CCND1 and hepatocellular carcinoma: For instance, AFP knockdown in hepatocellular carcinoma cells has been shown to induce G0/G1 cell cycle arrest via upregulation of p21 and downregulation of cyclin D1 and CDK4, highlighting a potential role in promoting cell proliferation,52 which mirrors our observation that AFP-KO iHLCs failed to suppress p21 expression in vivo.