Physicochemical properties, cytotoxic activity and topoisomerase II inhibition of 2,3-diaza-anthracenediones.

The physicochemical, cytotoxic and pharmacological properties of 2,3-diaza-anthracenedione derivatives were examined to gain insight into the structure-activity relationships in this class of compounds. Spectrophotometric, chiroptical and voltammetric measurements were performed, along with cell cytotoxicity, alkaline elution, topoisomerase II-mediated DNA cleavage and cellular drug-uptake determination. In comparison with classic anthracenediones such as mitoxantrone and ametantrone, the aza derivatives were characterized by less negative reduction potentials, lower affinity for DNA and modified geometry of intercalation.

Role of apoptosis and apoptosis-related proteins in the cisplatin-resistant phenotype of human tumor cell lines.

Since apoptosis is the primary mode of cell death induced by cisplatin, the role of apoptosis and apoptosis-related gene products in cisplatin resistance was investigated in four human cisplatin-resistant cell lines of different tumour type. A common feature of the resistant sublines was a reduced susceptibility to drug-induced apoptosis compared to parental sensitive lines. Loss of wild-type p53 function was not a general event associated with the development of drug resistance.

Drug sensitivity and sequence specificity of human recombinant DNA topoisomerases IIalpha (p170) and IIbeta (p180).

Effective anticancer agents, such as epipodophyllotoxins and anthracyclines, exert their antitumor activity through stabilization of cleavable topoisomerase II/DNA complexes, which may result in DNA breakage on detergent addition. Two isozymes (alpha and beta) of DNA topoisomerase II are present in human cells; however, their roles as drug targets have not been completely defined. We determined the in vitro isoenzyme sensitivities to VM-26 (teniposide) and 4-demethoxy-3'-deamino-3'-hydroxy-4'-epi-doxorubicin (an anthracycline analog) and established the sequence selectivity of isoenzyme-mediated DNA cleavage.

Gamma-glutamyltranspeptidase activity in human ovarian carcinoma.

Gamma-glutamyltranspeptidase (GGT) is a cell membrane enzyme involved in the hydrolysis and uptake of extracellular glutathione. Histochemically detectable GGT has been shown in several human neoplasms. However, few studies have addressed the quantitative biochemical assessment of GGT activity in human tumors, and the importance of GGT activity in human tumor biology remains to be elucidated.

Biochemical and pharmacological activity of novel 8-fluoroanthracyclines: influence of stereochemistry and conformation.

In an attempt to better understand the role of the cyclohexene ring (ring A) in the biochemical and pharmacological properties of anthracyclines related to doxorubicin and daunorubicin, we investigated the effects of introduction of a fluorine atom at position 8 of idarubicin (4-demethoxydaunorubicin) on drug molecular conformation and biochemical and pharmacological activities. The study showed that the stereochemistry of the substituent at position 8 influenced the "half-chair" conformation, so that in the (8R)-fluoroepimer the A ring retained the alpha half-chair conformation, which is the most stable for natural compounds (i.e.

Gene expression of DNA topoisomerases I, II alpha and II beta and response to cisplatin-based chemotherapy in advanced ovarian carcinoma.

DNA topoisomerases, nuclear enzymes that regulate DNA topology, are recognized as the primary targets of effective anti-tumor drugs. These enzymes may also have a role in the repair of DNA damage induced by alkylating agents and platinum compounds; therefore, their expression may be a determinant of tumor response to chemotherapy. Our study was undertaken in an attempt to establish a correlation between the enzyme expression and response of ovarian cancer to cisplatin-based chemotherapy.

Modulation of melphalan cytotoxic activity in human melanoma cell lines.

The aim of the present study was to potentiate the cytotoxic effects of melphalan through pharmacological and physical modulators. The combination of the cytotoxic agent with ethacrynic acid, a glutathione-S-transferase pi (GST pi) inhibitor, or topotecan, a topoisomerase I inhibitor, or mild hyperthermia was investigated. The selected cell lines exhibited variable levels of expression of GST pi, DNA topoisomerase I and heat-shock proteins.

Interaction of ionizing radiation with topotecan in two human tumor cell lines.

The effect of topotecan, a topoisomerase I inhibitor, on ionizing radiation-induced cytotoxicity was studied in 2 human tumor cell lines characterized by a different expression of the target enzyme. The cytotoxicity of topotecan alone or in combination with radiation was assessed in exponentially growing non-small-cell lung cancer (H460) and glioblastoma (GBM) cells using the colony-forming assay. An isobologram method was used to evaluate the treatment interaction.

Drug-specific sites of topoisomerase II DNA cleavage in Drosophila chromatin: heterogeneous localization and reversibility.

DNA cleavage stimulated by different topoisomerase II inhibitors shows in vitro a characteristic sequence specificity. Since chromatin structure and genome organization are expected to influence drug-enzyme interactions and repair of drug-induced DNA lesions, we investigated topoisomerase II DNA cleavage sites stimulated by teniposide (VM-26), 4-demethoxy-3'-deamino-3'-hydroxy-4'-epi-doxorubicin (dh-EPI, a doxorubicin derivative), 4'-(9-acridinylamino)-methanesulfon-m-anisidide, and amonafide in the histone gene locus and satellite III DNA of Drosophila cells with Southern blottings and genomic sequencing by primer extension. VM-26 stimulated cleavage in the satellite III DNA, whereas the other studied drugs did not.

Biophysical and biological evaluation of porphyrin-bisacridine conjugates.

Two novel porphyrin-bisacridine conjugates (1 and 2) were designed as bifunctional antitumour agents to combine the DNA-binding character of the acridines and the photosensitizing capacity of porphyrin, and have been subjected to biophysical and biological evaluation. The interactions of the conjugates with calf thymus DNA were evaluated using viscometric, spectrophotometric and stopped-flow sodium dodecyl sulphate (SDS) sequestration methods. Both conjugates acted as bis-intercalators via the two acridine chromophores and displayed a longer residence time on DNA relative to the parent acridine ligand.

A comparative study of p53 gene mutations, protein accumulation, and response to cisplatin-based chemotherapy in advanced ovarian carcinoma.

The p53 protein is a multifunctional transcriptional regulator involved in cellular response to DNA damage and has been implicated as a putative determinant of sensitivity of tumor cells to cytotoxic agents. Since the p53 gene becomes inactivated in over one-half of advanced ovarian carcinoma, in this study we have examined the relationships between p53 gene alterations, p53 immunoreactivity, and response to cisplatin-based chemotherapy in ovarian cancer patients. All patients had advanced (FIGO stage III or IV) ovarian carcinoma and, with one exception, were untreated at the time of collection of tumor specimens.

Induction of apoptosis by fenretinide (4HPR) in human ovarian carcinoma cells and its association with retinoic acid receptor expression.

We previously reported that fenretinide (4HPR) is effective against a human ovarian carcinoma xenografted in nude mice. The effects of 4HPR on ovarian tumors have been further studied in in vitro ovarian carcinoma cell lines A2780, IGROV-I, SW626 and OVCA432. A2780 was the most sensitive line: 50% growth inhibition was obtained after 3 days of exposure to 1 microM 4HPR, a pharmacologically achievable concentration, whereas approx.

Association between cisplatin resistance and mutation of p53 gene and reduced bax expression in ovarian carcinoma cell systems.

P53 status may be a determinant of chemosensitivity of tumor cells; however, its involvement in cellular resistance to cisplatin remains uncertain. To investigate the relationships between p53 and the development of resistance to cisplatin, the p53 gene status was studied in ovarian carcinoma cell systems which included two cisplatin-resistant variants (IGROV-1/Pt 0.5 and IGROV-1/Pt 1) selected in vitro after prolonged drug exposure of the cisplatin-sensitive parental IGROV-1 cell line.

Position-specific effects of base mismatch on mammalian topoisomerase II DNA cleaving activity.

To further define the nucleic acid determinants of DNA site recognition by mammalian topoisomerase II, base mismatch effects on the enzyme DNA cleavage activity were determined in a 36-bp synthetic oligonucleotide corresponding to SV40 DNA. DNA cleavage sites induced by topoisomerase II without or with the antitumor drugs teniposide, idarubicin, or amsacrine were mapped using sequencing gels. Selected mismatches were studied, and always one of the two strands had the wild-type sequence.

Efficacy of lonidamine combined with different DNA-damaging agents in the treatment of the MX-1 tumor xenograft.

Lonidamine is an antitumor agent with a peculiar mechanism of action, since it differentially impairs the energy metabolism of normal and neoplastic cells. We investigated the effects of lonidamine on the activity of DNA-damaging antitumor agents against the MX-1 human breast carcinoma xenograft. Athymic mice bearing measurable s.

Spontaneous lung metastases in a human lung tumor xenograft: a new experimental model.

The cell line NIH-H460, derived from a human large-cell carcinoma of the lung, because metastatic in the lung of athymic mice after S.C. injection.

Differential expression of DNA topoisomerases in non-small cell lung cancer and normal lung.

Unlabelled: DNA topoisomerases are ubiquitous nuclear enzymes, and important targets of cancer chemotherapy. Expression of topoisomerase genes is often correlated with in vitro chemosensitivity. We investigated the expression of the topoisomerase genes in normal lung and non-small cell lung cancer.

MRP gene overexpression in a human doxorubicin-resistant SCLC cell line: alterations in cellular pharmacokinetics and in pattern of cross-resistance.

The development of non-P-glycoprotein-mediated multi-drug resistance is a frequent event among lung-cancer cell lines. In an attempt to understand the underlying mechanisms of this phenotype, we have selected a multi-drug-resistant subline (POGB/DX) in vitro for doxorubicin resistance. The original cell line (POGB) was established in vitro from a non-treated patient with a small-cell lung cancer.

Mechanism of action of DNA topoisomerase inhibitors.

DNA topoisomerases are enzymes that regulate DNA topology and are essential for the integrity of the genetic material during transcription, replication and recombination processes. Inhibitors of the mammalian enzymes are widely used antitumor drugs. They stabilize topoisomerase-DNA cleavable complexes by hindering the DNA relegating step of the catalytic reaction, thus resulting in DNA cleavage stimulation.

Synthesis of alkyl chain-modified ether lipids and evaluation of their in vitro cytotoxicity.

A series of alkyl lysophospholipid (ALP) analogs of ET-18-OCH3 (1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine) containing modifications in the long C-1 chain has been synthesized and evaluated in human tumor cell line cytotoxicity assays. The compounds have also been evaluated in platelet activating factor (PAF) receptor agonism and hemolysis tests. Two modifications have been studied, introduction of a carbonyl group at different positions of the C-1 chain and branching of this chain, in some compounds with incorporation of a phenyl group.

Successful local regional therapy with topotecan of intraperitoneally growing human ovarian carcinoma xenografts.

The therapeutic effects of intraperitoneal topotecan, a water-soluble camptothecin analogue, were investigated in two models of human ovarian carcinoma xenografted intraperitoneally into nude mice: the IGROV-1 tumour, which originated from an untreated patient, and the A2780 tumour, selected for resistance in vitro to cisplatin (A2780DDP). In IGROV-1 tumour-bearing mice, the optimal dose (10 mg kg-1) of topotecan, given intraperitioneally every 4 days for four occasions markedly increased survival time over control mice (300 T/C%) and cured 4/9 mice, and such effects were not achieved by any of the clinically available drugs tested, i.e.

The role of the glutathione-dependent system in tumor sensitivity to cisplatin: a study of human tumor xenografts.

Background: Glutathione, the most important intracellular thiol, has been implicated in modulating tumor cell sensitivity to alkylating agents and cisplatin. However, the role of the glutathione-dependent detoxification system in mediating cisplatin resistance of human tumors remains unclear.

Design: Glutathione content and related enzyme activities were assessed in a series of human tumor xenografts representative of responsive (i.

Base sequence determinants of amonafide stimulation of topoisomerase II DNA cleavage.

A number of antitumor drugs including naphthalimides, a new class of intercalating agents, interfere with the DNA breakage-reunion activity of mammalian DNA topoisomerase II resulting in DNA cleavage stimulation. In this work, the sequence specificity of a lead compound of this series, amonafide, in stimulating DNA cleavage by murine topoisomerase II has been studied. Amonafide-stimulated cleavage intensity patterns were markedly different from those of other antitumor drugs by using pBR322 and SV40 DNAs.