title: Suppression of natural tumor resistance by tumor promoters.
abstract: The findings of the present and other studies (4,7) show that TPA and other tumor-promoting esters suppress various in vitro manifestations of natural cell-mediated tumor resistance: (a) prevention of enhancement of macrophage cytocidal activity; (b) suppression of cytocidal capacity by activated macrophages; and (c) suppression of cytolytic activity of NK cells. Moreover, they abrogate host tumor resistance in vivo. These suppressive effects of tumor promoters on natural antitumor effector systems may constitute a fundamental mechanism in carcinogenesis.
mesh_terms: D000818:Animals; D002460:Cell Line; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D008222:Lymphokines / Q000494:pharmacology; D008262:Macrophage Activation; D016215:Macrophage-Activating Factors; D008264:Macrophages / Q000276:immunology*; D009374:Neoplasms, Experimental / Q000276:immunology*; D010704:Phorbols / Q000494:pharmacology*; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D008222:Lymphokines; D016215:Macrophage-Activating Factors; D010704:Phorbols; D013755:Tetradecanoylphorbol Acetate