miR-491-3p is Downregulated in Retinoblastoma and Inhibit Tumor Cells Growth and Metastasis by Targeting SNN.

Retinoblastoma (Rb) is the most common pediatric malignant tumor of the eyes. Previous studies demonstrated that miR-491-3p is downregulated in various cancers. However, its function in Rb remains unknown. A total of 15 pairs of primary Rb tissues and adjacent noncancerous tissues were collected. Quantitative real-time PCR (qRT-PCR) was used to investigate the expression profiles of miR-491-3p. qRT-PCR, western blotting and in situ immunocytochemistry were performed to investigate the expression profiles of epithelial-mesenchymal transition-related proteins (E-cadherin, Vimentin and N-cadherin) in Rb tissues and Rb cell lines as well as cell morphology. Cell proliferation was estimated by MTS and colony formation assays. Apoptosis was determined by FACS, cell migration and invasion were analyzed using transwell chambers. MiR-491-3p's target genes were predicted using target gene prediction databases. The interplay between miR-491-3p and SNN was evaluated through dual luciferase reporter gene assay. MiR-491-3p was significantly downregulated in mixed collection of 15 pairs of Rb tissues and Rb cell lines. Overexpression of miR-491-3p enhanced apoptosis, and significantly suppressed proliferation, migration and invasion of Rb cells. In contrast, the present of miR-491-3p inhibitor showed reversed results which apoptosis decreased, while cell proliferation of ARPE-19 cells increased. In addition, miR-491-3p increased the expression of E-cadherin, and dramatically decreased the expression of Vimentin and N-cadherin in Rb tissues and Rb cell lines, noticeable changes in morphology, too, as cells became less cohesive and more adhering. We found out that SNN was the pairing target of miR-491-3p and result showed that miR-491-3p and SNN interacted with each other. We also found out that the effects of miR-491-3p were in Rb cells were almost entirely canceled out at the overexpression of SNN. Our findings collectively suggest that miR-491-3p is an important tumor suppressor in Rb, which inhibits tumor growth and metastasis in Rb. These implicate it may be explored as a new therapeutic target in Rb.