lncRNA-MEG3 Suppresses the Proliferation and Invasion of Melanoma by Regulating CYLD Expression Mediated by Sponging miR-499-5p

The abnormal expression of long noncoding RNA- (lncRNA-) MEG3 was clearly identified in a number of malignant tumors, but the specific function of MEG3 remains unknown in malignant melanoma until now. The research attempts to explore the effects of MEG3 on the growth and metastasis of malignant melanoma. MEG3 and miR-499-5p expression were determined by qRT-PCR method. Western blotting assay was applied to detect protein expression. Luciferase reporter assay was used to assess the correlation between MEG3 and miR-499-5p and between CYLD and miR-499-5p. Cell growth, cell cycle, and cell apoptosis were examined by CCK-8 assay, EdU assay, and flow cytometry assay, respectively. The invasion ability of melanoma cells was investigated by wound-healing and Transwell assays. The effect of MEG3 on growth of melanoma in vivo and cell chemosensitivity was detected by xenograft animal model and CCK-8 assay. As a result, the expression of MEG3 was decreased in melanoma tissues and cell lines. The level of MEG3 was significantly associated with poor prognosis. MEG3 could bind to miR-499-5p and CYLD mRNA contained a binding site of miR-499-5p. The expression of CYLD was reduced and the level of miR-499-5p was elevated in melanoma tissues and cell lines. Luciferase reporter assay and western blot assay confirmed that MEG3 regulated the expression of CYLD by sponging miR-499-5p. Functionally, upregulation of MEG3 inhibited melanoma cell proliferation, invasion, and migration, enhanced melanoma cell apoptosis, arrested melanoma cell cycle, and regulated the expression of E-cadherin, N-cadherin, and cyclin D1 by regulating CYLD expression mediated by sponging miR-499-5p. Importantly, overexpression of MEG3 suppressed the growth of xenograft tumor and improved chemotherapy sensitivity of A375 cells to cisplatin and 5-FU treatment. In conclusion, MEG3 has a crucial function in the tumorigenesis of melanoma, and MEG3 may be a potential therapeutic target in the treatment of melanoma.