Prostate Specific Membrane Antigen Expression in a Syngeneic Breast Cancer Mouse Model

PURPOSE

Prostate specific membrane antigen (PSMA) has been studied in human breast cancer (BCa) biopsies, however, lack of data on PSMA expression in mouse models impedes development of PSMA-targeted therapies, particularly in improving breast conserving surgery (BCS) margins. This study aimed to validate and characterize the expression of PSMA in murine BCa models, demonstrating that PSMA can be utilized to improve therapies and imaging techniques.

METHODS

Murine triple negative breast cancer 4T1 cells, and human cell lines, MDA-MB-231, MDA-MB-468, implanted into the mammary fat pads of BALB/c mice, were imaged by our PSMA targeted theranostic agent, PSMA-1-Pc413, and tumor to background ratios (TBR) were calculated to validate selective uptake. Immunohistochemistry was used to correlate PSMA expression in relation to CD31, an endothelial cell biomarker highlighting neovasculature. PSMA expression was also quantified by Reverse Transcriptase Polymerase Chain Reaction (RT-PCR).

RESULTS

Accumulation of PSMA-1-Pc413 was observed in 4T1 primary tumors and associated metastases. Average TBR of 4T1 tumors were calculated to be greater than 1.5-ratio at which tumor tissues can be distinguished from normal structures-at peak accumulation with the signal intensity in 4T1 tumors comparable to that in high PSMA expressing PC3-pip tumors. Extraction of 4T1 tumors and lung metastases followed by RT-PCR analysis and PSMA-CD31 co-staining shows that PSMA is consistently localized on tumor neovasculature with no expression in tumor cells and surrounding normal tissues.

CONCLUSION

The selective uptake of PSMA-1-Pc413 in these cancer tissues as well as the characterization and validation of PSMA expression on neovasculature in this syngeneic 4T1 model emphasizes their potential for advancements in targeted therapies and imaging techniques for BCa. PSMA holds great promise as an oncogenic target for BCa and its associated metastases.

Multispecies comparative prostate anatomy by imaging: Implications for experimental models of prostatic disease

BACKGROUND

There is an increasing interest in using preclinical models for development and assessment of medical devices and imaging techniques for prostatic disease care. Still, a comprehensive assessment of the prostate's radiological anatomy in primary preclinical models such as dogs, rabbits, and mice utilizing human anatomy as a reference point remains necessary with no optimal model for each purpose being clearly defined in the literature. Therefore, this study compares the anatomical characteristics of different animal models to the human prostatic gland from the imaging perspective.

METHODS

We imaged five Beagle laboratory dogs, five New Zealand White rabbits, and five mice, all sexually mature males, under Institutional Animal Care and Use Committee (IACUC) approval. Ultrasonography (US) was performed using the Vevo® F2 for mice (57 MHz probe). Rabbits and dogs were imaged using the Siemens® Acuson S3000 (17 MHz probe) and endocavitary (8 MHz) probes, respectively. Magnetic resonance imaging (MRI) was also conducted with a 7T scanner in mice and 3T scanner in rabbits and dogs.

RESULTS

Canine transrectal US emerged as the optimal method for US imaging, depicting a morphologically similar gland to humans but lacking echoic zonal differentiation. MRI findings in canines indicated a homogeneously structured gland similar to the human peripheral zone on T2-weighted images (T2W) and apparent diffusion coefficient (ADC). In rabbits, US imaging faced challenges due to the pubic symphysis, whereas MRI effectively visualized all structures with the prostate presenting a similar aspect to the human peripheral gland on T2W and ADC maps. Murine prostate assessment revealed poor visualization of the prostate glands in ultrasound due to its small size, while 7T MRI delineated the distinct prostates and its lobes, with the lateral and dorsal prostate resembling the peripheral zone and the anterior prostate the central zone of the human gland.

CONCLUSION

Dogs stand out as superior models for advanced preclinical studies in prostatic disease research. However, mice present as a good model for early stage studies and rabbits are a cost-effective alternative and serve as valuable tools in specific research domains when canine research is not feasible.

Ultrasound-mediated drug-free theranostics for treatment of prostate cancer

Rationale

Lipid-shelled nanobubbles (NBs) can be visualized and activated using noninvasive ultrasound (US) stimulation, leading to significant bioeffects. We have previously shown that active targeting of NBs to prostate-specific membrane antigen (PSMA) overexpressed in prostate cancer (PCa) enhances the cellular internalization and prolongs retention of NBs with persistent acoustic activity (~hrs.). In this work, we hypothesized that tumor-accumulated PSMA-NBs combined with low frequency therapeutic US (TUS) will lead to selective damage and induce a therapeutic effect in PSMA-expressing tumors compared to PSMA-negative tumors.

Methods

PSMA-targeted NBs were formulated by following our previously established protocol. Cellular internalization of fluorescent PSMA-NBs was evaluated by confocal imaging using late endosome/lysosome staining pre- and post-TUS application. Two animal models were used to assess the technique. Mice with dual tumors (PSMA expressing and PSMA negative) received PSMA-NB injection via the tail vein followed by TUS 1 hr. post injection (termed, targeted NB therapy or TNT). Twenty-four hours after treatment mice were euthanized and tumor cell apoptosis evaluated via TUNEL staining. Mice with single tumors (either PSMA + or -) were used for survival studies. Tumor size was measured for 80 days after four consecutive TNT treatments (every 3 days). To test the approach in a larger model, immunosuppressed rabbits with orthotopic human PSMA expressing tumors received PSMA-NB injection via the tail vein followed by TUS 30 min after injection. Tumor progression was assessed via US imaging and at the end point apoptosis was measured via TUNEL staining.

Results

In vitro TNT studies using confocal microscopy showed that the internalized NBs and cellular compartments were disrupted after the TUS application, yet treated cells remained intact and viable. In vivo, PSMA-expressing tumors in mice receiving TNT treatment demonstrated a significantly greater extent of apoptosis (78.45 ± 9.3%, p < 0.01) compared to the other groups. TNT treatment significantly inhibited the PSMA (+) tumor growth and overall survival significantly improved (median survival time increase by 103%, p < 0.001). A significant reduction in tumor progression compared to untreated control was also seen in the rabbit model in intraprostatic (90%) and in extraprostatic lesions (94%) (p = 0.069 and 0.003, respectively).

Conclusion

We demonstrate for the first time the effect of PSMA-targeted nanobubble intracellular cavitation on cancer cell viability and tumor progression in two animal models. Data demonstrate that the targeted nanobubble therapy (TNT) approach relies primarily on mechanical disruption of intracellular vesicles and the resulting bioeffects appear to be more specific to target cancer cells expressing the PSMA receptor. The effect, while not lethal in vitro, resulted in significant tumor apoptosis in vivo in both a mouse and a rabbit model of PCa. While the mechanism of action of these effects is yet unclear, it is likely related to a locally-induced immune response, opening the door to future investigations in this area.

Evaluation of a photodynamic therapy agent using a canine prostate cancer model

BACKGROUND

Male dogs can develop spontaneous prostate cancer, which is similar physiologically to human disease. Recently, Tweedle and coworkers have developed an orthotopic canine prostate model allowing implanted tumors and therapeutic agents to be tested in a more translational large animal model. We used the canine model to evaluate prostate-specific membrane antigen (PSMA)-targeted gold nanoparticles as a theranostic approach for fluorescence (FL) imaging and photodynamic therapy (PDT) of early stage prostate cancer.

METHODS

Dogs (four in total) were immunosuppressed with a cyclosporine-based immunosuppressant regimen and their prostate glands were injected with Ace-1-hPSMA cells using transabdominal ultrasound (US) guidance. Intraprostatic tumors grew in 4-5 weeks and were monitored by ultrasound (US). When tumors reached an appropriate size, dogs were injected intravenously (iv) with PSMA-targeted nano agents (AuNPs-Pc158) and underwent surgery 24 h later to expose the prostate tumors for FL imaging and PDT. Ex vivo FL imaging and histopathological studies were performed to confirm PDT efficacy.

RESULTS

All dogs had tumor growth in the prostate gland as revealed by US. Twenty-four hours after injection of PSMA-targeted nano agents (AuNPs-Pc158), the tumors were imaged using a Curadel FL imaging device. While normal prostate tissue had minimal fluorescent signal, the prostate tumors had significantly increased FL. PDT was activated by irradiating specific fluorescent tumor areas with laser light (672 nm). PDT bleached the FL signal, while fluorescent signals from the other unexposed tumor tissues were unaffected. Histological analysis of tumors and adjacent prostate revealed that PDT damaged the irradiated areas to a depth of 1-2 mms with the presence of necrosis, hemorrhage, secondary inflammation, and occasional focal thrombosis. The nonirradiated areas showed no visible damages by PDT.

CONCLUSION

We have successfully established a PSMA-expressing canine orthotopic prostate tumor model and used the model to evaluate the PSMA-targeted nano agents (AuNPs-Pc158) in the application of FL imaging and PDT. It was demonstrated that the nano agents allowed visualization of the cancer cells and enabled their destruction when they were irradiated with a specific wavelength of light.

Formulation of a Thermosensitive Imaging Hydrogel for Topical Application and Rapid Visualization of Tumor Margins in the Surgical Cavity

Simple Summary

We have developed a formulation for an innovative, quenched, cathepsin-targeted, fluorescent molecular probe to enhance resection quality for several solid-tumor cancers. Unlike other formulations for imaging probes or tracers in development and entering the clinic, which require systemic administration hours before the procedure, this current formulation is applied topically into the surgical cavity immediately after a standard of care resection. Within minutes of application, the probe activates in the presence of residual cancer in the surgical wound and provides a strong fluorescent signal that precisely delineates any remaining cancer, enabling a more complete resection. Utilization of this imaging gel formulation for topical application to detect breast cancer in the surgical cavity during surgery has the potential to reduce re-excisions, with consequent savings in healthcare costs and enhancement in patient quality of life.

Abstract

Background: Tumor-positive surgical margins during primary breast cancer (BCa) surgery are associated with a two-fold increase in the risk of local recurrence when compared with tumor-negative margins. Pathological microscopic evaluation of the samples only assesses about 1/10 of 1% of the entire volume of the removed BCa specimens, leading to margin under-sampling and potential local recurrence in patients with pathologically clean margins, i.e., false negative margins. In the case of tumor-positive margins, patients need to undergo re-excision and/or radiation therapy, resulting in increases in complications, morbidity, and healthcare costs. Development of a simple real-time imaging technique to identify residual BCa in the surgical cavity rapidly and precisely could significantly improve the quality of care. Methods: A small-molecule, fluorescently quenched protease-substrate probe, AKRO-QC-ICG, was tested as part of a thermosensitive imaging gel formulated for topical application and imaging of the BCa surgical cavity. Results: More than forty formulations of gel mixtures were investigated to enable easy fluid application and subsequent solidification once applied, preventing dripping and pooling in the surgical cavity. The final formulation was tested using human BCa orthotopic implants in nude and NSG patient-derived xenografts (PDX) mice. This formulation of Pluronic F-127/DMSO/AKRO-QC-ICG imaging gel was found to be a good solvent for the probe, with a desirable thermo-reversible solid–gel transition and mechanical strength for distribution of AKRO-QC-ICG on the surfaces of tissue. It demonstrated excellent ability to detect BCa tissue after 10 min exposure, with a high signal-to-noise ratio both in mouse xenografts and freshly excised human lumpectomy tissue. The in vivo efficacy of the AKRO-QC-ICG imaging gel to detect BCa revealed the levels of sensitivity/specificity = 0.92/1 in 12 nude mice, which was corroborated with the sensitivity/specificity = 0.94/1 in 10 PDX mice. Conclusions: Utilization of Pluronic F-127/DMSO/AKRO-QC-ICG imaging gel for topical application to detect BCa in the surgical cavity during surgery has the potential to reduce re-excisions, with consequent savings in healthcare costs and enhancement in patient quality of life.

Development of a novel castration-resistant orthotopic prostate cancer model in New Zealand White rabbit

BACKGROUND

Prostate cancer (PCa) models in mice and rats are limited by their size and lack of a clearly delineated or easily accessible prostate gland. The canine PCa model is currently the only large animal model which can be used to test new preclinical interventions but is costly and availability is sparse. As an alternative, we developed an orthotopic human prostate tumor model in an immunosuppressed New Zealand White rabbit. Rabbits are phylogenetically closer to humans, their prostate gland is anatomically similar, and its size allows for clinically-relevant testing of interventions.

METHODS

Rabbits were immunosuppressed via injection of cyclosporine. Human PC3pipGFP PCa cells were injected into the prostate via either (a) laparotomy or (b) transabdominal ultrasound (US) guided injection. Tumor growth was monitored using US and magnetic resonance imaging (MRI). Contrast-enhanced ultrasound (CEUS) imaging using nanobubbles and Lumason microbubbles was also performed to examine imaging features and determine the optimal contrast dose required for enhanced visualization of the tumor. Ex vivo fluorescence imaging, histopathology, and immunohistochemistry analyses of the collected tissues were performed to validate tumor morphology and prostate-specific membrane antigen (PSMA) expression.

RESULTS

Immunosuppression and tumor growth were, in general, well-tolerated by the rabbits. Fourteen out of 20 rabbits, with an average age of 8 months, successfully grew detectable tumors from Day 14 onwards after cell injection. The tumor growth rate was 39 ± 25 mm² per week. CEUS and MRI of tumors appear hypoechoic and T2 hypointense, respectively, relative to normal prostate tissue. Minimally invasive US-guided tumor cell injection proved to be a better method compared to laparotomy due to the shorter recovery time required for the rabbits following injection. Among the rabbits that grew tumors, seven had tumors both inside and outside the prostate, three had tumors only inside the prostate, and four had tumors exclusively outside of the prostate. All tumors expressed the PSMA receptor.

CONCLUSIONS

We have established, for the first time, an orthotopic PCa rabbit model via percutaneous US-guided tumor cell inoculation. This animal model is an attractive, clinically relevant intermediate step to assess preclinical diagnostic and therapeutic compounds.

Targeted Chemoradiotherapy of Prostate Cancer Using Gold Nanoclusters with Protease Activatable Monomethyl Auristatin E

Combined radiotherapy (RT) and chemotherapy are prescribed to patients with advanced prostate cancer (PCa) to increase their survival; however, radiation-related side effects and systematic toxicity caused by chemotherapeutic drugs are unavoidable. To improve the precision and efficacy of concurrent RT and chemotherapy, we have developed a PCa-targeted gold nanocluster radiosensitizer conjugated with a highly potent cytotoxin, monomethyl auristatin E, PSMA-AuNC-MMAE, for RT and chemotherapy of PCa. This approach resulted in enhanced uptake of NCs by PSMA-positive cancer cells, targeted chemotherapy, and increased efficacy of RT both in vitro and in vivo. In addition, the combination of gold and MMAE further increased the efficacy of either of the agents delivered alone or simultaneously but not covalently linked. The PSMA-AuNC-MMAE conjugates improve the specificity and efficacy of radiation and chemotherapy, potentially reducing the toxicity of each therapy and making this an attractive avenue for clinical treatment of advanced PCa.

Intracellular vesicle entrapment of nanobubble ultrasound contrast agents targeted to PSMA promotes prolonged enhancement and stability in vivo and in vitro

Gas-core nanoscale bubbles (or nanobubbles) have gained significant recent attention as promising contrast agents for cancer molecular imaging using medical ultrasound. Previous work has shown that active targeting of nanobubbles to tumor biomarkers such as the prostate-specific membrane antigen (PSMA) significantly prolongs ultrasound signal enhancement, which is a critical feature for successful tumor diagnosis. However, the specific mechanism behind this effect is not well understood, and has not been previously studied in detail. Thus, in the current work, we investigated the process of PMSA- targeted nanobubble transport in tumors across different scales from in vivo whole tumor imaging using high-frequency dynamic contrast-enhanced ultrasound to intracellular confocal imaging and, molecularly using headspace gas chromatography/mass spectrometry. Data demonstrated that, indeed, molecular targeting of nanobubbles to the PSMA biomarker prolongs their tumor uptake and retention across the entire tumor volume, but with variability due to the expected tumor heterogeneity. Importantly, in vitro, the active targeting of NBs results in internalization via receptor-mediated endocytosis into the target cells, and the co-localization with intracellular vesicles (late-stage endosomes/lysosomes) significantly prolongs perfluorocarbon gas retention within the cells. This has not been directly observed previously. These results support the potential for nanobubbles to enable highly specific, background-free diagnostic imaging of the target cells/tissues using ultrasound.

A low molecular weight multifunctional theranostic molecule for the treatment of prostate cancer

Rationale: Although surgery and radiation therapy in patients with low risk prostate cancer appear appropriate and effective, those with high-risk localized disease almost always become hormone refractory and then rapidly progress. A new treatment strategy is urgently needed for patients with high-risk localized prostate cancer, particularly an approach that combines two drugs with different mechanisms. Combinations of photodynamic therapy (PDT) and chemotherapy have shown synergistic effects in clinical trials, but are limited by off-target toxicity. Prostate specific membrane antigen (PSMA) is a well-established biomarker for prostate cancer. Here we describe the use of a PSMA ligand to selectively and simultaneously deliver a potent microtubule inhibiting agent, monomethyl auristatin E (MMAE), and a PDT agent, IR700, to prostate cancers.

Methods: Using a bifunctional PSMA ligand PSMA-1-Cys-C6-Lys, we created a novel theranostic molecule PSMA-1-MMAE-IR700. The molecule was tested in vitro and in vivo for selectivity and antitumor activity studies.

Results: PSMA-1-MMAE-IR700 showed selective and specific uptake in PSMA-positive PC3pip cells, but not in PSMA-negative PC3flu cells both in vitro and in vivo. In in vitro cytotoxicity studies, when exposed to 690 nm light, PSMA-1-MMAE-IR700 demonstrated a synergistic effect leading to greater cytotoxicity for PC3pip cells when compared to PSMA-1-IR700 with light irradiation or PSMA-1-MMAE-IR700 without light irradiation. In vivo antitumor activity studies further showed that PSMA-1-MMAE-IR700 with light irradiation significantly inhibited PC3pip tumor growth and prolonged survival time as compared to mice receiving an equimolar amount of PSMA-1-IR700 with light irradiation or PSMA-1-IR700-MMAE without light irradiation.

Conclusion: We have synthesized a new multifunctional theranostic molecule that combines imaging, chemotherapy, and PDT for therapy against PSMA-expressing cancer tissues. This work may provide a new treatment option for advanced prostate cancer.

Magnetic Resonance Imaging of PSMA-Positive Prostate Cancer by a Targeted and Activatable Gd(III) MR Contrast Agent

Prostate-specific membrane antigen (PSMA) is a transmembrane protein that is highly expressed in aggressive prostate cancer (PCa) and has been extensively studied as a PCa diagnostic imaging biomarker. Multiple imaging modalities have exploited PSMA as a biomarker including magnetic resonance (MR), Optical, and PET imaging. Of all the imaging MR imaging provides the most detailed information, concurrently providing anatomical, functional, and potentially molecular information. However, the lower sensitivity of MR requires development of molecular MR contrast agents that provides high signal-to-noise ratios. Herein, we report the first targeted and activatable Gd(III)-based MR contrast agents prostate cancer probe 1 and 2 (PCP-1 and -2). We successfully used PCP-2 to differentiate between PSMA+ and PSMA- prostate cancer cells with both in vitro fluorescence imaging and in vivo MR imaging. The in vivo MR imaging results were further supported by ex vivo fluorescence imaging studies, showcasing the unique bimodal feature of PCP-2. Furthermore, PCP-2 highlights a unique molecular MR probe design strategy that improved the sensitivity of traditional biomarker-targeted MR imaging, addressing a critical unmet need in molecular MR imaging field. This work represents the first example of a targeted and activatable MR contrast agent that can be systemically administered in vivo to highlight PSMA+ prostate tumors, paving the way for the clinical translation of MR PSMA imaging.

Photodynamic Therapy: Targeting Cancer Biomarkers for the Treatment of Cancers

Simple Summary

Photodynamic therapy (PDT) is a minimally invasive treatment option that can kill cancerous cells by subjecting them to light irradiation at a specific wavelength. The main problem related to most photosensitizers is the lack of tumor selectivity, which leads to undesired uptake in normal tissues resulting in side effects. Passive targeting and active targeting are the two strategies to improve uptake in tumor tissues. This review focused on active targeting and summarizes recent active targeting approaches in which highly potent photosensitizers are rendered tumor-specific by means of an appended targeting moiety that interacts with a protein unique to, or at least significantly more abundant on, tumor cell surfaces compared to normal cells.

Abstract

Photodynamic therapy (PDT) is a well-documented therapy that has emerged as an effective treatment modality of cancers. PDT utilizes harmless light to activate non- or minimally toxic photosensitizers to generate cytotoxic species for malignant cell eradication. Compared with conventional chemotherapy and radiotherapy, PDT is appealing by virtue of the minimal invasiveness, its safety, as well as its selectivity, and the fact that it can induce an immune response. Although local illumination of the cancer lesions renders intrinsic selectivity of PDT, most photosensitizers used in PDT do not display significant tumor tissue selectivity. There is a need for targeted delivery of photosensitizers. The molecular identification of cancer antigens has opened new possibilities for the development of effective targeted therapy for cancer patients. This review provides a brief overview of recent achievements of targeted delivery of photosensitizers to cancer cells by targeting well-established cancer biomarkers. Overall, targeted PDT offers enhanced intracellular accumulation of the photosensitizer, leading to improved PDT efficacy and reduced toxicity to normal tissues.

Recent Development of Gold Nanoparticles as Contrast Agents for Cancer Diagnosis

Simple Summary

The development of nanotechnology has brought revolution to the diagnosis and therapy of diseases, with a high precision and efficacy. Because nanoparticles can integrate multifunctions together including imaging, targeting, and therapeutics, they are more efficient than the standalone diagnostic or therapeutic entities. Among which, gold nanoparticles are most extensively investigated due to their excellent biocompatibility, versatility and ease of functionalization. Excepting the using of gold nanoparticles as vehicles for therapeutics delivery, they are also good candidates as contrast agents for imaging diagnosis, from magnetic resonance imaging, CT and nuclear imaging, fluorescence imaging, photoacoustic imaging to X-ray fluorescence imaging. We summarize their recent applications in these imaging modalities and challenges for their clinical translation.

Abstract

The last decade has witnessed the booming of preclinical studies of gold nanoparticles (AuNPs) in biomedical applications, from therapeutics delivery, imaging diagnostics, to cancer therapies. The synthetic versatility, unique optical and electronic properties, and ease of functionalization make AuNPs an excellent platform for cancer theranostics. This review summarizes the development of AuNPs as contrast agents to image cancers. First, we briefly describe the AuNP synthesis, their physical characteristics, surface functionalization and related biomedical uses. Then we focus on the performances of AuNPs as contrast agents to diagnose cancers, from magnetic resonance imaging, CT and nuclear imaging, fluorescence imaging, photoacoustic imaging to X-ray fluorescence imaging. We compare these imaging modalities and highlight the roles of AuNPs as contrast agents in cancer diagnosis accordingly, and address the challenges for their clinical translation.

Molecular imaging of orthotopic prostate cancer with nanobubble ultrasound contrast agents targeted to PSMA

Ultrasound imaging is routinely used to guide prostate biopsies, yet delineation of tumors within the prostate gland is extremely challenging, even with microbubble (MB) contrast. A more effective ultrasound protocol is needed that can effectively localize malignancies for targeted biopsy or aid in patient selection and treatment planning for organ-sparing focal therapy. This study focused on evaluating the application of a novel nanobubble ultrasound contrast agent targeted to the prostate specific membrane antigen (PSMA-targeted NBs) in ultrasound imaging of prostate cancer (PCa) in vivo using a clinically relevant orthotopic tumor model in nude mice. Our results demonstrated that PSMA-targeted NBs had increased extravasation and retention in PSMA-expressing orthotopic mouse tumors. These processes are reflected in significantly different time intensity curve (TIC) and several kinetic parameters for targeted versus non-targeted NBs or LUMASON MBs. These, may in turn, lead to improved image-based detection and diagnosis of PCa in the future.

Development of near-infrared imaging agents for detection of junction adhesion molecule-A protein

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Anti-junctional adhesion molecule-A (JAM-A) monoclonal antibodies (mAb) conjugated with near infra-red fluorescent dye, IR700 – as a JAM-A mAb/IR700 agent was developed.

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An in vivo JAM-A mAb/IR700-specific near infra-red imaging of human-derived prostate and breast cancer xenograft is presented.

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A single injection of the agent is diminished number of mitotic cells in cancerous tissue of mice bearing heterotopic tumors.

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Since, our agent depicts the specific accumulation within the targeted tumors, this agent may be adapted to solid tumor targeted photoimmunotherapy.

Introduction

Prostate and breast cancer are the most prevalent primary malignant human tumors globally. Prostatectomy and breast conservative surgery remain the most common definitive treatment option for the >500,000 men and women newly diagnosed with localized prostate and breast cancer each year only in the US. Morphological examination is the mainstay of diagnosis but margin under-sampling of the excised cancer tissue may lead to local recurrence. In despite of the progress of non-invasive optical imaging, there is still a clinical need for targeted optical imaging probes that could rapidly and globally visualize cancerous tissues.

Methods

Elevated expression of junctional adhesion molecule-A (JAM-A) on tumor cells and its multiple pro-tumorigenic activity make the JAM-A a candidate for molecular imaging. Near-infrared imaging probe, which employed anti-JAM-A monoclonal antibody (mAb) phthalocyanine dye IR700 conjugates (JAM-A mAb/IR700), was synthesized and used to identify and visualize heterotopic human prostate and breast tumor mouse xenografts in vivo.

Results

The intravenously injected JAM-A mAb/IR700 conjugates enabled the non-invasive detection of prostate and breast cancerous tissue by fluorescence imaging. A single dose of JAM-A mAb/IR700 reduced number of mitotic cancer cells in vivo, indicating theranostic ability of this imaging agent. The JAM-A mAb/IR700 conjugates allowed us to image a specific receptor expression in prostate and breast tumors without post-image processing.

Conclusion

This agent demonstrates promise as a method to image the extent of prostate and breast cancer in vivo and could assist with real-time visualization of extracapsular extension of cancerous tissue.

Nanoparticles Yield Increased Drug Uptake and Therapeutic Efficacy upon Sequential Near-Infrared Irradiation

Nanoparticles offer great opportunities for precision medicine. However, the use of nanoparticles as smart photosensitizers that target tumor biomarkers and are responsive to the tumor microenvironment has yet to be explored. Herein, prostate cancer (PCa)-selective theranostic gold nanoparticles (AuNPs) for precise cancer imaging and therapy are developed. Silicon phthalocyanine, Pc158, was synthesized and deactivated by conjugating it to AuNPs via a biocleavable linker. In vitro and in vivo, the targeted AuNPs show excellent selectivity for PSMA-positive tumor cells. Triggered release of the therapeutic, Pc158, followed by sequential photodynamic therapy (PDT) results in significant inhibition of tumor growth. Further, we demonstrate that multiple sequential PDT greatly enhances nanoparticle uptake and therapeutic efficacy. PSMA is highly expressed in the neovasculature of most other solid tumors in humans, as well as PCa, making this approach of great practical interest for precision PDT in a wide range of cancers.

Targeted Radiosensitizers for MR-Guided Radiation Therapy of Prostate Cancer

Adjuvant radiotherapy is frequently prescribed to treat cancer. To minimize radiation-related damage to healthy tissue, it requires high precision in tumor localization and radiation dose delivery. This can be achieved by MR guidance and targeted amplification of radiation dose selectively to tumors by using radiosensitizers. Here, we demonstrate prostate cancer-targeted gold nanoparticles (AuNPs) for MR-guided radiotherapy to improve the targeting precision and efficacy. By conjugating Gd(III) complexes and prostate-specific membrane antigen (PSMA) targeting ligands to AuNP surfaces, we found enhanced uptake of AuNPs by PSMA-expressing cancer cells with excellent MR contrast and radiation therapy outcome in vitro and in vivo. The AuNPs binding affinity and r₁ relaxivity were dramatically improved and the combination of Au and Gd(III)provided better tumor suppression after radiation. The precise tumor localization by MR and selective tumor targeting of the PSMA-1-targeted AuNPs could enable precise radiotherapy, reduction in irradiating dose, and minimization of healthy tissue damage.

Real time ultrasound molecular imaging of prostate cancer with PSMA-targeted nanobubbles

Contrast-enhanced ultrasound with microbubbles has shown promise in detection of prostate cancer (PCa), but sensitivity and specificity remain challenging. Targeted nanoscale-contrast agents with improved capability to accumulate in tumors may result in prolonged signal enhancement and improved detection of PCa with ultrasound. Here we report nanobubbles (NB) that specifically targets prostate specific membrane antigen (PSMA) overexpressed in PCa. The PSMA-targeted-NB (PSMA-NB) were utilized to simultaneously image dual-flank PCa (PSMA-positive PC3pip and PSMA-negative PC3flu) to examine whether the biomarker can be successfully detected and imaged in a mouse model. Results demonstrate that active targeting rapidly and selectively enhances tumor accumulation and tumor retention. Importantly, these processes could be visualized and quantified, in real-time, with clinical ultrasound. Such demonstration of the immense yet underutilized potential of ultrasound in the molecular imaging area can open the door to future opportunities for improving sensitivity and specificity of cancer detection using parametric NB-enhanced ultrasound imaging.

A Protease-Activated Fluorescent Probe Allows Rapid Visualization of Keratinocyte Carcinoma during Excision

Keratinocyte carcinomas, including basal and squamous cell carcinomas, are the most common human cancers worldwide. While 75% of all keratinocyte carcinoma (4 million annual cases in the United States) are treated with conventional excision, this surgical modality has much lower cure rates than Mohs micrographic surgery, likely due to the bread-loaf histopathologic assessment that visualizes <1% of the tissue margins. A quenched protease-activated fluorescent probe 6qcNIR, which produces a signal only in the protease-rich tumor microenvironment, was topically applied to 90 specimens ex vivo immediately following excision. "Puzzle-fit" analysis was used to correlate the fluorescent images with histology. Probe-dependent fluorescent images correlated with cancer determined by conventional histology. Point-of-care fluorescent detection of skin cancer had a clinically relevant sensitivity of 0.73 and corresponding specificity of 0.88. Importantly, clinicians were effectively trained to read fluorescent images within 15 minutes with reliability and confidence, resulting in sensitivities of 62%-78% and specificities of 92%-97%. Fluorescent imaging using 6qcNIR allows 100% tumor margin assessment by generating en face images that correlate with histology and may be used to overcome the limitations of conventional bread-loaf histology. The utility of 6qcNIR was validated in a busy real-world clinical setting, and clinicians were trained to effectively read fluorescent margins with a short guided instruction, highlighting clinical adaptability. When used in conventional excision, this approach may result in higher cure rates at a lower cost by allowing same-day reexcision when needed, reducing patient anxiety and improving compliance by expediting postsurgical specimen assessment. SIGNIFICANCE: A fluorescent-probe-tumor-visualization platform was developed and validated in human keratinocyte carcinoma excision specimens that may provide simple, rapid, and global assessment of margins during skin cancer excision, allowing same-day reexcision when needed.

Photodynamic Therapy Is an Effective Adjuvant Therapy for Image-Guided Surgery in Prostate Cancer

Local and metastatic relapses of prostate cancer often occur following attempted curative resection of the primary tumor, and up to 66% of local recurrences are associated with positive margins. Therefore, technologies that can improve the visualization of tumor margins and adjuvant therapies to ablate remaining tumor tissues are needed during surgical resection of prostate adenocarcinoma. Photodynamic agents have the potential to combine both fluorescence for image-guided surgery (IGS) and photodynamic therapy (PDT) to resect and ablate cancer cells. The objective of this study was to determine the utility of a targeted PDT agent for IGS and adjuvant PDT. Using a previously developed prostate-specific membrane antigen (PSMA)-targeted PDT agent, PSMA-1-Pc413, we showed that PSMA-1-Pc413 selectively highlighted PSMA-expressing tumors, allowing IGS and more complete tumor resection compared with white light surgery. Subsequent PDT further reduced tumor recurrence and extended animal survival significantly. This approach also enabled identification of tumor cells in lymph nodes. In summary, this study presents a potential new treatment option for patients with prostate cancer undergoing surgery, which improves tumor visualization and discrimination during surgery, including identification of cancer in lymph nodes. SIGNIFICANCE: These findings present a photodynamic agent that can be used for both photodynamic therapy and image-guided surgery, allowing better visualization of tumor margins and elimination of residual tumor tissues.

Targeted Gold Nanocluster-Enhanced Radiotherapy of Prostate Cancer

For over a hundred years, X-rays have been a main component of the radiotherapeutic approaches to treat cancer. Yet, to date, no radiosensitizer has been developed to selectively target prostate cancer. Gold has excellent X-ray absorptivity and is used as a radiotherapy enhancing material. In this work, ultrasmall Au₂₅ nanoclusters (NCs) are developed for selective prostate cancer targeting, radiotherapy enhancement, and rapid clearance from the body. Targeted-Au₂₅ NCs are rapidly and selectively taken up by prostate cancer in vitro and in vivo and also have fast renal clearance. When combined with X-ray irradiation of the targeted cancer tissues, radiotherapy is significantly enhanced. The selective targeting and rapid clearance of the nanoclusters may allow reductions in radiation dose, decreasing exposure to healthy tissue and making them highly attractive for clinical translation.

Prostate-specific membrane antigen targeted gold nanoparticles for prostate cancer radiotherapy: does size matter for targeted particles?

Prostate-Specific Membrane Antigen (PSMA) targeted radiosensitizers are developed for prostate cancer CT imaging and radiotherapy based on gold nanoparticles and a high-affinity targeting peptide, PSMA-1, revealing a size-dependent pattern.

Since the introduction of PSA testing, significantly more men have been diagnosed and treated for prostate cancer. Localized prostate cancer typically is treated with prostatectomy, however there is still a high risk of recurrence after surgery, and adjuvant radiation has been shown to mitigate disease progression. X-ray therapy is frequently used as an adjuvant to treat prostate cancer, but is an imperfect tool. In this report we describe the development of a targeted-radiosensitizing nanoparticle that significantly improves X-ray therapy. Taking advantage of the demonstrated radiosensitizing activity of gold nanoparticles (AuNPs) we developed targeted AuNPs and varied both surface ligand density and AuNP size to develop an optimized AuNP for X-ray radiotherapy. We conjugated a prostate-specific membrane antigen (PSMA) targeting ligand, PSMA-1, to AuNPs and found that the targeting ligand dramatically improved gold uptake by PSMA-expressing PC3pip cells compared with PC3flu cells lacking the PSMA receptors. Further, enhancement of radiotherapy was significantly more pronounced by internalization of smaller PSMA targeted-AuNPs. Our studies provide a foundation for design of size-selected AuNPs for targeted radiotherapy and, for the first time, systematically investigate both the effect of ligand and AuNP size on the cell uptake, tumor targeting and radiotherapy efficacy.

Molecular imaging and validation of margins in surgically excised nonmelanoma skin cancer specimens

In an effort to increase the efficiency and cure rate of nonmelanoma skin cancer (NMSC) excisions, we have developed a point-of-care method of imaging and evaluation of skin cancer margins. We evaluate the skin surgical specimens using a smart, near-infrared probe (6qcNIR) that fluoresces in the presence of cathepsin proteases overexpressed in NMSC. Imaging is done with an inverted, flying-spot fluorescence scanner that reduces scatter, giving a 70% improved step response as compared to a conventional imaging system. We develop a scheme for careful comparison of fluorescent signals to histological annotation, which involves image segmentation, fiducial-based registration, and nonrigid free-form deformation on fluorescence images, corresponding color images, "bread-loafed" tissue images, hematoxylin and eosin (H&E)-stained slides, and pathological annotations. From epidermal landmarks, spatial accuracy in the bulk of the sample is ∼ 500    μ m , which when extrapolated with a linear stretch model, suggests an error at the margin of ∼ 100    μ m , within clinical reporting standards. Cancer annotations on H&E slides are transformed and superimposed on the fluorescence images to generate the final results. Using this methodology, fluorescence cancer signals are generally found to correspond spatially with histological annotations. This method will allow us to accurately analyze molecular probes for imaging skin cancer margins.

Sink or float? Characterization of shell-stabilized bulk nanobubbles using a resonant mass measurement technique

Nano-sized shell-stabilized gas bubbles have applications in various fields ranging from environmental science to biomedical engineering. A resonant mass measurement (RMM) technique is demonstrated here as a new and only method capable of simultaneously measuring the size and concentration of buoyant and non-buoyant particles in a nanobubble sample used as a next-generation ultrasound contrast agent.

Prostate-Specific Membrane Antigen Targeted Gold Nanoparticles for Theranostics of Prostate Cancer

Prostate cancer is one of the most common cancers and among the leading causes of cancer deaths in the United States. Men diagnosed with the disease typically undergo radical prostatectomy, which often results in incontinence and impotence. Recurrence of the disease is often experienced by most patients with incomplete prostatectomy during surgery. Hence, the development of a technique that will enable surgeons to achieve a more precise prostatectomy remains an open challenge. In this contribution, we report a theranostic agent (AuNP-5kPEG-PSMA-1-Pc4) based on prostate-specific membrane antigen (PSMA-1)-targeted gold nanoparticles (AuNPs) loaded with a fluorescent photodynamic therapy (PDT) drug, Pc4. The fabricated nanoparticles are well-characterized by spectroscopic and imaging techniques and are found to be stable over a wide range of solvents, buffers, and media. In vitro cellular uptake experiments demonstrated significantly higher nanoparticle uptake in PSMA-positive PC3pip cells than in PSMA-negative PC3flu cells. Further, more complete cell killing was observed in Pc3pip than in PC3flu cells upon exposure to light at different doses, demonstrating active targeting followed by Pc4 delivery. Likewise, in vivo studies showed remission on PSMA-expressing tumors 14 days post-PDT. Atomic absorption spectroscopy revealed that targeted AuNPs accumulate 4-fold higher in PC3pip than in PC3flu tumors. The nanoparticle system described herein is envisioned to provide surgical guidance for prostate tumor resection and therapeutic intervention when surgery is insufficient.

Synthesis and evaluation of MR probes for targeted-reporter imaging

Visualizing disease heterogeneity remains a challenging task since most imaging agents are targeted to a single receptor. We describe the development of an MR platform able to report on multiple molecular events. Enzyme activation and enhanced cellular uptake of this modular probe make it suitable for subsequent targeted-reporter imaging applications.

Regulatory Aspects of Optical Methods and Exogenous Targets for Cancer Detection

Considerable advances in cancer-specific optical imaging have improved the precision of tumor resection. In comparison to traditional imaging modalities, this technology is unique in its ability to provide real-time feedback to the operating surgeon. Given the significant clinical implications of optical imaging, there is an urgent need to standardize surgical navigation tools and contrast agents to facilitate swift regulatory approval. Because fluorescence-enhanced surgery requires a combination of both device and drug, each may be developed in conjunction, or separately, which are important considerations in the approval process. This report is the result of a one-day meeting held on May 4, 2016 with officials from the National Cancer Institute, the FDA, members of the American Society of Image-Guided Surgery, and members of the World Molecular Imaging Society, which discussed consensus methods for FDA-directed human testing and approval of investigational optical imaging devices as well as contrast agents for surgical applications. The goal of this workshop was to discuss FDA approval requirements and the expectations for approval of these novel drugs and devices, packaged separately or in combination, within the context of optical surgical navigation. In addition, the workshop acted to provide clarity to the research community on data collection and trial design. Reported here are the specific discussion items and recommendations from this critical and timely meeting. Cancer Res; 77(9); 2197-206. ©2017 AACR.

Rapid visualization of nonmelanoma skin cancer

BACKGROUND

Mohs micrographic surgery examines all margins of the resected sample and has a 99% cure rate. However, many nonmelanoma skin cancers (NMSCs) are not readily amenable to Mohs micrographic surgery. This defines an unmet clinical need to assess the completeness of non-Mohs micrographic surgery resections during surgery to prevent re-excision/recurrence.

OBJECTIVE

We sought to examine the utility of quenched activity-based probe imaging to discriminate cancerous versus normal-appearing skin tissue.

METHODS

The quenched activity-based probe GB119 was applied to NMSC excised from 68 patients. We validated activation of the probe for hematoxylin-eosin-confirmed cancerous tissue versus normal-appearing skin tissue.

RESULTS

Topical application of the probe differentiated basal cell carcinoma and squamous cell carcinoma from normal-appearing skin with overall estimated sensitivity and specificity of 0.989 (95% confidence interval 0.940-1.00) and 0.894 (95% confidence interval 0.769-0.965), respectively. Probe activation accurately defined peripheral margins of NMSC as compared with conventional hematoxylin-eosin-based pathology.

LIMITATIONS

This study only examined NMSC debulking excision specimens. The sensitivity and specificity for this approach using final NMSC excision margins will be clinically important.

CONCLUSIONS

These findings merit further studies to determine whether quenched activity-based probe technology may enable cost-effective increased cure rates for patients with NMSC by reducing re-excision and recurrence rates with a rapid and easily interpretable technological advance.

Theranostic Agents for Photodynamic Therapy of Prostate Cancer by Targeting Prostate-Specific Membrane Antigen

Prostatectomy has been the mainstay treatment for men with localized prostate cancer. Surgery, however, often can result in major side effects, which are caused from damage and removal of nerves and muscles surrounding the prostate. A technology that can help surgeons more precisely identify and remove prostate cancer resulting in a more complete prostatectomy is needed. Prostate-specific membrane antigen (PSMA), a type II membrane antigen highly expressed in prostate cancer, has been an attractive target for imaging and therapy. The objective of this study is to develop low molecular weight PSMA-targeted photodynamic therapy (PDT) agents, which would provide image guidance for prostate tumor resection and allow for subsequent PDT to eliminate unresectable or remaining cancer cells. On the basis of our highly negatively charged, urea-based PSMA ligand PSMA-1, we synthesized two PSMA-targeting PDT conjugates named PSMA-1-Pc413 and PSMA-1-IR700. In in vitro cellular uptake experiments and in vivo animal imaging experiments, the two conjugates demonstrated selective and specific uptake in PSMA-positive PC3pip cells/tumors, but not in PSMA-negative PC3flu cells/tumors. Further in vivo photodynamic treatment proved that the two PSMA-1-PDT conjugates can effectively inhibit PC3pip tumor progression. The two PSMA-1-PDT conjugates reported here may have the potential to aid in the detection and resection of prostate cancers. It may also allow for the identification of unresectable cancer tissue and PDT ablation of such tissue after surgical resection with potentially less damage to surrounding tissues. Mol Cancer Ther; 15(8); 1834-44. ©2016 AACR.

Dynamic Quantitative T1 Mapping in Orthotopic Brain Tumor Xenografts

Human brain tumors such as glioblastomas are typically detected using conventional, nonquantitative magnetic resonance imaging (MRI) techniques, such as T2-weighted and contrast enhanced T1-weighted MRI. In this manuscript, we tested whether dynamic quantitative T1 mapping by MRI can localize orthotopic glioma tumors in an objective manner. Quantitative T1 mapping was performed by MRI over multiple time points using the conventional contrast agent Optimark. We compared signal differences to determine the gadolinium concentration in tissues over time. The T1 parametric maps made it easy to identify the regions of contrast enhancement and thus tumor location. Doubling the typical human dose of contrast agent resulted in a clearer demarcation of these tumors. Therefore, T1 mapping of brain tumors is gadolinium dose dependent and improves detection of tumors by MRI. The use of T1 maps provides a quantitative means to evaluate tumor detection by gadolinium-based contrast agents over time. This dynamic quantitative T1 mapping technique will also enable future quantitative evaluation of various targeted MRI contrast agents.

Successful Translation of Fluorescence Navigation During Oncologic Surgery: A Consensus Report

Navigation with fluorescence guidance has emerged in the last decade as a promising strategy to improve the efficacy of oncologic surgery. To achieve routine clinical use, the onus is on the surgical community to objectively assess the value of this technique. This assessment may facilitate both Food and Drug Administration approval of new optical imaging agents and reimbursement for the imaging procedures. It is critical to characterize fluorescence-guided procedural benefits over existing practices and to elucidate both the costs and the safety risks. This report is the result of a meeting of the International Society of Image Guided Surgery (www.isigs.org) on February 6, 2015, in Miami, Florida, and reflects a consensus of the participants' opinions. Our objective was to critically evaluate the imaging platform technology and optical imaging agents and to make recommendations for successful clinical trial development of this highly promising approach in oncologic surgery.

Peptide-Targeted Gold Nanoparticles for Photodynamic Therapy of Brain Cancer

Targeted drug delivery using epidermal growth factor peptide-targeted gold nanoparticles (EGFpep-Au NPs) is investigated as a novel approach for delivery of photodynamic therapy (PDT) agents, specifically Pc 4, to cancer. In vitro studies of PDT show that EGFpep-Au NP-Pc 4 is twofold better at killing tumor cells than free Pc 4 after increasing localization in early endosomes. In vivo studies show that targeting with EGFpep-Au NP-Pc 4 improves accumulation of fluorescence of Pc 4 in subcutaneous tumors by greater than threefold compared with untargeted Au NPs. Targeted drug delivery and treatment success can be imaged via the intrinsic fluorescence of the PDT drug Pc 4. Using Pc 4 fluorescence, it is demonstrated in vivo that EGFpep-Au NP-Pc 4 impacts biodistribution of the NPs by decreasing the initial uptake by the reticuloendothelial system (RES) and by increasing the amount of Au NPs circulating in the blood 4 h after IV injection. Interestingly, in vivo PDT with EGFpep-Au NP-Pc 4 results in interrupted tumor growth when compared with EGFpep-Au NP control mice when selectively activated with light. These data demonstrate that EGFpep-Au NP-Pc 4 utilizes cancer-specific biomarkers to improve drug delivery and therapeutic efficacy over untargeted drug delivery.

Treatment of Invasive Brain Tumors Using a Chain-like Nanoparticle

Glioblastoma multiforme is generally recalcitrant to current surgical and local radiotherapeutic approaches. Moreover, systemic chemotherapeutic approaches are impeded by the blood-tumor barrier. To circumvent limitations in the latter area, we developed a multicomponent, chain-like nanoparticle that can penetrate brain tumors, composed of three iron oxide nanospheres and one drug-loaded liposome linked chemically into a linear chain-like assembly. Unlike traditional small-molecule drugs or spherical nanotherapeutics, this oblong-shaped, flexible nanochain particle possessed a unique ability to gain access to and accumulate at glioma sites. Vascular targeting of nanochains to the αvβ3 integrin receptor resulted in a 18.6-fold greater drug dose administered to brain tumors than standard chemotherapy. By 2 hours after injection, when nanochains had exited the blood stream and docked at vascular beds in the brain, the application of an external low-power radiofrequency field was sufficient to remotely trigger rapid drug release. This effect was produced by mechanically induced defects in the liposomal membrane caused by the oscillation of the iron oxide portion of the nanochain. In vivo efficacy studies conducted in two different mouse orthotopic models of glioblastoma illustrated how enhanced targeting by the nanochain facilitates widespread site-specific drug delivery. Our findings offer preclinical proof-of-concept for a broadly improved method for glioblastoma treatment.

Biocompatible nanoparticles of KGd(H₂O)₂[Fe(CN)₆]·H₂O with extremely high T₁-weighted relaxivity owing to two water molecules directly bound to the Gd(III) center

A simple one-step method for preparing biocompatible nanoparticles of gadolinium ferrocyanide coordination polymer KGd(H2O)2[Fe(CN)6]·H2O is reported. The crystal structure of this coordination polymer is determined by X-ray powder diffraction using the bulk materials. The stability, cytotoxicity, cellular uptake, and MR phantom and cellular imaging studies suggest that this coordination-polymer structural platform offers a unique opportunity for developing the next generation of T1-weighted contrast agents with high relaxivity as cellular MR probes for biological receptors or markers. Such high-relaxivity MR probes may hold potential in the study of molecular events and may be used for in vivo MR imaging in biomedical research and clinical applications.

Abstract 4288: Molecular imaging of tumor-associated cathepsins: implication for rapid detection of human nonmelanoma skin cancer

Of the non-melanoma skin cancers, 75% are basal cell carcinomas (BCC) and rest is squamous cell carcinomas (SCC). They are the most common cancers in humans, and their incidence may soon surpass that of all other cancers. Four million people will be diagnosed with BCC/SCC this year in the US with the overall workload of diagnosis and management increasing by 50% by 2030. Mohs micrographic surgery (MMS), which examines all margins of the entire resected sample, is the treatment of choice for BCC/SCC. However, ¾ of skin cancer lesions are too large for their entire margins to be practically assessed for cancer using MMS. Therefore, 75% of BCC/SCC patients will undergo traditional surgery. Non-MMS assesses ∼1% of the margin with the results being available days after surgery. Thus, there exists an unmet clinical need to more completely assess surgical margins to increase cure rates and minimize removal of normal tissue. Here we test a quenched near infrared fluorescent contrast agent, GB119, to rapidly and globally detect cancer in skin samples. We first characterized the feasibility of ex vivo applied GB119, to penetrate human skin tissue and “find” BCC/SCC in skin cancer samples obtained from debulking MMS. Detection of the cancer was measured by increased fluorescence resulting from specific activation and de-quenching of GB119 as it encounters active cathepsin associated with BCC/SCC. Excised skin samples were pre-imaged and then, using an applicator pad, GB119 was topically applied onto the samples containing BCC (n=12) or SCC (n=3). Activation GB119 was measured (Maestro, PerkinElmer) and fluorescent “hot spots” on the surface of samples were marked with pathology ink followed by snap freezing for histology and IHC. 13 of 15 skin samples produced robust fluorescence spots that were marked with ink. Two samples did not produce any signal greater than pre-imaging auto-fluorescence. H/E staining of marked skin samples confirmed presence of ink nearby “nests” of cancerous tissue. The two samples that did not activate GB119 were determined by histology to be cancer free. Since it was not possible to detected GB119 fluorescence after H/E staining we developed an IHC assay to visualize the presence of activated de-quenched GB119 and used it to pathologically correlate GB119 activation with cancer. Using an anti-Cy5 antibody (Sigma) our immunoassay detected de-quenched GB119 and could be used to detect activated GB119 in tissue. Using this assay we detected low levels of GB119 activation in normal skin and cancer free samples from patients with BCC/SCC. In contrast, high levels of GB119 activation were found within “nests” of cancerous tissue for BCC/SCC samples. These data confirm the feasibility of topically applying GB119 to excised skin samples to rapidly detect the presence of cancer within the margins of the samples. If successful this technology could potentially impact MMS-like precision to non-MMS surgical techniques.

Citation Format: Ethan Walker, Margaret Mann, Galia Blum, Matthew Bogyo, James P. Basilion. Molecular imaging of tumor-associated cathepsins: implication for rapid detection of human nonmelanoma skin cancer. [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 4288. doi:10.1158/1538-7445.AM2014-4288

Development of targeted near-infrared imaging agents for prostate cancer

Prostate cancer is the most common noncutaneous malignancy affecting men in North America. Radical prostatectomy remains a definitive treatment for prostate cancer. However, prostate surgeries are still performed "blindly" with the extent of tumor infiltration past the margins of the surgery only being determined postoperatively. An imaging modality that can be used during surgery is needed to help define the tumor margins. With its abundant expression in prostate cancer, prostate-specific membrane antigen (PSMA) is an ideal target for detection of prostate cancer. The purpose of this study was to develop PSMA-targeted near-infrared (NIR) optical imaging probes for intraoperative visualization of prostate cancer. We synthesized a high-affinity PSMA ligand (PSMA-1) with low molecular weight and further labeled it with commercially available NIR dyes IRDy800 and Cy5.5. PSMA-1 and PSMA-1-NIR conjugates had binding affinities better than the parent ligand Cys-CO-Glu. Selective binding was measured for each of the probes in both in vitro and in vivo studies using competitive binding and uptake studies. Interestingly, the results indicated that the pharmacokinetics of the probes was dependent of the fluorophore conjugated to the PSMA-1 ligand and varied widely. These data suggest that PSMA-targeted probes have the potential to be further developed as contrast agents for clinical intraoperative fluorescence-guided surgery.

On-command drug release from nanochains inhibits growth of breast tumors

PURPOSE

To evaluate the ability of radiofrequency (RF)-triggered drug release from a multicomponent chain-shaped nanoparticle to inhibit the growth of an aggressive breast tumor.

METHODS

A two-step solid phase chemistry was employed to synthesize doxorubicin-loaded nanochains, which were composed of three iron oxide nanospheres and one doxorubicin-loaded liposome assembled in a 100-nm-long linear nanochain. The nanochains were tested in the 4T1-LUC-GFP orthotopic mouse model, which is a highly aggressive breast cancer model. The 4T1-LUC-GFP cell line stably expresses firefly luciferase, which allowed the non-invasive in vivo imaging of tumor response to the treatment using bioluminescence imaging (BLI).

RESULTS

Longitudinal BLI imaging showed that a single nanochain treatment followed by application of RF resulted in an at least 100-fold lower BLI signal compared to the groups treated with nanochains (without RF) or free doxorubicin followed by RF. A statistically significant increase in survival time of the nanochain-treated animals followed by RF (64.3 days) was observed when compared to the nanochain-treated group without RF (35.7 days), free doxorubicin-treated group followed by RF (38.5 days), and the untreated group (30.5 days; n=5 animals per group).

CONCLUSIONS

These studies showed that the combination of RF and nanochains has the potential to effectively treat highly aggressive cancers and prolong survival.

Nanoparticles for imaging and treating brain cancer

Brain cancer tumors cause disruption of the selective properties of vascular endothelia, even causing disruptions in the very selective blood-brain barrier, which are collectively referred to as the blood-brain-tumor barrier. Nanoparticles (NPs) have previously shown great promise in taking advantage of this increased vascular permeability in other cancers, which results in increased accumulation in these cancers over time due to the accompanying loss of an effective lymph system. NPs have therefore attracted increased attention for treating brain cancer. While this research is just beginning, there have been many successes demonstrated thus far in both the laboratory and clinical setting. This review serves to present the reader with an overview of NPs for treating brain cancer and to provide an outlook on what may come in the future. For NPs, just like the blood-brain-tumor barrier, the future is wide open.

Single cell molecular recognition of migrating and invading tumor cells using a targeted fluorescent probe to receptor PTPmu

Detection of an extracellular cleaved fragment of a cell-cell adhesion molecule represents a new paradigm in molecular recognition and imaging of tumors. We previously demonstrated that probes that recognize the cleaved extracellular domain of receptor protein tyrosine phosphatase mu (PTPmu) label human glioblastoma brain tumor sections and the main tumor mass of intracranial xenograft gliomas. In this article, we examine whether one of these probes, SBK2, can label dispersed glioma cells that are no longer connected to the main tumor mass. Live mice with highly dispersive glioma tumors were injected intravenously with the fluorescent PTPmu probe to test the ability of the probe to label the dispersive glioma cells in vivo. Analysis was performed using a unique three-dimensional (3D) cryo-imaging technique to reveal highly migratory and invasive glioma cell dispersal within the brain and the extent of colabeling by the PTPmu probe. The PTPmu probe labeled the main tumor site and dispersed cells up to 3.5 mm away. The cryo-images of tumors labeled with the PTPmu probe provide a novel, high-resolution view of molecular tumor recognition, with excellent 3D detail regarding the pathways of tumor cell migration. Our data demonstrate that the PTPmu probe recognizes distant tumor cells even in parts of the brain where the blood-brain barrier is likely intact. The PTPmu probe has potential translational significance for recognizing tumor cells to facilitate molecular imaging, a more complete tumor resection and to serve as a molecular targeting agent to deliver chemotherapeutics to the main tumor mass and distant dispersive tumor cells.

Cryo-image analysis of tumor cell migration, invasion, and dispersal in a mouse xenograft model of human glioblastoma multiforme

PURPOSE

The goals of this study were to create cryo-imaging methods to quantify characteristics (size, dispersal, and blood vessel density) of mouse orthotopic models of glioblastoma multiforme (GBM) and to enable studies of tumor biology, targeted imaging agents, and theranostic nanoparticles.

PROCEDURES

Green fluorescent protein-labeled, human glioma LN-229 cells were implanted into mouse brain. At 20-38 days, cryo-imaging gave whole brain, 4-GB, 3D microscopic images of bright field anatomy, including vasculature, and fluorescent tumor. Image analysis/visualization methods were developed.

RESULTS

Vessel visualization and segmentation methods successfully enabled analyses. The main tumor mass volume, the number of dispersed clusters, the number of cells/cluster, and the percent dispersed volume all increase with age of the tumor. Histograms of dispersal distance give a mean and median of 63 and 56 μm, respectively, averaged over all brains. Dispersal distance tends to increase with age of the tumors. Dispersal tends to occur along blood vessels. Blood vessel density did not appear to increase in and around the tumor with this cell line.

CONCLUSION

Cryo-imaging and software allow, for the first time, 3D, whole brain, microscopic characterization of a tumor from a particular cell line. LN-229 exhibits considerable dispersal along blood vessels, a characteristic of human tumors that limits treatment success.

An optical probe for noninvasive molecular imaging of orthotopic brain tumors overexpressing epidermal growth factor receptor

We have developed a near-infrared (NIR) probe that targets cells overexpressing the EGF receptor (EGFR) for imaging glioblastoma brain tumors in live subjects. A peptide specific for the EGFR was modified with various lengths of monodiscrete polyethylene glycol (PEG) units and a NIR Cy5.5 fluorescence dye. The lead compound, compound 2, with one unit of PEG displayed good binding (8.9 μmol/L) and cellular uptake in glioblastoma cells overexpressing EGFR in vitro. The in vivo studies have shown that the probe was able to selectively label glioblastoma-derived orthotopic brain tumors. In vivo image analyses of peptide binding to the tumors using fluorescence-mediated molecular tomography revealed that the compound could distinguish between tumors expressing different levels of EGFR. The data presented here represent the first demonstration of differential quantitation of tumors expressing EGFR in live animals by a targeted NIR fluorescence probe using a molecular imaging device.

Abstract 5711: Applying new light to the detection and treatment of brain cancers using targeted photodynamic therapy

Currently, an estimated 11.4 million people in the US have been affected by cancer and this number is expected to double by 2020 as indicated by the NIH NCI in 2006. Each year approximately 20% of these people are expected to die of cancer, with brain cancers among the most deadly. Brain cancer patients have a median life expectancy of only 6-10 months after diagnosis, and those with recurring brain cancer survive less than 20 weeks after any therapeutic regime. Consequently, there is a critical need to develop and improve the detection, diagnosis, and treatment of brain cancers, including gliomas. Theranostic drugs have the potential to do all of these and are becoming lifesaving alternatives. However, the current standard of care suffers from lack of specificity and systemic toxicity, often requiring invasive surgical procedures. These are significant obstacles when dealing with minimizing offsite damage to the healthy brain while maximizing treatment efficacy in the tumor. Our study presents a novel drug delivery platform using targeted-gold nanoparticles (Au NP) to deliver a therapeutic photodynamic therapy (PDT) drug, phthalocyanine 4 (Pc 4), across the blood-brain tumor barrier (BBTB), which allows both detection and treatment of gliomas within mere hours. Targeting Pc 4 to cancer-specific biomarkers concentrates the drug specifically at the brain tumor, significantly reducing collateral damage to healthy brain tissue. Once Pc 4 is delivered, it offers selectivity based on its defined light activation. Our targeted delivery vehicle possesses several advantages over systemic drug delivery: greater control over bioavailability of the drug, controlled release of Pc 4 directly to the site, lower concentration of drug required for PDT effect, and avoidance of systemic drug exposure. The drug delivery mechanism of targeted-Au NP Pc 4 was investigated utilizing in vivo and in vitro fluorescence imaging, immunohistochemistry, elemental analysis, biodistribution studies, and therapeutic efficacy. We are able to target cancer biomarkers specifically, deliver hydrophobic drugs across the BBTB, increase drug accumulation into the tumor, alter drug localization, and enhance PDT killing affect. As a result, this study presents a unique application of PDT to the treatment of brain tumors using photosensitizing drugs like Pc 4.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5711. doi:1538-7445.AM2012-5711

Abstract 2449: Molecular imaging of the cancer signature using targeted-split enzyme complementation

Noninvasive diagnosis of any disease is a crucial step in the prevention, treatment and reduction of the mortality rate. Further, tailoring clinical diagnostics and therapeutics to specific forms of cancer and even to the precise aberrant biological events underlying cancer development in a particular patient has focused significant research on molecular signatures. For instance, cell surface receptors important in tumorigenesis are expressed at different levels during the multistage process and are routinely used to guide treatment regimes. Moreover, mutational events that drive a normal cell to become a cancer cell require the coordinated overexpression of not just one receptor at a time, but rather multiple biomarkers. Many cancers, including gliomas, are characterized by an abnormal increase in the activity of epidermal growth factor receptors (EGFR) and transferrin receptors (TfR). Our data of representative human cancer cell lines demonstrate unique, observable expression patterns for the two receptors. Current diagnostic techniques such as medical imaging, tissue biopsy, and bioanalytical assay of body fluids are relatively insensitive and lack the specificity to detect these physiologic changes simultaneously. To develop imaging tools that take advantage of the molecular signature, new technologies must employ an activity-based imaging agent conjugated to a targeting element. By linking a reporter enzyme, such as α-gal, to a targeting moiety, either ligand or a short peptide, signal-amplification at the molecular level is achieved. We divided α-gal into unique, independent polypeptides that reassemble and complement enzymatic activity in bacteria and in mammalian cells. We created two sets of complementing pairs that individually have no enzymatic activity. However, when brought into close proximity, complementing pairs associate, resulting in detectable enzymatic activity. We then constructed a targeting complex composed of reporter fragment, linker, and targeting moiety. Our studies demonstrate a time course- and dose-dependent uptake in vitro. Further, we were able to simultaneously visualize the two cell surface receptors implicated in gliomas, EGFR and TfR, using complementing pairs of the targeted-reporter fragment complex. In addition, we were able to image orthotopic brain tumor accumulation and localization of the targeted-enzyme when a fluorescence reporter was added to the complex, as well as immunohistochemical staining of the α-gal reporter complex ex vivo. After fluorescence imaging localized the α-gal complexes to the brain tumor, we topically applied a bioluminescent α-gal substrate to serial sections of the brain to evaluate the delivery and integrity of enzyme. Robust bioluminescence was captured within the tumor after 3 min, indicating that α-gal maintained its activity. Current experiments are underway to image the enzyme complementation noninvasively in vivo.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2449. doi:1538-7445.AM2012-2449

Abstract 4637: Cell penetrating antibodies for intracellular targets: Expanding the antibody-based treatments for cancer

Antibody based therapeutics have gained significant interest in recent years. Herceptin, which targets cell surface protein, have been successful for the treatment of cancer. While antibodies are promising platforms for therapy, antibodies have been limited to targeting cell surface proteins because they cannot penetrate cells. Recently, we have developed cell penetrating antibodies engineered from the conjugation of a cell penetrating peptide (CPP) and an antibody. The CPP-mIgG and CPP-anti-RPA1 IgGs were internalized in cells as observed by fluorescence microscopy. Biological activities of these conjugates were determined and the expected anti-proliferative effects of the CPP-anti-RPA1 were subtly distinguishable from the control CPP-mIgG. While RPA1 is a valid anti-cancer target, its function depends on complicated pathways and cell cycle where dosing may have to be optimized. This demonstrates the difficulties in establishing CPP-IgG as an efficient therapeutic. To demonstrate that CPP-IgG bioconjugates are capable of inducing biological effects, we sought a different intracellular target. Antimitotic drugs are standard cancer chemotherapeutic agents. Recently, other proteins involved in the mitotic machinery have gained much attention. For example, kinesin motor protein Eg5 plays an important role in mitosis and inhibiting Eg5 prevents the formation of bipolar spindles resulting to an unmistakable change of morphology during mitosis_a star-like structure called “monoastral”. Small molecules, such as monastrol and (S)-trityl cysteine (STLC), lead to monastral formation. Thus, we chose Eg5 protein as an intracellular target to demonstrate that CPP-IgG bioconjugates are able to penetrate cells and have neutralizing activity. We expect that CPP-anti-Eg5 conjugates will penetrate cells and produce the canonical inhibition of Eg5 protein by observing for the monoastral morphology during mitosis. We tested whether CPP-anti-Eg5 IgG will present the same biological activity as STLC. We bioconjugated the anti-Eg5 with a CPP. Cell cycle synchronized cells were treated with the positive control STLC and CPP-anti-Eg5 showed an atypical star-like structure similar to monoastral. In whole, these studies show that CPP-IgG against intracellular targets are able to enter the cells and show inhibitory activities. We will describe our progress and discuss approaches to expanding the utility of antibodies as therapeutics for intracellular cancer targets.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4637. doi:1538-7445.AM2012-4637

Protein tyrosine phosphatase mu regulates glioblastoma cell growth and survival in vivo

Glioblastoma multiforme (GBM) is the most lethal primary brain tumor. Extensive proliferation and dispersal of GBM tumor cells within the brain limits patient survival to approximately 1 year. Hence, there is a great need for the development of better means to treat GBM. Receptor protein tyrosine phosphatase (PTP)µ is proteolytically cleaved in GBM to yield fragments that promote dispersal of GBM cells. While normal brain tissue retains expression of full-length PTPµ, low-grade human astrocytoma samples have varying amounts of full-length PTPµ and cleaved PTPµ. In the highest-grade astrocytomas (i.e., GBM), PTPµ is completely proteolyzed into fragments. We demonstrate that short hairpin RNA mediated knockdown of full-length PTPµ and PTPµ fragments reduces glioma cell growth and survival in vitro. The reduction in growth and survival following PTPµ knockdown is enhanced when cells are grown in the absence of serum, suggesting that PTPµ may regulate autocrine signaling. Furthermore, we show for the first time that reduction of PTPµ protein expression decreases the growth and survival of glioma cells in vivo using mouse xenograft flank and i.c. tumor models. Inhibitors of PTPµ could be used to reduce the growth and survival of GBM cells in the brain, representing a promising therapeutic target for GBM.

Cadherin-11, a marker of the mesenchymal phenotype, regulates glioblastoma cell migration and survival in vivo

Glioblastoma multiforme (GBM) is the most malignant and lethal form of astrocytoma. The GBM patient survival time of approximately 1 year necessitates the identification of novel molecular targets and more effective therapeutics. Cadherin-11, a calcium-dependent cell-cell adhesion molecule and mesenchymal marker, plays a role in both normal tissue development and in cancer cell migration. The functional significance of cadherin-11 in GBM has not been investigated. Here, we show that cadherin-11 is expressed in human GBM tumors and human glioma stem-like cells by immunohistochemical labeling. In addition, we show that cadherin-11 is expressed in human glioma cell lines by immunoblotting. Short hairpin RNA-mediated knockdown of cadherin-11 expression in human glioma cell lines results in decreased migration and growth factor-independent cell survival in vitro. More importantly, knockdown of cadherin-11 inhibits glioma cell survival in heterotopic and orthotopic mouse xenograft models. Together, our results show the functional significance of cadherin-11 expression in GBM and provide evidence for a novel role of cadherin-11 in promoting glioma cell survival in an in vivo environment. Thus, our studies suggest cadherin-11 is a viable molecular target for therapeutic intervention in GBM.

Nanoparticles of the novel coordination polymer KBi(H2O)2[Fe(CN)6]·H2O as a potential contrast agent for computed tomography

An aqueous synthetic procedure for preparing nanoparticles of the novel potassium bismuth ferrocyanide coordination polymer KBi(H(2)O)(2)[Fe(CN)(6)]·H(2)O is reported. The crystal structure of this coordination polymer is determined through X-ray powder diffraction using the bulk materials. The stability, cytotoxicity, and potential use of such nanoparticles coated with PVP as a CT contrast agent are investigated.

Novel cryo-imaging of the glioma tumor microenvironment reveals migration and dispersal pathways in vivid three-dimensional detail

Traditional methods of imaging cell migration in the tumor microenvironment include serial sections of xenografts and standard histologic stains. Current molecular imaging techniques suffer from low resolution and difficulty in imaging through the skull. Here we show how computer algorithms can be used to reconstruct images from tissue sections obtained from mouse xenograft models of human glioma and can be rendered into three-dimensional images offering exquisite anatomic detail of tumor cell dispersal. Our findings identify human LN-229 and rodent CNS-1 glioma cells as valid systems to study the highly dispersive nature of glioma tumor cells along blood vessels and white matter tracts in vivo. This novel cryo-imaging technique provides a valuable tool to evaluate therapeutic interventions targeted at limiting tumor cell invasion and dispersal.