Pierre Fons

Revascularization of ischemic tissues by PDGF-CC via effects on endothelial cells and their progenitors

The angiogenic mechanism and therapeutic potential of PDGF-CC, a recently discovered member of the VEGF/PDGF superfamily, remain incompletely characterized. Here we report that PDGF-CC mobilized endothelial progenitor cells in ischemic conditions; induced differentiation of bone marrow cells into ECs; and stimulated migration of ECs. Furthermore, PDGF-CC induced the differentiation of bone marrow cells into smooth muscle cells and stimulated their growth during vessel sprouting. Moreover, delivery of PDGF-CC enhanced postischemic revascularization of the heart and limb. Modulating the activity of PDGF-CC may provide novel opportunities for treating ischemic diseases.

VEGF-R2 and neuropilin-1 are involved in VEGF-A-induced differentiation of human bone marrow progenitor cells

Tumor growth and metastasis require the generation of new blood vessels, a process known as neo‐angiogenesis. Recent studies have indicated that early tumor vascularization is characterized by the differentiation and mobilization of human bone marrow cells. Vascular endothelial growth factor‐A (VEGF‐A) is one of the growth factors, which enhances their differentiation into endothelial cells, but little is known about the implication of the VEGF‐receptor tyrosine kinases and about the implication of the VEGF‐R co‐receptor, neuropilin‐1, in this process. In this context, the identification of the molecular pathways that support the proliferation and differentiation of vascular stem and progenitor cells was investigated in order to define the pharmaceutical targets involved in tissue vascularization associated with this process. For this purpose, an in vitro model of differentiation of human bone marrow AC133+ (BM‐AC133+) cells into vascular precursors was used. In this work, we have demonstrated for the first time that the effect of VEGF‐A on BM‐AC133+ cells relies on an early action of VEGF‐A on the expression of its tyrosine kinase receptors followed by an activation of a VEGF‐R2/neuropilin‐1‐dependent signaling pathway. This signaling promotes the differentiation of BM‐AC133+ cells into endothelial precursor cells, followed by the proliferation of these differentiated cells. Altogether, these results strongly suggest that VEGF inhibitors, acting at the level of VEGF‐R2 and/or neuropilin‐1, by inhibiting differentiation and proliferation of these cells, could be potentially active compounds to prevent progenitor cells to be involved in tumor angiogenesis leading to tumor growth.

Tumor vasculature is regulated by FGF/FGFR signaling-mediated angiogenesis and bone marrow-derived cell recruitment: this mechanism is inhibited by SSR128129E, the first allosteric antagonist of FGFRs.

Tumor angiogenesis is accompanied by vasculogenesis, which is involved in the differentiation and mobilization of human bone marrow cells. In order to further characterize the role of vasculogenesis in the tumor growth process, the effects of FGF2 on the differentiation of human bone marrow AC133+ cells (BM‐AC133+) into vascular precursors were studied in vitro. FGF2, like VEGFA, induced progenitor cell differentiation into cell types with endothelial cell characteristics. SSR128129E, a newly discovered specific FGFR antagonist acting by allosteric interaction with FGFR, abrogated FGF2‐induced endothelial cell differentiation, showing that FGFR signaling is essential during this process. To assess the involvement of the FGF/FRGR signaling in vivo, the pre‐clinical model of Lewis lung carcinoma (LL2) in mice was used. Subcutaneous injection of LL2 cells into mice induced an increase of circulating EPCs from peripheral blood associated with tumor growth and an increase of intra‐tumoral vascular index. Treatment with the FGFR antagonist SSR128129E strongly decreased LL2 tumor growth as well as the intra‐tumoral vascular index (41% and 50% decrease vs. vehicle‐treated mice respectively, P < 0.01). Interestingly, SSR128129E treatment significantly decreased the number of circulating EPCs from the peripheral blood (53% inhibition vs. vehicle‐treated mice, P < 0.01). These results demonstrate for the first time that the blockade of the FGF/FGFR pathway by SSR128129E reduces EPC recruitment during angiogenesis‐dependent tumor growth. In this context, circulating EPCs could be a reliable surrogate marker for tumor growth and angiogenic activity. J. Cell. Physiol. 230: 43–51, 2015.

Targeted Identification of Sialoglycoproteins in Hypoxic Endothelial Cells and Validation in Zebrafish Reveal Roles for Proteins in Angiogenesis

Background: Target identification on tumor microvascularization is an opportunity for cancer therapy. Results: Membrane and secreted glycoproteins were identified on endothelial cells under hypoxia, and their function was assessed in zebrafish. Conclusion: Three novel hypoxia-regulated glycoproteins involved in angiogenesis have been identified and validated. Significance: We describe an approach that can be used to rapidly identify novel angiogenesis-related genes and their protein products. The formation of new vessels in the tumor, termed angiogenesis, is essential for primary tumor growth and facilitates tumor invasion and metastasis. Hypoxia has been described as one trigger of angiogenesis. Indeed, hypoxia, which is characterized by areas of low oxygen levels, is a hallmark of solid tumors arising from an imbalance between oxygen delivery and consumption. Hypoxic conditions have profound effects on the different components of the tumoral environment. For example, hypoxia is able to activate endothelial cells, leading to angiogenesis but also thereby initiating a cascade of reactions involving neutrophils, smooth muscle cells, and fibroblasts. In addition, hypoxia directly regulates the expression of many genes for which the role and the importance in the tumoral environment remain to be completely elucidated. In this study, we used a method to selectively label sialoglycoproteins to identify new membrane and secreted proteins involved in the adaptative process of endothelial cells by mass spectrometry-based proteomics. We used an in vitro assay under hypoxic condition to observe an increase of protein expression or modifications of glycosylation. Then the function of the identified proteins was assessed in a vasculogenesis assay in vivo by using a morpholino strategy in zebrafish. First, our approach was validated by the identification of sialoglycoproteins such as CD105, neuropilin-1, and CLEC14A, which have already been described as playing key roles in angiogenesis. Second, we identified several new proteins regulated by hypoxia and demonstrated for the first time the pivotal role of GLUT-1, TMEM16F, and SDF4 in angiogenesis.

Automated Image Analysis of In Vitro Angiogenesis Assay

Angiogenesis is the biological process of generating new capillary blood vessels. It is a fundamental component of a number of normal (reproduction and wound healing) and pathological processes (diabetic retinopathy, rheumatoid arthritis, tumor growth, and metastasis). In vitro angiogenesis assays provide a platform for evaluating the effects of pro- or antiangiogenic compounds. One of the most informative assays is the endothelial cells capillary tube formation assay performed on a biological matrix. This assay is based on quantification of the stimulatory and inhibitory effects of various agents, which is estimated through the measurement of the pseudo-tubules network length. This standard measurement is usually carried out manually by trained operators but requires time, attention, and dedication to achieve a reasonable degree of accuracy. Moreover, the screening is operator dependent. In this article, we propose an automated procedure to evaluate the pseudo-tubule network lengths. We propose a series of image analysis procedures developed using a freely available image analysis software library. More than 800 images from 12 experiments were analyzed automatically and manually, and their results were compared to improve and validate the proposed image analysis procedure. The resulting image analysis software is currently running on a dedicated server, with comparable accuracy to manual measurements. Using this new automated procedure, we are able to treat 540 images, or three complete assays per hour.

Abstract 3970: Targeting the adenosine immunosuppressive pathway for cancer immunotherapy with small molecule agents

Standard Immune Checkpoint Therapies, such as anti-CTLA-4 or anti-PD-1/PD-L1 mAb, demonstrate long progression-free-survival for responding patients but with a low response rate. This can be due to additional immunosuppressive mechanisms developed by resistant tumors. The adenosine pathway is one of the main drivers of tumor progression by acting on two key features of the TME (Tumor Micro-Environment); immunity and angiogenesis. Expression of CD73 on tumor cells and on immunosuppressive cell subsets leads to the generation of adenosine from AMP. Adenosine inhibits the biological functions of T lymphocytes infiltrating the tumor by binding to the A2AR (receptor). Evotec and Exscientia are collaborating to accelerate small molecule drug discovery in the field of Immuno-Oncology by integrating a unique biophysical screening approach to the adenosine receptors and CD73 to drive automated medicinal chemistry design with a translational-focused screening cascade, to discover novel agents that target the adenosinergic pathway in immuno-oncology. We have firstly sought to generate novel A2AR antagonists and secondly to create A2AR/CD73 bi-specific inhibitory molecules with a dual pharmacological profile, from fragment screening and de novo design approaches. In vivo combination study demonstrate the advantages of targeting CD73 and A2AR. We have obtained active molecules illustrated by in vitro data on primary human T lymphocytes. These results, have paved the way to an optimized process to identify adenosinergic pathway inhibitors with properties optimized for immuno-oncology. Citation Format: Pierre Fons, Michael Esquerre, Stephanie Versluys, Gigliola Mambrini, Michael Paillasse, Andy Bell, Adrian Schreyer, Richard Cox, Richard Bickerton, Joanna Lisztwan, Mark Whittaker, Francoise Bono, Craig Johnstone, Andrew Hopkins. Targeting the adenosine immunosuppressive pathway for cancer immunotherapy with small molecule agents [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 3970. doi:10.1158/1538-7445.AM2017-3970

Abstract 2634: EVT801: Standalone cancer immunotherapy in VEGFR3+tumors and combination with immune checkpoint therapies in VEGFR3-tumors

In collaboration with Sanofi, we previously showed that inhibition of the VEGFR3 pathway by SAR131675 leads to reduction of tumor growth by acting on the tumor microenvironment. We have identified a new drug candidate, EVT801, and evaluated its activity on tumor models expressing VEGFR3. For proof-of-concept, we transfected the mouse BNL hepatoma cell line with VEGFR3. EVT801 displayed a strong therapeutic activity by acting on both VEGFR3+ tumor cells and on the Tumor Microenvironment (TME). By deciphering the mechanism of action of the compounds we showed that EVT801 strongly decreased tumor-associated immunosuppression by decreasing MDSCs (Myeloid Derived Suppressor cells) and CD4+ regulatory T cells and by increasing macrophages with a M1 phenotype inside the tumor. As a consequence the T-cell:MDSC ratios were increased in the TME and also in peripheral blood. In addition to its immunomodulatory properties, EVT801 decreased angiogenesis without increasing hypoxia. We have evaluated EVT801 therapeutic activity in syngeneic tumor mouse models which are not expressing VEGFR3 such as 4T1 mammary carcinoma and CT26 colon carcinoma models. As expected, we observed an intermediate therapeutic activity of the compound on both tumor models. Positive modulation of the TME was equivalent to what we observed with the VEGFR3+ tumor model. With this unique mechanism of action of EVT801 on the TME, we evaluated its ability to increase therapeutic activity of standard Immune Checkpoint Therapies (ICT) such as anti-CTLA-4 and anti-PD-1 mAbs. Strong additive therapeutic activities were observed with EVT801 in combination with these ICT as illustrated by the development of long-term tumor-specific memory CD8+ T cell responses. Toxicological data show that EVT801 has a favorable pharmacological profile consistent with its entry into pre-clinical development. Taken together, these results indicate that EVT801 represents an innovative drug for cancer Immunotherapy which provide a favorable microenvironment to promote tumor regression. In addition, EVT801 may improve the frequency of response to ICT. Citation Format: Michael Esquerre, Pierre Fons, Gaelle Badet, Pauline Barron, Jeremy Kagan, Antoine Alam, Jerome Meneyrol, Isabelle Blanc, Roselyne Broussy, Florence Gaujarengues, Joanna Lisztwan, Michael Paillasse, Mark Whittaker, Francoise Bono. EVT801: Standalone cancer immunotherapy in VEGFR3+ tumors and combination with immune checkpoint therapies in VEGFR3- tumors [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 2634. doi:10.1158/1538-7445.AM2017-2634