Glioblastoma stem cells (GSCs) isolated from patients with newly diagnosed disease are potent tumor initiators that express biomarkers associated with stem cells. These stem-like cells are thought to drive treatment resistance and tumor recurrence. Preclinical models suggest that the GSC subpopulation becomes enriched and re-populates the tumor milieu following conventional therapies. This talk will discuss the use of photodynamic therapy to overcome treatment resistance in a preclinical model of human GSC neurosphere cell cultures.
Lack of access to effective cancer therapeutics in resource-limited settings is widely implicated in global cancer health disparities. Here we evaluate low-cost devices to enable photodynamic therapy (PDT) and associated photosensitizer imaging in regions with little or no access to electricity or medical infrastructure. We demonstrate the efficacy of a battery-powered LED-based device following aminolevulinic acid (ALA) induced accumulation of protoporphyrin IX (PpIX). We further evaluate the capability of a consumer smartphone coupled with a 405nm LED array and a PpIX emission filter to image PpIX fluorescence. Collectively this work suggests the feasibility of image-guided ALA-PDT in resource-limited settings.
Photodynamic therapy (PDT) is a photochemistry-based modality in which a chemical (photosensitizer) is energized by light to produce cytotoxic molecular species. The current state of the art limits PDT to small isolated lesions. To make the modality more broadly applicable, new targeting strategies with high payloads of the photosensitizer are needed and several approaches are being evaluated. Nanoliposomes have attracted interest as efficient, biocompatible and biodegradable carriers of photosensitizers that broaden the applications of PDT through their multi-compartmental architecture and their tunable physicochemical characteristics. This chapter provides an overview of the theranostic aspects of liposomal constructs and their role in future advancements of PDT. It also elaborates on the photochemistry, physical properties and release mechanisms of photosensitizers entrapped within optimized liposomes that mediate effective PDT treatments.
Assessment of molecular signatures of tumors in addition to their anatomy and morphology is desired for effective diagnostic and therapeutic procedures. Development of in vivo imaging techniques that can identify and monitor molecular composition of tumors remains an important challenge in pre-clinical research and medical practice. Here we present a molecular photoacoustic imaging technique that can visualize the presence and activity of an important cancer biomarker – epidermal growth factor receptor (EGFR), utilizing the effect of plasmon resonance coupling between molecular targeted gold nanoparticles. Specifically, spectral analysis of photoacoustic images revealed profound changes in the optical absorption of systemically delivered EGFR-targeted gold nanospheres due to their molecular interactions with tumor cells overexpressing EGFR. In contrast, no changes in optical properties and, therefore, photoacoustic signal, were observed after systemic delivery of non-targeted gold nanoparticles to the tumors. The results indicate that multi-wavelength photoacoustic imaging augmented with molecularly targeted gold nanoparticles has the ability to monitor molecular specific interactions between nanoparticles and cell-surface receptors, allowing visualization of the presence and functional activity of tumor cells. Furthermore, the approach can be used for other cancer cell-surface receptors such as human epidermal growth factor receptor 2 (HER2). Therefore, ultrasound-guided molecular photoacoustic imaging can potentially aid in tumor diagnosis, selection of customized patient-specific treatment, and monitor the therapeutic progression and outcome in vivo.
Selection and design of individualized treatments remains a key goal in cancer therapeutics; prediction of response and tumor recurrence following a given therapy provides a basis for subsequent personalized treatment design. We demonstrate an approach towards this goal with the example of photodynamic therapy (PDT) as the treatment modality and photoacoustic imaging (PAI) as a non-invasive, response and disease recurrence monitor in a murine model of glioblastoma (GBM). PDT is a photochemistry-based, clinically-used technique that consumes oxygen to generate cytotoxic species, thus causing changes in blood oxygen saturation (StO2). We hypothesize that this change in StO2 can be a surrogate marker for predicting treatment efficacy and tumor recurrence. PAI is a technique that can provide a 3D atlas of tumor StO2 by measuring oxygenated and deoxygenated hemoglobin. We demonstrate that tumors responding to PDT undergo approximately 85% change in StO2 by 24-hrs post-therapy while there is no significant change in StO2 values in the non-responding group. Furthermore, the 3D tumor StO2 maps predicted whether a tumor was likely to regrow at a later time point post-therapy. Information on the likelihood of tumor regrowth that normally would have been available only upon actual regrowth (10-30 days post treatment) in a xenograft tumor model, was available within 24-hrs of treatment using PAI, thus making early intervention a possibility. Given the advances and push towards availability of PAI in the clinical settings, the results of this study encourage applicability of PAI as an important step to guide and monitor therapies (e.g. PDT, radiation, anti-angiogenic) involving a change in StO2.
The need for patient-specific photodynamic therapy (PDT) in dermatologic and oncologic applications has triggered several studies that explore the utility of surrogate parameters as predictive reporters of treatment outcome. Although photosensitizer (PS) fluorescence, a widely used parameter, can be viewed as emission from several fluorescent states of the PS (e.g., minimally aggregated and monomeric), we suggest that singlet oxygen luminescence (SOL) indicates only the active PS component responsible for the PDT. Here, the ability of discrete PS fluorescence-based metrics (absolute and percent PS photobleaching and PS re-accumulation post-PDT) to predict the clinical phototoxic response (erythema) resulting from 5-aminolevulinic acid PDT was compared with discrete SOL (DSOL)-based metrics (DSOL counts pre-PDT and change in DSOL counts pre/post-PDT) in healthy human skin. Receiver operating characteristic curve (ROC) analyses demonstrated that absolute fluorescence photobleaching metric (AFPM) exhibited the highest area under the curve (AUC) of all tested parameters, including DSOL based metrics. The combination of dose-metrics did not yield better AUC than AFPM alone. Although sophisticated real-time SOL measurements may improve the clinical utility of SOL-based dosimetry, discrete PS fluorescence-based metrics are easy to implement, and our results suggest that AFPM may sufficiently predict the PDT outcomes and identify treatment nonresponders with high specificity in clinical contexts.
A first approach toward understanding the targeted design of molecular photoacoustic contrast agents (MPACs) is presented. Optical and photoacoustic Z-scan spectroscopy was used to identify how nonlinear (excitedstate) absorption contributes to enhancing the photoacoustic emission of the curcuminBF2 and bis-styryl (MeOPh)2BODIPY dyes relative to Cy3.
A complete understanding of the biological mechanisms regulating devastating disease such as cancer remains elusive. Pancreatic and brain cancers are primary among the cancer types with poor prognosis. Molecular biomarkers have emerged as group of proteins that are preferentially overexpressed in cancers and with a key role in driving disease progression and resistance to chemotherapy. The epidermal growth factor receptor (EGFR), a cell proliferative biomarker is particularly highly expressed in most cancers including brain and pancreatic cancers. The ability of EGFR to sustain prolong cell proliferation is augmented by biomarkers such as Bax, Bcl-XL and Bcl-2, proteins regulating the apoptotic process. To better understand the role and effect of the microenvironment on these biomarkers in pancreatic cancer (PaCa); we analysed two pancreatic tumor lines (AsPc-1 and MiaPaCa-2) in 2D, 3D in-vitro cultures and in orthotopic tumors at different growth stages. We also investigated in patient derived glioblastoma (GBM) tumor cultures, the ability to utilize the EGFR expression to specifically deliver photosensitizer to the cells for photodynamic therapy. Overall, our results suggest that (1) microenvironment changes affect biomarker expression; thereby it is critical to understand these effects prior to designing combination therapies and (2) EGFR expression in tumor cells indeed could serve as a reliable and a robust biomarker that could be used to design targeted and image-guided photodynamic therapy.
The purpose of this study is to strategically combine two clinical-relevant, nanotechnology-based therapies to facilitate rapid clinical translation and immediately improve on the dismal statistics of pancreatic cancer (PanCa) patients. We hypothesized that benzoporphyrin derivative (BPD)-based photodynamic therapy (PDT) (Phase I/II study, solid PanCa) destroys tumor efflux transporters, which may help maintain high intracellular concentrations of Irinotecan (CPT-11) (Phase III study, metastatic PanCa) to reduce tumor burden and prolong survival. We test our hypothesis in orthotopic PanCa models.
Two types of liposomes were fabricated by adapting procedures from literature. They are: (i) Liposome with BPD in lipid bilayer (LBPD) and (ii) Liposome encapsulating CPT-11 in aqueous core (LCPT-11). Lipids (DPPC, DOTAP, Cholesterol, DSPE-mPEG at a molar ratio of 2:0.2:1.0:0.2) were mixed in chloroform (for LBPD, dissolve with 0.2 mM BPD), and the chloroform was evaporated. Lipid films were rehydrated for 2h in an aqueous solution (for LCPT-11, contain 7 mM CPT-11) with freeze thaw cycles. The resulting dispersion was extruded through polycarbonate membranes (100 nm pore size) to form unilamellar vesicles. Liposome size and polydispersity were measured by dynamic light scattering. BPD (or CPT-11) concentration was determined by UV-Vis spectroscopy. Human pancreatic cancer cells (MIA PaCa-2 or AsPC-1, ATCC) were implanted orthotopically in Swiss Nu/Nu mice (4-6 weeks old, ~25 mg) on day 0. Animals were anesthetized with Ketamine/Xylazine and the pancreas was exteriorized. Cells (1 x 106 in 50 μL of Matrigel-containing media) were injected into the pancreas using a 301/2-gauge needle, and the incision was closed with 4-0 sutures. Treatments were initiated when the tumors reach ~35 mm3 on day 9 (determined by ultrasound imaging). Tumor bearing mice were intravenously (tail vein) injected with LBPD (0.25 mg/kg) and LCPT-11 (20 mg/kg) 1h before light administration. Interstitial PDT (690 nm laser, 100mW/cm2, 75 J/cm2) was performed on the exteriorized pancreas of the anesthetized animal, and then followed by wound closure with sutures.
We have delivered reproducible LBPDs (137±9 nm) and LCPT-11s (122±5 nm), with a polydispersity index less than 0.05, were found stable for up to 3 weeks of storage. The BPD and CPT-11 loading efficiency in liposomes were found to be ~75% and ~50%, respectively. The longitudinal ultrasound monitoring of orthotopic tumor volume in response to combination LBPD-PDT and LCPT- 11 was carried out with appropriate controls. We observed that LBPD-PDT significantly enhances the tumoricidal efficacy of LCPT-11 and significantly inhibited tumor growth up to at least 3 weeks post-treatment (p < 0.05). Tumor volumes for the combination group on day 30 were ~3 fold and ~5 fold less than single treatments and no treatment groups, respectively.Photodynamic therapy (and Irinotecan chemotherapy) alone has already shown promise in treatment of PanCa in clinical studies. This study recognizes that the genetic complexity and heterogeneity of PanCa make it extremely difficult for any single treatment to impact outcome. To overcome therapy resistance, it is critical to understand the limitations of single treatment and develop new combination regimens based on interactive mechanisms. We performed pilot studies in orthotopic PanCa models that demonstrated LBPD-PDT could improve the efficacy of liposomal Irinotecan treatment. We anticipate the findings of this study, based on two clinically relevant treatments, will form the basis for rapid translation of a novel combination regimen for PanCa patients.
Glioblastoma (GBM) is an aggressive cancer with dismal survival rates and few new treatment options. Fluorescence guided resection of GBM followed by photodynamic therapy (PDT) has shown promise in several chemo- or radiotherapy non-responsive GBM treatments clinically. PDT is an emerging light and photosensitizer (PS) mediated cytotoxic method. However, as with other therapeutic modalities, the outcomes are variable largely due to the nonpersonalization of dose parameters. The variability can be attributed to the differences in heterogeneous photosensitizer accumulation in tumors. Building upon our previous findings on utilizing PS fluorescence for designing tumor-specific PDT dose, we explore the use of photoacoustic imaging, a technique that provides contrast based on the tissue optical absorption properties, to obtain 3D information on the tumoral photosensitizer accumulation. The findings of this study will form the basis for customized photodynamic therapy for glioblastoma and have the potential to serve as a platform for treatment of other cancers.