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Landomycin E (LE) is an angucycline antibiotic produced by Streptomyces globisporus.Previously, we have shown a broad anticancer activity of LE which is, in contrast to the structurally related and clinically used anthracycline doxorubicin (Dx), only mildly affected by multidrug resistance-mediated drug efflux. In the present study, cellular and molecular mechanisms underlying the anticancer activity of landomycin E towards Jurkat T-cell leukemia cells were dissected focusing on the involvement of radical oxygen species (ROS). LE-induced apoptosis distinctly differed in several aspects from the one induced by Dx. Rapid generation of hydrogen peroxide already at one hour drug exposure was observed in case of LE but not found before 24h for Dx. In contrast, Dx but not LE induced production of superoxide radicals. Mitochondrial damage, as revealed by JC-1 staining, was weakly enhanced already at 3h LE treatment and increased significantly with time. Accordingly, activation of the intrinsic apoptosis pathway initiator caspase-9 was not detectable before 12h exposure. In contrast, cleavage of the down-stream caspase substrate PARP-1 was clearly induced already at the three hour time point. Out of all caspases tested, only activation of effector caspase-7 was induced at this early time points paralleling the LE-induced oxidative burst. Accordingly, this massive cleavage of caspase-7 at early time points was inhibitable by the radical scavenger N-acetylcysteine (NAC). Additionally, only simultaneous inhibition of multiple caspases reduced LE-induced apoptosis. Both, a specific H 2 O 2 and an OH − scavenger (catalase and mannitol, respectively) effectively decreased LEinduced ROS production, but only partially inhibited LE-induced apoptosis. In contrast, NAC efficiently blocked both parameters. Summarizing, rapid H 2 O 2 generation and a complex caspase activation pattern contribute to the antileukemic effects of LE. As superoxide generation is HHS Public Access

AimTo use the antioxidant compounds (sodium selenite, selenomethionine, D-pantethine) for modulation of cytotoxic effect of doxorubicin and cisplatin toward wild type and drug-resistant mutants of several human tumor cells. Similar treatments were applied in vivo toward adult male Wistar rats.MethodsHuman tumor cells of different lines (HCT-116, Jurkat and HL-60) with various mechanisms of drug-resistance were treated with doxorubicin or cisplatin, alone or in combination with sodium selenite, selenomethionine, or D-pantethine. Cell viability, induction of apoptosis, and production of O2- radicals were measured. Activity of redox potential modulating enzymes was measured in the liver and blood plasma of adult male Wistar rats subjected to similar treatments.ResultsAll antioxidants used in physiologically harmless concentration inhibited cytotoxic action of doxorubicin toward tumor cells sensitive to chemotherapy treatment by 15%-30%, and slightly enhanced cytotoxic effect of this medicine toward drug-resistant malignant cells. At the same time, there was no significant effect of these antioxidants on cisplatin action. Such effects were accompanied by a complete inhibition of production of superoxide radicals induced by doxorubicin. The results of in vivo study in adult male Wistar rats were in agreement with the results of in vitro study of human tumor cells.ConclusionProtective effect of specific antioxidant agents during cytotoxic action of doxorubicin was demonstrated in vitro in drug-sensitive human tumor cells and in adult male Wistar rats, while there was no protective effect in drug-resistant sub-lines of these tumor cells during action of doxorubicin and cisplatin.

AimTo compare various pro-apoptotic effects of synthetic 4-thiazolidinone derivative (Les-3288), doxorubicin (Dox) and temozolomide (TMZ) in the treatment of human glioma U251 cells to improve treatment outcomes of glioblastoma and avoid anticancer drug resistance.MethodsThe cytotoxic effects of drugs used in human glioma U251 cells were measured by cell viability and proliferation assay (MTT), Trypan blue exclusion test, and Western-blot analysis of the apoptosis-related proteins. In addition, flow cytometry study of reactive oxygen species (ROS) level in glioma cells was carried out. Cytomorphological changes in treated cells were monitored by fluorescent microscopy after cell staining with Hoechst 33342 and ethydium bromide.ResultsHalf-maximal inhibitory concentration (IC50) of Les-3288, Dox, and TMZ was calculated for human glioblastoma U251 cells. The rating of the values of this indicator of cellular vitality was assessed. The results of MTT assay proved the superiority of Les-3288 vs Les-3288>Dox>TMZ, which is in agreement with the results of Trypan blue testing showing Les-3288 ≈ Dox>TMZ. In general, such ranking corresponded to a scale of pro-apoptotic impairments in the morphology of glioma U251 cells and the results of Western-blot analysis of cleaved Caspase 3. Contrary to Dox, Les-3288 and TMZ did not affect significantly ROS levels in the treated cells.ConclusionThe effect of the synthetic 4-thiazolidinone derivative Les-3288 is realized via apoptosis mechanisms and does not involve ROS. In comparison with Dox and TMZ, it is more effective in destroying human glioblastoma U251 cells. Les-3288 compound has a potential as an anticancer drug for glioblastoma. Nevertheless, further preclinical studies of the blood-brain barrier are needed.

Landomycin a (La) is a new antitumor antibiotic of angucycline group, possessing high antitumor activity against cancer cells of different origin, which induces early apoptosis in target cells. It was shown that under La action the level of reactive oxygen species (RoS) in human t-leukemia cells had increased 5.6 times in comparison to control already at the 1 st hour after the addition of studied antibiotic to the culture medium. at the 6 th hour after incubation of cells with La the nucleosomal DNa cleavage, chromatin condensation and nucleus fragmentation were observed, indicating apoptotic cell death. catalase (scavenger of hydrogen peroxide), mannitol (scavenger of hydroxyl radicals) and superoxide dismutase (scavenger of superoxide radicals) reduced the level of RoS production under La, suggesting the generation of h 2 o 2 , oh • and o 2 radicals, respectively. It was revealed that catalase and mannitol effectively inhibited La-mediated tumor cell death, increasing 2.5 times the percentage of alive cells in comparison to La. however, superoxide dismutase had no significant inhibitory effect on cytotoxic activity of LA, indicating the minor role of superoxide anions in the implementation of antitumor activity of this antibiotic. combination of catalase, mannitol and superoxide dismutase with La increased 4-fold the percentage of alive cells in comparison to the action of La. Dynamics of ROS formation confirms that the increase of ROS is a very rapid process, but at the same time it is not a direct consequence of apoptosis triggering, mediated by mitochondria. k e y w o r d s: landomycins, apoptosis, reactive oxygen species (RoS), malignant cells.

AimTo investigate the potential tissue-protective effects of antioxidants selenomethionine and D-pantethine applied together with doxorubicin (Dx) on NK/Ly lymphoma-bearing mice. The impact of this chemotherapy scheme on animal survival, blood cell profile, hepatotoxicity, glutathione level, and activity of glutathione-converting enzymes in the liver was compared with the action of Dx applied alone.MethodsThe hematological profile of animals was studied by the analysis of blood smears under light microscopy. Hepatotoxicity of studied drugs was evaluated measuring the activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) enzymes, De Ritis ratio, and coenzyme A fractions by McDougal assay. Glutathione level in animal tissues was measured with Ellman reagent, and the activity of glutathione reductase, transferase, and peroxidase was measured using standard biochemical assays.ResultsD-pantethine (500 mg/kg) and, to a lower extent, selenomethionine (600 µg/kg) partially reduced the negative side effects (leukocytopenia and erythropenia) of Dx (5 mg/kg) in NK/Ly lymphoma bearing animals on the 14th day of their treatment. This increased animal survival time from 47-48 to 60+ days and improved the quality of their life. This ability of D-pantethine and selenomethionine was realized via hepatoprotective and immunomodulating activities. D-pantethine also restored the levels of acid-soluble and free CoA in the liver of tumor-bearing animals, while selenomethionine caused the recovery of glutathione peroxidase levels in the liver, which was significantly diminished under Dx treatment. Both compounds decreased glutathione level in the liver, which was considerably induced by Dx.ConclusionsAntioxidants selenomethionine and D-pantethine partially reversed the negative side effects of Dx in NK/Ly lymphoma-bearing mice and significantly increased the therapeutic efficiency of this drug in tumor treatment.

AimTo evaluate molecular mechanisms of tissue-protective effects of antioxidants selenomethionine (SeMet) and D-pantethine (D-Pt) applied in combination with doxorubicin (Dx) in B16 melanoma-bearing-mice.MethodsImpact of the chemotherapy scheme on a survival of tumor-bearing animals, general nephro- and hepatotoxicity, blood cell profile in vivo, and ROS content in B16 melanoma cells in vitro was compared with the action of Dx applied alone. Nephrotoxicity of the drugs was evaluated by measuring creatinine indicator assay, hepatotoxicity was studied by measuring the activity of ALT/AST enzymes, and myelotoxicity was assessed by light microscopic analysis of blood smears. Changes in ROS content in B16 melanoma cells under Dx, SeMet, and D-Pt action in vitro were measured by incubation with fluorescent dyes dihydrodichlorofluoresceindiacetate (DCFDA, H2O2-specific) and dihydroethidium (DHE, O2--specific), and further analysis at FL1 (DCFDA) or FL2 channels (DHE) of FACScan flow cytometer. The impact of aforementioned compounds on functional status of mitochondria was measured by Rhodamine 123 assay and further analysis at FL1 channel of FACScan flow cytometer.ResultsSelenomethionine (1200 µg/kg) and D-pantethine (500 mg/kg) in combination with Dx (10 mg/kg) significantly reduced tumor-induced neutrophilia, lymphocytopenia, and leukocytosis in comparison to Dx treatment alone. Moreover, SeMet and D-Pt decreased several side effects of Dx, namely an elevated creatinine level in blood and monocytosis, thus normalizing health conditions of B16 melanoma-bearing animals.ConclusionsOur results showed that antioxidants selenomethionine and D-pantethine possess significant nephroprotective and myeloprotective activity toward Dx action on murine B16 melanoma in vivo, but fail to boost a survival of B16 melanoma-bearing animals. The observed cytoprotective effects of studied antioxidants are not directly connected with their ROS scavenging.