CXCL13 activation of c-Myc expression induces RANKL expression. (A) CXCL13 activation of ERK1/2 in human bone marrow stromal cells (SAKA-T) and murine preosteoblast (MC3T3-E1) cells. Cells were stimulated with CXCL13 (15 ng/ml) for different time points (0–60 min) and total cell lysates were subjected to Western blot analysis for ERK1/2 and pERK1/2 expression. (B) siRNA suppression of NFATc3 inhibits RANKL but not c-Myc expression and (C) siRNA suppression of c-Myc inhibits RANKL and NFATc3 expression in MC3T3-E1 cells. Cells were transiently transfected with double stranded siRNA against c-Myc or NFATc3 using oligofectamine. After 48 h, cells were treated with CXCL13 (15 ng/ml) for 6 h and total cell lysates were analyzed by Western blot for RANKL, c-Myc and NFATc3 expression. β-actin expression serves as control. Data shown are representative of three independent experiments.