Egfl7 promotes tumor escape from immunity by repressing endothelial cell activation

Structure, function, and recombinant production of EGFL7

The secreted factor Epidermal growth factor-like protein 7 (EGFL7) is involved in angiogenesis, vasculogenesis, as well as neurogenesis. Importantly, EGFL7 is also implicated in various pathological conditions, including tumor angiogenesis in human cancers. Thus, understanding the mechanisms through which EGFL7 regulates and promotes blood vessel formation is of clear practical importance. One principle means by which EGFL7's function is investigated is via the expression and purification of the recombinant protein. This mini-review describes three methods used to produce recombinant EGFL7 protein. First, a brief overview of EGFL7's genetics, structure, and function is provided. This is followed by an examination of the advantages and disadvantages of three common expression systems used in the production of recombinant EGFL7; (i) Escherichia coli (E. coli), (ii) human embryonic kidney (HEK) 293 cells or other mammalian cells, and (iii) a baculovirus-based Sf9 insect cell expression system. Based on the available evidence, we conclude that the baculovirus-based Sf9 insect cell expression currently has the advantages of producing active recombinant EGFL7 in the native conformation with the presence of acceptable posttranslational modifications, while providing sufficient yield and stability for experimental purposes.

Signaling crosstalk between tumor endothelial cells and immune cells in the microenvironment of solid tumors

Tumor-associated endothelial cells (TECs) are crucial mediators of immune surveillance and immune escape in the tumor microenvironment (TME). TECs driven by angiogenic growth factors form an abnormal vasculature which deploys molecular machinery to selectively promote the function and recruitment of immunosuppressive cells while simultaneously blocking the entry and function of anti-tumor immune cells. TECs also utilize a similar set of signaling regulators to promote the metastasis of tumor cells. Meanwhile, the tumor-infiltrating immune cells further induce the TEC anergy by secreting pro-angiogenic factors and prevents further immune cell penetration into the TME. Understanding the complex interactions between TECs and immune cells will be needed to successfully treat cancer patients with combined therapy to achieve vasculature normalization while augmenting antitumor immunity. In this review, we will discuss what is known about the signaling crosstalk between TECs and tumor-infiltrating immune cells to reveal insights and strategies for therapeutic targeting.

Single-cell transcriptomics dissects premalignant progression in proliferative verrucous leukoplakia

OBJECTIVE

Proliferative verrucous leukoplakia (PVL) is characterized by a spectrum of clinicopathological features and a high risk of malignant transformation. In this study, we aimed to delineate the dynamic changes in molecular signature during PVL progression and identify the potential cell subtypes that play a key role in the premalignant evolution of PVL.

METHODS

We performed single-cell RNA sequencing on three biopsy samples from a large PVL lesion. These samples exhibited a histopathological continuum of PVL progression.

RESULTS

By analyzing the transcriptome profiles of 27,611 cells from these samples, we identified ten major cell lineages and revealed that cellular remodeling occurred during the progression of PVL lesions, including epithelial, stromal, and immune cells. Epithelial cells are shifted to tumorigenic states and secretory patterns at the premalignant stage. Immune cells showed growing immunosuppressive phenotypes during PVL progression. Remarkably, two novel cell subtypes INSR+ endothelial cells and ASPN+ fibroblasts, were discovered and may play vital roles in microenvironment remodeling, such as angiogenesis and stromal fibrosis, which are closely involved in malignant transformation.

CONCLUSION

Our work is the first to depict the cellular landscape of PVL and speculate that disease progression may be driven by functional remodeling of multiple cell subtypes.

MicroRNAs as the critical regulators of tumor angiogenesis in liver cancer

Liver cancer is one of the most common malignancies in human digestive system. Despite the recent therapeutic methods, there is a high rate of mortality among liver cancer patients. Late diagnosis in the advanced tumor stages can be one of the main reasons for the poor prognosis in these patients. Therefore, investigating the molecular mechanisms of liver cancer can be helpful for the early stage tumor detection and treatment. Vascular expansion in liver tumors can be one of the important reasons for poor prognosis and aggressiveness. Therefore, anti-angiogenic drugs are widely used in liver cancer patients. MicroRNAs (miRNAs) have key roles in the regulation of angiogenesis in liver tumors. Due to the high stability of miRNAs in body fluids, these factors are widely used as the non-invasive diagnostic and prognostic markers in cancer patients. Regarding, the importance of angiogenesis during liver tumor growth and invasion, in the present review, we discussed the role of miRNAs in regulation of angiogenesis in these tumors. It has been reported that miRNAs mainly exert an anti-angiogenic function by regulation of tumor microenvironment, transcription factors, and signaling pathways in liver tumors. This review can be an effective step to suggest the miRNAs for the non-invasive early detection of malignant and invasive liver tumors.

Non-immune cell components in tumor microenvironment influencing lung cancer Immunotherapy

Lung cancer (LC) is one of the leading causes of cancer-related deaths worldwide, with a significant morbidity and mortality rate, endangering human life and health. The introduction of immunotherapies has significantly altered existing cancer treatment strategies and is expected to improve immune responses, objective response rates, and survival rates. However, a better understanding of the complex immunological networks of LC is required to improve immunotherapy efficacy further. Tumor-associated antigens (TAAs) and tumor-specific antigens (TSAs) are significantly expressed by LC cells, which activate dendritic cells, initiate antigen presentation, and activate lymphocytes to exert antitumor activity. However, as tumor cells combat the immune system, an immunosuppressive microenvironment forms, enabling the enactment of a series of immunological escape mechanisms, including the recruitment of immunosuppressive cells and induction of T cell exhaustion to decrease the antitumor immune response. In addition to the direct effect of LC cells on immune cell function, the secreting various cytokines, chemokines, and exosomes, changes in the intratumoral microbiome and the function of cancer-associated fibroblasts and endothelial cells contribute to LC cell immune escape. Accordingly, combining various immunotherapies with other therapies can elicit synergistic effects based on the complex immune network, improving immunotherapy efficacy through multi-target action on the tumor microenvironment (TME). Hence, this review provides guidance for understanding the complex immune network in the TME and designing novel and effective immunotherapy strategies for LC.

Identification of a distinct tumor endothelial cell-related gene expression signature associated with patient prognosis and immunotherapy response in multiple cancers

BACKGROUND

Tumor endothelial cells (TECs) play a significant role in regulating the tumor microenvironment, drug response, and immune cell activities in various cancers. However, the association between TEC gene expression signature and patient prognosis or therapeutic response remains poorly understood.

METHODS

We analyzed transcriptomics data of normal and tumor endothelial cells obtained from the GEO database to identify differentially expressed genes (DEGs) associated with TECs. We then compared these DEGs with those commonly found across five different tumor types from the TCGA database to determine their prognostic relevance. Using these genes, we constructed a prognostic risk model integrated with clinical features to develop a nomogram model, which we validated through biological experiments.

RESULTS

We identified 12 TEC-related prognostic genes across multiple tumor types, of which five genes were sufficient to construct a prognostic risk model with an AUC of 0.682. The risk scores effectively predicted patient prognosis and immunotherapeutic response. Our newly developed nomogram model provided more accurate prognostic estimates of cancer patients than the TNM staging method (AUC = 0.735) and was validated using external patient cohorts. Finally, RT-PCR and immunohistochemical analyses indicated that the expression of these 5 TEC-related prognostic genes was up-regulated in both patient-derived tumors and cancer cell lines, while depletion of the hub genes reduced cancer cell growth, migration and invasion, and enhanced their sensitivity to gemcitabine or cytarabine.

CONCLUSIONS

Our study discovered the first TEC-related gene expression signature that can be used to construct a prognostic risk model for guiding treatment options in multiple cancers.

Hepatocellular carcinoma cells remodel the pro-metastatic tumour microenvironment through recruitment and activation of fibroblasts via paracrine Egfl7 signaling

BACKGROUND

The tumour microenvironment consists of a complex and dynamic milieu of cancer cells, including tumour-associated stromal cells (leukocytes, fibroblasts, vascular cells, etc.) and their extracellular products. During invasion and metastasis, cancer cells actively remodel the tumour microenvironment and alterations of microenvironment, particularly cancer-associated fibroblasts (CAFs), can promote tumour progression. However, the underlying mechanisms of the CAF formation and their metastasis-promoting functions remain unclear.

METHODS

Primary liver fibroblasts and CAFs were isolated and characterized. CAFs in clinical samples were identified by immunohistochemical staining and the clinical significance of CAFs was also analysed in two independent cohorts. A transwell coculture system was used to confirm the role of HCC cells in CAF recruitment and activation. qRT-PCR, western blotting and ELISA were used to screen paracrine cytokines. The role and mechanism of Egfl7 in CAFs were explored via an in vitro coculture system and an in vivo mouse orthotopic transplantation model.

RESULTS

We showed that CAFs in hepatocellular carcinoma (HCC) are characterized by the expression of α-SMA and that HCC cells can recruit liver fibroblasts (LFs) and activate them to promote their transformation into CAFs. High α-SMA expression, indicating high CAF infiltration, was correlated with malignant characteristics. It was also an independent risk factor for HCC survival and could predict a poor prognosis in HCC patients. Then, we demonstrated that EGF-like domain multiple 7 (Egfl7) was preferentially secreted by HCC cells, and exhibited high potential to recruit and activate LFs into the CAF phenotype. The ability of Egfl7 to modulate LFs relies upon increased phosphorylation of FAK and AKT via the receptor α_νβ₃ integrin. Strikingly, CAFs activated by paracrine Egfl7 could further remodel the tumour microenvironment by depositing fibrils and collagen and in turn facilitate HCC cell proliferation, invasion and metastasis.

CONCLUSION

Our data highlighted a novel role of Egfl7 in remodelling the tumour microenvironment: it recruits LFs and activates them to promote their transformation into CAFs via the α_νβ₃ integrin signaling pathway, which further promotes HCC progression and contributes to poor clinical outcomes in HCC patients. Video Abstract.

Barriers to immune cell infiltration in tumors

Increased immune cell infiltration into tumors is associated with improved patient survival and predicts response to immune therapies. Thus, identification of factors that determine the extent of immune infiltration is crucial, so that methods to intervene on these targets can be developed. T cells enter tumor tissues through the vasculature, and under control of interactions between homing receptors on the T cells and homing receptor ligands (HRLs) expressed by tumor vascular endothelium and tumor cell nests. HRLs are often deficient in tumors, and there also may be active barriers to infiltration. These remain understudied but may be crucial for enhancing immune-mediated cancer control. Multiple intratumoral and systemic therapeutic approaches show promise to enhance T cell infiltration, including both approved therapies and experimental therapies. This review highlights the intracellular and extracellular determinants of immune cell infiltration into tumors, barriers to infiltration, and approaches for intervention to enhance infiltration and response to immune therapies.

Tumor Vasculature as an Emerging Pharmacological Target to Promote Anti-Tumor Immunity

Tumor vasculature abnormality creates a microenvironment that is not suitable for anti-tumor immune response and thereby induces resistance to immunotherapy. Remodeling of dysfunctional tumor blood vessels by anti-angiogenic approaches, known as vascular normalization, reshapes the tumor microenvironment toward an immune-favorable one and improves the effectiveness of immunotherapy. The tumor vasculature serves as a potential pharmacological target with the capacity of promoting an anti-tumor immune response. In this review, the molecular mechanisms involved in tumor vascular microenvironment-modulated immune reactions are summarized. In addition, the evidence of pre-clinical and clinical studies for the combined targeting of pro-angiogenic signaling and immune checkpoint molecules with therapeutic potential are highlighted. The heterogeneity of endothelial cells in tumors that regulate tissue-specific immune responses is also discussed. The crosstalk between tumor endothelial cells and immune cells in individual tissues is postulated to have a unique molecular signature and may be considered as a potential target for the development of new immunotherapeutic approaches.

EGFL7 Secreted By Human Bone Mesenchymal Stem Cells Promotes Osteoblast Differentiation Partly Via Downregulation Of Notch1-Hes1 Signaling Pathway

BACKGROUND

Epidermal growth factor-like domain protein 7 (EGFL7) is a secreted protein that is differentially expressed in the bone microenvironment; however, the effect of EGFL7 on the osteogenesis of human bone marrow mesenchymal stem cells (hBMSCs) is largely unknown.

METHODS

EGFL7 expression in the fracture microenvironment was analyzed based on the Gene Expression Omnibus (GEO) database. Knockdown of EGFL7 by small interfering RNA (siRNA) and in vitro stimulation with recombinant human EGFL7 (rhEGFL7) protein were used to assess alterations in downstream signaling and changes in the osteogenic differentiation and proliferation of hBMSCs. A γ-secretase inhibitor was used to further explore whether inhibition of Notch signaling rescued the osteogenic-inhibitory effect of EGFL7 knockdown in hBMSCs. A femoral defect model was established to verify the effect of recombinant mouse EGFL7 on bone healing in vivo.

RESULTS

EGFL7 expression increased during hBMSC osteogenesis. Knockdown of EGFL7 impaired hBMSC osteogenesis and activated Notch1/NICD/Hes1 signaling. rhEGFL7 promoted hBMSC osteogenesis and downregulated Notch1 signaling. The osteoblast-inhibitory effect of EGFL7 knockdown was rescued by Notch1 signaling inhibition. Recombinant EGFL7 led to enhanced bone healing in mice with femoral defects.

CONCLUSIONS

EGFL7 promotes osteogenesis of hBMSCs partly via downregulation of Notch1 signaling.

3D Collagen Fiber Concentration Regulates Treg Cell Infiltration in Triple Negative Breast Cancer

Background

Triple negative breast cancer (TNBC) is characterized by poor prognosis and a lack of effective therapeutic agents owing to the absence of biomarkers. A high abundance of tumor-infiltrating regulatory T cells (Tregs) was associated with worse prognosis in malignant disease. Exploring the association between Treg cell infiltration and TNBC will provide new insights for understanding TNBC immunosuppression and may pave the way for developing novel immune-based treatments.

Materials and Methods

Patients from TCGA were divided into Treg-high (Treg-H) and Treg-low (Treg-L) groups based on the abundance of Tregs according to CIBERSORT analysis. The association between expression level of Tregs and the clinical characteristics as well as prognosis of breast cancer were evaluated. Next, a Treg-related prognostic model was established after survival-dependent univariate Cox and LASSO regression analysis, companied with an external GEO cohort validation. Then, GO, KEGG and GSEA analyses were performed between the Treg-H and Treg-L groups. Masson and Sirius red/Fast Green staining were applied for ECM characterization. Accordingly, Jurkat T cells were encapsulated in 3D collagen to mimic the ECM microenvironment, and the expression levels of CD4, FOXP3 and CD25 were quantified according to immunofluorescence staining.

Results

The expression level of Tregs is significantly associated with the clinical characteristics of breast cancer patients, and a high level of Treg cell expression indicates a poor prognosis in TNBC. To further evaluate this, a Treg-related prognostic model was established that accurately predicted outcomes in both TCGA training and GEO validation cohorts of TNBC patients. Subsequently, ECM-associated signaling pathways were identified between the Treg-H and Treg-L groups, indicating the role of ECM in Treg infiltration. Since we found increasing collagen concentrations in TNBC patients with distant migration, we encapsulated Jurkat T cells within a 3D matrix with different collagen concentrations and observed that increasing collagen concentrations promoted the expression of Treg biomarkers, supporting the regulatory role of ECM in Treg infiltration.

Conclusion

Our results support the association between Treg expression and breast cancer progression as well as prognosis in the TNBC subtype. Moreover, increasing collagen density may promote Treg infiltration, and thus induce an immunosuppressed TME.

Recombinant EGFL7 Mitigated Pressure Overload-Induced Cardiac Remodeling by Blocking PI3Kγ/AKT/NFκB Signaling in Macrophages

Inflammation and endothelial dysfunction play an essential role in heart failure (HF). Epidermal growth factor-like protein 7 (EGFL7) is upregulated during pathological hypoxia and exerts a protective role. However, it is unclear whether there is a link between abnormal EGFL7 expression and inflammation in overload stress-induced heart failure. Our results showed that EGFL7 transiently increased during the early 4 weeks of TAC and in hypertensive patients without heart failure. However, it decreased to the basal line in the heart tissue 8 weeks post-transverse aortic constriction (TAC) or hypertensive patients with heart failure. Knockdown of EGFL7 with siRNA in vivo accelerated cardiac dysfunction, fibrosis, and macrophage infiltration 4 weeks after TAC. Deletion of macrophages in siRNA-EGFL7-TAC mice rescued that pathological phenotype. In vitro research revealed the mechanism. PI3Kγ/AKT/NFκB signaling in macrophages was activated by the supernatant from endothelial cells stimulated by siRNA-EGFL7+phenylephrine. More macrophages adhered to endothelial cells, but pretreatment of macrophages with PI3Kγ inhibitors decreased the adhesion of macrophages to endothelial cells. Ultimately, treatment with recombinant rmEGFL7 rescued cardiac dysfunction and macrophage infiltration in siRNA-EGFL7-TAC mice. In conclusion, EGFL7 is a potential inhibitor of macrophage adhesion to mouse aortic endothelial cells. The downregulation of EGFL7 combined with increased macrophage infiltration further promoted cardiac dysfunction under pressure overload stress. Mechanistically, EGFL7 reduced endothelial cell adhesion molecule expression and inhibited the PI3Kγ/AKT/NFκB signaling pathway in macrophages.

Impact of Activation of EGFL7 within Microenvironment of High Grade Ovarian Serous Carcinoma on Infiltration of CD4+ and CD8+ Lymphocytes

Background: It has been demonstrated that Egfl7 promotes tumor cell escape from immunity by downregulating the activation of tumor blood vessels. Aim: to analyze mRNA expression of EGFL7 within the tumor microenvironment of high-grade ovarian serous carcinoma and its association with a number of intraepithelial CD4+/CD8+ lymphocytes and ICAM-1 expression. Methods: qPCR analysis of EGFL7 mRNA in cancer cells and adjacent stromal endothelium microdissected from formalin-fixed paraffin-embedded tumors of 59 high-grade ovarian serous carcinoma patients, was performed. Infiltration of intraepithelial lymphocytes (CD4+/CD8+) and expression of ICAM-1 were evaluated by immunohistochemistry and compared between tumors with different statuses of EGFL7 expression. Results: EGFL7 was expressed in cancer cells (9/59, 15.25%), endothelium (8/59, 13.56%), or both cancer cells and adjacent endothelium (4/59, 6.78%). ICAM-1 was expressed on cancer cells (47/59, 79.66%), stromal endothelium (46/59, 77.97%), or both epithelium and endothelium (40 of 59, 67.8%). EGFL7-positivity of cancer cells and endothelium was associated with lower intraepithelial inflow of CD4+ (p = 0.022 and p = 0.029, respectively) and CD8+ lymphocytes (p = 0.004 and p = 0.031, respectively) but impact neither epithelial nor endothelial ICAM-1 expression (p = 0.098 and p = 0.119, respectively). The patients’ median follow-up was 23.83 months (range 1.07–78.07). Lack of prognostic significance of EGFL7-status and ICAM-1 expression was notified. Conclusion: EGFL7 is activated in the cancer cells as frequently as in the endothelium of human high-grade ovarian serous carcinoma. Activation of EGFL7 in cancer cells and/or endothelial cells could negatively impact diapedesis regardless of localization.

EGF repeats of epidermal growth factor‑like domain 7 promote endothelial cell activation and tumor escape from the immune system

The tumor blood vessel endothelium forms a barrier that must be crossed by circulating immune cells in order for them to reach and kill cancer cells. Epidermal growth factor‑like domain 7 (Egfl7) represses this immune infiltration by lowering the expression levels of leukocyte adhesion receptors on the surface of endothelial cells. However, the protein domains involved in these properties are not completely understood. Egfl7 is structurally composed of the predicted EMI‑, EGF‑ and C‑terminal domains. The present study aimed to investigate the roles of these different domains in tumor development by designing retroviruses coding for deletion mutants and then infecting 4T1 breast cancer cell populations, which consequently overexpressed the variants. By performing in vitro soft‑agar assays, it was found that Egfl7 and its deletion variants did not affect cell proliferation or anchorage‑independent growth. When 4T1 cells expressing either the wild‑type Egfl7 protein or Egfl7 domain variants were implanted in mice, Egfl7 expression markedly promoted tumor development and deletion of the EGF repeats decreased the tumor growth rate. By contrast, deleting any other domain displayed no significant effect on tumor development. The overexpression of Egfl7 also decreased T cell and natural killer cell infiltration in tumors, as determined by immunofluorescence staining of tumor sections, whereas deletion of the EGF repeats inhibited this effect. Reverse transcription‑quantitative PCR analysis of the mechanisms involved revealed that deleting the EGF repeats partially restored the expression levels of vascular cell adhesion molecule 1 and E‑selectin, which were suppressed by overexpression of Egfl7 in endothelial cells in vitro. This resulted in a higher number of lymphocytes bound to HUVEC expressing Egfl7‑ΔEGF compared with HUVEC expressing wild‑type Egfl7, as assessed by fluorescent‑THP‑1 adhesion assays onto endothelial cells. Overall, the present study demonstrated that the EGF repeats may participate in the protumoral and anti‑inflammatory effects of Egfl7.

Multiple targeted self-emulsifying compound RGO reveals obvious anti-tumor potential in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a highly vascularized, inflammatory, and abnormally proliferating tumor. Monotherapy is often unable to effectively and comprehensively inhibit the progress of HCC. In present study, we selected ginsenoside Rg3, ganoderma lucidum polysaccharide (GLP), and oridonin as the combined therapy. These three plant monomers play important roles in anti-angiogenesis, immunological activation, and apoptosis promotion, respectively. However, the low solubility and poor bioavailability seriously hinder their clinical application. To resolve these problems, we constructed a new drug, Rg3, GLP, and oridonin self-microemulsifying drug delivery system (RGO-SMEDDS). We found that this drug effectively inhibits the progression of HCC by simultaneously targeting multiple signaling pathways. RGO-SMEDDS restored immune function by suppressing the production of immunosuppressive cytokine and M2-polarized macrophages, reduced angiogenesis by downregulation of vascular endothelial growth factor and its receptor, and retarded proliferation by inhibiting the epidermal growth factor receptor EGFR/AKT/epidermal growth factor receptor/protein kinase B/glycogen synthase kinase-3 (GSK3) signaling pathway. In addition, RGO-SMEDDS showed considerable safety in acute toxicity tests. Results from this study show that RGO-SMEDDS is a promising therapy for the treatment of HCC.

A bi-directional dialog between vascular cells and monocytes/macrophages regulates tumor progression

Cancer progression largely depends on tumor blood vessels as well on immune cell infiltration. In various tumors, vascular cells, namely endothelial cells (ECs) and pericytes, strongly regulate leukocyte infiltration into tumors and immune cell activation, hence the immune response to cancers. Recently, a lot of compelling studies unraveled the molecular mechanisms by which tumor vascular cells regulate monocyte and tumor-associated macrophage (TAM) recruitment and phenotype, and consequently tumor progression. Reciprocally, TAMs and monocytes strongly modulate tumor blood vessel and tumor lymphatic vessel formation by exerting pro-angiogenic and lymphangiogenic effects, respectively. Finally, the interaction between monocytes/TAMs and vascular cells is also impacting several steps of the spread of cancer cells throughout the body, a process called metastasis. In this review, the impact of the bi-directional dialog between blood vascular cells and monocytes/TAMs in the regulation of tumor progression is discussed. All together, these data led to the design of combinations of anti-angiogenic and immunotherapy targeting TAMs/monocyte whose effects are briefly discussed in the last part of this review.

Aspects of the Tumor Microenvironment Involved in Immune Resistance and Drug Resistance

The tumor microenvironment (TME) is a complex and ever-changing "rogue organ" composed of its own blood supply, lymphatic and nervous systems, stroma, immune cells and extracellular matrix (ECM). These complex components, utilizing both benign and malignant cells, nurture the harsh, immunosuppressive and nutrient-deficient environment necessary for tumor cell growth, proliferation and phenotypic flexibility and variation. An important aspect of the TME is cellular crosstalk and cell-to-ECM communication. This interaction induces the release of soluble factors responsible for immune evasion and ECM remodeling, which further contribute to therapy resistance. Other aspects are the presence of exosomes contributed by both malignant and benign cells, circulating deregulated microRNAs and TME-specific metabolic patterns which further potentiate the progression and/or resistance to therapy. In addition to biochemical signaling, specific TME characteristics such as the hypoxic environment, metabolic derangements, and abnormal mechanical forces have been implicated in the development of treatment resistance. In this review, we will provide an overview of tumor microenvironmental composition, structure, and features that influence immune suppression and contribute to treatment resistance.

The Multifaceted Roles of EGFL7 in Cancer and Drug Resistance

Simple Summary

Cancer growth and metastasis require interactions with the extracellular matrix (ECM), which is home to many biomolecules that support the formation of new vessels and cancer growth. One of these biomolecules is epidermal growth factor-like protein-7 (EGFL7). EGFL7 alters cellular adhesion to the ECM and migratory behavior of tumor and immune cells contributing to tumor metastasis. EGFL7 is engaged in the formation of new vessels and changes in ECM stiffness. One of its binding partners on the endothelial and cancer cell surface is beta 3 integrin. Beta 3 integrin pathways are under intense investigation in search of new therapies to kill cancer cells. All these properties enable EGFL7 to contribute to drug resistance. In this review, we give insight into recent studies on EGFL7 and its engagement with beta3 integrin, a marker predicting cancer stem cells and drug resistance.

Abstract

Invasion of cancer cells into surrounding tissue and the vasculature is an important step for tumor progression and the establishment of distant metastasis. The extracellular matrix (ECM) is home to many biomolecules that support new vessel formation and cancer growth. Endothelial cells release growth factors such as epidermal growth factor-like protein-7 (EGFL7), which contributes to the formation of the tumor vasculature. The signaling axis formed by EGFL7 and one of its receptors, beta 3 integrin, has emerged as a key mediator in the regulation of tumor metastasis and drug resistance. Here we summarize recent studies on the role of the ECM-linked angiocrine factor EGFL7 in primary tumor growth, neoangiogenesis, tumor metastasis by enhancing epithelial-mesenchymal transition, alterations in ECM rigidity, and drug resistance. We discuss its role in cellular adhesion and migration, vascular leakiness, and the anti-cancer response and provide background on its transcriptional regulation. Finally, we discuss its potential as a drug target as an anti-cancer strategy.

Egfl7 promotes tumor escape from immunity

Egfl7 is an endothelial-specific gene which expression is deregulated in human cancers. We showed that Egfl7 promotes tumor escape from immunity by downregulating the expression of leukocyte adhesion molecules in endothelial cells, thus repressing immune cell extravasation into tumors.

A Pan-Cancer Study of Epidermal Growth Factor-Like Domains 6/7/8 as Therapeutic Targets in Cancer

With highly homologous epidermal growth factor (EGF)-like (EGFL) domains, the members of the EGFL family play crucial roles in growth, invasion, and metastasis of tumors and are closely associated with the apoptosis of tumor cells and tumor angiogenesis. Furthermore, their contribution to immunoreaction and tumor microenvironment is highly known. In this study, a comprehensive analysis of EGFL6, -7, and -8 was performed on the basis of their expression profiles and their relationship with the rate of patient survival. Through a pan-cancer study, their effects were correlated with immune subtypes, tumor microenvironment, and drug resistance. Using The Cancer Genome Atlas pan-cancer data, expression profiles of EGFL6, -7, and -8, and their association with the patient survival rate and tumor microenvironment were analyzed in 33 types of cancers. The expression of the EGFL family was different in different cancer types, revealing the heterogeneity among cancers. The results showed that the expression of EGFL8 was lower than EGFL6 and EGFL7 among all cancer types, wherein EGFL7 had the highest expression. The univariate Cox proportional hazard regression model showed that EGFL6 and EGFL7 were the risk factors to predict poor prognosis of cancers. Survival analysis was then used to verify the relationship between gene expression and patient survival. Furthermore, EGFL6, EGFL7, and EGFL8 genes revealed a clear association with immune infiltrate subtypes; they were also related to the infiltration level of stromal cells and immune cells with different degrees. Moreover, they were negatively correlated with the characteristics of cancer stem cells measured by DNAs and RNAs. In addition, EGFL6, -7, and -8 were more likely to contribute to the resistance of cancer cells. Our systematic analysis of EGFL gene expression and their correlation with immune infiltration, tumor microenvironment, and prognosis of cancer patients emphasized the necessity of studying each EGFL member as a separate entity within each particular type of cancer. Simultaneously, EGFL6, -7, and -8 signals were verified as promising targets for cancer therapies, although further laboratory validation is still required.

Cancer-Associated Angiogenesis: The Endothelial Cell as a Checkpoint for Immunological Patrolling

Simple Summary

A clinical decision and study design investigating the level and extent of angiogenesis modulation aimed at vascular normalization without rendering tissues hypoxic is key and represents an unmet medical need. Specifically, determining the active concentration and optimal times of the administration of antiangiogenetic drugs is crucial to inhibit the growth of any microscopic residual tumor after surgical resection and in the pre-malignant and smolder neoplastic state. This review uncovers the pre-clinical translational insights crucial to overcome the caveats faced so far while employing anti-angiogenesis. This literature revision also explores how abnormalities in the tumor endothelium harm the crosstalk with an effective immune cell response, envisioning a novel combination with other anti-cancer drugs and immunomodulatory agents. These insights hold vast potential to both repress tumorigenesis and unleash an effective immune response.

Abstract

Cancer-associated neo vessels’ formation acts as a gatekeeper that orchestrates the entrance and egress of patrolling immune cells within the tumor milieu. This is achieved, in part, via the directed chemokines’ expression and cell adhesion molecules on the endothelial cell surface that attract and retain circulating leukocytes. The crosstalk between adaptive immune cells and the cancer endothelium is thus essential for tumor immune surveillance and the success of immune-based therapies that harness immune cells to kill tumor cells. This review will focus on the biology of the endothelium and will explore the vascular-specific molecular mediators that control the recruitment, retention, and trafficking of immune cells that are essential for effective antitumor immunity. The literature revision will also explore how abnormalities in the tumor endothelium impair crosstalk with adaptive immune cells and how targeting these abnormalities can improve the success of immune-based therapies for different malignancies, with a particular focus on the paradigmatic example represented by multiple myeloma. We also generated and provide two original bio-informatic analyses, in order to sketch the physiopathology underlying the endothelial–neoplastic interactions in an easier manner, feeding into a vicious cycle propagating disease progression and highlighting novel pathways that might be exploited therapeutically.

Anti-angiogenic Agents in Combination With Immune Checkpoint Inhibitors: A Promising Strategy for Cancer Treatment

Advances in cancer immunity have promoted a major breakthrough in the field of cancer therapy. This is mainly associated with the successful development of immune checkpoint inhibitors (ICIs) for multiple types of human tumors. Blockade with different ICIs, including programmed cell death 1 (PD-1), programmed cell death-ligand 1 (PD-L1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors, may activate the immune system of the host against malignant cells. However, only a subgroup of patients with cancer would benefit from immune checkpoint blockade. Some patients experience primary resistance to initial immunotherapy, and a majority eventually develop acquired resistance to ICIs. However, the mechanisms involved in the development of drug resistance to immune checkpoint blockade remain unclear. Recent studies supported that combination of ICIs and anti-angiogenic agents could be a promising therapeutic strategy for overcoming the low efficacy of ICIs. Moreover, through their direct anti-cancer effect by inhibiting tumor growth and metastasis, anti-angiogenic drugs reprogram the tumor milieu from an immunosuppressive to an immune permissive microenvironment. Activated immunity by immune checkpoint blockade also facilitates anti-angiogenesis by downregulating the expression of vascular endothelial growth factor and alleviating hypoxia condition. Many clinical trials showed an improved anti-cancer efficacy and prolonged survival following the addition of anti-angiogenic agents to ICIs. This review summarizes the current understanding and clinical development of combination therapy with immune checkpoint blockade and anti-angiogenic strategy.

Tumor Endothelial Cells (TECs) as Potential Immune Directors of the Tumor Microenvironment - New Findings and Future Perspectives

The tumor microenvironment (TME) plays a central role in cancer development and progression. It represents a complex network of cancer cell (sub-)clones and a variety of stromal cell types. Recently, new technology platforms shed light on the cellular composition of the TME at very high resolution and identified a complex landscape of multi-lineage immune cells (e.g., T and B lymphocytes, myeloid cells, and dendritic cells), cancer associated fibroblasts (CAF) and tumor endothelial cells (TECs). A growing body of evidence suggests that metabolically, genetically and on their transcriptomic profile TECs exhibit unique phenotypic and functional characteristics when compared to normal endothelial cells (NECs). Furthermore, the functional role of TECs is multifaceted as they are not only relevant for promoting tumor angiogenesis but have also evolved as key mediators of immune regulation in the TME. Regulatory mechanisms are complex and profoundly impact peripheral immune cell trafficking into the tumor compartment by acting as major gatekeepers of cellular transmigration. Moreover, TECs are associated with T cell priming, activation and proliferation by acting as antigen-presenting cells themselves. TECs are also essential for the formation of tertiary lymphoid structures (TLS) within the tumor, which have recently been associated with treatment response to checkpoint antibody therapy. Further essential characteristics of TECs compared to NECs are their high proliferative potential as well as greatly altered gene expression profile (e.g., upregulation of pro-angiogenic, extracellular matrix remodeling, and stemness genes), which results in enhanced secretion of immunomodulatory cytokines and altered cell-surface receptors [e.g., major histocompatibility complex (MHC) and immune checkpoints]. The TEC phenotype may be rooted in an aggressive tumor micro-milieu based on cellular stress via hypoxia and reactive oxygen species (ROS). Vice versa TECs might modulate TME immunogenicity thereby fostering cancer-associated immune suppression. This review aims to elucidate the currently emergent pathophysiological aspects of TECs with a particular focus on their potential role as regulators of immune cell function in the TME. It is a main future challenge to deeply characterize the phenotypic and functional profile of TECs to illuminate their complex role within the TME. The ultimate goal is the identification of TEC-specific drug targets to improve cancer (immuno-)therapy.

Immuno-imaging of ICAM-1 in tumours by SPECT

PURPOSE

Molecular imaging of cancer cells' reaction to radiation damage can provide a non-invasive measure of tumour response to treatment. The cell surface glycoprotein ICAM-1 (CD54) was identified as a potential radiation response marker. SPECT imaging using an 111In-radiolabelled anti-ICAM-1 antibody was explored.

METHODS

PSN-1 cells were irradiated (10 Gy), and protein expression changes were investigated using an antibody array on cell lysates 24 h later. Results were confirmed by western blot, flow cytometry and immunofluorescence. We confirmed the affinity of an 111In-labelled anti-ICAM-1 antibody in vitro, and in vivo, in PSN-1-xenograft bearing mice. The xenografts were irradiated (0 or 10 Gy), and [111In]In-anti-ICAM-1 SPECT/CT images were acquired 24, 48 and 72 h after intravenous administration.

RESULTS

ICAM-1 was identified as a potential marker of radiation treatment using an antibody array in PSN-1 cell lysates following irradiation, showing a significant increase in ICAM-1 signal compared to non-irradiated cells. Western blot and immunohistochemistry confirmed this upregulation, with an up to 20-fold increase in ICAM-1 signal. Radiolabelled anti-ICAM-1 bound to ICAM-1 expressing cells with good affinity (Kd = 24.0 ± 4.0 nM). [111In]In-anti-ICAM-1 uptake in tumours at 72 h post injection was approximately 3-fold higher than non-specific isotype-matched [111In]In-mIgG2a control (19.3 ± 2.5%ID/g versus 6.3 ± 2.2%ID/g, P = 0.0002). However, ICAM1 levels, and [111In]In-anti-ICAM-1 uptake in tumours was no different after irradiation (uptake 9.2%ID/g versus 14.8%ID/g). Western blots of the xenograft lysates showed no significant differences, confirming these results.

CONCLUSION

Imaging of ICAM-1 is feasible in mouse models of pancreatic cancer. Although ICAM-1 is upregulated post-irradiation in in vitro models of pancreatic cancer, it shows little change in expression in an in vivo mouse xenograft model.

The EGFL7-ITGB3-KLF2 axis enhances survival of multiple myeloma in preclinical models

Angiogenic factors play a key role in multiple myeloma (MM) growth, relapse, and drug resistance. Here we show that malignant plasma cells (cell lines and patient-derived MM cells) express angiocrine factor EGF like-7 (EGFL7) mRNA and protein. MM cells both produced EGFL7 and expressed the functional EGFL7 receptor integrin β 3 (ITGB3), resulting in ITGB3 phosphorylation and focal adhesion kinase activation. Overexpression of ITGB3 or EGFL7 enhanced MM cell adhesion and proliferation. Intriguingly, ITGB3 overexpression upregulated the transcription factor Krüppel-like factor 2 (KLF2), which further enhanced EGFL7 transcription in MM cells, thereby establishing an EGFL7-ITGB3-KLF2-EGFL7 amplification loop that supports MM cell survival and proliferation. EGFL7 expression was found in certain plasma cells of patients with refractory MM and of patients at primary diagnosis. NOD.CB17-Prkdc/J mice transplanted with MM cells showed elevated human plasma EGFL7 levels. EGFL7 knockdown in patient-derived MM cells and treatment with neutralizing antibodies against EGFL7 inhibited MM cell growth in vitro and in vivo. We demonstrate that the standard-of-care MM drug bortezomib upregulates EGFL7, ITGB3, and KLF2 expression in MM cells. Inhibition of EGFL7 signaling in synergy with BTZ may provide a novel strategy for inhibiting MM cell proliferation.

Transcriptomic Features of T Cell-Barren Tumors Are Conserved Across Diverse Tumor Types

Background: Understanding how tumors subvert immune destruction is essential to the development of cancer immunotherapies. New evidence suggests that tumors limit anti-tumor immunity by exploiting transcriptional programs that regulate intratumoral trafficking and accumulation of effector cells. Here, we investigated the gene expression profiles that distinguish immunologically “cold” and “hot” tumors across diverse tumor types.

Methods: RNAseq profiles of tumors (n = 8,920) representing 23 solid tumor types were analyzed using immune gene signatures that quantify CD8+ T cell abundance. Genes and pathways associated with a low CD8+ T cell infiltration profile (CD8-Low) were identified by correlation, differential expression, and statistical ranking methods. Gene subsets were evaluated in immunotherapy treatment cohorts and functionally characterized in cell lines and mouse tumor models.

Results: Among different cancer types, we observed highly significant overlap of genes enriched in CD8-Low tumors, which included known immunomodulatory genes (e.g., BMP7, CMTM4, KDM5B, RCOR2) and exhibited significant associations with Wnt signaling, neurogenesis, cell-cell junctions, lipid biosynthesis, epidermal development, and cancer-testis antigens. Analysis of mutually exclusive gene clusters demonstrated that different transcriptional programs may converge on the T cell-cold phenotype as well as predict for response and survival of patients to Nivo treatment. Furthermore, we confirmed that a top-ranking candidate belonging to the TGF-β superfamily, BMP7, negatively regulates CD8+ T cell abundance in immunocompetent murine tumor models, with and without anti-PD-L1 treatment.

Conclusions: This study presents the first evidence that solid tumors of diverse anatomical origin acquire conserved transcriptional alterations that may be operative in the T cell-cold state. Our findings demonstrate the potential clinical utility of CD8-Low tumor-associated genes for predicting patient immunotherapy outcomes and point to novel mechanisms with potential for broad therapeutic exploitation.

Novel Expression of EGFL7 in Osteosarcoma and Sensitivity to Cisplatin

Epidermal growth factor-like domain 7 (EGFL7) is a protein specifically secreted by blood vessel endothelial cells, which plays an important role in angiogenesis. Considering the aberrant secretion of EGFL7 in osteosarcoma (OS) has not yet been elucidated, this study investigated the secretion of EGFL7 in OS and the changes in its secretion after chemotherapy. We observed increased varying secretion of EGFL7 in OS tissues compared with chondrosarcoma (CS) tissues. OS cell lines and HUVECs showed higher EGFL7 mRNA and protein expression than SW1353, with OS cells expressing the highest levels. In patient samples, EGFL7 was highly expressed in the cytoplasm of OS tumor cells and vascular endothelium cells. This overexpression was abolished in OS cell and tumor tissues when treated with chemotherapy. This study is a pioneering study to investigate EGFL7 expression and localization in human OS tissues and cell. Overexpression of EGFL-7 in response to chemotherapy suggests that it can be used as a therapeutic target for OS.

Comparing progression molecular mechanisms between lung adenocarcinoma and lung squamous cell carcinoma based on genetic and epigenetic networks: big data mining and genome-wide systems identification

Non-small-cell lung cancer (NSCLC) is the predominant type of lung cancer in the world. Lung adenocarcinoma (LADC) and lung squamous cell carcinoma (LSCC) are subtypes of NSCLC. We usually regard them as different disease due to their unique molecular characteristics, distinct cells of origin and dissimilar clinical response. However, the differences of genetic and epigenetic progression mechanism between LADC and LSCC are complicated to analyze. Therefore, we applied systems biology approaches and big databases mining to construct genetic and epigenetic networks (GENs) with next-generation sequencing data of LADC and LSCC. In order to obtain the real GENs, system identification and system order detection are conducted on gene regulatory networks (GRNs) and protein-protein interaction networks (PPINs) for each stage of LADC and LSCC. The core GENs were extracted via principal network projection (PNP). Based on the ranking of projection values, we got the core pathways in respect of KEGG pathway. Compared with the core pathways, we found significant differences between microenvironments, dysregulations of miRNAs, epigenetic modifications on certain signaling transduction proteins and target genes in each stage of LADC and LSCC. Finally, we proposed six genetic and epigenetic multiple-molecule drugs to target essential biomarkers in each progression stage of LADC and LSCC, respectively.

EGFL7 enhances surface expression of integrin α5β1 to promote angiogenesis in malignant brain tumors

Glioblastoma (GBM) is a typically lethal type of brain tumor with a median survival of 15 months postdiagnosis. This negative prognosis prompted the exploration of alternative treatment options. In particular, the reliance of GBM on angiogenesis triggered the development of anti-VEGF (vascular endothelial growth factor) blocking antibodies such as bevacizumab. Although its application in human GBM only increased progression-free periods but did not improve overall survival, physicians and researchers still utilize this treatment option due to the lack of adequate alternatives. In an attempt to improve the efficacy of anti-VEGF treatment, we explored the role of the egfl7 gene in malignant glioma. We found that the encoded extracellular matrix protein epidermal growth factor-like protein 7 (EGFL7) was secreted by glioma blood vessels but not glioma cells themselves, while no major role could be assigned to the parasitic miRNAs miR-126/126*. EGFL7 expression promoted glioma growth in experimental glioma models in vivo and stimulated tumor vascularization. Mechanistically, this was mediated by an upregulation of integrin α₅β₁ on the cellular surface of endothelial cells, which enhanced fibronectin-induced angiogenic sprouting. Glioma blood vessels that formed in vivo were more mature as determined by pericyte and smooth muscle cell coverage. Furthermore, these vessels were less leaky as measured by magnetic resonance imaging of extravasating contrast agent. EGFL7-inhibition using a specific blocking antibody reduced the vascularization of experimental gliomas and increased the life span of treated animals, in particular in combination with anti-VEGF and the chemotherapeutic agent temozolomide. Data allow for the conclusion that this combinatorial regimen may serve as a novel treatment option for GBM.

Effect of benzo[a]pyrene on the expression of miR-126, miR-190a and their target genes EGFL7, TP53INP1 and PHLPP1 in primary endometrial cells

The main topic of this study was to investigate the effect of benzo[a]pyrene (BP) on microRNAs and their target genes expression levels in primary cell cultures from normal and malignant endometrial tissue. MicroRNA-126 (miR-126) and miR-190a were most sensitive to BP treatment. The treatment of both cultures with BP was accompanied by a decrease of miR-126 level and an increase of EGFL7 gene expression level. BP-induced upregulation of miR-190a was detected only in normal cells and it was accompanied with decrease of mRNA levels of TP53INP1 and PHLPP1 genes. Taking into account that BP promoted the proliferation of normal cells and amplified apoptosis of cancer cells, it is possible that miR-190a is involved in general cellular response to BP. The findings of this study indicate that miR-190a and its target genes may be involved in the regulation of cell fate under BP treatment.

EGFL7 regulates sprouting angiogenesis and endothelial integrity in a human blood vessel model

Elucidating the mechanisms underlying sprouting angiogenesis and permeability should enable the development of more effective therapies for various diseases, including retinopathy, cancer, and other vascular disorders. We focused on epidermal growth factor-like domain 7 (EGFL7) which plays an important role in NOTCH signaling and in the organization of angiogenic sprouts. We developed an EGFL7-knockdown in vitro microvessel model and investigated the effect of EGFL7 at a tissue level. We found EGFL7 knockdown suppressed VEGF-A-induced sprouting angiogenesis accompanied by an overproduction of endothelial filopodia and reduced collagen IV deposition at the basal side of endothelial cells. We also observed impaired barrier function which reflected an inflammatory condition. Furthermore, our results showed that proper formation of adherens junctions and phosphorylation of VE-cadherin was disturbed. In conclusion, by using a 3D microvessel model we identified novel roles for EGFL7 in endothelial function during sprouting angiogenesis.

Vascular Targeting to Increase the Efficiency of Immune Checkpoint Blockade in Cancer

Boosting natural immunity against malignant cells has had a major breakthrough in clinical cancer therapy. This is mainly due to the successful development of immune checkpoint blocking antibodies, which release a break on cytolytic anti-tumor-directed T-lymphocytes. However, immune checkpoint blockade is only effective for a proportion of cancer patients, and a major challenge in the field is to understand and overcome treatment resistance. Immune checkpoint blockade relies on successful trafficking of tumor-targeted T-lymphocytes from the secondary lymphoid organs, through the blood stream and into the tumor tissue. Resistance to therapy is often associated with a low density of T-lymphocytes residing within the tumor tissue prior to treatment. The recruitment of leukocytes to the tumor tissue relies on up-regulation of adhesion molecules and chemokines by the tumor vasculature, which is denoted as endothelial activation. Tumor vessels are often poorly activated due to constitutive pro-angiogenic signaling in the tumor microenvironment, and therefore constitute barriers to efficient leukocyte recruitment. An emerging possibility to enhance the efficiency of cancer immunotherapy is to combine pro-inflammatory drugs with anti-angiogenic therapy, which can enable tumor-targeted T-lymphocytes to access the tumor tissue by relieving endothelial anergy and increasing adhesion molecule expression. This would pave the way for efficient immune checkpoint blockade. Here, we review the current understanding of the biological basis of endothelial anergy within the tumor microenvironment, and discuss the challenges and opportunities of combining vascular targeting with immunotherapeutic drugs as suggested by data from key pre-clinical and clinical studies.

Egfl7 Represses the Vasculogenic Potential of Human Endothelial Progenitor Cells

Egfl7 (VE-statin) is a secreted protein mostly specific to the endothelial lineage during development and in the adult and which expression is enhanced during angiogenesis. Egfl7 involvement in human postnatal vasculogenesis remains unresolved yet. Our aim was to assess Egfl7 expression in several angiogenic cell types originating from human bone marrow, peripheral blood, or cord blood. We found that only endothelial colony forming cells (ECFC), which are currently considered as the genuine endothelial precursor cells, expressed large amounts of Egfl7. In order to assess its potential roles in ECFC, Egfl7 was repressed in ECFC by RNA interference and ECFC angiogenic capacities were tested in vitro and in vivo. Cell proliferation, differentiation, and migration were significantly improved when Egfl7 was repressed in ECFC in vitro, whereas miR-126-3p levels remained unchanged. In vivo, repression of Egfl7 in ECFC significantly improved post-ischemic revascularization in a model of mouse hind-limb ischemia. In conclusion, ECFC are the sole postnatal angiogenic cells which express large amounts of Egfl7 and whose angiogenic properties are repressed by this factor. Thus, Egfl7 inhibition may be considered as a therapeutic option to improve ECFC-mediated postnatal vasculogenesis and to optimize in vitro ECFC expansion in order to develop an optimized cell therapy approach.

Attenuation of EGFL7 Expression Inhibits Growth Hormone-Producing Pituitary Adenomas Growth and Invasion

Invasiveness of growth hormone-producing pituitary adenomas (GHPAs) causes difficulties in safe and complete adenoma removal during surgery and often leads to high recurrence. Epidermal growth factor-like domain 7 (EGFL7) has been shown to be able to promote tumor angiogenesis, growth, invasiveness, and metastasis through the Notch signaling pathway. It was previously demonstrated that EGFL7 was overexpressed in GHPAs. This study reports that EGFL7 and Notch2 (positive correlation with EGFL7) are overexpressed in invasive GHPA. A long-rank test (Kaplan-Meier method) shows that invasive GHPAs with EGFL7 strong expression results in reduced recurrence-free survival. Multivariate Cox regression analysis reveals that weak EGFL7 expression is an independent prognostic factor for recurrence-free survival. In addition, knockdown of EGFL7 expression suppresses proliferation and invasion of GH3 and GT1-1 cells in vitro. Moreover, attenuation of EGFL7 inhibits human GHPA growth in vivo. The data suggest that as a Notch agonist, EGFL7 may potentially be an appropriate novel molecular target for future development of GHPA medical therapy.

Prognostic Value of ACVRL1 Expression in Metastatic Colorectal Cancer Patients Receiving First-line Chemotherapy With Bevacizumab: Results From the Triplet Plus Bevacizumab (TRIBE) Study

BACKGROUND

No biomarkers exist to predict benefit from antiangiogenic therapy in metastatic colorectal cancer patients. ACVRL1 (activin receptor like-protein 1) encodes for ALK1, a member of the transforming growth factor-β receptor family, which directs pathologic angiogenesis. We examined the intratumoral expression of ACVRL1 and other angiogenesis pathway-related genes to identify molecular markers in the TRIBE study.

MATERIALS AND METHODS

Of 503 randomized patients, 228 had sufficient tissue for analysis. Formalin-fixed paraffin-embedded specimens were examined for expression of VEGF-A, VEGF-B, VEGF-C, VEGFR1, VEGFR2, ACVRL1, EphB4, and EGFL7 using reverse transcription polymerase chain reaction. A maximal χ² approach was used to determine the messenger RNA levels associated with progression-free survival (PFS), overall survival (OS), response rate, early tumor shrinkage, and depth of response. Recursive partitioning trees were constructed to identify composite prognostic biomarker profiles. External validation was conducted in silico using the Oncomine database.

RESULTS

High ACVRL1 expression was associated with superior OS in both treatment arms (FOLFOXIRI [5-fluorouracil, leucovorin, oxaliplatin, irinotecan]-bevacizumab, 32.7 vs. 13.5 months, hazard ratio [HR], 0.38, P = .023; FOLFIRI [5-fluorouracil, leucovorin, irinotecan]-bevacizumab, 35.1 vs. 22.0 months, HR, 0.36, P = .006) and prolonged PFS (11.7 vs. 5.9 months, multivariate HR, 0.17; P = .001) for patients receiving FOLFOXIRI-bevacizumab on univariate and multivariate analyses. In recursive partitioning analysis, ACVRL1 was the strongest discriminator of the response rate, PFS, and OS in patients receiving FOLFOXIRI-bevacizumab and of OS in patients receiving FOLFIRI-bevacizumab. In silico validation revealed significant associations between ACVRL1 expression, disease recurrence, and 1-year survival (P < .05) among all colorectal cancer stages.

CONCLUSION

ACVRL1 expression could serve as a prognostic biomarker in metastatic colorectal cancer patients receiving chemotherapy and bevacizumab and warrants further evaluation in prospective studies.

The dark side of tumor-associated endothelial cells

Angiogenesis is a hallmark of cancer and a requisite that tumors must achieve to fulfill their metabolic needs of nutrients and oxygen. As a critical step in cancer progression, the 'angiogenic switch' allows tumor cells to survive and grow, and provides them access to vasculature resulting in metastatic progression and dissemination. Tumor-dependent triggering of the angiogenic switch has critical consequences on tumor progression which extends from an increased nutrient supply and relies instead on the ability of the tumor to hijack the host immune response for the generation of a local immunoprivileged microenvironment. Tumor angiogenic-mediated establishment of endothelial anergy is responsible for this process. However, tumor endothelium can also promote immune tolerance by unbalanced expression of co-stimulatory and co-inhibitory molecules and by releasing soluble factors that restrain T cell function and induce apoptosis. In this review, we discuss the molecular properties of the tumor endothelial barrier and endothelial anergy and discuss the main immunosuppressive mechanisms triggered by the tumor endothelium. Lastly, we describe the current anti-angiogenic therapeutic landscape and how targeting tumor angiogenesis can contribute to improve clinical benefits for patients.

EGFL7 reduces CNS inflammation in mouse

Extracellular matrix (ECM) proteins secreted by blood-brain barrier (BBB) endothelial cells (ECs) are implicated in cell trafficking. We discovered that the expression of ECM epidermal growth factor-like protein 7 (EGFL7) is increased in the CNS vasculature of patients with multiple sclerosis (MS), and in mice with experimental autoimmune encephalomyelitis (EAE). Perivascular CD4 T lymphocytes colocalize with ECM-bound EGFL7 in MS lesions. Human and mouse activated T cells upregulate EGFL7 ligand αvβ3 integrin and can adhere to EGFL7 through integrin αvβ3. EGFL7-knockout (KO) mice show earlier onset of EAE and increased brain and spinal cord parenchymal infiltration of T lymphocytes. Importantly, EC-restricted EGFL7-KO is associated with a similar EAE worsening. Finally, treatment with recombinant EGFL7 improves EAE, reduces MCAM expression, and tightens the BBB in mouse. Our data demonstrate that EGFL7 can limit CNS immune infiltration and may represent a novel therapeutic avenue in MS.

Endothelial cells release extracellular matrix components that regulate inflammation. Here the authors demonstrate that the extracellular matrix component epidermal growth factor-like protein 7 regulates inflammation in experimental autoimmune encephalomyelitis in the mouse.

Synthetic Biology: Immunotherapy by Design

Cellular immunotherapy holds great promise for the treatment of human disease. Clinical evidence suggests that T cell immunotherapies have the potential to combat cancers that evade traditional immunotherapy. Despite promising results, adverse effects leading to fatalities have left scientists seeking tighter control over these therapies, which is reflected in the growing body of synthetic biology literature focused on developing tightly controlled, context-independent parts. In addition, researchers are adapting these tools for other uses, such as for the treatment of autoimmune disease, HIV infection, and fungal interactions. We review this body of work and devote special attention to approaches that may lend themselves to the development of an "ideal" therapy: one that is safe, efficient, and easy to manufacture. We conclude with a look toward the future of immunotherapy: how synthetic biology can shift the paradigm from the treatment of disease to a focus on wellness and human health as a whole.

Viral nanoparticles decorated with novel EGFL7 ligands enable intravital imaging of tumor neovasculature

Angiogenesis is a dynamic process fundamental to the development of solid tumors. Epidermal growth factor-like domain 7 (EGFL7) is a protein whose expression is restricted to endothelial cells undergoing active remodeling that has emerged as a key mediator of this process. EGFL7 expression is associated with poor outcome in several cancers, making it a promising target for imaging or therapeutic strategies. Here, EGFL7 is explored as a molecular target for active neovascularization. Using a combinatorial peptide screening approach, we describe the discovery and characterization of a novel high affinity EGFL7-binding peptide, E7p72, that specifically targets human endothelial cells. Viral nanoparticles decorated with E7p72 peptides specifically target tumor-associated neovasculature with high specificity as assessed by intravital imaging. This work highlights the value of EGFL7 as a target for angiogenic vessels and opens the door for novel targeted therapeutic approaches.

Role of liver ICAM-1 in metastasis

Intercellular adhesion molecule (ICAM)-1, is a transmembrane glycoprotein of the immunoglobulin (Ig)-like superfamily, consisting of five extracellular Ig-like domains, a transmembrane domain and a short cytoplasmic tail. ICAM-1 is expressed in various cell types, including endothelial cells and leukocytes, and is involved in several physiological processes. Furthermore, it has additionally been reported to be expressed in various cancer cells, including melanoma, colorectal cancer and lymphoma. The majority of studies to date have focused on the expression of the ICAM-1 on the surface of tumor cells, without research into ICAM-1 expression at sites of metastasis. Cancer cells frequently metastasize to the liver, due to its unique physiology and specialized liver sinusoid capillary network. Liver sinusoidal endothelial cells constitutively express ICAM-1, which is upregulated under inflammatory conditions. Furthermore, liver ICAM-1 may be important during the development of liver metastasis. Therefore, it is necessary to improve the understanding of the mechanisms mediated by this adhesion molecule in order to develop host-directed anticancer therapies.

Fine-Tuning Tumor Endothelial Cells to Selectively Kill Cancer

Tumor endothelial cells regulate several aspects of tumor biology, from delivering oxygen and nutrients to shaping the immune response against a tumor and providing a barrier against tumor cell dissemination. Accordingly, targeting tumor endothelial cells represents an important modality in cancer therapy. Whereas initial anti-angiogenic treatments focused mainly on blocking the formation of new blood vessels in cancer, emerging strategies are specifically influencing certain aspects of tumor endothelial cells. For instance, efforts are generated to normalize tumor blood vessels in order to improve tumor perfusion and ameliorate the outcome of chemo-, radio-, and immunotherapy. In addition, treatment options that enhance the properties of tumor blood vessels that support a host’s anti-tumor immune response are being explored. Hence, upcoming anti-angiogenic strategies will shape some specific aspects of the tumor blood vessels that are no longer limited to abrogating angiogenesis. In this review, we enumerate approaches that target tumor endothelial cells to provide anti-cancer benefits and discuss their therapeutic potential.

Immunotherapeutic Targeting of Tumor-Associated Blood Vessels

Pathological angiogenesis occurs during tumor progression and leads in the formation of an abnormal vasculature in the tumor microenvironment (TME). The tumor vasculature is disorganized, tortuous and leaky, resulting in high interstitial pressure and hypoxia in the TME, all of which are events that support tumor growth and survival. Given the sustaining role of the tumor vasculature, it has become an increasingly attractive target for the development of anti-cancer therapies. Antibodies, tyrosine kinase inhibitors and cancer vaccines that target pro-angiogenic factors, angiogenesis-associated receptors or tumor blood vessel-associated antigens continue to be developed and tested for therapeutic efficacy. Preferred anti-angiogenic protocols include those that "normalize" the tumor-associated vasculature which reduce hypoxia and improve tumor blood perfusion, resulting in tumor cell apoptosis, decreased immunosuppression, and enhanced effector immune cell infiltration/tumoricidal action within the TME.

The Role of the Tumor Vasculature in the Host Immune Response: Implications for Therapeutic Strategies Targeting the Tumor Microenvironment

Recently developed cancer immunotherapy approaches including immune checkpoint inhibitors and chimeric antigen receptor T cell transfer are showing promising results both in trials and in clinical practice. These approaches reflect increasing recognition of the crucial role of the tumor microenvironment in cancer development and progression. Cancer cells do not act alone, but develop a complex relationship with the environment in which they reside. The host immune response to tumors is critical to the success of immunotherapy; however, the determinants of this response are incompletely understood. The immune cell infiltrate in tumors varies widely in density, composition, and clinical significance. The tumor vasculature is a key component of the microenvironment that can influence tumor behavior and treatment response and can be targeted through the use of antiangiogenic drugs. Blood vascular and lymphatic endothelial cells have important roles in the trafficking of immune cells, controlling the microenvironment, and modulating the immune response. Improving access to the tumor through vascular alteration with antiangiogenic drugs may prove an effective combinatorial strategy with immunotherapy approaches and might be applicable to many tumor types. In this review, we briefly discuss the host's immune response to cancer and the treatment strategies utilizing this response, before focusing on the pathological features of tumor blood and lymphatic vessels and the contribution these might make to tumor immune evasion.

Expression of epidermal growth factor-like domain 7 may be a predictive marker of the effect of neoadjuvant chemotherapy for locally advanced uterine cervical cancer

Neoadjuvant chemotherapy (NAC) followed by hysterectomy may be effective for the treatment of locally advanced uterine cervical cancer and improve patient prognosis. It is important to identify markers that are able to predict whether NAC may be successful. Epidermal growth factor-like domain 7 (EGFL7) regulates vascular sprouting in blood vessel formation. In numerous types of human cancer, EGFL7 is upregulated and inhibits endothelial cell adhesion molecules, decreasing vascular tightness and, thus, increasing vascular permeability. It is considered that the overexpression of EGFL7 is able to inhibit drug delivery, resistance to apoptosis and the epithelial-to-mesenchymal transition. In the current study, 63 patients with locally advanced uterine cervical cancer were reviewed and classified as stage IIIA-IIIB using the International Federation of Gynecology and Obstetrics criteria. These patients (aged <70 years) were treated at Osaka City University Medical School Hospital, Japan, between 1995 and 2010. Tumor tissue samples were obtained by biopsy prior to NAC. The tissue samples were classified as group 1 or 2 depending on the efficacy of NAC. Surgery and radiotherapy were administered in group 1 (n=36), for which NAC was effective. In the patients of group 2 NAC was not effective, and radiotherapy alone was administered (n=27). The expression of EGFL7 and Snail was examined in paraffin-embedded tissue sample sections using the avidin-biotin peroxidase complex method. The results indicated that EGFL7 expression levels were significantly higher in group 2, as compared with group 1 (P<0.001). A similar result was observed for the expression levels of Snail (P=0.001). Group 1 exhibited significantly longer overall survival times compared with group 2 (P=0.001). The patients were also classified into a low EGFL7 expression level group (weighted score of ≤6) and a high EGFL7 expression level group (weighted score of ≥8). NAC was observed to be significantly more effective in the low EGFL7 expression level group (P<0.001), as compared with the high expression level group. The results suggest that the expression levels of EGFL7 may be a potential predictive marker of the efficacy of NAC for the treatment of locally advanced uterine cervical cancer.

Endothelial Cell Activation Is Regulated by Epidermal Growth Factor-like Domain 7 (Egfl7) during Inflammation

Activation of the blood vessel endothelium is a critical step during inflammation. Endothelial cells stimulated by pro-inflammatory cytokines play an essential part in the adhesion and extravasation of circulating leukocytes into inflamed tissues. The endothelial egfl7 gene (VE-statin) represses endothelial cell activation in tumors, and prior observations suggested that it could also participate in the regulation of endothelial cell activation during inflammation. We show here that Egfl7 expression is strongly repressed in mouse lung endothelial cells during LPS- and TNFα-induced inflammation in vivo LPS have a limited effect on Egfl7 expression by endothelial cells in vitro, whereas the pro-inflammatory cytokine TNFα strongly represses Egfl7 expression in endothelial cells. TNFα regulates the egfl7 gene promoter through regions located between -7585 and -5550 bp ahead of the main transcription start site and via an NF-κB-dependent mechanism. Conversely, Egfl7 regulates the response of endothelial cells to TNFα by restraining the induced expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin, resulting in a decreased adhesion of leukocytes onto endothelial cells stimulated by TNFα. Egfl7 regulates the expression of these adhesion molecules through the NF-κB and MEK/Erk pathways, in particular by preventing the proteasome-mediated degradation of IkBα both in non-activated endothelial cells and during activation. Egfl7 is thus an endogenous and constitutive repressor of blood vessel endothelial cell activation in normal and inflammatory conditions and participates in a loop of regulation of activation of these cells by pro-inflammatory cytokines.

MicroRNA-126 inhibits tumor proliferation and angiogenesis of hepatocellular carcinoma by down-regulating EGFL7 expression

This study aims to explore the effects of microRNA-126 (miR-126) on tumor proliferation and angiogenesis of hepatocellular carcinoma (HCC) by targeting EGFL7. HCC tissues and adjacent normal tissues were obtained from 71 HCC patients. Immunohistochemistry (IHC) was conducted to detect expressions of EGFL7 and VEGF and the micro-vessel density (MVD). HCC cell lines were collected and assigned into the blank, miR-126 mimics, miR-126 inhibitors, miR-126 mimics negative control (NC), miR-126 inhibitors NC, si-EGFL7, and miR-126 inhibitors + si-EGFL7 groups. Expressions of miR-126 and EGFL7 mRNA were detected by qRT-PCR assay. The protein expressions of EGFL7 and VEGF were measured by Western blotting. MTT assay was used to measure the proliferation of HCC cells. Tumor xenograft model in nude mice was utilized to evaluate the influence of miR-126 on tumor growth. HCC tissues had higher miR-126 expression and lower EGFL7 mRNA expression than adjacent normal tissues. Compared with the blank, miR-126 mimic NC, miR-126 inhibitor NC and miR-126 inhibitors + si-EGFL7 groups, the protein expressions of EGFL7 and VEGF and cell proliferation were reduced in the miR-126 mimics and si-EGFL7 groups, while the opposite trend was found in the miR-126 inhibitors group. Compared with the blank and miR-126 inhibitors + siRNA-EGFL7 groups, tumor size, tumor weight, and MVD of transplanted tumors in nude mice were significantly reduced in the miR-126 mimics and siRNA-EGFL7 groups, while the opposite trend was found in the miR-126 inhibitors group. In conclusion, miR-126 could inhibit tumor proliferation and angiogenesis of HCC by down-regulating EGFL7 expression.

High expression levels of egfl7 correlate with low endothelial cell activation in peritumoral vessels of human breast cancer

Tumor blood vessels participate in the immune response against cancer cells and we previously used pre-clinical models to demonstrate that egfl7 (VE-statin) promotes tumor cell evasion from the immune system by repressing endothelial cell activation, preventing immune cells from entering the tumor mass. In the present study, the expression levels of egfl7 and that of ICAM-1 as a marker of endothelium activation, were evaluated in peritumoral vessels of human breast cancer samples. Breast cancer samples (174 invasive and 30 in situ) from 204 patients treated in 2005 were immunostained for CD31, ICAM-1 and stained for egfl7 using in situ hybridization. The expression levels of ICAM-1 and egfl7 were assessed in peritumoral areas using semi-quantitative scales. There was a strong and significant inverse correlation between the expression of ICAM-1 and that of egfl7 in CD31⁺ blood vessels. When the ICAM-1 score increased, the egfl7 score reduced significantly (P=0.004), and vice-versa (Cuzick's test for trend across ordered groups). In order to determine which gene influenced the other gene between egfl7 and ICAM-1, the expression levels of either gene were modulated in endothelial cells. Egfl7 regulated ICAM-1 expression while ICAM-1 had no effects on egfl7 expression in the same conditions. Altogether, these results provide further results that egfl7 serves a regulatory role in endothelial cell activation in relation to immune infiltration and that it is a potential therapeutic target to consider for improving anticancer immunotherapies.