Low Dose Suppression of Neoplastic Transformation in Vitro

[摘要] This grant was to study the low dose suppression of neoplastic transformation in vitro and the shape of the dose-response curve at low doses and dose-rates of ionizing radiation. Previous findings had indicated a suppression of transformation at dose <10cGy of low-LET radiation when delivered at high dose-rate. The present study indicates that such suppression extends out to doses in excess of 100cGy when the dose (from I-125 photons) is delivered at dose-rates as low as 0.2 mGy/min and out to in excess of {approx}25cGy the highest dose studied at the very low dose-rate of 0.5 mGy/day. We also examined dose-rate effects for high energy protons (which are a low-LET radiation) and suppression was evident below {approx}10cGy for high dose-rate delivery and at least out to 50cGy for low dose-rate (20cGy/h) delivery. Finally, we also examined the effect of low doses of 1 GeV/n iron ions (a high-LET radiation) delivered at high dose-rate on transformation at low doses and found a suppression below {approx}10cGy that could be attributable to an adaptive response in bystander cells induced by the associated low-LET delta rays. These results have implications for cancer risk assessment at low doses.

[发布日期] 2012-05-01

[学科分类] 放射科、核医学、医学影像

[关键词] DELTA RAYS;DOSE RATES;DOSE-RESPONSE RELATIONSHIPS;IN VITRO;IONIZING RADIATIONS;IRON IONS;NEOPLASMS;ONCOGENIC TRANSFORMATIONS;PHOTONS;PROTONS;RADIATIONS;RISK ASSESSMENT;SHAPE;TRANSFORMATIONS Low dose low-LET radiation;cancer risk