title: DNA-Dependent Protein Kinase As Molecular Target for Radiosensitization of Neuroblastoma Cells.
abstract: Tumor cells might resist therapy with ionizing radiation (IR) by non-homologous end-joining (NHEJ) of IR-induced double-strand breaks. One of the key players in NHEJ is DNA-dependent protein kinase (DNA-PK). The catalytic subunit of DNA-PK, i.e. DNA-PKcs, can be inhibited with the small-molecule inhibitor NU7026. In the current study, the in vitro potential of NU7026 to radiosensitize neuroblastoma cells was investigated. DNA-PKcs is encoded by the PRKDC (protein kinase, DNA-activated, catalytic polypeptide) gene. We showed that PRKDC levels were enhanced in neuroblastoma patients and correlated with a more advanced tumor stage and poor prognosis, making DNA-PKcs an interesting target for radiosensitization of neuroblastoma tumors. Optimal dose finding for combination treatment with NU7026 and IR was performed using NGP cells. One hour pre-treatment with 10 μM NU7026 synergistically sensitized NGP cells to 0.63 Gy IR. Radiosensitizing effects of NU7026 increased in time, with maximum effects observed from 96 h after IR-exposure on. Combined treatment of NGP cells with 10 μM NU7026 and 0.63 Gy IR resulted in apoptosis, while no apoptotic response was observed for either of the therapies alone. Inhibition of IR-induced DNA-PK activation by NU7026 confirmed the capability of NGP cells to, at least partially, resist IR by NHEJ. NU7026 also synergistically radiosensitized other neuroblastoma cell lines, while no synergistic effect was observed for low DNA-PKcs-expressing non-cancerous fibroblasts. Results obtained for NU7026 were confirmed by PRKDC knockdown in NGP cells. Taken together, the current study shows that DNA-PKcs is a promising target for neuroblastoma radiosensitization.
authors.affiliation: Department of Oncogenomics, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: M Emmy M
authors.initials: ME
authors.lastname: Dolman
authors.affiliation: Department of Oncogenomics, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Ida
authors.initials: I
authors.lastname: van der Ploeg
authors.affiliation: Department of Oncogenomics, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Jan
authors.initials: J
authors.lastname: Koster
authors.affiliation: Department of Oncogenomics, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Laurel Tabe
authors.initials: LT
authors.lastname: Bate-Eya
authors.affiliation: Department of Oncogenomics, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Rogier
authors.initials: R
authors.lastname: Versteeg
authors.affiliation: Department of Pediatric Oncology, Emma Kinderziekenhuis, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Huib N
authors.initials: HN
authors.lastname: Caron
authors.affiliation: Department of Oncogenomics, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Molenaar
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D002867:Chromones / Q000494:pharmacology; D004249:DNA Damage / Q000187:drug effects / Q000235:genetics; D059766:DNA End-Joining Repair / Q000187:drug effects / Q000235:genetics; D051747:DNA-Activated Protein Kinase / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D009025:Morpholines / Q000494:pharmacology; D009447:Neuroblastoma / Q000188:drug therapy / Q000378:metabolism* / Q000532:radiotherapy; D009687:Nuclear Proteins / Q000378:metabolism; D011836:Radiation Tolerance / Q000235:genetics; D011839:Radiation, Ionizing; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*
chemical_list: C479235:2-(morpholin-4-yl)benzo(h)chromen-4-one; D002867:Chromones; D004268:DNA-Binding Proteins; D009025:Morpholines; D009687:Nuclear Proteins; D011838:Radiation-Sensitizing Agents; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human