Evidence for altered gene regulation in HeLa cells returned to culture after growing in immunosuppressed rats.

HeLa TCRC-1, is a monophenotypic cell line for the production of the carcinoplacental Regan isoenzyme of alkaline phosphatase. It has been previously reported that, when this cell line is grown in immunosuppressed rats, there is an alteration of phenotypic expression in that an isoenzyme that is referred to as oncoamnion (FL) becomes the dominant enzyme form. This report describes the isoenzyme regulation after these cells are returned to culture for at least three months. These cells in culture demonstrate a density-dependent alteration in isoenzyme profiles. The Regan isoenzyme is the dominant isoenzyme form in new, sparsely populated cultures, while the oncoamnion isoenzyme predominates in the later high-density stages of growth. Prednisolone induction of enzyme activity is found to be most effective in the early stages of growth, and the previously reported specificity of hormone action on isoenzymes produced by cancer cells is maintained. Enzyme induction is restricted to the Regan isoenzyme, while hormone-mediated diminution in enzyme activity is confined to the oncoamnion (FL) isoenzyme.