Oncolytic Activity in vitro of Streptococci with Special Reference to " Cell-bound " Hemolysin

Living hemolytic streptococci could lyse in vitro not only erythrocytes but also tumor cells, through direct contact. The cytolytic reaction was temperature dependent, inhibited by trypan blue, EDTA, arsenite, chloramphenicol or puromycin, and occurred at the maximal rate only in the presence of phosphate, Mg++ and maltose (energy source). Like the hemolytic activity, the oncolytic activity was rather labile, and for its maintenance all the components of Bernheimer's basal medium were necessary. The inactivation of oncolytic activity was always accom-panied by a loss of hemolytic activity of the bacteria, and vice versa. Both activities were detected neither in streptococci grown in a glucose-broth nor in a mutant strain G203U lacking CBH. From these and other results, it was concluded that there is an exceedingly close relationship between the oncolytic activity of the organisms and cell-bound streptolysin S. There are many reports concerning the cytotoxic or cytopathogenic effect in vitro of streptococci on various tumor cell species (1—3). Although the anticancer activity ap-pears to be found specifically in Group A streptococci and seems to be closely related to the streptolysin S (SLS>forming ability, the actual mechanism involved remains to be elu-cidated. G i n s b u r g and Grossowicz (4) have shown that Group A streptococci possess a ' ' cell-bound " hemolysin (CBH) which could be demonstrated by the incubation of erythro-cytes with washed streptococci, in the presence of glucose, Mg++, and sulfhydryl compounds. * Abbreviations used