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An important stage in tumorigenesis is the ability of a precancerous cell to escape natural anticancer signals imposed on it by neighboring cells and its microenvironment. We have previously characterized a system of intercellular induction of apoptosis whereby nontransformed cells selectively remove transformed cells from coculture via cytokine and reactive oxygen/nitrogen species (ROS/RNS) signaling. We report that irradiation of nontransformed cells with low doses of either high linear energy transfer (LET) alpha-particles or low-LET gamma-rays leads to stimulation of intercellular induction of apoptosis. The use of scavengers and inhibitors confirms the involvement of ROS/RNS signaling and of the importance of transformed cell NADPH oxidase in the selectivity of the system. Doses as low as 2-mGy gamma-rays and 0.29-mGy alpha-particles were sufficient to produce an observable increase in transformed cell apoptosis. This radiation-stimulated effect saturates at very low doses (50 mGy for gamma-rays and 25 mGy for alpha-particles). The use of transforming growth factor-beta (TGF-beta) neutralizing antibody confirms a role for the cytokine in the radiation-induced signaling. The system may represent a natural anticancer mechanism stimulated by extremely low doses of ionizing radiation.

Original publication

DOI

10.1158/0008-5472.CAN-06-2985

Type

Journal article

Journal

Cancer Res

Publication Date

01/02/2007

Volume

67

Pages

1246 - 1253

Keywords

Alpha Particles, Animals, Antibodies, Apoptosis, Cell Line, Transformed, Cell Transformation, Neoplastic, Dose-Response Relationship, Radiation, Fibroblasts, Gamma Rays, NADPH Oxidases, Precancerous Conditions, Rats, Reactive Nitrogen Species, Reactive Oxygen Species, Signal Transduction, Transforming Growth Factor beta