Effect of dietary 18-carbon fatty acids on growth of transplantable mammary adenocarcinomas in mice.

The growth rates of 2 spontaneously developed mammary adenocarcinomas, one in a female C3H mouse and the other in a female BALB/c mouse, were determined after transplantation into isologous female mice fed a specific diet to which various edible fats or pure fatty acids were added. The 18-carbon fatty acids used contained one (oleate), two (linoleate), or three (linolenate and columbinate) double bonds in either the 5, 9, 12, or 15 positions. The transplanted tumors grew to a larger size in C3H mice fed the 10% corn oil diet (with approximately equal to 60% linoleate content) than in those fed the 10% hydrogenated oil diet (without linoleate). The C3H mice fed diets with 1% linoleic acid developed significantly larger tumors than did those fed 1% oleic acid, whereas those fed 1% columbinic acid did not develop significantly heavier tumors compared to 1% oleic acid-fed mice. This finding occurred despite the fact that both oleate and columbinate were taken up and were incorporated into complex lipids by the transplanted tumor and the ratio of monoenoic:dienoic:polyenoic fatty acids in the neoplasms' lipids from columbinate-fed mice was similar to that from linoleate-fed mice. Columbinate, similarly to linoleate, has both 9-cis and 12-cis double bonds, but it also possesses a trans double bond in the 5 position that apparently prevents its conversion to prostaglandins (PG). These results are entirely consistent with the view that production of PG is required for tumor enhancement by dietary polyunsaturated fat. In the experiment with BALB/c mice, tumor growth was stimulated by 1% dietary linoleic acid but not by 1% linolenic acid when compared with that observed with 1% oleic acid. Thus as a result of these new experiments, PG of series 1 or 2 are more likely to be involved in the process of tumor growth enhancement than are PG of series 3.