Effects of dietary N-3 and saturated fats on growth rates of the human colonic cancer cell lines SW-620 and LS 174T in vivo in relation to tissue and plasma lipids.

Ninety nude mice were inoculated subcutaneously with 1 x 10(7) cells of the human colonic cancer cell lines, SW-620 and LS174T. Tumour growth was assessed weekly for three weeks whilst the animals were receiving one of three diets: control (4.6% fat), coconut (20% fat, saturated fatty acids) and Maxepa (20% fat; n-3 fatty acids). At the end of the study SW-620 tumour weights (mean +/- SD, gm) were: control = 0.38 +/- 0.22, coconut = 0.43 +/- 0.31, Maxepa 0.20 +/- 0.16; the LS174T tumour weights were control = 1.33 +/- 1.27, coconut = 0.47 +/- 0.74, Maxepa = 0.38 +/- 0.56 (p less than 0.001, analysis of covariance). The Maxepa diet produced significant retardation in tumour growth (p less than 0.001). This was associated with reduced levels of linoleic acid and arachidonic acid in adipose tissue and tumour lipids with incorporation of n-3 fatty acids (all p less than 0.01 at least, analysis of variance). Moreover, the Maxepa diet produced significant reductions of plasma cholesterol, phospholipids and triglycerides (all p less than 0.01).