Bernhard Ortel

Photodynamic therapy of epithelial skin tumours using delta-aminolaevulinic acid and desferrioxamine

Photodynamic therapy (PDT) uses photosensitizing drugs, such as porphyrins, and light for cancer treatment. In the present clinical study we employed topical application of the porphyrin precursor delta‐aminolaevulinic acid (ALA) in combination with desferrioxamine (df) for the induction of endogenous porphyrin synthesis. Irradiation was performed with a light source consisting of a halogen lamp with a red filter and a fibreoptic device. Irradiances ranged from 50 to 300mW/cm2. We treated 49 patients with this PDT regimen. In 32 patients we treated a total of 34 superficial basal cell carcinomas (BCCs) and 22 nodular BCCs, in nine patients 43 solar keratoses, and in eight patients 10 lesions of Bowens disease. After a single treatment, 30 (88.2%) of the superficial and seven (31.8%) of the nodular BCCs, 35 of 43 (81.4%) solar keratoses. and three (30%) of the Bowens disease lesions showed complete remission. The post‐treatment observation period was up to 20 months. Repeat therapy was required in six nodular and four superficial BCCs. Biopsies were obtained before treatment, and at variable intervals after treatment. Topical PDT of skin tumours with ALA‐df‐induced porphyrins is effective in the management of epithelial skin tumours.

Polymorphous light eruption: Action spectrum and photoprotection

Polymorphous light eruption is a common seasonal photodermatosis with a typical history and clinical picture. In the interval, when no lesions are present, the diagnosis relies on artificial reproduction of polymorphous light eruption by phototesting. Photochemotherapy (psoralens with ultraviolet A [PUVA]) is currently an effective preventive treatment. One hundred sixty-seven patients with either a history of polymorphous light eruption or manifest disease entered our study. Of 142 patients tested, 49% developed typical lesions of polymorphous light eruption at the test sites. In 56% the action spectrum was found to be in the ultraviolet A range, in 17% in the ultraviolet B range, and in 26% in both ranges. A total of 122 patients received preventive treatment with PUVA. Of these, fifty-one returned for follow-up. Of the patients who were followed up, 64% reported total protection during outdoor activities in the summer, 26% reported partial protection, and 10% were not protected. Failure to improve was unrelated to the action spectrum. The action spectrum and the incidence of positive results on phototests in our patient population differed from those reported by others. It is possible that differences in the test protocols and in the light sources used may account for this discrepancy. There is clearly a need for a standardized test procedure. However, the majority of patients benefit from PUVA pretreatment regardless of their action spectrum.

Treatment of vitiligo with khellin and ultraviolet A

Twenty-eight patients with vitiligo were treated with a new photochemotherapeutic regimen using khellin, a furanochromone, as photosensitizer, together with ultraviolet A (UVA) irradiation. Twenty-five patients received khellin orally and three patients were treated with topical khellin. Treatments were given three times weekly. As opposed to psoralens, khellin did not induce skin phototoxicity with UVA but it induced repigmentation similar to psoralens. The treatment success strongly depended on the number of treatments. More than 70% repigmentation was achieved in 41% of the patients who had received 100 to 200 treatments. This success rate is comparable to the rate obtained with psoralens. Seven patients experienced a mild elevation of liver transaminases within the early treatment phase and their treatments were discontinued. No long-term internal organ or skin toxicity was observed. The major advantage of khellin is that it does not lead to phototoxic skin erythema and thus can be considered safe for home treatment. Because of its photochemistry it may be considered less hazardous than psoralens regarding mutagenicity and carcinogenicity.

Topical photodynamic therapy in dermatology.

Although photodynamic therapy (PDT) was first used in the treatment of skin diseases, phase-III-clinical trials were primarily conducted for the treatment of bladder cancer, endobronchial and oesophageal carcinoma. In dermatology PDT has most extensively been used for the treatment of malignant cutaneous lesions. Up to now those patients have been treated systemically with first-generation photosensitizers. However, prolonged skin photosensitivity is a major disadvantage of this form of therapy. Topical PDT utilizing a variety of sensitizers bypass this unwanted effect. Of strong interest is 5-aminolevulinic acid (ALA), first introduced in the topical PDT of skin disorders in 1990 by Kennedy and co-workers. ALA serves as a pro-drug, i.e. the active photosensitizing compound is protoporphyrin IX which is synthesized in vivo after exogenous application of ALA. In several oncologic and non-oncologic skin conditions including non-melanoma skin cancer, premalignant conditions like actinic keratoses and in psoriasis, topical ALA-PDT showed its effectiveness. Besides ALA, new sensitizers like benzoporphyrines and porphycenes may play a role in topical PDT. However, at the moment, there is still a need for comparative studies and standardized therapeutic protocols to define the place of topical PDT in Dermatology.

Methotrexate used in combination with aminolaevulinic acid for photodynamic killing of prostate cancer cells

Photodynamic therapy (PDT) using 5-aminolaevulinic acid (ALA) to drive production of an intracellular photosensitiser, protoporphyrin IX (PpIX), is a promising cancer treatment. However, ALA-PDT is still suboptimal for thick or refractory tumours. Searching for new approaches, we tested a known inducer of cellular differentiation, methotrexate (MTX), in combination with ALA-PDT in LNCaP cells. Methotrexate alone promoted growth arrest, differentiation, and apoptosis. Methotrexate pretreatment (1 mg l−1, 72 h) followed by ALA (0.3 mM, 4 h) resulted in a three-fold increase in intracellular PpIX, by biochemical and confocal analyses. After exposure to 512 nm light, killing was significantly enhanced in MTX-preconditioned cells. The reverse order of treatments, ALA-PDT followed by MTX, yielded no enhancement. Methotrexate caused a similar relative increase in PpIX, whether cells were incubated with ALA, methyl-ALA, or hexyl-ALA, arguing against a major effect upon ALA transport. Searching for an effect among porphyrin synthetic enzymes, we found that coproporphyrinogen oxidase (CPO) was increased three-fold by MTX at the mRNA and protein levels. Transfection of LNCaP cells with a CPO-expressing vector stimulated the accumulation of PpIX. Our data suggest that MTX, when used to modulate intracellular production of endogenous PpIX, may provide a new combination PDT approach for certain cancers.

Differentiation-specific increase in ALA-induced protoporphyrin IX accumulation in primary mouse keratinocytes

A treatment regimen that takes advantage of the induction of intracellular porphyrins such as protoporphyrin IX (PPIX) by exposure to exogenous 5-amino-laevulinic acid (ALA) followed by localized exposure to visible light represents a promising new approach to photodynamic therapy (PDT). Acting upon the suggestion that the effectiveness of ALA-dependent PDT may depend upon the state of cellular differentiation, we investigated the effect of terminal differentiation upon ALA-induced synthesis of and the subsequent phototoxicity attributable to PPIX in primary mouse keratinocytes. Induction of keratinocyte differentiation augmented intracellular PPIX accumulation in cells treated with ALA. These elevated PPIX levels resulted in an enhanced lethal photodynamic sensitization of differentiated cells. The differentiation-dependent increase in cellular PPIX levels resulted from several factors including: (a) increased ALA uptake, (b) enhanced PPIX production and (c) decreased PPIX export into the culture media. Simultaneously, steady-state levels of coproporphyrinogen oxidase mRNA increased but aminolaevulinic acid dehydratase mRNA levels remained unchanged. From experiments using 12-o-tetradecanoylphorbol-13-acetate, transforming growth factor beta 1 and calcimycin we demonstrated that the increase in PPIX concentration in terminally differentiating keratinocytes is calcium- and differentiation specific. Stimulation of the haem synthetic capacity is seen in primary keratinocytes, but not in PAM 212 cells that fail to undergo differentiation. Interestingly, increased PPIX formation and elevated coproporphyrinogen oxidase mRNA levels are not limited to differentiating keratinocytes; these were also elevated in the C2C12 myoblast and the PC12 adrenal cell lines upon induction of differentiation. Overall, the therapeutic implications of these results are that the effectiveness of ALA-dependent PDT depends on the differentiation status of the cell and that this may enable selective targeting of several tissue types.

BPD-MA-mediated photosensitization in vitro and in vivo : cellular adhesion and β1 integrin expression in ovarian cancer cells

SummaryBenzoporphyrin derivative monoacid (BPD-MA) photosensitization was examined for its effects on cellular adhesion of a human ovarian cancer cell line, OVCAR 3, to extracellular matrix (ECM) components. Mild BPD-MA photosensitization (~ 85% cell survival) of OVCAR 3 transiently decreased adhesion to collagen IV, fibronectin, laminin and vitronectin to a greater extent than could be attributed to cell death. The loss in adhesiveness was accompanied by a loss of β1 integrin-containing focal adhesion plaques (FAPs), although β1 subunits were still recognized by monoclonal antibody directed against human β1 subunits. In vivo BPD-MA photosensitization decreased OVCAR 3 adhesiveness as well. Photosensitized adhesion was reduced in the presence of sodium azide and enhanced in deuterium oxide, suggesting mediation by singlet oxygen. Co-localization studies of BPD-MA and Rhodamine 123 showed that the photosensitizer was largely mitochondrial, but also exhibited extramitochondrial, intracellullar, diffuse cytosolic fluorescence. Taken together, these data show that intracellular damage mediated by BPD-PDT remote from the FAP site can affect cellular–ECM interactions and result in loss of FAP formation. This may have an impact on long-term effects of photodynamic therapy. The topic merits further investigation.

Biomodulatory approaches to photodynamic therapy for solid tumors

Photodynamic Therapy (PDT) uses a photosensitizing drug in combination with visible light to kill cancer cells. PDT has an advantage over surgery or ionizing radiation because PDT can eliminate tumors without causing fibrosis or scarring. Disadvantages include the dual need for drug and light, and a generally lower efficacy for PDT vs. surgery. This minireview describes basic principles of PDT, photosensitizers available, and aspects of tumor biology that may provide further opportunities for treatment optimization. An emerging biomodulatory approach, using methotrexate or Vitamin D in combination with aminolevulinate-based PDT, is described. Finally, current clinical uses of PDT for solid malignancies are reviewed.

5-Methoxypsoralen (Bergapten) for photochemotherapy: Bioavailability, phototoxicity, and clinical efficacy in psoriasis of a new drug preparation

In a previous study we evaluated a microcrystalline preparation of 5-methoxypsoralen (5-MOP; Bergapten) for its photochemotherapeutic properties. Preliminary data indicated that the clinical efficacy of 5-MOP is comparable to that of 8-methoxypsoralen. 5-MOP appeared as a promising alternative photosensitizer for the management of psoriasis because of the almost complete lack of phototoxic and drug intolerance reactions that are frequently encountered in patients undergoing 8-MOP photochemotherapy. With a new liquid preparation of 5-MOP we have now extended our earlier investigation on a larger clinical scale and have correlated the clinical response with the bioavailability of the drug. Serum level determinations showed an absorption rate of only approximately 25% that of 8-MOP. When administered in the same dosage as 8-MOP, 5-MOP turned out to be significantly less effective; however, by doubling the oral dosage, comparable results in terms of clearing of psoriasis were obtained. Also with this high-dose 5-MOP regimen, no drug intolerance was noted and other side effects, such as severe erythema, pruritus, and nausea, occurred only rarely. We propose 5-MOP as a valuable alternative for photochemotherapy (PUVA) of PUVA-responsive diseases.

Scavenger‐Receptor Targeted Photodynamic Therapy¶

Abstract Covalent conjugation of a photosensitizer to a ligand that specifically recognized and internalized by a cell-surface receptor may be a way of improving the selectivity of photodynamic therapy (PDT). The class A Type-I scavenger receptor of macrophages, which among other ligands recognizes maleylated serum albumin and has a high capacity is a good candidate for testing this approach. Chlorine6 was covalently attached to bovine serum albumin to give conjugates with molar substitution ratios of 1:1 and 3:1 (dye to protein), and these conjugates could then be further modified by maleylation. A novel way of purifying the conjugates by acetone precipitation was developed in order to remove traces of unbound dye that could not be accomplished by size-exclusion chromatography. Conjugates were characterized by polyacrylamide gel electrophoresis and thin-layer chromatography. Photosensitizer uptake was measured by target J774 murine macrophage-like cells and nontarget OVCAR-5 human ovarian cancer cells, and phototoxicity was examined after illumination by a 660 nm diode laser by a tetrazolium assay. All of the purified conjugates were taken up by and after illumination killed J774 cells while there was only small uptake and no phototoxicity toward OVCAR-5 cells. The higher dye:protein ratio and maleylation of the conjugates both produced higher uptakes and lower survival ratios in J774 cells. The uptake and phototoxicity by J774 cells were decreased after incubation at 4°C demonstrating internalization, and confocal microscopy with organelle-specific green fluorescent probes showed largely lysosomal localization. Uptake and phototoxicity by J774 cells could both be competed by addition of the scavenger receptor ligand maleylated albumin. These data show that scavenger receptor–targeted PDT gives a high degree of specificity toward macrophages and may have applications in the treatment of tumors and atherosclerosis.