Abstract 4798: Subcellular translocation of β-catenin and its relationship with EGFR activation in HPV16 positive OPSCC.

Abstract

Abstract Background: The incidence of human papillomavirus (HPV)-associated oropharyngeal squamous cell carcinoma (OPSCC) has increased in recent years. HPV-associated OPSCC follows a distinct carcinogenic pathway from HPV-negative OPSCC. The molecular basis of the disease progression due to HPV remains to be elucidated. Clinical observations have revealed frequent and early lymph node metastasis and unusual distant metastasis in HPV-associated as compared with HPV-negative OPSCC. To understand the underlying molecular mechanism, we have studied whether β-catenin, one of the major proteins in the Wnt pathway, is involved in HPV-associated OPSCC metastasis. Methods: The study samples (n = 210) were collected from formalin-fixed and paraffin-embedded OPSCC tissues obtained from the Surgical Pathology files in the Department of Pathology at Emory University following the regulations of the Health Insurance Portability and Accountability Act (HIPAA). Expression levels of p16 as a surrogate marker for HPV-associated cancer, β-catenin, and epidermal growth factor receptor (EGFR) were determined by immunohistochemistry (IHC) analyses. Membrane expression of β-catenin and total EGFR level were scored as a weight index [WI = intensity (0, 1+, 2+, and 3+) x % of positive staining]. Nuclear β-catenin and p16 were recorded as positive and negative. Expression and subcellular localization of β-catenin as well as EGFR expression and activation were also studied in both HPV-positive and -negative head and neck SCC (HNSCC) cell lines (n =7) by Western blot analysis. SiRNA against HPV E6 was used to elucidate the effect of HPV on β-catenin translocation. Results: Our results showed that membrane WI of β-catenin was inversely correlated with p16 positivity (p < 0.0001), while nuclear staining of β-catenin was associated with p16 positive OPSCC (p = 0.007) and positive lymph nodes (p = 0.0304). A low level of membrane β-catenin (cut-off by the median value) was significantly associated with disease free survival and overall survival (p < 0.05 in both cases). Furthermore, WI EGFR was positively correlated with nuclear β-catenin (p = 0.0001). Our in vitro study showed that nuclear β-catenin level was higher in HPV16-positive HNSCC cell lines than in HPV16-negative cell lines. Furthermore, HPV16-positive cells showed higher EGFR activation than HPV16-negative cells. Reduction of HPV16 E6 led to the de-activation of EGFR and decreased level of β-catenin in the nucleus. Conclusion: Our findings suggest that HPV16 E6 mediates the translocation of β-catenin to the nucleus, which may be regulated by activated EGFR. The underlying mechanism deserves further investigation. (This study was supported by US National Institutes of Health (NIH/NCI) grant HHSN2610201000125C, R33 CA134392-01, and Georgia Cancer Coalition Distinguished Cancer Scholar Award to ZGC). Citation Format: Zhongliang Hu, Ning Jiang, Susan Muller, Nabil Saba, Dongsheng Wang, Hongzheng Zhang, Dong M. Shin, Zhuo Georgia Chen. Subcellular translocation of β-catenin and its relationship with EGFR activation in HPV16 positive OPSCC. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4798. doi:10.1158/1538-7445.AM2013-4798