Characterization of calcium-mobilizing, purinergic P2Y₂ receptors in human ovarian cancer cells

In human ovarian EFO-21 and EFO-27 carcinoma cells, extracellular ATP induced a concentration-dependent rise in intracellular calcium concentration ([Ca²⁺](i)), suggesting the expression of a purinoreceptor. ATP and UTP were equipotent in generating [Ca²⁺](i) signals, followed by ATP-γ-S and ADP, whereas β,γ-ATP, 2 methyl 1 thio-ATP, 3'-o-(4-benzoyl) benzoyl-ATP, AMP, and adenosine were ineffective. This pharmacological profile suggested the presence of the P2Y₂ subtype in both cell types, and this was confirmed by reverse transcription-polymerase chain reaction (RT-PCR) analysis using P2Y₂ primers. ATP-induced [Ca²⁺](i) signals were composed of two phases: an early and extracellular calcium-independent phase, followed by a sustained plateau phase that was dependent on capacitative calcium influx. In addition to the rise in the [Ca²⁺](i), a time- and concentration-dependent increase in phosphatidylethanol accumulation was observed in ATP-stimulated cells, indicating an increase in phospholipase D activity. RT-PCR analysis identified the expression of a transcript for the phospholipase D-1 subtype of this enzyme. Activation of these receptors by a slowly degradable analogue, ATP-γ-S, attenuated basal and fetal calf serum-induced cell proliferation in a time- and concentration-dependent manner. These results indicate that ATP may act as an extracellular messenger in controlling the ovarian epithelial cell cycle through P2Y₂ receptors.