miR-190 enhances endocrine therapy sensitivity by regulating SOX9 expression in breast cancer

The Role of SOX2 and SOX9 in Radioresistance and Tumor Recurrence

Head and neck squamous cell carcinoma (HNSCC) exhibits considerable variability in patient outcome. It has been reported that SOX2 plays a role in proliferation, tumor growth, drug resistance, and metastasis in a variety of cancer types. Additionally, SOX9 has been implicated in immune tolerance and treatment failures. SOX2 and SOX9 induce treatment failure by a molecular mechanism that has not yet been elucidated. This study explores the inverse association of SOX2/SOX9 and their distinct expression in tumors, influencing the tumor microenvironment and radiotherapy responses. Through public RNA sequencing data, human biopsy samples, and knockdown cellular models, we explored the effects of inverted SOX2 and SOX9 expression. We found that patients expressing SOX2LowSOX9High showed decreased survival compared to SOX2HighSOX9Low. A survival analysis of patients stratified by radiotherapy and human papillomavirus brings additional clinical relevance. We identified a gene set signature comprising newly discovered candidate genes resulting from inverted SOX2/SOX9 expression. Moreover, the TGF-β pathway emerges as a significant predicted contributor to the overexpression of these candidate genes. In vitro findings reveal that silencing SOX2 enhances tumor radioresistance, while SOX9 silencing enhances radiosensitivity. These discoveries lay the groundwork for further studies on the therapeutic potential of transcription factors in optimizing HNSCC treatment.

HuR (ELAVL1) Stabilizes SOX9 mRNA and Promotes Migration and Invasion in Breast Cancer Cells

RNA-binding proteins play diverse roles in cancer, influencing various facets of the disease, including proliferation, apoptosis, angiogenesis, senescence, invasion, epithelial-mesenchymal transition (EMT), and metastasis. HuR, a known RBP, is recognized for stabilizing mRNAs containing AU-rich elements (AREs), although its complete repertoire of mRNA targets remains undefined. Through a bioinformatics analysis of the gene expression profile of the Hs578T basal-like triple-negative breast cancer cell line with silenced HuR, we have identified SOX9 as a potential HuR-regulated target. SOX9 is a transcription factor involved in promoting EMT, metastasis, survival, and the maintenance of cancer stem cells (CSCs) in triple-negative breast cancer. Ribonucleoprotein immunoprecipitation assays confirm a direct interaction between HuR and SOX9 mRNA. The half-life of SOX9 mRNA and the levels of SOX9 protein decreased in cells lacking HuR. Cells silenced for HuR exhibit reduced migration and invasion compared to control cells, a phenotype similar to that described for SOX9-silenced cells.

Efficacy and safety of traditional Chinese medicine in the treatment of menopause-like syndrome for breast cancer survivors: a systematic review and meta-analysis

BACKGROUND

In recent years, breast cancer (BC) incidence and mortality have been the highest in females. Menopause-like syndrome (MLS), arising from hypoestrogenism caused by endocrine therapy, significantly affects the quality of life for females. Traditional Chinese Medicine (TCM) has advantages in ameliorating MLS, but the efficacy of TCM in patients with BC has not been systematically evaluated.

METHODS

A comprehensive search was performed on PubMed, Web of Science, Embase, Ovid, Cochrane Library, China National Knowledge Infrastructure, Wanfang database, Chinese Scientific Journals Database, and Clinical Trial Registry from inception to September 4, 2023. The Cochrane Risk of Bias assessment tool was used for the quality evaluation of the randomized controlled trials (RCTs). Review Manager 5.4 software was used for statistical analysis, and the Grading of Recommendations Assessment, Development, and Evaluation was used for quality evaluation of the synthesized evidence.

RESULTS

This review included 42 studies involving 3112 female patients with BC. The results showed that the TCM group was better at decreasing the Kupperman Menopausal Index (KMI) scores (standardized MD, SMD = - 1.84, 95% confidence interval, CI [- 2.21--1.46], Z = 9.63, P < 0.00001). Regarding the main symptoms of MLS, the TCM groups could significantly decrease the scores of hot flashes and night sweats (SMD = - 0.68, 95% CI [- 1.1--0.27], Z = 3.24, P = 0.001), paraesthesia (SMD = - 0.48, 95% CI [- 0.74--0.21], Z = 3.53, P = 0.0004), osteoarthralgia (SMD = - 0.41, 95% CI [- 0.6-0.21], Z = 4.09, P < 0.0001), anxiety (MD = - 0.85, 95% CI [- 1.13, - 0.58], Z = 6.08, P < 0.00001) and insomnia (MD = - 0.61, 95% CI [- 0.8, - 0.43], Z = 6.51, P < 0.00001). TCM can effectively improve the symptoms of MLS in patients with BC. Moreover, TCM could improve the objective response rate (ORR) by 50% (RR = 1.5, 95% CI [1.37-1.64], Z = 9.01, P < 0.00001). Follicle-stimulating hormone (FSH) and oestradiol (E2) had no significant difference compared with the control group (p = 0.81 and p = 0.87), and luteinizing hormone (LH) in the TCM group decreased significantly (MD = - 0.99, 95% CI [- 1.38, - 0.5], Z = 5.01, P < 0.00001). This means that the use of TCM does not negatively affect endocrine therapy and may even have a synergistic effect. The incidence of adverse events (AEs) was lower in the TCM groups than in the control groups.

CONCLUSIONS

The meta-analysis stated that TCM could better improve the MLS of patients, alleviate related symptoms, and did not increase adverse drug reactions in BC survivors. This review brings more attention to MLS, and the present findings shed light on the potential applications of TCM in the treatment of MLS in BC survivors.

Landscape of NcRNAs involved in drug resistance of breast cancer

Breast cancer (BC) leads to the most amounts of deaths among women. Chemo-, endocrine-, and targeted therapies are the mainstay drug treatments for BC in the clinic. However, drug resistance is a major obstacle for BC patients, and it leads to poor prognosis. Accumulating evidences suggested that noncoding RNAs (ncRNAs) are intricately linked to a wide range of pathological processes, including drug resistance. Till date, the correlation between drug resistance and ncRNAs is not completely understood in BC. Herein, we comprehensively summarized a dysregulated ncRNAs landscape that promotes or inhibits drug resistance in chemo-, endocrine-, and targeted BC therapies. Our review will pave way for the effective management of drug resistance by targeting oncogenic ncRNAs, which, in turn will promote drug sensitivity of BC in the future.

MIR497HG-Derived miR-195 and miR-497 Mediate Tamoxifen Resistance via PI3K/AKT Signaling in Breast Cancer

Tamoxifen is commonly used for the treatment of patients with estrogen receptor-positive (ER+) breast cancer, but the acquired resistance to tamoxifen presents a critical challenge of breast cancer therapeutics. Recently, long noncoding RNA MIR497HG and its embedded miR-497 and miR-195 are proved to play significant roles in many types of human cancers, but their roles in tamoxifen-resistant breast cancer remain unknown. The results indicate that MIR497HG deficiency induces breast cancer progression and tamoxifen resistance by inducing downregulation of miR-497/195. miR-497/195 coordinately represses five positive PI3K-AKT regulators (MAP2K1, AKT3, BCL2, RAF1, and CCND1), resulting in inhibition of PI3K-AKT signaling, and PI3K-AKT inhibition in tamoxifen-resistant cells restored tamoxifen responsiveness. Furthermore, ER α binds the MIR497HG promoter to activate its transcription in an estrogen-dependent manner. ZEB1 interacts with HDAC1/2 and DNMT3B at the MIR497HG promoter, resulting in promoter hypermethylation and histone deacetylation. The findings reveal that ZEB1-induced MIR497HG depletion contributes to breast cancer progression and tamoxifen resistance through PI3K-AKT signaling. MIR497HG can be used as a biomarker for predicting tamoxifen sensitivity in patients with ER+ breast cancer.

Prospects of circular RNAs: the regulators of drug resistance and metastasis in gastric cancer

Gastric cancer (GC) is one of the most common malignant tumors. Although there are multiple therapeutic methods, the 5-year survival rate for GC remains low primarily due to metastasis and resistance to chemotherapy. GC treatments, which include chemotherapy drugs, targeted drugs, and immunologic drugs, improve the prognosis of advanced GC patients. Nevertheless, resistance to these drugs may result in treatment failure. Tumor metastasis also plays a key role in tumor progression and limits the clinical efficacy of treatments. Recently, it has been reported that circular RNAs (circRNAs), non-coding RNAs, regulate GC drug resistance and metastasis to improve prognosis. In this review, we summarized systematically the underlying mechanisms of circRNA regulation of gastric neoplasm drug resistance and tumor metastasis. Thus we shed light on the potential of circRNAs to function as potential GC biomarkers and therapeutics.

MiR-139-3p Targets CHEK1 Modulating DNA Repair and Cell Viability in Lung Squamous Carcinoma Cells

Non-small-cell lung carcinoma (NSCLC) can be classified into several subtypes, where lung squamous carcinoma (LUSC) is one common subtype. Though miR-139-3p has been reported to be implicated in the development of various cancers, its mechanisms and functions remain unclear in LUSC. In this study, miR-139-3p was screened as one of the significantly down-regulated miRNAs in LUSC by an "edgeR" differential analysis based on TCGA database, which was verified by qRT-PCR in LUSC cell lines as well. The viability and cell cycle of the LUSC cells were examined by CCK-8 and flow cytometry, respectively, exhibiting that upregulating miR-139-3p restrained cell viability and thus accelerating the cell cycle. To explain this phenomenon, we further explored the downstream target gene through miRTarBase and starBase databases, where CHEK1 was predicted as one candidate. The targeting relationship was verified by a dual luciferase assay, identifying that CHEK1 could be targeted by miR-139-3p. Then, qRT-PCR and western blot analyses were performed to detect the expression of CHEK1 mRNA and proteins under the alteration of miR-139-3p expression. Rescue experiments were conducted to confirm the impacts of miR-139-3p/CHEK1 axis on the cell viability and cell cycle of LUSC. The results indicated that the effects of miR-139-3p on the LUSC cell phenotypes could be blocked by overexpressing CHEK1. In conclusion, our study provides a novel insight into the regulatory role of miR-139-3p in the development of LUSC.

LOC102724163 promotes breast cancer cell proliferation and invasion by stimulating MUC19 expression

Breast cancer (BC) is a malignant disease and the most commonly diagnosed cancer in women. Numerous studies have previously verified the important role of long non-coding RNAs in a number of biological processes in BC. In the present study, analysis of The Cancer Genome Atlas database and reverse transcription-quantitative PCR demonstrated that LOC102724163 expression levels were significantly upregulated in BC tissues compared to matched adjacent normal tissues and were associated with an unfavorable prognosis in patients with BC. Gain or loss of function assays indicated that overexpression of LOC102724163 significantly increased tumorgenicity in vivo and cell migration, proliferation and invasion in vitro. In the mechanistical aspect, LOC102724163 sponged microRNA (miR)-508-5p to elevate MUC19 expression. Additionally, rescue assays ascertained the function of the LOC102724163/miR-508-5p/MUC19 axis in the proliferation and invasion of BC cells. To the best of our knowledge, this is the first study to have demonstrated that LOC102724163 may act as a competing endogenous RNA to control MUC19 expression levels by competitively sponging miR-508-5p to modulate BC progression. Therefore, the present study has provided new insights into BC diagnosis and treatment.

The Human Positive Cofactor 4 is a Promising Chemotherapeutic Target in Lung Adenocarcinoma

Reduced sensitivity to chemotherapeutic drugs is almost inevitable in lung adenocarcinoma patients. Thus, understanding the relevant mechanisms is urgent. Positive cofactor 4 (PC4) was at first revealed to be a coactivator of basal transcription. Previous research has shown that PC4 participates in various cellular processes in normal and malignant cells. However, it is still unknown whether PC4 participates in altering the lung adenocarcinoma cell sensitivity to chemotherapy, and the relevant mechanisms remain to be explained. In this study, we discovered that PC4 was overexpressed in cisplatin-resistant lung adenocarcinoma cells. PC4 decreased cisplatin's cytotoxic effects on lung adenocarcinoma in vivo and in vitro. Furthermore, PC4 positively correlated with SOX9 in multiple cancers. PC4 was an upstream regulator of SOX9 in lung adenocarcinoma. Furthermore, PC4 mediated lung adenocarcinoma cell sensitivity to the HIF-PH inhibitor DMOG and the mTOR inhibitor rapamycin, and PC4 mediated the synergistic effect of DMOG and cisplatin. Finally, PC4 destabilized HIF-1α upon cisplatin treatment. Our research showed that PC4 participates in mediating lung adenocarcinoma cell sensitivity to multiple drugs. Mechanistically, PC4 governs multiple downstream pathways associated with chemotherapy resistance, including the SOX9 and HIF-1α pathways. Thus, PC4 is a promising chemotherapeutic target in lung adenocarcinoma.

Contribution of miRNAs in the Pathogenesis of Breast Cancer

Breast cancer is the most frequently diagnosed cancer among females. Gene expression profiling methods have shown the deregulation of several genes in breast cancer samples and have confirmed the heterogeneous nature of breast cancer at the genomic level. microRNAs (miRNAs) are among the recently appreciated contributors in breast carcinogenic processes. These small-sized transcripts have been shown to partake in breast carcinogenesis through modulation of apoptosis, autophagy, and epithelial-mesenchymal transition. Moreover, they can confer resistance to chemotherapy. Based on the contribution of miRNAs in almost all fundamental aspects of breast carcinogenesis, therapeutic intervention with their expression might affect the course of this disorder. Moreover, the presence of miRNAs in the peripheral blood of patients potentiates these transcripts as tools for non-invasive diagnosis of breast cancer.

ANLN Regulated by miR-30a-5p Mediates Malignant Progression of Lung Adenocarcinoma

BACKGROUND

ANLN and miR-30a-5p may be involved in the progression of lung adenocarcinoma (LUAD). However, their underlying mechanism in LUAD has not been completely comprehended.

METHODS

Differential expression analysis, binding site prediction, and survival analysis were conducted by bioinformatics approaches. ANLN mRNA and miR-30a-5p expression were detected by qRT-PCR. ANLN protein expression was detected by western blot. Cell behaviors in LUAD were examined by functional experiments.

RESULTS

ANLN was activated in LUAD cells in terms of mRNA and protein. High ANLN level was positively correlated with poor prognosis. Enforced ANLN stimulated protumorigenesis LUAD cell behaviors. miR-30a-5p could target ANLN mRNA, as revealed and verified through assays. Remarkably low miR-30a-5p expression was observed in LUAD cells, and it could repress ANLN expression. The accelerated cell behaviors by overexpression of ANLN were counteracted by upregulating miR-30a-5p.

CONCLUSION

Overall, miR-30a-5p remarkably restrained the malignant progression of LUAD cells by constraining ANLN expression. Thus, ANLN and miR-30a-5p could be novel therapeutic targets of LUAD.

miR-1207-5p suppresses laryngeal squamous cell carcinoma progression by downregulating SKA3 and inhibiting epithelial-mesenchymal transition

Laryngeal squamous cell carcinoma (LSCC) is the second most common head and neck cancer. Previously, we discovered that miR-1207-5p was downregulated in LSCC. In this study, the clinical significance, function, and mechanism of miR-1207-5p in LSCC were investigated. Downregulation of miR-1207-5p was found to be strongly linked to the malignant progression of LSCC. Functional studies revealed that miR-1207-5p upregulation suppressed LSCC cell proliferation, invasion, migration, and xenograft tumor growth. Bioinformatics analysis revealed that miR-1207-5p target genes were involved in cell cycle regulation, proliferation, adhesion, and the phosphatidylinositol 3-kinase (PI3K)/Akt pathway. Mechanistic studies revealed that miR-1207-5p interacts directly with the 3′ untranslated region of spindle and kinetochore associated complex subunit 3 (SKA3) and downregulates SKA3 expression. Furthermore, SKA3 was found to be overexpressed in LSCC, and its high expression was associated with tumor progression and a poor prognosis. Rescue experiments demonstrated that miR-1207-5p inhibited the malignant phenotypes of LSCC via SKA3. Furthermore, miR-1207-5p upregulation or knockdown of SKA3 inhibited the epithelial-mesenchymal transition (EMT). Collectively, miR-1207-5p inhibited LSCC malignant progression by downregulating SKA3 and preventing EMT. These findings provide new insights into the mechanism of LSCC progression, as well as new potential biomarkers and therapeutic targets for LSCC diagnosis and treatment.

MicroRNAs as a clue to overcome breast cancer treatment resistance

Breast cancer is the most frequent cancer in women worldwide. Despite the improvement in diagnosis and treatments, the rates of cancer relapse and resistance to therapies remain higher than desirable. Alterations in microRNAs have been linked to changes in critical processes related to cancer development and progression. Their involvement in resistance or sensitivity to breast cancer treatments has been documented by different in vivo and in vitro experiments. The most significant microRNAs implicated in modulating resistance to breast cancer therapies are summarized in this review. Resistance to therapy has been linked to cellular processes such as cell cycle, apoptosis, epithelial-to-mesenchymal transition, stemness phenotype, or receptor signaling pathways, and the role of microRNAs in their regulation has already been described. The modulation of specific microRNAs may modify treatment response and improve survival rates and cancer patients' quality of life. As a result, a greater understanding of microRNAs, their targets, and the signaling pathways through which they act is needed. This information could be useful to design new therapeutic strategies, to reduce resistance to the available treatments, and to open the door to possible new clinical approaches.

LINC01189-miR-586-ZEB1 feedback loop regulates breast cancer progression through Wnt/β-catenin signaling pathway

Non-coding RNAs play essential roles in breast cancer progression by regulating proliferation, differentiation, invasion, and metastasis. However, our understanding of most microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) in breast cancer is still limited. miR-586 has been identified as an important factor in the progression of some types of cancer, but its exact function and relative regulation mechanisms in breast cancer development need to be further investigated. In this study, we showed miR-586 functioned as an oncogene by promoting breast cancer proliferation and metastasis both in vitro and in vivo. Meanwhile, miR-586 induced Wnt/β-catenin activation by directly targeting Wnt/β-catenin signaling antagonists SFRP1 and DKK2/3. Moreover, we demonstrated that LINC01189 functioned as a tumor suppressor and inhibited breast cancer progression through inhibiting an epithelial-mesenchymal transition (EMT)-like phenotype by sponging miR-586. In addition, β-catenin/TCF4 transactivated ZEB1, resulting in a transcriptional repression of LINC01189 expression. In conclusion, our data uncovered the LINC01189-miR-586-ZEB1 feedback loop and provided a novel mechanism participating in the regulation of Wnt/β-catenin signaling in breast cancer progression.

A novel lncRNA derived from an ultraconserved region: lnc-uc.147, a potential biomarker in luminal A breast cancer

The human genome contains 481 ultraconserved regions (UCRs), which are genomic stretches of over 200 base pairs conserved among human, rat, and mouse. The majority of these regions are transcriptionally active (T-UCRs), and several have been found to be differentially expressed in tumours. Some T-UCRs have been functionally characterized, but of those few have been associated to breast cancer (BC). Using TCGA data, we found 302 T-UCRs related to clinical features in BC: 43% were associated with molecular subtypes, 36% with oestrogen-receptor positivity, 17% with HER2 expression, 12% with stage, and 10% with overall survival. The expression levels of 12 T-UCRs were further analysed in a cohort of 82 Brazilian BC patients using RT-qPCR. We found that uc.147 is high expressed in luminal A and B patients. For luminal A, a subtype usually associated with better prognosis, high uc.147 expression was associated with a poor prognosis and suggested as an independent prognostic factor. The lncRNA from uc.147 (lnc-uc.147) is located in the nucleus. Northern blotting results show that uc.147 is a 2,8 kb monoexonic trancript, and its sequence was confirmed by RACE. The silencing of uc.147 increases apoptosis, arrests cell cycle, and reduces cell viability and colony formation in BC cell lines. Additionally, we identifed 19 proteins that interact with lnc-uc.147 through mass spectrometry and demonstrated a high correlation of lnc-uc.147 with the neighbour gene expression and miR-18 and miR-190b. This is the first study to analyse the expression of all T-UCRs in BC and to functionally assess the lnc-uc.147.

MiR-30a-5p inhibits proliferation, migration and invasion of nasopharyngeal carcinoma cells by targeting NUCB2

BACKGROUND

Nasopharyngeal carcinoma (NPC) is a malignant head and neck tumor arising in the nasopharynx. MicroRNAs (miRNAs) are elucidated to exert tumor-suppressing function in human cancers. Numerous studies have manifested that miR-30a-5p serves as an anti-oncogene in various cancers.

OBJECTIVE

To research the biological function and molecular mechanism of miR-30a-5p in NPC.

METHODS

The morphology of NPC tissues was revealed by H&E staining. Transwell and wound healing assays were applied to investigate the effects of miR-30a-5p on NPC cell migration. The binding interaction between miR-30a-5p and nucleobindin 2 (NUCB2) was identified by luciferase reporter assay. Xenograft nude mice were used to detect the influence of miR-30a-5p on NPC tumor growth.

RESULTS

MiR-30a-5p was downregulated in NPC tissues and cells. The overexpression ofmiR-30a-5p inhibited proliferation, migration and invasion abilities of NPC cells. Moreover, NUCB2 was revealed to be a downstream target gene of miR-30a-5p, and knockdown of NUCB2 repressed the malignant behaviors of NPC cells and tumor growth. Additionally, rescue experiments revealed that miR-30a-5p suppressed the proliferation, migration and invasion of NPC cells via targeting NUCB2 in vitro. Meanwhile, in vivo assays depicted that NUCB2 overexpression rescued the effects induced by miR-30a-5p upregulation on tumor growth.

CONCLUSION

MiR-30a-5p modulates NPC progression by targeting NUCB2. These findings lay a foundation for exploring the clinical treatment of NPC.

Interplay between SOX9 transcription factor and microRNAs in cancer

SOX transcription factors are critical regulators of development, homeostasis and disease progression and their dysregulation is a common finding in various cancers. SOX9 belongs to SOXE family located on chromosome 17. MicroRNAs (miRNAs) possess the capacity of regulating different transcription factors in cancer cells by binding to 3'-UTR. Since miRNAs can affect differentiation, migration, proliferation and other physiological mechanisms, disturbances in their expression have been associated with cancer development. In this review, we evaluate the relationship between miRNAs and SOX9 in different cancers to reveal how this interaction can affect proliferation, metastasis and therapy response of cancer cells. The tumor-suppressor miRNAs can decrease the expression of SOX9 by binding to the 3'-UTR of mRNAs. Furthermore, the expression of downstream targets of SOX9, such as c-Myc, Wnt, PI3K/Akt can be affected by miRNAs. It is noteworthy that other non-coding RNAs including lncRNAs and circRNAs regulate miRNA/SOX9 expression to promote/inhibit cancer progression and malignancy. The pre-clinical findings can be applied as biomarkers for diagnosis and prognosis of cancer patients.

miR-190 promotes malignant transformation and progression of human urothelial cells through CDKN1B/p27 inhibition

Background

Although miR-190 has been reported to be related to human diseases, especially in the development and progression of cancer, its expression in human bladder cancer (BC) and potential contribution to BC remain unexplored.

Methods

RT-qPCR was used to verify the expression level of miR-190 and CDKN1B. Flow cytometry (FCM) assays were performed to detect cell cycle. Soft agar assay was used to measure anchorage-independent growth ability. Methylation-Specific PCR, Dual-luciferase reporter assay and Western blotting were used to elucidate the potential mechanisms involved.

Results

Our studies revealed that downregulation of the p27 (encoded by CDKN1B gene) protein is an important event related to miR-190, promoting the malignant transformation of bladder epithelial cells. miR-190 binds directly to CDKN1B 3’-UTR and destabilizes CDKN1B mRNA. Moreover, miR-190 downregulates TET1 by binding to the TET1 CDS region, which mediates hypermethylation of the CDKN1B promoter, thereby resulting in the downregulation of CDKN1B mRNA. These two aspects led to miR-190 inhibition of p27 protein expression in human BC cells. A more in-depth mechanistic study showed that c-Jun promotes the transcription of Talin2, the host gene of miR-190, thus upregulating the expression of miR-190 in human BC cells.

Conclusions

In this study, we found that miR-190 plays an important role in the development of BC. Taken together, these findings indicate that miR-190 may promote the malignant transformation of human urothelial cells by downregulating CDKN1B, which strengthens our understanding of miR-190 in regulating BC cell transformation.

Bone marrow mesenchymal stem cells-derived exosomal microRNA-19b-1-5p reduces proliferation and raises apoptosis of bladder cancer cells via targeting ABL2

BACKGROUND

Exosomes are involved in intercellular communication via specialized molecular cargo, such as microRNAs (miRNAs). However, the mechanisms underlying exosomal miR-19b-1-5p in bladder cancer remain largely unknown, thus, we aim to investigate the effect of exosomal miR-19b-1-5p on bladder cancer with the involvement of non-receptor protein tyrosine kinase Arg (ABL2).

METHODS

miR-19b-1-5p and ABL2 expression were tested in bladder cancer. miR-19b-1-5p inhibition/elevation assays were conducted to determine its role in bladder cancer. Exosomes were extracted from bone marrow mesenchymal stem cells (BMSCs). Exosomes and T24 cells were co-cultured to verify their function in biological characteristics of bladder cancer cells.

RESULTS

miR-19b-1-5p was down-regulated while ABL2 was upregulated in bladder cancer. Exosomal miR-19b-1-5p suppressed malignant behaviors of bladder cancer cells, and also inhibited tumor growth in vivo. Up-regulated ABL2 mitigated the effects of miR-19b-1-5p up-regulation on bladder cancer cells.

CONCLUSION

BMSCs-derived exosomal miR-19b-1-5p suppresses bladder cancer growth via decreasing ABL2.

Novel molecular regulators of breast cancer stem cell plasticity and heterogeneity

Tumors consist of heterogeneous cell populations, and tumor heterogeneity plays key roles in regulating tumorigenesis, metastasis, recurrence and resistance to anti-tumor therapies. More and more studies suggest that cancer stem cells (CSCs) promote tumorigenesis, metastasis, recurrence and drug resistance as well as are the major source for heterogeneity of cancer cells. CD24^-CD44⁺ and ALDH⁺ are the most common markers for breast cancer stem cells (BCSCs). Previous studies showed that different BCSC markers label different BCSC populations, indicating the heterogeneity of BCSCs. Therefore, defining the regulation mechanisms of heterogeneous BCSCs is essential for precisely targeting BCSCs and treating breast cancer. In this review, we summarized the novel regulators existed in BCSCs and their niches for BCSC heterogeneity which has been discovered in recent years, and discussed their regulation mechanisms and the latest corresponding cancer treatments, which will extend our understanding on BCSC heterogeneity and plasticity, and provide better prognosis prediction and more efficient novel therapeutic strategies for breast cancer.

Oleanolic acid inhibits osteosarcoma cell proliferation and invasion by suppressing the SOX9/Wnt1 signaling pathway

Osteosarcoma is the most common primary bone malignancy in children and adolescents. Inhibition of SOX9/Wnt1-mediated signaling might suppress osteosarcoma metastasis, and oleanolic acid (OA) might decrease the activity of the SOX9/Wnt1 signaling pathway. The aim of the present study was to determine the role of OA in osteosarcoma cell proliferation and invasion. Osteosarcoma cell lines (KHOS and U2OS) and an osteoblastic cell line (hFOB1.19) were used for cell viability, proliferation and invasion analysis. The data suggested that OA significantly inhibited cell viability on days 3, 4 and 5 compared with the control (Ctrl) group in both U2OS and KHOS cells. Cell proliferation in the OA-treated group was significantly decreased compared with the Ctrl group in the osteosarcoma cell lines. Analysis of the cell cycle indicated that OA significantly reduced the percentage of U2OS and KHOS cells in the S phase compared with the Ctrl group. The wound healing assay results indicated that the OA group displayed significantly decreased cell re-colonization of the wound at 48 h compared with the Ctrl group. The Transwell chamber assay results also indicated that cell invasion was significantly inhibited by OA compared with the Ctrl group. Furthermore, OA significantly increased osteosarcoma cell apoptosis compared with the Ctrl group. Similarly, the protein expression levels of SOX9 and Wnt1 were significantly decreased in OA-treated U2OS and KHOS cells compared with Ctrl cells. OA-mediated downregulation of Wnt1 expression was reversed following SOX9 small interfering RNA transfection. Collectively, the results indicated that OA inhibited SOX9/Wnt1-associated osteosarcoma cell proliferation, migration and invasion.

SOX9: An emerging driving factor from cancer progression to drug resistance

Dysregulation of transcription factors is one of the common problems in the pathogenesis of human cancer. Among them, SOX9 is one of the critical transcription factors involved in various diseases, including cancer. The expression of SOX9 is regulated by microRNAs (miRNAs), methylation, phosphorylation, and acetylation. Interestingly, SOX9 acts as a proto-oncogene or tumor suppressor gene, relying upon kinds of cancer. Recent studies have reported the critical role of SOX9 in the regulation of the tumor microenvironment (TME). Additionally, activation of SOX9 signaling or SOX9 regulated signaling pathways play a crucial role in cancer development and progression. Accumulating evidence also suggests that SOX9 acquires stem cell features to induce epithelial-mesenchymal transition (EMT). Moreover, SOX9 has been broadly studied in the field of cancer stem cell (CSC) and EMT in the last decades. However, the link between SOX9 and cancer drug resistance has only recently been discovered. Furthermore, its differential expression could be a potential biomarker for tumor prognosis and progression. This review outlined the various biological implications of SOX9 in cancer progression and cancer drug resistance and elucidated its signaling network, which could be a potential target for designing novel anticancer drugs.

MiRNA-190 exerts neuroprotective effects against ischemic stroke through Rho/Rho-kinase pathway

Ischemic stroke is an urgent public health concern and one of the major causes of deaths and disabilities over the world. MicroRNA (miRNA) has become a key mediator of cerebral ischemia-reperfusion (I/R) injuries. However, whether miR-190 is involved in cerebral I/R-induced neuronal damage remains unknown. This study was to investigate the role of miR-190 in the brain I/R injury. We divided the rats into sham, I/R, control, and miR-190-mim (miR-190 mimics) groups. Quantitative real-time polymerase chain reaction (qRT-PCR), Nissl staining, flow cytometry, and western blot were conducted to examine the expression of miR-190 and cell apoptosis in different groups. The results showed that the expression of miR-190 was greatly decreased in rats suffering with I/R. Overexpression of miR-190 significantly reduced the increased neurological scores, brain water contents, infarct volumes, and neuronal apoptosis in rats suffering with I/R. In addition, we found that the expression of RhoA and Rho kinase was greatly elevated in rats suffering with I/R. Bioinformatics analysis indicated that Rho was a target of miR-190. Moreover, overexpression of miR-190 significantly downregulated the increased mRNA and protein expression of Rho/Rho kinase and cell apoptosis, while inhibition of miR-190 further upregulated the increased mRNA and protein expression of Rho/Rho kinase and cell apoptosis in rats suffering with I/R. Furthermore, knockdown of Rho significantly downregulated the increased mRNA and protein expression of Rho/Rho kinase and cell apoptosis, while these effects were inhibited by miR-190 inhibitors in rats suffering with I/R. These results indicate that miR-190 confers protection against brain I/R damage by modulating Rho/Rho-kinase signaling.

Circular RNA circ_0032821 contributes to oxaliplatin (OXA) resistance of gastric cancer cells by regulating SOX9 via miR-515-5p

OBJECTIVES

Chemoresistance is one of the major obstacles for gastric cancer (GC) treatment. Exosome-mediated transfer of circular RNAs (circRNAs) is associated with the drug-resistance in GC. Circ_0032821 has been reported as an oncogene in GC. This study is designed to explore the function and mechanism of Exosomal circ_0032821 in oxaliplatin (OXA) resistance of GC.

RESULTS

Circ_0032821 was highly expressed in OXA-resistant GC cells, and exosomes secreted by OXA-resistant GC cells. Moreover, circ_0032821-containing exosomes secreted by OXA-resistant GC cells could boost OXA resistance, proliferation, migration, and invasion in OXA-sensitive GC cells. The mechanical analysis discovered that circ_0032821 acted as a sponge of miR-515-5p to regulate SOX9 expression. Circ_0032821 silencing and OXA treatment repressed tumor growth in the GC mice model.

CONCLUSIONS

Exosomal circ_0032821 boosted OXA resistance of GC cells partly by the miR-515-5p/SOX9 axis, hinting a promising therapeutic target for GC treatment.

Potential miRNAs for miRNA-Based Therapeutics in Breast Cancer

MicroRNAs (miRNAs) are small non-coding RNAs that can post-transcriptionally regulate the genes involved in critical cellular processes. The aberrant expressions of oncogenic or tumor suppressor miRNAs have been associated with cancer progression and malignancies. This resulted in the dysregulation of signaling pathways involved in cell proliferation, apoptosis and survival, metastasis, cancer recurrence and chemoresistance. In this review, we will first (i) provide an overview of the miRNA biogenesis pathways, and in vitro and in vivo models for research, (ii) summarize the most recent findings on the roles of microRNAs (miRNAs) that could potentially be used for miRNA-based therapy in the treatment of breast cancer and (iii) discuss the various therapeutic applications.

MiR-559 targets GP73 to suppress proliferation and invasion of hepatocellular carcinoma in vitro

Hepatocellular carcinoma (HCC) is one of the common malignant tumors with poor overall prognosis. As a tumor suppressor, the function of miR-559 in HCC is not clear. In this study, quantitative real-time PCR was carried out to measure the expression of miR-559 in HCC cell lines. The effects of miR-559 on HCC cell proliferation, migration, and invasion were evaluated through a series of functional assays. The mechanism through which miR-559 regulates HCC cells was investigated by dual-luciferase reporter assay and functional experiments. The results revealed that miR-559 expression was low in HCC cell lines. Upregulation of miR-559 suppressed HCC cell proliferation, migration, and invasion. Dual-luciferase reporter assay confirmed Golgi membrane protein 73 (GP73) as a target gene of miR-559. Moreover, miR-559 could negatively regulate GP73 expression in HCC cells. These results demonstrated that low-level expression of miR-559 was associated with HCC, and overexpression of miR-559 could inhibit HCC cell growth and invasion via targeting GP73.

DDP-resistant ovarian cancer cells-derived exosomal microRNA-30a-5p reduces the resistance of ovarian cancer cells to DDP

Exosomes carrying microRNAs (miRNAs) have been demonstrated to play critical roles in the regulation of development, growth and metastasis of cancer. Bioinformatic predictions identified differentially expressed SRY-box 9 (SOX9) in OC, and the regulatory miRNA miR-139-5p. Here, we aim to evaluate the function of exosomal miR-139-5p in the sensitivity of ovarian cancer (OC) cells to cis-diamminedichloroplatinum(II) (DDP). Expression pattern of miR-139-5p and SOX9 in ovarian cancer cells (SKOV3) and DDP-resistant cells (SKOV3/DDP) was identified using reverse transcription quantitative polymerase chain reaction and western blot analysis. The relationship between miR-139-5p and SOX9 was validated using a dual-luciferase reporter assay. SKOV3/DDP cell line was developed and introduced with miR-30a-5p mimic to analyse the effects of miR-30a-5p on resistance to DDP. The in vitro and in vivo effects of exosomal miR-30a-5p on resistance of SKOV3 cells to DDP were assessed in a co-culture system of exosomes and OC cells as well as in tumour-bearing nude mice. High expression of SOX9 and low expression of miR-30-5p were witnessed in OC. Furthermore, miR-30-5p, a downregulated miRNA in SKOV3/DDP cells, increased the rate of cell apoptosis and enhanced the sensitivity of SKOV3/DDP cells to DDP by targeting SOX9. Moreover, exosomes carrying miR-30a-5p were identified to sensitize SKOV3/DDP cells to DDP both in vitro and in vivo. These data together supported an important conclusion that DDP-resistant OC cell-derived exosomal miR-30a-5p enhanced cellular sensitivity to DDP, highlighting a potential strategy to overcome drug resistance.

Long noncoding RNA RHPN1-AS1 promotes colorectal cancer progression via targeting miR-7-5p/OGT axis

Background

Rhophilin Rho GTPase binding protein 1 antisense RNA 1 (RHPN1-AS1) is a newly discovered oncogene in several diseases, such as breast cancer, non-small cell lung cancer and uveal melanoma. Nevertheless, its molecular role in colorectal cancer (CRC) remains unknown. This paper explored the role of RHPN1-AS1 in CRC progression.

Methods

qRT-PCR was used to detect relevant RNAs expression. CCK-8, EdU, flow cytometry, Transwell and western blot assays were performed to investigate the function of RHPN1-AS1 in CRC cells. Xenograft model was constructed to evaluate the effects of RHPN1-AS1 on tumor growth in vivo. Mechanical experiments were performed to investigate the relationship between relative genes.

Results

RHPN1-AS1 was significantly overexpressed in CRC cell lines. Knockdown of RHPN1-AS1 could inhibit cell proliferation, while stimulating cell apoptosis in vitro. Cell migration and invasion abilities were greatly suppressed after silencing RHPN1-AS1. Besides, signal transducer and activator of transcription 3 (STAT3) served as transcription factor of RHPN1-AS1. Moreover, miR-7-5p was identified as a target of RHPN1-AS1 and was negatively regulated by RHPN1-AS1 in CRC. MiR-7-5p inhibition rescued the oncogenic function of RHPN1-AS1. Additionally, O-GlcNAcylation transferase (OGT) was the downstream target of miR-7-5p. OGT overexpression could abrogate the anti-tumor effects of RHPN1-AS1 knockdown on CRC.

Conclusion

RHPN1-AS1 regulates CRC by mediating OGT through sponging miR-7-5p, suggesting that RHPN1-AS1 might be a potential therapeutic target for CRC.

Cell-free miRNAs as non-invasive biomarkers in breast cancer: Significance in early diagnosis and metastasis prediction

Breast cancer is one of the genetic diseases causing a high mortality among women around the world. Despite the availability of advanced diagnostic tools and treatment strategies, the incidence of breast cancer is increasing every year. This is due to the lack of accurate and reliable biomarkers whose deficiency creates difficulty in early breast cancer recognition, subtypes determination, and metastasis prophecy. Although biomarkers such as ER, PR, Her2, Ki-67, and other genetic platforms e.g. MammaPrint®, Oncotype DX®, Prosigna® or EndoPredict® are available for determination of breast cancer diagnosis and prognosis. However, pertaining to heterogeneous nature, lack of sensitivity, and specificity of these markers, it is still incessant to overcome breast cancer burden. Therefore, a novel biomarker is urgently needed for therapeutic diagnosis and improving prognosis. Lately, it has become more evident that cell-free miRNAs might be useful as good non-invasive biomarkers that are associated with different events in carcinogenesis. For example, some known biomarkers such as miR-21, miR-23a, miR-34a are associated with molecular subtyping and different biomolecular aspects i.e. apoptosis, angiogenesis, metastasis, and miR-1, miR-10b, miR-16 are associated with drug response. Cell-free miRNAs present in human body fluids have proven to be potential biomarkers with significant prognostic and predictive values. Numerous studies have found a distinct expression profile of circulating miRNAs in breast tumour versus non-tumour and in early and advanced-stage, thus implicating its clinical relevance. This review article will highlight the importance of different cell-free miRNAs as a biomarker for early breast cancer detection, subtype classification, and metastasis forecast.

Identifying potential prognostic biomarkers in head and neck cancer based on the analysis of microRNA expression profiles in TCGA database

The present study aimed to identify sensitive, specific and independent prognostic biomarkers in head and neck cancer (HNC) based on microRNA expression profiles and other high‑throughput sequencing data in The Cancer Genome Atlas (TCGA) database. Identification of such prognostic biomarkers could provide insight into HNC diagnosis and treatment. The differential expression profiles of microRNAs between HNC tissues and adjacent cancer tissues in the TCGA database were analyzed (log fold‑change >2; P<0.01). Univariate and multivariate Cox regression analyses of the differentially expressed microRNAs were performed to determine those significantly related to the survival of patients with HNC. The identified microRNAs were verified by survival and receiver operating characteristic curve analyses. To better predict prognosis, a combined prognostic model (risk equation) was established based on the risk coefficient of each microRNA, calculated by a multivariate Cox regression analysis, and the risk score was calculated. To explore the signaling pathways related to prognosis, Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analyses were performed on the differentially expressed genes between the high‑risk and low‑risk groups, grouped according to the median risk score. A total of 89 differentially expressed microRNAs between HNC and adjacent cancer tissues were screened, 11 of which were identified as risk factors related to HNC survival by the univariate Cox regression analysis (P<0.05). The multivariate Cox regression analysis showed that three of the 11 microRNAs, hsa‑miR‑99a, hsa‑miR‑499a and hsa‑miR‑1911 (all P<0.01), were identified as independent risk factors significantly related to patient survival. The risk equation used was as follows: Risk score=(‑0.1597 x hsa‑miR‑99a) + (0.1871 x hsa‑miR‑499a) + (0.1033 x hsa‑miR‑1911). KEGG and GO analyses showed that the JAK‑STAT signaling pathway and some metabolic pathways were associated with HNC prognosis. The present study suggested that hsa‑miR‑99a, hsa‑miR‑499a and hsa‑miR‑1911 may serve as potential prognostic biomarkers in HNC.

Down-regulated lncRNA SBF2-AS1 inhibits tumorigenesis and progression of breast cancer by sponging microRNA-143 and repressing RRS1

Background

Recently, the roles of long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) in human diseases have been unveiled, this research was conducted to explore the impacts of lncRNA SET-binding factor 2-antisense RNA1 (SBF2-AS1), miR-143 and resistance to ralstonia solanacearum 1 (RRS1) on breast cancer (BC) development.

Methods

The expression of SBF2-AS1, miR-143 and RRS1 in BC tissues, as well as in MDA-MB-231 and MCF-7 cell lines were assessed. Subsequently, the cells were transfected with miR-143 mimics or/and silenced or overexpressed SBF2-AS1 plasmids, and their negative controls. Then the proliferation, colony formation ability, cell cycle arrest, apoptosis, invasion and migration of the cells were assessed through gain- and loss-of-function experiments. Furthermore, the tumor growth, ki-67 expression and apoptosis in vivo were observed by subcutaneous tumorigenesis in nude mice. Binding relation between SBF2-AS1 and miR-143, and that between miR-143 and RRS1 were confirmed.

Results

SBF2-AS1 and RRS1 were amplified, while miR-143 was reduced in BC tissues and cells. Reduced SBF2-AS1 and elevated miR-143 could repress the proliferation, invasion and migration via restraining RRS1 expression. Moreover, knockdown of SBF2-AS1 up-regulated miR-143 to promote the apoptosis of BC cells by downregulating RRS1, resulting in a prohibitive effect on the tumorigenesis and progression of BC. Results of in vivo experiments indicated that the inhibited SBF2-AS1 and overexpressed miR-143 could restrict BC cell proliferation and promote apoptosis, and decelerate tumor growth in xenografts.

Conclusion

We have discovered in this study that down-regulated SBF2-AS1 could inhibit tumorigenesis and progression of BC by up-regulation miR-143 and repressing RRS1, which provides basic therapeutic considerations for a novel target against BC.

LINC00665 promotes breast cancer progression through regulation of the miR-379-5p/LIN28B axis

Breast cancer is the most common malignant tumor among women worldwide. Although increasing evidence indicates that long noncoding RNAs (lncRNAs) play critical roles during breast tumorigenesis and progression, the involvement of most lncRNAs in breast cancer remains largely unknown. In the current study, we demonstrated that LINC00665 promotes breast cancer cell proliferation, migration, and invasion. Accumulating evidence indicates that many lncRNAs can function as endogenous miRNA sponges by competitively binding common miRNAs. In this study, we demonstrated that LINC00665 functions as a sponge for miR-379-5p, reducing the ability of miR-379-5p to repress LIN28B. LINC00665 promoted breast cancer progression and induced an epithelial-mesenchymal transition-like phenotype via the upregulation of LIN28B expression. Clinically, LINC00665 expression was increased but miR-379-5p expression was decreased in breast cancer tissues compared with that in normal breast tissues in the TCGA database. Furthermore, the expression of LINC00665 was negatively related with miR-379-5p expression. Collectively, our results reveal the LINC00665-miR-379-5p-LIN28B axis and shed light on breast cancer therapy.

SOX9: The master regulator of cell fate in breast cancer

SRY-related high-mobility group box 9 (SOX9) is an indispensable transcription factor that regulates multiple developmental pathways related to stemness, differentiation, and progenitor development. Previous studies have demonstrated that the SOX9 protein directs pathways involved in tumor initiation, proliferation, migration, chemoresistance, and stem cell maintenance, thereby regulating tumorigenesis as an oncogene. SOX9 overexpression is a frequent event in breast cancer (BC) subtypes. Of note, the molecular mechanisms and functional regulation underlying SOX9 upregulation during BC progression are still being uncovered. The focus of this review is to appraise recent advances regarding the involvement of SOX9 in BC pathogenesis. First, we provide a general overview of SOX9 structure and function, as well as its involvement in various kinds of cancer. Next, we discuss pathways of SOX9 regulation, particularly its miRNA-mediated regulation, in BC. Finally, we describe the involvement of SOX9 in BC pathogenesis via its regulation of pathways involved in regulating cancer hallmarks, as well as its clinical and therapeutic importance. In general, this review article aims to serve as an ample source of knowledge on the involvement of SOX9 in BC progression. Targeting SOX9 activity may improve therapeutic strategies to treat BC, but precisely inhibiting SOX9 using drugs and/or small peptides remains a huge challenge for forthcoming cancer research.

MicroRNA-139-3p Inhibits The Growth And Metastasis Of Ovarian Cancer By Inhibiting ELAVL1

Background

The aberrant expression of microRNA-139-3p (miR-139-3p) has been recently involved in the development of multiple tumor types, but its function in ovarian cancer remains not well investigated. In this study, we mainly investigated the function of miR-139-3p in the progression of ovarian cancer.

Methods

The levels of miR-139-3p in ovarian cancer cells and tissues were detected using quantitative real-time-PCR (qRT-PCR) assay. The proliferation, colony formation, migration and invasion of ovarian cancer cell were determined, respectively. A luciferase reporter assay was used to confirm ELAV Like RNA Binding Protein 1 (ELAVL1) was a target gene of miR-139-3p. The expression of ELAVL1 was detected using Western blotting and immunofluorescence staining assay. The roles of miR-139-3p on the growth and metastasis of ovarian cancer cell in vivo were explored using transplanted tumor model and experimental lung metastasis model.

Results

MiR-139-3p was down-regulated in ovarian cancer tissues and ovarian cancer cell lines (SK-OV-3, A2780 and OVCAR-3). Overexpression of miR-139-3p decreased the growth, colony formation, migration and invasiveness of SK-OV-3 and OVCAR-3 cells. Moreover, overexpression of miR-139-3p reduced the growth and lung metastasis of ovarian cancer cells in vivo. The luciferase reporter gene assay indicated that ELAVL1 was a target of miR-139-3p and its expression was negatively regulated by miR-139-3p. Furthermore, the expression of ELAVL1 was inversely correlated with miR-139-3p level in ovarian cancer tissue.

Conclusion

Taken together, we demonstrated that miR-139-3p regulated ovarian cancer growth and metastasis by modulating the expression of ELAVL1.

miR-190-5p in human diseases

miRNAs, a major class of small noncoding RNAs approximately 18-25 nucleotides in length, function by repressing the expression of target genes through binding to complementary sequences in the 3'-UTRs of target genes. Emerging evidence has highlighted their important roles in numerous diseases, including human cancers. Recently, miR-190 has been shown to be dysregulated in various types of human cancers that participates in cancer-related biological processes, including proliferation, apoptosis, metastasis, drug resistance, by regulating associated target genes, and to predict cancer diagnosis and prognosis. In this review, we summarized the roles of miR-190-5p in human diseases, especially in human cancers. Then we classified its target genes in tumorigenesis and progression, which might provide evidence for cancer diagnosis and prognosis, promising tools for cancer treatment, or leads for further investigation.

The Central Contributions of Breast Cancer Stem Cells in Developing Resistance to Endocrine Therapy in Estrogen Receptor (ER)-Positive Breast Cancer

Breast cancer stem cells (BCSC) play critical roles in the acquisition of resistance to endocrine therapy in estrogen receptor (ER)-positive (ER + ve) breast cancer (BC). The resistance results from complex alterations involving ER, growth factor receptors, NOTCH, Wnt/β-catenin, hedgehog, YAP/TAZ, and the tumor microenvironment. These mechanisms are likely converged on regulating BCSCs, which then drive the development of endocrine therapy resistance. In this regard, hormone therapies enrich BCSCs in ER + ve BCs under both pre-clinical and clinical settings along with upregulation of the core components of “stemness” transcriptional factors including SOX2, NANOG, and OCT4. SOX2 initiates a set of reactions involving SOX9, Wnt, FXY3D, and Src tyrosine kinase; these reactions stimulate BCSCs and contribute to endocrine resistance. The central contributions of BCSCs to endocrine resistance regulated by complex mechanisms offer a unified strategy to counter the resistance. ER + ve BCs constitute approximately 75% of BCs to which hormone therapy is the major therapeutic approach. Likewise, resistance to endocrine therapy remains the major challenge in the management of patients with ER + ve BC. In this review we will discuss evidence supporting a central role of BCSCs in developing endocrine resistance and outline the strategy of targeting BCSCs to reduce hormone therapy resistance.