ANPEP and colonic neoplasm: APN regulates cell growth in two ways, one is to inhibit leptin-induced NF-kB-dependent autocrine IL-6 production and trans-IL-6 signaling to pre-neoplastic colon epithelial cells, and the other is to inhibit IL-6-induced cell proliferation by reducing the phosphorylation and activation of STAT-3 in advanced colon cancer cells [24].