DNA CROSS-LINKING AND CYTO-TOXICITY IN NORMAL AND TRANSFORMED HUMAN-CELLS TREATED INVITRO WITH 8-CARBAMOYL-3-(2-CHLOROETHYL)IMIDAZO[5,1-D]-1,2,3,5-TETRAZIN-4(3H)-ONE

  • 1 January 1984
    • journal article
    • research article
    • Vol. 44  (5) , 1772-1775
Abstract
Normal [fibroblast] (IMR-90) and SV40-transformed (VA-13) human embryo cells were treated with 8-carbamoyl-3-(2-chloroethyl)imidazo[5,1-d]-1,2,3,5-tetrazin-4(3H)-one (M and B 39565) and the effects of the drug on cell viability and cellular DNA integrity were studied. The effects of M and B 39655 were compared with one of its potential decomposition products 5-[3-(2-chloroethyl)triazen-1-yl]imidazole-4-carboxamide (MCTIC). M and B 396565 and MCTIC were 5.sbd.6-fold more toxic to VA-13 cells than to IMR-90 cells for drug concentrations which produced a 2-log cell kill, as measured by colony-forming assays. Using alkaline elution analysis, VA-13 cells exhibited concentration-dependent DNA interstrand cross-link formation. In IMR-90 cells, little or no interstrand cross-link formation was detected. The DNA interstrand cross-link formation in VA-13 cells was found to peak 12 h after drug removal. A linear correlation between DNA interstrand cross-link formation and log cell kill was observed in VA-13 cells but not in IMR-90 cells. DNA-protein cross-link formation was comparable in both cell lines for each drug, suggesting that drug penetration and intracellular drug reactivity were similar. Initial chemical decomposition studies suggest that both M and B 39565 and MCTIC may produce a chloroethyldiazo species. This species has been implicated in the formation of chloroethyl-DNA adducts which convert to DNA interstrand cross-links in mammalian cells treated with chloroethylnitrosoureas. DNa interstrand cross-link formation may be a common mechanism for the in vitro cytotoxicity of M and B 39565 and MCTIC.