Induction of centrosome injury, multipolar spindles and multipolar division in cultured V79 cells exposed to dimethylarsinic acid: role for microtubules in centrosome dynamics

Centrosome amplification, chromosomal instability and cancer: mechanistic, clinical and therapeutic issues

Centrosomes, the main microtubule-organizing centers in most animal cells, are of crucial importance for the assembly of a bipolar mitotic spindle and subsequent faithful segregation of chromosomes into two daughter cells. Centrosome abnormalities can be found in virtually all cancer types and have been linked to chromosomal instability (CIN) and tumorigenesis. Although our knowledge on centrosome structure, replication, and amplification has greatly increased within recent years, still only very little is known on nature, causes, and consequences of centrosome aberrations in primary tumor tissues. In this review, we summarize our current insights into the mechanistic link between centrosome aberrations, aneuploidy, CIN and tumorigenesis. Mechanisms of induction and cellular consequences of aneuploidy, tetraploidization and CIN, as well as origin and effects of supernumerary centrosomes will be discussed. In addition, animal models for both CIN and centrosome amplification will be outlined. Finally, we describe approaches to exploit centrosome amplification, aneuploidy and CIN for novel and specific anticancer treatment strategies based on the modulation of chromosome missegregation rates.

Large tumor suppressors 1 and 2 regulate Aurora-B through phosphorylation of INCENP to ensure completion of cytokinesis

The tumor suppressor kinases LATS1 and LATS2 (LATS1/2) regulate not only organ size through the Hippo signaling pathway, but also cell-cycle checkpoints and apoptosis via other signaling cascades. We previously reported that LATS1/2 localize to the mitotic apparatus, where they are involved in the phosphorylation and activation of the mitotic kinase Aurora-B; however, the detailed mechanism of LATS1/2 action remains obscure. The activity of Aurora-B is stringently regulated by formation of the chromosomal passenger complex containing the inner centromere protein (INCENP), which leads to appropriate activation of Aurora-B during mitosis and cytokinesis. In this study, we found that LATS1/2 phosphorylated INCENP at S894 in the Thr-Ser-Ser motif. Moreover, the LATS-mediated phosphorylation of S894 was necessary and sufficient for the activation of Aurora-B, which is required for completion of cytokinesis in cells engaged in multipolar division. We propose a novel mechanism for regulation of Aurora-B via INCENP phosphorylation by LATS1/2 during cytokinesis.

Induction of Aneuploidy, Centrosome Abnormality, Multipolar Spindle, and Multipolar Division in Cultured Mammalian Cells Exposed to an Arsenic Metabolite, Dimethylarsinate

Toxicological studies of arsenic compounds were conducted in cultured mammalian cells to investigate the effects of glutathione (GSH) depletion. Dimethylarsinate DMA(V) was not cytotoxic in cells depleted of GSH, but was found to be cytotoxic when GSH was present outside the cells. The results suggested that a reactive form of DMA(V) was generated through interaction with GSH. Dimethylarsine iodide DMI(III) was used as a model compound of DMA(III), and the biological effects were investigated. DMI(III) was about 10000 times more toxic to the cells than DMA(V). Chromosome structural aberrations and numerical changes, such as aneuploidy, were induced by DMI(III). DMA(V) induced multiple foci of the centrosome protein, γ-tubulin, which were colocalized with multipolar spindles in mitotic cells. The multiple foci coalesced into a single dot on disruption of the microtubules (MT). However, reorganization of the MT caused multiple foci of γ-tubulin, suggesting that the induction of centrosome abnormalities by DMA(V) required intact MT. Inhibition of the MT-dependent motor, kinesin, prevented formation of multiple foci of γ-tubulin, which pointed to the involvement of the MT-dependent mitotic motor, kinesin, in the maintenance of centrosome abnormalities. DMI(III) caused abnormal cytokinesis (multipolar division). In addition, DMI(III) caused morphological transformation in Syrian hamster embryo cells. Consideration of the overall process following the centrosome abnormalities caused by DMA(V) suggested a mode of cytotoxicity in which the mitotic centrosome is a critical target.

Arsenic-induced promoter hypomethylation and over-expression of ERCC2 reduces DNA repair capacity in humans by non-disjunction of the ERCC2-Cdk7 complex

Arsenic in drinking water is of critical concern in West Bengal, India, as it results in several physiological symptoms including dermatological lesions and cancers. Impairment of the DNA repair mechanism has been associated with arsenic-induced genetic damage as well as with several cancers. ERCC2 (Excision Repair Cross-Complementing rodent repair, complementation group 2), mediates DNA-repair by interacting with Cdk-activating kinase (CAK) complex, which helps in DNA proof-reading during transcription. Arsenic metabolism alters epigenetic regulation; we tried to elucidate the regulation of ERCC2 in arsenic-exposed humans. Water, urine, nails, hair and blood samples from one hundred and fifty seven exposed and eighty eight unexposed individuals were collected. Dose dependent validation was done in vitro using HepG2 and HEK-293. Arsenic content in the biological samples was higher in the exposed individuals compared with the content in unexposed individuals (p < 0.001). Bisulfite-modified methylation specific PCR showed a significant (p < 0.0001) hypomethylation of the ERCC2 promoter in the arsenic-exposed individuals. Densitometric analysis of immunoblots showed a nearly two-fold increase in expression of ERCC2 in exposed individuals, but there was an enhanced genotoxic insult as measured by micronuclei frequency. Immuno-precipitation and western blotting revealed an increased (p < 0.001) association of Cdk7 with ERCC2 in highly arsenic exposed individuals. The decrease in CAK activity was determined by observing the intensity of Ser(392) phosphorylation in p53, in vitro, which decreased with an increase in arsenic dose. Thus we infer that arsenic biotransformation leads to promoter hypomethylation of ERCC2, which in turn inhibits the normal functioning of the CAK-complex, thus affecting DNA-repair; this effect was highest among the arsenic exposed individuals with dermatological lesions.

Chronic exposure to zinc chromate induces centrosome amplification and spindle assembly checkpoint bypass in human lung fibroblasts

Hexavalent chromium (Cr(VI)) compounds are known human lung carcinogens. Solubility plays an important role in its carcinogenicity with the particulate or insoluble form being the most potent. Of the particulate Cr(VI) compounds, zinc chromate appears to be the most potent carcinogen; however, very few studies have investigated its carcinogenic mechanism. In this study, we investigated the ability of chronic exposure to zinc chromate to induce numerical chromosome instability. We found no increase in aneuploidy after a 24 h exposure to zinc chromate, but with more chronic exposures, zinc chromate induced concentration- and time-dependent increases in aneuploidy in the form of hypodiploidy, hyperdiploidy, and tetraploidy. Zinc chromate also induced centrosome amplification in a concentration- and time-dependent manner in both interphase and mitotic cells after chronic exposure, producing cells with centriolar defects. Furthermore, chronic exposure to zinc chromate induced concentration- and time-dependent increases in spindle assembly checkpoint bypass with increases in centromere spreading, premature centromere division, and premature anaphase. Last, we found that chronic exposure to zinc chromate induced a G2 arrest. All together, these data indicate that zinc chromate can induce chromosome instability after prolonged exposures.

Methylated Arsenicals: The Implications of Metabolism and Carcinogenicity Studies in Rodents to Human Risk Assessment

Monomethylarsonic acid (MMA(V)) and dimethylarsinic acid (DMA(V)) are active ingredients in pesticidal products used mainly for weed control. MMA(V) and DMA(V) are also metabolites of inorganic arsenic, formed intracellularly, primarily in liver cells in a metabolic process of repeated reductions and oxidative methylations. Inorganic arsenic is a known human carcinogen, inducing tumors of the skin, urinary bladder, and lung. However, a good animal model has not yet been found. Although the metabolic process of inorganic arsenic appears to enhance the excretion of arsenic from the body, it also involves formation of methylated compounds of trivalent arsenic as intermediates. Trivalent arsenicals (whether inorganic or organic) are highly reactive compounds that can cause cytotoxicity and indirect genotoxicity in vitro. DMA(V) was found to be a bladder carcinogen only in rats and only when administered in the diet or drinking water at high doses. It was negative in a two-year bioassay in mice. MMA(V) was negative in 2-year bioassays in rats and mice. The mode of action for DMA(V)-induced bladder cancer in rats appears to not involve DNA reactivity, but rather involves cytotoxicity with consequent regenerative proliferation, ultimately leading to the formation of carcinoma. This critical review responds to the question of whether DMA(V)-induced bladder cancer in rats can be extrapolated to humans, based on detailed comparisons between inorganic and organic arsenicals, including their metabolism and disposition in various animal species. The further metabolism and disposition of MMA(V) and DMA(V) formed endogenously during the metabolism of inorganic arsenic is different from the metabolism and disposition of MMA(V) and DMA(V) from exogenous exposure. The trivalent arsenicals that are cytotoxic and indirectly genotoxic in vitro are hardly formed in an organism exposed to MMA(V) or DMA(V) because of poor cellular uptake and limited metabolism of the ingested compounds. Furthermore, the evidence strongly supports a nonlinear dose-response relationship for the biologic processes involved in the carcinogenicity of arsenicals. Based on an overall review of the evidence, using a margin-of-exposure approach for MMA(V) and DMA(V) risk assessment is appropriate. At anticipated environmental exposures to MMA(V) and DMA(V), there is not likely to be a carcinogenic risk to humans.

Aneugenic potential of the nitrogen mustard analogues melphalan, chlorambucil and p-N,N-bis(2-chloroethyl)aminophenylacetic acid in cell cultures in vitro

Melphalan (MEL), chlorambucil (CAB) and p-N,N-bis(2-chloroethyl)aminophenylacetic acid (PHE) are nitrogen mustard analogues, which are clinically used as chemotherapeutic agents. They also exert carcinogenic activity. The aim of this study was to investigate the aneugenic potential of the above drugs and the possible mechanism responsible for this activity. The Cytokinesis Block Micronucleus (CBMN) assay in combination with fluorescence in situ hybridization (FISH) was used in human lymphocyte cultures to evaluate micronucleus (MN) frequency. Pancentromeric probe (alpha-satellite) was applied to identify chromosomes in micronuclei and an X-chromosome specific centromeric probe was used to asses micronucleation and non-disjunction of this chromosome in binucleated cells. The effect of the above compounds on the organization of mitotic apparatus, as a possible target of chemicals with aneugenic potential, was investigated in C(2)C(12) mouse cell line by double immunofluorescence of alpha- and gamma-tubulin. We found that the studied drugs increased MN frequency in a linear dose-dependent manner primarily by chromosome breakage and in a lesser extent by an aneugenic mechanism. Non-disjunction and micronucleation of X-chromosome were also induced. Abnormal metaphase cells were linearly increased with concentration and characterized by abnormal centrosome number. Interphase cells with micronuclei and abnormal centrosome number were also observed. Since nitrogen mustards are highly reactive agents, with low selectivity and form covalent bonds with different nucleophilic sites in proteins and nucleic acids, it is reasonable to consider that one possible pathway for nitrogen mustard analogues to exert their aneugenic activity is through reaction with nucleophilic moieties of proteins or genes that are involved in the duplication and/or separation of centrosomes, resulting in abnormal centrosome number. Based on our results the carcinogenicity of nitrogen mustard analogues studied may be attributed not only to their activity to trigger gene mutation and chromosome breakage, but also to their aneugenic potential. Further studies are warranted to clarify the above two hypotheses.

Chronic Exposure to Lead Chromate Causes Centrosome Abnormalities and Aneuploidy in Human Lung Cells

Hexavalent chromium [Cr(VI)] compounds are established human lung carcinogens. The carcinogenicity of Cr(VI) is related to its solubility, with the most potent carcinogens being the insoluble particulate Cr(VI) compounds. However, it remains unknown why particulate Cr(VI) is more carcinogenic than soluble Cr(VI). One possible explanation is that particulates may provide more chronic exposures to chromate over time. We found that aneuploid cells increased in a concentration- and time-dependent manner after chronic exposure to lead chromate. Specifically, a 24-hour lead chromate exposure induced no aneugenic effect, whereas a 120-hour exposure to 0.5 and 1 microg/cm2 lead chromate induced 55% and 60% aneuploid metaphases, respectively. We also found that many of these aneuploid cells were able to continue to grow and form colonies. Centrosome defects are known to induce aneuploidy; therefore, we investigated the effects of chronic lead chromate exposure on centrosomes. We found that centrosome amplification in interphase and mitotic cells increased in a concentration- and time-dependent manner with 0.5 and 1 microg/cm2 lead chromate for 120 hours, inducing aberrant centrosomes in 18% and 21% of interphase cells and 32% and 69% of mitotic cells, respectively; however, lead oxide did not induce centrosome amplification in interphase or mitotic cells. There was also an increase in aberrant mitosis after chronic exposure to lead chromate with the emergence of disorganized anaphase and mitotic catastrophe. These data suggest that one possible mechanism for lead chromate-induced carcinogenesis is through centrosome dysfunction, leading to the induction of aneuploidy.

The impairments of neoblast division in regenerating planarian Polycelis felina (Daly.) caused by in vitro treatment with cadmium sulfate

The effects of cadmium sulfate on the neoblast mitotic activity in regenerating planarian Polycelis felina (Daly.) were investigated. Mitotic abnormalities and chromosomal aberrations were evaluated after 6-h treatment and 24-h recovery period. The blastema were fixed, and examined cytologically through routine lactoorceine squash preparations. Mitotic indices were also determined. Cadmium sulfate induced a dose-dependent decrease in neoblast mitotic activity, accompanied with disturbances in distribution of cells over mitotic phases. Different cytological abnormalities with varying frequency were observed. Marked mitotic depression was concentration-dependent. Toxic effects of cadmium in regenerating planarian were mainly associated with mitotic spindle disturbances. Immediately after treatment mitotic abnormalities were prevalent over chromosomal and C-mitosis was the most prominent one. After 24-h recovery period a prevalence of mitotic over chromosomal aberrations was still present in animals treated with two higher concentrations of cadmium sulfate. However, the proportions of cells with chromosome stickiness in all treated animals were significantly increased compared to their post-treatment values. Observed mitotic impairments could be related to mitotic arrest contributing to retardations and delays, especially in animals treated with the highest concentration tested. The results obtained indicated usefulness of short term invertebrate assays as an alternative to in vitro pre-screening of toxic chemicals.

A trivalent dimethylarsenic compound, dimethylarsine iodide, induces cellular transformation, aneuploidy, centrosome abnormality and multipolar spindle formation in Syrian hamster embryo cells

The abilities of dimethylarsine iodide (DMI), a model compound of trivalent dimethylarsenicals, to induce cellular transformation, aneuploidy, centrosome abnormality, and multipolar spindle formations were investigated using the Syrian hamster embryo (SHE) cell model. Cellular growth was decreased in a concentration-dependent manner by treatment with DMI at concentrations over 0.1 microM. Treatment with DMI at concentrations from 0.1 to 1.0 microM induced morphological transformation in SHE cells. The transforming activity of DMI, determined by the frequency of morphologically transformed colonies, was approximately 30 times higher than that induced by treatment with the same concentration of sodium arsenite. Flow cytometry suggested an increase in the aneuploid population caused by DMI, as shown by the appearance of hypo-2N, hypo-4N and hypo-8N. DMI also caused abnormal staining of gamma-tubulin, indicating loss of centrosome integrity and a resultant induction of multipolar spindles in mitotic cells. Mitotic cells with centrosomes that coalesced partly at the cell periphery, not the cell center, were detected as early changes that resulted in multipolar spindles. These findings indicate that DMI has transforming activity in SHE cells. Moreover, the results suggest the importance of centrosome abnormalities as a causal change of DMI-induced aneuploidy.

Methylated trivalent arsenicals as candidate ultimate genotoxic forms of arsenic: induction of chromosomal mutations but not gene mutations

Arsenic is a prevalent human carcinogen whose mutagenicity has not been characterized fully. Exposure to either form of inorganic arsenic, As(III) or As(V), can result in the formation of at least four organic metabolites: monomethylarsonic acid, monomethylarsonous acid (MMA(III)), dimethylarsinic acid, and dimethylarsinous acid (DMA(III)). The methylated trivalent species, as well as some of the other species, have not been evaluated previously for the induction of chromosome aberrations, sister chromatid exchanges (SCE), or toxicity in cultured human peripheral blood lymphocytes; for mutagenicity in L5178Y/Tk(+/-) mouse lymphoma cells or in the Salmonella reversion assay; or for prophage-induction in Escherichia coli. Here we evaluated the arsenicals in these assays and found that MMA(III) and DMA(III) were the most potent clastogens of the six arsenicals in human lymphocytes and the most potent mutagens of the six arsenicals at the Tk(+/-) locus in mouse lymphoma cells. The dimethylated arsenicals were also spindle poisons, suggesting that they may be ultimate forms of arsenic that induce aneuploidy. Although the arsenicals were potent clastogens, none were potent SCE inducers, similar to clastogens that act via reactive oxygen species. None of the six arsenicals were gene mutagens in Salmonella TA98, TA100, or TA104; and neither MMA(III) nor DMA(III) induced prophage. Our results show that both methylated As(V) compounds were less cytotoxic and genotoxic than As(V), whereas both methylated As(III) compounds were more cytotoxic and genotoxic than As(III). Our data support the view that MMA(III) and DMA(III) are candidate ultimate genotoxic forms of arsenic and that they are clastogens and not gene mutagens. We suggest that the clastogenicity of the other arsenicals is due to their metabolism by cells to MMA(III) or DMA(III).

Methylmercury, but not inorganic mercury, causes abnormality of centrosome integrity (multiple foci of gamma-tubulin), multipolar spindles and multinucleated cells without microtubule disruption in cultured Chinese hamster V79 cells

Abnormalities of centrosome integrity and spindle organization in the cultured Chinese hamster fibroblast cell line V79 exposed to methylmercury (MeHgCl) and inorganic mercury (Hg(2+)) were investigated in conjunction with inductions of mitotic arrest and multinucleated cells. The centrosome integrity and spindle organization were investigated by immunofluorescence of centrosome proteins, gamma-tubulin, and beta-tubulin, respectively. MeHgCl at subtoxic concentrations caused an increase in mitotic index 6 h after exposure. Ameboid cells with multiple pseudopodia were also induced and chromosomes were distributed even in the pseudopodia. After the increase in mitotic index caused by MeHgCl, multinucleated cells with multiple micronuclei appeared. MeHgCl caused abnormality of centrosome integrity (multiple foci of gamma-tubulin) colocalized with aberrant spindles in a concentration-dependent manner, while it did not cause disruption of centrosome integrity and microtubule organization in interphase cells. In addition, MeHgCl led to the appearance of monoastral cells with a one-dot signal of gamma-tubulin. By contrast, Hg(2+) did not cause any of the changes induced by MeHgCl. Thus, MeHgCl caused centrosome abnormality and the related changes without microtubule disruption, suggesting that the mitotic centrosome is a critical target for the cytotoxic effects of MeHgCl.

Involvement of microtubules and mitochondria in the antagonism of arsenic trioxide on paclitaxel-induced apoptosis

Arsenic trioxide (As(2)O(3)) at low concentrations (1-10 microM) is effective in the treatment of acute promyelocytic leukemia (APL) and lymphoma and is in clinical trials for treatment of solid tumors. Paclitaxel, an antimicrotubule agent, is highly efficacious in the treatment of adult tumors and is in clinical evaluation in childhood tumors. This study is the first to investigate the combination of arsenic and paclitaxel in the range of clinically achievable concentrations. We found that the simultaneous combination was antagonistic on proliferation of the neuroblastoma SK-N-SH cell line by using the combination index (CI) method. Moreover, a 40+/-5% decrease in paclitaxel-induced apoptosis in cells co-treated with As(2)O(3) confirmed the antagonism. The mechanism of antagonism was studied at the cellular level with 200 nM paclitaxel, twice the IC(50) value, and with 1 microM As(2)O(3) which administered singly did not affect cell survival or the microtubule network. As(2)O(3) antagonized the effects of paclitaxel on tubulin and microtubules. Paclitaxel-induced mitotic block was decreased by 20+/-2% and bundles induced by 200 nM paclitaxel were less condensed in the presence of 1 microM As(2)O(3). As(2)O(3) (10-200 microM) induced a concentration-dependent inhibition of tubulin polymerization in vitro which was maintained in presence of paclitaxel. Spectrophotometric and spectrofluorometric measurements indicated an interaction of As(2)O(3) with tubulin SH groups, without modification of the stoichiometry of paclitaxel binding to tubulin. Moreover, 4 microM As(2)O(3) inhibited the release of cytochrome c from isolated mitochondria by 78+/-10%. Our results show that As(2)O(3) and paclitaxel act antagonistically on mitochondria and microtubules and illustrate the need for careful evaluation of drug combinations.

Role of mitotic motors, dynein and kinesin, in the induction of abnormal centrosome integrity and multipolar spindles in cultured V79 cells exposed to dimethylarsinic acid

The role of microtubule-based motors in the induction of abnormal centrosome integrity by dimethylarsinic acid (DMAA) was investigated with the use of monastrol, a specific inhibitor of mitotic kinesin, and vanadate, an inhibitor of dynein ATPase. Cytoplasmic dynein co-localized with multiple foci of gamma-tubulin in mitotic cells arrested by DMAA. Disruption of microtubules caused dispersion of dynein while multiple foci of gamma-tubulin were coalesced to a single dot. Vanadate also caused dispersion of dynein, which had been co-localized with multiple foci of gamma-tubulin by DMAA, without affecting spindle organization. However, the dispersion of dynein did not prohibit the induction of abnormal centrosome integrity by DMAA. Inhibition of mitotic kinesin by monastrol resulted in monoastral cells with non-migrated centrosomes in the cell center. Monastrol, when applied to mitotic cells with abnormal centrosome integrity, rapidly reduced the incidence of cells with the centrosome abnormality. Moreover, monastrol completely inhibited reorganization of abnormal centrosomes that had been coalesced to a single dot by microtubule disruption. These results suggest that abnormal centrosome integrity caused by DMAA is not simply due to dispersion of fragments of microtubule-organizing centers, but is dependent on the action of kinesin. In addition, the results suggest that kinesin plays a role not only in the induction of mitotic centrosome abnormality, but also in maintenance.

Malsegregation as a possible mechanism of aneuploidy induction by metal salts in MRC-5 human cells

Many aneugenic compounds are known to affect one or more components of the mitotic apparatus leading to an erroneous migration of chromosomes. Malsegregation occurs when a chromosome (or a chromatid) fails to migrate and remains at the metaphase plate. Nondisjunction implies the lack of dissociation between sister chromatids and the migration of both together to the same pole. The aim of the present study was to provide evidence that the aneugenic effect of some metal salts is the consequence of malsegregation at anaphase and that it is not caused by nondisjunction mechanisms. The frequencies of lagging chromosomes at anaphase-telophase of mitosis, hypoploid metaphases, and kinetochore-positive micronuclei induced by cadmium chloride, potassium dichromate, and cacodilic acid (dimethylarsinic acid) in MRC-5 human cells were compared. The data indicate that all the tested compounds are able to induce aneuploidy in MRC-5 human cells. Positive, statistically significant correlations were found when kinetochore-positive micronuclei, hypoploidy, and lagging chromosome frequencies were compared. The results suggest that malsegregation is the main mechanism involved in the induction of aneuploidy by metal salts in MRC-5 cells.

Effects of heat shock protein 70 (Hsp70) on arsenite-induced genotoxicity

Arsenic, a human carcinogen, is genotoxic, although its mechanism(s) of action for tumorigenesis is not well understood. Among the toxicity-related properties of this chemical are its clastogenic and aneugenic activities, as well as its capacity for inducing stress-response in the form of elevated heat shock protein (HSP) expression. In the present study, we evaluated the effects of Hsp70 expression on arsenite (As)-induced structural and numerical chromosome anomalies in human cells. Human MCF-7 Tet-off cells stably transfected with a pTRE/Hsp70-1 transgene construct were used to regulate Hsp70 levels prior to in vitro As exposures. Separate cultures of relatively high vs. low Hsp70-expressing cells were established. A cytokinesis block micronucleus assay with kinetochore immunostaining was used to detect micronuclei (MN) derived from chromosome breakage (K-MN) or loss (K+MN). These studies demonstrated significant increases in micronucleus frequencies in response to As following either a long exposure (5 or 10 microM for 46 hr), or short exposure (10 or 40 microM for 8 hr) protocol. Overall, the long protocol was more efficient in producing K+MN and cells with multiple MN. Overexpressing Hsp70 resulted in significant reductions in the percent of cells positive for MN for both the long and short As exposure protocols. Both K+ and K- types of As-induced MN were lower in cells with elevated Hsp70 as compared to cells without overexpression of Hsp70. We conclude that the dose and duration of As exposure influence the type as well as amount of chromosomal alteration produced and that inducible Hsp70 protects against both the clastogenic and aneugenic effects of this chemical.

Induction of aneuploidy by nickel sulfate in V79 Chinese hamster cells

The ability of nickel sulfate (NiSO(4)) to induce chromosome aneuploidy was investigated in vitro using the V79 Chinese hamster cell line. V79 cells were treated with 100-400 microM NiSO(4) for 24h, and monitored up to 72 h following treatment with a chromosome aberration assay, a micronuclei assay using antikinetochore antibodies (CREST assay) and an anaphase/telophase assay. Aneuploid cells were induced in a significant fraction of the cell population 24-48 h following treatment with nickel sulfate. The majority of these cells were hyperdiploid. In addition, nickel sulfate caused increased frequency of cells with kinetochore-positive micronuclei as well as kinetochore-negative micronuclei. Abnormal chromosome segregation such as lagging chromosomes, chromosome bridges and asymmetric segregation were also observed in more than 50% of anaphase or telophase cells following treatment with NiSO(4). The incidences of these abnormalities were dose-dependent in general, although the effects were prominent in a sublethal dose. These results indicate that NiSO(4) has the ability to induce aneuploidy in V79 cells. In addition, the results in anaphase/telophase assay suggest that the compound may have an effect on spindle apparatus, which could result in aneuploidy following abnormal chromosome segregation.