Leptin interacts with its receptor ObR and activates pro‐survival pathways in cancer cells via effects on signaling through the Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3), extracellular signal‐regulated kinase (ERK), protein kinase B (AKT) and Jun N‐terminal kinase (JNK) pathways [87]. This evidence concerns the gene STAT3 and cancer.