Formation of large vacuoles in tumour cells grown in suspension.

In suspension cultures of JB-1-E cells approximately 11% of the cells contained a single large vacuole ("balloon cells") or signet-ring cells). Such cells were rarely observed in monolayer cultures, where the cells were attached to a substrate. Only a few "balloon cells" were observed in suspension cultures of HeLa S3 cells. Both cell lines were able to phagocytize latex particles of 5.7 micrometer mean diameter. Nocodazole significantly reduced the formation of "balloon cells" in suspension cultures of JB-1-E cells. Transmission electron microscopy indicated that various cytoplasmic membrane components probably could contribute to the membrane material of the vacuoles. It is believed that the formation of "balloon cells" is due to changes in the regulation of the cellular membrane material.