Antitumor effect of Streptococcus pyogenes by inducing hydrogen peroxide production.

The Su strain of Streptococcus pyogenes (S-coccus)-derived anticancer preparation, OK-432, which is immobilized by heating in the presence of penicillin G, is well known to have an immunopotentiating activity through activation of natural killer cells in vivo. In this study, a streptococcal anticancer preparation stronger than OK-432 was prepared. Live streptococci (S-cocci) of the Su strain were induced to acquire H202-producing ability by treatment with serum under aerobic conditions. The resulting preparation no longer possessed hemolytic activity, and was not viable. The serum-treated S-coccus preparation activated natural killer cells as well as OK-432 did, and had stronger antitumor activity than OK-432 did. These results suggest that the serum-treated S-coccus preparation would be a useful tool for chemotherapy, in addition to immunotherapy, for the treatment of cancer.