p16 INK4a is a tumor suppressor protein involved in the pathogenesis of a variety of malignancies. p16 INK4a is a 16.5 kDa protein expressed in the nucleoplasm of proliferating cells, functioning as an inhibitor of CDK4. Recent analyses of the p16 INK4a gene revealed homozygous deletions, nonsense, missense, or frameshift mutations in several human cancers (1).
The Ki-67 nuclear antigen is associated with cell proliferation. It is found throughout the cell cycle in the G1, S, G2, and M phases; but not the (G0) phase. It is commonly used to grade proliferation rates of tumors.
An optimized antibody cocktail for p16 INK4a and Ki-67 may aid in the identification of cells co-expressing markers for both tumor suppression and cell proliferation, an indicator of cell-cycle deregulation (2). Coexpression of p16 and Ki-67 has been observed in cervical intraepithelial neoplasia (CIN) lesions associated with high risk HPV infection, presenting potential utility in the classification of CIN lesions (3).]