Cancer is one of the leading causes of death all-overs the world. However, edible mushrooms have attracted a great attention due to their fame for anti-tumour and immune-stimulatory activities. In the present study, endopolysaccharides from the mushroom Pleurotus ostreatus (P. ostreatus) were extracted, partially purified and studied for their antitumour and immune-modulating effects both in vitro and in vivo. The in vitro results showed that P. ostreatus endopolysaccharide fractions at doses 0.01, 0.05, and 0.25 mg/2 ml inhibited the proliferation of Ehrlich ascites tumour (EAT) cells in a dose-dependent manner. The in vivo results showed that inoculation of EAT (4 x 106 cells) to mice altered the differential count of leukocytes, the cellularity of different lymphoid organs, as well as the total and differential count of peritoneal exudates cells. Pre-treatment of tumour-bearing mice with doses 0.1, 0.5, and 2.5 mg/20 g BW of P. ostreatus fraction III endopolysaccharide daily for consecutive 3 weeks recovered the disturbances in the cellularity of all studied lymphoid organs. Phagocytosis of macrophages, spleen-derived T-lymphocytes and spleen-derived B-lymphocytes functions were significantly decreased in EAT-bearing mice. P. ostreatus endopolysaccharide pre-treatment enhanced the phagocytic function of macrophages, as well as T- and B-cell functions of EAT-bearing mice. The in vitro results indicate that P. ostreatus endopolysaccharides can directly inhibit the cancer cell proliferation through cytotoxicity, and the in vivo results indicate that the anti-tumour effects may come through the indirect pathway by activating the host immune response, which thus leads to an increase in the hosts capacity to kill tumour cells and suppress tumour growth.
Key words: Pleurotus ostreatus, Endopolysaccharides, Ehrlich ascitis tumour, immune system
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