Peretinoin, an acyclic retinoid, inhibits hepatocarcinogenesis by suppressing sphingosine kinase 1 expression in vitro and in vivo

Masaya Funaki,Taro Yamashita,Yuriko Sakai,Kazuhisa Murai,Hikari Okada,Tetsuro Shimakami,Masao Honda,Takeru Oyama,Yoh Takuwa,Kai Takegoshi,Juria Kitabayashi,Shuichi Kaneko,Tsuguhito Ota,Takayoshi Shirasaki,Naoto Nagata

doi:10.1038/s41598-017-17285-2

Abstract

Sphingosine-1-phospate is a potent bioactive lipid metabolite that regulates cancer progression. Because sphingosine kinase 1 and sphingosine kinase 2 (SPHK 1/2) are both essential for sphingosine-1-phospate production, they could be a therapeutic target in various cancers. Peretinoin, an acyclic retinoid, inhibits post-therapeutic recurrence of hepatocellular carcinoma via unclear mechanisms. In this study, we assessed effects of peretinoin on SPHK expression and liver cancer development in vitro and in vivo. We examined effects of peretinoin on expression, enzymatic and promoter activity of SPHK1 in a human hepatoma cell line, Huh-7. We also investigated effects of SPHK1 on hepatocarcinogenesis induced by diethylnitrosamine using SPHK1 knockout mice. Peretinoin treatment of Huh-7 cells reduced mRNA levels, protein expression and enzymatic activity of SPHK1. Peretinoin reduced SPHK1 promoter activity; this effect of peretinoin was blocked by overexpression of Sp1, a transcription factor. Deletion of all Sp1 binding sites within the SPHK1 promoter region abolished SPHK1 promoter activity, suggesting that peretinoin reduced mRNA levels of SPHK1 via Sp1. Additionally, diethylnitrosamine-induced hepatoma was fewer and less frequent in SPHK1 knockout compared to wild-type mice. Our data showed crucial roles of SPHK1 in hepatocarcinogenesis and suggests that peretinoin prevents hepatocarcinogenesis by suppressing mRNA levels of SPHK1.

Highlights

Sphingosine-1-phospate is a potent bioactive lipid metabolite that regulates cancer progression
Diethylnitrosamine (DEN)-induced hepatoma was significantly fewer and less frequent in sphingosine kinase 1 (SPHK1) knockout mice compared to wild-type mice Collectively, our results suggest that one of the mechanisms by which peretinoin prevents hepatocarcinogenesis would be suppression of SPHK1 expression and that the SPHK–S1P axis could be a promising target for hepatocellular carcinoma (HCC) therapy
In the PDGF-C Tg model mouse, overexpression of PDGF-C in mouse liver results in hepatic fibrosis, steatosis, and HCC; this model is quite similar to human HCC, in that HCC usually develops from fibrotic liver

Summary

Introduction

Sphingosine-1-phospate is a potent bioactive lipid metabolite that regulates cancer progression. Peretinoin, an acyclic retinoid, inhibits post-therapeutic recurrence of hepatocellular carcinoma via unclear mechanisms. We assessed effects of peretinoin on SPHK expression and liver cancer development in vitro and in vivo. We examined effects of peretinoin on expression, enzymatic and promoter activity of SPHK1 in a human hepatoma cell line, Huh-7. Peretinoin treatment of Huh-7 cells reduced mRNA levels, protein expression and enzymatic activity of SPHK1. Curative resection or ablation is applied to early-stage HCC but the 3-year recurrence rate after curative treatment in the general population is 50%9,10. New therapeutic strategies to prevent HCC recurrence or hepatocarcinogenesis are urgently needed. Administration of peretinoin significantly reduces the incidence of post-therapeutic HCC recurrence and improves patient survival[13,14,15]. Larger-scale clinical studies are ongoing in various countries to confirm its clinical efficacy in preventing HCC after curative treatment

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Conclusion