Effects of insulin, dexamethasone and phorbol ester on virus production in cultivated DBA/2 mouse leukemia (MLA) cells.

The in vitro production of intracytoplasmic oncovirus A-particles and of atypical mammary tumor virus (MLAV) from a line of DBA/2 mouse leukemia (MLA) cells were compared in the presence of insulin, dexamethasone and 12-0-tetradecanoyl-phorbol-13-acetate (TPA), which are known to stimulate the synthesis of mouse mammary tumor virus. High amounts of A-particles were recovered from cells cultivated in the presence of dexamethasone (1 microgram/ml) as compared to untreated controls; in contrast, the production of MLAV was suppressed. Insulin and TPA did not show any significant effects.