The test measures the activity of alpha-N-acetylgalactosaminidase (nagalase) in blood.
Nagalase is an extracellular matrix-degrading enzyme that is (increased) secreted by cancerous cells in the process of tumor invasion. It also is an intrisic component of the envelope protein of various virions, such as HIV, Epstein-Barr virus (EBV), herpes zoster and the influenza virus. Thus, it is also secreted from virus-infected cells..
Ref:1,3,4,10
Nagalase deglycosylates the vitamin D3-binding protein DBP (in humans better known as Gc-protein). Gc-protein is the precursor for the major macrophage-activating factor (MAF). Gc-protein carries one trisaccharide consisting of N-acetylgalactosamine with dibranched galactose and sialic acid termini. By deglycosylation, the (complete) trisaccharide is removed from the Gc-protein. This glycosylated Gc-protein can no longer be converted to MAF.
Normally MAF is produced from the Gc-protein by sequential removal of the galactose and sialic acid termini by beta-galactosidase and sialidase, selectively, with N-acetylgalactosamine as the remaining sugar. Macrophage-activation for phagocytosis and antigen presentation is the first step in the immune development cascade. Lost precursor activity leads to immunosuppression.
Increased nagalase activity
has been detected in the blood of patients with a wide variety of cancers, like cancer of the prostate, breast, colon, lung, esophagus, stomach, liver, pancreas, kidney, bladder, testis, uterus and ovary, mesothelioma, melanoma, fibrosarcoma, glioblastoma, neuroblastoma and various leukeamias.
Ref: 1,3,4 For various types of tumors, various levels of nagalase activity were found.7 It appears that the secretory capacity of individual tumor tissue varies among tumor types depending upon tumor size, staging, and the degree of malignancy or invasiveness.7 Increased nagalase activity has not been detected in the blood of healthy humans. Ref:1
Is nagalase activity directly proportional to viable tumor burden?
Studies correlating nagalse levels with tumor burden suggest that the measurement of this enzyme can diagnose the presence of cancerous lesions below levels detectable by other diagnostic means.1 In research studies, nagalase activity decreased to near the tumor-free control level one day after surgical removal of primary tumors from cancer patients, suggesting that the half-life value of nagalse is less than 24 hous. Ref:1,6 The short half-life of nagalase is valuable for prognosis of the disease during various therapies.1,5
Nagalase is the intrinsic component of envelope protein gp160 of HIV-virions and of the envelope protein hemagglutinin (HA) of influenza virus. Nagalase activity is the sum of enzyme activities carried by both HIV virions and unassembled envelope proteins.
Ref. 4