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MiR?92b promotes autophagy and suppresses viability and invasion in breast cancer by targeting EZH2.

ABSTRACT: MicroRNAs (miRs) are a small non-coding RNA family with a length of 18-22 nucleotides. They are able to regulate gene expression by either triggering target messenger RNA degradation or by inhibiting mRNA translation. Enhancer of zeste homolog 2 (EZH2) is the core enzymatic subunit of polycomb repressor complex 2 and is responsible for the trimethylation of histone 3 on lysine 27 (H3K27me3); it is also able to silence a bundle of tumor suppressor genes through promoter binding. However, little is known regarding the effect of miR?92b on cell autophagy, viability and invasion as well as how it interacts with EZH2. The present study investigated the major role of miR?92b in the autophagy, viability and invasion of breast cancer. It was revealed that in MCF?7 and MDA?MB?453 cells, the expression of miR?92b promoted autophagy induced by starvation and rapamycin treatment. The results of in vitro experiments results demonstrated that miR?92b inhibited breast cancer cell viability, invasion and migration. To further elucidate the regulatory mechanisms of miR?92b in autophagy, a dual luciferase reporter assay was performed to determine whether miR?92b targeted the EZH2 gene. The expression of miR?92b was negatively correlated to EZH2 mRNA expression in breast cancer. Depletion of EZH2 induced phenocopied effects on miR?92b overexpression, thereby demonstrating its importance in autophagy. These results indicated that miR?92b may serve an important role in breast cancer in controlling autophagy, viability and invasion. The present study indicated that miR?92b and EZH2 may serve as potential biomarkers for cancer detection and highlighted their possible therapeutic implications.

SUBMITTER: Liu F

PROVIDER: S-EPMC6086627 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

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miR‑92b promotes autophagy and suppresses viability and invasion in breast cancer by targeting EZH2.

Liu Fei F Sang Meixiang M Meng Lingjiao L Gu Lina L Liu Shina S Li Juan J Geng Cuizhi C

International journal of oncology 20180718 4

MicroRNAs (miRs) are a small non-coding RNA family with a length of 18-22 nucleotides. They are able to regulate gene expression by either triggering target messenger RNA degradation or by inhibiting mRNA translation. Enhancer of zeste homolog 2 (EZH2) is the core enzymatic subunit of polycomb repressor complex 2 and is responsible for the trimethylation of histone 3 on lysine 27 (H3K27me3); it is also able to silence a bundle of tumor suppressor genes through promoter binding. However, little i ...[more]

PMID: 30066891

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Project description:ObjectivesCircular RNA (circRNA) is a novel class of RNA, which exhibits powerful biological function in regulating cellular fate of various tumors. Previously, we had demonstrated that over-expression of circRNA circCDYL promoted progression of HER2-negative (HER2-) breast cancer via miR-1275-ULK1/ATG7-autophagic axis. However, the role of circCDYL in HER2-positive (HER2+) breast cancer, in particular its role in modulating cell proliferation, one of the most important characteristics of cellular fate, is unclear.Materials and methodsqRT-PCR and in situ hybridization analyses were performed to examine the expression of circCDYL and miR-92b-3p in breast cancer tissues or cell lines. The biological function of circCDYL and miR-92b-3p were assessed by plate colony formation and cell viability assays and orthotopic animal models. In mechanistic study, circRNAs pull-down, RNA immunoprecipitation, dual luciferase report, western blot, immunohistochemical and immunofluorescence staining assays were performed.ResultsCircCDYL was high-expressed in HER2+ breast cancer tissue, similar with that in HER2- breast cancer tissue. Silencing HER2 gene had no effect on expression of circCDYL in HER2+ breast cancer cells. Over-expression of circCDYL promoted proliferation of HER2+ breast cancer cells but not through miR-1275-ULK1/ATG7-autophagic axis. CircRNA pull down and miRNA deep-sequencing demonstrated the binding of miR-92b-3p and circCDYL. Interestingly, circCDYL did not act as miR-92b-3p sponge, but was degraded in miR-92b-3p-dependent silencing manner. Clinically, expression of circCDYL and miR-92b-3p was associated with clinical outcome of HER2+ breast cancer patients.ConclusionMiR-92b-3p-dependent cleavage of circCDYL was an essential mechanism in regulating cell proliferation of HER2+ breast cancer cells. CircCDYL was proved to be a potential therapeutic target for HER2+ breast cancer, and both circCDYL and miR-92b-3p might be potential biomarkers in predicting clinical outcome of HER2+ breast cancer patients.

Project description:BackgroundTriple-negative breast cancer (TNBC) is the malignancy with the worst outcome among all breast cancer subtypes. We reported that ETV1 is a significant oncogene in TNBC tumourigenesis. Consequently, investigating the critical regulatory microRNAs (miRNAs) of ETV1 may be beneficial for TNBC targeted therapy.MethodsWe performed in situ hybridization (ISH) and immunohistochemistry (IHC) to detect the location of miR-17-5p and ETV1 in TNBC patient samples, respectively. miR-17-5p expression in TNBC tissues and cell lines was assessed by quantitative real-time PCR (qRT-PCR). ETV1 expression was evaluated by qRT-PCR, western blotting and IHC. Cell Counting Kit-8 (CCK-8), colony formation, Transwell and wound closure assays were utilized to determine the TNBC cell proliferation and migration capabilities. In vivo tumour metastatic assays were performed in a zebra fish model.ResultsThe abundance of miR-17-5p was significantly decreased in TNBC cell lines and clinical TNBC tissues. The miR-17-5p expression levels were closely correlated with tumour size (P < 0.05) and TNM stage (P < 0.05). By contrast, the expression of ETV1 was significantly up-regulated in TNBC cell lines and tissues. There is an inverse correlation between the expression status of miR-17-5p and ETV1 (r = -0.28, P = 3.88 × 10-3). Luciferase reporter assay confirmed that ETV1 was a direct target of miR-17-5p. Forced expression of miR-17-5p in MDA-MB-231 or BT549 cells significantly decreased ETV1 expression and suppressed cell proliferation, migration in vitro and tumour metastasis in vivo. However, rescuing the expression of ETV1 in the presence of miR-17-5p significantly recovered the cell phenotype. High miR-17-5p expression was associated with a significantly favourable prognosis, in either the ETV1-positive or ETV1-negative groups (log-rank test, P < 0.001; P < 0.001). Both univariate and multivariate analyses showed that miR-17-5p and ETV1 were independent risk factors in the prognosis of TNBC patient.ConclusionsOur data indicate that miR-17-5p acts as a tumour suppressor in TNBC by targeting ETV1, and a low-abundance of miR-17-5p may be involved in the pathogenesis of TNBC. These findings indicate that miR-17-5p may be a therapeutic target for TNBC.

Dataset Information

MiR?92b promotes autophagy and suppresses viability and invasion in breast cancer by targeting EZH2.

Publications

miR‑92b promotes autophagy and suppresses viability and invasion in breast cancer by targeting EZH2.

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