siRNA silencing of mRNA encoding 5 candidate proteins for efflux of Cbl. (A) The left lanes show RT-PCR analysis of ABCB6, MRP1, MRP3, MRP5, and ABCG2 RNA in HeLa cells incubated for 96 hours with specific siRNA probes targeting the mRNA encoding the indicated membrane transporters. The middle lanes show the same analysis of cells incubated with siCONTROL and the right lanes show the analysis of nontransfected cells. (B) ⁵⁷Co-Cbl 24-hour efflux (left) and cellular accumulation (right) of HeLa cells transfected with the siRNA probes for ABCB6, MRP1, MRP3, PMRP5, and ABCG2 mRNA (■). ▩ and □ show the same data for cells transfected with siCONTROL and nontransfected cells, respectively. All data are shown as mean of triplicates ± 1 SD. Asterisks indicate the P values less than .001 (t test) for the difference between transfected and nontransfected cells.