Allosteric inhibition enhances the efficacy of ABL kinase inhibitors to target unmutated BCR-ABL and BCR-ABL-T315I

Afsar Ali Mian,Oliver Gerhard Ottmann,Martin Ruthardt,Jamal Mahajna,Nili Ruimi,Mamduh Khateb,Susanne Badura,Anna Metodieva,Yousef Najajreh

doi:10.1186/1471-2407-12-411

Abstract

BackgroundChronic myelogenous leukemia (CML) and Philadelphia chromosome-positive (Ph+) acute lymphatic leukemia (Ph + ALL) are caused by the t(9;22), which fuses BCR to ABL resulting in deregulated ABL-tyrosine kinase activity. The constitutively activated BCR/ABL-kinase “escapes” the auto-inhibition mechanisms of c-ABL, such as allosteric inhibition. The ABL-kinase inhibitors (AKIs) Imatinib, Nilotinib or Dasatinib, which target the ATP-binding site, are effective in Ph + leukemia. Another molecular therapy approach targeting BCR/ABL restores allosteric inhibition. Given the fact that all AKIs fail to inhibit BCR/ABL harboring the ‘gatekeeper’ mutation T315I, we investigated the effects of AKIs in combination with the allosteric inhibitor GNF2 in Ph + leukemia.MethodsThe efficacy of this approach on the leukemogenic potential of BCR/ABL was studied in Ba/F3 cells, primary murine bone marrow cells, and untransformed Rat-1 fibroblasts expressing BCR/ABL or BCR/ABL-T315I as well as in patient-derived long-term cultures (PDLTC) from Ph + ALL-patients.ResultsHere, we show that GNF-2 increased the effects of AKIs on unmutated BCR/ABL. Interestingly, the combination of Dasatinib and GNF-2 overcame resistance of BCR/ABL-T315I in all models used in a synergistic manner.ConclusionsOur observations establish a new approach for the molecular targeting of BCR/ABL and its resistant mutants using a combination of AKIs and allosteric inhibitors.

Highlights

Chronic myelogenous leukemia (CML) and Philadelphia chromosome-positive (Ph+) acute lymphatic leukemia (Ph + ALL) are caused by the t(9;22), which fuses breakpoint cluster region (BCR) to ABL resulting in deregulated ABL-tyrosine kinase activity
The allosteric inhibitor GNF-2 improves the response of unmutated BCR/ABL to ABL-kinase inhibitors (AKIs) Unmutated BCR/ABL can be efficiently inhibited by AKIs and by allosteric inhibitors such as GNF-2 or GNF-5 [4,11,12]
To determine whether the allosteric inhibition can improve the response of BCR/ ABL-positive cells to AKIs, we exposed Ba/F3 cells previously rendered factor-independent by the expression of BCR/ABL to Dasatinib and GNF-2 at concentrations of 5 to 100 nM and 0.1 to 0.4 μM, respectively, upon factor withdrawal

Summary

Introduction

Chronic myelogenous leukemia (CML) and Philadelphia chromosome-positive (Ph+) acute lymphatic leukemia (Ph + ALL) are caused by the t(9;22), which fuses BCR to ABL resulting in deregulated ABL-tyrosine kinase activity. The ABL-kinase inhibitors (AKIs) Imatinib, Nilotinib or Dasatinib, which target the ATP-binding site, are effective in Ph + leukemia. Another molecular therapy approach targeting BCR/ABL restores allosteric inhibition. BCR/ABL results in a deregulated and constitutively activated tyrosine kinase, which is responsible for the induction of the phenotype of Ph + leukemia. Selective targeting of BCR/ABL by ABL-kinase inhibitors (AKI) such as Imatinib, Nilotinib or Dasatinib, all competitive ATP-analogues, leads to durable cytogenetic and molecular remissions in the majority of CML patients in the early chronic phase of the disease. T315I is the most clinically relevant mutation because it confers a global resistance against all available molecular therapy approaches [3,4]

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