title: Differential p53-dependent mechanism of radiosensitization in vitro and in vivo by the protein kinase C-specific inhibitor PKC412.
abstract: The cellular response to ionizing radiation is governed by the DNA-damage recognition process but is also modulated by cytoplasmic signal transduction cascades that are part of the cellular stress response. Growth-promoting protein kinase C activity antagonizes irradiation-induced cell death, and, therefore, protein kinase C inhibitors might be potent radiosensitizers. The antiproliferative and radiosensitizing effect of the novel N-benzoylated staurosporine analogue PKC412 was tested in vitro against genetically defined p53-wild type (+/+) and p53-deficient (-/-) murine fibrosarcoma cells and in vivo against radioresistant p53-/- murine fibrosarcoma and human colon adenocarcinoma tumor xenograft (SW480, p53-mutated). PKC412 sensitized both p53+/+ and p53-/- tumor cells in vitro and in vivo for treatment with ionizing radiation but with a different mechanism of radiosensitization depending on the p53 status. In p53+/+, cells combined treatment with PKC412 and ionizing radiation drastically induced apoptotic cell death, whereas no apoptosis induction could be observed in p53-deficient cells in vitro and in histological tumor sections. Combined treatment resulted in an increased G2 cell cycle distribution in p53-/- cells at PKC412 concentrations that did not alter cell cycle distribution when applied alone. In vivo, a minimal treatment regimen during 4 consecutive days of PKC412 (4 x 100 mg/kg) in combination with ionizing radiation (4 x 3 Gy) exerted a substantial tumor growth delay for both p53-disfunctional tumor xenografts and showed that the clinically relevant protein kinase C inhibitor PKC412 is a promising new radiosensitizer with a potentially broad therapeutic window.
authors.affiliation: Department of Radiation Oncology, University Hospital Zurich, Switzerland.
authors.forename: K
authors.initials: K
authors.lastname: Zaugg
authors.forename: S
authors.initials: S
authors.lastname: Rocha
authors.forename: H
authors.initials: H
authors.lastname: Resch
authors.forename: I
authors.initials: I
authors.lastname: Hegyi
authors.forename: C
authors.initials: C
authors.lastname: Oehler
authors.forename: C
authors.initials: C
authors.lastname: Glanzmann
authors.forename: D
authors.initials: D
authors.lastname: Fabbro
authors.forename: S
authors.initials: S
authors.lastname: Bodis
authors.forename: M
authors.initials: M
authors.lastname: Pruschy
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002478:Cells, Cultured; D003131:Combined Modality Therapy; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005838:Genotype; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D019311:Staurosporine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000528:radiation effects; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000502:physiology*; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D016159:Tumor Suppressor Protein p53; D011493:Protein Kinase C; D019311:Staurosporine; C059539:midostaurin