CircGFRA1 facilitates the malignant progression of HER-2-positive breast cancer via acting as a sponge of miR-1228 and enhancing AIFM2 expression

CircRNAs (circular RNA) are reported to regulate onset and progress multiple cancers. Nonetheless, the function along with the underlying mechanisms of circRNAs in HER-2-positive breast cancer (BC) remains unclear. CircRNA microarrays were performed to elucidate expression profiles of HER-2-positive BC cells. circRNA levels were quantified using qRT-PCR assay. Various in vitro along with in vivo assays were employed to further explore the effects of circGFRA1 in the progress of HER-2-positive BC and interactions of circGFRA1, miR-1228 and AIFM2 in Her-2-positive BC. CircGFRA1 was remarkably upregulated in HER-2-positive BC. Knockdown of circGFRA1 could attenuate HER-2-positive BC progression by inhibiting the proliferation, infiltration and migratory ability of HER-2-positive BC cells. Through ceRNA mechanism, circGFRA1 could bind to miR-1228 and alleviate inhibitory activity of miR-1228 on targeted gene AIFM2. In summary, circGFRA1-miR-1228-AIFM2 axis regulates HER-2-positive BC. CircGFRA1 is a novel promising treatment option for HER-2-positive BC.     

miR-34a is essential for p19Arf-driven cell cycle arrest

The Arf tumor suppressor gene product, p19^Arf, regulates cell proliferation in incipient cancer cells and during embryo development. Beyond its commonly accepted p53-dependent actions, p19^Arf also acts independently of p53 in both contexts. One such p53-independent effect with in vivo relevance includes its repression of Pdgfrβ, a process that is essential for vision in the mouse. We have utilized cell culture-based and mouse models to define a new role for miR-34a in this process. Ectopic expression of Arf in cultured cells enhanced the expression of several microRNAs predicted to target Pdgfrß synthesis, including the miR-34 family. Because miR-34a has been implicated as a p53-dependent effector, we investigated whether it also contributed to p53-independent effects of p19^Arf. Indeed, in mouse embryo fibroblasts (MEFs) lacking p53, Arf-driven repression of Pdgfrβ and its blockade of Pdgf-B stimulated DNA synthesis were both completely interrupted by anti-microRNA against miR-34a. Ectopic miR-34a directly targeted Pdgfrβ and a plasmid reporter containing wild-type Pdgfrβ 3′UTR sequence, but not one in which the miR-34a target sequence was mutated. Although miR-34a expression has been linked to p53—a well-known effector of p19^Arf—Arf expression and its knockdown correlated with miR-34a level in MEFs lacking p53. Finally, analysis of the mouse embryonic eye demonstrated that Arf controlled expression of miR-34a, and the related miR-34b and c, in vivo during normal mouse development. Our findings indicate that miR-34a provides an essential link between p19^Arf and its p53-independent capacity to block cell proliferation driven by Pdgfrβ. This has ramifications for developmental and tumor suppressor roles of Arf.     

miR-21 coordinates tumor growth and modulates KRIT1 levels

miR-21 is overexpressed in tumors and it displays oncogenic activity. Here, we show that expression of miR-21 in primary tumors anticorrelates with KRIT1/CCM1, an interacting partner of the Ras-like GTPase Rap1, involved in Cerebral Cavernous Malformations (CCM). We present evidences that miR-21 silences KRIT1 by targeting its mRNA 3′UTR and that this interaction is involved in tumor growth control. In fact, miR-21 over-expression or KRIT1 knock-down promote anchorage independent tumor cell growth compared to controls, whereas the opposite is observed when anti-miR-21 or KRIT1 overexpression are employed. Our findings suggest that miR-21 promotes tumor cell growth, at least in part, by down-modulating the potential tumor suppressor KRIT1.     

Probing the shRNA characteristics that hinder Dicer recognition and consequently allow Ago-mediated processing and AgoshRNA activity

Recent evidence indicates the presence of alternative pathways for microRNA (miRNA) and short hairpin (shRNA) processing. Specifically, some of these molecules are refractory to Dicer-mediated processing, which allows alternative processing routes via the Ago2 endonuclease. The resulting RNA molecules differ in size and sequence and will thus trigger the silencing of different target RNAs. It is, therefore, important to understand these processing routes in mechanistic detail such that one can design exclusive RNA reagents for a specific processing route. The exact sh/miRNA properties that determine this routing toward Dicer or Ago2 are incompletely understood. The size of the base-paired stem seems an important determinant, but other RNA elements may contribute as well. In this study, we document the importance of a weak G-U or U-G base pair at the top of the hairpin stem.     

Circular RNA WHSC1 exerts oncogenic properties by regulating miR-7/TAB2 in lung cancer

Circular RNA is a newly discovered member of non-coding RNA (ncRNA) and regulates the target gene by acting as a micro-RNA sponge. It plays vital roles in various diseases. However, the functions of circular RNA in non-small cell lung cancer (NSCLC) remain still unclear. Our data showed that circ-WHSC1 was highly expressed in NSCLC cells and tissues. Both in vitro and in vivo experiments showed that circ-WHSC1 promoted NSCLC proliferation. circ-WHSC1 also promoted the migration and invasion of lung cancer cells. Through bioinformatic analysis and functional experiments, we showed that circ-WHSC1 could act as a sponge for micro-RNA-7 (miR-7) and regulate the expression of TAB2 (TGF-beta activated kinase one binding protein two). Inhibition of the circ-WHSC1/miR-7/TAB2 pathway could effectively attenuate lung cancer progression. In summary, this study confirmed the existence and oncogenic function of circ-WHSC1 in NSCLC. The research suggests that the circ-WHSC1/miR-7/TAB2 axis might be a potential target for NSCLC therapy.     

CircRNA has_circ_0006427 suppresses the progression of lung adenocarcinoma by regulating miR-6783–3p/DKK1 axis and inactivating Wnt/β-catenin signaling pathway

Recently, circular RNAs (circRNAs) are identified as a novel class of noncoding RNAs playing important roles in human malignant tumors. However, the regulatory function of circRNA in lung adenocarcinoma (LUAD) is still largely unknown. Present study aimed to explore the role of circ_0006427 in LUAD progression. Firstly, the downregulation of circ_0006427 in LUAD tissues and cell lines was revealed by microarray analysis and qRT-PCR analysis. And we also confirmed the circ_0006427 as a prognostic target in LUAD patients. Functionally, overexpression of circ_0006427 effectively suppressed cell proliferation, migration and invasion. Mechanistically, circ_0006427 was found to be predominantly located in the cytoplasm of LUCA cell, and was further revealed to positively regulate DKK1 in LUAD by sponging miR-6783–3p. KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis and western blot analysis revealed that circ_0006427 inactivated Wnt/β-catenin signaling pathway by upregulating DKK1. At last, rescue assays proved the function of circ_0006427/miR-6783–3p/DKK1 axis in LUAD progression. In conclusion, our study revealed that circ_0006427 suppressed lung adenocarcinoma progression through regulating miR-6783–3p/DKK1 axis.