Transformation of both erythroid and myeloid cells by E26, an avian leukemia virus that contains the myb gene

E26 and avian myeloblastosis virus are replication-defective avian retroviruses that contain the myb oncogene and cause leukemia in chickens with short periods of latency. Animals infected with E26 develop erythroleukemia and also contain low numbers of transformed myeloid cells, while avian myeloblastosis virus induces a purely myeloid leukemia. In both cases the type of leukemia induced is independent of the subgroup of the helper virus used. E26-transformed erythroid and myeloid cells can each be propagated selectively from explanted leukemic cells with media supplemented with factors that promote the growth either of normal chicken erythroid precursors or of myeloid progenitor cells. E26 also induces the outgrowth of transformed cells from bone marrow cells infected in vitro. These cells are also either erythroid or myeloid, depending on the culture conditions employed. Most of the erythroid cells transformed by E26 are erythroblast-like, but a significant number are more mature, including erythrocyte-like cells as well as some cells that appear to be aberrant in differentiation. Both erythroid and myeloid E26-transformed cells produce infectious virus and express P135 E26, the putative (gag -myb- x) transforming protein of the virus. Thus E26 is a virus that is capable of generating factor-dependent transformed cells in two different hematopoietic lineages.