| For some decades now, dramatic changes have been in the natural, built, and social environments, as environment pollution is continuously serious, and the pressure of modern life is becoming increasingly greater. The WHO (World Health Organization) has officially classified8.2million people worldwide died from cancer in2012raised by40%in the past decade. However, traditional chemotherapy is worth expensive and causes lots of undesirable side effects. Therefore, to find new anti-cancer drugs with higher biologically activities and less or without side effects from nature is going to be extremely important.Recently, biologically active polysaccharide as a kind of biological response modifier (BRM) is widely researched now. As one of the most important part of the polysaccharides, fungi polysaccharide has drawn amounts of attention due to their immunomodulatory, antioxidant and anti-tumor effects in the biochemical and medical areas. Some of those have been developed into immune enhancement and anti-tumor drugs on clinical use, such as Lentinus edodes.Rhizopus nigricans is a kind of filamentous fungi and has been isolated in our laboratory. Two kinds of extracellular polysaccharides, EPS1-1and EPS-2are isolated from its fermentation liquid. The molecular weight of EPS1-1was31,930Da, and its monosaccharides consist of rhamnose, xylose, fructose, mannose, glucan and galactose in the relative proportions16.2:14.4:1:25.8:23.6:48.1. The molecular weight of EPS-2was18,325Da, and its monosaccharides consist of rhamnose, glucan and galactose in the relative proportions5.6:2.7:1.0. Preliminary tests confirmed the strong biologically activities of the two polysaccharides. EPS1-1and EPS-2can inhibit the proliferation of tumor cells, HCT-116and K562, significantly, shown dose dependent.But the research of the EPS is focused on experiments in vitro. As a fungi polysaccharide, rare research is about the anti-tumor and immune regulation of tumor-bearing animals. We study the effect of extracellular polysaccharides (EPS) from Rhizopus nigricans on tumor and immune of S180-bearing mice.1. In vitro experiments, the impact of EPS on S180cells and spleen lymphocyte proliferation was researched using MTT method. The results show that EPS in the concentration range50-1000μg/mL can inhibite S180cell proliferation in a dose dependent manner. EPS at the highest dose of1000μg/mL showed significantly antitumor activity against S180with inhibition rate of47.53%. However, EPS significantly simulated spleen lymphocytes in the concentration of500μg/mL, and the increase proliferation ability showed a dose-dependent effect with EPS at the dose of50to500μg/mL.2. In vivo, we studied the prophylactic anti-tumor effects of EPS in S180-beaing mice. The healthy mouses were treated with EPS orally in dose of10,25,50,75mg/kg/d for7days, then transplanted with S180cells in right axilla of each mouse and treated with EPS continually for10days. The results show that, In comparison with the control groups, the weights of tumor were declined and the inhibition rates of tumor were remarkably decreased in the treated groups. At the dose of75mg/kg/d, the inhibition rate was decreased by64.38%(P<0.05).EPS increased the concentrations of IL-2and TNF-a. The pathological changes of model control group were very obvious.3. We studied the directly anti-tumor effects of EPS in S180-beaing mice. The healthy mouses were transplanted with S180cells in right axilla firstly, then treated with EPS orally in dose of25,50,75mg/kg/d continually for10days. The results show that, EPS also has a strong antitumor effect to inhibit the growth of S180tumor direactly. At the dose of75mg/kg/d, the inhibition rate was decreased by37.3%(P<0.05).4. To observe the effects of EPS on survival period of S180tumor bearing mice, we established S180ascites tumor model. The results shown that, the life-prolonging rates of EPS at the dose of75mg/kg/d and combined with cyclophosphamide (20mg/kg/d) were43.36%and36.28%respectively compared to control groups (P<0.05).The results suggested EPS confirmed in vivo anti-tumor effects observed in vitro, and the mechanism of anti-tumor effect of EPS may be at least in part medidated by increased immune activity in host. All our findings provide a new evidence for the drug therapy of tumor; provide data and theoretical support for application of EPS as a novel adjuvant chemotherapeutic and chemo preventive strategy against tumor... |
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