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

Possible Involvement of Adipocyte-Derived Leucine Aminopeptidase via Angiotensin II in Endometrial Carcinoma

OBJECTIVE

It has recently been appreciated that a local autocrine or paracrine renin-angiotensin system (RAS) may exist in a number of tissues. Angiotensin II (AngII) is a potent RAS-derived vasoconstrictor peptide, and it is involved in tumor angiogenesis. We have cloned human adipocyte-derived leucine aminopeptidase (A-LAP), which degrades Ang II. This study investigated whether the expression of A-LAP, Ang II, angiotensin type I receptor (AT1R) and vascular endothelial growth factor (VEGF) correlates with clinicopathologic factors and prognosis in patients with endometrial endometrioid adenocarcinoma.

METHODS

Histologic sections of formalin-fixed, paraffin-embedded specimens from 94 primary endometrial carcinomas were stained for A-LAP, AngII, AT1R and VEGF using each antibody. Disease-free survival (DFS) and other clinicopathologic characteristics were analyzed according to the intensity of each staining.

RESULTS

Of 94 cases, 91 (96.8%) showed specific A-LAP immunostaining. A-LAP expression demonstrated negative correlations with myometrial invasion (p = 0.01) and vascular infiltration (p = 0.01). Of 94 cases, 77 (81.9%) showed specific AngII immunostaining. We found a positive correlation between AngII expression and surgical stage (p = 0.01). Of 94 cases, 56 (59.6%) showed specific AT1R immunostaining and 73 (77.7%) specific VEGF immunostaining. We found a positive correlation between VEGF expression and lymph node metastasis (p = 0.05). AngII and AT1R expression predicted a significantly poorer prognosis. Contrarily, A-LAP expression indicated a significantly more favorable prognosis in endometrial endometrioid adenocarcinoma patients. Multivariate analysis demonstrated that A-LAP expression (odds ratio, 0.12; 95% confidence interval, 0.025-0.618; p = 0.01) was an independent prognostic factor.

CONCLUSIONS

In this study, we demonstrated the existence of local RAS and A-LAP in endometrial endometrioid adenocarcinoma as prognostic predictors of clinical outcome. These findings suggest that the assessment of RAS and A-LAP status provides clinically useful prognostic information in patients with endometrial carcinoma.

The vascular network of tumours--what is it not for?

It is becoming almost a dogma that tumours cannot grow beyond 1-2 mm(3) unless they are supported by a rich vascular supply 1. It is true that tumours promote angiogenesis and that highly vascularized carcinomas have, in general, a more aggressive clinical course than carcinomas of low vascularization 23. However, a study of intratumoral angiogenesis reveals that the newly formed vessels are commonly deprived of those structural qualities that would allow them to perform an optimal oxygenation function 3. Thus, most tumours, irrespective of their angiogenic status, behave as if they were 'hypoxic', urging (via angiogenic mediators) for, what would look paradoxical at first sight, more defective angiogenesis. It is hypothesized that tumour cells can grow into solid neoplasms by exploiting the host's pre-existing vessels, without the need for new blood vessel formation. Neovascularization, however, may be important for tumours with an exophytic pattern of growth as these, by their very nature, lose the host's sheltering stroma. Shifting to anaerobic glycolysis and activation of anti-apoptotic pathways are complementary mechanisms for tumour cell survival and growth. Besides, continuous and indiscriminate production of a defective vascular network ensures an increased metastatic potential since the newly formed intratumoral vessels, simulating venular-like spaces, are easily permeable to tumour cells, facilitating metastases.

Non-endothelial KDR/flk-1 expression is associated with increased survival of patients with urothelial bladder carcinomas

AIMS

To investigate the immunohistochemical expression of KDR/flk-1 in a series of 114 urothelial bladder carcinomas in relation to clinicopathological parameters, Ki67, p53 and Bcl-2 protein expression and patient survival. KDR/flk-1 is a high-affinity tyrosine kinase receptor for vascular endothelial growth factor (VEGF), on vascular endothelium. However, there is increasing evidence that KDR/flk-1 is also expressed by normal non-endothelial and tumour cells.

METHODS AND RESULTS

Immunohistochemistry was performed on paraffin sections using monoclonal and polyclonal antibodies. Statistical analysis was univariate (chi2 log rank test) and multivariate (Cox's model). KDR/flk-1 expression was observed in the cytoplasm of cancerous cells in 68.4% of cases. No statistically significant associations were observed between KDR/flk-1 expression and grade or stage of urothelial carcinomas, Ki67, p53 or Bcl-2 expression. In contrast, widespread KDR/flk-1 expression in more than 50% of cancerous cells was associated with increased survival, on univariate and multivariate analysis (P = 0.0119 and P = 0.042, respectively).

CONCLUSIONS

Although the biological significance of non-endothelial KDR/flk-1 expression has not yet been elucidated, its association with better patient survival may be related to the failure of non-endothelial KDR/flk-1 to mediate angiogenic and mitogenic effects.

The angiogenic switch for vascular endothelial growth factor (VEGF)-A, VEGF-B, VEGF-C, and VEGF-D in the adenoma-carcinoma sequence during colorectal cancer progression

Angiogenesis is essential for tumour growth and metastasis. It is controlled by angiogenic factors, one of the most important being vascular endothelial growth factor (VEGF)-A. Although its role has been demonstrated in many tumour types including colorectal carcinoma (CRC), the importance of the newer family members in adenoma, invasive tumour growth, and progression to a metastatic phenotype has been poorly characterized in CRC. The aim of this study was to determine the role and timing of the VEGF angiogenic switch during CRC progression. We measured the gene expression of VEGF ligands (VEGF-A, VEGF-B, VEGF-C, and VEGF-D) and their receptors (VEGFR-1, VEGFR-2, and VEGFR-3), in normal colorectal tissues (n = 20), adenomas (n = 10), and in CRC (n = 71) representing different Duke's stages using ribonuclease protection assay, semi-quantitative relative reverse transcriptase polymerase chain reaction, together with the pattern of their expression by immunohistochemistry. VEGF-A mRNA was the most abundant in colorectal tissue, followed by VEGF-B, VEGF-C, and VEGF-D. VEGF-A and VEGF-B mRNAs were significantly more abundant in adenomas (p = 0.0003 and p = 0.04 respectively) compared with normal tissues, while VEGF-A and VEGF-C were significantly increased in carcinomas compared with normal tissues (p = 0.0006 and p = 0.0009 respectively). A significantly greater amount of VEGF-C mRNA was present in carcinomas compared with adenomas (p = 0.03), whereas there was a significant reduction of VEGF-B in carcinomas compared with adenomas (p = 0.0002). VEGF-D mRNA was significantly more abundant in normal tissues than in adenomas (p = 0.0001) and carcinomas (p < 0.0001). In normal tissues distant from the primary tumour, there was a significantly greater amount of VEGF-A and VEGF-D mRNA in patients with Duke's B and Duke's C respectively, compared with Duke's A stage tumours (p = 0.04 and p = 0.01 respectively). Immunohistochemistry showed low basal levels of all ligands in histologically normal tissues and their expression in the epithelium of tumours reflected the levels of mRNA expression identified. VEGF-A and VEGF-C mRNA levels correlated significantly with tumour grade (p = 0.01 and p = 0.01 respectively) and tumour size (p = 0.001 and p = 0.01 respectively), but not with patient age, sex, presence of infiltrative margin, lymphocytic response, vascular invasion, Duke's stage, or lymph node involvement (p > 0.05). VEGF-B mRNA correlated with an infiltrative margin (p = 0.04) but no other clinicopathological variable, and expression of VEGF-D demonstrated no association with any parameter examined. VEGFR-1 was significantly correlated with tumour grade (p = 0.02), Duke's stage (p < 0.001), and lymph node involvement (p = 0.004), VEGFR-2 with lymph node involvement (p = 0.02), and VEGFR-3 did not correlate with any of the clinicopathological variables tested. These results suggest that VEGF-A and VEGF-B play a role early in tumour development at the stage of adenoma formation and that VEGF-C plays a role in advanced disease when there is more likelihood of metastatic spread. The finding of increased levels of VEGF-A and VEGF-D expression in normal tissues collected from a site distant from the primary tumour indicates changes in the surrounding tumour environment that may enhance the subsequent spread of tumour cells.

Angiopoietin-1 is expressed in the synovium of patients with rheumatoid arthritis and is induced by tumour necrosis factor alpha

OBJECTIVES

To examine the potential role of the angiogenic growth factor angiopoietin-1 (Ang-1) in inflammatory arthritis.

METHODS

Eighteen synovial tissue samples were obtained from 17 patients with a clinical diagnosis of rheumatoid arthritis (RA) and compared with six synovial tissue samples from six patients with osteoarthritis (OA). Ang-1 expression in synovial tissues was determined by immunohistochemistry and in situ hybridisation. Ang-1 mRNA and protein expression were also examined by northern blot analysis and enzyme linked immunosorbent assay (ELISA) in cultured synovial fibroblasts and human umbilical vein endothelial cells (HUVECs) before and after treatment with tumour necrosis factor (TNF)alpha.

RESULTS

Ang-1 protein expression was detected by immunohistochemistry in 16/18 RA synovial tissue samples. Ang-1 protein was frequently observed in the synovial lining layer and in cells within the sublining synovial tissue, in both perivascular areas and in areas remote from vessels. In contrast, Ang-1 was only weakly detected in these sites in OA samples. Ang-1 mRNA and protein were also expressed in cultured synovial fibroblasts derived from patients with RA. In addition, induction of Ang-1 mRNA and protein was observed by northern blot analysis and ELISA after stimulation of RA synovial fibroblasts, but not HUVECs, with the proinflammatory cytokine TNF alpha.

CONCLUSIONS

Ang-1 mRNA and protein are expressed in the synovium of patients with RA, and are up regulated in synovial fibroblasts by TNF alpha. Ang-1 may therefore be an important regulator of angiogenesis in inflammatory arthritis.

Angiogenesis: prognostic and therapeutic implications in gynecologic and breast malignancies

PURPOSE OF REVIEW

Growth, invasion and metastasis of malignant tumors depend on angiogenesis, which is therefore considered an attractive therapeutic target and indicator of clinical outcome. Summarizing the results of very recent studies, we discuss the clinical relevance of vascularization of breast and gynecological tumors.

RECENT FINDINGS

The prognostic values of directly assessed vascularity (microvessel density) and angiogenic factors have been confirmed for these malignancies, despite few contradictory results that may be due to methodological inaccuracy. In addition, many studies point to a role of angiogenesis as a predictor of response to both antiangiogenic and conventional chemotherapy or radiotherapy. For a conclusive evaluation, however, further studies covering all clinically relevant subgroups of patients are needed. Novel therapeutic approaches with inhibitors of angiogenesis are promising, although the adaptation of most experimentally proven approaches to clinical practice appears to be a laborious process. Furthermore, for an appropriate clinical evaluation of these drugs, newly defined endpoints of treatment and new monitoring systems reflecting their mode of action and the anticipated biological effects are required.

SUMMARY

The prognostic and predictive value of angiogenic factors and microvessel density has been confirmed. Antiangiogenic therapy will most likely play an important role in future clinical management of malignant diseases.

Association of hypoxia-inducible factors 1alpha and 2alpha with activated angiogenic pathways and prognosis in patients with endometrial carcinoma

BACKGROUND

Hypoxia-inducible factor 1alpha (HIF-1alpha) and HIF-2alpha are essential regulatory proteins for the adaptation of tumor cells to hypoxia, and they stimulate angiogenesis through activation of the vascular endothelial growth factor (VEGF) gene.

METHODS

HIF-1alpha and HIF-2alpha proteins were studied immunohistochemically in a group of 81 patients with Stage I endometrial adenocarcinoma of the endometrioid cell type. The results were correlated with intratumoral angiogenesis, the expression of the angiogenic factors VEGF and thymidine phosphorylase (TP), and the VEGF/receptor (VEGF/KDR) complex. Relations also were sought with estrogen receptor (ER) and progesterone receptor (PR), with the apoptosis-related proteins bcl-2 and p53, with several histopathologic parameters, and with patient prognosis. In addition, a sample of 25 normal endometria at various phases of the menstrual cycle was studied for the presence of HIF-1alpha and HIF-2alpha.

RESULTS

HIF-1alpha expression was detected in 49% of endometrial carcinomas. The expression was cytoplasmic or mixed nuclear/cytoplasmic. HIF-1alpha expression was associated with up-regulation of the VEGF pathway and with increased standard microvessel density (sMVD) and activated VEGF/KDR microvessel density (aMVD). It also was associated with a poor prognosis in both univariate and multivariate analyses. HIF-2alpha protein showed a pattern of expression similar to the pattern seen in HIF-1alpha, but expression of HIF-2alpha protein occurred in only 17% of endometrial carcinomas, and it was associated with increased TP reactivity. There also was a relation of HIF-1alpha expression with well-differentiated endometrial neoplasms, and there was a marginal association of HIF-1alpha and HIF-2alpha with ER expression. With reference to normally cycling tissues, HIF-1alpha nuclear/cytoplasmic expression was particularly strong in the samples of early proliferative phase endometrium compared with HIF-2alpha protein expression, which showed a constant reaction throughout the menstrual cycle.

CONCLUSIONS

The up-regulation of HIF-1alpha and, to a lesser extent, of HIF-2alpha is a common event in Stage I endometrial adenocarcinomas. In these tumors, HIF-1alpha expression is related to increased angiogenesis, through activation of the VEGF angiogenic pathway, and to an unfavorable prognosis. HIF-2alpha accumulation is associated with increased expression of the angiogenic factor TP.

Intra-tumoural microvessel density in human solid tumours

Over the last decade assessment of angiogenesis has emerged as a potentially useful biological prognostic and predictive factor in human solid tumours. With the development of highly specific endothelial markers that can be assessed in histological archival specimens, several quantitative studies have been performed in various solid tumours. The majority of published studies have shown a positive correlation between intra-tumoural microvessel density, a measure of tumour angiogenesis, and prognosis in solid tumours. A minority of studies have not demonstrated an association and this may be attributed to significant differences in the methodologies employed for sample selection, immunostaining techniques, vessel counting and statistical analysis, although a number of biological differences may account for the discrepancy. In this review we evaluate the quantification of angiogenesis by immunohistochemistry, the relationship between tumour vascularity and metastasis, and the clinicopathological studies correlating intra-tumoral microvessel density with prognosis and response to anti-cancer therapy. In view of the extensive nature of this retrospective body of data, comparative studies are needed to identify the optimum technique and endothelial antigens (activated or pan-endothelial antigens) but subsequently prospective studies that allocate treatment on the basis of microvessel density are required.