title: Enhancement of tumor cell killing in vitro by pre- and post-irradiation exposure to aclacinomycin A.
abstract: Aclacinomycin A (ACM), a potent inducer of leukemic cell differentiation, significantly enhances the radiosensitivity of a human colon tumor cell line (Clone A) when cultures are exposed to 15-nM concentrations for 3 days before irradiation. We now demonstrate that incubation with ACM after irradiation can also enhance Clone A cell killing. The maximum increase in cell killing, based on colony-forming ability, occurred when Clone A cells were exposed for 1 h to 5 microM ACM added 1 or 2 h after irradiation. The post-irradiation ACM protocol reduced the terminal slope (as reflected by D0) of the radiation cell survival curve with no change in the low-dose, shoulder region of the curve (Dq value). In contrast, for pre-irradiation treatment with ACM (15 nM, 3 days), the shoulder region of the curve was reduced with no change in the terminal slope. For pre- and post-irradiation ACM treatment the dose enhancement factors at 0.10 survival were 1.22 and 1.28, respectively. When ACM was given both before and after irradiation both the shoulder and terminal slope values decreased to produce a dose enhancement factor at a surviving fraction of 0.10 of 1.50. These data suggest that the enhanced cell killing produced by pre- and post-irradiation treatment with ACM is achieved through different mechanisms.
authors.affiliation: Department of Experimental Radiotherapy, University of Texas M.D. Anderson Cancer Center, Houston 77030.
authors.forename: C A
authors.initials: CA
authors.lastname: Bill
authors.forename: E A
authors.initials: EA
authors.lastname: Mendoza
authors.forename: E
authors.initials: E
authors.lastname: Vrdoljak
authors.forename: P J
authors.initials: PJ
authors.lastname: Tofilon
mesh_terms: D015250:Aclarubicin / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002999:Clone Cells; D003110:Colonic Neoplasms / Q000473:pathology; D005720:Gamma Rays; D006801:Humans; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000187:drug effects*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000528:radiation effects
chemical_list: D015250:Aclarubicin