Inhibition of Ehrlich Ascites Tumor Growth by Nucleoprotein. I. In Vivo Characterization and Presumptive Chemical Identification

A badly degraded preparation of herring-sperm deoxyribonucleic acid (DNA) prevented the development of Ehrlich ascites tumor in mice, though, in large doses, this substance appeared to be nontoxic. The protective ability of the DNA preparation was destroyed completely by proteolytic enzymes, but only partially by deoxyribonuclease and not at all by ribonuclease. Biochemical fractionation revealed that the chloroform-extracted protein was active in this regard, but the relatively protein-free DNA part was not. There is evidence that the protective substance is probably the normal protamine of herring sperm (clupeine), with a small amount of residual DNA attached.