Changes In Tumor Vasculature Research Articles

Ultrafast Power Doppler Ultrasound Enables Longitudinal Tracking of Vascular Changes that Correlate with Immune Response After Radiotherapy.

While immunotherapy shows great promise in patients with triple negative breast cancer, many will not respond to treatment. Radiotherapy has the potential to prime the tumor-immune microenvironment for immunotherapy. However, predicting response is difficult due to tumor heterogeneity across patients, which necessitates personalized medicine strategies that incorporate tumor tracking into the therapeutic approach. Here, we investigated the use of ultrasound (US) imaging of the tumor vasculature to monitor the tumor response to treatment. We utilized ultrafast power doppler US to track the vascular response to radiotherapy over time. We used 4T1 (metastatic) and 67NR (non-metastatic) breast cancer models to determine if US measurements corroborate conventional immunostaining analysis of the tumor vasculature. To evaluate the effects of radiation, tumor volume and vascular index were calculated using US, and the correlation between vascular changes and immune cell infiltration was determined. US tumor measurements and the quantified vascular response to radiation were confirmed with caliper measurements and immunostaining, respectively, demonstrating a proof-of-principle method for non-invasive vascular monitoring. Additionally, we found significant infiltration of CD8 + T cells into irradiated tumors 10 days after radiation, which followed a sustained decline in vascular index and an increase in splenic CD8 + T cells that was first observed 1 day post-radiation. Our findings reveal that ultrafast power doppler US can evaluate changes in tumor vasculature that are indicative of shifts in the tumor-immune microenvironment. This work may lead to improved patient outcomes through observing and predicting response to therapy.

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.

Low-level whole-brain radiation enhances theranostic potential of single-domain antibody fragments for human epidermal growth factor receptor type 2 (HER2)-positive brain metastases.

BackgroundSingle-domain antibody fragments (aka VHH, ~ 13 kDa) are promising delivery systems for brain tumor theranostics; however, achieving efficient delivery of VHH to intracranial lesions remains challenging due to the tumor–brain barrier. Here, we evaluate low-dose whole-brain irradiation as a strategy to increase the delivery of an anti- human epidermal growth factor receptor type 2 (HER2) VHH to breast cancer-derived intracranial tumors in mice.MethodsMice with intracranial HER2-positive BT474BrM3 tumors received 10-Gy fractionated cranial irradiation and were evaluated by noninvasive imaging. Anti-HER2 VHH 5F7 was labeled with 18F, administered intravenously to irradiated mice and controls, and PET/CT imaging was conducted periodically after irradiation. Tumor uptake of 18F-labeled 5F7 in irradiated and control mice was compared by PET/CT image analysis and correlated with tumor volumes. In addition, longitudinal dynamic contrast-enhanced MRI (DCE-MRI) was conducted to visualize and quantify the potential effects of radiation on tumor perfusion and permeability.ResultsIncreased 18F-labeled 5F7 intracranial tumor uptake was observed with PET in mice receiving cranial irradiation, with maximum tumor accumulation seen approximately 12 days post initial radiation treatment. No radiation-induced changes in HER2 expression were detected by Western blot, flow cytometry, or on tissue sections. DCE-MRI imaging demonstrated transiently increased tumor perfusion and permeability after irradiation, consistent with the higher tumor uptake of 18F-labeled anti-HER2 5F7 in irradiated mice.ConclusionLow-level brain irradiation induces dynamic changes in tumor vasculature that increase the intracranial tumor delivery of an anti-HER2 VHH, which could facilitate the use of radiolabeled VHH to detect, monitor, and treat HER2-expressing brain metastases.

A Pilot Study to Evaluate Early Predictive Value of Thorax Perfusion-CT in Advanced NSCLC.

Simple SummaryThe use of targeted drugs has brought about the development of new imaging techniques which are able to assess in vivo processes and changes in vascularization parameters can be captured as part of the antitumor response to antiangiogenic therapies. This pilot study (IMPACT trial, NCT02316327) aimed to explore the capacity of Perfusion-Computed Tomography (pCT) to detect early changes in tumor vascularization in non-small cell lung cancer (NSCLC) patients treated with an antiangiogenic-based therapy. Our results confirm the feasibility of pCT to capture early changes in tumor vasculature and suggest the potential of blood volume (BV) to early identify differential tumor responses to antiangiogenic therapy.Background: The role of perfusion computed tomography (pCT) in detecting changes in tumor vascularization as part of a response to antiangiogenic therapy in non-small cell lung cancer (NSCLC) remains unclear. Methods: In this prospective pilot study (IMPACT trial, NCT02316327), we aimed to determine the ability of pCT to detect early changes in blood flow (BF), blood volume (BV), and permeability (PMB), and to explore whether these changes could predict the response at day +42 in patients with advanced, treatment-naive, non-squamous NSCLC treated with cisplatin and gemcitabine plus bevacizumab. Results: All of the perfusion parameters showed a consistent decrease during the course of treatment. The BV difference between baseline and early assessment was significant (p = 0.013), whereas all perfusion parameters showed significant differences between baseline and day +42 (p = 0.003, p = 0.049, and p = 0.002, respectively). Among the 16 patients evaluable for efficacy, a significant decline in BV at day +7 from baseline was observed in tumors with no response (p = 0.0418). Conclusions: Our results confirm that pCT can capture early changes in tumor vasculature. A substantial early decline of BV from baseline might identify tumors less likely responsive to antiangiogenic-drugs.

3D Microfluidic Platform and Tumor Vascular Mapping for Evaluating Anti-Angiogenic RNAi-Based Nanomedicine.

Three-dimensional (3D) visualization of tumor vasculature is a key factor in accurate evaluation of RNA interference (RNAi)-based antiangiogenic nanomedicine, a promising approach for cancer therapeutics. However, this remains challenging because there is not a physiologically relevant in vitro model or precise analytic methodology. To address this limitation, a strategy based on 3D microfluidic angiogenesis-on-a-chip and 3D tumor vascular mapping was developed for evaluating RNAi-based antiangiogenic nanomedicine. We developed a microfluidic model to recapitulate functional 3D angiogenic sprouting when co-cultured with various cancer cell types. This model enabled efficient and rapid assessment of antiangiogenic nanomedicine in treatment of hyper-angiogenic cancer. In addition, tissue-clearing-based whole vascular mapping of tumor xenograft allowed extraction of complex 3D morphological information in diverse quantitative parameters. Using this 3D imaging-based analysis, we observed tumor sub-regional differences in the antiangiogenic effect. Our systematic strategy can help in narrowing down the promising targets of antiangiogenic nanomedicine and then enables deep analysis of complex morphological changes in tumor vasculature, providing a powerful platform for the development of safe and effective nanomedicine for cancer therapeutics.

Photoacoustic imaging biomarkers for monitoring biophysical changes during nanobubble-mediated radiation treatment

The development of novel anticancer therapies warrants the parallel development of biomarkers that can quantify their effectiveness. Photoacoustic imaging has the potential to measure changes in tumor vasculature during treatment. Establishing the accuracy of imaging biomarkers requires direct comparisons with gold histological standards. In this work, we explore whether a new class of submicron, vascular disrupting, ultrasonically stimulated nanobubbles enhance radiation therapy. In vivo experiments were conducted on mice bearing prostate cancer tumors. Combined nanobubble plus radiation treatments were compared against conventional microbubbles and radiation alone (single 8 Gy fraction). Acoustic resolution photoacoustic imaging was used to monitor the effects of the treatments 2- and 24-hs post-administration. Histological examination provided metrics of tumor vascularity and tumoral cell death, both of which were compared to photoacoustic-derived biomarkers. Photoacoustic metrics of oxygen saturation reveal a 20 % decrease in oxygenation within 24 h post-treatment. The spectral slope metric could separate the response of the nanobubble treatments from the microbubble counterparts. This study shows that histopathological assessment correlated well with photoacoustic biomarkers of treatment response.

MRI changes in patients with newly diagnosed glioblastoma treated as part of a phase II trial with bavituximab, radiation, and temozolomide.

2546 Background: Glioblastoma and tumor endothelial cells express phosphatidylserine (PS), a highly immunosuppressive membrane phospholipid. Bavituximab – a chimeric monoclonal antibody – binds to β2-glycoprotein 1 (β2-GP1) to form a complex of β2-GP1 with PS, resulting in immune activation against tumor cells and anti-angiogenic effects. Phase I/II trials in other solid cancers demonstrated response rates up to 75% when bavituximab was given with cytotoxic chemotherapy. Pre-clinical data in glioblastoma models suggested synergistic effects of PS blockade, radiation, and temozolomide. Methods: 33 adult patients with IDH-wild-type, MGMT-methylated or -unmethylated newly diagnosed glioblastoma were enrolled in this phase II trial (NCT03139916) and received 6 weeks of chemoradiation, followed by 6 cycles of adjuvant temozolomide (C1-C6 aTMZ). Bavituximab (3 mg/kg) was given weekly, starting week 1 of chemoradiation, for 18 weeks with the option to continue if tolerated. Physiologic MRIs were performed pre-treatment, pre-C1, pre-C3, and pre-C5 aTMZ. Within the enhancing tumor region, median tumor Ktrans (reflecting vascular permeability) and relative cerebral blood flow (rCBF) were measured. Median percent changes during treatment were compared to pre-treatment values. Results: Median progression-free survival (mPFS) was 8 months. Based on a median overall survival (mOS) of 17.1 months, patients were categorized into above-median survivors (AMS) and below-median survivors (BMS). All patients had pre-treatment scans. 31 had evaluable pre-C1, 25 had pre-C3, and 7 had pre-C5 scans. Compared to BMS, AMS had a greater reuction in enhancing tumor volume and rCBF, and a greater increase in Ktrans during treatment (table). One patient remains on study; 23 patients have died. Bavituximab was well tolerated. Conclusions: mPFS and mOS in patients treated with bavituximab, radiation and temozolomide were comparable to standard chemoradiation and aTMZ. Lower rCBF in AMS may reflect decreased tumor perfusion while higher Ktrans could imply enhanced drug delivery to the tumor. Bavituximab induces changes in tumor vasculature that may improve survival in a subset of patients. Clinical trial information: NCT03139916 . [Table: see text]

Therapeutic vascular normalization to promote tumor-associated tertiary lymphoid structures

Abstract Tertiary lymphoid structures (TLS) are non-encapsulated immune cell aggregates that form at sites of chronic inflammation. Recent studies have shown that the presence of TLS in human tumors indicates positive clinical outcome. However, many tumors have poorly organized and leaky vasculature that impedes entry of immune effector cells into tumors and consequently TLS formation. Recently, studies have shown that low doses of antiangiogenic agents normalize tumor vasculature, leading us to hypothesize that treating tumors with low doses of vascular normalizing (VN) therapies will improve immune cell infiltration and TLS formation within the tumor microenvironment (TME). To test this hypothesis, tumor-bearing mice were treated intratumorally with VN agents. RNA was isolated from digested tumors and transcript levels of TLS-promoting factors and markers of inflammation/immune cell infiltration were measured and compared to PBS treated controls. Changes in tumor vasculature were evaluated using immunofluorescence microscopy. Additionally, primary cultures of murine T cells and DCs and the BPR melanoma cell line were treated in vitro with VN agents. We observed that the VN agents dasatinib, STING agonist, bevacizumab, and agonist anti-TNFR1 antibody each induced global changes in the TME that are potentially supportive of immune cell infiltration and TLS formation. In vitro, dasatinib induced DCs and BPR melanoma cells to express higher levels of co-stimulatory receptors, MHC class I and II, and TLS-promoting chemokines. Treatment with a STING agonist was able to enhance T cell activation, while treatment with dasatinib inhibited T cell activation.

Tracking Pharmacodynamics of Vascular Targeted Therapy with Photoacoustic Imaging.

HomeRadiology: Imaging CancerVol. 2, No. 1 PreviousNext Research HighlightsFree AccessTracking Pharmacodynamics of Vascular Targeted Therapy with Photoacoustic ImagingGary D. LukerGary D. LukerGary D. LukerPublished Online:Jan 31 2020https://doi.org/10.1148/rycan.2020204004MoreSectionsPDF ToolsImage ViewerAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked In Take-Away Points■ Major Focus: To investigate feasibility of noninvasive photoacoustic imaging for quantifying pharmacodynamics of vascular-targeted therapy in tumors.■ Key Result: Photoacoustic imaging measured time- and dose-dependent effects of an investigation of a vascular disrupting agent in two preclinical models of cancer.■ Impact: Photoacoustic imaging can successfully monitor pharmacodynamics of tumor vasculature during therapy, supporting applications in drug development and clinical translation for precision medicine.Imaging methods to analyze pharmacodynamics, the activity of a compound on its therapeutic target, potentially will increase development of new drugs for cancer and enable precision therapy for patients. Vascular disrupting agents represent a new class of anticancer compounds designed to target immature blood vessels typically associated with tumors. Success of these agents remains limited by a viable peripheral rim of cancer cells perfused by adjacent normal blood vessels and intertumor differences in susceptibility to hypoxia. Photoacoustic imaging, which uses low-intensity, nonionizing laser pulses to generate ultrasound waves for an image, provides an excellent method to image tumor blood vessels based on sensitive, high-contrast detection of hemoglobin. Using a high-resolution photoacoustic imaging instrument, Johnson et al measured the effects of the vascular disrupting agent OXi4503 in two different mouse models of colon cancer. In both models, photoacoustic imaging revealed initial ablation of internal blood vessels and subsequent regrowth of tumor vasculature over 16 days of treatment. For well-perfused tumors with extensive immature blood vessels, reductions in tumor blood vessels correlated highly with reductions in tumor volume over time. While poorly perfused tumors with larger, more mature blood vessels showed modest reductions in tumor blood vessels, changes in tumor vasculature did not predict effects on tumor volume. Treatment failures in poorly perfused tumors mirror past studies demonstrating resistance of such tumors to vascular disrupting therapy. Photoacoustic imaging also measured dose-dependent reductions in tumor blood vessels, establishing an approach to optimize doses and dosing schedules. These results establish photoacoustic imaging as a preclinical imaging method to advance development of vascular-targeted therapies. Furthermore, since photoacoustic instruments have entered clinical testing, this research supports future clinical applications of photoacoustic methods for pharmacodynamic imaging.Highlighted ArticleJohnson SP, Ogunlade O, Lythgoe MF, Beard P, Pedley RB. Longitudinal photacoustic imaging of the pharmacodynamics effect of vascular targeted therapy on tumors. Clin Cancer Res 2019;25:7436–7447. doi: 10.1158/1078-0432.CCR-19-036Highlighted ArticleJohnson SP, Ogunlade O, Lythgoe MF, Beard P, Pedley RB. Longitudinal photacoustic imaging of the pharmacodynamics effect of vascular targeted therapy on tumors. Clin Cancer Res 2019;25:7436–7447. doi: 10.1158/1078-0432.CCR-19-036 Crossref, Medline, Google ScholarArticle HistoryPublished online: Jan 31 2020 FiguresReferencesRelatedDetailsRecommended Articles Irreversible Electroporation versus Radiofrequency Ablation: A Comparison of Local and Systemic Effects in a Small-Animal ModelRadiology2016Volume: 280Issue: 2pp. 413-424Midterm Safety and Efficacy of Irreversible Electroporation of Malignant Liver Tumors Located Close to Major Portal or Hepatic VeinsRadiology2017Volume: 285Issue: 3pp. 1023-1031Local-Regional Treatment of Hepatocellular Carcinoma: A Primer for RadiologistsRadioGraphics2022Volume: 42Issue: 6pp. 1670-1689Nonthermal Ablation by Using Intravascular Oxygen Radical Generation with WST11: Dynamic Tissue Effects and Implications for Focal TherapyRadiology2016Volume: 281Issue: 1pp. 109-118Animal Models of Hepatocellular Carcinoma for Local-Regional Intraarterial TherapiesRadiology: Imaging Cancer2022Volume: 4Issue: 4See More RSNA Education Exhibits Novel Image-Guided Micro-Invasive Percutaneous Treatments of Breast Lesions: Where Do We Stand?Digital Posters2019Imaging Features at the Periphery – Hemodynamics, Pathophysiology and Impact on LI-RADS CategorizationDigital Posters2020A Practical Guide of Locoregional Treatment for Patients with Hepatocellular CarcinomaDigital Posters2019 RSNA Case Collection Adult colo-colonic intussusceptionRSNA Case Collection2020Cerebral Cavernous Venous MalformationRSNA Case Collection2021Pseudocirrhosis of Hepatic Breast MetastasesRSNA Case Collection2020 Vol. 2, No. 1 Metrics Altmetric Score PDF download

Electroporation-induced changes in tumor vasculature and microenvironment can promote the delivery and increase the efficacy of sorafenib nanoparticles

Blood vessels, the extracellular space, and the cell membrane represent physiologic barriers to nanoparticle-based drug delivery for cancer therapy. We demonstrate that electroporation (EP) can assist in the delivery of dye stabilized sorafenib nanoparticles (SFB-IR783) by increasing the permeability of endothelial monolayers, improving diffusion through the extracellular space in tumorspheres, and by disrupting plasma membrane function in cancer cells. These changes occur in a dose-dependent fashion, increasing proportionally with electric field strength. Cell death from irreversible electroporation (IRE) was observed to contribute to the persistent transport of SFB-IR783 through these physiologic barriers. In a model of mice bearing bilateral xenograft HCT116 colorectal tumors, treatment with EP resulted in the immediate and increased uptake of SFB-IR783 when compared with the untreated contralateral tumor. The uptake of SFB-IR783 was independent of direct transfection of cells through EP and was mediated by changes in vascular permeability and extracellular diffusion. The combination of EP and SFB-IR783 was observed to result in 40% reduction in mean tumor diameter when compared with sham treatment (p < .05) at the time of sacrifice, which was not observed in cohorts treated with EP alone or SFB-IR783 alone. Treatment of tumor with EP can augment the uptake and increase the efficacy of nanoparticle therapy.

Front Cover: Photoacoustic microscopy for evaluating combretastatin A4 phosphate induced vascular disruption in orthotopic glioma (J. Biophotonics 10/2018)

Optical resolution photoacoustic microscopy (OR‐PAM) imaging system is exploited to evaluate the vascular disruptive effect of Combretastatin A4 Phosphate (CA4P), a solid tumor drug, on a murine orthotopic glioma with intact skull. Hemodynamic changes in tumor vasculature are in agreement with the well documented shutdown and recovery associated CA4P administration. High resolution vasculature images obtained using OR‐PAM enable mapping of each individual blood vessel's response to the treatment.Further details can be found in the article by Renzhe Bi, Ghayathri Balasundaram, Seungwan Jeon, et al. (e201700327) image

Dynamic 18F-FLT PET imaging of spatiotemporal changes in tumor cell proliferation and vasculature reveals the mechanistic actions of anti-angiogenic therapy

Anti-angiogenic therapies target tumor vasculature and tumor cells, thus a concurrent assessment of these targets would lead to a greater understanding of therapeutic resistance and facilitate development of improved therapeutic strategies. We utilize dynamic 3′-deoxy-3′-18F-fluorothymidine positron emission tomography (18F-FLT PET) scanning to concurrently assess changes in tumor cell proliferation and vasculature during anti-angiogenic therapy, providing insight into how these therapies may be used effectively with combination chemotherapy. Thirty-three patients with advanced solid malignancies underwent treatment with vascular endothelial growth factor receptor inhibitor (VEGFR-TKI) axitinib on an intermittent schedule (two-weeks-on/one-week-off). Patients had up to three dynamic 18F-FLT PET/CT scans: at baseline, after two weeks of continuous VEGFR-TKI treatment, and following a one week treatment break. 18F-FLT kinetics were analyzed using a two-tissue compartment kinetic model. Kinetic parameters Vb and K1 were extracted to quantify changes in tumor vasculature and the 18F-FLT flux constant Ki was calculated to quantify changes in tumor cell proliferation. Two weeks of continuous axitinib exposure led to decreases in Vb (median −21%, P = 0.07), K1 (median −39%, P < 0.01), and Ki (median −37%, P < 0.01), corresponding to diminished tumor vasculature and cell proliferation that may antagonize treatment with concurrent chemotherapy. Axitinib treatment breaks led to significant increases in Vb (median +42%, P < 0.01), K1 (median +46%, P < 0.01), and Ki (median +39%, P < 0.01) that is suggestive of an optimal time to schedule synergistic chemotherapy. Significant negative correlations (rho ⩽ −0.70, P < 0.01) were found between changes in tumor vasculature during axitinib exposure weeks and changes in tumor vasculature during treatment breaks. Imaging with dynamic 18F-FLT PET revealed new insights relating to the interplay of vascular and proliferative pharmacodynamics of axitinib therapy, facilitating a greater understanding of the mechanistic actions of VEGFR-TKIs. Increases in tumor vasculature and cell proliferation during VEGFR-TKI treatment breaks, suggests this period is an optimal time to schedule synergistic chemotherapy and warrants further investigation.

Photoacoustic microscopy for evaluating combretastatin A4 phosphate induced vascular disruption in orthotopic glioma.

The use of an optical resolution photoacoustic microscopy (OR-PAM) system to evaluate the vascular disruptive effect of combretastatin A4 Phosphate (CA4P) on a murine orthotopic glioma with intact skull is described here. Second generation optical-resolution photoacoustic microscopy scanner with a 532 nm pulsed diode-pumped solid-state laser that specifically matches the absorption maximum of hemoglobin in tissues was used to image orthotopic glioma inoculated in mouse brain. Two-dimensional maps of brain vasculature with a lateral resolution of 5 μm and a depth of 700 μm at a field of view 5 × 4 mm were acquired on normal brain and glioma brain. Longitudinal imaging of the brain pre- and post-administration of CA4P, a FDA approved drug for solid tumors, enabled the monitoring of hemodynamic changes in tumor vasculature revealing the well documented vascular shutdown and recovery associated with this drug. Our study marks the beginning of potential prospects of this technology as an imaging tool for preclinical and clinical study of pathologies characterized by changes in the vasculature.

An Improved In Vivo Methodology to Visualise Tumour Induced Changes in Vasculature Using the Chick Chorionic Allantoic Membrane Assay.

Decreasing the vascularity of a tumour has proven to be an effective strategy to suppress tumour growth and metastasis. Anti-angiogenic therapies have revolutionized the treatment of advanced-stage cancers, however there is still demand for further improvement. This necessitates new experimental models that will allow researchers to reliably study aspects of angiogenesis. The aim of this study was to demonstrate an in vivo technique in which the highly vascular and accessible chorioallantoic membrane (CAM) of the chick embryo is used to study tumour-induced changes in the macro and microvessels. Two cancer cell lines (human melanoma (C8161) and human prostate cancer (PC3)) were selected as model cells. Human dermal fibroblasts were used as a control. One million cells were labelled with green fluorescent protein and implanted on the CAM of the chick embryo at embryonic development day (EDD) 7 and angiogenesis was evaluated at EDDs 10, 12 and 14. A fluorescently-tagged lectin (lens culinaris agglutinin (LCA)) was injected intravenously into the chick embryo to label endothelial cells. The LCA is known to label the luminal surface of endothelial cells, or dextrans, in the CAM vasculature. Macrovessels were imaged by a hand-held digital microscope and images were processed for quantification. Microvessels were evaluated by confocal microscopy. Tumour invasion was assessed by histological and optical sectioning. Tumour cells (C8161 and PC3) produced quantifiable increases in the total area covered by blood vessels, compared to fibroblasts when assessed by digital microscopy. Tumour invasion could be demonstrated by both histological and optical sectioning. The most significant changes in tumour vasculature observed were in the microvascular structures adjacent to the tumour cells, which showed an increase in the endothelial cell coverage. Additionally, tumour intravasation and tumour thrombus formation could be detected in the areas adjacent to tumour cells. The fragility of tumour blood vessels could be demonstrated when tumour cells seeded on a synthetic scaffold were grown on CAM. We report on a modification to a well-studied CAM in vivo assay, which can be effectively used to study tumour induced changes in macro and microvasculature.

Abstract PD4-08: A microenvironment secretome screen reveals FGF2 as a mediator of resistance to anti-estrogens and PI3K/mTOR pathway inhibitors in ER+ breast cancer

Abstract Despite the clinical success of anti-estrogen therapies, phosphatidylinositol 3-kinase inhibitors (PI3Ki), and mechanistic target of rapamycin complex I inhibitors (mTORC1i) for the treatment of patients with ER+ breast cancer, disease recurrence and progression are common. We found that a tumor transcriptional profile reflecting high stromal fibroblast content was associated with poor outcome in 3 cohorts of patients with ER+ breast cancer. We hypothesized that individual factors in the tumor microenvironment (TME) significantly contribute to drug resistance. To test this hypothesis, we screened 297 recombinant secreted proteins for ability to confer resistance to the anti-estrogen fulvestrant in MCF-7 and T47D ER+ breast cancer cells. Screen results were validated, and expansion screening included the anti-estrogen tamoxifen, the PI3Ki pictilisib, and the mTORC1i everolimus in 4 cell lines. To identify hits are most likely to be relevant to ER+ breast cancer, a bioinformatics filter was developed utilizing gene and protein expression in human tissues relevant to the TMEs of ER+ breast cancer. After filtering, the top screening hit was fibroblast growth factor 2 (FGF2), which confers resistance to anti-estrogens, PI3Ki, and mTORC1i, and is highly expressed in tissues and cell types associated with ER+ breast cancer. FGF2 did not rescue cells from the CDK4/6i palbociclib or the DNA-damaging agent doxorubicin, demonstrating pathway selectivity in the rescue phenotype. FGF2 rescued cells from anti-estrogen-, PI3Ki-, and mTORC1i-induced apoptosis and cell cycle arrest via activation of FGFR signaling through FRS2a, MEK1/2, ERK1/2, and downstream upregulation of cyclin D1 and degradation of Bim. FGF2-mediated anti-cancer effects were abrogated by co-treatment with the FGF2-neutralizing antibody GAL-F2, the pan-FGFR inhibitor PD-173074, the MEK inhibitor trametinib, or palbociclib. Cell cycle- and apoptosis-specific effects of FGF2 were abrogated by RNAi targeting cyclin D1 and Bim, respectively. We generated a transcriptional signature of FGF2 response by RNA-seq of fulvestrant-treated MCF-7 and T47D cells treated +/- FGF2. In 3 cohorts of patients with ER+ breast cancer, a signature of FGF2 signaling was significantly associated with poor prognosis and predictive of anti-estrogen resistance, including in a multivariate analysis including age, tumor grade, tumor stage, and FGFR amplification status. Finally, the therapeutic potential of targeting FGF2 was confirmed in 3 mouse models of ER+ breast cancer: 1) FGF2 rescue MCF-7 xenografts from fulvestrant; 2) GAL-F2 synergized with fulvestrant to suppress growth of 59-2-HI murine mammary adenocarcinomas that recruit FGF2-secreting stroma; 3) GAL-F2 synergized with fulvestrant to induce regression of HCI-003 patient-derived xenografts. Therapeutic effects coincided with increased tumor cell apoptosis and decreased proliferation, but not changes in tumor vasculature. These findings warrant consideration of FGF2 as a novel therapeutic target in ER+ breast cancer. Citation Format: Shee K, Hinds JW, Yang W, Hampsch RA, Patel K, Varn FS, Cheng C, Jenkins NP, Kettenbach AN, Demidenko E, Owens P, Lanari C, Faber AC, Golub TR, Straussman R, Miller TW. A microenvironment secretome screen reveals FGF2 as a mediator of resistance to anti-estrogens and PI3K/mTOR pathway inhibitors in ER+ breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD4-08.

Multiparametric characterization of response to anti-angiogenic therapy using USPIO contrast-enhanced MRI in combination with dynamic contrast-enhanced MRI.

Steady state susceptibility contrast (SSC)-MRI provides information on vascular morphology but is a rarely used method. To investigate the utility of the ultrasmall superparamagnetic iron oxide particles (USPIOs) GEH121333 for measuring tumor response to bevacizumab and compare this with gadolinium-based DCE-MRI. Prospective preclinical animal model study. Mice bearing subcutaneous TOV-21G human ovarian cancer xenografts treated with bevacizumab (n = 9) or saline (n = 9). Imaging was performed on a 7T Bruker Biospec. For SSC-MRI with GEH121333 we acquired R1 -maps (RARE-sequence with variable TR), R2 -maps (multi-spin echo), and R2*-maps (multi-gradient echo). Additionally, R1 and R2 maps were measured on the days after USPIO injection. For DCE-MRI with gadodiamide we acquired 200 T1 -weighted images (RARE-sequence). ΔR1 , ΔR2 , and ΔR2* maps were computed from SSC-MRI. DCE-MRI was analysed using the extended Tofts model. Results from pre- and 3 days posttreatment SSC-MRI were compared using paired-sample t-tests. Treatment and control groups were compared using independent sample t-tests. Performance of SSC- and DCE-MRI was compared using multivariate partial least squares discriminant analysis. Already one day after treatment and USPIO injection, R1 and R2 values were lower in treated (R1 = 0.49 ± 0.03s-1 , R2 = 23.07 ± 1.49s-1 ) compared with control tumors (R1 = 0.52 ± 0.02s-1 , R2 = 24.98 ± 1.01s-1 ), indicating lower USPIO accumulation. Posttreatment SSC-MRI displayed significantly decreased tumor blood volume (change in ΔR2 = -0.43 ± 0.26s-1 , P = 0.001) and vessel density (change in Q = -0.032 ± 0.020s-1/3 , P = 0.002). DCE-MRI showed among others lower Ktrans in treated tumors (control = 0.064 ± 0.011min-1 , tx = 0.046 ± 0.008min-1 , P = 0.002). Multivariate analysis suggests that SSC-MRI was slightly inferior to DCE-MRI in distinguishing treated from control tumors (accuracy = 75%, P = 0.058 versus 80%, P = 0.028), but a combination of both was best (accuracy = 85%; P = 0.003). SSC-MRI with GEH121333 is sensitive to early (<24 h) and late changes in tumor vasculature. SSC-MRI and DCE-MRI provide complementary information and can be used to assess different aspects of vascular responses to anti-angiogenic therapies. 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1589-1600.

Quantification of Tumor Vascular Permeability and Blood Volume by Positron Emission Tomography.

Purpose: Evans Blue (EB) is an azo dye that binds quantitatively with serum albumin. With an albumin binding, NOTA conjugated truncated Evan's blue (NEB) dye derived PET tracer, we aimed to establish a strategy for evaluating vascular permeability in malignant tumors via non-invasive PET. Experimental design: Sixty-minute dynamic PET using [18F]FAl-NEB was performed in three xenograft tumor models including INS-1 rat insulinoma, UM-SCC-22B human head and neck carcinoma and U-87 MG human glioblastoma. Tumor vascular permeability was quantified by the difference of the slopes between tumor and blood time-activity curve (TACs, expressed as Ps). The method was further substantiated by EB extraction and colorimetric assay and correlates with that calculated from dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). The changes in tumor vasculature at different time points were assessed with NEB PET in U-87 MG and UM-SCC-22B tumor models after treatment with bevacizumab or doxorubicin. Result: The Ps values calculated from tumor and blood TACs from multiple time-point static images are consistent with those from dynamic images. Moreover, the Ps showed a positive and significant correlation with extracted EB concentration and KPS-MRI generated from DCE-MRI, which further confirmed the soundness of this methodology. The antiangiogenic effect of bevacizumab could be revealed by NEB PET in U-87 MG tumors as early as 8 hrs after therapy, demonstrated by a substantial decrease of Ps. On the contrary, there was no significant change of Ps in bevacizumab treated UM-SCC-22B tumors, compared with control group. However, the significant changes of Pswere overestimated in doxorubicin treated UM-SCC-22B tumors. Conclusions: We successfully developed a relatively convenient and novel strategy to evaluate vascular permeability and blood volume using NEB PET. This method will be advantageous in evaluating vascular permeability, promoting drug delivery, and monitoring tumor response to therapeutics that affect tumor angiogenesis.

WE‐AB‐BRA‐05: PET‐Guided Delivery Quality Evaluation of Yttrium‐90 Microsphere Radioembolizaton for Hepatocellular Carcinoma Patients: The Optimal Sequence of Radioembolizaton and Chemoembolization Treatments

Purpose:Selective‐internal‐radiation‐therapy (SIRT) and transarterial‐chemoembolization (TACE) are commonly used for treatment of liver tumors. The use of TACE, which is macroembolic, prior to SIRT may cause hemodynamic changes in tumor vasculature that impair yttrium‐90 (90Y) microsphere delivery to the targeted lesions. This work aims to quantify dosimetric tumor coverage using 90Y positron emission tomography (PET) dosimetry after SIRT alone compared to TACE followed by SIRT.Methods:A total of 40 consecutive hepatocellular carcinoma (HCC) SIRT patients who had a post‐SIRT 90Y PET/CT scan were evaluated. The patient‐specific‐3D‐dose was reconstructed from the PET images. Patients were categorized into two groups: patients received TACE prior SIRT procedure (n=18) and patient received SIRT alone (n=22). The lesions and liver were delineated by a senior radiologist. We evaluated both the lesion‐specific dose‐volume‐histogram (DVH) and the selectivity index (SI) defined as the ratio of the average dose inside the total lesion(s) and the average dose of the normal liver. The SI values of patients were compared based on whether TACE was previously used.Results:A wide spectrum was observed in the lesion‐specific DVH‐evaluation and SI appeared to be suitable of evaluating the quality of each SIRT infusion. The average SI of the entire patient group was 3.0, i.e. targeted lesion receiving three times higher dose than normal liver. The average SI was 1.8 for patients who had prior TACE and 3.9 for patients who did not have prior TACE (p=0.008). 85% of the patients with prior TACE demonstrated poor 90Y‐microsphere delivery (SI &lt;2) while none demonstrated excellent delivery (SI &gt;4). On the other hand, the incidence SI &gt;4 among patients with no prior TACE was 37%.Conclusion:3D dose evaluation using post‐SIRT PET suggests that 90Y microsphere delivery to liver tumors is impaired among patients who received prior TACE compared to those who receive SIRT alone.

Effect of transarterial chemoembolization prior to selective internal radiation therapy on yttrium-90 microsphere delivery in hepatocellular carcinoma patients.

458 Background: Transarterial chemoembolization (TACE) and selective internal radiation therapy (SIRT) are commonly used for treatment of liver tumors. The use of TACE, which is macroembolic, prior to SIRT may cause hemodynamic changes in tumor vasculature that impair yttrium-90 (90Y) microsphere delivery to the targeted lesions. This work aims to quantify dosimetric tumor coverage using positron emission tomography (PET) dosimetry after SIRT alone compared to TACE followed by SIRT. Methods: A total of 40 consecutive hepatocellular carcinoma (HCC) SIRT patients who had a post-SIRT PET scan were evaluated. Yttrium-90 PET scan was performed within 2 hours after completion of SIRT. 3D dose distribution of each patient was then reconstructed from the PET images. To quantify the quality of SIRT microsphere delivery, we evaluated the selectivity index (SI) defined as the ratio of the average dose inside the treated lesion(s) and the average dose of the normal liver. The SI values of patients were compared based on whether TACE was previously used. Results: Thirty patients had complete data for analysis. The average dose for a total of 125 targeted lesions was 106 Gy (range 0 Gy – 495 Gy). The average SI of the entire patient group was 3.0, indicating that the targeted lesion dose was three times higher than normal liver dose. The average SI was 1.7 for the 13 patients who had prior TACE and 3.8 for the 17 patients who did not have prior TACE (p = 0.01). Nearly 80% of the patients with prior TACE demonstrated poor 90Ymicrosphere delivery (SI &lt; 2) while none demonstrated excellent microsphere delivery (SI &gt; 4). On the other hand, the incidence of SI &lt; 2 and SI &gt; 4 among patients with no prior TACE was 24% and 40%, respectively. Conclusions: 3D dose evaluation using post-SIRT PET suggests that 90Y microsphere delivery to liver tumors is impaired among patients who received prior TACE compared to those who receive SIRT alone. These data warrant evaluation of clinical outcomes in SIRT patients based on prior use of TACE and may provide a rationale for the use of SIRT prior to TACE.

Multimodal approach to assess tumour vasculature and potential treatment effect with DCE‐US and DCE‐MRI quantification in CWR22 prostate tumour xenografts

The aim of this study was to compare intratumoural heterogeneity and longitudinal changes assessed by dynamic contrast-enhanced ultrasound (DCE-US) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in prostate tumour xenografts. In vivo DCE-US and DCE-MRI were obtained 24 h pre- (day 0) and post- (day 2) radiation treatment with a single dose of 7.5 Gy. Characterization of the tumour vasculature was determined by Brix pharmacokinetic analysis of the time-intensity curves. Histogram analysis of voxels showed significant changes (p < 0.001) from day 0 to day 2 in both modalities for kep , the exchange rate constant from the extracellular extravascular space to the plasma, and kel , the elimination rate constant of the contrast. In addition, kep and kel values from DCE-US were significantly higher than those derived from DCE-MRI at day 0 (p < 0.0001) for both groups. At day 2, kel followed the same tendency for both groups, whereas kep showed this tendency only for the treated group in intermediate-enhancement regions. Regarding kep median values, longitudinal changes were not found for any modality. However, at day 2, kep linked to DCE-US was correlated to MVD in high-enhancement areas for the treated group (p = 0.05). In contrast, correlation to necrosis was detected for the control group in intermediate-enhancement areas (p < 0.1). Intratumoural heterogeneity and longitudinal changes in tumour vasculature were assessed for both modalities. Microvascular parameters derived from DCE-US seem to provide reliable biomarkers during radiotherapy as validated by histology. Furthermore, DCE-US could be a stand-alone or a complementary technique.