title: Tumor cell alpha-N-acetylgalactosaminidase activity and its involvement in GcMAF-related macrophage activation.
abstract: Alpha-N-acetyl galactosaminidase (alpha-NaGalase) has been reported to accumulate in serum of cancer patients and be responsible for deglycosylation of Gc protein, which is a precursor of GcMAF-mediated macrophage activation cascade, finally leading to immunosuppression in advanced cancer patients. We studied the biochemical characterization of alpha-NaGalase from several human tumor cell lines. We also examined its effect on the potency of GcMAF to activate mouse peritoneal macrophage to produce superoxide in GcMAF-mediated macrophage activation cascade. The specific activity of alpha-NaGalases from human colon tumor cell line HCT116, human hepatoma cell line HepG2, and normal human liver cells (Chang liver cell line) were evaluated using two types of substrates; GalNAc-alpha-PNP (exo-type substrate) and Gal-beta-GalNAc-alpha-PNP (endo-type substrate). Tumor-derived alpha-NaGalase having higher activity than normal alpha-NaGalase, had higher substrate specificity to the exo-type substrate than to the endo-type substrate, and still maintained its activity at pH 7. GcMAF enhance superoxide production in mouse macrophage, and pre-treatment of GcMAF with tumor cell lysate reduce the activity. We conclude that tumor-derived alpha-NaGalase is different in biochemical characterization compared to normal alpha-NaGalase from normal Chang liver cells. In addition, tumor cell-derived alpha-NaGalase decreases the potency of GcMAF on macrophage activation.
authors.affiliation: Department of Biological Science and Technology, Faculty of Engineering, The University of Tokushima, Tokushima 770-8506, Japan.
authors.forename: Saharuddin B
authors.initials: SB
authors.lastname: Mohamad
authors.forename: Hideko
authors.initials: H
authors.lastname: Nagasawa
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Uto
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Hori
mesh_terms: D000818:Animals; D002455:Cell Division; D006596:Hexosaminidases / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008070:Lipopolysaccharides / Q000494:pharmacology; D008262:Macrophage Activation / Q000187:drug effects*; D016215:Macrophage-Activating Factors / Q000494:pharmacology*; D051379:Mice; D015398:Signal Transduction / Q000187:drug effects; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured; D014809:Vitamin D-Binding Protein / Q000494:pharmacology*; D048809:alpha-N-Acetylgalactosaminidase
chemical_list: D008070:Lipopolysaccharides; D016215:Macrophage-Activating Factors; D014809:Vitamin D-Binding Protein; C101908:vitamin D-binding protein-macrophage activating factor; D006596:Hexosaminidases; C482722:NAGA protein, human; D048809:alpha-N-Acetylgalactosaminidase