Anti-cancer drug characterisation using a human cell line panel representing defined types of drug resistance

Assessment of Oxidative Stress-Induced Oral Epithelial Toxicity

Reactive oxygen species (ROS) are highly reactive molecules generated in living organisms and an excessive production of ROS culminates in oxidative stress and cellular damage. Notably, oxidative stress plays a critical role in the pathogenesis of a number of oral mucosal diseases, including oral mucositis, which remains one of cancer treatments' most common side effects. We have shown previously that oral keratinocytes are remarkably sensitive to oxidative stress, and this may hinder the development and reproducibility of epithelial cell-based models of oral disease. Here, we examined the oxidative stress signatures that parallel oral toxicity by reproducing the initial events taking place during cancer treatment-induced oral mucositis. We used three oral epithelial cell lines (an immortalized normal human oral keratinocyte cell line, OKF6, and malignant oral keratinocytes, H357 and H400), as well as a mouse model of mucositis. The cells were subjected to increasing oxidative stress by incubation with hydrogen peroxide (H2O2) at concentrations of 100 μM up to 1200 μM, for up to 24 h, and ROS production and real-time kinetics of oxidative stress were investigated using fluorescent dye-based probes. Cell viability was assessed using a trypan blue exclusion assay, a fluorescence-based live-dead assay, and a fluorometric cytotoxicity assay (FCA), while morphological changes were analyzed by means of a phase-contrast inverted microscope. Static and dynamic real-time detection of the redox changes in keratinocytes showed a time-dependent increase of ROS production during oxidative stress-induced epithelial injury. The survival rates of oral epithelial cells were significantly affected after exposure to oxidative stress in a dose- and cell line-dependent manner. Values of TC50 of 800 μM, 800 μM, and 400 μM were reported for H400 cells (54.21 ± 9.04, p < 0.01), H357 cells (53.48 ± 4.01, p < 0.01), and OKF6 cells (48.64 ± 3.09, p < 0.01), respectively. Oxidative stress markers (MPO and MDA) were also significantly increased in oral tissues in our dual mouse model of chemotherapy-induced mucositis. In summary, we characterized and validated an oxidative stress model in human oral keratinocytes and identified optimal experimental conditions for the study of oxidative stress-induced oral epithelial toxicity.

Machine Learning and Network Analyses Reveal Disease Subtypes of Pancreatic Cancer and their Molecular Characteristics

Given that the biological processes governing the oncogenesis of pancreatic cancers could present useful therapeutic targets, there is a pressing need to molecularly distinguish between different clinically relevant pancreatic cancer subtypes. To address this challenge, we used targeted proteomics and other molecular data compiled by The Cancer Genome Atlas to reveal that pancreatic tumours can be broadly segregated into two distinct subtypes. Besides being associated with substantially different clinical outcomes, tumours belonging to each of these subtypes also display notable differences in diverse signalling pathways and biological processes. At the proteome level, we show that tumours belonging to the less severe subtype are characterised by aberrant mTOR signalling, whereas those belonging to the more severe subtype are characterised by disruptions in SMAD and cell cycle-related processes. We use machine learning algorithms to define sets of proteins, mRNAs, miRNAs and DNA methylation patterns that could serve as biomarkers to accurately differentiate between the two pancreatic cancer subtypes. Lastly, we confirm the biological relevance of the identified biomarkers by showing that these can be used together with pattern-recognition algorithms to accurately infer the drug sensitivity of pancreatic cancer cell lines. Our study shows that integrative profiling of multiple data types enables a biological and clinical representation of pancreatic cancer that is comprehensive enough to provide a foundation for future therapeutic strategies.

4-Thiazolidinone derivative Les-3833 effectively inhibits viability of human melanoma cells through activating apoptotic mechanisms

Aim

To evaluate cytotoxic action of 4-thiazolidinone derivative Les-3833 and study the mechanisms of its pro-apoptotic action toward human melanoma cells and human tumor cell lines of other tissue origin.

Methods

The effect of Les-3833 or doxorubicin on the viability of 9 cell lines was studied using MTT assay, while human melanoma cells of WM793 line were additionally examined using light and fluorescent microscopies for evaluating cytomorphological changes. The Western-blot and flow cytometric analyses were carried out to study signaling pathways of melanoma cell cycling and death.

Results

Les-3833 was the most efficient against melanoma cells. Its half maximal inhibitory concentration (IC₅₀) was 0.22 μg/mL for WM793 cells and 0.3 μg/mL for SK-Mel-28 melanoma cells. For human lung A549, breast MCF-7, colon HCT116, and ovarian SKOV3 carcinoma cell lines IC₅₀ was in between 2.5 to >5.0 μg/mL. Les-3833 was relatively not toxic (IC₅₀ ˃ 5 μg/mL) for human embryonic kidney HEK293 cells. Results of Annexin V/PI staining of melanoma cells and activation of caspase 3, PARP, MAPK, and EndoG protein suggest apoptosis in Les-3833-treated cells. Les-3833 also induced ROS production in melanoma cells and their arrest in G₀/G₁ phase of cell cycle.

Conclusion

Novel 4-thiazolidinone derivative Les-3833 is effective against human melanoma cells in vitro, and such effect is tumor specific since it is much less pronounced in human carcinoma and leukemia cells. In melanoma cells Les-3833 induces apoptosis (morphological changes and increased pro-apoptotic proteins), ROS production, and arrest in G₀/G₁ phase of cell cycle.

A Nonclonogenic Cytotoxicity Assay Using Primary Cultures of Patient Tumor Cells for Anticancer Drug Screening

Primary cultures of cells from patients with chronic lymphocytic leukemia (CLL) and ovarian carcinoma (Ovca) were compared with the renal carcinoma ACHN and the lymphocytic CCRF-CEM human tumor cell lines in response to 63 toxic or nontoxic compounds. The experiments were conducted at 1, 10, and 100 μ/ml in 96-well microtiter plates for an assay time of 72 h. The plates were analyzed by the fully automated Dynatech Immuno Assay System (DIAS) using Alamar blue as a fluorometric/colorimetric indicator of metabolic activity. Drug response data were reported as the area under the tumor cell survival-concentration curve (AUC). Noncytotoxic compounds were classified as inactive by all cell systems. According to the AUC, CCRF-CEM and CLL cells were the most sensitive, followed by ACHN, and then Ovca. Many of the clinically active drugs were detected by all cell systems. However, the sensitivity pattern differed considerably between the cell types as judged from correlation analysis, and a higher proportion of clinically inactive drugs were scored as active by the cell lines compared with the primary cultures. Ovca showed the highest ratio of clinically solid tumor active/clinically inactive agents followed by CLL. The results indicate that primary cultures of human tumor cells may be a useful and valuable model for anticancer drug screening.

Doxorubicin-loaded silicon nanowires for the treatment of drug-resistant cancer cells

Multidrug resistance (MDR) remains a major challenge for cancer treatment thus far. Free doxorubicin (DOX, one of the most widely used chemotherapy agents for cancer treatment) generally features a large value of resistant factor (RF), which is regarded as a significant parameter to assess therapeutic efficiency of cross-resistance. To address this issue, we herein present a kind of silicon nanowires (SiNWs)-based drug nanocarriers (SiNW-DOX), which is high-efficacy for treatment of drug-resistant cancer cells. Typically, drug-resistance cancer cells (e.g., MCF-7/ADR cells) can be significantly inhibited by the SiNWs-based nanocarriers, exhibiting ∼10% cell viability during 72-h incubation with the SiNWs-DOX (80 μg mL(-1) DOX), which is in sharp contrast to free DOX-treated cells preserving ∼40% cell viability. Remarkably, the RF value of SiNW-DOX is as low as ∼2.0, which is much better than that (∼300) of free DOX under the same experiment conditions. To the best of our knowledge, it is the lowest RF value ever reported by nanomaterials-based drug carriers (3.3-24.7).

The traditional medical uses and cytotoxic activities of sixty-one Egyptian plants: discovery of an active cardiac glycoside from Urginea maritima

ETHNOPHARMACOLOGICAL RELEVANCE

Medicinal plants from the Sinai desert are widely used in traditional Bedouin medicine to treat a range of conditions including, cancers, and may thus be useful sources of novel anti-tumor compounds. Information on plants used in this way was obtained through collaboration with Bedouin herbalists.

AIM OF THE STUDY

To document the traditional uses of 61 species from 29 families of Egyptian medicinal plants and to investigate their biological activity using a cytotoxicity assay.

MATERIAL AND METHODS

MeOH extracts of the 61 plant species investigated were dissolved in 10% DMSO and their cytotoxic activity was evaluated. The extracts were tested in duplicate on three separate occasions at three different concentrations (1, 10 and 100μg/ml) against human lymphoma U-937 GTB. The most active extract was subjected to bioassay-guided fractionation using HPLC and LC/ESI-MS to isolate and identify its active components.

RESULTS AND DISCUSSION

The most potent extracts were those from Asclepias sinaica, Urginea maritima, Nerium oleander and Catharanthus roseus, followed by those from Cichorium endivia, Pulicaria undulate and Melia azedarach. Literature reports indicate that several of these plants produce cardiac glycosides. Bioassay-guided fractionation of alcoholic U. maritima extracts led to the isolation of a bioactive bufadienolide that was subsequently shown to be proscillaridin A, as determined by 1D and 2D NMR spectroscopy. This result demonstrates the value of plants used in traditional medicine as sources of medicinally interesting cytotoxic compounds.

Nullomer derived anticancer peptides (NulloPs): differential lethal effects on normal and cancer cells in vitro

We demonstrate the first use of the nullomer (absent sequences) approach to drug discovery and development. Nullomers are the shortest absent sequences determined in a species, or group of species. By identifying the shortest absent peptide sequences from the NCBI databases, we screened several potential anti-cancer peptides. In order to improve cell penetration and solubility we added short poly arginine tails (5Rs), and initially solubilized the peptides in 1M trehalose. The results for one of the absent sequences 9R (RRRRRNWMWC), and its scrambled version 9S1R (RRRRRWCMNW) are reported here. We refer to these peptides derived from nullomers as PolyArgNulloPs. A control PolyArgNulloP, 124R (RRRRRWFMHW), was also included. The lethal effects of 9R and 9S1R are mediated by mitochondrial impairment as demonstrated by increased ROS production, ATP depletion, cell growth inhibition, and ultimately cell death. These effects increase over time for cancer cells with a concomitant drop in IC-50 for breast and prostate cancer cells. This is in sharp contrast to the effects in normal cells, which show a decreased sensitivity to the NulloPs over time.

Novel activity of acriflavine against colorectal cancer tumor cells

A high-throughput screen of the cytotoxic activity of 2000 molecules from a commercial library in three human colon cancer cell lines and two normal cell types identified the acridine acriflavin to be a colorectal cancer (CRC) active drug. Acriflavine was active in cell spheroids, indicating good drug penetration and activity against hypoxic cells. In a validation step based on primary cultures of patient tumor cells, acriflavine was found to be more active against CRC than ovarian cancer and chronic lymphocytic leukemia. This contrasted to the activity pattern of the CRC active standard drugs 5-fluorouracil, irinotecan and oxaliplatin. Mechanistic studies indicated acriflavine to be a dual topoisomerase I and II inhibitor. In conclusion, the strategy used seems promising for identification of new diagnosis-specific cancer drugs.

Brunn: an open source laboratory information system for microplates with a graphical plate layout design process

Background

Compound profiling and drug screening generates large amounts of data and is generally based on microplate assays. Current information systems used for handling this are mainly commercial, closed source, expensive, and heavyweight and there is a need for a flexible lightweight open system for handling plate design, and validation and preparation of data.

Results

A Bioclipse plugin consisting of a client part and a relational database was constructed. A multiple-step plate layout point-and-click interface was implemented inside Bioclipse. The system contains a data validation step, where outliers can be removed, and finally a plate report with all relevant calculated data, including dose-response curves.

Conclusions

Brunn is capable of handling the data from microplate assays. It can create dose-response curves and calculate IC₅₀ values. Using a system of this sort facilitates work in the laboratory. Being able to reuse already constructed plates and plate layouts by starting out from an earlier step in the plate layout design process saves time and cuts down on error sources.

Evaluation of toxicity and antitumor activity of cycloviolacin O2 in mice

Cycloviolacin O2 is a small cyclic cysteine-rich protein belonging to the group of plant proteins called cyclotides. This cyclotide has been previously shown to exert cytotoxic activity against a variety of human tumor cell lines as well as primary cultures of human tumor cells in vitro. This study is the first evaluation of its tolerability and antitumor activity in vivo. Maximal-tolerated doses were estimated to 1.5 mg/kg for single intravenous (i.v.) dosing and 0.5 mg/kg for daily repeated dosing, respectively. Two different in vivo methods were used: the hollow fiber method with single dosing (i.v., 1.0 mg/kg) and traditional xenografts with repeated dosing over 2 weeks (i.v., 0.5 mg/kg daily, 5 days a week). The human tumor cell lines used displayed dose-dependent in vitro sensitivity (including growth in hollow fibers to confirm passage of cycloviolacin O2 through the polyvinylidene fluoride fibers), with IC5o values in the micromolar range. Despite this sensitivity in vitro, no significant antitumor effects were detected in vivo, neither with single dosing in the hollow fiber method nor with repeated dosing in xenografts. In summary, the results indicate that antitumor effects are minor or absent at tolerable (sublethal) doses, and cycloviolacin O2 has a very abrupt in vivo toxicity profile, with lethality after single injection at 2 mg/kg, but no signs of discomfort to the animals at 1.5 mg/kg. Repeated dosing of 1 mg/kg gave a local-inflammatory reaction at the site of injection after 2-3 days; lower doses were without complications.

Isolation, characterization, and bioactivity of cyclotides from the Micronesian plant Psychotria leptothyrsa

Cyclotides, the largest known family of head-to-tail cyclic peptides, have approximately 30 amino acid residues with a complex structure containing a circular peptide backbone and a cystine knot. They are found in plants from the Violaceae and Rubiaceae families and are speculated to function in plant protection. In addition to their insecticidal properties, cyclotides display cytotoxic, anti-HIV, antimicrobial, and inhibition of neurotensin binding activities. Although cyclotides are present in all violaceous species hitherto screened, their distribution and expression in Rubiaceae are not fully understood. In this study, we show that Psychotria leptothyrsa var. longicarpa (Rubiaceae) contains a suite of different cyclotides. The cyclotide fractions were isolated by RP-HPLC, and sequences of six new peptides, named psyles A-F, were determined by MS/MS sequencing. One of these, psyle C, is the first rubiaceous linear variant known. Psyles A, C, and E were analyzed in a fluorometric microculture assay to determine cytotoxicity toward the human lymphoma cell line U937-GTB. The IC(50) values of psyles A, C, and E were 26, 3.50, and 0.76 muM, respectively. This study expands the number of known rubiaceous cyclotides and shows that the linear cyclotide maintains cytotoxicity.

Is resistance useless? Multidrug resistance and collateral sensitivity

When cancer cells develop resistance to chemotherapeutics, it is frequently conferred by the ATP-dependent efflux pump P-glycoprotein (MDR1, P-gp, ABCB1). P-gp can efflux a wide range of cancer drugs; its expression confers cross-resistance, termed "multidrug resistance" (MDR), to a wide range of drugs. Strategies to overcome this resistance have been actively sought for more than 30 years, yet clinical solutions do not exist. A less understood aspect of MDR is the hypersensitivity of resistant cancer cells to other drugs, a phenomenon known as "collateral sensitivity" (CS). This review highlights the extent of this effect for the first time, and discusses hypotheses (e.g. generation of reactive oxygen species) to account for the underlying generality of this phenomenon, and proposes exploitation of CS as a strategy to improve response to chemotherapy.

Structure-activity relationship analysis of cytotoxic cyanoguanidines: selection of CHS 828 as candidate drug

Background

N-(6-(4-chlorophenoxy)hexyl)-N'-cyano-N''-4-pyridyl guanidine) (CHS 828) is the first candidate drug from a novel group of anti-tumour agents – the pyridyl cyanoguanidines, shown to be potent compounds interfering with cellular metabolism (inhibition of nicotinamide phosphoribosyl transferase) and NF-κB signalling. Substituted cyanoguanidines are also found in anti-hypertensive agents such as the potassium channel opener pinacidil (N-cyano-N'-(4-pyridyl)-N''-(1,2,2-trimethylpropyl)guanidine) and histamine-II receptor antagonists (e.g. cimetidine, N-cyano-N'-methyl-N''-[2-[[(5-methylimidazol-4-yl]methyl]thio]ethyl)guanidine). In animal studies, CHS 828 has shown very promising activity, and phase I and II studies resulted in further development of a with a water soluble prodrug.

Findings

To study the structural requirements for cyanoguanidine cytotoxicity a set of 19 analogues were synthesized. The cytotoxic effects were then studied in ten cell lines selected for different origins and mechanisms of resistance, using the fluorometric microculture cytotoxicity assay (FMCA). The compounds showed varying cytotoxic activity even though the dose-response curves for some analogues were very shallow. Pinacidil and cimetidine were found to be non-toxic in all ten cell lines. Starting with cyanoguanidine as the crucial core it was shown that 4-pyridyl substitution was more efficient than was 3-pyridyl substitution. The 4-pyridyl cyanoguanidine moiety should be linked by an alkyl chain, optimally a hexyl, heptyl or octyl chain, to a bulky end group. The exact composition of this end group did not seem to be of crucial importance; when the end group was a mono-substituted phenyl ring it was shown that the preferred position was 4-substitution, followed by 3- and, finally, 2-substitution as the least active. Whether the substituent was a chloro, nitro or methoxy substituent seemed to be of minor importance. Finally, the activity patterns in the ten cell lines were compared. Substances with similar structures correlated well, whilst substances with large differences in molecular structure demonstrated lower correlation coefficients.

Conclusion

According to this structure-activity relationship (SAR) study, CHS 828 meets the requirements for optimal cytotoxic activity for this class of compounds.

In vitro activity of bortezomib in cultures of patient tumour cells--potential utility in haematological malignancies

Bortezomib represents a new class of anti-cancer drugs, the proteasome inhibitors. We evaluated the in vitro activity of bortezomib with regard to tumour-type specificity and possible mechanisms of drug resistance in 115 samples of tumour cells from patients and in a cell-line panel, using the short-term fluorometric microculture cytotoxicity assay. Bortezomib generally showed dose-response curves with a steep slope. In patient cells, bortezomib was more active in haematological than in solid tumour samples. Myeloma and chronic myeloid leukaemia were the most sensitive tumour types although with great variability in drug response between the individual samples. Colorectal and kidney cancer samples were the least sensitive. In the cell-line panel, only small differences in response were seen between the different cell lines, and the proteasome inhibitors, lactacystin and MG 262, showed an activity pattern similar to that of bortezomib. The cell-line data suggest that resistance to bortezomib was not mediated by MRP-, PgP, GSH-; tubulin and topo II-associated MDR. Combination experiments indicated synergy between bortezomib and arsenic trioxide or irinotecan. The data support the current use of bortezomib but also points to its potential utility in other tumour types and in combination with cytotoxic drugs.

Characterization of the cytotoxic activity of the indoloquinoline alkaloid cryptolepine in human tumour cell lines and primary cultures of tumour cells from patients

The plant derived indoloquinoline alkaloid cryptolepine was investigated for its cytotoxic properties in 12 human tumour cell lines and in primary cultures of tumour cells from patients. The fluorometric microculture cytotoxicity assay was used to assess cytotoxicity and DNA micro-array analysis to evaluate gene expression. Cryptolepine mean IC(50) in the cell line panel was 0.9 microM compared with 1.0 and 2.8 microM in haematological and solid tumour malignancies, respectively. Among patient solid tumour samples, those from breast cancer were the most sensitive and essentially as sensitive as haematological malignancies. Cryptolepine activity showed highest correlations to topoisomerase II and microtubule targeting drugs. In the cell lines cryptolepine activity was essentially unaffected by established mechanisms of drug resistance. A number of genes were identified as associated with cryptolepine activity. In conclusion, cryptolepine shows interesting in vitro cytotoxic properties and its further evaluation as an anti-cancer drug seems warranted.

Synthesis, antimicrobial and antineoplastic activities for agelasine and agelasimine analogs with a beta-cyclocitral derived substituent

Agelasines and agelasimines are antimicrobial and cytotoxic purine derivatives isolated from marine sponges (Agelas sp.). We have synthesized structurally simplified analogs of these natural products starting from beta-cyclocitral. The novel compounds were found to be strong inhibitors of a wide variety of pathogenic microorganisms (incl. Mycobacterium tuberculosis) as well as cancer cell lines. The biological activities were generally in the same range as those previously found for the structurally more complex agelasines and agelasimines isolated in small amounts from natural sources. We also report for the first time that agelasine and agelasimine analogs inhibit growth of protozoa (Acanthamoeba castellanii and Acanthamoeba polyphaga). Acanthamoeba keratitis is an increasingly common and severe corneal infection, closely associated with contact lens wear.

The alpine violet, Viola biflora, is a rich source of cyclotides with potent cytotoxicity

The cyclotides are currently the largest known family of head-to-tail cyclic proteins. The complex structure of these small plant proteins, which consist of approximately 30 amino acid residues, contains both a circular peptide backbone and a cystine knot, the combination of which produces the cyclic cystine knot motif. To date, cyclotides have been found in plants from the Rubiaceae, Violaceace and Cucurbitaceae families, and are believed to be part of the host defence system. In addition to their insecticidal effect, cyclotides have also been shown to be cytotoxic, anti-HIV, antimicrobial and haemolytic agents. In this study, we show that the alpine violet Viola biflora (Violaceae) is a rich source of cyclotides. The sequences of 11 cyclotides, vibi A-K, were determined by isolation and MS/MS sequencing of proteins and screening of a cDNA library of V. biflora in parallel. For the cDNA screening, a degenerate primer against a conserved (AAFALPA) motif in the cyclotide precursor ER signal sequence yielded a series of predicted cyclotide sequences that were correlated to those of the isolated proteins. There was an apparent discrepancy between the results of the two strategies as only one of the isolated proteins could be identified as a cDNA clone. Finally, to correlate amino acid sequence to cytotoxic potency, vibi D, E, G and H were analysed using a fluorometric microculture cytotoxicity assay using a lymphoma cell line. The IC(50)-values of the bracelet cyclotides vibi E, G and H ranged between 0.96 and 5.0 microM while the Möbius cyclotide vibi D was not cytotoxic at 30 microM.

Antimicrobial and cytotoxic activity of agelasine and agelasimine analogs

Agelasine and agelasimine derivatives with substantially less complicated terpenoid side chains compared to the naturally occurring compounds have been synthesized and their ability to inhibit growth of microorganisms and cancer cells has been studied. Compounds with excellent activity against cancer cell lines (MIC ca. 1 microM for the most potent compounds), including a drug resistant renal cell line, have been identified. Most compounds studied also exhibited broad spectrum antimicrobial activity including activity against Mycobacterium tuberculosis.

Pharmacological profiling of novel non-COX-inhibiting indole-pyran analogues of etodolac reveals high solid tumour activity of SDX-308 in vitro

SDX-308 and SDX-309 are potent indole-pyran analogues of SDX-101 (R-etodolac) which has anti-tumour activity unrelated to cyclooxygenase-2 inhibition. Their cytotoxic activity was further studied herein using a well-characterized human tumour cell-line panel containing ten cell lines, as well as in 58 primary tumour cell samples from a variety of diagnoses. The indole-pyran analogues of SDX-101 were in general considerably more active in both cancer cell lines and primary tumour samples. Low cross-reactivity with standard agents was observed, indicating a unique mechanism of action. No apparent influence on efficacy was observed via classical mechanisms of multidrug-resistance. SDX-101 and SDX-309 showed higher relative activity in haematological compared to solid tumour samples, while SDX-308 had pronounced solid-tumour activity. High SDX-308 cytotoxic efficacy was observed in non-small cell lung cancer, renal cancer and ovarian cancer samples, and also in chronic lymphocytic leukaemia. In conclusion, the indole-pyran analogues showed a favourable pharmacological profile and represent a potentially important new class of drugs for cancer treatment.

Mechanism of action of cytotoxic cyclotides: cycloviolacin O2 disrupts lipid membranes

In recent years, the cyclotides have emerged as the largest family of naturally cyclized proteins. Cyclotides display potent cytotoxic activity that varies with the structure of the proteins, and combined with their unique structure, they represent novel cytotoxic agents. However, their mechanism of action is yet unknown. In this work we show that disruption of cell membranes plays a crucial role in the cytotoxic effect of the cyclotide cycloviolacin O2 (1), which has been isolated from Viola odorata. Cell viability and morphology studies on the human lymphoma cell line U-937 GTB showed that cells exposed to 1 displayed disintegrated cell membranes within 5 min. Functional studies on calcein-loaded HeLa cells and on liposomes showed rapid concentration-dependent release of their respective internal contents. The present results show that cyclotides have specific membrane-disrupting activity.

Allelic imbalance in gene expression as a guide to cis-acting regulatory single nucleotide polymorphisms in cancer cells

Using the relative expression levels of two SNP alleles of a gene in the same sample is an effective approach for identifying cis-acting regulatory SNPs (rSNPs). In the current study, we established a process for systematic screening for cis-acting rSNPs using experimental detection of AI as an initial approach. We selected 160 expressed candidate genes that are involved in cancer and anticancer drug resistance for analysis of AI in a panel of cell lines that represent different types of cancers and have been well characterized for their response patterns against anticancer drugs. Of these genes, 60 contained heterozygous SNPs in their coding regions, and 41 of the genes displayed imbalanced expression of the two cSNP alleles. Genes that displayed AI were subjected to bioinformatics-assisted identification of rSNPs that alter the strength of transcription factor binding. rSNPs in 15 genes were subjected to electrophoretic mobility shift assay, and in eight of these genes (APC, BCL2, CCND2, MLH1, PARP1, SLIT2, YES1, XRCC1) we identified differential protein binding from a nuclear extract between the SNP alleles. The screening process allowed us to zoom in from 160 candidate genes to eight genes that may contain functional rSNPs in their promoter regions.

Pharmacological profiling of disulfiram using human tumor cell lines and human tumor cells from patients

The thiocarbamate drug disulfiram has been used for decades in the treatment of alcohol abuse. Disulfiram induces apoptosis in a number of tumor cell lines and was recently by us proposed to act as a 26S proteasome inhibitor. In this work we characterized disulfiram in vitro with regard to tumor-type specificity, possible mechanisms of action and drug resistance and cell death in human tumor cell lines and in 78 samples of tumor cells from patients using the fluorometric microculture cytotoxicity assay and the automated fluorescence-imaging microscope ArrayScan((R)). Disulfiram induced cytotoxicity in a biphasic pattern in both cell lines and patient tumor cells. Disulfiram induced apoptosis as measured by cell membrane permeability, nuclear fragmentation/condensation and caspase-3/7 activation using high content screening assays. For many of the cell lines tested disulfiram was active in sub-micromolar concentrations. When comparing the logIC(50) patterns with other cytotoxic agents, disulfiram showed low correlation (R<0.5) with all drugs except lactacystin (R=0.69), a known proteasome inhibitor, indicating that the two substances may share mechanistic pathways. Disulfiram was more active in hematological than in solid tumor samples, but substantial activity was observed in carcinomas of the ovary and the breast and in non-small cell lung cancer. Disulfiram also displayed higher cytotoxic effect in cells from chronic lymphocytic leukemia than in normal lymphocytes (p<0.05), which may indicate some tumor selectivity. These results together with large clinical experience and relatively mild side effects encourage clinical studies of disulfiram as an anti-cancer agent.

In Vitro Drug Sensitivity-Gene Expression Correlations Involve a Tissue of Origin Dependency

A major concern of chemogenomics is to associate drug activity with biological variables. Several reports have clustered cell line drug activity profiles as well as drug activity-gene expression correlation profiles and noted that the resulting groupings differ but still reflect mechanism of action. The present paper shows that these discrepancies can be viewed as a weighting of drug-drug distances, the weights depending on which cell lines the two drugs differ in.

Phenotype-based screening of mechanistically annotated compounds in combination with gene expression and pathway analysis identifies candidate drug targets in a human squamous carcinoma cell model

The squamous cell carcinoma HeLa cell line and an epithelial cell line hTERT-RPE with a nonmalignant phenotype were interrogated for HeLa cell selectivity in response to 1267 annotated compounds representing 56 pharmacological classes. Selective cytotoxic activity was observed for 14 of these compounds dominated by cyclic adenosine monophosphate (cAMP) selective phosphodiesterase (PDE) inhibitors, which tended to span a representation of the chemical descriptor space of the library. The PDE inhibitors induced delayed cell death with features compatible with classical apoptosis. The PDE inhibitors were largely inactive when tested against a cell line panel consisting of hematological and nonsquamous epithelial phenotypes. In a genome-wide DNA microarray analysis, PDE3A and PDE2A were found to be significantly increased in HeLa cells compared to the other cell lines. The pathway analysis software PathwayAssist was subsequently used to extract a list of proteins and small molecules retrieved from Medline abstracts associated with the hit compounds. The resulting list consisted of major parts of the cAMP-protein kinase A pathway linking to ERK, P38, and AKT. This molecular network may provide a basis for further exploitation of novel candidate targets for the treatment of squamous cell carcinoma.

(+)-agelasine D: improved synthesis and evaluation of antibacterial and cytotoxic activities

An improved synthesis of (+)-agelasine D (10) from (+)-manool is reported together with cytotoxic and antibacterial data for agelasine D and structurally close synthetic analogues. These compounds display a broad spectrum of antibacterial activities including effects on M. tuberculosis and Gram-positive and Gram-negative bacteria (both aerobes and anaerobes). They exhibit profound cytotoxic activity against several cancer cells, including a multidrug-resistant cell line. (+)-Agelasine D (10) has been isolated earlier from a marine sponge (Agelas sp.).

Multitarget inhibition of drug-resistant multiple myeloma cell lines by dimethyl-celecoxib (DMC), a non–COX-2 inhibitory analog of celecoxib

2,5-dimethyl-celecoxib (DMC) is a close structural analog of the selective cyclooxygenase-2 (COX-2) inhibitor celecoxib that lacks COX-2 inhibitory function. We and others have demonstrated that DMC, despite its inability to block COX-2, is able to potently mimic the antitumor effects of celecoxib in vitro and in vivo. In this current study, we investigated whether DMC would also be able to inhibit the growth of highly drug-resistant tumor cell variants. We focused on human multiple myeloma (MM) cells, as patients with MM frequently develop drug-resistant disease and ultimately succumb to death. Here we show that DMC (and celecoxib) inhibits the proliferation of various multiple myeloma cell lines, including several (multi) drug-resistant variants. Growth inhibition in drug-sensitive and drug-resistant cells is mediated via multiple effects, which include diminished signal transducer and activator of transcription 3 (STAT-3) and mitogen-activated protein (MAP) kinase kinase (MEK) activity, reduced expression of survivin and various cyclins, and is followed by apoptotic cell death. Thus, our study demonstrates that inhibition of proliferation and induction of apoptosis by DMC (and celecoxib) can be accomplished even in highly drug-resistant multiple myeloma cells, and that this effect is achieved via the blockage of multiple targets that are critical for multiple myeloma cell growth and survival.

Identification of molecular mechanisms for cellular drug resistance by combining drug activity and gene expression profiles

Acquired drug resistance is a major problem in cancer treatment. To explore the genes involved in chemosensitivity and resistance, 10 human tumour cell lines, including parental cells and resistant subtypes selected for resistance against doxorubicin, melphalan, teniposide and vincristine, were profiled for mRNA expression of 7400 genes using cDNA microarray technology. The drug activity of 66 cancer agents was evaluated on the cell lines, and correlations between drug activity and gene expression were calculated and ranked. Hierarchical clustering of drugs based on their drug–gene correlations yielded clusters of drugs with similar mechanism of action. Genes correlated with drug sensitivity and resistance were imported into the PathwayAssist software to identify putative molecular pathways involved. A substantial number of both proapoptotic and antiapoptotic genes such as signal transducer and activator of transcription 1, mitogen-activated protein kinase 1 and focal adhesion kinase were found to be associated to drug resistance, whereas genes linked to cell cycle control and proliferation, such as cell division cycle 25A and signal transducer of activator of transcription 5A, were associated to general drug sensitivity. The results indicate that combined information from drug activity and gene expression in a resistance-based cell line panel may provide new knowledge of the genes involved in anticancer drug resistance and become a useful tool in drug development.

Cytotoxic activity of a new paclitaxel formulation, Pacliex, in vitro and in vivo

BACKGROUND

The paclitaxel formulation, Taxol (Bristol-Myers Squibb), is one of the most effective anticancer agents used today. However; it is associated with serious side effects believed to be caused by the Cremophor EL used for its formulation.

AIM

To evaluate the cytotoxic activity of a new paclitaxel formulation, Pacliex (developed by Oasmia Pharmaceutical, Uppsala, Sweden), a mixed micelles preparation in which an amphiphilic synthetic derivative of retinoic acid replaced Cremophor EL/ethanol vehicle.

METHOD

In this study, three model systems were used to evaluate the cytotoxic activity of Pacliex and other paclitaxel preparations. The cytotoxic activities of Pacliex, Taxol and paclitaxel in ethanol were investigated against a panel of ten human tumor cell lines using the fluorometric microculture cytotoxicity assay (FMCA). Low- and high- proliferating in vitro hollow fiber model of two cell lines, the leukemia CCRF-CEM and the myeloma RPMI 8226/S cell lines, were used to assess the cytotoxic activity of the three formulations. The in vivo hollow fiber model of the two cell lines was used for assessment of Pacliex and Taxol activity. The [3-4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay was utilized to analyze the in vitro and in vivo hollow fiber data.

RESULT

Pacliex was somewhat more effective than Taxol in the more sensitive cell lines. The activity of Taxol was more pronounced in the resistant cell lines due to an additive effect of the vehicle used. The three formulations showed similar activity in both the low- and high-proliferating in vitro hollow fiber cultures. The in vivo hollow fiber cytotoxic activity of Pacliex was similar to that of Taxol. Putting all the results together, it was found that all the three formulations had similar in vitro and in vivo activity.

CONCLUSION

The three in vitro and in vivo models confirmed the similarity of the cytotoxic activities of Pacliex and Taxol. Considering the above, Pacliex could be an interesting alternative Cremophor EL-free formulation of paclitaxel.

Activity of hydrolytic enzymes in tumour cells is a determinant for anti-tumour efficacy of the melphalan containing prodrug J1

Recently, we presented a series of melphalan containing di- and tripeptides with high cytotoxic activity and J1 (l-melphalanyl-p-l-fluorophenylalanine ethyl ester) was identified as one of the most interesting compounds. It was speculated that the increased activity compared to melphalan itself, demonstrated both in vitro and in vivo, resided in increased transport over the tumour cell membrane and/or hydrolytic cleavage and liberation of melphalan inside the cells. Indeed, overexpression of hydrolytic enzymes like peptidases, esterases and proteases has been described in several types of human malignancies, thus providing a target for selective chemotherapy. In this work, the details of the increased activity was further investigated and potential tumour selectivity is discussed. The intracellular delivery of melphalan is investigated in detail using peptidase resistant dipeptide derivatives, by enzyme inhibitors and probes for enzymatic activity and by studying the time dependency of drug effect as well as intracellular drug concentrations (cellular pharmacokinetics). The results show that the activity of the dipeptide mustards is highly dependent on intracellular hydrolysis, which result in rapid intracellular release of the alkylating unit (i.e. free melphalan) in cells with high enzymatic activity. The maximum intracellular melphalan concentration following J1 exposure was reached already after 15 min, thereafter declining with a half-life of approximately 1 h. This rapid intracellular loading resulted in less reduction of activity for J1 than for melphalan and six other standard drugs when human tumour cell lines were exposed to the drugs for a limited time (simulating short half-life in vivo). Peptidase inhibitors inhibited the activity and intracellular release of melphalan, and dipeptide derivatives designed to resist the action of peptidases was less active than the corresponding normal dipeptide.

Cytotoxic cyclotides from Viola tricolor

A crude fraction of Viola tricolor rich in small lipophilic proteins was prepared and subjected to fractionation guided by bioactivity, using RP-HPLC and a fluorometric cytotoxicity assay. Two human cancer cell lines, U-937 GTB (lymphoma) and RPMI-8226/s (myeloma), were used in this study. The most potent compounds isolated, that is, the compounds showing the lowest IC(50) values, were shown to be three small proteins: vitri A (IC(50) = 0.6 microM and IC(50) = 1 microM, respectively), varv A (IC(50) = 6 microM and IC(50) = 3 microM, respectively), and varv E (IC(50) = 4 microM in both cell lines). Their sequences, determined by automated Edman degradation, quantitative amino acid analysis, and mass spectrometry, were cyclo-GESCVWIPCITSAIGCSCKSKVCYRNGIPC (vitri A), cyclo-GETCVGGTCNTPGCSCSWPVCTRNGLPVC (varv A), and cyclo-GETCVGGTCNTPGCSCSWPVCTRNGLPIC (varv E), of which vitri A is described for the first time. Each forms a head-to-tail cyclic backbone, with six cysteine residues being involved in three disulfide bonds, characteristic of the family of small proteins called the cyclotides. This is the first report on cyclotides from the species V. tricolor and the first report on the sequence of the cytotoxic cyclotide vitri A.

Cytotoxic effect in vivo and in vitro of CHS 828 on human myeloma cell lines

CHS 828 is a pyridyl cyanoguanidine with promising antitumor activity both in vitro and in vivo, and has previously been found especially active against tumor cells obtained from patients with B cell chronic lymphocytic leukemia. In the present study the cytotoxic effect in vitro of CHS 828 was investigated on a panel of 10 human myeloma cell lines using the fluorometric microculture cytotoxicity assay. CHS 828 induced a concentration-dependent, but variable decrease in tumor cell survival in the cell line panel with inhibitory concentrations 50% (IC50) in the range 0.01-0.3 microM. These concentrations are below those achievable in vivo. There was no detectable dependence on P-glycoprotein-mediated or GSH-associated drug resistance and the drug showed low to moderate cross-resistance with standard drugs, including melphalan, vincristine and doxorubicin. Furthermore, sensitivity to CHS 828 showed no apparent relationship to growth factor dependence, tumor progression or phenotypic variability. CHS 828 was also tested in vivo using a hollow fiber model in rats with three of the cell lines. The results indicate a high cytotoxic activity of CHS 828. Overall, the results show a high cytotoxic activity of CHS 828 in the myeloma models, which might warrant its further development against myeloma.

Ligatoxin B, a new cytotoxic protein with a novel helix-turn-helix DNA-binding domain from the mistletoe Phoradendron liga

A new basic protein, designated ligatoxin B, containing 46 amino acid residues has been isolated from the mistletoe Phoradendron liga (Gill.) Eichl. (Viscaceae). The protein's primary structure, determined unambiguously using a combination of automated Edman degradation, trypsin enzymic digestion, and tandem MS analysis, was 1-KSCCPSTTAR-NIYNTCRLTG-ASRSVCASLS-GCKIISGSTC-DSGWNH-46. Ligatoxin B exhibited in vitro cytotoxic activities on the human lymphoma cell line U-937-GTB and the primary multidrug-resistant renal adenocarcinoma cell line ACHN, with IC50 values of 1.8 microM and 3.2 microM respectively. Sequence alignment with other thionins identified a new member of the class 3 thionins, ligatoxin B, which is similar to the earlier described ligatoxin A. As predicted by the method of homology modelling, ligatoxin B shares a three-dimensional structure with the viscotoxins and purothionins and so may have the same mode of cytotoxic action. The novel similarities observed by structural comparison of the helix-turn-helix (HTH) motifs of the thionins, including ligatoxin B, and the HTH DNA-binding proteins, led us to propose the working hypothesis that thionins represent a new group of DNA-binding proteins. This working hypothesis could be useful in further dissecting the molecular mechanisms of thionin cytotoxicity and of thionin opposition to multidrug resistance, and useful in clarifying the physiological function of thionins in plants.

Effect of cyclophosphamide on gene expression of cytochromes p450 and beta-actin in the HL-60 cell line

Many studies have demonstrated that cyclophosphamide (CPA) can affect hepatic cytochrome p450 (CYP) isoenzyme activity in animals. We have investigated the effect of CPA on gene expression of various CYP enzymes as well as beta-actin in the human acute promyelocytic leukemia cell line (HL-60S) and its multidrug-resistant (MDR) phenotype HL-60R. Cells were incubated at different concentrations of CPA ranging between 50 micro g/ml and 5 mg/ml. In determination of cytotoxicity and resistance factor (RF: IC(50) HL-60R/IC(50) HL-60S), concentrations of 100 and 500 micro g/ml CPA were selected to treat HL-60S and HL-60R up to 72 h. CYP gene expression in the cells prior to and after treatment with CPA was determined using semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and real-time PCR. Unexposed cell lines did not contain measurable levels of mRNA for CYP2B6, CYP3A4, CYP2C9 and CYP2C19 and no induction was observed after exposure. However, CYP1B1-specific mRNA, which is predominantly expressed in HL-60 cell line, was suppressed after exposure to CPA in a concentration-dependent manner. Beta-actin gene expression was also decreased. The HL-60 RF to CPA was calculated to 0.71, indicating that the multidrug-resistant (MDR) phenotype is not involved in the mechanism of resistance to CPA. No CYPs were induced by CPA in vitro, which probably indicates that the CYP inducibility in blood cells is poor. Our study suggests that suppression of beta-actin gene expression contributes or is involved in the CPA cytotoxicity.

Selective cytotoxicity evaluation in anticancer drug screening of fractionated plant extracts

Chosen to reflect biodiversity in a phylogenetic sense, 100 fractionated plant extracts were screened in vitro for cytotoxicity following extraction and fractionation (polypeptide isolation). Of these 100 extracts, 30 were selected and then characterized preliminarily for antitumor potency and mode of action by testing them on two cell lines and primary cultures of human tumor cells. On the basis of cytotoxicity potency, 10 of the extracts were further characterized for anticancer activity in 10 human tumor cell lines. This final testing resulted in seven potential lead plants with superior evidence of antitumor potential: Colchicum autumnale L. (Colchicaceae), Digitalis lanata Ehrh. and Digitalis purpurea L. (Plantaginaceae), Helleborus cyclophyllus Boiss. (Ranunculaceae), Menyanthes trifoliata L. (Menyanthaceae), and Viola arvensis Murr. and Viola patrinii Ging. (Violaceae). Within a database of antitumor compounds, the activity profiles of the extracts from these seven plants were compared, by correlation analysis, with those of more than 100 other compounds, including 39 standard drugs from different classes of cytotoxic mechanisms. The activity profiles of six of these candidates were uncorrelated with those of the standard drugs, possibly indicating new pathways of drug-mediated cell death.

In vitro evaluation of the efficacy of idarubicin in human tumour cells from patients with low-grade non-Hodgkin's lymphoma

Evaluating the potential benefit of the new anthracycline, idarubicin (Ida), in lymphoma, 58 tumour samples from patients suffering from low-grade non-Hodgkin's lymphoma (L-NHL), were analysed in vitro for their sensitivity to 0.5 microg/ml Ida. This was compared with the sensitivity to other anthracyclines (0.5 microg/ml), using the fluorometric microculture cytotoxicity assay. A total of 132 samples from patients with acute leukaemia and a cell-line panel representing different resistance mechanisms was included for comparison. The median cell survival of L-NHL cells did not differ after exposing the cells to Ida or daunorubicin (Dnr), whereas epirubicin, doxorubicin (Dox) and mitoxantrone (Mitox) were significantly less cytotoxic than Ida (P < 0.001). The median cell survival in L-NHL cells did not differ from that of acute leukaemia cells after exposure to 0.5 microg/ml Ida, Dnr, Dox and Mitox. Cells from previously treated patients with L-NHL had a higher median survival than cells from untreated patients after exposure to all drugs, except for Ida. In samples from previously untreated patients, Spearman rank correlations were high (Rho = 0.81-0.90) between cell survival after exposure to Ida and the other anthracyclines. The same pattern was observed in the cell-line panel (Rho = 0.78-0.91) (P < 0.05). In contrast, low correlations (Rho = 0.24-0.42) were observed among samples from previously treated patients. Our results indicate a potential benefit of Ida in previously drug-treated patients with L-NHL.

Quantification of lymphocytes propagating from rat-kidney allografts--a tool to monitor anti-rejection treatment

BACKGROUND

Morphological evaluation of kidney biopsies applying the Banff Classification is closely correlated to clinical parameters of rejection. However, this classification is insufficient for monitoring the effect of instituted anti-rejection therapy. The objective of the present study was to develop a diagnostic tool enabling rapid assessment of the effects of an attempted anti-rejection treatment.

MATERIALS AND METHODS

A kidney allotransplantation model in the rat was applied. All animals were initially maintained on cyclosporine A (CsA). In order to induce an episode of acute cellular rejection, CsA was withdrawn for 5 days. Thereafter, the immunosuppressive treatment was restarted. Core biopsies were taken before, and at various times after, the introduction of anti-rejection therapy. Infiltrating cells were isolated using an in vitro culture system, allowing cells to propagate from the biopsies to culture medium. Propagated cells were counted and analysed for subtype and activation markers using flow cytometry. The results were compared with immunohistochemical and morphological analyses of the grafts.

RESULTS

By applying the in vitro culture system it was possible to demonstrate a reduction in outgrowth of mononuclear cells from core biopsies as early as 2 days after the start of anti-rejection therapy. At this time-point, as well as 2 days later, morphological and immunohistochemical analyses of biopsies showed ongoing acute cellular rejection, with no differences between biopsies taken before and after restart of CsA-therapy. The percentage of propagating T lymphocytes expressing the activation markers CD25 or MHC class II did not differ between grafts with ongoing rejection and grafts obtained from CsA-treated rats, neither did the ratio of CD4/CD8-positive cells.

CONCLUSION

Our findings indicate that the ex vivo propagation method could function as a complement to routine histology, not only in the diagnosis of cellular rejection but also in order to rapidly reveal a failure of an anti-rejection therapy to halt the rejection process.

Cytotoxicity of digitoxin and related cardiac glycosides in human tumor cells

The saponin digitonin, the aglycone digitoxigenin and five cardiac glycosides were evaluated for cytotoxicity using primary cultures of tumor cells from patients and a human cell line panel (representing different cytotoxic drug-resistance patterns). Of these seven compounds, proscillaridin A was the most potent (IC(50): 6.4--76 nM), followed by digitoxin, and then ouabain, digoxin, lanatoside C, digitoxigenin and digitonin. Correlation analysis of the log IC(50) values for the cell lines in the panel showed that compound cytotoxicity was only slightly influenced by resistance mechanisms that involved P-glycoprotein, topoisomerase II, multidrug resistance-associated protein and glutathione-mediated drug resistance. Digitoxin and digoxin expressed selective toxicity against solid tumor cells from patients, while proscillaridin A expressed no selective toxicity against either solid or hematological tumor cells. The results revealed marked differences in cytotoxicity between the cardiac glycosides, both in potency and selectivity, and modes of action for cytotoxicity that differ from that of commonly used anticancer drugs.

Temporal effects of the novel antitumour pyridyl cyanoguanidine (CHS 828) on human lymphoma cells

CHS 828, a novel pyridyl cyanoguanidine, has shown potent antitumour activity both in vitro and in vivo and is currently undergoing phase I evaluation in humans in collaboration with the European Organization for Research and Treatment of Cancer (EORTC). Here we study the temporal effects of CHS 828 on cytotoxicity, protein and DNA synthesis, cellular morphology and ultra structure using the lymphoma cell line U-937 GTB as the primary tumour model. In vitro analysis of tumour cell survival in response to CHS 828 revealed a cytotoxic effect progressively increased as a function of exposure time with maximum efficacy observed after 72 h. Activity of CHS 828 on U-937 GTB cells grown in vivo was also found. CHS 828 induced-cell death was dependent on intact protein synthesis and most cells appeared to lose their membrane integrity in the presence of a relatively well preserved nuclear structure. The results indicate that CHS 828 induced active and delayed cell death with a non-apoptotic morphology.

Differential activity of topotecan, irinotecan and SN-38 in fresh human tumour cells but not in cell lines

The topoisomerase I inhibitors topotecan irinotecan (CPT-11) and its metabolite SN-38 were studied in a panel of cell lines and in primary tumour cells from patients, using a non-clonogenic cytotoxicity assay. All three substances showed similar activity patterns in the panel of cell lines established to classify the drugs mechanistically. In the patient tumour cells the drugs had different effects. In haematological and ovarian cancer samples, SN-38 was much more potent than topotecan, followed by irinotecan, while in colorectal cancer samples only irinotecan showed substantial activity. This in vitro activity pattern seems to agree with clinical experiences to date. The inactivity of SN-38 in colorectal cancer suggests irinotecan may also have some other role in addition to being a prodrug to SN-38. This study raises questions as to the role and relevance of early preclinical model systems in anticancer drug development, and suggests that important information can be obtained from studies using primary cultures of human tumour cells.

Use of cultured human fibroblasts for rapid evaluation of cytotoxic effects of bioactive substances

A test system for detecting cytotoxic effects of bioactive substances based on human fibroblast culture is proposed. The effects of acrylamide, streptomycin, cycloheximide, sodium dodecyl sulfate, sanguiritrine, and ethanol were evaluated by organic stain binding. Typical dose-effect relationships were detected for all substances except cycloheximide. The proposed test system can be used for screening of bioactive substances in preclinical trials.

Antitumour activity of suramin analogues in human tumour cell lines and primary cultures of tumour cells from patients

Suramin has shown promising antitumour activity against several tumour types, both in vitro and in vivo, but the clinical utility of this compound is hampered by its unfavourable toxicity profile. In the present study, the semi-automated fluorometric microculture cytotoxicity assay (FMCA) was employed for evaluation of the cytotoxicity of seven suramin analogues in vitro in a panel of human tumour cell lines and in primary cultures of tumour cells from patients. Like suramin, the analogues showed little sensitivity to resistance mechanisms involving P-glycoprotein, topoisomerase II, multidrug resistance associated protein and glutathione-mediated drug resistance. In the cell line panel, NF067 and FCE 26644 showed activity comparable with suramin. All analogues were less potent than suramin in patient cells except for FCE 26644. Correlation to suramin activity patterns in the cell line panel was highest for NF037 and low to moderate for the remaining analogues. In patient cells, high correlation coefficients were obtained for FCE 26644, NF110, NF031 and NF037. The results indicate that the cytotoxic activity of suramin on patient tumour cells is shared by the analogues with FCE 26644 being the most active. The pharmacophore for cytotoxicity in patient cells may be different from that observed in the cell lines.

On the mechanism underlying calcein-induced cytotoxicity

The cellular pharmacology of calcein acetoxymethyl ester (calcein/AM)-induced cytotoxicity was investigated in human tumor cell lines in order to identify tentative mechanisms of action. The activity profile in 10 cell lines with known mechanisms of resistance was compared with the activity profiles of standard drugs and experimental substances. The activity of calcein correlated with that of different topo II inhibitor/intercalating compounds and mitochondrial accumulating compounds, such as Rhodamine 123, Mito Fluor Green and Acridine Orange-10. Using U-937 GTB as a model cell line, calcein was found to distribute throughout the whole cell, nuclei and mitochondria included. In addition, studies of mitochondrial dehydrogenase activity and extracellular acidification rate showed an almost complete lack of dehydrogenase activity and extracellular acidification at 12 and 24 h, respectively. The results indicate that calcein/AM may induce cytotoxicity through interference with both mitochondrial and nuclear DNA.