Sharing of MEK/ERK signaling pathway by CD30, CD40, and RANK in HD cell lines. MEK/ERK signaling pathway is shared by CD30, CD40, and RANK in HD cell lines. (A) The L-428 cell line, which expresses CD30, CD40, and RANK receptors, was incubated with 1 μg/mL of CD30 ligand (CD30L), CD40 ligand (CD40L), and RANK ligand (RANKL) for 1 to 6 hours. Total ERK and p-ERK were determined by Western blot. All 3 ligands increased the phosphorylation of ERK in a time-dependent manner. (B) When the L-428 cell line was incubated with CD30L, CD40L, or RANKL for 6 hours, ERK phosphorylation was induced. UO126 (25 μM) inhibited the basal level of p-ERK, and the combination of UO126 with any of these 3 ligands inhibited the ligand-induced ERK phosphorylation. (C) Under serum deprivation conditions (1% FBS), any of the studied ligands (CD30L, CD40L, RANKL) enhanced the survival of the L-428 HD cell line, an effect that was inhibited by UO126.