Comparison of mutagenesis and malignant transformation by dihydrodiols from benz[a]anthracene and 7,12-dimethylbenz[a]anthracene

Abstract

Summary.-Five dihydrodiols derived from benz [a]anthracene (BA) and 4 dihydrodiols derived from 7,12-dimethylbenz [a]anthracene (DMBA) have been tested, together with the parent hydrocarbons, for their abilities to induce mutations to 8-azaguanine resistance in V79 Chinese hamster cells and malignant transformation in M2 mouse fibroblasts. The syn-and anti-isomers of benzLa]anthracene 8,9-diol 10,11-oxide were also tested for biological activity in these two systems. The non-Kregion 1,2-and 3,4-dihydrodiols of BA induced mutations but the non-K-region 8,9-dihydrodiol and the K-region 5,6-dihydrodiol were inactive as mutagens; none of these BA diols transformed M2 mouse fibroblasts. The 3,4-and the 8,9-dihydrodiols derived from 7,12-dimethylbenz[a]anthracene induced mutations in V79 cells and malignant transformation in M2 mouse fibroblasts and both were more active than the hydrocarbon itself. The K-region 5,6-dihydrodiol and the non-K-region 10,11-dihydrodiol of DMBA were inactive in both test systems. The results are not inconsistent with other data suggesting that the metabolic activation of both BA and DMBA occurs through conversion of the respective 3,4-dihydrodiols into the related vicinal diol-epoxides, although other dihydrodiols may also be involved in vivo. Both the BA diol-epoxides tested were mutagenic, but although the anti-isomer transformed M2 fibroblasts, the syn-isomer was inactive.

Chemical Carcinogen (Hydrazine et al.) Induced Carcinogenesis of Human Diploid Cells in Vitro

“…Earlier reports from our laboratory have shown that significant uptake of BP in the cytoplasm of human neonatal foreskin (HNF) cells in culture is observed at 12 hours; Cunder these conditions, BP has been shown to bind to a cytoplasmic protein complex (12). Subsequently, optimum accumulation in the nucleus is observed at 24 hours.…”

“…A major portion of the PNH (90%) was found bound to the cytoplasmic protein complex and eventually transported to the nucleus as unmetabolized BP (12). In addition, we found EG-3 H]BP bound to an acid extractable, non-histone, nuclear protein in the low passage cells, 24 hours after carcinogen treatment (J. Oldham, R. Tejwani and G.E.…”

“…The cell populations were serally passaged at a 1:10 split ratio into the selection digested to release the modified deoxyribonucleosides which medium. After 16 PDL, the cell populations were seeded into soft agar as were separated by chromatography on columns of Sephadex previously described (12,20). The soft agar cultures were incubated at 37*C in LH-20.…”

“…At 24 hours, 48 hours, 72 hours and 96 hours following initiation of LG-SH)BP treatment, the cells were harvested. The cytoplasmic and nuclear fractions were prepared as described earlier (12). The extracellular medium samples were also removed at these time intervals.…”

“…We have previously reported (12), that uptake of LG-3 H]BP by low passage HNF cells in culture is followed by binding to a cytoplasmic protein complex and transport to the nucleus within 24 hours. A major portion of the PNH (90%) was found bound to the cytoplasmic protein complex and eventually transported to the nucleus as unmetabolized BP (12).…”