Isolation, purification and identification of a serum DNA binding protein which increases in malignant diseases

A DNA binding protein in human serum was purified and identified. This protein was isolated from pooled human serum by DEAE Sephadex column chromatography, DNA cellulose affinity column chromatography, Sephadex G-200 gel filtration and Sepharose 6B gel filtration. It was found that the purified protein consisted of two subunits, one with a molecular weight of 80,000 and the other 25,000, evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The purified protein was in fact IgM determined by physicochemical and immunochemical characteristics.