Clinical applications of VEGF-trap (aflibercept) in cancer treatment

Advances in the treatment of malignant ascites in China

PURPOSE

Malignant ascites (MA) often occurs in recurrent abdominal malignant tumors, and the large amount of ascites associated with cancerous peritonitis not only leads to severe abdominal distension and breathing difficulties, but also reduces the patient's quality of life and ability to resist diseases, which usually makes it difficult to carry out anti-cancer treatment. The exploration of MA treatment methods is also a key link in MA treatment. This article is going to review the treatment of MA, to provide details for further research on the treatment of MA, and to provide some guidance for the clinical treatment of MA.

METHOD

This review analyzes various expert papers and summarizes them to obtain the paper.

RESULT

There are various treatment methods for MA, including systemic therapy and local therapy. Among them, systemic therapy includes diuretic therapy, chemotherapy, immunotherapy, targeted therapy, anti angiogenic therapy, CAR-T, and vaccine. Local therapy includes puncture surgery, peritoneal vein shunt surgery, acellular ascites infusion therapy, radioactive nuclide intraperitoneal injection therapy, tunnel catheter, and intraperitoneal hyperthermia chemotherapy. And traditional Chinese medicine treatment has also played a role in enhancing efficacy and reducing toxicity to a certain extent.

CONCLUSION

Although there has been significant progress in the treatment of MA, it is still one of the clinical difficulties. Exploring the combination or method of drugs with the best therapeutic effect and the least adverse reactions to control MA is still an urgent problem to be solved.

Angiogenesis in gastrointestinal stromal tumors: From bench to bedside

Gastrointestinal stromal tumors (GISTs) are rare neoplasms with an estimated incidence from 0.78 to 1-1.5 patients per 100000. They most commonly occur in the elderly during the eighth decade of life affecting predominantly the stomach, but also the small intestine, the omentum, mesentery and rectosigmoid. The available treatments for GIST are associated with a significant rate of recurrent disease and adverse events. Thorough understanding of GIST’s pathophysiology and translation of this knowledge into novel regimens or drug repurposing is essential to counter this challenge. The present review summarizes the existing evidence about the role of angiogenesis in GIST’s development and progression and discusses its clinical underpinnings.

DW-MRI for esophageal squamous cell carcinoma, correlations between ADC values with histologic differentiation and VEGF expression: A retrospective study

The aim of the present study was to assess the correlations between diffusion-weighted magnetic resonance imaging (DW-MRI) features with the histologic differentiation and the expression of vascular endothelial growth factor (VEGF) in esophageal squamous cell carcinoma (ESCC). A total of 52 patients with ESCC included in the present study received radiotherapy, and all patients underwent contrast enhanced MRI and DW-MRI prior to and following radiotherapy. The diffusion sensitivity coefficient (b value) was set as 800 s/mm². Apparent diffusion coefficient (ADC) values were automatically computed. VEGF expression was evaluated by immunohistochemical staining. The results demonstrated that the pathological grading of ESCC was positively correlated with ADC values (r=0.635, P=0.0007), and the VEGF expression was inversely correlated with ADC values (r=−0.321, P=0.008). However, no correlation was identified between the pathological grading and the VEGF expression (r=0.178, P=0.284). All patients were categorized as complete response (CR) or partial response (PR) and the ADC values were increased significantly following radiotherapy. The mean ADC values in the CR group were higher than the PR group prior to radiotherapy (t=5.156, P=0.0004). Therefore, we concluded that the DWI with ADC value measurement may represent the grade of tumor histologic differentiation and the degree of VEGF expression, and may also serve as a useful marker to predict radiotherapy and anti-VEGF response in ESCC. ADC value may be a substitution for assessing tumor angiogenesis and novel prognostic factor and contribute to the treatment of ESCC.

Targeting the Microenvironment in High Grade Serous Ovarian Cancer

Cancer⁻stroma interactions play a key role in cancer progression and response to standard chemotherapy. Here, we provide a summary of the mechanisms by which the major cellular components of the ovarian cancer (OC) tumor microenvironment (TME) including cancer-associated fibroblasts (CAFs), myeloid, immune, endothelial, and mesothelial cells potentiate cancer progression. High-grade serous ovarian cancer (HGSOC) is characterized by a pro-inflammatory and angiogenic signature. This profile is correlated with clinical outcomes and can be a target for therapy. Accumulation of malignant ascites in the peritoneal cavity allows for secreted factors to fuel paracrine and autocrine circuits that augment cancer cell proliferation and invasiveness. Adhesion of cancer cells to the mesothelial matrix promotes peritoneal tumor dissemination and represents another attractive target to prevent metastasis. The immunosuppressed tumor milieu of HGSOC is permissive for tumor growth and can be modulated therapeutically. Results of emerging preclinical and clinical trials testing TME-modulating therapeutics for the treatment of OC are highlighted.

MicroRNA-126 affects ovarian cancer cell differentiation and invasion by modulating expression of vascular endothelial growth factor

Primary ovarian cancer is the main cause of gynecological cancer-associated mortality. However, the mechanism behind the spread of ovarian cancer requires elucidation. The present study aimed to investigate the effects of microRNA-126 (miR-126) on differentiation and invasion, and its mechanism in primary ovarian cancer. Ovarian cancer SKOV3 cells transfected with LV3-has-miR-126 mimics and LV3-has-miR-126 inhibitor were produced; it was revealedthatLV-miR-126 mimics could induce cell cycle arrest at G₁ phase, suppress cell invasion through Matrigel-coated membranes and downregulate the expression of vascular endothelial growth factor (VEGF). Furthermore, LV-has-miR-126 inhibitor-transfected cells could increase the number of cells in S phase, induce cell invasion and upregulate the expression of VEGF. The present study, to the best of our knowledge, is the first to report that miR-126 may serve tumor suppressor roles by inducing G₁ cell cycle arrest and suppressing invasion in ovarian cancer cells, at least in part by targeting VEGF expression.

A novel engineered VEGF blocker with an excellent pharmacokinetic profile and robust anti-tumor activity

BACKGROUND

Relatively poor penetration and retention in tumor tissue has been documented for large molecule drugs including therapeutic antibodies and recombinant immunoglobulin constant region (Fc)-fusion proteins due to their large size, positive charge, and strong target binding affinity. Therefore, when designing a large molecular drug candidate, smaller size, neutral charge, and optimal affinity should be considered.

METHODS

We engineered a recombinant protein by molecular engineering the second domain of VEGFR1 and a few flanking residues fused with the Fc fragment of human IgG1, which we named HB-002.1. This recombinant protein was extensively characterized both in vitro and in vivo for its target-binding and target-blocking activities, pharmacokinetic profile, angiogenesis inhibition activity, and anti-tumor therapeutic efficacy.

RESULTS

HB-002.1 has a molecular weight of ~80 kDa, isoelectric point of ~6.7, and an optimal target binding affinity of <1 nM. The pharmacokinetic profile was excellent with a half-life of 5 days, maximal concentration of 20.27 μg/ml, and area under the curve of 81.46 μg·days/ml. When tested in a transgenic zebrafish embryonic angiogenesis model, dramatic inhibition in angiogenesis was exhibited by a markedly reduced number of subintestinal vessels. When tested for anti-tumor efficacy, HB-002.1 was confirmed in two xenograft tumor models (A549 and Colo-205) to have a robust tumor killing activity, showing a percentage of inhibition over 90% at the dose of 20 mg/kg. Most promisingly, HB-002.1 showed a superior therapeutic efficacy compared to bevacizumab in the A549 xenograft model (tumor inhibition: 84.7% for HB-002.1 versus 67.6% for bevacizumab, P<0.0001).

CONCLUSIONS

HB-002.1 is a strong angiogenesis inhibitor that has the potential to be a novel promising drug for angiogenesis-related diseases such as tumor neoplasms and age-related macular degeneration.

Development of DNA vaccines as an anti-hypertensive therapy or for anti-angiogenesis

INTRODUCTION

Vaccines are used as preventive medicine for infectious diseases worldwide; however, several recent studies have indicated the potential of therapeutic vaccines for managing Alzheimer's disease or hypertension.

AREAS COVERED

The concept and history of therapeutic vaccines for hypertension are introduced. The improvement of drug compliance associated with vaccines in hypertensive patients may assist in better control of blood pressure, leading to reduced complications. Recently, groups have attempted to develop a therapeutic vaccine against hypertension. The vaccine-induced anti-angiotensin II antibodies can efficiently ameliorate high blood pressure. DNA vaccines have also been designed via a similar strategy using a plasmid vector encoding a hepatitis B core (HBc)-angiotensin II fusion protein. The immunogenic molecule (i.e., HBc) is used to provide an antigen that supports the activation of T cells in this DNA vaccine system. The platform technology can also be applied to generate a VEGF vaccine for cancer.

EXPERT OPINION

To date, several clinical studies of DNA vaccines have been conducted, but their effectiveness has not been determined. We hope that the novel concept of DNA vaccines will contribute to promoting health and medicine in the future.

Prognostic and predictive role of vascular endothelial growth factor polymorphisms in breast cancer

Current evidence indicates that angiogenesis plays an important role in the pathogenesis of several malignancies, including breast cancer. The vascular endothelial growth factor (VEGF) pathway has been investigated extensively, due to its important role in angiogenesis. The major mediator of tumor angiogenesis is VEGF-A, frequently referred to as VEGF, which activates the VEGF receptor-2. The VEGF gene is located on chromosome 6 and constitutes a highly polymorphic gene. Numerous SNPs in the promoter, 5′- and 3′-untranslated regions (UTR) of VEGF gene have been recognized. This genetic variability possibly influences the production and function of VEGF. Subsequently, the VEGF SNPs may have an impact on breast cancer risk and disease outcome. Moreover, these SNPs may be of predictive value in patients receiving agents targeting the VEGF pathway. This review presents an update on the potential role of VEGF SNPs as prognostic and/or predictive markers in patients with breast cancer.

Role of aflibercept in the treatment of advanced colorectal cancer

SUMMARY Colorectal cancer is the third most common cancer in men, representing 10% of cases, and the second most common cancer in women, representing 9.4% of cases, worldwide. It is estimated that 50–60% of patients will develop metastases during the course of their disease, while 15–25% will present with synchronous metastatic lesions, reducing the probability of 5-year survival to 12%. Colon cancer represents the fourth most common cause of death from cancer worldwide and the second most common cause in developed countries. First-line therapy of advanced or metastatic colorectal carcinoma (mCRC) usually consists of the administration of oxaliplatin or irinotecan in combination with leucovorin and 5-fluorouracil. In the first- or second-line settings, monoclonal antibodies can be added to chemotherapy. Bevacizumab (anti-VEGF monoclonal antibody) is utilized with fluoropyrimidine-containing regimens in combination with oxaliplatin or irinotecan. Cetuximab can be administered in combination with irinotecan or as a single agent in patients who have wild-type KRAS. Panitumumab has also been approved for third-line single-agent therapy in KRAS wild-type patients and recently in first- and second-line therapy in combination with chemotherapy. There are no standard second-line treatments of mCRC specifically used in combination with FOLFIRI, and no drugs have been approved for patients with prior bevacizumab treatment. Aflibercept is a new angiogenesis inhibitor with a unique mechanism of action. Aflibercept is a recombinant fusion protein consisting of VEGF-binding portions from extracellular domains of the human VEGFR1 and 2 fused to the Fc portion of human IgG1. Aflibercept acts as a soluble decoy receptor that binds to VEGF-A with higher affinity than its native receptors, as well as the related ligands PIGF and VEGF-B. Aflibercept interferes with the biological actions of VEGF by ‘trapping’ VEGF and preventing it from interacting with its receptors on endothelial cells, blocking the activation of VEGFRs and the subsequent proliferation of endothelial cells; this results in inhibition of the growth of new vessels. The role of aflibercept in the management of mCRC was studied in the VELOUR trial, which showed that its addition to the FOLFIRI regimen resulted in a survival benefit, giving a statistically significant log-rank test with p = 0.0032 (hazard ratio: 0.817; 95.34% CI: 0.713–0.937). This benefit was supported by subgroup and sensitivity analyses, the increased median progression-free survival, and improved response rates observed in the aflibercept arm. Aflibercept toxicity is acceptable, manageable and within the established range of other VEGF inhibitors.

Renal cell carcinoma: how to hit the targets?

INTRODUCTION

Renal cell carcinoma (RCC) is a widespread oncourological disease with a tendency towards a slow increase of incidence. In the recent decade, there has been development of numerous effective drugs targeted at different molecules that play a dominant role in RCC carcinogenesis. Understanding of RCC carcinogenesis confirms the key role of angiogenesis in maintaining the viability of renal tumours and their metastases.

MATERIAL AND METHODS

We aimed to systemize numerous medicines, used to inhibit the angiogenesis in patients with advanced RCC according to their targets, and to analyze their efficacy.

RESULTS

There are roughly four main mechanisms of action of the targeted drugs:Blockade of circulating extracellular VEGF molecules.The selective blockade of tyrosine kinase receptors' domains.The simultaneous blockage of the tyrosine kinase receptors' domains and intracellular tyrosine kinases.The blockade of mammalian target of rapamycin (mTOR) which is responsible for support of vital functions of cancer cells. In addition to FDA officially approved drugs, numerous experimental agents have been synthesized, which are currently on initial stages of clinical studies in RCC treatment.

CONCLUSIONS

The results of the currently used targeted drugs demonstrate perspectives of metastatic RCC conservative treatment, that are able to prolong cancer-specific survival in previously doomed patients for up to 29 months. The development of schedules for sequential treatment or combination targeted therapy remains a current challenge. The quality of life is an important factor that influences remedy choice. The advantages and disadvantages of neoadjuvant and adjuvant targeted therapy are currently being intensively discussed.

Development of novel DNA vaccine for VEGF in murine cancer model

We developed DNA vaccine for vascular endothelial growth factor (VEGF), which may provide the therapeutic option instead of anti-VEGF antibody, bevacizumab. Plasmid containing VEGF mini-gene was constructed in the insertion of B-cell epitope of Hepatitis B core protein [HBc-VEGF], which was an epitope carrier. High titer of anti-VEGF antibody was observed in BALB/c mice which were intramuscularly immunized with HBc-VEGF by electropolator. In mice inoculated with colon 26 cells, tumor volume and microvessel density was decreased in HBc-VEGF with a significant prolonged survival. Co-treatment of purified IgG from immunized mice with HBc-VEGF showed in vitro neutralizing activity for VEGF-induced ERK phosphorylation and tube formation in cultured endothelial cells. Furthermore, intravitreally injection of this purified IgG reduced the neovessel formation in the mouse oxygen-induced retinopathy and laser-induced choroidal neovascularization models. These results first provided that DNA vaccine against VEGF possessed the anti-angiogenic effect, leading to prolonged survival in mouse cancer model.

Ziv-aflibercept: A novel angiogenesis inhibitor for the treatment of metastatic colorectal cancer

Purpose

The pharmacology, pharmacokinetics, clinical efficacy, safety, and administration of ziv-aflibercept in combination therapy for metastatic colorectal cancer (mCRC) are reviewed.

Summary

Ziv-aflibercept (Zaltrap, Regeneron Pharmaceuticals and sanofi-aventis) is a novel recombinant fusion protein that targets the angiogenesis signaling pathway of tumor cells by blocking vascular endothelial growth factor (VEGF) receptors that play a key role in tumor growth and metastasis; it is a more potent VEGF blocker than bevacizumab. Ziv-aflibercept is approved by the Food and Drug Administration for use in combination with fluorouracil, irinotecan, and leucovorin (the FOLFIRI regimen) for second-line treatment of patients with mCRC who have disease progression during first-line oxaliplatin-based chemotherapy. A Phase III trial demonstrated that relative to FOLFIRI therapy alone, the use of ziv-aflibercept was associated with significantly improved patient response, overall survival, and progression-free survival in patients with good performance status at baseline, including some who had received prior bevacizumab therapy. The most common grade 3 or 4 adverse effects associated with ziv-aflibercept use in clinical studies were neutropenia, hypertension, and diarrhea; the U.S. product labeling warns of potential hemorrhage and other treatment-related risks.

Conclusion

Current clinical data are insufficient to directly compare ziv-aflibercept and bevacizumab when used with standard combination chemotherapy as first- or second-line regimens for mCRC. The role of ziv-aflibercept is currently limited to the second-line setting in combination with irinotecan-based regimens in mCRC patients who have not received irinotecan previously. The role of ziv-aflibercept in chemotherapy for other tumor types is yet to be determined.

Receptor tyrosine kinase-mediated angiogenesis

The endothelial cell is the essential cell type forming the inner layer of the vasculature. Two families of receptor tyrosine kinases (RTKs) are almost completely endothelial cell specific: the vascular endothelial growth factor (VEGF) receptors (VEGFR1-3) and the Tie receptors (Tie1 and Tie2). Both are key players governing the generation of blood and lymphatic vessels during embryonic development. Because the growth of new blood and lymphatic vessels (or the lack thereof) is a central element in many diseases, the VEGF and the Tie receptors provide attractive therapeutic targets in various diseases. Indeed, several drugs directed to these RTK signaling pathways are already on the market, whereas many are in clinical trials. Here we review the VEGFR and Tie families, their involvement in developmental and pathological angiogenesis, and the different possibilities for targeting them to either block or enhance angiogenesis and lymphangiogenesis.

Anti-VEGF agents in metastatic colorectal cancer (mCRC): are they all alike?

Bevacizumab is a monoclonal antibody that binds and neutralizes vascular endothelial growth factor (VEGF)-A, a key player in the angiogenesis pathway. Despite benefits of bevacizumab in cancer therapy, it is clear that the VEGF pathway is complex, involving multiple isoforms, receptors, and alternative ligands such as VEGF-B, and placental growth factor, which could enable escape from VEGF-A-targeted angiogenesis inhibition. Recently developed therapies have targeted other ligands in the VEGF pathway (eg, aflibercept, known as ziv-aflibercept in the United States), VEGF receptors (eg, ramucirumab), and their tyrosine kinase signaling (ie, tyrosine kinase inhibitors). The goal of the current review was to identify comparative preclinical data for the currently available VEGF-targeted therapies. Sources were compiled using PubMed searches (2007 to 2012), using search terms including, but not limited to: “bevacizumab,” “aflibercept,” “ramucirumab,” and “IMC-18F1.” Two preclinical studies were identified that compared bevacizumab and the newer agent, aflibercept. These studies identified some important differences in binding and pharmacodynamic activity, although the potential clinical relevance of these findings is not known. Newer antiangiogenesis therapies should help further expand treatment options for colorectal and other cancers. Comparative preclinical data on these agents is currently lacking.

The evolving role of VEGF-targeted therapies in the treatment of metastatic colorectal cancer

Therapies that target angiogenesis and the VEGF pathway are a component of treatment for patients with metastatic colorectal cancer (mCRC). Bevacizumab is a humanized monoclonal antibody that binds to VEGFA. Chemotherapy plus bevacizumab has led to improved outcomes for mCRC patients. Despite these benefits, progressive disease invariably ensues. Multiple members of the VEGF family can potentially contribute to tumor angiogenesis and/or evasion of antiangiogenic therapy if one pathway should be inhibited. Aflibercept, a new biological agent, is a multiple angiogenic factor trap that prevents not only VEGFA, but also VEGFB and PlGF from activating their native receptors. Key clinical data for bevacizumab and aflibercept for treatment of mCRC, clinical evidence for use of these agents beyond progression, and the search for angiogenic biomarkers to better define patients most likely to benefit from these interventions will be reviewed.

Current and emerging treatments in the management of castration-resistant prostate cancer

Historically, patients diagnosed with castration-resistant prostate cancer (CRPC) have had poor survival rates. In recent years there have been significant advances in the treatment of CRPC. In addition to cytotoxic chemotherapy, treating physicians and their patients now have the option of several new agents that target not only androgen- and cytotoxic-mediated pathways, but also the patient's own immune system. In this review, we discuss the existing US FDA-approved therapies, a wide range of experimental treatments that are currently in development, and also palliative options for patients with symptoms secondary to metastatic disease. We also discuss the progression-free survival, overall survival, PSA levels and other end points used in clinical trials in order to evaluate and compare novel therapeutic options for CRPC. Currently, docetaxel and sipuleucel-T are the first line treatment options for patients with CRPC; approved second-line treatments for first line treatment failure are limited to cabazitaxel and abiraterone acetate. Recently, a few experimental agents, MDV3100 and radium-223, have demonstrated efficacy in improving overall survival in patients who had previously failed chemotherapy. These agents, and possibly others introduced in this review, are positioned to change the treatment landscape for CRPC.

Angiotensin-(1-7) reduces proliferation and angiogenesis of human prostate cancer xenografts with a decrease in angiogenic factors and an increase in sFlt-1

BACKGROUND

Prostate cancer is the most frequently diagnosed malignancy and the second-leading cause of cancer death in men. The purpose of this study was to determine the anti-proliferative and anti-angiogenic efficacy of angiotensin-(1-7) [Ang-(1-7)], an endogenous peptide hormone, in human prostate cancer xenografts.

METHODS

Human LNCaP prostate cancer cells were injected into the flank of athymic mice and tumors were treated with Ang-(1-7) for 54 days. Tumor growth and angiogenesis were determined by immunohistochemistry and western blot hybridization.

RESULTS

Ang-(1-7) markedly reduced the volume and wet weight of LNCaP xenograft tumors. Histological analysis of tumor sections from saline-treated mice showed increased Ki67 immunoreactivity and enhanced phosphorylation of the MAP kinases ERK1/2 compared to tumors from Ang-(1-7)-treated mice, suggesting that the heptapeptide reduces cell proliferation. Intratumoral vessel density was decreased in Ang-(1-7)-treated mice with an associated reduction in vascular endothelial growth factor (VEGF) and placental growth factor (PlGF), suggesting that the heptapeptide attenuates vascularization by reducing angiogenic factors. Ang-(1-7) administration markedly increased the soluble fraction of VEGF receptor 1 (sFlt-1), with a concomitant reduction in VEGF receptors 1 and 2. sFlt-1 serves as a decoy receptor that traps VEGF and PlGF, making the ligands unavailable to membrane-bound VEGF receptors and preventing activation of pro-angiogenic signaling.

CONCLUSIONS

The decrease in PlGF and VEGF coupled with the increase in sFlt-1 suggests that Ang-(1-7) may serve as a novel anti-angiogenic therapy for prostate cancer. Further, the pleiotropic mechanisms of action by Ang-(1-7) may limit angiogenic resistance that occurs with VEGF inhibitors or receptor blockers.

Antitumor effect of FP3 in a breast cancer xenograft model

FP3 is a novel vascular endothelial growth factor (VEGF) blocker proposed to have antiangiogenic properties. Previous studies revealed that FP3 is a new promising agent for treating human choroidal neovascularization (CNV)-associated age-associated macular degeneration (AMD) and has an inhibitory effect on VEGF-mediated proliferation and migration of human umbilical vein endothelial cells and VEGF-mediated vessel sprouting of the rat aortic ring in vitro. Previous studies have also revealed that FP3 has antitumor effects and antiangiogenic effects in a non-small cell lung cancer cell line (A549), as well as in patient-derived tumor tissue xenograft models of gastric cancer and colon carcinoma with lymphatic and hepatic metastases in nude mice. In the present study, the antitumor effect of FP3 in an MDA-MB-231 breast cancer xenograft model was investigated. Treatment with FP3 for 3 weeks significantly suppressed xenograft growth and this inhibition was associated with a significant decrease in angiogenesis and direct inhibition of tumor cells. The results of the present study indicate that FP3 inhibits breast cancer tumor growth via the indirect inhibition of angiogenesis as well as a direct effect on tumor cells.

Role of the VEGF/VEGFR axis in cancer biology and therapy

New vessel formation (angiogenesis) is an essential physiological process for embryologic development, normal growth, and tissue repair. Angiogenesis is tightly regulated at the molecular level; however, this process is dysregulated in several pathological conditions such as cancer. The imbalance between pro- and antiangiogenic signaling molecules within tumors creates an abnormal vascular network that is characterized by dilated, tortuous, and leaky vessels. The pathophysiological consequences of these vascular abnormalities include temporal and spatial heterogeneity in tumor blood flow, oxygenation, and increased tumor interstitial fluid pressure. The resultant microenvironment deeply impacts on tumor progression, and also leads to a reduction in therapy efficacy. The discovery of vascular endothelial growth factor (VEGF) as a major driver of tumor angiogenesis has led to efforts to develop novel therapeutics aimed at inhibiting its activity. Anti-VEGF therapy has become an important option for the management of several human malignancies; however, a significant number of patients do not respond to anti-VEGF therapy when used either as single agent or in combination with chemotherapy. In addition, the benefit of antiangiogenic therapy is relatively short lived and the majority of patients relapse and progress. An increasing amount of reports suggest several potential mechanisms of resistance to antiangiogenic therapy including, but not limited to, tumor hypoxia. This chapter discusses the role of the VEGF axis in tumor biology and highlights the clinical application of anti-VEGF therapies elaborating on pitfalls and strategies to improve clinical outcome.

Emerging treatment options for management of malignant ascites in patients with ovarian cancer

Malignant ascites affects approximately 10% of patients with recurrent epithelial ovarian cancer and is associated with troublesome symptoms, including abdominal pressure and distension, dyspnea, bloating, pelvic pain, and bowel/bladder dysfunction. To date, no effective therapy has been identified for the treatment of malignant ascites in patients with recurrent, advanced ovarian cancer. In this article, we discuss currently existing options for the treatment of ascites associated with ovarian cancer, and review the literature as it pertains to novel, targeted therapies. Specifically, preclinical and clinical trials exploring the use of the antiangiogenic agents, bevacizumab and vascular endothelial growth factor-trap, as well as the nonangiogenic agent, catumaxomab, will be reviewed. Despite current limitations in treatment, knowledge regarding management options in the palliation of ascites is critical to practicing physicians. Ultimately, as with all novel therapies, symptom relief and treatment goals must be weighed against patient discomfort and potentially significant adverse events.

Opportunities and challenges in tumor angiogenesis research: back and forth between bench and bed

Angiogenesis is essential for tumor growth and metastasis. Many signaling pathways are involved in regulating tumor angiogenesis, with the vascular endothelial growth factor pathway being of particular interest. The recognition of the heterogeneity in tumor vasculature has led to better predictions of prognosis through differential analyses of the vasculature. However, the clinical benefits from antiangiogenic therapy are limited, because many antiangiogenic agents cannot provide long-term survival benefits, suggesting the development of drug resistance. Activation of the hypoxia and c-Met pathways, as well as other proangiogenic factors, has been shown to be responsible for such resistance. Vessel co-option could be another important mechanism. For future development, research to improve the efficacy of antiangiogenic therapy includes (a) using tumor-derived endothelial cells for drug screening; (b) developing the drugs focusing on specific tumor types; (c) developing a better preclinical model for drug study; (d) developing more accurate biomarkers for patient selection; (e) targeting the c-Met pathway or other pathways; and (f) optimizing the dose and schedule of antiangiogenic therapy. In summary, the future of antiangiogenic therapy for cancer patients depends on our efforts to develop the right drugs, select the right patients, and optimize the treatment conditions.

Overcoming resistance to antiangiogenic therapies

The concept of targeting new blood vessel formation, or angiogenesis, in tumors is an important advancement in cancer therapy, resulting, in part, from the development of such biologic agents as bevacizumab, a monoclonal antibody directed against vascular endothelial growth factor (VEGF)-A. The rationale for antiangiogenic therapy is based on the hypothesis that if tumors are limited in their capacity to obtain a new blood supply, so too is their capacity for growth and metastasis. Additional evidence suggests that pruning and/or "normalization" of irregular tumor vasculature and reduction of hypoxia may facilitate greater access of cytotoxic chemotherapy (CT) to the tumor. Indeed, for metastatic colorectal cancer, bevacizumab in combination with established CT regimens has efficacy superior to that of CT alone. Despite ~2-month longer progression-free and overall survival times than with CT alone, patients still progress, possibly because of alternative angiogenic "escape" pathways that emerge independent of VEGF-A, or are driven by hypoxic stress on the tumor. Other VEGF family members may contribute to resistance, and many factors that contribute to the regulation of tumor angiogenesis function as part of a complex network, existing in different concentrations and spatiotemporal gradients and producing a wide range of biologic responses. Integrating these concepts into the design and evaluation of new antiangiogenic therapies may help overcome resistance mechanisms and allow for greater efficacy over longer treatment periods.

Targeted molecular therapies for ovarian cancer: an update and future perspectives (Review)

Identification of the potential gene expression profiles of epithelial ovarian cancer and the arrival of newly targeted therapies have advanced the strategies used for treatment of this disease. This review focuses on the design of ongoing and planned clinical trials and offers a synopsis of the English-language literature for preclinical and clinical targeted therapies for epithelial ovarian cancer. Among many targeted agents, a promising, novel class of targeted drugs for special patient populations expected to improve the effectiveness of current therapy include inhibitors of angiogenesis, poly (ADP ribose) polymerase (PARP) and DNA repair mechanisms. Inhibition of PARP or homologous recombination (HR) repair mediated by Chk1 (checkpoint kinase 1) would selectively sensitize p53 mutation, BRCAness phenotype (serous type ovarian cancer) or HNF (hepatocyte nuclear factor)-1β-overexpressing tumor cells (clear cell type ovarian cancer) to chemotherapeutic agents. The therapeutic response is likely to be limited to a targeted patient, but not to the broad population. This review discusses some of the key current developments and existing challenges.

Progress and contrasts of the development of tivozanib for therapy of kidney cancer

INTRODUCTION

Targets for drug development for the treatment of kidney cancer (renal cell carcinoma; RCC) include vascular endothelial growth factor (VEGF) and its receptors and mammalian target of rapamycin. Currently available oral multitargeted VEGF tyrosine kinase inhibitors (TKIs) that have been approved by the US Food and Drug Administration for advanced RCC, include sunitinib, sorafenib and pazopanib. Off-target TKI inhibition can potentially preclude full-dose combination with other targeted and chemotherapeutic agents. There is a need to develop more potent and selective targeted agents for RCC therapy, which are more effective and have minimal off-target effects.

AREAS COVERED

This drug evaluation review addresses the ongoing development for the treatment of RCC with tivozanib: a potent, selective and long-half-life VEGF TKI. The testing for clinical efficacy alone or in combination with other therapies for RCC and for other tumor types, and the clinical and market relevance of introducing another RCC therapy are discussed.

EXPERT OPINION

Tivozanib is distinguished by its high potency, selectivity, long-half-life and its potential to be effectively combined with other agents in RCC. This may offer more effective, yet well-tolerated treatment options. The relative clinical and market relevance remain to be seen, both for RCC therapy and other tumor types.

The effect of anti-VEGF drugs (bevacizumab and aflibercept) on the survival of patients with metastatic colorectal cancer (mCRC)

Significant progression has been achieved in the treatment of metastatic colorectal cancer (mCRC) in recent years. This has been partly attributed to successfully incorporating new drugs into combination chemotherapy. In addition to the traditional cytotoxic chemotherapeutic agents, molecularly targeted agents began to play an important role in the treatment of advanced solid tumors. To date, two classes of molecularly targeted agents have been approved for treatment of patients with mCRC: (1) antivascular endothelial growth factor (anti-VEGF) agents (such as bevacizumab and aflibercept) and (2) antiendothelial cell growth factor receptor (anti-EGFR) agents (such as cetuximab and panitumumab). Aflibercept is a new member of anti-VEGF agents which has demonstrated efficacy for treatment of mCRC. With the commencement of clinical trials and basic research into aflibercept, more data from the bedside and the bench have been obtained. This review will outline the application of anti-VEGF agents by reviewing clinic experiences of bevacizumab and aflibercept, and try to add perspectives on the use of anti-VEGF agents in mCRC.

Pharmacokinetics of recombinant bifunctional fusion proteins

INTRODUCTION

The development of biotechnology has enabled the creation of various recombinant fusion proteins as a new class of biotherapeutics. The uniqueness of fusion proteins lies in their ability to fuse two or more protein domains, providing vast opportunities to generate novel combinations of functions. Pharmacokinetic (PK) studies, which are critical components in preclinical and clinical drug development, have not been fully explored for fusion proteins. The lack of general PK models and study guidelines has become a bottleneck for translation of fusion proteins from basic research to the clinic.

AREAS COVERED

This article reviews the current status of PK studies for fusion proteins, covering the processes that affect PK. According to their PK properties, a classification of fusion proteins is suggested along with examples from the clinic or under development. Current limitations and future perspectives for PK of fusion proteins are also discussed.

EXPERT OPINION

A PK model for bifunctional fusion proteins is presented to highlight the importance of mechanistic studies for a thorough understanding of the PK properties of fusion proteins. The model suggests investigating the receptor binding and subsequent intracellular disposition of individual domains, which can have dramatic impact on the PK of fusion proteins.

FP3: a novel VEGF blocker with antiangiogenic effects in vitro and antitumour effects in vivo

BACKGROUND Vascular endothelial growth factor (VEGF) is a critical promoter of blood vessel growth during embryonic development and neovascularisation in tumours. VEGF serves as a logical target for antiangiogenic cancer therapy because of its fundamental role in tumour angiogenesis. This study is to investigate the inhibitory effects of FP3, a novel VEGF blocker, on angiogenesis in vitro and tumour growth in vivo. METHODS The inhibitory effects of FP3 on angiogenesis in vitro were evaluated by using human umbilical vein endothelial cells (HUVECs) and rat aortic ring. The inhibitory effects of FP3 on tumour growth and angiogenesis in vivo were evaluated in a human non-small-cell lung cancer (NSCLC) cell line A549 tumour xenograft model with the methods of tumour growth regression assay and immunohistochemical staining, respectively. RESULTS In experiments with HUVECs, FP3 inhibited cell proliferation and migration. In rat aortic ring assay, FP3 suppressed VEGF-induced vessel sprouting. In tumour growth regression assay, FP3 significantly blocked the growth of A549 tumour in the subcutaneous tumour xenograft model and dramatically decreased the vessel density of tumour. CONCLUSIONS FP3 has excellent inhibitory effects on tumour angiogenesis both in vitro and in vivo, therefore it could be used as an effective antiangiogenic agent.

Targeting the vasculature of visceral tumors: novel insights and treatment perspectives

BACKGROUND

Angiogenesis, the formation of new blood vessels from the endothelium of the existing vasculature, describes a crucial process in tumor growth, disease progression, and metastasis. Therefore, the upcoming strategy of inhibiting tumor angiogenesis has generated different treatment modalities, which have been transferred into clinical practice in recent years. Currently, this concept is applied to target the vasculature of different visceral tumors and intensive clinical research has just started.

MATERIALS AND METHODS

This review summarizes the modifications of systemic treatment of visceral tumors by targeting the vasculature in the past years. Moreover, novel targets and treatment strategies will be discussed to evaluate future directions.

RESULTS

Leading antiangiogenic drugs combined with systemic chemotherapy have been applied with increasing success during the last years. Therefore, the concept of combining vascular targeting agents with established chemotherapeutic regimens has been increasingly adopted into the therapies of different visceral tumors.

CONCLUSION

Targeting the vasculature of visceral tumors in combination with established standard tumor therapies includes major clinical potential for future therapy concepts.

Antitumor effect of FP3 in a patient-derived tumor tissue xenograft model of gastric carcinoma through an antiangiogenic mechanism

FP3 (KH902/KH903) is a novel vascular endothelial growth factor (VEGF) blocker with antiangiogenic properties. Previous studies revealed that FP3, a humanized fusion protein that combines ligand binding elements from the extracellular domains of VEGF receptors 1 and 2 and the Fc portion of IgG1, has an inhibitory effect on the VEGF-mediated proliferation and migration of human umbilical vein endothelial cells, and VEGF-mediated vessel sprouting of rat aortic rings in vitro. Thus, FP3 was considered as a new promising agent in treating human choroidal neovascularization (CNV) caused by age-related macular degeneration (AMD). FP3 also has an antitumor effect in a non-small cell lung cancer cell line (A549) xenograft model in nude mice. However, little is known of the direct effects of FP3 on tumor vessels. In this study, we investigated the effects of FP3 on blood vessels in a patient-derived tumor tissue (PDTT) xenograft model of gastric carcinoma, using large tumors with established vasculature. Treatment with FP3 caused robust and early changes in endothelial cells and pericytes of vessels in the PDTT xenograft model. Vascular density decreased and vascular sprouting was suppressed by treatment with FP3. Pericytes did not degenerate to the same extent as endothelial cells, and those on surviving tumor vessels achieved a more normal phenotype. Our results revealed that FP3 has a direct and rapid antiangiogenic effect on tumor vessels, which was achieved mainly via regression of tumor vasculature, inhibition of new and recurrent vessel growth, and normalization of existing tumor vasculature.

Aflibercept in the treatment of metastatic colorectal cancer

Colorectal cancer is the third most common cancer in the US. In recent decades, an improved understanding of the role of the angiogenesis pathway in colorectal cancer has led to advancements in treatment. Bevacizumab has been shown to improve the progression-free survival and overall survival when combined with cytotoxic chemotherapy in patients with metastatic colorectal cancer, and at present is the only antiangiogenesis agent approved for the treatment of this cancer. Aflibercept is a novel angiogenesis-targeting agent, and has demonstrated efficacy in treating metastatic colorectal cancer in a recent randomized Phase III trial. Here we review the role of angiogenesis in the tumorigenesis of colorectal cancer, strategies for targeting angiogenesis, and the clinical development of aflibercept.

Induction of antagonistic soluble decoy receptor tyrosine kinases by intronic polyA activation

Alternative intronic polyadenylation (IPA) can generate truncated protein isoforms with significantly altered functions. Here, we describe 31 dominant-negative, secreted variant isoforms of receptor tyrosine kinases (RTKs) that are produced by activation of intronic poly(A) sites. We show that blocking U1-snRNP can activate IPA, indicating a larger role for U1-snRNP in RNA surveillance. Moreover, we report the development of an antisense-based method to effectively and specifically activate expression of individual soluble decoy RTKs (sdRTKs) to alter signaling, with potential therapeutic implications. In particular, a quantitative switch from signal transducing full-length vascular endothelial growth factor receptor-2 (VEGFR2/KDR) to a dominant-negative sKDR results in a strong antiangiogenic effect both on directly targeted cells and on naive cells exposed to conditioned media, suggesting a role for this approach in interfering with angiogenic paracrine and autocrine loops.

Protease-activated receptors in cancer: A systematic review

The traditional view of the role of proteases in tumor growth, progression and metastasis has significantly changed. Apart from their contribution to cancer progression, it is evident that a subclass of proteases, such as thrombin, serves as signal molecules controlling cell functions through the protease-activated receptors (PARs). Among the four types of PAR (PAR1-4; cloned and named in order of their discovery), PAR1, PAR3 and PAR4 are activated by thrombin, unlike PAR2, which is activated by trypsin-like serine proteases. Thrombin has been proven to be a significant factor in both the behavior of cancer in its involvement in hemostasis and blood coagulation. Thrombin is a key supporter of various cellular effects relevant to tumor growth and metastasis, as well as a potent activator of angiogenesis, which is essential for the growth and development of all solid tumor types. This review presents an overview of the role of PAR-mediated thrombin in angiogenesis and cancer, focusing on the ability of PAR1- and PAR4-mediated thrombin to affect tumorigenesis and angiogenesis.

Vascular endothelial growth factors and receptors: anti-angiogenic therapy in the treatment of cancer

Vascular endothelial growth factors (VEGFs) are critical regulators of vascular and lymphatic function during development, in health and in disease. There are five mammalian VEGF ligands and three VEGF receptor tyrosine kinases. In addition, several VEGF co-receptors that lack intrinsic catalytic activity, but that indirectly modulate the responsiveness to VEGF contribute to the final biological effect. This review describes the molecular features of VEGFs, VEGFRs and co-receptors with focus on their role in the treatment of cancer.