Role of mesothelin in carbon nanotube-induced carcinogenic transformation of human bronchial epithelial cells

Our plain-English summary of Role of mesothelin in carbon nanotube-induced carcinogenic transformation of human bronchial epithelial cells, by X. He, E. Despeaux, T.A. Stueckle, et al (American Journal of Physiology. Lung Cellular and Molecular Physiology, 2016).

The study

• Authors: X. He, E. Despeaux, T.A. Stueckle, A. Chi, V. Castranova, C.Z. Dinu, L. Wang, Y. Rojanasakul
• Journal: American Journal of Physiology. Lung Cellular and Molecular Physiology
• Published: 2016;311(3):L538-49
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Carbon nanotubes (CNTs) have been likened to asbestos in terms of morphology and toxicity. CNT exposure can lead to pulmonary fibrosis and promotion of tumorigenesis. However, the mechanisms underlying CNT-induced carcinogenesis are not well defined. Mesothelin (MSLN) is overexpressed in many human tumors, including mesotheliomas and pancreatic and ovarian carcinomas. In this study, the role of MSLN in the carcinogenic transformation of human bronchial epithelial cells chronically exposed to single-walled CNT (BSW) was investigated. MSLN overexpression was found in human lung tumors, lung cancer cell lines, and BSW cells. The functional role of MSLN in the BSW cells was then investigated by using stably transfected MSLN knockdown (BSW shMSLN) cells. MSLN knockdown resulted in significantly decreased invasion, migration, colonies on soft agar, and tumor sphere formation. In vivo, BSW shMSLN cells formed smaller primary tumors and less metastases. The mechanism by which MSLN contributes to these more aggressive behaviors was investigated by using ingenuity pathway analysis, which predicted that increased MSLN could induce cyclin E expression. We found that BSW shMSLN cells had decreased cyclin E, and their proliferation rate was reverted to nearly that of untransformed cells. Cell cycle analysis showed that the BSW shMSLN cells had an increased G2 population and a decreased S phase population, which is consistent with the decreased rate of proliferation. Together, our results indicate a novel role of MSLN in the malignant transformation of bronchial epithelial cells following CNT exposure, suggesting its utility as a potential biomarker and drug target for CNT-induced malignancies.

Copyright © 2016 the American Physiological Society.

In plain English

This laboratory study examined the protein mesothelin (MSLN) in human bronchial epithelial BEAS-2B cells that the authors had previously transformed by culturing them with single-walled carbon nanotubes for 6 months (BSW cells); the authors note that carbon nanotubes have been likened to asbestos in morphology and toxicity. MSLN was measured in 10 paired human lung tumour and adjacent normal tissue lysates, in cell lines, and in BSW cells, and its function was tested using stable MSLN-knockdown BSW cells (BSW shMSLN), MSLN-overexpressing BEAS-2B cells, and mouse xenografts. Five of 10 tumour samples showed 2- to 10-fold more MSLN than their normal controls. MSLN knockdown reduced soft-agar colonies (23.7 plus or minus 5.1 versus 53.0 plus or minus 9.9), tumour spheres (50.2 plus or minus 10.9 versus 81.0 plus or minus 9.7), migration, invasion, cyclin E, proliferation, primary tumour size and metastases in mice. The authors concluded that MSLN contributes to, but is not the sole driver of, malignant transformation after nanotube exposure, and may be a biomarker and drug target.

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 study combining in vitro cell experiments (chronically carbon-nanotube-exposed human bronchial epithelial cell line, gene knockdown and overexpression) with a mouse tumour xenograft experiment and pathway analysis
• Who was studied: Human cell lines (BEAS-2B, BSW, A549, H460), 10 purchased human lung tumour lysates with paired adjacent normal tissue, and immunodeficient NOD/SCID mice, 6 per group, injected with BSW shMSLN or BSW shControl cells; work done at West Virginia University (submitted 2016)
• Exposure: Chronic in vitro exposure of BEAS-2B cells to single-walled carbon nanotubes (0.02 µg/cm2) for 6 months to create the BSW line; the experimental manipulation then studied was mesothelin knockdown or overexpression
• Main results:
  • In the human tissue lysates, 5 of 10 tumour samples had increased MSLN (2- to 10-fold above their paired normal tissue); no control sample had notable MSLN expression
  • BEAS-2B cells expressed less MSLN than BSW cells and the lung cancer lines A549 and H460
  • MSLN-knockdown BSW cells formed fewer soft-agar colonies than vector-control BSW cells (23.7 plus or minus 5.1 versus 53.0 plus or minus 9.9)
  • MSLN-knockdown BSW cells formed fewer tumour spheres than controls (50.2 plus or minus 10.9 versus 81.0 plus or minus 9.7)
  • MSLN-overexpressing BEAS-2B cells formed more soft-agar colonies than BEAS-2B cells (6.5 plus or minus 2.17 versus 0.17 plus or minus 0.51)
  • Control BSW cells showed 2.6 times as much migration and 2.8 times as much invasion as MSLN-knockdown BSW cells; MSLN overexpression in BEAS-2B cells increased migration sixfold and invasion fourfold
  • In mice, control BSW cells formed injection-site tumours three times larger than MSLN-knockdown cells, which formed 15 times fewer metastatic nodules (average of 1 per mouse); hepatic and pulmonary metastatic surface area was 56 plus or minus 31.27 for BSW shC versus 2.25 plus or minus 4.5 cm2 for BSW shMSLN
  • Cyclin E was highly expressed in control BSW cells but barely detectable in both MSLN-knockdown clones; by day 3 knockdown cells proliferated at half the rate of controls, with more cells in G2 and fewer in S phase
• The authors' conclusion: The authors concluded that MSLN knockdown reduced, but did not eliminate, the malignant behaviours of the nanotube-transformed cells, so MSLN is involved in but not the sole mechanism of primary tumour and metastasis formation, and may be a target for cancer therapeutics
• Limitations the authors state:
  • The authors state that working out the specific mechanism for the reduction in metastases was outside the scope of the study
  • The authors note that MSLN does not account for all the changes seen in the transformed cells and that other, unidentified mechanisms are likely involved
  • The authors note that how MSLN-mediated adhesion findings from other tumour types translate to other cancers, including the BSW cells, is not yet known

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelin, Carcinogenic, Pulmonary Fibrosis, Tumorigenesis, Carcinogenesis, Mesothelioma, Carcinoma, Lung Cancer.

Related studies

• Effect of surface functionalizations of multi-walled carbon nanotubes on neoplastic transformation potential in primary human lung epithelial cells — T.A. Stueckle, D.C. Davidson, et al. (2017)
• Chronic exposure to carbon nanotubes induces invasion of human mesothelial cells through matrix metalloproteinase-2 — W. Lohcharoenkal, L. Wang, et al. (2013)
• Neoplastic-like transformation effect of single-walled and multi-walled carbon nanotubes compared to asbestos on human lung small airway epithelial cells — L. Wang, T.A. Stueckle, et al. (2014)
• Distinct autophagy-apoptosis related pathways activated by Multi-walled (NM 400) and Single-walled carbon nanotubes (NIST-SRM2483) in human bronchial epithelial (16HBE14o-) cells — M. Ghosh, S. Murugadoss, et al. (2020)
• Free radical scavenging and formation by multi-walled carbon nanotubes in cell free conditions and in human bronchial epithelial cells — P. Nymark, K.A. Jensen, et al. (2014)
• Malignant transformation of immortalized human bronchial epithelial cells by asbestos fibers — T.K. Hei, L.J. Wu, et al. (1997)

Browse more research in American Journal of Physiology. Lung Cellular and Molecular Physiology, or return to medical research.