Aberrant methylation and downregulation of ZNF667-AS1 and ZNF667 promote the malignant progression of laryngeal squamous cell carcinoma.

BACKGROUND: Dysregulated long noncoding RNAs (lncRNAs) are involved in the development of tumor. Aberrant methylation is one of the most frequent epigenetic alterations that regulate the expression of genes. The aim of this study was to determine the expression and methylation status of ZNF667-AS1 and ZNF667, elucidate their biological function in the development of LSCC, and identify a cis-regulation of ZNF667-AS1 to ZNF667.

METHODS: The expression and methylation status of ZNF667-AS1 and ZNF667 in laryngeal cancer cell lines and LSCC samples were tested respectively. The function of two laryngeal cancer cell lines with overexpression of ZNF667-AS1 or ZNF667 was detected. The regulation between ZNF667-AS1 and ZNF667 was determined.

RESULTS: Significant downregulation of ZNF667-AS1 was detected in laryngeal cancer cell lines and LSCC tumor tissues. The reduced expression of ZNF667-AS1 was associated with moderate/poor pathological differentiation of LSCC tumor tissues. Aberrant hypermethylation of the CpG sites of ZNF667-AS1, closing to the transcriptional start site (TSS), was more critical for gene silencing, and associated with moderate/poor pathological differentiation. In vitro hypermethylation of promoter region closing to TSS of ZNF667-AS1 decreased the luciferase reporter activity. Overexpression of ZNF667-AS1 reduced the proliferation, migration, and invasion ability of AMC-HN-8 and TU177 cells. The sense strand, ZNF667, was positively correlated with ZNF667-AS1 in expression and function. Overexpression of ZNF667-AS1 led to increased expression of ZNF667 in mRNA and protein level. ZNF667-AS1 and ZNF667 may be associated with epithelial-mesenchymal transition (EMT) process.

CONCLUSIONS: ZNF667-AS1 and ZNF667 are both down-regulated by hypermethylation, and they serve as tumor suppressor genes in LSCC. ZNF667-AS1 regulates the expression of ZNF667 in cis.