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Tumor cell alpha-N-acetylgalactosaminidase activity and its involvement in GcMAF-related macrophage activation
Saharuddin B Mohamad1, Hideko Nagasawa, Yoshihiro Uto
1Department of Biological Science and Technology, Faculty of Engineering, The University of Tokushima, Tokushima 770-8506, Japan.
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.
Insights
Tumor-derived alpha-N-acetyl galactosaminidase (alpha-NaGalase) shows distinct biochemical properties compared to normal alpha-NaGalase. This enzyme impairs GcMAF
Area of Science:
- Biochemistry
- Immunology
- Oncology
Background:
- Alpha-N-acetyl galactosaminidase (alpha-NaGalase) accumulates in cancer patients' serum.
- It deglycosylates Gc protein, a GcMAF precursor, leading to immunosuppression.
Purpose of the Study:
- To biochemically characterize alpha-NaGalase from human tumor cell lines.
- To assess its impact on GcMAF's ability to activate macrophages.
Main Methods:
- Evaluated specific activity of alpha-NaGalases from HCT116, HepG2, and Chang liver cells using exo- and endo-type substrates.
- Assessed GcMAF-mediated superoxide production in mouse macrophages after pre-treatment with tumor cell lysate.
Main Results:
- Tumor-derived alpha-NaGalase exhibited higher activity and specificity for exo-type substrates than normal alpha-NaGalase.
- Tumor cell lysate pre-treatment significantly reduced GcMAF's potency in activating macrophages.
Conclusions:
- Tumor-derived alpha-NaGalase possesses unique biochemical characteristics compared to normal variants.
- Elevated tumor alpha-NaGalase activity diminishes GcMAF's effectiveness in macrophage activation, potentially contributing to cancer progression.
