Lipid A OM-174 increases the natural killer activity of peripheral blood cells from breast cancer patients

Abstract

Natural killer (NK) cells have been implicated in immune surveillance against tumors, but their activity is often impaired in cancer patients. Lipopolysaccharides (LPSs) are known to enhance NK activity, but their toxicity prevents their use in humans. OM-174, a purified 3,3′-O-deacylated Escherichia coli lipid A, is able to cure established tumors in the rat with little toxicity. We tested the ability of OM-174 to stimulate in vitro the lytic potential of peripheral blood cells from patients with non-metastatic breast tumor ( n = 48). After 24 h pre-incubation of nylon—non-adherent cells with OM-174, increased antitumor activity was observed toward the NK-sensitive target cells K562 but not the lymphokine-activated killer (LAK)-sensitive target cells Daudi. Both NK cells and a non-NK population are involved in this cytotoxicity. So, although the basal NK activity of blood cells was lower in tumor-bearing patients than in healthy donors, OM-174 may increase their toxicity toward cancer cells.