Cytogenetic evolution of Ehrlich ascites tumor in rats. A chromosome-banding study.

The injection of Ehrlich tumor cells into normal and immunosuppressed rats induced a transitory ascitic tumor. In an initial stage only Ehrlich metaphases were observed. The incidence of rat metaphases, which appeared later on, increased gradually reaching 100% in a stage when neither the viability nor the tumorigenicity of the Ehrlich cells were significantly modified. No mouse-rat hybrid cells were observed. The results suggest that cell hybridization may be essential for the "naturalization" of a heterologous tumor.