BMAL1 and neoplasm: In addition, the heterogenous down-regulation of BMAL1 across individual HCC cell lines and tumor tissues could be partially attributed to the variability in the expression of P2 isoform of hepatocyte nuclear factor 4 alpha (HNF4α), which has been shown to be over-expressed in HCC cells and represses the expression of BMAL1 32, 33.