Reduced tumour growth of the human colonic cancer cell lines COLO-320 and HT-29 in vivo by dietary n-3 lipids.

Seventy-five nude mice received subcutaneous inoculation with 1 X 10(7) cells of the human colonic cancer cell lines COLO-320 or HT-29. Tumour growth was assessed over 4 weeks in animals given one of three iso-caloric diets; standard diet, high saturated fat (20% coconut) diet and high n-3 fat (20% Maxepa fish oil) diet. The n-3 diet produced significant tumour growth reduction compared to the other diets for COLO-320 at 3 to 4 weeks (P less than 0.05 at least) and similarly for HT-29 at 4 weeks (P less than 0.05). Significant incorporation of n-3 fatty acids occurred in red cell membranes, adipose tissue and both neutral lipid and phospholipid fractions of tumour lipids in animals fed Maxepa (P less than 0.01 at least). This was accompanied by reduction of linoleic acid and arachidonic acid in these tissues (P less than 0.01 at least) but was most marked in the metabolically labile phospholipid fraction. There was high mitotic activity in the tumours from all the groups but there was no difference according to diet.