Daisy Abraham

Introduction: H.pylori is a bacteria that colonizes the gut of 50% of humans.⁷ Infection with Cag+ H.pylori is a primary cause of gastric cancer, which is the fourth leading cause of cancer-related death globally.⁸  Chemotherapy is a common treatment, but chemoresistance by cancers through the inhibition of apoptosis is a growing concern.^2,8  It is known that one of the mechanisms by which H.pylori causes cancer is apoptosis resistance, but the specific mechanism is still under investigation.2 Recent studies found that Brd4, a transcriptional gene regulator, is utilized by CagA+ H.pylori to form eRNAs that will then go on to activate the synthesis of Birc3 eRNAs^1,2 Additional studies proved that Birc3 increases the expression of cIAP2 in gastric cancer tissue and that cIAP2 can be utilized to prevent apoptosis.^1,2,3,5 These findings suggest that Brd4 is a potential target for gastric cancer therapy.⁵ Methods: Raptinal was found to easily induce apoptosis in three different gastric epithelial cell lines and to inhibit gastric cancer cell proliferation measured by flow cytometry. To determine how apoptosis resistance was induced, expression levels of different inhibitors of apoptosis were measured and H.pylori infected cells showed increased BIRC3 expression. Cell lines were infected with H.pylori and suppressed apoptosis by Raptinal. AGS cells were treated with an IAP inhibitor BV6, and more cells were found to undergo apoptosis after treatment. AGS cells were treated with a BRD4 inhibitor, and it was determined that it inhibited BIRC3 eRNA and mRNA synthesis. ChIPs were used to determine if Brd4 was brought to the enhancer portion of BIRC3. ² H.pylori infected cells had a significantly higher amount of Brd4 binding to the enhancer region. Two different strains of H.pylori were evaluated for their ability to induce the expression of BIRC3 mRNA and eRNA. AGS cells were infected with Cag+ H.pylori or Cag deficient strains of H.pylori, and then eRNA and mRNA expression was monitored by qRT-PCR. Only CagA+ strains of H.pylori induced expression of BIRC3 mRNA  and eRNA. ²The same process was repeated for cIAP2 and only CagA+ strains induced cIAP2 expression.² Results: From these experiments,  BRD4 plays a role in apoptosis resistance mediated by CagA+ H.pylori. Brd4 was proven to enhance the transcriptional activity of NF-kB leading to synthesis of eRNA resulting in the synthesis of BIRC3 eRNAs which encode cIAP2 proteins that will inhibit apoptosis.² This pathway is a potential target of future cancer therapies.²

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