circRAD18 sponges miR-208a/3164 to promote triple-negative breast cancer progression through regulating IGF1 and FGF2 expression.

As a new rising star of non-coding RNA, circular RNAs (circRNAs) emerged as vital regulators with biological functions in diverse of cancers. However, the function and precise mechanism of the vast majority of circRNAs in triple-negative breast cancer (TNBC) occurrence and progression have not been clearly elucidated. In the current study, we identified and further investigated hsa_circ_0002453 (circRAD18) by analyzing our previous microarray profiling. Expression of circRAD18 was found significantly upregulated in TNBC compared with normal mammary tissues and cell lines. circRAD18 was positively correlated with T stage, clinical stage and pathological grade and was an independent risk factor for TNBC patients. We performed proliferation, colony formation, cell migration, apoptosis and mouse xenograft assays to verify the functions of circRAD18. Knockdown of circRAD18 significantly suppressed cell proliferation and migration, promoted cell apoptosis and inhibited tumor growth in functional and xenograft experiments. Through luciferase reporter assays, we confirmed that circRAD18 acts as a sponge of miR-208a and miR-3164 and promotes TNBC progression through upregulating IGF1 and FGF2 expression. Altogether, our research revealed the pivotal role of circRAD18-miR-208a/3164-IGF1/FGF2 axis in TNBC tumorigenesis and metastasis though the mechanism of competing endogenous RNAs. Thus, circRAD18 may serve as a novel prognostic biomarker and potential target for TNBC treatment in the future.

Zou Y ，Zheng S ，Xiao W ，Xie X ，Yang A ，Gao G ，Xiong Z ，Xue Z ，Tang H ，Xie X ... -  《-》

Circ_0000520 contributes to triple-negative breast cancer progression through mediating the miR-1296/ZFX axis.

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with a high incidence of local recurrence and metastasis. Circular RNAs (circRNAs) are implicated in the pathomechanism of TNBC. Here, we investigated the function of circ_0000520 in TNBC and its associated mechanism. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blot assay were used to measure RNA and protein expression. Cell proliferation was analyzed by cell counting kit-8 (CCK8) assay, flow cytometry and colony formation assay. Cell apoptosis was assessed by flow cytometry. Cell migration ability was analyzed by transwell migration and wound healing assays. Transwell invasion assay was conducted to analyze the invasion ability. Dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay, and RNA-pulldown assay were performed to verify the interaction between microRNA-1296 (miR-1296) and circ_0000520 or zinc finger protein X-linked (ZFX). Xenograft mice model was established to analyze the role of circ_0000520 in xenograft tumor growth in vivo. Circ_0000520 expression was upregulated in TNBC tissues and cell lines. Circ_0000520 knockdown suppressed the proliferation, migration, and invasion whereas induced the apoptosis of TNBC cells. miR-1296 was verified as a target of circ_0000520, and circ_0000520 silencing-mediated suppressive effects on the malignant potential of TNBC cells were partly overturned by miR-1296 knockdown. miR-1296 interacted with the 3' untranslated region (3'UTR) of ZFX, and ZFX overexpression partly reversed miR-1296 overexpression-mediated effects in TNBC cells. Circ_0000520 absence reduced ZFX expression by upregulating miR-1296 in TNBC cells. Circ_0000520 silencing suppressed xenograft tumor growth in vivo. Circ_0000520 contributed to TNBC development by binding to miR-1296 to induce ZFX expression.

Zhou Y ，Ma G ，Peng S ，Tuo M ，Li Y ，Qin X ，Yu Q ，Kuang S ，Cheng H ，Li J ... -  《-》

Circular RNA circ-ZEB1 acts as an oncogene in triple negative breast cancer via sponging miR-448.

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

Pei X ，Zhang Y ，Wang X ，Xue B ，Sun M ，Li H ... -  《-》

The circRNA circAGFG1 acts as a sponge of miR-195-5p to promote triple-negative breast cancer progression through regulating CCNE1 expression.

Yang R ，Xing L ，Zheng X ，Sun Y ，Wang X ，Chen J ... -  《Molecular Cancer》

Hsa_circRNA_102229 facilitates the progression of triple-negative breast cancer via regulating the miR-152-3p/PFTK1 pathway.

Increasing evidence has suggested that circular RNAs (circRNAs) may act as an important regulatory factor in tumor progression. However, how circRNAs exert their functions in triple-negative breast cancer (TNBC) remains not clearly understood. First, circRNA microarrays were conducted to identify aberrantly expressed circRNAs in TNBC tissues. Kaplan-Meier survival analysis was conducted to calculate the correlation between the level of hsa_circRNA_102229 and outcomes of patients with TNBC. The effect of hsa_circRNA_102229 and serine/threonine-protein kinase PFTAIRE 1 (PFTK1) on TNBC cells was clarified by cell counting kit-8, transwell and wound healing assays, as well as by a flow cytometry. The molecular mechanism of hsa_circRNA_102229 was clarified through bioinformatics, a dual-luciferase reporter assay, western blotting, fluorescence in situ hybridization and real-time polymerase chain reaction. Tumor xenograft experiments were performed to analyze growth and metastasis of TNBC in vivo. In TNBC tissues and cells, hsa_circ_102229 was remarkably up-regulated. Patients with TNBC presenting high hsa_circ_102229 exhibited poor prognosis. Moreover, hsa_circ_102229 could promote the migration, proliferation and invasion, whereas it inhibited the apoptosis of TNBC cells. Furthermore, hsa_circ_102229 directly targeted miR-152-3p and could regulate the expression of PFTK1 by targeting miR-152-3p. Rescue assays suggested that hsa_circ_102229 may exert its function in TNBC cells by regulating PFTK1. Additionally, knockdown of hsa_circ_102229 slowed down TNBC tumorigenesis and lung metastasis in a tumor xenograft animal model. Hsa_circ_102229 might serve as a competing endogenous RNA (ceRNA) to modulate PFTK1 expression via regulating miR-152-3p to affect the functions of TNBC cells. Hsa_circ_102229 acts as a newly discovered biomarker for TNBC treatment.

Du C ，Zhang J ，Zhang L ，Zhang Y ，Wang Y ，Li J ... -  《-》