Glucocorticoids induce focus formation and increase sarcoma viral expression in a mink cell line that contains a murine sarcoma viral genome.

Dexamethasone (3 X 10(-10) to 3 X 10(-6) M) induced foci of morphologically transformed cells in a small proportion of a mink cell line that contains the Moloney murine sarcoma viral genome (S+L-). The induction was glucocorticoid specific, since other steroids with glucocorticoid activity (prednisolone, cortisol, and aldosterone) induced foci with an efficiency that paralleled their glucocorticoid activity, and steroids lacking glucocorticoid activity (17B-estradiol, testosterone, and progesterone) failed to induce foci. Viral antigen, as measured by specific immunofluorescence, was localized to the foci. The induction of foci by dexamethasone (3 X 10(-7)) was accompanied by an approximately 10-fold increase in intracellular Moloney murine sarcoma virus-specific RNA and viral p30 antigen. Removal of dexamethasone was followed by the disappearance of foci and a decrease in viral RNA and p30. In this cell system, therefore, glucocorticoids can affect the intracellular levels of type C viral RNA and protein.