A recombinant form of GC (group-specific component) protein-derived macrophage-activating factor (GC-MAF) with potential immunostimulating and antineoplastic activities. Upon administration, globulin component macrophage-activating factor is able to stimulate macrophages to kill cancer cells, inhibit angiogenesis and stimulate the immune system. This decreases tumor cell proliferation. GC, also known as vitamin D binding protein (VDBP), is converted to GC-MAF by enzymes located in the membrane of B- and T-lymphocytes. However, deglycosylated GC protein cannot be converted to GC-MAF. Endogenous GC-MAF is often not activated in patients with cancer due to an increased activity of nagalase (also called alpha-N-acetylgalactosaminidase), an enzyme secreted by cancer cells that mediates the deglycosylation of GC; thus preventing macrophage activation and immunosuppression.