Role of OATP2A1 in PGE2 secretion from human colorectal cancer cells via exocytosis in response to oxidative stress

Chronic inflammation induced by reactive oxygen species is associated with increased risk of developing colorectal cancer (CRC), and prostaglandin E-2 (PGE(2)), which serves as a key mediator of inflammatory responses, plays an important role in CRC initiation and progression. Therefore, in the present study, we aimed to investigate the role of prostaglandin transporter OATP2A1/SLCO2A1 in the changes of PGE(2) disposition in CRC cells in response to oxidative stress. H2O2 induced translocation of cytoplasmic OATP2A1 to plasma membranes in LoVo and COLO 320DM cells, but not in Caco-2 cells. The shift of subcellular OATP2A1 was abolished in the presence of anti-oxidant N-acetyl-L-cysteine or an inhibitor of protein kinase C, which evokes exocytosis. Exposure of LoVo cells to H2O2 caused an increase in the amount of extracellular PGE(2) without changing the sum of intra- and extracellular PGE(2). OATP2A1 knockdown decreased extracellular PGE(2) in LoVo cells. In addition, extracellular PGE(2) was significantly reduced by exocytosis inhibitor cytochalasin D, suggesting that H2O2-induced PGE(2) release occurs in an exocytotic manner. Furthermore, mRNA expression of vascular endothelial growth factor (VEGF) was significantly reduced in LoVo cells by knockdown of OATP2A1. These results suggest that cytoplasmic OATP2A1 likely facilitates PGE(2) loading into suitable intracellular compartment(s) for efficient exocytotic PGE(2) release from CRC cells exposed to oxidative stress. (C) 2016 Elsevier Inc. All rights reserved.