Enhanced growth rate of transplanted mammary adenocarcinoma induced in C3H mice by dietary linoleate.

Three-month-old C3H female mice were given injections of 5-mg pieces of mammary adenocarcinoma and were then fed diets that either were fat free or contained saturated fat (15% hydrogenated cottonseed oil) or linoleate (1-15% corn oil). After 6 weeks, the tumors in mice fed the linoleate diet weighed 3-4 times more than those in mice fed the fat-free or saturated-fat diets. Despite a linoleate-free diet, tumors contained appreciable amounts of linoleate and arachidonate (approximately 2 and 9% of the total fatty acids, respectively). When the level of dietary corn oil was increased from 1 to 15%, the linoleate content of the tumors increased from 4 to 18% of the total fatty acids. However, in these instances, the tumor arachidonate levels increased to maximum values even when the 1% corn oil diet was used. These observations showed that mammary tumor growth was depressed by a fat-free or saturated-fat diet and enhanced by dietary linoleate. Furthermore, they suggested that the growth rate was related to the arachidonate content rather than the linoleate content of the tumors.