VEGFs, receptors and angiogenesis

Assessing the in vivo efficacy of biologic antiangiogenic therapies

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Norcantharidin anti-angiogenesis activity possibly through an endothelial cell pathway in human colorectal cancer

The present study was based on the unexpected discovery that norcantharidin exerted anti-angiogenesis activity when effects on growth of human colon cancer were studied. The aim was to further verify this finding and explore possible mechanisms using a tumor xenograft model in nude mice. We confirmed that norcantharidin (5 or 15 mg/kg) could inhibit angiogenesis of human colon cancer in vivo. In vitro, crossing river assay, cell adhesion assay and tube formation assay indicated that NCTD could reduce the migration, adhesion and vascular network tube formation ability of HUVECs. At the same time, the expression levels of VEGF and VEGFR-2 proteins which play important roles in angiogenesis were reduced as examined by western blotting analysis. Taken together, the results firstly showed NCTD could inhibit angiogenesis of human colon cancer in vivo, probably associated with effects on migration, adhesion and vascular network tube formation of HUVECs and expression levels of VEGF and VEGFR-2 proteins.

Expression of VEGF-C/VEGFR-3 in human laryngeal squamous cell carcinomas and its significance for lymphatic metastasis

OBJECTIVES

Expression of vascular endothelial growth factor C (VEGF-C)and vascular endothelial growth factor receptor-3 (VEGFR-3) in laryngeal squamous carcinoma and its relationship to lymph node metastasis were investigated.

METHODS

VEGF-C and VEGFR-3 gene expression in 30 cases of normal laryngeal mucosa tissue (NLM), primary laryngeal carcinoma cell carcinomas (PLC) and cervical lymph nodes (CLN) was examined by reverse transcription polymerase chain reaction (RT-PCR). Protein levels of VEGF-C expression were determined by immunohistochemical staining in 60 cases of PLC.

RESULTS

Expression of VEGF-C and VEGFR-3 different among NLM, PLC and CLN in the same patient. In PLC, expression was significantly higher in lymph node positive group than in the lymph node negative group and associated with histological grade of differentiation; Expression of VEGF-C and VEGFR-3 was not linked with age, sex, site or T stage.

CONCLUSIONS

A close correlation was found between VEGF-C/VEGFR-3 expression and lymph node metastasis in PLC, suggesting a role in metastasis of laryngeal carcinomas.

CT322, a VEGFR-2 antagonist, demonstrates anti-glioma efficacy in orthotopic brain tumor model as a single agent or in combination with temozolomide and radiation therapy

Glioblastomas are among the most aggressive human cancers, and prognosis remains poor despite presently available therapies. Angiogenesis is a hallmark of glioblastoma, and the resultant vascularity is associated with poor prognosis. The proteins that mediate angiogenesis, including vascular endothelial growth factor (VEGF) signaling proteins, have emerged as attractive targets for therapeutic development. Since VEGF receptor-2 (VEGFR-2) is thought to be the primary receptor mediating angiogenesis, direct inhibition of this receptor may produce an ideal therapeutic effect. In this context, we tested the therapeutic effect of CT322, a selective inhibitor of VEGFR-2. Using an intracranial murine xenograft model (U87-EGFRvIII-luciferase), we demonstrate that CT322 inhibited glioblastoma growth in vivo and prolonged survival. Of note, the anti-neoplastic effect of CT322 is augmented by the incorporation of temozolomide or temozolomide with radiation therapy. Immunohistochemical analysis of CT322 treated tumors revealed decreased CD31 staining, suggesting that the tumoricidal effect is mediated by inhibition of angiogenesis. These pre-clinical results provide the foundation to further understand long term response and tumor escape mechanisms to anti-angiogenic treatments on EGFR over-expressing glioblastomas.

An experimental study of a modified dahuang zhechong pill on the--angiogenesis of RF/6A cells in vitro

OBJECTIVE

To investigate the effects of a modified Dahuang Zhechong Pill (MDZP) on the angiogenesis of rhesus choroid-retina endothelial (RF/6A) cells and its preliminary mechanism.

METHODS

A 3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) method was used to assess the effect of a MDZP on RF/6A cell proliferation induced by vascular endothelial growth factor (VEGF). Transwell inserts were used to assess the effect of the MDZP on RF/6A cell migration. Matrigel was used to assess the effect of the MDZP on the tube formation of RF/ 6A cells. Western blotting and quantitative real-time reverse transcription polymerase chain reaction (RT-PCR) were used to detect the protein and mRNA expression, respectively, of VEGF and matrix metalloproteinase-2 (MMP-2) in RF/6A cells treated with the MDZP.

RESULTS

RF/6A cell proliferation induced by VEGF was inhibited by 0.2 mg/mL MDZP. At 0, 12.5, 25 and 50 mg/mL MDZP, the number of cells that migrated through Transwell membranes was 73.33 +/- 4.51, 61.33 +/- 4.04, 28.67 +/- 6.66 and 17.67 +/- 4.16, respectively, and the number of tubes formed in Matrigel was 20.33 +/- 0.58, 13.33 +/- 1.53, 11.00 +/- 1.00 and 1.33 +/- 0.58, respectively. At 100 and 200 mg/mL MDZP, the protein and mRNA expression of VEGF and MMP-2 were inhibited in RF/6A cells. At 400 mg/mL MDZP, the expression of VEGF mRNA and MMP-2 protein were inhibited in RF/6A cells.

CONCLUSIONS

MDZP inhibits the angiogenesis of RF/6A cells via the suppression of proliferation, migration and tube formation of RF/6A cells. Inhibition of the protein and mRNA expression of VEGF and MMP-2 in RF/6A cells may be an important mechanism.

MEG3 noncoding RNA: a tumor suppressor

Maternally expressed gene 3 (MEG3) is an imprinted gene belonging to the imprinted DLK1-MEG3 locus located at chromosome 14q32.3 in humans. Its mouse ortholog, Meg3, also known as gene trap locus 2 (Gtl2), is located at distal chromosome 12. The MEG3 gene encodes a long noncoding RNA (lncRNA) and is expressed in many normal tissues. MEG3 gene expression is lost in an expanding list of primary human tumors and tumor cell lines. Multiple mechanisms contribute to the loss of MEG3 expression in tumors, including gene deletion, promoter hypermethylation, and hypermethylation of the intergenic differentially methylated region. Re-expression of MEG3 inhibits tumor cell proliferation in culture and colony formation in soft agar. This growth inhibition is partly the result of apoptosis induced by MEG3. MEG3 induces accumulation of p53 (TP53) protein, stimulates transcription from a p53-dependent promoter, and selectively regulates p53 target gene expression. Maternal deletion of the Meg3 gene in mice results in skeletal muscle defects and perinatal death. Inactivation of Meg3 leads to a significant increase in expression of angiogenesis-promoting genes and microvessel formation in the brain. These lines of evidence strongly suggest that MEG3 functions as a novel lncRNA tumor suppressor.

Fluorescein angiography, optical coherence tomography, and histopathologic findings in a VEGF(165) animal model of retinal angiogenesis

BACKGROUND

To establish an animal model of retinal neovascularization using vascular endothelial growth factor (VEGF165) and analyze the model using optical coherence tomography (OCT), fluorescein angiography (FA), and histopathologic evaluation.

METHODS

Twelve rabbits were divided into groups as follows: group 1 (n = 3), sham intravitreous injections of 0.1 ml of balanced saline; group 2 (n = 6), one 10-μg intravitreal injection of VEGF165 on day 0; and group 3 (n = 3), two 10-μg intravitreal injections of VEGF165, one on day 0 and one on day 7. Follow-up evaluations (days 0, 3, 7, 14, 21, 28) included obtaining fundus color photographs and FA, OCT, and histopathologic examinations. Eyes were enucleated and stained with hematoxylin and eosin (H&E).

RESULTS

One injection of VEGF (group 2) was associated with dilatation and tortuosity of the retinal blood vessels that developed within 72 h. Retinal neovascularization was present by day 7 and regressed by day 14. However, even on day 28, the capillaries were still tortuous. Two VEGF injections (group 3) caused increased leakage and neovascularization up to day 14; severe capillary nonperfusion was seen during week 4. At the end of the follow-up period, OCT and histopathologic examination of group 3 showed peripapillary tractional retinal detachments. By day 7, the differences between the retinal thickness seen on OCT in groups 2 and 3 and the group 1 control group were significant (p < 0.001). The histologic findings showed increased vessel size in groups 2 and 3 by days 14 and 28 compared with the controls.

CONCLUSIONS

FA, OCT, and histopathologic findings showed that this retinal neovascularization model is efficient, sustainable, and reliable. One injection of VEGF165 created neovascularization that peaked after 1 week; two injections created more intense neovascularization that evolved to retinal detachments after 4 weeks.

Sorafenib, a multikinase inhibitor, is effective in vitro against non-Hodgkin lymphoma and synergizes with the mTOR inhibitor rapamycin

Non-Hodgkin lymphoma (NHL) represents a heterogenous group of neoplasias originating from lymphoid cells. Increased angiogenesis and expression of Vascular Endothelial Growth Factor (VEGF) and its receptors (VEGFR) have been found to be associated with NHL disease progression. Increase in VEGF and other cytokines stimulate signaling cascades, including the Ras/Raf/Mek/Erk pathway, resulting in increased proliferation and decreased apoptosis. Here, we report the in vitro antilymphoma activity of sorafenib, an inhibitor of VEGFR and Raf kinase. Sorafenib induced potent cytotoxicity in NHL cell lines and patient samples. This induction of cytotoxicity was associated with a corresponding increase in apoptotic cell death. Mechanism of action of sorafenib was investigated in follicular (DoHH2) and Burkitt lymphoma (Raji) cell lines. pStat3, pAkt, Mcl1, and Xiap were downregulated in both cell lines, whereas pErk decreased in Raji but not in DoHH2 cells following sorafenib treatment. IL6 was unable to prevent sorafenib induced repression of pStat3, pAkt, Mcl1, and Bcl-Xl. Sorafenib in combination with an mTORC1 inhibitor rapamycin demonstrated synergy in inducing cytotoxicity in NHL cells. Sorafenib/rapamycin combination resulted in downregulation of pAkt, pmTOR, p-p70S6K, p4EBP1, pGSK3β, Mcl1, and Bcl-Xl. On the basis of our results, a clinical trial is underway using sorafenib with everolimus in NHL patients.

Mechanisms of resistance to vascular endothelial growth factor blockade

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

Expression of vascular endothelial growth factor (VEGF) transcript and protein in the testis of several vertebrates, including endangered species

Vascular endothelial growth factor (VEGF) is known to influence the testis function. To establish the role of VEGF in the testis of a variety of species, we analyzed the expression of VEGF transcript using human gene-specific primers by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis in the testes of 18 vertebrates, including a few endangered species. An amplicon of 566 bp representing VEGF(165) was identified in testis of all species in this study. Sequence analysis of these amplicons revealed 84 to 96% homology to available human VEGF sequence and to the VEGF sequences of other species in GenBank. Immunohistochemical analysis revealed expression of VEGF protein, primarily in Sertoli and Leydig cells and occasionally in the germ cells of the testis sections. It can be concluded from this study that expression of VEGF transcript is conserved in the testis of several vertebrates and may have a role in the process of spermatogenesis.

Suppressive effect of juzentaihoto on vascularization induced by b16 melanoma cells in vitro and in vivo

Juzentaihoto (JTT) is well known to be one of Japanese herbal medicines, and used for the supplemental therapy of cancer patients with remarkable success. The present study, therefore, was undertaken to examine the possible therapeutic mechanisms of JTT on cancer using B16 melanoma cell (B16 cell)/experimental mouse system. JTT was well mixed with rodent chow at 3.0% concentrations, and was administered orally ad libitum. Administration of JTT was started one week before tumor cell injection and continued throughout the experiment. Administration of JTT into mice significantly inhibited tumor metastasis in lungs after intravenous injection of 2 × 10⁵ B16 cells in a volume of 50 μL. JTT also significantly suppressed enlargement of tumor size in hind footpad after the subcutaneous injection of 2 × 10⁵ (50 μL) B16 cells. In the second part of experiments, the chamber that containing B16 cells was buried in the murine back. In JTT administrated group, vascular endothelial growth factor (VEGF) of chamber internal fluid significantly decreased, and vascularization of chamber circumference was also inhibited. These results strongly suggest that oral administration of JTT caused decrease in the generation of VEGF, which is responsible for vascularization, and results in inhibition of B16 cell metastasis.

Genomic profiling of glioblastoma: convergence of fundamental biologic tenets and novel insights

With advances in genomic profiling and sequencing technology, we are beginning to understand the landscape of the genetic events that accumulated during the neoplastic process. The insights gleamed from these genomic profiling studies with regards to glioblastoma etiology has been particularly satisfying because it cemented the clinical pertinence of major concepts in cancer biology-concepts developed over the past three decades. This article will review how the glioblastoma genomic data set serves as an illustrative platform for the concepts put forward by Hanahan and Weinberg on the cancer phenotype. The picture emerging suggests that most glioblastomas evolve along a multitude of pathways rather than a single defined pathway. In this context, the article will further provide a discussion of the subtypes of glioblastoma as they relate to key principles of developmental neurobiology.

Pathobiology and chemoprevention of bladder cancer

Our understanding of the pathogenesis of bladder cancer has improved considerably over the past decade. Translating these novel pathobiological discoveries into therapies, prevention, or strategies to manage patients who are suspected to have or who have been diagnosed with bladder cancer is the ultimate goal. In particular, the chemoprevention of bladder cancer development is important, since urothelial cancer frequently recurs, even if the primary cancer is completely removed. The numerous alterations of both oncogenes and tumor suppressor genes that have been implicated in bladder carcinogenesis represent novel targets for therapy and prevention. In addition, knowledge about these genetic alterations will help provide a better understanding of the biological significance of preneoplastic lesions of bladder cancer. Animal models for investigating bladder cancer development and prevention can also be developed based on these alterations. This paper summarizes the results of recent preclinical and clinical chemoprevention studies and discusses screening for bladder cancer.

Clinical significance of expression of caveolin-1 and vascular endothelial growth factor in colorectal carcinoma

AIM: To detect the expressions of caveolin-1 (Cav-1) and vascular endothelial growth factor (VEGF) in colorectal cancer and to analyze their correlation with the clinicopathological features of colorectal cancer.

METHODS: Immunohistochemistry was used to detect the expression of Cav-1 and VEGF in 83 colorectal carcinoma specimens and matched normal colorectal mucosal specimens.

RESULTS: The positive rate of Cav-1 expression was significantly lower in colorectal carcinoma than in normal colorectal mucosa (38.6% vs 81.9%, P < 0.01). VEGF was over-expressed in colorectal cancer compared to matched normal colorectal tissue (74.7% vs 13.3%, P < 0.01). The expression of Cav-1 and VEGF was significantly correlated with tumor differentiation, invasion depth and lymph node metastasis (all P < 0.05), but not with patient's age, sex or tumor size. There is a negative correlation between Cav-1 and VEGF expression in colorectal cancer (r = -0.393, P < 0.01).

CONCLUSION: The absent expression of Cav-1 and over-expression of VEGF may play an important role in the development and progression of colorectal carcinoma.

Angiogenesis: Future of pharmacological modulation

Angiogenesis is a fundamental biological process that is regulated by a fine balance between pro- and antiangiogenic molecules, and is deranged in various diseases. Historically, angiogenesis was only implicated in few diseases, such as, cancer, arthritis, and psoriasis. However, in recent years, it has been increasingly evident that excessive, insufficient or abnormal angiogenesis contributes to the pathogenesis of many more disorders. Research in angiogenesis offers a potential to cure a variety of diseases such as Alzheimer's and AIDS. Modulation of angiogenesis may have an impact on diseases in the twenty-first century similar to that which the discovery of antibiotics had in the twentieth century.

Vascular endothelial growth factor in the circulation in cancer patients may not be a relevant biomarker

BACKGROUND

Levels of circulating vascular endothelial growth factor (VEGF) have widely been used as biomarker for angiogenic activity in cancer. For this purpose, non-standardized measurements in plasma and serum were used, without correction for artificial VEGF release by platelets activated ex vivo. We hypothesize that "true" circulating (c)VEGF levels in most cancer patients are low and unrelated to cancer load or tumour angiogenesis.

METHODOLOGY

We determined VEGF levels in PECT, a medium that contains platelet activation inhibitors, in citrate plasma, and in isolated platelets in 16 healthy subjects, 18 patients with metastatic non-renal cancer (non-RCC) and 12 patients with renal cell carcinoma (RCC). In non-RCC patients, circulating plasma VEGF levels were low and similar to VEGF levels in controls if platelet activation was minimized during the harvest procedure by PECT medium. In citrate plasma, VEGF levels were elevated in non-RCC patients, but this could be explained by a combination of increased platelet activation during blood harvesting, and by a two-fold increase in VEGF content of individual platelets (controls: 3.4 IU/10(6), non-RCC: 6.2 IU/10(6) platelets, p = 0.001). In contrast, cVEGF levels in RCC patients were elevated (PECT plasma: 64 pg/ml vs. 21 pg/ml, RCC vs. non-RCC, p<0.0001), and not related to platelet VEGF concentration.

CONCLUSIONS

Our findings suggest that "true" freely cVEGF levels are not elevated in the majority of cancer patients. Previously reported elevated plasma VEGF levels in cancer appear to be due to artificial release from activated platelets, which in cancer have an increased VEGF content, during the blood harvest procedure. Only in patients with RCC, which is characterized by excessive VEGF production due to a specific genetic defect, were cVEGF levels elevated. This observation may be related to limited and selective success of anti-VEGF agents, such as bevacizumab and sorafenib, as monotherapy in RCC compared to other forms of cancer.

Discriminant analysis to classify glioma grading using dynamic contrast-enhanced MRI and immunohistochemical markers

INTRODUCTION

The purpose of the present study was to look for the possible predictors which might discriminate between high- and low-grade gliomas by pooling dynamic contrast-enhanced (DCE)-perfusion derived indices and immunohistochemical markers.

METHODS

DCE-MRI was performed in 76 patients with different grades of gliomas. Perfusion indices, i.e., relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), permeability (k (trans) and k (ep)), and leakage (v (e)) were quantified. MMP-9-, PRL-3-, HIF-1α-, and VEGF-expressing cells were quantified from the excised tumor tissues. Discriminant function analysis using these markers was used to identify discriminatory variables using a stepwise procedure. To look for correlations between immunohistochemical parameters and DCE metrics, Pearson's correlation coefficient was also used.

RESULTS

A discriminant function for differentiating between high- and low-grade tumors was constructed using DCE-MRI-derived rCBV, k (ep), and v (e). The form of the functions estimated are "D (1) = 0.642 × rCBV + 0.591 × k (ep) - 1.501 × v (e) - 1.550" and "D (2) = 1.608 × rCBV + 3.033 × k (ep) + 5.508 × v (e) - 8.784" for low- and high-grade tumors, respectively. This function classified overall 92.1% of the cases correctly (89.1% high-grade tumors and 100% low-grade tumors). In addition, VEGF expression correlated with rCBV and rCBF, whereas MMP-9 expression correlated with k (ep). A significant positive correlation of HIF-1α with rCBV and VEGF expression was also found.

CONCLUSION

DCE-MRI may be used to differentiate between high-grade and low-grade brain tumors non-invasively, which may be helpful in appropriate treatment planning and management of these patients. The correlation of its indices with immunohistochemical markers suggests that this imaging technique is useful in tissue characterization of gliomas.

Ramucirumab (IMC-1121B): Monoclonal antibody inhibition of vascular endothelial growth factor receptor-2

Angiogenesis, a well-recognized characteristic of malignancy, has been exploited more than any other pathway targeted by biologic anti-neoplastic therapies. Vascular endothelial growth factor receptor-2 (VEGFR-2) is the critical receptor involved in malignant angiogenesis with its activation inducing a number of other cellular modifications resulting in tumor growth and metastases. Ramucirumab (IMC-1121B; ImClone Systems Corporation, Branchburg, NJ) is a fully human monoclonal antibody developed to specifically inhibit VEGFR-2. Ramucirumab is currently being investigated in multiple clinical trials across a variety of tumor types. Herein, angiogenesis inhibition in cancer is reviewed and up-to-date information on the clinical development of ramucirumab is presented.

Expression of FLT4 in hypoxia-induced neovascular models in vitro and in vivo

AIM

To investigate the expression of FLT4 in retina with oxygen induced retinopathy (OIR) and in brain endothelial cell lines (bEnd3) under hypoxia conditions in mice.

METHODS

Fifty-two one-week-old C57BL/6J mice were divided into control group and hypoxia group. The mice of hypoxia group were exposed to 75% oxygen for 5 days and then returned to the room air to induce retinal neovascularization. Mice in control group were raised in the environment of room air at the same time. The expressions of FLT4 mRNA and protein were checked with RT-PCR and Western Blot analysis at postnatal day 14, 17 and 21 ( P14, P17 and P21) respectively. 125mmol/L CoCl(2) were added to the culture medium of bEnd3 cell, proteins were extracted in 12, 24, 48 and 72 hours and FLT4 levels were examined by Western Blot analysis.

RESULTS

The mRNA and protein level of FLT4 expressed in P14 and P17 OIR mice retina statistically up-regulated as compared with those in control group, but there was no statistical difference between OIR group and control group at P21. FLT4 levels increased significantly in 12, 24 and 48 hours hypoxia intervened bEnd3 cells, its levels in 72 hours increased mildly but showed no significance.

CONCLUSION

FLT4 levels increase in OIR mice retinas and bEnd3 cells in hypoxia. It may play an important role in endothelial cells proliferation in hypoxia and retinal neovascularization in OIR mice.

Vascular endothelial growth factor receptor tyrosine kinase inhibitors in non-small-cell lung cancer

Angiogenesis is essential for cancer growth and progression. Vascular endothelial growth factor (VEGF) plays a crucial role in angiogenesis. The addition of bevacizumab, an antibody to vascular endothelial growth factor (VEGF), to paclitaxel and carboplatin improves survival compared with chemotherapy alone in patients with previously untreated metastatic nonsquamous non-small-cell lung cancer (NSCLC). Vascular endothelial growth factor receptor tyrosine kinase inhibitors (VEGFR TKIs) are a new class of drugs that target the TK domain of the VEGF receptors. To evaluate the role of this class of agents in the treatment of NSCLC, some phase II and phase III studies using these agents alone or in combination with other agents have been completed. This review summarizes the currently available data on VEGFR TKIs in the treatment of NSCLC.

Angiogenic markers endoglin and vascular endothelial growth factor in gastroenteropancreatic neuroendocrine tumors

AIM: To investigate the expression and potential prognostic role of vascular endothelial growth factor (VEGF) and endoglin in gastroenteropancreatic neuroendocrine tumors (GEP-NETs).

METHODS: Microvessel density (MVD) in GEP-NETs was evaluated using endoglin and CD31 immunohistochemistry. In addition, tissue levels of endoglin and VEGF were determined in homogenates by ELISA.

RESULTS: Endoglin was highly expressed on tumor endothelial cells. CD31 MVD in GEP-NETs was significantly higher compared to endoglin MVD (P < 0.01). Two- to four-fold higher tissue levels of endoglin and VEGF were seen in tumors compared to associated normal tissue. This increased endoglin tissue expression in tumors was significantly related to tumor size (P < 0.01), presence of metastases (P = 0.04), and a more advanced tumor stage (P = 0.02), whereas expression of VEGF was not.

CONCLUSION: We suggest that endoglin is a potential marker to indicate and predict metastases, which might be useful in the post-resection therapeutic approach of patients with GEP-NETs.

[Expressions and their significances of vascular endothelial growth factor-c mrna and epidermal growth factor receptor mrna in non-small cell lung cancer tissues and lymph node tissues]

BACKGROUND AND OBJECTIVE

it has been proven that some molecular markers play important roles in diagnosis, clinical prediction and prognosis monitoring for lung cancer. The aim of this study is to investigate the expressions and their significances of vascular endothelial growth factor-C (VEGF-C) mRNA and epidermal growth factor receptor (EGFR) mRNA in non-small cell lung cancer (NSCLC) tissues and lymph node tissues.

METHODS

the expressions of VEGF-C mRNA and EGFR mRNA were detected in tumor tissues and lymph node tissues by reverse transcription polymerase chain reaction (RT-PCR) and real-time fluorescence quantitative PCR. The relationship and correlation between the expressions of VEGF-C mRNA, EGFR mRNA and clinicopathologic characteristics were analyzed.

RESULTS

the expressions of VEGF-C mRNA and EGFR mRNA in tumor tissues and lymph node tissues were significantly higher than those in control group (P < 0.05). The expressions of VEGF-C mRNA and EGFR mRNA were much higher in patients with lymph node metastasis than those without lymph node metastasis (P < 0.05). The expressions of VEGF-C mRNA and EGFR mRNA in tumor tissues and lymph node tissues were significantly correlated (r=0.834, P < 0.001; r=0.817, P < 0.001).

CONCLUSIONS

the overexpressions of VEGF-C and EGFR genes are closely related to lymph node metastasis. VEGF-C mRNA and EGFR mRNA are valuable biomarkers for early diagnosis, clinical prediction and prognosis for lung cancer.

In vivo correlation of tumor blood volume and permeability with histologic and molecular angiogenic markers in gliomas

BACKGROUND AND PURPOSE

Tumor angiogenesis is very heterogeneous and in vivo correlation of perfusion imaging parameters with angiogenic markers can help in better understanding the role of perfusion imaging as an imaging biomarker. The purpose of this study was to correlate PCT parameters such as CBV and PS with histologic and molecular angiogenic markers in gliomas.

MATERIALS AND METHODS

Thirty-six image-guided biopsy specimens in 23 patients with treatment-naive gliomas underwent PCT examinations. We correlated MVD, MVCP, VEGFR-2 expression, tumor cellularity, and WHO grade of the image-guided biopsy specimens with the PCT parameters. Histologic sections were stained with hematoxylin-eosin, CD34, and VEGFR-2 and examined under a light microscope. These histologic and molecular angiogenic markers were correlated with perfusion parameters of the region of interest corresponding to the biopsy specimen. Pearson correlation coefficients and multiple regression analyses by using clustering methods were performed to assess these correlations.

RESULTS

CBV showed a significant positive correlation with MVD (r = 0.596, P < .001), whereas PS showed a significant positive correlation with MVCP (r = 0.546, P = .001). Both CBV (r = 0.373, P = .031) and PS (r = 0.452, P = .039) also showed a significant correlation with WHO grade. VEGFR-2 positive specimens showed higher PS and CBV; however, neither was statistically significant at the .05 level.

CONCLUSIONS

CBV showed a significant positive correlation with MVD, whereas PS showed a significant positive correlation with MVCP, suggesting that these 2 perfusion parameters represent different aspects of tumor vessels; hence, in vivo evaluation of these could be important in a better understanding of tumor angiogenesis.

Antiangiogenic agents in advanced gastrointestinal malignancies: past, present and a novel future

Advanced gastrointestinal (GI) malignancies are varied in presentation, prognosis, and treatment options. With the exception of resectable recurrent colorectal cancer, metastatic GI malignancies are incurable. Cytotoxic chemotherapies have been the mainstay of therapy for decades but limited extension of survival or clinical benefit has been achieved in non-colorectal GI cancers. There has been great interest in the incorporation of antiangiogenic strategies to improve outcomes for these patients. Clear benefits have been identified with bevacizumab and sorafenib in colorectal cancer and hepatocellular cancer, respectively; other GI tumor sites have lacked impressive results with antiangiogenic agents. In this review, we will present the benefits, or lack thereof, of clinically tested antiangiogenic compounds in GI malignancies and explore some potential new therapeutic anti-angiogenesis options for these diseases.

Antiangiogenic agents in advanced gastrointestinal malignancies: past, present and a novel future

Advanced gastrointestinal (GI) malignancies are varied in presentation, prognosis, and treatment options. With the exception of resectable recurrent colorectal cancer, metastatic GI malignancies are incurable. Cytotoxic chemotherapies have been the mainstay of therapy for decades but limited extension of survival or clinical benefit has been achieved in non-colorectal GI cancers. There has been great interest in the incorporation of antiangiogenic strategies to improve outcomes for these patients. Clear benefits have been identified with bevacizumab and sorafenib in colorectal cancer and hepatocellular cancer, respectively; other GI tumor sites have lacked impressive results with antiangiogenic agents. In this review, we will present the benefits, or lack thereof, of clinically tested antiangiogenic compounds in GI malignancies and explore some potential new therapeutic anti-angiogenesis options for these diseases.

Longitudinal, multimodal functional imaging of microvascular response to photothermal therapy

Although studies have shown that photothermal therapy can coagulate selectively abnormal vasculature, the ability of this method to achieve consistent, complete removal of the vasculature is questionable. We present the use of multimodal, wide-field functional imaging to study, in greater detail, the biological response to selective laser injury. Specifically, a single-platform instrument capable of coregistered fluorescence imaging and laser speckle imaging was utilized to monitor vascular endothelial growth factor gene expression and blood flow, respectively, in a transgenic rodent model. Collectively, the longitudinal, in vivo data collected with our instrument suggest that the biological response to selective laser injury involves early-stage redistribution of blood flow, followed by increased vascular endothelial growth factor promoter activity to stimulate pro-angiogenic events.

Posttranscriptional regulation of cancer traits by HuR

Cancer-related gene expression programs are strongly influenced by posttranscriptional mechanisms. The RNA-binding protein HuR is highly abundant in many cancers. Numerous HuR-regulated mRNAs encode proteins implicated in carcinogenesis. Here, we review the collections of HuR target mRNAs that encode proteins responsible for implementing five major cancer traits. By interacting with specific mRNA subsets, HuR enhances the levels of proteins that (1) promote cell proliferation, (2) increase cell survival, (3) elevate local angiogenesis, (4) help the cancer cell evade immune recognition, and (5) facilitate cancer cell invasion and metastasis. We propose that HuR exerts a tumorigenic function by enabling these cancer phenotypes. We discuss evidence that links HuR to several specific cancers and suggests its potential usefulness in cancer diagnosis, prognosis, and therapy.

Serum levels of HMGB1, survivin, and VEGF in patients with advanced non-small cell lung cancer during chemotherapy

Recently, several reports have suggested that HMGB1 (the high-mobility group box-1) plays a key role in tumor angiogenesis through multiple mechanisms, including up-regulation of proangiogenic factors. This study was conducted to investigate the prognostic role and the effects of chemotherapy on serum (ELISA) angiogenic factors: HMGB1, survivin and VEGF (Vascular Endothelial Growth Factor) in patients with advanced stage non-small cell lung cancer (NSCLC). The study entered 40 patients (31 man) and 15 healthy volunteers (control group). Peripheral blood samples were taken before and after four cycles of chemotherapy. The mean serum HMGB1 and VEGF levels were significantly higher in patients with advanced NSCLC than in controls (p=0.024, p=0.028, respectively). The levels of survivin in NSCLC patients were comparable to controls. No correlation was found between HMGB1, survivin and VEGF concentrations and the histological type and staging of lung cancer. Similarly, no correlation was revealed between the concentrations of HMGB1, survivin and VEGF and the effect of chemotherapy. However, in patients with NSCLC, HMGB1 positevely correlated with survivin (R=0.814, p=0.007) before chemotherapy, and negatively with VEGF (R=-0.841, p=0.035) after chemotherapy. When the cut-off values of serum HMGB1, survivin and VEGF (2.38 ng/ml, 81.92 pg/ml, 443.26 pg/ml, respectively) were used, the prognoses of high and low groups were not different. Concluding, patients with NSCLC have a higher serum concentration of HMGB1 and VEGF, while survivin levels are comparable to healthy individuals. In our opinion, determination of HMGB1, survivin and VEGF concentrations has no clinical significance in the prognosis of the survival time in lung cancer.

Triple-negative breast cancer: role of antiangiogenic agents

New blood vessel formation plays an important role in breast cancer growth, invasion, and metastasis. Tumor growth is preceded by the development of new blood vessels, which provide a pathway for metastases and nutrients essential for growth. Vascular endothelial growth factor (VEGF) is a key angiogenic mediator that stimulates endothelial cell proliferation and regulates vascular permeability. Highly proliferative tumors, such as those that are negative for the estrogen, progesterone, and HER2/neu receptors have enhanced angiogenesis that supports rapid growth and early metastases and have been found to have high levels of VEGF. Drugs developed to inhibit the angiogenic process may be particularly effective in triple-negative breast cancer. Subset analyses have demonstrated efficacy with combinations of the VEGF antibody bevacizumab in combination with chemotherapy and, to a limited degree, with other antiangiogenic agents. Many targeted biologic agents in development inhibit angiogenesis including those that inhibit the mammalian target of rapamycin, fibroblast growth factor, Notch, hypoxic inducible factor, 2-methoxyestradiol, insulin like growth factor, matrix metalloproteinase, and others. Ongoing studies are focusing on the effects of these agents in triple-negative disease, and there is an urgent need to identify markers that can predict response to specific targeted therapy.

Serum VEGFR-3 and survival of advanced gastric cancer patients treated with FOLFOX

AIM: To explore if vascular endothelial growth factor receptor-3 (VEGFR-3) and carcinoembryonic antigen (CEA) can predict overall survival in advanced gastric cancer.

METHODS: VEGFR-3 level was assessed by enzyme-linked immunosorbent assay, and CEA was assessed by chemiluminescence immunoassay in the sera of 81 advanced gastric cancer patients before treatment with oxaliplatin plus 5-fluorouracil and folinic acid.

RESULTS: Median survival time in patients with a low serum VEGFR-3 level was significantly longer than in those with a higher VEGFR-3 level (15.4 mo vs 7.7 mo, P < 0.001). Patients with a low CEA level had a longer survival than those with a higher CEA level (15.8 mo vs 8.6 mo, P < 0.001). Thirty-nine patients with low VEGFR-3 and low CEA levels had a median survival of 19.7 mo (P = 0.0006). The hazard ratio for patients with a high VEGFR-3 level was 2.443 (P = 0.002).

CONCLUSION: High serum VEGFR-3 level is correlated significantly with poor survival. In patients with a high serum level of VEGFR-3, alternative chemotherapy regimens should be considered.

Beneficial effect of metronomic chemotherapy on tumor suppression and survival in a rat model of hepatocellular carcinoma with liver cirrhosis

PURPOSE

Recent studies have demonstrated that frequent, low-dose metronomic (MET) dosing of cytotoxic agents may not only be as efficient as conventional maximum tolerated dose (MTD) chemotherapy but also less toxic. In this study, we investigated the therapeutic effect and safety of MET chemotherapy using cyclophosphamide (CTX) in rats with chemically induced hepatocellular carcinoma (HCC).

METHODS

Rats received weekly intraperitoneal (i.p.) injections of diethylnitrosamine during 16 weeks for induction of HCC. The rats were divided into three groups: MTD group received 40 mg/kg CTX i.p. injection on days 1, 3, and 5 of a 21-day cycle; Control and MET groups received saline and 20 mg/kg CTX i.p. injection twice a week, respectively. The growth-modulating effects and overall survival were compared between the groups. Anti-angiogenic effects were evaluated by a measurement of endothelial cell and VEGFR-2 expression.

RESULTS

At 6 weeks of therapy, MTD and MET chemotherapy resulted in a significant reduction in tumor number and size compared with Control group. MET chemotherapy showed more prolonged survival than MTD chemotherapy and Control groups (P < 0.05). MET chemotherapy resulted in a significant decrease in both the micro-vessel density and endothelial proliferation index (P < 0.01). Furthermore, MET chemotherapy led to a greater decrease in VEGFR-2 expression at the mRNA and protein levels (P < 0.01).

CONCLUSIONS

MET scheduling not only exhibits anti-tumor and anti-angiogenic effects, but also prolongs survival without major toxicities in a rat model of HCC. Our results suggest that MET chemotherapy has a high therapeutic value and should be considered for future clinical trials.

ZIP4 upregulates the expression of neuropilin-1, vascular endothelial growth factor, and matrix metalloproteases in pancreatic cancer cell lines and xenografts

We have recently found that a zinc transporter, ZIP4, is overexpressed in human pancreatic cancer and contributes to pancreatic cancer pathogenesis and progression. However, the detailed mechanism that how ZIP4 regulates pancreatic cancer growth is not clear. In this study, we further investigated the key molecules regulated by ZIP4 in pancreatic cancer angiogenesis and metastasis. We found that overexpression of ZIP4 caused significantly increased expression of NRP-1, VEGF, MMP-2 and MMP-9 in both pancreatic cancer cell lines and xenografts. Conversely, silencing of ZIP4 by short hairpin RNA (shRNA) was associated with decreased expression of NRP-1 and VEGF in pancreatic cancer xenografts. The ZIP4 expression and NRP-1 level are also correlated in established human pancreatic cancer cell lines. These results indicate that ZIP4-mediated pancreatic cancer growth might involve angiogenesis, invasion and metastasis pathways, and NRP-1, VEGF and MMPs are important intermediate molecules in transducing the ZIP4 initiated signal cascades in pancreatic cancer.

Vascular endothelial growth factor and bladder from a different perspective: not only an angiogenic factor

Angiogenesis has a key role for embryonic development and is crucial in several major diseases. Molecular basis of angiogenesis has been widely investigated (J Biochem Mol Biol. 2006;39:469-478, Oncogene. 2000;19:5598-5605). In this review, vascular endothelial growth factor (VEGF) and related receptors and their key roles in embryonic bladder development are discussed. The normal VEGF expression and related angiogenesis pattern of embryonic bladder are highlighted. The VEGF family especially VEGF-A is the major player in angiogenesis as well as many other angiogenic factors and activates 2 tyrosine kinase receptors, VEGFR-1 and VEGFR-2 (J Biochem Mol Biol. 2006;39:469-478). Besides its worthy role in angiogenesis, VEGF-A also seems to participate in normal bladder development (J Urol. 2007;177:1552-1557, Br J Urol Int. 2006;98:217-225). In previous studies, we have shown that exogenous VEGF or hypoxia-induced endogenous upregulation of this protein accelerates the growth of the bladder by detrusor and urothelium hypertrophy and hyperplasia (J Urol. 2007;177:1552-1557, Br J Urol Int. 2006;98:217-225, Dev Biol. 1997;183:139-149, Neurourol Urodyn. 2004;23:342-348). This abrupt role of VEGF on detrusor muscle through a hypoxic pathway may potentially be a part of the solution for many urologic conditions such as remodeling of detrusor muscle in antenatal bladder outlet obstruction.

The role of MMP-9 in the anti-angiogenic effect of secreted protein acidic and rich in cysteine

Background:

Secreted protein acidic and rich in cysteine (SPARC), a matricellular glycoprotein, modulates cellular interaction with the extracellular matrix and is capable of altering the growth of various cancers. We therefore sought to determine the effect of SPARC expression on medulloblastoma tumour growth and angiogenesis.

Methods:

To this extent, we selected three SPARC full-length cDNA overexpressed clones (Daoy-SP). Consequences of SPARC overexpression were studied in terms of cell growth, angiogenesis using co-culture assay in vitro, dorsal skin-fold chamber assay in vivo, PCR Array for human angiogenic genes, as well as western blotting for angiogenic molecules and tumour growth, in an orthotopic tumour model.

Results:

The SPARC protein and mRNA levels were increased by approximately three-fold in Daoy-SP cells compared with parental (Daoy-P) and vector (Daoy-EV) controls. Daoy-SP clones reduced tumour cell-induced angiogenesis in vitro and in vivo, and formed small tumours with fewer blood vessels when compared with controls. Matrix metalloprotease-9 (MMP-9) and vascular endothelial growth factor (VEGF) expression were decreased in Daoy-SP clones. Further, inhibition of MMP-9 expression caused SPARC-mediated inhibition of angiogenesis and tumour growth as MMP-9 rescued SPARC-mediated anti-angiogenic effect in vitro and tumour growth inhibition in vivo.

Conclusion:

Overexpression of SPARC decreases angiogenesis, which leads to decreased tumour growth. Further, the role of MMP-9 could be attributed to the anti-angiogenic effect of SPARC.

RNA-binding proteins implicated in the hypoxic response

In cells responding to low oxygen levels, gene expression patterns are strongly influenced by post-transcriptional processes. RNA-binding proteins (RBPs) are pivotal regulators of gene expression in response to numerous stresses, including hypoxia. Here, we review the RBPs that modulate mRNA turnover and translation in response to hypoxic challenge. The RBPs HuR (human antigen R) and PTB (polypyrimidine tract-binding protein) associate with mRNAs encoding hypoxia-response proteins such as HIF-1α and VEGF mRNAs, enhance their expression after hypoxia and play a major role in establishing hypoxic gene expression patterns. Additional RBPs such as iron-response element-binding proteins (IRPs), cytoplasmic polyadenylation-element-binding proteins (CPEBs) and several heterogeneous nuclear ribonucleoproteins (hnRNPs) also bind to hypoxia-regulated transcripts and modulate the levels of the encoded proteins. We discuss the efficient regulation of hypoxic gene expression by RBPs and the mounting interest in targeting hypoxia-regulatory RBPs in diseases with aberrant hypoxic responses.

Angiogenesis in non-Hodgkin's lymphoma: Clinico-pathological correlations and prognostic significance in specific subtypes

The aim of the study was to evaluate angiogenesis in different subtypes of non-Hodgkin's lymphoma (NHL) and to correlate angiogenic scores to clinical endpoints. Pre-therapeutic lymph node biopsies from 308 patients with NHL [107 follicular B-cell lymphoma (FL), 94 diffuse large B-cell lymphoma (DLBCL), 107 peripheral T-cell lymphoma (PTCL)] were studied. Microvessels were scored according to the Chalkley and microvessel density method (MVD) methods. Vascular endothelial growth factor (VEGF) protein expression was evaluated by immunohistochemistry. Both Chalkley and MVD methods showed, that the lymphoma subtypes differed significantly in angiogenic scores (P < 0.001). Angiogenic scores in tumor area were highest in PTCL, and lowest in FL. However, a remarkable high microvessel density was found in interfollicular areas of FL. In FL, high interfollicular MVD scores predicted progressive disease and poorer overall and event-free survival (P = 0.024 and 0.013). High interfollicular Chalkley scores correlated with transformation to DLBCL (P = 0.01). VEGF expression was detected in all NHL subtype, and the strongest expression was found in PTCL. In FL, patients with diffuse VEGF expression in lymphoma cells had poorer overall survival than those with focal expression.

Angiogenesis and Anti-angiogenic Therapy in Myelofibrosis with Myeloid Metaplasia

Myelofibrosis with myeloid metaplasia (MMM) is a clonal stem cell disorder that is characterized by florid bone marrow stromal reaction including collagen fibrosis, osteosclerosis, and angiogenesis. Almost all patients with MMM display increased bone marrow microvessel density (MVD) and the extent is among the highest in hematological malignancies. This particular information has encouraged the therapeutic use of anti-angiogenic drugs in MMM. In the current review, we summarize the general concepts regarding angiogenesis, assessment of angiogenesis in hematological malignancies and then the current literature on angiogenesis and anti-angiogenic therapy in MMM.