Circulating erythroid progenitors in polycythemia vera are hypersensitive to insulin-like growth factor-1 in vitro: studies in an improved serum-free medium [see comments]

Abstract

We have investigated the question of erythropoietin (Epo) hypersensitivity versus Epo independence as the basis for the endogenous erythroid bursts (EEBs) that develop in cultures without added Epo from hematopoietic cells of polycythemia vera (PV) patients. Using an improved serum-free (SF) medium containing interleukin (IL)-3, but no insulin-like growth factor-1 (IGF-1), and devoid of contaminants that influence erythropoiesis, we compared circulating normal and PV early erythroid progenitors (BFU-E) with respect to their responses in vitro to recombinant human (rHu) Epo. Cultures were seeded with Ficoll- Hypaque density-separated peripheral blood (PB) mononuclear cells (MNCs), and erythroid bursts, together with their component colonies of > or = 50 cells, were scored in situ at 13 to 16 days of culture. The Epo dose-response curve of BFU-E from PV patients was found to be statistically indistinguishable from that of normal subjects. This observation provides compelling evidence against the Epo- hypersensitivity hypothesis. In the complete SF medium minus Epo, the sensitivity of BFU-E to IGF-1 was much greater in PV than in normals, the dose-response curve being shifted to the left by at least 2 orders of magnitude. These data show that the erythroid progenitor cell response in PV is hypersensitive to IGF-1, and independent of Epo. The data also emphasize the importance of truly SF medium conditions for assessment of progenitor cell sensitivities to recombinant growth factors. Depletion of adherent cells totally prevented erythroid burst formation by normal circulating progenitors, but did not prevent the hypersensitive response to IGF-1 of such cells from PV patients. Hence, again unlike its normal counterpart, the progenitor cell response in PV appears to be independent of adherent cell control.

The predictive value of clonogenic stem cell assays for the diagnosis of polycythaemia vera

“…This phenomenon is explained by the increased sensitivity of the pathological progenitor cells to EPO (Casadevall et al, 1982;Weinberg et al, 1989). The same phenomenon was also observed after addition of a cytokine cocktail, confirming the hypersensitivity of the affected progenitor cell to other cytokines including interleukin (IL) 1, IL-3, stem cell factor, insulin-like growth factor-1 and granulocyte-macrophage colony-stimulating factor (Dai et al, 1991(Dai et al, , 1992Correa et al, 1994;Dai et al, 1994).…”

Relevance of the criteria commonly used to diagnose myeloproliferative disorder in patients with splanchnic vein thrombosis

“…Nevertheless, EEC has been reported in healthy controls and isolated cases of reactive erythrocytosis and is not observed in about 50% of patients with well-documented ET (Dudley et al, 1990;Masters et al, 1990). Results obtained in serum-free cultures have demonstrated the need for greater standardization of the assay (Correa et al, 1994), and this standardization is now underway (Dobo et al, 2004). We found that EEC and BM findings were closely correlated, although this correlation was not perfect (84% and 86% for positive and negative predictive values, respectively).…”

Erythropoietin receptor and hematological disease

“…In retrospect it is not surprising that the EpoR has not been shown to be involved in the pathogenesis of PV. Erythroid progenitors from PV patients have been shown to be hypersensitive not only to Epo but also to a range of growth factors, and in fact, myeloid and megakaryocyte progenitors from these patients are also hypersensitive to growth factors [48,49]. It is likely that PV results from a somatic mutation of a multi-potent progenitor cell leading to dysregulated growth of a clone of abnormal cells; this is reviewed by Hinshelwood et al [50].…”