Abstract 3278: EOS100850 potently restores adenosine A2Areceptor-dependent suppression of T cell function in the adenosine rich tumor microenvironment

Adenosine is a potent immunosuppressive metabolite that is often found elevated in the extracellular tumor microenvironment (TME). We determined concentrations of extracellular adenosine in different patient-derived xenografts (PDX) from 7 different histological types, in which extracellular median adenosine concentrations were shown to range from 0.5 to 45 µM, with the overall median adenosine concentration being about 4.5 µM. Adenosine concentration in the non-tumorous subcutaneous space in mice was measured at about 0.5 µM. Adenosine in the TME is generated mainly by the concerted action of the ectonucleotidases CD39 and CD73. The expression of these enzymes across various cancer types was evaluated by flow cytometry in dissociated human tumor biopsies. CD73 and CD39 were strongly expressed by multiple tumor-infiltrating T cell types. Tumor-associated myeloid cells mostly expressed CD39 and high frequencies of EpCAM+ tumor cells strongly expressed CD73. These data strongly suggest that adenosine levels could be further increased compared to non-immune-infiltrated PDX.Adenosine activates 4 G protein-coupled receptor subtypes, of which the adenosine A2A receptor in particular suppresses innate and adaptive immune cell responses leading to suppression of anti-tumor immunity. Among the 4 adenosine receptors, we confirmed the A2A receptor as the main adenosine receptor expressed in CD4+ and CD8+ T cells, natural killer cells, monocytes, and dendritic cells. Stimulation of these immune cell subsets further increased A2A receptor expression. A2B receptor was expressed at very low levels in stimulated CD4+ and CD8+ T cells and in monocytes and immature DCs. A1 and A3 receptors were hardly detected in these subsets of immune cells. EOS100850, a highly potent and selective A2A receptor antagonist, was characterized in various in vitro functional assays. A2A receptor activation by a selective agonist suppressed priming of mouse OVA-specific OT1 T cells and subsequent antigen-specific CD8+ T cell cytotoxicity in a co-culture assay of effector CD8+ T cells and target cancer cells. This A2A receptor-mediated immune suppression was potently and dose-dependently reversed by EOS100850. In a mixed lymphocyte reaction between human dendritic cells and T cells, EOS100850 blocked the adenosine-dependent inhibition of T cell proliferation and secretion of IFNg, TNFa and IL-2 in a dose-dependent manner. In conclusion, extracellular adenosine as well as adenosine pathway components were strongly present across multiple tumor types, and across multiple tumor-associated cell types. In addition, EOS100850, a highly potent A2A receptor antagonist, reversed A2A receptor-mediated suppression of T cell priming, cytotoxicity, cytokine production and proliferation.

Citation Format: Erica Houthuys, Paola Basilico, Veronique Bodo, Margreet Brouwer, Michel Detheux, Gregory Driessens, Bruno Gomes, Annelise Hermant, Catherine Hoofd, Florence Lambolez, Xavier Leroy, Reece Marillier, Chiara Martinoli, Marjorie Mercier, Florence Nyawouame, Shruthi Prasad, Ariane Scoumanne, Stefano Crosignani. EOS100850 potently restores adenosine A2Areceptor-dependent suppression of T cell function in the adenosine rich tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3278.

Abstract 4612: Development and validation of a screening platform for the identification of novel immuno-oncology targets

Although immune therapy of cancer, including immune-checkpoint blockade have demonstrated therapeutic benefit in patients with various advanced cancers, further understanding of human immune pathology triggered by the tumor microenvironment, is essential to improve these therapeutic approaches.

In order to shed light on novel immune suppressive mechanisms in tumor, iTeos Therapeutics developed a target discovery and drug repurposing platform based on phenotypic screening assays. We established a co-culture assay combining tumor immune suppressive cells and T-cells. This assay is flexible to allow the screening of chemicogenomics, shRNA and cDNA libraries. Multi-parameter readouts are combined to assess both T cell activation and proliferation, through high content imaging of T cell clusters formation, complemented with detection of IFNγ secretion and tumor cell death, as assessed using a cytotoxicity assay. The 96-well format of the assay allows medium-throughput testing of up to 3000 samples/screen. From the technical point of view we were able to adapt the assay to low level of automation, making it affordable to the biotech start-ups and academic laboratories.

As a proof-of-concept we evaluated the assay for its ability to detect metabolic immune-oncology targets in A549 cells, a lung cancer immune suppressive cell line. A549 express indoleamine-2,3-dioxygenase 1 (IDO1), an enzyme expressed in many cancers that mediates local T-cell suppression through depleting the essential amino acid tryptophan. The assay conditions were validated with an IDO1 inhibitor as positive control and subsequently scaled up for automation. A commercially available small molecule library of 1900 compounds, with a high percentage of clinically tested drugs was screened. The library was tested at two different concentrations (0.3μM and 3μM), with two independent T-cell donors and spiked with IDO1 inhibitor as control. Combined analysis of T-cell activity and tumor killing led to the identification of 42 compounds with activity on multiple, potential immune suppressive pathways, including metabolism, epigenetics, autophagy, TGFβ, Wnt/β-catenin and TNFα/NF-κB signaling.

Citation Format: Ariane Scoumanne, Virginie Rabolli, Lea Legrand, Murielle Martini, marie-claire Letellier, Stefano Crosignani, Christophe Quéva, Michel Detheux, Sandra Cauwenberghs, Jakub Swiercz. Development and validation of a screening platform for the identification of novel immuno-oncology targets [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4612. doi:10.1158/1538-7445.AM2017-4612

Abstract B030: Development and validation of a phenotypic screening platform for the identification of novel immuno-oncology targets

iTeos Therapeutics developed a target discovery and drug repurposing platform based on phenotypic screening assays that mimic the immunosuppressive tumor microenvironment. Here, we present an immunosuppressive cell line/T cell co-culture assay that enables chemical and genomic screening. Multi-parameter readouts are combined to assess both T cell activity as well as tumor cell death. T cell activity is measured through high content imaging of cluster formation complemented with detection of INFγ secretion. Tumor cell death is assessed using a cytotoxicity assay. The current format of the assay (96-well) allows medium-throughput testing of up to 3,000 samples/screen.

As proof-of-concept we evaluated the assay for its ability to detect metabolic immune-oncology targets like indoleamine-2,3-dioxygenase 1 (IDO1). IDO1 is expressed in a wide range of cancers and mediates local T cell suppression through depletion of the essential amino acid tryptophan. The assay conditions were validated with an IDO1 inhibitor as positive control and subsequently scaled up for automation. A commercially available small molecule library [Selleck Bioactive Compound Library (cat number L1700), 1902 compounds] with a high percentage of clinically tested drugs was screened. The library was tested at two different concentrations (0.3 μM and 3 μM), with two independent T cell donors and spiked with IDO1 inhibitors as internal control. The combined analysis of T-cell activity and tumor killing led to the identification of 42 compounds with activity on multiple, potential immune suppressive pathways, including metabolism, epigenetics, autophagy, and TGFβ signaling.

This assay is also suitable for gene modulation strategy using shRNA or cDNA libraries enriched for genes expressed specifically in immune suppressive cells and tissues. Moreover the assay can be adapted to additional cell types such as MDSC or Treg, opening up opportunities for identification of novel immune suppressive targets.

In conclusion, this approach allows rapid identification of mechanisms and targets contributing to tumor resistance. Phenotypic screens allow higher confidence in the selection of targets with a potential for clinical translation.

[V.R., M.M., J.M.S., and S.C. contributed equally to this work.]

Citation Format: Virginie Rabolli, Murielle Martini, Ariane Scoumanne, Marie-Claire Letellier, Stefano Crosignani, Christophe Quéva, Michel Detheux, Jakub M. Swiercz, Sandra Cauwenberghs. Development and validation of a phenotypic screening platform for the identification of novel immuno-oncology targets [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B030.

Specific expression and function of inositol 1,4,5-trisphosphate 3-kinase C (ITPKC) in wild type and knock-out mice

Inositol 1,4,5-trisphosphate 3-kinase C (ITPKC) is the last identified member of the inositol 1,4,5-trisphosphate 3-kinases family which phosphorylates inositol 1,4,5-trisphosphate into inositol 1,3,4,5-tetrakisphosphate. Although expression and function of the two other family members ITPKA and ITPKB are rather well characterized, similar information is lacking for ITPKC. Here, we first defined the expression of Itpkc mRNA and protein in mouse tissues and cells using in situ hybridization and new antibodies. Surprisingly, we found that cells positive for ITPKC in the studied tissues express either a multicilium (tracheal and bronchial epithelia, brain ependymal cells), microvilli forming a brush border (small and large intestine, and kidney proximal tubule cells) or a flagellum (spermatozoa), suggesting a role for ITPKC either in the development or the function of these specialized cellular structures. Given this surprising expression, we then analyzed ITPKC function in multiciliated tracheal epithelial cells and sperm cells using our Itpkc knock-out mouse model. Unfortunately, no significant difference was observed between control and mutant mice for any of the parameters tested, leaving the exact in vivo function of this third Ins(1,4,5)P3 3-kinase still open.

Mice deficient in poly(C)-binding protein 4 are susceptible to spontaneous tumors through increased expression of ZFP871 that targets p53 for degradation

Poly(C)-binding protein 4 (PCBP4), also called MCG10 and a target of p53, plays a role in the cell cycle and is implicated in lung tumor suppression. Here, we found that PCBP4-deficient mice are prone to lung adenocarcinoma, lymphoma, and kidney tumor and that PCBP4-deficient mouse embryo fibroblasts (MEFs) exhibit enhanced cell proliferation but decreased cellular senescence. We also found that p53 expression is markedly reduced in PCBP4-deficient MEFs and mouse tissues, suggesting that PCBP4 in turn regulates p53 expression. To determine how PCBP4 regulates p53 expression, PCBP4 targets were identified by RNA immunoprecipitation followed by RNA sequencing (RNA-seq). We found that the transcript encoding ZFP871 (zinc finger protein 871; also called ZNF709 in humans) interacts with and is regulated by PCBP4 via mRNA stability. Additionally, we found that ZFP871 physically interacts with p53 and MDM2 proteins. Consistently, ectopic expression of ZFP871 decreases-whereas knockdown of ZFP871 increases-p53 protein stability through a proteasome-dependent degradation pathway. Moreover, loss of ZFP871 reverses the reduction of p53 expression by lack of PCBP4, and thus increased expression of ZFP871 is responsible for decreased expression of p53 in the PCBP4-deficient MEFs and mouse tissues. Interestingly, we found that, like PCBP4, ZFP871 is also regulated by DNA damage and p53. Finally, we showed that knockdown of ZFP871 markedly enhances p53 expression, leading to growth suppression and apoptosis in a p53-dependent manner. Thus, the p53-PCBP4-ZFP871 axis represents a novel feedback loop in the p53 pathway. Together, we hypothesize that PCBP4 is a potential tissue-specific tumor suppressor and that ZFP871 is part of MDM2 and possibly other ubiquitin E3 ligases that target p53 for degradation.

Regulation of NGF-driven neurite outgrowth by Ins(1,4,5)P3 kinase is specifically associated with the two isoenzymes Itpka and Itpkb in a model of PC12 cells

Four inositol phosphate kinases catalyze phosphorylation of the second messenger inositol 1,4,5-trisphosphate [Ins(1,4,5)P3 ] to inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4 ]: these enzymes comprise three isoenzymes of inositol 1,4,5-trisphosphate 3-kinase (Itpk), referred to as Itpka, Itpkb and Itpkc, and the inositol polyphosphate multikinase (IPMK). The four enzymes that act on Ins(1,4,5)P3 are all expressed in rat pheochromocytoma PC12 cells, a model that is used to study neurite outgrowth induced by nerve growth factor (NGF). We compared the effect of over-expression of the four GFP-tagged kinases on NGF-induced neurite outgrowth. Our data show that over-expression of the Itpka and Itpkb isoforms inhibits NGF-induced neurite outgrowth, but over-expression of Itpkc and IPMK does not. Surprisingly, over-expression of the N-terminal F-actin binding domain of Itpka, which lacks catalytic activity, was as effective at inhibiting neurite outgrowth as the full-length enzyme. Neurite length was also significantly decreased in cells over-expressing Itpka and Itpkb but not Itpkc or IPMK. This result did not depend on the over-expression level of any of the kinases. PC12 cells over-expressing GFP-tagged kinase-dead mutants Itpka/b have shorter neurites than GFP control cells. The decrease in neurite length was never as pronounced as observed with wild-type GFP-tagged Itpka/b. Finally, the percentage of neurite-bearing cells was increased in cells over-expressing the membranous type I Ins(1,4,5)P3 5-phosphatase. We conclude that Itpka and Itpkb inhibit neurite outgrowth through both F-actin binding and localized Ins(1,4,5)P3 3-kinase activity. Itpkc and IPMK do not influence neurite outgrowth or neurite length in this model.

Structural basis for gene activation by p53 family members

The p53 tumor suppressor is a modular transcription factor that determines cellular outcome (cell cycle arrest and DNA repair vs. apoptosis) in response to stress signals. The two p53 homologues, p63 and p73 play an important role in development but also act as tumor suppressors. The p53 family members are highly homologous in the activation domain (AD), the DNA-binding domain (DBD) and the tetramerization domain (TD) but differ in the C-terminus. Indeed, the p53 C-terminus contains a basic domain (BD) whereas p63/p73 have a sterile alpha motif (SAM) domain and an inhibitory domain (ID). In addition to the full-length proteins, the p53 family genes produce multiple isoforms truncated at the NH2- and/or C-terminus. Importantly, every functional domain is a determinant in the transactivation of specific target genes by the p53 family members. Distinct post-translational modifications and interactions with cofactors further modulate the transcriptional activity of the p53 family members in response to particular stress signals. Therefore, divergence in the composition of the p53 family proteins is responsible for the diversity of p53 family functions.

The Ras/Rap GTPase activating protein RASA3: from gene structure to in vivo functions

RASA3 (or GTPase Activating Protein III, R-Ras GTPase-activating protein, GAP1(IP4BP)) is a GTPase activating protein of the GAP1 subfamily which targets Ras and Rap1. RASA3 was originally purified from pig platelet membranes through its intrinsic ability to bind inositol 1,3,4,5-tetrakisphosphate (I(1,3,4,5)P4) with high affinity, hence its first name GAP1(IP4BP) (for GAP1 subfamily member which binds I(1,3,4,5)P4). RASA3 was thus the first I(1,3,4,5)P4 receptor identified and cloned. The in vitro and in vivo functions of RASA3 remained somewhat elusive for a long time. However, recently, using genetically-modified mice and cells derived from these mice, the function of RASA3 during megakaryopoiesis, megakaryocyte adhesion and migration as well as integrin signaling has been reported. The goal of this review is thus to summarize and comment recent and less recent data in the literature on RASA3, in particular on the in vivo function of this specific GAP1 subfamily member.

The cyclin-dependent kinase inhibitor p21 is regulated by RNA-binding protein PCBP4 via mRNA stability

RNA-binding proteins (RBPs) play a major role in many post-transcriptional processes, including mRNA stability, alternative splicing and translation. PCBP4, also called MCG10, is an RBP belonging to the poly(C)-binding protein family and a target of p53 tumor suppressor. Ectopic expression of PCBP4 induces cell-cycle arrest in G₂ and apoptosis. To identify RNA targets regulated by PCBP4 and further decipher its function, we generated multiple cell lines in which PCBP4 is either inducibly over-expressed or knocked down. We found that PCBP4 expression decreases cyclin-dependent kinase inhibitor p21 induction in response to DNA damage. We also provided evidence that PCBP4 regulates p21 expression independently of p53. In addition, we showed that a deficiency in PCBP4 enhances p21 induction upon DNA damage. To validate PCBP4 regulation of p21, we made PCBP4-deficient mice and showed that p21 expression is markedly increased in PCBP4-deficient primary mouse embryo fibroblasts compared to that in wild-type counterparts. Finally, we uncovered that PCBP4 binds to the 3′-UTR of p21 transcript in vitro and in vivo to regulate p21 mRNA stability. Taken together, we revealed that PCBP4 regulates both basal and stress-induced p21 expression through binding p21 3′-UTR and modulating p21 mRNA stability.

Abstract 3151: Posttranscriptional regulation of p21 by MCG10, an RNA-binding protein and a target of tumor suppressor p53

The tumor suppressor p53 plays a crucial role in regulating many cellular processes, such as cell cycle arrest, apoptosis, senescence and cell metabolism, in response to stress signals. As a transcription factor, p53 modulates the expression of a plethora of genes, including p21, Killer/DR5, GADD45, TIGAR and MDM2. The tumor suppressor function of p53 is further underscored by the high propensity of p53 mutations found in human cancer. RNA-binding proteins are key modulators in RNA metabolism involved in alternative splicing, mRNA stability, mRNA transport as well as translation. Abnormal expression of RNA-binding proteins is implicated in a growing number of human diseases ranging from neurological disorders to cancer. Here, we showed that MCG10, an RNA-binding protein and a target of p53, regulates the stability of cell cycle inhibitor p21 transcript. Indeed, we found that MCG10 decreases p21 levels induced upon DNA damage. In addition, we showed that MCG10 directly binds to the 3′untranslated region of p21 transcript to destabilize it. Furthermore, we generated MCF7 breast adenocarcinoma and RKO colon carcinoma cell lines in which MCG10 is inducibly knocked down. We found that MCG10 is required for cell proliferation. In addition, we showed that deficiency in MCG10 leads to an increase in basal and DNA damage-induced p21 levels. Taken together, we uncovered a role for RNA-binding protein MCG10 in modulating the p53 pathway through posttranscriptional regulation of p21.

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 3151.

G Protein-Coupled Receptor 87: a Promising Opportunity for Cancer Drug Discovery

G protein-coupled receptors (GPRs) constitute one of the largest families of membrane proteins encoded by the human genome. Upon binding to various ligands, these seven-transmembrane receptors play an essential role in many physiological processes, including neurotransmission, immunity, inflammation, regulation of mood and behavior. In view of their important functions, aberrant expression and activity of GPRs have been implicated in a wide spectrum of diseases, including tumorigenesis. GPR87, a cell surface GPR related to the LPA receptor family, is overexpressed in diverse carcinomas and plays an essential role in tumor cell survival. In our recent work, we uncovered that GPR87 expression is regulated by the tumor suppressor p53 and by DNA damage in a p53-dependent manner. Moreover, we found that a lack of GPR87 triggers an increase in p53, concomitant with a decrease in Akt, which results in the sensitization of tumor cells to DNA damage-induced apoptosis and growth suppression. Altogether, we uncovered an essential function for GPR87 in p53-dependent cell survival in response to stress signals. Due to their unique structure, localization and ligand binding ability, GPRs have been extensively used for drug development and are the most common targets of commercial drugs. Although studies are required to determine GPR87 natural ligand(s) and signaling pathways, GPR87 is undoubtedly a very promising novel target for cancer prevention and treatment.

PRMT5 is required for cell-cycle progression and p53 tumor suppressor function

Protein arginine methyltransferases (PRMTs) mediate the transfer of methyl groups to arginines in proteins involved in signal transduction, transcriptional regulation and RNA processing. Tumor suppressor p53 coordinates crucial cellular processes, including cell-cycle arrest and DNA repair, in response to stress signals. Post-translational modifications and interactions with co-factors are important to regulate p53 transcriptional activity. To explore whether PRMTs modulate p53 function, we generated multiple cell lines in which PRMT1, CARM1 and PRMT5 are inducibly knocked down. Here, we showed that PRMT5, but not PRMT1 or CARM1, is essential for cell proliferation and PRMT5 deficiency triggers cell-cycle arrest in G1. In addition, PRMT5 is required for p53 expression and induction of p53 targets MDM2 and p21 upon DNA damage. Importantly, we established that PRMT5 knockdown prevents p53 protein synthesis. Furthermore, we found that PRMT5 regulates the expression of translation initiation factor eIF4E and growth suppression mediated upon PRMT5 knockdown is independent of p53 but is dependent on eIF4E. Taken together, we uncovered that arginine methyltransferase PRMT5 is a major pro-survival factor regulating eIF4E expression and p53 translation.

Suppression of inhibitor of differentiation 2, a target of mutant p53, is required for gain-of-function mutations

Overexpression of mutant p53 is a common theme in human tumors, suggesting a tumor-promoting gain-of-function for mutant p53. To elucidate whether and how mutant p53 acquires its gain-of-function, mutant p53 is inducibly knocked down in the SW480 colon cancer cell line, which contains mutant p53(R273H/P309S), and the MIA PaCa-2 pancreatic cancer cell line, which contains mutant p53(R248W). We found that knockdown of mutant p53 markedly inhibits cell proliferation. In addition, knockdown of mutant p53 sensitizes tumor cells to growth suppression by various chemotherapeutic drugs. To determine whether a gene involved in cell growth and survival is regulated by mutant p53, gene expression profiling analysis was performed and showed that the expression level of Id2, a member of the inhibitor of differentiation (Id) family, was markedly increased upon knockdown of mutant p53. To confirm this, Northern blot analysis was performed and showed that the expression level of Id2 was regulated by various mutant p53s in multiple cell lines. In addition, we found that the Id2 promoter is responsive to mutant but not wild-type p53, and mutant p53 binds to the Id2 promoter. Consistent with these observations, expression of endogenous Id2 was found to be inhibited by exogenous mutant p53 in p53-null HCT116 cells. Finally, we showed that knockdown of Id2 can restore the proliferative potential of tumor cells inhibited by withdrawal of mutant p53. Together, these findings suggest that one mechanism by which mutant p53 acquires its gain-of-function is through the inhibition of Id2 expression.

Protein methylation: a new mechanism of p53 tumor suppressor regulation

The tumor suppressor p53 is the most frequently inactivated gene in human cancers. The p53 protein functions as a sequence-specific transcription factor to regulate key cellular processes, including cell-cycle arrest, DNA repair, apoptosis, and senescence in response to stress signals. P53 is maintained at a low level in the cell, but becomes rapidly stabilized and activated in response to DNA damage, hypoxia, hyperproliferation, and other types of cellular stresses. The stability and transcriptional activity of p53 are tightly regulated through multiple post-translational modifications, such as phosphorylation, acetylation, and ubiquitination. Within the past few years, several studies have established that protein methylation is a novel mechanism by which p53 is regulated. Indeed, histone lysine methyltransferases KMT5 (Set9), KMT3C (Smyd2), and KMT5A (Set8) methylate p53 at specific C-terminal lysines. Lysine methylation enhances or suppresses p53 transcriptional activity depending on the methylation site. Furthermore, the lysine-specific demethylase KDM1 (LSD1) mediates p53 demethylation, which prevents p53 interaction with its co-activator 53BP1 to induce apoptosis. Finally, protein arginine methyltransferases CARM1 and PRMT1 are co-activators of p53 involved in the methylation of histones H3 and H4 to facilitate p53-mediated transcription. In response to cellular stresses, the interplay between p53 methylation, demethylation, and other post-translational modifications fine-tunes the activity of p53 to ultimately prevent tumor formation.

The lysine-specific demethylase 1 is required for cell proliferation in both p53-dependent and -independent manners

The lysine-specific demethylase 1 (LSD1), a component of several histone deacetylase complexes, plays an important role in chromatin remodeling and transcriptional regulation. Here, we generated multiple cell lines in which LSD1 is inducibly expressed or knocked down and found that LSD1 is required for cell proliferation. In addition, we found that deficiency in LSD1 leads to a partial cell cycle arrest in G(2)/M and sensitizes cells to growth suppression induced by DNA damage or MDM2 inhibition in a p53-dependent manner. We also showed that LSD1 deficiency delays p53 stabilization induced by DNA damage, leading to a delayed induction of p21 and MDM2. Finally, we performed a microarray study and identified several novel LSD1 target genes, including S100A8, which encodes a calcium-binding protein, and DEK, a proto-oncogene. Taken together, we uncovered that LSD1 has a pro-oncogenic function by modulating pro-survival gene expression and p53 transcriptional activity.

The epithelial cell transforming sequence 2, a guanine nucleotide exchange factor for Rho GTPases, is repressed by p53 via protein methyltransferases and is required for G1-S transition

The epithelial cell transforming sequence 2 (ECT2), a member of the Dbl family of guanine nucleotide exchange factor for Rho GTPases, is required for cytokinesis. The tumor suppressor p53 plays a crucial role in coordinating cellular processes, such as cell cycle arrest and apoptosis, in response to stress signals. Here, we showed that ECT2 is negatively regulated by wild-type p53 but not tumor-derived mutant p53 or other p53 family members. In addition, ECT2 is down-regulated in multiple cell lines by DNA damage agents and Nutlin-3, an MDM2 antagonist, in a p53-dependent manner. We also showed that the activity of the ECT2 promoter is repressed by wild-type p53, and to a lesser extent, by p21. In addition, the second activation domain in p53 is necessary for the efficient repression of ECT2. Importantly, we found that the ECT2 gene is bound by p53 in vivo in response to DNA damage and Nutlin-3 treatment. Furthermore, we provided evidence that inhibition of protein methyltransferases, especially arginine methyltransferases, relieve the repression of ECT2 induced by DNA damage or Nutlin-3 in a p53-dependent manner. Finally, we generated multiple cell lines in which ECT2 is inducibly knocked down and found that ECT2 knockdown triggers cell cycle arrest in G1. Taken together, we uncovered a novel function for ECT2 and provided a novel mechanism by which p53 represses gene expression via protein methyltransferases.

Generation and characterisation of human saphenous vein endothelial cell lines

Primary human endothelial cells have a finite life span in vitro. After 3-4 passages, they tend to de-differentiate and eventually reach senescence. This limits their use in studies of endothelial cell function. To overcome this, we have developed human saphenous vein endothelial cell lines (HSVEC lines). Two cell lines were produced by infection with pZipSVtsA58-U19 which encodes the simian virus 40 large T-antigen, and one cell line was obtained by transfection with pLXSN16E6E7, which encodes the human papillomavirus type 16 E6 and E7 genes. Two of the three HSVEC lines exhibited an extended life span in vitro and retained characteristic endothelial "cobblestone" morphology. These cell lines expressed the known endothelial markers CD31 and vascular endothelial cadherin, and were able to bind Ulex europaeus lectin I, but they did not retain the expression of von Willebrand factor. Furthermore, one cell line was able to functionally up-regulate the expression of intercellular adhesion molecule-1 in response to stimulation with tumor necrosis factor alpha and was also able to incorporate acetylated low-density lipoprotein. Our results suggest that this latter HSVEC line will provide a useful resource to investigate selected responses of the vascular endothelium to physiological and pathological situations.

Induction of interleukin-6 (IL-6) autoantibodies through vaccination with an engineered IL-6 receptor antagonist

Neutralization of cytokine activity by monoclonal antibodies or receptor antagonists is beneficial in the treatment of immune and neoplastic diseases, but the necessity for continuous parenteral delivery of these anticytokine agents poses considerable practical limitations. A viable alternative is to induce a neutralizing antibody response. Using transgenic mice with high circulating levels of human interleukin-6 (hIL-6), we show that injection of the hIL-6 receptor antagonist Sant1 (an IL-6 variant with seven amino-acid substitutions) induces a strong anti-hIL-6 antibody response. The elicited antibodies bind circulating hIL-6 with very high affinity, totally masking it, and neutralize hIL-6 bioactivity both in vitro and in vivo.