Cytotoxic activity of the selected pyridinium salts against murine leukemia L1210.

The objective of this work was to evaluate the relationship between chemical reactivity of 3-substituted pyridinium salts and their cytotoxic properties against murine leukemia L1210. Chemical reactivity of pyridinium salts towards NADH oxidation following one-step hydride transfer depends strongly on their redox properties. The investigated reaction may reflect the ability of the salts to deplete NADH level in cells and to affect their metabolic functions. On the other hand, the cytotoxic activity against murine leukemia cells, expressed as ED50 values, varied strongly depending upon the compound used. The investigated salts showed also a diverse antileukemic effect in in vivo experiments as measured by the increase in the survival time of L1210 leukemia-bearing mice. These biological effects were correlated with equilibrium constants found for the reaction of pyridinium salts with NADH.

Comparative studies on the mechanism of cytotoxic action of novel platinum II complexes with pyrazole ligands.

In search for new platinum-based anticancer drugs, four cisplatin analogues, which contain pyrazole rings as non-leaving ligands, have been synthesized: cis-PtCl(2)(3,5-DM HMPz)(2), cis-PtCl(2)(Pz)(2), cis-PtCl(2)(ClMPz)(2), and cis-PtCl(2)(HMPz)(2), where Pz=pyrazole, H=hydroxyl, M=methyl. We tested their cytotoxicity, apoptosis induction ability, DNA damaging and modification properties comparing them in respect to the parent compound. The cytotoxic activity of these platinum pyrazole complexes toward the murine leukemia cell line was 2.9-3.8 times lower than actvity of cisplatin. The tested compounds varied in their mechanism of action by producing different DNA lesions. The most interesting compound seems to be the complex with chloromethyl groups at N1 of pyrazole rings, which exhibited the highest ability to form bifunctional adducts with DNA in vitro.

In vitro antileukemic, antioxidant and prooxidant activities of Antoksyd S (C/E/XXI): a comparison with baicalin and baicalein.

There is increasing interest concerning the use of natural antioxidants as low toxic antileukemic compounds. Antoksyd S (C/E/XXI), is a novel herbal drug derived in Poland from the powdered roots of Scutellaria baicalensis, and the biological activities of its major components (baicalin and baicalein) were compared on the human leukemia cell line HL-60. On MTT assay, Antoksyd S (C/E/XXI) showed an obvious cytotoxic effect on HL-60 cells, which was compared with those caused by cisplatin and doxorubicin under the same experimental conditions. A comparative assay of the antioxidative and prooxidative capacity of Antoksyd S (C/E/XXI) was also undertaken using two different reactive species: superoxide (O2-) and a transition metal (Cu2+). Antoksyd S (C/E/XXI) has low toxicity, acting as a modifier of HL-60 cells proliferation and as an antioxidant, which could act prooxidatively in the presence of transition metal ions. Taken together, it seems reasonable to suggest that Antoksyd S (C/E/XXI) as compared to baicalin and baicalein, or to the cytostatics cisplatin and doxorubicin, might be an especially good candidate for the future development of new therapeutic techniques, alone or in "combination treatment regimens", to enhance leukemia cell killing.

Evaluation of the genotoxicity of cis-bis(3-aminoflavone)dichloroplatinum(II) in comparison with cis-DDP.

Short-term tests that detect genetic damage have provided information needed for evaluating carcinogenic risks of chemicals to man. The mutagenicity of cis-bis(3-aminoflavone)dichloroplatinum(II) (cis-[Pt(AF)2Cl2]) in comparison with cis-diamminedichloroplatinum(II) (cis-DDP) was evaluated in the standard plate-incorporation assay in four strains of Salmonella typhimurium: TA97a, TA98, TA100 and TA102, in experiments with and without metabolic activation. It was shown that cis-[Pt(AF)2Cl2] acts directly and is mutagenic for three strains of S. typhimurium: TA97a, TA98 and TA100. In comparison with cis-DDP this compound showed a weaker genotoxicity. Contrary to cis-DDP it has not shown toxic properties in the tester bacteria. The genotoxicity of both tested compounds was evaluated using chromosomal aberration, sister chromatid exchange and micronucleus assays, without and with metabolic activation, in human lymphocytes in vitro. The inhibitory effects of both compounds on mitotic activity, cell proliferation kinetics and nuclear division index were also compared. In all test systems applied, cis-[Pt(AF)2Cl2] was a less effective clastogen and a weaker inducer of both sister chromatid exchanges and micronuclei in comparison with cis-DDP, with and without metabolic activation. cis-[Pt(AF)2Cl2] has a direct mechanism of action and is less cytostatic and cytotoxic than the other compound. These results provide important data on the genotoxicity of cis-[Pt(AF)2Cl2] and indicate its beneficial properties as a potential anticancer drug, especially in comparison with cis-DDP.

Induction of apoptosis and necrosis in lymphocytes by the cis-Pt(II) complex of 3-aminoflavone in comparison with cis-DDP.

cis-Diamminedichloroplatinum(II) (cis-DDP) is one of the most widely administrated antitumor drugs. However, the use of cis-DDP is severely limited because of its toxic side effects. Therefore, efforts are concentrated on the development of improved platinum compounds with a broader activity spectrum and effectiveness in chemotherapy, but lower toxicity. Beneficial properties of flavonoids, e.g. their antitumor activity, encouraged scientists to synthesize cis-bis(3-aminoflavone)dichloroplatinum(II). Abilities of these compounds to induce apoptosis and necrosis were compared by use of trypan blue, fluorochrome staining (Hoechst 33258/propidium iodide double staining) and TUNEL assays. The cytotoxicity was evaluated by MTT. The results obtained show that the cis-Pt(II) complex of 3-aminoflavone is less toxic than cis-DDP. However, the former compound has a faster rate of apoptosis induction in lymphocytes than the latter. The cis-Pt(II) complex of 3-aminoflavone induces apoptosis in normal lymphocytes to a lesser degree and could be a potential antitumor drug.

1-Methyl-3-nitropyridine: an efficient oxidant of NADH in non-enzymatic and enzyme-mediated processes.

It is shown that NADH can be effectively oxidized by 1-methyl-3-nitropyridine in non-enzymatic and enzyme-mediated processes. Mechanistic issues of these reactions are discussed. These processes seem to contribute to the observed cytotoxicity of 1-methyl-3-nitropyridine. A key role of 1-methyl-3-nitropyridinyl radical formed in the enzyme-mediated processes is emphasized.

Anthracyclines potentiate activity against murine leukemias L1210 and P388 in vivo and in vitro.

The interactions of 2-chlorodeoxyadenosine (2-CdA, cladribine) and three anthracyclines: doxorubicin (DOX), idarubicin (IDA) and mitoxantrone (MIT) were evaluated on murine leukemias P388 and L1210. Prolongation of survival time of animals receiving drugs in combination compared to mice treated with drugs in monotherapy was tested. We have also evaluated interactions of the cytostatics on murine leukemias in vitro by measuring their inhibitory effects on P388 and L1210 cell proliferation. We have observed a synergistic effect of MIT and IDA in combination with 2-CdA on P388 leukemia resulting in an increase of life span (ILS)=226% in case of MIT+2-CdA and ILS=126% in the case of IDA+2-CdA, whereas 2-CdA used as a sole drug resulted in an ILS=47%. The survival time of animals inoculated with P388 leukemic cells and treated with DOX+ 2-CdA was similar to ILS gained by DOX monotherapy (178% and 200% respectively). The mice bearing L1210 leukemia receiving combined chemotherapy lived significantly longer than the animals on single agent regimens. The animals treated with schedule 2-CdA+MIT lived significantly longer (P=0.004) as compared to the groups receiving drugs in monotherapy (ILS of 2-CdA+MIT group=60%, ILS of MIT group 33%, and 2-CdA group 33%). Finally, combination of DOX or IDA with 2-CdA resulted in ILS =73% (2-CdA+DOX regimen), and ILS=60% in case of 2-CdA+IDA regimen, which is significantly higher than ILS gained on monotherapy schedules. In vitro tests revealed that all tested anthracyclines enhance the antiproliferative activity of 2-CdA against L1210 and P388 leukemic cells (P<0.05). Our study has shown that all anthracyclines potentiate 2-CdA antileukemic activity, both in vivo and in vitro. It failed however to point the best one to be combined with cladribine. We suggests that further clinical trials with such combinations are needed.

Anticancer, antiradical and antioxidative actions of novel Antoksyd S and its major components, baicalin and baicalein.

Here we show for the first time that the novel designed drug, Antoksyd S and its polyphenolic flavones (baicalin and baicalein), act as cell proliferation modifiers of mouse leukemia cells (L1210). The cytotoxicity of Antoksyd S and baicalein in vitro was expressed as ED50 and compared with those of the cytostatics doxorubicin, cisplatin and DACA, under the same experimental conditions. Cell viability was determined by modified tetrazolium dye assay, using as a model cells with neoblastic phenotype (L1210). The antiradical activity of Antoksyd S and baicalin were investigated using the DPPH test in order to obtain their antioxidant characteristics. Structure- and concentration-dependent one electron bioactivations (peroxidative oxidation) of Antoksyd S and baicalin were performed in the absence or in the presence of GSH or SOD. It appears that Antoksyd S is a low toxic novel drug which could be effective in providing concentration-dependent antioxidative activity, acting as a cell proliferation modifier and, probably, as an apoptosis inducer in vitro, though this remains to be explored. These findings are discussed from a mechanistic standpoint as well as in terms of potential pharmacological applications under acute oxidative stress and apoptotic events. This work provides the basis for further investigations of Antoksyd S action in vitro and in vivo, since the presented results are indicative of its intracellular metabolic activation, which can only be partially associated with its observed action towards model cancer cells (mouse leukemia L1210).