Joseph D. Meyers

Deep Penetration of a PDT Drug into Tumors by Noncovalent Drug-Gold Nanoparticle Conjugates

Efficient drug delivery to tumors is of ever-increasing importance. Single-visit diagnosis and treatment sessions are the goal of future theranostics. In this work, a noncovalent PDT cancer drug-gold nanoparticle (Au NP) conjugate system performed a rapid drug release and deep penetration of the drug into tumors within hours. The drug delivery mechanism of the PDT drug through Au NPs into tumors by passive accumulation was investigated via fluorescence imaging, elemental analysis, and histological staining. The pharmacokinetics of the conjugates over a 7-day test period showed rapid drug excretion, as monitored via the fluorescence of the drug in urine. Moreover, the biodistribution of Au NPs in this study period indicated clearance of the NPs from the mice. This study suggests that noncovalent delivery via Au NPs provides an attractive approach for cancer drugs to penetrate deep into the center of tumors.

Addressing Brain Tumors with Targeted Gold Nanoparticles: A New Gold Standard for Hydrophobic Drug Delivery?

EGF-modified Au NP-Pc 4 conjugates showed 10-fold improved selectivity to the brain tumor compared to untargeted conjugates. The hydrophobic photodynamic therapy drug Pc 4 can be delivered efficiently into glioma brain tumors by EGF peptide-targeted Au NPs. Compared to the untargeted conjugates, EGF-Au NP-Pc 4 conjugates showed 10-fold improved selectivity to the brain tumor. This delivery system holds promise for future delivery of a wider range of hydrophobic therapeutic drugs for the treatment of hard-to-reach cancers.

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.

Multimodal In Vivo Imaging Exposes the Voyage of Nanoparticles in Tumor Microcirculation

Tumors present numerous biobarriers to the successful delivery of nanoparticles. Decreased blood flow and high interstitial pressure in tumors dictate the degree of resistance to extravasation of nanoparticles. To understand how a nanoparticle can overcome these biobarriers, we developed a multimodal in vivo imaging methodology, which enabled the noninvasive measurement of microvascular parameters and deposition of nanoparticles at the microscopic scale. To monitor the spatiotemporal progression of tumor vasculature and its vascular permeability to nanoparticles at the microcapillary level, we developed a quantitative in vivo imaging method using an iodinated liposomal contrast agent and a micro-CT. Following perfusion CT for quantitative assessment of blood flow, small animal fluorescence molecular tomography was used to image the in vivo fate of cocktails containing liposomes of different sizes labeled with different NIR fluorophores. The animal studies showed that the deposition of liposomes depended on local blood flow. Considering tumor regions of different blood flow, the deposition of liposomes followed a size-dependent pattern. In general, the larger liposomes effectively extravasated in fast flow regions, while smaller liposomes performed better in slow flow regions. We also evaluated whether the tumor retention of nanoparticles is dictated by targeting them to a receptor overexpressed by the cancer cells. Targeting of 100 nm liposomes showed no benefits at any flow rate. However, active targeting of 30 nm liposomes substantially increased their deposition in slow flow tumor regions (∼12-fold increase), which suggested that targeting prevented the washout of the smaller nanoparticles from the tumor interstitium back to blood circulation.

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.

Choline Molecular Imaging with Small-animal PET for Monitoring Tumor Cellular Response to Photodynamic Therapy of Cancer

We are developing and evaluating choline molecular imaging with positron emission tomography (PET) for monitoring tumor response to photodynamic therapy (PDT) in animal models. Human prostate cancer (PC-3) was studied in athymic nude mice. A second-generation photosensitizer Pc 4 was used for PDT in tumor-bearing mice. MicroPET images with 11C-choline were acquired before PDT and 48 h after PDT. Time-activity curves of 11C-choline uptake were analyzed before and after PDT. For treated tumors, normalized choline uptake decreased significantly 48 h after PDT, compared to the same tumors pre-PDT (p ⪅ 0.001). However, for the control tumors, normalized choline uptake increased significantly (p ⪅ 0.001). PET imaging with 11C-choline is sensitive to detect early tumor response to PDT in the animal model of human prostate cancer.

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

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL 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 1685: Nano-scale targeting of Pc 4 to improve drug delivery, accumulation, and PDT efficacy in brain tumors

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Malignant gliomas are among the most lethal cancers with a median survival expectancy of only 6-12 months. Surgical resection is the mainstay of treatment. However, curative resection is often not possible due to infiltrating growth of the tumor into normal brain. Photodynamic therapy (PDT) has been suggested as an additional therapy to guide tumor resections and enhance the effect of surgery via photoreactive treatment during or at the cessation of surgical intervention. The most difficult challenge in treating malignant brain tumors may be delivering targeted therapies that preserve healthy tissue while effectively eradicating the cancer. Therefore, improving drug delivery rate and tumor selectivity of the photosensitizing agent will dramatically reduce systemic toxicity and enhance the success of PDT. EGFR amplification is the most common genetic alteration in gliomas and plays a critical role in stimulating glioma progression, making it an ideal target. Consequently, we have developed a highly efficient EGFR-targeted gold-nanoparticle (EGF-Au NP) to improve delivery of PDT cancer drugs to tumors in vivo. EGF peptides attached to PEGylated Au NPs deliver hydrophobic PDT drug, Pc 4, to brain tumors overexpressing EGFR better than either the non-targeted Au NPs or Pc 4 alone. The drug rapidly releases and penetrates deep within tumors within 1-4 hrs. In vivo small animal imaging experiments show targeted delivery of Pc 4 to tumor sites. Ex vivo imaging of the tumors confirmed as much as a 4-fold increase in the intrinsic fluorescence of Pc 4 over non-targeted conjugates after systemic administration. Moreover, in vitro experiments show a higher concentration of Pc 4 uptake per Au NP over non-targeted Au NPs per cancer cell. Histological analysis, including confocal microscopy, shows that, after targeting, the delivered Pc 4 localizes in the endosomes of the cancer cells. Transmission electron micrographs show that Au NPs cluster along the cell surface or within discrete vesicles within the cell. Localization within the endosomal pathway may be more effective for PDT and produce less off-target toxicity than free Pc 4, which preferentially accumulates in mitochondria. Further, glioma cells treated for 4 hrs with EGF-targeted Au NP-Pc 4 and then exposed to PDT show an enhanced killing effect, especially when compared to either non-targeted Au NP-Pc 4 or free Pc 4 controls. Systemic delivery of EGF-Au NP-Pc 4 to heterotopic brain tumors reveals increasing tumor necrosis after PDT. Biodistribution experiments also show that the Au NPs and Pc 4 are effectively excreted over time. This study suggests that the EGFR-targeted Au NPs improve drug delivery to tumors for PDT and are removed from the body safely after treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1685. doi:10.1158/1538-7445.AM2011-1685

Choline molecular imaging with small-animal PET for monitoring tumor cellular response to photodynamic therapy of cancer

We are developing and evaluating choline molecular imaging with positron emission tomography (PET) for monitoring tumor response to photodynamic therapy (PDT) in animal models. Human prostate cancer (PC-3) was studied in athymic nude mice. A second-generation photosensitizer Pc 4 was used for PDT in tumor-bearing mice. MicroPET images with 11C-choline were acquired before PDT and 48 h after PDT. Time-activity curves of 11C-choline uptake were analyzed before and after PDT. For treated tumors, normalized choline uptake decreased significantly 48 h after PDT, compared to the same tumors pre-PDT (p ⪅ 0.001). However, for the control tumors, normalized choline uptake increased significantly (p ⪅ 0.001). PET imaging with 11C-choline is sensitive to detect early tumor response to PDT in the animal model of human prostate cancer.

In Vivo Small Animal Imaging for Early Assessment of Therapeutic Efficacy of Photodynamic Therapy for Prostate Cancer

We are developing in vivo small animal imaging techniques that can measure early effects of photodynamic therapy (PDT) for prostate cancer. PDT is an emerging therapeutic modality that continues to show promise in the treatment of cancer. At our institution, a new second-generation photosensitizing drug, the silicon phthalocyanine Pc 4, has been developed and evaluated at the Case Comprehensive Cancer Center. In this study, we are developing magnetic resonance imaging (MRI) techniques that provide therapy monitoring and early assessment of tumor response to PDT. We generated human prostate cancer xenografts in athymic nude mice. For the imaging experiments, we used a highfield 9.4-T small animal MR scanner (Bruker Biospec). High-resolution MR images were acquired from the treated and control tumors pre- and post-PDT and 24 hr after PDT. We utilized multi-slice multi-echo (MSME) MR sequences. During imaging acquisitions, the animals were anesthetized with a continuous supply of 2% isoflurane in oxygen and were continuously monitored for respiration and temperature. After imaging experiments, we manually segmented the tumors on each image slice for quantitative image analyses. We computed three-dimensional T2 maps for the tumor regions from the MSME images. We plotted the histograms of the T2 maps for each tumor pre- and post-PDT and 24 hr after PDT. After the imaging and PDT experiments, we dissected the tumor tissues and used the histologic slides to validate the MR images. In this study, six mice with human prostate cancer tumors were imaged and treated at the Case Center for Imaging Research. The T2 values of treated tumors increased by 24 ± 14% 24 hr after the therapy. The control tumors did not demonstrate significant changes of the T2 values. Inflammation and necrosis were observed within the treated tumors 24 hour after the treatment. Preliminary results show that Pc 4-PDT is effective for the treatment of human prostate cancer in mice. The small animal MR imaging provides a useful tool to evaluate early tumor response to photodynamic therapy in mice.