Different concanavalin A binding patterns of malignant and nonmalignant mouse mammary epithelia in monolayer culture

Concanavalin A (Con A) binding of fixed malignant and nonmalignant C3H/He mouse mammary epithelia in monolayer cultures was examined with markers and labels of various sizes. In Con A-mediated hemadsorption, high epithelial cell densities resulted in the adsorbance of more guinea pig red blood cells per culture dish but fewer per cell. Malignant epithelia adsorbed twice as many red blood cells as did nonmalignant cells at the same cell density. Ferritin-Con A tagged the budding particles of mouse mammary tumor virus and other parts of the epithelial surface evenly. Hemadsorption occurred at the particle-free part of the apical membrane. The amount of 125I-Con A bound per dish, however, was not related to cell density but was almost identical for cells from the same source. Nonmalignant cells bound twice as much 125I-Con A as did malignant cells. The calculated association constants of Con A-binding sites on malignant cells, however, were twice as large as those on nonmalignant cells. This explains, at least partly, the greater number of red blood cells adsorbed by malignant cells. Con A-labeled Sepharose 4B beads were not useful for our purposes, and fluorescein isothiocyanate-Con A did not distinguish between malignant and nonmalignant epithelia.