Effect of celecoxib on Ca²⁺ handling and viability in human prostate cancer cells (PC3)

Abstract

Celecoxib has been shown to have an antitumor effect in previous studies, but the mechanisms are unclear. Ca²⁺ is a key second messenger in most cells. The effect of celecoxib on cytosolic free Ca²⁺ concentrations ([Ca²⁺]_i) in human suspended PC3 prostate cancer cells was explored by using fura-2 as a fluorescent dye. Celecoxib at concentrations between 5 and 30 μM increased [Ca²⁺]_i in a concentration-dependent manner. The Ca²⁺ signal was reduced partly by removing extracellular Ca²⁺. Celecoxib-induced Ca²⁺ influx was not blocked by L-type Ca²⁺ entry inhibitors or protein kinase C/A modulators [phorbol 12-myristate 13-acetate (PMA), GF109203X, H-89], but was inhibited by the phospholipase A₂ inhibitor, aristolochic acid. In Ca²⁺-free medium, 30 μM of celecoxib failed to induce a [Ca²⁺]_i rise after pretreatment with thapsigargin (an endoplasmic reticulum [ER] Ca²⁺ pump inhibitor). Conversely, pretreatment with celecoxib inhibited thapsigargin-induced Ca²⁺ release. Inhibition of phospholipase C with U73122 did not change celecoxib-induced [Ca²⁺]_i rises. Celecoxib induced slight cell death in a concentration-dependent manner, which was enhanced by chelating cytosolic Ca²⁺ with BAPTA. Collectively, in PC3 cells, celecoxib induced [Ca²⁺]_i rises by causing phospholipase C–independent Ca²⁺ release from the ER and Ca²⁺ influx via non-L-type, phospholipase A₂-regulated Ca²⁺ channels. These data may contribute to the understanding of the effect of celecoxib on prostate cancer cells.

Keywords::

• Ca²⁺
• celecoxib
• PC3
• prostate cancer
• thapsigargin