Angiogenesis as a marker of preneoplastic lesions of the human breast

An Overview of the Use of Anti-Angiogenic Agents in the Treatment of Thymic Epithelial Tumors

Angiogenesis significantly influences the carcinogenesis of thymic epithelial tumors (TET). Both thymomas and thymic carcinoma (TC) overexpress VEGF-A and VEGFR-1 and -2. This review aims to provide an appraisal of the use of anti-angiogenics in the treatment of TET. The literature research identified 16 studies that were deemed eligible for further analysis. Seven studies assessed the clinical efficacy of sunitinib and five studies the use of apatinib and/or anlotinib. The multicenter Japanese phase II REMORA trial investigated the efficacy of lenvatinib, which is a multi-targeted inhibitor of VEGFR, FGFR, RET, c-Kit, and other kinases. The objective response rate was 38% (25.6-52%), which is the highest documented in TET that progressed after first-line chemotherapy. Anti-angiogenic agents may be useful in the treatment of TET, which are not amenable to curative treatment. Their toxicity profile seems to be acceptable. However, angiogenesis inhibitors do not appear to have a major influence on either thymomas or TC, although multikinase inhibitors may have some effect on TC. The current evidence suggests that the most active agent is lenvatinib, whereas sunitinib could be proposed as an acceptable second-line therapy for TC. Further research concerning the combination of immune checkpoint inhibitors with anti-angiogenic drugs is warranted.

The Role of the Stroma in Tumor Angiogenesis and Progression: The Fundamental Contribution of Pietro M. Gullino

The tumor stroma is the major factor influencing the growth of cancer. It is implicated in the regulation of tumor growth and metastatic potential and impacts the outcome of therapy. This article summarizes the fundamental contribution of the Italian scientist Pietro M. Gullino in the study of tumor stroma through the development of new experimental techniques and the characterization of novel angiogenic factors.

Ethanolic extract of Origanum syriacum L. leaves exhibits potent anti-breast cancer potential and robust antioxidant properties

Background: Breast cancer (BC) is the second most common cancer overall. In women, BC is the most prevalent cancer and the leading cause of cancer-related mortality. Triple-negative BC (TNBC) is the most aggressive BC, being resistant to hormonal and targeted therapies. Hypothesis/Purpose: The medicinal plant Origanum syriacum L. is a shrubby plant rich in bioactive compounds and widely used in traditional medicine to treat various diseases. However, its therapeutic potential against BC remains poorly investigated. In the present study, we screened the phytochemical content of an ethanolic extract of O. syriacum (OSEE) and investigated its anticancer effects and possible underlying mechanisms of action against the aggressive and highly metastatic human TNBC cell line MDA-MB-231. Methods: MTT, trans-well migration, and scratch assays were used to assess cell viability, invasion, or migration, respectively. Antioxidant potential was evaluated in vitro using the DPPH radical-scavenging assay and levels of reactive oxygen species (ROS) were assessed in cells in culture using DHE staining. Aggregation assays were used to determine cell-cell adhesion. Flow cytometry was used to analyze cell cycle progression. Protein levels of markers of apoptosis (BCL-2, pro-Caspase3, p53), proliferation (p21, Ki67), cell migration, invasion, or adhesion (FAK, E-cadherin), angiogenesis (iNOS), and cell signaling (STAT3, p38) were determined by immunoblotting. A chorioallantoic Membrane (CAM) assay evaluated in ovo angiogenesis. Results: We demonstrated that OSEE had potent radical scavenging activity in vitro and induced the generation of ROS in MDA-MB-231 cells, especially at higher OSEE concentrations. Non-cytotoxic concentrations of OSEE attenuated cell proliferation and induced G₀/G₁ cell cycle arrest, which was associated with phosphorylation of p38 MAPK, an increase in the levels of tumor suppressor protein p21, and a decrease of proliferation marker protein Ki67. Additionally, only higher concentrations of OSEE were able to attenuate inhibition of proliferation induced by the ROS scavenger N-acetyl cysteine (NAC), indicating that the anti-proliferative effects of OSEE could be ROS-dependent. OSEE stimulated apoptosis and its effector Caspase-3 in MDA-MB-231 cells, in correlation with activation of the STAT3/p53 pathway. Furthermore, the extract reduced the migration and invasive properties of MDA-MB-231 cells through the deactivation of focal adhesion kinase (FAK). OSEE also reduced the production of inducible nitric oxide synthase (iNOS) and inhibited in ovo angiogenesis. Conclusion: Our findings reveal that OSEE is a rich source of phytochemicals and has robust anti-breast cancer properties that significantly attenuate the malignant phenotype of MD-MB-231 cells, suggesting that O. syriacum may not only act as a rich source of potential TNBC therapeutics but may also provide new avenues for the design of novel TNBC drugs.

N-methyl-N-nitrosourea induces zebrafish anomalous angiogenesis through Wnt/β-catenin pathway

N-methyl-N-nitrosourea (MNU) is a prevalent environmental carcinogen, which leads to tumors in various organs in animal models, while the mechanisms involved were still not fully understood. It is well known that anomalous angiogenesis is a key step in tumorigenesis and progression. In this study, we found that MNU induced abnormal angiogenesis which was accompanied by upregulation of rspo1, p53 and vegfaa in zebrafish embryos. Moreover, it revealed that MNU-induced ectopic sprouting of blood vessels was significantly reduced in rspo1-knockdown but not p53-knockdown embryos, indicating that rspo1 was necessary for MNU-induced abnormal angiogenesis. Additionally, pharmaceutical activation or inhibition of Wnt/β-catenin signaling pathway using (2'Z,3'E)- 6-bromoindirubin-3'-oxime or CCT036477 significantly increased or inhibited the pro-angiogenic effect of MNU on developing zebrafish embryos, which was confirmed by the effect of proliferation and migration in MNU-treated bEnd.3 cells. These data together indicated that rspo1/Wnt/β-catenin/vegfaa axis is involved in the modulation of MNU-induced anomalous angiogenesis.

Origanum syriacum L. Attenuates the Malignant Phenotype of MDA-MB231 Breast Cancer Cells

Breast cancer is the leading cause of cancer-related deaths among women. Among breast cancer types, triple negative breast cancer (TNBC) is the most aggressive, and is resistant to hormonal and chemotherapeutic treatments. As such, alternative approaches that may provide some benefit in fighting this debilitating pathology are critically needed; hence the utilization of herbal medicine. Origanum syriacum L., one of the most regularly consumed plants in the Mediterranean region, exhibits antiproliferative effect on several cancer cell lines. However, whether this herb modulates the malignant phenotype of TNBC remains poorly investigated. Here, we show that in MDA-MB-231, a TNBC cell line, Origanum syriacum L. aqueous extract (OSE) inhibited cellular viability, induced autophagy determined by the accumulation of lipidized LC3 II, and triggered apoptosis. We also show that OSE significantly promoted homotypic cell-cell adhesion while it decreased cellular migration, adhesion to fibronectin, and invasion of MDA-MB-231 cells. This was supported by decreased activity of focal adhesion kinase (FAK), reduced α2 integrin expression, and downregulation of secreted PgE₂, MMP2 and MMP-9, in OSE-treated cells. Finally, we also show that OSE significantly inhibited angiogenesis and downregulated the level of nitric oxide (NO) production. Our findings demonstrate the ability of OSE to attenuate the malignant phenotype of the MDA-MB-231 cells, thus presenting Origanum syriacum L. as a promising potential source for therapeutic compounds for TNBC.

Controversial role of mast cells in breast cancer tumor progression and angiogenesis

Breast cancer is a neoplastic disease and is a cause of cancer-related mortality for women. Among cellular and molecular regulators of the microenvironment, mast cells and vascular endothelial growth factor (VEGF), are correlated with tumor progression and prognosis in breast cancer. Clinical and experimental studies on breast cancer have revealed a marked correlation between increased angiogenesis, metastasization, and poorer prognosis. After a brief introduction on angiogenesis evidence and angiogenic factors role in different breast cancer subtypes, in this article, we have discerned the relationship between mast cell infiltration, angiogenesis, and tumor progression in human breast cancer with particular reference to the dual role of mast cells, in terms of both pro- or anti-tumoral activity and poor or good biomarker.

Overview on the Different Patterns of Tumor Vascularization

Angiogenesis is a crucial event in the physiological processes of embryogenesis and wound healing. During malignant transformation, dysregulation of angiogenesis leads to the formation of a vascular network of tumor-associated capillaries promoting survival and proliferation of the tumor cells. Starting with the hypothesis formulated by Judah Folkman that tumor growth is angiogenesis-dependent, this area of research has a solid scientific foundation and inhibition of angiogenesis is a major area of therapeutic development for the treatment of cancer. Over this period numerous authors published data of vascularization of tumors, which attributed the cause of neo-vascularization to various factors including inflammation, release of angiogenic cytokines, vasodilatation, and increased tumor metabolism. More recently, it has been demonstrated that tumor vasculature is not necessarily derived by endothelial cell proliferation and sprouting of new capillaries, but alternative vascularization mechanisms have been described, namely vascular co-option and vasculogenic mimicry. In this article, we have analyzed the mechanisms involved in tumor vascularization in association with classical angiogenesis, including post-natal vasculogenesis, intussusceptive microvascular growth, vascular co-option, and vasculogenic mimicry. We have also discussed the role of these alternative mechanism in resistance to anti-angiogenic therapy and potential therapeutic approaches to overcome resistance.

Anti-Angiogenic Effects of Phytochemicals on miRNA Regulating Breast Cancer Progression

Several phytochemicals have been identified for their role in modifying miRNA regulating tumor progression. miRNAs modulate the expression of several oncogenes and tumor suppressor genes including the genes that regulate tumor angiogenesis. Hypoxia inducible factor-1 alpha (HIF-1α) signaling is a central axis that activates oncogenic signaling and acts as a metabolic switch in endothelial cell (EC) driven tumor angiogenesis. Tumor angiogenesis driven by metabolic reprogramming of EC is crucial for tumor progression and metastasis in many different cancers, including breast cancers, and has been linked to aberrant miRNA expression profiles. In the current article, we identify different miRNAs that regulate tumor angiogenesis in the context of oncogenic signaling and metabolic reprogramming in ECs and review how selected phytochemicals could modulate miRNA levels to induce an anti-angiogenic action in breast cancer. Studies involving genistein, epigallocatechin gallate (EGCG) and resveratrol demonstrate the regulation of miRNA-21, miRNA-221/222 and miRNA-27, which are prognostic markers in triple negative breast cancers (TNBCs). Modulating the metabolic pathway is a novel strategy for controlling tumor angiogenesis and tumor growth. Cardamonin, curcumin and resveratrol exhibit their anti-angiogenic property by targeting the miRNAs that regulate EC metabolism. Here we suggest that using phytochemicals to target miRNAs, which in turn suppresses tumor angiogenesis, should have the potential to inhibit tumor growth, progression, invasion and metastasis and may be developed into an effective therapeutic strategy for the treatment of many different cancers where tumor angiogenesis plays a significant role in tumor growth and progression.

Doppler Flowmetry and the Diagnosis of Breast Lumps

The aim of the study was to ascertain the reliability of a Doppler signal in the diagnosis of breast cancer. Computerized blood flow analysis was performed on 117 patients who presented with a breast lump at the Division of Diagnostic Oncology of the Istituto Nazionale Tumori of Milan. The values of systolic peak and diastolic frequency were evaluated in relation to the histologic diagnosis. Ten patients had a spontaneous regression of the lump and were excluded from the study. The number of evaluable cases with histologic confirmation was 107: 69 carcinomas and 38 benign lesions. Systolic peak values for the 69 carcinomas ranged from 1500 to 7400 Hz, with a mean value of 3243.4 Hz; diastolic frequency ranged from 200 to 3700 Hz, with mean value of 1413.9 Hz. No diagnostic signals were found in 4 breast cancers (false negatives). Twenty-three of 38 benign lesions (60.5 %) and 65 of 69 malignant nodes (94.2 %) were correctly diagnosed. The Doppler signal with computerized spectral analysis in addition to more specific ultrasonographic parameters could be considered a useful tool in the diagnosis of breast cancer.

Angiogenesis and Cancer Control: From Concept to Therapeutic Trial

Background

There is extraordinary interest in developing angiosuppressive agents for cancer treatment. Several new agents appear promising for the treatment of a variety of human cancers. Current concepts and new agents in clinical trials are the focus of this article. In particular, the introduction of a new treatment for human brain tumors is presented in detail, using an antiangiogenic agent, penicillamine, and depletion of an obligatory cofactor of angiogenesis, copper.

Methods

The explosive increase in literature on antiangiogenesis is reviewed using computerized search, findings presented at the recent national cancer and angiogenesis meetings. A specific protocol, NABTT 97-04, “Penicillamine and Copper Reduction for Newly Diagnosed Glioblastoma,” is presented as an example of angiotherapeutic drug discovery.

Results

A number of promising molecular approaches are being introduced to suppress tumor angiogenesis. Major categories of angiogenesis antagonists include protease inhibitors, direct inhibitors of endothelial cell proliferation and migration, suppression of angiogenic growth factors, inhibition of endothelial-specific integrin/survival signaling, chelators of copper, and inhibitors with specific other mechanisms. The preliminary results of early trials offer a glimpse into how antiangiogenesis therapy will be integrated into future care of the patient with cancer.

Conclusions

Thirty-five antiangiogenesis therapies are currently being evaluated in clinical trials. As we learn more about the fundamental mechanisms of angiogenesis, eg, the role of copper in growth factor activation, effective methods of cancer control will be implemented.

Patient-derived xenograft (PDX) models in basic and translational breast cancer research

Patient-derived xenograft (PDX) models of a growing spectrum of cancers are rapidly supplanting long-established traditional cell lines as preferred models for conducting basic and translational preclinical research. In breast cancer, to complement the now curated collection of approximately 45 long-established human breast cancer cell lines, a newly formed consortium of academic laboratories, currently from Europe, Australia, and North America, herein summarizes data on over 500 stably transplantable PDX models representing all three clinical subtypes of breast cancer (ER+, HER2+, and "Triple-negative" (TNBC)). Many of these models are well-characterized with respect to genomic, transcriptomic, and proteomic features, metastatic behavior, and treatment response to a variety of standard-of-care and experimental therapeutics. These stably transplantable PDX lines are generally available for dissemination to laboratories conducting translational research, and contact information for each collection is provided. This review summarizes current experiences related to PDX generation across participating groups, efforts to develop data standards for annotation and dissemination of patient clinical information that does not compromise patient privacy, efforts to develop complementary data standards for annotation of PDX characteristics and biology, and progress toward "credentialing" of PDX models as surrogates to represent individual patients for use in preclinical and co-clinical translational research. In addition, this review highlights important unresolved questions, as well as current limitations, that have hampered more efficient generation of PDX lines and more rapid adoption of PDX use in translational breast cancer research.

Angiogenesis and Antiangiogenesis in Triple-Negative Breast cancer

Several data support a central role for angiogenesis in breast cancer growth and metastasis. Observational studies have demonstrated that microvascular density (MVD) is a prognostic factor in invasive breast cancer, whereas others reached the opposite conclusion. Vascular endothelial growth factor is the most important angiogenic factor with proven significance in breast cancer, as it has been assessed in both experimental and clinical studies. Triple-negative breast cancer (TNBC) is a type of breast cancer which lacks estrogen, progesterone, and HER-2/neu receptors. MVD in both basal-like and TNBC is significantly higher than in non–basal-like and non-TNBC. In breast cancer and other malignancies, the development of agents that inhibit tumor angiogenesis has been an active area of investigation. In TNBC, clinical trials combining targeted agents and chemotherapy have failed to show substantial survival improvement. There is evidence that patients with TNBC may have a greater probability of obtaining some kind of clinical efficacy benefit from bevacizumab-based therapy.

Investigating the effect of tumor vascularization on magnetic targeting in vivo using retrospective design of experiment

Nanocarriers take advantages of the enhanced permeability and retention (EPR) to accumulate passively in solid tumors. Magnetic targeting has shown to further enhance tumor accumulation in response to a magnetic field gradient. It is widely known that passive accumulation of nanocarriers varies hugely in tumor tissues of different tumor vascularization. It is hypothesized that magnetic targeting is likely to be influenced by such factors. In this work, magnetic targeting is assessed in a range of subcutaneously implanted murine tumors, namely, colon (CT26), breast (4T1), lung (Lewis lung carcinoma) cancer and melanoma (B16F10). Passively- and magnetically-driven tumor accumulation of the radiolabeled polymeric magnetic nanocapsules are assessed with gamma counting. The influence of tumor vasculature, namely, the tumor microvessel density, permeability and diameter on passive and magnetic tumor targeting is assessed with the aid of the retrospective design of experiment (DoE) approach. It is clear that the three tumor vascular parameters contribute greatly to both passive and magnetically targeted tumor accumulation but play different roles when nanocarriers are targeted to the tumor with different strategies. It is concluded that tumor permeability is a rate-limiting factor in both targeting modes. Diameter and microvessel density influence passive and magnetic tumor targeting, respectively.

The Discovery of Tumor Angiogenesis Factors: A Historical Overview

Starting with the hypothesis formulated by Judah Folkman that tumor growth is angiogenesis-dependent, this area of research has a solid scientific foundation, and inhibition of angiogenesis is a major area of therapeutic development for the treatment of cancer. This chapter offers an account of the most relevant discoveries in this field of biomedical research.

Apoplexy of pituitary adenomas: the perfect storm

OBJECT

Pituitary adenomas occasionally undergo infarction, apoplexy, which often destroys much of the tumor. It is well known that apoplexy can be precipitated by several acute factors, including cardiac surgery, other types of surgery, trauma, insulin infusion, and stimulation with administration of hypothalamic releasing factors.

METHODS

The prior focus on mechanisms underlying pituitary apoplexy has been on these acute events. Less attention has been given to the endogenous features of pituitary tumors that make them susceptible to spontaneous infarction, despite that most pituitary apoplexy occurs in the absence of a recognized precipitating event. The authors examine intrinsic features of pituitary adenomas that render them vulnerable to apoplexy-features such as high metabolic demand, paucity of angiogenesis, and sparse vascularity, qualities that have previously not been linked with apoplexy-and argue that it is these features of adenomas that underlie their susceptibility to spontaneous infarction. The sensitivity of freshly cultured pituitary adenomas to hypoglycemia is assessed.

RESULTS

Adenomas have high metabolic demand, limited angiogenesis, and reduced vessel density compared with the normal gland. Pituitary adenoma cells do not survive in the presence of reduced or absent concentrations of glucose.

CONCLUSIONS

The authors propose that the frequent ischemic infarction of pituitary adenomas is the product of intrinsic features of these tumors. These endogenous qualities create a tenuous balance between high metabolic demand and marginal tissue perfusion. Thus, the tumor is vulnerable to spontaneous infarction or to acute ischemia by any event that acutely alters the balance between tumor perfusion and tumor metabolism, events such as acute systemic hypotension, abruptly decreased supply of nutrients, hypoglycemia with insulin administration, or increase in the tumor's metabolic demand due to administration of hypothalamic releasing factors. It may be possible to take advantage of these intrinsic features of pituitary adenomas by using aspects of this vulnerability for development of new approaches for treatment.

99mTc-3P4-RGD2 scintimammography in the assessment of breast lesions: comparative study with 99mTc-MIBI

Purpose

To compare the potential application of ^99mTc-3P-Arg-Gly-Asp (^99mTc-3P₄-RGD₂) scintimammography (SMM) and ^99mTc-methoxyisobutylisonitrile (^99mTc-MIBI) SMM for the differentiation of malignant from benign breast lesions.

Method

Thirty-six patients with breast masses on physical examination and/or suspicious mammography results that required fine needle aspiration cytology biopsy (FNAB) were included in the study. ^99mTc-3P₄-RGD₂ and ^99mTc-MIBI SMM were performed with single photon emission computed tomography (SPECT) at 60 min and 20 min respectively after intravenous injection of 738±86 MBq radiotracers on a separate day. Images were evaluated by the tumor to non-tumor localization ratios (T/NT). Receiver operating characteristic (ROC) curve analysis was performed on each radiotracer to calculate the cut-off values of quantitative indices and to compare the diagnostic performance for the ability to differentiate malignant from benign diseases.

Results

The mean T/NT ratio of ^99mTc-3P₄-RGD₂ in malignant lesions was significantly higher than that in benign lesions (3.54±1.51 vs. 1.83±0.98, p<0.001). The sensitivity, specificity, and accuracy of ^99mTc-3P₄-RGD₂ SMM were 89.3%, 90.9% and 89.7%, respectively, with a T/NT cut-off value of 2.40. The mean T/NT ratio of ^99mTc-MIBI in malignant lesions was also significantly higher than that in benign lesions (2.86±0.99 vs. 1.51±0.61, p<0.001). The sensitivity, specificity and accuracy of ^99mTc-MIBI SMM were 87.5%, 72.7% and 82.1%, respectively, with a T/NT cut-off value of 1.45. According to the ROC analysis, the area under the curve for ^99mTc-3P₄-RGD₂ SMM (area = 0.851) was higher than that for ^99mTc-MIBI SMM (area = 0.781), but the statistical difference was not significant.

Conclusion

^99mTc-3P₄-RGD₂ SMM does not provide any significant advantage over the established ^99mTc-MIBI SMM for the detection of primary breast cancer. The T/NT ratio of ^99mTc-3P₄-RGD₂ SMM was significantly higher than that of ^99mTc-MIBI SMM. Both tracers could offer an alternative method for elucidating non-diagnostic mammograms.

Significance of rat mammary tumors for human risk assessment

We have previously indicated that the ideal animal tumor model should mimic the human disease. This means that the investigator should be able to ascertain the influence of host factors on the initiation of tumorigenesis, mimic the susceptibility of tumor response based on age and reproductive history, and determine the response of the tumors induced to chemotherapy. The utilization of experimental models of mammary carcinogenesis in risk assessment requires that the influence of ovarian, pituitary, and placental hormones, among others, as well as overall reproductive events are taken into consideration, since they are important modifiers of the susceptibility of the organ to neoplastic development. Several species, such as rodents, dogs, cats, and monkeys, have been evaluated for these purposes; however, none of them fulfills all the criteria specified previously. Rodents, however, are the most widely used models; therefore, this work will concentrate on discussing the rat rodent model of mammary carcinogenesis.

Angiogenesis in pituitary adenomas: human studies and new mutant mouse models

The role of angiogenesis in pituitary tumor development has been questioned, as pituitary tumors have been usually found to be less vascularized than the normal pituitary tissue. Nevertheless, a significantly higher degree of vasculature has been shown in invasive or macropituitary prolactinomas when compared to noninvasive and microprolactinomas. Many growth factors and their receptors are involved in pituitary tumor development. For example, VEGF, FGF-2, FGFR1, and PTTG, which give a particular vascular phenotype, are modified in human and experimental pituitary adenomas of different histotypes. In particular, vascular endothelial growth factor, VEGF, the central mediator of angiogenesis in endocrine glands, was encountered in experimental and human pituitary tumors at different levels of expression and, in particular, was higher in dopamine agonist resistant prolactinomas. Furthermore, several anti-VEGF techniques lowered tumor burden in human and experimental pituitary adenomas. Therefore, even though the role of angiogenesis in pituitary adenomas is contentious, VEGF, making permeable pituitary endothelia, might contribute to adequate temporal vascular supply and mechanisms other than endothelial cell proliferation. The study of angiogenic factor expression in aggressive prolactinomas with resistance to dopamine agonists will yield important data in the search of therapeutical alternatives.

Enhanced nestin expression and small blood vessels in human pituitary adenomas

The role of angiogenesis in human pituitary tumor progression is questioned. Our aim was to characterize the morphologic changes that occur in the vasculature of pituitary adenomas, in correlation with the expression of nestin, a protein found in endothelial cells of newly formed vessels of developing organs. We also evaluated the relation of angiogenic markers and nestin with Ki-67 index. Immunohistochemical studies were performed on paraffin embedded samples of 47 pituitary adenomas and six normal pituitaries. We determined microvessel density (number of CD31+ or CD34+ vessels per square millimetre), vascular area (cumulative area occupied by vessels), average vessel size, and further classified vessels as small (< 100 μm2) or large (> 100 μm2). We correlated the above parameters with nestin expression and Ki-67 index. Lower vascular area compared to normal tissue was found in adenomas (p < 0.05). Interestingly, pituitary adenomas had significantly more small vessels than control pituitaries (p < 0.04 for CD31 and CD34). In tumors many capillaries were positive for nestin, while scarce staining was detected in controls, so that nestin positive area was significantly higher in tumors. Furthermore, nestin area correlated positively with the % of small vessels. Ki-67 correlated neither with vascular area nor with nestin expression. In human pituitary tumors there was a predominance of small capillaries in correlation with increased expression of the progenitor marker nestin. We suggest that angiogenesis is an active process in these tumors, in spite of their low total vascular area when compared to normal pituitaries.

Inhibition of Breast Tumor Cell Growth by Ectopic Expression of p16/INK4A Via Combined Effects of Cell Cycle Arrest, Senescence and Apoptotic Induction, and Angiogenesis Inhibition

p16-mediated inhibition of cancer cell proliferation and tumor suppression have been studied before,; the common consensus is that p16's cell-cycle arrest function plays a primary role in these actions, with some additional apoptotic induction by p16. However, other effects of p16 that may potentially contribute to p16-mediated anti-tumor ability have not been well studied. The emerging data including ours indicated that p16 contributes its anti-cancer ability by inducing tumor cells to senescence. Moreover, we showed that p16 inhibits breast cancer cell growth by inhibiting the VEGF signaling pathway and angiogenesis. In this study, we used adenoviral-mediated p16 expression (AdRSVp16) and breast cancer cell line MDA-MB-231 as the model to simultaneously analyze all these p16's anti-tumor functions. We demonstrated that adenoviral-mediated p16 expression exhibited multiple anti-tumor functions by simultaneously suppressing in vitro growth and in vivo angiogenesis of breast cancer cells, blocking cell division, as well as inducing senescence and apoptosis. The in vivo study implies that p16's effect on anti-angiogenesis may play a more significant role than its anti-cell proliferation in the overall suppression of tumor growth. These results suggest, for the first time, that AdRSVp16-mediated tumor suppression results from a combination of p16's multiple anti-tumor functions including p16's well-known anti-proliferation/cell division function, apoptotic and senescence induction function, and its lesser-known/under-investigated anti-angiogenesis function. These combined results strongly indicate that p16 gene therapy has a multi-module platform with different anti-tumor functions; therefore, this study justifies and promotes the viral-mediated p16 gene therapy as a promising and powerful treatment approach for cancer patients due to p16's multiple anti-tumor functions.

Photoacoustic mammography: initial clinical results

PURPOSE

Photoacoustic tomography can image the hemoglobin distribution and oxygenation state inside tissue with high spatial resolution. The purpose of this study is to investigate its clinical usefulness for diagnosis of breast cancer and evaluation of therapeutic response in relation to other diagnostic modalities.

MATERIALS AND METHODS

Using a prototype machine for photoacoustic mammography (PAM), 27 breast tumor lesions, including 21 invasive breast cancer (IBC), five ductal carcinoma in situ (DCIS), and one phyllodes tumor, were measured. Nine out of twenty-one IBC patients had received primary systemic therapy (PST).

RESULTS

Eight out of twelve IBC without PST were visible. Notably, detection was possible in all five cases with DCIS, whereas it was not in one case with phyllodes tumor. Seven out of nine IBC with PST were assigned as visible in spite of decreased size of tumor after PST. The mean value of hemoglobin saturation in the visible lesions was 78.6 %, and hemoglobin concentration was 207 μM. The tumor images of PAM were comparable to those of magnetic resonance imaging (MRI).

CONCLUSIONS

It is suggested that PAM can image tumor vascularity and oxygenation, which may be useful for diagnosis and characterization of breast cancer.

A distinct microvascular pattern accompanied by aggressive clinical course in breast carcinomas: a fact or a coincidence?

The aim of this study was to evaluate the potential relationship of microvascular growth patterns with survival in invasive breast carcinomas. Thirty-one invasive ductal carcinoma cases, followed up at least for 38 months, constituted our series. All cases had been studied for ER/PR and HER2/neu expression. Clinicopathological and survival data were obtained from the archives. Tissue sections from all cases were stained with CD34 antibody to highlight the microvascular network and to measure microvessel density (MVD). The cases were then classified according to the dominance of one of the five recognizable microvascular patterns. Cox proportional hazard regression model, Fisher's exact test, and multivariate general linear model (GLM) were used to uncover the effects of the variables, such as nodal status, distant metastasis, angiogenic patterns, and MVD, on survival. There was an association between only one of the microvascular patterns and aggressive clinical course. Increased blood-filled capillaries with some clustering in the tumor might be a predictor of aggressive biological behavior in invasive breast carcinomas. Similar studies investigating larger series are needed before a generalized conclusion can be made.

Angiogenesis in pre-malignant conditions

Angiogenesis is an essential process involved in the normal growth and differentiation. In its defective and excessive form, angiogenesis is a crucial event in the progression of many human diseases. Excessive angiogenesis was largely investigated in psoriasis, arthritis, diabetic retinopathy and malignant tumours. Soon after the discovery of angiogenic factors and their inhibitors, the angiogenesis jumped from the experimental studies to clinical application. Tumour-associated angiogenesis is nowadays considered as a priority in oncology based on numerous evidences that showed a significant reduction in tumour growth following anti-angiogenic therapy. However, few data are available on pre-malignant conditions. First evidences on angiogenesis in pre-malignant lesions came from the evaluation of microvessel density (MVD). MVD was found to be significantly increased in a relatively large spectrum of pre-malignant squamous cell lesions, such as in the oral mucosa, skin, uterine cervix, vulva and anal canal. For many of them, a correlation was found between MVD and the expression of vascular endothelial growth factor (VEGF). Based on these data, it was suggested that tumour angiogenesis is not necessarily a characteristic of invasive tumour, but may be an early event during tumourigenesis. Additional evidences came from pre-malignant lesions of glandular epithelia, in which the angiogenic switch was demonstrated by the immunohistochemical expression of VEGF in gastric metaplasia and dysplasia, in atypical adenoma of the colon, atypical hyperplasia and carcinoma in situ of the breast and others. Actually, there are convincing evidences for an active angiogenesis in many cases with pre-malignant conditions, and this supports a more accurate evaluation of different chemopreventive agents.

Breast tumour angiogenesis

The central importance of tumour neovascularization has been emphasized by clinical trials using antiangiogenic therapy in breast cancer. This review gives a background to breast tumour neovascularization in in situ and invasive breast cancer, outlines the mechanisms by which this is achieved and discusses the influence of the microenvironment, focusing on hypoxia. The regulation of angiogenesis and the antivascular agents that are used in an antiangiogenic dosing schedule, both novel and conventional, are also summarized.

Vascular damaging agents

To provide a comprehensive overview on vascular targeting agents and the application of radiobiological principles in pre-clinical and clinical studies, we completed a comprehensive review of published medical studies on vascular targeting agents using Pub Med. Vascular targeting agents are now divided into vascular disrupting agents (VDAs), which target the pre-existing tumour vasculature, and angiogenesis inhibitors (AIs), which prevent the formation of new blood vessels. Modest success has been seen when VDAs and AIs are used as single agents and therefore combination therapies that can work in a complimentary and synergistic manner, targeting both the tumour cells and endothelial cells, are needed. Radiobiological principles have been used to increase our understanding of these agents, and can explain the increased efficacy of combination treatments. In particular, the alteration of the tumour microenvironment by AIs and VDAs can lead to enhanced efficacy when combined with chemotherapy or radiotherapy, with phase II/III trials showing encouraging results. The optimal use and scheduling of AIs and VDAs remains to be determined. Further understanding of the mechanisms of action of these potentially very exciting anti-neoplastic agents is urgently required.

Emerging drugs to replace current leaders in first-line therapy for breast cancer

Increasing knowledge of drug resistance and side effects of currently approved agents, and of the biology of breast cancer, has given way to new treatment options that improve on previously available agents, or medications that target specific kinases and proteins associated with an oncogenic phenotype. This paper discusses new agents, including improved formulations of paclitaxel and epothilones, and molecularly targeted agents such as bevacizumab, sunitinib malate, pertuzumab, lapatinib, the mTOR inhibitors and farnesyl transferase inhibitors. Although endocrine therapy is a targeted therapy, it is not covered in this paper. These agents have increased excitement in the treatment of breast cancer and stand on the forefront of a potential improvement in quality of life and treatment options for patients afflicted with this deadly disease.

The history of the angiogenic switch concept

Spontaneously arising tumor cells are not usually angiogenic at first. The phenotypic switch to angiogenesis is usually accomplished by a substet that induces new capillaries that then converge toward the tumor. The switch clearly involves more than simple upregulation of angiogenic activity and is thought to be the result of a net balance of positive and negative regulators. Tumor growth is although to require disruption of this balance and hence this switch must turned on for cancer progression. Progenitor endothelial cells, the crosstalk between angiogenic factors and their receptors and the interaction between vasculogenesis and lymphangiogenesis are all factors that may contribute to the switch. Its promotion is also the outcome of genetic instability resulting in the emergence of tumor cell lines. This review describes the history of the angiogenic switch illustrated in the literature and with particular reference to the three transgenic mouse models, namely RIP1-TAG2, keratin-14 (K14) (human papilloma virus) HPV16 and papilloma virus, used for stage-specific assessment of the effects of antiangiogenic and antitumorigenic agents.

Dynamic MR imaging of breast lesions: correlation with microvessel distribution pattern and histologic characteristics of prognosis

PURPOSE

To evaluate the association of dynamic enhancement parameters of benign and malignant breast lesions at magnetic resonance (MR) imaging with microvessel distribution and histologic prognostic tumor characteristics.

MATERIALS AND METHODS

Regional review board approval and informed consent were obtained. Surgical resection specimens of breast lesions (32 benign, 86 malignant) in 118 patients (age range, 28-86 years; mean, 58 years) who had undergone dynamic T1-weighted MR imaging of both breasts were included in the study. Different MR enhancement parameters and microvessel density (MVD) distribution were determined. In malignant lesions, TNM stage, tumor grade, proliferative activity, and hormone receptor expression were determined. Spearman correlation coefficients; Wilcoxon, Fisher exact, Kruskal Wallis, and chi(2) tests; and logistic regression analysis were used for evaluation.

RESULTS

Malignant lesions exhibited a higher ratio of microvessels in tumor periphery versus tumor center than did benign lesions (P < .0005). High vessel ratios (P = .001) and low central vessel numbers (P = .007) were associated with high tumor grade. In malignant lesions, initial enhancement ratios of periphery to center of lesion correlated with the corresponding microvessel ratios (r = 0.61). Yet, a high peripheral MVD was not associated with strong peripheral enhancement (r = -0.09). High enhancement ratios, washout rates, and early enhancement peaks were associated with unfavorable, albeit not significant, prognostic indicators. Visible rim enhancement was the most accurate prognostic enhancement criterion for estrogen receptor status (P = .007), tumor grade (P = .06), and lymph node status (P = .046). Washout was the best discriminating criterion for proliferative activity.

CONCLUSION

The different enhancement behaviors of malignant and benign breast lesions cannot be explained by MVD alone; however, a low MVD in the center of carcinoma is reflected quantitatively by a high enhancement ratio and qualitatively by rim enhancement, with an implication of adverse prognosis.

Antiangiogenesis: A Possible Treatment Option for Prostate Cancer?

With a need for effective treatment modalities in prostate cancer, angiogenesis is a likely target for the interference of tumor progression. Angiogenesis promotes the vasculature of a tumor, allowing for tumor progression and for cancer cells to metastasize and spread throughout the circulatory system. To date, there are > 20 antiangiogenic drugs undergoing preclinical and clinical investigation alone and in conjunction with other treatment options to determine the validity of antiangiogenic agents in the treatment of prostate cancer. This article reviews several aspects of antiangiogenesis and its relationship to the treatment of prostate cancer.

Angiogenesis in prolactinomas: regulation and relationship with tumour behaviour

Tumours are dependent on angiogenesis for growth and inhibition of angiogenesis has become a target for antineoplastic therapy. In the pituitary, unlike other tissues, vascularization is lower in adenomas compared to the normal gland. Despite this finding, a relationship between increased vascularity and several aspects of prolactinoma behaviour such as size, invasiveness, surgical outcome and malignancy, has been demonstrated. The process of angiogenesis is the result of a balance of stimulating and inhibiting factors. It is likely that an interaction between gene expression (such as pituitary tumour transforming gene (PTTG) and a novel gene located within the Edpm5 quantitative trait locus), hormonal stimuli including oestrogens, dopamine, 16 kDa fragments of prolactin and proangiogenic and antiangiogenic growth factors (for example, vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF-2), determine the final angiogenic phenotype of prolactinomas, and thus subsequent tumour behaviour. The elucidation of all the factors involved in the regulation of angiogenesis and their interactions might open new possibilities in the treatment of prolactinomas, especially in those cases with resistance or intolerance to dopamine agonists.

Antiangiogenic strategies, compounds, and early clinical results in breast cancer

Angiogenesis is a multi-step process leading to the formation of new blood vessels from pre-existing vasculature and it is necessary for primary tumor growth, invasiveness and development of metastasis. Experimental and clinical data demonstrated that breast cancer is an angiogenesis-dependent disease and that the vascular endothelial growth factor (VEGF) family plays a key role it being a highly expressed and selective endothelial cell growth factor. Preclinical studies have shown that the angiogenic switch occurs early in the multistage process of breast cancer development. Targeting the molecular pathways involved in tumor progression by biologically-designed treatments is a new therapeutic paradigm aimed to reach cancer growth control. A number of possible therapeutic targets for antiangiogenic agents have been identified. Here we discuss the therapeutic approach based on inhibition of angiogenesis in the context of breast cancer with a focus on the early clinical studies on antiangiogenic agents in advanced disease.

Targeting Angiogenesis for Mammary Cancer Prevention: Factors to Consider in Experimental Design and Analysis

An experimental model developed to investigate premalignant stages of breast cancer was used to establish a rationale for designing experiments that target angiogenesis for cancer prevention. Blood vessels were identified via CD31 immunostaining, and all vessels that occurred in a 50 μm wide region circumscribing each pathology were counted using a digital imaging technique. The blood vessel density associated with terminal end buds was unaffected by carcinogen treatment, whereas vessel density was higher in intraductal proliferations and ductal carcinoma in situ than in terminal end buds (P &lt; 0.001) and total vascularity increased with morphologic progression. In comparison with intraductal proliferation or ductal carcinoma in situ, mammary carcinomas had higher vascular density in the tissue surrounding the cancer with a marked increase in the number of blood vessels &lt;25 μm2. These data suggest that antiangiogenic chemopreventive agents would inhibit cancer occurrence if initiated at any premalignant stage of the carcinogenic process. Because increased vascular density observed during premalignancy could be explained by the size expansion of the lesion and its encroachment on a preexisting blood supply, by pathology-associated vessel expansion, and/or by angiogenesis, it remains to be determined if antiangiogenic agents will reduce the prevalence of premalignant lesions or cause their accumulation by blocking conversion to carcinomas. Failure to recognize the patterns of vascularization that accompany morphologic progression could limit the success of efforts to target angiogenesis for cancer prevention and lead to misinformation about how agents that affect blood vessel formation or growth inhibit the carcinogenic process.

The Combination of Antiangiogenic and Cytotoxic Agents in the Treatment of Prostate Cancer

Metastatic prostate cancer is one of the leading causes of cancer death in men. Although initially responsive to hormone therapy, it eventually progresses in almost all patients. For this reason, there has been a search for novel agents to use in the fight against androgen-independent prostate cancer. Antiangiogenesis is a relatively new antitumor strategy that has been employed in the treatments of many malignancies. As prostate cancer is likely dependent on angiogenesis for its growth and progression, it would logically serve as a good target for this modality. Initially met with great enthusiasm, antiangiogenic drugs have seen only limited success when used as single agents. This has been attributed to many possible etiologies including lack of cytotoxicity and use in situations of large tumor burden. In order to overcome these problems, many investigators are combining antiangiogenic agents with more traditional cytotoxic chemotherapy regimens in hope of augmenting the effects of either drug alone. This article will review the background of angiogenesis inhibition and the use of such combinations in metastatic prostate cancer.

Angiogenesis in endocrine tumors

Angiogenesis is the process of new blood vessel development from preexisting vasculature. Although vascular endothelium is usually quiescent in the adult, active angiogenesis has been shown to be an important process for new vessel formation, tumor growth, progression, and spread. The angiogenic phenotype depends on the balance of proangiogenic growth factors such as vascular endothelial growth factor (VEGF) and inhibitors, as well as interactions with the extracellular matrix, allowing for endothelial migration. Endocrine glands are typically vascular organs, and their blood supply is essential for normal function and tight control of hormone feedback loops. In addition to metabolic factors such as hypoxia, the process of angiogenesis is also regulated by hormonal changes such as increased estrogen, IGF-I, and TSH levels. By measuring microvascular density, differences in angiogenesis have been related to differences in tumor behavior, and similar techniques have been applied to both benign and malignant endocrine tumors with the aim of identification of tumors that subsequently behave in an aggressive fashion. In contrast to other tumor types, pituitary tumors are less vascular than normal pituitary tissue, although the mechanism for this observation is not known. A relationship between angiogenesis and tumor size, tumor invasiveness, and aggressiveness has been shown in some pituitary tumor types, but not in others. There are few reports on the role of microvascular density or angiogenic factors in adrenal tumors. The mechanism of the vascular tumors, which include adrenomedullary tumors, found in patients with Von Hippel Lindau disease has been well characterized, and clinical trials of antiangiogenic therapy are currently being performed in patients with Von Hippel Lindau disease. Thyroid tumors are more vascular than normal thyroid tissue, and there is a clear correlation between increased VEGF expression and more aggressive thyroid tumor behavior and metastasis. Although parathyroid tissue induces angiogenesis when autotransplanted and PTH regulates both VEGF and MMP expression, there are few studies of angiogenesis and angiogenic factors in parathyroid tumors. An understanding of the balance of angiogenesis in these vascular tumors and mechanisms of vascular control may assist in therapeutic decisions and allow appropriately targeted treatment.

Angiogenesis in anal warts, anal intraepithelial neoplasia and anal squamous cell carcinoma

INTRODUCTION

Most cases of anal carcinoma seem to develop from high grade anal intraepithelial neoplasia (AIN) caused by persistent anal warts. Similar pre-invasive epithelial genital lesions (e.g. those of the cervix and vulva) have been shown to be associated with increased angiogenesis. In this study we examined biopsies of anal lesions ranging from warts to invasive anal carcinoma, with the aim of assessing the degree of angiogenesis in pre-invasive anal lesions.

METHOD

Samples from 70 patients (51 male) who had undergone excision biopsy or resection of anal wart lesions (20), low grade AIN (12), high grade AIN (27) and anal squamous cell carcinoma (SCC) (11) were studied. Samples (6) from normal HIV-anal skin were used as controls. The samples were stained for von Willebrand factor, a specific marker of endothelial cells. Angiogenesis was measured by microvessel density (MVD) analysis, quantifying the microvessels in the stroma adjacent to the epithelial lesion.

RESULTS

There was a statistically significant (P < 0.001) progressive increase in MVD between low grade AIN, high grade AIN and anal SCC. The difference in MVD between normal skin, warts and low grade AIN was not statistically significant.

CONCLUSION

There are progressive abnormal patterns of angiogenesis in highly dysplastic lesions, similar to those found in cervical and vulvar pathology. These findings may have biological, prognostic and therapeutic implications.

Angiogenesis in pituitary adenomas

Angiogenesis, which is the formation of new blood vessels from preexisting capillaries, plays an important role in tumor growth and metastasis. In this review, the focus is on angiogenesis in pituitary adenomas. Angiogenesis of pituitary adenomas has been assessed by studying tumor microvessel density using specific immunohistochemical markers to clarify the relationship between angiogenesis and tumor behavior. Unlike other organs, pituitary adenomas have significantly lower vascular densities as compared to nontumorous adenohypophysis, suggesting that the lack of significant angiogenesis may play a role in the slow pace of pituitary tumor growth and rarity of metastases. In addition, the relationship between microvessel density and various factors in pituitary adenomas is reviewed, including tumor types, age and sex, invasiveness, malignancy, several proliferative markers (MIB-1 or Ki-67). However, further studies will be needed, since many studies have reached opposite conclusions. Angiogenesis is a complex multistep process and several factors are found to be involved in each step of neovascularization, such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and various other cytokines. VEGF and bFGF (or FGF-2), which are the most potent angiogenesis inducers among them, have been studied by immunohistochemistry, in situ hybridization, or in vitro studies in normal or adenomatous pituitaries and these results are also discussed in this review.

Kallistatin is a new inhibitor of angiogenesis and tumor growth

Kallistatin is a unique serine proteinase inhibitor (serpin) and a heparin-binding protein. It has been localized in vascular smooth muscle cells and endothelial cells of human blood vessels, suggesting that kallistatin may be involved in the regulation of vascular function. Our previous study showed that kallistatin plays a role in neointima hyperplasia. In this study, we investigated the potential role of kallistatin in angiogenesis in vitro and in vivo. Purified human kallistatin significantly inhibited vascular endothelial growth factor (VEGF)- or basic fibroblast growth factor (bFGF)-induced proliferation, migration, and adhesion of cultured endothelial cells. Kallistatin attenuated VEGF- or bFGF-induced capillary density and hemoglobin content in subcutaneously implanted Matrigel plugs in mice. To further investigate the role of kallistatin in angiogenesis, we prepared adenovirus carrying the human kallistatin cDNA (Ad.HKBP) and evaluated the effect of kallistatin gene delivery on spontaneous angiogenesis in a rat model of hind-limb ischemia. Local kallistatin gene delivery significantly reduced capillary formation and regional blood perfusion recovery in the ischemic hind limb after removal of the femoral artery. Furthermore, a single intratumoral injection of Ad.HKBP into pre-established human breast tumor xenografts grown in athymic mice resulted in significant inhibition of tumor growth. CD31 immunostaining of tumor sections showed a decreased number of blood vessels in the kallistatin-treated group as compared to the control. These results demonstrate a novel role of kallistatin in the inhibition of angiogenesis and tumor growth.

Ductal carcinoma in situ of the breast: a comparative analysis of histology, nuclear area, ploidy, and neovascularization provides differentiation between low- and high-grade tumors

Ductal carcinoma in situ (DCIS) is a heterogeneous group of lesions that has been subdivided into three types: well differentiated (grade I), moderately differentiated (grade II), and poorly differentiated (grade III). Forty-five cases of DCIS were analyzed for image analysis: nuclear area, DNA ploidy, and vascularization in order to establish a more precise correlation between the histologic grade and these morphometric parameters. Our results confirm that the mean nuclear area, DNA ploidy, and microvessel density (MVD) progressively increased from DCIS grade I to DCIS grade III. The analysis of the nuclear area in relationship to DCIS grading demonstrated a progressive increase of values between grades I/II to grade III, but these data have no statistical significance. An analysis of DNA ploidy demonstrated significant differences between grades I/III (p < 0.05), but there was no statistical significance between grades I/II, grades II/III, or both (p > 0.005). The analysis of MVD was extremely significant between grades I/III (p < 0.001) and grades II/III (p < 0.001), but between grades I/II, these values showed no significant differences (p > 0.05). Based on this study, it can be concluded that image analysis techniques confirm how DCIS presents morphometric values that increase from DCIS grade I to DCIS grade III and that within this spectrum, DCIS grade III can be identified as a group of tumors presenting a large nuclear area, aneuploid DNA, and abundant vascular neogenesis, confirming that this neoplasm displays more aggressive patterns than the other two types. These criteria should justify a higher rate of tumor progression to DCIS grade III.

The role of angiogenesis in hematologic malignancies

Several reports have highlighted the biologic relevance of angiogenesis in neoplastic disorders and its potential impact on prognosis. In this review, we focus on recent findings about angiogenesis and angiogenetic factors in hematologic malignancies. We summarize the body of evidence supporting the hypothesis that a common progenitor gives rise to cells of both the endothelial and the hematopoietic lineages, and the current knowledge about the involvement of normal stromal cells in bone marrow angiogenesis. We also discuss the methodological aspects of microvessel count as a measure of tumor angiogenesis. Finally, we describe the current therapeutic role of angiogenesis inhibitors and possible future strategies involving these agents.

Angiogenesis as a biomarker and target in cancer chemoprevention

Angiogenesis, the formation of new blood vessels from existing vasculature, is essential to the late stages of carcinogenesis, allowing tumours to grow beyond 1-2 mm in diameter, invade surrounding tissue, and metastasise. However, more than two decades ago, angiogenesis that preceded neoplastic transformation was seen. Indeed, it can be detected in inflammatory and infectious diseases that increase the risk of developing cancer. Recent advances in fluorescence endoscopy and histological assessment suggest that, for certain cancers, the degree of new blood-vessel formation may differ between the early and late stages of carcinogenic progression. The association between angiogenesis and cancer occurrence, and ease of detection of this process in accessible tissues early in carcinogenesis, mean that angiogenesis fulfils the criteria for a biomarker of the effectiveness of chemopreventive intervention. There is also some evidence that biochemical assays of angiogenic growth factors may offer similar potential as surrogate biomarkers. Many natural and synthetic chemopreventive agents in development or in clinical use inhibit new vessel formation in vivo. Validation of angiogenesis as a biomarker for the effectiveness of chemoprevention should further the advancement of some chemopreventive agents.

Angiogenesis: pathological, prognostic, and growth-factor pathways and their link to trial design and anticancer drugs

Angiogenesis is essential for tumour growth, invasion, and metastasis. Tumour blood vessels show many differences from normal vessels and are not genetically unstable, so they form a potentially key area for therapy of all types of cancer including leukaemias. Here we review current knowledge on the multiple pathways controlling tumour angiogenesis and assess which are the most clinically relevant. We also review the clinical evidence that angiogenesis affects the behaviour of cancer. Retrospective studies on intratumoral vascularisation suggest that it is an independent prognostic factor that merits prospective validation. Also, the presence of vascular endothelial growth factor in high concentrations in primary cancers is associated with poor prognosis. Key targets for drug development, current clinical trials, and the problems of developing drugs that do not have direct cytotoxic effects are reviewed. Recommendations are made on organising and monitoring antiangiogenic trials.

Mechanisms of angiogenesis and their use in the inhibition of tumor growth and metastasis

There is a constant requirement for vascular supply in solid tumors. Tumor-associated neovascularization allows the tumor cells to express their critical growth advantage. Axillary lymph node status is the most important prognostic factor in operable breast cancer, and experimental and clinical evidence suggests that the process of metastasis is also angiogenesis-dependent. Various angiogenic growth factors and cytokines induce neovascularization in tumors, namely members of the vascular endothelial growth factor (VEGF) and angiopoietin (Ang) gene families. A strong correlation has been found between VEGF expression and increased tumor microvasculature, malignancy, and metastasis in breast cancer. Anti-angiogenic therapy approaches offer a new promising anti-cancer strategy and a remarkably diverse group of over 20 such drugs is currently undergoing evaluation in clinical trials.

Nonpalpable breast lesions: evaluation with power Doppler US and a microbubble contrast agent-initial experience

PURPOSE

To evaluate power Doppler ultrasonography (US) performed with a microbubble US contrast agent in the differentiation of nonpalpable breast lesions.

MATERIALS AND METHODS

Fifty nonpalpable breast lesions in 50 patients were prospectively evaluated with power Doppler US before and after injection of the contrast agent SH U 508A. Lesion vascularity and the morphology of vessels on US scans were analyzed and were correlated with histologic results.

RESULTS

Surgical excision revealed 22 cancers and 28 benign lesions. At nonenhanced power Doppler US, eight (36%) of 22 cancers and four (14%) of 28 benign lesions were vascular. At contrast agent-enhanced power Doppler US, 21 (95%) cancers and six (21%) benign lesions were vascular (P <.001). Irregular vessels were seen in three cancers and one benign lesion at nonenhanced power Doppler US and in 11 cancers and one benign lesion at contrast-enhanced power Doppler US. By using the presence of vascularity in the mass as the diagnostic criterion for malignancy, the sensitivity, specificity, and positive and negative predictive values of power Doppler US changed from 36%, 86%, 67%, and 63%, respectively, to 95%, 79%, 78%, and 96% after contrast agent injection.

CONCLUSION

Contrast-enhanced power Doppler US was superior to nonenhanced power Doppler US in the demonstration and characterization of tumor vascularity in nonpalpable breast lesions. Contrast-enhanced power Doppler US may be useful for the differentiation between nonpalpable breast cancers and benign tumors.

Xenograft models of premalignant breast disease

Dysplastic and hyperplastic proliferative lesions with graded severity of atypia are recognized in a number of tissues and are generally suspected to be premalignant, that is to say at high risk for further progressing to carcinoma in situ and invasive cancer. However, few xenograft models of premalignancy for any organ site have been successfully developed. A good model of human premalignant breast disease would lead to lesions which resemble high risk human breast disease in xenografts and sporadically progress to invasive cancer with time. In this chapter the use of breast tissue pieces and epithelial cells for establishment of xenografts and the development of human breast epithelial cell lines that form premalignant xenograft lesions are described. MCF10AT cells not only form simple differentiated ducts which persist in xenografts and sporadically progress to carcinoma, but also form intermediate proliferative lesions resembling proliferative disease without atypia, atypical hyperplasia, and carcinoma in situ.