Background: FoxO3a is a well-studied tumor suppressor gene in the forkhead transcriptional factor O (FoxO) subfamily and its downregulation is correlated with the occurrence of gastric cancer (GC). GC tissues had microRNA (miR)-372 upregulation, which has targeted relationship with 3'-untranslated region (3'-UTR) of FoxO3a gene. This study investigated if miR-372 plays a role in modulating FoxO3a expression, and affecting GC cell proliferation, apoptosis, and cisplatin (DDP) resistance. Materials and Methods: Dual luciferase reporter gene assay assessed the targeted regulation between miR-372 and FoxO3a. DDP-resistant cell lines MGC803/DDP and MKN28/DDP were compared for gene expression against parental cells. Cell proliferation was measured by Cell Counting Kit-8 (CCK-8) assay. Cultured cells were transfected with miR-372 mimic or miR-negative control (NC) to measure FoxO3a mRNA and protein expression. Cell apoptosis and proliferation were tested by flow cytometry and 5-Ethynyl-2'-deoxyuridine (EdU) staining, respectively. Results: miR-372 had a targeted relationship with FoxO3a mRNA. MGC803/DDP and MKN28/DDP cells had significantly elevated miR-372 level than parental cells, while Foxo3a mRNA or protein levels were significantly decreased. CCK-8 assay revealed significantly lower inhibitory activity on cell proliferation in drug-resistant cells. Compared with miR-NC group, miR-273 inhibitor transfected DDP-resistant cells had significantly increased Foxo3a expression, enhanced cell apoptosis, reduced proliferation, and drug resistance. Conclusions: miR-372 upregulation is associated with DPP resistance of GC cells. Downregulation of miR-372 can inhibit proliferation, facilitate apoptosis, and suppress DDP resistance of drug-resistant GC cells.
Keywords: DDP; Foxo3a; drug resistance; gastric cancer; miR-372.