Studies on virus particles resembling oncogenic RNA viruses in monkey breast carcinoma

A spontaneous breast tumor from an 8-year-old rhesus monkey, Macaco, mulatto., was investigated by electron microscopic and tissue culture techniques. Virus particles, morphologically resembling mouse mammary tumor virus, were detected in the tumor cells. The virus was isolated and propagated by cocultivation of the tumor tissue with the monkey embryo and monkey lung cells. Cell-free virus was found to be infectious for rhesus monkey embryo cells, rhesus monkey lung cells, chimpanzee lung cells, normal human leukocytes, and human embryonic cells. The morphological, biochemical, and immunologic evidence indicates the oncogenic nature of this virus, yet the biologic activity of this virus is still unknown.