RADIATION-INDUCED NEOPLASTIC TRANSFORMATION OF STATIONARY-PHASE C3H 10T1/2 CELLS IN RESPONSE TO DIFFERENT DOSE-RATES AND TO POSTIRRADIATIONTREATMENT WITH TUMOR PROMOTER/
A. Kolman et M. Harmsringdahl, RADIATION-INDUCED NEOPLASTIC TRANSFORMATION OF STATIONARY-PHASE C3H 10T1/2 CELLS IN RESPONSE TO DIFFERENT DOSE-RATES AND TO POSTIRRADIATIONTREATMENT WITH TUMOR PROMOTER/, Chemico-biological interactions, 101(1), 1996, pp. 59-69
The induction of neoplastic transformation by exposure to high (HDR, 0
.66 Gy/min) or very low (LDR, 4.8 x 10(-4) Gy/min) dose rates of Cs-13
7 gamma-rays was studied in C3W/10T1/2 mouse embryo fibroblasts. Cells
in stationary phase were exposed in the dose range 1-6 Gy in combinat
ion with a post-irradiation treatment with the tumor promoter, 12-O-te
tradecanoylphorbol-13-acetate (TPA). The post-irradiation treatment wi
th TPA during 6 weeks of transformation assay did not induce any notab
le increase in the slope of the dose-response curves for transformatio
n frequency, compared to the conditions without TPA treatment. The lac
k of an enhancing TPA effect at both dose rates applied in this study
may be related to the fact that the cells were irradiated in the stati
onary growth phase. Thus, the results differ from those generally obta
ined when exponentially growing cells are exposed to gamma-rays and af
terwards treated with TPA in the transformation assay. Earlier studies
of exponentially growing C3H/10T1/2 cells exposed to different dose r
ates show a significantly higher transformation frequency for high dos
e rate. This study, using stationary phase cells, also shows that the
slopes of dose response curves for transformed foci were somewhat high
er (about 1.5-fold) for HDR exposure compared with LDR exposure. Howev
er, the difference was not statistically significant.