Background of the antigen
May negatively regulate cell cycle progression. May act at least in part via inhibition of the cyclin-D1/CDK4 complex, thereby preventing phosphorylation of RB1 and blocking E2F-dependent transcription.Tissue specificity: Ubiquitously expressed. Expression is down-regulated in a variety of tumor types including breast, colon, prostate and rectal tumors, and is up-regulated in certain hepatic carcinomas.