Molecular response of CML patients treated with interferon-α monitored by quantitative Southern blot analysis

We analysed 459 samples from 206 chronic myeloid leukaemia (CML) patients at diagnosis and during or after treatment with interferon-α (IFN-α) by quantitative Southern blot analysis for BCR rearrangement. In a minority (2%) of Ph-positive patients, no BCR rearrangement was detectable due to breakpoints outside the major breakpoint cluster region (M-bcr) or possibly due to M-bcr deletions. Results from 235 samples were compared with the proportion of Ph-positive metaphases found in contemporaneous bone marrow specimens analysed by conventional cytogenetics. The rank correlation between both methods was 0.82 ( P <0.001). The proportion of CML cells in samples determined by Southern blot analysis (BCR ratio) was significantly different between cytogenetically-defined minor, partial, and complete response groups ( P <0.001). Empirically-derived cut-off points in the BCR ratio were introduced in order to define molecular response groups for comparison to standard cytogenetic response groups: a BCR ratio of 0% was defined as complete molecular response and ratios of 1–24%, 25–50%, and >50% were defined as partial, minor, and no molecular response, respectively. Using these cut-off points the concordance between both methods was 67% ( P <0.0001), a major cytogenetic response could be predicted or excluded in more than 90% of cases ( P <0.0001). Our findings demonstrated that quantitative Southern blot was as sensitive as cytogenetics and as peripheral blood samples are suitable for this technique it should be considered as the method of choice for routine monitoring IFN-α therapy in CML patients.     

Survival implications of molecular heterogeneity in variant Philadelphia-positive chronic myeloid leukaemia

The BCR-ABL fusion in chronic myeloid leukaemia (CML) is generated by the Philadelphia (Ph) translocation t(9;22) or, in 10% of patients, variants thereof (vPh). Deletion encompassing the reciprocal product (ABL-BCR) from the derivative chromosome 9 [der(9)] occurs in 15% of all patients, but with greater frequency in vPh patients. Reports of physical separation of ABL-BCR in non-deleted patients, as well as evolution from classical to variant Ph, introduce further heterogeneity to the vPh subgroup and raise the possibility that such translocations may herald disease progression. Survival analyses, however, have thus far yielded contradictory results. We assessed the frequency of der(9) deletions, ABL-BCR abrogation, cytogenetic evolution and cryptic rearrangement in a large cohort of 54 patients with vPh CML. Deletions encompassing ABL-BCR were detected in 37% of patients, consistent with a model in which a greater number of chromosome breaks increases the risk of genomic loss. The components of ABL-BCR were physically separated in a further 52% of patients while fused in the remaining 11%. Evolution from classical to vPh was demonstrated in three patients. The difference in survival, as indicated by Kaplan-Meier analysis, was marked between classical and vPh patients (105 vs 60 months respectively; P = 0.0002). Importantly, this difference disappeared when patients with deletions were removed from the analysis. Our study showed that, despite the existence of several levels of genomic heterogeneity in variant Ph-positive CML, der(9) deletion status is the key prognostic factor.     

Cytogenetic response to autografting in chronic myelogenous leukemia correlates with the amount of BCR-ABL positive cells in the graft

OBJECTIVE: An objective of autologous transplant in chronic myelogenous leukemia is to reinfuse the patient stem cells with the lowest amount of leukemic progenitors. We analyzed if the cytogenetic response after autografting was correlated with the amount of BCR ABL-positive cells present in the graft. MATERIALS AND METHODS: By BCR-ABL mRNA quantification, we studied the serial pheresis product from 40 Philadelphia (Ph)-positive patients who received ICE/mini-ICE mobilization therapy and underwent autologous stem cell transplant in our unit. Therefore, we correlated the residual disease in the graft reinfused to the patients with the cytogenetic response after autografting, taking into consideration only those responses that lasted 12 months or more. RESULTS: Thirty-two patients had a graft with 0-35% Ph-metaphases and 19 had a graft with BCR-ABL/ABL ratio < or =0.01. After a median of 27 months (range, 12-50) from transplant, 18 patients achieved complete or major cytogenetic response lasting at least 12 months and 14 of them (78%) had a graft with BCR-ABL/ABL ratio < or =0.01 (range, 0.0003-0.01). Twenty-two patients had short-lived response or showed to be >35% Ph-positive in the marrow after transplant, but only 5 of them (23%) had a graft with BCR-ABL/ABL ratio < or =0.01 (range, 0.001-0.01). Therefore, we found a strong association between BCR-ABL/ABL ratio < or =0.01 in the reinfused progenitor collections and the achievement of complete or major cytogenetic remission after autografting (chi2 test, p = 0.0001). Patients reinfused with low contaminated grafts also showed a longer duration of the response (logrank test, P = 0.0009). Eleven patients were reinfused with the lowest-contaminated stem cell collections, according to the BCR-ABL/ABL ratio. None of these patients had prolonged neutropenia or thrombocytopenia following stem cell reinfusion and 9 of them had long-lasting complete or major cytogenetic response after transplant. CONCLUSION: This study demonstrates that the amount of BCR-ABL positive cells present in the graft is an important predictive factor for the achievement and the duration of cytogenetic response after autografting.     

甲磺酸伊马替尼治疗120例慢性髓性白血病的临床研究

目的观察甲磺酸伊马替尼（IM）治疗Ph染色体阳性和（或）BCR／ABL基因阳性的慢性髓性白血病（CML）的疗效和安全性。方法对90例Ph染色体阳性和（或）BCR／ABL基因阳性CML慢性期（CP）患者,持续口服IM,400mg／d;30例CML疾病进展期（加速期／急变期）患者,持续口服IM,600mg／d。服药期间定期复查血常规、骨髓细胞学、染色体和（或）BCR／ABL基因等指标,并随访观察。结果（1）CML—CP患者总的完全血液学缓解率（CHR）、完全细胞遗传学缓解率（CCyR）和完全分子遗传学疗效（CMR）分别为73．3％（66／90）、66．7％（60／90）、54．4％（49／90）;治疗前是否接受过干扰素治疗对CHR、CCyR和CMR均无明显影响;服药前病程≤6个月的CMR优于〉6个月者。初次达到CHR的时间与首次达CCyR的时间、首次达CCyR的时间与BCR／ABL首次转阴时间之间均存在相关性,而初次达CHR的时间与BCR／ABL首次转阴时间则无明显相关性。（2）进展期CML患者的CHR、CCyR、CMR分别为43．3％（13／30）、25．9％（7／27）、25．0％（7／28）,总病死率为30．0％（9／30）。（3）年龄≤25岁患者的病死率高于〉25岁者,差异有统计学意义（P〈0．05）。（4）白细胞减少达Ⅲ级者有19例（16．0％）,发生于治疗后5～20周。血小板减少达Ⅲ级者有21例（18．0％）,发生于治疗后3～16周。主要的非血液系统毒性为双下肢水肿、骨痛和皮疹等,但均程度轻微。结论IM对初治CML及经干扰素治疗失败的CML有较高的CHR及CCyR且起效迅速,对CML—CP疗效显著优于进展期;不良反应程度轻微,患者易于耐受。     

Chronic myelogenous leukaemia with p185(BCR/ABL) expression: characteristics and clinical significance

We investigated the significance of p185BCR/ABL expression in patients with chronic myelogenous leukaemia (CML) in relation to disease features, therapy and outcome. Results of Western blot analysis for 1384 patients referred with a diagnosis of CML to our institution from 1989 to 1997 were reviewed. Clinical characteristics, results of cytogenetic analysis and RT-PCR for BCR rearrangement were analysed. Five patients with Ph-positive CML expressing the p185BCR/ABL hybrid protein were identified. By RT-PCR, bone marrow specimens of these patients were confirmed to have an e1a2 junction. The median age at diagnosis of these patients was 55 years (range 43-76). All had elevated white cell counts at diagnosis (median 50 x 109/l, range 11.7-163 x 109/l). Four patients had monocytosis (range 10-16%) with a low neutrophil/monocyte ratio in the peripheral blood (range 3.4-5.7). Patients presented with various stages of the disease (two in chronic-phase CP, two in accelerated-phase AP, and one in blastic-phase BP). The clinical course and therapy of the patients varied, with one patient receiving hydroxyurea only, three patients receiving hydroxyurea followed by interferon-alpha based regimens and bone marrow transplantation. The patient presenting in BP was treated with combination chemotherapy. The clinical outcome of the patients was also varied with one patient alive and in complete remission (with complete cytogenetic remission after transplant) and four patients dead after progression to more advanced stages. We conclude that patients with Ph-positive p185BCR/ABL CML frequently present with monocytosis and a low neutrophil/monocyte ratio in the peripheral blood, aiding the speculation that the presence of the p185BCR/ABL hybrid protein may contribute to a phenotype intermediate between CML and CMML. Of interest, the only other specific clinical feature identified was the absence of splenomegaly in four of five patients. There was no definite association with transformation to lymphoid blast phase.     

Elevated platelet count features the variant type of BCR/ABL junction in chronic myelogenous leukaemia

A variant form of BCR/ABL junction was identified in a patient with chronic myelogenous leukaemia (CML). The BCR/ABL fusion mRNA of this patient showed in-frame junction between BCR exon c3 and ABL exon 2. Although the diagnosis of CML was made, the patient showed clinical features of essential thrombocythaemia (ET) rather than that of typical CML. Treatment with interferon-α showed no cytogenetic response. The c3-a2 type of BCR/ABL junction seems to be associated with elevated platelet count and thus could form a novel clinical entity different from typical CML.     

Characterization of genomic BCR-ABL breakpoints in chronic myeloid leukaemia by PCR

In order to understand better the mechanism of translocation between the BCR and ABL genes in CML, we have exploited a'bubble PCR'technique to clone genomic breakpoints. BCR-ABL junction fragments were successfully amplified and sequenced in 14/32 (43%) patients tested. Breakpoints were dispersed throughout the major breakpoint cluster region without any clustering or hot spots. In three cases Alu sequences were found at or near the breakpoint on the ABL side of the translocation but no other obvious sequence homologies were found either in BCR or ABL. The translocation event was characterized further in three other patients by amplifying the reciprocal ABL-BCR junction on the 9q+ chromosome and also normal ABL around breakpoints. In two of these patients a few nucleotides of BCR and ABL were either duplicated or deleted on translocation, suggesting that staggered cuts had been made in the DNA strands prior to recombination. In the third patient 50 bp of ABL was deleted and 159 bp of M-BCR including exon b3 was duplicated, indicating either that the single-stranded cuts may span a larger distance than previously thought or that another mechanism, perhaps involving gene conversion, may be involved in this instance.     

Result of high-dose imatinib mesylate in patients with Philadelphia chromosome-positive chronic myeloid leukemia after failure of interferon-alpha

Imatinib at 400 mg daily is effective in chronic-phase chronic myeloid leukemia (CML) after interferon failure, although only a few patients achieve a molecular remission. We investigated whether higher doses of imatinib may be more effective. Thirty-six patients with chronic-phase CML after failure on interferon-alpha were treated with 400 mg imatinib twice daily. Median time from diagnosis was 25 months (range, 10-135 months); 4 patients (11%) had clonal evolution. All 11 patients with active disease achieved complete hematologic response. Excluding patients with fewer than 35% Ph-positive metaphases before the start of therapy, 19 (90%) of 21 evaluable patients achieved a major cytogenetic response. Of 27 evaluable patients, 24 (89%) achieved a complete cytogenetic response. Quantitative polymerase chain reaction was performed in bone marrow every 3 months. Of 32 evaluable patients, 18 (56%) showed BCR-ABL/ABL percentage ratios lower than 0.045%, including 13 (41%) with undetectable levels. With a median follow-up of 15 months, all patients were alive in chronic phase. Toxicities were similar to those reported with standard dose; 71% of patients continue to receive 600 mg or more of imatinib daily. In conclusion, high-dose imatinib induces complete cytogenetic responses in most patients with chronic-phase CML after interferon failure. This is accompanied by a high rate of molecular remission.     

High frequency of point mutations clustered within the adenosine triphosphate-binding region of BCR/ABL in patients with chronic myeloid leukemia or Ph-positive acute lymphoblastic leukemia who develop imatinib (STI571) resistance

Point mutations were found in the adenosine triphosphate (ATP) binding region of BCR/ABL in 12 of 18 patients with chronic myeloid leukemia (CML) or Ph-positive acute lymphoblastic leukemia (Ph(+) ALL) and imatinib resistance (defined as loss of established hematologic response), but they were found in only 1 of 10 patients with CML with imatinib refractoriness (failure to achieve cytogenetic response). In 10 of 10 patients for whom samples were available, the mutation was not detected before the initiation of imatinib therapy. Three mutations (T315I, Y253H, and F317L present in 3, 1, and 1 patients, respectively) have a predicted role in abrogating imatinib binding to BCR/ABL, whereas 3 other mutations (E255K, G250E, and M351T, present in 4, 2, and 2 patients, respectively) do not. Thus we confirm a high frequency of mutations clustered within the ATP-binding region of BCR/ABL in resistant patients. Screening may allow intervention before relapse by identifying emerging mutations with defined impacts on imatinib binding. Certain mutations may respond to higher doses of imatinib, whereas other mutations may mandate switching to another therapeutic strategy.     

Methylation of the ABL1 promoter in chronic myelogenous leukemia: lack of prognostic significance.

The BCR-ABL chromosomal translocation is a central event in the pathogenesis of chronic myelogenous leukemia (CML). One of the ABL1 promoters (Pa) and the coding region of the gene are usually translocated intact to the BCR locus, but the translocated promoter appears to be silent in most cases. Recently, hypermethylation of Pa was demonstrated in CML and was proposed to mark advanced stages of the disease. To study this issue, we measured Pa methylation in CML using Southern blot analysis. Of 110 evaluable samples, 23 (21%) had no methylation, 17 (15%) had minimal (<15%) methylation, 12 (11%) had moderate methylation (15% to 25%), and 58 (53%) had high levels of methylation (>25%) at the ABL1 locus. High methylation was more frequent in advanced cases of CML. Among the 76 evaluable patients in early chronic phase (ECP), a major cytogenetic response with interferon-based therapy was observed in 14 of 34 patients with high methylation compared with 19 of 42 among the others (41% v 45%; P value not significant). At a median follow-up of 7 years, there was no significant difference in survival by ABL1 methylation category. Among patients who achieved a major cytogenetic response, low levels of methylation were associated with a trend towards improved survival, but this trend did not reach statistical significance. Thus, Pa methylation in CML is associated with disease progression but does not appear to predict for survival or response to interferon-based therapy.