Malignant transformation and viral replication of rat bone and muscle cells after in vitro infection with rat-adapted murine sarcoma virus (Moloney).

Isolated bone and muscle cells from rat fetuses were infected with the rat-adapted osteosarcomogenic murine sarcoma virus (Moloney) for examination of malignant transformation and viral replication. After the infection, the bone cells underwent an unusual transformation characterized by two patients in the focus formation. In the early transformation (Transformation I), foci consisting of only morphologically altered cells appeared, but they soon disappeared. Focus formation of this type continued for subsequent cell passages. In the late transformation (Transformation II), typical foci of malignant cells were formed with rapid multiplication. The cells in both types of transformation produced sarcomogenic as well as leukemogenic viruses. They contained C-type particles showing varying morphology and dimensions. Distinct bone cell tropism of osteosarcomogenic murine sarcoma virus (Moloney) was shown for three in vitro passages through rat bone cells. The infected muscles cells produced Transformation I foci at an incidence lower than did the bone cells, being mostly nontransformed. The virus yielded from these cells was predominantly leukemogenic, consisting of typical C-type particles. Evidence presented suggests that the tissue dependency with replicating ability of murine sarcoma virus and murine leukemia virus present in osteosarcomogenic murine sarcoma virus (Moloney) preparation is responsible for exhibiting the tissue tropism of this virus.