Prognostic significance of vascular endothelial growth factor protein in node-negative breast carcinoma

Targeting signal transduction pathways in metastatic breast cancer: a comprehensive review

Greater understanding of the underlying etiology and biology of breast cancer is enabling the clinical development of targeted therapies for metastatic breast cancer (MBC). Following the successful introduction of trastuzumab, the first human epidermal growth factor receptor (HER) biologically targeted therapy to become widely used in MBC patients, other agents have been developed. Novel agents include monoclonal antibodies such as pertuzumab, which bind to receptors on the cell surface, and tyrosine kinase inhibitors (TKIs) such as lapatinib, which target intracellular pathways such as that of the epidermal growth factor receptor. There is also growing clinical experience with antiangiogenic agents, particularly in combination with chemotherapy. These include the monoclonal antibody bevacizumab, which targets vascular endothelial growth factor receptor, and multitargeted TKIs with antiangiogenic and antiproliferative activities, such as sunitinib. Combination treatment with multiple agents targeting both the HER family and angiogenic pathways (e.g., trastuzumab plus bevacizumab) is also showing activity in the clinical setting. Despite recent advances, there are unanswered questions regarding the management of MBC with targeted agents. Future studies are necessary to determine the optimal combinations, doses, and schedules required to maximize clinical activity while minimizing toxicity. Despite the temptation to use a targeted agent in all patients, identification of patient subgroups most likely to benefit must be a key goal and will be critical to the successful future use of these treatments. The aim of this review is to summarize some of the key signaling pathways involved in tumor progression and some of the novel therapies that are in development for MBC.

Bevacizumab and breast cancer: current therapeutic progress and future perspectives

Bevacizumab is a humanized monoclonal antibody to VEGF, and the incorporation of bevacizumab to chemotherapy is one of the rapidly evolving areas in the treatment of breast cancer. Bevacizumab in combination with chemotherapy versus chemotherapy alone improves progression-free survival and increases the response rate in first-line therapy for locally recurrent or metastatic breast cancer. This approach has been and is still being evaluated for early breast cancer in neoadjuvant and adjuvant settings. Bevacizumab is well tolerated and has an established tolerability profile. Both tumor- and host-related biomarkers of bevacizumab activity, response and benefit are emerging from Phase I, II and III clinical trials. The biomarkers of benefit will ultimately help identify the subgroups of patients who specifically benefit from anti-VEGF therapy with bevacizumab.

Axillary lymph node metastasis: CA-15-3 and carcinoembryonic antigen concentrations in fine-needle aspirates for preoperative diagnosis in patients with breast cancer

PURPOSE

To assess whether concentrations of the tumor markers breast cancer antigen 15-3 (CA-15-3) and carcinoembryonic antigen (CEA) in fine-needle aspirates (FNAs) differ between benign and malignant lymph nodes and whether FNA concentrations of the tumor markers can improve the sensitivity of axillary lymph node (ALN) FNA in patients with breast cancer.

MATERIALS AND METHODS

An Institutional Review Board approved this study. All subjects gave written informed consent. Ultrasonographically (US)-guided FNA was performed for 134 ALNs in 134 women (mean age, 49.6 years; range, 28-92 years) with breast cancer. Immediately after obtaining an FNA cytology specimen, the needle was rinsed with 1 mL of normal saline solution. CEA and CA-15-3 concentrations were measured in the washout. Of the 134 ALNs, 86 were malignant and 48 were benign. Sensitivity of FNA cytology alone was compared with the sensitivity of FNA cytology and CEA and CA-15-3 FNA concentrations.

RESULTS

Patients with a positive metastatic diagnosis had significantly higher FNA concentrations of CEA and CA-15-3 than did those with a negative diagnosis (both P = .02). FNA cytology sensitivity was 87.2%, and the combined sensitivity of FNA cytology and FNA tumor marker concentrations was 96.5% (P = .01).

CONCLUSION

Evaluation of CEA and CA-15-3 concentrations in FNA could be helpful for the preoperative diagnosis of ALN metastasis in patients with breast cancer. (c) RSNA, 2010.

Targeting miR-205 in breast cancer

As small non-coding regulatory RNAs, microRNAs are capable of silencing gene expression by translational repression or mRNA degradation. Accumulating evidence indicates that deregulation of microRNAs is often associated with human malignancies and suggests a causal role of microRNAs in neoplasia, presumably because microRNAs can function as oncogenes or tumor suppressors. Among them, miR-205 is significantly underexpressed in breast tumors compared with matched normal breast tissue although miR-205 has been shown to be upregulated in some other type of tumors. Furthermore, breast cancer cell lines, including MCF-7 and MDA-MB-231, express a lower level of miR-205 than the non-malignant MCF-10A cells. Ectopic expression of miR-205 significantly inhibits cell proliferation and anchorage-independent growth as well as cell invasion. These findings establish the tumor suppressive role of miR-205, which is probably through direct targeting of oncogenes such as ErbB3 and Zeb1. Therefore, miR-205 may serve as a unique therapeutic target for breast cancer.

Pazopanib: an antiangiogenic drug in perspective

Pazopanib, a tyrosine kinase inhibitor targeted to angiogenesis, has been tested in preclinical and clinical trials and has shown promising activity against a variety of solid tumors, such as renal cancer, all of which are related to the angiogenic pathway. It has a safety profile related to this mechanism of action. Diarrhea, hypertension, hair depigmentation and nausea are the most common side effects. Pazopanib is currently under evaluation as monotherapy and in combination with some potentially synergistic agents of proven activity.

Angiogenesis inhibition in cancer therapy: platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) and their receptors: biological functions and role in malignancy

Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen in vitro and an angiogenic inducer in a variety of in vivo models. VEGF gene transcription is induced in particular in hypoxic cells. In developmental angiogenesis, the role of VEGF is demonstrated by the finding that the loss of a single VEGF allele results in defective vascularization and early embryonic lethality. 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. Platelet-derived growth factor (PDGF) is mainly believed to be an important mitogen for connective tissue, and also has important roles during embryonal development. Its overexpression has been linked to different types of malignancies. Thus, it is important to understand the physiology of VEGF and PDGF and their receptors as well as their roles in malignancies in order to develop antiangiogenic strategies for the treatment of malignant disease.

Gastric cancer risk predisposition and prognostic significance of vascular endothelial growth factor (VEGF) gene polymorphisms--a case-control study in an Omani population

Vascular endothelial growth factor (VEGF) plays a central role in angiogenesis, tumor growth, and metastasis. We investigated the associations between VEGF gene polymorphisms and gastric cancer (GC) risk predisposition and prognostic characteristics in an Omani population, an ethnic group which has not been studied previously. We analyzed three VEGF polymorphisms (+405 G/C, -460 T/C, and +936 C/T) by the extraction of genomic DNA from peripheral blood of 130 GC patients and 130 control subjects followed by VEGF genotyping using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis. There were no significant associations between the VEGF polymorphisms and GC risk. There were significant correlations between the +405 C/C genotype and both poor tumor differentiation (P = 0.007) and lymph node metastasis (P = 0.03) and between the -460 T/T genotype and poor tumor differentiation (P = 0.03) with a statistical trend toward lymph node involvement (P = 0.05). VEGF gene polymorphisms had no significant effects on survival, but the VEGF +405 G/G genotype had a statistical trend toward lower survival rate with a hazard ratio of 1.6 [95% CI, 0.9-2.9] compared with the VEGF +405 CC/GC combined genotype (P = 0.049). Multivariate analysis showed that disease stage at diagnosis and the +405 G/G genotype were independent variables of adverse prognostic significance. There were no associations between the six common haplotypes identified and both GC risk predisposition and survival. The current study suggests that VEGF polymorphisms have no role in GC risk predisposition, but may have prognostic significance in GC patients.

The role of antiangiogenesis therapy: bevacizumab and beyond

The importance of angiogenesis in tumour growth and development is well known. Overexpression of vascular endothelial growth factor (VEGF), the key mediator of angiogenesis, is associated with poor prognosis in cancer. As a result, several therapeutic agents that inhibit the actions of VEGF or its receptors are currently in development for use in advanced solid tumours, such breast, colorectal, lung and renal cancer. Clinical data from trials of anti-VEGF agents in this group of tumours are discussed, with a particular focus on the efficacy and safety of bevacizumab, the anti-VEGF agent at the most advanced stage of development in those tumour types. Future potential uses of bevacizumab in cancer therapy will be discussed.

The role of vascular endothelial growth factor SNPs as predictive and prognostic markers for major solid tumors

Angiogenesis is crucial for development and metastasis of tumors, and vascular endothelial growth factor (VEGF) is a key mediator of this process. The importance of VEGF in tumorigenesis and tumor progression makes it an attractive target for the development of anticancer therapies. Inhibition of angiogenesis has shown promising clinical efficacy; however, not all patients treated with antiangiogenic agents derive benefit from them. Some patients are predisposed to refractory disease, whereas others develop resistance after initial response. Patients may also have different severity of drug-related adverse events. Optimization of drug administration based on disease status and individual responsiveness is important in limiting the treatment failure and minimization of side-effects. Single nucleotide polymorphisms (SNP) in VEGF may alter VEGF protein concentrations, influence the process of angiogenesis, and may relate to interindividual variation in the risk and progression of selected tumors, and their resistance to treatments. This review examines the role of SNPs in the VEGF gene as predictive and prognostic markers for major solid tumors, including the breast, non-small cell lung, colorectal, and prostate cancers. Selected VEGF SNPs seem to be associated with risk of these cancers; however, there is lack of unanimity in findings, in part influenced by differences in study design and analysis.

Significantly higher levels of vascular endothelial growth factor (VEGF) and shorter survival times for patients with primary operable triple-negative breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) lacking expression of steroid receptors and human epidermal growth factor receptor 2, having chemotherapy as the only therapeutic option, is characterised by early relapses and poor outcome. We investigated intratumoural (i.t.) levels of the pro-angiogenic cytokine vascular endothelial growth factor (VEGF) and survival in patients with TNBC compared with non-TNBC.

PATIENTS AND METHODS

VEGF levels were determined by an enzyme immunosorbent assay in a retrospective series consisting of 679 consecutive primary breast cancer patients.

RESULTS

Eighty-seven patients (13%) were classified as TNBC and had significantly higher VEGF levels; median value in TNBC was 8.2 pg/microg DNA compared with 2.7 pg/microg DNA in non-TNBC (P < 0.001). Patients with TNBC had statistically significant shorter recurrence-free survival [hazard ratio (HR) = 1.8; P = 0.0023], breast cancer-corrected survival (HR = 2.2; P = 0.004) and overall survival (HR = 1.8; P = 0.005) compared with non-TNBC. Patients with TNBC relapsed earlier than non-TNBC; mean time from diagnosis to first relapse was 18.8 and 30.7 months, respectively. The time between first relapse and death was also shorter in TNBC: 7.5 months versus 17.5 months in non-TNBC (P = 0.087).

CONCLUSIONS

Our results show that TNBC have higher i.t. VEGF levels compared with non-TNBC. Ongoing clinical trials will answer if therapy directed towards angiogenesis may be an alternative way to improve outcome in this poor prognosis group.

Cytokine Genotype Polymorphisms in Breast Carcinoma: Associations of TGF-β1 with Relapse

Markers of angiogenesis, cell proliferation, and cytokine regulation are associated with the development and course of autoimmune and malignant diseases. We investigated associations between cytokine production genotypes in breast cancer patients compared with controls and explored associations with known prognostic indices and relapse status. Eighty-eight females with breast carcinoma (BC) were studied in this case-control study comparing the cytokine genotypes of TNF-alpha TGF-beta1, IL-10, IL-6, and IFN-gamma with controls. Cytokine polymorphisms were identified by sequence-specific primers for codons, introns, or promoters regulating cytokine production. Patient characteristics, such as estrogen and progesterone receptor status, DNA ploidy, Her-2 neu expression, lymph node involvement, tumor size, and relapse status were evaluated. Cytokine genotypes were not associated with breast cancer compared with controls. Correlations between TGF-beta1 high-production genotypes and greater than four positive lymph nodes (OR=2.3; p=ns) and TNF-alpha high-production genotype and the mean level of estrogen receptor expression (66 +/- 24 vs. 34 +/- 36, p=0.016) were identified. The median patient follow-up interval from diagnosis to evaluation was 50.1 months (range 13-387 months). Relapse status was known for 84 of the patients. The odds of relapse in TGF-beta1 codon 10 CC genotypes was 2.81 times that in TGF-beta1 high-production genotypes (OR=2.81; 95% CI for OR: 1.0, 7.8; p=0.04). Mean progesterone receptor expression was decreased in relapsed patients (40.9 +/- 29.9% vs. 23.1 +/- 24.5, p=0.05). The other cytokine genotypes studied (IL-10, IL-6, IFN-gamma, and TNF-alpha production were not associated with breast cancer overall or relapse status. In this study, TGF-beta1 low-production genotypes (TGF-beta1 10 CC) were associated with an increased odds of disease relapse. This finding should be confirmed in a longitudinal study to further investigate the regulatory function of cytokine production as a prognostic indicator of relapse.

Broad antitumor activity in breast cancer xenografts by motesanib, a highly selective, oral inhibitor of vascular endothelial growth factor, platelet-derived growth factor, and Kit receptors

PURPOSE

Angiogenesis plays a critical role in breast cancer development and progression. Vascular endothelial growth factor (VEGF) is a potent angiogenic factor that regulates endothelial cell proliferation and survival. We investigated the effects of motesanib, a novel, oral inhibitor of VEGF receptors 1, 2, and 3; platelet-derived growth factor receptor; and Kit receptor, on the growth of xenografts representing various human breast cancer subtypes.

EXPERIMENTAL DESIGN

Athymic nude mice were implanted with MCF-7 (luminal) or MDA-MB-231 (mesenchymal) tumor fragments or Cal-51 (mixed/progenitor) tumor cells. Once tumors were established, animals were randomized to receive increasing doses of motesanib alone or motesanib plus cytotoxic chemotherapy (docetaxel, doxorubicin, or tamoxifen).

RESULTS

Across all three xenograft models, motesanib treatment resulted in significant dose-dependent reductions in tumor growth, compared with vehicle-treated controls, and in marked reductions in viable tumor fraction and blood vessel density. No significant effect on body weight was observed with compound treatment compared with control-treated animals. Motesanib did not affect the proliferation of tumor cells in vitro. There was a significantly greater reduction in xenograft tumor growth when motesanib was combined with docetaxel (MDA-MB-231 tumors) or with the estrogen receptor modulator tamoxifen (MCF-7 tumors), compared with either treatment alone, but not when combined with doxorubicin (Cal-51 tumors).

CONCLUSIONS

Treatment with motesanib alone or in combination with chemotherapy inhibits tumor growth in vivo in various models of human breast cancer. These data suggest that motesanib may have broad utility in the treatment of human breast cancer.

Value of dynamic contrast-enhanced MRI and correlation with tumor angiogenesis in bladder cancer

OBJECTIVE

The aim of this study was to investigate dynamic contrast-enhanced MRI (DCE-MRI) for the noninvasive measurement of bladder cancer angiogenesis by correlation with microvessel density, histologic grade, and tumor staging, and to predict the outcome of local recurrence.

MATERIALS AND METHODS

Twenty-four patients with bladder cancer were examined using DCE-MRI. Hemodynamic parameters obtained by DCE-MRI included peak time enhancement in the first minute (E(max/1)) after contrast administration, second minute (E(max/2)), third minute (E(max/3)), fourth minute (E(max/4)), and fifth minute (E(max/5)), and the steepest slope. Microvessel density was identified by immunostaining of endothelial cells using FVIII-related antigen. The Mann-Whitney U test, multivariate discriminant analysis, Spearman's correlation coefficient, and analysis of variance were used for statistical analysis.

RESULTS

Correlation was seen between DCE-MRI parameters (E(max/1) and steepest slope) and microvessel density (p < 0.05). E(max/1) and steepest slope were found to have a statistically significant correlation with histologic grade (p < 0.05 and p < 0.01, respectively). A significant difference was seen between groups of patients with and without local recurrence with regard to two of the DCE-MRI parameters (p < 0.05 for E(max/1) and E(max/2)).

CONCLUSION

The contrast enhancement patterns on DCE-MRI are influenced by tumor angiogenesis, as reflected by elevated microvessel density expression. Therefore, they are valuable indicators for assessing tumor angiogenic activity and tumor neovascularization in bladder cancers.

A specific vascular endothelial growth factor receptor tyrosine kinase inhibitor enhances the antiproliferative effect of trastuzumab in human epidermal growth factor receptor 2 overexpressing breast cancer cell lines

BACKGROUND

Trastuzumab has been found to have potent antiproliferative effects in human epidermal growth factor receptor 2 (HER-2)-overexpressing human breast tumors. Inhibition of vascular endothelial growth factor receptor (VEGFR), a protein often overexpressed in breast carcinoma, has been shown to induce apoptosis.

METHODS

Breast carcinoma cell lines were cultured with increasing doses of trastuzumab and/or a VEGFR tyrosine kinase inhibitor (TKI). Growth inhibition and apoptosis were assessed after 5 days and 48 hours of treatment, respectively. Combination index values were calculated to determine the effectiveness of this drug combination.

RESULTS

A dose-dependent growth inhibition was shown in all cell lines tested with the VEGFR TKI, whereas trastuzumab was effective only in the HER-2-positive cells. A synergistic interaction was shown in the HER-2-overexpressing cell lines, accompanied by an increase in apoptosis.

CONCLUSIONS

The combination of trastuzumab and a VEGFR TKI may be of therapeutic value in select breast cancer patients.

Autocrine human growth hormone promotes tumor angiogenesis in mammary carcinoma

Accumulating literature implicates pathological angiogenesis and lymphangiogenesis as playing key roles in tumor progression. Autocrine human growth hormone (hGH) is a wild-type orthotopically expressed oncogene for the human mammary epithelial cell. Herein we demonstrate that autocrine hGH expression in the human mammary carcinoma cell line MCF-7 stimulated the survival, proliferation, migration, and invasion of a human microvascular endothelial cell line (HMEC-1). Autocrine/paracrine hGH secreted from mammary carcinoma cells also promoted HMEC-1 in vitro tube formation as a consequence of increased vascular endothelial growth factor-A (VEGF-A) expression. Semiquantitative RT-PCR analysis demonstrated that HMEC-1 cells express both hGH and the hGH receptor (hGHR). Functional antagonism of HMEC-1-derived hGH reduced HMEC-1 survival, proliferation, migration/invasion, and tube formation in vitro. Autocrine/paracrine hGH secreted by mammary carcinoma cells increased tumor blood and lymphatic microvessel density in a xenograft model of human mammary carcinoma. Autocrine hGH is therefore a potential master regulator of tumor neovascularization, coordinating two critical processes in mammary neoplastic progression, angiogenesis and lymphangiogenesis. Consideration of hGH antagonism to inhibit angiogenic processes in mammary carcinoma is therefore warranted.

MYC in breast tumor progression

Breast cancer is the second leading cause of cancer deaths and is the most frequently diagnosed cancer in women of industrialized nations. Breast cancer progression is a multistep process involving genetic and epigenetic alterations that drive normal breast cells into highly malignant derivatives with metastatic potential. MYC is a proto-oncogene whose protein product contains a basic helix-loop-helix domain. MYC functions as a transcription factor regulating up to 15% of all human genes. MYC is regulated at multiple levels, and the protein is a downstream effector of several signaling pathways. In breast cancer cells, MYC target genes are involved in cell growth, transformation, angiogenesis and cell-cycle control. BRCA1 is linked to transcriptional regulation through interaction with MYC. Although the relationship between amplification and overexpression is not clearly delineated, MYC amplification is significantly correlated with aggressive tumor phenotypes and poor clinical outcomes. MYC amplification is emerging as an important predictor of response to HER2-targeted therapies and its role in BRCA1-associated breast cancer makes it an important target in basal-like/triple-negative breast cancers.

VEGF gene polymorphisms and susceptibility to colorectal cancer disease in Italian population

BACKGROUND

The vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen involved in the process of angiogenesis, a crucial phase in tumor growth and metastasis. We carried out a case-control study to evaluate whether polymorphisms of VEGF gene modulate the risk of developing colorectal cancer disease (CCD).

MATERIALS AND METHODS

We evaluated VEGF -2578A/C, -460T/C, and +405C/G genotypes obtained from a series of 302 CCD patients and 115 controls from the Italian population using polymerase chain reaction restriction fragment length polymorphism assay.

RESULTS

Strong linkage disequilibrium (LD) was detected between -2578A/C and -460T/C (D' = 0.97; CI = 0.93-1) and between -2578A/C and +405C/G (D' = 0.97; CI = 0.98-1) in the case group. Complete LD was detected between -2578A/C and +405C/G and between -460T/C and +405C/G (D' = 1; CI = 0.84-1; CI = 0.82-1, respectively) in the control group. A reduced risk for the disease was associated with -2578C/A and -2578C/C (odds ratio (OR) = 0.34, CI = 0.162-0.676 and OR = 0.38, CI = 0.181-0.775, respectively). A direct association was found for carriers of the VEGF -460C/C polymorphism (OR = 3.55; CI = 1.659-8.469). We identified a protective haplotype -2578A, -460T, and +405G (OR = 0.04; CI = 0.009-0.19) and two different high-risk haplotypes -2578A, -460C, and +405G (OR = 1.90; CI = 1.31-2.27) and -2578C, -460C, and +405C (OR = 9.62; CI = 1.3-70.87).

CONCLUSIONS

The present study suggests that the VEGF gene polymorphisms may play a role in the development of colorectal cancer.

Correlation between steroid receptors, angiogenic factors, and classical prognostic parameters in node-negative breast cancer patients

Breast cancer (BC) progression is an estrogen receptor (ER) signaling- and angiogenesis-dependent process. This study investigated relationships between classical prognostic factors and biomarkers ER, PR, VEGF, and bFGF in node-negative BC patients. Positive correlation between ER and both PR (p < 0.001) or FGF (p = 0.04) levels indicates ER-regulated expression of these factors and a potential synergistic effect of ER and bFGF in tumor progression. Aside from correlation of age with ER and bFGF levels (p = 0.003; p = 0.05; respectively), no correlation of biomarkers with classical prognostic parameters was found, indicating that those biomarkers could be independent prognostic factors.

Assessing tumor angiogenesis in histological samples

Tumor neovascularization acquires vessels through a number of processes, including angiogenesis, vasculogenesis, vascular remodelling, intussusception, and possibly vascular mimicry in certain tumors. The end result of the tumor vasculature has been quantified by counting the number of immunohistochemically identified microvessels in areas of maximal vascularity so-called hot spots. Other techniques have been developed, such as Chalkley counting and the use of image analysis systems that are robust and reproducible as well as more objective. Many of the molecular pathways that govern tumor neovascularization have been identified, and many reagents are now available to study these tissue sections. These include angiogenic growth factors and their receptors, cell adhesion molecules, proteases, and markers of activated, proliferating, cytokine-stimulated, or angiogenic vessels, such as CD105. It is also possible to differentiate quiescent from active vessels. Other reagents that can identify proteins involved in microenvironmental influences such as hypoxia have also been generated. Although the histological assessment of tumor vascularity is used mostly in the research context, it may also have clinical applications if appropriate methodology and trained observers perform the studies.

Hypoxia-inducible factor-2alpha correlates to distant recurrence and poor outcome in invasive breast cancer

Differential regulation as well as target gene specificity of the two hypoxia-inducible factor (HIF)-alpha subunits HIF-1alpha and HIF-2alpha in various tumors and cell lines have been suggested. In breast cancer, the prognostic significance of HIF-1alpha is not clear-cut and that of HIF-2alpha is largely unknown. Using IHC analyses of HIF-1alpha, HIF-2alpha, and vascular endothelial growth factor (VEGF) expression in a tissue microarray of invasive breast cancer specimens from 512 patients, we investigated the expression patterns of the 2 HIF-alpha subunits in relation to established clinicopathologic variables, VEGF expression, and survival. HIF-1alpha and HIF-2alpha protein levels and their effect on survival were additionally analyzed in a second cohort of 179 patients. To evaluate the individual role of each subunit in the hypoxic response and induction of VEGF, HIF-alpha protein and HIF-alpha and VEGF mRNA levels were further studied in cultured breast cancer cells after hypoxic induction and/or knockdown of HIF-alpha subunits by siRNA by Western blot and Quantitative Real-Time PCR techniques. We showed that although HIF-1alpha and HIF-2alpha protein levels in breast cancer specimens were not interrelated, high levels of both HIF-1alpha and HIF-2alpha associated to high VEGF expression. HIF-2alpha expression was an independent prognostic factor associated to reduced recurrence-free and breast cancer-specific survival, whereas HIF-1alpha did not exhibit these correlations. In cultured cells, acute hypoxia induced both HIF-proteins. At prolonged hypoxia, HIF-2alpha remained accumulated, whereas HIF-1alpha protein levels decreased, in agreement with the oxygen level and time-dependent induction of HIFs recently reported in neuroblastoma.

Can we circumvent resistance to ErbB2-targeted agents by targeting novel pathways?

The recent development of targeted therapies using monoclonal antibodies has added new dimensions to the rapidly evolving field of breast cancer treatment. In particular, the incorporation of trastuzumab into regimens containing existing chemotherapeutic agents has significantly improved clinical outcomes for patients with breast cancer in the adjuvant and metastatic settings. De novo and acquired resistance to this treatment, however, is widespread. A substantial amount of research has therefore been dedicated to the elucidation of molecular mechanisms that could explain resistance to this otherwise effective therapy. Potential mechanisms for resistance to trastuzumab include steric inhibition imposed by other extracellular factors, molecular changes in the target receptor itself (ErbB2), alterations in the regulation of downstream signaling components, and crosstalk with other pathways that could compensate for attenuated ErbB2 signaling. In addition, preclinical and clinical studies have been performed to identify potential methods for overcoming trastuzumab resistance, including targeting alternate ErbB2 epitopes and the combined inhibition of multiple signaling components and/or pathways (vertical or horizontal inhibition). Studies continue to evaluate the most promising approaches for overcoming mechanisms of resistance to trastuzumab and other ErbB2-targeted therapies. This review will summarize the most recent research designed to address this substantial clinical problem and provide clinicians with relevant background for understanding some of the potential molecular mechanisms for resistance to targeted therapies in the treatment of patients with breast cancer.

Study on relationship between angiogenesis and micrometastases of peripheral blood in breast cancer

PURPOSE

To investigate the relationship between microvessel density, expression of vascular endothelial growth factor A (VEGF-A) and micrometastases in peripheral blood of patients with breast cancer.

METHOD

Microvessel density (MVD) and expression of VEGF-A were detected by immunohistochemistry S-P. Nested RT-PCR was introduced to detect the expression of hMAM mRNA in peripheral blood of all cases.

RESULT

Average MVD was 28.95 +/- 6.95 microvessels/100x and positive rate of VEGF-A was 64.0% (32/50) in 50 cases with breast cancer. MVD count and expression of VEGF-A were related to tumor size, metastasis of axillary lymph nodes and clinical stages (P < 0.05), independent of age and histological classification (P > 0.05). The positive rate of hMAM mRNA in peripheral blood was 34.0% (17/50), which correlated with lymphatic metastasis and clinical stages (P < 0.05), independent of pathological category, menopause and hormone receptor (P > 0.05). MVD count and positive rate of VEGF-A in breast cancer with positive expression of hMAM mRNA was obviously higher than those without hMAM mRNA expression (chi (2) = 5.766, P = 0.032; t = 5.37, P = 0.002).

CONCLUSIONS

MVD count and positive expression of VEGF-A closely correlated to hMAM mRNA released from tumor cells in the circulation. hMAM mRNA is expected to become a valuable marker for further study on micrometastases of breast cancer.

Tamoxifen and aromatase inhibitors differentially affect vascular endothelial growth factor and endostatin levels in women with breast cancer

PURPOSE

Circulating and cellular proangiogenic and antiangiogenic proteins such as vascular endothelial growth factor (VEGF) and endostatin contribute to the local angiogenic balance. We explored the effects of tamoxifen and aromatase inhibitors on concentrations of VEGF and endostatin in plasma, serum, and platelet releasate (induced by platelet activation).

EXPERIMENTAL DESIGN

VEGF and endostatin concentrations were measured with a quantitative immunoassay before and after 1 to 5 weeks of treatment in 30 women with breast cancer treated with either tamoxifen (n = 14) or aromatase inhibitors (n = 16). Platelet activation was induced by a thrombin receptor agonist.

RESULTS

Tamoxifen therapy resulted in an increase in platelet releasate concentrations of VEGF (P = 0.01) but no change in plasma VEGF. In contrast, aromatase inhibitor therapy did not affect serum, plasma, or platelet releasate VEGF. In univariate analysis, aspirin use attenuated the tamoxifen-associated increase in VEGF in the platelet releasate and decreased serum levels of VEGF (P = 0.03). Aromatase inhibitor therapy resulted in a decrease in serum endostatin concentrations (P = 0.04), whereas plasma concentrations of endostatin tended to be higher during treatment with aromatase inhibitors (P = 0.06). Tamoxifen therapy resulted in no change in serum or plasma endostatin concentrations. Platelet releasate concentrations of endostatin did not change with either treatment. Interindividual variability was noted among both aromatase inhibitor--and tamoxifen-treated patients.

CONCLUSIONS

Tamoxifen and aromatase inhibitor therapy affect VEGF and endostatin levels and likely contribute to the angiogenic balance in breast cancer patients. Aspirin decreased the proangiogenic effects of tamoxifen, suggesting that antiplatelet and/or antiangiogenic therapy might improve the effectiveness of tamoxifen in women with breast cancer.

Prognostic value of pre-treatment DCE-MRI parameters in predicting disease free and overall survival for breast cancer patients undergoing neoadjuvant chemotherapy

The purpose of this study was to investigate whether dynamic contrast enhanced MRI (DCE-MRI) data, both pharmacokinetic and empirical, can predict, prior to neoadjuvant chemotherapy, which patients are likely to have a shorter disease free survival (DFS) and overall survival (OS) interval following surgery. Traditional prognostic parameters were also included in the survival analysis. Consequently, a comparison of the prognostic value could be made between all the parameters studied. MR examinations were conducted on a 1.5 T system in 68 patients prior to the initiation of neoadjuvant chemotherapy. DCE-MRI consisted of a fast spoiled gradient echo sequence acquired over 35 phases with a mean temporal resolution of 11.3s. Both pharmacokinetic and empirical parameters were derived from the DCE-MRI data. Kaplan-Meier survival plots were generated for each parameter and group comparisons were made utilising logrank tests. The results from the 54 patients entered into the univariate survival analysis demonstrated that traditional prognostic parameters (tumour grade, hormonal status and size), empirical parameters (maximum enhancement index, enhancement index at 30s, area under the curve and initial slope) and adjuvant therapies demonstrated significant differences in survival intervals. Further multivariate Cox regression survival analysis revealed that empirical enhancement parameters contributed the greatest prediction of both DFS and OS in the resulting models. In conclusion, this study has demonstrated that in patients who exhibit high levels of perfusion and vessel permeability pre-treatment, evidenced by elevated empirical DCE-MRI parameters, a significantly lower disease free survival and overall survival can be expected.

Vascular endothelial growth factor is a strong predictor of early distant recurrences in a prospective study of premenopausal women with lymph-node negative breast cancer

We investigate the prognostic significance of the pro-angiogenic cytokine vascular endothelial growth factor (VEGF), urokinase-type plasminogen activator (uPA), plasminogen activator inhibitor 1 (PAI-1), and S-phase fraction (SPF) for distant disease free survival (DDFS) in 219 premenopausal patients with node-negative breast cancer (NNBC). In univariate analysis significantly shorter DDFS was observed for patients with high VEGF (p=0.006), high uPA (p=0.001), and high SPF (p<0.001). The prognostic significance of VEGF varied over time being very strong for early relapses (0-2.25 years follow-up) (HR=7.9; p=0.006) while no difference was seen in the subsequent follow-up period (HR=1.3; p=0.62). In a series of bivariate analyses VEGF provided prognostic information during the whole observation period (0-72 months) in addition to age, tumour size, oestrogen receptor (ER), progesterone receptor (PgR), and uPA. Also this effect was more pronounced during the first follow-up period suggesting VEGF as a marker of early recurrences.

The potential of anti-vascular endothelial growth factor therapy in metastatic breast cancer: clinical experience with anti-angiogenic agents, focusing on bevacizumab

The importance of angiogenesis in tumour growth and development is well known. Overexpression of vascular endothelial growth factor (VEGF), the key mediator of angiogenesis, is associated with poor prognosis in breast cancer. As a result, several therapeutic agents that inhibit the actions of VEGF or its receptors are currently in development for use in metastatic breast cancer (MBC). This review describes the function of VEGF in normal and tumour angiogenesis, explores the rationale behind the use of anti-VEGF therapy in MBC and details the therapeutic impact of such agents on tumour vasculature. Clinical data from trials of anti-VEGF agents in MBC are discussed, with a particular focus on the efficacy and safety of bevacizumab, the anti-VEGF agent at the most advanced stage of development in this tumour type. Future potential uses of bevacizumab in breast cancer are introduced.

Unraveling the microenvironmental influences on the normal mammary gland and breast cancer

The normal mammary gland and invasive breast tumors are both complex 'organs' composed of multiple cell types as well as extracellular matrix in three-dimensional (3D) space. Conventionally, both normal and malignant breast cells are studied in vitro as two-dimensional monolayers of epithelial cells, which results in the loss of structure and tissue function. Many laboratories are now investigating regulation of signaling function in the normal mammary gland using 3D cultures. However, it is also important to assay malignant breast cells ex vivo in a physiologically relevant environment to more closely mimic tumor architecture, signal transduction regulation and tumor behavior in vivo. Here we present the potential of these 3D models for drug testing, target validation and guidance of patient selection for clinical trials. We also argue that in order to get full insight into the biology of the normal and malignant breast, and to create in vivo-like models for therapeutic approaches in humans, we need to continue to create more complex heterotypic models to approach the full context the cells encounter in the human body.

Intrinsic markers of tumour hypoxia and angiogenesis in localised prostate cancer and outcome of radical treatment: a retrospective analysis of two randomised radiotherapy trials and one surgical cohort study

BACKGROUND

Expression of intrinsic markers of tumour hypoxia and angiogenesis are important predictors of radiotherapeutic, and possibly surgical, outcome in several cancers. Extent of tumour hypoxia in localised prostate cancer is comparable to that in other cancers, but few data exist on the association of extent of tumour hypoxia with treatment outcome. We aimed to study the predictive value of intrinsic markers of tumour hypoxia and angiogenesis in localised prostate cancer, both in patients treated with radiotherapy and in those treated surgically.

METHODS

We applied a new, needle biopsy tissue microarray (TMA) technique to study diagnostic samples from men with localised, previously untreated prostate cancer treated in two randomised controlled trials of radiotherapy-dose escalation. Multivariate analysis by Cox proportional hazards was done to assess the association between clinical outcome, in terms of biochemical control, and immunohistochemical staining of hypoxia inducible factor-1 alpha (HIF-1 alpha), vascular endothelial growth factor (VEGF), and osteopontin expression. The analysis was repeated on an independent series of men with localised, previously untreated prostate cancer treated by radical prostatectomy. The main outcome was time to biochemical (ie, prostate-specific antigen [PSA]) failure.

FINDINGS

Between Oct 12, 1995, and Feb 5, 2002, 308 patients were identified from two prospective, randomised trials at the Royal Marsden Hospital, London and Sutton, UK, for the radiotherapy cohort and diagnostic biopsies were available for 201 of these patients. Between June 6, 1995, and Nov 4, 2005, 329 patients were identified from the Aarhus University Hospital, Skejby, Denmark, for the prostatectomy cohort; of these, 40 patients were excluded because the tumour was too small to sample (19 patients), because the paraffin block was too thin (19 patients), or because the blocks were missing (two patients), leaving 289 patients for analysis. For patients treated with radiotherapy, increased staining for VEGF (p=0.008) and HIF-1 alpha (p=0.02) expression, but not increased osteopontin expression (p=0.978), were significant predictors of a shorter time to biochemical failure on multivariate analysis, independent of clinical tumour stage, Gleason score, serum PSA concentration, and dose of radiotherapy. For patients treated with surgery, increased staining for VEGF (p<0.0001) and HIF-1 alpha (p<0.0001) expression, and increased osteopontin expression (p=0.0005) were each significantly associated with a shorter time to biochemical failure on multivariate analysis, independent of pathological tumour stage, Gleason score, serum PSA concentration, and margin status.

INTERPRETATION

To our knowledge, this is the largest study of intrinsic markers of hypoxia and angiogenesis in relation to the outcome of radical treatment of localised prostate cancer. Increased expression of VEGF, HIF-1 alpha, and, for patients treated with surgery, osteopontin, identifies patients at high risk of biochemical failure who would be suitable for enrolment into trials of treatment intensification.

VEGF and VEGFR-1 are coexpressed by epithelial and stromal cells of renal cell carcinoma

BACKGROUND

Tumor angiogenesis is a dynamic process that plays a major role in cancer progression. Vascular endothelial growth factor (VEGF) and its receptors play a pivotal role in angiogenesis. The expression of VEGF and its receptors VEGFR-1 and VEGFR-2 in renal cell carcinoma (RCC) was investigated in the perspective of anti-VEGF treatments.

METHODS

Total VEGF protein levels were quantified by enzyme-linked immunosorbent assay (ELISA) in tumor tissue samples from surgical specimens of 65 patients with clear cell RCC. At the cellular level the VEGF isoforms VEGFR-1 and VEGFR-2 mRNA were quantified by real-time quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) in laser-microdissected tumoral epithelial as stromal cells and in corresponding normal tissue compartments. Colocalization of VEGF and VEGFR-1 proteins was studied by triple immunofluorescent labeling.

RESULTS

Protein VEGF in cytosolic extracts was significantly higher in tumoral than in nontumoral tissue (P< .0001). Event-free survival was significantly longer for patients with cytosolic VEGF lower than the cutoff (75th percentile of VEGF protein levels, P= .02). In laser-microdissected epithelial cells, VEGF(121) and VEGFR-1 mRNA expressions were higher in RCC than in corresponding nontumoral kidney (P= .007 and P= .002, respectively); they were also higher in stromal cells of RCC compared with nontumoral kidney (P= .02 and P= .003, respectively). There was no differential VEGFR-2 expression in epithelial or in stromal cells of tumoral or nontumoral kidney. By immunofluorescent labeling VEGF and VEGFR-1 colocalized on RCC tumor epithelial and stromal cells.

CONCLUSIONS

Combined laser microdissection and quantitative RT-PCR, as triple immunofluorescent labeling, underlined the preferential expression of the most soluble VEGF isoform, VEGF(121), and its receptor VEGFR-1, but not VEGFR-2, in epithelial and stromal cells of RCC.

Downregulation of HER2 by RIG1 involves the PI3K/Akt pathway in ovarian cancer cells

Interferon-gamma (IFN-gamma) is known to downregulate HER2 oncoprotein (p185(HER2) or briefly p185) in prostate cancer cells. We demonstrate that the IFN-gamma-induced retinoid-inducible gene 1 (RIG1) acts as a transrepressor of p185. Furthermore, we exhibit that RIG1 downregulates the activated (phosphorylated) form of p185 and phosphoinositide-3 kinase (PI3K)/serine/threonine-specific protein kinase (Akt) and the mammalian target of rapamycin (mTOR), downstream substrates of HER2. We also elucidate that heregulin (HRG) specifically restores the activation of p185 and Akt after their activities are reduced by RIG1. Additionally, expression of vascular endothelial growth factor (VEGF) increases through the HER2- and Akt/mTOR-signaling pathways, indicating that VEGF is downregulated by RIG1 within the cell. These findings suggest that RIG1 plays a role in IFN-gamma-mediated therapy by downregulating p185 and its downstream PI3K/Akt/mTOR/VEGF-signaling pathway. These results may provide a new therapeutic mechanism for the clinical use of IFN-gamma and RIG1.

Preoperative CA 15-3 and CEA serum levels as predictor for breast cancer outcomes

BACKGROUND

To investigate the association between tumor markers [cancer antigen 15-3 (CA 15-3) and carcinoembryonic antigen (CEA)] and clinicopathological parameters and patient outcomes in breast cancer.

MATERIALS AND METHODS

A total of 740 patients with stages I-III breast cancer had preoperative CA 15-3 and CEA concentrations measured. Univariate and multivariate analyses were used to investigate associations between marker concentration and clinicopathological parameters and patient outcomes.

RESULTS

Among 740 patients, elevated preoperative levels of CA 15-3 and CEA were identified in 92 (12.4%) and 79 (10.7%) patients, respectively. Tumor size (>5 cm), node metastases (> or =4), and advanced stage (> or =III) were associated with higher preoperative levels. Elevated CA 15-3 and CEA levels were associated with poor disease-free survival (DFS, P = 0.0014, P = 0.0001, respectively) and overall survival (OS, P = 0.018, P = 0.015) even in stage-matched analysis. Patients with normal levels of both CA 15-3 and CEA showed better DFS and OS than those with elevated group. In multivariate analysis, age (<35 years), tumor size (>2 cm), node metastases, estrogen receptor expression, and elevated CA 15-3 and CEA preoperative values were independent prognostic factors for DFS.

CONCLUSION

High preoperative CA 15-3 and CEA levels may reflect tumor burden and are associated with advanced disease and poor outcome. Measuring preoperative levels of CA 15-3 and CEA can be helpful for predicting outcomes.

Integrated therapy of kidney cancer

Historically, treatment options for metastatic renal cell carcinoma (RCC) have been limited because of inherent tumor resistance to chemotherapy and radiotherapy. The only approved drug for RCC in the past 30 years has been high-dose interleukin-2. Its benefit is observed in a small percentage (20%-25%) of highly selected good performance status RCC patients. The treatment of advanced RCC has recently undergone a major change with the development of potent angiogenesis inhibitors and targeted agents. In fact, advanced RCC is a highly vascular tumor associated with expression of vascular endothelial growth factor (VEGF); thereafter, antiangiogenic strategies have become an attractive approach. Several multitargeted tyrosine kinase inhibitors (sorafenib and sunitinib) have already been approved for the treatment of advanced RCC; bevacizumab, a monoclonal antibody anti-VEGF, has shown promising clinical activity. Temsirolimus, a derivative of rapamycin (CCI-779), has also shown a survival advantage over interferon in advanced, poor-prognosis RCC patients. The aim of this review is to describe these agents in terms of mechanisms of action, efficacy, and toxicity profile and also to analyze future development strategies.

Mechanisms of disease: angiogenesis and the management of breast cancer

Demonstration of the clinically significant activity of bevacizumab in breast cancer has attracted a great deal of interest. Numerous other antiangiogenic treatments are in clinical development and some established therapies including tamoxifen and trastuzumab might function, in part, by suppressing angiogenesis. In this Review, we discuss the potential of various components of the angiogenic pathway as prognostic and predictive factors in breast cancer. In addition, we describe existing clinical trials of antiangiogenic agents and the challenges facing the clinical development and optimum use of these agents for the treatment of breast cancer.

Targeting angiogenesis in advanced breast cancer

Angiogenesis, the process of new blood vessel formation, is required for tumor growth and metastasis. There is substantial preclinical and clinical evidence supporting the central role of angiogenesis in tumor formation and metastasis. Thus, the inhibition of angiogenesis may provide more effective treatment for patients with advanced breast cancer. Several chemotherapeutic and hormonal agents routinely used in the treatment of advanced breast cancer have antiangiogenic properties. Novel antiangiogenic agents targeting the vascular endothelial growth factor (VEGF) ligand and receptor tyrosine kinase inhibitors are being developed. Recently, a large phase III clinical trial demonstrated a significant benefit in progression-free survival with the addition of anti-VEGF monoclonal antibody bevacizumab to paclitaxel for first-line treatment of advanced breast cancer. This study established that antiangiogenic therapy is effective in breast cancer, and additional studies of bevacizumab and other antiangiogenic agents are underway. This article reviews the evidence for the role of angiogenesis in breast cancer pathogenesis, the challenges of developing antiangiogenic agents, and current agents in clinical trials.

Vascular endothelial growth factor (VEGF), VEGF receptors expression and microvascular density in benign and malignant thyroid diseases

Angiogenesis is critical for the growth and metastatic spread of tumours. Vascular endothelial growth factor (VEGF) is the most potent inducer of neovasculature, and its increased expression has been related to a worse clinical outcome in many diseases. The purpose of this study was to evaluate the relation between VEGF, its receptors (VEGFR-1 and VEGFR-2) and microvessel density (MVD) in thyroid diseases. Immunostaining for VEGF and VEGF receptors was performed in 66 specimens of thyroid tissue, comprising 17 multinodular goitre (MNG), 14 Graves' disease, 10 follicular adenoma, 8 Hashimoto's thyroiditis, 7 papillary carcinoma and 10 normal thyroid specimens. Thyrocyte positivity for VEGF and VEGF receptors was scored 0-3. Immunohistochemistry for CD31, and CD34 on the same sections was performed to evaluate MVD. Immunohistochemical staining of VEGF in thyrocytes was positive in 92% of all the thyroid tissues studied. Using an immunostaining intensity cut off of 2, increased thyrocyte staining was seen in follicular adenoma specimens, MNG and normal thyroids compared with Hashimoto's thyroiditis and Graves' disease (P < 0.05). Similarly, VEGF thyrocyte expression in Graves' disease was less than other pathologies (P < 0.05). VEGFR-1 expression and the average MVD score did not differ between the different thyroid pathologies. VEGF expression was lower in autoimmune pathologies compared to autonomous growth processes. Conversely, both VEGFR-1 and VEGFR-2 were widely expressed in benign and neoplastic thyroid disease, suggesting that the up-regulation of VEGF and not its receptors occurs as tissue becomes autonomous. There was no clear relationship between MVD measurement and thyroid pathology.

Significance of Biological Markers for Predicting Prognosis and Selecting Chemotherapy Regimens of Advanced Gastric Cancer Patients between Continuous Infusion of 5-FU and a Combination of 5-FU and Cisplatin

BACKGROUND

Our previous phase II study of 5-fluorouracil (5-FU) and cisplatin (FP) for treatment of advanced gastric cancer showed that strong immunoreactivity for vascular endothelial growth factor (VEGF) is associated with chemoresponse. Patients with four or five of the favorable phenotypes, p53 (-), bcl-2 (-), gluthathione S-transferase pi (-), thymidylate synthase (-), and VEGF (+), survived longer than those with three or less of these phenotypes. The purpose of this study is to confirm our previous results and to compare the significance of those markers between continuous infusion of 5-FU (5-FUci) and FP.

METHODS

Pretreatment biopsies from 131 of 210 advanced gastric cancer patients enrolled to JCOG9205 were analyzed immunohistochemically for the presence of the five markers.

RESULTS

Median survival times of patients treated with 5-FUci (n = 65) or FP (n = 66) were 216 and 253 days, respectively (P = 0.6953). After FP treatment, patients with four or five favorable phenotypes (n = 20) survived longer than those with three or less favorable phenotypes (n = 46) (334 days and 243 days, respectively; P = 0.0463), and the survival times of 34 and 32 patients with VEGF (-) and (+) were similar (269 days and 253 days, respectively; P = 0.6317). After 5-FUci, 30 patients with VEGF (+) survived for a shorter time than 35 patients with VEGF (-) (142 days and 302 days, respectively; P = 0.0043).

CONCLUSION

The number of favorable phenotypes is prognostic for gastric cancer patients treated with FP, and VEGF has a different impact on survival between treatment with 5-FUci and FP.

FGFs, Wnts and BMPs mediate induction of VEGFR-2 (Quek-1) expression during avian somite development

Regulation of VEGFR-2 (Quek1) is an important mechanism during blood vessel formation. In the paraxial mesoderm, Quek1 expression is restricted to the lateral portion of the somite and later to sclerotomal cells surrounding the neural tube. By implanting FGF 8b/8c or SU 5402 beads into the paraxial mesoderm, we show that FGF8 in addition to BMP4 from the intermediate mesoderm (IM) is a positive regulator of VEGFR-2 (Quek1) expression in the quail embryo. The expression of Quek1 in the medial somite half is normally repressed by the notochord and Sfrps-expression in the neural tube. Over-expression of Wnt 1/3a also results in an up-regulation of Quek1 expression in the somites. We also show that up-regulation of FGF8/Wnt 1/3a leads to an increase in the number of endothelial cells, whereas inhibition of FGF and Wnt signaling by SU 5402 and Sfrp-2 results in a loss of endothelial cells. Our results demonstrate that the regulation of Quek1 expression in the somites is mediated by the cooperative actions of BMP4, FGF8 and Wnt-signaling pathways.

Challenges for patient selection with VEGF inhibitors

As targeted therapies for cancer become increasingly integrated into standard practice, appropriate selection of the patients most likely to benefit from these therapies is now receiving critical scrutiny. Early experience with therapies directed at targets that are definitively overactive (e.g. the bcr-abl tyrosine kinase targeted by imatinib) or over-expressed [e.g. the human epidermal growth factor receptor 2 (HER2) targeted by trastuzumab] has generated the perception that pre-treatment target assessment is a pre-requisite for therapy with all targeted agents. However, emerging evidence suggests that this is not presently feasible for anti-angiogenic agents. Despite considerable evidence for the association of intratumoral and/or plasma vascular endothelial growth factor (VEGF) levels with tumor progression and/or poor prognosis, pre-treatment VEGF levels do not appear to be predictive of response to anti-angiogenic therapy. This may possibly be due to the complexity of the angiogenic pathways and the limitations associated with current methods of VEGF detection and quantification; e.g. low assay sensitivity and lack of standardized methods could prevent detection of very small increases in VEGF, which may be clinically important in patients with tumors that are highly dependent on this growth factor. In addition to a general lack of agreement as to the relative clinical relevance of circulating versus tumor VEGF levels, the absence of a 'gold standard' VEGF detection assay and the lack of a predefined, clinically relevant cut-off pose a significant hindrance to the clinical utility of VEGF measurements for therapy selection. Given the fundamental importance of angiogenesis for tumor growth and progression, and the key role of VEGF in these processes, presently it seems appropriate to view anti-VEGF agents such as bevacizumab (Avastin) as having potential utility, independently of pre-treatment screening. Further research is needed to define the relationship between potential surrogate markers of VEGF pathway activity and clinical outcomes.

Drug insight: VEGF as a therapeutic target for breast cancer

Angiogenesis is implicated in the pathogenesis of malignancy and metastasis. Inhibition of angiogenesis has demonstrated clinically significant improvements in outcomes in a variety of malignancies, including breast cancer. The humanized monoclonal antibody against VEGF, bevacizumab, is the clinically most mature of the antiangiogenic agents and has recently been shown to improve outcome when combined with chemotherapy in the first-line metastatic setting of breast cancer. A variety of other antiangiogenic agents are currently under investigation, including drugs that inhibit the VEGF receptor 2, the cognate receptor for VEGF found on endothelial cells. The combination of antiangiogenic drugs with one another and with other biologic agents is also being explored in an attempt to improve efficacy and to overcome the drug resistance seen with the initial studies of antiangiogenic agents. This Review will focus on the current state of therapeutics designed to inhibit this angiogenic process in breast cancer.