Search

Tumor cell death in vitro by photodynamic therapy (PDT) has been related to the induction of apoptosis. We measured and compared changes in apoptosis and caspase 3 activity, an effector of apoptosis, in normal and neoplastic esophageal tissues during PDT. Apoptosis index, caspase 3 cleavage activity, pro-caspase 3, p53, and bcl-2 levels were measured in normal and neoplastic tissues of patients with esophageal adenocarcinoma before, during, and after PDT with Photofrin. The apoptotic index was greater in carcinoma tissue compared to adjacent normal tissues. In concert, pro-caspase 3 immunoreactivity was absent and caspase 3-like cleavage activity was over 30-fold greater in carcinoma tissue compared to normal esophageal tissues. These parameters were unaffected by PDT. Variable changes in bcl-2 and p53 immunoreactivity were noted in normal and carcinoma tissues during PDT. Greater levels of apoptosis and caspase 3 activity are hallmarks of esophageal adenocarcinoma compared to normal esophageal tissue. These differences were unaffected by PDT. This may be due to the fact that tissues were obtained 72 h post-PDT therapy. Changes in these parameters may have occurred early after PDT therapy. An assessment of apoptosis and caspase 3 activity prior to 72 h post-PDT may provide further insight into the mechanism involved, although no sustained effects on these parameters by PDT were noted.

The nuclear factor-kappa B (NF-kappaB) gene transactivator serves in the formation of immune, inflammatory, and stress responses. In quiescent cells, NF-kappaB principally resides within the cytoplasm in association with inhibitory kappa (IkappaB) proteins. The status of IkappaB and NF-kappaB proteins was evaluated for promyelocytic leukemia HL-60 cells treated at different intensities of photodynamic therapy (PDT). The action of the potent photosensitizer, benzoporphyrin derivative monoacid ring A (verteporfin), and visible light irradiation were assessed. At a verteporfin concentration that produced the death of a high proportion of cells after light irradiation, evidence of caspase-3 and caspase-9 processing and of poly(ADP-ribose) polymerase cleavage was present within whole cell lysates. The general caspase inhibitor Z-Val-Ala-Asp-fluoromethylketone (ZVAD.fmk) effectively blocked these apoptosis-related changes. Recent studies indicate that IkappaB proteins may be caspase substrates during apoptosis. However, the level of IkappaBbeta was unchanged for HL-60 cells undergoing PDT-induced apoptosis. IkappaBalpha levels decreased during PDT-induced apoptosis, though ZVAD.fmk did not affect this change. At a less intensive level of photosensitization, cellular IkappaBalpha levels were transiently depressed after PDT. At these times, p50 and RelA NF-kappaB species were increased within nuclear extracts, as revealed by electrophoretic mobility supershift assays. HL-60 cells transiently transfected with a kappaB-luciferase reporter construct exhibited elevated luciferase activity after PDT or treatment with tumor necrosis factor-alpha, a well-characterized NF-kappaB activator. Productive NF-kappaB activation and associated gene transcription may influence the phenotype and behavior of cells exposed to less intensive PDT regimens. However, IkappaBalpha is not subject to caspase-mediated degradation as a component of PDT-induced apoptosis. (Blood. 2000;95:256-262)

Object. The goal of this study was to develop a method of reducing neural xenograft rejection by pretreating the graft with photodynamic therapy (PDT).Methods. Xenograft cell suspensions were prepared from fetal mouse mesencephalon, after which they were incubated for 30 minutes with various concentrations of a photosensitizer, verteporfin for injection, and light exposure. The xenograft cell suspensions were injected into the dopamine-depleted striata of 40 hemiparkinsonian rats assigned to different treatment groups. Four weeks after transplantation, xenograft function (determined by methamphetamine-induced rotation) and survival (determined by immunohistochemical staining for murine neurons) were compared. Group 1 animals (xenografts pretreated with 25 ng/ml verteporfin) and Group 3 animals (no verteporfin pretreatment, but daily administration of cyclosporin A) had significantly better xenograft survival and function compared with control animals (no pretreatment with verteporfin). Group 2 animals (xenografts pretreated with 250 ng/ml verteporfin) had no significant improvement.Conclusions. This work demonstrates improved neural xenograft survival and function when using pretransplant PDT of the graft in a rodent model. The potential benefits of this new therapy are its convenience (one pretransplant treatment) and its compatibility with host immunosuppression.

The impact of the immunomodulatory photosensitizer benzoporphyrin derivative monoacid ring A (BPD-MA, verteporfin) and visible light on the survival and surface receptor pattern of resting and activated murine T cells was evaluated. T cells treated for 48 h with immobilized anti-CD3 monoclonal antibody upregulated expression of the interleukin-2 receptor alpha-chain (CD25), transferrin receptor (CD71), the apoptosis-regulating Fas receptor (CD95), contained a greater level of the anti-apoptotic protein Bcl-2 and accumulated significantly more BPD-MA than their unactivated counterparts. Activated T cells displayed a modestly greater susceptibility to the photodynamic induction of DNA fragmentation than resting T cells. Resting T cells treated with sub-lethal levels of BPD-MA and light did not exhibit changes in surface levels of CD3, CD4, CD8, CD28, CD45 or T cell receptor (TCR) beta-chain structures. However, levels of major histocompatibility complex (MHC) class I antigens were decreased while the density of Thy-1.2 (CD90) increased on these cells. Photodynamically treated T cells failed to express optimal CD25 levels when exposed to the mitogenic anti-CD3 antibody. Activated T cells treated with sub-lethal levels of BPD-MA and light exhibited lower CD25 levels, a temporary block in cell cycle transition, but unaltered expression of MHC Class I, CD3, CD4, CD8, CD45, CD54, CD71, CD122 (IL-2R beta-chain) or TCR beta-chain antigens 24 h afterward. Resting and activated T lymphocytes differ in susceptibility to PDT-mediated apoptosis but both types are sensitive to anti-proliferative effects the treatment exerts at sub-lethal photosensitizer levels. The marked sensitivity of activated T cells to photodynamic inactivation likely contributes to the immunomodulatory action of BPD-MA.

Treatment with the photosensitizer benzoporphyrin derivative monoacid ring A (BPD-MA, verteporfin) followed by irradiation with visible light induces apoptosis in human acute myelogenous leukaemia HL-60 cells. Photoactivation of BPD-MA induces procaspase 3 (CPP32/Yama/apopain) and procaspase 6 (Mch2) cleavage into their proteolytically active subunits in these cells. The Bcl-2 proto-oncogene product has been shown to protect cells from a number of proapoptotic stimuli. In the present study, the influence of Bcl-2 overexpression on cellular resistance to photoactivation of BPD-MA was studied. Overexpression of Bcl-2 in HL-60 cells prevented apoptosis-related events including caspase 3 and 6 activation, poly(ADP-ribose) polymerase cleavage and the formation of hypodiploid DNA produced by BPD-MA (0–200 ng ml−1) and light. However, Bcl-2 overexpression was less effective at preventing cell death that occurred after photoactivation at high levels (50–100 ng ml−1) compared with lower doses (10–25 ng ml−1) of BPD-MA. These results indicate that caspase 3 and 6 activation and their regulation by Bcl-2 may play important roles in photodynamic therapy (PDT)-induced cell killing. © 1999 Cancer Research Campaign

Treatment with benozopophyrin derivative monoacid ring A (BPD-MA, verteporfin) and broad-spectrum fluorescent light rapidly produced apoptosis in murine P815 mastocytoma cells. Fragmentation of DNA, a fundamental characteristic of cells undergoing apoptosis, was evident within 3 h following the photodynamic treatment. Western immunoblot analysis using the specific antiphosphotyrosine monoclonal antibody 4G10 indicated that molecular species of > 200 kDa were phosphorylated on tyrosine residues during or immediately following the irradiation of cells loaded with BPD-MA. Increased tyrosine phosphorylation of a 15 kDa protein was evident by 15 min postirradiation. In the absence of light, BPD-MA did not affect the status of cellular protein tyrosine phosphorylation or cause DNA fragmentation. The protein kinase inhibitor staurosporine prevented tyrosine phosphorylation of the > 200 kDa species but did not affect tyrosine phosphorylation of the 15 kDa protein or the level of DNA fragmentation produced by the photodynamic treatment. The protein tyrosine phosphorylation events observed for P815 cells treated with cytotoxic levels of BPD-MA and light may not be directly related to the induction of the apoptotic cell death pathway.

When given to normal male mice, the photochemotherapeutic agent Photofrin® (porfimer sodium), a complex mixture of monomeric and oligomeric non-metallic porphyrins, significantly increased relative spleen weight, spleen cell numbers, DNA replication, levels of granulocyte-macrophage and erythroid progenitors and cellular responsiveness to different recombinant (r) myeloid growth factors. In contrast, monomeric hematoporphyrin had no effect on spleen weight, cellularity, erythroid progenitor levels or spleen cell cycle status. Photofrin® significantly increased spleen cell expression of the receptor (CD71) for the iron transport protein transferrin by 72 h post-injection but did not affect levels of a receptor (CD25) for the T-cell growth factor interleukin-2 (IL-2) or spleen cell responsiveness to rIL-2. Further evidence of increased splenic erythropoietic activity in Photofrin®-treated mice was provided by double color flow cytometric studies which indicated that the treatment elevated the number of nucleated spleen cells recognized by the erythroid lineage-specific monoclonal antibody TER-119. A majority of TER-119+ cells also expressed CD71 and the heat stable antigen, a marker of developing hematopoietic cells as well as mature erythrocytes. The capacity of Photofrin® to stimulate murine hematopoietic activity appears to be a property not shared by other porphyrin photosensitizers.

Caspases have been shown to play a crucial role in apoptosis induced by various deleterious and physiologic stimuli. In this study, we show for the first time that photodynamic therapy (PDT), using benzoporphyrin derivative monoacid ring A (BPD-MA, verteporfin) as the photosensitizer, induces the complete cleavage and subsequent activation of caspase-3 (CPP32/Yama/Apopain) but not caspase-1 (ICE) in human promyelocytic leukemia HL-60 cells. Poly(ADP-ribose) polymerase (PARP) and the catalytic subunit of DNA dependent protein kinase (DNA PK(CS)) were cleaved within 60 min of light activation of BPD-MA. The general caspase inhibitor Z-Asp-2,6 dichlorobenzoyloxymethylketone (Z-Asp-DCB) blocked PARP cleavage while the serine protease inhibitors 3,4-dichloroisocoumarin (DCI) and N-tosyl-lysyl chloromethyl ketone (TLCK) blocked the cleavage of caspase-3 suggesting that they act upstream of caspase-3 activation. All three inhibitors were able to block DNA fragmentation that was induced by treatment with BPD-MA followed by light application. These studies demonstrate that protease activity, particularly that of caspase-3, is triggered in HL-60 cells treated with lethal levels of BPD-MA and visible light.

The porphyrin photochemotherapeutic agent Photofrin stimulates hematopoietic activity within the bone marrow (BM) and spleens of normal mice. We found that the intraperitoneal (i.p.) administration of Photofrin also caused a 3-4 fold increase in peritoneal cell (PC) numbers, particularly cells bearing granulocyte surface antigens. Little granulocyte-macrophage progenitor activity was detectable within the PC population of control and Photofrin-injected mice suggesting that Photofrin had elicited an influx of inflammatory cells into the region. In contrast to cells from control animals, PC obtained 6 h to 168 h after the i.p. injection of Photofrin exhibited a consistently inferior capacity to support the growth of BM colony forming units granulocyte-macrophage (CFU-GM). When PC from control or Photofrin-treated mice were added to the BM culture system in the presence of defined growth factors there was no effect on the number of colonies formed. This finding indicated that negative regulatory elements were not responsible for the reduced hematopoietic accessory activity exhibited by PC from Photofrin-treated mice. Supernatants conditioned by PC from Photofrin-injected mice poorly supported BM CFU-GM growth in vitro and in contrast to PC supernatants prepared from control mice did not contain detectable amounts of granulocyte-macrophage colony stimulating factor (GM-CSF). The cellular changes which occur within the peritoneal cavity represent bystander events not directly related to the hematostimulatory action of Photofrin.

Transcutaneous photodynamic therapy (PDT), utilizing benzoporphyrin derivative monoacid ring A (BPD, verteporfin) and whole-body light exposure, was assessed for its capacity to modify the course of adoptively transferred experimental autoimmune encephalomyelitis (EAE) in PL mice. Using a novel cell culture technique to facilitate the induction of this neurodegenerative condition, disease signs commenced 3-4 weeks after the transfer of myelin basic protein (MBP)-reactive lymph node or spleen cells to naive syngeneic recipients. Mice administered MBP-sensitized lymph node cells preincubated with BPD followed by whole-body 690 nm light irradiation (15 J/cm2) did not display symptoms of EAE. Although almost all animals given MBP-sensitized spleen cells developed EAE, mice given BPD (1 mg/kg) and the light treatment 24, 48 or 120 h after spleen cell transfer exhibited significantly less severe disease symptoms than control animals. Mice given the photodynamic treatment 24 h after spleen cell transfer also exhibited a significantly later disease onset than the control animals. Treatment of mice with PDT 24 h prior to spleen cell transfer did not influence subsequent disease severity but modestly delayed its onset. In the absence of directed light, BPD did not influence the development of EAE. Spinal cord tissues were evaluated for the presence of T cell receptor (TCR) V alpha 4 mRNA transcripts that specifically encode for the TCR alpha-chain of MBP-reactive T cells of PL mice. Using the polymerase chain reaction, V alpha 4 TCR mRNA transcripts were present in spinal cord samples prepared from almost all control mice but in only about one-half of spinal cord samples prepared from mice treated with PDT 24 h after spleen cell transfer. These observations indicated that PDT had limited the expansion of MBP-specific V alpha 4+ T cells within the central nervous system. Transcutaneous PDT represents a new technique with which to approach the treatment of autoimmune disease.

Benzoporphyrin derivative monoacid ring A (BPD), a hydrophobic chlorin-like porphyrin derivative, which fluoresces strongly at 690 nm, may have potential for both oncologic and nononcologic applications in photodynamic therapy (PDT). To study the influence of cellular characteristics on the uptake of BPD, the murine tumor cell line (P815), and in vitro and in vivo concanavalin A (Con A) -stimulated and unstimulated murine splenic lymphocytes were incubated with 2 micrograms/mL BPD at 37 degrees C for 0-60 min. At various times, cells were lysed and the amount of BPD taken up by cells was quantified by fluorescence measurements. The subsets of cells taking up BPD were analyzed using a panel of monoclonal antibodies and the Coulter XL fluorescence-activated cell sorter. Furthermore, Con A-stimulated and unstimulated spleen cells were incubated with 0-50 ng/mliter of BPD for 1 h prior to exposure to red light (7.2 J/cm2). Cell survival 24 h post-PDT was measured by the MTT assay. We found that the rapidly dividing tumor cell line and mitogen-stimulated murine T cells (mainly CD4+/IL-2R+) took up significantly more BPD (5-10-fold) than do unstimulated splenic lymphocytes. Increased BPD uptake correlated with greater photoinactivation when these cells were exposed to light at a wavelength of 690 nm. These findings suggest that activated cells of the immune system may be a target for photoinactivation by BPD.

— This study compared the ability of highly purified resting and activated DBA/2 mouse peritoneal macrophages to survive treatment with the photosensitizer benzoporphyrin derivative (BPD, verteporfin) and light. Culture of macrophages with recombinant murine interferon-γ (rIFN-γ, 100 U/mL) for 72 h imparted a phenotypic and functional activation by dramatically increasing cell surface expression of major histocompatibility complex Class II (Ia) molecules and the formation of nitric oxide. The rIFN-γ-activated macrophages were significantly (P < 0.05) more sensitive (lethal dose to cause a 50% reduction in cell survival, LD50= 14.4 ± 1.1 ng/mL) to photodynamic killing with BPD and light (10 J/cm2) than cells (LD50= 18.2 ± 2.0 ng/mL) cultured in medium alone. In contrast, macrophages treated with different concentrations of bacterial lipopolysaccharide (LPS) were as resistant or more resistant to photodynamic killing than cells cultured in medium alone. No cytotoxic effect of BPD was detected in cultures containing the drug but protected from light. Comparable amounts of BPD were taken up in vitro by unactivated and rIFN-γ-activated macrophages, as detected by flow cytometric analysis. However, cells cultured with LPS (10 μg/mL) took up more BPD than macrophages cultured in medium alone or with rIFN-γ. The DBA/2 P815 mastocytoma cells took up greater amounts of the drug and were subsequently more vulnerable to treatment with BPD and light (LD50= 6.9 ng/mL) than macrophages cultured under any condition. The explanation for the increased vulnerability of rIFN-γ-activated macrophages and the greater resistance of LPS-activated macrophages, relative to medium-cultured macrophages, to photodynamic killing with BPD is uncertain. However, the increased susceptibility of macrophages, activated with the immunomodulatory cytokine IFN-γ, to treatment with BPD and light might indicate how photodynamic therapy could interfere with the development of experimental autoimmune disease, conditions in which activated macrophages are known to be involved.

The pros and cons of purging of either bone marrow or peripheral blood stem cell preparations for autologous transplantation for cancer has been debated strongly over the past decade. Recent data implicating the role of minimal residual disease in autografted marrow in cancer relapse have renewed interest in this question. There is a considerable body of literature supporting the possibility that photosensitizer molecules in combination with light might provide a therapeutic window permitting selective elimination of malignant stem cells while sparing those of normal lineage. Molecules of this class are known to be taken up more actively by most malignant cells, and intracellular concentrations are critical in their cytotoxic effect when they are activated by light at an appropriate wavelength. The present paper reviews the observations made over the past decade on a variety of photosensitizers and their effects on hemopoietic progenitors.

Biodistribution studies were carried out on 14C-labeled benzoporphyrin derivative monoacid ring A (BPD), which had been formulated as a unilamellar liposome or taken from a stock solution in dimethyl sulfoxide diluted into phosphate-buffered saline immediately before intravenous injection into DBA/2 mice. By and large the general distribution of BPD to various organs and tissues was comparable for both formulations. It was noted, however, that liposomal material appeared to enter tissues more rapidly and to be cleared more rapidly, as demonstrated by shorter half-lives for a number of tissues including skin, lung and fat, and generally lower levels in most tissues 24 h following administration. Accumulation in tumor tissue was slightly higher with liposomal BPD, and clearance rates for this tissue were equivalent (half-lives 16.1 h for liposomal BPD and 16.9 h for aqueous BPD). When the two preparations were tested in a bioassay in tumor-bearing mice, photodynamic therapy (PDT) with liposomal BPD proved to be superior to the aqueous preparation when PDT was administered 3 h following intravenous administration of BPD. Plasma distribution studies in vitro demonstrated that 91.1 +/- 0.3% of the liposomal BPD distributed to the lipoprotein fraction within the first hour of mixing, whereas only 49.1 +/- 2.6% of nonliposomal BPD was associated with lipoprotein under the same conditions. Furthermore, while lipoprotein-associated liposomal BPD distributed evenly between all three types of lipoprotein (high, low and very low density), a majority of nonliposomal BPD associated with the high-density lipoprotein fraction.

Benzoporphyrin derivative, monoacid ring A (BPD-MA), currently in clinical trials as a photosensitizer for photodynamic therapy for cancer, consists of two regioisomers (A1 and A2) present in equal proportions. The contribution of the regioisomers to the overall photosensitizing potency of BPD-MA was tested in vitro and in vivo. The in vitro photosensitizing potencies of BPD-MA-A1 and -A2 were tested in a standard cytotoxicity assay using M1 (rhabdomyosarcoma of DBA/2 mice) tumor cells and were found to be equivalent. The in vivo photosensitizing efficacies of the regioisomers were tested in the M1 tumor model in DBA/2 mice and were also found to be equivalent. Biodistribution of the regioisomers in mouse plasma, tumor and liver was studied in M1 tumor-bearing DBA/2 mice at 15 min and 3 hr post intravenous injection of [14C]BPD-MA-A1/A2 at 4 mg/kg body weight. Plasma and extracts from tumor and liver were analysed by HPLC and tested for radioactivity. The two regioisomers were eliminated from plasma and liver at different rates, which resulted in A1:A2 ratios of 1:0.28 in plasma and 1:0.75 in liver at 3 hr post injection. The differential elimination was not observed to any significant degree in the tumor, where even at 3 hr post injection the A1:A2 ratio was 1:1.15. Therefore, we concluded that in tumor tissue, at 3 hr post injection, the time at which laser photodynamic therapy is carried out, both regioisomers were present in about equal proportions. Further, both regioisomers were fully active as determined by an in vitro cytotoxicity assay following extraction.

Photodynamic therapy (PDT) is now being tested and employed in a growing number of medical centers for the treatment of malignant tumors. This form of therapy selectively destroys cancer cells by activation of retained photosensitizer molecules by absorption of light at appropriate wavelengths. One major limitation of PDT is the potential damage of normal tissue due to nonspecific retention of photosensitizers. In an attempt to address this problem, two delivery systems, monoclonal antibody (MoAb) mediated and low density lipoprotein (LDL) mediated, have been tested. In this study, we first showed that the photosensitizer benzoporphyrin derivative monoacid ring A (BPD) could be covalently bound to a MoAb (5E8 ) via a modified polyvinyl alcohol (PVA ). We then demonstrated that both BPD-5E8 conjugate and BPD-LDL mixtures exhibited enhanced photodynamic killing on target cells. Finally, we showed that internalized BPD-5E8 and BPD-LDL displayed much higher cytotoxicity than that of surface associated BPD-5E8 and BPD-LDL, respectively. These results suggest that monoclonal antibody or LDL mediated delivery increases the selectivity and cytotoxicity of BPD. They also indicate that internalization of BPD via either delivery mode produces significantly enhanced cell killing.

Four structural analogs of benzoporphyrin derivative (BPD) have been studied and compared for photosensitizing activity in vitro. All analogs have an identical reduced tetrapyrrol porphyrin ring, and differ by the position of a cyclohexadiene ring (fused at either ring A or ring B of the porphyrin) and the presence of either two acid groups or one acid and one ester group at rings C and D of the porphyrin. Photosensitizer activity was tested with the M1 tumor cell line using an assay (the MTT assay) which detects mitochondrial hydrogenases as a measure of cell viability. This assay was shown to be equivalent to the standard clonogenicity or [3H]thymidine uptake assay. Comparative studies with the BPD analogs showed that the monoacid derivatives had equivalent cytotoxicity and were about five-fold more active than the diacid forms. This was the case whether the assays were performed in the presence or absence of fetal calf serum.

The purpose of this study was to determine whether the ultraviolet (UV) radiation-induced systemic suppression of the immune response results from the release of soluble suppressor factors (TsF) by UV-induced suppressor T cells (UV Ts). Injecting a TsF-specific monoclonal antibody (B16G) significantly reduced the UV radiation-induced suppression of contact hypersensitivity (CHS). The transfer of spleen cells from the UV-irradiated, B16G-treated mice into normal recipients suppressed CHS in the recipients, indicating that while the suppression of CHS was reversed in the UV-irradiated, B16G-treated mice, suppressor cells were still present. Supernatants from cultures containing UV Ts were incubated on B16G-immunoadsorbent columns. The antibody-bound fraction (45- to 60-kDa, non-disulfide-linked proteins) suppressed CHS when injected into normal recipients. These results demonstrate that the B16G antibody reacts with TsF from UV Ts and suggest that B16G acts in vivo by inhibiting the activity of TsF. Thus, suppressor factors appear to play an essential role in the regulation of immune responses by UV Ts.

The biodistribution of a new and very potent photosensitizer, benzoporphyrin derivative—monoacid, ring A (BPD-MA), was determined in normal and P815 (mastocytoma) or M1 (rhabdomyosarcoma) tumor-bearing DBA/2J mice. A dose of 80 μg Of 3H-BPD-MA was determined at 3, 24, 48, 72, 96 and 168 h post injection. The following tissues were tested: blood, brain, heart, intestine, kidney, lung, liver, muscle, skin, stomach, spleen, thymus and tumor. The biodistribution of 3H-BPD-MA in normal and tumor-bearing mice was comparable overall. 3H-BPD-MA localized in tumors better than in other tissues except kidney, liver and spleen. The tumor to tissue ratios were in the range 1.5 – 3 at 24 h post injection and increased further during the next 72 h. The highest levels of 3H-BPD-MA were observed in all tissues at 3 h post injection and decreased rapidly during the first 24 h. After 24 h the clearance from tissues was rather slow. The preliminary clearance data obtained in a group of five normal mice indicated that the majority of the injected dose (60%) cleared from the body via the bile and feces, while only about 4% cleared via kidneys and urine. Studies in which 3H-BPD-MA was extracted from tumor, kidney and liver 3 and 24 h after injection showed that, at 3 h, all the photosensitizing activity in tumor was retained. At 24 h only 39% of the activity was retained and considerably less active material was present in liver and kidney.

Benzoporphyrin derivatives (BPDs) are photosensitizers, which fluoresce strongly at 690 nm, and may be candidates for various applications of photodynamic therapy (PDT). Fluorescence-activated cell sorting (FACS) analysis, subsequent to ultraviolet light excitation, revealed pronounced differences in red fluorescence between leukemic cell lines (HL60, K562 and L1210), leukemic clinical isolates, and normal human or murine bone marrow cells incubated with BPD. These observed differences in BPD-mediated fluorescence provide the rationale for sorting leukemic from normal cells via FACS or may constitute a novel method for extracorporeal purging of remission marrow by photodynamic therapy in autologous bone marrow transplantation.

In its conventional form, photodynamic therapy (PDT) is a clinically effective technique with which to treat tumours accessible to visible light. PDT utilises light absorbing compounds which catalyse the generation of toxic oxygen species, to produce localised antitumour effects. It has become apparent over the past decade that PDT also exhibits immunomodulatory attributes. Experimental animals may possess heightened antitumour immunity after tumour ablation with PDT. In contrast, at sub-phototoxic levels of photosensitiser, in combination with whole body light irradiation, PDT lessened disease severity when applied in different models of autoimmunity. Although the behaviour of lymphocytes may be affected by treatment, the ability of PDT to down-regulate autoimmune processes appears to be related to its capacity to influence the immunostimulatory attributes of antigen presenting cells.

Photodynamic therapy is now recognized as a legitimate therapy for both palliative and potentially curative treatment of solid tumors. This represents a major achievement for investigators who have committed their careers to PDT. Scientific research characteristically runs well ahead of accepted views and technologies. This Symposium-in-Print perhaps provides a snapshot of the potential for this technology during the next two decades.

The potential for photodynamic therapy to provide new treatment options for patients with choroidal neovascularization has been of interest to ophthalmologists for many years. Verteporfin (Visudyne ®, Novartis AG) is the first photodynamic drug to receive regulatory approval for use in ophthalmology. The development of verteporfin therapy was more complex than that of many other drugs because of the need to develop both the light-activated drug and the laser system used to activate it. This article provides an overview of the development of verteporfin therapy, focussing on the contributions of the pharmaceutical companies, device manufacturers, and investigators who were involved in the program.

PDT may be an effective treatment for certain immune-mediated disorders. The immunomodulatory action of PDT is likely a consequence of effects exerted at a number of levels including stimulation of specific cell signaling pathways, selective depletion of activated immune cells, alteration of receptor expression by immune and non-immune cells, and the modulation of cytokine availability. QLT0074, a potent photosensitizer that exhibits rapid clearance kinetics in vivo, is in development for the treatment of immune disorders. In comparison to the well-characterized and structurally related photosensitizer verteporfin, lower concentrations of QLT0074 were required to induce apoptosis in human blood T cells and keratinocytes using blue light for photoactivation. Both photosensitizers triggered the stress activated protein kinase (SAPK) and p38 (HOG1) pathways but not extracellularly regulated kinase (ERK) activity in mouse Pam212 keratinocytes. In cell signaling responses, QLT0074 was active at lower concentrations than verteporfin. For all in vitro test systems, the stronger photodynamic activity of QLT0074 was associated with a greater cell uptake of this photosensitize than verteporfin. In mouse immune models, sub-erythemogenic doses of QLT0074 in combination with whole body blue light irradiation inhibited the contact hypersensitivity response and limited the development of adjuvant-induced arthritis. QLT0074 exhibits activities that indicate it may be a favorable agent for the photodynamic treatment of human immune disease.

We have explored the effect of photodynamic therapy (PDT) with verteporfin on the induction and expression of contact hypersensitivity (CHS) to 2,4-dinitrofluorobenzene (DNFB) in normal mice and IL-10-deficient mice. Our results indicate that DNFB sensitized mice given PDT with verteporfin and whole body red light irradiation exhibited a significant reduction in CHS compared with control animals. Administration of rIL-12 reversed the effect(s) of PDT as did treatment of mice with anti-IL-10-neutralizing Ab. Knockout mice deficient in IL-10 were found to be resistant to the inhibitory effects of PDT. In vitro proliferative responses using spleen cells from DNFB-sensitized and PDT-treated mice showed a significantly lower response to DNBS as compared with cells from DNFB-sensitized mice or DNFB and PDT-treated IL-10-deficient mice. Finally, naive mice exposed to PDT exhibited an increase in skin IL-10 levels, which peaked between 72 and 120 h post-PDT. Together these data support the role of IL-10 as a key modulator in the inhibition of the CHS response by whole body PDT.

Photodynamic Therapy (PDT) is accepted for treatment of superficial and lumen-occluding tumors in regions accessible to activating light and is now known to be effective in closure of choroidal neovasculature in Age Related Macular Degeneration. PDT utilizes light absorbing drugs (photosensitizers) that generate the localized formation of reactive oxygen species after light exposure. In a number of systems, PDT has immunomodulatory effects; Photodynamic Immune Modulation (PIM). Using low- intensity photodynamic regimens applied over a large body surface area, progression of mouse autoimmune disease could be inhibited. Further, this treatment strongly inhibited the immunologically- medicated contact hypersensitivity response to topically applied chemical haptens. Immune modulation appears to result from selective targeting of activated T lymphocytes and reduction in immunostimulation by antigen presenting cells. Psoriasis, an immune-mediated skin condition, exhibits heightened epidermal cell proliferation, epidermal layer thickening and plaque formation at different body sites. In a recent clinical trial, approximately one-third of patients with psoriasis and arthritis symptoms (psoriatic arthritis) displayed a significant clinical improvement in several psoriasis-related parameters after four weekly whole-body PIM treatments with verteporfin. The safety profile was favorable. The capacity of PIM to influence other human immune disorders including rheumatoid arthritis is under extensive evaluation.

Conventional photodynamic therapy (PDT) utilizes light-absorbing compounds that have anti-cancer activity upon visible light irradiation. PDT has also been utilized for the treatment of certain immune conditions. To further understand the action of PDT upon immune cells, DBA/2 mouse thymocytes were treated with the photosensitizer benzoporphyrin derivative monoacid ring A (BPD-MA, verteporfin) and/or an apoptosis-inducing anti-Fas (APO-1, CD95) monoclonal antibody. Nanomolar levels of BPD-MA in combination with nonthermal visible light irradiation rapidly induced apoptosis as gauged by DNA fragmentation assays. Thymocytes were modestly more sensitive to PDT-induced apoptosis than mature splenic T cells. BPD-MA and light or the anti-Fas antibody decreased CD4 + CD8 + cell numbers while relatively sparing CD4 − CD8 − , CD4 + CD8 − , and CD4 − CD8 + thymocytes. In combination, anti-Fas antibody and PDT augmented activity levels of the apoptosis-related protease caspase-3, cleavage of the caspase-3 substrate poly(ADP) polymerase, and the proportion of cells exhibiting DNA fragmentation and further impacted CD4 + CD8 + thymocyte survival. Although CD4 + CD8 + thymocytes had the greatest sensitivity to photodynamic depletion, BPD-MA was taken up by the other major thymocyte subsets with equal or greater avidity. Since CD4 + CD8 + thymocytes are selectively impacted by PDT and anti-Fas antibody can act in concert with PDT to further cytotoxicity, thymocytes may be useful for the identification of factors that govern immune cell susceptibility to this form of phototherapy.

Treatment of mice with certain photosensitizers combined with exposure to visible light limits the development of theimmunologically-mediated contact hypersensitivity (CHS) response against topically-applied chemical haptens. Understandingof the inhibitory action of photosensitizers upon the CHS response is incomplete. Benzoporphyrin derivative monoacid ring A(BPD-MA, verteporfm), a photosensitizer with immunomodulatory activity, strongly depressed CHS responses to the haptendinilrofluorobenzene (DNFB). However, if mice were administered 1 ig of a recombinant preparation of the pro-inflammatorycytokine interleukin-12 (rIL-12), full-fledged CHS responses to DNFB ensued in animals treated with BPD-MA and light. Incontrast, when rIL-12 was given in combination with an anti-IL-12 antibody the restorative effect ofrlL-12 on the CHS responseof PDT-treated mice was blocked. Evaluation of the cytokine status of spleen and draining lymph node cells showed for DNFBpainted animals, that the release of the immunosuppressive cytokine IL-lO was increased by PDT and rIL-12 counter-acted theincrease in IJ,.lO liberation associated with PDT. These studies indicate that IL-lO formation is upregulated and the availabilityofIL-12 may be limited in mice treated with PDT. These features may contribute to deficient CHS responses observed with PDTKey words: antigen presentation, benzoporphyrin derivative, contact hypersensitivity, cytokines, immune modulation,immunosuppression, interferon-y, interleukin-4, interleukin-lO, interleukin-12, photodynamic therapy, photosensitizers.Abbreviations: APC, antigen presenting cells; BPD-MA, benzoporphyrin derivative monoacid ring A, verteporfm; CHS,contact hypersensitivity; DC, dendritic cell; DNFB, 2,4-dinitrofluorobenzene; IFN-'y, interferon-y; IL, interleukin; LC,Langerhans cells; PDT, photodynamic therapy; r, recombinant.

Benzoporphyrin derivative monoacid ring A [BPD-MA (verteporfin) or BPD], a second generation photosensitizer tested in clinical trials in combination with red light was compared for its PDT efficiency in vitro and in vivo upon activation with light in the UVA, blue and red spectral ranges. PDT efficiency, calculated based on the BPD absorption spectrum and spectral output of the different light sources, was compared with actual PDT efficiency determined in vitro and in vivo. Results obtained in an in vitro cytotoxicity assay, in which aliquots of murine P815 cells, pre-incubated for 1 h with BPD at 5 ng/mL, were exposed simultaneously to various light doses delivered within UVA, blue and red spectral ranges showed that in this test system PDT efficiency was governed by BPD absorption and light source emission spectra. Similar results were obtained in an in vitro BPD photobleaching test. Thus in vitro, values for calculated, theoretical PDT efficiency corresponded to the actual PDT efficiency. However, in vivo factors, such as depth of tissue penetration with light and localization of the target, had an important influence on PDT efficiency. In mouse models of skin photosensitivity and the cutaneous hypersensitivity immune response (CHS) assay, because of the thinness of mouse skin, PDT efficiency approximated the theoretical PDT efficiency, although blue light was somewhat more efficient in PDT than UVA, and red light was somewhat more efficient than blue or UVA. In a pig skin photosensitivity model, red light induced the highest skin response manifested by erythema and swelling, while blue light caused erythema and minimal swelling and UVA caused only erythema. These differences could be related to the thickness of pig skin and the depth of tissue penetration characteristic of each spectral range. Fluence rate was found to be an additional factor which modifies the effect of BPD and light. In conclusion, BPD can be efficiently activated with light within the UVA, blue and red spectral ranges. Moreover, light doses, deemed safe for red light, can be utilized with light of other spectral ranges, but only after a very careful evaluation of the conditions under which they were determined and the conditions under which they will be used.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The impact of bensoporphyrin derivative monoacid ring A, and visible light was determined for mouse splenic dendritic cells (DC), potent antigen-presenting cells (APC) of the immune system. It was discovered that sub-lethal doses of BPD-MA and light significantly altered the surface receptor pattern of DC as well as diminishing the capacity of these cells to activate allogeneic T cells. Treatment of highly purified DC with BPD-MA and 690 nm wavelength light decreased DC expression of major histocompatibility (MHC) Class I and II antigens, leukocyte common antigen CD45, intercellular adhesion molecule-1 (ICAM-1, CD54), the co- stimulatory molecules CD80 and CD86, CD95 as well as integrin CD11c. In contrast, DC expression of leukocyte function-associated-1 (LFA-1, CD11a), CD11b, CD18, CD40, and the DC DEC-205 receptor increased after the treatment. Changes in receptor levels occurred rapidly. DC MHC Class I and ICAM-1 expression declined to 40 percent of control levels by 2 hours post-PDT. DC treated with BPD-MA and light were poor stimulators of allogeneic T cells in the mixed leukocyte reaction. BPD-MA, in the absence of light, had no effect on the immunostimulatory properties of these cells. The changes in DC receptor expression pattern produced by BPD-MA and light were comparable to those produced by ultraviolet B light, a treatment known to alter the immunostimulatory characteristics of DC. Photodynamic therapy with BPD-MA represents an innovative approach for the modification of immune reactivity.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The rat monoclonal antibody LR-1 was initially described to be reactive with an antigen present on murine splenic B lymphocytes. However, flow-cytometric analyses of cells obtained from thymus, bone marrow, spleen, and lymph nodes showed that LR-1 stained approximately 95, 95, 60–70 and 20% of cells present within these tissues in normal DBA/2 mice. The marker recognized by LR-1 was present on peripheral erythrocytes and splenic dendritic cells, and activation with lipopolysaccharide A further increased expression of this antigen by splenic B cells. This particular tissue and cellular distribution was similar to that delineated with monoclonal antibodies reactive with heat-stable antigen (HSA). Dual-labelling studies were conducted to compare the reactivity patterns of LR-1 and the HSA-reactive monoclonal antibody J11d and indicated that both antibodies recognized splenocytes bearing B cell (IgM) or erythroid (TER-119, CD71) but not T cell (CD4, CD8) markers. Splenocytes exposed to phosphoinostol-specific phospholipase C showed marked reduction in LR-1 binding, indicating that this antibody recognized a glycosylphosphatidylinositol-anchored cell surface protein, consistent with the known structure of HSA. Mixing of LR-1 with the HSA-specific antibodies Jlld or M1/69 provided flow-cytometric profiles indistinguishable from those obtained with either antibody alone. However, LR-1 inhibited M1/69 binding to splenocytes by 83%, while J11d reduced Ml/69 binding to these cells by only 18%. This finding suggested that LR-1 and Ml/69 recognize identical splenic HSA epitopes, while LR-1 and J11d bind distinct antigenic determinants of spleen HSA. Western blot analysis of splenocyte, thymocyte, bone marrow cell and erythrocyte detergent extracts revealed that LR-1 reacted with glycoforms of HSA of known molecular weights (30–55 kD). Thus, LR-1 recognizes HSA, the murine analogue of human CD24, and will be a useful reagent with which to investigate the role of HSA in the immune response and hematopoiesis.

Benzoporphyrin derivative (BPD) is a potent photosensitizer in biological systems. There are four structural analogues of BPD. The analogues share the same chromophor, which results in their having almost identical optical spectra, extinction coefficients, and yields of singlet oxygen. Small structural differences affect their photosensitizing potency in various biological systems, and thus make them an interesting tool to study the structure-activity relationship. The ranking of the photosensitizing potency of the analogues differed depending on the test system. The more efficient photosensitization of tumor cell lines by the highly lipophilic monoacids as compared to that by less lipophilic diacids correlated positively with the partition coefficient, and was related to the rate of diffusion into the cells. However, in the assay systems where PDT targets were located in the membrane (red blood cells hemolysis, enveloped vesicular stomatitis virus, isolated mitochondria) there was very little difference in photosensitizing potency of BPD analogues. The results indicate that the evaluation of photosensitizers is affected by the test system and thus for photosensitizers screening purposes, the choice of the test system should be made based on the intended ultimate use.

The capacity of photosensitizers and light to ablate cancerous tissues and unwanted neovasculature constitutes the classical application of photodynamic therapy (PDT). Cell death results from either necrotic or apoptotic processes. The use of photosensitizers and light at doses which do not cause death has been found to affect changes in certain cell populations which profoundly effect their expression of cell surface molecules and secretion of cytokines, thereby altering the functional attributes of the treated cells. Cells of the immune system and the skin may be sensitive to modulation by 'sub-lethal PDT.' Ongoing studies have been conducted to assess, at the molecular level, changes in both lymphocytes and epidermal cells (EC) caused by treatment with low levels of benzoporphyrin derivative monoacid ring A (BPD) (a photosensitizer currently in clinical trials for cancer, psoriasis, endometriosis and age-related macular degeneration) and light. Treatment of skin with BPD and light, at levels which significantly enhanced the length of murine skin allograft acceptance, have been found to down-regulate the expression of Langerhans cell (LC) surface antigen molecules [major histocompatibility complex (MHC) class II and intracellular adhesion molecule (ICAM)-1] and the formation of some cytokines (tumor necrosis factor-alpha (TNF- (alpha) ).

Skin photosensitivity is the most common side effect of photodynamic therapy (PDT) and in clinical situations needs to be avoided or at least minimized. However, because of the accessibility of skin tissue, skin photosensitivity represents a useful test system in vivo for evaluation of the pharmacokinetics of photosensitizers and light sources. Pig skin resembles in many aspects human skin and, therefore, is most suitable for these tests. Using pig skin photosensitivity as an end point, we evaluate the effect of cell loading with a photosensitizer, benzoporphyrin derivative (BPD verteporfin) following its intravenous administration either as a rapid bolus or slow infusion. Skin response to light activation indicated a very similar cell content of BPD. These results were in agrement with those obtained in an in vitro model. In addition, in the same pig skin photosensitivity model we compared the efficiency of activation of BPD with either laser (690 plus or minus 3 nm) or light-emitting diode (LED; 690 plus or minus 12 nm) light. Results indicated the equivalency of the two light sources in this test system, with LED light being slightly more efficient, due possibly to a fluence rate lower than laser light.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Benzoporphyrin derivative monoacid ring A (BPD) is currently in Phase II clinical trials for the treatment of cutaneous malignancies (basal cell carcinoma and cutaneous metastases) and psoriasis. Results to date suggest that this photosensitizer has potential in both of these areas. Recently, a clinical trial with BPD was initiated for the treatment of age related macular degeneration, a neovascular condition in the eye which leads to blindness. BPD is a lipophilic photosensitizer which is rapidly taken up by activated cells and the vascular endothelium of neovasculature. The PDT effects seen with BPD appear to be a combination of vascular occlusion and direct killing of target cells. Since many diseases involve either activated cells and/or neovasculature, PDT with photosensitizer with characteristics like those of BPD, has applications far wider than oncology. A new area of interest involving photosensitizers is that of immune modulation. A number of photosensitizers have been shown to effect immune modulation in animal models of immune dysfunction including autoimmunity (rheumatoid arthritis, lupus), cutaneous hypersensitivity and allografts. BPD and PHOTOFRINR have both been shown to be effective in ameliorating arthritic symptoms in a number of animal models. The mechanisms by which immune modulation is affected in these studies still remains to be resolved.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this study, the effect of transdermal photodynamic therapy (PDT) using benzoporphyrin derivative monoacid ring A (BPD) on the development of the immunologically mediated contact hypersensitivity (CHS) response against the hapten dinitrofluorobenzene (DNFB) and on the duration of skin allograft acceptance has been evaluated. In the CHS model it was found that the treatment of hairless strain mice with whole-body transdermal PDT using BPD (1 mg/kg) and LED light (15 J/cm2) resulted in a profound suppression of the CHS reaction if treatment was applied either 48 or 24 hours prior or up to 72 hours after sensitization of abdominal skin with DNFB. Less inhibition of the CHS response was observed if PDT was given one day before the ear challenge with DNFB which was applied 5 days following the initial DNFB sensitization. However, DNFB-exposed, PDT-treated mice retained the capacity to respond maximally to the unrelated contact sensitizer oxazolone. These results are consistent with other models of experimentally induced immune tolerance. allogeneic skin graft studies demonstrated that pretreatment of skin with BPD and light, at levels that did not cause significant tissue damage, significantly enhanced the length of engraftment. Using a separate protocol, photodynamic treatment of recipient mice at various times after transplant had no significant effect on allograft acceptance. Irradiation of skin in the presence of BPD may significantly inhibit the initiation of certain immunological responses within these tissues.

The photosensitizer benzoporphyrin derivative monoacid ring A (VerteporfinR or BPD) has maximum absorption characteristics (690 nm) and biodistribution characteristics which permit activation of the drug in capillaries of the skin without causing skin photosensitivity (transdermal PDT). This permits targeting of cells in the circulation for selective ablation. Since BPD has been shown to accumulate preferentially in activated lymphocytes and monocytes, studies have been undertaken to determine the effect of transdermal PDT on murine models for rheumatoid arthritis (the MRL/lpr adjuvant enhanced model) and multiple sclerosis (the experimental allergic encephalomyelitis (EAE) model in PL mice). Localized transdermal PDT with BPD was found to be completely successful in preventing the development of adjuvant enhanced arthritis in the MRL/lpr mouse as well as improving the underlying arthritic condition of these animals. In the EAE model, in which an adoptive transfer system was used, it was found that transdermal PDT of recipients was effective in preventing EAE if treatments were implemented up to 24 hours after cell transfer but was not effective if given later, indicating the requirement for circulating T cells for effective treatment.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The porphyrin photosensitizer, Photofrin® porfimer sodium (Photofrin®), has been widely studied for its capacity to evoke destruction of malignant tissues. In addition to its photosensitizing properties, Photofrin® may exert myelostimulatory effects in normal and immunosuppressed mice in the absence of activating light. In the present set of experiments, we examined the effect of Photofrin® upon the immunohematopoietic axis of sublethally irradiated DBA/2 mice. Administration of Photofrin® (10 mg/kg) I and 4 days following irradiation (4 Gy) significantly enhanced the recovery of spleen cellularity, spleen and bone granulocyte/macrophage progenitors (colony-forming units, CFU-GM) and peripheral blood leukocytes levels. Proliferative responses to the T-cell mitogen concanavalin A by spleen cells prepared from Photofrin®-treated mice were significantly less than those of cells from irradiated control mice 8 and 15 days post-irradiation. Photofrin® given 1, 4 and 7 days following irradiation elevated splenic CFU-GM 3 to 4-fold 10 days post-irradiation relative to the irradiated controls and mice given only two injections of Photofrin®. In contrast to the effect of two injections, multiple (three or four) injections of Photofrin® did not elevate bone marrow CFU-GM above control levels beyond 8 days post-irradiation. In addition, splenic CFU-GM levels in animals receiving three or four injections of Photofrin® were no different than those of the irradiated controls later than 10 days post-irradiation. These findings indicate that prolonged exposure to Photofrin® in sublethally irradiated mice may induce regulatory factors which dampen the enhanced myelopoietic recovery stimulated by only two injections of the drug.

Uptake and release/retention of the photosensitizer, benzoporphyrin derivative, monoacid ring A (BPD; 1 - 20 (mu) g/mL) was studied using cell lines (K562, L1210) and normal, non- activated and Concanavalin A-activated murine splenocytes. Concentrations of BPD in cell lysates were determined by fluorescence (440 nm excitation, 694 nm emission). The results showed that BPD was taken up and released rapidly by all types of cells within the same time frame. Maximum of BPD depended on the type of cells and was greatest in tumor cells, lowest in normal, non-activated cells and intermediate in activated cells. In addition, the maximum uptake depended on BPD concentration in the medium, length of incubation and presence of serum. All cells, regardless of type, retained a constant proportion (20 - 30%) of the amount of BPD taken up. This proportion was independent of length of incubation, BPD concentration in the medium and presence of serum. However, due to differences in maximum amounts of BPD taken up under the same conditions, tumor cells retained more BPD than normal cells and activated cells more than non-activated. The retained BPD was able to photosensitize the cells. The results were found to be relevant to the in vivo studies.

Photodynamic therapy (PDT) using benzoporphyrin derivative, monoacid ring A (BPD), and transdermal light was able to significantly treat symptoms of adjuvant-enhanced arthritis in MRL-lpr mice. Clinical and histological evaluation showed that PDT was able to modify the progression of adjuvant-enhanced arthritis up to 10 days after induction. When PDT was used on arthritic joints displaying swelling, it prevented further deterioration of clinical symptoms (76%, 16/21). However, it did not significantly effect the histopathologic parameters. As we have previously reported that mitogen activated MRL-lpr splenocytes were shown to be more susceptible to in vitro PDT we postulate that our findings reflect a selective destruction of adjuvant activated lymphocytes in the circulation and/or joints. The application of PDT to eliminate activated cells responsible for the inflammatory reaction at the arthritic site may have significant clinical implications for the treatment of rheumatoid arthritis.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Photodynamic therapy (PDT) using benzoporphyrin derivative (BPD, Verteporfin) and whole body irradiation, can affect the course of adoptively transferred experimental allergic (autoimmune) encephalomyelitis (EAE) in PL mice. Murine EAE is a T cell-mediated autoimmune disease which serves as a model for human multiple sclerosis. Using a novel disease induction protocol, we found that mice characteristically developed EAE within 3 weeks of receipt of myelin basic protein (MBP)-sensitized, in vitro-cultured spleen or lymph node cells. However, if animals were treated with PDT (1 mg BPD/kg bodyweight and exposed to whole body 15 Joules cm2 of LED light) 24 hours after receiving these cells, disease onset time was significantly delayed. PDT-treated mice developed disease symptoms 45 +/- 3 days following cell administration whereas untreated controls were affected within 23 +/- 2 days. In contrast, application of PDT 48 or 120 hours following injection of the pathogenic cells had no significant effect upon the development of EAE. Experiments are in progress to account for the protective effect of PDT in this animal model. These studies should provide evidence on the feasibility of PDT as a treatment for human autoimmune disease.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Benzoporphyrin derivative monoacid ring A (BPD-MA) is a chlorin-like photosensitizer currently in clinical trials for cancer and psoriasis. It has maximal absorption peaks at both 630 and 690 nm and can be activated at both these wavelengths. In vitro phototoxicity tests using the P8 15 murine mastocytoma cell lines conducted over wavelengths of light between 678 and 700 nm emitted by an argon-ion pumped dye laser showed that equivalent cell kill could be achieved between 682 and 690 nm. Tests on in vivo phototoxicity of normal skin of DBN2 mice injected with 2 mg/kg of BPD-MA and exposed to light at 125 J/cm2, between 620 and 700 nm, demonstrated peaks of normal skin damage occurring at 630–640 nm and 680–690 nm. In tests carried out with light between 620 and 700 nm, at 10 nm increments, it was seen that light delivered at 680–690 nm caused slightly more damage to normal skin than light delivered at 630–640 nm. When lower doses of light between 675 and 705 nm were tested using smaller increments, it was determined that equivalent skin damage occurred over a range of 68–95 nm. Antitumor efficacy in tumor-bearing DBN2 mice was tested between 683 and 695 nm. It was found that equivalent antitumor efficacy, determined by assessing tumor-free status at 20 days posttreatment, occurred at wavelengths between 685 and 693 nm. When tumor-bearing animals injected with BPD-MA at 2 mdkg and exposed to light 3 h later were treated with either 630 or 690 nm light at various doses, it was observed that 690 nm light was more effective at tumor ablation than was 630 nm light, demonstrating that while similar damage to normal skin may be effected by equivalent doses of light at either wavelength, tumor ablation was greater at 690 nm. Further, our data suggest that alternative light sources with bandwidths greater than those of the argon-ion pumped dye laser (±0.3 nm) may have equivalent efficacy with this photosensitizer.

Benzoporphyrin derivative monoacid ring A (BPD) is taken up rapidly (within 30 minutes) by most cells. Rapidly dividing tumor cell lines and mitogen activated murine T lymphocytes were found to take up significantly more (5 - 10 fold) BPD than do normal splenic lymphocytes making them a potential PDT target. Experiments have shown that BPD can be activated in the blood of animals by whole body irradiation with red light, shortly after intravenous administration, in the absence of skin photosensitivity. During the treatment time, plasma levels of BPD were between 0.7 and 1.0 (mu) g/mL. The light treatment resulted in between 70 and 80% photoinactivation of circulating BPD. When L1210 tumor cells were preincubated with BPD and injected i.v. into mice immediately before total body light treatment, significant reductions in circulating clonogenic tumor cells were observed in blood samples taken immediately following treatment. This `transdermal' treatment has been shown to be effective in preventing the development of hind limb arthritis in MRL/1pr mice.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In vitro experiments with benzoporphyrin derivative monoacid ring A (BPD) confirmed earlier studies that it was taken up rapidly (within 30 min) to maximum concentrations by all cells tested. It was also confirmed that rapidly dividing tumor cell lines and mitogen-activated murine T lymphocytes took up significantly more (5-10-fold) BPD than did normal splenic lymphocytes. Further experiments were undertaken to determine whether BPD could be activated by whole-body irradiation with red light in the blood of animals, shortly after intravenous (i.v.) administration, in the absence of skin photosensitivity. It was found that shaved and depilated mice injected i.v. 60 min earlier with BPD at between 0.5 and 1.0 mg/kg could tolerate 160 J/cm2 of broad-band red light (560-900 nm) delivered, at a relatively low rate, over a 90 min time interval without developing skin photosensitivity or general phototoxicity. During the treatment time, plasma levels of BPD were between 0.7 and 1.0 μg/mL. The light treatment resulted in between 70 and 80% photoinactivation of circulating BPD. When LI 210 tumor cells were preincubated with BPD and injected i.v. into mice immediately before total-body light treatment (160 J/cm2 of 590-900 nm light delivered over 90 min), significant reductions in circulating clonogenic tumor cells were observed in blood samples taken immediately following treatment. This indicated that sufficient light was being delivered to BPD in the blood flowing in the peripheral vasculature to effect cytotoxicity to cells containing the photosensitizer without causing either vascular or skin photosensitivity. Thus, activation of this photosensitizer in the circulation can be achieved by transdermal light exposure without causing skin photosensitivity provided that light exposure is performed at a time when the first phase of plasma clearance is complete and when the drug has not yet accumulated in skin.

Porphyrins are a group of organic compounds involved in a wide spectrum of fundamental biological processes. Non-metallic, naturally occurring and synthetic porphyrin derivatives may produce cytotoxic effects in malignant or normal tissues exposed to visible light. Supra-clinical doses of the photosensitizing porphyrin, Photofrin are hematostimulatory when administered to normal and immunosuppressed inbred mice. To determine if a non-photosensitizing metalloporphyrin has similar hematostimulatory activity, we have synthesized iron (III) hematoporphyrin chloride (FeHp) and administered it to sub-lethally irradiated mice. FeHp (10 mg/kg) given 1 and 4 days or 1, 4 and 7 days following sub-lethal (7 Gy) whole body irradiation significantly increased spleen colony forming units of progenitor cells of the granulocyte-macrophage lineage (CFU-GM) 14 days post-irradiation, relative to irradiated controls. In addition, total splenocyte numbers were significantly increased 17 days post-irradiation in mice that had received FeHp 1 and 4 days post-irradiation. When FeHp was given 24 hours prior to irradiation and again 48 hours or 48 and 96 hours post-irradiation, significant increases in splenic CFU-GM and spleen cell numbers, relative to control mice, were observed 15 days post-irradiation. A non-metallic photosensitizing monomeric fraction of Photofrin, deuteroporphyrin IX, 2,4 (4,2) hydroxyethyl vinyl (HVD) was compared to Photofrin for its ability to influence the hematopoietic recovery of irradiated mice. Only Photofrin but not HVD given in 3 doses (10 mg/kg) 1, 4 and 7 days following irradiation (4.8 Gy) significantly enhanced the recovery of spleen cellularity and splenic CFU-GM. In addition, Photofrin significantly increased bone marrow CFU-GM 7 and 10 days following the sub-lethal dose of gamma-radiation. The mechanism by which certain porphyrins augment hematopoiesis in the mouse is unknown. However, the identification of FeHp as a non-photosensitizing monomeric porphyrin with hematostimulatory activity in vivo, indicates that further study of metalloporphyrins is warranted and may reveal their clinical potential within the context of therapeutically-induced immunosuppression.

This report describes the effects of the porphyrin photosensitizers, Photofrin ® and benzoporphyrin derivative (BPD) on the immunohematopoietic system of normal and immunosuppressed DBA/2 mice in the absence of activating light. Photofrin ® (10 and 25 mg/kg) significantly increased in vitro colony formation by cells of the granulocyte-macrophage lineage in the spleen and bone marrow. Splenic hypercellularity, splenomegaly and elevated levels of blood leukocytes were observed in these mice 7 days following Photofrin ® injection. Evidence that Photofrin ® influenced the lymphohematopoietic compartment was suggested by a significant increase in blood lymphocytes and a population of spleen cells identified by a monoclonal antibody (LR-1) reactive with mouse splenic B lymphocytes. Proliferative reponses of spleen cells from Photofrin ® -treated mice to sub-optimal concentrations of Con A were greater than that observed for controls. However, spleen cell responses to LPS were unaltered by Photofrin ® administration. In contrast, BPD (10 mg/kg) did not alter any of the immunohematopoietic parameters studied. When Photofrin ® was administered to mice treated with the myeloablative agent 5-FU there was a significant acceleration in the recovery of total blood leukocyte and spleen cell numbers, relative to the controls. These studies demonstrate that, in addition to its previously documented activities as a photosensitizer, Photofrin ® can exert stimulatory effects upon murine hematopoiesis.

Intracellular events associated with photosensitizers and their subsequent activation with light are as yet poorly understood. Using a model photosensitizer, benzoporphyrin derivative, monoacid ring A (BPD), we have studied cellular uptake and release using both cell lines and normal murine splenocytes. These studies showed that maximum uptake was effected rapidly, peaking between 15 and 30 minutes following exposure to BPD. Absolute quantities taken up varies substantially between cell sources, malignant cell lines and activated normal cells taking up significantly higher levels. Release of BPD from cells occurred equally rapidly when they were removed from BPD-containing medium. Phototoxicity studies indicated that more sensitive cell structures were exposed to the photosensitizer with increased time of incubation. Further experiments were conducted to study protein expression in a murine tumor cell line following BPD treatment. We observed that the oxidative stress associated with photodynamic therapy resulted in the induction of a set of heat shock or stress proteins, and that the pattern of expression was similar when tumor cells were treated in vitro and in vivo.

Photosensitizing and biodistribution characteristics of a photosensitizer (benzoporphyrin derivative, monoacid ring A; BPD) conjugated to a macromolecule (modified polyvinyl alcohol; M-PVA, molecular weight = 10,000) were tested in vitro and in vivo. Modified PVA was loaded with BPD at molar ratios 1:12, 1:25, 1:50, 1:75 and 1:100. Most of the work was carried out with a conjugate having a 1:25 molar ratio. In vitro photosensitization was tested using A549 (human lung carcinoma), A432 (human epidermoid carcinoma) and P815 (mastocytoma of DBA/2 mice) cell lines. Photosensitization of M1 (rhabdomyosarcoma of DBA/2 mice) tumors was tested in an in vivo/in vitro assay, in which tumor-bearing mice were injected intravenously with free or conjugated 3H-BPD and 3 h later light activation of tumor cells was carried out in vitro. Biodistribution studies were carried out using M1 tumor-bearing DBA/2 mice and 3H-BPD either free or conjugated to M-PVA. The results of these studies showed that the conjugation of BPD to M-PVA resulted in the formation of a macromolecular photosensitizer that retained full photosensitizing activity of the photosensitizer molecules and at the same time gained new characteristics, advantageous for photodynamic treatment, especially in vivo. In vitro M-PVA-BPD conjugates were at least as efficient in photosensitization of tumor cells as an equivalent number of free BPD molecules, both in the presence and in the absence of serum. Although the biodistribution was in general comparable to free BPD, the conjugate (1:25) reached slightly higher levels in the blood, kidney, lung and spleen, and lower levels in the liver, brain, skin and muscle in comparison with free BPD.(ABSTRACT TRUNCATED AT 250 WORDS)