Guanyu Gong

Inflammation-induced cell proliferation potentiates DNA damage-induced mutations in vivo.

Mutations are a critical driver of cancer initiation. While extensive studies have focused on exposure-induced mutations, few studies have explored the importance of tissue physiology as a modulator of mutation susceptibility in vivo. Of particular interest is inflammation, a known cancer risk factor relevant to chronic inflammatory diseases and pathogen-induced inflammation. Here, we used the fluorescent yellow direct repeat (FYDR) mice that harbor a reporter to detect misalignments during homologous recombination (HR), an important class of mutations. FYDR mice were exposed to cerulein, a potent inducer of pancreatic inflammation. We show that inflammation induces DSBs (γH2AX foci) and that several days later there is an increase in cell proliferation. While isolated bouts of inflammation did not induce HR, overlap between inflammation-induced DNA damage and inflammation-induced cell proliferation induced HR significantly. To study exogenously-induced DNA damage, animals were exposed to methylnitrosourea, a model alkylating agent that creates DNA lesions relevant to both environmental exposures and cancer chemotherapy. We found that exposure to alkylation damage induces HR, and importantly, that inflammation-induced cell proliferation and alkylation induce HR in a synergistic fashion. Taken together, these results show that, during an acute bout of inflammation, there is a kinetic barrier separating DNA damage from cell proliferation that protects against mutations, and that inflammation-induced cell proliferation greatly potentiates exposure-induced mutations. These studies demonstrate a fundamental mechanism by which inflammation can act synergistically with DNA damage to induce mutations that drive cancer and cancer recurrence.

DNA glycosylase activity and cell proliferation are key factors in modulating homologous recombination in vivo

Cancer susceptibility varies between people, affected by genotoxic exposures, genetic makeup and physiological state. Yet, how these factors interact among each other to define cancer risk is largely unknown. Here, we uncover the interactive effects of genetical, environmental and physiological factors on genome rearrangements driven by homologous recombination (HR). Using FYDR mice to quantify HR-driven rearrangements in pancreas tissue, we show that DNA methylation damage (induced by methylnitrosourea) and cell proliferation (induced by thyroid hormone) each induce HR and together act synergistically to induce HR-driven rearrangements in vivo. These results imply that developmental or regenerative proliferation as well as mitogenic exposures may sensitize tissues to DNA damaging exposures. We exploited mice genetically deficient in alkyl-adenine DNA glycosylase (Aag) to analyse the relative contributions of unrepaired DNA base lesions versus intermediates formed during base excision repair (BER). Remarkably, results show that, in the pancreas, Aag is a major driver of spontaneous HR, indicating that BER intermediates (including abasic sites and single strand breaks) are more recombinogenic than the spontaneous base lesions removed by Aag. Given that mammals have about a dozen DNA glycosylases, these results point to BER as a major source of pressure on the HR pathway in vivo. Taken together, methylation damage, cell proliferation and Aag interact to define the risk of HR-driven sequence rearrangements in vivo. These data identify important sources of sequence changes in a cancer-relevant organ, and advance the effort to identify populations at high-risk for cancer.

Helicobacter saguini, a Novel Helicobacter Isolated from Cotton-Top Tamarins with Ulcerative Colitis, Has Proinflammatory Properties and Induces Typhlocolitis and Dysplasia in Gnotobiotic IL-10−/− Mice

ABSTRACT A urease-negative, fusiform, novel bacterium named Helicobacter saguini was isolated from the intestines and feces of cotton-top tamarins (CTTs) with chronic colitis. Helicobacter sp. was detected in 69% of feces or intestinal samples from 116 CTTs. The draft genome sequence, obtained by Illumina MiSeq sequencing, for H. saguini isolate MIT 97-6194-5, consisting of ∼2.9 Mb with a G+C content of 35% and 2,704 genes, was annotated using the NCBI Prokaryotic Genomes Automatic Annotation Pipeline. H. saguini contains homologous genes of known virulence factors found in other enterohepatic helicobacter species (EHS) and H. pylori. These include flagellin, γ-glutamyl transpeptidase (ggt), collagenase, the secreted serine protease htrA, and components of a type VI secretion system, but the genome does not harbor genes for cytolethal distending toxin (cdt). H. saguini MIT 97-6194-5 induced significant levels of interleukin-8 (IL-8) in HT-29 cell culture supernatants by 4 h, which increased through 24 h. mRNAs for the proinflammatory cytokines IL-1β, tumor necrosis factor alpha (TNF-α), IL-10, and IL-6 and the chemokine CXCL1 were upregulated in cocultured HT-29 cells at 4 h compared to levels in control cells. At 3 months postinfection, all H. saguini-monoassociated gnotobiotic C57BL/129 IL-10−/− mice were colonized and had seroconverted to H. saguini antigen with a significant Th1-associated increase in IgG2c (P < 0.0001). H. saguini induced a significant typhlocolitis, associated epithelial defects, mucosa-associated lymphoid tissue (MALT) hyperplasia, and dysplasia. Inflammatory cytokines IL-22, IL-17a, IL-1β, gamma interferon (IFN-γ), and TNF-α, as well as inducible nitric oxide synthase (iNOS) were significantly upregulated in the cecal tissues of infected mice. The expression of the DNA damage response molecule γ-H2AX was significantly higher in the ceca of H. saguini-infected gnotobiotic mice than in the controls. This model using a nonhuman primate Helicobacter sp. can be used to study the pathogenic potential of EHS isolated from primates with naturally occurring inflammatory bowel disease (IBD) and colon cancer.

Lamellipodin-Deficient Mice: A Model of Rectal Carcinoma

During a survey of clinical rectal prolapse (RP) cases in the mouse population at MIT animal research facilities, a high incidence of RP in the lamellipodin knock-out strain, C57BL/6-Raph1tm1Fbg (Lpd-/-) was documented. Upon further investigation, the Lpd-/- colony was found to be infected with multiple endemic enterohepatic Helicobacter species (EHS). Lpd-/- mice, a transgenic mouse strain produced at MIT, have not previously shown a distinct immune phenotype and are not highly susceptible to other opportunistic infections. Predominantly male Lpd-/- mice with RP exhibited lesions consistent with invasive rectal carcinoma concomitant to clinically evident RP. Multiple inflammatory cytokines, CD11b+Gr1+ myeloid-derived suppressor cell (MDSC) populations, and epithelial cells positive for a DNA damage biomarker, H2AX, were elevated in affected tissue, supporting their role in the neoplastic process. An evaluation of Lpd-/- mice with RP compared to EHS-infected, but clinically normal (CN) Lpd-/- animals indicated that all of these mice exhibit some degree of lower bowel inflammation; however, mice with prolapses had significantly higher degree of focal lesions at the colo-rectal junction. When Helicobacter spp. infections were eliminated in Lpd-/- mice by embryo transfer rederivation, the disease phenotype was abrogated, implicating EHS as a contributing factor in the development of rectal carcinoma. Here we describe lesions in Lpd-/- male mice consistent with a focal inflammation-induced neoplastic transformation and propose this strain as a mouse model of rectal carcinoma.

Automated Online Solid Phase Derivatization for Sensitive Quantification of Endogenous S-Nitrosoglutathione and Rapid Capture of Other Low-Molecular-Mass S-Nitrosothiols

S-Nitrosothiols (RSNOs) constitute a circulating endogenous reservoir of nitric oxide and have important biological activities. In this study, an online coupling of solid-phase derivatization (SPD) with liquid chromatography-mass spectrometry (LC-MS) was developed and applied in the analysis of low-molecular-mass RSNOs. A derivatizing-reagent-modified polymer monolithic column was prepared and adapted for online SPD-LC-MS. Analytes from the LC autosampler flowed through the monolithic column for derivatization and then directly into the LC-MS for analysis. This integration of the online derivatization, LC separation, and MS detection facilitated system automation, allowing rapid, laborsaving, and sensitive detection of RSNOs. S-Nitrosoglutathione (GSNO) was quantified using this automated online method with good linearity (R2 = 0.9994); the limit of detection was 0.015 nM. The online SPD-LC-MS method has been used to determine GSNO levels in mouse samples, 138 ± 13.2 nM of endogenous GSNO was detected in mouse plasma. Besides, the GSNO concentrations in liver (64.8 ± 11.3 pmol/mg protein), kidney (47.2 ± 6.1 pmol/mg protein), heart (8.9 ± 1.8 pmol/mg protein), muscle (1.9 ± 0.3 pmol/mg protein), hippocampus (5.3 ± 0.9 pmol/mg protein), striatum (6.7 ± 0.6 pmol/mg protein), cerebellum (31.4 ± 6.5 pmol/mg protein), and cortex (47.9 ± 4.6 pmol/mg protein) were also successfully quantified. When the derivatization was performed within 8 min, followed by LC-MS detection, samples could be rapidly analyzed compared with the offline manual method. Other low-molecular-mass RSNOs, such as S-nitrosocysteine and S-nitrosocysteinylglycine, were captured by rapid precursor-ion scanning, showing that the proposed method is a potentially powerful tool for capture, identification, and quantification of RSNOs in biological samples.

Shank3 mutation in a mouse model of autism leads to changes in the S-nitroso-proteome and affects key proteins involved in vesicle release and synaptic function

Mutation in the SHANK3 human gene leads to different neuropsychiatric diseases including Autism Spectrum Disorder (ASD), intellectual disabilities and Phelan-McDermid syndrome. Shank3 disruption in mice leads to dysfunction of synaptic transmission, behavior, and development. Protein S-nitrosylation, the nitric oxide (NO•)-mediated posttranslational modification (PTM) of cysteine thiols (SNO), modulates the activity of proteins that regulate key signaling pathways. We tested the hypothesis that Shank3 mutation would generate downstream effects on PTM of critical proteins that lead to modification of synaptic functions. SNO-proteins in two ASD-related brain regions, cortex and striatum of young and adult InsG3680(+/+) mice (a human mutation-based Shank3 mouse model), were identified by an innovative mass spectrometric method, SNOTRAP. We found changes of the SNO-proteome in the mutant compared to WT in both ages. Pathway analysis showed enrichment of processes affected in ASD. SNO-Calcineurin in mutant led to a significant increase of phosphorylated Synapsin1 and CREB, which affect synaptic vesicle mobilization and gene transcription, respectively. A significant increase of 3-nitrotyrosine was found in the cortical regions of the adult mutant, signaling both oxidative and nitrosative stress. Neuronal NO• Synthase (nNOS) was examined for levels and localization in neurons and no significant difference was found in WT vs. mutant. S-nitrosoglutathione concentrations were higher in mutant mice compared to WT. This is the first study on NO•-related molecular changes and SNO-signaling in the brain of an ASD mouse model that allows the characterization and identification of key proteins, cellular pathways, and neurobiological mechanisms that might be affected in ASD.

Abstract 2885: Features of innate immunity dominate serum and tissue protein and cytokine profiles in both mouse and human inflammatory bowel disease.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Inflammatory bowel disease (IBD) is a chronic and relapsing intestinal inflammatory disease that arises through unknown genetic, environmental, and bacterial origins. Ulcerative colitis (UC) and Crohns disease (CD) are the two main forms of IBD, and their incidence is increasing in industrialized countries. Further, IBD is a significant risk factor for the development of colon cancer. Though the specific determinants remain elusive, persistent inflammation is believed to play a significant role in colon cancer carcinogenesis. To better define the molecular mechanisms linking colitis to the identity of disease biomarkers, we performed a translational comparison of protein expression and protein damage products in mouse and human IBD. Helicobacter hepaticus-infected Rag2-/- mice emulate many aspects of human IBD, and our recent work with this model highlights the importance of neutrophils in the pathology of colitis and colon cancer. Analysis of neutrophil- and macrophage-derived damage products revealed accumulation of 3-chlorotyrosine (CTyr) and 3-nitrotyrosine (NTyr) in inflamed mice colons that increased with disease duration. These results were further corroborated in mouse studies by histological evaluation, which demonstrated strong infiltration of neutrophils and macrophages to the site of inflammation. Human studies revealed an increase in CTyr in the colon of UC and CD tissues relative to serum levels. The nucleic acid chlorination damage product, 5-chloro-2′-deoxycytidine (5-Cl-dC), was quantified in human colon and found to be present at similar levels to that of inflamed mice colons. Multivariate analysis of these markers along with serum proteins and cytokines revealed a general signature of activated innate immunity in human IBD. UC sera were strongly suggestive of neutrophil activity while CD and mouse sera were suggestive of macrophage and neutrophil activity. These data point to innate immunity as a major determinant of serum and tissue profiles and provide insight into disease activity in IBD. Citation Format: Charles G. Knutson, Aswin Mangerich, Yu Zeng, Arkadiusz R. Raczynski, Rosa G. Liberman, Pilsoo Kang, Wenjie Ye, Guanyu Gong, Erin Prestwich, Kun Lu, John S. Wishnok, Joshua R. Korzenik, Gerald N. Wogan, James G. Gox, Peter C. Dedon, Steven R. Tannenbaum. Features of innate immunity dominate serum and tissue protein and cytokine profiles in both mouse and human inflammatory bowel disease. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2885. doi:10.1158/1538-7445.AM2013-2885

Abstract A17: Colitis-associated tumorigenesis in the Rag2 -/- Helicobacter hepaticus-infected mouse features DNA damage and Retinoblastoma-mediated cell proliferation via nitric oxide but not hypochlorous acid

Colitis-associated cancer (CAC) is characterized by persistent exposure of colonic epithelial cells to inflammatory infiltrates-released free radicals including nitric oxide (NO) and hypochlorous acid (HOCl). These molecules are potential for DNA damage and meanwhile, rapid epithelial tissue renewal also occurs during inflammation, possibly accelerating DNA synthesis and/or limiting the time for DNA repair. In order to identify and elucidate this possible concurring event, the present study was designed to 1.) Quantitatively examine the presence of DNA damage in the proliferating epithelial cells in colitis; 2.) Investigate cell cycle regulation and screen for the highly responsible signaling pathway(s) to explain the increased proliferation; 3.) And differentiate the individual effect of NO and HOCl on DNA damage and cell proliferation. Experiments used 129/SvEv Rag2 −/− mouse, either infected with Helicobacter hepaticus (H. h .) (10-20 weeks) or uninfected as control. NO production was inhibited by addition of N-monomethyl arginine (NMA, an inhibitor of nitric oxide synthase) to the mice drinking water and HOCl production was inhibited by intraperitoneal injection of Gr-1 IgG that neutralizes neutrophils. Colon samples from these mouse experiments were analyzed for DNA damage and cell cycle markers using immunostaining and morphometric methods. The present study found that 1.) Colitis induced by H. h . exhibited a high amount of γH2AX (DNA damage marker) positive cells (~10% significantly increased versus control ~4%) and these cells co-localize with the proliferation marker Ki67 (~55%, significant increased versus control ~23%) in the colonic epithelial crypts. TUNEL assay confirmed that these cells are unlikely apoptotic as the predominant TUNEL positive cells were found in the mesenchyme, but not the epithelia. 2.) For cell cycle regulation, increased expression of cyclin E, but not cyclin D, was observed in the H. h . infection. Concordantly, phosphorylation of Retinoblastoma (RB) gene was found in a high level at the base of the proliferating crypts. Examination of the other proliferation signal transducers including β-catenin, smad4 and HP1γ showed no positive observations. Activation of p38 and ERK was found increased and yet localized in the luminal surface of the colonic crypts. 3.) Importantly, during the H. h . infection when NO production was inhibited by NMA, dramatic decreases of γH2AX (~3%) and Ki67 (~17%) expression levels were observed and NMA treatment also resulted in largely decreased RB phosphorylation. In comparison, inhibition of HOCl by neutrophil Gr1 antibody showed only a small reduction of γH2AX (~8.7%, marginally significant) expression and no changes in Ki67 (~49%) and RB immunostains. In summary, the present study found that the H. h .-induced colitis features co-localized γH2AX and Ki67 positive epithelial cells and mechanistic analysis suggested an essential role of nitric oxide, but not hypochlorous acid, affecting both DNA damage and RB phosphorylation-mediated cell proliferation signaling pathway, with the later possibly releasing high level of cyclin E that facilitates G1/S cell cycle entry. These results enlighten a previously underestimated mechanism for the tumorigenesis of CAC and based on this mechanistic plateau, more detailed investigations are carrying out in the near future. Citation Format: Guanyu Gong, Sureshkumar Muthupalani, Gerald N. Wogan, James G. Fox, Steven R. Tannenbaum. Colitis-associated tumorigenesis in the Rag2 -/- Helicobacter hepaticus-infected mouse features DNA damage and Retinoblastoma-mediated cell proliferation via nitric oxide but not hypochlorous acid. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr A17.