Multifaceted immunotherapeutic effects of vitamin D-binding protein-derived macrophage activating factor (GcMAF) on human breast cancer and neuroblastoma cells

The vitamin D axis includes vitamin D, its receptor (VDR) and vitamin D-binding protein (or Gc-globulin) that is the precursor of the Gc-globulin-derived Macrophage Activating Factor (GcMAF), a protein that has been proposed as an immunotherapeutic agent in the treatment a variety of conditions ranging from cancer to neurological disorders. Here we demonstrate that GcMAF (Immuno Biotech Ltd) added to human breast cancer cells (MCF-7, HPA Culture Collection) inhibited their proliferation, induced morphological changes, reduced vimentin expression and inhibited cancer cell-induced angiogenesis. We also describe the effects of GcMAF on the activation of macrophages added to MCF-7 cells. Macrophages (Raw 264.7, HPA Culture Collection) were activated by culturing them in the presence of 100 ng/ml GcMAF for 72 h prior to addition to the MCF-7 cells. The macrophages were added at a ratio of 1:1 to the MCF-7 cells. Photography was taken over a 60 h period using an Olympus CK2 microscope and a GXCAM-3 with NCH Debut capture software. After about 60 h, the irregular growth of the breast carcinoma cells was arrested and carcinoma cells were phagocytised by the activated macrophages. Finally, we demonstrate the GcMAF inhibited proliferation of human brain neuroblastoma cells (SH-SY5Y, ATCC) and induced morphological changes consistent with induction of apoptosis. Taken together, these results support the hypothesis that GcMAF has multiple biological effects: it inhibits cancer cell proliferation and metastatic potential; it reverts the neoplastic phenotype; it inhibits cancer cell-induced angiogenesis; and it stimulates tumoricidal macrophages that phagocytise cancer cells