Stable alterations at the cell membrane of Chinese hamster ovary cells resistant to the cytotoxicity of phytohemagglutinin

Abstract

Chinese hamster ovary (CHO) cells selected for resistance to the cytotoxicity of phytohemagglutin (PHA) have been found to exhibit stable alterations at their plasma membranes. The PHA-resistant (Pha ^R) cells bind markedly less¹²⁵ I -PHA than do sensitive CHO cells and also exhibit an increased sensitivity to the cytotoxicity of concanavalin A, a lectin of different receptor specificity. Mutagenesis with ethylmethanesulfonate increases the proportion of Pha ^R cells 20- to 100-fold. PHA-resistant cells maintained for up to 8 months in continuous culture in the absence of the selective agent have retained the Pha^R phenotype. These and other characteristics of the experimental system suggest that CHO cells selected for PHA resistance are authentic somatic cell mutants. The Pha marker appears to behave recessively in hybrids formed between Pha^R and Pha^S cells.