STAT3 and neuroblastoma: To assess the effect of homocysteine on leptin signaling, we pre-treated the SH-SY5Y-Ob-Rb human neuroblastoma cell line with homocysteine at 3 and 10 mM and analyzed the phosphorylation of STAT3 induced by leptin (0.01 μg/mL, equal to 0.6 nM).