Helen Mohan

Molecular Pathways: The Role of NR4A Orphan Nuclear Receptors in Cancer

Nuclear receptors are of integral importance in carcinogenesis. Manipulation of classic ligand-activated nuclear receptors, such as estrogen receptor blockade in breast cancer, is an important established cancer therapy. Orphan nuclear receptors, such as nuclear family 4 subgroup A (NR4A) receptors, have no known natural ligand(s). These elusive receptors are increasingly recognized as molecular switches in cell survival and a molecular link between inflammation and cancer. NR4A receptors act as transcription factors, altering expression of downstream genes in apoptosis (Fas-ligand, TRAIL), proliferation, DNA repair, metabolism, cell migration, inflammation (interleukin-8), and angiogenesis (VEGF). NR4A receptors are modulated by multiple cell-signaling pathways, including protein kinase A/CREB, NF-κB, phosphoinositide 3-kinase/AKT, c-jun-NH2-kinase, Wnt, and mitogen-activated protein kinase pathways. NR4A receptor effects are context and tissue specific, influenced by their levels of expression, posttranslational modification, and interaction with other transcription factors (RXR, PPAR-ϒ). The subcellular location of NR4A “nuclear receptors” is also important functionally; novel roles have been described in the cytoplasm where NR4A proteins act both indirectly and directly on the mitochondria to promote apoptosis via Bcl-2. NR4A receptors are implicated in a wide variety of malignancies, including breast, lung, colon, bladder, and prostate cancer; glioblastoma multiforme; sarcoma; and acute and/or chronic myeloid leukemia. NR4A receptors modulate response to conventional chemotherapy and represent an exciting frontier for chemotherapeutic intervention, as novel agents targeting NR4A receptors have now been developed. This review provides a concise clinical overview of current knowledge of NR4A signaling in cancer and the potential for therapeutic manipulation. Clin Cancer Res; 18(12); 3223–8. ©2012 AACR.

The end of the line? The Visual Analogue Scale and Verbal Numerical Rating Scale as pain assessment tools in the emergency department

Objectives To compare the Visual Analogue Scale (VAS) and the Verbal Numerical Rating Scale (VNRS), in the assessment of acute pain in the emergency department (ED). Furthermore, to determine the influence of demographics on this agreement and practical limitations of the scales. Setting St Vincents University Hospital, Dublin; a 479-bed teaching hospital; annual ED census 36 000 adult patients. Methods A prospective observational study was conducted on ED patients with acute pain as a component of their presenting complaint. Eligible patients scored their pain on both VAS and VNRS within 1 hour of arrival. They rescored their pain every 30 minutes for 2 hours using both scales. The primary outcome measure was agreement between VAS and VNRS. Secondary outcomes were ease of pain scale use and effect of patient demographics on pain scores. Agreement between scores was evaluated using the Bland-Altman method. Results 123 patients were included (median age 35; 43.9% male). There was a strong correlation between VAS and VNRS (rs=0.93). However, there was not perfect agreement between the two scales. Patient age (older age, p<0.005, t=−4.448), gender (female sex, p<0.005, t=4.903) and educational level attained (third level education, p<0.005, t=5.575) had a statistically significant influence on the agreement between VAS and VNRS. There was a preference for VNRS in those patients who expressed a preference for one pain scale over the other. Conclusions VAS and VNRS are not interchangeable in assessing an individual patients pain over time in the ED setting. VNRS has practical advantages over VAS in this setting.

Radiofrequency Ablation for Neuroendocrine Liver Metastases: A Systematic Review

To determine the efficacy of radiofrequency (RF) ablation in neuroendocrine tumor (NET) liver metastases. A systematic review was performed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Eight studies were included (N = 301). Twenty-six percent of RF ablation procedures were percutaneous (n = 156), with the remainder conducted at surgery. Forty-eight percent of patients had a concomitant liver resection. Fifty-four percent of patients presented with symptoms, with 92% reporting symptom improvement following RF ablation (alone or in combination with surgery). The median duration of symptom improvement was 14-27 months. However, recurrence was common (63%-87%). RF ablation can provide symptomatic relief in NET liver metastases alone or in combination with surgery.

The mycotoxin patulin increases colonic epithelial permeability in vitro.

The gastrointestinal lumen is directly exposed to dietary contaminants, including patulin, a mycotoxin produced by moulds. Patulin is known to increase permeability across intestinal Caco-2 monolayers. This study aimed to determine the effect of patulin on permeability, ion transport and morphology in isolated rat colonic mucosae. Mucosal sheets were mounted in Ussing chambers and voltage clamped. Apical addition of patulin (100-500 μM) rapidly reduced transepithelial electrical resistance (TEER) and increased permeability to [(14)C] mannitol (2.9-fold). Patulin also inhibited carbachol-induced electrogenic chloride secretion and histological evidence of mucosal damage was observed. To examine potential mechanisms of action of patulin on colonic epithelial cells, high-content analysis of Caco-2 cells was performed and this novel, quantitative fluorescence-based approach confirmed its cytotoxic effects. With regard to time course, the cytotoxicity determined by high content analysis took longer than the almost immediate reduction of electrical resistance in isolated mucosal sheets. These data indicate patulin is not only cytotoxic to enterocytes but also has the capacity to directly alter permeability and ion transport in intact intestinal mucosae. These data corroborate and extend findings in intestinal cell culture monolayers, and further suggest that safety limits on consumption of patulin may be warranted.

Adenosine Modulates NR4A Orphan Nuclear Receptors To Attenuate Hyperinflammatory Responses in Monocytic Cells

Adenosine receptor–mediated regulation of monocyte/macrophage inflammatory responses is critical in the maintenance of tissue homeostasis. In this study, we reveal that adenosine potently modulates the expression of NR4A1, 2, and 3 orphan nuclear receptors in myeloid cells, and this modulation is primarily through the adenosine A2a receptor subtype. We demonstrate that A2a receptor activation of NR4A1-3 receptor synthesis is further enhanced in TLR4-stimulated monocytes. After TLR4 stimulation, NR4A receptor–depleted monocyte/macrophage cells display significantly altered expression of cell-surface markers and produce increased inflammatory cytokine and chemokine secretion rendering the cells an enhanced proinflammatory phenotype. Exposure of TLR4 or TNF-α–stimulated monocytes to adenosine analogs directs changes in the expression of MIP-3α and IL-23p19, with NR4A2 depletion leading to significantly enhanced expression of these factors. Furthermore, we establish that nuclear levels of NF-κB/p65 are increased in TLR/adenosine-stimulated NR4A2-depleted cells. We show that, after TLR/adenosine receptor stimulation, NR4A2 depletion promotes significant binding of NF-κB/p65 to a κB consensus binding motif within the MIP-3α proximal promoter leading to increased protein secretion, confirming a pivotal role for NF-κB activity in controlling cellular responses and gene expression outcomes in response to these mediators. Thus, these data demonstrate that during an inflammatory response, adenosine modulation of NR4A receptor activity acts to limit NF-κB–mediated effects and that loss of NR4A2 expression leads to enhanced NF-κB activity and hyperinflammatory responses in myeloid cells.

Biomechanical abdominal wall model applied to hernia repair

Most surgical innovations require extensive preclinical testing before employment in the operative environment. There is currently no way to develop and test innovations for abdominal wall surgery that is cheap, repeatable and easy to use. In hernia repair, the required mesh overlap relative to defect size is not established. The aims of this study were to develop a biomechanical model of the abdominal wall based on in vivo pressure measurements, and to apply this to study mesh overlap in hernia repair.

Prognostic significance of detection of microscopic peritoneal disease in colorectal cancer: A systematic review

BACKGROUND Free intraperitoneal tumour cells are an independent indicator of poor prognosis, and are encorporated in current staging systems in upper gastrointestinal cancers, but not colorectal cancer. This systematic review aimed to evaluate the role and prognostic significance of positive peritoneal lavage in colorectal cancer. METHODS A search was undertaken of PUBMED/Medline and Cochrane databases for English language articles from 1990 to 2012 using a predefined search strategy. Both detection of free tumour cells and/or detection of tumour-associated antigens in peritoneal lavage fluid were considered a positive lavage. Primary endpoints were rates of positive lavage, recurrence and survival. RESULTS Of 3805 articles identified by title, 18 met inclusion criteria (n = 3197 patients, 59.5% colon, 40.5% rectal cancer). There was heterogeneity across studies in method of detection of peritoneal disease with 7 studies using more than one method (conventional cytology (14 studies), immunological techniques (6 studies), molecular techniques (4 studies)). The rate of positive lavage varied from 2.1% to 52% across studies, with a weighted mean rate of positive lavage of 13.17% overall (95% CI 12.74-13.59). In 10 studies (n = 2017) positive peritoneal lavage was associated with worse survival, and with increased recurrence in 12 (n = 2371). Clinicopathological factors frequently associated with positive lavage included macroscopic peritoneal disease, increasing tumour stage and nodal disease. CONCLUSION Positive peritoneal lavage is a negative prognostic factor in colorectal cancer. However, its utility in staging colorectal cancer is currently limited by wide variation in rates of positive lavage between studies due to differences in methods of peritoneal lavage fluid analysis.

The current value of determining the mismatch repair status of colorectal cancer: A rationale for routine testing

Colorectal Cancer (CRC) is the third most prevalent cancer in men and women. Up to 15% of CRCs display microsatellite instability (MSI). MSI is reflective of a deficient mismatch repair (MMR) system and is most commonly caused by hypermethylation of the MLH1 promoter. However, it may also be due to autosomal dominant constitutional mutations in DNA MMR, termed Lynch Syndrome. MSI may be diagnosed via polymerase chain reaction (PCR) or alternatively, immunohistochemistry (IHC) can identify MMR deficiency (dMMR). Many institutions now advocate universal tumor screening of CRC via either PCR for MSI or IHC for dMMR to guide Lynch Syndrome testing. The association of sporadic MSI with methylation of the MLH1 promoter and an activating BRAF mutation may offer further exclusion criteria for genetic testing. Aside from screening for Lynch syndrome, MMR testing is important because of its prognostic and therapeutic implications. Several studies have shown MSI CRCs exhibit different clinicopathological features and prognosis compared to microsatellite-stable (MSS) CRCs. For example, response to conventional chemotherapy has been reported to be less in MSI tumours. More recently, MSI tumours have been shown to be responsive to immune-checkpoint inhibition providing a novel therapeutic strategy. This provides a rationale for routine testing for MSI or dMMR in CRC.

Natural-orifice translumenal endoscopic surgery (NOTES): minimally invasive evolution or revolution?

Since the first animal experimental laparoscopy in 1902, minimal access techniques have revolutionized surgery. Using the natural orifice dates back to at least the second century when Soranus performed a vaginal hysterectomy. The main difference between traditional endolumenal surgery and the translumenal approach of natural-orifice translumenal endoscopic surgery (NOTES) is the intentional puncture of a healthy organ in NOTES to access a cavity or other organ. The aim of this review was to examine the past, present, and potential future role of NOTES in the context of other developments in minimal access surgery. NOTES is at an early stage in its development and a convincing benefit over laparoscopy has not been demonstrated. Concerns regarding complications, for example of viscerotomy closure, have limited the widespread uptake of pure NOTES. However, it is likely that technological advances for NOTES surgery will enhance conventional laparoscopic and endoscopic techniques.

The effects of polyamines on human colonic mucosal function

Electrogenic ion transport in human colon is a surrogate marker for colonic mucosal function, and may be manipulated by a variety of hormonal, neural, immune and paracrine mediators. Polyamines are present in vast quantities in the colonic lumen and appear to be integral to cellular function. This study explores some of the mechanisms of polyamine action on colonic tissue through study of their effects on differential secretory pathways, as well as examining their actions on intracellular cAMP and Ca(2+) accumulation. Human colonic mucosa was mounted in Ussing chambers and treated with polyamines (spermine, spermidine and putrescine) with changes in ion transport recorded. In separate experiments colonic crypts were treated with polyamines and intracellular cAMP levels determined by ELISA and intracellular calcium concentrations were quantified by fluorescent imaging. Polyamines at physiological concentrations (1mM) exert no effects on basal mucosal chloride secretion or transepithelial electrical resistance. Polyamines inhibit electrogenic ion secretion as stimulated by forskolin (cAMP-mediated), but not carbachol (Ach-mediated). All the polyamines used in this study inhibited intracellular cAMP accumulation, according to potency (spermine>spermidine>putrescine). Spermine increased intracellular Ca(2+) in a PKC-dependent manner, likely due to its effects on the extracellular calcium-sensing receptor (CaSR). Polyamines act to prevent cAMP-mediated Cl(-) hypersecretion in the colon, acting through CaSR to inhibit PKC-mediated [Ca(2+)]i release from intracellular stores.