Adenosine induces apoptosis in SBC-3 human lung cancer cells through A 3 adenosine receptor-dependent AMID upregulation

Abstract

Background/Aims: We have shown that A 3 adenosine receptor mediates apoptosis in human lung cancer cells such as A549 cells, an epithelial adenocarcinoma cell line, and Lu-65 cells, a giant cell cancer cell line, via each different signaling pathway. AMID, a pro-apoptotic protein, induces caspase-independent apoptosis by accumulating in the nucleus. The present study investigated AMID-dependent apoptosis through A 3 adenosine receptor in SBC-3 cells, a human small cell lung cancer cell line. Methods: MTT assay, TUNEL staining, flow cytometry using propidium iodide and annexin V-FITC, and Western blotting were carried out in SBC-3 cells transfected with and without the siRNA to silence the A 3 adenosine receptor-targeted gene or the AMID-targeted gene. Results: Adenosine induced SBC-3 cell apoptosis in a concentration (0.01-10 mM) and treatment time (24-72 h)-dependent manner, and a similar effect was obtained with the A 3 adenosine receptor agonist 2-Cl-IB-MECA. Adenosine-induced SBC-3 cell death was inhibited by the A 3 adenosine receptor inhibitor MRS1191, knocking-down A 3 adenosine receptor, or knocking-down AMID. Adenosine upregulated expression of the AMID mRNA and protein in SBC-3 cells, that is suppressed by knocking-down A 3 adenosine receptor. In addition, adenosine increased nuclear AMID localization in concert with decreased cytosolic AMID localization. Conclusion: The results of the present study show that adenosine induces SBC-3 cell apoptosis by upregulating AMID expression and promoting AMID translocation into the nucleus via A 3 adenosine receptor. Copyright © 2012 S. Karger AG, Basel.