Stability of polyoma DNA sequences and virus-coded proteins during tumor formation

To determine the stability of polyoma viral DNA in transformed rat cells during their growth in vivo, we compared the state and arrangement of polyoma virus DNA sequences in virus-transformed rat cell lines before and after their passage in vivo. In cell lines from 12 independent tumors induced by the inoculation of animals with three different transformed cell lines, we could detect no significant changes in the arrangement of viral DNA sequences associated with the in vivo passage of these cell lines. In 13 of 14 tumor cell lines examined, the pattern of polyoma virus tumor antigens, characterized by the presence of the polyoma virus large, middle, and small tumor antigens, was unchanged.