Tumor-infiltrating endothelial cells and endothelial precursor cells in inflammatory breast cancer

Inflammatory breast cancer biomarker identification by simultaneous TGIRT-seq profiling of coding and non-coding RNAs in tumors and blood

Inflammatory breast cancer (IBC) is the most aggressive and lethal breast cancer subtype, but lags in biomarker identification. Here, we used an improved Thermostable Group II Intron Reverse Transcriptase RNA sequencing (TGIRT-seq) method to simultaneously profile coding and non-coding RNAs from tumors, PBMCs, and plasma of IBC and non-IBC patients and healthy donors. Besides RNAs from known IBC-relevant genes, we identified hundreds of other overexpressed coding and non-coding RNAs (p≤0.001) in IBC tumors and PBMCs, including higher proportions with elevated intron-exon depth ratios (IDRs), likely reflecting enhanced transcription resulting in accumulation of intronic RNAs. As a consequence, differentially represented protein-coding gene RNAs in IBC plasma were largely intron RNA fragments, whereas those in healthy donor and non-IBC plasma were largely fragmented mRNAs. Potential IBC biomarkers in plasma included T-cell receptor pre-mRNA fragments traced to IBC tumors and PBMCs; intron RNA fragments correlated with high IDR genes; and LINE-1 and other retroelement RNAs that we found globally up-regulated in IBC and preferentially enriched in plasma. Our findings provide new insights into IBC and demonstrate advantages of broadly analyzing transcriptomes for biomarker identification. The RNA-seq and data analysis methods developed for this study may be broadly applicable to other diseases.

Comparative transcriptional analyses of preclinical models and patient samples reveal MYC and RELA driven expression patterns that define the molecular landscape of IBC

Inflammatory breast cancer (IBC) is an aggressive disease for which the spectrum of preclinical models was rather limited in the past. More recently, novel cell lines and xenografts have been developed. This study evaluates the transcriptome of an extended series of IBC preclinical models and performed a comparative analysis with patient samples to determine the extent to which the current models recapitulate the molecular characteristics of IBC observed clinically. We demonstrate that the IBC preclinical models are exclusively estrogen receptor (ER)-negative and of the basal-like subtype, which reflects to some extent the predominance of these subtypes in patient samples. The IBC-specific 79-signature we previously reported was retrained and discriminated between IBC and non-IBC preclinical models, but with a relatively high rate of false positive predictions. Further analyses of gene expression profiles revealed important roles for cell proliferation, MYC transcriptional activity, and TNFɑ/NFκB in the biology of IBC. Patterns of MYC expression and transcriptional activity were further explored in patient samples, which revealed interactions with ESR1 expression that are contrasting in IBC and nIBC and notable given the comparatively poor outcomes of ER+ IBC. Our analyses also suggest important roles for NMYC, MXD3, MAX, and MLX in shaping MYC signaling in IBC. Overall, we demonstrate that the IBC preclinical models can be used to unravel cancer cell intrinsic molecular features, and thus constitute valuable research tools. Nevertheless, the current lack of ER-positive IBC models remains a major hurdle, particularly since interactions with the ER pathway appear to be relevant for IBC.

Targeting Signaling Pathways in Inflammatory Breast Cancer

Inflammatory breast cancer (IBC), although rare, is the most aggressive type of breast cancer. Only 2-4% of breast cancer cases are classified as IBC, but-owing to its high rate of metastasis and poor prognosis-8% to 10% of breast cancer-related mortality occur in patients with IBC. Currently, IBC-specific targeted therapies are not available, and there is a critical need for novel therapies derived via understanding novel targets. In this review, we summarize the biological functions of critical signaling pathways in the progression of IBC and the preclinical and clinical studies of targeting these pathways in IBC. We also discuss studies of crosstalk between several signaling pathways and the IBC tumor microenvironment.

In vitro vascularized tumor platform for modeling tumor-vasculature interactions of inflammatory breast cancer

Inflammatory breast cancer (IBC), a rare form of breast cancer associated with increased angiogenesis and metastasis, is largely driven by tumor-stromal interactions with the vasculature and the extracellular matrix (ECM). However, there is currently a lack of understanding of the role these interactions play in initiation and progression of the disease. In this study, we developed the first three-dimensional, in vitro, vascularized, microfluidic IBC platform to quantify the spatial and temporal dynamics of tumor-vasculature and tumor-ECM interactions specific to IBC. Platforms consisting of collagen type 1 ECM with an endothelialized blood vessel were cultured with IBC cells, MDA-IBC3 (HER2+) or SUM149 (triple negative), and for comparison to non-IBC cells, MDA-MB-231 (triple negative). Acellular collagen platforms with endothelialized blood vessels served as controls. SUM149 and MDA-MB-231 platforms exhibited a significantly (p < .05) higher vessel permeability and decreased endothelial coverage of the vessel lumen compared to the control. Both IBC platforms, MDA-IBC3 and SUM149, expressed higher levels of vascular endothelial growth factor (p < .05) and increased collagen ECM porosity compared to non-IBCMDA-MB-231 (p < .05) and control (p < .01) platforms. Additionally, unique to the MDA-IBC3 platform, we observed progressive sprouting of the endothelium over time resulting in viable vessels with lumen. The newly sprouted vessels encircled clusters of MDA-IBC3 cells replicating a key feature of in vivo IBC. The IBC in vitro vascularized platforms introduced in this study model well-described in vivo and clinical IBC phenotypes and provide an adaptable, high throughput tool for systematically and quantitatively investigating tumor-stromal mechanisms and dynamics of tumor progression.

The use of systemic therapies to prevent progression of inflammatory breast cancer: which targeted therapies to add on cytotoxic combinations?

INTRODUCTION

Inflammatory breast cancer is a rare but frequently fatal disease, essentially because of its high ability to develop distant metastases. Even though the prognosis of IBC was significantly improved by multimodal management, including the systematic use of cytotoxic-based induction, the prognosis remains largely dismal. Areas covered: This review presents the main achievements in the systemic treatment of IBC during the past 30 years. It focuses more specifically on recent results obtained with targeted therapies, including anti-HER2 and anti-angiogenic agents. Novel approaches under investigation are presented. Expert commentary: Current management of IBC is subtype-specific and the largest benefit has been achieved in HER2-positive disease. The identification of breakthrough therapeutic advances is eagerly awaited and will require the development of IBC-specific clinical trials. Future clinical investigations should not only aim to increase the pathological response rate but also to eradicate distant metastases, which ultimately lead to patient death.

Management of locally advanced breast cancer-perspectives and future directions

Locally advanced breast cancer (LABC) constitutes a heterogeneous entity that includes advanced-stage primary tumours, cancers with extensive nodal involvement and inflammatory breast carcinomas. Although the definition of LABC can be broadened to include some large operable breast tumours, we use this term to strictly refer to inoperable cancers that are included in the above-mentioned categories. The prognosis of such tumours is often unfavourable; despite aggressive treatment, many patients eventually develop distant metastases and die from the disease. Advances in systemic therapy, including radiation treatment, surgical techniques and the development of new targeted agents have significantly improved clinical outcomes for patients with this disease. Notwithstanding these advances, LABC remains an important clinical problem, particularly in developing countries and those without widely adapted breast cancer awareness programmes. The optimal management of LABC requires a multidisciplinary approach, a well-coordinated treatment schedule and close cooperation between medical, surgical and radiation oncologists. In this Review, we discuss the current state of the art and possible future treatment strategies for patients with LABC.

Endothelial progenitor cells: current issues on characterization and challenging clinical applications

Since their discovery about a decade ago, endothelial precursor cells (EPC) have been subjected to intensive investigation. The vision to stimulate respectively suppress a key player of vasculogenesis opened a plethora of clinical applications. However, as research opened deeper insights into EPC biology, the enthusiasm of the pioneer era has been damped in favour of a more critical view. Recent research is focused on three major questions: The fact that the number of EPC in peripheral blood is exceedingly low has consistently raised suspicion whether these cells can plausibly have an impact on physiological or pathophysiological processes. Secondly, whereas the key role of EPC in tumourigenesis has been strongly emphasized by various groups in the past, recent publications are challenging this hypothesis. Thirdly, the lack of consensus on EPC-defining markers and standardized protocols for their detection have repeatedly led to difficulties concerning comparability between papers. In this current review, an overview on recent findings on EPC biology is given, their challenging clinical implications are discussed and the perplexity underlying the current controversial debate is illustrated.

Induced lymphatic sinus hyperplasia in sentinel lymph nodes by VEGF-C as the earliest premetastatic indicator

Research on tumor-induced lymphangiogenesis has predominantly focused on alterations and abnormal growth of peritumoral and intratumoral lymphatic vessels. However, recent evidence indicates that lymphangiogenesis of sentinel lymph nodes might also contribute to cancer progression. In clinical oncology, the sentinel lymph nodes play an important role in diagnosis, staging and management of disease. The prognostic value that may be placed in the analysis of various parameters in tumor-free lymph nodes is still under debate. We, therefore, chose to investigate genetically fluorescent MDA-MB-435/green fluorescent protein human cancer cells transfected to overexpress VEGF-C in a nude mouse model and investigated metastasis, lymph node lymphangiogenesis, lymph node angiogenesis and size of sentinel lymph nodes. The nature of MDA-MB-435, identified as a breast cancer cell line for several decades, has recently been reidentified as being from melanoma origin. Vascular endothelial growth factor-C overexpression induced early metastasis and significantly increased the lymphatic vessel area in sentinel lymph nodes even before the tumor metastasis. At early time-points, expansion of the lymphatic network was observed even though no difference of blood vessel area and lymph node size was detected. These results suggest that primary tumors -via secretion of VEGF-C- can induce hyperplasia of the sentinel lymph node lymphatic vessel network and thereby promote their further spread. In cases of tumor-free lymph nodes the increased lymphatic network of sentinel lymph nodes is a very early premetastatic sign and may provide a new prognostic indicator and target for aggressive diseases.

Tumor stromal vascular endothelial growth factor A is predictive of poor outcome in inflammatory breast cancer

Background

Inflammatory breast cancer (IBC) is a highly angiogenic disease; thus, antiangiogenic therapy should result in a clinical response. However, clinical trials have demonstrated only modest responses, and the reasons for these outcomes remain unknown. Therefore, the purpose of this retrospective study was to determine the prognostic value of protein levels of vascular endothelial growth factor (VEGF-A), one of the main targets of antiangiogenic therapy, and its receptors (VEGF-R1 and -R2) in IBC tumor specimens.

Patients and Methods

Specimens from IBC and normal breast tissues were obtained from Algerian patients. Tumor epithelial and stromal staining of VEGF-A, VEGF-R1, and VEGF-R2 was evaluated by immunohistochemical analysis in tumors and normal breast tissues; this expression was correlated with clinicopathological variables and breast cancer-specific survival (BCSS) and disease-free survival (DFS) duration.

Results

From a set of 117 IBC samples, we evaluated 103 ductal IBC tissues and 25 normal specimens. Significantly lower epithelial VEGF-A immunostaining was found in IBC tumor cells than in normal breast tissues (P <0.01), cytoplasmic VEGF-R1 and nuclear VEGF-R2 levels were slightly higher, and cytoplasmic VEGF-R2 levels were significantly higher (P = 0.04). Sixty-two percent of IBC tumors had high stromal VEGF-A expression. In univariate analysis, stromal VEGF-A levels predicted BCSS and DFS in IBC patients with estrogen receptor-positive (P <0.01 for both), progesterone receptor-positive (P = 0.04 and P = 0.03), HER2+ (P = 0.04 and P = 0.03), and lymph node involvement (P <0.01 for both). Strikingly, in a multivariate analysis, tumor stromal VEGF-A was identified as an independent predictor of poor BCSS (hazard ratio [HR]: 5.0; 95% CI: 2.0-12.3; P <0.01) and DFS (HR: 4.2; 95% CI: 1.7-10.3; P <0.01).

Conclusions

To our knowledge, this is the first study to demonstrate that tumor stromal VEGF-A expression is a valuable prognostic indicator of BCSS and DFS at diagnosis and can therefore be used to stratify IBC patients into low-risk and high-risk groups for death and relapses. High levels of tumor stromal VEGF-A may be useful for identifying IBC patients who will benefit from anti-angiogenic treatment.

Evaluation of lymphangiogenic factors, vascular endothelial growth factor D and E-cadherin in distinguishing inflammatory from locally advanced breast cancer

BACKGROUND

Inflammatory breast cancer (IBC) is an aggressive form of breast cancer that on presentation resembles locally advanced breast cancer (LABC). This study identified molecular features of IBC and LABC to investigate pathogenesis.

MATERIALS AND METHODS

This study involved 100 IBC cases identified in a national IBC registry and 107 non-IBC LABC cases from the National Cancer Institute's Cooperative Breast Cancer Tissue Resource (CBCTR). Vascular endothelial growth factor D (VEGF-D) and E-cadherin levels and lymphatic vessel density (LVD) measured by podoplanin staining were examined by immunohistochemistry on paraffin-embedded tumor specimens. Intralymphatic tumor emboli (ILTE) were assessed in IBC and non-IBC tumors. IBC cases diagnosed by clinicians but not meeting the case definitions of the American Joint Committee on Cancer (AJCC) or the Surveillance, Epidemiology and End Results (SEER) Program of the National Cancer Institute (NCI)(designated atypical IBC) were compared with AJCC- and/or SEER-defined cases (designated classic IBC).

RESULTS

E-cadherin levels were significantly higher in classic IBC cases compared with non-IBC cases (P = .031), whereas compared with classic IBC, patients with non-IBC LABC had significantly higher LVD (P = .0017) and VEGF-D levels (P < .0001). ILTE was marginally greater in classic IBC than in non-IBC (P = .046). The profile of laboratory values in atypical IBC cases more closely resembled those fitting classic IBC than LABC.

CONCLUSION

E-cadherin levels, LVD, VEGF-D expression, and to a lesser extent, ILTE differed between classic IBC and non-IBC LABC. The similarity of laboratory results between atypical IBC and classic IBC vs. LABC suggests the need for broadening both the AJCC and SEER case definitions for this disease.

Evidence of endothelial progenitor cells in the human brain and spinal cord arteriovenous malformations

BACKGROUND

Brain and spinal cord arteriovenous malformations (AVMs) are characterized by aberrant angiogenesis and vascular remodeling. Endothelial progenitor cells (EPCs) can be recruited by stromal cell-derived factor-1 (SDF-1), and participate in vascular remodeling in both physiological and pathological settings.

OBJECTIVE

To investigate whether there are increased EPC levels in the brain and spinal cord AVM nidus.

METHODS

Microsurgical specimens without endovascular embolization and radiosurgery from the brain (n = 12) and spinal cord (n = 5) AVMs were examined. Hemangioblastoma, meningioma, cerebral cortex obtained from epilepsy surgery, and the basilar artery from the autopsy were chosen for control comparisons. EPCs were identified as cells that were double-positive for the stem cell marker CD133 and the endothelial cell marker VEGFR-2 (vascular endothelial growth factor receptor-2 or KDR). In addition, SDF-1 was characterized by immunohistochemistry.

RESULTS

Both brain and spinal AVM tissues displayed more CD133-, SDF-1-, and CD68-positive signals than epilepsy and basilar artery control tissues. The level of EPCs was increased in the brain and spinal cord AVM nidus, mainly at the edge of the vessel wall. The expression of SDF-1 was colocalized with CD31-positive and α-smooth muscle cells, and was predominantly found within the vessel wall.

CONCLUSION

Our data demonstrate that EPCs are present in the nidus of the brain and spinal cord AVMs, which may mediate pathological vascular remodeling and impact the clinical course of AVMs.

Endosialin: from vascular target to biomarker for human sarcomas

Biomarkers have been the focus of investigations to diagnose disease, track response to therapy and predict prognosis. Meanwhile, the identification of new targets for therapeutic intervention is an ongoing quest in the field of oncology. The recognition of endosialin as an antigen that is selectively overexpressed in human tumor tissues offers new strategies for treating cancer. Not only do the tumor vasculature and stromal compartments upregulate endosialin but, importantly, the malignant cells of sarcomas strongly express endosialin as well. A diagnostic assay that measures the intensity of endosialin expression in malignant tissues would assist in selecting patients that could benefit from an antiendosialin therapy. Thus, endosialin holds potential value both as a therapeutic target and as a biomarker for certain human cancers.

Purinergic mechanisms in breast cancer support intravasation, extravasation and angiogenesis

Several advances have recently expanded models of tumor growth and promoted the concept of tumor homeostasis, the hypothesis that primary tumors exert an anti-proliferative effect on both themselves and subclinical secondary metastases. Recent trials indicate that the characterization of tumor growth as uncontrolled is inconsistent with animal models, clinical models, and epidemiological models. There is a growing body of evidence which lends support to an updated concept of tumor growth: tumor homeostasis. In the case of breast cancer, if not all metastasizing tumors, these advances suggest an inconvenient truth. That is, if breast tumor cells metastasize to distant sites early in the tumorigenesis process, then removal of a breast tumor may hasten the development of its metastases. We explore the heretofore unappreciated notion that nucleotides generated by tumor cells following the secretion of an ADP-kinase can promote metastasis and support angiogenesis. Evidence is presented that blockade of the actions of nucleotides in the setting of newly diagnosed breast cancer may provide a useful adjunct to current anti-angiogenesis treatment.

PDGF and vessel maturation

Pericytes are smooth muscle-like cells found in close contact with the endothelium in capillaries, where they regulate the morphology and function of the vessels. During vessel formation, platelet-derived growth factor-BB (PDGF-BB) is required for the recruitment and differentiation of pericytes. Tumor vessels display abnormal morphology and increased endothelial proliferation, resulting in leaky, tortuous vessels that are often poorly perfused. These vessels typically display decreased pericyte density, and the tumor-associated pericytes often express abnormal markers and show abnormal morphology. Anti-angiogenic therapy targeting pro-angiogenic growth factor pathways has been applied to a broad range of solid tumors with varying results. Studies utilizing mouse models indicate that the presence of pericytes protect endothelial cells against inhibition of vascular endothelial growth factor (VEGF) signaling. Simultaneous inhibition of PDGF receptors on pericytes therefore improves the effect of VEGF inhibitors on endothelial cells and enhances anti-angiogenic therapy.

Histological, Immunohistological, and Ultrastructural Description of Vasculogenic Mimicry in Canine Mammary Cancer

Canine inflammatory mammary cancer (IMC) and human inflammatory breast cancer (IBC) are the most aggressive and lethal type of mammary cancer in female dogs and in women. The generation of microvascular channels by malignant tumor cells (endothelial-like cells [ELCs]) without endothelial cell participation (vasculogenic mimicry) has been reported in human breast cancer, including IBC, and is considered a new type of tumor angiogenesis. The aim of this study was to investigate the presence of ELCs in highly malignant canine mammary tumors (IMC and non-IMC) by histology, inmunohistochemistry (pancytokeratin, cytokeratin 14, vimentin, actin, desmin, vWF, CD31, and CD34), and electron microscopy. This retrospective study included 21 female dogs with diagnoses of IMC and 20 animals with metastatic grade III noninflammatory malignant mammary tumors (MMT). IMC tumors (33.33%) and MMT (5%) showed ELCs forming structures similar to small capillaries. The histological, immunohistochemical (positive to AE1/AE3 and cytokeratin 14, mostly negative to endothelial markers), and ultrastructural characteristics of these cells indicated vasculogenic mimicry. The higher frequency of this phenomenon in inflammatory versus noninflammatory canine mammary cancer is in agreement with previous studies in experimental and spontaneous human IBC, and it could be in relation with the extremely high lymphangiogenic capacity and metastatic lymphangiotropism characteristics of inflammatory breast cancer.

Molecular targets for treatment of inflammatory breast cancer

Despite progress in combined-modality treatment with chemotherapy, surgery, and radiation therapy, the long-term outcome for patients with inflammatory breast cancer (IBC) remains poor. Therapies that target vasculolymphatic processes--angiogenesis, lymphangiogenesis, and vasculogenesis--have shown potential in the treatment for IBC, as represented by bevacizumab. Although the therapeutic effect of targeting lymphangiogenesis and vasculogenesis requires further investigation, targeting of angiogenesis has potential, not only through true antiangiogenic effects, but also through antitumor effects in concert with other pathways. Therapies that target cell proliferation pathways are the most promising targeted therapies for IBC. In particular, therapies that target human epidermal growth factor receptor 2 (for example, trastuzumab and lapatinib) have performed well in the clinical setting, leading to improved outcomes for patients with IBC. Metastatic pathways could have a unique, key role in the aggressiveness of the IBC phenotype. Further extensive work on the unique molecular characteristics of IBC is essential to ensure improved outcomes for patients with this disease. In this Review we discuss three pathways--vasculolymphatic, cell proliferation and metastatic--that could represent important targets in the treatment of IBC.

Tumour vascularisation: a druggable target

Tumour growth, spreading and metastasis require the development of a local vasculature. There have been great advances in the understanding of how this new vasculature arises, particularly in our increased knowledge of the process of angiogenesis, Although, a vast number of pro-angiogenic and anti-angiogenic mediators have been identified, one of the key signalling processes in the development of the tumour vasculature is the hypoxia-induced stimulation of vascular endothelial cell growth factors (VEGFs) production. Anti-VEGF therapy therefore not only provides a new paradigm for limiting tumour growth via targeting angiogenesis, but also provides prototypic agents to test the hypothesis that by controlling the development of the tumour vasculature we are able to limit, and potentially stop, tumour growth and spreading.

Human endothelial precursor cells express tumor endothelial marker 1/endosialin/CD248

Angiogenesis occurs during normal physiologic processes as well as under pathologic conditions such as tumor growth. Serial analysis of gene expression profiling revealed genes [tumor endothelial markers (TEM)] that are overexpressed in tumor endothelial cells compared with normal adult endothelial cells. Because blood vessel development of malignant tumors under certain conditions may include endothelial precursor cells (EPC) recruited from bone marrow, we investigated TEM expression in EPC. The expression of TEM1 or endosialin (CD248) and other TEM has been discovered in a population of vascular endothelial growth factor receptor 2+/CD31+/CD45-/VE-cadherin+ EPC derived from human CD133+/CD34+ cells. EPC share some properties with fully differentiated endothelial cells from normal tissue, yet reverse transcription-PCR and flow cytometry reveal that EPC express higher levels of endosialin at the molecular and protein levels. The elevated expression of endosialin in EPC versus mature endothelial cells suggests that endosialin is involved in the earlier stages of tumor angiogenesis. Anti-endosialin antibodies inhibited EPC migration and tube formation in vitro. In vivo, immunohistochemistry indicated that human EPC continued to express endosialin protein in a Matrigel plug angiogenesis assay established in nude mice. Anti-endosialin antibodies delivered systemically at 25 mg/kg were also able to inhibit circulating murine EPC in nude mice bearing s.c. SKNAS tumors. EPC and bone marrow-derived cells have been shown previously to incorporate into malignant blood vessels in some instances, yet they remain controversial in the field. The data presented here on endothelial genes that are up-regulated in tumor vasculature and in EPC support the hypothesis that the angiogenesis process in cancer can involve EPC.

Pathologic aspects of inflammatory breast cancer: part 2. Biologic insights into its aggressive phenotype

Inflammatory breast cancer (IBC) is the most aggressive and distinct form of primary breast cancer with a peculiar clinical presentation and dismal clinical outcome. This review addresses the pathologic aspects of this entity and discusses the molecular alterations involved in the highly malignant phenotype of IBC.

Inflammatory breast cancer: current understanding

PURPOSE OF REVIEW

Inflammatory breast cancer is a highly aggressive variant of locally advanced breast cancer that carries a significantly worse prognosis. The purpose of this review is to highlight recent advances in the molecular modus operandi of this particular form of breast cancer.

RECENT FINDINGS

Studies on tumor cell emboli, E-cadherin, chemokine receptors, steroid hormone receptor, angiogenesis, lymphangiogenesis and gene expression all suggest significant differences with noninflammatory breast cancer and are clearly in line with a different pathogenesis of the condition.

SUMMARY

This comprehensive review will hopefully allow for better treatment modalities with targeted approaches as suggested by the early data on anti-vascular endothelial growth factor treatment in inflammatory breast cancer.

Angiopoietin-2 decreases vascular endothelial growth factor expression by modulating HIF-1α levels in gliomas

Angiogenesis is thought to depend on a perfectly coordinated balance between endogenous-positive and negative regulatory factors. Of these factors, the vascular endothelial growth factor (VEGF) and angiopoietins (Angs) seem to play an essential role. Recently, we reported the expression of the Ang-natural receptor, Tie2, in neoplastic astrocytic cells within gliomas. Because of the VEGF/Ang2 functional partnership together with the presence of Tie2 in gliomas, we hypothesized a role of Ang2 on the modulation of VEGF levels in these tumors. We examined the effect of Ang2 on VEGF expression in a panel of glioma cells, which showed that Ang2 inhibited VEGF expression at both mRNA and protein levels in Tie2-expressing cells, but not in Tie2-negative cells. VEGF promoter analysis showed that Ang2 regulated VEGF expression at the transcriptional level in relation to a decrease in HIF-1alpha expression and HIF-DNA-binding activity. Tie2 silencing by siRNA rescued the Ang2-mediated downmodulation of VEGF, suggesting an essential role for Tie2 in this regulatory loop. To our knowledge, this is the first report on the role of Ang2/Tie2 in the regulation of HIF-1alpha/VEGF expression, providing additional evidence of the intrinsic coordination that occurs among these factors during angiogenesis.

A novel role for cyclooxygenase-2 in regulating vascular channel formation by human breast cancer cells

Introduction

Cyclo-oxygenase (COX)-2 expression correlates directly with highly aggressive and metastatic breast cancer, but the mechanism underlying this correlation remains obscure. We hypothesized that invasive human breast cancer cells that over-express COX-2 have the unique ability to differentiate into extracellular-matrix-rich vascular channels, also known as vasculogenic mimicry. Vascular channels have been associated with angiogenesis without involvement of endothelial cells, and may serve as another mechanism by which tumor cells obtain nutrients to survive, especially in less vascularized regions of the tumor.

Methods

To determine whether COX-2 regulates vascular channel formation, we assessed whether treatment with celecoxib (a selective COX-2 inhibitor) or silencing COX-2 synthesis by siRNA inhibits vascular channel formation by breast cancer cell lines. Cell lines were selected based on their invasive potential and COX-2 expression. Additionally, gene expression analysis was performed to identify candidate genes involved in COX-2-induced vascular channel formation. Finally, vascular channels were analyzed in surgically resected human breast cancer specimens that expressed varying levels of COX-2.

Results

We found that invasive human breast cancer cells that over-express COX-2 develop vascular channels when plated on three-dimensional matigel cultures, whereas non-invasive cell lines that express low levels of COX-2 did not develop such channels. Similarly, we identified vascular channels in high-grade invasive ductal carcinoma of the breast over-expressing COX-2, but not in low-grade breast tumors. Vascular channel formation was significantly suppressed when cells were treated with celecoxib or COX-2 siRNA. Inhibition of channel formation was abrogated by addition of exogenous prostaglandin E₂. In vitro results were corroborated in vivo in tumor-bearing mice treated with celecoxib. Using gene expression profiling, we identified several genes in the angiogenic and survival pathways that are engaged in vascular channel formation.

Conclusion

Antivascular therapies targeting tumor cell vasculogenic mimicry may be an effective approach to the treatment of patients with highly metastatic breast cancer.

Pericytes and endothelial precursor cells: cellular interactions and contributions to malignancy

Tumor vasculature is irregular, abnormal, and essential for tumor growth. Pericytes and endothelial precursor cells (EPC) contribute to the formation of blood vessels under angiogenic conditions. As primary cells in culture, pericytes and EPC share many properties such as tube/network formation and response to kinase inhibitors selective for angiogenic pathways. Expression of cell surface proteins including platelet-derived growth factor receptor, vascular cell adhesion molecule, intercellular adhesion molecule, CD105, desmin, and neural growth proteoglycan 2 was similar between pericytes and EPC, whereas expression of P1H12 and lymphocyte function-associated antigen-1 clearly differentiates the cell types. Further distinction was observed in the molecular profiles for expression of angiogenic genes. Pericytes or EPC enhanced the invasion of MDA-MB-231 breast cancer cells in a coculture assay system. The s.c. coinjection of live pericytes or EPC along with MDA-MB-231 cells resulted in an increased rate of tumor growth compared with coinjection of irradiated pericytes or EPC. Microvessel density analysis indicated there was no difference in MDA-MB-231 tumors with or without EPC or pericytes. However, immunohistochemical staining of vasculature suggested that EPC and pericytes may stabilize or normalize vasculature rather than initiate vasculogenesis. In addition, tumors arising from the coinjection of EPC and cancer cells were more likely to develop lymphatic vessels. These results support the notion that pericytes and EPC contribute to malignancy and that these cell types can be useful as cell-based models for tumor vascular development and selection of agents that may provide therapeutic benefit.

“Inflammatory” breast cancer

BACKGROUND

"Inflammatory" breast cancer is a rare and very aggressive form of the disease characterised by rapid onset and dismal outcome.

METHODS

This review describes the clinical and molecular aspects of inflammatory breast cancer. The relevant English language literature on of inflammatory breast cancer was searched via Medline and ISI Web of Knowledge Cross Search (1924-2005), cross-referencing with key articles on the subject.

RESULTS AND CONCLUSION

An increasing body of evidence demonstrates that inflammatory breast cancer is a unique form of breast cancer. A prompt diagnosis and multidisciplinary approach (based on neoadjuvant chemotherapy, loco-regional treatment with surgery and/or radiotherapy, followed in some cases by adjuvant systemic therapy) are the two factors most likely to have an impact on survival. As the molecular basis of the disease is becoming increasingly more defined, new potential therapeutic targets may arise in the future.

Increased angiogenesis and lymphangiogenesis in inflammatory versus noninflammatory breast cancer by real-time reverse transcriptase-PCR gene expression quantification

PURPOSE

Inflammatory breast cancer is a distinct and aggressive form of locally advanced breast cancer with unique clinical and pathological features. Recently, histologic evidence of intense angiogenesis was found in inflammatory breast cancer specimens. The aim of this study was to confirm the angiogenic phenotype of inflammatory breast cancer and to investigate its potential to induce lymphangiogenesis.

EXPERIMENTAL DESIGN

Real-time quantitative reverse transcriptase-PCR was used to measure levels of mRNA of tumor angiogenesis and lymphangiogenesis-related factors [vascular endothelial growth factor (VEGF)-A, VEGF-C, VEGF-D, Flt-1, KDR, Flt-4, Ang-1, Ang-2, Tie-1, Tie-2, cyclooxygenase-2, fibroblast growth factor-2 (FGF-2), Egr-1, Prox-1, and LYVE-1] in tumor specimens of 16 inflammatory breast cancer and 20 noninflammatory breast cancer patients. Tissue microarray technology and immunohistochemistry were used to study differential protein expression of some of the angiogenic factors in inflammatory breast cancer and noninflammatory breast cancer. Active lymphangiogenesis was further assessed by measuring lymphatic endothelial cell proliferation.

RESULTS

Inflammatory breast cancer specimens had significantly higher mRNA expression levels than noninflammatory breast cancer specimens of the following genes: KDR (P = 0.033), Ang-1, (P = 0.0001), Tie-1 (P = 0.001), Tie-2 (P = 0.001), FGF-2 (P = 0.002), VEGF-C (P = 0.001), VEGF-D (P = 0.012), Flt-4 (P = 0.001), Prox-1 (P = 0.005), and LYVE-1 (P = 0.013). High mRNA levels of FGF-2 and cyclooxygenase-2 corresponded to increased protein expression by immunohistochemistry. Inflammatory breast cancer specimens contained significantly higher fractions of proliferating lymphatic endothelial cells than noninflammatory breast cancer specimens (P = 0.033).

CONCLUSIONS

Using real-time quantitative reverse transcriptase-PCR and immunohistochemistry, we confirmed the intense angiogenic activity in inflammatory breast cancer and demonstrated the presence of active lymphangiogenesis in inflammatory breast cancer. This may help explain the high metastatic potential of inflammatory breast cancer by lymphatic and hematogenous route. Both pathways are potential targets for the treatment of inflammatory breast cancer.

Update on inflammatory breast cancer

Inflammatory breast cancer (IBC) is both the least frequent and the most severe form of epithelial breast cancer. The diagnosis is based on clinical inflammatory signs and is reinforced by pathological findings. Significant progress has been made in the management of IBC in the past 20 years. Yet survival among IBC patients is still only one-half that among patients with non-IBC. Identification of the molecular determinants of IBC would probably lead to more specific treatments and to improved survival. In the present article we review recent advances in the molecular pathogenesis of IBC. A more comprehensive view will probably be obtained by pan-genomic analysis of human IBC samples, and by functional in vitro and in vivo assays. These approaches may offer better patient outcome in the near future.

Murine endothelial cell lines as models of tumor endothelial cells

Identification of appropriate models for in vivo and in vitro preclinical testing of inhibitors of tumor angiogenesis and progression is vital to the successful development of anticancer therapeutics. Although the focus is on human molecular targets, most preclinical in vivo efficacy testing occurs in mice. The goal of the current studies was to identify a murine endothelial cell line to model tumor endothelium for studying the antiangiogenic activity of therapeutic compounds in vitro. In situ hybridization was performed on three s.c. grown syngeneic murine tumors (B16 melanoma, Lewis lung carcinoma, and CT26 colon carcinoma) to assess expression of murine homologs of human tumor endothelial cell markers in the vasculature of these tumor models. Seven murine endothelial cell lines were characterized for expression of the murine homologs of recognized endothelial cell surface markers as well as for tumor endothelial cell surface markers. The seven murine endothelial cell lines had similar generation times and five of the seven lines were able to form tubes on Matrigel. Real-time-PCR and flow cytometry analysis were used to evaluate relative mRNA and protein expression of murine homologs of several recognized endothelial cell surface markers in the seven cell lines. The expression of the mRNA for the murine homologs of five tumor endothelial cell surface markers was also evaluated. The 2H11 cell line expressed all five of the tumor endothelial cell surface markers as well as several well-recognized endothelial cells markers. The 2H11 cell line responds to known and novel antiangiogenic agents by inhibition of proliferation and tube formation. These cells can be used in in vitro angiogenesis assays for evaluating the potential antiangiogenic properties and interspecies cross-reactivity of novel compounds.

Genetic dissection of tumor angiogenesis: are PlGF and VEGFR-1 novel anti-cancer targets?

Many proliferative diseases, most typically cancer, are driven by uncontrolled blood vessel growth. Genetic studies have been very helpful in unraveling the cellular and molecular players in pathological blood vessel formation and have provided opportunities to reduce tumor growth and metastasis. The fact that tumor vessels and normal blood vessels have distinct properties may help in designing more specific--and therefore safer--anti-angiogenic strategies. Such strategies may interfere with angiogenesis at the cellular or molecular level. Possible molecular targets include angiogenic growth factors and their receptors, proteinases, coagulation factors, junctional/adhesion molecules and extracellular matrix (ECM) components. Some anti-angiogenic drugs, i.e., vascular endothelial growth factor (VEGF) antibodies and VEGF receptor-2 (VEGFR-2) inhibitors, have progressed into clinical cancer trials. While the results of these trials support the potential of anti-angiogenic therapy to treat cancer, they also demonstrate the need for more effective and safer alternatives. Targeting placental growth factor (PlGF) or VEGFR-1 may constitute such an alternative since animal studies have proven their pleiotropic working mechanism and attractive safety profile. Together, these insights may bring anti-angiogenic drugs closer from bench to bedside.

A Naturally Occurring Soluble Form of Vascular Endothelial Growth Factor Receptor 2 Detected in Mouse and Human Plasma

Angiogenesis and vasculogenesis are regulated in large part by several different growth factors and their associated receptor tyrosine kinases (RTKs). Foremost among these is the vascular endothelial growth factor (VEGF) family including VEGF receptor (VEGFR)-2 and -1. VEGFR ligand binding and biological activity are regulated at many levels, one of which is by a soluble, circulating form of VEGFR-1 (sVEGFR-1). This sVEGFR-1 can act as a competitive inhibitor of its ligand, serve as a possible biomarker, and play important roles in cancer and other diseases such as preeclampsia. Recombinant forms of sVEGFR-2 have been shown to have antiangiogenic activity, but a naturally occurring sVEGFR-2 has not been described previously. Here, we report such an entity. Having a molecular weight of ∼160 kDa, sVEGFR-2 can be detected in mouse and human plasma with several different monoclonal and polyclonal anti-VEGFR-2 antibodies using both ELISA and immunoprecipitation techniques. In vitro studies have determined that the sVEGFR-2 fragment can be found in the conditioned media of mouse and human endothelial cells, thus suggesting that it may be secreted, similar to sVEGFR-1, or proteolytically cleaved from the cell. Potential biological activity of this protein was inferred from experiments in which mouse sVEGFR-2 could bind to VEGF-coated plates. Similar to sVEGFR-1 and other soluble circulating RTKs, sVEGFR-2 may have regulatory consequences with respect to VEGF-mediated angiogenesis as well as potential to serve as a quantitative biomarker of angiogenesis and antiangiogenic drug activity, particularly for drugs that target VEGF or VEGFR-2.

Manipulating angiogenesis in medicine

Blood vessels nourish organs with vital nutrients and oxygen and, thus, new vessels form when the embryo needs to grow or wounds are to heal. However, forming new blood vessels is a complex and delicate process, which, unfortunately, is often derailed. Thus, when insufficient vessels form, the tissue becomes ischaemic and stops to function adequately. Conversely, when vessels grow excessively, malignant and inflamed tissues grow faster. It is now becoming increasingly evident that abnormal vessel growth contributes to the pathogenesis of numerous malignant, ischaemic, inflammatory, infectious and immune disorders. With an in-depth molecular understanding, we should be better armamented to combat such angiogenic disorders in the future. That such therapeutic strategies might change the face of medicine is witnessed by initial evidence of success in the clinic.

Update on the management of inflammatory breast cancer

Inflammatory breast cancer (IBC) is the most aggressive manifestation of primary breast carcinoma, with the clinical and biological characteristics of a rapidly proliferating disease. The multidisciplinary management of IBC has changed in the past 3 decades and is presently clearly outlined in sequence, with preoperative or neoadjuvant chemotherapy representing the mainstay of treatment. Anthracyclines and taxanes are the most effective cytotoxic agents in the management of primary breast cancer and should be the standard of treatment for women with IBC. Locoregional treatment includes radiotherapy with or without surgery and continues to play a major role after appropriate medical treatment. The many investigations into the particular molecular determinants of IBC development have provided several interesting new therapeutic targets. Combination regimens that include angiogenic modulators, farnesyl transferase inhibitors, and p53 modulators hold great promise in the medical management of IBC. Future therapeutic approaches should focus on these discoveries so that we can improve the overall prognosis for women with IBC.

New non-angiogenesis dependent pathways for tumour growth

The current wisdom is that tumours are endowed with an angiogenic capability and that their growth, invasion and metastasis are angiogenesis-dependent. This article summarises the literature concerning recent histomorphological studies that indicate that some tumours may be vascularised without significant angiogenesis, probably by using existing vessels, a process later described as vascular co-option, or even by forming vascular channels on their own through a non-endothelial cell process called "vascular mimicry". Moreover, the possibility that bone marrow-derived stem cells may also be a source of endothelial precursor cells recruited for tumour-induced neovascularisation, is reviewed. In fact, it has been assumed that the additional endothelial cells required to construct new tumour vessels come from the division and proliferation of local endothelial cells and that endothelial cells incorporated into sites of neovascularisation, including tumour-induced new blood vessels, may be derived from these precursor cells. Finally, lymphoangiogenesis as a mechanism of de novo formation of lymphatics, favouring the metastatic dissemination of tumour cells, is summarised. Potential therapeutic applications are also discussed.

Inflammatory breast cancer shows angiogenesis with high endothelial proliferation rate and strong E-cadherin expression

Inflammatory breast cancer (IBC) is the most aggressive form of breast cancer. Improved understanding of the mechanisms responsible for the differences between IBC and non-IBC might provide novel therapeutic targets. We studied 35 consecutive patients with IBC, biopsied prior to the initiation of chemotherapy. Angiogenesis was evaluated by Chalkley counting and by assessment of endothelial cell proliferation (ECP) and vessel maturity. The presence of fibrin, expression of the hypoxia marker carbonic anhydrase IX (CA IX) and epithelialcadherin (E-cadherin) expression were immunohistochemically detected. The same parameters were obtained in a group of 104 non-IBC patients. Vascular density, assessed by Chalkley counting (P<0.0001), and ECP (P=0.01) were significantly higher in IBC than in non-IBC. Abundant stromal fibrin deposition was observed in 26% of IBC and in only 8% of non-IBC (P=0.02). Expression of CA IX was significantly less frequent in IBC than in non-IBC with early metastasis (P=0.047). There was a significant positive correlation between the expression of CA IX and ECP in IBC (r=0.4, P=0.03), implying that the angiogenesis is partly hypoxia driven. However, the higher ECP in IBC and the less frequent expression of CA IX in IBC vs non-IBC points at a role for other factors than hypoxia in stimulating angiogenesis. Strong, homogeneous E-cadherin expression was found at cell-cell contacts in all but two IBC cases, both in lymphovascular tumour emboli and in infiltrating tumour cells, challenging our current understanding of the metastatic process. Both the intense angiogenesis and the strong E-cadherin expression may contribute to the highly metastatic phenotype of IBC.

Breast cancer-induced angiogenesis: multiple mechanisms and the role of the microenvironment

Growth and progression of breast cancers are accompanied by increased neovascularization (angiogenesis). A variety of factors, including hypoxia and genetic changes in the tumor cells, contribute to increased production of angiogenic factors. Furthermore, cells within the activated tumor stroma also contribute to the increase in production of vascular endothelial growth factor and other angiogenic factors, including basic fibroblast growth factor and platelet-derived growth factor. The contribution of the microenvironment to tumor-induced angiogenesis is underscored by findings that breast tumors implanted into different tissue sites show marked differences in the extent and nature of the angiogenic response. These findings have important implications for designing anti-angiogenic therapies.

Inflammatory breast cancer: vasculogenic mimicry and its hemodynamics of an inflammatory breast cancer xenograft model

We recently established a new human inflammatory breast cancer (IBC) xenograft (WIBC-9) originating from a patient with IBC. The original tumor and WIBC-9 revealed invasive ductal carcinoma with a hypervascular structure of solid nests and marked lymphatic permeation in the overlying dermis. In the central part of the solid nests, vasculogenic mimicry, which showed an absence of endothelial cells, was observed. Comparison of WIBC-9 with an established non-IBC xenograft (MC-5), using time-course dynamic micro-magnetic resonance angiography analysis (with a newly developed intravascular macromolecular contrast agent for magnetic resonance imaging) demonstrated that the WIBC-9 tumor had blood flow and a vascular mimicry-angiogenesis junction.

Induction of vasculogenesis in breast cancer models

Recently, there have been reports of postnatal vasculogenesis in cases of ischaemia models. The aim of the present study is to provide evidence of postnatal vasculogenesis in breast-cancer-bearing mice. Based on cell surface antigen expression, we isolated endothelial precursor cells from bone marrow, peripheral blood and tumour-infiltrating cells from mice that had received six human breast cancer xenografts. In all three areas (bone marrow, peripheral blood and tumour-infiltrating cells), endothelial precursor cell population was elevated in all transplanted mice. Differentiation and migration activities of endothelial precursor cells were measured by comparing levels of the endothelial precursor cell maturation markers Flk-1, Flt-1, Tie2, VE-cadherin and CD31 among these three areas. The endothelial precursor cell population was 14% or greater in the gated lymphocyte-size fraction of the inflammatory breast cancer xenograft named WIBC-9, which exhibits a hypervascular structure and de novo formation of vascular channels, namely vasculogenic mimicry (Shirakawa et al, 2001). In vitro, bone marrow-derived endothelial precursor cells from four human breast cancer xenografts proliferated and formed multiple clusters of spindle-shaped attaching cells on a vitronectin-coated dish. The attaching cells, which incorporated DiI-labelled acetylated low-density lipoprotein (DiI-acLDL) and were negative for Mac-1. The putative bone marrow derived endothelial precursor cell subset, which was double positive of CD34 and Flk-1, and comparative bone marrow derived CD34 positive with Flk-1 negative subset were cultured. The former subset incorporated DiI-acLDL and were integrated with HUVECs. Furthermore, they demonstrated significantly higher levels of murine vascular endothelial growth factor and interleukin-8 in culture supernatant on time course by enzyme-linked immunosorbent assay. These findings constitute direct evidence that breast cancer induces postnatal vasculogenesis in vivo.

Vasculogenic mimicry and pseudo-comedo formation in breast cancer

Tumors require a blood supply for growth and hematogenous metastases. Until recently, most research in this area has focused on the role of angiogenesis, the recruitment of new vessels into a tumor from preexisting vessels. Previously, in a study of breast cancer (IBC), in which we used established inflammatory breast cancer (IBC) xenografts (WIBC-9) originating from a patient with IBC (Shirakawa et al., Cancer Res 2001:61:445-451), we reported observing vasculogenic mimicry (VM), a condition in which bloodstreams within cancer tissue are not accompanied by a lining of endothelial cells (ECs) (Shirakawa et al., Cancer Res 2002:62:560-566). In the present study, we examined 331 surgically resected breast cancer specimens for evidence of VM, using immunohistochemistry and laser-captured microdissection (LCM) followed by nested reverse transcriptase polymerase chain reaction (RT-PCR). Surprisingly, 7.9% (26 specimens) of the 331 specimens exhibited evidence of VM. Of these 26 VM specimens, 84.6% (22 specimens) exhibited pseudo-comedo formation. RT-PCR analysis of 8 microdissected typical VM specimens revealed expression of Tie-2, Flt-1, thrombin receptor and CD31 in 63, 50, 0 and 0% of specimens, respectively. In contrast, results of RT-PCR analysis of 8 specimens from non-VM tumors were negative for expression of these genes. The 26 VM cases tended to have a higher percentage of hematogenous recurrence (p = 0.059) and a lower percentage of 5-year survival (p = 0.071) than the 305 non-VM cases. However, there were no significant differences in tumor size, lymph node metastasis, estrogen receptors or progesterone receptors between the 2 groups (p > 0.1). Our results suggest that the existence of VM increases the likelihood of hematogenous metastases and is in inverse proportion to prognosis.