Glucocorticoid-resistant lymphoma cell variants that contain functional glucocorticoid receptors

A mouse T-lymphosarcoma cell line stably infected with mouse mammary tumor virus (MMTV) was used as the parent line for a genetic analysis of two glucocorticoid hormone responses, hormone-induced cytolysis and stimulation of viral gene expression. Variants were selected for survival and elevated expression of MMTV proteins in the presence of the steroid. The MMTV marker provided a sensitive test for glucocorticoid receptor (GR) function in the hormone-resistant variants. This strategy resulted in the isolation of two novel types of hormone-resistant variants. One type of variant with only about 25% of the level of GR found in the parent line was resistant to the cytolytic effects of glucocorticoid but produced increased levels of MMTV gene products in response to the hormone. This variant phenotype demonstrated that the MMTV response requires fewer GR than the cytolytic response. Another variant, which required approximately 100-fold higher concentrations of hormone than the wild-type cells for both responses, apparently contained GR with altered hormone-binding properties.