Publications by authors named "Rei Ishibashi"

18 Publications

  • Page 1 of 1

Mutant KRAS drives metabolic reprogramming and autophagic flux in premalignant pancreatic cells.

Cancer Gene Ther 2021 Apr 8. Epub 2021 Apr 8.

Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan.

Mutational activation of the KRAS gene occurs in almost all pancreatic ductal adenocarcinoma (PDAC) and is the earliest molecular event in their carcinogenesis. Evidence has accumulated of the metabolic reprogramming in PDAC, such as amino acid homeostasis and autophagic flux. However, the biological effects of KRAS mutation on metabolic reprogramming at the earlier stages of PDAC carcinogenesis are unclear. Here we report dynamic metabolic reprogramming in immortalized human non-cancerous pancreatic ductal epithelial cells, in which a KRAS mutation was induced by gene-editing, which may mimic early pancreatic carcinogenesis. Similar to the cases of PDAC, KRAS gene mutation increased the dependency on glucose and glutamine for maintaining the intracellular redox balance. In addition, the intracellular levels of amino acids were significantly decreased because of active protein synthesis, and the cells required greater autophagic flux to maintain their viability. The lysosomal inhibitor chloroquine significantly inhibited cell proliferation. Therefore, metabolic reprogramming is an early event in carcinogenesis initiated by KRAS gene mutation, suggesting a rationale for the development of nutritional interventions that suppress or delay the development of PDAC.
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http://dx.doi.org/10.1038/s41417-021-00326-4DOI Listing
April 2021

Comparing the mechanical properties of a self-expandable metallic stent for colorectal obstruction: Proposed measurement method of axial force using a new measurement machine.

Dig Endosc 2021 Jan 11;33(1):170-178. Epub 2020 May 11.

Department of Gastroenterology, Graduate School of Medicine, Juntendo University, Tokyo, Japan.

Objectives: Colorectal stenting is widely performed using self-expandable metallic stents (SEMSs), but the mechanical properties have not been evaluated. Therefore, we conducted an in vitro study to evaluate the mechanical properties of colorectal SEMSs.

Methods: Eighteen individual types and sizes of uncovered SEMSs were evaluated for their mechanical properties. Radial force was measured using a measurement machine. Axial force (AF) was measured by two methods: a conventional manual method and a new method using a measurement machine. The correlation of these two methods was evaluated. We also proposed an "AF zero border" that was defined as the angle at which the torque force disappeared.

Results: Radial force versus diameter curves and AF versus angle curves were influenced by the structure and the size of each stent. There was excellent correlation of AFs measured by the new and conventional manual method (y = 21.434x, R = 0.881, P < 0.0001). Colorectal SEMSs could be categorized into five subgroups according to the mechanical properties. Most hook-wired SEMSs had the AF of zero border.

Conclusions: This is the first report to evaluate the mechanical properties of colorectal SEMSs, and these data may provide useful information for the clinical use and development of colorectal SEMS. Furthermore, the new measurement machine might standardize the measuring method of AF.
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http://dx.doi.org/10.1111/den.13671DOI Listing
January 2021

Detection of circulating colorectal cancer cells by a custom microfluid system before and after endoscopic metallic stent placement.

Oncol Lett 2019 Dec 4;18(6):6397-6404. Epub 2019 Nov 4.

Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan.

Although the detection of circulating tumor cells (CTCs) should be crucial for future personalized medicine, no efficient and flexible methods have been established. The current study established a polymeric custom-made chip for capturing CTCs with a high efficiency and flexibility. As an example of clinical application, the effects of self-expandable metallic stent (SEMS) placement on the release of cancer cells into the blood of patients with colorectal cancer and bowel obstruction were analyzed. This was assessed as the placement of SEMS may cause mechanical damage and physical force to malignant tissue, increasing the risk of cancer cell release into the bloodstream. The present study examined the number of CTCs using a custom-made chip, before, at 24 h after and at 4 days after SEMS placement in patients with colorectal cancer. The results revealed that, among the 13 patients examined, the number of CTCs was increased in three cases at 24 h after SEMS placement. However, this increase was temporary. The number of CTCs also decreased at 4 days after stent placement in most cases. The CTC chip of the current study detected the number of CD133-positive cancer stem-like cells, which did not change, even in the patient whose total number of CTCs temporarily increased. The results indicated that this custom-made microfluid system can efficiently and flexibly detect CTCs, demonstrating its potential for obtaining information during the management of patients with cancer.
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http://dx.doi.org/10.3892/ol.2019.11047DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6876337PMC
December 2019

Clinical usefulness of a deep learning-based system as the first screening on small-bowel capsule endoscopy reading.

Dig Endosc 2020 May 2;32(4):585-591. Epub 2019 Oct 2.

Department of Surgical Oncology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

Background And Aim: To examine whether our convolutional neural network (CNN) system based on deep learning can reduce the reading time of endoscopists without oversight of abnormalities in the capsule-endoscopy reading process.

Methods: Twenty videos of the entire small-bowel capsule endoscopy procedure were prepared, each of which included 0-5 lesions of small-bowel mucosal breaks (erosions or ulcerations). At another institute, two reading processes were compared: (A) endoscopist-alone readings and (B) endoscopist readings after the first screening by the proposed CNN. In process B, endoscopists read only images detected by CNN. Two experts and four trainees independently read 20 videos each (10 for process A and 10 for process B). Outcomes were reading time and detection rate of mucosal breaks by endoscopists. Gold standard was findings at the original institute by two experts.

Results: Mean reading time of small-bowel sections by endoscopists was significantly shorter during process B (expert, 3.1 min; trainee, 5.2 min) compared to process A (expert, 12.2 min; trainee, 20.7 min) (P < 0.001). For 37 mucosal breaks, detection rate by endoscopists did not significantly decrease in process B (expert, 87%; trainee, 55%) compared to process A (expert, 84%; trainee, 47%). Experts detected all eight large lesions (>5 mm), but trainees could not, even when supported by the CNN.

Conclusions: Our CNN-based system for capsule endoscopy videos reduced the reading time of endoscopists without decreasing the detection rate of mucosal breaks. However, the reading level of endoscopists should be considered when using the system.
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http://dx.doi.org/10.1111/den.13517DOI Listing
May 2020

Expression of circular RNA CDR1‑AS in colon cancer cells increases cell surface PD‑L1 protein levels.

Oncol Rep 2019 Oct 19;42(4):1459-1466. Epub 2019 Jul 19.

Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo 113‑8655, Japan.

The expression of CDR1‑AS, a representative circular RNA, is closely linked with poor prognosis in gastrointestinal cancers, such as colon, liver, and pancreatic cancers. Although it is well known that CDR1‑AS antagonizes microRNA‑7 function through its sequence similarities in the brain, its biological function and link with the malignant potential of cancer cells remain unclear, partly due to the difficulties of ectopic expression of circular RNAs. In the present study, SW620, a colon cancer cell line that stably expresses CDR1‑AS RNA circularized, was established using the laccase 2 gene cassette, and its biological function associated with malignant behavior was determined. In contrast to previous studies, cell growth or invasion ability was not altered by CDR1‑AS expression. However, the expression levels of CMTM4 and CMTM6, which were recently recognized as critical regulators of PD‑L1 protein expression at the cell surface, were significantly increased. Accordingly, the cell surface PD‑L1 protein levels were increased in CDR1‑AS‑expressing cells. Notably, the effects were not canceled out by overexpressing microRNA‑7, indicating that the increase in cell surface PD‑L1 in CDR1‑AS‑expressing cells was not dependent on microRNA‑7 function. These results indicated that expression of this circular RNA in cancer cells may lead to poor prognosis by increasing cell surface PD‑L1 levels through microRNA‑7‑independent mechanisms.
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http://dx.doi.org/10.3892/or.2019.7244DOI Listing
October 2019

Inhibition of HBV Transcription From cccDNA With Nitazoxanide by Targeting the HBx-DDB1 Interaction.

Cell Mol Gastroenterol Hepatol 2019 24;7(2):297-312. Epub 2018 Oct 24.

Department of Gastroenterology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.

Background & Aims: Hepatitis B virus (HBV) infection is a major health concern worldwide. Although currently used nucleos(t)ide analogs efficiently inhibit viral replication, viral proteins transcribed from the episomal viral covalently closed circular DNA (cccDNA) minichromosome continue to be expressed long-term. Because high viral RNA or antigen loads may play a biological role during this chronicity, the elimination of viral products is an ultimate goal of HBV treatment. HBV regulatory protein X (HBx) was recently found to promote transcription of cccDNA with degradation of Smc5/6 through the interaction of HBx with the host protein DDB1. Here, this protein-protein interaction was considered as a new molecular target of HBV treatment.

Methods: To identify candidate compounds that target the HBx-DDB1 interaction, a newly constructed split luciferase assay system was applied to comprehensive compound screening. The effects of the identified compounds on HBV transcription and cccDNA maintenance were determined using HBV minicircle DNA, which mimics HBV cccDNA, and the natural HBV infection model of human primary hepatocytes.

Results: We show that nitazoxanide (NTZ), a thiazolide anti-infective agent that has been approved by the FDA for protozoan enteritis, efficiently inhibits the HBx-DDB1 protein interaction. NTZ significantly restores Smc5 protein levels and suppresses viral transcription and viral protein production in the HBV minicircle system and in human primary hepatocytes naturally infected with HBV.

Conclusions: These results indicate that NTZ, which targets an HBV-related viral-host protein interaction, may be a promising new therapeutic agent and a step toward a functional HBV cure.
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http://dx.doi.org/10.1016/j.jcmgh.2018.10.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6357790PMC
May 2019

Pevonedistat, a Neuronal Precursor Cell-Expressed Developmentally Down-Regulated Protein 8-Activating Enzyme Inhibitor, Is a Potent Inhibitor of Hepatitis B Virus.

Hepatology 2019 05 13;69(5):1903-1915. Epub 2019 Mar 13.

Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan.

Hepatitis B virus (HBV) infection is a major health concern worldwide. To prevent HBV-related mortality, elimination of viral proteins is considered the ultimate goal of HBV treatment; however, currently available nucleos(t)ide analogs rarely achieve this goal, as viral transcription from episomal viral covalently closed circular DNA (cccDNA) is not prevented. HBV regulatory protein X was recently found to target the protein structural maintenance of chromosomes 5/6 (Smc5/6) for ubiquitination and degradation by DDB1-CUL4-ROC1 E3 ligase, resulting in enhanced viral transcription from cccDNA. This ubiquitin-dependent proteasomal pathway requires an additional ubiquitin-like protein for activation, neuronal precursor cell-expressed developmentally down-regulated protein 8 (NEDD8). Here, we show that pevonedistat, a NEDD8-activating enzyme inhibitor, works efficiently as an antiviral agent. Pevonedistat significantly restored Smc5/6 protein levels and suppressed viral transcription and protein production in the HBV minicircle system in in vitro HBV replication models and in human primary hepatocytes infected naturally with HBV. Conclusion: These results indicate that pevonedistat is a promising compound to treat chronic HBV infection.
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http://dx.doi.org/10.1002/hep.30491DOI Listing
May 2019

Prediction of the Clinical Outcomes of Sigmoid Volvulus by Abdominal X-Ray: AXIS Classification System.

Gastroenterol Res Pract 2018 15;2018:8493235. Epub 2018 Nov 15.

Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

Aim: Early diagnosis and evaluation of the severity of sigmoid volvulus are necessary for management and early intervention. We developed a new predictive classification system for sigmoid volvulus based on X-ray findings.

Methods: We retrospectively analyzed 66 patients diagnosed with sigmoid volvulus using the electronic medical records at the Osaki Citizen's Hospital and the University of Tokyo Hospital from 2008-2015. We classified patients according to the coffee-bean sign mesenteric axis on X-ray (AXIS classification: group A, 0-90°; group B, 90-135°; and group C, >135°). We examined the association between AXIS classification and severe sigmoid volvulus, intestinal necrosis, need for surgery, 30-day mortality, and length of stay using the Cochran-Armitage trend test.

Results: In total, 66 patients were analyzed. They had a mean age of 76.9 years, and 47 (71.0%) were male. They were classified into three groups according to the AXIS classification system (group A, 40 patients; group B, 23 patients; and group C, 3 patients). Group C had a significantly higher frequency of severe sigmoid volvulus (100%) compared to group B (30%) and group A (15%). AXIS classification was significantly associated with the severity of sigmoid volvulus ( = 0.003), necrosis ( = 0.004), and need for surgery ( = 0.001), but not with the 30-day mortality or the length of stay.

Conclusions: We developed the AXIS classification system to predict the severity of sigmoid volvulus. This new classification system may facilitate triage and therapeutic decision-making for sigmoid volvulus patients.
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http://dx.doi.org/10.1155/2018/8493235DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6276422PMC
November 2018

Inflammation and de-differentiation in pancreatic carcinogenesis.

World J Clin Cases 2018 Dec;6(15):882-891

Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan.

Pancreatic cancer is a malignancy with an extremely poor prognosis. Chronic pancreatitis is a well-known risk factor for pancreatic cancer. Inflammation is thought to influence carcinogenesis through DNA damage and activation of intracellular signaling pathways. Many transcription factors and signaling pathways co-operate to determine and maintain cell identity at each phase of pancreatic organogenesis and cell differentiation. Recent studies have shown that carcinogenesis is promoted through the suppression of transcription factors related to differentiation. Pancreatitis also demonstrates transcriptional changes, suggesting that multifactorial epigenetic changes lead to impaired differentiation. Taken together, these factors may constitute an important framework for pancreatic carcinogenesis. In this review, we discuss the role of inflammation and de-differentiation in the development of pancreatic cancer, as well as the future of novel therapeutic applications.
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http://dx.doi.org/10.12998/wjcc.v6.i15.882DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6288496PMC
December 2018

ISGF3 with reduced phosphorylation is associated with constitutive expression of interferon-induced genes in aging cells.

NPJ Aging Mech Dis 2018 15;4:11. Epub 2018 Nov 15.

Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655 Japan.

During cellular aging, many changes in cellular functions occur. A hallmark of aged cells is secretion of inflammatory mediators, which collectively is referred to as the senescence-associated secretory phenotype (SASP). However, the mechanisms underlying such changes are unclear. Canonically, the expression of interferon (IFN)-stimulated genes (ISGs) is induced by IFNs through the formation of the tripartite transcriptional factor ISGF3, which is composed of IRF9 and the phosphorylated forms of STAT1 and STAT2. However, in this study, the constitutive expression of ISGs in human-derived senescent fibroblasts and in fibroblasts from a patient with Werner syndrome, which leads to premature aging, was mediated mainly by the unphosphorylated forms of STATs in the absence of INF production. Under homeostatic conditions, STAT1, STAT2, and IRF9 were localized to the nucleus of aged cells. Although knockdown of JAK1, a key kinase of STAT1 and STAT2, did not affect ISG expression or IFN-stimulated response element (ISRE)-mediated promoter activities in these senescent cells, knockdown of STAT1 or STAT2 decreased ISG expression and ISRE activities. These results suggest that the ISGF3 complex without clear phosphorylation is required for IFN-independent constitutive ISG transcription in senescent cells.
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http://dx.doi.org/10.1038/s41514-018-0030-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6237867PMC
November 2018

Hepatitis B virus pathogenesis: Fresh insights into hepatitis B virus RNA.

World J Gastroenterol 2018 Jun;24(21):2261-2268

Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan.

Hepatitis B virus (HBV) is still a worldwide health concern. While divergent factors are involved in its pathogenesis, it is now clear that HBV RNAs, principally templates for viral proteins and viral DNAs, have diverse biological functions involved in HBV pathogenesis. These functions include viral replication, hepatic fibrosis and hepatocarcinogenesis. Depending on the sequence similarities, HBV RNAs may act as sponges for host miRNAs and may deregulate miRNA functions, possibly leading to pathological consequences. Some parts of the HBV RNA molecule may function as viral-derived miRNA, which regulates viral replication. HBV DNA can integrate into the host genomic DNA and produce novel viral-host fusion RNA, which may have pathological functions. To date, elimination of HBV-derived covalently closed circular DNA has not been achieved. However, RNA transcription silencing may be an alternative practical approach to treat HBV-induced pathogenesis. A full understanding of HBV RNA transcription and the biological functions of HBV RNA may open a new avenue for the development of novel HBV therapeutics.
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http://dx.doi.org/10.3748/wjg.v24.i21.2261DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5989240PMC
June 2018

DHX9 regulates production of hepatitis B virus-derived circular RNA and viral protein levels.

Oncotarget 2018 Apr 20;9(30):20953-20964. Epub 2018 Apr 20.

Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan.

Hepatitis B virus (HBV) infection, which is a major health concern worldwide, can lead to liver cirrhosis and hepatocellular carcinoma. Although current nucleos(t)ide analogs efficiently inhibit viral reverse transcription and viral DNA load clinically, episomal viral covalently closed circular DNA (cccDNA) minichromosomes and transcripts from cccDNA continue to be expressed over the long term. We hypothesized that, under these conditions, viral transcripts may have biological functions involved in pathogenesis. Here, we show that the host protein DExH-box helicase 9 (DXH9) is associated with viral RNAs. We also show that viral-derived circular RNA is produced during HBV replication, and the amount is increased by knockdown of the DHX9 protein, which, in turn, results in decreased viral protein levels but does not affect the levels of HBV DNA. These phenomena were observed in the HBV-producing cell culture model and HBV mini-circle model mimicking HBV cccDNA, as well as in human primary hepatocytes infected with HBV. Based on these results, we conclude that, in HBV infection, the RNA binding factor DHX9 is a novel regulator of viral circular RNA and viral protein levels.
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http://dx.doi.org/10.18632/oncotarget.25104DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5940377PMC
April 2018

Satellite RNA Increases DNA Damage and Accelerates Tumor Formation in Mouse Models of Pancreatic Cancer.

Mol Cancer Res 2018 08 10;16(8):1255-1262. Epub 2018 May 10.

Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

Highly repetitive tandem arrays such as satellite sequences in the centromeric and pericentromeric regions of chromosomes, which were previously considered to be silent, are actively transcribed in various biological processes, including cancers. In the pancreas, this aberrant expression occurs even in Kras-mutated pancreatic intraepithelial neoplasia (PanIN) tissues, which are precancerous lesions. To determine the biological role of satellite RNAs in carcinogenesis , we constructed mouse major satellite (MajSAT) RNA-expressing transgenic mice. However, these transgenic mice did not show spontaneous malignant tumor formation under normal breeding. Importantly, however, DNA damage was increased in pancreatic tissues induced by caerulein treatment or high-fat diet, which may be due to impaired nuclear localization of Y-Box Binding Protein 1 (YBX1), a component of the DNA damage repair machinery. In addition, when crossed with pancreas-specific Kras-mutant mice, MajSAT RNA expression resulted in an earlier increase in PanIN formation. These results suggest that aberrant MajSAT RNA expression accelerates oncogenesis by increasing the probability of a second driver mutation, thus accelerating cells to exit from the breakthrough phase to the expansion phase. Aberrant expression of satellite RNAs accelerates oncogenesis through a mechanism involving increased DNA damage. .
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http://dx.doi.org/10.1158/1541-7786.MCR-18-0139DOI Listing
August 2018

RASAL1 is a potent regulator of hepatic stellate cell activity and liver fibrosis.

Oncotarget 2017 Sep 4;8(39):64840-64852. Epub 2017 May 4.

Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

Liver fibrosis, leading to cirrhosis and liver failure, can occur after chronic liver injury. The transition of hepatic stellate cells (HSCs) from quiescent cells into proliferative and fibrogenic cells is a central event in liver fibrosis. Here, we show that RAS protein activator like-1 (RASAL1), a RAS-GTPase-activating protein, which switches off RAS activity, is significantly decreased during HSC activation, and that HSC activation can be antagonized by forced expression of the RASAL1 protein. We demonstrate that RASAL1 suppresses HSC proliferation by regulating the Ras-MAPK pathway, and that RASAL1 suppresses HSC fibrogenic activity by regulating the PKA-LKB1-AMPK-SRF pathway by interacting with angiotensin II receptor, type 1. We also show that RASAL1-deficient mice are more susceptible to liver fibrosis. These data demonstrate that deregulated RASAL1 expression levels and the affected downstream intracellular signaling are central mediators of perpetuated HSC activation and fibrogenesis in the liver.
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http://dx.doi.org/10.18632/oncotarget.17609DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5630295PMC
September 2017

Laparoscopic and endoscopic cooperative surgery for gastrointestinal tumor.

Ann Transl Med 2017 Apr;5(8):187

Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

With technological progress of endoscopic submucosal dissection (ESD) in the last decade, several laparoscopic and endoscopic cooperative surgeries (LECS) for gastrointestinal tumor have recently been developed. LECS is definitely favorable to the minimization of surgical margin, which leads to functional and anatomical preservation of gastrointestinal tract. LECS for gastrointestinal tumor is mainly sorted by two categories: exposure procedures and non-exposure procedures between endoluminal and extraluminal spaces. Exposure procedures have the potential risk of gastric contents or tumor cells spilling out over the abdominal cavity, because the stomach wall has to be perforated intentionally during the procedure. In order to avoid the potential these risks, non-exposure procedures have been developed. Currently, the LECS concept has rapidly permeated for treatment of gastrointestinal tumor due to its certainty and safety, although there is still room for improvement to lessen its technical difficulty. This review describes the current LECS for gastrointestinal tumor based on the several articles.
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http://dx.doi.org/10.21037/atm.2017.03.35DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5464944PMC
April 2017

Transcriptional activation of the MICA gene with an engineered CRISPR-Cas9 system.

Biochem Biophys Res Commun 2017 04 18;486(2):521-525. Epub 2017 Mar 18.

Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

Major histocompatibility complex class I polypeptide-related sequence A (MICA) is a prototypical NKG2D ligand. Because immune cells, such as natural killer (NK) cells, recognize virally infected or transformed cells and eliminate them through the interaction between NKG2D receptors on NK cells and NKG2D ligands on pathogenic cells, MICA expression levels are associated with NK cell-mediated immunity. Here, we report that an engineered clustered regularly interspaced short palindromic repeats-Cas9-related complex targeting MICA gene promoter sequences activates transcription of the MICA gene from its endogenous locus. Inhibiting microRNA function, which targets the 3' untranslated region of the MICA gene, enhances this activation. These results demonstrate that the combination of Cas9-based transcriptional activators and simultaneous modulation of microRNA function may be a powerful tool for enhancing MICA protein expression and efficient anti-pathogenic cell immunity.
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http://dx.doi.org/10.1016/j.bbrc.2017.03.076DOI Listing
April 2017

Repression of MicroRNA Function Mediates Inflammation-associated Colon Tumorigenesis.

Gastroenterology 2017 02 5;152(3):631-643. Epub 2016 Nov 5.

Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

Background & Aims: Little is known about the mechanisms by which chronic inflammation contributes to carcinogenesis, such as the development of colon tumors in patients with inflammatory bowel diseases. Specific microRNA (miRNAs) can function as suppressors or oncogenes, and widespread alterations in miRNA expression have been associated with tumorigenesis. We studied whether alterations in miRNA function contribute to inflammation-associated colon carcinogenesis.

Methods: We studied the effects of inflammatory cytokines, such as tumor necrosis factor, interleukin-1α (IL1A), and IL1β (IL1B), on miRNA function, measured by activity of reporter constructs containing miRNA-binding sites in their 3' untranslated regions, in human 293T embryonic kidney, Caco-2, HT29, and HCT116 colon carcinoma cells, as well as dicer and dicer, and Apobec3 and Apobec3 mouse embryonic fibroblasts. Cells were analyzed by immunoblots, immunohistochemistry, and flow cytometry. We generated transgenic mice expressing reporter constructs regulated by LET7B, MIR122, and MIR29b response elements; some mice were given injections of miRNA inhibitors (anti-MIR122 or anti-LET7B), a negative control, or tumor necrosis factor. Liver tissues were collected and analyzed by immunoblotting. Reporter mice were given azoxymethane followed by dextran sulfate sodium to induce colitis and colon tumors; some mice were given the ROCK inhibitor fasudil along with these agents (ROCK inhibitors increase miRNA function). Colon tissues were collected and analyzed by immunohistochemistry, immunoblots, and fluorescence microscopy.

Results: Incubation of cell lines with inflammatory cytokines reduced the ability of miRNAs to down-regulate expression from reporter constructs; dicer was required for this effect, so these cytokines relieve miRNA-dependent reductions in expression. The cytokines promoted degradation of APOBEC3G, which normally promotes miRNA loading into argonaute 2-related complexes. Mice with colitis had reduced miRNA function, based on increased expression of reporter genes. Administration of fasudil to mice did not reduce the severity of colitis that developed but greatly reduced the numbers of colon tumors formed (mean 2 tumors/colon in mice given fasudil vs 9 tumors/colon in mice given control agent). We made similar observations in IL10-deficient mice.

Conclusions: We found inflammatory cytokines to reduce the activities of miRNAs. In mice with colitis, activities of miRNAs are reduced; administration of an agent that increases miRNA function prevents colon tumor formation in these mice. This pathway might be targeted to prevent colon carcinogenesis in patients with inflammatory bowel diseases.
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http://dx.doi.org/10.1053/j.gastro.2016.10.043DOI Listing
February 2017

MicroRNAs and liver disease.

J Hum Genet 2017 Jan 26;62(1):75-80. Epub 2016 May 26.

Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

The biological roles of microRNAs (miRNAs) have been extensively studied. miRNA122 represents more than half of the miRNAs expressed in the liver and has various physiological and pathological functions, which include enhancing hepatitis virus replication, regulating lipid metabolism and suppressing hepatocellular carcinoma. miRNAs, whether globally or individually, have been linked with hepatocarcinogenesis. Furthermore, some miRNAs have been shown to be involved in the pathogenesis of nonalcoholic steatohepatitis. Using nucleotide-based strategies, these miRNAs may be developed as potential therapeutic targets. Because changes in miRNA expression can be measured in sera, they may be used as non-invasive biomarkers if they correctly reflect the pathological state of the liver. In this review, we show the biological roles of representative miRNAs in liver disease and discuss the current issues that remain to be clarified for future clinical applications.
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http://dx.doi.org/10.1038/jhg.2016.53DOI Listing
January 2017
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