DUSP4 (MKP-2), a member of the mitogen-activated protein kinase phosphatase (MKP) family and potential tumor suppressor, negatively regulates the MAPKs (mitogen-activated protein kinases) ERK, p38 and JNK. MAPKs play a crucial role in cancer development and progression. Previously, using microarray analyses we found a conspicuously frequent overexpression of DUSP4 in colorectal cancer (CRC) with high frequent microsatellite instability (MSI-H) compared to microsatellite stable (MSS) CRC. Here we studied DUSP4 expression on mRNA level in 38 CRC (19 MSI-H and 19 MSS) compared to matched normal tissue as well as in CRC cell lines by RT-qPCR. DUSP4 was overexpressed in all 19 MSI-H tumors and in 14 MSS tumors. Median expression levels in MSI-H tumors were significantly higher than in MSS-tumors (p < 0.001). Consistently, MSI-H CRC cell lines showed 6.8-fold higher DUSP4 mRNA levels than MSS cell lines. DUSP4 expression was not regulated by promoter methylation since no methylation was found by quantitative methylation analysis of DUSP4 promoter in CRC cell lines neither in tumor samples. Furthermore, no DUSP4 mutation was found on genomic DNA level in four CRC cell lines. DUSP4 overexpression in CRC cell lines through DUSP4 transfection caused upregulated expression of MAPK targets CDC25A, CCND1, EGR1, FOS, MYC and CDKN1A in HCT116 as well as downregulation of mismatch repair gene MSH2 in SW480. Furthermore, DUSP4 overexpression led to increased proliferation in CRC cell lines. Our findings suggest that DUSP4 acts as an important regulator of cell growth within the MAPK pathway and causes enhanced cell growth in MSI-H CRC.Dual-specificity protein phosphatases (DUSPs) are members of the type I cysteine-based protein-tyrosine phosphatase superfamily. A subgroup of DUSPs is known as mitogen-activated protein kinase phosphatases (MKPs) which plays a crucial role in regulating the tumor relevant MAP kinase (mitogen-activated protein kinase) pathways which in turn drive proliferation, differentiation, 1-5 apoptosis and inflammation. 6All MKPs carry an N-terminal kinase interaction motive (KIM), essential for substrate binding, and a C-terminal catalytic domain for substrate dephosphorylation. 7 MKPs negatively regulate MAP kinase signals and thus provide a negative feedback mechanism for MAP kinase activity [8][9][10][11] by dephosphorylating the phospho-tyrosine and phospho-threonine residues within the T-X-Y activation site located in all MAP kinases. 12 DUSP4, also called MKP2, is a member of the inducible nuclear MKP group and specifically dephosphorylates the MAP kinases ERK1/2, p38 and JNK.13 DUSP4 expression has been confirmed in human melanoma cell lines 14 and ovarian cancer in serous borderline tumors but not in serous carcinoma. 15 In mouse models, DUSP4 has been associated with regulatory mechanisms in inflammatory response in sepsis. 16 Studies in breast cancer are controversial as DUSP4 expression is reported in primary tumor tissue 17 but can also be lost in early-onset and high-grade tumors indicating that...

Aldehyde oxidase 1 (AOX1) is highly abundant in the liver and oxidizes aldehydes thereby generating reactive oxygen species. Enzymes involved in detoxification of aldehydes are expressed in adipocytes and alter adipogenesis, therefore the functional role of AOX1 in adipocytes was analyzed. AOX1 mRNA was higher in visceral compared to subcutaneous human adipose tissue but AOX1 protein was detected in both fat depots. AOX1 expression in adipocytes was confirmed by immunohistochemistry and immunoblot. AOX1 was induced during adipocytic differentiation and was downregulated by fenofibrate in differentiated cells. Knock-down of AOX1 in preadipocytes led to impaired lipid storage and adiponectin release in the differentiated cells. These data indicate that AOX1 is essential for adipogenesis and may link energy and drug metabolism.

IQGAP2 is a member of three IQGAP scaffolding proteins and involved in cytoskeletal reorganization and adhesion of cells. It has been described as a putative tumor suppressor affecting tumor development and progression. Our aim in this study was to analyze the role of IQGAP2 in colorectal cancer (CRC). By means of microarray analyses we previously found IQGAP2 expression to be downregulated in CRC and suppressed by Maspin. Here we measured IQGAP2 expression by RT-qPCR in 17 MSI-H (high microsatellite instability) and 19 MSS (microsatellite stable) CRCs as well as in three MSI and three MSS CRC cell lines, respectively. Furthermore, we analyzed the methylation status of the IQGAP2 promoter and studied the subcellular localization of the IQGAP2 protein. Using an in vitro system for overexpressing and silencing IQGAP2 we investigated the effect of IQGAP2 on cellular migration applying Real-Time Cell Analyzer (RTCA) technology. Stably overexpressing Maspin transfected CRC cell line SW480 showed IQGAP2 loss on mRNA and protein level. IQGAP2 expression was reduced in 86% (30/36) of tumors compared to normal tissue (p&lt;0.001) and lower in MSS tumors compared to MSI tumors (p=0.039). Consistently, IQGAP2 mRNA levels were also downregulated in CRC cell lines. None of the cell lines, tumor or normal tissue samples analyzed showed IQGAP2 promoter methylation. Immunofluorescence analysis of CRC cells revealed IQGAP2 distribution in plasma membranes and more intensely in areas of cell-cell contacts. Migration assays showed increased cellular migration after IQGAP2 knockdown and impaired migration after overexpression of IQGAP2. We provide evidence that IQGAP2 expression is regulated by Maspin and may have an important effect on cellular migration in colorectal cancer. Citation Format: Benedikt Gröschl, Marcus Bettstetter, Tamara Widmann, Ferdinand Hofstädter, Wolfgang Dietmaier. Iqgap2 is downregulated in colorectal cancer (crc) and involved in cellular migration. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5004. doi:10.1158/1538-7445.AM2014-5004

DUSP4, also termed MKP2 is a member of the mitogen-activated protein kinase phosphatase (MKP) family which negatively regulates the MAPKs (Mitogen-activated protein kinases) ERK, p38 and JNK. Using microarray analyses we found previously DUSP4 frequently overexpressed in high frequent microsatellite unstable (MSI-H) colorectal cancer CRC. Here we analysed DUSP4 expression on mRNA level in 38 CRC (19 MSI-H and 19 MSS) compared to matched normal tissue as well as in CRC cell lines by RT-qPCR. All 19 MSI-H tumors (100%) and 14/19 (73.7%) MSS tumors showed overexpressed DUSP4. However, median expression levels in MSI-H tumors were significantly higher than in MSS-tumors (p&lt;0.001). Likewise, MSI-H CRC cell lines showed 5.1-fold higher DUSP4 mRNA levels than MSS cell lines. Using quantitative methylation analysis (MethyQESD) we did not find DUSP4 expression regulated by promoter methylation in CRC cell lines as well as in tumor samples. DUSP4 overexpression in CRC cell lines through DUSP4 transfection caused increased expression of the MAPK targets CDC25A, CCND1, EGR1, MYC and CDKN1A in HCT116 cells as well as downregulation of the mismatch repair gene MSH2 in SW480 cells. Furthermore, DUSP4 overexpression caused increased proliferation in CRC cells using Real Time Cell Analysis (RTCA) system. Our findings suggest that DUSP4 plays as an important role in regulating cell growth within the MAPK pathway and causes enhanced cell growth in MSI-H colorectal cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 235. doi:1538-7445.AM2012-235