Endogenous and extracellular roles of a tumor suppressor miR-379-5p in gastric cancer

Introduction: MiRNAs play important roles in development of various cancers including gastric cancer. Exosomes are extracellular vesicles for translocating molecules. This study aims to investigate the tumor suppressive roles of miR-379-5p in gastric cancer, and to investigate the roles of exosomes in transporting miR-379-5p from intracellular to extracellular. Methods: Fifty-three pairs of gastric cancer and non-tumor tissue samples were collected. Five cell lines were applied. Functional assays including cell proliferation, cell migration and invasion, and cell adhesion assay were performed. Targets of miR-379-5p were screened and validated by western blot. Expressions of endogenous miR-379-5p in gastric cancer cells and exosomal miR-379-5p in cell culture medium were evaluated by RT-qPCR. Medium of culturing AGS or BCG23 was applied for culturing MKN45 and HEK293T. Results: The results indicated that miR-379-5p was significantly downregulated in gastric cancer tissue samples and cell lines. Enforced expression of miR-379-5p inhibited gastric cancer cell proliferation, migration, and invasion, while miR-379-5p mimic enhanced cell adhesion to extracellular matrix. IGF1R was a potential target of miR-379-5p in gastric cancer. Expression of miR-379-5p was dramatically higher in exosomes in cell culture medium than its endogenous expression. Exosomes from cell culture medium of AGS or BCG23 could regulate endogenous expression of miR-379-5p in HEK293T cells. Conclusions: MiR-379-5p was significantly downregulated and it functioned as a tumor suppressor in gastric cancer. MiR-379-5p was higher expressed in exosomes of culture medium than its endogenous expression. MiR-379-5p could be translocated from cells into cell culture medium and entered certain cell types via exosomes.