Mechanism Underlying the Antitumor Activity of Proteins from the Ling Zhi or Reishi Medicinal Mushroom, Ganoderma lucidum (W. Curt.: Fr.) P. Karst. (Aphyllophoromycetideae) In Vitro

The extracts of Ganoderma lucidum (Ling Zhi or Reishi) medicinal mushroom show antitumor activity in vivo. The functional activities of proteins from G. lucidum or selenium-enriched G. lucidum (Se-G. lucidum) have been reported in many studies. However, the mechanism underlying the antitumor activity of proteins from G. lucidum has not been clarified. It is interesting to know how selenium influences the antitumor activity of the proteins in Se-G. lucidum. In the present study, the inhibitory effects of protein extracts from G. lucidum and Se-G. lucidum on several tumor cells were investigated, and the activities of the mixtures of these proteins and inorganic selenium (Na2SeO3) were compared under the same conditions. Results showed that Na2SeO3 and Se-GL-P exhibit relatively high activity among six samples to inhibit the multiplication of tumor cells. The incorporation of Se into the proteins, in the form of selenocysteine and selenomethionine, apparently enhances their activity. Na2SeO3 does not exhibit effective antitumor activity unless the concentration is high enough. In conclusion, the immune-regulation activity and selenium-containing property of proteins from G. lucidum or Se-G. lucidum presumably contribute to their antitumor activity.