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Background/Aim: Aggressive breast cancer (BC) cells show high expression of Rho GTPase activating protein 29 (ARHGAP29), a negative regulator of RhoA. In breast cancer cells in which mesenchymal transformation was induced, ARHGAP29 was the only one of 32 GTPaseactivating enzymes whose expression increased significantly. Therefore, we investigated whether there is a correlation between expression of ARHGAP29 and tumor progression in BC. Since tamoxifen-resistant BC cells exhibit increased mesenchymal properties and invasiveness, we additionally investigated the relationship between ARHGAP29 and increased invasion rate in tamoxifen resistance. The question arises as to whether ARHGAP29 is a suitable prognostic marker for the progression of BC. Materials and Methods: Tissue microarrays were used to investigate expression of ARHGAP29 in BC and adjacent normal breast tissues. Knockdown experiments using siRNA were performed to investigate the influence of ARHGAP29 and the possible downstream actors RhoC and pAKT1 on invasive growth of tamoxifen-resistant BC spheroids in vitro. Results: Expression of ARHGAP29 was frequently increased in BC tissues compared to adjacent normal breast tissues. In addition, there was evidence of a correlation between high ARHGAP29 expression and advanced clinical tumor stage. Tamoxifenresistant BC cells show a significantly higher expression of ARHGAP29 compared to their parental wild-type cells. After knockdown of ARHGAP29 in tamoxifen-resistant BC cells, expression of RhoC was significantly reduced. Further, expression of pAKT1 decreased significantly. Invasive growth of three-dimensional tamoxifen-resistant BC spheroids was reduced after knockdown of ARHGAP29. This could be partially reversed by AKT1 activator SC79. Conclusion: Expression of ARHGAP29 correlates with the clinical tumor parameters of BC patients. In addition, ARHGAP29 is involved in increased invasiveness of tamoxifen-resistant BC cells. ARHGAP29 alone or in combination with its downstream partners RhoC and pAKT1 could be suitable prognostic markers for BC progression. [ABSTRACT FROM AUTHOR]

Constitutive activation of GNAQ/11 is the initiative oncogenic event in uveal melanoma (UM). Direct targeting GNAQ/11 has yet to be proven feasible as they are vital for a plethora of cellular functions. In search of genetic vulnerability for UM, we found that inhibition of euchromatic histone lysine methyltransferase 2 (EHMT2) expression or activity significantly reduced the proliferation and migration capacity of cancer cells. Notably, elevated expression of EHMT2 had been validated in UM samples. Furthermore, Kaplan–Meier survival analysis indicated high EHMT2 protein level was related to poor recurrence-free survival and a more advanced T stage. Chromatin immunoprecipitation sequencing analysis and the following mechanistic investigation showed that ARHGAP29 was a downstream target of EHMT2. Its transcription was suppressed by EHMT2 in a methyltransferase-dependent pattern in GNAQ/11-mutant UM cells, leading to elevated RhoA activity. Rescuing constitutively active RhoA in UM cells lacking EHMT2 restored oncogenic phenotypes. Simultaneously blocking EHMT2 and GNAQ/11 signaling in vitro and in vivo showed a synergistic effect on UM growth, suggesting the driver role of these two key molecules. In summary, our study shows evidence for an epigenetic program of EHMT2 regulation that influences UM progression and indicates inhibiting EHMT2 and MEK/ERK simultaneously as a therapeutic strategy in GNAQ/11-mutant UM.

Constitutive activation of GNAQ/11 is the initiative oncogenic event in uveal melanoma (UM). Direct targeting GNAQ/11 has yet to be proven feasible as they are vital for a plethora of cellular functions. In search of genetic vulnerability for UM, we found that inhibition of euchromatic histone lysine methyltransferase 2 (EHMT2) expression or activity significantly reduced the proliferation and migration capacity of cancer cells. Notably, elevated expression of EHMT2 had been validated in UM samples. Furthermore, Kaplan–Meier survival analysis indicated high EHMT2 protein level was related to poor recurrence-free survival and a more advanced T stage. Chromatin immunoprecipitation sequencing analysis and the following mechanistic investigation showed that ARHGAP29 was a downstream target of EHMT2. Its transcription was suppressed by EHMT2 in a methyltransferase-dependent pattern in GNAQ/11- mutant UM cells, leading to elevated RhoA activity. Rescuing constitutively active RhoA in UM cells lacking EHMT2 restored oncogenic phenotypes. Simultaneously blocking EHMT2 and GNAQ/11 signaling in vitro and in vivo showed a synergistic effect on UM growth, suggesting the driver role of these two key molecules. In summary, our study shows evidence for an epigenetic program of EHMT2 regulation that influences UM progression and indicates inhibiting EHMT2 and MEK/ERK simultaneously as a therapeutic strategy in GNAQ/11- mutant UM. EHMT2-dependent epigenetic program promotes RhoA signaling in GNAQ/11 -mutant uveal melanoma and targeting EHMT2 and MEK/ERK simultaneously is a therapeutic strategy to overcome resistance. [Display omitted] [ABSTRACT FROM AUTHOR]

Glomerular disease due to podocyte malfunction is a major factor in the pathogenesis of chronic kidney disease. Identification of podocyte-specific signaling pathways is therefore a prerequisite to characterizing relevant disease pathways and developing novel treatment approaches. Here, we employed loss of function studies for EPB41L5 (Yurt) as a central podocyte gene to generate a cell type-specific disease model. Loss of Yurt in fly nephrocytes caused protein uptake and slit diaphragm defects. Transcriptomic and proteomic analysis of human EPB41L5 knockout podocytes demonstrated impaired mechanotransduction via the YAP/TAZ signaling pathway. Further analysis of specific inhibition of the YAP/TAZ-TEAD transcription factor complex by TEADi led to the identification of ARGHAP29 as an EPB41L5 and YAP/TAZ-dependently expressed podocyte RhoGAP. Knockdown of ARHGAP29 caused increased RhoA activation, defective lamellipodia formation, and increased maturation of integrin adhesion complexes, explaining similar phenotypes caused by loss of EPB41L5 and TEADi expression in podocytes. Detection of increased levels of ARHGAP29 in early disease stages of human glomerular disease implies a novel negative feedback loop for mechanotransductive RhoA—YAP/TAZ signaling in podocyte physiology and disease. [ABSTRACT FROM AUTHOR]

Glomerular disease due to podocyte malfunction is a major factor in the pathogenesis of chronic kidney disease. Identification of podocyte-specific signaling pathways is therefore a prerequisite to characterizing relevant disease pathways and developing novel treatment approaches. Here, we employed loss of function studies for EPB41L5 (Yurt) as a central podocyte gene to generate a cell type-specific disease model. Loss of Yurt in fly nephrocytes caused protein uptake and slit diaphragm defects. Transcriptomic and proteomic analysis of human EPB41L5 knockout podocytes demonstrated impaired mechanotransduction via the YAP/TAZ signaling pathway. Further analysis of specific inhibition of the YAP/TAZ-TEAD transcription factor complex by TEADi led to the identification of ARGHAP29 as an EPB41L5 and YAP/TAZ-dependently expressed podocyte RhoGAP. Knockdown of ARHGAP29 caused increased RhoA activation, defective lamellipodia formation, and increased maturation of integrin adhesion complexes, explaining similar phenotypes caused by loss of EPB41L5 and TEADi expression in podocytes. Detection of increased levels of ARHGAP29 in early disease stages of human glomerular disease implies a novel negative feedback loop for mechanotransductive RhoA—YAP/TAZ signaling in podocyte physiology and disease.

Yes-associated protein (YAP) is regulated by mechanical cues via the interaction of the Hippo pathway with cytoskeleton. Previous studies showed that YAP plays a role in regulating the actomyosin network by suppressing Rho GTPase in medaka fish. Here, we identify Rho GTPase activating protein 29 (ARHGAP29) as a transcriptional target of YAP in a human gastric cancer cell line. YAP promotes the expression of ARHGAP29 to suppress the RhoA-LIMK-cofilin pathway, destabilizing F-actin. The overexpression of YAP causes cytoskeletal rearrangement by altering the dynamics of F-actin/G-actin turnover, thus promoting migration. In a mouse model, circulating tumor cells (CTCs) exhibit an increased ARHGAP29 RNA level compared with cells at primary tumor sites, and the metastatic potential of CTCs is positively correlated with ARHGAP29 expression. Moreover, increased ARHGAP29 expression is correlated with shortened survival of human gastric cancer patients. Our study provides a model to understand YAP’s contribution to cancer metastasis via regulation of actin dynamics.

Fibroblasts show a high range of phenotypic plasticity, including transdifferentiation into myofibroblasts. Myofibroblasts are responsible for generation of the contraction forces that are important for wound healing and scar formation. Overactive myofibroblasts, by contrast, are involved in abnormal scarring. Cell stretching and extracellular signals such as transforming growth factor β can induce the myofibroblastic program, whereas microenvironmental conditions such as reduced tissue oxygenation have an inhibitory effect. We investigated the effects of hypoxia on myofibroblastic properties and linked this to RhoA activity. Hypoxia reversed the myofibroblastic phenotype of primary fibroblasts. This was accompanied by decreased αSMA (ACTA2) expression, alterations in cell contractility, actin reorganization and RhoA activity. We identified a hypoxia-inducible induction of ARHGAP29, which is critically involved in myocardin-related transcription factor-A (MRTF-A) signaling, the differentiation state of myofibroblasts and modulates RhoA activity. This novel link between hypoxia and MRTF-A signaling is likely to be important for ischemiainduced tissue remodeling and the fibrotic response. This article has an associated First Person interview with the first author of the paper [ABSTRACT FROM AUTHOR]

Aggressive and mesenchymal-transformed breast cancer cells show high expression levels of Rho GTPase activating protein 29 (ARHGAP29), a negative regulator of RhoA. ARHGAP29 was the only one of 32 GTPase-activating enzymes whose expression significantly increased after the induction of mesenchymal transformation in breast cancer cells. Therefore, we investigated the influence of ARHGAP29 on the invasiveness of aggressive and mesenchymal-transformed breast cancer cells. After knock-down of ARHGAP29 using siRNA, invasion of HCC1806, MCF-7-EMT, and T-47D-EMT breast cancer cells was significantly reduced. This could be explained by reduced inhibition of RhoA and a consequent increase in stress fiber formation. Proliferation of the breast cancer cell line T-47D-EMT was slightly increased by reduced expression of ARHGAP29, whereas that of HCC1806 and MCF-7-EMT significantly increased. Using interaction analyses we found that AKT1 is a possible interaction partner of ARHGAP29. Therefore, the expression of AKT1 after siRNA knock-down of ARHGAP29 was tested. Reduced ARHGAP29 expression was accompanied by significantly reduced AKT1 expression. However, the ratio of active pAKT1 to total AKT1 remained unchanged or was significantly increased after ARHGAP29 knock-down. Our results show that ARHGAP29 could be an important factor in the invasion of aggressive and mesenchymal-transformed breast cancer cells. Further research is required to fully understand the underlying mechanisms.

Aggressive and mesenchymal-transformed breast cancer cells show high expression levels of Rho GTPase activating protein 29 (ARHGAP29), a negative regulator of RhoA. ARHGAP29 was the only one of 32 GTPase-activating enzymes whose expression significantly increased after the induction of mesenchymal transformation in breast cancer cells. Therefore, we investigated the influence of ARHGAP29 on the invasiveness of aggressive and mesenchymal-transformed breast cancer cells. After knock-down of ARHGAP29 using siRNA, invasion of HCC1806, MCF-7-EMT, and T-47D-EMT breast cancer cells was significantly reduced. This could be explained by reduced inhibition of RhoA and a consequent increase in stress fiber formation. Proliferation of the breast cancer cell line T-47D-EMT was slightly increased by reduced expression of ARHGAP29, whereas that of HCC1806 and MCF-7-EMT significantly increased. Using interaction analyses we found that AKT1 is a possible interaction partner of ARHGAP29. Therefore, the expression of AKT1 after siRNA knock-down of ARHGAP29 was tested. Reduced ARHGAP29 expression was accompanied by significantly reduced AKT1 expression. However, the ratio of active pAKT1 to total AKT1 remained unchanged or was significantly increased after ARHGAP29 knock-down. Our results show that ARHGAP29 could be an important factor in the invasion of aggressive and mesenchymal-transformed breast cancer cells. Further research is required to fully understand the underlying mechanisms. [ABSTRACT FROM AUTHOR]

Yes-associated protein (YAP) is regulated by mechanical cues via the interaction of the Hippo pathway with cytoskeleton. Previous studies showed that YAP plays a role in regulating the actomyosin network by suppressing Rho GTPase in medaka fish. Here, we identify Rho GTPase activating protein 29 (ARHGAP29) as a transcriptional target of YAP in a human gastric cancer cell line. YAP promotes the expression of ARHGAP29 to suppress the RhoA-LIMK-cofilin pathway, destabilizing F-actin. The overexpression of YAP causes cytoskeletal rearrangement by altering the dynamics of F-actin/G-actin turnover, thus promoting migration. In a mouse model, circulating tumor cells (CTCs) exhibit an increased ARHGAP29 RNA level compared with cells at primary tumor sites, and the metastatic potential of CTCs is positively correlated with ARHGAP29 expression. Moreover, increased ARHGAP29 expression is correlated with shortened survival of human gastric cancer patients. Our study provides a model to understand YAP's contribution to cancer metastasis via regulation of actin dynamics., (Copyright © 2017 National University of Singapore. Published by Elsevier Inc. All rights reserved.)

Objective: Mutations in exon 1 of ARHGAP29, a RhoA specific GTPase have been identified in North American and Filipino subjects with nonsyndromic cleft palate and cleft lip with or without cleft palate. Since the genetic status of ARHGAP29 in Indian subjects with nonsyndromic oral clefts is not known, we designed the present study to investigate the occurrence of the above mutations in them., Materials and Methods: Total genomic DNA extracted from peripheral blood of 60 subjects with nonsyndromic cleft palate and cleft lip with or without cleft palate, and equal number of control healthy subjects were amplified with primers flanking exon 1 of ARHGAP29 gene and subjected to direct sequencing., Results: Sequencing analysis identified a nonsense mutation in exon 1 of ARHGAP29 that caused substitution of lysine to stop codon at codon position 32 in a subject with nonsyndromic cleft lip with cleft palate. The mutation, however, occurred in heterozygous condition. None of the other subjects carried mutation in this region., Conclusion: The study has thus identified a rare but novel truncation mutation in ARHGAP29 gene for the first time in nonsyndromic oral clefts.