Out of Field Cancer Risk in Mice Following Exposure to a Clinical Proton Beam

(37 C, 5% CO2) for 7 days before being assayed for survival using a standard clonogenic assay. Results: Data indicated that both miso and 10mM genistein treatments resulted in a reduction in PC3 cell colony number of w20%, suggesting a marked growth inhibitory action for these compounds. Treatment with 30mM genistein enhanced PC3 cell growth inhibition even more substantially, resulting in an 85% reduction in cell colony number compared to untreated controls. Additionally, data from these studies suggested that both miso and genistein continued to exert their growth inhibitory effect on the PC3 cells over a range of radiation exposures up to 300cGy. However, a differential response was seen between the misotreated and 10mM genistein-treated radiation cell survival curves and the 30mM genistein-treated radiation cell survival curve. Specifically, both the miso and 10mM genistein treatments interacted with radiation treatments in an additive manner, resulting in enhanced tumor cell kill, but producing radiation cell survival curves whose shape was almost identical to the untreated irradiated control. In contrast, the reduction in colony number in PC3 cells treated with 30mM genistein plus radiation resulted in a highly supra-additive reduction in colony number, especially at doses greater than 50cGy, thereby, producing a markedly steeper radiation cell survival curve than observed for the untreated irradiated control. Conclusions: Data suggest that administration of either miso or genistein may potentiate radiation-induced prostate tumor cell kill. This is particularly true when combining higher doses of genistein (30mM) with radiation, where synergistic cell kill appears to occur. These results may have consequence as a way to improve the outcome of radiation therapy regimens for prostate cancer patients. Author Disclosure: J. Sattler: None. C.R. Kempf: None. R.M. Johnke: None.