Anti-VEGF/VEGFR therapy for cancer: reassessing the target

Exploitation of receptor tyrosine kinases by viral-encoded growth factors

Receptor tyrosine kinases (RTKs) are essential components of cell communication pathways utilized from the embryonic to adult stages of life. These transmembrane receptors bind polypeptide ligands, such as growth factors, inducing signalling cascades that control cellular processes such as proliferation, survival, differentiation, motility and inflammation. Many viruses have acquired homologs of growth factors encoded by the hosts that they infect. Production of growth factors during infection allows viruses to exploit RTKs for entry and replication in cells, as well as for host and environmental dissemination. This review describes the genetic diversity amongst virus-derived growth factors and the mechanisms by which RTK exploitation enhances virus survival, then highlights how viral ligands can be used to further understanding of RTK signalling and function during embryogenesis, homeostasis and disease scenarios.

Histidine-rich glycoprotein-induced vascular normalization improves EPR-mediated drug targeting to and into tumors

Tumors are characterized by leaky blood vessels, and by an abnormal and heterogeneous vascular network. These pathophysiological characteristics contribute to the enhanced permeability and retention (EPR) effect, which is one of the key rationales for developing tumor-targeted drug delivery systems. Vessel abnormality and heterogeneity, however, which typically result from excessive pro-angiogenic signaling, can also hinder efficient drug delivery to and into tumors. Using histidine-rich glycoprotein (HRG) knockout and wild type mice, and HRG-overexpressing and normal t241 fibrosarcoma cells, we evaluated the effect of genetically induced and macrophage-mediated vascular normalization on the tumor accumulation and penetration of 10-20 nm-sized polymeric drug carriers based on poly(N-(2-hydroxypropyl)methacrylamide). Multimodal and multiscale optical imaging was employed to show that normalizing the tumor vasculature improves the accumulation of fluorophore-labeled polymers in tumors, and promotes their penetration out of tumor blood vessels deep into the interstitium.

Tumor endothelial marker 8 promotes cancer progression and metastasis

Every year more than 8 million people suffer from cancer-related deaths worldwide [1]. Metastasis, the spread of cancer to distant sites, accounts for 90% of these deaths. A promising target for blocking tumor progression, without causing severe side effects [2], is Tumor Endothelial Marker 8 (TEM8), an integrin-like cell surface protein expressed predominantly in the tumor endothelium and in cancer cells [3, 4]. Here, we have investigated the role of TEM8 in cancer progression, angiogenesis and metastasis in invasive breast cancer, and validated the main findings and important results in colorectal cancer. We show that the loss of TEM8 in cancer cells results in inhibition of cancer progression, reduction in tumor angiogenesis and reduced metastatic burden in breast cancer mouse models. Furthermore, we show that TEM8 regulates cancer progression by affecting the expression levels of cell cycle-related genes. Taken together, our findings may have broad clinical and therapeutic potential for breast and colorectal primary tumor and metastasis treatment by targeting TEM8.

The impact of toceranib, piroxicam and thalidomide with or without hypofractionated radiation therapy on clinical outcome in dogs with inflammatory mammary carcinoma

In dogs, inflammatory mammary carcinoma is a clinicopathological entity characterized by rapid progression and aggressive behavior from onset of disease. Reported median survival time is short, with no effective treatment options. The aims of this prospective, noncontrolled clinical trial were to investigate outcome variables and safety profile of toceranib, thalidomide and piroxicam with or without hypofractionated radiation therapy in dogs with measurable histologically confirmed inflammatory mammary carcinoma that underwent a complete staging. Eighteen dogs were enrolled: 14 received medical treatment, and 4 were treated with hypofractionated radiation therapy and medical therapy. Overall, median time to progression was 34 days and median survival time was 109 days. In dogs treated with medical therapy, overall response rate was 21%, and clinical benefit rate (CBR) was 64%; median time to progression was 28 days and median survival time was 59 days. In dogs receiving medical therapy and undergoing radiation therapy, overall response rate and clinical benefit rate were 100%, with significantly longer time to progression (156 days) and survival time (180 days). Overall, treatment was well tolerated, with mild gastrointestinal and dermatological adverse events. Although the optimal treatment to this disease remains uncertain, the current approach consisting of systemic anti-angiogenic drugs with or without hypofractionated radiation therapy, provided clinical benefit in a significant proportion of dogs and should, therefore, be further explored.

The synergistic effects of Apatinib combined with cytotoxic chemotherapeutic agents on gastric cancer cells and in a fluorescence imaging gastric cancer xenograft model

Introduction

Methylsulfonic apatinib (hereinafter referred to as Apatinib) is a small-molecule angiogenesis inhibitor highly and selectively targeted to vascular endothelial growth factor receptor-2. At present, a series of basic and clinical studies have confirmed that Apatinib mono-therapy can inhibit the growth of different carcinomas. Our experiment aimed to determine whether there is a synergistic effect between the combination of the traditional cytotoxic chemotherapy drugs paclitaxel (TAX), oxaliplatin (L-OHP), 5-fluorouracil (5-FU), and Apatinib.

Materials and methods

We evaluated the combined effect using cytological experiments and a fluorescence imaging xenograft model. In vitro, the inhibition of cell proliferation increased notably when Apatinib was combined with TAX, L-OHP, and 5-FU. Then, for the mechanistic research, we selected the optimal dose of drugs that also had a synergistic effect. Apatinib combined with the aforementioned drugs, especially the combination of Apatinib and 5-FU, decreased the invasion and migration ability of the cells and increased the apoptosis ratio; expression of the anti-apoptotic protein Bcl-2 significantly decreased, and expression of the pro-apoptotic protein Bax increased. In vivo, when Apatinib was combined with TAX, L-OHP, and 5-FU, the volume of the xenograft model was significantly inhibited, the strength of the green fluorescence was weakened and the microvessel density decreased.

Results

The combination of Apatinib with TAX and 5-FU was synergistic (coefficient of drug interaction <1); the combination effect of Apatinib and L-OHP was only additive, with a shorter associated survival time.

Conclusion

The combination of Apatinib and classical chemotherapy drugs may be an optimal choice for gastric cancer treatment.

The complex ecosystem in non small cell lung cancer invasion

Many tumors are characterized by genetic instability, producing an assortment of genetic variants of tumor cells called subclones. These tumors and their surrounding environments form complex multi-cellular ecosystems, where subclones compete for resources and cooperate to perform multiple tasks, including cancer invasion. Our recent empirical studies revealed existence of such distinct phenotypes of cancer cells, leaders and followers, in lung cancer. These two cellular subclones exchange a complex array of extracellular signals demonstrating a symbiotic relationship at the cellular level. Here, we develop a computational model of the microenvironment of the lung cancer ecosystem to explore how the interactions between subclones can advance or inhibit invasion. We found that, due to the complexity of the ecosystem, invasion may have very different dynamics characterized by the different levels of aggressiveness. By altering the signaling environment, we could alter the ecological relationship between the cell types and the overall ecosystem development. Competition between leader and follower cell populations (defined by the limited amount of resources), positive feedback within the leader cell population (controlled by the focal adhesion kinase and fibronectin signaling), and impact of the follower cells to the leaders (represented by yet undetermined proliferation signal) all had major effects on the outcome of the collective dynamics. Specifically, our analysis revealed a class of tumors (defined by the strengths of fibronectin signaling and competition) that are particularly sensitive to manipulations of the signaling environment. These tumors can undergo irreversible changes to the tumor ecosystem that outlast the manipulations of feedbacks and have a profound impact on invasive potential. Our study predicts a complex division of labor between cancer cell subclones and suggests new treatment strategies targeting signaling within the tumor ecosystem.

PPARα mediates sunitinib resistance via NF-κB activation in clear cell renal cell carcinoma

Sunitinib is used as standard treatment for metastatic or unresectable clear cell renal cell carcinoma (ccRCC). However, ccRCC eventually develops resistance to sunitinib in most cases, and the mechanisms underlying such resistance have not been fully determined. Nuclear receptors (NRs) are a class of transcription factors that regulate many cellular functions by controlling gene expression, and they also play important roles in tumor development, proliferation and progression in various types of cancers. In the present study, we aimed to explore the mechanisms underlying sunitinib resistance in RCC and the potential role of NRs in sunitinib resistance. The expression profile of NRs was obtained from the Gene Expression Omnibus (GEO) RNAseq database. A total of 138 patients from GSE65615 were examined in this study. From the GEO metadata, we found that the expressions of three genes, encoding peroxisome proliferator activated receptor alpha (PPARα), androgen receptor (AR) and PPARγ, were significantly increased in sunitinib-treated samples compared with control samples. RT-PCR analysis showed that the PPARα expression at the mRNA level was significantly increased in sunitinib-resistant A498, CaKi-1 and 780-O ccRCC lines compared with their sunitinib-sensitive parental cells. Furthermore, knockdown of PPARα significantly inhibited cell proliferation in all three sunitinib-resistant ccRCC lines, successfully overcoming the resistance to sunitinib. Our results also showed that nuclear factor kappa B (NF-κB) signaling pathway was activated in sunitinib-resistant ccRCC lines, indicating that PPARα and NF-κB inhibition could play a synergistic role to modulate sunitinib resistance and suggesting that PPARα could be used as a potential target to overcome sunitinib resistance via the NF-κB pathway.

Vascular Endothelial Growth Factor-A Exerts Diverse Cellular Effects via Small G Proteins, Rho and Rap

Vascular endothelial growth factors (VEGFs) include five molecules (VEGF-A, -B, -C, -D, and placental growth factor), and have various roles that crucially regulate cellular functions in many kinds of cells and tissues. Intracellular signal transduction induced by VEGFs has been extensively studied and is usually initiated by their binding to two classes of transmembrane receptors: receptor tyrosine kinase VEGF receptors (VEGF receptor-1, -2 and -3) and neuropilins (NRP1 and NRP2). In addition to many established results reported by other research groups, we have previously identified small G proteins, especially Ras homologue gene (Rho) and Ras-related protein (Rap), as important mediators of VEGF-A-stimulated signaling in cancer cells as well as endothelial cells. This review article describes the VEGF-A-induced signaling pathways underlying diverse cellular functions, including cell proliferation, migration, and angiogenesis, and the involvement of Rho, Rap, and their related molecules in these pathways.

Sulfatinib, a novel kinase inhibitor, in patients with advanced solid tumors: results from a phase I study

Sulfatinib is a small molecule kinase inhibitor that targets tumor angiogenesis and immune modulation. This phase I study (NCT02133157) investigated the safety, pharmacokinetic characteristics, and preliminary anti-tumor activity of sulfatinib in patients with advanced solid tumors. The study included a dose-escalation phase (50-350 mg/day, 28-day cycle) with a Fibonacci (3+3) design, and a tumor-specific expansion phase investigating the tumor response to treatment. Two sulfatinib formulations were assessed: formulation 1 (5, 25, and 50 mg capsules) and formulation 2 (50 and 200 mg capsules). Seventy-seven Chinese patients received oral sulfatinib; the maximum tolerated dose was not reached. Dose-limiting toxicities included abnormal hepatic function and coagulation tests, and upper gastrointestinal hemorrhage. The most common treatment-related adverse events were proteinuria, hypertension and diarrhea. Among 34 patients receiving sulfatinib formulation 2, one patient with hepatocellular carcinoma and eight with neuroendocrine tumors exhibited a partial response; 15 had stable disease. The objective response rate was 26.5% (9/34) and the disease control rate was 70.6% (24/34). Pharmacokinetic, safety, and efficacy data supported continuous oral administration of sulfatinib at 300 mg as the recommended phase II dose. Sulfatinib exhibited an acceptable safety profile and encouraging antitumor activity in patients with advanced solid tumors, particularly neuroendocrine tumors.

Catecholamines facilitate VEGF-dependent angiogenesis via β2-adrenoceptor-induced Epac1 and PKA activation

Chronic stress has been associated with the progression of cancer and antagonists for β-adrenoceptors (βAR) are regarded as therapeutic option. As they are also used to treat hemangiomas as well as retinopathy of prematurity, a role of endothelial β₂AR in angiogenesis can be envisioned. We therefore investigated the role of β₂AR-induced cAMP formation by analyzing the role of the cAMP effector molecules exchange factor directly activated by cAMP 1 (Epac1) and protein kinase A (PKA) in endothelial cells (EC). Epac1-deficient mice showed a reduced amount of pre-retinal neovascularizations in the model of oxygen-induced retinopathy, which is predominantly driven by vascular endothelial growth factor (VEGF). siRNA-mediated knockdown of Epac1 in human umbilical vein EC (HUVEC) decreased angiogenic sprouting by lowering the expression of the endothelial VEGF-receptor-2 (VEGFR-2). Conversely, Epac1 activation by β₂AR stimulation or the Epac-selective activator cAMP analog 8-p-CPT-2’-O-Me-cAMP (8-pCPT) increased VEGFR-2 levels and VEGF-dependent sprouting. Similar to Epac1 knockdown, depletion of the monomeric GTPase Rac1 decreased VEGFR-2 expression. As Epac1 stimulation induces Rac1 activation, Epac1 might regulate VEGFR-2 expression through Rac1. In addition, we found that PKA was also involved in the regulation of angiogenesis in EC since the adenylyl cyclase (AC) activator forskolin (Fsk), but not 8-pCPT, increased sprouting in Epac1-depleted HUVEC and this increase was sensitive to a selective synthetic peptide PKA inhibitor. In accordance, β₂AR- and AC-activation, but not Epac1 stimulation increased VEGF secretion in HUVEC.

Our data indicate that high levels of catecholamines, which occur during chronic stress, prime the endothelium for angiogenesis through a β₂AR-mediated increase in endothelial VEGFR-2 expression and VEGF secretion.

Molecular Targeted Drugs and Treatment of Colorectal Cancer: Recent Progress and Future Perspectives

Nowadays, colorectal cancer is the fourth most common type of tumor all over the world. When diagnosed, ∼50%-60% of tumors have metastasized, thus resulting in a grim prognosis. Chemotherapy is regarded as standard treatment for patients with colorectal cancer, however, limitations of chemotherapy cannot be ignored, such as low selectivity, insufficient concentrations in tumor tissues, and systemic toxicity. Recently, six targeted drugs have been approved by the U.S. Food and Drug Administration (FDA) for treatment of metastatic colorectal cancer (mCRC), including bevacizumab, aflibercept, regorafenib, cetuximab, and panitumumab. The development of these drugs marked significant advancement in the field of mCRC therapy. The addition of biologic agents to chemotherapy has prolonged the median overall survival. Now, many investigational drugs are under clinical trials, of which programmed death (PD)-1/L1 has drawn much attention. In this review, new biologic agents under clinical trials such as MEK/MET/RAS/RAF/PD-1 inhibitors with potentials for mCRC treatment are concluded by describing targeted drugs approved by FDA, to offer new insights into global trends and future development.

Size shrinkable drug delivery nanosystems and priming the tumor microenvironment for deep intratumoral penetration of nanoparticles

The penetration of nanomedicine into solid tumor still constitutes a great challenge for cancer therapy, which lead to the failure of thorough clearance of tumor cells. Aiming at solving this issue, lots of encouraging progress has been made in the development of multistage nanoparticles triggered by various stimuli in the past few years. Besides, the therapeutical effects of nanoagents are also greatly impacted by the complex tumor microenvironment, and remodeling tumor microenvironment has become another important approach for promoting nanoparticles penetration. In this review, we summarize and analyze recent research progress and challenges in promoting nanoparticle penetration based on two kinds of different strategies, which include size shrinkable nanoparticles and priming tumor microenvironments. Especially, many recent reported multi-strategy approaches based on particle size reduction in conjugated with other therapeutic strategies are discussed. And we expect to provide some useful enlightenments and proposals on nanotechnology-based drug delivery systems for more effective therapy of solid tumors.

Discovery of cell surface vimentin targeting mAb for direct disruption of GBM tumor initiating cells

Intracellular vimentin overexpression has been associated with epithelial–mesenchymal transition, metastasis, invasion, and proliferation, but cell surface vimentin (CSV) is less understood. Furthermore, it remains unknown whether CSV can serve as a therapeutic target in CSV-expressing tumor cells. We found that CSV was present on glioblastoma multiforme (GBM) cancer stem cells and that CSV expression was associated with spheroid formation in those cells. A newly developed monoclonal antibody against CSV, 86C, specifically and significantly induced apoptosis and inhibited spheroid formation in GBM cells in vitro. The addition of 86C to GBM cells in vitro also led to rapid internalization of vimentin and decreased GBM cell viability. These findings were associated with an increase in caspase-3 activity, indicating activation of apoptosis. Finally, treatment with 86C inhibited GBM progression in vivo. In conclusion, CSV-expressing GBM cells have properties of tumor initiating cells, and targeting CSV with the monoclonal antibody 86C is a promising approach in the treatment of GBM.

VEGF pathway targeting agents, vessel normalization and tumor drug uptake: from bench to bedside

Vascular endothelial growth factor (VEGF) pathway targeting agents have been combined with other anticancer drugs, leading to improved efficacy in carcinoma of the cervix, stomach, lung, colon and rectum, ovary, and breast. Vessel normalization induced by VEGF pathway targeting agents influences tumor drug uptake. Following bevacizumab treatment, preclinical and clinical studies have shown a decrease in tumor delivery of radiolabeled antibodies and two chemotherapeutic drugs. The decrease in vessel pore size during vessel normalization might explain the decrease in tumor drug uptake. Moreover, the addition of bevacizumab to cetuximab, or panitumumab in colorectal cancer patients or to trastuzumab in breast cancer patients, did not improve efficacy. However, combining bevacizumab with chemotherapy did increase efficacy in some cancer types. Novel biomarkers to select patients who may benefit from combination therapies, such as the effect of an angiogenesis inhibitor on tumor perfusion, requires innovative trial designs and large clinical trials. Small imaging studies with radiolabeled drugs could be used in the interphase to gain further insight into the interplay between VEGF targeted therapy, vessel normalization and tumor drug delivery.

Successful treatment using apatinib with or without docetaxel in heavily pretreated advanced non-squamous non-small cell lung cancer: A case report and literature review

Although targeted therapy directed toward driver mutations has produced a significant efficacy benefit for patients with non-small cell lung cancer (NSCLC), many patients do not possess mutations associated with the approved targeted drugs. Angiogenic agents play an important role in the therapeutic strategy for advanced NSCLC. Apatinib is a novel tyrosine kinase inhibitor that targets vascular endothelial growth factor receptor-2. A phase II clinical trial demonstrated the survival benefit of apatinib monotherapy in advanced NSCLC. Moreover, addition of anti-angiogenic agents to chemotherapy showed robust efficacy in advanced NSCLC, regardless of tumor histology. Here, we present the case of a heavily pretreated lung adenocarcinoma patient who was treated with apatinib and apatinib continuation plus docetaxel re-challenge. He was negative for several driver genes, including EGFR, ALK, KRAS, ROS1, HER2, RET and BRAF. The previous treatment included platinum-based doublets, pemetrexed monotherapy, docetaxel plus bevacizumab, gefitinib monotherapy, nab-paclitaxel monotherapy, irinotecan plus oxaliplatin and radiotherapy. He obtained a partial response after both apatinib monotherapy and apatinib plus docetaxel treatment, with progression-free survival durations of 5 months and 6 months, respectively. This case indicated that apatinib monotherapy or apatinib plus docetaxel might be regarded as a therapeutic option for heavily pretreated patients with advanced non-squamous NSCLC.

REST upregulates gremlin to modulate diffuse intrinsic pontine glioma vasculature

Diffuse intrinsic pontine glioma (DIPG) is a highly aggressive glial tumor that occurs in children. The extremely poor median and 5-year survival in children afflicted with DIPG highlights the need for novel biology-driven therapeutics. Here, we have implicated the chromatin remodeler and regulator of brain development called RE1 Silencing Transcription Factor (REST), in DIPG pathology. We show that REST protein is aberrantly elevated in at least 21% of DIPG tumors compared to normal controls. Its knockdown in DIPG cell lines diminished cell growth and decreased their tumorigenicity in mouse intracranial models. DIPGs are vascularized tumors and interestingly, REST loss in DIPG cells also caused a substantial decline in tumor vasculature as measured by a decrease in CD31 and VEGFR2 staining. These observations were validated in vitro, where a significant decline in tube formation by human umbilical vein endothelial cells (HUVEC) was seen following REST-loss in DIPG cells. Mechanistically, REST controlled the secretion of a pro-angiogenic molecule and ligand for VEGFR2 called Gremlin-1 (GREM-1), and was associated with enhanced AKT activation. Importantly, the decline in tube formation caused by REST loss could be rescued by addition of recombinant GREM-1, which also caused AKT activation in HUVECs and human brain microvascular endothelial cells (HBMECs). In summary, our study is the first to demonstrate autocrine and paracrine functions for REST in DIPG development. It also provides the foundation for future investigations on anti-angiogenic therapies targeting GREM-1 in combination with drugs that target REST-associated chromatin remodeling activities.

VEGF and SEMA4D have synergistic effects on the promotion of angiogenesis in epithelial ovarian cancer

BACKGROUND

Anti-angiogenesis therapy that targets VEGF is one of the important treatment strategies in advanced ovarian cancer. However, depending on the pharmaceutical agent, treatment can have undesirable side effects. SEMA4D has recently gained interest for its role in promoting angiogenesis. Here, we try to further understand the mechanism by which SEMA4D promotes angiogenesis in ovarian cancer.

METHODS

Correlation and western blot assaya were used to detect the relationship between VEGF and SEMA4D in clinical tissues and cells. Vasculogenic mimicry and transwell migration analyses were used to detect the roles of VEGF, SEMA4D and plexin-B1 on vasculogenic mimicry and migration. Vascular density and SEMA4D expression was determined using immunofluorescence staining in clinical tissues of EOC. Western blot was used to detect the expressions of CD31, MMP2 and VE-cadherin. We also analyzed the relationship between VEGF-SEMA4D and malignant tumor prognosis.

RESULTS

We found that knockdown of VEGF could suppress SEMA4D expression and that the expressions of VEGF and SEMA4D have a positive correlation in EOC cancer tissues. Vasculogenic mimicry and transwell migration analyses showed that SEMA4D and VEGF have a synergistic effect on the promotion of angiogenesis in A2780 and HUVEC cells. Soluble SEMA4D (sSEMA4D) could promote VM and migration in A2780 and HUVEC cells via the SEMA4D/plexin-B1 pathway, but the effect was not noted in stably transfected shR-plexin-B1 cells. In clinical tissues of EOC, the vascular density and SEMA4D/plexin-B1 expression were higher. When VEGF, SEMA4D and plexin-B1 was knocked down, the expression of CD31, MMP2 and VE-cadherin, which are the markers and initiators of angiogenesis and the epithelial-mesenchymal transition (EMT) process were reduced. VEGF and SEMA4D had a positive correlation with the malignant degree of ovarian cancer, and SEMA4D can serve as an independent prognostic factor.

CONCLUSIONS

VEGF and SEMA4D have synergistic effects on the promotion of angiogenesis in epithelial ovarian cancer. Targeting VEGF and the SEMA4D signaling pathway could be important for the therapy for EOC.

The GDNF Family: A Role in Cancer?

The glial cell line-derived neurotrophic factor (GDNF) family of ligands (GFLs) comprising of GDNF, neurturin, artemin, and persephin plays an important role in the development and maintenance of the central and peripheral nervous system, renal morphogenesis, and spermatogenesis. Here we review our current understanding of GFL biology, and supported by recent progress in the area, we examine their emerging role in endocrine-related and other non-hormone-dependent solid neoplasms. The ability of GFLs to elicit actions that resemble those perturbed in an oncogenic phenotype, alongside mounting evidence of GFL involvement in tumor progression, presents novel opportunities for therapeutic intervention.

LW-215, a newly synthesized flavonoid, exhibits potent anti-angiogenic activity in vitro and in vivo

LW-215 is a newly synthesized flavonoid, which is the derivative of wogonin. Our group has previously confirmed that wogonin has an anti-angiogenic activity, while the anti-angiogenic effect of LW-215 is unclear. In this study, we explored whether LW-215 can inhibit angiogenesis and further probed the potential molecular mechanisms. We found that LW-215 inhibited migration and tube formation in human umbilical vein endothelial cells (HUVECs) and immortalized endothelial EA.hy926 cells without a significant decrease in cell viability. Microvessels sprouting from rat aortic ring and chicken chorioallantoic membrane (CAM) model also revealed that LW-215 could suppress angiogenesis in vivo. Western blot and ELISA analysis indicated that LW-215 could prevent VEGFR2 activation though reducing VEGF autocrine other than VEGFR1. Thus, its downstream kinases, such as Akt, ERK and p38 signaling, were inhibited. Taken together, these results fully showed that LW-215 might be a promising anti-angiogenesis agent.

Macrophages Facilitate Resistance to Anti-VEGF Therapy by Altered VEGFR Expression

Purpose: VEGF-targeted therapies have modest efficacy in cancer patients, but acquired resistance is common. The mechanisms underlying such resistance are poorly understood.Experimental Design: To evaluate the potential role of immune cells in the development of resistance to VEGF blockade, we first established a preclinical model of adaptive resistance to anti-VEGF therapy. Additional in vitro and in vivo studies were carried out to characterize the role of macrophages in such resistance.Results: Using murine cancer models of adaptive resistance to anti-VEGF antibody (AVA), we found a previously unrecognized role of macrophages in such resistance. Macrophages were actively recruited to the tumor microenvironment and were responsible for the emergence of AVA resistance. Depletion of macrophages following emergence of resistance halted tumor growth and prolonged survival of tumor-bearing mice. In a macrophage-deficient mouse model, resistance to AVA failed to develop, but could be induced by injection of macrophages. Downregulation of macrophage VEGFR-1 and VEGFR-3 expression accompanied upregulation of alternative angiogenic pathways, facilitating escape from anti-VEGF therapy.Conclusions: These findings provide a new understanding of the mechanisms underlying the modest efficacy of current antiangiogenesis therapies and identify new opportunities for combination approaches for ovarian and other cancers. Clin Cancer Res; 23(22); 7034-46. ©2017 AACR.

Macrophages Facilitate Resistance to Anti-VEGF Therapy by Altered VEGFR Expression

Purpose: VEGF-targeted therapies have modest efficacy in cancer patients, but acquired resistance is common. The mechanisms underlying such resistance are poorly understood.Experimental Design: To evaluate the potential role of immune cells in the development of resistance to VEGF blockade, we first established a preclinical model of adaptive resistance to anti-VEGF therapy. Additional in vitro and in vivo studies were carried out to characterize the role of macrophages in such resistance.Results: Using murine cancer models of adaptive resistance to anti-VEGF antibody (AVA), we found a previously unrecognized role of macrophages in such resistance. Macrophages were actively recruited to the tumor microenvironment and were responsible for the emergence of AVA resistance. Depletion of macrophages following emergence of resistance halted tumor growth and prolonged survival of tumor-bearing mice. In a macrophage-deficient mouse model, resistance to AVA failed to develop, but could be induced by injection of macrophages. Downregulation of macrophage VEGFR-1 and VEGFR-3 expression accompanied upregulation of alternative angiogenic pathways, facilitating escape from anti-VEGF therapy.Conclusions: These findings provide a new understanding of the mechanisms underlying the modest efficacy of current antiangiogenesis therapies and identify new opportunities for combination approaches for ovarian and other cancers. Clin Cancer Res; 23(22); 7034-46. ©2017 AACR.

Prospect of divergent roles for the CUL3 system in vascular endothelial cell function and angiogenesis

Tissue remodelling and regeneration in various pathophysiological conditions (e.g. the processes of development, pregnancy, inflammation, wound healing, tissue regeneration, tumor growth, etc.) require angiogenesis, a dynamically coordinated response to stimuli from the extracellular microenvironment. During angiogenic and angiostatic responses, endothelial cells play a central role in the blood vessel formation and regression. Angiostatic responses, which are evoked by crucial factors such as VEGF and DLL4, have been elucidated. However, it has not been revealed, how endothelial cells process these conflicting signals. The study of VEGFR-Notch cross-signalling provided some clues. We discuss here the potential roles of cullin 3-based ubiquitin E3 ligases as key players in the process of various signals in endothelial cell function and angiogenesis. Our recent findings show that they function as units to process conflicting signalling crosstalk, epigenetic regulation of key factors, and functional barrier maintenance. We also expect more divergent roles of cullin 3-based ubiquitin E3 ligases in endothelial cell function and angiogenesis, and for their potential use as therapeutic targets.

Targeting CXCR4-dependent immunosuppressive Ly6Clow monocytes improves antiangiogenic therapy in colorectal cancer

Antiangiogenic therapy with antibodies against VEGF (bevacizumab) or VEGFR2 (ramucirumab) has been proven efficacious in colorectal cancer (CRC) patients. However, the improvement in overall survival is modest and only in combination with chemotherapy. Thus, there is an urgent need to identify potential underlying mechanisms of resistance specific to antiangiogenic therapy and develop strategies to overcome them. Here we found that anti-VEGFR2 therapy up-regulates both C-X-C chemokine ligand 12 (CXCL12) and C-X-C chemokine receptor 4 (CXCR4) in orthotopic murine CRC models, including SL4 and CT26. Blockade of CXCR4 signaling significantly enhanced treatment efficacy of anti-VEGFR2 treatment in both CRC models. CXCR4 was predominantly expressed in immunosuppressive innate immune cells, which are recruited to CRCs upon anti-VEGFR2 treatment. Blockade of CXCR4 abrogated the recruitment of these innate immune cells. Importantly, these myeloid cells were mostly Ly6Clow monocytes and not Ly6Chigh monocytes. To selectively deplete individual innate immune cell populations, we targeted key pathways in Ly6Clow monocytes (Cx3cr1-/- mice), Ly6Chigh monocytes (CCR2-/- mice), and neutrophils (anti-Ly6G antibody) in combination with CXCR4 blockade in SL4 CRCs. Depletion of Ly6Clow monocytes or neutrophils improved anti-VEGFR2-induced SL4 tumor growth delay similar to the CXCR4 blockade. In CT26 CRCs, highly resistant to anti-VEGFR2 therapy, CXCR4 blockade enhanced anti-VEGFR2-induced tumor growth delay but specific depletion of Ly6G+ neutrophils did not. The discovery of CXCR4-dependent recruitment of Ly6Clow monocytes in tumors unveiled a heretofore unknown mechanism of resistance to anti-VEGF therapies. Our findings also provide a rapidly translatable strategy to enhance the outcome of anti-VEGF cancer therapies.

VEGF as a potential target in lung cancer

Introduction The vascular endothelial growth factor A (VEGF) is the main mediator of angiogenesis. In addition, VEGF contributes to cancer growth and metastasis directly targeting tumor cells. VEGF overexpression and/or high VEGF serum levels have been reported in lung cancer. Areas covered We searched Pubmed for relevant preclinical studies with the terms 'lung cancer' 'VEGF' and 'in vivo'. We also searched the Clinicaltrials.gov database, the FDA and the EMA websites for the most recent updates on clinical development of anti-VEGF agents. Expert opinion VEGF plays an important role in sustaining the development and progression of lung cancer and it might represent an attractive target for therapeutic strategies. Nevertheless, clinical trials failed to attend the promising expectations deriving from preclinical studies with anti-VEGF agents. To improve the efficacy of anti-VEGF therapies in lung cancer, potential strategies might be the employment of combinatory therapies with immune checkpoint inhibitors or agents that inhibit signaling pathways and proangiogenic factors activated in response to VEGF blockade, and the identification of novel targets in the VEGF cascade. Finally, the identification of predictive markers might help to select patients who are more likely to respond to anti-angiogenic drugs.

Dextran-Catechin inhibits angiogenesis by disrupting copper homeostasis in endothelial cells

Formation of blood vessels, or angiogenesis, is crucial to cancer progression. Thus, inhibiting angiogenesis can limit the growth and spread of tumors. The natural polyphenol catechin has moderate anti-tumor activity and interacts with copper, which is essential for angiogenesis. Catechin is easily metabolized in the body and this limits its clinical application. We have recently shown that conjugation of catechin with dextran (Dextran-Catechin) improves its serum stability, and exhibits potent anti-tumor activity against neuroblastoma by targeting copper homeostasis. Herein, we investigated the antiangiogenic activity of Dextran-Catechin and its mechanism. We found that Dextran-Catechin displayed potent antiangiogenic activity in vitro and in vivo. We demonstrated Dextran-Catechin generates reactive oxygen species which in turns disrupts copper homeostasis by depleting the copper importer CTR-1 and copper trafficking ATOX-1 protein. Mechanistically, we showed that disrupting copper homeostasis by knockdown of either CTR-1 or ATOX-1 protein can inhibit angiogenesis in endothelial cells. This data strongly suggests the Dextran-Catechin potent antiangiogenic activity is mediated by disrupting copper homeostasis. Thus, compounds such as Dextran-Catechin that affects both tumor growth and angiogenesis could lead the way for development of new drugs against high copper levels tumors.

Evaluation of epigenetic inactivation of vascular endothelial growth factor receptors in head and neck squamous cell carcinoma

The aim of this study was to determine the methylation status of the genes encoding the vascular endothelial growth factor receptors and to evaluate the usefulness of VEGFR methylation as a prognostic indicator in head and neck squamous cell carcinoma. VEGFR messenger RNA expression and promoter methylation were examined in a panel of cell lines via quantitative reverse transcription and methylation-specific polymerase chain reaction, respectively. Promoter methylation was compared with clinical characteristics in 128 head and neck squamous cell carcinoma samples. The normalized methylation values for the VEGFR1, VEGFR2 and VEGFR3 promoters tended to be higher in the tumour cell lines than in normal tonsil samples, whereas amounts of VEGFR1, VEGFR2 and VEGFR3 messenger RNA were significantly higher. Methylation of the VEGFR1 promoter (p = 0.003; 66/128 head and neck squamous cell carcinoma samples, 52%) and VEGFR3 promoter (p = 0.043; 53/128 head and neck squamous cell carcinoma samples, 41%) significantly correlated with recurrence, whereas methylation of the VEGFR2 promoter significantly correlated with lymph node metastasis (p = 0.046; 47/128 head and neck squamous cell carcinoma samples, 37%). Concurrent methylation of the VEGFR1 and VEGFR3 promoters significantly correlated with reduced disease-free survival (log-rank test, p = 0.009). In a multivariate logistic regression analysis, methylation of the VEGFR1, VEGFR3 and both the VEGFR1 and VEGFR3 promoters independently predicted recurrence (odds ratios and 95% confidence intervals: 3.19, 1.51-6.75 (p = 0.002); 2.24, 1.06-4.76 (p = 0.035); and 2.56, 1.09-6.05 (p = 0.032), respectively). Methylation of the VEGFR promoters predicts poor prognosis in head and neck squamous cell carcinoma patients.

Stromal-Based Signatures for the Classification of Gastric Cancer

Treatment of metastatic gastric cancer typically involves chemotherapy and monoclonal antibodies targeting HER2 (ERBB2) and VEGFR2 (KDR). However, reliable methods to identify patients who would benefit most from a combination of treatment modalities targeting the tumor stroma, including new immunotherapy approaches, are still lacking. Therefore, we integrated a mouse model of stromal activation and gastric cancer genomic information to identify gene expression signatures that may inform treatment strategies. We generated a mouse model in which VEGF-A is expressed via adenovirus, enabling a stromal response marked by immune infiltration and angiogenesis at the injection site, and identified distinct stromal gene expression signatures. With these data, we designed multiplexed IHC assays that were applied to human primary gastric tumors and classified each tumor to a dominant stromal phenotype representative of the vascular and immune diversity found in gastric cancer. We also refined the stromal gene signatures and explored their relation to the dominant patient phenotypes identified by recent large-scale studies of gastric cancer genomics (The Cancer Genome Atlas and Asian Cancer Research Group), revealing four distinct stromal phenotypes. Collectively, these findings suggest that a genomics-based systems approach focused on the tumor stroma can be used to discover putative predictive biomarkers of treatment response, especially to antiangiogenesis agents and immunotherapy, thus offering an opportunity to improve patient stratification. Cancer Res; 76(9); 2573-86. ©2016 AACR.

Early Actions of Anti-Vascular Endothelial Growth Factor/Vascular Endothelial Growth Factor Receptor Drugs on Angiogenic Blood Vessels

Tumors induce their heterogeneous vasculature by secreting vascular endothelial growth factor (VEGF)-A. Anti-VEGF/VEGF receptor (VEGFR) drugs treat cancer, but the underlying mechanisms remain unclear. An adenovirus expressing VEGF-A (Ad-VEGF-A¹⁶⁴) replicates the tumor vasculature in mice without tumor cells. Mother vessels (MV) are the first angiogenic vessel type to form in tumors and after Ad-VEGF-A¹⁶⁴. Multiday treatments with a VEGF trap reverted MV back to normal microvessels. We now show that, within hours, a single dose of several anti-VEGF drugs collapsed MV to form glomeruloid microvascular proliferations (GMP), accompanied by only modest endothelial cell death. GMP, common in many human cancers but of uncertain origin, served as an intermediary step in MV reversion to normal microvessels. The vasodisruptive drug combretastatin CA4 also targeted MV selectively but acted differently, extensively killing MV endothelium. Antivascular changes were quantified with a novel Evans blue dye assay that measured vascular volumes. As in tumors, Ad-VEGF-A¹⁶⁴ strikingly increased endothelial nitric oxide synthase (eNOS) expression. The eNOS inhibitor N(G)-Nitro-l-arginine methyl ester mimicked anti-VEGF/VEGFR drugs, rapidly collapsing MV to GMP. Inhibition of eNOS reduces synthesis of its vasodilatory product, nitric oxide, leading to arterial contraction. Patients and mice receiving anti-VEGF/VEGFR drugs develop hypertension, reflecting systemic arterial contraction. Together, anti-VEGF/VEGFR drugs act in part by inhibiting eNOS, causing vasocontraction, MV collapse to GMP, and subsequent reversion of GMP to normal microvessels, all without extensive vascular killing.

Loss of Complement Factor H in Plasma Increases Endothelial Cell Migration

Tumor growth depends on angiogenesis, the growth of new blood vessels. Complement factor H (CFH) is a plasma glycoprotein that functions as a regulator of the complement system. The aim of this study is to delineate the role of CFH in angiogenesis. A conditional null allele of the Cfh gene was generated in C57BL/6J mice by flanking the exon 3 with loxP sites. The Cfh^flox/flox mice were crossed with Rosa26-Cre mice to obtain the mice homozygotes of Cfh deletion (Cfh^-/-). The Cfh^-/- mice were examined by in vivo angiogenesis assays. Mouse endothelial cells were treated with media containing 5% of mouse plasma from the wildtype or Cfh^-/- mice and assayed for proliferation, viability and migration. The Cfh^-/- mice did not display any obvious abnormalities. They demonstrated a pro-angiogenic phenotype in matrigel plug assay, but not in aorta ring assay. In vitro, loss of Cfh in plasma does not affect proliferation or viability, but significantly increases migration of mouse endothelial cells. Our findings suggest that plasma CFH inhibits angiogenesis by reduction of endothelial cell migration. Thus the mutation of CFH might lead to excessive tumor angiogenesis.

Ly6Clo monocytes drive immunosuppression and confer resistance to anti-VEGFR2 cancer therapy

Current anti-VEGF therapies for colorectal cancer (CRC) provide limited survival benefit, as tumors rapidly develop resistance to these agents. Here, we have uncovered an immunosuppressive role for nonclassical Ly6Clo monocytes that mediates resistance to anti-VEGFR2 treatment. We found that the chemokine CX3CL1 was upregulated in both human and murine tumors following VEGF signaling blockade, resulting in recruitment of CX3CR1+Ly6Clo monocytes into the tumor. We also found that treatment with VEGFA reduced expression of CX3CL1 in endothelial cells in vitro. Intravital microscopy revealed that CX3CR1 is critical for Ly6Clo monocyte transmigration across the endothelium in murine CRC tumors. Moreover, Ly6Clo monocytes recruit Ly6G+ neutrophils via CXCL5 and produce IL-10, which inhibits adaptive immunity. Preventing Ly6Clo monocyte or Ly6G+ neutrophil infiltration into tumors enhanced inhibition of tumor growth with anti-VEGFR2 therapy. Furthermore, a gene therapy using a nanoparticle formulated with an siRNA against CX3CL1 reduced Ly6Clo monocyte recruitment and improved outcome of anti-VEGFR2 therapy in mouse CRCs. Our study unveils an immunosuppressive function of Ly6Clo monocytes that, to our knowledge, has yet to be reported in any context. We also reveal molecular mechanisms underlying antiangiogenic treatment resistance, suggesting potential immunomodulatory strategies to enhance the long-term clinical outcome of anti-VEGF therapies.

Pro- and antiangiogenic VEGF and its receptor status for the severity of diabetic retinopathy

PURPOSE

Alteration of pro- and antiangiogenic homeostasis of vascular endothelial growth factor (VEGF) isoforms in patients with hyperglycemia seems crucial but substantially unexplored at least quantitatively for diabetic retinopathy (DR). Therefore, in the present study we aimed to estimate the difference between the pro- (VEGF₁₆₅a) and antiangiogenic (VEGF₁₆₅b) VEGF isoforms and its soluble receptors for severity of DR.

METHODS

The study included 123 participants (diabetic retinopathy: 81, diabetic control: 20, non-diabetic control: 22) from the Regional Institute of Ophthalmology, Kolkata. The protein levels of VEGF₁₆₅a (proangiogenic), VEGF₁₆₅b (antiangiogenic), VEGF receptor 1 (VEGFR1), VEGFR2, and VEGFR3 in plasma were determined with enzyme-linked immunosorbent assay (ELISA).

RESULTS

An imbalance in VEGF homeostasis, a statistically significant concomitant increase (p<0.0001) in the level of VEGF₁₆₅a and a decrease in the level of VEGF₁₆₅b, was observed with the severity of the disease. Increased differences between VEGF₁₆₅a and VEGF₁₆₅b i.e. VEGF₁₆₅a-b concomitantly increased statistically significantly with the severity of the disease (p<0.0001), patients with diffuse diabetic macular edema (DME) with proliferative DR (PDR) had the highest imbalance. The plasma soluble form of VEGFR2 concentration consistently increased statistically significantly with the severity of the disease (p<0.0001).

CONCLUSIONS

The increased difference or imbalance between the pro- (VEGF₁₆₅a) and antiangiogenic (VEGF₁₆₅b) homeostasis of the VEGF isoforms, seems crucial for an adverse prognosis of DR and may be a better explanatory marker compared with either VEGF isoform.

Early changes in glioblastoma metabolism measured by MR spectroscopic imaging during combination of anti-angiogenic cediranib and chemoradiation therapy are associated with survival

Precise assessment of treatment response in glioblastoma during combined anti-angiogenic and chemoradiation remains a challenge. In particular, early detection of treatment response by standard anatomical imaging is confounded by pseudo-response or pseudo-progression. Metabolic changes may be more specific for tumor physiology and less confounded by changes in blood-brain barrier permeability. We hypothesize that metabolic changes probed by magnetic resonance spectroscopic imaging can stratify patient response early during combination therapy. We performed a prospective longitudinal imaging study in newly diagnosed glioblastoma patients enrolled in a phase II clinical trial of the pan-vascular endothelial growth factor receptor inhibitor cediranib in combination with standard fractionated radiation and temozolomide (chemoradiation). Forty patients were imaged weekly during therapy with an imaging protocol that included magnetic resonance spectroscopic imaging, perfusion magnetic resonance imaging, and anatomical magnetic resonance imaging. Data were analyzed using receiver operator characteristics, Cox proportional hazards model, and Kaplan-Meier survival plots. We observed that the ratio of total choline to healthy creatine after 1 month of treatment was significantly associated with overall survival, and provided as single parameter: (1) the largest area under curve (0.859) in receiver operator characteristics, (2) the highest hazard ratio (HR = 85.85, P = 0.006) in Cox proportional hazards model, (3) the largest separation (P = 0.004) in Kaplan-Meier survival plots. An inverse correlation was observed between total choline/healthy creatine and cerebral blood flow, but no significant relation to tumor volumetrics was identified. Our results suggest that in vivo metabolic biomarkers obtained by magnetic resonance spectroscopic imaging may be an early indicator of response to anti-angiogenic therapy combined with standard chemoradiation in newly diagnosed glioblastoma.

Recruitment of CD11b+Ly6C+ monocytes in non-small cell lung cancer xenografts challenged by anti-VEGF antibody

A series of antibodies against vascular endothelial growth factor (VEGF) have been developed for the treatment of various types of cancer, including non-small cell lung cancer (NSCLC) in recent years. However, tumors frequently demonstrate resistance to these strategies of VEGF inhibition. Efforts to better understand the mechanism underlying the acquired resistance to anti-VEGF antibodies are warranted. In the present study, in order to develop a xenograft model of acquired resistance to anti-VEGF antibody, xenografts of human adenocarcinoma A549 cells were generated through the successive inoculation of tumor tissue explants into first (F1), second (F2) and third (F3) generations of mice treated with the anti-VEGF antibody B20. Tumor growth rate and vessel-forming ability, assessed via cluster of differentiation (CD) 31 staining, were significantly lower in the F1, F2 and F3 groups compared with in the F0 control group (P<0.01), suggesting that drug resistance was not successfully acquired. The percentages of CD11b⁺ myeloid-derived suppressor cells and lymphocyte antigen 6C (Ly6C)⁺ subsets were significantly smaller in F1, F2 and F3 groups compared with in F0 (P<0.01). However, the ratio of Ly6C⁺ to CD11b⁺ cells was significantly higher in the F3 group compared with in F0 and F1 groups (P<0.01), indicating increasing recruitment of the Ly6C⁺ subset with successive challenges with the anti-VEGF antibody. In conclusion, the recruitment of CD11b⁺Ly6C⁺ monocytes increased with successive generations of NSCLC-xenografted mice challenged by B20, an anti-VEGF agent.

Transcriptional changes induced by bevacizumab combination therapy in responding and non-responding recurrent glioblastoma patients

Background

Bevacizumab combined with chemotherapy produces clinical durable response in 25–30% of recurrent glioblastoma patients. This group of patients has shown improved survival and quality of life. The aim of this study was to investigate changes in gene expression associated with response and resistance to bevacizumab combination therapy.

Methods

Recurrent glioblastoma patients who had biomarker-accessible tumor tissue surgically removed both before bevacizumab treatment and at time of progression were included. Patients were grouped into responders (n = 7) and non-responders (n = 14). Gene expression profiling of formalin-fixed paraffin-embedded tumor tissue was performed using RNA-sequencing.

Results

By comparing pretreatment samples of responders with those of non-responders no significant difference was observed. In a paired comparison analysis of pre- and posttreatment samples of non-responders 1 gene was significantly differentially expressed. In responders, this approach revealed 256 significantly differentially expressed genes (72 down- and 184 up-regulated genes at the time of progression). Genes differentially expressed in responders revealed a shift towards a more proneural and less mesenchymal phenotype at the time of progression.

Conclusions

Bevacizumab combination treatment demonstrated a significant impact on the transcriptional changes in responders; but only minimal changes in non-responders. This suggests that non-responding glioblastomas progress chaotically without following distinct gene expression changes while responding tumors adaptively respond or progress by means of the same transcriptional changes. In conclusion, we hypothesize that the identified gene expression changes of responding tumors are associated to bevacizumab response or resistance mechanisms.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3251-3) contains supplementary material, which is available to authorized users.

Killers creating new life: caspases drive apoptosis-induced proliferation in tissue repair and disease

Apoptosis is a carefully orchestrated and tightly controlled form of cell death, conserved across metazoans. As the executioners of apoptotic cell death, cysteine-dependent aspartate-directed proteases (caspases) are critical drivers of this cellular disassembly. Early studies of genetically programmed cell death demonstrated that the selective activation of caspases induces apoptosis and the precise elimination of excess cells, thereby sculpting structures and refining tissues. However, over the past decade there has been a fundamental shift in our understanding of the roles of caspases during cell death-a shift precipitated by the revelation that apoptotic cells actively engage with their surrounding environment throughout the death process, and caspases can trigger a myriad of signals, some of which drive concurrent cell proliferation regenerating damaged structures and building up lost tissues. This caspase-driven compensatory proliferation is referred to as apoptosis-induced proliferation (AiP). Diverse mechanisms of AiP have been found across species, ranging from planaria to mammals. In this review, we summarize the current knowledge of AiP and we highlight recent advances in the field including the involvement of reactive oxygen species and macrophage-like immune cells in one form of AiP, novel regulatory mechanisms affecting caspases during AiP, and emerging clinical data demonstrating the critical importance of AiP in cancer.

Posttreatment Evaluation of Brain Gliomas

The imaging of treated gliomas is complicated by a variety of treatment related effects, which can falsely simulate disease improvement or progression. Distinguishing between disease progression and treatment effects is difficult with standard MR imaging pulse sequences and added specificity can be gained by the addition of advanced imaging techniques.

Prognostic impact of margin status in liver resections for colorectal metastases after bevacizumab

BACKGROUND

Margin status with resection of colorectal liver metastasis (CRLM) was an important prognostic factor in the years before the introduction of biological chemotherapy. This study examined outcomes following CRLM resection in patients who received neoadjuvant chemotherapy with or without the monoclonal antiangiogenic antibody bevacizumab.

METHODS

Patients who underwent surgery for CRLM at the Johns Hopkins Hospital between 2000 and 2015 were identified from an institutional database. Data regarding surgical margin status, preoperative bevacizumab administration and overall survival (OS) were assessed using multivariable analyses.

RESULTS

Of 630 patients who underwent CRLM resection, 417 (66·2 per cent) received neoadjuvant chemotherapy with (214, 34·0 per cent) or without (203, 32·2 per cent) bevacizumab. The remaining 213 (33·8 per cent) did not receive neoadjuvant chemotherapy. Univariable analysis found that positive margins were associated with worse 5-year OS than R0 resection (36·2 versus 54·9 per cent; P = 0·005). After dichotomizing by the receipt of preoperative bevacizumab versus chemotherapy alone, the prognostic value of pathological margin persisted among patients who did not receive preoperative bevacizumab (5-year OS 53·0 versus 37 per cent after R0 versus R1 resection; P = 0·010). OS was not significantly associated with margin status in bevacizumab-treated patients (5-year OS 46·8 versus 33 per cent after R0 versus R1 resection; P = 0·081), in whom 5-year survival was slightly worse (presumably reflecting more advanced disease) than among patients treated with cytotoxic agents alone. Pathological margin status was not significantly associated with 5-year OS in patients with a complete or near-complete response to chemotherapy and bevacizumab (43 versus 30 per cent after R0 versus R1 resection; P = 0·917), but this may be due to a type II error.

CONCLUSION

The impact of margin status varied according to the receipt of bevacizumab. Bevacizumab may have a role to play in improving outcomes among patients with more advanced disease.

Self-Assembled Nanoconstructs Modified with Amplified Aptamers Inhibited Tumor Growth and Retinal Vascular Hyperpermeability via Vascular Endothelial Growth Factor Capturing

Here, nanoconstructs consisting of a DNA-amplified aptamer with a biocompatible polymer backbone for capturing target biomolecules are presented. First, the polymer-DNA nanoconstructs were prepared by hybridization of two complementary single-stranded DNAs that were each conjugated to a dextran polymer backbone. The designed polymer-DNA amplified aptamer nanoconstructs (PA-aNCs) were then prepared by utilizing polymer-DNA nanoconstructs conjugated with an aptamer (PA-NCs) using a rolling circle amplification reaction to amplify the aptamer. These PA-aNCs were successfully applied to alleviate tumor growth and vascular endothelial growth factor (VEGF)-induced retinal vascular hyperpermeability in vivo through the highly effective capture of human VEGF as a target molecule. These PA-aNCs could be used as therapeutic agent for anti-VEGF therapy by efficiently capturing human VEGF.

How tumour-induced vascular changes alter angiogenesis: Insights from a computational model

A computational model was developed to describe experimentally observed vascular changes induced by the introduction of a tumour on a mouse equipped with a dorsal skinfold chamber. The vascular structure of the host tissue was segmented from in vivo images and transposed into the computational framework. Simulations of tumour-induced vascular changes were performed and include the destabilizing effects of the growth factor VEGF on the integrity of the vessels walls. The integration of those effects, that include alteration of the vessel wall elasticity and wall breaching, were required to realistically reproduce the experimental observations. The model was then used to investigate the importance of the vascular changes for oxygen delivery and tumour development. To that end, we compared simulations obtained with a dynamic vasculature with those obtained with a static one. The results showed that the tumour growth was strongly impeded by the constant vascular changes. More precisely, it is the angiogenic process itself that was affected by vascular changes occurring in bigger upstream vessels and resulting in a less efficient angiogenic network for oxygen delivery. As a consequence, tumour cells are mostly kept in a non-proliferative hypoxic state. Tumour dormancy thus appears as one potential consequence of the intense vascular changes in the host tissue.

A novel synthetic small molecule YF-452 inhibits tumor growth through antiangiogenesis by suppressing VEGF receptor 2 signaling

Tumor angiogenesis is characterized by abnormal vessel morphology, endowing tumor with highly hypoxia and unresponsive toward treatment. To date, mounting angiogenic factors have been discovered as therapeutic targets in antiangiogenic drug development. Among them, vascular endothelial growth factor receptor 2 (VEGFR2) inhibitors exerts potent antiangiogenic activity in tumor therapy. Therefore, it may provide a valid strategy for cancer treatment through targeting the tumor angiogenesis via VEGFR2 pathway. In this study, we established a high-profile compounds library and certificated a novel compound named N-(N-pyrrolidylacetyl)-9-(4-bromobenzyl)-1,3,4,9-tetrahydro-β-carboline (YF-452), which remarkably inhibited the migration, invasion and tube-like structure formation of human umbilical vein endothelial cells (HUVECs) with little toxicity invitro. Rat thoracic aorta ring assay indicated that YF-452 significantly blocked the formation of microvascular exvivo. In addition, YF-452 inhibited angiogenesis in chick chorioallantoic membrane (CAM) and mouse corneal micropocket assays. Moreover, YF-452 remarkably suppressed tumor growth in xenografts mice model. Furthermore, investigation of molecular mechanism revealed that YF-452 inhibited VEGF-induced phosphorylation of VEGFR2 kinase and the downstream protein kinases including extracellular signal regulated kinase (ERK), focal adhesion kinase (FAK) and Src. These results indicate that YF-452 inhibits angiogenesis and may be a potential antiangiogenic drug candidate for cancer therapy.

High-precision, non-invasive anti-microvascular approach via concurrent ultrasound and laser irradiation

Antivascular therapy represents a proven strategy to treat angiogenesis. By applying synchronized ultrasound bursts and nanosecond laser irradiation, we developed a novel, selective, non-invasive, localized antivascular method, termed photo-mediated ultrasound therapy (PUT). PUT takes advantage of the high native optical contrast among biological tissues and can treat microvessels without causing collateral damage to the surrounding tissue. In a chicken yolk sac membrane model, under the same ultrasound parameters (1 MHz at 0.45 MPa and 10 Hz with 10% duty cycle), PUT with 4 mJ/cm² and 6 mJ/cm² laser fluence induced 51% (p = 0.001) and 37% (p = 0.018) vessel diameter reductions respectively. With 8 mJ/cm² laser fluence, PUT would yield vessel disruption (90%, p < 0.01). Selectivity of PUT was demonstrated by utilizing laser wavelengths at 578 nm or 650 nm, where PUT selectively shrank veins or occluded arteries. In a rabbit ear model, PUT induced a 68.5% reduction in blood perfusion after 7 days (p < 0.001) without damaging the surrounding cells. In vitro experiments in human blood suggested that cavitation may play a role in PUT. In conclusion, PUT holds significant promise as a novel non-invasive antivascular method with the capability to precisely target blood vessels.

Tumor angiogenesis of SCLC inhibited by decreased expression of FMOD via downregulating angiogenic factors of endothelial cells

Fibromodulin (FMOD), an ECM small leucine-rich proteoglycan (SLRP), was reported to promote angiogenesis not only during wound healing, but also in optical and cutaneous angiogenesis-dependent diseases. However, whether it plays important roles in tumor angiogenesis remains unclear. To explore the role of FMOD in tumor angiogenesis of human small cell lung cancer (SCLC), initially the study analyzed the relationship of FMOD expression in cancer tissues of SCLC with clinical characteristics. The analysis revealed that the positive FMOD expression was significantly associated with extensive stage of SCLC and higher vascular density. In mouse models, xenograft tumors developed with FMOD-silenced H446 cells (H446-shFMOD) exhibited slowed growth rate, decreased microvessel density, and reduced blood perfusion related to that of controls (H446-shCON). Additionally, compared with that of controls, the decreased secretion of FMOD in conditioned medium (CM) from H446-shFMOD inhibited proliferation, migration, and invasion of human umbilical vessel endothelial cells (HUVECs). Moreover, the decreased secretion of FMOD downregulated the expression of VEGF, TGF-β1, FGF-2, and PDGF-B in HUVECs. The findings strongly suggested that the autocrine FMOD of cancer cells may promote tumor angiogenesis of SCLC by upregulating the expression of angiogenic factors that act in concert to facilitate the angiogenic phenotype of endothelial cells as a proangiogenic factor. Therefore, silencing FMOD may be a potentially clinical therapy for repressing tumor angiogenesis.

Anti-angiogenic Therapy in Cancer: Downsides and New Pivots for Precision Medicine

Primary solid tumors originate close to pre-existing tissue vasculature, initially growing along such tissue blood vessels, and this phenomenon is important for the metastatic potential which frequently occurs in highly vascularized tissues. Unfortunately, preclinic and clinic anti-angiogenic approaches have not been very successful, and multiple factors have been found to contribute to toxicity and tumor resistance. Moreover, tumors can highlight intrinsic or acquired resistances, or show adaptation to the VEGF-targeted therapies. Furthermore, different mechanisms of vascularization, activation of alternative signaling pathways, and increased tumor aggressiveness make this context even more complex. On the other hand, it has to be considered that the transitional restoration of normal, not fenestrated, microvessels allows the drug to reach the tumor and act with the maximum efficiency. However, these effects are time-limited and different, depending on the various types of cancer, and clearly define a specific “normalization window.” So, new horizons in the therapeutic approaches consist on the treatment of the tumor with pro- (instead of anti-) angiogenic therapies, which could strengthen a network of well-structured blood vessels that facilitate the transport of the drug.

Carbohydrate-binding protein CLEC14A regulates VEGFR-2- and VEGFR-3-dependent signals during angiogenesis and lymphangiogenesis

Controlled angiogenesis and lymphangiogenesis are essential for tissue development, function, and repair. However, aberrant neovascularization is an essential pathogenic mechanism in many human diseases, including diseases involving tumor growth and survival. Here, we have demonstrated that mice deficient in C-type lectin family 14 member A (CLEC14A) display enhanced angiogenic sprouting and hemorrhage as well as enlarged jugular lymph sacs and lymphatic vessels. CLEC14A formed a complex with VEGFR-3 in endothelial cells (ECs), and CLEC14A KO resulted in a marked reduction in VEGFR-3 that was concomitant with increases in VEGFR-2 expression and downstream signaling. Implanted tumor growth was profoundly reduced in CLEC14A-KO mice compared with that seen in WT littermates, but tumor-bearing CLEC14A-KO mice died sooner. Tumors in CLEC14A-KO mice had increased numbers of nonfunctional blood vessels and severe hemorrhaging. Blockade of VEGFR-2 signaling suppressed these vascular abnormalities and enhanced the survival of tumor-bearing CLEC14A-KO mice. We conclude that CLEC14A acts in vascular homeostasis by fine-tuning VEGFR-2 and VEGFR-3 signaling in ECs, suggesting its relevance in the pathogenesis of angiogenesis-related human disorders.

Synergic effects of VEGF-A and SDF-1 on the angiogenic properties of endothelial progenitor cells

Here we investigated the impact of hypoxic environment on the angiogenic properties of early-outgrowth endothelial progenitor cells (EPCs), with particular focus on the role of secreted vascular endothelial growth factor-A (VEGF-A) and stromal derived factor-1 (SDF-1) in mediating these effects. We found that cultured EPCs secreted factors with paracrine effects on chemotaxis, migration, proliferation and tube formation of mature endothelial cells (ECs), and these properties were not affected by hypoxia. Depletion of VEGF-A did not change the ability of EPC-conditioned medium (CM) to promote EC migration and tube formation in vitro, suggesting that the pro-angiogenic paracrine effects of EPCs did not totally rely on the presence of VEGF-A. These findings were confirmed by in vivo experiments, on a mouse model of hind limb ischaemia, which showed that VEGF-depleted EPC-CM sustained tissue perfusion at the same level as complete EPC-CM. However, concomitant deletion of VEGF-A and SDF-1 in EPC-CM impaired the pro-angiogenic properties of EPC-CM, by inhibition of EC spreading in culture, tube-like structure formation on Matrigel support, in vivo neovessels formation and ischaemic hind limb regeneration. Taken together, our data demonstrate that: (i) hypoxia does not affect the capacity of EPCs to support the angiogenic process; (ii) the absence of either VEGF-A or SDF-1 from EPC-CM can be rescued by the presence of the other one, so that the overall angiogenic effects remain unchanged; and (iii) and the concomitant deletion of VEGF-A and SDF-1 from EPC-CM impairs its pro-angiogenic effect, both in vitro and in vivo. Copyright © 2016 John Wiley & Sons, Ltd.

Suppression of tumor angiogenesis by metformin treatment via a mechanism linked to targeting of HER2/HIF-1α/VEGF secretion axis

Anti-angiogenesis is currently considered as one of the major antitumor strategies for its protective effects against tumor emergency and later progression. The anti-diabetic drug metformin has been demonstrated to significantly inhibit tumor angiogenesis based on recent studies. However, the mechanism underlying this anti-angiogenic effect still remains an enigma. In this study, we investigated metformin-induced inhibitory effect on tumor angiogenesis in vitro and in vivo. Metformin pretreatment significantly suppressed tumor paracrine signaling-induced angiogenic promotion even in the presence of heregulin (HRG)-β1 (a co-activator of HER2) pretreatment of HER2+ tumor cells. Similar to that of AG825, a specific inhibitor of HER2 phosphorylation, metformin treatment decreased both total and phosphorylation (Tyr 1221/1222) levels of HER2 protein and significantly reduced microvessel density and the amount of Fitc-conjugated Dextran leaking outside the vessel. Furthermore, our results of VEGF-neutralizing and -rescuing tests showed that metformin markedly abrogated HER2 signaling-induced tumor angiogenesis by inhibiting VEGF secretion. Inhibition of HIF-1α signaling by using RNAi or YC-1, a specific inhibitor of HIF-1α synthesis, both completely diminished mRNA level of VEGF and greatly inhibited endothelial cell proliferation promoted by HER2+ tumor cell-conditioned medium in both the absence and presence of HRG-β1 pretreatment. Importantly, metformin treatment decreased the number of HIF-1α nucleus positive cells in 4T1 tumors, accompanied by decreased microvessel density. Our data thus provides novel insight into the mechanism underlying the metformin-induced inhibition of tumor angiogenesis and indicates possibilities of HIF-1α-VEGF signaling axis in mediating HER2-induced tumor angiogenesis.

Characterization of Semaphorin 6A-Mediated Effects on Angiogenesis Through Regulation of VEGF Signaling

Angiogenesis identifies the process of endothelial cell sprouting and remodeling leading to the formation of new and functional blood vessels. Vascular expansion during development and in the adult mammal provides nutrients and oxygen to areas with increased need. Although many molecules and pathways have been identified as regulators of angiogenesis, aspects of this complex process remain unclear. Particularly undefined are the signals that orchestrate vessel survival and pruning once new blood vessels have sprouted. These poorly characterized aspects of angiogenesis need exploration. This chapter describes the experiments and methods enabling the characterization of Semaphorin 6A as a critical regulator of endothelial cell survival and vessel function.