Asbestos induces aberrant crypt foci in the colon of rats

Our plain-English summary of Asbestos induces aberrant crypt foci in the colon of rats, by D.E. Corpet, V. Pirot, I. Goubet (Cancer Letters, 1993).

The study

• Authors: D.E. Corpet, V. Pirot, I. Goubet
• Journal: Cancer Letters
• Published: 1993;74(3):183-7
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The carcinogenicity of asbestos to the gut is controversial. The aberrant crypt focus (ACF) assay is proposed as a test for colon carcinogens. We have scored ACF in the colon of rats and mice, one month after per os gavages with suspensions of asbestos fibers. Crocidolite asbestos induced ACF in the colon of rats in two independent experiments (P = 0.02 and P < 0.01 compared to controls given water), and was ten times less effective than the carcinogen azoxymethane. Chrysotile asbestos also induced ACF in rats. Neither crocidolite nor chrysotile induced ACF in mice. The data suggest that ingested asbestos may be carcinogenic to the colon.

In plain English

This was an animal experiment. The authors gave rats and mice asbestos fibers by stomach tube (gavage) and, about a month later, counted aberrant crypt foci (ACF) in the colon. The authors describe ACF, small abnormal patches of the colon lining, as putative precursor lesions of colon cancer. The study did not look for cancer itself. In the first experiment, rats given crocidolite had more ACF than control rats given water (P = 0.006). By weight, crocidolite was about ten times less effective than the carcinogen azoxymethane. Giving both together did not significantly increase ACF compared with giving either alone. In the second experiment, control rats had no ACF. Each group of rats given chrysotile or crocidolite had more ACF on average than controls, but higher crocidolite doses did not produce more ACF. Mice given crocidolite or chrysotile alone developed no ACF. The authors concluded that the findings support the speculation that swallowed asbestos can lead to colorectal cancer. They also noted that the ACF they found might not be precancerous lesions.

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: Animal experiment: two experiments in rats and mice using the aberrant crypt focus (ACF) assay, with colons scored about one month after asbestos was given by gavage
• Who was studied: First experiment: 4 groups of 8 female Fischer 344 rats and 4 groups of 12 female OF1 mice, all 5 weeks old. Second experiment: 6 groups of 9 rats and 3 groups of 12 mice
• Exposure: First experiment: crocidolite by gavage (rats 33 mg/kg, mice 50 mg/kg, on days 1, 4 and 5), azoxymethane (AOM) injections, both, or vehicles. Second experiment: a single gavage of chrysotile (rats 70 mg/kg, mice 100 mg/kg), AOM or water, plus three rat groups given a single gavage of crocidolite at 40, 80 or 160 mg/kg
• Main results:
  • First experiment: rats given crocidolite had more colon ACF than control rats (P = 0.006)
  • By weight of total dose, crocidolite was about ten times less effective than AOM: rats given 100 mg/kg crocidolite and rats given 10 mg/kg AOM had comparable numbers of ACF (P = 0.16)
  • Rats given both AOM and crocidolite did not have significantly more ACF than rats given either compound alone. The authors said the data do not support a cocarcinogenic effect
  • First experiment, mice: no ACF in mice given crocidolite alone or water, while mice given 10 mg/kg AOM had a mean of 15 ACF
  • Mice given AOM together with crocidolite had a mean of 14 ACF, no different from mice given AOM alone (P = 0.85). The authors observed no cocarcinogenic effect in mice
  • Second experiment: control rats given water had no ACF, and each of the 4 asbestos-treated rat groups had more ACF on average than controls (P less than 0.05 for each)
  • In rats, chrysotile (70 mg/kg) induced about as many ACF as crocidolite (80 mg/kg): group means of 0.6 and 0.9 ACF per colon, P = 0.5
  • No dose-effect relationship in rats: crocidolite at 40, 80 and 160 mg/kg gave group means of 1.0, 0.9 and 0.3 ACF per colon. All differed from controls, but the treated groups did not differ from each other (all P greater than 0.20)
  • No ACF were found in mice given chrysotile (100 mg/kg)
• The authors' conclusion: The authors concluded that the induction of preneoplastic lesions in the rat colon supports the speculation that ingesting asbestos can lead to colorectal cancer
• Limitations the authors state:
  • The ACF detected might not be precancerous lesions
  • A single large dose (bolus) might have a stronger effect than continuous intake of fibers
  • The study failed to show a dose-effect relationship. The authors said this should be confirmed with a wider range of doses
  • Gavage is a short-term, high-dose exposure, unlike the low doses the general population ingests through drinking water or filtered juices
  • The difference in sensitivity between rats and mice was unexpected

Topics

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

Medical terms in this study, explained in our Lexicon: Crocidolite, Chrysotile, Carcinogenic.

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