It appears that leptin-mediated proliferation of these cancers occurs through the activation of the JAK-STAT [25, 27, 29–31, 34, 41], PI3K [24, 31, 33, 36], and MAPK [24, 31] pathways, whereas apoptosis avoidance is promoted by leptin via the JAK-STAT [28, 34] and PI3K [33, 36] pathways (Figure 1). The gene discussed is LEP; the disease is cancer.