Utility of muropeptide ligase for identification of inhibitors of the cell wall biosynthesis enzyme MurF

MurF is a key enzyme in the biosynthesis of the bacterial cell wall in both gram-positive and gram-negative bacteria. This enzyme has not been extensively exploited as a drug target, possibly due to the difficulty in obtaining one of the substrates, UDP-MurNAc-L-Ala-gamma-D-Glu-meso-diaminopimelate, which is usually purified from bacteria. We have identified putative inhibitors of Escherichia coli MurF by a binding assay, thus bypassing the need for substrate. Inhibition of enzymatic activity was demonstrated in a high-performance liquid chromatography-based secondary assay with UDP-MurNAc-L-Ala-gamma-D-Glu-diaminopimelate substrate prepared in a novel way by using muropeptide ligase enzyme to add UDP-MurNAc to synthetic L-Ala-gamma-D-Glu-diaminopimelate; the substrate specificity of muropeptide ligase for peptides containing L-Lys in place of diaminopimelate was also investigated. Using the muropeptide ligase-generated MurF substrate, a thiazolylaminopyrimidine series of MurF enzyme inhibitors with 50% inhibitory concentration values as low as 2.5 microM was identified.     

S1P3 confers differential S1P‐induced migration by autoreactive and non‐autoreactive immature B cells and is required for normal B‐cell development

During B‐cell development, immature B‐cell fate is determined by whether the BCR is engaged in the bone marrow. Immature B cells that are non‐autoreactive continue maturation and emigrate from the marrow, whereas autoreactive immature B cells remain and are tolerized. However, the microenvironment where these events occur and the chemoattractants responsible for immature B‐cell trafficking within and out of the bone marrow remain largely undefined. Sphingosine 1‐phosphate (S1P) is a chemoattractant that directs lymphocyte trafficking and thymocyte egress and in this study we investigated whether S1P contributes to B‐cell development, egress and positioning within the bone marrow. Our findings show that immature B cells are chemotactic toward S1P but that this response is dependent on Ag receptor specificity: non‐autoreactive, but not autoreactive, immature B cells migrate toward S1P and are shown to require S1P3 receptor for this response. Despite this response, S1P3 is shown not to facilitate immature B‐cell egress but is required for normal B‐cell development including the positioning of transitional B cells within bone marrow sinusoids. These data indicate that S1P3 signaling directs immature B cells to a bone marrow microenvironment important for both tolerance induction and maturation.     

Treatment outcome in older patients with childhood acute myeloid leukemia

BACKGROUND.

Older age has historically been an adverse prognostic factor in pediatric acute myeloid leukemia (AML). To the authors' knowledge, the impact of age relative to that of other prognostic factors on the outcome of patients treated in recent trials is unknown.

METHODS.

Clinical outcome and causes of treatment failure of 351 patients enrolled on 3 consecutive protocols for childhood AML between 1991 and 2008 were analyzed according to age and protocol.

RESULTS.

The more recent protocol (AML02) produced improved outcomes for patients aged 10 years to 21 years compared with 2 earlier studies (AML91 and AML97), with 3‐year rates of event‐free survival (EFS), overall survival (OS), and cumulative incidence of refractory leukemia or recurrence (CIR) for this group being similar to those of patients aged birth to 9 years: EFS: 58.3% ± 5.4% versus 66.6% ± 4.9% (P = .20); OS: 68.9% ± 5.1% versus 75.1% ± 4.5% (P = .36); and CIR: 21.9% ± 4.4% versus 25.3% ± 4.2% (P = .59). The EFS and OS estimates for patients aged 10 to 15 years overlapped those for patients aged 16 to 21 years. However, the cumulative incidence of toxic death was significantly higher for patients aged 10 to 21 years compared with younger patients (13.2% ± 3.6% vs 4.5% ± 2.0%; P = .028).

CONCLUSIONS.

The survival rate for older children with AML has improved on the results of a recent trial and is now similar to that of younger patients. However, deaths from toxicity remain a significant problem for patients in the older age group. Future trials should focus on improving supportive care while striving to develop more effective antileukemic therapy. Cancer 2012. © 2012 American Cancer Society.     

Advances in LC platforms for drug discovery

Importance of the field: The major application areas of liquid chromatography (LC) in modern drug discovery are the identification and structural characterization of new potential lead compounds from natural and/or synthetic sources and the determination of their physico-chemical and pharmacokinetic properties. Areas covered in this review: Significant advances in terms of LC platforms achieved in the last 5 years are highlighted in this review. Special attention is paid to novel LC strategies used in the discovery of new bioactive molecules and the determination of lipophilicity, pK(a) values, passive drug permeability and in vitro metabolism of new chemical entities. What the reader will gain: Many improvements were achieved in terms of LC instrumentation, columns technology and analytes detection to attain ultra-fast and/or high-resolution chromatographic separations. These advances are particularly beneficial to face the complexity and high number of samples studied in the early phases of the discovery process. Advantages and drawbacks of each strategy are discussed. Take home message: LC and ultra high pressure liquid chromatography coupled with mass spectrometry detection constitute the most promising strategies to achieve high-throughput and/or high-resolution analyses in a drug discovery environment.     

Relief of severe immediate postoperative superior vena cava stenosis with covered stent: Case report with midterm follow up

Sinus venous atrial septal defects are commonly associated with abnormal pulmonary venous connection. Numerous surgical techniques have been proposed with excellent short‐ and long‐term outcomes. Pulmonary and superior vena cava obstructions, as well as rhythm disturbances, are the most common problems seen during follow up. However, acute postoperative superior vena cava obstruction with successful percutaneous covered‐stent implantation has not been reported in the literature. The objective of this study is to report a unique case of acute obstruction of the superior vena cava on the first postoperative day after sinus venous atrial septal defect repair in an infant who was successfully relieved by a percutaneous angioplasty with covered‐stent implantation, and the midterm follow up after this intervention. © 2009 Wiley‐Liss, Inc.     

Genomic analysis reveals few genetic alterations in pediatric acute myeloid leukemia

Pediatric de novo acute myeloid leukemia (AML) is an aggressive malignancy with current therapy resulting in cure rates of only 60%. To better understand the cause of the marked heterogeneity in therapeutic response and to identify new prognostic markers and therapeutic targets a comprehensive list of the genetic mutations that underlie the pathogenesis of AML is needed. To approach this goal, we examined diagnostic leukemic samples from a cohort of 111 children with de novo AML using single-nucleotide-polymorphism microarrays and candidate gene resequencing. Our data demonstrate that, in contrast to pediatric acute lymphoblastic leukemia (ALL), de novo AML is characterized by a very low burden of genomic alterations, with a mean of only 2.38 somatic copy-number alterations per leukemia, and less than 1 nonsynonymous point mutation per leukemia in the 25 genes analyzed. Even more surprising was the observation that 34% of the leukemias lacked any identifiable copy-number alterations, and 28% of the leukemias with recurrent translocations lacked any identifiable sequence or numerical abnormalities. The only exception to the presence of few mutations was acute megakaryocytic leukemias, with the majority of these leukemias being characterized by a high number of copy-number alterations but rare point mutations. Despite the low overall number of lesions across the patient cohort, novel recurring regions of genetic alteration were identified that harbor known, and potential new cancer genes. These data reflect a remarkably low burden of genomic alterations within pediatric de novo AML, which is in stark contrast to most other human malignancies.     

Concomitant choroid plexus papillomas involving the third and fourth ventricles: A case report and review of the literature

Choroid plexus papillomas (CPP) are histopathologically benign and rare central nervous system (CNS) neoplasms arising from the epithelium of the choroid plexus. The most common site of presentation of these lesions is in the fourth ventricle in adults and lateral ventricles in children. Third ventricular CPP are uncommon. In this study, we present a case of a 66-year-old woman with complaints of progressive confusion, lethargy, and weakness who was found to have concomitant third and fourth ventricular masses on imaging studies. The patient underwent a biopsy of the third ventricular mass. The biopsy was followed by staged resections of the fourth and third ventricular masses, respectively. Pathology from the biopsy and both resections was benign CPP. Multifocal concomitant CPP is rare. Concomitant CPPs may be secondary to mere coincidental tumor occurrence or to biologic seeding of cerebrospinal fluid (CSF) from a primary CPP despite otherwise benign histopathology. The primary treatment for CPP is surgical resection. Post-operative chemotherapy or radiation for CPP is of controversial benefit.