Circ_0001667 knockdown blocks cancer progression and attenuates adriamycin resistance by depleting NCOA3 via releasing miR-4458 in breast cancer.

Accumulating evidence suggests that developmental chemoresistance in cancers is closely associated with the dysregulation of circular RNA transcriptions. The objective of this study is to disclose the role of circ_0001667 and provide a potential functional mechanism in breast cancer. Quantitative real-time PCR was applied for the analysis of circ_0001667, microRNA-4458 (miR-4458) and nuclear receptor coactivator 3 (NCOA3) expression. In adriamycin (ADM)-resistant cell lines, we investigated cell proliferation using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay and colony formation assay. Cell migration and cell invasion were determined by transwell assay. The protein levels of multi-drug resistance-1, matrix metalloproteinases-9, cleaved-caspase3, cleaved-caspase9 and NCOA3 were detected by western blot. ADM resistance was ascertained by IC50 value using MTT assay. Cell apoptosis was checked by flow cytometry assay. The putative relationship between miR-4458 and circ_0001667 and NCOA3 was validated by pull-down assay, dual-luciferase reporter assay or RNA Immunoprecipitation assay. Circ_0001667 knockdown inhibited MCF-7/ADM and MDA-MB-231/ADM cell proliferation, migration, invasion and ADM resistance. MiR-4458 was a target of circ_0001667, and its expression was decreased in ADM-resistant tumor tissues and cells. MiR-4458 inhibition reversed the effects of circ_0001667 knockdown. In depth, NCOA3 was a target of circ_0001667, and circ_0001667 knockdown weakened NCOA3 expression by releasing miR-4458. MCF-7/ADM and MDA-MB-231/ADM cell proliferation, migration, invasion, and ADM resistance inhibited by miR-4458 restoration were recovered by NCOA3 overexpression. Circ_0001667 knockdown also repressed tumor growth and ADM resistance in vivo. Circ_0001667 knockdown blocks cancer progression and attenuates ADM resistance by depleting NCOA3 via releasing miR-4458 in breast cancer.

Circ_0001667 accelerates breast cancer proliferation and angiogenesis through regulating CXCL10 expression by sponging miR-6838-5p.

BACKGROUND: An increasing number of circular RNAs (circRNAs) have been shown to play an important role in the tumorigenesis of breast cancer. The aim of this study was to investigate the expression and function of circ_0001667 and its potential molecular mechanisms in breast cancer. METHODS: The expression levels of circ_0001667, miR-6838-5p and CXC chemokine ligand 10 (CXCL10) in breast cancer tissues and cells were detected by quantitative real-time PCR. Cell counting kit-8 assay, EdU assay, flow cytometry, colony formation and tube formation assays were used to detect cell proliferation and angiogenesis. The binding relationship between miR-6838-5p and circ_0001667 or CXCL10 was predicted using the starBase3.0 database and verified by dual-luciferase reporter gene assay, RIP and RNA pulldown. Animal experiments were performed to assess the function of circ_0001667 knockdown on breast cancer tumor growth. RESULTS: Circ_0001667 was highly expressed in breast cancer tissues and cells, and its knockdown inhibited proliferation and angiogenesis of breast cancer cells. Circ_0001667 sponged miR-6838-5p, and inhibition of miR-6838-5p reversed the inhibitory effect of silencing circ_0001667 on proliferation and angiogenesis of breast cancer cells. MiR-6838-5p targeted CXCL10, and overexpression of CXCL10 reverses the effect of miR-6838-5p overexpression on breast cancer cell proliferation and angiogenesis. In addition, circ_0001667 interference also reduced breast cancer tumor growth in vivo. CONCLUSION: Circ_0001667 is involved in breast cancer cell proliferation and angiogenesis through regulation of the miR-6838-5p/CXCL10 axis.

Circ_0001667 Promotes Adriamycin Resistance and Malignant Progression via Targeting the miR-193a-5p/Rap2A Molecular Axis in Breast Cancer.

BACKGROUND: The therapeutic effect of adriamycin (ADM) has been limited by chemoresistance in breast cancer (BC). Circular RNAs are involved in resistance regulation by mediating the miRNA/mRNA axis. Circ_0001667 enhanced ADM resistance via the miR-4458/NCOA3 axis in BC. This study was to investigate the other miRNA/mRNA network for circ_0001667. METHODS: The level detection of circ_0001667, microRNA-193a-5p (miR-193a-5p) or Ras-Related Protein 2a (Rap2A) was conducted by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Half inhibitory concentration (IC50) of ADM was detected through cell counting kit-8 (CCK-8) assay. The proliferation analysis was performed by colony formation assay and EdU assay. Flow cytometry was used for assessing apoptosis. Transwell assay was applied for examining cell migration and invasion. The protein detection was carried out by western blot. In vivo assay was performed using xenograft tumor model. Dual-luciferase reporter and RNA immunoprecipitation (RIP) assays were implemented to validate the target interaction. RESULTS: Circ_0001667 was highly expressed in ADM-resistant BC tissues and cells. Downregulation of circ_0001667 reduced ADM resistance and inhibited proliferation, migration, invasion in ADM-resistant BC cells. Tumor growth was repressed by circ_0001667 knockdown in ADM-resistant xenograft model. Circ_0001667 has induced the sponge effect on miR-193a-5p. The circ_0001667 function was partly achieved by targeting miR-193a-5p. Rap2A expression was positively regulated by circ_0001667 through sponging miR-193a-5p. The miR-193a-5p upregulation restrained chemoresistance and BC progression by the downregulation of Rap2A. CONCLUSION: All results unraveled that circ_0001667 contributed to ADM resistance and tumor development in BC via the miR-193a-5p-mediated Rap2A expression change, providing a novel regulatory mechanism for circ_0001667.

Circ_0001667 promotes breast cancer cell proliferation and survival via Hippo signal pathway by regulating TAZ.

BACKGROUND: Breast cancer is a most common type of cancer in women. Circular RNAs (circRNAs) are involved in cancer development and progression, but their roles and regulatory mechanisms are unclear in breast cancer. Our previous study indicated that has_circ_0001667 (circ_0001667) was up-regulated in breast cancer from the array and might play an oncogenic role, however, the roles of circ_0001667 were not known. This study was aimed to investigate the role and the underlying molecular mechanism of circ_0001667 in breast cancer. RESULTS: The real-time PCR result showed that circ_0001667 was overexpressed in breast cancer tissues or cell lines compared to the adjacent normal tissues or normal cells. There was a negative relationship between circ_0001667 levels and the life time of breast cancer patients. Meanwhile, the inhibition of circ_0001667 suppressed the proliferation and metastasis of human breast cancer cells. Further bioinformatical analysis indicated that circ_0001667 sponged miR-125a-5p to regulate TAZ expression by Targetscan and miRanda. Dual luciferase reporter assay and western blotting experiments revealed that circ_0001667 negatively regulated miR-125a-5p expression leading to promoting TAZ expression through Hippo signal pathway in breast cancer cells. CONCLUSIONS: This study uncovered that circ_0001667 was a potential breast cancer prognostic marker, as well as a potential therapeutic target to inhibit breast cancer metastasis by circ_0001667/miR-125a-5p/TAZ axis.