Inolitazone (RS5444) upregulates the cell cycle kinase inhibitor, p21 WAF1/CIP1 . Silencing p21 WAF1/CIP1 rendered cells insensitive to Inolitazone. A 10 nM The dose of Inolitazone activates PPARγ:RXRα-dependent transcription as demonstrated in a transient transfection assay utilizing a PPRE response element fused to a luciferase reporter gene (PPRE3-tk-luc). DRO cells are treated in culture with Inolitazone, Rosiglitazone, or Troglitazone at the indicated concentrations. DRO cells are transiently transfected with PPRE3-tk-luc to examine effective concentrations at which EC 50 occurs. The EC 50 s are 1 nM (Inolitazone), 65 nM (Rosiglitazone) and 631 nM (Troglitazone). Similarly, the calculated inhibitory concentration at IC 50 is 0.8 nM for Inolitazone, 75 nM for Rosiglitazone, and 1412 nM for Troglitazone. Inolitazone specifically activates PPARγ, but not PPARα or PPARδ. Exposure of 10 nM Inolitazone following tran sient transfection with the appropriate PPAR isoform (γ, α, or δ) and PPAR response element linked to a luciferase reporter in RIE rat small intestinal cell line, which does not express PPARs, yields increased luciferase activity only in the presence of PPARγ and PPRE3 -tk-luc. DRO cells are growth inhibited by 10 nM Inolitazone (RS5444) through a PPARγ-dependent mechanism.
