Growth characteristics and enzyme activities in a survey of transformation markers in adult rat liver epithelial-like cell cultures.

An extensive survey of markers for transformation of adult rat liver-derived epithelial-like cell lines was conducted. The cell surface properties associated with tumorigenicity were reported earlier. Now we report the correlation of various growth characteristics and enzyme activities with tumorigenic ity. Among markers identified that correlated with tumorigenic ity within the population, biochemical assay of y-glutamyl transpeptidase activity was specific but not sensitive. Rapid growth rate accompanied by increased cell density showed a positive trend with tumorigenicity. Activity of plasminogen activator in cell lysates was not correlated with tumorigenicity. Among identified markers that gave an estimate of the fraction of tumorigenic cells in cultures, growth in soft agar was a good quantitative marker. Cytochemical activity of y-glutamyl transpeptidase was a specific and sensitive marker. Colony-forma tion in low-calcium medium also distinguished tumorigenic cells from nontumorigenic ones. Colony-forming efficiency in both 10 and 1% serum media was somewhat higher for tumorigenic lines, but the difference from non-tumorigenic lines was not great enough to make this a useful marker. Thus, among 11 properties examined in both parts of this survey, biochemical assay of y-glutamyl transpeptidase activity, high uptake of 2deoxy-D-glucose, and growth pattern in liquid medium can serve as population markers, while growth in soft agar, cytochemical assay of y-glutamyl transpeptidase activity, and growth in low-calcium medium can be used as cell markers. Combined use of these markers in adult rat liver lines provides a reliable means of identifying transformation in an epithelial cell system.