial. Two historical cohorts of MM patients who received G- or GM-CSF and HDC at the dose of either 7 g/m(2) (HDC7, n = 74) or 4 g/m (HDC4, n = 42) were compared. As patients in the HDC4 group were more likely to have received G-CSF than GM-CSF (P < 10(-3)) and fewer previous alkylating agents (P = 0.004), multivariate logistic regression analysis was performed. In the HDC4 group, patients had a shorter median duration of neutropenia (P < 10(-4)), fewer RBC (P < 10(-3)) and platelet transfusions (P < 10(-3)) with fewer patients with platelets <20 x 10(9)/l (P = 0.004). Moreover, fewer febrile episodes (P < 10(-3)) and less need of intravenous antibiotics (P < 10(-3)) were found in the HDC4 group. No statistical difference was observed with regard to CD34(+) cell collection efficiency. Thus, the use of HDC at the dose of 4 g/m(2) for the collection of PBPC in MM patients decreases hematological and extrahematological toxicity with an equivalent CD34(+) cell collection efficiency.

Noninvasive ventilation in immunosuppressed patients with pulmonary infiltrates, fever, and acute respiratory failure

BACKGROUND

Avoiding intubation is a major goal in the management of respiratory failure, particularly in immunosuppressed patients. Nevertheless, there are only limited data on the efficacy of noninvasive ventilation in these high-risk patients.

METHODS

We conducted a prospective, randomized trial of intermittent noninvasive ventilation, as compared with standard treatment with supplemental oxygen and no ventilatory support, in 52 immunosuppressed patients with pulmonary infiltrates, fever, and an early stage of hypoxemic acute respiratory failure. Periods of noninvasive ventilation delivered through a face mask were alternated every three hours with periods of spontaneous breathing with supplemental oxygen. The ventilation periods lasted at least 45 minutes. Decisions to intubate were made according to standard, predetermined criteria.

RESULTS

The base-line characteristics of the two groups were similar; each group of 26 patients included 15 patients with hematologic cancer and neutropenia. Fewer patients in the noninvasive-ventilation group than in the standard-treatment group required endotracheal intubation (12 vs. 20, P=0.03), had serious complications (13 vs. 21, P=0.02), died in the intensive care unit (10 vs. 18, P=0.03), or died in the hospital (13 vs. 21, P=0.02).

CONCLUSIONS

In selected immunosuppressed patients with pneumonitis and acute respiratory failure, early initiation of noninvasive ventilation is associated with significant reductions in the rates of endotracheal intubation and serious complications and an improved likelihood of survival to hospital discharge.

Long-term outcome after allogeneic hematopoietic stem cell transplantation for advanced stage acute myeloblastic leukemia: a retrospective study of 379 patients reported to the Société Française de Greffe de Moelle (SFGM)

To assess the place of allogeneic hematopoietic stem cell transplantation (HSCT) in the advanced stage of acute myeloid leukemia (AML), we retrospectively analyzed 379 consecutive patients who underwent allogeneic HSCT for advanced AML. The median follow-up of the entire cohort was 7.5 years. Sixty-nine patients (18%) were transplanted with primary resistant disease. Three hundred and ten (82%) were relapsed patients, 94 (30%) of whom were in untreated relapse, 67 (22%) in refractory relapse and 149 (48%) in 2nd or 3rd complete remission at time of transplantation. The 5-year probabilities of overall survival (OS), disease-free survival (DFS), and transplant-related mortality (TRM) were 22 +/- 4%, 20 +/- 4%, 45 +/- 6%, respectively. In multivariate analysis, we demonstrated the favorable impact on OS, DFS and TRM of two factors over which we have no control (age <15 years, complete remission achievement) and three factors over which we have some control (female donor, acute and chronic graft-versus-host disease). The results of this study suggest that the graft-versus-leukemia effect is important in advanced AML and that new HSCT modalities are needed for some patients with this indication.

Adult acute lymphocytic leukemia study testing chemotherapy and autologous and allogeneic transplantation. A follow-up report of the French protocol LALA 87

The French protocol LALA 87 was designed to compare three different postinduction strategies in adult acute lymphocytic leukemia (ALL): chemotherapy, autologous transplantation, and allogeneic transplantation. This trial demonstrated a significant superiority of allogeneic bone marrow transplantation (BMT) in high-risk ALL patients. Similarly, there was a trend in favor of autologous BMT over chemotherapy in those same patients. Allogeneic BMT was not superior to autologous BMT or chemotherapy in less aggressive leukemia (standard-risk ALL). Further improvements are warranted in the treatment of adult ALL. The authors' current ongoing study is stratifying patients to allocate them to regimens with risk-adapted treatment intensity.

Lineage switch from acute myeloid leukemia to acute lymphoblastic leukemia: report of an adult case and review of the literature

Lineage switch from AML to ALL is an extremely rare phenomenon, and we report the case of an adult diagnosed with AML at 46 years of age who relapsed with ALL. At initial diagnosis, blast cell morphology and immunophenotyping were consistent with the diagnosis of M4-AML. Complete remission was achieved, and the patient underwent autologous BMT. At relapse, six months after ABMT, blast cells were different from those seen at initial diagnosis, for morphology (L2-ALL), cytochemistry, and immunophenotyping. The karyotype was normal at both diagnosis and relapse. No evidence of bcr-abl fusion genes was found by RT-PCR. Monoclonal IgH and TCR gamma gene rearrangement were evidenced by PCR analysis at relapse but not on blast cells at AML diagnosis.

Second early allogeneic stem cell transplantations for graft failure in acute leukaemia, chronic myeloid leukaemia and aplastic anaemia. French Society of Bone Marrow Transplantation

In this retrospective multicentre study, we analysed the results of 82 consecutive second early allogeneic transplants for primary (n = 28) or secondary ([n = 54) graft failures performed between 1985 and 1997 in patients with acute leukaemia (n = 33), aplastic anaemia (n = 29) or chronic myeloid leukaemia (n = 20). HLA-matched siblings were used in 64 cases. The same donors were used for both transplants in 56 cases and the first transplant was T-cell depleted in 30 cases. The median age at transplant was 25 years and the median intertransplant time interval was 2 months. Estimates of the 3-year overall survival and day 100 transplant-related mortality were 30% and 53% respectively. A recipient age < 34 years at transplant, an intertransplant time interval > or = 80 d and a positive recipient cytomegalovirus serology were predictors of a better outcome. The use of cyclosporin A (CsA) after second transplant had a dramatic impact on outcome, the best results being observed with CsA alone. The day 40 probability of neutrophil recovery was 73%. The use of peripheral blood progenitor cells (PBPCs) was associated with a higher and faster neutrophil recovery. Other factors associated with neutrophil recovery were an intertransplant time interval > or = 80 d and a positive recipient cytomegalovirus serology. Therefore, second early allogeneic transplantation for graft failure is an effective treatment, especially if patients can receive CsA for graft-versus-host disease prevention and are retransplanted more than 80 d from first transplant.

Noninvasive continuous positive airway pressure in neutropenic patients with acute respiratory failure requiring intensive care unit admission

OBJECTIVE

To evaluate the tolerance and the efficacy of noninvasive continuous positive airway pressure (CPAP) in severe acute respiratory failure occurring in intensive care unit (ICU) neutropenic patients with hematologic malignancies, and to establish predictive variables of efficacy of this method.

DESIGN

Prospective study over a 5-yr period.

SETTING

Hematologic and medical intensive care unit of a teaching hospital.

METHODS

Among 129 neutropenic patients admitted to the ICU, 64 patients presented with febrile acute hypoxemic normocapnic respiratory failure (PaO2/FIO2 ratio <200) and were enrolled. In addition to standard therapy, patients received CPAP with a facial mask. The initial settings of the CPAP were 6 cm H2O positive end-expiratory pressure and FIO2 0.8 (80%). Physiologic measurements were performed at the end of 45 mins of ventilation with first adjustments. CPAP was used with a sequential mode (45 mins/3 hrs). CPAP was efficient if intubation was avoided.

RESULTS

The setting of CPAP, after adjustments, was as follows: positive end-expiratory pressure 7 +/- 1 cm H2O and FIO2 0.7 +/- 0.1 (70% +/- 10%). For the 64 patients, CPAP was administered for a total of 6 +/- 2 hrs during the first 24 hrs. The mean duration of CPAP was 7 +/- 3 days. A reduction in respiratory rate to less than 25 breaths/min was achieved in 53% of patients. PaO2/FIO2 ratio increased from 128 +/- 32 to 218 +/- 28. CPAP was successful in avoiding endotracheal intubation in 16/64 patients. A total of 16 responders and four nonresponders survived. Hepatic failure was a criterion indicating the failure of CPAP: 1/16 vs. 26/48 (p = .001). In multivariate analysis, two variables were predictive of failure of CPAP: Simplified Acute Physiology Score II (58 +/- 14 vs. 41 +/- 11) and a hepatic failure at the entry into the study.

CONCLUSION

CPAP was efficient in 25% of cases. All the responders survived. This noninvasive method was used as a way to avoid mechanical ventilation, which is well correlated with a poor prognosis in neutropenic ICU patients. Further controlled studies are needed to confirm the efficacy of noninvasive CPAP and to evaluate the most appropriate selection of immunocompromised patients.

Impact of colony-stimulating factor therapy on clinical outcome and frequency rate of nosocomial infections in intensive care unit neutropenic patients

OBJECTIVES

To determine whether the use of recombinant human granulocyte colony-stimulating factor (G-CSF, filgrastim) reduces the mortality rate and the frequency rate of nosocomial infections in neutropenic patients requiring intensive care unit (ICU) admission.

DESIGN

Retrospective consecutive case series analysis.

SETTING

Medical ICU of a teaching hospital.

PATIENTS

We compared two groups of patients, according to whether or not they received G-CSF. In the ICU, 28 leukopenic patients received filgrastim (5 microg of body weight per day intravenously). In all these patients, G-CSF was continued until recovery from leukopenia, defined as a leukocyte count >1,000/mm3. A total of 33 ICU leukopenic patients did not receive G-CSF. End points included leukocyte count, bone marrow recovery, frequency of ICU nosocomial infections (pneumonia, urinary tract, and catheter-related infections), and mortality rate.

MEASUREMENTS AND MAIN RESULTS

There were no differences in number of patients who recovered from leukopenia or in whom blood leukocyte count increased. Nosocomial infections occurred in the same percentage in both groups. The percentage of patients who died was identical in both groups. The percentage of patients with and without filgrastim therapy who recovered from leukopenia but died, was 86% and 78%, respectively.

CONCLUSION

In the ICU, clinical outcome of neutropenic patients was not changed by G-CSF therapy. It is possible that G-CSF therapy may not be helpful in improving the ICU clinical outcome of neutropenic patients. Additional controlled studies designed to address this question are warranted.

Selection and characterization of BCR-ABL positive cell lines with differential sensitivity to the tyrosine kinase inhibitor STI571: diverse mechanisms of resistance

Targeting the tyrosine kinase activity of Bcr-Abl with STI571 is an attractive therapeutic strategy in chronic myelogenous leukemia (CML). A few CML cell lines and primary progenitors are, however, resistant to this compound. We investigated the mechanism of this resistance in clones of the murine BaF/3 cells transfected with BCR-ABL and in 4 human cell lines from which sensitive (s) and resistant (r) clones were generated by various methods. Although the resistant cells were able to survive in the presence of STI571, their proliferation was approximately 30% lower than that of their sensitive counterparts in the absence of the compound. The concentration of STI571 needed for a 50% reduction in viable cells after a 3-day exposure was on average 10 times higher in the resistant (2-3 micromol/L) than in the sensitive (0.2-0.25 micromol/L) clones. The mechanism of resistance to STI571 varied among the cell lines. Thus, in Baf/BCR-ABL-r, LAMA84-r, and AR230-r, there was up-regulation of the Bcr-Abl protein associated with amplification of the BCR-ABL gene. In K562-r, there was no Bcr-Abl overexpression, but the IC(50) for the inhibition of Bcr-Abl autophosphorylation was increased in the resistant clones. Sequencing of the Abl kinase domain revealed no mutations. The multidrug resistance P-glycoprotein (Pgp) was overexpressed in LAMA84-r, indicating that at least 2 mechanisms of resistance operate in this cell line. KCL22-r showed neither Bcr-Abl up-regulation nor a higher threshold for tyrosine kinase inhibition by STI571. We conclude that BCR-ABL-positive cells can evade the inhibitory effect of STI571 by different mechanisms, such as Bcr-Abl overexpression, reduced intake mediated by Pgp, and, possibly, acquisition of compensatory mutations in genes other than BCR-ABL.