Asbestos, radiation and oncogenic transformation

Our plain-English summary of Asbestos, radiation and oncogenic transformation, by T.K. Hei, E.J. Hall, R.S. Osmak (British Journal of Cancer, 1984).

The study

• Authors: T.K. Hei, E.J. Hall, R.S. Osmak
• Journal: British Journal of Cancer
• Published: 1984;50(5):717-20
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Summary of the article

This short communication reported a laboratory study of how asbestos and gamma radiation interact in damaging cells and making them cancerous (oncogenic transformation). The authors wanted to clarify how asbestos causes cancer and whether its known synergism with cigarette smoke also occurs with agents other than chemicals. They used C3H 10T1/2 mouse embryo fibroblasts and UICC standard samples of crocidolite and amosite. Crocidolite at 2.5-50 µg/ml for 24 h caused a sharp, dose-dependent fall in colony survival and slowed cell growth, without appreciably changing saturation density. Amosite was similarly cytotoxic. For the transformation assays, cells received 5 µg/ml of fibres for 24 h, 4 Gy of gamma rays from a cesium-137 source, or both, and transformed foci were scored after 6 weeks. Five experiments involving 1,500 dishes were included. Neither fibre alone raised transformation significantly above the spontaneous rate. Fibre pretreatment followed by irradiation gave significantly higher transformation frequencies than radiation alone (P<0.001 for crocidolite, P<0.01 for amosite). Per surviving cell, these were 5.18-6.42 x 10^-4 with crocidolite plus radiation and 3.10-5.04 x 10^-4 with amosite plus radiation, against 1.47-1.70 x 10^-4 with radiation alone. Adding 0.1 or 1.0 µg/ml fibres 3 days after 2 Gy of radiation produced no enhancement. The authors concluded that asbestos acted as a co-carcinogen rather than a promoter in this system.

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In plain English

This laboratory study used cultured mouse embryo cells (the C3H 10T1/2 line). No people or live animals were studied. The authors tested whether asbestos and gamma radiation, alone or together, killed cells or caused oncogenic (cancer-like) transformation. They used UICC standard reference samples of crocidolite and amosite. Both fibre types killed cells. For crocidolite, colony numbers fell as concentration rose from 2.5 to 50 micrograms per millilitre. A concentration of 5 micrograms per millilitre, which caused only moderate cell killing, was chosen for the transformation tests. These involved five experiments and 1,500 dishes. Neither fibre alone produced transformation rates significantly different from the spontaneous rate. Cells treated with either fibre for 24 hours and then given 4 Gy of gamma rays had significantly higher transformation rates than cells given radiation alone (P<0.001 for crocidolite, P<0.01 for amosite). Asbestos at 0.1 or 1.0 micrograms per millilitre added three days after a 2 Gy dose gave no enhancement. Based on these cell-culture results, the authors concluded that, in the context of the two-stage model of carcinogenesis, asbestos can be categorized as a co-carcinogen.

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 mouse embryo cells
• Who was studied: C3H 10T1/2 mouse embryo fibroblast cells in culture. The transformation work comprised 5 experiments with a total of 1,500 dishes.
• Exposure: UICC standard reference samples of crocidolite and amosite asbestos, alone and combined with gamma radiation
• Main results:
  • Both crocidolite and amosite killed the cells. With crocidolite, the number of colonies per dish fell as fibre concentration rose from 2.5 to 50 micrograms per millilitre.
  • A concentration of 5 micrograms per millilitre of each fibre was chosen for the transformation studies because it caused only moderate cell killing.
  • Neither crocidolite nor amosite alone produced transformation frequencies significantly different from the spontaneous rate.
  • Cells pretreated with asbestos for 24 hours and then given 4 Gy of gamma rays had significantly higher transformation frequencies than cells given radiation alone (P<0.001 for crocidolite, P<0.01 for amosite).
  • No enhancement of transformation was found when asbestos at 0.1 or 1.0 micrograms per millilitre was added 3 days after a 2 Gy dose of gamma rays (data not shown).
• The authors' conclusion: The authors concluded that, in the context of the two-stage model of carcinogenesis, asbestos can be categorized as a co-carcinogen, based on their cell-culture findings.

Topics

Medical terms in this study, explained in our Lexicon: Fibroblast, UICC, Crocidolite, Amosite.

Related studies

• Modulating factors in the expression of radiation-induced oncogenic transformation — E.J. Hall, T.K. Hei (1990)
• Long-term exposure of mesothelial cells to SV40 and asbestos leads to malignant transformation and chemotherapy resistance — A.L. Cleaver, K. Bhamidipaty, et al. (2014)
• The influence of asbestos dust on the oncogenic transformation of C3H10T 1/2 cells — R.C. Brown, A. Poole, et al. (1983)
• Malignant transformation of immortalized human bronchial epithelial cells by asbestos fibers — T.K. Hei, L.J. Wu, et al. (1997)
• Promotion of morphological transformation by Di-n-butyltin dichloride in C3H/10T1/2 cells: prediction by prior expression of tumour promoter-responsive genes — C.L. Parfett, T. Marquardt, et al. (2000)
• Asbestos promotes morphological transformation and elevates expression of a gene family invariably induced by tumor promoters in C3H/10T1/2 cells — C.L. Parfett, R. Pilon, et al. (1996)

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