Background

Circular RNAs (circRNAs) play an important role in tumor development. The miRNA sponge is a common role played by circRNAs in various tumors, including breast cancer.

Objective

This study aimed to explore the role of circ-ZEB1 in the proliferation and apoptosis of triple negative breast cancer (TNBC) cells.

Methods

The expressions of several circRNAs which were predicted to be bound with miR-448 were detected in 30 clinical TNBC tumor tissues and paired paracancer tissues. The cell counting kit-8 assay was performed to detect the TNBC cell proliferation. The TNBC cell apoptosis was detected using the TUNEL assay. The binding between circ-ZEB1 and miR-448, as well as between miR-448 and eukaryotic elongation factor 2 kinase (eEF2 K), was detected using the RNA pull-down assay and/or the luciferase reporter assay. The effect of circ-ZEB1 knockdown on TNBC tumor growth was detected using the mouse xenograft model.

Results

Compared with normal tissues and breast epithelial cells, the expression of circ-ZEB1 was markedly higher in TNBC tumor tissues and tumor cell lines. The small hairpin RNA-mediated circ-ZEB1 knockdown inhibited TNBC cell proliferation and induced cell apoptosis. The RNA pull-down assay and the luciferase reporter assay confirmed the binding between circ-ZEB1 and miR-448, as well as between miR-448 and eEF2 K. The knockdown of circ-ZEB1 was proven to inhibit TNBC cell proliferation and tumor growth via releasing miR-448, and subsequently reducing the expression of the miR-448 target, eEF2 K.

Conclusion

In conclusion, our findings identified a new functional circ-ZEB1 in TNBC tumorigenesis, and revealed the important regulatory role of circ-ZEB1 via sponging miR-448, providing a novel insight for TNBC pathogenesis.

中文翻译：

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环状RNA circ-ZEB1通过海绵状miR-448在三阴性乳腺癌中作为癌基因。

背景

环状RNA（circRNA）在肿瘤发展中起重要作用。miRNA海绵是circRNA在包括乳腺癌在内的各种肿瘤中扮演的共同角色。

目的

本研究旨在探讨circ-ZEB1在三阴性乳腺癌细胞（TNBC）增殖和凋亡中的作用。

方法

在30个临床TNBC肿瘤组织和成对的癌旁组织中检测到了预计与miR-448结合的几种circRNA的表达。进行细胞计数试剂盒8测定以检测TNBC细胞增殖。使用TUNEL测定法检测TNBC细胞凋亡。使用RNA下拉测定法和/或荧光素酶报告基因测定法检测circ-ZEB1与miR-448之间以及miR-448与真核伸长因子2激酶（eEF2 K）之间的结合。使用小鼠异种移植模型检测了circ-ZEB1敲低对TNBC肿瘤生长的影响。

结果

与正常组织和乳腺上皮细胞相比，circ-ZEB1在TNBC肿瘤组织和肿瘤细胞系中的表达明显升高。小发夹RNA介导的circ-ZEB1敲低抑制TNBC细胞增殖并诱导细胞凋亡。RNA下拉测定和荧光素酶报告基因测定证实了circ-ZEB1和miR-448之间以及miR-448和eEF2 K之间的结合。证明circ-ZEB1的敲低抑制了TNBC细胞的增殖和肿瘤的生长。通过释放miR-448，随后降低miR-448靶标eEF2 K的表达。

结论

总之，我们的发现确定了新的功能性circ-ZEB1在TNBC肿瘤发生中，并通过海绵化miR-448揭示了circ-ZEB1的重要调节作用，为TNBC发病机理提供了新的见解。