Cumulative mechanism of several major imatinib-resistant mutations in Abl kinase
Marc Hoemberger, Warintra Pitsawong, Dorothee Kern
Abstract
Significance One obstacle for the prolonged success of the wonder drug imatinib in leukemia has been the emergence of resistance mutations within the Abl kinase domain. Here, we elucidate the molecular mechanism for resistance of three major mutations in patients treated with imatinib. Unpredictably, the single-site resistance mutations act via a cumulative effect of an only modest decrease in drug affinity, combined with an increase in enzyme activity and altered substrate affinity/cooperativity. Strikingly, this combination indeed leads to at least an order-of-magnitude higher IC 50 values for imatinib, but only under cellular ATP concentrations. Our findings settle a longstanding controversy, and concepts found here are likely to play a role in drug resistance in other targets.