Malignant transformation of human cell in vitro by the SV 40 DNA and related alteration in biological activity of cell membranes

In vitro cell transformation of human embryonic cells could be induced by DNA extracted from virions of SV 40 purified by density gradient centrifugation. The result shows clearly that cell transformation is in· duced by incorporation ofa part of viral DNA into the genome. In addition, for the purpose of clarifing the biological differences between the normal and transformant, the alteration of the cell membrane structures of transformants was observed from the mechanism of phagocytosis. The iron colloid particles are taken up by normal diploid fibroblasts but not by the human and hamster transformants. This fact suggests a difference in the molecular arrangement of the cell membranes between the normal and transformants. In the presence of histones, however, the transformants phagocytize the colloid particles very actively. The results show cell membranes of transformants are altered in the molecular structure responsible for the surface charge.