Tumorigenicity and karyotype of rat embryo cell lines transformed by BK virus

A rat embryo cell line transformed by BK virus was used to induce tumors in rats. Cell lines were established from these tumors. Other sublines were obtained by in vitro cloning of the parental line. Growth characteristics and karyotypes were compared to the tumorigenicity of these cell lines. The in vitro cloned sublines had a low tumorigenicity. Tumorigenicity of the tumor cell lines varied from high to undetectable. The tumor cell line with the highest tumorigenicity also had the highest saturation density in vitro, but otherwise there was little correlation between tumorigenicity and the in vitro characteristics of the cells. Karyotype analysis was done for two cell lines with high or low tumorigenicity which both had a near-diploid complement of chromosomes. The findings were in agreement with the expression-supression model of Rabinowitz and Sachs (1970). The suppression chromosomes seemed to be confined in group A, the expression chromosomes in group B.