Comparative genotoxic effect of vincristine, vinblastine, and vinorelbine in somatic cells of Drosophila melanogaster

Genotoxic Assessment of the Dry Decoction of Myracrodruon urundeuva Allemão (Anacardiaceae) Leaves in Somatic Cells of Drosophila melanogaster by the Comet and SMART Assays

Medicinal plants are worldwide used as an efficient treatment of many diseases. Myracrodruon urundeuva Allemão (Anacardiaceae) is widely used Brazilian folk medicine to treat inflammations and infections of the female genital tract, conditions of the stomach and throat, and to heal wounds on the skin and mucous membranes. Several pharmacological properties of extracts and compounds isolated from M. urundeuva are found in the literature, corroborating its uses as antiulcer and gastroprotective, anti-inflammatory and analgesic, as well as antimicrobial. Despite these many uses in traditional herbal medicine, there are few reports of its toxic-genetic effect. This work aimed to investigate the genotoxic and mutagenic potential in vivo of the dry decoction of M. urundeuva leaves on somatic cells of Drosophila melanogaster, through the Comet assay and somatic mutation and recombination test (SMART). Six concentrations (0.5, 1.0, 2.0, 4.0, 8.0, and 16.0 mg/mL) were studied after feeding individuals for 24 hr in culture medium hydrated with extracts of M. urundeuva. In the Comet assay, all concentrations showed a genotoxic effect significantly higher than the negative control group, treated with distilled water. The two highest concentrations were also superior to the positive control group, treated with cyclophosphamide (1 mg/mL). In the SMART, there was a mutagenic effect at all concentrations tested, with a clear dose-dependent relationship. Both recombination and mutation account for these mutagenic effects. The set of results indicate that the dry decoction of M. urundeuva leaves is genotoxic and mutagenic for D. melanogaster under the experimental conditions of this study. Environ. Mol. Mutagen. 61:329-337, 2020. © 2019 Wiley Periodicals, Inc.

Therapy-induced mutations drive the genomic landscape of relapsed acute lymphoblastic leukemia

To study the mechanisms of relapse in acute lymphoblastic leukemia (ALL), we performed whole-genome sequencing of 103 diagnosis-relapse-germline trios and ultra-deep sequencing of 208 serial samples in 16 patients. Relapse-specific somatic alterations were enriched in 12 genes (NR3C1, NR3C2, TP53, NT5C2, FPGS, CREBBP, MSH2, MSH6, PMS2, WHSC1, PRPS1, and PRPS2) involved in drug response. Their prevalence was 17% in very early relapse (<9 months from diagnosis), 65% in early relapse (9-36 months), and 32% in late relapse (>36 months) groups. Convergent evolution, in which multiple subclones harbor mutations in the same drug resistance gene, was observed in 6 relapses and confirmed by single-cell sequencing in 1 case. Mathematical modeling and mutational signature analysis indicated that early relapse resistance acquisition was frequently a 2-step process in which a persistent clone survived initial therapy and later acquired bona fide resistance mutations during therapy. In contrast, very early relapses arose from preexisting resistant clone(s). Two novel relapse-specific mutational signatures, one of which was caused by thiopurine treatment based on in vitro drug exposure experiments, were identified in early and late relapses but were absent from 2540 pan-cancer diagnosis samples and 129 non-ALL relapses. The novel signatures were detected in 27% of relapsed ALLs and were responsible for 46% of acquired resistance mutations in NT5C2, PRPS1, NR3C1, and TP53. These results suggest that chemotherapy-induced drug resistance mutations facilitate a subset of pediatric ALL relapses.

Cytogenotoxic effects of Adenium obesum seeds extracts on breast cancer cells

The extracts prepared from various areal parts of the Adenium obesum (Forssk.) Roem. & Schult. (Family: Apocynaceae) including leaves, fruit and seeds ethanolic extracts and seed aqueous extract were evaluated against MCF-7 cells in order to investigate its potential of cytogenotoxicity and induction of apoptosis. The ethanolic seeds extract had comparatively higher cytotoxicity (IC₅₀ ∼ 337 µg/ml). Further, apoptosis and DNA damaging potential of seeds ethanolic extract was analyzed by applying multiple sub-lethal concentrations and durations. Flow cytometry results revealed that maximum percentage of early apoptosis (37%) and late apoptosis (35%) were observed after 12 h exposure in concentrations 200 µg/ml and 300 µg/ml, respectively. Similarly, the higher effect of extract in terms of DNA damage by alkaline comet assay was registered after 12 h treatment at concentrations 200 and 300 µg/mL. The calculated total damage score (TDS) for these concentrations were 614 and 617, respectively. The above findings indicate that A. obesum ethanolic seeds extracts has cytogenotoxic properties that could be further explored for the potential source of chemotherapeutic lead against cancer.

Lead modulated Heme synthesis inducing oxidative stress mediated Genotoxicity in Drosophila melanogaster

The mechanism of lead (Pb) modulated heme synthesis pathway induced oxidative stress mediated genotoxicity using standard (ST) and high bioactivation (HB) crosses of Drosophila melanogaster was addressed in the present study. Third instar larvae derived from the ST or HB crosses were reared in sub lethal concentrations of lead acetate (PbAc) treated food media and showed that Pb was readily taken up and accumulated in the said crosses. Pb modulated heme synthesis was evident by significant reductions of δ-aminolevulinic acid dehydratase (δ-ALA-D) and cytochrome P450 (CYP450) and increased accumulation of δ-aminolevulinic acid (δ-ALA). The results have also demonstrated that Pb induced oxidative stress by overproducing reactive oxygen species (ROS) and lipid peroxidation (LPO) and depletion of the antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and glutathione-s-transferase (GST). Wing somatic mutation and recombination test (SMART) using ST and HB crosses revealed that Pb is mutagenic and weakly recombinogenic. By employing larval hemocytes, there was an increase in percent of tail DNA in alkaline comet compared to that of neutral comet revealing the DNA single strand breaks were the products of Pb modulated heme synthesis pathway induced oxidative free radicals. Based on these findings, it can be concluded that Pb modulated heme synthesis pathway induces oxidative stress that mediates the genotoxicity in D. melanogaster.

Assessment of genotoxicity of vincristine, vinblastine and vinorelbine in human cultured lymphocytes: a comparative study

Vincristine (VCR), vinblastine (VBL) and vinorelbine (VRL) are anticancer agents from the Vinca alkaloid family that have the potential to induce genotoxic effect. The aim of the present study was to compare the genotoxic effect of VCR, VBL and VRL. Levels of 8-hydroxy-2-deoxy guanosine (8-OHdG) and sister chromatid exchanges (SCEs) were measured in cultured human blood lymphocytes treated with VCR, VBL and VRL at concentrations of 0.01 and 0.1 μg/mL. Results showed that VCR, VBL and VRL significantly increased the 8-OHdG levels (p <0.05), whereas it did not cause a significant increase in the frequencies of SCEs in human blood lymphocytes as compared to controls. On the other hand, all three agents significantly increased cells mitotic index (p <0.05). At both tested concentrations, the magnitude of the increase in 8-OHdG was VBL>VCR>VRL. In conclusion, VCR, VBL and VRL induce DNA damage as indicated by the increase in the 8-OHdG biomarker but with different magnitude.

Homologous recombination induced by doxazosin mesylate and saw palmetto in the Drosophila wing-spot test

Benign prostatic hyperplasia (BPH) is the most common tumor in men over 40 years of age. Acute urinary retention (AUR) is regarded as the most serious hazard of untreated BPH. α-Blockers, such as doxazosin mesylate, and 5-α reductase inhibitors, such as finasteride, are frequently used because they decrease both AUR and the need for BPH-related surgery. An extract of the fruit from American saw palmetto plant has also been used as an alternative treatment for BPH. The paucity of information available concerning the genotoxic action of these compounds led us to assess their activity as inducers of different types of DNA lesions using the somatic mutation and recombination test in Drosophila melanogaster. Finasteride did not induce gene mutation, chromosomal mutation or mitotic recombination, which means it was nongenotoxic in our experimental conditions. On the other hand, doxazosin mesylate and saw palmetto induced significant increases in spot frequencies in trans-heterozygous flies. In order to establish the actual role played by mitotic recombination and by mutation in the genotoxicity observed, the balancer-heterozygous flies were also analyzed, showing no increment in the total spot frequencies in relation to the negative control, for both drugs. Doxazosin mesylate and saw palmetto were classified as specific inducers of homologous recombination in Drosophila proliferative cells, an event linked to the loss of heterozygosity.

Combinatorial effect of maytansinol and radiation in Drosophila and human cancer cells

Combination therapy, in which two or more agents are applied, is more effective than single therapies for combating cancer. For this reason, combinations of chemotherapy with radiation are being explored in clinical trials, albeit with an empirical approach. We developed a screen to identify, from the onset, molecules that act in vivo in conjunction with radiation, using Drosophila as a model. Screens through two small molecule libraries from the NCI Developmental Therapeutics Program yielded microtubule poisons; this class of agents is known to enhance the effect of radiation in mammalian cancer models. Here we report an analysis of one microtubule depolymerizing agent, maytansinol isobutyrate (NSC292222; maytansinol), in Drosophila and in human cancer cells. We find that the effect of maytansinol is p53 dependent in Drosophila cells and human cancer cells, that maytansinol enhances the effect of radiation in both systems, and that the combinatorial effect of drug and radiation is additive. We also uncover a differential sensitivity to maytansinol between Drosophila cells and Drosophila larvae, which illustrates the value of studying cell behavior in the context of a whole organism. On the basis of these results, we propose that Drosophila might be a useful model for unbiased screens through new molecule libraries to find cancer drugs for combination therapy.

Mutagenic evaluation of combined paclitaxel and cisplatin treatment in somatic cells of Drosophila melanogaster

Recent studies have added paclitaxel (PAC) to traditional cisplatin (CIS) regimen to treat squamous cell carcinoma of the head and neck. The target of these antineoplastic agents is nuclear DNA for CIS and microtubules for PAC, although it is not restricted to malignant cells. In this study, the genotoxicity of the combined treatment of PAC and CIS was investigated using the standard version of the wing Somatic Mutation and Recombination Test (SMART) in Drosophila melanogaster. Quantitative and qualitative genotoxic effects of these compounds were estimated by comparing wing spot frequencies in marker-heterozygous to balancer-heterozygous flies. Two different concentrations of PAC (0.0025 and 0.005mM) and CIS (0.025 and 0.05mM) as well as combinations of them were employed. The results demonstrated that the spindle poison PAC alone was not genotoxic in this test system, while CIS was able to induce a high incidence of DNA damage in both genotypes, mainly related to somatic recombination. The data obtained for the combined treatments showed that its genotoxicity varied with the concentrations used. In small concentrations the number of total spots induced by combination was reduced in relation to CIS 0.025mM just for marker-heterozygous flies, showing that somatic recombination was the prevalent event involved. At higher concentrations the combined treatment showed significant reductions in the frequencies of large single spots, for both genotypes, and twin spots for marker-heterozygous flies, but did not significantly reduce the total spots frequency in either genotype. The data suggest that aneugenic activity of PAC could be responsible for the reduction in the genotoxicity of CIS.

Genotoxicity Testing of Four Textile Dyes in Two Crosses of Drosophila Using Wing Somatic Mutation and Recombination Test

In this study, four textile dyes, namely Astrazon Yellow, Red, Blue, and Black, were tested for their genotoxic effects in the wing cells of Drosophila melanogaster. Two crosses were used, the standard cross (ST) and the improved high-bioactivation cross (HB), the latter being characterized by increased sensitivity to the genotoxic effects of promutagens and procarcinogens. Three-day-old larvae were exposed to different concentrations of dyes. Commonly known mutagens were applied as positive controls. All concentrations of textile dyes, ethyl methanesulfonate (EMS), and urethane caused a decrease in survival proportional to concentration used. EMS and urethane caused an increase in the number of all types of spots in both standard and high-bioactivation crosses. Compared to ST crosses, the number of induced spots in the HB cross treated with urethane was considerably high. Treatment of the standard and the high-bioactivation crosses with textile dyes gave positive results, apparent from increase in the frequency of the small single spots. Yellow and red dyes also increased the number of large single spots in both crosses, whereas the twin spots were positive only at the highest dose of yellow dye. All these results indicate that D. melanogaster wing spot test can be recommended as a suitable in vivo test for the determination of genotoxicity of textile dyes.

Ryegrass leaf fructan synthesis is oxygen dependent and abolished by endomembrane inhibitors

Valid models are the foundation of systems biology. However, even well-established models may warrant reassessment. A testable feature of the currently accepted vacuolar model for fructan biosynthesis is its independence from metabolic energy at substrate level. The effects of limiting energy provision on fructan biosynthesis in grass leaves were determined. It was found that, in darkness in air, the rate of fructan accumulation was reduced to half relative to a light control. In darkness under anoxia the process was immediately abolished. In the light, the leaf sucrose concentration remained high, but in darkness +/- O(2), 40% of this sucrose was rapidly degraded. The constant rate of dark-aerobic fructan accumulation was independent of the decrease in sucrose concentration. Constant rates of aerobic fructan synthesis were independent of marked changes in extractable polymerase rates. In the dark under anoxia, fructan accumulation was abolished but leaves maintained > or = 80% of the extractable polymerase. Extractable polymerase rates cannot explain the rates of fructan accumulation observed in vivo, if the process is vacuolar. It was shown that the results were inconsistent with a vacuolar site for fructan synthesis. Six inhibitors of endomembrane function were shown to abolish fructan synthesis in vivo.

Mutagenic and recombinagenic activity of airborne particulates, PM10 and TSP, organic extracts in the Drosophila wing-spot test

The genotoxicity associated with air pollution in the city of Canoas, Rio Grande do Sul (Brazil), was assessed in November (spring) and January (summer). We applied the somatic mutation and recombination test (SMART) in Drosophila melanogaster in its standard version with normal bioactivation (ST) and in its variant with increased cytochrome P450-dependent biotransformation capacity (HB). The data indicated the genotoxicity of TSP and PM10 collected in November, in both ST and HB crosses. The genotoxic activity of the PM10 material in the spring sample was exclusively associated with the induction of mitotic recombination, whereas the TSP genetic toxicity was due to both recombinational as well as point and/or chromosomal mutation events. Considering PM10 collected in January, a positive response--100% (17.10 m3/ml) concentration--was observed in the HB cross, which was not detected in the ST cross.

Comparative genotoxicity evaluation of imidazolinone herbicides in somatic cells of Drosophila melanogaster

In the present study, five analogous herbicides, namely Imazapyr (IMZR), Imazapic (IMZC), Imazethapyr (IMZT), Imazamox (IMZX) and Imazaquin (IMZQ), were evaluated for genotoxicity (mutagenic and recombinagenic activity) in the wing somatic mutation and recombination test (SMART) of Drosophila melanogaster. They are classified as imidazolinone (IMI) herbicides and their mode of action is to inhibit acetohydroxyacid synthase (AHAS), an enzyme involved in the biosynthesis of the amino acids leucine, isoleucine and valine. Two crosses were used: the standard (ST) cross and the high bioactivation (HB) cross. The latter is characterized by high levels of cytochrome P450 conferring increased sensitivity to promutagens and procarcinogens. Three-day-old larvae were exposed by chronic feeding (48 h) to four different concentrations of these herbicides (2.5, 5.0, 10.0 or 20.0 mM). For the evaluation of genotoxic effects, the frequencies of spots per individual in the treated series were compared to the concurrent negative control series (ultrapure water). Imazapyr, Imazapic and Imazethapyr gave negative results with both crosses of the wing spot test. In the ST cross, Imazamox showed positive results only for large single spots (20.0 mM IMZX) and weak positive results for total spots (10.0 and 20.0 mM IMZX), while Imazaquin showed positive results only for large single spots (5.0 and 20.0mM IMZQ) and a weak positive result for total spots (20.0 mM IMZQ). These positive results are mainly due to induced recombination and to a minor extent to mutations. In the HB cross, only Imazamox (5.0 mM IMZX) showed a weak positive result for small single spots. The positive control urethane, a promutagen, caused an increase in the number of all types of spots in both crosses. In conclusion, the results of chronic treatments performed at high doses (toxicity was observed at higher doses) shows the existence of a genotoxic risk for IMZX and IMZQ exposure under these experimental conditions, and indicate the need for further research to delineate the exact mechanisms involved.

Detecting the cytogenetic effects in workers occupationally exposed to vincristine with four genetic tests

To study the human genetic damage induced by vincristine (VCR), the cytogenetic effects in workers occupationally exposed to vincristine were studied with micronucleus (MN) test, comet assay, hypoxantinepho-guanine phosphoribosyl-transferase (hprt) gene mutation assay and T-cells receptor (TCR) gene mutation assay. Fresh peripheral blood samples were collected from the workers and controls. Fifteen workers from a plant producing antineoplastic drug (vincristine) and 15 controls were matched according to age, gender and smoking. The results of MN test showed that the mean micronuclei rate (MNR) and mean micronucleated cells rate (MCR) in 15 workers were 17.80+/-1.88 per thousand and 13.67+/-1.56 per thousand, respectively, which were significantly higher than those (3.73+/-0.80 per thousand and 3.13+/-0.59 per thousand) in controls (P<0.01). It was found in the comet assay that the mean tail length (MTL) of 15 workers and 15 controls were 1.72+/-0.15 microm and 0.71+/-0.01 microm, respectively, there was significant difference between workers and controls for MTL (P<0.05), but the difference between the mean tail moment (MTM, 0.29+/-0.03) of 15 workers and MTM (0.17+/-0.05) of 15 controls was not significant (P>0.05). The results of hprt gene mutation assay showed that the average mutation frequency of hprt (Mf-hprt) in workers was 1.03+/-0.02 per thousand, which was significantly higher than that (0.87+/-0.01 per thousand) in controls (P<0.05). Meanwhile, the results of TCR gene mutation assay indicated that Mfs-TCR of workers and controls were 2.52+/-0.34 x 10(-4) and 1.51+/-0.11 x 10(-4), respectively, there was a significant difference between workers and controls (P<0.01). It is found in the results of our study that the genetic damage is detectable in 15 workers occupationally exposed to vincristine.

Genetic toxicity in surface water from Guaíba Hydrographic Region under the influence of industrial, urban and agricultural sewage in the Drosophila wing-spot test

Mutagenic and recombinagenic activity of surface waters in the Guaíba Hydrographic Region (RS, Brazil) was investigated using the SMART in Drosophila melanogaster. Two positive results in Caí River (September 2000 and August 2001) and in Taquari River (August 2001 and February 2002)--linked to direct recombinagenic toxicants were observed. In Jacuí samples, an indirect mutagenic and recombinagenic action was detected in a September 2000 collection and a direct recombinational activity was observed in February 2002. Also in February 2002--samples from Dilúvio Brook and Guaíba Lake (GPC) were able to induce wing spots by mitotic recombinagenesis. The former sampling site showed toxicants to have a direct action, and the latter an increment in mitotic recombination that depended on metabolic action. The SMART wing test shows that all positive responses were mainly related to homologous mitotic recombination.

Regulation of Hepatocyte Engraftment and Proliferation after Cytotoxic Drug-Induced Perturbation of the Rat Liver

BACKGROUND

Perturbations in specific liver cell compartments benefit transplanted cell engraftment and/or proliferation. We analyzed whether cytotoxic drugs interfering with the integrity of genomic DNA or cell division could be useful for liver cell transplantation.

METHODS

We used dipeptidyl peptidase IV deficient (DPPIV-) rats as recipients of syngeneic F344 rat hepatocytes. Rats were pretreated with doxorubicin, irinotecan, or vincristine prior to cell transplantation and synergistic liver perturbations were induced by drug administration followed by partial hepatectomy or carbon tetrachloride treatments. Transplanted cells were identified by DPPIV histochemistry and cell engraftment and proliferation were analyzed morphometrically. Perturbations in endothelial, Kupffer cell, and hepatocyte compartments were analyzed by electron microscopy, carbon incorporation, and blood tests, respectively.

RESULTS

Cell engraftment was improved in rats treated with doxorubicin but not with irinotecan or vincristine. Doxorubicin disrupted endothelial cells for up to seven days without causing Kupffer cell or hepatocellular toxicity. Neither doxorubicin nor vincristine induced liver repopulation in animals up to three months, including after partial hepatectomy or carbon tetrachloride-induced additional liver injury.

CONCLUSIONS

Doxorubicin-induced hepatic endothelial damage enhanced cell engraftment, which should be useful in cell therapy strategies.

Drosophila wing-spot test for genotoxic assessment of pollutants in water samples from urban and industrial origin

The Caí River (Rio Grande do Sul, Brazil) is an important watercourse that receives large amounts of industrial and untreated municipal discharges in its lower course. We employed the SMART in Drosophila melanogaster to evaluate the genotoxicity of surface waters collected from Caí sites receiving direct sewage discharge: from Montenegro (Km 52) and from São Sebastião do Caí (Km 78 and 80), and from two sites under the industrial influence (Km 13.6 and 18.6). The genotoxic analysis included three collections: March, June and September 1999, which were tested at crude sample and at 50 and 25% concentrations. Considering the industrial samples from Km 18.6 and 13.6, collected in March, June and September 1999, they were characterized as not having genetic toxicity. The urban samples collected in March--Km 52, 78 and 80--showed a significant increment in the frequencies of total spots. In Km 52 and 78 the genotoxic effect was associated to both mutational and recombinational events, although for Km 80 the increases observed were mainly related to the occurrence of homologous recombination. Moreover, the Km 80 crude sample from June and all the concentrations analyzed for Km 52 in September were also able to induce mitotic recombination. These effects were only observed in the ST cross, demonstrating the genotoxins present in the urban discharges act by direct interaction with the DNA of the somatic cells. The SMART in D. melanogaster was shown to be highly sensitive to detect genotoxic agents present in the aquatic environment, and must be better exploited for monitoring areas under anthropogenic discharges.

Cytogenetic Consequences of Vinblastine Treatment in Mouse Bone Marrow

BACKGROUND

Vinblastine (VBL), a vinca alkaloid, has very often been included in different cancer chemotherapeutic treatment regimens. Chemotherapy cures certain cancers and, at least, increases the life expectancy of cancer patients. However, in cancer survivors, a second malignancy frequently occurs after chemotherapy, which warrants detailed genotoxicity testing of the chemotherapeutic agents. The available genotoxicity test reports on VBL are self-contradictory and inconclusive. Thus, following a suitable experimental protocol, it is necessary to test the cytogenetic consequences of VBL treatment in mammals.

METHODS

Swiss mice received 1 of 3 different doses of VBL (0.5, 1.0 and 1.5 mg/kg body weight) as a single intraperitoneal injection. The cytogenetic toxicity of VBL was assessed from the induced aberrant metaphases, chromosomal aberrations (CAs) excluding gaps and the mitotic index (MI) 24 h after treatment, and micronuclei (MN) 30 h after treatment.

RESULTS

All 3 doses of VBL induced statistically significant (p < or = 0.01) percentages of aberrant metaphases and CAs, but there was no significant change in the MI. The induced percentage of aberrant metaphases and CAs were decreased with the increase in the dose of VBL. On the other hand, there was a dose-dependent and significant (p < or = 0.01) increase in MN induction.

CONCLUSIONS

The results of this study indicate the clastogenic potential of VBL in the mouse bone marrow. In the present study, the induction of numerous relatively large-sized MN by VBL is in agreement with the reported aneugenic action of the drug. Although VBL is cytotoxic and is a spindle poison, the mechanism(s) involved in bringing about its clastogenic effects is yet to be elucidated.