Transformed cell lines derived from progressor Sarcoma virus (Moloney) induced tumors. I. Differences in pathogenicity between C type viruses from producer and helper virus infected nonproducer cells

The present communication deals with the comparison of oneogenicity and focus forming capacity of C type virus released from the two producer and the five nonproducer cell lines; the latter after infection with Moloney helper virus (MLV-M) obtained from cells continuously producing MLV-M. It is demonstrated that P-MSV-M infection leads to oncogenic transformants which differ in their rescuability of the P-MSV-M genome, and it describes transformation defective MSV-M variants until now unknown to occur in MSV-M.