Novel di- and tetracarboxylatoplatinum(IV) complexes. Synthesis, characterization, cytotoxic activity, and DNA platination

Octahedrally configured diaminedichloro- and diamineoxalatoplatinum(IV) complexes with axial hydroxo ligands were carboxylated with succinic or glutaric anhydride. The free, uncoordinated carboxylic acid groups were further derivatized with amines and alcohols to the respective amides and esters and characterized in detail by elemental analysis, mass spectrometry, and multinuclear (1H, 13C, 15N, and 195Pt) NMR spectroscopy. Cytotoxicity of the complexes was studied in four human cancer cell lines derived from ovarian carcinoma (CH1, SK-OV-3), cervical carcinoma (HeLa), and colon carcinoma (SW480) by means of the MTT assay. Structure-activity relationships revealed a low activity for platinum complexes with underivatized carboxylic acid moieties and amide derivatives displaying the hydroxyethylamino residue. Within the series of amides, cyclopentylamino analogues were equipped with the highest cytotoxic potential. However, ester derivatives yielded IC50 values mostly in the low micromolar range and comparable to those of cisplatin. DNA platination studies of selected complexes revealed a high DNA platination capacity in parallel to a high cytotoxic potential and vice versa.     

Synthesis and Cytotoxic Activity of Novel Amidine Analogues of Bis(2‐chloroethyl)amine

Novel nitrogen mustard agents 7 – 12 involving 4‐(N,N‐bis(2‐chloroethyl)aminophenyl)propylamine linked to a 5‐(4‐N‐alkylamidinophenyl)‐2‐furancarboxylic acid moiety by the formation of an amide bond have been synthesized, characterized, and evaluated for their in‐vitro cytotoxic activity against MDA‐MB‐231 and MCF‐7 human breast cancer cells. Evaluation of the cytotoxicity of 7 – 12 employing a MTT assay and inhibition of [³H]thymidine incorporation into DNA demonstrated that these compounds exhibit remarkable cytotoxic effects in comparison with 4‐[bis(2‐chloroethyl)amino]benzenebutanoic acid. Compounds 7 and 9 , which possess a cationic amidine and 4,5‐dihydro‐1H‐imidazol function moiety are approximately ten times more potent than 4‐[bis(2‐chloroethyl)amino]benzenebutanoic acid. The new compounds were evaluated as DNA topoisomerase II inhibitors. The cytotoxicity of the compounds 7 – 12 correlates with their DNA‐binding affinities and their relative potency as topoisomerase II inhibitors.     

Studies on the mechanism of action of quinone antitumor agents

The presence of a quinone group in the structure of a compound has been shown to produce cell kill and DNA strand breaks by a mechanism involving free radicals and active oxygen species. The ability of the compound to bind to DNA appeared to increase the DNA damage induced and the cytotoxic activity. A new series of model compounds has been used to investigate further the role of the quinone group in the mechanism of action of quinone antitumor agents. Bis(dimethylamino)benzoquinone, which contains a quinone group, produced significant cell kill of L5178Y lymphoblasts and induced concentration-dependent single-strand and double-strand breaks in the DNA of these cells. Benzoquinone dimustard, which possesses a quinone moiety and active alkylating groups, was approximately 2500 times more cycotoxic to L5178Y cells than was bis(dimethylamino)benzoquinone and was approximately 200-fold more active in inducing DNA double-strand breaks than was the quinone agent. Benzoquinone dimustard induced no apparent DNA single-strand breaks, but produced significant DNA cross-linking, a process which interferes with the assay for single-strand breaks. The cell kill produced by both quinone agents was inhibited by catalase, but not by superoxide dismutase. The cytotoxic activity of bis(dimethylamino)benzoquinone and two other quinone model compounds, hydrolyzed benzoquinone mustard and benzoquinone mustard, appeared to correlate with the induction of DNA strand breaks, while there appeared to be no correlation between cell kill and DNA double-strand breaks induced by benzoquinone dimustard. However, the cytotoxicity of benzoquinone dimustard appeared to be related to the cross-linking activity of this agent. These studies have provided additional evidence that the presence of a quinone group in the structure of a compound can result in significant cell kill by a mechanism that appears to involve active oxygen species. Quinone containing agents can induce DNA strand breaks, and this effect is enhanced when the agent is able to bind to DNA. The induction of DNA strand breaks appeared to correlate with cytotoxic activity for bis(dimethylamino)benzoquinone, hydrolyzed benzoquinone mustard and benzoquinone mustard, but not for benzoquinone dimustard, suggesting that the contribution of quinone-induced strand breaks to the overall cytotoxicity of an agent may vary considerably.     

Substituent Effects on Cytotoxic Activity,Spectroscopic Property,and DNA Binding Property of Naphthalimide Derivatives

A series of novel naphthalimide derivatives NI 1‐5 containing piperazine moieties (N‐(2‐hydroxyethyl)piperazine and 1‐piperazinepropanol) and piperidine moieties (4‐piperidinemethanol, 4‐hydroxypiperidine and 4‐piperidineethanol) have been synthesized and evaluated for their cytotoxic activity, spectroscopic property, and DNA binding behaviors. It was found that substituents at the 4‐position remarkably influence the various activities of this series of compound. Compounds NI 3‐5 modified with piperidines exhibited potent cytotoxic activities against Hela, SGC‐7901, and A549 cells with the IC₅₀ values from 0.73 μm to 6.80 μm , which are better than NI 1‐2 functionalized with piperazines. Compounds NI 1‐2 showed higher binding capacity with Ct‐DNA than compounds NI 3‐5 based on studies of UV–vis, fluorescence and CD spectra. Furthermore, compounds NI 3‐5 , as DNA intercalators, showed fluorescence enhancement upon binding with Ct‐DNA. More interestingly, fluorescence imaging studies of compound NI 4 with A549 cells showed that the fluorescence predominantly appeared in the cytoplasm. These results provided a potential application of NI 3‐5 as anticancer therapeutic and cancer cell imaging agents.     

Anthracene-9,10-diones as potential anticancer agents. Synthesis, DNA-binding, and biological studies on a series of 2,6-disubstituted derivatives.

A series of 2,6-bis(omega-aminoalkanamido)anthracene-9,10-diones (9,10-anthraquinones), of general formula Ar(NHCO(CH2)nNR2)2, where Ar = anthracene-9,10-dione and n = 1 or 2, have been synthesized by treatment of the corresponding bis(omega-haloalkanamido) derivatives with appropriate secondary amines. The DNA-binding properties of these compounds were evaluated by thermal denaturation studies, unwinding of closed-circular DNA, determination of association constants in solution, and examined by molecular modeling. A representative compound in the series has been examined by X-ray crystallography. In vitro cytotoxicity data is reported for the compounds and some indications of structure-activity relationships have been discerned. In particular, those compounds with two methylene links (n = 2) in each side chain separating the amide and terminal amine moieties have superior activity and, in general, enhanced DNA binding characteristics. It is postulated that the mode of reversible binding of these compounds to DNA involves the side chains occupying both major and minor grooves and, further, that this may confer cytotoxic properties which are distinct from those of previously reported anthracene-9,10-dione cytotoxins.     

Cytotoxic activities of some mono and bis Mannich bases derived from acetophenone in brine shrimp bioassay

Some mono Mannich bases (1-phenyl-3-amino-1-propanone salts) and bis Mannich bases (1-phenyl-3-amino-2-amino-methyl-1-propanone salts) derived from acetophenone and a few representative quaternary derivatives were synthesised and their cytotoxicity was tested using the brine shrimp bioassay. This assay may serve as an intermediate test before further in vivo animal experiments in large scale, since brine shrimp nauplii as whole organisms were used in this test. Mono Mannich bases were generally more cytotoxic than their corresponding bis Mannich bases. Mannich bases synthesised were cytotoxic in both brine shrimp bioassay in this study and cell culture tests using Jurkat and Renca cells in a previous study. However, the order of the cytotoxic potency of the compounds were reverse, which may result from faster deamination of bis derivatives than optimal level, and different species and test media used in the two test systems. Faster deamination of bis derivatives might have led to elimination of active metabolites before reaching its target. The cytotoxicity of the compounds might have been altered by amino acids and proteins present in cell culture medium but not in sea water used in brine shrimp bioassay affecting their transport through the cell membrane and metabolism in the cell by binding with the compounds. With higher cytotoxic activity compared with 5-fluorouracil (CAS 51-21-8) in brine shrimp bioassay, mono Mannich base 1 and its quaternary derivative 4 and quaternary bis derivative 8 seem to be candidate compounds for further drug design.     

Rational design, synthesis, and biological evaluation of bis(pyrimido[5,6,1-de]acridines) and bis(pyrazolo[3,4,5-kl]acridine-5-carboxamides) as new anticancer agents

The good results obtained with pyrimido[5,6,1-de]acridines 7 and with pyrazolo[3,4,5-kl]acridinecarboxamides 8 prompted us to the synthesis of two new series of bis acridine derivatives: the bis(pyrimidoacridines) 5 and the bis(pyrazoloacridinecarboxamides) 6. Compounds 5 can be regarded also as cyclized derivatives of bis(acridine-4-carboxamides) 3 and compounds 6 as cyclized derivatives of bis(acridine-4-carboxamides) 4. The noncovalent DNA-binding properties of these compounds have been examined using fluorometric techniques. The results indicate that (i) the target compounds are excellent DNA ligands; (ii) the bis derivatives 5 and 6 are more DNA-affinic than corresponding monomers 7 and 8; (iii) the new bis 5 and 6 result always less efficient in binding than related bis(acridine-4-carboxamides) 3 and 4; and (iv) in both series 5 and 6 a clear, remarkable in some cases, preference for binding to AT rich duplexes can be noted. In vitro cytotoxic potency of these derivatives toward the human colon adenocarcinoma cell line (HT29) is described and compared to that of reference drugs. Structure-activity relationships are discussed. We could identify six very potent cytotoxic compounds for further in vitro studies: a cytotoxic screening against six human cancer cell lines and the National Cancer Institute (NCI) screening on 60 human tumor cell lines. Finally, compound 6a was selected for evaluation in a NCI in vivo hollow fiber assay.     

Synthesis and antitumor evaluation of bis aza-anthracene-9,10-diones and bis aza-anthrapyrazole-6-ones

The good results obtained as potential antitumor drugs with aza-anthracenediones and aza-anthrapyrazoles, e.g. pixantrone, 1a, and 1b (Chart 1), prompted us to design and synthesize a series of symmetrical bis derivatives, compounds 7-10 (Chart 1). These compounds are dimers of different aza-anthracenedione and aza-anthrapyrazolone monomers connected by the linker found to be the most appropriate among potential bis intercalators synthesized by us. The DNA-binding properties of bis derivatives 7 and 8 have been examined using fluorometric techniques: these target compounds are excellent DNA ligands, with a clear binding site preference for AT-rich duplexes. In vitro cytotoxic activity of all target compounds 7-10 and of reference compound pixantrone toward human cancer adenocarcinoma cell line HT29 is also described. Two selected compounds have been investigated for their capacity of inducing early apoptosis.     

Potential new antitumor agents from an innovative combination of demethylcantharidin, a modified traditional Chinese medicine, with a platinum moiety

A combination of demethylcantharidin, a modified component of a traditional Chinese medicine (TCM), with a platinum moiety has produced a series of TCM-based platinum compounds [Pt(C(8)H(8)O(5))(NH(2)R)(2)] 1-5, which demonstrate selective cytotoxicity toward SK-Hep-1 (human liver) cell line, and circumvention of cross-resistance. The inclusion of demethylcantharidin rendered the compounds highly active as protein phosphatase (PP2A) inhibitors. The new TCM-Pt compounds may possess a novel dual mechanism of antitumor action: inhibition of PP2A and platination of DNA.     

Syntheses and stability studies of some Mannich bases of acetophenones and evaluation of their cytotoxicity against Jurkat cells

Mannich bases, namely 1-aryl-3-dimethylamino-1-propanone hydrochlorides (Ia-f) as mono-Mannich bases (series I), bis(beta-aroylethyl)ethylamine hydrochlorides (IIa, IIb, IId, IIe) as bis-Mannich bases (series II), 3-aroyl-4-aryl-1-ethyl-4-piperidinol hydrochlorides (series III), which are structural isomers of bis derivatives and some representative quaternary salts (Ig, IIIf, IIIg), were synthesized to investigate the effect of chemical structure and ring substituents on cytotoxic activity in Jurkat cells. Stability studies of some representative compounds have also been realised. Compounds IIb, IId, IIe, and IIIe were reported for the first time. Id-g, IIa, IId, IIe, IIIf,g were 1.25-6.55 times more potent than 5-fluorouracil (CAS 51-21-8). However, the cytotoxic activity of the most potent compounds. Ig and IIIf, were one fifth of that of melphalan (CAS 148-82-3). The formation of compound IV during the stability studies of Ig, IIa, and IIIf suggested that they may be thiol alkylators. Bis-Mannich base IIa in nonsubstituted derivatives, piperidinol derivative IIIb in methyl substituted compounds, mono derivative Id in chloro substituted compounds were the most potent compounds when the cytotoxicity of the compound series which have the same substituents in benzene ring are compared. Replacement of the benzene with thiophene improved the cytotoxicity in both series I and II. Quaternization procedure also increased the cytotoxicity in both series I and III. Quaternary derivatives seem to be promising compounds for further studies to develop new anticancer drugs.     

Celecoxib antagonizes the cytotoxicity of cisplatin in human esophageal squamous cell carcinoma cells by reducing intracellular cisplatin accumulation

High cyclooxygenase 2 (COX-2) expression has been reported to be clinically associated with reduced cisplatin-based therapy efficacy in esophageal cancer. However, the benefit of including COX-2-selective inhibitors in therapeutic regimens remains uncertain. Thus, we sought to determine the effects of COX inhibitors on the cytotoxicity of cisplatin and to further explore the mechanism involved in human esophageal squamous cell carcinoma cells. Among the four tested COX inhibitors [celecoxib, 4-[5-(4-chlorophenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]benzenesulfonamide (SC-236), nimesulide, and indomethacin], all of which substantially suppressed prostaglandin E(2) production to a similar extent; only the COX-2-selective inhibitors celecoxib and SC-236 antagonized cisplatin-induced cytotoxicity and apoptosis in both cisplatin-resistant cells and their wild-type counterparts. Knockdown of COX-2 by small interference RNA failed to mimic the antagonizing effects of celecoxib and SC-236, implying that their action is COX-2-independent. Further mechanistic analysis revealed that the antagonizing effect of celecoxib and SC-236 on cytotoxic action of cisplatin was associated with decreased whole-cell cisplatin accumulation and DNA platination. Reduced influx, accompanied by the reduction of protein level of copper transporter 1, accounts for decreased intracellular cisplatin accumulation. In addition, combined treatment did not elicit greater antitumor activity than cisplatin or celecoxib monotherapy in vivo in an esophageal cancer xenograft model. Collectively, these data demonstrate that celecoxib antagonizes the cytotoxicity of cisplatin by decreasing intracellular cisplatin and DNA platination. The combination treatment also shows no beneficial effect compared with cisplatin or celecoxib monotherapy in vivo. Therefore, current clinical trials with celecoxib in combination with cisplatin should be approached with caution.     

海洋真菌Aspergillus sp.HH-3中1个新的抗肿瘤硫代二酮哌嗪类化合物

目的 研究海泥真菌Aspergillus sp.HH-3的次级代谢产物及其抗肿瘤活性。方法 使用硅胶色谱柱、LH-20凝胶色谱等对代谢粗提物进行分离纯化;运用核磁共振、质谱等方法并结合文献报道数据确定化合物的结构;采用CCK-8法评价化合物对三种肿瘤细胞(A549、HepG2、Hela)的抑制活性。结果 从Aspergillus sp.HH-3中分离获得六个化合物,包括一个新的硫代二酮哌嗪类化合物aspersin(1)与五个已知化合物dehydroxymethylbis(dethio)bis(methylthio)gliotoxin(2)、trypacidin(3)、monomethylsubchrin(4)、verruculogen(5)及chaetominine(6)。化合物1、2和6显示有一定的肿瘤细胞抑制活性。结论 化合物1为新的硫代二酮哌嗪类化合物;化合物1、2和4具有肿瘤细胞毒活性。     

The formation of DNA interstrand cross-links by a novel bis-[Pt2Cl4(diminazene aceturate)2]Cl4.4H2O complex inhibits the B to Z transition

We present data demonstrating that the cytotoxic compound [Pt2Cl4(diminazene aceturate)2]Cl4.4H2O (Pt-berenil) circumvents cisplatin resistance in ovarian carcinoma cells. The analysis of the interaction of Pt-berenil with linear and supercoiled DNA indicates that this compound induces the formation of a large number of covalent interstrand cross-links on DNA and that this number is significantly higher than that produced by cis-diamminedichloroplatinum(II) (cis-DDP). Renaturation experiments, interstrand cross-link assays, and electron microscopy indicate that the kinetics of DNA interstrand cross-link formation caused by Pt-berenil binding is faster than that caused by cis-DDP at similar levels of platinum bound to DNA. Furthermore, the number of DNA interstrand cross-links in Pt-berenil-DNA complexes is influenced by supercoiling. Circular dichroism experiments show that Pt-berenil strongly inhibits the B-DNA-to-Z-DNA transition of poly(dG-m5 dC). poly(dG-m5dC) at salt concentrations (3 mM MgCl2) at which the native methylated polynucleotide readily adopts the Z-DNA conformation, which suggests that the induction of interstrand cross-links by Pt-berenil inhibits the Z-DNA transition. On the basis of these results, we propose that bis(platinum) compounds with structure similar to Pt-berenil may act as blockers of DNA conformational changes and may also display activity in cisplatin-resistant cells.     

2,2,2-Trichloro-N-({2-[2-(dimethylamino)ethyl]-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin- 5-yl}carbamoyl)acetamide (UNBS3157), a novel nonhematotoxic naphthalimide derivative with potent antitumor activity

Amonafide (1), a naphthalimide which binds to DNA by intercalation and poisons topoisomerase IIalpha, has demonstrated activity in phase II breast cancer trials, but has failed thus far to enter clinical phase III because of dose-limiting bone marrow toxicity. Compound 17 (one of 41 new compounds synthesized) is a novel anticancer naphthalimide with a distinct mechanism of action, notably inducing autophagy and senescence in cancer cells. Compound 17 (2,2,2-trichloro-N-({2-[2-(dimethylamino)ethyl]-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-5-yl}carbamoyl)acetamide (UNBS3157)) was found to have a 3-4-fold higher maximum tolerated dose compared to amonafide and not to provoke hematotoxicity in mice at doses that display significant antitumor effects. Furthermore, 17 has shown itself to be superior to amonafide in vivo in models of (i) L1210 murine leukemia, (ii) MXT-HI murine mammary adenocarcinoma, and (iii) orthotopic models of human A549 NSCLC and BxPC3 pancreatic cancer. Compound 17, therefore, merits further investigation as a potential anticancer agent.     

Interaction of 2-halogenated dATP analogs (F, Cl, and Br) with human DNA polymerases, DNA primase, and ribonucleotide reductase

Recently, 2-halogenated deoxyadenosine analogs (F, Cl, and Br) have been shown to have antitumor activity. These analogs are phosphorylated by cells and are believed to exert their cytotoxic action at the nucleoside triphosphate level. In this work the interaction of these nucleoside triphosphate analogs with potential targets, such as DNA polymerase alpha, beta, and gamma, DNA primase, and ribonucleotide reductase was examined in detail. All of these compounds competitively inhibited the incorporation of dAMP into DNA by DNA polymerase alpha, beta, or gamma. F-dATP was able to completely substitute for dATP using DNA polymerase alpha and gamma, but not with DNA polymerase beta. Cl-dATP and Br-dATP substituted poorly for dATP using DNA polymerase alpha and beta. Extension of a 32P-labeled primer by DNA polymerase alpha, beta, or gamma on a single-stranded M13 template showed that these compounds were incorporated into the 3' end of the growing DNA chain and that elongation beyond the incorporated analogs was significantly retarded for Cl-dATP and Br-dATP using either DNA polymerase alpha or beta. DNA primase using poly(dC) as template was inhibited by these compounds at a concentration 4 to 5 times greater than that required for 2-F-araATP. The 2-halogenated dATP analogs were potent inhibitors of ADP reduction by ribonucleotide reductase. In conclusion, the cytotoxic action of 2-Cl-deoxyadenosine and 2-Br-deoxyadenosine may partially be mediated through the mechanism of "self-potentiation," by depression of the deoxynucleoside triphosphate pools due to inhibition of ribonucleotide reductase, which would facilitate their incorporation into DNA and result in the inhibition of DNA synthesis.     

Toxic effects of bis(thiosemicarbazone) compounds and its palladium(II) complexes on herpes simplex virus growth

Here, we present data on the activity of benzyl bis(thiosemicarbazone); 3,5-diacyl-1,2,4-triazole bis(4-methylthiosemicarbazone) and their Pd(II) complexes against the replication of wild type and of acyclovir (ACV)-resistant, herpes simplex virus type 1 (HSV 1) and type 2 (HSV 2) strains. The data were compared to those under the action of acyclovir. The testing of cytotoxic activity suggests that these compounds may be endowed with important antiviral properties. It is interesting to note that the Pd(II)-benzyl bis(thiosemicarbazone) complex, 2, exhibits a significant activity against acyclovir-resistant viruses R-100 (HSV 1) and PU (HSV 2) with an in vitro selectivity index (SI) of 8.0 vs. 0.01 for acyclovir. This complex also negatively influenced the expression of key structural HSV 1 proteins (VP23, gH and gG/gD), thus suppressing simultaneously virus entry, transactivation of virus genome, capsid assembly, and cell-to-cell spread of infectious HSV progeny.     

Apoptosis-inducing oxovanadium(IV) complexes of 1,10-phenanthroline against human ovarian cancer

In a systematic effort to identify a potent anticancer agent against human ovarian cancer, we synthesized 15 oxovanadium(IV) complexes, and examined their cytotoxic activity against human ovarian cancer cell lines PA-1, SKOV-3, ES-2 and OVCAR-3 using a MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyletetrazolium bromide]-based assay. The apoptosis-inducing ability of the oxovanadium compounds was evaluated by the two-color flow cytometric terminal deoxynucleotidyl transferase-based assay that labels 3'-hydroxyl ends of fragmented DNA (TUNEL) assay and confocal laser scanning microscopy. Notably, all eight oxovanadium complexes of 1,10 phenanthroline exhibited significant cytotoxicity and induced apoptosis within 24 h. The mono-chelated, VO(NO2-phen) and bis-chelated, VO(Me2-phen)2, VO(Cl-phen)2 and VO(NO2-phen)2 complexes were the most potent oxovanadium compounds, and killed target cancer cells at low micromolar concentrations. The marked differences in the cytotoxic activity of oxovanadium(IV) complexes containing different heterocyclic ancillary ligands suggest that the cytotoxic activity of these compounds is determined by the identity of the five-member bidentate ligands, as well as the nature of the substituents on the heterocyclic aromatic rings. Our results presented herein provide experimental evidence that oxovanadium compounds induce apoptosis in human ovarian cancer cells. The lead compounds, VO(Me2-phen)2 and VO(NO2-phen)2, may be useful in the treatment of ovarian cancer.     

Synthesis of novel fluoro 1,2,3-triazole tagged amino bis(benzothiazole) derivatives,their antimicrobial and anticancer activity

A new series of fluoro 1,2,3-triazole tagged amino bis (benzothiazole) derivatives 8, 9 were prepared starting from 2-amino benzothiazole in four steps via amination, cyclization, alkylation followed by reaction with various azides under sharpless conditions through click chemistry approach. All newly synthesized compounds were screened for their antimicrobial and cytotoxic activity against four human cancer cell lines (U937, THP-1, Colo205, and A549), and promising compounds have been identified.     

Kinetics of cisplatin binding to cellular DNA and modulations by thiol-blocking agents and thiol drugs.

DNA platination by cisplatin (CDDP) was investigated in peripheral blood mononuclear cells and ovarian cancer cells using atomic absorption spectroscopy. Plots showing the amount of platinum (Pt) bound to DNA versus the molar concentration of cisplatin in the incubation medium ([CDDP]) were nonlinear. For [CDDP] < about 5 microM, the amount of Pt bound to DNA increased slowly with added drug. However, for larger [CDDP], the slope of the plot increased significantly. To study the role of thiols in affecting cisplatin binding to DNA, cells were treated with N-ethylmaleimide, which modifies thiol groups, rendering them incapable of binding cisplatin. Analysis using high-pressure liquid chromatography showed that approximately 99% of cellular glutathione was modified by N-ethylmaleimide. A plot of the amount of Pt bound to DNA versus [CDDP] for thiol-blocked cells is linear, with a slope similar to that of unblocked cells at high [CDDP]. Neither S-2-(3 aminopropylamino)ethanethiol (WR-1065) nor mesna, when added at clinically achievable concentrations (i.e., < approximately 300 microM), affected DNA platination. However, DNA platination was totally abolished by millimolar concentrations of the drug thiols (approximately 1.25 mM WR-1065 or approximately 5 mM mesna). Thus, the data show that endogenous thiols intercept cellular cisplatin, but this mechanism is less important at high [CDDP]. Moreover, therapeutic concentrations of drug thiols do not significantly affect DNA platination. A simple model that reproduces the experimental results of the amount of cisplatin binding to DNA as a function of [CDDP], time, and thiol content is proposed. The model takes into account passage of cisplatin and thiols through the cell membrane, binding of cisplatin to cellular thiols, and platination of DNA.     

Cytotoxic, antiviral (in-vitro and in-vivo), immunomodulatory activity and influence on mitotic divisions of three taxol derivatives: 10-deacetyl-baccatin III, methyl (N-benzoyl-(2'R,3'S)-3'-phenylisoserinate) and N-benzoyl-(2'R,3'S)-3'-phenylisoserine

The aim of this study was to evaluate cytotoxic, antiviral (in-vitro and in-vivo) and immunomodulatory activity, as well as the influence on mitotic division, of three taxol derivatives representing modified parts of its molecule: 10-deacetyl-baccatin III, methyl (N-benzoyl-(2'R,3'S)-3'-phenylisoserinate) and N-benzoyl(2'R,3'S)-3'-phenylisoserine. The cytotoxicity of the compounds, assessed by the formazane method, was relatively low, with a 50% cytotoxic concentration (CC50)>500 microg mL-1. Moreover, all tested compounds inhibited Herpes simplex type 1 virus (HSV-1) replication in non-cytotoxic concentrations in-vitro. Selectivity indices were in the range 9.5-46.7. Anti-HSV-1 activity of the compounds may be associated with their influence on mitotic division. All of the compounds decreased the number of cell divisions. Mitotic indices ranged from 40/1000 (4.0%) to 62/1000 (6.2%). One compound, 10-deacetyl-baccatin III, influenced the growth of tumours induced in mice by infection with Moloney murine sarcoma virus. The effect of the tested compounds on T lymphocyte proliferation was evaluated by measurement of the activity of tritiated thymidine incorporated into DNA of dividing cells. One compound, methyl (N-benzoyl-(2'R,3'S)-3'-phenylisoserinate), inhibited T lymphocyte proliferation. This paper demonstrates that modified parts of the taxol molecule possess various types of biological activity in-vitro and in-vivo. Further experiments, focused on revealing their mechanisms of action, are necessary.