Biology of angiogenesis in tumors of the gastrointestinal tract

Selective blockade of vascular endothelial growth factor receptor 2 with an antibody against tumor-derived vascular endothelial growth factor controls the growth of human pancreatic adenocarcinoma xenografts

BACKGROUND

Vascular endothelial growth factor (VEGF), a key regulator of angiogenesis, is critical for growth of human pancreatic adenocarcinoma. Preclinical studies demonstrate that blockade of VEGF activity can control the growth of pancreatic tumors in mice. In this study, we evaluated the efficacy of 2C3, an antibody that inhibits VEGF receptor 2 activation by human VEGF, to inhibit the growth of human pancreatic adenocarcinoma in mice.

METHODS

Human pancreatic cancer cell lines (MiaPaca-2, Panc-1, and Capan-1) were used to establish xenografts in nu/nu mice. The expression of VEGF and its receptors was determined in each cell line. Proliferation of tumor cells in vitro and tumor growth in vivo in the presence of 2C3 or a control antibody was evaluated. The effect of 2C3 on tumor weight, total vessel density, number of pericyte-associated vessels, and tumor perfusion was determined, and the level of 2C3 in the serum of animals was measured by enzyme-linked immunosorbent assay.

RESULTS

2C3 did not affect the proliferation of cells in culture. 2C3 was present and active in the serum of tumor-bearing animals treated with 2C3, and these animals showed a decrease in tumor burden compared with control-treated mice. Therapy with 2C3 resulted in reduced vascular function, measured by a decrease in vessel density and in the percentage of vessels associated with pericytes. Furthermore, tumors derived from Capan-1 cells demonstrated decreased perfusion after treatment with 2C3.

CONCLUSIONS

Blockade of VEGF receptor 2 activation by tumor-derived VEGF decreases tumor vessel function and growth of some human pancreatic adenocarcinoma cell lines in mice.

Endoglin (CD105) as a prognostic factor in head and neck squamous cell carcinoma

Endoglin (CD105) is a proliferation-associated protein abundantly expressed in angiogenic endothelial cells. Recent studies revealed that CD105 is intensively expressed in tumor vasculature, whereas intratumoral microvessel density (MVD) determined with the use of antibodies to CD105 has been found to be an important prognostic indicator for the outcome in a number of malignancies. In the current study, we investigated endoglin expression and evaluated MVD in 108 patients with head and neck squamous cell carcinoma. Endoglin was intensively expressed in intratumoral blood vessels, whilst lymphatics were rarely positive for CD105. High microvessel density was associated with a more aggressive tumor phenotype, including advanced clinical stage (p = 0.008) and the presence of lymph node metastasis at the time of diagnosis (p = 0.02). When microvessel counts were assessed for their prognostic values (high vs low MVD), there was a statistically significant difference in the overall survival among patients with tumors of the oral cavity and larynx (p < 0.001) and in the disease-free survival among patients with tumors of the lower lip (p = 0.01). The prognostic impact of microvessel density was not dependent on clinical stage or lymph node status. The results of the current study suggest that CD105 is a promising target for tumor imaging and prognosis.

Anti-angiogenic strategies in gastrointestinal malignancies

Advances in our understanding of the mechanisms underlying tumor progression suggest that angiogenesis plays a key role in gastrointestinal malignancies. Vascular endothelial growth factor (VEGF) has emerged as an important therapeutic target, and a variety of strategies to inhibit VEGF are under investigation. The approval of bevacizumab for use in patients with previously untreated metastatic colorectal cancer was based on clinical data suggesting that VEGF is a valid therapeutic target in this disease. As the data mature from ongoing trials, the role of angiogenesis inhibitors in the treatment of colon cancer and other gastrointestinal malignancies will be more clearly defined. Additional information is needed to identify the diseases and stages most likely to benefit from anti-angiogenic agents and the optimal sequences and therapeutic combinations that should be studied.

Modulation of VEGF/Flk-1 receptor expression in the rat pituitary GH3 cell line by growth factors

Both vascular endothelial growth factor (VEGF) and its receptor Flk-1 are expressed in normal pituitary cells and in the prolactin- and growth hormone-producing GH3 cell line of the rat, thus suggesting autocrine/paracrine function. Regulation of the Flk-1 receptor system in pituitary cells is poorly understood, but evidence suggests that up-regulated growth factors play a role in its expression and activation. To study the role of growth factors in this process, we examined changes in VEGF and Flk-1 expression in GH3 cells following varied exposure to betaFGF, EGF, and TGFbeta1. Immunofluorescence labelling and laser scanning cytometry were used to measure changes in VEGF and Flk-1 expression. Results showed that betaFGF, EGF and TGFbeta up-regulated the VEGF/FLK-1 receptor system. Distinct patterns of activation were detected. At 2 hours, EGF and TGFbeta caused no significant changes in VEGF and Flk-1 expression; however, betaFGF up-regulated VEGF expression in 99% of cells but only induced modest changes in Flk-1 overexpression. A similar percentage of cells overexpressed VEGF after 24-hour incubation with betaFGF, but more prominent Flk-1 overexpression was detected. At 24 hours, EGF and TGFbeta1 induced a significant increase in both VEGF and Flk-1 expression. In summary, our findings show that VEGF/Flk-1 expression in pituitary cells may be altered by different growth factors. This may affect angiogenesis and the progression of pituitary tumors.

Effect of N-desulfated heparin on angiogenesis and vascular endothelial growth factor expression in mice with severe combined immunodeficiency

AIM: To investigate the effect of N-desulfated heparin on tumor metastasis, angiogenesis, and expression of vascular endothelial growth factor (VEGF) after ortho-topic implantation of human gastric carcinoma in mice with severe combined immunodeficiency (SCID).

METHODS: The SCID mice metastasis model was established by in situ implantation of human gastric carcinoma tissue, then the mice were randomly divided into two groups: the normal saline group (treated with normal saline) and NNH group [treated with N-desulfat-ed heparin, 10 mg/(kg·d) iv, 2/wk, for 3 wk]. The mice were sacrificed 6 wk after the implantation. The tumor metastasis, intratumoral microvessel density (MVD), and VEGF expression were evaluated respectively..

RESULTS: The tumor metastasis rates were significan-tly different between normal saline and NNH group (80% vs 20%, P < 0.05). No side effect such as hemorrhage was observed in the mice. The MVD was 8.0 ± 3.1 in the normal saline group and 4.3 ± 1.8 in the NNH group, and there was significant difference between those 2 groups (P < 0.05). The positive rate of VEGF expressi-on was significantly higher in the normal saline group than that in the NNH group (90% vs 20%, P < 0.05).

CONCLUSION: N-desulfated heparin can inhibit the metastasis of gastric cancer through inhibiting the ex-pression of tumor VEGF and angiogenesis with no ob-vious side effect such as hemorrhage

Molecular consequences of silencing mutant K-ras in pancreatic cancer cells: justification for K-ras-directed therapy

Mutation of the K-ras gene is an early event in the development of pancreatic adenocarcinoma and, therefore, RNA interference (RNAi) directed toward mutant K-ras could represent a novel therapy. In this study, we examine the phenotypic and molecular consequences of exposure of pancreatic tumor cells to mutant-specific K-ras small interfering RNA. Specific reduction of activated K-ras via RNAi in Panc-1 and MiaPaca-2 cells resulted in cellular changes consistent with a reduced capacity to form malignant tumors. These changes occur through distinct mechanisms but likely reflect an addiction of each cell line to oncogene stimulation. Both cell lines show reduced proliferation after K-ras RNAi, but only MiaPaca-2 cells showed increased apoptosis. Both cell lines showed reduced migration after K-ras knockdown, but changes in integrin levels were not consistent between the cell lines. Both cell lines showed alteration of the level of GLUT-1, a metabolism-associated gene that is downstream of c-myc, with Panc-1 cells demonstrating decreased GLUT-1 levels, whereas MiaPaca-2 cells showed increased levels of expression after K-ras knockdown. Furthermore, after K-ras RNAi, there was a reduction in angiogenic potential of both Panc-1 and MiaPaca-2 cells. Panc-1 cells increased the level of expression of thrombospondin-1, an endogenous inhibitor of angiogenesis, whereas MiaPaca-2 cells decreased the production of vascular endothelial growth factor, a primary stimulant of angiogenesis in pancreatic tumors. We have found that silencing mutant K-ras through RNAi results in alteration of tumor cell behavior in vitro and suggests that targeting mutant K-ras specifically might be effective against pancreatic cancer in vivo.

Vascular endothelial growth factor (VEGF) in physiological and pathological conditions

Vascular endothelial growth factor (VEGF) is the major endothelial-cell specific stimulatory factor regarded as the most important positive regulator of angiogenesis and vascular permeability. Due to its powerful angiogenic and mitogenic properties, VEGF takes part in a variety of crucial biological processes, including wound repair and tumorigenesis. The elevated expression of VEGF and its receptors has been found in malignancies of various origin as being associated with metastasis formation and poor prognosis. Recently, some possibilities appeared to block the VEGF action when it is undesirable or promote its activity when it can be useful. These new therapeutic strategies based upon the knowledge of VEGF biological role, are being tried and up till now they proved to be successful, especially in anticancer therapy and the coronary heart disease treatment.

Prognostic significance of vascular endothelial growth factor immunohistochemical expression in head and neck squamous cell carcinoma: a meta-analysis

PURPOSE

Vascular endothelial growth factor (VEGF) is considered as a prime mediator of angiogenesis. Various studies examining the relationship between VEGF protein overexpression with the clinical outcome in patients with head and neck squamous cell carcinoma have yielded inconclusive results.

EXPERIMENTAL DESIGN

We conducted a meta-analysis of 12 studies (n = 1.002 patients) that evaluated the correlation between VEGF (detected by immunohistochemistry) and 2-year overall survival. The relation between VEGF and lymph node involvement (11 studies, n = 722) was also examined. Data were synthesized with random effect and fixed effect risk ratios.

RESULTS

The estimated risk of death in 2 years was 1.88-fold higher in the VEGF-positive patients [95% confidence interval, 1.43-2.45; P < 0.001 random effect calculations]. Between-study heterogeneity was nonsignificant (P = 0.15) but larger studies tended to provide more conservative estimates (P = 0.097). VEGF overexpression was not significantly associated with the presence of lymph node metastasis (risk ratio, 1.20; 95% confidence interval, 0.97-1.49; P = 0.087) and there was significant between-study heterogeneity (P = 0.08).

CONCLUSIONS

Although some modest bias cannot be excluded, VEGF positivity seems to be associated with worse overall survival in patients with head and neck squamous cell carcinoma.

Prognostic significance of VEGF immunohistochemical expression and tumor angiogenesis in head and neck squamous cell carcinoma

PURPOSE

Tumor angiogenesis is crucial for both the growth of the primary tumor and the development of metastases. Among the factors causing tumor angiogenesis, vascular endothelial growth factor (VEGF) is considered as a leading candidate. We aimed to assess the prognostic significance of VEGF and tumor angiogenesis in head and neck squamous cell carcinoma (HNSCC).

METHODS

We performed a retrospective study of 69 patients with HNSCC, in order to investigate whether VEGF immunohistochemical expression and tumor angiogenesis correlate with clinicopathological parameters and outcome. Tumor angiogenesis was estimated by determining microvessel density (MVD), and VEGF expression was assessed quantitatively.

RESULTS

Vascular endothelial growth factor and MVD correlated statistically significant with the clinical stage, but not with the presence of lymph node metastasis at the time of diagnosis. Tumors located in the oral cavity and larynx more often expressed high VEGF immunostaining compared with tumors located in the lower lip. High VEGF expression was associated with higher clinical stage and worse overall survival in this cohort of patients.

CONCLUSIONS

Vascular endothelial growth factor expression may have prognostic significance for patients with HNSCC.

Hypoxia-induced tumor angiogenic pathway in head and neck cancer: an in vivo study

Numerous studies indicate the importance of hypoxia-induced pathway in tumor angiogenesis, but in vivo studies examining the importance of this mechanism in prognosis of patients with head and neck squamous cell carcinoma present conflicting results. We performed a retrospective analysis of 81 patients with head and neck squamous cell carcinoma in order to investigate whether hypoxia-inducible factor 1a (HIF-1a) immunohistochemical expression correlates with vascular endothelial growth factor (VEGF) expression and clinicopathologic parameters or prognosis. Our results showed a statistically significant association between HIF-1a and VEGF expression in tumors located in the lower lip and in larynx, but not in those located in the oral cavity. HIF-1a expression had no impact on prognosis, while VEGF expression correlated significantly with adverse prognosis. These findings support the hypothesis that tumor angiogenesis is close related, but not strictly dependent, on the hypoxic conditions of tumor's microenvironment.

Improving delivery of antineoplastic agents with anti-vascular endothelial growth factor therapy

It is believed that impairments in delivery of antineoplastic agents to solid tumors result from abnormalities of the tumor microenvironment. Vascular endothelial growth factor (VEGF), the prototypical angiogenic molecule, is one of the main factors responsible for the development and maintenance of the aberrant tumor vascular network, which is characterized by chaotic, leaky blood vessels with high interstitial fluid pressure and inefficient blood flow. The authors proposed that anti-VEGF therapy would reduce the elevated interstitial fluid pressure in tumors, thereby improving blood flow and potentially improving delivery of cytotoxic agents to tumor cells. For the current report, the authors reviewed characteristics of the abnormal tumor vasculature created under the influence of VEGF, the resulting tumor microenvironment, how the tumor microenvironment may impede delivery of antineoplastic agents, and how the combination of anti-VEGF and cytotoxic therapy may maximize the efficacy of antineoplastic treatment regimens.

Potential autocrine function of vascular endothelial growth factor in head and neck cancer via vascular endothelial growth factor receptor-2

Vascular endothelial growth factor is a peptide with well-defined actions on the vasculature and fundamental role in tumor angiogenesis. Its action in vascular endothelium is exerted in a paracrine manner. The immunohistochemical expression of this protein by cancer cells in head and neck squamous cell carcinoma was correlated with increased tumor aggressiveness and poor survival in previous studies. In the past years, an increasing amount of studies demonstrated potential autocrine action of vascular endothelial growth factor in various neoplasms. However, the existence and the impact of such autocrine action in head and neck cancer have not been demonstrated yet. In this retrospective study, we evaluated the expression of vascular endothelial growth factor and its receptors in neoplastic cells, in a cohort of patients with head and neck squamous cell carcinoma, and compared this expression with tumor aggressiveness, clinicopathologic parameters and outcome. High expression of vascular endothelial growth factor was strongly correlated with high expression of vascular endothelial growth factor receptor-2 (but not vascular endothelial growth factor receptor-1) on the cancer cells (P<0.001). The co-overexpression of both the protein and vascular endothelial growth factor receptor-2 was associated with higher tumor proliferation rate (P<0.001). The above co-overexpression also correlated with worse survival (log rank P<0.05) in patients with oral-larynx squamous cell carcinoma. Our results suggest that an autocrine vascular endothelial growth factor loop, mediated via vascular endothelial growth factor receptor-2, probably exists in head and neck squamous cell carcinoma. These observations support the hypothesis that the use of vascular endothelial growth factor receptor-2 inhibitors as adjuvant antiangiogenic therapy might have beneficial effects for these patients, by disrupting both paracrine (endothelial-dependent) and autocrine actions of vascular endothelial growth factor.

Oncogenes as Novel Targets for Cancer Therapy (Part I)

In the past 10 years, progress made in cancer biology, genetics, and biotechnology has led to a major transition in cancer drug design and development. There has been a change from an emphasis on non-specific, cytotoxic agents to specific, molecular-based therapeutics. Mechanism-based therapy is designed to act on cellular and molecular targets that are causally involved in the formation, growth, and progression of human cancers. These agents, which may have greater selectivity for cancer versus normal cells, and which may produce better anti-tumor efficacy and lower host toxicity, can be small molecules, natural or engineered peptides, proteins, antibodies, or synthetic nucleic acids (e.g. antisense oligonucleotides, ribozymes, and siRNAs). Novel targets are identified and validated by state-of-the-art approaches, including high-throughput screening, combinatorial chemistry, and gene expression arrays, which increase the speed and efficiency of drug discovery and development. Examples of oncogene-based, molecular therapeutics that show promising clinical activity include trastuzumab (Herceptin), imatinib (Gleevec), and gefitinib (Iressa). However, the full potential of oncogenes as novel targets for cancer therapy has not been realized and many challenges remain, from the validation of novel targets, to the design of specific agents, to the evaluation of these agents in both preclinical and clinical settings. In maximizing the benefits of molecular therapeutics in monotherapy or combination therapy of cancer, it is necessary to have an understanding of the underlying molecular abnormalities and mechanisms involved. This is the first part of a four-part review in which we discuss progress made in the last decade as it relates to the discovery of novel oncogenes and signal transduction pathways, in the context of their potential as targets for cancer therapy. This part delineates the latest discoveries about the potential use of growth factors and protein tyrosine kinases as targets for therapy. Later parts focus on intermediate signaling pathways, transcription factors, and proteins involved in cell cycle, DNA damage, and apoptotic pathways.

New method of dynamic color doppler signal quantification in metastatic lymph nodes compared to direct polarographic measurements of tissue oxygenation

Tumor growth depends on sufficient blood and oxygen supply. Hypoxia stimulates neovascularization and is a known cause for radio- and chemoresistance. The objective of this study was to investigate the use of a novel ultrasound technique for the dynamic assessment of vascularization and oxygenation in metastatic lymph nodes. Twenty-four patients (age 44-78 years) with cervical lymph node metastases of squamous cell head and neck cancer were investigated by color duplex sonography and 17 (age 46-78 years) were investigated additionally with polarography. Sonography was performed after contrast enhancer infusion under defined conditions. Intranodal perfusion data (color hue, colored area) were measured automatically by a novel software technique. This allows an evaluation of blood flow dynamics by calculating perfusion intensity--velocity, perfused area, as well as the novel parameters tissue resistance index (TRI) and tissue pulsatility index (TPI)--for each point of a complete heart cycle. Tumor tissue pO(2) was measured by means of polarographic needle electrodes placed intranodally. The sonographic and polarographic data were correlated using Pearson's test. Sonography demonstrated a statistically significant inverse correlation between hypoxia and perfusion and significant TPI and TRI changes with different N-stages. The percentage of nodal fraction with less than 10 mmHg oxygen saturation was significantly inversely correlated with lymph node perfusion (r = -0.551; p = 0.021). Nodes with a perfusion of less than 0.05 cm/sec flow velocity showed significantly larger hypoxic areas (p = 0.006). Significant differences of TPI and TRI existed between nodes in stage N(1) and N(2)/N(3) (p = 0.028 and 0.048, respectively). This new method of dynamic signal quantification allows a noninvasive and quantitative assessment of tumor and metastatic lymph node perfusion by means of commonly available ultrasound equipment.

Role of the vascular endothelial growth factor pathway in tumor growth and angiogenesis

New blood vessel formation (angiogenesis) is a fundamental event in the process of tumor growth and metastatic dissemination. Hence, the molecular basis of tumor angiogenesis has been of keen interest in the field of cancer research. The vascular endothelial growth factor (VEGF) pathway is well established as one of the key regulators of this process. The VEGF/VEGF-receptor axis is composed of multiple ligands and receptors with overlapping and distinct ligand-receptor binding specificities, cell-type expression, and function. Activation of the VEGF-receptor pathway triggers a network of signaling processes that promote endothelial cell growth, migration, and survival from pre-existing vasculature. In addition, VEGF mediates vessel permeability, and has been associated with malignant effusions. More recently, an important role for VEGF has emerged in mobilization of endothelial progenitor cells from the bone marrow to distant sites of neovascularization. The well-established role of VEGF in promoting tumor angiogenesis and the pathogenesis of human cancers has led to the rational design and development of agents that selectively target this pathway. Studies with various anti-VEGF/VEGF-receptor therapies have shown that these agents can potently inhibit angiogenesis and tumor growth in preclinical models. Recently, an anti-VEGF antibody (bevacizumab), when used in combination with chemotherapy, was shown to significantly improve survival and response rates in patients with metastatic colorectal cancer and thus, validate VEGF pathway inhibitors as an important new treatment modality in cancer therapy.

The vascular endothelial growth factor family and its receptors

This article focuses on describing the biology of vascular endothelial growth factor (VEGF) and its receptors as well as the regulation of their expression. A thorough understanding of the VEGF system is paramount in optimizing antiangiogenic therapies as a component of antineoplastic regimens.

Combining Anti-VEGF Approaches with Oxaliplatin in Advanced Colorectal Cancer

Angiogenesis, the formation of blood vessels, is a vital process in tumor growth and metastasis. Vascular endothelial growth factor (VEGF) is a potential target for antiangiogenic therapy because its overexpression has been associated with tumor vascularity, poor prognosis, and aggressive disease in many malignancies, including colorectal cancer (CRC). Bevacizumab is a recombinant humanized monoclonal antibody against VEGF. It is the first angiogenesis inhibitor to show significant activity in patients and, when combined with chemotherapy, leads to a significant survival benefit in CRC. This monoclonal antibody has been approved for first-line therapy in combination with intravenous 5-fluorouracil-containing regimens in patients with metastatic CRC. Vatalanib (PTK787/ZK222584) is an oral antiangiogenic tyrosine kinase inhibitor of the VEGF receptor. Currently, it is being evaluated in combination with FOLFOX (5-fluorouracil/leucovorin/oxaliplatin) in metastatic CRC. This article reviews the process of angiogenesis and the successful translation of antiangiogenic agents into the clinic. Specifically, studies evaluating VEGF-targeted agents in combination with oxaliplatin-containing regimens in CRC are discussed.

Immunohistochemical expression of vascular endothelial growth factor correlates with positive surgical margins and recurrence in T1 and T2 squamous cell carcinoma (SCC) of the lower lip

Tumor angiogenesis is associated with tumor progression and aggressiveness in a number of malignancies, and vascular endothelial growth factor (VEGF) is considered as a leading candidate in this process. The aim of the present study was to investigate the role of VEGF immunohistochemical expression and tumor angiogenesis in predicting local recurrence in surgically treated lip SCC. We performed a retrospective analysis of 50 patients with lip SCC in order to investigate whether VEGF immunohistochemical expression and tumor angiogenesis correlate with clinicopathologic parameters and outcome. Tumor angiogenesis was estimated by determining microvessel density (MVD) with the use of CD34 antibody. Our results showed that VEGF was strongly correlated with tumor invasion towards the surgical margin. There was also a significant association of high VEGF expression with a higher incidence of local recurrence (p < 0.001). We suggest that VEGF expression may be used as an index to distinguish patients with higher risk of relapse.

Angiogenesis in colorectal cancer: therapeutic implications and future directions

This article discusses the therapeutic implications and future directions of angiogenesis in colorectal cancer.

Vascular endothelial growth factor in esophageal cancer

Vascular endothelial growth factor (VEGF) plays a crucial role in angiogenesis of many solid malignancies. The influence of angiogenesis and VEGF expression on progression and recurrence of esophageal cancer has been investigated over the last years. This article reviews the prognostic significance of VEGF expression, microvessel density (MVD), and lymphangiogenic factors in squamous cell carcinoma (SCC), Barrett's dysplasia, and adenocarcinoma (AC) of the esophagus, their predictive value for treatment response to chemo-radiotherapy and new anti-angiogenic treatment strategies.

Role of hypoxia-inducible factor 1alpha in gastric cancer cell growth, angiogenesis, and vessel maturation

BACKGROUND

Hypoxia-inducible factor 1 (HIF-1), a heterodimer comprising the oxygen-regulated subunit, HIF-1alpha, and HIF-1beta, mediates transcription of the gene for vascular endothelial growth factor (VEGF). Overexpression of HIF-1alpha is associated with tumor angiogenesis and tumor cell proliferation and invasion. We examined the effects of inhibiting HIF-1alpha activity on angiogenesis and human gastric cancer growth in vivo.

METHODS

Human gastric cancer TMK-1 cells were stably transfected with pHIF-1alphaDN, an expression plasmid encoding a dominant-negative form of HIF-1alpha that dimerizes with endogenous HIF-1beta to produce HIF-1 complexes that cannot activate transcription, or with the empty expression vector (pCEP4). Two clones of pHIF-1alphaDN-transfected cells, DN2 and DN3, were tested in all experiments. We used an enzyme-linked immunosorbent assay to measure VEGF secretion by transfected cells cultured in hypoxic (1% O2) or nonhypoxic (20% O2) conditions. We used subcutaneous and orthotopic mouse tumor models to examine the growth of tumors derived from injected pHIF-1alphaDN-or pCEP4-transfected cells. Tumor cell proliferation, vessel area (a measure of functional vascular volume), and tumor endothelial cell association with pericyte-like cells (a measure of vessel maturation) were analyzed by immunohistochemical or immunofluorescent staining. All statistical tests were two-sided.

RESULTS

DN2 cells and DN3 cells secreted less VEGF than pCEP4-transfected TMK-1 cells when cultured in nonhypoxic or hypoxic conditions (e.g., DN2 versus pCEP4 in nonhypoxic conditions: 645 pg of VEGF/10(6) cells versus 1591 pg of VEGF/10(6) cells, difference = 946 pg of VEGF/10(6) cells [95% confidence interval [CI] = 640 to 1251 pg of VEGF/10(6) cells; P =.006]; DN2 versus pCEP4 in hypoxic conditions: 785 pg of VEGF/10(6) cells versus 2807 pg of VEGF/10(6) cells, difference = 2022 pg of VEGF/10(6) cells [95% CI = 1871 to 2152 pg of VEGF/10(6) cells; P<.001]). In the subcutaneous tumor model, tumors derived from DN2 or DN3 cells had lower final volumes, weights, and vessel areas, less tumor endothelial cell association with desmin-positive cells, and fewer proliferating tumor cells than tumors derived from pCEP4-transfected cells. In the orthotopic tumor model, tumors derived from DN2 cells had smaller volumes and less vessel area and maturation than tumors derived from pCEP4-transfected cells.

CONCLUSIONS

Inhibition of HIF-1alpha activity impairs gastric tumor growth, angiogenesis, and vessel maturation.

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.

Current Approaches to First-Line Treatment of Advanced Colorectal Cancer

The multiplicity of chemotherapy regimens currently available to treat colorectal cancer in the first-line setting precludes the identification of a single standard regimen for front-line therapy. The previous standard, 5-fluorouracil (5-FU), formerly the only agent with any significant activity against colorectal cancer, is now the base for newer combination regimens that are improving survival in this disease. When irinotecan and oxaliplatin were proven to be active in colorectal cancer, the pursuit of combination regimens began. Targeted agents such as bevacizumab also show activity and improve the outcome of 5-FU-based regimens. The history and development of 5-FU-based treatment regimens that include the newer drugs irinotecan, oxaliplatin, and bevacizumab are discussed in light of the impact these advances have made in the treatment of colorectal cancer