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Background and purpose: Circular RNA (CircRNA) is a type of non-coding RNA with a closed circular structure, which has important potential in gene expression regulation. CircRNA is closely related to the occurrence and development of tumor. This study aimed to explore the influence of hsa_circ_0001573 on the biological behavior of breast cancer cells and its mechanism. Methods: Breast cancer tissues and paracancerous tissues of 4 patients surgically removed at the First Affiliated Hospital of Chongqing Medical University from January 2020 to January 2021 were collected, sequenced and analyzed by RNA microarray analysis. Real-time fluorescence quantitative polymerase chain reaction (RTFQ-PCR) was used to detect the relative expression of hsa_circ_0001573 in breast cancer tissues and paracancerous tissues of 40 cases, as well as normal human breast cancer epithelial cell MCF-10A and breast cancer cells (MCF-7 and SK-BR-3), and the location and expression were further examined by fluorescence in situ hybridization (FISH) assay. The interference vector was transfected into breast cancer cells. Cell counting kit-8 (CCK-8), EdU, wound healing, clonal formation, Hoechst 33342, TUNEL, flow cytometry and transwell assays were adopted to determine cell migration, invasion, proliferation and apoptosis. Western blot was employed to measure the expressions of CCND1, CCND2 and CDK4. The effect of hsa_circ_0001573 on the growth of xenograft tumors was observed in nude mice. RNA pulldown assay was performed to identify hsa_circ_0001573-associated proteins. Subcellular localization of hsa_circ_0001573 and GNB4 was clarified by FISH and immunofluorescence (FISH-IF), to explore potential molecular mechanisms. Results: The expression level of hsa_circ_0001573 was high in breast cancer (P

Objective To explore the effects of the interaction between circular RNA hsa_circ_0000231 and HnRNPK on the proliferation, migration and apoptosis in breast cancer. Methods Microarray analysis was used to investigate the expression profile of circRNAs in 4 pairs of breast cancer tissues and corresponding adjacent normal tissues. A total of 35 breast cancer tissue specimens were collected from the patients admitted in the First Affiliated Hospital of Chongqing Medical University from September 2019 to January 2021. qRT-PCR was carried out to detect the relative expression of hsa_circ_0000231, and fluorescence in situ hybridization (FISH) assay was performed to observe its location and expression in the cells. Breast cancer MCF-7 and SK-BR-3 cells were transfected with the interference vector of hsa_circ_0000231 respectively. Then cell wound healing assay, CCK-8 assay, EdU cell proliferation assay, clone formation experiment, hoechst33342 staining, TUNEL, flow cytometry and Transwell assay were adopted to determine cell migration, invasion, proliferation and apoptosis, and Western blotting was employed to measure the expression of CCND2, CCND1 and CDK4 after the knockdown. The effect of hsa_circ_0000231 on the growth of transplanted tumors was observed in nude mice. RNA pulldown assay was performed to identify hsa_circ_0000231-associated proteins, and FISH-immunofluorescence (IF) assay were employed to clarify the subcellular localization of hsa_circ_0000231 and HnRNPK. qRT-PCR and Western blotting were conducted to detect the expression of c-Myc. Results Circular RNA hsa_circ_ 0000231 was highly expressed in breast cancer tissues (P < 0.001) and breast cancer cells (P < 0.01). Down-regulation of hsa_ circ_ 0000231 inhibited the proliferation, migration and invasion of breast cancer cells, induced cell apoptosis, led to cell cycle arrest in G1 phase, and obviously decreased the expression of CCND2, CCND1 and CDK4. The results of in vivo experiments showed that knockdown of hsa_circ_0000231 inhibited the growth of tumor xenograft. HnRNPK was co-localized in the nucleus with hsa_circ_0000231, and interacted with hsa_circ_0000231 to promote c-Myc expression. Conclusion Knockdown of hsa_ circ_ 0000231 could suppress the proliferation, migration and invasion of breast cancer cells, induce cell apoptosis and cell cycle arrest, and inhibit tumor growth in vivo. The interaction of hsa_circ_0000231 with HnRNPK enhances the expression of c-Myc, and thus promotes the occurrence and development of breast cancer.

Objective To investigate the expression of circular RNA circACTN4 (also called hsa_circ_0050900) in breast cancer (BC) and its effect on the proliferation, invasion and metastasis of BC cells. Methods The circRNA expression profiles of 4 pairs of BC tissues and adjacent tissues were analyzed by circRNA chip analysis, and the relative expression level of circACTN4 was detected by qRT-PCR. After BC cell lines MCF-7/MDA-MB-231 were transfected with circACTN4 overexpression plasmid and control plasmid, respectively, the effects of circACTN4 on cell proliferation, migration and invasion were tested by Cell Counting Kit-8 (CCK-8), EdU assay, colony formation, scratching assay, and Transwell migration and invasion assay. Western blotting was executed to determine the protein expression of CCND1, CCND2 and CDK4. The effects of circACTN4 on the growth and metastasis of transplanted tumors were also observed in nude mice. Results The expression of circACTN4 was significantly higher in BC tissues and cells than in the paired adjacent tissues and normal breast epithelial cells (P < 0.01). Up-regulation of circACTN4 enhanced the proliferation, migration and invasion of BC cells (P < 0.05), and facilitated the expression of CCND1, CCND2 and CDK4 (P < 0.01). The results of in vivo experiments also showed that up-regulation of circACTN4 promoted the growth and metastasis of transplanted tumors, with the tumor microvascular density and the number of lung metastatic nodules significantly increased in the circACTN4 group, as compared with the control group (P < 0.05). Conclusion circACTN4 is highly expressed in BC tissues and cells. It can promote the proliferation, migration and invasion of BC cells, and facilitate the growth and metastasis of transplanted tumors in vivo.

Background: In recent years, circular RNAs (circRNAs), a new star of non-coding RNA, have been emerged as vital regulators and gained much attention for involvement of initiation and progression of diverse kinds of human diseases, especially cancer. However, regulatory role, clinical significance and underlying mechanisms of circRNAs in triple-negative breast cancer (TNBC) still remain largely unknown. Methods: Here, the expression profile of circRNAs in 4 pairs of TNBC tissues and adjacent non-tumor tissues was analyzed by RNA-sequencing. Quantitative real-time PCR and in situ hybridization were used to determine the level and prognostic values of circAGFG1 in two TNBC cohorts. Then, functional experiments in vitro and in vivo were performed to investigate the effects of circAGFG1 on tumor growth and metastasis in TNBC. Mechanistically, fluorescent in situ hybridization, dual luciferase reporter assay, RNA pull-down and RNA immunoprecipitation experiments were performed to confirm the interaction between circAGFG1 and miR-195-5p in TNBC. Results: We found that circAGFG1 was evidently up-regulated in TNBC, and its level was correlated with clinical stage, pathological grade and poor prognosis of patients with TNBC. The results indicated that circAGFG1 could promote TNBC cell proliferation, mobility and invasion as well as tumorigenesis and metastasis in vivo. Mechanistic analysis showed that circAGFG1 may act as a ceRNA (competing endogenous RNA) of miR-195-5p to relieve the repressive effect of miR-195-5p on its target cyclin E1 (CCNE1). Conclusions: Our findings suggest that circAGFG1 promotes TNBC progression through circAGFG1/miR-195-5p/CCNE1 axis and it may serve as a new diagnostic marker or target for treatment of TNBC patients. [ABSTRACT FROM AUTHOR]