Long non-coding RNA LINC00992 promotes hepatocellular carcinoma cell proliferation, metastasis, and invasiveness by downregulating MicroRNA miR-361-5p expression to increase levels of the transcription factor twist1.

Hepatocellular carcinoma (HCC) is one of the most common cancers, and has an extremely poor prognosis. Our previous study confirmed that the microRNA miR-361-5p inhibited the proliferation, metastasis, invasiveness, and epithelial-to-mesenchymal transition (EMT) process of HCC by targeting the transcription factor Twist1. Long non-coding RNAs (lncRNAs) are key regulators of processes such as cell differentiation, inflammation, tumor formation, and immune escape. However, the underlying interactions between the lncRNA LINC00992, miR-361-5p, and Twist1 in HCC progression is still elusive. In the current study, the DIANA-lncBase database was used to identify regulatory genes upstream of miR-361-5p. Reverse transcription-quantitative PCR (RT-qPCR) was used to quantify the expression of the genes encoding LINC00992, miR-361-5p, and Twist1 in HCC cells. The cell counting kit-8 (CCK-8) was used to measure HCC cell proliferation and Transwell was used to measure HCC cell migration and invasion. The dual-luciferase reporter assay and RNA pull-down assay were performed to examine the interaction between LINC00992 and miR-361-5p. Western blotting was used to detect the levels of Twist1 protein. The result confirmed that, among three lncRNAs tested, miR-361-5p was the one most significantly affected by LINC00992. RT-qPCR revealed that LINC00992 was highly expressed in HCC tissues and cells. The follow-up results showed that the expression of LINC00992 and miR-361-5p in HCC tissues were closely correlated with the rate of metastasis or recurrence of the HCC patients. Our result showed that the expression of miR-361-5p was lower in the LINC00992 (+) group than in the LINC00992 (-) group. CCK-8 and Transwell showed that LINC00992 promoted HCC cell proliferation, migration, and invasion, whereas dual-luciferase reporter assay and RNA pull-down assay showed that LINC00992 combined with miR-361-5p to act as a miRNA decoy in HCC. RT-qPCR and Western blotting confirmed that LINC00992 upregulated the expression of the Twist1 gene in HCC cells by downregulating expression of miR-361-5p. CCK-8 and Transwell assays confirmed that LINC00992 promoted the proliferation, metastasis, and invasiveness of HCC cells by downregulating miR-361-5p levels and consequently upregulating Twist1 expression, implying that these three elements may be promising targets for HCC therapy.
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