OMEGA-3-FATTY-ACID MODIFICATION OF MEMBRANE-STRUCTURE AND FUNCTION .1. DIETARY MANIPULATION OF TUMOR-CELL SUSCEPTIBILITY TO CELL-MEDIATED AND COMPLEMENT-MEDIATED LYSIS

Omega-3 fatty acids, abundant in fish oil, are reported to alter membr ane properties when incorporated into membrane phospholipids. We,repor t that dietary omega-3 fatty acids, incorporated into tumor cell membr anes, alter tumor recognition and cytolysis by the immune system. Mice were fed diets rich in corn oil, hydrogenated coconut oil or menhaden (fish) oil. T27A leukemia cells were grown as an ascites tumor in the se mice and harvested for biochemical and immunologic assays. The inco rporation of the long-chain omega-3 fatty acid docosahexaenoic acid (2 2:6) into tumor plasma membranes correlated with an increased suscepti bility to tumor cytolysis by alloreactive cytotoxic T lymphocytes and decreased expression of a class I major histocompatibility complex epi tope, monitored by complement-mediated lysis and radioimmunoassay. Thu s the immunologic phenotype of this ascites tumor reflected the source of oil present in the diet during tumor growth.