Protein tyrosine kinase 2: a novel therapeutic target to overcome acquired EGFR-TKI resistance in non-small cell lung cancer

Xuexia Tong,Ryosuke Tanino,Rong Sun,Yukari Tsubata,Mayumi Takechi,Takeshi Isobe,Tamio Okimoto

doi:10.1186/s12931-019-1244-2

Abstract

BackgroundProtein tyrosine kinase 2 (PTK2) expression has been reported in various types of human epithelial cancers including lung cancer; however, the role of PTK2 in epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) has not been elucidated. We previously reported that pemetrexed-resistant NSCLC cell line PC-9/PEM also acquired EGFR-TKI resistance with constitutive Akt activation, but we could not find a therapeutic target.MethodsCell viability in EGFR-mutant NSCLC cell lines was measured by the WST-8 assay. Phosphorylation antibody array assay for receptor tyrosine kinases was performed in PC-9 and PC-9/PEM cell lines. We evaluated the efficacy of EGFR and PTK2 co-inhibition in EGFR-TKI-resistant NSCLC in vitro. Oral defactinib and osimertinib were administered in mice bearing subcutaneous xenografts to evaluate the efficacy of the treatment combination in vivo. Both the PTK2 phosphorylation and the treatment combination efficacy were evaluated in erlotinib-resistant EGFR-mutant NSCLC cell lines.ResultsPTK2 was hyperphosphorylated in PC-9/PEM. Defactinib (PTK2 inhibitor) and PD173074 (FGFR inhibitor) inhibited PTK2 phosphorylation. Combination of PTK2 inhibitor and EGFR-TKI inhibited Akt and induced apoptosis in PC-9/PEM. The combination treatment showed improved in vivo therapeutic efficacy compared to the single-agent treatments. Furthermore, erlotinib-resistant NSCLC cell lines showed PTK2 hyperphosphorylation. PTK2 inhibition in the PTK2 hyperphosphorylated erlotinib-resistant cell lines also recovered EGFR-TKI sensitivity.ConclusionPTK2 hyperphosphorylation occurs in various EGFR-TKI-resistant NSCLCs. Combination of PTK2 inhibitor and EGFR-TKI (defactinib and osimertinib) recovered EGFR-TKI sensitivity in the EGFR-TKI-resistant NSCLC. Our study result suggests that this combination therapy may be a viable option to overcome EGFR-TKI resistance in NSCLC.

Highlights

Lung cancer is the leading cause of cancer-related mortality worldwide with non-small cell lung cancer (NSCLC) being the largest subgroup
PC-9/PEM have hyperphosphorylated Protein tyrosine kinase 2 (PTK2), which activates Akt signaling To confirm whether PC-9/PEM is genetically altered for epidermal growth factor receptor (EGFR)-Tyrosine kinase inhibitor (TKI) resistance, we conducted direct sequencing of EGFR
We evaluated the MET copy number as changes in MET confer acquired EGFR-TKI resistance in nonsmall cell lung cancer (NSCLC)

Summary

Introduction

Lung cancer is the leading cause of cancer-related mortality worldwide with non-small cell lung cancer (NSCLC) being the largest subgroup. Platinum-based chemotherapy is used as second-line therapy, whereas pemetrexed or docetaxel is used as third-line therapy in NSCLC patients in the event of disease progression after first-line EGFR-TKI therapy. They showed a median PFS of 6.4 months and a median overall survival of 19.2 months as salvage chemotherapies [6, 7]. Protein tyrosine kinase 2 (PTK2) expression has been reported in various types of human epithelial cancers including lung cancer; the role of PTK2 in epidermal growth factor receptor (EGFR)-mutant nonsmall cell lung cancer (NSCLC) has not been elucidated. We previously reported that pemetrexed-resistant NSCLC cell line PC-9/PEM acquired EGFR-TKI resistance with constitutive Akt activation, but we could not find a therapeutic target

Objectives

Methods

Results

Conclusion