A secreted Mr ∼ 40,000 glycoprotein specifically induced by glucocorticoids in a rat colon carcinoma cell line

Glucocorticoid hormones are thought to play a role in car-cinogenesis, as they regulate cell differentiation and proliferation. We have previously shown that dexamethasone inhibits the growth of a rat colon carcinoma cell line, and induces the secretion of an Mr ∼ 40,000 protein. We now report that the synthesis and the release in the culture medium of this protein is stimulated specifically by glucocorticoid agonists, and not by other steroid hormones. The anti-glucocorticoid RU 38486 is inefficient and suppresses the induction of this protein by dexamethasone. Induction is sensitive to actinomycin D, suggesting that regulation may be exerted by altering the rate of mRNA synthesis. Characterization of culture medium from dexamethasone-treated cells revealed that the Mr ∼ 40,000 protein is glycosylated, and can be further separated from other secreted proteins by high-performance anion-exchange chromatography.