Purification and characterization of an antitumor principle from Streptococcus hemolyticus, Su strain

An antitumor principle (SAGP) has been purified from cell-free crude extract (CE) of group A Streptococcus hemolyticus, Su strain. The antitumor activity of each fraction was evaluated by measuring the in vitro growth inhibitory effect on transformed hamster embryonic lung cells (THEL). CE was subjected to thermal treatment, streptomycin precipitation, ammonium sulfate precipitation, and chromatography on octyl-Sepharose CL-4B, DEAE-cellulose, and Sephadex G-200 in that order. The active fraction from the last chromatography was dialyzed against distilled water. The resulting precipitate was removed and the supernatant was lyophilized (SAGP). SAGP is a homogeneous glycoprotein as judged by polyacrylamide gel electrophoresis, gel filtration, immunodiffusion, and PAS-staining. The molecular weight of SAGP was determined to be 140,000 to 150,000 by the gel filtration technique. SAGP is composed of subunits, each of which has a molecular weight of about 50,000. The isoelectric point of SAGP is 4.3. Amino acid analysis revealed an abundance of aspartic and glutamic acid residues in SAGP. The 50% growth inhibitory dose of SAGP on THEL was 0.062 micrograms/ml. Intraperitoneal administration of SAGP (20 mg/kg/day X 4) to ICR mice bearing Ehrlich ascites carcinoma cells increased their life span to 254% of the control.