Transplantable hamster tumors induced with the BK virus

Two tumors induced by BK virus in hamsters of an inbred strain were serially transplanted by subcutaneous injection of tumor explants. Both the original tumors as well as the transplants grew as solid, localized, encapsulated tumors. Histologically tumors were classified as fusocellular fibrosarcomas. Polymorphic tumor tissue was by an abundance of collagen fibers and multinucleated giant cells. Cell lines established from tumors contained nuclear T antigen which stained with sera from a number of tumor-carrying hamsters, but also with SV40 T antiserum. Viron antigens were not detected in these cell lines, and no virus was isolated when tumor extracts were inoculated in Vero cells.