Department of Immunology, Institute for Biological Research Sinisa Stankovi?, Belgrade University, Belgrade, Serbia.
Abstract
Numerous studies have shown immunostimulatory and anti-tumor effects of water and standardized aqueous ethanol extracts derived from the medicinal mushroom, Coriolus versicolor, but the biological activity of methanol extracts has not been examined so far. In the present study we investigated the anti-tumor effect of C. versicolor methanol extract (which contains terpenoids and polyphenols) on B16 mouse melanoma cells both in vitro and in vivo. In vitro treatment of the cells with the methanol extract (25-1600 microg/ml) reduced melanoma cell viability in a dose-dependent manner. Furthermore, in the presence of the methanol extract (200 microg/ml, concentration IC(50)) the proliferation of B16 cells was arrested in the G(0)/G(1) phase of the cell cycle, followed by both apoptotic and secondary necrotic cell death. In vivo methanol extract treatment (i.p. 50 mg/kg, for 14 days) inhibited tumor growth in C57BL/6 mice inoculated with syngeneic B16 tumor cells. Moreover, peritoneal macrophages collected 21 days after tumor implantation from methanol extract-treated animals exerted stronger tumoristatic activity ex vivo than macrophages from control melanoma-bearing mice. Taken together, our results demonstrate that C. versicolor methanol extract exerts pronounced anti-melanoma activity, both directly through antiproliferative and cytotoxic effects on tumor cells and indirectly through promotion of macrophage anti-tumor activity.
Servicio de Análisis Clínicos e Inmunologia, Hospital Universitario Virgen de las Nieves, Universidad de Granada, Av, de las Fuerzas Armadas 2, 18014 Granada, Spain. evajimenez@fundacionhvn.org
Abstract
BACKGROUND: Protein-bound polysaccharide (PSK) is derived from the CM-101 strain of the fungus Coriolus versicolor and has shown anticancer activity in vitro and in in vivo experimental models and human cancers. Several randomized clinical trials have demonstrated that PSK has great potential in adjuvant cancer therapy, with positive results in the adjuvant treatment of gastric, esophageal, colorectal, breast and lung cancers. These studies have suggested the efficacy of PSK as an immunomodulator of biological responses. The precise molecular mechanisms responsible for its biological activity have yet to be fully elucidated.
METHODS: The in vitro cytotoxic anti-tumour activity of PSK has been evaluated in various tumour cell lines derived from leukaemias, melanomas, fibrosarcomas and cervix, lung, pancreas and gastric cancers. Tumour cell proliferation in vitro was measured by BrdU incorporation and viable cell count. Effect of PSK on human peripheral blood lymphocyte (PBL) proliferation in vitro was also analyzed. Studies of cell cycle and apoptosis were performed in PSK-treated cells.
RESULTS: PSK showed in vitro inhibition of tumour cell proliferation as measured by BrdU incorporation and viable cell count. The inhibition ranged from 22 to 84%. Inhibition mechanisms were identified as cell cycle arrest, with cell accumulation in G0/G1 phase and increase in apoptosis and caspase-3 expression. These results indicate that PSK has a direct cytotoxic activity in vitro, inhibiting tumour cell proliferation. In contrast, PSK shows a synergistic effect with IL-2 that increases PBL proliferation.
CONCLUSION: These results indicate that PSK has cytotoxic activity in vitro on tumour cell lines. This new cytotoxic activity of PSK on tumour cells is independent of its previously described immunomodulatory activity on NK cells.
PMID: 18366723 [PubMed – indexed for MEDLINE]PMCID: PMC2291471Free PMC Article
Polysaccharopeptide (PSP) is a substance produced by an edible mushroom, Coriolus versicolor which has been claimed to possess antitumor activity. However, neither tumoricidal activity nor cytotoxicity was observed when five tumor cell lines and mouse peritoneal macrophages were cultured in vitro in the presence of 2.5-10 ?g/ml PSP. An increase in the production of reactive nitrogen intermediates, reactive oxygen intermediates (superoxide anions) and tumor necrosis factor was measured in peritoneal macrophages collected from inbred C57 mice which had received PSP in the drinking water for 2 weeks. Northern blot analysis also demonstrated that PSP activated the transcription of tumor necrosis factor gene in these cells, indicating that PSP exerted an immunomodulatory effect on the defensive cells.
The protein-bound polysaccharide PSK was tested for the ability to activate human natural killer (NK) cells. When blood lymphocytes and purified CD3-CD16 ÷ large granular lymphocytes (LGL) were treated in vitro overnight with PSK, they demonstrated enhanced NK cell activity against K562. The PSK-activated killer cells also lysed NK-resistant targets and freshly isolated autologous and allogeneic tumor cells. The PSK effect was observed with concentrations that could be obtained in the blood of cancer patients receiving oral administration of PSK. PSK-induced enhancement of NK activity was not abrogated by monoclonal antibodies (mAb) that neutralized interferon (IFN)o~, IFN3,, or interleukin-2 (IL-2). In addition, mAb reactive with p55 (~ chain) or p75 (/3 chain) glycoproteins of IL-2 receptors had no effects on PSK-enhanced NK activity even when used simultaneously. These results indicate that the PSK could activate human NK cells independently of IFN and IL-2/IL-2R systems.
We found that PSK has an antiviral effect on human immunodeficiency virus (HIV) in vitro. One of the mechanisms of this effect is attributable to the inhibition of binding of HIV with lymphocytes. Here, we found that PSK inhibits reverse transcriptase in a non-competitive way in vitro. Such inhibition may be important in its anti-HIV effect as well as its inhibitory effect on the binding of HIV with lymphocytes.