Abstract
BackgroundDUSP3 phosphatase, also known as V accinia-H1 Related (VHR) phosphatase, encoded by DUSP3/Dusp3 gene, is a relatively small member of the dual-specificity protein phosphatases. In vitro studies showed that DUSP3 is a negative regulator of ERK and JNK pathways in several cell lines. On the other hand, DUSP3 is implicated in human cancer. It has been alternatively described as having tumor suppressive and oncogenic properties. Thus, the available data suggest that DUSP3 plays complex and contradictory roles in tumorigenesis that could be cell type-dependent. Since most of these studies were performed using recombinant proteins or in cell-transfection based assays, the physiological function of DUSP3 has remained elusive.ResultsUsing immunohistochemistry on human cervical sections, we observed a strong expression of DUSP3 in endothelial cells (EC) suggesting a contribution for this phosphatase to EC functions. DUSP3 downregulation, using RNA interference, in human EC reduced significantly in vitro tube formation on Matrigel and spheroid angiogenic sprouting. However, this defect was not associated with an altered phosphorylation of the documented in vitro DUSP3 substrates, ERK1/2, JNK1/2 and EGFR but was associated with an increased PKC phosphorylation. To investigate the physiological function of DUSP3, we generated Dusp3-deficient mice by homologous recombination. The obtained DUSP3−/− mice were healthy, fertile, with no spontaneous phenotype and no vascular defect. However, DUSP3 deficiency prevented neo-vascularization of transplanted b-FGF containing Matrigel and LLC xenograft tumors as evidenced by hemoglobin (Hb) and FITC-dextran quantifications. Furthermore, we found that DUSP3 is required for b-FGF-induced microvessel outgrowth in the aortic ring assay.ConclusionsAll together, our data identify DUSP3 as a new important player in angiogenesis.
Highlights
DUSP3 phosphatase, known as Vaccinia-H1 Related (VHR) phosphatase, encoded by DUSP3/ Dusp3 gene, is a relatively small member of the dual-specificity protein phosphatases
DUSP3 is highly expressed in human endothelial cells and its expression is required for in vitro tubulogenesis During our previous study investigating the role of DUSP3 in human cervical cancer [13], we noticed that all the blood vessel walls present in the tissue sections were highly immunoreactive to anti-DUSP3 antibody, suggesting that DUSP3 is highly expressed in endothelial and/or smooth muscle cells, the 2 major blood vessels cell components
To assess the role of DUSP3 in endothelial cells (EC), we downregulated its expression in the primary Human Umbilical Vein Endothelial cells (HUVEC) using DUSP3 targeting siRNA and conducted a tube formation assay on Matrigel
Summary
DUSP3 phosphatase, known as Vaccinia-H1 Related (VHR) phosphatase, encoded by DUSP3/ Dusp gene, is a relatively small member of the dual-specificity protein phosphatases. We have shown that in HeLa cells, the knockdown of endogenous DUSP3 using RNA interference induces cell cycle arrest at G1/S and G2/M phases and is accompanied by the hyperactivation of ERK1/2 and JNK1/2 [11,12] In line with this finding, DUSP3 was found up-regulated in human cancers and in several cancer cell lines. DUSP3 has been found downregulated in breast carcinomas [16] These studies clearly suggest that DUSP3 plays complex and contradictory roles in tumorigenesis that could be cell type-dependent. Most of these studies were performed either in vitro, using recombinant proteins, or in cell lines, using transient overexpression or siRNA knockdown.
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