Characteristics of BCR-ABL kinase domain mutations in chronic myeloid leukemia from India: not just missense mutations but insertions and deletions are also associated with TKI resistance.

We document the characteristics of BCR-ABL kinase domain mutations (KDM) in the largest study from India comprising of 385 patients and demonstrate that more than half (51.9%) of these patients have detectable abnormalities in the KD both in adult and in pediatric chronic myelogenous leukemia (CML). These comprise singly occurring missense mutations (25.5%), polyclonal/compound point mutations (4.9%), and insertions/deletions (29.6%). Missense mutations were most commonly seen in the imatinib-binding region followed by the P-loop. The commonest mutation in our dataset was T315I. Other common missense mutations were Y253H, M244V, and F317L. A high prevalence of BCR-ABL exon7 deletion (p.R362fs*) was also seen (25.5% of the entire cohort), whereas the 35bpintron-derived insertion/truncation mutation detected in 12 patients. In the pediatric age group, 58.8% of patients harbored missense mutations, polyclonal/compound mutations as well as insertions and deletions. We detected 11 novel mutations (seven missense mutations and four insertions/deletions).