Publications by authors named "Najah T Nassif"

20 Publications

  • Page 1 of 1

Studying the Oncosuppressive Functions of PTENP1 as a ceRNA.

Methods Mol Biol 2021 ;2324:165-185

School of Life Sciences, Faculty of Science, University of Technology Sydney, Ultimo, NSW, Australia.

PTENP1 is a processed pseudogene of the tumour suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN). It functions posttranscriptionally to regulate PTEN by acting as a sponge for microRNAs that target PTEN. PTENP1 therefore functions as a competitive endogenous RNA (ceRNA), competing with PTEN for binding of microRNAs (miRNA) and thereby modulating PTEN cellular abundance. Studies of the overexpression of PTENP1 all confirm its oncosuppressive function to be mediated through the suppression of cell proliferation, induction of apoptosis, and inhibition of cell migration and invasion of cancer cells of differing types. These oncosuppressive functions are a direct consequence of miRNA binding by PTENP1 and the subsequent liberation of PTEN from miRNA induced suppression. In this chapter, we will focus initially on the description of a high efficiency transient transfection method to introduce and overexpress PTENP1 in the cell type of interest, followed by accurate methodologies to measure transfection efficiency by flow cytometry. We will then continue to describe two methods to analyze cell proliferation, namely the CCK-8 assay and Click-iT EdU assay. Due to commonalities in the manifestation of the oncosuppressive effects of PTENP1, mediated through its role as a ceRNA, the methods presented in this chapter will have wide applicability to a variety of different cell types.
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http://dx.doi.org/10.1007/978-1-0716-1503-4_11DOI Listing
January 2021

Use of a Hybrid Adeno-Associated Viral Vector Transposon System to Deliver the Insulin Gene to Diabetic NOD Mice.

Cells 2020 10 2;9(10). Epub 2020 Oct 2.

School of Life Sciences, University of Technology Sydney, 15 Broadway, Ultimo, NSW 2007, Australia.

Previously, we used a lentiviral vector to deliver furin-cleavable human insulin () to the livers in several animal models of diabetes using intervallic infusion in full flow occlusion (FFO), with resultant reversal of diabetes, restoration of glucose tolerance and pancreatic transdifferentiation (PT), due to the expression of beta (β)-cell transcription factors (β-TFs). The present study aimed to determine whether we could similarly reverse diabetes in the non-obese diabetic (NOD) mouse using an adeno-associated viral vector (AAV) to deliver - ± the β-TF to the livers of diabetic mice. The traditional AAV8, which provides episomal expression, and the hybrid AAV8/ that results in transgene integration were used. Diabetic mice that received AAV8- became hypoglycaemic with abnormal intraperitoneal glucose tolerance tests (IPGTTs). Expression of β-TFs was not detected in the livers. Reversal of diabetes was not achieved in mice that received AAV8--FUR and AAV8- and IPGTTs were abnormal. Normoglycaemia and glucose tolerance were achieved in mice that received AAV8/-/FFO. Definitive evidence of PT was not observed. This is the first in vivo study using the hybrid AAV8/ system to treat Type 1 diabetes (T1D). However, further development is required before the system can be used for gene therapy of T1D.
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http://dx.doi.org/10.3390/cells9102227DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7600325PMC
October 2020

Electroencephalographic prediction of global and domain specific cognitive performance of clinically active Australian Nurses.

Physiol Meas 2020 10 6;41(9):095001. Epub 2020 Oct 6.

Edna Bennett Pierce Prevention Research Center, Pennsylvania State University, 115 Health & Human Development Building, University Park, PA 16802, United States of America.

Objective: To investigate the relationship between EEG activity and the global and domain specific cognitive performance of healthy nurses, and determine the predictive capabilities of these relationships.

Approach: Sixty-four nurses were recruited for the present study, and data from 61 were utilised in the present analysis. Global and domain specific cognitive performance of each participant was assessed psychometrically using the Mini-mental state exam and the Cognistat, and a 32-lead monopolar EEG was recorded during a resting baseline phase and an active phase in which participants completed the Stroop test.

Main Results: Global cognitive performance was successfully predicted (81%-85% of variance) by a combination of fast wave activity variables in the alpha, beta and theta frequency bands. Interestingly, predicting domain specific performance had varying degrees of success (42%-99% of the variance predicted) and relied on combinations of both slow and fast wave activity, with delta and gamma activity predicting attention performance; delta, theta, and gamma activity predicting memory performance; and delta and beta variables predicting judgement performance.

Significance: Global and domain specific cognitive performance of Australian nurses may be predicted with varying degrees of success by a unique combination of EEG variables. These proposed models image transitory cognitive declines and as such may prove useful in the prediction of early cognitive impairment, and may enable better diagnosis, and management of cognitive impairment.
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http://dx.doi.org/10.1088/1361-6579/abb12aDOI Listing
October 2020

Targeting the SphK-S1P-SIPR Pathway as a Potential Therapeutic Approach for COVID-19.

Int J Mol Sci 2020 Sep 29;21(19). Epub 2020 Sep 29.

Guangdong Provincial Engineering Research Center for Esophageal Cancer Precise Therapy, Guangdong Pharmaceutical University, Guangzhou 510080, China.

The world is currently experiencing the worst health pandemic since the Spanish flu in 1918-the COVID-19 pandemic-caused by the coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This pandemic is the world's third wake-up call this century. In 2003 and 2012, the world experienced two major coronavirus outbreaks, SARS-CoV-1 and Middle East Respiratory syndrome coronavirus (MERS-CoV), causing major respiratory tract infections. At present, there is neither a vaccine nor a cure for COVID-19. The severe COVID-19 symptoms of hyperinflammation, catastrophic damage to the vascular endothelium, thrombotic complications, septic shock, brain damage, acute disseminated encephalomyelitis (ADEM), and acute neurological and psychiatric complications are unprecedented. Many COVID-19 deaths result from the aftermath of hyperinflammatory complications, also referred to as the "cytokine storm syndrome", endotheliitus and blood clotting, all with the potential to cause multiorgan dysfunction. The sphingolipid rheostat plays integral roles in viral replication, activation/modulation of the immune response, and importantly in maintaining vasculature integrity, with sphingosine 1 phosphate (S1P) and its cognate receptors (SIPRs: G-protein-coupled receptors) being key factors in vascular protection against endotheliitus. Hence, modulation of sphingosine kinase (SphK), S1P, and the S1P receptor pathway may provide significant beneficial effects towards counteracting the life-threatening, acute, and chronic complications associated with SARS-CoV-2 infection. This review provides a comprehensive overview of SARS-CoV-2 infection and disease, prospective vaccines, and current treatments. We then discuss the evidence supporting the targeting of SphK/S1P and S1P receptors in the repertoire of COVID-19 therapies to control viral replication and alleviate the known and emerging acute and chronic symptoms of COVID-19. Three clinical trials using FDA-approved sphingolipid-based drugs being repurposed and evaluated to help in alleviating COVID-19 symptoms are discussed.
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http://dx.doi.org/10.3390/ijms21197189DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7583882PMC
September 2020

Toward Systems Pathology for PTEN Diagnostics.

Cold Spring Harb Perspect Med 2020 05 1;10(5). Epub 2020 May 1.

School of Life Sciences, University of Technology Sydney, Ultimo, New South Wales 2007, Australia.

Germline alterations of the tumor suppressor PTEN have been extensively characterized in patients with PTEN hamartoma tumor syndromes, encompassing subsets of Cowden syndrome, Bannayan-Riley-Ruvalcaba syndrome, Proteus and Proteus-like syndromes, as well as autism spectrum disorder. Studies have shown an increase in the risk of developing specific cancer types in the presence of a germline mutation. Furthermore, outside of the familial setting, somatic variants of occur in numerous malignancies. Here we introduce and discuss the prospect of moving toward a systems pathology approach for PTEN diagnostics, incorporating clinical and molecular pathology data with the goal of improving the clinical management of patients with a mutation. Detection of a germline mutation can inform cancer surveillance and in the case of somatic mutation, have value in predicting disease course. Given that PTEN functions in the PI3K/AKT/mTOR pathway, identification of a mutation may highlight new therapeutic opportunities and/or inform therapeutic choices.
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http://dx.doi.org/10.1101/cshperspect.a037127DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7197423PMC
May 2020

Heart Rate Variability as a Biomarker for Predicting Stroke, Post-stroke Complications and Functionality.

Biomark Insights 2018 18;13:1177271918786931. Epub 2018 Jul 18.

Neuroscience Research Unit, School of Life Sciences, University of Technology Sydney, Broadway, NSW, Australia.

Background: Heart rate variability (HRV) is a non-invasive measure of the function of the autonomic nervous system, and its dynamic nature may provide a means through which stroke and its associated complications may be predicted, monitored, and managed.

Objective: The objective of this review is to identify and provide a critique on the most recent uses of HRV in stroke diagnosis/management and highlight areas that warrant further research.

Methods: The MEDLINE, CINAHL, and OVID MEDLINE databases were canvassed using a systematic search strategy, for articles investigating the use of HRV in stroke diagnosis and management. Initial paper selections were based on title alone, and final paper inclusion was informed by a full-text critical appraisal.

Results: The systematic search returned 98 records, of which 51 were unique. Following screening, 22 records were included in the final systematic review. The included papers provided some information regarding predicting incident stroke, which largely seems to be best predicted by time- and frequency-domain HRV parameters. Furthermore, post-stroke complications and functionality are similarly predicted by time- and frequency-domain parameters, as well as non-linear parameters in some instances.

Conclusions: Current research provides good evidence that HRV parameters may have utility as a biomarker for stroke and for post-stroke complications and/or functionality. Future research would benefit from the integration of non-linear, and novel parameters, the hybridisation of HRV parameters, and the expansion of the utilisation of predictive regression and hazard modelling.
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http://dx.doi.org/10.1177/1177271918786931DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6052496PMC
July 2018

Partial pancreatic transdifferentiation of primary human hepatocytes in the livers of a humanised mouse model.

J Gene Med 2018 05 16;20(5):e3017. Epub 2018 Apr 16.

School of Life Sciences, University of Technology Sydney, Sydney, Australia.

Background: Gene therapy is one treatment that may ultimately cure type 1 diabetes. We have previously shown that the introduction of furin-cleavable human insulin (INS-FUR) to the livers in several animal models of diabetes resulted in the reversal of diabetes and partial pancreatic transdifferentiation of liver cells. The present study investigated whether streptozotocin-diabetes could be reversed in FRG mice in which chimeric mouse-human livers can readily be established and, in addition, whether pancreatic transdifferentiation occurred in the engrafted human hepatocytes.

Methods: Engraftment of human hepatocytes was confirmed by measuring human albumin levels. Following delivery of the empty vector or the INS-FUR vector to diabetic FRG mice, mice were monitored for weight and blood glucose levels. Intraperitoneal glucose tolerance tests (IPGTTs) were performed. Expression levels of pancreatic hormones and transcription factors were determined by a reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry.

Results: Diabetes was reversed for a period of 60 days (experimental endpoint) after transduction with INS-FUR. IPGTTs of the insulin-transduced animals were not significantly different from nondiabetic animals. Immunofluorescence microscopy revealed the expression of human albumin and insulin in transduced liver samples. Quantitative RT-PCR showed expression of human and mouse endocrine hormones and β-cell transcription factors, indicating partial pancreatic transdifferentiation of mouse and human hepatocytes. Nonfasting human C-peptide levels were significantly higher than mouse levels, suggesting that transdifferentiated human hepatocytes made a significant contribution to the reversal of diabetes.

Conclusions: These data show that human hepatocytes can be induced to undergo partial pancreatic transdifferentiation in vivo, indicating that the technology holds promise for the treatment of type 1 diabetes.
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http://dx.doi.org/10.1002/jgm.3017DOI Listing
May 2018

PTEN/PTENP1: 'Regulating the regulator of RTK-dependent PI3K/Akt signalling', new targets for cancer therapy.

Mol Cancer 2018 02 19;17(1):37. Epub 2018 Feb 19.

Central Laboratory, The First Affiliated Hospital of Guangdong Pharmaceutical University, Guangzhou, 510080, China.

Regulation of the PI-3 kinase (PI3K)/Akt signalling pathway is essential for maintaining the integrity of fundamental cellular processes, cell growth, survival, death and metabolism, and dysregulation of this pathway is implicated in the development and progression of cancers. Receptor tyrosine kinases (RTKs) are major upstream regulators of PI3K/Akt signalling. The phosphatase and tensin homologue (PTEN), a well characterised tumour suppressor, is a prime antagonist of PI3K and therefore a negative regulator of this pathway. Loss or inactivation of PTEN, which occurs in many tumour types, leads to overactivation of RTK/PI3K/Akt signalling driving tumourigenesis. Cellular PTEN levels are tightly regulated by a number of transcriptional, post-transcriptional and post-translational regulatory mechanisms. Of particular interest, transcription of the PTEN pseudogene, PTENP1, produces sense and antisense transcripts that exhibit post-transcriptional and transcriptional modulation of PTEN expression respectively. These additional levels of regulatory complexity governing PTEN expression add to the overall intricacies of the regulation of RTK/PI-3 K/Akt signalling. This review will discuss the regulation of oncogenic PI3K signalling by PTEN (the regulator) with a focus on the modulatory effects of the sense and antisense transcripts of PTENP1 on PTEN expression, and will further explore the potential for new therapeutic opportunities in cancer treatment.
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http://dx.doi.org/10.1186/s12943-018-0803-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5817727PMC
February 2018

"Dicing and Splicing" Sphingosine Kinase and Relevance to Cancer.

Int J Mol Sci 2017 Sep 2;18(9). Epub 2017 Sep 2.

School of Life Sciences, Faculty of Science, University of Technology Sydney, 15 Broadway, Ultimo, Sydney, NSW 2007, Australia.

Sphingosine kinase (SphK) is a lipid enzyme that maintains cellular lipid homeostasis. Two SphK isozymes, SphK1 and SphK2, are expressed from different chromosomes and several variant isoforms are expressed from each of the isozymes, allowing for the multi-faceted biological diversity of SphK activity. Historically, SphK1 is mainly associated with oncogenicity, however in reality, both SphK1 and SphK2 isozymes possess oncogenic properties and are recognized therapeutic targets. The absence of mutations of SphK in various cancer types has led to the theory that cancer cells develop a dependency on SphK signaling (hyper-SphK signaling) or "non-oncogenic addiction". Here we discuss additional theories of SphK cellular mislocation and aberrant "dicing and splicing" as contributors to cancer cell biology and as key determinants of the success or failure of SphK/S1P (sphingosine 1 phosphate) based therapeutics.
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http://dx.doi.org/10.3390/ijms18091891DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5618540PMC
September 2017

Mammalian sphingosine kinase (SphK) isoenzymes and isoform expression: challenges for SphK as an oncotarget.

Oncotarget 2017 May;8(22):36898-36929

School of Life Sciences, University of Technology Sydney, Ultimo, Sydney, NSW 2007, Australia.

The various sphingosine kinase (SphK) isoenzymes (isozymes) and isoforms, key players in normal cellular physiology, are strongly implicated in cancer and other diseases. Mutations in SphKs, that may justify abnormal physiological function, have not been recorded. Nonetheless, there is a large and growing body of evidence demonstrating the contribution of gain or loss of function and the imbalance in the SphK/S1P rheostat to a plethora of pathological conditions including cancer, diabetes and inflammatory diseases. SphK is expressed as two isozymes SphK1 and SphK2, transcribed from genes located on different chromosomes and both isozymes catalyze the phosphorylation of sphingosine to S1P. Expression of each SphK isozyme produces alternately spliced isoforms. In recent years the importance of the contribution of SpK1 expression to treatment resistance in cancer has been highlighted and, additionally, differences in treatment outcome appear to also be dependent upon SphK isoform expression. This review focuses on an exciting emerging area of research involving SphKs functions, expression and subcellular localization, highlighting the complexity of targeting SphK in cancer and also comorbid diseases. This review also covers the SphK isoenzymes and isoforms from a historical perspective, from their first discovery in murine species and then in humans, their role(s) in normal cellular function and in disease processes, to advancement of SphK as an oncotarget.
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http://dx.doi.org/10.18632/oncotarget.16370DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5482707PMC
May 2017

Annexin/S100A Protein Family Regulation through p14ARF-p53 Activation: A Role in Cell Survival and Predicting Treatment Outcomes in Breast Cancer.

PLoS One 2017 9;12(1):e0169925. Epub 2017 Jan 9.

School of Life Sciences, Faculty of Science, Faculty of Engineering and IT, University of Technology Sydney, Sydney, New South Wales, Australia.

The annexin family and S100A associated proteins are important regulators of diverse calcium-dependent cellular processes including cell division, growth regulation and apoptosis. Dysfunction of individual annexin and S100A proteins is associated with cancer progression, metastasis and cancer drug resistance. This manuscript describes the novel finding of differential regulation of the annexin and S100A family of proteins by activation of p53 in breast cancer cells. Additionally, the observed differential regulation is found to be beneficial to the survival of breast cancer cells and to influence treatment efficacy. We have used unbiased, quantitative proteomics to determine the proteomic changes occurring post p14ARF-p53 activation in estrogen receptor (ER) breast cancer cells. In this report we identified differential regulation of the annexin/S100A family, through unique peptide recognition at the N-terminal regions, demonstrating p14ARF-p53 is a central orchestrator of the annexin/S100A family of calcium regulators in favor of pro-survival functions in the breast cancer cell. This regulation was found to be cell-type specific. Retrospective human breast cancer studies have demonstrated that tumors with functional wild type p53 (p53wt) respond poorly to some chemotherapy agents compared to tumors with a non-functional p53. Given that modulation of calcium signaling has been demonstrated to change sensitivity of chemotherapeutic agents to apoptotic signals, in principle, we explored the paradigm of how p53 modulation of calcium regulators in ER+ breast cancer patients impacts and influences therapeutic outcomes.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0169925PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5222396PMC
August 2017

Pancreatic Transdifferentiation and Glucose-Regulated Production of Human Insulin in the H4IIE Rat Liver Cell Line.

Int J Mol Sci 2016 Apr 8;17(4):534. Epub 2016 Apr 8.

School of Life Sciences and Centre for Health Technologies, University of Technology Sydney, P.O. Box 123, Broadway, 2007 Sydney, NSW, Australia.

Due to the limitations of current treatment regimes, gene therapy is a promising strategy being explored to correct blood glucose concentrations in diabetic patients. In the current study, we used a retroviral vector to deliver either the human insulin gene alone, the rat NeuroD1 gene alone, or the human insulin gene and rat NeuroD1 genes together, to the rat liver cell line, H4IIE, to determine if storage of insulin and pancreatic transdifferentiation occurred. Stable clones were selected and expanded into cell lines: H4IIEins (insulin gene alone), H4IIE/ND (NeuroD1 gene alone), and H4IIEins/ND (insulin and NeuroD1 genes). The H4IIEins cells did not store insulin; however, H4IIE/ND and H4IIEins/ND cells stored 65.5 ± 5.6 and 1475.4 ± 171.8 pmol/insulin/5 × 10⁶ cells, respectively. Additionally, several β cell transcription factors and pancreatic hormones were expressed in both H4IIE/ND and H4IIEins/ND cells. Electron microscopy revealed insulin storage vesicles in the H4IIE/ND and H4IIEins/ND cell lines. Regulated secretion of insulin to glucose (0-20 mmol/L) was seen in the H4IIEins/ND cell line. The H4IIEins/ND cells were transplanted into diabetic immunoincompetent mice, resulting in normalization of blood glucose. This data shows that the expression of NeuroD1 and insulin in liver cells may be a useful strategy for inducing islet neogenesis and reversing diabetes.
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http://dx.doi.org/10.3390/ijms17040534DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4848990PMC
April 2016

Reversal of diabetes following transplantation of an insulin-secreting human liver cell line: Melligen cells.

Mol Ther Methods Clin Dev 2015 8;2:15011. Epub 2015 Apr 8.

School of Medical and Molecular Biosciences and Centre for Health Technologies, University of Technology Sydney , Sydney, Australia.

As an alternative to the transplantation of islets, a human liver cell line has been genetically engineered to reverse type 1 diabetes (TID). The initial liver cell line (Huh7ins) commenced secretion of insulin in response to a glucose concentration of 2.5 mmol/l. After transfection of the Huh7ins cells with human islet glucokinase, the resultant Melligen cells secreted insulin in response to glucose within the physiological range; commencing at 4.25 mmol/l. Melligen cells exhibited increased glucokinase enzymatic activity in response to physiological glucose concentrations, as compared with Huh7ins cells. When transplanted into diabetic immunoincompetent mice, Melligen cells restored normoglycemia. Quantitative real-time polymerase chain reaction (qRT-PCR) revealed that both cell lines expressed a range of β-cell transcription factors and pancreatic hormones. Exposure of Melligen and Huh7ins cells to proinflammatory cytokines (TNF-α, IL-1β, and IFN-γ) affected neither their viability nor their ability to secrete insulin to glucose. Gene expression (microarray and qRT-PCR) analyses indicated the survival of Melligen cells in the presence of known β-cell cytotoxins was associated with the expression of NF-κB and antiapoptotic genes (such as BIRC3). This study describes the successful generation of an artificial β-cell line, which, if encapsulated to avoid allograft rejection, may offer a clinically applicable cure for T1D.
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http://dx.doi.org/10.1038/mtm.2015.11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4445011PMC
June 2015

Long-term reversal of diabetes in non-obese diabetic mice by liver-directed gene therapy.

J Gene Med 2013 Jan;15(1):28-41

School of Medical & Molecular Biosciences, University of Technology Sydney, Sydney, Australia.

Background: Type 1 diabetes (T1D) results from an autoimmune attack against the insulin-producing β-cells of the pancreas. The present study aimed to reverse T1D by gene therapy.

Methods: We used a novel surgical technique, which involves isolating the liver from the circulation before the delivery of a lentiviral vector carrying furin-cleavable human insulin (INS-FUR) or empty vector to the livers of diabetic non-obese diabetic mice (NOD). This was compared with the direct injection of the vector into the portal circulation. Mice were monitored for body weight and blood glucose. Intravenous glucose tolerance tests were performed. Expression of insulin and pancreatic transcription factors was determined by the reverse transcriptase-polymerase chain reaction and immunohistochemistry and immunoelectron microscopy was used to localise insulin.

Results: Using the novel surgical technique, we achieved long-term transduction (42% efficiency) of hepatocytes, restored normoglycaemia for 150 days (experimental endpoint) and re-established normal glucose tolerance. We showed the expression of β-cell transcription factors, murine insulin, glucagon and somatostatin, and hepatic storage of insulin in granules. The expression of hepatic markers, C/EBP-β, G6PC, AAT and GLUI was down-regulated in INS-FUR-treated livers. Liver function tests remained normal, with no evidence of intrahepatic inflammation or autoimmune destruction of the insulin-secreting liver tissue. By comparison, direct injection of INS-FUR reduced blood glucose levels, and no pancreatic transdifferentiation or normal glucose tolerance was observed.

Conclusions: This gene therapy protocol has, for the first time, permanently reversed T1D with normal glucose tolerance in NOD mice and, as such, represents a novel therapeutic strategy for the treatment of T1D.
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http://dx.doi.org/10.1002/jgm.2692DOI Listing
January 2013

Germline and somatic cancer-associated mutations in the ATP-binding motifs of PTEN influence its subcellular localization and tumor suppressive function.

Hum Mol Genet 2009 Aug 20;18(15):2851-62. Epub 2009 May 20.

Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.

Germline and somatic PTEN mutations are found in Cowden syndrome (CS) and multiple sporadic malignancies, respectively. PTEN function appears to be modulated by subcellular compartmentalization, and mislocalization may affect function. We have shown that cellular ATP levels affect nuclear PTEN levels. Here, we examined the ATP-binding capabilities of PTEN and functional consequences, relevant to cancer-associated mutations. PTEN mutation analysis of CS patients and sporadic colorectal carcinomas and comparative aminoacid analysis were utilized to identify mutations in ATP-binding motifs. The ability of wild-type (WT) or mutant PTEN to bind ATP was assessed by ATP-agarose-binding assays. Subcellular fractionation, western blotting, confocal microscopy and growth assays were used to determine relative nuclear-cytoplasmic localization and function. Somatic colorectal carcinoma-derived PTEN missense mutations were associated with nuclear mislocalization. These mutations altered cellular proliferation, apoptosis and anchorage-dependent growth. Examination of PTEN's amino acid sequence revealed these mutations resided in previously undescribed ATP-binding motifs (c.60-73; c.122-136). In contrast to WT PTEN, both cancer-associated somatic and germline-derived PTEN missense mutations, which lie within the ATP-binding motifs, result in mutant PTEN that does not bind ATP efficiently. We also show that CS patients with germline ATP-binding motif-mutations had nuclear PTEN mislocalization. Of four unrelated patients with functional germline ATP-binding domain mutations, all three female patients had breast cancers. Germline and somatic mutations within PTEN's ATP-binding domain play important pathogenic roles in both heritable and sporadic carcinogenesis by PTEN nuclear mislocalization resulting in altered signaling and growth. Manipulation of ATP may represent novel therapies in tumors with such PTEN alterations.
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http://dx.doi.org/10.1093/hmg/ddp220DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2706686PMC
August 2009

Association of SLC11A1 promoter polymorphisms with the incidence of autoimmune and inflammatory diseases: a meta-analysis.

J Autoimmun 2008 Aug 28;31(1):42-51. Epub 2008 Mar 28.

Department of Medical and Molecular Biosciences, University of Technology Sydney, PO Box 123, Broadway, NSW 2007, Australia.

Solute carrier family 11 member a1 (SLC11A1) exerts pleiotropic effects on macrophage function. Expression of SLC11A1 is regulated by a (GT)(n) microsatellite promoter repeat polymorphism of which nine alleles have been described. Enhanced activation of macrophages, associated with increased expression from allele 3, may be functionally linked to the development of autoimmune and inflammatory diseases. Conversely, low expression, driven by allele 2, may afford resistance. We have performed a meta-analysis to determine the association of SLC11A1 promoter alleles 2 and 3 with autoimmunity and inflammation. A random effects pooled odds ratio (OR) of 1.04 (95% confidence interval [CI]=0.20) for allele 3 suggested a weak association of this allele with an increased risk of disease. Calculation of the OR in the absence of asymmetry yielded a random effects pooled OR of 0.88 (95% CI=0.66), effectively reversing the above association. A fixed effects pooled OR of 0.90 (95% CI=0.24) was obtained for allele 2, suggesting a weak predominance of disease in the absence of this allele. Application of the trim-and-fill method resulted in a fixed effects OR of 0.80 (95% CI=0.22), thus strengthening this association. Associations of allele 3 with autoimmune and inflammatory diseases reported in several association studies may be attributable to some form of bias amongst published results.
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http://dx.doi.org/10.1016/j.jaut.2008.02.002DOI Listing
August 2008

PTEN mutations are common in sporadic microsatellite stable colorectal cancer.

Oncogene 2004 Jan;23(2):617-28

Cancer Research Laboratories, South West Sydney Clinical School, University of New South Wales, Liverpool Hospital, Liverpool, NSW 2170, Australia.

The tumour suppressor gene PTEN, located at chromosome sub-band 10q23.3, encodes a dual-specificity phosphatase that negatively regulates the phosphatidylinositol 3'-kinase (PI3 K)/Akt-dependent cellular survival pathway. PTEN is frequently inactivated in many tumour types including glioblastoma, prostate and endometrial cancers. While initial studies reported that PTEN gene mutations were rare in colorectal cancer, more recent reports have shown an approximate 18% incidence of somatic PTEN mutations in colorectal tumours exhibiting microsatellite instability (MSI+). To verify the role of this gene in colorectal tumorigenesis, we analysed paired normal and tumour DNA from 41 unselected primary sporadic colorectal cancers for PTEN inactivation by mutation and/or allelic loss. We now report PTEN gene mutations in 19.5% (8/41) of tumours and allele loss, including all or part of the PTEN gene, in a further 17% (7/41) of the cases. Both PTEN alleles were affected in over half (9/15) of these cases showing PTEN genetic abnormalities. Using immunohistochemistry, we have further shown that all tumours harbouring PTEN alterations have either reduced or absent PTEN expression and this correlated strongly with later clinical stage of tumour at presentation (P=0.02). In contrast to previous reports, all but one of the tumours with PTEN gene mutations were microsatellite stable (MSI-), suggesting that PTEN is involved in a distinct pathway of colorectal tumorigenesis that is separate from the pathway of mismatch repair deficiency. This work therefore establishes the importance of PTEN in primary sporadic colorectal cancer.
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http://dx.doi.org/10.1038/sj.onc.1207059DOI Listing
January 2004

Frequent loss of heterozygosity targeting the inactive X chromosome in melanoma.

Clin Cancer Res 2003 Dec;9(17):6476-82

Westmead Institute for Cancer Research, University of Sydney at Westmead Millennium Institute, Westmead, New South Wales, Australia.

After previous preliminary observations of paradoxical deletion events affecting the inactive X chromosome in melanoma, we have surveyed the X chromosome for deletions using 23 polymorphic microsatellite markers in 28 informative (female XX) metastatic melanomas. Ten tumors (36%) showed at least one loss of heterozygosity (LOH) event, and in two cases an entire chromosome showed LOH at all informative loci. Four distinct X chromosome smallest regions of overlap can be resolved. An 18.6-Mb region on the p arm involving 9 of 28 (32%) samples lies between the markers DXS1061 and DXS1068. An equally frequently deleted smallest region of overlap straddled the centromere, bounded by DX1204 on the p arm and DXS983 14.6 Mb away in Xq11-12. One tumor potentially defines this region more tightly to a 10.6-Mb smallest region of overlap bounded by DXS1190 and DXS981 that contains the androgen receptor (AR) gene. A 6.2-Mb deleted region can be defined between the markers DXS8051 and DXS9902 in 8 of 28 (28%) tumors. An additional, less frequently deleted region of 25.7 Mb was found on distal Xq between the markers DXS1212 and DXS1193 in 5 of 28 (18%) tumors. X inactivation analysis of five tumors with LOH, using the AR exon 1 CAG repeat, showed that in each case, the inactive, hypermethylated allele was the one deleted. Analysis of copy number in this region by quantitative PCR showed restoration to disomy and, in one case, trisomy at AR.
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December 2003

Germline PTEN promoter mutations and deletions in Cowden/Bannayan-Riley-Ruvalcaba syndrome result in aberrant PTEN protein and dysregulation of the phosphoinositol-3-kinase/Akt pathway.

Am J Hum Genet 2003 Aug 3;73(2):404-11. Epub 2003 Jul 3.

Clinical Cancer Genetics Program, Comprehensive Cancer Center, and Division of Human Genetics, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA.

Germline intragenic mutations in PTEN are associated with 80% of patients with Cowden syndrome (CS) and 60% of patients with Bannayan-Riley-Ruvalcaba syndrome (BRRS). The underlying genetic causes remain to be determined in a considerable proportion of classic CS and BRRS without a polymerase chain reaction (PCR)-detectable PTEN mutation. We hypothesized that gross gene deletions and mutations in the PTEN promoter might alternatively account for a subset of apparently mutation-negative patients with CS and BRRS. Using real time and multiplex PCR techniques, we identified three germline hemizygous PTEN deletions in 122 apparently mutation-negative patients with classic CS (N=95) or BRRS (N=27). Fine mapping suggested that one deletion encompassed the whole gene and the other two included exon 1 and encompassed exons 1-5 of PTEN, respectively. Two patients with the deletion were diagnosed with BRRS, and one patient with the deletion was diagnosed with BRRS/CS overlap (features of both). Thus 3 (11%) of 27 patients with BRRS or BRRS/CS-overlap had PTEN deletions. Analysis of the PTEN promoter revealed nine cases (7.4%) harboring heterozygous germline mutations. All nine had classic CS, representing almost 10% of all subjects with CS. Eight had breast cancers and/or benign breast tumors but, otherwise, oligo-organ involvement. PTEN protein analysis, from one deletion-positive and five PTEN-promoter-mutation-positive samples, revealed a 50% reduction in protein and multiple bands of immunoreactive protein, respectively. In contrast, control samples showed only the expected band. Further, an elevated level of phosphorylated Akt was detected in the five promoter-mutation-positive samples, compared with controls, indicating an absence of or marked reduction in functional PTEN. These data suggest that patients with BRRS and CS without PCR-detected intragenic PTEN mutations be offered clinical deletion analysis and promoter-mutation analysis, respectively.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1180378PMC
http://dx.doi.org/10.1086/377109DOI Listing
August 2003
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