Multiple circulating proangiogenic factors induced by sunitinib malate are tumor-independent and correlate with antitumor efficacy. Proc Natl Acad Sci U S A. 2007;104:17069-17074. [PMID: 17942672 DOI: 10.1073/pnas.0708148104]

Assessing the in vivo efficacy of biologic antiangiogenic therapies

PURPOSE

To review key clinical issues underlying the assessment of in vivo efficacy when using antiangiogenic therapies for cancer treatment.

METHODS

Literature relevant to use of antiangiogenic therapies in cancer was reviewed, with particular emphasis on the assessment of in vivo efficacy of these agents, as well as additional angiogenic factors that could play a role in escape from angiogenesis inhibition.

RESULTS

In order to grow and metastasize, tumors need to continually acquire new blood supplies; therefore, therapeutic inhibition of angiogenesis has become a component of anticancer treatment for many tumor types. Bevacizumab, a humanized monoclonal antibody directed at vascular endothelial growth factor A (VEGF-A), has shown activity in combination with chemotherapy in metastatic colorectal cancer. Nevertheless, the use of antiangiogenic therapies remains suboptimal; specifically, optimal dose, duration of therapy, and combination of agents remain unknown. Also, at present, it is not possible to determine which patients are most likely to respond to a given form of antiangiogenic therapy. There has been increased recognition of alternative pathways possibly associated with disease progression in patients undergoing antiangiogenic therapy targeted at VEGF-A. Multiligand-targeted antiangiogenic therapies, such as ziv-aflibercept (formerly known as aflibercept, VEGF Trap), are currently undergoing clinical evaluation. Ziv-aflibercept forms monomeric complexes with VEGF-A, VEGF-B, and PlGF, which have a long half-life, allowing optimization of ziv-aflibercept doses and angiogenic blockage.

CONCLUSIONS

Although antiangiogenic therapies have increased treatment options for cancer patients, their use is limited by a lack of established and standardized methodology to evaluate their efficacy in vivo. Circulating endothelial cells, hypertension, and several molecular and imaging-based markers have potential for use as biomarkers in these patients and may better define appropriate patient populations.

Pharmacogenetic biomarkers for the prediction of response to antiangiogenic treatment

Antiangiogenic treatments have shown activity across multiple tumour types and in various settings. Despite having been approved on the basis of efficacy, the therapeutic index varies substantially in different settings for many of these agents. A major limitation is the current inability to personalise treatment a priori according to findings on measurement of a predictive biomarker. The roles of germline single-nucleotide polymorphisms have been investigated as potential biomarkers for antiangiogenic treatments. The rationale is founded on the understanding that the drugs target the vasculature rather than the tumour, which could mean that much of the variability is regulated by the host. Several single-nucleotide polymorphisms have been associated with differential outcomes and toxic effects in clinical trials. In this Review we provide an overview of available data with particular attention paid to the pitfalls and strengths of potential biomarkers. We also highlight continuing work and plans for confirmatory studies.

Anti-VEGF therapies in the clinic

The development and use of antiangiogenesis agents, particularly those targeting vascular endothelial growth factor (VEGF), has become an integral component of anticancer regimens for many tumor types. This review is intended to highlight some of the most important clinical successes and failures of anti-VEGF therapies, and where possible, to suggest important lessons that have been learned. This review emphasizes data from agents that have been FDA approved and/or have completed phase III studies.

Multiscale models of breast cancer progression

Breast cancer initiation, invasion and metastasis span multiple length and time scales. Molecular events at short length scales lead to an initial tumorigenic population, which left unchecked by immune action, acts at increasingly longer length scales until eventually the cancer cells escape from the primary tumor site. This series of events is highly complex, involving multiple cell types interacting with (and shaping) the microenvironment. Multiscale mathematical models have emerged as a powerful tool to quantitatively integrate the convective-diffusion-reaction processes occurring on the systemic scale, with the molecular signaling processes occurring on the cellular and subcellular scales. In this study, we reviewed the current state of the art in cancer modeling across multiple length scales, with an emphasis on the integration of intracellular signal transduction models with pro-tumorigenic chemical and mechanical microenvironmental cues. First, we reviewed the underlying biomolecular origin of breast cancer, with a special emphasis on angiogenesis. Then, we summarized the development of tissue engineering platforms which could provide high-fidelity ex vivo experimental models to identify and validate multiscale simulations. Lastly, we reviewed top-down and bottom-up multiscale strategies that integrate subcellular networks with the microenvironment. We present models of a variety of cancers, in addition to breast cancer specific models. Taken together, we expect as the sophistication of the simulations increase, that multiscale modeling and bottom-up agent-based models in particular will become an increasingly important platform technology for basic scientific discovery, as well as the identification and validation of potentially novel therapeutic targets.

Resistance and escape from antiangiogenesis therapy: clinical implications and future strategies

Angiogenesis has long been considered an important target for cancer therapy. Initial efforts have primarily focused on targeting of endothelial and tumor-derived vascular endothelial growth factor signaling. As evidence emerges that angiogenesis has significant mechanistic complexity, therapeutic resistance and escape have become practical limitations to drug development. Here, we review the mechanisms by which dynamic changes occur in the tumor microenvironment in response to antiangiogenic therapy, leading to drug resistance. These mechanisms include direct selection of clonal cell populations with the capacity to rapidly upregulate alternative proangiogenic pathways, increased invasive capacity, and intrinsic resistance to hypoxia. The implications of normalization of vasculature with subsequently improved vascular function as a result of antiangiogenic therapy are explored, as are the implications of the ability to incorporate and co-opt otherwise normal vasculature. Finally, we consider the extent to which a better understanding of the biology of hypoxia and reoxygenation, as well as the depth and breadth of systems invested in angiogenesis, may offer putative biomarkers and novel therapeutic targets. Insights gained through this work may offer solutions for personalizing antiangiogenesis approaches and improving the outcome of patients with cancer.

Erlotinib and sorafenib in an orthotopic rat model of hepatocellular carcinoma

BACKGROUND & AIMS

The combination of erlotinib with sorafenib is currently being investigated in a phase III RCT. We studied the effect of erlotinib and sorafenib on HCC in a preclinical model.

METHODS

The Morris Hepatoma (MH) and HepG2 cells were treated in vitro with sorafenib (1-10 μM) and erlotinib (1-5 μM) and evaluated for tumor cell viability, apoptosis, and target regulation. Antiangiogenic effects were studied by measuring VEGF levels, endothelial cell viability, apoptosis, migration, and the aortic ring assay. In vivo, MH cells were implanted into the liver of syngeneic rats and treated with vehicle, sorafenib 5-10mg/kg, erlotinib 10mg/kg, and respective combinations.

RESULTS

In vitro, erlotinib downregulated p-ERK but showed no significant effect on tumor cell viability in MH and HEPG2 cells. Despite a similar target regulation, sorafenib significantly reduced cell viability of HCC cells by induction of apoptosis, in a dose-dependent manner (11 ± 5%; 20 ± 10%; 51 ± 5% for sorafenib 1, 5, 10 μM). No additional effect was observed upon combination with erlotinib. Of note, erlotinib treatment resulted in endothelial cell migration and vascular sprouting of aortic rings through induction of VEGF mRNA and protein levels in endothelial and tumor cells, which was blocked by sorafenib. In vivo, erlotinib had no single agent antitumor activity, raised serum-VEGF levels, and lacked a synergistic effect in combination with sorafenib.

CONCLUSIONS

Erlotinib had no antitumor effect on HCC in vitro nor in vivo, but induced VEGF, which may reflect a resistance mechanism to erlotinib monotherapy. No improvement of sorafenib efficacy was observed upon combination with erlotinib.

Therapeutic targeting of VEGF in the treatment of glioblastoma

INTRODUCTION

Glioblastoma (GBM) is the most common and aggressive type of primary malignant brain tumor in adults. Despite therapy with maximal safe surgical resection, radiation and temozolomide, prognosis remains poor at 14.6 months. Hence, there is an urgent need for developing novel therapeutic agents. In GBMs, the balance of angiogenic growth factors is skewed toward pro-angiogenesis and VEGF is identified as the key growth factor responsible for neovasculature. Targeting angiogenesis is hypothesized to arrest tumor growth and hence VEGF is an attractive therapeutic target.

AREAS COVERED

The purpose of this review is to discuss VEGF pathway inhibitors, their efficacy as monotherapy or in combination with other drugs, the effects on the radiographic response/assessment for GBMs, mechanisms of resistance and associated biomarkers. A short summary of angiogenesis and of the biological characteristics of angiogenesis will also be provided to enhance the understanding of VEGF pathway inhibitors.

EXPERT OPINION

Therapeutic targeting of VEGF has lead to improvements in progression-free survival in GBM patients without any change in the overall survival. VEGF-targeted therapy remains a promising therapeutic opportunity if improvements in biomarkers, imaging techniques and rational combination therapy are used to help advance the clinical efficacy of this approach.

Contrasting effects of sunitinib within in vivo models of metastasis

Sunitinib is a potent and clinically approved tyrosine kinase inhibitor that can suppress tumour growth by inhibiting angiogenesis. However, conflicting data exist regarding the effects of this drug on the growth of metastases in preclinical models. Here we use 4T1 and RENCA tumour cells, which both form lung metastases in Balb/c mice, to re-address the effects of sunitinib on the progression of metastatic disease in mice. We show that treatment of mice with sunitinib prior to intravenous injection of tumour cells can promote the seeding and growth of 4T1 lung metastases, but not RENCA lung metastases, showing that this effect is cell line dependent. However, increased metastasis occurred only upon administration of a very high sunitinib dose, but not when lower, clinically relevant doses were used. Mechanistically, high dose sunitinib led to a pericyte depletion effect in the lung vasculature that correlated with increased seeding of metastasis. By administering sunitinib to mice after intravenous injection of tumour cells, we demonstrate that while sunitinib does not inhibit the growth of 4T1 lung tumour nodules, it does block the growth of RENCA lung tumour nodules. This contrasting response was correlated with increased myeloid cell recruitment and persistent vascularisation in 4T1 tumours, whereas RENCA tumours recruited less myeloid cells and were more profoundly devascularised upon sunitinib treatment. Finally, we show that progression of 4T1 tumours in sunitinib treated mice results in increased hypoxia and increased glucose metabolism in these tumours and that this is associated with a poor outcome. Taken together, these data suggest that the effects of sunitinib on tumour progression are dose-dependent and tumour model-dependent. These findings have relevance for understanding how anti-angiogenic agents may influence disease progression when used in the adjuvant or metastatic setting in cancer patients.

Circulating biomarkers in advanced renal cell carcinoma: clinical applications

Advances in understanding the biology of renal cell carcinoma (RCC) have resulted in treatment strategies based on molecularly targeted agents that have substantially improved the outcomes of patients with metastatic RCC. Agents targeting the vascular endothelial growth factor pathway and the mammalian target of rapamycin have shown efficacy in randomized clinical trials and received international approval for treating RCC. Multiple candidate biomarkers of the biologic activity of such targeted therapies as well as markers of treatment response and patients' prognosis are being evaluated to improve drug development and to identify patients who may obtain the greatest benefit from the various treatment options. This review summarizes recent developments in identifying circulating biomarkers of targeted therapies for metastatic RCC, including soluble proteins and circulating cells.

Novel antiangiogenic therapies against advanced hepatocellular carcinoma (HCC)

Angiogenesis is a cornerstone in the process of hepatocarcinogenesis. In the sorafenib era, other antiangiogenic targeted drugs, such as monoclonal antibodies and a new generation of tyrosine kinase inhibitors, have been shown in phase II trials to be safe and effective in the treatment of advanced hepatocellular carcinoma. Several currently active phase III trials are testing these drugs, both in first- and second-line settings. Strategies to overcome primary and acquired resistance to antiangiogenic therapy are urgently needed. Novel biomarkers may help in improving the efficacy of drugs targeting angiogenesis.

Cytokine and angiogenic factors associated with efficacy and toxicity of pazopanib in advanced soft-tissue sarcoma: an EORTC-STBSG study

BACKGROUND

Pazopanib has activity in relapsed non-adipocytic soft-tissue sarcomas (STS). A series of serum cytokines and angiogenic factors (CAFs) at baseline and changes in soluble vascular endothelial growth factor receptor-2 (sVEGFR2) or placental-derived growth factor (PlGF) levels during treatment were explored for their association with outcome.

METHODS

Twenty-three baseline CAFs, and sVEGFR2 and PlGF changes were measured in 85 and 32 patients, respectively. Associations between baseline CAF levels and efficacy parameters, plus between-week 12 sVEGFR2 and PlGF levels and pazopanib-specific toxicities were investigated.

RESULTS

At baseline, low interleukin (IL)-12 p40 subunit and MPC3 levels were associated with better progression-free survival (PFS) at 12 weeks (PFS(12wks)), low basic nerve growth factor and hepatocyte growth factor with a better PFS, and low inter-cellular adhesion molecule-1 and IL-2 receptor alpha with prolonged overall survival (OS; all P<0.05). Pazopanib decreased sVEGFR2 and increased PlGF levels. Low sVEGFR2 and high PlGF levels at week 12 were associated with higher-grade hypertension, with TSH elevations and with poorer PFS(12wks), and OS (both P<0.05).

CONCLUSION

Several baseline CAFs were related to outcome parameters. Low sVEGFR2 and high PlGF at week 12 associate with several pazopanib-specific toxicities and poorer efficacy. If confirmed, these factors may be used as early markers for response to and toxicity from pazopanib, enabling further individualisation of STS treatment.

Differential drug class-specific metastatic effects following treatment with a panel of angiogenesis inhibitors

Inhibiting angiogenesis has become an important therapeutic strategy for cancer treatment but, like other current targeted therapies, benefits experienced for late-stage cancers can be curtailed by inherent refractoriness or by acquired drug resistance, requiring a need for better mechanistic understanding of such effects. Numerous preclinical studies have demonstrated that VEGF pathway inhibitors suppress primary tumour growth and metastasis. However, it has been recently reported that short-term VEGF and VEGFR inhibition can paradoxically accelerate tumour invasiveness and metastasis in certain models. Here we comprehensively compare the effects of both antibody and small molecule receptor tyrosine kinase (RTK) inhibitors targeting the VEGF-VEGFR pathway, using short-term therapy in various mouse models of metastasis. Our findings demonstrate that antibody inhibition of VEGF pathway molecules does not promote metastasis, in contrast to selected small molecule RTK inhibitors at elevated-therapeutic drug dosages. In particular, a multi-targeted RTK inhibitor, sunitinib, which most profoundly potentiated metastasis, also increased lung vascular permeability and promoted tumour cell extravasation. Mechanistically, sunitinib, but not anti-VEGF treatment, attenuated endothelial barrier function in culture and caused a global inhibition of protein tyrosine phosphorylation, including molecules important for maintaining endothelial cell-cell junctions. Together these findings indicate that, rather than a specific consequence of inhibiting the VEGF signalling pathway, pharmacological inhibitors of the VEGF pathway can have dose- and drug class-dependent side-effects on the host vasculature. These findings also advocate for the continued identification of mechanisms of resistance to anti-angiogenics and for therapy development to overcome it.

Live imaging in zebrafish reveals neu(trophil) insight into the metastatic niche

Non-cancerous immune cells can significantly contribute to tumour progression and metastases. Neutrophils associated with tumours can both promote and inhibit tumour progression, but less is known about how non-associated immune cells contribute to cancer biology. In a recent issue of the Journal of Pathology, He and colleagues use non-invasive, high-resolution imaging of the whole living animal to provide a compelling glimpse at how physiological migration of neutrophils can prepare a metastatic niche and how their activities can be altered by the unintended consequences of targeted therapeutics.

Exercise modulation of the host-tumor interaction in an orthotopic model of murine prostate cancer

The purpose of this study is to investigate the effects of exercise on cancer progression, metastasis, and underlying mechanisms in an orthotopic model of murine prostate cancer. C57BL/6 male mice (6-8 wk of age) were orthotopically injected with transgenic adenocarcinoma of mouse prostate C-1 cells (5 × 10(5)) and randomly assigned to exercise (n = 28) or a non-intervention control (n = 31) groups. The exercise group was given voluntary access to a wheel 24 h/day for the duration of the study. Four mice per group were serially killed on days 14, 31, and 36; the remaining 38 mice (exercise, n = 18; control, n = 20) were killed on day 53. Before death, MRI was performed to assess tumor blood perfusion. Primary tumor growth rate was comparable between groups, but expression of prometastatic genes was significantly modulated in exercising animals with a shift toward reduced metastasis. Exercise was associated with increased activity of protein kinases within the MEK/MAPK and PI3K/mTOR signaling cascades with subsequent increased intratumoral protein levels of HIF-1α and VEGF. This was associated with improved tumor vascularization. Multiplex ELISAs revealed distinct reductions in plasma concentrations of several angiogenic cytokines in the exercise group, which was associated with increased expression of angiogenic and metabolic genes in the skeletal muscle. Exercise-induced stabilization of HIF-1α and subsequent upregulation of VEGF was associated with "productive" tumor vascularization with a shift toward suppressed metastasis in an orthotopic model of prostate cancer.

Turning promise into progress for antiangiogenic agents in epithelial ovarian cancer

Despite efforts to improve chemotherapeutic efficacy in epithelial ovarian cancer, outcome for patients with advanced disease has remained unchanged since the introduction of standard carboplatin and paclitaxel. Interest has therefore shifted toward molecularly targeted therapies that interfere with important features of ovarian carcinogenesis, such as angiogenesis. Several angiogenesis inhibitors, targeting vascular endothelial growth factor (VEGF) ligands (bevacizumab, VEGF-Trap) or their receptors (VEGFR-targeted tyrosine kinase inhibitors) have been clinically evaluated. These agents demonstrated efficacy in phase II clinical trials. Results from phase III trials, in which bevacizumab was added to standard frontline chemotherapy, show a modest effect. Although the initial expectations for angiogenesis inhibitors have been tempered, further research is warranted to define their precise place in the treatment of ovarian cancer. This review summarizes the performed and ongoing studies with regard to angiogenesis inhibitors in ovarian cancer, and the available data on biomarkers for response prediction. Preclinical studies evaluating alternative angiogenesis inhibitors will also be discussed.

Forty-year journey of angiogenesis translational research

Forty years ago, Judah Folkman predicted that tumor growth is dependent on angiogenesis and that inhibiting this process might be a new strategy for cancer therapy. This hypothesis formed the foundation of a new field of research that represents an excellent example of how a groundbreaking scientific discovery can be translated to yield benefits for patients. Today, antiangiogenic drugs are used to treat human cancers and retinal vascular diseases. Here, we guide readers through 40 years of angiogenesis research and discuss challenges of antiangiogenic therapy.

Anti-angiogenesis therapy in cancer: current challenges and future perspectives

It has been nearly 9years since the FDA (Food and Drug Administration) approved the first anti-angiogenic drug (bevacizumab) for treatment of metastatic colorectal cancer. Other angiogenic inhibitors have since been approved or are in different stages of clinical trials. However, continued clinical and preclinical investigations have identified major drawbacks associated with the application of this class of agents, including inherent/acquired resistance and induction of tumor invasiveness. In addition, lack of thoroughly validated predictive biomarkers has been one of the major hurdles to stratify cancer patients and to monitor tumor progression and response to the therapy. Investigations in clinic and preclinical models have provided some molecular and cellular mechanisms for the above challenges. This review aims to provide a concise update from recent findings.

Antiangiogenic agents increase breast cancer stem cells via the generation of tumor hypoxia

Antiangiogenic therapy has been thought to hold significant potential for the treatment of cancer. However, the efficacy of such treatments, especially in breast cancer patients, has been called into question, as recent clinical trials reveal only limited effectiveness of antiangiogenic agents in prolonging patient survival. New research using preclinical models further suggests that antiangiogenic agents actually increase invasive and metastatic properties of breast cancer cells. We demonstrate that by generating intratumoral hypoxia in human breast cancer xenografts, the antiangiogenic agents sunitinib and bevacizumab increase the population of cancer stem cells. In vitro studies revealed that hypoxia-driven stem/progenitor cell enrichment is primarily mediated by hypoxia-inducible factor 1α. We further show that the Akt/β-catenin cancer stem cell regulatory pathway is activated in breast cancer cells under hypoxic conditions in vitro and in sunitinib-treated mouse xenografts. These studies demonstrate that hypoxia-driven cancer stem cell stimulation limits the effectiveness of antiangiogenic agents, and suggest that to improve patient outcome, these agents might have to be combined with cancer stem cell-targeting drugs.

A dickens tale of the treatment of advanced breast cancer: the past, the present, and the future

Metastatic breast cancer (MBC), a usually incurable disease, continues to vex physicians and patients. Recent decades have seen great improvements in the treatment of MBC, based on the availability of novel targeted therapeutics and more standard chemotherapeutic agents. This article describes the goals of therapy for MBC, the progress made against MBC in recent decades, the current standard of care, and the ongoing efforts of basic and translational researchers to transfer the fruits of modern scientific discovery to patients in the clinic.

Lysosomal sequestration of sunitinib: a novel mechanism of drug resistance

PURPOSE

Resistance to antiangiogenic tyrosine kinase inhibitors such as sunitinib is an important clinical problem, but its underlying mechanisms are largely unknown. We analyzed tumor sunitinib levels in mice and patients and studied sensitivity and resistance mechanisms to sunitinib.

EXPERIMENTAL DESIGN

Intratumoral and plasma sunitinib concentrations in mice and patients were determined. Sunitinib exposure on tumor cell proliferation was examined. Resistant tumor cells were derived by continuous exposure and studied for alterations in intracellular sunitinib accumulation and activity.

RESULTS

Intratumoral concentrations of sunitinib in mice and patients were 10.9 ± 0.5 and 9.5 ± 2.4 μmol/L, respectively, whereas plasma concentrations were 10-fold lower, 1.0 ± 0.1 and 0.3 ± 0.1 μmol/L, respectively. Sunitinib inhibited tumor cell growth at clinically relevant concentrations in vitro, with IC(50) values of 1.4 to 2.3 μmol/L. Continuous exposure to sunitinib resulted in resistance of 786-O renal and HT-29 colon cancer cells. Fluorescent microscopy revealed intracellular sunitinib distribution to acidic lysosomes, which were significantly higher expressed in resistant cells. A 1.7- to 2.5-fold higher sunitinib concentration in resistant cells was measured because of increased lysosomal sequestration. Despite the higher intracellular sunitinib accumulation, levels of the key signaling p-Akt and p-ERK 1/2 were unaffected and comparable with untreated parental cells, indicating reduced effectiveness of sunitinib.

CONCLUSION

We report that sunitinib inhibits tumor cell proliferation at clinically relevant concentrations and found lysosomal sequestration to be a novel mechanism of sunitinib resistance. This finding warrants clinical evaluation whether targeting lysosomal function will overcome sunitinib resistance.

Lymphangiogenesis is required for pancreatic islet inflammation and diabetes

Lymphangiogenesis is a common phenomenon observed during inflammation and engraftment of transplants, but its precise role in the immune response and underlying mechanisms of regulation remain poorly defined. Here we showed that in response to injury and autoimmunity, lymphangiogenesis occurred around islets and played a key role in the islet inflammation in mice. Vascular endothelial growth factors receptor 3 (VEGFR3) is specifically involved in lymphangiogenesis, and blockade of VEGFR3 potently inhibited lymphangiogenesis in both islets and the draining LN during multiple low-dose streptozotocin (MLDS) induced autoimmune insulitis, which resulted in less T cell infiltration, preservation of islets and prevention of the onset of diabetes. In addition to their well-known conduit function, lymphatic endothelial cells (LEC) also produced chemokines in response to inflammation. These LEC attracted two distinct CX3CR1^hi and LYVE-1⁺ macrophage subsets to the inflamed islets and CX3CR1^hi cells were influenced by LEC to differentiate into LYVE-1⁺ cells closely associated with lymphatic vessels. These observations indicate a linkage among lymphangiogenesis and myeloid cell inflammation during insulitis. Thus, inhibition of lymphangiogenesis holds potential for treating insulitis and autoimmune diabetes.

Advances in research of antiangiogenic drugs for gastric cancer

Gastric cancer is the most common cancer of the digestive system and the first leading cause of cancer deaths in China. Conventional surgery and chemotherapeutic regimens can not significantly improve the poor prognosis of gastric cancer. In recent years, molecular targeted therapy has become a hot topic in the treatment of cancers, and many antiangiogenic drugs for treatment of gastric cancer have been developed, including monoclonal antibodies or soluble receptors that bind and neutralize vascular endothelial growth factor (VEGF), tyrosine kinase receptor inhibitors, and antibodies against VEGF receptors (VEGFRs).

Mechanisms of resistance to vascular endothelial growth factor blockade

Angiogenesis is essential for the growth of primary tumors and for their metastasis. This process is induced by factors, such as vascular endothelial growth factors (VEGFs), that bind to transmembrane VEGF receptors (VEGFRs). VEGF-A is the primary factor involved with angiogenesis; it binds to both VEGFR-1 and VEGFR-2. The inhibition of angiogenesis by obstructing VEGF-A signaling has been investigated as a method to treat solid tumors, but the development of resistance to this blockade has complicated treatment. The major mechanisms of this resistance to VEGF-A blockade include signaling by redundant receptors, such as the fibroblast growth factors, angiopoietin-1, ephrins, and other forms of VEGF. Other major mechanisms of resistance are increased metastasis of hypoxia-resistant tumor cells, recruitment of cell types capable of promoting VEGF-independent angiogenesis, and increased circulation of nontumor proangiogenic factors. Additional mechanisms of resistance to VEGF-A blockade include heterogeneity of responsiveness among tumor cells, use of anti-VEGF-A agents at insufficient doses or for insufficient duration, altered sensitivity to anti-VEGF-A agents by mutations in endothelial cells or vascular remodeling, maintenance of vascular sleeves that allow for easy regrowth of tumor vasculature upon discontinuation of therapy, vascular cooption, and intussusceptive angiogenesis. An understanding of these mechanisms may lead to the development of targeted therapies that overcome this resistance. Some of these approaches include the combined inhibition of redundant angiogenic pathways, proper patient selection for various therapies based on gene expression profiles, blockade of cellular migration by inhibition of colony-stimulating factor, or the use of agents to disrupt vascular architecture.

Mechanisms of resistance to anti-angiogenic therapy and development of third-generation anti-angiogenic drug candidates

The concept of inhibiting tumor neovessels has taken the hurdle from the bench to the bedside and now represents an extra pillar of anticancer treatment. So far, anti-angiogenic therapy prolongs survival in the order of months in some settings while failing to induce a survival benefit in others, in part because of intrinsic refractoriness or evasive escape. This review provides an update on recent mechanisms via which tumor and stromal cells induce resistance and discusses recent evolutions in the (pre)clinical development of novel third-generation anti-angiogenic agents to overcome this problem.

Angiogenesis in head and neck cancer: a review of the literature

Angiogenesis is a necessary process for tumor growth, progression and diffusion. In the last years many efforts have been made to understand the mechanisms necessary to the formation of new vessels in tumor tissue and how to integrate these findings in the treatment of different type of cancer. Thanks to these studies there are today many anti-angiogenic drugs with established activity in cancer and approved in clinical practice. Head and neck cancer is a common tumor worldwide that often has advanced stage at diagnosis and poor prognosis. Angiogenesis has a well recognized role in head and neck cancer progression and resistance to drugs and radiotherapy and many clinical trials has been conducted with antiangiogenic agents in this disease, even if they often showed limited efficacy. In this review we summarize the main trials published about angiogenesis in head and neck cancer with particular attention to factors involved in this process and the available data on the efficacy of treatment with anti-angiogenic agents in this disease.

Sunitinib-induced changes in circulating endothelial cell-related proteins in patients with metastatic renal cell cancer

Vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors are effective agents in the treatment of metastatic renal cell cancer (mRCC). We here investigated whether inhibition of VEGFR signalin by sunitinib causes changes in plasma proteins associated with tumor endothelium. Forty-three patients with mRCC received sunitinib 50 mg/day in a 4-weeks on 2-weeks off schedule. Sequential plasma samples were obtained before treatment (C1D1), on C1D14, on C1D28, and on C2D1 before start of cycle 2. Plasma levels were assessed for VEGF, soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble intercellular cell adhesion molecule-1 (sICAM-1), von Willebrand factor (vWF), circulating angiopoietin-2 (Ang-2) and soluble Tie-2 (sTie-2). Total tumor burden was calculated at baseline and at first evaluation. Progression-free survival (PFS) and overall survival (OS) were determined. Tumor burden was positively associated with baseline circulating Ang-2 [Spearman's rho (ρ) = 0.378, p = 0.028] and vWF (ρ = 0.417, p = 0.008). During sunitinib treatment, circulating Ang-2 and sTie-2 significantly decreased (p < 0.001 for both), plasma levels of sVCAM-1 and VEGF significantly increased (p = 0.022 and p < 0.001), whereas those of sICAM-1 and vWF remained stable. These protein changes had recovered on C2D1. The reduction in circulating Ang-2 levels on C1D28 was positively correlated with the percentage decrease in tumor burden (ρ = 0.605; p = 0.002). Baseline protein levels and subsequent changes were not associated with PFS or OS. In conclusion, sunitinib-induced changes in Ang-2, sTie-2, sVCAM-1 and VEGF are related to the administration schedule, while reduction in Ang-2 is also associated with decrease in tumor burden.

Predictive factors of response to treatment in patients with metastatic renal cell carcinoma: new evidence

Renal cell carcinoma represents approximately 3% of adult malignancies and 90-95% of neoplasms arising from the kidney. Many agents that target angiogenesis (e.g., sunitinib, sorafenib, bevacizumab and pazopanib) and mTOR-targeted therapy (e.g., temsirolimus and everolimus) have been approved as first-line agents. The choice of the most suitable treatment for advanced renal cell carcinoma depends on the definition of risk. In this article, we reviewed the scientific literature identifying predictive factors on the activity/efficacy of a specific therapy.

Host response to short-term, single-agent chemotherapy induces matrix metalloproteinase-9 expression and accelerates metastasis in mice

Mounting evidence suggests that bone marrow-derived cells (BMDC) contribute to tumor growth, angiogenesis, and metastasis. In acute reactions to cancer therapy, several types of BMDCs are rapidly mobilized to home tumors. Although this host reaction to therapy can promote tumor regrowth, its contribution to metastasis has not been explored. To focus only on the effects of chemotherapy on the host, we studied non-tumor-bearing mice. Plasma from animals treated with the chemotherapy paclitaxel induced angiogenesis, migration, and invasion of tumor cells along with host cell colonization. Lesser effects were seen with the chemotherapy gemcitabine. Conditioned medium from BMDCs and plasma from chemotherapy-treated mice each promoted metastatic properties in tumor cells by inducing matrix metalloproteinase-9 (MMP9) and epithelial-to-mesenchymal transition. In mice in which Lewis lung carcinoma cells were injected intravenously, treatment with paclitaxel, but not gemcitabine or vehicle, accelerated metastases in a manner that could be blocked by an MMP9 inhibitor. Moreover, chimeric mice reconstituted with BMDC where MMP9 activity was attenuated did not support accelerated metastasis by carcinoma cells that were pretreated with chemotherapy before their introduction to host animals. Taken together, our findings illustrate how some chemotherapies can exert prometastatic effects that may confound treatment outcomes.

Phase I/II and pharmacodynamic study of dovitinib (TKI258), an inhibitor of fibroblast growth factor receptors and VEGF receptors, in patients with advanced melanoma

PURPOSE

Dovitinib (TKI258) is an orally available inhibitor of fibroblast growth factor (FGF), VEGF, and platelet-derived growth factor receptors. This phase I/II dose-escalation study was conducted to evaluate the safety, pharmacodynamics, and preliminary efficacy of dovitinib in the treatment of advanced melanoma.

EXPERIMENTAL DESIGN

Patients with advanced melanoma resistant or refractory to standard therapies or for whom no standard therapy was available were enrolled. Dovitinib was administered at doses ranging from 200 to 500 mg/d.

RESULTS

Forty-seven patients were enrolled. The most frequently reported adverse events were fatigue (77%; grade ≥3, 28%), diarrhea (77%; grade ≥3, 11%), and nausea (77%; grade ≥3, 9%). Six dose-limiting toxicities were observed in the 400-mg and 500-mg dose cohorts, which consisted of grade 3 nausea, fatigue, and diarrhea and grade 4 fatigue events. The maximum tolerated dose was 400 mg/d. The best tumor response was stable disease, which was observed in 12 patients. Increases in plasma FGF23, VEGF, and placental growth factor and decreases in soluble VEGF receptor 2 were noted during the first cycle of treatment, consistent with FGF receptor (FGFR) and VEGF receptor (VEGFR) inhibition. Dynamic contrast-enhanced MRI analysis showed a dose-dependent decrease in tumor blood flow and vascular permeability with dovitinib therapy. A decrease in FGFR phosphorylation was observed in paired tumor biopsy samples from a patient treated with dovitinib at a dose of 400 mg/d.

CONCLUSIONS

At a dose of 400 mg/d, dovitinib showed an acceptable safety profile and limited clinical benefit and inhibited FGFR and VEGFR.

Multicenter, phase II study of axitinib, a selective second-generation inhibitor of vascular endothelial growth factor receptors 1, 2, and 3, in patients with metastatic melanoma

PURPOSE

This multicenter, open-label, phase II study evaluated the safety and clinical activity of axitinib, a potent and selective second-generation inhibitor of vascular endothelial growth factor receptors (VEGFR)-1, 2, and 3, in patients with metastatic melanoma.

EXPERIMENTAL DESIGN

Thirty-two patients with a maximum of one prior systemic therapy received axitinib at a starting dose of 5 mg twice daily. The primary endpoint was objective response rate.

RESULTS

Objective response rate was 18.8% [95% confidence interval (CI), 7.2-36.4], comprising one complete and five partial responses with a median response duration of 5.9 months (95% CI, 5.0-17.0). Stable disease at 16 weeks was noted in six patients (18.8%), with an overall clinical benefit rate of 37.5%. Six-month progression-free survival rate was 33.9%, 1-year overall survival rate was 28.1%, and median overall survival was 6.6 months (95% CI, 5.2-9.0). The most frequently (>15%) reported nonhematologic, treatment-related adverse events were fatigue, hypertension, hoarseness, and diarrhea. Treatment-related fatal bowel perforation, a known class effect, occurred in one patient. Axitinib selectively decreased plasma concentrations of soluble VEGFR (sVEGFR)-2 and sVEGFR-3 compared with soluble stem cell factor receptor (sKIT). No significant association was noted between plasma levels of axitinib and response. However, post hoc analyses indicated potential relationships between efficacy endpoints and diastolic blood pressure of 90 mm Hg or higher as well as baseline serum lactate dehydrogenase levels.

CONCLUSIONS

Axitinib was well tolerated, showed a selective VEGFR-inhibitory profile, and showed single-agent activity in metastatic melanoma. Further evaluations of axitinib, alone and combined with chemotherapy, are ongoing.

Angiogenesis and immunity: a bidirectional link potentially relevant for the monitoring of antiangiogenic therapy and the development of novel therapeutic combination with immunotherapy

The immune system regulates angiogenesis in cancer with both pro- and antiangiogenic activities. The induction of angiogenesis is mediated by tumor-associated macrophages and myeloid-derived suppressor cells (MDSC) which produce proinflammatory cytokines, endothelial growth factors (VEGF, bFGF…), and protease (MMP9) implicated in neoangiogenesis. Some cytokines (IL-6, IL-17…) activated Stat3 which also led to the production of VEGF and bFGF. In contrast, other cytokines (IFN, IL-12, IL-21, and IL-27) display an antiangiogenic activity. Recently, it has been shown that some antiangiogenic molecules alleviates immunosuppression associated with cancer by decreasing immunosuppressive cells (MDSC, regulatory T cells), immunosuppressive cytokines (IL-10, TGFβ), and inhibitory molecules on T cells (PD-1). Some of these broad effects may result from the ability of some antiangiogenic molecules, especially cytokines to inhibit the Stat3 transcription factor. The association often observed between angiogenesis and immunosuppression may be related to hypoxia which induces both neoangiogenesis via activation of HIF-1 and VEGF and favors the intratumor recruitment and differentiation of regulatory T cells and MDSC. Preliminary studies suggest that modulation of immune markers (intratumoral MDSC and IL-8, peripheral regulatory T cells…) may predict clinical response to antiangiogenic therapy. In preclinical models, a synergy has been observed between antiangiogenic molecules and immunotherapy which may be explained by an improvement of immune status in tumor-bearing mice after antiangiogenic therapy. In preclinical models, antiangiogenic molecules promoted intratumor trafficking of effector cells, enhance endogenous anti-tumor response, and synergyzed with immunotherapy protocols to cure established murine tumors. All these results warrant the development of clinical trials combining antiangiogenic drugs and immunotherapy.

Targeting lymphangiogenesis after islet transplantation prolongs islet allograft survival

BACKGROUND

Lymphatics are important for their conduit functions of transporting antigen, immune cells, and inflammatory mediators to draining lymph nodes and to the general circulation. Lymphangiogenesis is involved in many pathologic processes; however, the roles for lymphatic responses in transplantation have not been thoroughly investigated.

METHODS

Mice were made diabetic by a single high dose of streptozotocin and then received islet allografts. Animals were treated with three different lymphatic inhibitors. FTY720, an analog of sphingosine 1-phosphate, inhibited lymphocyte migration into afferent and efferent lymphatics. Sunitinib, a kinase inhibitor, blocked several receptors, including vascular endothelial growth factor receptor 3 (VEGFR3), the major growth factor receptor for lymphatic endothelial cells. Anti-VEGFR3 monoclonal antibody specifically inhibited VEGFR3. Diabetes was determined by daily monitoring of blood glucose levels. Inflammation within islet grafts was assessed by immunohistochemistry for insulin, T cells (CD3), and lymphatics (LYVE-1).

RESULTS

After transplantation, lymphangiogenesis occurred in islet allografts and in draining lymph nodes. FTY720, sunitinib, and anti-VEGFR3 each inhibited lymphangiogenesis in the islets and significantly prolonged allograft survival. Immunofluorescent staining demonstrated that administration of each of the lymphatic inhibitors resulted in preservation of islets and β-cells along with a markedly reduced infiltration of T cells into the grafts.

CONCLUSION

Lymphangiogenesis occurs in islet allografts in response to inflammation and plays a key role in the islet inflammation in alloimmunity. Interfering with lymphatic function leads to inhibition of lymphangiogenesis and prolonged or indefinite allograft survival. These observations suggest new therapeutic targets for rejection and tolerance.

Therapeutic effect of lenalidomide in a novel xenograft mouse model of human blastic NK cell lymphoma/blastic plasmacytoid dendritic cell neoplasm

PURPOSE

Blastic natural killer (NK) cell lymphoma/blastic plasmacytoid dendritic cell neoplasm (BNKL) is a rare and aggressive neoplasia characterized by infiltration of blast CD4(+)/CD56(+) cells in the skin, the bone marrow, and peripheral blood. Currently, more efforts are required to better define molecular and biological mechanisms associated with this pathology. To the best of our knowledge, no mouse model recapitulated human BNKL so far.

EXPERIMENTAL DESIGN

Primary bone marrow cells from a BNKL patient were injected in nonobese diabetes/severe combined immunodeficient interleukin (IL) 2rγ(-/-) mice with the intent to generate the first BNKL orthotopic mouse model. Moreover, because of the lack of efficient treatments for BNKL, we treated mice with lenalidomide, an immunomodulatory and antiangiogenic drug.

RESULTS

We generated in mice a fatal disease resembling human BNKL. After lenalidomide treatment, we observed a significant reduction in the number of peripheral blood, bone marrow, and spleen BNKL cells. Tumor reduction parallels with a significant decrease in the number of circulating endothelial and progenitor cells and CD31(+) murine endothelial cells. In mice treated with lenalidomide, BNKL levels of active caspase-3 were significantly augmented, thus showing proapoptotic and cytotoxic effects of this drug in vivo. An opposite result was found for proliferating cell nuclear antigen, a proliferation marker.

CONCLUSIONS

Our BNKL model might better define the cellular and molecular mechanisms involved in this disease, and lenalidomide might be considered for the future therapy of BNKL patients.

Angiogenesis and melanoma - from basic science to clinical trials

The effective management of malignant melanoma has remained centred around the surgeon. The arrival of anti-angiogenic agents as the 'fourth' cancer treatment joining the ranks of surgery, chemotherapy and radiotherapy has been a source of renewed hope. This article provides an up-to-date review of the focus, state and rationale of clinical trials of anti-angiogenic therapies in metastatic malignant melanoma. Vascular Endothelial Growth Factor (VEGF) is by no means the only target, although perhaps the most extensively studied following the successful introduction of the anti-VEGF Antibody bevacizumab. This has been combined with other established therapies to try and improve outcomes in metastatic disease, and is being trialled in the UK to prevent metastasis in high-risk patients. We describe the encouraging preclinical work that lead to great enthusiasm for these agents, assess the key trials and their outcomes, discuss why these therapies have not revolutionised melanoma care and explore how they might be better targeted in the future.

Moving forward with metronomic chemotherapy: meeting report of the 2nd International Workshop on Metronomic and Anti-Angiogenic Chemotherapy in Paediatric Oncology

Metronomic chemotherapy, which is defined by the frequent, repetitive administration of chemotherapeutic drugs at relatively low doses, and without prolonged drug-free break, is an emerging strategy to fight cancer. Initially thought to act by targeting tumor angiogenesis, additional mechanisms have been recently unveiled, and metronomic chemotherapy is now considered to represent a form of multitargeted therapy. Despite representing a genuine alternative for advanced and/or high-risk cancer therapy, the development of metronomic approaches in pediatric oncology is still in the early stage. The few numbers of large-scale state-of-the-art clinical trials, issues regarding terminology and the limited understanding of the complex and intertwined mechanisms of action of metronomic treatments have limited progress in this important field of research. On March 18 and 19, 2010, the 2nd International Workshop on Metronomic and Anti-Angiogenic Chemotherapy in Paediatric Oncology was held in Marseille, France, and brought together clinicians, basic scientists, physician-scientists, trainees, and students from all around the world. The main aim of this international meeting was to provide a unique forum to 1) reflect on the major advances that have been made in this field of research since its creation, 2) communicate results from the most recent clinical trials and preclinical studies, 3) discuss the current and future challenges of the field, and 4) set forth a solid framework for future collaborative biologic and clinical studies. The present report documents the main preclinical and clinical data that were presented in the keynote and best abstract sessions and delivers the key messages from the meeting.

Identification of novel therapeutic targets in microdissected clear cell ovarian cancers

Clear cell ovarian cancer is an epithelial ovarian cancer histotype that is less responsive to chemotherapy and carries poorer prognosis than serous and endometrioid histotypes. Despite this, patients with these tumors are treated in a similar fashion as all other ovarian cancers. Previous genomic analysis has suggested that clear cell cancers represent a unique tumor subtype. Here we generated the first whole genomic expression profiling using epithelial component of clear cell ovarian cancers and normal ovarian surface specimens isolated by laser capture microdissection. All the arrays were analyzed using BRB ArrayTools and PathwayStudio software to identify the signaling pathways. Identified pathways validated using serous, clear cell cancer cell lines and RNAi technology. In vivo validations carried out using an orthotopic mouse model and liposomal encapsulated siRNA. Patient-derived clear cell and serous ovarian tumors were grafted under the renal capsule of NOD-SCID mice to evaluate the therapeutic potential of the identified pathway. We identified major activated pathways in clear cells involving in hypoxic cell growth, angiogenesis, and glucose metabolism not seen in other histotypes. Knockdown of key genes in these pathways sensitized clear cell ovarian cancer cell lines to hypoxia/glucose deprivation. In vivo experiments using patient derived tumors demonstrate that clear cell tumors are exquisitely sensitive to antiangiogenesis therapy (i.e. sunitinib) compared with serous tumors. We generated a histotype specific, gene signature associated with clear cell ovarian cancer which identifies important activated pathways critical for their clinicopathologic characteristics. These results provide a rational basis for a radically different treatment for ovarian clear cell patients.

Irinotecan synergistically enhances the antiproliferative and proapoptotic effects of axitinib in vitro and improves its anticancer activity in vivo

AIMS

To demonstrate the synergistic antiproliferative and proapoptotic activity of irinotecan and axitinib in vitro and the improvement of the in vivo effects on angiogenesis and pancreatic cancer.

METHODS

Proliferation and apoptotic assays were performed on human dermal microvascular endothelial cells and pancreas cancer (MIAPaCa-2, Capan-1) cell lines exposed to SN-38, the active metabolite of irinotecan, axitinib, or their simultaneous combination for 72 hours. ERK1/2 and Akt phosphorylation, the vascular endothelial growth factor (VEGF), VEGF receptor-2, and thrombospondin-1 (TSP-1) concentration were measured by ELISAs. ATP7A and ABCG2 gene expression was performed with real-time polymerase chain reaction and SN-38 intracellular concentrations were measured by high-performance liquid chromatography. Capan-1 xenografts in nude mice were treated with irinotecan and axitinib alone or in simultaneous combination.

RESULTS

A strong synergistic effect on antiproliferative and proapoptotic activity was found with the axitinib/SN-38 combination on endothelial and cancer cells. ERK1/2 and Akt phosphorylation were significantly inhibited by lower concentrations of the combined drugs in all the cell lines. Axitinib and SN-38 combined treatment greatly inhibited the expression of the ATP7A and ABCG2 genes in endothelial and cancer cells, increasing the SN-38 intracellular concentration. Moreover, TSP-1 secretion was increased in cells treated with both drugs, whereas VEGFR-2 levels significantly decreased. In vivo administration of the simultaneous combination determined an almost complete regression of tumors and tumor neovascularization.

CONCLUSIONS

In vitro results show the highly synergistic properties of simultaneous combination of irinotecan and axitinib on endothelial and pancreas cancer cells, suggesting a possible translation of this schedule into the clinics.

G-CSF supplementation with chemotherapy can promote revascularization and subsequent tumor regrowth: prevention by a CXCR4 antagonist

Recombinant granulocyte colony-stimulating factor (G-CSF) is used to accelerate recovery from chemotherapy-induced myelosuppression. G-CSF has been recently shown to stimulate angiogenesis mediated by several types of bone marrow-derived cell populations. To investigate whether G-CSF may alter tumor response to therapy, we studied Lewis lung and EMT/6 breast carcinomas in mice treated with paclitaxel (PTX) chemotherapy in combination with G-CSF. We compared the results obtained to mice treated with PTX and AMD3100, a small-molecule drug antagonist of CXCR4 which, like G-CSF, can be used to mobilize hematopoietic cells. We show that PTX combined with G-CSF treatment facilitates revascularization, leading to an improvement in blood perfusion in LLC tumors, and a decrease in hypoxia in EMT/6 tumors, thus enhancing tumor growth in comparison to PTX or PTX and AMD3100 therapies. We found that hemangiocytes but not Gr-1(+) CD11b(+) cells colonize EMT/6 tumors after treatment with PTX and G-CSF, but not PTX and AMD3100, and therefore may contribute to angiogenesis. However, increases in hemangiocyte colonization were not observed in LLC PTX and G-CSF-treated tumors, suggesting distinct mechanisms of tumor revascularization after G-CSF. Overall, our observations suggest that despite its known considerable clinical benefits, G-CSF might contribute to tumor revascularization by various mechanisms, and diminish the antitumor activity of chemotherapy, an effect that can be prevented by AMD3100.

Safety, Efficacy, and Biomarker Exploration in a Phase II Study of Bevacizumab, Oxaliplatin, and Gemcitabine in Recurrent Müllerian Carcinoma

OBJECTIVE: To explore the safety, efficacy, and biomarkers of bevacizumab with gemcitabine and oxaliplatin in women with recurrent platinum-sensitive ovarian carcinoma. METHODS: The patients received bevacizumab (10 mg/kg), gemcitabine (1000 mg/m(2)), and oxaliplatin (65 mg/m(2)) on days 1 and 15 in 28-day cycles. The patients with safely accessible tumor underwent intratumoral fluid pressure (IFP) measurements and positron-emission tomographies immediately and 2 weeks after treatment. Blood biomarkers were evaluated at 5 time points. RESULTS: The trial was closed after enrolling 19 of the 53 projected patient accrual. Thirteen (68.5%) of 19 patients showed a response (1 complete response, 12 partial responses), and 6 patients showed stable disease (31.6%). Median progressive-free survival was 36.9 weeks (258.3 days), and the median overall survival was 112.3 weeks (633 days, not reached). Toxicity was acceptable, and there were no arterial thromboses, serious bleeding, gastrointestinal perforations, or complications from the invasive procedures. Bevacizumab with chemotherapy induced a substantial drop in tumor IFP after treatment. The regimen induced sustained elevation in circulating plasma vascular endothelial growth factor (VEGF), placental growth factor (PlGF), basic fibroblast growth factor (bFGF), soluable vascular endothelial growth factor receptor 2 (sVEGFR2), and circulating progenitor cells. Plasma PlGF, VEGFR2(+) monocytes, and urinary matrix metalloproteinase 2 activity showed differential associations with treatment outcome when evaluated at baseline and after 14 days of treatment. CONCLUSIONS: Despite early termination of the study, the results indicate that the regimen was well tolerated and demonstrated activity in platinum-sensitive ovarian cancer. Biomarker evaluations showed that bevacizumab with chemotherapy significantly changed the levels of several circulating cellular and molecular biomarkers. The increases in plasma PlGF and VEGFR2(+) monocytes showed correlations with outcome. These exploratory data should be further evaluated in future studies of bevacizumab in ovarian cancer.

Phase II study of metronomic chemotherapy with bevacizumab for recurrent glioblastoma after progression on bevacizumab therapy

We evaluated the efficacy of metronomic etoposide or temozolomide administered with bevacizumab among recurrent glioblastoma (GBM) patients who progressed on prior bevacizumab therapy in a phase 2, open-label, two-arm trial. Twenty-three patients received bevacizumab (10 mg/kg) every 2 weeks with either oral etoposide (50 mg/m2) daily for 21 consecutive days each month or daily temozolomide (50 mg/m2). The primary endpoint was 6-month progression-free survival (PFS-6) and secondary endpoints included safety and overall survival. Both the etoposide and temozolomide arms of the study closed at the interim analysis due to lack of adequate anti-tumor activity. No radiographic responses were observed. Although 12 patients (52%) achieved stable disease, PFS-6 was 4.4% and the median PFS was 7.3 weeks. The only grade 4 adverse event was reversible neutropenia. Grade 3 toxicities included fatigue (n = 2) and infection (n = 1). Metronomic etoposide or temozolomide is ineffective when administered with bevacizumab among recurrent GBM patients who have progressed on prior bevacizumab therapy. Alternative treatment strategies remain critically needed for this indication.

A decrease of regulatory T cells correlates with overall survival after sunitinib-based antiangiogenic therapy in metastatic renal cancer patients

Sunitinib, an antiangiogenic molecule, is one of the first-line standard of care in the treatment of patients with metastatic renal cell carcinoma. However, it only benefits to a subgroup of patients and no predictive markers of sunitinib efficacy have been identified. Twenty-eight metastatic renal cell carcinomas were treated with sunitinib-based therapy and another subgroup of 7 primary renal cell cancer patients were also treated by sunitinib in a neoadjuvant trial. Measurements of CD3+CD4+CD25(hi) Foxp3+ regulatory T cells, an immunosuppressive cell population, were performed before and after each cycle of treatment in blood and tumor in a prospective study. We observed a decrease in the number of peripheral blood Foxp3+ regulatory T cells after each cycle of sunitinib-based therapy. The overall survival was significantly longer in patients showing a decrease in the number of Foxp3+ regulatory T cells after 2 or 3 cycles of treatment (P<0.05). The decrease in the number of regulatory T cells positively correlated with their number at baseline (P<0.01), but not with modification of tumor volume defined by Response Evaluation Criteria in Solid Tumors criteria. The clinical relevance of these results was also supported by an intratumoral decrease of regulatory T cells in 5 out of 7 patients treated by sunitinib in a neoadjuvant trial. Our study represents the first work reporting that the measurement of regulatory T cells may have a predictive value on antiangiogenic response. Antiangiogenic therapy also reversed immunosuppression in the tumor microenvironment which provides novel argument in human to favor its combination with immunotherapy.