Morphology of angiogenesis in human cancer: a conceptual overview, histoprognostic perspective and significance of neoangiogenesis

Fractal dimension as a quantitator of the microvasculature of normal and adenomatous pituitary tissue

It is well known that angiogenesis is a complex process that accompanies neoplastic growth, but pituitary tumours are less vascularized than normal pituitary glands. Several analytical methods aimed at quantifying the vascular system in two-dimensional histological sections have been proposed, with very discordant results. In this study we investigated the non-Euclidean geometrical complexity of the two-dimensional microvasculature of normal pituitary glands and pituitary adenomas by quantifying the surface fractal dimension that measures its space-filling property. We found a statistical significant difference between the mean vascular surface fractal dimension estimated in normal versus adenomatous tissues (P = 0.01), normal versus secreting adenomatous tissues (P = 0.0003), and normal versus non-secreting adenomatous tissues (P = 0.047), whereas the difference between the secreting and non-secreting adenomatous tissues was not statistically significant. This study provides the first demonstration that fractal dimension is an objective and valid quantitator of the two-dimensional geometrical complexity of the pituitary gland microvascular network in physiological and pathological states. Further studies are needed to compare the vascular surface fractal dimension estimates in different subtypes of pituitary tumours and correlate them with clinical parameters in order to evaluate whether the distribution pattern of vascular growth is related to a particular state of the pituitary gland.

[Assessment of angiogenesis expression and its relationship with prognosis of colorectal cancer by conventional and computer-assisted histopathological image analysis]

PURPOSE

To quantify the degree of angiogenesis by conventional method (microvessel density, MVD) and computerized method (endothelial area, EA), and to evaluate their relationships with the prognosis of patients operated on for colorectal adenocarcinoma.

METHODS

Tumoral angiogenesis was studied by means of an immunohistochemical technique, using CD 34, on 126 patients; to quantify the angiogenesis, MVD (defined as number of microvessels per mm(2)) and EA measurement (defined as the area occupied by EA in the microscope field). A computerized method, IMAGELab software was utilized to quantify endothelial area.

RESULTS

The mean number of microvessels was 128.6 MV/mm(2) (SD = 44.5) and the mean EA was 4.3% (SD = 2.1). The Pearson method demonstrated a low correlation coefficient between MVD and EA (r = 0.429). No relationship between MVD and EA was observed with regard to relapse-free interval and overall survival.

CONCLUSION

The histological analysis of angiogenesis expression in patients with colorectal adenocarcinoma can be performed either by computer-assisted image analysis of endothelial area or by conventional microvessels counting. Both methods did not show any significant relationship between these angiogenesis parameters with relapse-free interval and overall survival.

Vascular architecture: is it a helpful histopathological biomarker for hepatocellular carcinoma?

Hepatocellular carcinoma (HCC) remains one of the major public health problems throughout the world. Although originally associated with tumorigenic processes, liver angiogenesis has also been observed in the context of different liver inflammatory, fibrotic, and ischemic conditions. Here we investigate the fractal dimension as a quantitator of non-Euclidean two-dimensional vascular geometry in a series of paired specimens of primary HCC and surrounding non-tumoral tissue, and discuss why this parameter might provide additional information regarding cancer behavior. The application of fractal geometry to the measurement of liver vascularity and the availability of a computer-aided quantitative method can eliminate errors in visual interpretation, and make it possible to obtain closer-to-reality numerals that are compulsory for any measurement process.

Geometry of human vascular system: is it an obstacle for quantifying antiangiogenic therapies?

It is now recognized that all human natural and diseased anatomic systems are characterized by irregular shapes and very complex behaviors. In geometrical terms, tumor vascularity (which is the result of a nonlinear dynamic process called angiogenesis) is an archetypal anatomic system that irregularly fills a 3-dimensional Euclidean space. This characteristic, together with the highly variable nature of vessel shapes and surfaces, leads to considerable spatial and temporal heterogeneity in the delivery of oxygen, nutrients, and drugs, and the removal of metabolites. Although these biologic features have been well established, the quantitative analysis of neovascularity in 2-dimensional histologic sections still fails to view its architecture as a non-Euclidean geometrical object, thus allowing errors in visual interpretation and discordant results concerning the same tumor from different laboratories. We discuss here the tumor-induced vascular system as a fractal object, and what changes this new way of observing may bring to the quantification of effective antiangiogenic therapies.

Angiogenic switch during tumor progression of carcinoma ex-pleomorphic adenoma

We analyzed the tumor vascularization in carcinomas ex-pleomorphic adenoma (CXPA) to investigate the angiogenic switch during the malignant transformation of pleomorphic adenoma (PA) to carcinoma and during tumor progression. In eight cases of early CXPA (intracapsular and minimally invasive tumors), eight of advanced CXPA (widely invasive tumors), and ten of PA without malignant transformation, tumor vascularization was assessed in histological samples by measuring total microvascular area (TVA) and microvessel density (MVD) using CD34 and CD105 antibodies. MVD for CD105 increased significantly during tumor progression, whereas this was not the case for CD34 MVD. Comparing widely invasive CXPA with and without myoepithelial differentiation, CXPA with myoepithelial differentiation showed a significantly lower number of CD105 positive vessels but revealed higher TVA values. In these tumors, the neoplastic cells usually formed larger hypovascularized aggregates that were often surrounded by large-sized vessels. In conclusion, the antibody CD105 reveals an angiogenic switch during the progression from adenoma to carcinoma in salivary glands. The degree of angiogenesis and the total vascular area have distinctive patterns in CXPA with and without myoepithelial differentiation. Low angiogenesis associated with high TVA value is more characteristic of CXPA with myoepithelial differentiation.

Immunoexpression of endoglin in brain metastasis secondary to malignant melanoma: evaluation of angiogenesis and comparison with brain metastasis secondary to breast and lung carcinomas

Brain metastases are linked to poor prognosis. After carcinomas of the lung and breast, malignant melanomas (MM) are the next type of neoplasm with the higher metastatic dissemination involving the central nervous system and that has the worst prognosis after metastasis has been diagnosed. Angiogenesis has been linked to tumor growth and metastasis. Among the immunomarkers of angiogenesis, endoglin (CD105) is the most specific antibody, since it is a marker for tumor endothelium, and expression of CD105 has been observed to be associated with prognosis in several types of tumor, which is not always observed in melanomas. This study investigated angiogenesis in brain metastasis secondary to malignant melanomas and compared these with brain metastasis secondary to carcinomas of the lung and breast, through expression of CD105 (endoglin). The study investigated 93 cases of brain metastasis secondary to MM (33) and carcinomas of the lung (31) and breast (29), assessing endoglin immunoexpression, number of microvessels and diameter of tumor vessels. Tumor microvessels were counted using a modified version of the Chalkley technique. The observed difference between MM and breast carcinoma was statistically significant (P = 0.026). The difference between MM and lung carcinoma was not significant (P = 0.218). Vascular diameter observation revealed no statistical difference between the vascular size of neoplastic vessels in MM and in breast and lung carcinomas. Of the tumors investigated here, malignant melanomas were shown to have the lowest number of microvessels and had intermediate tumor vessel diameter as compared to carcinomas of the lungs and breast. Such results were not expected to be found in neoplasms such as melanomas that, besides presenting high dissemination capacity, have a high index of hemorrhage secondary to brain metastasis.

Expression of vascular endothelial-cadherin in human hepatocellular carcinoma tissues

AIM

Angiogenesis is important in tumor growth and progression to metastasis. Vascular endothelial (VE)-cadherin is an endothelial cell-specific cadherin required for angiogenesis, but its expression in hepatocellular carcinoma (HCC) tissues has not been examined.

METHODS

Expression of VE-cadherin was analyzed in 31 HCC frozen tissue specimens by immunohistochemical and immunoelectron microscopic procedures. In addition, the association of its expression with clinicopathological parameters was investigated to determine the possible diagnostic or predictive value of VE-cadherin expression in neoplastic and non-neoplastic liver lesions.

RESULTS

Immunoreactive VE-cadherin expression was faint or barely detectable on sinusoidal endothelial cells of normal liver but was evident on sinusoidal or capillary endothelium of chronic hepatitis, cirrhosis, and HCC tissues. VE-cadherin expression was more intense on capillary endothelium of HCC tissues in 26 (84%) of 31 patients than on sinusoidal endothelium of surrounding non-tumorous liver tissues with chronic liver diseases. The intensity or intracapillary extent of positive stain for VE-cadherin on capillary endothelium of HCC tissues was significantly associated with tumor size, capsular invasion and tumor cell differentiation in HCC.

CONCLUSIONS

Intense VE-cadherin expression was evident in capillary endothelium of HCC tissues, giving the first indication of association with clinicopathological features of HCC patients.

Differential angiogenic regulation of experimental colitis

Inflammatory bowel diseases (IBDs) are chronic inflammatory disorders of the intestinal tract with unknown multifactorial etiology that, among other things, result in alteration and dysfunction of the intestinal microvasculature. Clinical observations of increased colon microvascular density during IBD have been made. However, there have been no reports investigating the physiological or pathological importance of angiogenic stimulation during the development of intestinal inflammation. Here we report that the dextran sodium sulfate and CD4+CD45RBhigh T-cell transfer models of colitis stimulate angiogenesis that results in increased blood vessel density concomitant with increased histopathology, suggesting that the neovasculature contributes to tissue damage during colitis. We also show that leukocyte infiltration is an obligatory requirement for the stimulation of angiogenesis. The angiogenic response during experimental colitis was differentially regulated in that the production of various angiogenic mediators was diverse between the two models with only a small group of molecules being similarly controlled. Importantly, treatment with the anti-angiogenic agent thalidomide or ATN-161 significantly reduced angiogenic activity and associated tissue histopathology during experimental colitis. Our findings identify a direct pathological link between angiogenesis and the development of experimental colitis, representing a novel therapeutic target for IBD.

A comparative study of neovascularisation in atherosclerotic plaques using CD31, CD105 and TGF beta 1

OBJECTIVES

This study aims to identify plaque neovascularisation using antibodies to CD31, CD105 and TGFbeta1, and to compare their patterns of expression.

METHODS

Tissue expression of CD31, CD105 and TGFbeta1 was examined immunohistologically in atherosclerotic plaques from 53 patients who had undergone carotid endarterectomy and in 10 controls.

RESULTS

CD31 was observed in a proportion of the microvessels within atheroma. The expression of CD105 was barely visible in normal arteries, but was markedly enhanced in atherosclerotic plaques. The vast majority of the microvessels in atheroma were positive for CD105 with pronounced expression around the periphery of the lipid core. In consecutive sections, microvessels showing negative staining for CD31 were positive for CD105. Although TGFbeta1 was seen in the thickened intima, it was more strongly expressed in well-formed fibrous plaques. Consecutive sections showed that some microvessels were stained by both CD105 and TGFbeta1, but in certain areas microvessels were exclusively CD105 positive.

CONCLUSIONS

These observations highlight the distinctive expression patterns of CD31, CD105 and TGFbeta1, suggesting their specific roles in the development of atherosclerotic plaques. CD105 is almost universally expressed in microvessels within the atheroma and is therefore a better vascular marker than CD31 and TGFbeta1for assessing neovascularisation in atherosclerotic plaques.

Effects of prostaglandin E2 on expression of vascular endothelial growth factor in human gastric cancer cell line MKN28

AIM: To investigate the expression of vascular endothelial growth factor (VEGF) in human gastric cell line MKN28 in vitro, and identify whether exogenous prostaglandin E₂ (PGE₂) can increase the expression of VEGF.

METHODS: Human gastric cell line MKN28 was culture in vitro and then treated with 0.1, 1, 5, and 10 μmol/L PGE₂ for 3 h. Real-time polymerase chain reaction (PCR) and Western blot were used to detect the expression of VEGF mRNA and protein, respectively.

RESULTS: The transcription of VEGF mRNA increased in a dose-dependent manner after PGE₂ treatment, and the difference between the groups of 0.1, 1, 5, 10 μmol/L PGE₂ treatment and the control group had statistical significances (0.67 ± 0.093, 0.74 ± 0.13, 0.87 ± 0.07, 1.49 ± 0.15 vs 0.42 ± 0.10, P < 0.05 or P < 0.01). PGE₂ also up-regulated the expression of VEGF protein in a dose-dependent manner, and except 0.1 μmol/L PGE₂ treatment group, the difference between the groups of 1, 5, 10 μmol/L PGE₂ treatment and the control group had statistical significances (51.02 ± 2.16, 66.69 ± 9.85, 136.49 ± 6.89 vs 26.87 ± 3.98, P < 0.05 or P < 0.01).

CONCLUSION: PGE₂ can promote VEGF mRNA transcription and protein expression in human gastric cancer cell line MKN28.

Expression and possible role of hPTTG1/securin in cutaneous malignant melanoma

Human pituitary tumour-transforming gene 1 or hPTTG1 is a proto-oncogene that codes for securin, a protein involved in sister chromatid separation. Based on previous microarray data, we studied the expression of hPTTG1/securin in melanocytic lesions. In contrast to nevi and radial growth phase melanomas, securin was expressed by scattered cells in the vertical growth phase, suggesting a role in tumour progression. In a series of 29 nodular and 29 superficial spreading melanomas, matched for all histological prognostic parameters, securin expression was significantly correlated with the nodular subtype (P=0.018) and not related to thickness. In other cancers, hPTTG1 is involved in various oncogenic pathways, including induction of neovascularisation and aneuploidy, and inhibition of p53 activity. We found coexpression of securin with wild-type p53 in the same neoplastic cells in a minority of melanomas. Expression of securin was significantly correlated with the extent of aneuploidy but not with basic fibroblast growth factor immunoreactivity or microvessel density. DNA cytometry revealed that nuclei-overexpressing securin frequently showed tetraploidy or aneuploidy. Our data show that hPTTG1 is frequently overexpressed in nodular melanoma, and suggest that hPTTG1 may act as an oncogene in the vertical growth phase, either by inhibiting anaphase, thereby causing aneuploidy and genomic instability, or by modulating the function of p53, thereby impairing apoptosis.

Angiogenesis in Atherogenesis

Atherogenesis is the pathobiological process, which underlies atherosclerotic cardiovascular disease and evolves in the 3 stages of initiation, progression, and complication to clinical significance. Of note, this process is associated with neovascularization, and it was not until recently that the implications of angiogenesis in atherogenesis were delineated. This article gives an updated overview on this topic and briefly reflects on the similarities with neovessel formation in carcinogenesis.

Histopathologic assessment of hot-spot microvessel density and vascular patterns in glioblastoma: Poor observer agreement limits clinical utility as prognostic factors: a translational research project of the European Organization for Research and Treatment of Cancer Brain Tumor Group

BACKGROUND

Hot-spot microvessel density (MVD) and vascular patterns have been reported as histopathologic factors that influence prognosis in retrospective series of malignant gliomas. To investigate clinical utility, the authors systematically studied observer agreement on MVD and vascular patterns and the influence of repeatedly assessed data on patient outcomes in 2 independent glioblastoma series.

METHODS

MVD and vascular patterns were assessed retrospectively by 5 observers in 1) a retrospectively compiled glioblastoma series that included 110 patients and 2) a glioblastoma series that included 233 patients who were treated within a randomized trial. MVD was determined in the field of greatest density ("hot-spot"). Predominantly classic or bizarre vascular patterns were determined by using a previously defined algorithm.

RESULTS

Observer agreement on MVD was highly variable (range of kappa values, 0.464-0.901). The worst observer agreement was achieved when both the selection of hot-spots and MVD counts were performed independently. Survival analysis did not show a consistent association between repeatedly assessed MVD and patient outcome. Observer agreement on vascular patterns was poor (kappa = 0.297). Survival analysis did not show a consistent association between repeatedly assessed vascular patterns and patient outcome.

CONCLUSIONS

Observer agreement on hot-spot MVD and vascular patterns in patients with glioblastoma was poor in independent assessments. MVD and vascular patterns were not associated consistently with patient outcome. Based on these findings, the authors concluded that poor observer agreement limits the clinical utility of histopathologically assessed hot-spot MVD and vascular patterns as prognostic factors in patients with glioblastoma. Improved methodologies for morphologic assessment of glioblastoma vascularization need to be identified.

Comparative evaluation of microvessel density determined by CD34 or CD105 in benign and malignant gastric lesions

Microvessel density (MVD) is regarded as a surrogate marker for angiogenesis and has been used for tumor prognosis. In this study, MVD was identified immunohistochemically by monoclonal antibodies against CD105 and CD34 in the tissues representing gastric carcinoma, chronic gastritis, and hyperplastic polyps, and the results were correlated with clinicopathologic features. The expression of CD105 in the microvessels within benign lesions was barely visible, and MVD was markedly lower than that determined by CD34. CD34 was strongly expressed in the microvessels within hyperplastic polyps and tissues with gastritis. In gastric carcinoma, CD105 expression in microvessels was as high as the MVD, compared with benign lesions. CD105 stained well-formed mature and newly formed immature vessels within the cancer mass. Correlation analysis showed that MVD determined by CD105 correlated with blood vessel invasion, distant metastasis, and formation of ascites. Survival analysis demonstrated an inverse correlation between MVD count and overall survival: patients with MVD counts of 32 or higher survived for a much shorter time than those with counts lower than 32. Multivariate analysis confirmed that MVD determined by CD105 was an independent prognostic factor for survival. Microvessel density determined by CD34 inversely correlated with overall survival, but it did not correlate with other clinicopathologic parameters except formation of ascites. In conclusion, CD34 was universally expressed in blood vessels within benign and malignant tissues, whereas CD105 expression was minimal in benign tissues but stronger in gastric carcinoma. These data suggest that both CD105 and CD34 could be used for quantification of angiogenesis, but preference should be given to CD105 in the evaluation of prognosis in gastric carcinoma.

Angiogenic patterns and their quantitation in high grade astrocytic tumors

BACKGROUND

The objectives of this study on high grade astrocytic tumors were (i) to establish differences, if any, between grades III & IV tumors among angiogenic parameters, both qualitative and quantitative, and (ii) to correlate angiogenic parameters with proliferation indices, namely T2a and MIB1 labeling indices.

DESIGN

Twenty nine consecutive cases of WHO grades III (11) and IV (18) astrocytic tumors diagnosed in the year-2004 were studied, using H&E and CD34, MIB1 and T2a immunostaining by streptavidin biotin technique. Angiogenic patterns were studied and parameters quantitated using Image Pro Plus software (four hotspots) on CD34 immunostained sections to determine intratumoral microvessel density (iMVD), microvascular area (MVA), aspect, mean diameter (MD) and fractal dimension (FD).

RESULTS

Main angiogenic patterns of capillary (18) and glomeruloid (9) types were best developed in glioblastomas. Statistically significant differences (P<0.05) were seen between grades III and IV in iMVD, aspect, MD and FD, but not in angiogenic patterns or MVA (P = 0.27). Statistically significant differences (P<0.05) were seen between glioblastomas with glomeruloid vs. capillary types in iMVD and FD, but not in MVA, aspect and mean vessel diameter. T2a values correlated with MIB1 labeling indices (R = 0.965, P<0.001). Intratumoral endothelial MIB1 LI was significantly higher in grade IV as compared to grade III, but did not correlate with angiogenic parameters. No correlation of angiogenic patterns and proliferation indices was noted (R = -0.221, P = 0.26). Limited follow up data showed all recurrent grade IV tumors to be of glomeruloid type.

CONCLUSION

Increased angiogenesis in grade IV, as compared to grade III, astrocytic tumors is characterized by an increased number/density of vessels: an increase in vessels characterized by disproportionate lengthening and likely associated with the infiltrative properties of the tumors; and an increase in pliable, irregularly shaped or structured vessels. In addition, there is a greater frequency of glomeruloid structures indicating inadequate directional migration of the newly formed vessels. The lack of correlation of these angiogenesis parameters with the MIB1 and T2a proliferation indices reflects the complexity of angiogenesis parameters in high grade gliomas. Further studies are needed to determine the usefulness of the angiogenic parameters in the improved diagnosis (grading) and prognosis of astrocytic tumors.

Ephrin B expression in epithelial ovarian neoplasms correlates with tumor differentiation and angiogenesis

Differential gene expression studies are identifying new sets of genes with a role in the classification, differential diagnosis, and prognosis of some human tumors. Ephrin B1, a factor involved in angiogenesis, has been shown to be up-regulated in ovarian carcinomas, making it a potential target for cancer treatment. This study investigates ephrin B expression in ovarian tumors to validate results from gene expression studies and evaluates its significance with a clinical-pathological correlation. Specimens from 112 benign, borderline, and malignant epithelial ovarian tumors were examined. Tissue microarrays were constructed, and ephrin B expression was studied by immunohistochemistry. To correlate ephrin B expression with angiogenesis, CD31 immunostaining was performed to assess microvessel density. Ephrin B was detected in 50% of ovarian tumors: clear cell carcinomas (93%), serous carcinomas (74%), mucinous carcinomas (29%), and endometrioid carcinomas (27%). High-grade carcinomas showed greatest ephrin B expression, whereas benign tumors and low-grade carcinomas were rarely positive. A correlation was found between ephrin B expression and microvessel density, supporting the angiogenic role of this factor in ovarian carcinomas. Ephrin B expression was associated with higher rates of disease recurrence and a decrease in overall survival. A distinctive pattern of ephrin B expression was observed in ovarian tumors: high-grade tumors and clear cell and serous carcinomas show higher expression, correlating with the aggressiveness. On the other hand, ephrin B expression correlated with microvessel density of the tumors. Because Eph receptors and ephrins are targets for new therapeutic inhibitors, this pattern of ephrin B expression should be considered in future clinical studies.

Angiogenesis in gliomas: imaging and experimental therapeutics

Much of the interest in angiogenesis and hypoxia has led to investigating diagnostic imaging methodologies and developing efficacious agents against angiogenesis in gliomas. In many ways, because of the cytostatic effects of these agents on tumor growth and tumor-associated endothelial cells, the effects of therapy are not immediately evident. Hence finding clinically applicable imaging tools and pathologic surrogate markers is an important step in translating glioma biology to therapeutics. There are a variety of strategies in the approach to experimental therapeutics that target the hypoxia-inducible factor pathway, the endogenous antiangiogenic and proangiogenic factors and their receptors, adhesion molecules, matrix proteases and cytokines, and the existing vasculature. We discuss the rationale for antiangiogenesis as a treatment strategy, the preclinical and clinical assessment of antiangiogenic interventions and finally focus on the various treatment strategies, including combining antiangiogenic drugs with radiation and chemotherapy.

Clinicopathologic significance of CD105 expression in squamous cell carcinoma of the hypopharynx

BACKGROUND

Induction of angiogenesis is a key process in tumor growth and metastasis. We studied the CD105 (endoglin) and vascular endothelial growth factor (VEGF) in hypopharyngeal cancer to evaluate their clinicopathologic significance.

METHODS

Seventy-three patients who underwent complete excision of hypopharyngeal cancer were included in this study. Clinicopathologic data were collected retrospectively. Immunohistochemical analysis was performed with antibodies of CD105 and VEGF. Positive-stained microvessels for CD105 were counted on hot spots of tumors. The staining intensity for VEGF was also evaluated.

RESULTS

High expression of CD105 correlated significantly with positive nodal metastasis (p < .001) and TNM stage (p < .01). High expression of VEGF correlated significantly with advanced tumor (T) classification (p < .01). The overall 5-year survival rate was worse in patients with higher CD105 expression (p < .001), advanced TNM stage (p < .01), advanced T classification (p < .01), and positive nodal metastasis (p < .001). Furthermore, Cox regression analysis revealed that CD105 expression in microvessels of tumor tissue, advanced T classification, and nodal status were independent factors for survival.

CONCLUSION

Our results suggest that expression of CD105 is a useful predictive prognostic factor in hypopharyngeal cancer.