Isolation of murine sarcoma virus‐transormed mouse cells which are negative for leukemia virus from agar suspension cultures

Friend strain of spleen focus-forming virus is a recombinant between ecotropic murine type C virus and the env gene region of xenotropic type C virus.

“…F-MuLV and BALB clone 4/F-MuLV, a virus complex containing SFFV and F-MuLV, have been described (5) 4 and 83 were obtained in our laboratory by end-point dilution cloning in Microtest II culture plates on SC-i cells of an uncloned stock of Mo-MuLV obtained from Robert Bassin, National Cancer Institute (9). N-Tropic AKR MuLV, AKR-MCF no.…”

Host Restriction of Friend Leukemia Virus. Role of the Viral Outer Coat

“…The cells were used at the second or third passage for all experiments and maintained the in vitro characteristics of restriction described by Pincus et al (7,8). S+L-(sarcoma-positive, leukemia-negative) cells, kindly provided by Dr. Robert Bases, are Swiss 3T3 cells transformed with the Moloney strain of murine sarcoma virus as described by Bassin (11). All cell lines were maintained in Eagle's minimal essential medium supplemented with 10% fetal-calf serum (Grand Island Biologicals), iglutamine, and penicillin-streptomycin.…”

Helper virus is not required for in vitro erythroid transformation of hematopoietic cells by Friend virus

“…The formation of these small and delayed foci followed a one-hit titration pattern and resulted from the proliferation of fibroblasts transformed by MSV without the MuLV. The most convincing evidence that MSV is competent for transformation came with the isolation of clones of transformed cells that contained the MSV genome but did not produce virus (29).…”