Selection and characterization of chinese hamster ovary cells resistant to the cytotoxicity of lectins

Summary Chinese hamster ovary (CHO) cells selected in a single step for resistance to the cytotoxicity of the lectin from red kidney beans (PHA) behave as authentic somatic cell mutants. The PHA-resistant (Pha^R) phenotype is stable in the absence of selection; its frequency in a sensitive population is increased several-fold by mutagenesis; and it behaves recessively in somatic cell hybrids. The activity of a specific glycosyl transferase which transfers N-acetylglucosamine (GlcNAc) to terminalα-mannose residues is dramatically reduced (⩽5% of the activity detected in wild-type CHO cells) in several independent Pha^R clones. These clones also exhibit (a) a decreased ability to bind ¹²⁵I]-PHA; (b) a marked resistance to the cytotoxicity of wheat germ agglutinin (WGA), Ricin (RIC) andLens culinaris agglutinin (LCA); (c) a 4- to 5-fold increased sensitivity to the cytotoxicity of concanavalin A (Con A); (d) an increased ability to bind¹²⁵I-Con A; and (e) decreased surface galactose residues—all properties consistent with the specific loss of the GlcNAc transferase activity. The lectins WGA, RIC, LCA and Con A have also been used to select, in a single step, resistant clones from each of two complementary CHO auxotrophic lines. These lectin-resistant clones have been characterized by their ability to survive cytotoxic doses of PHA, Con A, WGA, RIC or LCA, and 4–5 “lectin-resistance” phenotypes have been demonstrated. Complementation data is being sought by somatic cell hybridization. Preliminary results show that two phenotypically-distinct Con A^R mutants are complementary in that hybrid cells formed between them exhibit wild-type sensitivity to Con A. Presented in the formal symposium on Information Transfer in Eukaryotic Cells, at the 26th Annual Meeting of the Tissue Culture Association, Montreal, Quebec, June 2–5, 1975.