TUMOR-INITIATING ACTIVITY OF BENZ[C]ACRIDINE AND 12 OF ITS DERIVATIVES ON MOUSE SKIN

  • 1 January 1983
    • journal article
    • research article
    • Vol. 43  (10) , 4625-4628
Abstract
Benz[c]acridine (B[c]ACR) and 12 of its derivatives, including the 5 metabolically possible trans-dihydrodiols, the diastereomeric bay-region diol-epoxides, 2 non-bay-region diol-epoxides, and the K-region arene oxide, were tested for tumor-initiating activity on mouse skin. A single topical application of 0.4-2.5 .mu.mol of compound was followed 12 days later by twice-weekly applications of the tumor promoter 12-O-tetradecanoylphorbol-13-acetate for 25 wk. B[c]ACR was a weak tumor initiator on mouse skin, producing a 37% tumor incidence and 1.33 tumors/mouse at the 2.5 .mu.mol dose. Of the 5 metabolically possible trans-dihydrodiols of B[c]ACR, only trans-3,4-dihydroxy-3,4-dihydro-B[c]ARC had significant tumor-initiating activity. This compound was at least 6-fold more active than was the parent compound at the 3 doses tested. The diastereomeric bay-region diol-epoxides, in which the epoxide oxygen is either cis(isomer 1) or trans(isomer 2) to the benzylic hydroxyl group, each had significant tumor-initiating activity, although isomer 2 was at least 5-fold more active than was isomer 1 and had activity equal to that of it potential metabolic precursor, trans-3,4-dihydroxy-3,4-dihydro-B[c]ACR. Two non-bay-region diol-epoxides (isomer 2 of the 8,9-diol-10,11-epoxide and the 10,11-diol-8,9-epoxide) and the 5,6-arene oxide (K-region) were inactive at the doses tested. 3,4-Dihydro-B[c]ACR, the potential metabolic precursor of a bay-region tetrahydroepoxide, was the most potent tumor initiator analyzed. At an initiating dose of 0.4 .mu.mol, this compound produced a 97% tumor incidence and 7.90 tumors/mouse after 15 wk of promotion with 12-O-tetradecanoylphorbol-13-acetate. B[c]ACR, the N-12 analog of benz[a]anthracene, apparently undergoes metabolic activation to an ultimate carcinogenic metabolite via formation of a bay-region diol-epoxide, as was already demonstrated for benz[a]anthracene.