<i>MicroRNA e il recettore adenosinico A3 come biomarcatori del mesotelioma maligno della pleura</i>

Abstract

Background: Malignant pleural mesothelioma (MPM) is an aggressive asbestosrelated cancer that develops via mesothelial cell transformation. At present there are no effective therapies for MPM. Great efforts have been made in finding specific markers/mechanisms for MPM onset, including studies into microRNAs and adenosine receptors (ARs). Recent studies have shown the differential expression of mature microRNAs in several human cancers, suggesting their potential role as oncogenes or tumor suppressor genes, and the involvement of ARs in the regulation of cell death and proliferation. Methods: In this study, we investigated miRNAs profile and the expression of A3ARs in MPM. MiRNAs profile was investigated in 5 HMCs (human normal pleural mesothelial short term cell cultures) and 5 MPMs, with microarray approach. These results were confirmed by Real Time quantitative RT-PCR and western blotting. ARs were analyzed by using RT-PCR, western blotting and saturation binding assays. HMC were treated with crocidolite asbestos which is the principal risk factor of MM. The role of A3ARs on these cellular models, evaluating cAMP production, Akt phosphorylation and NF-kB 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: A comparative analysis of miRNA expression in MPM and HMCs was carried out. Microarray profiling showed different miRNA expression between MPM and HMCs. Specifically, 13 miRNAs (17-5p, 18a, 19b, 20a, 20b, 25, 92, 106a, 106b), members of the oncomiRNA miR 17-92 and its paralogs were markedly dysregulated. Besides, in our investigation, additional miRNAs, such as miR-7, miR-182, miR-214 and miR-497 were found to be dysregulated in MPM. A3AR was up-regulated by 2.5 fold (P<0.01) in MMP when compared with HMP. Stimulation of A3ARs decreases proliferation and exerts cytotoxic and proapoptotic effect on MMC and on HMC exposed to asbestos and TNF-�, but not in HMC with an involvement of the de-regulation of Akt/NF-kB cell survival pathway. Conclusion: These data are in agreement with results which have previously been reported on dysregulated miRNAs for other solid human tumors. Moreover, in our investigation, additional miRNAs were found to be dysregulated in MPM. Interestingly, gene products which regulate the cell cycle are targets and predicted targets for these miRNAs. Our data suggest that specific miRNAs and A3ARs could be key players in MPM development/progression. In addition, some of these miRNAs may represent MPM markers and potential targets for new therapeutic approaches. Besides, our data suggest that A3AR could represent a pharmacological target to prevent tumor development after asbestos exposure and to treat full blown MPM.