Comparative Gene Expression Analysis of Malignant Mesothelioma and Lung Adenocarcinomas Induced by Multi-Walled Carbon Nanotube-7 and Double-Walled Carbon Nanotubes in Rats: Distinct Molecular Signatures and Canonical Pathways

Our plain-English summary of Comparative Gene Expression Analysis of Malignant Mesothelioma and Lung Adenocarcinomas Induced by Multi-Walled Carbon Nanotube-7 and Double-Walled Carbon Nanotubes in Rats: Distinct Molecular Signatures and Canonical Pathways, by M. Gi, S. Suzuki, D.M. Saleh, et al (Nanomaterials, 2025).

The study

• Authors: M. Gi, S. Suzuki, D.M. Saleh, O.H.M. Ahmed, W.T. Alexander, M. Fujioka, A. Vachiraarunwong, R. Guo, G. Qiu, I. Noura, A. Kakehashi, X.L. Xie, S. Tsuruoka, A. Hirose, A. Naiki-Ito, H. Tsuda, H. Wanibuchi
• Journal: Nanomaterials
• Published: 2025;15(23)
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Although numerous experimental studies have demonstrated the carcinogenic potential of multi-walled carbon nanotubes (MWCNTs) in lungs, the underlying molecular mechanisms-especially gene expression changes associated with different tumor types-remain poorly characterized. To elucidate the molecular signatures associated with MWCNT-induced carcinogenesis, we performed microarray-based gene expression profiling of rat lung tumors induced by MWCNT-7, including both adenocarcinoma (ADC) and malignant mesothelioma (MM), as well as ADCs induced by two types of double-walled CNTs (DWCNTs) differing in fiber length (1.5 µm and 7 µm). Hierarchical clustering revealed that the MWCNT-7-induced MM exhibited a gene expression profile distinct from the ADCs. The ADCs induced by the DWCNTs and the ADC induced by MWCNT-7 shared several pathways that were distinct from those of the MWCNT-7 induced MM. The distinct pathways upregulated in the ADCs versus the MM support the conclusion that MWCNT-induced ADCs arise through distinct biological mechanisms compared to MWCNT-induced MMs and identified tumor-type-specific biomarker candidates: complement factor I (CFI) and secreted phosphoprotein 1 (SPP1) for ADCs, and fibronectin 1 (FN1) for MM. In addition, the gene expression profiles of the ADCs induced by the three fiber types indicate that both types of thin flexible DWCNTs used in the present study promoted a number of carcinogenic pathways in the rat lung that were also promoted by MWCNT-7, which is a class 2B carcinogen. These results support the conclusion that DWCNTs are carcinogenic in the rat lung and highlight the importance of further assessments of the potential lung carcinogenicity of inhaled thin flexible CNTs.

In plain English

This animal study measured gene activity in tumors from male F344 rats in the authors' companion two-year study. There, carbon nanotubes were sprayed into the rats' lungs eight times over 15 days. The study did not involve asbestos. Using microarrays, the authors compared four tumors with lung tissue from three control rats. Three were lung adenocarcinomas, one each from rats given 1.5 µm or 7 µm double-walled carbon nanotubes (DWCNTs) or the multi-walled nanotube MWCNT-7. The fourth was a pleural malignant mesothelioma from an MWCNT-7 rat. The mesothelioma's profile clustered apart from the adenocarcinomas. None of the 413 genes changed in all three adenocarcinomas were changed in the mesothelioma, which showed pathways linked to tissue remodeling and fibrosis. The proposed markers, not yet validated, were CFI and SPP1 for adenocarcinoma. For mesothelioma it was FN1, 10-fold higher than in control lung tissue. The authors concluded that the adenocarcinomas in DWCNT-treated rats were induced by the DWCNTs, not spontaneous. They noted three limits: only one tumor per type was analyzed, doses were substantially higher than those behind the NIOSH exposure limit, and relevance to humans is uncertain.

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: microarray gene expression profiling of rat tumors collected in the authors' companion 104-week carcinogenicity study
• Who was studied: Male F344 rats (nine weeks old at purchase) from a 104-week study in Japan. Analyzed were one lung adenocarcinoma each from the 1.5 µm DWCNT, 7 µm DWCNT and MWCNT-7 groups, one pleural malignant mesothelioma from the MWCNT-7 group, and lung tissue from three vehicle-control rats.
• Exposure: Intratracheal intrapulmonary spraying (TIPS) of 1.5 µm DWCNT, 7 µm DWCNT or MWCNT-7, every other day over 15 days (eight doses). Total doses were 50.4 µg, 232 µg and 504 µg per rat respectively.
• Main results:
  • Differentially expressed genes: 785 in the 1.5 µm DWCNT adenocarcinoma (312 up, 473 down), 983 in the 7 µm DWCNT adenocarcinoma (348 up, 635 down), and 950 in the MWCNT-7 adenocarcinoma.
  • The MWCNT-7 mesothelioma had 1031 differentially expressed genes (515 up, 516 down).
  • None of the 413 genes changed in all three adenocarcinomas were changed in the mesothelioma.
  • In pathway clustering, the mesothelioma formed its own cluster, separate from the adenocarcinomas.
  • Among the adenocarcinomas, the 7 µm DWCNT and MWCNT-7 tumors grouped together.
  • Six canonical pathways were downregulated in all four tumors.
  • In the mesothelioma only, 26 pathways were uniquely upregulated and 11 uniquely downregulated.
  • The mesothelioma's upregulated pathways were mainly linked to extracellular matrix remodeling and fibrosis.
  • One pathway was uniquely upregulated and 13 uniquely downregulated across all three adenocarcinomas but not in the mesothelioma.
  • Candidate adenocarcinoma marker CFI was raised 162-, 202- and 36-fold in the 1.5 µm DWCNT, 7 µm DWCNT and MWCNT-7 adenocarcinomas respectively. SPP1 values were 147, 138 and 9.
  • In the mesothelioma, only FN1 was identified as a potential diagnostic biomarker. Its gene expression was 10-fold higher than in control lung tissue.
• The authors' conclusion: The authors concluded that the lung adenocarcinomas in DWCNT-treated rats in their companion study were induced by the DWCNTs, not spontaneous. They also concluded that thin flexible carbon nanotubes are carcinogenic in the rat lung but not in the pleural cavity.
• Limitations the authors state:
  • Only a single tumor sample per cancer type was analyzed, so the findings may reflect variation within and between tumors.
  • Changed genes were defined by z-scores, and their effects still need functional validation.
  • The candidate biomarkers have not been confirmed in body fluids or in human cohorts.
  • Whether the results apply to human disease is uncertain.
  • The doses given were substantially higher than those used to set the NIOSH recommended exposure limit for humans.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Lung Adenocarcinoma, Carcinogenic, Carcinogenesis, Adenocarcinoma, Fiber Length, Biomarker.

Related studies

• Comparative Carcinogenicity of Double-Walled Carbon Nanotubes of Different Lengths Administered by Intratracheal Installation into Rat Lungs — O.H.M. Ahmed, D.M. Saleh, et al. (2025)
• Comparative carcinogenicity study of a thick, straight-type and a thin, tangled-type multi-walled carbon nanotube administered by intra-tracheal instillation in the rat — D.M. Saleh, W.T. Alexander, et al. (2020)
• Assessment of the toxicity and carcinogenicity of double-walled carbon nanotubes in the rat lung after intratracheal instillation: a two-year study — D.M. Saleh, S. Luo, et al. (2022)
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• Epithelial-mesenchymal transition involved in pulmonary fibrosis induced by multi-walled carbon nanotubes via TGF-beta/Smad signaling pathway — T. Chen, H. Nie, et al. (2014)
• Extensive temporal transcriptome and microRNA analyses identify molecular mechanisms underlying mitochondrial dysfunction induced by multi-walled carbon nanotubes in human lung cells — P. Nymark, P. Wijshoff, et al. (2015)

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