Polyoncogenicity and insulinoma-inducing ability of BK Virus, a human Papovavirus, in Syrian golden hamsters

Newborn hamsters were inoculated intracerebrally with a series of purified and concentrated BK virus samples originating from a single stock of Gardner's original strain. Most (60-100%) of the hamsters developed various tumors 3-9 months later. The frequent types of tumors were ventricular tumors (choroid plexus papillomas and ependymomas: 7-53%), malignant insulinomas (0-92%), and osteosarcomas (0-50%). The T-antigen was positive in 59 of 60 tumors tested, but the virus was rescued by the cell fusion method from only 1 of 11 cell lines derived from these tumors. The incidence of insulinomas varied greatly with the virus sample; the two samples that showed the highest incidence (47 and 92%) originated from one parental virus stock, and all the other samples with the lower incidences (0-9%) originated from another ancestral stock. These results suggest the presence of a BK virus mutant(s) differing in capacity to induce insulinoma. A functional insulinoma cell line was thus established.