Kinase domain mutations of BCR-ABL frequently precede imatinib-based therapy and give rise to relapse in patients with de novo Philadelphia-positive acute lymphoblastic leukemia (Ph+ ALL)

Abstract

Acquired imatinib resistance in advanced Philadelphia-positive acute lymphoblastic leukemia (Ph ؉ ALL) has been associated with mutations in the kinase domain (KD) of BCR-ABL. We examined the prevalence of KD mutations in newly diagnosed and imatinib-naive Ph ؉ ALL patients and assessed their clinical relevance in the setting of uniform frontline therapy with imatinib in combination with chemotherapy. Patients enrolled in the German Multicenter Study Group for Adult Acute Lymphoblastic Leukemia (GMALL) trial ADE10 for newly diagnosed elderly Ph ؉ ALL were retrospectively examined for the presence of BCR-ABL KD mutations by denaturing highperformance liquid chromatography (D-HPLC), cDNA sequencing, and allelespecific polymerase chain reaction (PCR). A KD mutation was detected in a minor subpopulation of leukemic cells in 40% of newly diagnosed and imatinib-naive patients. At relapse, the dominant cell clone harbored an identical mutation in 90% of cases, the overall prevalence of mutations at relapse was 80%. P-loop mutations predominated and were not associ- IntroductionIncorporation of the ABL kinase inhibitor imatinib into frontline treatment of Philadelphia-positive acute lymphoblastic leukemia (Ph ϩ ALL) has significantly improved the antileukemic efficacy of induction therapy. Several cooperative ALL study groups have demonstrated complete remission rates consistently above 90%, irrespective of whether imatinib is used alone or combined with multiagent chemotherapy. [1][2][3][4][5][6][7][8][9] These results are superior to previously reported complete remission (CR) rates of 65% to 90% in younger patients [10][11][12][13] and 40% to 60% in Ph ϩ ALL patients older than 60 to 65 years of age. [14][15][16][17] Although accumulating evidence suggests that imatinib-containing therapeutic regimens may also improve long-term outcome in these patients, 3,[6][7][8]14 relapse remains a predominant cause of treatment failure. 3,[7][8][9] Numerous point mutations in the kinase domain (KD) of BCR-ABL that impair imatinib binding to varying degrees have been identified as a major mechanism of acquired resistance in patients with chronic myeloid leukemia (CML). [18][19][20][21][22][23][24][25] Data on BCR-ABL mutations in patients with Ph ϩ ALL or lymphoid blast crisis of CML are more limited. Two studies of patients with advanced Ph ϩ lymphoid leukemias identified 5 different KD mutations in 14 of the 17 evaluated patients with acquired resistance to imatinib. 26,27 Preponderance of the E255K/V P-loop mutation, which occurred in 6 of 9 patients (67%) following their treatment with imatinib was suggested by one of these reports 26 but not by the other. 27 However, all point mutations arose at positions within the KD that are known to be important for drug binding and to confer significant resistance to imatinib in vitro. [18][19][20] This demonstrated that different mutations within the BCR-ABL KD can be responsible for refractoriness of Ph ϩ lymphoid leukemias to imatinib, and also suggested that KD mutations may be a f...

Impact of minimal residual disease kinetics during imatinib-based treatment on transplantation outcome in Philadelphia chromosome-positive acute lymphoblastic leukemia

“…To date, only limited data on prevalence of BCR-ABL1 tyrosine kinase domain mutations in imatinib-naïve patients with Ph-positive ALL are available. 30,31 Using a more sensitive technique than direct sequencing, the presence of low-level BCR-ABL1 tyrosine kinase domain mutations conferring imatinib resistance has been identified in a substantial proportion of imatinib-naïve patients with Ph-positive ALL with a high degree of concordance between the type of mutation detected at baseline and at relapse. 30 Remarkably, these preexisting mutant clones did not predict a response rate or remission duration and were suppressed for certain time periods by imatinib-based chemotherapy, but they almost gave rise to eventual relapse.…”

Prevalence and dynamics of bcr-abl kinase domain mutations during imatinib treatment differ in patients with newly diagnosed and recurrent bcr-abl positive acute lymphoblastic leukemia

“…2 Results of mutational analyses performed in the latter study have been published previously, 16 but did not include data on the dynamics and absolute levels of bcr-abl mutations during imatinib monotherapy, the central elements of the present communication. The studies were approved by the responsible Institutional Review Boards, and all patients gave informed consent according to the Declaration of Helsinki.…”

“…On the basis of a sensitive denaturing high-performance liquid chromatography (DHPLC) method, we previously demonstrated that TKD mutations are present in approximately 40% of elderly patients with newly diagnosed, imatinib-naïve Ph þ ALL, with a high degree of concordance between the type of mutation detected at baseline and at relapse. 16 Remarkably, the CR rate achieved with imatinib alone did not differ in patients with pre-existing TKD mutations and those in whom only unmutated BCR-ABL was detected, suggesting that bcr-abl mutations have an only limited role during the initial treatment for de novo Ph þ ALL. Moreover, it has not been established to what degree TKD mutations contribute to the primary imatinib resistance commonly observed in patients with Ph þ ALL recurring after chemotherapy.…”

“…16 Direct sequencing of the PCR products encoding the BCR-ABL ATP binding pocket (exons 4 --7) was performed by a commercial laboratory (MWG Biotech, Ebersberg, Germany). For high sensitivity detection of bcr-abl TKD mutations, a semi-automated, high-throughput DHPLC system (WAVE, Transgenomic Ltd, Omaha, NE, USA) was used as described.…”

“…12 --21 Bcr-abl mutations may pre-exist at low levels in a subset of patients with relapsed Ph þ ALL before salvage therapy with imatinib, and they have also been detected with variable frequency in imatinib-naïve patients with newly diagnosed Ph þ ALL. 12,16,19 Although no mutations were detected in 12 patients using standard sequencing or pyrosequencing for the T315I and Y253H mutations, 14 a more sensitive cloning and sequencing approach used by Soverini et al 19 showed the presence of low frequency TKD mutations in all imatinib-naïve patients analyzed. This study identified a broad spectrum of mutations, most of which have not been linked to clinical resistance.…”