title: Proteomic Analysis Reveals GMP Synthetase as p53 Repression Target in Liver Cancer.
abstract: Disruption of the tumor-suppressive p53 network is a key event in human malignancies, including primary liver cancer. In response to different types of stress, p53 mediates several antiproliferative cellular outcomes, such as cell cycle arrest, apoptosis, and senescence, by activation or repression of its target genes. Metabolic alterations initiating or being part of the p53 response have become an actively studied research area in the p53 field, with several aspects that still remain to be elucidated. Herein, we identified GMP synthetase (GMPS), a key enzyme of de novo purine biosynthesis, as an important p53 repression target using a large-scale proteomics approach. This p53-mediated repression of GMPS could be validated by immunoblotting in Sk-Hep1, HepG2, and HuH6 cells. Moreover, we found GMPS transcriptionally repressed in a p21-dependent manner and its repression maintained in the context of p53-mediated cellular senescence. More important, direct knockdown of GMPS by RNA interference resulted in reduced cell viability and was sufficient to trigger cellular senescence. Finally, by comparing murine hepatocellular carcinomas, which developed in p53 wild-type (+/+) versus p53 null (-/-) mice, we observed higher GMPS expression in the latter, supporting the in vivo relevance of our findings. We conclude that repression of GMPS by p53 through p21 is a functionally relevant part of the p53-mediated senescence program limiting tumor cell growth in liver cancer.
authors.affiliation: Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Holzer
authors.affiliation: Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Drucker
authors.affiliation: Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Roessler
authors.affiliation: Division of Translational Gastrointestinal Oncology, Department of Internal Medicine I, University of Tuebingen, Tuebingen, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Dauch
authors.affiliation: Division of Translational Gastrointestinal Oncology, Department of Internal Medicine I, University of Tuebingen, Tuebingen, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Heinzmann
authors.affiliation: Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Waldburger
authors.affiliation: Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Eiteneuer
authors.affiliation: Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: Esther
authors.initials: E
authors.lastname: Herpel
authors.affiliation: Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Breuhahn
authors.affiliation: Division of Translational Gastrointestinal Oncology, Department of Internal Medicine I, University of Tuebingen, Tuebingen, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Zender
authors.affiliation: Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Schirmacher
authors.affiliation: Leibniz-Institute on Aging-Fritz-Lipmann-Institute, Jena, Germany.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Ori
authors.affiliation: Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany; European Molecular Biology Laboratory, Structural and Computational Biology Unit, Heidelberg, Germany. Electronic address: stephan.singer@med.uni-heidelberg.de.
authors.forename: Stephan
authors.initials: S
authors.lastname: Singer
mesh_terms: D000818:Animals; D019731:Carbon-Nitrogen Ligases / Q000378:metabolism*; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D045744:Cell Line, Tumor; D016922:Cellular Senescence / Q000502:physiology*; D002853:Chromatography, Liquid; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006801:Humans; D015151:Immunoblotting; D008113:Liver Neoplasms / Q000378:metabolism*; D051379:Mice; D040901:Proteomics; D060888:Real-Time Polymerase Chain Reaction; D053719:Tandem Mass Spectrometry; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D016159:Tumor Suppressor Protein p53; D019731:Carbon-Nitrogen Ligases; C020828:GMP synthase (glutamine-hydrolyzing)