Incorporation of polyunsaturated fatty acids into CT-26, a transplantable murine colonic adenocarcinoma

Previous studies in our laboratory have shown that marine oils, with high l evels of eicosapentaenoic (EPA, 20:5n-3) and docosahexaenoic acids (DHA, 22 :6n-3), inhibit the growth of CT-26, a murine colon carcinoma cell line, wh en implanted into the colons of male BALB/c mice. An in vitro model was dev eloped to study the incorporation of polyunsaturated fatty acids (PUFA) int o CT-26 cells in culture. PU FA-induced changes in the phospholipid fatty a cid composition and the affinity with which different fatty acids enter the various phospholipid species and subspecies were examined. We found that s upplementation of cultured CT-26 cells with either 50 mu M linoleic acid (L IN, 18:2n-6), arachidonic acid (AA, 20:4n-6), EPA, or DHA significantly alt ers the fatty acid composition of CT-26 cells. Incorporation of these fatty acids resulted in decreased levels of monounsaturated fatty acids, while E PA and DHA also resulted in lower levels of AA. While significant elongatio n of both AA and EPA occurred, LIN remained relatively unmodified. Incorpor ation of radiolabeled fatty acids into different phospholipid species varie d significantly. LIN was incorporated predominantly into phosphatidylcholin e and had a much lower affinity for the ethanolamine phospholipids. DHA had a higher affinity for plasmenylethanolamine (1-O-alk-1'-enyl-2-acyl-sn-gly cero-3-phosphoethanolamine) than the other fatty acids, while EPA had the h ighest affinity for phosphatidylethanol-amine (1,2-diacyl-sn-glycero-3-phos phoethanolamine). These results demonstrate that, in vitro, significant dif ferences are seen between the various PUFA in CT-26 cells with respect to m etabolism and distribution, and these may help to explain differences obser ved with respect to their effects on tumor growth and metastasis in the tra nsplantable model.