Differential Susceptibility of Human Pleural and Peritoneal Mesothelial Cells to Asbestos Exposure

Our plain-English summary of Differential Susceptibility of Human Pleural and Peritoneal Mesothelial Cells to Asbestos Exposure, by J. Dragon, J. Thompson, M. MacPherson, et al (Journal of Cellular Biochemistry, 2015).

The study

• Authors: J. Dragon, J. Thompson, M. MacPherson, A. Shukla
• Journal: Journal of Cellular Biochemistry
• Published: 2015;116(8):1540-52
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant mesothelioma (MM) is an aggressive cancer of mesothelial cells of pleural and peritoneal cavities. In 85% of cases both pleural and peritoneal MM is caused by asbestos exposure. Although both are asbestos-induced cancers, the incidence of pleural MM is significantly higher (85%) than peritoneal MM (15%). It has been proposed that carcinogenesis is a result of asbestos-induced inflammation but it is not clear what contributes to the differences observed between incidences of these two cancers. We hypothesize that the observed differences in incidences of pleural and peritoneal MM are the result of differences in the direct response of these cell types to asbestos rather than to differences mediated by the in vivo microenvironment. To test this hypothesis we characterized cellular responses to asbestos in a controlled environment. We found significantly greater changes in genome-wide expression in response to asbestos exposure in pleural mesothelial cells as compared to peritoneal mesothelial cells. In particular, a greater response in many common genes (IL-8, ATF3, CXCL2, CXCL3, IL-6, GOS2) was seen in pleural mesothelial cells as compared to peritoneal mesothelial cells. Unique genes expressed in pleural mesothelial cells were mainly pro-inflammatory (G-CSF, IL-1β, IL-1α, GREM1) and have previously been shown to be involved in development of MM. Our results are consistent with the hypothesis that differences in incidences of pleural and peritoneal MM upon exposure to asbestos are the result of differences in mesothelial cell physiology that lead to differences in the inflammatory response, which leads to cancer.

© 2015 Wiley Periodicals, Inc.

In plain English

This was a laboratory study of human mesothelial cells grown in culture, not a study of people. The authors exposed four cell lines to crocidolite asbestos for 8 hours and measured genome-wide gene activity by RNA sequencing. Two lines came from the pleural cavity (chest lining) and two from the peritoneum (abdominal lining); one of the peritoneal lines was immortalized. After 24 hours of asbestos exposure, both peritoneal lines showed more cell killing, while the pleural lines showed no significant killing. Asbestos changed more genes in pleural cells. Under the authors' combined filter, 843 and 481 transcripts changed in the two pleural lines, compared with 224 and 85 in the peritoneal lines. Changes mostly went in the same direction in both cell types, including increases in inflammation-related genes such as IL-6 and IL-8, but they were larger in pleural cells. Some pro-inflammatory genes, including IL-1 alpha, IL-1 beta, CSF3 and GREM1, responded uniquely in pleural cells. The authors suggested that this greater responsiveness could help explain why pleural mesothelioma is more frequent than peritoneal mesothelioma. They noted that the cell lines were not matched for age or sex.

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 human mesothelial cell lines, with genome-wide gene expression measured by RNA sequencing (massively parallel sequencing)
• Who was studied: Four human mesothelial cell lines bought from the Rheinwald lab (Brigham and Women's Hospital, Boston). Two were primary pleural lines: HPM3 (male donor, 64 years) and HPM4 (female donor, 65 years). Two were peritoneal lines: primary HM3 (female donor, 29 years) and immortalized LP9/hTERT (female donor, 26 years).
• Exposure: Crocidolite asbestos fibers added to the cell culture medium at a surface-area-based dose printed as "5 mg/cm2" (the unit symbols appear damaged in the text). Exposure lasted 8 hours for gene expression and 24 hours for the cell viability test. Glass beads at the same surface area were the negative control; they had almost no effect and were dropped from the analysis.
• Main results:
  • After 24 hours of asbestos exposure, both peritoneal cell lines (LP9, HM3) showed more cell killing than the pleural lines (HPM3, HPM4), which showed no significant killing.
  • Number of transcripts changed by asbestos compared with controls (combined filter: FDR below 0.05, P below 0.05 and at least a 2-fold change): HPM3 (pleural) 843 and HPM4 (pleural) 481, against HM3 (peritoneal) 224 and LP9 (immortalized peritoneal) 85.
  • Among the three primary cell lines, 165 transcripts responded to asbestos in all of them. A further 29 were unique to HM3, 121 to HPM4 and 473 to HPM3.
  • The shared responses included increased IL-6, IL-8, CXCL1, CXCL2, CXCL3, ATF3 and NR4A1, and decreased ID1.
  • The response to asbestos went in the same direction in every cell line but was larger in the pleural cells.
  • IL-17 and IL-6 signaling were the most enriched pathways in all primary cell lines.
  • Genes that responded to asbestos only in pleural cells were mostly pro-inflammatory, including CSF3/G-CSF, IL-1 beta, IL-1 alpha and GREM1.
  • At the protein level, asbestos exposure increased IL-6, IL-8 and IL-1 beta released by pleural HPM3 cells.
• The authors' conclusion: The authors concluded that pleural cells showed a response similar to peritoneal cells but larger in magnitude. They suggested this greater responsiveness could provide a mechanism to explain why pleural mesothelioma is more frequent than peritoneal mesothelioma.
• Limitations the authors state:
  • Age- and gender-matched pleural and peritoneal cell lines were not available. The pleural donors were in their 60s and the peritoneal donors in their 20s.
  • The cell-killing finding needs to be checked in many more cell lines of both types.
  • The authors could not justify the assumptions of one statistical method (PERMANOVA) and used it only to rank sources of variation.
  • No loading control was available for the Western blot protein measurements.
  • The 8-hour exposure was short. The authors suggested this could explain why no IL-17 gene expression was seen, compared with 7 to 8 months of exposure in published animal studies.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Crocidolite, Lung cancer, Mesothelioma, Peritoneal mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelial Cells, Asbestos Exposure, Malignant Mesothelioma, Carcinogenesis, Inflammation.

Related studies

• Hemizygosity of Nf2 is associated with increased susceptibility to asbestos-induced peritoneal tumours — J. Fleury-Feith, C. Lecomte, et al. (2003)
• Crocidolite asbestos and SV40 are cocarcinogens in human mesothelial cells and in causing mesothelioma in hamsters — B. Kroczynska, R. Cutrone, et al. (2006)
• Patterns of 8-hydroxydeoxyguanosine formation in DNA and indications of oxidative stress in rat and human pleural mesothelial cells after exposure to crocidolite asbestos — H. Fung, Y.W. Kow, et al. (1997)
• Asbestos induction of extended lifespan in normal human mesothelial cells: interindividual susceptibility and SV40 T antigen — L. Xu, B.J. Flynn, et al. (1999)
• Identification of a differential expression of two cDNAs between malignant mesothelioma and normal mesothelial cells using the RNA fingerprint method — S. Frank, B.U. von Specht, et al. (1998)
• Indications for distinct pathogenic mechanisms of asbestos and silica through gene expression profiling of the response of lung epithelial cells — T.N. Perkins, P.M. Peeters, et al. (2015)

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