Human papillomavirus oncoprotein E6 upregulates c-Met through p53 downregulation

Purpose: Human papillomavirus (HPV)-associated oropharyngeal squamous cell carcinoma (OPSCC) carries a distinct clinical behaviour. c-Met oncogene is an important driver for tumour progression and its relationship with HPV in OPSCC was explored in the present study. Experimental design: Knockdown of HPV oncogene E6 or p53 alone and in combination was performed to examine their effects on c-Met expression by Western blot and quantitative realtime polymerase chain reaction. The effects of c-Met inhibition on cell proliferation, migration, and colony formation were examined in HPV-positive head and neck squamous cell carcinoma (HNSCC) cells. Retrospectively collected OPSCC patient specimens (N = 78) were stained for c-Met by immunohistochemistry and the staining levels were correlated with HPV status and patient outcomes. Results: E6 knockdown decreased c-Met protein and mRNA expression in HPV-positive HNSCC cells, which was partially abolished by the elimination of p53. Reducing c-Met decreased cell proliferation, migration, and colony formation in HPV-positive HNSCC cells. In OPSCC patient samples, high c-Met expression was associated with HPV-positive status (OR = 4.11, 95%CI: 1.16-14.55, P = 0.028) and tumour stage (OR = 0.27, 95%CI: 0.08 -0.93, P = 0.039) by multivariable analysis. In T3/T4 stage patients, high c-Met expression was associated with HPV positivity and low p53 levels, supporting an axis of E6-p53-c-Met regulation. Furthermore, high c-Met expression was marginally associated with poor disease-free survival in HPV-positive patients. Conclusions: Our results suggest that c-Met may serve as a novel target for treating HPV-associated OPSCC. The data also demonstrate that HPV E6 upregulates c-Met expression partially through p53 downregulation. (C) 2016 Elsevier Ltd. All rights reserved.