Aqueous Extract of Inonotus bliquus (Fr.) Pilat (Hymenochaetaceae) Significantly Inhibits the Growth of Sarcoma 180 by Inducing Apoptosis

Inonotus obliquus (Fr.) Pilat (Hymenochaetaceae) has been widely used as a folk medicine to treat various cancers in Russia, Poland and most of Baltic countries for literally more than four centuries. However, in spite of its therapeutic significance for cancers, this fungus has not been studied systematically for the mechanisms of antitumor activity. In this study, we report the effects of aqueous extracts of I. obliquus (AEI) on inducing apoptosis of Sarcoma 180. AEI prepared from the sclerotium of I. obliquus was either administered to Sarcoma 180-bearing mice or supplemented into the culture of Sarcoma 180 cells. Oral administration of AEI significantly inhibited Sarcoma 180-induced reduction of splenic lymphocytes and proliferation potentials and elicited over-expression of bax gene in Sarcoma 180 cells, leading to the regression of Sarcoma 180 in mice. Supplementation of AEI into the culture of Sarcoma 180 cells resulted in a significant increase in the number of cells in G0-G1 phase and triggered remarkable increment in programmed death (apoptosis) of Sarcoma 180 cells. In addition, AEI showed stimulatory effect on TNF-α release by mice peritoneal macrophages. These results indicated that the antitumor activity of AEI was mediated by protecting splenic lymphocytes from tumor-induced apoptosis and by triggering apoptosis of tumor cells.