Malignant and transforming activity of rous sarcoma virus. I. Malignant effect of rous sarcoma virus

Abstract

Cultures of cells from embryos of Af, C3H-Hg and (CBAT6T6 x Af)F, mice rapidly developed oncogenicity for syngeneic animals after exposure to RSV (Carr-Zilber strain). The tumours of mice were virogenic and contained the group-specific antigen of avian sarcoma-leukosis complex. However, when the infected cells became transformed in morphology, they lost their oncogenicity for syngeneic animals.The high oncogenicity of Af mouse embryonic cells infected with Carr-Zilber strain of RSV for the syngeneic animals was described in our previous communication (Kryukova et al., 1968).The tumours were virogenic, i.e. the introduction of the intact cells into chicks produced Rous sarcomas. After transplantation of these virogenic tumours into chicks and passing through chicks the resulting virus could induce tumours in mice. The transformed cultures appeared to be non-oncogenic for syngeneic Af mice. The further investigation of this phenomenon is described in this paper. MATERIAL AND METHODS Preparation of virus (Carr-Zilber strain)Virus-containing chicken tumour extract, diluted 1 :3 and centrifuged at 400 x g for 20 min, was injected intramuscularly into 7to 10-day-old White Leghorn chicks. Five or 6 days after injection the tumours were excised, pooled, homogenized, frozen in a dry-iceacetone mixture, and then stored at -30" C.