title: Control of radiosensitivity of F9 mouse teratocarcinoma cells by regulation of histone H2AX gene expression using a tetracycline turn-off system.
abstract: The mouse histone H2AX has unique COOH-terminal serine residues that are phosphorylated in response to double-strand DNA breaks introduced by ionizing radiation. This suggests that H2AX acts to maintain genomic stability. We constructed a tetracycline (tet)-directed turn-off vector and integrated it into F9 mouse teratocarcinoma cells by homologous recombination. In homozygously recombined cells, expression of the histone H2AX gene was repressed to 0.02% of the expression observed in wild-type cells by the addition of doxycycline, an analog of tet. Sensitivity of cells with repressed H2AX expression to X-irradiation was increased 1.95x, indicating that DNA repair was impaired by repression of H2AX. When we s.c. injected tet-regulated F9 cells into the flanks of mice, tumor growth was slightly suppressed by X-irradiation in H2AX-repressed tumors, whereas without X-irradiation, tumor growth did not differ by H2AX status. Thus, H2AX might be a potential molecular target for sensitizing cancer cells to radiotherapy to minimize required irradiation doses.
authors.affiliation: Department of Molecular Genetics, Graduate School of Medicine, Osaka City University, Osaka, Japan.
authors.forename: Kayo
authors.initials: K
authors.lastname: Yoshida
authors.forename: Takashi
authors.initials: T
authors.lastname: Morita
mesh_terms: D000818:Animals; D002455:Cell Division / Q000235:genetics / Q000528:radiation effects; D045744:Cell Line, Tumor; D042622:DNA Repeat Expansion; D004318:Doxycycline / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D005822:Genetic Vectors / Q000235:genetics; D006657:Histones / Q000096:biosynthesis / Q000235:genetics*; D051379:Mice; D010957:Plasmids / Q000235:genetics; D011836:Radiation Tolerance / Q000235:genetics*; D018243:Teratocarcinoma / Q000235:genetics* / Q000378:metabolism / Q000532:radiotherapy*; D013752:Tetracycline / Q000494:pharmacology; D014162:Transfection
chemical_list: D004318:Doxycycline; D006657:Histones; D013752:Tetracycline; C475961:gamma-H2AX protein, mouse