Nuclear localization of BRCA1-associated protein 1 is important in suppressing hepatocellular carcinoma metastasis via CTCF and NRF1/OGT axis.

Germline mutations of the deubiquitinase BRCA1-associated protein 1 (BAP1) lead to the "BAP1 cancer syndrome" characterized by development of cancers. However, the role of BAP1 in hepatocellular carcinoma (HCC) is unclear. We found that BAP1 was upregulated at mRNA level in human HCCs and significantly correlated with a more aggressive tumour behaviour. Intriguingly, we observed cytoplasmic but no or minimal nuclear BAP1 in human HCC samples by immunohistochemistry. We observed that, while BAP1 protein was found mainly in the cytoplasm and less in the nuclei of HCC cell lines, BAP1 expression was predominantly nuclear in HepG2 cells, by cell fractionation and immunofluorescence analyses. Functionally, in the orthotopic liver injection mouse model, silencing the BAP1 predominant nuclear expression of HepG2 cells promoted intrahepatic tumor metastasis, with more frequent tumor microsatellite formation and venous invasion. With transcriptomic profiling, we identified RHOJ amongst the downregulated targets in HepG2 cells upon BAP1 knockdown. Subsequent overexpression of RHOJ suppressed cell migration in HCC cells, suggesting that BAP1 might upregulate RHOJ resulting in reduced cell migratory ability of HCC cells. Furthermore, we identified two transcription factors, CTCF and NRF1, which activated BAP1 transcription by binding to BAP1 promoter region. On the other hand, we uncovered that O-linked N-acetylglucosamine (GlcNAc) transferase (OGT) physically bound to BAP1 in the nucleus, resulting in diminished stability of the nuclear BAP1. Intriguingly, OGT transcription was upregulated and was also under the control of CTCF and NRF1 in human HCC, acting as a negative regulator of BAP1. To summarize, this study uncovered the underlying mechanisms of the regulation of BAP1 and that loss of the nuclear localization of BAP1 protein contributed to enhanced cell migration in vitro and more aggressive tumor behavior in human HCCs.

Xie X ，Tsui YM ，Zhang VX ，Yu TC ，Husain A ，Chiu YT ，Tian L ，Lee E ，Lee JM ，Ma HT ，Ho DW ，Sze KM ，Ng IO ... -  《Cell Death & Disease》

Neuroglobin, a novel intracellular hexa-coordinated globin, functions as a tumor suppressor in hepatocellular carcinoma via Raf/MAPK/Erk.

Zhang J ，Lan SJ ，Liu QR ，Liu JM ，Chen XQ ... -  《-》

LncRNA SNHG7 accelerates the proliferation, migration and invasion of hepatocellular carcinoma cells via regulating miR-122-5p and RPL4.

Long noncoding RNAs (lncRNAs) play vital roles in the development and progression of hepatocellular carcinoma (HCC). The recent study finds a strong correlation between lncRNA small nucleolar RNA host gene 7 (SNHG7) and HCC metastasis. However, the molecular mechanism by which SNHG7 regulates HCC progression has not been investigated. In this study, we found that SNHG7 was highly expressed in HCC tissues compared to non-tumor tissues. Data from public databases consistently indicated the up-regulated expression of SNHG7 in HCC. Furthermore, the levels of SNHG7 were up-regulated in four HCC cell lines (Huh7, Hep3B, HCCLM3, MHCC97 H) compared with LO2 cells. Interestingly, the elevated expression of SNHG7 was closely correlated with advanced tumor stages, high tumor grades, vascular invasion and poor prognosis of HCC. Knockdown of SNHG7 markedly inhibited cell proliferation, migration and invasion in HCCLM3 and MHCC97H cells, and prominently suppressed the growth and metastasis of HCCLM3 cells in vivo. Mechanistically, SNHG7 silencing increased the level of miR-122-5p in HCC cells. Luciferase reporter assay revealed the direct interaction between SNHG7 and miR-122-5p. Moreover, SNHG7 knockdown decreased the levels of ribosomal protein L4 (RPL4) mRNA and protein in HCC cells. Accordingly, the stability of RPL4 mRNA was reduced by SNHG7 silencing. More importantly, either miR-122-5p knockdown or RPL4 restoration partially reversed SNHG7 silencing-induced tumor suppressive effects on HCC cells. In conclusion, we demonstrated that SNHG7 expression was up-regulated in HCC. SNHG7 contributed to HCC progression by regulating miR-122-5p and RPL4. Therefore, SNHG7 might be a potential biomarker and therapeutic target for HCC.

Yang X ，Sun L ，Wang L ，Yao B ，Mo H ，Yang W ... -  《-》

RNA-binding protein Trx regulates alternative splicing and promotes metastasis of HCC via interacting with LINC00152.

Epithelial-mesenchymal transition (EMT) is central to HCC metastasis, in which RNA-binding proteins (RBPs) play a key role. To explore the role of RBPs in metastasis of hepatocellular carcinoma (HCC), whole transcriptome sequencing was conducted to identify differential RBPs between HCC with metastasis and HCC without metastasis. The influence of RBPs on metastasis of HCC was verified by in vitro and in vivo experiments. The interaction of RBPs with non-coding RNAs was evaluated by RNA immunoprecipitation and pull-down assays. RNA sequencing, whole-genome sequencing, and alternative splicing analysis were further performed to clarify post-transcriptional regulation mechanisms. Whole transcriptome sequencing results showed that expression of thioredoxin (Trx) was significantly upregulated in HCC patients with metastasis. Trx was also found to be associated with poor prognosis in HCC patients. Overexpression of Trx could promote migration and invasion of HCC cells in vitro and increase the rate of lung metastasis of HCC cells in vivo. Moreover, binding assays showed that Trx could bind to LINC00152. As a result, LINC00152 was verified to determine the pro-metastasis function of Trx by knockdown assay. Furthermore, we revealed that Trx could regulate metastasis-associated alternative splicing program. Specifically, angiopoietin 1 (ANGPT1) was the splicing target; the splicing isoform switching of ANGPT1 could activate the PI3K-Akt pathway, upregulate EMT-associated proteins, and promote migration and invasion of HCC cells. We found that Trx could interact with LINC00152 and promote HCC metastasis via regulating alternative splicing, indicating that Trx may serve as a novel therapeutic target for HCC treatment.

Teng X ，Shang J ，Du L ，Huang W ，Wang Y ，Liu M ，Ma Y ，Wang M ，Tang H ，Bai L ... -  《-》

The survival prediction analysis and preliminary study of the biological function of YEATS2 in hepatocellular carcinoma.

Our study aims to develop and validate a novel molecular marker for the prognosis and diagnosis of hepatocellular carcinoma (HCC) MATERIALS & METHODS: We retrospectively analyzed mRNA expression profile and clinicopathological data of HCC patients fetched from The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO) and The International Cancer Genome Consortium (ICGC) datasets. Univariate Cox regression analysis was performed to collect differentially expressed mRNA (DEmRNAs) from HCC and non-tumor tissues, and YEATS2, a prognostic marker, was identified by further analysis. ROC curve, survival analysis and multivariate Cox regression analysis as well as nomograms were used to evaluate the prognosis of this gene. Finally, the biological function of this gene was preliminarily discussed by using single gene Gene Set Enrichment Analysis (GSEA), and the YEATS2 overexpression and knockdown hepatoma cell line was used to verify the results in vitro and in vivo. Based on the clinical information of HCC in TCGA, GEO and ICGC databases, the gene YEATS2 with significant differences from HCC was identified. There was a statistical difference in the survival prognosis between the two databases and the ROC curve showed that the survival of HCC in both TCGA, GSE14520 and ICGC groups had a satisfactory predictive effect. Univariate and multivariate Cox regression analysis showed that YEATS2 was an independent prognostic factor for HCC, and Nomograms, which combined this prognostic feature with significant clinical features, provided an important reference for the clinical prognostic diagnosis of HCC. Next, we constructed overexpression and knockdown YEATS2 cell line in Hep3B and LM3 cells, and further proved that overexpression YEATS2 promote the proliferation and migration of HCC cells by CCK8, colony formation experiment, and transwell assays, and knockdown YEATS2 inhibited the proliferation and migration of HCC cells by CCK8, colony formation experiment, and transwell assays. Finally, the biological function of YEATS2 was preliminarily explored through GSEA analysis of a single gene, and it was found that it was significantly correlated with cell cycle and DNA repair, which provided us with ideas for further analysis. Furthermore, the knockdown of YEATS2 promoted radiation-induced DNA damage, enhanced radiosensitivity, and ultimately inhibited the proliferation of hepatocellular carcinoma cells in vitro and in vivo. Our study identified a promising prognostic marker for hepatocellular carcinoma that is useful for clinical decision-making and individualized treatment.

Long Y ，Wang W ，Liu S ，Wang X ，Tao Y ... -  《-》