Modelling ponatinib resistance in tyrosine kinase inhibitor-naïve and dasatinib resistant BCR-ABL1+ cell lines.

Liu Lu,Timothy Peter Hughes,Jueqiong Wang,Verity Ann Saunders,Jennifer Anne Mclean,Deborah Lee White,Chung Hoow Kok

doi:10.18632/oncotarget.26187

Abstract

TKI resistance remains a major impediment to successful treatment of CML. In this study, we investigated the emerging modes of ponatinib resistance in TKI-naïve and dasatinib resistant BCR-ABL1+ cell lines. To investigate potential resistance mechanisms, ponatinib resistance was generated in BCR-ABL1+ cell-lines by long-term exposure to increasing concentrations of ponatinib. Two cell lines with prior dasatinib resistance demonstrated BCR-ABL1 kinase domain (KD) mutation(s) upon exposure to ponatinib. In one of these cell lines the T315I mutation had emerged during dasatinib exposure. When further cultured with ponatinib, the T315I mutation level and BCR-ABL1 mRNA expression level were increased. In the other cell line, compound mutations G250E/E255K developed with ponatinib exposure. In contrast, the ponatinib resistant cell lines that had no prior exposure to other TKIs (TKI-naïve) did not develop BCR-ABL1 KD mutations. Rather, both of these cell lines demonstrated Bcr-Abl-independent resistance via Axl overexpression. Axl, a receptor tyrosine kinase, has previously been associated with imatinib and nilotinib resistance. Ponatinib sensitivity was restored following Axl inhibition or shRNA-mediated-knockdown of Axl, suggesting that Axl was the primary driver of resistance and a potential target for therapy in this setting.

Highlights

Since its clinical introduction over a decade ago, imatinib has revolutionized the treatment of chronic phase-chronic myeloid leukaemia (CP-CML)
After long-term ponatinib culture, four ponatinib resistant cell lines were established (Table 1 and Supplementary Figure 1) and all were cross-resistant to imatinib, nilotinib and dasatinib
These results suggested that Bcr-Abl independent mechanisms were likely involved in the development of ponatinib resistance in these two cell lines

Summary

Introduction

Since its clinical introduction over a decade ago, imatinib has revolutionized the treatment of chronic phase-chronic myeloid leukaemia (CP-CML). Approximately 30-40% of patients fail to respond optimally to imatinib [1]. The best-characterized mechanism of secondary imatinib resistance is the development of mutations within the BCR-ABL1 kinase domain (KD). More than 100 mutations have been identified which either prevent or significantly disrupt the binding of imatinib to Bcr-Abl [2]. Second generation tyrosine kinase inhibitors (TKIs) including nilotinib and dasatinib were developed. For many imatinib resistant patients, second generation TKIs are an effective salvage strategy. These TKIs are completely ineffective against the BCR-ABL1 T315I mutation (commonly referred to as the gatekeeper mutation), which accounts for approximately 15-20% of clinically observed BCR-ABL1 mutations [2, 3]

Methods

Results

Conclusion