A Glycoprotein Extracted from Golden Oyster Mushroom Pleurotus citrinopileatus Exhibiting Growth Inhibitory Effect against U937 Leukemia Cells

Mushrooms have become popular sources of natural antitumor, antiviral, antibacterial, antioxidative, and immunomodulatory agents. Golden oyster mushroom, Pleurotus citrinopileatus, is a common mushroom in oriental countries for human consumption. We isolated a functional protein (PCP-3A) from the fresh fruiting body of this mushroom. The isolation procedure included ammonium sulfate fractionation, DEAE-Sepharose CL-6B ion exchange chromatography, and Sephacryl S-300 gel filtration. Electrophoresis demonstrated that PCP-3A is a glycoprotein composed of 10 subunits, each approximately 45.0 kDa in size. In vitro cell study showed that PCP-3A at a concentration about 12.5 mu g/mL inhibits the proliferation of human tumor cell line U937, in a time- dependent manner (24, 48, and 72 h). It failed to agglutinate rabbit and human erythrocytes, excluding its possibility from being a lectin. Flow cytometry revealed that it is capable of inhibiting the growth of U937 cells by way of S phase arrest and apoptotic induction. We suggest that PCP-3A is worth further investigating for antitumor use.