HPV E6 and E7 Mediated Regulation of HPV(–) HNSCC Cell Lines

Abstract

Objective: 1) Determine the capacity of HPV16 E6 and E7 viral oncoproteins to regulate cellular levels of p53 and Rb in the absence of the complete viral genome. 2) Understand the interaction between viral E6 and endogenous p53 by observing the effect of E6 on mutant p53. Method: Two HPV negative HNSCC cell lines with DNA binding domain mutations of p53 were infected with lentiviral vectors containing either HPV16 E6, E7, and luciferase or luciferase alone. Naturally infected HPV16 and18 positive cell lines were evaluated as controls. Expression of p53 and Rb was evaluated with PCR and immunohistochemistry. Cell proliferation was monitored by time to confluence. Results: PCR analysis of cDNA confirmed expression of E6 and E7 in the transduced and naturally infected cell populations and the absence of E6 and E7 expression in the HPV negative cell lines. E6 and E7 transduced cell lines demonstrated reduced staining intensity for p53 and Rb compared to the HPV negative parental cells. Naturally infected HPV positive cell line controls stained weakly for Rb and p53 as expected. Cell proliferation was modestly decreased in E6 and E7 transduced cell lines compared to the parental controls. Conclusion: E6 and E7 viral oncoproteins affect cellular levels of p53 and Rb in the absence of a complete HPV genome. Viral E6 maintains the capacity to target p53 for degradation in HPV negative HNSCC cell lines with mutant p53. Individual oncoproteins can modify the behavior of HPV negative cell lines.