Di Stadio, Chiara Stella (2017) Epigenetic mechanisms underlying Gastrokine 1 gene silencing in gastric cancer progression. [Tesi di dottorato]

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Item Type: Tesi di dottorato
Lingua: English
Title: Epigenetic mechanisms underlying Gastrokine 1 gene silencing in gastric cancer progression
Creators:
CreatorsEmail
Di Stadio, Chiara Stellakstella@hotmail.it
Date: 10 April 2017
Number of Pages: 53
Institution: Università degli Studi di Napoli Federico II
Department: Medicina Molecolare e Biotecnologie Mediche
Dottorato: Medicina molecolare e biotecnologie mediche
Ciclo di dottorato: 29
Coordinatore del Corso di dottorato:
nomeemail
Avvedimento, Vittorio Enricoavvedim@unina.it
Tutor:
nomeemail
ARCARI, PAOLOUNSPECIFIED
Date: 10 April 2017
Number of Pages: 53
Uncontrolled Keywords: GKN1
Settori scientifico-disciplinari del MIUR: Area 05 - Scienze biologiche > BIO/10 - Biochimica
Date Deposited: 02 May 2017 14:00
Last Modified: 13 Mar 2018 11:26
URI: http://www.fedoa.unina.it/id/eprint/11754
DOI: 10.6093/UNINA/FEDOA/11754

Abstract

Gastric cancer (GC) is still one of the leading causes of cancer-related deaths worldwide and high mortality rate is mainly due to late-stage diagnosis. New insights show that epigenetic alterations contribute significantly to the development and progression of GC and if nowadays the role of somatic mutations as drivers of carcinogenesis in the alimentary tract is well established, the importance of gene silencing by epigenetic mechanisms is increasingly recognized. Gastrokine1 (GKN1) is a highly expressed stomach protein important for maintaining the physiological function of the gastric mucosa. GKN1 is down-regulated in gastric tumor tissues and derived cell lines so it has recently emerged as a potential biomarker for gastric cancer. It has also been demonstrated that GKN1 expression induces apoptosis in gastric cancer cells thus suggesting a possible role of the protein as tumor suppressor. The mechanism by which GKN1 gene is inactivated in GC remains still unknown, so here I have investigated on the possible causes of GKN1 gene silencing in order to determine if epigenetic mechanisms could also contribute to its down-regulation. To these aim, chromatin immunoprecipitation (ChIP) assays for the repressive trimethylation of histone 3 at lysine 9 (H3K9triMe) and its specific histone-lysine Nmethyltransferase (SUV39H1) were performed on biopsies of normal and tumor human gastric tissues. The results showed that GKN1 downregulation in gastric cancer tissues is associated with high levels of H3K9triMe and with the recruitment of SUV39H1 on GKN1 promoter, suggesting the presence of an epigenetic transcriptional complex that negatively regulates GKN1 expression in gastric tumor. It was also investigated whether underacetylation might contribute to GKN1 transcriptional inhibition using TSA to increase general histone acetylation. The results showed that inhibition of HDACs leads to GKN1 restoration at transcriptional level, but no at traslational level. These findings led to hypothesize that a second regulatory block occurs at translational level, perhaps by mechanisms mediated by microRNAs (miRNAs), resulting in translational repression and gene silencing. So, the possible involvment of miRNAs in this process was investigated. The results demostrated that GKN1 3’UTR was a direct target of hsa-miR-544a and miR-1245b-3p and showed an increase of miR-544a expression in the gastric cancer cell lines after TSA treatment. The up-regulation of miR-544a could be the cause of the GKN1 translational repression, thus suggesting its potential role as biomarker and therapeutic target in GC patients. These findings indicate that epigenetic mechanisms leading to the inactivation of GKN1 play a key role in the multi-step process of gastric 2 carcinogenesis and would provide an essential starting point for the development of new therapeutic strategies based on epigenetic targets for alternatives gene.

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