The overall objective of the currently funded grant was to elucidate the mechanism of differential efficacy of garlic organosulfides (OSCs) against benzo(a)pyrene (BP)-induced cancer in mice. We fond that differential anti-cancer efficacy of OSCs against forestomach cancer is largely due to differences in their inductive effects on forestomach and hepatic Pi class glutathione transferase (mGSTP1-1). In contrast to forestomach, we found an apparent correlation in lung between anti-cancer efficacy of OSCs and their effects on pulmonary mGSTP1-1. This indicates that, unlike forestomach, induction of mGSTP1-1 alone cannot account for the majority of OSC chemoprotection in the lung. To elucidate the additional mechanisms contributing to OSC chemoprotection in the lung, we will characterize a process that is proximate to tumorigenesis, namely DNA modification, by determining the effects of OSCs (a) on kinetics of antiBPDE-DNA adduct formation and decay in lung, liver, and forestomach of mice, and (b) formation of anti-BPDE adducts at guanine in codons 157, 248 and 273 of P53 in cell culture as well as in mice (aim 1). Damage to DNA is intimately linked to another novel topic to be investigated under the present application, i.e. the role of biodistribution of GSH conjugate of anti-BPDE (BPD-SG) in BP-linked cancer. The rationale for these studies stems from our recent unpublished studies, which reveal that purified BDP-SG can form adduct with DNA in vitro . Therefore, the tissue distribution and transport of BPD-SG are relevant to tumorigenesis. Consequently, we will characterize the transporter responsible for transport of BPD-SG, and determine the effects of the OSCs on its/their expression. In addition, we will determine the effects of the OSCs on biodistribution of anti-BPDE and its conjugated metabolites (aim 2). The above novel aspects of OSC function may be especially relevant to lung tumorigenicity. At the same time, we will continue and extend our previous work on forestomach where the pertinent effect of OSCs is mGSTP1-1 induction. Here, we will focus our studies on the mechanisms of OSC-mediated induction of mGSTP1-1 using two complementary approaches: determining the structural features of OSCs necessary for induction (aim 3), and characterizing the requisite elements in the mGSTP1-gene (aim 4). In the long-term, these studies may be beneficial not only in identifying most active natural OSC, but also in the synthesis of OSC analogues that retain biological activity without having properties that limit their usefulness as chemoprotective agents. Insights gained from these studies should help in devising practical dietary recommendation for humans.
