Hydrocortisone inhibits the spontaneous detachment of viable mammary tumor cells from monolayer cultures.

Primary mammary adenocarcinomas of C3H mice were dissociated to single cells. These cells were seeded at a density of 5 x 10(5)/cm2 substrate area and were grown as monolayers for 36 days in high-serum medium supplemented with insulin. Cultures became confluent within a few days and confluence was maintained throughout the culture period. Viable cells (representing amitotic cell population) were released spontaneously from the confluent monolayer and could be harvested from the culture fluid. The rate of cell release declined after about 30 days, apparently due to mitotic pool depletion. Release of cells from the monolayer was strongly depressed in medium containing hydrocortisone. The cell release event and its alteration by hydrocortisone can be interpreted as reflecting the propensity towards shedding of cells from these tumors in vivo and the alteration of metastatic incidence by adrenal steroids.