Abstract 199: HPV-16 E6 silencing of p16INK4a in human cervical cancer cells

Aberrant promoter methylation and silencing of tumor suppressor genes such as p16INK4a were reported in association with cervical carcinogenesis. Persistent infection with high-risk human papillomavirus (HPVs), such as HPV-16, contributes significantly towards the cervical cancer development. One of the HPV-16 early proteins E6 is considered to function as an oncoprotein. In the present study, the role of HPV-16 E6 in the regulation of p16INK4a silencing was investigated. Knockdown of E6 in HPV-16 positive human cervical carcinoma SiHa cells by the technique of small interfering RNA (siRNA) led to an increase in p16INK4a mRNA expression as assessed by quantitative RT-PCR analysis. Addition of DNA demethylating agent, 5-aza-2’-deoxyctidine, also had similar effect. Moreover, by methylation-specific PCR analysis, hypo-methylation of p16INK4a promoter was detected in HPV-16 E6 knockdown SiHa cells. The results indicated that HPV-16 E6 may regulate the expression of p16INK4a through promoter methylation. By Western blot analysis, the expression of DNA methyltransferase DNMT1 was repressed in HPV-16 E6 knockdown SiHa cells while it was induced in HPV-16 E6 over-expressed cells. In addition, decrease in p16INK4a mRNA expression and hyper-methylation of its promoter were observed in SiHa cells upon DNMT1 cDNA transfection. To sum up, HPV-16 E6 silencing of p16INK4a may be through the upregulation of DNMT1 which in turn induces the hyper-methylation of p16INK4a promoter and thus suppresses p16INK4a expression. This pathway may be one of the possible mechanisms for the oncogenic function of HPV-16 E6 in human cervical cancer development. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 199.