Intracellular Gal-1 is involved in signaling pathways, whereas extracellular Gal-1 protein interacts with cell surface glycoproteins, forming multivalent complexes on the cell surface termed “lattices.” Several lines of evidence show increased extracellular Gal-1 in many types of cancer and its overexpression is associated with poor prognosis [55]. This evidence concerns the gene LGALS1 and cancer.