Leptin levels in human and rodent: measurement of plasma leptin and ob RNA in obese and weight-reduced subjects

Leptin, the gene product of the obese gene, may play an important role in regulating body weight by signalling the size of the adipose tissue mass. Plasma leptin was found to be highly correlated with body mass index (BMI) in rodents and in 87 lean and obese humans. In humans, there was variability in plasma leptin at each BMI suggesting that there are differences in its secretion rate from fat. Weight loss due to food restriction was associated with a decrease in plasma leptin in samples from mice and obese humans.

Polarization of tumor-associated neutrophil phenotype by TGF-beta: "N1" versus "N2" TAN

TGF-beta blockade significantly slows tumor growth through many mechanisms, including activation of CD8(+) T cells and macrophages. Here, we show that TGF-beta blockade also increases neutrophil-attracting chemokines, resulting in an influx of CD11b(+)/Ly6G(+) tumor-associated neutrophils (TANs) that are hypersegmented, more cytotoxic to tumor cells, and express higher levels of proinflammatory cytokines. Accordingly, following TGF-beta blockade, depletion of these neutrophils significantly blunts antitumor effects of treatment and reduces CD8(+) T cell activation. In contrast, in control tumors, neutrophil depletion decreases tumor growth and results in more activated CD8(+) T cells intratumorally. Together, these data suggest that TGF-beta within the tumor microenvironment induces a population of TAN with a protumor phenotype. TGF-beta blockade results in the recruitment and activation of TANs with an antitumor phenotype.

Managing toxicities associated with immune checkpoint inhibitors: consensus recommendations from the Society for Immunotherapy of Cancer (SITC) Toxicity Management Working Group

Cancer immunotherapy has transformed the treatment of cancer. However, increasing use of immune-based therapies, including the widely used class of agents known as immune checkpoint inhibitors, has exposed a discrete group of immune-related adverse events (irAEs). Many of these are driven by the same immunologic mechanisms responsible for the drugs' therapeutic effects, namely blockade of inhibitory mechanisms that suppress the immune system and protect body tissues from an unconstrained acute or chronic immune response. Skin, gut, endocrine, lung and musculoskeletal irAEs are relatively common, whereas cardiovascular, hematologic, renal, neurologic and ophthalmologic irAEs occur much less frequently. The majority of irAEs are mild to moderate in severity; however, serious and occasionally life-threatening irAEs are reported in the literature, and treatment-related deaths occur in up to 2% of patients, varying by ICI. Immunotherapy-related irAEs typically have a delayed onset and prolonged duration compared to adverse events from chemotherapy, and effective management depends on early recognition and prompt intervention with immune suppression and/or immunomodulatory strategies. There is an urgent need for multidisciplinary guidance reflecting broad-based perspectives on how to recognize, report and manage organ-specific toxicities until evidence-based data are available to inform clinical decision-making. The Society for Immunotherapy of Cancer (SITC) established a multidisciplinary Toxicity Management Working Group, which met for a full-day workshop to develop recommendations to standardize management of irAEs. Here we present their consensus recommendations on managing toxicities associated with immune checkpoint inhibitor therapy.

Mutant presenilins of Alzheimer's disease increase production of 42-residue amyloid beta-protein in both transfected cells and transgenic mice

The mechanism by which mutations in the presenilin (PS) genes cause the most aggressive form of early-onset Alzheimer's disease (AD) is unknown, but fibroblasts from mutation carriers secrete increased levels of the amyloidogenic A beta 42 peptide, the main component of AD plaques. We established transfected cell and transgenic mouse models that coexpress human PS and amyloid beta-protein precursor (APP) genes and analyzed quantitatively the effects of PS expression on APP processing. In both models, expression of wild-type PS genes did not alter APP levels, alpha- and beta-secretase activity and A beta production. In the transfected cells, PS1 and PS2 mutations caused a highly significant increase in A beta 42 secretion in all mutant clones. Likewise, mutant but not wildtype PS1 transgenic mice showed significant overproduction of A beta 42 in the brain, and this effect was detectable as early as 2-4 months of age. Different PS mutations had differential effects on A beta generation. The extent of A beta 42 increase did not correlate with presenilin expression levels. Our data demonstrate that the presenilin mutations cause a dominant gain of function and may induce AD by enhancing A beta 42 production, thus promoting cerebral beta-amyloidosis.

REST: a mammalian silencer protein that restricts sodium channel gene expression to neurons

Expression of the type II voltage-dependent sodium channel gene is restricted to neurons by a silencer element active in nonneuronal cells. We have cloned cDNA coding for a transcription factor (REST) that binds to this silencer element. Expression of a recombinant REST protein confers the ability to silence type II reporter genes in neuronal cell types lacking the native REST protein, whereas expression of a dominant negative form of REST in nonneuronal cells relieves silencing mediated by the native protein. REST transcripts in developing mouse embryos are detected ubiquitously outside of the nervous system. We propose that expression of the type II sodium channel gene in neurons reflects a default pathway that is blocked in nonneuronal cells by the presence of REST.

Activin receptor-like kinase 1 modulates transforming growth factor-beta 1 signaling in the regulation of angiogenesis

The activin receptor-like kinase 1 (ALK1) is a type I receptor for transforming growth factor-beta (TGF-beta) family proteins. Expression of ALK1 in blood vessels and mutations of the ALK1 gene in human type II hereditary hemorrhagic telangiectasia patients suggest that ALK1 may have an important role during vascular development. To define the function of ALK1 during development, we inactivated the ALK1 gene in mice by gene targeting. The ALK1 homozygous embryos die at midgestation, exhibiting severe vascular abnormalities characterized by excessive fusion of capillary plexes into cavernous vessels and hyperdilation of large vessels. These vascular defects are associated with enhanced expression of angiogenic factors and proteases and are characterized by deficient differentiation and recruitment of vascular smooth muscle cells. The blood vessel defects in ALK1-deficient mice are reminiscent of mice lacking TGF-beta1, TGF-beta type II receptor (TbetaR-II), or endoglin, suggesting that ALK1 may mediate TGF-beta1 signal in endothelial cells. Consistent with this hypothesis, we demonstrate that ALK1 in endothelial cells binds to TGF-beta1 and TbetaR-II. Furthermore, the ALK1 signaling pathway can inhibit TGF-beta1-dependent transcriptional activation mediated by the known TGF-beta1 type I receptor, ALK5. Taken together, our results suggest that the balance between the ALK1 and ALK5 signaling pathways in endothelial cells plays a crucial role in determining vascular endothelial properties during angiogenesis.

Deregulation of glucose transporter 1 and glycolytic gene expression by c-Myc

Unlike normal mammalian cells, which use oxygen to generate energy, cancer cells rely on glycolysis for energy and are therefore less dependent on oxygen. We previously observed that the c-Myc oncogenic transcription factor regulates lactate dehydrogenase A and induces lactate overproduction. We, therefore, sought to determine whether c-Myc controls other genes regulating glucose metabolism. In Rat1a fibroblasts and murine livers overexpressing c-Myc, the mRNA levels of the glucose transporter GLUT1, phosphoglucose isomerase, phosphofructokinase, glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase, and enolase were elevated. c-Myc directly transactivates genes encoding GLUT1, phosphofructokinase, and enolase and increases glucose uptake in Rat1 fibroblasts. Nuclear run-on studies confirmed that the GLUT1 transcriptional rate is elevated by c-Myc. Our findings suggest that overexpression of the c-Myc oncoprotein deregulates glycolysis through the activation of several components of the glucose metabolic pathway.

Cerberus is a head-inducing secreted factor expressed in the anterior endoderm of Spemann's organizer

An abundant cDNA enriched in Spemann's organizer, cerberus, was isolated by differential screening. It encodes a secreted protein that is expressed in the anterior endomesoderm. Microinjection of cerberus mRNA into Xenopus embryos induces ectopic heads, and duplicated hearts and livers. The results suggest a role for a molecule expressed in the anterior endoderm in the induction of head structures in the vertebrate embryo.

The genome of the natural genetic engineer Agrobacterium tumefaciens C58

The 5.67-megabase genome of the plant pathogen Agrobacterium tumefaciens C58 consists of a circular chromosome, a linear chromosome, and two plasmids. Extensive orthology and nucleotide colinearity between the genomes of A. tumefaciens and the plant symbiont Sinorhizobium meliloti suggest a recent evolutionary divergence. Their similarities include metabolic, transport, and regulatory systems that promote survival in the highly competitive rhizosphere; differences are apparent in their genome structure and virulence gene complement. Availability of the A. tumefaciens sequence will facilitate investigations into the molecular basis of pathogenesis and the evolutionary divergence of pathogenic and symbiotic lifestyles.

C-Reactive protein binds to apoptotic cells, protects the cells from assembly of the terminal complement components, and sustains an antiinflammatory innate immune response: implications for systemic autoimmunity

C-reactive protein (CRP) is a serum protein that is massively induced as part of the innate immune response to infection and tissue injury. As CRP has been detected in damaged tissues and is known to activate complement, we assessed whether apoptotic lymphocytes bound CRP and determined the effect of binding on innate immunity. CRP bound to apoptotic cells in a Ca(2+)-dependent manner and augmented the classical pathway of complement activation but protected the cells from assembly of the terminal complement components. Furthermore, CRP enhanced opsonization and phagocytosis of apoptotic cells by macrophages associated with the expression of the antiinflammatory cytokine transforming growth factor beta. The antiinflammatory effects of CRP required C1q and factor H and were not effective once cells had become necrotic. These observations demonstrate that CRP and the classical complement components act in concert to promote noninflammatory clearance of apoptotic cells and may help to explain how deficiencies of the classical pathway and certain pentraxins lead to impaired handling of apoptotic cells and increased necrosis with the likelihood of immune response to self.

Regulation of angiogenesis in vivo by ligation of integrin alpha5beta1 with the central cell-binding domain of fibronectin

Angiogenesis depends on the cooperation of growth factors and cell adhesion events. Although alphav integrins have been shown to play critical roles in angiogenesis, recent studies in alphav-null mice suggest that other adhesion receptors and their ligands also regulate this process. Evidence is now provided that the integrin alpha5beta1 and its ligand fibronectin are coordinately up-regulated on blood vessels in human tumor biopsies and play critical roles in angiogenesis, resulting in tumor growth in vivo. Angiogenesis induced by multiple growth factors in chick embryos was blocked by monoclonal antibodies to the cell-binding domain of fibronectin. Furthermore, application of fibronectin or a proteolytic fragment of fibronectin containing the central cell-binding domain to the chick chorioallantoic membrane enhanced angiogenesis in an integrin alpha5beta1-dependent manner. Importantly, antibody, peptide, and novel nonpeptide antagonists of integrin alpha5beta1 blocked angiogenesis induced by several growth factors but had little effect on angiogenesis induced by vascular endothelial growth factor (VEGF) in both chick embryo and murine models. In fact, these alpha5beta1 antagonists inhibited tumor angiogenesis, thereby causing regression of human tumors in animal models. Thus, fibronectin and integrin alpha5beta1, like integrin alphavbeta3, contribute to an angiogenesis pathway that is distinct from VEGF-mediated angiogenesis, yet important for the growth of tumors.

Radiation hybrid mapping: a somatic cell genetic method for constructing high-resolution maps of mammalian chromosomes

Radiation hybrid (RH) mapping, a somatic cell genetic technique, was developed as a general approach for constructing long-range maps of mammalian chromosomes. This statistical method depends on x-ray breakage of chromosomes to determine the distances between DNA markers, as well as their order on the chromosome. In addition, the method allows the relative likelihoods of alternative marker orders to be determined. The RH procedure was used to map 14 DNA probes from a region of human chromosome 21 spanning 20 megabase pairs. The map was confirmed by pulsed-field gel electrophoretic analysis. The results demonstrate the effectiveness of RH mapping for constructing high-resolution, contiguous maps of mammalian chromosomes.

Structural basis of the redox switch in the OxyR transcription factor

The Escherichia coli OxyR transcription factor senses H2O2 and is activated through the formation of an intramolecular disulfide bond. Here we present the crystal structures of the regulatory domain of OxyR in its reduced and oxidized forms, determined at 2.7 A and 2.3 A resolutions, respectively. In the reduced form, the two redox-active cysteines are separated by approximately 17 A. Disulfide bond formation in the oxidized form results in a significant structural change in the regulatory domain. The structural remodeling, which leads to different oligomeric associations, accounts for the redox-dependent switch in OxyR and provides a novel example of protein regulation by "fold editing" through a reversible disulfide bond formation within a folded domain.

Akt/PKB promotes cancer cell invasion via increased motility and metalloproteinase production

The Akt/protein kinase B (PKB) serine/threonine kinase is well known as an important mediator of many cell survival signaling pathways. Here, we demonstrate for the first time a major role of Akt/PKB in the cell invasion properties of the highly metastatic cell line HT1080. Using confocal microscopic analyses of live samples, we found Akt/PKB to be localized in the leading edge membrane area of migrating HT1080 cells. This localization was dependent on phosphoinositide 3-kinase and required the lipid binding ability of the phosphoinositide binding pleckstrin homology domain of Akt/PKB. We examined the possible function of Akt/PKB in HT1080 invasion. Surprisingly, Akt/PKB potently promoted HT1080 invasion, by increasing cell motility and matrix metalloproteinase-9 (MMP-9) production, in a manner highly dependent on its kinase activity and membrane-translocating ability. The increase in MMP-9 production was mediated by activation of nuclear factor-kappaB transcriptional activity by Akt/PKB. However, Akt/PKB did not affect the cell-cell or cell-matrix adhesion properties of HT1080. Our findings thus establish Akt/PKB as a major factor in the invasive abilities of cancer cells.

Lack of the burst firing of thalamocortical relay neurons and resistance to absence seizures in mice lacking alpha(1G) T-type Ca(2+) channels

T-type Ca(2+) currents have been proposed to be involved in the genesis of spike-and-wave discharges, a sign of absence seizures, but direct evidence in vivo to support this hypothesis has been lacking. To address this question, we generated a null mutation of the alpha(1G) subunit of T-type Ca(2+) channels. The thalamocortical relay neurons of the alpha(1G)-deficient mice lacked the burst mode firing of action potentials, whereas they showed the normal pattern of tonic mode firing. The alpha(1G)-deficient thalamus was specifically resistant to the generation of spike-and-wave discharges in response to GABA(B) receptor activation. Thus, the modulation of the intrinsic firing pattern mediated by alpha(1G) T-type Ca(2+) channels plays a critical role in the genesis of absence seizures in the thalamocortical pathway.

PRMT1 is the predominant type I protein arginine methyltransferase in mammalian cells

Type I protein arginine methyltransferases catalyze the formation of asymmetric omega-N(G),N(G)-dimethylarginine residues by transferring methyl groups from S-adenosyl-L-methionine to guanidino groups of arginine residues in a variety of eucaryotic proteins. The predominant type I enzyme activity is found in mammalian cells as a high molecular weight complex (300-400 kDa). In a previous study, this protein arginine methyltransferase activity was identified as an additional activity of 10-formyltetrahydrofolate dehydrogenase (FDH) protein. However, immunodepletion of FDH activity in RAT1 cells and in murine tissue extracts with antibody to FDH does not diminish type I methyltransferase activity toward the methyl-accepting substrates glutathione S-transferase fibrillarin glycine arginine domain fusion protein or heterogeneous nuclear ribonucleoprotein A1. Similarly, immunodepletion with anti-FDH antibody does not remove the endogenous methylating activity for hypomethylated proteins present in extracts from adenosine dialdehyde-treated RAT1 cells. In contrast, anti-PRMT1 antibody can remove PRMT1 activity from RAT1 extracts, murine tissue extracts, and purified rat liver FDH preparations. Tissue extracts from FDH(+/+), FDH(+/-), and FDH(-/-) mice have similar protein arginine methyltransferase activities but high, intermediate, and undetectable FDH activities, respectively. Recombinant glutathione S-transferase-PRMT1, but not purified FDH, can be cross-linked to the methyl-donor substrate S-adenosyl-L-methionine. We conclude that PRMT1 contributes the major type I protein arginine methyltransferase enzyme activity present in mammalian cells and tissues.

Specific and nonspecific NK cell activation during virus infection

The natural killer (NK) cell activation receptor Ly49H is required for resistance to murine cytomegalovirus (MCMV). We show here that NK cell proliferation and production of interferon-gamma (IFN-gamma) was not dependent on Ly49H expression during early MCMV infection. During a later phase of infection, however, Ly49H+ NK cells selectively proliferated and this expansion was blocked by anti-Ly49H administration. With vaccinia virus infection, neither the early nor late phase of NK cell proliferation was selective for Ly49H+ NK cells. These findings indicated that Ly49H+ NK cells were specifically activated by MCMV and that MCMV infection was characterized by nonspecific and specific phases of NK cell activation in vivo.

In vivo natural killer cell activities revealed by natural killer cell-deficient mice

Studies of natural killer (NK) cell function in vivo have been challenging primarily due to the lack of animal models in which NK cells are genetically and selectively deficient. Here, we describe a transgenic mouse with defective natural killing and selective deficiency in NK1.1(+) CD3(-) cells. Despite functionally normal B, T, and NK/T cells, transgenic mice displayed impaired acute in vivo rejection of tumor cells. Adoptive transfer experiments confirmed that NK1.1(+) CD3(-) cells were responsible for acute tumor rejection, establishing the relationship of NK1.1(+) CD3(-) cells to NK cells. Additional studies provided evidence that (i) NK cells play an important role in suppressing tumor metastasis and outgrowth; (ii) NK cells are major producers of IFNgamma in response to bacterial endotoxin but not to interleukin-12, and; (iii) NK cells are not essential for humoral responses to T cell-independent type 2 antigen or the generalized Shwartzman reaction, both of which were previously proposed to involve NK cells.

Weighted-ensemble Brownian dynamics simulations for protein association reactions

A new method, weighted-ensemble Brownian dynamics, is proposed for the simulation of protein-association reactions and other events whose frequencies of outcomes are constricted by free energy barriers. The method features a weighted ensemble of trajectories in configuration space with energy levels dictating the proper correspondence between "particles" and probability. Instead of waiting a very long time for an unlikely event to occur, the probability packets are split, and small packets of probability are allowed to diffuse almost immediately into regions of configuration space that are less likely to be sampled. The method has been applied to the Northrup and Erickson (1992) model of docking-type diffusion-limited reactions and yields reaction rate constants in agreement with those obtained by direct Brownian simulation, but at a fraction of the CPU time (10(-4) to 10(-3), depending on the model). Because the method is essentially a variant of standard Brownian dynamics algorithms, it is anticipated that weighted-ensemble Brownian dynamics, in conjunction with biophysical force models, can be applied to a large class of association reactions of interest to the biophysics community.

Phage treatment of an aortic graft infected with Pseudomonas aeruginosa

Management of prosthetic vascular graft infections caused by Pseudomonas aeruginosa can be a significant challenge to clinicians. These infections often do not resolve with antibiotic therapy alone due to antibiotic resistance/tolerance by bacteria, poor ability of antibiotics to permeate/reduce biofilms and/or other factors. Bacteriophage OMKO1 binding to efflux pump proteins in P. aeruginosa was consistent with an evolutionary trade-off: wildtype bacteria were killed by phage whereas evolution of phage-resistance led to increased antibiotic sensitivity. However, phage clinical-use has not been demonstrated. Here, we present a case report detailing therapeutic application of phage OMKO1 to treat a chronic P. aeruginosa infection of an aortic Dacron graft with associated aorto-cutaneous fistula. Following a single application of phage OMKO1 and ceftazidime, the infection appeared to resolve with no signs of recurrence.

Estrogen inhibits the vascular injury response in estrogen receptor alpha-deficient mice

The atheroprotective effects of estrogen in women are well recognized, but the underlying mechanisms responsible are not well understood. Blood vessel cells express the classic estrogen receptor, ER alpha (ref. 2-6), and are directly affected by estrogen, which inhibits the development of atherosclerotic and injury-induced vascular lesions. We have generated mice in which the ER alpha gene is disrupted and have used a mouse model of carotid arterial injury to compare the effects of estrogen on wild-type and estrogen receptor-deficient mice. Increases in vascular medial area and smooth muscle cell proliferation were quantified following vascular injury in ovariectomized mice treated with vehicle or with physiologic levels of 17 beta-estradiol. Surprisingly, in both wild-type and estrogen receptor-deficient mice, 17 beta-estradiol markedly inhibited to the same degree all measures of vascular injury. These data demonstrate that estrogen inhibits vascular by a novel mechanism that is independent of the classic estrogen receptor, ER alpha.

"Fluorescent timer": protein that changes color with time

We generated a mutant of the red fluorescent protein drFP583. The mutant (E5) changes its fluorescence from green to red over time. The rate of color conversion is independent of protein concentration and therefore can be used to trace time-dependent expression. We used in vivo labeling with E5 to measure expression from the heat shock-dependent promoter in Caenorhabditis elegans and from the Otx-2 promoter in developing Xenopus embryos. Thus, E5 is a "fluorescent timer" that can be used to monitor both activation and down-regulation of target promoters on the whole-organism scale.

Elevated levels of circulating platelet microparticles, VEGF, IL-6 and RANTES in patients with gastric cancer: possible role of a metastasis predictor

The activation of coagulation, angiogenesis and inflammatory cytokines are considered to be related with tumour growth and metastasis. We investigated the plasma levels of platelet microparticles (PMP), vascular endothelial growth factor (VEGF), IL-6, and the chemokine RANTES in patients with gastric cancer (n=109) and in healthy controls (n=29). The plasma levels of PMP, IL-6 and RANTES were significantly higher in the patients than in the healthy controls, and plasma levels of PMP, VEGF, IL-6 and RANTES were significantly higher in patients with stage IV disease than those in patients with stage I or stage II/III. In terms of predicting distant metastasis, the sensitivities of PMP, VEGF, IL-6 and RANTES were 93.3%, 56.7%, 70.0% and 81.8%, respectively, and the corresponding specificities were 91.1%, 64.6%, 79.7% and 50.0%. Among these parameters, PMP had the highest diagnostic accuracy. Significant correlations were found between PMP, VEGF, IL-6 and RANTES. This study demonstrates that the plasma levels of PMP, VEGF, IL-6 and RANTES were markedly increased in patients with stage IV disease, and that these increased plasma levels of IL-6, RANTES, and especially PMP, might be useful for identifying metastatic gastric patients.

Coupling of a replicative polymerase and helicase: a tau-DnaB interaction mediates rapid replication fork movement

The E. coli replication fork synthesizes DNA at the rate of nearly 1000 nt/s. We show here that an interaction between the tau subunit of the replicative polymerase (the DNA polymerase III holoenzyme) and the replication fork DNA helicase (DnaB) is required to mediate this high rate of replication fork movement. In the absence of this interaction, the polymerase follows behind the helicase at a rate equal to the slow (approximately 35 nt/s) unwinding rate of the helicase alone, whereas upon establishing a tau-DnaB contact, DnaB becomes a more effective helicase, increasing its translocation rate by more than 10-fold. This finding establishes the existence of both a physical and communications link between the two major replication machines in the replisome: the DNA polymerase and the primosome.

Function of the c-Myc oncogenic transcription factor

The c-myc gene and the expression of the c-Myc protein are frequently altered in human cancers. The c-myc gene encodes the transcription factor c-Myc, which heterodimerizes with a partner protein, termed Max, to regulate gene expression. Max also heterodimerizes with the Mad family of proteins to repress transcription, antagonize c-Myc, and promote cellular differentiation. The constitutive activation of c-myc expression is key to the genesis of many cancers, and hence the understanding of c-Myc function depends on our understanding of its target genes. In this review, we attempt to place the putative target genes of c-Myc in the context of c-Myc-mediated phenotypes. From this perspective, c-Myc emerges as an oncogenic transcription factor that integrates the cell cycle machinery with cell adhesion, cellular metabolism, and the apoptotic pathways.