Precision Measurement of the Proton Flux in Primary Cosmic Rays from Rigidity 1 GV to 1.8 TV with the Alpha Magnetic Spectrometer on the International Space Station

A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 GV to 1.8 TV is presented based on 300 million events. Knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. We present the detailed variation with rigidity of the flux spectral index for the first time. The spectral index progressively hardens at high rigidities.

Precision Measurement of the (e^{+}+e^{-}) Flux in Primary Cosmic Rays from 0.5 GeV to 1 TeV with the Alpha Magnetic Spectrometer on the International Space Station

We present a measurement of the cosmic ray (e^{+}+e^{-}) flux in the range 0.5 GeV to 1 TeV based on the analysis of 10.6 million (e^{+}+e^{-}) events collected by AMS. The statistics and the resolution of AMS provide a precision measurement of the flux. The flux is smooth and reveals new and distinct information. Above 30.2 GeV, the flux can be described by a single power law with a spectral index γ=-3.170±0.008(stat+syst)±0.008(energy scale).

Endothelin A receptor/β-arrestin signaling to the Wnt pathway renders ovarian cancer cells resistant to chemotherapy

The high mortality of epithelial ovarian cancer (EOC) is mainly caused by resistance to the available therapies. In EOC, the endothelin-1 (ET-1, EDN1)-endothelin A receptor (ETAR, EDNRA) signaling axis regulates the epithelial-mesenchymal transition (EMT) and a chemoresistant phenotype. However, there is a paucity of knowledge about how ET-1 mediates drug resistance. Here, we define a novel bypass mechanism through which ETAR/β-arrestin-1 (β-arr1, ARRB1) links Wnt signaling to acquire chemoresistant and EMT phenotype. We found that ETAR/β-arr1 activity promoted nuclear complex with β-catenin and p300, resulting in histone acetylation, chromatin reorganization, and enhanced transcription of genes, such as ET-1, enhancing the network that sustains chemoresistance. Silencing of β-arr1 or pharmacologic treatment with the dual ETAR/ETBR antagonist macitentan prevented core complex formation and restored drug sensitivity, impairing the signaling pathways involved in cell survival, EMT, and invasion. In vivo macitentan treatment reduced tumor growth, vascularization, intravasation, and metastatic progression. The combination of macitentan and cisplatinum resulted in the potentiation of the cytotoxic effect, indicating that macitentan can enhance sensitivity to chemotherapy. Investigations in clinical specimens of chemoresistant EOC tissues confirmed increased recruitment of β-arr1 and β-catenin to ET-1 gene promoter. In these tissues, high expression of ETAR significantly associated with poor clinical outcome and chemoresistance. Collectively, our findings reveal the existence of a novel mechanism by which ETAR/β-arr1 signaling is integrated with the Wnt/β-catenin pathway to sustain chemoresistance in EOC, and they offer a solid rationale for clinical evaluation of macitentan in combination with chemotherapy to overcome chemoresistance in this setting.

Abstract 2684: Inhibition of tumor growth and angiogenesis by SP-2, an anti-LGALS3BP antibody

Background: Accumulating evidence indicates that serum and tissue levels of the lectin galactoside-binding soluble 3 binding protein (LGALS3BP), a secreted glycoprotein, are elevated in human cancer. Recently, we have identified LGALS3BP as a factor capable of stimulating angiogenesis of microvascular endothelial cells in culture as well as in vivo. However, the potential therapeutic implications of LGALS3BP function blockade, has not been explored yet.

Methods: Here we tested the ability of an anti-LGALS3BP monoclonal antibody, named SP-2, to antagonize LGALS3BP-induced angiogenesis and tumor growth.

Results: SP-2 dose-dependently inhibited HUVEC tubulogenesis induced by either conditioned medium of breast cancer and melanoma cells or purified recombinant LGALS3BP. This was accompanied by inhibition of FAK, Akt and ERKs phosphorylation as well as FAK recruitment to membrane sites and actin remodeling. In vivo, SP-2 inhibited LGALS3BP-stimulated angiogenesis and restrained growth of different xenograft models of human cancer. Finally, the combination of SP-2 with low-dose Bevacizumab was more effective than either agent alone in suppressing angiogenesis and tumor growth.

Conclusions: Targeting LGALS3BP with SP-2 could represent a promising therapeutic approach for LGALS3BP expressing tumors.

Citation Format: Enza Piccolo, Sara Trani, Nicola Tinari, Cosmo Rossi, Rossana La Sorda, Rossano Lattanzio, Maurizia D'Egidio, Annalisa Di Risio, Antonino Grassadonia, Francesca Spinella, Anna Bagnato, Mauro Piantelli, Clara Natoli, Stefano Iacobelli. Inhibition of tumor growth and angiogenesis by SP-2, an anti-LGALS3BP antibody. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2684. doi:10.1158/1538-7445.AM2014-2684

Electron and positron fluxes in primary cosmic rays measured with the alpha magnetic spectrometer on the international space station

Precision measurements by the Alpha Magnetic Spectrometer on the International Space Station of the primary cosmic-ray electron flux in the range 0.5 to 700 GeV and the positron flux in the range 0.5 to 500 GeV are presented. The electron flux and the positron flux each require a description beyond a single power-law spectrum. Both the electron flux and the positron flux change their behavior at ∼30  GeV but the fluxes are significantly different in their magnitude and energy dependence. Between 20 and 200 GeV the positron spectral index is significantly harder than the electron spectral index. The determination of the differing behavior of the spectral indices versus energy is a new observation and provides important information on the origins of cosmic-ray electrons and positrons.

High statistics measurement of the positron fraction in primary cosmic rays of 0.5-500 GeV with the alpha magnetic spectrometer on the international space station

A precision measurement by AMS of the positron fraction in primary cosmic rays in the energy range from 0.5 to 500 GeV based on 10.9 million positron and electron events is presented. This measurement extends the energy range of our previous observation and increases its precision. The new results show, for the first time, that above ∼200  GeV the positron fraction no longer exhibits an increase with energy.

Observation of the resonant character of the Z(4430)(-) state

Resonant structures in B^{0}→ψ^{'}π^{-}K^{+} decays are analyzed by performing a four-dimensional fit of the decay amplitude, using pp collision data corresponding to 3  fb^{-1} collected with the LHCb detector. The data cannot be described with K^{+}π^{-} resonances alone, which is confirmed with a model-independent approach. A highly significant Z(4430)^{-}→ψ^{'}π^{-} component is required, thus confirming the existence of this state. The observed evolution of the Z(4430)^{-} amplitude with the ψ^{'}π^{-} mass establishes the resonant nature of this particle. The mass and width measurements are substantially improved. The spin parity is determined unambiguously to be 1^{+}.

Measurement of charged particle multiplicities and densities in [Formula: see text] collisions at [Formula: see text]TeV in the forward region

Charged particle multiplicities are studied in proton-proton collisions in the forward region at a centre-of-mass energy of [Formula: see text]TeV with data collected by the LHCb detector. The forward spectrometer allows access to a kinematic range of [Formula: see text] in pseudorapidity, momenta greater than [Formula: see text] and transverse momenta greater than [Formula: see text]. The measurements are performed using events with at least one charged particle in the kinematic acceptance. The results are presented as functions of pseudorapidity and transverse momentum and are compared to predictions from several Monte Carlo event generators.

Measurement of [Formula: see text] polarisation in [Formula: see text] collisions at [Formula: see text] = 7 TeV

The polarisation of prompt [Formula: see text] mesons is measured by performing an angular analysis of [Formula: see text] decays using proton-proton collision data, corresponding to an integrated luminosity of 1.0[Formula: see text], collected by the LHCb detector at a centre-of-mass energy of 7 TeV. The polarisation is measured in bins of transverse momentum [Formula: see text] and rapidity [Formula: see text] in the kinematic region [Formula: see text] and [Formula: see text], and is compared to theoretical models. No significant polarisation is observed.

Measurement of the [Formula: see text] meson lifetime using [Formula: see text] decays

The lifetime of the [Formula: see text] meson is measured using semileptonic decays having a [Formula: see text] meson and a muon in the final state. The data, corresponding to an integrated luminosity of [Formula: see text], are collected by the LHCb detector in [Formula: see text] collisions at a centre-of-mass energy of 8 TeV. The measured lifetime is [Formula: see text]where the first uncertainty is statistical and the second is systematic.

Observation of photon polarization in the b→sγ transition

This Letter presents a study of the flavor-changing neutral current radiative B±→K±π∓π±γ decays performed using data collected in proton-proton collisions with the LHCb detector at 7 and 8 TeV center-of-mass energies. In this sample, corresponding to an integrated luminosity of 3  fb-1, nearly 14 000 signal events are reconstructed and selected, containing all possible intermediate resonances with a K±π∓π± final state in the [1.1,1.9]  GeV/c2 mass range. The distribution of the angle of the photon direction with respect to the plane defined by the final-state hadrons in their rest frame is studied in intervals of K±π∓π± mass and the asymmetry between the number of signal events found on each side of the plane is obtained. The first direct observation of the photon polarization in the b→sγ transition is reported with a significance of 5.2σ.

Search for Majorana neutrinos in B- → π+ μ- μ- decays

A search for heavy Majorana neutrinos produced in the B- → π+ μ- μ- decay mode is performed using 3  fb(-1) of integrated luminosity collected with the LHCb detector in pp collisions at center-of-mass energies of 7 and 8 TeV at the LHC. Neutrinos with masses in the range 250 to 5000 MeV and lifetimes from zero to 1000 ps are probed. In the absence of a signal, upper limits are set on the branching fraction B(B- → π+ μ- μ-) as functions of neutrino mass and lifetime. These limits are on the order of 10(-9) for short neutrino lifetimes of 1 ps or less. Limits are also set on the coupling between the muon and a possible fourth-generation neutrino.

Inhibition of tumor growth and angiogenesis by SP-2, an anti-lectin, galactoside-binding soluble 3 binding protein (LGALS3BP) antibody

Accumulating evidence indicates that serum and tissue levels of lectin, galactoside-binding soluble 3 binding protein (LGALS3BP), a secreted glycoprotein, are elevated in human cancers. Recently, we have identified LGALS3BP as a factor capable of stimulating angiogenesis of microvascular endothelial cells in vitro as well as in vivo. However, the potential therapeutic implications of LGALS3BP function blockade have not been explored yet. Here, we tested the ability of an anti-LGALS3BP mouse monoclonal antibody, SP-2, to antagonize LGALS3BP-induced angiogenesis and tumor growth. The antibody was found to inhibit endothelial cell tubulogenesis induced by either conditioned medium of breast cancer and melanoma cells or human recombinant LGALS3BP. In addition, SP-2 inhibited phosphorylation of FAK and its recruitment to membrane sites as well as AKT and ERK phosphorylation promoted by LGALS3BP. When used in vivo, the antibody restrained LGALS3BP-stimulated angiogenesis and growth of tumor xenografts. Furthermore, the combination of SP-2 and low-dose bevacizumab was more effective than either agent alone. Taken together, these results lead to consideration of SP-2 as a promising candidate for LGALS3BP-targeted therapy.

The interplay between hypoxia, endothelial and melanoma cells regulates vascularization and cell motility through endothelin-1 and vascular endothelial growth factor

Reciprocal growth factor exchanges between endothelial and malignant cells within the hypoxic microenvironment determine tumor progression. However, the nature of these exchanges has not yet been fully explored. We studied the mutual regulation between endothelial cells (EC), melanoma cells and hypoxia that dictate tumor aggressiveness and angiogenic activity. Here, we investigated the presence of bidirectional autocrine/paracrine endothelin (ET)-1/ET receptor (ETBR) signaling in melanoma cells, blood and lymphatic EC. In all these cells, hypoxia enhanced ET-1 expression, which in turn induced vascular endothelial growth factor (VEGF)-A and VEGF-C secretion, through the hypoxia-inducible growth factor (HIF)-1α and HIF-2α. Autocrine/paracrine exchanges of ET-1, VEGF-A and VEGF-C promoted tumor aggressiveness and morphological changes in blood and lymphatic EC. Furthermore, conditioned media from EC enhanced melanoma cell migration and vessel-like channel formation. This regulation was inhibited by ETBR blockade, by using the selective ETBR antagonist, or ETBR small interfering RNA (siRNA), and by VEGFR-2/-3 antibodies, indicating that ET-1, VEGF-A/VEGF-C, produced by melanoma cells or EC mediated inter-regulation between these cells. Interestingly, HIF-1α/HIF-2α siRNA, impaired this reciprocal regulation, demonstrating the key role of these transcriptional factors in signaling exchanges. In melanoma xenografts, the ETBR antagonist reduced tumor growth and the number of blood and lymphatic vessels. These results reveal an interplay between melanoma cells and EC mediated by ET-1 and VEGF-A/-C and coordinated by the hypoxic microenvironment through HIF-1α/2α transcriptional programs. Thus, targeting ETBR may improve melanoma treatment for tumor and EC, by inhibiting autocrine/paracrine signaling that sustains melanoma progression.

Evidence for G-quadruplex in the promoter of vegfr-2 and its targeting to inhibit tumor angiogenesis

Tumor angiogenesis is mainly mediated by vascular endothelial growth factor (VEGF), a pro-angiogenic factor produced by cancer cells and active on the endothelium through the VEGF receptor 2 (VEGFR-2). Here we identify a G-rich sequence within the proximal promoter region of vegfr-2, able to form an antiparallel G-quadruplex (G4) structure. This G4 structure can be efficiently stabilized by small molecules with the consequent inhibition of vegfr-2 expression. Functionally, the G4-mediated reduction of VEGFR-2 protein causes a switching off of signaling components that, converging on actin cytoskeleton, regulate the cellular events leading to endothelial cell proliferation, migration and differentiation. As a result of endothelial cell function impairment, angiogenic process is strongly inhibited by G4 ligands both in vitro and in vivo. Interestingly, the G4-mediated antiangiogenic effect seems to recapitulate that observed by using a specific interference RNA against vegfr-2, and it is strongly antagonized by overexpressing the vegfr-2 gene. In conclusion, we describe the evidence for the existence of G4 in the promoter of vegfr-2, whose expression and function can be markedly inhibited by G4 ligands, thereby revealing a new, and so far undescribed, way to block VEGFR-2 as target for anticancer therapy.

Endothelin 1 in cancer: biological implications and therapeutic opportunities

Activation of autocrine and paracrine signalling by endothelin 1 (ET1) binding to its receptors elicits pleiotropic effects on tumour cells and on the host microenvironment. This activation modulates cell proliferation, apoptosis, migration, epithelial-to-mesenchymal transition, chemoresistance and neovascularization, thus providing a strong rationale for targeting ET1 receptors in cancer. In this Review, we discuss the advances in our understanding of the diverse biological roles of ET1 in cancer and describe the latest preclinical and clinical progress that has been made using small-molecule antagonists of ET1 receptors that inhibit ET1-driven signalling.

Abstract 756: Endothelin-induced multifunctional complex regulates β-arrestin-1 nuclear activity to promote EMT in chemoresistant ovarian cancer cells

Chemotherapy is the preferred therapeutic approach for advanced epithelial ovarian cancer (EOC), but a successful long-term treatment is prevented by the development of drug resistance. In EOC cells, there are ample evidences supporting the role of the endothelin-1 (ET-1)/ ET A receptor (ETAR) signaling in invasive and drug-resistant cells. Moreover, in these cells ET-1/ETAR pathway promotes the epithelial-mesenchymal transition (EMT), a phenotype that is closely linked with the development of drug resistance and metastasis. To decipher ETAR signaling complexity in EMT and chemoresistance, we explored the role of β-arrestin-1 (β-arr1), a protein that mediates signals in response to receptor recruitment, as nuclear scaffold to control gene transcription in chemoresistant EOC cells. To this end we used cisplatin-sensitive EOC cell lines (A2780 and 2008) and their resistant variants. In chemoresistant cells, β-arr1 and ETAR were ovexpressed. In response to ETAR activation by ET-1, β-arr1 increases its nuclear translocation, and its interaction with transcription factors critically involved in EMT, such as β-catenin, Snail, and HIF-1α, and forms nuclear complexes capable to localize these transcription factors on the promoter regions of their target genes, such as ET-1, Axin2, matrix-metalloproteinase-2, and Cyclin D1. Moreover, β-arr1, by promoting the dissociation of transcriptional repressors, such as HDAC1, and the recruitment of transcriptional activator, such as p300 acetyltransferase, controls epigenetic modifications and gene transcription. These effects are abrogated by β-arr1 silencing or by expression of a mutant β-arr1 incapable of nuclear distribution, confirming that nuclear β-arr1 forms functional complex capable of regulating epigenetic changes in ET-1-driven invasive behaviour. At functional level, β-arr1 silencing or expression of mutant β-arr1, as well as ET-1 receptor blockade resulted in reduced cell invasion, and EMT determinant expression, as well as metastasis inhibition in sensitive and resistant EOC xenografts, providing evidence that blockade of ETAR/β-arr1-driven EMT can overcome chemoresistance and inhibit tumor progression. In human EOC tissues, β-arr1-dependent nuclear complexes are selectively enriched at target gene promoters, correlating with tumor grade, confirming a direct in vivo β-arr1 association at specific set of genes involved in EOC progression. Collectively, our findings provide insights into how β-arr1-mediated epigenetic mechanism driven by ETAR controls EMT transcriptional responses and chemoresistance. Supported by AIRC.

Citation Format: Laura Rosanò, Roberta Cianfrocca, Piera Tocci, Elisa Semprucci, Francesca Spinella, Valeriana Di Castro, Anna Bagnato. Endothelin-induced multifunctional complex regulates β-arrestin-1 nuclear activity to promote EMT in chemoresistant ovarian cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 756. doi:10.1158/1538-7445.AM2013-756

First result from the Alpha Magnetic Spectrometer on the International Space Station: precision measurement of the positron fraction in primary cosmic rays of 0.5-350 GeV

A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 × 10(6) positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250  GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena.

Endothelin-1 induces the transactivation of vascular endothelial growth factor receptor-3 and modulates cell migration and vasculogenic mimicry in melanoma cells

Endothelin receptor B (ET(B)R) is a G-protein-coupled receptor overexpressed in melanoma, blood, and lymphatic endothelial cells. Given that aberrant signal transduction can be mediated through cross talk between receptors, here, we explore the functional relationship between ET(B)R and the vascular endothelial growth factor receptor (VEGFR)-3 system and how this cross talk might influence the aggressive behavior of melanoma cells. The expression of VEGFR-3 and its ligands, VEGF-C and VEGF-D, significantly increased after activating ET(B)R by ET-1 in primary and metastatic melanoma cell lines. These effects, similarly to those induced by hypoxia, were mediated by hypoxia-inducible factor (HIF)-1α and HIF-2α. ET-1 caused the phosphorylation of VEGFR-3, which was accompanied by the activation of the downstream signaling molecules, such as MAPK and AKT. Inhibition of c-Src activity or silencing of the scaffold protein β-arrestin-1 reduced ET-1-induced VEGFR-3 phosphorylation, demonstrating that, upon ET-1 stimulus, β-arrestin-1 is involved with c-Src in the ET(B)R-mediated VEGFR-3 transactivation. Moreover, ET-1 in combination with VEGF-C further increased VEGFR-3, MAPK, and AKT phosphorylation and markedly promoted cell migration and vasculogenic mimicry. Dual inhibition of ET(B)R and VEGFR-3 was required for the effective inhibition of these effects, as well as for VEGFR-3 phosphorylation, demonstrating that ET(B)R cross talk with VEGFR-3 enhances cell plasticity and motility. Finally, in melanoma xenografts, ET(B)R antagonist inhibited tumor growth and the activation of the VEGF-C/VEGFR-3 axis, indicating that targeting ET(B)R may improve melanoma treatment acting directly or indirectly by impairing ET(B)R cross talk with VEGFR-3.

Abstract 493: Endothelin-1 induces activation of vascular endothelial growth factor receptor-3 and modulates cell migration and vasculogenic mimicry in melanoma cells

Phenotypic and genotypic analyses of cutaneous melanoma have identified endothelin B receptor (ETBR) as tumor progression marker, thus representing a potential therapeutic target. We previously reported that the binding of ET-1 to ETBR stimulates angiogenesis and lymphangiogenesis directly and by stimulating vascular endothelial growth factor (VEGF)-A and VEGF-C production. In this study we investigated as to whether in melanoma cells ET-1 axis may interact with VEGF-A and VEGF-C signaling pathways to heighten cellular responsiveness. We found that in primary and metastatic melanoma cell lines, ET-1 increased VEGF-A, VEGF-C and its selective receptor VEGFR-3, at mRNA and protein level. Following ET-1 stimulation, VEGF-A and VEGF-C were upregulated, VEGFR-3 was rapidly phosphorylated and downstream signaling intermediates, such as p42/44 MAPK and Akt, were activated through ETBR. Inhibition of c-Src activity by PP2, reduced ET-1-induced VEGFR-3 phosphorylation, demonstrating that ET-1 transactivates VEGFR-3 through an intracellular mechanism mediated by c-Src. Stimulation with ET-1 in combination with VEGF-A or VEGF-C increased p42/44 MAPK and AKT phosphorylation, and resulted in a greater degree of melanoma cell migration compared to a single factor. Furthermore, this combination significantly enhanced the ET-1-induced vasculogenic differentiation of melanoma cells in capillary-like structures, vasculogenic mimicry, indicating that crosstalk between ET-1/ETBR axis with VEGFR-3/VEGF-C system may enhance cancer cell motility and invasiveness and contributes to the promotion of cancer metastasis. Finally, in melanoma xenografts, ETBR antagonist suppressed tumor growth and neovascularization-related effectors, indicating that targeting ETBR related signalling cascade may represent a novel treatment of melanoma by impairing the crosstalk between ET-1 axis and VEGF in melanoma. Supported by AIRC

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 493. doi:1538-7445.AM2012-493

Abstract 3086: α-arrestin-1 acts as a nuclear transcriptional regulator of endothelin A receptor signalling to promote ovarian cancer progression

In epithelial ovarian cancer (EOC), endothelin (ET)-1/endothelin A receptor (ETAR) autocrine loop activates epithelial to mesenchymal transition (EMT) and malignant progression through the activation of β-catenin-driven transcriptional programs. Although it has been demonstrated that α-arrestin-1 (α-arr1) is involved in ETAR signalling acting as cytoplasmic scaffold protein, the specific contribution to ETAR-regulated EOC progression in the nuclear compartment remains undefined. In this study, we demonstrated that in response to ETAR activation by ET-1, endogenous as well as exogenous α-arr1 translocated to the nucleus in different EOC cell lines. To study a putative role of α-arr1 in controlling gene expression, we investigated the relationship of α-arr1 with β-catenin. We found that ET-1-driven α-arr1 nuclear translocation is associated with a nuclear translocation of with β-catenin and their physical interaction, as shown by microscopy and biochemical analysis. This nuclear complex, that include TCF4 transcription factor, is localized in ET-1-dependent manner on the promoter regions of specific β-catenin target genes, such as ET-1, matrix-metalloproteinase-2, and Cyclin D1, thus promoting their transcription. Gain/loss of function approaches as well as nuclear mutant α-arr1 expression demonstrated that this complex is critical for the recruitment and binding of p300 acetyltransferase on these promoters, resulting in enhanced H3 and H4 histone acetylation, enhanced promoter activity and gene expression, specifically required for ETAR-induced cell migration, invasion, and EMT. In a murine orthotopic model of metastatic human EOC, silencing of α-arr1 or expression of nuclear mutant α-arr1, as well as ETAR blockade, by the specific antagonist zibotentan, inhibits metastasis and intravasation. Finely, in human EOC tissues, α-arr1/β-catenin nuclear complexes are selectively enriched at specific gene promoters compared to non-tumoral ovarian tissues. Therefore, our study provides insights into how a nuclear α-arr1-mediated epigenetic mechanism controls β-catenin activity in response to ETAR activation, deciphering a novel function for α-arr1 as signal transducer for the nuclear compartmentalization of ETAR signalling in promoting tumor metastasis. Supported by AIRC, AstraZeneca

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3086. doi:1538-7445.AM2012-3086

Endothelin-1 cooperates with hypoxia to induce vascular-like structures through vascular endothelial growth factor-C, -D and -A in lymphatic endothelial cells

AIMS

Lymphangiogenesis refers to the formation of new lymphatic vessels and is thought to constitute conduits for the tumor cells to metastasize. We previously demonstrated that endothelin (ET)-1 through its binding with ETB receptor (ET(B)R) expressed on lymphatic endothelial cells (LEC), induced cell growth and invasiveness. Since vascular endothelial growth factor (VEGF)-A/-C/-D, and hypoxia play key role in lymphatic differentiation, in this study we investigated the involvement of these growth factors and hypoxia in ET-1-induced lymphangiogenesis.

MAIN METHODS

Real time PCR and ELISA were used to quantify VEGF-A/-C/-D. LEC morphological differentiation was analyzed by tube formation assay on Matrigel.

KEY FINDINGS

Hypoxia, as well as ET-1, induced an increase in VEGF-A/-C and -D expression that was reduced in the presence of a selective ET(B)R antagonist, BQ788, and enhanced when ET-1 was administered under hypoxic conditions. We analyzed the role of hypoxia on LEC morphological differentiation, and found that hypoxia increased the formation of vascular-like structures on Matrigel and that in combination with ET-1 this effect was markedly enhanced. The use of specific antibodies neutralizing VEGF-A, or recombinant VEGFR-3/(Flt-4)/Fc that block VEGF-C/-D, inhibited the effect of ET-1 as well that of hypoxia.

SIGNIFICANCE

These results demonstrated that ET-1 and hypoxia act, at list in part, through VEGF to induce lymphangiogenic events and that these two stimuli may cooperate to induce VEGF-A/-C/-D expression and lymphatic differentiation. These data further support the role of ET-1 as potent lymphangiogenic factor that relies on the interplay with hypoxic microenvironment and with VEGF family members.

Abstract 698: β-arrestin-1 as nuclear signalling element essential for endothelin A receptor-induced epithelial to mesenchymal transition and chemoresistance

The onset of chemoresistance is the major challenge in epithelial ovarian cancer (EOC). Emerging evidence suggests molecular and phenotypic association between chemoresistance and epithelial-mesenchymal transition (EMT) in cancer. We recently demonstrated that β-arrestin-1, scaffold and signaling protein of G-protein-coupled receptors, is recruited to endothelin A receptor (ETAR) to form molecular signaling complexes which concur to activate β-catenin transcriptional activity, EMT and metastasis. Here, by using biochemical and imaging techniques, we provide evidence that in EOC cells, ETAR activation by endothelin-1 (ET-1) induces nuclear translocation of β-arrestin-1 and its association with β-catenin. ChIP assays demonstrated that following this translocation, β-arrestin-1 was selectively enriched at specific promoters of β-catenin target genes, such as ET-1, MMP-2, cyclin D1. Further experiments showed that ET-1 promotes the nuclear association between histone acetyltransferase p300 and β-arrestin and the recruitment of p300 on these promoters, resulting in H3 and H4 histone acetylation and enhanced gene transcription. In chemoresistant EOC cells, ET-1/ETAR axis is overexpressed associated with EMT marker expression. Most importantly, the transcriptional activity of β-catenin was upregulated in chemoresistant EOC cells, associated with enhanced ETAR and β-arrestin-1 expression, providing molecular evidence that the ETAR/β-arrestin-1-mediated EMT signaling in EOC can represent a “salvage pathway” occurring during chemoresistance development. Interestingly, ETAR blockade with zibotentan, a specific ETAR antagonist, or its silencing with siRNA, abrogates both the engagement of β-arrestin-1 in the nucleus and the interplay between ET-1 and the β-catenin in controlling gene transcription. In vivo, zibotentan inhibited tumor growth of sensitive and resistant EOC xenografts, associated with reduction of EMT markers, and sensitized to chemotherapy. Analysis of EOC human tissues revealed that ETAR is overexpressed in resistant tumors and is associated with EMT phenotype. Our data provide the first evidence that blockade of ETAR/β-arrestin-1-driven EMT can overcome chemoresistance and inhibit tumor progression, improving the outcome of EOC patients’ treatment. Supported by AIRC

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 698. doi:10.1158/1538-7445.AM2011-698

Abstract 3473: Endothelin axis autocrine loop is positively regulated by the interplay between ET-1 and hypoxia-inducible factor-1α in melanoma cells

Phenotypic and genotypic analyses of cutaneous melanoma have identified the endothelin B receptor (ETBR) as tumor progression marker, thus representing a potential therapeutic target. We previously demonstrated that ETBR activation by endothelin (ET)-1, promotes melanoma progression and lymphatic vessel growth through a hypoxia-inducible factor (HIF)-1α-mediated mechanism and cooperates with hypoxia to increase this effect. In this study we show that in melanoma cells ETs increase ET-1 and ETBR mRNA and protein expression and their promoter activity that were completely blocked by the selective ETBR antagonist, BQ788, supporting the presence of a positive ET-1-autocrine loop. Moreover when melanoma cells were exposed to hypoxia the induction of both ETBR and ET-1 was markedly enhanced demonstrating that hypoxia potentiates the ET-1-autocrine loop by reinforcing the expression of ETBR and the secretion of ET-1 that, in turn, increases simultaneously ET-1/ETBR expression. Silencing HIF-1α or HIF-2α significantly reduced the promoter activity and the expression of ET-1 and ETBR in response to hypoxia or ETs. Chromatin immunoprecipitation assay showed increased HIF-1α and HIF-2α binding to ET-1 and ETBR promoter in response to hypoxia or ET-1 stimulation. Interestingly, ETs through ETBR enhance both vascular endothelial growth factor (VEGF)-A and VEGF-C mRNA and protein expression and promoter activity. At functional level silencing of HIF-1α and HIF-2α inhibited the ET-1 and hypoxia-induced VEGF-A and VEGF-C expression, providing that hypoxia and ET-1 axis share the same transcriptional machinery through which may control angiogenic and lymphangiogenic response. Moreover, in melanoma xenografts, ETBR antagonist suppressed tumor growth, neovascularization-related effectors, indicating that targeting ETBR related signalling cascade may represent a novel treatment of melanoma by impairing the positive feedback loop between ET axis and hypoxic melanoma microenvironment. Supported by AIRC.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3473. doi:10.1158/1538-7445.AM2011-3473

Abstract 707: Acquisition of chemoresistance and epithelial to mesenchymal phenotype is linked with activation of the endothelin A receptor pathway in ovarian carcinoma cells

Understanding the molecular mechanisms underlying chemoresistance is of utmost importance for improving the treatment of epithelial ovarian cancer (EOC). Emerging evidence suggests molecular and phenotypic association between chemoresistance and epithelial-mesenchymal transition (EMT) in cancer cells. Endothelin-1 (ET-1) and the endothelin A receptor (ETAR) axis is implicated in the pathobiology of EOC by driving different tumor-promoting effects, including EMT. By employing two cisplatin- and taxol-resistant ovarian cancer cell lines, we demonstrated that in the resistant EOC cells ET-1 and ETAR are upregulated, at both mRNA and protein level, paralleled by enhanced MAPK and AKT phosphorylation and cell proliferation. To assess whether the chemoresistance in A2780 cells was associated with EMT molecular changes, we examined the expression of epithelial and mesenchymal markers. Enhanced Snail, Slug, Twist, N-cadherin and vimentin mRNA expression was observed in resistant cells, associated with a concomitant decrease in E-cadherin expression and promoter activity. Moreover, ET-1 induced a significant induction of Snail promoter activity in resistant cells, and the E-cadherin promoter sequences were detected bound to Snail in a time-dependent manner, as demonstrated by chromatin immunoprecipitation assays, suggesting that the ET-1-dependent and sustained binding of Snail in the E-cadherin promoter might account for EMT and chemoresistant phenotype of these cells. Moreover, the invasiveness and proteinase activity of chemoresistant cells was greater, compared with sensitive cells. Interestingly, ETAR blockade with the specific ETAR antagonist, zibotentan, or its silencing with siRNA, reverted EMT, restored drug sensitivity to cytotoxic-induced apoptosis, and inhibited the invasive potential of resistant cells. In vivo, zibotentan inhibited tumor growth of sensitive and resistant EOC xenografts, and sensitized to chemotherapy. Finally, analysis of EOC tissues, with different responses to chemotherapy, revealed that ETAR is overexpressed in resistant tumors and is associated with EMT marker expression. All these data indicate that blockade of ETAR-driven EMT can overcome chemoresistance in EOC, improving the outcome of EOC patients’ treatment. Supported by AIRC

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 707. doi:10.1158/1538-7445.AM2011-707

Combination therapy of zibotentan with cisplatinum and paclitaxel is an effective regimen for epithelial ovarian cancer

In human ovarian carcinoma, the endothelin-1 (ET-1) / endothelin A receptor (ETAR) axis is overexpressed, correlating with tumor grade. Moreover, ETAR activation by ET-1 affects cell proliferation, survival, angiogenesis, and invasion. ETAR blockade with zibotentan (ZD4054), a specific ETAR antagonist, significantly inhibits ovarian cancer growth in vitro and in vivo, underscoring the relevance of this pathway as a target for cancer therapy. Since clinical trial results have defined the combination of platinum and taxane as the standard of care in the management of ovarian cancer, here we explored the therapeutic efficacy of the integration of zibotentan with cytotoxic drugs having different modes of action. We found that the combination of zibotentan with cisplatinum as well as zibotentan with paclitaxel was more effective at inhibiting ovarian cancer HEY cell proliferation induced by endogenous ET-1 than were the single agents alone. However, a significantly enhanced efficacy was observed when we combined zibotentan, cisplatinum, and paclitaxel. Accordingly, in HEY xenografts the coadministration of zibotentan with cisplatinum enhanced the efficacy of the cytotoxic drug alone in controlling tumor growth, associated with reduction in proliferation index and microvessel density. Remarkably, the combination of zibotentan with both cisplatinum and paclitaxel was very effective in inhibiting tumor growth, neovascularization, and cell proliferation, representing a preclinical endpoint to guide combination therapy in clinical trials.

Beta-arrestin-1 mediates the endothelin-1-induced activation of Akt and integrin-linked kinase

The contribution of the endothelin-1 (ET-1)/ET A receptor (ETAR) axis in tumor growth and progression is investigated in many tumor types, including ovarian carcinoma. In ovarian cancer cells, ET-1 acts as an autocrine growth factor selectively through the ETAR triggering the concomitant activation of multiple pathways. In these cells, the involvement of beta-arrestin-1 as signal transducer in ET-1-dependent signalling pathways has been recently highlighted. Because several G protein-coupled receptors have been shown to activate signalling pathways in a beta-arrestin-dependent manner, in this study we explored whether beta-arrestin-1 is involved in a distinct signalling mechanism linking the ETAR to phosphoinositide 3-kinase (PI3K)/integrin-linked kinase (ILK)/Akt in HEY ovarian cancer cells. The inhibitory effects of ZD4054 (zibotentan), a specific ETAR antagonist, in ET-1-dependent phosphorylation of ILK, Akt, and glycogen synthase kinase (GSK-3beta) demonstrated the involvement of the ETAR in these effects. By using a kinase assay, we demonstrate that beta-arrestin-1 silencing inhibits the ET-1-induced ILK activity in a time-dependent manner and downstream Akt and GSK-3beta phosphorylation. These results reveal that beta-arrestin-1 is implicated as an ETAR-transducer in the activation of ILK and Akt and in the inactivation of GSK-3beta in response to ET-1 and further support the role of beta-arrestin-1 as a multifunctional adaptor facilitating interprotein interactions critically involved in ETAR-mediated signalling that regulate invasive and metastatic behaviour of ovarian cancer.

Acquisition of chemoresistance and EMT phenotype is linked with activation of the endothelin A receptor pathway in ovarian carcinoma cells

PURPOSE

Emerging evidence suggests molecular and phenotypic association between chemoresistance and epithelial-mesenchymal transition (EMT) in cancer. Endothelin-1 (ET-1)/endothelin A receptor (ET(A)R) axis is implicated in the pathobiology of epithelial ovarian cancer (EOC) by driving tumor-promoting effects, including EMT. Here, we analyzed how ET(A)R regulates chemoresistance and EMT in EOC.

EXPERIMENTAL DESIGN

The effects of ET-1 axis on cell proliferation, drug-induced apoptosis, invasiveness, and EMT were analyzed in cultured EOC cells sensitive and resistant to cisplatinum and taxol. Tumor growth in response to ET(A)R antagonist was examined in EOC xenografts. ET(A)R expression was examined in 60 human EOC tumors by immunohistochemistry and correlated with chemoresistance and EMT.

RESULTS

In resistant EOC cells ET-1 and ET(A)R are upregulated, paralleled by enhanced mitogen activated protein kinase (MAPK) and Akt phosphorylation and cell proliferation. Moreover, in these cells the expression of E-cadherin transcriptional repressors, including Snail, Slug, and Twist, as well as of mesenchymal markers, such as vimentin and N-cadherin, were upregulated and linked with enhanced invasive behavior. Interestingly, ET(A)R blockade with zibotentan, a specific ET(A)R antagonist, or its silencing, downregulated Snail activity, restored drug sensitivity to cytotoxic-induced apoptosis, and inhibited the invasiveness of resistant cells. In vivo, zibotentan inhibited tumor growth of sensitive and resistant EOC xenografts, and sensitized to chemotherapy. Analysis of EOC human tissues revealed that ET(A)R is overexpressed in resistant tumors and is associated with EMT phenotype.

CONCLUSIONS

Our data provide the first evidence that blockade of ET(A)R-driven EMT can overcome chemoresistance and inhibit tumor progression, improving the outcome of EOC patients' treatment.

Endothelin axis induces metalloproteinase activation and invasiveness in human lymphatic endothelial cellsThis article is one of a selection of papers published in the two-part special issue entitled 20 Years of Endothelin Research

The molecular mechanisms involved in lymphangiogenesis were unknown until recently. We previously demonstrated that the endothelin-1 (ET-1) axis stimulates lymphatic endothelial cells (LEC) and lymphatic vessels to grow and invade. Here we further investigated the effect of ET-1 on lymphatic vessels and evaluated whether ET-1 actions result in the functional activation of lymphangiogenesis. Using highly purified human LEC, characterized for the expression of ET-1 axis members by quantitative real-time PCR, we found that the endothelin B receptor (ETB), upon activation by ET-1, induced matrix-metalloproteinase activation, demonstrating that ET-1 influenced the activity of the proteolytic enzymes required for LEC invasion. Functional assays performed by using intradermal lymphangiography demonstrated that ET-1 promoted the formation of lymphatic vessels and that these vessels were capable of lymphatic flow. ETB blockade with the specific antagonist BQ788 inhibited matrix-metalloproteinase activation and dye transport within the lymphatic vessels, demonstrating that ETB is involved in the regulation of the growth of and in the formation of functional vessels upon activation by ET-1. Our results suggest that ET-1 is a lymphangiogenic mediator and that targeting pharmacologically ETB may be therapeutically exploited in a variety of diseases, including cancer.

Endothelin-1 inhibits prolyl hydroxylase domain 2 to activate hypoxia-inducible factor-1alpha in melanoma cells

BACKGROUND

The endothelin B receptor (ET(B)R) promotes tumorigenesis and melanoma progression through activation by endothelin (ET)-1, thus representing a promising therapeutic target. The stability of hypoxia-inducible factor (HIF)-1alpha is essential for melanomagenesis and progression, and is controlled by site-specific hydroxylation carried out by HIF-prolyl hydroxylase domain (PHD) and subsequent proteosomal degradation.

PRINCIPAL FINDINGS

Here we found that in melanoma cells ET-1, ET-2, and ET-3 through ET(B)R, enhance the expression and activity of HIF-1alpha and HIF-2alpha that in turn regulate the expression of vascular endothelial growth factor (VEGF) in response to ETs or hypoxia. Under normoxic conditions, ET-1 controls HIF-alpha stability by inhibiting its degradation, as determined by impaired degradation of a reporter gene containing the HIF-1alpha oxygen-dependent degradation domain encompassing the PHD-targeted prolines. In particular, ETs through ET(B)R markedly decrease PHD2 mRNA and protein levels and promoter activity. In addition, activation of phosphatidylinositol 3-kinase (PI3K)-dependent integrin linked kinase (ILK)-AKT-mammalian target of rapamycin (mTOR) pathway is required for ET(B)R-mediated PHD2 inhibition, HIF-1alpha, HIF-2alpha, and VEGF expression. At functional level, PHD2 knockdown does not further increase ETs-induced in vitro tube formation of endothelial cells and melanoma cell invasiveness, demonstrating that these processes are regulated in a PHD2-dependent manner. In human primary and metastatic melanoma tissues as well as in cell lines, that express high levels of HIF-1alpha, ET(B)R expression is associated with low PHD2 levels. In melanoma xenografts, ET(B)R blockade by ET(B)R antagonist results in a concomitant reduction of tumor growth, angiogenesis, HIF-1alpha, and HIF-2alpha expression, and an increase in PHD2 levels.

CONCLUSIONS

In this study we identified the underlying mechanism by which ET-1, through the regulation of PHD2, controls HIF-1alpha stability and thereby regulates angiogenesis and melanoma cell invasion. These results further indicate that targeting ET(B)R may represent a potential therapeutic treatment of melanoma by impairing HIF-1alpha stability.

The importance of endothelin axis in initiation, progression, and therapy of ovarian cancer

The endothelin-1 (ET-1)/ET A receptor (ET(A)R) axis is involved in the pathobiology of different tumors, including ovarian carcinoma. Acting selectively on ET(A)R, ET-1 regulates, through multiple signaling pathways, mitogenesis, cell survival, angiogenesis, lymphangiogenesis, invasion, and metastatic dissemination. Moreover, ET-1/ET(A)R axis appears to be critical in epithelial-to-mesenchymal transition (EMT), providing a mechanism of escape to a new, less adverse niche, in which resistance to apoptosis ensures cell survival in conditions of stress in the primary tumor, and acquisition of "stemness" ensures generation of the critical mass required for tumor progression. Emerging experimental and preclinical data demonstrate that interfering with ET(A)R pathways provides an opportunity for the development of new mechanism-based antitumor strategies by using ET(A)R antagonists alone and in combination with cytotoxic drugs or molecular inhibitors. A specific ET(A)R antagonist in combination with standard chemotherapy is currently evaluated in clinical and translational studies to provide us with new options to treat ovarian cancer and to predict response to therapy. Deeper understanding of molecular mechanism activated by ET(A)R in ovarian cancer will be of paramount importance in the study of ET(A)R-targeted therapy that, regulating EMT and other tumor-associated processes, represents an attractive but challenging approach to improve clinical management of ovarian cancer.

Abstract 2363: Positive inter-regulation between β-catenin and endothelin signaling in ovarian cancer cells: Epigenetic regulation of gene transcription

Although endothelin-1 (ET-1) and the endothelin A receptor (ETAR) regulate different steps of ovarian tumor progression, the molecular mechanism controlling the expression of ET-1 in this tumor is unknown. We previously demonstrated that ET-1 activates β-catenin/TCF4 transcriptional activity to promote cell invasion and metastasis. Here, we show that ET-1 gene is directly regulated by β-catenin in ovarian cancer cells. Thus, inhibition of β-catenin signalling results in lowered ET-1 promoter activity and expression, while enhanced β-catenin signalling leads to further activation of this gene. Chromatin immunoprecipitation (ChIP) demonstrated that, after ET-1 stimulus, β-catenin and its cognate DNA binding partner, TCF4, are recruited on the specific DNA element within the ET-1 promoter. Unravelling the role of the scaffold protein β-arrestin-1 as nucleus chaperone controlling β-catenin transcription activity, we demonstrated that β-arrestin-1 is required for the activation of ET-1 promoter, and for the recruitment of β-catenin/TCF4 on this promoter. In agreement with these findings, immunoprecipitation assay demonstrated that ET-1 promotes the interaction between endogenous β-catenin and β-arrestin-1 both in the cytoplasm and in the nucleus. Moreover, β-arrestin-1 siRNA leads to the loss of ET-1 mRNA expression and ET-1 secretion, as well as a significant inhibition of ET-1 promoter activity, thus suggesting the critical role of β-arrestin-1 in the β-catenin-dependent ET-1 gene expression. Further experiments showed that ET-1 promotes the nuclear association between histone acetyltransferase p300 and β-arrestin and the recruitment of p300 on the ET-1 promoter, resulting in H3 and H4 histone acetylation and enhanced ET-1 transcription. Besides ET-1, β-arrestin-1 represents a platform for achieving signal specificity that converges on β-catenin-mediated transcription of defined genes, such as cyclin D1 and matrix metalloprotease (MMP)-2, but not MMP-9. Moreover, ETAR blockade with the specific ETAR antagonist, zibontentan (ZD4054), abrogates both the engagement of β-arrestin and the interplay between ET-1 and the β-catenin in controlling gene transcription. In an intraperitoneal model of ovarian cancer metastasis, HEY cells expressing the mutant β-arrestin-1, or treatment with zibontentan, significantly reduced peritoneal tumor-cell dissemination and β-catenin expression, highlighting the importance of β-arrestin-mediated signaling in metastasis formation. Altogether these results reveal a positive inter-regulation between β-catenin and ET-1 that amplify the ET-1/ETAR autocrine loop in ovarian cancer cells, in which β-arrestin-1 acts as a nuclear messenger mediating epigenetic mechanism in β-catenin-mediated ET-1 transcription. Supported by AIRC, AstraZeneca

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2363.

Abstract 2551: Acquisition of epithelial-mesenchymal transition phenotype of chemoresistant ovarian cancer cells is linked with activation of the endothelin signaling pathway

Chemoresistance is a major challenge in ovarian cancer (OC). High-throughput analysis has shown that the endothelin A receptor (ETAR) is overexpressed in post-chemotherapy OCs, suggesting a role in the chemoresistance onset. To identify ETAR-driven molecular determinants involved in chemoresistance to cisplatin and paclitaxel, we used the A2780 WT, cisplatin-resistant A2780 CIS, and taxol-resistant A2780 TAX human OC cells. ET-1 and ETAR mRNA and protein expression as well as ET-1 secretion were higher in the resistant OC cells, associated with increased ET-1-induced MAPK and AKT activation and cell proliferation. These effects were reverted by treatment with zibotentan (ZD4054), a specific ETAR antagonist. In sensitive OC cells, zibotentan enhanced the number of early apoptotic cells, similar to cisplatinum. Furthermore, zibotentan sensitized resistant A2780 CIS cells to cisplatinum-induced apoptosis, confirming the role of ET-1 as survival factor. Given the documented role of the epithelial to mesenchymal transition (EMT) in the chemoresistance development and the ability of the ET-1/ETAR axis to regulate EMT effectors, such as Snail and β-catenin, we analyzed whether ETAR-driven EMT molecular changes were linked with the chemoresistance in EOC cells. Decreased expression of the epithelial adhesion molecule E-cadherin and an increased expression of mesenchymal markers, such as Snail and Slug, the principal transcriptional repressor of E-cadherin, as well as Snail promoter activity were observed in sensitive OC cells after ET-1 treatment. Moreover, these effects were upregulated in resistant OC cells and were blocked in the presence of zibotentan, providing molecular evidence that the ETAR-mediated EMT signaling in EOC can represent a “salvage pathway” occurring during chemoresistance development. In sensitive A2780, as well as in resistant A2780 CIS and TAX xenografts, zibotentan induced a significant tumor growth inhibition, associated with reduction of Snail and upregulation of E-cadherin, suggesting a specific therapeutic window in which combination therapy of zibotentan with cytotoxic drugs is effective also in resistant OC. Finally immunohistochemical analysis of human OC, with different responses to chemotherapy, showed that ET-1 and ETAR are overexpressed in the resistant tumors, associated with upregulation of E-cadherin and with downregulation of N-cadherin and β-catenin. In conclusion, our study suggest that ETAR blockade with the specific antagonist zibotentan can revert EMT and increase the sensitivity to chemotherapeutic agents, representing a potential strategy to overcome chemoresistance in OC. Supported by AIRC, Ministero della Salute, AstraZeneca.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2551.

Abstract 1286: Endothelin-1-induced angiogenesis is regulated by PHD2 in a HIF-1α-dependent manner

The endothelin B receptor (ETBR) promotes tumorigenesis and melanoma progression through activation by endothelin (ET)-1, thus representing a promising therapeutic target. The stability of hypoxia-inducible factor (HIF)-1α is essential for melanomagenesis and progression. In melanoma cells cultured in normoxic conditions, ET-1, ET-2, and ET-3 through ETBR enhance HIF-1α and HIF-2α expression, and activity and both transcriptional factors regulate the expression of target genes, such as vascular endothelial growth factor (VEGF) and ET-1 in response to ETs or hypoxia. In turn, ETs control HIF-1α stability by inhibiting its degradation. In particular, ETs through ETBR markedly decrease prolyl hydroxylase domain (PHD)2 mRNA and protein levels and promoter activity. In addition, we found that activation of phosphatidylinositol 3-kinase (PI3K)-dependent integrin linked kinase (ILK)-AKT-mammalian target of rapamycin (mTOR) pathway is required for ETBR-mediated PHD2 inhibition, HIF-1α, HIF-2α, and VEGF expression. At functional level, PHD2 knockdown does not further increase ETs-induced angiogenesis and melanoma cell invasiveness demonstrating that these processes are regulated in a PHD2-dependent manner. In human primary and metastatic melanomas, that express high level of HIF-1α, ETBR expression is associated with low PHD2 levels. In melanoma xenografts, ETBR blockade by ETBR antagonist results in a concomitant reduction of angiogenesis, HIF-1α, HIF-2α and VEGF expression, and an increase in PHD2 levels. In conclusion, we identified the underlying mechanism by which ET-1 controls HIF-1α stability and thereby regulates angiogenesis and tumor invasion through the regulation of PHD2. These results further indicate that targeting ETBR may represent a potential therapeutic treatment of melanoma by impairing HIF-1α stability. Supported by AIRC.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1286.

Endothelin-1 stimulates lymphatic endothelial cells and lymphatic vessels to grow and invade

The lymphatic vasculature is essential for tissue fluid homeostasis and cancer metastasis, although the molecular mechanisms involved remain poorly characterized. Endothelin-1 (ET-1) axis plays a crucial role in angiogenesis and tumorigenesis. Here, we first report that ET-1 acts as a lymphangiogenic mediator. We performed in vitro and in vivo studies and show that lymphatic endothelial cells produce ET-1, ET-3, and express the endothelin B receptor (ET(B)R). In these cells, ET-1 promotes proliferation, invasiveness, vascular-like structures formation, and phosphorylation of AKT and p42/44 mitogen-activated protein kinase through ET(B)R. In normoxic conditions, ET-1 is also able to up-regulate the expression of vascular endothelial growth factor (VEGF)-C, VEGF receptor-3, and VEGF-A, and to stimulate hypoxia-inducible factor (HIF)-1alpha expression similarly to hypoxia. Moreover, HIF-1alpha silencing by siRNA desensitizes VEGF-C and VEGF-A production in response to ET-1 or hypoxia, implicating HIF-1alpha/VEGF as downstream signaling molecules of ET-1 axis. Double immunofluorescence analysis of human lymph nodes reveals that lymphatic vessels express ET(B)R together with the lymphatic marker podoplanin. Furthermore, a Matrigel plug assay shows that ET-1 promotes the outgrowth of lymphatic vessels in vivo. ET(B)R blockade with the specific antagonist, BQ788, inhibits in vitro and in vivo ET-1-induced effects, demonstrating that ET-1 through ET(B)R directly regulates lymphatic vessel formation and by interacting with the HIF-1alpha-dependent machinery can amplify the VEGF-mediated lymphatic vascularization. Our results suggest that ET-1 axis is indeed a new player in lymphangiogenesis and that targeting pharmacologically ET(B)R and related signaling cascade may be therapeutically exploited in a variety of diseases including cancer.

Search for maximal flavor violating scalars in same-charge lepton pairs in pp collisions at sqrt[s]=1.96 TeV

Models of maximal flavor violation (MxFV) in elementary particle physics may contain at least one new scalar SU(2) doublet field Phi(FV)=(eta(0),eta(+)) that couples the first and third generation quarks (q_(1), q_(3)) via a Lagrangian term L(FV)=xi(13)Phi(FV)q(1)q(3). These models have a distinctive signature of same-charge top-quark pairs and evade flavor-changing limits from meson mixing measurements. Data corresponding to 2 fb(-1) collected by the Collider Dectector at Fermilab II detector in pp[over ] collisions at sqrt[s]=1.96 TeV are analyzed for evidence of the MxFV signature. For a neutral scalar eta(0) with m_(eta;(0))=200 GeV/c(2) and coupling xi(13)=1, approximately 11 signal events are expected over a background of 2.1+/-1.8 events. Three events are observed in the data, consistent with background expectations, and limits are set on the coupling xi(13) for m(eta(0)=180-300 GeV/c(2).

The endothelin axis in cancer: the promise and the challenges of molecularly targeted therapy

The endothelin (ET) axis, which includes ET-1, ET-2, ET-3, and 2 G protein-coupled receptor subtypes, ET AR and ET BR, promotes growth and progression of a variety of tumors, such as prostatic, ovarian, renal, pulmonary, colorectal, cervical, breast, lung, bladder, endometrial carcinoma, Kaposi's sarcoma, brain tumors, and melanoma. Acting on selective receptors, ET-1 regulates mitogenesis, cell survival, angiogenesis, bone remodeling, stimulation of nociceptors, tumor-infiltrating immune cells, epithelial-to-mesenchymal transition, invasion, and metastatic dissemination. At the molecular level, endothelin receptor antagonists, besides providing ideal tools for dissecting the ET axis, have demonstrated their potential in developing novel therapeutic strategies. Emerging experimental and clinical data demonstrate that interfering with endothelin receptors provides an opportunity for the development of rational combinatorial approaches using endothelin receptor antagonists in combination with chemotherapy or molecularly targeted therapy.

Therapeutic targeting of the endothelin-A receptor in human ovarian carcinoma: efficacy of cytotoxic agents is markedly enhanced by co-administration with atrasentan

The endothelin-1/endothelin-A receptor autocrine pathway is overexpressed in ovarian carcinoma. We explored the efficacy of atrasentan (ABT-627), a small orally active endothelin- A receptor antagonist, in monotherapy and combination therapy on HEY ovarian carcinoma xenografts. Atrasentan (2 mg/kg per 24 hours i.p. for 21 days) induced similar inhibition of tumor growth as paclitaxel (20 mg/kg i.v. three times a day every 4 days) with a reduction of 65% compared to control. The co-administration of atrasentan enhanced the efficacy of cytotoxic agents, such as taxanes or platinum compounds. Administration of atrasentan in combination with paclitaxel caused a strong antitumor effect. Remarkably, four of ten mice bearing HEY xenografts had no histological evidence of tumors. Tumor growth inhibition was accompanied by a significant decrease of molecular effectors involved in angiogenesis and invasion and by enhanced tumor cell apoptosis. Moreover, although cisplatinum as a single agent (5 mg/kg i.p. on day 1) markedly inhibited HEY tumors, atrasentan was very effective in potentiating this effect, with partial or complete tumor regression. The antitumor, anti-angiogenic, and apoptotic activities obtained with atrasentan and the enhanced efficacy of cytotoxic agents provide a rationale for its clinical evaluation in ovarian carcinoma.

Endothelin-B receptor blockade inhibits molecular effectors of melanoma cell progression

Expression of endothelin-B receptor gradually increases as melanocytic lesions progress to melanoma, suggesting that endothelin-B receptor and its ligands, endothelin-1 and endothelin- 3, play a role in the melanoma progression. The selective blockade of endothelin-B receptor results in inhibition of focal adhesion kinase and mitogen-activated protein kinase phosphorylation and cell proliferation induced by endothelins in human melanoma cell lines. In these cells, endothelins induce downregulation of E-cadherin expression and concomitant upregulation of transcriptional factor Snail. Activation of the endothelin-B receptor pathway by endothelins also upregulates N-cadherin, phosphorylates the gap junctional protein connexin 43, increases alphavbeta3 and alpha2beta1 integrin expression and tumor proteolytic activity, thus enhancing endothelin-B receptor-mediated cell adhesion, migration and invasiveness. In this study we demonstrated that activation of the endothelin-B receptor pathway by endothelin-1 and endothelin-3 contributes to disruption of normal host-tumor interactions by downregulating, at mRNA and protein levels, the expression of E-cadherin and associated alpha-catenin and beta-catenin adhesion proteins, which are critical for E-cadherin function. A-192621, an orally active non-peptide endothelin-B receptor antagonist, significantly inhibited melanoma growth in nude mice, suggesting that the pharmacological interruption of endothelin-B receptor signaling by endothelin-B receptor antagonist may represent a new therapeutic approach in the treatment of cutaneous melanoma.

Endothelin-1 stimulates cyclooxygenase-2 expression in ovarian cancer cells through multiple signaling pathways: evidence for involvement of transactivation of the epidermal growth factor receptor

Ovarian carcinoma cells release high amounts of endothelin-1 and exhibit increased expression of endothelin-A receptor. Engagement of the endothelin-A receptor triggers tumor growth, survival, neoangiogenesis and invasion. Cyclooxygenase-1 and cyclooxygenase-2 are enzymes involved in the production of prostaglandins and play a role in the regulation of tumor progression in several malignancies, including ovarian carcinomas. Endothelin-1 significantly increases the expression of cyclooxygenase-1 and cyclooxygenase-2 mRNA and protein, the activity of the cyclooxygenase- 2 promoter, and the release of prostaglandin E2 from two ovarian carcinoma cell lines, HEY and OVCA 433. The cyclooxygenase- 2 inhibitor, NS-398 drastically decreased the endothelin- 1-induced prostaglandin E2 production and vascular endothelial growth factor upregulation, indicating a role for cyclooxygenase-2 in endothelin-1-induced vascular endothelial growth factor-mediated angiogenesis. In this study we demonstrated that endothelin-1-induced cyclooxygenase-2 and related prostaglandin E2 release were dependent upon the activation of endothelin-A receptor and of multiple mitogen-activated protein kinase signal pathways, including extracellular signal-regulated kinase 1/2 kinase, p38 mitogen-activated protein kinase and the transactivation of the epidermal growth factor receptor. In human ovarian xenografts, the levels of cyclooxygenase-2 protein expression were significantly reduced following treatment with the endothelin-A receptor selective antagonist, atrasentan, compared with untreated mice. These results suggest that the pharmacological blocking of endothelin-A receptor is an attractive strategy to control the cyclooxygenase-2 protein expression in ovarian carcinoma.

Search for doubly charged Higgs bosons with lepton-flavor-violating decays involving tau leptons

We search for pair production of doubly charged Higgs particles (H+/- +/-) followed by decays into electron-tau (etau) and muon-tau (mutau) pairs using data (350 pb(-1) collected from [over]pp collisions at sqrt[s]=1.96 TeV by the CDF II experiment. We search separately for cases where three or four final-state leptons are detected, and combine results for exclusive decays to left-handed etau (mutau) pairs. We set an H+/- +/- lower mass limit of 114(112) GeV/c(2) at the 95% confidence level.

Search for pair production of scalar top quarks decaying to a tau lepton and a b quark in pp over collisions at sqrt s=1.96 TeV

We search for pair production of supersymmetric top quarks (t over1), followed by R-parity violating decay t over1-->taub with a branching ratio beta, using 322 pb(-1) of pp over collisions at sqrt s=1.96 TeV collected by the upgraded Collider Detector at Fermilab. Two candidate events pass our final selection criteria, consistent with the standard model expectation. We set upper limits on the cross section sigma(t over1t over1) x beta2 as a function of the top-squark mass m(t over1). Assuming beta=1, we set a 95% confidence level limit m(t over1)>153 GeV/c2. The limits are also applicable to the case of a third-generation scalar leptoquark (LQ3) decaying LQ3-->taub.

Search for resonant tt[overline] production in pp[overline] collisions at sqrt[s]=1.96 TeV

We report on a search for narrow-width particles decaying to a top and antitop quark pair. The data set used in the analysis corresponds to an integrated luminosity of 680 pb(-1) collected with the Collider Detector at Fermilab in run II. We present 95% confidence level upper limits on the cross section times branching ratio. Assuming a specific top-color-assisted technicolor production model, the leptophobic Z' with width Gamma(Z')=0.012M(Z'), we exclude the mass range M(Z')<725 GeV/c(2) at the 95% confidence level.

Search for the Higgs boson in events with missing transverse energy and b quark jets produced in pp collisions at square root(s)=1.96 TeV

We search for the standard model Higgs boson produced in association with an electroweak vector boson in events with no identified charged leptons, large imbalance in transverse momentum, and two jets where at least one contains a secondary vertex consistent with the decay of b hadrons. We use approximately 1 fb(-1) integrated luminosity of pp collisions at square root(s)=1.96 TeV recorded by the Collider Detector at Fermilab II experiment at the Tevatron. We find 268 (16) single (double) b-tagged candidate events, where 248+/-43 (14.4+/-2.7) are expected from standard model background processes. We observe no significant excess over the expected background and thus set 95% confidence level upper limits on the Higgs boson production cross section for several Higgs boson masses ranging from 110 to 140 GeV/c(2). For a mass of 115 GeV/c(2), the observed (expected) limit is 20.4 (14.2) times the standard model prediction.