The fate of chrysotile-induced multipolar mitosis and aneuploid population in cultured lung cancer cells

Our plain-English summary of The fate of chrysotile-induced multipolar mitosis and aneuploid population in cultured lung cancer cells, by A. Cortez Bde, G. Quassollo, A. Caceres, et al (PloS One, 2011).

The study

• Authors: A. Cortez Bde, G. Quassollo, A. Caceres, G.M. Machado-Santelli
• Journal: PloS One
• Published: 2011;6(4):e18600
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Chrysotile is one of the six types of asbestos, and it is the only one that can still be commercialized in many countries. Exposure to other types of asbestos has been associated with serious diseases, such as lung carcinomas and pleural mesotheliomas. The association of chrysotile exposure with disease is controversial. However, in vitro studies show the mutagenic potential of chrysotile, which can induce DNA and cell damage. The present work aimed to analyze alterations in lung small cell carcinoma cultures after 48 h of chrysotile exposure, followed by 2, 4 and 8 days of recovery in fiber-free culture medium. Some alterations, such as aneuploid cell formation, increased number of cells in G2/M phase and cells in multipolar mitosis were observed even after 8 days of recovery. The presence of chrysotile fibers in the cell cultures was detected and cell morphology was observed by laser scanning confocal microscopy. After 4 and 8 days of recovery, only a few chrysotile fragments were present in some cells, and the cellular morphology was similar to that of control cells. Cells transfected with the GFP-tagged α-tubulin plasmid were treated with chrysotile for 24 or 48 h and cells in multipolar mitosis were observed by time-lapse microscopy. Fates of these cells were established: retention in metaphase, cell death, progression through M phase generating more than two daughter cells or cell fusion during telophase or cytokinesis. Some of them were related to the formation of aneuploid cells and cells with abnormal number of centrosomes.

In plain English

This laboratory study used cells in culture, not people. The authors exposed HK2 human lung carcinoma cells to chrysotile asbestos for 48 hours at three concentrations, then grew them in fiber-free medium for 2, 4 or 8 days. They counted as aneuploid only nuclei with DNA content above 5.1 C. In control cells 0.25% of nuclei were aneuploid. Two days after the highest concentration, 7% were, rising to 10.5% after 8 days. Flow cytometry, done only at the middle concentration, showed more cells in the G2/M phase. Multipolar mitoses, divisions with more than two poles, made up 7.23% of dividing cells after 48 hours of exposure, against 2.37% in controls. They stayed above control levels after 8 days, when few fiber fragments remained. Of 30 treated cells tracked by video microscopy in multipolar division, about half did not progress to anaphase while observed; some died, and others produced three daughter cells or fused. Monkey kidney (VERO) cells also showed more micronuclei and multipolar mitoses. The authors concluded that some of the aneuploid cells were viable.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: In vitro (cell culture) laboratory experiment, including flow cytometry, DNA image analysis, confocal microscopy and time-lapse microscopy
• Who was studied: HK2 cells, a human lung carcinoma cell line (described in the methods as non-small cell lung carcinoma), plus VERO cells, an epithelial line from green monkey kidney used as a normal comparison; for DNA quantification, 1200 nuclei were analyzed per group
• Exposure: Chrysotile 5R (Quebec Standard) fibers for 24 h or 48 h at concentrations printed as 250, 125 or 62.5 mg/ml, followed by 2, 4 or 8 days in fiber-free medium; flow cytometry and microscopy used the 125 concentration
• Main results:
  • For the aneuploidy percentages, only nuclei with DNA content above 5.1 C (the hypertetraploid class) were counted as aneuploid
  • After 48 h of chrysotile and 2 days of recovery, HK2 cells had 7% aneuploid nuclei at the highest concentration, 4.5% at the middle concentration and 3.5% at the lowest, against 0.25% in control cells
  • After 8 days of recovery, aneuploid nuclei reached 10.5% at the highest concentration; the text gives 5.9% for the middle concentration and 4.67% for the lowest
  • By flow cytometry, done only at the 125 concentration, treated HK2 cells had 12% fewer G1 cells and 5% more G2/M cells than control cells
  • The number of S-phase cells did not differ between treated and control HK2 cells, and total numbers of dividing cells were similar
  • Multipolar mitoses made up 7.23% of all dividing HK2 cells after 48 h of chrysotile exposure, against 2.37% in control cells
  • After 8 days of recovery, treated HK2 cells still had more multipolar mitoses than control cells
  • After 8 days of recovery, no long fibers and only a few small fiber fragments were seen inside HK2 cells
  • After 8 days of recovery, the percentage of micronucleated HK2 cells had fallen to a level similar to control cells
  • In time-lapse microscopy, all control divisions were bipolar, while around 40% of metaphases in treated HK2 cells were multipolar; the fates of 30 of these cells were tracked
  • About half of the tracked HK2 cells in multipolar metaphase did not progress to anaphase while observed; others died, produced three daughter cells, or fused during telophase or cytokinesis
  • In VERO cells after 48 h of chrysotile and 24 h of recovery, bi/multinucleated cells were 6.34% and micronucleated cells 3.89% (against 1.55% micronucleated and no abnormal mitosis in controls); multipolar mitoses were 7.18% of all cell divisions
• The authors' conclusion: The authors concluded that chrysotile-exposed HK2 cells showed aneuploidy and multipolar mitosis that persisted for up to 8 days, when only a few fiber fragments remained, and that some of the aneuploid cells were viable
• Limitations the authors state:
  • No established normal lung epithelial cell line was available for comparison, so VERO monkey kidney cells were used instead
  • HK2 cells are tumor cells that probably carry mutations allowing division to continue after abnormal mitosis
  • The cell culture setting lacks the interactions between cell types, extracellular matrix and growth factors present in lung tissue
  • Cytokinesis failure takes too long to be observed in the time-lapse experiments

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile, Lung cancer.

Medical terms in this study, explained in our Lexicon: Chrysotile, Lung Cancer, Carcinoma, Pleural Mesothelioma.

Related studies

• Multipolar mitosis and aneuploidy after chrysotile treatment: a consequence of abscission failure and cytokinesis regression — B.A. Cortez, P. Rezende-Teixeira, et al. (2016)
• Chromosome nondisjunction during bipolar mitoses of binucleated intermediates promote aneuploidy formation along with multipolar mitoses rather than chromosome loss in micronuclei induced by asbestos — T. Zhang, L. Lv, et al. (2017)
• Chrysotile effects on human lung cell carcinoma in culture: 3-D reconstruction and DNA quantification by image analysis — B.A. Cortez, G.M. Machado-Santelli (2008)
• Genotoxicity and cytotoxicity of multi-wall carbon nanotubes in cultured Chinese hamster lung cells in comparison with chrysotile A fibers — M. Asakura, T. Sasaki, et al. (2010)
• Evaluation of the dose-response and fate in the lung and pleura of chrysotile-containing brake dust compared to chrysotile or crocidolite asbestos in a 28-day quantitative inhalation toxicology study — D.M. Bernstein, B. Toth, et al. (2018)
• Inhibitory effects of anti-oxidants on apoptosis of a human polyclonal T-cell line, MT-2, induced by an asbestos, chrysotile-A — F. Hyodoh, A. Takata-Tomokuni, et al. (2005)

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