LEP and renal cell carcinoma: Choi et al. prospectively evaluated the associations between the plasma levels of four plasma adipokines, leptin, adiponectin, retinol binding protein 4 (RBP-4), nicotinamide phosphoribosyltransferase (NAMPT), and RCC, and they determined that adiponectin, RBP-4, and NAMPT, but not leptin, were significantly associated with RCC [22].