Epigenetic mediated zinc finger protein 671 downregulation promotes cell proliferation and tumorigenicity in nasopharyngeal carcinoma by inhibiting cell cycle arrest

Background: Epigenetic abnormalities play important roles in nasopharyngeal cancer (NPC), however, the epigenetic changes associated with abnormal cell proliferation remain unclear. Methods: We detected epigenetic change of ZNF671 in NPC tissues and cell lines by bisulfite pyrosequencing. We evaluated zinc finger protein 671 (ZNF671) expression in NPC cell lines and clinical tissues using real- time PCR and western blotting. Then, we established NPC cell lines that stably overexpressed ZNF671 and knocked down ZNF671 expression to explore its function in NPC in vitro and in vivo. Additionally, we investigated the potential mechanism of ZNF671 by identifying the mitotic spindle and G2/M checkpoint pathways pathway downstream genes using gene set enrichment analysis, flow cytometry and western blotting. Results: ZNF671 was hypermethylated in NPC tissues and cell lines. The mRNA and protein expression of ZNF671 was down- regulated in NPC tissues and cell lines and the mRNA expression could be upregulated after the demethylation agent 5- aza- 2'- deoxycytidine treatment. Overexpression of ZNF671 suppressed NPC cell proliferation and colony formation in vitro; silencing ZNF671 using a siRNA had the opposite effects. Additionally, overexpression of ZNF671 reduced the tumorigenicity of NPC cells in xenograft model in vivo. The mechanism study determined that overexpressing ZNF671 induced S phase arrest in NPC cells by upregulating p21 and downregulating cyclin D1 and c- myc. Conclusions: Epigenetic mediated zinc finger protein 671 downregulation promotes cell proliferation and enhances tumorigenicity by inhibiting cell cycle arrest in NPC, which may represent a novel potential therapeutic target.