zn(ii)-phthalocyanine and Necrosis

Zinc(II)-phthalocyanine is the active component of the liposomal formulation CGP 55847 which showed a highly activity in photodynamic therapy studies on a variety of animal tumours (K. Schieweck et al., SPIE Conf. Proc., 2078 (1994) 107-118). The photophysical properties of zinc(II)-phthalocyanine have been studied in detail and compared with those of Photofrin II(R), the only sensitizing agent approved so far for Phase III and IV clinical trials (M. Ochsner-Bruderer, Inaugural Dissertation, University of Basle, 1994). As will be shown in a series of papers, the main photophysical properties of zinc(II)-phthalocyanine are significantly better than those of Photofrin II(R) (M. Ochsner-Bruderer, Inaugural Dissertation, University of Basle, 1994). In this paper we especially consider the effect of the absorption wavelength on the penetration of light into the human skin. The results clearly show that the longer absorption wavelength of zinc(II)-phthalocyanine causes a deeper penetration of light into the human skin as compared with Photofrin II(R). In addition to this, the higher extinction coefficient (epsilon S) lowers the zinc(II)-phthalocyanine dose required to induce a tumour necrosis.

Topics: Animals; Dihematoporphyrin Ether; Drug Carriers; Humans; Indoles; Isoindoles; Light; Liposomes; Necrosis; Organometallic Compounds; Photochemotherapy; Photosensitizing Agents; Scattering, Radiation; Skin; Skin Neoplasms; Zinc; Zinc Compounds

Melanoma is an aggressive form of skin carcinoma, highly resistant to traditional therapies. Photodynamic therapy (PDT) is a non-invasive therapeutic procedure that can exert a selective cytotoxic activity toward malignant cells. In this work we evaluated the effect of a cationic zinc(II) phthalocyanine (Pc13) as photosensitizer on a panel of melanoma cells. Incubation with Pc13 and irradiation induced a concentration and light dose-dependent phototoxicity. In order to study the mechanism underlying Pc13-related cell death and to compare the effect of different doses of PDT, the most sensitive melanoma B16F0 cells were employed. By confocal imaging we showed that Pc13 targeted lysosomes and mitochondria. After irradiation, a marked increase in intracellular reactive oxygen species was observed and a complete protection from Pc13 phototoxicity was reached in the presence of the antioxidant trolox. Acridine orange/ethidium bromide staining showed morphological changes indicative of both apoptosis and necrosis. Biochemical hallmarks of apoptosis, including a significant decrease in the expression levels of Bcl-2, Bcl-xL and Bid and mitochondrial membrane permeabilization, were observed at short times post irradiation. The consequent release of cytochrome c to cytosol and caspase-3 activation led to PARP-1 cleavage and DNA fragmentation. Simultaneously, a dose dependent increase of lactate dehydrogenase in the extracellular compartment of treated cells revealed plasma membrane damage characteristic of necrosis. Taken together, these results indicate that a dual apoptotic and necrotic response is triggered by Pc13 PDT-induced oxidative stress, suggesting that combined mechanisms of cell death could result in a potent alternative for melanoma treatment.

Topics: Animals; Apoptosis; Cell Death; Cell Line, Tumor; Humans; Indoles; Infrared Rays; Isoindoles; Melanoma; Melanoma, Experimental; Mice; Necrosis; Organometallic Compounds; Oxidative Stress; Photochemotherapy; Photosensitizing Agents; Reactive Oxygen Species; Skin Neoplasms; Zinc Compounds

Regarding post-complication of convenient therapies against breast cancer, the emergence of effective approaches is essential. Photodynamic therapy is touted as a novel invasive therapeutic approach by the application of a photosensitizer promoted by laser irradiation. This study aimed to investigate the combined regime of low-level laser irradiation with zinc phthalocyanine in human breast cancer ZR-75-1 cell line. Cells were treated with 0.01 and 5 μg/ml of ZnPc for 24 h and exposed to radiation (70 mW) for 60 s. Cell viability was evaluated by MTT and flow cytometry. Cell migration capacity was monitored by scratch test, Transwell migration insert, and gelatin zymography. The function of MDR in treated cells was examined by Rhodamine 123 exclusion test. The level of GALNT11 was measured by ELISA. The expression of Bax and Bcl-2 genes was evaluated by real-time PCR. Laser irradiation and zinc phthalocyanine induced cell cytotoxicity in a dose-dependent manner. Flow cytometry analysis showed the induction of apoptotic and necrotic changes in treated cells. We found a reduction in migration rate and MMP-9 activity in cells undergoing the experimental procedure (p < 0.05). Immunofluorescence imaging revealed the intracellular accumulation of Rhodamine 123 coincided with a reduction in the level of GALNT11 in treated cells, showing the reduction of MDR activity and tumor cell resistance. Similar to flow cytometry assay, the reduction of Bcl-2 (approximately twofold) and upregulation of Bax genes were found in treated cells. Photodynamic therapy could be as an effective and alternative method for the treatment of breast cancer in a human.

Topics: Apoptosis; ATP Binding Cassette Transporter, Subfamily B; bcl-2-Associated X Protein; Breast Neoplasms; Cell Count; Cell Line, Tumor; Cell Movement; Cell Survival; Drug Resistance, Neoplasm; Female; Humans; Indoles; Isoindoles; Light; Matrix Metalloproteinase 9; N-Acetylgalactosaminyltransferases; Necrosis; Organometallic Compounds; Photochemotherapy; Photosensitizing Agents; Rhodamine 123; Zinc Compounds

Photodynamic therapy (PDT) is a clinically approved therapeutic modality for the treatment of diseases characterized by uncontrolled cell proliferation, mainly cancer. It involves the selective uptake of a photosensitizer (PS) by neoplastic tissue, which is able to produce reactive oxygen species upon irradiation with light, leading to tumor regression. Here a synergistic cell photoinactivation is reported based on the simultaneous administration of two PSs, zinc(II)-phthalocyanine (ZnPc) and the cationic porphyrin meso-tetrakis(4-N-methylpyridyl)porphine (TMPyP) in three cell lines (HeLa, HaCaT and MCF-7), using very low doses of PDT. We detected changes from predominant apoptosis (without cell detachment) to predominant necrosis, depending on the light dose used (2.4 and 3.6 J/cm(2), respectively). Analysis of changes in cytoskeleton components (microtubules and F-actin), FAK protein, as well as time-lapse video microscopy evidenced that HeLa cells were induced to undergo apoptosis, without losing adhesion to the substrate. Moreover, 24 h after intravenous injection into tumor-bearing mice, ZnPc and TMPyP were preferentially accumulated in the tumor area. PDT with combined treatment produced significant retardation of tumor growth. We believe that this combined and highly efficient strategy (two PSs) may provide synergistic curative rates regarding conventional photodynamic treatments (with one PS alone).

Topics: Actins; Animals; Apoptosis; Dose-Response Relationship, Radiation; Drug Synergism; Female; Focal Adhesion Kinase 1; HeLa Cells; Humans; Indoles; Injections, Intravenous; Isoindoles; MCF-7 Cells; Mice; Mice, Inbred C57BL; Microscopy, Video; Microtubules; Necrosis; Neoplasms; Organometallic Compounds; Photochemotherapy; Photosensitizing Agents; Porphyrins; Time Factors; Time-Lapse Imaging; Tumor Burden; Xenograft Model Antitumor Assays; Zinc Compounds

Subcellular localization of photosensitizers (PSs) determines the therapeutic efficacy in the photodynamic therapy. However, among the subcellular compartments, there has been little effort to deliver the PSs selectively into the plasma membrane and examine the phototherapeutic efficacy of membrane-localized PSs. Here, we developed a liposomal delivery system to localize the hydrophobic PSs selectively into the plasma membrane. The membrane fusogenic liposomes (MFLs), the membrane of which is engineered to fuse with the plasma membrane, was prepared for the membrane localization of PSs. The phototherapeutic efficacy of cells treated with ZnPc-loaded MFLs was superior over that of cells treated with ZnPc-loaded non-fusogenic liposomes, which is the conventional liposomal formulation that delivers the PSs into the intracellular compartments via endocytosis. The membrane localization of ZnPc molecules led to rapid membrane disruption upon irradiation and subsequent necrosis-like cell death. The membrane-localized generation of reactive oxygen species in the cells treated with ZnPc-loaded MFLs was likely to account for the effective disruption of plasma membrane. Thus, this work provides a novel delivery method to localize the PSs selectively into the plasma membrane with the enhanced phototherapeutic efficacy.

Topics: Animals; Cell Line, Tumor; Cell Membrane; Cell Survival; Chemistry, Pharmaceutical; Dose-Response Relationship, Drug; Humans; Hydrophobic and Hydrophilic Interactions; Indoles; Isoindoles; Lipids; Liposomes; Membrane Fusion; Mice; Necrosis; Neoplasms; Organometallic Compounds; Photochemotherapy; Photosensitizing Agents; Reactive Oxygen Species; Technology, Pharmaceutical; Zinc Compounds

Photodynamic therapy (PDT) is a cancer treatment modality based on the administration of a photosensitizer (PS), which accumulates preferentially in tumor cells. Subsequent irradiation of the neoplastic area triggers a cascade of photochemical reactions that leads to the formation of highly reactive oxygen species responsible for cell inactivation. Photodynamic treatments in vitro are performed with the PS, zinc-phthalocyanine (ZnPc). The PS is near the plasma membrane during uptake and internalization. Inactivation clearly occurs by a necrotic process, manifested by nuclear pyknosis, negative TUNEL and Annexin V assays and non-relocation of cytochrome c. In contrast, by increasing the incubation time, ZnPc is accumulated in the Golgi apparatus and produces cell inactivation with characteristics of apoptosis and necrosis: TUNEL positive, relocated cytochrome c and negative Annexin V assay. This type of death produces a still undescribed granulated nuclear morphology, which is different from that of necrosis or apoptosis. This morphology is inhibited by necrostatin-1, a specific inhibitor of regulated necrosis.

Topics: Biological Transport; Cell Death; Cell Nucleus; Cell Survival; Dose-Response Relationship, Drug; HeLa Cells; Humans; Imidazoles; Indoles; Isoindoles; Necrosis; Organometallic Compounds; Photochemotherapy; Photosensitizing Agents; Zinc Compounds

One of the limitations for clinical applications of dendritic cell (DC)-based cancer immunotherapy is the low potency in generating tumor antigen specific T cell responses. We examined the immunotherapeutic potential of a mitochondria-targeted nanoparticle (NP) based on a biodegradable polymer and zinc phthalocyanine (ZnPc) photosensitizer (T-ZnPc-NPs). Here, we report that tumor antigens generated from treatment of breast cancer cells with T-ZnPc-NPs upon light stimulation activate DCs to produce high levels of interferon-gamma, an important cytokine considered as a product of T and natural killer cells. The remarkable ex vivo DC stimulation ability of this tumor cell supernatant is a result of an interleukin (IL)-12/IL-18 autocrine effect. These findings contribute to the understanding of how in situ light activation amplifies the host immune responses when NPs deliver the photosensitizer to the mitochondria and open up the possibility of using mitochondria-targeted-NP-treated, light-activated cancer cell supernatants as possible vaccines.

Topics: Animals; Antigens, Neoplasm; Apoptosis; Biocompatible Materials; Cancer Vaccines; Cell Line, Tumor; Dendritic Cells; HeLa Cells; Humans; Immunotherapy; Indoles; Interferon-gamma; Isoindoles; MCF-7 Cells; Mice; Mice, Inbred C57BL; Mitochondria; Nanoparticles; Necrosis; Neoplasms; Organometallic Compounds; Photosensitizing Agents; Polymers; Zinc Compounds

To explore the effective dose range of PHOTOCYANINE, the intensity and duration of irradiation using a 670-nm laser, and changes of local tissues after photodynamic therapy (PDT) in mice with S180 tumors to provide evidence for the clinical application of PDT.. Kunming mice were administered the photosensitizer PHOTOCYANINE. After the administration of PHOTOCYANINE, irradiation with 670-nm laser had a remarkable inhibitory effect on the growth of the grafted tumor S180.. Within the power densities 36-144J/cm(2), the irradiation dose showed a significant dose-response relationship; under the same drug dosage, an increase in irradiation dose could enhance the inhibitory effect on tumor growth. In the groups administered PHOTOCYANINE and irradiated with a 670-nm laser, the temperature of the local surface did not increase remarkably, an effect also seen in the negative control group. Local swelling around the tumor occurred immediately after PHOTOCYANINE administration and laser irradiation, and could last for about 3 days. Vertical resection of the tumors 72 h after irradiation showed that the depth of local-tissue necrosis after PHOTOCYANINE administration and laser irradiation was 5.7-7.5mm.. The efficacy of PHOTOCYANINE was significantly correlated with its dose; under identical irradiation conditions, the increase in drug dose increased the tumor inhibition rate (TIR) within a certain dose range. The efficacy of PHOTOCYANINE also showed significant irradiation-dependent characteristics.

Topics: Animals; Antineoplastic Agents; Body Temperature; Body Weight; Dose-Response Relationship, Drug; Dose-Response Relationship, Radiation; Indoles; Isoindoles; Lasers; Mice; Necrosis; Organometallic Compounds; Photochemotherapy; Photosensitizing Agents; Radiation Dosage; Random Allocation; Sarcoma, Experimental; Skin Neoplasms; Time Factors; Tumor Burden; Zinc; Zinc Compounds

Photodynamic therapy (PDT) is an alternative modality for cancer therapy. It induces neoplasic cells death through photoachievable sensitizers. The aim of this work was to evaluate the pharmacokinetic, toxic and phototherapeutic effects of the phthalocyanine ZnPcCF(3) in a Balb/c mice tumor model. Biodistribution studies were carried out by intraperitoneal injection of 0.2mg/kg ZnPcCF(3). Histological studies and serum biochemical parameters were used to evaluate hepatic and renal toxicity and functionality. After tumor irradiation (210J/cm(2)), an analysis of tumor necrosis degree was used to evaluate the phototherapeutic effects. It was measured at 1, 2, 3 and 4 days after PDT. Vital staining was performed by intraperitoneal injection of 0.35ml 1% Evans Blue solution. Six hours later, tumors were excised and examined. The unstained area was attributed to necrotic tissue, whereas the stained area showed tissue with preserved blood supply. ZnPcCF(3) was accumulated in spleen, liver and duodenum. It suggests that ZnPcCF(3) is eliminated from the body via bile-gut. The phthalocyanine was not found in brain, therefore, it would not cross the blood-brain barrier, thus toxicity risk in the central nervous system is not probable. Moreover, ZnPcCF(3) does not accumulate in skin, it would eliminate cutaneous photosensitizing risks. The dose of 0.2mg/kg ZnPcCF(3) resulted in a low acute toxicity with revertible damages, which indicates that this dose can be used for PDT. The tumor death was of 89% 4 days after PDT. It indicates that ZnPcCF(3) would be effective in PDT.

Topics: Animals; Evans Blue; Female; Indoles; Injections, Intraperitoneal; Isoindoles; Mammary Neoplasms, Experimental; Mice; Mice, Inbred BALB C; Necrosis; Organometallic Compounds; Photochemotherapy; Photosensitizing Agents; Staining and Labeling; Time Factors; Tissue Distribution; Toxicity Tests; Zinc Compounds

Photodynamic therapy (PDT) is a tool against neoplastic and non-neoplastic diseases. PDT is capable to induce different cell death mechanisms in vitro, triggered in a dose-dependent manner. Relationships between PDT and apoptosis or necrosis induction are well-known, but other cell death mechanisms triggered after PDT are less understood. Here we present our results in p53-deficient human cervix carcinoma HeLa cells subjected to sublethal PDT treatments (mortality about 40%) using Zn(II)-phthalocyanine (ZnPc) incorporated into liposomes. We obtained a rapid metaphase blockage of cells that also showed clearly altered configurations of the mitotic spindle. Cell cycle arrest was followed by aneuploidisation and cell death with apoptotic morphology. Apoptosis was also confirmed by occurrence of PARP cleavage and Bax translocation to mitochondria. These features are components of the cell death mechanism known as mitotic catastrophe and represent, to our knowledge, the first description of this cell death modality after PDT with ZnPc.

Topics: Aneuploidy; Apoptosis; bcl-2-Associated X Protein; HeLa Cells; Humans; Indoles; Isoindoles; Liposomes; Mitochondria; Necrosis; Organometallic Compounds; Photochemotherapy; Photosensitizing Agents; Poly(ADP-ribose) Polymerases; Protein Transport; Spindle Apparatus; Zinc; Zinc Compounds

Photodynamic therapy is a promising approach for the prevention of arterial restenosis, which frequently occurs after balloon angioplasty, largely owing to abnormal proliferation of vascular smooth muscle cells (VSMC) and their migration from the media to the intima, where they originate intimal hyperplasia (IH). We investigated the efficacy of Zn(II)-phthalocyanine-photosensitised processes in promoting the inactivation of VSMC. This liposome delivered phthalocyanine is readily taken up by VSMC, largely partitions in the Golgi apparatus, and upon photoactivation causes >95% cell mortality using mild irradiation conditions (e.g. 5 min irradiation at 1 microM ZnPc). Cell death occurs through the parallel development of random necrotic and apoptotic processes.

Topics: Animals; Apoptosis; Cell Line; Golgi Apparatus; Hyperplasia; Indoles; Isoindoles; Liposomes; Muscle, Smooth, Vascular; Necrosis; Organometallic Compounds; Photochemotherapy; Photosensitizing Agents; Rats; Time Factors; Tunica Intima; Zinc Compounds

Photodynamic treatment with different photosensitizers (PSs) can result in the specific induction of apoptosis in many cell types. It is commonly accepted that this apoptotic response depends on the mitochondrial accumulation of the PS. Accumulation in other cellular organelles, such as lysosomes or the Golgi complex, and subsequent photodamage resulting in an apoptotic process has been also described. However, the role played by cell adhesion in apoptosis induced in epithelial cells after photodynamic treatment is not well characterized. Here, we have used a murine keratinocyte line, showing a strong dependence on E-cadherin for cell-cell adhesion and survival, to analyze the relevance of this adhesion complex in the context of zinc(II)-phthalocyanine (ZnPc) photodynamic treatment. We report that under apoptotic conditions, ZnPc phototreatment induces a rapid disorganization of the E-cadherin mediated cell-cell adhesion, which largely preceded both the detachment of cells from the substrate, via beta-1 integrins and the induction of apoptotic mitochondrial markers. Therefore, the alteration in E-cadherin, alpha- and beta-catenins adhesion proteins preceded the release of cytochrome c (cyt c) from mitochondria to the cytosol and the activation of caspase 3. In addition, blocking E-cadherin function with a specific antibody (Decma-1) induced apoptosis in this cell system. These results strongly suggest that the E-cadherin adhesion complex could be the primary target of ZnPc phototreatment, and that loss of E-cadherin mediated cell adhesion after early photodamage triggers an apoptotic response.

Topics: Animals; Apoptosis; Cadherins; Cell Adhesion; Cell Line; Indoles; Isoindoles; Keratinocytes; Light; Mice; Mitochondria; Necrosis; Organometallic Compounds; Photochemotherapy; Photosensitizing Agents; Time Factors; Zinc Compounds

Photodynamic therapy (PDT) of tumors and other diseases is based on the uptake of a photosensitizing dye in target cells, which are damaged by reactive oxygen intermediates generated on irradiation with light in which the wavelengths match the dye absorption spectrum. PDT can induce cell death by necrosis and apoptosis both in vivo and in vitro, but the factors determining the contribution of either mechanism to the overall process are not completely defined. Our studies on the photosensitization of 4R transformed fibroblasts with the second-generation photosensitizer zinc (II) phthalocyanine (ZnPc) aim at determining the effect of important experimental parameters such as time of cell incubation (2 or 24 h) with ZnPc before irradiation and ZnPc concentration in the incubation medium on cell death. Furthermore, we propose possible correlations between the cell death mechanism and primary photo-damage sites; these are mainly determined by the intracellular localization of the photosensitizer. The mechanism of cell death was determined by both electron microscopy analysis of the morphological alterations induced by photosensitization and measurement of caspase 3 activation. The initial photodamage sites were determined by measuring the activities of several functions typical of mitochondria, lysosomes, Golgi apparatus, cytosol, and plasma membrane. The intracellular localization of ZnPc after 2- or 24-h incubation was determined by fluorescence microscopy. Necrosis, associated with early loss of plasma membrane integrity and complete depletion of intracellular ATP, represents the prevailing mode of death for 4R cells dark-incubated for 2 h with ZnPc and irradiated with light doses reducing viability by 99.9%. In contrast, irradiation performed 24 h after ZnPc incubation causes only partial inhibition of plasma membrane activities, and cell death occurs largely by apoptosis. ZnPc is mainly localized in the Golgi apparatus after 2- and 24-h incubation, and in all of the cases this compartment represents a primary target of photodamage. Only after prolonged incubation is mitochondrial localization of ZnPc clearly detected by fluorescence microscopy; this could be a determining factor for promotion of apoptosis. Our data demonstrate that it is possible to modulate the mechanism of cell death by appropriate protocols; this may be relevant for enhancing the therapeutic efficacy of PDT.

Topics: Animals; Apoptosis; Cell Line, Transformed; Fibroblasts; Indoles; Isoindoles; Necrosis; Organometallic Compounds; Photochemotherapy; Photosensitizing Agents; Rats; Subcellular Fractions; Zinc Compounds

The photosensitizing effects of liposomal zinc(II)-phthalocyanine (ZnPc) on HeLa cells, with emphasis on morphological changes and mechanisms for cell death, have been studied. No dark toxicity for ZnPc alone was found. Incubation for 1 h with ZnPc followed by red light irradiation induced a variable decrease in the surviving of cells, which was related to both drug concentration and irradiation time. A lethal photodynamic effect (100% of the cells are killed: LD100) was induced by 5 x 10-6 M ZnPc and 5-min irradiation, whereas a sublethal effect (60% of the cells are killed: LD60) was detected with 10 7 M ZnPc and 3 min of red light. Toluidine blue and Hoechst 33258 staining showed characteristic alterations of cell morphology. Numerous bubbles on the plasma membrane were found immediately after an LD100 treatment, and a necrotic morphology appeared 24 h later. On the contrary, severe cell shrinkage with nuclear fragmentation. characteristic of apoptosis. was observed 8 and 24 h after LD60 treatments. In this case, propidium iodide-acridine orange labeling and the TUNEL assay confirmed the occurrence of apoptosis. The highest amount of apoptotic cells appeared 24 h after LD60 treatments, particularly in detached cells, as revealed by cell counting and DNA electrophoresis. Both apoptotic and necrotic mechanisms for cell death occur in HeLa cells in dependence on the experimental protocol of ZnPc photodynamic treatments.

Topics: Apoptosis; Cell Survival; Dose-Response Relationship, Drug; Electrophoresis, Agar Gel; HeLa Cells; Humans; Indoles; Isoindoles; Kinetics; Light; Liposomes; Microscopy, Fluorescence; Necrosis; Organometallic Compounds; Photochemotherapy; Photosensitizing Agents; Time Factors; Tumor Cells, Cultured; Zinc Compounds

Zn(II)-phthalocyanines (ZnPc) and its octapentyl (ZnOPPc) and octadecyl (ZnODPc) derivatives have been intravenously injected at a dose of 1.46 mumol/kg into female Balb/c mice bearing an intramuscularly transplanted MS-2 fibrosarcoma. Pharmacokinetic studies show that in all cases the maximal concentration of phthalocyanine in the tumour is reached at 24 h post-injection: the efficiency and selectivity of tumour targeting slightly increase upon increasing the length of the alkyl substituents. Irradiation of the neoplastic lesion (620-700 nm light, 180 MW/cm2, 300 J/cm2) 24 h after photosensitizer administration induces a significant delay of tumour growth, which was largest (approximately 11 days) for ZnPc and smallest (approximately 3.5 days) for ZnODPc. Electron microscopy investigations of irradiated tumour specimens show that ZnPc causes an early direct damage of malignant cells, largely via processes leading to random necrotic pathways, although a limited contribution of apoptotic pathways is detected. The importance of this increased upon using ZnOPPc and especially ZnODPc as the photosensitizers, possibly due to a different partitioning in different compartments of cell membranes.

Topics: Animals; Apoptosis; Female; Fibrosarcoma; Indoles; Isoindoles; Mice; Mice, Inbred BALB C; Molecular Structure; Necrosis; Organometallic Compounds; Photochemotherapy; Photosensitizing Agents; Zinc Compounds

CGP55847, liposomal zinc(II)-phthalocyanine (Zn-Pc), was administered by the intravenous route to Swiss mice bearing intramuscularly implanted Ehrlich carcinomas or to C57/BL6 mice bearing subcutaneously implanted B16 melanomas. Tumors were removed 3 h or 24 h after dosing the intratumoral distribution determined by fluorescence microscopy. Localization of the photosensitizer occurred more rapidly in the Ehrlich carcinoma than in the B16 melanoma; this difference in photosensitizer uptake may be related to a higher degree of vascularization of the carcinoma. The photosensitizer was found in association with blood vessels at 3 h but not 24 h after dosing and appeared to have a greater affinity for areas of tissue necrosis within the tumor compared to viable tumor tissue. Little or no Zn-Pc was detected in the muscle tissue invaded by the Ehrlich carcinoma and was associated with the membranes and the cytosol, but not the nucleus, of cells in both tumors.

Topics: Animals; Carcinoma, Ehrlich Tumor; Drug Carriers; False Positive Reactions; Indoles; Injections, Intravenous; Isoindoles; Liposomes; Melanoma, Experimental; Mice; Mice, Inbred C57BL; Microscopy, Fluorescence; Muscle, Skeletal; Necrosis; Organometallic Compounds; Photosensitizing Agents; Tissue Distribution; Zinc; Zinc Compounds

The mechanism of tumour necrosis photosensitised by liposome-delivered Zn(II) phthalocyanine (Zn-Pc) has been studied in mice bearing a transplanted MS-2 fibrosarcoma. Ultrastructural analyses of tumour specimens obtained at different times after red light-irradiation (300 J cm-2, dose-rate 180 mW cm-2) indicate an early (3 h) photodamage of malignant cells especially at the level of the mitochondria and rough endoplasmic reticulum. The cellular damage becomes more evident between 6 h and 15 h after photodynamic therapy. On the other hand, the capillaries supplying the tumour tissue are modified at a much slower rate and appear to be severely damaged only after 15 h from irradiation, when the whole tissue becomes necrotic. Occasionally, mildly damaged capillaries are observed even at 72 h after irradiation. These findings support the hypothesis that low density lipoproteins (LDL) play a major role in the delivery of Zn-Pc to the tumour tissue; the photosensitiser is released specifically to malignant cells as a consequence of a receptor-mediated endocytosis of LDL.

Topics: Animals; Fibrosarcoma; Indoles; Isoindoles; Mice; Mice, Inbred BALB C; Microscopy, Electron; Necrosis; Organometallic Compounds; Photochemotherapy; Tumor Cells, Cultured; Zinc Compounds