Persistence of circulating endothelial microparticles in COPD despite smoking cessation.

INTRODUCTION: Increasing evidence links COPD pathogenesis with pulmonary capillary apoptosis. We previously demonstrated that plasma levels of circulating microparticles released from endothelial cells (EMPs) due to apoptosis are elevated in smokers with normal spirometry but low diffusion capacity, that is, with early evidence of lung destruction. We hypothesised that pulmonary capillary apoptosis persists with the development of COPD and assessed its reversibility in healthy smokers and COPD smokers following smoking cessation. METHODS: Pulmonary function and high-resolution CT (HRCT) were assessed in 28 non-smokers, 61 healthy smokers and 49 COPD smokers; 17 healthy smokers and 18 COPD smokers quit smoking for 12 months following the baseline visit. Total EMP (CD42b-CD31+), pulmonary capillary EMP (CD42b-CD31+ACE+) and apoptotic EMP (CD42b-CD62E+/CD42b-CD31+) levels were quantified by flow cytometry. RESULTS: Compared with non-smokers, healthy smokers and COPD smokers had elevated levels of circulating EMPs due to active pulmonary capillary endothelial apoptosis. Levels remained elevated over 12 months in healthy smokers and COPD smokers who continued smoking, but returned to non-smoker levels in healthy smokers who quit. In contrast, levels remained significantly abnormal in COPD smokers who quit. CONCLUSIONS: Pulmonary capillary apoptosis is reversible in healthy smokers who quit, but continues to play a role in COPD pathogenesis in smokers who progressed to airflow obstruction despite smoking cessation. TRIAL REGISTRATION NUMBER: NCT00974064; NCT01776398.

Cigarette smoking induces small airway epithelial epigenetic changes with corresponding modulation of gene expression.

The small airway epithelium (SAE), the first site of smoking-induced lung pathology, exhibits genome-wide changes in gene expression in response to cigarette smoking. Based on the increasing evidence that the epigenome can respond to external stimuli in a rapid manner, we assessed the SAE of smokers for genome-wide DNA methylation changes compared with nonsmokers, and whether changes in SAE DNA methylation were linked to the transcriptional output of these cells. Using genome-wide methylation analysis of SAE DNA of nonsmokers and smokers, the data identified 204 unique genes differentially methylated in SAE DNA of smokers compared with nonsmokers, with 67% of the regions with differential methylation occurring within 2 kb of the transcriptional start site. Among the genes with differential methylation were those related to metabolism, transcription, signal transduction and transport. For the differentially methylated genes, 35 exhibited a correlation with gene expression, 54% with an inverse correlation of DNA methylation with gene expression and 46% a direct correlation. These observations provide evidence that cigarette smoking alters the DNA methylation patterning of the SAE and that, for some genes, these changes are associated with the smoking-related changes in gene expression.

RAS mutations in cutaneous squamous-cell carcinomas in patients treated with BRAF inhibitors.

BACKGROUND: Cutaneous squamous-cell carcinomas and keratoacanthomas are common findings in patients treated with BRAF inhibitors. METHODS: We performed a molecular analysis to identify oncogenic mutations (HRAS, KRAS, NRAS, CDKN2A, and TP53) in the lesions from patients treated with the BRAF inhibitor vemurafenib. An analysis of an independent validation set and functional studies with BRAF inhibitors in the presence of the prevalent RAS mutation was also performed. RESULTS: Among 21 tumor samples, 13 had RAS mutations (12 in HRAS). In a validation set of 14 samples, 8 had RAS mutations (4 in HRAS). Thus, 60% (21 of 35) of the specimens harbored RAS mutations, the most prevalent being HRAS Q61L. Increased proliferation of HRAS Q61L-mutant cell lines exposed to vemurafenib was associated with mitogen-activated protein kinase (MAPK)-pathway signaling and activation of ERK-mediated transcription. In a mouse model of HRAS Q61L-mediated skin carcinogenesis, the vemurafenib analogue PLX4720 was not an initiator or a promoter of carcinogenesis but accelerated growth of the lesions harboring HRAS mutations, and this growth was blocked by concomitant treatment with a MEK inhibitor. CONCLUSIONS: Mutations in RAS, particularly HRAS, are frequent in cutaneous squamous-cell carcinomas and keratoacanthomas that develop in patients treated with vemurafenib. The molecular mechanism is consistent with the paradoxical activation of MAPK signaling and leads to accelerated growth of these lesions. (Funded by Hoffmann-La Roche and others; ClinicalTrials.gov numbers, NCT00405587, NCT00949702, NCT01001299, and NCT01006980.).

Suppression of glomerulonephritis in lupus-prone NZB × NZW mice by RN486, a selective inhibitor of Bruton's tyrosine kinase.

OBJECTIVE: Bruton's tyrosine kinase (BTK) plays a critical role in B cell development and function. We recently described a selective BTK inhibitor, RN486, that blocks B cell receptor (BCR) and Fcγ receptor signaling and is efficacious in animal models of arthritis. The aim of this study was to examine the potential efficacy of BTK in systemic lupus erythematosus (SLE), using an NZB × NZW mouse model of spontaneous SLE. METHODS: Mice received RN486 or its vehicle (administered in chow) at a final concentration of 30 mg/kg for 8 weeks, starting at 32 weeks of age. RESULTS: The administration of RN486 completely stopped disease progression, as determined by histologic and functional analyses of glomerular nephritis. The efficacy was associated with striking inhibition of B cell activation, as demonstrated by a significant reduction in CD69 expression in response to BCR crosslinking. RN486 markedly reduced the secretion of IgG anti-double-stranded DNA (anti-dsDNA) secretion, as determined by enzyme-linked immunosorbent and enzyme-linked immunospot assays. Flow cytometric analysis demonstrated depletion of CD138(high) B220(low) plasma cells in the spleen. RN486 inhibited secretion of IgG anti-dsDNA but not IgM anti-dsDNA, suggesting that pharmacologic blockade of BTK resembles the reported transgenic expression of low levels of endogenous BTK in B cells. In addition, RN486 may also impact the effector function of autoantibodies, as evidenced by a significant reduction in immune complex-mediated activation of human monocytes in vitro and down-regulation of the expression of macrophage-related and interferon-inducible genes in both the kidneys and spleens of treated mice. CONCLUSION: Collectively, our data suggest that BTK inhibitors may simultaneously target autoantibody-producing and effector cells in SLE, thus constituting a promising therapeutic alternative for this disease.

The mRNA level of Charcot-Leyden crystal protein/galectin-10 is a marker for CRTH2 activation in human whole blood in vitro.

CRTH2 is one of the prostaglandin D2 receptors and plays a proinflammatory role in allergic diseases. Gene expression markers in whole blood induced by CRTH2 activation have not previously been reported. Using microarray analyses of 54 675 genes, we revealed modest gene expression changes in human whole blood stimulated in vitro by a selective CRTH2 agonist, DK-PGD2. Five genes were found to exhibit 1.5- to 2.6-fold changes in expression. The expression of Charcot-Leyden crystal protein/galectin-10 (CLC/Gal-10) in particular was consistently enhanced in human whole blood stimulated by DK-PGD2, as confirmed by quantitative real-time polymerase chain reaction analyses. DK-PGD(2)-induced increases in blood CLC/Gal-10 mRNA levels were largely attenuated by the CRTH2 antagonist CAY10471.Thus, the DK-PGD2-induced CLC/Gal-10 mRNA level can serve as a potential marker for monitoring pharmacodynamic effects of blood exposure to CRTH2 modulating agents.

Temporal gene expression profiling indicates early up-regulation of interleukin-6 in isoproterenol-induced myocardial necrosis in rat.

Gene expression was evaluated in the myocardium of male Wistar rats after a single subcutaneous administration of 0.5 mg of isoproterenol, a beta-adrenergic agonist that causes acute tachycardia with subsequent myocardial necrosis. Histology of the heart, clinical chemistry, and hematology were evaluated at 9 time points (0.5 hours to 14 days postinjection). Myocardial gene expression was evaluated at 4 time points (1 hour to 3 days). Contraction bands and loss of cross-striation were identified on phosphotungstic acid-hematoxylin-stained sections 0.5 hours postdosing. Plasma troponin I elevation was detected at 0.5 hours, peaked at 3 hours, and returned to baseline values at 3 days postdosing. Interleukin 6 (Il6) expression spiked at 1 to 3 hours and was followed by a short-lived, time-dependent dysregulation of its downstream targets. Concurrently and consistent with the kinetics of the histologic findings, many pathways indicative of necrosis/apoptosis (p38 mitogen-activated protein kinase [MAPK] signaling, NF-kappaB signaling) and adaptation to hypertension (PPAR signaling) were overrepresented at 3 hours. The 1-day and 3-day time points indicated an adaptive response, with down-regulation of the fatty acid metabolism pathway, up-regulation of the fetal gene program, and superimposed inflammation and repair at 3 days. These results suggest early involvement of Il6 in isoproterenol-induced myocardial necrosis and emphasize the value of early time points in transcriptomic studies.

Learning Science Communication Skills Using Improvisation, Video Recordings, and Practice, Practice, Practice.

Doctoral students in science disciplines spend countless hours learning how to conduct cutting-edge research but very little time learning to communicate the nature and significance of their science to people outside their field. To narrow this disparity, we created an unusual course titled Communicating Science for doctoral science trainees at Rutgers University. Our goal was to help students develop an advanced ability to communicate their research clearly and accurately and to emphasize its value and significance to diverse audiences. Course design included classroom instruction supplemented with improvisation, video recordings, and ample opportunity for students to practice and receive immediate, constructive feedback in a supportive environment. A multidisciplinary faculty with expertise in science, education, communication, and theater arts taught this course. PhD students came from diverse scientific disciplines, ranging from biology and chemistry to civil engineering. Students also completed a capstone project in which they worked with a professional in the academic or private sector to explore a possible career aspiration. Assessment was in the form of feedback on students' oral and poster presentations, and written abstracts about their research. Student evaluations and comments about course format and content were mostly positive and also provided input for ways to improve the course. We discovered that the diversity of scientific backgrounds among our students enhanced their ability to learn how to communicate their science to others outside their disciplines. We are leveraging the success of our initial course offering to reach other student and faculty groups at Rutgers.

Evaluation of a developmental hierarchy for breast cancer cells to assess risk-based patient selection for targeted treatment.

This study proposes that a novel developmental hierarchy of breast cancer (BC) cells (BCCs) could predict treatment response and outcome. The continued challenge to treat BC requires stratification of BCCs into distinct subsets. This would provide insights on how BCCs evade treatment and adapt dormancy for decades. We selected three subsets, based on the relative expression of octamer-binding transcription factor 4 A (Oct4A) and then analysed each with Affymetrix gene chip. Oct4A is a stem cell gene and would separate subsets based on maturation. Data analyses and gene validation identified three membrane proteins, TMEM98, GPR64 and FAT4. BCCs from cell lines and blood from BC patients were analysed for these three membrane proteins by flow cytometry, along with known markers of cancer stem cells (CSCs), CD44, CD24 and Oct4, aldehyde dehydrogenase 1 (ALDH1) activity and telomere length. A novel working hierarchy of BCCs was established with the most immature subset as CSCs. This group was further subdivided into long- and short-term CSCs. Analyses of 20 post-treatment blood indicated that circulating CSCs and early BC progenitors may be associated with recurrence or early death. These results suggest that the novel hierarchy may predict treatment response and prognosis.

Computational dissection of tissue contamination for identification of colon cancer-specific expression profiles.

Microarray profiles of bulk tumor tissues reflect gene expression corresponding to malignant cells as well as to many different types of contaminating normal cells. In this report, we assess the feasibility of querying baseline multitissue transcriptome databases to dissect disease-specific genes. Using colon cancer as a model tumor, we show that the application of Boolean operators (AND, OR, BUTNOT) for database searches leads to genes with expression patterns of interest. The BUTNOT operator for example allows the assignment of "expression signatures" to normal tissue specimens. These expression signatures were then used to computationally identify contaminating cells within conventionally dissected tissue specimens. The combination of several logic operators together with an expression database based on multiple human tissue specimens can resolve the problem of tissue contamination, revealing novel cancer-specific gene expression. Several markers, previously not known to be colon cancer associated, are provided.

Cascades of transcriptional induction during dendritic cell maturation revealed by genome-wide expression analysis.

Dendritic cells (DC) are central regulators of immunity. Signal-induced maturation of DCs is assumed to be the starting point for specific immune responses. To further understand this process, we analyzed the alteration of transcript profiles along the time course of CD40 ligand-induced maturation of human myeloid DCs by Affymetrix GeneChip microarrays covering >6800 genes. Besides rediscovery of genes already described as associated with DC maturation proving reliability of the methods used, we identified clusterin as novel maturation marker. Looking across the time course, we observed synchronized kinetics of distinct functional groups of molecules whose temporal coregulation underscores known cellular events during dendritic cell maturation. For example, an early-peaking wave of inflammatory chemokines was followed by a sustained increase of constitutive chemokines and accompanied by slow but continuous induction of survival proteins. After an immediate but transient induction of cytokine-responsive transcripts, there was an increased expression of a group of genes involved in not only the regulation of cytokine effects, but also of transcription in general. Our results demonstrate that microarray studies along time courses combined with real-time PCR not only discover new marker molecules with functional implications, but also dissect the molecular kinetics of biological processes identifying complex pathways of regulation.

Persistence of smoking-induced dysregulation of miRNA expression in the small airway epithelium despite smoking cessation.

Even after quitting smoking, the risk of the development of chronic obstructive pulmonary disease (COPD) and lung cancer remains significantly higher compared to healthy nonsmokers. Based on the knowledge that COPD and most lung cancers start in the small airway epithelium (SAE), we hypothesized that smoking modulates miRNA expression in the SAE linked to the pathogenesis of smoking-induced airway disease, and that some of these changes persist after smoking cessation. SAE was collected from 10th to 12th order bronchi using fiberoptic bronchoscopy. Affymetrix miRNA 2.0 arrays were used to assess miRNA expression in the SAE from 9 healthy nonsmokers and 10 healthy smokers, before and after they quit smoking for 3 months. Smoking status was determined by urine nicotine and cotinine measurement. There were significant differences in the expression of 34 miRNAs between healthy smokers and healthy nonsmokers (p<0.01, fold-change >1.5), with functions associated with lung development, airway epithelium differentiation, inflammation and cancer. After quitting smoking for 3 months, 12 out of the 34 miRNAs did not return to normal levels, with Wnt/ß-catenin signaling pathway being the top identified enriched pathway of the target genes of the persistent dysregulated miRNAs. In the context that many of these persistent smoking-dependent miRNAs are associated with differentiation, inflammatory diseases or lung cancer, it is likely that persistent smoking-related changes in SAE miRNAs play a role in the subsequent development of these disorders.

Intraflagellar transport gene expression associated with short cilia in smoking and COPD.

Smoking and COPD are associated with decreased mucociliary clearance, and healthy smokers have shorter cilia in the large airway than nonsmokers. We hypothesized that changes in cilia length are consistent throughout the airway, and we further hypothesized that smokers with COPD have shorter cilia than healthy smokers. Because intraflagellar transport (IFT) is the process by which cilia of normal length are produced and maintained, and alterations in IFT lead to short cilia in model organisms, we also hypothesized that smoking induces changes in the expression of IFT-related genes in the airway epithelium of smokers and smokers with COPD. To assess these hypotheses, airway epithelium was obtained via bronchoscopic brushing. Cilia length was assessed by measuring 100 cilia (10 cilia on each of 10 cells) per subject and Affymetrix microarrays were used to evaluate IFT gene expression in nonsmokers and healthy smokers in 2 independent data sets from large and small airway as well as in COPD smokers in a data set from the small airway. In the large and small airway epithelium, cilia were significantly shorter in healthy smokers than nonsmokers, and significantly shorter in COPD smokers than in both healthy smokers and nonsmokers. The gene expression data confirmed that a set of 8 IFT genes were down-regulated in smokers in both data sets; however, no differences were seen in COPD smokers compared to healthy smokers. These results support the concept that loss of cilia length contributes to defective mucociliary clearance in COPD, and that smoking-induced changes in expression of IFT genes may be one mechanism of abnormally short cilia in smokers. Strategies to normalize cilia length may be an important avenue for novel COPD therapies.

RG7212 anti-TWEAK mAb inhibits tumor growth through inhibition of tumor cell proliferation and survival signaling and by enhancing the host antitumor immune response.

PURPOSE: To explore the role of TWEAK in tumor growth and antitumor immune response and the activity and mechanism of RG7212, an antagonistic anti-TWEAK antibody, in tumor models. EXPERIMENTAL DESIGN: TWEAK-induced signaling and gene expression were explored in tumor cell lines and inhibition of these effects and antitumor efficacy with RG7212 treatment was assessed in human tumor xenograft-, patient-derived xenograft, and syngeneic tumor models and phase I patients. Genetic features correlated with antitumor activity were characterized. RESULTS: In tumor cell lines, TWEAK induces proliferation, survival, and NF-κB signaling and gene expression that promote tumor growth and suppress antitumor immune responses. TWEAK-inducible CD274, CCL2, CXCL-10 and -11 modulate T-cell and monocyte recruitment, T-cell activation, and macrophage differentiation. These factors and TWEAK-induced signaling were decreased, and tumor, blood, and spleen immune cell composition was altered with RG7212 treatment in mice. RG7212 inhibits tumor growth in vivo in models with TWEAK receptor, Fn14, expression, and markers of pathway activation. In phase I testing, signs of tumor shrinkage and stable disease were observed without dose-limiting toxicity. In a patient with advanced, Fn14-positive, malignant melanoma with evidence of tumor regression, proliferation markers were dramatically reduced, tumor T-cell infiltration increased, and tumor macrophage content decreased. Antitumor activity, a lack of toxicity in humans and animals and no evidence of antagonism with standard of care or targeted agents in mice, suggests that RG7212 is a promising agent for use in combination therapies in patients with Fn14-positive tumors.

The multifaceted exosome: biogenesis, role in normal and aberrant cellular function, and frontiers for pharmacological and biomarker opportunities.

Exosomes are bioactive vesicles derived from the cell's endosomal membrane system and secreted into surrounding body fluids. Exosomes contain cell and cell-state specific cargos of protein, mRNA and miRNA. Exosome formation, cargo content, and delivery to surrounding cells is of immense biological interest considering the role that exosomes are believed to play in various pathological conditions. They aid antigen presentation by immune cells and can exhibit either anti-inflammatory or pro-inflammatory properties depending on the parent antigen-presenting cell's conditioning. Viruses can hijack a host cell's exosomal machinery to evade host defense systems aiding in the trans-infection of viruses. Tumor derived exosomes may help establish an oncogenic niche systemically via delivery of protein, mRNA, and miRNA that can aid angiogenesis, cell proliferation, and cell survival. Exosomes have also been implicated in the spread of neurodegenerative diseases. Studies have shown that exosomes are selectively taken up by cells distal from their release. They can reprogram the recipient cells due to their active molecular cargo. Cell-lineage and state-specific exosomes imply that they may therefore harbor body fluid-based biomarkers of unparalleled accuracy, particularly for tissues that are difficult or impossible to access. Exosome-specific membrane proteins provide markers enabling exosome identity and selection, while cell type and cell condition-specific protein, mRNA and miRNA cargo provide a rich potential source of biomarkers. This review serves to provide an overview of the current state of the science in the burgeoning field of exosome biology.

Systemic biomarkers of neutrophilic inflammation, tissue injury and repair in COPD patients with differing levels of disease severity.

The identification and validation of biomarkers to support the assessment of novel therapeutics for COPD continues to be an important area of research. The aim of the current study was to identify systemic protein biomarkers correlated with measures of COPD severity, as well as specific protein signatures associated with comorbidities such as metabolic syndrome. 142 protein analytes were measured in serum of 140 patients with stable COPD, 15 smokers without COPD and 30 non-smoking controls. Seven analytes (sRAGE, EN-RAGE, NGAL, Fibrinogen, MPO, TGF-α and HB-EGF) showed significant differences between severe/very severe COPD, mild/moderate COPD, smoking and non-smoking control groups. Within the COPD subjects, univariate and multivariate analyses identified analytes significantly associated with FEV(1), FEV(1)/FVC and DLCO. Most notably, a set of 5 analytes (HB-EGF, Fibrinogen, MCP-4, sRAGE and Sortilin) predicted 21% of the variability in DLCO values. To determine common functions/pathways, analytes were clustered in a correlation network by similarity of expression profile. While analytes related to neutrophil function (EN-RAGE, NGAL, MPO) grouped together to form a cluster associated with FEV(1) related parameters, analytes related to the EGFR pathway (HB-EGF, TGF-α) formed another cluster associated with both DLCO and FEV(1) related parameters. Associations of Fibrinogen with DLCO and MPO with FEV(1)/FVC were stronger in patients without metabolic syndrome (r  =  -0.52, p  =  0.005 and r  =  -0.61, p =  0.023, respectively) compared to patients with coexisting metabolic syndrome (r  =  -0.25, p  =  0.47 and r  =  -0.15, p  =  0.96, respectively), and may be driving overall associations in the general cohort. In summary, our study has identified known and novel serum protein biomarkers and has demonstrated specific associations with COPD disease severity, FEV(1), FEV(1)/FVC and DLCO. These data highlight systemic inflammatory pathways, neutrophil activation and epithelial tissue injury/repair processes as key pathways associated with COPD.

Cellular and molecular characterization of ozone-induced pulmonary inflammation in the Cynomolgus monkey.

We investigated the cellular and molecular effects of ozone exposure in Cynomolgus monkeys. Thirty-six Cynomolgus monkeys were exposed to single or repeat ozone challenge. Pulmonary inflammation was assessed using bronchoalveolar lavage fluid (BAL) and histology. Gene expression profiling in lung and blood was performed. Ozone challenge evoked BAL cellular inflammation and increases in total protein, alkaline phosphatase and cytokines. Lung histology revealed cellular inflammation and epithelial necrosis. Gene expression profiling identified oxidative phosphorylation, immune response and cell adhesion pathways altered in response to ozone, with common and unique profiles in lung and blood. Lipocalin 2, CD177, the FK-506 and S100A8 binding proteins and ST-2 represent novel peripheral biomarkers of ozone toxicity. Repeat ozone challenge evoked reproducible inflammation but attenuated cell damage. These studies provide data on the molecular mechanisms and biomarker identification of ozone-evoked toxicity, and support the use of the Cynomolgus monkey as a model of human ozone challenge.

Primary endothelial damage is the mechanism of cardiotoxicity of tubulin-binding drugs.

The use of tubulin binders (TBs) in the treatment of cancer often is associated with cardiotoxicity, the mechanism of which has not been elucidated. To test the hypothesis that interstitial cells of the myocardium are the primary target of TBs, we evaluated the acute effects of a single iv administration of three reference TBs: colchicine (0.2 and 2 mg/kg), vinblastine (0.5 and 3 mg/kg), and vincristine (0.1 and 1 mg/kg) 6 and 24 h after dosing. Mitotic arrest was identified at 24 h in all high-dose groups based on an increase in the number of mitotic figures in the interstitium coupled with a decrease in the number of Ki67-positive interstitial cells. Analysis of the myocardial transcriptomic data further supported G2/M cell cycle arrest 6 h after dosing with the high-dose groups of all three compounds. Apoptotic figures and an increase in the number of cleaved caspase 3-positive cells were identified at 6 and 24 h at the highest dose of each compound predominantly in interstitial cells, whereas a few cardiomyocytes were affected as well. Transcriptomic profiling of the myocardium further suggested that some of the affected interstitial cells were endothelial cells based on the upregulation of genes typically associated with vascular damage and downregulation of endothelial cell-specific molecule 1 and apelin. Taken together, these data identify endothelial cells of the myocardium as the primary target of the cardiotoxicity of TBs and identify cell cycle arrest as the mechanism of this toxicity.

Preclinical biomarkers for a cyclin-dependent kinase inhibitor translate to candidate pharmacodynamic biomarkers in phase I patients.

A genomics-based approach to identify pharmacodynamic biomarkers was used for a cyclin-dependent kinase inhibitory drug. R547 is a potent cyclin-dependent kinase inhibitor with a potent antiproliferative effect at pharmacologically relevant doses and is currently in phase I clinical trials. Using preclinical data derived from microarray experiments, we identified pharmacodynamic biomarkers to test in blood samples from patients in clinical trials. These candidate biomarkers were chosen based on several criteria: relevance to the mechanism of action of R547, dose responsiveness in preclinical models, and measurable expression in blood samples. We identified 26 potential biomarkers of R547 action and tested their clinical validity in patient blood samples by quantitative real-time PCR analysis. Based on the results, eight genes (FLJ44342, CD86, EGR1, MKI67, CCNB1, JUN, HEXIM1, and PFAAP5) were selected as dose-responsive pharmacodynamic biomarkers for phase II clinical trials.

Preclinical profile of a potent gamma-secretase inhibitor targeting notch signaling with in vivo efficacy and pharmacodynamic properties.

Notch signaling is an area of great interest in oncology. RO4929097 is a potent and selective inhibitor of gamma-secretase, producing inhibitory activity of Notch signaling in tumor cells. The RO4929097 IC50 in cell-free and cellular assays is in the low nanomolar range with >100-fold selectivity with respect to 75 other proteins of various types (receptors, ion channels, and enzymes). RO4929097 inhibits Notch processing in tumor cells as measured by the reduction of intracellular Notch expression by Western blot. This leads to reduced expression of the Notch transcriptional target gene Hes1. RO4929097 does not block tumor cell proliferation or induce apoptosis but instead produces a less transformed, flattened, slower-growing phenotype. RO4929097 is active following oral dosing. Antitumor activity was shown in 7 of 8 xenografts tested on an intermittent or daily schedule in the absence of body weight loss or Notch-related toxicities. Importantly, efficacy is maintained after dosing is terminated. Angiogenesis reverse transcription-PCR array data show reduced expression of several key angiogenic genes. In addition, comparative microarray analysis suggests tumor cell differentiation as an additional mode of action. These preclinical results support evaluation of RO4929097 in clinical studies using an intermittent dosing schedule. A multicenter phase I dose escalation study in oncology is under way.

Small-molecule MDM2 antagonists reveal aberrant p53 signaling in cancer: implications for therapy.

The p53 tumor suppressor retains its wild-type conformation and transcriptional activity in half of all human tumors, and its activation may offer a therapeutic benefit. However, p53 function could be compromised by defective signaling in the p53 pathway. Using a small-molecule MDM2 antagonist, nutlin-3, to probe downstream p53 signaling we find that the cell-cycle arrest function of the p53 pathway is preserved in multiple tumor-derived cell lines expressing wild-type p53, but many have a reduced ability to undergo p53-dependent apoptosis. Gene array analysis revealed attenuated expression of multiple apoptosis-related genes. Cancer cells with mdm2 gene amplification were most sensitive to nutlin-3 in vitro and in vivo, suggesting that MDM2 overexpression may be the only abnormality in the p53 pathway of these cells. Nutlin-3 also showed good efficacy against tumors with normal MDM2 expression, suggesting that many of the patients with wild-type p53 tumors may benefit from antagonists of the p53-MDM2 interaction.