Of them, leptin has been shown to upregulate the expression of phosphorylated-STAT3 (signal transducers and activators of transcription 3), phosphorylated-ERK (extracellular signal-regulated kinase), and AP-1 (transcript activator protein 1), which might confer the proliferative effect on tumor cells [28]. The gene discussed is STAT3; the disease is neoplasm.