Understanding signaling cascades in melanoma

Understanding regulatory pathways involved in melanoma development and progression has advanced significantly in recent years. It is now appreciated that melanoma is the result of complex changes in multiple signaling pathways that affect growth control, metabolism, motility and the ability to escape cell death programs. Here we review the major signaling pathways currently known to be deregulated in melanoma with an implication to its development and progression. Among these pathways are Ras, B-Raf, MEK, PTEN, phosphatidylinositol-3 kinase (PI3Ks) and Akt which are constitutively activated in a significant number of melanoma tumors, in most cases due to genomic change. Other pathways discussed in this review include the [Janus kinase/signal transducer and activator of transcription (JAK/STAT), transforming growth factor-beta pathways which are also activated in melanoma, although the underlying mechanism is not yet clear. As a paradigm for remodeled signaling pathways, melanoma also offers a unique opportunity for targeted drug development.Fil: Lopez Bergami, Pablo Roberto. Sanford-burnham Medical Research Institute; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Fitchmann, B. Sanford-burnham Medical Research Institute; Estados UnidosFil: Ronai, Ze´ev. Sanford-burnham Medical Research Institute; Estados Unido

BMP-2 Up-Regulates PTEN Expression and Induces Apoptosis of Pulmonary Artery Smooth Muscle Cells under Hypoxia

To investigate the role of bone morphogenetic protein 2 (BMP-2) in regulation of phosphatase and tensin homologue deleted on chromosome ten (PTEN) and apoptosis of pulmonary artery smooth muscle cells (PASMCs) under hypoxia.Normal human PASMCs were cultured in growth medium (GM) and treated with BMP-2 from 5-80 ng/ml under hypoxia (5% CO(2)+94% N(2)+1% O(2)) for 72 hours. Gene expression of PTEN, AKT-1 and AKT-2 were determined by quantitative RT-PCR (QRT-PCR). Protein expression levels of PTEN, AKT and phosph-AKT (pAKT) were determined. Apoptosis of PASMCs were determined by measuring activities of caspases-3, -8 and -9. siRNA-smad-4, bpV(HOpic) (PTEN inhibitor) and GW9662 (PPARγ antagonist) were used to determine the signalling pathways.Proliferation of PASMCs showed dose dependence of BMP-2, the lowest proliferation rate was achieved at 60 ng/ml concentration under hypoxia (82.2±2.8%). BMP-2 increased PTEN gene expression level, while AKT-1 and AKT-2 did not change. Consistently, the PTEN protein expression also showed dose dependence of BMP-2. AKT activity significantly reduced in BMP-2 treated PASMCs. Increased activities of caspase-3, -8 and -9 of PASMCs were found after cultured with BMP-2. PTEN expression remained unchanged when Smad-4 expression was inhibited by siRNA-Smad-4. bpV(HOpic) and GW9662 (PPARγ inhibitor) inhibited PTEN protein expression and recovered PASMCs proliferation rate.BMP-2 increased PTEN expression under hypoxia in a dose dependent pattern. BMP-2 reduced AKT activity and increased caspase activity of PASMCs under hypoxia. The increased PTEN expression may be mediated through PPARγ signalling pathway, instead of BMP/Smad signalling pathway

Control region mutations and the 'common deletion' are frequent in the mitochondrial DNA of patients with esophageal squamous cell carcinoma

BACKGROUND: North central China has some of the highest rates of esophageal squamous cell carcinoma in the world with cumulative mortality surpassing 20%. Mitochondrial DNA (mtDNA) accumulates more mutations than nuclear DNA and because of its high abundance has been proposed as a early detection device for subjects with cancer at various sites. We wished to examine the prevalence of mtDNA mutation and polymorphism in subjects from this high risk area of China. METHODS: We used DNA samples isolated from tumors, adjacent normal esophageal tissue, and blood from 21 esophageal squamous cell carcinoma cases and DNA isolated from blood from 23 healthy persons. We completely sequenced the control region (D-Loop) from each of these samples and used a PCR assay to assess the presence of the 4977 bp common deletion. RESULTS: Direct DNA sequencing revealed that 7/21 (33%, 95% CI = 17–55%) tumor samples had mutations in the control region, with clustering evident in the hyper-variable segment 1 (HSV1) and the homopolymeric stretch surrounding position 309. The number of mutations per subject ranged from 1 to 16 and there were a number of instances of heteroplasmy. We detected the 4977 bp 'common deletion' in 92% of the tumor and adjacent normal esophageal tissue samples examined, whereas no evidence of the common deletion was found in corresponding peripheral blood samples. CONCLUSIONS: Control region mutations were insufficiently common to warrant attempts to develop mtDNA mutation screening as a clinical test for ESCC. The common deletion was highly prevalent in the esophageal tissue of cancer cases but absent from peripheral blood. The potential utility of the common deletion in an early detection system will be pursued in further studies

Adverse prognosis of epigenetic inactivation in RUNX3 gene at 1p36 in human pancreatic cancer

Alteration in transforming growth factor-β signalling pathway is one of the main causes of pancreatic cancer. The human runt-related transcription factor 3 gene (RUNX3) is an important component of this pathway. RUNX3 locus 1p36 is commonly deleted in a variety of human cancers, including pancreatic cancer. Therefore, we examined genetic and epigenetic alterations of RUNX3 in human pancreatic cancer. Thirty-two patients with pancreatic cancer were investigated in this study. We examined the methylation status of RUNX3 promoter region, loss of heterozygosity (LOH) at 1p36, and conducted a mutation analysis. The results were compared with clinicopathological data. Promoter hypermethylation was detected in 20 (62.5%) of 32 pancreatic cancer tissues, confirmed by sequence of bisulphite-treated DNA. Loss of heterozygosity was detected in 11 (34.3%) of 32 pancreatic cancers. In comparison with clinicopathological data, hypermethylation showed a relation with a worse prognosis (P=0.0143). Hypermethylation and LOH appear to be common mechanisms for inactivation of RUNX3 in pancreatic cancer. Therefore, RUNX3 may be an important tumour suppressor gene related to pancreatic cancer

Controversy surrounding the increased expression of TGFβ1 in asthma

Asthma is a waxing and waning disease that leads to structural changes in the airways, such as subepithelial fibrosis, increased mass of airway smooth muscle and epithelial metaplasia. Such a remodeling of the airways futher amplifies asthma symptoms, but its etiology is unknown. Transforming growth factor β1 is a pleiotropic cytokine involved in many fibrotic, oncologic and immunologic diseases and is believed to play an essential role in airway remodeling that occurs in asthmatic patients. Since it is secreted in an inactive form, the overall activity of this cytokine is not exclusively determined by its level of expression, but also by extensive and complex post-translational mechanisms, which are all importanin modulating the magnitude of the TGFβ1 response. Even if TGFβ1 upregulation in asthma is considered as a dogma by certain investigators in the field, the overall picture of the published litterature is not that clear and the cellular origin of this cytokine in the airways of asthmatics is still a contemporaneous debate. On the other hand, it is becoming clear that TGFβ1 signaling is increased in the lungs of asthmatics, which testifies the increased activity of this cytokine in asthma pathogenesis. The current work is an impartial and exhaustive compilation of the reported papers regarding the expression of TGFβ1 in human asthmatics. For the sake of comparison, several studies performed in animal models of the disease are also included. Inconsistencies observed in human studies are discussed and conclusions as well as trends from the current state of the litterature on the matter are proposed. Finally, the different points of regulation that can affect the amplitude of the TGFβ1 response are briefly revised and the possibility that TGFβ1 is disregulated at another level in asthma, rather than simply in its expression, is highlighted

A Small Peptide Modeled after the NRAGE Repeat Domain Inhibits XIAP-TAB1-TAK1 Signaling for NF-κB Activation and Apoptosis in P19 Cells

In normal growth and development, apoptosis is necessary to shape the central nervous system and to eliminate excess neurons which are not required for innervation. In some diseases, however, apoptosis can be either overactive as in some neurodegenerative disorders or severely attenuated as in the spread of certain cancers. Bone morphogenetic proteins (BMPs) transmit signals for regulating cell growth, differentiation, and apoptosis. Responding to BMP receptors stimulated from BMP ligands, neurotrophin receptor-mediated MAGE homolog (NRAGE) binds and functions with the XIAP-TAK1-TAB1 complex to activate p38MAPK and induces apoptosis in cortical neural progenitors. NRAGE contains a unique repeat domain that is only found in human, mouse, and rat homologs that we theorize is pivotal in its BMP MAPK role. Previously, we showed that deletion of the repeat domain inhibits apoptosis, p38MAPK phosphorylation, and caspase-3 cleavage in P19 neural progenitor cells. We also showed that the XIAP-TAB1-TAK1 complex is dependent on NRAGE for IKK-α/β phosphorylation and NF-κB activation. XIAP is a major inhibitor of caspases, the main executioners of apoptosis. Although it has been shown previously that NRAGE binds to the RING domain of XIAP, it has not been determined which NRAGE domain binds to XIAP. Here, we used fluorescence resonance energy transfer (FRET) to determine that there is a strong likelihood of a direct interaction between NRAGE and XIAP occurring at NRAGE's unique repeat domain which we also attribute to be the domain responsible for downstream signaling of NF-κB and activating IKK subunits. From these results, we designed a small peptide modeled after the NRAGE repeat domain which we have determined inhibits NF-κB activation and apoptosis in P19 cells. These intriguing results illustrate that the paradigm of the NRAGE repeat domain may hold promising therapeutic strategies in developing pharmaceutical solutions for combating harmful diseases involving excessive downstream BMP signaling, including apoptosis

The Ethics of Delusional Belief

In this paper we address the ethics of adopting delusional beliefs and we apply consequentialist and deontological considerations to the epistemic evaluation of delusions. Delusions are characterised by their epistemic shortcomings and they are often defined as false and irrational beliefs. Despite this, when agents are overwhelmed by negative emotions due to the effects of trauma or previous adversities, or when they are subject to anxiety and stress as a result of hypersalient experience, the adoption of a delusional belief can prevent a serious epistemic harm from occurring. For instance, delusions can allow agents to remain in touch with their environment overcoming the disruptive effect of negative emotions and anxiety. Moreover, agents are not blameworthy for adopting their delusions if their ability to believe otherwise is compromised. There is evidence suggesting that no evidence-related action that would counterfactually lead them to believe otherwise is typically available to them. The lack of ability to believe otherwise, together with some other conditions, implies that the agents are not blameworthy for their delusions. The examination of the epistemic status of delusions prompts us to acknowledge the complexity and contextual nature of epistemic evaluation, establish connections between consequentialist and deontological frameworks in epistemology, and introduce the notion of epistemic innocence into the vocabulary of epistemic evaluatio