Malignant peritoneal mesotheliomas of rats induced by multiwalled carbon nanotubes and amosite asbestos: transcriptome and epigenetic profiles

Our plain-English summary of Malignant peritoneal mesotheliomas of rats induced by multiwalled carbon nanotubes and amosite asbestos: transcriptome and epigenetic profiles, by S.M. Reamon-Buettner, S. Rittinghausen, A. Klauke, et al (Particle and Fibre Toxicology, 2024).

The study

• Authors: S.M. Reamon-Buettner, S. Rittinghausen, A. Klauke, A. Hiemisch, C. Ziemann
• Journal: Particle and Fibre Toxicology
• Published: 2024;21(1):3
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Malignant mesothelioma is an aggressive cancer that often originates in the pleural and peritoneal mesothelium. Exposure to asbestos is a frequent cause. However, studies in rodents have shown that certain multiwalled carbon nanotubes (MWCNTs) can also induce malignant mesothelioma. The exact mechanisms are still unclear. To gain further insights into molecular pathways leading to carcinogenesis, we analyzed tumors in Wistar rats induced by intraperitoneal application of MWCNTs and amosite asbestos. Using transcriptomic and epigenetic approaches, we compared the tumors by inducer (MWCNTs or amosite asbestos) or by tumor type (sarcomatoid, epithelioid, or biphasic).

Results: Genome-wide transcriptome datasets, whether grouped by inducer or tumor type, showed a high number of significant differentially expressed genes (DEGs) relative to control peritoneal tissues. Bioinformatic evaluations using Ingenuity Pathway Analysis (IPA) revealed that while the transcriptome datasets shared commonalities, they also showed differences in DEGs, regulated canonical pathways, and affected molecular functions. In all datasets, among highly- scoring predicted canonical pathways were Phagosome Formation, IL8 Signaling, Integrin Signaling, RAC Signaling, and TREM1 Signaling. Top-scoring activated molecular functions included cell movement, invasion of cells, migration of cells, cell transformation, and metastasis. Notably, we found many genes associated with malignant mesothelioma in humans, which showed similar expression changes in the rat tumor transcriptome datasets. Furthermore, RT-qPCR revealed downregulation of Hrasls, Nr4a1, Fgfr4, and Ret or upregulation of Rnd3 and Gadd45b in all or most of the 36 tumors analyzed. Bisulfite sequencing of Hrasls, Nr4a1, Fgfr4, and Ret revealed heterogeneity in DNA methylation of promoter regions. However, higher methylation percentages were observed in some tumors compared to control tissues. Lastly, global 5mC DNA, m6A RNA and 5mC RNA methylation levels were also higher in tumors than in control tissues.

Conclusions: Our findings may help better understand how exposure to MWCNTs can lead to carcinogenesis. This information is valuable for risk assessment and in the development of safe-by-design strategies.

© 2024. The Author(s).

In plain English

This laboratory study analyzed peritoneal mesothelioma tumors from male Wistar rats in an earlier carcinogenicity study. In that study, rats received intraperitoneal injections of multiwalled carbon nanotubes (MWCNTs) or amosite asbestos. The authors examined tumors induced by three MWCNTs (B, C and D) and by amosite, and compared them with peritoneal tissue from untreated rats. Gene-activity profiling of 11 tumors and 3 control tissues found, on average, 9806 genes with changed activity in tumors grouped by inducer. Thirty-eight genes linked to mesothelioma changed consistently across all tumor groups. Seventeen of these showed similar changes in a public dataset of human pleural mesotheliomas. In 36 tumors compared with 4 control tissues, six selected genes were lowered or raised in all or most tumors. DNA methylation (a chemical mark on genes) at four gene control regions varied between tumors and did not differ significantly from controls overall, though some tumors had higher levels. Overall DNA and RNA methylation was higher in tumors. The authors noted they studied only late-stage tumors. They concluded that MWCNT-induced mesothelioma likely results from an interplay of impaired pathways.

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: Retrospective laboratory (gene-expression and DNA/RNA methylation) analysis of tumor tissue from an earlier animal carcinogenicity experiment
• Who was studied: Tumors from male Wistar rats in an earlier study, in which a total of 500 rats (50 per group) were treated. The present study analyzed tumors induced by MWCNT B, MWCNT C, MWCNT D and amosite asbestos, plus peritoneal tissue from untreated control rats. Gene-activity profiling used 11 tumors and 3 control tissues. RT-qPCR and global methylation tests used 36 tumors and 4 control tissues. Gene-specific methylation used 11 tumors and 3 control tissues. Work was done at the Fraunhofer Institute for Toxicology and Experimental Medicine, Hannover, Germany. Dates are not given.
• Exposure: Intraperitoneal application of tailor-made multiwalled carbon nanotubes (MWCNT B, C and D, lengths 9.30, 10.24 and 7.91 µm) or amosite asbestos (length 13.95 µm, diameter 394 nm). Doses were described in the earlier carcinogenicity study, not in this article.
• Main results:
  • In tumors grouped by inducer, compared with control peritoneal tissue, an average of 9806 genes showed changed activity, of which 68.6% were increased.
  • 38 genes implicated in mesothelioma or mesothelioma formation changed consistently across all rat tumor datasets, whether grouped by inducer or by tumor type.
  • 17 of the 38 genes were similarly expressed in a public dataset of 55 human malignant pleural mesotheliomas, compared with only 9 of the 38 in a human small cell lung cancer dataset.
  • By RT-qPCR, Hrasls, Nr4a1, Fgfr4 and Ret were downregulated, and Rnd3 and Gadd45b upregulated, in all or most of 36 tumors compared with control tissues.
  • Fgfr4 was downregulated in 34 of 36 tumors and Ret in 33 of 36 tumors.
  • Gadd45b was upregulated in 27 of 36 tumors.
  • For the Hrasls gene control region, overall DNA methylation did not differ significantly between tumors and controls. Percent methylation ranged from 3.13 to 12.3% in tumors and from 3.03 to 4.64% in controls.
  • For the Ret gene control region, overall methylation also did not differ significantly between tumors and controls. Percent methylation ranged from 2.95 to 13.78% in tumors and from 2.7 to 4.05% in controls.
  • Global 5mC DNA, m6A RNA and 5mC RNA methylation levels were higher in the 36 tumors than in the 4 control tissues, regardless of inducer or tumor type.
• The authors' conclusion: The authors concluded that mesothelioma development from MWCNT exposure likely results from an interplay of impaired pathways affecting the genome, epigenome and translatome, in combination with the immune response. They said their findings may help understand MWCNT-induced carcinogenesis and inform risk assessment and safe-by-design strategies.
• Limitations the authors state:
  • The study was retrospective and analyzed only late-stage tumors, which may not give a full picture of the processes involved.
  • Only mRNA changes were analyzed, in late-stage tumors. It is unclear whether these changes truly reflect the process of carcinogenesis.

Topics

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

Medical terms in this study, explained in our Lexicon: Peritoneal Mesothelioma, Amosite, Malignant Mesothelioma, Mesothelium, Carcinogenesis, Sarcomatoid, Epithelioid, Biphasic Mesothelioma.

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