Modulation Of Signal Transduction Pathways Research Articles

Cancer Prevention and Treatment with Resveratrol: From Rodent Studies to Clinical Trials

Resveratrol (3,4',5-trihydroxy-trans-stilbene) is a dietary polyphenol derived from grapes, berries, peanuts, and other plant sources. During the last decade, resveratrol has been shown to possess a fascinating spectrum of pharmacologic properties. Multiple biochemical and molecular actions seem to contribute to resveratrol effects against precancerous or cancer cells. Resveratrol affects all three discrete stages of carcinogenesis (initiation, promotion, and progression) by modulating signal transduction pathways that control cell division and growth, apoptosis, inflammation, angiogenesis, and metastasis. The anticancer property of resveratrol has been supported by its ability to inhibit proliferation of a wide variety of human tumor cells in vitro. These in vitro data have led to numerous preclinical animal studies to evaluate the potential of this drug for cancer chemoprevention and chemotherapy. This review provides concise, comprehensive data from preclinical in vivo studies in various rodent models of human cancers, highlighting the related mechanisms of action. Bioavailability, pharmacokinetic, and potential toxicity studies of resveratrol in humans and ongoing interventional clinical trials are also presented. The conclusion describes directions for future resveratrol research to establish its activity and utility as a human cancer preventive and therapeutic drug.

Are We Hitting the Right Combination for Hormonally Sensitive Breast Cancer?

Are We Hitting the Right Combination for Hormonally Sensitive Breast Cancer?

Modulators of signal transduction pathways can promote axonal regeneration in entorhino-hippocampal slice cultures

Axonal regeneration after lesions is usually not possible in the adult central nervous system but can occur in the embryonic and young postnatal nervous system. In this study we used the model system of mouse entorhino-hippocampal slice cultures to assess the potential of pharmacological treatments with compounds targeting signal transduction pathways to promote growth of entorhinal fibers after mechanical lesions across the lesion site to their target region in the dentate gyrus. Compounds acting on the cyclic AMP-system, protein kinase C and G-proteins have been shown before to be able to promote regeneration. In this study we have confirmed the potential of drugs affecting these systems to promote axonal regeneration in the central nervous system. In addition we have found that inhibition of the phosphoinositide 3-kinase pathway and of the inositol triphosphate receptor also promoted axonal growth across the lesion site and are thus potential novel drug targets for promoting axonal regeneration after central nervous system lesions. Our findings demonstrate that slice culture models can be used to evaluate compounds for their potential to promote axonal regeneration and that the pharmacological modulation of signal transduction pathways is a promising approach for promoting axonal repair.

Interferon β-1a Induces Tumor Necrosis Factor Receptor 1 but Decreases Tumor Necrosis Factor Receptor 2 Leukocyte mRNA Levels in Relapsing-Remitting Multiple Sclerosis

Objective: Members of the tumor necrosis factor (TNF) receptor superfamily play a major role in the pathogenesis of multiple sclerosis. To elucidate the role of TNF receptors, in 53 relapsing-remitting multiple sclerosis patients, we measured the TNF receptor 1 and receptor 2 (TNF-R1 and TNF-R2) mRNA levels in peripheral blood leukocytes in natural history (n = 27) and during administration of interferon (IFN) β-1a (n = 26). Methods: Every 3 months for the duration of 1 year peripheral blood leukocytes were investigated by quantitative reverse transcription polymerase chain reaction. Every 6 months, MRI scans of the brain were analyzed semiquantitatively. Results: At baseline, clinical expanded disability status scale score and TNF-R1 mRNA level were correlated. In the therapy group, the difference between T2 lesion load at baseline and after 12 months correlated negatively with the difference between TNF-R1 mRNA level at baseline and after 12 months. Subcutaneously applied IFN β increased the amount of TNF-R1 mRNA, but partly decreased the amount of TNF-R2 mRNA in clinically and subclinically defined responders to therapy after 1 year compared to baseline. Conclusion: This result might support the notion that due to different signal transduction properties of both receptors in the natural course of multiple sclerosis, TNF-α signaling in leukocytes via TNF-R1 might be beneficial, but detrimental via proinflammatory TNF-R2: part of the therapeutic efficacy of current first-line standard therapy with IFN might be due to the modulation of signal transduction pathways.

Down-regulation of c-Src/EGFR-mediated signaling activation is involved in the honokiol-induced cell cycle arrest and apoptosis in MDA-MB-231 human breast cancer cells

Honokiol is a naturally occurring neolignan abundant in Magnoliae Cortex and has showed anti-proliferative and pro-apoptotic effects in a wide range of human cancer cells. However, the molecular mechanisms on the anti-proliferative activity in cancer cells have been poorly elucidated. In this study, we evaluated the growth inhibitory activity of honokiol in cultured estrogen receptor (ER)-negative MDA-MB-231 human breast cancer cells. Honokiol exerted anti-proliferative activity with the cell cycle arrest at the G0/G1 phase and sequential induction of apoptotic cell death in a concentration-dependent manner. The honokiol-induced cell cycle arrest was well correlated with the suppressive expression of CDK4, cyclin D1, CDK2, cyclin E, c-Myc, and phosphorylated retinoblastoma protein (pRb) at Ser780. Apoptosis caused by honokiol was also concomitant with the cleavage of caspases (caspase-3, -8, and -9) and Bid along with the suppressive expression of Bcl-2, but it was independent on the expression of Bax and p53. In addition, honokiol-treated cells exhibited the cleavage of poly (ADP-ribose) polymerase (PARP) and DNA fragmentation. In the analysis of signal transduction pathway, honokiol down-regulated the expression and phosphorylation of c-Src, epidermal growth factor receptor (EGFR), and Akt, and consequently led to the inactivation of mTOR and its downstream signal molecules including 4E-binding protein (4E-BP) and p70 S6 kinase. These findings suggest that honokiol-mediated inhibitory activity of cancer cell growth might be related with the cell cycle arrest and induction of apoptosis via modulating signal transduction pathways.

Cancer Chemopreventive Potential of Apples, Apple Juice, and Apple Components

Apples ( MALUS sp., Rosaceae) are a rich source of nutrient as well as non-nutrient components and contain high levels of polyphenols and other phytochemicals. Main structural classes of apple constituents include hydroxycinnamic acids, dihydrochalcones, flavonols (quercetin glycosides), catechins and oligomeric procyanidins, as well as triterpenoids in apple peel and anthocyanins in red apples. Several lines of evidence suggest that apples and apple products possess a wide range of biological activities which may contribute to health beneficial effects against cardiovascular disease, asthma and pulmonary dysfunction, diabetes, obesity, and cancer (reviewed by Boyer and Liu, Nutr J 2004). The present review will summarize the current knowledge on potential cancer preventive effects of apples, apple juice and apple extracts (jointly designated as apple products). In brief, apple extracts and components, especially oligomeric procyanidins, have been shown to influence multiple mechanisms relevant for cancer prevention in IN VITRO studies. These include antimutagenic activity, modulation of carcinogen metabolism, antioxidant activity, anti-inflammatory mechanisms, modulation of signal transduction pathways, antiproliferative and apoptosis-inducing activity, as well as novel mechanisms on epigenetic events and innate immunity. Apple products have been shown to prevent skin, mammary and colon carcinogenesis in animal models. Epidemiological observations indicate that regular consumption of one or more apples a day may reduce the risk for lung and colon cancer.

Chemical and Pathway Proteomics: Powerful Tools for Oncology Drug Discovery and Personalized Health Care

In recent years mass spectrometry-based proteomics has moved beyond a mere quantitative description of protein expression levels and their possible correlation with disease or drug action. Impressive progress in LC-MS instrumentation together with the availability of new enabling tools and methods for quantitative proteome analysis and for identification of posttranslational modifications has triggered a surge of chemical and functional proteomics studies dissecting mechanisms of action of cancer drugs and molecular mechanisms that modulate signal transduction pathways. Despite the tremendous progress that has been made in the field, major challenges, relating to sensitivity, dynamic range, and throughput of the described methods, remain. In this review we summarize recent advances in LC-MS-based approaches and their application to cancer drug discovery and to studies of cancer-related pathways in cell culture models with particular emphasis on mechanistic studies of drug action in these systems. Moreover we highlight the emerging utility of pathway and chemical proteomics techniques for translational research in patient tissue.

NCAM in Long-Term Potentiation and Learning

The neural cell adhesion molecule (NCAM) is important in regulating neuronal development and plasticity by modulating cell adhesion and signal transduction. Studies using NCAM antibodies have demonstrated a role of NCAM in hippocampal long-term potentiation and in animal learning models. These findings have been supported by the observation that NCAM-deficient mice show altered LTP as well as learning deficits. A particular carbohydrate modification of NCAM, polysialic acid (PSA), has been shown to be important for synaptic plasticity, as demonstrated by impaired LTP and learning in mice deficient in polysialyltransferase enzymes necessary for adding PSA to the NCAM protein as well as in wildtype mice after enzymatic removal of PSA. It is suggested that NCAM and its PSA moiety are involved in synaptic remodeling in LTP and learning, possibly by modulating signal transduction pathways as well as by mediating and permitting adhesive changes in an activity-dependent manner.

Targeting Multiple Neurodegenerative Diseases Etiologies with Multimodal-Acting Green Tea Catechins

Green tea is currently considered a source of dietary constituents endowed with biological and pharmacological activities relevant to human health. Human epidemiological and new animal data suggest that the pharmacological benefits of tea drinking may help to protect the brain as we age. Indeed, tea consumption is inversely correlated with the incidence of dementia and Alzheimer’s and Parkinson’s diseases. In particular, its main catechin polyphenol constituent (−)-epigallocatechin-3-gallate has been shown to exert neuroprotective/neurorescue activities in a wide array of cellular and animal models of neurological disorders. The intense efforts dedicated in recent years to shed light on the molecular mechanisms participating in the brain protective action of green tea indicate that in addition to the known antioxidant activity of catechins, the modulation of signal transduction pathways, cell survival/death genes, and mitochondrial function all contribute significantly to the induction of neuron viability. Because of the multietiological character of neurodegenerative disease pathology, these natural compounds are receiving significant attention as therapeutic cytoprotective agents that simultaneously manipulate multiple desired targets in the central nervous system. This article elaborates on the multimodal activities of green tea polyphenols with emphasis on their recently described neurorescue/neuroregenerative and mitochondrial stabilization actions.

Lipoic Acid: A Novel Therapeutic Approach for Multiple Sclerosis and Other Chronic Inflammatory Diseases of the CNS

The naturally occurring antioxidant lipoic acid (LA) was first described as an essential cofactor for the conversion of pyruvate to Acetyl-CoA, a critical step in respiration. LA is now recognized as a compound that has many biological functions. Along with its reduced form dihydrolipoic acid (DHLA), LA reduces and recycles cellular antioxidants such as glutathione, and chelates zinc, copper and other transition metal ions in addition to heavy metals. LA can also act as a scavenger of reactive oxygen and nitrogen species. By acting as an insulin mimetic agent, LA stimulates glucose uptake in many different cell types and can also modulate insulin signaling. The p38 and ERK MAP kinase pathways, AKT and NFkappaB are all regulated by LA. In addition, LA activates the prostaglandin EP2 and EP4 receptors to stimulate the production of the small molecule cyclic adenosine 5' monophosphate (cAMP). These diverse actions suggest that LA may be therapeutically effective in treating oxidative stress associated diseases. This review discusses the known biochemical properties of LA, its antioxidant properties, its ability to modulate signal transduction pathways, and the recent progress made in the utilization of LA as a therapeutic alternative for multiple sclerosis, Alzheimer's disease and diabetic neuropathy.

Modulation of signal transduction pathways in lymphocytes due to sub-lethal toxicity of chlorinated phenol

Chlorophenols and their derivatives are a major component of environmental pollutants that are potential immunotoxicants. Deaminase assay performed on peripheral blood mononuclear cells (PBMCs) exposed to chlorophenolic compounds and its derivatives demonstrated a decreased proliferation rate and cell death. Chlorophenolic exposure also led to impaired production of IL-21 and IL-9 along with many other cytokines and chemokines that potentiate the inflammatory response. Using the PBMC activation model and gene expression profiling we provide insights into mechanisms by which the chlorophenolic compounds and their derivatives, especially pentachlorophenol (PCP) dysregulate the inflammatory response. We have shown here that PCP represses IL21 and IL9 expression thus affecting various downstream signaling pathways. We propose that PCP, a potent pollutant, imparts its cytotoxicity by evading the immune response by simultaneously affecting multiple signaling pathways in lymphocytes.

Modulation of Endocrine Pancreas Development but not β-Cell Carcinogenesis by Sprouty4

Sprouty (Spry) proteins modulate signal transduction pathways elicited by receptor tyrosine kinases (RTK). Depending on cell type and the particular RTK, Spry proteins exert dual functions: They can either repress RTK-mediated signaling pathways, mainly by interfering with the Ras/Raf/mitogen-activated protein kinase pathway or sustaining RTK signal transduction, for example by sequestering the E3 ubiquitin-ligase c-Cbl and thus preventing ubiquitylation, internalization, and degradation of RTKs. Here, by the inducible expression of murine Spry4 in pancreatic beta cells, we have assessed the functional role of Spry proteins in the development of pancreatic islets of Langerhans in normal mice and in the Rip1Tag2 transgenic mouse model of beta-cell carcinogenesis. beta cell-specific expression of mSpry4 provokes a significant reduction in islet size, an increased number of alpha cells per islet area, and impaired islet cell type segregation. Functional analysis of islet cell differentiation in cultured PANC-1 cells shows that mSpry4 represses adhesion and migration of differentiating pancreatic endocrine cells, most likely by affecting the subcellular localization of the protein tyrosine phosphatase PTP1B. In contrast, transgenic expression of mSpry4 during beta-cell carcinogenesis does not significantly affect tumor outgrowth and progression to tumor malignancy. Rather, tumor cells seem to escape mSpry4 transgene expression.

Physiological implications of the interaction between the plasma membrane calcium pump and nNOS

The tight regulation of intracellular calcium levels is essential for the normal function of a great many cellular processes, and disruption of this regulation, resulting in sustained increases in intracellular-free calcium, has been associated with numerous diseases. One of the several transporters involved in calcium homeostasis is a P-type ATPase known as the plasma membrane calcium/calmodulin-dependent ATPase (PMCA) which is involved in calcium extrusion from the cytosol to the extracellular compartment. It has long been established that in many cell types, in particular non-excitable cells, the primary role of PMCA is in the bulk transport of intracellular calcium; however, its role in excitable cells is less clear. In the heart, for example, calcium is essential for contractile function as well as being a key messenger in signal transduction pathways; however, the mechanisms by which the cardiomyocyte distinguishes between these roles of calcium remain unclear. It is perhaps the transporters not involved in the contractile cycle (such as PMCA) that are able to carry non-contractile signals. This review will highlight the role of PMCA as a modulator of signal transduction pathways and in particular the role of isoform 4 in the regulation of the nitric oxide signalling pathway.

Insulin Inhibits LPS-Induced Signaling Pathways in Alveolar Macrophages

The systemic inflammatory response syndrome (SIRS) is triggered by lipopolysaccharide (LPS) from Gram-negative bacteria. Insulin was shown to have a protective role in SIRS related to sepsis. Lungs are particularly affected in this condition and provide a second wave of mediators/cytokines which amplifies SIRS. The aim of the present study was to investigate the effect of insulin on the signaling pathways elicited by LPS in alveolar macrophages (AMs) and its consequence in cellular response to LPS measured as production of tumor necrosis factor (TNF). To this purpose, resident AMs from male Wistar rats were obtained by lung lavage and stimulated by LPS (100 ng/mL). Insulin (1 mU/mL) was added 10 min before LPS. Activation (phosphorylation) of signaling molecules by LPS was analyzed by western blot, 30 min after LPS stimulation. TNF was measured in the AMs culture supernatants by bioassay using L-929 tumor cells. Relative to controls, LPS induced a significant increase in the activation of ERK (3.6-fold), p38 (4.4-fold), Tyr-326 Akt (4.7-fold), Ser-473 Akt (6.9-fold), PKCα (4.7-fold) and PKCδ (2.3-fold). Treatment of AMs with insulin before LPS stimulation, significantly reduced the activation of ERK (54%), p38 (48%), Tyr-326 Akt (64%), Ser-473 Akt (41%), PKCα (62%) and PKCδ (39%). LPS induced TNF production in AMs which was also inhibited by insulin (60%). These results show that insulin down-regulates MAPK, PI3K and PKCs and inhibits a downstream effect of LPS, TNF production, in rat AMs stimulated with LPS and suggest that the protective effect of insulin in sepsis could be through modulation of signal transduction pathways elicited by LPS in lung macrophages.

Modulation in the activity of lactate dehydrogenase and level of c-Myc and c-Fos by modified base queuine in cancer

Cancer is characterized by uncontrolled cell growth, which results from unlimited proliferation and disturbs various cellular activities. Queuine is a highly modified base analogue of guanine found at first anti-codon position of specific tRNAs i.e. tRNATyr, tRNAHis, tRNAAsp and tRNAAsn. These tRNAs are known as Q-family of tRNA. The tRNAs of Q-family are completely modified to Q-tRNAs in terminally differentiated somatic cells, however hypomodification of Q-tRNA is closely associated with cell proliferation and malignancy. Queuosine modification of tRNAs may be essential for normal development, differentiation and cellular functions. Physiological role of queuine remains ill defined but direct or indirect evidences suggest that queuine or Q-tRNA participates in many cellular functions such as regulation of cell proliferation, control of glycolytic metabolism, alteration in expression of proto-oncogenes, modulation of signal transduction pathways but the mechanism is not well known. Increase in LDH-A expression regulated by c-myc is well documented in a variety of tumor cells. Over expression of proto-oncogenes cause deregulated cellular responses which may lead to development of cancer. The cellular proto-oncogenes like c-myc and c-fos have important role in cell growth, proliferation and differentiation. The present study is aimed to investigate queuine mediated modulation in the activity of lactate dehydrogenase and expression of proto-oncogenes like c-myc and c-fos in T-cell lymphoma (DLAT) induced cancerous mouse. The results indicate that elevated lactate dehydrogenase activity is brought down by queuine treatments and the elevated levels of c-myc and c-fos in DLAT cancerous mouse are down regulated, suggesting that queuine inhibits anaerobic metabolism and cell proliferation.

Vitamin E Isoforms Inhibit Cell Proliferation and Downregulate Homeobox Protein Expression in the Leukemic KG-1 Cells.

Vitamin E is a fat-soluble vitamin that exists in eight different isoforms: four tocopherols (alpha, beta-, gamma- and delta-), and four tocotrienols (also alpha-, beta-, gamma- and delta-). Studies are underway to determine whether vitamin E, through its ability to limit production of free radicals, might help prevent or delay the development of cancer. Other studies suggest that vitamin E may modulate signal transduction pathways to prevent or reverse the effects of cancer. In our study, we examined the effect of vitamin E isotypes on some gene products involved in acute leukemia such as HOXA9 (Homeobox A9), PBX1 (Pre-B cell leukemia transcription factor 1) and E2A-PBX1. HOXA9 is a transcription factor with a central role in both hemopoiesis and leukemia. A high level of HOXA9 is a characteristic feature of acute myeloid leukemia (AML) and may be sufficient to cause this disease. PBX1 is involved in a form of pre-B-cell acute lymphoblastic leukemia (B-ALL). E2A-PBX1 is a protein resulting from a chromosomal translocation t(1;19)(q23;p13.3) which involves PBX1 and E2A genes. E2A-PBX1 transforms cells by constitutively activating transcription of genes regulated by PBX1 or by other members of the PBX protein family. KG-1 cells were treated with 20 micromolar (μM) gamma tocotrienol (γT3) and delta tocotrienol (δT3) for 48 hours, and 50 μM gamma tocopherol (γT) and delta tocopherol (δT) for 72 hours. MTT Assays demonstrate 30% inhibition of cell proliferation using 50 μM γT after 72 hours, 60% inhibition of cell proliferation using 50 μM δT after 48 hours, 70% inhibition of cell proliferation using 25 μM γT3 after 48 hours, and 75% inhibition of cell proliferation using 25 μM δT3 after 48 hours. Western Blot analysis was performed on the cell lysates using HOXA9, PBX1 and E2A-PBX-1 antibodies. Our results showed that both δT and γT when used at a 50 μM concentration for 72 hours treatment, as well as δT3 and γT3 when used at a 20 μM concentration for 48 hours treatment, have a down regulatory effect on HOXA9, PBX1 and E2A-PBX-1 protein expression in the leukemic KG-1 cells. A down regulatory effect on cyclin D1 and cyclin D3 was also demonstrated.

Neurocognitive Impairment and Dementia in Mood Disorders

Neurocognitive Impairment and Dementia in Mood Disorders

Guest Editorial: Oxygen balance – What’s that?

Guest Editorial: Oxygen balance – What’s that?

α7β1 Integrin

See related article, pages 672–681 Modulation of smooth muscle cell (SMC) differentiation status is an important aspect of vascular development, normal differentiation and function, and pathogenesis of various diseases including atherosclerosis, hypertension, and aneurysms. SMCs are not terminally differentiated and possess the ability to change phenotype in response to local environmental cues. Thus, changes in the local environment contribute to the switching of SMCs from the normal contractile phenotype to more proliferative, synthetic phenotypes that are present in these diseases.1,2 The molecular mechanisms regulating smooth muscle phenotypic modulation are only now beginning to be understood, and how input from the extracellular matrix impacts these changes is still an area of ongoing research. In the current issue of Circulation Research , Welser et al3 investigate the contribution of the laminin binding integrin α7β1 to phenotypic modulation of SMCs. Adhesion to specific extracellular matrix (ECM) proteins is known to modulate the phenotypic status of SMCs in culture, and altered expression of ECM proteins in vivo correlate with changes in the status of SMCs and with vascular pathologies such as hypertension and atherosclerosis.4,5 Thyberg6 reviewed the contributions of various ECM molecules to smooth muscle status and reported that SMCs grown on fibronectin (and other transitional matrices) showed increased proliferation, whereas cells on laminin and other basement membrane proteins proliferated slower and expressed larger quantities of smooth muscle specific contractile proteins. In addition, we7,8and others9 showed that the type of ECM influences the response of SMC to mechanical stimulation. The differences between these SMCs are thought to arise because of differential stimulation of specific integrins and modulation of signal transduction pathways that regulate …

P-Rex1 Links Mammalian Target of Rapamycin Signaling to Rac Activation and Cell Migration

Polarized cell migration results from the transduction of extra-cellular cues promoting the activation of Rho GTPases with the intervention of multidomain proteins, including guanine exchange factors. P-Rex1 and P-Rex2 are Rac GEFs connecting Gbetagamma and phosphatidylinositol 3-kinase signaling to Rac activation. Their complex architecture suggests their regulation by protein-protein interactions. Novel mechanisms of activation of Rho GTPases are associated with mammalian target of rapamycin (mTOR), a serine/threonine kinase known as a central regulator of cell growth and proliferation. Recently, two independent multiprotein complexes containing mTOR have been described. mTORC1 links to the classical rapamycin-sensitive pathways relevant for protein synthesis; mTORC2 links to the activation of Rho GTPases and cytoskeletal events via undefined mechanisms. Here we demonstrate that P-Rex1 and P-Rex2 establish, through their tandem DEP domains, interactions with mTOR, suggesting their potential as effectors in the signaling of mTOR to Rac activation and cell migration. This possibility was consistent with the effect of dominant-negative constructs and short hairpin RNA-mediated knockdown of P-Rex1, which decreased mTOR-dependent leucine-induced activation of Rac and cell migration. Rapamycin, a widely used inhibitor of mTOR signaling, did not inhibit Rac activity and cell migration induced by leucine, indicating that P-Rex1, which we found associated to both mTOR complexes, is only active when in the mTORC2 complex. mTORC2 has been described as the catalytic complex that phosphorylates AKT/PKB at Ser-473 and elicits activation of Rho GTPases and cytoskeletal reorganization. Thus, P-Rex1 links mTOR signaling to Rac activation and cell migration.