Use of the ATG-treated newborn rat for in vivo tumorigenicity testing of cell substrates.

The ATG-treated newborn rat proved to be a sensitive model for tumorigenicity testing of cell substrates. HeLa cells in this model formed progressively growing tumors that regularly metastasized. Other cell types, among them third passage normal monkey kidney cells and Vero cells, gave rise to small cell nodules at the site of inoculation. These nodules were non-progressive in growth and did not metastasize.