Adenosine A(3) receptor (A3AR) is coupled to
G proteins that are involved in a variety of intracellular signaling pathways and physiological functions. 2-Chloro-N(6)-(3-iodobenzyl) adenosine-5'-N-methylcarboxamide (Cl-
IB-MECA), an agonist of A3AR, has been reported to induce cell death in various
cancer cells. However, the effect of CI-
IB-MECA on
glioma cell growth is not clear. This study was undertaken to examine the effect of CI-
IB-MECA on
glioma cell viability and to determine its molecular mechanism. CI-
IB-MECA inhibited cell proliferation and induced cell death in a dose- and time-dependent manner. Treatment of CI-
IB-MECA resulted in an increase in intracellular Ca(2+) followed by enhanced
reactive oxygen species (ROS) generation.
EGTA and
N-acetylcysteine (NAC) blocked the cell death induced by CI-
IB-MECA, suggesting that Ca(2+) and ROS are involved in the Cl-
IB-MECA-induced cell death. Western blot analysis showed that CI-
IB-MECA induced the down-regulation of
extracellular signal-regulated kinases (ERK) and Akt, which was prevented by
EGTA, NAC, and the A3AR antagonist MRS1191. Transfection of constitutively active forms of
MEK, the upstream
kinase of ERK, and Akt prevented the cell death. CI-
IB-MECA induced
caspase-3 activation and the CI-
IB-MECA-induced cell death was blocked by the
caspase inhibitors DEVD-CHO and
z-VAD-FMK. In addition, expression of XIAP and
Survivin were decreased in cells treated with Cl-
IB-MECA. Collectively, these findings demonstrate that CI-
IB-MECA induce a
caspase-dependent cell death through suppression of ERK and Akt mediated by an increase in intracellular Ca(2+) and ROS generation in human
glioma cells. These suggest that A3AR agonists may be a potential therapeutic agent for induction of apoptosis in human
glioma cells.