S1P Stimulates Proliferation by Upregulating CTGF Expression through S1PR2-Mediated YAP Activation

Mol Cancer Res. 2018 Oct;16(10):1543-1555. doi: 10.1158/1541-7786.MCR-17-0681. Epub 2018 Jun 14.

Abstract

Dysregulation of the Hippo pathway in the liver results in overgrowth and eventually tumorigenesis. To date, several upstream mechanisms have been identified that affect the Hippo pathway, which ultimately regulate YAP, the major downstream effector of the pathway. However, upstream regulators of the Hippo pathway in the liver remain poorly defined. Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid metabolite that has been shown to stimulate hepatocellular carcinoma (HCC) cell proliferation, but whether the Hippo pathway is involved in S1P-stimulated HCC cell proliferation remains to be determined. Here it is demonstrated that S1P activates YAP and that the S1P receptor 2 (S1PR2/S1P2) mediates S1P-induced YAP activation in both human and mouse HCC cells. S1P promotes YAP-mediated upregulation of cysteine-rich protein 61 and connective tissue growth factor (CTGF), and stimulates HCC cell proliferation. By using siRNA-mediated knockdown approaches, only CTGF was required for S1P-stimulated cell proliferation. Of note, S1P activates YAP in a MST1/2-independent manner suggesting that the canonical Hippo kinase is not required for S1P-mediated proliferation in liver. The upregulation of CTGF and S1P2 were also observed in liver-specific YAP overexpression transgenic mouse hepatocytes. Moreover, YAP regulated liver differentiation-dependent gene expression by influencing the chromatin binding of HNF4α based on ChIP-seq analysis. Finally, results using gain- and loss-of-function approaches demonstrate that HNF4α negatively regulated S1P-induced CTGF expression.Implications: These findings reveal a role for S1P in stimulating HCC cell proliferation by upregulating CTGF expression through S1P2-mediated YAP activation. Mol Cancer Res; 16(10); 1543-55. ©2018 AACR.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics*
  • Animals
  • Carcinoma, Hepatocellular / genetics*
  • Carcinoma, Hepatocellular / pathology
  • Cell Proliferation / genetics
  • Connective Tissue Growth Factor / genetics*
  • Gene Expression Regulation, Neoplastic
  • Hepatocyte Nuclear Factor 4 / genetics
  • Hepatocytes / metabolism
  • Hepatocytes / pathology
  • Humans
  • Liver / metabolism
  • Liver / pathology
  • Liver Neoplasms / genetics*
  • Liver Neoplasms / pathology
  • Lysophospholipids / genetics
  • Lysophospholipids / metabolism
  • Mice
  • Mice, Transgenic
  • Phosphoproteins / genetics*
  • RNA, Small Interfering / genetics
  • Receptors, Lysosphingolipid / genetics*
  • Sphingosine / analogs & derivatives
  • Sphingosine / genetics
  • Sphingosine / metabolism
  • Sphingosine-1-Phosphate Receptors
  • Transcription Factors
  • YAP-Signaling Proteins

Substances

  • Adaptor Proteins, Signal Transducing
  • CCN2 protein, human
  • HNF4A protein, human
  • Hepatocyte Nuclear Factor 4
  • Lysophospholipids
  • Phosphoproteins
  • RNA, Small Interfering
  • Receptors, Lysosphingolipid
  • S1PR2 protein, human
  • Sphingosine-1-Phosphate Receptors
  • Transcription Factors
  • YAP-Signaling Proteins
  • YAP1 protein, human
  • Connective Tissue Growth Factor
  • sphingosine 1-phosphate
  • Sphingosine