sphingosine-1-phosphate and Cholangiocarcinoma

Bile duct obstruction is a potent stimulus for cholangiocyte proliferation, especially for large cholangiocytes. Our previous studies reported that conjugated bile acids (CBAs) activate the protein kinase B (AKT) and extracellular signal-regulated kinase 1 and 2 (ERK1/2) signaling pathways through sphingosine 1-phosphate receptor (S1PR) 2 in hepatocytes and cholangiocarcinoma cells. It also has been reported that taurocholate (TCA) promotes large cholangiocyte proliferation and protects cholangiocytes from bile duct ligation (BDL)-induced apoptosis. However, the role of S1PR2 in bile-acid-mediated cholangiocyte proliferation and cholestatic liver injury has not been elucidated. Here, we report that S1PR2 is the predominant S1PR expressed in cholangiocytes. Both TCA- and sphingosine-1-phosphate (S1P)-induced activation of ERK1/2 and AKT were inhibited by JTE-013, a specific antagonist of S1PR2, in cholangiocytes. In addition, TCA- and S1P-induced cell proliferation and migration were inhibited by JTE-013 and a specific short hairpin RNA of S1PR2, as well as chemical inhibitors of ERK1/2 and AKT in mouse cholangiocytes. In BDL mice, expression of S1PR2 was up-regulated in whole liver and cholangiocytes. S1PR2 deficiency significantly reduced BDL-induced cholangiocyte proliferation and cholestatic injury, as indicated by significant reductions in inflammation and liver fibrosis in S1PR2 knockout mice. Treatment of BDL mice with JTE-013 significantly reduced total bile acid levels in serum and cholestatic liver injury.. This study suggests that CBA-induced activation of S1PR2-mediated signaling pathways plays a critical role in obstructive cholestasis and may represent a novel therapeutic target for cholestatic liver diseases. (Hepatology 2017;65:2005-2018).

Topics: Analysis of Variance; Animals; Bile Acids and Salts; Bile Duct Neoplasms; Bile Ducts; Cell Proliferation; Cholangiocarcinoma; Cholangitis, Sclerosing; Cholestasis; Disease Models, Animal; Ligation; Liver; Liver Cirrhosis; Lysophospholipids; Male; Mice; Mice, Inbred CBA; Mice, Knockout; Mitogen-Activated Protein Kinase 1; Random Allocation; Receptors, Lysosphingolipid; Role; Signal Transduction; Sphingosine; Sphingosine-1-Phosphate Receptors; Up-Regulation

Cholangiocarcinoma (CCA) is characterized by a uniquely aggressive behavior and lack of effective targeted therapies. After analyzing the gene expression profiles of seven paired intrahepatic CCA microarrays, a novel sphingosine kinase 1 (SPHK1)/sphingosine-1-phosphate (S1P) pathway and a novel target gene, SPHK1, were identified. We hypothesized that therapeutic targeting of this pathway can be used to kill intrahepatic cholangiocarcinoma (CCA) cells. High levels of SPHK1 protein expression, which was evaluated by immunohistochemical staining of samples from 96 patients with intrahepatic CCA, correlated with poor overall survival. The SPHK1 inhibitor SK1-I demonstrated potent antiproliferative activity in vitro and in vivo. SK1-I modulated the balance of ceramide-sphinogosine-S1P and induced CCA apoptosis. Furthermore, SK1-I combined with JTE013, an antagonist of the predominant S1P receptor S1PR2, inhibited the AKT and ERK signaling pathways in CCA cells. Our preclinical data suggest SPHK1/S1P pathway targeting may be an effective treatment option for patients with CCA.

Topics: Adaptor Proteins, Signal Transducing; Amino Alcohols; Animals; Apoptosis; Bile Duct Neoplasms; Bile Ducts; Cell Line, Tumor; Cell Proliferation; Cell Survival; Ceramides; Cholangiocarcinoma; Extracellular Signal-Regulated MAP Kinases; Female; Gene Expression Profiling; Humans; Lysophospholipids; Male; MAP Kinase Signaling System; Mice; Mice, Inbred BALB C; Middle Aged; Prognosis; Proto-Oncogene Proteins c-akt; Pyrazoles; Pyridines; Receptors, Lysosphingolipid; Sphingosine; Sphingosine-1-Phosphate Receptors; Xenograft Model Antitumor Assays