Inhibition of chemically induced carcinogenesis

Inhibition of Chemically Induced Carcinogenesis by 2-/i-Heptylfuran and 2-7i-Butylthiophene from Roast Beef Aroma... 

Hix LM, Frey DA, McLaws MD, 0sterlie M, Lockwood SF, and Bertram JS. 2005. Inhibition of chemically-induced neoplastic transformation by a novel tetrasodium diphosphate astaxanthin derivative. Carcinogenesis 26(9) 1634-1641. 

There have been several epidemiological and several case reports inversely relating ascorbic acid intake from food to human cancer mortality. These studies are interesting, but may be confounded with the fact that the same ascorbic acid containing foods, namely fruits and vegetables, also contain large amounts of vitamin A and fiber. Both vitamin A and fiber have been inversely related to human cancer mortality and have been shown to inhibit several types of chemically-induced carcinogenesis in animals. Therefore, the possible anti cancer effect of ascorbic acid may be due to other factors. 

Fat-soluble vitamins, in addition to their antioxidative effects on lipids, appear to exert a general protective effect in animals. Vitamin A and beta-carotenes protect lab animals from toxicity of citral, cyclophosphamide and some hydrocarbons (Seifter et al, (A2.) In related but independent studies, it was observed that high levels of vitamin A inhibit tumorogenesis and that low levels of vitamin A appear to enhance tumorogenesis (Baird, (1 ). vitamin E inhibited chemically-induced carcinogenesis in test systems (Shamberger, ) and also reduced the susceptibility of rats to cigarette smoke (Chow,... 

The hallmark of the anticarcinogenic effect of DR is the ability of diet restriction to prevent chemical-induced tumors. The first reports of inhibition of chemical carcinogenesis came in the 1940s. 

In mice topically and orally administered 2 mg of a pepper extract 3 days a week for 3 months, an increase in incidences of tumors was observed. A reduction in the increase of tumor formation was observed in rats orally and topically administered 5 or 10 mg of vitamin A pal-mitate twice weekly for 3 months during and after pepper administration. No impact on carcinogenesis was observed in mice fed diets containing 1.6% pepper (Shwaireb et al. 1990). Conversely, another study indicated that pepper inhibited chemically induced carcinogenesis in rats (Nalini 1998). 

Various organic sulfides present in Allium have been found to have anticar-cinogenic activity. For example, allyl sulfide, a constituent of garlic oil, inhibited colon cancer in mice exposed to 1,2-dimethylhydrazine, and allyl methyl trisulfide, allyl methyl disulfide, aUyl trisulfide, and allyl sulfide all inhibited benzo[a]pyrene-induced neoplasma of the forestomach and lung in female mice (55). Lam et al. (Chapter 22) investigated the ability of 2-n-butyl thiophene, a constituent of roast beef aroma, to inhibit chemically induced carcinogenesis in three different tumor systems. This compound was found to be effective in the forestomach, lung, and colon models. 

Citrus limonoids are furanoid natural products found in citrus fruits. The most abundant limonoids, limonin and nomdin, have been determined to induce increased activity of GST and inhibit chemically induced carcinogenesis (6,7). These findings with furan containing natural products led to the investigation of mono and disubstituted furan and the corresponding sulfur containing thiophene compounds that are found in complex mixtures of beef aroma. 

CLA, the acronym for a series of conjugated dienoic isomers of linoleic acid, occurs naturally in many foods, particularly dairy products and other foods derived from ruminant animals (6). Synthetically prepared CLA inhibits chemically-induced mouse epidermal and forestomach neoplasia (7,8) and rat mammary neoplasia (9). Hence, the effect of CLA on carcinogenesis is opposite that of linoleic acid. 

The effects of dietary fiber on chemically-induced colon cancer in rats are variable being dependent on the carcinogen used and its mode of administration as well as the sex and strain of the rat. In most cases, however, dietary fiber has been found to inhibit carcinogenesis. 

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