Circular RNAs (circRNAs) are a type of noncoding RNAs generated from back-splicing, which have been verified to mediate multiple tumorigenesis. With the development of high-throughput sequencing, massive circRNAs are discovered in tumorous tissue. However, the potential physiological effect of circRNAs in breast cancer is still unknown. The purpose of this study is to investigate the expression profile of circRNA in breast cancer tissue and explore the in-depth regulatory mechanism in breast cancer tumorigenesis. In the present study, we screened the circRNA expression profiles in breast cancer tissue using circRNA microarray analysis. Totally 1705 circRNAs were identified to be significantly aberrant. Among these dysregulated circRNAs, hsa_circ_0001982 was markedly overexpressed in breast cancer tissue and cell lines. Bioinformatics analysis predicted that miR-143 acted as target of hsa_circ_0001982, which was confirmed by Dual-luciferase reporter assay. Loss-of-function and rescue experiments revealed that hsa_circ_0001982 knockdown suppressed breast cancer cell proliferation and invasion and induced apoptosis by targeting miR-143. In summary, our study preliminarily investigates the circRNA expression in breast cancer tissue and explores the role of competing endogenous RNA (ceRNA) mechanism in the progression, providing a novel insight for breast cancer tumorigenesis.

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Breast cancer is one of the most common metastatic tumor types. Reports have suggested that Tunicamycin may inhibit the aggressiveness of cancer cells by promoting their apoptosis. In the present study, the inhibitory effects of Tunicamycin were investigated and the potential molecular mechanism underlying the Tunicamycin-inhibited growth and aggressiveness of breast cancer cells was explored. In vitro assays demonstrated that Tunicamycin significantly inhibited growth and arrested the cell cycle of breast cancer cells in a dose-dependent manner, compared with control cells. Results revealed that Tunicamycin treatment suppressed the migration and invasion of breast cancer cells. Significantly increased apoptosis of breast cancer cells was observed subsequent to Tunicamycin treatment, as compared with control cells. Mechanism analysis demonstrated that Tunicamycin inhibited the protein kinase B (Akt) and nuclear factor-κB (NF-κB) signaling pathways, whilst Akt overexpression significantly cancelled out the Tunicamycin-inhibited growth and aggressiveness of breast cancer cells, as compared with control cells. In vivo assays revealed that Tunicamycin treatment significantly inhibited tumor growth and significantly prolonged the survival of tumor-bearing mice, compared with the PBS-treated group. In conclusion, these results indicate that Tunicamycin may inhibit the growth and aggressiveness of breast cancer cells via regulation of the Akt/NF-κB signaling pathway.

Emerging evidence has demonstrated that microRNAs ( miRNAs/miRs) have various biological functions in the development of human epidermal growth factor receptor 2 (HER2) positive breast cancer. The aim of the present study is to reveal the mechanism of miR-193a-3p inhibiting the progress of HER2 positive breast cancer. The expression of miR-193a-3p was evaluated by quantitative polymerase chain reaction (PCR). The methylation status of miR-193a-3p was evaluated by PCR and pyrosequencing analysis. Overexpression of miR-193a-3p and growth factor receptor bound protein 7 (GRB7) combined with in vitro tumorigenic assays were conducted to determine the carcinostatic capacities of miR-193a-3p in HER2 positive breast cancer cells. The association between miR-193a-3p and GRB7 was determined by luciferase reporter assay. Protein level was evaluated using western blot analysis. miR-193a-3p was down-regulated in HER2 positive breast cancer cells and clinical tissues. Methylation-mediated silencing led to decreased expression of miR-193a-3p in HER2 positive breast cancer. Overexpression of miR-193a-3p could inhibit proliferation, migration and invasion of breast cancer cells. Overexpression of GRB7 could abolish this effect. miR-193a-3p could directly target the 3′ untranslated region of GRB7. miR-193a-3p could directly or indirectly target extracellular signal-regulated kinase 1/2 (ERK1/2) and forkhead box M1 (FOXM1) signaling. In conclusion, it was identified that silencing of miR-193a-3p through hypermethylation can promote HER2 positive breast cancer progress by targeting GRB7, ERK1/2 and FOXM1 signaling. The function of miR-193a-3p in HER2 positive breast cancer implicates its potential application in therapy.