Accumulating evidence has associated purinergic signals, which are induced by extracellular nucleotides, to the processes of several diseases[
1]. Extracellular nucleotides, particularly ATP, are important transmitters that mediate various biological effects via purinergic receptors (P2-receptors) in many cell types[
2], and several studies have found that ATP can inhibit tumor growth[
3‐
6]. P2 receptors are subclassified into two main types: P2X and P2Y receptors[
7]. P2X receptors are ligand-gated ion channels that are activated by extracellular ATP to elicit a flow of cations[
2], seven of which, P2X1 to P2X7, have been cloned[
8]. The metabotropic P2Y receptors belonging to the G-protein-coupled receptor (GPCR) family play important roles in several signaling pathways, and eight P2Y receptors have been cloned and identified as GPCRs in mammals[
2,
9]. Although P2Y receptors are distributed in a wide range of normal tissues, P2X receptors are mainly expressed in the nervous system, platelets, and smooth muscle cells (SMCs)[
10,
11]. P2Y2 has often been reported to be a functional receptor that transduces several biological signals induced by ATP and UTP, studies largely conducted in normal cells, such as epithelial cells, smooth muscle cells, leukocytes, and nerve cells. It has also been reported that P2Y2 activates nerve growth factor signaling to enhance neuronal differentiation and is also involved in phagocytic clearance[
12‐
15]. However, the role of P2Y2 in tumor cells remains poorly understood, though some reports have described the possible role of P2Y2 in effects of extracellular nucleotides on tumor cells[
4]. Osteopontin (OPN) is a secreted arginine-glycine-aspartic acid (RGD)-containing phosphoprotein with a thrombin cleavage site. By binding to several integrins and CD44 variants, OPN plays an important role in tumorigenesis, tumor invasion, tumor growth, and metastasis in many types of cancers[
16‐
18]. OPN has been shown to promote cell survival through the inhibition of apoptosis, and OPN downregulation decreases the motility and invasiveness of tumor cells[
19,
20]. Although it has been reported that extracellular nucleotides induce OPN expression in arterial SMCs[
21], their effect on OPN expression in tumor cells has not been examined.
Purinergic signaling has thus far not been investigated in NPC cells, and the effect of extracellular ATP on tumor cell OPN levels is unclear. Therefore, the effects of ATP on NPC cell apoptosis, cell cycle arrest, and cell migration were investigated in the present study, and we also explored whether the effects were caused through P2Y2 and OPN.