Depletion of the cdk Inhibitor p16 INK4a Differentially Affects Proliferation of Established Cervical Carcinoma Cells

Abstract

Infections with high-risk human papillomaviruses (hrHPV) contribute to cervical carcinoma. The cdk inhibitor and tumor suppressor p16 INK4A is consistently upregulated in cervical carcinoma cells for reasons that are poorly understood. We report here that downregulation of p16 INK4A gene expression in three different cervical carcinoma cell lines reduced expression of the E7 oncogene, suggesting a positive feedback loop involving E7 and p16 INK4A . p16 INK4A depletion induced cellular senescence in HeLa but not CaSki and MS-751 cervical carcinoma cells. IMPORTANCE This study demonstrates that the cdk inhibitor p16 INK4A , frequently used as surrogate marker for transforming infections by human papillomaviruses of the high-risk group, is required for high-level expression of the E7 oncoproteins of HPV-16, HPV-18, and HPV-45 in cervical carcinoma cells. It is also demonstrated that depletion of p16 INK4A induces senescence in HeLa but not CaSki or MS-751 cervical carcinoma cells.