Leptin exerts its growth effect on breast cancer cell lines through activation of multiple signaling cascades, including the JAK/STAT, ERK1/2, PKC- alpha and PPAR signaling pathways (Hu et al. 2002; Okumura et al. 2002; Garofalo et al. 2004; Yin et al. 2004). Here, LEP is linked to breast cancer.