ABSTRACT
BACKGROUND & AIMS: Accumulating data from epidemiological and experimental studies have suggested that retinoids, which are vitamin A derivatives, exert antitumor activity in various organs. We performed a gene screening based on in silico analysis of retinoic acid response elements (RAREs) to identify the genes facilitating the antitumor activity of retinoic acid (RA) and investigated their clinical significance in hepatocellular carcinoma (HCC). METHODS: In silico analysis of RAREs was performed in the 5-kb upstream region of EST clusters. Chromatin immunoprecipitation analysis of the retinoic acid receptors and gene expression analysis were performed in HuH7, HepG2, and MCF7 cells treated with all-trans RA (ATRA). mRNA expression of RA-responsive genes was investigated using tumor and non-tumor tissues of clinical HCC samples from 171 patients. The association between gene expression and survival of patients was examined by Cox regression analysis. RESULTS: We identified 201 candidate genes with promoter regions containing consensus RARE and finally selected 26 RA-responsive genes. Of these, downregulation of OTU domain-containing 7B (OTUD7B) gene, which was upregulated by ATRA, in tumor tissue was associated with a low cancer-specific survival of HCC patients. Functional analyses revealed that OTUD7B negatively regulates nuclear factor κB (NF-κB) signaling and decreases the survival of HCC cells. CONCLUSIONS: We identified RA-responsive genes which are regulated by retinoid signal and found that low-OTUD7B mRNA expression is associated with a poor prognosis for HCC patients. OTUD7B-mediated inhibition of NF-κB signaling may be an effective target for antitumor therapy for HCC.
Subject(s)
Antineoplastic Agents/pharmacology , Carcinoma, Hepatocellular/genetics , Genes, Neoplasm/drug effects , Liver Neoplasms/genetics , Response Elements/drug effects , Tretinoin/pharmacology , Antineoplastic Agents/therapeutic use , Carcinoma, Hepatocellular/drug therapy , Carcinoma, Hepatocellular/pathology , Cell Line, Tumor , Cell Survival/drug effects , Down-Regulation/drug effects , Down-Regulation/genetics , Endopeptidases/drug effects , Endopeptidases/genetics , Genes, Neoplasm/genetics , Humans , Liver Neoplasms/drug therapy , Liver Neoplasms/pathology , NF-kappa B/drug effects , Prognosis , Response Elements/genetics , Signal Transduction/drug effects , Tretinoin/therapeutic useABSTRACT
CD437, a synthetic retinoid, has a potent antitumor activity, in which an RAR-independent mechanism may be involved. Our previous study showed that CD437 transcriptionally upregulates the expression of thioredoxin-binding protein 2 (TBP2), leading to c-Jun N-terminal kinase 1 (JNK1)-mediated apoptosis. In the present study, we addressed the mechanism, by which CD437 induces TBP2 mRNA expression. CD437 efficiently caused the cell death of human osteosarcoma cells via apoptosis. CD437 also induced JNK1 activation through the upregulation of TBP2 mRNA, in consistent with our previous observation. A luciferase reporter assay for TBP2 promoter activation suggested that CD437-regulated TBP2 mRNA transcription requires the region between -400 and -300, which contains multiple possible ETS-binding sites. Finally, we demonstrated CD437-dependent recruitment of ETS1 transcription factor to this region by chromatin immunoprecipitation assay. These data suggest that ETS1 is involved in CD437-induced TBP2 mRNA expression in human osteosarcoma MG-63 cells.
