Dihematoporphyrin Ether Research Articles

Photodynamic Therapy for Barrett's Esophagus and Esophageal Carcinoma

This paper reviews the use of photodynamic therapy (PDT) in patients with Barrett's esophagus and esophageal carcinoma. We describe the history of PDT, mechanics, photosensitizers for PDT in patients with esophageal disease. Finally, we discuss its utility and limitations in this setting.

PHOTOFRIN‐mediated photodynamic therapy for treatment of early stage (Tis‐T2N0M0) SqCCa of oral cavity and oropharynx

To evaluate the efficacy of dihematoporphyrin ether (PHOTOFRIN)-mediated photodynamic therapy (PDT) for the treatment of diffuse field cancerization and Tis-T2N0M0 squamous cell carcinoma (SqCCA) of the oral cavity and oropharynx in patients not amenable to or that have failed conventional head and neck cancer treatment. This is a retrospective study of 30 patients with Tis-T2N0M0 SqCCA of the oral cavity/oropharynx treated with PDT. Intravenous PHOTOFRIN (porfimer sodium) (dose 2.0 mg/kg) was administered outpatient, followed 48-60 hours later by intraoperative photoactivation at 630 nm via fiberoptic microlens surface delivery (light dose 50-100 J/cm(2)) or interstitial implantation via cylindrical diffuser fiberoptic delivery (light dose 50-100 J/cm). Twenty-four of 30 patients (80%) have demonstrated complete remission (follow-up 3-144 months). There were six patients who had partial remission with recurrence observed at 3, 3, 5, 9, 23, and 26 months subsequently retreated with conventional therapy. Eleven of 24 patients were cancer disease free at 2 years following PDT. PDT provides a surgical oncologic modality for potentially curative treatment of early stage oral cavity and oropharyngeal malignancies either as a primary modality or for treatment in patients that have previously failed surgery and/or radiation therapy.

Identification of porphyrin modified photosensitizer porfimer sodium and its precursors by high performance liquid chromatography and mass spectrometry

Photodit ® (porfimer sodium) is a complex mixture of porphyrin-modified oligomers that has demonstrated high photoactivity during photodynamic therapy of malignant tumors. Hematoporphyrin derivative monomer precursors of Photodit ® and its oligomers were analyzed using liquid chromatography and mass spectrometry to determine their chemical composition and structures. Hematoporphyrin ( M-3), O, O′-diacetylhematoporphyrin ( M-6), and isomers of 8(-3)-hydroxyethyl-3(-8)-vinyldeuteroporphyrin ( M-2), 8(-3)-(1-acetoxyethyl)-3(-8)-vinyldeuteroporphyrin ( M-4), and O-acetylhematoporphyrin ( M-5), in ratio 0.59:0.94:0.21:0.34:1.00, were identified as hematoporphyrin derivative monomer precursors. The main compounds of Photodit ® as a porfimer sodium salt were dimers: D-1 {di-[8(-3)-hydroxyethyl-3(-8)-vinyldeuteroporphyrin] ether}, D-2 {[Hematoporphyrin-8(-3)-hydroxyethyl-3(-8)-vinyldeutroporphyrin] ether}, and D-3 {Dihematoporphyrin ether} in ratio 0.51:1.00:0.50, and trimers: T-1 {(M-2)–(D-2) ether}, T-2 {(D-2)–(M-3) ether}, and T-3 {(D-3)–(M-3) ether} in ratio 0.98:1.00:0.44, respectively. An average oligomer length of 2.23 porphyrin units was determined.

Argon Laser Photodynamic Therapy of Human Corneal Neovascularization After Intravenous Administration of Dihematoporphyrin Ether

Long-term evaluation of dihematoporphyrin ether (DHE) safety and efficacy as photodynamic therapy (PDT) for patients with corneal neovascularization (KNV). Prospective multi-center interventional case series. Seven patients were enrolled after Institutional Review Board approval and a detailed informed consent were obtained. Eligible patients presented with clinically stable KNV without active vessel progression or inflammation. All patients with severe hypertension, history of renal or hepatic disease, or sensitivity to porphyrins, and those with active keratitis or uncontrolled ocular surface disease were excluded. DHE was administered as an intravenous bolus (2 mg/kg). Seventy-two hours later, PDT was carried out using argon green laser (514 nm). The main outcome measure, extent of vascular thrombosis, was estimated during postoperative follow-up examinations performed at day 1, 1 week, 6 months, and up to 12 years postoperative. All patients obtained an immediate reduction in measurable corneal vascularization. With at least 6 months of follow-up, six of seven patients maintained a significant reduction (52.5% +/- 19.6%, P < .01) in KNV. The mean length of followup was 5.4 years (Range = 6 months to 12 years) during which time there were no other ocular changes attributable to laser treatment. Three patients suffered significant systemic short-term phototoxicity reactions. Intravenous DHE followed by photodynamic treatment in humans is effective for the reduction of inactive, established KNV. However, the significant short-term adverse effects related to systemic administration of this drug are of particular concern and warrant further investigation.

Is Autofluorescence Bronchoscopy Needed to Diagnose Early Bronchogenic Carcinoma?

Is Autofluorescence Bronchoscopy Needed to Diagnose Early Bronchogenic Carcinoma?

Photodynamic Therapy

Photodynamic Therapy

Survival after photodynamic therapy to non-pulmonary metastatic endobronchial tumors

For the past 15 years we have used photodynamic therapy (PDT) to treat endobronchial tumors. Unfortunately patients who have non-primary lung cancer metastatic to bronchi and who have failed other treatment regimens may not be offered endobronchial tumor management. Thirteen patients with endobronchial tumors metastatic from non-pulmonary primaries were treated with PDT. We: 1) evaluated the effects of PDT on the tumor, the quality of life, and the length of survival; and 2) compared their survival after PDT to that of 27 patients with stage IV primary endobronchial tumors treated with PDT after they failed all other treatment regimens.Photodynamic therapy was performed using 630-nm light delivered through cylinder diffusing tip quartz fibers passed through the biopsy channel of a flexible bronchoscope after intravenous injection of the photosensitizer dihematoporphyrin ether. One to two days after PDT bronchoscopy was repeated and necrotic tissue was mechanically removed and, if necessary, that site or other new sites were treated. Two days after this another bronchoscopy was performed and the necrotic tissue was mechanically removed. Bronchoscopy was repeated one month after PDT and periodically thereafter as needed to re-treat symptomatic residual tumor. The percent obstruction of the bronchus due to tumor was estimated before and at the end of each bronchoscopy. Clinical effects were evaluated using Wilcoxon signed rank tests for scaled parameters of dyspnea, cough, hemoptysis, and Karnofsky Performance Status (KPS) before and one month after PDT. All patients were followed until their death.The mean percent obstruction due to metastatic non-pulmonary tumors at 38 different endobronchial treated sites decreased from 85% to 13% at discharge after PDT. The 72% mean decrease of obstruction was statistically significant using the Wilcoxon signed rank test (P < .0001). There was a statistically significant improvement in the level of dyspnea (P = .012), hemoptysis (P = .028), cough (P = .027), and KPS (P = .020). Kaplan-Meier survival curves and Mann-Whitney U rank tests showed the median survival of stage IV primary tumor patients (4 months) vs. metastatic tumor patients (14 months) was statistically significant (P = .008).PDT of endobronchial metastatic tumors effectively decreased the amount of endobronchial obstruction, and improved the quality of life.

Photophysical properties of porphyrins, phthalocyanines, and benzochlorins

This work examines the photophysical properties of a series of porphyrin, phthalocyanine, and benzochlorin derivatives. The porphyrin group includes tetraphenylporphyrin, divinylporphyrin ether, dihematoporphyrin ether, the trivinylporphyrin ether, and the trihematoporphyrin ether. The phthalocyanine group includes phthalocyanine tetrasulfonate, chloroaluminum phthalocyanine tetrasulfonate, zinc phthalocyanine tetrasulfonate, and aluminum naphthalocyanine tetrasulfonate. The chlorins include octaethylbenzochlorin, zinc octaethylbenzochlorin, octaethylbenzochlorin sulfonic acid, and zinc octaethylbenzochlorin sulfonic acid. Ethyl etiopurpurin is also studied. The UV-Vis and fluorescence emission spectra, fluorescence quantum yields, fluorescence rate constants, radiative and singlet state lifetimes are compared for the series of compounds. Results indicate that while the octaethylbenzochlorin and phthalocyanine photosensitizers profile, this profile is very different from that observed for the porphyrin photosensitizers.

Photodynamic therapy for endobronchial malignant disease: A prospective fourteen-year study

Background: After intravenous injection, the photosensitizer dihematoporphyrin ether is selectively retained in tumor cells. This photosensitizer absorbs 630 nm wavelength light energy and produces a singlet oxygen that destroys the tumor. Photodynamic therapy was performed on endobronchial tumors with the use of light generated by an argon dye laser system delivered through cylinder diffusing tip quartz fibers passed through the biopsy channel of a flexible endoscope. Objectives: Our objectives were to determine factors affecting survivals, benefits, and complications. Methods: From 1982 to May 1996, photodynamic therapy was performed on 175 patients with endobronchial tumors. Sixteen had stage I disease, 9 stage II, 42 stage IIIA, 64 stage IIIB, and 44 stage IV. All were followed up until death or November 1996. Results: Multivariate analysis of survival of the effects of age, sex, race, histologic features, Karnofsky Performance Status, and clinical stage showed the clinical stage ( p < 0.0001) to be the most statistically significant factor. Sixteen patients with stage I disease had a 93% 5-year disease-related estimated survival. Median (months) survivals were as follows: stage I = not reached; stage II = 22.5; stage IIIA = 5.7; stage IIIB = 55; and stage IV = 5.0. Performance status does become significant when it reaches 50 but was not significant for stages I or II. Conclusions: Photodynamic therapy may be considered as an alternative treatment for patients under consideration for surgical treatment for stage I carcinoma in whom the risk of surgery is high. The length of palliation for patients with noncurative disease was equal to or better than that reported historically for most other treatment regimens. (J Thorac Cardiovasc Surg 1997;114:940-7)

Photodynamic Therapy Using Topically Applied Dihematoporphyrin Ether in the Treatment of Cervical Intraepithelial Neoplasia

Objective: To perform a phase I study of topically applied dihematoporphyrin ether (DHE) in the photodynamic treatment (PDT) of cervical intraepithelial neoplasia (CIN) using fixed DHE doses and application schedules, and a variable dose of 630 nm red light delivered by an argon-pumped dye laser. Methods: Between February 1993 and April 1994, 24 nonpregnant women with a histologic diagnosis of CIN were enrolled. All patients had lesions involving at least 25% of the cervix that were colposcopically visible. Using a cervical cap, 2 ml of a 1% solution of DHE (Photofrin) in a 4% Azone and isopropyl alcohol vehicle were applied to the cervix 24 hr prior to PDT. An argon-pumped dye laser providing light at 630 nm was then used to perform PDT. Light was coupled into a 400-μm silica fiber optic terminating in a microlens which focused the laser radiation onto a circular field of uniform light intensity perpendicular to the tissue. The entire ectocervix was treated in a single field including a margin of 3–5 mm of normal cervix. Using a constant power density (150 mW/cm2) to avoid thermal injury, the PDT energy was increased every 4 patients in a phase I fashion (40, 60, 80, 100, 120, and 140 J/cm2). Results: Thirteen patients with CIN I, 7 patients with CIN II, and 4 patients with CIN III were treated. The maximal energy density was well tolerated. Toxicity was minimal with no patients experiencing local necrosis, sloughing, or scarring; however, a mild vaginal discharge was noted in several patients. Systemic effects were absent. After 12 months of follow-up at 3-month intervals, 22 patients are evaluable of whom 15 (68%) are disease free. One patient was lost to follow-up and in another the cervical cap was dislodged. Four of the 7 failures or recurrences occurred at energy densities of 80 J/cm2or less, while 8 of 11 (73%) patients were treated successfully with PDT at an energy density of 100 to 140 J/cm2. Conclusions: PDT with DHE and an argon-pumped dye laser at 630-nm wavelength delivering an energy density of 140 J/cm2is safe and effective in treating CIN. Phase II studies using PDT at the prescribed application schedule and dose are indicated.

Porphyrin-mediated photosensitization has a weak tumor promoting activity in mouse skin: possible role of in situ-generated reactive oxygen species.

Reactive oxygen species (ROS) have been implicated in skin tumor promotion. Earlier, we showed that porphyrin-mediated cutaneous photosensitization results in the in situ generation of ROS. Recently, we have provided the first in situ evidence for the involvement of ROS in stage I tumor promotion. In this study we further show that in situ-generated ROS act as weak complete tumor promoters in 7,12-dimethylbenz[a]anthracene (DMBA)-initiated mouse skin. Papillomas were induced in Swiss albino mice by a single topical application of DMBA as initiator. The promotion was achieved in these mice by the sustained generation of ROS through dihematoporphyrin ether (DHE)-mediated cutaneous photosensitization, which was done once every day (six times a week) for 24 weeks. The first appearance of visible papillomas could be recorded 24 weeks after the initiation. The highest tumor incidence of 60% occurred at a dose of 2.5 mg/kg body wt DHE. Increasing the dose of DHE produced a decrease in the incidence as well as in the number of papillomas. In contrast, the number of carcinomas/mouse increased with increasing dose of DHE. Histopathology of the tumor samples indicated the formation of in situ carcinoma also in skin. ROS generated through DHE-mediated photosensitization resulted in a approximately 3 fold induction of ODC activity 9 h after photosensitization. DHE-mediated photosensitization enhanced [3H]thymidine incorporation in cutaneous DNA in a dose-dependent manner. A maximum 5-fold induction of [3H]thymidine incorporation was observed at a dose of 10 mg/kg body wt DHE. The longer latency period, low incidence of tumor induction, low tumor yield and low induction of ODC activity as compared with TPA represent the weak but complete tumor promoting potential of in situ-generated ROS. The low tumor incidence and tumor yield observed at higher doses of DHE may be due to the ablation of tumors at early stages due to the strong photodynamic action of DHE.Our data indicate that porphyrin-mediated photosensitization has a weak tumor promoting effect in mouse skin and in situ-generated ROS may play an important role in the development of this response.

Effect of heparin on distal anastomotic intimal hyperplasia (DAIH)

Objective: To perform a phase I study of topically applied dihematoporphyrin ether (DHE) in the photodynamic treatment (PDT) of cervical intraepithelial neoplasia (CIN) using fixed DHE doses and application schedules, and a variable dose of 630 nm red light delivered by an argon-pumped dye laser. Methods: Between February 1993 and April 1994, 24 nonpregnant women with a histologic diagnosis of CIN were enrolled. All patients had lesions involving at least 25% of the cervix that were colposcopically visible. Using a cervical cap, 2 ml of a 1% solution of DHE (Photofrin) in a 4% Azone and isopropyl alcohol vehicle were applied to the cervix 24 hr prior to PDT. An argon-pumped dye laser providing light at 630 nm was then used to perform PDT. Light was coupled into a 400-μm silica fiber optic terminating in a microlens which focused the laser radiation onto a circular field of uniform light intensity perpendicular to the tissue. The entire ectocervix was treated in a single field including a margin of 3–5 mm of normal cervix. Using a constant power density (150 mW/cm2) to avoid thermal injury, the PDT energy was increased every 4 patients in a phase I fashion (40, 60, 80, 100, 120, and 140 J/cm2). Results: Thirteen patients with CIN I, 7 patients with CIN II, and 4 patients with CIN III were treated. The maximal energy density was well tolerated. Toxicity was minimal with no patients experiencing local necrosis, sloughing, or scarring; however, a mild vaginal discharge was noted in several patients. Systemic effects were absent. After 12 months of follow-up at 3-month intervals, 22 patients are evaluable of whom 15 (68%) are disease free. One patient was lost to follow-up and in another the cervical cap was dislodged. Four of the 7 failures or recurrences occurred at energy densities of 80 J/cm2or less, while 8 of 11 (73%) patients were treated successfully with PDT at an energy density of 100 to 140 J/cm2. Conclusions: PDT with DHE and an argon-pumped dye laser at 630-nm wavelength delivering an energy density of 140 J/cm2is safe and effective in treating CIN. Phase II studies using PDT at the prescribed application schedule and dose are indicated.

Variable Light-Dose Effect on Photodynamic Therapy for Laryngeal Papillomas

We investigated photodynamic therapy (PDT) as an alternative treatment modality for recurrent respiratory papillomatosis. To optimize the effect of PDT, the light dose in this study was increased from 50 to 80 J/cm2. The clinical effect of these two light doses will be discussed and compared. Each patient's response was based on the growth rate of their papilloma before and after PDT. Disease response following 50 J/cm2 was compared with that after 80 J/cm2. The two study groups were also compared with a control group. Each patient received the dihematoporphyrin ether as an outpatient and underwent direct laryngoscopy and PDT at our institution. Twenty-eight patients (16 male and 12 female) with moderate to severe laryngeal disease and an age range of 18 months to 80 years were treated with a light dose of 80 J/cm2, 11 of those had been previously treated with 50 J/cm2. Seven patients had undergone photoactivation to the trachea. Twenty-four hours prior to photoactivation, patients received 2.5 mg/kg of dihematoporphyrin ether intravenously. Photodynamic therapy was given using an argon pump dye laser system. Reduction in disease severity greater than that achieved with 50 J/cm2. For patients treated initially with 80 J/cm2, the mean rate of papilloma growth decreased by approximately 50%, the same response seen with 50 J/cm2 of treatment. No additional benefit was found for those patients initially activated at 50 J/cm2 and then re-treated at 80 J/cm2. Although PDT has a beneficial effect on laryngeal papilloma growth rate, no significant change in response was obtained by increasing the light dose from 50 to 80 J/cm2.

Dose-dependent destruction of human gastrointestinal neoplasms by photodynamic therapy

Background Photodynamic therapy (PDT) appears to be a promising method for the local treatment of malignant tumors. However, little data are available concerning the relationship between administered energy density and photosensitizer concentration with respect to the degree of tumor destruction. The present study was designed to evaluate this functional relationship in an in vivo tumor model with human gastrointestinal carcinomas. Methods Sixteen different human gastrointestinal tumors (two esophageal, five gastric, five colonic and four rectal), heterotransplanted into nude mice (NMRI—nu/nu), were treated either with different energy densities between 25 and 300J/cm2 at a constant sensitizer dose of 9 mg/kg or, alternatively, treated with different sensitizer dosages of 1.5 to 9 mg/kg at a constant energy density of 150J/cm2. Photosan containing the enriched active component dihematoporphyrinether (DHE) was used as a photosensitizer. Tumor necrosis was semiquantitatively measured by light microscopy. Results All tumors underwent tissue necrosis following PDT. When the drug dose was kept constant, the amount of tumor necrosis varied according to the applied energy density. For esophageal, gastric (150–300J/cm2) and colorectal cancers (75–100J/cm2), we were able to establish different threshold values for tumor necrosis ≥ 90%. When the energy density was kept constant, tumor necrosis increased as a function of the administered drug dose. Different threshold values for tumor necrosis ≥ 90% were determined for gastric (> 9 mg/kg), esophageal and colorectal (4.5 mg/kg) cancers with respect to the photosensitizer dose. Reciprocity of the applied photosensitizer and energy dose values could not be determined. Conclusions We conclude that human gastrointestinal carcinomas transplanted into nude mice exhibit different reactions to PDT. Both the photosensitizer dose and the energy density influence the extent of tumor necrosis. Our study shows that the prevailing clinical dosimetry for gastrointestinal tumors may result in inadequate treatment by under-or overdosing of the applied energy density or photosensitizer dose, the two most important treatment parameters in PDT.

Newer options for treating drug-resistant (MDR+) cancer cells using photoradiation therapy.

Emergence of drug resistance with conventional cytotoxic therapy is a major challenge towards the curability of many cancers, especially in patients undergoing autologous BMT with ex-vivo purged hematopoietic support. We have explored the potential role of photoradiation therapy in purging hematopoietic stem cells of various hematological malignancies. Benzoporphyrin derivative, monoacid ring A (BPD-MA), dihematoporphyrin ether (DHE), and MC-540 were evaluated for the "ex-vivo" purging of residual tumor cells from autologous bone marrow (BM) grafts. BPD-MA and DHE photosensitizing activity was tested against two human large cell lymphoma cell lines and colony forming-unit leukemia (CFU-L) derived from patients with acute myelogenous leukemia (AML). In mixing experiments four log elimination of tumor cell lines was observed after 1 hr of incubation with BPD-MA or DHE followed by white light exposure. By comparison, using the same concentration of BPD-MA or DHE, the mean recovery of normal BM progenitors was 4-5.2% for granulocyte-macrophage colony forming unit (CFU-GM) and 5-9.8% for burst forming unit erythroid (BFU-E). The T lymphoblastic leukemia cell line CEM and its vinblastine (VBL)-resistant subline CEM/VBL100, along with the acute promyelocyte leukemia cell line HL-60 and its vincristine (VCR)-resistant subline HL-60/VCR, were also tested. Our results demonstrated the preferential cytotoxicity of BPD-MA and DHE toward neoplastic cell lines and CFU-L from AML patients. In addition, DHE was slightly more effective in purging tumor cells expressing the p-170 glycoprotein.(ABSTRACT TRUNCATED AT 250 WORDS)

Application of photodynamic therapy to the treatment of atherosclerotic plaques.

Photodynamic therapy is a therapeutic modality long studies for its application to the treatment of malignant neoplasms. Recently, studies have suggested its potential use in the treatment of atherosclerosis. In this study, two atherosclerotic plaques were induced in the abdominal aortas of 35 rabbits. The animals then received Photofrin II (Quadralogic Technologies Inc., Pearl River, NY), a photosensitizer, at doses of 5 mg/kg and 2.5 mg/kg. After 48 hours, the plaques were irradiated by a fiberoptic connected to an argon ion laser. Fluency rates from 32 mW to 256 mW and energy doses from 1.6 to 60 joules were applied. Only one of the paired plaques was irradiated, the other remaining as a control. Four weeks after treatment, the vessels were assessed. Of 26 plaques treated with photodynamic therapy, 22 were no longer grossly visible, while the nine animals that received light irradiation but no Photofrin II all had visible plaque (P < 0.001). Studies of the vessel sections confirmed a reduction in intimal thickness from 0.74 +/- 0.15 mm in matched controls as compared with 0.51 +/- 0.13 mm in animals with treated plaques. There was a concomitant enlargement of the luminal diameter from 1.13 +/- 0.51 to 1.41 +/- 0.72. On the microscopic level, plaque reduction was most complete in the groups treated with 40 and 60 joules. Different fluency rates and drug dosages did not lead to differing outcomes. Our findings indicate that photodynamic therapy with dihematoporphyrin ether met our goal of reducing plaque size and may represent a means of treating atherosclerotic plaques.

Dye-Mediated Photolysis Is Capable of Eliminating Drug-Resistant (MDR +) Tumor Cells

Abstract We evaluated the potential role of photoradiation therapy with a benzoporphyrin derivative, monoacid ring A (BPD-MA), and dihematoporphyrin ether (DHE), for the ex vivo purging of residual tumor cells from autologous bone marrow (BM) grafts. BPD-MA and DHE photosensitizing activity was tested against two human large-cell lymphoma cell lines and colony-forming unit-leukemia (CFU-L) derived from patients with acute myelogenous leukemia (AML). In mixing experiments, 4-log elimination of tumor cell lines was observed after 1 hour of incubation with 75 ng/mL of BPD-MA or 30 minutes of treatment with 12.5 micrograms/mL of DHE followed by white light exposure. By comparison, using the same concentration of BPD-MA, the mean recovery of normal BM progenitors was 4% +/- 0.8% (mean +/- SD) for granulocyte- macrophage colony-forming unit (CFU-GM) and 5% +/- 0.8% for burst- forming unit-erythroid (BFU-E). Similarly, DHE treatment resulted in the recovery of 5.2% +/- 2% and 9.8% +/- 3% of CFU-GM and BFU-E, respectively. Furthermore, equivalently cytotoxic concentrations of both DHE and BPD-MA and light were found not to kill normal pluripotent stem cells in BM, as demonstrated by their survival in two-step long- term marrow culture at levels equal to untreated controls. The T- lymphoblastic leukemia cell line CEM and its vinblastine (VBL)- resistant subline CEM/VBL, along with the acute promyelocyte leukemia cell line HL-60 and its vincristine (VCR)-resistant subline HL-60/VCR, were also tested. BPD-MA at 75 ng/mL was able to provide a greater than 4-log elimination of the drug-sensitive cell lines, but only a 34% and 55% decrease of the drug-resistant HL-60/VCR and CEM/VBL cell lines, respectively. On the contrary, 12.5 micrograms/mL of DHE reduced the clonogenic growth of all the cell lines by more than 4 logs. Further experiments demonstrated decreased uptake of both BPD-MA and DHE by the resistant cell lines. However, all the cell lines took up more DHE than BPD-MA under similar experimental conditions. Our results demonstrate the preferential cytotoxicity of BPD-MA and DHE toward neoplastic cell lines and CFU-L from AML patients. In addition, DHE was slightly more effective in purging tumor cells expressing the p-170 glycoprotein. These results suggest that photoradiation with DHE would be useful for in vitro purging of residual drug-resistant leukemia and lymphoma cells.

Dye-mediated photolysis is capable of eliminating drug-resistant (MDR+) tumor cells

We evaluated the potential role of photoradiation therapy with a benzoporphyrin derivative, monoacid ring A (BPD-MA), and dihematoporphyrin ether (DHE), for the ex vivo purging of residual tumor cells from autologous bone marrow (BM) grafts. BPD-MA and DHE photosensitizing activity was tested against two human large-cell lymphoma cell lines and colony-forming unit-leukemia (CFU-L) derived from patients with acute myelogenous leukemia (AML). In mixing experiments, 4-log elimination of tumor cell lines was observed after 1 hour of incubation with 75 ng/mL of BPD-MA or 30 minutes of treatment with 12.5 micrograms/mL of DHE followed by white light exposure. By comparison, using the same concentration of BPD-MA, the mean recovery of normal BM progenitors was 4% +/- 0.8% (mean +/- SD) for granulocyte-macrophage colony-forming unit (CFU-GM) and 5% +/- 0.8% for burst-forming unit-erythroid (BFU-E). Similarly, DHE treatment resulted in the recovery of 5.2% +/- 2% and 9.8% +/- 3% of CFU-GM and BFU-E, respectively. Furthermore, equivalently cytotoxic concentrations of both DHE and BPD-MA and light were found not to kill normal pluripotent stem cells in BM, as demonstrated by their survival in two-step long-term marrow culture at levels equal to untreated controls. The T-lymphoblastic leukemia cell line CEM and its vinblastine (VBL)-resistant subline CEM/VBL, along with the acute promyelocyte leukemia cell line HL-60 and its vincristine (VCR)-resistant subline HL-60/VCR, were also tested. BPD-MA at 75 ng/mL was able to provide a greater than 4-log elimination of the drug-sensitive cell lines, but only a 34% and 55% decrease of the drug-resistant HL-60/VCR and CEM/VBL cell lines, respectively. On the contrary, 12.5 micrograms/mL of DHE reduced the clonogenic growth of all the cell lines by more than 4 logs. Further experiments demonstrated decreased uptake of both BPD-MA and DHE by the resistant cell lines. However, all the cell lines took up more DHE than BPD-MA under similar experimental conditions. Our results demonstrate the preferential cytotoxicity of BPD-MA and DHE toward neoplastic cell lines and CFU-L from AML patients. In addition, DHE was slightly more effective in purging tumor cells expressing the p-170 glycoprotein. These results suggest that photoradiation with DHE would be useful for in vitro purging of residual drug-resistant leukemia and lymphoma cells.

Fluorescence detection of tumors early diagnosis of microscopic lesions in preclinical studies

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. 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. 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. 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.

Effect of light dose on the photodynamic destruction of endobronchial tumors

The effects of various light power densities (milliwatts per centimeter of diffusing fiber [mW/cf]) and light doses (joules per centimeter of diffusing fiber [J/cf]) on the effectiveness of photodynamic therapy to endobronchial and tracheal tumors were evaluated at 46 different sites. All patients had squamous cell carcinoma or adenocarcinoma. They received 2 mg/kg body weight dihematoporphyrin ether intravenously 2 days before treatment bronchoscopy. Only one light treatment was delivered to the site. Patients were treated with diffusing cylinder light tips and underwent toilet bronchoscopy 2 days after photodynamic therapy. The percentage of obstruction was estimated before and after treatment and before and after toilet bronchoscopy. There was no difference between the effects resulting from power densities of 400 and 500 mW/cf, nor were there differences in the reactions between squamous cell carcinoma and adenocarcinoma. The amount of tumor that could be removed at the end of the treatment bronchoscopy, the amount of reobstruction by secretions and exudate seen at toilet bronchoscopy, and the final percent decrease in obstruction at the end of toilet bronchoscopy were proportional to the light dose. Because the final percentage decrease in obstruction plateaued at light doses of 400 to 500 J/cf and there was no statistically significant difference between 400 and 500 J/cf, we recommend using a power density of 500 mW/cf and a light dose of 400 J/cf during photodynamic therapy.