Utilizing endoscopic technology to reveal real-time proteomic alterations in response to chemoprevention

Effects of Walnut Consumption on Colon Carcinogenesis and Microbial Community Structure

Walnuts are composed of a complex array of biologically active constituents with individual cancer-protective properties. Here, we assessed the potential benefit of whole walnut consumption in a mouse tumor bioassay using azoxymethane. In study 1, a modest reduction (1.3-fold) in tumor numbers was observed in mice fed a standard diet (AIN-76A) containing 9.4% walnuts (15% of total fat). In study 2, the effects of walnut supplementation was tested in the Total Western Diet (TWD). There was a significant reduction (2.3-fold; P < 0.02) in tumor numbers in male mice fed TWD containing 7% walnuts (10.5% of total fat). Higher concentrations of walnuts lacked inhibitory effects, particularly in female mice, indicating there may be optimal levels of dietary walnut intake for cancer prevention. Since components of the Mediterranean diet have been shown to affect the gut microbiome, the effects of walnuts were therefore tested in fecal samples using 16S rRNA gene sequencing. Carcinogen treatment reduced the diversity and richness of the gut microbiome, especially in male mice, which exhibited lower variability and greater sensitivity to environmental changes. Analysis of individual operational taxonomic units (OTU) identified specific groups of bacteria associated with carcinogen exposure, walnut consumption, and/or both variables. Correlation analysis also identified specific OTU clades that were strongly associated with the presence and number of tumors. Taken together, our results indicate that walnuts afford partial protection to the colon against a potent carcinogenic insult, and this may be due, in part, to walnut-induced changes to the gut microbiome. Cancer Prev Res; 9(8); 692-703. ©2016 AACR.

Endoscopy-guided orthotopic implantation of colorectal cancer cells results in metastatic colorectal cancer in mice

Advanced stage colorectal cancer (CRC) is still associated with limited prognosis. For preclinical evaluation of novel therapeutic approaches, murine models with orthotopic tumor growth and distant metastases are required. However, these models usually require surgical procedures possibly influencing tumor immunogenicity and development. The aim of this study was to establish a minimal-invasive endoscopy-based murine orthotopic model of metastatic CRC. During colonoscopy of CD-1 nude and non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice, implantation of Caco-2 and HT-29 CRC cells was performed subcutaneously (s.c.) or orthotopic into the colonic submucosa. White light endoscopy (WLE) and fluorescence endoscopy (FE) were applied for tumor detection in vivo. Ex vivo, resected tumors were examined by fluorescence reflectance imaging (FRI), histology, gelatin zymography and immunohistochemistry. In CD-1 nude mice, marked tumor growth was observed within 14 days after subcutaneous implantation while submucosal implantation failed to induce CRC after 17 weeks. In contrast, in NOD/SCID mice submucosal injection of HT-29 cells resulted in pronounced tumor growth 12 days post injectionem. Subsequently, rapid tumor expansion occurred, occupying the entire colonic circumference. Importantly, post mortem histological analyses confirmed liver metastases in 28.6 % and peritoneal metastases in 14.3 % of all mice. FRI and gelatin zymography did not detect a significantly increased matrix metalloproteinases (MMPs) expression in s.c. implanted tumors while MMP-tracer uptake was significantly enhanced in orthotopic implanted tumors. Neither s.c. nor orthotopic Caco-2 cell implantation resulted in tumor development. We successfully established an endoscopy-based model of metastatic CRC in immunodeficient mice.

Transition from identity to bioactivity-guided proteomics for biomarker discovery with focus on the PF2D platform

Proteomic strategies provide a valuable tool kit to identify proteins involved in diseases. With recent progress in MS technology, high throughput proteomics has accelerated protein identification for potential biomarkers. Numerous biomarker candidates have been identified in several diseases, and many are common among pathologies. An overall strategy that could complement and strengthen the search for biomarkers is combining protein identity with biological outcomes. This review describes an emerging framework of bridging bioactivity to protein identity, exploring the possibility that some biomarkers will have a mechanistic role in the disease process. A review of pulmonary, cardiovascular, and CNS biomarkers will be discussed to demonstrate the utility of combining bioactivity with identification as a means to not only find meaningful biomarkers, but also to uncover functional mediators of disease.

Suppression of colon carcinogenesis by targeting Notch signaling

Recent studies have shown that aberrant Notch signaling contributes to the pathogenesis of colorectal cancer (CRC). However, the potential therapeutic benefits of Notch pathway inhibitors, including gamma-secretase inhibitors (GSIs) on colon carcinogenesis are still unclear. In this study, the effects of the GSI, N-[N-3,5-difluorophenacetyl]-L-alanyl-S-phenylglycine methyl ester (DAPM) on colon carcinogenesis were investigated. In vitro, DAPM suppressed cell proliferation and induced the expression of Krüppel-like factor 4 (KLF4) and p21 in human colon cancer cells. Interestingly, p21-null HCT 116 cells were largely resistant to the suppressive effects of DAPM on cell proliferation compared with the parental cells. To investigate the effects of DAPM in vivo, colonoscopy was performed to establish the presence of colon tumors 9 weeks after azoxymethane treatment. After tumors were identified, mice were injected intraperitoneally every other day with either DAPM or vehicle for 4 weeks. The frequency of both large (>4mm) and small (<1mm) colon tumors was significantly reduced by DAPM treatment. Colon tumors in the DAPM-treated mice displayed increased levels of KLF4 and p21, accompanied by reduced Ki-67 staining compared with controls. Notably, in human colon tumor biopsies, KLF4 and p21 expressions were present within hyperplastic polyps, but the levels of both proteins were markedly reduced in tubular adenomas. Our results suggest that inhibition of Notch signaling by DAPM provides a potential chemopreventive strategy for patients with tubular adenomas, in part via activation of the KLF4-p21 axis.

Differential proteomics identifies PDIA3 as a novel chemoprevention target in human colon cancer cells

Chemoprevention offers a promising strategy to prevent or delay the development of various cancers. Critical to this approach is the identification of molecular targets that may track with chemopreventive efficacy. To address this issue, we screened a panel of chemoprevention agents, including resveratrol, epigallocatechin-3-gallate, ursodeoxycholic acid, and sulindac sulfide for their effects on human colon cancer cell viability. Resveratrol elicited the most potent effect in HCT116 cells and was selected for further study. Proteomic PF 2D maps were generated from HCT116 cells treated with resveratrol versus vehicle alone. Analysis of proteomic maps using tandem mass spectrometry (MS) identified a panel of differentially modified proteins. Two proteins, actin and Hsp60, were previously shown in other cell culture systems to be affected by resveratrol, validating our approach. PDIA3, RPL19, histone H2B and TCP1β were uniquely identified by our proteomic discovery platform. PDIA3 was of particular interest given its potential role in regulating chemosensitivity of cancer cells. Total levels of PDIA3 in HCT116 cells were unchanged following 24 h of resveratrol treatment, confirmed by Western blot analysis. Immunoprecipitation of PDIA3 revealed a new set of client proteins following resveratrol treatment, including α, β, and δ-catenins, and cellular fractionation identified decreased nuclear localization of α-catenin by resveratrol. These data establish differential proteomic mapping as a powerful tool for identifying novel molecular targets of chemopreventive agents.

Cytochrome b5 and cytokeratin 17 are biomarkers in bronchoalveolar fluid signifying onset of acute lung injury

Acute lung injury (ALI) is characterized by pulmonary edema and acute inflammation leading to pulmonary dysfunction and potentially death. Early medical intervention may ameliorate the severity of ALI, but unfortunately, there are no reliable biomarkers for early diagnosis. We screened for biomarkers in a mouse model of ALI. In this model, inhalation of S. aureus enterotoxin A causes increased capillary permeability, cell damage, and increase protein and cytokine concentration in the lungs. We set out to find predictive biomarkers of ALI in bronchoalveolar lavage (BAL) fluid before the onset of clinical manifestations. A cutting edge proteomic approach was used to compare BAL fluid harvested 16 h post S. aureus enterotoxin A inhalation versus BAL fluid from vehicle alone treated mice. The proteomic PF 2D platform permitted comparative analysis of proteomic maps and mass spectrometry identified cytochrome b5 and cytokeratin 17 in BAL fluid of mice challenged with S. aureus enterotoxin A. Validation of cytochrome b5 showed tropic expression in epithelial cells of the bronchioles. Importantly, S. aureus enterotoxin A inhalation significantly decreased cytochrome b5 during the onset of lung injury. Validation of cytokeratin 17 showed ubiquitous expression in lung tissue and increased presence in BAL fluid after S. aureus enterotoxin A inhalation. Therefore, these new biomarkers may be predictive of ALI onset in patients and could provide insight regarding the basis of lung injury and inflammation.

Utilization of murine colonoscopy for orthotopic implantation of colorectal cancer

Background

Colorectal-cancer (CRC) research has greatly benefited from the availability of small animal tumor models. Spontaneous and chemically-induced CRC models are widely used yet limited in their resemblance to human disease and are often prolonged, not accurately repetitive, and associated with inflammatory side effects. In-situ murine or human tumor implantation in the gastrointestinal tract of mice is extremely challenging, and limited by inter-animal variability and procedure-related complications and mortality. As a result, in frequent studies CRC is implanted in distal sites, most commonly the subcutaneous region, an approach that is greatly limited by the absence of normal gastrointestinal tumor milieu and has substantial effects on tumor development.

Aims

In this study we aimed to develop a well-tolerated repetitive tool to study CRC in small animals by adapting the murine colonoscopy system to serve as a platform for colonic sub-mucosal orthotopic implantation of human and murine CRC tumor cells.

Results

We report the establishment of a novel small-animal CRC model that is minimally invasive, rapid, well-tolerated, highly reproducible, and confers precise control of tumor number, location and growth rate. Moreover, we show that this model uniquely allows the side-by-side induction of distinct genetically manipulated tumors, enabling the mechanistic study of tumor interaction and cross-talk within the native intestinal microenvironment.

Conclusions

Employment of this new approach may represent a major technical advance for the in-vivo study of CRC.

The oxazolidinone derivative locostatin induces cytokine appeasement

Damaging inflammation arising from autoimmune pathology and septic responses results in severe cases of disease. In both instances, anti-inflammatory compounds are used to limit the excessive or deregulated cytokine responses. We used a model of robust T cell stimulation to identify new proteins involved in triggering a cytokine storm. A comparative proteomic mining approach revealed the differential mapping of Raf kinase inhibitory protein after T cell recall in vivo. Treatment with locostatin, an Raf kinase inhibitory protein inhibitor, induced T cell anergy by blocking cytokine production after Ag recall. This was associated with a reduction in Erk phosphorylation. Importantly, in vivo treatment with locostatin profoundly inhibited TNF-alpha production upon triggering the Ag-specific T cells. This effect was not limited to a murine model because locostatin efficiently inhibited cytokine secretion by human lymphocytes. Therefore, locostatin should be a useful therapeutic to control inflammation, sepsis, and autoimmune diseases.