DIBENZ[A,C]ANTHRACENE - POTENT INHIBITOR OF SKIN-TUMOR INITIATION BY 7,12-DIMETHYLBENZ[A]ANTHRACENE

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  • 1 January 1978
    • journal article
    • research article
    • Vol. 19  (3) , 477-483
Abstract
The mechanism by which the weak tumor initiator dibenz[a,c]anthracene (DB[a,c]A) inhibits the skin-tumor initiating activity of 7,12-dimethylbenz[a]anthracene (DMBA) was investigated. DB[a,c] was a potent inhibitor of DMBA initiation when given either 5 min, or l, 12 or 36 h before DMBA. Pretreatment of mice with unlabeled DB[a,c]A at either 1, 12 or 36 h before killing increased the in vitro epidermally mediated covalent binding of [3H]DMBA to DNA more than pretreatment with unlabeled DMBA at comparable times. Only when the tumor experiments were mimicked did a decrease in DMBA covalent binding to DNA in vitro occur. Some competition at the level of polycyclic hydrocarbon metabolism or at the genome level may exist between metabolites of the weak carcinogen and those of the strong carcinogen.

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