BACKGROUND Protein 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. METHODS Cell 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. RESULTS PTK2 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. CONCLUSION PTK2 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.

中文翻译：

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蛋白质酪氨酸激酶2：一种新的治疗靶标，可克服非小细胞肺癌中获得性EGFR-TKI耐药性。

背景技术已经在包括肺癌在内的各种类型的人类上皮癌中报道了蛋白质酪氨酸激酶2（PTK2）的表达。然而，尚未阐明PTK2在表皮生长因子受体（EGFR）突变的非小细胞肺癌（NSCLC）中的作用。我们先前曾报道耐培美曲塞的NSCLC细胞系PC-9 / PEM还通过组成性Akt激活获得了EGFR-TKI耐药性，但我们找不到治疗靶点。方法采用WST-8法检测EGFR突变的NSCLC细胞系中的细胞活力。在PC-9和PC-9 / PEM细胞系中进行了受体酪氨酸激酶的磷酸化抗体阵列分析。我们评估了EGFR和PTK2共抑制在体外对EGFR-TKI耐药的NSCLC的疗效。在携带皮下异种移植物的小鼠中给予口服defactinib和osimertinib以评估体内治疗组合的功效。在耐厄洛替尼的EGFR突变型NSCLC细胞系中评估了PTK2的磷酸化和治疗组合的功效。结果PTK2在PC-9 / PEM中被过度磷酸化。Defactinib（PTK2抑制剂）和PD173074（FGFR抑制剂）抑制PTK2磷酸化。PTK2抑制剂和EGFR-TKI的组合抑制PC-9 / PEM中的Akt并诱导细胞凋亡。与单药治疗相比，联合治疗显示出改善的体内治疗功效。此外，耐厄洛替尼的NSCLC细胞系显示PTK2过度磷酸化。PTK2过度磷酸化的厄洛替尼耐药细胞系中的PTK2抑制作用也恢复了EGFR-TKI敏感性。结论PTK2过度磷酸化发生在各种EGFR-TKI耐药的NSCLC中。PTK2抑制剂和EGFR-TKI（defactinib和osimertinib）的组合可恢复对EGFR-TKI耐药的NSCLC的EGFR-TKI敏感性。我们的研究结果表明，这种联合疗法可能是克服NSCLC中EGFR-TKI耐药性的可行选择。