AMP Converted from Intracellularly Transported Adenosine Upregulates p53 Expression to Induce Malignant Pleural Mesothelioma Cell Apoptosis

Abstract

Background/Aims: The present study investigated adenosine-induced apoptosis in human malignant pleural mesothelioma cells. Methods: MTT assay, TUNEL staining, flow cytometry using propidium iodide and annexin V-FITC, real-time RT-PCR, Western blotting, and assay of caspase-3, -8, and -9 activities were carried out using malignant pleural mesothelioma cell lines such as NCI-H28, NCI-H2052, NCI-H2452, and MSTO-211H cells, and p53 or A₃adenosine receptor was knocked-down by transfecting each siRNA into cells. Results: Adenosine induced apoptosis in all the malignant pleural mesothelioma cells used here, independently of caspase activation. The adenosine effect was prevented by the adenosine transporter inhibitor dipyridamole, the adenosine kinase inhibitor ABT-702, or the A₃adenosine receptor inhibitor MRS1191. Adenosine upregulated expression of the p53 mRNA and protein, that is abolished by ABT-702, but not by knocking-down A₃adenosine receptor. Adenosine-induced apoptosis in NCI-H28 cells was significantly inhibited by knocking-down p53 and in part by knocking-down A₃adenosine receptor. Conclusion: The results of the present study show that AMP converted from intracellularly transported adenosine upregulates p53 expression to induce caspase-independent apoptosis in malignant pleural mesothelioma cells and that A₃adenosine receptor also participates partially in the apoptosis by the different mechanism.

Prostaglandin E2-mediated adenosinergic effects on CD14+cells: Self-amplifying immunosuppression in cancer

“…6,33 In mesothelioma, high concentration of extracellular adenosine (3 mM) has been reported to cause apoptosis of tumor cells. 34 However, we show here that physiological concentrations support tumor growth, indicating the relevance of adenosine in the progression of this disease.…”

Adenosine Inhibits Tumor Cell Invasion via Receptor-Independent Mechanisms

“…Yet another approach includes tumor treatment with adenosine as a "kindred" metabolite; however, most of the proapoptotic and antiproliferative effects of adenosine reported in studies with different malignant cells required continuous presence of supra-physiological nucleoside concentrations (0.1-20 mmol/L) in the assay mixture (15,(17)(18)(19).…”

“…Most of these effects occur at high micromolar and even millimolar nucleoside concentrations, which are at least two orders of magnitude higher than adenosine receptor affinities and generally imply the uptake of extracellular adenosine and/or its metabolites into the cells through adenosine transporters and their ensuing interconversion into AMP and further to ADP/ATP. As a consequence of these metabolic shifts, adenosine may induce apoptosis of different malignant cells via upregulation of p53 (17) or AMP-activated protein kinase (AMPK; ref. 18) activities, translocation of apoptosis-inducing factor AMID from the cytosol into the nucleus (19), and other mitochondrial apoptotic pathways (15).…”

The A3Adenosine Receptor: History and Perspectives

“…Finally, very high A 3 AR protein expression was observed in a variety of cancer cell lines (Gessi et al, , 2007Merighi et al, 2001Merighi et al, , 2009Suh et al, 2001;Morello et al, 2009;Jajoo et al, 2009;Cohen et al, 2011;Hofer et al, 2011;Varani et al, 2011aVarani et al, , 2013Kanno et al, 2012;Nogi et al, 2012;Kamiya et al, 2012;Otsuki et al, 2012;Vincenzi et al, 2012;Nagaya et al, 2013;Sakowicz-Burkiewicz et al, 2013;Madi et al, 2013) and in cancer tissues (Gessi et al, 2004a;Madi et al, 2004;Bar-Yehuda et al, 2008;Varani et al, 2011a), thus suggesting a role for this subtype as a tumoral marker.…”