Comparative analysis of galectins in primary tumors and tumor metastasis in human pancreatic cancer

Galectins are galactoside-binding proteins that exhibit an important functi on in tumor progression by promoting cancer cell invasion and metastasis fo rmation. Using Northern blotting and Western blotting analysis, in situ hyb ridization (ISH), and immunohistochemistry (IHC), we studied galectin-1 and galectin-3 in tissue samples of 33 primary pancreatic cancers and in tumor metastases in comparison to 28 normal pancreases. Furthermore, the molecul ar findings were correlated with the clinical and histopathological paramet ers of the patients. Northern blotting and Western blotting ana lysis showe d significantly higher galectin-1 and galectin-3 mRNA and protein levels in pancreatic cancer samples than in normal controls. For galectin-1, no ISH signals and immunoreactivity were observed in acinar or ductal cells in the normal pancreas and in pancreatic cancer cells, whereas fibroblasts and ex tracellular matrix cells around the cancer mass exhibited strong mRNA signa ls and immunoreactivity. Galectin-3 mRNA signals and immunoreactivity were strongly present in most pancreatic cancer cells, whereas in the normal con trols only faint ISH and IHC signals were seen in some ductal cells. Metast atic pancreatic cancer cells exhibited moderate to strong galectin-3 immuno reactivity but were negative for galectin-1. No relationship between the ga lectin-1 and galectin-3 mRNA levels and the tumor stage or between the IHC staining score and the tumor stage was found. However, galectin-1 mRNA leve ls and the IHC staining score were significantly higher in poorly different iated tumors compared with well/moderately differentiated tumors, whereas f or galectin 3 no differences were found. The expression pattern of galectin -1 and galectin-3 in pancreatic cancer tissues indicates that galectin-1 pl ays a role in the desmoplastic reaction that occurrs around pancreatic canc er cells, whereas galectin-3 appears to be involved in cancer cell prolifer ation. High levels of galectin-3 in metastatic cancer cells suggest an impa ct on metastasis formation.