title: Enhancement by X-ray irradiation of target cell susceptibility to natural killer cells.
abstract: The in vitro effect of X-ray irradiation on tumor cell susceptibility to lysis by natural killer (NK) cells was studied in human systems. When relatively NK-resistant T24 bladder transitional carcinoma cells were irradiated with X-rays and cultured for 18 h, they showed increased sensitivity to lysis by blood lymphocytes in a 4-h 51Cr release assay. No enhancement was seen when irradiated target cells were tested immediately after exposure to X-rays. The X-ray-induced augmentation was observed with as little as 1 Gy of irradiation, the level of which was comparable to that observed at higher doses. The doses of X-rays did not influence the viability and spontaneous release of the target cells. Treatment with mitomycin C of target cells did not change their NK sensitivity. On the other hand, irradiation with X-rays of blood lymphocytes resulted in a transient increase in NK activity at 3 h, and then the activity declined and was completely lost by 24 h. However, when irradiated lymphocytes were stimulated with interferon (IFN), they maintained the high activity against untreated T24 cells. These results suggest the possible use of relatively low doses of X-ray irradiation in combination with IFN for treatment of human cancer.
authors.affiliation: Radiation Biology Center, Kyoto University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Mizutani
authors.forename: A
authors.initials: A
authors.lastname: Uchida
authors.forename: T
authors.initials: T
authors.lastname: Fujimoto
authors.forename: M
authors.initials: M
authors.lastname: Ikenaga
authors.forename: O
authors.initials: O
authors.lastname: Yoshida
mesh_terms: D003601:Cytotoxicity Tests, Immunologic; D006801:Humans; D007370:Interferon Type I / Q000494:pharmacology; D007694:Killer Cells, Natural / Q000276:immunology / Q000528:radiation effects*; D007700:Kinetics; D008214:Lymphocytes; D016685:Mitomycin; D008937:Mitomycins / Q000494:pharmacology; D011994:Recombinant Proteins; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms / Q000276:immunology* / Q000532:radiotherapy
chemical_list: D007370:Interferon Type I; D008937:Mitomycins; D011994:Recombinant Proteins; D016685:Mitomycin