Gastroenterology

Gastroenterology

Volume 128, Issue 1, January 2005, Pages 86-95
Gastroenterology

Basic-liver, pancreas, and biliary tract
Acyclic retinoid inhibits human hepatoma cell growth by suppressing fibroblast growth factor-mediated signaling pathways

https://doi.org/10.1053/j.gastro.2004.09.077Get rights and content

Background & Aims: Hepatocellular carcinoma (HCC) is one of the most common human malignancies. Its high mortality rate is mainly a result of high intrahepatic recurrence. The novel synthetic retinoid acyclic retinoid (ACR) has been reported to prevent the recurrence of human HCC after surgical resection of primary tumors, but the molecular mechanisms underlying its effects remain to be elucidated. In this study, we clarified the molecular targets of ACR. Methods: The inhibitory effects by ACR on growth were examined. Intracellular signaling induced by ACR was comprehensively studied by a reporter assay. Gene expression changes by ACR were examined using a microarray. From these results, a candidate signaling pathway modulated by ACR was determined and whether antagonizing this pathway reverses the effect was examined. Results: We show that ACR inhibits the growth of HCC cells through the down-regulation of fibroblast growth factor (FGF) receptor 3 expression and FGF-mediated signaling, which in turn suppresses the activity of Rho and serum response factor-mediated transcription. Conversely, overexpression of the active form of FGF receptor 3 or the addition of FGF reverses the ACR-mediated inhibition of growth. In addition, silencing the FGF receptor 3 gene by RNA interference inhibits cell growth. Conclusions: These studies show that ACR is a potent inhibitor of FGF signaling and that selective blocking of the FGFmediated pathway could be a promising therapeutic approach for the management of patients with HCC.

Section snippets

Cell lines

Human liver tumor cell lines (HepG2, HLF, and HuH7) were obtained from the Riken cell bank (Tsukuba Science City, Japan). These cell lines were maintained in Dulbecco’s modified Eagle medium (GIBCO BRL, Gaithersburg, MD) supplemented with 10% heat-inactivated fetal bovine serum in an atmosphere containing 5% CO2.

Cell growth assays

To examine the effect of ACR on cell growth, 5 × 104 cells/well were seeded onto 6-well plates. The medium was changed the next day, and 0, 15, 30, 45, 60, or 90 μmol/L ACR (NIK-333;

ACR reduces the growth of human hepatoma cells

Because Muto et al had reported that an ACR prevented the occurrence of second primary tumors in patients with HCC,9 we evaluated the function of ACR on liver tumor cell growth in vitro. ACR exerted a dose-dependent inhibition of the growth of HLF, HuH7, and HepG2 human hepatoma cell lines, with median inhibitory concentrations of 10 μmol/L, 45 μmol/L, and 45 μmol/L, respectively (Figure 1 and data not shown), which were consistent with a previous report.10 The growth inhibitory effect was not

Discussion

ACR is the object of increasing interest because it has been shown to prevent the recurrence of human HCC after treatment of primary tumors.35 However, the underlying mechanisms of the clinical effects have not been fully elucidated. In this study, we found that ACR inhibits FGF receptor 3 expression, Rho activity, and SRF-mediated transcription, resulting in the inhibition of tumor cell growth. Conversely, these effects were completely neutralized by the overexpression of activated FGF

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    Supported in part by grants-in-aid for scientific research from the Japanese Ministry of Education, Culture, Sports, Science, and Technology and by Health and Labor Sciences Research Grants for Research on Hepatitis from the Ministry of Health, Labor, and Welfare of Japan.

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