Transformation of a mouse cell line by murine sarcoma virus (Moloney)

Murine sarcoma virus (Moloney) (MSV) transformed C3H2K cells originating from the kidney tissues of a newborn C3H/He mouse. Titration of the virus showed a one‐hit dose response in the presence of an excess of Friend leukemia virus (FLV) and a two‐hit dose response in the absence of FLV, indicating that MSV was defective and a dual infection by MSV and a murine leukemia virus was required for MSV focus formation. Preinfection with FLV interfered with focus formation by MSV. The MSV foci appeared most abundantly when the cells in the S phase were infected with the virus. Remarkable similarities between murine and avian sarcoma viruses were thus established. Focus center assay on either uninfected or FLV‐infected C3H2K cell monolayer indicated that MSV foci did not arise by cellular division alone but required secondary infection, while RSV foci arose by cellular division alone.