Patrick McConville

Vascular Targeted Nanoparticles for Imaging and Treatment of Brain Tumors

Purpose: Development of new therapeutic drug delivery systems is an area of significant research interest. The ability to directly target a therapeutic agent to a tumor site would minimize systemic drug exposure, thus providing the potential for increasing the therapeutic index. Experimental Design: Photodynamic therapy (PDT) involves the uptake of a sensitizer by the cancer cells followed by photoirradiation to activate the sensitizer. PDT using Photofrin has certain disadvantages that include prolonged cutaneous photosensitization. Delivery of nanoparticles encapsulated with photodynamic agent specifically to a tumor site could potentially overcome the drawbacks of systemic therapy. In this study, we have developed a multifunctional polymeric nanoparticle consisting of a surface-localized tumor vasculature targeting F3 peptide and encapsulated PDT and imaging agents. Results: The nanoparticles specifically bound to the surface of MDA-435 cells in vitro and were internalized conferring photosensitivity to the cells. Significant magnetic resonance imaging contrast enhancement was achieved in i.c. rat 9L gliomas following i.v. nanoparticle administration. Serial magnetic resonance imaging was used for determination of pharmacokinetics and distribution of nanoparticles within the tumor. Treatment of glioma-bearing rats with targeted nanoparticles followed by PDT showed a significant improvement in survival rate when compared with animals who received PDT after administration of nontargeted nanoparticles or systemic Photofrin. Conclusions: This study reveals the versatility and efficacy of the multifunctional nanoparticle for the targeted detection and treatment of cancer.

A Novel Polyacrylamide Magnetic Nanoparticle Contrast Agent for Molecular Imaging using MRI

A novel polyacrylamide superparamagnetic iron oxide nanoparticle platform is described which has been synthetically prepared such that multiple crystals of iron oxide are encapsulated within a single polyacrylamide matrix (PolyAcrylamide Magnetic [PAM] nanoparticles). This formulation provides for an extremely large T2 and T2* relaxivity of between 620 and 1140 sec(-1) mM(-1). Administration of PAM nanoparticles into rats bearing orthotopic 9L gliomas allowed quantitative pharmacokinetic analysis of the uptake of nanoparticles in the vasculature, brain, and glioma. Addition of polyethylene glycol of varying sizes (0.6, 2, and 10 kDa) to the surface of the PAM nanoparticles resulted in an increase in plasma half-life and affected tumor uptake and retention of the nanoparticles as quantified by changes in tissue contrast using MRI. The flexible formulation of these nanoparticles suggests that future modifications could be accomplished allowing for their use as a targeted molecular imaging contrast agent and/or therapeutic platform for multiple indications.

Diffusion imaging for evaluation of tumor therapies in preclinical animal models

The increasing development of novel targeted therapies for treating solid tumors has necessitated the development of technology to determine their efficacy in preclinical animal models. One such technology that can non-invasively quantify early changes in tumor cellularity as a result of an efficacious therapy is diffusion MRI. In this overview we present some theories as to the origin of diffusion changes as a result of tumor therapy, a robust methodology for acquisition of apparent diffusion coefficient maps and some applications of determining therapeutic efficacy in a variety therapeutic regimens and animal models.

Magnetic Resonance Imaging Determination of Tumor Grade and Early Response to Temozolomide in a Genetically Engineered Mouse Model of Glioma

Purpose: The median survival for patients diagnosed with glioblastoma multiforme, the most common type of brain tumor, is less than 1 year. Animal glioma models that are more predictive of therapeutic response in human patients than traditional models and that are genetically and histologically accurate are an unmet need. The nestin tv-a (Ntv-a) genetically engineered mouse spontaneously develops glioma when infected with ALV-A expressing platelet-derived growth factor, resulting in autocrine platelet-derived growth factor signaling. Experimental Design: In the Ntv-a genetically engineered mouse model, T2-weighted and T1-weighted, contrast-enhanced magnetic resonance images were correlated with histology, glioma grade (high or low), and survival. Magnetic resonance imaging (MRI) was therefore used to enroll mice with high-grade gliomas into a second study that tested efficacy of the current standard of care for glioma, temozolomide (100 mg/kg qdx5 i.p., n = 13). Results: The Ntv-a model generated a heterogeneous group of gliomas, some with high-grade growth rate and histologic characteristics and others with characteristics of lower-grade gliomas. We showed that MRI could be used to predict tumor grade and survival. Temozolomide treatment of high-grade tv-a gliomas provided a 14-day growth delay compared with vehicle controls. Diffusion MRI measurement of the apparent diffusion coefficient showed an early decrease in cellularity with temozolomide, similar to that observed in humans. Conclusions: The use of MRI in the Ntv-a model allows determination of glioma grade and survival prediction, distribution of mice with specific tumor types into preclinical trials, and efficacy determination both by tumor growth and early apparent diffusion coefficient response.

Preclinical Models of Tumor Growth and Response

an important role in cancer drug discovery for more than 60 years. The same models have proven critical as tools for the elucidation of the molecular basis of neoplastic transformation, the processes involved in tumor progression and metastasis, and the determinants of therapeutic success or failure. More recently, transgenic models in particular have been used to “validate” and prioritize new strategies for therapeutic intervention. In vivo cancer models can be considered to fall within two broad classes, transplantable models, and in situ models, each with a number of subtypes (Fig. 1). For pragmatic reasons, transplantable models as a group are the most commonly used for drug evaluation, while in situ models such as cancer-prone transgenic mice provide a rich source of information on cancer etiology. It should be noted that each transplantable model represents the tumor of a single patient, not a tumor type. This discussion is centered on the application of both model types, and the potential impact of imaging technologies for cancer drug discovery. However, with recent advances in preclinical imaging technologies, these models are also proving useful in the development and testing of new imaging techniques and contrast agents. Increasingly, with the expanding role of drugs tied to specific molecular targets, these models are also being used to optimize and validate clinical imaging strategies. Finally, molecular imaging techniques are finding a critical role preclinically in the simultaneous confirmation of mechanism of action and assessment of efficacy. This is particularly true in orthotopic or transgenic model systems. Open image in new window Fig. 1. Schematic representation of the broad categories of preclinical cancer models in use today. In situ tumor models can be subcategorized by the method for induction of the tumor. Transplantable tumor models are commonly subcategorized according to whether the tumor is implanted in the organ in which the cell line originated (orthotopic versus ectopic) and in the species in which it originated (syngeneic versus xenogeneic).

Imaging Efficacy in Tumor Models

Imaging modalities such as magnetic resonance imaging (MRI), positron emission tomography (PET), single-photon emission computed tomography (SPECT), X-ray computed tomography (CT), ultrasound imaging and optical imaging techniques are increasingly being used to assess disease progression and response to therapeutics in animal models of disease. In oncology, the applications of these modalities range from volumetric assessment of tumor burden to imaging of functional parameters such as tumor vascularity and permeability, cell proliferation and tissue hypoxia. Quantitative assessment of molecular events such as receptor occupancy or upregulation of enzymes (e.g.matrix metalloproteinases) is also possible. Further, the use of imaging has enabled the use of more realistic models of disease (e.g. orthotopic/metastatic models) and the generation of more predictive data in a noninvasive manner. This chapter aims to provide a brief overview of the various imaging modalities, followed by a discussion of the most relevant oncology endpoints that are accessible by imaging.

Abstract 2066: Comparison of ADC MRI, T2-weighted MRI and combined T2-weighted/T1-contrast-enhanced/ADC MRI quantification of cerebral edema in an intracranial glioma model

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Introduction: Brain edema is a prominent feature of brain cancer and contributes to neurologic dysfunction and impaired quality of life. Efficacious treatments with minimal side effects are sought after in this indication. Quantitative, non-invasive methods for detecting and measuring brain tumor associated edema are needed to facilitate therapeutic discovery efforts. In this work, an intracranial U251-luc human glioma model was characterized for edema incidence and progression. Multiple MRI scan protocols were used to detect tumor, edema and fluid and quantify the volume of each. Apparent diffusion coefficient (ADC) based quantification was compared with a combined T2-weighted/T1-contrast-enhanced method. Methods: Female nude mice were implanted intracranially with 1x106 U251-luc (Luc-mCherry) glioma cells. A multi-modal MRI scan approach consisting of T2-weighted (T2w), T1-weighted (T1w) contrast-enhanced and ADC scans were used to detect and delineate tumor, fluid, edema and normal brain tissue. These scans yielded: V(T2): volume defined by hyper intense T2 - assumed to be volume[tumor + edema + fluid] V(CE): contrast enhancing volume - assumed to be volume[tumor] V(ADC_high): volume with ADC > threshold value that delineated fluid - assumed to be volume[fluid] A combinatorial approach to yield the volume of edema, V(edema) was used with: V(edema) = V(T2) - V(CE) - V(ADC_high) This approach was then used to examine the ADC and T2 distributions within each of these volumes to determine the sensitivity of T2 and ADC alone for distinguishing tumor, fluid and edema and quantifying edema volume. Results: The edema incidence was 100% based on T2w and T1w CE scans in orthotopically implanted U251-luc (Luc-mCherry) gliomas. Edema volume could be quantified using the multi-modal MRI scan protocol. Edema progression occurred with increasing tumor volume over time. Regions of edema exhibited greater T2 and ADC values compared to tumor tissue regions (that also had a greater T2 signal than normal tissue). This is consistent with edematous tissue water content, compared with tumor tissue and normal brain. The use of T2 and ADC alone provided good delineation of fluid from other tissues, and reasonable delineation of edema from tumor (based on the initial compartmentalization analysis). However, the combined T2w/ T1w-CE/ADC protocol was considered more precise. Conclusion: These results support the use of intracranial U251-luc (Luc-mCherry) as a reliable model for studying the effects of therapies targeting tumor-related cerebral edema. The application of multi-parametric MRI was an effective method for quantifying cerebral edema longitudinally in vivo. Citation Format: Deanne Lister, Deepa Balagurunathan, Meridith Baugher, Athena Flecha, Erin Trachet, Scott Wise, W.R. Leopold, Patrick McConville. Comparison of ADC MRI, T2-weighted MRI and combined T2-weighted/T1-contrast-enhanced/ADC MRI quantification of cerebral edema in an intracranial glioma model. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2066. doi:10.1158/1538-7445.AM2014-2066

Abstract 4945: Evaluating the feasibility and throughput of quintuple modality imaging in a prostate cancer bone metastasis model with PET, SPECT, CT, MRI, and bioluminescence imaging

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Background: Multimodality imaging presents a unique opportunity to image the efficacy of candidate compounds against various models of cancer. The challenge is in integrating the complimentary data that these modalities can provide. The purpose of this study was to evaluate the feasibility of quintuple modality image in order to optimize workflows for maximal efficacy testing of candidate compounds using PET, SPECT, CT, MRI, and Bioluminescence imaging (BLI). Materials and Methods: Male nude mice were injected into the left ventricle with 3x106 PC-3M-luc-C6 cells. BLI was performed to track disease progression and ensure that animals exhibited established metastatic disease prior to initiation of multimodality imaging. Animals were injected with 500µCi Tc99m-MDP and allowed a 1h uptake period prior to imaging. The animals were then placed into an Animal Handling System (AHS, ASI Instruments) that coupled to multiple integrated Positioning Receiver Assemblies (PRAs, ASI Instruments) designed for the PET, SPECT, CT, and MRI scanners, and a 15min, multi-pinhole SPECT scan was acquired. After completion of the SPECT scan, 200µCi of 18F-FDG was administered under anesthesia. MicroCT and MRI anatomical images were acquired during the FDG uptake period. Body temperature was maintained via the integrated warm water circulation in the AHS to ensure adequate FDG uptake and clearance during the procedures. Whole body CT images were acquired at 512 projections, 75kVp, and 220µA. A series of T2-weighted and T1-weighted gadolinium-enhanced images were acquired using a 7T MRI system. At 1h post-FDG administration, a 10min static PET emission scan was acquired and reconstructed using a 3DOSEM/MAP algorithm. Results: Animals were maintained under anesthesia for a total of approximately 2 hours in order to acquire data from all the modalities. Data was able to be co-registered in various forms in order to verify the location and extent of disease, as well as the usefulness of 18F-FDG PET and Tc99m-MDP to serve as biomarker probes for tumor cell metabolism, and osteolytic and osteoblastic activity in bone lesions. Conclusions: Animals tolerated the length of anesthesia well. The feasibility of this imaging was only made possible through the use of the multimodality AHS bed and docking system that permitted reproducible imaging across the different platforms. In order to further optimize workflows, multiple AHS bed systems should be employed so that data can be acquired on the various modalities in parallel, instead of sequentially, thereby greatly increasing animal throughputs. Citation Format: John L. Chunta, Deanne Lister, Chris Bull, Deepa Balagurunathan, Erin Trachet, Chris Chiodo, Scott Wise, Dick Leopold, Patrick McConville. Evaluating the feasibility and throughput of quintuple modality imaging in a prostate cancer bone metastasis model with PET, SPECT, CT, MRI, and bioluminescence imaging. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4945. doi:10.1158/1538-7445.AM2014-4945

Abstract 3929: Orthotopic human choroidal melanoma model characterization with bioluminescence and magnetic resonance imaging for therapeutic efficacy evaluation

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA BACKGROUND: Intraocular melanomas in the West represents 70% of all primary eye cancers with a mortality rate greater than 50%. Current treatment options include enucleation, plaque radiotherapy, and proton beam radiotherapy. While enucleation is a highly invasive surgical procedure that removes the eye, the side effects of the two different radiotherapies include cataracts, retinopathy, cystoid macular edema, and secondary retinal detachment. Due to the relatively protected nature of the eye within the orbit, most topical treatment applications are precluded and systemic treatments increases the chance and incidence of off-target side effects. Up and coming targeted therapies that may not be constrained by such limitations require a non-invasive, imaging-relevant model in order to evaluate their efficacy. Therefore, the aim of this study was to characterize the imaging of orthotopic luc-enabled OCM-1 human choroidal melanoma tumors using bioluminescence imaging (BLI) and magnetic resonance imaging (MRI) for future use in anti-cancer drug efficacy testing. MATERIALS & METHODS: Human choroidal melanoma cells were modified to express luciferase. 8-12 week old female NIH-Foxn1rnu rats were implanted in the suprachoroidal space with OCM-1-luc tumor spheroids on Day 0. BLI and MRI imaging was performed every 5-7 days starting at Day 7 after implantation of the OCM-1-luc spheroids until animals reached a moribund state to monitor disease progression. For BLI, animals were injected with 150mg/kg luciferin, anesthetized with isoflurane in air and imaged at 10 minutes following luciferin administration. Anatomical MRI was performed using a gradient-echo pulse sequence on a 7T MRI system. After euthanasia, eyes were removed and preserved in formalin for histological analysis. RESULTS & CONCLUSIONS: Animals tolerated the ocular tumor implant well. As a result of these efforts, we have successfully characterized the growth of orthotopic luc-enabled OCM-1 choroidal melanomas using both bioluminescence and magnetic resonance imaging. This provides a simple approach with which to monitor tumor growth and treatment response in a highly efficient way which should allow a high daily animal throughput. These promising results will serve as a solid foundation with which dose routes and levels of anti-cancer drugs can be optimized and their efficacy evaluated with noninvasive imaging. Citation Format: John L. Chunta, Meridith Baugher, Deanne Lister, Erin Trachet, Kevin P. Guley, Chris Bull, Scott Wise, Wilbur R. Leopold, Patrick McConville. Orthotopic human choroidal melanoma model characterization with bioluminescence and magnetic resonance imaging for therapeutic efficacy evaluation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3929. doi:10.1158/1538-7445.AM2014-3929

Abstract B152: MR-based assessment and quantification of cerebral edema in an orthotopic mouse glioma model.

Introduction: Brain edema is a prominent feature of brain cancer and contributes to neurologic dysfunction and impaired quality of life. While corticosteroids are the standard of care, improved treatments that are more efficacious and reduce side effects are sought after. In discovery of novel therapies for edema, animal brain tumor models that show relevant, reproducible and high incidence of tumor and cerebral edema are needed. Additionally, quantitative, non-invasive methods for detecting and measuring brain tumor associated edema are needed to facilitate therapeutic discovery efforts. In this work, an intracranial U251-luc human glioma model was characterized for edema incidence and progression. MRI-based relaxivity and contrast-enhancement protocols for edema detection and delineation from tumor tissue, were tested and characterized in the model. Methods: Female nude mice were implanted intracranially with 1×10∧6 U251-luc (Luc-mCherry) glioma cells. Tumor volume assessment was performed by manual segmentation of T1-weighted, gadolinium-enhanced anatomical brain images based on the assumption of tumor enhancement due to leaky vessels or compromised blood-brain barrier. Edema assessment was performed by manual segmentation of T2-weighted anatomical brain images based on the assumption that enhancing regions include tumor tissue in addition to regions of brain edema. The difference in T2-weighted and T1-weighted volumes was assumed to be edema. T2 maps were also generated over the whole brain to measure T2 values over the respective regions of interest, and confirm the differentiation between tumor tissue and edema. Results: Edema volume was successfully distinguished from contrast enhancing tumor tissue and quantified in orthotopically implanted U251-luc (Luc-mCherry) glioma. Incidence was 100%. Edema progression occurred with increasing tumor volume over time. Regions of edema exhibited greater T2 values compared to tumor tissue regions (that also had greater T2 than normal tissue). This is consistent with edematous tissue water content, compared with tumor tissue and normal brain. These results support the use of intracranial U251-luc (Luc-mCherry) as a reliable model for studying the effects of therapies targeting tumor-related cerebral edema, and the application of MR imaging for quantifying those effects real-time in vivo. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B152. Citation Format: Deanne R. Lister, Deepa Balagurunathan, Meridith Baugher, Erin Trachet, Patrick McConville, Scott Wise, W.R. Leopold. MR-based assessment and quantification of cerebral edema in an orthotopic mouse glioma model. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B152.