Hypoxia-Driven HIF-2α Transcriptionally Activates Exosomal ITGβ5 to Promote Gastric Cancer Progression

Gastric cancer (GC) is the fifth most diagnosed malignancy and the fifth leading cause of cancer-related deaths, with a poor overall survival of under one year. Metastatic tumors that arise from malignant primary tumors account for the majority of cancer-related deaths for GC. Hypoxia-inducible transcription factors (HIFs), including HIF-2α, and integrin such as ITGβ5 play important roles in tumor metastasis. However, the regulatory relationship and functional significance between HIF-2α and ITGβ5 in GC remain poorly understood. We analyzed TCGA RNA-seq data to identify hypoxia-related biological processes and signaling pathways in GC. Exosome proteomics was used to characterize the protein profiles of extracellular vesicles (EVs) derived from GC cells under hypoxia. Under hypoxic conditions, ITGβ5 expression in GC showed a positive correlation with HIF-2α levels. Clinical analysis confirmed the overexpression of ITGβ5, which was further validated by RT-qPCR, western blot, and flow cytometry. The chromatin immunoprecipitation (ChIP) was performed to confirm the binding of HIF-2α to the promoter of ITGβ5. The role of ITGβ5 in GC cell proliferation, invasion, and migration was investigated through gain- and loss-of-function studies conducted both in vivo and in vitro. Our results showed that HIF-2α directly binds to the promoter of ITGβ5, thereby transcriptionally activating its expression. In vivo and in vitro studies revealed that the overexpression of ITGβ5 significantly enhanced the invasion, migration, and growth of GC. Our study uncovers a novel pathway in which hypoxia-induced activation of HIF-2α promotes the proliferation, invasion, and metastasis of GC by directly upregulating the expression of exosomal ITGβ5. Given these findings, ITGβ5 may serve as a potential prognostic biomarker and therapeutic target for GC.