Crocidolite induces cell transformation and p53 gene mutation in BALB/c-3T3 cells

Our plain-English summary of Crocidolite induces cell transformation and p53 gene mutation in BALB/c-3T3 cells, by F. Lin, Y. Liu, Y. Liu, et al (Teratogenesis, Carcinogenesis, and Mutagenesis, 2000).

The study

• Authors: F. Lin, Y. Liu, Y. Liu, N. Keshava, S. Li
• Journal: Teratogenesis, Carcinogenesis, and Mutagenesis
• Published: 2000;20(5):273-81
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Cell transformation is one of the most common assays used to study morphological changes in the multistep process of carcinogenesis. The present study was initiated to investigate the ability of crocidolite to induce cell transformation in BALB/c-3T3 cells and to analyze the relationship between p53 mutations and crocidolite-induced cell transformation, if any. Cell transformation was carried out according to standard procedures. Exponentially growing cells were exposed to different concentrations (0.2-20 microg/cm(2)) of crocidolite fibers for 72 h. Foci obtained from cell transformation were analyzed for their ability to grow in soft agar (anchorage-independence) and p53 alterations. The results of this study demonstrate that there was an increase in transformation frequency (TF) with an increase in concentration of crocidolite. Also, focal cells were able to grow on soft agar, indicating anchorage-independence. cDNA was prepared from RNA isolated from Type 3 foci and subjected to mutational analysis. Eleven exons of the p53 gene from eight transformed cell lines were analyzed for alterations using polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP). Alterations were found in seven of eight cell lines, two of them were in exons 4-6, and five in exons 9-11. The alterations were randomly scattered among the crocidolite dose groups. These results suggest that crocidolite induces mutations predominantly in exons 9-11 of the p53 gene in a nondose-dependent manner.

In plain English

In this laboratory study, the authors exposed a mouse cell line, BALB/c-3T3 cells, to crocidolite fibers. Concentrations were 0.2 to 20 micrograms per square centimetre, for 72 hours. The authors looked for cell transformation, a laboratory model of steps toward cancer. No people or animals were studied. Transformed patches of cells (foci) increased at concentrations above 0.2. At 20, fewer foci formed, but transformation frequency, adjusted for surviving cells, was highest: 1.818 per thousand, versus 0.045 in saline controls. Cells from all six transformed foci tested grew in soft agar, more so at higher doses. Seven of eight transformed cell lines had p53 gene changes: two in exons 4 to 6, five in exons 9 to 11. A figure legend lists two of those lines as treated with a comparison chemical, benzo[a]pyrene. No changes were found in untransformed cells. The authors wrote that these results suggest crocidolite induces p53 mutations mainly in exons 9 to 11, not dependent on dose. They noted they tested only eight transformed cell lines, and their method could not show the type or exact location of the mutations.

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) cell culture experiment: cytotoxicity, cell transformation, soft agar growth and p53 gene mutation analysis by PCR-SSCP
• Who was studied: Mouse BALB/c-3T3 clone A31-I-13 cells grown in culture. No humans or animals were studied.
• Exposure: Crocidolite fibers from Yaoan County, Yunnan Province, China, applied at 0.2 to 20 µg/cm2 for 72 hours. Fiber lengths were 22% over 10 µm, 51% 5 to 10 µm and 27% under 5 µm, all under 1 µm in diameter. Saline was the solvent control and benzo[a]pyrene (0.2 µg/ml) the positive control.
• Main results:
  • Relative colony-forming efficiency of crocidolite-treated cells fell from 84.5% at 0.2 µg/cm2 to 5.0% at 20 µg/cm2.
  • Crocidolite increased the number of transformed foci at concentrations above 0.2 µg/cm2 (P less than or equal to 0.05), except at 20 µg/cm2, where the number of foci decreased.
  • Transformation frequency, normalized for surviving cells, was higher at 20 µg/cm2. Table I gives 0.045‰ for saline and 0.300‰ for benzo[a]pyrene. For crocidolite it gives 0.067‰ at 0.2, 0.154‰ at 1 (P less than or equal to 0.05), and 0.541‰, 1.182‰ and 1.818‰ at 5, 10 and 20 µg/cm2 (each P less than or equal to 0.01).
  • Cells from all six transformed foci tested formed colonies in soft agar. Colony numbers rose with crocidolite concentration, reaching a maximum average of 84.5 colonies in the highest dose group (20 µg/cm2).
  • Seven of eight transformed cell lines carried p53 alterations: two in exons 4–6 and five in exons 9–11. None were found in exons 1–3 or 7–9.
  • No p53 mutations were found in nontransformed BALB/c-3T3 cells.
• The authors' conclusion: The authors concluded that crocidolite induced cell transformation in a dose-dependent manner. They wrote that the results suggest crocidolite induces p53 mutations mainly in exons 9–11, in a manner that does not depend on dose.
• Limitations the authors state:
  • Only eight transformed cell lines were tested for p53 mutations.
  • The PCR-SSCP method shows that a mutation exists but not its type or exact location.
  • Whether p53 mutations in a transformed mouse cell line differ from those found in humans needs further investigation.
  • Morphological transformation in a dish may be analogous to cancer development in the body, but the processes may not be identical.

Topics

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

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

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