The mode of action of cytotoxic and antitumor 1-nitroacridines. III. In vivo interstrand cross-linking of DNA of mammalian or bacterial cells by 1-nitroacridines

To define a critical lesion in presumable target DNA cause in vivo by the antitumor and cytotoxic 1-nitroacridines, Ehrlich ascites tumor (Eat) cells implanted into mice, HeLa cells grown in monolayer culture or Bacillus subtilis SB 1058 strain cells were exposed to Ledakrin [Nitracrine; 1-nitro-9-(3'-dimethylamino-n-propylamino)acridine], its non-antitumor congeners, or mitomycin C tested for comparison; total intracellular DNA was isolated from control or treated cells and denatured by heat, alkali or formamide, after which the chemically-induced fraction of interstrand cross-linked DNA molecules was assessed by thermal denaturation-renaturation curve analysis, hydroxylapatite column chromatography, or partitioning in a Dextran T500-polyethylene glycol 6000 biphasic system. Ledakrin, as compared to mitomycin C, was a very effective cross-linking agent, inducing one covalent cross-link per approx. 20 X 10(3) (B. subtilis), 56 X 10(3) (HeLa) or 80 X 10(3) (Eat) DNA base pairs. The first cross-links were introduced in B. subtilis cell genomes at minimal bactericidal concentrations of Ledakrin of mitomycin C. Ledakrin failed to induce discernible cross-linking of bihelical DNA when complexed with in cell-free system. Unlike the other two 1-nitroacridines which cross-linked DNA of cultured HeLa or B. subtilis cells, the non-antitumor 2-, 3- or 4-nitroacridines did not cause such effect and diminished cross-linking by Ledakrin or mitomycin C. Hence, upon metabolic activation in mammalian or bacterial cell Ledakrin and, most probably other 1-nitroacridines, become very effective DNA cross-linking agents and such effects appear to be responsible for the antitumor and potent cytotoxic activities of 1-nitroacridines.     

The mode of action of cytotoxic and antitumor 1-nitroacridines. II. In vivo enzyme-mediated covalent binding of a 1-nitroacridine derivative, Ledakrin or Nitracrine, with dna and other macromolecules of mammalian or bacterial cells

Earlier evidence, in Part I of this paper, has shown that cytotoxic and antitumor 1-nitroacridines did not primarily exert their potent inhibitory effects on cultured mammalian cells by physicochemical binding with DNA, although it undoubtedly occurred (Chem.-Biol. Interact., 43 (1983) 131). As a result it was investigated (i) whether 9-14C- or 1'-14C-labeled derivatives of their representative, 1-nitro-9-/3'-dimethylamino-n-propylamino/acridine (Ledakrin or Nitracrine), were capable of covalent binding with nucleic acids and other suitable macromolecules in target cells in vivo and/or (ii) whether activation of the agent in the cell was a necessary prerequisite for such binding. Using the criteria of resistance to exhaustive extractions with trichloroacetic acid and/or organic solvents, [14C]Ledakrin was found to bind covalently, with relatively little discrimination, with: (i) intracellular macromolecules, including DNA, of cultured tumor HeLa cells (370-2500 DNA base pairs/one Ledakrin molecule; (ii) experimental animal tumor Ehrlich ascites (Eat) cells in vivo (650-5880 DNA base pairs/one Ledakrin molecule); (iii) bacterial Bacillus subtilis SB 1058 cells (7000-33 000 Ledakrin links/one cell genome); (iv) NADPH-fortified rat liver homogenates in vitro (25.6 nmol/mg microsomal protein under air). These results far exceed the common levels reported for alkylating agents or chemical carcinogens. Unlike [ethyl-14C]quinacrine, compared in vitro, covalent macromolecules binding with Ledakrin in vitro, and most probably in vivo, can be equated to NADPH-dependent activation(s) by oxidoreductase systems and the presence of DNA alone was not satisfactory in itself to attain Ledakrin binding. Fractionation of the enzymatic digest of 14C-associated DNA, isolated from Eat cells exposed in vivo to [9-14C]Ledakrin, by Sephadex LH-20 column chromatography followed by mass spectrometry analyses of modified nucleosides, indicated that both mono- and dinucleosidical Ledakrin metabolites were the products of an in vivo reaction. This implied that the lethal reaction of the drug could be its cross-linking of the target macromolecules and/or its monofunctional attack on vitally important cellular components.     

DNA damage in HeLa S3 cells by an antitumor drug ledakrin and other antitumor 1-nitro-9-aminoacridines

Ledakrin and seven other antitumor and cytotoxic derivatives of 1-nitro-9-aminoacridine were shown to induce DNA-single strand breaks in HeLa S3 cells as found by alkaline sucrose gradient centrifugation. The induced DNA damage is of non-random character. Some of Ledakrin-induced DNA breaks are probably generated by endonucleolytic cleavage in the course of repair processes as indicated by experiments with Novobiocin, an antibiotic preventing the incision step of DNA repair. Other Ledakrin-induced DNA breaks observed on alkaline sucrose gradients may arise from alkali-labile sites in DNA. Most of such sites seem to be converted to breaks after brief exposure to alkali. The extent of DNA damage by 1-nitro-9-aminoacridines was found to be correlated with cytotoxic activities of these compounds against HeLa S3 cells. Furthermore, Ledakrin and other derivatives seem to induce DNA-repair synthesis in HeLa S3 cells as judged by the stimulation of hydroxyurea (HU)-resistant incorporation of [³H] thymidine into DNA. The agents studied differ in their concentrations required to produce a considerable stimulation of DNA repair, whereas the maximal level of this effect is similar for all the derivatives assayed. The former values are correlated with cytotoxic activites of these compounds and seem to reflect the overall extent of DNA damage by 1-nitro-9-aminoacridines. Stimulation of DNA-repair synthesis is gradually shut off during prolonged incubation of the cells with Ledakrin or during postincubation of the cells in a drug-free medium. Such postincubation results also in the gradual accumulation of DNA-single strand breaks as observed by alkaline sucrose centrifugation. Hence, HeLa S3 cells are incapable of efficiently removing DNA damage by 1-nitro-9-aminoacridines, though the drug's action activates temporarily some repair mechanisms.The reported results suggest that overall DNA damage may contribute to the cytotoxic effects of 1-nitro-9-aminoacridines besides previously found ability of these agents to form interstrand DNA cross-links.     

Induction of genotoxic and cytotoxic damage by aclarubicin, a dual topoisomerase inhibitor

The anthracycline aclarubicin (ACLA) is an intercalative antibiotic and antineoplastic agent that efficiently binds to DNA, leading to a secondary inhibition of the catalytic activity of topoisomerase II (topo II) on DNA. Besides this activity, ACLA has been reported to exert a concomitant poisoning effect on topo I, in a fashion similar to that of the antitumor drug camptothecin and its derivatives. As a consequence of this dual (topo II catalytic inhibiting/topo I poisoning) activity of ACLA, the picture is somewhat confusing with regards to DNA damage and cytotoxicity. We studied the capacity of ACLA to induce catalytic inhibition of topo II as well as cytotoxic effects and DNA damage in cultured Chinese hamster V79 cells and their radiosensitive counterparts irs-2. The ultimate purpose was to find out whether differences could be observed between the two cell lines in their response to ACLA, as has been widely reported for radiosensitive cells treated with topo poisons. Our results seem to agree with the view that the radiosensitive irs-2 cells appear as hypersensitive ACLA as compared with radiation repair-proficient V79 cells. The recovery after ACLA treatment was also followed-up, and the irs-2 mutant was found to be less proficient than V79 to repair DNA strand breaks induced by ACLA.     

The synthesis of ursolic acid derivatives with cytotoxic activity and the investigation of their preliminary mechanism of action

Nineteen ursolic acid derivatives (15 novel compounds) modified at the C-3 and the C-28 positions were synthesized. The cytotoxic activity of the derivatives was evaluated against HeLa, BGC-823 and SKOV3 cells by MTT assay. Inducing apoptosis and affecting cell cycle distribution by the derivatives in HeLa cells were assessed by flow cytometry and DNA fragmentation. Compounds 10b and 11b were particularly active to inhibit HeLa cells growth through inducing apoptosis and arresting cell cycle progression. The typical ‘sub-G1 peak’ and DNA ladder formation were checked and cell cycle was arrested at the S phase in a dose-dependent manner.     

Mechanisms underlying the cytotoxic effects of Tachpyr--a novel metal chelator

Tachpyr (N,N'N"-tris(2-pyridylmethyl)-cis,cis-1,3,5-triaminocyclohexane), a novel metal chelator, was previously shown to deplete intracellular iron and exert a cytotoxic effect on cultured bladder cancer cells. Tachpyr binds Fe(II) and readily reduces Fe(III). The iron(II)-Tachpyr chelate undergoes intramolecular oxidative dehydrogenation resulting in mono- and diimino Fe(II) complexes. The present study investigates the redox-activity of the Tachpyr-iron complex to better define the mechanism of Tachpyr's cytotoxicity. Tachpyr's mechanism of cytotoxicity was studied using cell-free solutions, isolated DNA, and cultured mammalian cells by employing UV-VIS spectrophotometry, oximetry, spin-trapping technique, and electron paramagnetic resonance (EPR) spectrometry. The results show that: (1) Tachpyr by itself after 24 h of incubation had a cytotoxic effect on cultured cells; (2) fully oxidized Tachpyr had no cytotoxic effects on cultured cells even after 24 h of incubation; (3) Tachpyr protected isolated DNA against H(2)O(2)-induced damage, but not against HX/XO-induced damage; and (4) Tachpyr-Fe(II) chelate slows down but does not block oxidation of Fe(II), allows O*(-)(2)-induced or Tachpyr-induced reduction of Fe(III), and consequently promotes production of *OH through the Haber-Weiss reaction cycle. The results indicate that Tachpyr can protect cells against short-term, metal-mediated damage. However, upon prolonged incubation, Tachpyr exerts cytotoxic effects. Therefore, in addition to iron depletion, low-level oxidative stress, which in part occurs because of redox cycling of the coordinated iron ion, may contribute to the cytotoxic effects of Tachpyr.     

Evaluation of the cytotoxic mechanisms mediated by the broad-spectrum antitumor alkaloid acronycine and selected semisynthetic derivatives.

Acronycine (I) is a broad-spectrum antitumor agent whose development as a clinically useful agent has been hindered, in part, due to its poor solubility characteristics. With the goal of acquiring information that may prove of value in the development of structurally related compounds of greater clinical utility, mechanistic studies were performed with acronycine (I) and two semisynthetic derivatives, 2-nitroacronycine (II) and acronycine azine (III). These three substances demonstrated cytotoxic activity with several human tumor cell lines (breast, colon, lung, melanoma, KB-3, and drug-resistant KB-V1). Compounds II and III demonstrated greater activity than I, and more detailed studies were performed with cultured human breast cancer cells (UISO-BCA-1). Acronycine azine (III) induced the cells to accumulate in the G0/G1 phase of the cell cycle. It effectively inhibited the in vitro catalytic activities of partially purified DNA and RNA polymerases in a manner that was competitive with respect to DNA substrate. As judged by spectrophotometric titration, compound III interacted with calf thymus DNA, calf liver RNA, and a variety of single- and double-stranded (deoxy)ribonucleotides. Although no nucleic acid base specificity was discernable, this interaction appeared to be related to the cytotoxic mechanism of this dimeric substance. Monomeric compounds I and II did not interact with nucleic acids, but were effective inhibitors of DNA and RNA synthesis as judged by in vitro systems comprised of cultured UISO-BCA-1 cells or homogenates derived from these cells. The relative inhibitory activities of compounds I and II correlated with their cytotoxic activities suggesting a causal relationship. In addition, these two compounds induced cultured cells to accumulate in the phase of the cell cycle wherein the DNA content ranged from 2n-4n (S + G2/M), and inhibited in vitro DNA and RNA synthesis in a manner that was competitive with respect to nucleotide (TTP or UTP) substrate. Compounds I and II demonstrated greater cytotoxic activity with drug-resistant KB-V1 cells as compared with the parent (drug-sensitive) cell line, whereas this was not the case with compound III. Based on these results and previous literature reports, compounds I, II and III are likely to function by multiple mechanisms of action. However, it appears that alteration of nucleic acid metabolism is key to the activity of each of the substances.     

Immunomodulating activity of 1-methyl and 1-ethylascorbigens

1-Methyl- and 1-ethylascorbigens, derivatives of indole and ascorbic acid are the vitamin C depo-forms with antitumor activity. Relation between the antitumor activity of the derivatives and their immunostimulating action was studied. The derivatives showed similar properties in vitro: they stimulated lymphocyte blast transformation, insignificantly stimulated formation of cytotoxic T-lymphocytes (CTL) in the allogenic mixed culture of lymphocytes (AMLC), inhibited cytotoxicity of natural killer cells (NKC) and had no cytotoxic action in cultures of tumors CaOv and others. In vivo 1-methylascorbigen promoted an increase in the splenocyte count in mice, stimulated 16-fold generation of CTL in AMLC of the splenocytes and retarded the growth of ACATOL tumor in thymus-free mice. 1-Ethylascorbigen had no such effects. The antitumor action of 1-methylascorbigen is likely to be associated with stimulation of CTL generation and not with the increase in the activity of NKC.     

Biological activity of bis-benzimidazole derivatives on DNA topoisomerase I and HeLa, MCF7 and A431 cells

Benzimidazoles of both natural and synthetic sources are the key components of many bio-active compounds. Several reports have shown antifungal, antiviral, H(2) receptor blocker and antitumor activities for benzimidazoles and their derivatives. In this study, we synthesized twelve bis-benzimidazole derivatives by selecting di(1H-benzo[d]imidazol-2-yl)methane as the main compound. The numbers of carbons at 2 positions of bis-benzimidazole derivatives were changed from 1 to 4, and derivatives were synthesized with methyl substitutions at 5- and/or 6- positions. The compounds were screened via in vitro plasmid superciol relaxation assays using mammalian DNA topoisomerase I and cytostatic assays were carried out against HeLa (cervix adenocarcinoma), MCF7 (breast adenocarcinoma) and A431 (skin epidermoid carcinoma) cells for selected derivatives. Our results suggest that the malonic acid derivatives of bis-benzimidazoles, namely, bis(5-methyl-1H-benzo[d]imidazol-2-yl)methane and bis(5,6-dimethyl-1H-benzo[d]imidazol-2-yl)methane, were remarkably active compounds in interfering with DNA topoisomerase I and the former compound was also found to be cytotoxic against MCF7 and A431 cells. The inhibitory effects obtained with these derivatives are significant as these compounds can be potential sources of anticancer agents.     

Synthesis, DNA interaction, and cytotoxic activity of a novel proflavine-dithiazolidinone pharmacophore

Five novel proflavine-dithiazolidinone derivatives 4a-4e have been designed and synthesized by the reaction of dialkyl acridin-3,6-diyl dithioureas 3a-3e with methyl bromoacetate. The binding affinity of dithiazolidinone hydrochlorides 5a-5e with calf thymus DNA and plasmid (pUC19) DNA was investigated by a variety of spectroscopic techniques including UV-vis, fluorescence, and CD spectroscopy. The effects of 5a-5e on the thermal denaturation profiles of calf thymus DNA were also studied. From spectrophotometric and spectrofluorimetric titrations, the binding constants for the pUC19 DNA-drug complexes were determined (K = 6.2-2.2 x 104 M-1). In vitro cytotoxic activities of compounds 5a-5e toward murine leukemia cell line L1210 and human uterus carcinoma HeLa cells were also examined. 2',2' '-[(Acridin-3,6-diyl)diimino]-3',3' '-dipropyl-1,3-dithiazolidin-4-one hydrochloride (5b) showed the highest activity against these cells with IC50 values of 6.3 microM and 12.9 microM over the course of 72 h.     

Overexpressed human RAD50 exhibits cell death in a p21(WAF1/CIP1)-dependent manner: its potential utility in local gene therapy of tumor.

Previously, mouse RAD50, one of the mammalian DNA recombination repair genes, was reported to have limited epitopic homology to p53. Here we report the functional characteristics of overexpressed human RAD50 (hRAD50). Transient transfection of hRAD50 in several cultured cells caused cytotoxicity. We established tetracycline-regulated, stable hRAD50 expression systems in SaOS-2 cells, which retain mutated p53, and in HeLa cells. After tetracycline withdrawal, cell death and multinucleated giant cells were observed with increased hRAD50 expression, and p21(WAF1/CIP1) but not p53 was increased. Transient transfection of hRAD50 in HCT116 p21(-/-) cells caused no cytotoxicity, but there was a significantly decreased survival rate in p21(+/+) cells. These cytotoxic effects of overexpressed hRAD50 in HeLa, SaOS-2, and HCT116 p21(+/+) cells were partially blocked by pretreatment of cells with N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, a pan-caspase inhibitor. When the hRAD50 expression cDNA was injected intratumorally with liposomes, it regressed or delayed tumor development in the animal model and nitric oxide synthase expression was induced in the tumor tissues that had regressed. Our results indicate that overexpressed hRAD50 has an antiproliferation activity in vitro and in vivo in a p21-dependent manner.     

The synthesis of doxorubicin-conjugated magnetite nanoparticles and their magnetic resonance and cytotoxic properties

The possibility of increasing the effectiveness of antitumor drugs such as doxorubicin by preparing its complex with ultrafine magnetic iron oxide nanoparticles is considered. A method for binding doxorubicin molecules to magnetic nanoparticles via citric acid is proposed. The main magnetic properties of the obtained conjugates were studied by proton relaxometry and Mössbauer spectroscopy, while their cytotoxic activity was evaluated via spectrophotometric MTT assay in HeLa cells. It was shown that the conjugates of magnetite nanoparticles with doxorubicin are characterized by a high level of contrast in magnetic resonance imaging. The magnetic properties of doxorubicin-free and bound magnetite nanoparticles are mainly determined by the average size of nanoobjects and the phase composition and slightly depend on the composition of the stabilizing shell. The cytotoxic effect of the synthesized conjugates of magnetite nanoparticles with doxorubicin is higher than that of unbound doxorubicin. This makes it possible to increase the antitumor effect of doxorubicin and control the dynamics of its delivery in the form of a conjugate into the disease focus due to the magnetic contrast properties of nanoparticles.     

The antitumor drug, cis diamminedichloro-platinum, inhibits trans plasmalemma electron transport in HeLa cells

Transplasmalemma electron transport which stimulates the growth of HeLa cells is inhibited by the antitumor drug cis diammine dichloro platinum II at concentrations which correlate with cytotoxic effects. The less cytotoxic trans diammine dichloro platinum II has very little effect on the transmembrane dehydrogenase. This selectivity contrasts with the similarity of these compounds in binding to DNA. We propose that part of the selective antitumor action of the cis compound can be based on its inhibition of the transplasmalemma dehydrogenase which stimulates growth.     

The cytotoxic process of CD4 Th1 clones.

Previous studies have demonstrated that murine CD4 Th1 cells lack perforin and use a pathway distinctive from CD8 CTL to express cytotoxicity. Whether the cytotoxic process of Th1 cells can be separated into identifiable stages and how these differences affect this process were determined in this study. We have resolved the cytotoxic process of Th1 clones into three stages identical with those of CD8 CTL, namely, conjugate formation/activation, lethal hit, and effector-independent programming for target DNA fragmentation. By comparing the cytotoxic processes between Th1 clones on Ag-pulsed targets and (PMA+A23187)-activated Th1 clones on unpulsed targets, we have also demonstrated that 1) the requirement of CD4 Th1 cells for de novo synthesis of cytotoxic machinery was partly responsible for the lag time in the induction of target DNA fragmentation by Th1 clones; 2) lethal hit was delivered rapidly; 3) lethal hit under forced contact by centrifugation did not need extracellular Ca2+ and Mg2+; 4) without centrifugation, lethal hit required extracellular Mg2+, but not Ca2+; 5) the average functional half life of the cytotoxic machinery was 54 +/- 24 (n = 4) min. The data demonstrate that the cytotoxic process of Th1 clones uses an activation-dependent cytotoxic machinery to deliver a short-lived, short-ranged, and quick-acting lethal hit to target, which induces a program in target for DNA fragmentation.     

Enhancement of mixed leukocyte reaction and cytotoxic antitumor responses by heparin

The immunomodulating effects of heparin and natural and synthetic heparinoids (which are now undergoing clinical trials for the treatment of AIDS) on cellular immunity (DNA synthesis and cytotoxic responses of mouse lymphocytes to allogeneic cells and histocompatible tumors) were studied. The results showed that (1) high and low m.w. heparin enhanced mouse antitumor and antiallogeneic cell responses in vitro; (2) other sulfated heparinoids did not have this enhancing activity and some of them (including dextran sulfate) totally suppressed generation of cytotoxic cells; (3) these immunomodulating activities of heparin and heparinoids did not correlate with their anticoagulant effects, degree of sulfation, and mitogenic activity; (4) heparin did not increase the production of IL-2 and did not enhance the action of IL-2 on the cells in MLC, heparin also had no effect on the growth-promoting activity of IL-2 on cloned cytotoxic T cells; (5) heparin had a synergistic enhancing effect with IL-1 on the generation of cytotoxic cells in MLC; and (6) heparin abolished endothelial cell growth factor-induced suppression of cytotoxic response. The latter two effects by themselves, however, could not fully explain the entire immunoenhancing activity of heparin. These results indicate that heparin and heparinoids have multiple effects on the immune system and that some of them can enhance, whereas others can suppress cell-mediated responses.     

The mechanism of inhibition of DNA replication in HeLa S3 cells by the antitumor drug Ledakrin and other antitumor 1-nitro-9-aminoacridines

These studies were aimed at characterizing the capability of an antitumor DNA-damaging drug, Ledakrin, and its analogs to inhibit DNA replication in HeLa S3 cells. The studied agents are extremely potent inhibitors of [³H]thymidine incorporation in whole cells. These compounds produced also a potent dose- and time-dependent inhibition of DNA synthesis in subcellular systems derived from drug-treated cells, as found by [³H]dGTP incorporation in cellular lysates and nuclei. Experiments in which nuclei from control and drug-treated cells were supplemented with cytoplasmic fractions from either control or drug-treated cells, or with exogenous DNA, demonstrate that Ledakrin and other 1-nitro-9-aminoacridines inhibit DNA replication in HeLa S3 cells by interfering with the DNA template, while not affecting DNA polymerase(s) or other enzymes and replication factors. The negligible effect of Ledakrin added to lysates or nuclei from untreated cells suggests that metabolic activation is a prerequisite for replication inhibition by Ledakrin. Analysis of the size of newly synthesized DNA, by alkaline sucrose gradient sedimentation, indicates that Ledakrin does not inhibit the initiation of replication but does interfere with chain growth. Impairment of DNA replication by 1-nitro-9-aminoacridines seems to originate from DNA damage and to result in the inhibition of cellular growth.     

Synthesis and cytotoxic activity of novel C7-functionalized spongiane diterpenes

Based on two lead cytotoxic spongiane diterpenes, a new series of C7-oxygenated derivatives were synthesized and evaluated for their antitumor activity in vitro against the cancer cell lines HeLa and HEp-2. In general, introduction of either hydroxyl or acetoxy groups at C-7 did not improve the resultant cytotoxicity, while the presence of a butyrate ester led to more active compounds (CC(50)=4.0-9.5 microM).     

Properties of mer HeLa cells sensitive or resistant to the cytotoxic effects of MNU; effects on DNA synthesis and of post treatment with caffeine

A line of HeLa cells was shown to be particularly sensitive to N-methyl-N-nitrosourea (MNU) and N-methyl-N′-nitro-N-nitrosoguanidine (MNNG), but not to variety of other cytotoxic agents. A resistant line (designated HeLa/A22), was derived by treating Hela cells repeatedly with MNU. Both the sensitive (HeLa) and resistant (Hela/A22) cells have a mer⁻ phenotype based both on their reduced rates of loss of O⁶-methylguanine (O⁶-MeG) from DNA and their low levels of the enzyme O⁶-methylguanine methyltransferase (MT). HeLa cells are therfore sensitive to unrepaired O⁶-MeG in DNA while the Hela/A22 cells are resistant to unexcised O⁶-MeG and thus the A22 cells have the mer⁻ rem⁺ phentype. MNU produced an imediate dose-dependent inhibition of DNA synthesis in cultures of both sensitive resistant cells which increased with time until about 4 h after treatment. DNA synthesis then recovered to near control rates in both sensitive and resistant cells before then exhibiting a progressive decrease after 24 h. DNA synthesis was more depressed at these late times after treatment in cultures of sensitive cells than in those of similarly-treated resistant cells. DNA synthesis remained depressed in sensitive cells but recovered 3 days after treatment in resistant cells.

Post treatment of incubation of MNU-treated HeLa cells with caffeine did not increase the toxic action of MNU. In contrast, post treatment of the resistant HeLa/A22 cells with caffeine resulted in a dramatic increase in the toxic effects of a higher equitoxic dose of MNU. The depressed rate of DNA synthesis observed in both cell lines after doses of MNU was partially reversed by post treatment with caffeine in both sensitive and resistant cells. These observations can be interpreted in terms of the effects of caffeine on DNA replication in treated cells.     

Novel angular furoquinolinones bearing flexible chain as antitumor agent: design, synthesis, cytotoxic evaluation, and DNA-binding studies

A series of novel N-substituted angular furoquinolinone derivatives were synthesized and evaluated for their antitumor activities against QGY, K562, HeLa, P388, and A549 cell lines in vitro. The derivatives bearing basic amino side chain showed an improved antitumor activity. Compound 5h N-(2-dimethylamino-ethyl)-2-(4,8,9-trimethyl-2-oxo-2H-furo[2,3-h]quinolin-1-yl)-acetamide exhibited the highest activities against P388 and A549 cell lines, which are evidenced by the IC(50) values that are four to five fold lower than that for unsubstituted parent compound. DNA-binding experiments suggested that these derivatives bind to DNA through intercalation.     

Antifungal and cytotoxic effects of cyanein derivatives

The effects of cyanein, tetrahydrocyanein and diacetyl-O-cyanein on the growth and morphology of fungi and HeLa cells were studied. The change of cyanein structure decreased its cytotoxic effect (HeLa cell) to approx. a half and the antifungal effect up to 100 times (Saccharomyces cerevisiae andEremothecium ashbyi). Cyanein caused characteristic changes in morphology ofBotrytis cinerea (“bulging effect”, branching of hyphae) andPaecilomyces viridis (branching of hyphase, yeast-like growth). Except for flexuose ofPaecilomyces viridis hyphae caused by diacetyl-O-cyanein the cyanein derivatives did not induce the above mentioned morphologic changes.