Biochemical purification of antineoplastic agents obtained from sturgeon serum

Discontinuous and continuous DEAE-Sephadex ion-exchange gradients were utilized to purify two sturgeon serum factors (A2 and B2) that possessed cytotoxic activity in vitro against human tumor cells but not against normal cells. After rabbit antisturgeon factor A2 or B2 was prepared, the antibodies were insolubilized. Sturgeon serum then was adsorbed to the insolubilized antibodies, and factors A2 and B2 were isolated in quantities large enough to conduct biologic studies. When the two factors purified either by ion-exchange chromatography or immunoadsorbent columns were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing, factor A2 consisted of one protein band with a molecular weight greater than 68,000 and an isoelectric point of approximately 6.5. Likewise, factor B2 also consisted of one protein band with a molecular weight in excess of 68,000 and an isoelectric point of approximately 7.5. Both factors A2 and B2 were destroyed either by heating at 56 degrees C for 30 minutes or by heating at 100 degrees C for 2 minutes. Furthermore, the mechanism of tumor killing by the sturgeon factors appears to be by means of a soluble factor. When the kinetics of tumor killing was studied, the sturgeon factors were noncytotoxic after 4 or 8 hours of incubation and became cytotoxic after 24 hours of incubation.