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The carcinogenic effect of various multi-walled carbon nanotubes (MWCNTs) after intraperitoneal injection in rats
Open accessAbstract
BACKGROUND: Biological effects of tailor-made multi-walled carbon nanotubes (MWCNTs) without functionalization were investigated in vivo in a two-year carcinogenicity study. In the past, intraperitoneal carcinogenicity studies in rats using biopersistent granular dusts had always been negative, whereas a number of such studies with different asbestos fibers had shown tumor induction. The aim of this study was to identify possible carcinogenic effects of MWCNTs. We compared induced tumors with asbestos-induced mesotheliomas and evaluated their relevance for humans by immunohistochemical methods. METHODS: A total of 500 male Wistar rats (50 per group) were treated once by intraperitoneal injection with 10⁹ or 5 × 10⁹ WHO carbon nanotubes of one of four different MWCNTs suspended in artificial lung medium, which was also used as negative control. Amosite asbestos (10⁸ WHO fibers) served as positive control. Morbid rats were sacrificed and necropsy comprising all organs was performed. Histopathological classification of tumors and, additionally, immunohistochemistry were conducted for podoplanin, pan-cytokeratin, and vimentin to compare induced tumors with malignant mesotheliomas occurring in humans. RESULTS: Treatments induced tumors in all dose groups, but incidences and times to tumor differed between groups. Most tumors were histologically and immunohistochemically classified as malignant mesotheliomas, revealing a predominantly superficial spread on the serosal surface of the abdominal cavity. Furthermore, most tumors showed invasion of peritoneal organs, especially the diaphragm. All tested MWCNT types caused mesotheliomas. We observed highest frequencies and earliest appearances after treatment with the rather straight MWCNT types A and B. In the MWCNT C groups, first appearances of morbid mesothelioma-bearing rats were only slightly later. Later during the two-year study, we found mesotheliomas also in rats treated with MWCNT D - the most curved type of nanotubes. Malignant mesotheliomas induced by intraperitoneal injection of different MWCNTs and of asbestos were histopathologically and immunohistochemically similar, also compared with mesotheliomas in man, suggesting similar pathogenesis. CONCLUSION: We showed a carcinogenic effect for all tested MWCNTs. Besides aspect ratio, curvature seems to be an important parameter influencing the carcinogenicity of MWCNTs.
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“In addition, this rigidity range is similar to the bounds of the critical rigidity value of 7”
From Macrophages bend long fibres with flexural rigidity lower than 3 mN·nm2 to avoid frustrated phagocytosis (2026) · cites this paper as [25]
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“Intraperitoneal injection of suspensions of different MWCNT materials in rodents that were kept for 24 months showed fibre-specific toxicity for critical fibres exhibiting different geometric mean diameters except thinnest with a diameter of 37”
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Poland, C. A., Duffin, R., Kinloch, I., Maynard, A., Wallace, W. A. H., Seaton, A., Stone, V., Brown, S., MacNee, W., & Donaldson, K. (2008) · Nature Nanotechnology · doi:10.1038/nnano.2008.111 · Cited by 2,645
Histological Typing of Lung and Pleural Tumours
Travis, W. D., Colby, T. V., CORRIN, B., Shimosato, Y., & Brambilla, E. M. (1999) · Springer eBooks · doi:10.1007/978-3-642-60049-4 · Cited by 1,534
Donaldson, K., Aitken, R., Tran, L., Stone, V., Duffin, R., Forrest, G., & Alexander, A. (2006) · Toxicological Sciences · doi:10.1093/toxsci/kfj130 · Cited by 1,167
The new World Health Organization classification of lung tumours
Brambilla, E. M., Travis, W. D., Colby, T. V., CORRIN, B., & Shimosato, Y. (2001) · European Respiratory Journal · doi:10.1183/09031936.01.00275301 · Cited by 1,129
Donaldson, K., Murphy, F. A., Duffin, R., & Poland, C. A. (2010) · Particle and Fibre Toxicology · doi:10.1186/1743-8977-7-5 · Cited by 916
Takagi, A., Hirose, A., Nishimura, T., Fukumori, N., Ogata, A., Ohashi, N., Kitajima, S., & Kanno, J. (2008) · The Journal of Toxicological Sciences · doi:10.2131/jts.33.105 · Cited by 832
Nagai, H., Okazaki, Y., Chew, S. H., Misawa, N., Yamashita, Y., Akatsuka, S., Ishihara, T., Yamashita, K., Yoshikawa, Y., Yasui, H., et al. (2011) · Proceedings of the National Academy of Sciences · doi:10.1073/pnas.1110013108 · Cited by 535
Husain, A. N., Colby, T. V., Ordóǹez, N. G., Krausz, T. N., Attanoos, R. L., Beasley, M. B., Borczuk, A., Butnor, K. J., Cagle, P. T., Chirieac, L. R., et al. (2012) · Archives of Pathology & Laboratory Medicine · doi:10.5858/arpa.2012-0214-oa · Cited by 470
Pulmonary toxicity of carbon nanotubes and asbestos — Similarities and differences
Donaldson, K., Poland, C. A., Murphy, F. A., MacFarlane, M., Chernova, T., & Schinwald, A. (2013) · Advanced Drug Delivery Reviews · doi:10.1016/j.addr.2013.07.014 · Cited by 339
Husain, A. N., Colby, T. V., Ordóǹez, N. G., Krausz, T. N., Borczuk, A., Cagle, P. T., Chirieac, L. R., Churg, A., Galateau-Sallé, F., Gibbs, A. R., et al. (2009) · Archives of Pathology & Laboratory Medicine · doi:10.5858/133.8.1317 · Cited by 332
Sakamoto, Y., Nakae, D., Fukumori, N., Tayama, K., Maekawa, A., Imai, K., Hirose, A., Nishimura, T., Ohashi, N., & Ogata, A. (2009) · The Journal of Toxicological Sciences · doi:10.2131/jts.34.65 · Cited by 322
Abid, A. D., Anderson, D. S., Das, G. K., Winkle, L. S. V., & Kennedy, I. M. (2013) · Particle and Fibre Toxicology · doi:10.1186/1743-8977-10-1 · Cited by 271
Muller, J. M., Delos, M., Panin, N., Rabolli, V., Huaux, F., & Lison, D. (2009) · Toxicological Sciences · doi:10.1093/toxsci/kfp100 · Cited by 265
Promotion of lung adenocarcinoma following inhalation exposure to multi-walled carbon nanotubes
Sargent, L. M., Porter, D. W., Staska, L. M., Hubbs, A. F., Lowry, D. T., Battelli, L. A., Siegrist, K. J., Kashon, M. L., Mercer, R. R., Bauer, A. K., et al. (2014) · Particle and Fibre Toxicology · doi:10.1186/1743-8977-11-3 · Cited by 256
Distribution and persistence of pleural penetrations by multi-walled carbon nanotubes
Mercer, R. R., Hubbs, A. F., Scabilloni, J. F., Wang, L., Battelli, L. A., Schwegler‐Berry, D., Castranova, V., & Porter, D. W. (2010) · Particle and Fibre Toxicology · doi:10.1186/1743-8977-7-28 · Cited by 236
Takagi, A., Hirose, A., Futakuchi, M., Tsuda, H., & Kanno, J. (2012) · Cancer Science · doi:10.1111/j.1349-7006.2012.02318.x · Cited by 202
Ma‐Hock, L., Strauss, V., Treumann, S., Küttler, K., Wohlleben, W., Hofmann, T., Gröters, S., Wiench, K., van Ravenzwaay, B., & Landsiedel, R. (2013) · Particle and Fibre Toxicology · doi:10.1186/1743-8977-10-23 · Cited by 202
A biocompatible medium for nanoparticle dispersion
Porter, D. W., Sriram, K., Wolfarth, M. G., Jefferson, A., Schwegler-Berry, D., Andrew, M. E., & Castranova, V. (2008) · Nanotoxicology · doi:10.1080/17435390802318349 · Cited by 197
The role of the diaphragm in lymphatic absorption from the peritoneal cavity.
Abu-Hijleh, M. F., Habbal, O. A., & Moqattash, S. T. (1995) · PubMed · Cited by 195
Yaziji, H., Battifora, H. A., Barry, T. S., Hwang, H. C., Bacchi, C. E., McIntosh, M. W., Kussick, S. J., & Gown, A. M. (2006) · Modern Pathology · doi:10.1038/modpathol.3800534 · Cited by 188
Schinwald, A., Murphy, F. A., Prina-Mello, A., Poland, C. A., Byrne, F., Movia, D., Glass, J. R., Dickerson, J. C., Schultz, D. A., Jeffree, C. E., et al. (2012) · Toxicological Sciences · doi:10.1093/toxsci/kfs171 · Cited by 181
Asbestos‐like Pathogenicity of Long Carbon Nanotubes Alleviated by Chemical Functionalization
Ali‐Boucetta, H., Nunes, A., Sainz, R., Herrero, M. A., Tian, B., Prato, M., Bianco, A., & Kostarelos, K. (2013) · Angewandte Chemie International Edition · doi:10.1002/anie.201207664 · Cited by 173
Ordóǹez, N. G. (2006) · Human Pathology · doi:10.1016/j.humpath.2006.08.010 · Cited by 172
Hydrogen adsorption/desorption behavior of multi-walled carbon nanotubes with different diameters
Hou, P., Xu, S., Ying, Z., Yang, Q., Liu, C., & Cheng, H. (2003) · Carbon · doi:10.1016/s0008-6223(03)00271-9 · Cited by 172
Induction of aneuploidy by single‐walled carbon nanotubes
Sargent, L. M., Shvedova, A. A., Hubbs, A. F., Salisbury, J. L., Benkovic, S. A., Kashon, M. L., Lowry, D. T., Murray, A. R., Kisin, E. R., Friend, S. A., et al. (2009) · Environmental and Molecular Mutagenesis · doi:10.1002/em.20529 · Cited by 170
Nanotoxicology—A Pathologist’s Perspective
Hubbs, A. F., Mercer, R. R., Benkovic, S. A., Harkema, J. R., Sriram, K., Schwegler‐Berry, D., Goravanahally, M. P., Nurkiewicz, T. R., Castranova, V., & Sargent, L. M. (2010) · Toxicologic Pathology · doi:10.1177/0192623310390705 · Cited by 165
Role of Mutagenicity in Asbestos Fiber-Induced Carcinogenicity and Other Diseases
Huang, S. X. L., Jaurand, M.-C., Kamp, D. W., Whysner, J., & Hei, T. K. (2011) · Journal of Toxicology and Environmental Health, Part B · doi:10.1080/10937404.2011.556051 · Cited by 163
Multi-walled carbon nanotubes (Baytubes®): Approach for derivation of occupational exposure limit
Pauluhn, J. (2010) · Regulatory Toxicology and Pharmacology · doi:10.1016/j.yrtph.2009.12.012 · Cited by 161
Hamilton, R. F., Wu, Z., Mitra, S., Shaw, P. K., & Holian, A. (2013) · Particle and Fibre Toxicology · doi:10.1186/1743-8977-10-57 · Cited by 155
Genotoxicity of multi-walled carbon nanotubes at occupationally relevant doses
Siegrist, K. J., Reynolds, S. H., Kashon, M. L., Lowry, D. T., Dong, C., Hubbs, A. F., Young, S., Salisbury, J. L., Porter, D. W., Benkovic, S. A., et al. (2014) · Particle and Fibre Toxicology · doi:10.1186/1743-8977-11-6 · Cited by 152
Epithelial–mesenchymal transition in malignant mesothelioma
Fassina, A., Cappellesso, R., Guzzardo, V., Via, L. D., Piccolo, S., Ventura, L., & Fassan, M. (2011) · Modern Pathology · doi:10.1038/modpathol.2011.144 · Cited by 149
Application of immunohistochemistry to the diagnosis of malignant mesothelioma.
Marchevsky, A. M. (2008) · PubMed · doi:10.5858/2008-132-397-aoittd · Cited by 107
Asbestos: Mechanisms of Toxicity and Carcinogenicity in the Respiratory Tract
Mossman, B., Light, W., & Wei, E. (1983) · Annual Review of Pharmacology and Toxicology · doi:10.1146/annurev.pa.23.040183.003115 · Cited by 102
INHALATION AND INJECTION EXPERIMENTS IN RATS TO TEST THE CARCINOGENICITY OF MMMF
Muhle, H., POTT, F., Bellmann, B., Takenaka, S., & Ziem, U. (1987) · The Annals of Occupational Hygiene · doi:10.1093/annhyg/31.4b.755 · Cited by 97
Gasser, M., Wick, P., Clift, M. J. D., Blank, F., Diener, L., Yan, B., Gehr, P., Krug, H. F., & Rothen‐Rutishauser, B. (2012) · Particle and Fibre Toxicology · doi:10.1186/1743-8977-9-17 · Cited by 92
A Novel Targeting Therapy of Malignant Mesothelioma Using Anti-Podoplanin Antibody
Abe, S., Morita, Y., Kaneko, M. K., Hanibuchi, M., Tsujimoto, Y., Goto, H., Kakiuchi, S., Aono, Y., Huang, J. T., Sato, S., et al. (2013) · The Journal of Immunology · doi:10.4049/jimmunol.1300448 · Cited by 85
Miller, B. G. (1999) · The Annals of Occupational Hygiene · doi:10.1016/s0003-4878(99)00018-6 · Cited by 83
Mechanisms in Fibre Carcinogenesis
Brown, R. C., Hoskins, J. A., & Johnson, N. F. (1991) · Springer eBooks · doi:10.1007/978-1-4684-1363-2 · Cited by 81
Greaves, P., Chouinard, L., Ernst, H., Mecklenburg, L., Pruimboom‐Brees, I., Rinke, M., Rittinghausen, S., Thibault, S., von Erichsen, J., & Yoshida, T. (2013) · Journal of Toxicologic Pathology · doi:10.1293/tox.26.1s · Cited by 80
Self-citationCarbon nanotubes: an insight into the mechanisms of their potential genotoxicity
van Berlo, D., Clift, M. J. D., Albrecht, C., & Schins, R. P. F. (2012) · Swiss Medical Weekly · doi:10.4414/smw.2012.13698 · Cited by 78
Mesothelioma Not Associated With Asbestos Exposure
Jasani, B., & Gibbs, A. R. (2012) · Archives of Pathology & Laboratory Medicine · doi:10.5858/arpa.2011-0039-ra · Cited by 77
Recent Advances in the Research of Lymphatic Stomata
Wang, Z., Li, M., & Li, J. (2010) · The Anatomical Record · doi:10.1002/ar.21101 · Cited by 69
Michailova, K. N., Wassilev, W. A., & Wedel, T. (1999) · Annals of Anatomy - Anatomischer Anzeiger · doi:10.1016/s0940-9602(99)80040-5 · Cited by 57
Functional arrangement of rat diaphragmatic initial lymphatic network
Grimaldi, A., Moriondo, A., Sciacca, L., Guidali, M. L., Tettamanti, G., & Negrini, D. (2006) · American Journal of Physiology-Heart and Circulatory Physiology · doi:10.1152/ajpheart.01276.2005 · Cited by 57
Mesothelioma dose response following intraperitoneal injection of mineral fibres.
Davis, J. M., Bolton, R., Miller, B. G., & Niven, K. (1991) · Europe PMC (PubMed Central) · Cited by 56
Tomatis, M., Turci, F., Ceschino, R., Riganti, C., Gazzano, E., Martra, G., Ghigo, D., & Fubini, B. (2010) · Inhalation Toxicology · doi:10.3109/08958378.2010.504243 · Cited by 53
The immunohistochemical characterization of sarcomatoid malignant mesothelioma of the pleura.
Chirieac, L. R., Pinkus, G. S., Pinkus, J. L., Godleski, J. J., Sugarbaker, D. J., & Corson, J. M. (2011) · Europe PMC (PubMed Central) · Cited by 52
Nagai, H., Okazaki, Y., Chew, S. H., Misawa, N., Miyata, Y., Shinohara, H., & Toyokuni, S. (2013) · Pathology International · doi:10.1111/pin.12093 · Cited by 48
Carcinogenicity evaluation for the application of carbon nanotubes as biomaterials in rasH2 mice
Takanashi, S., Hara, K., Aoki, K., Usui, Y., Shimizu, M., Haniu, H., Ogihara, N., Ishigaki, N., Nakamura, K., Okamoto, M., et al. (2012) · Scientific Reports · doi:10.1038/srep00498 · Cited by 48
David, B., & Juan, R. S. (1999) · Joint Research Centre (European Commission) · Cited by 48
POTT, F., Roller, M., Rippe, R. M., Germann, P., & Bellmann, B. (1991) · Springer eBooks · doi:10.1007/978-1-4684-1363-2_48 · Cited by 45
Roe, F. J. C., Carter, R. L., Walters, M. A., & Harington, J. S. (1967) · International Journal of Cancer · doi:10.1002/ijc.2910020624 · Cited by 42
Carthew, P., Hill, R. J., Edwards, R., & Lee, P. N. (1992) · Human & Experimental Toxicology · doi:10.1177/096032719201100615 · Cited by 41
Mesothelioma with signet-ring cell features: report of 23 cases
Ordóǹez, N. G. (2012) · Modern Pathology · doi:10.1038/modpathol.2012.172 · Cited by 40
Carbon nanotubes induce granulomas but not mesotheliomas.
Varga, C., & Szendi, K. (2010) · PubMed · Cited by 33
Orley, J. (2000) · Oxford University Press eBooks · doi:10.1037/10523-121 · Cited by 33
Rittinghausen, S., Ernst, H., Muhle, H., & Möhr, U. (1992) · Experimental and Toxicologic Pathology · doi:10.1016/s0940-2993(11)80138-7 · Cited by 24
Self-citationLi, Y., & Li, J. (2004) · Annals of Anatomy - Anatomischer Anzeiger · doi:10.1016/s0940-9602(04)80114-6 · Cited by 16
Blackshear, P. E., Pandiri, A. R., Ton, T.-V. T., Clayton, N. P., Shockley, K. R., Peddada, S. D., Gerrish, K., Sills, R. C., & Hoenerhoff, M. J. (2013) · Toxicologic Pathology · doi:10.1177/0192623313501894 · Cited by 11
Ohnuma-Koyama, A., Yoshida, T., Takahashi, N., AKEMA, S., Kashimoto, Y., Kuwahara, M., Nagaike, M., Inui, K., Nakashima, N., & Harada, T. (2013) · Journal of Toxicologic Pathology · doi:10.1293/tox.26.197 · Cited by 5
The transendothelial passage in the absorbing peripheral lymphatic vessel of the rodent diaphragm.
Azzali, G. (1995) · PubMed · Cited by 3
MILLER, B. G., Searl, A., Davis, J. M., et al. (1999) · The Annals of Occupational Hygiene · doi:10.1093/annhyg/43.3.155
Research works printed but not linked: 2
- Recommendation from the Scientific Committee on Occupational Exposure Limits for man-made mineral fibres (MMMF) with no indication for carcinogenicity and not specified elsewhere SCOEL/SUM/88 2012, 2012: 1–17.
- Technical rules for hazardous substances 905. Technical Rules (TRGS) established by the Committee on Hazardous Substances (AGS). Verzeichnis krebserzeugender, erbgutverändernder oder fortpflanzungsgefährdender Stoffe German Federal Institute for Occupational Safety and Health (BAuA) 2014, 24: 3–4.
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Metadata
- Authors
- Rittinghausen, S., Hackbarth, A., Creutzenberg, O., Ernst, H., Heinrich, U., Leonhardt, A., & Schaudien, D.
- Affiliations
- Fraunhofer Institute for Toxicology and Experimental Medicine (DE)
- Leibniz Institute for Solid State and Materials Research (DE)
- Corresponding author
- Rittinghausen, Susanne
- Venue
- Particle and Fibre Toxicology
- Published
- 2014-11-20
- Volume
- 11
- Issue
- 1
- Pages
- 59-59
- ISSN
- 1743-8977 (ISSN-L)
- PMC
- PMC4243371
- OpenAlex
- W2152314477
- Cited by
- 193
- References
- 61
- Citations by year
- 2026: 5 · 2025: 8 · 2024: 16 · 2023: 15 · 2022: 16 · 2021: 21 · 2020: 25 · 2019: 17 · 2018: 24 · 2017: 22 · 2016: 13 · 2015: 11
- FWCI
- 12.28
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Locations
- Particle and Fibre Toxicology (publishedVersion, cc-by)
- Europe PMC (PubMed Central) (publishedVersion, cc-by)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- Fraunhofer-Publica (Fraunhofer-Gesellschaft) (submittedVersion, other-oa)
- Fraunhofer-Publica (Fraunhofer-Gesellschaft) (submittedVersion)
- Funders
- Bundesministerium für Bildung und Forschung (03X0109A)
- Topics
- Health Sciences › Medicine › Pulmonary and Respiratory Medicine › Occupational and environmental lung diseases
- Physical Sciences › Engineering › Biomedical Engineering › Graphene and Nanomaterials Applications
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Cancer Research › Carcinogens and Genotoxicity Assessment
- Keywords
- multi-walled carbon nanotubes, carcinogenicity, malignant mesothelioma, intraperitoneal injection, asbestos, amosite, nanotube curvature, aspect ratio, podoplanin, pancytokeratin, vimentin, rats, nanotube toxicity
- MeSH terms
- Abdominal Neoplasms, Animals, Carcinogens, Dose-Response Relationship, Drug, Immunohistochemistry, Injections, Intraperitoneal, Male, Mesothelioma, Microscopy, Electron, Scanning, Neoplasm Invasiveness, Neoplasm Proteins, Particle Size, Serous Membrane, Carcinogenicity Tests, Survival Analysis, Rats, Wistar, Nanotubes, Carbon
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