Stimulated hepatic stellate cell promotes progression of hepatocellular carcinoma due to protein kinase R activation

PLoS One. 2019 Feb 22;14(2):e0212589. doi: 10.1371/journal.pone.0212589. eCollection 2019.

Abstract

Hepatic stellate cells (HSCs) were reported to promote the progression of hepatocellular carcinoma (HCC), however its mechanism is uncertain. We previously reported that protein kinase R (PKR) in hepatocytes regulated HCC proliferation. In this study, we focused on the role of PKR in HSCs, and clarified the mechanism of its association with HCC progression. We confirmed the activation of PKR in a human HSC cell line (LX-2 cell). IL-1β is produced from HSCs stimulated by lipopolysaccharide (LPS) or palmitic acid which are likely activators of PKR in non-alcoholic steatohepatitis (NASH). Production was assessed by real-time PCR and ELISA. C16 and small interfering RNA (siRNA) were used to inhibit PKR in HSCs. The HCC cell line (HepG2 cell) was cultured with HSC conditioning medium to assess HCC progression, which was evaluated by proliferation and scratch assays. Expression of PKR was increased and activated in stimulated HSCs, and IL-1β production was also increased molecular. Key molecules of the mitogen-activated protein kinase pathway were also upregulated and activated by LPS. Otherwise, PKR inhibition by C16 and PKR siRNA decreased IL-1β production. HCC progression was promoted by HSC-stimulated conditioning medium although it was reduced by the conditioning medium from PKR-inhibited HSCs. Moreover, palmitic acid also upregulated IL-1β expression in HSCs, and conditioning medium from palmitic acid-stimulated HSCs promoted HCC proliferation. Stimulated HSCs by activators of PKR in NASH could play a role in promoting HCC progression through the production of IL-1β, via a mechanism that seems to be dependent on PKR activation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carcinoma, Hepatocellular / enzymology*
  • Carcinoma, Hepatocellular / pathology
  • Cell Proliferation*
  • Enzyme Activation
  • Hep G2 Cells
  • Hepatic Stellate Cells / enzymology*
  • Hepatic Stellate Cells / pathology
  • Humans
  • Interleukin-1beta / metabolism
  • Liver Neoplasms / enzymology*
  • Liver Neoplasms / pathology
  • Neoplasm Proteins / metabolism*
  • eIF-2 Kinase / metabolism*

Substances

  • IL1B protein, human
  • Interleukin-1beta
  • Neoplasm Proteins
  • EIF2AK2 protein, human
  • eIF-2 Kinase

Grants and funding

This work was supported in part by Grant-in-Aid for Scientific Research (C) (Grant no.18K08007) from the Japan Society for the Promotion of Science (JSPS) (http://www.jsps.go.jp) to YH and Grant-in-Aid for Young Scientists (B) (Grant no. 15K19336, 17K15952) from JSPS to OY. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. There was no additional external funding received for this study.