Morphological transformation of mouse and rat embryo cells in vitro by an agent from S37 ascites tumour.

When normal rat and mouse embryo cells were treated with a cell free extract of S37 ascites tumour, morphological transformations occurred in both. The transformed cells readily induced lymphosarcoma-type tumours in the mice inoculated when newborn or young adults (8-12 weeks old), but not so readily in rats.Various tests carried out with these cells strongly indicate the presence of an oncogenic and transmissible agent in S37 ascites tumour. This agent appears to be related to mouse sarcoma virus isolated from animals with Moloney leukaemia but differs in only producing characteristic lymphosarcoma-type tumours.