Figure 4

Effect of tumor primary culture (TPC) conditioned medium (CM) and leukemia inhibitory factor (LIF)-neutralizing antibody. (a) Stat3 (signal transduction and activators of transcription 3) and phospho-Stat3 (p-Stat3) in HC11 and LM3 cells treated with increasing concentrations of CM (30%, 50% and 80%). (b) Stat3 and p-Stat3 levels in HC11 and TPC cells treated with CM that had been preincubated with or without LIF-neutralizing antibody. (c) Phosphorylation levels of Stat3 and extracellular signal-regulated kinase (ERK)1/2 in HC11 cells treated with LIF (3 and 5 ng/ml) preincubated with or without LIF-neutralizing antibody. (d) Expression of CCAAT-enhancer-binding protein (C/EBP)δ in TPC cells treated with CM with or without neutralizing antibody. (e) Phosphorylation of Stat3 and ERK1/2 in HC11 cells treated with LIF with or without the MAP kinase/ERK kinase inhibitor PD98059. (f) p-Stat3 and Stat3 in HC11 and TPC cells treated with LIF with or without the Src-specific inhibitor PP2. Experiments were repeated at least three times with similar results. No effect was observed on phosphorylation levels of either Stat3 or ERK1/2 when HC11 cells were treated with the PD98059 vehicle, dimethyl sulfoxide (data not shown).