Photodynamic effects of Photofrin II on cell division in human NHIK 3025 cells

Light-controlled endosomal escape of the novel CD133-targeting immunotoxin AC133-saporin by photochemical internalization - A minimally invasive cancer stem cell-targeting strategy

The cancer stem cell (CSC) marker CD133 is an attractive target to improve antitumor therapy. We have used photochemical internalization (PCI) for the endosomal escape of the novel CD133-targeting immunotoxin AC133-saporin (PCIAC133-saporin). PCI employs an endocytic vesicle-localizing photosensitizer, which generates reactive oxygen species upon light-activation causing a rupture of the vesicle membranes and endosomal escape of entrapped drugs. Here we show that AC133-saporin co-localizes with the PCI-photosensitizer TPCS2a, which upon light exposure induces cytosolic release of AC133-saporin. PCI of picomolar levels of AC133-saporin in colorectal adenocarcinoma WiDr cells blocked cell proliferation and induced 100% inhibition of cell viability and colony forming ability at the highest light doses, whereas no cytotoxicity was obtained in the absence of light. Efficient PCI-based CD133-targeting was in addition demonstrated in the stem-cell-like, triple negative breast cancer cell line MDA-MB-231 and in the aggressive malignant melanoma cell line FEMX-1, whereas no enhanced targeting was obtained in the CD133-negative breast cancer cell line MCF-7. PCIAC133-saporin induced mainly necrosis and a minimal apoptotic response based on assessing cleavage of caspase-3 and PARP, and the TUNEL assay. PCIAC133-saporin resulted in S phase arrest and reduced LC3-II conversion compared to control treatments. Notably, co-treatment with Bafilomycin A1 and PCIAC133-saporin blocked LC3-II conversion, indicating a termination of the autophagic flux in WiDr cells. For the first time, we demonstrate laser-controlled targeting of CD133 in vivo. After only one systemic injection of AC133-saporin and TPCS2a, a strong anti-tumor response was observed after PCIAC133-saporin. The present PCI-based endosomal escape technology represents a minimally invasive strategy for spatio-temporal, light-controlled targeting of CD133+ cells in localized primary tumors or metastasis.

Preclinical photodynamic therapy research in Spain 4: Cytoskeleton and adhesion complexes of cultured tumor cells as targets of photosensitizers

Tumor cell death induced by photodynamic therapy (PDT) with different photosensitizers (PSs) is due to the selective damage of several membranous organelles including mitochondria, lysosomes and Golgi apparatus. Other cell structures such as the cytoskeleton (CSK) (microtubules, actin microfilaments and cytokeratin intermediate filaments) and the cell adhesion components (cadherins and integrins) are also implicated in cell death induced by PSs. CSK and adhesion components are responsible for many cellular functions such as the maintenance of morphology, motility, division and adhesion, all of them of fundamental importance for growth and dissemination of tumors. Therefore, they are considered very important targets for anticancer therapies, including PDT. In addition, similarly to the rest of the anticancer therapies, PDT often leaves a significant number of surviving tumor cells. The reorganization of CSK as well as the adhesion proteins in the PDT resistant cells affect their invasive migratory capabilities. Taking into account all these features, both CSK and adhesion proteins are crucial targets of PDT.

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

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

Intracellular localization of photosensitizers

The intracellular localization of photosensitizers can be studied by different methods. One method involves homogenization of the cells followed by differential ultracentrifugation which leads to fractions enriched in nuclear, mitochondrial, and microsomal material as well as a supernatant fraction. More detailed information can be obtained by electron microscopy of cells exposed to light in the presence of photosensitizers. This method is based on the assumption that damage is primarily induced at intracellular sites where the concentration of photosensitizer is high. By irradiating the cells at 6 degrees C, where biochemical reactions are slow, and then incubating them for different times at 37 degrees C, it is possible to follow the development of damage. The amount of photosensitized damage to enzymes or cell functions whose localization in the cells is known gives information about the intracellular localization of the sensitizer. Fluorescence microscopy is the most direct method and is widely applicable because most photosensitizers fluoresce. Lipophilic dyes generally localize in membrane structures. In future more attention should be paid to the localization of dyes in lysosomes, as suggested by early reports. Mitochondria, the endoplasmic reticulum and nuclear membrane are other important loci for intracellular localization of sensitizers.

Cell-cycle-dependent efficacy of photodynamic therapy with ATX-S10(Na)

Photodynamic therapy (PDT) is a useful strategy for treating various cancers. Details of the mechanisms of PDT have not been made clear yet. We intended to study the efficacy of PDT in relation to the cell cycle. HeLa S3 cells were synchronized by the thymidine block method. Cells in different cell cycle phases after release were treated with the water-soluble photosensitizer, ATX-S10(Na). The cellular viability after PDT was determined by the MTT assay. Intracellular levels of ATX-S10(Na) in different cell cycle phases were also determined. We found that cells in the S and G(2)/M phases were hypersensitive to PDT with ATX-S10(Na) in comparison with those in the G(1) phase, and that cellular levels of ATX-S10(Na) were increased in cells in the S and G(2)/M phases compared to those in the G(1) phase. We conclude that cellular ATX-S10(Na) levels differ among the different cell cycle phases, which is associated with the cell-cycle-dependent efficacy of PDT with ATX-S10(Na).

Bystander effects in cell death induced by photodynamic treatment UVA radiation and inhibitors of ATP synthesis

Confluent layers of MDCK II cells were treated with four different photosensitizers (a purified version of hematoporphyrin derivative [Photofrin], tetra(3-hydroxyphenyl)porphine [3-THPP], meso-tetra(4-sulphonatophenyl)porphine [TPPS4] and ALA-induced Protoporphyrin IX) and irradiated with blue light, with UVA without exogenous photosensitizers, or incubated with the metabolic inhibitors carbonyl cyanide m-chlorophenylhydrazone and 2-deoxy-D-glucose. Necrotic and apoptotic cells were detected about 4 h later by fluorescence microscopy. Dead cells appeared in distinct clusters in the confluent layers. The number of dead cells in these clusters was determined by manual counting and image analysis. Forty-one of the 43 experimental distributions of dead cells in clusters were found to be significantly different from a Monte Carlo simulation of the distribution of independently inactivated cells. However, a Monte Carlo simulation model, assuming that each dead cell increased the probability of inactivation of adjacent cells, fitted 34 of the 43 observed distributions of dead cells in clusters, indicating a significant bystander effect for all the investigated treatments. The bystander-effect model parameter, defined as a cell's increase in probability of dying when it has dead neighbors, was significantly lower for 3-THPP-PDT and TPPS4-PDT than for Photofrin-PDT, ALA-PDT and treatment with metabolic inhibitors.

Chromosomes are target sites for photodynamic therapy as demonstrated by subcellular laser microirradiation

The present investigation has been undertaken to examine the possibility that the cell nucleus, and specifically the genetic material, is a target site for photodynamic therapy. PTK2 and Hep-2 cells are pretreated with a medium containing 15 microg/ml (0.09 mM) 5-aminolevulinic acid (ALA). Individual fluorescence images are recorded for each selected cell using a cooled charge-coupled device (CCD). A laser microbeam system generating 630 nm is used for subcellular-region irradiation of specific targets: chromosomes, the mitotic spindle, the perispindle region and the peripheral cytoplasm. Nuclei of interphase cells are also irradiated. Data comparing the sensitivities of the different subcellular microirradiation sites in ALA-treated mitotic cells demonstrate that under the irradiation conditions used, the chromosome is the most sensitive subcellular target followed by the perispindle region, the peripheral cytoplasm and spindle, and, lastly, the interphase nucleus.

Apoptosis induction by different pathways with methylene blue derivative and light from mitochondrial sites in V79 cells

The importance of mitochondria for the induction of apoptosis by photodynamic therapy (PDT) was studied with a new photosensitizing dye, methylene blue derivative (MBD), and light. By using fluorescence microscopy and by measuring the MBD-PDT-induced inhibition of specifically subcellularly localized marker enzymes, we show that MBD is localized in mitochondria and not in lysosomes, endoplasmic reticulum or Golgi apparatus of V79 Chinese hamster fibroblasts. Cellular uptake kinetics and fluorescence properties of the dye in cells were characterized. Cell death was studied by a cell survival assay and by flow cytometry of cells stained using the terminal deoxynucleotidyl transferase (TdT) assay. MBD with light induced cell death by apoptosis via 2 different pathways, one rapid and one delayed, depending on the amount of dye in the cells. Cells treated with an MBD concentration higher than 0.05 microg/ml died by apoptosis within 3 hr after light exposure. At a concentration of 0.05 microg/ml MBD, cell death was induced slowly, and apoptotic cells appeared increasingly from the second day after PDT. Combination studies with 2-deoxyglucose (2-DOG) and carbonylcyanide-m-chlorophenylhydrazone (CCCP), inhibitors of glycolysis and oxidative phosphorylation, respectively, indicated that MBD and light inhibited mitochondrial oxidative phosphorylation. Abolishment of both energy sources led to cell death by necrosis within 6 hr. Inhibition of glycolysis alone induced apoptosis between 3 and 6 hr, while inhibition of mitochondrial oxidative phosphorylation alone led to delayed apoptosis within days.

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.

Enhanced antitumour effect of photodynamic therapy by microtubule inhibitors

The combination of photodynamic therapy (PDT) and the microtubule (MT) inhibitor, vincristine (VCR) or taxol, was studied in the CaD2 mammary tumour model in mice. Meso-tetra(di-adjacent-sulphonatophenyl) porphine (TPPS2a) was used as a photosensitizer. An enhanced antitumour effect was found when VCR, at an almost non-toxic dose (1 mg/kg1, was injected i.p. into the mice 6 h before PDT, while no such enhanced effect was observed when the same dose of VCR was given either 12 or 24 h before PDT or immediately before PDT. Furthermore, it was found that the number of mitotic cells increased 4-5-fold 6 h after the injection of VCR into the mice. VCR did not enhance the sensitivity of normal skin to PDT. Combination of PDT and taxol was also studied. The antitumour activity of PDT could be increased by taxol when the drug (35 mg/kg) was administered i.p. either 6 h prior to PDT or immediately after or before PDT. No significant enhancement in PDT efficiency was found when PDT with photofrin was combined with VCR.

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.

Photodynamic effects of the cationic porphyrin, mesotetra(4N-methylpyridyl)porphine, on microtubules of HeLa cells

The treatment of HeLa human carcinoma cells with mesotetra(4N-methylpyridyl)porphine (T4MPyP) and blue light led to damage of the microtubules (MTs). The morphologies of interphase MTs and the mitotic spindle apparatus were analysed by immunofluorescence staining of alpha-tubulin. The extent of MT damage depended on the light dose and the time after photodynamic treatment. After a period of 1 h after irradiation with doses of 0.3 or 1.5 J cm-2 (sublethal conditions, corresponding to survival rates of 90% and 60% respectively), the normal MT network arrangement of interphase cells and the mitotic spindle apparatus of many cells were clearly affected. However, these effects were found to be transient, and several hours after irradiation most MTs resumed control morphology. Higher irradiation doses (4.5 J cm-2, lethal conditions, less than 10% cell survival) resulted in the irreversible alteration of interphase and mitotic MTs. The change in MT organization appeared to be the reason for the observed increase in the mitotic index (MI) after sublethal doses. The largest increase in MI was detected 6 h after treatment (twofold increase over untreated cells) for both sublethal light doses. Most of the cells in mitosis corresponded to metaphase, the number of ana-telophase cells being greatly reduced for the first hours after irradiation with a dose of 1.5 J cm-2. The results, which resemble those observed with inhibitors of MT assembly, suggest that MTs might represent an important target for T4MPyP action.

Effects of photodynamic therapy on xenografts of human mesothelioma and rat mammary carcinoma in nude mice

We have examined the effectiveness of photodynamic therapy against R3230AC rat mammary adenocarcinoma and human mesothelioma as xenografts in the same host. The results demonstrate that the xenografted human tumour is significantly more responsive to photodynamic treatment than the rodent mammary tumour. Studies also showed that the mesothelioma xenograft was fluence rate- and fluence-dependent while the rat tumour exposed to the same conditions demonstrated neither of these dependencies. This disparity in response was not attributable to a difference in either whole-tumour uptake or subcellular distribution of the porphyrin photosensitiser. Analysis of the effects of visible irradiation on cytochrome c oxidase activity, measured in mitochondria prepared from tumours borne on hosts injected with photosensitiser, demonstrated that photoradiation-induced enzyme inhibition was significantly greater in mesothelioma than in R3230AC mammary tumour preparations. However, in parallel studies conducted in vitro, when photosensitiser and light were delivered to previously unperturbed mitochondria, rates of enzyme inhibition were not significantly different. Both tumours were established in long-term cell culture. While the uptake of porphyrin photosensitiser was equivalent in both cell lines, the R3230AC cells displayed a significantly greater photosensitivity than the mesothelioma cells. The data presented here demonstrate that the mechanisms that govern response to photodynamic therapy are complex, but in the case of these two xenografted tumours host response to therapy is not likely to play a significant role.

Cytotoxicity and cytokinetic effects of mitomycin C and/or photochemotherapy in a human colon adenocarcinoma cell line

1. The cytotoxicity and cytokinetic effects of Mitomycin C (MC) and/or photochemotherapy (PCT) in cultured human colon adenocarcinoma (WiDr) cells were investigated using colony formation to determine cell survival and DNA flow cytometry to analyze cell kinetics. 2. A low concentration of MC (0.01 micrograms/ml) caused accumulation of cells in late S and early G2 phase; higher concentrations (0.05-0.5 micrograms/ml) induced accumulation of the cells in mid and early S phase. 3. The effects of the lowest concentration of MC (0.01 micrograms/ml) were reversible upon removal of the drug, whereas a higher concentration of MC (0.1 micrograms/ml) resulted in a permanent inhibition of cell cycle progression. 4. The sensitivity of Photofrin II-loaded cells to PCT can be enhanced significantly by the addition of MC. 5. The MC-induced accumulation of the cells in S phase may be one reason for the increased cytotoxicity of PCT combined with MC. 6. The data suggest that MC may also inhibit repair of PCT-induced DNA damage.

Mitotic inhibition by phenylporphines and tetrasulfonated aluminium phthalocyanine in combination with light

This work relates to studies on modes of phototoxicity by tetrasulfonated aluminium phthalocyanine (AlPcS4), tetrahydroxy- and monosulfonated meso-tetraphenylporphines (3-THPP and TPPS1) on culture cells. Toxicity at moderate light exposures appears to be related to inhibition of microtubule function. Treatment of human cervix carcinoma cells of the line NHIK 3025 incubated for 18 h with the sensitizers and exposed to light inhibits multiplication for the first hours after light exposure, a significant fraction of the cells accumulating in mitosis. For the first hours after treatment, the mitotic cells were always mainly found in metaphase; generally seen as c-metaphases and three-group metaphases. During this time, anaphase and telophase cells were absent or greatly reduced in number. Indirect immunofluorescence staining of beta-tubulin showed that the spindle apparatus of mitotic cells was perturbed in all cases. The accumulation in mitosis was more extensive after treatment with AlPcS4 and light than after treatment with 3-THPP or TPPS1 and light. This may be related to the great difference in the lipophilic properties of these sensitizers; i.e. AlPcS4 being highly water soluble while TPPS1 and 3-THPP are lipophilic sensitizers. The lipophilicity of several sensitizers has been measured by two different methods, the partition between an aqueous and a lipophilic phase (Triton X-114) and the binding strength to a reverse phase column. The results show that the measured relative lipophilicity of the sensitizers may be influenced by the method of analysis.

Effect of mitomycin C on the uptake of photofrin II in a human colon adenocarcinoma cell line

Flow cytometry (FCM) was used to investigate the effect of mitomycin C (MC) on the cellular uptake of Photofrin II (PII) in a cultured human colon adenocarcinoma cell line (WiDr). The surface area of the cells increased as they passed through the cell cycle from G0/G1 to G2/M phase. MC retarded the cells in G2/M phase and enhanced the surface area of the cells. A 1.3-2.3-fold increase in the cell surface area and a 1.3-2.7-fold increase in the cellular uptake of PII in the tumor cells was observed after 2 h-8 h incubation with MC. Within each sample, an almost linear relationship between the intensity of PII fluorescence in the cells and the surface area of the cells was found. However, for the cells incubated with MC the surface area was not the only determinant of PII uptake. Effects of MC on the cell cycle, the cell surface area and the permeability of the cell membrane are suggested as possible reasons for the increase of cellular uptake of PII in the tumor cells.

The unpolymerized form of tubulin is the target for microtubule inhibition by photoactivated tetra(4-sulfonatophenyl)porphine

Several porphyrins, including tetra(4-sulfonatophenyl)porphine, sensitize cells to photoinactivation. The treatment leads to an accumulation of cells in mitosis, directly or indirectly due to a perturbation of the mitotic spindle. The present work relates to the target for this mode of action. Cells incubated with tetra(4-sulfonatophenyl)porphine were exposed to light and the microtubules were quantified 30 min after light exposure. The amount of microtubules decreased with increasing fluences. The reduction in the amount of microtubules after light exposure was enhanced by prior treatment with nocodazole (1 microgram/ml for 20 min) or low temperature (1 degree C for 60 min). When nocodazole was combined with the photochemical treatment the extent of the inhibition of microtubule formation was dose-dependent only for the lowest fluences applied. Additional light exposure did not further reduce the amount of microtubules 30 min after light exposure. The results presented indicate that the unpolymerized fraction of tubulin is the target for photochemical inhibition of microtubule formation.

Synergistic effects of photoactivated tetra(4-sulfonatophenyl)porphine and nocodazole on microtubule assembly, accumulation of cells in mitosis and cell survival

Human carcinoma cells of the line NHIK 3025 were incubated with meso-tetra(4-sulfonatophenyl)porphine (TPPS4) for 18 h and exposed to light in the absence or presence of nocodazole. Nocodazole (1 microgram ml-1) was applied to the cells 15 min prior to light exposure and washed off the cells immediately afterwards. The presence of nocodazole during photoactivation of TPPS4-loaded cells leads to a significantly reduced ability of tubulin to repolymerize after withdrawal of nocodazole, an increased accumulation of the cells in mitosis with a larger fraction in c-metaphase and a higher yield of photoactivated cells. A higher proportion of the cells accumulating in mitosis 6-12 h after exposure to light is unable to form colonies when exposed to light in the presence of nocodazole than in its absence. The present results are consistent with a specific TPPS4-induced photodamage to the unpolymerized form of the microtubule components.

Concentration and fluence dependence of the disturbance of the membrane integrity of human fibroblasts by the photodynamic action of Photosan III

Two human fibroblast cell lines were treated with varying concentrations of the photosensitizer Photosan III for different incubation times, and subsequently irradiated with an He-Ne laser. The biological parameter investigated was trypan blue exclusion by the cells. For each given drug concentration and incubation time, a threshold fluence was observed, which resulted in the complete loss of the cell membrane integrity. Using the equation tcr = b X CPS-a, the correlation between threshold light dose (tcr) and the concentration of the photosensitizer (CPS) can be described for all three incubation times (10 min, 2 h, 20 h) characterized by different sets of a and b values. This power function implies that these parameters are inversely correlated to each other. A correlation of incubation time with critical exposure time for different drug concentrations gave saturation curves. No differences were observed between the two cell lines. The method applied may be useful for a fast comparison of the sensitizing efficiencies of different treatment protocols for the in vitro investigation of photodynamic laser therapy.

Light induced relocalization of sulfonated meso-tetraphenylporphines in NHIK 3025 cells and effects of dose fractionation

Human cervix carcinoma cells of the line NHIK 3025 were incubated for 18 h with sulfonated meso-tetraphenylporphines (TPPSn where n = 1, 2a, 2o or 4) followed by 1 h in sensitizer-free medium and then exposed to light. The fluorescing fraction of TPPS4, TPPS2o and TPPS2a has recently been shown to be located intracellularly in extracellular granules which are intracellularly localized in a similar pattern as acridine orange-stained granules, assumed to be endosomes and lysosomes (Berg, K., A. Western, J. Bommer and J. Moan. Photochem. Photobiol. 52, 481-487). Light exposure induced a relocalization of TPPS4 from its granular pattern to mainly the nuclear area while TPPS2o and TPPS2a relocalized mainly to cytoplasmic areas. After the light-induced relocalization TPPS4 became less efficient in sensitizing photoinactivation of cells as measured per fluorescing cellbound TPPS4 molecules while TPPS2a and TPPS2o became more efficient. These changes were independent of the extracellular concentration of TPPSn applied to the cells, except for cells incubated with 75 micrograms/mL TPPS4. These cells became more sensitive to light after a light exposure inactivating 20% of the cells. This increased photosensitivity seems to be related to a 2-2.5 fold increase in the amount of fluorescing cellbound TPPS4 induced by the first light exposure.

Genotoxicity of singlet oxygen

Singlet oxygen, 1O2 (1 delta g), fulfills essential prerequisites for a genotoxic substance, like hydroxyl radicals and other oxygen radicals: it can react efficiently with DNA and it can be generated inside cells, e.g. by photosensitization and enzymatic oxidation. As might be anticipated from the non-radical character of singlet oxygen, the pattern of DNA modifications it produces is very different from that caused by hydroxyl radicals. While hydroxyl radicals produce DNA strand breaks and sites of base loss (AP sites) in high yield and react with all four bases of DNA, singlet oxygen generates predominantly modified guanine residues and few strand breaks and AP sites. There is now convincing evidence that a major product of base modification caused by singlet oxygen is 8-hydroxyguanine (7,8-dihydro-8-oxoguanine). Indeed, the recently reported miscoding properties of 8-hydroxyguanine can explain the predominant type of mutations observed when DNA modified by singlet oxygen is replicated in cells. There are also strong indications that singlet oxygen generated by photosensitization can act as an ultimate DNA modifying species inside cells. However, indirect genotoxic mechanisms involving other reactive oxygen species produced from singlet oxygen are also possible and appear to predominate in some cases. The cellular defense system against oxidants consists of effective singlet oxygen scavengers such as carotenoids. The observation that carotenoids can inhibit neoplastic cell transformation when administered not only together with but also after the application of chemical or physical carcinogens might indicate a role of singlet oxygen in tumor promotion that could be independent of the direct or indirect DNA damaging properties.

Cellular uptake and relative efficiency in cell inactivation by photoactivated sulfonated meso-tetraphenylporphines

The cellular uptake, relative fluorescence quantum yields and photosensitizing efficiencies of meso-tetraphenylporphines sulfonated to different degrees (TPPSn) have been investigated using the human carcinoma cell line NHIK 3025. The efficiencies of these dyes in photoinactivation of cells were highly dependent on the number of sulfonate groups on the derivatives. These differences in phototoxicity were primarily due to different abilities to be taken up by cells, but were also dependent upon the cellular localization of the dyes. TPPS1 and TPPS2a were more efficiently taken up by the cells than TPPS2o and TPPS4. Plasma membrane associated TPPS4 was less efficient in cell inactivation per quantum of fluorescence emitted than intracellularly located dye. This was also to some extent the case for TPPS1 but not for TPPS2a and TPPS2o. The results presented here indicate that TPPS2a and TPPS1 are the most promising of the TPPSns for possible future use in photodynamic therapy.

Cellular inhibition of microtubule assembly by photoactivated sulphonated meso-tetraphenylporphines

This work relates to studies on modes of phototoxicity by sulphonated mesotetraphenylporphines on cultured cells. Toxicity appears to be related to inhibition of microtubule function. Treatment of human cervix carcinoma cells of the line NHIK 3025 incubated for 18 h with meso-tetraphenylporphine sulphonates (TPPSn where n = 2a, 2o or 4) and exposed to light, inhibits multiplication for the first hours after light exposure, a significant fraction of the cells accumulating in mitosis. The maximal number of cells in mitosis after treatment (approximately 20%) is dependent on the fluence but is similar for all three photosensitizers. For the first hours after treatment the mitotic cells were always mainly in metaphase; mainly seen as c-metaphases and three-group metaphases. During this time anaphase and telophase cells were absent or greatly reduced in number. Indirect immunofluorescence staining of beta-tubulin showed that the spindle apparatus of mitotic cells was perturbed in all cases. Results are presented which indicate that photoactivation of TPPSn located on the plasma membrane destroys microtubules in interphase cells and leads to arrest of the cells in mitosis. The localization of the dye which sensitizes the photoinduced perturbation of microtubules is further discussed.

Effects of UV radiation of cells

UV radiation interacts with mammalian cells in a very complex manner, although DNA appears to be the main chromophore. Recent literature within this field is reviewed. The review is concentrated on the following main topics: Chromophores for UV action, photoproducts in DNA, repair of UV-induced DNA damage, wavelength interactions, inactivation, mutagenesis, transformation and protection mechanisms against UV damage.