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

Abstract

BackgroundHuman 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. MethodsWe characterized epigenetic changes in tumor-related genes (TRGs) that are known to be associated with HNC development and its progression. ResultsThe expression levels of 42 candidate HNC-associated genes were analyzed. Of these, 7 TGRs (CHFR, RARβ, 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). ConclusionWe 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.