The amount and type of dietary
lipid can significantly influence spontaneous
tumor development and
tumor progression. To determine the effect of
fish oil (rich in omega-3
polyunsaturated fatty acids) and
corn oil (rich in omega-6
polyunsaturated fatty acids) on primary
tumor growth,
metastasis and carcass weight, 45 female Lewis/Wistar rats with subcutaneous mammary
tumor implants (MAC-33) were randomized to 1 of 3 diets with 30%
lipid consisting of: (i)
corn oil alone, (ii) combined 50%:50%
corn oil:
fish oil, or (iii)
fish oil alone. Primary
tumor weight was significantly reduced in animals which were fed
fish oil or
corn oil alone compared to animals given combined
corn oil:
fish oil diet. Biochemical analysis (
protein,
DNA,
RNA) of the primary revealed no difference between dietary groups. Cell cycle analysis of the primary
tumor showed no difference in percent G(0)-G(1), S, G(2)-M or growth fraction (% S + G(2)-M) between dietary groups. In contrast, lung
metastasis, was reduced in animals fed the combined
corn oil:
fish oil diet. Thus, dietary,
lipid intake can significantly influence primary
tumor growth and
tumor metastasis. Differential effects of omega-3 and omega-6
polyunsaturated fatty acids occur on primary
tumor growth and development of distant pulmonary
metastases in this animal model.