Aneta Rogalska

Aclarubicin-induced ROS generation and collapse of mitochondrial membrane potential in human cancer cell lines

The cytotoxicity of aclarubicin (ACL) in A549 (human non-small lung), HepG2 (human hepatoma) and MCF-7 (human breast adenocarcinoma) cancer cell lines was evaluated and compared with that of doxorubicin (DOX). Changes in mitochondrial transmembrane potential (DeltaPsim), and production of reactive oxygen species (ROS) of drug-treated cells were monitored. Moreover, morphological changes associated with apoptosis were examined using double staining with Hoechst 33258-propidium iodide (PI). The results showed that ACL was much more cytotoxic than DOX in all investigated cell lines. Furthermore, ACL induced a concentration- and time-dependent increase in ROS production and decrease in mitochondrial membrane potential. The drugs, especially ACL, also induced ROS mediated apoptosis and necrosis pathways in all cell lines depending on the length of the post-treatment time. All these processes were partially inhibited by the antioxidants: N-acetylcysteine (NAC) and alpha-tocopherol. Of both drugs, DOX caused considerably weaker depolarization of the mitochondrial membrane. Its 10-fold higher concentration, as compared to ACL, was required to induce a similar effect, in accordance with the highly distinct cytotoxicity of these drugs towards investigated cells. In conclusion, ROS production preceded a decrease in mitochondrial membrane potential, but only changes in DeltaPsim were correlated with drug cytotoxicity in particular cell line. These results suggest that the impairment of DeltaPsim and an increase in ROS level might be important mechanisms of ACL cytotoxicity in cancer cells in solid tumors.

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.

Gliclazide may have an antiapoptotic effect related to its antioxidant properties in human normal and cancer cells

Experimental and clinical studies suggest that gliclazide may protect pancreatic β-cells from apoptosis induced by an oxidative stress. However, the precise mechanism(s) of this action are not fully understood and requires further clarification. Therefore, using human normal and cancer cells we examined whether the anti-apoptotic effects of this sulfonylurea is due to its free radical scavenger properties. Hydrogen peroxide (H2O2) as a model trigger of oxidative stress was used to induce cell death. Our experiments were performed on human normal cell line (human umbilical vein endothelial cell line, HUVEC-c) and human cancer cell lines (human mammary gland cell line, Hs578T; human pancreatic duct epithelioid carcinoma cell line, PANC-1). To assess the effect of gliclazide the cells were pre-treated with the drug. The 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay was employed to measure the impact of gliclazide on cell viability. Generation of reactive oxygen species, mitochondrial membrane potential (∆Ψm), and intracellular Ca2+ concentration [Ca2+] were monitored. Furthermore, the morphological changes associated with apoptosis were determined using double staining with Hoechst 33258-propidium iodide (PI). Gliclazide protects the tested cells from H2O2-induced cell death most likely throughout the inhibition of ROS production. Moreover, the drug restored loss of ΔΨm and diminished intracellular [Ca2+] evoked by H2O2. Double staining with Hoechst 33258-PI revealed that pre-treatment with gliclazide diminished the number of apoptotic cells. Our findings indicate that gliclazide may protect both normal and cancer human cells against apoptosis induced by H2O2. It appears that the anti-apoptotic effect of the drug is most likely associated with reduction of oxidative stress.

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.

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.

Aclarubicin-induced apoptosis and necrosis in cells derived from human solid tumours

In the present study, we investigated the response of A549 (non-small cell lung-cancer), HepG2 (human hepatoma) and MCF-7 (human breast adenocarcinoma) cell lines to treatment with aclarubicin (ACL). The aim of this research was to compare the ability of ACL to induce apoptosis or necrosis in solid tumours. The mode of cell death induced by ACL was evaluated by flow-cytometry and fluorescence microscopy. We show that the drug induced both apoptosis and necrosis in the cells. Apoptotic cell death was associated with morphological changes, DNA fragmentation, changes in activity of poly(ADP-ribose)polymerase (PARP) and drug-mediated activation of caspase-3 and caspase-8. The occurrence of all these events was time-dependent. The extent of apoptosis was also dependent on the kind of cell line, the sensitivity to ACL and the intracellular drug content. This study demonstrates that the cells most sensitive to ACL, A549, accumulated a significantly higher level of the drug and were also more susceptible to apoptosis than the other cells. In contrast, the relatively less sensitive HepG2 and MCF-7 cell lines appeared more resistant to apoptosis induction. On the basis of these results, it seems that aclarubicin is able to induce apoptosis in human solid tumours.

The Connection between the Toxicity of Anthracyclines and Their Ability to Modulate the P-Glycoprotein-Mediated Transport in A549, HepG2, and MCF-7 Cells

Multidrug resistance (MDR) is a major obstacle to the successful chemotherapy of solid tumors. We compared the resistance of the most popular solid tumors, breast adenocarcinoma (MCF-7 cell line) and nonsmall cell lung (A549 cell line) hepatocellular liver carcinoma (HepG2 cells), to aclarubicin (ACL) and doxorubicin (DOX). This research aimed at determining the relation between the toxicity of ACL and DOX, their cell accumulation, and then effect on P-glycoprotein functionality. ACL is more cytotoxic for tumor cells compared to DOX. The intracellular concentration of drugs in cancer cells was dependent on the dose of the drugs and the time of incubation. The P-gp inhibitor Verapamil (V) increased DOX accumulation in all tested cell lines. By contrast, the intracellular level of ACL was not affected by this modifying agent. The assessment of the uptake of 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolocarbocyanine iodide (JC-1) or Rhodamine 123 (R123) allows the evaluation of the different influence of drugs on P-gp activity which is in agreement with the estimation of expression measured by MDR-1 shift assay. These data suggest that ACL is less P-gp dependent than DOX and consequently may be used in a clinical setting to increase treatment efficacy in resistant human tumors.

WP 631 and Epo B synergize in SKOV-3 human ovarian cancer cells

Combined therapy is one of the basic methods of treatment different types of cancer. It allows to reduce the side effects of each component while maximizing the therapeutic action. The aim of this study was to evaluate the impact of two new drugs: WP 631 (bisanthracycline) and epothilone B (Epo B), added in combination on the SKOV-3 human ovarian cancer cells. To assess the type of interaction between WP 631 and Epo B isobolografic analysis was applied based on the cytotoxicity of drugs determined by the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolinum bromide) assay. Apoptotic and necrotic cell levels were measured by double staining with Hoechst 33258 and propidium iodide, Annexin V-FITC staining and by using TUNEL assay. The combination of WP 631 and Epo B is more potent than drugs added alone. The quantitative analysis indicated that the major mode of cell death induced by the combination after 72 h treatment was early apoptosis, whereas drugs administered alone generated less intensive apoptosis. The present report demonstrates for the first time that WP 631 and Epo B co-administered synergize in SKOV-3 cell line (Z(ex)/Z(th)<1).

New potential chemotherapy for ovarian cancer - Combined therapy with WP 631 and epothilone B.

Despite more modern therapeutics approaches and the use of new drugs for chemotherapy, patients with ovarian cancer still have poor prognosis and therefore, new strategies for its cure are highly needed. One of the promising ways is combined therapy, which has many advantages as minimizing drug resistance, enhancing efficacy of treatment, and reducing toxicity. Combined therapy has rich and successful history in the field of ovarian cancer treatment. Currently use therapy is usually based on platinum-containing agent (carboplatin or cisplatin) and a member of taxanes (paclitaxel or docetaxel). In the mid-2000s this standard regimen has been expanded with bevacizumab, monoclonal antibody directed to Vascular Endothelial Growth Factor (VEGF). Another drug combination with promising perspectives is WP 631 given together with epothilone B (Epo B). WP 631 is a bisanthracycline composed of two molecules of daunorubicin linked with a p-xylenyl linker. Epo B is a 16-membered macrolide manifesting similar mechanism of action to taxanes. Their effectiveness against ovarian cancer as single agents is well established. However, the combination of WP 631 and Epo B appeared to act synergistically, meaning that it is much more potent than the single drugs. The mechanism lying under its efficacy includes disturbing essential cell cycle-regulating proteins leading to mitotic slippage and following apoptosis, as well as affecting EpCAM and HMGB1 expression. In this article, we summarized the current state of knowledge regarding combined therapy based on WP 631 and Epo B as a potential way of ovarian cancer treatment.