Long noncoding RNAs (lncRNAs) have been reported to play pivotal roles in a variety of cancers. However, lncRNAs involved in hepatocellular carcinoma (HCC) initiation and progression remain largely unclear. In this study, we identified an lncRNA gradually increased during hepatocarcinogenesis (lncRNA-GIHCG) using publicly available microarray data. Our results further revealed that GIHCG is upregulated in HCC tissues in comparison with adjacent non-tumor tissues. High GIHCG expression is correlated with large tumor size, microvascular invasion, advanced BCLC stage, and poor survival of HCC patients. Functional experiments showed that GIHCG promotes HCC cells proliferation, migration, and invasion in vitro, and promotes xenografts growth and metastasis in vivo. Mechanistically, we demonstrated that GIHCG physically associates with EZH2 and the promoter of miR-200b/a/429, recruits EZH2 and DNMT1 to the miR-200b/a/429 promoter regions, upregulates histone H3K27 trimethylation and DNA methylation levels on the miR-200b/a/429 promoter, and dramatically silences miR-200b/a/429 expression. Furthermore, the biological functions of GIHCG on HCC are dependent on the silencing of miR-200b/a/429. Collectively, our results demonstrated the roles and functional mechanisms of GIHCG in HCC, and indicated GIHCG may act as a prognostic biomarker and potential therapeutic target for HCC. KEY MESSAGE: lncRNA-GIHCG is upregulated in HCC and associated with poor survival of patients. GIHCG significantly promotes tumor growth and metastasis of HCC. GIHCG physically associates with EZH2. GIHCG upregulates H3K27me3 and DNA methylation levels on the miR-200b/a/429 promoter. GIHCG epigenetically silences miR-200b/a/429 expression.

Sustained endoplasmic reticulum (ER) stress has been linked to cell death and the pathogenesis of many liver diseases, including toxic liver, cholestasis, and infectious liver disease. The cellular pathways that attenuate hepatic ER stress have been the focus of many recent studies, but the role of microRNAs (miRNA) in this process remains unknown. Here, we report that one of the most abundant miRNAs in hepatocytes, miR-199a-5p, was elevated in both bile acid- and thapsigargin (TG)-stimulated cultured hepatocytes, as well as in the liver of bile duct-ligated mice. We identify the misfolded protein chaperone GRP78, as well as the unfolded protein response transducers endoplasmic reticulum to nucleus signaling 1 and activating transcription factor 6 as direct targets of miR-199a-5p, and show that endogenous miR-199a-5p represses the 3′ untranslated regions (UTRs) of their mRNAs. Through gain-of-function and loss of function approaches, we demonstrate that the elevated miR-199-5p disrupts sustained ER stress and prevents hepatocytes from undergoing bile acid- or TG-induced cell death. Furthermore, we reveal that the transcription factor AP-1 is a strong positive regulator of miR-199a-5p. In brief, our study demonstrates that AP-1/miR-199a-5p and ER stress mediators form a feedback loop, which shields hepatocytes from sustained ER stress and protects the liver from injury. On the basis of these findings, we also suggest that the miRNA miR-199a-5p is a potential target for clinical approaches aiming to protect hepatocytes in liver disease.

BACKGROUND Genomic alterations of small bowel cancers remain poorly understood due to the rarity of these diseases. In the current study, the authors report the identification of somatic mutations from patients with duodenal adenocarcinoma by whole‐exome sequencing. METHODS Whole‐exome sequencing and follow‐up analysis were conducted in 12 matched tumor‐normal tissue duodenal adenocarcinoma tissue pairs to examine the genetic characteristics of this disease. Somatic mutations (single‐nucleotide variants and short insertion/deletions) were obtained and filtered and then searched for recurrently mutated genes and pathways. RESULTS An excess of C‐to‐T transitions at the CpG dinucleotide was observed in the substitution of bases. The authors identified recurrent mutations in tumor protein p53 (TP53), KRAS, catenin (cadherin‐associated protein) β‐1 (CTNNB1), AT‐rich interactive domain 2 (ARID2), adenomatous polyposis coli (APC), erb‐b2 receptor tyrosine kinase 2 (ERBB2), ARID1A, cadherin‐related family member 1 (CDHR1), NRAS, Bcl‐2‐related ovarian killer (BOK), radial spoke head 14 homolog (chlamydomonas) (RTDR1), cell division cycle 27 (CDC27), catalytic subunit of phosphoinositide‐3‐kinase (PIK3CA), and SMAD family member 4 (SMAD4). Pathway scan indicated that the Wnt signaling pathway, regulation of the actin cytoskeleton pathway, ErbB signaling pathway, and the pathway of focal adhesion were the most extensively affected pathways. CONCLUSIONS This genomic characterization of duodenal adenocarcinoma provides researchers with insight into its somatic landscape and highlights the vital role of the Wnt/β‐catenin signaling pathway. The study data also indicate that duodenal adenocarcinomas have a genetic resemblance to gastric and colorectal cancers. These discoveries may benefit the future development of molecular diagnosis and personalized therapies. Cancer 2016;122:1689‐96. © 2016 American Cancer Society.

Understanding differences in DNA double-strand break (DSB) repair between tumor and normal tissues would provide a rationale for developing DNA repair-targeted cancer therapy. Here, using knock-in mouse models for measuring the efficiency of two DSB repair pathways, homologous recombination (HR) and nonhomologous end-joining (NHEJ), we demonstrated that both pathways are up-regulated in hepatocellular carcinoma (HCC) compared with adjacent normal tissues due to altered expression of DNA repair factors, including PARP1 and DNA-PKcs. Surprisingly, inhibiting PARP1 with olaparib abrogated HR repair in HCC. Mechanistically, inhibiting PARP1 suppressed the clearance of nucleosomes at DNA damage sites by blocking the recruitment of ALC1 to DSB sites, thereby inhibiting RPA2 and RAD51 recruitment. Importantly, combining olaparib with NU7441, a DNA-PKcs inhibitor that blocks NHEJ in HCC, synergistically suppressed HCC growth in both mice and HCC patient-derived-xenograft models. Our results suggest the combined inhibition of both HR and NHEJ as a potential therapy for HCC.

In recent years, circular RNAs (circRNAs) have been shown to have critical regulatory roles in the resistance to anti-cancer drugs. However, the contributions of circRNAs to sorafenib resistance in hepatocellular carcinoma (HCC) remain largely unknown. The present study aims to explore the involvement of circFN1 in sorafenib resistance and how circFN1 is associated with the miR-1205/E2F1 pathway, which have been demonstrated to mediate this resistance in HCC cells. We investigated the expression of circRNAs in five paired sorafenib-sensitive HepG2 cells and sorafenib-resistant (SR)-HepG2 cells by microarray analysis. The quantitative real-time PCR analysis was used to investigate the expression pattern of circFN1 in HCC patient tissues and cell lines. Then, the effects of circFN1 on sorafenib resistance, cell proliferation, and apoptosis were assessed in HCC in vitro and in vivo . In this study, circFN1 was observed to be upregulated in HCC patient tissues and cell lines. Overexpression of circFN1 in HCC was significantly correlated with aggressive characteristics and served as an independent risk factor for overall survival in patients with HCC. Our in vivo and in vitro data indicated that inhibition of circFN1 enhances the sorafenib sensitivity of HCC cells. Mechanistically, we found that circFN1 could promote the expression of E2F1 by sponging miR-1205. In summary, our study demonstrated that circFN1 contributes to sorafenib resistance by regulating the miR-1205/E2F1 signaling pathway. These results indicate that circFN1 may represent a potentially valuable target for overcoming sorafenib resistance for HCC.