EFFECT OF TIME AND DURATION OF EXPOSURE TO 12-O-TETRADECANOYLPHORBOL-13-ACETATE ON X-RAY TRANSFORMATION OF C3H 10T1/2 CELLS

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  • 1 January 1980
    • journal article
    • research article
    • Vol. 40  (6) , 1915-1920
Abstract
The tumor-promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) enhances transformation induced by low doses of X-rays. TPA exerts its effect primarily on actively proliferating [mouse embryonic fibroblast] cells and has little promoting effect once the cells have reached confluency. However, previously irradiated cells seeded at low density, allowed to reach confluency and then reseeded at low density maintain the capacity to respond to TPA treatment during this 2nd round of proliferation. As in vivo, TPA is effective even when treatment begins a long time after exposure to the initiating agent. The enhancement of expression of X-ray transformation by TPA is not due to a simple stimulation of cell proliferation, nor does it result primarily from the conversion of premutational lesions in DNA to mutations. The promotional effects of TPA are probably not related to an effect on a DNA repair process.