Summary
Inoculation of B-RSV(-) avian sarcoma virus transformed, but infectious virus-free hamster tumor cells into diverse strains of chicks resulted in the induction of sarcomas at the site of inoculation in the inoculated chicks. The induced sarcoma cells were of chicken karyotype. They contained high titers of the group specific (gs) antigens of the viruses of the avian leukosis-sarcoma virus group. Sarcomas induced in chicks with no demonstrable avian leukosis gs antigen or rescuable chicken endogenous virus (chick helper factor) contained no demonstrable infectious virus, whereas, those induced in genetic lines of chickens which express the chicken endogenous type C RNA virus either as infectious virus or as rescuable chick helper factor contained the chicken endogenous virus pseudotype of the defective avian sarcoma virus (Bryan Rous sarcoma virus). Our studies suggested that B-RSV(-) viral gene sequences responsible for the sarcomagenic transformation of the chick cells and gag gene sequences responsible for the expression of the avian leukosis-sarcoma gs antigens in the induced chick sarcomas occurred by the transfer of the genetic information of B-RSV(-) from the hamster tumor cells to supporting stromal chick cells in contact with the hamster tumor cells.
We are indebted to the late Dr. C. S. Stulberg and his colleagues at the Child Research Center of Michigan, Detroit, Michigan, for karyological and immunological studies to determine the species of cells we cultured in vitro from the chick tumors we induced by the transplantation of B-RSV(-) hamster tumor cells. We are also indebted to Dr. Mina L. Vernon of the National Cancer Institute for electron microscopic studies of the hamster tumor cells.
