Leptin, a 16-kDa nonglycosylated protein encoded by the Ob gene and mainly secreted by adipose tissue (Friedman and Halaas, 1998), is a protein hormone with relevant roles in cell survival, differentiation, inflammation and angiogenesis which indicate its potential activities in cancer development and progression (Sierra-Honigmann et al., 1998; Somasundar et al., 2004). This evidence concerns the gene LEP and cancer.