Discovery and Protein Modeling Studies of Novel Compound Mutations Causing Resistance to Multiple Tyrosine Kinase Inhibitors in Chronic Myeloid Leukemia.

Zafar Iqbal,Janhangir Iqbal,Afia Akram,Nawaf Alanazi,Zeenat Mirza,Muhammad Sabar,Aamer Aleem,Khalid Aljarrah,Ijaz Shah,Muhammad Khalid,Mudassar Iqbal,Ahmad Khalid,Abid Jameel,Muhammad Absar,Sajjad Karim,Mahmood Rasool,Amer Mahmood,Tanveer Akhtar

doi:10.31557/apjcp.2020.21.12.3517

Abstract

Objective:BCR-ABL fusion oncogene is the hallmark of chronic myeloid leukemia (CML), causing genomic instability which leads to accumulation of mutations in BCR-ABL as well as other genes. BCR-ABL mutations are the cause of tyrosine kinase inhibitors (TKIs) resistance in CML. Recently, compound BCR-ABL mutations have been reported to resist all FDA approved TKIs. Therefore, finding novel compound BCR-ABL mutations can help and clinically manage CML. Therefore, our objective was to find out novel drug-resistant compound BCR-ABL mutations in CML and carry out their protein modelling studies. Methodology:Peripheral blood samples were collected from ten imatinib resistant CML patients receiving nilotinib treatment. BCR-ABL transcript mutations were investigated by employing capillary sequencing. Patient follow-up was carried out using European LeukemiaNet guidelines. Protein modeling studies were carried out for new compound mutations using PyMol to see the effects of mutations at structural level. Results:A novel compound mutation (K245N mutation along with G250W mutation) and previously known T351I utation was detected in two of the nilotinib resistance CML patients respectively while in the rest of 8 nilotinib responders, no resistant mutations were detected. Protein modelling studies indicated changes in BCR-ABL mutant protein which may have negatively impacted its binding with nilotinib leading to drug resistance. Conclusion:We report a novel nilotinib resistant BCR-ABL compound mutation (K245N along with G250W mutation) which impacts structural modification in BCR-ABL mutant protein leading to drug resistance. As compound mutations pose a new threat by causing resistance to all FDA approved tyrosine kinase inhibitors in BCR-ABL+ leukemias, our study opens a new direction for in vitro characterization of novel BCR-ABL compound mutations and their resistant to second generation and third generation TKIs.

Highlights

Chronic myeloid leukemia, a myeloproliferative disorder, is reported in roughly 15% of newly diagnosedAsian Pacific Journal of Cancer Prevention, Vol 21 3517Zafar Iqbal et al leukemia in adults (Izzo et al, 2019)
breakpoint cluster region (BCR)-Abelson murine leukemia (ABL) fusion oncogene is the hallmark of chronic myeloid leukemia (CML), causing genomic instability which leads to accumulation of mutations in BCR-ABL as well as other genes
We report a novel nilotinib resistant BCR-ABL compound mutation (K245N along with G250W mutation) which impacts structural modification in BCR-ABL mutant protein leading to drug resistance

Summary

Introduction

A myeloproliferative disorder, is reported in roughly 15% of newly diagnosedAsian Pacific Journal of Cancer Prevention, Vol 21 3517Zafar Iqbal et al leukemia in adults (Izzo et al, 2019). BCR-ABL, an oncoprotein central to the pathogenesis of CML, is fusion product of Abelson murine leukemia (ABL) and breakpoint cluster region (BCR) genes located on chromosome 9 and 22 respectively (Rowley, 1973). Imatinib mesylate (Gleevec® USA; Glivec-Europe/ Australia; formerly STI571) is a BCR-ABL TKI which has intensely improved the treatment outcomes in chronic-phase CML patients (CML-CP). A simple mechanism of resistance to TKI treatment is owing to mutations in the kinase domain of BCR-ABL. Such mutations have been reported in 40% to 60% of imatinibresistant patients (Jabbour et al, 2006). More than 90 distinct mutations in BCR-ABL have been recognized, each conferring variable degrees of resistance to imatinib treatment (Soverini et al, 2010)

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