COS-1 cells were transfected with hCAR1 expression vector along with the 3.1-RXRα expression vector, pRL-CMV normalization vector and CYP2B6-PBREM/XREM reporter. Transfected cells were treated with either vehicle (0.1% DMSO), CITCO (2 µM), MG-132 (MG) (0.1, 1 and 10 µM) or Lac (0.5, 1 and 5 µM). After 24 h treatments, luciferase activities were determined and expressed relative to vehicle control. Data are the means ± S.D. (n = 3). Significantly different from DMSO and CITCO (*), P < 0.05.