Galectin-3 binding and metastasis.

ABSTRACT

Galectin-3 is a member of a family of carbohydrate-binding proteins. It is present in the nucleus, the -cytoplasm, and also the extracellular matrix (ECM) of many normal and neoplastic cell types. Reports show an upregulation of this protein in transformed and metastatic cell lines (Raz and Lotan Cancer Metastasis Rev 6 433-452, 1987; Raz et al. Int J Cancer 46 871-877, 1990). Moreover, in many human carcinomas, an increased expression of galectin-3 correlates with progressive tumor stages (Lotan et al. Int J Cancer 56 474-480, 1994; Bresalier et al. Gastroenterology 115 287-296, 1998; Nangia-Makker et al. Int J Oncol 7 1079-1087, 1995; Xu et al. Am J Pathol 147 815-822, 1995).Several lines of analysis have demonstrated that the galectins participate in cell-cell and cell-matrix interactions by recognizing and binding complementary glycoconjugates and thereby play a crucial role in normal and pathological processes. Elevated expression of the protein is associated with an increased capacity for anchorage-independent growth, homotypic aggregation, and tumor cell lung colonization (Lotan et al. Cancer Res 45 4349-4353, 1985; Lotan and Raz J Cell Biochem 37 107-117, 1988; Meromsky et al. Cancer Res 46 5270-5275, 1986). In this chapter we describe the methods of purification of galectin-3 from transformed Escherichia coli and some of the commonly used functional assays for analyzing galectin-3 binding.