A quantitative analysis of the reduction in oxygen levels required to induce up-regulation of vascular endothelial growth factor (VEGF) mRNA in cervical cancer cell lines

Hypoxia signaling in cancer: Implications for therapeutic interventions

Hypoxia is a persistent physiological feature of many different solid tumors and a key driver of malignancy, and in recent years, it has been recognized as an important target for cancer therapy. Hypoxia occurs in the majority of solid tumors due to a poor vascular oxygen supply that is not sufficient to meet the needs of rapidly proliferating cancer cells. A hypoxic tumor microenvironment (TME) can reduce the effectiveness of other tumor therapies, such as radiotherapy, chemotherapy, and immunotherapy. In this review, we discuss the critical role of hypoxia in tumor development, including tumor metabolism, tumor immunity, and tumor angiogenesis. The treatment methods for hypoxic TME are summarized, including hypoxia-targeted therapy and improving oxygenation by alleviating tumor hypoxia itself. Hyperoxia therapy can be used to improve tissue oxygen partial pressure and relieve tumor hypoxia. We focus on the underlying mechanisms of hyperoxia and their impact on current cancer therapies and discuss the prospects of hyperoxia therapy in cancer treatment.

Tumor Hypoxia as a Barrier in Cancer Therapy: Why Levels Matter

Simple Summary

Hypoxia is a common feature of solid tumors and associated with poor outcome in most cancer types and treatment modalities, including radiotherapy, chemotherapy, surgery and, most likely, immunotherapy. Emerging strategies, such as proton therapy and combination therapies with radiation and hypoxia targeted drugs, provide new opportunities to overcome the hypoxia barrier and improve therapeutic outcome. Hypoxia is heterogeneously distributed both between and within tumors and shows large variations across patients not only in prevalence, but importantly, also in level. To best exploit the emerging strategies, a better understanding of how individual hypoxia levels from mild to severe affect tumor biology is vital. Here, we discuss our current knowledge on this topic and how we should proceed to gain more insight into the field.

Abstract

Hypoxia arises in tumor regions with insufficient oxygen supply and is a major barrier in cancer treatment. The distribution of hypoxia levels is highly heterogeneous, ranging from mild, almost non-hypoxic, to severe and anoxic levels. The individual hypoxia levels induce a variety of biological responses that impair the treatment effect. A stronger focus on hypoxia levels rather than the absence or presence of hypoxia in our investigations will help development of improved strategies to treat patients with hypoxic tumors. Current knowledge on how hypoxia levels are sensed by cancer cells and mediate cellular responses that promote treatment resistance is comprehensive. Recently, it has become evident that hypoxia also has an important, more unexplored role in the interaction between cancer cells, stroma and immune cells, influencing the composition and structure of the tumor microenvironment. Establishment of how such processes depend on the hypoxia level requires more advanced tumor models and methodology. In this review, we describe promising model systems and tools for investigations of hypoxia levels in tumors. We further present current knowledge and emerging research on cellular responses to individual levels, and discuss their impact in novel therapeutic approaches to overcome the hypoxia barrier.

Time Course and Quantification of Pancreatic Islet Revasculariztion following Intraportal Transplantation

A large proportion of islets are lost after transplantation partly due to a lack of functional vasculature. Islets revascularize from host tissue but the process takes up to 2 weeks and has been suggested to result in reduced vascular density in engrafted islets. We describe a method for observing and quantifying the revascularization of intraportally transplanted islets that includes number, density, and branching of islet capillaries. Syngeneic islets were transplanted selectively into the two right posterior lobes of the liver of adult Lewis rats. Sections of the livers were dual stained for insulin and Bandeiraea simplicifolia and analyzed for islet morphology, area, and vascular density from day 0 to day 14 posttransplant and compared to native islets. Vascular density was 1431 ± 75.7 vessels/mm2 in native islets and fell to 325.3 ± 30.8 vessels/mm2 (p < 0.001) by day 1 posttransplant and subsequently increased until day 14 when it was significantly higher than in native islets (2612.5 ± 107.8 vessels/mm2, p < 0.001). The percentage of islet area occupied by vascular space was 9.1 ± 0.9% in native islets. After falling to 2.3 ± 0.3% (p < 0.001) 1 day posttransplant this rose to supranormal levels (21.5 ± 0.8%, p < 0.001) by day 14. The index of capillary branching was 0.771 ± 0.017 in native islets and fell to 0.465 ± 0.02 (p = 0.001) by day 3 but returned to native values by day 7 posttransplantation (0.726 ± 0.03). This technique provides a robust method for tracking and quantifying the revascularization of intraportally transplanted islets, which should enable the comparison of different strategies aimed at accelerating islet revascularization.

Hypoxia-activated cytotoxic agent tirapazamine enhances hepatic artery ligation-induced killing of liver tumor in HBx transgenic mice

Transarterial chemoembolization (TACE) is the main treatment for intermediate stage hepatocellular carcinoma (HCC) with Barcelona Clinic Liver Cancer classification because of its exclusive arterial blood supply. Although TACE achieves substantial necrosis of the tumor, complete tumor necrosis is uncommon, and the residual tumor generally rapidly recurs. We combined tirapazamine (TPZ), a hypoxia-activated cytotoxic agent, with hepatic artery ligation (HAL), which recapitulates transarterial embolization in mouse models, to enhance the efficacy of TACE. The effectiveness of this combination treatment was examined in HCC that spontaneously developed in hepatitis B virus X protein (HBx) transgenic mice. We proved that the tumor blood flow in this model was exclusively supplied by the hepatic artery, in contrast to conventional orthotopic HCC xenografts that receive both arterial and venous blood supplies. At levels below the threshold oxygen levels created by HAL, TPZ was activated and killed the hypoxic cells, but spared the normoxic cells. This combination treatment clearly limited the toxicity of TPZ to HCC, which caused the rapid and near-complete necrosis of HCC. In conclusion, the combination of TPZ and HAL showed a synergistic tumor killing activity that was specific for HCC in HBx transgenic mice. This preclinical study forms the basis for the ongoing clinical program for the TPZ-TACE regimen in HCC treatment.

Prostate-specific membrane antigen as a potential novel vascular target for treatment of glioblastoma multiforme

CONTEXT

Prostate-specific membrane antigen (PSMA) is expressed in endothelium of vessels in malignant solid tumors but not in normal vessels.

OBJECTIVE

To examine whether neovasculature of glioblastoma multiforme (GBM) expresses PSMA. Design.-After institutional review board approval at Memorial Sloan-Kettering Cancer Center, formalin-fixed paraffin-embedded tissue from 32 patients who underwent a maximally safe neurologic resection during 2004 to 2005 for GBM (World Health Organization criteria) was obtained. We performed immunohistochemical staining on the vessels of the GBM specimens for PSMA expression in tumor endothelium. The tissue samples were also stained for CD31 to verify that the PSMA was staining tumor vessels. The PSMA percent staining was scored: less than 5%, 6% to 25%, 26% to 50%, 51% to 75%, and 76% to 100%. Staining intensity was ranked as follows: 0 (none), 1+ (faint), 2+ (moderately-intense), and 3+ (maximum-intensity).

RESULTS

Immunohistochemical staining on the vessels of 32 paraffin-embedded GBM specimens revealed that all 32 (100%) specimens exhibited staining for PSMA to a variable extent. Of these, 22 of 32 specimens (69%) had more than 51% vascular staining for PSMA. The intensity of staining was 2+ to 3+ in most of the specimens (29 of 32; 91%).

CONCLUSIONS

Prostate-specific membrane antigen is expressed in the vasculature of GBM vessels, thus rendering a potential novel therapeutic vascular target. A clinical trial with a cytotoxin-conjugated antibody to PSMA is planned.

Assessment of hypoxia inducible factor levels in cancer cell lines upon hypoxic induction using a novel reporter construct

Hypoxia Inducible Factor (HIF) signaling pathway is important for tumor cells with limited oxygen supplies, as it is shown to be involved in the process of proliferation and angiogenesis. Given its pivotal role in cancer biology, robust assays for tracking changes in HIF expression are necessary for understanding its regulation in cancer as well as developing therapies that target HIF signaling. Here we report a novel HIF reporter construct containing tandem repeats of minimum HIF binding sites upstream of eYFP coding sequence. We show that the reporter construct has an excellent signal to background ratio and the reporter activity is HIF dependent and directly correlates with HIF protein levels. By utilizing this new construct, we assayed HIF activity levels in different cancer cell lines cultured in various degrees of hypoxia. This analysis reveals a surprising cancer cell line specific variation of HIF activity in the same level of hypoxia. We further show that in two cervical cancer cell lines, ME180 and HeLa, the different HIF activity levels observed correlate with the levels of hsp90, a cofactor that protects HIF against VHL-independent degradation. This novel HIF reporter construct serves as a tool to rapidly define HIF activity levels and therefore the therapeutic capacity of potential HIF repressors in individual cancers.

Oxygen saturation in premature infants at risk for threshold retinopathy of prematurity

PURPOSE

We aimed to determine if oxygen saturation, desaturations, and saturation variability play a role in progression of retinopathy of prematurity (ROP) and need for laser treatment.

METHODS

This was a retrospective case-control study. We performed chart review of premature infants in a university hospital neonatal intensive care unit consecutively examined for ROP between May 2000 and December 2001. We compared birthweight, postmenstrual age, and oxygen saturation for 3 weeks before laser treatment for threshold ROP in group 1 (n=19) (average weight at treatment 2508 grams) and group 2 (n=18) before they reached 2500 grams. Outcome measures were retinopathy progression and need for treatment.

RESULTS

Adjusting for birthweight and postmenstrual age, known predictors of ROP progression, we found that babies requiring laser treatment (group 1) had lower average daily oxygen saturation levels in the study period, significantly on 5/20 days (25%). These babies had saturations below 95% on 18/20 days (90%). Babies not requiring laser (group 2) had saturations below 95% on 2/20 days (10%). The last day on which pretreatment saturations differed significantly was 2 days before laser. Group 1 had more desaturations below 80% (6.0±3.2) than group 2 (3.2±1.2), p=0.0002 (independent samples t tests). Saturations varied more for individual group 1 infants.

CONCLUSIONS

Decreased oxygen saturation as early as 3 weeks and as late as 2 days before laser, increased number of desaturations, and saturation variability were seen in babies eventually requiring laser treatment for ROP.

Graded hypoxia modulates the invasive potential of HT1080 fibrosarcoma and MDA MB231 carcinoma cells

Spatial and temporal oxygen heterogeneity exists in most solid tumour microenvironments due to an inadequate vascular network supplying a dense population of tumour cells. An imbalance between oxygen supply and demand leads to hypoxia within a significant proportion of a tumour, which has been correlated to the likelihood of metastatic dissemination in both rodent tumour models and human patients. Experimentally, it has been demonstrated that near-anoxic in vitro exposure results in transiently increased metastatic potential in some tumour cell lines. The purpose of this study was to examine the effect of graded low oxygen conditions on the invasive phenotype of human tumour cells using an in vitro model of basement membrane invasion, in which we measured oxygen availability directly at the invasion surface of the transwell chamber. Our results show a relationship between culture vessel geometry and time to achieve hypoxia which may affect the interpretation of low oxygen experiments. We exposed the human tumour cell lines, HT1080 and MDA MB231, to graded normobaric oxygen (5% O(2)-0.2% O(2)) either during or prior to in vitro basement membrane invasion to simulate conditions of intravasation and extravasation. A secondary aim was to investigate the potential regulation of matrix metalloproteinase activity by oxygen availability. We identified significant reductions in invasive ability under low oxygen conditions for the HT1080 cell line and an increase in invasion at intermediate oxygen conditions for the MDA MB231 cell line. There were differences in the absolute activity of the individual matrix metalloproteinases, MMP-2, -9, -14, between the two cell lines, however there were no significant changes following exposure to hypoxic conditions. This study demonstrates cell line specific effects of graded oxygen levels on invasive potential and suggests that intermediate levels of low oxygen may increase metastatic dissemination.

Comparison of molecular markers of hypoxia and imaging with (60)Cu-ATSM in cancer of the uterine cervix

PURPOSE

To determine if hypoxia-related molecular markers are associated with (60)Cu labeled diacetyl-bis (N4 -methylthiosemicarbazone); ((60)Cu-ATSM) imaging of tumor hypoxia in cervical cancer.

PROCEDURES

Fifteen patients were enrolled in a prospective study and underwent evaluation of tumor hypoxia with positron emission tomography (PET) using (60)Cu-ATSM. (60)Cu-ATSM-PET imaging was compared with the expression of tissue molecular markers, which included vascular endothelial growth factor (VEGF), cyclo-oxygenase-2 (COX-2), epidermal growth factor receptor (EGFR), carbonic anyhdrase IX (CA-9), and apoptotic index.

RESULTS

Six patients had hypoxic tumors determined by (60)Cu-ATSM, and nine had non-hypoxic tumors. The 4-year overall survival estimates were 75% for patients with non-hypoxic tumors and 33% for those with hypoxic tumors (p = 0.04). Overexpression of VEGF (p = 0.13), EGFR (p = 0.05), CA-9 (p = 0.02), COX-2 (p = 0.08), and the presence of apoptosis (p = 0.005) occurred in patients with hypoxic tumors. Cox proportional hazards modeling demonstrated hypoxia as determined by (60)Cu-ATSM to be a significant independent predictor of tumor recurrence (p = 0.0287).

CONCLUSIONS

(60)Cu-ATSM hypoxia was correlated with overexpression of VEGF, EGFR, COX-2, CA-9, an increase in apoptosis, and a poor outcome.

Plausible linkage of hypoxia inducible factor-1alpha in uterine cervical cancer

Angiogenesis is essential for the development, growth and advancement of solid tumors. Angiogenesis is induced by hypoxia with angiogenic transcription factor hypoxia inducible factors (HIF). This prompted us to study the clinical implications of HIF relative to angiogenesis in uterine cervical cancers. Although there was no significant difference in HIF-1alpha histoscores and mRNA levels according to histopathological type or lymph node metastasis, HIF-1alpha histoscores and mRNA levels increased significantly with advancing cancer stages. The prognosis of 30 patients with high HIF-1alpha in uterine cervical cancers was poor (73% survival), whereas the 24-month survival rate of the other 30 patients with low HIF-1alpha was 93%. HIF-1alpha histoscores and mRNA levels were correlated with the levels of the angiogenic factors thymidine phosphorylase and interleukin-8, and HIF-1alpha might be linked with these factors in cervical cancer tissue. HIF-1alpha is a candidate for prognostic indicator as an angiogenic mediator in uterine cervical cancer.

VEGF is up-regulated by hypoxic stimulation and related to tumour angiogenesis and severity of disease in oral squamous cell carcinoma: in vitro and in vivo studies

The present study was aimed to speculate whether the up-regulation of VEGF in oral squamous cell carcinoma (OSCC) is associated with oxygen levels, tumor angiogenesis and severity of disease. Under different oxygen levels, VEGF protein production in two oral cancer cell lines was quantitatively documented by using ELISA kit. Correlations between expression of VEGF, microvessel density, and various clinico-pathologic factors were studied in forty patients with OSCC. VEGF production was continuously elevated in supernatants from both cell lines in respond to the drop of oxygen levels. When oxygen level decreased to 1%, there was a 2.1-fold and nearly a 2.9-fold elevation of VEGF production in TSCCa and GNM cell line, respectively. On hypoxia VEGF production also presented a time-dependent up-regulation in both oral cancer cell lines. VEGF positivity was correlated with regional lymph nodal involvement and clinical stage. Microvessel density was significantly higher in VEGF-positive tumors than in VEGF-negative tumors. The presence of hypoxia in oral cancers is partly responsible for the up-regulation of VEGF. The elevation of VEGF expression in OSCC tissues correlates with the increased microvessel density and severity of the disease.

Consecutive Adenine Sequences Are Potential Targets in Photosensitized DNA Damage

Based on direct spectroscopic measurements of hole transfer in DNA and quantification of the yield of DNA oxidative damage, consecutive adenine sequences were found to be a good launching site for photosensitizers to inject a hole in DNA, where the following rapid hole transfer between adenines causes a long-lived charge-separated state leading to DNA oxidative damage. According to the results, the essential requisites for an efficient and/or harmful photosensitizer are determined as follows: to be able to oxidize adenine to trigger hole transfer between adenines, and react rapidly with molecular oxygen following its reduction, avoiding charge recombination and making the reaction irreversible. These results will greatly help us to classify photosensitizers harmful to human health, and to design an improved photosensitizer for biochemical applications.

Imaging and Cancer: Research Strategy of the American College of Radiology Imaging Network

The American College of Radiology Imaging Network (ACRIN) is a cooperative group funded by the National Cancer Institute and dedicated to developing and conducting clinical trials of diagnostic imaging and image-guided treatment technologies. ACRIN's six disease site committees are responsible for developing scientific strategies and resultant trials within the framework of ACRIN's five key hypotheses: (a) Screening and early detection with imaging can reduce cancer-specific mortality. (b) Less invasive image-guided therapeutic methods can reduce the mortality and morbidity associated with treating cancer. (c) Molecular-based physiologic and functional imaging can improve the diagnosis and staging of cancer, thus improving treatment. (d) Functional imaging can portray the effectiveness of treatment earlier and more accurately, thus reducing mortality and improving the likelihood of a cure. (e) Informatics and other "smart systems" can improve the evaluation of patients with cancer, thus leading to better and more effective treatments. This article details ACRIN's research strategy according to disease site through the year 2007.

Tumor oxygenation status as a prognostic marker

Tumor oxygenation status is an independent prognostic indicator in cancer because it influences tumor progression and treatment outcome. Its quantitative value is determined by a number of tumor vascular parameters such as microvascular density, blood flow, blood volume, blood oxygen saturation, tumor tissue pO2, and resistance to oxygen diffusion within the tumor. Over the past several years, considerable time and effort have been invested into developing techniques to effectively and reliably measure the oxygenation status of a tumor. The measurement and interpretation of data obtained with currently available methods is complicated by the heterogeneity in tumor oxygenation. Currently available techniques can be broadly classified into direct invasive methods, direct non-invasive methods, and measurement of surrogate endogenous markers of tumor oxygenation. Of these methods, the Eppendorf pO2 histograph is considered the 'gold standard' and even so has several limitations. Given the importance of tumor oxygenation status in therapy and in predicting disease progression, it is imperative that reliable, globally usable, and technically simplistic methods be developed to yield a consistent, comprehensive, and reliable profile of tumor oxygenation. Until newer more reliable techniques are developed, existing independent techniques or appropriate combinations of techniques should be optimized and validated using known endpoints in tumor oxygenation status and/or treatment outcomes.

Hypoxia Is Important in the Biology and Aggression of Human Glial Brain Tumors

We investigated whether increasing levels of tissue hypoxia, measured by the binding of EF5 [2-(2-nitro-1-H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl) acetamide] or by Eppendorf needle electrodes, were associated with tumor aggressiveness in patients with previously untreated glial brain tumors. We hypothesized that more extensive and severe hypoxia would be present in tumor cells from patients bearing more clinically aggressive tumors. Hypoxia was measured with the 2-nitroimidazole imaging agent EF5 in 18 patients with supratentorial glial neoplasms. In 12 patients, needle electrode measurements were made intraoperatively. Time to recurrence was used as an indicator of tumor aggression and was analyzed as a function of EF5 binding, electrode values and recursive partitioning analysis (RPA) classification. On the basis of EF5 binding, WHO grade 2 tumors were characterized by modest cellular hypoxia (pO2s approximately 10%) and grade 3 tumors by modest-to-moderate hypoxia (pO2s approximately 10%- 2.5%). Severe hypoxia (approximately 0.1% oxygen) was present in 5 of 12 grade 4 tumors. A correlation between more rapid tumor recurrence and hypoxia was demonstrated with EF5 binding, but this relationship was not predicted by Eppendorf measurements.

Down-regulation of Rad51 and decreased homologous recombination in hypoxic cancer cells

There is an emerging concept that acquired genetic instability in cancer cells can arise from the dysregulation of critical DNA repair pathways due to cell stresses such as inflammation and hypoxia. Here we report that hypoxia specifically down-regulates the expression of RAD51, a key mediator of homologous recombination in mammalian cells. Decreased levels of Rad51 were observed in multiple cancer cell types during hypoxic exposure and were not associated with the cell cycle profile or with expression of hypoxia-inducible factor. Analyses of RAD51 gene promoter activity, as well as mRNA and protein stability, indicate that the hypoxia-mediated regulation of this gene occurs via transcriptional repression. Decreased expression of Rad51 was also observed to persist in posthypoxic cells for as long as 48 h following reoxygenation. Correspondingly, we found reduced levels of homologous recombination in both hypoxic and posthypoxic cells, suggesting that the hypoxia-associated reduction in Rad51 expression has functional consequences for DNA repair. In addition, hypoxia-mediated down-regulation of Rad51 was confirmed in vivo via immunofluorescent image analysis of experimental tumors in mice. Based on these findings, we propose a novel mechanism of genetic instability in the tumor microenvironment mediated by hypoxia-induced suppression of the homologous recombination pathway in cancer cells. The aberrant regulation of Rad51 expression may also create heterogeneity in the DNA damage response among cells within tumors, with implications for the response to cancer therapies.

Evidence that involucrin, a marker for differentiation, is oxygen regulated in human squamous cell carcinomas

The majority of hypoxic cells in squamous cell carcinomas of the head and neck and cervix express involucrin, a molecular marker for differentiation. This raises the question of whether involucrin is an oxygen-regulated protein and, if so, whether it could serve as an endogenous marker for tumour hypoxia. Consistent with oxygen regulation, involucrin protein was found to increase with increasing hypoxia in confluent cultures of moderately differentiated human SCC9 cells. Cells harvested at the point of confluence and exposed to graded concentrations of oxygen revealed a K_m of approximately 15 mmHg for involucrin induction. This is similar to K_ms for HIF-1α, CAIX and VEGF. Involucrin induction showed a steep dependence on pO₂ with a transition from minimum to maximum expression occurring over less than an order of magnitude change in pO₂. In contrast to SCC9 cells, involucrin was not induced by hypoxia in poorly differentiated SCC4 cells. It is concluded that involucrin is an oxygen-regulated protein, but that differentiation modulates its transcription status with respect to hypoxia induction.

Prognostic significance of tumor oxygenation in humans

Low tissue oxygen concentration has been shown to be important in the response of human tumors to radiation therapy, chemotherapy and other treatment modalities. Hypoxia is also known to be a prognostic indicator, as hypoxic human tumors are more biologically aggressive and are more likely to recur locally and metastasize. Herein, we discuss and summarize the various methods under investigation to directly or indirectly measure tissue oxygen in vivo. Secondly, we consider the advantages and disadvantages of each of these techniques. These considerations are made in light of our specific hypotheses that hypoxia should be measured as a continuum, not a binary measurement and that moderate, not severe hypoxia is of great biological consequence.

Tissue uptake of BSH in patients with glioblastoma in the EORTC 11961 phase I BNCT trial

PURPOSE

The uptake of the boron compound Na2B12H10-SH (BSH) in tumor and normal tissues was investigated in the frame of the EORTC phase I trial 'Postoperative treatment of glioblastoma with BNCT at the Petten Irradiation Facility' (protocol 11961).

METHODS AND MATERIALS

The boron concentration in blood, tumor, normal brain, dura, muscle, skin and bone was detected using inductively coupled plasma-atomic emission spectroscopy in 13 evaluable patients. In a first group of 10 patients 100 mg BSH/kg bodyweight (BW) were administered; a second group of 3 patients received 22.9 mg BSH/kg BW. The toxicity due to BSH was evaluated.

RESULTS

The average boron concentration in the tumor was 19.9 +/- 9.1 ppm (1 standard deviation (SD)) in the high dose group and 9.8 +/- 3.3 ppm in the low dose group, the tumor/blood ratios were 0.6 +/- 0.2 and 0.9 +/- 0.2, respectively. The highest boron uptake has been detected in the dura, very low uptake was found in the bone, the cerebro-spinal fluid and especially in the brain (brain/blood ratio 0.2 +/- 0.02 and 0.4 +/- 0.2). No toxicity was detected except flush-like symptoms in 2 cases during a BSH infusion at a much higher speed than prescribed.

CONCLUSION

BSH proved to be safe for clinical application at a dose of 100 mg BSH/kg infused and at a dose rate of 1 mg/kg/min. The study underlines the importance of a further investigation of BSH uptake in order to obtain enough data for significant statistical analysis. The boron concentration in blood seems to be a quite reliable parameter to predict the boron concentration in other tissues.

Targeting the tumor blood vessel network to enhance the efficacy of radiation therapy

It has been well established that the vascularization of solid tumors is a prerequisite if a clinically relevant size is to be reached. For progressive tumor growth, the vessel network must continuously expand to satisfy the neoplastic cells' nutritional needs and waste product removal requirements. This utter reliance of the tumor on its vasculature provides a logical target for new approaches to cancer therapy. Indeed, there currently exists a great deal of enthusiasm for the development of interventions that compromise the growth and/or function of the tumor neovasculature. Two primary directions are being pursued. Inhibitors of angiogenesis seek to interrupt the angiogenic process to prevent new vessel formation. Antivascular approaches aim to cause direct damage to the tumor endothelium and thus lead to extensive secondary neoplastic cell death. The application of such strategies as adjuvants to conventional radiation treatments offers unique opportunities to develop more effective cancer therapies.

Prognostic value of vascular endothelial growth factor in Stage IB carcinoma of the uterine cervix

PURPOSE

To clarify the role of vascular endothelial growth factor (VEGF) expression as an independent prognostic factor in Stage IB cervical cancer.

METHODS AND MATERIALS

A total of 117 patients with Stage IB cervical cancer who had undergone radical hysterectomy and pelvic lymph node dissection with complete histopathologic examination were included. Eighty-eight (75.2%) patients received postoperative radiotherapy and/or chemotherapy. VEGF expression was examined using immunohistochemistry.

RESULTS

Of 117 patients, 35 (29.9%) showed high-intensity VEGF expression and 69 (59%) had a high score for area of VEGF expression. Strong correlations were found between high VEGF intensity and both deep stromal invasion (p = 0.01) and positive pelvic lymph nodes (p = 0.03). The area of VEGF expression was significantly associated with tumor size (p = 0.02). In a multivariate analysis, high VEGF intensity (p = 0.009) and tumor size (p = 0.01) were significant prognostic factors for overall survival and disease-free survival (p = 0.001 and p = 0.003, respectively). However, the area of VEGF expression was not a prognostic factor for overall survival or disease-free survival.

CONCLUSION

Our findings on the correlation between VEGF expression and prognosis were conflicting. Functional and quantitative tools to assess tumor angiogenesis in addition to the expression of VEGF need to be developed and would be helpful to support the finding that tumor angiogenesis correlates significantly with prognosis in early-stage cervical cancer.

Circulating levels of vascular endothelial growth factor in patients with oral squamous cell carcinoma

Angiogenesis is a crucial step in tumour growth, progression, and metastasis. Recently, many angiogenic factors have been identified. Vascular endothelial growth factor (VEGF) is thought to be one such angiogenic factor and is also thought to be a selective mitogen for vascular endothelial cells. The present study was designed to determine the circulating levels of VEGF in human oral squamous cell carcinoma (OSCC) and to investigate its correlation with the clinicopathologic features and prognosis. The study consisted of 10 healthy volunteers and 31 patients with OSCC. A quantitative sandwich enzyme immunoassay technique was used to measure the concentrations of VEGF in the sera. The data obtained from the experiment were analysed with independent-samples t-test. The mean concentrations of serum VEGF were 148.80 +/- 64.17 pg x ml(-1) (range, 59-231 pg x ml(-1)) in normal controls and 567.97 +/- 338.17 pg x ml(-1) (range, 136-1,892 pg x ml(-1)) in OSCC group. Statistical analysis showed that the mean VEGF level in sera of OSCC patients was significantly higher than that in healthy controls (P<0.001). The serum VEGF levels of OSCC patients correlated with condition of nodal metastasis (P<0.05) and clinical stage (P<0.05) but not with sex (P>0.05) and degree of differentiation (P>0.05). Our study showed that OSCC was associated with significantly elevated serum VEGF concentration. Higher level of serum VEGF also correlated with lymph node metastasis and clinical stage of OSCC. Determination of serum VEGF concentration may be helpful to distinguish OSCC patients from the normal individuals.

Serum VEGF levels in patients undergoing primary radiotherapy for cervical cancer: impact on progression-free survival

Vascular endothelial growth factor (VEGF) plays an important role in the regulation of tumour growth and metastasis. It was the aim of this study to examine the impact of serum VEGF levels on the likelihood of response to radiotherapy and on the disease-free survival in patients with cervical cancer. Blood was taken before commencing treatment and serum VEGF was assessed by quantitative ELISA in 23 patients with cervical cancer stage IB-IVA undergoing primary radiotherapy. Serum VEGF levels were correlated with clinical and histopathologic factors as well as with response to radiotherapy and time to progression. Nineteen of the 23 patients had a complete response and four patients had persistent disease at 3 months. The median follow-up was 25 months (95% confidence interval: 23.5-26.5 months). At the time of analysis, eight patients were tumour-free and 15 patients had tumour progression; 12 of these 15 patients died of disease. Overall, the median serum VEGF level was 244 pg/ml (range 31.9-817.6 pg/ml). All four patients with local failure had VEGF levels >244 pg/ml, whereas 11 of the 19 patients with complete response had serum VEGF of < or =244 pg/ml (P=0.035). The median time to progression was 5 months in patients with VEGF of >244 pg/ml compared to 19 months in patients with VEGF of < or = 244 pg/ml (log rank, P=0.003). In multivariate analysis, serum VEGF, tumour size and histological type, but not the patient's age, stage and grade of histological differentiation influenced the progression-free survival. Elevated pre-therapeutic serum VEGF levels are associated with poor response and a shorter time to progression in patients with cervical cancer undergoing primary radiotherapy.

Differences of vascular endothelial growth factor (VEGF) expression between liver and abdominal metastases from colon cancer. Implications for the treatment with VEGF inhibitors

The vascular endothelial growth factor (VEGF) plays a central role in promoting angiogenesis, and it is the target of innovative anti-cancer therapies. In colorectal carcinomas, differences in the VEGF expression have been found between the primary tumor and its metastases. We postulated that differences in the VEGF expression may also exist between liver and abdominal metastases from colon cancer. Consecutive colon cancer patients with liver or abdominal metastases were considered eligible for the study. Biopsies had to be performed before chemotherapy and the VEGF analysis were conducted through immunohistochemistry. The staining results were correlated to the metastatic pattern. The study population consisted of 41 patients with a metastatic site in the liver in 19 patients and the abdomen in 22 patients. A positive VEGF staining was found in 19 of the 41 metastatic samples (46%). Cases with positive VEGF expression were found more frequently in abdominal (15 out of 22 patients; 68%) than in liver metastases (4 out of 19 patients; 21%). Also, the degree of VEGF immunoreactivity was significantly higher in abdominal than in liver metastases. Evidence is supported that the VEGF expression may be different between colon cancer metastatic sites. The efficacy of anti-VEGF treatments may depend on the VEGF expression status, and this finding deserves further investigation.

Tumor hypoxia: definitions and current clinical, biologic, and molecular aspects

Tissue hypoxia results from an inadequate supply of oxygen (O(2)) that compromises biologic functions. Evidence from experimental and clinical studies increasingly points to a fundamental role for hypoxia in solid tumors. Hypoxia in tumors is primarily a pathophysiologic consequence of structurally and functionally disturbed microcirculation and the deterioration of diffusion conditions. Tumor hypoxia appears to be strongly associated with tumor propagation, malignant progression, and resistance to therapy, and it has thus become a central issue in tumor physiology and cancer treatment. Biochemists and clinicians (as well as physiologists) define hypoxia differently; biochemists define it as O(2)-limited electron transport, and physiologists and clinicians define it as a state of reduced O(2) availability or decreased O(2) partial pressure that restricts or even abolishes functions of organs, tissues, or cells. Because malignant tumors no longer execute functions necessary for homeostasis (such as the production of adequate amounts of adenosine triphosphate), the physiology-based definitions of the term "hypoxia" are not necessarily valid for malignant tumors. Instead, alternative definitions based on clinical, biologic, and molecular effects that are observed at O(2) partial pressures below a critical level have to be applied.

Targeting tumor blood vessels: an adjuvant strategy for radiation therapy

BACKGROUND AND PURPOSE

The neovascularization of tumor cells is a prerequisite if a clinically relevant tumor size is to be reached. A continuously expanding vessel network supplying nutritional requirements and removing waste products is essential for continued tumor development, growth and survival.

RESULTS

In many tumors, the growing endothelium is unable to fully support the demands of the neoplastic cell population. As a consequence of the inadequacies of the resulting aberrant vasculature, microenvironmental conditions develop in tumors which are not only detrimental to the response of tumors to conventional anticancer treatments, but may lead to or predispose cells to genetic modifications resulting in more aggressive phenotypes and higher metastatic potential. Yet the utter dependence of the tumor on its induced vessel formation for growth, survival and spread has also created a great deal of enthusiasm for developing therapeutic approaches to specifically targeting the tumor microcirculation.

CONCLUSIONS

The application of such strategies as adjuvants to conventional radiation treatments offers unique opportunities to develop more effective cancer therapies.

Vascular endothelial growth factor (VEGF) expression is a prognostic factor for radiotherapy outcome in advanced carcinoma of the cervix

The aim of the study was to evaluate VEGF expression in tumour biopsies as a prognostic factor for radiotherapy outcome in advanced carcinoma of the cervix. A retrospective study was carried out on 100 patients. Pre-treatment tumour VEGF expression was examined immunohistochemically in formalin-fixed, paraffin-embedded biopsies using a widely available commercial antibody. A semi-quantitative analysis was made using a scoring system of 0, 1, 2, and 3, for increasing intensity of staining. High VEGF expression was associated with a poor prognosis. A univariate log rank analysis found a significant relationship with overall survival (P = 0.0008) and metastasis-free survival (P = 0.0062), but not local control (P = 0.23). There was no correlation between VEGF expression and disease stage, tumour differentiation, patient age, or tumour radiosensitivity (SF2). In a Cox multivariate analysis of survival VEGF expression was the most significant independent prognostic factor (P = 0.001). After allowing for VEGF only SF2 was a significant prognostic factor (P = 0.003). In conclusion, immunohistochemical analysis of VEGF expression is a highly significant and independent prognostic indicator of overall and metastasis-free survival for patients treated with radiotherapy for advanced carcinoma of the cervix. It is also a rapid and easy method that could be used in the clinical setting, to identify patients at high risk of failure with conventional radiotherapy who may benefit from novel approaches or chemoradiotherapy.

Clinical benefit from erythropoietin

Advances continue in erythropoietin biology, and additional data reviewed here have recently become available on complex feedback mechanisms describing the interrelations of hypoxia and its effects on anemia and tumor behavior (eg, apoptosis, angiogenesis). In addition to biology, other clinically relevant data in oncology are included and an attempt is made to identify patients who are most likely to benefit from treatment. The latter aspects will better define the profile of the target patient, probably prevent overtreatment, and improve cost-benefit ratios. Interesting data on radiotherapy results improved by increasing tissue hemoglobin have been published but will need further confirmation.

The constitutive level of vascular endothelial growth factor (VEGF) is more important than hypoxia-induced VEGF up-regulation in the angiogenesis of human melanoma xenografts

Angiogenesis of tumours might develop as a result of environmental conditions, such as hypoxia, and/or as a result of genetic alterations specific for tumour cells. The relative contributions of these mechanisms were investigated by comparing the in vivo expression of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) to the hypoxic fraction, the angiogenic potential and the vascular density of four human melanoma lines (A-07, D-12, R-18, U-25) grown intradermally in Balb/c nu/nu mice. VEGF expression, bFGF expression and expression of pimonidazole, a marker of hypoxic cells, were investigated by immunohistochemistry. An association between high VEGF and bFGF expression and high angiogenic potential was detected, suggesting an important role for VEGF/bFGF in the angiogenesis of melanomas. High VEGF/bFGF expression was also related to low hypoxic fraction and high vascular density. Thus, the constitutive, genetically determined level of VEGF was probably more important than hypoxia-induced upregulation in the angiogenesis of the melanoma xenografts.