Promotional phase of carcinogenesis

Also, selenium-dependent glutathione peroxidase activity has been shown to be reduced in selenium-deficient rats (C. Reddy, ( li). Selenium appears to inhibit both the initiation and promotion phases of carcinogenesis (Milner,... 

Current research in animal models which suggests that the carcinogenic response to a variety of colon carcinogens is enhanced by the dietary fat and inhibited by several dietary fibers, indicates that these nutritional factors may operate during the promotional phase of carcinogenesis. The carcinogenic process in humans may... 

In summary, it has been shown that dietary protein levels can influence the metabolism of the mycotoxin AFBi. Altered metabolism is, in part, responsible for the protective role of low protein diets with respect to carcinogenicity and possibly with its increased toxicity in protein deficient rats. Dietary protein levels can also influence the promotional phase of carcinogenesis. Further research is required to determine the mechanisms associated with the influence of dietary protein on both the initiation and promotional phases of carcinogenesis. 

Furthermore, while the effect of selenium on the action of direct acting carcinogens is less than observed with compounds requiring metabolic activation, a reduction in total tumor number is often observed. Therefore, selenium probably inhibits both the initiation and promotion phases of carcinogenesis. 

More recently, quercetin has been investigated for its ability to prevent the promotion phase of carcinogenesis. Nlshino et al. 

The demonstration of two stages in experimentally induced cancer in animal models suggests that there are two stages in environmentally induced cancer in humans (57). Most human cancers probably result from a complex interaction of carcinogens, co-carcinogens, and tumor promoters. Most of nutritional or dietary factors act at the promotional phase of carcinogenesis. 

The promotion phase of carcinogenesis is associated with chemicals that ... 

The stage of carcinogenesis at which the effect of dietary fat is exerted appears to be during the promotional phase of carcino-... 

These results implicate BHT as having a role in the activation, initiation or early promotional phase of DMBA-induced chemical carcinogenesis. A definite possibility is that it may require this period of time to allow for the induction of specific metabolic enzymes involved in the handling of DMBA. This time may be required for the attainment of sufficient levels in the tissues to allow effectiveness as an inhibitor. Further studies are certainly needed to narrow the wide range of possibilities. 

As previously mentioned, carcinogenesis is a complex process and it would be naive to believe that dietary protein alters only the initiation phase. A series of eloquent studies by Appleton and Campbell (22, 23, 24) have indicated that the effects exerted by dietary protein during the promotional phase of AFBi hepatocar-cinogenesis are as important, if not more so, than the effects seen during the initiation phase. 

The interactions of dietary fat and protein on the promotion phase of breast carcinogenesis were examined by feeding weanling rats a control diet (16% of kcal from protein and 24% of kcal from fat) for 4 weeks and subsequent assignment to the 9 dietary treatments following DMBA administration. As in the combined phase study we observed no protein by fat interactions or main effects of... 

Ip C. 1981. Prophylaxis of mammary neoplasia by selenium supplementation in the initiation and promotion phases of chemical carcinogenesis. Cancer Res 41 4386-4390. 

Eicosanoids derived from AA are biologically active in small quantities. Their large amounts lead to the formation of thrombi and atheromas, and to the development of allergic and inflammatory disorders (Simopoulos, 2002a,b). In general, co-6 PUFAs have been associated with the enhancement of the promotional phase of mammary carcinogenesis (Rose, 1997). 

From our observations, it was also apparent that the tumors appeared at essentially the same time in the hamsters in the two experimental groups. These results indicate that 3-methoxybenzamide is not a promoter, but an initiator. If this proves to be true, then it is possible that the activity of poly(ADP-ribose) polymerase may be critical during the initiation phase of carcinogenesis. 

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