Agnieszka Marczak

The role of reactive oxygen species in WP 631-induced death of human ovarian cancer cells: a comparison with the effect of doxorubicin.

In the present study, we investigated the anticancer activity of WP 631, a new anthracycline analog, in weakly doxorubicin-resistant SKOV-3 ovarian cancer cells. We studied the time-course of apoptotic and necrotic events: the production of reactive oxygen species (ROS) and changes in the mitochondrial membrane potential in human ovarian cancer cells exposed to WP 631 in the presence and absence of an antioxidant, N-acetylcysteine (NAC). The effect of WP 631 was compared with the activity of doxorubicin (DOX), the best known first-generation anthracycline. Cytotoxic activity was determined by the MTT assay. The morphological changes characteristic of apoptosis and necrosis in drug-treated cells were analyzed by double staining with Hoechst 33258 and propidium iodide (PI) using fluorescence microscopy. The production of reactive oxygen species and changes in mitochondrial membrane potential were studied using specific fluorescence probes: DCFH2-DA and JC-1, respectively. The experiments showed that WP 631 was three times more cytotoxic than DOX in the tested cell line. It was found that the new anthracycline analog induced mainly apoptosis and, marginally, necrosis. Apoptotic cell death was associated with morphological changes and a decrease in mitochondrial membrane potential. In comparison to DOX, the novel bisanthracycline induced a significantly higher level of ROS and a greater drop in the membrane potential. The results provide direct evidence that the novel anthracycline WP 631 is considerably more cytotoxic to human SKOV-3 ovarian cancer cells than doxorubicin. The drug can produce ROS, which are immediately involved in the induction of apoptotic cell death.

Interaction of doxorubicin and idarubicin with red blood cells from acute myeloid leukaemia patients

Doxorubicin (DOX) and idarubicin (IDA) are anthracycline antibiotics, widely used in human cancer treatment. The present study addressed the effects of these two drugs on lipid bilayer fluidity, protein conformation and microviscosity in erythrocytes from acute myeloid leukaemia patients, using electron spin resonance (ESR) spectroscopy and fluorescence measurements. Only DOX caused statistically significant changes in the parameters examined. Within 30 min of drug injection, changes were observed in the fluidity of the hydrophobic parts of the lipid bilayer and erythrocyte membrane protein conformation. These changes persisted for up to 24 h. Analysis of the EPR Tempamine spectrum also showed that the microviscosity of the erythrocyte interior increased during the early stages of the drug effect. Idarubicin, in contrast, caused no identifiable change in any of the parameters studied and therefore seems to be safe for erythrocytes. We conclude that IDA is markedly less toxic than DOX to erythrocytes from acute myeloid leukaemia patients.

Pro-apoptotic activity of new analog of anthracyclines--WP 631 in advanced ovarian cancer cell line.

In this work we investigated the mode of cell death induced by WP 631, a novel anthracycline antibiotic, in the ovarian cancer cell line (OV-90) derived from the malignant ascites of a patient diagnosed with advanced disease. The effects were compared with those of doxorubicin (DOX), a first generation anthracycline. The ability of WP 631 to induce apoptosis and necrosis was examined by double staining with Annexin V and propidium iodide, measurements of the level of intracellular calcium ions and cytochrome c, PARP cleavage. We also investigated the possible involvement of the caspases activation, DNA degradation (comet assay) and intracellular reactive oxygen species (ROS) production in the development of the apoptotic events and their significance for drug efficiency. The results obtained clearly demonstrate that antiproliferative capacity of WP 631 in tested cell line was a few times greater than that of DOX. Furthermore, ovarian cancer cells treated with WP 631 showed a higher mean level of basal DNA damage in comparison to DOX. In conclusion, WP 631 is able to induce caspase - dependent apoptosis in human ovarian cancer cells. Obtained results suggested that WP 631 may be a candidate for further evaluation as chemotherapeutic agents for human cancers.

Damage to the cell antioxidative system in human erythrocytes incubated with idarubicin and glutaraldehyde.

Encapsulation of antineoplastic drugs within erythrocytes is one of the studied strategies to diminish the toxic side effects of anthracycline antibiotics. Glutaraldehyde is often used as crosslinking agent to link the drugs, including idarubicin (IDA) to the cells. The previous studies indicated that in glutaraldehyde-treated human erythrocytes the elevated level of drug was observed but also the various changes in the organization of the red cells were noted. In this study, we continue our investigations and now we concentrate on the effect of these compounds on antioxidative system in erythrocytes. We determined reactive oxygen species (ROS) production, glutathione content and alterations in the activity of enzymes responsible for maintaining glutathione in reduced form in human erythrocytes. Measurements of both reduced and total glutathione levels and the activity of glutathione reductase and glucose-6-phosphate dehydrogenase were performed spectrophotometrically. The results show that ROS were produced in erythrocytes treated with IDA and with IDA and glutaraldehyde. IDA at a concentration of 10 microg/ml did not cause any changes in total or reduced glutathione levels. When IDA-preincubated erythrocytes were treated with glutaraldehyde, significant changes in the determined parameters were observed in a glutaraldehyde concentration dependent manner. It was correlated with decreased activity of glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G6PD). Together with the significant changes in reduced form of glutathione (GSH)/total glutathione ratio, the exposure of phosphatidylserine at the cell surface was also observed.

Epothilone B induces extrinsic pathway of apoptosis in human SKOV-3 ovarian cancer cells

The molecular mechanisms underlying epothilone B (EpoB) induced apoptosis were investigated in SKOV-3 human ovarian cancer cells. The aim of this research was to compare EpoBs, which belongs to the new class of anticancer drugs, with paclitaxels (PTX) ability to induce apoptosis. The mode of cell death was assessed colorimetrically, fluorimetrically and by immunoblot analyses through measuring DNA fragmentation, the level of intracellular calcium, the level of cytochrome c, TRAIL, the cleavage of poly(ADP-ribose) polymerase (PARP) and the activation of caspase-9, -8 and -3. EpoB leads to an increase of the cytosolic level of cytochrome c after 4 h of cell treatment. After 24 and 48 h of cell treatment the level of intracellular calcium also increased by about 21% and 24% respectively. Moreover, EpoB, similarly to PTX, promoted the expression of TRAIL in lymphocytes, although high TRAIL expression on tumor cells was detected only after adding EpoB to SKOV-3 cells. EpoB mediates caspases-8 and -3 activation, which is independent of the reduction in the amount of caspase-9. Epitope-specific monoclonal and polyclonal antibodies revealed characteristic apoptotic changes that included cleavage of the 116 kDa PARP polypeptide to 25 kDa fragments. The results of our study show that EpoB induces mainly the extrinsic pathway.

Activation of apoptotic pathway in normal, cancer ovarian cells by epothilone B

The epothilones, a new class of microtubule-targeting agents, seem to be a very promising alternative to the current strategy of cancer treatment. We have analyzed the aspects of epothilone B (Epo B) on cellular metabolism of tumor (OV-90) and normal (MM 14) ovarian cells. The observed effects were compared with those of paclitaxel (PTX), which is now a standard for the treatment of ovarian cancer. The results provide direct evidence that Epo B is considerably more cytotoxic to human OV-90 ovarian cancer cells than PTX. We have found, that antitumor efficacy of this new drug is related to its apoptosis-inducing ability, which was confirmed during measurements typical markers of the process. Epo B induced changes in morphology of cells, mitochondrial membrane potential and cytochrome c release. Also a slight increase of the intracellular calcium level was observed. Moreover, we have found that ROS production, stimulated by Epo B, is directly involved in the induction of apoptosis via mitochondrial pathway.

Doxorubicin-transferrin conjugate triggers pro-oxidative disorders in solid tumor cells.

The formation of reactive oxygen species (ROS) is a widely accepted mechanism of doxorubicin (DOX) toxicity toward cancer cells. However, little is known about the potential of new systems, designed for more efficient and targeted doxorubicin delivery (i.e. protein conjugates, polymeric micelles, liposomes, monoclonal antibodies), to induce oxidative stress (OS) in tumors and hematological malignancies. Therefore, the objective of our study was to determine the relation between the toxicity of doxorubicin-transferring (DOX-TRF) conjugate and its capability to generate oxidative/nitrosative stress in solid tumor cells. Our research proves that DOX-TRF conjugate displays higher cytotoxicity towards lung adenocarcinoma epithelial (A549) and hepatocellular carcinoma (HepG2) cell lines than the reference free drug (DOX) and induces more extensive OS, characterized by a significant decrease in the total cellular antioxidant capacity, glutathione level and amount of -SH groups and an increase in hydroperoxide content. The intracellular redox imbalance was accompanied by changes in the transcription of genes encoding key antioxidant enzymes engaged in the sustaining of cellular redox homeostasis: superoxide dismutase (SOD), catalase (CAT), glutathione transferase (GST) and glutathione peroxidase (GP).

Two drugs are better than one. A short history of combined therapy of ovarian cancer

Combined therapy of ovarian cancer has a long history. It has been applied for many years. The first drug which was commonly combined with other chemotherapeutics was cisplatin. It turned out to be effective given together with alkylating agents as well as with taxanes. Another drug which is often the basis of first-line therapy is doxorubicin. The use of traditional chemotherapy is often limited due to side effects. This is why new drugs, targeted specifically at cancer cells (e.g. monoclonal antibodies or epidermal growth factor receptor inhibitors), offer a welcome addition when used in combination with conventional anticancer agents. Drugs applied in combination should be synergistic or at least additive. To evaluate the type of interaction between drugs in a plausible sequence, isobolographic analysis is used. This method allows one to assess whether the two agents could make an efficient combination, which might improve the therapy of ovarian cancer.

Influence of Pre-Storage Irradiation on the Oxidative Stress Markers, Membrane Integrity, Size and Shape of the Cold Stored Red Blood Cells

Background: To investigate the extent of oxidative damage and changes in morphology of manually isolated red blood cells (RBCs) from whole blood, cold stored (up to 20 days) in polystyrene tubes and subjected to pre-storage irradiation (50 Gy) and to compare the properties of SAGM-preserved RBCs stored under experimental conditions (polystyrene tubes) with RBCs from standard blood bag storage. Methods: The percentage of hemolysis as well as the extracellular activity of LDH, thiobarbituric acid-reactive substances, reduced glutathione (GSH), and total antioxidant capacity (TAC) were measured. Changes in the topology of RBC membrane, shape, and size were evaluated by flow cytometry and judged against microscopy images. Results: Irradiation caused significant LDH release as well as increased hemolysis and lipid peroxidation, GSH depletion, and reduction of TAC. Prolonged storage of irradiated RBCs resulted in phosphatidylserine exposure on the cell surface. By day 20, approximately 60% of RBCs displayed non-discoid shape. We did not notice significant differences in percentage of altered cells and cell volume between RBCs exposed to irradiation and those not exposed. Conclusion: Irradiation of RBC transfusion units with a dose of 50 Gy should be avoided. For research purposes such as studying the role of antioxidants, storage of small volumes of RBCs derived from the same donor would be more useful, cheaper, and blood-saving.

Comparison of the effect of phenoxyherbicides on human erythrocyte membrane (in vitro)

The molecular mechanisms of phenoxyherbicides action in animals have been insufficiently studied. Now, we have investigated the interaction of sodium salts of phenoxyherbicides, e.g., 2,4-dichlorophenoxyacetic acid (2,4-D-Na), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T-Na) and 4-chloro-2-methylphenoxyacetic acid (MCPA-Na) with human erythrocytes. In this study, we evaluated the effect of these compounds on erythrocyte membrane fluidity as well as changes in membrane proteins content. It was observed that all of the compounds studied altered membrane fluidity, changed the size and shape of the erythrocytes and provoked echinocytes formation. It was also revealed that 2,4-D-Na and 2,4,5-T-Na changed the content of erythrocyte membrane proteins mainly by a decrease in the level of spectrin and low molecular weight proteins. The comparison of the action of phenoxyherbicides examined showed that 2,4,5-T-Na caused the greatest changes in the erythrocytes membrane, whereas MCPA-Na induced the lowest alterations in the incubated cells. It must be noted that changes of the investigated parameters were observed only at presence of significant concentrations of these compounds that may penetrate human organism only as a result of acute poisoning.