RETINOIC ACID AND SYNTHETIC ANALOGS DIFFERENTIALLY ACTIVATE RETINOIC ACID RECEPTOR DEPENDENT TRANSCRIPTION

We have developed an assay where the potency of retinoids in retinoic acid receptor (RAR) mediated transcriptional activation can be rapidly evaluated. In this assay hRAR-α, hRAR-β and hRAR-γ were expressed in CV-1 cells together with a reporter gene containing a retinoic acid responsive element (TRE3-tk-CAT). Concentrations required to obtain half-maximum induction (ED50 of CAT-activity were determined for several retinoids, e.g., all-trans-retinoic acid (RA), 13-cis-retinoic acid (13-cis-RA), arotinoid acid (TTNPB) and m-carboxy-arotinoid acid (m-carboxy-TTNPB, an inactive arotinoid analog). The ED50 values for RA decreased in the order of RAR-α (24 nM) > RAR-β (4.0 nM) > RAR-γ (1.3 nM), while the ED50 values for TTNPB and 13-cis-RA decreased in the order of RAR-α (6.5 nM, 190 nM) > RAR-γ (2.3 nM, 140 nM) > RAR-β (0.6 nM, 43 nM), respectively. No significant inductions were obtained when cells were treated with m-carboxy-TTNPB, even at 10 μM concentrations. The fold induction of CAT-activity for all compounds tested decreased in the order of RAR-α > RAR-β > RAR-γ. © 1990 Academic Press, Inc.