Gene expression of tumor angiogenesis dissected: specific targeting of colon cancer angiogenic vasculature

Metabolic reprogramming and interventions in angiogenesis

BACKGROUND

Endothelial cell (EC) metabolism plays a crucial role in the process of angiogenesis. Intrinsic metabolic events such as glycolysis, fatty acid oxidation, and glutamine metabolism, support secure vascular migration and proliferation, energy and biomass production, as well as redox homeostasis maintenance during vessel formation. Nevertheless, perturbation of EC metabolism instigates vascular dysregulation-associated diseases, especially cancer.

AIM OF REVIEW

In this review, we aim to discuss the metabolic regulation of angiogenesis by EC metabolites and metabolic enzymes, as well as prospect the possible therapeutic opportunities and strategies targeting EC metabolism.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this work, we discuss various aspects of EC metabolism considering normal and diseased vasculature. Of relevance, we highlight that the implications of EC metabolism-targeted intervention (chiefly by metabolic enzymes or metabolites) could be harnessed in orchestrating a spectrum of pathological angiogenesis-associated diseases.

Extracellular vimentin as a versatile immune suppressive protein in cancer

The interest in finding new targets in the tumor microenvironment for anti-cancer therapy has increased rapidly over the years. More specifically, the tumor-associated blood vessels are a promising target. We recently found that the intermediate filament protein vimentin is externalized by endothelial cells of the tumor vasculature. Extracellular vimentin was shown to sustain angiogenesis by mimicking VEGF and supporting cell migration, as well as endothelial cell anergy, the unresponsiveness of the endothelium to proinflammatory cytokines. The latter hampers immune cell infiltration and subsequently provides escape from tumor immunity. Other studies showed that extracellular vimentin plays a role in sustained systemic and local inflammation. Here we will review the reported roles of extracellular vimentin with a particular emphasis on its involvement in the interactions between immune cells and the endothelium in the tumor microenvironment. To this end, we discuss the different ways by which extracellular vimentin modulates the immune system. Moreover, we review how this protein can alter immune cell-vessel wall adhesion by altering the expression of adhesion proteins, attenuating immune cell infiltration into the tumor parenchyma. Finally, we discuss how vimentin-targeting therapy can reverse endothelial cell anergy and promote immune infiltration, supporting anti-tumor immunity.

Vaccination against Extracellular Vimentin for Treatment of Urothelial Cancer of the Bladder in Client-Owned Dogs

It was recently shown that targeting extracellular vimentin (eVim) is safe and effective in preclinical models. Here, we report the safety and efficacy in client-owned dogs with spontaneous bladder cancer of CVx1, an iBoost technology-based vaccine targeting eVim in combination with COX-2 inhibition. This was a single-arm prospective phase 1/2 study with CVx1 in 20 client-owned dogs with spontaneous UC which involved four subcutaneous vaccinations with CVx1 at 2-week intervals for induction of antibody titers, followed by maintenance vaccinations at 2-month intervals. Additionally, daily cyclooxygenase (COX)-2 inhibition with meloxicam was given. The response was assessed by antibody titers, physical condition, abdominal ultrasound and thorax X-ray. The primary endpoints were the development of antibody titers, as well as overall survival compared to a historical control group receiving carboplatin and COX-2 inhibition with piroxicam. Kaplan-Meier survival analysis was performed. All dogs developed antibodies against eVim. Titers were adequately maintained for the duration of this study. A median overall survival of 374 days was observed, which was 196 days for the historical control group (p < 0.01). Short-term grade 1-2 toxicity at the injection site and some related systemic symptoms peri-vaccination were observed. No toxicity was observed related to the induced antibody response. A limitation of this study is the single-arm prospective setting. CVx1 plus meloxicam consistently induced efficient antibody titers, was well tolerated and showed prolonged survival. The results obtained merit further development for human clinical care.

Fibroblasts as Turned Agents in Cancer Progression

Differentiated epithelial cells reside in the homeostatic microenvironment of the native organ stroma. The stroma supports their normal function, their G0 differentiated state, and their expansion/contraction through the various stages of the life cycle and physiologic functions of the host. When malignant transformation begins, the microenvironment tries to suppress and eliminate the transformed cells, while cancer cells, in turn, try to resist these suppressive efforts. The tumor microenvironment encompasses a large variety of cell types recruited by the tumor to perform different functions, among which fibroblasts are the most abundant. The dynamics of the mutual relationship change as the sides undertake an epic battle for control of the other. In the process, the cancer “wounds” the microenvironment through a variety of mechanisms and attracts distant mesenchymal stem cells to change their function from one attempting to suppress the cancer, to one that supports its growth, survival, and metastasis. Analogous reciprocal interactions occur as well between disseminated cancer cells and the metastatic microenvironment, where the microenvironment attempts to eliminate cancer cells or suppress their proliferation. However, the altered microenvironmental cells acquire novel characteristics that support malignant progression. Investigations have attempted to use these traits as targets of novel therapeutic approaches.

Molecular differences of angiogenic versus vessel co-opting colorectal cancer liver metastases at single-cell resolution

BACKGROUND

Colorectal cancer liver metastases (CRCLM) are associated with a poor prognosis, reflected by a five-year survival rate of 14%. Anti-angiogenic therapy through anti-VEGF antibody administration is one of the limited therapies available. However, only a subgroup of metastases uses sprouting angiogenesis to secure their nutrients and oxygen supply, while others rely on vessel co-option (VCO). The distinct mode of vascularization is reflected by specific histopathological growth patterns (HGPs), which have proven prognostic and predictive significance. Nevertheless, their molecular mechanisms are poorly understood.

METHODS

We evaluated CRCLM from 225 patients regarding their HGP and clinical data. Moreover, we performed spatial (21,804 spots) and single-cell (22,419 cells) RNA sequencing analyses to explore molecular differences in detail, further validated in vitro through immunohistochemical analysis and patient-derived organoid cultures.

RESULTS

We detected specific metabolic alterations and a signature of WNT signalling activation in metastatic cancer cells related to the VCO phenotype. Importantly, in the corresponding healthy liver of CRCLM displaying sprouting angiogenesis, we identified a predominantly expressed capillary subtype of endothelial cells, which could be further explored as a possible predictor for HGP relying on sprouting angiogenesis.

CONCLUSION

These findings may prove to be novel therapeutic targets to the treatment of CRCLM, in special the ones relying on VCO.

Targeting endothelial cell metabolism in cancerous microenvironment: a new approach for anti-angiogenic therapy

Anti-angiogenic therapy is a practical approach to managing diseases with increased angiogenesis, such as cancer, maculopathies, and retinopathies. Considering the fundamental gaps in the knowledge of the vital pathways involved in angiogenesis and its inhibition and the insufficient efficiency of existing angiogenesis inhibitors, there is an increasing focus on the emergence of new therapeutic strategies aimed at inhibiting pathological angiogenesis. Angiogenesis is forming a new vascular network from existing vessels; endothelial cells (ECs), vascular lining cells, are the main actors of angiogenesis in physiological or pathological conditions. Switching from a quiescent state to a highly migratory and proliferative state during new vessel formation called "angiogenic switch" is driven by a "metabolic switch" in ECs, angiogenic growth factors, and other signals. As the characteristics of ECs change by altering the surrounding environment, they appear to have a different metabolism in a tumor microenvironment (TME). Therefore, pathological angiogenesis can be inhibited by targeting metabolic pathways. In the current review, we aim to discuss the EC metabolic pathways under normal and TME conditions to verify the suitability of targeting them with novel therapies.

Catulin reporter marks a heterogeneous population of invasive breast cancer cells with some demonstrating plasticity and participating in vascular mimicry

Breast cancer is the most commonly diagnosed cancer in women worldwide. The activation of partial or more complete epithelial–mesenchymal transition in cancer cells enhances acquisition of invasive behaviors and expands their generation of cancer stem cells. Increased by EMT plasticity of tumor cells could promote vascular mimicry, a newly defined pattern of tumor microvascularization by which aggressive tumor cells can form vessel-like structures themselves. VM is strongly associated with a poor prognosis, but biological features of tumor cells that form VM remains unknown. Here we show that catulin is expressed in human BC samples and its expression correlates with the tumor progression. Ablation of catulin in hBC cell lines decreases their invasive potential in the 3D assays. Using a novel catulin promoter based reporter we tracked and characterized the small population of invasive BC cells in xenograft model. RNAseq analysis revealed enrichment in genes important for cellular movement, invasion and interestingly for tumor-vasculature interactions. Analysis of tumors unveiled that catulin reporter marks not only invasive cancer cells but also rare population of plastic, MCAM positive cancer cells that participate in vascular mimicry. Ablation of catulin in the xenograft model revealed deregulation of genes involved in cellular movement, and adhesive properties with striking decrease in CD44 which may impact stemness potential, and plasticity of breast cancer cells. These findings show directly that some plastic tumor cells can change the fate into endothelial-like, expressing MCAM and emphasize the importance of catulin in this process and breast cancer progression.

Stromal Co-Cultivation for Modeling Breast Cancer Dormancy in the Bone Marrow

Cancers metastasize to the bone marrow before primary tumors can be detected. Bone marrow micrometastases are resistant to therapy, and while they are able to remain dormant for decades, they recur steadily and result in incurable metastatic disease. The bone marrow microenvironment maintains the dormancy and chemoresistance of micrometastases through interactions with multiple cell types and through structural and soluble factors. Modeling dormancy in vitro can identify the mechanisms of these interactions. Modeling also identifies mechanisms able to disrupt these interactions or define novel interactions that promote the reawakening of dormant cells. The in vitro modeling of the interactions of cancer cells with various bone marrow elements can generate hypotheses on the mechanisms that control dormancy, treatment resistance and reawakening in vivo. These hypotheses can guide in vivo murine experiments that have high probabilities of succeeding in order to verify in vitro findings while minimizing the use of animals in experiments. This review outlines the existing data on predominant stromal cell types and their use in 2D co-cultures with cancer cells.

Cancer Vaccination against Extracellular Vimentin Efficiently Adjuvanted with Montanide ISA 720/CpG

Simple Summary

Vaccination against specific proteins in the tumor vasculature has already shown promising results in several preclinical studies. However, the efficacy of vaccination highly depends on the adjuvant used. This study aimed to assess the potential use of the biodegradable adjuvant Montanide ISA 720 in combination with our vaccine against extracellular vimentin, a protein specifically secreted by the tumor vasculature. Compared to the potent but toxic Freund’s adjuvant, Montanide showed a comparable immune response and tumor growth inhibition in a preclinical vaccination experiment in mice, especially when supplemented with the immune stimulatory molecule CpG. We also observed that vaccination reduced the blood vessel count and increased the infiltration of immune cells. We conclude that Montanide ISA 720 shows potential to be used as an adjuvant for vaccination against extracellular vimentin for future clinical studies in cancer patients.

Abstract

Extracellular vimentin is a specific marker of the tumor vasculature, where it is secreted by tumor endothelial cells. Vaccination with a conjugate vaccine targeting extracellular vimentin was previously shown to induce a potent humoral immune response and tumor growth inhibition in mice. These data were obtained by vaccination using the toxic Freund’s adjuvant (FA) and are therefore not directly translatable into the clinic. In the present study, we aimed to investigate the potential of the biodegradable Montanide ISA 720 adjuvant. We tested Montanide either alone (MN) or supplemented with CpG 1826 (MN-C). Both adjuvant compositions, as well as FA, resulted in a significant tumor growth inhibition and decreased vessel density in the B16F10 melanoma tumor model. Vaccination of mice with either FA or MN-C resulted in an equally potent humoral immune response towards vimentin, while the antibody titers obtained with MN alone were significantly lower compared to FA. Vaccination coincided with the infiltration of immune cells. The highest number of intratumoral immune cells was seen in tumors from the MN-C group. Therefore, we conclude that Montanide ISA 720 supplemented with CpG allows efficient vaccination against extracellular vimentin, which is a prerequisite for the transfer of the vaccine into the clinic.

Extracellular vimentin mimics VEGF and is a target for anti-angiogenic immunotherapy

Anti-angiogenic cancer therapies possess immune-stimulatory properties by counteracting pro-angiogenic molecular mechanisms. We report that tumor endothelial cells ubiquitously overexpress and secrete the intermediate filament protein vimentin through type III unconventional secretion mechanisms. Extracellular vimentin is pro-angiogenic and functionally mimics VEGF action, while concomitantly acting as inhibitor of leukocyte-endothelial interactions. Antibody targeting of extracellular vimentin shows inhibition of angiogenesis in vitro and in vivo. Effective and safe inhibition of angiogenesis and tumor growth in several preclinical and clinical studies is demonstrated using a vaccination strategy against extracellular vimentin. Targeting vimentin induces a pro-inflammatory condition in the tumor, exemplified by induction of the endothelial adhesion molecule ICAM1, suppression of PD-L1, and altered immune cell profiles. Our findings show that extracellular vimentin contributes to immune suppression and functions as a vascular immune checkpoint molecule. Targeting of extracellular vimentin presents therefore an anti-angiogenic immunotherapy strategy against cancer.

The pro-tumorigenic effects of vimentin have been attributed to intracellular functions in tumour cells so far. Here, the authors show that tumour endothelial cells can secrete vimentin as a pro-angiogenic factor and that targeting of vimentin can be used as an immunotherapeutic strategy.

Expression of vimentin, TPI and MAT2A in human dermal microvascular endothelial cells during angiogenesis in vitro

Introduction

In vitro assays of angiogenesis face immense problems considering their reproducibility based on the inhomogeneous characters of endothelial cells (ECs). It is necessary to detect influencing factors, which affect the angiogenic potency of ECs.

Objective

This study aimed to analyse expression profiles of vimentin (VIM), triosephosphate isomerase (TPI) and adenosylmethionine synthetase isoform type–2 (MAT2A) during the whole angiogenic cascade in vitro. Furthermore, the impact of knocking down vimentin (VIM) on angiogenesis in vitro was evaluated, while monitoring TPI and MAT2A expression.

Methods

A long–term cultivation and angiogenic stimulation of human dermal microvascular ECs was performed. Cells were characterized via VEGFR–1 and VEGFR–2 expression and a shRNA–mediated knockdown of VIM was performed. The process of angiogenesis in vitro was quantified via morphological staging and mRNA–and protein–levels of all proteins were analysed.

Results

While native cells ran through the angiogenic cascade chronologically, knockdown cells only entered beginning stages of angiogenesis and died eventually. Cell cultures showing a higher VEGFR–1 expression survived exclusively and displayed an upregulation of MAT2A and TPI expression. Native cells highly expressed VIM in early stages, MAT2A mainly in the beginning and TPI during the course of angiogenesis in vitro.

Conclusion

VIM knockdown led to a deceleration of angiogenesis in vitro and knockdown cells displayed expressional changes in TPI and MAT2A. Cell populations with a higher number of stalk cells emerged as being more stable against manipulations and native expression profiles provided an indication of VIM and MAT2A being relevant predominantly in beginning stages and TPI during the whole angiogenic cascade in vitro.

Reprogramming Carbohydrate Metabolism in Cancer and Its Role in Regulating the Tumor Microenvironment

Altered metabolism has become an emerging feature of cancer cells impacting their proliferation and metastatic potential in myriad ways. Proliferating heterogeneous tumor cells are surrounded by other resident or infiltrating cells, along with extracellular matrix proteins, and other secretory factors constituting the tumor microenvironment. The diverse cell types of the tumor microenvironment exhibit different molecular signatures that are regulated at their genetic and epigenetic levels. The cancer cells elicit intricate crosstalks with these supporting cells, exchanging essential metabolites which support their anabolic processes and can promote their survival, proliferation, EMT, angiogenesis, metastasis and even therapeutic resistance. In this context, carbohydrate metabolism ensures constant energy supply being a central axis from which other metabolic and biosynthetic pathways including amino acid and lipid metabolism and pentose phosphate pathway are diverged. In contrast to normal cells, increased glycolytic flux is a distinguishing feature of the highly proliferative cancer cells, which supports them to adapt to a hypoxic environment and also protects them from oxidative stress. Such rewired metabolic properties are often a result of epigenetic alterations in the cancer cells, which are mediated by several factors including, DNA, histone and non-histone protein modifications and non-coding RNAs. Conversely, epigenetic landscapes of the cancer cells are also dictated by their diverse metabolomes. Altogether, this metabolic and epigenetic interplay has immense potential for the development of efficient anti-cancer therapeutic strategies. In this book chapter we emphasize upon the significance of reprogrammed carbohydrate metabolism in regulating the tumor microenvironment and cancer progression, with an aim to explore the different metabolic and epigenetic targets for better cancer treatment.

A perspective on the role of autophagy in cancer

Autophagy refers to a ubiquitous set of catabolic pathways required to achieve proper cellular homeostasis. Aberrant autophagy has been implicated in a multitude of diseases including cancer. In this review, we highlight pioneering and groundbreaking research that centers on delineating the role of autophagy in cancer initiation, proliferation and metastasis. First, we discuss the autophagy-related (ATG) proteins and their respective roles in the de novo formation of autophagosomes and the subsequent delivery of cargo to the lysosome for recycling. Next, we touch upon the history of cancer research that centers upon ATG proteins and regulatory mechanisms that control an appropriate autophagic response and how these are altered in the diseased state. Then, we discuss the various discoveries that led to the idea of autophagy as a double-edged sword when it comes to cancer therapy. This review also briefly narrates how different types of autophagy-selective macroautophagy and chaperone-mediated autophagy, have been linked to different cancers. Overall, these studies build upon a steadfast trajectory that aims to solve the monumentally daunting challenge of finding a cure for many types of cancer by modulating autophagy either through inhibition or induction.

Somatic Genetic Mosaicism in the Apolipoprotein E-null Mouse Aorta

In addition to genetic and epigenetic inheritance, somatic variation may contribute to cardiovascular disease (CVD) risk. CVD-associated somatic mutations have been reported in human clonal hematopoiesis, but evidence in the atheroma is lacking. To probe for somatic variation in atherosclerosis, we sought single-nucleotide private variants (PVs) in whole-exome sequencing (WES) data of aorta, liver, and skeletal muscle of two C57BL/6J coisogenic male ApoE null/wild-type (WT) sibling pairs, and RNA-seq data of one of the two pairs. Relative to the C57BL/6 reference genome, we identified 9 and 11 ApoE null aorta- and liver-specific PVs that were shared by all WES and RNA-seq datasets. Corresponding PVs in WT sibling aorta and liver were 1 and 0, respectively, and not overlapping with ApoE null PVs. Pyrosequencing analysis of 4 representative PVs in 17 ApoE null aortas and livers confirmed tissue-specific shifts toward the alternative allele, in addition to significant deviations from mendelian allele ratios. Notably, all aorta and liver PVs were present in the dbSNP database and were predominantly transition mutations within atherosclerosis-related genes. The majority of PVs were in discrete clusters approximately 3 Mb and 65 to 73 Mb away from hypermutable immunoglobin loci in chromosome 6. These features were largely shared with previously reported CVD-associated somatic mutations in human clonal hematopoiesis. The observation that SNPs exhibit tissue-specific somatic DNA mosaicism in ApoE null mice is potentially relevant for genetic association study design. The proximity of PVs to hypermutable loci suggests testable mechanistic hypotheses.

A ligand-insensitive UNC5B splicing isoform regulates angiogenesis by promoting apoptosis

The Netrin-1 receptor UNC5B is an axon guidance regulator that is also expressed in endothelial cells (ECs), where it finely controls developmental and tumor angiogenesis. In the absence of Netrin-1, UNC5B induces apoptosis that is blocked upon Netrin-1 binding. Here, we identify an UNC5B splicing isoform (called UNC5B-Δ8) expressed exclusively by ECs and generated through exon skipping by NOVA2, an alternative splicing factor regulating vascular development. We show that UNC5B-Δ8 is a constitutively pro-apoptotic splicing isoform insensitive to Netrin-1 and required for specific blood vessel development in an apoptosis-dependent manner. Like NOVA2, UNC5B-Δ8 is aberrantly expressed in colon cancer vasculature where its expression correlates with tumor angiogenesis and poor patient outcome. Collectively, our data identify a mechanism controlling UNC5B’s necessary apoptotic function in ECs and suggest that the NOVA2/UNC5B circuit represents a post-transcriptional pathway regulating angiogenesis.

UNC5B is a Netrin-1 receptor expressed in endothelial cells that in the absence of ligand induces apoptosis. Here the authors identify an UNC5B splicing isoform that is insensitive to the pro-survival ligand Netrin-1 and is required for apoptosis-dependent blood vessel development.

Transcriptomic Analysis of LNCaP Tumor Xenograft to Elucidate the Components and Mechanisms Contributed by Tumor Environment as Targets for Dietary Prostate Cancer Prevention Studies

LNCaP athymic xenograft model has been widely used to allow researchers to examine the effects and mechanisms of experimental treatments such as diet and diet-derived cancer preventive and therapeutic compounds on prostate cancer. However, the biological characteristics of human LNCaP cells before/after implanting in athymic mouse and its relevance to clinical human prostate outcomes remain unclear and may dictate interpretation of biological efficacies/mechanisms of diet/diet-derived experimental treatments. In this study, transcriptome profiles and pathways of human prostate LNCaP cells before (in vitro) and after (in vivo) implanting into xenograft mouse were compared using RNA-sequencing technology (RNA-seq) followed by bioinformatic analysis. A shift from androgen-responsive to androgen nonresponsive status was observed when comparing LNCaP xenograft tumor to culture cells. Androgen receptor and aryl-hydrocarbon pathway were found to be inhibited and interleukin-1 (IL-1) mediated pathways contributed to these changes. Coupled with in vitro experiments modeling for androgen exposure, cell-matrix interaction, inflammation, and hypoxia, we identified specific mechanisms that may contribute to the observed changes in genes and pathways. Our results provide critical baseline transcriptomic information for a tumor xenograft model and the tumor environments that might be associated with regulating the progression of the xenograft tumor, which may influence interpretation of diet/diet-derived experimental treatments.

Endothelial Cell Glucose Metabolism and Angiogenesis

Angiogenesis, a process of new blood vessel formation from the pre-existing vascular bed, is a critical event in various physiological and pathological settings. Over the last few years, the role of endothelial cell (EC) metabolism in angiogenesis has received considerable attention. Accumulating studies suggest that ECs rely on aerobic glycolysis, rather than the oxidative phosphorylation pathway, to produce ATP during angiogenesis. To date, numerous critical regulators of glucose metabolism, fatty acid oxidation, and glutamine metabolism have been identified to modulate the EC angiogenic switch and pathological angiogenesis. The unique glycolytic feature of ECs is critical for cell proliferation, migration, and responses to environmental changes. In this review, we provide an overview of recent EC glucose metabolism studies, particularly glycolysis, in quiescent and angiogenic ECs. We also summarize and discuss potential therapeutic strategies that take advantage of EC metabolism. The elucidation of metabolic regulation and the precise underlying mechanisms could facilitate drug development targeting EC metabolism to treat angiogenesis-related diseases.

Biological functions and theranostic potential of HMGB family members in human cancers

The high mobility group box (HMGB) protein family consists of four members: HMGB1, 2, 3, and 4. They share similar amino acid sequences and identical functional regions, especially HMGB1, 2, and 3. The homology in structure may lead to similarity in function. In fact, though their targets may be different, they all possess the fundamental function of binding and distorting target DNAs. However, further research confirmed they are distributed differently in tissues and involved in various distinct physiological and pathological cellular processes, including cell proliferation, division, migration, and differentiation. Recently, the roles of HMGB family members in carcinogenesis has been widely investigated; however, systematic discussion on their functions and clinical values in malignant tumors is limited. In this review, we mainly review and summarize recent advances in knowledge of HMGB family members in terms of structure, distribution, biochemical cascades, and specific mechanisms regarding tumor progression. Importantly, the diagnostic, prognostic, and therapeutic value of these proteins in cancers is discussed. Finally, we envisage the orientation and challenges of this field in further studies.

Secreted frizzled-related protein 2: a key player in noncanonical Wnt signaling and tumor angiogenesis

Secreted frizzled-related proteins (SFRP) are glycoproteins containing a so-called frizzled-like cysteine-rich domain. This domain enables them to bind to Wnt ligands or frizzled (FzD) receptors, making potent regulators of Wnt signaling. As Wnt signaling is often altered in cancer, it is not surprising that Wnt regulators such as SFRP proteins are often differentially expressed in the tumor microenvironment, both in a metastatic and non-metastatic setting. Indeed, SFRP2 is shown to be specifically upregulated in the tumor vasculature of several types of cancer. Several studies investigated the functional role of SFRP2 in the tumor vasculature, showing that SFRP2 binds to FzD receptors on the surface of tumor endothelial cells. This activates downstream Wnt signaling and which is, thereby, stimulating angiogenesis. Interestingly, not the well-known canonical Wnt signaling pathway, but the noncanonical Wnt/Ca²⁺ pathway seems to be a key player in this event. In tumor models, the pro-angiogenic effect of SFRP2 could be counteracted by antibodies targeting SFRP2, without the occurrence of toxicity. Since tumor angiogenesis is an important process in tumorigenesis and metastasis formation, specific tumor endothelial markers such as SFRP2 show great promise as targets for anti-cancer therapies. This review discusses the role of SFRP2 in noncanonical Wnt signaling and tumor angiogenesis, and highlights its potential as anti-angiogenic therapeutic target in cancer.

IGF-Binding Proteins, Adiponectin, and Survival in Metastatic Colorectal Cancer: Results From CALGB (Alliance)/SWOG 80405

Background

Energy balance-related biomarkers are associated with risk and prognosis of various malignancies. Their relationship to survival in metastatic colorectal cancer (mCRC) requires further study.

Methods

Baseline plasma insulin-like growth factor (IGF)-1, IGF-binding protein (IGFBP)-3, IGFBP-7, C-peptide, and adiponectin were measured at time of trial registration in a prospective cohort of patients with mCRC participating in a National Cancer Institute–sponsored trial of first-line systemic therapy. We used Cox proportional hazards regression to adjust for confounders and examine associations of each biomarker with overall survival (OS) and progression-free survival (PFS). P values are 2-sided.

Results

Median follow-up for 1086 patients was 6.2 years. Compared with patients in the lowest IGFBP-3 quintile, patients in the highest IGFBP-3 quintile experienced an adjusted hazard ratio (HR) for OS of 0.57 (95% confidence interval [CI] = 0.42 to 0.78; P_nonlinearity < .001) and for PFS of 0.61 (95% CI = 0.45 to 0.82; P_trend = .003). Compared with patients in the lowest IGFBP-7 quintile, patients in the highest IGFBP-7 quintile experienced an adjusted hazard ratio for OS of 1.60 (95% CI = 1.30 to 1.97; P_trend < .001) and for PFS of 1.38 (95% CI = 1.13 to 1.69; P_trend < .001). Plasma C-peptide and IGF-1 were not associated with patient outcomes. Adiponectin was not associated with OS; there was a nonlinear U-shaped association between adiponectin and PFS (P_nonlinearity = .03).

Conclusions

Among patients with mCRC, high plasma IGFBP-3 and low IGFBP-7 were associated with longer OS and PFS. Extreme levels of adiponectin were associated with shorter PFS. These findings suggest potential avenues for prognostic and therapeutic innovation.

Metabolic Pathways Fueling the Endothelial Cell Drive

Endothelial cell (EC) metabolism is important for health and disease. Metabolic pathways, such as glycolysis, fatty acid oxidation, and amino acid metabolism, determine vasculature formation. These metabolic pathways have different roles in securing the production of energy and biomass and the maintenance of redox homeostasis in vascular migratory tip cells, proliferating stalk cells, and quiescent phalanx cells, respectively. Emerging evidence demonstrates that perturbation of EC metabolism results in EC dysfunction and vascular pathologies. Here, we summarize recent insights into EC metabolic pathways and their deregulation in vascular diseases. We further discuss the therapeutic implications of targeting EC metabolism in various pathologies.

A pan-cancer blueprint of the heterogeneous tumor microenvironment revealed by single-cell profiling

The stromal compartment of the tumor microenvironment consists of a heterogeneous set of tissue-resident and tumor-infiltrating cells, which are profoundly moulded by cancer cells. An outstanding question is to what extent this heterogeneity is similar between cancers affecting different organs. Here, we profile 233,591 single cells from patients with lung, colorectal, ovary and breast cancer (n = 36) and construct a pan-cancer blueprint of stromal cell heterogeneity using different single-cell RNA and protein-based technologies. We identify 68 stromal cell populations, of which 46 are shared between cancer types and 22 are unique. We also characterise each population phenotypically by highlighting its marker genes, transcription factors, metabolic activities and tissue-specific expression differences. Resident cell types are characterised by substantial tissue specificity, while tumor-infiltrating cell types are largely shared across cancer types. Finally, by applying the blueprint to melanoma tumors treated with checkpoint immunotherapy and identifying a naïve CD4⁺ T-cell phenotype predictive of response to checkpoint immunotherapy, we illustrate how it can serve as a guide to interpret scRNA-seq data. In conclusion, by providing a comprehensive blueprint through an interactive web server, we generate the first panoramic view on the shared complexity of stromal cells in different cancers.

Discovery of Cell-Surface Vimentin (CSV) as a Sarcoma Target and Development of CSV-Targeted IL12 Immune Therapy

This chapter discusses a novel target of osteosarcoma (OS), cell-surface vimentin (CSV), and a novel generation of interleukin-12 (IL12), CSV-targeted IL12, for treating OS tumor metastasis. Vimentin is a known intracellular structural protein for mesenchymal cells but is also documented in tumor cells. Our recent study definitively revealed that vimentin can be translocated to the surface of very aggressive tumor cells, such as metastatic cells. This CSV property allows investigators to capture circulating tumor cells (CTCs) across any type of tumor, including OS. CTCs are known as the seeds of metastasis; therefore, targeting these cells using CSV is a logical approach for use in a metastatic OS setting. Interestingly, we found that the peptide VNTANST can bind to CSV when fused to the p40 subunit encoding the DNA of IL12. Systemic delivery of this CSV-targeted IL12 immune therapy inhibited OS metastasis and relapse in a mouse tumor model as detailed in this chapter. This CSV-targeted delivery of IL12 also reduced toxicity of IL12. In summary, this chapter details a novel approach for safe IL12 immune therapy via targeting CSV.

Upregulation of adipocyte enhancer-binding protein 1 in endothelial cells promotes tumor angiogenesis in colorectal cancer

Tumor angiogenesis is an important therapeutic target in colorectal cancer (CRC). We aimed to identify novel genes associated with angiogenesis in CRC. Using RNA sequencing analysis in normal and tumor endothelial cells (TECs) isolated from primary CRC tissues, we detected frequent upregulation of adipocyte enhancer‐binding protein 1 (AEBP1) in TECs. Immunohistochemical analysis revealed that AEBP1 is upregulated in TECs and stromal cells in CRC tissues. Quantitative RT‐PCR analysis showed that there is little or no AEBP1 expression in CRC cell lines, but that AEBP1 is well expressed in vascular endothelial cells. Levels of AEBP1 expression in Human umbilical vein endothelial cells (HUVECs) were upregulated by tumor conditioned medium derived from CRC cells or by direct coculture with CRC cells. Knockdown of AEBP1 suppressed proliferation, migration, and in vitro tube formation by HUVECs. In xenograft experiments, AEBP1 knockdown suppressed tumorigenesis and microvessel formation. Depletion of AEBP1 in HUVECs downregulated a series of genes associated with angiogenesis or endothelial function, including aquaporin 1 (AQP1) and periostin (POSTN), suggesting that AEBP1 might promote angiogenesis through regulation of those genes. These results suggest that upregulation of AEBP1 contributes to tumor angiogenesis in CRC, which makes AEBP1 a potentially useful therapeutic target.

Destruction in maternal-fetal interface of URSA patients via the increase of the HMGB1-RAGE/TLR2/TLR4-NF-κB signaling pathway

AIMS

HMGB1 has been reported to play a crucial role in the physiological and pathophysiological responses during pregnancy. However, it is still unknown whether excessively expressed HMGB1 at the maternal-fetal interface related to Unexplained Recurrent Spontaneous Abortion (URSA). This study was designed to investigate the local capability of HMGB1 in the pathology of URSA, determined the distributions and characteristics of HMGB1, its receptors (RAGE/TLR2/TLR4) and important signaling molecule NF-κB p65 expression at the maternal-fetal interface，as well as compared the differences of HMGB1 expression between the URSA group, control group and aspirin treatment group.

MATERIAL AND METHODS

H&E staining, Western blot analysis, immunofluorescence assay and immunohistochemical staining were applied to determine the effect of HMGB1 and its receptors at the maternal-fetal interface. ELISA was utilized to detect the concentration of HMGB1 in plasma.

KEY FINDINGS

Our study demonstrated that the activation of the HMGB1-RAGE/TLR2/TLR4-NF-κB pathway at the maternal-fetal interface may have occurred in the URSA group. HMGB1 concentration in plasma was higher in the URSA group than the control group. Furthermore, the levels of HMGB1 of subjects with URSA could be reduced by administrating low doses of aspirin (ASPL).

SIGNIFICANCE

This is the first report indicating the roles of HMGB1 at the maternal-fetal interface of URSA patients and broadening the horizons for clinical treatment of URSA. HMGB1-RAGE/TLR2/TLR4-NF-κB signaling pathway may be activated at the maternal-fetal interface in URSA and account for its pathogenesis. HMGB1 have the potential to be promising biomarkers in prevention and therapy of URSA.

Role of fibrillin-2 in the control of TGF-β activation in tumor angiogenesis and connective tissue disorders

Fibrillins constitute a family of large extracellular glycoproteins which multimerize to form microfibrils, an important structure in the extracellular matrix. It has long been assumed that fibrillin-2 was barely present during postnatal life, but it is now clear that fibrillin-2 molecules form the structural core of microfibrils, and are masked by an outer layer of fibrillin-1. Mutations in fibrillins give rise to heritable connective tissue disorders, including Marfan syndrome and congenital contractural arachnodactyly. Fibrillins also play an important role in matrix sequestering of members of the transforming growth factor-β family, and in context of Marfan syndrome excessive TGF-β activation has been observed. TGF-β activation is highly dependent on integrin binding, including integrin αvβ8 and αvβ6, which are upregulated upon TGF-β exposure. TGF-β is also involved in tumor progression, metastasis, epithelial-to-mesenchymal transition and tumor angiogenesis. In several highly vascularized types of cancer such as hepatocellular carcinoma, a positive correlation was found between increased TGF-β plasma concentrations and tumor vascularity. Interestingly, fibrillin-1 has a higher affinity to TGF-β and, therefore, has a higher capacity to sequester TGF-β compared to fibrillin-2. The previously reported downregulation of fibrillin-1 in tumor endothelium affects the fibrillin-1/fibrillin-2 ratio in the microfibrils, exposing the normally hidden fibrillin-2. We postulate that fibrillin-2 exposure in the tumor endothelium directly stimulates tumor angiogenesis by influencing TGF-β sequestering by microfibrils, leading to a locally higher active TGF-β concentration in the tumor microenvironment. From a therapeutic perspective, fibrillin-2 might serve as a potential target for future anti-cancer therapies.

HMGB1 upregulates NF-kB by inhibiting IKB-α and associates with diabetic retinopathy

AIMS

Diabetic retinopathy (DR) is the main cause of blindness in adults and investigating new therapeutic targets for DR is necessary. This study aimed to investigate the effect of high-mobility group box 1 (HMGB1) protein and its mechanism in diabetic retinopathy (DR) were investigated.

MAIN METHODS

Human retinal endothelial cells (HREC) were uesd for chip-seq. Sprague Dawley (SD) rats were randomly divided into control group, HMGB1 group, diabetes mellitus (DM) combined with HMGB1 siRNA group, and DM group. Next, eyeballs were removed and retinas were detached for western blot. The DM model of cell was built by increasing the glucose concentration in cell culture medium. The regulation of HMGB1 was achieved by short hairpin (sh)-HMGB1 transfection, then, the transfected cells were harvested for luciferase assay, western blot and qRT-PCR analyses as well as proliferation and apoptosis detection.

KEY FINDINGS

Chip-seq and luciferase assay showed the possible transcription factor functions of HMGB1 and IKB-α was one of the HMGB1 binding sites. In vivo and in vitro results indicated high expression of HMGB1 and NF-kB and low expression of IKB-α in DR and the expression of IKB-α and NF-kB was regulated by HMGB1. Moreover, cell assays showed that HMGB1 inhibited cell proliferation and promoted apoptosis.

SIGNIFICANCE

The results from the present study showed that HMGB1 may be involved in the pathogenesis of DR as a transcription factor through NF-kB pathway. Therefore, blockade of HMGB1 may be a new method for the treatment of DR.

SANTAVACTM: Summary of Research and Development

SANTAVAC is an antigen composition developed via proteomics and cell culture technology that is intended for the development of cancer vaccines against various solid tumors. Its mechanism of action is based on the heterogeneity of endothelial cells, the polypeptides of which are similar to the surface antigens of tumor-vessel cells, allowing targeted destruction by vaccination. While research and development work with SANTAVAC is ongoing, the existing data provide strong evidence that allogeneic SANTAVAC is an ideal candidate for the development of cancer vaccines with significant efficacy and safety. The SANTAVAC compositions described here demonstrated the ability to inhibit the growth of tumor vessel-specific endothelial cells up to 60 fold, with minimal effect on normal vasculature. Innovation, background, description of product development, and summary of nonclinical studies with SANTAVAC to date are presented in this review.

HMGB1: an overview of its versatile roles in the pathogenesis of colorectal cancer

BACKGROUND

In recent years, the high mobility group box-1 (HMGB1) protein, a damage-associated molecular pattern (DAMP) molecule, has been found to play multifunctional roles in the pathogenesis of colorectal cancer. Although much attention has been given to the diagnostic and prognostic values of HMGB1 in colorectal cancer, the exact functional roles of the protein as well as the mechanistic pathways involved have remained poorly defined. This systematic review aims to discuss what is currently known about the roles of HMGB1 in colorectal cancer development, growth and progression, and to highlight critical areas for future investigations. To achieve this, the bibliographic databases Pubmed, Scopus, Web of Science and ScienceDirect were systematically screened for articles from inception till June 2018, which address associations of HMGB1 with colorectal cancer.

CONCLUSIONS

HMGB1 plays multiple roles in promoting the pathogenesis of colorectal cancer, despite a few contradicting studies. HMGB1 may differentially regulate disease-related processes, depending on the redox status of the protein in colorectal cancer. Binding of HMGB1 to various protein partners may alter the impact of HMGB1 on disease progression. As HMGB1 is heavily implicated in the pathogenesis of colorectal cancer, it is crucial to further improve our understanding of the functional roles of HMGB1 not only in colorectal cancer, but ultimately in all types of cancers.

SOX4 is activated by C-MYC in prostate cancer

Although MYC proto-oncogene (C-MYC) amplification has been consistently reported to be a potential marker for prostate cancer (PCa) progression and prognosis, the clinicopathological and prognostic significance of C-MYC protein expression remains controversial. Overexpression of SOX4 has been shown to play important roles in multiple cancers including PCa. However, the link between these two critical genetic aberrations is unclear. In the current study, we showed that C-MYC was overexpressed in 16.2% (17/105) of Chinese patients with localized PCa. Overexpression of C-MYC was significantly associated with high Gleason scores (P = 0.012) and high Ki67 labeling index (P = 0.005). C-MYC overexpression was correlated with cancer-related mortality and suggested to be an unfavorable prognostic factor in Chinese PCa patients (P = 0.018). Overexpression of C-MYC is associated with SOX4 overexpression in PCa tissues. Notably, SOX4 is a direct target gene of C-MYC; C-MYC activates SOX4 expression via binding to its promoter. In addition, Co-IP analysis demonstrated a physical interaction between C-MYC and SOX4 protein in PCa cells. Clinically, C-MYC+/SOX4+ characterized poor prognosis in a subset of PCa patients. In total, C-MYC overexpression may contribute to PCa progression by activating SOX4. Our findings highlight an important role of C-MYC/SOX4 in PCa progression in a subset of PCa patients.

Lymphatic and blood systems: Identical or fraternal twins?

Blood and lymphatic systems work in close collaboration to ensure their respective physiological functions. The lymphatic vessel network is being extensively studied, but has been overlooked as compared to the blood vasculature mainly due to the problematic discrimination of lymphatic vessels from the blood ones. This issue has been fortunately resolved in the past decade leading to the emergence of a huge amount of data in lymphatic biology revealing many shared features with the blood vasculature. However, this likeliness between the two vascular systems may lead to a simplistic view of lymphatics and a direct transcription of what is known for the blood system to the lymphatic one, thereby neglecting the lymphatic specificities. In this context, this review aims to clarify the main differences between the two vascular systems focusing on recently discovered lymphatic features.

High-mobility group box 1 protein modulated proliferation and radioresistance in esophageal squamous cell carcinoma

BACKGROUND AND AIM

The high-mobility group box 1 (HMGB1) protein plays an important role in a lot of biological behaviors, including DNA damage repair, gene transcription, cell replication, and cell death, and its expression is higher in many solid tumors tissues than in their adjacent normal tissues, and it is always involved in tumor proliferation, metastasis, therapeutic tolerance, and poor prognosis. However, HMGB1 in proliferation and radioresistance of esophageal squamous cell carcinoma (ESCC) remains poorly understood. In this study, the effect of HMGB1 on proliferation, cell death, DNA damage repair and radioresistance, and its underlying mechanism was investigated in human ESCC.

METHODS

The immunohistochemistry scores of tumor and adjacent normal tissues in ESCC tissue microarray were analyzed. Stable HMGB1 knockdown cell lines were constructed using Kyse150 and Kyse450 cells. Cell viability, radioresistance, apoptosis, autophagy, and DNA damage were determined using CCK-8, 5-ethynyl-2'-deoxyuridine, clonogenic survival assay, immunofluorescence, flow cytometry, and western blot assays.

RESULTS

Differential analyses showed that the expression of HMGB1 in esophageal cancer tissue was significantly higher than that in adjacent normal tissues. The downregulation of HMGB1 could effectively inhibit proliferation, increase radiosensitivity, impair DNA damage repair abilities, reduce autophagy, and increase apoptosis rates in ESCC cells after irradiation.

CONCLUSIONS

HMGB1 is expected to be a potential target for ESCC therapy and radiosensitization.

Autophagy in endothelial cells and tumor angiogenesis

In mammalian cells, autophagy is the major pathway for the degradation and recycling of obsolete and potentially noxious cytoplasmic materials, including proteins, lipids, and whole organelles, through the lysosomes. Autophagy maintains cellular and tissue homeostasis and provides a mechanism to adapt to extracellular cues and metabolic stressors. Emerging evidence unravels a critical function of autophagy in endothelial cells (ECs), the major components of the blood vasculature, which delivers nutrients and oxygen to the parenchymal tissue. EC-intrinsic autophagy modulates the response of ECs to various metabolic stressors and has a fundamental role in redox homeostasis and EC plasticity. In recent years moreover, genetic evidence suggests that autophagy regulates pathological angiogenesis, a hallmark of solid tumors. In the hypoxic, nutrient-deprived, and pro-angiogenic tumor microenvironment, heightened autophagy in the blood vessels is emerging as a critical mechanism enabling ECs to dynamically accommodate their higher bioenergetics demands to the extracellular environment and connect with other components of the tumor stroma through paracrine signaling. In this review, we provide an overview of the major cellular mechanisms regulated by autophagy in ECs and discuss their potential role in tumor angiogenesis, tumor growth, and response to anticancer therapy.

Vascular homeostasis relies on the proper behavior of endothelial cells (ECs). Emerging evidence indicate a critical role of autophagy, a vesicular process for lysosomal degradation of cytoplasmic content, in EC biology. While EC-intrinsic autophagy promotes EC function and quiescent state through redox homeostasis and possibly metabolic control, a role for EC-associated autophagy in cancer seems more complex.

High-Mobility Group Box 1 in Dry Eye Inflammation

Purpose

To determine high-mobility group box 1 (HMGB1) expression during experimental dry eye (EDE) and dry eye-like culture conditions and elucidate its role in corneal dry eye-related inflammation.

Methods

EDE was induced in 8- to 12-week-old C57BL/6 mice. Corneal tissue sections and lysates from EDE and untreated mice were evaluated for HMGB1 expression by immunostaining and quantitative real-time PCR (qPCR). For in vitro studies, human corneal epithelial cells (HCEC) were treated with hyperosmolar media, toll-like receptor (TLR) agonists, or proinflammatory cytokines to determine HMGB1 expression. HCEC were also treated with human recombinant HMGB1 (hrHMGB1) alone or in combination with inflammatory stimuli, and TNFα, IL-6, and IL-8 expression evaluated by qPCR and ELISA. Nuclear factor-κB (NF-κB) p65 nuclear translocation was determined by immunostaining.

Results

EDE mice had higher corneal HMGB1 RNA and protein expression compared to untreated animals. In HCEC, hyperosmolar stress and TNFα treatment stimulated HMGB1 production and secretion into culture supernatants. However, in vitro stimulation with hrHMGB1 did not induce secretion of TNFα, IL-6, or IL-8 or NF-κB p65 nuclear translocation. In addition, the inflammatory response elicited by TLR agonists fibroblast-stimulating lipopeptide-1 and lipopolysaccharide was not enhanced by hrHMGB1 treatment.

Conclusions

HMGB1 expression was enhanced by dry eye conditions in vivo as well as in vitro, during hyperosmolar stress and cytokine exposure, suggesting an important role for HMGB1 in dry eye disease. However, no direct inflammatory effect was observed with HMGB1 treatment. Therefore, under these conditions, HMGB1 does not contribute directly to dry eye-induced inflammation and its function at the ocular surface needs to be explored further.

Oncofoetal insulin receptor isoform A marks the tumour endothelium; an underestimated pathway during tumour angiogenesis and angiostatic treatment

Background

In a genomic screen for determinants of the tumour vasculature, we identified insulin receptor (INSR) to mark the tumour endothelium. As a functional role for insulin/INSR in cancer has been suggested and markers of the tumour endothelium may be attractive therapeutic targets, we investigated the role of INSR in angiogenesis.

Methods

In a genomic screen for determinants of the tumour vasculature we identified insulin receptor to mark the tumour endothelium.

Results

The current report demonstrates the following: (i) the heavy overexpression of INSR on angiogenic vasculature in human tumours and the correlation to short survival, (ii) that INSR expression in the tumour vasculature is mainly representing the short oncofoetal and non-metabolic isoform INSR-A, (iii) the angiogenic activity of insulin on endothelial cells (EC) in vitro and in vivo, (iv) suppression of proliferation and sprouting of EC in vitro after antibody targeting or siRNA knockdown, and (v) inhibition of in vivo angiogenesis in the chicken chorioallantoic membrane (CAM) by anti-INSR antibodies. We additionally show, using preclinical mouse as well as patient data, that treatment with the inhibitor sunitinib significantly reduces the expression of INSR-A.

Conclusions

The current study underscores the oncogenic impact of INSR and suggests that targeting the INSR-A isoform should be considered in therapeutic settings.

Consensus guidelines for the use and interpretation of angiogenesis assays

The formation of new blood vessels, or angiogenesis, is a complex process that plays important roles in growth and development, tissue and organ regeneration, as well as numerous pathological conditions. Angiogenesis undergoes multiple discrete steps that can be individually evaluated and quantified by a large number of bioassays. These independent assessments hold advantages but also have limitations. This article describes in vivo, ex vivo, and in vitro bioassays that are available for the evaluation of angiogenesis and highlights critical aspects that are relevant for their execution and proper interpretation. As such, this collaborative work is the first edition of consensus guidelines on angiogenesis bioassays to serve for current and future reference.

Identification of specifically activated angiogenic molecules in HMGB-1-induced angiogenesis

High-mobility group box-1 (HMGB-1) is expressed in almost all cells, and its dysregulated expression correlates with inflammatory diseases, ischemia, and cancer. Some of these conditions accompany HMGB-1-mediated abnormal angiogenesis. Thus far, the mechanism of HMGB-1-induced angiogenesis remains largely unknown. In this study, we performed time-dependent DNA microarray analysis of endothelial cells (ECs) after HMGB-1 or VEGF treatment. The pathway analysis of each gene set upregulated by HMGB-1 or VEGF showed that most HMGB-1-induced angiogenic pathways were also activated by VEGF, although the activation time and gene sets belonging to the pathways differed. In addition, HMGB-1 upregulated some VEGFR signaling-related angiogenic factors including EGR1 and, importantly, novel angiogenic factors, such as ABL2, CEACAM1, KIT, and VIPR1, which are reported to independently promote angiogenesis under physiological and pathological conditions. Our findings suggest that HMGB-1 independently induces angiogenesis by activating HMGB-1-specific angiogenic factors and also functions as an accelerator for VEGF-mediated conventional angiogenesis.

High-mobility group box 1 protein orchestrates responses to tissue damage via inflammation, innate and adaptive immunity, and tissue repair

A single protein, HMGB1, directs the triggering of inflammation, innate and adaptive immune responses, and tissue healing after damage. HMGB1 is the best characterized damage-associated molecular pattern (DAMP), proteins that are normally inside the cell but are released after cell death, and allow the immune system to distinguish between antigens that are dangerous or not. Notably, cells undergoing severe stress actively secrete HMGB1 via a dedicated secretion pathway: HMGB1 is relocated from the nucleus to the cytoplasm and then to secretory lysosomes or directly to the extracellular space. Extracellular HMGB1 (either released or secreted) triggers inflammation and adaptive immunological responses by switching among multiple oxidation states, which direct the mutually exclusive choices of different binding partners and receptors. Immune cells are first recruited to the damaged tissue and then activated; thereafter, HMGB1 supports tissue repair and healing, by coordinating the switch of macrophages to a tissue-healing phenotype, activation and proliferation of stem cells, and neoangiogenesis. Inevitably, HMGB1 also orchestrates the support of stressed but illegitimate tissues: tumors. Concomitantly, HMGB1 enhances the immunogenicity of mutated proteins in the tumor (neoantigens), promoting anti-tumor responses and immunological memory. Tweaking the activities of HMGB1 in inflammation, immune responses and tissue repair could bring large rewards in the therapy of multiple medical conditions, including cancer.

In wound repair vimentin mediates the transition of mesenchymal leader cells to a myofibroblast phenotype

Following injury, mesenchymal repair cells are activated to function as leader cells that modulate wound healing. These cells have the potential to differentiate to myofibroblasts, resulting in fibrosis and scarring. The signals underlying these differing pathways are complex and incompletely understood. The ex vivo mock cataract surgery cultures are an attractive model with which to address this question. With this model we study, concurrently, the mechanisms that control mesenchymal leader cell function in injury repair within their native microenvironment and the signals that induce this same cell population to acquire a myofibroblast phenotype when these cells encounter the environment of the adjacent tissue culture platform. Here we show that on injury, the cytoskeletal protein vimentin is released into the extracellular space, binds to the cell surface of the mesenchymal leader cells located at the wound edge in the native matrix environment, and supports wound closure. In profibrotic environments, the extracellular vimentin pool also links specifically to the mesenchymal leader cells and has an essential role in signaling their fate change to a myofibroblast. These findings suggest a novel role for extracellular, cell-surface–associated vimentin in mediating repair-cell function in wound repair and in transitioning these cells to a myofibroblast phenotype.

Contribution of Tumor Endothelial Cells in Cancer Progression

Tumor progression depends on the process of angiogenesis, which is the formation of new blood vessels. These newly formed blood vessels supply oxygen and nutrients to the tumor, supporting its progression and providing a gateway for tumor metastasis. Tumor angiogenesis is regulated by the balance between angiogenic activators and inhibitors within the tumor microenvironment. Because the newly formed tumor blood vessels originate from preexisting normal vessels, tumor blood vessels, and tumor endothelial cells (TECs) have historically been considered to be the same as normal blood vessels and endothelial cells; however, evidence of TECs’ distinctive abnormal phenotypes has increased. In addition, it has been revealed that TECs constitute a heterogeneous population. Thus, TECs that line tumor blood vessels are important targets in cancer therapy. We have previously reported that TECs induce cancer metastasis. In this review, we describe recent studies on TEC abnormalities related to cancer progression to provide insight into new anticancer therapies.

Apelin: A putative novel predictive biomarker for bevacizumab response in colorectal cancer

Bevacizumab (bvz) is currently employed as an anti-angiogenic therapy across several cancer indications. Bvz response heterogeneity has been well documented, with only 10-15% of colorectal cancer (CRC) patients benefitting in general. For other patients, clinical efficacy is limited and side effects are significant. This reinforces the need for a robust predictive biomarker of response. To identify such a biomarker, we performed a DNA microarray-based transcriptional profiling screen with primary endothelial cells (ECs) isolated from normal and tumour colon tissues. Thirteen separate populations of tumour-associated ECs and 10 of normal ECs were isolated using fluorescence-activated cell sorting. We hypothesised that VEGF-induced genes were overexpressed in tumour ECs; these genes could relate to bvz response and serve as potential predictive biomarkers. Transcriptional profiling revealed a total of 2,610 differentially expressed genes when tumour and normal ECs were compared. To explore their relation to bvz response, the mRNA expression levels of top-ranked genes were examined using quantitative PCR in 30 independent tumour tissues from CRC patients that received bvz in the adjuvant setting. These analyses revealed that the expression of MMP12 and APLN mRNA was significantly higher in bvz non-responders compared to responders. At the protein level, high APLN expression was correlated with poor progression-free survival in bvz-treated patients. Thus, high APLN expression may represent a novel predictive biomarker for bvz unresponsiveness.

Endothelial Cell Metabolism

Endothelial cells (ECs) are more than inert blood vessel lining material. Instead, they are active players in the formation of new blood vessels (angiogenesis) both in health and (life-threatening) diseases. Recently, a new concept arose by which EC metabolism drives angiogenesis in parallel to well-established angiogenic growth factors (e.g., vascular endothelial growth factor). 6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3-driven glycolysis generates energy to sustain competitive behavior of the ECs at the tip of a growing vessel sprout, whereas carnitine palmitoyltransferase 1a-controlled fatty acid oxidation regulates nucleotide synthesis and proliferation of ECs in the stalk of the sprout. To maintain vascular homeostasis, ECs rely on an intricate metabolic wiring characterized by intracellular compartmentalization, use metabolites for epigenetic regulation of EC subtype differentiation, crosstalk through metabolite release with other cell types, and exhibit EC subtype-specific metabolic traits. Importantly, maladaptation of EC metabolism contributes to vascular disorders, through EC dysfunction or excess angiogenesis, and presents new opportunities for anti-angiogenic strategies. Here we provide a comprehensive overview of established as well as newly uncovered aspects of EC metabolism.

DPP4 Inhibition Ameliorates Cardiac Function by Blocking the Cleavage of HMGB1 in Diabetic Mice After Myocardial Infarction

High mobility group box 1 (HMGB1), a ubiquitous DNA-binding protein, promotes angiogenesis and tissue repair, resulting in restored cardiac function after myocardial infarction (MI). Although dipeptidyl peptidase 4 (DPP4) degrades certain peptides, it remains unclear as to whether HMGB1 is a substrate of DPP4 and whether DPP4 inhibition prevents the cleavage of HMGB1.In transgenic mice with cardiac-specific overexpression of HMGB1 (TG) and wild-type mice (WT), a diabetic state was induced by streptozotocin, and MI was created by ligation of the left anterior descending coronary artery. To inhibit DPP4 activity, a DPP4 inhibitor anagliptin was used. The plasma levels of HMGB1, infarct size, echocardiographic data, angiogenesis, and vascular endothelial growth factor (VEGF) expression in the peri-infarct area were compared among non-diabetic MI WT/TG, diabetic MI WT/TG, and anagliptin-treated diabetic MI WT/TG mice.DPP4 activity was increased in the diabetic state and blocked by anagliptin administration. The HMGB1 plasma levels were reduced in the diabetic TG compared with the non-diabetic TG mice, but DPP4 inhibition with anagliptin increased HMGB1 plasma levels in the diabetic TG mice. The infarct area was significantly larger in the diabetic TG than in the non-diabetic TG mice, and it was reduced by DPP4 inhibition. Cardiac function, angiogenesis, and VEGF expression were impaired in the diabetic TG mice, but they were ameliorated by the DPP4 inhibition to levels similar to those found in the non-diabetic TG mice.The DPP4 inhibitor ameliorated cardiac function by inhibiting the inactivation of HMGB1 in diabetic mice after MI.

A genomic screen for angiosuppressor genes in the tumor endothelium identifies a multifaceted angiostatic role for bromodomain containing 7 (BRD7)

Tumor angiogenesis is characterized by deregulated gene expression in endothelial cells (EC). While studies until now have mainly focused on overexpressed genes in tumor endothelium, we here describe the identification of transcripts that are repressed in tumor endothelium and thus have potential suppressive effects on angiogenesis. We identified nineteen putative angiosuppressor genes, one of them being bromodomain containing 7 (BRD7), a gene that has been assigned tumor suppressor properties. BRD7 was studied in more detail, and we demonstrate that BRD7 expression is inversely related to EC activation. Ectopic expression of BRD7 resulted in a dramatic reduction of EC proliferation and viability. Furthermore, overexpression of BRD7 resulted in a bromodomain-dependent induction of NFκB-activity and NFκB-dependent gene expression, including ICAM1, enabling leukocyte–endothelial interactions. In silico functional annotation analysis of genome-wide expression data on BRD7 knockdown and overexpression revealed that the transcriptional signature of low BRD7 expressing cells is associated with increased angiogenesis (a.o. upregulation of angiopoietin-2, VEGF receptor-1 and neuropilin-1), cytokine activity (a.o. upregulation of CXCL1 and CXCL6), and a reduction of immune surveillance (TNF-α, NFκB, ICAM1). Thus, combining in silico and in vitro data reveals multiple pathways of angiosuppressor and anti-tumor activities of BRD7.

The angiogenic properties of human adipose-derived stem cells (HASCs) are modulated by the High mobility group box protein 1 (HMGB1)

Peripheral arterial disease (PAD), is a major health problem. Many studies have been focused on the possibilities of treatment offered by vascular regeneration. Human adipose-derived stem cells (HASCs), multipotent CD34+ stem cells found in the stromal-vascular fraction of adipose tissues, which are capable to differentiate into multiple mesenchymal cell types. The High mobility group box 1 protein (HMGB1) is a nuclear protein involved in angiogenesis. The aim of the study was to define the role of HMGB1 in cell therapy with HASCs, in an animal model of PAD. We induced unilateral ischemia in mice and we treated them with HASCs, with the specific HMGB1-inihibitor BoxA, with HMGB1 protein, and with the specific VEGF inhibitor sFlt1, alternately or concurrently. We measured the blood flow recovery in all mice. Immunohistochemical and ELISA analyses was performed to evaluate the number of vessels and the VEGF tissue content. None auto-amputation occurred and there have been no rejection reactions to the administration of HASCs. Animals co-treated with HASCs and HMGB1 protein had an improved blood flow recovery, compared to HASCs-treated mice. The post-ischemic angiogenesis was reduced when the HMGB1 pathway was blocked or when the VEGF activity was inhibited, in mice co-treated with HASCs and HMGB1. In conclusion, the HASCs treatment can be used in a mouse model of PAD to induce post-ischemic angiogenesis, modulating angiogenesis by HMGB1. This effect is mediated by VEGF activity. Although further data are needed, these findings shed light on possible new cell treatments for patients with PAD.

HMGB1 promotes myeloid-derived suppressor cells and renal cell carcinoma immune escape

Despite high immunogenicity and marked presence of immune cells in the RCC(renal cell carcinoma), immunotherapy fails to develop effective anti-tumor immune responses. This is due to the negative regulatory factors in the tumor microenvironment. As the main contributor of immunosuppression, myeloid-derived suppressor cells (MDSCs) inhibited anti-tumor immunity and promoted tumor progression. Meanwhile, it is confirmed that high mobility group box-1 protein (HMGB1) shows a high expression in many solid tumors and HMGB1 with high expression is involved in tumor immune escape. However, the mechanisms linking HMGB1 with tumor immune escape are unclear. The present study aimed to explore whether HMGB1 can promote RCC immune escape by inducing the generation of MDSCs. In this study, Renca mouse model was established and the influence of HMGB1 on MDSCs was investigated by using HMGB1 antibody to downregulate the expression of HMGB1 in tumor-bearing mice. The result showed that with the down-regulation of HMGB1, the tumor growth was inhibited significantly and the mice survival was prolonged greatly. Furthermore, the differentiation and proliferation of MDSCs were inhibited both in vitro and in vivo, and the inhibition rate showed a positive correlation with the degree of down-regulation of HMGB1. When MDSCs were eliminated with Gr-1 antibody in vivo, the ability of the HMGB1 to promote tumor growth was severely impaired. Thus, our findings indicated that HMGB1 might mediate tumor immune escape by promoting MDSCs cell proliferation, which provided a novel theoretical basis for preventing RCC using HMGB1 as the target.