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Angiogenesis is a complex biological process involving the coordinated modulation of many genes. Histone deacetylases (HDAC) are a growing family of enzymes that mediate the availability of chromatin to the transcriptional machinery. Trichostatin-A (TSA) and suberoylanilide hydroxamic acid (SAHA), two HDAC inhibitors known to relieve gene silencing, were evaluated as potential antiangiogenic agents. TSA and SAHA were shown to prevent vascular endothelial growth factor (VEGF)-stimulated human umbilical cord endothelial cells (HUVEC) from invading a type I collagen gel and forming capillary-like structures. SAHA and TSA inhibited the VEGF-induced formation of a CD31-positive capillary-like network in embryoid bodies and inhibited the VEGF-induced angiogenesis in the CAM assay. TSA also prevented, in a dose-response relationship, the sprouting of capillaries from rat aortic rings. TSA inhibited in a dose-dependent and reversible fashion the VEGF-induced expression of VEGF receptors, VEGFR1, VEGFR2, and neuropilin-1. TSA and SAHA upregulated the expression by HUVEC of semaphorin III, a recently described VEGF competitor, at both mRNA and protein levels. This effect was specific to endothelial cells and was not observed in human fibroblasts neither in vascular smooth muscle cells. These observations provide a conspicuous demonstration that HDAC inhibitors are potent anti-angiogenic factors altering VEGF signaling.

BackgroundKISIMATM platform-derived recombinant chimeric protein vaccines were shown to elicit both CD8 and CD4 T cell responses against model or tumor associated antigens, resulting in control of tumor growth in different preclinical models.1 Vesicular stomatitis virus (VSV)-GP is a chimeric variant of VSV modified to avoid neurotoxicity, which is exploited for cancer therapy thanks to its oncolytic activity and also as a potent vaccine vector for delivering of tumor associated antigen. Previously, we have shown that therapeutic heterologous prime-boost vaccination with KISIMA protein vaccine and a tumor-antigen armed VSV-GP (VSV-GP-TAg) oncolytic virus elicits a potent CD8 T cell response, enhances the infiltration and functionality of antigen-specific CD8 T cells, and inflames the tumor microenvironment in different mouse models, resulting in increased anti-tumoral efficacy.2 However, the efficacy of tumor-specific immune responses could be limited by intratumoral T cell exhaustion which can results in tumor escape and disease relapse. Immune check point inhibitors changed the landscape of cancer therapy, but their efficacy is often restricted to highly T cell infiltrated tumor, making them attractive for combination therapy with cancer vaccines.MethodsIn this study, we evaluate the combination of NKG2A blockade and KISIMA – VSV-GP-TAg heterologous prime-boost vaccination focusing on modulation of T cell phenotype and antitumoral efficacy in TC-1 tumor model, a lung epithelial cell line transfected with HPV16 E6/E7 and c-H ras oncogene.ResultsKISIMA – VSV-GP-TAg prime-boost vaccination strongly increased the expression of NKG2A on both circulating and tumor infiltrating antigen-specific CD8 T cells. Vaccination of TC-1 tumor-bearing mice in combination with NKG2A blocking antibody resulted in inhibition of tumor growth, induced complete tumor remission and prolonged survival. Mechanistically, NKG2A blockade did not enhance the infiltration nor the ability to secrete cytokine of antigen-specific CD8 T cells induced by heterologous prime-boost vaccination, but it significantly reduced exhaustion. Surprisingly, NKG2A blockade reduced the expansion and activation of circulating antigen-specific CD8 T cells elicited by KISIMA – VSV-GP-TAg vaccination. Consistently, combination treatment resulted in decreased number of long-lasting antigen-specific effector memory CD8 T cells in secondary lymphoid organs, while complete responders were only partially protected against homologous tumor rechallenge, highlighting a negative impact of NKG2A blockade on immune memory.ConclusionsTaken together, these data suggest a dual role of NKG2A blockade on cancer vaccine-induced T cells, increasing early antitumoral efficacy by reducing intratumoral T cell exhaustion but impairing the establishment of long-term immunity.ReferencesBelnoue E, Mayol JF, Carboni S, Di Berardino Besson W, Dupuychaffray E, Nelde A, Stevanovic S, Santiago-Raber ML, Walker PR, Derouazi M. Targeting self and neo-epitopes with a modular self-adjuvanting cancer vaccine. JCI Insight. 2019 Apr 23;5(11):e127305. doi: 10.1172/jci.insight.127305. PMID: 31013258; PMCID: PMC6629093.Das K, Belnoue E, Rossi M, Hofer T, Danklmaier S, Nolden T, Schreiber LM, Angerer K, Kimpel J, Hoegler S, Spiesschaert B, Kenner L, von Laer D, Elbers K, Derouazi M, Wollmann G. A modular self-adjuvanting cancer vaccine combined with an oncolytic vaccine induces potent antitumor immunity. Nat Commun. 2021 Aug 31;12(1):5195. doi: 10.1038/s41467-021-25506-6. PMID: 34465781; PMCID: PMC8408233.Ethics ApprovalThis study has been approved by the Cantonal veterinary authority of Geneva, under the authorization number GE193.

In vitro angiogenesis assays are essential for the identification of potential angiogenic agents and screening for pharmacological inhibitors. Among these assays, the rat aortic ring model developed by Nicosia bridges the gap between in vivo and in vitro models. The quantification of angiogenesis on this system must be applicable to characterise vascular networks of various states of complexity. We present here an improved computer-assisted image analysis which allows: (1) the determination of the aortic ring area and its factor shape; (2) the number of microvessels, the total number of branchings, the maximal microvessel length and the microvessel distribution; (3) the total number of isolated fibroblast-like cells and their distribution. We show that this method is suitable to quantify spontaneous angiogenesis as well as to analyse a complex microvascular network induced by various concentrations of vascular endothelial growth factor (VEGF). In addition, by evaluating a new parameter, the fibroblast-like cell distribution, our results show that: (1) during spontaneous angiogenic response, maximal fibroblast-like cell migration delimits microvascular outgrowth; and (2) the known angiogenic inhibitor Batimastat prevents endothelial cell sprouting without completely blocking fibroblast-like cell migration. Finally, this new method of quantification is of great interest to better understand angiogenesis and to test pro- or anti-angiogenic agents.

Angiogenesis is a complex biological process involving the coordinated modulation of many genes. Histone deacetylases (HDAC) are a growing family of enzymes that mediate the availability of chromatin to the transcriptional machinery. Trichostatin-A (TSA) and suberoylanilide hydroxamic acid (SAHA), two HDAC inhibitors known to relieve gene silencing, were evaluated as potential antiangiogenic agents. TSA and SAHA were shown to prevent vascular endothelial growth factor (VEGF)-stimulated human umbilical cord endothelial cells (HUVEC) from invading a type I collagen gel and forming capillary-like structures. SAHA and TSA inhibited the VEGF-induced formation of a CD31-positive capillary-like network in embryoid bodies and inhibited the VEGF-induced angiogenesis in the CAM assay. TSA also prevented, in a dose-response relationship, the sprouting of capillaries from rat aortic rings. TSA inhibited in a dose-dependent and reversible fashion the VEGF-induced expression of VEGF receptors, VEGFR1, VEGFR2, and neuropilin-1. TSA and SAHA upregulated the expression by HUVEC of semaphorin III, a recently described VEGF competitor, at both mRNA and protein levels. This effect was specific to endothelial cells and was not observed in human fibroblasts neither in vascular smooth muscle cells. These observations provide a conspicuous demonstration that HDAC inhibitors are potent anti-angiogenic factors altering VEGF signaling.

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.

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.

Immune check-point blockade (ICB) has revitalized cancer immunotherapy, showing unprecedented efficacy despite only a narrow number of indications and with limited long-term protection. Cancer vaccines are promising combination partners for ICB to widen the patient population profiting from these treatments. Therapeutic heterologous prime-boost vaccination with KISIMATM protein vaccine and VSV-GP-TAg oncolytic virus was shown to inflame the tumor microenvironment, promoting significant infiltration of antigen-specific CD8 T cells resulting in robust antitumoral efficacy in mouse tumor models, and clinical trials are currently ongoing. Here, we report the impact of NKG2A blockade on antitumoral CD8 T cell immune response elicited by KISIMA—VSV-GP-TAg vaccination in tumor mouse models. Combination therapy significantly reduced the amount of vaccine-induced exhausted CD8 T cells infiltrating the tumor, resulting in short-term improved tumor growth control and prolonged mouse survival, while it also influenced the establishment of systemic effector memory CD8 T cell response. Taken together, these data show a compartment-dependent effect of NKG2A blockade on cancer vaccine-induced T cell immunity, increasing intratumoral T cell efficacy and attenuating the development of peripheral effector memory CD8 T cell response.