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Cancer Research

Galectins

Galectins are a family of animal carbohydrate binding proteins; the name is from their description as β–galactoside-specific lectins. They have been strongly implicated in inflammation and cancer and may be useful as targets for the development of new anti-inflammatory and anti-cancer therapies.

Galectins occur at high concentration in a limited range of cell types, different for each galectin. Galectins bind to sugar molecules on the surface of cells. All galectins bind lactose and other β-galactosides, but they differ in their affinity for more complex saccharides.1 The galectins are defined by their structural similarities in their carbohydrate recognition domains (CRD) and by their affinity for β-galactosides; fourteen human members have been reported so far.2 The galectins have been classified into three classes, prototype, chimera, and tandem-repeat galectins. The prototype galectins (-1, -2, -5, -7, -10, -11, -13, -14), all containing one CRD and are either monomers or noncovalent homodimers. The only chimera galectin currently identified (galectin-3) contains one CRD connected to a non-lectin domain. The tandem-repeat galectins (-4, -6, -8, -9, -12) consist of two CRDs joined by a linker peptide.

Extracellular galectins crosslink cell-surface and extracellular glycoproteins and may thereby modulate cell adhesion and induce intracellular signals. Galectins may also bind intracellular non-carbohydrate ligands and have intracellular regulatory roles in processes such as RNA splicing, apoptosis, and, suggested most recently, the cell cycle.1

Galectin-3, G5170

Galectin-3, also called Mac-2, L29, CBP35 and εBP, is a chimera galectin that is expressed in tumor cells, macrophages, activated T cells, epithelial cells, and fibroblasts. It binds a variety of matrix glycoproteins including laminin and fibronectin. Intracellularly, galectin-3 acts to prevent apoptosis. Depending on the cell type, galectin-3 can be localized in the extracellular matrix, the cell surface, in the cytoplasm, or in the nucleus. Galectin-3 has been shown to exhibit proinflammatory activities in vitro and in vivo; it induces pro-inflammatory and inhibits Th2 type cytokine production.3 High levels of circulating galectin-3 have been shown to correlate with the malignancy potential of several types of cancer. Galectin-3 is known to play a role in tumor growth, metastasis, and cell-to-cell adhesion. It also serves as a preferred substrate for matrix metalloproteinase-9 (MMP-9), M4809 and M1552.4 Human and mouse Galectin-3 share approximately 80% homology in their amino acid sequence.5


Product No. Product Description Technical Bulletin
G5170 Galectin-3, human, recombinant, expressed in E. coli  

Galectin-3C, G5295

Galectin-3C is a truncated form of galectin-3 that contains the carboxy-terminus carbohydrate-binding domain. Recombinant galectin-3C competes with endogenous galactin-3 for carbohydrate binding sites and acts as a negative inhibitor of galectin-36 in promoting cell adhesion7 and cell signaling. Galectin-3C has been found to be effective in reducing metastases and tumor volumes and weights in primary tumors in an orthotropic nude mouse model of human breast cancer.8


Product No. Product Description Technical Bulletin
G5295 Galectin-3C, human, recombinant, expressed in E. coli  

Galectin-8, G3670

Galectin-8, also known as prostate carcinoma tumor antigen 1 (PCTA1) in human, is a tandem repeat-type galectin. High levels of circulating galectin-8 have been shown to correlate with lung carcinomas, certain forms of prostate carcinomas, as well as other tumor cells.9 It binds to a subset of cell surface integrins to modulate ECM-integrin interactions. It acts as a physiological modulator of cell adhesion and cellular growth, and may be involved in neoplastic transformation.10,11,12 Human and mouse galectin-8 share approximately 80% homology in their amino acid sequence.5


Product No. Product Description Technical Bulletin
G3670 Galectin-8, rat, recombinant, expressed in E. coli  

References:

  1. Leffler H., Galectins structure and function--a synopsis. Results Probl Cell Differ. 33:57-83 (2001).
  2. Cooper DN. Galectinomics: finding themes in complexity. Biochim Biophys Acta., 1572, 209-231 (2002).
  3. Rabinovich GA, et.al., Galectins and their ligands: amplifiers, silencers or tuners of the inflammatory response? Trends Immunol., 23, 313-320 (2002).
  4. Ortega N., et. al. Galectin-3 Is a Downstream Regulator of Matrix Metalloproteinase-9 Function during Endochondral Bone Formation. Mol Biol Cell., 16, 3028-3039 (2005).
  5. Bidon N., et. al., Two messenger RNAs and five isoforms for Po66-CBP, a galectin-8 homolog in a human lung carcinoma cell line. Gene, 274, 253-262 (2001).
  6. Liu, F.T., et. al., Modulation of functional properties of galectin-3 by monoclonal antibodies binding to the non-lectin domains. Biochemistry, 35: 6073-9 (1996).
  7. Ochieng, J., et al, Modulation of the biological functions of galectin-3 by matrix metalloproteinases. Biochim. Biophys. Acta, 1379: 97-106 (1998).
  8. John, C.M., et. al., Truncated galectin-3 inhibits tumor growth and metastasis in orthotopic nude mouse model of human breast cancer. Clin. Cancer Research. 9:2374-2383 (2003).
  9. Rabinovich, A. et. al., Unlocking the secrets of galectins: a challenge at the frontier of glyco-immunology, J. Leukocyte Biology 71:741 (2002).
  10. Levy, Y., et. al., Galectin 8 functions as a matricellular modulator of cell adhesion. J. Biol. Chem., 17, 31285-31295 (2001).
  11. Hadari, Y.R., et. al., Galectin 8 binding to integrins inhibits cell adhesion and induces apoptosis. J. Cell Sci., 113, 2385-2397 (2000).
  12. Camby, I., et. al., Galectins are differentially expressed in supratentorial pilocytic astrocytomas, astrocytomas, anaplastic astrocytomas, and glioblastomas and significantly modulate tumor astrocyte migration. Brain Pathol., 11, 12-26 (2001).

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