CDKN1A and hepatocellular carcinoma: In hepatocellular carcinoma (HCC), BMP4 promotes cell cycle progression by upregulating the expression of cyclin-dependent kinase (CDK)1 and cyclin B1 in HCC cells, while in diffuse-type gastric carcinoma cells, BMP4 induces G1 arrest by upregulating the expression of p21 cyclin kinase inhibitor via the SMAD pathway [30].