Genotoxicity assessment of a selected cytostatic drug mixture in human lymphocytes: A study based on concentrations relevant for occupational exposure

The use of effect biomarkers in chemical mixtures risk assessment - Are they still important?

Human epidemiological studies with biomarkers of effect play an invaluable role in identifying health effects with chemical exposures and in disease prevention. Effect biomarkers that measure genetic damage are potent tools to address the carcinogenic and/or mutagenic potential of chemical exposures, increasing confidence in regulatory risk assessment decision-making processes. The micronucleus (MN) test is recognized as one of the most successful and reliable assays to assess genotoxic events, which are associated with exposures that may cause cancer. To move towards the next generation risk assessment is crucial to establish bridges between standard approaches, new approach methodologies (NAMs) and tools for increase the mechanistically-based biological plausibility in human studies, such as the adverse outcome pathways (AOPs) framework. This paper aims to highlight the still active role of MN as biomarker of effect in the evolution and applicability of new methods and approaches in human risk assessment, with the positive consequence, that the new methods provide a deeper knowledge of the mechanistically-based biology of these endpoints.

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.

Antineoplastic drugs in environmentally relevant concentrations cause endocrine disruption and testicular dysfunction in experimental conditions

5-fluorouracil (5-FU) and methotrexate (MTX) are among the most widely consumed antineoplastic drugs worldwide. These drugs are known as emerging pollutants, once after consumption are excreted by feces and/or urine in a mixture of compounds and metabolites, entering the aquatic environment due to low efficiency in drug removal by effluent treatment plants. Considering that these substances may interact with the DNA, causing metabolic and morphological changes, leading to cell death, the present study aimed to investigate the potential impact of a long-term exposure to these antineoplastic drugs in environmentally relevant concentrations, on testicular morphophysiology of rats. Male Wistar rats (70 days old) were distributed into 4 groups (n = 10 / group): control, received only vehicle; MTX, received methotrexate at 10ngL-1 in drinking water; 5-FU received 5-fluorouracil at 10ngL-1 in drinking water; and MTX+ 5FU, received the combination of MTX and 5-FU at 10ngL-1 each. The treatment period was from postnatal day (PND)70 to PND160, when the animals were euthanized for evaluation of testicular toxicity and changes in endocrine signaling. In these experimental conditions, both drugs acted as endocrine disruptors causing cytotoxic effects in the testes of exposed rats, altering the structural pattern of seminiferous tubules and leading to oxidative stress even at environmental concentrations.

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.

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.

Acute Toxic and Genotoxic Effects of Aluminum and Manganese Using In Vitro Models

The objective of this study was to use the same concentrations of aluminum (Al) and manganese (Mn) detected previously in groundwater above those permitted by Brazilian law and assess their cytotoxic and genotoxic effects in hamster ovary cell lines and their mutagenic effects through the Salmonella microsome assay. Chinese hamster ovary (CHO) and CHO-XRS5 cells were treated with different concentrations of Al and Mn (0.2 to 2.0 mg/L and 0.1 to 3.0 mg/L, respectively). The Ames test was used to analyze the concentrations of Al and Mn ranging from 0.025 to 1.0 mg/L and 0.0125 to 1.5 mg/L, respectively. Both metals showed cytotoxic effects on both cell lines and two bacterial strains (TA98 and TA100). The genotoxic effects of the highest concentrations of Al and Mn in cell lines showed nuclear buds, micronuclei, and DNA damage; however, none of the concentrations showed a positive mutagenic response in the Ames test. This is one of the few studies to demonstrate the cytotoxic effects of Al and Mn through the Ames test. In addition, the metals caused genomic instability in cell lines. Therefore, this study may help hasten the review of established regulatory standards for human consumption of groundwater.

Evaluation of cytotoxic and genotoxic effects of paclitaxel-loaded PLGA nanoparticles in neuroblastoma cells

Neuroblastoma, a neoplasm of the sympathetic nervous system, is the second most common extracranial malignant tumor of childhood and the most common solid tumor of infancy. Paclitaxel (taxol), a diterpenoid pseudoalkaloid isolated from the shells of Taxus brevifolia, is the first taxane derivative used in the clinic for cancer treatment. Poly (lactic-co-glycolic acid) (PLGA) is one of the most successfully used biodegradable polymers for drug delivery which has a minimum systemic toxicity. This study aimed to evaluate the cytotoxicity and genotoxicity of paclitaxel nanoencapsulated with PLGA. Cytotoxic effects were determined by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method and genotoxic effects were determined by single cell gel electrophoresis (Comet) method in human neuroblastoma cells (SH-SY5Y). According to our results, the viability of cells treated with concentrations higher than 10 nM of free paclitaxel and paclitaxel loaded PLGA nanoparticles for 48 and 72 h was found lower than 50%. Additionally, DNA damage increased with the increase of nanoparticle dose when the cells exposed to paclitaxel loaded PLGA nanoparticles for 24, 48 and 72 h. It can be concluded that PLGA nanoparticles can be considered as a biocompatible carrier system for drug delivery and might be promising agent against neuroblastoma.

The comet assay in animal models: From bugs to whales - (Part 2 Vertebrates)

The comet assay has become one of the methods of choice for the evaluation and measurement of DNA damage. It is sensitive, quick to perform and relatively affordable for the evaluation of DNA damage and repair at the level of individual cells. The comet assay can be applied to virtually any cell type derived from different organs and tissues. Even though the comet assay is predominantly used on human cells, the application of the assay for the evaluation of DNA damage in yeast, plant and animal cells is also quite high, especially in terms of biomonitoring. The present extensive overview on the usage of the comet assay in animal models will cover both terrestrial and water environments. The first part of the review was focused on studies describing the comet assay applied in invertebrates. The second part of the review, (Part 2) will discuss the application of the comet assay in vertebrates covering cyclostomata, fishes, amphibians, reptiles, birds and mammals, in addition to chordates that are regarded as a transitional form towards vertebrates. Besides numerous vertebrate species, the assay is also performed on a range of cells, which includes blood, liver, kidney, brain, gill, bone marrow and sperm cells. These cells are readily used for the evaluation of a wide spectrum of genotoxic agents both in vitro and in vivo. Moreover, the use of vertebrate models and their role in environmental biomonitoring will also be discussed as well as the comparison of the use of the comet assay in vertebrate and human models in line with ethical principles. Although the comet assay in vertebrates is most commonly used in laboratory animals such as mice, rats and lately zebrafish, this paper will only briefly review its use regarding laboratory animal models and rather give special emphasis to the increasing usage of the assay in domestic and wildlife animals as well as in various ecotoxicological studies.

Occupational exposure to cytotoxic drugs: the importance of surface cleaning to prevent or minimise exposure

Healthcare workers who prepare or administer cytotoxic agents run the risk of exposure, and the risks for health are real even at doses lower than those applied in cancer patients, because, in theory, no dose is safe. The most common and problematic route of exposure is through the skin, especially as work surfaces can remain contaminated even after cleaning. This pilot study aimed to demonstrate the importance of having an effective surface decontamination protocol by determining surface contamination with cyclophosphamide, 5-fluorouracil, and paclitaxel as the most common cytotoxic drugs in an oncology day service. Samples were collected before and after drug handling and analysed with high performance liquid chromatography with diode array detection (HPLC-DAD). Of the 29 samples collected before drug handling 23 were contaminated, five of which with more than one drug. Of the 30 samples collected after drug handling 25 were contaminated, eight of which with more than one drug. The two time points did not significantly differ, which evidences a widespread contamination and ineffective cleaning. This calls for revising the cleaning protocol and handling procedure to place contamination under control as much as possible.

Hyperthermia enhances methyl methanesulfonate-induced adaptive response in meiotic cells of grasshopper Poecilocerus pictus

To understand the role of hyperthermia (HT) in adaptive response, methyl methanesulfonate (MMS) adapted meiotic cells of Poecilocerus pictus were used. Poecilocerus pictus were treated with conditioning (L) or challenging (H) dose of MMS and 2-h time lag (TL) between these doses (L-2h-H) (combined) was employed. Different treatment schedules were used to analyse the influence of HT on MMS-induced adaptive response namely pre; inter; post-treatment and cross-adaptation. After each treatment schedules, chromosomal anomalies were analysed. The frequencies of chromosomal anomalies induced by conditioning and challenging doses of MMS were significantly higher (P < 0.0001) compared to that of the control or HT groups. The combined treatments resulted in significant reduction of chromosomal anomalies compared to additive effect of MMS (P < 0.0001). The pre, inter, post and cross-adaptation treatments with HT reduced the frequencies of chromosomal anomalies compared to the challenge and combined treatments with MMS. There is a protection against MMS-induced chromosomal anomalies by HT in in vivo P.pictus. This is the first report to demonstrate that HT enhances the MMS-induced adaptive response in in vivo meiotic cells.

Chemoresistance to Cancer Treatment: Benzo-α-Pyrene as Friend or Foe?

Background: Environmental pollution such as exposure to pro-carcinogens including benzo-α-pyrene is becoming a major problem globally. Moreover, the effects of benzo-α-pyrene (BaP) on drug pharmacokinetics, pharmacodynamics, and drug resistance warrant further investigation, especially in cancer outpatient chemotherapy where exposure to environmental pollutants might occur. Method: We report here on the effects of benzo-α-pyrene on esophageal cancer cells in vitro, alone, or in combination with chemotherapeutic drugs cisplatin, 5-flurouracil, or paclitaxel. As the study endpoints, we employed expression of proteins involved in cell proliferation, drug metabolism, apoptosis, cell cycle analysis, colony formation, migration, and signaling cascades in the WHCO1 esophageal cancer cell line after 24 h of treatment. Results: Benzo-α-pyrene had no significant effect on WHCO1 cancer cell proliferation but reversed the effect of chemotherapeutic drugs by reducing drug-induced cell death and apoptosis by 30−40% compared to drug-treated cells. The three drugs significantly reduced WHCO1 cell migration by 40−50% compared to control and BaP-treated cells. Combined exposure to drugs was associated with significantly increased apoptosis and reduced colony formation. Evaluation of survival signaling cascades showed that although the MEK-ERK and Akt pathways were activated in the presence of drugs, BaP was a stronger activator of the MEK-ERK and Akt pathways than the drugs. Conclusion: The present study suggest that BaP can reverse the effects of drugs on cancer cells via the activation of survival signaling pathways and upregulation of anti-apoptotic proteins such as Bcl-2 and Bcl-xL. Our data show that BaP contribute to the development of chemoresistant cancer cells.