Apoptosis occurs in lymphoma cells but not in hepatoma cells following ionizing radiation and photodynamic therapy

RNA expression profiling of normal and tumor cells following photodynamic therapy with 5-aminolevulinic acid-induced protoporphyrin IX in vitro

Photodynamic therapy using 5-aminolevulinic acid-induced protoporphyrin IX synthesis as a photosensitizing reagent is an encouraging modality for cancer treatment. Understanding the mechanism of tumor phototoxicity is important to provide a basis for combinatory therapy regimens. A normal cell line (UROtsa, urothelial) and two tumor cell lines (RT4, urothelial; HT29, colonic) were treated with cell line-specific LD50 doses of light after exposure to 5-aminolevulinic acid (100 microg/mL), and harvested for RNA extraction 0, 10, and 30 minutes after irradiation. The RNA was hybridized to the metg001A Affymetrix GeneChip containing 2,800 genes, focusing on cancer-related and growth regulatory targets. Comparing the gene expression profiles between the different samples, 40 genes (e.g., SOD2, LUC7A, CASP8, and DUSP1) were identified as significantly altered in comparison with the control samples, and grouped according to their gene ontology. We selected caspase-8 (CASP8) and dual specificity phosphatase 1 (DUSP1) for further validation of the array findings, and compared their expression with the expression of the immediate early gene FOS by quantitative reverse transcription-PCR. RNA expression of CASP8 stayed unchanged whereas DUSP1 RNA was up-regulated in normal and tumor cells starting 30 minutes after irradiation. In contrast, FOS RNA was found continuously up-regulated over time in all three cell lines. Induction of DUSP1 protein expression was clearly shown after 1 hour using Western blot analysis. Interestingly, no changes of caspase-8 protein expression but activation of catalytic activity was detected only in UROtsa cells starting 1 hour after photodynamic therapy, whereas no changes were seen in both tumor cell lines. According to caspase-8, the active caspase 3 fragment was found only in the normal urothelial cell line (UROtsa) 1 hour after photodynamic therapy. Combined data analysis suggests that photodynamic therapy in vitro (LD50) leads to apoptosis in UROtsa and to necrosis in the tumor cell lines, respectively. RNA expression profiling of normal and tumor cell lines following photodynamic therapy with 5-aminolevulinic acid gave insight into the major molecular mechanisms induced by photodynamic therapy.

Apoptosis of gastric cancer cell line MKN45 by photodynamic treatment with photofrin

The aim of this study was to investigate the mechanism of cell death by photodynamic therapy (PDT) in the gastric cancer cell line MKN45 with focus on the mechanism of apoptosis. Gastric cancer cells (MKN45) were incubated with Photofrin for up to 24 h before exposure to He-Cd laser (441 nm, 1 J/cm2). Cell viability was assessed by the methyl-tetra-zolium assay after exposure to light. A 95% cell death (LD95) was measured with 10 microg/ml of Photofrin. DNA ladder formation and chromatin condensation were seen within 60 min. Caspase-3-like and caspase-9-like activities increased from 15 min after exposure to light. Reduction of rhodamine 123 uptake started at 30 min. Caspase-inhibitor VAD-fmk (10 mM) inhibited apoptosis, but did not influence cell viability. In conclusion, Photofrin-mediated PDT in the gastric cancer cell line MKN45 induces apoptosis within 60 min, and mitochondrial damage is likely as the first event of apoptosis.

Intracellular signaling mechanisms in photodynamic therapy

In photodynamic therapy (PDT) a sensitizer, light and oxygen are used to induce death of tumor cells and in the treatment of certain noncancerous conditions. Cell death in PDT may occur by apoptosis or by necrosis, depending on the sensitizer, on the PDT dose and on the cell genotype. Some sensitizers that have been used in PDT are accumulated in the mitochondria, and this may explain their efficiency in inducing apoptotic cell death, both in vitro and in vivo. In this review we will focus on the events that characterize apoptotic death in PDT and on the intracellular signaling events that are set in motion in photosensitized cells. Activation of phospholipases, changes in ceramide metabolism, a rise in the cytosolic free Ca2+ concentration, stimulation of nitric oxide synthase (NOS), changes in protein phosphorylation and alterations in the activity of transcription factors and on gene expression have all been observed in PDT-treated cells. Although many of these metabolic reactions contribute to the demise process, some of them may antagonize cell death. Understanding the signaling mechanisms in PDT may provide means to modulate the PDT effects at the molecular level and potentiate its antitumor effectiveness.

Effects of 5-aminolaevulinic acid on human ovarian cancer cells and human vascular endothelial cells in vitro

Results are reported on the cellular effects and the sensitivity of cultured tumor epithelial cells (TEC) derived from human ovarian cystadenocarcinoma and human umbilical vein-derived endothelial cells (HUVEC) to exogenous 5-aminolaevulinic acid (ALA) and ALA-induced photodynamic therapy (PDT). Cellular alterations and PDT efficiency were evaluated using colorimetric thiazolyl blue (MTT) assay, trypan blue exclusion assay, electron microscopy, and gel electrophoresis. ALA-induced protoporphyrin IX (PpIX) accumulation in TEC was associated with a concentration and time-dependent significant decrease in mitochondrial activity, increase in cell membrane permeability, and dark toxicity. Maximum PpIX loaded TEC demonstrated a high sensitivity to PDT. Neither cellular alterations nor PDT effects were observed in HUVEC under identical experimental conditions. These results indicate a potential clinical value for the use of ALA-mediated PDT to treat minimal residual disease in mucinous ovarian carcinoma. In addition, the ALA-induced PpIX cytotoxicity may be exported to a new chemotherapeutic regimen via a conventionally viewed photochemotherapeutic agent.

Enhanced cell death in NR-S1 tumor by photodynamic therapy: possible involvement of Fas and Fas ligand system

BACKGROUND AND OBJECTIVES

To investigate the effect of photodynamic therapy (PDT) on cell death in malignant tumor tissue, the frequency of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells and the possible involvement of Fas and Fas ligand system were evaluated.

STUDY DESIGN/MATERIALS AND METHODS

NR-S1 tumor-bearing C3H/HeNCrj mice were treated by PDT with Photofrin(R) (12 mg/kg body weight) and Nd:YAG dye laser (630 nm, 10 Hz, 150 J/cm(2)). Paraffin-embedded tissue sections from the excised tumor tissues at 6, 12, 24, 48 hours after PDT were analyzed by TUNEL for the occurrence of apoptosis and by immunohistochemistry for Fas and Fas ligand (FasL) expression. TUNEL-positive cells as well as Fas- or FasL-positive cells were counted and expressed as a percentage of positive cells per total cells.

RESULTS

Based on the percent area of tumor necrotic foci, the most effective conditions for PDT were first determined. Under these conditions, PDT increased the number of TUNEL-positive tumor cells at 12 hours after irradiation. In parallel with the increase in TUNEL-positive cells, Fas-positive tumor cells were also found in the same area where many TUNEL-positive tumor cells were found. The expression of Fas ligand was found in the tumor cells surrounding TUNEL-positive cells on serial sections. A significant increase in FasL-positive lymphocytes was observed at 12 hours, whereas the infiltration of such lymphocytes into the area where TUNEL-positive tumor cells were observed was rare.

CONCLUSION

The possible role of Fas/FasL system in the cell death induced by PDT with Photofrin(R) and Nd:YAG dye laser was suggested. Moreover, the role of infiltrated lymphocytes seemed not to be so much in this model.

Signaling pathways in cell death and survival after photodynamic therapy

Photodynamic therapy (PDT) is a cytotoxic treatment, which can induce cells to initiate a rescue response, or to undergo cell death, either apoptosis or necrosis. The many signaling pathways involved in these processes are the topic of this review. The subcellular localization of the photosensitizer has been shown to be a key factor in the outcome of PDT. Mitochondrial localized photosensitizers are able to induce apoptosis very rapidly. Lysosomal localized photosensitizers can elicit either a necrotic or an apoptotic response. In the plasma membrane, a target for various photosensitizers, rescue responses, apoptosis and necrosis is initiated. Several protein phosphorylation cascades are involved in the regulation of the response to PDT. Finally, a number of stress-induced proteins play a role in the rescue response after PDT. Notably, the induction of apoptosis by PDT might not be crucial for an optimal outcome. Recent studies indicate that abrogation of the apoptotic pathway does alter the clonogenic survival of the cells after PDT. Further studies, both in vitro and especially in vivo could lead to more efficient combination therapies in which signaling pathways, involved in cell death or rescue, are either up- or downregulated before PDT.

Changes in intracellular Ca2+ concentrations related to PDT-induced apoptosis in photosensitized human cancer cells

For photodynamic therapy (PDT), human squamous cell carcinoma cells (HSC-2) were treated with 3 microg/ml of photofrin 24 h prior to irradiating the cultures with the excimer dye laser at a dose of 2 J/cm2. Extensive DNA fragmentation was recognized within 2 h of PDT. The proportion of cells with DNA fragmentation on flow cytometric analysis was significantly increased to 44 and 78% at 1 and 2 h after PDT, respectively, compared to control groups. Confocal laser scanning microscopy revealed a slight change in the intracellular Ca2+ concentration occurring at 30 min after PDT and a subsequent marked increase in the Ca2+ concentration 1-2 h after PDT, but no change was observed in the cells exposed to laser irradiation alone and to photofrin alone and in the cells immediately after PDT. These findings suggest that an increase in the intracellular Ca2+ concentration may play an important role in the induction of PDT-induced apoptosis.

Amelioration of antigen-induced arthritis in rabbits by induction of apoptosis of inflammatory cells with local application of transdermal photodynamic therapy

OBJECTIVE

To study the efficacy and mechanism of local transdermal photodynamic therapy (tPDT) in rabbits with antigen-induced arthritis (AIA).

METHODS

AIA in rabbits on day 14 postinduction was treated with an intravenous injection of benzoporphyrin-derivative monoacid ring A (BPD; Verteporfin) and subsequent transdermal exposure of the knee joint to light. BPD uptake and PDT-induced apoptosis of the synovium was studied applying fluorescence confocal microscopy and immunohistochemistry. The (histo)pathology of the joints was assessed at day 28.

RESULTS

Treatment with tPDT resulted in significant amelioration of synovial inflammation and an almost complete prevention of pannus formation and bone and cartilage destruction. BPD uptake was detectable in activated T cells and macrophages, and there was significant PDT-induced increase in the number of apoptotic cells in the synovium.

CONCLUSION

Because photodynamic therapy is both specific and noninvasive, our findings suggest that it could be used for treating arthritic joints in humans.

Tumour-localizing and tumour-photosensitizing properties of zinc(II)-octapentyl-phthalocyanine

Zn(II)-octapentyl-phthalocyanine (ZnOPPc), incorporated into a Cremophor oil emulsion, was found to be a highly selective tumour-targeting agent (50-fold larger concentration in the tumour than in the peritumoral tissue) when injected at a dose of 1.46 mumol (kg body weight)-1 in Balb/c mice bearing an intramuscularly transplanted MS-2 fibrosarcoma. The pharmacokinetic properties of this phthalocyanine were closely similar to those found for the analogous octadecyl derivative, whereas the unsubstituted Zn(II)-phthalocyanine showed a lower efficiency and selectivity of tumour targeting than the octaalkyl-substituted phthalocyanines. Irradiation of the ZnOPPc-loaded tumour with 620-700 nm light 24 h after injection caused a significant delay of tumour growth with a gradual shrinkage of the neoplastic mass; the damage involved important contributions from both random necrosis and apoptosis of malignant cells.

Rapid tyrosine phosphorylation of HS1 in the response of mouse lymphoma L5178Y-R cells to photodynamic treatment sensitized by the phthalocyanine Pc 4

The ability of photodynamic treatment (PDT) with the phthalocyanine Pc 4 to activate cellular signal transduction pathways in murine lymphoma L5178Y-R cells has been assessed by observing increases in protein tyrosine phosphorylation at early times post-PDT. Western blot analysis with an anti-phosphotyrosine antibody revealed a dramatic increase in phosphorylation of two major protein bands of Mr approximately 80,000 and approximately 55,000 in response to PDT. The increase was PDT dose-dependent, occurred as early as 20 s after initiation of light exposure of Pc 4-preloaded cells and was amplified by the presence of the protein tyrosine phosphatase inhibitor, sodium orthovanadate (NaVO4). By immunoprecipitation, one of the Mr approximately 80,000 phosphorylated proteins has been identified as HS1, a substrate of nonreceptor-type protein tyrosine kinases. Although vanadate greatly enhanced the level and extent of PDT-induced phosphorylation, it had no influence on overall photocytotoxicity or on the rate of apoptotic DNA fragmentation. Genistein, an inhibitor of protein tyrosine kinases, diminished tyrosine phosphorylation of the Mr approximately 80,000 and other proteins and dramatically potentiated cell killing induced by PDT but did not significantly affect PDT-induced apoptosis. The results suggest that PDT rapidly activates a membrane-associated src family kinase(s) in L5178Y-R cells, one substrate of which is HS1, and that protein tyrosine phosphorylation is part of a stress response, protecting a portion of the cells from the lethal effects of PDT but not altering the mechanism by which they die.

The biology of photodynamic therapy

The subcellular, cellular and tissue/tumour interactions with non-toxic photosensitizing chemicals plus non-thermal visible light (photodynamic therapy (PDT) are reviewed. The extent to which endothelium/vasculature is the primary target is discussed, and the biochemical opportunities for manipulating outcome highlighted. The nature of tumour destruction by PDT lends itself to imaging outcome by MRI and PET.

Preclinical assessment of hypocrellin B and hypocrellin B derivatives as sensitizers for photodynamic therapy of cancer: progress update

Hypocrellins are perylenequinone pigments with substantial absorption in the red spectral region and high singlet oxygen yield. They are available in pure monomeric form and may be derivatized to optimize properties of red light absorption, tissue biodistribution and toxicity. In vitro screening of synthetic derivatives of the naturally occurring compound, hypocrellin B (HB), for optimal properties of cyto-(dark) toxicity and phototoxicity resulted in selection of three compounds for preclinical evaluation: HBEA-R1 (ethanolaminated HB), HBBA-R2 (butylaminated HB) and HBDP-R1 [2-(N,N-dimethylamino)-propylamine-HB]. Extinction coefficients at 630 nm (epsilon 630) are 6230, 6190 and 4800, respectively; and 1O2 quantum yields, phi, 0.60, 0.32 and 0.42. Intracellular uptake is essentially complete within 2 h (HBEA-R1, HBBA-R2) and 20 h (HBDP-R1). Greatest uptake is associated with lysosomes and Golgi. The HBEA-R1 and HBBA-R2 elicit phototoxicity in vitro primarily via the type II mechanism, with some type I activity under stringently hypoxic conditions. Transcutaneous phototherapy with HBEA-R1 permanently ablates EMT6/Ed tumors growing in the flanks of Balb/c mice, with minimal cutaneous effects. The HBBA-R2 does not elicit mutagenic activity in strains TA98 and TA100 of Salmonella typhimurium. Further development of selected hypocrellin derivatives as photosensitizers for photodynamic therapy is warranted.

Liver apoptosis

Apoptosis, also called programmed cell death, is a peculiar form of cell death different from cell necrosis in many morphological and biochemical aspects. Like mitosis or differentiation, apoptosis is a normal cell phenomenon which depends on the expression of genes capable of inducing or inhibiting this type of cell destruction. But apoptosis can also be triggered by many external factors and has been described in many diseases. The very different conditions where programmed cell death occurs suggest that the mechanisms leading to the activation of apoptosis-controlling genes are variable. As in other cells, apoptosis occurs in the liver cells, first in the normal state during liver development and then in the adult liver, respectively for liver organogenesis and the renewal of hepatocytes. But apoptosis is also present in various viral, immunological, malignant or drug-induced human liver diseases. In addition, in the animal, hepatocyte apoptosis can be triggered either in vivo or in vitro by many toxic agents. In contrast to other cells, the mechanisms leading to liver cell apoptosis remain poorly investigated. However, two proteins could play an important role in this field, the fas/apo-1 protein present at the surface of hepatocytes and the bcl-2 protein localized in biliary cells. Analysis of the genes controlling the expression of these two proteins could provide essential information on the mechanisms of liver apoptosis.

Photodynamic therapy in neurosurgery: a review

Photodynamic therapy (PDT) has been investigated extensively, both experimentally and clinically, as an adjunctive treatment in the neuro-oncological field. It is based on the more selective accumulation of a photosensitizer in malignant than normal tissue with low systemic toxicity. Subsequent light activation induces photo-oxidation, followed by selective tumour destruction via vascular and direct cellular mechanisms. Malignant brain tumours carry a lethal prognosis with a median survival of 15 months despite surgery, radiotherapy and chemotherapy. PDT is therefore a logical therapeutic concept for brain tumours infiltrating into normal brain. In this review, all the available data on patients treated with haematoporphyrin derivative-mediated PDT are critically analysed. Over 310 patients have been reported in the literature suffering from primary or recurrent malignant brain tumours which were treated with PDT following tumour resection in open clinical phase I/II trials. This number includes 58 patients treated at our own institution. Variations in the treatment protocols make evaluation scientifically difficult; however, there is a clear trend of increased median survival after surgical resection and one single photodynamic treatment. PDT is generally well tolerated and side effects consist of moderate increased intracranial pressure and prolonged skin sensitivity to direct sunlight. The current available data indicate that PDT is a safe treatment, which is well tolerated by the patients and yields an improvement in survival of those with malignant brain tumours. Conclusive information can be expected from controlled clinical trials which are currently being designed. The results raise the hope that PDT will be a valuable addition to the armamentarium for the treatment of cerebral malignancies.

Apoptosis or necrosis following Photofrin photosensitization: influence of the incubation protocol

Photosensitization using the tumor-localizing porphyrin Photofrin induces cell death both in vitro and in vivo, but the mechanism of cell death is not well understood. Cell lysis (necrosis) and apoptosis have both been observed. The latter seems restricted mainly to lymphoma and epithelial cell lines. To check the influence of the incubation protocol on the cell death mechanism, CV-1 cells were loaded with Photofrin using two different protocols. In both protocols, photosensitized CV-1 cells underwent severe morphological changes before cell death. Many cells treated with protocol 1 (24 h with 1 microgram/mL of Photofrin in culture medium) underwent apoptosis, as demonstrated by plasma membrane blebbing and fragmentation into vesicles, condensation of the chromatin and fragmentation of the nucleus with oligonucleosomic degradation of the DNA. In contrast, cells treated with protocol 2 (1 h with 10 micrograms/mL of Photofrin in phosphate-buffered saline) lysed instead of fragmented, without oligonucleosomic degradation of the DNA. This type of cell death looks much like necrosis. However, early morphological changes suggest that it is, in fact, apoptosis stopped by plasma membrane leakage. It is concluded that apoptosis is primarily induced in CV-1 cells but may be arrested by membrane lysis, depending on the incubation protocol.

Apoptosis of mouse MS-2 fibrosarcoma cells induced by photodynamic therapy with Zn (II)-phthalocyanine

The destructive process of mouse MS-2 fibrosarcoma induced by photodynamic therapy (PDT) with liposome-administered Zn(II)-phthalocyanine (ZnPc) was studied by electron microscopy. Pronounced ultrastructural changes characteristic of apoptosis were observed for several tumour cells, including early occurrence of condensation and margination of chromatin, disappearance of nuclear pores, karyopyknosis, karyorrhexis, protuberance formation at the cell surface and cell fragmentation. The findings indicate that apoptosis was involved in the process of tumour cell death induced by ZnPc-PDT. The detailed mechanism and pathways controlling this phenomenon need to be elucidated further.