The Function of circRNA-0047604 in Regulating the Tumor Suppressor Gene DACH1 in Breast Cancer.
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ABSTRACT:
SUBMITTER: Zhao B
PROVIDER: S-EPMC8794664 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundTriple-negative breast cancer (TNBC) is one of the most aggressive breast cancer (BC) subtypes. Circular ribonucleic acids (circRNAs) are a class of novel stable and conserved forms of ribonucleic acids (RNAs). circRNAs have been documented to be involved in multiple diseases, especially malignancies, through a competing endogenous RNA (ceRNA) mechanism. However, few studies have been conducted on the function of circRNAs in TNBC. Previously, hsa_circ_0006220 was found to be downregulated in BC tissues. The present study sought to explore the mechanism of hsa_circ_0006220 in TNBC progression.MethodsA real-time polymerase chain reaction (PCR) was used to validate the expression of hsa_circ_0006220 in TNBC tissues and cells. In addition, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT), wound-healing and Transwell assays were conducted to measure the inhibition effects of hsa_circ_0006220 on TNBC cells in vitro. Further, a dual-luciferase reporter assay was performed to confirm the interaction between hsa_circ_0006220 and miR-197-5p. A mimic and an inhibitor of miR-197-5p were constructed to confirm the downstream mechanism of hsa_circ_0006220 in TNBC cells.ResultsHsa_circ_0006220 was more downregulated in TNBC than other subtypes of BC tissues and cell lines. In vitro data showed that hsa_circ_0006220 remarkably inhibited the proliferation, migration, and invasion of TNBC cells. Further, hsa_circ_0006220 was confirmed to be a sponge of miR-197-5p, and to indirectly regulate CDH19 expression. A rescue assay indicated the biological function of the hsa_circ_0006220/miR-197-5p/CDH19 pathway in TNBC cells.Conclusionshsa_circ_0006220 plays an inhibitory role in TNBC progression. It might be a potential diagnostic marker and therapeutic target for TNBC patients.
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Project description:Breast cancer progression is driven by altered gene expression. We show that the RIN1 gene, which encodes a RAS effector regulating epithelial cell properties, is silenced in breast tumor cell lines compared with cultured human mammary epithelial cells. We also report that RIN1 is often reduced in human breast tumor cells compared with morphologically normal breast glandular cells. At least two silencing mechanisms seem to be involved. Overexpression of the transcription repressor SNAI1 (Snail) was observed in ZR75-1 cells, and SNAI1 knockdown restored RIN1 expression. In addition, DNA methylation within the RIN1 promoter and the first exon in KPL-1 cells suggested that epigenetic modifications may contribute to silencing, and demethylation was shown to restore RIN1 expression. Reexpression of RIN1 was shown to inhibit anchorage-independent growth in soft agar. In addition, RIN1 expression inhibited both the initiation and progression of tumorigenesis for two breast tumor cell lines in a mouse model, consistent with a tumor suppressor function. We also show that RIN1 acts as a negative regulator of tumor cell invasive growth and that this requires the ABL kinase-signaling function of RIN1, suggesting a mechanism through which RIN1 silencing may contribute to breast cancer progression.
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Project description:The expression of several members of the FOX gene family is known to be altered in a variety of cancers. We show that in breast cancer, FOXF1 gene is a target of epigenetic inactivation and that its gene product exhibits tumor-suppressive properties. Loss or downregulation of FOXF1 expression is associated with FOXF1 promoter hypermethylation in breast cancer cell lines and in invasive ductal carcinomas. Methylation of FOXF1 in invasive ductal carcinoma (37.6% of 117 cases) correlated with high tumor grade. Pharmacologic unmasking of epigenetic silencing in breast cancer cells restored FOXF1 expression. Re-expression of FOXF1 in breast cancer cells with epigenetically silenced FOXF1 genes led to G(1) arrest concurrent with or without apoptosis to suppress both in vitro cell growth and in vivo tumor formation. FOXF1-induced G(1) arrest resulted from a blockage at G(1)-S transition of the cell cycle through inhibition of the CDK2-RB-E2F cascade. Small interfering RNA-mediated depletion of FOXF1 in breast cancer cells led to increased DNA re-replication, suggesting that FOXF1 is required for maintaining the stringency of DNA replication and genomic stability. Furthermore, expression profiling of cell cycle regulatory genes showed that abrogation of FOXF1 function resulted in increased expression of E2F-induced genes involved in promoting the progression of S and G(2) phases. Therefore, our studies have identified FOXF1 as a potential tumor suppressor gene that is epigenetically silenced in breast cancer, which plays an essential role in regulating cell cycle progression to maintain genomic stability.
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Project description:A previously uncharacterized gene, DBC2 (deleted in breast cancer), was cloned from a homozygously deleted region at human chromosome 8p21. DBC2 contains a highly conserved RAS domain and two putative protein interacting domains. Our analyses indicate that DBC2 is the best candidate tumor suppressor gene from this region. It lies within the epicenter of the deletions and is homozygously deleted in 3.5% (7/200) of breast tumors. Mutation analysis of DBC2 led to discovery of two instances of somatic missense mutations in breast tumor specimens, whereas no missense mutations were found in other candidates from the region. Unlike other genes in the region, expression of DBC2 is often extinguished in breast cancer cells or tissues. Moreover, our functional analysis revealed that DBC2 expression in breast cancer cells lacking DBC2 transcripts causes growth inhibition. By contrast, expression of a somatic mutant discovered in a breast cancer specimen does not suppress the growth of breast cancer cells.
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Project description:Membrane-associated guanylate kinase (MAGUK) with inverted domain structure-1 (MAGI1) is an intracellular adaptor protein that stabilizes epithelial junctions consistent with a tumor suppressive function in several cancers of epithelial origin. Here we report, based on experimental results and human breast cancer (BC) patients' gene expression data, that MAGI1 is highly expressed and acts as tumor suppressor in estrogen receptor (ER)+/HER2- but not in HER2+ or triple negative breast cancer (TNBC). Within the ER+/HER2- subset, high MAGI1 expression associates with ESR1 and luminal genes GATA3 and FOXA1 expression and better prognosis, while low MAGI1 levels correlates with higher histological grade, more aggressive phenotype and worse prognosis. Experimentally, MAGI1 downregulation in the ER+ human BC cells MCF7 impairs ER expression and signaling, promotes cell proliferation, and reduces apoptosis and epithelial differentiation. MAGI1 downregulation in the ER+ murine BC cell line 67NR accelerates primary tumor growth and enhances experimental lung metastasis formation. MAGI1 expression is upregulated by estrogen/ER, downregulated by prostaglandin E2/COX-2axis, and negatively correlates with inflammation in ER+/HER2- BC patients. Taken together, we show that MAGI1 is a new potential tumor suppressor in ER+/HER2- breast cancer with possible prognostic value for the identification of patients at high-risk of relapse within this subset.
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Project description:INTRODUCTION:ECRG4/C2ORF40 is a potential tumor suppressor gene (TSG) recently identified in esophageal carcinoma. Its expression, gene copy number and prognostic value have never been explored in breast cancer. METHODS:Using DNA microarray and array-based comparative genomic hybridization (aCGH), we examined ECRG4 mRNA expression and copy number alterations in 353 invasive breast cancer samples and normal breast (NB) samples. A meta-analysis was done on a large public retrospective gene expression dataset (n?=?1,387) in search of correlations between ECRG4 expression and histo-clinical features including survival. RESULTS:ECRG4 was underexpressed in 94.3% of cancers when compared to NB. aCGH data revealed ECRG4 loss in 18% of tumors, suggesting that DNA loss is not the main mechanism of underexpression. Meta-analysis showed that ECRG4 expression was significantly higher in tumors displaying earlier stage, smaller size, negative axillary lymph node status, lower grade, and normal-like subtype. Higher expression was also associated with disease-free survival (DFS; HR?=?0.84 [0.76-0.92], p?=?0.0002) and overall survival (OS; HR?=?0.72 [0.63-0.83], p?=?5.0E-06). In multivariate analysis including the other histo-clinical prognostic features, ECRG4 expression remained the only prognostic factor for DFS and OS. CONCLUSIONS:Our data suggest that ECRG4 is a candidate TSG in breast cancer, the expression of which may help improve the prognostication. If functional analyses confirm this TSG role, restoring ECRG4 expression in the tumor may represent a promising therapeutic approach.
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Project description:Alteration of metabolism in cancer cells is a central aspect of the mechanisms that sustain aggressive traits. Aldo-keto reductase 1 B1 (AKR1B1) catalyzes the reduction of several aldehydes to alcohols consuming NADPH. Nevertheless, the ability of AKR1B1 to reduce different substrates renders difficult to comprehensively ascertain its biological role. Recent evidence has implicated AKR1B1 in cancer, however, the mechanisms underlying its pro-oncogenic function remain largely unknown. In this work, we report that AKR1B1 expression is controlled by the p53 tumor suppressor. We found that breast cancer patients bearing wild type TP53 have reduced AKR1B1 expression. In cancer cell lines, p53 reduced AKR1B1 mRNA and protein levels, and repressed promoter activity in luciferase assays. Furthermore, chromatin immunoprecipitation assays indicated that p53 is recruited to the AKR1B1 promoter. We also observed that AKR1B1 overexpression promoted metastasis in the 4T1 orthotopic model of triple negative breast cancer. Proteomic analysis of 4T1 cells overexpressing AKR1B1 showed that AKR1B1 exerts a marked effect on proteins related to metabolism, with particular impact on mitochondrial function. This work provides novel insights on the link between the p53 pathway and metabolism in cancer cells and contributes to characterizing the alterations associated to the pathologic role of AKR1B1.
2023-09-19 | PXD045048 | Pride