The role of different types of human papillomavirus (HPV) in the development of oral and oropharyngeal papillomas remains unclear. High-risk HPV (HR-HPV) was shown to be involved in the pathogenesis of significant proportion of squamous cell carcinomas of the oropharynx. In this study, we hypothesized that in some oropharyngeal papillomas, low-risk HPV (LR-HPV) and HR-HPV infection could co-exist, similar to what is observed in genital warts, and thus contribute to the elevated risk of malignancy. To test this hypothesis, we used real-time PCR to assess the presence of HPV DNA of 16 types (2 LR-HPV and 14 HR-HPV), in 75 formalin-fixed and paraffin-embedded histopathological samples of oral and oropharyngeal papillomas and in 57 squamous cell carcinomas from the same regions. We investigated the biological activity of HPV by demonstrating accumulation of P16(INK4A) protein in the viral-infected tissue samples. The presence of the LR-HPV genome from the HPV6 or HPV11 types was confirmed in 42 (56%) papillomas and in no carcinomas. HPV6/HPV11 co-infection was detected in 17 (22.7%) of the papillomas. HR-HPV DNA presence and HR-HPV activity hallmarks were not observed in any of the investigated papillomas. Thus, a causative role for HR-HPV or its contribution to LR/HR-HPV co-infection in the pathogenesis of oral or oropharyngeal papillomas is unlikely. Additionally, HR-HPV and LR-HPV infections seem to be mutually exclusive in papillomas and squamous cell carcinomas of the oral cavity and oropharynx.
Keywords: Human papillomavirus; Oropharyngeal cancer; Pharyngeal papilloma; Pharyngeal warts.