In vitro genotoxic activities of fibrous erionite

Our plain-English summary of In vitro genotoxic activities of fibrous erionite, by A. Poole, R.C. Brown, C.J. Turver, et al (British Journal of Cancer, 1983).

The study

• Authors: A. Poole, R.C. Brown, C.J. Turver, J.W. Skidmore, D.M. Griffiths
• Journal: British Journal of Cancer
• Published: 1983;47(5):697-705
• Cited by: 37 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

A high incidence of mesothelioma has been reported from some villages in Cappadocia, Turkey. This type of cancer is usually associated with the inhalation of asbestos, but on the basis of the most prevalent fibre in the dust from these villages, the Turkish outbreak has been attributed to the inhalation of zeolite fibres. A counter hypothesis, based on the detection of very small quantities of chrysotile and tremolite in strata samples and human lung tissue, postulates a significant role of these minerals as one of several factors contributing to pleural disease. A respirable fraction of erionite, (from Oregon, USA, but with similar characteristics to the fibres found in Turkey), has some in vitro genotoxic properties associated with many conventional carcinogens. In this study these fibres caused an increase in morphological transformation and unscheduled DNA repair synthesis (UDS) in C3H10T1/2 cells and UDS in the human lung cell line--A549. It is therefore suggested that exposure to fibrous erionite alone may be sufficient to cause the high incidence of pleural tumours observed in Turkey.

In plain English

This was a laboratory study of cells grown in culture. The authors tested fibrous erionite, a zeolite mineral, using a sample from Rome, Oregon, USA, because a fibre-enriched sample from the Turkish village of Karain could not be prepared. Elemental analysis showed the Oregon and Karain fibres had similar composition. The authors exposed a mouse embryo cell line (C3H10T1/2) and a human lung cell line (A549) to the fibres. In the mouse cells, erionite increased the number of transformed cell clusters (foci) compared with untreated cultures, at concentrations greater than 10 micrograms per ml. Erionite also increased unscheduled DNA synthesis, a sign of DNA repair, in both cell lines. By one counting method the increase was significant at 100, 150 and 200 micrograms per ml and disappeared at higher concentrations. The authors concluded that erionite was more active in vitro than other disease-causing fibrous dusts. They also concluded that their findings support the hypothesis that erionite exposure is the cause of the pleural tumours in Turkey. They noted that extrapolating from cell tests to living animals is difficult.

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) experiments: a cell transformation assay and unscheduled DNA synthesis (DNA repair) assays measured by autoradiographic and scintillometric methods
• Who was studied: C3H10T1/2 cells derived from mouse embryo fibroblasts, and the human lung cell line A549
• Exposure: A respirable fraction of fibrous erionite (a zeolite mineral) from Rome, Oregon, USA, used because a fibre-enriched sample from Karain, Turkey could not be prepared. Concentrations were 5 to 30 micrograms per ml in the transformation assay and 25 to 500 micrograms per ml in the DNA repair assays. Positive controls were benzo(a)pyrene and nitroquinoline-N-oxide (NQO).
• Main results:
  • In the mouse C3H10T1/2 cells, erionite increased the number of transformed (type III) foci compared with negative control cultures.
  • In both transformation experiments, transformed foci appeared at erionite concentrations greater than 10 micrograms per ml, which the authors considered a positive effect.
  • In the first transformation experiment, 4 of 20 flasks treated with erionite at 20 micrograms per ml had type III foci, versus 0 of 20 control flasks.
  • In the second transformation experiment, 6 of 12 flasks treated with erionite at 20 micrograms per ml had type III foci, versus 0 of 30 control flasks.
  • By the autoradiographic method in C3H10T1/2 cells, erionite caused a significant increase in nuclear labelling at 100, 150 and 200 micrograms per ml.
  • The positive effect in the autoradiographic DNA repair assay diminished and disappeared at higher erionite concentrations, which the authors attributed presumably to cytotoxicity.
  • The scintillometric method confirmed that fibrous erionite can induce unscheduled DNA synthesis in both C3H10T1/2 and A549 cells.
  • In C3H10T1/2 cells, DNA specific activity was 3.28 (s.d. 0.55) dpm per ng DNA with erionite at 100 micrograms per ml, versus 1.16 (s.d. 0.29) in controls.
  • In A549 cells, DNA specific activity was 1.66 (s.d. 0.77) dpm per ng DNA with erionite at 50 micrograms per ml, versus 0.68 (s.d. 0.24) in controls.
  • The erionite concentrations needed to produce measurable unscheduled DNA synthesis were much higher than those causing transformation.
• The authors' conclusion: The authors concluded that erionite is at the very least quantitatively more active in vitro than other pathogenic fibrous dusts. They concluded that their findings support the hypothesis that exposure to erionite is the cause of the pleural tumours in Turkey, and that exposure to other agents need not be invoked to explain the epidemiological findings.
• Limitations the authors state:
  • The authors could not prepare an adequately fibre-enriched sample of erionite from Karain, Turkey, so they tested erionite from Oregon, USA instead.
  • With the autoradiographic technique, it was difficult to score the nuclei of cells containing dust, so a truly random selection of nuclei could not be counted.
  • The authors stated that extrapolating from in vitro to in vivo activity is difficult.

Topics

Medical terms in this study, explained in our Lexicon: erionite, Mesothelioma, Cappadocia, Zeolite, Chrysotile, Tremolite, Respirable Fraction.

Related studies

• The in vitro activities of a highly carcinogenic mineral fibre--potassium octatitanate — A. Poole, R.C. Brown, et al. (1986)
• The in vitro genetic effects of fibrous erionite and crocidolite asbestos — K.T. Kelsey, E. Yano, et al. (1986)
• Study of the cell-transforming ability of amosite and crocidolite asbestos and the ability to induce changes in the metabolism and macromolecular binding of benzo(a)pyrene in C3H10T1/2 cells — A. Poole, R.C. Brown, et al. (1983)
• CT findings in malignant pleural mesothelioma related to nonoccupational exposure to asbestos and fibrous zeolite (erionite) — C. Erzen, M. Eryilmaz, et al. (1991)
• Erionite and asbestos differently cause transformation of human mesothelial cells — P. Bertino, A. Marconi, et al. (2007)
• Erionite exposure and mesotheliomas in rats — J.C. Wagner, J.W. Skidmore, et al. (1985)

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