Inhibiting vasculogenesis after radiation: a new paradigm to improve local control by radiotherapy

Development of a prediction model for radiotherapy response among patients with head and neck squamous cell carcinoma based on the tumor immune microenvironment and hypoxia signature

INTRODUCTION

The immune system and hypoxia are major factors influencing radiosensitivity in patients with different cancer types. This study aimed at developing a model to predict radiotherapy response in patients with head and neck squamous cell carcinoma (HNSCC) based on the tumor immune microenvironment and hypoxia signature.

MATERIALS AND METHODS

We first evaluated the hypoxia status and tumor immune microenvironment in the Cancer Genome Atlas (TCGA) cohort by using transcriptomic data. Differentially expressed genes (DEGs) were identified between the "high immunity and low hypoxia" and "low immunity and high hypoxia" groups and those DEGs significantly associated with disease-specific survival in the univariate Cox regression analysis were selected as the prognostic DEGs. We selected the immune hypoxia-related genes (IHRGs) by intersecting prognostic DEGs with immune and hypoxia gene sets. We used the IHRGs to train a multivariate Cox regression model in the TCGA cohort, based on which we calculated the IHRG prognostic index (IHRGPI) for each patient and validated its efficacy in predicting radiotherapy response in the Gene Expression Omnibus cohorts. Furthermore, we explored potential mechanisms and effective combinational treatment strategies for different IHRGPI groups.

RESULTS

Five IHRGs were used to construct the IHRGPI, which was used to dichotomize the cohorts. The patients with lower IHRGPI showed a better radiotherapy response across different cohorts and endpoints, including overall survival, progression-free survival, and recurrence-free survival (p < 0.05). Patients with higher IHRGPI showed greater hypoxia and lesser immune cell infiltration. A lower IHRGPI indicated a better immunotherapy response, while a higher IHRGPI indicated a better chemotherapy response.

CONCLUSIONS

IHRGPI is promising for predicting radiotherapy response and guiding combinational treatment strategies in patients with HNSCC.

The Role of VEGFA, COX2, HUR and CUGBP2 in Predicting the Response to Neoadjuvant Therapy in Rectal Cancer Patients

Background and objectives: The effectiveness of neoadjuvant therapy, which is commonly used for stage II-III rectal cancer (RC) treatment, is limited. Genes associated with the pathogenesis of RC could determine response to this treatment. Therefore, the aim of this study was to investigate the potential predictive value of VEGFA, COX2, HUR and CUGBP2 genes and the associations between post-treatment changes in gene expression and the efficacy of neoadjuvant therapy. Materials and Methods: Biopsies from RC and healthy rectal tissue of 28 RC patients were collected before neoadjuvant therapy and 6-8 weeks after neoadjuvant therapy. The expression levels of VEGFA, COX2, HUR, CUGBP2 genes were evaluated using a quantitative real-time polymerase chain reaction. Results: The results reveal a significantly higher expression of VEGFA, COX2 and HUR mRNA in RC tissue compared to healthy rectal tissue (p < 0.05), and elevated VEGFA gene expression in pre-treatment tissues was associated with a better response to neoadjuvant therapy based on T-stage downstaging (p < 0.05). The expression of VEGFA, HUR and CUGBP2 genes significantly decreased after neoadjuvant therapy (p < 0.05). Responders to treatment demonstrated a significantly stronger decrease of VEGFA and COX2 expression after neoadjuvant therapy than non-responders (p < 0.05). Conclusions: The findings of this study suggest that the pre-treatment VEGFA gene expression might have predictive value for the response to neoadjuvant therapy, while the post-treatment decrease in VEGFA and COX2 gene expression could indicate the effectiveness of neoadjuvant therapy in RC patients.

Bystander effects of ionizing radiation: conditioned media from X-ray irradiated MCF-7 cells increases the angiogenic ability of endothelial cells

BACKGROUND

Non-targeting effects of radiotherapy have become as clinical concern due to secondary tumorigenesis in the patients receiving radiotherapy. Radiotherapy also affects non-tumoral cells present in the tumor microenvironment and surrounding tissues. As such, the irradiated cells are thought to communicate the signals that promote secondary tumorigenesis by affecting the function and fate of non-irradiated cells in the vicinity including endothelial cells. This may include up-regulation of genes in irradiated cells, secretion of paracrine factors and induction of gene expression in surrounding non-irradiated cells, which favor cell survival and secondary tumorigenesis. In the current study, we aimed to investigate whether the conditioned media from X-ray irradiated MCF-7 cells contribute to induction of gene expression in human umbilical vein endothelial cells (HUVECs) in vitro and modulate their angiogenic capability and migration.

METHODS

Following the co-culturing of X-ray irradiated MCF-7 media with HUVECs, the migration and wound healing rate of HUVECs was monitored using Transwell plate and scratch wound healing assay, respectively. The levels of angiogenic protein i.e. vascular endothelial growth factor (VEGF-A) in the conditioned media of MCF-7 cells was measured using ELISA. Additionally, we quantified mRNA levels of VEGFR-2, HSP-70, Ang-2, and Ang-1 genes in HUVECs by real time-PCR. Tubulogenesis capacity of endothelial cells was measured by growth factor reduced Matrigel matrix, whereas expression of CD34 (a marker of angiogenic tip cells) was detected by flow cytometry.

RESULTS

Data showed that VEGF-A protein content of conditioned media of irradiated MCF-7 cells was increased (P < 0.05) with increase in dose. Data showed that irradiated conditioned media from MCF-7 cells, when incubated with HUVECs, significantly enhanced the cell migration and wound healing rate of HUVECs in a dose-dependent manner (P < 0.05). The mRNA levels of VEGFR-2, HSP-70, Ang-2, and Ang-1 were dose-dependently enhanced in HUVECs incubated with irradiated conditioned media (P < 0.05). Importantly, HUVECs treated with irradiated conditioned media showed a marked increase in the tube formation capability as well as in expression of CD34 marker (P < 0.05).

CONCLUSIONS

Our findings indicate that conditioned media from irradiated MCF-7 cells induce angiogenic responses in endothelial cells in vitro, which could be due to transfer of overexpressed VEGF-A and possibly other factors secreted from irradiated MCF-7 cells to endothelial cells, and induction of intrinsic genes (VEGFR-2, HSP-70, Ang-2, and Ang-1) in endothelial cells. Video abstract.

Radiation treatment monitoring with DCE-US in CWR22 prostate tumor xenografts

BACKGROUND

Longitudinal monitoring of potential radiotherapy treatment effects can be determined by dynamic contrast-enhanced ultrasound (DCE-US).

PURPOSE

To assess functional parameters by means of DCE-US in a murine subcutaneous model of human prostate cancer, and their relationship to dose deposition and time-frame after treatment. A special focus has been placed to evaluate the vascular heterogeneity of the tumor and on the most suitable data analysis approach that reflects this heterogeneity.

MATERIAL AND METHODS

In vivo DCE-US was acquired 24 h and 48 h after radiation treatment with a single dose of 7.5 Gy and 10 Gy, respectively. Tumor vasculature was characterized pixelwise using the Brix pharmacokinetic analysis of the time-intensity curves.

RESULTS

Longitudinal changes were detected ( P < 0.001) at 24 h and 48 h after treatment. At 48 h, the eliminating rate constant of the contrast agent from the plasma, k_el, was correlated ( P ≤ 0.05) positively with microvessel density (MVD; r_τ = 0.7) and negatively with necrosis (r_τ = -0.6) for the treated group. Furthermore, Ak_ep, a parameter related to transcapillary transport properties, was also correlated to MVD (r_τ = 0.6, P ≤ 0.05).

CONCLUSION

DCE-US has been shown to detect vascular changes at a very early stage after radiotherapy, which is a great advantage since DCE-US is non-invasive, available at most hospitals, and is low in cost compared to other techniques used in clinical practice.

Support of Tumor Endothelial Cells by Chemokine Receptors

Tumor-associated vascular endothelium comprises a specialized and diverse group of endothelial cells that, although not cancer themselves, are integral to cancer progression. Targeting the tumor vasculature can have significant efficacy in reducing tumor burden, although loss of efficacy due to acquisition of resistance mechanisms is common. Here we review mechanisms by which tumor endothelial cells (TEC) utilize chemokine receptors to support tumor progression. We illustrate how chemokine receptors support and may serve as functional markers of the diverse TEC population. We focus on ACKR1 (DARC), ACKR3 (CXCR7), CXCR4, and CCR2, as these are the best studied chemokine receptors in TEC; and suggest that targeting these receptors on the tumor vasculature may prove efficacious in slowing or reversing tumor growth. We also mention CXCR2 and CXCR3 as important mediators or tumor angiogenesis, given their distinct roles with angiogenic and angiostatic chemokines, respectively.

Combining Radiotherapy With Anti-angiogenic Therapy and Immunotherapy; A Therapeutic Triad for Cancer?

Radiotherapy has been used for the treatment of cancer for over a century. Throughout this period, the therapeutic benefit of radiotherapy has continuously progressed due to technical developments and increased insight in the biological mechanisms underlying the cellular responses to irradiation. In order to further improve radiotherapy efficacy, there is a mounting interest in combining radiotherapy with other forms of therapy such as anti-angiogenic therapy or immunotherapy. These strategies provide different opportunities and challenges, especially with regard to dose scheduling and timing. Addressing these issues requires insight in the interaction between the different treatment modalities. In the current review, we describe the basic principles of the effects of radiotherapy on tumor vascularization and tumor immunity and vice versa. We discuss the main strategies to combine these treatment modalities and the hurdles that have to be overcome in order to maximize therapeutic effectivity. Finally, we evaluate the outstanding questions and present future prospects of a therapeutic triad for cancer.

Tumour-vasculature development via endothelial-to-mesenchymal transition after radiotherapy controls CD44v6+ cancer cell and macrophage polarization

It remains controversial whether targeting tumour vasculature can improve radiotherapeutic efficacy. We report that radiation-induced endothelial-to-mesenchymal transition (EndMT) leads to tumour vasculature with abnormal SMA⁺NG2⁺ pericyte recruitment during tumour regrowth after radiotherapy. Trp53 (but not Tgfbr2) deletion in endothelial cells (ECs) inhibited radiation-induced EndMT, reducing tumour regrowth and metastases with a high CD44v6⁺ cancer-stem-cell (CSC) content after radiotherapy. Osteopontin, an EndMT-related angiocrine factor suppressed by EC-Trp53 deletion, stimulated proliferation in dormant CD44v6⁺ cells in severely hypoxic regions after radiation. Radiation-induced EndMT significantly regulated tumour-associated macrophage (TAM) polarization. CXCR4 upregulation in radioresistant tumour ECs was highly associated with SDF-1⁺ TAM recruitment and M2 polarization of TAMs, which was suppressed by Trp53 deletion. These EndMT-related phenomena were also observed in irradiated human lung cancer tissues. Our findings suggest that targeting tumour EndMT might enhance radiotherapy efficacy by inhibiting the re-activation of dormant hypoxic CSCs and promoting anti-tumour immune responses.

Radiotherapy is the main treatment for most cancer, but it is unclear if targeting tumour vasculature can enhance tumour radiosensitivity. Here, the authors show that tumour endothelial-mesenchymal transition after radiotherapy leads to proliferation of radioresistant CSCs and tumour associated macrophages polarization.

Paragangliomas arise through an autonomous vasculo-angio-neurogenic program inhibited by imatinib

Tumours can be viewed as aberrant tissues or organs sustained by tumorigenic stem-like cells that engage into dysregulated histo/organogenetic processes. Paragangliomas, prototypical organoid tumours constituted by dysmorphic variants of the vascular and neural tissues found in normal paraganglia, provide a model to test this hypothesis. To understand the origin of paragangliomas, we built a biobank comprising 77 cases, 18 primary cultures, 4 derived cell lines, 80 patient-derived xenografts and 11 cell-derived xenografts. We comparatively investigated these unique complementary materials using morphofunctional, ultrastructural and flow cytometric assays accompanied by microRNA studies. We found that paragangliomas contain stem-like cells with hybrid mesenchymal/vasculoneural phenotype, stabilized and expanded in the derived cultures. The viability and growth of such cultures depended on the downregulation of the miR-200 and miR-34 families, which allowed high PDGFRA and ZEB1 protein expression levels. Both tumour tissue- and cell culture-derived xenografts recapitulated the vasculoneural paraganglioma structure and arose from mesenchymal-like cells through a fixed developmental sequence. First, vasculoangiogenesis organized the microenvironment, building a perivascular niche which in turn supported neurogenesis. Neuroepithelial differentiation was associated with severe mitochondrial dysfunction, not present in cultured paraganglioma cells, but acquired in vivo during xenograft formation. Vasculogenesis was the Achilles’ heel of xenograft development. In fact, imatinib, that targets endothelial-mural signalling, blocked paraganglioma xenograft formation (11 xenografts from 12 cell transplants in the control group versus 2 out of 10 in the treated group, P = 0.0015). Overall our key results were unaffected by the SDHx gene carrier status of the patient, characterized for 70 out of 77 cases. In conclusion, we explain the biphasic vasculoneural structure of paragangliomas and identify an early and pharmacologically actionable phase of paraganglioma organization.

The Impact of Radiation on the Tumor Microenvironment: Effect of Dose and Fractionation Schedules

In addition to inducing lethal DNA damage in tumor and stromal cells, radiation can alter the interactions of tumor cells with their microenvironment. Recent technological advances in planning and delivery of external beam radiotherapy have allowed delivery of larger doses per fraction (hypofractionation) while minimizing dose to normal tissues with higher precision. The effects of radiation on the tumor microenvironment vary with dose and fractionation schedule. In this review, we summarize the effects of conventional and hypofractionated radiation regimens on the immune system and tumor stroma. We discuss how these interactions may provide therapeutic benefit in combination with targeted therapies. Understanding the differential effects of radiation dose and fractionation can have implications for choice of combination therapies.

The potential role of angiogenesis in the development of shoulder pain, shoulder dysfunction, and lymphedema after breast cancer treatment

Shoulder morbidity is a well-documented sequela of breast cancer treatment, which includes various manifestations such as pain, reduced range of motion, and lymphedema, among others. The multifactorial nature of such morbidities has long been appreciated, and research on reliable risk predictors of development thereof still continues. Previous studies have demonstrated the potential of different types of physical therapy to treat such shoulder problems, and the integration of such interventions into routine care for breast cancer survivors is a requirement in most high-income countries. Although patients at risk for developing shoulder problems would most likely benefit from posttreatment physical therapy, currently, there is no gold standard for identifying this patient group. This is particularly important in low- and middle-income countries where scarce monetary resources need to be directed specifically to those most in need. Modulators of the angiogenesis pathway have been implicated in noncancer shoulder conditions such as rotator cuff disease, adhesive capsulitis, and tendon injuries. The present review summarizes the role of angiogenesis in the development of shoulder morbidity among breast cancer survivors and sets forth the rationale for our belief that angiogenesis signaling may help explain a proportion of the reported clinical variability noted in the development of shoulder pain and dysfunction and upper-limb lymphedema after breast cancer treatment.

Clinical evaluation of macrophages in cancer: role in treatment, modulation and challenges

The focus of immunotherapeutics has been placed firmly on anti-tumour T cell responses. Significant progress has been made in the treatment of both local and systemic malignancies, but low response rates and rising toxicities are limiting this approach. Advancements in the understanding of tumour immunology are opening up a new range of therapeutic targets, including immunosuppressive factors in the tumour microenvironment. Macrophages are a heterogeneous group of cells that have roles in innate and adaptive immunity and tissue repair, but become co-opted by tumours to support tumour growth, survival, metastasis and immunosuppression. Macrophages also support tumour resistance to conventional therapy. In preclinical models, interference with macrophage migration, macrophage depletion and macrophage re-education have all been shown to reduce tumour growth and support anti-tumour immune responses. Here we discuss the role of macrophages in prognosis and sensitivity to therapy, while examining the significant progress which has been made in modulating the behaviour of these cells in cancer patients.

Antagonism in effectiveness of evofosfamide and doxorubicin through intermolecular electron transfer

Hypoxic cells pose a problem in anticancer chemotherapy, in which often drugs require oxygen as an electron acceptor to bring about the death of actively cycling cells. Bioreductive anticancer drugs, which are selectively activated in the hypoxic regions of tumours through enzymatic one-electron reduction, are being developed for combination with chemotherapy-, radiotherapy- and immunotherapy-containing regimens to kill treatment-resistant hypoxic cells. The most clinically-advanced bioreductive drug, evofosfamide (TH-302), which acts by releasing a DNA-crosslinking mustard, failed to extend overall survival in combination with doxorubicin, a topoisomerase II inhibitor, for advanced soft tissue sarcoma in a pivotal clinical trial. However, the reasons for the lack of additive efficacy with this combination are unknown. Here, we show that the radical anion of evofosfamide undergoes electron transfer to doxorubicin in kinetic competition to fragmentation of the radical anion, thus suppressing the release the cytotoxic mustard. This electron transfer process may account, at least in part, for the lack of overall survival improvement in the recent clinical trial. This study underlines the need to consider both redox and electron transfer chemistry when combining bioreductive prodrugs with other redox-active drugs in cancer treatment.

Locoregional Confinement and Major Clinical Benefit of 188Re-Loaded CXCR4-Targeted Nanocarriers in an Orthotopic Human to Mouse Model of Glioblastoma

PURPOSE

Gold standard beam radiation for glioblastoma (GBM) treatment is challenged by resistance phenomena occurring in cellular populations well prepared to survive or to repair damage caused by radiation. Among signals that have been linked with radio-resistance, the SDF1/CXCR4 axis, associated with cancer stem-like cell, may be an opportune target. To avoid the problem of systemic toxicity and blood-brain barrier crossing, the relevance and efficacy of an original system of local brain internal radiation therapy combining a radiopharmaceutical with an immuno-nanoparticle was investigated.

EXPERIMENT DESIGN

The nanocarrier combined lipophilic thiobenzoate complexes of rhenium-188 loaded in the core of a lipid nanocapsule (LNC¹⁸⁸Re) with a function-blocking antibody, 12G5 directed at the CXCR4, on its surface. The efficiency of 12G5-LNC¹⁸⁸Re was investigated in an orthotopic and xenogenic GBM model of CXCR4-positive U87MG cells implanted in the striatum of Scid mice.

RESULTS

We demonstrated that 12G5-LNC¹⁸⁸Re single infusion treatment by convection-enhanced delivery resulted in a major clinical improvement in median survival that was accompanied by locoregional effects on tumor development including hypovascularization and stimulation of the recruitment of bone marrow derived CD11b- or CD68-positive cells as confirmed by immunohistochemistry analysis. Interestingly, thorough analysis by spectral imaging in a chimeric U87MG GBM model containing CXCR4-positive/red fluorescent protein (RFP)-positive- and CXCR4-negative/RFP-negative-GBM cells revealed greater confinement of DiD-labeled 12G5-LNCs than control IgG2a-LNCs in RFP compartments. Main conclusion: These findings on locoregional impact and targeting of disseminated cancer cells in tumor margins suggest that intracerebral active targeting of nanocarriers loaded with radiopharmaceuticals may have considerable benefits in clinical applications.

Comparative transcriptome analysis of equine alveolar macrophages

REASONS FOR PERFORMING STUDY

Alveolar macrophages (AMs) are the first line of defence against pathogens in the lungs of all mammalian species and thus may constitute appropriate therapeutic target cells in the treatment and prevention of opportunistic airway infections. Therefore, acquiring a better understanding of equine macrophage biology is of paramount importance in addressing this issue in relation to the horse.

OBJECTIVES

To compare the transcriptome of equine AMs with that of equine peritoneal macrophages (PMs) and to investigate the effect of lipopolysaccharide (LPS) on equine AM.

STUDY DESIGN

Gene expression study of equine AMs.

METHODS

Cells from both bronchoalveolar and peritoneal lavage fluid were isolated from systemically healthy horses that had been submitted to euthanasia. Cells were cryopreserved. RNA was extracted and comparative microarray analyses were performed in AMs and PMs, and in AMs treated and untreated with LPS. Comparisons with published data derived from human AM studies were made, with particular focus on LPS-induced inflammatory status.

RESULTS

The comparison between AMs and PMs revealed the differential basal expression of 451 genes. Gene expression analysis revealed an alternative (M2) macrophage polarisation profile in AMs and a hybrid macrophage activation profile in PMs, a phenomenon potentially attributable to a degree of induced endotoxin tolerance. The gene expression profile of equine AMs following LPS stimulation revealed significant changes in the expression of 240 genes, including well-known upregulated inflammatory genes. This LPS-induced gene expression profile of equine AMs more closely resembles that of human rather than murine macrophages.

CONCLUSIONS

This study improves current understanding of equine macrophage biology. These data suggest that the horse may represent a suitable animal model for the study of human macrophage-associated lung inflammation and data derived from human macrophage studies may have significant relevance to the horse.

In-vivo quantification of the revascularization of a human acellular dermis seeded with EPCs and MSCs in co-culture with fibroblasts and pericytes in the dorsal chamber model in pre-irradiated tissue

INTRODUCTION

Transplantation of a cell-seeded graft may improve wound healing after radiotherapy. However, the survival of the seeded cells depends on a rapid vascularization of the graft. Co-culturing of adult stem cells may be a promising strategy to accelerate the vessel formation inside the graft. Thus, we compared the in vivo angiogenic potency of mesenchymal stem cells (MSC) and endothelial progenitor cells (EPC) using dorsal skinfold chambers and intravital microscopy.

MATERIALS AND METHODS

Cells were isolated from rat bone marrow and adipose tissue and characterized by immunostaining and flow cytometry. Forty-eight rats received a dorsal skinfold chamber and were divided into 2 main groups, irradiated and non-irradiated. Each of these 2 groups were further subdivided into 4 groups: unseeded matrices, matrices + fibroblasts + pericytes, matrices + fibroblasts + pericytes + MSCs and matrices + fibroblasts + pericytes + EPCs. Vessel densities were quantified semi-automatically using FIJI.

RESULTS

Fibroblasts + pericytes - seeded matrices showed a significantly higher vascular density in all groups with an exception of non-irradiated rats at day 12 compared to unseeded matrices. Co-seeding of MSCs increased vessel densities in both, irradiated and non-irradiated groups. Co-seeding with EPCs did not result in an increase of vascularization in none of the groups.

DISCUSSION

We demonstrated that the pre-radiation treatment led to a significant decreased vascularization of the implanted grafts. The augmentation of the matrices with fibroblasts and pericytes in co-culture increased the vascularization compared to the non-seeded matrices. A further significant enhancement of vessel ingrowth into the matrices could be achieved by the co-seeding with MSCs in both, irradiated and non-irradiated groups.

Impacts of Ionizing Radiation on the Different Compartments of the Tumor Microenvironment

Radiotherapy (RT) is one of the most important modalities for cancer treatment. For many years, the impact of RT on cancer cells has been extensively studied. Recently, the tumor microenvironment (TME) emerged as one of the key factors in therapy resistance. RT is known to influence and modify diverse components of the TME. Hence, we intent to review data from the literature on the impact of low and high single dose, as well as fractionated RT on host cells (endothelial cells, fibroblasts, immune and inflammatory cells) and the extracellular matrix. Optimizing the schedule of RT (i.e., dose per fraction) and other treatment modalities is a current challenge. A better understanding of the cascade of events and TME remodeling following RT would be helpful to design optimal treatment combination.

The role of exosomes in tumor progression and metastasis (Review)

Tumor cells have developed various mechanisms in defense against applied treatment, which prevent their total elimination from an organism. One of the underestimated mechanisms of defense is secretion of highly specialized double-membrane structures called exosomes. They play a crucial role in the control of the local microenvironment and intracellular communication. It has been shown that the exosomes can be carriers of various proteins, lipids, miRNAs and mRNAs. There are extensive data concerning the influence and participation by exosomes in metastasis and cancer progression. It has been demonstrated that exosomes are involved in multidrug resistance mechanisms, radiation-induced bystander effect and epithelial-mesenchymal transition. Furthermore, exosomes are able to form a premetastatic niche and enable the escape of cancer cells from recognition by host immune cells. Moreover, exosomes are responsible for the formation of vessels. This indicates the significance of secreted extracellular vesicles in the development and prognosis of cancer. The aim of the present review is to briefly describe the role of exosomes in tumor biology.

Clinical applications of iron oxide nanoparticles for magnetic resonance imaging of brain tumors

Current neuroimaging provides detailed anatomic and functional evaluation of brain tumors, allowing for improved diagnostic and prognostic capabilities. Some challenges persist even with today's advanced imaging techniques, including accurate delineation of tumor margins and distinguishing treatment effects from residual or recurrent tumor. Ultrasmall superparamagnetic iron oxide nanoparticles are an emerging tool that can add clinically useful information due to their distinct physiochemical features and biodistribution, while having a good safety profile. Nanoparticles can be used as a platform for theranostic drugs, which have shown great promise for the treatment of CNS malignancies. This review will provide an overview of clinical ultrasmall superparamagnetic iron oxides and how they can be applied to the diagnostic and therapeutic neuro-oncologic setting.

Regulation of vascular endothelial growth factor in prostate cancer

Prostate cancer (PCa) is the most common malignancy affecting men in the western world. Although radical prostatectomy and radiation therapy can successfully treat PCa in the majority of patients, up to ~30% will experience local recurrence or metastatic disease. Prostate carcinogenesis and progression is typically an androgen-dependent process. For this reason, therapies for recurrent PCa target androgen biosynthesis and androgen receptor function. Such androgen deprivation therapies (ADT) are effective initially, but the duration of response is typically ≤24 months. Although ADT and taxane-based chemotherapy have delivered survival benefits, metastatic PCa remains incurable. Therefore, it is essential to establish the cellular and molecular mechanisms that enable localized PCas to invade and disseminate. It has long been accepted that metastases require angiogenesis. In the present review, we examine the essential role for angiogenesis in PCa metastases, and we focus in particular on the current understanding of the regulation of vascular endothelial growth factor (VEGF) in localized and metastatic PCa. We highlight recent advances in understanding the role of VEGF in regulating the interaction of cancer cells with tumor-associated immune cells during the metastatic process of PCa. We summarize the established mechanisms of transcriptional and post-transcriptional regulation of VEGF in PCa cells and outline the molecular insights obtained from preclinical animal models of PCa. Finally, we summarize the current state of anti-angiogenesis therapies for PCa and consider how existing therapies impact VEGF signaling.

In vivo Quantification of the Effects of Radiation and Presence of Hair Follicle Pores on the Proliferation of Fibroblasts in an Acellular Human Dermis in a Dorsal Skinfold Chamber: Relevance for Tissue Reconstruction following Neoadjuvant Therapy

INTRODUCTION

In neoadjuvant therapy, irradiation has a deleterious effect on neoangiogenesis. The aim of this study was to examine the post-implantation effects of neoadjuvant irradiation on the survival and proliferation of autologous cells seeded onto an acellular human dermis (hAD; Epiflex). Additionally, we examined the influence of dermal hair follicle pores on viability and proliferation. We used dorsal skinfold chambers implanted in rats and in-situ microscopy to quantify cell numbers over 9 days.

METHODS

24 rats received a skinfold chamber and were divided into 2 main groups; irradiated and unirradiated. In the irradiated groups 20Gy were applied epicutaneously at the dorsum. Epiflex pieces were cut to size 5x5mm such that each piece had either one or more visible hair follicle pores, or no such visible pores. Fibroblasts were transduced lentiviral with a fluorescent protein for cell tracking. Matrices were seeded statically with 2.5x104 fluorescent fibroblasts and implanted into the chambers. In each of the two main groups, half of the rats received Epiflex with hair follicle pores and half received Epiflex without pores. Scaffolds were examined in-situ at 0, 3, 6 and 9 days after transplantation. Visible cells on the surface were quantified using ImageJ.

RESULTS

In all groups cell numbers were decreased on day 3. A treatment-dependent increase in cell numbers was observed at subsequent time points. Irradiation had an adverse effect on cell survival and proliferation. The number of cells detected in both irradiated and non-irradiated subjects was increased in those subjects that received transplants with hair follicle pores.

DISCUSSION

This in-vivo study confirms that radiation negatively affects the survival and proliferation of fibroblasts seeded onto a human dermis transplant. The presence of hair follicle pores in the dermis transplants is shown to have a positive effect on cell survival and proliferation even in irradiated subjects.

Combinations of immunotherapy and radiation in cancer therapy

The immune system has the ability to recognize and specifically reject tumors, and tumors only become clinically apparent once they have evaded immune destruction by creating an immunosuppressive tumor microenvironment. Radiotherapy (RT) can cause immunogenic tumor cell death resulting in cross-priming of tumor-specific T-cells, acting as an in situ tumor vaccine; however, RT alone rarely induces effective anti-tumor immunity resulting in systemic tumor rejection. Immunotherapy can complement RT to help overcome tumor-induced immune suppression, as demonstrated in pre-clinical tumor models. Here, we provide the rationale for combinations of different immunotherapies and RT, and review the pre-clinical and emerging clinical evidence for these combinations in the treatment of cancer.

CXCR4 as biomarker for radioresistant cancer stem cells

PURPOSE

Radioresistance of cancer cells remains a fundamental barrier for maximum efficient radiotherapy. Tumor heterogeneity and the existence of distinct cell subpopulations exhibiting different genotypes and biological behaviors raise difficulties to eradicate all tumorigenic cells. Recent evidence indicates that a distinct population of tumor cells, called cancer stem cells (CSC), is involved in tumor initiation and recurrence and is a putative cause of tumor radioresistance. There is an urgent need to identify the intrinsic molecular mechanisms regulating the generation and maintenance of resistance to radiotherapy, especially within the CSC subset. The chemokine C-X-C motif receptor 4 (CXCR4) has been found to be a prognostic marker in various types of cancer, being involved in chemotaxis, stemness and drug resistance. The interaction of CXCR4 with its ligand, the chemokine C-X-C motif ligand 12 (CXCL12), plays an important role in modulating the tumor microenvironment, angiogenesis and CSC niche. Moreover, the therapeutic inhibition of the CXCR4/CXCL12 signaling pathway is sensitizing the malignant cells to conventional anti-cancer therapy.

CONTENT

Within this review we are summarizing the role of the CXCR4/CXCL12 axis in the modulation of CSC properties, the regulation of the tumor microenvironment in response to irradiation, therapy resistance and tumor relapse.

CONCLUSION

In light of recent findings, the inhibition of the CXCR4/CXCL12 signaling pathway is a promising therapeutic option to refine radiotherapy.

Head and neck cancer relapse after chemoradiotherapy correlates with CD163+ macrophages in primary tumour and CD11b+ myeloid cells in recurrences

Background:

We investigated the prognostic role of tumour-associated macrophages (TAMs) in patients with head and neck squamous cell carcinoma (HNSCC) treated with definitive chemoradiotherapy (CRT).

Methods:

The expression of CD68+, CD163+ and CD11b+ cells was assessed using immunohistochemistry in n=106 pre-treatment tumour biopsy samples and was correlated with clinicopathological characteristics, including T-stage, N-stage, grading, tumour localisation, age and sex as well as local failure-free survival (LFFS), distant metastases-free survival (DMFS), progression-free (PFS), and overall survival (OS). Finally, TAMs expression and vessel density (CD31) were examined in n=12 available early local recurrence samples and compared with their matched primary tumours . The diagnostic images and radiotherapy plans of these 12 patients were also analysed. All local recurrences occurred in the high radiation dose region (⩾70 Gy).

Results:

With a median follow-up of 40 months, OS at 2 years was 60.5%. High CD163 expression in primary tumours was associated with decreased OS (P=0.010), PFS (P=0.033), LFFS (P=0.036) and DMFS (P=0.038) in multivariate analysis. CD163 demonstrated a strong prognostic value only in human papillomavirus (p16^INK4)-negative patients. Early local recurrence specimens demonstrated a significantly increased infiltration of CD11b+ myeloid cells (P=0.0097) but decreased CD31-positive vessel density (P=0.0004) compared with their matched primary samples.

Conclusions:

Altogether, baseline CD163 expression predicts for an unfavourable clinical outcome in HNSCC after definitive CRT. Early local recurrences showed increased infiltration by CD11b+ cells. These data provide important insight on the role of TAMs in mediating response to CRT in patients with HNSCC.

Chemokine receptor CXCR7 is a functional receptor for CXCL12 in brain endothelial cells

The chemokine CXCL12 regulates multiple cell functions through its receptor, CXCR4. However, recent studies have shown that CXCL12 also binds a second receptor, CXCR7, to potentiate signal transduction and cell activity. In contrast to CXCL12/CXCR4, few studies have focused on the role of CXCR7 in vascular biology and its role in human brain microvascular endothelial cells (HBMECs) remains unclear. In this report, we used complementary methods, including immunocytofluorescence, Western blot, and flow cytometry analyses, to demonstrate that CXCR7 was expressed on HBMECs. We then employed short hairpin RNA (shRNA) technology to knockdown CXCR7 in HBMECs. Knockdown of CXCR7 in HBMECs resulted in significantly reduced HBMEC proliferation, tube formation, and migration, as well as adhesion to matrigel and tumor cells. Blocking CXCR7 with a specific antibody or small molecule antagonist similarly disrupted HBMEC binding to matrigel or tumor cells. We found that tumor necrosis factor (TNF)-α induced CXCR7 in a time and dose-response manner and that this increase preceded an increase in vascular cell adhesion molecule-1 (VCAM-1). Knockdown of CXCR7 resulted in suppression of VCAM-1, suggesting that the reduced binding of CXCR7-knockdown HBMECs may result from suppression of VCAM-1. Collectively, CXCR7 acted as a functional receptor for CXCL12 in brain endothelial cells. Targeting CXCR7 in tumor vasculature may provide novel opportunities for improving brain tumor therapy.

Radiotherapy and the tumor stroma: the importance of dose and fractionation

Ionizing radiation is a non-specific but highly effective way to kill malignant cells. However, tumor recurrence sustained by a minor fraction of surviving tumor cells is a commonplace phenomenon caused by the activation of both cancer cell intrinsic resistance mechanisms, and also extrinsic intermediaries of therapy resistance, represented by non-malignant cells and structural components of the tumor stroma. The improved accuracy offered by advanced radiotherapy (RT)-technology permits reduced volume of healthy tissue in the irradiated field, and has been triggering an increase in the prescription of high-dose oligo-fractionated regimens in the clinics. Given the remarkable clinical success of high-dose RT and the current therapeutic shift occurring in the field, in this review we revise the existing knowledge on the effects that different radiation regimens exert on the different compartments of the tumor microenvironment, and highlight the importance of anti-tumor immunity and other tumor cell extrinsic mechanisms influencing therapeutic responses to high-dose radiation.