NO activation of Ets-1 requires the MEK/ERK signaling pathway. (a) Western blot of relative MEK1/2 (ser 217/221) and ERK1/2 (thr 202/tyr204) phosphorylation in MDA-MB-468 cells transfected with control or NOS2 expression plasmid and cultured with L-Arg or AG. (b) Western blot of relative MEK1/2 (ser 217/221) and ERK1/2 (thr 202/tyr204) phosphorylation in serum-starved cells exposed to EGF or DETANO. (c) Western blot of ERK1/2 (thr 202/tyr204) and Ets-1 (thr 38) phosphorylation in serum-starved MDA-MB-468 cells exposed to EGF (10 ng/ml) or DETANO (0.5 mM), with and without the MEK inhibitor PD 184161. (d) Ets-luciferase activity in serum-starved MDA-MB-468 cells exposed to conditions described in (c). AG, aminoguanidine; DETANO, diethlylenetriamine NONOate; EGF, epidermal growth factor; ERK, extracellular signal-regulated protein kinase; Ets-1, erythroblastosis virus E26 oncogene homolog 1; L-Arg, L-arginine; MEK, mitogen-activated protein kinase; NOS2, nitric oxide synthase.