An oligosaccharide biosynthetic defect in concanavalin A-resistant Chinese hamster ovary (CHO) cells that enhances NK reactivity <i>in vitro</i> and <i>in vivo</i>.

Abstract

We have examined a concanavalin A-resistant (Con AR) Chinese hamster ovary cell (CR-7) that has a defect in the synthesis of asparagine-linked oligosaccharides and consequently an altered expression of membrane carbohydrate. The CR-7 mutant, which has a decreased ability to incorporate mannose into oligolipid and membrane glycoprotein and an increased membrane fucose, was more sensitive to natural killer (NK) cell lysis than the parental wild type (CHO-WT). Splenocytes mediating the lysis of the CR-7 line were asialo GM1+, nonadherent, IFN stimulatable, absent in the bg/bg mutant, and co-fractionated on Percoll density gradients with cells mediating lysis of the YAC-1 murine lymphoma. The increase in NK lysis correlated with enhanced binding of NK cells to the mutant determined by adsorption on tumor monolayers, cold target inhibition, and target binding analysis. A revertant of CR-7 (RCR-7), which showed wild-type levels of NK lysis, was intermediate in its ability to bind or cold target inhibit NK cells. The CR-7, CHO-WT, and RCR-7 lines were equally sensitive to hypotonic lysis and cytotoxicity by human lymphokine-activated killer (LAK) cells suggesting that the mutation did not nonspecifically alter membrane fragility. The NK-sensitive CR-7 line was less tumorigenic after subcutaneous injection in nude mice when compared with the parental CHO-WT or RCR-7 lines. This decreased tumorigenicity could be reversed by the i.v. injection of antiserum directed at the NK cell determinant asialo GM1. In conclusion, a ConAR tumor cell with a demonstrable oligosaccharide biosynthetic defect, exhibited enhanced NK lytic sensitivity and was poorly tumorigenic in vivo, a feature which may also be a consequence of its altered NK reactivity.