Anti-tumor activity of exopolysaccharide from Rhizopus nigricans Ehrenb on S180 tumor-bearing mice.

In this study, the effect of antitumor and immune activities of extracellular polysaccharides (EPS) from Rhizopus nigricans Ehrenb were investigated using S180 bearing mice. The results revealed that EPS in the concentration range 50-1000 μg/mL can inhibited S180 cell proliferation in a dose dependent manner. EPS at the highest dose of 1000 μg/mL showed significantly antitumor activity against S180 with inhibition rate of 47.53%. However, EPS significantly simulated spleen lymphocytes in the concentration of 500 μg/mL, and the increase proliferation ability showed a dose-dependent effect with EPS at the dose of 50-500 μg/mL. 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. Pretreatment with EPS at the dose of 75 mg/kg/day, the inhibition rate was decreased by 44.38% (P<0.05). EPS increased the concentrations of IL-2 and TNF-a. The pathological changes of model control group were very obvious. Meanwhile, the prophylactic administration of EPS could more efficiently inhibit the growth of S180 tumor than direct administration of EPS. EPS could prolong the survival period of S180 tumor bearing mice, and the doses 75 mg/kg/day of EPS and combined with cyclophosphamide (20 mg/kg/day) were 43.36% and 36.28% 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 mediated by increased immune activity in host.