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Intestine-specific homeobox (ISX) upregulates E2F1 expression and related oncogenic activities in HCC.

ABSTRACT: Intestine-specific homeobox (ISX), a newly identified proto-oncogene, is involved in cell proliferation and progression of hepatocellular carcinoma (HCC). However, the underlying mechanisms linking gene expression and tumor formation remain unclear. In this study, we found that ISX transcriptionally activated E2F transcription factor 1 (E2F1) and associated oncogenic activity by directly binding to the E2 site of its promoter. Forced expression of ISX increased the expression of and phosphorylated the serine residue at position 332 of E2F1, which may be translocated into the nucleus to form the E2F1-DP-1 complex, suggesting that the promotion of oncogenic activities of the ISX-E2F1 axis plays a critical role in hepatoma cells. Coexpression of ISX and E2F1 significantly promoted p53 and RB-mediated cell proliferation and anti-apoptosis, and repressed apoptosis and autophagy. In contrast, short hairpin RNAi-mediated attenuation of ISX and E2F1 decreased cell proliferation and malignant transformation, respectively, in hepatoma cells in vitro and in vivo. The mRNA expression of E2F1 and ISX in 238 paired specimens from human HCC patients, and the adjacent, normal tissues exhibited a tumor-specific expression pattern which was highly correlated with disease pathogenesis, patient survival time, progression stage, and poor prognosis. Therefore, our results indicate that E2F1 is an important downstream gene of ISX in hepatoma progression.

SUBMITTER: Wang SN

PROVIDER: S-EPMC5095049 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature

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Intestine-specific homeobox (ISX) upregulates E2F1 expression and related oncogenic activities in HCC.

Wang Shen-Nien SN Wang Li-Ting LT Sun Ding-Ping DP Chai Chee-Yin CY Hsi Edward E Kuo Hsing-Tao HT Yokoyama Kazunari K KK Hsu Shih-Hsien SH

Oncotarget 20160601 24

Intestine-specific homeobox (ISX), a newly identified proto-oncogene, is involved in cell proliferation and progression of hepatocellular carcinoma (HCC). However, the underlying mechanisms linking gene expression and tumor formation remain unclear. In this study, we found that ISX transcriptionally activated E2F transcription factor 1 (E2F1) and associated oncogenic activity by directly binding to the E2 site of its promoter. Forced expression of ISX increased the expression of and phosphorylat ...[more]

PMID: 27175585

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Project description:BackgroundGrowing evidences have been revealing that long noncoding RNAs are vital factors in oncogenesis and tumor development. Among them, cancer susceptibility candidate 11 (CASC11) has displayed an impressively essential role in various kinds of cancers including hepatocellular carcinoma (HCC). Nevertheless, its role and potential mechanism in HCC still remain to be fully investigated.MethodsCASC11 expression level was evaluated by real-time polymerase chain reaction, western blotting, and in situ hybridization staining in HCC patients, and its prognostic effect was analyzed. The role of CASC11 in HCC tumorigenesis and progression was investigated by cell proliferation assay, transwell assay, extracellular acidification rate, western blotting, flow cytometry, and an in vivo xenograft model. The interactions among CASC11, E2F transcription factor 1 (E2F1), and eukaryotic translation initiation factor 4A3 (EIF4A3) were explored by using quantitative reverse transcriptase polymerase chain reaction, western blotting, RNA-binding protein immunoprecipitation assay, and chromatin immunoprecipitation assays.ResultsUpregulation of CASC11 was confirmed in HCC tissues and associated with poor prognosis. Loss of function assays showed inhibition of CASC11 expression suppressed HCC cells proliferation, mobility, and glucose metabolism and promoted apoptosis. E2F1 expression significantly decreased after inhibition of CASC11. Rescue experiments illustrated that E2F1 overexpression alleviated the suppression of CASC11 inhibition on HCC progression in vitro and in vivo. Mechanistically, CASC11 recruited EIF4A3 to enhance the stability of E2F1 mRNA. CASC11 and E2F1 impacted the activation of the NF-κB signaling and PI3K/AKT/mTOR pathway and further regulated the expression PD-L1 that is an important target of immunotherapy. In addition, we identified YY1 could modulate CASC11 expression by binding to its promoter.ConclusionsOur data revealed that CASC11 promoted the progression of HCC by means of EIF4A3-mediated E2F1 upregulation, indicating CASC11 is a promising diagnostic biomarker and therapeutic target for HCC.

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Dataset Information

Intestine-specific homeobox (ISX) upregulates E2F1 expression and related oncogenic activities in HCC.

Publications

Intestine-specific homeobox (ISX) upregulates E2F1 expression and related oncogenic activities in HCC.

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