Galectin-1 is expressed in various soft tissues (liver, lung, skeletal muscles, etc.) but also in tumors. Sézary cells also express galectin-1 (Nicolay). The tissue-specific expression of galectin-1 is controlled by DNA methylation. Galectin-1 interacts with the extracellular matrix (ECM) of various normal and neoplastic tissues via its surface carbohydrate residues.
Intracellularly, galectin-1 is mainly located in the cytoplasm and nucleus.
Expression of galectin-1 has been observed in various tumor types. A correlation of galectin-1 expression with the aggressiveness of tumours and their metastasis potential (Rabinovich) has been demonstrated. Concerning the influence of galectin-1 on the growth processes of cells contradictory results have been found. Extracellularly, galectin-1 binds to the disaccharide N-acetyllactosamine (LacNAc; Galbeta1-4GlcAc). Certain glycoproteins such as the matrix proteins laminin and fibronectin are ligands for galectin-1. Accordingly, it has been shown on different cell types that extracellularly occurring galectin-1 increases the adhesion of cells to matrix proteins such as laminin or fibronectin. Using melanoma cells as an example, it was also shown that galectin-1 and galectin-3 lead to the formation of multicellular aggregates. For example, it could be shown that galectin-1 interacts with oncogenic Ras and thus plays a key role in the initiation of Ras-induced tumours (Paz et al.). Furthermore, an overexpression of galectin-1 increases the membrane association of Ras and leads to oncogenic transformation of cells (Paz et al.).