A study of rat embryo cells transformed in vitro by the bovine adenovirus type 3 (BAV-3) DNA before and after a passage in the host

Abstract

Cloned cultures of rat embryo cells transformed by BAV-3 DNA were obtained. Passage of the in vitro-transformed cells through the animal organism was accompanied with an increase in their oncogenicity. This had no effect on the cell morphology, the dependence of their growth on serum factors, the number of colonies in soft agar, their karyotype, and the content of fibronectin. BAV-3 DNA was mapped using restriction endonucleases XbaI, BamHI, and BglII. Rat cells transformed by BAV-3 DNA were found to contain 1.1 and 1.2 copies from 13.2% of the left terminus of the viral DNA molecule if calculated per cell DNA diploid content; 4.5 to 6.2 copies were found in these tumor cells in culture. Hence, a passage of the in vitro-transformed cells in the host results in the increase of oncogenicity and of the number of oncogene copies in the cell genome. However, there was no direct correlation between the increase in the number of oncogene copies in the genome of tumor cells and the rise of their oncogenicity after a passage through the animal.