The involvement of CHD5 hypermethylation in laryngeal squamous cell carcinoma.

Chromodomain helicase DNA-binding protein 5 (CHD5) has been found to be a candidate tumor suppressor gene (TSG) in malignant neural tumors. In mice heterozygous for chd5 deficiency, the first tumor observed was pathological squamous cell carcinoma. More than 95% of primary laryngeal cancer is squamous cell carcinoma. Thus, we explored the expression of CHD5 in 65 patients with laryngeal squamous cell carcinoma (LSCC) using real-time PCR, immunohistochemistry and Western blotting. DNA methylation was detected using bisulfate-specific sequencing. The potential function of CHD5 was determined using MTT, apoptosis and transwell migration assays in CHD5-transfected Hep-2 cells. Our results revealed that the mRNA and protein expression levels of CHD5 in LSCC tissues were significantly lower than those in clear surgical margin tissues (p<0.05), and there is a significant correlation between the mRNA and protein expression levels of CHD5 (p<0.01). In addition, there were significant differences in CHD5 mRNA and protein levels with respect to the patient's clinical stage (p<0.05). Aberrant methylation of the CHD5 promoter was frequently found in the Hep-2 cell line and LSCC tumor tissues, especially tumor tissues from advanced TNM (p<0.05) or older patients (p<0.05). Finally, ectopic expression of CHD5 in laryngeal cancer cells led to significant inhibition of growth and invasiveness. Our data suggest that CHD5 is a tumor suppressor gene that is epigenetically downregulated in LSCC.