EFFECTS OF DIETARY FATTY-ACIDS ON DU145 HUMAN PROSTATE-CANCER CELL-GROWTH IN ATHYMIC NUDE-MICE

The purpose of this study was to examine the effects of diets containi ng different unsaturated fatty acids (FAs) on DU145 human prostate can cer cell growth in nude mice. In Experiment 1, groups of 25 mice were fed 23% (wt/wt) fat diets containing 18% corn oil (CO)-5% linseed oil (18:2n-6 FA-rich), 18% linseed oil (LO)-5% CO (18:3n-3 FA-rich), or 18 % menhaden oil (MO)-5% CO (20:5 and 22:6n-3 FA-rich), and seven days l ater they were injected subcutaneously with 1 x 10(6) DU145 cells. The diets were continued for six weeks. The growth rates and final weight s of tumors from the 18% CO-5% LO and 18% LO-5% CO mice were similar; there was a 30% reduction in tumor growth in the 18% MO-5% CO group (p < 0.001). The tumor phospholipid FA patterns suggested that the inhib itory effect of the high-MO diet was due, at least in part, to a reduc tion of arachidonic acid available for prostaglandin biosynthesis. In Experiment 2, groups of 25 mice were injected with 5 x 10(5) or 1 x 10 (6) DU145 cells directly into the prostate gland and fed a high-fat li noleic acid (n-6 FA)-rich or a low-fat diet for 10 weeks. At necropsy macroscopic cancers and microscopic intraprostatic tumors were evaluat ed. When the initial tamer load was 1 x 10(6) cells, all but 7 of the 50 mice had developed large macroscopic tumors; the mean tumor weight in the high-fat group was twice that in the low-fat group (p = 0.047). A stimulatory effect of dietary n-6 FA on DU145 prostate cancer cell growth may require a critical initial tumor cell mass.