Antitumor Activity of Protoplast Membrane from Group A Streptococcus

: Cytoplasmic membrane of Group A streptococcus has been obtained by treatment of the cells with a phage-associated lytic enzyme to dissolve the streptococcal cell wall, followed by shocking osmotically. The protoplast membrane fraction (PMF) remained as a distinct homogeneous structure in the electron micrograph and analysis showed a low rhamnose content. Febrile response produced by PMF was very slightly exhibited or not at all. PMF showed weak suppression against the growth of rat Yoshida sarcoma cells in culture and inhibition of [3H]-uridine incorporation into the sarcoma cells in vitro. In vivo antitumor experiments demonstrated that PMF has a mild inhibiting effect against mouse Ehrlich ascites carcinoma, though there was not observed a definite correlation between survival rate and dose level. Antitumor activity of PMF was thermo-labile and was strikingly abolished by treatment with a bacterial enzyme, Nagarse, but not so much by alpha-chymotrypsin.