Prediction and assessment of ecogenotoxicity of antineoplastic drugs in binary mixtures

Toxicity toward freshwater and marine water organisms of the cytostatic drugs bleomycin and vincristine and their binary mixture

Antineoplastic drugs are not effectively removed by wastewater treatment plants, ending up in surface waters. Since these drugs can interfere with the structure and functions of DNA, they pose a potential threat to aquatic biota. Unfortunately, many chemotherapeutic agents have not been studied in an environmental context. Additionally, there is a significant lack of information about the impact of anticancer drugs on marine organisms compared to freshwater species, and most studies only focus on the toxicity of single compounds rather than considering their occurrence as complex mixtures in the environment. Therefore, the aim of this study was to evaluate the ecotoxicity of two commonly used cytostatics, bleomycin and vincristine, toward six biomodels: Pseudokirchneriella subcapitata, Phaeodactylum tricornutum, Brachionus plicatilis, Brachionus calyciflorus, Thamnocephalus platyurus, and Artemia franciscana. These selected aquatic organisms are representatives of both freshwater and marine environments and belong to different trophic levels. The pharmaceuticals were investigated both individually and in combination. Binary mixture toxicity predictions were performed according to the Response Additivity and Independent Action models. Additionally, the toxicity data obtained from these experiments were utilized for risk assessment in the context of the drugs' environmental occurrence. The results indicated that freshwater species were generally more sensitive to both tested compounds than marine organisms, with T. platyurus being the most sensitive. Based on the tests performed on this biomodel, bleomycin was categorized as extremely toxic, while vincristine was considered moderately toxic. Neither of the applied models suitably predicted binary mixture toxicity, as the combination of drugs showed additive, synergistic, and antagonistic effects, suggesting that single compound toxicity data are insufficient for predicting the aquatic toxicities of cytostatics mixtures. The environmental risk of vincristine ranged from low to high, and for bleomycin varied from moderate to high, depending on the matrices examined. Therefore, further research on drug removal is recommended.

Waterborne exposure to the antineoplastic 5-fluorouracil alters lipid composition in larval zebrafish (Danio rerio)

Antineoplastic medications are present in aquatic environments and are measured at relatively high concentrations in hospital sewage effluent. Thus, it is important to characterize risk associated with waterborne exposures to anticancer drugs. The drug 5-fluorouracil (5-FU) is used to treat several types of cancers, acting to inhibit cell division and cellular metabolism. The objectives of this study were to determine the effects of 5-FU on developmental endpoints and lipid composition in zebrafish. 5-FU did not negatively affect development nor survival in developing zebrafish at concentrations up to 1000 μg/L. However, 5-FU increased neutral lipid content in zebrafish larvae, indicating potential for lipid dysregulation. To further discern effects on lipids, lipidomics was conducted and a total of 164 lipids belonging to 14 lipid classes were identified. Significant changes (false discovery rate < 0.05) in abundance were detected for 19 lipids including some ceramides, ether-linked phosphatidylethanolamines, and sphingomyelins among others. We also measured the expression levels of 14 lipid-related enzymes and transporters (e.g., acox3, dgat1, fads2, fasn, elovl2) using real-time PCR; however, mRNA abundance levels were not affected, suggesting transcriptional changes may not be a primary mechanism underlying lipid dysregulation. Locomotor activity was measured in zebrafish as lipids are needed for swimming activity in larvae. Exposure to 5-FU did not affect locomotor activity up to 1000 μg/L. We conclude that lipids accumulate in larval zebrafish with exposure to 5-FU, which can subsequently affect lipid composition. These data reveal potential lipid signatures of 5-FU exposure and contribute to risk assessments for antineoplastic exposure in aquatic environments.

Antagonistic effects of a COX1/2 inhibitor drug in human HepG2 cells exposed to an environmental carcinogen

Understanding interactions between legacy and emerging environmental contaminants has important implications for risk assessment, especially when mutagens and carcinogens are involved, whose critical effects are chronic and therefore difficult to predict. The current work aimed to investigate potential interactions between benzo[a]pyrene (B[a]P), a carcinogenic polycyclic aromatic hydrocarbon and legacy pollutant, and diclofenac (DFC), a non-steroidal anti-inflammatory drug and pollutant of emerging concern, and how DFC affects B[a]P toxicity. Exposure to binary mixtures of these chemicals resulted in substantially reduced cytotoxicity in human HepG2 cells compared to single-chemical exposures. Significant antagonistic effects were observed in response to high concentrations of B[a]P in combination with DFC at IC50 and ⅕ IC50. While additive effects were found for levels of intracellular reactive oxygen species, antagonistic mixture effects were observed for genotoxicity. B[a]P induced DNA strand breaks, γH2AX activation, and micronuclei formation at ½ IC50 concentrations or lower, whereas DFC induced only low levels of DNA strand breaks. Their mixture caused significantly lower levels of genotoxicity by all three endpoints compared to those expected based on concentration additivity. In addition, antagonistic mixture effects on CYP1 enzyme activity suggested that the observed reduced genotoxicity of B[a]P was due to its reduced metabolic activation as a result of enzymatic inhibition by DFC. Overall, the findings further support the growing concern that co-exposure to environmental toxicants and their non-additive interactions may be a confounding factor that should not be neglected in environmental and human health risk assessment.

Hazard assessment of antineoplastic drugs and metabolites using cytotoxicity and genotoxicity assays

Antineoplastic drugs are among the most toxic pharmaceuticals. Their release into the aquatic ecosystems has been reported, giving rise to concerns about the adverse effects, including cytotoxicity and genotoxicity, that they may have on exposed organisms. In this study, we analyzed the cytotoxicity and genotoxicity of 5-fluorouracil (5-FU) and its metabolite alpha-fluoro-beta-alanine (3-NH2-F); gemcitabine (GEM) and its metabolite 2'-deoxy-2',2'-difluorouridine (2-DOH-DiF); as well as cyclophosphamide (CP) on the HepG2 cell line. Drug concentrations were based on those previously observed in the effluent of a major cancer hospital in Brazil. The study found that GEM, 2-DOH-DiF and 5-FU resulted in reduced cell viability. No reduction in cell viability was observed for CP and 3-NH2-F. Genotoxic assessment revealed damage in the form of nucleoplasmic bridges for CP and 3-NH2-F. The tested concentrations of all compounds resulted in significantly increased MNi and NBUDs. The results showed that these compounds induced cytotoxic and genotoxic effects in HepG2 cells at concentrations found in the environment. To the best of our knowledge, this study is the first to report on the cytogenotoxic impacts of the metabolites 3-NH2-F and 2-DOH-DiF in HepG2 cells. These findings may help in the development of public policies that could minimize potential environmental contamination.

Anticancer drugs in wastewater and natural environments: A review on their occurrence, environmental persistence, treatment, and ecological risks

The consumption of anticancer drugs (also known as chemotherapy drugs or antineoplastic drugs) has augmented over the last decades due to increased cancer incidence. Although there is an increasing concern about the presence of pharmaceutical compounds in natural environments and urban/domestic wastewater, anticancer drugs used in chemotherapy and anticancer medication have received less attention. In this review, the occurrence, environmental persistence, and known and potential ecological impacts of anticancer drugs is discussed. This review shows that these compounds are being increasingly detected in effluents of hospitals, influents and effluents of wastewater treatment plants, river surface water and sediments, groundwater, and even drinking water. Anticancer drugs can impact aquatic organisms such as algae, crustaceans, rotifers, and fish and may promote changes in soil and water microbial communities that may alter ecosystem functioning. Our knowledge of technologies for the removal of anticancer drugs is still limited, and these drugs can be dispersed in nature in a diffuse way in an uncontrolled manner. For this reason, an improved understanding of the presence, persistence, and ecological impacts of anticancer drugs in wastewater and natural environments is needed to help design management strategies, protect aquatic microorganisms, and mitigate potential ecological impacts.

Measuring DNA modifications with the comet assay: a compendium of protocols

The comet assay is a versatile method to detect nuclear DNA damage in individual eukaryotic cells, from yeast to human. The types of damage detected encompass DNA strand breaks and alkali-labile sites (e.g., apurinic/apyrimidinic sites), alkylated and oxidized nucleobases, DNA-DNA crosslinks, UV-induced cyclobutane pyrimidine dimers and some chemically induced DNA adducts. Depending on the specimen type, there are important modifications to the comet assay protocol to avoid the formation of additional DNA damage during the processing of samples and to ensure sufficient sensitivity to detect differences in damage levels between sample groups. Various applications of the comet assay have been validated by research groups in academia, industry and regulatory agencies, and its strengths are highlighted by the adoption of the comet assay as an in vivo test for genotoxicity in animal organs by the Organisation for Economic Co-operation and Development. The present document includes a series of consensus protocols that describe the application of the comet assay to a wide variety of cell types, species and types of DNA damage, thereby demonstrating its versatility.

Characterization of the genotoxic profile of antineoplastic drugs using the cytokinesis-block micronucleus cytome assay

Since antineoplastic agents are frequently used in cancer therapy and able to affect the patient's DNA, it is important to know the genotoxic consequences on non-cancerous tissue. Therefore, we aimed to characterize the genotoxic profile of antineoplastic drugs belonging to different classes, using the cytokinesis-block micronucleus cytome assay in a human monocytic cell line (THP-1). All tested antineoplastic agents resulted in increased micronucleus formation. Exposure to anthracyclines led to an increased number of vacuolated cells and cell death, while for mitotic spindle inhibitors, (different stages of) cell death and an increased nuclear bud formation was observed. Alkylating agents induce a high proportion of vacuolated cells and increased nuclear bud formation. No striking differences of nuclear division index or nucleoplasmic bridge formation were observed between exposed and non-exposed cells. The here presented class-specific aberrations may facilitate interpretation of genotoxic aberrations when evaluating clinical samples from patients treated with these antineoplastic agents.

Toxic impact of polystyrene microplastic particles in freshwater organisms

The ongoing COVID-19 pandemic is leading to an increase of the global production of plastics since the use of personal protective equipment (PPEs, i.e. gloves, gowns, masks, packaging items), has become mandatory to prevent the spread of the virus. Plastic breaks down into micro/nano particles due to physical or chemical or biological actions into environment. Due to small dimensions, ubiquitous and persistent nature, the plastic particles represent a significant threat to ecosystems and can entry into food chains. Among the plastic polymers used for PPEs, polystyrene is less studied regarding its eco-geno-toxicity. This study aims to investigate acute, chronic and subchronic effects of the microplastic polystyrene beads (PS-MP, size 1.0 μm) on three freshwater species, the alga Raphidocelis subcapitata, the rotifer Brachionus calyciflorus, the crustacean Ceriodaphnia dubia and the benthic ostracod Heterocypris incongruens. Furthermore, the potential genotoxicity and the ROS production due to the PS-MP were also determined in C. dubia. Results revealed that the acute effects occurred at concentrations of PS-MP in the order of dozens of mg/L in B. calyciflorus and C. dubia and hundreds of mg/L in H. incongruens. Regarding long-term toxicity, increasing chronic effects with EC50s in the order of units (C. dubia), hundreds (B. calyciflorus) and thousands (R. subcapitata) of μg/L were observed. Both for acute and chronic/sub chronic toxicity, daphnids were more sensitive to polystyrene than ostracods. Moreover, when C. dubia neonates were exposed to the PS-MP, alterations in genetic material as well as the production of ROS occurred, starting from concentrations in the order of units of μg/L, probably due to inflammatory responses. At last, the risk quotient (RQ) as a measure of risk posed by PS-MPs in freshwater environment, was calculated obtaining a value of 7.2, higher than the threshold value of 1.

Aquatic ecotoxicology of anticancer drugs: A systematic review

Anticancer drugs in the aquatic environment have drawn a lot of attention in the last decade. Since wastewater treatment plants are inefficient at fully eliminating trace concentrations of anticancer drugs, these compounds are continuously discharged into the aquatic environment. Subsequently, non-target organisms such as the aquatic biota are directly exposed to a variety of anticancer drugs. To understand the potential impact on the aquatic organisms, a systematic review was conducted in compliance with the PRISMA guidelines. The results acquired from the 152 included studies were analysed and sorted into four categories: the impact of each included anticancer drug, the effect of metabolites, the effect of a mixture of drugs, and risk assessment. Findings showed that risk to the aquatic biota was unlikely to occur as the concentrations needed to induce effects were much higher than those detected in the environment. However, these data were based on acute toxicity and included only basic toxicity endpoints. The concentrations that produced significant effects were much lower when tested in the long-term or in multi-generational studies. Heterogeneity in results was also observed; this depended on the organism tested, the assessment adopted, and the endpoints selected. In this systematic review, an overall view of the research studies was generated by which all the variability factors to be considered were reported and recommendations to guide future studies were proposed.

Anticancer drugs in the aquatic ecosystem: Environmental occurrence, ecotoxicological effect and risk assessment

Anticancer drugs are a group of therapeutic agents used to enhance cell death in targeted cell types of neoplasia. Because of frequent use and eventual discharge, they have been often detected in wastewater from pharmaceutical factories and hospitals, domestic wastewater, and surface waters. The occurrence of these drugs in aquatic ecosystems and their effects on aquatic organisms have been poorly characterized. This review focuses on the global occurrence of major classes of anticancer drugs in water and sediments of freshwater ecosystems and their ecotoxicological effects at different biological levels. While the availability of data is fairly limited, concentrations of most anticancer drugs range from < 2 ng/L to 762 µg/L in receiving water, while levels in sediments and sludge vary from 0.25 to 42.5 µg/kg. Their detection frequencies were 58%, 52% (78%) and 59% in hospital wastewater, wastewater treatment plant effluents (influents) and surface water, respectively. Predicted log K_ow values of vincristine, imatinib mesylate and tamoxifen are higher than 3 and have estimated half-lives>60 d in waters using quantitative structure-activity relationship models, indicating high potential for persistence and bioaccumulation. Based on a species sensitivity distribution evaluation of 9 compounds, crustaceans are most sensitive to anticancer drugs. The most hazardous compound is cisplatin which has a hazard concentration at the 5th percentile. For Daphnia magna, the acute toxicities of major classes of anticancer drugs are ranked as platinum complexes > endocrine therapy agents > antibiotics > antimetabolite agents > alkylating agents. Using hazard quotient analysis based primarily on the lowest observed effect concentrations (LOECs), cyclophosphamide, cisplatin, 5-fluorouracil, imatinib mesylate, bicalutamide, etoposide and paclitaxel have the highest hazard for aquatic organisms. Further research is needed to identify appropriate chronic endpoints for risk assessment thresholds as well as to better understand the mechanisms of action and the potential multigenerational toxicity, and trophic transfer in ecosystems.

The antineoplastic drugs cyclophosphamide and cisplatin in the aquatic environment - Review

Cyclophosphamide (CP) and Cisplatin (CDDP) are antineoplastic drugs widely used in the treatment of neoplastic diseases that have been detected in the aquatic environment. This review summarizes the current knowledge on the presence in the aquatic environment of these two drugs and their effects on freshwater and marine invertebrates, which includes good model species in ecotoxicology and risk assessment programs. The consumption levels, occurrence in freshwater and marine ecosystems, and the impacts exerted on aquatic organisms, even at low concentrations, justifies this review and the selection of these two drugs. Both pharmaceuticals were detected in different aquatic environments, with concentrations ranging from ng L^-1 up to 687.0 μg L^-1 (CP) and 250 μg L^-1 (CDDP). The available studies showed that CP and CDDP induce individual and sub-individual impacts on aquatic invertebrate species. The most common effects reported were changes in the reproductive function, oxidative stress, genotoxicity, cytotoxicity and neurotoxicity. The literature used in this review supports the need to increase monitoring studies concerning the occurrence of antineoplastic drugs in the aquatic environment since negative effects have been reported even at trace concentrations (ng L^-1). Furthermore, marine ecosystems should be considered as a priority since less is known on the occurrence and effects of antineoplastic drugs in this environment comparing to freshwater ecosystems.

Ecotoxicological assessment of chemotherapeutic agents using toxicity tests with embryos of Mellita quinquiesperforata

The consumption of anticancer agents has increased in the recent decades, and these substances may be present in sewage. Consequently, they may reach the environment when sanitation infrastructure is ineffective. This study evaluated the toxicity of three anticancer agents-Tamoxifen (TAM), Cisplatin (CisPt), and Cyclophosphamide (CP)-on the development of embryos of the sand-dollar Mellita quinquiesperforata. Adult individuals were collected in sandy beaches, and gametes were obtained. Freshly-fertilized eggs were exposed to increasing sets of concentrations of each compound, and the effective concentrations needed to cause a 50% effect in the organisms (EC50) were calculated. The three compounds were toxic, and their EC50 values were 16.78 ± 2.42 ng·L^-1 (TAM), 27.20 ± 38.26 ng·L^-1 (CisPt), and 101.82 ± 70.96 ng·L^-1 (CP). There is no information on the environmental levels of these compounds in Brazil, but as they were already detected in ng·L^-1 levels worldwide, it can be expected that these substances pose environmental risks to the marine biota.

Cisplatin affects locomotor activity and physiological endpoints of Daphnia magna

Cisplatin (CPL) is a common antineoplastic drug used in human medicine for treatment of various cancer types. Since the knowledge about its effects on crustacean behavioral and physiological parameters is very scarce, the aim of our study was to determine the influence of CPL at concentrations of 125 μg/L, 200 μg/L, 500 μg/L and 1000 μg/L on swimming behavior (swimming speed, distance travelled, hopping frequency, propelling efficiency index - a novel parameter) and physiological parameters (heart rate, thoracic limb activity) of Daphnia magna with the use of video digital analysis. The results showed that distance travelled, swimming speed, hopping frequency and propelling efficiency were inhibited as early as after 24 h in concentration- and time-dependent manner. On the other hand, heart rate was stimulated in the animals treated with 125 μg/L of CPL after 48 h, 72 h and 120 h of the exposure, however it was decreased at the higher concentrations. Although thoracic limb activity was considerably increased in daphnids exposed to 125 μg/L and 200 μg/L after 72 h, it was inhibited at the higher concentrations of the drug. The study suggests that since CPL affected daphnid parameters at the environmental concentration, it should be considered as hazardous to zooplankton.

Environmental risk assessment of widely used anticancer drugs (5-fluorouracil, cisplatin, etoposide, imatinib mesylate)

Anticancer drugs are among the most toxic chemicals, which are commercially produced; therefore, their release in aquatic ecosystems raised concerns in regard to potential adverse effects. This article describes the results of risk assessments concerning their environmental safety, which are based on data generated in the frame of a coordinated EU project ("Cytothreat"). Eight research institutions participated in the project and four widely used anticancer drugs with different mechanisms of therapeutic action (5-fluorouracil 5FU, cisplatin CDDP, imatinib mesylate IM and etoposide ET) were tested in a variety of indicator organisms (cyanobacteria, algae, higher plants, rotifers, crustacea, fish and also in human and fish derived cell lines) in acute/subacute/chronic toxicity assays. Furthermore, genotoxic effects in micronucleus assays, single cell gel electrophoresis experiments and γH2AX tests were studied in plants, crustacea, fish and in various cell lines. We used the results to calculate the predicted no effect concentrations (PNEC) and risk quotients (RQ) by comparing PNEC with predicted environmental concentrations (PEC values) and measured concentrations (MEC) in wastewaters. The most sensitive species in experiments concerning acute toxic and long term effects were in general crustacea (daphnids) after chronic treatment the most pronounced effects were detected with IM followed by CDDP and 5FU. Comparisons between PNEC and PEC values indicate that it is unlikely that the release of these drugs in the aquatic environments leads to adverse effects (RQ values < 1). However, when the assessments were performed with MEC found in highly contaminated municipal wastewaters and hospital effluents, RQ values were obtained which are indicative for moderate adverse effects of IM. Calculations with data from genotoxicity experiments and PEC values are indicative for increased RQ values for all compounds except ET. The most sensitive species were fish (Danio rerio) which were highly responsive towards 5FU and daphnids which were sensitive towards CDDP and IM. When environmental data (from waste waters) were used for the calculations, high RQ values (>100) were obtained for CDDP and IM. These overall conclusions were not substantially altered when the effects of other frequently used cytostatic drugs and combined effects of mixtures of anticancer drugs were taken into consideration. The results of these assessments underline the importance of efficient removal of these chemicals by improved sewage treatment strategies and the need for further investigations of adverse the long term effects of cytostatics in aquatic biota as a consequence of damage of the genetic material in highly sensitive species.

Benzalkonium Chloride and Anticancer Drugs in Binary Mixtures: Reproductive Toxicity and Genotoxicity in the Freshwater Crustacean Ceriodaphnia dubia

Benzalkonium chloride (BAC) is a cationic surfactant commonly used as a disinfectant. Its ubiquitous nature is the result of high usage and frequent discharge into the environment and evidence of interaction with numerous contaminants, such as pharmaceutical active compound residues. Anticancer drugs, among these compounds, are able to exert eco-genotoxic effects at sub ng-µg/L. The purpose of this study was to assess the reproductive toxicity and the genotoxicity of 5-fluorouracil (5-FU), cisplatin (CDDP), etoposide (ET), and imatinib mesylate (IM)-binary mixtures combined with BAC in Ceriodaphnia dubia. The effects of the mixtures were assessed under the assumption of independent action in experiments that applied two effect levels. The type of interaction was not the same over the range of effect sizes. The combined action experiment on reproduction showed an antagonistic effect at higher effect levels for all binary combinations, except for BAC/IM, whereas independent action was observed in all mixtures at a low effect level. The results of binary combinations on genotoxicity showed antagonistic effects for BAC + ET and BAC + CDDP, whereas independence was expressed in BAC + IM and BAC + 5-FU. The antagonistic interactions still led to higher effects than those observed after single exposures at the same doses in most cases. The effects of mixtures of drugs should be taken into account for environmental risk assessment.

Cytotoxicity and genotoxicity of anticancer drug residues and their mixtures in experimental model with zebrafish liver cells

Anticancer drugs enter aquatic environment predominantly via hospital and municipal wastewater effluents where they may, due to their genotoxic potential, cause adverse environmental effects even at very low doses. In this study we evaluated cytotoxic and genotoxic potential of two widely used anticancer drugs, cyclophosphamide (CP) and ifosfamide (IF) as individual compounds and in a complex mixture together with 5-fluorouracil (5-FU) and cisplatin (CDDP) because these four drugs have been frequently detected in an oncological ward effluents. As an experimental model we used zebrafish liver cell (ZFL) line. The cytotoxicity was determined with the MTS assay and genotoxicity with the comet assay and cytokinesis block micronucleus (CBMN) assay that measure the formation of DNA strand breaks and genomic instability, respectively. CP and IF exerted low cytotoxicity towards ZFL cells. Both compounds induced DNA strand breaks and genomic instability, however at relatively high concentrations that are not relevant for the contamination of aquatic environment. The mixture of CP, IF, 5-FU and CDDP was tested at maximal detected concentrations of each drug as determined in the effluents from the oncological ward. The mixture was not cytotoxic and did not induce genomic instability, but it induced significant increase in the formation of DNA strand breaks at concentrations of individual compounds that were several orders of magnitude lower from those that were effective when tested as individual compounds. The results indicate that such mixtures of anticancer drugs may pose a threat to aquatic organisms at environmentally relevant concentrations and contribute to the accumulating evidence that it is not always possible to predict adverse effects of complex mixtures based on the toxicological data for individual compounds.

Acute aquatic toxicity assessment of six anti-cancer drugs and one metabolite using biotest battery - Biological effects and stability under test conditions

Available ecotoxicological data for anti-cancer drugs and their metabolites are incomplete, and only some studies have been accompanied by chemical analysis. Therefore, the main aim of this study was to evaluate the acute toxicity of the six most commonly used cytostatics, namely cyclophosphamide (CF), ifosfamide (IF), 5-fluorouracil (5-FU), imatinib (IMT), tamoxifen (TAM) and methotrexate (MET) and its metabolite - 7-hydroxymethotrexate (7-OH-MET), towards selected aquatic organisms, namely bacteria Vibrio fischeri, algae Raphidocelis subcapitata, crustaceans Daphnia magna and duckweed Lemna minor. All ecotoxicological tests were accompanied by chemical analysis to determine the differences between nominal and actual concentrations of investigated compounds and their stability under test conditions. For unstable compounds, tests were performed in static and semi-static conditions. It was observed that L. minor was the most sensitive organism. The compounds that were most toxic to aquatic organisms were 5-FU (highly toxic to algae, EC₅₀ = 0.075 mg L^-1), MET and TAM (very toxic to highly toxic to duckweed depending on the test conditions; EC_50MET 0.08-0.16 mg L^-1, EC_50TAM 0.18-0.23 mg L^-1). It is suspected that MET and 5-FU mainly affected algae and plants most probably because the exposure time was long enough for them to cause a specific effect (they inhibit DNA replication and act predominantly on actively dividing cells). Furthermore, the obtained results also suggest that the toxicity of the metabolites/potentially produced degradation products of MET towards duckweed is lower than that of the parent form, whereas the toxicity of TAM degradation products is in the same range as that of TAM.

Analyses of combined effects of cytostatic drugs on micronucleus formation in the Tradescantia

Recent experiments showed that 5-fluorouracil (5FU), cisplatin (CDDP), etoposide (ET), and imatinib mesylate (IM), which are currently among the most widely used anticancer drugs, cause damage of the genetic material in higher plants. The aim of the present study was to determine whether mixtures of these drugs cause synergistic or antagonistic effects which may have an impact on their environmental safety. Therefore, the effects of binary mixtures of these anticancer drugs on the induction of micronuclei (MN) which reflect structural and numerical chromosomal aberrations were assessed in Tradescantia tetrads. Synergistic/antagonistic effects were determined by comparison with single exposures that would be equally effective in a reference model of independent action. This comparison was performed at two distinct effect sizes. We found clear evidence for synergisms in combination experiments with IM and antagonism in a high-dose experiment with ET and 5FU. Our findings indicate that IM increases the genotoxic effects of other anticancer drugs. The maximal effects which we found were in the range between 19 and 38 % in the excess of effect sizes predicted under independent action. These effects may have an impact on the overall genotoxic activities of untreated hospital waste waters but not on the environment in general as the predicted environmental concentrations of the studied drugs are several orders of magnitude lower as the levels which are required to cause induction of MN in higher plants.