CCND1 and hepatocellular carcinoma: Thus, nontransformed cells as well as HNF4α-positive and -negative HCC cells can exhibit 24-h rhythmicity, and in nontransformed liver cells, P1/P2-HNF4α represses the circadian expression of Myc, Ccnb1, and Ccnd1, which are involved in cell growth and proliferation.