Examination of a liver cell line tumorigenically transformed by DL-ethionine

Abstract

A nontumorigenic cell line derived from rat hepatocytes became tumorigenic subsequent to its cultivation for 3 months in medium containing 7.5 mM DL ethionine. We used light and electron microscopy in order to observe the structural effects of this treatment. At confluence, both experimental and control cultures appeared as monolayers of contiguous polygonal cells. Subconfluent cultures of ethionine-treated cells had a minor population of elongated cells, with extended cytoplasmic processes, which were not seen in control cultures. Actin cables (visualized with a NBD-phallacidin probe), which were routinely visible in polygonal cells, were not as pronounced in elongated cells (Fig. 1). Likewise, the arrangement of microtubules (stained with FITC-antitubulin) was characteristically altered from a mainly circumferential distribution at the periphery of the cytoplasm in polygonal cells to longitudinal arrays in elongated cells.Examination by transmission electron microscopy of confluent cell cultures revealed a marked decrease in the length of desmosomal contacts between ethionine-treated cells accompanied by an increase in extracellular fibrillar material (Fig. 2).