title: Cell cycle-dependent intervention by benzamide of carcinogen-induced neoplastic transformation and in vitro poly(ADP-ribosyl)ation of nuclear proteins in human fibroblasts.
abstract: Human fibroblasts were subjected to nutritionally induced G1 block, followed by release and subsequent entry into S phase, and exposed to nontoxic concentrations of carcinogens in early S phase. Cell transformation occurred as determined by early morphologic cell alterations, anchorage-independent colony formation, cell invasiveness, and augmentation of Ab 376 human malignancy-specific cell-surface antigenic determinant. Methylazoxymethanol acetate was the most potent transforming agent at doses that were negative in toxicity tests. Benzamide (10 microM intracellular concentration), a specific inhibitor of poly(ADP-ribose) polymerase, prevented transformation in a cell cycle-specific manner, maximal prevention coinciding with early S phase, also characteristic of maximal susceptibility to transformation. Neither an interference of carcinogen deoxyguanosine nucleoside adduct formation nor a chemical reaction between benzamide and carcinogens was detected. Methylazoxymethanol acetate at transforming but nontoxic dose partially inhibited poly(ADP-ribosyl)ation to about the same extent as benzamide. However, simultaneous exposure of cells to both agents in early S phase, resulting in the prevention of transformation, augmented poly(ADP-ribosyl)ation above the controls. Enzymatic activities ran parallel with the formation of DNA-associating polymer-nonhistone protein adducts that are assumed to regulate the physiological function of chromatin at the structural level.
mesh_terms: D000951:Antigens, Neoplasm / Q000032:analysis; D001549:Benzamides / Q000378:metabolism / Q000494:pharmacology*; D002273:Carcinogens / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000187:drug effects*; D000939:Epitopes / Q000032:analysis; D005347:Fibroblasts / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007700:Kinetics; D009698:Nucleoproteins / Q000378:metabolism*; D009702:Nucleoside Diphosphate Sugars / Q000378:metabolism*; D011064:Poly Adenosine Diphosphate Ribose / Q000378:metabolism*
chemical_list: D000951:Antigens, Neoplasm; D001549:Benzamides; D002273:Carcinogens; D000939:Epitopes; D009698:Nucleoproteins; D009702:Nucleoside Diphosphate Sugars; D011064:Poly Adenosine Diphosphate Ribose; C037689:benzamide