407047

MIR9-2

microRNA 9-2;MIR9-2;microRNA 9-2

-

5q14.3

ncRNA

Recent evidence shows that altered microRNA-9 (miR-9) expression is implicated in the progression of gastric cancer. However, the exact roles and underlying mechanisms of miR-9 in the proliferation, invasion and metastasis of gastric cancer still remain unknown. In this study, miR-9 was found to be down-regulated and inversely correlated with the expression of cyclin D1 and v-ets erythroblastosis virus E26 oncogene homolog 1 (Ets1) in gastric cancer tissues and cell lines. Bioinformatics analysis revealed the putative miR-9 binding sites in the 3-untranslated regions (3-UTR) of cyclin D1 and Ets1 mRNA. Ectopic expression or knockdown of miR-9 resulted in responsively altered expression of cyclin D1, Ets1 and their downstream targets phosphorylated retinoblastoma and matrix metalloproteinase 9 in cultured gastric cancer cell lines SGC-7901 and AGS. In the luciferase reporter system, miR-9 directly targeted the 3-UTR of cyclin D1 and Ets1, and these effects were abolished by mutating the miR-9 binding sites. Over-expression of miR-9 suppressed the proliferation, invasion, and metastasis of SGC-7901 and AGS cells in vitro and in vivo. Restoration of miR-9-mediated down-regulation of cyclin D1 and Ets1 by transient transfection, rescued the cancer cells from decrease in proliferation, migration and invasion. Furthermore, anti-miR-9 inhibitor promoted the proliferation, migration and invasion of gastric cancer cells, while knocking down of cyclin D1 or Ets1 partially phenocopied the effects of miR-9 over-expression. These data indicate that miR-9 suppresses the expression of cyclin D1 and Ets1 via the binding sites in their 3-UTR, thus inhibiting the proliferation, invasion and metastasis of gastric cancer.

Matrix metalloproteinase (MMP)-14 is the only membrane-anchored MMP that plays a critical role in tumor metastasis and angiogenesis. However, the mechanisms underlying MMP-14 expression in tumors still remain largely unknown. In this study, MMP-14 immunostaining was identified in 29/42 neuroblastoma tissues, which was correlated with clinicopathologic features and shorter patients' survival. In subtotal 20 neuroblastoma cases, microRNA 9 (miR-9) was downregulated and inversely correlated with MMP-14 expression. Bioinformatics analysis revealed a putative miR-9-binding site in the 3'-untranslated region (3'-UTR) of MMP-14 mRNA. Overexpression or knockdown of miR-9 responsively altered both the mRNA and protein levels of MMP-14 and its downstream gene, vascular endothelial growth factor, in cultured neuroblastoma cell lines SH-SY5Y and SK-N-SH. In an MMP-14 3'-UTR luciferase reporter system, miR-9 downregulated the luciferase activity, and these effects were abolished by a mutation in the putative miR-9-binding site. Overexpression of miR-9 suppressed the invasion, metastasis, and angiogenesis of SH-SY5Y and SK-N-SH cells in vitro and in vivo. In addition, the effects of miR-9 on MMP-14 expression, adhesion, migration, invasion, and angiogenesis were rescued by overexpression of MMP-14 in these cells. Furthermore, anti-miR-9 inhibitor or knockdown of MMP-14 respectively increased or inhibited the migration, invasion, and angiogenesis of neuroblastoma cells. These data indicate that miR-9 suppresses MMP-14 expression via the binding site in the 3'-UTR, thus inhibiting the invasion, metastasis, and angiogenesis of neuroblastoma.