Cytotoxic and Photodynamic Effects of Photofrin® on Sensitive and Multi-drug-resistant Friend Leukaemia Cells

To study cross-resistance to Photofrin (PF) photosensitization, a Friend leukaemia cell line (ADM-RFLC) with a high level of multi-drug resistance (MDR) and the parental sensitive cell line (FLC) have been used. PF uptake measured by HPLC shows a similar intracellular drug accumulation in both cell lines. The ID50s for cell growth inhibition by PF are also similar after exposure in the dark in the two cell lines, while after illumination they are slightly lower in ADM-RFLC than in FLC cells. Moreover, verapamil, known to reverse the MDR phenotype induced by P-glycoprotein over-expression (the drug efflux mechanism), affects equally ADM-RFLC and FLC cells sensitivity to PF. In addition, photodynamic treatment with PF did not reverse the resistance to rhodamine 123 and aclarubicin, but partly reverses resistance of ADM-RFLC cells to antitubulin drugs such as vinblastine or vincristine. These latter results could have clinical application in the treatment of tumours expressing the MDR phenotype.

[Clinical study of 1949 cases of port wine stains treated with vascular photodynamic therapy (Gu's PDT)]

BACKGROUND

Complete fading of port wine stains (PWS) is difficult to achieve with current laser treatments. Photodynamic therapy (Gu's PDT) could offer a very efficient alternative for PWS therapy.

PATIENTS AND METHOD

1949 lesions in 1385 patients were treated by PDT. Each patient received an intravenous injection of hematoporphyrin derivative (HpD) or hematoporphyrin monomethyl ether (HMME) at 3-7 mg/kg. Laser irradiation was performed on a 2 to 8 cm spot size. Different wavelengths (488.0 nm to 578.2 nm) were evaluated with a power density of 50-100 mW/cm2. Fluences ranged from 90 to 540 J/cm2.

RESULTS

Among the 1942 lesions, PWS clearance was observed in 99.7% of cases. Excellent results were achieved in 128 lesions (6.6%) (100% clearance), 746 lesions (38.3%) yielded to good results (clearance > 75%), 923 lesions (47.4%) showed moderate results (clearance 50-75%), 145 lesions (7.4%) showed poor results (clearance<50%) and in 7 lesions (0.3%) no visible change was observed. The pink port wine stains revealed better response to Gu's PDT with only one session. Conversely, purple stains in adult patients required 2 sessions or more.

CONCLUSION

This new PDT technique is effective and highly selective, with almost no risk of scarring.

Synovial ablation in a rabbit rheumatoid arthritis model using photodynamic therapy

BACKGROUND

At present there is no ideal minimally invasive method for ablating inflamed synovium in joints that has been unresponsive to optimal medical management in patients with rheumatoid arthritis. The aim of this study was to determine whether photo-dynamic therapy could be used for this purpose.

METHODS

In a rabbit knee model of rheumatoid arthritis the pharmacokinetics of the photosensitizer Haematoporphyrin Derivative (HpD) into periarticular tissues and blood was measured following intravenous injection of HpD. The second phase of the study was to determine the histological effect of HpD activation by 63 nm light delivered via an intra-articular optic fibre using a dye pumped KTP-YAG laser. The light dose was varied from 0-200 joule/cm2.

RESULTS

Pharmacokinetic studies determined that inflamed synovium rapidly accumulated HpD, with peak levels being reached 12 h following intravenous injection. The ratio of HpD uptake into inflamed synovium versus peri-articular quadriceps muscle was found to be 22.8. Histological examination of the treated knees indicated that selective destruction of inflamed synovium was achieved at light doses 100 joules/cm2 and above. No significant effect was observed on normal intra-articular tissues.

CONCLUSION

We have demonstrated that the first generation photosensitizer HpD selectively accumulates within inflamed -synovium. Activation of HpD by intra-articular light administration resulted in selective ablation of the inflamed synovium. These findings indicate that PDT offers potential as a new selective, minimally invasive synovectomy technique.

Effects of photodynamic treatment on biological antioxidant systems in rats

Effects of photodynamic treatments on inherent antioxidant metabolites and cellular defence enzymes have been investigated in rats. Wistar rats were grouped into untreated controls, light controls, hematoporphyrin derivative (Hpd) (treated with 5 and 10 mg Hpd/kg body weight and kept in dark) and sets treated with both Hpd and red light (dose 172 and 344 j/m2 ). After 2, 24, 48 and 72 hr of Hpd injection the rats sacrificed, livers quickly excised to analyze Hpd uptake, activities of enzymes like catalase, GSH-Px and antioxidants like GSH, vitamin A, vitamin E and vitamin C. The results showed that the loss of Hpd from liver as a function of post- injection time was non- linear. An increased generation of lipid radicals was observed in the groups treated with 5 mg Hpd and higher dose of light and in groups treated with 10 mg Hpd at both the doses of light. Combination of light and Hpd reduced hepatic GSH content with a concomitant reduction in GSH-Px. At higher doses of Hpd and light, there was a significant reduction in hepatic vitamin A levels. Combination of Hpd and light in all doses reduced vitamin E content in liver. The decreased biological antioxidant contents and GSH-Px may be attributed to their utilization for the scavenging of free radicals generated by Hpd and light in tissues. However, no change in catalase activity and vitamin C content in liver was noted in experimental rats. The results suggest that exposure to higher doses of Hpd with light alters oxidant stress system and TBARS content in rat.

Fluorescence lifetime imaging of experimental tumors in hematoporphyrin derivative-sensitized mice

Tumor detection has been carried out in mice sensitized with hematoporphyrin derivative (HpD) by measuring the spatial distribution of the fluorescence lifetime of the exogenous compound. This result has been achieved using a time-gated video camera and a suitable mathematical processing that led to the so-called "lifetime images." Extensive experimental tests have been performed on mice bearing the MS-2 fibrosarcoma or the L1210 leukemia. Lifetime images of mice show that the fluorescence decay of HpD is appreciably slower in the tumor than in healthy tissues nearby, allowing a reliable detection of the neoplasia. The lengthening of the lifetime in tumors depends little on the drug dose, which in our experiments could be lowered down to 0.1 mg/kg body weight, still allowing a definite tumor detection. In order to ascertain the results achieved with the imaging apparatus, high-resolution spectroscopy, based on a time-correlated single photon counting system, has also been performed to measure the fluorescence lifetime of the drug inside the tumor and outside. The outcomes obtained with two techniques are in good agreement.

A solubilization technique for photosensitizer quantification in ex vivo tissue samples

The determination of the photosensitizer concentration in ex vivo tissue samples is commonly used for pharmacokinetic and dosimetric studies of photodynamic therapy, both clinically and pre-clinically. In this report, a new method is presented based on tissue solubilization and subsequent fluorometry. This method has the advantages of good sensitivity, accuracy and reproducibility, as well as low cost and ease of handling of the tissue samples. The method was tested for six different photosensitizers in a variety of tissues. The accuracy and concentration detection limits are compared with those of other published extraction methods.

Cellular accumulation and biological activity of hematoporphyrin derivative(L) in comparison with photofrin II

Hematoporphyrin derivative, a drug used in the photodynamic therapy of solid tumours was synthesized in the laboratory and was called Hpd(L). Physico-chemical and biological properties of this drug have been compared with Photofrin II, the commercially available drug. Both Hpd(L) and Photofrin II possess similar properties qualitatively. Quantitatively, Hpd(L) was half as active as Photofrin II in its efficacy in causing photodynamic cytotoxicity or in the optical densities at the absorption peaks. These differences could be due to the differences in the compositions. Hpd(L) is a non-purified complex mixture of a number of porphyrin derivatives whereas Photofrin II is a relatively purer compound consisting of di- and tri-hematoporphyrins linked through ether or ester bonds. In vitro cellular uptake and retention of these drugs has been found to be a passive process not involving energy expenditure. pH and temperature of the incubation media have been found to profoundly influence these processes, while a complex relation seems to exist between physiological state of a cell and accumulation of these photosensitizers.

Determination of the maximal tumor/normal skin ratio after HpD or m-THPC administration in hairless mouse (SKh-1) by fluorescence spectroscopy--a non-invasive method

Two major steps in our study on the treatment of skin tumors by photochemotherapy (PCT) were the development of a skin tumor model in hairless mice by chemical carcinogenesis and by the use fluorescence spectroscopy, a semi-quantitative and non-invasive method, to determine the time after i.p. injection of photosensitizer when the tumor/normal skin ratio is the highest. Carcinogenesis provided mice bearing many benign papillomas 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)-chlorin (m-THPC) (0.3 mg/kg body weight) were injected, and fluorescence measured at 4, 8, 24, 48, 72 and 96 h after injection. The tumor/normal skin ratio was 6.2 for HpD and 5.1 for m-THPC. The times required to reach these ratios were 48 h for HpD and 72 h for m-THPC. Published reports indicate that m-THPC gives a much higher tumor/normal skin ratio than HpD. These results must be confirmed by organic extraction. Photodynamic therapy with the same doses of HpD and m-THPC used in this pharmacokinetic study must also be carried out to compare the toxicities of the two photosensitizers and to determine which is best for this type of tumor.

Subcellular localization of Photofrin and aminolevulinic acid and photodynamic cross-resistance in vitro in radiation-induced fibrosarcoma cells sensitive or resistant to photofrin-mediated photodynamic therapy

The subcellular and, specifically, mitochondrial localization of the photodynamic sensitizers Photofrin and aminolevulinic acid (ALA)-induced protoporphyrin-IX (PpIX) has been investigated in vitro in radiation-induced fibrosarcoma (RIF) tumor cells. Comparisons were made of parental RIF-1 cells and cells (RIF-8A) in which resistance to Photofrin-mediated photodynamic therapy (PDT) had been induced. The effect on the uptake kinetics of Photofrin of coincubation with one of the mitochondria-specific probes 10N-Nonyl acridine orange (NAO) or rhodamine-123 (Rh-123) and vice versa was examined. The subcellular colocalization of Photofrin and PpIX with Rh-123 was determined by double-label confocal fluorescence microscopy. Clonogenic cell survival after ALA-mediated PDT was determined in RIF-1 and RIF-8A cells to investigate cross-resistance with Photofrin-mediated PDT. At long (18 h) Photofrin incubation times, stronger colocalization of Photofrin and Rh-123 was seen in RIF-1 than in RIF-8A cells. Differences between RIF-1 and RIF-8A in the competitive mitochondrial binding of NAO or Rh-123 with Photofrin suggest that the inner mitochondrial membrane is a significant Photofrin binding site. The differences in this binding may account for the PDT resistance in RIF-8A cells. With ALA, the peak accumulations of PpIX occurred at 5 h for both cells, and followed a diffuse cytoplasmic distribution compared to mitochondrial localization at 1 h ALA incubation. There was rapid efflux of PpIX from both RIF-1 and RIF-8A. As with Photofrin, ALA-induced PpIX exhibited weaker mitochondrial localization in RIF-8A than in RIF-1 cells. Clonogenic survival demonstrated cross-resistance to incubation in PpIX but not to ALA-induced PpIX, implying differences in mitochondrial localization and/or binding, depending on the source of the PpIX within the cells.

Sensitivity of 9L gliosarcomas to photodynamic therapy

Photodynamic therapy (PDT) has been used clinically for the treatment of malignant brain gliomas. However, the efficacy of this treatment to date has remained equivocal. This study focused on determining the sensitivity of 9L glio sarcoma in Fischer 344 rats to PDT with increasing doses of 632 nm light and making a comparison of the responses of normal and tumor tissue in the brain at these doses. This sensitivity was then correlated with the concentrations of Photoforin present in these tissues at the time of treatment. Our study indicates that the level of Photofrin in the tumor was 13 times that present in normal brain 48 h after injection. However, this selective localization of the photosensitizer was not reflected in a selective tissue response to PDT. There was minimal tumor response to a dose of 35 J cm-2, which has been reported previously to cause necrosis to the normal brain. Increasing energy dose levels resulted in an increased tumor response to PDT; however, normal tissue remained more sensitive than tumor tissue at all energy dose levels examined. These data indicate that, although Photofrin is retained to a significantly higher degree in the tumor than in the normal brain tissue, the normal brain is more sensitive than the tumor to PDT under the conditions outlined in this study.

Structure and biodistribution relationships of photodynamic sensitizers

Photodynamic therapy (PDT) has, during the last quarter century, developed into a fully fledged biomedical field with its own association, the International Photodynamic Association (IPA) and regular conferences devoted solely to this topic. Recent approval of the first PDT sensitizer, Photofrin (porfimer sodium), by health boards in Canada, Japan, the Netherlands and United States for use against certain types of solid tumors represents, perhaps, the single most significant-indicator of the progress of PDT from a laboratory research concept to clinical reality. The approval of Photofrin will undoubtedly encourage the accelerated development of second-generation photosensitizers, which have recently been the subject of intense study. Many of these second-generation drugs show significant differences, when compared to Photofrin, in terms of treatment times postinjection, light doses and drug doses required for optimal results. These differences can ultimately be attributed to variations in either the quantum efficiency of the photosensitizer in situ, which is in turn affected by aggregation state, localized concentration of endogenous quenchers and primary photophysics of the dye, or the intratumoral and intracellular localization of the photosensitizer at the time of activation with light. The purpose of this review is to bring together data relating to the biodistribution and pharmacokinetics of second-generation sensitizers and attempt to correlate this with structural and electronic features of these molecules. As this requires a clear knowledge of photosensitizer structure, only chemically well-characterized compounds are included, e.g. Photofrin and crude sulfonated phthalocyanines have been excluded as they are known to be complex mixtures. Nonporphyrin-based photosensitizers, e.g. rose bengal and the hypericins, have also been omitted to allow meaningful comparisons to be made between different compounds. As the intracellular distribution of photosensitizers to organelles and other subcellular structures can have a large effect on PDT efficacy, a section will be devoted to this topic.

Photodynamic therapy: a 5-year study of its effectiveness in the treatment of posterior uveal melanoma, and evaluation of haematoporphyrin uptake and photocytotoxicity of melanoma cells in tissue culture

A human melanoma cell line RVH-421 which selectively demonstrates melanin synthesis when cultured in L15 Leibowitz medium but not in RPMI medium was used as a model to examine haematoporphyrin derivative (HPD) uptake and the photocytotoxicity of photodynamic therapy (PDT). Confocal scanning microscopy and extraction fluorometry showed HPD uptake in both non-pigmented and pigmented melanoma cells. Phototoxicity was determined by incubating pigmented and non-pigmented monolayer cells with HPD, exposing them to variable periods of white fluorescent light and calculating the number of viable cells in the samples relative to the controls. Both the non-pigmented and pigmented melanoma cells were affected by light-dependent cytotoxicity which was greater in the non-pigmented cells. Melanin or other substances may reduce the photo-oxidative effects of PDT. Posterior uveal melanomas in 36 patients were treated with PDT with the longest duration of tumour control being 6.5 years. Kaplan-Meier survival analysis showed that 76% of melanomas were not growing at the end of the first year, declining to 62% at the end of the second year, with 38% showing no signs of growth at the end of the fifth year. No eyes were lost as a result of PDT. Cox's hazards analysis showed that the degree of tumour pigmentation and patient age at therapy significantly influence the tumour response to PDT.

Correlation of distribution of sulphonated aluminium phthalocyanines with their photodynamic effect in tumour and skin of mice bearing CaD2 mammary carcinoma

A chemical extraction assay and fluorescence microscopy incorporating a light-sensitive thermoelectrically cooled charge-coupled device (CCD) camera was used to study the kinetics of uptake, retention and localisation of disulphonated aluminium phthalocyanine (A1PcS2) and tetrasulphonated aluminium phthalocyanine (A1PcS4) at different time intervals after an i.p. injection at a dose of 10 mg kg-1 body weight (b.w.) in tumour and surrounding normal skin and muscle of female C3D2/F1 mice bearing CaD2 mammary carcinoma. Moreover, the photodynamic effect on the tumour and normal skin using sulphonated aluminium phthalocyanines (A1PcS1, A1PcS2, A1pcS4) and Photofrin was compared with respect to dye, dye dose and time interval between dye administration and light exposure. The maximal concentrations of A1PcS2 in the tumour tissue were reached 2-24 h after injection of the dye, while the amounts of A1PcS4 peaked 1-2 h after the dye administration. A1PcS2 was simultaneously localised in the interstitium and in the neoplastic cells of the tumour, whereas A1PcS4 appeared to localise only in the stroma of the tumour. The photodynamic efficiency (light was applied 24 h after dye injection at a dose of 10 mg kg-1 b.w.) of the tumours was found to decrease in the following order: A1PcS2 > A1PcS4 > Photofrin > A1PcS1. Furthermore, photodynamic efficacy was strongly dependent upon dye doses and time intervals between dye administration and light exposure: the higher the dose, the higher the photodynamic efficiency. The most efficient photodynamic therapy (PDT) of the tumour was reached (day 20 tumour-free) when light exposure took place 2 h after injection of A1PcS2 (10 mg kg-1). A dual intratumoral localisation pattern of the dye, as found for A1PcS2, seems desirable to obtain a high photodynamic efficiency. The kinetic patterns of uptake, retention and localisation of A1PcS2 and A1PcS4 are roughly correlated with their photodynamic effect on the tumour and normal skin.

Study of porphyrin fluorescence in tissue samples of tumour-bearing mice

A time-gated fluorescence-imaging technique was applied to study the distribution of sensitizer in porphyrin-treated tumour-bearing mice. The animals were administered with either haematoporphyrin derivative (HpD) or Photofrin and sacrificed 4 or 12 h later. Fluorescence images were acquired from tumour, skin, muscle, fat, brain, lymph node, bowel and bone of both treated and untreated mice. The results obtained with HpD and Photofrin are similar. In images acquired 30 ns after excitation a bright exogenous fluorescence allows clear detection of the tumour. Nevertheless, the images show that porphyrins localize with different concentrations in all the examined tissues except the brain. Moreover, an appreciable long-living endogenous emission was observed in the bone.

Lack of reciprocity in drug and light dose dependence of photodynamic therapy of pancreatic adenocarcinoma in vitro

Two human pancreatic cell lines, MIA PaCa 2 and Capan 2, were treated by photodynamic therapy in vitro with Photophrin (0.01-25 micrograms/ml; 24 h) and then light (1-50 J/cm2; lambda = 630 nm). The following model was fit to 6 datasets with weighted nonlinear regression: [sequence: see text] The symbols are: E, cell growth; Econ, control growth in the absence of the combination; B, background signal; m, slope parameter; gamma, interaction parameter; D, concentration of Photofrin; L, light dose; F, fraction of Photofrin not photobleached by the light dose; k, k1, k2, bleaching parameters; A, distribution parameter for biexponential bleaching equation. Simple reciprocity of photosensitizer concentration and light dose was not found; compensation for photobleaching was critical. MIA PaCa2 required the monoexponential bleaching factor, whereas Capan 2 required the biexponential bleaching factor. The greater photosensitivity of MIA PaCa2 over Capan 2 can be best explained not by differences in the interaction parameter but rather by differences in the photobleaching pattern and rate. It may be possible to further enhance the selectivity of photodynamic therapy if differences in photobleaching between different cell types can be exploited by adequate dosimetry.

Clinical pharmacokinetic studies of photofrin by fluorescence spectroscopy in the oral cavity, the esophagus, and the bronchi

BACKGROUND

To optimize photodynamic therapy (PDT) and photodetection of cancer, two important variables that must be considered are the uptake of the dye and the dye contrast between normal and neoplastic tissue after injection.

METHODS

To study these variables in a clinical context, an apparatus based on a noninvasive optical fiber that detects the dye by light-induced fluorescence (LIF) was constructed.

RESULTS

Studies on the pharmacokinetics of the fluorescent fraction of Photofrin in patients with early squamous cell carcinoma in the oral cavity, esophagus or bronchi show a signal contrast ranging from 1.5 to 3.5 a short time after intravenous injection that rapidly decreases and tends to unity (one) about 12 hours later. The magnitude of this contrast appears to correlate with the staging of the cancer, the more invasive tumors showing the highest contrast. The more invasive tumors also show the highest uptake. The oral cavity pharmacokinetics are similar to those found in the esophagus and the bronchi.

CONCLUSIONS

The oral cavity appears to be a good model, with easy access for optimizing photodetection and PDT in the esophagus and the bronchi. These pharmacokinetics can be used directly for optimizing photodetection. However, complementary information on the detailed localization of the drug by fluorescence microscopy and a correlation of these data with tumor necrosis efficacy are necessary to optimize PDT timing and therapeutic gain.

Decreased expression and function of alpha-2 macroglobulin receptor/low density lipoprotein receptor-related protein in photodynamic therapy-resistant mouse tumor cells

Parental and photodynamic therapy (PDT)-resistant mouse, radiation-induced fibrosarcoma cell lines were evaluated using mRNA differential display in an attempt to identify unique transcripts. We detected one transcript that was consistently present in the parental cells but absent in PDT-resistant cells. The transcript was cloned, sequenced, and identified as alpha-2 macroglobulin receptor/low density lipoprotein receptor-related protein (alpha-2 MR/LRP). Northern and Western immunoblot analysis confirmed that receptor expression was present in the parental cell line but barely detectable in PDT-resistant cells. Functionality of the receptor was evaluated by exposing cells to Pseudomonas exotoxin A. alpha-2 MR/LRP is responsible for Pseudomonas exotoxin A internalization, and only the parental cells exhibited toxin-mediated cytotoxicity. The binding and endocytosis of activated alpha-2 macroglobulin and lipoproteins by alpha-2 MR/LRP are consistent with modulating uptake and localization of photosensitizers. Our results demonstrate that PDT-resistant murine tumor cells exhibit minimal alpha-2 MR/LRP activity and suggest that this receptor plays a role in PDT sensitivity by modulating photosensitizer uptake and/or subcellular localization.

Photofrin-induced fluorescence in progressive and regressive murine colonic cancer cells: correlation with cell photosensitivity

Microspectrofluorometry and fluorescence imaging were used to investigate the intracellular fluorescence of two murine colonic cancer cell lines--a progressive cell line (PROb) and a regressive cell line (REGb)--incubated with Photofrin. These two cell lines, which were initially cloned from the same chemically induced colonic murine cancer, differ in their metastatic properties and have been considered as models to mimic the tumoral cell heterogeneity. The fluorescence from cytoplasmic area of cells incubated with Photofrin appeared as a complex emission, with two maxima at 632 and 695 nm assigned to monomer species, and a poorly resolved band around 665 nm assigned to aggregates. The spectral distribution was shown to depend on the incubation time, with an aggregate contribution increasing for extended periods. The amount of Photofrin uptake, as determined from the total fluorescence intensity, was found for PROb to be twice that for REGb. However, the phototoxicities were quite similar for both cell lines, suggesting that drug concentration may not be the only determining factor in photobiological efficiency.

The quantitative determination of Photofrin and Polyhaematoporphyrin in plasma: pitfalls and inaccuracies

An accurate and relatively rapid fluorometric assay for Photofrin, or our own preparation Polyhaematoporphyrin (PHP), in plasma has been developed. This method takes into account the significant proportion of hydrolysis-resistant material now known to be present in these sensitizers, which has undoubtedly led to the inaccurate assessment of these drugs and other preparations of haematoporphyrin derivative (HPD) in numerous studies. The method was devised to allow for incomplete hydrolysis by calibration with plasma samples to which known amounts of photosensitizer were added in vitro. It was then compared with an "absolute" method in which plasma from animals that had received 14C-labelled drug was subjected to radioactivity assay. The two approaches gave almost identical results. The calibration method is applicable to the determination of any HPD-derived drug from patient or animal studies. As an example of its use in the present study, it was applied to the determination of the pharmacokinetics of PHP in the rat.

Biodistribution of haematoporphyrin analogues in a lung carcinoma model

In an attempt to identify novel compounds useful for the optimization of Photodynamic Therapy (PDT), the tissue localization of new synthetic porphyrins was compared with Photofrin II in nude mice xenografted with a human small cell lung cancer (POVD). Three haematoporphyrin analogues were selected for this study based on prior in vitro photosensitivity screening of a series of 15 such derivatives, as well as on the basis of improved localization in C6 gliomas in mice. Two of the porphyrins yielded better tumour:normal lung ratios than Photofrin II and, of these two, one (P13) is known to exhibit good photosensitization properties both in vitro and in vivo, and is therefore a good candidate as a lead compound for the development of porphyrins suitable for the photodynamic treatment of lung tumours.

Rat reproductive performance following photodynamic therapy with topically administered Photofrin

A rat animal model was used for comparing the photodynamic efficacy of two formulations of topically administered Photofrin in the uterus: 0.7 mg/kg Photofrin and 0.7 mg/kg Photofrin + 4% Azone, a penetration-enhancing agent. Uterine structure and reproductive performance were evaluated following illumination with 80 J/cm2 of 630 nm light. Fluorescence microscopy was employed to determine drug localization in frozen uterine sections at various times after drug administration. Functionality studies demonstrated a significant reduction in the number of implantations per treated uterine horn compared to controls. The mean number of implantations decreased systematically on increasing the interval between Photofrin administration and light application. At 72 h, 0.88 +/- 0.52 gestational sacs per rat were recorded with Photofrin therapy, compared with 8.1 +/- 1.12 (P = 0.01) on the untreated side, indicating nearly complete loss of reproductive capability. Similar results were achieved after only 3 h treatment with Photofrin + Azone (0.38 +/- 0.26 sacs per rat versus 7.5 +/- 1.07 on the untreated side; P = 0.01). This indicates that the effect of Photofrin can be enhanced either by extending the drug incubation period from 3 to 72 h or by adding the penetration-enhancing drug Azone. Fluorescence pharmacokinetic studies suggest that both forms of topically administered Photofrin are diffusely distributed throughout the endometrium at virtually the same rate. However, Azone may enhance the selectivity of photodynamic therapy by facilitating drug targeting to critical endometrial structures.

Fluorescence localization in tumour and normal brain after intratumoral injection of haematoporphyrin derivative into rat brain tumour

In the intracerebral 9L rat gliosarcoma, the spatial distribution of the photosensitizer haematoporphyrin derivative (HpD) was studied after intratumoral injection. The fluorescence volume was measured in histological sections from 10 min up to 5 days after injection. Complete sensitization of the tumours could not be achieved by slow stereotactical injection of 4 mm3 HpD (mean HpD fluorescence volume, 13 +/- 11 mm3). Larger parts of the tumour could be loaded with HpD (39 +/- 23 mm3, p = 0.0001) by increasing the injection velocity and the volume to 50 mm3. Again, complete sensitization of the tumours was not achieved during a time scale of 5 days after intratumoral injection. Although the fluorescence volume did not change significantly with time, it was influenced by the injection site within the tumour. Injection of HpD within 1 mm from the tumour border resulted in significantly smaller fluorescence volumes in the tumour than injection into the tumour centre. Large injection volumes caused an increased leakage of HpD to normal brain, leading to the loss of selectivity of photosensitizer content and the occurrence of dark toxicity of normal brain while the tumours still appeared vital.

Absorption spectrum of hematoporphyrin derivative in vivo in a murine tumor model

Time-resolved reflectance was used to measure the absorption spectrum of hematoporphyrin derivative (HpD) in vivo in a murine tumor model. Reflectance measurements were performed in the 600-640 nm range on mice bearing the L1210 leukemia. Then the animals were administered 25 mg/kg body weight of HpD intraperitoneally. One hour later the reflectance measurements were repeated. Fitting of the data using the diffusion theory allowed assessment of the absorption coefficient before and after the administration. As a difference between the latter and the former data, the in vivo absorption spectrum of HpD was evaluated. Maximum absorption was measured at 620-625 nm. Similar spectral behavior was obtained for HpD in solution in the presence of low-density lipoproteins.

On the relationship between rate of uptake of Photofrin and cellular responses to photodynamic treatment in vitro

The Burkitt's lymphoma cell line Namalva was used as an in vitro model to study the accumulation and photocytotoxic properties of Photofrin, the photosensitizer currently in clinical trials. Photofrin uptake and intracellular protein binding were evaluated as a function of the incubation time using fluorescence spectroscopy. The drug concentration strongly affected the intracellular distribution pattern of Photofrin, which in turn was shown to correlate with the Namalva cell response to photodynamic action. At low drug load, a gradual cell response varying from transient cell cycle arrest (predominantly S-phase) to marked photocytotoxicity modulated by incubation time and light dose was observed. High drug load resulted in lethality without cell cycle selectivity. The data suggest possible Photofrin targeting of protein factors involved in cell proliferation.

[The distribution of hematoporphyrin derivatives in the animal body]

The pharmacokinetic distribution of haematoporphyrin derivative (HPD) and synthetic oligomeric haematoporphyrin (OG) which showed various lipophilicity was studied in animal tumor and normal tissues. The accumulation of dyes in tissue and their tumor-seeking capacity depended on the degree of polymerization, lipophilicity, and ratio of dye components. The difference in the absolute concentrations of HPD and OG (6.9 and 16.1 micrograms per g tissue, respectively) in tumor after dye injection in an adequate concentration (10 mg/kg b. w.) indicates that synthetic OG is beneficial for tumor diagnosis and photodynamic therapy.

The uptake of porphyrin and zinc-metalloporphyrin by the primate prostate

The relative distribution of sensitizer drugs in the prostate and its contiguous organs is of importance in the treatment of localized prostatic cancer with photodynamic therapy. Using the primate model, whose prostate is both morphologically and physiologically homologous with its human counterpart, the distribution of hematoporphyrin derivative (HpD) amongst organs of urological interest was determined. Hematoporphyrin derivative levels were comparatively low in both caudal and cranial prostatic lobes (0.93-1.77 micrograms/g) and were similar to those in rectum, urethra and the skin. The reticuloendothelial organs, liver, spleen and also the kidney accumulated the highest quantities of porphyrin (4.76-9.8 micrograms/g, liver > spleen > kidney). Despite a high avidity of prostatic tissue for zinc, a zinc-metalloporphyrin (Zn-HpD) did not concentrate selectively in the prostate. The results are of clinical value in view of the homology between the primate and the human.

Effect of administration route and estrogen manipulation on endometrial uptake of Photofrin porfimer sodium

OBJECTIVE

Our purpose was to evaluate the influence of the route of drug administration and target tissue vascularity on the distribution of a photosensitizer, Photofrin porfimer sodium, in the uterus.

STUDY DESIGN

The study was divided in two phases. In phase I 80 mature female rats were hormonally suppressed and then stimulated with estrogen. They were randomized to receive intravenous, intraperitoneal, or intrauterine Photofrin and killed 3, 6, 24, or 48 hours later. Drug distribution and levels were then determined. In phase II 40 female rats were randomized to receive hormonal stimulation, suppression, both, or neither. All received intrauterine Photofrin and were killed 24 hours later. Statistical analysis was performed with the unpaired t test and the two-way analysis of variance.

RESULTS

Intrauterine administration was determined to be the simplest and most effective method of delivery because it provided for optimal uptake and distribution (p = 0.05) within the uterus, at lower doses.

CONCLUSIONS

Selective localization of photosensitizer within the target tissue suggests that highly selective photodynamic destruction of endometrial tissue can be achieved. Furthermore, the combination of intrauterine administration of photosensitizer with estrogen adjuvant may minimize the most debilitating side effect of Photofrin, cutaneous phototoxicity.

Fluorescence detection of tumors. Early diagnosis of microscopic lesions in preclinical studies

BACKGROUND

The growth of microscopic tumor lesions at or beyond treatment field margins poses a major problem in the diagnosis and treatment of cancer. Early detection techniques that clearly define the location or field spread of disease may improve the planning of disease treatment.

METHODS

In vivo fluorescence photometry is a non-imaging technique that digitally displays relative fluorescence values in volts proportional to the luminescence intensity detected by a silicon photodiode. The sensitivity of the instrument has allowed the detection of micrometastases in preclinical studies.

RESULTS

Statistical analysis demonstrates that the photosensitizer Photofrin (dihematoporphyrin ether and/or ester) (Quadra Logic Technologies, QLT, Vancouver, B.C., Canada), currently used for photodynamic therapy, administered in doses lower than those used in clinical studies, is useful for the detection of occult disease. With the drug doses used, cutaneous photosensitivity was avoided in the animal models tested. The results in Lobund-Wistar rats with transplantable prostatic adenocarcinoma (PA-III) demonstrated the utility of this technique in detecting clinically occult disease, with a prediction rate of approximately 94% with drug doses as low as 0.25-0.5 mg/kg.

CONCLUSIONS

With the use of the hamster buccal cavity model involving the initiation and promotion of premalignant and malignant conditions by 9,10 dimethyl-1,2-benzanthracene, the technique could discern these two stages of disease with significance levels that were less than 0.05 and 0.01, respectively.

Assessing Photofrin uptake in atherosclerosis with a fluorescent probe: comparison with photography and tissue measurements

The purpose of this study was to assess Photofrin porfimer sodium (P*) concentration in atherosclerotic plaque (ASP) using a fluorescence detector (Fluoroprobe) compared with fluorescent photography and chemical extraction of P*. ASP was created in the aortoiliac segments of Yucatan miniswine by a combination of balloon endothelial injury and 2% cholesterol and 15% lard diet for 7 weeks. At that time, swine were given P* I.V. in one of the following single dosages: Group I, 2.5; Group II, 1.0; or Group III, 0.5 mg/kg. Swine were sacrificed 24 hours later and aortoiliac and control carotid artery segments removed. Fluorescence was determined from these segments using photographic techniques, the Fluoroprobe, and a spectrofluorometer after chemical extraction. ASP were identified in all swine using photography and the Fluoroprobe. The intensity of fluorescence measured with the Fluoroprobe for Groups I to III was 1,098 +/- 524, 471 +/- 337, and 295 +/- 173 units, respectively (P < 0.01). The tissue concentration of P* in ASP from each group was 130.4 +/- 82.7, 10.0 +/- 1.2, and 9.1 +/- 0.6 ng/g, respectively (P < 0.01). There was a linear correlation between the fluorescence intensity measured with the Fluoroprobe and the extracted tissue concentration (r = 0.88, P < 0.0001). This study showed that a fluorescent detector such as the Fluoroprobe accurately detects the uptake of P* into atherosclerotic plaque.

Fluorospectral study of the rat brain and glioma in vivo

An animal model of cerebral glioma was utilized by implanting C6 glioma cells into the brains of adult Wistar rats. Once tumors developed to 7-12 mm in diameter, we conducted continuous fluorimetry monitoring of glioma up to 24 hours using a fibre-optic system connected to an intensified multichannel photodetector after an intravenous injection of hematoporphyrin derivative (HPD) into the rats. The intensity of the fluorescence in normal brain reached a plateau 6 hours after intravenous injection of HPD while that in glioma reached a plateau 80 minutes after injection. These fluorescence intensities of glioma, brain adjacent to tumor (BAT), and surrounding normal brain were measured in vivo 24 hours after intravenous administration of 5 mg/kg of HPD. The ratio of fluorescence intensities between glioma and brain was 6.1 while the ratio between BAT and brain was 3.9. There were no obvious differences in shapes between the spectra of the natural fluorescence (autofluorescence) of rat glioma and brain but the intensity of autofluorescence was much weaker in glioma. There are many problems in spectroscopic studies of biological tissues in vivo. It cannot be overemphasized that very strict criteria must be applied in order to get accurate data. Fluorescence from HPD administration may be used to discriminate tumor tissue from surrounding normal brain tissue during operation if the measuring conditions could be kept constant. It is important to understand the photospectral properties of glioma and brain tissue in order to get the most benefits in clinical application of light-induced fluorescence or photoradiation therapy.

Haematoporphyrin derivatives: distribution in a living organism

Pharmacokinetics of accumulation in organs and tissues was studied for two haematoporphyrin-based photosensitizers. These sensitizers, haematoporphyrin derivative (HpD) and an oligomeric haematoporphyrin (OHp), contained different amounts of monomeric fraction (25% and 5% respectively) and in OHp the macrocycles were bonded together with ether bonds. OHp was shown to accumulate in tumours in higher amounts than HpD. The maximal tumour to tissue concentration ratio for OHp was 6.7 observed 54 h after injection; the same ratio for HpD was 2.8 after 48 h.

Experimental photodynamic therapy with a copper metal vapor laser in colorectal cancer

In an attempt to define the best conditions for an adjunctive treatment of residual colonic microtumors by photodynamic therapy (PDT), an experimental model has been defined. S.c. HT29 colonic-cancer-cell tumors grown in nude mice were used and, 48 hr after i.p. administration of 30 mg/kg Photofrin (PH), laser illumination was performed with 75 or 150 Joules/cm2. The efficiencies of 2 lasers, the classically used rhodamine laser (RL) and a copper metal vapor laser (CMVL), were compared. The effects of PDT were assessed by histological and immunocytochemical (detection of a digestive enzyme, dipeptidyl-peptidase IV, as a marker of cell viability) follow-up and by the growth curve of the tumors after illumination. We conclude that, although the depth of necrosis resulting from PDT was nearly 3 mm at 75 J/cm2 and nearly 4-5 mm at 150 J/cm2 with both lasers, complete necrosis was obtained only with the CMVL at 150 J/cm2 (in 50% of the tumors). Under the other conditions, a layer of unaffected cells persisted at the pole opposite to laser illumination, resulting in growth curves lower than but parallel to those of the controls. Analysis of drug concentrations in the tumors and various organs, 48 hr after injection, i.e., at the time of laser illumination, revealed the presence of 21 micrograms/g dry weight PH in the tumors. The tumor vs. host-organ ratios were equal to or higher than 1 for the small bowel, colon, stomach, lung, skin and muscle. In contrast, the ratios were below 1 for the spleen, pancreas, kidney and liver.