Catherine Streutker

Identification of an innate T helper type 17 response to intestinal bacterial pathogens

Interleukin 17 (IL-17) is a central cytokine implicated in inflammation and antimicrobial defense. After infection, both innate and adaptive IL-17 responses have been reported, but the type of cells involved in innate IL-17 induction, as well as their contribution to in vivo responses, are poorly understood. Here we found that Citrobacter and Salmonella infection triggered early IL-17 production, which was crucial for host defense and was mediated by CD4+ T helper cells. Enteric innate T helper type 17 (iTH17) responses occurred principally in the cecum, were dependent on the Nod-like receptors Nod1 and Nod2, required IL-6 induction and were associated with a decrease in mucosal CD103+ dendritic cells. Moreover, imprinting by the intestinal microbiota was fully required for the generation of iTH17 responses. Together, these results identify the Nod-iTH17 axis as a central element in controlling enteric pathogens, which may implicate Nod-driven iTH17 responses in the development of inflammatory bowel diseases.

GLP-1 Receptor Activation Indirectly Reduces Hepatic Lipid Accumulation But Does Not Attenuate Development of Atherosclerosis in Diabetic Male ApoE−/− Mice

Glucagon-like peptide-1 receptor (GLP-1R) agonists reduce lipid accumulation in peripheral tissues, attenuating atherosclerosis and hepatic steatosis in preclinical studies. We examined whether GLP-1R activation decreases atherosclerosis progression in high-fat diet-fed male ApoE(-/-) mice after administration of streptozotocin and treatment with the long-acting GLP-1R agonist taspoglutide administered once monthly vs. metformin in the drinking water for 12 wk. Taspoglutide did not reduce plaque area or lipid content in the aortic arch or abdominal aorta, and no significant change in aortic macrophage accumulation was detected after taspoglutide or metformin. In contrast, hepatic triglyceride levels were significantly reduced in livers from taspoglutide-treated mice. Both peripheral and intracerebroventricular administration of exendin-4 rapidly decreased plasma triglyceride levels in fasted mice, and taspoglutide therapy in ApoE(-/-) mice modulated the expression of hepatic genes controlling fatty acid uptake and oxidation. We were unable to detect expression of the entire Glp1r coding sequence in macrophages isolated from ApoE(-/-), C57BL/6, and IL10(-/-) mice. Similarly, Glp1r mRNA transcripts were not detected in RNA from isolated murine hepatocytes. Using Western blotting and tissue extracts from Glp1r(+/+) and Glp1r(-/-) mice, and cells transfected with a tagged murine GLP-1R cDNA, we could not validate the sensitivity and specificity of three different GLP-1R antisera commonly used for the detection of GLP-1R protein. Taken together, these findings illustrate divergent actions of GLP-1R agonists on atherosclerosis progression and accumulation of ectopic lipid in ApoE(-/-) mice and highlight the importance of indirect GLP-1R actions for the control of hepatic lipid accumulation.

Gut Microbial Metabolism Drives Transformation of Msh2-Deficient Colon Epithelial Cells

The etiology of colorectal cancer (CRC) has been linked to deficiencies in mismatch repair and adenomatous polyposis coli (APC) proteins, diet, inflammatory processes, and gut microbiota. However, the mechanism through which the microbiota synergizes with these etiologic factors to promote CRC is not clear. We report that altering the microbiota composition reduces CRC in APC(Min/+)MSH2(-/-) mice, and that a diet reduced in carbohydrates phenocopies this effect. Gut microbes did not induce CRC in these mice through an inflammatory response or the production of DNA mutagens but rather by providing carbohydrate-derived metabolites such as butyrate that fuel hyperproliferation of MSH2(-/-) colon epithelial cells. Further, we provide evidence that the mismatch repair pathway has a role in regulating β-catenin activity and modulating the differentiation of transit-amplifying cells in the colon. These data thereby provide an explanation for the interaction between microbiota, diet, and mismatch repair deficiency in CRC induction. PAPERCLIP:

Nod1 and Nod2 Regulation of Inflammation in the Salmonella Colitis Model

ABSTRACT The pattern recognition molecules Nod1 and Nod2 play important roles in intestinal homeostasis; however, how these proteins impact on the development of inflammation during bacterial colitis has not been examined. In the streptomycin-treated mouse model of Salmonella colitis, we found that mice deficient for both Nod1 and Nod2 had attenuated inflammatory pathology, reduced levels of inflammatory cytokines, and increased colonization of the mucosal tissue. Nod1 and Nod2 from both hematopoietic and nonhematopoietic sources contributed to the pathology, and all phenotypes were recapitulated in mice deficient for the signaling adaptor protein Rip2. However, the influence of Rip2 was strictly dependent on infection conditions that favored expression of the Salmonella pathogenicity island 2 (SPI-2) type III secretion system (TTSS), as Rip2 was dispensable for inflammation when mice were infected with bacteria grown under conditions that promoted expression of the SPI-1 TTSS. Thus, Nod1 and Nod2 can modulate inflammation and mediate efficient clearance of bacteria from the mucosal tissue during Salmonella colitis, but their role is dependent on the expression of the SPI-2 TTSS.

Loss of CD117 (c-kit)- and CD34-positive ICC and associated CD34-positive fibroblasts defines a subpopulation of chronic intestinal pseudo-obstruction.

Chronic idiopathic intestinal pseudo-obstruction is a syndrome in which symptoms of intestinal obstruction are present in the absence of mechanical obstruction. Lack of normal pacemaker activity, usually generated by the interstitial cells of Cajal (ICC), could account for the apparent obstruction. ICC are normally located around and between the myenteric plexus ganglia and within muscle and also in the deep muscular plexus of the small bowel and the submuscular plexus of the large intestine, just within the circular muscle. ICC can be demonstrated immunohistochemically with CD117 (c-kit) as well as with CD34, although this is less specific. CD34 also stains a population of fibroblasts that are intimately associated with ICC. To determine whether there is a relative deficiency of ICC and CD34-positive fibroblasts in patients with chronic idiopathic intestinal pseudo-obstruction, tissue from 30 patients of large intestine and eight patients with small intestine pseudo-obstruction was obtained. Controls (large intestinal specimens from 12 patients, small intestinal specimens from six patients) were chosen from resections for Crohns disease and colorectal neoplasia, both with and without dilatation. Examination of pseudo-obstruction cases identified 10 patients (nine large intestinal and one small intestinal) in which both CD117 and CD34 were absent or severely reduced in all three of the examined areas. In contrast, the control cases, including those with preobstructive dilatation, showed relatively constant ICC staining. These results suggest that there is a proportion of pseudo-obstruction cases in which the ICC are markedly reduced. These results also demonstrate that, in these cases, loss of the kit immunoreactivity is correlated with the loss of CD34 staining: this indicates that both the ICC and the CD34-positive fibroblasts associated with the ICC are absent. These findings will allow surgical pathologists to identify this subpopulation of patients with CIIP using tissue obtained by laparoscopic biopsy of the muscularis propria or surgical resection.

Venous Invasion in Colorectal Cancer Impact of an Elastin Stain on Detection and Interobserver Agreement Among Gastrointestinal and Nongastrointestinal Pathologists

Venous invasion (VI) is an independent prognostic indicator in colorectal cancer and may prompt consideration for adjuvant chemotherapy in patients with stage II tumors. Recent evidence suggests that VI is underreported in colorectal cancer and that detection may be enhanced by an elastin stain. This study aimed (1) to determine the impact of an elastin stain on VI detection and on interobserver agreement between gastrointestinal (GI) and non-GI pathologists, and (2) to identify factors associated with increased VI detection. Forty hematoxylin and eosin (H&E)-stained slides were circulated to 6 GI and 6 non-GI pathologists who independently assessed the VI status as positive, negative, or equivocal. Six weeks later, 40 corresponding Movat-stained slides were recirculated together with the original H&E slides and reassessed for VI status. Detection of VI was >2-fold higher with a Movat stain compared with an H&E stain alone (46.4% vs. 19.6%, P=0.001). GI pathologists detected VI more frequently than non-GI pathologists on both H&E (30.0% vs. 9.2%, P=0.029) and Movat (58.3% vs. 34.6%, P=0.018) stains. There was higher interobserver agreement in the case of a Movat stain, particularly for extramural VI (H&E: &kgr;=0.23 vs. Movat: &kgr;=0.41). A poststudy survey indicated that GI pathologists and non-GI pathologists applied similar diagnostic criteria but that GI pathologists more frequently applied “orphan arteriole” and “protruding tongue” signs as diagnostic clues to VI. This study confirms that VI is underdetected on H&E and highlights the role of elastin staining in improving VI detection and interobserver agreement. Strategies to improve VI detection are warranted.

HER2 Testing and Clinical Decision Making in Gastroesophageal Adenocarcinoma: Guideline From the College of American Pathologists, American Society for Clinical Pathology, and the American Society of Clinical Oncology

Context ERBB2 (erb-b2 receptor tyrosine kinase 2 or HER2) is currently the only biomarker established for selection of a specific therapy for patients with advanced gastroesophageal adenocarcinoma (GEA). However, there are no comprehensive guidelines for the assessment of HER2 in patients with GEA. Objectives To establish an evidence-based guideline for HER2 testing in patients with GEA, formalize the algorithms for methods to improve the accuracy of HER2 testing while addressing which patients and tumor specimens are appropriate, and to provide guidance on clinical decision making. Design The College of American Pathologists (CAP), American Society for Clinical Pathology (ASCP), and the American Society of Clinical Oncology (ASCO) convened an Expert Panel to conduct a systematic review of the literature to develop an evidence-based guideline with recommendations for optimal HER2 testing in patients with GEA. Results The Panel is proposing 11 recommendations with strong agreement from the open comment participants. Recommendations The Panel recommends that tumor specimen(s) from all patients with advanced GEA, who are candidates for HER2-targeted therapy, should be assessed for HER2 status before the initiation of HER2-targeted therapy. Clinicians should offer combination chemotherapy and an HER2-targeted agent as initial therapy for all patients with HER2-positive advanced GEA. For pathologists, guidance is provided for morphologic selection of neoplastic tissue, testing algorithms, scoring methods, interpretation and reporting of results, and laboratory quality assurance. Conclusion This guideline provides specific recommendations for assessment of HER2 in patients with advanced GEA while addressing pertinent technical issues and clinical implications of the results.

The mitochondrial protein NLRX1 controls the balance between extrinsic and intrinsic apoptosis.

Background: NLRX1 is a member of the Nod-like receptor family that localizes to the mitochondrial matrix and whose function remains poorly understood. Results: NLRX1 plays a key role in regulating apoptotic cell death and is important in the control of tumorigenesis. Conclusion: NLRX1 regulates the balance between extrinsic and intrinsic apoptosis in cancer cells. Significance: Targeting NLRX1 function could be an interesting strategy against cancer. NLRX1 is a mitochondrial Nod-like receptor (NLR) protein whose function remains enigmatic. Here, we observed that NLRX1 expression was glucose-regulated and blunted by SV40 transformation. In transformed but not primary murine embryonic fibroblasts, NLRX1 expression mediated resistance to an extrinsic apoptotic signal, whereas conferring susceptibility to intrinsic apoptotic signals, such as glycolysis inhibition, increased cytosolic calcium and endoplasmic reticulum stress. In a murine model of colorectal cancer induced by azoxymethane, NLRX1−/− mice developed fewer tumors than wild type mice. In contrast, in a colitis-associated cancer model combining azoxymethane and dextran sulfate sodium, NLRX1−/− mice developed a more severe pathology likely due to the increased sensitivity to dextran sulfate sodium colitis. Together, these results identify NLRX1 as a critical mitochondrial protein implicated in the regulation of apoptosis in cancer cells. The unique capacity of NLRX1 to regulate the cellular sensitivity toward intrinsic versus extrinsic apoptotic signals suggests a critical role for this protein in numerous physiological processes and pathological conditions.

Microvascular density as an independent predictor of clinical outcome in renal cell carcinoma: an automated image analysis study

Tumor microvascular density (MVD) has been shown to correlate with the aggressiveness of several cancers. With the introduction of targeted anti-angiogenic therapy, assessment of MVD has the potential not only as a prognostic but also as a therapeutic marker. The significance of tumor vascularity in clear cell renal cell carcinoma (ccRCC) has been debated, with studies showing contradictory results. Previous studies were limited by manual quantification of MVD within a small area of tumor. Since then, the validity of this method has been questioned. To avoid the inaccuracies of manual quantification, we employed a computerized image analysis, which allowed assessment of large areas of tumor and adjacent normal tissue. The latter was used as an internal reference for normalization. MVD and vascular endothelial growth factor (VEGF) were assessed in 57 cases of ccRCC. Sections were immunostained for CD34 and VEGF. Areas of ccRCC and normal kidney medulla were analyzed within scanned images using software that counted CD34-positive vessels and measured the intensity of VEGF staining. We obtained unadjusted values from tumoral areas and calculated adjusted values as tumor/normal ratios. Unadjusted MVD had no association with clinical outcome. However, similarly to tumor stage, higher adjusted MVD was associated with shorter disease-free survival (log-rank P=0.037, Cox P=0.02). This was significant in univariate and multivariate analyses. MVD did not correlate with tumor stage, pointing to its independent prognostic value. As expected due to the known molecular abnormalities in ccRCC, most tumors showed higher VEGF expression than normal tissue. Higher adjusted VEGF was associated with high tumor grade (P=0.049). The finding of increased MVD as an independent marker of tumor aggressiveness may prove useful in the development of new tests for prognostic and therapeutic guidance. Digital techniques can provide more accurate assessment of immunomarkers and may reveal less obvious associations.

Systemic Erdheim-Chester disease

Erdheim–Chester disease is a rare xanthomatosis that may present with characteristic radiologic and histologic features. There have been conflicting reports regarding the nature of this process, including whether it represents a reactive or neoplastic lesion. We present the clinical histories, pathologic findings, and an analysis of clonality using the HUMARA assay in two patients diagnosed with Erdheim–Chester disease. One case has previously been documented in the literature. Histologically, both cases demonstrated sheets of foamy xanthomatous histiocytes with widespread infiltration of the viscera. These regions were punctuated by variable amounts of inflammation, including lymphocytes, plasma cells, and occasional Touton-type giant cells. The histiocytes were immunoreactive for CD68 and CD163; they did not stain with S100 or CD1a. One case was found to be monoclonal; however, the second case had extensive DNA degradation; thus, clonality could not be assessed. In addition to contributing an additional report of this rare disease to the literature, we demonstrate the histiocytes to express CD163, thereby further supporting a monocyte/macrophage basis. Moreover, in confirming clonality, our observations lend additional evidence to the view that Erdheim–Chester disease represents a neoplastic process.