Protein synthesis in differentiated and dedifferentiated hepatoma cell lines. Effect of glucocorticoids

The pattern of protein synthesis in hepatoma cell clones was analysed by two-dimensional separation of [35S]methionine-labelled proteins. The clones were derived from the differentiated Reuber H 35 hepatoma and showed differences in the expression of a number of liver-specific functions and the resistance to the growth-inhibitory effect of glucocorticoids. Five protein spots were observed in the extracts of the differentiated Faza 967 cells that were absent from the electrophoretogram of the dedifferentiated H 56 cells. This clone, on the other hand, displayed six spots absent from Faza 967 cells. The growth of both Faza 967 and H 56 cells was strongly inhibited by 1 microM dexamethasone. The dexamethasone-resistant clone 2, a dedifferentiated derivative of Faza 967 cells, synthesized two polypeptides that were not present in Faza 967 or H 56 cells and produced four polypeptides at a lower level than Faza 967 cells. The examination of the short-term effect of dexamethasone on protein synthesis in Faza 967 cells revealed nine induced and one repressed protein spots, which appeared to be in good agreement with earlier published data. It is concluded that dedifferentiation, although bringing about marked changes in certain liver-specific functions, such as enzyme activities or protein secretion, affects only a relatively small fraction of the genes expressed.