Circ_0004676 exacerbates triple-negative breast cancer progression through regulation of the miR-377-3p/E2F6/PNO1 axis.

The significant roles of circular RNAs (circRNAs) in different cancers and diseases have been reported. We now focused on the possible role of a newly recognized circRNA, circ_0004674 in triple-negative breast cancer (TNBC), and the related downstream mechanism. The expression of circ_0004674 in TNBC tissues and cells was determined followed by analysis of the correlation between circ_0004674 and TNBC patients' prognosis. The interaction between circ_0004674, miR-377-3p, E2F6, and PNO1 was then identified using bioinformatics analysis combined with FISH, RIP, RNA pull-down, RT-qPCR, and Western blot analysis. Using gain-of-function and loss-of-function methods, we analyzed the effect of circ_0004674, miR-377-3p, E2F6, and PNO1 on TNBC in vivo and in vitro. Increased circ_0004674 and E2F6 but decreased miR-377-3p were observed in TNBC tissues and MDA-MB-231 TNBC cells, all of which findings were associated with poor prognosis in patients with TNBC. Silencing of circ_0004676 remarkably suppressed the proliferation, cell cycle progression, and migration of TNBC cells in vitro, as well as inhibiting tumorigenesis and metastasis in vivo. Additionally, circ_0004676 served as a sponge of miR-377-3p which bound to the transcription factor E2F6. In the presence of overexpression of circ_0004676, E2F6 expression and its target PNO1 expression were elevated, while miR-377-3p expression was decreased. Interestingly, overexpression of E2F6 could reverse the inhibitory effect on tumor growth caused by downregulation of circ_0004676. Our study highlighted the carcinogenic effect of circ_0004676 on TNBC through regulation of the miR-377-3p/E2F6/PNO1 axis. 1. Circ_0004674 is highly expressed in TNBC tissues and cells. 2. Circ_0004674 upregulates the expression of E2F6 by sponging miR-377-3p. 3. E2F6 upregulates PNO1 by binding to the PNO1 promoter. 4. Circ_0004674 favors TNBC progression by regulating the miR-377-3p/E2F6/PNO1 axis. 5. This study provides a new target for the treatment of TNBC.

Shao G ，Fan X ，Zhang P ，Liu X ，Huang L ，Ji S ... -  《-》

The novel circRNA circ_0045881 inhibits cell proliferation and invasion by targeting mir-214-3p in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is the most lethal subtype of breast cancer (BC). The circRNA-miRNA‒mRNA axis is a promising biomarker for the early diagnosis and prognosis of BC. However, the critical circRNA mediators involved in TNBC progression and the underlying regulatory mechanism involved remain largely unclear. In this study, we carried out a circRNA microarray analysis of 6 TNBC patients and performed a gene ontology (GO) analysis. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis was used to characterize important circRNAs involved in TNBC progression. The interaction between circRNAs and miRNAs was determined by dual luciferase and RNA immunoprecipitation (RIP) assays. Moreover, Transwell, wound healing and Cell Counting Kit-8 (CCK8) assays were performed with altered circRNA or miRNA expression in MDA-MB-231 and BT-549 cells to investigate the roles of these genes in cell invasion, migration and proliferation. A total of 78 circRNAs were differentially expressed in TNBC tissues, and the hsa_circ_0045881 level was significantly decreased in TNBC tissues and cells. Lentivirus-mediated hsa_circ_0045881 overexpression in MDA-MB-231 and BT-549 cells significantly reduced cell invasion and migration capacity. Additionally, hsa_circ_0045881 interacted with miR-214-3p in MDA-MB-231 cells. miR-214-3p mimics in MDA-MB-231 and BT-549 cells significantly enhanced cell invasion, migration and proliferation, but the other combinations of inhibitors had opposite effects on cell activity. Our data indicated that the circRNA has_circ_0045881 plays key roles in TNBC progression and that hsa_circ_0045881 might act as a sponge for miR-214-3p to modulate its levels in TNBC cells, thereby regulating cell invasion, metastasis and proliferation. hsa_circ_004588 might be a potential prognostic marker and therapeutic target for TNBC.

Ren J ，Chen W ，Zhou Y ，Sun J ，Jiang G ... -  《BMC CANCER》

Circ_0062558 promotes growth, migration, and glutamine metabolism in triple-negative breast cancer by targeting the miR-876-3p/SLC1A5 axis.

Circular RNAs (circRNAs) have been reported to function as vital regulators in cancers, including triple-negative breast cancer (TNBC). This study aimed to explore the role of circ_0062558 in TNBC. The real-time quantitative polymerase chain reaction (RT-qPCR) was conducted to quantify the expressions of circ_0062558, microRNA-876-3p (miR-876-3p), and solute carrier family 1 (neutral amino acid transporter), member 5 (SLC1A5) in TNBC tissues and cells. 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyl-2H-tetrazol-3-ium bromide (MTT), thymidine analog 5-ethynyl-2'-deoxyuridine (EdU), flow cytometry, wound healing, and Transwell assays were employed for cell phenotype analyses. Protein expression was tested by western blot analysis. Dual-luciferase reporter was used to confirm the association among circ_0062558, miR-876-3p, and SLC1A5 in TNBC. Xenograft experiments were performed to elucidate the function of circ_0062558 in vivo. TNBC tissues and cells showed the higher level of circ_0062558 when compared with control samples. Downregulation of circ_0062558 inhibited proliferation, migration, invasion, and glutamine metabolism, while enhanced apoptosis of TNBC cells, and silencing of circ_0062558 also inhibited the growth of tumor in vivo. MiR-876-3p was confirmed as a target of circ_0062558, and circ_0062558 knockdown repressed TNBC cell malignant behaviors by increasing miR-876-3p. Furthermore, miR-876-3p inhibited malignant behaviors of TNBC cells by down-regulating SLC1A5, a newly identified target of miR-876-3p. Circ_0062558 promoted TNBC progression by enhancing proliferation, survival, migration, invasion, and glutamine metabolism via miR-876-3p/SLC1A5 axis, which was helpful for understanding the carcinogenic roles of circ_0062558.

Yuan M ，Zhang J ，He Y ，Yi G ，Rong L ，Zheng L ，Zhan T ，Zhou C ... -  《-》

circ_0089153 exacerbates breast cancer cells proliferation and metastasis via sponging miR-2467-3p/E2F6.

The role of circ_0089153 in breast cancer (BCa) malignancy development was explored. circ_0089153 expression in BCa was analyzed by Gene Expression Omnibus database. Clinical tissues were obtained from 90 BCa patients. Cell counting kit-8 assay, 5-ethnyl-2 deoxyuridine assay and colony formation experiment were applied for proliferation detection. Wound healing assay and Transwell experiment were used for migration and invasion detection. Dual luciferase reporter gene assay, RNA immunoprecipitation assay and RNA pull-down assay were conducted. In vivo growth and metastasis of BCa cells were performed. Quantitative real-time polymerase chain reaction, Western blot and immunohistochemistry were applied for RNAs and proteins expression. The up-modulated circ_0089153 indicated an unfavorable survival of BCa patients. circ_0089153 knockdown attenuated BCa cells proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) (P < .01). circ_0089153 was miR-2467-3p sponge. Low miR-2467-3p expression indicated a worse survival of BCa patients. miR-2467-3p overexpression reduced BCa cells proliferation, migration, invasion and EMT (P < .05). circ_0089153 enhanced BCa cells proliferation, migration, invasion and EMT by sponging miR-2467-3p (P < .05). E2F6 was directly suppressed by miR-2467-3p. E2F6 high expression in BCa patients associated with worse survival. circ_0089153 knockdown suppressed in vivo BCa cells growth and lung metastasis (P < .01). circ_0089153 was an oncogene in breast cancer, which enhanced proliferation and metastasis through sponging miR-2467-3p/E2F6. circ_0089153 was suggested to be a potential target for BCa target treatment.

Gao SL ，Fan Y ，Liu XD ，Liu W ，Zhao M ... -  《-》

Circular RNA ZNF609 functions as a competing endogenous RNA in regulating E2F transcription factor 6 through competitively binding to microRNA-197-3p to promote the progression of cervical cancer progression.

Gu Q ，Hou W ，Shi L ，Liu H ，Zhu Z ，Ye W ... -  《-》