The mechanism of differential efficacies of
diallyl sulfide (
DAS),
diallyl disulfide (DADS),
diallyl trisulfide (DATS),
dipropyl sulfide (DPS) and
dipropyl disulfide (DPDS) in preventing
benzo(a)pyrene (BP)-induced
cancer in mice has been investigated by determining their effects on the
enzymes of BP activation/inactivation pathways. With the exception of DATS, treatment of mice with other organosulfides (OSCs) caused a small but significant increase (37-44%) in hepatic
ethoxyresorufin O-deethylase (
EROD) activity. However, the forestomach
EROD activity did not differ significantly between control and treated groups. Only
DAS treatment caused a modest but statistically significant reduction (about 25%) in pulmonary
EROD activity. These results suggest that while reduction of
EROD activity may, at least in part, contribute to the
DAS-mediated inhibition of BP-induced
lung cancer,
anticarcinogenic effects of OSCs against BP-induced forestomach
carcinogenesis seems to be independent of this mechanism. Treatment of mice with
DAS, DADS and DATS resulted in a significant increase, as compared with control, in both hepatic (3.0-, 3.2- and 4.4-fold, respectively) and forestomach (1.5-, 2.7- and 2.7-fold, respectively)
glutathione transferase (GST) activity toward anti-7beta,8alpha-dihydroxy-9alpha,10alpha-oxy-7,8,9,10-tetrahydrobenzo(a)pyrene (anti-
BPDE), which is the ultimate
carcinogen of BP. The pulmonary GST activity was not increased by any of the OSCs. Even though
epoxide hydrolase (EH) activity was differentially altered by these OSCs, a correlation between chemopreventive efficacy of OSCs and their effects on EH activity was not apparent. The results of the present study suggest that differences in the ability of OSCs to modulate GST activity toward anti-
BPDE may, at least in part, account for their differential chemopreventive efficacy against BP-induced
cancer in mice.