A RARα1/3 plasmid construct and the corresponding control void vector were stably transfected into ATRA-resistantMDA-MB453 cells. Two cell clones over-expressing RARα (RARA-C5 andRARA-C7) and two appropriate control clones (Vect-C1 andVect-C2) were isolated. A RARα3 shRNA plasmid construct and the corresponding void vector were stably transfected into ATRA-sensitiveSKBR3 cells. After selection, two cell clones silenced for RARα3 (RARA-sh18 andRARA-sh19) and two appropriate control clones (Vect-C6 andVect-C8) were isolated.A, D The indicated clones and the parental cell line (WT) were transiently transfected with the RARE-DR5-Lucretinoid reporter construct and the level of luciferase activity was measured 24 h after treatment with vehicle (DMSO) and ATRA (100 nM), as illustrated in the upper bar graph. Each value is the mean ± SD of three replicate cultures. The levels of the RARα protein measured in the indicated clones by Western blotanalysis is shown under the bar graph. To demonstrate that similar levels of total proteins were loaded in each lane, the β-actin band signal obtained after re-blotting of the gel is shown. FI = Fluorescence intensity. 