Modulation of Mammary Carcinogenesis by Eicosanoid Synthesis Inhibitors in Rats Fed High Levels of Linoleate
Diets containing relatively high amounts of polyunsaturated fat have been demonstrated to stimulate the development of a wide variety of mammary tumors in rodents (reviewed in ref. 1). Using the dimethylbenz(α)anthracene (DMBA)-induced mammary tumor model in rats, Carroll and Hopkins (2) reported that addition of as little as 3% of a linoleic acid-rich sunflower seed oil to a diet containing 17% beef tallow or coconut oil (saturated fats) was just as effective as a 20% sunflower seed oil diet in enhancing tumor development. Furthermore, rats on these diets produced twice as many tumors as those fed diets containing 20% of the saturated fats alone. These findings suggest that there may be a requirement for linoleate in mammary carcinogenesis that is not satisfied by fats such as beef tallow and coconut oil, but can be provided by adding 3% sunflower seed oil to diets containing these fats. More recently, we have shown that mammary tumorigenesis in the DMBA model was very sensitive to linoleate intake and increased proportionately in the range of 0.5% to 4% of dietary linoleate (3). Beyond this point and up to, 12% linoleate, there was no further enhancement, suggesting that the level of linoleate necessary to elicit the maximal tumorigenic response was around 4% by weight in the diet.
KeywordsBeef Tallow PGE2 Level Cyclooxygenase Inhibitor Mammary Carcinogenesis Mammary Tumorigenesis
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