p21/WAF1 [CIP1/4377R]

p21 / WAF1, also known as cyclin-dependent kinase inhibitor 1 or CDK-interacting protein 1, is a protein that in humans is encoded by the CDKN1A gene located on chromosome 6 (6p21.2). The p21 protein binds to and inhibits the activity of cyclin-CDK2 or -CDK4 complexes, and thus functions as a regulator of cell cycle progression at G1. p21 is expressed in all adult human tissues. In tumors, the expression of p21 has been studied by immunohistochemical methods in a wide range of human tumors, such as gastric carcinoma, non-small cell lung carcinoma, and thyroid carcinoma. The expression of p21 is associated with favorable prognosis in various tumors.