Coriolus versicolor is thought to be a biological response modifier. The proteoglycan constituents are responsible for its immunostimulant and anticancer activities. Many different mechanisms of action have been proposed. PSK has been found to induce cytokine expression in human peripheral blood mononuclear cells in vitro. In another studies, PSP, as well as Coriolus extract, selectively induced apoptosis of human promyelocytic leukemia HL-60 cells (13) (23). It also increased apoptotic cell death in cells that had been treated with camptothecin. In these cells, PSP reduced cellular proliferation, inhibited cell progression through both the S and G2 phases of DNA replication, reduced 3H - thymidine uptake, and prolonged DNA synthesis time (14). An additional in vitro study showed that a medicinal mushroom blend that included Coriolus Versicolor inhibited cell proliferation and induced cell cycle arrest at the G2/M phase in the invasive human breast cancer cell line MDA-MB-231 (15). DNA-microarray analysis indicated that the mushroom extract inhibited the expression of cell cycle regulatory genes and suppressed metastatic behavior through the inhibition of cell adhesion, cell migration, and cell invasion . The inhibition of metastatic behavior was linked to the suppression of urokinase plasminogen activator (uPA) (15). PSP has also been shown to inhibit the interaction between HIV-1 gp120 and CD4 receptor, HIV-1 transcriptase activity, and glycohydrolase enzyme activity associated with viral glycosylation (16). Several animal studies report of synergism between PSK and biologic therapies, including a concanavalin A-bound L1210 vaccine and the IgG2a monoclonal antibody against human colon cancer cells (17). PSP induces cytokine production and T-cell proliferation and prevents immune suppression due to cyclophosphamide in animal models. Peritoneal macrophages isolated from mice that were fed PSP show increased production of reactive nitrogen intermediates, superoxide anions, and tumor necrosis factor (18). PSP also shows analgesic activity in mouse models (19). Non-small cell lung cancer patients have increased leukocyte and neutrophil counts, and increased serum IgG and IgM after consumption of PSP (6). Healthy volunteers as well as breast cancer patients who used a formula containing Coriolus and Salvia were found to have elevated counts of T-helper lymphocytes (CD4+), high ratio of CD4+/CD8+), and elevated absolute counts of B-lymphocytes (7) (8). TNF-alpha and IL-8 gene expression were also found to be significantly induced after PSK administration in healthy volunteers and gastric cancer patients, although individual response varied (20).