LEP and neoplasm: Leptin secreted by adipose tissues can activate the signaling pathways of Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3), extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun (transcription factor Jun), and AKT (protein kinase B) to promote tumor progression and migration [35,36].