Genomic Profiling Identifies GATA6 as a Candidate Oncogene Amplified in Pancreatobiliary Cancer

Pancreatobiliary cancers have among the highest mortality rates of any cancer type. Discovering the full spectrum of molecular genetic alterations may suggest new avenues for therapy. To catalogue genomic alterations, we carried out array-based genomic profiling of 31 exocrine pancreatic cancers and 6 distal bile duct cancers, expanded as xenografts to enrich the tumor cell fraction. We identified numerous focal DNA amplifications and deletions, including in 19% of pancreatobiliary cases gain at cytoband 18q11.2, a locus uncommonly amplified in other tumor types. The smallest shared amplification at 18q11.2 included GATA6, a transcriptional regulator previously linked to normal pancreas development. When amplified, GATA6 was overexpressed at both the mRNA and protein levels, and strong immunostaining was observed in 25 of 54 (46%) primary pancreatic cancers compared to 0 of 33 normal pancreas specimens surveyed. GATA6 expression in xenografts was associated with specific microarray gene-expression patterns, enriched for GATA binding sites and mitochondrial oxidative phosphorylation activity. siRNA mediated knockdown of GATA6 in pancreatic cancer cell lines with amplification led to reduced cell proliferation, cell cycle progression, and colony formation. Our findings indicate that GATA6 amplification and overexpression contribute to the oncogenic phenotypes of pancreatic cancer cells, and identify GATA6 as a candidate lineage-specific oncogene in pancreatobiliary cancer, with implications for novel treatment strategies

Corticosterone targets distinct steps of synaptic transmission via concentration specific activation of mineralocorticoid and glucocorticoid receptors

Hippocampal neurons are affected by chronic stress and have a high density of cytoplasmic mineralocorticoid and glucocorticoid receptors (MR and GR). Detailed studies on the genomic effects of the stress hormone corticosterone at physiologically relevant concentrations on different steps in synaptic transmission are limited. In this study, we tried to delineate how activation of MR and GR by different concentrations of corticosterone affects synaptic transmission at various levels. The effect of 3-h corticosterone (25, 50, and 100nM) treatment on depolarization-mediated calcium influx, vesicular release and properties of miniature excitatory post-synaptic currents (mEPSCs) were studied in cultured hippocampal neurons. Activation of MR with 25nM corticosterone treatment resulted in enhanced depolarization-mediated calcium influx via a transcription-dependent process and increased frequency of mEPSCs with larger amplitude. On the other hand, activation of GR upon 100nM corticosterone treatment resulted in increase in the rate of vesicular release via the genomic actions of GR. Furthermore, GR activation led to significant increase in the frequency of mEPSCs with larger amplitude and faster decay. Our studies indicate that differential activation of the dual receptor system of MR and GR by corticosterone targets the steps in synaptic transmission differently

Corticosterone Treatment Results in Enhanced Release of Peptidergic Vesicles in Astrocytes via Cytoskeletal Rearrangements

While the effect of stress on neuronal physiology is widely studied, its effect on the functionality of astrocytes is not well understood. We studied the effect of high doses of stress hormone corticosterone, on two physiological properties of astrocytes, i.e., gliotransmission and interastrocytic calcium waves. To study the release of peptidergic vesicles from astrocytes, hippocampal astrocyte cultures were transfected with a plasmid to express pro-atrial natriuretic peptide (ANP) fused with the emerald green fluorescent protein (ANP.emd). The rate of decrease in fluorescence of ANP.emd on application of ionomycin, a calcium ionophore was monitored. Significant increase in the rate of calcium-dependent exocytosis of ANP.emd was observed with the 100 nM and 1 M corticosterone treatments for 3 h, which depended on the activation of the glucocorticoid receptor. ANP.emd tagged vesicles exhibited increased mobility in astrocyte culture upon corticosterone treatment. Increasing corticosterone concentrations also resulted in concomitant increase in the calcium wave propagation velocity, initiated by focal ATP application. Corticosterone treatment also resulted in increased GFAP expression and F-actin rearrangements. FITC-Phalloidin immunostaining revealed increased formation of cross linked F-actin networks with the 100 nM and 1 M corticosterone treatment. Alternatively, blockade of actin polymerization and disruption of microtubules prevented the corticosterone-mediated increase in ANP.emd release kinetics. This study reports for the first time the effect of corticosterone on gliotransmission via modulation of cytoskeletal elements. As ANP acts on both neurons and blood vessels, modulation of its release could have functional implications in neurovascular coupling under pathophysiological conditions of stress

Vitiligo: Pathomechanisms and genetic polymorphism of susceptible genes

526-539Vitiligo is a depigmenting disorder resulting from the loss of melanocytes in the skin and affects 1-4% of the world population. Incidence of vitiligo is found to be 0.5-2.5% in India with a high prevalence of 8.8% in Gujarat and Rajasthan states. The cellular and molecular mechanisms that lead to melanocyte destruction in this disorder are not yet been fully elucidated. Genetic factors, neural factors, toxic ROS metabolites, autoantibodies and autoreactive T lymphocytes may be the causative agents for the selective destruction of melanocytes. Three major hypotheses of pathogenesis of vitiligo are neural, autoimmune and oxidative stress hypotheses, however none of them explains the pathogenesis of vitiligo in toto. Genetics of vitiligo is characterized by incomplete penetrance, multiple susceptibility loci and genetic heterogeneity. Recent advances in this field are linkage and association of candidate gene studies. The linkage and association studies provide a strong evidence for the presence of multiple vitiligo susceptibility genes on different chromosomes. Several candidate genes for vitiligo are identified from different populations. In this review, we have provide an overview of different hypotheses of vitiligo pathogenesis, and discuss the recent advances in this field with special reference to linkage, association and candidate gene approach

Anti-Retroviral Protease Inhibitors Regulate Human Papillomavirus 16 Infection of Primary Oral and Cervical Epithelium

Epidemiology studies suggest that Human Immunodeficiency Virus (HIV)-infected patients on highly active anti-retroviral therapy (HAART) may be at increased risk of acquiring opportunistic Human Papillomavirus (HPV) infections and developing oral and cervical cancers. Effective HAART usage has improved survival but increased the risk for HPV-associated cancers. In this manuscript, we report that Protease Inhibitors (PI) treatment of three-dimensional tissues derived from primary human gingiva and cervical epithelial cells compromised cell-cell junctions within stratified epithelium and enhanced paracellular permeability of HPV16 to the basal layer for infection, culminating in de novo biosynthesis of progeny HPV16 as determined using 5-Bromo-2′-deoxyuridine (BrdU) labeling of newly synthesized genomes. We propose that HAART/PI represent a novel class of co-factors that modulate HPV infection of the target epithelium. Our in vitro tissue culture model is an important tool to study the mechanistic role of anti-retroviral drugs in promoting HPV infections in HAART-naïve primary epithelium. Changes in subsequent viral load could promote new infections, create HPV reservoirs that increase virus persistence, and increase the risk of oral and cervical cancer development in HIV-positive patients undergoing long-term HAART treatment