Regulation of Wnt signaling pathway by galectin-3 in hepato-biliary-pancreatic cancer : Special reference to mutation of galectin-3

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Galectin-3 (gal-3), a pleiotrophic protein, is an important regulator of tumor metastasis, which like beta-catenin shuttles between the nucleus and the cytosol in a phosphorylation-dependent manner. We report herein that beta-catenin stimulation of cyclin D1 and c-myc expression is gal-3 dependent. Gal-3 binds to beta-catenin/Tcf complex, colocalizes with beta-catenin in the nucleus, and induces the transcriptional activity of Tcf-4 as determined by the TOP/FOPFLASH reporter system. We have identified the beta-catenin gal-3-binding sequences, which are in the NH2 and COOH termini of the proteins encompassing amino acid residues 1 to 131 and 143 to 250, respectively. These data indicate that gal-3 is a novel binding partner for beta-catenin involved in the regulation of Wnt/beta-catenin signaling pathway.Analysis of the human gal-3 sequence reveled a structural similarity to beta-catenin as it also contains the consensus sequence (S92XXXS96) for glycogen synthase kinase-3beta (GSK-3beta … More ) phosphorylation and can serve as its substrate. In addition, Axin, a regulator protein of Wnt that complexes with beta-catenin, also binds gal-3 using the same sequence motif identified here by a deletion mutant analysis. The data presented here give credence to the suggestion that gal-3 is a key regulator in the Wnt/beta-catenin signaling pathway and highlight the functional similarities between gal-3 and beta-catenin.Gal-3 and Ki-67 expressions were assessed by immunohistochemistry in 115 patients with gastric cancer. PCR-single strand conformation polymorphism (SSCP)-sequence analysis and the levels of gal-3 mRNA were also examined. The present study demonstrated that gal-3 expression was correlated with nodal status, lymphatic inivasion, pathological stage and histological parameters. On the other hand, gal-3 expression did not correlate with the expression of Ki-67. Reduced expression of gal-3 was significantly associated with a poor prognosis and multivariate analysis showed that gal-3 expression was an independent prognostic factor. On PCR-SSCP-sequence analysis, 2 single nucleotide polymorphisms (SNPs) were detected in the gal-3 gene, but none showed mutations. Reduced gal-3 expression was associated with lymph node metastasis, advanced stage and tumor differentiation in gastric cancer. Gal-3 expression could be a useful prognostic factor in gastric cancer.Immunohistochemical assessment of galectin-3, beta-catenin and Ki-67 expression was performed on samples from 108 patients with colorectal cancer. The expression of galectin-3 was classified at the tumor surface and the invasive front, and its relationship with clinicopathological factors was considered from a statistical viewpoint. There was significant liver metastasis when the expression of galectin-3 was lower at the invasive front of a tumor compared to its surface (p = 0.04). There were also significant correlations between beta-catenin expression at the tumor surface and liver metastasis and tumor stage (p=0.03, p=0.04 respectively). The reduction of galectin-3 expression in tumor invasion, metastasis and proliferation in patients with colorectal cancer is suggested. Less