shMRP4 down-regulates MRP4 protein and mRNA expression. MRP4 protein expression analyzed by immunocytochemistry in HEK-MRP4 cells transduced with pRetroSUPER.puro.vector (A, left; control) or pRetroSUPER.shMRP4.puro (A, right) or LC cultures from MUTZ3 stably transfected with pRetroSUPER.GFP.vector (B, left; control), or pRetroSUPER.GFP.shMRP4 (B, right). Original magnification, 100×. (C) Triplicate MRP4 mRNA levels measured by low-density array in MUTZ3-vector control (left) or MUTZ3-shMRP4 cells (right). Numbers indicate the fold increase (+) or decrease (−) with respect to MUTZ3-vector control levels (*P < .05).