Comparative dose-response tumorigenicity studies of dibenzo[alpha,l]pyrene versus 7,12-dimethylbenz[alpha]anthracene, benzo[alpha]pyrene and two dibenzo[alpha,l]pyrene dihydrodiols in mouse skin and rat mammary gland.
Comparative studies were conducted of the tumor-initiating activity in mouse skin and carcinogenicity in rat mammary gland of dibenzo[a,l]pyrene (DB[a,l]P) versus 7,12-dimethyl-benz[a]anthracene (DMBA), the most potent recognized carcinogenic polycyclic aromatic hydrocarbon (PAH); benzo[a]pyrene (B[a]P), the most potent recognized carcinogenic environmental PAH; DB[a,l]P 8,9-dihydrodiol, the K-region dihydrodiol; and DB[a,l]P 11,12-dihydrodiol, precursor to the bay-region diolepoxide. The tumor-initiating activity of DB[a,l]P and B[a]P was compared in the skin of female SENCAR mice at doses of 300, 100 and 33.3 nmol. The mice were promoted with 12-O-tetradecanoylphorbol-13-acetate (TPA) twice-weekly for 13 weeks. DB[a,l]P at all doses induced significantly more tumors than B[a]P at the corresponding dose, with a significantly shorter latency. Subsequently, the tumor-initiating activity of DB[a,l]P was compared in the skin of female SENCAR mice to that of DMBA, B[a]P, DB[a,l]P 8,9-dihydrodiol and DB[a,l]P 11,12-dihydrodiol at doses of 100, 20 and 4 nmol. The mice were promoted with TPA twice-weekly for 24 weeks. In addition, groups of mice were initiated with 100 nmol of DB[a,l]P, DMBA, B[a]P, DB[a,l]P 8,9-dihydrodiol or DB[a,l]P 11,12-dihydrodiol and kept without promotion. This experiment showed that in the mouse skin, DB[a,l]P and DB[a,l]P 11,12-dihydrodiol displayed similar tumor-initiating activity with a response inversely proportional to the dose, presumably due to the toxicity of the compounds. At the high dose they elicited tumors earlier than DMBA, though DMBA produced a much higher tumor multiplicity. At the low dose, DMBA, DB[a,l]P and DB[a,l]P 11,12-dihydrodiol exhibited similar tumorigenicities. DB[a,l]P 8,9-dihydrodiol was a marginal tumor initiator. Once again, DB[a,l]P was by far a much stronger tumor initiator than B[a]P. Female Sprague-Dawley rats were treated with 1.0 or 0.25 mumol of DB[a,l]P, DMBA or B[a]P by intramammillary injection at eight teats. DB[a,l]P at both doses was a more potent carcinogen than DMBA at the corresponding dose in the rat mammary gland. B[a]P was a marginal mammary carcinogen, eliciting only a few fibrosarcomas. Thus, these data suggest that DB[a,l]P is the strongest PAH carcinogen ever tested.
Eppley Institute for Research in Cancer, University of Nebraska Medical Center, Omaha 68198-6805.
E L
EL
Cavalieri
S
S
Higginbotham
N V
NV
RamaKrishna
P D
PD
Devanesan
R
R
Todorovic
E G
EG
Rogan
S
S
Salmasi
D015127:9,10-Dimethyl-1,2-benzanthracene / Q000633:toxicity*; D000818:Animals; D001564:Benzo(a)pyrene / Q000633:toxicity*; D001580:Benzopyrenes / Q000633:toxicity*; D015197:Carcinogenicity Tests; D002273:Carcinogens / Q000633:toxicity*; D004101:Dihydroxydihydrobenzopyrenes / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced*; D051379:Mice; D012878:Skin Neoplasms / Q000139:chemically induced*
D001580:Benzopyrenes; D002273:Carcinogens; D004101:Dihydroxydihydrobenzopyrenes; C071370:dibenzo(a,l)pyrene 8,9-dihydrodiol; D001564:Benzo(a)pyrene; D015127:9,10-Dimethyl-1,2-benzanthracene; C071371:dibenzo(a,l)pyrene 11,12-dihydrodiol; C041517:dibenzo(a,l)pyrene