A₃ receptors are overexpressed in pleura from patients with mesothelioma and reduce cell growth via Akt/nuclear factor-κB pathway

Our plain-English summary of A₃ receptors are overexpressed in pleura from patients with mesothelioma and reduce cell growth via Akt/nuclear factor-κB pathway, by K. Varani, S. Maniero, F. Vincenzi, et al (American Journal of Respiratory and Critical Care Medicine, 2011).

The study

• Authors: K. Varani, S. Maniero, F. Vincenzi, M. Targa, A. Stefanelli, P. Maniscalco, F. Martini, M. Tognon, P.A. Borea
• Journal: American Journal of Respiratory and Critical Care Medicine
• Published: 2011;183(4):522-30
• Cited by: 43 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Rationale: A strong link has been established between exposure to asbestos and increased risk for pleural malignant mesothelioma (MM). Adenosine plays a key role in inflammatory processes and cancer, where it is involved in the regulation of cell death and proliferation.

Objectives: The primary aim of this study was to investigate the presence of adenosine receptors (ARs) in human MM pleura (MMP) and healthy mesothelial pleura (HMP). To shed some light on the interaction between adenosine and MM, the presence and functionality of ARs were explored in human healthy mesothelial cells (HMC) and in malignant mesothelioma cells (MMC).

Methods: ARs were analyzed by using reverse transcriptase-polymerase chain reaction, Western blotting, and saturation binding assays. HMC were treated with crocidolite asbestos, which is the principal risk factor for MM. The role of A₃ ARs on these cellular models, evaluating cAMP production, Akt phosphorylation, and nuclear factor (NF)-κB activation, was investigated. The dual effect of A₃AR stimulation on healthy and cancer cell growth was studied by means of proliferation, apoptosis, and cytotoxicity assays.

Measurements And Main Results: A₃AR was up-regulated by 2.5-fold (P < 0.01) in MMP when compared with HMP. Stimulation of A₃ARs decreased proliferation and exerted a cytotoxic and proapoptotic effect on MMC and on HMC exposed to asbestos and tumor necrosis factor-α, but not on HMC with an involvement of the deregulation of Akt/NF-κB cell survival pathway.

Conclusions: These new findings suggest that A₃AR could represent a pharmacological target to prevent tumor development after asbestos exposure and to treat full-blown MM.

In plain English

This laboratory study from the University of Ferrara, Italy, examined adenosine receptors in pleura removed during surgery between June 2007 and September 2009. The tissue came from 17 patients with pleural malignant mesothelioma and 16 patients without pleural disease, and the study also used cells grown from these tissues. The article did not report the patients' asbestos exposure histories. Of four receptor types, only the A3 receptor differed. Its density was 282 versus 113 fmol/mg protein in mesothelioma pleura compared with healthy pleura, which the authors described as a 2.5-fold increase. Mesothelioma cells had 3.5-fold more A3 receptors than healthy mesothelial cells, and healthy cells treated with crocidolite asbestos for 24 hours also showed an increase. In laboratory cell experiments, a drug that stimulates A3 receptors (Cl-IB-MECA) lowered cell-survival signals, reduced growth and increased cell death in mesothelioma cells and in healthy cells exposed to asbestos plus TNF-alpha, but not in untreated healthy cells. The authors concluded that A3 receptors could be a drug target to prevent tumor development after asbestos exposure and to treat mesothelioma. No treatment was tested in patients.

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 of human pleura tissue samples and of healthy and mesothelioma cells grown in culture from that tissue (in vitro)
• Who was studied: 33 surgical patients at the University of Ferrara, Italy, operated on between June 2007 and September 2009. Seventeen had pleural malignant mesothelioma (13 men, 4 women; 14 epithelial, 3 biphasic; mean age 61.7 years). Sixteen had healthy pleura (10 men, 6 women; surgery for spontaneous pneumothorax in 11 and primary hyperhidrosis in 5; mean age 42.3 years). Tissue from 9 mesothelioma and 8 healthy patients was frozen for tests; tissue from 8 and 8 was used to grow cells.
• Exposure: Healthy mesothelial cells were treated in the laboratory with crocidolite asbestos (24-hour exposure in binding experiments), alone or with TNF-alpha. Cells were also treated with the A3 receptor stimulating drug Cl-IB-MECA and the A3 receptor blocking drug MRE3008F20.
• Main results:
  • In mesothelioma pleura compared with healthy pleura, A3 receptor protein was 61% higher on Western blotting (A3AR to beta-actin ratio 1.42 plus or minus 0.09 vs 0.88 plus or minus 0.06, P less than 0.01). No differences were found for A1, A2A and A2B receptors.
  • A3 receptor density (Bmax) was 113 plus or minus 14 fmol/mg protein in healthy pleura and 282 plus or minus 24 fmol/mg protein in mesothelioma pleura (P less than 0.01), described by the authors as a 2.5-fold increase.
  • In mesothelioma cells compared with healthy mesothelial cells, A3 receptor density was 3.5-fold higher and A3 receptor mRNA was 3.2-fold higher.
  • In healthy mesothelial cells treated with crocidolite asbestos for 24 hours, A3 receptor density was 260 plus or minus 24 fmol/mg protein, which the authors reported as a statistically significant increase.
  • In healthy mesothelial cells, asbestos raised levels of the survival protein phospho-Akt 1.4-fold. Cl-IB-MECA at 10 nM and 100 nM reduced this rise by 42% and 74%, respectively.
  • In mesothelioma cells, Cl-IB-MECA reduced basal NF-kB activation by 35% at 10 nM and by 58% at 100 nM.
  • Cl-IB-MECA did not affect growth of healthy mesothelial cells but reduced growth of mesothelioma cells. In healthy cells exposed to asbestos plus TNF-alpha, it reduced growth by removing TNF-alpha's pro-survival effect.
  • In mesothelioma cells, Cl-IB-MECA at 100 nM increased active caspase-3 (a marker of programmed cell death) by 29%; at 10 nM it was ineffective.
  • In mesothelioma cells, Cl-IB-MECA increased LDH release, which the authors interpreted as a toxic effect on these tumor cells.
• The authors' conclusion: The authors concluded that their findings suggest the A3 receptor could be a drug target to prevent tumor development after asbestos exposure and to treat full-blown mesothelioma.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleura, Mesothelioma, Malignant Mesothelioma, Mesothelial Cells, Crocidolite, Apoptosis, Necrosis, Asbestos Exposure.

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• Increased expression of epidermal growth factor receptor in rat pleural mesothelial cells correlates with carcinogenicity of mineral fibres — S.P. Faux, C.E. Houghton, et al. (2000)
• Raw single-wall carbon nanotubes induce oxidative stress and activate MAPKs, AP-1, NF-kappaB, and Akt in normal and malignant human mesothelial cells — M. Pacurari, X.J. Yin, et al. (2008)
• Transforming growth factor-β-induced protein (TGFBI) suppresses mesothelioma progression through the Akt/mTOR pathway — G. Wen, M. Hong, et al. (2011)
• Hepatocyte growth factor/scatter factor and its receptor c-Met are overexpressed and associated with an increased microvessel density in malignant pleural mesothelioma — E. Tolnay, C. Kuhnen, et al. (1998)

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