The influence of diet on the regression of the Walker carcinosarcoma 256 in rats

Regression of the Walker carcinosarcoma 256 has been observed in rats inoculated with 10(4) viable tumor cells. The regression was found to be affected by dietary composition. Tumors in rats fed a commercial laboratory diet (CLD) regressed after a 9-day initial growth period while tumors in rats fed a purified diet high in free fatty acids continued to grow. Diets with 20% corn oil promoted tumor regression, but rats fed diets containing 20% free fatty acids from corn oil had tumors that continued to grow. The nonsaponifiable fraction (NSF) of corn oil appeared to promote tumor regression when this fraction was added to diets containing corn oil fatty acids. At the end of the experiment (14 days), the tumors of rats fed a free fatty acid diet weighed 13-17 g. The tumors of rats fed CLD, corn oil diet and the corn oil free fatty acid diet plus the NSF of corn oil weighed 1-5 g. These results indicate that something in the NSF of corn oil was associated with the regression of the tumor. However, the nature of the dietary components promoting tumor regression, and the host response to those components, have not been determined.