Lung Organotypic Slices Enable Rapid Quantification of Acute Radiotherapy Induced Toxicity.

To rapidly assess healthy tissue toxicities induced by new anti-cancer therapies (i.e., radiation alone or in combination with drugs), there is a critical need for relevant and easy-to-use models. Consistent with the ethical desire to reduce the use of animals in medical research, we propose to monitor lung toxicity using an ex vivo model. Briefly, freshly prepared organotypic lung slices from mice were irradiated, with or without being previously exposed to chemotherapy, and treatment toxicity was evaluated by analysis of cell division and viability of the slices. When exposed to different doses of radiation, this ex vivo model showed a dose-dependent decrease in cell division and viability. Interestingly, monitoring cell division was sensitive enough to detect a sparing effect induced by FLASH radiotherapy as well as the effect of combined treatment. Altogether, the organotypic lung slices can be used as a screening platform to rapidly determine in a quantitative manner the level of lung toxicity induced by different treatments alone or in combination with chemotherapy while drastically reducing the number of animals. Translated to human lung samples, this ex vivo assay could serve as an innovative method to investigate patients' sensitivity to radiation and drugs.

CCX559 is a potent, orally-administered small molecule PD-L1 inhibitor that induces anti-tumor immunity.

The interaction of PD-L1 with PD-1 is a major immune checkpoint that limits effector T cell function against cancer cells; monoclonal antibodies that block this pathway have been approved in multiple tumor indications. As a next generation therapy, small molecule inhibitors of PD-L1 have inherent drug properties that may be advantageous for certain patient populations compared to antibody therapies. In this report we present the pharmacology of the orally-available, small molecule PD-L1 inhibitor CCX559 for cancer immunotherapy. CCX559 potently and selectively inhibited PD-L1 binding to PD-1 and CD80 in vitro, and increased activation of primary human T cells in a T cell receptor-dependent fashion. Oral administration of CCX559 demonstrated anti-tumor activity similar to an anti-human PD-L1 antibody in two murine tumor models. Treatment of cells with CCX559 induced PD-L1 dimer formation and internalization, which prevented interaction with PD-1. Cell surface PD-L1 expression recovered in MC38 tumors upon CCX559 clearance post dosing. In a cynomolgus monkey pharmacodynamic study, CCX559 increased plasma levels of soluble PD-L1. These results support the clinical development of CCX559 for solid tumors; CCX559 is currently in a Phase 1, first in patient, multicenter, open-label, dose-escalation study (ACTRN12621001342808).

Comparing radiolytic production of H2O2 and development of Zebrafish embryos after ultra high dose rate exposure with electron and transmission proton beams.

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.

The HIF target MAFF promotes tumor invasion and metastasis through IL11 and STAT3 signaling.

Hypoxia plays a critical role in tumor progression including invasion and metastasis. To determine critical genes regulated by hypoxia that promote invasion and metastasis, we screen fifty hypoxia inducible genes for their effects on invasion. In this study, we identify v-maf musculoaponeurotic fibrosarcoma oncogene homolog F (MAFF) as a potent regulator of tumor invasion without affecting cell viability. MAFF expression is elevated in metastatic breast cancer patients and is specifically correlated with hypoxic tumors. Combined ChIP- and RNA-sequencing identifies IL11 as a direct transcriptional target of the heterodimer between MAFF and BACH1, which leads to activation of STAT3 signaling. Inhibition of IL11 results in similar levels of metastatic suppression as inhibition of MAFF. This study demonstrates the oncogenic role of MAFF as an activator of the IL11/STAT3 pathways in breast cancer.

Macrophages Promote Circulating Tumor Cell-Mediated Local Recurrence following Radiotherapy in Immunosuppressed Patients.

Although radiotherapy (RT) decreases the incidence of locoregional recurrence in breast cancer, patients with triple-negative breast cancer (TNBC) have increased risk of local recurrence following breast-conserving therapy. The relationship between RT and local recurrence is unknown. Here, we tested the hypothesis that recurrence in some instances is due to the attraction of circulating tumor cells to irradiated tissues. To evaluate the effect of absolute lymphocyte count on local recurrence after RT in patients with TNBC, we analyzed radiation effects on tumor and immune cell recruitment to tissues in an orthotopic breast cancer model. Recurrent patients exhibited a prolonged low absolute lymphocyte count when compared with nonrecurrent patients following RT. Recruitment of tumor cells to irradiated normal tissues was enhanced in the absence of CD8+ T cells. Macrophages (CD11b+F480+) preceded tumor cell infiltration and were recruited to tissues following RT. Tumor cell recruitment was mitigated by inhibiting macrophage infiltration using maraviroc, an FDA-approved CCR5 receptor antagonist. Our work poses the intriguing possibility that excessive macrophage infiltration in the absence of lymphocytes promotes local recurrence after RT. This combination thus defines a high-risk group of patients with TNBC.Significance: This study establishes the importance of macrophages in driving tumor cell recruitment to sites of local radiation therapy and suggests that this mechanism contributes to local recurrence in women with TNBC that are also immunosuppressed.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/15/4241/F1.large.jpg Cancer Res; 78(15); 4241-52. ©2018 AACR.

The role of granulocyte macrophage colony stimulating factor (GM-CSF) in radiation-induced tumor cell migration.

Recently it has been observed in preclinical models that that radiation enhances the recruitment of circulating tumor cells to primary tumors, and results in tumor regrowth after treatment. This process may have implications for clinical radiotherapy, which improves control of a number of tumor types but which, despite continued dose escalation and aggressive fractionation, is unable to fully prevent local recurrences. By irradiating a single tumor within an animal bearing multiple lesions, we observed an increase in tumor cell migration to irradiated and unirradiated sites, suggesting a systemic component to this process. Previous work has identified the cytokine GM-CSF, produced by tumor cells following irradiation, as a key effector of this process. We evaluated the ability of systemic injections of a PEGylated form of GM-CSF to stimulate tumor cell migration. While increases in invasion and migration were observed for tumor cells in a transwell assay, we found that daily injections of PEG-GM-CSF to tumor-bearing animals did not increase migration of cells to tumors, despite the anticipated changes in circulating levels of granulocytes and monocytes produced by this treatment. Combination of PEG-GM-CSF treatment with radiation also did not increase tumor cell migration. These findings suggest that clinical use of GM-CSF to treat neutropenia in cancer patients will not have negative effects on the aggressiveness of residual cancer cells. However, further work is needed to characterize the mechanism by which GM-CSF facilitates systemic recruitment of trafficking tumor cells to tumors.

Patterns of Vasculature in Mouse Models of Lung Cancer Are Dependent on Location.

PURPOSE: Preclinical 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. PROCEDURES: To compare the presence and functionality of vessels in these tumor models, we studied vascular perfusion in vivo in real time. RESULTS: Orthotopically 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. CONCLUSIONS: From 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.

Erratum: Induction of LIFR confers a dormancy phenotype in breast cancer cells disseminated to the bone marrow.

This corrects the article DOI: 10.1038/ncb3408.

Induction of LIFR confers a dormancy phenotype in breast cancer cells disseminated to the bone marrow.

Breast cancer cells frequently home to the bone marrow, where they may enter a dormant state before forming a bone metastasis. Several members of the interleukin-6 (IL-6) cytokine family are implicated in breast cancer bone colonization, but the role for the IL-6 cytokine leukaemia inhibitory factor (LIF) in this process is unknown. We tested the hypothesis that LIF provides a pro-dormancy signal to breast cancer cells in the bone. In breast cancer patients, LIF receptor (LIFR) levels are lower with bone metastases and are significantly and inversely correlated with patient outcome and hypoxia gene activity. Hypoxia also reduces the LIFR:STAT3:SOCS3 signalling pathway in breast cancer cells. Loss of the LIFR or STAT3 enables otherwise dormant breast cancer cells to downregulate dormancy-, quiescence- and cancer stem cell-associated genes, and to proliferate in and specifically colonize the bone, suggesting that LIFR:STAT3 signalling confers a dormancy phenotype in breast cancer cells disseminated to bone.

Effects of radiation on metastasis and tumor cell migration.

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.

18F-EF5 PET Is Predictive of Response to Fractionated Radiotherapy in Preclinical Tumor Models.

We evaluated the relationship between pre-treatment positron emission tomography (PET) using the hypoxic tracer 18F-[2-(2-nitro-1-H-imidazol-1-yl)-N-(2,2,3,3,3- pentafluoropropyl) acetamide] (18F-EF5) and the response of preclinical tumor models to a range of fractionated radiotherapies. Subcutaneous HT29, A549 and RKO tumors grown in nude mice were imaged using 18F-EF5 positron emission tomography (PET) in order to characterize the extent and heterogeneity of hypoxia in these systems. Based on these results, 80 A549 tumors were subsequently grown and imaged using 18F-EF5 PET, and then treated with one, two, or four fraction radiation treatments to a total dose of 10-40 Gy. Response was monitored by serial caliper measurements of tumor volume. Longitudinal post-treatment 18F-EF5 PET imaging was performed on a subset of tumors. Terminal histologic analysis was performed to validate 18F-EF5 PET measures of hypoxia. EF5-positive tumors responded more poorly to low dose single fraction irradiation relative to EF5-negative tumors, however both groups responded similarly to larger single fraction doses. Irradiated tumors exhibited reduced 18F-EF5 uptake one month after treatment compared to control tumors. These findings indicate that pre- treatment 18F-EF5 PET can predict the response of tumors to single fraction radiation treatment. However, increasing the number of fractions delivered abrogates the difference in response between tumors with high and low EF5 uptake pre-treatment, in agreement with traditional radiobiology.

Single-Cell Analysis of [18F]Fluorodeoxyglucose Uptake by Droplet Radiofluidics.

Radiolabels can be used to detect small biomolecules with high sensitivity and specificity without interfering with the biochemical activity of the labeled molecule. For instance, the radiolabeled glucose analogue, [18F]fluorodeoxyglucose (FDG), is routinely used in positron emission tomography (PET) scans for cancer diagnosis, staging, and monitoring. However, despite their widespread usage, conventional radionuclide techniques are unable to measure the variability and modulation of FDG uptake in single cells. We present here a novel microfluidic technique, dubbed droplet radiofluidics, that can measure radiotracer uptake for single cells encapsulated into an array of microdroplets. The advantages of this approach are multiple. First, droplets can be quickly and easily positioned in a predetermined pattern for optimal imaging throughput. Second, droplet encapsulation reduces cell efflux as a confounding factor, because any effluxed radionuclide is trapped in the droplet. Last, multiplexed measurements can be performed using fluorescent labels. In this new approach, intracellular radiotracers are imaged on a conventional fluorescence microscope by capturing individual flashes of visible light that are produced as individual positrons, emitted during radioactive decay, traverse a scintillator plate placed below the cells. This method is used to measure the cell-to-cell heterogeneity in the uptake of tracers such as FDG in cell lines and cultured primary cells. The capacity of the platform to perform multiplexed measurements was demonstrated by measuring differential FDG uptake in single cells subjected to different incubation conditions and expressing different types of glucose transporters. This method opens many new avenues of research in basic cell biology and human disease by capturing the full range of stochastic variations in highly heterogeneous cell populations in a repeatable and high-throughput manner.

Hypoxic induction of AKAP12 variant 2 shifts PKA-mediated protein phosphorylation to enhance migration and metastasis of melanoma cells.

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.

Recruitment of circulating breast cancer cells is stimulated by radiotherapy.

Radiotherapy (RT) is a localized therapy that is highly effective in killing primary tumor cells located within the field of the radiation beam. We present evidence that irradiation of breast tumors can attract migrating breast cancer cells. Granulocyte-macrophage colony stimulating factor (GM-CSF) produced by tumor cells in response to radiation stimulates the recruitment of migrating tumor cells to irradiated tumors, suggesting a mechanism of tumor recurrence after radiation facilitated by transit of unirradiated, viable circulating tumor cells to irradiated tumors. Data supporting this hypothesis are presented through in vitro invasion assays and in vivo orthotopic models of breast cancer. Our work provides a mechanism for tumor recurrence in which RT attracts cells outside the radiation field to migrate to the site of treatment.

Facilitating multimodal preclinical imaging studies in mice by using an immobilization bed.

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.

Hypoxia in models of lung cancer: implications for targeted therapeutics.

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.

Exposure to cardiomyogenic stimuli fails to transdifferentiate human umbilical cord blood-derived mesenchymal stem cells.

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.

Dual luciferase labelling for non-invasive bioluminescence imaging of mesenchymal stromal cell chondrogenic differentiation in demineralized bone matrix scaffolds.

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.

The effect of self-assembling peptide nanofiber scaffolds on mouse embryonic fibroblast implantation and proliferation.

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.

Biodistribution, long-term survival, and safety of human adipose tissue-derived mesenchymal stem cells transplanted in nude mice by high sensitivity non-invasive bioluminescence imaging.

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.