Different fractions of human serum glycoproteins bind galectin-1 or galectin-8, and their ratio may provide a refined biomarker for pathophysiological conditions in cancer and inflammatory disease

Abstract

Background: Changes in glycosylation of serum proteins are common, and various glycoforms are being explored as biomarkers in cancer and inflammation. We recently showed that glycoforms detected by endogenous galectins not only provide potential biomarkers, but also have different functions when they encounter galectins in tissue cells. Now we have explored the use of a combination of two galectins with different specificities, to further increase biomarker sensitivity and specificity. less thanbrgreater than less thanbrgreater thanMethods: Sera from 14 women with metastatic breast cancer, 12 healthy controls, 14 patients with IgA-nephritis (IgAN), and 12 patients with other glomerulonephritis were fractionated by affinity chromatography on immobilized human galectin-1 or galectin-8N, and the protein amounts of the bound and unbound fractions for each galectin were determined. less thanbrgreater than less thanbrgreater thanResults: Each galectin bound largely different fractions of the serum glycoproteins, including different glycoforms of haptoglobin. In the cancer sera, the level of galectin-1 bound glycoproteins was higher and galectin-8N bound glycoproteins lower compared to the other patients groups, whereas in IgAN sera the level of galectin-8N bound glycoproteins were higher. less thanbrgreater than less thanbrgreater thanConclusion: The ratio of galectin-1 bound/galectin-8N bound glycoproteins showed high discriminatory power between cancer patients and healthy, with AUC of 0.98 in ROC analysis, and thus provides an interesting novel cancer biomarker candidate. less thanbrgreater than less thanbrgreater thanGeneral significance: The galectin-binding ability of a glycoprotein is not only a promising biomarker candidate but may also have a specific function when the glycoprotein encounters the galectin in tissue cells, and thus be related to the pathophysiological state of the patient. This article is part of a Special Issue entitled Glycoproteomics.<p>Funding Agencies|Swedish Research Council (Vetenskapsradet)||Region Skane||Swedish Cancer Society||Lund University Hospital Foundation||Swedish Research Council|2008-3356|Swedish Foundation for Swedish Research|FFL4|Crafoord Foundation||Swedish Healthcare System||</p

Galectin binding to cells and glycoproteins with genetically modified glycosylation reveals galectin–glycan specificities in a natural context

“…Second, galectin-8N has a particularly high affinity for ␣2,3-sialylated ␤-galactosides present in the common core-1 O-glycan structure (29). This binding pattern can also be seen for serum glycoproteins, where galectin-8N binds a large fraction of the heavily O-glycosylated IgA1, without binding N-glycosylated IgM; galectin-1 shows the opposite profile (30). The future generation of cells lacking both O-linked glycans, N-linked glycans, and glycosphingolipids will enable further clarification of the individual role of each class of glycans in galectin binding.…”

“…Past studies have shown that both N-and mucin type O-glycans act as ligands for galectins, although the vast majority of the published data report complex N-glycans as the primary interaction partners (22,30,(35)(36)(37). To determine the contributions of N-and O-linked glycans as ligands for the individual galectins, we probed the binding of galectins to CHO cells and EPO with or without complex-type N-linked glycans and with and without core-1 O-linked glycans.…”

“…For example, glycans capped with ␣2,6-sialic acid globally block galectin binding (17,19,27), whereas galectin-8N has a particularly high affinity for galactose residues with a terminal ␣2,3-sialic acid (28,29). It has also been suggested that the unique specificity of the N-terminal CRD of galectin-8 enables high-affinity binding to O-glycans (22,30). These investigations have contributed greatly to our current understanding of galectin specificity, but most are limited by their evaluation of synthetic glycans in the absence of any appropriate protein or cellular context.…”

Galectin-3 Guides Intracellular Trafficking of Some Human Serotransferrin Glycoforms

“…We recently found that a fraction (ϳ5%) of normal transferrin is bound by galectin-3 (9), a member of a protein family defined by affinity for ␤-galactoside containing glycans, such as found in transferrin. Altered glycosylations are a hallmark of oncogenic transformation (10), and have been shown to alter galectin binding of glycoproteins (11)(12)(13). Galectin-3, like other galectins, has diverse roles in cancer, inflammation, and development (14), and one cellular mechanism for this is that it regulates the intracellular traffic of certain cellular glycoproteins by binding their glycans (11,13,15,16).…”

Knockdown of galectin-1 suppresses the growth and invasion of osteosarcoma cells through inhibition of the MAPK/ERK pathway

“…GAL1 may provide a novel candidate target for pancreatic cancer (10). Interestingly, the galectin-binding ability of a glycoprotein is not only a promising biomarker candidate but also may be related to the pathophysiological state of the patient (11). In addition, the interaction between cancer cells and their microenvironment is a vicious cycle that enhances the survival and progression of cancer, resulting in metastasis.…”