p16 is a protein that slows down cell division by slowing the progression of the cell cycle from G1 phase to S phase, thereby acting as a tumor suppressor. Deletion in this gene can lead to insufficient or non-functioning p16, thereby accelerating the cell cycle and causing many types of cancer. p16 can be used as a biomarker to improve the histologic diagnostic accuracy of grade 3 cervical intraepithelial neoplasia (CIN). The expression of p16 (p16-positive) is strongly correlated with human papillomavirus (HPV) infection in head and neck squamous cell carcinoma (HNSCC). p16 is also involved in the prevention of melanoma and oropharynx.