| ABSTRACT: |
|
We have employed a previously described cell-free system to assess the
ability of 27 known or suspected chemopreventive agents to alter
activation of the lung carcinogen, BP and the potent mammary carcinogen,
DBP. BP or DBP (10 uM) was incubated with DNA (300 ug/ml) in the presence
of aroclor 1254-induced rat liver microsomes, with and without
chemopreventive agents (150 uM), followed by 32P-postlabeling analysis of
purified DNA. BP treatment yielded two major adducts: BPDE-dG and a
9-OH-BP-derived adduct. Treatment with DBP produced two major and five
minor, dA- and dG-derived adducts of both anti- and
syn-DBP-11,12-diol-13,14-epoxide. Both BP adducts were reduced by greater
than or equal to 70% by ellagic acid, oltipraz, genistein, and benzyl
isothiocyanate and 40-65% by vitamin H, acetylsalicylic acid, and
beta-carotene; BPDE-dG, but not the 9-OH-BP adduct, was inhibited (60-70%)
by linoleic acid ethyl ester, biochanin A, indole-3-carboxylic acid,
vitamin D3, reduced glutathione, and alpha-tocopherol; and BPDE-dG was
inhibited (30-80%), but the 9-OH-BP adduct was enhanced (70-700%) by
chlorophyllin, curcumin, butylated hydroxytoluene (BHT), and linoleic acid
sodium; or unaffected by ten other compounds. Some of these agents tested
also inhibited DBP-DNA adducts: greater than or equal to 75% inhibition by
ellagic acid, chlorophyllin, oltipraz, genistein, and benzyl
isothiocyanate; 25-40% inhibition by curcumin, BHT, and linoleic acid
sodium; or unaffected by N-acetylcysteine. Consistent with our previous
observation that ellagic acid inhibits anti-BPDE-dG formation, this agent
also inhibited the formation of anti-DBP diolepoxide-DNA adducts. These
data support the use of this cell-free system to study mechanism and
efficacy of chemopreventive agents. |