Translation of the circular RNA circß-catenin promotes liver cancer cell growth through activation of the Wnt pathway.

BACKGROUND: Circular RNAs are a class of regulatory RNA transcripts, which are ubiquitously expressed in eukaryotes. In the current study, we evaluate the function of a novel circRNA derived from the ß-catenin gene locus, circß-catenin. RESULTS: Circß-catenin is predominantly localized in the cytoplasm and displays resistance to RNase-R treatment. We find that circß-catenin is highly expressed in liver cancer tissues when compared to adjacent normal tissues. Silencing of circß-catenin significantly suppresses malignant phenotypes in vitro and in vivo, and knockdown of this circRNA reduces the protein level of ß-catenin without affecting its mRNA level. We show that circß-catenin affects a wide spectrum of Wnt pathway-related genes, and furthermore, circß-catenin produces a novel 370-amino acid ß-catenin isoform that uses the start codon as the linear ß-catenin mRNA transcript and translation is terminated at a new stop codon created by circularization. We find that this novel isoform can stabilize full-length ß-catenin by antagonizing GSK3ß-induced ß-catenin phosphorylation and degradation, leading to activation of the Wnt pathway. CONCLUSIONS: Our findings illustrate a non-canonical function of circRNA in modulating liver cancer cell growth through the Wnt pathway, which can provide novel mechanistic insights into the underlying mechanisms of hepatocellular carcinoma.

LncRNA-NEF antagonized epithelial to mesenchymal transition and cancer metastasis via cis-regulating FOXA2 and inactivating Wnt/ß-catenin signaling.

Emerging evidence indicates that the long noncoding RNAs extensively participate in cancer progression. Nevertheless, the molecular pathogenesis of how these lncRNAs regulate tumorigenesis has not been fully elucidated especially in hepatocellular carcinoma (HCC). Here, we sought to define the role of a novel lncRNA named lncRNA-NEF in modulating epithelial to mesenchymal transition (EMT) in HCC. It was found that the lncRNA-NEF was transcriptionally activated by EMT suppressor FOXA2 and frequently downregulated in HCC cell lines as well as clinical specimens. Although enhanced expression of lncRNA-NEF did not affect tumor cell growth, ectopic expression of lncRNA-NEF significantly suppressed EMT program and cell migration. Animal studies validated that lncRNA-NEF alleviated in vivo tumor metastasis and protected mice from tumor-induced mortality. Interestingly, we verified that lncRNA-NEF acted as a novel activator of its neighbor gene FOXA2, which formed a positive feedback loop. Subsequent studies revealed that lncRNA-NEF physically interacted with ß-catenin to increase the binding of GSK3ß with ß-catenin and therefore promoted the inhibitory phosphorylation of ß-catenin, leading to the suppression on Wnt/ß-catenin signaling and activation of FOXA2 expression. Hence, our findings illustrated a novel feedback loop including FOXA2 and its neighboring gene lncRNA-NEF, which might provide mechanistic insights into the metastatic progress of HCC.

CRISPR/Cas9 Technology Targeting Fas Gene Protects Mice From Concanavalin-A Induced Fulminant Hepatic Failure.

Fulminant hepatic failure is a life-threatening disease which occurs in patients without preexisting liver disease. Nowadays, there is no ideal therapeutic tool in the treatment of fulminant hepatic failure. Recent studies suggested that a novel technology termed CRISPR/Cas9 may be a promising approach for the treatment of fulminant hepatic failure. In this project, we have designed single chimeric guide RNAs specifically targeting the genomic regions of mouse Fas gene. The in vitro and in vivo effects of sgRNAs on the production of Fas protein were examined in cultured mouse cells and in a hydrodynamic injection-based mouse model, respectively. The in vivo delivery of CRISPR/Cas9 could maintain liver homeostasis and protect hepatocytes from Fas-mediated cell apoptosis in the fulminant hepatic failure model. Our study indicates the clinical potential of developing the CRISPR/Cas9 system as a novel therapeutic strategy to rescue Concanavalin-A-induced fulminant hepatic failure in the mouse model. J. Cell. Biochem. 118: 530-536, 2017. © 2016 Wiley Periodicals, Inc.

H19 activates Wnt signaling and promotes osteoblast differentiation by functioning as a competing endogenous RNA.

Bone homeostasis is tightly orchestrated and maintained by the balance between osteoblasts and osteoclasts. Recent studies have greatly expanded our understanding of the molecular mechanisms of cellular differentiation. However, the functional roles of non-coding RNAs particularly lncRNAs in remodeling bone architecture remain elusive. In our study, lncRNA H19 was found to be upregulated during osteogenesis in hMSCs. Stable expression of H19 significantly accelerated in vivo and in vitro osteoblast differentiation. Meanwhile, by using bioinformatic investigations and RIP assays combined with luciferase reporter assays, we demonstrated that H19 functioned as an miRNA sponge for miR-141 and miR-22, both of which were negative regulators of osteogenesis and Wnt/ß-catenin pathway. Further investigations revealed that H19 antagonized the functions of these two miRNAs and led to de-repression of their shared target gene ß-catenin, which eventually activated Wnt/ß-catenin pathway and hence potentiated osteogenesis. In addition, we also identified a novel regulatory feedback loop between H19 and its encoded miR-675-5p. And miR-675-5p was found to directly target H19 and counteracted osteoblast differentiation. To sum up, these observations indicate that the lncRNA H19 modulates Wnt/ß-catenin pathway by acting as a competing endogenous RNA, which may shed light on the functional role of lncRNAs in coordinating osteogenesis.

The lncRNA H19 promotes epithelial to mesenchymal transition by functioning as miRNA sponges in colorectal cancer.

Recently, the long non-coding RNA (lncRNA) H19 has been identified as an oncogenic gene in multiple cancer types and elevated expression of H19 was tightly linked to tumorigenesis and cancer progression. However, the molecular basis for this observation has not been characterized in colorectal cancer (CRC) especially during epithelial to mesenchymal transition (EMT) progression. In our studies, H19 was characterized as a novel regulator of EMT in CRC. We found that H19 was highly expressed in mesenchymal-like cancer cells and primary CRC tissues. Stable expression of H19 significantly promotes EMT progression and accelerates in vivo and in vitro tumor growth. Furthermore, by using bioinformatics study and RNA immunoprecipitation combined with luciferase reporter assays, we demonstrated that H19 functioned as a competing endogenous RNA (ceRNA) for miR-138 and miR-200a, antagonized their functions and led to the de-repression of their endogenous targets Vimentin, ZEB1, and ZEB2, all of which were core marker genes for mesenchymal cells. Taken together, these observations imply that the lncRNA H19 modulated the expression of multiple genes involved in EMT by acting as a competing endogenous RNA, which may build up the missing link between the regulatory miRNA network and EMT progression.