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

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.

Pancreatic acinar cell carcinoma with extensive tumor embolism at the trunk of portal vein and pancreatic intraductal infiltration.

A 59-year-old man was admitted to the hospital with acute pancreatitis. The cause was suggested to be a pancreatic tumor based on computed tomography (CT). The pancreatic tumor was 45 mm with an extensive tumor embolism at the trunk of the portal vein and intraductal infiltration of the main pancreatic duct (MPD). The pancreatic tumor was diagnosed as acinar cell carcinoma (ACC) by endoscopic ultrasound guided fine needle aspiration. Therefore, the cause of acute pancreatitis was diagnosed to be intraductal infiltration of ACC in the MPD. Chemotherapy was initially performed because it was difficult to perform surgery due to extensive tumor embolism at the trunk of the portal vein. Degeneration and reduction of ACC and tumor embolism of the portal vein was noted on CT after chemotherapy, and extended distal pancreatectomy with portal vein reconstruction was performed. There has been no relapse for 5 years postoperative follow-up. This is an interesting and rare case because ACC with intraductal infiltration of MPD is low in frequency; most ACCs are asymptomatic when they are found, and many cases tend to have poor prognosis in spite of surgical cases.

Peretinoin, an acyclic retinoid, suppresses steatohepatitis and tumorigenesis by activating autophagy in mice fed an atherogenic high-fat diet.

The pathogenesis of non-alcoholic steatohepatitis (NASH) is still unclear and the prevention of the development of hepatocellular carcinoma (HCC) has not been established. We established an atherogenic and high-fat diet mouse model that develops hepatic steatosis, inflammation, fibrosis, and liver tumors at a high frequency. Using two NASH-HCC mouse models, we showed that peretinoin, an acyclic retinoid, significantly improved liver histology and reduced the incidence of liver tumors. Interestingly, we found that peretinoin induced autophagy in the liver of mice, which was characterized by the increased co-localized expression of microtubule-associated protein light chain 3B-II and lysosome-associated membrane protein 2, and increased autophagosome formation and autophagy flux in the liver. These findings were confirmed using primary mouse hepatocytes. Among representative autophagy pathways, the autophagy related (Atg) 5-Atg12-Atg16L1 pathway was impaired; especially, Atg16L1 was repressed at both the mRNA and protein level. Decreased Atg16L1 mRNA expression was also found in the liver of patients with NASH according to disease progression. Promoter analysis revealed that peretinoin activated the promoter of Atg16L1 by increasing the expression of CCAAT/enhancer-binding-protein-alpha. Interestingly, Atg16L1 overexpression in HepG2 cells inhibited palmitate-induced NF-kB activation and interleukin-6-induced STAT3 activation. We showed that Atg16L1 induced the de-phosphorylation of Gp130, a receptor subunit of interleukin-6 family cytokines, which subsequently repressed phosphorylated-STAT3 (Tyr705) levels, and this process might be independent of autophagy function. Thus, peretinoin prevents the progression of NASH and the development of HCC through activating the autophagy pathway by increased Atg16L1 expression, which is an essential regulator of autophagy and anti-inflammatory proteins.

Branched-chain amino acids prevent hepatic fibrosis and development of hepatocellular carcinoma in a non-alcoholic steatohepatitis mouse model.

Oral supplementation with branched-chain amino acids (BCAA; leucine, isoleucine, and valine) in patients with liver cirrhosis potentially suppresses the incidence of hepatocellular carcinoma (HCC) and improves event-free survival. However, the detailed mechanisms of BCAA action have not been fully elucidated. BCAA were administered to atherogenic and high-fat (Ath+HF) diet-induced nonalcoholic steatohepatitis (NASH) model mice. Liver histology, tumor incidence, and gene expression profiles were evaluated. Ath+HF diet mice developed hepatic tumors at a high frequency at 68 weeks. BCAA supplementation significantly improved hepatic steatosis, inflammation, fibrosis, and tumors in Ath+HF mice at 68 weeks. GeneChip analysis demonstrated the significant resolution of pro-fibrotic gene expression by BCAA supplementation. The anti-fibrotic effect of BCAA was confirmed further using platelet-derived growth factor C transgenic mice, which develop hepatic fibrosis and tumors. In vitro, BCAA restored the transforming growth factor (TGF)-ß1-stimulated expression of pro-fibrotic genes in hepatic stellate cells (HSC). In hepatocytes, BCAA restored TGF-ß1-induced apoptosis, lipogenesis, and Wnt/ß-Catenin signaling, and inhibited the transformation of WB-F344 rat liver epithelial stem-like cells. BCAA repressed the promoter activity of TGFß1R1 by inhibiting the expression of the transcription factor NFY and histone acetyltransferase p300. Interestingly, the inhibitory effect of BCAA on TGF-ß1 signaling was mTORC1 activity-dependent, suggesting the presence of negative feedback regulation from mTORC1 to TGF-ß1 signaling. Thus, BCAA induce an anti-fibrotic effect in HSC, prevent apoptosis in hepatocytes, and decrease the incidence of HCC; therefore, BCAA supplementation would be beneficial for patients with advanced liver fibrosis with a high risk of HCC.

Inhibition of microRNA-214 ameliorates hepatic fibrosis and tumor incidence in platelet-derived growth factor C transgenic mice.

Differentially regulated microRNA (miRNA) are associated with hepatic fibrosis; however, their potential usefulness for blocking hepatic fibrosis has not been exploited fully. We examined the expression of miRNA in the liver of a transgenic mouse model in which platelet-derived growth factor C (PDGF-C) is overexpressed (Pdgf-c Tg), resulting in hepatic fibrosis and steatosis and the eventual development of hepatocellular carcinoma (HCC). Robust induction of miR-214 correlated with fibrogenesis in the liver of Pdgf-c Tg mice, atherogenic high-fat diet-induced NASH mice, and patients with chronic hepatitis B or C. Pdgf-c Tg mice were injected with locked nucleic acid (LNA)-antimiR-214 via the tail vein using Invivofectamine 2.0 and the degree of hepatic fibrosis and tumor incidence were evaluated. Pdgf-c Tg mice treated with LNA-antimiR-214 showed a marked reduction in fibrosis and tumor incidence compared with saline or LNA-miR-control-injected control mice. In vitro, LNA-antimiR-214 significantly ameliorated TGF-ß1-induced pro-fibrotic gene expression in Lx-2 cells. MiR-214 targets a negative regulator of EGFR signaling, Mig-6. Mimic-miR-214 decreased the expression of Mig-6 and increased the levels of EGF-mediated p-EGFR (Y1173 and Y845) and p-Met (Tyr1234/1235) in Huh-7 cells. Conversely, LNA-antimiR-214 repressed the expression of these genes. In conclusion, miR-214 appears to participate in the development of hepatic fibrosis by modulating the EGFR and TGF-ß signaling pathways. LNA-antimiR-214 is a potential therapy for the prevention of hepatic fibrosis.