Suppression of dual-specificity phosphatase–2 by hypoxia increases chemoresistance and malignancy in human cancer cells
Shih-Chieh Lin, … , Shao-Chieh Lin, Shaw-Jenq Tsai
Shih-Chieh Lin, … , Shao-Chieh Lin, Shaw-Jenq Tsai
Published April 1, 2011
Citation Information: J Clin Invest. 2011;121(5):1905-1916. https://doi.org/10.1172/JCI44362.
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Research Article Oncology

Suppression of dual-specificity phosphatase–2 by hypoxia increases chemoresistance and malignancy in human cancer cells

Abstract

Hypoxia inducible factor–1 (HIF-1) is the master transcriptional regulator of the cellular response to altered oxygen levels. HIF-1α protein is elevated in most solid tumors and contributes to poor disease outcome by promoting tumor progression, metastasis, and resistance to chemotherapy. To date, the relationship between HIF-1 and these processes, particularly chemoresistance, has remained largely unexplored. Here, we show that expression of the MAPK-specific phosphatase dual-specificity phosphatase–2 (DUSP2) is markedly reduced or completely absent in many human cancers and that its level of expression inversely correlates with that of HIF-1α and with cancer malignancy. Analysis of human cancer cell lines indicated that HIF-1α inhibited DUSP2 transcription, which resulted in prolonged phosphorylation of ERK and, hence, increased chemoresistance. Knockdown of DUSP2 increased drug resistance under normoxia, while forced expression of DUSP2 abolished hypoxia-induced chemoresistance. Further, reexpression of DUSP2 during cancer progression caused tumor regression and markedly increased drug sensitivity in mice xenografted with human tumor cell lines. Furthermore, a variety of genes involved in drug response, angiogenesis, cell survival, and apoptosis were found to be downregulated by DUSP2. Our results demonstrate that DUSP2 is a key downstream regulator of HIF-1–mediated tumor progression and chemoresistance. DUSP2 therefore may represent a novel drug target of particular relevance in tumors resistant to conventional chemotherapy.

Authors

Shih-Chieh Lin, Chun-Wei Chien, Jenq-Chang Lee, Yi-Chun Yeh, Keng-Fu Hsu, Yen-Yu Lai, Shao-Chieh Lin, Shaw-Jenq Tsai

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Figure 3

Suppression of DUSP2 by hypoxia leads to prolonged ERK phosphorylation.

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Suppression of DUSP2 by hypoxia leads to prolonged ERK phosphorylation. ...
(A) Representative Western blots of HeLa cells cultured under normoxia or hypoxia for 24 or 48 hours showing levels of phosphorylated ERK (P-ERK), total ERK (T-ERK), HIF-1α, and HIF-1β. Arrow indicates HIF-1α. (B) Representative Western blots of HeLa cells treated with DFO, DMOG, or vehicle (Con) showing levels of phosphorylated ERK (P-ERK), total ERK (T-ERK), HIF-1α, and HIF-1β. (C) Representative Western blots of HeLa cells transiently transfected with wild-type HIF-1α, HIF-1α–Dm, or empty vector (pcDNA6.0) under normoxia showing the levels of DUSP2, phosphorylated ERK, total ERK, HIF-1α, and HIF-1β. (D) Confocal photomicrographs showing HeLa cells stained for P-ERK under normoxia and hypoxia (left panels) and merged with images from DAPI staining (Merge). Scale bars: 20 μm. (E) Amounts of mRNA encoding for DUSP1 and -2 in HeLa cells exposed to normoxia or hypoxia for various times. *P < 0.05 compared with normoxia group (dashed line). (F) Representative Western blots of HeLa cells exposed to normoxia or hypoxia for various times showing levels of phosphorylated ERK, total ERK, HIF-1α, HIF-2α, and HIF-1β. (G) Representative Western blots of HeLa cells transiently transfected with GFP alone or DUSP2-GFP fusion gene cultured under normoxia or hypoxia showing levels of GFP, DUSP2-GFP, phosphorylated ERK, and total ERK. (H) Confocal photomicrographs showing green fluorescence and P-ERK staining, and merged with images from DAPI staining (Merge) in HeLa cells transfected with the DUSP2-GFP fusion gene or GFP alone. Scale bars: 20 μm.