Graduate Institute of Oncology, College of Medicine, National Taiwan University, Taipei, Republic of China; Centers of Genomic and Precision Medicine, National Taiwan University, Taipei, Republic of China; National Taiwan University Cancer Center, College of Medicine, National Taiwan University, Taipei, Republic of China.
Graduate Institute of Oncology, College of Medicine, National Taiwan University, Taipei, Republic of China; Centers of Genomic and Precision Medicine, National Taiwan University, Taipei, Republic of China; Department of Oncology, National Taiwan University Hospital, Taipei, Republic of China.
J Thorac Oncol. 2020 Jan;15(1):50-61. doi: 10.1016/j.jtho.2019.09.006. Epub 2019 Sep 23.
Osimertinib is the current recommended treatment for EGFR T790M-positive NSCLC after EGFR tyrosine kinase inhibitor therapy. However, resistance to osimertinib therapy is inevitably acquired after a period of effective treatment. We had a patient with EGFR L858R/T790M-positive NSCLC who initially responded to osimertinib therapy but eventually experienced development of resistance. Plasma cell-free DNA analysis revealed the occurrence of exon 16-skipping HER2, which may have resulted in the erb-b2 receptor tyrosine kinase 2 gene (HER2) splice variant HER2D16. HER2D16 has never been reported in lung cancer, and HER2D16-driven signaling is known to be regulated by Src kinase in breast cancer. We investigated the role of HER2D16 as an osimertinib-resistant mechanism.
We constructed and established H1975 cells stably expressing HER2D16. The dimeric formation of HER2D16 was tested by using nonreducing polyacrylamide gel electrophoresis. The effects of the study drugs on signaling transduction were examined by using Western blot. Synergistic effect was assessed by using the Chou-Talalay method.
We found that HER2D16 can form a homodimer in NSCLC cells. HER2D16-expressing H1975 cells were resistant to osimertinib treatment. We also found that mutant EGFR and HER2D16 cooperated to activate downstream signaling for osimertinib resistance. In addition, cotreatment with osimertinib and an Src kinase inhibitor failed to reverse resistance, indicating that HER2D16-driven signaling in NSCLC did not occur through a canonical pathway. Finally, we revealed that the combination of osimertinib with the pan-HER small-molecule inhibitor afatinib could synergistically repress cell growth and signaling in H1975-HER2D16 cells.
HER2D16 can contribute to osimertinib resistance through an Src-independent pathway. HER2D16 should be included in the molecular diagnosis panel for lung cancer.
奥希替尼是 EGFR 酪氨酸激酶抑制剂治疗后 EGFR T790M 阳性 NSCLC 的推荐治疗方法。然而，奥希替尼治疗的耐药性在有效治疗一段时间后不可避免地会出现。我们有一位 EGFR L858R/T790M 阳性 NSCLC 患者，最初对奥希替尼治疗有反应，但最终出现耐药。血浆无细胞 DNA 分析显示存在外显子 16 跳跃 HER2，这可能导致 erb-b2 受体酪氨酸激酶 2 基因（HER2）剪接变异体 HER2D16。HER2D16 在肺癌中从未有过报道，已知 HER2D16 驱动的信号受乳腺癌中的Src 激酶调节。我们研究了 HER2D16 作为奥希替尼耐药机制的作用。
我们构建并建立了稳定表达 HER2D16 的 H1975 细胞。通过非还原聚丙烯酰胺凝胶电泳测试 HER2D16 的二聚化形成。通过 Western blot 检测研究药物对信号转导的影响。通过 Chou-Talalay 方法评估协同作用。
我们发现 HER2D16 可在 NSCLC 细胞中形成同源二聚体。表达 HER2D16 的 H1975 细胞对奥希替尼治疗耐药。我们还发现突变型 EGFR 和 HER2D16 合作激活奥希替尼耐药的下游信号。此外，奥希替尼和 Src 激酶抑制剂的联合治疗未能逆转耐药性，表明 NSCLC 中 HER2D16 驱动的信号不通过经典途径发生。最后，我们揭示了奥希替尼与泛 HER 小分子抑制剂阿法替尼的联合使用可以协同抑制 H1975-HER2D16 细胞的生长和信号。
HER2D16 可通过非 Src 依赖途径促进奥希替尼耐药。HER2D16 应纳入肺癌的分子诊断面板。
