SUZ12 knockdown restrains the proliferation, migration, and invasion of oral tongue squamous cell carcinoma through inhibiting DNMT1-mediated ZNF582 promoter methylation.

BACKGROUND: Suppressor of zest 12 (SUZ12) upregulation is related to cervical node metastasis in oral tongue squamous cell carcinoma (OTSCC). This study explored the roles and mechanism of SUZ12 in OTSCC progression. METHODS: SUZ12 protein levels in OTSCC tissues and cell lines were determined using immunohistochemistry assay and Western blot analysis. SUZ12 was overexpressed or silenced through transfection of Overexpression plasmids or small interfering RNA targeting SUZ12 were transfected into CAL27 and SCC9 cells to achieve SUZ12 overexpression or knockdown. Subsequently, cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) markers (E-cadherin, N-cadherin and Vimentin) were determined. Zinc finger protein 582 (ZNF582) promoter methylation was detected using the methylation-specific PCR assay. Then, the effects of ZNF582 on CAL27 cell behaviors were also evaluated using gain/loss function experiments. Moreover, rescue experiments were conducted to investigate the role of the SUZ12/ZNF582 axis in regulating CAL27 cell progression. Additionally, SUZ12-silenced CAL27 cells were subcutaneously injected into the posterior flank of mice, followed by tumor growth detection within a 28 day period. RESULTS: SUZ12 protein was significantly upregulated in OTSCC tissues and cell lines. SUZ12 overexpression augmented proliferation, migration, invasion and EMT in both CAL27 and SCC9 cells, while SUZ12 knockdown showed the opposite results. SUZ12 inhibited ZNF582 expression by promoting DNA methyltransferase 1 (DNMT1)-mediated ZNF582 promoter methylation. Moreover, ZNF582 knockdown promoted OTSCC cell proliferation, migration, invasion and EMT, while ZNF582 overexpression led to the opposite results. Rescue experiments demonstrated that ZNF582 knockdown abrogated SUZ12 knockdown-mediated inhibition of CAL27 cell malignant progression. Besides, SUZ12 knockdown suppressed xenograft tumor growth of OTSCC in nude mice. CONCLUSION: SUZ12 knockdown inhibits the proliferation, migration, invasion and EMT in OTSCC cells by inhibiting DNMT1-mediated ZNF582 promoter methylation, thereby suppressing tumor growth in vivo.