The Profile of MicroRNA Expression and Potential Role in the Regulation of Drug-Resistant Genes in Doxorubicin and Topotecan Resistant Ovarian Cancer Cell Lines

Epithelial ovarian cancer has the highest mortality among all gynecological malignancies. The main reasons for high mortality are late diagnosis and development of resistance to chemotherapy. Resistance to chemotherapeutic drugs can result from altered expression of drug-resistance genes regulated by miRNA. The main goal of our study was to detect differences in miRNA expression levels in two doxorubicin (DOX)- and two topotecan (TOP)-resistant variants of the A2780 drug-sensitive ovarian cancer cell line by miRNA microarray. The next aim was to recognize miRNAs as factors responsible for the regulation of drug-resistance genes. We observed altered expression of 28 miRNA that may be related to drug resistance. The upregulation of miR-125b-5p and miR-935 and downregulation of miR-218-5p was observed in both DOX-resistant cell lines. In both TOP-resistant cell lines, we noted the overexpression of miR-99a-5p, miR-100-5p, miR-125b-5p, and miR-125b-2-3p and decreased expression of miR-551b-3p, miR-551b-5p, and miR-383-5p. Analysis of the targets suggested that expression of important drug-resistant genes such as the collagen type I alpha 2 chain (COL1A2), protein Tyrosine Phosphatase Receptor Type K (PTPRK), receptor tyrosine kinase—EPHA7, Roundabout Guidance Receptor 2 (ROBO2), myristoylated alanine-rich C-kinase substrate (MARCK), and the ATP-binding cassette subfamily G member 2 (ABCG2) can be regulated by miRNA.     

circRNA-Mediated Inhibin–Activin Balance Regulation in Ovarian Granulosa Cell Apoptosis and Follicular Atresia

Ovarian granulosa cells (GC) play an essential role in the development and atresia of follicles. Emerging studies suggest that non-coding RNAs are involved in the regulation of GC apoptosis. Here, we aimed to analyze the function of ssc-circINHA-001, coded by the first exon of the inhibin subunit α gene (INHA), in resisting GC apoptosis and follicular atresia by enhancing the expression of the inhibin subunit β A (INHBA) through a cluster of miRNAs. A higher expression of ssc-circINHA-001 in healthy follicles compared to early atretic follicles was detected by qRT-PCR. Its circular structure was confirmed by RNase R treatment and reversed PCR. The function of ssc-circINHA-001 in GC resistance to apoptosis was detected by in vitro transfection of its si-RNA. Furthermore, the dual-luciferase reporter assay suggested that ssc-circINHA-001 adsorbed three miRNAs, termed miR-214-5p, miR-7144-3p, and miR-9830-5p, which share the common target INHBA. A low expression of ssc-circINHA-001 increased the levels of the free miRNAs, inhibited INHBA expression, and thus raised GCs apoptosis through a shift from the secretion of activin to that of inhibin. Our study demonstrated the existence of a circRNA–microRNAs–INHBA regulatory axis in follicular GC apoptosis and provides insight into the relationship between circRNA function and its coding gene in inhibin/activin balance and ovarian physiological functions.     

The Profile of MicroRNA Expression and Potential Role in the Regulation of Drug-Resistant Genes in Cisplatin- and Paclitaxel-Resistant Ovarian Cancer Cell Lines

Ovarian cancer is the most lethal gynecological malignancy. The high mortality results from late diagnosis and the development of drug resistance. Drug resistance results from changes in the expression of different drug-resistance genes that may be regulated miRNA. The main aim of our study was to detect changes in miRNA expression levels in two cisplatin (CIS) and two paclitaxel (PAC)—resistant variants of the A2780 drug-sensitive ovarian cancer cell line—by miRNA microarray. The next goal was to identify miRNAs responsible for the regulation of drug-resistance genes. We observed changes in the expression of 46 miRNA that may be related to drug resistance. The overexpression of miR-125b-5p, miR-99a-5p, miR-296-3p, and miR-887-3p and downregulation of miR-218-5p, miR-221-3p, and miR-222-3p was observed in both CIS-resistant cell lines. In both PAC-resistant cell lines, we observed the upregulation of miR-221-3p, miR-222-3p, and miR-4485, and decreased expression of miR-551b-3p, miR-551b-5p, and miR-218-5p. Analysis of targets suggest that expression of important drug-resistant genes like protein Tyrosine Phosphatase Receptor Type K (PTPRK), receptor tyrosine kinase—EPHA7, Semaphorin 3A (SEMA3A), or the ATP-binding cassette subfamily B member 1 gene (ABCB1) can be regulated by miRNA.     

Transcriptome Analyses Identify Potential Key microRNAs and Their Target Genes Contributing to Ovarian Reserve

Female endocrinological symptoms, such as premature ovarian inefficiency (POI) are caused by diminished ovarian reserve and chemotherapy. The etiology of POI remains unknown, but this can lead to infertility. This has accelerated the search for master regulator genes or other molecules that contribute as enhancers or silencers. The impact of regulatory microRNAs (miRNAs) on POI has gained attention; however, their regulatory function in this condition is not well known. RNA sequencing was performed at four stages, 2-(2 W), 6-(6 W), 15-(15 W), and 20-(20 W) weeks, on ovarian tissue samples and 5058 differentially expressed genes (DEGs) were identified. Gene expression and enrichment were analyzed based on the gene ontology and KEGG databases, and their association with other proteins was assessed using the STRING database. Gene set enrichment analysis was performed to identify the key target genes. The DEGs were most highly enriched in 6 W and 15 W groups. Figla, GDF9, Nobox, and Pou51 were significantly in-creased at 2 W compared with levels at 6 W and 20 W, whereas the expression of Foxo1, Inha, and Taf4b was significantly de-creased at 20 W. Ccnd2 and Igf1 expression was maintained at similar levels in each stage. In total, 27 genes were upregulated and 26 genes interacted with miRNAs; moreover, stage-specific upregulated and downregulated interactions were demonstrated. Increased and decreased miRNAs were identified at each stage in the ovaries. The constitutively expressed genes, Ccnd2 and Igf1, were identified as the major targets of many miRNAs (p < 0.05), and Fshr and Foxo3 interacted with miRNAs, namely mmu-miR-670-3p and mmu-miR-153-3p. miR-26a-5p interacted with Piwil2, and its target genes were downregulated in the 20 W mouse ovary. In this study, we aimed to identify key miRNAs and their target genes encompassing the reproductive span of mouse ovaries using mRNA and miRNA sequencing. These results indicated that gene sets are regulated in the reproductive stage-specific manner via interaction with miRNAs. Furthermore, consistent expression of Ccnd2 and Igf1 is considered crucial for the ovarian reserve and is regulated by many interactive miRNAs.     

Prenatal Exposure to Delta-9-tetrahydrocannabinol (THC) Alters the Expression of miR-122-5p and Its Target Igf1r in the Adult Rat Ovary

As cannabis use during pregnancy increases, it is important to understand its effects on the developing fetus. Particularly, the long-term effects of its psychoactive component, delta-9-tetrahydrocannabinol (THC), on the offspring’s reproductive health are not fully understood. This study examined the impact of gestational THC exposure on the miRNA profile in adult rat ovaries and the possible consequences on ovarian health. Prenatal THC exposure resulted in the differential expression of 12 out of 420 evaluated miRNAs. From the differentially expressed miRNAs, miR-122-5p, which is highly conserved among species, was the only upregulated target and had the greatest fold change. The upregulation of miR-122-5p and the downregulation of its target insulin-like growth factor 1 receptor (Igf1r) were confirmed by RT-qPCR. Prenatally THC-exposed ovaries had decreased IGF-1R-positive follicular cells and increased follicular apoptosis. Furthermore, THC decreased Igf1r expression in ovarian explants and granulosa cells after 48 h. As decreased IGF-1R has been associated with diminished ovarian health and fertility, we propose that these THC-induced changes may partially explain the altered ovarian follicle dynamics observed in THC-exposed offspring. Taken together, our data suggests that prenatal THC exposure may impact key pathways in the developing ovary, which could lead to subfertility or premature reproductive senescence.     

miR-30-5p Regulates Muscle Differentiation and Alternative Splicing of Muscle-Related Genes by Targeting MBNL

MicroRNAs (miRNAs), a class of single stranded, small (~22 nucleotides), non-coding RNAs, play an important role in muscle development. We focused on the role of the miR-30-5p family during bovine muscle development from previous high-throughput sequencing results and analyzed their expression profiles. MHC and MyoG mRNAs expression as well as their proteins were suppressed in differentiated C2C12 cells, suggesting the importance of miR-30-5p in muscle development. MBNL, the candidate target of miR-30-5p, is an alternative splicing regulation factor. MBNL1 and MBNL3 have opposite effects on muscle differentiation. Our results confirmed that miR-30a-5p and miR-30e-5p repress the expression of MBNL1, MBNL2 and MBNL3, whereas miR-30b-5p inhibits MBNL1 and MBNL2 expression. This provides direct evidence that MBNL expression can be flexibly regulated by miR-30-5p. Previous studies showed that MBNL1 promotes exon inclusion of two muscle-related genes (Trim55 and INSR). Through RNA splicing studies, we found that miR-30-5p had an effect on their alternative splicing, which means miR-30-5p via MBNL1 could be integrated into muscle signaling pathways in which INSR or Trim55 are located. In conclusion, miR-30-5p could inhibit muscle cell differentiation and regulate the alternative splicing of Trim55 and INSR by targeting MBNL. These results promote the understanding of the function of miRNAs in muscle development.     

The Increase of miR-195-5p Reduces Intestinal Permeability in Ulcerative Colitis,Modulating Tight Junctions’ Expression

Defects in the intestinal epithelial barrier functions characterize inflammatory conditions such as Inflammatory Bowel Disease (IBD). Overexpression of pro-inflammatory cytokines such as TNF-α, IL-1B, IL-6 and INF-γ trigger epithelial damage. These cytokines are due to upregulation of claudin-2 (CLDN2) that form a pore channel, resulting in redistribution of TJs and an alteration of barrier permeability. Recently, we demonstrated that miR-195-5p is able to regulate CLDN2 and indirectly also CLDN1 in intestinal epithelial cells. Now, we aimed to investigate the modulation of miR-195-5p on the expression of CLDN2 and other TJs under inflammatory conditions induced by TNF-α. We demonstrated that miR-195-5p also modulated the expression of CLDN2 levels after stimulation with TNF-α. In addition, we discovered the role of miR-195-5p in the integrity of the intestinal barrier and in promoting the restoration of the intestinal epithelial. Moreover, we established that replacement of miR-195-5p attenuated the colonic inflammatory response in DSS-induced, colitis and it reduced colonic permeability. In conclusion, our data revealed the role of miR-195-5p in intestinal inflammation in ulcerative colitis, suggesting a potential pharmacological target for new therapeutic approaches.     

miR-9-5p,miR-675-5p and miR-138-5p Damages the Strontium and LRP5-Mediated Skeletal Cell Proliferation,Differentiation, and Adhesion

This study was designed to evaluate the effects of strontium on the expression levels of microRNAs (miRNAs) and to explore their effects on skeletal cell proliferation, differentiation, adhesion, and apoptosis. The targets of these miRNAs were also studied. Molecular cloning, cell proliferation assay, cell apoptosis assay, quantitative real-time PCR, and luciferase reporter assay were used. Strontium altered the expression levels of miRNAs in vitro and in vivo. miR-9-5p, miR-675-5p, and miR-138-5p impaired skeletal cell proliferation, cell differentiation and cell adhesion. miR-9-5p and miR-675-5p induced MC3T3-E1 cell apoptosis more specifically than miR-138-5p. miR-9-5p, miR-675-5p, and miR-138-5p targeted glycogen synthase kinase 3 β (GSK3β), ATPase Aminophospholipid Transporter Class I Type 8A Member 2 (ATP8A2), and Eukaryotic Translation Initiation Factor 4E Binding Protein 1 (EIF4EBP1), respectively. Low-density lipoprotein receptor-related protein 5 (LRP5) played a positive role in skeletal development. miR-9-5p, miR-675-5p, and miR-138-5p damage strontium and LRP5-mediated skeletal cell proliferation, differentiation, and adhesion, and induce cell apoptosis by targeting GSK3β, ATP8A2, and EIF4EBP1, respectively.     

The Involvement of RhoA and Wnt-5a in the Tumorigenesis and Progression of Ovarian Epithelial Carcinoma

Background

Ras homolog gene family member A (RhoA) is involved in Wnt-5a–induced migration of gastric and breast cancer cells. We investigated the roles of RhoA and Wnt-5a in ovarian carcinoma.

Methods

RhoA and Wnt-5a mRNA and protein expression in normal fallopian tube epithelium, benign tumors, primary ovarian carcinomas, and metastatic omentum were quantified. RhoA or Wnt-5a was knocked down in OVCAR3 ovarian carcinoma cells using siRNAs and cell phenotype and expression of relevant molecules were assayed.

Results

RhoA and Wnt-5a mRNA and protein expression were found to be significantly higher in metastatic omentum than in ovarian carcinomas, benign tumors, and normal fallopian tube epithelium (p < 0.05), and positively associated with differentiation and FIGO staging (stage I/II vs. stage III/IV) in ovarian carcinoma (p < 0.05). RhoA and Wnt-5a expression were positively correlated in ovarian carcinoma (p = 0.001, R² = 0.1669). RhoA or Wnt-5a knockdown downregulated RhoA and Wnt-5a expression; reduced cell proliferation; promoted G₁ arrest and apoptosis; suppressed lamellipodia formation, cell migration, and invasion; and reduced PI3K, Akt, p70S6k, Bcl-xL, survivin, and VEGF mRNA or protein expression.

Conclusions

This is the first demonstration that RhoA and Wnt-5a are associated with ovarian carcinogenesis and apoptosis inhibition; there might be positive correlation between RhoA and Wnt-5a expression. RhoA is a potential tumorigenesis, differentiation, and progression biomarker in ovarian carcinoma.     

Serum miR-373-3p and miR-194-5p Are Associated with Early Tumor Progression during FOLFIRINOX Treatment in Pancreatic Cancer Patients: A Prospective Multicenter Study

In this study, we explored the predictive value of serum microRNA (miRNA) expression for early tumor progression during FOLFIRINOX chemotherapy and its association with overall survival (OS) in patients with pancreatic ductal adenocarcinoma (PDAC). A total of 132 PDAC patients of all disease stages were included in this study, of whom 25% showed progressive disease during FOLFIRINOX according to the RECIST criteria. MiRNA expression was analyzed in serum collected before the start and after one cycle of chemotherapy. In the discovery cohort (n = 12), a 352-miRNA RT-qPCR panel was used. In the validation cohorts (total n = 120), miRNA expression was detected using individual RT-qPCR miRNA primers. Before the start of FOLFIRINOX, serum miR-373-3p expression was higher in patients with progressive disease compared to patients with disease control after FOLFIRINOX (Log2 fold difference (FD) 0.88, p = 0.006). MiR-194-5p expression after one cycle of FOLFIRINOX was lower in patients with progressive disease (Log2 FD −0.29, p = 0.044). Both miRNAs were predictors of early tumor progression in a multivariable model including disease stage and baseline CA19-9 level (miR-373-3p odds ratio (OR) 3.99, 95% CI 1.10–14.49; miR-194-5p OR 0.91, 95% CI 0.83–0.99). MiR-373-3p and miR-194-5p did not show an association with OS after adjustment for disease stage, baseline CA19-9, and chemotherapy response. In conclusion, high serum miR-373-3p before the start and low serum miR-194-5p after one cycle are associated with early tumor progression during FOLFIRINOX.     

MiR-7-5p Is Involved in Ferroptosis Signaling and Radioresistance Thru the Generation of ROS in Radioresistant HeLa and SAS Cell Lines

In cancer therapy, radioresistance or chemoresistance cells are major problems. We established clinically relevant radioresistant (CRR) cells that can survive over 30 days after 2 Gy/day X-ray exposures. These cells also show resistance to anticancer agents and hydrogen peroxide (H₂O₂). We have previously demonstrated that all the CRR cells examined had up-regulated miR-7-5p and after miR-7-5p knockdown, they lost radioresistance. However, the mechanism of losing radioresistance remains to be elucidated. Therefore, we investigated the role of miR-7-5p in radioresistance by knockdown of miR-7-5p using CRR cells. As a result, knockdown of miR-7-5p increased reactive oxygen species (ROS), mitochondrial membrane potential, and intracellular Fe²⁺ amount. Furthermore, miR-7-5p knockdown results in the down-regulation of the iron storage gene expression such as ferritin, up-regulation of the ferroptosis marker ALOX12 gene expression, and increases of Liperfluo amount. H₂O₂ treatment after ALOX12 overexpression led to the enhancement of intracellular H₂O₂ amount and lipid peroxidation. By contrast, miR-7-5p knockdown seemed not to be involved in COX-2 and glycolysis signaling but affected the morphology of CRR cells. These results indicate that miR-7-5p control radioresistance via ROS generation that leads to ferroptosis.     

Analysis of miR-9-5p,miR-124-3p,miR-21-5p,miR-138-5p,and miR-1-3p in Glioblastoma Cell Lines and Extracellular Vesicles

Glioblastoma (GBM), the most common primary brain tumor, is a complex and extremely aggressive disease. Despite recent advances in molecular biology, there is a lack of biomarkers, which would improve GBM’s diagnosis, prognosis, and therapy. Here, we analyzed by qPCR the expression levels of a set of miRNAs in GBM and lower-grade glioma human tissue samples and performed a survival analysis in silico. We then determined the expression of same miRNAs and their selected target mRNAs in small extracellular vesicles (sEVs) of GBM cell lines. We showed that the expression of miR-21-5p was significantly increased in GBM tissue compared to lower-grade glioma and reference brain tissue, while miR-124-3p and miR-138-5p were overexpressed in reference brain tissue compared to GBM. We also demonstrated that miR-9-5p and miR-124-3p were overexpressed in the sEVs of GBM stem cell lines (NCH421k or NCH644, respectively) compared to the sEVs of all other GBM cell lines and astrocytes. VIM mRNA, a target of miR-124-3p and miR-138-5p, was overexpressed in the sEVs of U251 and U87 GBM cell lines compared to the sEVs of GBM stem cell line and also astrocytes. Our results suggest VIM mRNA, miR-9-5p miRNA, and miR-124-3p miRNA could serve as biomarkers of the sEVs of GBM cells.     

Dysregulated Expression of Arterial MicroRNAs and Their Target Gene Networks in Temporal Arteries of Treatment-Naïve Patients with Giant Cell Arteritis

In this study, we explored expression of microRNA (miR), miR-target genes and matrix remodelling molecules in temporal artery biopsies (TABs) from treatment-naïve patients with giant cell arteritis (GCA, n = 41) and integrated these analyses with clinical, laboratory, ultrasound and histological manifestations of GCA. NonGCA patients (n = 4) served as controls. GCA TABs exhibited deregulated expression of several miRs (miR-21-5p, -145-5p, -146a-5p, -146b-5p, -155-5p, 424-3p, -424-5p, -503-5p), putative miR-target genes (YAP1, PELI1, FGF2, VEGFA, KLF4) and matrix remodelling factors (MMP2, MMP9, TIMP1, TIPM2) with key roles in Toll-like receptor signaling, mechanotransduction and extracellular matrix biology. MiR-424-3p, -503-5p, KLF4, PELI1 and YAP1 were identified as new deregulated molecular factors in GCA TABs. Quantities of miR-146a-5p, YAP1, PELI1, FGF2, TIMP2 and MMP9 were particularly high in histologically positive GCA TABs with occluded temporal artery lumen. MiR-424-5p expression in TABs and the presence of facial or carotid arteritis on ultrasound were associated with vision disturbances in GCA patients. Correlative analysis of miR-mRNA quantities demonstrated a highly interrelated expression network of deregulated miRs and mRNAs in temporal arteries and identified KLF4 as a candidate target gene of deregulated miR-21-5p, -146a-5p and -155-5p network in GCA TABs. Meanwhile, arterial miR and mRNA expression did not correlate with constitutive symptoms and signs of GCA, elevated markers of systemic inflammation nor sonographic characteristics of GCA. Our study provides new insights into GCA pathophysiology and uncovers new candidate biomarkers of vision impairment in GCA.     

MiR-132-3p Regulates the Osteogenic Differentiation of Thoracic Ligamentum Flavum Cells by Inhibiting Multiple Osteogenesis-Related Genes

Ossification of the ligamentum flavum (OLF) is a disorder of heterotopic ossification of spinal ligaments and is the main cause of thoracic spinal canal stenosis. Previous studies suggested that miR-132-3p negatively regulates osteoblast differentiation. However, whether miR-132-3p is involved in the process of OLF has not been investigated. In this study, we investigated the effect of miR-132-3p and its target genes forkhead box O1 (FOXO1), growth differentiation factor 5 (GDF5) and SRY-box 6 (SOX6) on the osteogenic differentiation of ligamentum flavum (LF) cells. We demonstrated that miR-132-3p was down-regulated during the osteogenic differentiation of LF cells and negatively regulated the osteoblast differentiation. Further, miR-132-3p targeted FOXO1, GDF5 and SOX6 and down-regulated the protein expression of these genes. Meanwhile, FOXO1, GDF5 and SOX6 were up-regulated after osteogenic differentiation and the down-regulation of endogenous FOXO1, GDF5 or SOX6 suppressed the osteogenic differentiation of LF cells. In addition, we also found FOXO1, GDF5 and SOX6 expression in the ossification front of OLF samples. Overall, these results suggest that miR-132-3p inhibits the osteogenic differentiation of LF cells by targeting FOXO1, GDF5 and SOX6.     

MicroRNA-mRNA Regulatory Network Mediates Activation of mTOR and VEGF Signaling in African American Prostate Cancer

African American (AA) men exhibit 1.6-fold higher prostate cancer (PCa) incidence and 2.4-fold higher mortality rates compared to European American (EA) men. In addition to socioeconomic factors, emerging evidence suggests that intrinsic biological differences may explain part of PCa disparities. In this study, we applied microRNA (miRNA)-driven bioinformatics to evaluate whether differential miRNA-mRNA regulatory networks play a role in promoting the AA PCa disparities. 10 differentially expressed miRNAs were imported to mirPath V.3 algorithm, leading to identification of 58 signaling pathways differentially regulated in AA PCa versus EA PCa. Among these pathways, we particularly focused on mTOR and VEGF signaling, where we identified 5 reciprocal miRNA-mRNA pairings: miR-34a-5p/HIF1A, miR-34a-5p/PIK3CB, miR-34a-5p/IGFBP2, miR-99b-5p/MTOR and miR-96-5p/MAPKAPK2 in AA PCa versus EA PCa. RT-qPCR validation confirmed that miR-34a-5p, miR-99b-5p and MAPKAPK2 were downregulated, while miR-96-5p, IGFBP2, HIF1A, PIK3CB and MTOR were upregulated in AA PCa versus EA PCa cells. Transfection of miRNA mimics/antagomir followed by RT-qPCR and Western blot analysis further verified that IGFBP2, HIF1A and PIK3CB are negatively regulated by miR-34a-5p, whereas MTOR and MAPKAPK2 are negatively regulated by miR-99b-5p and miR-96-5p, respectively, at mRNA and protein levels. Targeting reciprocal pairings by miR-34a-5p mimic, miR-99b-5p mimic or miR-96-5p antagomir downregulates HIF1α, PI3Kβ, mTOR, IGFBP2 but upregulates MAPKAPK2, subsequently reducing cell proliferation and sensitizing docetaxel-induced cytotoxicity in PCa cells. These results suggest that miRNA-mRNA regulatory network plays a critical role in AA PCa disparities, and targeting these core miRNA-mRNA pairings may reduce PCa aggressiveness and overcome the chemoresistance in AA patients.     

Long Noncoding RNA GAS5 in Breast Cancer: Epigenetic Mechanisms and Biological Functions

Long noncoding RNAs (lncRNAs) have been identified as contributors to the development and progression of cancer through various functions and mechanisms. LncRNA GAS5 is downregulated in multiple cancers and acts as a tumor suppressor in breast cancer. GAS5 interacts with various proteins (e.g., E2F1, EZH2, and YAP), DNA (e.g., the insulin receptor promoter), and various microRNAs (miRNAs). In breast cancer, GAS5 binds with miR-21, miR-222, miR-221-3p, miR-196a-5p, and miR-378a-5p that indicates the presence of several elements for miRNA binding (MREs) in GAS5. Mediated by the listed miRNAs, GAS5 is involved in the upregulation of a number of mRNAs of suppressor proteins such as PTEN, PDCD4, DKK2, FOXO1, and SUFU. Furthermore, the aberrant promoter methylation is involved in the regulation of GAS5 gene expression in triple-negative breast cancer and some other carcinomas. GAS5 can stimulate apoptosis in breast cancer via diverse pathways, including cell death receptors and mitochondrial signaling pathways. GAS5 is also a key player in the regulation of some crucial signal pathways in breast cancer, such as PI3K/AKT/mTOR, Wnt/β-catenin, and NF-κB signaling. Through epigenetic and other mechanisms, GAS5 can increase sensitivity to multiple drugs and improve prognosis. GAS5 is thus a promising target in the treatment of breast cancer patients.