Caveolin-1 inhibits the proliferation and invasion of lung adenocarcinoma via EGFR degradation.

Lung adenocarcinoma (LUAD) has become the most common pathological pattern of lung cancer in recent decades. Prediction of biological behavior of LUAD is crucial for disease management and treatment options. The objective of this study was to identify significant genes related with prognosis of LUAD, and to investigate the role and biological mechanism of caveolin-1 (CAV1) in LUAD. Bioinformatical analysis was used to identify significant genes related to the prognosis of LUAD based on GEO datasets. Then the mechanisms underlying these critical genes were explored. Enrichment analysis was implemented based on CAV1 related differentially expressed genes subsequently. The expressions of CAV1 and EGFR in LUAD tissues and adjacent tissues were detected by Western blotting, immunohistochemistry and microarray technology. Kaplan-Meier survival analysis and cox regression analysis were performed to verify the correlation between CAV1 expression level and the prognosis of LUAD. The expression of CAV1 in PC-9, H1299 and H1975 cells was inhibited by siRNA transfection. CAV1 overexpression plasmid was constructed and transfected into A549 cells. Cell proliferation was detected by cell Titer-Glo, CCK-8 and colony formation assay. Scratch test was used to compare cell migration ability. Transwell assay was used to compare cell invasion ability. Cell apoptosis and cell cycle were detected by flow cytometry. The effect of CAV1 on EGFR degradation was verified by cycloheximide inhibition assay. Western blotting was used to detect the phosphorylation of AKT and STAT3, the expression of epithelial-mesenchymal transition (EMT) -related molecular markers and apoptosis-related Bax/Caspase-3/Bcl-2 pathway. The GFP plasmid loaded with shRNA was transfected into PC-9 cell line by lentivirus infection. Three groups of stable PC-9 cell lines, including shNC, shCAV1-1 and shCAV1-2 were obtained. The phenotypic experiments of proliferation, invasion, migration and apoptosis were completed. Western blotting was used to detect the phosphorylation of AKT and STAT3, as well as apoptosis-related Bax/Caspase-3/Bcl-2 pathway markers. In vivo experiments, including subcutaneous tumor formation experiment and immunohistochemical detection of CAV1, EGFR and Ki-67 were performed. Comprehensive analysis of GSE130779, GSE32863 and GSE85841 datasets identified 3 up-regulated DEGs and 86 down-regulated DEGs, which were significantly enriched in malaria pathway and proteoglycans in cancer pathway. CAV1 and CAV2 may inhibit tumor growth by degrading EGFR. Thirteen core genes including ADH1B, ALDH1A1, CAV1, CAV2, CLDN18, CXCL2 (GRO2), EDNRB, GNG11, LPL, PDK4, SCGB1A1, SDPR and SFTPC were down-regulated in LUAD tissues, which were associated with better prognosis of lung cancer significantly. Enrichment analysis of CAV1-related DEGs identified the endocytosis pathway, suggesting that CAV1 was involved in the development of LUAD by degrading EGFR through endocytosis. CAV1 was highly expressed in paracancerous tissues, and there was a negative correlation between the tissue locations of CAV1 and EGFR. Kaplan-Meier survival analysis of the cohort study showed that higher Cav-1 levels were associated with longer overall survival, and the difference was significant. Both in vitro and in vivo, CAV1 knockdown increased EGFR level, while CAV1 overexpression decreased EGFR level. This effect was mediated by Cav-1 promoting EGFR degradation. Cav-1 further inhibited the phosphorylation of downstream AKT/STAT3 pathway of EGFR. Caveolin-1 positively regulated the Bax/Caspase-3/Bcl-2 pathway, thereby participating in mediating apoptosis. Cav-1 can suppress the proliferation, migration and invasion of LUAD, while promote cell apoptosis. Our findings demonstrate that CAV1 exerts its anti-tumor effects, at least in part, by inhibiting EGFR degradation and modulating the AKT/STAT3 pathway, as well as enhancing the Bax/Caspase-3/Bcl-2 signaling pathway in LUAD cells. These results suggest that targeting CAV1 may represent a promising therapeutic strategy for the treatment of LUAD patients.