Antitumour Effects of Selected Pyridinium Salts on Sensitive Leukaemia HL60 Cells and Their Multidrug Resistant Topoisomerase II-Defective HL60/MX2 Counterparts.

Multidrug resistance (MDR), having a multifactorial nature, is one of the major clinical problems causing the failure of anticancer therapy. The aim of this study was to examine the antitumour effects of selected pyridinium salts, 1-methyl-3-nitropyridine chloride (MNP) and 3,3,6,6,10-pentamethyl-3,4,6,7-tetrahydro-[1,8(2H,5H)-dion]acridine chloride (MDION), on sensitive leukaemia HL60 cells and resistant topoisomerase II-defective HL60/MX2 cells. Cell growth was determined by the MTT test. Intracellular ROS level was measured with the aid of 2',7'-DCF-DA. The cell cycle distribution was investigated by performing PI staining. DSB formation was examined using the γ-H2AX histone phosphorylation assay. The activity of caspase-3 and caspase-8 was measured with the use of the FLICA test. The assays for examining the lysosome membrane permeabilization were carried out with the aid of LysoTracker Green DND-26. Both studied compounds exerted very similar cytotoxic activities towards sensitive HL60 cells and their MDR counterparts. They modulated the cellular ROS level in a dose-dependent and time-dependent manner and significantly increased the percentage of sensitive HL60 and resistant HL60/MX2 cells with sub-diploid DNA (sub-G1 fraction). However, the induction of DSB formation was not a significant mechanism of action of these pyridinium salts in studied cells. Both examined compounds triggered caspase-3/caspase-8-dependent apoptosis of sensitive HL60 cells and their MDR counterparts. Additionally, the findings of the study indicate that lysosomes may also participate in the programmed death of HL60 as well as HL60/MX2 cells induced by MDION. The data obtained in this work showed that both examined pyridinium salts, MNP and MDION, are able to retain high antileukaemic effects against multidrug resistant topoisomerase II-defective HL60/MX2 cells.

Bioreductive Activation of Antitumour Drugs, Doxorubicin and Pirarubicin, Does Not Affect Their Ability to Induce Apoptosis of Sensitive and Multidrug Resistant Leukaemia HL60 Cells.

BACKGROUND/AIM: Clinical significance of antitumour drugs is limited by multidrug resistance (MDR). We examined the effect of bioreductive activation of the anthracyclines, doxorubicin (DOX) and pirarubicin (PIRA), by cytochrome P450 reductase (CPR) on triggering apoptosis of leukaemia HL60 cells and their MDR counterparts. MATERIALS AND METHODS: Cell cycle and FAS expression were investigated by flow cytometry. DNA fragmentation was examined by electrophoretic analysis and caspase-3/8 activities were determined colorimetrically. RESULTS: Non-activated and CPR-activated forms of DOX and PIRA (IC90) had similar efficacy in provoking G2/M arrest of sensitive HL60 as well as resistant HL60/VINC and HL60/DOX cells and in causing DNA degradation. Interestingly, HL60/VINC cells were more prone to apoptosis induced by all studied forms of these drugs. However, no change in Fas expression was observed. CONCLUSION: Bioreductive activation of DOX and PIRA does not affect their ability to induce apoptosis of sensitive and resistant HL60 leukaemia cells.

Quercetin Triggers Induction of Apoptotic and Lysosomal Death of Sensitive and Multidrug Resistant Leukaemia HL60 Cells.

Multidrug resistance (MDR) constitutes the major cause of the failure in anticancer therapy. One of the most important mechanisms leading to the occurrence of MDR is related to the modulation of cellular death pathways. The aim of this study was to determine the effect of quercetin (Q) on triggering the programed death of human promyelocytic leukemia sensitive cells HL60 as well as multidrug resistant HL60/VINC cells overexpressing P-glycoprotein and HL60/MX2 cells characterized by the presence of mutated α isoform of topoisomerase II and the absence of ß isoform of this enzyme. Q exerted comparable cytotoxic activities toward sensitive HL60 cells and their MDR counterparts. It was also found that this compound modulated the cellular level of reactive oxygen species (ROS) and led to the marked decrease in cellular GSH level. Furthermore, it was demonstrated that Q used at IC50 and IC90 significantly increased the percentage of sub-G1 subpopulation of all studied leukemia cells causing oligonucleosomal DNA fragmentation. The present study also indicated that Q used at IC90 triggers predominantly programed cell death of sensitive HL60 cells and their MDR counterparts by induction of apoptosis occurring with the involvement of caspase-3 and caspase-8 as well as by lysosome membrane permeabilization-dependent mechanisms.

Antitumour effects of selected plant polyphenols, gallic acid and ellagic acid, on sensitive and multidrug-resistant leukaemia HL60 cells.

The aim of this study was to examine the antitumour effects of plant phenolic acids, gallic acid (GA) and ellagic acid (EA), on human promyelocytic leukaemia sensitive HL60 cell line and its resistant sublines exhibiting two MDR phenotypes: HL60/VINC (overexpressing P-glycoprotein) and HL60/MX2 (characterized by the presence of mutated α isoform of topoisomerase II). Both studied compounds exerted comparable cytotoxic activities towards sensitive HL60 cells and their MDR counterparts. It was also found that GA and EA modulated the cellular level of reactive oxygen species in a dose-dependent and time-dependent manner. Furthermore, it was demonstrated that GA (IC90 ) and EA (IC50 and IC90 ) significantly increased the percentage of sub-G1 subpopulation of all studied leukaemia cells causing oligonucleosomal DNA fragmentation. Both compounds used at IC90 triggered mainly the apoptotic death of these cells. However, GA had no effect on the activity of caspase-3 as well as caspase-8 in sensitive HL60 cells and their MDR counterparts. In contrast, EA provoked a significant activation of these caspases in all studied leukaemia cells. It was also found that lysosomes were not involved in triggering programmed death of sensitive HL60 and MDR cells by GA and EA.

Invasion and metastasis of tumour cells resistant to chemotherapy.

Metastatic tumours resistant to chemotherapy are the major cause of the clinical failure in the treatment of malignant diseases. It is observed often that drugs active against primary tumours do not exhibit the same efficacy towards metastatic tumour cells having modified signaling pathways. Among cellular factors involved in the development of the metastatic potential of multidrug resistant tumour cells are some oncoproteins, antiapoptotic proteins, mutated suppressor proteins, integrins and CD44 receptor. It was also demonstrated that numerous chemotherapeutics have the effect on the emergence of the metastatic potential and multidrug resistance (MDR) phenomenon of tumour cells. The results of numerous studies suggest that genes involved in the development of MDR and metastatic phenotype of tumour cells are regulated by the same signaling pathways. They lead to the activation of transcription factors e.g. HIF-1α, NF-κB, Ets1 and AP-1 controlling the expression of genes involved in the development of the metastatic potential of multidrug resistant tumour cells. The identification of key cellular factors responsible for the emergence of the metastatic potential of MDR tumour cells could lead to the development of new efficient strategies for the treatment of metastatic tumours resistant to the conventional chemotherapy.

DNA damage induced by NADPH cytochrome P450 reductase-activated idarubicin in sensitive and multidrug resistant MCF7 breast cancer cells.

BACKGROUND: Idarubicin (IDA) is one of clinically important anticancer drugs belonging to the anthracycline antibiotic family. The aim of this study was to examine DNA damage induced by NADPH cytochrome P450 reductase (CPR)-activated IDA in human sensitive MCF7 and multidrug resistant MCF7/DOX500 (overexpressing P-gp) breast adenocarcinoma cells. METHODS: The evaluation of DNA fragmentation caused by single strand breaks (SSB) and double strand breaks (DSB) was performed using terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) test. Additionally, DSB formation was examined using H2AX histone phosphorylation assays. RESULTS: It was found that IDA alone and CPR-activated used at IC90 caused a higher level of DNA strand breaks in sensitive MCF7 cells detected by TUNEL assessments (p=0.0011 for IDA alone and p=0.0109 for IDA reductively activated, Kruskal-Wallis test) and γ-H2AX-positive staining (p=0.0003 for IDA alone and p=0.0193 for IDA reductively activated, Kruskal-Wallis test) than in multidrug resistant MCF7/DOX500 cells. However, no changes were observed in the percentage of TUNEL-positive and DSB-positive cells for MCF7 as well as MCF7/DOX500 cells in the case of IDA alone and the drug pretreated in the presence of the activating system. CONCLUSIONS: The obtained results suggest that CPR-activation of IDA does not significantly change the cellular DNA damage response of studied sensitive MCF7 and multidrug resistant MCF7/DOX500 breast cancer cells, even if the results concerning the interaction of IDA undergoing CPR activation with naked DNA showed the important differences in comparison with the drug alone (non-activated).

Comparative effects of selected plant polyphenols, gallic acid and epigallocatechin gallate, on matrix metalloproteinases activity in multidrug resistant MCF7/DOX breast cancer cells.

The aim of the study was to investigate the effect of selected polyphenols: gallic acid (GA) and epigallocatechin gallate (EGCG) on matrix metalloproteinase (MMP-2 and MMP-9) activity in multidrug resistant (MDR) human breast adenocarcinoma cells: MCF7/DOX cells and obtained recently in our laboratory MCF7/DOX500 cells by the permanent selection of MCF7/DOX cells with 500 nM doxorubicin (DOX). The activity of MMP-2 and MMP-9 and the effect of studied polyphenols on these matrix proteases were examined by gelatin zymography assays. We have found that the activity of MMP-2 and MMP-9 significantly increased in resistant MCF7/DOX and MCF7/DOX500 cells whereas they were not detected in sensitive MCF7 cells. It was also observed that GA (30, 60, 100 and 120 µM) and EGCG (5, 10 and 20 µM) caused a comparable concentration-dependent inhibition of MMP-2 and MMP-9 activity in MCF7/DOX and MCF7/DOX500 cells. Control experiments confirmed that examined compounds in these ranges of concentration did not affect the cell growth of MCF7/DOX and MCF7/DOX500 sublines (80-100% of control cell growth was observed in the presence of studied polyphenols).

Bioreductive activation of mitoxantrone by NADPH cytochrome P450 reductase does not change its apoptotic stimuli properties in regard to sensitive and multidrug resistant leukaemia HL60 cells.

The objective of this study was to examine the effect of bioreductive activation of antitumour drug, mitoxantrone (MX), by liver NADPH cytochrome P450 reductase (CPR) on inducing apoptosis of human promyelocytic sensitive leukaemia HL60 cell line and its multidrug resistance (MDR) sublines exhibiting two different phenotypes of MDR related to the overexpression of P-glycoprotein (HL60/VINC) or MRP1 (HL60/DOX). It was found that non-activated as well as CPR-activated form of MX used at IC90 were able to influence cell cycle of sensitive HL60 as well as resistant cells and induce apoptosis. Interestingly, it was evidenced that HL60/VINC cells were more susceptible to undergo caspase-3/caspase-8-dependent apoptosis induced by both studied forms of MX compared to HL60 and HL60/DOX cells. However, the examined agent did not change the expression of Fas receptors on the surface of HL60 sensitive as well as resistant cells regardless of its form used in the study. Obtained results suggest that CPR-dependent reductive activation of MX does not change its apoptotic stimuli properties in regard to sensitive HL60 and multidrug resistant (HL60/VINC and HL60/DOX) leukaemia cells. Nevertheless, taking into account that side toxic effects observed in course of patient treatment with antitumour drugs are dose-dependent, it seems that the reported increase in antiproliferative activity and ability to induce apoptosis of MX after its reductive activation by exogenous CPR against the MDR cells overexpressing both P-glycoprotein and MRP1 at much more lower concentrations of this drug could be of clinical importance for the treatment of tumours resistant to classical chemotherapy.

Retaining cytotoxic activity of anthrapyridone CO1 against multidrug resistant cells is related to the ability to induce concomitantly apoptosis and lysosomal death of leukaemia HL60/VINC and HL60/DOX cells.

OBJECTIVES: The effect of anthrapyridone compound CO1 retaining cytotoxic activity against multidrug resistant (MDR) tumour cells on inducing cell death of the sensitive leukaemia HL60 cell line and its MDR sublines (HL60/VINC and HL60/DOX) was examined. METHODS: The effects of CO1 and the reference compound doxorubicin (DOX) on examined cells were analysed by studying their cytotoxicity, drug intracellular accumulation, cell cycle distribution, caspase-3 and caspase-8 activity, Fas expression and lysosomal integrity. KEY FINDINGS: CO1 was much less effective at influencing the cell cycle of examined cells than DOX a well-known antitumour drug targeting cellular DNA and causing G2/M checkpoint arrest. CO1 caused much less pronounced appearance of the sub-G1 population and oligonucleosomal DNA fragmentation, characteristic of apoptosis, compared with DOX. Significantly lower caspase-3 and caspase-8 activity was also observed in the response of these cells to CO1 compared with DOX treatment. CO1 did not change the expression of the Fas death receptor, characteristic of apoptotic pathways, on the surface of studied cells. Interestingly, the results showed that CO1 caused lysosomal membrane permeability (LMP) of the cells, whereas DOX did not perturb the lysosomal integrity of the studied cells. CONCLUSIONS: The results suggest that CO1 could induce LMP-mediated cell death as a main lethal effect in a caspase-independent fashion.

The role of bioreductive activation of antitumour anthracycline drugs in cytotoxic activity against sensitive and multidrug resistant leukaemia HL60 cells.

Clinical usefulness of anthracyclines belonging to bioreductive antitumour drugs is limited by the occurrence of multidrug resistance (MDR). The aim of this study was to examine the role of structural factors of antitumour anthracycline drugs in the ability to undergo bioreductive activation by NADPH cytochrome P450 reductase (CPR) and determine the impact of this activation on increasing the activity especially in regard to MDR tumour cells. It was evidenced that at high NADPH concentration (500 µM) anthracyclines having non-modified quinone structure: doxorubicin (DOX), daunorubicin (DR) and idarubicin (IDA) were susceptible upon CPR catalysis to undergo a multi-stage chemical transformation concerning their chromophore part. Additionally, it was evidenced that the modification of the sugar moiety of DOX did not disturb the susceptibility of the obtained derivative (4'-O-tetrahydropyranyl-doxorubicin, pirarubicin, PIRA) to undergo CPR reductive activation. It was also evidenced that the derivatives having modified quinone groupment (5-iminodaunorubicin, 5-Im-DR) were not able to undergo reductive activation by CPR. The high impact of CPR-dependent reductive activation of anthracycline drugs on increasing the activity in regard to sensitive leukaemia HL60 cell line and its MDR sublines overexpressing P-glycoprotein (HL60/VINC) and MRP1 (HL60/DOX) was evidenced. Furthermore, significant changes in binding manner of activated compounds to naked DNA and cellular nucleus in comparison to their non-activated forms were also observed. It could prevent the export of formed adducts out of the cell by MDR proteins and may explain significant increases in intracellular accumulation of these compounds in HL60/VINC and HL60/DOX cells.

Anthraquinone antitumour agents, doxorubicin, pirarubicin and benzoperimidine BP1, trigger caspase-3/caspase-8-dependent apoptosis of leukaemia sensitive HL60 and resistant HL60/VINC and HL60/DOX cells.

We examined the effect of selected anthraquinone antitumour agents - doxorubicin (DOX), pirarubicin (PIRA) and benzoperimidine BP1 - on inducing apoptosis of the sensitive leukaemia HL60 cell line and its multidrug resistance sublines overexpressing P-glycoprotein (HL60/VINC) and multidrug resistance-associated protein 1 (HL60/DOX). All agents used at IC50 and IC90 were able to influence the cell cycle of sensitive HL60 and resistant cells and induce apoptosis. Interestingly, it was seen that HL60/VINC cells were more susceptible to undergo caspase-3/caspase-8-dependent apoptosis induced by the studied anthraquinone compounds compared with HL60 and HL60/DOX cells. However, the examined agents did not change the expression of Fas receptors on the surface of HL60-sensitive and-resistant cells.

Role of structural factors of antitumour anthraquinone derivatives and analogues in the ability to undergo bioreductive activation by NADPH cytochrome P450 reductase: implications for increasing the activity against sensitive and multidrug-resistant leukaemia HL60 cells.

The aim of this study was to examine the role of structural factors of antitumour anthraquinone derivatives and analogues in the ability to undergo bioreductive activation by NADPH cytochrome P450 reductase (CPR) and determine the impact of this activation on increasing the activity especially with regard to multidrug resistant (MDR) tumour cells. It was found that at a high NADPH concentration (500 µmol/l), the anthracenedione agent ametantrone, with an unmodified quinone structure, was susceptible to CPR-dependent reductive activation. In contrast, it was shown that compounds with modified quinone grouping (benzoperimidine BP1, anthrapyridone CO1 and pyrazolopyrimidoacridine PPAC2) did not undergo reductive activation by CPR. This suggests that the presence of a modified quinone function is the structural factor excluding reductive activation of antitumour anthraquinone derivatives and analogues by CPR. In the second part of the work, the ability of antitumour anthraquinone derivatives and analogues to inhibit the growth of the human promyelocytic, sensitive leukaemia HL60 cell line as well as its MDR sublines exhibiting two different phenotypes of MDR related to the overexpression of P-glycoprotein (HL60/VINC) or MRP1 (HL60/DOX) was studied in the presence of exogenously added CPR. A significant increase in the activity of ametantrone with an unmodified quinone structure after its reductive conversion by CPR was observed against HL60 as well as HL60/VINC and HL60/DOX cells, whereas in the case of quinone-modified compounds (BP1, CO1 and PPAC2), the presence of the activation system had no effect on their activity against the sensitive and MDR tumour cells examined.

Effect of selected NAD+ analogues on mitochondria activity and proliferation of endothelial EA.hy926 cells.

The aim of the study was to examine the effect of 1-methylnicotinamide (MNA) and 1-methyl-3-nitropyridine (MNP) on mitochondria activity and proliferation of endothelial EA.hy926 cells. The activity of MNA was also referred to nicotinamide (NAM) being MNA metabolic precursor. NAM and MNA used at high concentrations (up to 1 mM) had no effect on mitochondria metabolism and proliferation of EA.hy926 cells. It could be related to the fact that these compounds hardly cross the cell membrane. It supports the results of our previous study suggesting that anti-inflammatory and anti-thrombotic effects of MNA could be associated with its ability to bind to glycosaminoglycans, especially heparins, located on the endothelium membrane without entering into target cells. In contrast, MNP caused substantial changes in mitochondria activity and proliferation of EA.hy926 cells. This compound used at low concentrations (below 100 microM) blocked the cell cycle of EA.hy926 cells in G1 phase and was very effective in inhibiting cell growth (IC50=13.8+/-2.4 microM). At higher concentrations (0.1-1 mM) MNP caused a significant reduction of cell survival. The observed effects of MNP could be related, at least in part, to its ability to influence the ATP and NAD+ intracellular levels. MNP caused also important changes in Ca2+ intracellular concentration, significant decrease in inner mitochondrial membrane potential and high increase in mitochondrial respiration of EA.hy926 cells. The observed effects of MNP may be related in part to its cellular metabolites detected after 45 min incubation with 250 microM MNP.

The ability of selected pyridinium salts to increase the cytotoxic activity of vincristine but not doxorubicin towards sensitive and multidrug resistant promyelocytic leukaemia HL60 cells.

The aim of this study was to examine the effect of selected pyridinium salts, 1-methyl-3-nitropyridine chloride (MNP(+)Cl(-)) and 3,3,6,6,10-pentamethyl-3,4,6,7-tetrahydro-[1,8(2H,5H)-dion]acridine chloride (MDION(+)Cl(-)), on the activity of doxorubicin (DOX) and vincristine (VINC) towards human promyelocytic leukaemia HL60 cells as well as its multidrug resistant (MDR) sublines exhibiting two different phenotypes of MDR related to the overexpression of P-glycoprotein (HL60/VINC) or MRP1 (HL60/DOX). MNP and MDION salts were much less cytotoxic themselves (about 100-fold and 2000-fold compared with DOX and VINC, respectively) against HL60 cells but, in contrast to DOX and VINC, they conserved an important cytotoxic activity towards resistant HL60/VINC and HL60/DOX cells (resistance factor, RF = 2-4.5). It was shown that MNP(+)Cl(-) and MDION(+)Cl(-) increased the cytotoxicity of non-bioreductive antitumour agent VINC towards human promyelocytic leukaemia HL60 cells and its resistant sublines HL60/VINC and HL60/DOX. However, in the case of DOX the decrease in its cytotoxic activity towards all studied cell lines was observed in the presence of MNP(+)Cl(-) and MDION(+)Cl(-). Presented data suggest that the bioreductive drug DOX, in contrast to VINC, could compete with pyridinium salts (MNP(+)Cl(-) and MDION(+)Cl(-)) for NADPH-dependent oxidoreductases and for undergoing cellular reductive activation. This could explain the inefficiency of these salts to increase the cytotoxic activity of DOX against examined leukaemic HL60 cell line and its MDR sublines, HL60/VINC and HL60/DOX.

In vitro antileukaemic activity of extracts from chokeberry (Aronia melanocarpa [Michx] Elliott) and mulberry (Morus alba L.) leaves against sensitive and multidrug resistant HL60 cells.

The aim of the present study was to determine in vitro antileukaemic activities of extracts obtained from chokeberry (Aronia melanocarpa [Michx] Elliot) and mulberry (Morus alba L.) leaves against promyelocytic HL60 cell line and its multidrug resistant sublines exhibiting two different MDR phenotypes: HL60/VINC (overexpressing P-glycoprotein) and HL60/DOX (overexpressing MRP1 protein). It was found that the extracts from chokeberry and mulberry leaves were active against the sensitive leukaemic cell line HL60 and retained the in vitro activity against multidrug resistant sublines (HL60/VINC and HL60/DOX). The values of resistance factor (RF) found for these extracts were very low lying in the range 1.2-1.6.

Bioreductive activation of mitoxantrone by NADPH cytochrome P450 reductase. Implications for increasing its ability to inhibit the growth of sensitive and multidrug resistant leukaemia HL60 cells.

The aim of this study was to examine the role of reductive activation of mitoxantrone (MX) by human liver NADPH cytochrome P450 reductase (CPR) in increasing its ability to inhibit the growth of human promyelocytic sensitive leukaemia HL60 cell line as well as its MDR sublines exhibiting two different phenotypes of MDR related to the overexpression of P-glycoprotein (HL60/VINC) or MRP1 (HL60/DOX). Our assays showed that the reduction of MX by exogenously added CPR in the presence of low NADPH concentration had no effect in increasing its ability to inhibit the growth of sensitive and MDR tumour cells. In contrast, an important increase in antiproliferative activity of MX after its reductive activation by CPR at high NADPH concentration was observed against HL60/VINC as well as HL60/DOX cells.

In vitro antileukaemic activity of extracts from berry plant leaves against sensitive and multidrug resistant HL60 cells.

The aim of the present study was to determine in vitro antileukaemic activity of extracts obtained from selected berry plant leaves (Fragaria x ananassa Duch. cv Elsanta, raspberry Rubus ideus L. cv Polana and blueberry Vaccinium corymbosum L. cv Bluecrop) against promyelocytic HL60 cell line and its multidrug resistant sublines exhibiting two different MDR phenotypes: HL60/VINC (overexpressing P-glycoprotein) and HL60/DOX (overexpressing MRP1 protein). It was found that the blueberry extract was the most efficient against sensitive HL60 cell line (about 2-fold more active than strawberry and raspberry extracts) but presented much lower activity towards resistant cells. In contrast, strawberry and raspberry extracts exhibited the high cytotoxic activity against sensitive leukaemia HL60 cell line as well as its MDR sublines. The values of resistance factor (RF) found for these extracts were very low lying in the range 0.32/2.0.

The effect of new non-cross resistant antitumour agents on the energy state of human erythrocytes.

Multidrug resistance (MDR) of tumour cells is related to the overexpression of ATP-dependent pumps responsible for the active efflux of antitumour agents out of resistant cells. Benzoperimidine and anthrapyridone compounds exhibit comparable cytotoxic activity against sensitive and MDR tumour cells. They diffuse extremely rapidly across the plasma membrane and render the ATP-dependent efflux inefficient. Such uptake could disturb an energy metabolism of normal cells possessing an elevated level of ATP-dependent proteins, especially erythrocytes having a high level of the MRP1, MRP4 and MRP5 proteins. In this study the effect of five antitumour agents: benzoperimidine (BP1), anthrapyridones (CO1, CO7) and reference drugs used in the clinic: doxorubicin (DOX) and pirarubicin (PIRA), on the energetic state in human erythrocytes has been examined. These compounds have various types of structure and kinetics of cellular uptake (slow--DOX, CO7, moderate--PIRA, fast--BP1, CO1) resulting in their different ability to saturate ATP-dependent transporters. The energetic state of erythrocytes was examined by determination of purine nucleotide contents (ATP, ADP, AMP), NAD(+) and values of adenylate energy charge (AEC) using an HPLC method. It was found that the level of nucleotides as well as the AEC value of erythrocytes were not changed during 24 h of incubation with these agents independently of their structure and ability to saturate ATP-dependent pumps. This is a very promising result in view of their potential use in the clinic as antitumour drugs against multidrug resistant cancers.

The purine nucleotide content in human leukemia cell lines.

The HPLC method was used to determine the purine nucleotide (ATP, ADP, AMP, GTP, GDP, GMP, NAD(+)) contents and the values of the adenylate energy charge (AEC) and guanylate energy charge (GEC) for three human acute myelogenous leukemia (AML) cell lines: HL60 (M3 subtype of AML), THP1 (M5 subtype of AML), and HEL (M6 subtype of AML) in French-American-British classification (FAB) and for one chronic myelogenous leukemia (CML) cell line: K562. The results showed that the examined leukemic cells had some significant changes in their purine nucleotide concentrations relative to healthy cells. On the basis of the obtained results, it seems that two of the tested acute myelogenous leukemia cell lines, HL60 and HEL, have similar purine nucleotide metabolisms, while the third AML cell line, THP1, has a purine nucleotide metabolism like that of the chronic myelogenous leukemia cell line, K562.

Molecular basis of the low activity of antitumor anthracenediones, mitoxantrone and ametantrone, in oxygen radical generation catalyzed by NADH dehydrogenase. Enzymatic and molecular modelling studies.

Synthetic antitumor anthracenedione drugs, in contrast to anthracycline antibiotics, are ineffective in free radical formation in NADH dehydrogenase system. Our results have indicated that neither the reduction potential nor the side chain conformation and the energies of border orbitals (HOMO and LUMO) determine the ability of anthracenediones to stimulate reactive oxygen species formation in NADH dehydrogenase system. It was shown that the distribution of the molecular electrostatic potential (MEP), around the quinone system was crucial for this ability. We have found for non-stimulating anthracenediones that the clouds of positive MEP cover the quinone carbon atoms while for agents effective in stimulating reactive oxygen species formation the clouds of negative MEP cover continuously the aromatic core together with the quinone system.