BCR-ABL kinase domain mutations in CML patients, experience from a tertiary care center in North India

Chronic Myeloid Leukemia is characterized by the presence of the Philadelphia Chromosome (Ph) which contains the BCR::ABL1 fusion gene that occurs due to a reciprocal translocation between chromosomes 9 and 22. This accounts for up to 15 % of all adult leukemias [1]. Most patients treated with first line tyrosine kinase inhibitor (TKI) imatinib achieve durable response but may undergo relapse at some stage [2]. The most important mechanism that may confer imatinib resistance is point mutation within BCR::ABL kinase domain. Other generation ABL tyrosine kinase inhibitors such as dasatinib, nilotinib, bosutinib and ponatinib help to overcome imatinib resistance [3]. Sensitivity of the patient to each of the above TKIs depends upon the individual candidate mutation present. Thus, it is important to perform mutation analysis for effective therapeutic management of CML patients once they show imatinib resistance. We used direct sequencing to identify the different types of mutations responsible for resistance of imatinib treatment from north India.

In this study, the patient resistance for the imatinib were analyzed for BCR::ABL kinase domain mutation by direct sequencing and the detected mutations along with their percentage prevalence were reported.

329 patients with CML-CP were analyzed for BCR::ABL kinase domain mutation. Total 66 (20.06 %) patients out of 329 had mutation in at least one of the domains of BCR::ABL conferring resistance to different generations of TKI. Mutations in BCR::ABL kinase domain was observed in different domain of BCR::ABL. ATP binding P-Loop (42.42 %), Direct binding site (36.36 %), C-Loop (10.60 %), A-Loop (6.06 %), SH2 contact (3.03 %), SH3 contact (1.51 %).

Total 20.06 % patients (66/329) show mutation in at least one of the structural motifs of BCR-ABL kinase domain, which further confer the resistance to a particular generation of TKI.