A and B. The relative expression of ABCA1, ABCB1, ABCC2, and ABCG2 in control and L1-depleted Y79 cells (A) or control and L1-overexpressing SNUOT-Rb1 cells on RT-PCR. C and D. The relative fluorescence intensity of control, L1-depleted or -overexpressing cells, and control cells with the treatment of MDR inhibitors on the MDR assay (C, Y79 cells; D, SNUOT-Rb1 cells). E. The expression of L1, phospho-Akt (p-Akt), Akt, phospho-ERK (p-ERK), ERK, phospho-p38 (p-p38), and p38 in Y79 cells upon the treatment with LY294002 (an Akt inhibitor), PD98059 (an ERK inhibitor), and SB203580 (a p38 inhibitor) on Western blot analyses. F. The relative expression of ABCA1, ABCB1, ABCC2, and ABCG2 upon the treatment with ERK and p38 pathway inhibitors. Control, Y79 cells or SNUOT-Rb1 cells; shL1, Y79 cells transfected with L1-specific shRNA; L1 OE, SNUOT-Rb1 cells transfected with a lentiviral vector containing full length L1. Bars, SD. *, P < 0.05; **, P < 0.01; ***, P < 0.001 (one-way ANOVA with post-hoc Bonferroni's multiple comparison test).