Expression of deleted in malignant brain tumor-1 (DMBT1) molecule in biliary epithelium is augmented in hepatolithiasis: possible participation in lithogenesis.

Deleted in malignant brain tumor-1 (DMBT1) is a mucin-like molecule participating in mucosal immune defense. Given that bovine gallbladder mucin, which accelerates cholesterol crystallization, is a DMBT1 homolog, DMBT1 expression was examined immunohistochemically in biliary epithelial cells in livers with hepatolithiasis (N = 25), primary sclerosing cholangitis (N = 7), large bile duct obstruction (N = 12), and control normal livers (N = 10). DMBT1 protein was determined in the hepatic bile samples of hepatolithiasis (N = 12) and other hepatobiliary diseases (N = 8) by immunoblot. While DMBT1 was faintly expressed in normal livers (20%), it was significantly augmented in hepatolithiasis (76%) (P < 0.05). DMBT1 was mildly expressed in primary sclerosing cholangitis and large bile duct obstruction. DMBT1 protein was detected frequently in hepatic bile samples of hepatolithiasis (50%) (P < 0.05), but in the other bile samples. The percentage of cholesterol in intrahepatic calculi was significantly higher in the patients with DMBT1-positive bile. Augmented expression and secretion of DMBT1 in intrahepatic large bile ducts in hepatolithiasis suggests its role in lithogenesis.