The investigation of circRNA profiling reveals the regulatory role of the has_circ_0000375/miR-7706 pathway in breast cancer

Abstract Circular RNAs (circRNAs) take an effect on tumorigenesis and progression. However, circRNAs have not been systematically identified in breast cancer (BC) as crucial regulators in multitudinous biological processes. This study is conducted to explore novel circRNAs in BC and the corresponding mechanisms of their action. The circRNA expression profile and RNA-sequencing data about BC were respectively downloaded from public database. Differentially expressed circRNAs, miRNA, and mRNA were identified by fold change filtering. The competing endogenous RNAs (ceRNAs) network was established based on the relationship between circular RNAs, miRNAs and mRNAs. GO and KEGG enrichment analysis of the overlapped genes were carried out to predict the potential functions and mechanisms of circRNAs in BC. The CytoHubba plugin in Cytoscape was applied to identify the hub genes from the PPI regulatory network. Kaplan–Meier plotter was used to perform survival analysis of these hub genes further. Real-time PCR was performed to test the expression of circRNA in breast cancer tissues. Cell function studies including transwell analysis and CCK-8 analysis were used to investigate circRNAs’ biological functions. We identified a total of 7 differentially expressed circRNAs. After the intersection between the predicted target miRNA and the down-regulated differential miRNAs (DEmiRNAs), circRNA-miRNA interactions involving 3 circRNAs (hsa_circ_0028899, hsa_circ_0000375, hsa_circ_0000376) and 4 miRNAs (hsa-miR-934, hsa-miR-7706, hsa-miR-4443, hsa-miR-4784) were identified. Venn diagram was utilized to intersect the predicted target genes of the 4 miRNAs and the down-regulated differential genes in BC, and 149 overlapped genes were screened out ulteriorly. Additionally, we built a protein-protein interaction (PPI) network and selected six hub genes. Moreover, the survival data of BC patients suggested that low expression of ADIPOQ, LPL and LEP were significantly correlated with poor prognosis. Results from real-time PCR indicated that has_circ_0000375 was significantly down-regulated in breast cancer tissues. Functional in vitro experiments showed that over-expression of hsa_circ_0000375 can restrain proliferation, migration and invasion abilities of breast cancer cells. Further verification indicated that hsa_circ_0000375 exerted its anti-oncogene effect via sponge of miR-7706. This study constructed and analyzed a circRNA-associated ceRNA regulatory network and uncovered that hsa_circ_0000375 exerted its anti-oncogene effect via sponge of miR-7706.