Dietary polyunsaturated n-6 lipids effects on the growth and fatty acid composition of rat mammary tumors

The aim of this study was to analyze the effects of a polyunsaturated n-6 h igh-fat diet on rat DMBA-induced breast cancer at different stages of the c arcinogenesis and to investigate if changes in the tumor fatty acid composi tion are one of the mechanisms by which dietary lipids could exert their ef fects. 14 fatty acids were evaluated in 6 lipid fractions. The results firs tly showed that this high-fat diet stimulated the malignant mammary tumor g rowth, mainly all in the promotion group. The tumor lipid analysis indicate d: 1) that each lipid fraction presented distinct major fatty acids (>5%) w hich were not the most abundant in the diet, except in the case of the tria cylglicerides, suggesting the different resistance to dietary fatty acid mo dification of the tumor lipid fractions; 2) a higher arachidonic acid conte nt in the fractions with less linoleic acid, above all in phospholipids, pa rticularly in the phosphatidylethanolamine, indicating a different efficien cy of conversion; 3) the three most abundant fatty acids in the dietary lip id (18:2n-6, 18:1n-9 and 16:0) were those which essentially displayed the d ifferences between groups; thus, the high-fat diet changed the tumor lipid profile, increasing the 18:2n-6 relative content and decreasing that of the 18:1n-9; differences were significant in phosphatidylcholine, free fatty a cids and triacylglycerides. Any change was obtained in the phosphatidylinos itol. The greatest number of differences was found in the promotion group. Taken as a whole, our results suggest the different roles of lipid fraction s in breast cancer cells and an association between cancer malignancy and t he content of linoleic and oleic acids. (C) 2001 Elsevier Science Inc. All rights reserved.