Immunohistochemical analysis of the progression of flat and papillary preneoplastic lesions in intrahepatic cholangiocarcinogenesis in hepatolithiasis

Background: Two types of precursor lesions, flat-type 'biliary intraepithelial neoplasia (BilIN)' and papillary-type ` intraductal papillary neoplasm of the bile duct (IPNB)', are proposed in the tumorigenesis of intrahepatic cholangiocarcinoma (ICC) in hepatolithiasis. Methods: In this study, the participation of cancer-related molecules in the progression of these two precursor lesions was examined, using 64 hepatolithiatic livers with BilIN lesions ( 45 livers) and IPNB lesions ( 19 livers) and 10 hepatolithiatic livers without neoplastic lesions as a control. The expression of E-cadherin, beta-catenin, matrix metalloproteinase-7 (MMP-7), membrane type 1-MMP (MT1-MMP), cyclin D1 and c-myc was immunohistochemically examined. Results: The membranous expression of beta-catenin decreased along with the progression in both BilIN and IPNB lineages. Membranous expression of E-cadherin was significantly decreased in invasive ICC with BilIN and IPNB in comparison with non-invasive counterparts. MMP-7 and MT1-MMP were commonly expressed in invasive ICC with BilIN (100%), while non-invasive lesions (BilIN-1, -2, -3) and the IPNB lineage were only occasionally and weakly positive for these molecules. Cyclin D1 and c-myc, target molecules of Wnt signalling, were frequently positive in the IPNB lineage ( 65 and 54% respectively), and interestingly nuclear beta-catenin staining, reflecting activation of Wnt signalling, was observed only in the IPNB lineage (22%) (P < 0.05). Conclusions: Decreased membranous expression of beta-catenin and E-cadherin is an early event in the tumorigenesis of both BilIN and IPNB lineages. The expression of MMP-7 and MT1-MMP was closely associated with invasive growth of the BilIN lineage. The Wnt signalling pathway may play an important role in the tumorigenesis of the IPNB lineage.