Expression of Toll-like Receptors in HPV-positive and HPV-negative Oropharyngeal Squamous Cell Carcinoma--an in Vivo and in Vitro Study

The incidence of oropharyngeal squamous cell carcinoma (OPSCC) has increased over the past decades in many western countries. This trend is mainly attributed to the human papillomavirus (HPV). Cancer-related actions of immunological defense systems are being intensively researched. Human toll-like receptors (TLRs) are a family of pattern recognition receptors that participate in the immunological defense against pathogens, but their actions are also linked to cancer. The expression of TLRs in cervical epithelium alters both during the clearance of HPV infection and the HPV-induced neoplasia, but the expression of TLRs has not been studied in OPSCC. Thirty-five paraffin-embedded, formalin-fixed, squamous cell carcinoma tissue specimens were analyzed for TLRs 2, 3, 4, 5, 7, and 9 and HPV and p16 statuses. The TLR 9 expression was lower in HPV-positive tumors compared with HPV-negative tumors. TLR 7 was expressed in all cancer specimens, but elevated expression was evident in HPV and/or p16-positive tumors. The majority of p16-positive tumors did not express TLR 5, whereas its expression was stronger in p16-negative tumors. The results of in vitro analysis of five human OPSCC cell lines and one human oral tongue squamous cell carcinoma cell line agree with the in vivo trends: low levels of TLR 5 and high levels of TLR 7 in p16-positive OPSCC. Overall, TLR 7 and 9 expression patterns are demonstrated here to relate to the HPV status in vivo and TLR 5 and 7 expression patterns to the p16 status in vivo and in vitro.