Induction of erythroid tumorigenic colonies by friend helper virus F‐MuLV alone and isolation of a new class of friend erythroleukemic cells

Abstract

Friend erythroleukemia virus (FLV) is a complex of two viruses, a defective spleen focus virus component (SFFV) and a helper independent virus, F‐MuLV. The virus complex induces in susceptible mice a multistage disease, an early stage (1–3 weeks) of rapid erythropoietic changes and a late stage, from which erythroleukemic cell lines (FLC) can be established. While the F‐MuLV alone does not induce any detectable changes in adult mice, it has been found recently to induce, in newborn BALB/c and NIH/Swiss mice, splenomegaly and certain early erythropoietic changes. The present study indicates that if the infected mice were kept alive by red cell transfusion and the cells from these F‐MuLV‐induced enlarged spleens were transplanted repeatedly in adult mice, erythroid tumorigenic colonies (CFU‐FV) can be detected. These helper virus of induced CFU‐FV (CFU‐FV‐H) have properties that differed from those CFU‐FVs induced by the FLV complexes. The colonies are more diffuse in morphology and do not release any detectable SFFV activities. In addition, FLC lines can also be established from these F‐MuLV infected spleens and CFU‐FV‐H and have been in culture for eight months. They are found to be distinct from those established from CFU‐FV induced by the FLV complexes. First, these FLC lines are more selective in the type of medium they can grow in, for while FLC lines induced by FLV complexes will grow in both α‐medium and Iscove medium, the FLC induced by F‐MuLV will only grow in Iscove medium and not in α‐medium. Secondly, the growth of the F‐MuLV induced FLC lines are cell density dependent and will not proliferate below 105 cells/ml. Thirdly, the growth of the F‐MuLV‐induced FLC lines can be greatly enhanced by the addition of erythropoietin (epo). Finally, the F‐MuLV induced FLC lines will not respond to either dimethylsulphoxide (DMSO) or epo to induce along the erythroid pathway. These studies indicate that similar to the disease induced by FLV complexes, the erythroleukemia induced by F‐MuLV is also a multistage disease and a new class of erythroid tumorigenic cells and FLC lines can also be established from the spleens of these mice infected by the F‐MuLV alone. Copyright © 1982 Wiley‐Liss, Inc.