CDK4-I is the product of the INK-4 gene. It binds to cyclin 4/6 complexes to control the cell cycle at G1S.
There is increased expression of p16 in both high-grade cervical intra-epithelial neoplasia and in low-grade neoplasia associated with high-risk HPV. There is also immunoreactivity in both cervical glandular intra-epithelial neoplasia and cervical adenocarcinoma.
In most non-small cell carcinomas of lung, inactivation of p16 and/or upregulation of cyclin D1 leads to disruption of the retinoblastoma-mediated of cell cycle arrest. Aberrant p16 methylation is an early event in pulmonary non-small cell carcinogenesis, leading to loss of both p16 activity and expression2.
Diagnostic value
Endometrial versus endocervical adenocarcinoma: diffuse positivity favours endocervical carcinoma. Note that benign squamous morules in endometrial adenocarcinoma are commonly positive for p16.
Small cell versus poorly differentiated squamous cell carcinoma of lung2.
2 Zhang H, Liu J, Cagle PT, Allen TC, Laga AC,Zander DS Distinction of pulmonary small cell carcinoma from poorly differentiated squamous cell carcinoma: an immunohistochemical approach. Mod Pathol 2005; 18:111-8
This page last revised 18.7.2005.
©SMUHT/PW Bishop