α-N-acetylgalactosaminidase (nagalase) accumulates in the serum of cancer patients and its activity correlates with tumor burden, aggressiveness and clinical disease progression. The administration of GC protein-derived macrophage-activating factor (GcMAF) to cancer patients with elevated levels of nagalase has been associated with a decrease of serum nagalase activity and with significant clinical benefits. Here, we report the results of the administration of GcMAF to a heterogeneous cohort of patients with histologically diverse, advanced neoplasms, generally considered as “incurable” diseases. In most cases, GcMAF therapy was initiated at late stages of tumor progression. As this is an open-label, non-controlled, retrospective analysis, caution must be employed when establishing cause-effect relationships between the administration GcMAF and disease outcome. However, the response to GcMAF was generally robust and some trends emerged. All patients (n = 20) presented with elevated serum nagalase activity, well above normal values. All patients but one showed a significant decrease of serum nagalase activity upon weekly GcMAF injections. Decreased nagalase activity was associated with improved clinical conditions and no adverse side effects were reported. The observations reported here confirm and extend previous results and pave the way to further studies aimed at assessing the precise role and indications for GcMAF-based anticancer immunotherapy.
α-N-acetylgalactosaminidase (nagalase) is known to accumulate in the serum of cancer patients, where it mediates the deglycosylation of group-specific component (GC), best known as vitamin D-binding protein (VDBP), which is the precursor of GC protein-derived macrophage-activating factor (GcMAF). Deglycosylated VDBP cannot be converted into GcMAF1 and decreased GcMAF levels reportedly promote immunodeficiency in individuals bearing advanced neoplasms.2 The increase in nagalase activity observed in cancer patients is mostly due to the fact that malignant cells release enzymatically active nagalase.3 Thus, serum nagalase activity reflects not only tumor burden and aggressiveness, but also the clinical progression of the disease.4–7 Nowadays, the assessment of serum nagalase activity is proposed as a reliable means to determine the clinical severity of multiple neoplasms.3
In serum, nagalase acts as an endo- (but not as an exo-) enzyme, being unable to deglycosylate an N-acetylgalactosamine (GalNAc) residue of GcMAF.5 Thus, circulating nagalase cannot degrade exogenous GcMAF.5–7 This observation suggested that patients with elevated nagalase activity may benefit from the exogenous provision of GcMAF. Alongside, GcMAF was observed to exert multiple anticancer effects in vivo and in vitro, both in experimental and in spontaneous tumor models. Given the impact of GcMAF on macrophages and their central role anticancer immune responses, GcMAF is widely considered as an immunotherapeutic agent.7
However, in addition to stimulating tumor-infiltrating macrophages,8 GcMAF not only directly inhibits the proliferation of various human cancer cells in vitro,9,10 but also reverts the malignant phenotype of human breast cancer cells.10 Moreover, GcMAF reportedly inhibits angiogenesis, thus depriving neoplastic lesions of the oxygen and nutrient supplies that are needed for tumor progression and metastasis.10–13 Recently, it has been proposed that the antineoplastic effects of GcMAF are mediated by the vitamin D receptor (VDR), and it was demonstrated that GcMAF stimulates an intracellular signaling pathway impinging on cyclic AMP. This signal transduction cascade could actually be responsible for death of malignant cells exposed to GcMAF.12 Taken together, these in vitro and in vivo findings lend a rationale to the observation that GcMAF exert dramatic anticancer effects in (at least a fraction of) patients with advanced cancer.5–7 Of note, in the aforementioned studies, the anticancer effects of GcMAF were evaluated by measuring serum nagalase activity as a marker of tumor burden and progression.2,3,14
The biological effects of GcMAF have been documented in a variety of experimental systems and make the subject of more than 50 peer-reviewed papers published during the past 20 y.15 Because of the solid scientific rationale underlying the compassionate use of GcMAF in advanced cancer patients, hundreds of physicians in all parts of the world have adopted this approach for a variety of indications in which it could prove useful. Here, we present a series of clinical cases exemplifying the results that have been obtained with the administration of GcMAF to patients with diverse types of advanced cancers, with a particular focus on the effects of GcMAF on serum nagalase activity. We are well aware that these cases, because of their heterogeneity and reduced number, can be considered anecdotal. However, a very recent study on the evaluation of clinical practice strongly encourages the re-evaluation of individual cases such as those presented here.16 Thus, while some studies present large and impressive statistics obtained from large clinical cohorts, others may report a limited number of noteworthy cases, as we do here. According to this novel, authoritative, epistemological approach, “all of these stories become evidence of what works in medicine.”16 Therefore, we believe that the clinical cases reported below point to beneficial effects for the administration of GcMAF to advanced cancer patients, prompting further studies to formally address this possibility.
The mean pre-GcMAF treatment serum nagalase activity documented in our patient cohort was 2.84 ± 0.26 nM/min/mg, with a range of 1.00–5.60 nM/min/mg (Table 1). At the time of second testing (average interval = 112 d), the mean serum nagalase activity in the course of GcMAF treatment was 2.01 ± 0.22 nM/min/mg, with a range of 1.00–3.20 nM/min/mg. The difference between these values was statistically significant (p < 0.05). Of note, no patient of this cohort was initially observed to be within the laboratory reference range for serum nagalase activity (0.90–0.92 nM/min/mg). At the time of final testing (average interval = 263 d), the mean serum nagalase activity of the patient cohort was 1.59 ± 0.17 nM/min/mg, with a range of 0.60–2.80 nM/min/mg. The difference between this value and the serum nagalase activity recorded before the initiation of GcMAF treatment was also statistically significant (p < 0.01).
Narrative description of some notable clinical cases from The Netherlands
The following reports were collected and communicated by Dr. Steven Hofman (CMC, Capelle aan den Ijssel; The Netherlands) and refer to the years 2011–2012. In addition to GcMAF, most patients were prescribed supplementation of vitamins D and A. Additional supplements are indicated when assumed. Most of the patients did not assume conventional anticancer chemotherapy along with GcMAF. However, several patients had been subjected to conventional anticancer therapies in the previous years, as indicated in individual reports. When patients assumed conventional therapeutics, such as hormones, in the course of GcMAF administration (e.g., patient #8), this is indicated in the individual report. When not indicated otherwise, patients received 100 ng GcMAF weekly, as a single intramuscular injection, in line the commonly accepted recommendations.5–7 Original reports are in italics. Each case is referred to with progressive numbers, as in Table 1.
In Figure 1, the decrease of serum nagalase activity in the patient cohort is plotted in function of the consecutive testing. Of note, since this is a retrospective analysis and not a clinical trial, nagalase determinations were not performed at the same time point in each individual patient. The overall shape of the graph, however, is very similar if not completely superimposable to that of other graphs of the same type that have previously been reported.5–7,17