Comparison of the in vivo efficiency of photofrin II-, mTHPC-, mTHPC-PEG- and mTHPCnPEG-mediated PDT in a human xenografted head and neck carcinoma

Nanoparticle-mediated Photodynamic Therapy as a Method to Ablate Oral Cavity Squamous Cell Carcinoma in Preclinical Models

Photodynamic therapy (PDT) is a tissue ablation technique able to selectively target tumor cells by activating the cytotoxicity of photosensitizer dyes with light. PDT is nonsurgical and tissue sparing, two advantages for treatments in anatomically complex disease sites such as the oral cavity. We have previously developed PORPHYSOME (PS) nanoparticles assembled from chlorin photosensitizer-containing building blocks (∼94,000 photosensitizers per particle) and capable of potent PDT. In this study, we demonstrate the selective uptake and curative tumor ablation of PS-enabled PDT in three preclinical models of oral cavity squamous cell carcinoma (OCSCC): biologically relevant subcutaneous Cal-33 (cell line) and MOC22 (syngeneic) mouse models, and an anatomically relevant orthotopic VX-2 rabbit model. Tumors selectively uptake PS (10 mg/kg, i.v.) with 6-to 40-fold greater concentration versus muscle 24 hours post-injection. Single PS nanoparticle-mediated PDT (PS-PDT) treatment (100 J/cm2, 100 mW/cm2) of Cal-33 tumors yielded significant apoptosis in 65.7% of tumor cells. Survival studies following PS-PDT treatments demonstrated 90% (36/40) overall response rate across all three tumor models. Complete tumor response was achieved in 65% of Cal-33 and 91% of MOC22 tumor mouse models 14 days after PS-PDT, and partial responses obtained in 25% and 9% of Cal-33 and MOC22 tumors, respectively. In buccal VX-2 rabbit tumors, combined surface and interstitial PS-PDT (200 J total) yielded complete responses in only 60% of rabbits 6 weeks after a single treatment whereas three repeated weekly treatments with PS-PDT (200 J/week) achieved complete ablation in 100% of tumors. PS-PDT treatments were well tolerated by animals with no treatment-associated toxicities and excellent cosmetic outcomes.

SIGNIFICANCE

PS-PDT is a safe and repeatable treatment modality for OCSCC ablation. PS demonstrated tumor selective uptake and PS-PDT treatments achieved reproducible efficacy and effectiveness in multiple tumor models superior to other clinically tested photosensitizer drugs. Cosmetic and functional outcomes were excellent, and no clinically significant treatment-associated toxicities were detected. These results are enabling of window of opportunity trials for fluorescence-guided PS-PDT in patients with early-stage OCSCC scheduled for surgery.

Current state of the nanoscale delivery systems for temoporfin-based photodynamic therapy: Advanced delivery strategies

Enthusiasm for photodynamic therapy (PDT) as a promising technique to eradicate various cancers has increased exponentially in recent decades. The majority of clinically approved photosensitizers are hydrophobic in nature, thus, the effective delivery of photosensitizers at the targeted site is the main hurdle associated with PDT. Temoporfin (mTHPC, medicinal product name: Foscan®), is one of the most potent clinically approved photosensitizers, is not an exception. Successful temoporfin-PDT requires nanoscale delivery systems for selective delivery of photosensitizer. Over the last 25 years, the number of papers on nanoplatforms developed for mTHPC delivery such as conjugates, host-guest inclusion complexes, lipid-and polymer-based nanoparticles and carbon nanotubes is burgeoning. However, none of them appeared to be "ultimate". The present review offers the description of different challenges and achievements in nanoparticle-based mTHPC delivery focusing on the synergetic combination of various nano-platforms to improve temoporfin delivery at all stages of biodistribution. Furthermore, the association of different nanoparticles in one nanoplatform might be considered as an advanced strategy allowing the combination of several treatment modalities.

Comparison of Cellular Death Pathways after mTHPC-mediated Photodynamic Therapy (PDT) in Five Human Cancer Cell Lines

One of the most promising photosensitizers (PS) used in photodynamic therapy (PDT) is the porphyrin derivative 5,10,15,20-tetra(m-hydroxyphenyl)chlorin (mTHPC, temoporfin), marketed in Europe under the trade name Foscan^®. A set of five human cancer cell lines from head and neck and other PDT-relevant tissues was used to investigate oxidative stress and underlying cell death mechanisms of mTHPC-mediated PDT in vitro. Cells were treated with mTHPC in equitoxic concentrations and illuminated with light doses of 1.8-7.0 J/cm² and harvested immediately, 6, 24, or 48 h post illumination for analyses. Our results confirm the induction of oxidative stress after mTHPC-based PDT by detecting a total loss of mitochondrial membrane potential (Δψ_m) and increased formation of ROS. However, lipid peroxidation (LPO) and loss of cell membrane integrity play only a minor role in cell death in most cell lines. Based on our results, apoptosis is the predominant death mechanism following mTHPC-mediated PDT. Autophagy can occur in parallel to apoptosis or the former can be dominant first, yet ultimately leading to autophagy-associated apoptosis. The death of the cells is in some cases accompanied by DNA fragmentation and a G₂/M phase arrest. In general, the overall phototoxic effects and the concentrations as well as the time to establish these effects varies between cell lines, suggesting that the cancer cells are not all dying by one defined mechanism, but rather succumb to an individual interplay of different cell death mechanisms. Besides the evaluation of the underlying cell death mechanisms, we focused on the comparison of results in a set of five identically treated cell lines in this study. Although cells were treated under equitoxic conditions and PDT acts via a rather unspecific ROS formation, very heterogeneous results were obtained with different cell lines. This study shows that general conclusions after PDT in vitro require testing on several cell lines to be reliable, which has too often been ignored in the past.

Translating phototherapeutic indices from in vitro to in vivo photodynamic therapy with bacteriochlorins

OBJECTIVE

To compare hydrophilic and lipophilic bacteriochlorin photosensitizers in the photodynamic therapy of cancer, and relate their properties and in vitro phototoxicities to the efficacy of in vivo PDT treatments.

MATERIALS AND METHODS

Photochemical characterization of a hydrophilic bacteriochlorin (F₂ BOH) photosensitizer, and its use in PDT was compared with the performance of a closely related but water-insoluble bacteriochlorin (F₂ BMet or redaporfin). Biodistribution, pharmacokinetics, skin photosensitivity, PDT efficacy and immune responses of two bacteriochlorins were compared. PDT in vitro employed CT26 colon carcinoma cells. BALB/c mice bearing CT26 cells were treated according to a protocol where the illumination of the subcutaneous tumor is performed 15 minute after intravenous administration of the photosensitizer, while it is in the vascular compartment (vascular-PDT).

RESULTS

F₂ BOH has photochemical properties comparable to redaporfin and both are promising photosensitizers for PDT. Although, F₂ BOH is 10 times less phototoxic in vitro than redaporfin, the phototoxicity of F₂ BOH in vascular-PDT is comparable to that of redaporfin. This is consistent with the fact that the vasculature is the main target of vascular-PDT. F₂ BOH-PDT led to long-term cures and stimulation of the immune system.

CONCLUSION

F₂ BOH is soluble in aqueous media, photostable, has a convenient elimination half-life of 44 hours and leads to very low skin photosensitivity one week after administration. F₂ BOH and redaporfin are both very phototoxic in vascular-PDT, but this could not be anticipated from their widely different phototherapeutic indices in vitro. PDT with F₂ BOH enabled long-term cures of BALB/c mice with subcutaneously implanted CT26 tumors, and the cured mice rejected tumor re-inoculation one year after the treatment. Lasers Surg. Med. 50:451-459, 2018. © 2018 Wiley Periodicals, Inc.

Modifications of Porphyrins and Hydroporphyrins for Their Solubilization in Aqueous Media

The increasing popularity of porphyrins and hydroporphyrins for use in a variety of biomedical (photodynamic therapy, fluorescence tagging and imaging, photoacoustic imaging) and technical (chemosensing, catalysis, light harvesting) applications is also associated with the growing number of methodologies that enable their solubilization in aqueous media. Natively, the vast majority of synthetic porphyrinic compounds are not water-soluble. Moreover, any water-solubility imposes several restrictions on the synthetic chemist on when to install solubilizing groups in the synthetic sequence, and how to isolate and purify these compounds. This review summarizes the chemical modifications to render synthetic porphyrins water-soluble, with a focus on the work disclosed since 2000. Where available, practical data such as solubility, indicators for the degree of aggregation, and special notes for the practitioner are listed. We hope that this review will guide synthetic chemists through the many strategies known to make porphyrins and hydroporphyrins water soluble.

Targeted photodynamic therapy in head and neck squamous cell carcinoma: heading into the future

The aim of this article is to give an insight into the future of photodynamic therapy (PDT) in head and neck squamous cell carcinoma (HNSCC). Through the combination of a photosensitizing agent with light and oxygen, PDT produces highly cytotoxic reactive oxygen species leading to selective tumor eradication. PDT is an attractive treatment for focal therapy of localized tumors, especially in the case of unresectable tumors. In HNSCC, over 1500 patients have been treated by PDT, and the majority of them responded quite favorably to this treatment. However, the non-negligible photosensitization of healthy tissue is a major limitation for the clinical application of PDT. Improvement in tumor selectivity is the main challenge that can be taken up by the use of a new generation of photosensitizing nanoparticles. Passive targeting, by using functionalised nanocarriers to target to overexpressed transmembrane receptors afford attractive solutions. To this day, epidermal growth factor receptor (EGFR) remains the only validated molecular target for HNSCC, and photosensitizer immunoconjugates to EGFR have been developed for the intracellular delivery of photosensitizing agents. Depending on coordinated research between biomarkers, specific ligands, and photosensitizers, similar approaches could be rapidly developed. In addition, some photosensitizers hold high fluorescence yield and therefore could emerge as theranostic agents.

Fluorescence localization and kinetics of mTHPC and liposomal formulations of mTHPC in the window-chamber tumor model

BACKGROUND AND OBJECTIVE

Foslip® and Fospeg® are liposomal formulations of the photosensitizer mTHPC, intended for use in Photodynamic Therapy (PDT) of malignancies. Foslip consists of mTHPC encapsulated in conventional liposomes, Fospeg consists of mTHPC encapsulated in pegylated liposomes. Possible differences in tumor fluorescence and vasculature kinetics between Foslip, Fospeg, and Foscan® were studied using the rat window-chamber model.

MATERIAL AND METHODS

In 18 rats a dorsal skin fold window chamber was installed and a mammary carcinoma was transplanted in the subcutaneous tissue. The dosage used for intravenous injection was 0.15 mg/kg mTHPC for each formulation. At seven time-points after injection (5 minutes to 96 hours) fluorescence images were made with a CCD. The achieved mTHPC fluorescence images were corrected for tissue optical properties and autofluorescence by the ratio fluorescence imaging technique of Kascakova et al. Fluorescence intensities of three different regions of interest (ROI) were assessed; tumor tissue, vasculature, and surrounding connective tissue.

RESULTS

The three mTHPC formulations showed marked differences in their fluorescence kinetic profile. After injection, vascular mTHPC fluorescence increased for Foslip and Fospeg but decreased for Foscan. Maximum tumor fluorescence is reached at 8 hours for Fospeg and at 24 hours for Foscan and Foslip with overall higher fluorescence for both liposomal formulations. Foscan showed no significant difference in fluorescence intensity between surrounding tissue and tumor tissue (selectivity). However, Fospeg showed a trend toward tumor selectivity at early time points, while Foslip reached a significant difference (P < 0.05) at these time points.

CONCLUSIONS

Our results showed marked differences in fluorescence intensities of Fospeg, Foslip, and Foscan, which suggest overall higher bioavailability for the liposomal formulations. Pegylated liposomes seemed most promising for future application; as Fospeg showed highest tumor fluorescence at the earlier time points.

Temoporfin (Foscan®, 5,10,15,20-tetra(m-hydroxyphenyl)chlorin)--a second-generation photosensitizer

This review traces the development and study of the second-generation photosensitizer 5,10,15,20-tetra(m-hydroxyphenyl)chlorin through to its acceptance and clinical use in modern photodynamic (cancer) therapy. The literature has been covered up to early 2011.

Synthesis and in vitro studies of biodegradable modified chitosan nanoparticles for photodynamic treatment of cancer

The main aim of this research is to study the in vitro photocytotoxicity and cellular uptake of biodegradable polymeric nanoparticles loaded with photosensitizer mTHPP. As the first part of a continued research on conversion of N-sulfonato-N,O-carboxymethylchitosan (NOCCS) to useful biopolymer-based materials, large numbers of carboxylic functional groups were introduced onto NOCCS by grafting with polymethacrylic acid (PMAA). The free radical graft copolymerization was carried out at 70°C, bis-acrylamide as a cross-linking agent and persulfate as an initiator. These results show that the nanoparticles have high loading capacity and stability. These nanoparticles are suitable as carriers for photodynamic therapy in vivo.

Photodynamic therapy using an anti-EGF receptor antibody complexed with verteporfin nanoparticles: a proof of concept study

Photodynamic therapy (PDT) is a noninvasive optical treatment method in which the topical or systemic delivery of photosensitizing drugs is followed by irradiation with broadband red light. Coupling photosensitizers with a specific antibody may allow this approach to target specific cancers. This study determines the antitumor efficacy of coupling verteporfin (Visudyne(®)), a hydrophobic polyporphryin oligomer, with an antiepidermal growth factor receptor (anti-EGFR) antibody. Poly[2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate-co-p-nitrophenylcarbonyloxyethyl methacrylate] (PMBN) was conjugated with an anti-EGFR antibody and mixed with verteporfin (verteporfin-PMBN-antibody complex). Tumor-bearing mice were intravenously injected with the verteporfin-PMBN-antibody complex or verteporfin plus PMBN without the antibody. Irradiation was conducted at 640 nm with a dose of 75 J/cm(2). The fluorescence intensity in A431 cells in vitro was threefold higher after exposure to verteporfin-PMBN-antibody complex than after exposure to verteporfin-PMBN. In A431 tumor-bearing mice, the intratumor concentration of verteporfin was 9.4 times higher than that of the skin, following administration of the verteporfin-PMBN-antibody complex. Tumor size significantly decreased within 8 days in mice treated with verteporfin-PMBN-antibody complex compared with those treated with verteporfin-PMBN. PDT using a PMBN-verteporfin-antibody complex offers a promising anticancer therapy.

Comparison of intracellular accumulation and cytotoxicity of free mTHPC and mTHPC-loaded PLGA nanoparticles in human colon carcinoma cells

The second generation photosensitizer mTHPC was approved by the European Medicines Agency (EMA) for the palliative treatment of advanced head and neck cancer in October 2001. It is known that mTHPC possesses a significant phototoxicity against a variety of human cancer cells in vitro but also exhibits dark toxicity and can cause adverse effects (especially skin photosensitization). Due to its poor water solubility, the administration of hydrophobic photosensitizer still presents several difficulties. To overcome the administration problems, the use of nanoparticles as drug carrier systems is much investigated. Nanoparticles based on poly(lactic-co-glycolic acid) (PLGA) have been extensively studied as delivery systems into tumours due to their biocompatibility and biodegradability. The goal of this study was the comparison of free mTHPC and mTHPC-loaded PLGA nanoparticles concerning cytotoxicity and intracellular accumulation in human colon carcinoma cells (HT29). The nanoparticles delivered the photosensitizer to the colon carcinoma cells and enabled drug release without losing its activity. The cytotoxicity assays showed a time- and concentration-dependent decrease in cell proliferation and viability after illumination. However, first and foremost mTHPC lost its dark toxic effects using the PLGA nanoparticles as a drug carrier system. Therefore, PLGA nanoparticles are a promising drug carrier system for the hydrophobic photosensitizer mTHPC.

Comparative in vitro study on the characteristics of different photosensitizers employed in PDT

At present a wide range of photosensitizers are employed in photodynamic therapy (PDT) that have very different characteristics. Although, countless in vitro studies on the attributes of photosensitizers do exist, a direct comparison of these substances on one cell line are rare and may contribute to the choice of the optimal photoactive substance for a specific application. We therefore evaluated the properties of six widespread photosensitizers, namely Foscan, Fospeg, hypericin, aluminum (III) phthalocyanine tetrasulfonate chloride (AlPcS(4)), 5-aminolevulinic acid (ALA), and Photofrin in terms of: (i) cytotoxicity without illumination, (ii) phototoxicity, (iii) cellular uptake and release, and (iv) apoptosis induction in A431 human epidermoid carcinoma cells using comparable illumination regimens. We clearly show that meso-tetrahydroxyphenylchlorin (mTHPC, Foscan) is a very effective photosensitizer inducing high phototoxicity at very low concentrations. Similar in vitro characteristics and phototoxicity were observed for Fospeg, the water-soluble formulation of mTHPC. Hypericin, a photosensitizer extracted from plants of the Hypericum genus, is very effective in inducing apoptosis over a wide range of light fluences. AlPcS(4) absorbs light of 674 nm wavelength providing a higher penetration depth in tissue. Its hydrophilic character allows for application as aqueous solution. ALA can be administered at very high concentrations without producing cytotoxic effects in the dark. The intracellular concentration of protoporphyrin IX rapidly decreases after withdrawal of ALA, thus minimizing the period of light sensitivity post PDT. Among all photosensitizers Photofrin has most clinical approvals and serves as standard.

The cellular uptake of meta-tetra(hydroxyphenyl)chlorin entrapped in organically modified silica nanoparticles is mediated by serum proteins

Nanosized objects made of various materials are gaining increasing attention as promising vehicles for the delivery of therapeutic and diagnostic agents for cancer. Photodynamic therapy (PDT) appears to offer a very attractive opportunity to implement drug delivery systems since no release of the sensitizer is needed to obtain the therapeutic effect and the design of the nanovehicle should be much easier. The aim of our study was to investigate the use of organic-modified silica nanoparticles (NPs) for the delivery of the second-generation photosensitizer meta-tetra(hydroxyphenyl)chlorin (mTHPC) to cancer cells in vitro. mTHPC was entrapped in NPs (approximately 33 nm diameter) in a monomeric form which produced singlet oxygen with a high efficiency. In aqueous media with high salt concentrations, the NPs underwent aggregation and precipitation but their stability could be preserved in the presence of foetal bovine serum. The cellular uptake, localization and phototoxic activity of mTHPC was determined comparatively in human oesophageal cancer cells after its delivery by the NPs and the standard solvent ethanol/poly(ethylene glycol) 400/water (20:30:50, by vol). The NP formulation reduced the cellular uptake of mTHPC by about 50% in comparison to standard solvent while it did not affect the concentration-dependent photokilling activity of mTHPC and its intracellular localization. Fluorescence resonance energy transfer measurements, using NPs with mTHPC physically entrapped and a cyanine covalently linked, and ultracentrifugation experiments indicated that mTHPC is transferred from NPs to serum proteins when present in the medium. However, the coating of the NP surface with poly(ethylene glycol) largely prevented the transfer to proteins. In conclusion, mTHPC is rapidly transferred from the uncoated nanoparticles to the serum proteins and then internalized by the cells as a protein complex, irrespective of its modality of delivery.

High-yielding syntheses of hydrophilic conjugatable chlorins and bacteriochlorins

Next-generation photodynamic therapy agents based upon the conjugation of multiple photosensitizers to a targeting backbone will allow for more efficacious light-based therapies. To this end, we have developed glucose-modified chlorins and bacteriochlorins featuring a reactive carboxylic acid linker for conjugation to targeting moieties. The photosensitizers were synthesized in relatively high yields from meso-tetra(p-aminophenyl)porphyrin, and resulted in neutral, hydrophilic chromophores with superb absorption profiles in the far-red and near-infrared portions of the electromagnetic spectrum. In addition, conjugation of these photosensitizers to a model nanoscaffold (crosslinked dextran-coated nanoparticles) demonstrated that the inclusion of hydrophilic sugar moieties increased the number of dyes that can be loaded while maintaining suspension stability. The described compounds are expected to be particularly useful in the synthesis of a number of targeted nanotherapeutic systems.

Photocytotoxicity of mTHPC (temoporfin) loaded polymeric micelles mediated by lipase catalyzed degradation

PURPOSE

To study the in vitro photocytotoxicity and cellular uptake of biodegradable polymeric micelles loaded with the photosensitizer mTHPC, including the effect of lipase-catalyzed micelle degradation.

METHODS

Micelles of mPEG750-b-oligo(epsilon-caprolactone)5 (mPEG750-b-OCL5) with a hydroxyl (OH), benzoyl (Bz) or naphthoyl (Np) end group were formed and loaded with mTHPC by the film hydration method. The cellular uptake of the loaded micelles, and their photocytotoxicity on human neck squamous carcinoma cells in the absence and presence of lipase were compared with free and liposomal mTHPC (Fospeg).

RESULTS

Micelles composed of mPEG750-b-OCL5 with benzoyl and naphtoyl end groups had the highest loading capacity up to 30% (w/w), likely due to pi-pi interactions between the aromatic end group and the photosensitizer. MTHPC-loaded benzoylated micelles (0.5 mg/mL polymer) did not display photocytotoxicity or any mTHPC-uptake by the cells, in contrast to free and liposomal mTHPC. After dilution of the micelles below the critical aggregation concentration (CAC), or after micelle degradation by lipase, photocytotoxicity and cellular uptake of mTHPC were restored.

CONCLUSION

The high loading capacity of the micelles, the high stability of mTHPC-loaded micelles above the CAC, and the lipase-induced release of the photosensitizer makes these micelles very promising carriers for photodynamic therapy in vivo.

Synthesis and cellular studies of PEG-functionalized meso-tetraphenylporphyrins

The total syntheses of four PEG-functionalized porphyrins, containing one to four low molecular weight PEG chains linked via amide bonds to the para-phenyl positions of meso-tetraphenylporphyrin, are reported. The hydrophobic character of the PEG-porphyrins decreases with the number of PEG chains linked to the porphyrin ring, while their tendency for aggregation in buffered aqueous solution increases. The porphyrins containing one or two PEG chains accumulated within human HEp2 cells to a much higher extent than those having three or four PEGs at the macrocycle periphery. All PEG-porphyrins were found to be non-toxic in the dark, and only those containing one or two PEG chains were phototoxic (IC(50)=2 microM at 1J/cm(2) light dose). The preferential sites of subcellular localization of the porphyrins containing one or two PEG chains were found to be the mitochondria and endoplasmic reticulum (ER), while those containing three or four PEG chains localize preferentially in the lysosomes.

Photodynamic effects of porphyrin and chlorin photosensitizers in human colon adenocarcinoma cells

Photodynamic therapy (PDT) is a cancer treatment involving systemic administration of a tumor-localizing photosensitizer; this, when activated by the appropriate wavelength of light, interacts with molecular oxygen to form a toxic, short-lived species known as singlet oxygen, which is thought to mediate cellular death. Photofrin, a complex mixture of porphyrin oligomers has recently received FDA approval for the photodynamic treatment of esophageal and endobronchial carcinoma, but its photodynamic and toxicity profiles are far from ideal. In the present study we evaluated a series of porphyrin-based PSs, some of which newly synthesized by our group, with the aim to identify agents with more favorable characteristics. For the most effective compounds in the porphyrin series, chlorin analogs were also synthesized; for comparison, the screening also included Photofrin. Cytotoxicity studies were performed by the MTT assay on a cultured human colon adenocarcinoma cell line (HCT116); the results indicate that the 3,4,5-trimethoxyphenyl, 3OH- and 4OH-phenyl, and the sulfonamidophenyl derivatives are significantly more potent than Photofrin. Flow cytometric studies and fluorescence microscopy indicate that in PDT-treated HCT116 cells death occurs mainly by apoptosis. In summary, novel PSs described in the present study, belonging both to the porphyrin and chlorin series, have proven more effective than Photofrin in killing colon cancer cells in vitro; extending these observation to in vivo models, particularly regarding the deeper reaching chlorin derivatives, might lead to significant advances in the development of tumor PDT.

Treatment of conjunctival squamous cell carcinoma with photodynamic therapy

PURPOSE

The aim of this study was to describe the clinical and angiographic response of squamous cell carcinoma (SCC) of the conjunctiva to treatment with photodynamic therapy (PDT).

DESIGN

Interventional case series.

METHODS

In a prospective study, three patients (62 to 86 years old) with SCC of the conjunctiva were treated with PDT. Patients received one to three treatments of verteporfin (6 mg/m(2) body surface area, intravenously). The light dose was calculated as 50 J/cm(2). All tumors were irradiated 1 minute after injection. The mean follow-up time was 8.6 months (7 to 12 months). Main outcome measurements were clinical and angiographic response and treatment-related side effects.

RESULTS

One week after treatment, angiographic occlusion of tumor vasculature and normal conjunctival vessels was observed in all patients. Tumor regression was noted in all patients 1 month after treatment. Two patients had complete regression (clinical and angiographic observation) after one or two treatments for the entire follow-up time. One tumor involved large aspects of the conjunctiva and cornea. In this case, only the treated areas showed tumor regression. PDT caused minimal temporary local irritation in two patients, and small conjunctival hemorrhages and mild transient chemosis in the three eyes directly after treatment. One patient had infusion-related back pain.

CONCLUSION

The preliminary results of this study suggest that PDT may be a valuable addition to the treatment of patients with SCC of the conjunctiva. However, longer follow-up is necessary to assess the duration and degree of tumor control.

Photodynamic effects of anthracyclin derivatives on squamous cell carcinoma cell lines of the head and neck

BACKGROUND AND OBJECTIVE

In the last years, photodynamic therapy, performed with hematoporphyrin derivatives, gained in importance for the treatment of superficially situated malignomas. The use of hematoporphyrin as photosensitizer is limited especially by the low depth of penetration and its side effects. The aim of the present study was to evaluate the effectiveness of photodynamic therapy with anthracyclin derivates in squamous cell carcinoma cell lines.

STUDY DESIGN/MATERIALS AND METHODS

The photodynamic effects of the anthracyclin derivates adriamycin and epirubicin as well as the effects of the hematoporphyrin derivatives photofrin-II and photosan-3 were examined and compared in 10 squamous cell carcinoma cell lines derived from head and neck tumors.

RESULTS

Beside their cytostatic effect, the applied cytostatics revealed a marked photodynamic effect. A statistically significant difference for photodynamic effects of both cytostatic agents and the hematoporphyrin derivates could not be shown.

CONCLUSIONS

These results revealed that the above mentioned cytostatics could be considered as possible alternative photosensitizer for photodynamic therapy.

Photodynamic therapy of virus-associated epithelial tumours of the face in organ transplant recipients

PURPOSE

The benefit for organ recipients is still counteracted by the side effects of immunosuppression. Among other effects, there is a 50-250 times increased risk of developing malignant skin tumours. Because these malignomas are known to develop particularly aggressivly, there is a special need for an efficient therapy. Here we demonstrate the treatment response to aminolaevulinic acid (ALA)-based photodynamic therapy (PDT) in these patients.

METHODS

Five organ recipients with multiple tumours of the face were multifocally treated with ALA-PDT (32 tumours in all). After topical application of ALA using a thermogel, irradiation was done with a 635 nm diode laser (Ceralas 635, Biolitec, Jena, Germany). After intervals of 2 weeks, 4 weeks, and 12 weeks, therapeutic efficacy was assessed.

RESULTS

There was complete remission in 24 tumours (75%). In six tumours (18.8%) a second or third PDT session was necessary for complete clinical remission. In two tumours (5.6%, invasive squamous cell carcinomas) the lesions were refractory to PDT.

CONCLUSIONS

ALA-PDT is a valuable therapeutic alternative for the treatment of multifocal skin tumours in organ-transplanted patients. Furthermore, we see a growing role of ALA-PDT also for patients with frequently relapsing tumours of the skin with known genetically determined tumourigenesis (Gorlin-Goltz syndrome).

Antiangiogenic photodynamic therapy (PDT) using Visudyne causes effective suppression of tumor growth

We previously observed that antiangiogenic photodynamic therapy (PDT), namely, laser irradiation at 15 min after administration of photosensitizer, by using stable liposomal benzoporphyrin derivative monoacid ring A (BPD-MA), in which the liposomes were composed of dipalmitoylphosphatidylcholine, palmitoyloleoylphosphatidylcholine, cholesterol, and dipalmitoylphosphatidylglycerol (10:10:10:2.5 as a molar ratio), was quite effective for cancer treatment. On the other hand, Visudyne, a commercialized liposomal formulation of BPD-MA, is based on more fluid lipids, namely, dimyristoylphosphatidylcholine and egg yolk phosphatidylglycerol, and is thought to be less stable in the presence of serum. The data of spin column chromatography indicated a little faster transfer of BPD-MA from Visudyne to lipoprotein fraction when Visudyne was incubated with serum than when the stable liposomal BPD-MA was used. The phototoxicity of Visudyne against a human endothelial cell line, ECV304, was almost the same as that of stable liposomal BPD-MA after PDT treatment. Therefore, we examined the antiangiogenic scheduling of PDT with Visudyne. Tumor growth of Meth-A sarcoma-bearing mice was strongly suppressed when the antiangiogenic scheduling was performed with Visudyne, namely, irradiation at 15 min after injection of the drug, in comparison with the conventional scheduling in which laser irradiation is done at 3 h post-injection. This greater effectiveness of PDT at 15 min was suggested to be caused by hemostasis, based on observations made in a dorsal air sac angiogenesis model. Visudyne-mediated antiangiogenic PDT cured 40 or 60% of Meth-A-bearing mice completely when 0.25 or 0.5 mg/kg BPD-MA, respectively, was used. These data suggest that the antiangiogenic scheduling is effective in Visudyne-mediated cancer PDT despite the transferring of BPD-MA from the liposomal fraction to lipoproteins in the bloodstream.