Tumor-derived Vascular Endothelial Growth Factor Research Articles

A Remitting Seronegative Symmetrical Synovitis With Pitting Edema (RS3PE) Syndrome Patient With High-Grade Serous Ovarian Cancer: A Possible Pathogenesis of Tumor-Derived Vascular Endothelial Growth Factor

A Remitting Seronegative Symmetrical Synovitis With Pitting Edema (RS3PE) Syndrome Patient With High-Grade Serous Ovarian Cancer: A Possible Pathogenesis of Tumor-Derived Vascular Endothelial Growth Factor

Vascular endothelial growth factor plays a critical role in the formation of the pre-metastatic niche via prostaglandin E2.

Factors secreted by primary tumors can alter the microenvironment at distant organ sites, generating pre-metastatic niches for subsequent metastatic cancer cell colonization. Breast cancer cells have a propensity to home preferentially to the lung, but the underlying molecular mechanisms whereby primary breast carcinoma-derived factors affect the pre-metastatic lung environment before the arrival of the tumor cells are poorly understood. In this study, 4T1 mammary carcinoma cells were subcutaneously injected into the mammary glands of mice, resulting in the induction of inflammation, increased total vessel density and recruitment of bone marrow-derived cells (BMDCs) in pre-metastatic lungs. Subsequent examination revealed that the sites of inflammatory cell clusters in the lungs were tumor metastasis sites. Moreover, vascular endothelial growth factor (VEGF) induced prostaglandin E2(PGE2) production in mouse pulmonary microvascular endothelial cells (MPVECs) and enhanced the adhesion of 4T1 cells. Treatment with the cyclooxygenase-2 inhibitor celecoxib significantly reduced 4T1 cell adhesion to MPVECs, and also reduced cancer metastasis and the inflammatory response. These results suggest that VEGF may be an underlying carcinoma-derived factor responsible for formation of the pre-metastatic niche in the lung of 4T1 cell-bearing mice. This study, therefore, demonstrated that primary tumors can alter the lung microenvironment during the pre-metastatic phase by triggering an inflammatory response and PGE2 production. Primary tumor-derived VEGF might thus be a crucial factor responsible for the formation of the pre-metastatic niche by inducing PGE2 production.

ATL-1, a synthetic analog of lipoxin, modulates endothelial permeability and interaction with tumor cells through a VEGF-dependent mechanism

Lipoxins (LX) and 15-epi-LX are lipids with a potent inhibitory effect on angiogenesis, in different models in vivo and in vitro. ATL-1, a synthetic analog of 15-epi-LXA4, inhibits various actions stimulated by vascular endothelial growth factor (VEGF). However, LX actions on endothelial cells (EC) in tumor-related contexts are still unknown. Here, we investigated the modulation of EC by ATL-1, in a model that mimics tumor extravasation. We observed that the analog inhibited endothelial permeability induced by VEGF, through the stabilization of VE-cadherin/β-catenin-dependent adherens junctions. We tested the ability of MV3 cells, a highly metastatic melanoma cell line, to transmigrate across unchallenged EC monolayers for 18h, as compared to NGM normal melanocytes. ATL-1 was able to inhibit only melanoma extravasation. MV3 cells secrete large amounts of VEGF and we observed that ATL-1 per se did not alter this ability. Melanoma cells skills to crossing endothelial monolayers were due to the steady accumulation of tumor-derived VEGF. When endothelial cells were challenged with exogenous VEGF, added at levels comparable to those secreted by MV3 cells over 18h, and a short-term (4h) transendothelial migration assay was performed, both melanoma and melanocyte cells were able to extravasate, and ATL-1 was able to block the passage of both cells. These results indicate that ATL-1 has a potent inhibitory effect on the permeability induced by VEGF, and that this pharmacological effect could be used to block tumor extravasation across endothelial barriers, with a possible prospect of reducing the haematogenic spread of cancer cells.

Tumor endothelium FasL establishes a selective immune barrier promoting tolerance in tumors.

We describe a novel mechanism regulating the tumor endothelial barrier and T cell homing to tumors. Selective expression of the death mediator Fas ligand (FasL/CD95L) was detected in the vasculature of many human and mouse solid tumors but not in normal vasculature, and in these tumors it was associated with scarce CD8+ infiltration and predominance of FoxP3+ T regulatory (Treg) cells. Tumor-derived vascular endothelial growth factor A (VEGF-A), interleukin 10 (IL-10) and prostaglandin E2 (PGE2) cooperatively induced FasL expression on endothelial cells, which acquired the ability to kill effector CD8+ T cells, but not Treg cells, due to higher levels of cFLIP expression in Tregs. In the mouse, genetic or pharmacologic suppression of FasL produced a significant increase in the influx of tumor-rejecting CD8+ over FoxP3+ T cells. Pharmacologic inhibition of VEGF and PGE2 attenuated tumor endothelial FasL expression, produced a significant increase in the influx of tumor-rejecting CD8+ over FoxP3+ T cells, which was FasL-dependent, and led to CD8-dependent tumor growth suppression. Thus, tumor paracrine mechanisms establish a tumor endothelial death barrier, which plays a critical role in establishing immune tolerance and determining the fate of tumors.

Combination of anti-angiogenic therapies reduces osteolysis and tumor burden in experimental breast cancer bone metastasis

The clinical efficacy of anti-angiogenic monotherapies in metastatic breast cancer is less than originally anticipated, and it is not clear what the response of bone metastasis to anti-angiogenic therapies is. Here, we examined the impact of neutralizing tumor-derived vascular endothelial growth factor (VEGF) in animal models of subcutaneous tumor growth and bone metastasis formation. Silencing of VEGF expression (Sh-VEGF) in osteotropic human MDA-MB-231/B02 breast cancer cells led to a substantial growth inhibition of subcutaneous Sh-VEGF B02 tumor xenografts, as a result of reduced angiogenesis, when compared to that observed with animals bearing mock-transfected (Sc-VEGF) B02 tumors. However, there was scant evidence that either the silencing of tumor-derived VEGF or the use of a VEGF-neutralizing antibody (bevacizumab) affected B02 breast cancer bone metastasis progression in animals. We also examined the effect of vatalanib (a VEGF receptor tyrosine kinase inhibitor) in this mouse model of bone metastasis. However, vatalanib failed to inhibit bone metastasis caused by B02 breast cancer cells. In sharp contrast, vatalanib in combination with bevacizumab reduced not only bone destruction but also skeletal tumor growth in animals bearing breast cancer bone metastases, when compared with either agent alone. Thus, our study highlights the importance of targeting both the tumor compartment and the host tissue (i.e., skeleton) to efficiently block the development of bone metastasis. We believe this is a crucially important observation as the clinical benefit of anti-angiogenic monotherapies in metastatic breast cancer is relatively modest.

Neuropilin 1 deficiency on CD4+Foxp3+ regulatory T cells impairs mouse melanoma growth

Infiltration of Foxp3(+) regulatory T (T reg) cells is considered to be a critical step during tumor development and progression. T reg cells supposedly suppress locally an effective anti-tumor immune response within tumor tissues, although the precise mechanism by which T reg cells infiltrate the tumor is still unclear. We provide evidence that Neuropilin 1 (Nrp-1), highly expressed by Foxp3(+) T reg cells, regulates the immunological anti-tumor control by guiding T reg cells into the tumor in response to tumor-derived vascular endothelial growth factor (VEGF). We demonstrate for the first time that T cell-specific ablation of Nrp-1 expression results in a significant breakdown in tumor immune escape in various transplantation models and in a spontaneous, endogenously driven melanoma model associated with strongly reduced tumor growth and prolonged tumor-free survival. Strikingly, numbers of tumor-infiltrating Foxp3(+) T reg cells were significantly reduced accompanied by enhanced activation of CD8(+) T cells within tumors of T cell-specific Nrp-1-deficient mice. This phenotype can be reversed by adoptive transfer of Nrp-1(+) T reg cells from wild-type mice. Thus, our data strongly suggest that Nrp-1 acts as a key mediator of Foxp3(+) T reg cell infiltration into the tumor site resulting in a dampened anti-tumor immune response and enhanced tumor progression.

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.

Immunologic changes in patients with metastatic melanoma on bevacizumab and chemotherapy versus chemotherapy alone.

e21112 Background: Metastatic malignant melanoma is difficult to treat and has a poor prognosis. Systemic therapy for metastatic melanoma has had limited success and novel drug combinations need to be tested. To that end, we have combined anti-angiogenic therapy (bevacizumab) with chemotherapy in clinical trials and have shown some clinical efficacy. Vascular endothelial growth factor (VEGF) is increasingly seen as an immunosuppressive factor that hampers dendritic cell maturation and reduces antigen presentation. We have recently shown that tumor-derived VEGF plays a role in Th-2 driven systemic chronic inflammation seen in advanced melanoma patients. Therefore, our data suggest that blocking tumor derived VEGF with the monoclonal antibody bevacizumab may impact immunity in such a way that augments anti-tumor immunity enhancing clinical efficacy. Methods: In order to understand the immune status in metastatic melanoma patients on chemotherapy (n=55) or chemotherapy plus bevacizumab (n=73), we measured levels of 42 cytokines, chemokines and growth factors in plasma by a mulit-plex bead assay. Matched pairs analysis was performed to determine if the average responses of the measured cytokines were different between the patients that received chemotherapy with bevacizumab or chemotherapy alone. The pre-treatment levels were compared with levels drawn four weeks after the first treatment. Results: There were significant differences in IL-1a, IL-1ra, IL-6, IL-8 and IP-10 between patients treated with chemotherapy alone relative to patients treated with chemotherapy plus bevacizumab. In all cases of patients treated with chemotherapy plus bevacizumab, the levels of these cytokines all decreased relative to pre-treatment samples. In patients treated with chemotherapy alone the levels of these cytokines increased relative to pre-treatment samples. Conclusions: Our data suggest that treating patients with the anti-angiogenic drug bevacizumab may affect the plasma cytokine milieu by reducing the level of many key inflammatory cytokines. Therefore, the use of bevacizumab in combination with chemotherapy may augment host immunity and elicit a more effective anti-tumor immune response.

Expression of Tumor-Derived Vascular Endothelial Growth Factor and Its Receptors Is Associated With Outcome in Early Squamous Cell Carcinoma of the Lung

Antiangiogenic therapies targeting the vascular endothelial growth factor (VEGF) pathway have yielded more modest clinical benefit to patients with non-small-cell lung cancer (NSCLC) than initially expected. Clinical data suggest a distinct biologic role of the VEGF pathway in the different histologic subtypes of lung cancer. To clarify the influence of histologic differentiation in the prognostic relevance of VEGF-mediated signaling in NSCLC, we performed a concomitant analysis of the expression of three key elements of the VEGF pathway in the earliest stages of the following two principal histologic subtypes: squamous cell carcinoma (SCC) and adenocarcinoma (ADC). We evaluated tumor cell expression of VEGF, VEGF receptor (VEGFR) 1, and VEGFR2 using automatic immunostaining in a series of 298 patients with early-stage NSCLC recruited as part of the multicenter European Early Lung Cancer Detection Group project. A score measuring the VEGF signaling pathway was calculated by adding the tumor cell expression value of VEGF and its two receptors. The results were validated in two additional independent cohorts of patients with NSCLC. The combination of high VEGF, VEGFR1, and VEGFR2 protein expression was associated with lower risk of disease progression in early SCC (univariate analysis, P = .008; multivariate analysis, hazard ratio, 0.62; 95% CI, 0.42 to 0.92; P = .02). The results were validated in two independent patient cohorts, confirming the favorable prognostic value of high VEGF signaling score in early lung SCC. Our results clearly indicate that the combination of high expression of the three key elements in the VEGF pathway is associated with a good prognosis in patients with early SCC but not in patients with ADC.

Paraneoplastic syndrome in mice bearing high-angiogenic variant of Lewis lung carcinoma: Relations with tumor derived VEGF

BackgroundIt is well-known that tumor exerts nonmetastatic systemic effect on organism caused the development of paraneoplastic syndrome (PNS). Recent findings point to relationships between development of PNS and tumor-derived vascular endothelial growth factor (VEGF). AimComparative study of PNS manifestations in mice with transplanted two variants of Lewis lung carcinoma with different angiogenic potential. MethodsPlasma VEGF level was determined by immunoenzyme method, hematological indices were estimated with the use of hematological analyzer, the weight and cellularity of spleen and thymus were registered and histological analysis of tissue section of these organs was performed. ResultsManifestations of anemia, extramedullary hemopoiesis and tumor-associated inflammatory disease was observed in animals with high angiogenic LLC/R9 variant and was not registered in low angiogenic LLC. The emergence of PNS symptoms correlated with elevated level of circulating VEGF at the early stages of LLC/R9 growth. ConclusionManifestation of the paraneoplastic hematological syndrome most likely is conditioned on the ability of cancer cell to secrete VEGF in a high rate.

Tumor-derived vascular endothelial growth factor (VEGF)-A facilitates tumor metastasis through the VEGF-VEGFR1 signaling pathway

Vascular endothelial growth factor (VEGF) and its receptors are involved in carcinogenesis, invasion and tumor angiogenesis, but the underlying mechanism by which VEGF promotes tumor metastasis is poorly understood. In this study, we show that in cancer patients high expression of VEGF is correlated with metastasis, and anti-VEGF treatment (bevacizumab) has clinical effects on tumor metastasis. Two human lung carcinoma cell lines (A549 and SPCA1 cells) with distinct VEGF expression were injected intravenously through the lateral tail vein of SCID mice and a murine model was developed. We investigated the association between the expression of VEGF and tumor metastasis by microvessel density, immunohistochemistry and whole mount staining. At sacrifice, in the high VEGF expression A549 cell line group, the induced tumor was distinctively larger in size and multiple metastatic lesions were found in lung tissues. Two specific neutralizing anti-mouse VEGFR1 and VEGFR2 antibodies were administered to the tumor-bearing mice; anti-VEGFR1, but not anti-VEGFR2 treatment produced inhibitive effects on VEGF-induced tumor metastasis. These findings demonstrate that the VEGF-VEGFR1 signaling pathway is crucial for tumor metastasis and the blockade of VEGF-VEGFR1-induced metastasis may provide a novel approach for the prevention and treatment of tumor metastasis.

Angiopoietin-1/Tie2 Signal Augments Basal Notch Signal Controlling Vascular Quiescence by Inducing Delta-Like 4 Expression through AKT-mediated Activation of β-Catenin

Angiopoietin-1 (Ang1) regulates both vascular quiescence and angiogenesis through the receptor tyrosine kinase Tie2. We and another group previously showed that Ang1 and Tie2 form distinct signaling complexes at cell-cell and cell-matrix contacts. We further demonstrated that the former up-regulates Notch ligand delta-like 4 (Dll4) only in the presence of cell-cell contacts. Because Dll4/Notch signal restricts sprouting angiogenesis and promotes vascular stabilization, we investigated the mechanism of how the Ang1/Tie2 signal induces Dll4 expression to clarify the role of the Dll4/Notch signal in Ang1/Tie2 signal-mediated vascular quiescence. Under confluent endothelial cells, the basal Notch signal was observed. Ang1, moreover, induced Dll4 expression and production of the Notch intracellular domain (NICD). Ang1 stimulated transcriptional activity of β-catenin through phosphoinositide 3-kinase (PI3K)/AKT-mediated phosphorylation of glycogen synthase kinase 3β (GSK3β). Correspondingly, the GSK3β inhibitor up-regulated Dll4, whereas depletion of β-catenin by siRNA blocked Ang1-induced Dll4 expression, indicating the indispensability of β-catenin in Ang1-mediated up-regulation of Dll4. In addition, Dll4 expression by the GSK3β inhibitor was only observed in confluent cells, and was impeded by DAPT, a γ-secretase inhibitor, implying requirement of the Notch signal in β-catenin-dependent Dll4 expression. Consistently, we found that either Ang1 or NICD up-regulates Dll4 through the RBP-J binding site within intron 3 of the DLL4 gene and that β-catenin forms a complex with NICD/RBP-J to enhance Dll4 expression. Ang1 induced the deposition of extracellular matrix that is preferable for basement membrane formation through Dll4/Notch signaling. Collectively, the Ang1/Tie2 signal potentiates basal Notch signal controlling vascular quiescence by up-regulating Dll4 through AKT-mediated activation of β-catenin.

The Insulin-like Growth Factor-1 Receptor–Targeting Antibody, CP-751,871, Suppresses Tumor-Derived VEGF and Synergizes with Rapamycin in Models of Childhood Sarcoma

Signaling through the type 1 insulin-like growth factor receptor (IGF-1R) occurs in many human cancers, including childhood sarcomas. As a consequence, targeting the IGF-1R has become a focus for cancer drug development. We examined the antitumor activity of CP-751,871, a human antibody that blocks IGF-1R ligand binding, alone and in combination with rapamycin against sarcoma cell lines in vitro and xenograft models in vivo. In Ewing sarcoma (EWS) cell lines, CP751,871 inhibited growth poorly (<50%), but prevented rapamycin-induced hyperphosphorylation of AKT(Ser473) and induced greater than additive apoptosis. Rapamycin treatment also increased secretion of IGF-1 resulting in phosphorylation of IGF-1R (Tyr1131) that was blocked by CP751,871. In vivo CP-751,871, rapamycin, or the combination were evaluated against EWS, osteosarcoma, and rhabdomyosarcoma xenografts. CP751871 induced significant growth inhibition [EFS(T/C) >2] in four models. Rapamycin induced significant growth inhibition [EFS(T/C) >2] in nine models. Although neither agent given alone caused tumor regressions, in combination, these agents had greater than additive activity against 5 of 13 xenografts and induced complete remissions in one model each of rhabdomyosarcoma and EWS, and in three of four osteosarcoma models. CP751,871 caused complete IGF-1R down-regulation, suppression of AKT phosphorylation, and dramatically suppressed tumor-derived vascular endothelial growth factor (VEGF) in some sarcoma xenografts. Rapamycin treatment did not markedly suppress VEGF in tumors and synergized only in tumor lines where VEGF was dramatically inhibited by CP751,871. These data suggest a model in which blockade of IGF-1R suppresses tumor-derived VEGF to a level where rapamycin can effectively suppress the response in vascular endothelial cells.

Combined Vascular Endothelial Growth Factor Receptor and Epidermal Growth Factor Receptor (EGFR) Blockade Inhibits Tumor Growth in Xenograft Models of EGFR Inhibitor Resistance

The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) gefitinib and erlotinib benefit some non-small cell lung cancer (NSCLC) patients, but most do not respond (primary resistance) and those who initially respond eventually progress (acquired resistance). EGFR TKI resistance is not completely understood and has been associated with certain EGFR and K-RAS mutations and MET amplification. We hypothesized that dual inhibition of the vascular endothelial growth factor (VEGF) and EGFR pathways may overcome primary and acquired resistance. We investigated the VEGF receptor/EGFR TKI vandetanib, and the combination of bevacizumab and erlotinib in vivo using xenograft models of EGFR TKI sensitivity, primary resistance, and three models of acquired resistance, including models with mutated K-RAS and secondary EGFR T790M mutation. Vandetanib, gefitinib, and erlotinib had similar profiles of in vitro activity and caused sustained tumor regressions in vivo in the sensitive HCC827 model. In all four resistant models, vandetanib and bevacizumab/erlotinib were significantly more effective than erlotinib or gefitinib alone. Erlotinib resistance was associated with a rise in both host and tumor-derived VEGF but not EGFR secondary mutations in the KRAS mutant-bearing A549 xenografts. Dual inhibition reduced tumor endothelial proliferation compared with VEGF or EGFR blockade alone, suggesting that the enhanced activity of dual inhibition is due at least in part to antiendothelial effects. These studies suggest that erlotinib resistance may be associated with a rise in both tumor cell and host stromal VEGF and that combined blockade of the VEGFR and EGFR pathways can abrogate primary or acquired resistance to EGFR TKIs. This approach merits further evaluation in NSCLC patients.

Tumor-derived Vascular Endothelial Growth Factor and Angiopoietin-2 in Non-small Cell Lung Cancer

Lung cancer is a common disease with a dismal prognosis. Accurate staging is crucial for defining operability, selecting treatment regimens, and predicting survival. Methods of mediastinal lymph node staging include imaging and surgical sampling by different tools with many disadvantages. Angiogenesis is essential process in tumor growth, maintenance and metastasis. The tumor with high vessels density is related to metastasis and poor clinical outcome. Angiogenesis is regulated by balance between stimulatory and inhibitory regulators of endothelial cell activation. Vascular endothelial growth factor (VEGF) and Angiopoietin-2 (Ang-2) are two of the most potent angiogenic molecules. In this study we were evaluated the clinical effectiveness of serum level of Ang-2 and VEGF to aid management decision relating to diagnosis and staging of non-small cell lung cancer (NSCLC). The present work was conducted on 60 subjects. They were divided into 3 groups. Group 1 (15 healthy volunteers), Group 2 (15 patients with pulmonary diseases other than cancer) and Group 3 (30 patients with NSCLC).The latter were divided into two subgroups: Group 3a:15 patients with operable (NSCLC), and Group 3b:15 patients with non-operable NSCLC). Serum levels of Ang-2 and VEGF in different groups were measured using ELISA technique. The serum Ang-2 and VEGF were significantly higher in patients with NSCLC than patients with non-neoplastic lesions compared to healthy controls (p<0.001).There was a significant positive correlation between both levels in patients with NSCLC. With stage progression in NSCLC, the non-operable group (3b) had significantly higher levels than operable group (3a). Patients with distant metastasis had higher levels than those without (p< 0.001). But, no notable significant differences were found in either serum levels of VEGF or Ang-2 concerning the cell type .Among 30 NSCLC patients, stages of 7 patients (23.3%) were misdiagnosed because of they had normal sized lymph node on CT image . Five of them were Squamous carcinoma and the other two were adenocarcinoma on histopathological examination that need mediastioscopy. But, all NSCLC patients had high level of both markers according to their nodal staging. The operable group (3a)showed significant decrease in both levels after surgical resection (P<0.001). Conclusion:The present findings suggest that assessment of circulating levels of VEGF and Ang-2 may be simple noninvasive future tools for diagnosis, staging, treatment planning and monitoring of treatment in patients with NSCLC

VEGF-Trap (V-T) overcomes defects in dendritic cell (DC) differentiation without improvement in antigen-specific immune responses

21087 Background: Induction of antitumor immune responses requires adequate DC function. Well-documented DC defects in cancer mediated through tumor-derived vascular endothelial growth factor (VEGF) may lead to tumor escape and limit efficacy of cancer vaccines. V-T with extracellular domains of VEGFR 1/ 2 coupled to Fc IgG1 binds all VEGF-A isoforms. Methods: To determine if inhibition of VEGF signaling improves immune responses, we evaluated 15 cancer pts treated with V-T (2.0–7.0 mg/kg) IV over 1 hr Q 2 wks on a phase I trial. To evaluate immune parameters, PBMC were collected prior to, days 15, 29, and 57 of V-T treatment. Ligand blockade was achieved in all patients. Mature DCs (myeloid and plasmacytoid subsets), and regulatory T cells (T regs) were characterized by expression pattern of CD11c, CD86, CD40, CCR7, CD83, CD123, CD4, CD25, and GITR. T cell function was assessed by allogeneic mixed leukocyte reaction (MLR) and proliferation to tetanus toxoid, influenza, or PHA. Results: V-T treatment did not affect the presence of the total population of DCs, myeloid or plasmacytoid subsets, or myeloid-derived suppressor cells (MDSC). It significantly increased the proportion of mature DCs expressing CD86, CD40, CD83, and CCR7R (p&lt;0.05) without overall improvement in T cell immunity. At 8 wks, 11 pts had either stable disease (SD) or partial response (PR) to the therapy and 4 pts had progressive disease (PD), both with no significant differences in the proportion of MDSC or total DCs. The proportion of mature DCs was significantly increased in pts with SD and PR (p&lt;0.025), but remained unchanged in PD pts. However, functional tests were similar in both groups. Another subset analysis revealed significant improvement in immune responses in 6 pts who had stable or decrease in the MDSC proportion, but not in 9 pts with increases in MDSC. During V-T treatment, Tregs further increased above baseline in pts (p=0.048). Conclusions: These data demonstrate that inhibition of VEGF signaling improves differentiation of DCs in cancer patients, while alone it was not sufficient to improve immune responses. These data illustrates the multifaceted nature of immune deficiency in cancer pts and points to a need for complex approaches to modulation of immune reactivity. No significant financial relationships to disclose.

Defective Differentiation of Myeloid and Plasmacytoid Dendritic Cells in Advanced Cancer Patients is not Normalized by Tyrosine Kinase Inhibition of the Vascular Endothelial Growth Factor Receptor

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.

Selective Blockade of Vascular Endothelial Growth Factor Receptor 2 With an Antibody Against Tumor-Derived Vascular Endothelial Growth Factor Controls the Growth of Human Pancreatic Adenocarcinoma Xenografts

Vascular endothelial growth factor (VEGF), a key regulator of angiogenesis, is critical for growth of human pancreatic adenocarcinoma. Preclinical studies demonstrate that blockade of VEGF activity can control the growth of pancreatic tumors in mice. In this study, we evaluated the efficacy of 2C3, an antibody that inhibits VEGF receptor 2 activation by human VEGF, to inhibit the growth of human pancreatic adenocarcinoma in mice. Human pancreatic cancer cell lines (MiaPaca-2, Panc-1, and Capan-1) were used to establish xenografts in nu/nu mice. The expression of VEGF and its receptors was determined in each cell line. Proliferation of tumor cells in vitro and tumor growth in vivo in the presence of 2C3 or a control antibody was evaluated. The effect of 2C3 on tumor weight, total vessel density, number of pericyte-associated vessels, and tumor perfusion was determined, and the level of 2C3 in the serum of animals was measured by enzyme-linked immunosorbent assay. 2C3 did not affect the proliferation of cells in culture. 2C3 was present and active in the serum of tumor-bearing animals treated with 2C3, and these animals showed a decrease in tumor burden compared with control-treated mice. Therapy with 2C3 resulted in reduced vascular function, measured by a decrease in vessel density and in the percentage of vessels associated with pericytes. Furthermore, tumors derived from Capan-1 cells demonstrated decreased perfusion after treatment with 2C3. Blockade of VEGF receptor 2 activation by tumor-derived VEGF decreases tumor vessel function and growth of some human pancreatic adenocarcinoma cell lines in mice.

Cross-species Vascular Endothelial Growth Factor (VEGF)-blocking Antibodies Completely Inhibit the Growth of Human Tumor Xenografts and Measure the Contribution of Stromal VEGF

To fully assess the role of VEGF-A in tumor angiogenesis, antibodies that can block all sources of vascular endothelial growth factor (VEGF) are desired. Selectively targeting tumor-derived VEGF overlooks the contribution of host stromal VEGF. Other strategies, such as targeting VEGF receptors directly or using receptor decoys, result in inhibiting not only VEGF-A but also VEGF homologues (e.g. placental growth factor, VEGF-B, and VEGF-C), which may play a role in angiogenesis. Here we report the identification of novel anti-VEGF antibodies, B20 and G6, from synthetic antibody phage libraries, which block both human and murine VEGF action in vitro. Their affinity-improved variants completely inhibit three human tumor xenografts in mice of skeletal muscle, colorectal, and pancreatic origins (A673, HM-7, and HPAC). Avastin, which only inhibits the tumor-derived human VEGF, is approximately 90% effective at inhibiting HM-7 and A673 growth but is <50% effective at inhibiting HPAC growth. Indeed, HPAC tumors contain more host stroma invasion and stroma-derived VEGF than other tumors. Thus, the functional contribution of stromal VEGF varies greatly among tumors, and systemic blockade of both tumor and stroma-derived VEGF is sufficient for inhibiting the growth of tumor xenografts.

Induction of reactive oxygen intermediates—dependent programmed cell death in human malignant ex vivo glioma cells and inhibition of the vascular endothelial growth factor production by taurolidine

Taurolidine, a derivative of the amino acid taurin, was recently found to display a potent antineoplastic effect both in vitro and in vivo. The authors therefore initiated studies to assess the potential antineoplastic activity of taurolidine in human glioma cell lines and in ex vivo malignant cell cultures. They also studied the mechanisms that induce cell death and the impact of taurolidine on tumor-derived vascular endothelial growth factor (VEGF) production. Cytotoxicity and clonogenic assays were performed using crystal violet staining. In the cytotoxicity assay 100% of glioma cell lines (eight of eight) and 74% of ex vivo glioma cultures (14 of 19) demonstrated sensitivity to taurolidine, with a mean median effective concentration (EC50) of 51 +/- 28 microg/ml and 56 +/- 23 microg/ml, respectively. Colony formation was inhibited by taurolidine, with a mean EC50 of 7 +/- 3 microg/ml for the cell lines and a mean EC50 of 3.5 +/- 1.7 microg/ml for the ex vivo glioma cultures. On observing this high activity of taurolidine in both assays, the authors decided to evaluate its cell death mechanisms. Fragmentation of DNA, externalization of phosphatidylserine, activation of poly(adenosine diphosphate-ribose) polymerase, loss of the mitochondrial membrane potential followed by a release of apoptosis-inducing factor, and typical apoptotic features were found after taurolidine treatment. Cell death was preceded by the generation of reactive O2 intermediates, which was abrogated by N-acetylcysteine but not by benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone. Moreover, taurolidine also induced suppression of VEGF production on the protein and messenger RNA level, as shown by an enzyme-linked immunosorbent assay and by reverse transcription-polymerase chain reaction. Given all these findings, taurolidine may be a promising new agent in the treatment of malignant gliomas; it displays a combination of antineoplastic and antiangiogenic activities, inducing tumor cell apoptosis and inhibiting tumor-derived VEGF production.