Crosstalk between DNA Damage Repair and Metabolic Regulation in Hematopoietic Stem Cells.

Self-renewal and differentiation are two characteristics of hematopoietic stem cells (HSCs). Under steady physiological conditions, most primitive HSCs remain quiescent in the bone marrow (BM). They respond to different stimuli to refresh the blood system. The transition from quiescence to activation is accompanied by major changes in metabolism, a fundamental cellular process in living organisms that produces or consumes energy. Cellular metabolism is now considered to be a key regulator of HSC maintenance. Interestingly, HSCs possess a distinct metabolic profile with a preference for glycolysis rather than oxidative phosphorylation (OXPHOS) for energy production. Byproducts from the cellular metabolism can also damage DNA. To counteract such insults, mammalian cells have evolved a complex and efficient DNA damage repair (DDR) system to eliminate various DNA lesions and guard genomic stability. Given the enormous regenerative potential coupled with the lifetime persistence of HSCs, tight control of HSC genome stability is essential. The intersection of DDR and the HSC metabolism has recently emerged as an area of intense research interest, unraveling the profound connections between genomic stability and cellular energetics. In this brief review, we delve into the interplay between DDR deficiency and the metabolic reprogramming of HSCs, shedding light on the dynamic relationship that governs the fate and functionality of these remarkable stem cells. Understanding the crosstalk between DDR and the cellular metabolism will open a new avenue of research designed to target these interacting pathways for improving HSC function and treating hematologic disorders.

Antibiotic therapy and necrotizing enterocolitis.

Antibiotic therapy remains a cornerstone of treatment of both medical and surgical presentations of necrotizing enterocolitis (NEC). However, guidelines regarding the administration of antibiotics for the treatment of NEC are lacking and practices vary amongst clinicians. Although the pathogenesis of NEC is unknown, there is consensus that the infant gastrointestinal microbiome contributes to the disease. The presumed connection between dysbiosis and NEC has prompted some to study whether early prophylactic enteral antibiotics can prevent NEC. Yet others have taken an opposing approach, studying whether perinatal antibiotic exposure increases the risk of NEC by inducing a state of dysbiosis. This narrative review summarizes what is known about antibiotics and their association with the infant microbiome and NEC, current antibiotic prescribing practices for infants with medical and surgical NEC, as well as potential strategies to further optimize the use of antibiotics in this population of infants.

Contamination source modeling with SCRuB improves cancer phenotype prediction from microbiome data.

Sequencing-based approaches for the analysis of microbial communities are susceptible to contamination, which could mask biological signals or generate artifactual ones. Methods for in silico decontamination using controls are routinely used, but do not make optimal use of information shared across samples and cannot handle taxa that only partially originate in contamination or leakage of biological material into controls. Here we present Source tracking for Contamination Removal in microBiomes (SCRuB), a probabilistic in silico decontamination method that incorporates shared information across multiple samples and controls to precisely identify and remove contamination. We validate the accuracy of SCRuB in multiple data-driven simulations and experiments, including induced contamination, and demonstrate that it outperforms state-of-the-art methods by an average of 15-20 times. We showcase the robustness of SCRuB across multiple ecosystems, data types and sequencing depths. Demonstrating its applicability to microbiome research, SCRuB facilitates improved predictions of host phenotypes, most notably the prediction of treatment response in melanoma patients using decontaminated tumor microbiome data.

Cyclic GMP-AMP synthase contributes to epithelial homeostasis in intestinal inflammation via Beclin-1-mediated autophagy.

Inflammatory bowel disease (IBD) represents a set of idiopathic and chronic inflammatory diseases of the gastrointestinal tract. Central to the pathogenesis of IBD is a dysregulation of normal intestinal epithelial homeostasis. cGAS is a DNA-sensing receptor demonstrated to promote autophagy, a mechanism that removes dysfunctional cellular components. Beclin-1 is a crucial protein involved in the initiation of autophagy. We hypothesized that cGAS plays a key role in intestinal homeostasis by upregulating Beclin-1-mediated autophagy. We evaluated intestinal cGAS levels in humans with IBD and in murine colonic tissue after performing a 2% dextran sulfate sodium (DSS) colitis model. Autophagy and cell death mechanisms were studied in cGAS KO and WT mice via qPCR, WB analysis, H&E, IF, and TUNEL staining. Autophagy was measured in stimulated intestinal epithelial cells (IECs) via WB analysis. Our data demonstrates cGAS to be upregulated during human and murine colitis. Furthermore, cGAS deficiency leads to worsened colitis and decreased levels of autophagy proteins including Beclin-1 and LC3-II. Co-IP demonstrates a direct binding between cGAS and Beclin-1 in IECs. Transfection of cGAS in stimulated HCT-116 cells leads to increased autophagy. IECs isolated from cGAS KO have diminished autophagic flux. cGAS KO mice subjected to DSS have increased cell death and cleaved caspase-3. Lastly, treatment of cGAS KO mice with rapamycin decreased the severity of colitis. Our data suggest that cGAS maintains intestinal epithelial homeostasis during human IBD and murine colitis by upregulating Beclin-1-mediated autophagy and preventing IEC death. Rescue of autophagy can attenuate the severity of colitis associated with cGAS deficiency.

Temporal and Spatial Changes in the Microbiome Following Pediatric Severe Traumatic Brain Injury.

OBJECTIVES: The microbiome may be affected by trauma and critical illness. Many studies of the microbiome in critical illness are restricted to a single body site or time point and confounded by preexisting conditions. We report temporal and spatial alterations in the microbiome of previously healthy children with severe traumatic brain injury (TBI). DESIGN: We collected oral, rectal, and skin swabs within 72 hours of admission and then twice weekly until ICU discharge. Samples were analyzed by 16S rRNA gene amplicon sequencing. Children undergoing elective outpatient surgery served as controls. Alpha and beta diversity comparisons were performed with Phyloseq, and differentially abundant taxa were predicted using Analysis of Composition of Microbiomes. SETTING: Five quaternary-care PICUs. PATIENTS: Patients less than 18 years with severe TBI requiring placement of an intracranial pressure monitor. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Three hundred twenty-seven samples were analyzed from 23 children with severe TBI and 35 controls. The community composition of initial oral (F = 3.2756, R2 = 0.0535, p = 0.012) and rectal (F = 3.0702, R2 = 0.0649, p = 0.007) samples differed between TBI and control patients. Rectal samples were depleted of commensal bacteria from Ruminococcaceae, Bacteroidaceae, and Lachnospiraceae families and enriched in Staphylococcaceae after TBI (p < 0.05). In exploratory analyses, antibiotic exposure, presence of an endotracheal tube, and occurrence of an infection were associated with greater differences of the rectal and oral microbiomes between TBI patients and healthy controls, whereas enteral nutrition was associated with smaller differences (p < 0.05). CONCLUSIONS: The microbiome of children with severe TBI is characterized by early depletion of commensal bacteria, loss of site specificity, and an enrichment of potential pathogens. Additional studies are needed to determine the impact of these changes on clinical outcomes.

Infant gut strain persistence is associated with maternal origin, phylogeny, and traits including surface adhesion and iron acquisition.

Gut microbiome succession affects infant development. However, it remains unclear what factors promote persistence of initial bacterial colonizers in the developing gut. Here, we perform strain-resolved analyses to compare gut colonization of preterm and full-term infants throughout the first year of life and evaluate associations between strain persistence and strain origin as well as genetic potential. Analysis of fecal metagenomes collected from 13 full-term and 9 preterm infants reveals that infants' initially distinct microbiomes converge by age 1 year. Approximately 11% of early colonizers, primarily Bacteroides and Bifidobacterium, persist during the first year of life, and those are more prevalent in full-term, compared with preterm infants. Examination of 17 mother-infant pairs reveals maternal gut strains are significantly more likely to persist in the infant gut than other strains. Enrichment in genes for surface adhesion, iron acquisition, and carbohydrate degradation may explain persistence of some strains through the first year of life.

Time-Dependent Displacement of Commensal Skin Microbes by Pathogens at the Site of Colorectal Surgery.

BACKGROUND: Although the healthy human skin microbiome has been the subject of recent studies, it is not known whether alterations among commensal microbes contribute to surgical site infections (SSIs). Our objective in this study was to characterize temporal and spatial variation in the skin microbiota of patients undergoing colorectal surgery and determine if dysbiosis contributes to SSIs. METHODS: Sixty one adults scheduled to undergo elective colon or rectal resection were identified by convenience sampling. By analyzing bacterial 16S rRNA gene sequences isolated from clinical samples, we used a culture-independent strategy to monitor perioperative changes in microbial diversity of fecal samples and the skin. RESULTS: A total of 990 samples from 61 patients were analyzed. Alpha diversity on the skin decreased after surgery but later recovered at the postoperative clinic visit. In most patients, we observed a transient postoperative loss of skin commensals (Corynebacterium and Propionibacterium) at the surgical site, which were replaced by potential pathogens and intestinal anaerobes (eg, Enterobacteriaceae). These changes were not observed on skin that was uninvolved in the surgical incision (chest wall). One patient developed a wound infection. Incisional skin swabs from this patient demonstrated a sharp postoperative increase in the abundance of Enterococcus, which was also cultured from wound drainage. CONCLUSIONS: We observed reproducible perioperative changes in the skin microbiome following surgery. The low incidence of SSIs in this cohort precluded analysis of associations between dysbiosis and infection. We postulate that real-time monitoring of the skin microbiome could provide actionable findings about the pathogenesis of SSIs.

The Pediatric Surgeon-Scientist: Succeeding in Today's Academic Environment.

BACKGROUND: Pediatric surgeons have long been advocates of basic science research. However, new challenges facing the scientific community have threatened the success of academic surgeons pursuing basic science careers. The purpose of this study was to compare academic pediatric surgeons' perceptions of their ability to effectively conduct basic science research to those of other surgical subspecialties. METHODS: An online survey was distributed to all members of the Association for Academic Surgery and Society of University Surgeons. A total of 1033 members (41%) responded, and 137 (13.3%) were pediatric surgeons. Comparisons were made between the five most-represented surgical subspecialties. Data are presented as reporting percentage and P values by Student's t-test. RESULTS: Among the specialists studied, pediatric surgeons are those most likely to believe that surgeons can succeed as basic scientists in today's research environment. Pediatric surgery reported the highest rates of National Institutes of Health funding of all surgical specialties and the lowest rates of perceived external pressures related to clinical demands, hospital administrative duties, and work-life balance concerns than their surgical peers. CONCLUSIONS: Pediatric surgeons have a more optimistic perspective on the state of basic science research in surgery while exhibiting an enhanced ability to overcome the challenges that surgeon-scientists currently face. Our findings suggest that pediatric surgery may provide a model for succeeding in basic science in today's challenging surgical research environment.

Dietary Cellulose Supplementation Modulates the Immune Response in a Murine Endotoxemia Model.

The role of dietary fiber in chronic inflammatory disorders has been explored, but very little is known about its benefits in acute inflammation. Previously, we have demonstrated that dietary cellulose supplementation confers protection in a murine model of sepsis by promoting the growth of the gut microbiota that are linked to metabolic health. The survival benefit is associated with a decrease in serum concentration of proinflammatory cytokines, reduced neutrophil infiltration in the lungs, and diminished hepatic inflammation. Here, we aim to understand if the benefit of manipulating the gut microbiome exerts a broader "systemic" influence on the immune system in a lethal murine endotoxemia model. We hypothesize that mice-fed high-fiber cellulose (HF) diet will demonstrate a reduction in activated macrophages and dendritic cells (DCs) and a concomitant increase in the suppressive capacity of T-regulatory cells (Tregs) toward T cells responsiveness. We characterized the immunological profile and activation status of macrophages, DCs, and T cells in mice on HF diet that were then subjected to endotoxemia. Supplementation with HF diet decreased the number and activation of splenic macrophages and DCs in mice after LPS administration. Similarly, HF diet amplified the suppressive function of Tregs and induced anergy in T cells as compared with mice on a regular diet. Our data suggest that the use of HF diet can be a simple, yet effective tool that decreases the hepatic DNA-binding activity of NF-κB leading to a reduction in proinflammatory cytokine response in a murine endotoxemia model.

Dysbiosis Across Multiple Body Sites in Critically Ill Adult Surgical Patients.

The microbiota of critically ill patients likely undergoes dramatic changes but has not been rigorously studied with a culture-independent high-throughput approach. The aim of this study was to characterize spatial and temporal variation in the microbiota of critically ill patients. Trauma and acute surgery patients admitted to the intensive care unit (ICU) were sampled at five body sites (stool, tongue, skin, trachea, urine) every 3 to 4 days. A mean of 10.8 samples was collected from 32 patients with a mean sampling period of 8.8 days. Bacterial 16S rRNA sequences were amplified and sequenced for microbiota analyses. Results were compared to data from unhospitalized adult participants in the American Gut and Human Microbiome Projects. Relative to healthy adults, alpha diversity was decreased in ICU gut and skin samples at all time points. Diversity in tongue swabs decreased over time. Beta diversity measures indicated differences in community membership between critically ill and healthy adults at each body site. Taxonomic alterations in the ICU included depletion of important commensal bacteria such as Faecalibacterium in GI samples and Corynebacterium in skin swabs and enrichment with pathogens such as Enterococcus, Mycoplasma, and Staphylococcus. A high proportion of ICU sample sets contained pathogens present simultaneously at three body sites indicating widespread colonization. In several cases, clinically relevant airway infections were preceded by the appearance of the causative pathogen in tracheal microbiome profiles. These results demonstrate that the microbiome of critically ill patients undergoes a loss of diversity, loss of site specificity, and a shift toward dominant pathogens. These changes may provide opportunities to precisely modulate the microbiome and thereby improve patient outcomes.

Acute Appendicitis in Children Is Associated With a Local Expansion of Fusobacteria.

BACKGROUND: Lumenal obstruction has typically been regarded as the cause of acute appendicitis (AA). Recent evidence including data from "antibiotics first" trials suggests that this disease may result from invasion of the appendix by specific pathogens. Small studies have identified an abundance of bacteria from the genus Fusobacterium in appendixes from patients with AA. We aimed to validate these findings in a larger cohort of children with appendicitis in addition to profiling the appendiceal microbiota in a population of children without appendicitis. METHODS: Appendix swabs were collected from children undergoing appendectomy for AA (n = 60), incidental appendectomy for reasons other than appendicitis (n = 18), or ileocecectomy for inflammatory bowel disease (n = 7), in addition to samples from other sites. Bacterial 16S ribosomal RNA gene sequences from each sample were amplified, sequenced, and analyzed with the UPARSE and QIIME programs. RESULTS: We found that the normal human appendix harbors populations of Fusobacteria that are generally absent in fecal samples from healthy adults and children. In patients with AA, Fusobacteria populations proliferate and often persist despite several weeks of broad-spectrum antibiotics prior to surgery. Relative to non-AA samples, AA samples were depleted of sequences from the genus Bacteroides Phylogenetic analysis of sequence data indicates that F. nucleatum, F. necrophorum, and F. varium are the species of Fusobacterium observed in AA samples. CONCLUSIONS: These results indicate that the appendiceal niche harbors distinct microbial populations that likely contribute to the pathogenesis of appendicitis, which may one day be leveraged to improve the diagnosis and/or treatment of patients with AA.

What does it take to be a successful pediatric surgeon-scientist?

BACKGROUND: The factors that contribute to success as a pediatric surgeon-scientist are not well defined. The purpose of this study is to define a group of NIH-funded pediatric surgeons, assess their academic productivity, and elucidate factors that have contributed to their success. METHODS: Pediatric surgeons were queried in the NIH report database to determine NIH funding awarded. Academic productivity was then assessed. An online survey was then targeted to NIH-funded pediatric surgeons. RESULTS: Since 1988, 83 pediatric surgeon-investigators have received major NIH funding. Currently, there are 37 pediatric surgeons with 43 NIH-sponsored awards. The mean h-index of this group of pediatric surgeons was 18 ± 1.1, mean number of publications (since 2001) was 21 ± 2.1, and both increase commensurate with academic rank. In response to the survey, 81% engaged in research during their surgical residency, and 48% were mentored by a pediatric surgeon-scientist. More than 60% of respondents had significant protected time and financial support. Factors felt to be most significant for academic success included mentorship, perseverance, and protected time. CONCLUSIONS: Mentorship, perseverance, institutional commitment to protected research time, and financial support are considered to be important to facilitate the successes of pediatric surgeon-scientists. These results will be useful to aspiring pediatric surgeon-scientists and departments wishing to develop a robust research program.

Acute appendicitis in children is associated with an abundance of bacteria from the phylum Fusobacteria.

BACKGROUND: Although luminal obstruction has traditionally been viewed as the underlying cause of appendicitis, recent evidence has suggested that the disease may result directly from invasion by specific pathogens, e.g. Fusobacterium nucleatum. The purpose of this study was to survey microbial communities within pediatric appendectomy specimens using a culture-independent approach. METHODS: We performed 16S ribosomal gene sequence analysis to profile the microbiota present within luminal fluid obtained from 22 pediatric appendectomy specimens. These included 10 simple appendicitis cases, 5 perforated appendicitis cases, 2 interval appendectomies, and 5 incidental appendectomies. RESULTS: Samples could be divided into 2 distinct clusters based upon the composition of the appendiceal bacterial communities. Appendicitis samples contained an increased abundance of Fusobacterium spp. and a reduced abundance of Bacteroides spp. relative to non-appendicitis cases. Appendicitis samples also contained variable amounts of other oral taxa such as Porphyromonas, Parvimonas, and Gemella, whereas these taxa were generally absent from non-appendicitis samples. CONCLUSIONS: Acute appendicitis is associated with an abundance of Fusobacterium spp. and other pathogens commonly found in the oral cavity. Further research is needed to determine whether these organisms directly cause appendicitis or rather proliferate in the appendix as a secondary consequence of inflammation.

Murine gut microbiota and transcriptome are diet dependent.

OBJECTIVE: Here, we determine how formula feeding impacts the gut microbiota and host transcriptome. BACKGROUND: Formula-fed (FF) infants are at risk for diseases that involve complex interactions between microbes and host immune elements such as necrotizing enterocolitis. The aims of this study were to simultaneously examine the microbiota and host transcriptional profiles of FF and maternal-fed (MF) mice to evaluate how diet impacts gut colonization and host genes. METHODS: After 72 hours of FF or MF, colonic tissue was collected. 16S ribosomal RNA was sequenced with Roche GS-FLX (Genome Sequencer-FLX) pyrosequencing. Operational taxonomical unit clustering, diversity analysis, and principal coordinate analysis (PCA) were performed. Complementary DNA libraries were sequenced by Solexa. Reads were annotated by BLAST (Basic Local Alignment Search Tool) search against mouse RNA database [National Center for Biotechnology Information (NCBI) build-37] and functionally classified using the KOG (Eukaryotic Orthologous Groups) database (NCBI). RESULTS: Firmicutes (P < 0.001) was the dominant phylum in MF pups, whereas Proteobacteria (P < 0.001) and Bacteroidetes (P < 0.05) were dominant in FF mice. On the genus level, FF mice had increased Serratia (P < 0.001) and Lactococcus (P < 0.05) whereas MF mice had increased Lactobacillus (P < 0.001). PCA confirmed clustering by diet. Solexa sequencing demonstrated different (P < 0.05) messenger RNA transcript levels in 148 genes. Heme oxygenase 1 (P < 0.01), an oxidative stress marker, was increased 25-fold in FF mice. In addition, decreased vinculin (P < 0.05), a cytoskeletal protein associated with adherens junctions in FF pups suggested impaired gut structural integrity. Diet also impacted immune regulation, cell cycle control/gene expression, cell motility, and vascular function genes. CONCLUSIONS: FF shifted gut microbiota and structural integrity, oxidative stress, and immune function genes, presumably increasing vulnerability to disease in FF mice. Interrogation of microbial and host gene expression in FF neonates may offer new insight on how diet affects disease pathogenesis.

Intestinal epithelial Toll-like receptor 4 regulates goblet cell development and is required for necrotizing enterocolitis in mice.

BACKGROUND & AIMS: Little is known about factors that regulate intestinal epithelial differentiation; microbial recognition receptors such as Toll-like receptor (TLR)4 might be involved. We investigated whether intestinal TLR4 regulates epithelial differentiation and is involved in development of necrotizing enterocolitis (NEC) of the immature intestine. METHODS: Mice with conditional disruption of TLR4 in the intestinal epithelium and TLR4 knockout (TLR4(-/-)) mice were generated by breeding TLR4(loxp/loxp) mice with villin-cre and Ella-cre, respectively. Enterocytes that did not express or overexpressed TLR4 were created by lentiviral or adenoviral transduction. Intestinal organoids were cultured on tissue matrices. Bile acids were measured by colorimetric assays, and microbial composition was determined by 16S pyrosequencing. NEC was induced in 7- to 10-day-old mice by induction of hypoxia twice daily for 4 days. RESULTS: TLR4(-/-) mice and mice with enterocyte-specific deletion of TLR4 were protected from NEC; epithelial differentiation into goblet cells was increased via suppressed Notch signaling in the small intestinal epithelium. TLR4 also regulates differentiation of goblet cells in intestinal organoid and enterocyte cell cultures; differentiation was increased on deletion of TLR4 and restored when TLR4 was expressed ectopically. TLR4 signaling via Notch was increased in intestinal tissue samples from patients with NEC, and numbers of goblet cells were reduced. 16S pyrosequencing revealed that wild-type and TLR4-deficient mice had similar microbial profiles; increased numbers of goblet cells were observed in mice given antibiotics. TLR4 deficiency reduced levels of luminal bile acids in vivo, and addition of bile acids to TLR4-deficient cell cultures prevented differentiation of goblet cells. CONCLUSIONS: TLR4 signaling and Notch are increased in intestinal tissues of patients with NEC and required for induction of NEC in mice. TLR4 prevents goblet cell differentiation, independently of the microbiota. Bile acids might initiate goblet cell development.

Pediatric surgery and the human microbiome.

Bold advances in the past decade have made it possible to carefully study the contributions of microbes to normal human development and to disease pathogenesis. The intestinal microbiota has been implicated in adult diseases ranging from obesity to cancer, but there have been relatively few investigations of bacteria in surgical diseases of infancy and childhood. In this review, we discuss how novel culture-independent approaches have been harnessed to profile microbes present within clinical specimens. Unique features of the pediatric microbiota and innovative approaches to manipulate the gut flora are also reviewed. Finally, we detail the contributions of gut microbes to 3 diseases relevant to pediatric surgeons: necrotizing enterocolitis, obesity, and inflammatory bowel disease. Current and future research regarding the pediatric microbiota is likely to translate to improved outcomes for infants and children with surgical diseases.

The human microbiome and surgical disease.

OBJECTIVE: The purpose of this review article is to summarize what is currently known about microbes associated with the human body and to provide examples of how this knowledge impacts the care of surgical patients. BACKGROUND: Pioneering research over the past decade has demonstrated that human beings live in close, constant contact with dynamic communities of microbial organisms. This new reality has wide-ranging implications for the care of surgical patients. METHODS AND RESULTS: Recent advances in the culture-independent study of the human microbiome are reviewed. To illustrate the translational relevance of these studies to surgical disease, we discuss in detail what is known about the role of microbes in the pathogenesis of obesity, gastrointestinal malignancies, Crohn disease, and perioperative complications including surgical site infections and sepsis. The topics of mechanical bowel preparation and perioperative antibiotics are also discussed. CONCLUSIONS: Heightened understanding of the microbiome in coming years will likely offer opportunities to refine the prevention and treatment of a wide variety of surgical conditions.

The H+-linked monocarboxylate transporter (MCT1/SLC16A1): a potential therapeutic target for high-risk neuroblastoma.

Neuroblastomas produce high amounts of lactic acid and upregulate the H(+)-linked monocarboxylate transporter isoform 1 (MCT1/SLC16A1). We found elevated MCT1 mRNA levels in fresh neuroblastoma biopsy samples that correlated positively with risk of fatal disease and amplification of the "proto-oncogenic" transcription factor MYCN. We further investigated MCT as a potential therapeutic target in vitro. The neuroblastoma cell lines evaluated were Sk-N-SH, CHP134, IMR32, and NGP. All lines exhibited decreased intracellular pH at low tumor-like extracellular pH. Lonidamine or exogenous lactate further lowered intracellular pH. Immediate early lowering of intracellular pH with lonidamine or lactate at extracellular pH 6.5 correlated positively with diminished cell viability within 48 h. These findings indicate that MCT1 is a potential therapeutic target and that neuroblastoma therapy may be enhanced by therapeutic strategies to inhibit or overwhelm MCT. Additional experiments indicated that the mechanism of cell death by lonidamine or exogenous lactate is similar to that obtained using alpha-cyano-4-OH-cinnamate, a well established MCT inhibitor. Because lactate production is also high in melanoma and many other tumor types, MCT inhibitors may have broad application in cancer treatment. Such treatment would have selectivity by virtue of the acidic milieu surrounding tumors, because MCT is increasingly active as extracellular pH decreases below 7.0 and lactic acid production increases.

Methionine aminopeptidase 2 inhibition is an effective treatment strategy for neuroblastoma in preclinical models.

Tumor vascularity is correlated with an aggressive disease phenotype in neuroblastoma, suggesting that angiogenesis inhibitors may be a useful addition to current therapeutic strategies. We previously showed that the antiangiogenic compound TNP-470, an irreversible methionine aminopeptidase 2 (MetAP2) inhibitor, suppressed local and disseminated human neuroblastoma growth rates in murine models but had significant associated toxicity at the effective dose. We have recently shown that a novel, reversible MetAP2 inhibitor, A-357300, significantly inhibits CHP-134-derived neuroblastoma s.c. xenograft growth rate with a treatment-to-control (T/C) ratio at day 24 of 0.19 (P < 0.001) without toxicity. We now show that the combination of A-357300 with cyclophosphamide at the maximal tolerated dose sustained tumor regression with a T/C at day 48 of 0.16 (P < 0.001) in the CHP-134 xenograft model. A-357300 also significantly inhibited establishment and growth rate of hematogenous metastatic deposits following tail vein inoculation of CHP-134 cells and increased overall survival (P = 0.021). Lastly, A-357300 caused regression of established tumors in a genetically engineered murine model with progression-free survival in five of eight mice (P < 0.0001). There was no evidence of toxicity. These data show that MetAP2 may be an important molecular target for high-risk human neuroblastomas. We speculate that the growth inhibition may be through both tumor cell intrinsic and extrinsic (antiangiogenic) mechanisms. The potential for a wide therapeutic index may allow for treatment strategies that integrate MetAP2 inhibition with conventional cytotoxic compounds.

Dieulafoy's lesion and segmental dilatation of the small bowel: an uncommon cause of gastrointestinal bleeding.

Segmental dilatation of the bowel and Dieulafoy's lesions are uncommon but important causes of gastrointestinal bleeding. These conditions are well described in adults but can occur in children as well. Here, the authors present a case of a boy with gastrointestinal bleeding from an ulcerated Dieulafoy's lesion found concomitantly within a segment of idiopathically dilated ileum. The simultaneous occurrence of both of these lesions in a symptomatic child has not been reported previously.