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

Abstract

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 alpha (HIF-1 alpha) contributes to the differentiation of acute myeloid leukemia cells via transcriptional activity-independent mechanisms. We investigated whether all-trans retinoic acid affects HIF-1 alpha 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 alpha/HIF-1 beta 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 alpha in all-trans retinoic acid-induced differentiation, NB4 cells, U937 cells, U937 cells in which HIF-1 alpha was induced by the withdrawal of tetracycline and U937 cells with stable expression of specific short hairpin RNA against HIF-1 alpha, Runx1, C/EBP alpha and PU.1, were treated with all-trans retinoic acid and/or the hypoxiamimetic agent cobalt chloride (CoCl(2)). Cellular differentiation was evaluated by morphological criteria and myeloid differentiation antigens.

RESULTS:

all-trans retinoic acid rapidly increased endogenous and inducible expressed or CoCl(2)-stabilized HIF-1 alpha protein in leukemic cells under normoxia. Importantly, suppression of HIF-1 alpha 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 alpha induction and HIF-1 alpha-stabilizing CoCl(2) treatment. Furthermore, knock-down of PU.1, Runx1 and C/EBP alpha, three transcriptional factors crucial for normal hematopoiesis, greatly inhibited the differentiation cooperation of all-trans retinoic acid and HIF-1 alpha induction.

CONCLUSIONS:

This work provides the first demonstration that HIF-1 alpha, 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.

• Authors: Jing Zhang, Li-Ping Song, Ying Huang, Qian Zhao, Ke-Wen Zhao, Guo-Qiang Chen
• Journal: Haematologica (Haematologica) Vol. 93 Issue 10 Pg. 1480-7 (Oct 2008) ISSN: 1592-8721 [Electronic] Italy
• PMID: 18728026 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• CCAAT-Enhancer-Binding Protein-alpha
• Core Binding Factor Alpha 2 Subunit
• Hypoxia-Inducible Factor 1, alpha Subunit
• Proto-Oncogene Proteins
• RNA, Messenger
• Trans-Activators
• proto-oncogene protein Spi-1
• Tretinoin
• Copper
• cupric chloride

Topics

• CCAAT-Enhancer-Binding Protein-alpha (metabolism)
• Cell Differentiation (drug effects)
• Cell Line, Tumor
• Copper (pharmacology)
• Core Binding Factor Alpha 2 Subunit (metabolism)
• Gene Expression Regulation, Neoplastic (drug effects, genetics)
• Humans
• Hypoxia-Inducible Factor 1, alpha Subunit (genetics, metabolism)
• Leukemia, Myeloid (genetics, metabolism, pathology)
• Proto-Oncogene Proteins (metabolism)
• RNA Interference
• RNA, Messenger (genetics)
• Trans-Activators (metabolism)
• Tretinoin (pharmacology)