Analysis of ABL kinase domain mutations as a probable cause of imatinib resistance in Chronic Myeloid Leukemia patients of Kashmir

Abstract

The phenomenon of imatinib resistance in Chronic Myeloid Leukemia (CML) can be mediated by “BCR-ABL fusion transcript dependent” and “BCR-ABL fusion transcript independent” pathways. The main means of “BCR-ABL fusion transcript dependent” pathway, responsible for 40–90% of such cases, is the occurrence of Kinase Domain (KD) mutations. The aim of this study was to evaluate the commonly occurring KD mutations like G250, Y253, E255, T315, F317, M351, F359, and H396 for imatinib resistance in CML patients from Kashmir (North India).A total of 42 confirmed cases of CML were subjected to reverse transcriptase polymerase chain reaction (RT-PCR). Kinase Domain PCR-amplicons, derived from the amplification of respective patient's cDNA following reverse transcription of BCR-ABL fusion mRNA, were subjected to nucleotide sequence analysis by ‘Genetic Analyser’ sequencing platform ABI 3500.CML patients included 18 males (42.85%) and 24 females (57.14%) aged from 7 to 75 years, of which 19 cases (45.23%) belonged to age group of ≤45 years and the rest 23 cases (54.76%) were >45 years of age. Sequence analysis was carried out to all the 42 patients at baseline and only on suspected resistant cases at designated follow-ups of 3 months, 6 months and one year.The overall incidence of imatinib resistance in our patients was very low as there were only 8 patients (19.04%), of which 6 cases (14.28%) reported with ‘No cytogenetic response’ (NCR) at 3 months and 1 each having lost earlier attained ‘Complete cytogenetic response’ (CCR) and molecular response at 6 months. These 8 patients were enlisted as suspected imatinib resistant cases and were subjected to imatinib resistance mutation analysis (IRMA) by sequencing at successive designated follow-up periods as applicable.No imatinib resistance mutations were detected in the patients either at baseline or across all the follow-up durations implying other causes for imatinib resistance in CML patients of our region.