Production of erythropoietin by cloned malignant murine erythroid cells

A specific immunological assay was used to demonstrate that the erythropoietic factor produced by the recently described FMuLV-induced murine erythroleukemic cell line IW32 is an authentic erythropoietin (epo). Several independent virus-induced erythroleukemic and myeloblastic cell lines were tested for epo production. Among six erythroleukemic cell lines induced by FMuLV, another (NN10) was shown to produce epo by biological and immunological assays. Four Friend-virus-induced erythroleukemias and four FMuLV-induced myeloblastic cells were negative. The amounts of epo produced were similar in IW32 and NN10 supernatants after 48 h in culture. The in vitro bioassay gave the highest levels (up to 1000 mU/ml), the in vivo bioassay the lowest, and the radioimmunoassay gave intermediate results. NN10 and IW32 cell lines have been induced by two different FMuLV and were shown to be independent by cytogenetic studies. The molecular weights of IW32 and NN10 epo were close to the molecular weight of mouse plasma epo but elution profiles suggested that some differences might exist between these epos. Cloned IW32 and NN10 cells were shown to retain both the ability for erythroid differentiation after incubation with chemical inducers and the ability to produce epo. This demonstrates that malignant erythroid cells were the source of epo production in these cell lines.