Erythropoietin-induced erythroid differentiation of the human erythroleukemia cell line TF-1 correlates with impaired STAT5 activation.

Abstract

The TF‐1 cell line has been established from a patient with erythroleukemia. While various cytokines induce TF‐1 cell proliferation, erythropoietin (Epo) only sustains the short‐term growth of these cells and induces their differentiation along the erythroid lineage. A truncated Epo receptor (EpoR) is overexpressed in these cells. The truncation removed the 96 C‐terminal amino acids, including seven tyrosine residues. An additional single mutation at position +3 of Tyr344 led to the replacement of leucine 347 by proline. Stimulation by Epo induced an impaired activation of the STAT5 transcription factor in these cells. The same defect in STAT5 activation was found in the murine FDCP‐1 cell line transfected with a chimeric EpoR containing the abnormal TF‐1 EpoR cytoplasmic domain. Infection of TF‐1 cells with a retrovirus containing a normal murine EpoR was able to restore both Epo‐induced STAT5 activity and cellular proliferation. In contrast, Epo‐induced differentiation was reduced strongly in infected TF‐1ER cells. These results suggest that Epo‐induced differentiation correlates with impaired Epo‐induced STAT5 activation.

Erythropoietin Induces the Tyrosine Phosphorylation of Insulin Receptor Substrate-2

“…Indeed, it has been shown that erythroid or megakaryocytic differentiation markers are expressed in UT-7 cells stimulated by Epo (49) or by thrombopoietin (50), respectively. TF-1 and HCD57 cells seem to be strictly committed in the erythroid differentiation pathway, whereas Mo7E cells exhibit megakaryocytic characteristics (38,39,41,51). T3Cl2 cells are Friend virus-transformed cells that correspond to erythroid cells blocked at the colony-forming unit erythroid/proerythroblast stage (52).…”

The role of STATs in myeloid differentiation and leukemia

“…In this model, high-level activation may in fact be inhibitory by the induction of`aspeci®c' genes not normally associated with activation of endogenous STAT proteins . This is demonstrated by the low level of STAT5 activation and induction of di erentiation observed when TF1 cells are treated with EPO due to the expression of a mutant receptor (Chretien et al, 1996). However, as mentioned above, introduction of a wild-type receptor results in high-level STAT5 activation and stimulates proliferation rather than di erentiation.…”

“…Thus the ability of a speci®c STAT to induce or inhibit the process of myelopoiesis appears to be cell type speci®c. In a similar study utilizing the erythroleukemic cell line TF-1, STAT5 has been implicated in erythropoietin-induced proliferation (Chretien et al, 1996). TF-1 cells express a truncated EPO-receptor (EpoR) that is defective in STAT5 activation and induces erythroid di erentiation rather than proliferation.…”

Dominant action of mutated erythropoietin receptors on differentiation in vitro and erythroleukemia development in vivo

“…Nakamura and Nakauchi (1994) proposed that the dominant negative e ect of a truncated receptor over the wild type receptor was most probably due to receptor heterodimerization. Signi®cantly, Chretien et al (1996) found that coexpression of wild type and truncated epo receptors in¯uenced epo-induced di erentiation of TF-1 cells. These results highlight the importance of xepo receptor dimerization in accurate transmission of intracellular signals and biological outcomes.…”