Roles of lysophosphatidic acid (LPA) receptor-2 (LPA2) in the regulation of cellular responses induced by X-ray irradiation and hydrogen peroxide in pancreatic cancer cells.

PURPOSE: Lysophosphatidic acid (LPA) receptor-mediated signaling regulates various biological functions in cancer cells. This study aimed to evaluate the roles of LPA receptor-2 (LPA2) in cellular responses induced by X-ray irradiation in pancreatic cancer PANC-1 cells. Since X-ray irradiation generates reactive oxygen species (ROS), PANC-1 cells were treated with hydrogen peroxide (H2O2). H2O2 is a key member of ROS. METHODS: To investigate the cell survival rate to X-ray irradiation, PANC-1 cells were irradiated with X-rays (2.5-15 Gy). LPAR2 expression levels were measured by quantitative real-time RT-PCR analysis. The effects of LPA2 on the cell survival and motility were evaluated using LPA2 knockdown cells. To establish H2O2 treated cells, PANC-1 cells were cultured in 10% FBS-DMEM with H2O2 (30 µM) for 2 weeks. The cell motility and survival rate to cisplatin (CDDP) of H2O2 treated cells were examined. RESULTS: LPAR2 expression was significantly increased in PANC-1 cells irradiated with X-rays. PANC-1 cell motility was markedly decreased by X-ray irradiation. The reduced cell motility activity by X-ray irradiation was enhanced by LPA2 knockdown. The cell survival to X-ray irradiation was elevated in PANC-1 cells treated with GRI-977143 (LPA2 agonist) and suppressed by LPA2 knockdown. On the other hand, LPAR2 expression was markedly higher in H2O2 treated cells than in H2O2 untreated cells. H2O2 treated cells showed the high cell survival to CDDP in comparison with H2O2 untreated cells. GRI-977143 increased the cell survival to CDDP of H2O2 treated cells, while LPA2 knockdown suppressed. CONCLUSIONS: The present results suggest that the activation of LPA2-mediated signaling plays an important role in the modulation of cellular functions induced by X-ray irradiation and H2O2 in PANC-1 cells.

Autotaxin in Breast Cancer: Role, Epigenetic Regulation and Clinical Implications.

Autotaxin (ATX), the protein product of Ectonucleotide Pyrophosphatase Phosphodiesterase 2 (ENPP2), is a secreted lysophospholipase D (lysoPLD) responsible for the extracellular production of lysophosphatidic acid (LPA). ATX-LPA pathway signaling participates in several normal biological functions, but it has also been connected to cancer progression, metastasis and inflammatory processes. Significant research has established a role in breast cancer and it has been suggested as a therapeutic target and/or a clinically relevant biomarker. Recently, ENPP2 methylation was described, revealing a potential for clinical exploitation in liquid biopsy. The current review aims to gather the latest findings about aberrant signaling through ATX-LPA in breast cancer and discusses the role of ENPP2 expression and epigenetic modification, giving insights with translational value.

Endosomal H2O2 production leads to localized cysteine sulfenic acid formation on proteins during lysophosphatidic acid-mediated cell signaling.

Lysophosphatidic acid (LPA) is a growth factor for many cells including prostate and ovarian cancer-derived cell lines. LPA stimulates H2O2 production which is required for growth. However, there are significant gaps in our understanding of the spatial and temporal regulation of H2O2-dependent signaling and the way in which signals are transmitted following receptor activation. Herein, we describe the use of two reagents, DCP-Bio1 and DCP-Rho1, to evaluate the localization of active protein oxidation after LPA stimulation by detection of nascent protein sulfenic acids. We found that LPA stimulation causes internalization of LPA receptors into early endosomes that contain NADPH oxidase components and are sites of H2O2 generation. DCP-Rho1 allowed visualization of sulfenic acid formation, indicative of active protein oxidation, which was stimulated by LPA and decreased by an LPA receptor antagonist. Protein oxidation sites colocalized with LPAR1 and the endosomal marker EEA1. Concurrent with the generation of these redox signaling-active endosomes (redoxosomes) is the H2O2- and NADPH oxidase-dependent oxidation of Akt2 and PTP1B detected using DCP-Bio1. These new approaches therefore enable detection of active, H2O2-dependent protein oxidation linked to cell signaling processes. DCP-Rho1 may be a particularly useful protein oxidation imaging agent enabling spatial resolution due to the transient nature of the sulfenic acid intermediate it detects.