Appearance of aberrant mitosis in murine leukemia cells upon combined treatment with low concentrations of cisplatin and teniposide.

The combination of cis-diamminedichloroplatinum (II) (DDP, cisplatin) and topoisomerase II inhibitor teniposide (VM-26) has been shown to exert a synergistic effect in the clinical treatment of cancer. In this study, the combined effect of DDP and VM-26 on the growth and induction of apoptosis in synchronized murine erythroleukemia (MEL) cells, treated at the beginning or in the middle of S-phase of cell cycle, was examined. MEL cells, clone F4 N, were synchronized by a double thymidine block leading to accumulation of 70% of cells at the G1/S boundary. The growth-inhibitory effect of DDP and VM-26 applied alone were stronger in the middle of the S-phase than at the beginning. Morphological analysis showed that the majority of the cells revealed typical signs of apoptosis: nuclei fragmentation and appearance of apoptotic bodies. The combination of both agents at low concentrations had a synergistic effect on cytotoxicity. At higher concentrations the effect was additive. The remainder of the cells were characterized by unbalanced growth, aberrant mitosis and appearance of multinucleated cells. These processes led to delayed cell death. The appearance of aberrant mitosis was more expressed after treatment in the middle of the S-phase. It is likely that as a result of the combined action of cisplatin and VM-26, cells become supersensitive to the ability of topoisomerase II inhibitor to influence mitosis, and this increased sensitivity may contribute to the observed synergism.

Inhibition of UDP-glucuronosyltransferase by 5'-O-amino acid and oligopeptide derivatives of uridine: structure-activity relationships.

The inhibitory effect of a series of 5'-O-amino acid and oligopeptide derivatives of uridine on rat liver UDP-glucuronosyltransferase (UGT) activities was investigated using two assay systems. A quantitative structure-activity relationship (QSAR) study was performed. The compounds include a lipophilic residue linked to the nucleoside by a variable spacer. Moreover, half of the derivatives have two spacers linked to the uridine moiety. Compound 1, a serine derivative of isopropylideneuridine, was found to be the most potent inhibitor of both 4-nitrophenol (4-NP) and phenolphthalein (PPh) glucuronidation, with an I50 of 0.45 mM and 0.22 mM, respectively. Kinetic studies with this substance revealed a mixed type of inhibition towards 4-NP and UDP-glucuronic acid, with apparent Ki values of 150 microM and 120 microM, respectively. The dipeptide derivatives 11-14 exhibited a low activity against 4-NP conjugation. However, a marked suppression of PPh glucuronidation was found with compounds 11 and 13. Generally, compounds with two spacers are more inhibitory against the UGT activities studied. The QSAR analysis outlined the significance of the spacers with a minimum length of 5 atoms and lipophilic residues linked to them for the inhibitory effect of the compounds. The most significant contribution to this effect is given by the six-atom spacer for both 4-NP and PPh substrates. 4-NP converting UGT isoforms seem to respond more specifically to the inhibitors: a five-atom for the first and six-atom for the second spacer enhance binding to both 4-NP and PPh conjugating isoenzymes, while a long second spacer contributes to inhibitor binding to UGT isoforms only converting PPH.

Interaction of histone H1 with cis-platinum modified DNA.

Cis-diamminedichloroplatinum(II) (cis-DDP) is known as an effective anticancer drug. Its therapeutic effect is supposed to be a consequence of the covalent binding to DNA. A number of cellular proteins were found to bind selectively to DNA modified by cis-DDP (but not by its isomer trans-DDP). Here we present our observations on interaction of the linker histone H1 with cis- and trans-DDP modified DNA fragments. The results afford new experimental information about the preferential binding of histone H1 to cis-DDP-distorted DNAs versus trans-DDP modified ones.

Cytotoxicity and antitumor activity of platinum (II) complexes of aromatic and cycloalkanecarboxylic acid hydrazides.

New platinum (II) complexes of cyclohexanecarboxylic acid hydrazide (chcah) were synthesized and characterized by elemental analysis, IR, and 1H NMR spectra. Their inhibitory effects on cell growth and macromolecular synthesis of Friend leukemia cells in culture as well as the in vivo antitumor activity towards L1210 leukemia in mice were compared with those of complexes containing differently substituted aromatic acid hydrazides. Some of the complexes exhibited antineoplastic activity. No correlation between the in vivo cytotoxicity and the in vivo antitumor activity was found. However, there was a relationship between the in vitro macromolecular synthesis inhibition profile and the in vivo antineoplastic effect, similar to that of cisplatin. On the other hand, only agents containing one amine ligand were active in vivo. The substitution of the aromatic ring by a cycloalkane residue increased significantly the antitumor effect, with [Pt(NH3)(chcah)Cl2] being the most active compound in this study.

Inhibition of DNA synthesis in different tissues of L1210-leukemia-bearing mice by new platinum (II) complexes.

The inhibition of [14C]thymidine incorporation into DNA of tumor and normal tissues of L1210-leukemia-bearing mice by single doses of cis-diamminedichloroplatinum (II) (cisplatin, cis-DDP) and two newly synthesized platinum (II) complexes containing as ligands dimethyl aminomethylphosphine oxide (complex I) and methyl bis(aminomethyl)phosphine oxide (complex II) was studied and used as an indication of drug toxicity. All three complexes caused selective inhibition of precursor incorporation in L1210 cells as compared to host tissue cells. cis-DDP caused a complete block of incorporated thymidine in tumor cells during more than 48 h, whereas in intestinal mucosa and bone marrow reverse inhibition was observed. In spleen, liver and kidney the inhibition was about 50% and endured up to 96 h without reversal. Complex I treatment of L1210 cells resulted in an earlier recovery of thymidine incorporation into DNA in comparison with cis-DDP. Towards all other normal tissues compound I was less toxic than cis-DDP. Unlike cis-DDP and complex I, complex II was less active against L1210 cells and most toxic against bone marrow and kidney.

Synthesis and cytotoxic effects of hydroxymethyl-3-pyridyl- and 2-chloro-5-pyridyltriazene derivatives.

3-Hydroxymethyl-3-methyl-1-(3-pyridyl)-triazene (III) and 3-hydroxymethyl-3-methyl-1-(2-chloro-5-pyridyl)-triazene (VI) were synthesized and their cytotoxic effects towards S180 cells compared with those of the corresponding dimethyltriazene and monomethyltriazene derivatives. The hydroxy-methyltriazenes were one to two orders of magnitude more inhibitory than the corresponding dimethyl analogs, as assessed by cell growth, colony forming and macromolecular synthesis assays. Comparable effects were observed with the related monomethyl triazenes indicating that the activity of (III) and (VI) could result, at least in part, from release of monomethyl derivatives. The corresponding dimethyltriazenes were much less toxic to S180 cells and exerted only an unspecific cytotoxic activity at the maximal attainable dose (5 X 10(-3) M). The cytotoxic activities of the tested triazenes were correlated with their chemical half-lives under near physiological conditions (pH 7.5).

Cyanopyrazoles as analogs of purine precursors--II. Effects on macromolecular synthesis and cell cycle progression.

The cytotoxic and cytokinetic effects, and in vitro inhibition of macromolecular synthesis by cyanopyrazoles were studied using Friend leukemia and Ehrlich ascites tumor cells. At concentrations in the range of 2.5 mM to 50 microM analog 3(5)-amino-4-cyano-5(3)-trichloromethylpyrazole (I) was highly cytotoxic and completely inhibited thymidine, uridine and leucine incorporation into macromolecular material. 24 hr incubation of FL cells with cytostatic concentrations of compound I (in the range of 2 to 0.5 microM) resulted in an accumulation of cells in the G2 + M phase. Analogs N-hydroxyethyl-3(5)-amino-4-cyano-5(3)-trichloromethylpyrazole (II) and 3(5)-amino-4-cyanopyrazole (III) were not cytotoxic at concentrations up to 5 mM and did not substantially inhibit precursor incorporation into macromolecules but exhibited a cytostatic activity. These compounds caused a decrease of FL cells in the G2 + M phase and an accumulation in the S phase. Analogs I and II displayed a similar in vivo inhibitory effect on thymidine incorporation into DNA in EAT cells. The results indicate that the cytotoxicity of cyanopyrazoles correlates with their ability to inhibit precursor incorporation into macromolecular material. On the other hand, the cytostatic action of compound I is not coupled to a block of nucleic acid synthesis.

Cyanopyrazoles as analogs of purine precursors--I. Inhibitory effect on purine biosynthesis de novo.

The in vitro inhibition of purine biosynthesis de novo by a series of cyanopyrazoles was studied. At concentration 1 mM trichloromethyl analogs (3(5)-amino-4-cyano-5(3)-trichloromethylpyrazole and N-hydroxyethyl-3(5)-amino-4-cyano-5(3)-trichloromethylpyrazole) were found to inhibit IMP synthesis 80 and 30% respectively. GAR synthesis was inhibited at a lower degree at the same range of concentrations. The compounds demonstrated a similar pattern of inhibition of the last steps, e.g. AICAR formylation and cyclization as found on the whole pathway.