Vessel counts and vascular endothelial growth factor expression in pancreatic adenocarcinoma

Dkk-3 expression in the tumor endothelium: a novel prognostic marker of pancreatic adenocarcinomas

Dkk-3 is proposed to be a new specific marker for tumor endothelial cells. Here we analyzed the clinical relevance of Dkk-3 expression in pancreas adenocarcinomas and determined its role on endothelial cell growth in vitro. Microvessel density in tumor samples was immunohistochemically determined using Dkk-3 and CD31 as endothelial cell markers, respectively. Based on the median microvessel density as a cut-off point, patients were categorized into high and low microvessel density groups and a correlation with survival and clinical parameters was assessed. Moreover, the role of Dkk-3 expression on chemosensitivity of endothelial cells was analyzed. In contrast to CD31 staining, Dkk-3-positive vessels were found only in tumor tissue and Dkk-3 microvessel density significantly correlated negative with tumor grading. In survival analysis the median survival time was 7 months for patients with Dkk-3 low, and 15 months for Dkk-3 high microvessel density (P = 0.0013). Subset analysis of patients receiving gemcitabine therapy showed that overall survival was significantly decreased in Dkk-3 low tumors than in high tumors (P = 0.009). In Cox regression Dkk-3 emerged as a significant independent parameter (P = 0.024). Dkk-3 overexpression in endothelial cells resulted in significantly enhanced growth inhibition after 5-fluorouracil or gemcitabine treatment compared to control endothelial cells and cancer cell lines. Dkk-3 low microvessel density was associated with tumor progression and worse clinical outcome. Overexpression of Dkk-3 enhanced endothelial cell growth inhibition to chemotherapeutic drugs. Therefore, we suggest that Dkk-3 high microvessel density may help to select patients who may benefit from chemotherapy.

Targeting the Vascular Endothelial Growth Factor Pathway in the Treatment of Human Malignancy

Over 30 years ago, it was proposed that blocking new blood vessel formation would significantly inhibit solid tumor growth and hence, limit cancer progression. Efforts guided by this philosophy have resulted in a better understanding of the molecular basis of tumor angiogenesis. The first successful therapeutic to emerge from this work, an antibody (bevacizumab) targeting the vascular endothelial growth factor (VEGF), was recently approved for the treatment of colorectal cancer. Additional positive clinical data with bevacizumab in the treatment of breast and lung carcinoma have also been reported. These clinical achievements have validated the approach of anti-angiogenesis therapy for cancer and provided further confirmation for antibodies as a therapeutic class in this disease. Nevertheless, important unanswered questions with regard to preclinical and clinical results of VEGF pathway inhibitors remain. For example, preclinical models with a number of VEGF pathway inhibitors suggest that these agents would have significant clinical activity on their own; yet, clinical activity in patients with bevacizumab or other VEGF pathway inhibitors as monotherapy have been disappointing. Moreover, while bevacizumab is approved for the treatment of colorectal cancer in combination with cytotoxics, the mechanism for the benefits of this combination are still poorly understood, with a number of viable mechanisms under active experimental evaluation. The 3-8-month survival benefit in colorectal cancer patients treated with bevacizumab is a positive step forward. However, improving our understanding of the mechanism for these effects, as well as the mechanism underlying the inability as yet to achieve greater effects, is needed in order to follow up on the positive clinical results with improved strategies. This review discusses the experimental results surrounding the current status of our understanding of the mechanism of action of VEGF signaling inhibitors, and the potential for utilizing these agents in the future so that clinical benefits will be measured in years rather than months.

Does contrast-enhanced ultrasound reveal tumor angiogenesis in pancreatic ductal carcinoma? A prospective study

The purpose of this study is to evaluate tumor vascularity of pancreatic carcinoma noninvasively by contrast-enhanced ultrasound (US) and clarify the diagnostic value of tumor vascularity in subjects with nonresectable advanced pancreatic carcinoma. The study was approved by our institutional review board and written informed consent was obtained from all subjects. Twenty-seven subjects with advanced pancreatic ductal carcinoma were treated by chemoradiotherapy. Contrast-enhanced US, US guided biopsies and dynamic computed tomography (CT) were performed before and after the therapy. We assigned the intratumoral enhancement pattern of US as an enhanced ultrasound (EU) score, from 1 to 4, according to the degree of enhancement area. Intratumoral microvessel density (IMD) and average vessel diameter (AVD) were calculated by means of CD 34 immunostaining. Vascular endothelial growth factor (VEGF) staining was graded on a scale of 1 to 3. EU scores before chemoradiotherapy were compared with IMD, AVD, VEGF, histological grading and hepatic metastasis. After the therapy, local treatment response was evaluated by dynamic CT calculating the maximum area of the tumor, by comparing it with its size in pre- therapy. Subjects who had at least a 50% or more decrease of tumor size lasting more than 4 wk were estimated as partial response (PR), more than a 50% of increase progressive disease (PD) and if neither PR nor PD criteria were met, they were classified as stabled disease (SD). Next, EU scores were compared with IMD, AVD, VEGF and treatment response. Statistically significant differences were evaluated by Pearson's correlation, post-hoc, Spearman's rank correlation, Wilcoxon rank sum and Student's t-test. A p < 0.05 was defined as being statistically significant. Before the therapy, the EU score and IMD were significantly correlated (r = 0.50, p < 0.02), as was VEGF (r = 0.45, p < 0.05). The EU score and AVD were negatively correlated (r = - 0.56, p < 0.02). Significant correlation was found between the EU score and histological grading (p < 0.004). The EU score was higher in subjects who had hepatic metastasis compared with subjects who had no hepatic metastasis (p < 0.05). After chemoradiotherapy, 14 subjects exhibited PR, while 13 showed SD. None of the subjects showed PD. The EU score was smaller in PR than SD (p < 0.05). The EU score significantly decreased after the therapy in PR (p < 0.01) but not in SD. IMD and AVD did not significantly decrease in either PR or SD; however, VEGF decreased significantly in PR (p < 0.01) but not in SD. Contrast-enhanced US could reveal tumor vascularity of pancreatic ductal carcinoma and could be potentially useful to evaluate treatment effect of subjects who receive chemoradiotherapy. Further investigation will be needed to prove the usefulness of contrast-enhanced US.

Changes in tumor vascularity depicted by contrast-enhanced ultrasonography as a predictor of chemotherapeutic effect in patients with unresectable pancreatic cancer

OBJECTIVES

This study was conducted to assess changes in tumor vascularity using contrast-enhanced ultrasonography in patients with pancreatic carcinoma under systemic chemotherapy and to examine the correlation among vascular change, clinicopathologic factors, and outcome.

METHODS

Forty-one consecutive patients with histopathologically confirmed pancreatic carcinoma who had distant metastases and were under systemic chemotherapy were recruited. Contrast-enhanced ultrasonography was performed before and after 1 and 2 cycles of treatment.The vascular signals from the tumor were continuously recorded,and the highest signal intensity was selected and classified into 5 categories by their intensity.

RESULTS

As for the tumor response determined by dynamic computed tomography after 2 cycles, 6 patients showed a partial response, 25 remained stable, and in 10 patients, the disease progressed. A significant relationship was observed between vascular change after 1 cycle and tumor response (P G 0.001). Progression-free survival and overall survival were significantly short in the case of patients showing increased vascularity after 1 and 2 cycles of chemotherapy, compared with those who did not (P G 0.001).

CONCLUSIONS

Contrast-enhanced ultrasonography was useful to evaluate tumor vascular changes and thereby the effect of systemic chemotherapy, as well as the prognosis of patients with advanced pancreatic carcinoma.

Pancreatic endocrine tumors: tumor blood flow assessed with perfusion CT reflects angiogenesis and correlates with prognostic factors

PURPOSE

To prospectively correlate multidetector computed tomographic (CT) perfusion measurement of pancreatic endocrine tumors with tumor microvascular density (MVD) assessed by using histologic techniques and to determine whether perfusion CT parameters differ between tumor grades.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Thirty-six patients (15 men, 21 women; mean age, 53 years; range, 18-78 years) with resectable pancreatic endocrine tumors underwent presurgical dynamic perfusion CT. Twenty-eight (78%) of 36 patients were included in the study group; eight were excluded because of artifacts that were not compatible with perfusion postprocessing. Multidetector CT perfusion data were analyzed to calculate tumor and normal pancreatic blood flow, blood volume, mean transit time, and permeability-surface area product. Multidetector CT perfusion parameters were compared with intratumoral MVD by using the Spearman correlation coefficient and with World Health Organization (WHO) classification, tumor size, tumor proliferation index, hormonal profile, and presence of metastases by using Mann-Whitney tests.

RESULTS

High correlation (r = 0.620, P < .001) was observed between tumor blood flow and intratumoral MVD. Blood flow was significantly higher (P = .02) in the group of benign tumors (WHO 1) than in the groups of tumors of indeterminate prognosis (WHO 2) or well-differentiated carcinomas (WHO 3). Blood flow was significantly higher in tumors with a proliferation index of 2% or less (P = .005) and in those without histologic signs of microscopic vascular involvement (P = .008). Mean transit time was longer in tumors with lymph node (P = .02) or liver (P = .05) metastasis.

CONCLUSION

Perfusion CT is feasible in patients with pancreatic endocrine tumors and reflects MVD. Perfusion CT measurements are correlated with histoprognostic factors, such as proliferation index and WHO classification.

Quantitative analysis of vascular endothelial growth factor in liver metastases from pancreatic carcinoma as a predictor of chemotherapeutic effect and prognosis

PURPOSE

In pancreatic carcinoma, vascular endothelial growth factor (VEGF) expression at the primary site has been suggested to be a prognostic parameter. We quantitatively analyzed VEGF expression in liver metastases from pancreatic carcinoma and examined the correlation among VEGF expression in liver metastases, clinicopathologic factors, and clinical outcome.

EXPERIMENTAL DESIGN

The subjects consisted of 23 patients with pancreatic adenocarcinoma who had liver metastases and were treated with S-1 and gemcitabine as the first-line treatment. VEGF expression was quantitated by enzyme immunoassay in biopsy specimens of liver metastases and nontumorous liver tissue, and in plasma. In 10 of the 23 patients, VEGF expression was also quantitated in biopsy specimens of the primary pancreatic tumor. All samples were collected before treatment.

RESULTS

The VEGF level in nontumorous liver tissue was 36.6 +/- 10.0 pg/mg protein versus 376.8 +/- 106.1 pg/mg protein in liver metastases (P = 0.0016). Pretreatment VEGF levels in plasma and in primary pancreatic carcinoma did not correlate with VEGF levels in the corresponding liver metastases. The median VEGF level in liver metastases (138.9 pg/mg protein) was used as the cutoff value between high and low VEGF expression in liver metastases. Patients showing high VEGF expression had a significantly longer progression-free survival and overall survival than patients showing low VEGF expression in liver metastases (P = 0.0219 and P = 0.0074, respectively).

CONCLUSIONS

Evaluation of VEGF levels in liver metastases might be useful in assessing the prognosis of patients with metastatic pancreatic carcinoma who are under systemic chemotherapy.

Analysis of microvessels in pancreatic cancer: by light microscopy, confocal laser scan microscopy, and electron microscopy

BACKGROUND/PURPOSE

The microvessel density (MVD) of most malignant tumors is considered to be strongly related to metastasis and prognosis. Weidner's "hot spot method" for determining MVD is in general use, but it is possible that cells other than endothelial cells will also be stained. In our previous study, no correlations were observed between MVD determined by the "hot spot method" and prognosis/metastasis. But, using the "lumen method," we found a correlation with the number of vessel structures only. In the present study, we analyzed the staining of microvessels in pancreatic cancer, using light microscopy, confocal laser scan microscopy (CLSM), and transmission electron microscopy (TEM).

METHODS

Microvessel staining of pancreatic cancer with CD34, factor VIII, and CD45 antibodies was examined in consecutive slices by light microscopy. For CLSM, freshly resected specimens were immunostained with factor VIII and fluorescein isothiocyanate. For TEM, specimens were fixed with 2.5% glutaraldehyde, treated with 1% osmium tetroxide, and embedded in epoxy resin.

RESULTS

Staining of vessels with CD34 and factor VIII antibodies appeared similar under light microscopy. However, CD34-stained consecutive slices were judged not to reveal vessel structures, and some cells stained with CD45 antibody were similar in appearance to CD34-stained cells. Under CLSM, irregular arrangements of neovascularization, consisting of many branches, were observed, but many positively stained cells not identified as vessels were also seen. Microvessels were distinctly identified under TEM, but the types of individual cells could not be determined.

CONCLUSIONS

An integrated, reproducible method for the measurement of MVD is vital. For pancreatic cancer, the "lumen method" is recommended.

Serum vascular endothelial growth factor/soluble vascular endothelial growth factor receptor 1 ratio is an independent prognostic marker in pancreatic cancer

OBJECTIVES

Tumor angiogenesis is the consequence of an imbalance between positive and negative angiogenic regulatory factors. We sought to determine the role of pretreated serum angiogenic factors, including vascular endothelial growth factor (VEGF), placental growth factor (PlGF), and soluble vascular endothelial growth factor receptor 1 (sVEGFR-1), in predicting clinical outcome in patients with pancreatic cancer.

METHODS

We assessed pretreated serum VEGF, PlGF, and sVEGFR-1 levels in 92 patients with pancreatic adenocarcinoma and 60 healthy control subjects using an enzyme-linked immunosorbent assay. The correlation between these angiogenesis-related factors and clinicopathologic factors, including staging and overall survival, was analyzed.

RESULTS

Serum levels of VEGF, PlGF, and sVEGFR-1 were significantly higher in patients with pancreatic cancer compared with those in controls (583.8 +/- 559.5 vs 187.63 +/- 393.32, 17.65 +/- 7.34 vs 10.93 +/- 1.21, and 50.94 +/- 51.17 vs 15.55 +/- 1.98 pg/mL, respectively; P < 0.0001). A reverse correlation was observed between sVEGFR-1 level and the advance of tumor stage. Cox regression analysis showed that the VEGF/sVEGFR-1 ratio was an independent predictor for pancreatic cancer survival. Higher VEGF/sVEGFR-1 ratio was significantly correlated with poor outcome in patents with pancreatic cancer.

CONCLUSIONS

Vascular endothelial growth factor/sVEGF-1 ratio is an independent prognostic factor for survival in pancreatic cancer. Its significance should be assessed when considering antiangiogenic therapy in treating pancreatic cancer patients.

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.

RNAi-mediated gene silencing of vascular endothelial growth factor inhibits growth of colorectal cancer

Vascular endothelial growth factor (VEGF) is overexpressed in colorectal cancer (CRCs) cells and plays a critical role in angiopoiesis and cell proliferation, making it a potential target for cancer therapy. We developed a system that blocks VEGF in the human colorectal cancer cell line, HCT116, using RNA interference. By transfecting CRCs with the small interfering RNA (siRNA) that targets human VEGF, we were able to establish a stable clones in which VEGF expression was significantly downregulated (p<0.01). This resulted in the decreased proliferation of HCT116 cells in vitro and suppressed the size of subcutaneous (s.c.) tumors and the microvessel density in an HCT116 s.c. nude mouse xenograft model in vivo (p<0.01). These results suggest that a strategy based on siRNA targeting of VEGF may build the foundation to the clinical management of CRC.

Molecular basis of the synergistic antiangiogenic activity of bevacizumab and mithramycin A

The impact of antiangiogenic therapy on the Sp1/vascular endothelial growth factor (VEGF) pathway and that of alteration of Sp1 signaling on the efficacy of antiangiogenic therapy is unclear, yet understanding their interactions has significant clinical implications. Treatment with bevacizumab, a neutralizing antibody against VEGF, suppressed human pancreatic cancer growth in nude mice. Gene expression analyses revealed that this treatment substantially up-regulated the expression of Sp1 and its downstream target genes, including VEGF and epidermal growth factor receptor, in tumor tissues, whereas it did not have this effect on pancreatic cancer cells in culture. Treatment with mithramycin A, an Sp1 inhibitor, suppressed the expression of Sp1 and its downstream target genes in both cell culture and tumors growing in nude mice. Combined treatment with bevacizumab and mithramycin A produced synergistic tumor suppression, which was consistent with suppression of the expression of Sp1 and its downstream target genes. Thus, treatment with bevacizumab may block VEGF function but activate the pathway of its expression via positive feedback. Given the fact that Sp1 is an important regulator of the expression of multiple angiogenic factors, bevacizumab-initiated up-regulation of Sp1 and subsequent overexpression of its downstream target genes may profoundly affect the potential angiogenic phenotype and effectiveness of antiangiogenic strategies for human pancreatic cancer. Therefore, this study is the first to show the significance and clinical implications of alteration of Sp1 signaling in antiangiogenic therapy for pancreatic cancer and other cancers.

Morphometric microvascular characteristics in the prognosis of pancreatic and ampullary carcinoma

OBJECTIVES

To evaluate multiple morphometric microvascular characteristics in addition to microvascular density (MVD) in pancreatic ductal and ampullary adenocarcinomas and provide a better approach in examining the relationship among angiogenesis, several clinicopathologic parameters, and prognosis.

METHODS

Histological sections from 32 pancreatic ductal and 17 ampullary adenocarcinomas, immunostained with CD34, were evaluated by image analysis for the quantification of MVD, total vascular area, and microvascular branching, as well as several morphometric parameters related to the vessel size and shape factor.

RESULTS

In pancreatic ductal carcinoma, higher levels of MVD, total vascular area, branching, and shape factor were related to N1 tumors. Moreover, MVD, shape factor, and minor axis length were identified as independent prognostic factors of survival. In the ampullary carcinoma group, higher shape factor values were observed in well-differentiated tumors.

CONCLUSIONS

In pancreatic ductal carcinoma patients, the assessment of MVD and several morphometric microvascular characteristics provides significant prognostic information. The biologic behavior of the ampullary carcinomas does not seem to be dependent on any of the above mentioned factors of angiogenesis.

Clinical implications of angiogenesis in cancers

Angiogenesis plays an important role in the growth and progression of cancer. The regulation of tumor angiogenesis depends on a net balance of angiogenic factors and antiangiogenic factors, which are secreted by both tumor cells and host-infiltrating cells. Numerous studies have indicated that assessment of angiogenic activity by either microvessel density or expression of angiogenic factors in cancer can provide prognostic information independent of conventional clinicopathological factors such as tumor staging. Some studies also suggested that assessment of tumor angiogenesis may predict cancer response to chemotherapy or radiotherapy. However, the most important clinical implication of tumor angiogenesis is the development of a novel strategy of anticancer therapy targeting tumor vessels instead of cancer cells. Antiangiogenic therapy aims to inhibit the growth of tumor, and current evidence suggests that it works best in combination with conventional cytotoxic chemotherapy. Recently, a monoclonal antibody against vascular endothelial growth factor, which is one of the most potent angiogenic factors, has been approved for clinical use in colorectal cancer patients after a clinical trial confirmed that combining the antibody with standard chemotherapy regimen could prolong patient survival. The clinical implications of angiogenesis in cancer are reviewed in this article.

Hypoxia and angiogenesis in pancreatic cancer

BACKGROUND

Pancreatic cancer remains one of the most lethal of all solid tumours of the gastrointestinal tract. It is characterized by late diagnosis, aggressive local invasion, early metastasis and resistance to chemoradiotherapy. Increasing knowledge regarding the molecular events behind the growth and invasion of pancreatic cancer may lead to new targets for intervention.

METHODS

A search of Pubmed and Medline databases was undertaken using the keywords pancreatic cancer, gastrointestinal cancer, hypoxia, angiogenesis and anti-angiogenesis therapy.

RESULTS

Hypoxia is the driving force behind angiogenesis in pancreatic cancers. Research into angiogenesis has shown many different sites that can be targeted by agents such as tyrosine kinase inhibitors.

CONCLUSION

Anti-angiogenic therapy could be an important adjunct to conventional chemotherapy treatment of gastrointestinal neoplasia.

Vascular endothelial growth factor, FLT-1, and FLK-1 analysis in a pancreatic cancer tissue microarray

BACKGROUND

Measures of vascular endothelial growth factor (VEGF) expression in pancreatic cancer typically have been qualitative or semiquantitative. The objective of this study was to use a series of algorithms called AQUA that quantitatively assesses protein expression on tissue microarrays (TMAs) to compare in situ expression of VEGF and its primary receptors, VEGF receptor 1 (FLT-1) and VEGF receptor 1 (FLK-1), on a pancreatic cancer TMA.

METHODS

TMAs were constructed by arraying 1.5-mm cores from 76 samples of pancreatic adenocarcinoma (1996-2002) that were obtained from the archives of the Yale Department of Pathology. The staining for AQUA was similar to standard immunohistochemistry and involved antigen retrieval and the application of primary antibodies, but with epifluorescence detection. Slides were counterstained with 4',6-diamidino-2-phenylindole for nuclear visualization and cytokeratin for membrane visualization. The primary antibodies used were VEGF, FLT-1, FLK-1, and cytokeratin.

RESULTS

Disease stage was highly prognostic for outcome, as expected. Total amounts of VEGF and its receptors were assessed within the tumor mask and were divided into quartiles. Kaplan-Meier survival curves showed that VEGF and FLK-1 were not associated clearly with outcome. However, the expression of FLT-1 was correlated significantly, and the patients who had tumors with the lowest expression FLT-1 levels had the worst survival (P = .0038). In multivariate analysis, FLT-1 expression was an independent prognostic factor for overall survival (P = .0044).

CONCLUSIONS

VEGF and its 2 principal receptors were expressed to varying degrees in tumors of the pancreas. A significant association was found between low expression of FLT-1 and both poor prognosis and advanced stage, suggesting that tumor expression of this VEGF receptor is a marker of less aggressive disease.

Angiogenesis in non-small cell lung cancer: The prognostic impact of neoangiogenesis and the cytokines VEGF and bFGF in tumours and blood

BACKGROUND

Due to a dismal prognosis of advanced lung cancer, novel screening tools and more effective treatments are clearly needed. Lately, an increasing number of tumour-released angiogenic cytokines which affect vessel formation, tumour growth, invasion, and metastasis have been identified. Vascular endothelial growth factors (VEGFs) and basic fibroblast growth factor (bFGF) are among the most important angiogenic factors. Based on available literature, we have explored the mechanisms of angiogenesis and its prognostic significance in non-small cell lung cancer, estimated by microvessel density (MVD) and the presence of VEGF and bFGF in the tumour and blood from NSCLC patients.

METHODS

Several comprehensive Pubmed searches for the period January 1993 to May 2005 were performed using strategic combinations of the terms non-small cell lung cancer, angiogenesis, vascular endothelial growth factor, basic fibroblast growth factor, tumour expression, microvessel density, circulating, and serum.

RESULTS

NSCLC neoangiogenesis, as measured by MVD, and tumour expression of VEGF are poor prognostic factors for survival (MVD, HR 1.8-2.0; VEGF, HR 1.5). bFGF tumour expression is also associated with poor survival and more aggressive disease. When evaluating the prognostic impact of elevated VEGF levels in blood, 10 of 16 studies (63%) indicated a negative prognostic impact. Of five studies on the prognostic value of circulating bFGF, three studies reported a negative prognostic impact, while one indicated bFGF as a good prognostic factor and one was inconclusive.

CONCLUSION

Angiogenic factors are poor prognostic indicators for tumour aggressiveness and survival in NSCLC. Assessments of circulating levels of VEGF and possibly bFGF may be valuable future tools for treatment planning and monitoring of treatment effect and relapse. First, however, these blood tests need to be standardised and validated in large-scale prospective clinical trials.

Phase II Trial of Bevacizumab Plus Gemcitabine in Patients With Advanced Pancreatic Cancer

Purpose

Vascular endothelial growth factor (VEGF) plays a key role in the biology and prognosis of pancreatic cancer. Inhibitors of VEGF suppress the growth of pancreatic cancer in preclinical models. The objectives of this phase II study were to assess the response rate and overall survival of pancreatic cancer patients who received gemcitabine with the recombinant humanized anti-VEGF monoclonal antibody bevacizumab.

Patients and Methods

Patients with previously untreated advanced pancreatic cancer received gemcitabine 1,000 mg/m2 intravenously over 30 minutes on days 1, 8, and 15 every 28 days. Bevacizumab, 10 mg/kg, was administered after gemcitabine on days 1 and 15. Tumor measurements were assessed every two cycles. Plasma VEGF levels were obtained pretreatment.

Results

Fifty-two patients were enrolled at seven centers between November 2001 and March 2004. All patients had metastatic disease, and 83% had liver metastases. Eleven patients (21%) had confirmed partial responses, and 24 (46%) had stable disease. The 6-month survival rate was 77%. Median survival was 8.8 months; median progression-free survival was 5.4 months. Pretreatment plasma VEGF levels did not correlate with outcome. Grade 3 and 4 toxicities included hypertension in 19% of the patients, thrombosis in 13%, visceral perforation in 8%, and bleeding in 2%.

Conclusion

The combination of bevacizumab plus gemcitabine is active in advanced pancreatic cancer patients. Additional study is warranted. A randomized phase III trial of gemcitabine plus bevacizumab versus gemcitabine plus placebo is ongoing in the Cancer and Leukemia Group B.

Characterization of the Bystander Effect of Somatostatin Receptor sst2 After In Vivo Gene Transfer into Human Pancreatic Cancer Cells

Pancreatic cancer is one of the most aggressive and devastating human malignancies. The present study was conducted to determine whether in vivo sst2 gene transfer into human pancreatic tumors would impair tumor progression, and to characterize sst2 antitumoral bystander mechanisms. sst2 administration, using the synthetic vector PEI, strongly inhibited tumor progression of human pancreatic adenocarcinoma, in vivo. sst2 gene transfer induced intratumoral production of its ligand somatostatin. Disruption of this autocrine loop by RNA interference completely reversed sst2 antitumoral activity. Mice depleted of natural killer (NK) cells did not hamper sst2 tumor growth inhibition. However, microvessel density and vascular endothelial growth factor (VEGF) expression were markedly reduced in sst2-transfected tumors, whereas sst3 somatostatin receptor was upregulated. Depleting somatostatin by RNA interference completely abolished the sst2 inhibitory effect on VEGF expression and tumor angiogenesis, and sst2-induced sst3 expression in peripheral tumor vessels. We conclude that in vivo sst2 gene transfer elicited intratumoral somatostatin production and strongly impaired human pancreatic tumor growth. NK cells were not involved in this antitumoral bystander effect. VEGF and tumor vascularization were identified as novel targets for sst2-mediated antitumoral bystander effect. sst3 somatostatin receptor was upregulated in sst2-transfected tumors. Therefore, in vivo gene delivery of sst2 receptor to target the angiogenic process in pancreatic ductal adenocarcinoma might be a new therapeutic approach for treatment of pancreatic cancer in patients with unresectable disease.

Molecular prognostic markers in pancreatic cancer: a systematic review

Pancreatic cancer is one of the most lethal tumours of the gastrointestinal tract. The ability to predict which patients would benefit most from surgical intervention and/or chemotherapy would be a great clinical asset. Considerable research has focused on identifying molecular events in pancreatic carcinogenesis, and their correlation with clinicopathological variables of pancreatic tumours and survival. This systematic review examined evidence from published manuscripts looking at molecular markers in pancreatic cancer and their correlation with tumour stage and grade, response to chemotherapy and long-term survival. A literature search was undertaken using PubMed and MEDLINE search engines, using the keywords p53, p21, p16, p27, SMAD4, K-ras, cyclin D1, Bax, Bcl-2, EGFR, EGF, c-erbB2, HB-EGF, TGFbeta, FGF, MMP, uPA, cathepsin, heparanase, E-cadherin, laminins, integrins, TMSF, CD44, cytokines, angiogenesis, VEGF, IL-8, beta-catenin, DNA microarray, and gene profiling. A bewildering number of biomarkers are currently under evaluation. For the most part, the evidence regarding their application as prognostic indicators is conflicting. The advent of gene microarray and mass spectrometric protein profiling offers the potential to examine many different biomarkers simultaneously. This 'protein/gene signature' could revolutionise work in this field and allow researchers to develop accurate and reproducible predictions of survival based on protein or gene profiles.

A phase I surrogate endpoint study of SU6668 in patients with solid tumors

PURPOSE

To evaluate the biologic effects of SU6668 in patients with solid tumors using comprehensive measures of pharmacokinetics (PK), functional imaging, and tissue correlative studies.

EXPERIMENTAL DESIGN

Eligible patients with tumors accessible for core needle biopsy were treated with SU6668 at doses of 200 or 400 mg/m(2)/day. Functional computed tomography (CT) scan and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) were performed at baseline and repeated 4 weeks and 12 weeks after treatment for analysis of tumor angiogenesis. The PK was analyzed using a high-performance liquid chromatography assay. Tumor specimens obtained via core needle biopsy at baseline and 4 weeks later were analyzed for the biologic effects of SU6668.

RESULTS

Six of a total of seven patients received treatment for at least 3 months and underwent comprehensive correlative studies, including PK, imaging, and tissue biopsy. Functional CT showed that five of six patients had decreased blood flow in tumors in response to treatment, and DCE-MRI results indicated significant change of area under the signal intensity vs. time curve (AUC) and/or maximum slope (maximum rate of signal intensity change) in two of four patients evaluated with this technique. PK studies showed that the mean apparent oral clearance (Cl(oral)) measured on day 1 was 6.3 +/- 2.7 L/hr/m(2), yielding a mean AUC of 16.6 +/- 4.3 mg/L.hr. By day 22, the Cl(oral) was 40% more than that observed on day 1.

CONCLUSION

It is feasible to evaluate the biologic effects of antiangiogenic agents using comprehensive surrogate measures.

Bevacizumab (Avastin), a humanized anti-VEGF monoclonal antibody for cancer therapy

Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen in vitro and an angiogenic inducer in vivo. The tyrosine kinases Flt-1 (VEGFR-1) and Flk-1/KDR (VEGFR-2) are high affinity VEGF receptors. VEGF plays an essential role in developmental angiogenesis and is important also for reproductive and bone angiogenesis. Substantial evidence also implicates VEGF as a mediator of pathological angiogenesis. Anti-VEGF monoclonal antibodies and other VEGF inhibitors block the growth of several tumor cell lines in nude mice. Clinical trials with VEGF inhibitors in a variety of malignancies are ongoing. Recently, a humanized anti-VEGF monoclonal antibody (bevacizumab; Avastin) has been approved by the FDA 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.

Angiogenesis and its role in colorectal tumor and metastasis formation

Advances in our comprehension of cancer biology and metastasis formation have led to the development of new therapeutic approaches that target tumor biology. The survival and establishment of metastatic lesions depend on a shift in the normal balance of key regulatory factors in favor of angiogenesis. Although a number of these factors have been identified, the most potent regulator of angiogenesis is vascular endothelial growth factor (VEGF). In phase I trials, targeting VEGF with single-agent therapy did not produce clinical benefit for patients, despite promise in preclinical trials. However, the recent data showing that anti-VEGF therapy can enhance the effects of chemotherapy demonstrate the utility in targeting angiogenic factors as a component of antineoplastic regimens. A better understanding of the functions of VEGF allows the development of new hypotheses with regard to its mechanism of action. This article will highlight what is known about colorectal cancer angiogenesis, and will discuss how therapy targeting VEGF may enhance the effects of chemotherapy (and radiation therapy).

Endostatin expression in pancreatic tissue is modulated by elastase

Pancreatic tumours are scirrhous, avascular tumours, suggesting that they may produce angiogenesis inhibitors that suppress the growth of the vasculature to the tumour and metastases. We have sought evidence for the angiogenesis inhibitor, endostatin, in normal and cancerous pancreatic tissue. Using Western blotting, we found mature 20 kDa endostatin in cancer tissue but not in normal tissue. Several endostatin-related peptides of higher mol wt were present in both tissues. Extracts from normal tissue were able to degrade exogenous endostatin, whereas extracts from cancer were without effect. Although the exocrine pancreas secretes inactive proenzymes of trypsin, chymotrypsin and elastase, their possible role in this degradation was examined. The trypsin/chymotrypsin inhibitor, Glycine max, did not prevent the degradation of endostatin by normal pancreatic extracts but elastatinal, a specific inhibitor of elastase, reduced the rate of degradation. Extracts of pancreatic tumours did not express any detectable elastase activity, but an elastase (Km 1.1 mM) was expressed by extracts of normal pancreas. We conclude that endostatin is present and stable in pancreatic cancer tissues, which may explain their avascular nature, but that normal pancreatic tissue expresses enzymes, including elastase, which rapidly degrade endostatin. The stability of endostatin may have implications for its therapeutic use.

VEGF trap as a novel antiangiogenic treatment currently in clinical trials for cancer and eye diseases, and VelociGene- based discovery of the next generation of angiogenesis targets

The concept that tumors can be controlled by directly targeting their vascular supply has finally come of age, because clinical trials using a humanized monoclonal antibody that blocks VEGF have demonstrated exciting efficacy in cancer patients, as well as in vascular eye diseases that can lead to blindness. However, data suggest that these current regimens may not provide complete VEGF inhibition and, thus, that the maximum therapeutic potential of VEGF blockade has not yet been achieved. We describe the status of a very potent and high-affinity VEGF blocker, termed the VEGF Trap, that may provide the opportunity to maximize the potential of VEGF blockade in cancer as well as in vascular eye diseases. We also describe use of the VEGF Trap as a research tool, when coupled to high-throughput mouse genetics approaches such as VelociGene that can be exploited in strategies to discover and validate the next generation of angiogenesis targets.

The pathophysiologic role of VEGF in hematologic malignancies: therapeutic implications

Besides its role as an essential regulator of physiologic and pathologic angiogenesis, vascular endothelial growth factor (VEGF) triggers growth, survival, and migration of leukemia and multiple myeloma cells; plays a pivotal role in hematopoiesis; inhibits maturation of dendritic cells; and increases osteoclastic bone-resorbing activity as well as osteoclast chemotaxis. Dysregulation of VEGF expression and signaling pathways therefore plays an important role in the pathogenesis and clinical features of hematologic malignancies, in particular multiple myeloma. Direct and indirect targeting of VEGF and its receptors therefore may provide a potent novel therapeutic approach to overcome resistance to therapies and thereby improve patient outcome.

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.

Expanding the Clinical Development of Bevacizumab

Bevacizumab (Avastin; Genentech, Inc.; South San Francisco, CA) is a recombinant, humanized monoclonal antibody to vascular endothelial growth factor, a key regulator of tumor angiogenesis. Bevacizumab demonstrated potent antitumor activity in preclinical models and has also shown biologic activity and clinical benefit in clinical studies. Notably, a randomized, placebo-controlled phase II trial in renal cell carcinoma demonstrated a significantly longer time to tumor progression with bevacizumab monotherapy. Furthermore, in a phase III trial for untreated advanced colorectal cancer, the addition of bevacizumab to chemotherapy led to significantly longer overall survival and progression-free survival times than chemotherapy alone. The clinical development of bevacizumab has been expanded to include confirmatory phase III trials and exploratory phase II trials in a variety of solid tumors and hematologic malignancies. Treatment regimens being examined include bevacizumab alone and in combination with conventional chemotherapy, radiation, immune therapy, and biologically targeted agents.

Angiogenesis of gastrointestinal tumours and their metastases – a target for intervention?

Angiogenesis is an obligatory event for the growth of tumours beyond 2 mm in diameter, above which simple oxygen diffusion can no longer support the rapid proliferation of malignant cells. Angiogenesis is a fine balance between inhibitory and stimulatory factors, the knowledge of which offers novel targets for the treatment of gastrointestinal neoplasia. A literature search of Pubmed and Medline databases was undertaken, using the keywords colorectal cancer, pancreatic cancer, gastrointestinal cancer, angiogenesis and anti-angiogenesis therapy. It was found that angiogenesis in primary tumours is a sequential and highly complex cascade of molecular events resulting in the rapid exponential growth of the tumour. Hepatic metastases of primary tumours may be less reliant on traditional angiogenic pathways, by co-opting pre-existing hepatic vasculature. Research into angiogenesis has revealed many different sites that can be targeted by agents such as tyrosine kinase inhibitors. Many anti-angiogenic agents are undergoing preclinical evaluation, with only a few entering phase I and phase III clinical trials. However, early results suggest that anti-angiogenic therapy could be an important adjunct to conventional chemotherapy treatment of gastrointestinal neoplasia.

Vascular endothelial growth factor-trap suppresses tumorigenicity of multiple pancreatic cancer cell lines

PURPOSE

Vascular endothelial growth factor A (VEGF-A) is a potent angiogenic agent that binds to two high affinity VEGF receptors (VEGFRs), a process facilitated by the low affinity neuropilin receptors. Although VEGF-A is overexpressed in pancreatic ductal adenocarcinoma, it is not known whether the in vivo growth of multiple pancreatic cancer cells can be efficiently blocked by VEGF-A sequestration.

EXPERIMENTAL DESIGN

Four human pancreatic cancer cell lines were grown s.c. in athymic nude mice. One cell line also was used to generate an orthotopic model of metastatic pancreatic cancer. The consequences of VEGF-A sequestration on tumor growth and metastasis were examined by injecting the mice with a soluble VEGFR chimer (VEGF-Trap) that binds VEGF-A with high affinity.

RESULTS

VEGF-Trap, initiated 2 days after tumor cell inoculation, suppressed the s.c. growth of four pancreatic cancer cell lines and markedly decreased tumor microvessel density. Analysis of RNA from tumors generated with T3M4 cells revealed that VEGF-Trap decreased the expression of VEGFR-1 and neuropilin-1 and -2. VEGF-Trap, initiated 3 weeks after tumor implantation, also attenuated intrapancreatic tumor growth and metastasis in an orthotopic model using PANC-1 cells.

CONCLUSIONS

VEGF-Trap is a potent suppressor of pancreatic tumor growth and metastasis and also may act to attenuate neuropilin-1 and -2 and VEGFR-1 expression. Therefore, VEGF-Trap may represent an exceedingly useful therapeutic modality for pancreatic ductal adenocarcinoma.

Overexpression of Id-1 is significantly associated with tumour angiogenesis in human pancreas cancers

It has been suggested that Id-1 has a critical role in the tumour progression and aggressiveness of several human cancers. However, the clinicopathological and biological significance of Id-1 overexpression remains unclear in human primary cancer. To investigate the association between Id-1 expression and cell proliferation or tumour angiogenesis, we examined the cell cycle kinetic indices (the proliferation and apoptotic indices, PI and AI) and intratumoral microvessel density (MVD) in 65 human pancreatic cancers. We also investigated the relationship between its expression and various clinicopathological factors to determine the clinical significance of Id-1 overexpression. Out of a total 65 cases, 32 (49.3%) showed overexpression of Id-1 vs normal tissues. Id-1 expression was found to be significantly associated with MVD (P=0.002). In further analysis of subgroups with higher and lower Id-1 expression, tumours with higher Id-1 expression (scores 4 and 5) showed significantly higher MVD than tumours with lower expression of Id-1 (scores 2 and 3) (111.18+/-57.14 vs 64.13+/-28.19, P<0.001). However, no significant association was found between Id-1 overexpression and patient survival rate. No significant association was also found between Id-1 expression and cell cycle kinetic indices (PI or AI) in pancreatic cancer. Moreover, the overexpression of Id-1 protein was not correlated with any significant clinicopathologic factors. These findings indicate that Id-1 overexpression is closely related with tumour angiogenesis and a higher density of intratumoral vessel, but that it is not associated with a poorer prognosis of survival or a higher cell proliferative potential in human pancreatic cancer.

Evaluation of blood flow in pancreatic ductal carcinoma using contrast-enhanced, wide-band Doppler ultrasonography: correlation with tumor characteristics and vascular endothelial growth factor

BACKGROUND AND AIMS

Tumor vascularization has been attracting attention. However, there have been only a few reports on tumor vascularization in pancreatic ductal carcinoma, especially on vascularization depicted by imaging modalities. We investigated the relationship among wide-band Doppler signals, clinicopathological factors, and vascular endothelial growth factor (VEGF) expression.

METHODS

Sixty-nine patients with pancreatic ductal carcinoma were investigated. The vascular signals from carcinoma lesions were assessed by contrast-enhanced, wide-band Doppler ultrasonography (dynamic flow). VEGF expression was quantitated by enzyme immunoassay for 28 patients. Depending on the intensity of the signals, the patients were classified into type A (definite vascular signal) or type B (almost no vascular signal).

RESULTS

Type A patients and type B patients accounted for 65% and 35% of patients, respectively. According to multivariate analysis of vascular signal type and clinicopathological factors, liver metastasis occurred significantly more frequently in the type A group. VEGF expression was also significantly higher in the type A group than in the type B group.

CONCLUSIONS

Dynamic flow has very high sensitivity for detecting the vascular signals from pancreatic ductal carcinoma. The quantity of vascular signals correlated with tumor characteristics and VEGF.

Aberrant expression of neuropilin-1 and -2 in human pancreatic cancer cells

PURPOSE

Neuropilin (Np)-1 and -2 are coreceptors for vascular endothelial growth factor (VEGF). This study was designed to assess their role in pancreatic ductal adenocarcinoma (PDAC).

EXPERIMENTAL DESIGN

We assessed Np-1 and Np-2 expression by real-time quantitative PCR in relation to the expression of VEGF ligands and receptors in pancreatic cancer cell lines and tissues.

RESULTS

ASPC-1, CAPAN-1, and PANC-1 pancreatic cancer cells and tumor-derived, laser-captured pancreatic cancer cells exhibited higher Np-1 and Np-2 mRNA levels than VEGF receptor-1, -2, or -3 mRNA levels. Transfection of Np-1 and Np-2 cDNAs in COS-7 cells, and treatment with tunicamycin revealed that both proteins were glycosylated. Both proteins were expressed in pancreatic cancer cell lines, in the PDAC samples, and in acinar cells adjacent to the cancer cells. The normal pancreas was devoid of Np-1 immunoreactivity, whereas Np-2 immunoreactivity was present in the endocrine islets and in some acinar cells, but not in ductal cells.

CONCLUSIONS

The aberrant localization of Np-1 and Np-2 in the cancer cells in PDAC suggests that in addition to exerting proangiogenic effects, these coreceptors may contribute to novel autocrine-paracrine interactions in this malignancy.

Pancreatic carcinoma cells express neuropilins and vascular endothelial growth factor, but not vascular endothelial growth factor receptors

BACKGROUND

Neuropilins (NRPs) are characterized as coreceptors of vascular endothelial growth factor (VEGF). In the current study, the authors assessed the expression of NRPs, VEGF, and vascular endothelial growth factor receptors (VEGFRs), as well as VEGF-induced cell proliferation, in pancreatic carcinoma cell lines and tissue specimens.

METHODS

Human pancreatic carcinoma cell lines (Panc-1 and MIA PaCa-2), normal human pancreatic ductal epithelial cells (HPDE), and human umbilical vein endothelial cells (HUVECs) were cultured. Human pancreatic adenocarcinoma tissue specimens were also studied. Expression levels of NRPs, VEGFRs, and VEGF were determined by real-time polymerase chain reaction analysis and immunostaining. Cell proliferation was examined using a [3H]thymidine incorporation assay.

RESULTS

Both NRP-1 and NRP-2 were expressed in Panc-1 cells, HPDE cells, and HUVECs but were expressed minimally in MIA PaCa-2 cells. Panc-1 expressed 30 times more NRP-1 mRNA than NRP-2 mRNA. NRP-1 levels in Panc-1 cells were 5.3 times higher than in HPDE cells but were similar to NRP-1 levels in HUVECs. NRP-2 levels in Panc-1 cells were similar to NRP-2 levels in HPDE cells but lower than NRP-2 levels in HUVECs. Expression of all three VEGFRs was observed only in HUVECs. However, VEGF mRNA was detected in all cell types except for HUVECs. NRP-1 immunoreactivity levels were much higher than NRP-2 immunoreactivity levels in Panc-1 and human pancreatic adenocarcinoma tissue specimens, whereas VEGFRs were not detected in either of these two settings. In response to VEGF165, [3H]thymidine incorporation in Panc-1 cells increased significantly (by 61%; P < 0.01). A monoclonal antibody against human NRP-1 significantly blocked VEGF-induced cell proliferation in Panc-1 cells.

CONCLUSIONS

The pancreatic carcinoma cell line Panc-1 and adenocarcinoma tissue specimens expressed high levels of NRP-1 and VEGF, but not VEGFRs, and exogenous VEGF significantly increased NRP-1-mediated, but not VEGFR-mediated, Panc-1 cell proliferation. These data suggested that NRP-1 may be involved in the pathogenesis of pancreatic carcinoma.

Low microvessel density is an unfavorable histoprognostic factor in pancreatic endocrine tumors

BACKGROUND AND AIMS

In many malignant tumors, intratumoral microvascular density (MVD) has been suggested to be a prognostic parameter. We aimed to provide a quantitative evaluation of intratumoral microvascular density in a large series of resected endocrine tumors of the pancreas and to evaluate the potential prognostic significance of this parameter.

METHODS

Eighty-two tumors from 77 patients have been studied. MVD was evaluated by 2 observers after CD34 immunostaining and correlated with the following parameters: WHO classification, hormonal profile, tumor size, vascular endothelial growth factor expression, occurrence of metastasis, duration of survival.

RESULTS

MVD ranged from 5 to 92 vessels/field. MVD was significantly higher in well-differentiated benign endocrine tumors than in tumors of uncertain behavior and in carcinomas. No close correlation was found between MVD and the hormonal profile. MVD was significantly higher in tumors characterized by the following histoprognostic parameters: size <2 cm, proliferation index <2%, no evidence of metastasis. No close correlation was observed between MVD and VEGF expression. Finally, a MVD <30 vessels/field was associated with the occurrence of metastasis in tumors <2 cm and/or with a proliferation index <2% and with a significantly shorter survival after surgery.

CONCLUSIONS

The quantitative analysis of microvessel density in pancreatic endocrine tumors may identify patients who, despite favorable conventional histoprognostic factors, are at risk of unfavorable evolution.

Clinical significance of angiogenesis in gastrointestinal cancers: a target for novel prognostic and therapeutic approaches

OBJECTIVE

To review the current data on the prognostic and therapeutic implications of tumor angiogenesis in gastrointestinal cancers.

SUMMARY BACKGROUND DATA

Numerous studies have evaluated the prognostic value of tumor angiogenesis and the potential role of antiangiogenic therapy in various gastrointestinal cancers.

METHODS

A Medline literature search was conducted using "angiogenesis" or the names of various angiogenic factors in combination with the names of gastrointestinal cancers as the key words.

RESULTS

Several studies have demonstrated a significant prognostic impact of tumor microvessel density and tumor expression of angiogenic factors, in particular vascular endothelial growth factor (VEGF), in various gastrointestinal cancers. A few studies have suggested that circulating VEGF might be a useful prognostic marker. However, results were not consistent across all studies and were limited by the retrospective nature of most studies. Antiangiogenic therapy has been shown to be effective against all common gastrointestinal cancers in preclinical studies, but currently there are few clinical data with regard to antiangiogenic therapy in gastrointestinal cancers.

CONCLUSIONS

There is mounting evidence to suggest that assessment of tumor angiogenesis might provide a novel approach of prognostication in patients with gastrointestinal cancers. However, current results from retrospective studies need to be validated by prospective studies. Antiangiogenic therapy is a promising strategy of cancer treatment that might be particularly useful in combination therapy for unresectable cancers or as an adjuvant therapy for resectable tumors.

Expression and regulation of the novel vascular endothelial growth factor receptor neuropilin-1 by epidermal growth factor in human pancreatic carcinoma

BACKGROUND

It was recently shown that neuropilin-1 (NRP-1), which was described originally as a receptor for the semaphorins/collapsins (ligands involved in neuronal guidance), is a coreceptor for vascular endothelial growth factor (VEGF) and increases the affinity of specific isoforms of VEGF to its receptor, VEGF-R2.

METHODS

The authors investigated the expression and regulation of NRP-1 in human pancreatic adenocarcinoma specimens and cell lines.

RESULTS

Immunohistochemical analysis revealed that NRP-1 was expressed in 12 of 12 human pancreatic adenocarcinoma specimens but was absent in nonmalignant pancreatic tissue. Northern blot analysis revealed NRP-1 mRNA expression in 8 of 11 human pancreatic adenocarcinoma cell lines. NRP-1 mRNA expression was increased by epidermal growth factor (EGF) but not by tumor necrosis factor alpha in several of the human pancreatic adenocarcinoma cell lines studied. Treating human Panc-48 adenocarcinoma cells with EGF activated Akt and Erk but not P-38. Blockade of the phosphatidylinositol-3 kinase (PI-3K)/Akt, mitogen-activated protein kinase (MAPK)/Erk, or P-38 pathways abrogated EGF-induced NRP-1 expression. Finally, EGF receptor blockade in vivo led to a decrease in NRP-1 expression in an orthotopic model of human pancreatic carcinoma.

CONCLUSIONS

NRP-1 is expressed in most human pancreatic adenocarcinomas and cell lines but not in nonmalignant pancreatic tissue. EGF regulates NRP-1 expression through the PI-3K/Akt and MAPK/Erk signaling pathways, and blockade of the EGF receptor is associated with decreased expression of NRP-1 in vivo. NRP-1 may act as a coreceptor for VEGF in pancreatic carcinoma, as it does in other tumor systems, thereby enhancing angiogenesis and the effect of VEGF on the growth of pancreatic adenocarcinoma.

Liver metastases from pancreatic adenocarcinoma: MR imaging characteristics

PURPOSE

To describe the magnetic resonance imaging spectrum of appearances of liver metastases from pancreatic ductal adenocarcinoma.

MATERIALS AND METHODS

We retrospectively evaluated the MRI exams performed between July 1996 and August 2001 in all patients who had liver metastases from pancreatic adenocarcinoma and histopathologic diagnosis from either the primary pancreatic tumor, liver metastases, or both. Sixteen patients were included in the study. All MR studies were performed at 1.5 T with a standard protocol including T1- and T2-weighted images and serial post-gadolinium spoiled gradient echo (SGE) images. Location, size, number, signal characteristics on T1- and T2-weighted images, and pattern of enhancement on serial gadolinium-enhanced SGE images were assessed.

RESULTS

The diameter of metastases ranged from a few millimetres to 4 cm, and 12 patients (75%) had only lesions of 1.5 cm or less. Capsular-based liver metastases were found in 13 patients (81%) and three patients had only capsular-based lesions with a diameter under 1.5 cm. Hypervascular lesions were found in six patients (38%) and hypovascular lesions in 10 patients (62%). Perilesional enhancement was present in 10 patients (62%), with six patients (38%) having ring perilesional enhancement and eight patients (50%) having wedge-shaped perilesional enhancement.

CONCLUSION

On MR imaging, hepatic metastases from pancreatic adenocarcinoma show a range of enhancement patterns. Hypervascular metastases are not rare. Capsular based distribution, small diameter, and perilesional enhancement are common features. This retrospective study describes the MR imaging spectrum of appearances of liver metastases from pancreatic adenocarcinoma in patients with histopathologic confirmation of the diagnosis.

Clinical significance of angiogenesis in gastrointestinal cancers: a target for novel prognostic and therapeutic approaches

OBJECTIVE

To review the current data on the prognostic and therapeutic implications of tumor angiogenesis in gastrointestinal cancers.

SUMMARY BACKGROUND DATA

Numerous studies have evaluated the prognostic value of tumor angiogenesis and the potential role of antiangiogenic therapy in various gastrointestinal cancers.

METHODS

A Medline literature search was conducted using "angiogenesis" or the names of various angiogenic factors in combination with the names of gastrointestinal cancers as the key words.

RESULTS

Several studies have demonstrated a significant prognostic impact of tumor microvessel density and tumor expression of angiogenic factors, in particular vascular endothelial growth factor (VEGF), in various gastrointestinal cancers. A few studies have suggested that circulating VEGF might be a useful prognostic marker. However, results were not consistent across all studies and were limited by the retrospective nature of most studies. Antiangiogenic therapy has been shown to be effective against all common gastrointestinal cancers in preclinical studies, but currently there are few clinical data with regard to antiangiogenic therapy in gastrointestinal cancers.

CONCLUSIONS

There is mounting evidence to suggest that assessment of tumor angiogenesis might provide a novel approach of prognostication in patients with gastrointestinal cancers. However, current results from retrospective studies need to be validated by prospective studies. Antiangiogenic therapy is a promising strategy of cancer treatment that might be particularly useful in combination therapy for unresectable cancers or as an adjuvant therapy for resectable tumors.

Serum vascular endothelial growth factor levels in pancreatic cancer patients correlate with advanced and metastatic disease and poor prognosis

The serum concentrations of vascular endothelial growth factor (VEGF) were measured by an enzyme linked immunosorbent assay in 51 healthy controls and in 58 patients with pancreatic cancer before and 30 days after surgery. Pancreatic cancer patients had significantly higher serum VEGF levels compared with healthy controls with a significant association between serum VEGF levels, disease stage and the presence of both lymph node and distant metastases. Serum levels of VEGF decreased significantly after radical resection of the tumor. Elevated preoperative serum VEGF level was a significant prognostic factor, although not independent of stage, for patient survival. These findings suggest that serum VEGF concentrations may reflect pancreatic cancer progression and that their determination may be clinically useful.

Biology of angiogenesis in tumors of the gastrointestinal tract

The realization that the growth and spread of tumors are dependent on angiogenesis has created new avenues of research designed to help us to better understand cancer biology and to facilitate the development of new therapeutic strategies. However, the process of angiogenesis consists of multiple, sequential, and interdependent steps with a myriad of positive and negative regulators of angiogenesis being involved. The survival of tumors and thus their metastases are dependent upon the balance of endogenous angiogenic and anti-angiogenic factors such that the outcome favors increased angiogenesis. Several growth factors have been identified that regulate angiogenesis in cancers of the gastrointestinal tract. These include pro-angiogenic factors like vascular endothelial growth factor (VEGF) and anti-angiogenic factors, i.e., thrombospondin. The following review provides a brief overview about the most important factors that are involved in the angiogenic process in tumors derived from colon, stomach, and pancreas. A thorough understanding of the role these factors play in the angiogenic process may lead to the development of novel therapeutic antineoplastic strategies.

Influence of hypoxia and neoangiogenesis on the growth of pancreatic cancer

As with other solid tumors, the growth and metastasis of pancreatic cancer is critically dependent on tumor angiogenesis. A major stimulus for a tumor's recruitment of additional blood vessels is cellular hypoxia, a condition which is especially pronounced in this neoplasm. Hypoxia induces transcriptional activation of genes that alter cellular metabolism and promote neoangiogenesis. Pancreatic cancer cells have demonstrated activation of such adaptive pathways even in the absence of hypoxia. A highly-angiogenic response in this neoplasm correlates with increased tumor growth, increased metastasis, and decreased survival. Pancreatic cancers expressing high levels of vascular endothelial growth factor, a potent pro-angiogenic cytokine, also have a higher incidence of metastasis and poorer prognosis. Pancreatic cancer cells uniquely express receptors for vascular endothelial growth factor, indicating a role for an autocrine loop in tumor proliferation and invasion. Multiple experimental anti-angiogenic strategies, many of which target vascular endothelial growth factor, reduce pancreatic cancer growth, spread, and angiogenesis. Anti-angiogenic treatments for pancreatic cancer will likely be most effective when used as an integral part of a combination chemotherapeutic regimen.

Pathways for aberrant angiogenesis in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease. Although the specific mechanisms that dictate its biological aggressiveness are not clearly established, it is characterized by a variety of molecular alterations as well as by the overexpression of mitogenic and angiogenic growth factors and their receptors. PDACs also express high levels of vascular endothelial growth factor (VEGF). Recent studies indicate that suppression of VEGF expression attenuates pancreatic cancer cell tumorigenicity in a nude mouse model, and that VEGF can exert direct mitogenic effects on some pancreatic cancer cells. These findings suggest that cancer cell derived VEGF promotes pancreatic cancer growth in vivo via a paracrine angiogenic pathway and an autocrine mitogenic pathway, and provide novel opportunities for therapeutic intervention in this deadly disease.

Vascular endothelial growth factor mediated angiogenic potential of pancreatic ductal carcinomas enhanced by hypoxia: an in vitro and in vivo study

Angiogenesis in pancreatic ductal adenocarcinomas depends on the presence of angiogenic factors such as vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) and is thought to be stimulated by hypoxia. We tested the angiogenic potential of 9 cell lines of pancreatic ductal carcinoma origin by screening mRNA and protein expression of VEGF and bFGF and the release of VEGF into culture medium under normoxic and hypoxic (5% or 0.2% O2) conditions. Angiogenic activity was determined using 2- and 3-D endothelial cell assays. Furthermore, VEGF expression and tumor vascularization were studied in human pancreatic carcinoma tissues from orthotopic xenografts and resection specimens. All cell lines expressed (mRNA, protein) and secreted VEGF, whereas bFGF was only found in 3 cell lines and was secreted into the medium in low concentrations. In addition to the dominant isoforms VEGF121,VEGF165 and VEGF189, 2 isoforms described recently, VEGF145 and VEGF183, were detected. Severe hypoxia (0.2% O2), but not moderate hypoxia (5% O2) raised VEGF mRNA expression and protein secretion in 7/9 and 5/9 cell lines, respectively. Conditioned media from 7/9, 6/9, 8/9 and 7/9 cell lines stimulated endothelial cell proliferation under normoxic (24 and 48 hr) or hypoxic (24 hr, 0.2% and 48 hr 5% O2) conditions, respectively. Conditioned media from 4/9 cell lines also induced capillary-like sprouting under normoxic conditions and from 6/9 under hypoxic (0.2% O2) conditions. In xenografted carcinoma tissues microvessel density was found not to be increased around areas of ischemic necrosis. In resected ductal carcinomas showing tumor necrosis VEGF expression and microvessel density were only increased in 3/12 and 2/13 cases, respectively. In conclusion, in vitro most pancreatic ductal carcinomas show a distinct VEGF related angiogenic potential, as demonstrated by 2- and 3-D endothelial cell proliferation, which may be promoted by severe hypoxia. Surprisingly, perinecrotic tumor areas, which are supposed to be hypoxic, only rarely showed the expected increase in microvessel density and VEGF expression.

Prognostic significance of intratumoural microvessel density (IMD) in resected pancreatic and ampullary cancers to standard histopathological variables and survival

AIM

Angiogenesis is required for tumour growth. Its evaluation, by intratumoural microvessel density (IMD), has prognostic significance in many solid tumours. There is controversy regarding its use in pancreatic cancer and little is known about its role in ampullary tumours. The aim is to study IMD as a prognostic marker in resected ductal adenocarcinomas of head of pancreas and cancers of the ampullary region.

METHODS

Forty-seven patients (23 pancreatic and 24 ampullary, mean age 62.0 years) surviving a potentially curative (R0/R1) resection were analysed. Paraffin-embedded sections of these tumours were immunohistochemically stained for CD-34 and IMD was determined (magnification x200). This was correlated with histopathological data and survival using Cox's multivariate analysis.

RESULTS

Mean survival for the pancreatic cancer group was 18.4 months (SE=2.7) and 81.2 months (SE=9.9) for the ampullary cancer group. In the pancreatic cancer group, IMD was found to have independent prognostic significance to survival on multivariate analysis (P=0.002, Hazard Ratio (HR) 13.60) along with microscopic resection margin involvement (P=0.003, HR 15.18). For ampullary cancers, IMD was higher in those with lymph node metastasis (P=0.02, Mann-Whitney U -test).

CONCLUSION

IMD in resected pancreatic cancers correlates with survival.

Expression of vascular endothelial growth factor and p53 in pancreatic carcinomas

BACKGROUND

Angiogenesis has been shown to be a critical aspect of tumor growth and progression. Vascular endothelial growth factor (VEGF) has potent angiogenic activity and has been identified in a wide variety of malignancies, including pancreatic carcinoma. The tumor-suppressor gene p53 has been thought to regulate VEGF in angiogenesis. The aim of the current study was conducted to investigate the association between p53 mutation and VEGF expression and the prognostic value of these factors in pancreatic carcinoma.

METHODS

Formalin-fixed, paraffin-embedded tissue specimens were obtained from 30 patients who underwent surgery for pancreatic carcinoma. We used an immunohistochemical technique to localize VEGF and p53 in pancreatic carcinoma tissues.

RESULTS

Positive expression of VEGF was detected in 17 out of 30 (56.7%) tumors. Positive expression of VEGF correlated with the depth of tumor invasion (p = 0.002). There was a trend towards an association between positive expression of VEGF and distant metastasis, although these associations were not statistically significant (p = 0.070). p53 mutations were identified in 18 out of 30 (60.0%) tumors. However, no significant correlation was found between p53 expression and various clinicopathological parameters. The correlation between p53 mutation and VEGF expression was statistically significant (p = 0.004).

CONCLUSION

VEGF, a key factor for the induction of tumor-associated angiogenesis, may be involved in tumor characteristics, including tumor invasion and metastasis. And p53 mutation may be implicated in the regulation of angiogenesis through a VEGF up-regulation.