Cellular distribution and phototoxicity of benzoporphyrin derivative and Photofrin

Photodynamic therapy by lysosomal-targeted drug delivery using talaporfin sodium incorporated into inactivated virus particles

Background

Photodynamic therapy (PDT), a minimally invasive cancer treatment involving the activation of photosensitizer by a specific wavelength of light, is considered to be a promising treatment option for drug-resistant prostate cancer. Hemagglutinating virus of Japan envelope (HVJ-E) has the potential to serve as a highly effective cancer therapy through selective drug delivery and enhancement of the anti-tumor immune response.

Objectives

To improve therapeutic efficacy and selective accumulation of photosensitizer into tumor cells, we developed a novel photosensitizer, Laserphyrin^®-HVJ-E (L-HVJ-E), by incorporating talaporfin sodium (Laserphyrin^®, Meiji Seika Pharma) into HVJ-E.

Materials and Methods

The therapeutic effect of PDT with Laserphyrin^® or L-HVJ-E was evaluated in the human prostate cancer cell line PC-3 in vitro. The subcellular localizations of Laserphyrin^® and L-HVJ-E were observed by confocal microscopy. Apoptosis or necrosis following PDT was detected by annexin V-fluorescein/propidium iodide double staining.

Results

The cytotoxic effect of Laserphyrin^®- and L-HVJ-E-mediated PDT were determined by evaluating cell survival rate and production of reactive oxygen species. The cytotoxicity of L-HVJ-E-mediated PDT was dependent on drug concentration and light dose. Laserphyrin^® and L-HVJ-E gradually entered cells as incubation time increased, and both agents tended to be distributed in lysosomes rather than mitochondria. Time and dose dependent increase in ROS production was observed, and induction of both apoptotic and necrotic cell death was confirmed.

Conclusions

Laserphyrin^® and L-HVJ-E were distributed mainly in lysosomes and induced cell death by both apoptosis and necrosis. Furthermore, L-HVJ-E-mediated PDT effectively killed cultured PC-3 cells and exerted higher photocytotoxicity than Laserphyrin^®-mediated PDT.

A threshold dose distribution approach for the study of PDT resistance development: A threshold distribution approach for the study of PDT resistance

Photodynamic therapy (PDT) is a technique with well-established principles that often demands repeated applications for sequential elimination of tumor cells. An important question concerns the way surviving cells from a treatment behave in the subsequent one. Threshold dose is a core concept in PDT dosimetry, as the minimum amount of energy to be delivered for cell destruction via PDT. Concepts of threshold distribution have shown to be an important tool for PDT results analysis in vitro. In this study, we used some of these concepts for demonstrating subsequent treatments with partial elimination of cells modify the distribution, which represents an increased resistance of the cells to the photodynamic action. HepG2 and HepaRG were used as models of tumor and normal liver cells and a protocol to induce resistance, consisted of repeated PDT sessions using Photogem® as a photosensitizer, was applied to the tumor ones. The response of these cells to PDT was assessed using a standard viability assay and the dose response curves were used for deriving the threshold distributions. The changes in the distribution revealed that the resistance protocol effectively eliminated the most sensitive cells. Nevertheless, HepaRG cell line was the most resistant one among the cells analyzed, which indicates a specificity in clinical applications that enables the use of high doses and drug concentrations with minimal damage to the surrounding normal tissue.

Photodynamic effects of zinc oxide nanowires in skin cancer and fibroblast

Cytotoxic effects of zinc oxide (ZnO) nanomaterials, individual and conjugated with a photosensitizer (protoporphyrin IX), were studied in the presence and absence of ultraviolet light exposure (240 nm of light wavelength for a very short time exposure) in cell cultures of human normal and cancerous skin models. Zinc Oxide nanowires (ZnO NWs) were grown on the capillary tip and conjugated with protoporphyrin IX (PpIX). This coated tip was used as tool/pointer for intracellular drug delivery protocol in suggested normal as well as carcinogenic cellular models. After true delivery of optimal drug, the labelled biological model was irradiated with UV-A, which led to a loss of mitochondrial membrane potential, as tested by neutral red assay (NRA).

Evaluation of verteporfin pharmakokinetics--redefining the need of photosensitizers in ophthalmology

INTRODUCTION

The benzoporphyrine derivative verteporfin has lost its importance to the treatment of the most frequent neovascular eye diseases. Nevertheless, it is still mandatory to define the remaining applications, role, and potential of verteporfin in ocular photodynamic therapy (PDT), including the dosages of administration, effectiveness, and safety profile.

AREAS COVERED

Although verteporfin PDT has forfeited the first-line status and value of treating subfoveal choroidal neovascularization (CNV) due to age-related macular degeneration or pathologic myopia, the treatment remains the standard of care for choroidal haemangioma and polypoidal choroidal vasculopathy. PDT is effective in less pigmented choroidal melanoma as well as in retinal vascular proliferations and retinal angioma. Verteporfin was granted the orphan drug designation for the treatment of chronic or recurrent central serous chorioretinopathy (CSC).

EXPERT OPINION

Evidence-based data regarding optimized parameters (low fluence, reduced dose, fractionated irradiation) adapted to the treated diseases (target structure, dosimetry, blood supply) are scarce. Prospective and large clinical trials are missing, although the scientific community agrees on the fact that the standard treatment protocol does not necessarily provide the optimal efficacy to the specific disease or individual patient. Within the reviewed indications, the adverse effect profile is favorable compared with other therapies.

New sulfonamide and sulfonic ester porphyrins as sensitizers for photodynamic therapy

New sulfonamide and sulfonic ester porphyrins were prepared and their in vitro characteristics as sensitizers for photodynamic therapy were assessed. Fluorescence spectra were characterised by two main peaks, located between 650-680 nm and 705-740 nm, respectively. Some of these new porphyrins (three out of nine) showed good photodynamic properties in the in vitro assays. In the absence of light, these porphyrins are not toxic. With 50 J.cm−2 illumination light (514 nm) they induced mortality in 50% of HT29 cells with 2 to 4.5 μg/ml. Comparison of in vitro phototoxic efficacy of these three compounds with other photosensitizers already described confirms interest in their phototoxic properties.

Bax is essential for Drp1-mediated mitochondrial fission but not for mitochondrial outer membrane permeabilization caused by photodynamic therapy

Bcl-2 family proteins are critical for the regulation of apoptosis, with the pro-apoptotic members Bax essential for the release of cytochrome c from mitochondria in many instances. However, we found that Bax was activated after mitochondrial depolarization and the completion of cytochrome c release induced by photodynamic therapy (PDT) with the photosensitizer Photofrin in human lung adenocarcinoma cells (ASTC-a-1). Besides, knockdown of Bax expression by gene silencing had no effect on mitochondrial depolarization and cytochrome c release, indicating that Bax makes no contribution to mitochondrial outer membrane permeabilization (MOMP) following PDT. Further study revealed that Bax knockdown only slowed down the speed of cell death induced by PDT, indicating that Bax is not essential for PDT-induced apoptosis. The fact that Bax knockdown totally inhibited the mitochondrial accumulation of dynamin-related protein (Drp1) and Drp1 knockdown attenuated cell apoptosis suggest that Bax can promote PDT-induced apoptosis through promoting Drp1 activation. Besides, Drp1 knockdown also failed to inhibit PDT-induced cell death finally, indicating that Bax-mediated Drp1's mitochondrial translocation is not essential for PDT-induced cell apoptosis. On the other hand, we found that protein kinase Cδ (PKCδ), Bim L and glycogen synthase kinase 3β (GSK3β) were activated upon PDT treatment and might contribute to the activation of Bax under the condition. Taken together, Bax activation is not essential for MOMP but essential for Drp1-mediated mitochondrial fission during the apoptosis caused by Photofrin-PDT.

Treatment of canine osseous tumors with photodynamic therapy: a pilot study

Photodynamic therapy uses nonthermal coherent light delivered via fiber optic cable to locally activate a photosensitive chemotherapeutic agent that ablates tumor tissue. Owing to the limitations of light penetration, it is unknown whether photodynamic therapy can treat large osseous tumors. We determined whether photodynamic therapy can induce necrosis in large osseous tumors, and if so, to quantify the volume of treated tissue. In a pilot study we treated seven dogs with spontaneous osteosarcomas of the distal radius. Tumors were imaged with MRI before and 48 hours after treatment, and the volumes of hypointense regions were compared. The treated limbs were amputated immediately after imaging at 48 hours and sectioned corresponding to the MR axial images. We identified tumor necrosis histologically; the regions of necrosis corresponded anatomically to hypointense tissue on MRI. The mean volume of necrotic tissue seen on MRI after photodynamic therapy was 21,305 mm(3) compared with a pretreatment volume of 6108 mm(3). These pilot data suggest photodynamic therapy penetrates relatively large canine osseous tumors and may be a useful adjunct for treatment of bone tumors.

The effect of photodynamic therapy on squamous cell carcinoma in a murine model: evaluation of time between intralesional injection to laser irradiation

Successful treatment of naturally occurring periocular squamous cell carcinoma (SCC) in horses with photodynamic therapy (PDT) has been performed by injecting residual tumor with verteporfin and applying laser irradiation immediately following injection. This study used a murine model to evaluate the influence of time between intralesional injection of verteporfin to laser irradiation on tumor growth inhibition with PDT. Mice were randomized into six groups (n=10/group). Each tumor was injected with either 0.1mg/cm(3) of verteporfin (Tx) or 5% dextrose in water (C). Tx and C groups 1, 2, and 3 were irradiated at 1, 30, and 180min after injection. Wilcoxon-rank sum test (P< or =0.05) was performed to determine the relative change in tumor volume (RCTV) between groups. Statistical significance was demonstrated between treatment groups. Although verteporfin-PDT treated mice in Tx1 and Tx2 demonstrated a lower RCTV compared to C1 and C2 mice, the differences were not statistically significant.

Intracellular localization and concentration as well as photodynamic effects of benzoporphyrin derivative monoacid ring A in four types of rodent tumor cells

The relative sensitivities of different tumor cells to photodynamic therapy (PDT) with benzoporphyrin derivative monoacid ring A (BPD-MA) were compared in the four tumor cells. A good correlation was observed between the cell survival at 0.1 microg/ml of BPD-MA and sensitizer uptake/10(6) cells (r = -0.99) or the plating efficiency of cells (r = 0.99). At 3 h after the irradiation, a significant difference was observed in the proportion of apoptotic cells among the four tumor cells (p = 0.024). In conclusion, cell responses to PDT depend on the several factors such as the cell line, photosensitizer dose, and fluence.

Mitochondrion-targeted photosensitizer enhances the photodynamic effect-induced mitochondrial dysfunction and apoptosis

Recently, the mitochondrion has been considered as a novel pharmacological target for anticancer therapy due to its crucial role involved in arbitrating cell apoptosis. We have previously demonstrated that 488-nm laser irradiation induced a specific mitochondrial reactive oxygen species (mROS) formation and apoptotic death. In this study, we used a second generation of photosensitizers, the benzoporphyrin-derivative monoacid ring A (BPD-MA). We investigated specifically mechanisms at the mitochondrial level for BPD-MA coupled with 690-nm laser irradiation, the photodynamic effect (PDE) of BPD-MA, using conventional and laser scanning imaging microscopy in intact C6 glioma cells. We demonstrated BPD-MA localized mainly in the mitochondrial area. The phototoxicity induced by 1-10 J 690-nm laser irradiation was minor as compared to that induced by 488-nm laser irradiation. Unlike other mitochondrion-targeted photosensitizers, the dark toxicity induced by BPD-MA (0.05-5 mg/mL, effective doses used for the PDE) was relatively low. Nevertheless, the PDE of BPD-MA using 0.5 mg/mL coupled with 5J 690-nm irradiation induced profound and rapid (< 1 min) mitochondrial swelling, mROS formation, and severe plasma membrane blebbing as compared to that induced by 488-nm laser irradiation (< 10 min). Later, the PDE of BPD-MA resulted in positive propidium iodide cell-death stain and positive TUNEL apoptotic nuclear stain and DNA laddering. Finally, the PDT of BPD-MA also instantaneously promoted the mitochondrion to diminish its covalent binding with a mitochondrial marker, MitoTracker Green. We conclude that the PDT of BPD-MA targeted primarily and compellingly the mitochondrion to induce effective mitochondria-mediated apoptosis and thus may serve as a powerful photosensitizer for clinical cancer therapy.

Purging of murine erythroblastic leukemia by ZnPcS2P2-based-photodynamic therapy

A key point for successful transplantation of autologous hematopoietic stem cells in the treatment of leukemia is the purging technique, of which photodynamic therapy (PDT) proved effective and promising. The aim of this study was to evaluate the purging effect of a novel amphipathic photosensitizer, di-sulfo-di-phthalimidomethyl phthalolcyanine zinc (ZnPcS2P2)-based PDT (ZnPcS2P2-PDT) on murine erythroblastic leukemic EL9611 cells. Bone marrow cells (BMC), harvested from normal BALB/c mice, were contaminated with variable EL9611 cells. Cell suspensions were incubated with 4 microg/ml ZnPcS2P2 for 5 h and then exposed to 2.1 J/cm2 irradiation by a semiconductor laser 670 nm. Lethally irradiated recipient BALB/c mice (7 Gy) received syngeneic bone marrow transplantation with purged or nonpurged cell mixtures of 10(7) BMC contaminated with variable numbers (10(2)-10(5)) of EL9611 cells. All of the irradiated controls died due to sepsis. All of the mice injected with nonpurged cell mixtures developed leukemia and died, whereas the mice transplanted with ZnPcS2P2-PDT-treated mixtures had a longer survival time, and the fewer leukemic cells there were in the cell mixtures, the higher the leukemia-free survival rate. We conclude that ZnPcS2P2-PDT could purge leukemic cells from bone marrow autografts but could retain sufficient progenitor cells for the hematopoietic activity.

Photodynamic therapy for the treatment of metastatic lesions in bone: studies in rat and porcine models

This study represents the first reported use of photodynamic therapy (PDT) for metastatic bone lesions and specifically, as a treatment for spinal metastases. A model of bone metastasis in rat confirmed the efficacy of benzoporphyrin derivative-monoacid-mediated PDT for treating lesions within the spine and appendicular bone. Fluorimetry confirmed the selective accumulation of drug into the tumor(s) at 3 h post-injection. 48 h post-light delivery into the vertebral body of the rat spine loss of bioluminescent signal and histological analyses of sectioned spine confirmed MT-1 tumor cell kill in vivo as previously confirmed in vitro using an established cell viability assay. Porcine vertebrae provided a model comparable to that of human for light propagation and PDT response. Histological examination of vertebrae 48 h post-PDT revealed a necrotic radius of 0.6 cm with an average fluence rate of 4.3 mW/cm2. Non-necrotic tissue damage was evident up to 2 cm out from the treatment fiber. Results support the application of PDT to the treatment of primary or metastatic lesions within bone.

Verteporfin : a review of its use in the management of subfoveal choroidal neovascularisation

Verteporfin (Visudyne) therapy (photodynamic therapy with intravenous liposomal verteporfin) is the first treatment to effectively prevent the loss of visual acuity in patients with subfoveal choroidal neovascularisation (CNV) secondary to age-related macular degeneration (AMD), pathological myopia or presumed ocular histoplasmosis syndrome (POHS). In adult patients with classic subfoveal CNV or occult with no classic subfoveal CNV secondary to AMD, or subfoveal CNV secondary to pathological myopia or POHS, verteporfin therapy slows or prevents loss of visual acuity. In well designed clinical trials, verteporfin therapy was superior to placebo in patients with subfoveal classic-containing CNV and occult with no classic CNV secondary to AMD at 12 and/or 24 months (Treatment of Age-related macular degeneration with Photodynamic therapy [TAP] Investigation and Verteporfin In Photodynamic therapy [VIP-AMD] trial) and in patients with pathological myopia at 12 months (Verteporfin In Photodynamic therapy [VIP-PM] trial). Limited data suggest that verteporfin therapy also prevents loss of visual acuity in patients with subfoveal CNV secondary to POHS. Verteporfin therapy was generally well tolerated in clinical trials; most adverse events were mild to moderate in intensity and transient. The most frequently reported verteporfin therapy-related adverse events (incidence >2%) were visual disturbance, injection-site reactions, photosensitivity reactions and infusion-related back pain. Approximately 5% of patients with occult with no classic subfoveal CNV secondary to AMD reported severe vision decrease within 7 days of treatment in clinical trials; 3 months later, several patients had recovered some of this loss.

CONCLUSION

Photodynamic therapy with verteporfin, the first photosensitiser approved for the treatment of subfoveal CNV, is a well tolerated treatment that stabilises or slows visual acuity loss in adult patients with predominantly classic or occult with no classic subfoveal CNV secondary to AMD, and subfoveal CNV secondary to pathological myopia or POHS. Thus, verteporfin therapy provides a valuable option for the management of these patients for whom treatment options are few, and should be considered as a first-line therapy in these difficult-to-manage conditions.

Biodistribution Assessment of a Lutetium(III) Texaphyrin Analogue in Tumor-bearing Mice Using NIR Fourier-transform Raman Spectroscopy¶

The use of near-infrared (NIR)-excited Fourier-transform (FT) Raman spectroscopy as a technique for evaluating the extent of photosensitizer localization in tumor (human pancreatic adenocarcinomas)-bearing mice has been tested using lutetium(III) texaphyrin analogue Lu-T2B2Tex. The complex was injected subcutaneously in the form of three injections given during the course of 3 days. The kinetics of biodistribution were then followed over a time scale of 1-6 days. The NIR-FT-Raman spectra of tissue samples obtained from the xenographic tumor, muscle, heart, brain, liver, spleen, kidney and blood were recorded and used to identify the presence of Lu-T2B2Tex in these tissues. Five Raman sensitizer markers were used to estimate the relative content of Lu-T2B2Tex in tumor at various postinjection times. UV-Visible (Vis) absorption spectroscopic detection of this sensitizer in tissue extracts was applied as a conventional method. Both spectroscopic methods were in good agreement with each other and confirm that Lu-T2B2Tex localizes well in tumor tissue. Maximal drug content was observed 3 days after the final injection. This time delay seems to be optimal for tumor irradiation in photodynamic therapy.

"Mitochondrial" photochemical drugs do not release toxic amounts of 1O(2) within the mitochondrial matrix space

Previously, we demonstrated that mitochondrial NAD(P)H is the primary target of singlet oxygen (1O(2)) generated by photoactivation of mitochondria-selective rhodamine derivatives. Hence, local NAD(P)H oxidation/fluorescence decrease may be used to reveal the site of intracellular 1O(2) generation. Therefore, in addition to the previously used tetramethylrhodamine methylester (TMRM), 2('),4('),5('),7(')-tetrabromorhodamine 123 bromide (TBRB) and rhodamine 123 (Rho 123), we tested here whether mitochondrial NAD(P)H of cultured hepatocytes is directly oxidized upon irradiation of different "mitochondrial" photosensitizers (Photofrin; protoporphyrin IX; Al(III) phthalocyanine chloride tetrasulfonic acid; meso-tetra(4-sulfonatophenyl)porphine dihydrochloride; Visudyne). In contrast to TMRM and Rho 123, which directly oxidized NAD(P)H upon irradiation, irradiation of intracellular TBRB and the photochemical drugs only indirectly affected mitochondrial NAD(P)H due to loss of mitochondrial integrity. In line with this result only TMRM and Rho 123 exclusively localized within the mitochondrial matrix. Due to these results it is doubtful whether real mitochondrial photosensitizers actually exist among the photochemical drugs applicable/used for photodynamic therapy.

Subcellular localization of Photofrin determines the death phenotype of human epidermoid carcinoma A431 cells triggered by photodynamic therapy: when plasma membranes are the main targets

Photodynamic therapy (PDT) is a kind of photochemo-therapeutic treatment that exerts its effect mainly through the induction of cell death. Distinct types of cell death may be elicited by different PDT regimes. In this study, the mechanisms involved in the death of human epidermoid carcinoma A431 cells triggered by PDT with Photofrin (a clinically approved photosensitizer) were characterized. Photofrin distributes dynamically in A431 cells; the plasma membranes and Golgi complex are the main target sites of Photofrin after a brief (3 h) and prolonged (24 h) incubation, respectively. Cells with differentially localized Photofrin displayed distinct death phenotypes in response to PDT. The effects of PDT on cells with plasma membrane-localized Photofrin were further studied in details. Cells stopped proliferating post PDT at Photofrin dose >7 micro g/ml, and at higher dose (28 micro g/ml) plasma membrane disruption and cell swelling were observed immediately after PDT. Dramatic alterations of several important signaling events were detected in A431 cells post Photofrin-PDT, including (i) immediate formation of reactive oxygen species (ROS), (ii) rapid activation of c-Jun N-terminal kinase, (iii) delayed activation of caspase-3 and cleavage of polyADP-ribose polymerase and p21-activated kinase 2, and (iv) loss of mitochondrial membrane potential. Intriguingly, the characteristics of typical apoptosis such as phosphatidylserine externalization and DNA fragmentation were not detected in the cell death process caused by this PDT regime. In conclusion, our results show that when plasma membranes are the main targets, Photofrin-PDT can lead to instant ROS formation and subsequent activation of downstream signaling events similar to those elicited by many apoptotic stimuli, but the damage of plasma membranes renders the death phenotype more necrosis like.