Characterization of alkylating versus intercalating anticancer drug-induced effects on cell survival, cell cycle kinetic and morphonuclear pattern of three neoplastic cells lines growing in vitro

Mutagenic and cytotoxic effect of planifolin: A naphthopyranone dimer isolated from Paepalanthus planifolius

A naphthopyranone dimer, named planifolin, was isolated from a methylene chloride extract of the capitula of Paepalanthus planifolius Koern. The molecule (C(31)H(26)O(10)) appeared to be made up of two monomeric portions, semi-vioxanthin and paepalantine (an isocoumarin), linked by an ether bond, and it may possess several kinds of biological activity that can be related to its polyphenolic structure. Short-term tests that detect genetic damage can afford the information needed to evaluate carcinogenic risks of chemicals to humans. The Ames test, recommended for testing the mutagenicity of chemical compounds with potential pharmacological application, was used in the present study. The mutagenic activity was evaluated in Salmonella typhimurium strains TA100, TA98, TA102 and TA97a and the cytotoxic effect in McCoy cells. The in vitro cytotoxicity of planifolin to McCoy cells, tested in microculture with neutral red, showed a significant cytotoxic index (CI(50)) of 12.83 microg/mL. Planifolin showed mutagenic activity for TA100, TA98 and TA97a. The results indicate that this new naphthopyranone dimer causes mutations by substitution and by addition and deletion of bases in the sequence of DNA. Moreover, its mutagenic potential was increased by metabolic activation.

Monitoring cell cycle distributions in living cells by videomicrofluorometry and discriminant factorial analysis

BACKGROUND

The study of the cell cycle of living cells is often based on quantification of nuclear DNA. These studies may be improved by multifactorial analysis evaluating several parameters for each cell.

METHODS

Single lymphoblastoid living cells were labeled with three fluorescent markers: Hoechst 33342 for nuclear DNA, Rhodamine 123 for mitochondria, and Nile Red for plasma membrane. Numerical image analysis allowed us to obtain, for each cell, morphological parameters (e.g., cell size, nuclear size, and shape) and functional information (e.g., nuclear DNA content, level of mitochondria energetic state, and the amount and properties of the plasma membrane) by fluorescence intensity. These parameters were used in a typological analysis that separated control cells into four groups.

RESULTS

A discriminant factorial analysis (DFA) confirmed the four groups: G0-G1, S, G2+M, and polyploid cells called Gn. These groups were significantly different, with a classification probability of 0.9999; these control cells defined a learning population. Different populations of untreated and adriamycin-treated cells were analyzed as additional individuals within a DFA and were classified into the G0-G1, S, G2+M, and Gn groups by their probability of belonging to each of the groups.

CONCLUSIONS

This approach is particularly efficient when it is used to determine variations in cellular properties and to objectively study cellular populations.

Synthesis and in vitro antitumor activity of an isomer of the marine pyridoacridine alkaloid ascididemin and related compounds

The isomer (9H-quino[4,3,2-de][1,7]phenanthroline-9-one) (2) of the marine alkaloid ascididemin (9H-quino[4,3,2-de][1,10]phenanthroline-9-one) (1) has been synthesized in six steps from 1,4-dimethoxyacridine (10) with an overall yield of 12%. Different related compounds were prepared and tested in vitro at six different concentrations on 12 different human cancer cell lines of various histopathological types (glioblastomas and breast, colon, lung, prostate and bladder cancers). Almost all the compounds present cytotoxic activity of micromolar order.

Synthesis and in vitro antitumor activity of phenanthrolin-7-one derivatives, analogues of the marine pyridoacridine alkaloids ascididemin and meridine: structure-activity relationship

A series of substituted pyrido[4,3,2-de][1,7] or [1,10]-phenanthrolin-7-ones, analogues of the marine pyridoacridines meridine and ascididemin, have been synthesized on the basis of Diels-Alder reactions involving different quinoline-5,8-diones and N,N-aldehyde-dimethylhydrazones. All the compounds were evaluated for in vitro cytotoxic activity against 12 distinct human cancer cell lines. They all exhibit cytotoxic activity with IC(50) values at least of micromolar order.

Synthesis and cytotoxic evaluation of analogues of the marine pyridoacridine amphimedine

4-Substituted-7H-pyrido-[4,3,2-de][1,8] or [1,9]-phenanthroline-7-ones and 9-methyl-1,4-diazanaphtacene-3,10-dione, analogues of the marine pyridoacridine amphimedine were synthesised from isoquinoline-5,8-dione. The first compounds were obtained starting from a Diels-Alder reaction whereas the synthesis of the last compound was initiated by a reaction of condensation with 2-aminoacetophenone. The different tetra- and pentacyclic compounds were evaluated for in vitro cytotoxic activities against six distinct human cancer cell lines. All the compounds exhibit cytotoxic activity with IC(50) values (i.e., the drug concentration inhibiting the mean growth value of the six cell lines by 50%)<10(-7)M for two of them.

Synthesis and in vitro antitumor activity of novel ring D analogues of the marine pyridoacridine ascididemin: structure-activity relationship

Marine compounds with pyridoacridine skeletons are known to exhibit interesting antitumor activities. Ascididemin has already been reported as displaying significant antitumor activities in vitro and has also been found to have a relatively high global toxicity in vivo. We synthesized a series of 16 analogues (among which 11 compounds were different from previously described ones) with the aim of developing new anticancer agents with significantly improved efficacy/tolerability ratios. These compounds were obtained either by total synthesis from 5,8-quinolinedione and substituted 2-aminoacetophenones or by the direct substitution of ascididemin. The different compounds and ascididemin used as the control compound were tested at six different concentrations on 12 different human cancer cell lines of various histopathological types (glioblastomas and breast, colon, lung, prostate, and bladder cancers). The IC(50) value (i.e., the drug concentration inhibiting the mean growth value of the 12 cell lines by 50%) of these compounds ranged over five log concentrations, i.e., between 10 000 and 0.1 nM. For several new chemical entities, the antitumor activity (determined in vitro) and tolerability (determined in vivo) were superior to those of the parent alkaloids, i.e., ascididemin and 2-bromoleptoclinidone.

Schedule-dependent interaction between vinblastine and cisplatin in Ehrlich ascites tumors in mice

Information on the in vivo antitumor efficiency of the combination of Vinca alkaloids in animal tumor models, especially vinblastine (VLB) with cisplatin [cis-diamminedichloroplatinum(II); CDDP] is very limited. Therefore, the aim of our study was to explore whether antitumor schedule dependence exists for the combination of CDDP and VLB on i.p. Ehrlich ascites tumors in mice. Animals were treated 3 days after tumor transplantation with VLB (0.006 mg/kg) or CDDP (0.05 mg/kg) alone, VLB followed by CDDP, and CDDP followed by VLB. The time interval between i.p. injections of the drugs was 24 h. Cell number was measured by counting viable cells using the trypan blue exclusion assay, cell platinum content by electrothermal atomic absorption spectrometry, DNA distribution pattern using flow cytometry, apoptosis by flow-cytometric terminal deoxynucleotidyl transferase dUTP nick-end labeling assay, and cell morphology. Combination of CDDP and VLB resulted in additive interaction when VLB preceded CDDP as determined from cell survival data 24 h after completion of the therapy and in increased platinum content (two times) compared with the same combination in a reverse schedule (CDDP given before VLB), which resulted in antagonism. None of the treatment combinations induced apoptosis. We propose that the observed increase in antitumor effectiveness is mainly due to higher platinum accumulation in tumor cells, which we unambiguously demonstrated by measurement of platinum content in the tumor cells, leading to increased cytotoxicity as well as to cell cycle-dependent effects of VLB and CDDP.

Cellular effects of purvalanol A: a specific inhibitor of cyclin-dependent kinase activities

We have studied the effects of purvalanol A on the cell cycle progression, proliferation and viability. In synchronized cells, purvalanol A induced a reversible arrest the progression in G1 and G2 phase of the cell cycle, but did not prevent the completion of DNA synthesis in S-phase cells. The specificity of action of the drug was supported by the selective inhibition of the phosphorylation of cyclin-dependent kinase (cdk) substrates such as Rb and cyclin E. The cell contents of cyclins D1 and E were lower in cells incubated with purvalanol A compared to controls, but the level of the cdk inhibitory protein p21(WAF1/CIP1) was increased, indicating that the drug did not cause a general inhibition of gene expression. Purvalanol A did not inhibit transcription under cell-free conditions. This compound, however, caused an inhibition of the estradiol-induced expression of an integrated luciferase gene, suggesting that cdk or related enzymes may participate in the regulation of the activity of certain promoters. When exponentially growing cells, both mouse fibroblasts and human cancer cell lines, were incubated with purvalanol A for prolonged periods of time (24 hr), a lasting inhibition of cell proliferation as well as cell death were observed. In contrast, a 24 hr incubation of quiescent (non-transformed) cells with purvalanol A did not prevent their resumption of cell cycle after removal of the drug.

Synthesis and cytotoxicity on sensitive and doxorubicin-resistant cell lines of new pyrrolo[2,1-c][1,4]benzodiazepines related to anthramycin

A new 7,8-methylenedioxy analogue (4) of (+)-porothramycin B (2) and its water-soluble sodium bisulfite derivative (15) have been synthesized in high yields and have been shown to exhibit high cytotoxic activities against several tumor cell lines. The new pyrrolo[2,1-c][1,4]benzodiazepine 4 was as effective against the resistant cell lines as against the doxorubicin-sensitive cell lines tested.

Synthesis and characterization of the antitumor activities of analogues of meridine, a marine pyridoacridine alkaloid

Marine compounds with pyridoacridine skeletons are known to exhibit interesting antitumor activities. Among these compounds, meridine has already been reported as having significant antitumor activities in vitro. We synthesized 24 analogues of meridine substituted on ring A with the aim of obtaining compounds that display significantly higher in vitro antitumor activities than meridine. The 24 compounds and meridine used as a control compound were tested at 6 different concentrations on 12 different human cancer cell lines including various histopathological types (glioblastomas and breast, colon, lung, prostate, and bladder cancers). The IC(50) value (i.e., the drug concentration inhibiting the mean growth value of the 12 cell lines by 50%) of these 25 compounds ranged over 5 log concentrations, i.e., between 10 and 0.0001 microM, with four of the compounds exhibiting a significantly higher in vitro antitumor activity than meridine. These compounds will now be subjected to further pharmacological investigation including in vivo testing on both conventional murine tumors and human tumors grafted onto nude mice.

Determination of the mechanism of action of anticancer drugs by means of the computer-assisted microscope image analysis of Feulgen-stained nuclei

The antitumoral effects of 30 drugs was monitored in vitro on three neoplastic cell lines. These 30 drugs belonged to various pharmacological classes which included alkylating agents, antimetabolites, Vinca alkaloids, topoisomerase II inhibitors, and intercalating agents. The aim of the present work is to use the same methodology to characterize the drug-induced effects at several biological levels. The drug-induced modifications were, therefore, monitored by means of the digital cell image analysis of Feulgen-stained nuclei. This methodology enabled the cell cycle kinetics to be studied. Furthermore, the numerical data quantitatively describing chromatin patterns were submitted to multivariate (principal-components) analyses, with the canonical transformation of the data. Statistical analysis shows that each pharmacological class of anticancer drugs induces specific modifications to the chromatin patterns. The present study, therefore, shows that it is possible to identify distinct classes of antineoplastic drugs on the basis of their mechanisms of action by means of the quantitative chromatin pattern description of Feulgen-stained nuclei.

In vivo characterization by means of digital cell image analysis of early-induced fractionated radiotherapy effects on the MXT mouse mammary tumor

PURPOSE

To study the cell kinetics and chromatin modifications occurring in function of the fractionated irradiation administered to the MXT mouse mammary adenocarcinoma.

METHODS AND MATERIALS

The MXT tumor cells were submitted to three fractions of a 4.8 Gy dose delivered at 24-h intervals. MXT tumor cells were collected by means of fine needle aspirations (between 5 and 10 samples were obtained after each irradiation) during treatment and submitted to the computer-assisted microscope analysis of Feulgen-stained specimens. Three groups of parameters has been described: i.e., the geometry of the nucleus, the nuclear DNA content, and the chromatin texture. Furthermore, cell cycle parameters were studied in the aim to know the distribution of the cells within the cell cycle.

RESULTS

The mean values relating to geometric parameters (i.e., the nuclear area and its standard deviation) decreased during treatment. Variations in the nuclear DNA content appeared as being cyclical and could be explained in terms of the modifications in the distribution of the cells within the cell cycle. The quantitative analysis of the cell cycle parameters revealed that the percentage of S cells increased regularly after each irradiation. In contrast, the percentage of G2 cells decreased between each irradiation. The parameters describing nuclear texture showed regular variations between each irradiation. These variations consisted in two cycles constituted by a decrease in chromatin condensation, followed by an increase.

CONCLUSIONS

The development of the geometric parameters indicates that fractionated radiotherapy leads to the emergence of a more homogeneous population. The effects of the radiotherapy on the distribution of the cells within the cell cycle could be explained through the phenomenon of repopulation and by the high degree of radiosensitivity of the G2 cells (decrease in the percentage of G2 cells). Last, the variations observed at chromatin pattern level could be explained through DNA repair processes.