title: Hypoxia suppresses chemotherapeutic drug-induced p53 Serine 46 phosphorylation by triggering HIPK2 degradation.
abstract: The molecular mechanisms by which hypoxic tumor cells escape radio- and chemotherapy are largely unclear. Homeodomain-interacting protein kinase 2 (HIPK2) drives the apoptotic program in response to DNA-damaging chemotherapeutic drug treatment by phosphorylating the tumor suppressor protein p53 at Ser46. HIPK2 is kept inactive in unstressed cells through ubiquitination and degradation facilitated by the ubiquitin ligases WSB1 and Siah1. Here, we demonstrate that HIPK2 is degraded during hypoxia in a proteasome-dependent and partially Siah1-dependent fashion. Concordantly, hypoxic tumor cells show an impaired p53 Ser46 phosphorylation in response to treatment with the chemotherapeutic Adriamycin. Remarkably, proteasome-inhibition rescues HIPK2 expression in hypoxic hepatoma cells and restores p53 Ser46 phosphorylation and caspase activity after Adriamycin treatment. Our findings suggest a molecular mechanism by which hypoxic cancer cells can escape chemotherapeutic drug treatment and suggest proteasome-inhibition as a promising approach to sensitise hypoxic cancer cells to therapy.
authors.affiliation: German Cancer Research Center, Cellular Senescence Group, DKFZ-ZMBH Alliance, Heidelberg, Germany.
authors.forename: Jutta
authors.initials: J
authors.lastname: Moehlenbrink
authors.forename: Nadja
authors.initials: N
authors.lastname: Bitomsky
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Hofmann
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D015687:Cell Hypoxia / Q000187:drug effects; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000494:pharmacology*; D061988:Proteasome Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012694:Serine / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D000098563:Seven in Absentia Proteins
chemical_list: D002352:Carrier Proteins; D009687:Nuclear Proteins; D061988:Proteasome Inhibitors; D016159:Tumor Suppressor Protein p53; D012694:Serine; D004317:Doxorubicin; D044767:Ubiquitin-Protein Ligases; D000098563:Seven in Absentia Proteins; C115114:HIPK2 protein, human; D017346:Protein Serine-Threonine Kinases; D046988:Proteasome Endopeptidase Complex