Carcinogenicity, DNA adduct formation and K-ras activation by 7H-dibenzo[c,g]carbazole in strain A/J mouse lung.
N-Heterocyclic polynuclear aromatic hydrocarbons (NHA) are environmental pollutants formed during the combustion of organic materials. 7-H-Dibenzo[c,g]carbazole (DBC) is a potent carcinogen in lung, liver and skin. We undertook these studies to determine whether tissue specificity for DBC lung carcinogenicity in the strain A/J mouse is mirrored by formation of DBC-DNA adducts in lung tissue and whether these adducts are consistent with mutation patterns in the K-ras gene. Strain A/J mice were given a single i.p. injection of DBC at doses of 0, 5, 10, 20 or 40 mg/kg and levels of DNA adducts in the lung were monitored by 32P-postlabeling on days 1, 3, 5, 7, 14 and 21. The remaining animals were sacrificed 8 months after DBC treatment and lung tumor multiplicity and K-ras mutation patterns in the tumors were determined. The lung tumor response to DBC was dose related, with an average of 4.7 +/- 1.2 tumors/mouse at 5 mg/kg and 48.1 +/- 5.5 tumors/mouse at 40 mg/kg. As many as seven DBC-DNA adducts were observed in the lung. DNA binding levels in the lung were highest at 40 mg/kg, with maximum binding at 5-7 days. At lower dose levels the maximum binding to DNA decreased and shifted to earlier time points. The DBC-DNA adduct in the lung with the highest level of binding at all dose levels was DBC-DNA adduct 3. The majority of DBC-induced mutations in the K-ras gene in the lung were A-->T (80%) transversions in the third base of codon 61, a mutation that has not been previously observed in chemically induced lung tumors in strain A/J mice.
Warshawsky
D
D
Department of Environmental Health, University of Cincinnati, OH 45267-0056, USA.
Talaska
G
G
Jaeger
M
M
Collins
T
T
Galati
A
A
You
L
L
Stoner
G
G
D000818:Animals; D001483:Base Sequence; D002227:Carbazoles / Q000633:toxicity*; D002273:Carcinogens / Q000633:toxicity*; D004247:DNA / Q000187:drug effects / Q000378:metabolism; D018736:DNA Adducts; D011905:Genes, ras; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced; D008168:Lung / Q000187:drug effects* / Q000378:metabolism; D008175:Lung Neoplasms / Q000139:chemically induced; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D012878:Skin Neoplasms / Q000139:chemically induced
D002227:Carbazoles; D002273:Carcinogens; D018736:DNA Adducts; D004247:DNA; C013478:7H-dibenzo(c,g)carbazole