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The physico-chemical and biological response to conventional and UHDR electron and proton beams was investigated, along with conventional photons. The temporal structure and nature of the beam affected both, with electron beam at ≥1400 Gy/s and proton beam at 0.1 and 1260 Gy/s found to be isoefficient at sparing zebrafish embryos.

PurposePreclinical studies of hypoxia are generally done using ectopic xenograft tumors, which behave differently from human tumors. Our previous findings have shown that subcutaneously implanted lung tumors exhibit more hypoxia than their orthotopic implanted or spontaneous K-ras-induced counterparts. We hypothesize that differences in hypoxia are due to site-specific differences in vascularity and perfusion.ProceduresTo compare the presence and functionality of vessels in these tumor models, we studied vascular perfusion in vivo in real time.ResultsOrthotopically implanted and spontaneous K-ras-induced lung tumors showed elevated perfusion, demonstrating vasculature functionality. Little contrast agent uptake was observed within the subcutaneously implanted tumors, indicating vascular dysfunction. These findings were corroborated at the microscopic level with Hoechst 33342 and Meca-32 staining.ConclusionsFrom these observations, we concluded that differences in hypoxia in experimental models is related to vessel perfusion. Thus, appropriate selection of preclinical lung tumor models is essential for the study of hypoxia, angiogenesis and therapies targeting these phenomena.

It is well known that tumor cells migrate from the primary lesion to distant sites to form metastases and that these lesions limit patient outcome in a majority of cases. However, the extent to which radiation influences this process and to which migration in turn alters radiation response remains controversial. There are preclinical and clinical reports showing that focal radiotherapy can both increase the development of distant metastasis, as well as that it can induce the regression of established metastases through the abscopal effect. More recently, preclinical studies have suggested that radiation can attract migrating tumor cells and may, thereby, facilitate tumor recurrence. In this review, we summarize these phenomena and their potential mechanisms of action, and evaluate their significance for modern radiation therapy strategies.

Scaffold proteins are critical hubs within cells that have the ability to modulate upstream signaling molecules and their downstream effectors to fine-tune biological responses. Although they can serve as focal points for association of signaling molecules and downstream pathways that regulate tumorigenesis, little is known about how the tumor microenvironment affects the expression and activity of scaffold proteins. This study demonstrates that hypoxia, a common element of solid tumors harboring low oxygen levels, regulates expression of a specific variant of the scaffold protein AKAP12 (A-kinase anchor protein 12), AKAP12v2, in metastatic melanoma. In turn, through a kinome-wide phosphoproteomic and MS study, we demonstrate that this scaffolding protein regulates a shift in protein kinase A (PKA)-mediated phosphorylation events under hypoxia, causing alterations in tumor cell invasion and migration in vitro, as well as metastasis in an in vivo orthotopic model of melanoma. Mechanistically, the shift in AKAP12-dependent PKA-mediated phosphorylations under hypoxia is due to changes in AKAP12 localization vs. structural differences between its two variants. Importantly, our work defines a mechanism through which a scaffold protein can be regulated by the tumor microenvironment and further explains how a tumor cell can coordinate many critical signaling pathways that are essential for tumor growth through one individual scaffolding protein.

International audience; Osteosarcoma is the most prevalent primary pediatric cancer-related bone disease. These tumors frequently develop resistance to chemotherapy and are highly metastatic, leading to poor outcome. Thus, there is a need for new therapeutic strategies that can prevent cell dissemination. We previously showed that CYR61/CCN1 expression in osteosarcoma cells is correlated to aggressiveness both in vitro and in vivo in mouse models, as well as in patients. In this study, we found that CYR61 is a critical contributor to the vascularization of primary tumor. We demonstrate that silencing CYR61, using lentiviral transduction, leads to a significant reduction in expression level of pro-angiogenic markers such as VEGF, FGF2, PECAM and angiopoietins concomitantly to an increased expression of major anti-angiogenic markers such as thrombospondin-1 and SPARC. Matrix metalloproteinase-2 family member expression, a key pathway in osteosarcoma metastatic capacity was also downregulated when CYR61 was downregulated in osteosarcoma cells. Using a metastatic murine model, we show that CYR61 silencing in osteosarcoma cells results in reduced tumor vasculature and slows tumor growth compared with control. We also find that microvessel density correlates with lung metastasis occurrence and that CYR61 silencing in osteosarcoma cells limits the number of metastases. Taken together, our data indicate that CYR61 silencing can blunt the malignant behavior of osteosarcoma tumor cells by limiting primary tumor growth and dissemination process. INTRODUCTION Osteosarcoma is a highly vascular and extremely destructive bone malignancy that mainly affects children and young adults. It represents the most frequent pediatric cancer-related disease. Despite the introduction, during the 70 s, of aggressive multi-agent chemotherapy in addition to tumor ablation surgery, the long-term survival (45 years) increased from 10-60% for patients with localized primary tumors, but to o 30% for patients presenting metastases at initial diagnosis. Nowadays, knowledge of the mechanisms underlying osteosarcoma metastasis is quite limited. Thus, in order to improve the clinical outcomes for patients with poor prognosis and to manage primary osteosar-coma by preventing development of metastatic disease, it is imperative to find new approaches to block the metastasis process. Degradation of the extracellular matrix, facilitated by the action of matrix metalloproteinases (MMPs), is a prerequisite of tumor invasion and metastasis in a variety of cancers including osteosarcoma. MMP-2 and MMP-9 have been repetitively implicated in osteosarcoma cell invasion, 1-3 and increased expression of membrane type-1 MMP correlated with decreased overall survival. 4 A correlation was recently reported between the expression of the extracellular MMP inducer EMMPRIN (CD147) and vascular endothelial growth factor (VEGF) in osteosarcoma

Purpose: To efficiently translate experimental methods from bench to bedside, it is imperative that laboratory models of cancer mimic human disease as closely as possible. In this study, we sought to compare patterns of hypoxia in several standard and emerging mouse models of lung cancer to establish the appropriateness of each for evaluating the role of oxygen in lung cancer progression and therapeutic response. Experimental Design: Subcutaneous and orthotopic human A549 lung carcinomas growing in nude mice as well as spontaneous K-ras or Myc-induced lung tumors grown in situ or subcutaneously were studied using fluorodeoxyglucose and fluoroazomycin arabinoside positron emission tomography, and postmortem by immunohistochemical observation of the hypoxia marker pimonidazole. The response of these models to the hypoxia-activated cytotoxin PR-104 was also quantified by the formation of γH2AX foci in vitro and in vivo. Finally, our findings were compared with oxygen electrode measurements of human lung cancers. Results: Minimal fluoroazomycin arabinoside and pimonidazole accumulation was seen in tumors growing within the lungs, whereas subcutaneous tumors showed substantial trapping of both hypoxia probes. These observations correlated with the response of these tumors to PR-104, and with the reduced incidence of hypoxia in human lung cancers relative to other solid tumor types. Conclusions: These findings suggest that in situ models of lung cancer in mice may be more reflective of the human disease, and encourage judicious selection of preclinical tumor models for the study of hypoxia imaging and antihypoxic cell therapies. Clin Cancer Res; 16(19); 4843–52. ©2010 AACR.

The ability of human umbilical cord blood-derived mesenchymal stem cells (UCBMSCs) to transdifferentiate towards cardiomyocytes remains unclear. The aim of this study was to direct UCBMSCs to the cardiac lineage by exposure to: (1) 5-azacytidine (AZ) or dimethyl sulfoxide (DMSO); (2) a combination of growth factors involved in early cardiomyogenesis (BMP-2 + bFGF + IGF-1); (3) the Wnt signaling activators lithium chloride (LiCl) and phorbol-12-myristate-13-acetate (PMA); and (4) direct contact with neonatal rat cardiomyocytes. Expression of cardiomyocyte-specific proteins and beta-catenin were assessed by quantitative RT-PCR, immunofluorescence and Western blot. Cocultures of human UCBMSCs with neonatal rat cardiomyocytes were also analyzed for the presence of calcium oscillations and changes in electrical potential using Fura Red and di-4-ANEPPS confocal imaging, respectively. Induction of cardiac-specific proteins was not detected in 5-AZ- or DMSO-treated cells. Following DMSO addition, beta-catenin cytoplasmic expression increased, but did not translocate into cell nuclei to promote cardiac gene activation. Likewise, neither co-stimulation with BMP-2 + bFGF + IGF-1, nor exposure to LiCl and PMA resulted in the acquisition of a cardiac phenotype by UCBMSCs. Direct contact with neonatal rat cardiomyocytes promoted neither the expression of cardiomyocyte-specific proteins, nor the presence of calcium rhythmic oscillations and potential-dependent fluorescence emission in UCBMSCs. The cardiomyogenic stimuli investigated in this study failed to transdifferentiate human UCBMSCs. Alternative strategies or regulatory factors and signaling pathways may be better suited to recruit UCBMSCs into cardiac cell lineage.

Non-invasive bioluminescence imaging (BLI) to monitor changes in gene expression of cells implanted in live animals should facilitate the development of biomaterial scaffolds for tissue regeneration. We show that, in vitro, induction of chondrogenic differentiation in mouse bone marrow stromal cell line (CL1) and human adipose tissue derived mesenchymal stromal cells (hAMSCs), permanently transduced with a procollagen II (COL2A1) promoter driving a firefly luciferase gene reporter (PLuc) (COL2A1p·PLuc), induces PLuc expression in correlation with increases in COL2A1 and Sox9 mRNA expression and acquisition of chondrocytic phenotype. To be able to simultaneously monitor in vivo cell differentiation and proliferation, COL2A1p·PLuc labelled cells were also genetically labelled with a renilla luciferase (RLuc) gene driven by a constitutively active cytomegalovirus promoter, and then seeded in demineralized bone matrix (DBM) subcutaneously implanted in SCID mice. Non-invasive BLI monitoring of the implanted mice showed that the PLuc/RLuc ratio reports on gene expression changes indicative of cell differentiation. Large (CL1) and moderated (hAMSCs) changes in the PLuc/RLuc ratio over a 6 week period, revealed different patterns of in vivo chondrogenic differentiation for the CL1 cell line and primary MSCs, in agreement with in vitro published data and our results from histological analysis of DBM sections. This double bioluminescence labelling strategy together with BLI imaging to analyze behaviour of cells implanted in live animals should facilitate the development of progenitor cell/scaffold combinations for tissue repair.

Development of new materials for tissue engineering can be facilitated by the capacity to efficiently monitor in vivo the survival, proliferation and differentiation behaviour of cells implanted in different target tissues. We present here the application of a previously developed platform that allows to monitor in real time the survival and proliferative behaviour of implanted cells in two anatomical sites: subcutaneous and intramuscular. Basically, the system is based on the use of a non-invasive bioluminescence imaging (BLI) technique to detect luciferase expressing C57BL/6 cells, mouse embryonic fibroblasts, seeded in two sets of scaffolds: 1, a RAD16-I self-assembling peptide nanofiber matrix and 2, a composite consisted of the same RAD16-I nanofibers contained into a microporous biorubber scaffold. Interestingly, our results indicated considerable differences in the behaviour of implanted cells in each scaffold type. We observed that the self-assembling peptide scaffold alone foster cell survival and promotes cell proliferation where the composite scaffold not. Since self-assembling peptide scaffolds presents value stiffness proximal to the implanted tissues it is suggestive to think that harder materials will provide a physical constriction for cells to proliferate as well as mechanical discontinuity. We therefore propose that it is important to close match the implantation environment with the cell/material constructs in order to obtain the best response of the cells, illustrating the convenience of this strategy for the development of new tissue engineering platforms.

Human adipose tissue mesenchymal stromal cells (AMSCs) share common traits, including similar differentiation potential and cell surface markers, with their bone marrow counterparts. Owing to their general availability, higher abundance and ease of isolation AMSCs may be convenient autologous delivery vehicles for localized tumor therapy. We demonstrate a model for tumor therapy development based on the use of AMSCs expressing renilla luciferase and thymidine kinase, as cellular vehicles for ganciclovir-mediated bystander killing of firefly luciferase expressing tumors, and noninvasive bioluminescence imaging to continuously monitor both, tumor cells and AMSCs. We show that the therapy delivering AMSCs survive long time within tumors, optimize the ratio of AMSCs to tumor cells for therapy, and asses the therapeutic effect in real time. Treatment of mice bearing prostate tumors plus therapeutic AMSCs with the prodrug ganciclovir induced bystander killing effect, reducing the number of tumor cells to 1.5 % that of control tumors. Thus, AMSCs could be useful vehicles to deliver localized therapy, with potential for clinical application in inoperable tumors and surgical borders after tumor resection. This approach, useful to evaluate efficiency of therapeutic models, should facilitate the selection of cell types, dosages, therapeutic agents and treatment protocols for cell-based therapies of specific tumors.

Cultivated murine bone marrow mesenchymal stem cells (MSCs) frequently accumulate chromosome abnormalities, become oncogenically transformed, and generate sarcomas when transplanted in mice. Although human MSCs appear to be more resistant, oncogenic transformation has also been observed in MSCs cultivated past the senescence phase. Cell therapy for tissue regeneration using human autologous MSCs requires transplantation of cells previously expanded in vitro. Thus, an important concern is to determine if oncogenic transformation is a necessary outcome of the expansion procedures. We have analyzed the proliferation capacity, organ colonization, and oncogenicity of enhanced green fluorescent protein and luciferase-labeled human adipose tissue-derived mesenchymal stem cells (hAMSCs), implanted in immunocompromised mice during a prolonged time period (8 months) using a non-invasive bioluminescence imaging procedure. Our data indicates that the liver was the preferred target organ for colonization by intramuscular or intravenous implantation of hAMSCs. The implanted cells tended to maintain a steady state, population did not proliferate rapidly after implantation, and no detectable chromosomal abnormalities nor tumors formed during the 8 months of residence in the host's tissues. It would appear that hAMSCs, contrary to their murine correlatives, could be safe candidates for autologous cell therapy procedures since in our experiments they show undetectable predisposition to oncogenic transformation after cultivation in vitro and implantation in mice.

A combined strategy using bioluminescence imaging, bone densitometry and histology was used to analyze the bone regeneration capacity of human bone marrow (hBMSC) and adipose tissue (hAMSC) mesenchymal stem cells, seeded in an osteoconductive arginine-glycine-aspartate (RGD) crosslinked hydrogel scaffold, implanted in a mouse calvarial bone defect. We show that firefly luciferase labeled stem cells can be monitored in vivo through a prolonged 90 days period, during which hBMSCs survive better than hAMSCs and that the density of scaffold bearing defects increased significantly more than that of defects without scaffolds. (c) 2007 Elsevier Ltd. All rights reserved.

Recent developments in stem cell research have promoted a flourishing of new biomaterials and scaffolds for tissue repair. However, there is a scarcity of procedures to monitor the performance of scaffold-stem cell combinations implanted in live animals, avoiding the inherent artefacts associated with in vitro assay conditions. We report the implementation of a procedure based on the use of the luciferase gene as a cell proliferation tracer to monitor, by in vivo non-invasive imaging, the performance of stem cell-biomaterial combinations used for tissue regeneration. In a model system using immunodepressed mice we show preference of a mouse embryonic mesenchymal cell line (C3H/10T1/2) for specific implantation sites and biomaterials during a prolonged in vivo growth period (3 months). Moreover, we analyzed the safety of implanted cells using a sensitive luminometric procedure and showed that the implanted cells did not spread to other organs. Our results demonstrate the utility of this simple and resource-saving procedure in the development and screening of biomaterials for tissue engineering.

We have designed an immobilization bed that accommodates mice of all ages and sizes, to improve image registration for multimodal scans and for longitudinal preclinical imaging studies. Stationary pegs were placed such that they effectively immobilized mice and reduced set-up time. (22)Na fiducial markers were placed into the pegs at unique depths to provide 3D references to facilitate image registration. Multiple users registered positron emission tomographic (PET) and CT data obtained with and without the bed to examine the effect of the bed on registration accuracy and interuser variability. The image registrations performed by different users were evaluated for their similarity by using the Entropy Correlation Coefficient as a metric. The immobilization bed significantly reduced variations in body movement and interuser variability. Average differences in quantification of tumor PET signal among users when registering images without versus with the fiduciary-marker bed fell from 9.1% to 0.8% for maximal percentage injected dose per gram (%ID/g), from 15.6% to 2.3% for mean %ID/g, and from 9.4% to 0.7% for the 90th percentile of the maximum %ID/g. The bed improves animal immobilization, greatly reduces interuser variability, and supports registration of image data acquired from different imaging sessions.