Presence of viral DNA sequences in hamster tumors induced by BK virus, a human papovavirus.

DNA prepared from cell lines and transplanted tumors originating from five representative types of BKV-induced hamster tumors was examined for the presence of the BKV genome by analyzing DNA/DNA reassociation kinetics. BKV DNA sequences were detected in all cases. There were only a few (1--4) copies of BKV DNA per cell in one osteosarcoma and two ventricular tumors (one choroid plexus papilloma and one ependymoma), but there were multiple (up to 150) copies in one osteosarcoma, one ventricular tumor (choroid plexus papilloma), two insulinomas, one pineocytoma, and one cerebral neuroblastoma. In some cases the number of copies of the viral DNA differed among sister cell clones derived from the same primary tumor. Apparently some tumors contained nonintegrated free viral DNA besides the integrated BKV genome.