title: Differential sensitization of human tumor cells by ara-A to X irradiation and its relationship to inherent radioresponse.
abstract: We have previously shown that pretreatment of plateau-phase cultures of human tumor cells with ara-A can markedly sensitize them to the cytotoxic effects of X irradiation; the degree of sensitization varied in two different cell lines. The present study was undertaken to determine whether variability in radiosensitization by ara-A occurs at random in human tumor cell lines or if it is related to their intrinsic radiosensitivity (human tumor radioresponse). The interaction between ara-A and X irradiation was examined in plateau-phase cultures of early-passage tumor cell lines of varying radioresponse (D0 range 0.85-3.15 Gy) subcultured immediately after irradiation to measure survival. In six of the eight cell lines studied, pretreatment with ara-A greatly enhanced the lethal effects of X irradiation in a concentration-dependent fashion. Little or no effect was observed in the two radiosensitive cell lines. When ara-A sensitization was plotted as a function of D10 or D, a linear relationship was observed. These data suggest that pretreatment with ara-A is effective in sensitizing radiation-resistant human tumor cells to the lethal effects of X rays, and that this phenomenon may be dependent upon inherent tumor cell radiosensitivity.
authors.affiliation: Laboratory of Radiobiology, Harvard School of Public Health, Boston, Massachusetts 02115.
authors.forename: W K
authors.initials: WK
authors.lastname: Dahlberg
authors.forename: J B
authors.initials: JB
authors.lastname: Little
mesh_terms: D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D066298:In Vitro Techniques; D011836:Radiation Tolerance / Q000187:drug effects* / Q000502:physiology; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000528:radiation effects*; D014740:Vidarabine / Q000494:pharmacology*
chemical_list: D014740:Vidarabine