Search

Angiogenesis is a complex phenomenon that involves interaction between growth factors/cytokines and their receptors, and proteolytic enzymes and their inhibitors, which, in addition to and in accordance with their main roles, act together during this multistep process. Cancer angiogenesis is specific, because the same factors that enable angiogenesis are involved in the process of carcinogenesis. The aim of this review was to analyze the current knowledge regarding the significance of selected biomarkers in cancer angiogenesis, with emphasis on their prognostic value in the circulation.

Aims of the Study: Studies on circulating VEGF have reported mixed results, possibly due to a lack of standardization of the pre-analytical phase. The aim of our investigation was to standardize the sampling procedure for the determination of VEGF in different blood fractions., Basic Procedures: We evaluated various clotting times for obtaining serum in 30 subjects, as well as different procedures for the preparation of plasma Edinburgh anticoagulant mixture (EDTA, PGE1, theophylline) and CTAD. VEGF was also assayed in lysed whole blood. In vitro platelet activation was monitored by measuring the levels of PF4. VEGF and PF4 were measured using commercially available enzyme-linked immunoassays., Main Findings: Clotting time increased the release of VEGF, which reached a plateau between 2 and 4 hours. The percent increase of VEGF at 2 hours ranged from 118% to 4,515% (median 327%) compared to samples centrifuged within 10 min from withdrawal. VEGF was not different and PF4 was very low or undetectable in Edinburgh plasma and CTAD plasma, while it was significantly higher in sodium citrate plasma. VEGF in CTAD plasma was not correlated with platelet count or leukocytes. Serum VEGF did not correlate with the leukocyte number, but it correlated significantly with the platelet count., Principal Conclusions: The procedures for sample collection described above are highly standardized and easy to perform in a routine setting. We therefore suggest systematic evaluation of VEGF in CTAD plasma, in serum (clotting for 2 hours at room temperature) and in whole blood, until prospective controlled clinical studies will have clarified in which blood compartment(s) VEGF provides clinically relevant information.

Background/aims: To date, numerous studies have demonstrated that several angiogenesis regulators circulate in the blood and may function as endocrine factors in cancer patients. This review aims to give a comprehensive insight into the possible clinical value of circulating angiogenesis regulators, mainly basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), and hepatocyte growth factor (HGF), angiogenin, pleiotrophin, thrombospondin (TSP) and endostatin (ES) in cancer patients., Methods: A computerized (MEDLINE) and a manual search based on the reference lists of the publications were performed to identify articles published on this topic., Results: In a detailed literature search, approximately 100 publications were found up to the end of 1999. Circulating angiogenic factors such as bFGF, VEGF, HGF and angiogenin have been evaluated not only as diagnostic and/or prognostic factors but also as predictive factors in cancer patients. On the other hand, little is known about the clinical significance of negative regulators. Neither the source nor the mechanism of protein externalization has been clarified in detail., Conclusions: Although there are no known factors with established clinical utility, circulating angiogenesis regulators may be useful in several situations. They could be used to determine the risk of developing cancer, to screen for early detection, to distinguish benign from malignant disease, and to distinguish between different types of malignancies. In patients with established malignancies such factors might be used to determine prognosis, to predict the response to therapy, and to monitor the clinical course. Further investigations are warranted to assess the specific utility of each factor.

Angiogenesis is essential for tumor growth. Since vascular endothelial growth factor (VEGF) represents the main angiogenic factor, the control of VEGF secretion could constitute the most important mechanism to achieve the inhibition of angiogenesis-related processes. High blood concentrations have been proven to correlate with poor prognosis in advanced cancer. In experimental conditions, chemotherapeutic agents such as taxol appeared to inhibit VEGF-induced angiogenesis, while at present there are no data about the influence of chemotherapy on VEGF secretion in cancer patients. This preliminary study was performed to evaluate the effect of taxol therapy on VEGF secretion in advanced cancer patients in relation to the clinical response. The study included 14 patients with metastatic breast cancer who were treated with taxol monochemotherapy (175 mg/m2 i.v. every 21 days for three cycles). Serum levels of VEGF were measured by ELISA in blood samples collected before therapy and at 21-day intervals. The clinical response consisted of partial response (PR) in three and stable disease (SD) in six patients, whereas the other five patients had progressive disease (PD). Abnormally high pre-treatment levels of VEGF were seen in 8/14 patients. VEGF mean values significantly decreased during taxol therapy in patients with PR or SD, whereas no decline was observed in patients with PD. Moreover, the percent of normalization or decline greater than 50% in VEGF levels was significantly higher in patients with PR or SD than in those with PD (5/9 vs. 0/5). This preliminary study would suggest that the efficacy of taxol therapy in metastatic breast cancer - at least in terms of disease stabilization - may be associated with a decrease in VEGF blood levels followed by potential inhibition of cancer-related neovascularization.

Background: Angiogenesis is a prerequisite for tumor growth and metastasis. Vascular cell adhesion molecule1 (VCAM-1) is expressed on endothelial cells as a result of vascular endothelial growth factor (VEGF) stimulation., Purpose: To determine if measurement in serum of VEGF or VCAM-1 provides an accurate measure of tumor angiogenesis., Methods: VCAM-1 and VEGF were measured in the serum of women with early and advanced breast cancer by ELISA. Levels were compared to levels of VCAM-1 and VEGF in women with normal breasts and levels of the endothelial glycoprotein von Willebrand factor. Levels of VEGF and VCAM-1 in women with early breast cancer were correlated with established clinicopathological prognostic markers and intratumoral microvessel density (IMD)., Results: In early breast cancer serum VCAM-1 correlated closely with the microvessel density in tumors (r=0.61, p<0.001). Women with lymph node-positive and high-grade tumors had higher levels of serum VCAM-1 than women with lymph node-negative and low-grade tumors. Serum VEGF demonstrated no correlation with established prognostic features or IMD. Levels of VCAM-1 and VEGF were raised in women with advanced breast cancer., Conclusion: Serum VCAM-1 is a surrogate marker of angiogenesis in breast cancer and its measurement may help in the assessment of antiangiogenic drugs currently in phase II trials.

Angiogenesis and immunosuppression are the main biological mechanisms responsible for cancer progression. Moreover, recent observations suggesting a negative influence of angiogenesis on anticancer immunity have shown that some angiogenic factors, such as VEGF, may induce immunosuppression. In addition, the evidence of abnormally high blood levels of VEGF has been proven to be associated with resistance to IL-2 immunotherapy. The present study was performed to establish a possible relation ship between the efficacy of IL-2 cancer immunotherapy and changes in circulating levels of VEGF, IL-12, mature and immature dendritic cells (DC). The study included 25 metastatic renal cell cancer patients who underwent subcutaneous low-dose IL-2 immunotherapy (6 MIU/day for 6 days/week for 4 weeks). Immature and mature DCs were identified as CD123+ and CD11c+ cells, respectively. The clinical response consisted of partial response (PR) in five, stable disease (SD) in 11 and progressive disease (PD) in the remaining nine patients. The mean IL-12 levels observed during IL-2 immunotherapy were significantly higher in patients with PR or SD than in those with PD, whereas the mean VEGF concentrations were significantly higher in patients who had PD than in those with PR or SD. Finally, a significant increase in the mean number of circulating mature DCs occurred only in patients with PR or SD, whereas no significant change was seen in patients with PD. By contrast, no significant change was observed in the mean number of immature DCs. This study shows that the efficacy of IL-2 immunotherapy is associated with a significant increase in circulating mature DCs and IL-12, without any concomitant increase in VEGF concentrations. Further studies will be required to better define the relationship between activation of anticancer immunity and control of angiogenesis-related mechanisms.