Expression of vascular permeability factor (vascular endothelial growth factor) and its receptors in endometrial carcinoma

TRIMming Down Hormone-Driven Cancers: The Biological Impact of TRIM Proteins on Tumor Development, Progression and Prognostication

The tripartite motif (TRIM) protein family is attracting increasing interest in oncology. As a protein family based on structure rather than function, a plethora of biological activities are described for TRIM proteins, which are implicated in multiple diseases including cancer. With hormone-driven cancers being among the leading causes of cancer-related death, TRIM proteins have been described to portrait tumor suppressive or oncogenic activities in these tumor types. This review describes the biological impact of TRIM proteins in relation to hormone receptor biology, as well as hormone-independent mechanisms that contribute to tumor cell biology in prostate, breast, ovarian and endometrial cancer. Furthermore, we point out common functions of TRIM proteins throughout the group of hormone-driven cancers. An improved understanding of the biological impact of TRIM proteins in cancer may pave the way for improved prognostication and novel therapeutics, ultimately improving cancer care for patients with hormone-driven cancers.

Angiogenesis in gynecological cancers and the options for anti-angiogenesis therapy

Angiogenesis is required in cancer, including gynecological cancers, for the growth of primary tumors and secondary metastases. Development of anti-angiogenesis therapy in gynecological cancers and improvement of its efficacy have been a major focus of fundamental and clinical research. However, survival benefits of current anti-angiogenic agents, such as bevacizumab, in patients with gynecological cancer, are modest. Therefore, a better understanding of angiogenesis and the tumor microenvironment in gynecological cancers is urgently needed to develop more effective anti-angiogenic therapies, either or not in combination with other therapeutic approaches. We describe the molecular aspects of (tumor) blood vessel formation and the tumor microenvironment and provide an extensive clinical overview of current anti-angiogenic therapies for gynecological cancers. We discuss the different phenotypes of angiogenic endothelial cells as potential therapeutic targets, strategies aimed at intervention in their metabolism, and approaches targeting their (inflammatory) tumor microenvironment.

Changes in the Expression Profile of VEGF-A, VEGF-B, VEGFR-1, VEGFR-2 in Different Grades of Endometrial Cancer

Background

VEGF-A, VEGF-B, VEGFR-1 and VEGFR-2 are important proteins involved in the induction and development of a new blood vessel network through which the tumor is properly nourished and oxygenated.

Objectives

The aim of the study was to evaluate changes in VEGF-A, VEGF-B, VEGFR-1 and VEGFR-2 expression in endometrial cancer depending on its grade and to determine the VEGFR-1 to VEGFR-2 concentration ratio.

Methods

The study group consisted of 45 patients diagnosed with endometrial cancer (G1, 17; G2, 15; G3, 13). The control group included 15 patients. VEGF-A, VEGF-B, VEGF-R1, VEGFR-2 expression was assessed using the immunohistochemical method. Statistical analysis was carried out using the Statistica 12 PL program (StatSoft, Cracow, Poland). It included the one-way ANOVA and Tukey's post-hoc test (p<0.05).

Results

Statistically significant differences in the level of VEGF-A, VEGF-B, VEGF-R1, VEGFR-2 were observed between the majority of analyzed groups (except for VEGF-B; G3 vs. G1, p=0.997700). The expression pattern of VEGF-A, VEGF-R1, VEGFR-2 was as follows: G3>G2>G1>C; VEGF-B: G2> G3> G1>C. A lower concentration of VEGFR-1 than VEGFR-2 was found regardless of the cancer grade.

Conclusion

VEGF-A, VEGF-B, VEGF-R1, VEGFR-2 are key proteins involved in tumor angiogenesis. The analysis of the entire panel of proteins participating in a given process is an important element of modern diagnostics. The concentration ratio of VEGFR-1 to VEGFR-2 appears to be a determining factor in the patients' survival prognosis.

Stomatitis and VEGFR-Tyrosine Kinase Inhibitors (VR-TKIs): A Review of Current Literature in 4369 Patients

Background

Multitargeted tyrosine kinase inhibitors (TKIs) represent a new class of target-specific antineoplastic agents. These agents show some specific adverse events such as fatigue/asthenia, anorexia/loss of appetite, dysgeusia, diarrhea/abdominal pain, hypothyroidism, hypertension, myelosuppression, and stomatitis.

Materials and Methods

A systematic search was performed on PubMed online database using a combination of MESH terms and free text words, “sunitinib” OR “sorafenib” OR “axitinib” OR “cabozantinib” OR “pazopanib” OR “regorafenib” OR “nintedanib” OR “vatalanib” combined through the use of Boolean operator AND with the key words “stomatitis” OR “mucositis,” (i) on human subjects, (ii) written in the English language, and (iii) reporting about the incidence of stomatitis or oral mucositis.

Results

The incidence of stomatitis of any grade was 35.2% for sunitinib, 20.52% for sorafenib, 20.63% for axitinib, and 34.21% for cabozantinib. All the agents showed high rates of low-grade stomatitis (G1-G2), while the onset of severe stomatitis (G3-G4) was very low.

Conclusions

Analysis of the reports with patients treated with sunitinib, sorafenib, axitinib, and cabozantinib showed a clear prevalence of stomatitis grade 1 or grade 2. These data differ from those of patients treated with conventional chemotherapy in which mucositis is predominantly of grade 3 or grade 4.

Antiangiogenics and immunotherapies in cervical cancer: an update and future's view

Despite availability of primary and secondary prevention measures, cervical cancer (CC) persists as one of the most common cancers among women around the world, and more than 70% of cases are diagnosed at advanced stages. Although significant progress has been made in the treatment of CC, around 15-61% of patients develop a recurrence in lymph nodes or distant sites within the first 2 years of completing treatment and the prognosis for these patients remains poor. During the last decades, in an attempt to improve the outcome in these patients, novel agents as combination therapy that target known dysfunctional molecular pathways have been developed with the most attention to the inhibitors of the angiogenesis process. One therapeutic target is the vascular endothelial growth factor, which has been shown to play a key role in tumor angiogenesis, not only for growth of new tissue but also in tumor proliferation. Bevacizumab is recognized as a potent antiangiogenic agent in ovarian cancer but has also demonstrated encouraging antitumor activity in recurrent CC. Moreover, other antiangiogenic agents were recently under study including: sunitinib, sorafenib, pazopanib, cediranib and nintedanib with interesting preliminary results. Moreover, over the last few years there has been increasing interest in cellular immunotherapy as a strategy to harness the immune system to fight tumors. This article focuses on recent discoveries about antiangiogenic agents and immunotherapies in the treatment of CC highlighting on future's view.

Effect of intravitreal injection of ranibizumab on retinal ganglion cells and microvessels in the early stage of diabetic retinopathy in rats with streptozotocin-induced diabetes

The aim of the present study was to investigate the effect of intravitreal injection of ranibizumab on retinal ganglion cells and microvessels at the early stage of diabetic retinopathy (DR) in rats with streptozotocin-induced diabetes mellitus (DM). DM was induced by a single intraperitoneal injection of 60 mg/kg body weight streptozotocin. A total of 80 diabetic rats were randomly assigned to four treatment groups (n=20 in each group) and were treated with an oculus dexter intravitreal injection of ranibizumab. Groups A and B were injected with ranibizumab two and four weeks after DM-induction, respectively, while groups a and b (controls) were injected with phosphate-buffered saline at the same time points. In addition, 20 normal rats were assigned to group N (blank control; without intraocular injection). Vitreous humors were isolated for vascular endothelial growth factor (VEGF)-A ELISA and retinas were obtained for hematoxylin and eosin staining, periodic acid-Schiff staining and fluorescence imaging techniques at six and eight weeks after the onset of DM. At six and eight weeks, a significantly increased in retinal ganglion cells (RGCs) was observed in group A compared with group a (P<0.01), and in group B compared with group b (P<0.01). In addition, there was a significant difference in the RGC level between groups A and B at six weeks after DM induction (P<0.01), but not at eight weeks (P>0.05). VEGF-A concentrations in rat vitreous humors were significantly lower in groups A and B compared with groups a and b at six and eight weeks after DM induction (P<0.01). Furthermore, the ratio of endotheliocytes to pericytes in groups A and B was significantly lower compared with groups a and b at six and eight weeks (P<0.05). Furthermore, it was also demonstrated that type IV collagen-positive strands were not present in group A during the eight-week observation period, which was significantly different from groups a, b and B (P<0.01). In conclusion, intravitreal injection of ranibizumab at a very early stage of DR in streptozotocin-induced DM rats slowed the progression of DR by reducing vascular regression or damage and maintaining RGC numbers, as well as reducing VEGF-A concentrations.

Functionalized nanoceria exhibit improved angiogenic properties

Overall schematic representation of the synthesis, characterization and proangiogenic activity of functionalized nanoceria.

Antiangiogenic agents in gynecological cancer: State of art and perspectives of clinical research

Vascular endothelial growth factor [VEGF] pathway, which plays a key role in angiogenesis, may be blocked by either extracellular interference with VEGF itself (bevacizumab [BEV] or aflibercept), or intracytoplasmic inhibition of VEGF receptor (pazopanib, nintedanib, cediranid, sunitinib and sorafenib). An alternative approach is represented by trebananib, a fusion protein that prevents the interaction of angiopoietin [Ang]-1 and Ang-2 with Tie2 receptor on vascular endothelium. The combination of antiangiogenic agents, especially BEV, and chemotherapy is a rational therapeutic option for primary or recurrent ovarian carcinoma. However, it will be difficult to accept that it represents the new standard treatment, until biological characterization of ovarian carcinoma has not identified subsets of tumors with different responsiveness to BEV. Anti-angiogenesis is an interesting target also for recurrent cervical or endometrial cancer, but nowadays the use of anti-angiogenic agents in these malignancies should be reserved to patients enrolled in clinical trials.

Upregulation of vascular endothelial growth factor mRNA level is significantly related to progression and prognosis of oral squamous cell carcinomas

BACKGROUND/PURPOSE

Vascular endothelial growth factor (VEGF) is a potent angiogenic factor. This study evaluated whether the VEGF mRNA level in oral squamous cell carcinoma (OSCC) tissue could be a biomarker to predict the progression and prognosis of OSCCs in Taiwan.

METHODS

This study used quantitative real-time reverse transcription-polymerase chain reaction (quantitative RT-PCR) to detect the VEGF mRNA levels in 60 OSCC specimens. Threshold cycle (CT) was defined as the PCR cycle number needed to generate a predetermined amount of DNA (threshold). The relative amount of tissue VEGF mRNA, standardized against the amount of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA, was expressed as ΔCT = (VEGF CT - GAPDH CT). For a chosen threshold, a smaller starting copy number of mRNA results in a higher CT value. Thus, the lower the ΔCT, the greater the copy number of VEGF mRNA in tissues.

RESULTS

The lower mean VEGF mRNA ΔCT value was significantly associated with OSCCs with larger tumor size (p = 0.040), positive lymph node metastasis (p = 0.023), and more advanced clinical stages (p = 0.008). VEGF mRNA ΔCT value < 4.2 (p = 0.026) was identified as an independent unfavorable prognosis factor using multivariate regression analyses. Moreover, Kaplan-Meier curve showed that OSCC patients with a VEGF mRNA ΔCT value < 4.2 had a significantly poorer overall survival than those with a VEGF mRNA ΔCT value ≥4.2 (log-rank test, p = 0.0427).

CONCLUSION

The OSCC tissue VEGF mRNA level can be used to predict the progression and prognosis of OSCCs in Taiwan.

The growth and aggressive behavior of human osteosarcoma is regulated by a CaMKII-controlled autocrine VEGF signaling mechanism

Osteosarcoma (OS) is a hyperproliferative malignant tumor that requires a high vascular density to maintain its large volume. Vascular Endothelial Growth Factor (VEGF) plays a crucial role in angiogenesis and acts as a paracrine and autocrine agent affecting both endothelial and tumor cells. The alpha-Ca²⁺/Calmodulin kinase two (α-CaMKII) protein is an important regulator of OS growth. Here, we investigate the role of α-CaMKII-induced VEGF in the growth and tumorigenicity of OS. We show that the pharmacologic and genetic inhibition of α-CaMKII results in decreases in VEGF gene expression (50%) and protein secretion (55%), while α- CaMKII overexpression increases VEGF gene expression (250%) and protein secretion (1,200%). We show that aggressive OS cells (143B) express high levels of VEGF receptor 2 (VEGFR-2) and respond to exogenous VEGF (100nm) by increasing intracellular calcium (30%). This response is ameliorated by the VEGFR inhibitor CBO-P11, suggesting that secreted VEGF results in autocrine stimulated α-CaMKII activation. Furthermore, we show that VEGF and α-CaMKII inhibition decreases the transactivation of the HIF-1α and AP-1 reporter constructs. Additionally, chromatin immunoprecipitation assay shows significantly decreased binding of HIF-1α and AP-1 to their responsive elements in the VEGF promoter. These data suggest that α-CaMKII regulates VEGF transcription by controlling HIF-1α and AP-1 transcriptional activities. Finally, CBO-P11, KN-93 (CaMKII inhibitor) and combination therapy significantly reduced tumor burden in vivo. Our results suggest that VEGF-induced OS tumor growth is controlled by CaMKII and dual therapy by CaMKII and VEGF inhibitors could be a promising therapy against this devastating adolescent disease.

Are we causing the recurrence-impact of perioperative period on long-term cancer prognosis: Review of current evidence and practice

Newer developments in the field of chemotherapeutic drug regimes, radiotherapy, and surgical techniques have improved the prognosis of cancer patients tremendously. Today increasing numbers of patients with aggressive disease are posted for surgical resection. The advances in reconstructive flap surgery offer the patient a near normal dignified postresection life. Hence, the expectations from the patients are also on the rise. Anesthetic challenges known in oncosurgery are that of difficult airway, maintenance of hemodynamics and temperature during long surgical hours, pain management, and postoperative intensive care management. But, recently acquired data raised the possibility of the anesthetic technique and conduct of perioperative period as a possible contributory factor in the growth and possible recurrence of the primary tumor. The foundation of the concept is somewhat fragile and not supported by conclusive evidence. In fact, like any other controversial topic in medicine, contradictory reports of the favorable effects of anesthetic technique and medications are plenty in the literature. This is the basis of our article where we have analyzed the current evidence available in the literature and how these and the forthcoming large scale studies may revolutionize the practice of oncoanesthesia.

The role of angiogenic factors in endometrial cancer

Endometrial cancer is the most common malignancy within the female reproductive system (37.7%). The incidence increases with age. Frequently this type of cancer is diagnosed in peri- and post-menopausal women. 60-70% of cancers occur in women over 60 years of age, and less than 5% in women below 40 years of age.

Angiogenesis is a process of formation of new microvessels from existing capillaries. There are four different mechanisms of new vessel growth: sprouting, intussusception, vessel elongation and incorporation of endothelial progenitor cells into new microvessels. Angiogenesis plays important roles in growth of endometrial cancers. This process is controlled by many angiogenic factors, for example vascular endothelial growth factor (VEGF). VEGF is the most powerful and most specific endothelial cell growth factor. It plays a crucial role in the initiation of physiological and pathological angiogenesis, lymphangiogenesis, and vasculogenesis. The VEGF family consists of VEGF-A, VEGF-B, VEGF-C, VEGF-D, VEGF-E, VEGF-F and PLGF (placental growth factor). The effects of VEGF are mediated through binding to the two specific and homologous receptors VEGFR-1 (FLT-1) and VEGFR-2 (KDR). Placental growth factor (PLGF) belongs to the VEGF family and it is also a very important growth factor. So far four isoforms of PLGF have been identified: PLGF-1 (PLGF131), PLGF-2 (PLGF152), PLGF-3 (PLGF203) and PLGF-4 (PLGF224).

Expression profiling and significance of VEGF-A, VEGFR2, VEGFR3 and related proteins in endometrial carcinoma

BACKGROUND

Angiogenesis plays a key role in the progression of various tumors, including endometrial carcinomas. Several cytokines and their associated receptors are shown to be involved, particularly VEGF-A with VEGFR1, -2 and -3.

METHODS

The expressions of VEGF-A, VEGFR2 and VEGFR3 were studied in by immunohistochemistry in 76 endometrial carcinoma specimens. VEGFR2 and VEGFR3 receptor expression were also studied by qRT-PCR in 17 tumors in comparison to normal endometrium. The expression profiles were correlated with tumor type, grade, stage, lymphovascular invasion, disease free survival, and the expressions of other cytokine receptors (EGFR, CXCR1 and CXCR2).

RESULTS

Immunohistochemically, 63% of endometrial cancers expressed VEGF-A, 55% VEGFR2 and 26% VEGFR3. VEGFR3 was significantly correlated with tumor stage (p=0.02), with a trend towards poorer disease free survival (p=0.09). VEGF-A was significantly correlated with microvessel density (p<0.01). Using qRT-PCR, increased expression of VEGFR2 (17.2-fold) and VEGFR3 (21.9-fold) was seen in endometrial carcinomas compared with normal endometrium, with significant correlations among the expression levels of VEGFR2, VEGFR3, EGFR, CXCR1 and CXCR2.

CONCLUSION

Our study suggests that evaluation of VEGFR3 expression in tumors may provide prognostic data, and help identify patients who would best benefit from anti-angiogenic therapeutic agents. This is the first report showing correlations between the expressions levels of the different receptors.

Relationship between preoperative serum TSH levels and expression of VEGF in papillary thyroid carcinoma

AIM

Vascular endothelial growth factor (VEGF) stimulates angiogenesis, increases vascular permeability and seems to correlate to aggressiveness of tumors. Increased expression of VEGF has been observed in papillary thyroid carcinoma (PTC). Thyroid stimulating hormone (TSH) is the major thyroid hormone, but its relationship with VEGF has seldom been studied. Therefore, we explored whether the immunohistochemical expression of VEGF was related to the serum TSH level.

METHODS

VEGF expression was analyzed in 43 archived PTC specimens using immunohistochemistry, with adjacent normal thyroid tissues used as controls. Serum TSH was measured by immunoradiometric assay before surgery and correlated to VEGF expression.

RESULTS

Positive VEGF expression was found in 90% of 43 PTC tissue specimens, but not in normal tissue. The serum TSH levels revealed a positive correlation with VEGF expression, R = 0.592 (P < 0.01).

CONCLUSIONS

TSH is a major thyroid hormone. Whether TSH promotes the progression of PTC is not known but the serum TSH levels reveal a positive correlation with VEGF expression.

Promoting melanoma growth and metastasis by enhancing VEGF expression

Angiogenesis plays an essential role in tumor growth and metastasis and is a promising target for cancer therapy. Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis. The present study was designed to determine the role of VEGF in tumor growth and metastasis. The sequences for the VEGF gene were cloned into expression plasmids and then transfected into melanoma B16 cells. Overexpression of VEGF transfected with expression plasmids or given exogenous VEGF and epidermal growth factor (EGF) significantly enhanced tumor cell proliferation, migration, and invasion. Tumor growth and metastasis of melanoma B16 cells transfected with VEGF plasmid were significantly promoted compared with those of cells administered with exogenous VEGF or EGF. These results indicated that VEGF can be an effective antiangiogenic strategy for melanoma.

Prognostic value of tgfb1 protein in endometrioid adenocarcinoma

BACKGROUND

Angiogenesis is a prerequisite for tumour development, progression and metastasis; however, its underlying molecular mechanisms in endometrial carcinoma are poorly understood.

DESIGN

In this study, the mRNA and protein expression profiles of two key regulators of angiogenesis, vascular endothelial growth factor (VEGF) and transforming growth factor beta-1 (TGFB1), were evaluated by real-time PCR and western blot analysis in 23 endometrial cancer tissue-paired specimens (malignant vs. adjacent normal tissues). We aimed to investigate whether VEGF and TGFB1 serve as markers of the malignant transformation of the endometrium and whether VEGF or TGFB1 expression can constitute a useful prognostic marker of survival in patients with endometrial carcinoma.

RESULTS

Tissue-pair analysis revealed VEGF transcriptional up-regulation and TGFB1 mRNA down-regulation as the most frequent transcriptional features. VEGF and TGFB1 mRNA were positively correlated (P < 0·001). VEGF protein levels were higher in endometrioid-type tissue pairs (P = 0·047). TGFB1 protein and mRNA levels were negatively correlated (P = 0·042). TGFB1 protein expression was related to survival only in patients with endometrioid adenocarcinoma (P = 0·045).

CONCLUSIONS

Tissue-pair mRNA and protein analysis reveals VEGF transcriptional up-regulation and TGFB1 down-regulation that are correlated with the malignant transformation of the endometrium, while post-transcriptional mechanisms control VEGF and TGFB1 protein. TGFB1 protein demonstrated a prognostic value only in endometrioid adenocarcinoma.

Blockade of NFκB activity by Sunitinib increases cell death in Bortezomib-treated endometrial carcinoma cells

Endometrial carcinoma is one of the most common malignancies in the female genital tract, usually treated by surgery and radiotherapy. Chemotherapy is used when endometrial carcinoma is associated with widespread metastasis or when the tumor recurs after radiation therapy. In the present study, we demonstrate that the tyrosine kinase receptor inhibitor Sunitinib reduces cell viability, proliferation, clonogenicity and induces apoptotic cell death in endometrial carcinoma cell lines, which is not due to its action through the most known targets like VEGFR, nor through EGFR as demonstrated in this work. Interestingly, Sunitinib reduces NFκB transcriptional activity either at basal level or activation by EGF or TNF-α. We observed that Sunitinib was able to inhibit the Bortezomib-induced NFκB transcriptional activity which correlates with a decrease of the phosphorylated levels of IKKα and β, p65 and IκBα. We evaluated the nature of the interaction between Sunitinib and Bortezomib by the dose effect method and identified a synergistic effect (combination index < 1). Analogously, silencing of p65 expression by lentiviral-mediated short-hairpin RNA delivery in Bortezomib treated cells leads to a strongly increased sensitivity to Bortezomib apoptotic cell death. Altogether our results suggest that the combination of Sunitinib and Bortezomib could be considered a promising treatment for endometrial carcinoma after failure of surgery and radiation.

Significance of vascular endothelial growth factor in growth and peritoneal dissemination of ovarian cancer

Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis which drives endothelial cell survival, proliferation, and migration while increasing vascular permeability. Playing an important role in the physiology of normal ovaries, VEGF has also been implicated in the pathogenesis of ovarian cancer. Essentially by promoting tumor angiogenesis and enhancing vascular permeability, VEGF contributes to the development of peritoneal carcinomatosis associated with malignant ascites formation, the characteristic feature of advanced ovarian cancer at diagnosis. In both experimental and clinical studies, VEGF levels have been inversely correlated with survival. Moreover, VEGF inhibition has been shown to inhibit tumor growth and ascites production and to suppress tumor invasion and metastasis. These findings have laid the basis for the clinical evaluation of agents targeting VEGF signaling pathway in patients with ovarian cancer. In this review, we will focus on VEGF involvement in the pathophysiology of ovarian cancer and its contribution to the disease progression and dissemination.

Concomitant vascular GRP-receptor and VEGF-receptor expression in human tumors: molecular basis for dual targeting of tumoral vasculature

Gastrin-releasing peptide (GRP) and GRP receptors (GRPR) play a role in tumor angiogenesis. Recently, GRPR were found to be frequently expressed in the vasculature of a large variety of human cancers. Here, we characterize these GRPR by comparing the vascular GRPR expression and localization in a selection of human cancers with that of an established biological marker of neoangiogenesis, the vascular endothelial growth factor (VEGF) receptor. In vitro quantitative receptor autoradiography was performed in parallel for GRPR and VEGF receptors (VEGFR) in 32 human tumors of various origins, using ¹²⁵I-Tyr-bombesin and ¹²⁵I-VEGF₁₆₅ as radioligands, respectively. Moreover, VEGFR-2 was evaluated immunohistochemically. All tumors expressed GRPR and VEGFR in their vascular system. VEGFR were expressed in the endothelium in the majority of the vessels. GRPR were expressed in a subpopulation of vessels, preferably in their muscular coat. The vessels expressing GRPR were all VEGFR-positive whereas the VEGFR-expressing vessels were not all GRPR-positive. GRPR expressing vessels were found immunohistochemically to co-express VEGFR-2. Remarkably, the density of vascular GRPR was much higher than that of VEGFR. The concomitant expression of GRPR with VEGFR appears to be a frequent phenomenon in many human cancers. The GRPR, localized and expressed in extremely high density in a subgroup of vessels, may function as target for antiangiogenic tumor therapy or angiodestructive targeted radiotherapy with radiolabeled bombesin analogs alone, or preferably together with VEGFR targeted therapy.

Angiogenesis inhibition in cancer therapy: platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) and their receptors: biological functions and role in malignancy

Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen in vitro and an angiogenic inducer in a variety of in vivo models. VEGF gene transcription is induced in particular in hypoxic cells. In developmental angiogenesis, the role of VEGF is demonstrated by the finding that the loss of a single VEGF allele results in defective vascularization and early embryonic lethality. Substantial evidence also implicates VEGF as a mediator of pathological angiogenesis. In situ hybridization studies demonstrate expression of VEGF mRNA in the majority of human tumors. Platelet-derived growth factor (PDGF) is mainly believed to be an important mitogen for connective tissue, and also has important roles during embryonal development. Its overexpression has been linked to different types of malignancies. Thus, it is important to understand the physiology of VEGF and PDGF and their receptors as well as their roles in malignancies in order to develop antiangiogenic strategies for the treatment of malignant disease.

Phase I study of intravenous vascular endothelial growth factor trap, aflibercept, in patients with advanced solid tumors

PURPOSE

Vascular endothelial growth factor (VEGF) Trap (aflibercept) is an angiogenesis inhibitor comprising portions of the extracellular domains of human VEGF receptors 1 and 2 fused to the Fc portion of human immunoglobulin G. This phase I study was designed to evaluate the safety, pharmacokinetics, and pharmacodynamics of VEGF Trap administered intravenously (IV) every 2 weeks.

PATIENTS AND METHODS

Patients with refractory solid tumors or non-Hodgkin's lymphoma with adequate organ function were eligible. Pharmacokinetic/pharmacodynamic markers included measurement of plasma VEGF bound to VEGF Trap and free VEGF Trap. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was incorporated to measure the biologic effects of the drug on tumor vascularity and permeability.

RESULTS

The study enrolled 47 patients at doses ranging from 0.3 to 7.0 mg/kg IV every 2 weeks. Dose-limiting toxicities were rectal ulceration and proteinuria at the 7.0 mg/kg dose. Other mechanism-specific toxicities included hypertension. On the basis of these observations and on pharmacokinetics, the recommended phase II dose of VEGF Trap as a single agent is 4 mg/kg every 2 weeks. Three RECIST (Response Evaluation Criteria in Solid Tumors) -defined partial responses were observed, one at the 3.0 mg/kg and two at the 7.0 mg/kg dose level. Maximum plasma concentration of free VEGF Trap increased proportionally with dose. Maximal VEGF-bound VEGF Trap complex levels were reached at doses > or = 2.0 mg/kg. Changes in volume transfer constant measured by DCE-MRI at baseline and at 24 hours after administration indicate a possible dose-related change in this pharmacodynamic marker.

CONCLUSION

IV VEGF Trap was well tolerated at the dose levels tested. Pharmacodynamic and pharmacokinetic markers were indicative of VEGF blockade.

Sunitinib malate in the treatment of recurrent or persistent uterine leiomyosarcoma: a Gynecologic Oncology Group phase II study

PURPOSE

New agents are needed for patients with metastatic uterine leiomyosarcoma who progress after treatment with doxorubicin or gemcitabine-docetaxel. Agents targeting tumor vasculature have potential for activity in leiomyosarcoma. We aimed to assess the activity of sunitinib in patients with recurrent uterine leiomyosarcoma who had received one or two prior therapies by determining the frequency of patients who survived progression-free for at least 6 months or who achieved objective tumor response. We also aimed to characterize the toxicity of sunitinib and to estimate time-to-progression.

PATIENTS AND METHODS

Eligible patients with uterine leiomyosarcoma were treated with sunitinib 50 mg by mouth daily for 4 weeks, with 2 weeks rest. Tumor response and progression-free status were assessed every 6 weeks.

RESULTS

Twenty-three of 25 patients enrolled were evaluable for efficacy (two wrong histologies). The median number of cycles was one. Two of 23 patients achieved a partial response (8.7%, 90% two-sided, binomial confidence interval (CI) 1.6-24.9%). Four patients remained progression-free at 6 months (17.4%, 90% two-sided, binomial confidence interval 6.2-35.5%). Toxicities included: grade 3 neutropenia (17.4%); grade 3 thrombocytopenia (13%); grade 3 anemia (17.4%); grades 3-4 lymphopenia (8.7%); grades 3-4 fatigue (30%); grade 3 vomiting/diarrhea (21.7%); skin rash/hand-foot syndrome, grade 2 (13%), grade 3 (4.3%); hypertension, grade 2 (39%), grade 3 (4.3%); grade 2 decrease in cardiac ejection fraction (4.3%), and grade 3 thrombosis (4.3%) Median progression-free survival (PFS) was 1.5 months.

CONCLUSION

Sunitinib fails to achieve sufficient objective response or sustained disease stabilization as second- or third-line treatment for uterine leiomyosarcoma.

Inhibiting colorectal carcinoma growth and metastasis by blocking the expression of VEGF using RNA interference

Angiogenesis plays an essential role in tumor growth and metastasis and is a promising target for cancer therapy. Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis. The present study was designed to determine the role of VEGF in tumor growth and metastasis using RNA interference (RNAi) technology. Four small interfering RNA (siRNA) sequences for the VEGF gene were cloned into expression plasmids and transfected into human colorectal carcinoma (CRC) SW620 cells. Stable transfection of these plasmids decreased VEGF protein expression, leading to the potent suppression of tumor cell proliferation, migration, invasion, and angiogenesis in vitro. Furthermore, in subcutaneous and intrasplenic/portal injection models involving athymic nude mice, the tumor growth and metastasis of SW620 cells expressing VEGF siRNA were significantly inhibited compared with untransfected cells or cells transfected with control vector alone. Immunohistochemical analyses of tumor sections revealed a decreased vessel density and decreased VEGF expression in the animals where siRNA against VEGF were expressed. These results indicate that RNAi of VEGF can be an effective antiangiogenic strategy for CRC.

VEGF/VEGFR signalling as a target for inhibiting angiogenesis

VEGFs and a respective family of tyrosine kinases receptors (VEGFRs) are key proteins modulating angiogenesis, the formation of new vasculature from an existing vascular network. There has been considerable evidence in vivo, including clinical observations, that abnormal angiogenesis is implicated in a number of disease conditions, which include rheumatoid arthritis, inflammation, cancer, psoriasis, degenerative eye conditions and others. Antiangiogenic therapies based on inhibition of VEGF/VEGFR signalling were reported to be powerful clinical strategies in oncology and ophthalmology. Current efforts have yielded promising clinical data for several antiangiogenic therapeutics. In this review, the authors elucidate key aspects of VEGFR signalling, as well as clinically relevant strategies for the inhibition of VEGF-induced angiogenesis, with an emphasis on small-molecule VEGFR inhibitors.

Molecular alterations in the pathogenesis of endometrial adenocarcinoma. Therapeutic implications

Molecular genetic evidence indicates that endometrial carcinoma likely develops as the result of a multistep process of oncogene activation and tumor suppressor gene inactivation. These molecular alterations appear to be specific for Type I (endometrioid) and Type II (non endometrioid) cancers. Type I cancers are characterized by mutation of PTEN, KRAS2, defects in DNA mismatch repair, as evidenced by the microsatellite instability phenotype, and a near diploid karyotype. Type II cancers often contain mutations of TP53 and Her-2/neu and are usually nondiploid. The clinical value of many of these molecular markers is now being tested and it may help to refine diagnosis and establish an accurate prognosis. Furthermore, some of these tumor biomarkers constitute the targets for emerging therapies. Transtuzumab against Her-2/neu and bevacizumab against VEGF overexpressing carcinomas are among the promising novel treatments. Additional translational research is needed to identify molecular and genetic alterations with potential for therapeutic interventions.

The role of vascular endothelial growth factor and its receptor Flk-1/KDR in promoting tumour angiogenesis in feline and canine mammary carcinomas: a preliminary study of autocrine and paracrine loops

Vascular Endothelial Growth Factor (VEGF) and its receptor KDR are involved in the regulation of angiogenesis and are up-regulated in a number of tumours in humans and in particular, breast cancer. We therefore evaluated the prognostic potential of the angiogenetic process in feline and canine mammary carcinomas by the immunohistochemical assessment of VEGF expression and micro vessel density (MVD) quantification and examined the interplay between VEGF and KDR. These variables were related to some relevant clinicopathological parameters and to overall survival (OS). VEGF and KDR expression were evaluated in epithelial, stromal and endothelial compartments in order to identify autocrine and/or paracrine loops. In dogs an increased VEGF expression did not show any statistical correlation with the clinicopathological parameters examined and was not correlated to a poorer prognosis. MVD was found to be significantly correlated to the histologic type (P=0.04), tumour grading (P=0.02), and to the OS (P=0.01). In cats VEGF expression was significantly correlated to tumor grading (P=0.01) and OS (P=0.03), while no significant associations were found between MVD and the other parameters. VEGF and KDR were found to be detected on the epithelial, and/or endothelial and/or stromal cells of the carcinomas in both species, suggesting indications for some possible autocrine and paracrine loops. Our results encourage further studies on the possible prognostic role of VEGF and MVD in canine and feline mammary tumours and on the role of growth factors and their receptors in promoting tumour proliferation and an "angiogenetic shift". The VEGF/KDR system may play a role in malignant transformation and tumor progression.

Update on angiogenesis inhibitors

PURPOSE OF REVIEW

A number of therapeutic agents have been developed which have anti-angiogenic potential. Here we present the most recent data from clinical trials with some of the promising inhibitors of angiogenesis.

RECENT FINDINGS

Agents that target the vascular endothelial growth factor signaling pathway are the furthest along in clinical development. The last year has brought US Food and Drug Administration approval of bevacizumab (Avastin), a recombinant humanized anti-vascular endothelial growth factor monoclonal antibody. Bevacizumab has demonstrated a survival advantage in combination with chemotherapy for patients with metastatic colorectal cancer. Other agents with early promising results include PTK787/ZK 222584 (Vatalanib), ZD6474, and BAY 43-9006 (Sorafenib).

SUMMARY

Angiogenesis inhibitors show promise, but evaluation for optimal efficacy has been a problem, given that the mechanisms of action of these agents differ from conventional cytotoxic agents and surrogate markers for inhibition of angiogenesis are not available.

Neovascularization and mast cells with tryptase activity increase simultaneously with pathologic progression in human endometrial cancer

OBJECTIVE

In vitro and in vivo studies have linked mast cell (MC) degranulation and activation with angiogenesis and neovascularization. This assumption is partially supported by the close anatomic association between MC and the vasculature and the recruitment of these cells during tumor growth. The aim of this study was to correlate the extent of angiogenesis with the number of MC expressing tryptase in human endometrial adenocarcinoma.

STUDY DESIGN

Tissues from human endometrial hyperplasia and endometrial adenocarcinoma were investigated immunohistochemically, using 2 murine monoclonal antibodies against the endothelial cell marker CD31 and the MC marker tryptase.

RESULTS

Angiogenesis, measured as microvessel counts, was highly correlated with MC tryptase-positive cell counts and that these parameters increase in agreement with tumor progression.

CONCLUSION

These results suggest that angiogenesis in endometrial cancer increases with tumor progression and that angiogenic tryptase secreted by host MC cooperate in its induction.

A novel angiogenic role for prostaglandin F2alpha-FP receptor interaction in human endometrial adenocarcinomas

Prostaglandins have been implicated in several neovascular diseases. In the present study, we found elevated FP receptor and vascular endothelial growth factor (VEGF) expression colocalized in glandular epithelial and vascular cells lining the blood vessels in endometrial adenocarcinomas. We investigated the signaling pathways activated by the FP receptor and their role in modulating VEGF expression in endometrial adenocarcinoma (Ishikawa) cells. Ishikawa cells were stably transfected with FP receptor cDNA in the sense or antisense orientations. Treatment of Ishikawa cells with prostaglandin F2alpha (PGF2alpha) rapidly induced transphosphorylation of the epidermal growth factor receptor (EGFR) and phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 via the FP receptor. Activation of EGFR-Ras-mitogen-activated protein kinase/ERK kinase (MEK) signaling via the FP receptor resulted in an increase in VEGF promoter activity, expression of VEGF mRNA, and secretion of VEGF protein. These effects of PGF2alpha on the FP receptor could be abolished by treatment of cells with a specific FP receptor antagonist, chemical inhibitors of c-Src, matrix metalloproteinase, and EGFR kinase or by inactivation of signaling with dominant-negative mutant isoforms of EGFR, Ras, or MEK or with small inhibitory RNA oligonucleotides targeted against the EGFR. Finally, we confirmed that PGF2alpha could potentiate angiogenesis in endometrial adenocarcinoma explants by transactivation of the EGFR and induction of VEGF mRNA expression.

Transcriptional deregulation of VEGF, FGF2, TGF-beta1, 2, 3 and cognate receptors in breast tumorigenesis

Angiogenesis is an important event during the neoplastic process and is induced by the secretion of numerous growth factors from endothelial cells. Vascular endothelial growth factor (VEGF), basic fibroblastic growth factor (FGF2), and transforming growth factor-beta1, beta2, beta3 (TGF-beta1, 2, 3) and cognate receptors (TGF-betaRI, II, III) mRNA expression pattern was evaluated by RT-PCR in 25 breast cancer tissue samples and adjacent normal tissues, and correlated to clinicopathological features. Western blot analysis was performed to evaluate VEGF and TGF-beta1 protein levels. TGF-beta1 and TGF-beta3 mRNA levels were significantly different in breast cancer specimens of differing histology (ductal, lobular, other) (P=0.020 and P=0.043). No statistically significant difference was observed at the mRNA level of VEGF between normal and tumor tissues while elevated VEGF protein levels in tumors were associated with patients' menopausal status. A strong hormonal influence of ER and PR on TGF-beta mRNA expression was established. FGF2 transcript levels were substantially decreased in cancer compared to adjacent normal specimens (P=0.031). A disruption of mRNA co-expression patterns was observed in malignant breast tissues compared to controls. Western blot analysis revealed differences between VEGF and TGFbeta1 mRNA and their corresponding protein levels. A substantial negative correlation of TGF-beta1 protein and TGF-beta1 mRNA levels (P=0.016) was demonstrated by breast tissue-pair analysis. Summarizing, our findings suggest that transcript levels of the examined markers in breast cancer are associated with menopausal and hormonal status, while their co-expression pattern is altered in malignant tissues compared to controls. In addition the difference between VEGF and TGF-beta1 mRNA and protein levels observed, indicates that post-transcriptional mechanisms may regulate expression of these molecules in breast cancer.

VEGF, FGF2, TGFB1 and TGFBR1 mRNA expression levels correlate with the malignant transformation of the uterine cervix

Angiogenesis is a complex procedure induced by the secretion of numerous growth factors from endothelial cells. Vascular endothelial growth factor (VEGF), basic fibroblastic growth factor (FGF2), transforming growth factor-beta1, 2, 3 (TGFB1, 2, 3), and transforming growth factor-beta receptors (TGFBR1, 2, 3) mRNA expression pattern was evaluated in tissue samples with cervical intraepithelial neoplasia (CIN) and cervical cancer, compared to that of normal cervical tissues, and correlated to the clinical stage of the disease. Transcript levels of the above genes were assessed by RT-PCR analysis in a total of 44 cervical specimens. VEGF, TGFB1, TGFBR1, and FGF2 transcript levels were significantly different in the normal, CIN and cancer specimen groups (P=0.015, 0.001, 0.008, and 0.029, respectively). Higher TGFBR1 mRNA levels were observed in parallel with increased severity of the lesion, whereas FGF2 exhibited lower transcript levels. A highly significant increase of VEGF mRNA expression was found upon cervical neoplastic transformation (P<0.0001). High-grade squamous intraepithelial lesions exhibited higher VEGF mRNA levels than low-grade lesions (P=0.039). TGFBR1 and TGFBR3 receptors demonstrated significant co-expressions with TGFB2 (P<0.0001), and TGFB1 (P=0.005 and 0.002, respectively) in normal cervical specimens. However, a disruption of co-expression patterns was observed in the groups of CIN and cancer cases, compared to normal tissues. Our findings show that VEGF, FGF2, TGFB1 and TGFBR1 mRNA expression levels correlate with the malignant transformation of the uterine cervix. The involvement of the examined markers in cervical carcinogenesis is furthermore supported by the observed disruption of their mRNA co-expression patterns.

Localization of the VEGF and angiopoietin genes in uterine carcinosarcoma

OBJECTIVE

Carcinosarcoma of the uterus is a highly aggressive tumor. However, the angiogenesis in this tumor remains unclear. This is the first study to examine the characteristics of angiogenesis in this tumor at the molecular level while also comparing the findings with those of high-grade endometrial carcinoma.

METHODS

The expression of vascular endothelial growth factors (VEGF) and angiopoietins (Ang) genes were examined in 35 primary uterine carcinosarcomas as well as in 12 high-grade endometrial carcinomas by in situ hybridization.

RESULTS

A strong expression of VEGF-A mRNA was significantly seen in carcinosarcomas compared to high-grade endometrial carcinomas. Interestingly, in uterine carcinosarcoma, VEGF-A mRNA was more strongly expressed in the carcinoma cells than in the sarcoma cells. In addition, a decrease in the VEGF-A mRNA expression was found in the transitional areas between carcinomatous and sarcomatous elements in most carcinosarcomas evaluated. Moreover, the Ang-2 mRNA expression was significantly seen in the vasculature adjacent to the periphery of the carcinoma cells in most carcinosarcomas, in comparison to that of endometrial carcinomas.

CONCLUSIONS

A high angiogenic activity in uterine carcinosarcoma was shown, in comparison to that of endometrial carcinoma. Tumor angiogenesis in uterine carcinosarcoma might be chiefly influenced by VEGF-A in the carcinoma cells, in cooperation with Ang-2 in the surrounding microvessels, however, this is not fully usually the case in sarcoma cells.

Vascular endothelial growth factor: basic science and clinical progress

Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen in vitro and an angiogenic inducer in a variety of in vivo models. Hypoxia has been shown to be a major inducer of VEGF gene transcription. The tyrosine kinases Flt-1 (VEGFR-1) and Flk-1/KDR (VEGFR-2) are high-affinity VEGF receptors. The role of VEGF in developmental angiogenesis is emphasized by the finding that loss of a single VEGF allele results in defective vascularization and early embryonic lethality. VEGF is critical also for reproductive and bone angiogenesis. Substantial evidence also implicates VEGF as a mediator of pathological angiogenesis. In situ hybridization studies demonstrate expression of VEGF mRNA in the majority of human tumors. Anti-VEGF monoclonal antibodies and other VEGF inhibitors block the growth of several tumor cell lines in nude mice. Clinical trials with various VEGF inhibitors in a variety of malignancies are ongoing. Very recently, an anti-VEGF monoclonal antibody (bevacizumab; Avastin) has been approved by the Food and Drug Administration as a first-line treatment for metastatic colorectal cancer in combination with chemotherapy. Furthermore, VEGF is implicated in intraocular neovascularization associated with diabetic retinopathy and age-related macular degeneration.

Expression of the VEGF and angiopoietin genes in endometrial atypical hyperplasia and endometrial cancer

Angiogenesis is critical for the growth and metastasis of endometrial cancer and is therefore an important therapeutic target. Vascular endothelial growth factor-A (VEGF-A) is a key molecule in angiogenesis, but the identification of related molecules and the angiopoietins suggests a more complex picture. We investigated the presence of transcripts for VEGF-A, VEGF-B, VEGF-C, VEGF-D, Angiopoietin-1 and Angiopoietin-2 in benign endometrium, atypical complex hyperplasia (ACH) and endometrioid endometrial carcinoma using in situ hybridisation. We confirmed the presence of VEGF-A mRNA in the epithelial cells of cancers examined (13 out of 13), but not in benign endometrium or ACH. We also demonstrate, using quantitative polymerase chain reaction, that levels of VEGF-B mRNA are significantly lower in endometrial cancer than benign endometrium. We conclude that loss of VEGF-B may contribute to the development of endometrial carcinoma by modulating availability of receptors for VEGF-A.

Endoglin (CD105) expression in endometrial carcinoma

Tumor angiogenesis plays an important role in tumor growth and metastasis. We evaluated endoglin (CD105) as an endothelial marker of angiogenesis in endometrial carcinoma (EC) and its prognostic significance. Fifty-five cases of EC, 10 cases of complex endometrial hyperplasia with atypia (CHA), and 10 cases of simple hyperplasia (SH) were immunohistochemically stained for endoglin, CD31, and vascular endothelial growth factor (VEGF). Positively stained microvessels (MV) were counted in densely vascular foci (hot spots) in a 400x field in each specimen. For VEGF, intensity of staining was scored on three-tiered scale. Results were correlated with other prognostic parameters using appropriate statistics. Endoglin staining demonstrated significantly more MV than did CD31 (mean 30.8 +/- 10.95 vs. 13.38 +/- 7.53, p < 0.001). There was a positive correlation of both endoglin and CD31 MV counts with tumor differentiation (p < 0.05) and the depth of invasion (p < 0.01). However, only endoglin counts correlated significantly with the presence of angiolymphatic invasion (p < 0.01), lymph nodes metastases (p < 0.01), and tumor stage (p < 0.001). VEGF expression in EC had a significant correlation with angiolymphatic invasion (p < 0.01) and lymph node status (p < 0.05) but not with other prognostic parameters. Endoglin and VEGF showed significant differences between CHA and SH (p < 0.001). Our study showed that endoglin, by staining the proliferating MV in EC, is a more specific and sensitive marker for tumor angiogenesis than is the commonly used pan-endothelial marker, CD31. Endoglin staining also had prognostic significance, with positive correlation with angiolymphatic invasion, lymph node metastases, and tumor stage.

Therapies directed at vascular endothelial growth factor

The inhibition of angiogenesis through vascular endothelial growth factor (VEGF) receptor targeting is a strategy that is relatively tumour selective. The high selectivity achieved with neutralising antibodies, soluble receptors and ribozymes reduces the risk of adverse reactions not related to VEGF inhibition itself. Small-molecule, orally-active protein kinase inhibitors provide an attractive alternative for chronic therapy, although specifically targeting a small subset of protein kinases from the approximately 550 expressed in mammalian cells is a challenge. Current efforts have resulted in promising clinical data for several synthetic VEGF receptor kinase inhibitors, of which PTK787/ZK222584 and ZD6474 are proceeding into large size clinical trials. It seems likely that blockers of the VEGF signalling pathway will be unsuitable for monotherapy, and that their role will be as an adjunct to additional antiangiogenic agents together with directly-acting antitumour agents or radiation therapy. Caution is needed with combinations of anti-VEGF therapies and cytotoxic agents, as coadministration of cytotoxic agents with either the kinase inhibitor SU5416 or the VEGF antibody avastin appears to be associated with bleeding and thrombotic adverse events.

Antiangiogenic effects of somatostatin analogues

Inhibition of angiogenesis has become a target for antineoplastic therapy and for treatment of retinal neovascularization. The presence of somatostatin receptors on tumour cells and on the proliferating vascular endothelium has led to several in vitro and in vivo studies to investigate the antiproliferative and antiangiogenic effects of somatostatin analogues. Currently available data suggest that somatostatin analogues might inhibit angiogenesis directly through somatostatin receptors present on endothelial cells and also indirectly through the inhibition of growth factor secretion such as IGF-I and vascular endothelial growth factor (VEGF) and reducing monocyte chemotaxis. However, beneficial effects on inhibition of neovascularization have been questioned by some studies. More work is therefore required to firmly establish the role of somatostatin analogues as potential antiangiogenic therapy. The currently available somatostatin analogues have high affinity for somatostatin receptor subtype 2 (sst2) and, to a lesser extent, sst5 and sst3. However, because vascular endothelial cells express several types of somatostatin receptors, it will be important to investigate somatostatin analogues with different receptor subtype affinities, which might increase the spectrum of available therapy for tumours.

Angiogenesis and vascular architecture in pheochromocytomas: distinctive traits in malignant tumors

Angiogenesis is a critical step in tumor growth and metastatic invasion. We here report the study of the vascular status of 10 benign and 9 malignant pheochromocytomas. We examined the vascular architecture after immunostaining endothelial cells (CD34) and vascular smooth muscle cells (alpha-actin) and identified a vascular pattern characteristic of malignant lesions. To define a gene expression profile indicative of the invasive phenotype, we studied by in situ hybridization the expression of genes encoding several pro- and anti-angiogenic factors [hypoxia-inducible factor (HIF-1 alpha), EPAS1, vascular endothelial growth factor (VEGF), VEGF receptors, angiopoietins and their receptor Tie2, five genes of the endothelin system, and thrombospondin 1]. A semiquantitative evaluation of the labeling revealed an induction of genes encoding EPAS1, VEGF, VEGFR-1, VEGFR-2, endothelin receptor, type B (ETB) and endothelin receptor, type A (ETA) in malignant pheochromocytomas as compared to benign tumors. These differences were observed in tumor cells, in endothelial cells, or in both. Quantification by real-time reverse-transcriptase polymerase chain reaction showed an increase of EPAS1, VEGF, and ETB transcripts of 4.5-, 3.5-, and 10-fold, respectively, in malignant versus benign tumors. Furthermore, we observed a strong correlation between the expression of EPAS1 and VEGF in tumoral tissue and between EPAS1 and ETB in endothelial cells. Altogether, our observations show that analysis of angiogenesis provides promising new criteria for the diagnosis of malignant pheochromocytomas.

Angiogenesis in the female reproductive organs: pathological implications

The female reproductive organs (ovary, uterus, and placenta) are some of the few adult tissues that exhibit regular intervals of rapid growth. They also are highly vascular and have high rates of blood flow. Angiogenesis, or vascular growth, is therefore an important component of the growth and function of these tissues. As with many other tissues, vascular endothelial growth factors (VEGFs) and fibroblast growth factors (FGFs) appear to be major angiogenic factors in the female reproductive organs. A variety of pathologies of the female reproductive organs are associated with disturbances of the angiogenic process, including dysfunctional uterine bleeding, endometrial hyperplasia and carcinoma, endometriosis, failed implantation and subnormal foetal growth, myometrial fibroids (uterine leiomyomas) and adenomyosis, ovarian hyperstimulation syndrome, ovarian carcinoma, and polycystic ovary syndrome. These pathologies are also associated with altered expression of VEGFs and/or FGFs. In the near future, angiogenic or antiangiogenic compounds may prove to be effective therapeutic agents for treating these pathologies. In addition, monitoring of angiogenesis or angiogenic factor expression may provide a means of assessing the efficacy of these therapies.

Inhibition of vascular endothelial growth factor in the treatment of solid tumors

Vascular endothelial growth factor (VEGF) is the term used for a family of tumor-derived angiogenic factors that mediate endothelial proliferation and vascular permeability. Preclinical models have demonstrated the essential nature of VEGF in the angiogenesis of solid tumor growth and metastasis, whereas pathologic investigations have revealed strong correlations between VEGF production, microvessel density, and overall aggressiveness of many human solid tumors. Recent advances in the understanding of the molecular mechanisms of VEGF action have led to successful models for intervention in VEGF-mediated pathways in therapy for solid tumors. These include antibodies to block the binding of VEGF to its cellular receptors, small-molecule chemical inhibitors of the tyrosine kinase functions of the VEGF receptors, and antisense nucleic acids to interfere with cellular production of VEGF. Clinical investigations are ongoing to test the value of VEGF-based intervention alone or in combination with other anticancer agents.

Microvessel density, vascular endothelial growth factor and its receptors Flt-1 and Flk-1/KDR in hepatocellular carcinoma

Assessment of angiogenesis may yield important information for an effective antiangiogenic treatment for hepatocellular carcinoma (HCC) because HCC is characteristically hypervascular We examined the relationship of microvessel density (MVD), vascular endothelial growth factor (VEGF), and VEGF receptors Flt-1 and Flk-1/KDR in 50 patients with HCC and in 3 hepatoma cell lines. VEGF messenger RNA (mRNA) was overexpressed in 26 tumors (52%), and the 3 VEGF isoforms (121, 165, and 189) were present in high frequencies. Flt-1 mRNA was overexpressed in 34 tumors (68%), with levels significantly increased in HCCs compared with the nontumorous livers. Tumor Flt-1 mRNA significantly correlated with tumor VEGF mRNA levels. Within the group of tumors 8.5 cm or less in diameter, tumors with intrahepatic metastasis in the form of tumor microsatellite formation had significantly higher VEGF mRNA levels. MVD assessed by immunohistochemical analysis with CD34 antibody was inversely related to tumor size. Angiogenesis as assessed by MVD and tumor VEGF expression seems to have a more important role in tumor growth and intrahepatic metastasis in smaller HCCs. The differential up-regulation of Flt-1 suggests that it may have an important role in angiogenesis in HCC.

The angiogenic "vascular endothelial growth factor/flk-1(KDR) receptor" pathway in patients with endometrial carcinoma: prognostic and therapeutic implications

BACKGROUND

Vascular endothelial growth factor (VEGF) is an important endothelial cell mitogen associated with increased angiogenesis and aggressive tumor behavior. Its stimulating effect on endothelial cells basically is dependent on the presence of specific VEGF receptors, such as the flk-1(KDR) receptor. This study investigates the roles of VEGF and of a functionally intact angiogenic pathway, "VEGF/flk-1(KDR)," in patients with endometrial carcinoma and their significance in prognosis and therapy.

METHODS

A series of 121 endometrial carcinomas were studied. The expression of VEGF by endometrial tumor cells was assessed using the monoclonal antibody (MoAb) VG1. VEGF/KDR complexes on tumor endothelium or activated microvessel density (aMVD) were identified using the MoAb 11B5. In addition, the standard microvessel density (sMVD) was assessed with anti-CD31. In all tumors, the alkaline phosphatase/antialkaline phosphatase technique was employed. A Fisher exact test or an unpaired, two-tailed t test was used for testing correlations between categoric tumor variables, whereas a log-rank test was used to determine statistical differences between life tables. A Cox proportional hazards model was used to assess the effect of tumor variables on overall survival.

RESULTS

Cytoplasmic VEGF expression in > 50% of tumor cells was associated significantly with aMVD (P < 0.0001) and with sMVD (P < 0.003). In univariate survival analysis, VEGF (P = 0.0002), aMVD (P = 0.001), and sMVD (P = 0.0009) were significant prognostic variables. Equally important were the histologic parameters tumor type (P = 0.03), tumor grade (P = 0.003), and disease stage (P < 0.0001). In multivariate analysis, disease stage was the most important independent prognostic factor (P < 0.0001), followed by VEGF/KDR (P < 0.01), and VEGF (P < 0.04). Furthermore, VEGF and VEGF/KDR were the only independent prognostic variables for patients with Stage I endometrioid adenocarcinoma.

CONCLUSIONS

sMVD and the angiogenic factor VEGF are important indicators of a poor prognosis in patients with endometrial carcinoma. VEGF/KDR complexes define a subgroup of patients with endometrial carcinoma with an even worse prognosis.

Tumor specific activation of the VEGF/KDR angiogenic pathway in a subset of locally advanced squamous cell head and neck carcinomas

Vascular endothelial growth factor (VEGF) and its receptors, Flt-1 and flk-1(KDR), constitute an important angiogenic pathway which, under hypoxic conditions, is up-regulated in many solid tumours. We used the monoclonal antibody 11B5, specific for recognizing VEGF expression and the 'VEGF/flk-1(KDR) complex' on tumour endothelium, to assess free VEGF protein expression and VEGF/receptor activated microvessel density (aMVD) in a series of 104 inoperable locally advanced squamous cell carcinomas of the head and neck, treated with chemo-radiotherapy. High VEGF expression in cancer cells was strongly associated with high VEGF/receptor expression in the vasculature. The high VEGF expression and the aMVD were not associated with the standard microvessel density (sMVD), as assessed with the monoclonal antibody anti-CD31 and, were not detected in normal tissue. An increased sMVD, however, was significantly related with the expression thymidine phosphorylase (TP), and also with the nuclear accumulation of the oncoprotein p53, but neither p53 nor TP was associated with VEGF expression by cancer cells or VEGF/receptor complex aMVD. In 35% of cancer cases examined, more than 20% of the microvessels assessed with anti-CD31 also expressed the VEGF/KDR complex. The vasculature of the normal head and neck mucosa did not express the VEGF/KDR complex. There was no association between VEGF expression or VEGF/receptor complex aMVD and response to chemo-radiotherapy or patient's survival. It is concluded that activation of the angiogenic pathway VEGF/flk-1(KDR) is tumor specific in a subgroup of locally advanced squamous cell carcinomas of the head and neck. Selective destruction of this type of vasculature, using immunoconjugates directed against the VEGF/receptor complex, may prove therapeutically useful for patients with a high tumoral VEGF/flk-1(KDR) activated microvessel fraction.

Expression of vascular endothelial growth factors (VEGF-A/VEGF-1 and VEGF-C/VEGF-2) in postmenopausal uterine endometrial carcinoma

OBJECTIVE

We investigated the expression of two angiogenic vascular endothelial growth factors, VEGF-A/VEGF-1 and VEGF-C/VEGF-2, in 228 cases of uterine endometrial carcinomas from postmenopausal patients to evaluate the correlation with histopathologic features and clinical outcome.

METHODS

Immunohistochemistry was used to assess VEGF-A/VEGF-1 and VEGF-C/VEGF-2 expression in 228 primary surgically treated cases of postmenopausal endometrial carcinomas and the results were statistically analyzed in relation to vascular invasion, depth of invasion (myometrial vs serosal-parametrial invasion), lymphatic vessel invasion, lymph node metastasis, disease-free 5-year survival rate (DF5YR), and disease-free 10 year-survival rate (DF10YR).

RESULTS

The results of univariate analysis showed that VEGF-A/VEGF-1 and VEGF-C/VEGF-2 expression correlated with vascular invasion (P < 0.0001, P = 0.0006), depth of invasion (P = 0.0004, P = 0.043), lymphatic vessel invasion (P = 0.021, P < 0.0001), lymph node metastasis (P = 0.0017, P = 0.0008), DF5YR (P = 0.0081, P = 0.0002), and DF10YR (P = 0.0077, P = 0.0001). Multivariate analysis showed that lymph node metastasis (P = 0.0017, P = 0.0008), parametrial-serosal invasion (P < 0.0001, P < 0.0001), and VEGF-C/VEGF-2-positive status (P = 0.03, P = 0.01) were significant factors in DF5YR and DF10YR.

CONCLUSIONS

We conclude that VEGF-A/VEGF-1 and VEGF-C/VEGF-2 expression was predictive of these histopathologic features of endometrial carcinoma and clinical outcome.

Monomethyl selenium--specific inhibition of MMP-2 and VEGF expression: implications for angiogenic switch regulation

Previous work suggested that antiangiogenic activity may be a novel mechanism contributing to the cancer chemopreventive activity of selenium (Se). Because methylselenol has been implicated as an in vivo active chemopreventive Se metabolite, experiments were conducted to test the hypothesis that this metabolite pool might inhibit the expression of matrix metalloproteinase-2 (MMP-2) by vascular endothelial cells and of vascular endothelial growth factor (VEGF) by cancer epithelial cells, two proteins critical for angiogenesis and its regulation. In human umbilical vein endothelial cells (HUVECs), zymographic analyses showed that short-term exposure to methylseleninic acid (MSeA) and methylselenocyanate (MSeCN), both immediate methylselenol precursors, decreased the MMP-2 gelatinolytic activity in a concentration-dependent manner. In contrast, Se forms that enter the hydrogen selenide pool lacked any inhibitory effect. The methyl Se inhibitory effect on MMP-2 was cell dependent because direct incubation with Se compounds in the test tube did not result in its inactivation. Immunoblot and enzyme-linked immunosorbent assay analyses showed that a decrease of the MMP-2 protein level largely accounted for the methyl Se-induced reduction of gelatinolytic activity. The effect of MSeA on MMP-2 expression occurred within 0.5 h of exposure and preceded MSeA-induced reduction of the phosphorylation level of mitogen-activated protein kinases (MAPKs) 1 and 2 (approximately 3 h) and endothelial apoptosis (approximately 25 h). In addition to these biochemical effects in monolayer culture, MSeA and MSeCN exposure decreased HUVEC viability and cell retraction in a three-dimensional context of capillary tubes formed on Matrigel, whereas comparable or higher concentrations of selenite failed to exert such effects. In human prostate cancer (DU145) and breast cancer (MCF-7 and MDA-MB-468) cell lines, exposure to MSeA but not to selenite led to a rapid and sustained decrease of cellular (lysate) and secreted (conditioned medium) VEGF protein levels irrespective of the serum level (serum-free medium vs. 10% fetal bovine serum) in which Se treatments were carried out. The concentration of MSeA required for suppressing VEGF expression was much lower than that needed for apoptosis induction. Taken together, the data support the hypothesis that the monomethyl Se pool is a proximal Se for inhibiting the expression of MMP-2 and VEGF and of angiogenesis. The data also indicate that the methyl Se-specific inhibitory effects on these proteins are rapid and primary actions, preceding or independent of inhibitory effects on mitogenic signaling at the level of MAPK1/2 and on cell growth and survival.

Growth factors and epithelial-stromal interactions in prostate cancer development

Epithelial-stromal interactions are important not only in growth, development, and functional cytodifferentiation of the prostate but also in derangements of prostate gland such as BPH and prostate carcinoma. This chapter explores the roles of epithelium and stroma during this delicate process and highlights the role and mutual influence of each on the other. It also examines the importance of ECM in mediating the effects of androgens and drawn attention to estrogen and genetic factors in the process. During this process of epithelial-stromal interaction, growth factors play a central role in mediating the interactions. This chapter focuses on the role of several growth factors including epidermal growth factor, fibroblast growth factor, transforming growth factor alpha, transforming growth factor beta, insulin-like growth factor-1, vascular endothelial growth factor, nerve growth factor, platelet-derived growth factor, and hepatocyte growth factor. This chapter emphasizes the importance of epithelial-stromal interactions in tumorigenesis and highlights the switch of paracrine to autocrine mode during the process of carcinogenesis.