Gastrotropin, also known as Fatty acid-binding protein 6, Ileal lipid-binding protein, ILBP, Intestinal 15 kDa protein, Intestinal bile acid-binding protein, I-BABP and FABP6, is a cytoplasm protein which belongs to the calycin superfamily and Fatty-acid binding protein (FABP) family. Isoform 2 of FABP6 is expressed in colorectal adenocarcinomas and their adjacent normal mucosa (at protein level). Isoform 1 of FABP6 is expressed in the jejunum, ileum, cecum and ascending colon intestine. Isoform 2 is expressed in the gallbladder, duodenum, jejunum, ileum, cecum, ascending, transverse and descending colon, sigmoid colon and rectum. FABP6 / I-BABP is a cancer-related protein that acts as an intracellular transporter of bile acid in the ileal epithelium. FABP6 / I-BABP may also play an important role in early carcinogenesis.