Neurological issues in children with COVID-19

Coronavirus disease 2019 (COVID-19) usually leads to a mild infectious disease course in children, but serious complications may occur in conjunction with both acute infection and associated phenomena such as the multisystem inflammatory syndrome in children (MIS-C). Neurological symptoms, which have been predominantly reported in adults, range from mild headache to seizure, peripheral neuropathy, stroke, demyelinating disorders, and encephalopathy. Similar to respiratory and cardiac manifestations of COVID-19, neurological complications present differently based on age and underlying comorbidities. This review provides a concise overview of the neurological conditions seen in the context of COVID-19, as well as potential mechanisms and long-term implications of COVID-19 in the pediatric population from literature reviews and primary data collected at NewYork-Presbyterian Morgan Stanley Children's Hospital.

GUCY2C Signaling Opposes the Acute Radiation-Induced GI Syndrome

High doses of ionizing radiation induce acute damage to epithelial cells of the gastrointestinal (GI) tract, mediating toxicities restricting the therapeutic efficacy of radiation in cancer and morbidity and mortality in nuclear disasters. No approved prophylaxis or therapy exists for these toxicities, in part reflecting an incomplete understanding of mechanisms contributing to the acute radiation-induced GI syndrome (RIGS). Guanylate cyclase C (GUCY2C) and its hormones guanylin and uroguanylin have recently emerged as one paracrine axis defending intestinal mucosal integrity against mutational, chemical, and inflammatory injury. Here, we reveal a role for the GUCY2C paracrine axis in compensatory mechanisms opposing RIGS. Eliminating GUCY2C signaling exacerbated RIGS, amplifying radiation-induced mortality, weight loss, mucosal bleeding, debilitation, and intestinal dysfunction. Durable expression of GUCY2C, guanylin, and uroguanylin mRNA and protein by intestinal epithelial cells was preserved following lethal irradiation inducing RIGS. Oral delivery of the heat-stable enterotoxin (ST), an exogenous GUCY2C ligand, opposed RIGS, a process requiring p53 activation mediated by dissociation from MDM2. In turn, p53 activation prevented cell death by selectively limiting mitotic catastrophe, but not apoptosis. These studies reveal a role for the GUCY2C paracrine hormone axis as a novel compensatory mechanism opposing RIGS, and they highlight the potential of oral GUCY2C agonists (Linzess; Trulance) to prevent and treat RIGS in cancer therapy and nuclear disasters. Cancer Res; 77(18); 5095-106. ©2017 AACR.

ST-Producing E. coli Oppose Carcinogen-Induced Colorectal Tumorigenesis in Mice

There is a geographic inequality in the incidence of colorectal cancer, lowest in developing countries, and greatest in developed countries. This disparity suggests an environmental contribution to cancer resistance in endemic populations. Enterotoxigenic bacteria associated with diarrheal disease are prevalent in developing countries, including enterotoxigenic E. coli (ETEC) producing heat-stable enterotoxins (STs). STs are peptides that are structurally homologous to paracrine hormones that regulate the intestinal guanylyl cyclase C (GUCY2C) receptor. Beyond secretion, GUCY2C is a tumor suppressor universally silenced by loss of expression of its paracrine hormone during carcinogenesis. Thus, the geographic imbalance in colorectal cancer, in part, may reflect chronic exposure to ST-producing organisms that restore GUCY2C signaling silenced by hormone loss during transformation. Here, mice colonized for 18 weeks with control E. coli or those engineered to secrete ST exhibited normal growth, with comparable weight gain and normal stool water content, without evidence of secretory diarrhea. Enterotoxin-producing, but not control, E. coli, generated ST that activated colonic GUCY2C signaling, cyclic guanosine monophosphate (cGMP) production, and cGMP-dependent protein phosphorylation in colonized mice. Moreover, mice colonized with ST-producing E. coli exhibited a 50% reduction in carcinogen-induced colorectal tumor burden. Thus, chronic colonization with ETEC producing ST could contribute to endemic cancer resistance in developing countries, reinforcing a novel paradigm of colorectal cancer chemoprevention with oral GUCY2C-targeted agents.

Bioactivity of Oral Linaclotide in Human Colorectum for Cancer Chemoprevention

Guanylate cyclase C (GUCY2C) is a tumor-suppressing receptor silenced by loss of expression of its luminocrine hormones guanylin and uroguanylin early in colorectal carcinogenesis. This observation suggests oral replacement with a GUCY2C agonist may be an effective targeted chemoprevention agent. Linaclotide is an FDA-approved oral GUCY2C agonist formulated for gastric release, inducing fluid secretion into the small bowel to treat chronic idiopathic constipation. The ability of oral linaclotide to induce a pharmacodynamic response in epithelial cells of the colorectum in humans remains undefined. Here, we demonstrate that administration of 0.87 mg of oral linaclotide daily for 7 days to healthy volunteers, after oral colon preparation with polyethylene glycol solution (MoviPrep), activates GUCY2C, resulting in accumulation of its product cyclic (c)GMP in epithelial cells of the cecum, transverse colon, and distal rectum. GUCY2C activation by oral linaclotide was associated with homeostatic signaling, including phosphorylation of vasodilator-stimulated phosphoprotein and inhibition of proliferation quantified by reduced Ki67-positive epithelial cells. In the absence of the complete oral colonoscopy preparation, linaclotide did not alter cGMP production in epithelial cells of the colorectum, demonstrating that there was an effect related to the laxative preparation. These data show that the current FDA-approved formulation of oral linaclotide developed for small-bowel delivery to treat chronic idiopathic constipation is inadequate for reliably regulating GUCY2C in the colorectum to prevent tumorigenesis. The study results highlight the importance of developing a novel GUCY2C agonist formulated for release and activity targeted to the large intestine for colorectal cancer prevention. Cancer Prev Res; 10(6); 345-54. ©2017 AACR.

Obesity-Induced Colorectal Cancer Is Driven by Caloric Silencing of the Guanylin-GUCY2C Paracrine Signaling Axis

Obesity is a well-known risk factor for colorectal cancer but precisely how it influences risks of malignancy remains unclear. During colon cancer development in humans or animals, attenuation of the colonic cell surface receptor guanylyl cyclase C (GUCY2C) that occurs due to loss of its paracrine hormone ligand guanylin contributes universally to malignant progression. In this study, we explored a link between obesity and GUCY2C silencing in colorectal cancer. Using genetically engineered mice on different diets, we found that diet-induced obesity caused a loss of guanylin expression in the colon with subsequent GUCY2C silencing, epithelial dysfunction, and tumorigenesis. Mechanistic investigations revealed that obesity reversibly silenced guanylin expression through calorie-dependent induction of endoplasmic reticulum stress and the unfolded protein response in intestinal epithelial cells. In transgenic mice, enforcing specific expression of guanylin in intestinal epithelial cells restored GUCY2C signaling, eliminating intestinal tumors associated with a high calorie diet. Our findings show how caloric suppression of the guanylin-GUCY2C signaling axis links obesity to negation of a universal tumor suppressor pathway in colorectal cancer, suggesting an opportunity to prevent colorectal cancer in obese patients through hormone replacement with the FDA-approved oral GUCY2C ligand linaclotide.

Cardioprotective effect of notoginsenoside R1 in a rabbit lung remote ischemic postconditioning model via activation of the TGF-β1/TAK1 signaling pathway

Pharmacological postconditioning using cardioprotective agents is able to reduce myocardial infarct size. Notoginsenoside R1 (NG-R1), a phytoestrogen isolated from Panax notoginseng saponins (PNS), is considered to have anti-oxidative and anti-apoptotic properties. However, its cardioprotective properties and underlying mechanisms remain largely unknown. The aim of the present study was to determine the cardioprotective and anti-apoptotic effects of NG-R1 in an ischemia-reperfusion (IR)-induced myocardial injury rabbit model. A total of 45 Japanese big-ear rabbits were equally randomized to three groups: Control group, remote ischemic postconditioning (RIP) group and NG-R1 intervention group. At the endpoint of the experiment, the animals were sacrificed to remove myocardial tissues for the detection of transforming growth factor (TGF)-β1-TGF-β activated kinase 1 (TAK1) pathway-related proteins by immunohistochemistry and western blot analysis, the activities of caspase-3, -8 and -9 in myocardial cells by fluorometric assay, and the apoptosis of myocardial cells by terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling. Right and left lung tissues were stained with hematoxylin and eosin (H&E) to observe the severity of injury. NG-R1 treatment reduced the activity of superoxide dismutase, increased the content of malondialdehyde, reduced the activities of caspase-3, -8 and -9, and inhibited the apoptosis of myocardial cells in rabbits undergoing RIP. In addition, the expression of TGF-β1-TAK1 signaling pathway-related proteins was downregulated following NG-R1 intervention. H&E staining of bilateral lung tissues showed that cell morphology was generally intact without significant alveolar congestion, and there was no significant difference among the three groups. These results indicate that NG-R1 protects the heart against IR injury, possibly by inhibiting the activation of the TGF-β1-TAK1 signaling pathway and attenuating apoptotic stress in the myocardium.

The paracrine hormone for the GUCY2C tumor suppressor, guanylin, is universally lost in colorectal cancer

BACKGROUND

Although colorectal cancer is a disease characterized by sequential accumulation of mutations in epithelial cells, mechanisms leading to genomic vulnerability contributing to tumor initiation remain undefined. GUCY2C has emerged as an intestine-specific tumor suppressor controlling epithelial homeostasis through circuits canonically disrupted in cancer. Surprisingly, the GUCY2C tumor suppressor is universally overexpressed by human colorectal cancer cells. This apparent paradox likely reflects silencing of GUCY2C through loss of its paracrine hormone guanylin. Here, we quantified expression of guanylin mRNA and protein in tumors and normal epithelia from patients with colorectal cancer.

METHODS

Guanylin mRNA was quantified in tumors and normal adjacent epithelia from 281 patients by the reverse transcriptase-polymerase chain reaction. Separately, the guanylin protein was quantified by immunohistochemistry in 54 colorectal tumors and 30 specimens of normal intestinal epithelium.

RESULTS

Guanylin mRNA in colorectum varied more than a 100-fold across the population. Guanylin mRNA was reduced 100- to 1,000-fold in >85% of tumors compared with matched normal adjacent mucosa (P < 0.001). Loss of guanylin mRNA was greatest in tumors from patients <50 years old (P < 0.005) and with the highest expression in normal adjacent mucosa (Spearman correlation coefficient = 0.61; P < 0.001). In a separate validation cohort, guanylin protein was detected in all 30 normal colorectal mucosa specimens, but in none of 54 colorectal tumors.

CONCLUSIONS

Colorectal cancer may initiate as a disease of paracrine hormone insufficiency through loss of guanylin expression, silencing the GUCY2C tumor suppressor and disrupting homeostatic mechanisms regulating colorectal epithelia cells.

IMPACT

Intestinal tumorigenesis may be prevented by oral GUCY2C hormone replacement therapy.

A novel CDX2 isoform regulates alternative splicing

Gene expression is a dynamic and coordinated process coupling transcription with pre-mRNA processing. This regulation enables tissue-specific transcription factors to induce expression of specific transcripts that are subsequently amplified by alternative splicing allowing for increased proteome complexity and functional diversity. The intestine-specific transcription factor CDX2 regulates development and maintenance of the intestinal epithelium by inducing expression of genes characteristic of the mature enterocyte phenotype. Here, sequence analysis of CDX2 mRNA from colonic mucosa-derived tissues revealed an alternatively spliced transcript (CDX2/AS) that encodes a protein with a truncated homeodomain and a novel carboxy-terminal domain enriched in serine and arginine residues (RS domain). CDX2 and CDX2/AS exhibited distinct nuclear expression patterns with minimal areas of co-localization. CDX2/AS did not activate the CDX2-dependent promoter of guanylyl cyclase C nor inhibit transcriptional activity of CDX2. Unlike CDX2, CDX2/AS co-localized with the putative splicing factors ASF/SF2 and SC35. CDX2/AS altered splicing patterns of CD44v5 and Tra2-β1 minigenes in Lovo colon cancer cells independent of CDX2 expression. These data demonstrate unique dual functions of the CDX2 gene enabling it to regulate gene expression through both transcription (CDX2) and pre-mRNA processing (CDX2/AS).

Antiobesity pharmacotherapy: new drugs and emerging targets

Obesity is a growing pandemic, and related health and economic costs are staggering. Pharmacotherapy, partnered with lifestyle modifications, forms the core of current strategies to reduce the burden of this disease and its sequelae. However, therapies targeting weight loss have a significant history of safety risks, including cardiovascular and psychiatric events. Here, evolving strategies for developing antiobesity therapies, including targets, mechanisms, and developmental status, are highlighted. Progress in this field is underscored by Belviq (lorcaserin) and Qsymia (phentermine/topiramate), the first agents in more than 10 years to achieve regulatory approval for chronic weight management in obese patients. On the horizon, novel insights into metabolism and energy homeostasis reveal guanosine 3',5'-cyclic monophosphate (cGMP) signaling circuits as emerging targets for antiobesity pharmacotherapy. These innovations in molecular discovery may elegantly align with practical off-the-shelf approaches, leveraging existing approved drugs that modulate cGMP levels for the management of obesity.

Intestinal GUCY2C prevents TGF-β secretion coordinating desmoplasia and hyperproliferation in colorectal cancer

Tumorigenesis is a multistep process that reflects intimate reciprocal interactions between epithelia and underlying stroma. However, tumor-initiating mechanisms coordinating transformation of both epithelial and stromal components are not defined. In humans and mice, initiation of colorectal cancer is universally associated with loss of guanylin and uroguanylin, the endogenous ligands for the tumor suppressor guanylyl cyclase C (GUCY2C), disrupting a network of homeostatic mechanisms along the crypt-surface axis. Here, we reveal that silencing GUCY2C in human colon cancer cells increases Akt-dependent TGF-β secretion, activating fibroblasts through TGF-β type I receptors and Smad3 phosphorylation. In turn, activating TGF-β signaling induces fibroblasts to secrete hepatocyte growth factor (HGF), reciprocally driving colon cancer cell proliferation through cMET-dependent signaling. Elimination of GUCY2C signaling in mice (Gucy2c(-/-)) produces intestinal desmoplasia, with increased reactive myofibroblasts, which is suppressed by anti-TGF-β antibodies or genetic silencing of Akt. Thus, GUCY2C coordinates intestinal epithelial-mesenchymal homeostasis through reciprocal paracrine circuits mediated by TGF-β and HGF. In that context, GUCY2C signaling constitutes a direct link between the initiation of colorectal cancer and the induction of its associated desmoplastic stromal niche. The recent regulatory approval of oral GUCY2C ligands to treat chronic gastrointestinal disorders underscores the potential therapeutic opportunity for oral GUCY2C hormone replacement to prevent remodeling of the microenvironment essential for colorectal tumorigenesis.

New advances in models and strategies for developing anti-obesity drugs

INTRODUCTION

Obesity is a worldwide pandemic. Obesity-related health and economic costs are staggering. Existing strategies to combat obesity through lifestyle improvements and medical intervention have had limited success. Pharmacotherapy, in combination with lifestyle modification, may play a vital role in reversing the disease burden. However, past and current weight-loss medications have had serious safety risks, notably cardiovascular and psychiatric events.

AREAS COVERED

The authors review the strategies for designing new anti-obesity drugs by describing those currently in development. They describe their target, mechanism of action and developmental or regulatory status. Furthermore, they discuss the problem of weight regain following weight loss, and its relevance to the long-term success of anti-obesity pharmacotherapy.

EXPERT OPINION

For weight management drugs to achieve the safety and efficacy required to be impactful, current studies are uncovering and characterizing new targets, including new signaling circuits and hormones regulating appetite and metabolism, and re-evaluating the role of pharmacotherapy in weight management. To avoid the safety failures of many past weight-loss drugs, the models and strategies covered in this article incorporate recent advances in knowledge and technology. We discuss the emergence of cGMP signaling as a potentially transformative target in weight management. Modulating cGMP signaling may represent an ideal goal for an anti-obesity pharmacotherapy, reflecting some of the major themes described in the present review: targeting pathways that are newly realized as relevant for weight management; promoting safety by re-purposing drugs that are safe, proven, and approved for clinical use; and having a synergistic effect on multiple, reinforcing pathways.

GUCY2C: at the intersection of obesity and cancer

Guanylyl cyclase C (GUCY2C) has canonical centrality in defense of key intestinal homeostatic mechanisms, encompassing fluid and electrolyte balance, epithelial dynamics, antitumorigenesis, and intestinal barrier function. Recent discoveries expand the homeostatic role of GUCY2C to reveal a novel gut-brain endocrine axis regulating appetite, anchored by hypothalamic GUCY2C which is responsive to intestine-derived uroguanylin. Thus, GUCY2C may represent a new target for anti-obesity pharmacotherapy. Moreover, the coincident regulation of energy balance and tumor suppression by a single hormone receptor system suggests that the GUCY2C axis might contribute to the established relationship between obesity and colorectal cancer. This confluence suggests that hormone supplementation to reconstitute GUCY2C signaling may be an elegant strategy to reverse both pathophysiologic processes.

Obesity pharmacotherapy: what is next?

The increase in obesity in the Unites States and around the world in the last decade is overwhelming. The number of overweight adults in the world surpassed 1 billion in 2008. Health hazards associated with obesity are serious and include heart disease, sleep apnea, diabetes, and cancer. Although lifestyle modifications are the most straightforward way to control weight, a large portion of the population may not be able to rely on this modality alone. Thus, the development of anti-obesity therapeutics represents a major unmet medical need. Historically, anti-obesity pharmacotherapies have been unsafe and minimally efficacious. A better understanding of the biology of appetite and metabolism provides an opportunity to develop drugs that may offer safer and more effective alternatives for weight management. This review discusses drugs that are currently on the market and in development as anti-obesity therapeutics based on their target and mechanism of action. It should serve as a roadmap to establish expectations for the near future for anti-obesity drug development.

Regulation of appetite to treat obesity

Obesity has escalated into a pandemic over the past few decades. In turn, research efforts have sought to elucidate the molecular mechanisms underlying the regulation of energy balance. A host of endogenous mediators regulate appetite and metabolism, and thereby control both short- and long-term energy balance. These mediators, which include gut, pancreatic and adipose neuropeptides, have been targeted in the development of anti-obesity pharmacotherapy, with the goal of amplifying anorexigenic and lipolytic signaling or blocking orexigenic and lipogenic signaling. This article presents the efficacy and safety of these anti-obesity drugs.

P5-13-05: Non-Invasive In Vivo 1H Magnetic Resonance Spectroscopy (MRS) Monitoring of Breast Tumor Response to IGF1R Targeted Therapy

Drugs targeting IGF1R are in clinical trials for breast cancer therapy. To date no suitable biomarkers of response have been identified for this therapy. It is important to select patients with tumors sensitive to disruption of IGF1R signaling. In addition, predicting response in patients quickly following initial treatment would also assist in the development of these strategies. While expression of IGF1R must be a minimum requirement for enrolling patients in trials with IGF1R agents, the mere expression of IGF1R is not necessarily sufficient for IGF-driven biology. We have previously shown that monitoring levels of total choline-containing compounds (tCho) non-invasively in breast cancer patients with locally advanced breast cancer is a useful predictor of response to primary systemic therapy. The tCho measured in these studies included choline, phosphocholine (pCho) and glycerophosphocholine (GPC). In this study, we examined if changes in tCho could be used as a marker of response to anti-IGF1R therapy. We tested the effect of two antibodies against IGF1R on intratumoral tCho levels in vivo. Mice bearing MCF-7 xenografts were subjected to MR imaging (MRI) and spectroscopy (MRS) to measure baseline tCho levels. MRI was performed at 4.7 Tesla (200 mHz) with a transceive surface coil. Single-voxel 1H spectroscopy was performed using water suppression and TE-averaging. A fully relaxed, unsuppressed water spectrum from the same voxel was acquired and tCho signal was referenced against the tissue water signal and expressed as mmol/kg water. The next day, mice were treated with 500 μg of scFv-Fc or phosphate buffered saline, or 800 μg EM164 or isotype-matched control antibody. 24 hours post-treatment, tCho was measured. The percent change in tCho 24h after treatment (% tCho24) was determined using the formula 100[(tCho24-tCho0)/tCho0]. In 9 out 10 mice treated with scFv-Fc, % tCho24 ranged from −26 to −81% of baseline levels while in mice treated with PBS the change was from 0% to +46%. EM164 treatment also caused decrease in tCho levels in 3 out of 3 mice while the control antibody did not. tCho was also monitored for a period of 2 weeks during the course of treatment with EM164 or control antibody; EM164 caused a decrease in tCho with % tCho of −35% while the control antibody treated mice showed % tCho of +43% over the two-week treatment. To further delineate the precise choline species regulated by IGF signaling, MCF-7 cells were treated in vitro with IGF-I for 24h and cell extracts subjected to MRS at 14.1 Tesla using a NMR scanner. IGF-I enhanced levels of pCho compared to choline and GPC. We next investigated if there is a mechanistic link between IGF signaling and choline metabolism. MCF-7 cells were treated with IGF-I for 10 minutes or 24h and levels of choline kinase (ChoK), the rate-limiting enzyme that converts choline to pCho and then phosphatidylcholine were examined. Surprisingly, IGF-I signaling enhanced ChoK levels. Our data show that decrease in tCho could be a surrogate marker of early response to anti-IGF1R therapy. Thus, MRS to measure tCho levels could be included in the design of clinical trials with such reagents to quickly identify patients whose tumors are sensitive to inhibition of IGF1R.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-13-05.

A uroguanylin-GUCY2C endocrine axis regulates feeding in mice

Intestinal enteroendocrine cells are critical to central regulation of caloric consumption, since they activate hypothalamic circuits that decrease appetite and thereby restrict meal size by secreting hormones in response to nutrients in the gut. Although guanylyl cyclase and downstream cGMP are essential regulators of centrally regulated feeding behavior in invertebrates, the role of this primordial signaling mechanism in mammalian appetite regulation has eluded definition. In intestinal epithelial cells, guanylyl cyclase 2C (GUCY2C) is a transmembrane receptor that makes cGMP in response to the paracrine hormones guanylin and uroguanylin, which regulate epithelial cell dynamics along the crypt-villus axis. Here, we show that silencing of GUCY2C in mice disrupts satiation, resulting in hyperphagia and subsequent obesity and metabolic syndrome. This defined an appetite-regulating uroguanylin-GUCY2C endocrine axis, which we confirmed by showing that nutrient intake induces intestinal prouroguanylin secretion into the circulation. The prohormone signal is selectively decoded in the hypothalamus by proteolytic liberation of uroguanylin, inducing GUCY2C signaling and consequent activation of downstream anorexigenic pathways. Thus, evolutionary diversification of primitive guanylyl cyclase signaling pathways allows GUCY2C to coordinate endocrine regulation of central food acquisition pathways with paracrine control of intestinal homeostasis. Moreover, the uroguanylin-GUCY2C endocrine axis may provide a therapeutic target to control appetite, obesity, and metabolic syndrome.

Current trends in targeting the hormonal regulation of appetite and energy balance to treat obesity

With the eruption of the obesity pandemic over the past few decades, much research has been devoted to understanding the molecular mechanisms by which the human body regulates energy balance. These studies have revealed several mediators, including gut/pancreatic/adipose hormones and neuropeptides that control both short- and long-term energy balance by regulating appetite and/or metabolism. These endogenous mediators of energy balance have been the focus of many anti-obesity drug-development programs aimed at either amplifying endogenous anorexigenic/lipolytic signaling or blocking endogenous orexigenic/lipogenic signaling. Here, we discuss the efficacy and safety of targeting these pathways for the pharmacologic treatment of obesity.

Bile acids initiate lineage-addicted gastroesophageal tumorigenesis by suppressing the EGF receptor-AKT axis

While bile acids are a risk factor for tumorigenesis induced by reflux disease, the mechanisms by which they contribute to neoplasia remain undefined. Here, we reveal that in gastroesophageal junction (GEJ) cells bile acids activate a tissue-specific developmental program defining the intestinal epithelial cell phenotype characterizing GEJ metaplasia. Deoxycholic acid (DCA) inhibited phosphorylation of EGF receptors (EGFRs) suppressing the proto-oncogene AKT. Suppression of EGFRs and AKT by DCA actuated an intestine-specific cascade in which NF-kappaB transactivated the tissue-specific transcription factor CDX2. In turn, CDX2 orchestrated a lineage-specific differentiation program encompassing genes characterizing intestinal epithelial cells. Conversely, progression from metaplasia to invasive carcinoma in patients, universally associated with autonomous activation of EGFRs and/or AKT, was coupled with loss of this intestinal program. Thus, bile acids induce intestinal metaplasia at the GEJ by activating the lineage-specific differentiation program involving suppression of EGFR and AKT, activating the NF-kappaB-CDX2 axis. Induction of this axis provides the context for lineage-addicted tumorigenesis, in which autonomous activation of AKT corrupts adaptive intestinal NF-kappaB signaling, amplifying tumorigenic programs.

Can colorectal cancer be prevented or treated by oral hormone replacement therapy?

Guanylyl cyclase C (GCC) is the receptor specifically expressed by intestinal cells for the paracrine hormones guanylin and uroguanylin and diarrheagenic bacterial heat-stable enterotoxins. This tissue-specific receptor coordinates lineage-dependent regulation of epithelial homeostasis, and its disruption contributes to intestinal tumorigenesis. It coordinates regenerative and metabolic circuits by restricting the cell cycle and proliferation and programming metabolic transitions central to organizing the dynamic crypt-surface axis. Further, mice deficient in GCC signaling are more susceptible to colon cancer induced by Apc mutations or the carcinogen azoxymethane. Moreover, guanylin and uroguanylin are gene products most commonly lost, early, in colon cancer in animals and humans. The role of GCC as a tumor suppressing receptor regulating proliferation and metabolism, together with the universal loss of guanylin and uroguanylin in tumorigenesis, suggests a model in which colorectal cancer is a paracrine hormone deficiency syndrome. In that context, activation of GCC reverses the tumorigenic phenotype by limiting growth of colorectal cancer cells by restricting progression through the G1/S transition and reprogramming metabolic circuits from glycolysis to oxidative phosphorylation, limiting bioenergetic support for rapid proliferation. These observations suggest a pathophysiological hypothesis in which GCC is a lineage-dependent tumor suppressing receptor coordinating proliferative homeostasis whose dysregulation through hormone loss contributes to neoplasia. The correlative therapeutic hypothesis suggests that colorectal cancer is a disease of hormone insufficiency that can be prevented or treated by oral supplementation with GCC ligands.

GCC signaling in colorectal cancer: Is colorectal cancer a paracrine deficiency syndrome?

Guanylyl cyclase C (GCC) is the receptor expressed by intestinal cells for the paracrine hormones guanylin and uroguanylin that coordinate mucosal homeostasis and its silencing contributes to intestinal transformation. It orchestrates proliferative and metabolic circuits by limiting the cell cycle and programming metabolic transitions central to regeneration along the crypt-villus axis. Mice deficient in GCC are more susceptible to colon cancer induced by germline mutations or carcinogens. Moreover, guanylin and uroguanylin are the most commonly lost gene products in colon cancer. The role of GCC as a tumor suppressor and the universal loss of its hormones in transformation suggest a paradigm in which colorectal cancer is a disease of paracrine hormone insufficiency. Indeed, GCC signaling reverses the tumorigenic phenotype of human colon cancer cells by regulating proliferation and metabolism. These data suggest a pathophysiological hypothesis in which GCC is a tumor suppressor coordinating proliferative homeostasis whose silencing through hormone loss initiates transformation. The correlative therapeutic hypothesis suggests that colorectal cancer is a disease of hormone insufficiency that can be prevented or treated by oral hormone replacement therapy employing GCC ligands.

Guanylyl cyclase C in colorectal cancer: susceptibility gene and potential therapeutic target

Colorectal cancer is one of the leading causes of tumor-related morbidity and mortality worldwide. While mechanisms underlying this disease have been elucidated over the past two decades, these molecular insights have failed to translate into efficacious therapy. The oncogenomic view of cancer suggests that terminal transformation reflects the sequential corruption of signal transduction circuits regulating key homeostatic mechanisms, whose multiplicity underlies the therapeutic resistance of most tumors to interventions targeting individual pathways. Conversely, the paucity of mechanistic insights into proximal pathophysiological processes that initiate and amplify oncogenic circuits preceding accumulation of mutations and transformation impedes development of effective prevention and therapy. In that context, guanylyl cyclase C (GCC), the intestinal receptor for the paracrine hormones guanylin and uroguanylin, whose early loss characterizes colorectal transformation, has emerged as a component of lineage-specific homeostatic programs organizing spatiotemporal patterning along the crypt-surface axis. Dysregulation of GCC signaling, reflecting hormone loss, promotes tumorigenesis through reprogramming of replicative and bioenergetic circuits and genomic instability. Compensatory upregulation of GCC in response to hormone loss provides a unique translational opportunity for prevention and treatment of colorectal tumors by hormone-replacement therapy.

Guanylyl cyclase C as a biomarker for targeted imaging and therapy of metastatic colorectal cancer

The guanylyl cyclase C (GCC) receptor posseses several well-established properties ideal for use as a biomarker in gastrointestinal malignancies. The GCC receptor is constitutively expressed in the apical membranes of the intestine and its expression is universally preserved in primary colorectal tumors and their metastases. Moreover, receptor binding is retained by GCC’s cognate ligand, the bacterial enterotoxin ST, even after conjugation to functional moieties. Selective tumor, but not gastrointestinal, uptake of ST in mice bearing GCC-expressing colon cancer xenografts demonstrates the potential of exploiting ST–GCC interaction for diagnostic imaging and targeted therapy of metastatic colorectal cancer. We expect this specific targeting provided by ST–GCC interaction to improve diagnosis, staging and management of colorectal cancer metastases, and ultimately prolong patient survival in this disease.

Enterotoxin preconditioning restores calcium-sensing receptor-mediated cytostasis in colon cancer cells

Guanylyl cyclase C (GCC), the receptor for diarrheagenic bacterial heat-stable enterotoxins (STs), inhibits colorectal cancer cell proliferation by co-opting Ca(2+) as the intracellular messenger. Similarly, extracellular Ca(2+) (Ca(2+)(o)) opposes proliferation and induces terminal differentiation in intestinal epithelial cells. In that context, human colon cancer cells develop a phenotype characterized by insensitivity to cytostasis imposed by Ca(2+)(o). Here, preconditioning with ST, mediated by GCC signaling through cyclic nucleotide-gated channels, restored Ca(2+)(o)-dependent cytostasis, reflecting posttranscriptional regulation of calcium-sensing receptors (CaRs). ST-induced GCC signaling deployed CaRs to the surface of human colon cancer cells, whereas elimination of GCC signaling in mice nearly abolished CaR expression in enterocytes. Moreover, ST-induced Ca(2+)(o)-dependent cytostasis was abrogated by CaR-specific antisense oligonucleotides. Importantly, following ST preconditioning, newly expressed CaRs at the cell surface represented tumor cell receptor targets for antiproliferative signaling by CaR agonists. Since expression of the endogenous paracrine hormones for GCC is uniformly lost early in carcinogenesis, these observations offer a mechanistic explanation for the Ca(2+)(o)-resistant phenotype of colon cancer cells. Restoration of antitumorigenic CaR signaling by GCC ligand replacement therapy represents a previously unrecognized paradigm for the prevention and treatment of human colorectal cancer employing dietary Ca(2+) supplementation.

Homeostatic control of the crypt-villus axis by the bacterial enterotoxin receptor guanylyl cyclase C restricts the proliferating compartment in intestine

Guanylyl cyclase C (GC-C), the receptor for diarrheagenic enterotoxins and the paracrine ligands guanylin and uroguanylin, regulates intestinal secretion. Beyond volume homeostasis, its importance in modulating cancer cell proliferation and its uniform dysregulation early in colon carcinogenesis, reflecting loss of ligand expression, suggests a role for GC-C in organizing the crypt-villus axis. Here, eliminating GC-C expression in mice increased crypt length along a decreasing rostral-caudal gradient by disrupting component homeostatic processes. Crypt expansion reflected hyperplasia of the proliferating compartment with reciprocal increases in rapidly cycling progenitor cells and reductions in differentiated cells of the secretory lineage, including Paneth and goblet cells, but not enteroendocrine cells. GC-C signaling regulated proliferation by restricting the cell cycle at the G(1)/S transition. Moreover, crypt expansion in GC-C(-/-) mice was associated with adaptive increases in cell migration and apoptosis. Reciprocal alterations in proliferation and differentiation resulting in expansion associated with adaptive responses in migration and apoptosis suggest that GC-C coordinates component processes maintaining homeostasis of the crypt progenitor compartment. In the context of uniform loss of GC-C signaling during tumorigenesis, dysregulation of those homeostatic processes may contribute to mechanisms underlying colon cancer.

The paracrine hormone hypothesis of colorectal cancer

Colorectal carcinogenesis originates in the context of dysregulated epithelial cell homeostasis, wherein hyperproliferation, hypodifferentiation, metabolic reprogramming, and mesenchymal remodeling reflect recursive mutually reinforcing mechanisms contributing to progressive genomic instability. Although genotypic and phenotypic elements characterizing the terminal integration of these pathophysiological processes defining cancer are well enumerated, events initiating, coordinating, and sustaining this hierarchical maladaptive systems evolution remain elusive for most tumors. In the intestine, guanylyl cyclase C (GCC) and its paracrine ligands organize and regulate the homeostatic integrity of the crypt-villus axis, forming a hormonal tumor suppressor signaling sequence, whose dysfunction defines the initiation of neoplastic transformation and creates a permissive niche for tumor progression.

Guanylyl cyclase is an ATP sensor coupling nitric oxide signaling to cell metabolism

Defending cellular integrity against disturbances in intracellular concentrations of ATP ([ATP](i)) is predicated on coordinating the selection of substrates and their flux through metabolic pathways (metabolic signaling), ATP transfer from sites of production to utilization (energetic signaling), and the regulation of processes consuming energy (cell signaling). Whereas NO and its receptor, soluble guanylyl cyclase (sGC), are emerging as key mediators coordinating ATP supply and demand, mechanisms coupling this pathway with metabolic and energetic signaling remain undefined. Here, we demonstrate that sGC is a nucleotide sensor whose responsiveness to NO is regulated by [ATP](i). Indeed, ATP inhibits purified sGC with a K(i) predicting >60% inhibition of NO signaling in cells maintaining physiological [nucleotide](i). ATP inhibits sGC by interacting with a regulatory site that prefers ATP > GTP. Moreover, alterations in [ATP](i), by permeabilization and nucleotide clamping or inhibition of mitochondrial ATP synthase, regulate NO signaling by sGC. Thus, [ATP](i) serves as a "gain control" for NO signaling by sGC. At homeostatic [ATP](i), NO activation of sGC is repressed, whereas insults that reduce [ATP](i,) derepress sGC and amplify responses to NO. Hence, sGC forms a key synapse integrating metabolic, energetic, and cell signaling, wherein ATP is the transmitter, allosteric inhibition the coupling mechanism, and regulated accumulation of cGMP the response.

[Exploration of nursing diagnosis with a cognitive reasoning model]

One of the important topics in theoretic studies on nursing diagnosis, still a new concept in China, is to explore the logical reasoning process from collecting data to making diagnoses. This paper introduced an epistemological model which mentions every step in detail on how to make a nursing diagnosis. The model was built on the basis of analyzing the knowledge structure of nursing diagnosis and applying the methodology of cognitive psychology.

Carpal tunnel syndrome in paraplegic patients

Median nerve compression at the wrist (Carpal Tunnel Syndrome) is commonly associated with local trauma around the flexor retinaculum. Repeated manual activity also exacerbates the disease severity. We undertook a prospective study of the incidence of Carpal Tunnel Syndrome (CTS) in 47 paraplegic patients who have used their hands extensively for daily activity. Since surgical decompression generally provides excellent relief of symptoms, early detection of CTS will be particularly important in these patients. Of the 47 patients studied, 19 had clinical CTS (40%). A total of 91 hands (nerves) were tested with motor and sensory nerve conduction of the median and ulnar nerves. Electrophysiological evidence of CTS was noted in 57 hands (63%). The incidence of CTS appears to be related to the duration of Spinal Cord Injury. Concurrent ulnar neuropathy at the elbow was noted in 19 patients (40%). There was no predisposing factor such as diabetes mellitus in any of these patients, and the compressive neuropathy appears to be purely mechanical.