P16

p16 (also known as p16^INK4a, cyclin-dependent kinase inhibitor 2A, multiple tumor suppressor 1 and CDKN2A) is a tumor suppressor protein, that in humans is encoded by the CDKN2A gene. p16 plays a crucial role in regulating the cell cycle.

Function

p16 specifically inhibits cyclin-dependent kinase 4 (CDK4) and 6 (CDK6), and thus regulates the cell cycle progression at G1 phase. The inhibition of CDK4/6 prevents the phosphorylation of retinoblastoma protein (RB), which in turn prevents the cell from entering S phase of the cell cycle. This means that p16 acts as a checkpoint molecule to maintain the cell cycle, and prevent uncontrolled cell growth that could lead to cancer.

Clinical significance

Alterations in the function of p16 are associated with many types of cancer. For example, mutations in the CDKN2A gene that reduce the function of p16 are found in many types of human cancer. In addition, increased expression of p16 is often found in senescent cells, and is associated with age-related diseases.

See also

• Cyclin-dependent kinase
• Cell cycle
• Tumor suppressor

References

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  P16

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  High grade squamous intraepithelial lesion - p16 - high magnification

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  Immunohistochemistry for p16 in uterine papillary serous adenocarcinoma showing both nuclear and cytoplasmic staining