Abstract 813: Human papillomavirus 16 oncoprotein E6 upregulates c-Met partially through p53 in squamous cell carcinoma of the head and neck

Background: Human papillomavirus (HPV)-associated oropharyngeal squamous cell carcinoma (OPSCC) carries a distinct clinical behavior. The c-Met oncogene is an important driver for tumorigenesis, however, its relationship with HPV oncoproteins remains unclear. The present study aims to uncover the role of HPV in regulation of c-Met in OPSCC. Methods: We first knocked down the HPV oncogene E6 by siRNA to check alteration of c-Met expression through western blot and qRT-PCR in several HPV-positive HNSCC cell lines and the cervical cancer cell line CaSki. Next, we tested if E6 regulated c-Met expression is p53 dependent. Simultaneous knockdown of p53 and E6 was compared to E6 knockdown alone for the impact of p53 on c-Met expression using western blot analysis. In addition, the effects of c-Met inhibition by both siRNA and a c-Met specific inhibitor SU11274 on cell proliferation, migration, and colony formation were tested by sulforhodamine B colorimetric assay (SRB), wound healing assay, and colony formation assay, respectively, in HPV-positive cancer cell lines. Using retrospectively collected tissue specimens from 78 patients with OPSCC (N = 58 for HPV-positive vs. N = 20 for HPV-negative), we stained for c-Met and p53 by immunohistochemistry and correlated their expression with HPV status determined by HPV DNA in situ hybridization as well as other clinical characteristics. Results: E6 knockdown significantly decreased c-Met protein and mRNA expression in HPV-associated HNSCC and CaSki cell lines. E6 regulated c-Met expression was partially blocked by the elimination of p53. c-Met inhibition significantly decreased cell proliferation, migration, and colony formation. In patient samples, multivariate analysis revealed a significant association of c-Met expression with HPV status (positive vs. negative, OR = 4.11, 95%CI: 1.16-14.55, P = 0.028) as well as tumor stage (T1/2 vs. T3/4, OR = 0.27, 95%CI: 0.08-0.93, P = 0.039). In T3/T4 stage patients (N = 21), c-Met expression was significantly higher in HPV-positive patients and inversely related with p53 levels, supporting an axis of E6-p53-c-Met regulation. Conclusion: Our results show that c-Met expression is upregulated by HPV E6, which is partially mediated by p53. The data suggest that targeting c-Met may serve as a novel approach for treating HPV-associated OPSCC. (This study was supported by grants from Small Business Innovation Research (SBIR) Program (HHSN261201200097C), National Institutes of Health (R33 CA161873), and National Cancer Institute (NCI P50 CA 128613, Head and Neck SPORE). Citation Format: Guoqing Qian, Dongsheng Wang, Kelly R. Magliocca, Praveen Duggal, Sreenivas Nannapaneni, Sungjin Kim, Zhengjia Chen, Dong M. Shin, Nabil F. Saba, Zhuo G. Chen. Human papillomavirus 16 oncoprotein E6 upregulates c-Met partially through p53 in squamous cell carcinoma of the head and neck. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 813. doi:10.1158/1538-7445.AM2015-813