The kinetics of protoporphyrin fluorescence during ALA-PDT in human malignant skin tumors

Unleashing the potential of 5-Aminolevulinic acid: Unveiling a promising target for cancer diagnosis and treatment beyond photodynamic therapy

The therapeutic properties of 5-aminolevulinic acid (5-ALA) have been extensively studied for cancer detection and treatment using photodynamic therapy (PDT). When administered externally, 5-ALA is converted to protoporphyrin IX (PpIX) in cancer cells, which generates reactive oxygen species (ROS) upon exposure to light. This process enables targeted cell death induction and cancer detection. Given the highly conserved nature of heme biosynthesis over billions of years, we hypothesized that natural mechanisms might exist to prevent excessive accumulation of PpIX or heme resulting from 5-ALA overload. Therefore, we anticipated alterations in protein expression profiles upon exogenous administration of 5-ALA. To understand cellular responses to 5-ALA, we investigated protein expression changes and identified OR1B1 as a promising target in bladder, prostate, lung, and cervical cancer cells. OR1B1 expression was observed only with 5-ALA and ferrous chloride, highlighting the central role of heme in this discovery. Immunofluorescence and electron microscopy confirmed OR1B1's sub-cellular localization. These findings suggest that 5-ALA transformation in cancer cells and OR1B1 expression have potential for enhancing cancer detection and developing alternative treatments, including immunotherapy. This approach overcomes the limitations of PDT and opens new avenues for effective and targeted cancer interventions.

Light fractionated ALA-PDT enhances therapeutic efficacy in vitro; the influence of PpIX concentration and illumination parameters

Light fractionation, with a long dark interval, significantly increases the response to ALA-PDT in pre-clinical models and in non-melanoma skin cancer. We investigated if this increase in efficacy can be replicated in PAM 212 cells in vitro. The results show a significant decrease in cell survival after light fractionation which is dependent on the PpIX concentration and light dose of the first light fraction. This study supports the hypothesis that an underlying cellular mechanism is involved in the response to light fractionation in which a first light fraction leads to sub-lethally damaged cells that are sensitised to a second light fraction 2 hours later. The current study reveals the in vitro circumstances under which we can investigate the cellular pathways involved.

On the basis for tumor selectivity in the 5-aminolevulinic acid-induced synthesis of protoporphyrin IX

When 5-aminolevulinic acid ( ALA ) is administered topically, intravenously or intraperitoneally to tumor-bearing animals or humans, tumor selective production of protoporphyrin IX ( PpIX ) is frequently observed. Several biophysical, biochemical and physiological factors explain this tumor selectivity, among which the most important ones seem to be: (1) a relatively high concentration of the rate-limiting enzyme porphobilinogen deaminase (PBGD) in tumors; (2) relatively low concentrations of ferrochelatase (FC) and iron in many tumors; (3) a slightly elevated tumor temperature, related to inflammation; and (4) a compromised barrier of the skin overlying tumors, leading to an increased penetration of ALA into tumors. All these factors are discussed in the present work and new data concerning the significance of the skin barrier and the tumor temperature are presented. It is shown that compromising the skin of mice by tape-stripping the stratum corneum leads to a strongly enhanced ALA penetration into the skin and even into the circulation. The skin overlying tumors (WiDr colon carcinoma tumors transplanted subcutaneously to mice) is also much more permeable to ALA than normal skin, even through no physical damage of the tumor skin can be seen. PpIX formation from ALA can be increased by increasing the temperature.

Modulating ALA-PDT efficacy of mutlidrug resistant MCF-7 breast cancer cells using ALA prodrug

Multi-drug resistance of breast cancer is a major obstacle in chemotherapy of cancer treatments. Recently it was suggested that photodynamic therapy (PDT) can overcome drug resistance of tumors. ALA-PDT is based on the administration of 5-aminolevulinic acid (ALA), the natural precursor for the PpIX biosynthesis, which is a potent natural photosensitizer. In the present study we used the AlaAcBu, a multifunctional ALA-prodrug for photodynamic inactivation of drug resistant MCF-7/DOX breast cancer cells. Supplementation of low doses (0.2mM) of AlaAcBu to the cells significantly increased accumulation of PpIX in both MCF-7/WT and MCF-7/DOX cells in comparison to ALA, or ALA + butyric acid (BA). In addition, our results show that MCF-7/DOX cells are capable of producing higher levels of porphyrins than MCF-7/WT cells due to low expression of the enzyme ferrochelatase, which inserts iron into the tetra-pyrrol ring to form the end product heme. Light irradiation of the AlaAcBu treated cells activated efficient photodynamic killing of MCF-7/DOX cells similar to the parent MCF-7/WT cells, depicted by low mitochondrial enzymatic activity, LDH leakage and decreased cell survival following PDT. These results indicate that the pro-drug AlaAcBu is an effective ALA derivative for PDT treatments of multidrug resistant tumors.

Reduction of cutaneous photosensitivity by application of ointment containing ferrous or cobaltous ions concomitant with the use of topical protoporphyrin IX precursors

BACKGROUND

5-Aminolevulinic acid (ALA) or its methyl ester mediated photodynamic therapy (PDT) is the most widely practiced form of PDT in dermatology. One of the advantages of topical PDT is that undesirable photosensitization lasts only for 24-48 h. However, patients are still sensitive in the areas where the cream has been applied, and are advised to avoid exposure to the sun and other light sources for at least 40 h after ALA-PDT. Therefore, the main aim of this work is to improve post-treatment procedures for increasing patient's comfort. The present study was carried out to investigate clearance of protoporphyrin IX (PpIX) in the presence of metal ions in the cream applied on healthy skin of mice in vivo.

METHODS

The photosensitizer PpIX was induced in normal mouse skin by topical application of ALA. Fluorescence spectroscopy was used to study porphyrin kinetics.

RESULTS

Topical application of ferrous, cobalt or zinc sulphate significantly diminished the fluorescence of PpIX in mouse skin. These results show that the clearance kinetics of PpIX observed after exogenous application of ALA are determined by the conversion of PpIX into haem, and not by the clearance of PpIX from the body.

CONCLUSIONS

Application of a vehicle containing ferrous or cobalt sulphate after PDT might be an approach in clinical practice for the reduction of cutaneous photosensitivity and elimination of undesirable photoreactions in skin and lesions.

A Ratiometric Fluorescence Imaging System for Surgical Guidance

A 3-chip CCD imaging system has been developed for quantitative in vivo fluorescence imaging. This incorporates a ratiometric algorithm to correct for the effects of tissue optical absorption and scattering, imaging “geometry” and tissue autofluorescence background. The performance was characterized, and the algorithm was validated in tissue-simulating optical phantoms for quantitative measurement of the fluorescent molecule protoporphyrin IX (PpIX). The technical feasibility to use this system for fluorescence-guided surgical resection of malignant brain tumor tissue was assessed in an animal model in which PpIX was induced exogenously in the tumor cells by systemic administration of aminolevulinic acid (ALA).

Increase in protoporphyrin IX after 5-aminolevulinic acid based photodynamic therapy is due to local re-synthesis

Protoporphyrin IX (PpIX) fluorescence that is bleached during aminolevulinic acid (ALA) mediated photodynamic therapy (PDT) increases again in time after treatment. In the present study we investigated if this increase in PpIX fluorescence after illumination is the result of local re-synthesis or of systemic redistribution of PpIX. We studied the spatial distribution of PpIX after PDT with and without cooling using the skin-fold observation chamber model. We were unable to show a correlation between the local PpIX fluorescence increase and the distance from a blood vessel. The spatial distribution of PpIX fluorescence within normal tissue or tumour is not changed in response to the illumination. These observations suggest that there is no diffusion of PpIX into the treated tissue. Cooling the tissue to 12 degrees C, a temperature at which PpIX synthesis is inhibited, inhibited the PpIX fluorescence increase normally observed after illumination. We also found a strong correlation between local PpIX photobleaching during illumination and the fluorescence intensity 1 h after illumination similar to what we have observed in patients treated with ALA-PDT. Therefore we conclude that the increase in PpIX fluorescence after illumination is due to local cellular re-synthesis.

Comparison between sonodynamic effect with protoporphyrin IX and hematoporphyrin on sarcoma 180

PURPOSE

The comparison between sonodynamic antitumor effect with protoporphyrin IX (PPIX) and hematoporphyrin (Hp) at a concentration of 5 mg/kg on Sarcoma 180 (S180) cells was studied in vivo, and the potential cell damage mechanism was also investigated.

METHODS

The sonodynamically induced anti-tumor effect of PPIX was studied in mice bearing S180 solid tumors. In order to determine the optimum timing of ultrasound exposure after administration of PPIX, the PPIX concentrations in plasma, skin, muscle and tumor were determined by the fluorescence intensity of tissue extractions with a fluorescence spectrophotometer based on the standard curve. Anti-tumor effects were estimated by measuring the tumor size and the tumor weight. Additionally, the morphological changes of S180 cells were evaluated by transmission electron microscope (TEM) observation immediately after sonodynamic therapy (SDT) treatment.

RESULTS

A time of 24 h after the intravenous administration of PPIX was chosen as the best time for ultrasound exposure. The antitumor effect induced by PPIX mediated sonodynamic therapy (PPIX-SDT) was in a dose dependent manner when ultrasound intensity was at or above the inertial cavitation threshold (5 W/cm(2)). A significant tumor growth delay was observed both in PPIX mediated sonodynamic therapy and in Hp mediated sonodynamic therapy treatments (Hp-SDT), and the tumor weight inhibition ratios after the synergistic treatments were 42.82 +/- 0.03 and 35.22 +/- 0.03%, respectively, this difference was significant at P < 0.05. While ultrasound alone (5 W/cm(2)) showed a slight tumor growth inhibitory effect compared with the control group, and PPIX or Hp alone showed almost no significant effect. Furthermore, TEM observation indicated cell damage was more serious in PPIX-SDT treatment group than in Hp-SDT treatment group. After sonication, the cell ultra-structure such as cell membrane destruction, mitochondria swelling, chromatin condensation might be important factors that inhibited the tumor growth and even induced cell death.

CONCLUSIONS

The comparative results suggested that PPIX as a sonosensitizer might have more potential cytotoxicity than Hp when irradiated with ultrasound, and the ultra-structural changes may account for cell destruction induced by sonodynamic therapy in our experiment mode.

Fractionated Illumination Significantly Improves the Response of Superficial Basal Cell Carcinoma to Aminolevulinic Acid Photodynamic Therapy

Photodynamic therapy (PDT) of superficial basal cell carcinoma (sBCC) using topical 5-aminolevulinic acid (ALA) and a light fluence of 75-100 J cm(-2) yields unsatisfactory long-term results. In several animal models, illumination with two light fractions 2 hours apart was considerably more effective than single illumination. Response is further enhanced if the fluence of the first light fraction is reduced, although the cumulative fluence is maintained. We compared the response of sBCC to a single illumination and 2-fold illumination scheme in which two light fractions of 20 and 80 J cm(-2) are performed 4 and 6 hours after the application of a single dose of 20% ALA. We randomly assigned 154 patients with a total of 505 primary sBCC into two treatment groups. Two hundred and forty-three lesions were treated using a single illumination of 75 J cm(-2) at a fluence rate of 50 mW cm(-2). Fractionated PDT, at the same fluence rate, was performed on 262 lesions. The complete response (CR) following a 2-fold illumination scheme is significantly greater than that following a single light fraction (P=0.002, log-rank test). Twelve months after therapy, CR rate to a 2-fold illumination is 97%, whereas the CR to a single illumination is 89%.

New Photodynamic Therapy Protocol to Treat AIDS-Related Kaposi's Sarcoma

OBJECTIVE

The aim of this study was to evaluate the efficiency of photodynamic therapy (PDT) with phenotiazinium compounds (methylene blue and toluidine blue) and excitation by a non-coherent light source (RL50) to treat AIDS-related Kaposi's sarcoma (Sk-AIDS).

BACKGROUND DATA

Sk-AIDS is a malignant disease that is recurrent in AIDS patients. Laser-based PDT protocols have been applied to treat Sk-AIDS with relative success.

METHODS

A single patient with multiple lesions who had undergone chemotherapy without success was treated with several applications of PDT, and the patient was closely evaluated. The PDT protocol consisted of injecting a mixture of phenotiazinium compounds into the lesions and applying RL50 at 18 J/cm(2).

RESULTS

Complete remission with excellent cosmetic result was observed. This result was discussed in terms of the known mechanisms of PDT action and compared with other PDT protocols.

CONCLUSION

This inexpensive PDT protocol, which is based on phenothiazinium compounds and RL50, is efficient to treat Sk-AIDS.

Photodynamic therapy for Bowen's disease and squamous cell carcinoma of the skin

BACKGROUND

Photodynamic therapy involves the activation by visible light of a previously administered photosensitizing agent in order to cause tumor necrosis. Skin tumors can be treated with topical photosensitizers and thus avoiding systemic side effects. In this study we evaluate the immediate and long-term effects of photodynamic therapy (PDT), using aminolevulinic acid (ALA) as a photosensitizer and a non-laser light source, on Bowen's disease (intra-epithelial squamous cell carcinoma) and on frank squamous cell carcinoma (SCC) of the skin.

METHODS

ALA in cream form (20%) was topically applied on biopsy-proven Bowen's disease or SCC of the skin. The lesions were covered with occlusive and light-shielding dressing. Sixteen hours later, they were submitted to a 10-min light session using Versa-Light™, a non-laser light source (spectral output of 580-720nm and 1250-1600nm, 100J/cm(2)). The initial evaluation was done 21 days post-treatment and every 3m thereafter. Patients that did not respond to treatment after two to three sessions were referred to surgery.

RESULTS

Forty Bowen's disease lesions (24 patients) and 43 SCC lesions (18 patients) underwent treatment. Median follow-up was 21±8m. No patient had any remarkable side effects. Thirty-four Bowen's disease (85%) lesions completely responded as did 32 SCC lesions (74%).

CONCLUSIONS

Our findings showed that PDT is highly effective in treating Bowen's disease and SCC lesions and can be used as a first treatment modality in so far as its use does not preclude the subsequent surgery recommended for the small percentage of failures.

In vivo measurement of 5-aminolaevulinic acid-induced protoporphyrin IX photobleaching: a comparison of red and blue light of various intensities

BACKGROUND

In recent years, 5-aminolaevulinic acid (ALA) has become an increasingly popular photosensitizing drug for use in both photodynamic therapy (PDT) and photodetection (PD) of cancers. ALA metabolizes within tissue to form the photosensitizer protoporphyrin IX (PpIX). Like most photosensitizers, PpIX is fluorescent, and this fluorescence progressively decreases during PDT. This phenomenon is referred to as photobleaching.

AIM

Our aim in carrying out this experiment was twofold: firstly, to compare the relative capacity of red and blue light to cause photobleaching; and secondly, to compare the capacity of a fixed light dose to cause photobleaching, when delivered at different intensities.

METHOD

In this paper, we describe the implementation of a compact fluorescence spectrometer in monitoring the photobleaching of ALA-induced PpIX in vivo on the skin of healthy volunteers.

RESULTS

We have been able to show that blue light causes more rapid photobleaching than red light, and that under illumination with red or blue light, delivery of a fixed light dose at a lower intensity results in more photobleaching.

CONCLUSION

Comparison of the photobleaching rates suggests that a blue light intensity of 5 mW/cm(2) gives the same rate of photobleaching as the typical red light PDT intensity of 100 mW/cm(2). Further investigation of the correlation between PpIX photobleaching and PDT effect would be beneficial in interpreting the clinical significance of our findings.

Chronic UVB exposure enhances in vitro percutaneous penetration of 5-aminulevulinic acid in hairless mouse skin

BACKGROUND AND OBJECTIVES

(Pre)cancerous skin lesions accumulate more protoporphyrin IX (PpIX) upon topical application of 5-aminolevulinic acid (ALA) than the surrounding normal skin. This might be the result of a higher percutaneous penetration of ALA into (pre)cancerous skin.

STUDY DESIGN/MATERIALS AND METHODS

ALA penetration through (1) healthy skin with intact stratum corneum, (2) healthy skin with reduced stratum corneum (i.e. tape stripped skin) and (3) diseased skin with dysplastic and thickened epidermis (chronically UVB-exposed skin) was determined in an in vitro model with hairless mouse skin.

RESULTS

More ALA had penetrated through chronically UVB-exposed skin than through normal non-exposed skin after 8 hours ALA application. The amount of ALA penetrated through chronically UVB-exposed skin was smaller than through tape stripped skin.

CONCLUSIONS

The stratum corneum barrier function is less effective in chronically UVB-exposed skin than in normal non-exposed skin, but more effective than in tape stripped skin. A higher penetration rate of ALA into (pre)cancerous lesions may be (partly) responsible for the greater accumulation of PpIX in such lesions.

Specificity of photosensitizer accumulation in undifferentiated versus differentiated colon carcinoma cells

The relationship between tumor cell differentiation and photosensitizer accumulation used in PDT is poorly defined. In the present work, specific cell differentiation of colon carcinoma CT26 cells induced by sodium butyrate was manifested by morphological changes, proliferation and protein expression and was correlated with the accumulation of endogenous and exogenous photosensitizes. Reduced accumulation of the endogenous protoporphyrin IX and the exogenous hypericin and MC540 was detected in differentiated cells. In contrast, a differentiation-dependent increase was measured with TPPS4, TMPyP, the pheophorbides (C5, C6, C12), HypS4 and helianthrone. In conclusion, PpIX, Hypericin and MC540 show specific binding and accumulation in poorly differentiated tumors, giving these tumors tissue-specific advantage in photo-diagnostic PDT applications.

Photodynamic diagnosis of ovarian cancer using hexaminolaevulinate: a preclinical study

The unfailing detection of micrometastases during surgery of patients suffering from ovarian cancer is mandatory for the optimal management of this disease. Thus, the present study aimed at determining the feasibility of detecting micrometastases in an ovarian cancer model using the intraperitoneal administration of the photosensitiser precursor hexaminolaevulinate (HAL). For this purpose, HAL was applied intraperitoneally at different concentrations (4-12 mM) to immunocompetent Fischer 344 rats bearing a syngeneic epithelial ovarian carcinoma. The tumours were visualised laparoscopically using both white and blue light (D-light, Karl Storz, Tuttlingen, Germany), and the number of peritoneal micrometastases detected through HAL-induced photodiagnosis (PD) was compared to standard white light visualisation. Fluorescence spectra were recorded with an optical fibre-based spectrofluorometer and the fluorescence intensities were compared to the protoporphyrin IX (PpIX) fluorescence induced by 5-aminolevulinic acid under similar conditions. The number of metastases detected by the PD blue light mode was higher than when using standard white light abdominal inspection for all applied concentrations. Twice as many cancer lesions were detected by fluorescence than by white light inspection. The hexyl-ester derivative produced higher PpIX fluorescence than its parent substance aminolevulinic acid at the same concentration and application time. Fluorescence contrast between healthy and cancerous tissue was excellent for both compounds. To overcome poor diagnostic efficiency and to detect peritoneal ovarian carcinoma foci in the large surface area of the human peritoneal cavity, HAL fluorescence-based visualisation techniques may acquire importance in future and lead to a more correct staging of early ovarian cancer.

Determination of the maximal tumor:normal bladder ratio after i.p. or bladder administration of 5-aminolevulinic acid in Fischer 344 rats by fluorescence spectroscopy in situ

The two major steps in our study on the treatment of bladder tumors by photodynamic therapy (PDT) were the development of a new bladder tumor model in Fischer rats by implantation of tumor cells and the use of fluorescence spectroscopy, a semi-quantitative and non-invasive method, in order to determine the time after general or local administration of a photosensitizer when the tumor:normal bladder ratio was at its highest. 5-Aminolevulinic acid (5-ALA) (250 mg/kg body weight) was injected i.p. or instilled directly into the bladder cavity for 1, 2 or 4 h and fluorescence was measured on normal and bladder tumor tissues every 30 min for 8-10 h after administration, with a special miniaturized optical-fiber captor. The better tumor:normal bladder ratios were 2.85+/-1.2 at 3.5 h after i.p. administration and 3.96+/-1.04 after bladder instillation for 4 h, respectively. These results were confirmed by fluorescence microscopy. PDT with the same dose of 5-ALA as in this pharmacokinetic study must also be carried out in order to compare the toxicity of the two administration routes of the photosensitizer and to determine which one is the better for this bladder tumor model.

In vivo pharmacokinetics of 8-aminolevulinic acid-induced protoporphyrin IX during pre- and post-photodynamic therapy in 7,12-dimethylbenz(a)nthracene-treated skin carcinogenesis in Swiss mice: a comparison by three-compartment model

Delta-aminolevulinic acid-photodynamic therapy (ALA-PDT) has emerged as a useful technique in the treatment of superficial basal cell carcinoma, actinic keratosis, squamous cell carcinoma and tumors of other organs. Earlier reports mention that there is reappearance of protoporphyrin IX (PpIX) after photoirradiation of tumors. This property of reappearance of PpIX is being utilized to treat nodular tumors by fractionated light dose delivery. However, there is still no unanimously accepted reason for this reappearance phenomenon and the rate of resynthesis after PDT. On account of this, studies are carried out on the estimation of the pharmacokinetics of the ALA-induced PpIX in mice tumor models and the surrounding normal tissues before and after PDT. Further, a mathematical model based on a multiple compartment system is proposed to estimate the rate parameter for the diffusion of PpIX from the surrounding normal tissues into the tumor tissue (km) caused by photobleaching during PDT with irradiating fluences of 36.0 and 57.6 J/cm2. The km value at two different fluences, 36.0 and 57.6 J/cm2, are estimated as 3.0636+/-0.7083 h(-1) and 6.9231+/-2.17651 h(-1), respectively. Further, the rate parameter for the cleavage and efflux of ALA (k1) and the rate parameter for the evasion of PpIX from the tumor tissues after PDT (kt) were also estimated by fitting the experimental data to the developed mathematical model. The statistical significance of the estimated parameters was determined using Student's t-test. The experimental results and the rate parameters obtained using the proposed compartment model suggest that in addition to the earlier reported reasons, the invasion or diffusion of PpIX from the surrounding tissues to the tumor tissues after photoirradiation might also contribute to the reappearance of PpIX after PDT.

Nuclear distribution of porphobilinogen deaminase (PBGD) in glioma cells: a regulatory role in cancer transformation?

Recently, considerable interest has been directed to red-fluorescence photodiagnosis of brain and other tumours during surgery using the protoporphyrin IX natural precursor, 5-aminolaevulinic acid. In the present study we focused on the role of the rate-limiting enzyme porphobilinogen deaminase in glioma C6 cell activity, differentiation and sub-cellular distribution. Over-expression of the human housekeeping porphobilinogen deaminase in the glioma cells, using the housekeeping-porphobilinogen deaminase plasmid, induced a G1 cell cycle attenuation accompanied by increases in enzyme activity and c6 differentiation toward astrocytes. Visualisation of subcellular localisation of the porphobilinogen deaminase using the independent techniques of fluorescence immuno-staining with specific anti-human porphobilinogen deaminase antibodies and cellular expression of porphobilinogen deaminase fused to green fluorescent protein, revealed (unexpectedly) a major fraction of porphobilinogen deaminase in the nucleus and only a minor fraction in the cytoplasm. Both C and N terminals of porphobilinogen deaminase fused to green fluorescent protein revealed a major fraction of the newly synthesized fused porphobilinogen deaminase in the nucleus. Furthermore, newborn rat brain cells grown in a primary culture showed the same localisation pattern of porphobilinogen deaminase in the nuclei. Stimulation of C6 glioma cell differentiation by butyrate induced a marked decrease in porphobilinogen deaminase both in the nucleus and in the cytoplasm as determined by Western blotting and fluorescence immuno-localisation. These findings suggest a possible dual role for housekeeping porphobilinogen deaminase in fast dividing glioma cells, one related to the porphyrin synthesis pathway and another coupled to nuclear function, which might be linked to tumorigenesis.

Photodynamic Therapy for Bowen's Disease (Squamous Cell Carcinoma in situ) of the Digit

BACKGROUND

Surgical excision is the preferred method of eradicating Bowen's disease (BD). However, when BD occurs on the digit, surgical intervention can sometimes lead to scar contracture and loss of function of the digit.

OBJECTIVE

To evaluate the effectiveness of photodynamic therapy (PDT) in eradicating BD of the digit while preserving the full function of the digit.

METHODS

Four patients of chronic arsenism with biopsy-proven BD on the digit were treated with PDT by using a newly designed light-emitting diode (LED) array with a peak wavelength of 630 nm (630 +/- 40 nm; 40 mW/cm2 at skin surface). After partial removal of the thickened horny layer and 16 hours of occlusion with a 2% aminolevulinic acid (ALA) solution, each lesion was irradiated with 240 J/cm2 in two fractions with a 90-minute interval.

RESULTS

All patients experienced a significant burning, tingling sensation that was tolerable during the procedure except one who needed local anesthesia. All treated digits healed without scarring in 2 weeks. Posttreatment biopsy in one patient showed normal epidermis and a slight fibrosis in the papillary dermis. Three patients remained free of recurrence (75%) at 15-17 months (average 16 months) after one treatment. One patient's BD recurred at 8 months, but was successfully treated without recurrence after 20 months.

CONCLUSION

Our preliminary study suggests that PDT using 2% 5-ALA solution and an LED array is an effective, noninvasive method to treat digital BD with the benefit of scar-free contracture and loss of digital function. Among the various factors that would affect the results of PDT, we feel that partial removal of the thickened horny layer is the most important step to achieve sufficient therapeutic effect in digital BDs.

Topical 5-aminolevulinic acid-photodynamic therapy of hairless mouse skin using two-fold illumination schemes: PpIX fluorescence kinetics, photobleaching and biological effect

Light fractionation with dark periods of the order of hours has been shown to considerably increase the efficacy of 5-aminolevulinic acid-photodynamic therapy (ALA-PDT). Recent investigations have suggested that this increase may be due to the resynthesis of protoporphyrin IX (PpIX) during the dark period following the first illumination that is then utilized in the second light fraction. We have investigated the kinetics of PpIX fluorescence and PDT-induced damage during PDT in the normal skin of the SKH1 HR hairless mouse. A single illumination (514 nm), with light fluences of 5, 10 and 50 J cm-2 was performed 4 h after the application of 20% ALA, to determine the effect of PDT on the synthesis of PpIX. Results show that the kinetics of PpIX fluorescence after illumination are dependent on the fluence delivered; the resynthesis of PpIX is progressively inhibited following fluences above 10 J cm-2. In order to determine the influence of the PpIX fluorescence intensity at the time of the second illumination on the visual skin damage, 5 + 95 and 50 + 50 J cm-2 (when significantly less PpIX fluorescence is present before the second illumination), were delivered with a dark interval of 2 h between light fractions. Each scheme was compared to illumination with 100 J cm-2 in a single fraction delivered 4 or 6 h after the application of ALA. As we have shown previously greater skin damage results when an equal light fluence is delivered in two fractions. However, significantly more damage results when 5 J cm-2 is delivered in the first light fraction. Also, delivering 5 J cm-2 at 5 mW cm-2 + 95 J cm-2 at 50 mW cm-2 results in a reduction in visual skin damage from that obtained with 5 + 95 J cm-2 at 50 mW cm-2. A similar reduction in damage is observed if 5 + 45 J cm-2 are delivered at 50 mW cm-2. PpIX photoproducts are formed during illumination and subsequently photobleached. PpIX photoproducts do not dissipate in the 2 h dark interval between illuminations.

Photodynamic therapy of cutaneous lymphoma using 5-aminolevulinic acid topical application

BACKGROUND

Photodynamic therapy (PDT) with topical application of 5-aminolevulinic acid (ALA) is a new and effective modality for treatment of superficial basal and squamous cell carcinomas.

OBJECTIVE

We present the kinetics of ALA-induced protoporphyrin IX (PP) accumulation and the results of ALA PDT treatment on two patients with different stages (stage I and stage III) of mycosis fungoides (MF)-type cutaneous T-cell lymphoma (CTCL).

METHODS

ALA-Decoderm cream was applied to the lesions for 16 hours. Spectrofluorescence measurements of PP accumulation were carried out before, during, and 1 hour after photoirradiation (580-720 nm) using the VersaLight system.

RESULTS

Different patterns of PP fluorescence kinetics were observed in patients with early and advanced stages of the disease. During photoirradiation the intensity of fluorescence decreased depending on the lesion thickness. One hour after the photoirradiation procedure no PP fluorescence was observed in the stage I MF lesion, while in the thick stage III MF lesions, PP fluorescence reappeared; after an additional 10-15 minutes of irradiation PP fluorescence disappeared. Complete response with excellent cosmetic results was observed in the stage I lesion after a single irradiation with a light dose of 170 J/cm2; in five stage III lesions, complete response was achieved after fractionated irradiation with a total light dose of 380 J/cm2 (follow-up at 27 and 24 months, respectively).

CONCLUSION

The results showed a high response of both stage I and stage III MF lesions to ALA PDT. This modality appears to be very effective and can be used successfully for MF treatment.

Photodynamic therapy of superficial basal cell carcinoma with 5-aminolevulinic acid with dimethylsulfoxide and ethylendiaminetetraacetic acid: a comparison of two light sources

The aim of this prospective randomized study was to compare the clinical and cosmetic outcome of superficial basal cell carcinomas (BCC), using either laser or broadband halogen light, in photodynamic therapy with topical 5-aminolevulinic acid (ALA). A total of 83 patients with 245 superficial BCC were included in the study. Standard treatment involved 15 min of local pretreatment with 99% dimethylsulfoxide (DMSO) before topical application of 20% ALA with DMSO (2%) and ethylendiaminetetraacetic acid (2%) as cofactors for 3 h before light exposure with either laser or a broadband lamp (BL). A complete response was achieved in 95 lesions (86%) in the laser group and 110 lesions (82%) in the BL group 6 months after treatment. Of these, 80 lesions (84%) in the laser group and 101 lesions (92%) in the lamp group were independently evaluated to have an excellent or good cosmetic post-treatment score. No serious adverse events were reported. This study shows that there is no statistical significant difference in cure the rate (P = 0.49) and the cosmetic outcome (P = 0.075) with topical application of a modified ALA-cream between light exposure from a simple BL with continuous spectrum (570-740 nm) or from a red-light laser (monochromatic 630 nm). Cost and safety are further elements in favor of the BL in this setting.

Wavelength and fluence effect on vascular damage with photodynamic therapy on skin

Normal skin phototoxicity is clinically predictable during photodynamic therapy with light at 690 and 458 nm wavelengths, in the first 5 h after intravenous bolus infusion of benzoporphyrin derivative mono-acid ring A. This study goal was to determine histologic milestones that lead to tissue necrosis with exposure to red (690 nm) and blue (458 nm) light. The threshold doses for skin necrosis on rabbits were equal at both wavelengths. Lower, equal to, and higher than threshold fluences were delivered in duplicates at hourly intervals, with 40% increments, at constant irradiance. Pathology specimens from irradiated and control sites, were collected at 0, 2, 7, 24, 48 h, and 2 wk after treatment and were paired to equivalent treated sites for clinical evaluation. Immediately after irradiation, at 690 and 458 nm thresholds, light microscopy showed stasis and inflammatory infiltrate in the papillary dermis, respectively; electron microscopy demonstrated pericyte and endothelial cell damage - greater at 690 than 458 nm. At day 1, vascular stasis in the dermis showed a steeper dose-response with red than blue light, and led to necrosis of skin appendages (day 1) and epidermis (days 1-2) at both wavelengths. Sub-threshold fluences induced similar, but significantly milder (p < 0.05) changes and epidermis recovered. Skin necrosis, at threshold fluences in photodynamic therapy with benzoporphyrin derivative mono-acid ring A, was primarily due to vascular compromise to a depth potentially reaching the subcutaneous muscle at 690 nm, whereas at 458 nm vascular damage was confined to upper dermis. This system facilitates selective destruction of skin vasculature, sparing normal epidermis.

Determination of the maximal carcinoma/normal skin ratio after HpD or m-THPC administration in Hairless mice (SKH-1) by fluorescence spectroscopy

The two major steps in our study on the treatment of skin carcinomas by photochemotherapy (PCT) were the development of a skin tumor model in Hairless mice by a chemical carcinogenesis and the use of fluorescence spectroscopy, a semi-quantitative and non-invasive method, in order to determine the time after i.p. injection of photosensitizer when the tumor/normal skin ratio was the highest. A three-step carcinogenesis protocol provided mice bearing carcinomas and these were used to determine the tumor/normal skin ratios of two photosensitizers by fluorescence spectroscopy. Hematoporphyrin derivative (HpD) (5 mg/kg body weight) and m-tetra(hydroxyphenyl) chlorine (m-THPC) (0.3 mg/kg body weight) were injected i.p., and fluorescence was measured at 1, 4, 8, 12, 24, 48, 72 and 96 h after injection. The best carcinoma/normal skin ratio would be 3.2+/-1.4 for HpD and 2.7+/-2.1 for m-THPC, respectively. The delays required to reach these ratios were 72 h for HpD and 24 h for m-THPC. These results have to be considered with caution due to the high SEs and they must be confirmed by organic extraction. Photodynamic therapy with the same doses of HpD and m-THPC used in this pharmacokinetic study has to be carried out in order to compare the toxicities of the two photosensitizers and to determine which one is the best for this type of tumor.

Photodynamic parameters in the chick chorioallantoic membrane (CAM) bioassay for topically applied photosensitizers

The relative efficacy of Photofrin-based photodynamic therapy (PDT) has been compared with that of the second-generation photosensitizers 5-aminolevulinic acid (ALA), sulfonated chloro-aluminum phthalocyanine (AlPcSn), benzoporphyrin derivative monoacid ring A (BPD-MA), and lutetium texaphyrin (Lutex). PDT-induced vascular damage in the chick chorioallantoic membrane (CAM) is measured following topical application of the photosensitizers. In order to make meaningful comparisons, care is taken to keep treatment variables the same. These include light dose (5 and 10 J/cm2), power density (33 and 100 mW/cm2), and drug uptake time (30 and 90 min). The drug dose ranges from 0.1 microgram/cm2 for BPD to 5000 micrograms/cm2 for ALA. Results are also analyzed statistically according to CAM vessel type (arterioles versus venules), vessel diameter, and vessel development (embryonic age). For each photosensitizer, the order of importance for the various PDT parameters is found to be unique. The differences between the sensitizers are most likely due to variation in biophysical and biochemical characteristics, biodistribution, and uptake kinetics.

Photodynamic therapy of cancer of the esophagus using systemic aminolevulinic acid and a non laser light source: a phase I/II study

BACKGROUND

Surgery is the mainstay for the treatment of carcinoma of the esophagus and is also considered to be effective for palliation of dysphagia. Patients who are unfit for surgery represent a difficult therapeutic problem. The goal of the present study was to evaluate the effects of photodynamic therapy by using systemic administration of 5-aminolevulinic acid and a non laser light source on carcinoma of the esophagus.

METHODS

Patients were given 60 mg/kg 5-aminolevulinic acid orally. Twenty-four hours later gastroscopy was performed. After initial localization of the tumor with the use of white light, the light source was switched to the red light band at 100 J/cm2 for 600 seconds. Gastroscopy was repeated at 48 hours and 7 days after the treatment. The degree of dysphagia was recorded before and 14 days after treatment.

RESULTS

Five patients with advanced nonresectable tumors or who were unfit for surgery were treated. Two patients had squamous cell carcinoma of the mid-esophagus and three had adenocarcinoma of the distal esophagus. Mild self-limiting photosensitivity was noted in all patients. Liver and renal function tests as well as hemoglobin level and white blood cell count were not affected by the treatment. Improvement of dysphagia was observed in four patients who had pretreatment dysphagia. The patient with the early stage of disease continued to eat a normal diet.

CONCLUSIONS

Photodynamic therapy with systemic aminolevulinic acid as a photosensitizer and a non laser light source is feasible and safe in advanced-stage esophageal cancer. It can be an effective modality for the relief of dysphagia in these patients.

The role of photodynamic therapy in dermatology

Photodynamic therapy (PDT) involves selective photosensitization of a target tissue by means of a topically or systemically administered agent which is then activated by light to effect an oxygen dependent cytotoxic reaction. The production of reactive oxygen intermediates, including singlet oxygen, is localized to where the photosensitizer accumulates and induces apoptosis and vascular endothelial damage. First-generation photosensitizers are haematoporphyrin derivatives and are effective in treating certain nonmelanoma skin cancers. However, they induce cutaneous photosensitization for at least 4-6 weeks and have a limited role in dermatology. Many second-generation photosensitizers, such as 5-aminolaevulinic acid, are associated with less prolonged photosensitization. Although PDT remains largely experimental, it has potential applications in both benign and malignant skin disease.

Kinetic fluorescence studies of 5-aminolaevulinic acid-induced protoporphyrin IX accumulation in basal cell carcinomas

Laser-induced fluorescence (LIF) investigations have been performed in connection with photodynamic therapy (PDT) of basal cell carcinomas and adjacent normal skin following topical application of 5-aminolaevulinic acid (ALA) in order to study the kinetics of the protoporphyrin IX (PpIX) build-up. Five superficial and 10 nodular lesions in 15 patients are included in the study. Fluorescence measurements are performed prior to the application of ALA, 2, 4 and 6 h post ALA application, immediately post PDT (60 J cm-2 at 635 nm), and 2 h after the treatment. Hence, the build-up, photobleaching and re-accumulation of PpIX can be followed. Superficial lesions show a maximum PpIX fluorescence 6 h post ALA application, whereas the intensity is already the highest 2-4 h after the application in nodular lesions. Immediately post PDT, the fluorescence contribution at 670 nm from the photoproducts is about 2% of the pre-PDT PpIX fluorescence at 635 nm. Two hours after the treatment, a uniform distribution of PpIX is found in the lesion and surrounding normal tissue. During the whole procedure, the autofluorescence of the lesions and the normal skin does not vary significantly from the values recorded before the application of ALA.

Systemic application of photosensitizers in the chick chorioallantoic membrane (CAM) model: photodynamic response of CAM vessels and 5-aminolevulinic acid uptake kinetics by transplantable tumors

The aim of this study is to modify the chick chorioallantoic membrane (CAM) model into a whole-animal tumor model for photodynamic therapy (PDT). By using intraperitoneal (i.p.) photosensitizer injection of the chick embryo, use of the CAM for PDT has been extended to include systemic delivery as well as topical application of photosensitizers. The model has been tested for its capability to mimic an animal tumor model and to serve for PDT studies by measuring drug fluorescence and PDT-induced effects. Three second-generation photosensitizers have been tested for their ability to produce photodynamic response in the chick embryo/CAM system when delivered by i.p. injection: 5-aminolevulinic acid (ALA), benzoporphyrin derivative monoacid ring A (BPD-MA), and Lutetium-texaphyrin (Lu-Tex). Exposure of the CAM vasculature to the appropriate laser light results in light-dose-dependent vascular damage with all three compounds. Localization of ALA following i.p. injections in embryos, whose CAMs have been implanted with rat ovarian cancer cells to produce nodules, is determined in real time by fluorescence of the photoactive metabolite protoporphyrin IX (PpIX). Dose-dependent fluorescence in the normal CAM vasculature and the tumor implants confirms the uptake of ALA from the peritoneum, systemic circulation of the drug, and its conversion to PpIX.