Isolation and fractionation of cell-free extract from streptolysin-S-forming streptococci.

A series of procedures have been developed for obtaining a partially purified fractions possessing anticancer activity using live streptolysin S-forming streptococci (Su strain) harvested from their yeast extract-culture fluid. These procedures consist principally of (1) preparing cell-free extract (CFE) from homogenized streptococci, (2) streptomycin-treatment of CFE (S-CFE) to remove nucleic acids, and (3) stepwise fractionations of S-CFE with 0.4, 0.5, 0.6, and 1.0 saturated solutions of ammonium sulfate, each fraction being dialyzed against distilled water followed by lyophilization. The 60-F product, which was precipitated by the 0.6-saturated solution, was found to be the most potent among six products obtained and to be about 4 times more effective than the original CFE in depriving the invasiveness of Ehrlich carcinoma cells in mice. Data on physical and biochemical properties of 60-F product are also presented.