Many human cancers that are widely prevalent today can be prevented through modifications in life-styles, of which diet appears to be an important agent. Several dietary constituents modulate the process of carcinogenesis and prevent genotoxicity. Many plant constituents including turmeric appear to be potent antimutagens and antioxidants. Therefore the modulatory effects of turmeric and curcumin on the levels of benzo[a]pyrene induced DNA adducts in the livers of rats were studied by the newly developed 32P-postlabelling assay method. Turmeric when fed at 0.1, 0.5 and 3% and the active principle of turmeric (curcumin) when fed at a level of 0.03% in the diet for 4 weeks significantly reduced the level of BP-DNA adducts including the major adduct dG-N2-BP, formed within 24 h in response to a single i.p. injection of benzo[a]pyrene. The significance of these effects in terms of the potential anticarcinogenic effects of turmeric is discussed. Further, these results strengthen the various other biological effects of turmeric which have direct relevance to anticarcinogenesis and chemoprevention.

Tobacco and its combustion products contain several known or potential human carcinogens and studies are now beginning to emerge for detecting DNA and protein adducts in tobacco users. A highly sensitive 32P-adduct assay, capable of measuring a wide spectra of aromatic and/or hydrophobic DNA adducts, was used to evaluate tobacco use-related adducts in human oral mucosal cells. Two volunteer groups of people participated: one, a random group of cigarette smokers (n = 28) with non-smoker controls (n = 13) from our Institute, and the other, a fisherfolk community of tobacco chewers (n = 19) with appropriate non-chewer controls (n = 15) from Bombay. The cells were dislodged from the oral cavity with either a cotton swab or a toothbrush. One to as many as 16 adduct spots in the range of 5-200 amol/micrograms DNA were detected in tobacco users as well as non-users. No adduct spot was detected in the tobacco users' samples that was not present in the controls, suggesting that tobacco use may not be responsible for the formation of these DNA adducts detected in the oral mucosa. The chromatographic behavior of the oral mucosal DNA adducts by selective PEI--cellulose TLC and their extractability in 1-butanol suggest that they have an aromatic and/or hydrophobic moiety and two of the major adducts have been tentatively assigned as aromatic amine derivatives. We have discussed various possibilities of endogenous and/or exogenous factors being involved in the formation of these adducts.

Measurement of specific DNA adduct concentrations in target tissues of organisms may provide a key biologic end-point of exposure to environmental carcinogens. Using a general and highly sensitive assay with 32-P-postlabeling, we found that natural populations of freshwater fish species chub, barbel, bream and carp, as well as a marine fish mugil, revealed the presence of four to nine qualitatively similar adducts irrespective of whether they were caught from unpolluted or polluted waters. No statistically significant differences were observed between the adduct levels of fish from the unpolluted waters and those of fish from the polluted waters. A dominant feature of the fish DNA adducts was a species specificity. The finding that a vast majority of DNA modifications in fish are caused by natural factors rather than man-made chemicals offers a basis for a more realistic view in assessing the genotoxic risks in any aquatic environment.

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