title: Roscovitine-activated HIP2 kinase induces phosphorylation of wt p53 at Ser-46 in human MCF-7 breast cancer cells.
abstract: Human MCF-7 breast cancer cells are relatively resistant to conventional chemotherapy due to the lack of caspase-3 activity. We reported recently that roscovitine (ROSC), a potent cyclin-dependent kinase 2 inhibitor, arrests human MCF-7 breast cancer cells in the G(2) phase of the cell cycle and concomitantly induces apoptosis. Exposure of MCF-7 cells to ROSC also strongly activates the wt p53 tumor suppressor protein in a time- and dose-dependent manner. The p53 level increased despite upregulation of Hdm-2 protein and was attributable to the site-specific phosphorylation at Ser-46. The p53 protein phosphorylated at serine 46 causes the up-regulation of the p53AIP1 protein, a component of mitochondria. In the present study we identified the pathway mediating ROSC-induced p53 activation. Exposure of MCF-7 cells to ROSC activated homeodomain-intereacting protein kinase-2 (HIPK2). The overexpression of wild-type but not kinase inactive HIPK2 increased the basal and ROSC-induced level of p53 phosphorylation at Ser-46 and strongly enhanced the rate of apoptosis in cells exposed to ROSC. We show that HIPK2 is activated by ROSC and mediates ROSC-induced P-Ser-46-p53, thereby stabilizing wt p53 and increasing the efficacy of drug-induced apoptosis in MCF-7 cells. These results identify HIPK2 as a component of the ROSC-induced signaling pathway leading to the stabilization and activation of wt p53 protein.
authors.affiliation: Cell Cycle Regulation Group, Division: Institute of Cancer Research, Department of Medicine I, Medical University of Vienna, Borschkegasse 8 a, A-1090 Vienna, Austria. jozefa.gadek-wesierski@meduniwien.ac.at
authors.forename: Józefa
authors.initials: J
authors.lastname: Wesierska-Gadek
authors.forename: M Lienhard
authors.initials: ML
authors.lastname: Schmitz
authors.forename: Carmen
authors.initials: C
authors.lastname: Ranftler
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D015151:Immunoblotting; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011687:Purines / Q000494:pharmacology*; D000077546:Roscovitine; D012694:Serine / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D011687:Purines; D016159:Tumor Suppressor Protein p53; D000077546:Roscovitine; D012694:Serine; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D018844:Cyclin-Dependent Kinases