EFFECT OF DIETARY N-3 AND N-6 POLYUNSATURATED FATTY ACIDS ON LIVER METASTASIS OF HUMAN COLONIC ADENOCARCINOMAS IN NUDE MICE

Abstract

Nude mice at 4-6weeks of age were fed diets containing 10% oil with different α-linolenic acid (α-LnA, n-3)/linoleic acid (LA, n-6) ratios ; Group A (n-3/n-6 =0.01), Group B (0.30), GroupC (0.87) and GroupD (3.37). After 10 days, each dietary group of mice received intrasplenic (i.s.) transplantation of human colonic adenocar- cinomas and was fed the same diet. Animals were sacrificed at 3 weeks after i.s. transplan- tation of COL 5 with a higher'metastatic potential and at 2 months in the case of COL 4 with a lower metastatic potential. The incidence of liver metastasis and the average number of metastatic nodules per mouce decreased in the order of Groups B＜C＜D, A. Dietary α-LnA (n-3)/LA (n-6) ratio was reflected mainly in eicosapentaenoate (EPA, n-3)/arachidonate (AA, n-6) ratio in the phospholipid fractions and mainly in α-LnA (n-3)/LA (n-6) ratio in the triacylglycerol fractions from both the non-cancerous referertce tissues and the metastatic tumor tissues in liver, similarly. The thromboxane (TX) A₂ and prostaglandin (PG) I₂ levels decreased along with the increase in EPA/AA ratio of phospholipids, but the TXA₂/PGI₂ ratio was the highest and the bleeding time was the shortest in Group B as compared with the other dietary groups. Thus, the metastatic potential of intrasplenically transplanted human colonic carcinoma cells was positively correlated with both the TXA₂ /PGI₂ ratio in liver and thrombotic tendency, but not with dietary α-LnA/LA ratios in nude mice.