title: MYC activates stem-like cell potential in hepatocarcinoma by a p53-dependent mechanism.
abstract: Activation of c-MYC is an oncogenic hallmark of many cancers, including liver cancer, and is associated with a variety of adverse prognostic characteristics. Despite a causative role during malignant transformation and progression in hepatocarcinogenesis, consequences of c-MYC activation for the biology of hepatic cancer stem cells (CSC) are undefined. Here, distinct levels of c-MYC overexpression were established by using two dose-dependent tetracycline-inducible systems in four hepatoma cell lines with different p53 mutational status. The CSCs were evaluated using side population (SP) approach as well as standard in vitro and in vivo assays. Functional repression of p53 was achieved by lentiviral shRNA transduction. The results show that c-MYC expression levels have a differential impact on liver CSC characteristics. At low levels, c-MYC activation led to increased proliferation and enhanced CSC properties including activation of reprogramming transcription factors and CSC marker expression (e.g., NANOG, OCT4, and EpCAM), expansion of SP, and acceleration of tumor growth upon subcutaneous transplantation into immunocompromised mice. However, when exceeding a threshold level, c-MYC induced a proapoptotic program and loss of CSC potential both in vitro and in vivo. Mechanistically, c-MYC-induced self-renewal capacity of liver cancer cells was exerted in a p53-dependent manner. Low c-MYC activation increased spheroid formation in p53-deficient tumor cells, whereas p53-dependent effects were blunted in the absence of c-MYC overexpression. Together, our results confirm the role of c-MYC as a master regulator during hepatocarcinogenesis and establish a new gatekeeper role for p53 in repressing c-MYC-induced CSC phenotype in liver cancer cells.
authors.affiliation: Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Akita
authors.affiliation: Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland. Department of Medicine I, Johannes Gutenberg University, Mainz, Germany.
authors.forename: Jens U
authors.initials: JU
authors.lastname: Marquardt
authors.affiliation: Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland.
authors.forename: Marian E
authors.initials: ME
authors.lastname: Durkin
authors.affiliation: Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland.
authors.forename: Mitsuteru
authors.initials: M
authors.lastname: Kitade
authors.affiliation: Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland.
authors.forename: Daekwan
authors.initials: D
authors.lastname: Seo
authors.affiliation: Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Conner
authors.affiliation: Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland. Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Jesper B
authors.initials: JB
authors.lastname: Andersen
authors.affiliation: Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland.
authors.forename: Valentina M
authors.initials: VM
authors.lastname: Factor
authors.affiliation: Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland. snorri_thorgeirsson@nih.gov.
authors.forename: Snorri S
authors.initials: SS
authors.lastname: Thorgeirsson
mesh_terms: D000818:Animals; D063646:Carcinogenesis / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000473:pathology; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D014411:Neoplastic Stem Cells / Q000502:physiology*; D010641:Phenotype; D016271:Proto-Oncogene Proteins c-myc / Q000502:physiology*; D047368:Tumor Burden; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: C489427:MYC protein, human; D016271:Proto-Oncogene Proteins c-myc; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53