Evidence of functional ryanodine receptor involved in apoptosis of prostate cancer (LNCaP) cells

BACKGROUND. Very little is known about the functional expression and the ph ysiological role of ryanodine receptors in nonexcitable cells, and in prost ate cancer cells in particular. Nonetheless, different studies have demonst rated that calcium is a major factor involved in apoptosis. Therefore, the calcium-regulatory mechanisms, such as ryanodine-mediated calcium release, may play a substantial role in the regulation of apoptosis. METHODS. We assessed the presence of such functional receptors in LNCaP pro state cancer cells, using fluorimetric measurements of intracellular calciu m and expression assays of mRNA encoding ryanodine receptors. RESULTS. We show here that LNCaP cells responded to caffeine, a ryanodine r eceptor agonist, by mobilizing calcium. Another ryanodine receptor agonist, 4-chloro-m-cresol, had a similar effect and promoted calcium release. Thes e effects were inhibited by pretreatment with ryanodine or thapsigargin. In addition to a calcium release, caffeine was able to produce a calcium entr y blocked by nickel. We used a reverse transcription-polymerase chain react ion assay to investigate the expression of ryanodine receptors in LNCaP cel ls. Two types of ryanodine receptor mRNAs were expressed in LNCaP cells: Ry R1 and RyR2 mRNAs. Finally, we show that ryanodine receptor activation by c affeine slightly stimulates apoptosis of prostate cancer cells, and that th e inhibition of these receptors by ryanodine protects the cells against apo ptosis. CONCLUSIONS. The combination of results showed that LNCaP cells, derived fr om a human prostate cancer, express functional RyRs able to mobilize Ca2+ f rom intracellular stores and which might control apoptosis. Prostate 43:205 -214, 2000. (C) 2000 Wiley-Liss, Inc.