Chrysotile effects on human lung cell carcinoma in culture: 3-D reconstruction and DNA quantification by image analysis

Our plain-English summary of Chrysotile effects on human lung cell carcinoma in culture: 3-D reconstruction and DNA quantification by image analysis, by B.A. Cortez, G.M. Machado-Santelli (BMC Cancer, 2008).

The study

• Authors: B.A. Cortez, G.M. Machado-Santelli
• Journal: BMC Cancer
• Published: 2008;8:181
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Chrysotile is considered less harmful to human health than other types of asbestos fibers. Its clearance from the lung is faster and, in comparison to amphibole forms of asbestos, chrysotile asbestos fail to accumulate in the lung tissue due to a mechanism involving fibers fragmentation in short pieces. Short exposure to chrysotile has not been associated with any histopathological alteration of lung tissue.

Methods: The present work focuses on the association of small chrysotile fibers with interphasic and mitotic human lung cancer cells in culture, using for analyses confocal laser scanning microscopy and 3D reconstructions. The main goal was to perform the analysis of abnormalities in mitosis of fibers-containing cells as well as to quantify nuclear DNA content of treated cells during their recovery in fiber-free culture medium.

Results: HK2 cells treated with chrysotile for 48 h and recovered in additional periods of 24, 48 and 72 h in normal medium showed increased frequency of multinucleated and apoptotic cells. DNA ploidy of the cells submitted to the same chrysotile treatment schedules showed enhanced aneuploidy values. The results were consistent with the high frequency of multipolar spindles observed and with the presence of fibers in the intercellular bridge during cytokinesis.

Conclusion: The present data show that 48 h chrysotile exposure can cause centrosome amplification, apoptosis and aneuploid cell formation even when long periods of recovery were provided. Internalized fibers seem to interact with the chromatin during mitosis, and they could also interfere in cytokinesis, leading to cytokinesis failure which forms aneuploid or multinucleated cells with centrosome amplification.

In plain English

In this laboratory study, the authors exposed HK2 cells, grown from a human non-small cell lung carcinoma, to chrysotile asbestos at about 0.25 mg/mL for 48 hours. The cells then recovered in fiber-free medium for 24, 48 or 72 hours. The authors called this dose high fiber exposure. The share of cells with two or more nuclei rose from about 15% in untreated cells to 45% in treated cells, and reached about 65% after longer recovery. Dying (apoptotic) cells were 0.26% of untreated cells; among treated cells that detached, 34% looked apoptotic after 24 hours of recovery. Nuclei with abnormally high DNA content (above 5C) rose from 0.2% to 10%. Multipolar spindles (division structures with more than two poles) appeared in more than 50% of treated cells in metaphase or anaphase, versus around 5% of untreated metaphases. Fibers were seen inside cells, including between dividing daughter cells. The authors concluded that 48 hours of chrysotile exposure can cause centrosome amplification, apoptosis and aneuploid cells in HK2 cells. They noted that these cancer cells carry mutations that might affect cell-division checkpoints.

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: laboratory (in vitro) experiment on cultured human lung cancer cells, using confocal microscopy, 3D reconstruction and DNA quantification by image analysis
• Who was studied: HK2 cell line established from human non-small cell lung carcinoma, grown in culture; three independent experiments, with more than 500 nuclei analysed for each treatment and for control cells (University of Sao Paulo, Brazil)
• Exposure: Chrysotile 5R (Quebec Standard) from SAMA Mineração de Amianto Ltda (Minaçu, GO, Brazil), at an approximate final concentration of 0.25 mg/mL for 48 h, followed by 24, 48 or 72 h of recovery in fiber-free medium; cells interacted with fibers of 0.3 to 30 μm length. Lower concentrations (0.125 and 0.0625 mg/mL) were also tested for one measure.
• Main results:
  • The frequency of cells with two or more nuclei increased from about 15% in control cells to 45% in chrysotile-treated cells, reaching approximately 65% after longer recovery (P < 0.01).
  • Apoptotic cells were 0.26% of control cells. Among cells that detached from the dish during chrysotile treatment, 34% showed apoptotic morphology after 24 h of recovery.
  • The share of nuclei with DNA content above 5C rose progressively from 0.2% (control) to 10% with longer recovery after chrysotile treatment.
  • The highest DNA values observed in each cell population increased progressively across the recovery times, from 7C to 17C.
  • At lower chrysotile concentrations (0.125 and 0.0625 mg/mL, 48 h treatment plus 48 h recovery), the frequencies of nuclei above 5C were 4.8% and 3.8%, respectively (data not shown in the article). The authors said this frequency seems to be dose-dependent.
  • Multipolar spindles were seen in more than 50% of metaphase/anaphase cells among chrysotile-treated cells, compared with around 5% of metaphases in control cells.
  • Fibers were seen inside treated cells, including in the intercellular bridge between daughter cells in late telophase.
  • Metaphase and anaphase cells with more than two centrosomes were observed in treated cells at a frequency similar to that of cells with multipolar spindles.
• The authors' conclusion: The authors concluded that 48 h of chrysotile exposure can cause centrosome amplification, apoptosis and aneuploid cell formation in HK2 cells, even with long recovery periods. They suggested that fibers appear to interact with chromatin and could lead to cytokinesis failure.
• Limitations the authors state:
  • The study used human lung cancer cells, which carry mutations that might interfere with mitotic checkpoint functions. The authors argued that these mutations probably do not affect the cell-fiber interaction itself.
  • The final fiber concentration in the culture medium was difficult to determine because some fibers float in serum-supplemented medium.
  • The authors described the 0.25 mg/mL treatment as a situation of high fiber exposure.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Cana Brava mine, Uruaçu, Goiás

All asbestos mines

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, Carcinoma, Amphibole Group, Lung Cancer, Apoptosis.

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