1. ¹Institute of Health Science, Shanghai Institutes for Biological Sciences and Graduate School of Chinese Academy of Sciences-Shanghai Jiao-Tong University School of Medicine (SJTU-SM), Shanghai, China
2. ²Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, SJTU-SM, Shanghai, China

Correspondence: Dr G-Q Chen, Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, SJTU-SM, Shanghai 200025, China. E-mail: chengq@shsmu.edu.cn or gqchen@sibs.ac.cn

³These authors contributed equally to this work.

Received 26 February 2007; Revised 10 May 2007; Accepted 13 June 2007; Published online 16 July 2007.

Abstract

Hypoxia or hypoxia mimetic has been shown to induce differentiation together with the accumulation of hypoxia-inducible factor-1 (HIF-1) protein of myeloid leukemic cells and normal hematopoietic progenitors. To provide direct evidence for the role of HIF-1 in acute myeloid leukemia (AML) cell differentiation and its mechanisms, we generated myeloid leukemic U937T transformants, in which HIF-1 was tightly induced by tetracycline withdrawal. The results showed that the conditional HIF-1 induction triggered granulocytic differentiation of these transformants, while the suppression of HIF-1 expression by specific short hairpin RNAs (shRNAs) effectively inhibited hypoxia-induced differentiation of U937 cells, as evidenced by morphology, maturation-related antigens as well as expressions of myeloid differentiation signatures and hematopoietic cells-specific cytokine receptors. The specific shRNAs-inhibited expression of HIF-1, an essential partner for transcription activity of HIF-1, failed, while the inhibition of hematopoietic differentiation-critical CCAAT/enhancer-binding protein- (C/EBP) significantly eliminated HIF-1-mediated myeloid leukemic cell differentiation. Collectively, this work provided several lines of direct evidence for the role of HIF-1 protein through its nontranscriptional activity in myeloid cell differentiation, in which C/EBP elicits a role as an effector downstream to HIF-1. These discoveries would shed new insights for understanding mechanisms underlying leukemogenesis and designing the new therapeutic strategy for differentiation induction of AML.