Wnt/beta-catenin signaling plays an important role in normal development. However, its aberrant activation is associated with several cancers. The aim of this study is to examine the Wnt/beta-catenin pathway in patients with advanced pancreatic adenocarcinoma (n = 31). Paraffin sections from tumors (n = 16) and normal pancreata (n = 3) were used to determine the localization of beta-catenin. An additional 15 frozen tumors, adjacent normal pancreata (n = 5), or normal pancreata (n = 4) were utilized for protein isolation. Tumors were also examined for mutations in exon 3 of the CTNNB1 gene. More than 65% of the tumors showed an increase in total beta-catenin, consistent with its enhanced membranous, cytoplasmic, and nuclear localization, but only two showed mutations in CTNNB1. The majority of the remaining tumors demonstrated concurrent increases in Wnt-1 and frizzled-2 (positive regulators) and a decrease in Ser45/Thr41-phospho-beta-catenin. Electrophoretic mobility shift assay demonstrated beta-catenin-T-cell factor binding in tumors only. Adenomatous polyposis coli and axin, which are both negative regulators, remained unchanged. Unexpectedly, total glycogen synthase kinase-3beta protein was elevated in these tumors. Elevated levels of E-cadherin were also observed, although E-cadherin-beta-catenin association in tumors remained unaffected. Thus, Wnt/beta-catenin activation was observed in 65% of pancreatic adenocarcinomas, independently of beta-catenin gene mutations in most tumors.

Hepatocytes in primary cultures de-differentiate and re-differentiate following addition of Engelbreth-Holm-Swarm mouse sarcoma (matrigel) to the cultures. The Wnt/beta-catenin pathway has been shown to be important in liver growth and development. Here, we investigate changes in beta-catenin and its mechanism, during matrigel-induced hepatocyte differentiation. Primary rat hepatocytes were cultured for 8 days, and matrigel was added to half of the cultures. Total and nuclear protein and total RNA were extracted at different days of culture and examined for beta-catenin and other Wnt pathway components. A significant increase in total beta-catenin protein was observed upon matrigel addition, during hepatocyte differentiation, despite a decrease in beta-catenin and frizzled-1 (Wnt receptor) expression. A concurrent decrease in the glycogen synthase kinase-3beta (GSK3beta), axin, and ser45/thr41-phosphorylated beta-catenin proteins was observed in matrigel-treated cultures, implying decreased degradation of beta-catenin. Interestingly, a decrease in nuclear beta-catenin and total active beta-catenin was observed in the presence of matrigel. Matrigel also induced an increased association of beta-catenin with Met (hepatocyte growth factor receptor), whereas association with E-cadherin remained unchanged. This coexisted with decreased beta-catenin tyrosine phosphorylation. Thus, beta-catenin undergoes multifactorial regulation during matrigel-induced hepatocyte differentiation and maturation; this induces its stabilization and membrane translocation, possibly contributing to hepatocyte differentiation.