Alcohol Treatment of Oral Streptococcus Spp. Increased the Entry of Human Papillomavirus Type 16 into Non-Malignant and Oral Squamous Cell Carcinoma Cells

Background: Oropharyngeal carcinoma is often associated with human papilloma virus subtype 16 (HPV) infections; however events that lead to HPV entry and carcinoma are poorly understood. We simulated a clinical situation in the laboratory by examining human epithelial and oral keratinocyte (HOK) responses to oral commensal bacteria (Streptococcus spp.) and metabolism of ethyl alcohol (ETOH). These studies led us to conclude that oral bacteria and ethyl alcohol through keratinocyte membrane signals act as co-factors for HPV 16 entry. Methods: We tested ETOH exposure responses of Streptococcus spp., ETOH-sensitive, acetaldehyde (AA) producers: S. mutans (LT11), S. salivarius strain, 109-2 and S. gordonii (V2016; wild type). In comparison to ETOH-resistant, non-producers of AA: S. salivarius strain, 101-7 or S. gordonii (adh ABE mutant). 5×105 per cfu/mL of bacteria were exposed to ETOH (5%,v/v) for 1h and then co-incubated for 3h with epithelial targets: immortalized: 293TT; HPV 16 (HOK/HPV 16B cells), or telomerase: hTERT HOK. Streptococci spp. attachment to epithelial cells and subsequent effects were enumerated with immune cytochemistry; Western immunoblotting, and immunoprecipitation techniques. These methods delineated expressions of syndecans-1, 4; phospho-L-tyrosine epidermal growth factor receptor (EGFR), and furin convertase (FC) with HPV 16 pseudo virus (PsV) entry into 293TT, hTERT HOKs and oral squamous cell carcinoma (SCC-25). To verify these relationships we used inhibitors of alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH), and FC. Results: Streptococcus spp. metabolism of ETOH released AA to trigger HOK expressions of syndecans 1 and 4 and heparin sulfate binding proteins were degraded by heparanase. Following these events enhanced phosphorylated EGFR expression and HPV 16 entry through FC activity were recorded. Conclusions: Some oral Streptococcus spp. response to ETOH mediates epithelial cell susceptibility to HPV 16 entry. This occurs through membrane associated expression changes of proteoglycans and EGFR. Moreover, oral cancer cell differentiation and growth may be dependent upon these associations.