Models and molecular mechanisms of blood vessel co-option by cancer cells

Milestones in tumor vascularization and its therapeutic targeting

Research into the mechanisms and manifestations of solid tumor vascularization was launched more than 50 years ago with the proposition and experimental demonstrations that angiogenesis is instrumental for tumor growth and was, therefore, a promising therapeutic target. The biological knowledge and therapeutic insights forthcoming have been remarkable, punctuated by new concepts, many of which were not foreseen in the early decades. This article presents a perspective on tumor vascularization and its therapeutic targeting but does not portray a historical timeline. Rather, we highlight eight conceptual milestones, integrating initial discoveries and recent progress and posing open questions for the future.

Vessel co-option: a unique vascular-immune niche in liver cancer

Tumor vasculature is pivotal in regulating tumor perfusion, immune cell infiltration, metastasis, and invasion. The vascular status of the tumor is intricately linked to its immune landscape and response to immunotherapy. Vessel co-option means that tumor tissue adeptly exploits pre-existing blood vessels in the para-carcinoma region to foster its growth rather than inducing angiogenesis. It emerges as a significant mechanism contributing to anti-angiogenic therapy resistance. Different from angiogenic tumors, vessel co-option presents a distinctive vascular-immune niche characterized by varying states and distribution of immune cells, including T-cells, tumor-associated macrophages, neutrophils, and hepatic stellate cells. This unique composition contributes to an immunosuppressive tumor microenvironment that is crucial in modulating the response to cancer immunotherapy. In this review, we systematically reviewed the evidence and molecular mechanisms of vessel co-option in liver cancer, while also exploring its implications for anti-angiogenic drug resistance and the immune microenvironment, to provide new ideas and clues for screening patients with liver cancer who are effective in immunotherapy.

Mechanisms of angiogenesis in tumour

Angiogenesis is essential for tumour growth and metastasis. Antiangiogenic factor-targeting drugs have been approved as first line agents in a variety of oncology treatments. Clinical drugs frequently target the VEGF signalling pathway during sprouting angiogenesis. Accumulating evidence suggests that tumours can evade antiangiogenic therapy through other angiogenesis mechanisms in addition to the vascular sprouting mechanism involving endothelial cells. These mechanisms include (1) sprouting angiogenesis, (2) vasculogenic mimicry, (3) vessel intussusception, (4) vascular co-option, (5) cancer stem cell-derived angiogenesis, and (6) bone marrow-derived angiogenesis. Other non-sprouting angiogenic mechanisms are not entirely dependent on the VEGF signalling pathway. In clinical practice, the conversion of vascular mechanisms is closely related to the enhancement of tumour drug resistance, which often leads to clinical treatment failure. This article summarizes recent studies on six processes of tumour angiogenesis and provides suggestions for developing more effective techniques to improve the efficacy of antiangiogenic treatment.

PTEN-restoration abrogates brain colonisation and perivascular niche invasion by melanoma cells

BACKGROUND

Melanoma brain metastases (MBM) continue to be a significant clinical problem with limited treatment options. Highly invasive melanoma cells migrate along the vasculature and perivascular cells may contribute to residual disease and recurrence. PTEN loss and hyperactivation of AKT occur in MBM; however, a role for PTEN/AKT in perivascular invasion has not been described.

METHODS

We used in vivo intracranial injections of murine melanoma and bulk RNA sequencing of melanoma cells co-cultured with brain endothelial cells (brECs) to investigate brain colonisation and perivascular invasion.

RESULTS

We found that PTEN-null melanoma cells were highly efficient at colonising the perivascular niche relative to PTEN-expressing counterparts. PTEN re-expression (PTEN-RE) in melanoma cells significantly reduced brain colonisation and migration along the vasculature. We hypothesised this phenotype was mediated through vascular-induced TGFβ secretion, which drives AKT phosphorylation. Disabling TGFβ signalling in melanoma cells reduced colonisation and perivascular invasion; however, the introduction of constitutively active myristolated-AKT (myrAKT) restored overall tumour size but not perivascular invasion.

CONCLUSIONS

PTEN loss facilitates perivascular brain colonisation and invasion of melanoma. TGFβ-AKT signalling partially contributes to this phenotype, but further studies are needed to determine the complementary mechanisms that enable melanoma cells to both survive and spread along the brain vasculature.

Glucagon Enhances Chemotherapy Efficacy By Inhibition of Tumor Vessels in Colorectal Cancer

Chemotherapy is widely used to treat colorectal cancer (CRC). Despite its substantial benefits, the development of drug resistance and adverse effects remain challenging. This study aimed to elucidate a novel role of glucagon in anti-cancer therapy. In a series of in vitro experiments, glucagon inhibited cell migration and tube formation in both endothelial and tumor cells. In vivo studies demonstrated decreased tumor blood vessels and fewer pseudo-vessels in mice treated with glucagon. The combination of glucagon and chemotherapy exhibited enhanced tumor inhibition. Mechanistic studies demonstrated that glucagon increased the permeability of blood vessels, leading to a pronounced disruption of vessel morphology. Signaling pathway analysis identified a VEGF/VEGFR-dependent mechanism whereby glucagon attenuated angiogenesis through its receptor. Clinical data analysis revealed a positive correlation between elevated glucagon expression and chemotherapy response. This is the first study to reveal a role for glucagon in inhibiting angiogenesis and vascular mimicry. Additionally, the delivery of glucagon-encapsulated PEGylated liposomes to tumor-bearing mice amplified the inhibition of angiogenesis and vascular mimicry, consequently reinforcing chemotherapy efficacy. Collectively, the findings demonstrate the role of glucagon in inhibiting tumor vessel network and suggest the potential utility of glucagon as a promising predictive marker for patients with CRC receiving chemotherapy.

The Inhibition of Vessel Co-Option as an Emerging Strategy for Cancer Therapy

Vessel co-option (VCO) is a non-angiogenic mechanism of vascularization that has been associated to anti-angiogenic therapy. In VCO, cancer cells hijack the pre-existing blood vessels and use them to obtain oxygen and nutrients and invade adjacent tissue. Multiple primary tumors and metastases undergo VCO in highly vascularized tissues such as the lungs, liver or brain. VCO has been associated with a worse prognosis. The cellular and molecular mechanisms that undergo VCO are poorly understood. Recent studies have demonstrated that co-opted vessels show a quiescent phenotype in contrast to angiogenic tumor blood vessels. On the other hand, it is believed that during VCO, cancer cells are adhered to basement membrane from pre-existing blood vessels by using integrins, show enhanced motility and a mesenchymal phenotype. Other components of the tumor microenvironment (TME) such as extracellular matrix, immune cells or extracellular vesicles play important roles in vessel co-option maintenance. There are no strategies to inhibit VCO, and thus, to eliminate resistance to anti-angiogenic therapy. This review summarizes all the molecular mechanisms involved in vessel co-option analyzing the possible therapeutic strategies to inhibit this process.

Modelling 3D Tumour Microenvironment In Vivo: A Tool to Predict Cancer Fate

Recently, many studies demonstrated the fundamental role of the tumour microenvironment (TME) in cancer progression. Here, we describe a method to visualize in 3D the behaviour of tumours in zebrafish embryos. We highlight two major actors of the TME, macrophages and vessels. This valuable tool is transposable to Patient-Derived Xenograft imaging in order to predict the fate of malignant tumours according to the dynamics of their TME.

Biology and therapeutic targeting of vascular endothelial growth factor A

The formation of new blood vessels, called angiogenesis, is an essential pathophysiological process in which several families of regulators have been implicated. Among these, vascular endothelial growth factor A (VEGFA; also known as VEGF) and its two tyrosine kinase receptors, VEGFR1 and VEGFR2, represent a key signalling pathway mediating physiological angiogenesis and are also major therapeutic targets. VEGFA is a member of the gene family that includes VEGFB, VEGFC, VEGFD and placental growth factor (PLGF). Three decades after its initial isolation and cloning, VEGFA is arguably the most extensively investigated signalling system in angiogenesis. Although many mediators of angiogenesis have been identified, including members of the FGF family, angiopoietins, TGFβ and sphingosine 1-phosphate, all current FDA-approved anti-angiogenic drugs target the VEGF pathway. Anti-VEGF agents are widely used in oncology and, in combination with chemotherapy or immunotherapy, are now the standard of care in multiple malignancies. Anti-VEGF drugs have also revolutionized the treatment of neovascular eye disorders such as age-related macular degeneration and ischaemic retinal disorders. In this Review, we emphasize the molecular, structural and cellular basis of VEGFA action as well as recent findings illustrating unexpected interactions with other pathways and provocative reports on the role of VEGFA in regenerative medicine. We also discuss clinical and translational aspects of VEGFA. Given the crucial role that VEGFA plays in regulating angiogenesis in health and disease, this molecule is largely the focus of this Review.

The modes of angiogenesis: an updated perspective

Following the process of vasculogenesis during development, angiogenesis generates new vascular structures through a variety of different mechanisms or modes. These different modes of angiogenesis involve, for example, increasing microvasculature density by sprouting of endothelial cells, splitting of vessels to increase vascular surface area by intussusceptive angiogenesis, fusion of capillaries to increase blood flow by coalescent angiogenesis, and the recruitment of non-endothelial cells by vasculogenic mimicry. The recent reporting on coalescent angiogenesis as a new mode of vessel formation warrants a brief overview of angiogenesis mechanisms to provide a more complete picture. The journal Angiogenesis is devoted to the delineation of the different modes and mechanisms that collectively dictate blood vessel formation, inhibition, and function in health and disease.

Pathological angiogenesis: mechanisms and therapeutic strategies

In multicellular organisms, angiogenesis, the formation of new blood vessels from pre-existing ones, is an essential process for growth and development. Different mechanisms such as vasculogenesis, sprouting, intussusceptive, and coalescent angiogenesis, as well as vessel co-option, vasculogenic mimicry and lymphangiogenesis, underlie the formation of new vasculature. In many pathological conditions, such as cancer, atherosclerosis, arthritis, psoriasis, endometriosis, obesity and SARS-CoV-2(COVID-19), developmental angiogenic processes are recapitulated, but are often done so without the normal feedback mechanisms that regulate the ordinary spatial and temporal patterns of blood vessel formation. Thus, pathological angiogenesis presents new challenges yet new opportunities for the design of vascular-directed therapies. Here, we provide an overview of recent insights into blood vessel development and highlight novel therapeutic strategies that promote or inhibit the process of angiogenesis to stabilize, reverse, or even halt disease progression. In our review, we will also explore several additional aspects (the angiogenic switch, hypoxia, angiocrine signals, endothelial plasticity, vessel normalization, and endothelial cell anergy) that operate in parallel to canonical angiogenesis mechanisms and speculate how these processes may also be targeted with anti-angiogenic or vascular-directed therapies.

Angiogenesis and prostate cancer: MicroRNAs comes into view

Angiogenesis, the formation of new blood vessels, is an important stage in the growth of cancer. Extracellular matrix, endothelial cells, and soluble substances must be carefully coordinated during the multistep procedure of angiogenesis. Inducers and inhibitors have been found to control pretty much every phase. In addition to benign prostatic hyperplasia, prostatic intraepithelial neoplasia, and angiogenesis have a critical role in the initiation and progression of prostate cancer. MicroRNA (miRNA) is endogenous, short, non-coding RNA molecules of almost 22 nucleotides play a role in regulating cellular processes and regulating several genes' expression. Through controlling endothelial migration, differentiation, death, and cell proliferation, miRNAs have a significant function in angiogenesis. A number of pathological and physiological processes, particularly prostate cancer's emergence, depend on the regulation of angiogenesis. Investigating the functions played with miRNAs in angiogenesis is crucial because it might result in the creation of novel prostate cancer therapies that entail regulating angiogenesis. The function of several miRNAs and its targeting genes engaged in cancer of the prostate angiogenesis will be reviewed in this review in light of the most recent developments. The potential clinical utility of miRNAs potentially a novel therapeutic targets will also be explored, as well as their capacity to control prostate cancer angiogenesis and the underlying mechanisms.

Comprehensive Analysis for Anti-Cancer Target-Indication Prioritization of Placental Growth Factor Inhibitor (PGF) by Use of Omics and Patient Survival Data

The expression of the placental growth factor (PGF) in cancer cells and the tumor microenvironment can contribute to the induction of angiogenesis, supporting cancer cell metabolism by ensuring an adequate blood supply. Angiogenesis is a key component of cancer metabolism as it facilitates the delivery of nutrients and oxygen to rapidly growing tumor cells. PGF is recognized as a novel target for anti-cancer treatment due to its ability to overcome resistance to existing angiogenesis inhibitors and its impact on the tumor microenvironment. We aimed to integrate bioinformatics evidence using various data sources and analytic tools for target-indication identification of the PGF target and prioritize the indication across various cancer types as an initial step of drug development. The data analysis included PGF gene function, molecular pathway, protein interaction, gene expression and mutation across cancer type, survival prognosis and tumor immune infiltration association with PGF. The overall evaluation was conducted given the totality of evidence, to target the PGF gene to treat the cancer where the PGF level was highly expressed in a certain tumor type with poor survival prognosis as well as possibly associated with poor tumor infiltration level. PGF showed a significant impact on overall survival in several cancers through univariate or multivariate survival analysis. The cancers considered as target diseases for PGF inhibitors, due to their potential effects on PGF, are adrenocortical carcinoma, kidney cancers, liver hepatocellular carcinoma, stomach adenocarcinoma, and uveal melanoma.

Vascular Growth in Lymphomas: Angiogenesis and Alternative Ways

The formation of new blood vessels is a critical process for tumor growth and may be achieved through different mechanisms. Angiogenesis represents the first described and most studied mode of vessel formation, but tumors may also use alternative ways to secure blood supply and eventually acquire resistance to anti-angiogenic treatments. These non-angiogenic mechanisms have been described more recently, including intussusceptive microvascular growth (IMG), vascular co-option, and vasculogenic mimicry. Like solid tumors, angiogenic and non-angiogenic pathways in lymphomas play a fundamental role in tumor growth and progression. In view of the relevant prognostic and therapeutic implications, a comprehensive understanding of these mechanisms is of paramount importance for improving the efficacy of treatment in patients with lymphoma. In this review, we summarize the current knowledge on angiogenic and non-angiogenic mechanisms involved in the formation of new blood vessels in Hodgkin's and non-Hodgkin's lymphomas.

VE-Cadherin in Cancer-Associated Angiogenesis: A Deceptive Strategy of Blood Vessel Formation

Tumor growth depends on the vascular system, either through the expansion of blood vessels or novel adaptation by tumor cells. One of these novel pathways is vasculogenic mimicry (VM), which is defined as a tumor-provided vascular system apart from endothelial cell-lined vessels, and its origin is partly unknown. It involves highly aggressive tumor cells expressing endothelial cell markers that line the tumor irrigation. VM has been correlated with high tumor grade, cancer cell invasion, cancer cell metastasis, and reduced survival of cancer patients. In this review, we summarize the most relevant studies in the field of angiogenesis and cover the various aspects and functionality of aberrant angiogenesis by tumor cells. We also discuss the intracellular signaling mechanisms involved in the abnormal presence of VE-cadherin (CDH5) and its role in VM formation. Finally, we present the implications for the paradigm of tumor angiogenesis and how targeted therapy and individualized studies can be applied in scientific analysis and clinical settings.

lncRNA SYTL5-OT4 promotes vessel co-option by inhibiting the autophagic degradation of ASCT2

AIMS

Vessel co-option is responsible for tumor resistance to antiangiogenic therapies (AATs) in patients with colorectal cancer liver metastasis (CRCLM). However, the mechanisms underlying vessel co-option remain largely unknown. Herein, we investigated the roles of a novel lncRNA SYTL5-OT4 and Alanine-Serine-Cysteine Transporter 2 (ASCT2) in vessel co-option-mediated AAT resistance.

METHODS

SYTL5-OT4 was identified by RNA-sequencing and verified by RT-qPCR and RNA fluorescence in situ hybridization assays. The effects of SYTL5-OT4 and ASCT2 on tumor cells were investigated by gain- and loss-of-function experiments, and those of SYTL5-OT4 on ASCT2 expression were analyzed by RNA immunoprecipitation and co-immunoprecipitation assays. The roles of SYTL5-OT4 and ASCT2 in vessel co-option were detected by histological, immunohistochemical, and immunofluorescence analyses.

RESULTS

The expression of SYTL5-OT4 and ASCT2 was higher in patients with AAT-resistant CRCLM. SYTL5-OT4 enhanced the expression of ASCT2 by inhibiting its autophagic degradation. SYTL5-OT4 and ASCT2 promoted vessel co-option by increasing the proliferation and epithelial-mesenchymal transition of tumor cells. Combination therapy of ASCT2 inhibitor and antiangiogenic agents overcame vessel co-option-mediated AAT resistance in CRCLM.

CONCLUSION

This study highlights the crucial roles of lncRNA and glutamine metabolism in vessel co-option and provides a potential therapeutic strategy for patients with AAT-resistant CRCLM.

Proinflammatory activity of VEGF-targeted treatment through reversal of tumor endothelial cell anergy

Purpose

Ongoing angiogenesis renders the tumor endothelium unresponsive to inflammatory cytokines and interferes with adhesion of leukocytes, resulting in escape from immunity. This process is referred to as tumor endothelial cell anergy. We aimed to investigate whether anti-angiogenic agents can overcome endothelial cell anergy and provide pro-inflammatory conditions.

Experimental design

Tissues of renal cell carcinoma (RCC) patients treated with VEGF pathway-targeted drugs and control tissues were subject to RNAseq and immunohistochemical profiling of the leukocyte infiltrate. Analysis of adhesion molecule regulation in cultured endothelial cells, in a preclinical model and in human tissues was performed and correlated to leukocyte infiltration.

Results

It is shown that treatment of RCC patients with the drugs sunitinib or bevacizumab overcomes tumor endothelial cell anergy. This treatment resulted in an augmented inflammatory state of the tumor, characterized by enhanced infiltration of all major leukocyte subsets, including T cells, regulatory T cells, macrophages of both M1- and M2-like phenotypes and activated dendritic cells. In vitro, exposure of angiogenic endothelial cells to anti-angiogenic drugs normalized ICAM-1 expression. In addition, a panel of tyrosine kinase inhibitors was shown to increase transendothelial migration of both non-adherent and monocytic leukocytes. In primary tumors of RCC patients, ICAM-1 expression was found to be significantly increased in both the sunitinib and bevacizumab-treated groups. Genomic analysis confirmed the correlation between increased immune cell infiltration and ICAM-1 expression upon VEGF-targeted treatment.

Conclusion

The results support the emerging concept that anti-angiogenic therapy can boost immunity and show how immunotherapy approaches can benefit from combination with anti-angiogenic compounds.

Targeting FAPα-expressing hepatic stellate cells overcomes resistance to antiangiogenics in colorectal cancer liver metastasis models

Vessel co-option has been demonstrated to mediate colorectal cancer liver metastasis (CRCLM) resistance to antiangiogenic therapy. The current mechanisms underlying vessel co-option have mainly focused on "hijacker" tumor cells, whereas the function of the "hijackee" sinusoidal blood vessels has not been explored. Here, we found that the occurrence of vessel co-option in bevacizumab-resistant CRCLM xenografts was associated with increased expression of fibroblast activation protein α (FAPα) in the co-opted hepatic stellate cells (HSCs), which was dramatically attenuated in HSC-specific conditional Fap-knockout mice bearing CRCLM allografts. Mechanistically, bevacizumab treatment induced hypoxia to upregulate the expression of fibroblast growth factor-binding protein 1 (FGFBP1) in tumor cells. Gain- or loss-of-function experiments revealed that the bevacizumab-resistant tumor cell-derived FGFBP1 induced FAPα expression by enhancing the paracrine FGF2/FGFR1/ERK1/-2/EGR1 signaling pathway in HSCs. FAPα promoted CXCL5 secretion in HSCs, which activated CXCR2 to promote the epithelial-mesenchymal transition of tumor cells and the recruitment of myeloid-derived suppressor cells. These findings were further validated in tumor tissues derived from patients with CRCLM. Targeting FAPα+ HSCs effectively disrupted the co-opted sinusoidal blood vessels and overcame bevacizumab resistance. Our study highlights the role of FAPα+ HSCs in vessel co-option and provides an effective strategy to overcome the vessel co-option-mediated bevacizumab resistance.

Curcumin activates Nrf2/HO-1 signaling to relieve diabetic cardiomyopathy injury by reducing ROS in vitro and in vivo

The hallmark feature of Diabetes mellitus (DM) is hyperglycemia which can lead to excess production of reactive oxygen species (ROS) in the myocardium, contributing to diabetic cardiomyopathy (DCM). Nuclear factor erythroid2-related factor2 (Nrf2), a transcriptional activator, enhances its ability to resist oxidative stress by activating multiple downstream anti-oxidants, anti-inflammatory proteins, and detoxifying enzymes. However, the mechanism of Nrf2 signaling in HG-induced DCM is unclear. In this study, we used HG pretreated H9c2 cells as the experimental basis in vitro, and established a high fat-diet, streptozotocin (STZ) induced Type 2 diabetic rat model in vivo. Meanwhile, we used shRNA-Nrf2 and curcumin (CUR) (as an activator) to affect H9c2 cells, to verify the role of the Nrf2 signaling pathway in DCM. The results showed that the excessive production of ROS caused by HG, which could inhibit the activation of Nrf2-related signaling, resulting in a decrease in cell energy metabolism and an increase in cell apoptosis. Surprisingly, we found that the activation of the Nrf2 signaling pathway significantly increased cardiomyocyte viability, reduced ROS formation, increased antioxidant enzyme activity, and inhibited cardiomyocyte apoptosis. In conclusion, these findings conclusively infer that CUR activation of the Nrf2/HO-1 signaling pathway exerts myocardial protection by reducing ROS formation.

Tumor vessel co-option: The past & the future

Tumor vessel co-option (VCO) is a non-angiogenic vascularization mechanism that is a possible cause of resistance to anti-angiogenic therapy (AAT). Multiple tumors are hypothesized to primarily rely on growth factor signaling-induced sprouting angiogenesis, which is often inhibited during AAT. During VCO however, tumors invade healthy tissues by hijacking pre-existing blood vessels of the host organ to secure their blood and nutrient supply. Although VCO has been described in the context of AAT resistance, the molecular mechanisms underlying this process and the profile and characteristics of co-opted vascular cell types (endothelial cells (ECs) and pericytes) remain poorly understood, resulting in the lack of therapeutic strategies to inhibit VCO (and to overcome AAT resistance). In the past few years, novel next-generation technologies (such as single-cell RNA sequencing) have emerged and revolutionized the way of analyzing and understanding cancer biology. While most studies utilizing single-cell RNA sequencing with focus on cancer vascularization have centered around ECs during sprouting angiogenesis, we propose that this and other novel technologies can be used in future investigations to shed light on tumor EC biology during VCO. In this review, we summarize the molecular mechanisms driving VCO known to date and introduce the models used to study this phenomenon to date. We highlight VCO studies that recently emerged using sequencing approaches and propose how these and other novel state-of-the-art methods can be used in the future to further explore ECs and other cell types in the VCO process and to identify potential vulnerabilities in tumors relying on VCO. A better understanding of VCO by using novel approaches could provide new answers to the many open questions, and thus pave the way to develop new strategies to control and target tumor vascularization.

The mechanistic immunosuppressive role of the tumour vasculature and potential nanoparticle-mediated therapeutic strategies

The tumour vasculature is well-established to display irregular structure and hierarchy that is conducive to promoting tumour growth and metastasis while maintaining immunosuppression. As tumours grow, their metabolic rate increases while their distance from blood vessels furthers, generating a hypoxic and acidic tumour microenvironment. Consequently, cancer cells upregulate the expression of pro-angiogenic factors which propagate aberrant blood vessel formation. This generates atypical vascular features that reduce chemotherapy, radiotherapy, and immunotherapy efficacy. Therefore, the development of therapies aiming to restore the vasculature to a functional state remains a necessary research target. Many anti-angiogenic therapies aim to target this such as bevacizumab or sunitinib but have shown variable efficacy in solid tumours due to intrinsic or acquired resistance. Therefore, novel therapeutic strategies such as combination therapies and nanotechnology-mediated therapies may provide alternatives to overcoming the barriers generated by the tumour vasculature. This review summarises the mechanisms that induce abnormal tumour angiogenesis and how the vasculature’s features elicit immunosuppression. Furthermore, the review explores examples of treatment regiments that target the tumour vasculature.

Co-Delivery of Repurposing Itraconazole and VEGF siRNA by Composite Nanoparticulate System for Collaborative Anti-Angiogenesis and Anti-Tumor Efficacy against Breast Cancer

Combinations of two different therapeutic modalities of VEGF inhibitors against angiogenesis can cooperatively impede breast cancer tumor growth and enhance therapeutic efficacy. Itraconazole (ITZ) is a conventional antifungal drug with high safety; however, it has been repurposed to be a multi target anti-angiogenesis agent for cancer therapy in recent years. In the present study, composite nanoparticles co-loaded with ITZ and VEGF siRNA were prepared in order to investigate their anti-angiogenesis efficacy and synergistic anticancer effect against breast cancer. The nanoparticles had a suitable particle size (117.9 ± 10.3 nm) and weak positive surface charge (6.69 ± 2.46 mV), as well as good stability and drug release profile in vitro. Moreover, the nanoparticles successfully escaped from endosomes and realized cell apoptosis and cell proliferation inhibition in vitro. In vitro and in vivo experiments showed that the nanoparticles could induce the silencing of VEGF-related expressions as well as anti-angiogenesis efficacy, and the co-loaded ITZ-VEGF siRNA NPs could inhibit tumor growth effectively with low toxicity and side effects. Taken together, the as-prepared delivery vehicles are a simple and safe nano-platform that improves the antitumor efficacy of VEGF siRNA and ITZ, which allows the repositioning of the generic drug ITZ as a great candidate for antitumor therapy.

Vascular Co-Option and Other Alternative Modalities of Growth of Tumor Vasculature in Glioblastoma

Non-angiogenic tumors grow in the absence of angiogenesis by two main mechanisms: cancer cells infiltrating and occupying the normal tissues to exploit pre-existing vessels (vascular co-option); the cancer cells themselves forms channels able to provide blood flow (the so called vasculogenic mimicry). In the original work on vascular co-option initiated by Francesco Pezzella, the non-angiogenic cancer cells were described as “exploiting” pre-existing vessels. Vascular co-option has been described in primary and secondary (metastatic) sites. Vascular co-option is defined as a process in which tumor cells interact with and exploit the pre-existing vasculature of the normal tissue in which they grow. As part of this process, cancer cells first migrate toward vessels of the primary tumor, or extravasate at a metastatic site and rest along the ab-luminal vascular surface. The second hallmark of vascular co-option is the interaction of cancer cells with the ab-luminal vascular surface. The first evidence for this was provided in a rat C6 glioblastoma model, showing that the initial tumor growth phase was not always avascular as these initial tumors can be vascularized by pre-existing vessels. The aim of this review article is to analyze together with vascular co-option, other alternative mode of vascularization occurring in glioblastoma multiforme (GBM), including vasculogenic mimicry, angiotropism and trans-differentiation of glioblastoma stem cells.

The Paracrine Effect of Hypoxic and Normoxic Cancer Secretion on the Proliferation of Brain Endothelial Cells (bEnd.3)

Background: This study aimed to investigate the disruption of cell cycle phases of bEnd.3 cells exposed to cancer paracrine secretion. Cancer cells have been reported to use the secretion of paracrine factors to compromise the endothelial barrier to prepare for their passage into the parenchyma. As cancer cells are known to act differently under conditions of hypoxia, we investigated how conditional media (CM) derived from breast and glioblastoma cells incubated under conditions of normoxia and hypoxia would affect proliferation of brain endothelial cells (bEnd.3). Methods: Brain endothelial cells (bEnd.3) were cultivated with normoxic and hypoxic CM generated from breast cancer MCF7 cells and glioblastoma U-87 cells. Cell proliferation was evaluated using the trypan blue exclusion assay and phases of the cell cycle were evaluated using flow cytometry. Results: bEnd.3 proliferations was suppressed more aggressively with hypoxic CM after 72 and 96 h; cell cycle analysis showed that paracrine treatment tended to prevent BECs from entering the G2 phase, thus suppressing cell division. Conclusions: MCF7 and U-87 cells induce suppressed proliferation of BECs deferentially under hypoxia by blocking cell cycle progression to the G2 phase.

Vessel co-option and angiotropic extravascular migratory metastasis: a continuum of tumour growth and spread?

Two fields of cancer research have emerged dealing with the biology of tumour cells localised to the abluminal vascular surface: vessel co-option (VCo), a non-angiogenic mode of tumour growth and angiotropic extravascular migratory metastasis (EVMM), a non-hematogenous mode of tumour migration and metastasis. VCo is a mechanism by which tumour cells gain access to a blood supply by spreading along existing blood vessels in order to grow locally. Angiotropic EVMM involves "pericytic mimicry" (PM), which is characterised by tumour cells continuously migrating in the place of pericytes distantly along abluminal vascular surfaces. When cancer cells are engaged in PM and EVMM, they migrate along blood vessels beyond the advancing front of the tumour to secondary sites with the formation of regional and distant metastases. In the present perspective, the authors review the current scientific literature, emphasising the analogies between embryogenesis and cancer progression, the re-activation of embryonic signals by "cancer stem cells", and the important role of laminins and epithelial-mesenchymal-transition. This perspective maintains that VCo and angiotropic EVMM constitute complementary processes and represent a continuum of cancer progression from the primary tumour to metastases and of tumour growth to EVMM, analogous to the embryonic development program.

TMEM60 Promotes the Proliferation and Migration and Inhibits the Apoptosis of Glioma through Modulating AKT Signaling

Glioma is a highly fatal malignancy with aggressive proliferation, migration, and invasion metastasis due to aberrant genetic regulation. This work aimed to determine the function of transmembrane protein 60 (TMEM60) during glioma development. The level of TMEM60 in glioma tissues and normal tissues and its correlation with glioma prognosis were checked in The Cancer Genome Atlas (TCGA) database. The levels of TMEM60 in glioma cell lines and normal astrocytes were determined by quantitative real-time PCR and western blotting assay. TMEM60 knockdown and overexpression were conducted, followed by detection of cell viability, migration, invasion, and apoptosis. CCK-8 and colony formation assay were adopted to detect cell viability proliferation. Transwell assay was performed to measure cell migration and invasion. Cell apoptosis was evaluated by flow cytometry. The alternation of key proteins in the PI3K/Akt signaling pathway was measured by western blotting. TMEM60 expression was significantly higher in glioma tissues than that in the healthy control and was correlated with poor overall survival of patients. The protein and mRNA levels of TMEM60 were both elevated in glioma cell lines in comparison with the normal cell lines. Elevated level of TMEM60 led to enhanced proliferation, migration, and invasion and suppressed cell apoptosis. TMEM60 promoted the activation of PI3K/Akt signaling. Our data suggested that TMEM60 plays an oncogenic role in glioma progression via activating the PI3K/Akt signaling pathway.

Transmembrane Protein TMEM230, a Target of Glioblastoma Therapy

Glioblastomas (GBM) are the most aggressive tumors originating in the brain. Histopathologic features include circuitous, disorganized, and highly permeable blood vessels with intermittent blood flow. These features contribute to the inability to direct therapeutic agents to tumor cells. Known targets for anti-angiogenic therapies provide minimal or no effect in overall survival of 12–15 months following diagnosis. Identification of novel targets therefore remains an important goal for effective treatment of highly vascularized tumors such as GBM. We previously demonstrated in zebrafish that a balanced level of expression of the transmembrane protein TMEM230/C20ORF30 was required to maintain normal blood vessel structural integrity and promote proper vessel network formation. To investigate whether TMEM230 has a role in the pathogenesis of GBM, we analyzed its prognostic value in patient tumor gene expression datasets and performed cell functional analysis. TMEM230 was found necessary for growth of U87-MG cells, a model of human GBM. Downregulation of TMEM230 resulted in loss of U87 migration, substratum adhesion, and re-passaging capacity. Conditioned media from U87 expressing endogenous TMEM230 induced sprouting and tubule-like structure formation of HUVECs. Moreover, TMEM230 promoted vascular mimicry-like behavior of U87 cells. Gene expression analysis of 702 patients identified that TMEM230 expression levels distinguished high from low grade gliomas. Transcriptomic analysis of patients with gliomas revealed molecular pathways consistent with properties observed in U87 cell assays. Within low grade gliomas, elevated TMEM230 expression levels correlated with reduced overall survival independent from tumor subtype. Highest level of TMEM230 correlated with glioblastoma and ATP-dependent microtubule kinesin motor activity, providing a direction for future therapeutic intervention. Our studies support that TMEM230 has both glial tumor and endothelial cell intracellular and extracellular functions. Elevated levels of TMEM230 promote glial tumor cell migration, extracellular scaffold remodeling, and hypervascularization and abnormal formation of blood vessels. Downregulation of TMEM230 expression may inhibit both low grade glioma and glioblastoma tumor progression and promote normalization of abnormally formed blood vessels. TMEM230 therefore is both a promising anticancer and antiangiogenic therapeutic target for inhibiting GBM tumor cells and tumor-driven angiogenesis.

Novel Insights Into the Role of Mitochondria-Derived Peptides in Myocardial Infarction

Mitochondria-derived peptides (MDPs) are a new class of bioactive peptides encoded by small open reading frames (sORFs) within known mitochondrial DNA (mtDNA) genes. MDPs may affect the expression of nuclear genes and play cytoprotective roles against chronic and age-related diseases by maintaining mitochondrial function and cell viability in the face of metabolic stress and cytotoxic insults. In this review, we summarize clinical and experimental findings indicating that MDPs act as local and systemic regulators of glucose homeostasis, immune and inflammatory responses, mitochondrial function, and adaptive stress responses, and focus on evidence supporting the protective effects of MDPs against myocardial infarction. These insights into MDPs actions suggest their potential in the treatment of cardiovascular diseases and should encourage further research in this field.

Irisin Attenuates Oxidative Stress, Mitochondrial Dysfunction, and Apoptosis in the H9C2 Cellular Model of Septic Cardiomyopathy through Augmenting Fundc1-Dependent Mitophagy

In the present study, we used lipopolysaccharide- (LPS-) stimulated H9C2 cardiomyocytes to investigate whether irisin treatment attenuates septic cardiomyopathy via Fundc1-related mitophagy. Fundc1 levels and mitophagy were significantly reduced in LPS-stimulated H9C2 cardiomyocytes but were significantly increased by irisin treatment. Irisin significantly increased ATP production and the activities of mitochondrial complexes I and III in the LPS-stimulated cardiomyocytes. Irisin also improved glucose metabolism and significantly reduced LPS-induced levels of reactive oxygen species by increasing the activities of antioxidant enzymes, glutathione peroxidase (GPX), and superoxide dismutase (SOD), as well as levels of reduced glutathione (GSH). TUNEL assays showed that irisin significantly reduced LPS-stimulated cardiomyocyte apoptosis by suppressing the activation of caspase-3 and caspase-9. However, the beneficial effects of irisin on oxidative stress, mitochondrial metabolism, and viability of LPS-stimulated H9C2 cardiomyocytes were abolished by silencing Fundc1. These results demonstrate that irisin abrogates mitochondrial dysfunction, oxidative stress, and apoptosis through Fundc1-related mitophagy in LPS-stimulated H9C2 cardiomyocytes. This suggests irisin is a potentially useful treatment for septic cardiomyopathy, though further investigations are necessary to confirm our findings.

TFPI2 Promotes Perivascular Migration in an Angiotropism Model of Melanoma

Purpose

Angiotropism is the process by which cancer cells attach to and migrate along blood vessels to acquire vasculature, disseminate, and metastasize. However, the molecular basis for such vessel–tumor interactions has not been fully elucidated, partly due to limited experimental models. In this study, we aimed to observe and explore the molecular mechanism underlying angiotropism in melanoma.

Methods

To monitor the interactions of human melanoma cells with the vasculature in vivo, a murine coxenograft model was employed by co-injecting highly and poorly invasive melanoma cells subcutaneously. To identify key pathways and genes involved in the angiotropic phenotype of melanoma, analysis of differentially expressed genes (DEGs) and gene set enrichment analysis (GSEA) were performed. The role of tissue factor pathway inhibitor 2 (TFPI2) in angiotropism was evaluated by immunostaining, adhesion assay, shRNA, and in vivo tumorigenicity. Angiotropism and TFPI2 expression were examined in surgical specimens of melanoma by immunohistochemical staining. Data from The Cancer Genome Atlas (TCGA) were analyzed to explore the expression and prognostic implications of TFPI2 in uveal and cutaneous melanoma.

Results

Highly invasive melanoma cells spread along the branches of intratumor blood vessels to the leading edge of invasion in the coxenograft model, resembling angiotropic migration. Mechanisms underlying angiotropism were primarily associated with molecular function regulators, regulation of cell population proliferation, developmental processes, cell differentiation, responses to cytokines and cell motility/locomotion. TFPI2 downregulation weakened the perivascular migration of highly invasive melanoma cells. High levels of TFPI2 were correlated with worse and better survival in uveal and cutaneous melanoma, respectively.

Conclusion

These results provide a straightforward in vivo model for the observation of angiotropism and suggest that TFPI2 could inhibit the angiotropic phenotype of melanoma.

Tumor Vessels Fuel the Fire in Glioblastoma

Glioblastoma, a subset of aggressive brain tumors, deploy several means to increase blood vessel supply dedicated to the tumor mass. This includes typical program borrowed from embryonic development, such as vasculogenesis and sprouting angiogenesis, as well as unconventional processes, including co-option, vascular mimicry, and transdifferentiation, in which tumor cells are pro-actively engaged. However, these neo-generated vascular networks are morphologically and functionally abnormal, suggesting that the vascularization processes are rather inefficient in the tumor ecosystem. In this review, we reiterate the specificities of each neovascularization modality in glioblastoma, and, how they can be hampered mechanistically in the perspective of anti-cancer therapies.

Could Extracellular Vesicles Contribute to Generation or Awakening of "Sleepy" Metastatic Niches?

Pre-metastatic niches provide favorable conditions for tumor cells to disseminate, home to and grow in otherwise unfamiliar and distal microenvironments. Tumor-derived extracellular vesicles are now recognized as carriers of key messengers secreted by primary tumors, signals that induce the formation of pre-metastatic niches. Recent evidence suggests that tumor cells can disseminate from the very earliest stages of primary tumor development. However, once they reach distal sites, tumor cells can persist in a dormant state for long periods of time until their growth is reactivated and they produce metastatic lesions. In this new scenario, the question arises as to whether extracellular vesicles could influence the formation of these metastatic niches with dormant tumor cells? (here defined as "sleepy niches"). If so, what are the molecular mechanisms involved? In this perspective-review article, we discuss the possible influence of extracellular vesicles in early metastatic dissemination and whether they might play a role in tumor cell dormancy. In addition, we comment whether extracellular vesicle-mediated signals may be involved in tumor cell awakening, considering the possibility that extracellular vesicles might serve as biomarkers to detect early metastasis and/or minimal residual disease (MRD) monitoring.

Differences of Angiogenesis Factors in Tumor and Diabetes Mellitus

Angiogenesis, as a process occurring under the regulation of a variety of factors, is one of the important ways of vascular development. It coexists in a variety of pathological and physiological processes. Now a large number of studies have proved that tumor growth, metastasis, and various vascular complications of diabetes are closely related to angiogenesis, and an increasing number of studies have shown that there are many common factors between the two. But angiogenesis is the opposite of the two: it is enhanced in tumors and suppressed in diabetes. Therefore, this review discusses the causes of the phenomenon from the expression of various factors affecting angiogenesis in these two diseases and their effects on angiogenesis in the relevant microenvironment, as well as the application status of these factors or cells as therapeutic targets in the treatment of these two diseases.

Angiogenesis in gynecological cancers and the options for anti-angiogenesis therapy

Angiogenesis is required in cancer, including gynecological cancers, for the growth of primary tumors and secondary metastases. Development of anti-angiogenesis therapy in gynecological cancers and improvement of its efficacy have been a major focus of fundamental and clinical research. However, survival benefits of current anti-angiogenic agents, such as bevacizumab, in patients with gynecological cancer, are modest. Therefore, a better understanding of angiogenesis and the tumor microenvironment in gynecological cancers is urgently needed to develop more effective anti-angiogenic therapies, either or not in combination with other therapeutic approaches. We describe the molecular aspects of (tumor) blood vessel formation and the tumor microenvironment and provide an extensive clinical overview of current anti-angiogenic therapies for gynecological cancers. We discuss the different phenotypes of angiogenic endothelial cells as potential therapeutic targets, strategies aimed at intervention in their metabolism, and approaches targeting their (inflammatory) tumor microenvironment.

Interorgan communication in development and cancer

Studies in model organisms have demonstrated that extensive communication occurs between distant organs both during development and in diseases such as cancer. Organs communicate with each other to coordinate growth and reach the correct size, while the fate of tumor cells depend on the outcome of their interaction with the immune system and peripheral tissues. In this review, we outline recent studies in Drosophila, which have enabled an improved understanding of the complex crosstalk between organs in the context of both organismal and tumor growth. We argue that Drosophila is a powerful model organism for studying these interactions, and these studies have the potential for improving our understanding of signaling pathways and candidate factors that mediate this conserved interorgan crosstalk. This article is categorized under: Establishment of Spatial and Temporal Patterns > Regulation of Size, Proportion, and Timing Early Embryonic Development > Development to the Basic Body Plan Invertebrate Organogenesis > Flies.

Influence of tumor microenvironment on angiogenesis in hepatocellular carcinoma

Liver cancer is one of the main malignant tumors that endanger human health, and hepatocellular carcinoma (HCC) is the most common histological type of this heterogeneous cancer. The tumor microenvironment (TME) is a dynamic system composed of tumor cells and tumor-related stroma. HCC can form tumor-related blood vessels through a variety of angiogenesis modes. Previous studies have shown that various components of TME mediate HCC angiogenesis in multiple ways, which brings big challenges to clinical anti-angiogenesis therapy. This article reviews the research progress of HCC angiogenesis model and the role of TME in the regulation of HCC angiogenesis, with an aim to provide a reference for basic and clinical research of liver cancer.