Amplification of lncRNA PVT1 promotes ovarian cancer proliferation by binding to miR-140

Gene deletion or gene amplification acts as a driving factor of onset, progress, and metastasis in various cancers, including ovarian cancers. By mining the whole genome data of ovarian cancer patients, we identify the long noncoding RNA PVT1 as the most amplified gene. Knockdown of PVT1 was then achieved using a shRNA in two ovarian cancer cell lines, and cell viability was determined by trypan blue exclusion assay, cell metabolism by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay, and cell cycle alteration by propidium iodide cell cycle analysis. Potential targeting microRNAs were predicted with starBase v2.0, and direct binding of miR-140 on PVT1 was confirmed by luciferase reporter assay and microRNA pull-down assay. Evolutionary conserved transcription factor-binding site was predicted via rVista 2.0. Our results show that PVT1 was the most amplified gene in ovarian cancer patients, and it was highly correlated with poor survival outcomes. Knockdown of PVT1 caused decreased cell viability, metabolic activity, and smaller proportion of S-phase cells. PVT1 directly bound to miR-140 and acted as a microRNA sponge, while transcription of PVT1 was regulated by the transcription factor FOXO4. In conclusion, viability, metabolism, and cell cycle of ovarian cancers are regulated by the FOXO4/PVT1/miR-140 signaling pathway.