Extracellular signal-regulated protein kinase (ERK) and p38 activations are crucial for MYC expression after receptor activator of nuclear factor-κB ligand (RANKL) stimulation. Mouse osteoclast precursor cells (OCPs) were pretreated with either DMSO (vehicle), U0126 (5 μM), SP600125 (5 μM), SB203580 (10 μM) or LY294002 (5 μM) for 30 min and then stimulated with RANKL (50 ng/mL) for 6 h. (A) The mRNA expression of Myc (relative to the hypoxanthine guanine phosphoribosyl transferase (Hprt) housekeeping gene, n = 3). (B) Immunoblot of nuclear protein lysates using c-Myc and Lamin B antibodies. Lamin B served as the loading control. Data are representative of three experiments. (C) Signal intensity of the c-Myc immunoblot in B quantified using densitometry and normalized to Lamin B and to vehicle-treated RANKL control (n > 3). All data are shown as mean ± s.e.m. ** p < 0.01, *** p < 0.001 and **** p < 0.0001 using one-way ANOVA in (A,C); NS, not significant in (C).