LncRNA MALAT-1 promotes growth and metastasis of epithelial ovarian cancer via sponging microrna-22.

LncRNAs and miRNAs are emerging players in epithelial ovarian cancer (EOC). LncRNA MALAT-1 and miR-22 play vital roles in the onset and development of multiple cancers. Both of them are abnormally expressed in ovarian cancer, but the molecular basis for their involvement in EOC is unclear. In this study, we found MALAT-1 was up-regulated but miR-22 was down-regulated in EOC tissues and cell lines when compared to normal ovarian epithelial cell line IOSE80. Both of MALAT-1shRNA and miR-22 mimics inhibited ovarian cell proliferation, migration, and invasion, while simultaneously overexpressing MALAT-1 and miR-22 largely canceled out this inhibitory effect. Consistently, MALAT-1 silencing and miR-22 overexpression restrained tumor growth and metastasis to lungs in nude mice, which could be largely counteracted by co-overexpressing MALAT-1 and miR-22. Mechanistically, MALAT-1 targeted and sponged miR-22, counteracting its inhibitory effect on c-myc and c-myc-mediated epithelial-mesenchymal transition. Our findings for the first time demonstrated that MALAT-1 supports EOC progression through sponging miR-22, providing a novel insight into the role of MALAT-1 in ovarian cancer.