Human papillomavirus 16 oncoprotein regulates the translocation of β‐catenin via the activation of epidermal growth factor receptor

BACKGROUND To understand the mechanism of frequent and early lymph node metastasis in high-risk human papillomavirus (HPV)–associated oropharyngeal squamous cell carcinoma (OPSCC), this study investigated whether β-catenin is regulated by the HPV oncoprotein and contributes to OPSCC metastasis. METHODS Expression levels of p16, β-catenin, and epidermal growth factor receptor (EGFR) were examined in OPSCC samples (n = 208) by immunohistochemistry. The expression and subcellular localization of β-catenin and EGFR activation were also studied in HPV-positive and HPV-negative head and neck squamous cell carcinoma cell lines with western blot analysis. HPV16 E6 small interfering RNA was used to elucidate the effect of the HPV oncoprotein on β-catenin translocation. The involvement of EGFR in β-catenin translocation was confirmed by treatment with erlotinib. Moreover, the invasive capacity was evaluated after HPV16 E6/E7 repression. RESULTS The results showed that the membrane weighted index of β-catenin was inversely correlated with p16 positivity (P < .001) and lymph node metastasis (P = .026), whereas nuclear staining of β-catenin was associated with p16-positive OPSCC (P < .001). A low level of membrane β-catenin expression was significantly associated with disease-free and overall survival (P < .0001 in both cases). Furthermore, the membrane weighted index of EGFR was inversely correlated with p16 positivity (P < .001) and positively correlated with membrane β-catenin (P < .001). The in vitro study showed that HPV16 E6 repression led to reductions of phospho-EGFR and nuclear β-catenin, which were also observed after erlotinib treatment, and inhibition of invasion. CONCLUSIONS The findings suggest that HPV16 E6 mediates the translocation of β-catenin to the nucleus, which may be regulated by activated EGFR. Cancer 2015;121:214–25. © 2014 American Cancer Society.