Antitumor activity of irradiated riboflavin on human renal carcinoma cell line 786-O

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Quantitative proteomic analysis and functional studies reveal that nucleophosmin is involved in cell death in glioblastoma cell line transfected with siRNA

Previously, we reported that nucleophosmin (NPM) was increased in glioblastoma multiforme (GBM). NPM is a phosphoprotein related to apoptosis, ribosome biogenesis, mitosis, and DNA repair, but details about its function remain unclear. We treated U87MG and A172 cells with small interference RNA (siRNA) and obtained a reduction of 80% in NPM1 expression. Knockdown at the protein level was evident after the 4th day and was maintained until the 7th day of transfection that was investigated by quantitative proteomic analysis using isobaric tags. The comparison of proteomic analysis of NPM1-siRNA against controls allowed the identification of 14 proteins, two proteins showed increase and 12 presented a reduction of expression levels. Gene ontology assigned most of the hypoexpressed proteins to apoptosis regulation, including GRP78. NPM1 silencing did not impair cell proliferation until the 7th day after transfection, but sensitized U87MG cells to temozolomide (TMZ), culminating with an increase in cell death and provoking at a later period a reduction of colony formation. In a large data set of GBM patients, both GRP78 and NPM1 genes were upregulated and presented a tendency to shorter overall survival time. In conclusion, NPM proved to participate in the apoptotic process, sensitizing TMZ-treated U87MG and A172 cells to cell death, and in association with upregulation of GRP78 may be helpful as a predictive factor of poor prognosis in GBM patients.

Influence of N-methyl-D-aspartate receptors on ouabain activation of nuclear factor-kappa B in the rat hippocampus

It has been shown that ouabain (OUA) can activate the Na,K-ATPase complex and mediate intracellular signaling in the central nervous system (CNS). Inflammatory stimulus increases glutamatergic transmission, especially at N-methyl-D-aspartate (NMDA) receptors, which are usually coupled to the activation of nitric oxide synthase (NOS). Nuclear factor-kappa B (NF-kappa B) activation modulates the expression of genes involved in development, plasticity, and inflammation. The present work investigated the effects of OUA on NF-kappa B binding activity in rat hippocampus and the influence of this OUA-Na,K-ATPase signaling cascade in NMDA-mediated NF-kappa B activation. The findings presented here are the first report indicating that intrahippocampal administration of OUA, in a concentration that did not alter Na,K-ATPase or NOS activity, induced an activation of NF-kappa B, leading to increases in brain-derived neurotrophic factor (Bdnf), inducible NOS (iNos), tumor necrosis factor-alpha (Tnf-alpha), and B-cell leukemia/lymphoma 2 (Bcl2) mRNA levels. This response was not linked to any significant signs of neurodegeneration as showed via Fluoro-Jade B and Nissl stain. Intrahippocampal administration of NMDA induced NF alpha B activation and increased NOS and alpha 2/3-Na,K-ATPase activities. NMDA treatment further increased OUA-induced NF-kappa B activation, which was partially blocked by MK-801, an antagonist of NMDA receptor. These results suggest that OUA-induced NF-kappa B activation is at least in part dependent on Na,K-ATPase modulatory action of NMDA receptor in hippocampus. The interaction of these signaling pathways could be associated with biological mechanisms that may underlie the basal homeostatic state linked to the inflammatory signaling cascade in the brain. (c) 2011 Wiley Periodicals, Inc.

Quantitative correlation between transcriptional levels of ER chaperone, peroximal protein and FVIII productivity in human Hek-293 cell line

Hek-293 cell line presents good production platform for recombinant therapeutic proteins, however little is known about the components that contribute to the cellular control of recombinant protein production. In this study, we generated a Hek-293 producing recombinant factor VIII (FVIII) and we evaluated the immunoglobulin-binding protein (BiP) and phytanoil-CoA α-hydroxylase (PAHX) expression levels which are known for diminishing FVIII production. Our analyses showed that the recombinant cell population expresses 3.1 ± 1.4 fold of BIP mRNA (P = 0.0054) and 97.8 ± 0.5 fold of PAHX mRNA (P = 0.0016) compared to nontransduced cells. The amount of these proteins was inversely correlated to the secreted FVIII. In conclusion, BIP and PAHX expression are augmented in human cells producing FVIII and they antagonize the amount of therapeutic factor VIII in the cell culture.

Influence of the dopaminergic system, CREB, and transcription factor-κB on cocaine neurotoxicity

Cocaine is a widely used drug and its abuse is associated with physical, psychiatric and social problems. Abnormalities in newborns have been demonstrated to be due to the toxic effects of cocaine during fetal development. The mechanism by which cocaine causes neurological damage is complex and involves interactions of the drug with several neurotransmitter systems, such as the increase of extracellular levels of dopamine and free radicals, and modulation of transcription factors. The aim of this review was to evaluate the importance of the dopaminergic system and the participation of inflammatory signaling in cocaine neurotoxicity. Our study showed that cocaine activates the transcription factors NF-κB and CREB, which regulate genes involved in cellular death. GBR 12909 (an inhibitor of dopamine reuptake), lidocaine (a local anesthetic), and dopamine did not activate NF-κB in the same way as cocaine. However, the attenuation of NF-κB activity after the pretreatment of the cells with SCH 23390, a D1 receptor antagonist, suggests that the activation of NF-κB by cocaine is, at least partially, due to activation of D1 receptors. NF-κB seems to have a protective role in these cells because its inhibition increased cellular death caused by cocaine. The increase in BDNF (brain-derived neurotrophic factor) mRNA can also be related to the protective role of both CREB and NF-κB transcription factors. An understanding of the mechanisms by which cocaine induces cell death in the brain will contribute to the development of new therapies for drug abusers, which can help to slow down the progress of degenerative processes.

Cellular and molecular effects of cross reacting material 197 (CRM197) on HT-29 colon cancer cell line

Cross Reacting Material 197(CRM197) is a Diphteria toxin non toxic mutant that had shown anti-tumor activity in mice and humans. CRM197 is utilized as a specific inhibitor of heparin-binding epidermal growth factor (HB-EGF), that competes for the epidermal growth factor receptor (EGFR), overexpressed in colorectal cancer and implicated in its progression. We evaluated the effects of CRM197 on HT-29 human colon cancer cell line behaviour and, for CRM197 recognized ability to inhibit HB-EGF, its possible effects on EGFR activation. In particular, while HT-29 does not show any reduction of viability after CRM197 treatment, or changes in cell cycle distribution, in EGFR localization or activation, they show a change in gene expression profile analyzed by microarray. This is the first study where the CRM197 treatment on HT-29 show the alteration of a specific and selected number of genes.

Charakterisierung der neuroprotektiven Eigenschaften des Corticotropin-Releasing-Hormons

Das Corticotropin Releasing Hormon (CRH) ist ein zentraler Mediator des neuroendokrinen Systems von Säugetieren und kontrolliert die physiologische Stressreaktion des Körpers. Zudem zeigten in vitro Daten, dass es Neuroprotektion gegenüber oxidativem Stress induzieren kann. In der vorliegenden Arbeit konnte erstmals ein neuroprotektiver Effekt des CRH in vivo gezeigt werden. Die Überexpression des CRH im ZNS von Mäusen konnte Nervenzellen in vivo vor Exzitotoxizität schützen; nach Injektion des Exzitotoxins Kainat verkürzte die CRH-Überexpression die Dauer der epileptischen Anfälle, schützte die Neurone der betroffenen Hippocampusregion vor Zelltod und verhinderte die bei Exzitotoxizität und vielen neurodegenerativen Erkrankungen auftretende Neuroinflammation. Desweiteren konnten in CRH-überexprimierenden Tieren erhöhte BDNF-Proteinspiegel nachgewiesen werden. BDNF, ein bedeutender neurotropher Faktor im ZNS, vermittelt daher teilweise die CRH-induzierte Neuroprotektion gegenüber der Exzitotoxizität in vivo. Im Rahmen dieser Arbeit wurde mit Connexin43, dem Haupt-Gap Junction-Protein der Astrozyten, ein neues CRH-Zielgen im ZNS identifiziert. Es konnte erstmals gezeigt werden, dass CRH sowohl die Expression des Connexin43-Gens als auch den Connexin43-Proteinspiegel in vitro und in vivo erhöht. Diese Effekte werden über die Aktivierung des CRH-Rezeptor 1 und nachfolgend der PKA- und MAPK-Signalwege vermittelt. In Übereinstimmung mit der Hochregulation des Connexin43-Proteinspiegels verstärkte CRH auch die interzelluläre Kommunikation über Gap Junctions. Physiologisch hat diese CRH-induzierte Verstärkung der astrozytären Gap Junction-Kommunikation eine große Bedeutung für die Neuroprotektion, da eine Hochregulation der interzellulären Kommunikation schnell toxische Moleküle verdünnt, Energiesubstrate und protektive Faktoren verteilt und Ionen abpuffert. Dadurch werden Schädigungen durch oxidativen Stress in den Zellen reduziert, was über die Analyse der Proteincarbonylierung gezeigt wurde. Die Relevanz der astrozytären Gap Junction-Kommunikation für das Überleben der Neurone konnte in organotypischen hippocampalen Schnitten und in Neuron-Astrozyten-Co-Kulturen deutlich gemacht werden. Die im Rahmen der vorliegenden Arbeit gewonnenen Daten zeigen, dass die Stress-induzierte Sekretion von CRH im ZNS zur verstärkten Expression neuroprotektiver Moleküle wie BDNF und Connexin43 beiträgt. Diese vermögen Neurone gegenüber toxischen Einflüssen zu schützen und zum Erhalt ihrer Funktion beizutragen. Die protektiven CRH-Effekte könnten speziell bei chronischen neurodegenerativen Krankheiten wie der Alzheimerschen Demenz und der Parkinsonschen Krankheit hilfreich sein.

Stromal derived growth factor alpha (SDF-1α) induces the differentiation of bone marrow progenitor cells (BMCs) into pericytes by regulating platelet derived growth factor B (PDGF-B) transcription

We previously demonstrated that bone marrow cells (BMCs) migrate to TC71 and A4573 Ewing’s sarcoma tumors where they can differentiate into endothelial cells (ECs) and pericytes and, participate in the tumor vascular development. This process of neo-vascularization, known as vasculogenesis, is essential for Ewing’s sarcoma growth with the soluble vascular endothelial growth factor, VEGF165, being the chemotactic factor for BMC migration to the tumor site. Inhibiting VEGF165 in TC71 tumors (TC/siVEGF7-1) inhibited BMC infiltration to the tumor site and tumor growth. Introducing the stromal-derived growth factor (SDF-1α) into the TC/siVEGF7-1 tumors partially restored vasculogenesis with infiltration of BMCs to a perivascular area where they differentiated into pericytes and rescued tumor growth. RNA collected from the SDF-1α-treated TC/siVEGF7-1 tumors also revealed an increase in platelet-derived growth factor B (PDGF-B) mRNA levels. PDGF-B expression is elevated in several cancer types and the role of PDGF-B and its receptor, PDGFR-β, has been extensively described in the process of pericyte maturation. However, the mechanisms by which PDGF-B expression is up-regulated during vascular remodeling and the process by which BMCs differentiate into pericytes during tumor vasculogenesis remain areas of investigation. In this study, we are the first to demonstrate that SDF-1α regulates the expression of PDGF-B via a transcriptional mechanism which involves binding of the ELK-1 transcription factor to the pdgf-b promoter. We are also first to validate the critical role of the SDF-1α/PDGF-B pathway in the differentiation of BMCs into pericytes both in vitro and in vivo. SDF-1α up-regulated PDGF-B expression in both TC/siVEGF7-1 and HEK293 cells. In contrast, down-regulating SDF-1α, down-regulated PDGF-B. We cloned the 2 kb pdgf-b promoter fragment into the pGL3 reporter vector and showed that SDF-1α induced pdgf-b promoter activity. We used chromatin immunoprecipitation (ChIP) and demonstrated that the ELK-1 transcription factor bound to the pdgf-b promoter in response to SDF-1α stimulation in both TC/siVEGF7-1 and HEK293 cells. We collected BMCs from the hind femurs of mice and cultured the cells in medium containing SDF-1α and PDGF-B and found that PDGFR-β+ BMCs differentiated into NG2 and desmin positive pericytes in vitro. In contrast, inhibiting SDF-1α and PDGF-B abolished this differentiation process. In vivo, we injected TC71 or A4573 tumor-bearing mice with the SDF-1α antagonist, AMD3100 and found that inhibiting SDF-1α signaling in the tumor microenvironment decreased the tumor microvessel density, decreased the tumor blood vessel perfusion and, increased tumor cell apoptosis. We then analyzed the effect of AMD3100 on vasculogenesis of Ewing’s sarcoma and found that BMCs migrated to the tumor site where they differentiated into ECs but, they did not form thick perivascular layers of NG2 and desmin positive pericytes. Finally, we stained the AMD3100-treated tumors for PDGF-B and showed that inhibiting SDF-1α signaling also inhibited PDGF-B expression. All together, these findings demonstrated that the SDF-1α/PDGF-B pathway plays a critical role in the formation of BM-derived pericytes during vasculogenesis of Ewing’s sarcoma tumors.

Antibodies targeting hepatoma-derived growth factor as a novel strategy in treating lung cancer.

Hepatoma-derived growth factor (HDGF) is overexpressed in lung cancer and the overexpression correlates with aggressive biological behaviors and poor clinical outcomes. We developed anti-HDGF monoclonal antibodies and tested their antitumor activity in lung cancer xenograft models. We also determined biological effects in tumors treated with the antibody alone or in combination with bevacizumab/avastin (an anti-vascular endothelial growth factor antibody) and/or gemcitabine (a chemotherapeutic agent). We found the anti-HDGF was effective to inhibit tumor growth in non-small cell lung cancer xenograft models. In the A549 model, compared with control IgG, tumor growth was substantially inhibited in animals treated with anti-HDGF antibodies, particularly HDGF-C1 (P = 0.002) and HDGF-H3 (P = 0.005). When HDGF-H3 was combined with either bevacizumab or gemcitabine, we observed enhanced tumor growth inhibition, particularly when the three agents were used together. HDGF-H3-treated tumors exhibited significant reduction of microvessel density with a pattern distinctive from the microvessel reduction pattern observed in bevacizumab-treated tumors. HDGF-H3-treated but not bevacizumab-treated tumors also showed a significant increase of apoptosis. Interestingly, many of the apoptotic cells in HDGF-H3-treated tumors are stroma cells, suggesting that the mechanism of the antitumor activity is, at least in part, through disrupting formation of tumor-stroma structures. Our results show that HDGF is a novel therapeutic target for lung cancer and can be effectively targeted by an antibody-based approach.

Expression, induction and regulation of the cytochrome P450 monooxygenase system in the rat glioma C6 cell line

The cytochrome P450 monooxygenase system consists of NADPH- cytochrome P450 reductase (P450 reductase) and cytochromes P450, which can catalyze the oxidation of a wide variety of endogenous and exogenous compounds, including steroid hormones, fatty acids, drugs, and pollutants. The functions of this system are as diverse as the substrates. P450 reductase transfers reducing equivalents from NADPH to P450, which in turn catalyzes metabolic reactions. This enzyme system has the highest level of activity in the liver. It is also present in other tissues, including brain. The functions of this enzyme system in brain seem to include: neurotransmission, neuroendocrinology, developmental and behavioral modulation, regulation of intracellular levels of cholesterol, and potential neurotoxicity.^ In this study, we have set up the rat glioma C6 cell line as an in vitro model system to examine the expression, induction, and tissue-specific regulation of P450s and P450 reductase. Rat glioma C6 cells were treated with P450 inducers phenobarbital (PB) or benzo(a)anthracene (BA). The presence of P450 reductase and of cytochrome P450 1A1, 1A2, 2A1, 2B1/2, 2C7, 2D1-5 and 2E1 was detected by reverse transcription followed by polymerase chain reaction (RT-PCR) and confirmed by restriction digestion. The induction of P450 1A1 and 2B1/2 and P450 reductase was quantified using competitive PCR. Ten- and five-fold inductions of P450 1A and 2B mRNA after BA or PB treatments, respectively, were detected. Western blot analysis of microsomal preparations of glioma C6 cells demonstrated the presence of P450 1A, 2B and P450 reductase at the protein level. ELISAs showed that BA and PB induce P450 1A and 2B proteins 7.3- and 13.5-fold, respectively. Microsomes prepared from rat glioma C6 cells showed cytochrome P450 CO difference spectra with absorption at or near 450 nm. Microsomes prepared from rat glioma C6 cells demonstrated much higher levels of ethoxyresorufin O-deethylase (EROD) and pentoxyresorufin O-dealkylase (PROD) activity, when treated with BA or PB, respectively. These experiments provide further evidence that the rat glioma C6 cell line contains an active cytochrome P450 monooxygenase system which can be induced by P450 inducers. The mRNAs of P450 1A1 and 2B1/2 can not bind to the oligo(dT) column efficiently, indicating they have very short poly(A) tails. This finding leads us to study the tissue specific regulation of P450s at post-transcriptional level. The half lives of P450 1A1 and 2B1/2 mRNA in glioma C6 cells are only 1/10 and 1/3 of that in liver. This may partly contribute to the low expression level of P450s in glial cells. The induction of P450s by BA or PB did not change their mRNA half lives, indicating the induction may be due to transcriptional regulation. In summary of this study, we believe the presence of the cytochrome P450 monooxygenase system in glial cells of the brain may be important in chemotherapy and carcinogenesis of brain tumors. ^

106: Synthetic preimplantation factor (sPIF*) promotes neuroprotection by modulating PKA/PKC kinases

OBJECTIVE: Survivors of premature birth suffer from long term disabilities. Synthetic PreImplantation Factor (sPIF*) modulates inflammatory responses and reverses neuroinflammation. Proteinkinase A (PKA) and protein kinase C (PKC) are crucial signaling molecules. PKA up-regulates IL-10 and brain-derived neurotrophic factor (BDNF) expression, which exert neuroprotective effects. Anti-apoptotic phosphorylation of Bad is mediated by PKA. PKC phosphorylates GAP-43, a marker for neuronal plasticity and structural recovery. We explored sPIF protective role in neuronal (N2a) cells and in a rat model of encephalopathy of prematurity. *proprietary. STUDY DESIGN: Cells were subjected to LPS and treated with sPIF or scrambled sPIF. Neonatal rats (postnatal day 3: P3) were subjected to LPS, ligation of carotid artery, and hypoxia (8% O2, 65min; n¼ 30). sPIF (0.75mg/kg twice daily) was injected (P6-13) and brains harvested at P13. sPIF’s potential and mechanisms were evaluated using immunohistochemistry, ELISA, Western Blot, and qRT-PCR. Data were analyzed using two-tailed Student’s t-test. P<0.05 wasconsidered statistically significant. RESULTS: In vitro sPIF increased PKA/PKC activity in time dependent manner (Fig. 1A). sPIF induced higher IL-10, BDNF, and GAP-43 and lower CASP3, BAD, and TNF-a mRNA levels (Fig. 1B,C). sPIF increased pGap-43/Gap-43 and decreased pBad/Bad ratio while decreasing Bad (Fig. 1 D,E). In brain tissue sPIF treatment resulted in rescued neuronal number (NeuN positive cells) and reduced apoptosis (Casp-3 positive cells) with decreased glial (Iba-1 positive cells) activation (Fig. 2A,B). The Iba-1 morphology changed from predominantly amoeboid to ramified state. Additionally sPIF increased IL-10 mRNA levels (Fig. 2C) and pGap-43/Gap-43 ratio (Fig. 2D). CONCLUSION: sPIF modulates PKA/PKC pathways reducing apoptosis and inflammatory responses while increasing neuronal plasticity and survival. The identified PKA/PKC regulatory axis strengthens the potential of sPIF in reducing the burden of prematurity.

Chronic stress promotes tumor growth through increased BDNF production and neo-innervation

Background: Activation of the sympathetic nervous system (SNS) in response to chronic biobehavioral stress results in high levels of catecholamines and persistent activation of adrenergic signaling, which promotes tumor growth and progression. However it is unknown how catecholamine levels within the tumor exceed systemic levels in circulation. I hypothesized that neo-innervation of tumors is required for stress-mediated effects on tumor growth. Results: First, I examined whether sympathetic nerves are present in human ovarian cancer samples as well as orthotopic ovarian cancer models. Immunohistochemical (IHC) staining for neurofilament revealed that catecholaminergic neurons are present within tumor tissue. In order to determine whether chronic stress affects the density of nerves in the tumor, I utilized an orthotopic mouse model of ovarian cancer that was exposed to daily restraint stress. IHC analysis revealed that nerve density in tumors increased by more than three-fold in stressed animals versus non-stressed controls. IHC analysis suggested that this results from both recruitment of existing neurons (axonogenesis) as well as new neuron formation (neurogenesis) within the tumor. To determine how tumors are recruiting nerve growth, I utilized a PCR array analysis of 84 nerve growth related genes and their receptors, which showed that stimulation of the SKOV3 ovarian cancer cell line with norepinephrine (NE) leads to increased expression of several neurotrophins, including brain-derived neurotrophic factor (BDNF). Neurite extension assays showed that media conditioned by ovarian cancer cell lines is capable of inducing neurite outgrowth in differentiated neuron-like PC12 cells, and NE treatment of cancer cells potentiates this effect. Norepinephrine-induced neurite extension was abolished after BDNF silencing by siRNA, suggesting that BDNF is critical to tumor cell-induced nerve growth. in vivo BDNF inhibition resulted in complete abrogation of stress-induced increases in tumor weight and nerve density, as well as downstream markers of stress. Discussion: These studies indicate that adrenergic signalling induced by chronic stress promotes neo-innervation in the tumor microenvironment. This results in a mutually beneficial relationship between the tumor cells and neurons. This work is crucial for providing a link between chronic stress and its effects on the tumor and its microenvironment. The data shown here aims to open new venues that can be used in development of therapies designed to block the stress effects on tumor growth.

Aberrant regulation of the Src -FAK signaling pathway in the human colon adenocarcinoma cell line HT-29

c-Src, a protein tyrosine kinase (PTK) the specific activity of which is increased $>$20-fold in $\sim$80% of colon tumors and colon tumor cell lines, plays a role in both growth regulation and tumorigenicity of colon tumor cells. To examine the effect of increased c-Src specific activity on colon tumor cells, coumarin-derived tyrosine analog PTK inhibitors were assessed in a standard colon tumor cell line, HT-29. Of the nine compounds tested for inhibiting c-Src activity in a standard immune complex kinase assay from c-Src precipitated from HT-29 cells, the 7,8-dihydroxy-containing compounds daphnetin and fraxetin were most effective, with IC$\sb{50}$s of 0.6 $\pm$ 0.2 mM and 0.6 $\pm$ 0.3 mM, respectively. Treatment of HT-29 cells with daphnetin resulted in inhibition of cell growth in a dose-dependent manner. In contrast, scopoletin, a relatively poor Src inhibitor in vitro, did not inhibit HT-29 cell growth in the concentration range tested. In daphnetin treated cells, a dose-dependent decrease of c-Src activity paralleling cell growth inhibition was also observed; the IC$\sb{50}$ was 0.3 $\pm$ 0.1 mM for c-Src autophosphorylation. In contrast, the IC$\sb{50}$ for c-Src protein level was $>$ 0.6 mM, indicating that the effects of daphnetin were primarily an enzymatic activity of c-Src, rather than protein level in HT-29 cells. These results are the first to demonstrate that c-Src specific activity regulates colon tumor cell growth.^ To elucidate the signaling pathways activated by c-Src in colon tumor cells, the Src family substrate FAK, which has been shown to play a role in both extracellular matrix-dependent cell growth and survival, was examined. Coprecipitation assays showed Src-FAK association in detergent insoluble fractions of both attached and detached HT-29 cells, indicating that Src-FAK association in HT-29 cells is stable and, unlike untransformed cells, not dependent on cell-substratum contact. FAK also coprecipitated with Grb2, an adaptor protein also playing a role in cell proliferation and survival, in both attached and detached HT-29 cells, suggesting that a Src-FAK-Grb2-mediated signaling pathway(s) in HT-29 cells is/are constitutively activated.^ FAK was also analyzed in c-src antisense HT-29 clones AS15 and AS33 in which c-Src is specifically reduced by transfection of an antisense expression vector. FAK protein level is unexpectedly decreased in both AS15 and AS33 cells by 5-fold and 1.5-fold compared to HT-29, respectively, corresponding with the decreased expression of c-Src observed in these cells. FAK protein level was not decreased compared to parental in the c-src "sense" clone S8. Northern blot analyses showed decreased FAK mRNA levels compared to parental in AS15 and AS33, correlating with decreased FAK protein level, indicating that FAK activity in the antisense cells is regulated, at least in part, by altering FAK expression, and that this regulation is Src dependent. Because FAK has been implicated in anoikis, the ability of c-src antisense cells to survive in the absence of cell-substratum contact was examined. Decreased cell survival is seen in both AS15 and AS33, correlating with the decreases in c-Src and FAK levels and tumorigenicity in these cells. These results suggest that at least one mechanism by which activation of c-Src contributes to tumorigenic phenotype of colon tumor cells is by aberrantly promoting a survival signal through unregulated Src-FAK-Grb2 complexes. (Abstract shortened by UMI.) ^

The role of platelet -derived growth factor (PDGF) signaling in gliomagenesis

Gliomas are primary central nervous system (CNS) neoplasms that are believed to arise from astrocytes, oligodendrocytes or their precursors. Gliomas can be classified into two major histopathological groups: oligodendroglial and astroglial tumors. The most malignant of the astroglial tumors is glioblastoma multiforme (GBM). A great deal of genetic and epigenetic alterations have been implicated in gliomagenesis. In particular, PDGF signaling is frequently over-activated in a large number of human gliomas. In order to gain insights into the biology of gliomas, we manage to model human gliomas in mice using a somatic gene transfer approach—RCAS/TVA system. In our previous study, combined activation of AKT and RAS pathways gave rise to glioblastomas from CNS progenitors. In the present study, we demonstrate that in vivo autocrine PDGF stimulation induces oligodendrogliomas and mixed oligoastrocytomas from CNS progenitors and differentiated astrocytes respectively. In culture autocrine PDGF stimulation dedifferentiates astrocytes into progenitor-like cells and blockade of PDGF signaling reverses these phenotypic changes. Experimental disruption of cell cycle arrest pathway, such as Ink4a-Arf loss, is not required for the initiation of PDGF-induced gliomagenesis; instead, this mutation contributes to the tumor progression by enhancing tumor malignancy and shortening tumor latency. P53 deficiency does not promote the PDGF-induced gliomagenesis. In addition, 1p and 19q, often deleted in human oligodendrogliomas, remain intact in these PDGF-induced gliomas. Therefore, our studies suggest that autocrine PDGF stimulation alone may be sufficient to induce gliomagenesis. In contrast to transient stimulation in vitro, constitutive PDGF stimulation activates neither AKT nor RAS/MAPK pathways during gliomagenesis. This results in the formation of oligodendrogliomas, instead of glioblastomas. Sustained activation of the AKT pathway converts PDGF-induced oligodendrogliomas into astrocytomas. Our studies suggest that constitutive PDGF stimulation is not equivalent to transient PDGF stimulation, and that a transition between oligodendroglial and astroglial tumors in humans may be possible, depending on additional alterations. In summary, PDGF signaling plays a pivotal role in gliomagenesis in the mouse, and its hyperactivity is capable of contributing to both oligodendroglial and astroglial tumorigenesis. ^

The activation domain of the enhancer binding protein p45NF-E2 interacts with TAFII130 and mediates long-range activation of the α- and β-globin gene loci in an erythroid cell line

We have used the interaction between the erythroid-specific enhancer in hypersensitivity site 2 of the human β-globin locus control region and the globin gene promoters as a paradigm to examine the mechanisms governing promoter/enhancer interactions in this locus. We have demonstrated that enhancer-dependent activation of the globin promoters is dependent on the presence of both a TATA box in the proximal promoter and the binding site for the erythroid-specific heteromeric transcription factor NF-E2 in the enhancer. Mutational analysis of the transcriptionally active component of NF-E2, p45NF-E2, localizes the critical region for this function to a proline-rich transcriptional activation domain in the NH2-terminal 80 amino acids of the protein. In contrast to the wild-type protein, expression of p45 NF-E2 lacking this activation domain in an NF-E2 null cell line fails to support enhancer-dependent transcription in transient assays. More significantly, the mutated protein also fails to reactivate expression of the endogenous β- or α-globin loci in this cell line. Protein-protein interaction studies reveal that this domain of p45 NF-E2 binds specifically to a component of the transcription initiation complex, TATA binding protein associated factor TAFII130. These findings suggest one potential mechanism for direct recruitment of distal regulatory regions of the globin loci to the individual promoters.