Photodynamic Therapy in Oncology

Photodynamic therapy for non-resectable perihilar cholangiocarcinoma

Photodynamic therapy (PDT) has emerged as a useful tool for palliative treatment of the otherwise difficult to treat perihilar cholangiocarcinoma (CC). PDT is a minimally invasive and effective technique for local tumour ablation with rare and predictable side effects. A modest number of studies and randomised trials using porfimer (Photofrin) could demonstrate an improvement in quality of life and survival time. A novel approach to a priori non-resectable perihilar CC was proven in a pilot study using neoadjuvant porfimer-PDT for down-sizing of the tumour followed by R0 resection. These days, active phase II and phase III trials investigate if the tumouricidal activity can be increased using temoporfin (Foscan) as an alternative photosensitiser with higher penetration capability and whether porfimer-based PDT plus stenting is superior to biliary stenting alone in terms of overall survival, respectively. The local tumour ablation and correction of obstructive cholestasis with PDT will allow for novel multimodal strategies to treat cholangiocarcinoma.

Nanoparticles as vehicles for delivery of photodynamic therapy agents

Photodynamic therapy (PDT) in cancer treatment involves the uptake of a photosensitizer by cancer tissue followed by photoirradiation. The use of nanoparticles as carriers of photosensitizers is a very promising approach because these nanomaterials can satisfy all the requirements for an ideal PDT agent. This review describes and compares the different individual types of nanoparticles that are currently in use for PDT applications. Recent advances in the use of nanoparticles, including inorganic oxide-, metallic-, ceramic-, and biodegradable polymer-based nanomaterials as carriers of photosensitizing agents, are highlighted. We describe the nanoparticles in terms of stability, photocytotoxic efficiency, biodistribution and therapeutic efficiency. Finally, we summarize exciting new results concerning the improvement of the photophysical properties of nanoparticles by means of biphotonic absorption and upconversion.

Effect of (R)L-sulforaphane on 5-aminolevulinic acid-mediated photodynamic therapy

Topical photodynamic therapy (PDT) with 5-aminolevulinic acid (ALA), or so-called ALA-PDT, is a standard procedure in the clinical practice. For optimal treatment of nonmelanoma skin cancer, actinic keratoses and other dermatoses improvements are required because of adverse side effects, which include pruritus, erythema, edema, and pain. (R)L-sulforaphane (SF) is a compound that protects against erythema, but it can also induce DNA fragmentation that leads to cell death by apoptosis. The aim of our study was to investigate whether SF has any impact on protoporphyrin IX (PpIX) production and on PDT effectiveness. We have investigated some relevant properties of SF: its photostability in dimethyl sulfoxide (DMSO), its effect on ALA-induced production of PpIX in A431 human squamous carcinoma cells and in human skin, its effect on the photoinactivation of PpIX sensitized cells, and its effect on the rate of photobleaching of PpIX. SF had no influence on PpIX photodegradation, neither in solution nor in A431 cells. The synthesis of PpIX was increased by SF in human skin, but not in A431 cells. The average increase in PpIX fluorescence in human skin was 18% +/- 6% and 43% +/- 10% for ALA combined with 80 nmol/L SF and 120 nmol/L SF, respectively. Pretreatment with (R)L-sulforaphane before topical ALA-PDT may improve penetration of ALA through the stratum corneum, and, subsequently, increase PpIX synthesis.

Regulation of singlet oxygen generation using single-walled carbon nanotubes

We have designed a novel photodynamic therapy (PDT) agent using protein binding aptamer, photosensitizer, and single-walled carbon nanotube (SWNT). The PDT is based on covalently linking a photosensitizer with an aptamer then wrapping onto the surface of SWNTs, such that the photosensitizer can only be activated by light upon target binding. We have chosen the human alpha-thrombin aptamer and covalently linked it with Chlorin e6 (Ce6), which is a second generation photosensitizer. Our results showed that SWNTs are great quenchers to singlet oxygen generation (SOG). In the presence of its target, the binding of target thrombin will disturb the DNA interaction with the SWNTs and cause the DNA aptamer to fall off the SWNT surface, resulting in the restoration of SOG. This study validated the potential of our design as a novel PDT agent with regulation by target molecules, enhanced specificity, and efficacy of therapeutic function, which directs the development of photodynamic therapy to be safer and more selective.

Photosensitized oxidation of hypoxanthine and xanthine by aluminum phthalocyanine tetrasulfonate. Role of the alkylating quinone 2,5-dichloro-diaziridinyl-1,4-benzoquinone

Photoirradiation of nitrogen-saturated aqueous solutions containing aluminum phthalocyanine tetrasulfonate (AlPcS4) at 675 nm in the presence of 2,5-dichloro-diaziridinyl-1,4-benzoquinone (AZDClQ) and hypoxanthine (HX) produces the oxidized HX derivatives, xanthine (X) and uric acid (UA). Concentrations of the AZDClQ semiquinone, X and UA increase at the expense of HX with an increase in irradiation time. Almost negligible decomposition of HX, as well as very low amounts of X, are detected if photolysis occurs under identical conditions but in the absence of AZDClQ. Addition of calf-thymus DNA produces quinone-DNA covalent adducts after photolysis of anaerobic samples containing quinone, DNA and AlPcS4, in the presence or absence of HX and at pH 5.5. However, larger amounts of quinone-DNA adducts are detected if HX is present. The results presented here could have applications in the photodynamic treatment of hypoxic tissues such as solid tumors, under conditions of high HX concentration, where Type-I pathways could be more important than singlet oxygen generation.

Immunophototherapy using PDT combined with rapid intratumoral dendritic cell injection

The capacity of photodynamic therapy (PDT) to induce localized cell death and tissue damage suggests that when applied to tumors it could create a local depot of tumor-associated antigens, which would be available for uptake and presentation to the immune system, potentially leading to improved tumor control. Dendritic cells (DCs) are the most potent cells for antigen uptake, presentation, and stimulation of the immune system. However, it is unclear whether DCs would retain their viability and functional capacity for the requisite trafficking to draining lymph nodes when adoptively transferred in close temporal and anatomic proximity to the site of PDT-induced cytotoxicity. We conducted studies of combined PDT and adoptive DC therapy, "immunophototherapy," in a female, Fisher 344 rat orthotopic mammary tumor model. Using 5-aminolevulinic acid as a pro-drug, we demonstrated kinetically favorable biologic conversion to the photosensitive protoporphyrin IX, appropriate trafficking of syngeneic bone marrow-derived DCs injected into PDT-treated tumors within 15 min of completion of therapy, and improved survival over either modality alone. These data indicate that DCs rapidly administered into the site of PDT retain their viability and functional status, supporting the further evaluation of immunophototherapy strategies.

Involvement of caspase 8 in apoptosis induced by ultrasound-activated hematoporphyrin in sarcoma 180 cells in vitro

OBJECTIVE

Sonodynamic therapy (SDT), a novel and promising cancer therapy that uses a combination of ultrasound and hematoporphyrin, can induce apoptosis in some cancer cells. However, the mechanism(s) of SDT-induced cell apoptosis is not well understood. This study investigated SDT-induced apoptosis in sarcoma 180 cells.

METHODS

Cell suspension were treated by 1.75-MHz continuous focused ultrasound in the presence of hematoporphyrin for 3 minutes, and apoptosis was assessed by flow cytometry, scanning electron microscopy, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling, confocal microscopy, and apoptosis-related protein analysis.

RESULTS

DNA breaks, apoptotic bodies, and cleaved poly (adenosine triphosphate-ribose) polymerase were observed 1 hour after SDT. By using laser-scanning confocal microscopy, we found that the Fas-associated death domain and caspase 8 translocated from the cytoplasm to the plasma membrane. Activities of caspase 8 and caspase 3 were detected by an immunohistochemical assay. The results suggested that SDT led to activation of caspase 8, which in turn activated downstream caspase 3. In addition, Z-Ile-Glu-Thr-Asp-fluoromethylketone, a specific inhibitor for caspase 8, was used to confirm the effect of caspase 8 in apoptosis.

CONCLUSIONS

Our data primarily show that SDT can induce apoptosis in sarcoma 180 cells in vitro, and caspase 8 may play an important role in SDT-induced apoptosis.

Photodynamic activity of BAM-SiPc, an unsymmetrical bisamino silicon(IV) phthalocyanine, in tumour-bearing nude mice

BACKGROUND AND PURPOSE

Ever since the discovery of photodynamic therapy, there has been a continuous search for more potent photosensitizers. Towards that end, we have synthesized a number of novel phthalocyanine derivatives. The unsymmetrical bisamino silicon(IV) phthalocyanine BAM-SiPc is one of the most potent compounds. In in vitro cell culture, it exhibits high phototoxicity against a number of cancer cell lines.

EXPERIMENTAL APPROACH

In the present investigation, the in vivo effect of BAM-SiPc was studied in the tumour-bearing nude mice model. The biodistribution of BAM-SiPc was followed to evaluate its tumour selectivity and rate of clearance. The tumour volume in the hepatocarcinoma HepG2- and the colorectal adenocarcinoma HT29-bearing nude mice was measured after photodynamic therapy. The level of intrinsic toxicity induced was also investigated. Finally, the metabolism of BAM-SiPc in the 'normal' WRL68 liver cells and the hepatocarcinoma HepG2 cells was compared.

KEY RESULTS

The results not only showed significant tumour regression of HepG2 and growth inhibition of HT29 in the tumour-bearing nude mice, but also no apparent hepatic or cardiac injury with the protocol used. Histological analyses showed that apoptosis was induced in the solid tumour. BAM-SiPc could be metabolized by WRL68 liver cells but not by the hepatocarcinoma HepG2 cells. Unfortunately, BAM-SiPc did not show any specific targeting towards the tumour tissue.

CONCLUSIONS AND IMPLICATIONS

The efficiency of BAM-SiPc in inhibiting tumour growth makes it a good candidate for further evaluation. Enhancement of its uptake in tumour tissue by conjugation with biomolecules is currently under investigation.

Photophysics and photochemistry of photodynamic therapy: fundamental aspects

Photodynamic therapy (PDT) is a treatment modality for cancer and various other diseases. The clinical protocol covers the illumination of target cells (or tissue), which have been loaded with a photoactive drug (photosensitizer). In this review we describe the photophysical and primary photochemical processes that occur during PDT. Interaction of light with tissue results in attenuation of the incident light energy due to reflectance, absorption, scattering, and refraction. Refraction and reflection are reduced by perpendicular light application, whereas absorption can be minimized by the choice of a photosensitizer that absorbs in the far red region of the electromagnetic spectrum. Interaction of light and the photosensitizer can result in degradation, modification or relocalization of the drug, which differently affect the effectiveness of PDT. Photodynamic therapy itself, however, employs the light-induced chemical reactions of the activated photosensitizer (triplet state), resulting in the production of various reactive oxygen species, amongst them singlet oxygen as the primary photochemical product. Based on these considerations, the properties of an ideal photosensitizer for PDT are discussed. According to the clinical experience with PDT, it is proposed that the innovative concept of PDT is most successfully implemented into the mainstream of anticancer therapies by following an application-, i.e. tumor-centered approach with a focus on the actual clinical requirements of the respective tumor type.

Photodynamic therapy: basic principles and potential uses for the veterinary ophthalmologist

Photodynamic therapy (PDT) involves the use of photochemical reactions mediated through the interaction of photosensitizing agents, light and oxygen. PDT, while now commonly used in physician ophthalmology and oncology, is uncommonly used for the veterinary ophthalmic patient. It is an emerging new therapy in veterinary ophthalmology for the treatment of periocular tumors. This article reviews the basic principles of PDT to provide the veterinary ophthalmologic community with a succinct reference for this emerging treatment modality in our field.

CHAINED LIGHTNING

RADIOSURGERY IS FUNDAMENTALLY the harnessing of energy and delivering it to a focal target for a therapeutic effect. The evolution of radiosurgical technology and practice has served toward refining methodologies for better conformal energy delivery. In the past, this has resulted in developing strategies for improved beam generation and delivery. Ultimately, however, our current instrumentation and treatment modalities may be approaching a practical limit with regard to further optimizing energy containment.

In looking forward, several strategies are emerging to circumvent these limitations and improve conformal radiosurgery. Refinement of imaging techniques through functional imaging and nanoprobes for cancer detection may benefit lesion localization and targeting. Methods for enhancing the biological effect while reducing radiation-induced changes are being examined through dose fractionation schedules. Radiosensitizers and photosensitizers are being investigated as agents for modulating the biological response of tissues to radiation and alternative energy forms. Discovery of new energy modalities is being pursued through development of microplanar beams, free electron lasers, and high-intensity focused ultrasound. The exploration of these future possibilities will provide the tools for radiosurgical treatment of a broader spectrum of diseases for the next generation.

Intraperitoneal photodynamic therapy for an ovarian cancer ascite model in Fischer 344 rat using hematoporphyrin monomethyl ether

With limited treatment options, intraperitoneal spread of ovarian cancer is a common problem leading to high morbidity. Intraperitoneal photodynamic therapy combined with debulking surgery to treat residual disease is an alternative choice for clinicians. Hematoporphyrin monomethyl ether (HMME) is a promising second-generation photosensitizer developed in China. Our study was designed to investigate the phototoxicity of HMME on ovarian cancer. NuTu-19, a cell line derived from adenocarcinoma of Fischer 344 rat, and its allogeneic graft ascites tumor model was used in this study. HMME was confirmed to be localized in cytolysosome, and HMME-based photosensitization induced direct necrosis as well as mitochondria damage. The photocytotoxicity of HMME was both light- and drug dose-dependent and no significant dark cytotoxicity was observed in NuTu-19 cells. With the ascite tumor-bearing Fischer 344 rat model, HMME-based intraperitoneal photodynamic therapy was proved to be useful in improving the prognosis of ovarian cancer. Thus, this study provides evidence that HMME-based photodynamic therapy is an effective adjuvant therapy for ovarian cancer.

Local photodynamic therapy for equine squamous cell carcinoma: evaluation of a novel treatment method in a murine model

The objective of this study was to evaluate the effect of local photodynamic therapy (PDT) with verteporfin on tumor growth inhibition of squamous cell carcinoma (SCC) in a murine model. SCC was implanted in 85 nude mice by subcutaneous injection of A-431 SCC cells. Treatment groups (10 mice/group) received an intra-tumoral injection of verteporfin dissolved in dimethyl sulfoxide (DMSO) or 5% dextrose solution at a dose of 0.01 or 0.1mg/cm3. Controls received only solvent, or no injectate. All groups received identical light illumination (100J/cm2). Relative change in tumor volume (RCTV) at day 30 was compared between groups using the Wilcoxon rank sum test (P< 0.05). Local PDT with verteporfin at a dose of 0.1mg/cm3 resulted in significantly lower RCTV at day 30 compared to controls. Choice of solvent (DMSO versus D5W) did not affect the results. Local PDT may be an effective adjunctive therapy for the treatment of periocular equine SCC.

Functionalized fullerenes mediate photodynamic killing of cancer cells: Type I versus Type II photochemical mechanism

Photodynamic therapy (PDT) employs the combination of nontoxic photosensitizers (PS) and harmless visible light to generate reactive oxygen species (ROS) and kill cells. Most clinically studied PS are based on the tetrapyrrole structure of porphyrins, chlorines, and related molecules, but new nontetrapyrrole PS are being sought. Fullerenes are soccer-ball shaped molecules composed of 60 or 70 carbon atoms and have attracted interest in connection with the search for biomedical applications of nanotechnology. Fullerenes are biologically inert unless derivatized with functional groups, whereupon they become soluble and can act as PS. We have compared the photodynamic activity of six functionalized fullerenes with 1, 2, or 3 hydrophilic or 1, 2, or 3 cationic groups. The octanol-water partition coefficients were determined and the relative contributions of Type I photochemistry (photogeneration of superoxide in the presence of NADH) and Type II photochemistry (photogeneration of singlet oxygen) were studied by measurement of oxygen consumption, 1270-nm luminescence and EPR spin trapping of the superoxide product. We studied three mouse cancer cell lines: (J774, LLC, and CT26) incubated for 24 h with fullerenes and illuminated with white light. The order of effectiveness as PS was inversely proportional to the degree of substitution of the fullerene nucleus for both the neutral and the cationic series. The monopyrrolidinium fullerene was the most active PS against all cell lines and induced apoptosis 4-6 h after illumination. It produced diffuse intracellular fluorescence when dichlorodihydrofluorescein was added as an ROS probe, suggesting a Type I mechanism for phototoxicity. We conclude that certain functionalized fullerenes have potential as novel PDT agents and phototoxicity may be mediated both by superoxide and by singlet oxygen.

Survivin, a member of the inhibitor of apoptosis family, is induced by photodynamic therapy and is a target for improving treatment response

We observed that photodynamic therapy (PDT) induces the expression and phosphorylation of the inhibitor of apoptosis (IAP) protein survivin in murine and human cancer cells and tumors. Survivin inhibits caspase-9, blocks apoptosis, and is associated with resistance to chemotherapy and radiation. Survivin is a client protein for the 90-kDa heat shock protein (Hsp-90), and the binding of survivin to Hsp-90 assists in the maturation, proper folding, assembly, and transport of this IAP protein. A derivative of the antibiotic geldanamycin, 17-allylamino-17-demethoxygeldanamycin (17-AAG), interferes with proper binding of client proteins, such as survivin, to Hsp-90 and leads to misfolding of client proteins, ubiquination, and proteasome degradation. We hypothesized that PDT efficacy may be reduced by treatment-mediated expression and phosphorylation of survivin, and therefore, targeting the survivin pathway could increase PDT responsiveness. To address this hypothesis, we examined cellular and molecular responses following exposure to PDT, 17-AAG, and the combination of PDT plus 17-AAG in human BT-474 breast cancer cells using Photofrin and NPe6 as photosensitizers. Cells treated with the combination of PDT and 17-AAG exhibited decreased expression of the Hsp-90 client proteins phosphorylated survivin, phosphorylated Akt, and Bcl-2. The decreased expression of these client proteins was accompanied by higher apoptotic indexes and increased cytotoxicity. To confirm a specific role for survivin in modulating PDT, we used a human melanoma cell line, YUSAC2/T34A-C4, stably transfected with an inducible dominant-negative survivin gene under the control of a tetracycline-regulated (tet-off) promoter. PDT treatment of melanoma cells expressing the dominant-negative survivin resulted in increased cleavage of the caspase substrate poly(ADP-ribose) polymerase, apoptosis, and cytotoxicity when compared with results following PDT of the same melanoma cell line expressing wild-type survivin. These results show for the first time that targeting survivin and possibly other Hsp-90 client proteins improves in vitro PDT responsiveness and suggest that manipulation of the antiapoptotic pathway maintained by survivin may enhance PDT-mediated cancer therapy.

Photodynamic therapy for pancreatic cancer

OBJECTIVES

This study examined the status of photodynamic therapy (PDT) in the treatment of cancers of the pancreas.

METHODS

Original and review articles, editorials, and case reports published primarily in English and listed in Medline/ISI up to October 2006 or identified by a manual search have been reviewed in an attempt to provide a comprehensive overview of the mechanisms of PDT action and clinical application of PDT in the treatment of pancreatic cancers.

RESULTS

Photodynamic therapy represents a novel treatment of pancreatic malignancy; it produces local necrosis of tissue with light after administration of a photosensitizing agent. Evidences from in vivo and in vitro results have shown that PDT significantly decreases pancreatic cancer cell growth, destroys pancreatic carcinoma, and prolongs the survival of patients with unresectable pancreatic malignancy, and also show that PDT has disadvantages and limitations for the treatment of pancreatic cancer.

CONCLUSIONS

Photodynamic therapy can be an effective treatment of patients with pancreatic cancer, but more extensive preclinical and clinical trials are needed for further improvement in the clinical application of PDT, especially in avoidance of complications during PDT.

Photodynamic therapy with the phthalocyanine photosensitizer Pc 4: the case experience with preclinical mechanistic and early clinical-translational studies

Photodynamic therapy (PDT) is emerging as a promising non-invasive treatment for cancers. PDT involves either local or systemic administration of a photosensitizing drug, which preferentially localizes within the tumor, followed by illumination of the involved organ with light, usually from a laser source. Here, we provide a selective overview of our experience with PDT at Case Western Reserve University, specifically with the silicon phthalocyanine photosensitizer Pc 4. We first review our in vitro studies evaluating the mechanism of cell killing by Pc 4-PDT. Then we briefly describe our clinical experience in a Phase I trial of Pc 4-PDT and our preliminary translational studies evaluating the mechanisms behind tumor responses. Preclinical work identified (a) cardiolipin and the anti-apoptotic proteins Bcl-2 and Bcl-xL as targets of Pc 4-PDT, (b) the intrinsic pathway of apoptosis, with the key participation of caspase-3, as a central response of many human cancer cells to Pc 4-PDT, (c) signaling pathways that could modify apoptosis, and (d) a formulation by which Pc 4 could be applied topically to human skin and penetrate at least through the basal layer of the epidermis. Clinical-translational studies enabled us to develop an immunohistochemical assay for caspase-3 activation, using biopsies from patients treated with topical Pc 4 in a Phase I PDT trial for cutaneous T-cell lymphoma. Results suggest that this assay may be used as an early biomarker of clinical response.

Catalytic therapy of cancer with porphyrins and ascorbate

Catalytic therapy (CT) is a cancer treatment modality based on the generation of reactive oxygen species (ROS) using a combination of substrate molecules and a catalyst. The most frequently used substrate and catalyst pair is ascorbate/Co phthalocyanine (PcCo). In the present study, porphyrins containing transition metal ions as catalysts in place of PcCo were studied. Porphyrins that are expected to be as efficient as phthalocyanines, but may have fewer side effects, were analyzed. ROS production through the combined use of ascorbate and porphyrins decreased the number of breast cancer tumor cells by 20-40% after a single in vitro treatment, as compared to control cells. Treatment with ascorbate in conjunction with porphyrins stimulated apoptosis and disrupted the cell cycle. These treatments enhanced apoptosis by 20-40% when compared to treatments with ascorbate and porphyrins. In addition, the number of cells accumulating in the sub G0/G1 stage of the cell cycle increased from 3- to 10-fold, potentially reflecting that the treatment was highly effective in inducing DNA damage in the tumor cells, suggesting that porphyrins may be beneficial as a CT catalyst in the treatment of cancer.