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Background: Increasing studies have shown that circRNA is closely related to the carcinogenesis and development of many cancers. However, biological functions and the underlying molecular mechanism of circRNAs in triplenegative breast cancer (TNBC) remain largely unclear so far. Methods: Here, we investigated the expression pattern of circRNAs in four pairs of TNBC tissues and paracancerous normal tissues using RNA-sequencing. The expression and prognostic significance of circSEPT9 were evaluated with qRT-PCR and in situ hybridization in two TNBC cohorts. The survival curves were drawn by the Kaplan-Meier method, and statistical significance was estimated with the log-rank test. A series of in vitro and in vivo functional experiments were executed to investigate the role of circSEPT9 in the carcinogenesis and development of TNBC. Mechanistically, we explored the potential regulatory effects of E2F1 and EIF4A3 on biogenesis of circSEPT9 with chromatin immunoprecipitation (ChIP), luciferase reporter and RNA immunoprecipitation (RIP) assays. Furthermore, fluorescent in situ hybridization (FISH), luciferase reporter and biotin-coupled RNA pull-down assays were implemented to verify the relationship between the circSEPT9 and miR-637 in TNBC. Results: Increased expression of circSEPT9 was found in TNBC tissues, which was positively correlated with advanced clinical stage and poor prognosis. Knockdown of circSEPT9 significantly suppressed the proliferation, migration and invasion of TNBC cells, induced apoptosis and autophagy in TNBC cells as well as inhibited tumor growth and metastasis in vivo. Whereas up-regulation of circSEPT9 exerted opposite effects. Further mechanism research demonstrated that circSEPT9 could regulate the expression of Leukemia Inhibitory Factor (LIF) via sponging miR-637 and activate LIF/Stat3 signaling pathway involved in progression of TNBC. More importantly, we discovered that E2F1 and EIF4A3 might promote the biogenesis of circSEPT9. Conclusions: Our data reveal that the circSEPT9 mediated by E2F1 and EIF4A3 facilitates the carcinogenesis and development of triple-negative breast cancer through circSEPT9/miR-637/LIF axis. Therefore, circSEPT9 could be used as a potential prognostic marker and therapeutical target for TNBC.

Accumulating evidences indicate that long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) play important roles in tumorigenesis. However, the mechanisms remain largely unknown. To explore lncRNAs and circRNAs expression profiling and their biological functions in bladder cancer, we surveyed the lncRNA/circRNA and mRNA expression profiles of bladder cancer and para-cancer tissues using microarray for four patients. Thousands of significantly changed lncRNAs and mRNAs as well as hundreds of circRNAs were identified. Five dysregulated lncRNAs and four mRNAs were confirmed by quantitative real-time PCR in 30 pairs of samples. GO and KEGG pathway enrichment analyses were executed to determine the principal functions of the significantly deregulated genes. Further more, we constructed correlated expression networks including coding-noncoding co-expression (CNC), competing endogenous RNAs (ceRNA), cis regulation, lncRNAs-transcription factor (TF)-mRNA with bioinformatics methods. Co-expression analysis showed lncRNA APLP2 expression is correlated with apoptosis-related genes, including PTEN and TP53INP1. CeRNA network inferred that lncRNA H19 and circRNA MYLK could bind competitively with miRNA-29a-3p increasing target gene DNMT3B, VEGFA and ITGB1 expressions. Moreover, the nearby genes pattern displayed that overexpressing ADAM2 and C8orf4 are cis-regulated by lncRNA RP11-359E19.2, involving in progression of bladder cancer. In addition, lncRNAs-TF-mRNA diagram indicated that lncRNA BC041488 could trans-regulate CDK1 mRNA expression through SRF transcription factor. Taken together, these results suggested lncRNAs and circRNAs could implicate in the pathogenesis and development of bladder cancer. Our findings provide a novel perspective on lncRNAs and circRNAs and lay the foundation for future research of potential roles of lncRNAs and circRNAs in bladder carcinoma.

Accumulating evidences indicate that long noncoding RNAs (lncRNAs) might play important roles in tumorigenesis and metastasis. EMT (epithelial-to-mesenchymal transition) is considered as a critical step in invasion and metastasis of various tumors including bladder cancer (BC). Recent researches have showed that lncRNA H19 is implicated in metastasis through regulating EMT and the reverse MET (mesenchymal-to-epithelial transition). However, underlying mechanisms remain largely unknown. Here, we screened lncRNA and mRNA expression profiles of BC with microarray assay. We found that H19 and DNMT3B displayed a higher co-expression in BC tissues and cells. Functionally, we demonstrated that H19 could increase proliferation, invasion and migration, regulate EMT as well as rearrange cytoskeleton of BC cells in vitro. Moreover, ectopic expression of H19 promoted tumorigenesis, angiogenesis and pulmonary metastasis in vivo, whereas knockdown of H19 has a contrary role in vivo and in vitro. Mechanistically, we proved that H19 could directly bind to miR-29b-3p (miR-29b) and derepress the expression of target DNMT3B. H19 and miR-29b-3p showed a co-localization. More importantly, up-regulating H19 antagonized miR-29b-3p-mediated proliferation, migration and EMT suppression in BC cells. Furthermore, H19 knockdown partially reversed the function of miR-29b-3p inhibitor on DNMT3B and facilitated miR-29b-3p-induced MET. Taken together, we demonstrated for the first time that H19 might function as ceRNA (competing endogenous RNA) for miR-29b-3p and relieve the suppression for DNMT3B, which led to EMT and metastasis of BC. Our findings highlight a novel mechanism of H19 in progression of BC and provide H19/miR-29b-3p/DNMT3B axis as a promising therapeutic target for BC.