THE EFFECT OF CELL-TO-CELL CONTACT ON THE SURFACE MORPHOLOGY OF CHINESE HAMSTER OVARY CELLS

In the previous report (Porter et al., in this issue) morphological changes in Chinese hamster ovary (CHO) cells during the cell cycle were described. In this report we describe the role of intercellular contact on these changes. We find that intercellular contact is required for cells to exhibit the morphologies Porter et al. described for S and G₂. When cells are synchronized by mitotic selection and plated onto cover slips at very low density such that no intercellular contact occurs, the cells remain in a G₁ configuration (rounded and highly blebbed through G₁, S, and G₂). This G₁ morphology is also observed in nonsynchronized log phase cells plated at low densities and allowed to grow for several generations. The addition of conditioned medium from confluent cultures does not induce low density cells to change morphology during the cell cycle. These results indicate that extensive intercellular contact is required for the complete expression of the morphological changes associated with the cell cycle (as described by Porter et al.). It is concluded that although classic contact inhibition of movement and of growth may be absent in this transformed cell line, some contact-dependent response persists.