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.
aflibercept; antiangiogenesis; metastatic colorectal cancer (mCRC); tyrosine kinase inhibitor (TKI); vascular endothelial growth factor (VEGF)
There is growing evidence that vascular endothelial growth factor-A (VEGF-A), a ligand of the receptor tyrosine kinases VEGFR1 and VEGFR2, promotes lymphangiogenesis. However, the underlying mechanisms by which VEGF-A induces the growth of lymphatic vessels remain poorly defined. Here we report that VEGFR2, not VEGFR1, is the primary receptor regulating VEGF-A-induced lymphangiogenesis. We show that specific inhibition of VEGF-A/VEGFR2 signaling with the fully human monoclonal antibody r84 significantly inhibits lymphangiogenesis in MDA-MB-231 tumors. In vitro experiments with primary human dermal lymphatic endothelial cells (LECs) demonstrate that blocking VEGF-A activation of VEGFR2, not VEGFR1, significantly inhibits VEGF-A-induced proliferation and migration of LECs. We show that VEGF-A stimulation of LECs leads to the phosphorylation of VEGFR2 (Tyr 951, 1054, 1059, 1175, and 1214) which subsequently triggers PKC dependent phosphorylation of ERK1/2 and PI3-K dependent phosphorylation of Akt. Additionally, we demonstrate that inhibitors that suppress the phosphorylation of ERK1/2 and Akt significantly block VEGF-A- induced proliferation and migration of LECs. Together, these results shed light on the mechanisms regulating VEGF-A-induced proliferation and migration of LECs, reveal that VEGFR2 is the primary signaling VEGF-A receptor on lymphatic endothelium, and suggest that therapeutic agents targeting the VEGF-A/VEGFR2 axis could be useful in blocking the pathological formation of lymphatic vessels.
Vascular endothelial growth factor (VEGF) is critical for physiological and pathological angiogenesis. Within the tumor microenvironment, VEGF functions as an endothelial cell survival factor, permeability factor, mitogen, and chemotactic agent. The majority of these functions are mediated by VEGF-induced activation of VEGF receptor 2 (VEGFR2), a high affinity receptor tyrosine kinase expressed by endothelial cells and other cell types in the tumor microenvironment. VEGF can also ligate other cell surface receptors including VEGFR1 and neuropilin-1 and -2. However, the importance of VEGF-induced activation of these receptors in tumorigenesis is still unclear. We report the development and characterization of r84, a fully human monoclonal antibody that binds human and mouse VEGF and selectively blocks VEGF from interacting with VEGFR2 but does not interfere with VEGF∶VEGFR1 interaction. Selective blockade of VEGF binding to VEGFR2 by r84 is shown through ELISA, receptor binding assays, receptor activation assays, and cell-based functional assays. Furthermore, we show that r84 has potent anti-tumor activity and does not alter tissue histology or blood and urine chemistry after chronic high dose therapy in mice. In addition, chronic r84 therapy does not induce elevated blood pressure levels in some models. The ability of r84 to specifically block VEGF∶VEGFR2 binding provides a valuable tool for the characterization of VEGF receptor pathway activation during tumor progression and highlights the utility and safety of selective blockade of VEGF-induced VEGFR2 signaling in tumors.
Gastric cancer (GC) is currently the second leading cause of cancer death worldwide; unfortunately, most patients will present with locally advanced or metastatic disease. Despite recent progress in diagnosis, surgery, chemotherapy, and radiotherapy, prognosis remains poor. A better understanding of GC biology and signaling pathways is expected to improve GC therapy, and the integration of targeted therapies has recently become possible and appears to be promising. This article focuses on anti-Her-2 therapy, specifically trastuzumab, as well as other epidermal growth factor receptor antagonists such as cetuximab, panitumub, matuzumab, nimotzumab, gefitinib, and erlotinib. Additionally, drugs that target angiogenesis pathways are also under investigation, particulary bevacizumab, ramucirumab, sorafenib, sunitinib, and cediranib. Other targeted agents in preclinical or early clinical development include mTOR inhibitors, anti c-MET, polo-like kinase 1 inhibitors, anti-insulin-like growth factor, anti-heat shock proteins, and small molecules targeting Hedgehog signaling.
gastric cancer; targeted therapy; antiangiogenesis drugs; anti-EGFR drugs
XL184 (cabozantinib) is a potent inhibitor of MET, vascular endothelial growth factor receptor 2 (VEGFR2), and RET, with robust antiangiogenic, antitumor, and anti-invasive effects in preclinical models. Early observations of clinical benefit in a phase I study of cabozantinib, which included patients with medullary thyroid cancer (MTC), led to expansion of an MTC-enriched cohort, which is the focus of this article.
Patients and Methods
A phase I dose-escalation study of oral cabozantinib was conducted in patients with advanced solid tumors. Primary end points included evaluation of safety, pharmacokinetics, and maximum-tolerated dose (MTD) determination. Additional end points included RECIST (Response Evaluation Criteria in Solid Tumors) response, pharmacodynamics, RET mutational status, and biomarker analyses.
Eighty-five patients were enrolled, including 37 with MTC. The MTD was 175 mg daily. Dose-limiting toxicities were grade 3 palmar plantar erythrodysesthesia (PPE), mucositis, and AST, ALT, and lipase elevations and grade 2 mucositis that resulted in dose interruption and reduction. Ten (29%) of 35 patients with MTC with measurable disease had a confirmed partial response. Overall, 18 patients experienced tumor shrinkage of 30% or more, including 17 (49%) of 35 patients with MTC with measurable disease. Additionally, 15 (41%) of 37 patients with MTC had stable disease (SD) for at least 6 months, resulting in SD for 6 months or longer or confirmed partial response in 68% of patients with MTC.
Cabozantinib has an acceptable safety profile and is active in MTC. Cabozantinib may provide clinical benefit by simultaneously targeting multiple pathways of importance in MTC, including MET, VEGFR2, and RET. A global phase III pivotal study in MTC is ongoing (ClinicalTrials.gov number NCT00215605).
This review describes the clinical development of everolimus in advanced renal cell carcinoma and the rationale for the use of mammalian target of rapamycin inhibitors after failure of vascular endothelial growth factor/vascular endothelial growth factor receptor inhibitors.
Historically, there have been few treatment options for patients with advanced renal cell carcinoma (RCC) besides immunotherapy with interleukin-2 and interferon (IFN)-α. Targeted therapies have improved clinical outcomes over the past several years. These include the vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors sunitinib and sorafenib, which inhibit angiogenic signaling in endothelial cells and vascular pericytes predominantly through VEGFR and platelet-derived growth factor receptor β. Also included is the anti-VEGF monoclonal antibody bevacizumab used in combination with IFN-α. These agents mediate their antitumor effects by interfering with the VEGF signaling pathway, thereby inhibiting angiogenesis and causing tumor shrinkage. However, ultimately, most patients develop resistance and experience disease progression during VEGF/VEGFR-targeted therapy, and until the recent approval of the mammalian target of rapamycin (mTOR) inhibitor everolimus (RAD001), there were no agents available with proven activity in this setting. This review describes the clinical development of everolimus in advanced RCC and the rationale for the use of mTOR inhibitors after failure of VEGF/VEGFR inhibitors.
Everolimus; mTOR protein; Carcinoma; Renal cell; Receptors; Vascular endothelial growth factor; Receptor protein tyrosine kinases; Inhibitors; Angiogenesis; Targeted therapy
SU5416 (Z-3-[(2,4-dimethylpyrrol-5-yl)methylidenyl]-2-indolinone; semaxanib) is a small molecule inhibitor of the vascular endothelial growth factor receptor (VEGFR)2. A Phase I dose escalation study was performed. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was used as a pharmacodynamic assessment tool. In all, 27 patients were recruited. SU5416 was administered twice weekly by fixed rate intravenous infusion. Patients were treated in sequential cohorts of three patients at 48, 65, 85 110 and 145 mg m−2. A further dose level of 190 mg m−2 after a 2-week lead in period at a lower dose was completed; thereafter, the cohort at 145 mg m−2 was expanded. SU5416 showed linear pharmacokinetics to 145 mg m−2 with a large volume of distribution and rapid clearance. A significant degree of interpatient variability was seen. SU5416 was well tolerated, by definition a maximum-tolerated dose was not defined. No reproducible changes were seen in DCE-MRI end points. Serial assessments of VEGF in a cohort of patients treated at 145 mg m−2 did not show a statistically significant treatment-related change. Parallel assessments of the impact of SU5416 on coagulation profiles in six patients showed a transient effect within the fibrinolytic pathway. Clinical experience showed that patients who had breaks of therapy longer than a week could not have treatment reinitiated at a dose of 190 mg m−2 without unacceptable toxicity. The 145 mg m−2 dose level is thus the recommended dose for future study.
antiangiogenic therapy; phase I clinical trial; pharmacokinetics; pharmacodynamics
Vascular endothelial growth factor (VEGF) signaling is critical for tumor angiogenesis. However, therapies based on the inhibition of VEGF receptors have shown modest results in patients with cancer. Surprisingly little is known about mechanisms underlying the regulation of VEGFR1 and VEGFR2 expression, the main targets of these drugs. Here, analysis of tissue microarrays revealed an inversely reciprocal pattern of VEGF receptor regulation in the endothelium of human squamous cell carcinomas (high VEGFR1, low VEGFR2), as compared to the endothelium of control tissues (low VEGFR1, high VEGFR2). Mechanistic studies demonstrated that VEGF signals through the Akt/ERK pathway to inhibit constitutive ubiquitination and induce rapid VEGFR1 accumulation in endothelial cells. Surprisingly, VEGFR1 is primarily localized in the nucleus of endothelial cells. In contrast, VEGF signals through the JNK/c-Jun pathway to induce endocytosis, nuclear translocation, and downregulation of VEGFR2 via ubiquitination. VEGFR1 signaling is required for endothelial cell survival, while VEGFR2 regulates capillary tube formation. Notably, the antiangiogenic effect of Bevacizumab (anti-VEGF antibody) requires the normalization of VEGFR1 and VEGFR2 levels in human squamous cell carcinomas vascularized with human blood vessels in immunodeficient mice. Collectively, this work demonstrate that VEGF-induced angiogenesis requires the inverse regulation of VEGFR1 and VEGFR2 in tumor-associated endothelial cells.
Angiogenesis; Apoptosis; Receptor Tyrosine Kinase; Differentiation; Tumor Microenvironment
Angiogenesis, the growth of new blood vessels, involves specification of endothelial cells to tip cells and stalk cells, which is controlled by Notch signalling, whereas vascular endothelial growth factor receptor (VEGFR)-2 and VEGFR-3 have been implicated in angiogenic sprouting. Surprisingly, we found that endothelial deletion of Vegfr3, but not VEGFR-3-blocking antibodies, postnatally led to excessive angiogenic sprouting and branching, and decreased the level of Notch signalling, indicating that VEGFR-3 possesses passive and active signalling modalities. Furthermore, macrophages expressing the VEGFR-3 and VEGFR-2 ligand VEGF-C localized to vessel branch points, and Vegfc heterozygous mice exhibited inefficient angiogenesis characterized by decreased vascular branching. FoxC2 is a known regulator of Notch ligand and target gene expression, and Foxc2+/−; Vegfr3+/− compound heterozygosity recapitulated homozygous loss of Vegfr3. These results indicate that macrophage-derived VEGF-C activates VEGFR-3 in tip cells to reinforce Notch signalling, which contributes to the phenotypic conversion of endothelial cells at fusion points of vessel sprouts.
This review summarizes the preclinical and clinical pharmacokinetics and pharmacodynamics of pazopanib, as well as data on clinical activity, that ultimately resulted in its recent approval.
Pazopanib is a recently approved, novel tyrosine kinase inhibitor specifically designed to impair angiogenesis by abrogating vascular endothelial growth factor receptor 2 (VEGFR-2) to exert its function. Pazopanib inhibits VEGF-induced endothelial cell proliferation in vitro and angiogenesis in vivo and demonstrates antitumor activity in mouse models. Furthermore, the pazopanib concentration resulting in maximal inhibition of VEGFR-2 phosphorylation in vivo was in line with the steady-state concentration required to inhibit growth of tumor xenografts, suggesting that pazopanib's mechanism of action is indeed through VEGFR-2 inhibition.
In a phase I trial, a generally well-tolerated dose was identified at which the majority of patients achieved pazopanib plasma concentrations above the concentration required for maximal in vivo inhibition of VEGFR-2 phosphorylation in preclinical models. Administered as monotherapy, evidence of antitumor activity was observed in phase II studies in several tumor types, including soft tissue sarcoma, renal cell cancer (RCC), ovarian cancer, and non-small cell lung cancer. Recently, the U.S. Food and Drug Administration granted approval for treatment with pazopanib in patients with RCC based on the longer progression-free survival time observed with this agent in a placebo-controlled, randomized trial. This review summarizes the preclinical and clinical pharmacokinetics and pharmacodynamics of pazopanib, as well as data on clinical activity, that ultimately resulted in its recent approval.
Pazopanib; Angiogenesis; Tyrosine kinase inhibitor; Renal cell cancer
Tumor-derived vascular endothelial growth factor (VEGF) has previously been identified as a causative factor in the disturbed differentiation of myeloid dendritic cells (DC) in advanced cancer patients. Here, we investigated the potential of vascular endothelial growth factor receptor (VEGFR) tyrosine kinase (TK) inhibition to overcome this defective DC differentiation. To this end, peripheral blood DC (PBDC) precursor and subset frequencies were measured in 13 patients with advanced cancer before and after treatment with AZD2171, a TK inhibitor (TKI) of VEGFR, coadministered with gefitinib, and an epidermal growth factor receptor (EGFR) TKI. Of note, not only myeloid DC but also plasmacytoid DC frequencies were significantly reduced in the blood of the cancer patients prior to treatment, as compared to healthy controls. Moreover, besides an accumulated population of immature myeloid cells (ImC), a population of myeloid suppressor cells (MSC) was significantly increased. Upon systemic VEGFR TK inhibition, DC frequencies did not increase, whereas the rate of circulating MSC showed a slight, but not significant, decrease. In conclusion, TK inhibition of VEGFR with AZD2171 does not restore the defective PBDC differentiation observed in advanced cancer patients.
JNJ-26483327 is an oral, potent, multi-targeted tyrosine kinase inhibitor, inhibiting kinases of epidermal growth factor receptor (EGFR)-1, -2 and -4, rearranged during transfection (RET) receptor, vascular endothelial growth factor receptor (VEGFR)-3 and Src family (Lyn, Fyn, Yes) at low nanomolar concentrations. This phase I, accelerated titration study assessed maximum tolerated dose, safety, pharmacokinetics and pharmacodynamic effects of JNJ-26483327.
Nineteen patients with advanced cancers received JNJ-26483327 continuous twice daily (BID) in escalating dose cohorts ranging from 100 to 2100 mg. Pharmacodynamic effects were assessed in paired skin biopsies and blood.
JNJ-26483327 was well tolerated in doses up to 1500 mg BID, with target-inhibition-related toxicity such as diarrhoea and skin rash, and other common reported toxicities being nausea, vomiting, anorexia and fatigue. At 2100 mg, two episodes of dose-limiting toxicity were observed, consisting of grade 3 anorexia and a combination of grade 3 anorexia and fatigue, respectively. Pharmacokinetics were dose proportional up to 1500 mg in which plasma levels were obtained showing anti-tumour activity in xenograft mouse models. Pharmacodynamic analysis did not show a substantial effect on expression of Ki-67, p27kip1, phosphorylated mitogen-activated protein kinase, phosphorylated Akt and EGFR, and serum levels of sVEGFR-2, VEGF-C and VEGF-D remained unchanged. Stable disease was noted in six patients (32%).
JNJ-26483327 is well tolerated and shows a predictable pharmacokinetic profile; the recommended dose for further studies is 1500 mg BID.
phase I; JNJ-26483327; pharmacokinetics; pharmacodynamics; tyrosine kinase inhibitor
AIM: To gain mechanistic insights into the role played by epidermal growth factor receptor (EGFR) in the regulation of vascular endothelial growth factors (VEGFs) in colorectal cancer (CRC).
METHODS: The impact of high-level expression of the growth factor receptors EGFR and VEGF receptor (VEGFR)3 and the VEGFR3 ligands VEGF-C and VEGF-D on disease progression and prognosis in human CRC was investigated in 108 patients using immunohistochemistry. Furthermore, the expression of the lymphangiogenic factors in response to the modulation of EGFR signalling by the EGFR-targeted monoclonal antibody cetuximab was investigated at the mRNA and protein level in human SW480 and SW620 CRC cell lines and a mouse xenograft model.
RESULTS: Human CRC specimens and cell lines displayed EGFR, VEGF-C and VEGF-D expression with varying intensities. VEGF-C expression was associated with histological grade. Strong expression of VEGF-D was significantly associated with lymph node metastases and linked to a trend for decreased survival in lymph node-positive patients. EGFR blockade with cetuximab resulted in a significant decrease of VEGF-D expression in vitro and in vivo.
CONCLUSION: In conclusion, the expression of VEGF-D in colorectal tumours is significantly associated with lymphatic involvement in CRC patients and such expression might be blocked effectively by cetuximab.
Human colorectal cancer; Lymphangiogenesis; Vascular endothelial growth factor-C; Vascular endothelial growth factor-D; Epidermal growth factor receptor
Several therapies targeting angiogenesis are currently in development for non-small cell lung cancer (NSCLC). This review discusses results of recent clinical trials evaluating chemotherapy plus antiangiogenic therapy for NSCLC. Bevacizumab, an anti-VEGF antibody, is currently approved for the treatment of advanced NSCLC in combination with carboplatin and paclitaxel. Completed phase III trials evaluating bevacizumab plus chemotherapy have shown prolonged progression-free survival; however, not all trials showed significant improvement in overall survival (OS). Phase III trials of the tyrosine kinase inhibitors (TKIs) vandetanib and sorafenib and the vascular disrupting agent ASA404 also failed to improve OS compared with chemotherapy alone. Clinical trials are ongoing involving several new antiangiogenic therapies, including ramucirumab, aflibercept, cediranib, nintedanib (BIBF 1120), sunitinib, pazopanib, brivanib, ABT-869, axitinib, ABT-751 and NPI-2358; several of these agents have shown promising phase I/II results. Results from recently completed and ongoing phase III trials will determine if these newer antiangiogenic agents will be incorporated into clinical practice.
non-small cell lung cancer; antiangiogenic therapy; vascular endothelial growth factor; angiogenesis; tyrosine kinase inhibitor; monoclonal antibody; chemotherapy
Vascular endothelial growth factor A (VEGF-A) binds to the VEGFR2 receptor tyrosine kinase, regulating endothelial function, vascular physiology and angiogenesis. However, the mechanism underlying VEGFR2 turnover and degradation in this response is unclear. Here, we tested a role for heat-shock proteins in regulating the presentation of VEGFR2 to a degradative pathway. Pharmacological inhibition of HSP90 stimulated VEGFR2 degradation in primary endothelial cells and blocked VEGF-A-stimulated intracellular signaling via VEGFR2. HSP90 inhibition stimulated the formation of a VEGFR2-HSP70 complex. Clathrin-mediated VEGFR2 endocytosis is required for this HSP-linked degradative pathway for targeting VEGFR2 to the endosome-lysosome system. HSP90 perturbation selectively inhibited VEGF-A-stimulated human endothelial cell migration in vitro. A mouse femoral artery model showed that HSP90 inhibition also blocked blood vessel repair in vivo consistent with decreased endothelial regeneration. Depletion of either HSP70 or HSP90 caused defects in blood vessel formation in a transgenic zebrafish model. We conclude that perturbation of the HSP70-HSP90 heat-shock protein axis stimulates degradation of endothelial VEGFR2 and modulates VEGF-A-stimulated intracellular signaling, endothelial cell migration, blood vessel development and repair.
Angiogenesis is essential to tumor progression and a precise evaluation of angiogenesis is important for tumor early diagnosis and treatment. The quantitative and dynamic in vivo assessment of tumor angiogenesis can be achieved by molecular magnetic resonance imaging (mMRI). Vascular endothelial growth factor (VEGF) and VEGF receptors (VEGFRs) are the main regulatory system in angiogenesis and have been used as hot targets for radionuclide-based molecular imaging. However, little research has been accomplished in targeting VEGF/VEGFRs by mMRI. In our study, we aimed to assess the expression of VEGFR2 in C6 gliomas by using a specific molecular probe with mMRI. The differential uptake of the probe conjugated to anti-VEGFR2 monoclonal antibody, shown by varied increases in T1 signal intensity during a two-hour period, demonstrated the heterogeneous expression of VEGFR2 in different tumor regions. Microscopic fluorescence imaging, obtained for the biotin group in the probe with streptavidin-Cy3, along with staining for cellular VEGFR2 levels, laminin and CD45, confirmed the differential distribution of the probe which targeted VEGFR2 on endothelial cells. The angiogenesis process was also assessed using MR angiography (MRA), which quantified tumor blood volume and provided a macroscopic view and a dynamic change of the correlation between tumor vasculature and VEGFR2 expression. Together these results suggest mMRI can be very useful in assessing and characterizing the expression of specific angiogenic markers in vivo and help evaluate angiogenesis associated with tumor progression.
VEGFR2; molecular MRI (mMRI); biotin-Gd-DTPA-albumin-anti-VEGFR2 probe; angiogenesis; C6 rat glioma
Lung cancer is the leading cause of mortality worldwide. Non-small cell lung cancer (NSCLC) is a particularly aggressive cancer, the optimum management of which is still being determined. In the metastatic disease, the standard therapy is a platinum-based combination chemotherapy; however, in spite of available treatment options for patients who progress beyond first-line therapy, prognosis remains poor. Angiogenesis is a tightly regulated process which comprises a complex, complementary, and overlapping network. Inhibition of tumor-related angiogenesis has become an attractive target for anticancer therapy. Antiangiogenic strategy includes: monoclonal antibodies against vascular endothelial growth factor (VEGF) and VEGF receptor (VEGFR), small molecule inhibitors of VEGF tyrosine kinase activity, VEGF Trap, and a new class named “vascular disrupting agents,” tested in ongoing clinical trials which will further define their role in the management of NSCLC. BIBF 1120 is an investigational orally administered receptor tyrosine kinase inhibitor that has shown antiangiogenic and antineoplastic activity, inhibiting VEGFR, platelet-derived growth factor receptor, and fibroblast growth factor receptor tyrosine kinases, preventing tumor growth and interfering with the angiogenesis-signaling cascade and overcoming drug resistances.
NSCLC; angiogenesis; oral antiangiogenic agents; VEGF; PDGF; FGF
Diffuse large B cell lymphoma (DLBCL) is clinically and biologically heterogeneous. In most cases of DLBCL, lymphoma cells coexpress vascular endothelial growth factor (VEGF) and its receptors VEGFR1 and VEGFR2, suggesting autocrine in addition to angiogenic effects. We enumerated microvessel density and scored lymphoma cell expression of VEGF, VEGFR1, VEGFR2 and phosphorylated VEGFR2 in 162 de novo DLBCL patients treated with R-CHOP (rituximab, cyclophosphamide, vincristine, doxorubicin and prednisone)-like regimens. VEGFR2 expression correlated with shorter overall survival (OS) independent of International Prognostic Index (IPI) (p=0.0028). Phosphorylated VEGFR2 (detected in 13% of cases) correlated with shorter progression-free survival (PFS, p=0.044) and trended toward shorter OS on univariate analysis. VEGFR1 was not predictive of survival on univariate analysis, but it did correlate with better OS on multivariate analysis with VEGF, VEGFR2, and IPI (p=0.036); in patients with weak VEGFR2, lack of VEGFR1 coexpression was significantly correlated with poor OS independent of IPI (p=0.01). These results are concordant with our prior finding of an association of VEGFR1 with longer OS in DLBCL treated with chemotherapy alone. We postulate that VEGFR1 may oppose autocrine VEGFR2 signaling in DLBCL by competing for VEGF binding. In contrast to our prior results with chemotherapy alone, microvessel density was not prognostic of PFS or OS with R-CHOP-like therapy.
Non-Hodgkin lymphoma; VEGF; angiogenesis; tumour biology; prognostic factors
Tumors induce new blood vessel growth primarily from host organ microvascular endothelial cells (ECs), and microvasculature differs significantly between the lung and liver. Vascular endothelial growth factor (VEGF or VEGF-A) promotion of tumor angiogenesis is thought to be mediated primarily by VEGF receptor (VEGFR) 2. In this study, VEGFR-2 antibody (DC101) inhibited growth of RenCa renal cell carcinoma lung metastases by 26% while VEGFR-1 antibody (MF-1) had no effect. However, VEGFR-2 neutralization had no effect on RenCa liver metastases while VEGFR-1 neutralization decreased RenCa liver metastases by 31%. For CT26 colon carcinoma liver metastases, inhibition of both VEGFR-1 and VEGFR-2 was required to induce growth delay. VEGFR-1 or VEGFR-2 inhibition decreased tumor burden not by preventing the establishment of micrometastases but rather by preventing vascularization and growth of micrometastases by 55% and 43%, respectively. VEGF induced greater phosphorylation of VEGFR-2 in lung ECs and of VEGFR-1 in liver ECs. EC proliferation, migration, and capillary tube formation in vitro were suppressed more by VEGFR-2 inhibition for lung EC and more by VEGFR-1 inhibition for liver EC. Collectively, our results indicate that liver metastases are more reliant on VEGFR-1 than lung metastases to mediate angiogenesis due to differential activity of VEGFRs on liver EC versus lung EC. Thus, therapies inhibiting specific VEGF receptors should consider the targeted sites of metastatic disease.
For individualized bevacizumab-based therapy, non-invasive biomarkers are necessary. This study assessed the predictive value of plasma vascular endothelial growth factor (VEGF)-A, soluble VEGF receptor (sVEGFR)-1 and sVEGFR-2 levels as biomarkers for clinical response and survival in advanced colorectal cancer (CRC) patients treated with bevacizumab and modified FOLFOX6 (mFOLFOX6). Forty-six unresectable advanced CRC patients and 20 healthy controls were included in this study. CRC patients were treated with bevacizumab and mFOLFOX6. Pretreatment plasma VEGF-A, sVEGFR-1 and sVEGFR-2 levels were measured using the multiplex immunoassay. Plasma VEGF-A, sVEGFR-1 and sVEGFR-2 levels were significantly higher in CRC patients than in the healthy subjects. The plasma sVEGFR-1 levels in the responder patients [complete response (CR)/partial response (PR)] and stable disease (SD) patients were significantly lower than those in the progressive disease (PD) patients (CR/PR vs. PD, p=0.025; SD vs. PD, p=0.032), while the plasma VEGF-A and sVEGFR-2 levels did not show any significant differences between the two groups of patients. Patients with higher sVEGFR-1 levels showed a significantly poorer progression-free survival (PFS) and overall survival (OS) than those with lower VEGFR-1 levels. In contrast, VEGF-A and sVEGFR-2 did not show any significant relationship between PFS and OS according to the status of each level. In the multivariate Cox proportional hazard regression analysis, sVEGFR-1 levels showed a significant relationship between PFS and OS. These results suggest that plasma sVEGFR-1 levels have a predictive value for clinical response and survival in advanced CRC patients treated with bevacizumab and mFOLFOX6. Larger scale studies are needed to further validate our results.
vascular endothelial growth factor-A; vascular endothelial growth factor receptor-1; vascular endothelial growth factor receptor-2; bevacizumab; FOLFOX; colorectal cancer
There is an unmet need for biomarkers for identifying patients likely to benefit from anticancer treatments, selecting dose, and understanding mechanisms of resistance. Plasma vascular endothelial growth factor (VEGF) and soluble VEGF receptor 2 (sVEGFR-2) are known to be modulated by VEGF pathway inhibitors. It is unknown whether chemotherapy or VEGFR inhibitor/chemotherapy combinations induce changes in these or other cytokines and angiogenic factors (CAFs) and whether such changes could be markers of benefit.
Thirty-five plasma CAFs were analyzed using multiplexed bead arrays and enzyme-linked immunosorbent assays from 123 patients with non–small-cell lung cancer in a randomized phase II study who received vandetanib, a VEGFR and epidermal growth factor receptor inhibitor, monotherapy carboplatin and paclitaxel (CP), or the combination (VCP). Changes in CAFs at days 8, 22, and 43 from baseline were correlated with progression risk.
VEGF increased and sVEGFR-2 decreased by day 43 in the vandetanib arm, whereas a distinct pattern was observed in the CP and VCP arms, with significant decreases in interleukin (IL) -12, IL-1 receptor antagonist, and matrix metalloproteinase 9 (MMP-9) and increased macrophage chemoattractant protein 1. In each treatment arm, changes in different markers were associated with progression risk. For example, increases in IL-8 with VCP, MMP-9 with CP, and VEGF with vandetanib monotherapy were associated with increased progression risk, and increase in intercellular adhesion molecule 1 with vandetanib was associated with decreased risk.
Vandetanib and chemotherapy treatment led to distinct patterns of CAF changes; the combination resembled chemotherapy alone. Changes in specific CAFs correlated with clinical outcome, but markers differed for each treatment arm. CAF profiling may provide insights into the biologic effects of treatment and identify drug-specific markers of activity and clinical benefit.
Vascular endothelial growth factor receptor 2 (VEGFR2) is a primary responder to vascular endothelial growth factor signal, and thereby regulates endothelial migration and proliferation. This receptor is expressed in endothelial cells and some vascular tumors, but many reports also detail its expression in carcinomas and lymphomas. VEGFR2 is a potential cell type marker, and data on VEGFR2 expression may also have therapeutic significance in view of recent availability of VEGFR2 inhibitors. In this study we immunohistochemically examined 262 vascular endothelial and 1640 non-vascular tumors and selected non-neoplastic tissues with a VEGFR2-specific rabbit monoclonal antibody 55B11. In early human embryo, VEFGR2 was expressed in endothelia of developing capillaries, thoracic duct, great vessels, hepatic sinusoids, epidermis, and mesothelia. In late first trimester fetus peripheral soft tissues, VEGFR2 was restricted to capillary endothelia, chrondrocytes, and superficial portion of the epidermis. In normal adult tissues, it was restricted to endothelia and mesothelia. VEGFR2 was consistently expressed in angiosarcomas, Kaposi sarcomas, and retiform hemangioendotheliomas. It was detected only in half of epithelioid hemangioendotheliomas (15/27), usually focally. VEGFR2 was strongly expressed in most capillary hemangiomas and weakly or focally in cavernous, venous, and spindle cell hemangiomas, and lymphangiomas. Malignant epithelial mesothelioma was found to be a unique epithelial neoplasm with a strong and nearly consistent VEGFR2 expression, including membrane staining (35/38). Approximately 10% of squamous cell carcinomas and 23% of pulmonary adenocarcinomas contained focal positivity. The only non-endothelial mesenchymal tumors found VEGFR2-positive were biphasic synovial sarcoma (focal epithelial expression), and chordoma. All melanomas and lymphomas were negative. VEGFR2 is a promising marker for malignant vascular tumors and malignant epithelioid mesothelioma. Expression in biphasic synovial sarcoma epithelium, chordoma, and some carcinomas has to be considered in differential diagnosis. Information on VEGFR2 tissue expression may be useful in development of targeted oncologic therapy via VEGFR2-specific tyrosine kinase inhibitors.
angiosarcoma; Kaposi sarcoma; malignant mesothelioma; VEGFR2; endothelial cell; mesothelial cell; fetal tissue; adult tissue
The present study was designed to investigate the role of vascular endothelial growth factor receptor (VEGFR)-3/Flt-4 in the early stages of cervical cancer. VEGFR-3/Flt-4 expression, vascular endothelial growth factor (VEGF)-C and VEGF-D in the early stages (Ia-IIa) of cervical cancer in 41 patients was examined by immunohistochemical analysis. Additionally, the VEGFR-3/Flt-4-marked vascular density (MVD) was examined and the relationship of these factors with clinicopathological factors was analyzed. VEGFR-3/Flt-4 was found to be expressed in lymphatic endothelial cells and, to a certain extent, in vascular endothelial cells. The VEGFR-3/Flt-4-positive vessels were largely distributed in the stroma surrounding the tumor tissues, and these vessels were morphologically divided into blood and lymphatic vessels, respectively. Cancer cells were found to express VEGF-C, VEGF-D and VEGFR-3/Flt-4, and their positive expression rate was 48.7% (20/41), 58.5% (24/41) and 63.4% (26/41), respectively. VEGFR-3/Flt-4 expression in the cancer cells of the cervical cancer patients in our study was found to be correlated to the clinical stage, lymph node metastasis, lymphatic invasion and expression of VEGF-C and VEGF-D. However, this expression was unrelated to menstrual status, histological grade and histological classification. MVD was correlated to the clinical stage and expression of VEGF-C and VEGF-D, but was unrelated to menstrual status, histological grade, histological classification, lymph node metastasis and lymphatic invasion. In conclusion, VEGFR-3/Flt-4 plays an important role in the early stages of cervical cancer.
cervical cancer; vascular endothelial growth factor receptor-3/Flt-4; vascular endothelial growth factor-C; vascular endothelial growth factor-D
We determined the maximum tolerated dose (MTD) and dose-limiting toxicities (DLT) of the oral vascular endothelial growth factor receptor (VEGFR) inhibitor, vatalanib, when administered with imatinib and hydroxyurea on a continuous daily schedule among recurrent malignant glioma patients.
All patients received 500 mg of hydroxyurea twice daily. Imatinib was dosed at 400 mg per day for patients not taking enzyme-inducing antiepileptic drugs (EIAEDs; stratum A) and at 500 mg twice-a-day for patients taking EIAEDs (stratum B). Vatalanib was escalated from 500 mg to 1250 mg twice daily in successive cohorts, independently for each stratum. Pharmacokinetics of each drug were assessed.
Thirty-seven recurrent patients, including 34 (92%) with glioblastoma and 3 (8%) with grade 3 malignant glioma, were enrolled. Nineteen patients (51%) were taking EIAEDs. The MTD of vatalanib for all patients was 1000 mg twice-a-day. DLTs were hematologic, gastrointestinal, renal and hepatic. No patients developed intracranial hemorrhage. Concurrent administration of imatinib and hydroxyurea did not affect vatalanib exposure, but EIAEDs decreased vatalanib and imatinib plasma exposures.
Vatalanib doses up to 1000 mg twice-a-day combined with imatinib and hydroxyurea are well tolerated. Strategies to target tumor blood vessel endothelial cells and pericytes by inhibiting VEGFR and PDGFR, respectively, are safe among recurrent malignant glioma patients and may enhance anti-angiogenesis activity.
Malignant glioma; imatinib mesylate; vascular endothelial growth factor; platelet-derived growth factor; vatalanib; hydroxyurea
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.
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).
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.
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.
Allograft; Lymphangiogenesis; Islet; Tolerance