p16 （also known as p16INK4a, cyclin-dependent kinase inhibitor 2A, CDKN2A, multiple tumor suppressor 1 and numerous other synonyms）, is a protein that slows cell division by slowing the progression of the cell cycle from the G1 phase to the S phase, thereby acting as a tumor suppressor. p16 can be used as a biomarker to improve the histological diagnostic accuracy of grade 3 cervical intraepithelial neoplasia （CIN）. p16 is also implicated in the prevention of melanoma, oropharyngeal squamous cell carcinoma, cervical cancer, vulvar cancer and esophageal cancer.