Tumor Vessel Permeability Research Articles

Microbeam Radiation Therapy Opens a Several Days’ Vessel Permeability Window for Small Molecules in Brain Tumor Vessels

PurposeSynchrotron microbeam radiation therapy (MRT), based on an inhomogeneous geometric and microscopic irradiation pattern of the tissues with high dose and high dose rate X-rays, enhances the permeability of brain tumor vessels. This study attempts to determine time and size range of the permeability window induced by MRT in the blood brain (tumor) barrier. Methods and MaterialsRats-bearing 9L gliomas were exposed to MRT, either unidirectional (tumor dose 406 Gy), or bidirectional (crossfired) (2 × 203 Gy). We measured vessel permeability to molecules of 3 sizes (Gd-DOTA, Dotarem®, 0.56 kDa; gadolinium-labeled albumin, ∼74 kDa; gadolinium-labeled IgG, 160 kDa) by daily in vivo magnetic resonance imaging (MRI), from 1 day before to 10 days post-irradiation. ResultsAn equivalent tumor dose of bidirectional MRT delivered from two orthogonal directions increased tumor vessel permeability for the smallest molecule tested more effectively than unidirectional MRT. Bidirectional MRT also affected the permeability of normal contralateral vessels to a different extent than unidirectional MRT. Conversely, bidirectional MRT did not modify the permeability of normal or tumor vessels for both larger molecules (74 and 160 kDa). ConclusionsHigh-dose bidirectional (cross-fired) MRT induced a significant increase in tumor vessel permeability for small molecules between the first and the seventh day after irradiation, while permeability of vessels in normal brain tissue remained stable. Such a permeability window could facilitate an efficient and safe delivery of intravenous small molecules (≤0.56 kDa) to tumoral tissues. A permeability window was not achieved by molecules larger than gado-grafted albumin (74 kDa). Vascular permeability for molecules between these two sizes has not been determined.

Review of tracer kinetic models in evaluation of gliomas using dynamic contrast-enhanced imaging.

Glioma is the most common type of primary malignant tumor of the central nervous system (CNS), and is characterized by high malignancy, high recurrence rate and poor survival. Conventional imaging techniques only provide information regarding the anatomical location, morphological characteristics, and enhancement patterns. In contrast, advanced imaging techniques such as dynamic contrast-enhanced (DCE) MRI or DCE CT can reflect tissue microcirculation, including tumor vascular hyperplasia and vessel permeability. Although several studies have used DCE imaging to evaluate gliomas, the results of data analysis using conventional tracer kinetic models (TKMs) such as Tofts or extended-Tofts model (ETM) have been ambiguous. More advanced models such as Brix's conventional two-compartment model (Brix), tissue homogeneity model (TH) and distributed parameter (DP) model have been developed, but their application in clinical trials has been limited. This review attempts to appraise issues on glioma studies using conventional TKMs, such as Tofts or ETM model, highlight advancement of DCE imaging techniques and provides insights on the clinical value of glioma management using more advanced TKMs.

The Efficacy of Nanoparticle Delivery to Hypoxic Solid Tumors by ciRGD Co-Administration Depends on Neuropilin-1 and Neutrophil Levels.

The ability to improve nanoparticle delivery to solid tumors is an actively studied domain, where various mechanisms are looked into. In previous work, the authors have looked into nanoparticle size, tumor vessel normalization, and disintegration, and here it is aimed to continue this work by performing an in-depth mechanistic study on the use of ciRGD peptide co-administration. Using a multiparametric approach, it is observed that ciRGD can improve nanoparticle delivery to the tumor itself, but also to tumor cells specifically better than vessel normalization strategies. The effect depends on the level of tumor perfusion, hypoxia, neutrophil levels, and vessel permeability. This work shows that upon characterizing tumors for these parameters, conditions can be selected that can optimally benefit from ciRGD co-administration as a means to improve NP delivery to solid tumors.

Vascular response patterns to targeted therapies in murine breast cancer models with divergent degrees of malignancy

BackgroundResponse assessment of targeted cancer therapies is becoming increasingly challenging, as it is not adequately assessable with conventional morphological and volumetric analyses of tumor lesions. The tumor microenvironment is particularly constituted by tumor vasculature which is altered by various targeted therapies. The aim of this study was to noninvasively assess changes in tumor perfusion and vessel permeability after targeted therapy in murine models of breast cancer with divergent degrees of malignancy.MethodsLow malignant 67NR or highly malignant 4T1 tumor-bearing mice were treated with either the multi-kinase inhibitor sorafenib or immune checkpoint inhibitors (ICI, combination of anti-PD1 and anti-CTLA4). Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with i.v. injection of albumin-binding gadofosveset was conducted on a 9.4 T small animal MRI. Ex vivo validation of MRI results was achieved by transmission electron microscopy, immunohistochemistry and laser ablation-inductively coupled plasma-mass spectrometry.ResultsTherapy-induced changes in tumor vasculature differed between low and highly malignant tumors. Sorafenib treatment led to decreased tumor perfusion and endothelial permeability in low malignant 67NR tumors. In contrast, highly malignant 4T1 tumors demonstrated characteristics of a transient window of vascular normalization with an increase in tumor perfusion and permeability early after therapy initiation, followed by decreased perfusion and permeability parameters. In the low malignant 67NR model, ICI treatment also mediated vessel-stabilizing effects with decreased tumor perfusion and permeability, while ICI-treated 4T1 tumors exhibited increasing tumor perfusion with excessive vascular leakage.ConclusionDCE-MRI enables noninvasive assessment of early changes in tumor vasculature after targeted therapies, revealing different response patterns between tumors with divergent degrees of malignancy. DCE-derived tumor perfusion and permeability parameters may serve as vascular biomarkers that allow for repetitive examination of response to antiangiogenic treatment or immunotherapy.

Cascade Drug Delivery through Tumor Barriers of Pancreatic Cancer via Ultrasound in Combination with Functional Microbubbles.

The abundant desmoplastic stroma and the lack of sufficient targets on pancreatic cancer cells render poor drug penetration and cellular uptake, which significantly compromise the chemotherapy efficacy. Herein, we reported a three-step cascade delivery strategy for selective delivery of paclitaxel (PTX) to achieve a targeted therapy for pancreatic cancer. cRGD and cCLT1 peptides, which could target the integrin and fibronectin, respectively, overexpressed in pancreatic cancer cells and stroma, were decorated on PTX-loaded microbubbles, resulting in the formation of dual-targeting PTX-RCMBs. In this strategy, ultrasound in combination with PTX-RCMBs first enhanced the permeability of tumor vessels via cavitation effects and simultaneously helped the generated PTX-RCNPs penetrate into the stroma. Then, the cCLT1 peptide modified on PTX-RCNPs selectively bound the fibronectin highly expressed in the stroma and later targeted the integrin (α5β1) on the cell surface. Finally, another targeting cRGD peptide modified on PTX-RCNPs would further promote PTX uptake via targeting the integrin (αvβ3) on the cell surface. This strategy significantly increased the delivery of PTX into tumor tissues. Moreover, the in vivo effective accumulation of PTX was monitored by ultrasound and fluorescence bimodal imaging. The tumor growth inhibition was investigated on subcutaneous tumor mouse models with 89.8% growth inhibition rate during 21 days of treatment, showing great potential for improving pancreatic cancer therapy.

ESDN inhibits melanoma progression by blocking E-selectin expression in endothelial cells via STAT3

An interactive crosstalk between tumor and stroma cells is essential for metastatic melanoma progression. We evidenced that ESDN/DCBLD2/CLCP1 plays a crucial role in endothelial cells during the spread of melanoma. Precisely, increased extravasation and metastasis formation were revealed in ESDN-null mice injected with melanoma cells, even if the primary tumor growth, vessel permeability, and angiogenesis were not enhanced. Interestingly, improved adhesion of melanoma cells to ESDN-depleted endothelial cells was observed, due to the presence of higher levels of E-selectin transcripts/proteins in ESDN-defective cells. In accordance with these results, anticorrelation was observed between ESDN and E-selectin in human endothelial cells. Most importantly, our data revealed that cimetidine, an E-selectin inhibitor, was able to block cell adhesion, extravasation, and metastasis formation in ESDN-null mice, underlying a major role of ESDN in E-selectin transcription upregulation, which according to our data, may presumably be linked to STAT3. Based on our results, we propose a protective role for ESDN during the spread of melanoma and reveal its therapeutic potential.

Nanodrug Delivery Systems Modulate Tumor Vessels to Increase the Enhanced Permeability and Retention Effect.

The use of nanomedicine for antitumor therapy has been extensively investigated for a long time. Enhanced permeability and retention (EPR) effect-mediated drug delivery is currently regarded as an effective way to bring drugs to tumors, especially macromolecular drugs and drug-loaded pharmaceutical nanocarriers. However, a disordered vessel network, and occluded or embolized tumor blood vessels seriously limit the EPR effect. To augment the EPR effect and improve curative effects, in this review, we focused on the perspective of tumor blood vessels, and analyzed the relationship among abnormal angiogenesis, abnormal vascular structure, irregular blood flow, extensive permeability of tumor vessels, and the EPR effect. In this commentary, nanoparticles including liposomes, micelles, and polymers extravasate through the tumor vasculature, which are based on modulating tumor vessels, to increase the EPR effect, thereby increasing their therapeutic effect.

Effects of contrast-enhanced ultrasound treatment on neoadjuvant chemotherapy in breast cancer.

Purpose: Preclinical and clinical data indicate that contrast-enhanced ultrasound can enhance tumor perfusion and vessel permeability, thus, improving chemotherapy accumulation and therapeutic outcome. Therefore, we investigated the effects of high mechanical index (MI) contrast-enhanced Doppler ultrasound (CDUS) on tumor perfusion in breast cancer.Methods: In this prospective study, breast cancer patients were randomly assigned to receive either 18 minutes of high MI CDUS during chemotherapy infusion (n = 6) or chemotherapy alone (n = 5). Tumor perfusion was measured before and after at least six chemotherapy cycles using motion-model ultrasound localization microscopy. Additionally, acute effects of CDUS on vessel perfusion and chemotherapy distribution were evaluated in mice bearing triple-negative breast cancer (TNBC).Results: Morphological and functional vascular characteristics of breast cancer in patients were not significantly influenced by high MI CDUS. However, complete clinical tumor response after neoadjuvant chemotherapy was lower in high MI CDUS-treated (1/6) compared to untreated patients (4/5) and size reduction of high MI CDUS treated tumors tended to be delayed at early chemotherapy cycles. In mice with TNBC high MI CDUS decreased the perfused tumor vessel fraction (p < 0.01) without affecting carboplatin accumulation or distribution. Higher vascular immaturity and lower stromal stabilization may explain the stronger vascular response in murine than human tumors.Conclusion: High MI CDUS had no detectable effect on breast cancer vascularization in patients. In mice, the same high MI CDUS setting did not affect chemotherapy accumulation although strong effects on the tumor vasculature were detected histologically. Thus, sonopermeabilization in human breast cancers might not be effective using high MI CDUS protocols and future applications may rather focus on low MI approaches triggering microbubble oscillations instead of destruction. Furthermore, our results show that there are profound differences in the response of mouse and human tumor vasculature to high MI CDUS, which need to be further explored and considered in clinical translation.

Manipulating dynamic tumor vessel permeability to enhance polymeric micelle accumulation

Selectively delivering anticancer drugs to solid tumors while avoiding their accumulation in healthy tissues is a major goal in polymeric micelle research. We have recently discovered that the extravasation and permeation of polymeric micelles occur in a dynamic manner characterized by vascular bursts followed by a brief and vigorous outward flow of fluid (called “nano-eruptions”). Nano-eruptions allow delivery of polymeric micelle-associated drugs, though delivery can be heterogeneous both among tumors and within an individual tumor, leading to suboptimal intratumoral distribution. Manipulation of nano-eruptions is expected to improve the efficiency of drug delivery systems (DDSs). By using compounds that affect the intratumoral environment, i.e. a TGF-β inhibitor and chloroquine, the possibility of manipulating nano-eruptions to improve delivery efficiency was investigated. Both compounds were tested in a mouse xenograft model of GFP-labeled pancreatic tumor cells by tracing nano-eruption events and extravasation of size-modulated polymeric micelles in real-time through intravital confocal laser scanning microscopy. The TGF-β inhibitor increased the number of dynamic vents, extended duration time, and generated dynamic vents with a wide range of sizes. Chloroquine did not affect the frequency of nano-eruptions, but it increased tumor vessel diameter, maximum nano-eruption area, and maximum radial increase. Both the TGF-β inhibitor and chloroquine augmented nano-eruptions to diffuse polymeric micelles through tumor stroma, and these medications had a greater effect on the polymeric micelles with larger size, i.e. 70-nm, than on the smaller polymeric micelles having a 30-nm diameter. The results indicate that TGF-β inhibition and chloroquine refashion the intratumoral distribution of DDSs by different mechanisms.

Candesartan treatment enhances liposome penetration and anti-tumor effect via depletion of tumor stroma and normalization of tumor vessel.

The poor penetration of nanoparticles in solid tumors has been a critical factor limiting the clinical benefits of nanomedicine. Therefore, we depleted the dense extracellular matrix (ECM) and normalized tumor vessels to enhance drug delivery and therapeutic efficacy. We used candesartan as an angiotensin system inhibitor, which reduced ECM content and facilitated "vascular normalization" by targeting the angiotensin-signaling axis, resulting in improved anti-cancer therapeutic effects. We also combined candesartan with PEGylated liposome-encapsulated zoledronic acid (ZOL) (PEG-ZOL-LPs) to assess how this affected anti-tumor therapy. Our findings indicated that the migration of 4T1 mouse breast cancer cells was inhibited by candesartan. Moreover, the ECM depletion (including collagen I and hyaluronan) by candesartan was achieved through the downregulation of TGF-β1 in vitro, consistent with in vivo results. Furthermore, treatment groups that received candesartan also had significantly decreased tumor vessel permeability and proportions of circulating endothelial progenitor cells (CEPCs) in the serum, which resulted in normalization of tumor vasculature and improved delivery of PEG-ZOL-LPs. Finally, the positive effect candesartan in terms of tumor growth was found not to have an impact of the efficacy of the PEG-ZOL-LPs treatment. This unexpected lack of effect of candesartan on the performance of PEG-ZOL-LPs would be due to dynamics of the effect of both treatments. It might be possible that a different protocol of administration could lead to a synergistic effect. Graphical abstract The schematic illustration showed that candesartan favored depletion of tumor stroma and tumor vascular normalization to improve the anti-cancer efficacy of PEG-ZOL-LPs.

Mechanistic Insights Into Using Aerobic Exercise To Remodel Tumor Vasculature And Increase Chemotherapy Efficacy

Tumor blood vessels pose obstacles for drug delivery because they are hyper-permeable and non-functional. There is a critical need to identify safe methods to increase chemotherapy delivery to the tumor. PURPOSE: We demonstrated that aerobic exercise improves tumor vasculature function, in multiple disparate tumor models, causing increased chemotherapy delivery and efficacy in mice. Across models, exercise reduced tumor vessel permeability. Because aerobic exercise increases blood flow both in healthy and tumor vessels, we aimed to investigate shear stress responsive mechanisms by which exercise may reduce tumor vessel permeability. METHODS:In vivo approaches including pharmacologic agents, a forced treadmill model of moderate aerobic exercise, and transgenic mouse models were utilized in combination with in vitro modeling of exercise induced shear stress, using a cone and plate viscometer. RESULTS: In tumor endothelium, we found the flow responsive kinase and co-transcriptional activator extracellular signal-regulated kinase 5 (ERK5) regulates tumor vessel permeability, similar to exercise. ERK5 activation in response to exercise was investigated in vivo, using a Krϋppel like factor 2 (KLF2) reporter mouse. KLF2 is a well-defined downstream target of ERK5. KLF2 was upregulated by exercise in the lung and aorta endothelium providing the first evidence for the involvement of ERK5 activation in response to aerobic exercise. Based on this and our previous data demonstrating that exercise induced shear stress upregulates spingosine-1 phosphate receptor 1 (S1PR1) on tumor vessels, we hypothesized that exercise activates ERK5, causing S1PR1 upregulation and decreasing permeability in tumor endothelium. To investigate this, we modeled basal tumor vasculature (low shear stress, 3 dynes/cm2) and exercise-induced flow (high shear stress, 15 dynes/cm2) with a cone and plate viscometer in vitro. We found the ERK5 axis has a similar flow responsive pattern as S1PR1. Further, ERK5 directly regulates S1PR1 in cultured endothelial cells revealing a novel EC pathway, the ERK5-S1PR1 axis. CONCLUSION: In summary, our data identifies the ERK5-S1PR1 axis as a potential exercise responsive pathway in tumor and healthy vasculature. We are currently investigating activation of the ERK5 axis in tumor vasculature.

Modulating sphingosine-1-phosphate receptors to improve chemotherapy efficacy against Ewing sarcoma.

Tumor vasculature is innately dysfunctional. Poorly functional tumor vessels inefficiently deliver chemotherapy to tumor cells; vessel hyper-permeability promotes chemotherapy delivery primarily to a tumor's periphery. Here, we identify a method for enhancing chemotherapy efficacy in Ewing sarcoma (ES) in mice by modulating tumor vessel permeability. Vessel permeability is partially controlled by the G protein-coupled Sphinosine-1-phosphate receptors 1 and 2 (S1PR1 and S1PR2) on endothelial cells. S1PR1 promotes endothelial cell junction integrity while S1PR2 destabilizes it. We hypothesize that an imbalance of S1PR1:S1PR2 is partially responsible for the dysfunctional vascular phenotype characteristic of ES and that by altering the balance in favor of S1PR1, ES vessel hyper-permeability can be reversed. In our study, we demonstrate that pharmacologic activation of S1PR1 by SEW2871 or inhibition of S1PR2 by JTE-013 caused more organized, mature and functional tumor vessels. Importantly, S1PR1 activation or S1PR2 inhibition improved antitumor efficacy. Our data suggests that pharmacologic targeting of S1PR1 and S1PR2 may be a useful adjuvant to standard chemotherapy for ES patients.

Acute cellular and vascular responses to photodynamic therapy using EGFR-targeted nanobody-photosensitizer conjugates studied with intravital optical imaging and magnetic resonance imaging.

Targeted photodynamic therapy (PDT) has the potential to selectively damage tumor tissue and to increase tumor vessel permeability. Here we characterize the tissue biodistribution of two EGFR-targeted nanobody-photosensitizer conjugates (NB-PS), the monovalent 7D12-PS and the biparatopic 7D12-9G8-PS. In addition, we report on the local and acute phototoxic effects triggered by illumination of these NB-PS which have previously shown to lead to extensive tumor damage.Methods: Intravital microscopy and the skin-fold chamber model, containing OSC-19-luc2-cGFP tumors, were used to investigate: a) the fluorescence kinetics and distribution, b) the vascular response and c) the induction of necrosis after illumination at 1 or 24 h post administration of 7D12-PS and 7D12-9G8-PS. In addition, dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) of a solid tumor model was used to investigate the microvascular status 2 h after 7D12-PS mediated PDT.Results: Image analysis showed significant tumor colocalization for both NB-PS which was higher for 7D12-9G8-PS. Intravital imaging showed clear tumor cell membrane localization 1 and 2 h after administration of 7D12-9G8-PS, and fluorescence in or close to endothelial cells in normal tissue for both NB-PS. PDT lead to vasoconstriction and leakage of tumor and normal tissue vessels in the skin-fold chamber model. DCE-MRI confirmed the reduction of tumor perfusion after 7D12-PS mediated PDT. PDT induced extensive tumor necrosis and moderate normal tissue damage, which was similar for both NB-PS conjugates. This was significantly reduced when illumination was performed at 24 h compared to 1 h after administration.Discussion: Although differences were observed in distribution of the two NB-PS conjugates, both led to similar necrosis. Clearly, the response to PDT using NB-PS conjugates is the result of a complex mixture of tumor cell responses and vascular effects, which is likely to be necessary for a maximally effective treatment.

Smart Nanotherapeutic Targeting of Tumor Vasculature.

The past decades have witnessed the development of a field dedicated to targeting tumor vasculature for cancer therapy. In contrast to conventional chemotherapeutics that need to penetrate into tumor tissues for killing tumor cells, the agents targeting tumor vascular system have two major advantages: direct contact with vascular endothelial cells or the blood and less possibility to induce drug resistance because of high gene stability of endothelial cells. More specifically, various angiogenesis inhibitors (AIs) and vascular disrupting agents (VDAs) that block tumor blood supply to inhibit tumor progression, some of which have been applied clinically, have been described. However, off-target effects and high effective doses limit the utility of these formulations in cancer patients. Thus, new strategies with improved therapeutic efficacy and safety are needed for tumor vessel targeting therapy. With the burgeoning developments in nanotechnology, smart nanotherapeutics now offer unprecedented potential for targeting tumor vasculature. Based on specific structural and functional features of the tumor vasculature, a number of different nanoscale delivery systems have been proposed for cancer therapy. In this Account, we summarize several distinct strategies to modulate tumor vasculature with various smart nanotherapeutics for safe and effective tumor therapy developed by our research programs. Inspired by the blood coagulation cascade, we generated nanoparticle-mediated tumor vessel infarction strategies that selectively block tumor blood supply to starve the tumor to death. By specifically delivering thrombin loaded DNA nanorobots (Nanorobot-Th) into tumor vessels, an intratumoral thrombosis is triggered to induce vascular infarction and, ultimately, tumor necrosis. Mimicking the coagulation cascade, a smart polymeric nanogel achieves permanent and peripheral embolization of liver tumors. Considering the critical role of platelets in maintaining tumor vessel integrity, a hybrid (PLP-D-R) nanoparticle selectively depleting tumor-associated platelets (TAP) to boost tumor vessel permeability was developed for enhancing intratumoral drug accumulation. In addition, benefiting from a better understanding of the molecular and cellular underpinnings of vascular normalization, several tumor acidity responsive nanotherapeutics, encapsulating therapeutic peptides, and small interfering RNA were developed to correct the abnormal features of the tumor vasculature. This made the tumor vessels more efficient for drug delivery. While we are still exploring the mechanisms of action of these novel nanoformulations, we expect that the strategies summarized here will offer a promising platform to design effective next-generation nanotherapeutics against cancer and facilitate the clinical translation of smart nanotherapeutics that target tumor vasculature.

Gd-encapsulated carbonaceous dots for accurate characterization of tumor vessel permeability in magnetic resonance imaging

The assessment of vascular permeability of malignant tumor plays an important role in the diagnosis and treatment of cancer. Dynamic contrast-enhanced magnetic resonance image (DCE-MRI) using Gd-encapsulated carbonaceous dots and Gd-DTPA-BMA as contrast agents was performed in 4T1 mouse breast cancer and HCC827 human non-small-cell lung cancer (NSNLC) xenograft models. Histopathological parameters of tumor vascularity microvessel density (MVD), microvessel area (MVA), endothelial area (EA) and α-SMA CD31 Co-expression (α-SMA/CD31%) were compared with the DCE-MRI parameters. Results demonstrated that DCE-MRI with the new nanoparticle Gd@C-dots can noninvasively evaluate vascular permeability. Ktrans measured by DCE-MRI with Gd@C-dots is an accurate parameter for the characterization of tumor permeability. EA is a reliable microvessel parameter to evaluate vessel permeability.

Abstract 2865: AsiDNATM, a novel DNA repair inhibitor to sensitize aggressive medulloblastoma subtypes

Abstract Purpose: Medulloblastoma is paediatric tumor of the cerebellum. It represents the most frequent malignant brain tumor in childhood. It can be classified into four disparate molecular subgroups but current therapies are not yet tailored to their specificities. This is particularly important for subgroups with worse prognosis as Group3. Patients who survive often present severe treatment-related morbidity, which can be largely attributed to brain radiation in ages of development. It is therefore important to improve treatment efficacy in more aggressive subgroups as well as reduce treatment-related morbidity across all subgroups. We investigated whether AsiDNATM, a radiosensitizer in clinical trials which works through DNA repair inhibition, could be used to improve radiotherapy efficacy with no additional toxicity allowing radiation dose de-escalation in groups with better prognosis and improved radiotherapy efficacy in those with high-risk disease. Experimental design: The cytotoxic effect of AsiDNATM was determined in a panel of 4 human medulloblastoma cell lines from different subgroups and different P53 status. We analyzed the ability of AsiDNATM to reach brain tissue and toxicity of treatments with or without irradiation in pups (10 days old mice). Distribution of AsiDNA was estimated by quantification of Cy-5-AsiDNA in brain tissues. Radiation toxicity was estimated by survival to high doses, monitoring of circulating growth hormone (GH), weight loss, bones size at adult age and neuro histology analysis. We assessed the AsiDNATM radio-enhancing efficacy in Group3 xenografted preclinical models using X-RAD 320 (PXI Inc) X-ray irradiator. Local brain irradiation was performed with an image-guided X-ray system (SARPP, Xstrahl Ldt), in which dosimetry and animal setting were controlled at each treatment session. Results: AsiDNATM treatments exhibit an additive effect to radiation in all cell lines, leading to an approximate 2-fold reduction of the radiation dose to reach 50% survival. Cy5-AsiDNA distributed to pup brain but not to adult brain devoid of tumors. However, in adults AsiDNATM distributed in tumors in brain through permeability of tumor vessels. Irradiation toxicity in pups was confirmed by a significant decrease in GH secretion and associated reduction of bone size. The lethal dose after irradiation was 20 Gy. No increase of irradiation toxicity was observed with AsiDNATM. In vivo, AsiDNATM alone significantly enhances survival rates (p=0.005) and increases radiotherapy efficacy. When combined with radiotherapy, AsiDNATM led to delay in tumor growth and survival improvement as compared to radiotherapy alone. Conclusion: Overall, our current results show AsiDNATM as an attractive candidate to improve radiation therapy in medulloblastoma in both standard- and high-risk patients with no indication of additional toxicity in healthy developing brain tissues. Citation Format: Sofia Ferreira, Chloe Foray, Sophie Heinrich, Celio Pouponnot, Marie Dutreix. AsiDNATM, a novel DNA repair inhibitor to sensitize aggressive medulloblastoma subtypes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2865.

Numerical modeling of high-intensity focused ultrasound-mediated intraperitoneal delivery of thermosensitive liposomal doxorubicin for cancer chemotherapy

Although intraperitoneal chemotherapy (IPC) has been suggested as a promising method for the management of peritoneal dissemination (PD) of ovarian or colorectal cancers, the actual clinical use of this method has been restricted due to such problems as poor drug penetration into the tumor and high side effects. It is, therefore, necessary to develop new strategies to improve the efficacy of this approach. In the present work, a new strategy is proposed based on intraperitoneal (IP) injection of thermosensitive liposomal doxorubicin (TSL-Dox) with triggered release by mild hyperthermia induced by high intensity focused ultrasound (HIFU). A computational model is developed to evaluate the proposed drug delivery system. Results show an order of magnitude increase in drug penetration depth into the tumor compared to the conventional IP delivery. Furthermore, the effects of thermal conditions applied to the tumor, TSL size, tumor vessel permeability, and tumor size are investigated. Results indicate an improved efficiency of the drug delivery by expanding the heated region, yet, it increases the risk of unintentional TSL drug load release in the peritoneal cavity. Results also indicate that smaller TSLs have better treatment outcome. However, there is a significant reduction in treatment efficacy for TSLs with sizes smaller than the vessel wall pore size. Thus, tuning the size of TSL should be based on the tumor microvascular permeability. The simulation results suggest that the TSL-Dox delivery system in smaller tumors is far advantageous than larger ones. Results of our model can be used as guidelines for future preclinical studies.

Abstract 2111: The tumor microenvironment of preclinical tumor models may have an impact on the therapeutic index of nanotherapeutics

Abstract Rapid development in nanotechnology allows the incorporation of multiple therapeutic agents (e.g. liposomes) into nanoparticle with a size range from 1 to 1000 nm. These nanocarrier systems provide new approaches to treat aggressive malignancy. Nano-based delivery systems hold an advantage over traditional small molecule therapy in that they can deliver drugs preferentially to tumors due to the enhanced permeability and retention (EPR) effect. On one hand, high permeability of the tumor vessels and a lack of functional lymphatic vessels results in the EPR effect, driving nanoparticle extravasation. On the other hand, these phenomena lead to high interstitial fluid pressure (IFP), limiting nanoparticle extravasation. In this study, we have used dynamic-contrast enhanced (DCE) MRI with small (Dotarem, 5 nm) and large (Vistarem, 25 nm) contrast agents (CAs) to examine tumor vessel permeability in SJSA-1 osteosarcoma tumor-bearing rats. An inversion-recovery true fast imaging with steady state precession (TrueFISP) was employed to determine the transfer constant Ktrans in subcutaneous and intra-tibia tumor models. When the tumor cells were injected in both niches within the same animal, Ktrans was significantly lower in intra-tibia tumors with both CAs, and blood vessels significantly less and larger compared to subcutaneous tumors. Moreover, Ktrans negatively correlated with tumor bioluminescence for the intra-tibia model, suggesting that EPR decreased inversely with tumor size, while the opposite was noticed for the subcutaneous tumors. These data demonstrate for the first time that the EPR of tumors with a similar size within the same animal can be influenced by the microenvironment. Moreover, they show that the therapeutic index of a nanotherapeutics may be different if it's determined with either an orthotopic or ectopic model. Citation Format: Stephane Ferretti, Nicolau Beckmann, laura Holzer, Michael Obrecht, Marjorie Berger, Michael Rugaard Jensen. The tumor microenvironment of preclinical tumor models may have an impact on the therapeutic index of nanotherapeutics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2111.

Functional Characterization of VEGF- and FGF-induced Tumor Blood Vessel Models in Human Cancer Xenografts.

Tumor angiogenesis induced by vascular endothelial growth factor (VEGF) and/or fibroblast growth factor (FGF) plays an important role in tumor growth, metastasis, and drug resistance. However, the characteristics of tumor vessels derived from these angiogenic factors have not been fully explored. To functionally examine tumor vessels, we developed in vivo VEGF- and FGF-induced tumor blood vessel models. We performed immunohistochemistry and Hoechst perfusion assay to elucidate histopathological differences between the derived tumor vessels. To kinetically understand tumor perfusion, we employed radiolabeled PEGylated liposomes. While tumor vessel density was substantially increased by enhanced expression levels of VEGF and FGF, permeability of VEGF-driven tumor vessels was significantly higher than that of FGF-driven ones, the latter demonstrating an increased number of pericyte-covered vessels. Accordingly, we observed an increased tumor retention of the PEGylated liposomes in the VEGF-driven tumor. Our in vivo models of tumor vessel demonstrate the frequency of pericyte coverage and tumor perfusion levels as major functional differences between VEGF- and FGF-driven tumor vessels.

Abstract 870: Radiation-induced PD-L1 upregulation can be detected by Zr-89-PD-L1 PET/CT in the tumor micro-environment of murine HPV positive HNSCC model and melanoma model

Abstract Background: Radiation therapy (RT) can induce upregulation of programmed death ligand 1 (PD-L1) on tumor cells or myeloid cells, which might affect the response to RT with or without anti-PD-1/PD-L1 blockade. RT-induced PD-L1 expression during therapy could be a predictive marker for the therapy response, however, serial biopsies to monitor its distribution may be unreliable because its expression is heterogeneous. Therefore, non-invasive imaging of tumor PD-L1 expression could be more helpful. Materials and Methods: Two different murine tumor models (MEER and B16F10) were established in two locations, at the back of the neck and at the right flank of C57BL/6 mouse. Then fractionated RT (2Gyx4 or 2GyX10) with or without anti PD-1 therapy was delivered only to the neck tumor. PD-L1 expression was measured by PET/CT and biodistrubtion with Zr-89-DFO-anti-mouse PD-L1 monoclonal Ab (clone 10F.9G2) and the results were corroborated by flow cytometric analysis and immunohistochemistry. PET/CT imaging and biodistributions were performed 48 or 96 hours after tracer-injection. The change of PD-L1 expression on irradiated neck tumor was evaluated using non-irradiated flank tumor as a control. Endothelial cell morphology in tumor vessels was also analyzed by CD31 staining to determine whether RT-induced increased permeability of tumor vessels might result in increased non-specific tracer accumulations in the irradiated tumors. Results: PET/CT imaging and biodistribution study of ex-vivo tracer uptake values demonstrated significant increased tracer uptake in irradiated neck tumor compared to non-irradiated flank tumor in either case of MEER and B16F10. Tracer uptakes in the spleens were significantly decreased if high dose of non-labeled anti-mouse PD-L1 monoclonal Ab was given in advance before tracer-injection, which indicates the tracer is fully functional. Flow cytometry and immunohistochemistry showed PD-L1 upregulation in both irradiated tumors corroborating PET/CT imaging of RT-induced PD-L1 upregulation. Flow cytometry also revealed RT-induced PD-L1 upregulation on myeloid cells is more prominent than that of tumor cells in both MEER and B16F10. CD31-positive staining in the irradiated tumors was not different from that of non-irradiated tumors, which shows RT did not induce alterations in tumor blood vessels. PD-L1 upregulation of MEER was not seen unless it was performed 2GyX10 RT, however, that of B16F10 could be seen at an earlier time-point of 2GyX4. Combination therapy of anti PD-1 with RT did not show further PD-L1 upregulation compared to RT without anti PD-1 therapy. Conclusion: RT-induced PD-L1 upregulation in different tumor models of MEER and B16F10 was identified by PET/CT using Zr-89 labeled PD-L1 monoclonal Ab and its validity was corroborated by flow cytometric analysis and immunohistochemistry. Citation Format: Masahiro Kikuchi, Raghvendra M Srivastava, David A Clump, Julio A Diaz-Perez, Lingyi Sun, Dexing Zeng, W. Barry Edwards, Carolyn J Anderson, Robert L Ferris. Radiation-induced PD-L1 upregulation can be detected by Zr-89-PD-L1 PET/CT in the tumor micro-environment of murine HPV positive HNSCC model and melanoma model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 870. doi:10.1158/1538-7445.AM2017-870