DNA-PK：the Major Target for Wortmannin-mediated Radiosensitization by the Inhibition of DSB Repair via NHEJ Pathway

• Published in: JOURNAL OF RADIATION RESEARCH Vol. 44; no. 2; pp. 151 - 159
• Main Authors: Hashimoto, Mitsumasa, Rao, Satish, Tokuno, Osamu, Yamamoto, Ken-Ichi, Takata, Minoru, Takeda, Shunichi, Utsumi, Hiroshi
• Format: Journal Article
• Language: English
• Published: England THE JAPAN RADIATION RESEARCH SOCIETY 01-06-2003; Oxford University Press
• Subjects: Androstadienes - pharmacology; Animals; Cells (Biology); Cells, Cultured; Chickens; Cricetinae; Cricetulus; DNA; DNA - drug effects; DNA Damage - drug effects; DNA Repair; DNA-Activated Protein Kinase; DNA-Binding Proteins; Genetic research; Humans; Mice; Mice, SCID; Nuclear Proteins; Protein-Serine-Threonine Kinases - drug effects; Proteins; Radiation-Sensitizing Agents - pharmacology; Wortmannin
• ISSN: 0449-3060
• DOI: 10.1269/jrr.44.151

The effect of wortmannin posttreatment was studied in cells derived from different species (hamster, mouse, chicken, and human) with normal and defective DNA-dependent protein kinase (DNA-PK) activity, cells with and without the ataxia telangiectasia (ATM) gene, and cells lacking other regulatory proteins involved in the DNA double-strand break (DSB) repair pathways. Clonogenic assays were used to obtain all results. Wortmannin radiosensitization was observed in Chinese hamster cells (V79-B310H , CHO-K1), mouse mammary carcinoma cells (SR-1), transformed human fibroblast (N2KYSV), chicken B lymphocyte wild-type cells (DT40), and chicken Rad54 knockout cells (Rad54-/-). However, mouse mammary carcinoma cells (SX9) with defects in the DNA-PK and chicken DNA-PK catalytic subunit (DNA-PKcs) knockout cells (DNA-PKcs-/-/-) failed to exhibit wortmannin radiosensitization. On the other hand, SCID mouse cells (SC3VA2) exposed to wortmannin exhibited significant increases in radiosensitivity, possibly because of some residual function of DNA-PKcs. Moreover, the transformed human cells derived from AT patients (AT2KYSV) and chicken ATM knockout cells (ATM-/-) showed pronounced wortmannin radiosensitization. These studies demonstrate confirm that the mechanism underlying wortmannin radiosensitization is the inhibition of DNA-PK, but not of ATM, thereby resulting in the inhibition of DSB repair via nonhomologous endjoining (NHEJ).