Abstract 3326: Upregulation of epigenetic changes acquired by HPV16 E6/E7 oncoproteins in mouse keratinocytes: Targeting ATM/PI3K

Abstract

Abstract Human Papillomavirus (HPV), a non-enveloped epitheliotropic double stranded DNA virus, is an etiological agent of oral cancer. Oral cancer is related to the persistent infection by high-risk HPV type 16, E6/E7 oncoproteins. The E6/E7 oncoproteins significantly contribute to the carcinogenic genetic instability effect of high-risk HPV through the degradation of two gatekeeper proteins, p53 and pRB, respectively. The ATM gene, also known as a gatekeeper protein plays a central role in the complex processes that repair DNA strand breaks. The ATM gene is located at 11q22.3 and belongs to a protein family known as the PI3K. Many studies have tried to clarify the epigenetic instability role of ATM in cancer function and susceptibility. However, there are no studies addressing the relationship between HPV infection-oral cancer, ATM/PI3K expression, and genomic instability. The aim of this study is to analyze the influence of HPV16 E6/E7 oncoproteins in oral cancer and the epigenetic profile. In our experimental procedures, we proposed a novel approach to study HPV-induced epigenetic changes with reconstructed human oral epithelium in SCID mouse. We used HPV-16, which is the most common HPV type found in oral cancer. Two plasmids were used to produce HPV-16 E6/E7. The first plasmid p16sheLL expresses the two viral capsid proteins, L1 and L2. The second plasmid pBR322HPV16 contains the full length HPV-16 genome. This approach closely mimics the architecture of normal human oral epithelium. In our study, we first focused on analyzing selected cellular gene loci where DNA methylation profiles are known to be altered, either by HPV infection or in oral cancer. We examined the following gene promoters DcR1/DcR2 (apoptosis regulation), p16 (cell cycle control), DAPK (cancer metastasis), and MGMT (DNA repair). We also analyzed progressive morphological and cytopathic changes in the HPV-infected oral epithelia. These data indicate that HPV E6/E7 oncoproteins can promote increased upregulation of apoptosis, disrupt cell cycle regulation, and decrease DNA double strand break repair. Epigenetics and chromosomal instability events were noted, specifically, the deletion of the distal region of chromosome 11q22-23 in the E6/E7 transfected keratinocytes. These results indicate that HPV-16, E6/E7 oncoproteins induced epigenetic changes in mouse keratinocytes, which may further promote oral carcinogenesis. Citation Format: Eva McGhee, Mengtao Li, Yi-Ling Lin, Liliana Zarate, Naomi Long, Mai Do, Chinelo Ezechukwu, Nichelle Cox, Hyun Chung, Jenna Cormier, Meidrah Tyler, Victoria Vidal, Billy Ballard, Roland Pattillo, Jay Vadgama. Upregulation of epigenetic changes acquired by HPV16 E6/E7 oncoproteins in mouse keratinocytes: Targeting ATM/PI3K [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3326.