CAGE, a cancer/testis antigen, was originally isolated from the sera of patients with gastric cancers. Previously, we have shown the role of CAGE in resistance to chemotherapy and target therapy. The aim of this study was to investigate the role of CAGE in osimertinib resistance and determine the prognostic value of CAGE in patients with pulmonary adenocarcinomas. The clinicopathological correlation with CAGE and autophagy flux in patients was examined using immunohistochemistry and in situ hybridization. The possible role of autophagy in osimertinib resistance was analyzed using immune blot, immune fluorescence staining and immunohistochemistry. This study found that immunohistochemical staining (IHC) showed CAGE expression in more than 50% of patients with pulmonary adenocarcinomas (pADCs). CAGE expression was increased in pADCs after the acquisition of EGFR-TKIs resistance. High expression of CAGE was correlated with shorter overall survival and progression free survival in patients with pADCs. Thus, CAGE mediates osimertinib resistance and predicts poor prognosis in patients with pADCs. Osimertinib-resistant non-small cell lung cancer cells (PC-9/OSI) were established and mechanistic studies of CAGE-mediated osimertinib resistance were performed. PC-9/OSI cells showed increased autophagic flux and CAGE expression compared with parental sensitive PC-9 cells. PC-9/OSI cells showed higher tumorigenic, metastatic, and angiogenic potential compared with parental PC-9 cells. CAGE CRISPR-Cas9 cell lines showed decreased autophagic flux, invasion, migration potential, and tumorigenic potential compared with PC-9/OSI cells in vitro and in vivo. CAGE plays a crucial role in the cancer progression by modulating autophagy and can predict the poor prognosis of patients with pulmonary adenocarcinomas. Our findings propose CAGE as a potential therapeutic target for developing anticancer drugs that can overcome osimertinib resistance.
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