Cooperative Regulation of Normal and Neoplastic Hepatocyte Proliferation by Myc and ChREBP

By analogy to the c-Myc (Myc)/Max family of transcription factors, there also exists a “parallel” network of structurally and functionally related bHLH-ZIP proteins with certain Myc-like functions. Two closely related “Myc-like” paralogs termed Mondo A and MondoB/ChREBP (ChREBP) positively regulate gene expression in heterodimeric association with the Max-like factor Mlx. Myc is necessary to support liver cancer cell growth but not for normal hepatocyte proliferation. Here, we investigated the role for ChREBP and its relationship to Myc in these processes. Unlike Myc, ChREBP loss conferred a marked proliferative disadvantage to normal hepatocytes as did the loss of both ChREBP and Myc. In addition, hepatoblastomas (HBs) originating in myc-/-, chrebp-/- or myc-/-/chrebp-/- backgrounds grew significantly more slowly. Metabolic studies performed on livers and HBs arising in all three backgrounds showed marked differences in oxidative phosphorylation, fatty acid -oxidation (FAO) and the activity of pyruvate dehydrogenase. RNAseq of livers and HBs indicated seven distinct forms of target transcript regulation. Gene ontology analysis indicated that many transcripts de-regulated in the chrebp-/- background encode enzymes functioning in glycolysis, the TCA cycle and - and-FAO whereas those in myc-/- background encode enzymes for glycolysis, glutaminolysis and sterol biosynthesis. Transcript de-regulation in the double knockout group was similar but also included those involved in peroxisomal - and -FAO. Finally, we identified cooperative positive regulation by Myc and ChREBP of virtually all ribosomal protein genes. Our findings define the global proliferative, metabolic and transcriptional roles for the more general “Extended Myc Network” under both normal and neoplastic conditions. Total 40 samples from 8 groups, 5 repeat in each group. Group 1( wild type liver-control), Group 2 ( Myc KO Liver), Group 3 (ChREBP KO Liver), Group 4 ( Myc KO plus ChREBP KO Liver--Double KO Liver), Group 5( wild type hepatoblastomasl), Group 6 ( Myc KOhepatoblastomas), Group 7 (ChREBP KO hepatoblastomas), Group 8 ( Myc KO plus ChREBP KO hepatoblastomas--Double KO hepatoblastomas)