Human papillomavirus-positivity is associated with EREG down-regulation and promoter hypermethylation in head and neck squamous cell carcinoma.

ABSTRACT

BACKGROUND: Human papillomavirus (HPV) etiology has become evident in head and neck cancers (HNCs) and HPV positivity showed a strong association with its malignant progression. Since aberrant DNA methylation is known to drive carcinogenesis and progression in HNCs, we investigated to determine target gene(s) associated with this modification. METHODS: We characterized epigenetic changes in tumor-related genes (TRGs) that are known to be associated with HNC development and its progression. RESULTS: The expression levels of 42 candidate HNC-associated genes were analyzed. Of these, 7 TGRs (CHFR, RARß, GRB7, EREG, RUNX2, RUNX3, and SMG-1) showed decreased expressions in HPV-positive (+) HNC cells compared with HPV-negative (-) HNC cells. When gene expression levels were compared corresponding to the DNA methylation conditions, GRB7 and EREG showed significant differential expression between HPV+ and HPV- cells, which suggested these genes as primary targets of epigenetic regulation in HPV-induced carcinogenesis. Furthermore, treatment with a demethylation agent, 5-aza-2'-deoxycytidine (5-aza-dc), caused restoration of EREG expression and was associated with hypomethylation of its promoter in HPV+ cells, while no changes was noted in HPV- cells. EREG promoter hypermethylation in HPV+ cells was confirmed using methylation-specific PCR (MS-PCR). CONCLUSION: We conclude that EREG is the target of epigenetic regulation in HPV+ HNCs and its suppressed expression through promoter hypermethylation is associated with the development of HPV-associated HNCs.