Tumor angiogenesis: molecular facts and therapeutic opportunities

Solid tumors do not grow beyond a size of a few millimetres without supply of nutrients and growth factors by the vascular system. Only when tumors produce angiogenic growth factors new vessels are formed by sprouting of capillaries from the existing vascular system. The tumor can grow and tumor cells reach the circulation through these new and permeable vessels. The vascular endothelial growth factor (VEGF) is the most prominent angiogenic growth factor. VEGF is produced by almost all solid tumors: its receptors are expressed only on vascular endothelial cells and predominantly in vessels in the proximity of the tumor. Therefore, the VEGF/VEGF-receptor system is a target for anti-angiogenic cancer therapy. Experiments show that inhibition of the VEGF-mediated endothelial cell activation interferes with tumor growth and metastases formation. Appropriate therapeutic strategies are currently under clinical investigation.     

Angiogenesis in cancer: molecular mechanisms,clinical impact

Background Angiogenesis, the formation of new blood vessels from the endothelium of the existing vasculature, is fundamental in tumor growth, progression, and metastasis. Inhibiting tumor angiogenesis is a promising strategy for treatment of cancer and has been successfully transferred from preclinical to clinical application in recent years. Whereas conventional therapeutic approaches, e.g. chemotherapy and radiation, are focussing on tumor cells, antiangiogenic therapy is directed against the tumor supplying blood vessels. Materials and methods This review will summarize important molecular mechanisms of tumor angiogenesis and advances in the design of antiangiogenic drugs. Furthermore, clinical implications of antiangiogenic therapy in surgical oncology will be discussed. Results First antiangiogenic drugs have been approved for treatment of advanced solid tumors in several countries. Leading antiangiogenic drugs are designed to inhibit vascular endothelial growth factor-mediated tumor angiogenesis. Combining antiangiogenic agents with conventional chemotherapy or radiation is currently investigated clinically with great emphasis to realize a multimodal tumor therapy, targeting both the tumor cell and tumor vascular compartment. Conclusion Antiangiogenic tumor therapy represents a promising strategy for treatment of cancer and will most likely exhibit its clinical potential in combination with established standard tumor therapies in the future.     

Tumor angiogenesis predicts recurrence with normal serum carcinoembryonic antigen in advanced rectal carcinoma patients

P = 0.001, 0.043, respectively). These results suggest that a high degree of tumor angiogenesis in sections of T3/T4 rectal cancer may therefore be an important predictor for CEA-negative recurrence. (Received for publication on June 8, 1998; accepted on Mar. 11, 1999)     

Tumor cell dissemination during laparoscopy: prevention and therapeutic opportunities

Port-site recurrences (PSRs) are abdominal wall recurrences that occur in the subcutaneous tissue within a trocar site after cancer laparoscopy and are not associated with peritoneal carcinomatosis. In order to develop PSRs, viable tumor cells must be liberated from the primary tumor, be transported to a wound, and find there a favorable environment for growth. The short clinical delay in the occurrence of PSRs and their size suggest massive cell seeding into the abdominal wall. Traumatic handling of the tumor, slipping of trocars, liquid projection, as well as poor extraction techniques can all cause implantation of malignant cells into the subcutaneous tissue. Such contact can also occur postoperatively if the trocar channels remain open. Some histologies (e.g. gallbladder adenocarcinoma), the presence of ascites and advanced tumor stage are risk factors for PSRs. Further conditions--including the use of gas--might also play a limited role. The first preventive measure is the correct indication for a laparoscopic approach. Several techniques have been demonstrated to prevent PSRs in the animal model: (a) fixation of trocars to the abdominal wall; (b) prevention of leakage; (c) careful specimen handling; (d) reducing trauma to the abdominal wall; (e) specimen isolation before extraction from the abdominal cavity; (f) trocar-site irrigation with a cytotoxic solution, and (g) closure of peritoneum. Further innovative therapies are currently under investigation. In the clinical setting, correct indication, surgical expertise and application of prophylactic measures seem to be the best way to prevent the occurrence of PSRs.     

Biology of vascular endothelial growth factor and its receptors in head and neck cancer: beyond angiogenesis

Angiogenesis is a necessary process for tumor progression and is driven through molecular interactions between cancer cells and neighboring vascular endothelial cells. The primary mediators of angiogenesis are the vascular endothelial growth factors and their respective receptors on endothelial cells. There are several U.S. Food and Drug Administration-approved anti-angiogenic agents in clinical use. In head and neck cancer there are clinical trials assessing the efficacy of anti-angiogenic agents in combination with chemoradiation therapy. Although the aforementioned growth factors and receptors have been traditionally viewed as anti-angiogenic targets, there are concomitant efforts to understand the role these molecules play within the tumor cells. In this review, we first discuss the biology of angiogenic proteins and the targeting of angiogenic molecules for cancer treatment. We summarize the current clinical trials of anti-angiogenic therapies in head and neck squamous cell carcinoma. Finally, the additional role these molecules play in tumor progression independent of angiogenesis is discussed.     

Expression of angiogenesis and angiogenic factors in human aortic vascular disease

BACKGROUND: This paper presents an investigation into the expression of endothelial cells and vascular endothelial growth factor (VEGF) in the aortic wall in vascular diseases such as atherosclerotic abdominal aortic aneurysm (AAAA), inflammatory abdominal aortic aneurysm (IAAA), and aortic occlusive disease (AOD) to determine whether the differences in both neovascularization and angiogenic factor expression are related to the pathogenesis of aortic vascular disease. MATERIALS AND METHODS: Surgical specimens of aorta (10 IAAA, 13 AAAA, 6 AOD) were studied pathologically and immunohistochemically. Representative sections of aorta were stained with hematoxylin-eosin, elastica von Gieson, CD34, and VEGF antibody. CD34-positive microvessels and VEGF-positive cells in the media and adventitia were counted, respectively. RESULTS: CD34-positive microvessels were detected in IAAA > AAAA > AOD (one-way analysis of variance (ANOVA), P < 0.0001). VEGF expression was widely detected in macrophages, monocytes, and smooth muscle cells of IAAA and AAAA; however, it was hardly recognized in AOD. VEGF-positive cells were detected in IAAA > AAAA > AOD specimens (ANOVA, P < 0.0001). CONCLUSIONS: VEGF is known to be a regulator of angiogenesis and to simultaneously stimulate elastolytic proteinases. The results of this study suggest that an angiogenic factor, such as VEGF, may play an important role in the degeneration of the aortic wall and could be strongly related to the pathogenesis of IAAA, AAAA, and AOD.     

Digital subtraction angiography and computer assisted image analysis for the evaluation of the antiangiogenetic effect of ionizing radiation on tumor angiogenesis

Purpose: The aim of the present study was to evaluate and quantify the antiangiogenetic effect of ionizing radiation on tumor angiogenesis using digital subtraction angiography (DSA) in conjunction with computer assisted image analysis (CAIA). Methods: Walker 256 carcinosarcoma was inoculated in both glutei of 12 Wistar rats. When the tumors reached a diameter of 1.5 cm, local irradiation of the right gluteus was performed. The left gluteus of each animal served as a control. After 24 hours of irradiation, angiography was performed, and images where digitized and subsequently processed. The effect of irradiation was observed both in big and small vessels (smaller or greater than 200 μm). Results: Irradiated areas of both small and big vessels showed a statistically significant reduction in both total vessel area and length. Small vessels showed a greater trend toward suppression by irradiation (not statistically significant). Conclusion: Irradiation had a deleterious effect in both macro- and micro-blood supply of a tumor. The use of CAIA enhanced the efficacy of DSA and enabled the in vivo identification of the effect of irradiation on various caliber vessels as well as the ratios of total length and total area of small and big vessels.     

Tumor angiogenesis, apoptosis, and p53 oncogene in stage I lung adenocarcinoma

The purpose of this study was to clarify which factors are important as predictors not only of patient survival but also of hematogenic metastasis in 15 patients with stage I lung adenocarcinoma who underwent curative operation. The relationship between tumor angiogenesis, apoptosis, and p53 oncogene was also studied. A total of 15 patients were divided into two groups: surviving group (n=7) and nonsurviving (metastasis) group (n=8). We studied the medical charts, operative records, pathologic reports, and tumor specimens taken at surgical resection. We measured the apoptotic index using the ApopTag kit and the intratumoral microvessel count using an anti-CD34 monoclonal antibody. In addition, immunohistochemical staining for the expression of p53 was conducted simultaneously. The clinicopathological characteristics, including age, sex, tumor size (pT), and histological differentiation, were not significantly different between the surviving and the nonsurviving group. The microvessel count was significantly higher in nonsurviving group than in the surviving group. The apoptotic index and the expression of p53 was not significantly different between the two groups. An inverse correlation between the apoptotic index and microvessel count, and a positive correlation between the expression of p53 and microvessel count, were observed. Angiogenesis may be an important prognostic factor in patients with stage I lung adenocarcinoma.     

Vascular Endothelial Growth Factor and Soft Tissue Sarcomas: Tumor Expression Correlates With Grade

Introduction: Vascular endothelial growth factor (VEGF), an endothelial–specific mitogen overexpressed in various epithelial malignancies is thought to be a potent regulator of angiogenesis. We hypothesized that some soft tissue sarcomas, due to their high propensity for hematogenous metastases (1) would overexpress VEGF, (2) that the degree of expression may represent a significant biologic predictor for disease-specific survival, and (3) that recurrent tumor would express as high or higher VEGF compared with the primary tumor.Methods: Selected paraffin-embedded tissue of surgical specimens from 79 patients with soft tissue sarcomas, treated between 1989 and 1995 were stained with a rabbit polyclonal anti-VEGF antibody at a concentration of 2 g/ml. Slides were assessed for VEGF expression as high or low by two investigators blinded to the clinicopathologic data. Twelve patients had VEGF expression of their primary tumors, and their recurrent tumors were compared. The Fishers exact test assessed for differences in VEGF expression; survival analyses were performed according to the methods of Kaplan and Meier.Results: Seventy-eight percent (29 of 37) of patients who died of disease had high VEGF expression. However, VEGF expression was not an independent predictor of either overall or disease-free survival. Tumor grade correlated with VEGF expression significantly. For the low-grade tumors, 7 of 13 expressed low VEGF, whereas for high-grade tumors, 53 of 66 expressed high VEGF (P = .016). Seven of the 12 paired tumor samples expressed identical VEGF immunostaining.Conclusions: The majority of high-grade soft tissue sarcomas in this study have high intensity VEGF expression. This finding may provide useful information on individual soft tissue sarcomas and offer the basis for therapeutic and biologic targeting in high-risk patients using anti-angiogenesis strategies. However, in our analysis, after accounting for tumor grade, VEGF does not seem to be an independent predictor of clinical outcome.Presented at the 53rd Annual Cancer Symposium of the Society of Surgical Oncology Poster Session, New Orleans, Louisiana, March 16-19, 2010434_2001_Article_260.     

Ⅱ型环氧合酶在膀胱移行细胞癌中的表达及与肿瘤血管发生的关系

目的:研究Ⅱ型环氧合酶(Cox -2)在膀胱移行细胞癌中的表达,探讨它与膀胱癌病理分级及临床分期的关系及其临床意义,并研究它与血管内皮细胞生长因子(VEGF)及微血管密度(MVD)表达的关系,从而探讨Cox- 2在膀胱肿瘤血管发生中所起的作用。方法:应用免疫组化方法检测Cox- 2、VEGF及MVD在94 例膀胱移行细胞癌、12例膀胱良性病变和5例膀胱癌旁正常组织中的表达。结果:Cox- 2的表达随着膀胱癌分级分期的上升而呈上升趋势(P<0.05);在膀胱癌中,Cox 2 表达与VEGF表达( r=0.716, P=0.000)关系十分密切,与MVD表达存在明显相关性( r=0.458,P=0.000)。结论:Cox- 2在膀胱癌中均为高表达,它的表达参与了肿瘤的发生及恶性进展,并且与膀胱肿瘤新生血管发生有着密切关系。     

Inflammation in prostate cancer progression and therapeutic targeting

Chronic inflammation contributes to the onset and progression of human cancer, via modifications in the tumor microenvironment by remodeling the extracellular matrix (ECM) and initiating epithelial mesenchymal transition (EMT). At the biological level, chronically inflamed cells release cytokines that are functionally dictating a constitutively active stroma, promoting tumor growth and metastasis. In prostate cancer, inflammation correlates with increased development of “risk factor” lesions or proliferative inflammatory atrophy (PIA). Chronic inflammation in benign prostate biopsy specimens can be associated with high-grade prostate tumors in adjacent areas. In this article, we discuss the current understanding of the incidence of inflammation in prostate cancer progression and the significance of the process in therapeutic targeting of specific inflammatory signaling pathways and critical effectors during tumor progression. Further understanding of the process of chronic inflammation in prostate tumor progression to metastasis will enable development and optimization of novel therapeutic modalities for the treatment of high-risk patients with advanced disease.     

Influence of postoperative acute-phase response on angiogenesis and tumor growth: Open vs. laparoscopic-assisted surgery in mice

Inflammatory responses and tumor growth are increased after laparotomy compared with laparoscopy in some animal models. Proinflammatory cytokines interleukin-6 (IL-6) and interleukin-1 beta (IL-1β) upregulate the expression of vascular endothelial growth factor (VEGF). Our aim was to investigate the influence of postoperative inflammatory responses on angiogenesis and tumor growth. 5 Χ 10⁶ B51LiM cells were injected into the cecal wall of Balb/c mice. After 2 weeks, the animals were randomized into the following three groups: open cecectomy (OC), CO₂-laparoscopic-assisted cecectomy (LC), and helium-laparoscopic-assisted cecectomy (LH). On postoperative day 12, the mice were killed. Tumor load scores and weight were significantly greater after laparotomy than after laparoscopy. Serum IL-6 levels 6 hours after surgery (OC: 4157 ± 1297 pg/ml vs. LC: 2514 ± 1417 pg/ml vs. LH: 2255 ± 1714 pg/ml) and VEGF levels on postoperative day 12 (OC: 231 ± 125 pg/ml vs. LC: 45 ± 9 pg/ml vs. LH: 49 ± 8 pg/ml), measured by enzyme-linked immunosorbent assay, were significantly higher in the laparotomy group. Microvessel density was also significantly higher in the OC group (OC: 34.3 ± 11.5 vs. LC: 15.5 ± 12.5 vs. LH: 18.5 ± 11.9). There was a positive correlation between IL-6 and VEGF postoperative serum levels (rho = 0.67; P < 0.001). We concluded that increased systemic levels of proinflammatory cytokines and VEGF are associated with increased angiogenesis and tumor growth after laparotomy compared to laparoscopy in mice. Presented at the Fifty-Seventh Annual Sessions of the Owen H. Wangensteen Surgical Forum, The American College of Surgeons Clinical Congress, San Francisco, California, October 6–10, 2002; and published as an abstract in Journal ofthe American College of Surgeons 2002; 195:S69. Supported by an International Fellowship Grant from the American Society of Colon and Rectal Surgeons (M.P.) and by a Postdoctoral Grant (EX2001-35105008) from the Ministry of Education and Culture of Spain.     

血管内皮生长因子反义核酸对胰腺癌细胞增殖、凋亡和血管生成的影响

目的探讨腺病毒介导的血管内皮生长因子(VEGF)反义核酸对胰腺癌细胞增殖、凋亡和血管生成的作用。方法构建反向插入VEGF165基因的复制缺陷型腺病毒载体(Ad-αVEGF)。18只裸鼠皮下接种人胰腺癌细胞株SW1990,随机分成3组(n=3),1周后瘤体内分别注射磷酸盐缓冲液(PBS,100μl,PBS对照组)、报告基因LacZ重组腺病毒(100μl,Ad-LacZ对照组)、反义VEGF重组腺病毒(100μl,Ad-αVEGF治疗组),隔日1次,共4次。1个月后处死动物。PCNA染色、TUNEL法和CD31染色观察反义VEGF165基因转染对胰腺癌细胞增殖、凋亡和血管生成的影响。结果Ad-αVEGF治疗组PCNA阳性表达率为(38.1±6.8)%,较LacZ组(89.6±4.3)%、PBS对照组(92.1±5.2)%明显降低(P<0.01),LacZ组与PBS对照组之间差异无统计学意义(P>0.05)。Ad-αVEGF治疗组细胞凋亡率(32.3±3.8)%,明显多于LacZ组(8.6±7.6)%和PBS对照组(9.9±4.2)%(P<0.01),LacZ组与PBS对照组之间差异无统计学意义(P>0.05)。Ad-αVEGF治疗组肿瘤微血管密度(12±3),明显少于LacZ组(26±5)和PBS对照组(25±4)(P<0.01),LacZ组与PBS对照组之间差异无统计学意义(P>0.05)。结论反义VEGF165基因转染可以抑制肿瘤细胞增殖,增加细胞凋亡,减少了肿瘤内微血管数量,从而抑制肿瘤生长。