Chia-Chi Hsu1, Bin-Chi Liao2, Wei-Yu Liao3, Aleksandra Markovets4, Daniel Stetson4, Kenneth Thress5, James Chih-Hsin Yang6. 1. 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. 2. 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. 3. Department of Internal Medicine, National Taiwan University Hospital, Taipei, Republic of China. 4. AstraZeneca Pharmaceuticals PLC, Oncology Bioscience, Waltham, Massachusetts. 5. TESARO, Translational Strategy and Research, Waltham, Massachusetts. 6. 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. Electronic address: chihyang@ntu.edu.tw.
Abstract
INTRODUCTION: 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. METHODS: 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. RESULTS: 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. CONCLUSION: HER2D16 can contribute to osimertinib resistance through an Src-independent pathway. HER2D16 should be included in the molecular diagnosis panel for lung cancer.
INTRODUCTION: 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. METHODS: 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. RESULTS: 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. CONCLUSION: HER2D16 can contribute to osimertinib resistance through an Src-independent pathway. HER2D16 should be included in the molecular diagnosis panel for lung cancer.
Authors: Harvey W Smith; Lei Yang; Chen Ling; Arlan Walsh; Victor D Martinez; Jonathan Boucher; Dongmei Zuo; Ethan S Sokol; Dean C Pavlick; Garrett M Frampton; Juliann Chmielecki; Laura M Jones; Philippe P Roux; William W Lockwood; William J Muller Journal: Proc Natl Acad Sci U S A Date: 2020-07-29 Impact factor: 11.205