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


OBJECTIVE
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.


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.
Varani
Katia
K
Department of Clinical and Experimental Medicine, Pharmacology Unit, University of Ferrara, Ferrara, Italy.
Maniero
Stefania
S
Vincenzi
Fabrizio
F
Targa
Martina
M
Stefanelli
Angela
A
Maniscalco
Pio
P
Martini
Fernanda
F
Tognon
Mauro
M
Borea
Pier Andrea
PA
D000328:Adult; D017209:Apoptosis; D017638:Asbestos, Crocidolite; D015153:Blotting, Western; D049109:Cell Proliferation; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D008297:Male; D008654:Mesothelioma / Q000378:metabolism* / Q000473:pathology*; D008875:Middle Aged; D016328:NF-kappa B / Q000378:metabolism*; D010994:Pleura / Q000378:metabolism / Q000473:pathology; D010997:Pleural Neoplasms / Q000378:metabolism* / Q000473:pathology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D043684:Receptor, Adenosine A3 / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation
D016328:NF-kappa B; D043684:Receptor, Adenosine A3; D017638:Asbestos, Crocidolite; D051057:Proto-Oncogene Proteins c-akt