The Experts below are selected from a list of 369 Experts worldwide ranked by ideXlab platform
Heidi Friedrichs - One of the best experts on this subject based on the ideXlab platform.
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a cag repeat polymorphism of kcnn3 predicts sk3 channel function and cognitive performance in schizophrenia
Embo Molecular Medicine, 2011Co-Authors: Sabrina Grube, Sabine Martin, Martin Fungisai Gerchen, Bartosz Adamcio, Dorthe Malzahn, Sergi Papiol, Martin Begemann, Katja Ribbe, Luis A Pardo, Heidi FriedrichsAbstract:KCNN3, encoding the small conductance calcium-activated potassium channel SK3, harbours a polymorphic CAG repeat in the amino-terminal coding region with yet unproven function. Hypothesizing that KCNN3 genotypes do not influence susceptibility to schizophrenia but modify its phenotype, we explored their contribution to specific schizophrenic symptoms. Using the Gottingen Research Association for Schizophrenia (GRAS) data collection of schizophrenic patients (n = 1074), we performed a phenotype-based genetic association study (PGAS) of KCNN3. We show that long CAG repeats in the schizophrenic sample are specifically associated with better performance in higher cognitive tasks, comprising the capacity to discriminate, select and execute (p < 0.0001). Long repeats reduce SK3 channel function, as we demonstrate by patch-clamping of transfected HEK293 cells. In contrast, modelling the opposite in mice, i.e. KCNN3 overexpression/channel hyperfunction, leads to selective deficits in higher brain functions comparable to those influenced by SK3 conductance in humans. To conclude, KCNN3 genotypes modify cognitive performance, shown here in a large sample of schizophrenic patients. Reduction of SK3 function may constitute a pharmacological target to improve cognition in schizophrenia and other conditions with cognitive impairment.
Hubert Hackl - One of the best experts on this subject based on the ideXlab platform.
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KCNJ3 is a new independent prognostic marker for estrogen receptor positive breast cancer patients
Oncotarget, 2016Co-Authors: Sarah Kammerer, Stephan W Jahn, Martin Pichler, Armin Sokolowski, Hubert Hackl, Dieter Platzer, Amin Elheliebi, Daniela Schwarzenbacher, Verena Stiegelbauer, Simin RezaniaAbstract:// Sarah Kammerer 1, 2 , Armin Sokolowski 1, 9 , Hubert Hackl 3 , Dieter Platzer 1 , Stephan Wenzel Jahn 4 , Amin El-Heliebi 5 , Daniela Schwarzenbacher 6 , Verena Stiegelbauer 6 , Martin Pichler 6, 7 , Simin Rezania 1, 2 , Heidelinde Fiegl 8 , Florentia Peintinger 4 , Peter Regitnig 4 , Gerald Hoefler 4 , Wolfgang Schreibmayer 1, 2 , Thomas Bauernhofer 2, 6 1 Molecular Physiology Group, Institute of Biophysics, Medical University of Graz, Austria 2 Research Unit on Ion Channels and Cancer Biology, Medical University of Graz, Austria 3 Division of Bioinformatics, Biocenter, Medical University of Innsbruck, Austria 4 Institute of Pathology, Medical University of Graz, Austria 5 Institute of Cell Biology, Histology and Embryology, Medical University of Graz, Austria 6 Division of Oncology, Department of Internal Medicine, Medical University of Graz, Austria 7 Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA 8 Department of Gynecology and Obstetrics, Medical University of Innsbruck, Austria 9 Present address: Division of Prosthodontics, Restorative Dentistry, Periodontology and Implantology, Medical University of Graz, Austria Correspondence to: Thomas Bauernhofer, email: thomas.bauernhofer@medunigraz.at Keywords: KCNJ3, GIRK1, biomarker, estrogen receptor positive breast cancer, RNA in situ hybridization Received: June 04, 2016 Accepted: October 26, 2016 Published: November 08, 2016 ABSTRACT Numerous studies showed abnormal expression of ion channels in different cancer types. Amongst these, the potassium channel gene KCNJ3 (encoding for GIRK1 proteins) has been reported to be upregulated in tumors of patients with breast cancer and to correlate with positive lymph node status. We aimed to study KCNJ3 levels in different breast cancer subtypes using gene expression data from the TCGA, to validate our findings using RNA in situ hybridization in a validation cohort (GEO ID GSE17705), and to study the prognostic value of KCNJ3 using survival analysis. In a total of > 1000 breast cancer patients of two independent data sets we showed a) that KCNJ3 expression is upregulated in tumor tissue compared to corresponding normal tissue ( p < 0.001), b) that KCNJ3 expression is associated with estrogen receptor (ER) positive tumors ( p < 0.001), but that KCNJ3 expression is variable within this group, and c) that ER positive patients with high KCNJ3 levels have worse overall ( p < 0.05) and disease free survival probabilities ( p < 0.01), whereby KCNJ3 is an independent prognostic factor ( p <0.05). In conclusion, our data suggest that patients with ER positive breast cancer might be stratified into high risk and low risk groups based on the KCNJ3 levels in the tumor.
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KCNJ3 is a new independent prognostic marker for estrogen receptor positive breast cancer patients.
Oncotarget, 2016Co-Authors: Sarah Kammerer, Stephan W Jahn, Martin Pichler, Armin Sokolowski, Hubert Hackl, Dieter Platzer, Daniela Schwarzenbacher, Verena Stiegelbauer, Amin El-heliebi, Simin RezaniaAbstract:// Sarah Kammerer 1, 2 , Armin Sokolowski 1, 9 , Hubert Hackl 3 , Dieter Platzer 1 , Stephan Wenzel Jahn 4 , Amin El-Heliebi 5 , Daniela Schwarzenbacher 6 , Verena Stiegelbauer 6 , Martin Pichler 6, 7 , Simin Rezania 1, 2 , Heidelinde Fiegl 8 , Florentia Peintinger 4 , Peter Regitnig 4 , Gerald Hoefler 4 , Wolfgang Schreibmayer 1, 2 , Thomas Bauernhofer 2, 6 1 Molecular Physiology Group, Institute of Biophysics, Medical University of Graz, Austria 2 Research Unit on Ion Channels and Cancer Biology, Medical University of Graz, Austria 3 Division of Bioinformatics, Biocenter, Medical University of Innsbruck, Austria 4 Institute of Pathology, Medical University of Graz, Austria 5 Institute of Cell Biology, Histology and Embryology, Medical University of Graz, Austria 6 Division of Oncology, Department of Internal Medicine, Medical University of Graz, Austria 7 Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA 8 Department of Gynecology and Obstetrics, Medical University of Innsbruck, Austria 9 Present address: Division of Prosthodontics, Restorative Dentistry, Periodontology and Implantology, Medical University of Graz, Austria Correspondence to: Thomas Bauernhofer, email: thomas.bauernhofer@medunigraz.at Keywords: KCNJ3, GIRK1, biomarker, estrogen receptor positive breast cancer, RNA in situ hybridization Received: June 04, 2016 Accepted: October 26, 2016 Published: November 08, 2016 ABSTRACT Numerous studies showed abnormal expression of ion channels in different cancer types. Amongst these, the potassium channel gene KCNJ3 (encoding for GIRK1 proteins) has been reported to be upregulated in tumors of patients with breast cancer and to correlate with positive lymph node status. We aimed to study KCNJ3 levels in different breast cancer subtypes using gene expression data from the TCGA, to validate our findings using RNA in situ hybridization in a validation cohort (GEO ID GSE17705), and to study the prognostic value of KCNJ3 using survival analysis. In a total of > 1000 breast cancer patients of two independent data sets we showed a) that KCNJ3 expression is upregulated in tumor tissue compared to corresponding normal tissue ( p < 0.001), b) that KCNJ3 expression is associated with estrogen receptor (ER) positive tumors ( p < 0.001), but that KCNJ3 expression is variable within this group, and c) that ER positive patients with high KCNJ3 levels have worse overall ( p < 0.05) and disease free survival probabilities ( p < 0.01), whereby KCNJ3 is an independent prognostic factor ( p
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overexpression of KCNJ3 gene splice variants affects vital parameters of the malignant breast cancer cell line mcf 7 in an opposing manner
BMC Cancer, 2016Co-Authors: Simin Rezania, Sarah Kammerer, C. Li, A. Gorischek, T. T. J. Devaney, S. Verheyen, C. A. Passegger, Bibiane Steineckerfrohnwieser, Ghaffari N Tabriziwizsy, Hubert HacklAbstract:Overexpression the KCNJ3, a gene that encodes subunit 1 of G-protein activated inwardly rectifying K+ channel (GIRK1) in the primary tumor has been found to be associated with reduced survival times and increased lymph node metastasis in breast cancer patients. In order to survey possible tumorigenic properties of GIRK1 overexpression, a range of malignant mammary epithelial cells, based on the MCF-7 cell line that permanently overexpress different splice variants of the KCNJ3 gene (GIRK1a, GIRK1c, GIRK1d and as a control, eYFP) were produced. Subsequently, selected cardinal neoplasia associated cellular parameters were assessed and compared. Adhesion to fibronectin coated surface as well as cell proliferation remained unaffected. Other vital parameters intimately linked to malignancy, i.e. wound healing, chemoinvasion, cellular velocities / motilities and angiogenesis were massively affected by GIRK1 overexpression. Overexpression of different GIRK1 splice variants exerted differential actions. While GIRK1a and GIRK1c overexpression reinforced the affected parameters towards malignancy, overexpression of GIRK1d resulted in the opposite. Single channel recording using the patch clamp technique revealed functional GIRK channels in the plasma membrane of MCF-7 cells albeit at very low frequency. We conclude that GIRK1d acts as a dominant negative constituent of functional GIRK complexes present in the plasma membrane of MCF-7 cells, while overexpression of GIRK1a and GIRK1c augmented their activity. The core component responsible for the cancerogenic action of GIRK1 is apparently presented by a segment comprising aminoacids 235–402, that is present exclusively in GIRK1a and GIRK1c, but not GIRK1d (positions according to GIRK1a primary structure). The current study provides insight into the cellular and molecular consequences of KCNJ3 overexpression in breast cancer cells and the mechanism upon clinical outcome in patients suffering from breast cancer.
Geoffrey W. Abbott - One of the best experts on this subject based on the ideXlab platform.
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kcne1 and kcne3 the yin and yang of voltage gated k channel regulation
Gene, 2016Co-Authors: Geoffrey W. AbbottAbstract:Abstract The human KCNE gene family comprises five genes encoding single transmembrane-spanning ion channel regulatory subunits. The primary function of KCNE subunits appears to be regulation of voltage-gated potassium (Kv) channels, and the best-understood KCNE complexes are with the KCNQ1 Kv α subunit. Here, we review the often opposite effects of KCNE1 and KCNE3 on Kv channel biology, with an emphasis on regulation of KCNQ1. Slow-activating I Ks channel complexes formed by KCNQ1 and KCNE1 are essential for human ventricular myocyte repolarization, while constitutively active KCNQ1-KCNE3 channels are important in the intestine. Inherited sequence variants in human KCNE1 and KCNE3 cause cardiac arrhythmias but by different mechanisms, and each is important for hearing in unique ways. Because of their contrasting effects on KCNQ1 function, KCNE1 and KCNE3 have proved invaluable tools in the mechanistic understanding of how channel gating can be manipulated, and each may also provide a window into novel insights and new therapeutic opportunities in K + channel pharmacology. Finally, findings from studies of Kcne1 −/− and Kcne3 −/− mouse lines serve to illustrate the complexity of KCNE biology and KCNE-linked disease states.
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KCNE1 and KCNE3: The yin and yang of voltage-gated K(+) channel regulation.
Gene, 2015Co-Authors: Geoffrey W. AbbottAbstract:The human KCNE gene family comprises five genes encoding single transmembrane-spanning ion channel regulatory subunits. The primary function of KCNE subunits appears to be regulation of voltage-gated potassium (Kv) channels, and the best-understood KCNE complexes are with the KCNQ1 Kv α subunit. Here, we review the often opposite effects of KCNE1 and KCNE3 on Kv channel biology, with an emphasis on regulation of KCNQ1. Slow-activating IKs channel complexes formed by KCNQ1 and KCNE1 are essential for human ventricular myocyte repolarization, while constitutively active KCNQ1-KCNE3 channels are important in the intestine. Inherited sequence variants in human KCNE1 and KCNE3 cause cardiac arrhythmias but by different mechanisms, and each is important for hearing in unique ways. Because of their contrasting effects on KCNQ1 function, KCNE1 and KCNE3 have proved invaluable tools in the mechanistic understanding of how channel gating can be manipulated, and each may also provide a window into novel insights and new therapeutic opportunities in K(+) channel pharmacology. Finally, findings from studies of Kcne1(-/-) and Kcne3(-/-) mouse lines serve to illustrate the complexity of KCNE biology and KCNE-linked disease states.
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effects of kcne subunit deletion on polarized trafficking of the kcnq1 potassium channel in vivo
Biophysical Journal, 2010Co-Authors: Geoffrey W. Abbott, Kerry Purtell, Elizabeth C King, Gianina Panaghie, Daniel Lerner, Torsten K RoepkeAbstract:The KCNQ1 potassium channel alpha subunit generates essential K+ currents in human heart and in a range of polarized secretory epithelia. The polarity of KCNQ1 trafficking varies between different epithelia, but neither the importance nor the mechanism for this polarity are well understood. KCNQ1 co-localizes apically with the KCNE2 beta subunit in gastric parietal cells but basolaterally with KCNE3 in colonic crypts. Both KCNE2 and KCNE3 convert KCNQ1 to a constitutively active channel. Here, genetic deletion of Kcne2 in mice resulted in 5-fold upregulation of Kcne3, formation of Kcnq1-Kcne3 complexes, and basolateral Kcnq1 targeting in parietal cells, and gastritis cystica profunda stemming from achlorhydria and earlier hyperplasia. In contrast, Kcne2-/-Kcne3-/- mice exhibited apical parietal cell Kcnq1 localization. Thus, in parietal cells, apical Kcnq1 localization is required for gastric acid secretion, and the apical localization per se does not require Kcne2. Kcne3, if present, actively targets Kcnq1 basolaterally, ultimately causing a preneoplastic condition which in humans could predispose to gastric cancer.View Large Image | View Hi-Res Image | Download PowerPoint Slide
Peter H Larsson - One of the best experts on this subject based on the ideXlab platform.
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kcne1 and kcne3 modulate kcnq1 channels by affecting different gating transitions
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Rene Barrosoria, Rosamary Ramentol, Sara I Liin, Marta E Perez, Robert S Kass, Peter H LarssonAbstract:Abstract KCNE β-subunits assemble with and modulate the properties of voltage-gated K+ channels. In the heart, KCNE1 associates with the α-subunit KCNQ1 to generate the slowly activating, voltage-dependent potassium current (IKs) in the heart that controls the repolarization phase of cardiac action potentials. By contrast, in epithelial cells from the colon, stomach, and kidney, KCNE3 coassembles with KCNQ1 to form K+ channels that are voltage-independent K+ channels in the physiological voltage range and important for controlling water and salt secretion and absorption. How KCNE1 and KCNE3 subunits modify KCNQ1 channel gating so differently is largely unknown. Here, we use voltage clamp fluorometry to determine how KCNE1 and KCNE3 affect the voltage sensor and the gate of KCNQ1. By separating S4 movement and gate opening by mutations or phosphatidylinositol 4,5-bisphosphate depletion, we show that KCNE1 affects both the S4 movement and the gate, whereas KCNE3 affects the S4 movement and only affects the gate in KCNQ1 if an intact S4-to-gate coupling is present. Further, we show that a triple mutation in the middle of the transmembrane (TM) segment of KCNE3 introduces KCNE1-like effects on the second S4 movement and the gate. In addition, we show that differences in two residues at the external end of the KCNE TM segments underlie differences in the effects of the different KCNEs on the first S4 movement and the voltage sensor-to-gate coupling.
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kcne1 and kcne3 modulate kcnq1 channels by affecting different gating transitions
Biophysical Journal, 2017Co-Authors: Rene Barrosoria, Rosamary Ramentol, Sara I Liin, Marta E Perez, Robert S Kass, Peter H LarssonAbstract:KCNE β subunits assemble with and modulate the properties of voltage-gated K+ channels. In the heart, KCNE1 associates with KCNQ1 to generate the slowly activating, voltage-dependent IKs current that controls the repolarization phase of cardiac action potentials. By contrast, in epithelial cells from the colon, stomach and kidney, KCNE3 coassembles with the α-subunit KCNQ1 to form apparent voltage-independent K+ channels important for controlling water and salt secretion. How KCNE1 and KCNE3 subunits modify KCNQ1 channel gating so differently is largely unknown. Different molecular mechanisms have been proposed to explain the effects of KCNE1 and KCNE3 on KCNQ1 channels. Here, we use voltage clamp fluorometry to determine how KCNE1 and KCNE3 affect the voltage sensor and the gate of KCNQ1. By separating S4 movement and gate opening by a mutation, we show that KCNE1 affects both the S4 movement and the gate, whereas KCNE3 directly affects the S4 movement and only indirectly affects the gate in KCNQ1. Further, we show that a triple mutation in KCNE3 converts KCNQ1/KCNE3 channels into KCNQ1/KCNE1-like channels by introducing KCNE1-like effects on the KCNQ1 gate. Our results suggest that the difference between the effects of KCNE1 and KCNE3 on KCNQ1 is that KCNE1 affects both the voltage-sensing domain and the gate, whereas KCNE3 primarily affects the voltage-sensing domain and only indirectly affects the gate.
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kcne3 stabilizes the voltage sensor s4 of kcnq1 channel kcne1 uncouples s4 and the gate
Biophysical Journal, 2015Co-Authors: Rene Barrosoria, Robert S Kass, Kevin J Sampson, Gary Peng, Peter H LarssonAbstract:KCNEs are single-span transmembrane β-subunits that assemble with and modulate the biophysical properties of voltage-gated K+ (Kv) channels. In the heart, the pore forming α-subunit KCNQ1 associates with KCNE1 to form the slowly-activating, voltage-gated IKs channels that contribute to the repolarization of the cardiac action potential. In tissues such as the colon, stomach and kidney, KCNQ1 coassembles with the β-subunit KCNE3 to form voltage-independent K+ channels important for K+ and Cl- secretion. KCNE3 has also been shown to be expressed in the human heart, although its physiological function remains unknown. Different mechanisms have been proposed to explain how different KCNE subunits alter KCNQ1 gating and permeation. For instance, KCNE3 is assumed to lock the voltage sensor (S4) of KCNQ1 channel in the activated state, resulting in a constitutively open channel. Here, we use voltage clamp fluorometry (VCF) to understand how KCNE3 affects the voltage sensor and the gate of KCNQ1 channel. We show that KCNE3, contrary to what was previously assumed, allows S4 movement in KCNQ1/KCNE3 channels. KCNE3 shifts the closing and S4 movement of KCNQ1 to extreme hyperpolarized potentials, such that at physiological voltage range (−80 mV to +40 mV), the channel is always open. By decoupling S4 and the gate, either by mutations or PIP2 depletion, we show that KCNE3 mainly affects S4 movement in KCNQ1. Two negatively charged residues in the N-terminus of KCNE3 (D54 and D55) are, at least partly, responsible for stabilizing S4 in an outward position, therefore stabilizing KCNQ1/KCNE3 channels in the activated open state. Further, we unitized a triple mutation of KCNE3, previously shown to convert KCNQ1/KCNE1 channel to a KCNQ1/KCNE1-like current, and observe a decoupling of S4 and the gate
Simin Rezania - One of the best experts on this subject based on the ideXlab platform.
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critical evaluation of KCNJ3 gene product detection in human breast cancer mrna in situ hybridisation is superior to immunohistochemistry
Journal of Clinical Pathology, 2016Co-Authors: Sarah Kammerer, Stephan W Jahn, Elke Winter, Sylvia Eidenhammer, Simin Rezania, Peter Regitnig, Martin Pichler, Wolfgang Schreibmayer, Thomas BauernhoferAbstract:Increased expression levels of KCNJ3 have been correlated with lymph node metastases and poor prognosis in patients with breast cancer, suggesting a prognostic role of KCNJ3 . We aimed to establish protocols for the detection of KCNJ3 in formalin-fixed, paraffin-embedded (FFPE) breast cancer tissue. Several antibodies were tested for sensitivity and specificity by western blot, followed by optimisation of the immunohistochemistry (IHC) procedure and establishment of KCNJ3 mRNA in situ hybridisation (ISH). Methods were validated by processing 15 FFPE breast cancer samples for which microarray data were available. Spearman9s rank correlation analysis resulted in borderline significant correlation for IHC versus ISH ( r S : 0.625; p r S : 0.668; p r S : 0.861; p KCNJ3 in both malignant and physiological conditions.
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KCNJ3 is a new independent prognostic marker for estrogen receptor positive breast cancer patients
Oncotarget, 2016Co-Authors: Sarah Kammerer, Stephan W Jahn, Martin Pichler, Armin Sokolowski, Hubert Hackl, Dieter Platzer, Amin Elheliebi, Daniela Schwarzenbacher, Verena Stiegelbauer, Simin RezaniaAbstract:// Sarah Kammerer 1, 2 , Armin Sokolowski 1, 9 , Hubert Hackl 3 , Dieter Platzer 1 , Stephan Wenzel Jahn 4 , Amin El-Heliebi 5 , Daniela Schwarzenbacher 6 , Verena Stiegelbauer 6 , Martin Pichler 6, 7 , Simin Rezania 1, 2 , Heidelinde Fiegl 8 , Florentia Peintinger 4 , Peter Regitnig 4 , Gerald Hoefler 4 , Wolfgang Schreibmayer 1, 2 , Thomas Bauernhofer 2, 6 1 Molecular Physiology Group, Institute of Biophysics, Medical University of Graz, Austria 2 Research Unit on Ion Channels and Cancer Biology, Medical University of Graz, Austria 3 Division of Bioinformatics, Biocenter, Medical University of Innsbruck, Austria 4 Institute of Pathology, Medical University of Graz, Austria 5 Institute of Cell Biology, Histology and Embryology, Medical University of Graz, Austria 6 Division of Oncology, Department of Internal Medicine, Medical University of Graz, Austria 7 Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA 8 Department of Gynecology and Obstetrics, Medical University of Innsbruck, Austria 9 Present address: Division of Prosthodontics, Restorative Dentistry, Periodontology and Implantology, Medical University of Graz, Austria Correspondence to: Thomas Bauernhofer, email: thomas.bauernhofer@medunigraz.at Keywords: KCNJ3, GIRK1, biomarker, estrogen receptor positive breast cancer, RNA in situ hybridization Received: June 04, 2016 Accepted: October 26, 2016 Published: November 08, 2016 ABSTRACT Numerous studies showed abnormal expression of ion channels in different cancer types. Amongst these, the potassium channel gene KCNJ3 (encoding for GIRK1 proteins) has been reported to be upregulated in tumors of patients with breast cancer and to correlate with positive lymph node status. We aimed to study KCNJ3 levels in different breast cancer subtypes using gene expression data from the TCGA, to validate our findings using RNA in situ hybridization in a validation cohort (GEO ID GSE17705), and to study the prognostic value of KCNJ3 using survival analysis. In a total of > 1000 breast cancer patients of two independent data sets we showed a) that KCNJ3 expression is upregulated in tumor tissue compared to corresponding normal tissue ( p < 0.001), b) that KCNJ3 expression is associated with estrogen receptor (ER) positive tumors ( p < 0.001), but that KCNJ3 expression is variable within this group, and c) that ER positive patients with high KCNJ3 levels have worse overall ( p < 0.05) and disease free survival probabilities ( p < 0.01), whereby KCNJ3 is an independent prognostic factor ( p <0.05). In conclusion, our data suggest that patients with ER positive breast cancer might be stratified into high risk and low risk groups based on the KCNJ3 levels in the tumor.
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KCNJ3 is a new independent prognostic marker for estrogen receptor positive breast cancer patients.
Oncotarget, 2016Co-Authors: Sarah Kammerer, Stephan W Jahn, Martin Pichler, Armin Sokolowski, Hubert Hackl, Dieter Platzer, Daniela Schwarzenbacher, Verena Stiegelbauer, Amin El-heliebi, Simin RezaniaAbstract:// Sarah Kammerer 1, 2 , Armin Sokolowski 1, 9 , Hubert Hackl 3 , Dieter Platzer 1 , Stephan Wenzel Jahn 4 , Amin El-Heliebi 5 , Daniela Schwarzenbacher 6 , Verena Stiegelbauer 6 , Martin Pichler 6, 7 , Simin Rezania 1, 2 , Heidelinde Fiegl 8 , Florentia Peintinger 4 , Peter Regitnig 4 , Gerald Hoefler 4 , Wolfgang Schreibmayer 1, 2 , Thomas Bauernhofer 2, 6 1 Molecular Physiology Group, Institute of Biophysics, Medical University of Graz, Austria 2 Research Unit on Ion Channels and Cancer Biology, Medical University of Graz, Austria 3 Division of Bioinformatics, Biocenter, Medical University of Innsbruck, Austria 4 Institute of Pathology, Medical University of Graz, Austria 5 Institute of Cell Biology, Histology and Embryology, Medical University of Graz, Austria 6 Division of Oncology, Department of Internal Medicine, Medical University of Graz, Austria 7 Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA 8 Department of Gynecology and Obstetrics, Medical University of Innsbruck, Austria 9 Present address: Division of Prosthodontics, Restorative Dentistry, Periodontology and Implantology, Medical University of Graz, Austria Correspondence to: Thomas Bauernhofer, email: thomas.bauernhofer@medunigraz.at Keywords: KCNJ3, GIRK1, biomarker, estrogen receptor positive breast cancer, RNA in situ hybridization Received: June 04, 2016 Accepted: October 26, 2016 Published: November 08, 2016 ABSTRACT Numerous studies showed abnormal expression of ion channels in different cancer types. Amongst these, the potassium channel gene KCNJ3 (encoding for GIRK1 proteins) has been reported to be upregulated in tumors of patients with breast cancer and to correlate with positive lymph node status. We aimed to study KCNJ3 levels in different breast cancer subtypes using gene expression data from the TCGA, to validate our findings using RNA in situ hybridization in a validation cohort (GEO ID GSE17705), and to study the prognostic value of KCNJ3 using survival analysis. In a total of > 1000 breast cancer patients of two independent data sets we showed a) that KCNJ3 expression is upregulated in tumor tissue compared to corresponding normal tissue ( p < 0.001), b) that KCNJ3 expression is associated with estrogen receptor (ER) positive tumors ( p < 0.001), but that KCNJ3 expression is variable within this group, and c) that ER positive patients with high KCNJ3 levels have worse overall ( p < 0.05) and disease free survival probabilities ( p < 0.01), whereby KCNJ3 is an independent prognostic factor ( p
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overexpression of KCNJ3 gene splice variants affects vital parameters of the malignant breast cancer cell line mcf 7 in an opposing manner
BMC Cancer, 2016Co-Authors: Simin Rezania, Sarah Kammerer, C. Li, A. Gorischek, T. T. J. Devaney, S. Verheyen, C. A. Passegger, Bibiane Steineckerfrohnwieser, Ghaffari N Tabriziwizsy, Hubert HacklAbstract:Overexpression the KCNJ3, a gene that encodes subunit 1 of G-protein activated inwardly rectifying K+ channel (GIRK1) in the primary tumor has been found to be associated with reduced survival times and increased lymph node metastasis in breast cancer patients. In order to survey possible tumorigenic properties of GIRK1 overexpression, a range of malignant mammary epithelial cells, based on the MCF-7 cell line that permanently overexpress different splice variants of the KCNJ3 gene (GIRK1a, GIRK1c, GIRK1d and as a control, eYFP) were produced. Subsequently, selected cardinal neoplasia associated cellular parameters were assessed and compared. Adhesion to fibronectin coated surface as well as cell proliferation remained unaffected. Other vital parameters intimately linked to malignancy, i.e. wound healing, chemoinvasion, cellular velocities / motilities and angiogenesis were massively affected by GIRK1 overexpression. Overexpression of different GIRK1 splice variants exerted differential actions. While GIRK1a and GIRK1c overexpression reinforced the affected parameters towards malignancy, overexpression of GIRK1d resulted in the opposite. Single channel recording using the patch clamp technique revealed functional GIRK channels in the plasma membrane of MCF-7 cells albeit at very low frequency. We conclude that GIRK1d acts as a dominant negative constituent of functional GIRK complexes present in the plasma membrane of MCF-7 cells, while overexpression of GIRK1a and GIRK1c augmented their activity. The core component responsible for the cancerogenic action of GIRK1 is apparently presented by a segment comprising aminoacids 235–402, that is present exclusively in GIRK1a and GIRK1c, but not GIRK1d (positions according to GIRK1a primary structure). The current study provides insight into the cellular and molecular consequences of KCNJ3 overexpression in breast cancer cells and the mechanism upon clinical outcome in patients suffering from breast cancer.
