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Blood, 1 September 2006, Vol. 108, No. 5, pp. 1551-1554. Prepublished online as a Blood First Edition Paper on May 9, 2006; DOI 10.1182/blood-2005-10-009514.
HEMATOPOIESIS Constitutive activation of STAT5 and Bcl-xL overexpression can induce endogenous erythroid colony formation in human primary cellsFrom the Unité (U) 790 Institut National de la Santé et de la Recherche Médicale (INSERM), Institut Gustave Roussy, Villejuif, France; Laboratoire d'Hématologie, Hôpital de Bicêtre, Le Kremlin-Bicêtre, France; and Laboratoire d'Hématologie, Centre Hospitalo-Universitaire (CHU) de Brest-Hôpital Morvan, Institut Gustave Roussy, Villejuif, France.
The biologic hallmark of polycythemia vera (PV) is the formation of endogenous erythroid colonies (EECs) with an erythropoietin-independent differentiation. Recently, it has been shown that an activating mutation of JAK2 (V617F) was at the origin of PV. In this work, we studied whether the STAT5/Bcl-xL pathway could be responsible for EEC formation. A constitutively active form of STAT5 was transduced into human erythroid progenitors and induced an erythropoietin-independent terminal differentiation and EEC formation. Furthermore, Bcl-xL overexpression in erythroid progenitors was also able to induce erythroid colonies despite the absence of erythropoietin. Conversely, siRNA-mediated STAT5 and Bcl-xL knock-down in human erythroid progenitors inhibited colony-forming unit-erythroid (CFU-E) formation in the presence of Epo. Altogether, these results demonstrate that a sustained level of the sole Bcl-xL is capable of giving rise to Epo-independent erythroid colony formation and suggest that, in PV patients, JAK2V617F may induce EEC via the STAT5/Bcl-xL pathway.
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