Alternative vascularization mechanisms in cancer: Pathology and therapeutic implications

HIF-1α stabilization by mitochondrial ROS promotes Met-dependent invasive growth and vasculogenic mimicry in melanoma cells

The "angiogenic switch" during tumor progression is increasingly recognized as a milestone event in tumorigenesis, although the surprising prometastatic effect of antiangiogenic therapies has recently shaken the scientific community. Tumor hypoxia has been singled out as a possible responsible factor in this prometastatic effect, although the molecular pathways are completely unknown. We report herein that human melanoma cells respond to hypoxia through a deregulation of the mitochondrial release of reactive oxygen species (ROS) by the electron transfer chain complex III. These ROS are mandatory to stabilize hypoxia-inducible factor-1α (HIF-1α), the master transcriptional regulator of the hypoxic response. We found that melanoma cells sense hypoxia-enhancing expression/activation of the Met proto-oncogene, which drives a motogenic escape program. Silencing analyses revealed a definite hierarchy of this process, in which mitochondrial ROS drive HIF-1α stabilization, which in turn activates the Met proto-oncogene. This pathway elicits a clear metastatic program of melanoma cells, enhancing spreading on extracellular matrix, motility, and invasion of 3D matrices, as well as growth of metastatic colonies and the ability to form capillary-like structures by vasculogenic mimicry. Both pharmacological and genetic interference with mitochondrial ROS delivery or Met expression block the hypoxia-driven metastatic program. Hence, we propose that hypoxia-driven ROS act as a primary driving force to elicit an invasive program exploited by aggressive melanoma cells to escape from a hypoxic hostile environment.

Exploring and challenging the network of angiogenesis

Angiogenesis is one of the hallmarks of cancer and, as such, one of the alternative general targets for anticancer therapy. Since angiogenesis is a complex process involving a high number of interconnected components, a network approach would be a convenient systemic way to analyse responses to directed drug attacks. Herein we show that, although the angiogenic network is easily broken by short combinations of directed attacks, it still remains essentially functional by keeping the global patterns and local efficiency essentially unaltered after these attacks. This is a clear sign of its high robustness and resilience and stresses the need of directed, combined attacks for an effective blockade of the process. The results of this theoretical study could be relevant for the design of new antiangiogenic therapies and the selection of their targets.

A new mechanism for pillar formation during tumor-induced intussusceptive angiogenesis: inverse sprouting

One of the hallmarks of intussusceptive angiogenesis is the development of intraluminal connective tissue pillars. The exact mechanism of pillar formation has not yet been elucidated. By using electron and confocal microscopy, we observed intraluminal nascent pillars that contain a collagen bundle covered by endothelial cells (ECs) in the vasculature of experimental tumors. We proposed a new mechanism for the development of these pillars. First, intraluminal endothelial bridges are formed. Second, localized dissolution of the basement membrane occurs and a bridging EC attaches to a collagen bundle in the underlying connective tissue. A pulling force is then exerted by the actin cytoskeleton of the ECs via specific attachment points, which contain vinculin, to the collagen bundle, resulting in suction and subsequent transport of the collagen bundle into and through the vessel lumen. Third, the pillar matures through the immigration of connective tissue cells and the deposition of new collagenous connective tissue. The proposed simple mechanism generates a connection between the processes of endothelial bridging and intussusceptive angiogenesis and identifies the source of the force behind pillar formation. Moreover, it ensures the rapid formation of pillars from pre-existing building blocks and the maintenance of EC polarity. To describe it, we coined the term inverse sprouting.

Tumor-associated macrophages (TAMs) form an interconnected cellular supportive network in anaplastic thyroid carcinoma

BACKGROUND

A relationship between the increased density of tumor-associated macrophages (TAMs) and decreased survival was recently reported in thyroid cancer patients. Among these tumors, anaplastic thyroid cancer (ATC) is one of the most aggressive solid tumors in humans. TAMs (type M2) have been recognized as promoting tumor growth. The purpose of our study was to analyze with immunohistochemistry the presence of TAMs in a series of 27 ATC.

METHODOLOGY/PRINCIPAL FINDINGS

Several macrophages markers such as NADPH oxidase complex NOX2-p22phox, CD163 and CD 68 were used. Immunostainings showed that TAMs represent more than 50% of nucleated cells in all ATCs. Moreover, these markers allowed the identification of elongated thin ramified cytoplasmic extensions, bestowing a "microglia-like" appearance on these cells which we termed "Ramified TAMs" (RTAMs). In contrast, cancer cells were totally negative. Cellular stroma was highly simplified since apart from cancer cells and blood vessels, RTAMs were the only other cellular component. RTAMs were evenly distributed and intermingled with cancer cells, and were in direct contact with other RTAMs via their ramifications. Moreover, RTAMs displayed strong immunostaining for connexin Cx43. Long chains of interconnected RTAMs arose from perivascular clusters and were dispersed within the tumor parenchyma. When expressed, the glucose transporter Glut1 was found in RTAMs and blood vessels, but rarely in cancer cells.

CONCLUSION

ATCs display a very dense network of interconnected RTAMs in direct contact with intermingled cancer cells. To our knowledge this is the first time that such a network is described in a malignant tumor. This network was found in all our studied cases and appeared specific to ATC, since it was not found in differentiated thyroid cancers specimens. Taken together, these results suggest that RTAMs network is directly related to the aggressiveness of the disease via metabolic and trophic functions which remain to be determined.

Bone marrow angiogenesis and progression in multiple myeloma

Multiple myeloma plasma cells home and expand in the bone marrow where cause an unbalanced bone remodelling with increased bone resorption and low bone formation that represent the typical feature in the majority of patients. A clinically relevant aspect of the interactions of multiple myeloma plasma cells in the bone marrow microenvironment is neovascularization, a constant hallmark of disease progression. This process is only partially supported by factors such as vascular endothelial growth factor, fibroblast growth factor-2 and metalloproteinases, which are directly secreted by the tumor cells. In fact, the presence in the bone marrow microenvironment of cytokines, in particular interleukin-6, as a consequence of plasma cell-stromal cell interactions, induces the production and secretion of angiogenic factors by other cells present in the bone microenvironment, thus contributing to the angiogenic switch during the progression of the disease. Near angiogenesis vasculogenesis occur in the bone marrow of myeloma patients and contribute to the vascular three formation. In the bone marrow of myeloma patients haematopoietic stem cells are recruited and induced to differentiate into endothelial cells by the angiogenic cytokines present in the microenvironment. Myeloma plasma cells also induce angiogenesis indirectly via recruitment and activation of stromal inflammatory cells (i.e.: macrophages and mast cells) to secrete their own angiogenic factors. They are recruited and activated by tumor plasma cells through the secretion of fibroblast growth factor-2, interleukin-8, and other chemokines, such as ITAC, Mig, IP-10. When macrophages and mast cells are activated they secrete their angiogenic factors: fibroblast growth factor-2, vascular endothelial growth factor, granulocyte-colony stimulating factor, granulocyte macrophage-colony stimulating factor, which contribute to enhance the tumor neovascularization. Finally, myeloma macrophages when exposed to vascular endothelial growth factor and fibroblast growth factor-2 secreted by plasma cells shows vasculogenic ability and acquire endothelial cell markers and transform into cells functionally and phenotypically similar to paired bone marrow endothelial cells. So they participate to the formation of the bone marrow capillary network (vasculogenic mimicry).

Embryonic signaling in melanoma: potential for diagnosis and therapy

As the frequency of melanoma diagnosis increases, current treatment strategies are still struggling to significantly impact patient survival. Some promise has been shown in treating certain melanomas by targeting activated signaling pathways resulting from specific mutations in proteins, such as BRAF and NRAS. Recently, the identification of embryonic signaling pathways in melanoma has helped us better understand certain biological characteristics, such as cellular heterogeneity and phenotypic plasticity, and has provided novel insight pertinent to diagnosis and therapy. For instance, our studies have shown that the TGF-β family member, Nodal, is expressed in melanoma and is responsible, at least in part, for tumor cell plasticity and aggressiveness. Since the majority of normal adult tissues do not express Nodal, we reason that this embryonic morphogen could be used to identify and target aggressive melanoma cells. We have also identified that molecular cross-talk between the Notch and Nodal pathways may represent a mechanism responsible for the overexpression of Nodal in melanoma. Further exploitation of the relationship between embryonic signaling pathways and cancer pathogenesis could lead to novel approaches for diagnosis and therapy in cancers, such as melanoma.

Distinct contributions of angiogenesis and vascular co-option during the initiation of primary microtumors and micrometastases

Primary tumors and metastases have been thought to initiate avascularly as multicellular aggregates and later induce angiogenesis or initiate vascularly by co-opting pre-existing host blood vessels without inducing angiogenesis. These two distinct concepts of microtumor vascularization have raised significant controversies. To clarify intratumoral vascularization and tumor cell behaviors at single-cell level during the earliest stage of microtumor initiation, we established primary and metastatic microtumor models in Tg(flk1:EGFP) transgenic zebrafish. We found that tumor cells preferred to initiate avascularly as multicellular aggregates and only later (50-100 cells in size) induced angiogenesis in blood-supply-sufficient microenvironments. In blood-supply-deficient microenvironments, less tumor cells (20-30 cells per fish) managed to co-opt and migrate along host vessels, whereas more tumor cells (100-300 cells per fish) could immediately induce angiogenesis without obvious cell migration. In a metastatic model, we clearly observed that tumor cells co-opted, migrated along and proliferated on the surface of host vessels at an early stage after they extravasated from host vessels and induced angiogenesis later when micromatastases comprised only 15-30 tumor cells. Moreover, the inducement of neovessels accelerated the growth of micromatastases in size, meanwhile, decreased the migration of tumor cells on the surface of host vessels. These results suggest that vessel co-option and angiogenesis have distinct contributions during the initiation of microtumors. Microtumors initiated reasonably through co-opting host vessels or inducing angiogenesis, depending on the differences of local microenvironments and cell numbers in microtumors. The results in this study may have important implications for the therapeutic application of antiangiogenic strategies.

Leptin promotes melanoma tumor growth in mice related to increasing circulating endothelial progenitor cells numbers and plasma NO production

Background

Epidemiological studies propose that obesity increases the risk of several cancers, including melanoma. Obesity increases the expression of leptin, a multifunctional peptide produced predominantly by adipocytes which may promote tumor growth. Several recently experiments have suggested that the tumors growth is in need of endothelial progenitor cell (EPC) dependent generation of new blood vessels.

Our objectives in the present study were to examine the effects of leptin on melanoma growth, circulating EPCs number and plasma levels of nitric oxide metabolites (NOx).

Methods

2 × 10⁶ B16F10 melanoma cells were injected to thirty two C57BL6 mice subcutaneously. The mice were randomly divided into 4 groups (n = 8) in 8th day. Two groups were received twice daily intraperitoneal(i.p) injections of either PBS or recombinant murine leptin (1 μg/g initial body weight). Two groups were received i.p. injections of either 9F8 an anti leptin receptor antibody or the control mouse IgG at 50 μg/mouse every 3 consecutive days. By the end of the second week the animals were euthanized and blood samples and tumors were analyzed.

Results

The tumor weight, EPC numbers and NOx level in leptin, PBS, 9F8, and IgG group were (3.2 ± 0.6, 1.7 ± 0.3, 1.61 ± 0.2,1.7 ± 0.3 g), (222.66 ± 36.5, 133.33 ± 171, 23.33 ± 18, 132.66 ± 27.26/ml of blood), and (22.47 ± 5.5, 12.30 ± 1.5, 6.26 ± 0.84, 15.75 ± 6.3 μmol/L) respectively. Tumors weight and size, circulating EPC numbers and plasma levels of NOx were significantly more in the leptin than 9f8 and both control groups (p < 0.05). The plasma concentration of NOx significantly decreased in 9f8 treated mice compare to control group (p < 0.05).

Conclusions

In conclusion, our observations indicate that leptin causes melanoma growth likely through increased NO production and circulating EPC numbers and consequently vasculogenesis.

Integration of genotypic and phenotypic screening reveals molecular mediators of melanoma-stromal interaction

Tumor-endothelium interactions are critical for tumor survival and metastasis. Melanomas can rapidly metastasize early in tumor progression, but the dependence of this aggressive behavior on tumor-stromal interaction is poorly understood. To probe the mechanisms involved, we developed a heterotypic coculture methodology, allowing simultaneous tracking of genomic and phenotypic changes in interacting tumor and endothelial cells in vitro. We found a dramatic rearrangement of endothelial cell networks into patterns reminiscent of vascular beds, even on plastic and glass. Multiple genes were upregulated in the process, many coding for cell surface and secreted proteins, including Neuropilin-2 (NRP2). A critical role of NRP2 in coordinated cell patterning and growth was confirmed using the coculture system. We conclude that NRP2 represents an important mediator of melanoma-endothelial interactions. Furthermore, the described methodology represents a powerful yet simple system to elucidate heterotypic intercellular interactions mediating diverse physiological and pathological processes.

Identification of novel prognostic markers in relapsing localized resectable neuroblastoma

Patients with localized resectable neuroblastoma (NB) generally have an excellent prognosis and can be treated by surgery alone, but approximately 10% of them develop local recurrences or metastatic progression. The known predictive risk factors are important for the identification of localized resectable NB patients at risk of relapse and/or progression, who may benefit from early and aggressive treatment. These factors, however, identify only a subset of patients at risk, and the search for novel prognostic markers is warranted. This review focuses on the recent advances in the identification of new prognostic markers. Recently we addressed the search of novel genetic prognostic markers in a selected cohort of patients with stroma-poor localized resectable NB who underwent disease relapse or progression (group 1) or complete remission (group 2). High-resolution array-comparative genomic hybridization (CGH) DNA copy-number analysis technology was used. Chromosome 1p36.22p36.32 loss and 1q22qter gain, detected almost exclusively in group 1 patients, were significantly associated with poor event-free survival (EFS). Increasing evidence points to anaplastic lymphoma kinase (ALK) as a fundamental oncogene associated with NB. The immunohistochemical analysis of sporadic NB localized resectable primary tumors (stage 1-2) showed a correlation between aberrant ALK level of expression and tumor progression and clinical outcome. Moreover, other factors that might influence the clinical behavior of these tumors will be reviewed.

Circulating endothelial and endothelial progenitor cells in non-small-cell lung cancer

New treatments have recently been introduced for treating non-small-cell lung cancer. Chemotherapeutic agents, such as pemetrexed, and targeted therapies, such as bevacizumab, erlotinib or gefitinib, have extended treatment options for selected histological subgroups. Antiangiogenic treatments, either associated with conventional chemotherapeutic drugs or given alone as maintenance therapy, constitute an active clinical research field. However, not all lung cancer patients benefit from antiangiogenic compounds. Moreover, tumour response assessment is often difficult when using these drugs, since targeted therapies generally do not cause rapid and measurable tumour shrinkage but, rather, long stabilisations and slight density changes on imaging tests. The finding of clinical or biological factors that might identify patients who will better benefit from these treatments, as well as identifying surrogate markers of tumour response and prognosis, is an issue of great interest. In that sense, different research lines have investigated the epidermal growth factor receptor (EGFR) and the vascular endothelial growth factor receptor (VEGFR) pathways. Circulating endothelial (CECs) and endothelial progenitor cells (CEPCs) are of prognostic value in different types of cancers, and relevant data are published about their potential usefulness as predictors of response to chemotherapy and antiangiogenic treatments. In this review, we discuss the data available on the role of CECs and CEPCs as prognostic factors and as surrogate markers of treatment response in non-small-cell lung cancer.

Apelin expression in human non-small cell lung cancer: role in angiogenesis and prognosis

INTRODUCTION

The recently discovered bioactive peptide, apelin, has been demonstrated to stimulate angiogenesis in various experimental systems. However, its clinical significance and role in tumor vascularization have not yet been investigated in a human malignancy. Therefore, our aim was to study whether apelin expression is associated with angiogenesis and/or tumor growth/behavior in human non-small cell lung cancer (NSCLC).

METHODS

A total of 94 patients with stage I-IIIA NSCLC and complete follow-up information were included. Apelin expression in human NSCLC samples and cell lines was measured by quantitative reverse-transcriptase polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistochemistry. Effects of exogenous apelin and apelin transfection were studied on NSCLC cell lines in vitro. In vivo growth of tumors expressing apelin or control vectors were also assessed. Morphometric variables of human and mouse tumor capillaries were determined by anti-CD31 labeling.

RESULTS

Apelin was expressed in all of the six investigated NSCLC cell lines both at the mRNA and protein levels. Although apelin overexpression or apelin treatments did not increase NSCLC cell proliferation in vitro, increasing apelin levels by gene transfer to NSCLC cells significantly stimulated tumor growth and microvessel densities and perimeters in vivo. Apelin mRNA levels were significantly increased in human NSCLC samples compared with normal lung tissue, and high apelin protein levels were associated with elevated microvessel densities and poor overall survival.

CONCLUSIONS

This study reveals apelin as a novel angiogenic factor in human NSCLC. Moreover, it also provides the first evidence for a direct association of apelin expression with clinical outcome in a human cancer.

Tumour vascularization via endothelial differentiation of glioblastoma stem-like cells

Glioblastoma is a highly angiogenetic malignancy, the neoformed vessels of which are thought to arise by sprouting of pre-existing brain capillaries. The recent demonstration that a population of glioblastoma stem-like cells (GSCs) maintains glioblastomas indicates that the progeny of these cells may not be confined to the neural lineage. Normal neural stem cells are able to differentiate into functional endothelial cells. The connection between neural stem cells and the endothelial compartment seems to be critical in glioblastoma, where cancer stem cells closely interact with the vascular niche and promote angiogenesis through the release of vascular endothelial growth factor (VEGF) and stromal-derived factor 1 (refs 5-9). Here we show that a variable number (range 20-90%, mean 60.7%) of endothelial cells in glioblastoma carry the same genomic alteration as tumour cells, indicating that a significant portion of the vascular endothelium has a neoplastic origin. The vascular endothelium contained a subset of tumorigenic cells that produced highly vascularized anaplastic tumours with areas of vasculogenic mimicry in immunocompromised mice. In vitro culture of GSCs in endothelial conditions generated progeny with phenotypic and functional features of endothelial cells. Likewise, orthotopic or subcutaneous injection of GSCs in immunocompromised mice produced tumour xenografts, the vessels of which were primarily composed of human endothelial cells. Selective targeting of endothelial cells generated by GSCs in mouse xenografts resulted in tumour reduction and degeneration, indicating the functional relevance of the GSC-derived endothelial vessels. These findings describe a new mechanism for tumour vasculogenesis and may explain the presence of cancer-derived endothelial-like cells in several malignancies.

Physical determinants of vascular network remodeling during tumor growth

The process in which a growing tumor transforms a hierarchically organized arterio-venous blood vessel network into a tumor specific vasculature is analyzed with a theoretical model. The physical determinants of this remodeling involve the morphological and hydrodynamic properties of the initial network, generation of new vessels (sprouting angiogenesis), vessel dilation (circumferential growth), vessel regression, tumor cell proliferation and death, and the interdependence of these processes via spatio-temporal changes of blood flow parameters, oxygen/nutrient supply and growth factor concentration fields. The emerging tumor vasculature is non-hierarchical, compartmentalized into well-characterized zones, displays a complex geometry with necrotic zones and "hot spots" of increased vascular density and blood flow of varying size, and transports drug injections efficiently. Implications for current theoretical views on tumor-induced angiogenesis are discussed.

Bevacizumab in the treatment of patients with advanced breast cancer: where have we landed?

Vast preclinical and clinical evidence has made angiogenesis one of the hallmarks of cancer. In many human tumours, vascular endothelial growth factor (VEGF) has been identified as the crucial mediator of this process. Initial studies suggested that angiogenesis, and VEGF in particular, could be inhibited without the risk of major side effects. After the pivotal data in first-line studies in patients with colorectal cancer, numerous clinical trials have been undertaken in patients with breast cancer. This review attempts to update these investigations and define the role of anti-VEGF antibody treatment in advanced breast cancer.

Proliferation of vascular smooth muscle cells in glioblastoma multiforme

OBJECT

Glioblastomas multiforme (GBM) contain a higher number of alpha-smooth muscle actin (SMA)-positive vascular smooth muscle cells (VSMCs) than those in the respective normal neuronal tissue. The role of VSMCs during angiogenesis is unclear, and it is also uncertain whether and to what extent angiogenic factors might be involved in GBM VSMCs. In GBMs, the contribution of VSMCs in angiogenesis accompanying endothelial proliferation and the correlation of VSMC proliferation with vascular endothelial growth factor (VEGF) expression were examined using an immunohistochemical method.

METHODS

The examined material, including surrounding brain tissue, came from 12 cases (6 men and 6 women) with classic GBM. Microvessel densities (MVDs) of CD31-immunoreactive vessels (CD31-MVD) and SMA-immunoreactive vessels (SMA-MVD) were obtained in areas selected from white matter, boundary, tumor (concentrated area of tumor cells), and perinecrosis. Subsequently, the SMA-MVD/CD31-MVD (SMA/CD31) rate, representing the percentage of vessels with VSMCs in the region, was calculated in each area. The VEGF immunoreactivity of tumor cells was examined, and cases were divided into 2 groups: < 30% VEGF expression of tumor cells (low VEGF group) and > 30% VEGF expression of tumor cells (high VEGF group).

RESULTS

The SMA/CD31 rate of the boundary was significantly lower than that of the tumor (p < 0.005) and perinecrosis (p < 0.001). The SMA/CD31 rate of the high VEGF group was significantly higher than that of the low VEGF group (p < 0.05) in the tumor.

CONCLUSIONS

In GBMs, the transformation and proliferation of VSMCs may accompany neovascularization and may also be induced by angiogenic factors.

Future prospects and challenges of antiangiogenic cancer gene therapy

In 1971 Judah Folkman proposed the concept of antiangiogenesis as a therapeutic target for cancer. More than 30 years later, concept became reality with the approval of the antivascular endothelial growth factor (VEGF) monoclonal antibody bevacizumab as a first-line treatment for metastatic colorectal cancer. Monoclonal antibodies and small molecular drugs are the most widely applied methods for inhibition of angiogenesis. The efficacy of these antiangiogenic modalities has been proven, in both preclinical and clinical settings. Although angiogenesis plays a major role in wound healing, hypoxia, and in the female reproductive cycle, inhibition of angiogenesis seems to be a relatively safe therapeutic option against cancers, and has therefore become a logical arena for a wide range of experimentation. The twentieth century has shown the boom of gene therapy and thus it has been applied also in the antiangiogenic setting. This review summarizes methods to induce antiangiogenic responses with gene therapy and discusses the obstacles and future prospects of antiangiogenic cancer gene therapy.

The role and therapeutic potential of endothelial progenitor cells in tumor neovascularization

Although the cellular and molecular mechanisms of tumor growth and metastasis are not completely understood, it is established that formation and growth of new blood vessels is a conditio sine qua non for tumor survival, growth, and expansion. Numerous studies over the past decades demonstrated that neovascularization associated with tumor growth occurs via angiogenic and vasculogenic mechanisms that involve sprouting angiogenesis, intussusceptive angiogenesis, vessel co-option, vasculogenic mimicry, lymphangiogenesis, and the recruitment of endothelial progenitor cells (EPCs). Due to their ability to self-renew, circulate, home to the ischemic sites, and differentiate into mature endothelial cells, EPCs hold enormous potential to be used as a diagnostic and/or therapeutic agent in antitumor therapies. Hence, this review focuses on EPCs and their role in tumor angiogenesis with the emphasis on EPC recruitment/migration, and the potential use of EPCs as a therapeutic tool and imaging probe.

ADAMTS1 contributes to the acquisition of an endothelial-like phenotype in plastic tumor cells

Cancer stem cells have been hypothesized to explain tumor plasticity, including the capability to adopt distinct differentiation commitments. Among the mechanisms of tumor neovascularization, the ability of some malignant cells to mimic an endothelial phenotype has been recognized by a capacity to form matrix-enriched pseudovascular structures. In addition to the expression of genes associated with an endothelial nature, the molecular dynamism of specific microenvironments may also be critical. Here, we report the identification of the extracellular protease ADAMTS1 as a critical molecule for tumor cells to acquire endothelial-like properties. In a fibrosarcoma model, ADAMTS1 increased tumor growth rate in an angiogenesis-independent manner, influencing the tumor cells to display an exclusive endothelial-like gene signature. We documented the relevant expression of ADAMTS1 in aggressive and highly plastic melanoma and Ewing sarcoma cells. Notably, inhibiting ADAMTS1 action compromised the endothelial mimetic attributes observed in this setting. Our findings provide insights into how the tumor microenvironment can elicit endothelial mimicry by tumor cells.

Targeting angiogenesis with multitargeted tyrosine kinase inhibitors in the treatment of non-small cell lung cancer

It has been >35 years since the link between angiogenesis and the growth of tumors was first reported. Targeting angiogenesis became feasible with the availability of bevacizumab, an anti-vascular endothelial growth factor monoclonal antibody. Initial studies revealed that the combination of bevacizumab and chemotherapy led to longer overall survival times than with chemotherapy alone in patients with advanced colorectal cancer. Since then, drug development strategies have added small molecule tyrosine kinase inhibitors to the panel of antiangiogenic agents under evaluation; data from numerous trials are now available. The challenge now is to identify the optimal antiangiogenic agent for specific patient groups and to understand not only the mechanistic differences between agents, but also the variability in their antitumor activity across different tumor types and their differing side-effect profiles. As in other solid tumors, angiogenesis contributes to the development of non-small cell lung cancer (NSCLC), and this review summarizes the role of angiogenesis in this disease. We review the current developmental status of antiangiogenic tyrosine kinase inhibitors (including vandetanib, sunitinib, axitinib, sorafenib, vatalanib, and pazopanib) in NSCLC and conclude by briefly discussing the need for optimal patient selection and potential future directions.

Angiogenesis in cutaneous malignant melanoma and potential therapeutic strategies

Metastatic melanoma (MM) carries a dismal prognosis, as it is largely resistant to conventional cytotoxic chemotherapy, biochemotherapy and immunotherapy. There is, therefore, a pressing need to identify new, effective treatments to improve outcomes from MM. Innovative approaches in oncology drug development include anti-angiogenic strategies, in the form of monoclonal antibodies and small-molecule kinase inhibitors. In this review we aim to present current concepts and controversies surrounding the role of angiogenesis and anti-angiogenic therapies in MM, alluding to other tumor types in which increasing knowledge may supply avenues for future directions in melanoma research and management. An overview of angiogenesis and its importance in melanoma progression is presented, highlighting the key molecules that represent potential therapeutic targets. The results of using anti-angiogenic strategies in preclinical and clinical trials are discussed and future perspectives for anti-angiogenic therapies in MM are considered.

Alteration of angiogenic patterns on B16BL6 melanoma development promoted in Matrigel

Because the progression and metastasis of solid tumors depend on their local microcirculation, we sought to characterize tumor angiogenesis three dimensionally in a highly metastatic mouse melanoma model, B16BL6 (B16), injected with Matrigel into the subcutis in the skin on the back of syngeneic C57BL/6 mice. We found that B16 with Matrigel grew significantly faster than B16 alone and had altered tumor angiogenesis. Tumor vessels apparently grew vigorously in the opposite direction of the tumor without invading the tumor mass until at least day 10 of injection. In addition, vascular branching resulted not only from sprouting as was seen in B16 without Matrigel but also from vascular splitting, either because of compression from outside the vessels or from septum formation by endothelial cells. This phenomenon was characteristic of B16 cells, but not of other tumor cells, including Lewis lung carcinoma and ASH-1 hybridoma cell lines, both of which were tested under the same conditions. The reduction in various angiogenic factors in Matrigel did not affect the angiogenic patterns and tumor growth. We hypothesize that tumor vessels may vigorously alter their angiogenic patterns in response to the local microenvironment.

Tumor angiogenesis and novel antiangiogenic strategies

Angiogenesis is essential for the development and growth of tumors. It is a highly regulated process that requires cross-talk between signaling pathways at all stages of blood vessel development and tumor growth, from the recruitment of endothelial cells to vessel maturation. This review summarizes tumor angiogenesis and describes the key signaling pathways governing blood vessel development. The role of angiogenesis in various tumor types is discussed, but the focus is on invasive breast cancer, a disease that will affect approximately 182,000 women in the USA in 2008. Research efforts over the past decade have identified numerous potential, as well as proven therapies with activity in breast cancer. These include chemotherapeutics as well as therapies that inhibit specific angiogenic pathways known as targeted agents. Some of the data from single- and multitargeted antiangiogenic agents are described in this review. "Published 2008 Wiley-Liss, Inc. This article is a US Government work, and, as such, is in the public domain in the United States of America."

Hepatocellular carcinomas in cirrhotic and noncirrhotic human livers share angiogenic characteristics

BACKGROUND

The antiangiogenic drug sorafenib has been shown to be an effective treatment for hepatocellular carcinoma (HCC) in patients with liver cirrhosis. It might also be effective in noncirrhotic HCC provided that the angiogenic properties of both tumor types are comparable. The aim of this study is to compare endothelial cell dynamics, microvessel density (MVD), and vessel maturation as indirect markers of angiogenesis in human HCC in cirrhotic and noncirrhotic livers.

MATERIALS AND METHODS

In a tertiary care setting, 70 consecutive HCC tumors were analyzed for endothelial cell dynamics. CD34 was applied to identify tumor microvessels, double immunolabeling Ki67/CD34 and activated caspase-3/CD34 to assess endothelial cell proliferation and apoptosis, and alpha-smooth muscle actin/CD34 for pericyte coverage. These characteristics were compared in cirrhotic (n = 33) and noncirrhotic HCCs (n = 37). Microvessel density was correlated with radiological signs of hypervascularity as obtained with dynamic four-phase CT scans during the arterial and portal phase of contrast enhancement.

RESULTS

Microvessels in cirrhotic and noncirrhotic HCC were mainly mature. In both groups endothelial cell turnover was low and MVD was not different. There was no correlation between MVD and venous invasion, tumor size, and turnover of tumor cells or endothelial cells. MVD was negatively correlated with contrast washout in the portal venous phase of CT scanning. In transplanted patients, MVD was not correlated with survival, whereas in patients after liver resection a high MVD was associated with a better prognosis.

CONCLUSION

Angiogenic characteristics of HCC in cirrhotic and noncirrhotic livers have a remarkable similarity.

Chronic whole-body hypoxia induces intussusceptive angiogenesis and microvascular remodeling in the mouse retina

Currently, little is known about the response of the adult retinal microvasculature to hypoxia. To test the hypothesis that chronic systemic hypoxia induces angiogenesis and microvascular remodeling in the adult mouse retina, adult 10-week old female C57Bl/6 mice were exposed to 10% O(2) for 2 or 3 weeks. After hypoxia exposure, retinas were harvested, whole-mounted, and processed for immunohistochemistry. Retinas were stained with lectin, anti-smooth muscle alpha-actin antibody, and anti-NG2 antibody to visualize microvascular networks and their cellular components. Confocal microscopy was used to obtain images of superficial retinal networks. Images were analyzed to assess vessel diameter, vascular length density, branch point density, and the presence of vascular loops, a hallmark of intussusceptive angiogenesis. Both 2 and 3 weeks of hypoxia exposure resulted in a significant increase in the diameters of arterioles and post-arteriole capillaries (p<0.003). After 3 weeks of hypoxia, vascular length density and branch point density were significantly increased in retinas exposed to hypoxia as compared to normoxic controls (p<0.001). The number of vascular loops in the superficial retinal networks was significantly greater in hypoxia-exposed retinas (p < or = 0.001). Our results demonstrate, for the first time, intussusceptive angiogenesis as a tissue-level mechanism of vascular adaptation to chronic systemic hypoxia in the adult mouse retina and contribute to our understanding of hypoxia-induced angiogenesis and microvascular remodeling in the adult animal.

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.

Prognostic role of vasculogenic mimicry in colorectal cancer

PURPOSE

Angiogenesis, as measured by degree of microvessel density, has been associated with tumor progression in many tumor types but does not always correlate with clinical outcome. In 1999, aggressive tumor cells were shown to form blood-conducting tubes not lined by endothelial cells, and this phenomenon was termed vasculogenic mimicry. We investigated angiogenesis and the presence of vasculogenic mimicry in colorectal carcinoma in relation to tumor stage, patient survival, and genetic indicators of tumor cell plasticity.

METHODS

Paraffin-embedded tissue samples were examined from a study of 117 patients with colorectal carcinoma with a 12-year follow-up. Immunohistochemical analysis was used to measure microvessel density and proliferating endothelial cells and to detect vasculogenic mimicry (scored by 3 independent observers). Cell cultures from 7 colon cell lines, real-time polymerase chain reaction (PCR) on cell lines, frozen tissue material from 4 colorectal cancer patients with and 4 without vasculogenic mimicry, and fresh colorectal cancer tissue from 2 patients were used to investigate the relationship between vasculogenic mimicry and tumor cell plasticity.

RESULTS

Microvessel density was not a prognostic marker in our patients. We found vasculogenic mimicry in 23 (19.7%) of 117 colorectal tumor samples. Cell culture experiments and real-time PCR on human colorectal carcinoma material showed evidence for vasculogenic mimicry with overexpression of EPHA2 and LAMC2, known to be important for the tube-forming capacity of melanoma tumor cells. The presence of vasculogenic mimicry was associated with significantly shortened survival, both overall (P < 0.0001) and within intermediate cancer stages (Dukes B, P = 0.0277; Dukes C, P < 0.0001).

CONCLUSIONS

Vasculogenic mimicry can occur in colorectal carcinoma and appears to be comparable to vasculogenic mimicry described in other tumors. Moreover, vasculogenic mimicry in colorectal carcinoma may be a strong independent prognostic marker for survival.

Imaging glioma cell invasion in vivo reveals mechanisms of dissemination and peritumoral angiogenesis

Infiltration of cancer cells into normal tissue is a hallmark of malignant gliomas and compromises treatment options. A lack of appropriate models limits the study of this invasion in vivo, which makes it difficult to fully understand its anatomy and the role of dynamic interactions with structures of the normal brain. We developed a novel methodology by utilizing multiphoton laser scanning microscopy (MPLSM) to image the movement of glioma cells deep within the normal brain of live mice in real time. This allowed us to track the invasion of individual RFP-expressing GL261 cells in relation to perfused vasculature or GFP-labeled endothelial cells repetitively over days, up to a depth of 0.5 mm. Glioma cells moved faster and more efficiently when the abluminal site of a blood vessel was utilized for invasion. Cells that invaded perivascularly were frequently found next to (a) multiple capillary structures where microvessels run parallel to each other, (b) capillary loops or glomeruloid-like bodies, and (c) dilated capillaries. Dynamic MPLSM for more than 48 h revealed that single invasive glioma cells induced intussusceptive microvascular growth and capillary loop formation, specifically at the microvascular site with which they had contact. As the main tumor grew by cooption of existing brain vessels, these peritumoral vascular changes may create a beneficial environment for glioma growth. In conclusion, our study revealed new mechanisms of peritumoral angiogenesis and invasion in gliomas, providing an explanation for their interdependence.

Dynamic contrast-enhanced MR imaging in the evaluation of patients with prostate cancer

Prostate cancer is a common tumor among men, with increasing diagnosis at an earlier stage and a lower volume of disease because of screening with prostate-specific antigen (PSA). The need for imaging of the prostate stems from a desire to optimize treatment strategy on a patient and tumor-specific level. The major goals of prostate imaging are (1) staging of known cancer, (2) determination of tumor aggressiveness, (3) diagnosis of cancer in patients who have elevated PSA but a negative biopsy, (4) treatment planning, and (5) the evaluation of therapy response. This article concentrates on the role of dynamic contrast-enhanced MR imaging in the evaluation of patients who have prostate cancer and how it might be used to help achieve the above goals. Various dynamic contrast enhancement approaches (quantitative/semiquantitative/qualitative, high temporal versus high spatial resolution) are summarized with reference to the relevant strengths and compromises of each approach.

Circulating endothelial progenitor cells and depression: a possible novel link between heart and soul

Although depression is known to be an independent risk factor for cardiovascular disorders, the mechanisms behind this connection are not well understood. However, the reduction in the number of endothelial progenitor cells (EPCs) in patients with cardiovascular risk factors has led us to hypothesize that depression influences the number of EPCs. EPCs labeled with CD34, CD133 and vascular endothelial growth factor receptor-2 (VEGFR2) antibodies were counted by flow cytometry in the peripheral blood (PB) of 33 patients with a current episode of major depression and of 16 control subjects. Mature (CD34+/VEGFR2+) and immature (CD133+/VEGFR2+) EPC counts were decreased in patients (vs controls; P<0.01 for both comparisons), and there was a significant inverse relationship between EPC levels and the severity of depressive symptoms (P<0.01 for both EPC phenotypes). Additionally, we assayed the plasma levels of VEGF, C-reactive protein (CRP) and tumor necrosis factor (TNF)-alpha and observed significantly elevated TNF-alpha concentrations in patients (vs controls; P<0.05) and, moreover, a significant inverse correlation between TNF-alpha and EPC levels (P<0.05). Moreover, by means of a quantitative RT-PCR approach, we measured CD34, CD133 and VEGFR2 mRNA levels of PB samples and found a net trend toward a decrease in all the investigated EPC-specific mRNA levels in patients as compared with controls. However, statistical significance was reached only for VEGFR2 and CD133 levels (P<0.01 for both markers). This is the first paper that demonstrates evidence of decreased numbers of circulating EPCs in patients with a current episode of major depression.

[Potential role of antiangiogenic treatment in neuroblastoma]

Focus on new drug development over the last few years has yielded new agents that differ from unspecific classical chemotherapeutics and ionizing radiation, while still targeting the cancer cell itself. Antiangiogenesis is a totally distinct approach targeting the tumor's blood vessels. This concept has now found its eligibility for the treatment of several adult solid tumors: the human antivascular endothelial growth factor (VEGF) antibody bevacizumab, as well as the VEGF receptor tyrosine kinase inhibitors, sunitinib and sorafinib, have recently been licensed by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) for the treatment of colorectal, renal, and lung cancer. Other antiangiogenic drugs are under preclinical and early clinical evaluation. However, what do we know of the use of these drugs in pediatric solid tumors, such as sarcomas and embryonal and neuronal tumors? For some time now, neuroblastoma has been shown to be dependent on angiogenesis. However, the first preclinical data on antiangiogenic drugs in neuroblastoma have not been published until recently, and clinical trials with antiangiogenic agents in neuroblastoma treatment protocols are scarce. This review adresses current knowledge on the important role and mechanisms of angiogenesis in neuroblastoma and summarizes available preclinical and clinical results of antiangiogenic agents used to treat neuroblastoma. Our review clearly demonstrates that clinical trials are urgently needed to bring forward promising antiangiogenesis concepts in neuroblastoma therapy.

High VEGFR-3-positive circulating lymphatic/vascular endothelial progenitor cell level is associated with poor prognosis in human small cell lung cancer

PURPOSE

The newly identified bone marrow-derived cell population, called lymphatic/vascular endothelial progenitor cells (LVEPC), has been shown to contribute to lymph capillary growth in experimental tumor systems. The clinical significance of these cells has not yet been investigated in a human malignancy. Our aim was to study whether peripheral blood circulating LVEPCs participate in the progression of human small cell lung cancer (SCLC).

EXPERIMENTAL DESIGN

A total of 88 patients with limited-stage SCLC and 32 tumor-free control subjects were included. Peripheral blood circulating LVEPC labeled with CD34 and vascular endothelial growth factor receptor-3 (VEGFR3) antibodies and the serum levels of the key lymphangiogenic molecule VEGF-C were measured by flow cytometry and ELISA, respectively.

RESULTS

CD34-positive/VEGFR3-positive LVEPC levels were significantly increased in patients (versus controls; P<0.01), and there was also a significant relationship between LVEPC counts and lymph node metastasis (P<0.01). High pretreatment circulating LVEPC numbers correlated with poor overall survival (P<0.01). Although we observed significantly elevated VEGF-C concentrations in patients (versus controls; P<0.01), there was no significant correlation between VEGF-C and LVEPC levels. Moreover, no significant differences in peripheral blood VEGF-C levels were seen between patients subgrouped by clinicopathologic variables including tumor and lymph node stages and survival.

CONCLUSIONS

Peripheral blood levels of bone marrow-derived LVEPCs are significantly increased in patients with SCLC and correlate with lymphatic involvement and prognosis. This is the first study that shows evidence of increased numbers of circulating LVEPC in patients with a malignant tumor.

Combination of antiangiogenesis with chemotherapy for more effective cancer treatment

Angiogenesis is a hallmark of tumor development and metastasis and is now a validated target for cancer treatment. However, the survival benefits of antiangiogenic drugs have thus far been rather modest, stimulating interest in developing more effective ways to combine antiangiogenic drugs with established chemotherapies. This review discusses recent progress and emerging challenges in this field; interactions between antiangiogenic drugs and conventional chemotherapeutic agents are examined, and strategies for the optimization of combination therapies are discussed. Antiangiogenic drugs such as the anti-vascular endothelial growth factor antibody bevacizumab can induce a functional normalization of the tumor vasculature that is transient and can potentiate the activity of coadministered chemoradiotherapies. However, chronic angiogenesis inhibition typically reduces tumor uptake of coadministered chemotherapeutics, indicating a need to explore new approaches, including intermittent treatment schedules and provascular strategies to increase chemotherapeutic drug exposure. In cases where antiangiogenesis-induced tumor cell starvation augments the intrinsic cytotoxic effects of a conventional chemotherapeutic drug, combination therapy may increase antitumor activity despite a decrease in cytotoxic drug exposure. As new angiogenesis inhibitors enter the clinic, reliable surrogate markers are needed to monitor the progress of antiangiogenic therapies and to identify responsive patients. New targets for antiangiogenesis continue to be discovered, increasing the opportunities to interdict tumor angiogenesis and circumvent resistance mechanisms that may emerge with chronic use of these drugs.

[Tumor vasculature as a therapeutic target in non-small cell lung cancer]

Despite developments in conventional (chemo)radiotherapy and surgery, survival of non-small cell lung cancer (NSCLC) patients remains poor. Treatments with targeted molecular drugs offer novel therapeutic strategies. Bevacizumab, a recombinant anti-vascular endothelial growth factor (VEGF) antibody, is the antiangiogenic drug at the most advanced stage of development in the therapy of NSCLC. However, a number of questions and future challenges relating to the use of bevacizumab in NSCLC remain. Furthermore, novel agents targeting the pre-existing NSCLC vasculature (i.e. vascular disrupting agents, VDAs) or multiple tyrosine kinase inhibitors have emerged as unique drug classes delivering promising results in several preclinical and clinical studies. Herein, we review the most recent data using these novel targeted agents either alone or in combination with chemotherapy in NSCLC.

The angiogenic makeup of human hepatocellular carcinoma does not favor vascular endothelial growth factor/angiopoietin-driven sprouting neovascularization

Quantitative data on the expression of multiple factors that control angiogenesis in hepatocellular carcinoma (HCC) are limited. A better understanding of the mechanisms underlying angiogenesis in HCC will improve the rational choice of anti-angiogenic treatment. We quantified gene and protein expression of members of the vascular endothelial growth factor (VEGF) and angiopoietin systems and studied localization of VEGF, its receptors VEGFR-1 and VEGFR-2, Angiopoietin (Ang)-1 and Ang-2, and their receptor, in HCC in noncirrhotic and cirrhotic livers. We employed real-time reverse transcription polymerase chain reaction (RT-PCR), western blot, and immunohistology, and compared the outcome with highly angiogenic human renal cell carcinoma (RCC). HCC in noncirrhotic and cirrhotic livers expressed VEGF and its receptors to a similar extent as normal liver, although in cirrhotic background, VEGFR-2 levels in both tumor and adjacent tissue were decreased. Ang-1 expression was slightly increased compared with normal liver, whereas Tie-2 was strongly down-regulated in the tumor vasculature. Ang-2 messenger RNA (mRNA) levels were also low in HCCs of both noncirrhotic and cirrhotic livers, implying that VEGF-driven angiogenic sprouting accompanied by angiopoietin-driven vascular destabilization is not pronounced. In RCC, VEGF-A levels were one order of magnitude higher. At the same time, endothelially expressed Ang-2 was over 30-fold increased compared with expression in normal kidney, whereas Ang-1 expression was decreased.

CONCLUSION

In hepatocellular carcinoma, tumor vascularization is not per se VEGF/angiopoietin driven. However, increased CD31 expression and morphological changes representative of sinusoidal capillarization in tumor vasculature indicate that vascular remodeling is taking place. This portends that therapeutic intervention of HCC at the level of the vasculature is optional, and that further studies into the molecular control thereof are warranted.

Targeting cancer stem cells to modulate alternative vascularization mechanisms

Recently, many papers have shown that tumor vascularization can be explained by angiogenesis, recruitment, cooption, vasculogenic mimicry and by mosaic vessels. In particular, vasculogenic mimicry seems to be different from mosaic blood vessels, where tumor cells form a part of the surface of the vessel while the remaining part is covered by endothelium. In this case, tumor cells in apparent contact with the lumen do not show an endothelial phenotype. More recently, vasculogenic mimicry was proposed to occur in patients with multiple myeloma due to bone marrow macrophages. Herein, all these data are, for the first time, discussed critically in comparison to cancer stem cells-which show high trans-differentiative capacity-and bone-marrow derived stem cells. In fact, the presence of alternative vasculogenic patterns might be due to the presence of stem cell population (cancer stem cells or bone-marrow stem cells). In this connection, the literature is discussed extensively and possible models are proposed. Pharmacological perspectives will also discuss.

Circulating endothelial cells, bone marrow-derived endothelial progenitor cells and proangiogenic hematopoietic cells in cancer: From biology to therapy

Vascularization, a hallmark of tumorigenesis, is classically thought to occur exclusively through angiogenesis (i.e. endothelial sprouting). However, there is a growing body of evidence that endothelial progenitor cells (EPCs) and proangiogenic hematopoietic cells (HCs) are able to support the vascularization of tumors and may therefore play a synergistic role with angiogenesis. An additional cell type being studied in the field of tumor vascularization is the circulating endothelial cell (CEC), whose presence in elevated numbers reflects vascular injury. Levels of EPCs and CECs are reported to correlate with tumor stage and have been evaluated as biomarkers of the efficacy of anticancer/antiangiogenic treatments. Furthermore, because EPCs and subtypes of proangiogenic HCs are actively participating in capillary growth, these cells are attractive potential vehicles for delivering therapeutic molecules. The current paper provides an update on the biology of CECs, EPCs and proangiogenic HCs, and explores the utility of these cell populations for clinical oncology.

An illustration of the potential for mapping MRI/MRS parameters with genetic over-expression profiles in human prostate cancer

INTRODUCTION

Magnetic resonance imaging (MRI) and MR spectroscopy can probe a variety of physiological (e.g. blood vessel permeability) and metabolic characteristics of prostate cancer. However, little is known about the changes in gene expression that underlie the spectral and imaging features observed in prostate cancer. Tumor induced changes in vascular permeability and angiogenesis are thought to contribute to patterns of dynamic contrast enhanced (DCE) MRI images of prostate cancer even though the genetic basis of tumor vasculogenesis is complex and the specific mechanisms underlying these DCEMRI features have not yet been determined.

MATERIALS AND METHODS

In order to identify the changes in gene expression that correspond to MRS and DCEMRI patterns in human prostate cancers, we have utilized tissue print micropeel techniques to generate "whole mount" molecular maps of radical prostatectomy specimens that correspond to pre-surgical MRI/MRS studies. These molecular maps include RNA expression profiles from both Affymetrix GeneChip microarrays and quantitative reverse transcriptase PCR (qrt-PCR) analysis, as well as immunohistochemical studies.

RESULTS

Using these methods on patients with prostate cancer, we found robust over-expression of choline kinase a in the majority of primary tumors. We also observed overexpression of neuropeptide Y (NPY), a newly identified angiogenic factor, in a subset of prostate cancers, visualized on DCEMRI.

CONCLUSION

These studies set the stage for establishing MRI/MRS parameters as validated biomarkers for human prostate cancer.

Dynamic schema for near infrared detection of pressure-induced changes in solid tumors

Differentiation among malignant tumors, benign tumors, and normal tissue is highly important in the diagnosis and treatment of many malignancies. We have proposed a dynamic schema for noninvasive characterization of pressure-induced changes in solid tumors. Our hypothesis has been that the altered neovascularization processes within cancer-bearing tissues may significantly increase vascular resistance and cause a much slower response of hemoglobin concentration during a dynamic compression stimulus. This hypothesis was tested by the evaluation of data generated from human tumor clinical testing and from animal tumor model testing. In the human tumor clinical testing, a unified diagnostic criterion was derived that integrated the relative characteristics of tumor oxygen, hemoglobin, and hemoglobin dynamics. By applying such a unified criterion, we were able to differentiate benign breast lesions and malignant breast tumors with high sensitivity and specificity within a subset of 14 suspicious breast lesions with similar size and depth characteristics. In the animal testing, a stepped compression load was applied to the subcutaneous tumor deposit on an athymic NU/NU nude mouse model with subcutaneous xenograft BxPC-3 cancer. Characteristic differences were observed between the premortem tumor and the postmortem tumor in terms of pressure-induced tumor structural and functional changes.

A CD28 superagonistic antibody elicits 2 functionally distinct waves of T cell activation in rats

Administration of the CD28 superagonistic antibody JJ316 is an efficient means to treat autoimmune diseases in rats, but the humanized antibody TGN1412 caused devastating side effects in healthy volunteers during a clinical trial. Here we show that JJ316 treatment of rats induced a dramatic redistribution of T lymphocytes from the periphery to the secondary lymphoid organs, resulting in severe T lymphopenia. Live imaging of secondary lymphoid organs revealed that JJ316 administration almost instantaneously (<2 minutes) arrested T cells in situ. This reduction in T cell motility was accompanied by profound cytoskeletal rearrangements and increased cell size. In addition, surface expression of lymphocyte function-associated antigen-1 was enhanced, endothelial differentiation sphingolipid G protein-coupled receptor 1 and L selectin levels were downregulated, and the cells lost their responsiveness to sphingosine 1-phosphate-directed migration. These proadhesive alterations were accompanied by signs of strong activation, including upregulation of CD25, CD69, CD134, and proinflammatory mediators. However, this did not lead to a cytokine storm similar to the clinical trial. While most of the early changes disappeared within 48 hours, we observed that CD4+CD25+FoxP3+ regulatory T cells experienced a second phase of activation, which resulted in massive cell enlargement, extensive polarization, and increased motility. These data suggest that CD28 superagonists elicit 2 qualitatively distinct waves of activation.