Direct interaction between Rab5a and Rab4a enhanced epidermal growth factor-stimulated proliferation of gastric cancer cells

BACKGROUND: Gastric cancer (GC) is one of the leading causes of cancer-related death worldwide. Although targeted therapies such as antibodies against human epidermal growth factor receptor 2 or vascular endothelial growth factor receptor 2 have been widely used in the treatment of metastatic cancer, the overall outcomes are poor. Therefore, elucidation of the mechanism underlying cancer progression is important to improve prognosis. Overexpression of the Rab5a gene has been confirmed to correlate with tumorigenesis of many cancers, but the mechanism underling, especially of GC, is still unclear. AIM: To investigate the effects of Rab5a overexpression on the tumorigenesis of GC. METHODS: First, the expression levels of Rab5a and Rab4a in primary tumorous tissues of GC patients diagnosed between 2015 and 2018 were analyzed. Then we constructed HGC-27 cell lines overexpressing green fluorescent protein-Rab5a or red fluorescent protein-Rab4a and investigated the interaction between Rab5a or Rab4a using Western blotting, co-immunoprecipitation, confocal microscopy, and colocalization analysis. Finally, epidermal growth factor-stimulated proliferation of these cell lines was analyzed using cell counting kit-8 cell viability assay. RESULTS: Compared with normal gastric tissues, the expression levels of Rab5a and Rab4a increased progressively both in paracancerous tissues and in advanced cancerous tissues. Epidermal growth factor could promote the proliferation of HGC-27 cells, especially Rab5a-overexpressing HGC-27 cells. Notably, Rab5a and Rab4a co-overexpression promoted the proliferation of HGC-27 cells to the greatest extent. Further analysis identified a direct interaction between Rab5a and Rab4a in HGC-27 cells. CONCLUSION: Co-overexpression of Rab5a and Rab4a in GC may promote the endosomal recycling of epidermal growth factor receptor, which in turn contributes to poor prognosis and tumor progression in GC patients. Inhibition of Rab5a or Rab4a expression might be a promising therapy for refractory GC.