Chronic Myeloid Leukemia |
From Hematology Department, Hôpital E. Herriot, 69437 Lyon(FEN, EB, QL, MM); Laboratory for Hematology and Cytogenetics, Centre Hospitalier Lyon Sud, 69495 Pierre-Bénite(SH); 3Hematology Department, CHRU 59037, Lille (SC); Laboratory for Hematology, Hôpital Henri Mondor, 94000 Créteil (DB, MT); Oncology, Cellular Therapy and Hematology Department, Hôpital J. Bernard, 86021 Poitiers (FG); Hematology Department, Hôpital de lArchet, 06202 Nice (LL); Hematology Department, Hôpital Civil, 67100 Strasbourg (FM); Hematology Department, Hôpital Avicenne, 93000 Bobigny (J-JK); Laboratory for Hematology, Hôpital Pellegrin, 33076 Bordeaux (FXM); Laboratory for Medical Genetics, Hôpital Jeanne de Flandre, CHRU 59037 and U817 Inserm Lille (CR-L); Laboratory for Hematology, Hôpital Calmette, CHRU 59037 Lille and U817 Inserm Lille, France (CP)
Correspondence: Franck E. Nicolini, MD PhD, Hematology department, E Pavilion, Hôpital Edouard Herriot, 5, place dArsonval, 69437 Lyon, Cédex 03, France. E-mail: franck-emmanuel.nicolini{at}chu-lyon.fr
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Key words: CML, imatinib mesylate, BCR-ABL mutation, T315I.
Imatinib mesylate revolutionized the management of chronic myelogenous leukemia and represents the new standard of care for this disease.1 Most patients retain a residual disease and increasing numbers of resistant patients accumulate. The onset of ABL point mutations is the most frequent identified mechanism responsible for resistance.2 Up to 30 different mutations have been described, mostly in advanced phase,3 and confer different levels of clinical resistance. In this setting, trials with second generation tyrosine kinase inhibitors (TKIs)4,5 provide encouraging results, however neither in vitro nor clinical activity was demonstrated when a T315I was identified.6,7 In this multicentric retrospective study, we analysed 27 BCR-ABLT315I mutated CML patients exhibiting either clinical, cytological, cytogenetic resistance or molecular progression.
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2 logs) of CML in a previously IM-responsive patient was observed. The mutation was detected on blood samples analyzed according to the methods described by Branford et al.8 by direct sequencing (on both strands) encompassing the entire ABL kinase and ATP-loop domains [residues 242–487].
Survival and time-to-progression curves were established from IM initiation to death or progression, according to Kaplan-Meier method. Progression was defined as any loss of previous response, and transition to a more advanced disease phase.
Calculations were performed using S-plus program (Insightful, Seattle, WA, USA).
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View this table: [in a new window] [Download PPT slide] |
Table 1. Main characteristics of the 27 CML patients harboring a BCR-ABLT315I mutation. F stands for female, M for male. CP stands for chronic phase, Acc P for accelerated phase, MBC for myeloid blast crisis, LBC for lymphoid blast crisis. H, I, and L stand for high, intermediate and low Sokal scores respectively. CHR stands for complete hematologic remission, PCyR for partial cytogenetic remission, CCyR for complete cytogenetic remission. NA: data not available. This table has been generated by Dr F-E. Nicolini from the raw database.
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Figure 1. (A) Time to progression of CML since IM initiation, in patients harboring a BCR-ABLT315I mutation. Plain line represents all phases of CML, dotted line chronic phase only and dashed line accelerated + blastic phases at onset of T315I mutation. (B) Kaplan-Meier overall survival since initiation of IM in patients harboring a BCR-ABLT315I mutation, broken down by disease phase at onset of T315I mutation. These 2 figures have been generated through a S-plus program by Dr. Q-H. Lê and reformatted to Powerpoint by F-E. Nicolini.
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The onset of BCR-ABLT315I mutations during the treatment of CML with TKIs remains challenging, because this mutation is the most frequently identified in IM–treated patients6, and none of the TKIs clinically available to date4,5,6 retain any activity in vitro. More over, the continuation of these inhibitors might elicit the outgrowth of T315I clones as shown in the past.9,10,11 In 5/6 patients receiving dasatinib, the BCR-ABLT315I mutation was assessed (through direct sequencing method) and absent before the introduction of this TKI, but present after a median of 4 months. The PCR-ASO was retrospectively performed in 2 patients (UPN#16 and 17) and demonstrated that the BCR-ABLT315I mutation was already present at low levels before dasatinib. Two/6 patients remained alive at latest follow-up, as dasatinib was immediately withdrawn when the T315I was identified. Thus, if a BCR-ABLT315I mutation is identified in a CML patient, TKI treatment withdrawal should be the first therapeutic intervention recommended.
Despite low number of patients and the limitations of such an analysis, we were able to show in this study that the onset of BCR-ABLT315I mutations occurs in a category of CML patients with poor initial prognostic features (poor Sokal scores, additional chromosomal abnormalities, poor response to IM), mostly in advanced phases. It is unknown whether the presence of a BCR-ABLT315I mutation is actually responsible for progression or if this mutation simply co-migrates with other general factors of progression such as clonal evolution or additional mutations. The first hypothesis is supported by in vitro studies12 which demonstrate that a BCR-ABL mutation provides the mutated clone with a proliferative advantage over BCR-ABLWT cells and favors disease transformation potency. In our study, it is of note that 3/16 evaluable patients (UPN# 11, 17, 19) had neither chromosomal abnormalities other than the Ph1, nor additional mutation at T315I identification. In addition, previous studies13,14 have failed to detect c-kit and PDGF-R mutations in patients resistant to IM, suggesting that disease progression might be induced solely by BCR-ABL modifications. However, additional genetics abnormalities affecting other not-investigated/unknown BCR-ABL independent mechanisms of IM resistance/progression cannot be excluded. Furthermore, in addition to the disruption of IM binding, it is debatable if a BCR-ABLT315I mutation increases ABL tyrosine kinase activity and enhances progression as suggested by some authors15 though not by others12. The second hypothesis is supported by crystallographic analysis16 showing that the lack of the critical hydrogen bond that disrupts IM binding during T315I residues exchanges is associated with the modification of multiple other protein-drug interactions that could participate to the deregulation of ABL tyrosine kinase activity. Others have shown15 that various intracellular proteins, including STAT-5, might be altered in BCR-ABLT315I+ cells.
In conclusion, despite the obvious limits of such a retrospective study, we show that the BCR-ABLT315I mutation occurs probably in CML patients with poor initial prognostic features, and at high risk of disease progression. Subsequently, serial BCR-ABL mutation assessments throughout the course of the disease is recommended for IM-resistant patients for early detection of the BCR-ABL mutations.
Simple TKI withdrawal might-at least transiently-slow down disease progression and allow a sufficient time-frame for the seek of alternative therapeutic options such as the identification of a suitable donor for allogeneic stem cell transplantation, a suitable option to consider17 or the use of aurora-kinase inhibitors (i. e. MK 0457) that might be active in this setting.18
F-EN and SC designed the study, acquired, analyzed and interpreted the data, F-EN and CR-L wrote the paper. SH, MM participated in the acquisition, analysis and interpretation of data. EB, DB, MT, FG, LL, FX-M, FM, CR-L participated in the acquisition of the data. F-EN and Q-HL performed statistical analysis. CP helped with the analysis of the data and proofread the final manuscript version.
The authors reported no potential conflicts of interest.
Funding: this study was partly funded by grants from "Cancéropôle Lyon Auvergne Rhône-Alpes" 2003 (F-EN, SH), the "Ligue contre le cancer du Rhône" 2005 (to F-EN, SH), and "Association 100 pour Sang La Vie" 2003 (to F-EN, SH).
Received for publication February 11, 2007. Accepted for publication June 27, 2007.
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