The Expression And Function Of MicroRNA-15a In Gastric Cancer

Background and aim:miR-15a is a tumor suppressor like microRNA which plays an important role in tumourigenesis and cancer progression. By regulating expression of target genes, such as BCL-2 and Cyclin D1, miR-15a could regulate cell cycle, inhibit tumor cell proliferation and promote cell apoptosis.miR-15ahas been found to be down-regulated in chronic lymphocytic leukemia, ovarian, prostate, lung, colon and pancreatic cancer. However, none is known about miR-15a in gastric cancer. This study is aimed to investigate the expression of miR-15a and its function and regulation pathway in gastric caner.Methods:RT-qPCR was used to analyze the expression level of miR-15a in gastric tumor tissues, adjacent non-tumorous tissues, gastric cancer cell lines BGC-823、SGC-7901、AGS、MKN-45、MKN-28 and non-malignant gastric epithelial cell line GES-1. A recombinant pri-miR-15a expression vector was constructed and transfected into MKN-45 cells to over-express miR-15a. MTT, in vitro cell migration and invasion assay were performed to investigate the effect of miR-15a on proliferationary, migratory and invasive ability of MKN-45. xenograft models of gastric cancer in nude mice were used to study the influence of miR-15a on tumor growth. RT-qPCR was also used to determine the expression level of miR-15a target genes, including Bcl-2, Cyclin D1, Cyclin E, FGF2, FGF7, FGFR1, Bmi-1, C-myb, WNT3A and BRCA1, in the transfected NKN-45 gastric cancer cells.Results:miR-15a was significantly down-regulate in gastric tumor tissues compared to the adjacent non-tumorous tissues (0.0014±0.00091 VS 0.0022±0.000183, P<0.05), and its expression level was also much lower in BGC-823、SGC-7901、AGS、MKN-45、MKN-28 than in GES-1 cells. Over-expression of miR-15a in MKN-45 effectively inhibited the cellular viability of proliferation, migration and invasion. miR-15a also inhibited tumor growth in MKN-45 mouse xenograft model. Up-regulation of miR-15a reduced the expression of miR-15a target genes, especially Bcl-2, Cyclin D1, Bmi-1 and FGF2. However, miR-15a showed no influence on expression of BRCA1Conclusion:miR-15a is down-regulated in gastric cancer tissues and cell lines. miR-15a function as a tumor suppressor in gastric cancer, since it could inhibit the proliferation, migration and invasion of MKN-45 in vitro and tumor growth in vivo by negative regulating the expression of Bcl-2, Cyclin D1 and Bmi-1.