Inhibition of tumor angiogenesis and melanoma growth by targeting vascular E-selectin

E-selectin in vascular pathophysiology

Selectins are a group of Ca2+-dependent, transmembrane type I glycoproteins which attract cell adhesion and migration. E-selectin is exclusively expressed in endothelial cells, and its expression is strongly enhanced upon activation by pro-inflammatory cytokines. The interaction of E-selectin with its ligands on circulating leukocytes captures and slows them down, further facilitating integrin activation, firm adhesion to endothelial cells and transmigration to tissues. Oxidative stress induces endothelial cell injury, leading to aberrant expression of E-selectin. In addition, the elevated level of E-selectin is positively related to high risk of inflammation. Dysregulation of E-selectin has been found in several pathological conditions including acute kidney injury (AKI), pulmonary diseases, hepatic pathology, Venous thromboembolism (VTE). Deletion of the E-selectin gene in mice somewhat ameliorates these complications. In this review, we describe the mechanisms regulating E-selectin expression, the interaction of E-selectin with its ligands, the E-selectin physiological and pathophysiological roles, and the therapeutical potential of targeting E-selectin.

Identification of New Markers of Angiogenic Sprouting Using Transcriptomics: New Role for RND3

BACKGROUND

New blood vessel formation requires endothelial cells to transition from a quiescent to an invasive phenotype. Transcriptional changes are vital for this switch, but a comprehensive genome-wide approach focused exclusively on endothelial cell sprout initiation has not been reported.

METHODS

Using a model of human endothelial cell sprout initiation, we developed a protocol to physically separate cells that initiate the process of new blood vessel formation (invading cells) from noninvading cells. We used this model to perform multiple transcriptomics analyses from independent donors to monitor endothelial gene expression changes.

RESULTS

Single-cell population analyses, single-cell cluster analyses, and bulk RNA sequencing revealed common transcriptomic changes associated with invading cells. We also found that collagenase digestion used to isolate single cells upregulated the Fos proto-oncogene transcription factor. Exclusion of Fos proto-oncogene expressing cells revealed a gene signature consistent with activation of signal transduction, morphogenesis, and immune responses. Many of the genes were previously shown to regulate angiogenesis and included multiple tip cell markers. Upregulation of SNAI1 (snail family transcriptional repressor 1), PTGS2 (prostaglandin synthase 2), and JUNB (JunB proto-oncogene) protein expression was confirmed in invading cells, and silencing JunB and SNAI1 significantly reduced invasion responses. Separate studies investigated rounding 3, also known as RhoE, which has not yet been implicated in angiogenesis. Silencing rounding 3 reduced endothelial invasion distance as well as filopodia length, fitting with a pathfinding role for rounding 3 via regulation of filopodial extensions. Analysis of in vivo retinal angiogenesis in Rnd3 heterozygous mice confirmed a decrease in filopodial length compared with wild-type littermates.

CONCLUSIONS

Validation of multiple genes, including rounding 3, revealed a functional role for this gene signature early in the angiogenic process. This study expands the list of genes associated with the acquisition of a tip cell phenotype during endothelial cell sprout initiation.

Therapeutic effect and study of human umbilical cord blood mononuclear cells in patients with ischaemic bowel disease

Ischaemic bowel disease (ICBD) is a group of intestinal ischaemia syndromes caused by various aetiologies of reduced intestinal blood flow or vascular occlusion. ICBD can present as abdominal pain, bloody stool, and diarrhoea. This disease often occurs in middle-aged and elderly individuals with cardiovascular and cerebrovascular diseases. The incidence of ischaemic bowel disease has been increasing for decades, and it is difficult to diagnose, resulting in rapid disease progression and a high mortality rate. Therefore, fully understanding this disease, improving the diagnosis rate of this disease, and finding appropriate treatment methods are urgently needed to improve the condition and prognosis of patients. Umbilical cord blood stem cells are accessible, have weak immunogenicity, and have various biological functions, such as angiogenesis, inflammation and immune regulation. Many studies have confirmed that cord blood stem cells can relieve ischaemia, and these cells have attracted tremendous amounts of attention in regenerative medicine in recent years. In this paper, we discuss the clinical characteristics of ICBD, analyse the characteristics of human umbilical cord blood mononuclear cells (HUCB-MNCs), and use its to treat ischaemic bowel disease. Additionally, we compare the clinical manifestations and related indicators before and after treatment to evaluate the efficacy and safety of these methods.

The evaluation of tumor microenvironment infiltration and the identification of angiogenesis-related subgroups in skin cutaneous melanoma

BACKGROUND

There are limited studies on the association between angiogenesis-related genes (ARGs) and the predictive risk of melanoma, even though angiogenic factors, which are essential for tumor growth and metastasis, might be secreted by angiogenesis-related protein in skin cutaneous melanoma (SKCM). To forecast patient outcomes, this study attempts to develop a predictive risk signature linked to angiogenesis in cutaneous melanoma.

METHODS

In 650 patients with SKCM, the expression and mutation of ARGs were examined, and this information was related to the clinical prognosis. SKCM patients were split into two groups based on how well they performed on the ARG. The link between ARGs, risk genes, and immunological microenvironment was examined using a range of algorithmic analysis techniques. Based on these five risk genes, an angiogenesis risk signature was created. We developed a nomogram and examined the sensitivity of antineoplastic medications to help the proposed risk model's clinical applicability.

RESULTS

The risk model developed by ARGs revealed that the prognosis for the two groups was significantly different. The predictive risk score was negatively connected with memory B cells, activated memory CD4 + T cells, M1 macrophages, and CD8 + T cells, and favorably correlated with dendritic cells, mast cells, and neutrophils.

CONCLUSIONS

Our findings offer fresh perspectives on prognostic evaluation and imply that ARG modulation is implicated in SKCM. Potential medications for the treatment of individuals with various SKCM subtypes were predicted by drug sensitivity analysis.

Construction and validation of a prognostic risk model of angiogenesis factors in skin cutaneous melanoma

Melanoma can secrete tumor angiogenesis factors, which is the essential factor for tumor growth and metastasis. However, there are few reports on the relationship between angiogenesis factors and prognosis risk in melanoma. This study aimed to develop a prognostic risk model of angiogenesis for melanoma. Forty-nine differentially expressed angiogenesis were identified from the TCGA database, which were mainly involved in PI3K/Akt pathway, focal adhesion, and MAPK signaling pathway. We then establish an eleven-gene signature. The model indicated a strong prognostic capability in both the discovery cohort and the validation cohort. Patients of smaller height (<170 cm) and lower weight (<80 kg) and those with advanced-stage and ulcerated melanoma had higher risk scores. The risk score was positively correlated with mutation load, homologous recombination defect, neoantigen load and chromosome instability. In addition, the high-risk group had a higher degree of immune cell infiltration, better response to immunotherapy and lower immune score. Therefore, these results indicate that the risk model is an effective method to predict the prognosis of melanoma.

Therapeutic angiogenesis in Buerger's disease: reviewing the treatment landscape

Thromboangiitis obliterans, also known as Buerger's disease, is a rare inflammatory vasculitis that predominantly develops in smokers and characteristically affects the small- and medium-sized peripheral arteries and veins. Patients typically present with extremity claudication, but symptoms may progress to rest pain and tissue loss, especially in those unable to abstain from tobacco use. Unfortunately, traditional medical treatments are largely ineffective and due to the small caliber of affected vessels and lack of suitable distal targets or venous conduits, endovascular and open surgical approaches are often not possible. Eventually, a significant number of patients require major amputation. For these reasons, much research effort has been made in developing techniques of therapeutic angiogenesis to improve limb perfusion, both for atherosclerotic peripheral arterial disease and the smaller subset of patients with critical limb ischemia due to Buerger's disease. Neovascularization in response to ischemia relies on a complex interplay between the local tissue microenvironment and circulating stem and progenitor cells. To date, studies of therapeutic angiogenesis have therefore focused on exploiting known angiogenic factors and stem cells to induce neovascularization in ischemic tissues. This review summarizes the available clinical data regarding the safety and efficacy of various angiogenic therapies, notably injection of naked DNA plasmids, viral gene constructs, and cell-based preparations, and describes techniques for potentiating in vivo efficacy of gene- and cell-based therapies as well as ongoing developments in exosome-based cell-free approaches for therapeutic angiogenesis.

Plain Language Title and Summary

A review of available and emerging treatments for improving blood flow and wound healing in patients with Buerger's disease, a rare disorder of blood vessels Buerger's disease is a rare disorder of the small- and medium-sized blood vessels in the arms and legs that almost exclusively develops in young smokers. Buerger's disease causes inflammation in arteries and veins, which leads to blockage of these vessels and reduces blood flow to and from the extremities. Decreased blood flow to the arms and legs can lead to development of nonhealing wounds and infection for which some patients may eventually require amputation. Unfortunately, traditional medical and surgical treatments are not effective in Buerger's disease, so other methods for improving blood flow are needed for these patients. There are several different ways to stimulate new blood vessel formation, both in humans and animal models. The most common treatments involve injection of DNA or viruses that express genes related to blood vessel formation or, alternatively, stem cell-based treatments that help regenerate blood vessels and repair wound tissue. This review explores how safe and effective these various treatments are and describes recent research developments that may lead to better therapies for patients with Buerger's disease and other vascular disorders.

Quinic Acid-Conjugated Nanoparticles Enhance Drug Delivery to Solid Tumors via Interactions with Endothelial Selectins

Current nanoparticle (NP) drug carriers mostly depend on the enhanced permeability and retention (EPR) effect for selective drug delivery to solid tumors. However, in the absence of a persistent EPR effect, the peritumoral endothelium can function as an access barrier to tumors and negatively affect the effectiveness of NPs. In recognition of the peritumoral endothelium as a potential barrier in drug delivery to tumors, poly(lactic-co-glycolic acid) (PLGA) NPs are modified with a quinic acid (QA) derivative, synthetic mimic of selectin ligands. QA-decorated NPs (QA-NP) interact with human umbilical vein endothelial cells expressing E-/P-selectins and induce transient increase in endothelial permeability to translocate across the layer. QA-NP reach selectin-upregulated tumors, achieving greater tumor accumulation and paclitaxel (PTX) delivery than polyethylene glycol-decorated NPs (PEG-NP). PTX-loaded QA-NP show greater anticancer efficacy than Taxol or PTX-loaded PEG-NP at the equivalent PTX dose in different animal models and dosing regimens. Repeated dosing of PTX-loaded QA-NP for two weeks results in complete tumor remission in 40-60% of MDA-MB-231 tumor-bearing mice, while those receiving control treatments succumb to death. QA-NP can exploit the interaction with selectin-expressing peritumoral endothelium and deliver anticancer drugs to tumors to a greater extent than the level currently possible with the EPR effect.

A Molecular and Clinical Review of Stem Cell Therapy in Critical Limb Ischemia

Peripheral artery disease (PAD) is one of the major vascular complications in individuals suffering from diabetes and in the elderly that can progress to critical limb ischemia (CLI), portending significant burden in terms of patient morbidity and mortality. Over the last two decades, stem cell therapy (SCT) has risen as an attractive alternative to traditional surgical and/or endovascular revascularization to treat this disorder. The primary benefit of SCT is to induce therapeutic neovascularization and promote collateral vessel formation to increase blood flow in the ischemic limb and soft tissue. Existing evidence provides a solid rationale for ongoing in-depth studies aimed at advancing current SCT that may change the way PAD/CLI patients are treated.

SDF-1α-induced dual pairs of E-selectin/ligand mediate endothelial progenitor cell homing to critical ischemia

Homing of endothelial progenitor cells (EPC) to the ischemic tissues is a key event in neovascularization and tissue regeneration. In response to ischemic insult, injured tissues secrete several chemo-cytokines, including stromal cell-derived factor-1α (SDF-1α), which triggers mobilization and homing of bone marrow-derived EPC (BMD-EPC). We previously reported that SDF-1α-induced EPC homing is mediated by a panel of adhesion molecules highly or selectively expressed on the activated endothelium in ischemic tissues, including E-selectin. Elevated E-selectin on wound vasculature serve as docking sites for circulating EPC, which express counterpart E-selectin ligands. Here, we show that SDF-1α presented in wound tissue and released into circulation can act both locally and remotely to induce ischemic tissue endothelium and BMD-EPC to express both E-selectin and its ligands. By performing BM transplantation using E-selectin^−/− and E-selectin^+/+ mice as the donors and recipients respectively, we demonstrate that upregulated dual E-selectin/ligand pairs reciprocally expressed on ischemic tissue endothelium and BMD-EPC act as double-locks to secure targeted EPC- endothelium interactions by which to facilitate EPC homing and promote neovascularization and tissue repair. These findings describe a novel mechanism for BMD-EPC homing and indicate that dual E-selectin/ligand pairs may be effective targets/tools for therapeutic neovascularization and targeted cell delivery.

E-Selectin Mediates Immune Cell Trafficking in Corneal Transplantation

BACKGROUND

Immune rejection continues to threaten all tissue transplants. Here we sought to determine whether platelet (P)- and endothelial (E)-selectin mediate T cell recruitment in corneal transplantation and whether their blockade can reduce T cell graft infiltration and improve long-term corneal allograft survival.

METHODS

In a murine model of allogeneic corneal transplantation, we used PCR and immunohistochemistry to investigate expression of P- and E-selectin in rejected versus accepted allografts and lymph node flow cytometry to assess expression of selectin ligands by effector T cells. Using P- and E-selectin neutralizing antibodies, we evaluated the effect of blockade on CD4 T cell recruitment, as well as the effect of anti-E-selectin on long-term allograft survival.

RESULTS

The P- (93.3-fold, P < 0.05) and E-selectin (17.1-fold, P < 0.005) are upregulated in rejected versus accepted allogeneic transplants. Type 1 T helper cells from hosts with accepted and rejected grafts express high levels of P-selectin glycoprotein ligand 1 and glycosylated CD43. In vivo blockade of P (0.47 ± 0.03, P < 0.05) and E selectin (0.49 ± 0.1, P < 0.05) reduced the number of recruited T cells compared with IgG control (0.98 ± 0.1). Anti-E-selectin reduced the number of mature antigen-presenting cells trafficking to lymphoid tissue compared with control (6.96 ± 0.9 vs 12.67 ± 0.5, P < 0.05). Anti-E-selectin treatment delayed graft rejection and increased survival compared with control, although this difference did not reach statistical significance.

CONCLUSIONS

In a model of corneal transplantation, P- and E-selectin mediate T cell recruitment to the graft, E-selectin mediates APC trafficking to lymphoid tissue, and blockade of E-selectin has a modest effect on improving long-term graft survival.

Directing and Potentiating Stem Cell-Mediated Angiogenesis and Tissue Repair by Cell Surface E-Selectin Coating

Stem cell therapy has emerged as a promising approach for treatment of a number of diseases, including delayed and non-healing wounds. However, targeted systemic delivery of therapeutic cells to the dysfunctional tissues remains one formidable challenge. Herein, we present a targeted nanocarrier-mediated cell delivery method by coating the surface of the cell to be delivered with dendrimer nanocarriers modified with adhesion molecules. Infused nanocarrier-coated cells reach to destination via recognition and association with the counterpart adhesion molecules highly or selectively expressed on the activated endothelium in diseased tissues. Once anchored on the activated endothelium, nanocarriers-coated transporting cells undergo transendothelial migration, extravasation and homing to the targeted tissues to execute their therapeutic role. We now demonstrate feasibility, efficacy and safety of our targeted nanocarrier for delivery of bone marrow cells (BMC) to cutaneous wound tissues and grafted corneas and its advantages over conventional BMC transplantation in mouse models for wound healing and neovascularization. This versatile platform is suited for targeted systemic delivery of virtually any type of therapeutic cell.

Gene expression profiling of DMU-212-induced apoptosis and anti-angiogenesis in vascular endothelial cells

CONTEXT

trans-3,4,5,4'-Tetramethoxystilbene (DMU-212), an derivative of resveratrol, shows strong antiproliferative activities against many cancer cells. In our previous study, we demonstrated that DMU-212 possesses potent proapoptosis and antiangiogenesis effects on vascular endothelial cells (VECs), which made it a promising agent for the treatment of angiogenesis-related diseases.

OBJECTIVE

We studied the gene expression profile of DMU-212-treated VECs to gain further insight into the mechanisms by which DMU-212 exerts its potent pro-apoptosis and antiangiogenesis effects.

MATERIALS AND METHODS

The potential changes in the gene expression of VECs incubated with DMU-212 were identified and analyzed using the Affymetrix HG-U133 Plus 1.0 array. In addition, the gene expression profile was validated by quantitative real-time PCR (qRT-PCR) analysis for seven of those altered genes.

RESULTS AND CONCLUSION

DMU-212 was found to regulate a diverse range of genes, including cytokines (IL8, selectin E, MPZL2, EGR1, CCL20, ITGB8, CXCL1, VCAM1, KITLG, and AREG), transport proteins (TRPC4, SLC41A2, SLC17A5, and CREB5), metabolism (CYP1B1, CYP1A1, PDK4, CSNK1G1, MVK, TCEB3C, and CDKN3), enzymes (RAB23, SPHK1, CHSY3, PLAU, PLA2G4C, and MMP10), and genes involved in signal transduction (TMEM217, DUSP8, and SPRY4), chromosome organization (HIST1H2BH and GEM), cell migration and angiogenesis (ERRFI1, HBEGF, and NEDD9), and apoptosis (TNFSF15, TNFRSF9, CD274, BCL2L11, BIRC3, TNFAIP3, and TIFA), as well as other genes with unknown function (PGM5P2, SNORD1142, LOC151760, KRTAP5-2, C1orf110, SNORA14A, MIR31, C2CD4B, SCARNA4, C2orf66, SC4MOL, LOC644714, and LOC283392). This is the first application of microarray technique to investigate and analyze the profile of genes regulated by DMU-212 in VECs. Our results lead to an increased understanding of the signaling pathways involved in DMU-212-induced apoptosis and antiangiogenesis.

Modulation, bioinformatic screening, and assessment of small molecular peptides targeting the vascular endothelial growth factor receptor

Vascular endothelial growth factor (VEGF) and VEGF receptor (VEGFR) are important factors in tumor growth and metastasis. Molecular probes or drugs designed to target VEGF/VEGFR interactions are crucial in tumor molecular imaging and targeted therapy. Bioinformatic methods enable molecular design based on the structure of bio-macromolecules and their interactions. This study was aimed to identify tumor-targeting small-molecule peptides with high affinity for VEGFR using bioinformatics screening. The VEGFR extracellular immunoglobulin-like modules Ig1–Ig3 were used as the target to systematically alter the primary peptide sequence of VEGF_125–136. Molecular docking and surface functional group interaction methods were combined in an in silico screen for polypeptides, which in theory, would have higher affinities for VEGFR. In vitro receptor competition binding assays were used to assess the affinity of the putative VEGFR-binding polypeptides. Rhodamine-conjugated peptides were used to label and visualize peptide-binding sites on A549 cells. Using bioinformatic screening, we identified 20 polypeptides with potentially higher affinity for VEGFR. The polypeptides were capable of inhibiting the binding of ¹²⁵I-VEGF to VEGFR in a dose-dependent manner. The IC₅₀ values of QKRKRKKSRKKH and RKRKRKKSRYIVLS (80 and 185 nmol/L, respectively) were significantly lower than that of VEGF_125–136 (464 nmol/L); thus, the affinity of these peptides for VEGFR was 6- and 2.5-fold higher, respectively, than that of VEGF_125–136. Rhodamine labeling of A549 cells revealed peptide binding mainly on the plasma membrane and in the cytoplasm. Bioinformatic approaches hold promise for the development of molecular imaging probes. Using this approach, we designed two peptides that showed higher affinity toward VEGFR. These polypeptides may be used as molecular probes or drugs targeting VEGFR, which can be utilized in molecular imaging and targeted therapy of certain tumors.

Melanoma cell therapy: Endothelial progenitor cells as shuttle of the MMP12 uPAR-degrading enzyme

The receptor for the urokinase-type plasminogen activator (uPAR) accounts for many features of cancer progression, and is therefore considered a target for anti-tumoral therapy. Only full length uPAR mediates tumor progression. Matrix-metallo-proteinase-12 (MMP12)-dependent uPAR cleavage results into the loss of invasion properties and angiogenesis. MMP12 can be employed in the field of “targeted therapies” as a biological drug to be delivered directly in patient's tumor mass. Endothelial Progenitor Cells (EPCs) are selectively recruited within the tumor and could be used as cellular vehicles for delivering anti-cancer molecules. The aim of our study is to inhibit cancer progression by engeneering ECFCs, a subset of EPC, with a lentivirus encoding the anti-tumor uPAR-degrading enzyme MMP12. Ex vivo manipulated ECFCs lost the capacity to perform capillary morphogenesis and acquired the anti-tumor and anti-angiogenetic activity. In vivo MMP12-engineered ECFCs cleaved uPAR within the tumor mass and strongly inhibited tumor growth, tumor angiogenesis and development of lung metastasis.

The possibility to exploit tumor homing and activity of autologous MMP12-engineered ECFCs represents a novel way to combat melanoma by a “personalized therapy”, without rejection risk.

The i.v. injection of radiolabelled MMP12-ECFCs can thus provide a new theranostic approach to control melanoma progression and metastasis.

The GroEL protein of Porphyromonas gingivalis accelerates tumor growth by enhancing endothelial progenitor cell function and neovascularization

Porphyromonas gingivalis is a bacterial species that causes destruction of periodontal tissues. Additionally, previous evidence indicates that GroEL from P. gingivalis may possess biological activities involved in systemic inflammation, especially inflammation involved in the progression of periodontal diseases. The literature has established a relationship between periodontal disease and cancer. However, it is unclear whether P. gingivalis GroEL enhances tumor growth. Here, we investigated the effects of P. gingivalis GroEL on neovasculogenesis in C26 carcinoma cell-carrying BALB/c mice and chick eggs in vivo as well as its effect on human endothelial progenitor cells (EPC) in vitro. We found that GroEL treatment accelerated tumor growth (tumor volume and weight) and increased the mortality rate in C26 cell-carrying BALB/c mice. GroEL promoted neovasculogenesis in chicken embryonic allantois and increased the circulating EPC level in BALB/c mice. Furthermore, GroEL effectively stimulated EPC migration and tube formation and increased E-selectin expression, which is mediated by eNOS production and p38 mitogen-activated protein kinase activation. Additionally, GroEL may enhance resistance against paclitaxel-induced cell cytotoxicity and senescence in EPC. In conclusion, P. gingivalis GroEL may act as a potent virulence factor, contributing to the neovasculogenesis of tumor cells and resulting in accelerated tumor growth.

The role of chemoattractant receptors in shaping the tumor microenvironment

Chemoattractant receptors are a family of seven transmembrane G protein coupled receptors (GPCRs) initially found to mediate the chemotaxis and activation of immune cells. During the past decades, the functions of these GPCRs have been discovered to not only regulate leukocyte trafficking and promote immune responses, but also play important roles in homeostasis, development, angiogenesis, and tumor progression. Accumulating evidence indicates that chemoattractant GPCRs and their ligands promote the progression of malignant tumors based on their capacity to orchestrate the infiltration of the tumor microenvironment by immune cells, endothelial cells, fibroblasts, and mesenchymal cells. This facilitates the interaction of tumor cells with host cells, tumor cells with tumor cells, and host cells with host cells to provide a basis for the expansion of established tumors and development of distant metastasis. In addition, many malignant tumors of the nonhematopoietic origin express multiple chemoattractant GPCRs that increase the invasiveness and metastasis of tumor cells. Therefore, GPCRs and their ligands constitute targets for the development of novel antitumor therapeutics.

Targeting liposomes loaded with melphalan prodrug to tumour vasculature via the Sialyl Lewis X selectin ligand

Earlier we showed that liposome formulation of DL-melphalan lipophilic prodrug bearing tetrasaccharide Sialyl Lewis X (SiaLe^X) caused prolonged therapeutic effect on mammary cancer in mice. Here, we compare antivascular effect of SiaLe^X-liposomes loaded with diglyceride ester of melphalan (Mlph) against SiaLe^X-free formulation in Lewis lung carcinoma model.

METHODS

Liposomes of egg phosphatidylcholine/yeast phosphatidylinositol/1,2-dioleoyl glycerol (DOG) conjugate of Mlph/±SiaLe^X-PEG_8-15-DOG, 8:1:1:0.2 by mol, were prepared by standard extrusion. After two intravenous injections with Mlph or liposomes under either standard or delayed treatment protocols, vascular-disrupting effects of the preparations were evaluated basing on tumour section histomorphology, lectin perfusion assay and immunohistochemistry (anti-CD31 staining) data. Also, untreated mice were administered with fluorescently-labelled liposomes to assess their distribution in tumour sections with confocal laser scanning microscopy.

RESULTS

Two injections of SiaLe^X-liposomes reproducibly caused severe injuries of tumour vessels. SiaLe^X-liposomes co-localized with CD31 marker on vascular endothelium while the non-targeted formulation extravasated into tumour.

DISCUSSION

Cytotoxic SiaLe^X-liposomes exhibit superior vascular-disrupting properties compared to non-targeted liposomes, yet the effect starts to transform into gain in tumour growth inhibition only under delayed treatment regimen.

CONCLUSION

SiaLe^X-ligand provides targeting of cytotoxic liposomes to tumour endothelium and subsequent antivascular effect.

TNFα signals via p66(Shc) to induce E-Selectin, promote leukocyte transmigration and enhance permeability in human endothelial cells

Endothelial cells participate in inflammatory events leading to atherogenesis by regulating endothelial cell permeability via the expression of VE-Cadherin and β-catenin and leukocyte recruitment via the expression of E-Selectins and other adhesion molecules. The protein p66^Shc acts as a sensor/inducer of oxidative stress and may promote vascular dysfunction. The objective of this study was to investigate the role of p66^Shc in tumor necrosis factor TNFα-induced E-Selectin expression and function in human umbilical vein endothelial cells (HUVEC). Exposure of HUVEC to 50 ng/ml TNFα resulted in increased leukocyte transmigration through the endothelial monolayer and E-Selectin expression, in association with augmented phosphorylation of both p66^Shc on Ser³⁶ and the stress kinase c-Jun NH₂-terminal protein kinase (JNK)-1/2, and higher intracellular reactive oxygen species (ROS) levels. Overexpression of p66^Shc in HUVEC resulted in enhanced p66^Shc phosphorylation on Ser³⁶, increased ROS and E-Selectin levels, and amplified endothelial cell permeability and leukocyte transmigration through the HUVEC monolayer. Conversely, overexpression of a phosphorylation-defective p66^Shc protein, in which Ser³⁶ was replaced by Ala, did not augment ROS and E-Selectin levels, nor modify cell permeability or leukocyte transmigration beyond those found in wild-type cells. Moreover, siRNA-mediated silencing of p66^Shc resulted in marked reduction of E-Selectin expression and leukocyte transmigration. In conclusion, p66^Shc acts as a novel intermediate in the TNFα pathway mediating endothelial dysfunction, and its action requires JNK-dependent phosphorylation of p66^Shc on Ser³⁶.

Biology of brain metastases and novel targeted therapies: time to translate the research

Brain metastases (BM) occur in 20% to 40% of patients with cancer and result in significant morbidity and poor survival. The main therapeutic options include surgery, whole brain radiotherapy, stereotactic radiosurgery and chemotherapy. Although significant progress has been made in diagnostic and therapeutic methods, the prognosis in these patients remains poor. Furthermore, the poor penetrability of chemotherapy agents through the blood brain barrier (BBB) continues to pose a challenge in the management of this disease. Preclinical evidence suggests that new targeted treatments can improve local tumor control but our clinical experience with these agents remains limited. In addition, several clinical studies with these novel agents have produced disappointing results. This review will examine the knowledge of targeted therapies in BM. The preclinical and clinical evidence of their use in BM induced by breast cancer, non-small cell lung cancer and melanoma will be presented. In addition, we will discuss the role of antiangiogenic and radiosensitising agents in the treatment of BM and the current strategies available to increase BBB permeability. A better understanding of the mechanism of action of these agents will help us to identify the best targets for testing in future clinical studies.

E-selectin mediates stem cell adhesion and formation of blood vessels in a murine model of infantile hemangioma

Hemangioma stem cells (HemSCs) are multipotent cells isolated from infantile hemangioma (IH), which form hemangioma-like lesions when injected subcutaneously into immune-deficient mice. In this murine model, HemSCs are the primary target of corticosteroid, a mainstay therapy for problematic IH. The relationship between HemSCs and endothelial cells that reside in IH is not clearly understood. Adhesive interactions might be critical for the preferential accumulation of HemSCs and/or endothelial cells in the tumor. Therefore, we studied the interactions between HemSCs and endothelial cells (HemECs) isolated from IH surgical specimens. We found that HemECs isolated from proliferating phase IH, but not involuting phase, constitutively express E-selectin, a cell adhesion molecule not present in quiescent endothelial cells. E-selectin was further increased when HemECs were exposed to vascular endothelial growth factor-A or tumor necrosis factor-α. In vitro, HemSC migration and adhesion was enhanced by recombinant E-selectin but not P-selectin; both processes were neutralized by E-selectin-blocking antibodies. E-selectin-positive HemECs also stimulated migration and adhesion of HemSCs. In vivo, neutralizing antibodies to E-selectin strongly inhibited formation of blood vessels when HemSCs and HemECs were co-implanted in Matrigel. These data suggest that endothelial E-selectin could be a major ligand for HemSCs and thereby promote cellular interactions and vasculogenesis in IH. We propose that constitutively expressed E-selectin on endothelial cells in the proliferating phase is one mediator of the stem cell tropism in IH.

Vascular density and endothelial cell expression of integrin alpha v beta 3 and E-selectin in murine tumours

The endothelial cell adhesion molecules, including the integrin alpha v beta 3 (αvβ3) and E-selectin, are involved in the process of angiogenesis required for tumour growth, cell migration and metastasis. The purpose of this study was to assess and compare widely used tumour models to select the ones most suitable for angiogenesis research. Fifteen murine tumours were selected including melanoma (B16), colon (C26, C38, C51), mammary (MA13, MA16, MA16/Adr, MA17, MA17/Adr, MA25, MA44), pancreatic (PO2, PO3), Glasgow osteogenic sarcoma (GOS) and Lewis lung carcinoma (LLC). The tumour vascular density, assessed using the platelet endothelial cell adhesion molecule 1 (PECAM-1; CD31) immunostaining, revealed that B16 melanoma was poorly vascularized (<5 %), whereas the colon and mammary tumours were well vascularized (5-15 %). The most vascularized tumours (>15 %) were the pancreatic tumours (PO2 and PO3), the sarcoma (GOS) and the lung tumour (LLC). The integrin αvβ3 and E-selectin, evaluated by immunohistology, showed that 7/15 tumours expressed the αvβ3 integrin which was homogeneously distributed on all tumour sections (B16, C26, MA17/Adr, MA25, MA44, PO2, LLC). E-selectin was expressed in 4/15 tumours and its expression was restricted to the tumour periphery. Only 2/15 tumours (B16 and C26) were shown to express both integrin αvβ3 and E-selectin. In conclusion, these data not only contribute to a better understanding of the tumour biology of murine tumours but can also guide the choice of appropriate models for antiangiogenic therapy, for selective drug delivery to tumours and the validation of tumour imaging modalities targeting these endothelial cell adhesion molecules.