{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"p16 is a tumor suppressor encoded by CDKN2A gene, also known as multiple tumor suppressor 1, cyclin-dependent kinase inhibitor 2A (CDKN2A), or p16INK4a. This protein regulates the cell cycle by deactivating CDK4 and CDK6 cyclin D complexes, preventing the release of E2F transcription factor from retinoblastoma protein (Rb). Ultimately, the bound E2F cannot drive the transcription of downstream gene products, and transition from G1 to S phase is blocked. The overexpression of the E7 oncoprotein following HPV integration into the host genome can disrupt the E2F-Rb complex by displacing and activating E2F and allowing the cells to pass G1 to S checkpoint. In a regulatory feedback attempt to inhibit further cell proliferation, p16 is upregulated. Therefore, p16 antibody is commonly used in the evaluation of HPV-associated lesions. Loss of p16 expression or mutations in the CDKN2A gene are observed in melanoma, subtypes of glioma, non-small-cell lung carcinoma, pancreatic cancer, esophageal cancer, and various other cancers, contributing to the dysregulation of cell cycle control and tumor progression."}]}]}