Response of plateau-phase C3H 10T1/2 cells to radiation and concurrent administration of bleomycin.
The mode and extent of interaction between bleomycin and radiation were assessed in contact-inhibited cultures of C3H 10T1/2 cells, which in confluent monolayers display a low turnover rate and behave more like late-responding normal tissues in vivo with respect to response to fractionated radiotherapy (i.e., having a low alpha/beta value). Plateau-phase C3H 10T1/2 cultures were exposed to gamma rays delivered in 1, 2, 5, or 10 fractions. The radiation doses administered ranged from 2 Gy in one exposure to 26 Gy in 10 fractions. Half of the cultures were also treated with 1 micrograms/ml of bleomycin for 5 days during which radiation was also given. It was found that 1 micrograms/ml of bleomycin sterilized approximately 40% of the C3H 10T1/2 cells in the cultures. The radiation dose-survival curves of various fractionation schedules (1, 2, 5, and 10 fractions) plus bleomycin were displaced downward (i.e., to lower survival levels) but not modified in shape. The alpha/beta ratios, parameters of the linear-quadratic model of cell survival, were 2.6 (2.2-3.1) and 2.4 (1.8-3.1) Gy for radiation only and radiation plus bleomycin, respectively. This observation indicates that the effect of combining irradiation and bleomycin on C3H 10T1/2 cells in monolayers was additive.
Jiang
G L
GL
Division of Radiotherapy, University of Texas M. D. Anderson Cancer Center, Houston 77030.
Ang
K K
KK
Thames
H D
HD
Wong
C S
CS
Wendt
C D
CD
D000818:Animals; D001761:Bleomycin / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects*; D002588:Cesium Radioisotopes; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D051379:Mice
D002588:Cesium Radioisotopes; D001761:Bleomycin