Antitumor activity of streptococcal acid glycoprotein produced by Streptococcus pyogenes Su.

Streptococcal acid glycoprotein (SAGP) was purified from the cultured cells of Streptococcus pyogenes Su, and its in vitro and in vivo antitumor activities were investigated in comparison with those of OK-432, a cell preparation of S. pyogenes Su which is used clinically as a potent antitumor agent. SAGP inhibited the growth of several tumor cell lines in vitro at less than 0.1 microgram/ml, while it did not affect the growth of the other tumor and normal cell lines even at 10 micrograms/ml. This selective cytotoxicity is a unique characteristic of SAGP. OK-432 did not show cytotoxicity in vitro. SAGP also showed a considerable life-span-prolonging effect on mice bearing Meth A tumor and inhibited the growth of sarcoma 180 tumor implanted im. The comparison of antitumor activities between SAGP and OK-432 definitely suggested a difference in the mechanisms of their actions, even though they were derived from the same bacterial strain.