A novel strategy for ABL tyrosine kinase inhibitor resistant ph-chromosome positive leukemia cells

Abstract

Although ABL tyrosine kinase inhibitors (TKIs) such as imatinib have demonstrated the potency against Philadelphia chromosome (Ph)-positive leukemia patients, resistance to ABL TKI can develop in chronic myeloid leukemia (CML) patients. We hypothesized that ABL TKI resistance may often happen due to additional somatic mutations in the oncogene. We established several TKI-resistant in vitro cell line models. We also investigated model to evaluate the next-generation sequencing (NGS) panel. We established ABL TKI resistant cell lines (K562 imatinib-R, K562 nilotinib-R, K562 dasatinib-R, K562 ponatinib-R, Ba/F3 T315I and Ba/F3 ponatinib-R) in this study. BCR-ABL expression levels were not increased. We could not detect the BCR-ABL point mutation. However, the exon 4 deletion in the BCR-ABL gene was found in K562 ponatinib-R cells. In contrast, compound mutations in BCR-ABL were found in Ba/F3 ponatinib-R cells. We next evaluated the NGS panel (GeneRead DNAseq Targeted Panels V2) to investigate the mutation. We found that several somatic mutations in TET2, FLT3, RB1, TP53, SETBP1, ASXL1, and BCORL1 in parental K562 cells. We also found that additional somatic mutations in K562 imatinib-R (IDH1 and KRAS), K562 dasatinib-R (IDH1) and K562 ponatinib-R (SF3A1). We could not detect additional mutation in K562 nilotinib-R cells. Combined treatment of ABL TKI resistant K562 with imatinib or dasatinib and MEK inhibitor or IDH1 inhibitor caused more cytotoxicity. Because aberrant activation of PI3K signaling pathway and deregulation of HDAC activity may be a cause of malignant disease in humans, we examined the PI3K and HDAC inhibitor in ABL TKI resistant cells. The inhibitor of class I PI3K as well as class I and II HDAC enzymes, CUDC-907 exhibits cell growth inhibition. Our study indicated that leukemia cells have acquired resistance through somatic mutation or exon 4 deletion in the BCR-ABL gene, suggested that individual based investigations may be important to evaluate the ABL TKI resistance. We also provide the promising clinical relevance as a candidate drug for treatment of ABL TKI resistant leukemia patients.