HOME HELP FEEDBACK TABLE OF CONTENTS ARCHIVE SUBSCRIPTIONS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Zhang, J. Articles by Chen, G.-Q. PubMed PubMed Citation Articles by Zhang, J. Articles by Chen, G.-Q.

Accumulation of hypoxia-inducible factor-1 protein and its role in the differentiation of myeloid leukemic cells induced by all-trans retinoic acid

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

Correspondence: Guo-Qiang Chen, No. 280, Chong-Qing South Rd, Shanghai 200025, China. E-mail:chengq{at}shsmu.edu.cn

Background: The clinical activities of all-trans retinoic acid in the treatment of acute promyelocytic leukemia, a unique subtype of acute myeloid leukemia, have triggered extensive studies aimed at defining the mechanisms by which this compound induces differentiation of leukemic cells. Recent studies show that hypoxia-inducible factor-1 (HIF-1) contributes to the differentiation of acute myeloid leukemia cells via transcriptional activity-independent mechanisms. We investigated whether all-trans retinoic acid affects HIF-1 protein and whether this has a role in all-trans retinoic acid-induced differentiation.

Design and Methods: The acute myeloid leukemia cell lines NB4 and U937 were treated with all-trans retinoic acid, and HIF-1/HIF-1β mRNA and proteins were measured respectively by real-time quantitative reverse transcriptase polymerase chain reaction and western blotting. To investigate the role of HIF-1 in all-trans retinoic acid-induced differentiation, NB4 cells, U937 cells, U937 cells in which HIF-1 was induced by the withdrawal of tetracycline and U937 cells with stable expression of specific short hairpin RNA against HIF-1, Runx1, C/EBP and PU.1, were treated with all-trans retinoic acid and/or the hypoxiamimetic agent cobalt chloride (CoCl₂). Cellular differentiation was evaluated by morphological criteria and myeloid differentiation antigens.

Results: all-trans retinoic acid rapidly increased endogenous and inducible expressed or CoCl₂-stabilized HIF-1 protein in leukemic cells under normoxia. Importantly, suppression of HIF-1 expression by specific short hairpin RNA partially but significantly inhibited all-trans retinoic acid-induced differentiation of the U937 cell line. Reciprocally, the differentiation induced by all-trans retinoic acid was significantly enhanced by conditional HIF-1 induction and HIF-1-stabilizing CoCl₂ treatment. Furthermore, knock-down of PU.1, Runx1 and C/EBP, three transcriptional factors crucial for normal hematopoiesis, greatly inhibited the differentiation cooperation of all-trans retinoic acid and HIF-1 induction.

Conclusions: This work provides the first demonstration that HIF-1, a protein rapidly responsive to all-trans retinoic acid, plays a role in all-trans retinoic acid-induced differentiation of leukemic cells. These observations shed new light on the molecular mechanisms underlying all-trans retinoic acid-induced differentiation of acute myeloid leukemia cells.

Key words: hypoxia inducible factor-1, all-trans retinoid acid, differentiation, leukemia.