R5020 and RU486 act as progesterone receptor agonists to enhance Sp1/Sp4-dependent gene transcription by an indirect mechanism.

It has been suggested that ligand-dependent gene activation by the progesterone receptor (PR) can result from recruitment of PR by the promoter bound Sp1. A detailed investigation of the Sp1-dependent agonistic activity of RU486 and R5020 on the folate receptor (FR) type alpha, p27, thymidine kinase 1 and p21 genes reveals a different mechanism. The FR-alpha P4 promoter and the endogenous FR-alpha gene were up-regulated by the PR agonist R5020 through either PR-A or PR-B.

Enhancement of folate receptor alpha expression in tumor cells through the glucocorticoid receptor: a promising means to improved tumor detection and targeting.

The utility of the folate receptor (FR) type alpha, in a broad range of targeted therapies and as a diagnostic serum marker in cancer, is confounded by its variable tumor expression levels. FR-alpha, its mRNA and its promoter activity were coordinately up-regulated by the glucocorticoid receptor (GR) agonist, dexamethasone. Optimal promoter activation which occurred at <50 nmol/L dexamethasone was inhibited by the GR antagonist, RU486, and was enhanced by coactivators, supporting GR mediation of the dexamethasone effect.