Roles for miRNAs in endocrine resistance in breast cancer

Novel Endocrine Therapeutic Opportunities for Estrogen Receptor-Positive Ovarian Cancer-What Can We Learn from Breast Cancer?

Low-grade serous ovarian cancer (LGSOC) is a rare ovarian malignancy primarily affecting younger women and is characterized by an indolent growth pattern. It exhibits indolent growth and high estrogen/progesterone receptor expression, suggesting potential responsiveness to endocrine therapy. However, treatment efficacy remains limited due to the development of endocrine resistance. The mechanisms of resistance, whether primary or acquired, are still largely unknown and present a significant hurdle in achieving favorable treatment outcomes with endocrine therapy in these patients. In estrogen receptor-positive breast cancer, mechanisms of endocrine resistance have been largely explored and novel treatment strategies to overcome resistance have emerged. Considering the shared estrogen receptor positivity in LGSOC and breast cancer, we wanted to explore whether there are any parallel mechanisms of resistance and whether we can extend endocrine breast cancer treatments to LGSOC. This review aims to highlight the underlying molecular mechanisms possibly driving endocrine resistance in ovarian cancer, while also exploring the available therapeutic opportunities to overcome this resistance. By unraveling the potential pathways involved and examining emerging strategies, this review explores valuable insights for advancing treatment options and improving patient outcomes in LGSOC, which has limited therapeutic options available.

Dual-target inhibitors based on ERα: Novel therapeutic approaches for endocrine resistant breast cancer

Estrogen receptor alpha (ERα), a nuclear transcription factor, is a well-validated therapeutic target for more than 70% of all breast cancers (BCs). Antagonizing ERα either by selective estrogen receptor modulators (SERMs) or selective estrogen receptor degraders (SERDs) forms the foundation of endocrine therapy and has achieved great success in the treatment of ERα positive (ERα+) BCs. Unfortunately, despite initial effectiveness, endocrine resistance eventually emerges in up to 30% of ERα+ BC patients and remains a significant medical challenge. Several mechanisms implicated in endocrine resistance have been extensively studied, including aberrantly activated growth factor receptors and downstream signaling pathways. Hence, the crosstalk between ERα and another oncogenic signaling has led to surge of interest to develop combination therapies and dual-target single agents. This review briefly introduces the synergisms between ERα and another anticancer target and summarizes the recent advances of ERα-based dual-targeting inhibitors from a medicinal chemistry perspective. Accordingly, their rational design strategies, structure-activity relationships (SARs) and biological activities are also dissected to provide some perspectives on future directions for ERα-based dual target drug discovery in BC therapy.

MicroRNA regulation of the serine synthesis pathway in endocrine-resistant breast cancer cells

Despite the successful combination of therapies improving survival of estrogen receptor α (ER+) breast cancer patients with metastatic disease, mechanisms for acquired endocrine resistance remain to be fully elucidated. The RNA binding protein HNRNPA2B1 (A2B1), a reader of N(6)-methyladenosine (m6A) in transcribed RNA, is upregulated in endocrine-resistant, ER+ LCC9 and LY2 cells compared to parental MCF-7 endocrine-sensitive luminal A breast cancer cells. The miRNA-seq transcriptome of MCF-7 cells overexpressing A2B1 identified the serine metabolic processes pathway. Increased expression of two key enzymes in the serine synthesis pathway (SSP), phosphoserine aminotransferase 1 (PSAT1) and phosphoglycerate dehydrogenase (PHGDH), correlates with poor outcomes in ER+ breast patients who received tamoxifen (TAM). We reported that PSAT1 and PHGDH were higher in LCC9 and LY2 cells compared to MCF-7 cells and their knockdown enhanced TAM sensitivity in these-resistant cells. Here we demonstrate that stable, modest overexpression of A2B1 in MCF-7 cells increased PSAT1 and PHGDH and endocrine resistance. We identified four miRNAs downregulated in MCF-7-A2B1 cells that directly target the PSAT1 3'UTR (miR-145-5p and miR-424-5p), and the PHGDH 3'UTR (miR-34b-5p and miR-876-5p) in dual luciferase assays. Lower expression of miR-145-5p and miR-424-5p in LCC9 and ZR-75-1-4-OHT cells correlated with increased PSAT1 and lower expression of miR-34b-5p and miR-876-5p in LCC9 and ZR-75-1-4-OHT cells correlated with increased PHGDH. Transient transfection of these miRNAs restored endocrine-therapy sensitivity in LCC9 and ZR-75-1-4-OHT cells. Overall, our data suggest a role for decreased A2B1-regulated miRNAs in endocrine resistance and upregulation of the SSP to promote tumor progression in ER+ breast cancer.

Breast cancer: miRNAs monitoring chemoresistance and systemic therapy

With a high mortality rate that accounts for millions of cancer-related deaths each year, breast cancer is the second most common malignancy in women. Chemotherapy has significant potential in the prevention and spreading of breast cancer; however, drug resistance often hinders therapy in breast cancer patients. The identification and the use of novel molecular biomarkers, which can predict response to chemotherapy, might lead to tailoring breast cancer treatment. In this context, accumulating research has reported microRNAs (miRNAs) as potential biomarkers for early cancer detection, and are conducive to designing a more specific treatment plan by helping analyze drug resistance and sensitivity in breast cancer treatment. In this review, miRNAs are discussed in two alternative ways-as tumor suppressors to be used in miRNA replacement therapy to reduce oncogenesis and as oncomirs to lessen the translation of the target miRNA. Different miRNAs like miR-638, miR-17, miR-20b, miR-342, miR-484, miR-21, miR-24, miR-27, miR-23 and miR-200 are involved in the regulation of chemoresistance through diverse genetic targets. For instance, tumor-suppressing miRNAs like miR-342, miR-16, miR-214, and miR-128 and tumor-promoting miRNAs like miR101 and miR-106-25 cluster regulate the cell cycle, apoptosis, epithelial to mesenchymal transition and other pathways to impart breast cancer drug resistance. Hence, in this review, we have discussed the significance of miRNA biomarkers that could assist in providing novel therapeutic targets to overcome potential chemotherapy resistance to systemic therapy and further facilitate the design of tailored therapy for enhanced efficacy against breast cancer.

Therapeutic Delivery of Tumor Suppressor miRNAs for Breast Cancer Treatment

The death rate from breast cancer (BC) has dropped due to early detection and sophisticated therapeutic options, yet drug resistance and relapse remain barriers to effective, systematic treatment. Multiple mechanisms underlying miRNAs appear crucial in practically every aspect of cancer progression, including carcinogenesis, metastasis, and drug resistance, as evidenced by the elucidation of drug resistance. Non-coding RNAs called microRNAs (miRNAs) attach to complementary messenger RNAs and degrade them to inhibit the expression and translation to proteins. Evidence suggests that miRNAs play a vital role in developing numerous diseases, including cancer. They affect genes critical for cellular differentiation, proliferation, apoptosis, and metabolism. Recently studies have demonstrated that miRNAs serve as valuable biomarkers for BC. The contrast in the expression of miRNAs in normal tissue cells and tumors suggest that miRNAs are involved in breast cancer. The important aspect behind cancer etiology is the deregulation of miRNAs that can specifically influence cellular physiology. The main objective of this review is to emphasize the role and therapeutic capacity of tumor suppressor miRNAs in BC and the advancement in the delivery system that can deliver miRNAs specifically to cancerous cells. Various approaches are used to deliver these miRNAs to the cancer cells with the help of carrier molecules, like nanoparticles, poly D, L-lactic-co-glycolic acid (PLGA) particles, PEI polymers, modified extracellular vesicles, dendrimers, and liposomes. Additionally, we discuss advanced strategies of TS miRNA delivery techniques such as viral delivery, self-assembled RNA-triple-helix hydrogel drug delivery systems, and hyaluronic acid/protamine sulfate inter-polyelectrolyte complexes. Subsequently, we discuss challenges and prospects on TS miRNA therapeutic delivery in BC management so that miRNAs will become a routine technique in developing individualized patient profiles.

Comprehensive analysis of long noncoding RNAs and lncRNA-mRNA networks in snakehead (Channa argus) response to Nocardia seriolae infection

Evidence has been demonstrated that lncRNAs are involved in a variety of immune responses in vertebrate. It has been demonstrated that immune-related lncRNAs play vital functions in immune regulation against infections in teleost. Nocardia seriolae, as one of the Gram-positive bacteria, can cause chronic systemic granulomatous disease for snakehead (Channa argus). However, how lncRNAs function in the immune regulation process once snakehead was infected with N. seriolae infection has not been studied so far. Accordingly, transcription landscapes of lncRNAs and mRNAs in snakehead were investigated. A total of 1,991 lncRNA were obtained. Totally, we predicted 57,584 co-expression and 16,047 co-location lncRNA-mRNA pairs. To further analyze the potential function of these lncRNAs, GO enrichment analysis and KEGG signal pathways were performed on the target mRNAs of these differently expressed lncRNAs, suggesting that lncRNAs may play essential roles in modulating mRNA expression levels, and subsequently trigger downstream immune signaling pathways to regulate the immune response in snakehead. In addition, 9 DEmRNA and 3 lncRNAs were randomly selected for qRT-PCR analyzed, which confirmed the accuracy of transcriptome data. These results can provide novel knowledge about lncRNAs in immune responses process in snakehead, and can serve as important resources for further investigating the roles of lncRNAs during pathogen infections in teleost.

Breast cancer: molecular mechanisms of underlying resistance and therapeutic approaches

Breast cancer (BC) affects over 250,000 women in the US each year. Drug-resistant cancer cells are responsible for most breast cancer fatalities. Scientists are developing novel chemotherapeutic drugs and targeted therapy combinations to overcome cancer cell resistance. Combining drugs can reduce the chances of a tumor developing resistance to treatment. Clinical research has shown that combination chemotherapy enhances or improves survival, depending on the patient's response to treatment. Combination therapy is a highly successful supplemental cancer treatment. This review sheds light on intrinsic resistance to BC drugs and the importance of combination therapy for BC treatment. In addition to recurrence and metastasis of BC, the article discussed biomarkers for BC.

Effects of iron modulation on mesenchymal stem cell-induced drug resistance in estrogen receptor-positive breast cancer

Patients with estrogen receptor-positive (ER+) breast cancer, the most common subtype, remain at risk for lethal metastatic disease years after diagnosis. Recurrence arises partly because tumor cells in bone marrow become resistant to estrogen-targeted therapy. Here, we utilized a co-culture model of bone marrow mesenchymal stem cells (MSCs) and ER+ breast cancer cells to recapitulate interactions of cancer cells in bone marrow niches. ER+ breast cancer cells in direct contact with MSCs acquire cancer stem-like (CSC) phenotypes with increased resistance to standard antiestrogenic drugs. We confirmed that co-culture with MSCs increased labile iron in breast cancer cells, a phenotype associated with CSCs and disease progression. Clinically approved iron chelators and in-house lysosomal iron-targeting compounds restored sensitivity to antiestrogenic therapy. These findings establish iron modulation as a mechanism to reverse MSC-induced drug resistance and suggest iron modulation in combination with estrogen-targeted therapy as a promising, translatable strategy to treat ER+ breast cancer.

microRNA-221 and tamoxifen resistance in luminal-subtype breast cancer patients: A case-control study

Background

Around 70% of breast cancers (BCs) are estrogen receptor-α (ERα)-positive. Adjuvant endocrine therapy is used to reduce estrogen levels and inhibit signal transduction through the ER. The anti-estrogen drugs that are most commonly used in endocrine therapy belong to the selective ER modulator (SERM) class and include tamoxifen. Although it has been used for three decades in cases of early-stage and ERα-positive BC, resistance to tamoxifen is a common problem. microRNAs (miRNAs) have a potential role in demonstrating BC resistance to tamoxifen therapy. Hence, there is a need to investigate the expression of miRNA-221 (miR-221) in luminal-subtype BC patients receiving tamoxifen therapy.

Methods

This case-control study investigated luminal-subtype BC patients who had undergone endocrine therapy for at least 1 year. The case group comprised patients with local or metastatic recurrence, and the control group comprised patients without local or metastatic recurrence.

Results

There was a significant difference in miR-221 expression (p = 0.005) between the case and control groups. There were no significant differences between the groups that were positive and negative for the progesterone receptor (PR) (p = 0.25), had high and low marker of proliferation Ki-67 levels (p = 0.60), were positive and negative for lymphovascular invasion (p = 0.14), and had stage 2 and stage 3 cancer (p = 0.25).

Conclusion

miR-221 expression was higher in tamoxifen-resistant BC cases. miR-221 is a potential biomarker of tamoxifen resistance.

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Tamoxifen is used to treat early-stage and estrogen receptor-α-positive breast cancer.

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Resistance to tamoxifen is a common problem.

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Serum microRNA-221 levels were higher in patients with local recurrence and metastasis.

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microRNA-221 is a potential serum biomarker of tamoxifen resistance.

Advances of Exosomal miRNAs in Breast Cancer Progression and Diagnosis

Breast cancer is one of the most commonly diagnosed malignancies and the leading cause of cancer death in women worldwide. Although many factors associated with breast cancer have been identified, the definite etiology of breast cancer is still unclear. In addition, early diagnosis of breast cancer remains challenging. Exosomes are membrane-bound nanovesicles secreted by most types of cells and contain a series of biologically important molecules, such as lipids, proteins, and miRNAs, etc. Emerging evidence shows that exosomes can affect the status of cells by transmitting substances and messages among cells and are involved in various physiological and pathological processes. In breast cancer, exosomes play a significant role in breast tumorigenesis and progression through transfer miRNAs which can be potential biomarkers for early diagnosis of breast cancer. This review discusses the potential utility of exosomal miRNAs in breast cancer progression such as tumorigenesis, metastasis, immune regulation and drug resistance, and further in breast cancer diagnosis.

MicroRNA Expression Profiles and Breast Cancer Chemotherapy

Breast cancer is the most common malignancy diagnosed in women. Traditionally, radical surgical resection was the cornerstone of breast cancer management, with limited exceptions. In recent times, our enhanced appreciation of the biomolecular characteristics of breast cancer has transformed the treatment paradigm to include prescription of chemotherapeutical agents, radiotherapies, targeted therapies, as well as more refined surgical approaches. While treatments with such modalities have enhanced clinico-oncological outcomes for breast cancer patients, the efforts of oncological and translational research have concentrated on the identification of novel biomarkers which may successfully inform prognosis and response to therapies, improve current therapeutic strategies, and enhance prognostication. Mi(cro)RNAs are small, non-coding molecules which are known to play regulatory roles in governing gene expression and cellular activity. Measurement of miRNA expression profiles have been illustrated to inform the response to therapies, such as conventional chemotherapy, and are currently undergoing assessment as means of enhancing treatment strategies with these cytotoxic agents. Herein, this review outlines how chemotherapy prescription has revolutionised breast cancer treatment and illustrates the novel role of miRNAs as biomarkers capable of enhancing current therapeutic strategies using chemotherapy in patients being treated with curative intent for breast cancer.

Nuclear Mechanisms Involved in Endocrine Resistance

Endocrine therapy is a standard treatment offered to patients with ERα (estrogen receptor α)-positive breast cancer. In endocrine therapy, ERα is either directly targeted by anti-estrogens or indirectly by aromatase inhibitors which cause estrogen deficiency. Resistance to these drugs (endocrine resistance) compromises the efficiency of this treatment and requires additional measures. Endocrine resistance is often caused by deregulation of the PI3K/AKT/mTOR pathway and/or cyclin-dependent kinase 4 and 6 activities allowing inhibitors of these factors to be used clinically to counteract endocrine resistance. The nuclear mechanisms involved in endocrine resistance are beginning to emerge. Exploring these mechanisms may reveal additional druggable targets, which could help to further improve patients' outcome in an endocrine resistance setting. This review intends to summarize our current knowledge on the nuclear mechanisms linked to endocrine resistance.

HOTAIR Facilitates Endocrine Resistance in Breast Cancer Through ESR1/miR-130b-3p Axis: Comprehensive Analysis of mRNA-miRNA-lncRNA Network

Background

To summarize the regulatory role of mRNA-miRNA-lncRNA network associated with endocrine therapy resistance (ETR) in breast cancer.

Methods

We analyzed the differentially expressed genes (DEGs), differentially expressed lncRNAs (DELs), and differentially expressed miRNAs (DEMs) in long-term estrogen-deprived (LTED) estrogen receptor (ER)-positive breast cancer cells (LTED MCF7) (modeling relapse on endocrine therapy) and MCF7 cells in the presence of estrogen (E2) (modeling a patient at primary diagnosis) by mining GSE120929 and GSE120930 datasets. The mRNA-miRNA-lncRNA network was constructed by multiple bioinformatic tools. The prognosis of genes from the network was validated in breast cancer patients with following systemic treatment (endocrine therapy) by GEPIA, Kaplan–Meier plotter and UALCAN database.

Results

Totally, 769 DEGs, 33 DEMs, and 10 DELs were selected. The mRNA-miRNA-lncRNA network was established including 60 mRNA nodes, 6 miRNA nodes and 3 lncRNA nodes. A significant module containing 3 nodes and 3 edges was calculated based on the mRNA-miRNA-lncRNA network. The hub genes in the network are ABCG2, ESR1 and GJA1. ESR1/miR-130b-3p/HOTAIR are significantly correlated with the prognosis of breast cancer patients with endocrine therapy.

Conclusion

This study provides a novel ETR-related mRNA-miRNA-lncRNA network. Further, we suggest that ESR1/miR-130b-3p/HOTAIR may be promising targets for clinical treatment of endocrine therapy-resistant breast cancer.

MicroRNAs as Potential Predictors of Response to CDK4/6 Inhibitor Treatment

Simple Summary

MicroRNAs are endogenous non-coding 20–22 nucleotide long RNAs that play a fundamental role in the post-transcriptional control of gene expression. Consequently, microRNAs are involved in multiple biological processes of cancer and could be used as biomarkers with prognostic and predictive significance. Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors have become a mainstay of treatment for patients with advanced hormone receptor-positive (HR) breast cancer. Despite the initial high response rates, approximately 10% of patients demonstrate primary resistance to CDK4/6 inhibitors while acquired resistance is almost inevitable. Considering the fundamental role of miRNAs in tumorigenesis, we aimed to explore the potential involvement of microRNAs in response to CDK4/6 inhibition in solid tumors. A number of microRNAs were shown to confer resistance or sensitivity to CDK4/6 inhibitors in preclinical studies, although this remains to be proved in human studies.

Abstract

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors have emerged as novel treatment options in the management of advanced or metastatic breast cancer. MicroRNAs are endogenous non-coding 19–22-nucleotide-long RNAs that regulate gene expression in development and tumorigenesis. Herein, we systematically review all microRNAs associated with response to CDK4/6 inhibitors in solid tumors and hematological malignancies. Eligible articles were identified by a search of the MEDLINE and ClinicalTrials.gov databases for the period up to1 January 2021; the algorithm consisted of a predefined combination of the words “microRNAs”, “cancer” and “CDK 4/6 inhibitors”. Overall, 15 studies were retrieved. Six microRNAs (miR-126, miR-326, miR3613-3p, miR-29b-3p, miR-497 and miR-17-92) were associated with sensitivity to CDK4/6 inhibitors. Conversely, six microRNAs (miR-193b, miR-432-5p, miR-200a, miR-223, Let-7a and miR-21) conferred resistance to treatment with CDK4/6 inhibitors. An additional number of microRNAs (miR-124a, miR9, miR200b and miR-106b) were shown to mediate cellular response to CDK4/6 inhibitors without affecting sensitivity to treatment. Collectively, our review provides evidence that microRNAs could serve as predictive biomarkers for treatment with CDK4/6 inhibitors. Moreover, microRNA-targeted therapy could potentially maximize sensitivity to CDK4/6 inhibition.

Identification and Roles of miR-29b-1-3p and miR29a-3p-Regulated and Non-Regulated lncRNAs in Endocrine-Sensitive and Resistant Breast Cancer Cells

Despite improvements in the treatment of endocrine-resistant metastatic disease using combination therapies in patients with estrogen receptor α (ERα) primary tumors, the mechanisms underlying endocrine resistance remain to be elucidated. Non-coding RNAs (ncRNAs), including microRNAs (miRNA) and long non-coding RNAs (lncRNA), are targets and regulators of cell signaling pathways and their exosomal transport may contribute to metastasis. Previous studies have shown that a low expression of miR-29a-3p and miR-29b-3p is associated with lower overall breast cancer survival before 150 mos. Transient, modest overexpression of miR-29b1-3p or miR-29a-3p inhibited MCF-7 tamoxifen-sensitive and LCC9 tamoxifen-resistant cell proliferation. Here, we identify miR-29b-1/a-regulated and non-regulated differentially expressed lncRNAs in MCF-7 and LCC9 cells using next-generation RNA seq. More lncRNAs were miR-29b-1/a-regulated in LCC9 cells than in MCF-7 cells, including DANCR, GAS5, DSCAM-AS1, SNHG5, and CRND. We examined the roles of miR-29-regulated and differentially expressed lncRNAs in endocrine-resistant breast cancer, including putative and proven targets and expression patterns in survival analysis using the KM Plotter and TCGA databases. This study provides new insights into lncRNAs in endocrine-resistant breast cancer.

Tamoxifen resistance alters sensitivity to 5-fluorouracil in a subset of estrogen receptor-positive breast cancer

Sequential treatment with endocrine or chemotherapy is generally used in the treatment of estrogen receptor (ER)-positive recurrent breast cancer. To date, few studies have investigated the effect of long-term endocrine therapy on the response to subsequent chemotherapy in ER-positive breast cancer. We examined whether a preceding endocrine therapy affects the sensitivity to subsequent chemotherapy in ER-positive breast cancer cells. Three ER-positive breast cancer cell lines (T47D, MCF7, BT474) and tamoxifen-resistant sublines (T47D/T, MCF7/T, BT474/T) were analyzed for sensitivity to 5-fluorouracil, paclitaxel, and doxorubicin. The mRNA levels of factors related to drug sensitivity were analyzed by RT-PCR. MCF7/T cells became more sensitive to 5-fluorouracil than wild-type (wt)-MCF7 cells. In addition, the apoptosis induced by 5-fluorouracil was significantly increased in MCF7/T cells. However, no difference in sensitivity to chemotherapeutic agents was observed in T47D/T and BT474/T cells compared with their wt cells. Dihydropyrimidine dehydrogenase (DPYD) mRNA expression was significantly decreased in MCF7/T cells compared with wt-MCF7 cells. The expression of DPYD mRNA was restored with 5-azacytidine treatment in MCF7/T cells. In addition, DPYD 3'-UTR luciferase activity was significantly reduced in MCF7/T cells. These data indicated that the expression of DPYD mRNA was repressed by methylation of the DPYD promoter region and post-transcriptional regulation by miRNA in MCF7/T cells. In the mouse xenograft model, capecitabine significantly reduced the tumor volume in MCF7/T compared with MCF7. The results of this study indicate that endocrine therapy could alter the sensitivity to chemotherapeutic agents in a subset of breast cancers, and 5-fluorouracil may be effective in tamoxifen-resistant breast cancers.

Regulatory Interplay between miR-181a-5p and Estrogen Receptor Signaling Cascade in Breast Cancer

Simple Summary

Despite huge efforts in breast cancer care programs, patient’s survival rates greatly vary. Differences in response to therapy still represent the major challenge for clinicians and biologists. Define new anticancer mechanisms and innovative predictors for resistance could be a valid strategy to permanently defeat breast cancer. Here we propose the epigenetic based reprogramming of breast cancer, which leverages on the crosstalk between miR-181a-5p and Estrogen Receptor α. This simultaneously approach allows to induce miR-181a-5p and reduce the receptor expression, blocking the estrogen-dependent proliferative pathway underlying breast cancer progression. Since the epigenetic approach insists on transcriptional regulation, it is mostly independent of the acquired resistance mechanisms typically induced by prolonged endocrine therapy and therefore can be used as a sensitizer, neoadjuvant, or in combination with the standard in care treatments against breast cancer.

Abstract

The efficacy and side effects of endocrine therapy in breast cancer (BC) depend largely on estrogen receptor alpha (ERα) expression, the specific drug administered, and treatment scheduling. Although the benefits of endocrine therapy outweigh any adverse effects in the initial stages of BC, later- or advanced-stage tumors acquire resistance to treatments. The mechanisms underlying tumor resistance to therapy are still not well understood, posing a major challenge for BC patient care. Epigenetic regulation and miRNA expression may be involved in the switch from a treatment-sensitive to a treatment-resistant state and could provide a valid therapeutic strategy for ERα negative BC. Here, a hybrid lysine-specific histone demethylase inhibitor, MC3324, displaying selective estrogen receptor down-regulator-like activities in BC, was used to highlight the interplay between epigenetic and ERα signaling. MC3324 anticancer action is mediated by microRNA (miRNA) expression regulation, indicating an innovative function for this molecule. Integrated analysis suggests a crosstalk between estrogen signaling, ERα interactors, miRNAs, and their putative targets. Specifically, miR-181a-5p expression is regulated by MC3324 and has an impact on cellular levels of ERα. A comparison of breast tumor versus healthy mammary tissues confirmed the important role of miR-181a-5p in ERα regulation and points to its putative predictive function in BC therapy.

Regulation of breast cancer metastasis signaling by miRNAs

Despite the decline in death rate from breast cancer and recent advances in targeted therapies and combinations for the treatment of metastatic disease, metastatic breast cancer remains the second leading cause of cancer-associated death in U.S. women. The invasion-metastasis cascade involves a number of steps and multitudes of proteins and signaling molecules. The pathways include invasion, intravasation, circulation, extravasation, infiltration into a distant site to form a metastatic niche, and micrometastasis formation in a new environment. Each of these processes is regulated by changes in gene expression. Noncoding RNAs including microRNAs (miRNAs) are involved in breast cancer tumorigenesis, progression, and metastasis by post-transcriptional regulation of target gene expression. miRNAs can stimulate oncogenesis (oncomiRs), inhibit tumor growth (tumor suppressors or miRsupps), and regulate gene targets in metastasis (metastamiRs). The goal of this review is to summarize some of the key miRNAs that regulate genes and pathways involved in metastatic breast cancer with an emphasis on estrogen receptor α (ERα+) breast cancer. We reviewed the identity, regulation, human breast tumor expression, and reported prognostic significance of miRNAs that have been documented to directly target key genes in pathways, including epithelial-to-mesenchymal transition (EMT) contributing to the metastatic cascade. We critically evaluated the evidence for metastamiRs and their targets and miRNA regulation of metastasis suppressor genes in breast cancer progression and metastasis. It is clear that our understanding of miRNA regulation of targets in metastasis is incomplete.

Role of miRNAs in regulating responses to radiotherapy in human breast cancer

Breast cancer is the most common type of cancer that affects females globally. Radiotherapy is a standard treatment option for breast cancer, where one of its most significant limitations is radioresistance development. MicroRNAs (miRNAs) are small, non-protein-coding RNAs that have been widely studied for their roles as disease biomarkers. To date, several in vitro, in vivo, and clinical studies have reported the roles of miRNAs in regulating radiosensitivity and radioresistance in breast cancer cells. This article reviews the roles of miRNAs in regulating treatment response toward radiotherapy and the associating cellular pathways. We identified 36 miRNAs that play a role in mediating radio-responses; 22 were radiosensitizing, 12 were radioresistance-promoting, and two miRNAs were reported to promote both effects. A brief overview of breast cancer therapy options, mechanism of action of radiation, and molecular mechanism of radioresistance was provided in this article. A summary of the latest clinical researches involving miRNAs in breast cancer radiotherapy was also included.

Epigenetic and breast cancer therapy: Promising diagnostic and therapeutic applications

The global burden of breast cancer (BC) is increasing significantly. This trend is caused by several factors such as late diagnosis, limited treatment options for certain BC subtypes, drug resistance which all lead to poor clinical outcomes. Recent research has reported the role of epigenetic alterations in the mechanism of BC pathogenesis and its hallmarks include drug resistance and stemness features. The understanding of these modifications and their significance in the management of BC carcinogenesis is challenging and requires further attention. Nevertheless, it promises to provide novel insight needed for utilizing these alterations as potential diagnostic, prognostic markers, predict treatment efficacy, as well as therapeutic agents. This highlights the importance of continuing research development to further advance the existing knowledge on epigenetics and BC carcinogenesis to overcome the current challenges. Hence, this review aims to shed light and discuss the current state of epigenetics research in the diagnosis and management of BC.

Long Non-Coding RNA HOTAIR in Breast Cancer Therapy

Breast cancer (BC) is the most common cancer type among women, and morbidity and mortality rates are still very high. Despite new innovative therapeutic approaches for all BC molecular subtypes, the discovery of new molecular biomarkers involved in tumor progression has been fundamental for the implementation of personalized treatment strategies and improvement of patient management. Many experimental studies indicate that long non-coding RNAs (lncRNAs) are strongly involved in BC initiation, metastatic progression, and drug resistance. In particular, aberrant expression of HOX transcript antisense intergenic RNA (HOTAIR) lncRNA plays an important role in BC contributing to its progression and represents a predictor of BC metastasis. For its proven prognostic value, HOTAIR could represent a potential therapeutic target in BC. In the present review, we summarize the role of HOTAIR in cancer progression and drug resistance, in particular in BC, and we illustrate the main approaches for silencing it.

Estrogen Receptor α (ERα)-targeting Compounds and Derivatives: Recent Advances in Structural Modification and Bioactivity

Breast cancer is the most common cancer suffered by female, and the second highest cause of cancer-related death among women worldwide. At present, hormone therapy is still the main treatment route and can be divided into three main categories: selective estrogen receptor modulators (SERMs), selective estrogen receptor downregulators (SERDs), and aromatase inhibitors (AIs). However, breast cancer is difficult to cure even after several rounds of anti-estrogen therapy and most drugs have serious side-effects. Here, we review the literature published over the past five years regarding the isolation and synthesis of analogs and their derivatives.

Predictive and Prognostic Value of Selected MicroRNAs in Luminal Breast Cancer

Breast cancer (BrC) is the most frequent malignancy and the leading cause of cancer death among women worldwide. Approximately 70% of BrC are classified as luminal-like subtype, expressing the estrogen receptor. One of the most common and effective adjuvant therapies for this BrC subtype is endocrine therapy. However, its effectiveness is limited, with relapse occurring in up to 40% of patients. Because microRNAs have been associated with several mechanisms underlying endocrine resistance and sensitivity, they may serve as predictive and/or prognostic biomarkers in this setting. Hence, the main goal of this study was to investigate whether miRNAs deregulated in endocrine-resistant BrC may be clinically relevant as prognostic and predictive biomarkers in patients treated with adjuvant endocrine therapy. A global expression assay allowed for the identification of microRNAs differentially expressed between luminal BrC patients with or without recurrence after endocrine adjuvant therapy. Then, six microRNAs were chosen for validation using quantitative reverse transcription polymerase chain reaction in a larger set of tissue samples. Thus, miR-30c-5p, miR-30b-5p, miR-182-5p, and miR-200b-3p were found to be independent predictors of clinical benefit from endocrine therapy. Moreover, miR-182-5p and miR-200b-3p displayed independent prognostic value for disease recurrence in luminal BrC patients after endocrine therapy. Our results indicate that selected miRNAs’ panels may constitute clinically useful ancillary tools for management of luminal BrC patients. Nevertheless, additional validation, ideally in a multicentric setting, is required to confirm our findings.

Effect of a high-intensity interval training on serum microRNA levels in women with breast cancer undergoing hormone therapy. A single-blind randomized trial

BACKGROUND

The role of microRNAs (miRs) in hormone therapy (HT) is of keen interest in developing biomarkers and treatments for individuals with breast cancer. Although miRs are often moderate regulators under homeostatic conditions, their function is changed more in response to physical activity.

OBJECTIVE

This single-blind randomized trial aimed to explore the effect of high-intensity interval training (HIIT) on serum levels of miRs in individuals with early-stage breast cancer undergoing HT.

METHODS

Hormone receptor-positive women with breast cancer and healthy women were randomly assigned to a healthy control group (n=15), healthy group with HIIT (n=15), breast cancer group with HT (HT, n=26), and breast cancer group with HT and HIIT (HT+HIIT, n=26). The exercise groups underwent interval uphill walking training on a treadmill 3 times a week for 12weeks. At the end of the study, we analyzed changes in levels of cancer-related miRs (oncomiRs) and tumour suppressor miRs (TSmiRs) in response to the HT and HIIT.

RESULTS

In women with breast cancer versus healthy controls, the expression of some oncomiRs was significantly increased - miR-21 (P<0.001), miR-155 (P=0.001), miR-221 (P=0.008), miR-27a (P<0.001), and miR-10b (P=0.007) - and that of some TSmiRs was significantly decreased - miR-206 (P=0.048), miR-145 (P=0.011), miR-143 (P=0.008), miR-9 (P=0.020), and let-7a (P=0.005). Moreover, HT considerably downregulated oncomiRs and upregulated TSmiRs. HIIT for 12weeks with HT significantly decreased the expression of the oncomiRs and significantly increased that of the TSmiRs as compared with HT alone.

CONCLUSIONS

HITT could amplify the decrease and/or increase in expression of miRs associated with HT in women with breast cancer. A prospective trial could determine whether the use of circulating miRs for monitoring treatment can be useful in therapy decisions.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials (No.: IRCT201202289171N1).

HNRNPA2/B1 is upregulated in endocrine-resistant LCC9 breast cancer cells and alters the miRNA transcriptome when overexpressed in MCF-7 cells

MicroRNAs are dysregulated in breast cancer. Heterogeneous Nuclear Ribonucleoprotein A2/B1 (HNRNPA2/B1) is a reader of the N(6)-methyladenosine (m6A) mark in primary-miRNAs (pri-miRNAs) and promotes DROSHA processing to precursor-miRNAs (pre-miRNAs). We examined the expression of writers, readers, and erasers of m6A and report that HNRNPA2/B1 expression is higher in tamoxifen-resistant LCC9 breast cancer cells as compared to parental, tamoxifen-sensitive MCF-7 cells. To examine how increased expression of HNRNPA2/B1 affects miRNA expression, HNRNPA2/B1 was transiently overexpressed (~5.4-fold) in MCF-7 cells for whole genome miRNA profiling (miRNA-seq). 148 and 88 miRNAs were up- and down-regulated, respectively, 48 h after transfection and 177 and 172 up- and down-regulated, respectively, 72 h after transfection. MetaCore Enrichment analysis identified progesterone receptor action and transforming growth factor β (TGFβ) signaling via miRNA in breast cancer as pathways downstream of the upregulated miRNAs and TGFβ signaling via SMADs and Notch signaling as pathways of the downregulated miRNAs. GO biological processes for mRNA targets of HNRNPA2/B1-regulated miRNAs included response to estradiol and cell-substrate adhesion. qPCR confirmed HNRNPA2B1 downregulation of miR-29a-3p, miR-29b-3p, and miR-222 and upregulation of miR-1266-5p, miR-1268a, miR-671-3p. Transient overexpression of HNRNPA2/B1 reduced MCF-7 sensitivity to 4-hydroxytamoxifen and fulvestrant, suggesting a role for HNRNPA2/B1 in endocrine-resistance.

Differential microRNA profiles between fulvestrant-resistant and tamoxifen-resistant human breast cancer cells

Increasing evidence has shown that the dysregulation of microRNAs (miRNAs) is associated with drug resistance. Fulvestrant and tamoxifen represent the major endocrine drugs for the treatment of breast cancer patients, and yet little is known about the biological mechanisms of acquiring resistance to fulvestrant and tamoxifen, let alone the differences between cell lines resistant to these two drugs. Exploration of the differential miRNA profiles between these two cell lines is a useful way to further clarify these resistance mechanisms. The fulvestrant-resistant cell line (MCF7-F) and the tamoxifen-resistant cell line (MCF7-T) were established from the drug-sensitive parental MCF7 cell line using a 21-day high-dose antiestrogen induction method. Differentially expressed miRNA profiles of MCF7-F and MCF7-T were detected using microarray; then, multiple bioinformatic analyses were carried out, including protein-protein interaction network, Gene Ontology, and Kyoto Encyclopedia of Genes and Genomes pathway analysis. Compared with the parental MCF7 cell line, more miRNAs were found to be participating in the process of acquiring fulvestrant resistance than tamoxifen resistance. miR-4532, miR-486-5p, miR-138, miR-1228, and miR-3178 could be new targets for combating both fulvestrant resistance and tamoxifen resistance. miR-3188, miR-21, miR-149, and others may be associated with fulvestrant resistance, whereas miR-342 and miR-1226 may be associated with tamoxifen resistance in breast cancer cells. We found differential miRNA profiles between fulvestrant-resistant and tamoxifen-resistant breast cancer cells, but the definite mechanism involved in gaining resistance still needs further study.

Chemoresistance mechanisms of breast cancer and their countermeasures

Chemoresistance is one of the major challenges for the breast cancer treatment. Owing to its heterogeneous nature, the chemoresistance mechanisms of breast cancer are complicated, and not been fully elucidated. The existing treatments fall short of offering adequate solution to drug resistance, so more effective approaches are desperately needed to improve existing therapeutic regimens. To overcome this hurdle, a number of strategies are being investigated, such as novel agents or drug carriers and combination treatment. In addition, some new therapeutics including gene therapy and immunotherapy may be promising for dealing with the resistance. In this article, we review the mechanisms of chemoresistance in breast cancer. Furthermore, the potential therapeutic methods to overcome the resistance were discussed.

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

Background

Breast cancer is the most common cancer among women worldwide, and approximately 70% of breast cancers are hormone receptor-positive and express estrogen receptor-α (ERα) or/and progesterone receptor. Therapies targeting ERα have been successfully used in patients with ERα⁺ breast cancer. However, intrinsic or acquired resistance to anti-estrogen therapy presents a major challenge. The Wnt/β-catenin signaling pathway regulates various processes that are important for cancer progression, and emerging evidences have shown a close interaction between Wnt/β-catenin and ERα signaling. miR-190 is also involved in ER signaling and our previous study indicated that miR-190 suppresses breast cancer metastasis.

Methods

The effect of miR-190 on breast cancer anti-estrogen sensitivity was investigated both in vitro and in vivo. The protein expression levels and localization were analyzed by western blotting and immunofluorescence, respectively. Chromatin immunoprecipitation and dual-luciferase reporter assays were used to validate the regulation of the zinc-finger E-box binding homeobox 1/ ERα-miR-190-SRY-related high mobility group box 9 (ZEB1/ERα-miR-190-SOX9) axis.

Results

miR-190 increased the anti-estrogen sensitivity of breast cancer cells both in vitro and in vivo. miR-190 inhibited Wnt/β-catenin signaling by targeting SOX9, and its expression inversely correlated with that of SOX9 in breast cancer samples. Furthermore, ERα and ZEB1 competitively regulated miR-190 expression.

Conclusions

Our data uncover the ZEB1/ERα-miR-190-SOX9 axis and suggest a mechanism by which the Wnt/β-catenin signaling pathway is involved in breast cancer anti-estrogen therapy.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1039-9) contains supplementary material, which is available to authorized users.

Pathways to Endocrine Therapy Resistance in Breast Cancer

Breast cancers with positive expression of Estrogen Receptor (ER+) are treated with anti-hormone/endocrine therapy which targets the activity of the receptor, the half-life of the receptor or the availability of estrogen. This has significantly decreased mortality in women with ER+ breast cancer, however, about 25-30% of treated women run the risk or recurrence due to either intrinsic or acquired resistance to endocrine therapies. While ER itself is a predictor of response to such therapies, there exists a need to find more biomarkers and novel targets to treat resistant tumors. In this review, we summarize the known mechanisms and describe the ability of genomics in unraveling rare mutations and gene rearrangements that may impact the development of resistance and therefore treatment of ER+ breast cancer in the near future.

Non-Coding RNAs in Breast Cancer: Intracellular and Intercellular Communication

Non-coding RNAs (ncRNAs) are regulators of intracellular and intercellular signaling in breast cancer. ncRNAs modulate intracellular signaling to control diverse cellular processes, including levels and activity of estrogen receptor α (ERα), proliferation, invasion, migration, apoptosis, and stemness. In addition, ncRNAs can be packaged into exosomes to provide intercellular communication by the transmission of microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) to cells locally or systemically. This review provides an overview of the biogenesis and roles of ncRNAs: small nucleolar RNA (snRNA), circular RNAs (circRNAs), PIWI-interacting RNAs (piRNAs), miRNAs, and lncRNAs in breast cancer. Since more is known about the miRNAs and lncRNAs that are expressed in breast tumors, their established targets as oncogenic drivers and tumor suppressors will be reviewed. The focus is on miRNAs and lncRNAs identified in breast tumors, since a number of ncRNAs identified in breast cancer cells are not dysregulated in breast tumors. The identity and putative function of selected lncRNAs increased: nuclear paraspeckle assembly transcript 1 (NEAT1), metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), steroid receptor RNA activator 1 (SRA1), colon cancer associated transcript 2 (CCAT2), colorectal neoplasia differentially expressed (CRNDE), myocardial infarction associated transcript (MIAT), and long intergenic non-protein coding RNA, Regulator of Reprogramming (LINC-ROR); and decreased levels of maternally-expressed 3 (MEG3) in breast tumors have been observed as well. miRNAs and lncRNAs are considered targets of therapeutic intervention in breast cancer, but further work is needed to bring the promise of regulating their activities to clinical use.

Non-coding RNAs Function as Immune Regulators in Teleost Fish

Non-coding RNAs (ncRNAs) are functional RNA molecules that are transcribed from DNA but not translated into proteins. ncRNAs function as key regulators of gene expression and chromatin modification. Recently, the functional role of ncRNAs in teleost fish has been extensively studied. Teleost fish are a highly diverse group among the vertebrate lineage. Fish are also important in terms of aquatic ecosystem, food production and human life, being the source of animal proteins worldwide and models of biomedical research. However, teleost fish always suffer from the invasion of infectious pathogens including viruses and bacteria, which has resulted in a tremendous economic loss to the fishing industry worldwide. Emerging evidence suggests that ncRNAs, especially miRNAs and lncRNAs, may serve as important regulators in cytokine and chemokine signaling, antigen presentation, complement and coagulation cascades, and T cell response in teleost fish. In this review, we summarize current knowledge and understanding of the roles of both miRNAs and lncRNAs in immune regulation in teleost fish. Molecular mechanism insights into the function of ncRNAs in fish immune response may contribute to the development of potential biomarkers and therapeutic targets for the prevention and treatment of fish diseases.

Polyubiquitination inhibition of estrogen receptor alpha and its implications in breast cancer

Estrogen receptor alpha (ERα) is detected in more than 70% of the cases of breast cancer. Nuclear activity of ERα, a transcriptional regulator, is linked to the development of mammary tumors, whereas the extranuclear activity of ERα is related to endocrine therapy resistance. ERα polyubiquitination is induced by the estradiol hormone, and also by selective estrogen receptor degraders, resulting in ERα degradation via the ubiquitin proteasome system. Moreover, polyubiquitination is related to the ERα transcription cycle, and some E3-ubiquitin ligases also function as coactivators for ERα. Several studies have demonstrated that ERα polyubiquitination is inhibited by multiple mechanisms that include posttranslational modifications, interactions with coregulators, and formation of specific protein complexes with ERα. These events are responsible for an increase in ERα protein levels and deregulation of its signaling in breast cancers. Thus, ERα polyubiquitination inhibition may be a key factor in the progression of breast cancer and resistance to endocrine therapy.

Acquired resistance to aromatase inhibitors: where we stand!

Aromatase inhibitors (AIs) are one of the principal therapeutic approaches for estrogen receptor-positive (ER⁺) breast cancer in postmenopausal women. They block estrogen biosynthesis through aromatase inhibition, thus preventing tumour progression. Besides the therapeutic success of the third-generation AIs, acquired resistance may develop, leading to tumour relapse. This resistance is thought to be the result of a change in the behaviour of ER in these breast cancer cells, presumably by PI3K/AKT pathway enhancement along with alterations in other signalling pathways. Nevertheless, biological mechanisms, such as apoptosis, autophagy, cell cycle modulation and activation of androgen receptor (AR), are also implicated in acquired resistance. Moreover, clinical evidence demonstrated that there is a lack of cross-resistance among AIs, although the reason is not fully understood. Thus, there is a demand to understand the mechanisms involved in endocrine resistance to each AI, since the search for new strategies to surpass breast cancer acquired resistance is of major concern.

microRNAs in the haemostatic system: More than witnesses of thromboembolic diseases?

MicroRNAs (miRNAs) are small endogenous RNAs that post-transcriptionally regulate gene expression. In the last few years, these molecules have been implicated in the regulation of haemostasis, and an increasing number of studies have investigated their relationship with the development of thrombosis. In this review, we discuss the latest developments regarding the role of miRNAs in the regulation of platelet function and secondary haemostasis. We also discuss the genetic and environmental factors that regulate miRNAs. Finally, we address the potential use of miRNAs as prognostic and diagnostic tools in thrombosis.

Non-coding RNAs: long non-coding RNAs and microRNAs in endocrine-related cancers

The human genome is 'pervasively transcribed' leading to a complex array of non-coding RNAs (ncRNAs) that far outnumber coding mRNAs. ncRNAs have regulatory roles in transcription and post-transcriptional processes as well numerous cellular functions that remain to be fully described. Best characterized of the 'expanding universe' of ncRNAs are the ~22 nucleotide microRNAs (miRNAs) that base-pair to target mRNA's 3' untranslated region within the RNA-induced silencing complex (RISC) and block translation and may stimulate mRNA transcript degradation. Long non-coding RNAs (lncRNAs) are classified as >200 nucleotides in length, but range up to several kb and are heterogeneous in genomic origin and function. lncRNAs fold into structures that interact with DNA, RNA and proteins to regulate chromatin dynamics, protein complex assembly, transcription, telomere biology and splicing. Some lncRNAs act as sponges for miRNAs and decoys for proteins. Nuclear-encoded lncRNAs can be taken up by mitochondria and lncRNAs are transcribed from mtDNA. Both miRNAs and lncRNAs are dysregulated in endocrine cancers. This review provides an overview on the current understanding of the regulation and function of selected lncRNAs and miRNAs, and their interaction, in endocrine-related cancers: breast, prostate, endometrial and thyroid.

Long non-coding RNA XIST exerts oncogenic functions in pancreatic cancer via miR-34a-5p

Long non-coding RNAs (lncRNAs) have been implicated in the occurrence and progression of multiple cancers. In the present study, we investigated the role of lncRNA X inactive-specific transcript (XIST) in the development and progression of pancreatic cancer (PC). Firstly, we found that lncRNA XIST was markedly upregulated in PC tissues and PC cell lines, respectively. Overexpression of XIST significantly promoted the proliferation, migration and invasion, and suppressed cell apoptosis of BxPC-3 cells; knockdown of XIST significantly inhibited the proliferation, migration and invasion, and accelerated cell apoptosis of PANC-1 cells. Furthermore, BxPC-3 and PANC-1 cells transfected with different vectors were injected subcutaneously into nude mice to explore tumor formation. We found that XIST promoted tumor formation in vivo. Subsequently, we found that microRNA-34a-5p (miR‑34a-5p) was downregulated in PC tissues, and predicted a poor prognosis in PC patients. In addition, the results indicated that miR-34a-5p is a target gene of XIST and was significantly negatively correlated with XIST. More importantly, we found that miR-34a-5p rescued the facilitation of malignant behavior mediated by XIST. These results indicated that XIST and miR-34a-5p may be potential effective therapeutic targets for PC.

MiR-4653-3p and its target gene FRS2 are prognostic biomarkers for hormone receptor positive breast cancer patients receiving tamoxifen as adjuvant endocrine therapy

Long-term tamoxifen treatment significantly improves the survival of hormone receptor-positive (HR+) breast cancer (BC) patients. However, tamoxifen resistance remains a challenge. We aimed to identify prognostic biomarkers for tamoxifen resistance and reveal the underlying mechanism. From March 2001 to September 2013, 400 HR+ BC women (stage I~III) were treated with adjuvant tamoxifen for 5 years or until relapse in West China Hospital. We included a discovery set of 6 patients who were refractory to tamoxifen, and a validation cohort of 88 patients including 35 cases with relapse. In the discovery set, microRNA microarray showed that miR-4653-3p decreased in recurrent/metastatic lesions compared to the matched primary lesions. In the validation cohort, real-time RT-PCR demonstrated that, following tamoxifen treatment, miR-4653-3p overexpression in the primary tumors decreased the risk of relapse (adjusted hazard ratio [HR] = 0.17, 95% confidence interval [CI] = 0.05~0.57, P = 0.004). Conversely, high expression of FRS2, the key adaptor protein required by FGFR signaling, predicted poor disease-free survival (DFS) (adjusted HR = 2.70, 95% CI = 1.11~6.56, P = 0.03). MiR-4653-3p down regulated FRS2 by binding to its 3′ untranslated region. Either overexpressing miR-4653-3p or attenuating FRS2 expression could restore TAM sensitivity in two tamoxifen-resistant BC cell lines. In conclusion, high miR-4653-3p level was the potential predictor for favorable DFS, while FRS2 overexpression was potential high-risk factor for relapse in HR+ BC patients receiving TAM adjuvant therapy. FGFR/FRS2 signaling might be a promising target for reversing tamoxifen resistance.

A feedback loop consisting of RUNX2/LncRNA-PVT1/miR-455 is involved in the progression of colorectal cancer

Long non-coding RNAs (lncRNAs) have been shown to participate in cancer progression. In the present study, we explored the potential roles of lncRNA-PVT1 in the development process of colorectal cancer (CRC) via miR-455. We found that PVT1 is up-regulated in human CRC tissues compared to adjacent normal tissues. A functional study showed that the silencing of PVT1 expression by siRNAs inhibited cell proliferation, migration and invasion, whereas the overexpression of PVT1 accelerated cell proliferation, migration and invasion in vitro. A mechanistic study indicated PVT1 regulated the growth of CRC tumors by acting as a competing endogenous RNAs (ceRNA) and negatively regulated miR-455. Furthermore, we discovered that RUNX2, a functional transcription factor in CRC, up-regulated PVT1 expression. Therefore, our study suggested that the RUNX2/PVT1/miR-455 regulatory axis plays an important role in CRC tumorigenesis and may be a therapeutic target for the treatment of CRC.

Profiles of miRNAs matched to biology in aromatase inhibitor resistant breast cancer

Aromatase inhibitor (AI) resistance during breast cancer treatment is mimicked by MCF-7:5C (5C) and MCF-7:2A (2A) cell lines that grow spontaneously. Survival signaling is reconfigured but cells are vulnerable to estradiol (E₂)-inducible apoptosis. These model systems have alterations of stress related pathways including the accumulation of endoplasmic reticulum, oxidative, and inflammatory stress that occur prior to E₂-induced apoptosis. We investigated miRNA expression profiles of 5C and 2A to characterize their AI resistance phenotypes. Affymetrix GeneChip miRNA2.0 arrays identified 184 miRNAs differentially expressed in 2A and 5C compared to E₂-free wild-type MCF-7:WS8. In 5C, 34 miRNAs of the DLK1-DIO3 locus and miR-31 were overexpressed, whereas miR-222 was low. TCGA data revealed poor and favorable overall survival for low miR-31 and miR-222 levels, respectively (HR=3.0, 95% CI:1.9-4.8; HR=0.3, 95% CI:0.1-0.6). Targets of deregulated miRNAs were identified using CLIP-confirmed TargetScan predictions. KEGG enrichment analyses for 5C- and 2A-specific target gene sets revealed pathways associated with cell proliferation including insulin, mTOR, and ErbB signaling as well as immune response and metabolism. Key genes overrepresented in 5C- and 2A-specific pathway interaction networks including EGFR, IGF1R and PIK3R1 had lower protein levels in 5C compared to 2A and were found to be differentially modulated by respective miRNA sets. Distinct up-regulated miRNAs from the DLK1-DIO3 locus may cause these attenuative effects as they are predicted to interact with corresponding 3′ untranslated regions. These new miRNA profiles become an important regulatory database to explore E₂-induced apoptotic mechanisms of clinical relevance for the treatment of resistant breast cancer.

High N-Acetyltransferase 1 Expression Is Associated with Estrogen Receptor Expression in Breast Tumors, but Is not Under Direct Regulation by Estradiol, 5α-androstane-3β,17β-Diol, or Dihydrotestosterone in Breast Cancer Cells

N-acetyltransferase 1 (NAT1) is an enzyme that metabolizes carcinogens, which suggests a potential role in breast carcinogenesis. High NAT1 expression in breast tumors is associated with estrogen receptor α (ERα+) and the luminal subtype. We report that NAT1 mRNA transcript, protein, and enzyme activity were higher in human breast tumors with high expression of ERα/ESR1 compared with normal breast tissue. There was a strong correlation between NATb promoter and NAT1 protein expression/enzyme activity. High NAT1 expression in tumors was not the result of adipocytes, as evidenced by low perilipin (PLIN) expression. ESR1, NAT1, and XBP1 expression were associated in tumor biopsies. Direct regulation of NAT1 transcription by estradiol (E₂) was investigated in ERα (+) MCF-7 and T47D breast cancer cells. E₂ did not increase NAT1 transcript expression but increased progesterone receptor expression in a dose-dependent manner. Likewise, NAT1 transcript levels were not increased by dihydrotestosterone (DHT) or 5α-androstane-3β, (3β-adiol) 17β-diol. Dithiothreitol increased levels of the activated, spliced XBP1 in ERα (+) MCF-7 and T47D breast cancer cells but did not affect NAT1 or ESR1 expression. We conclude that NAT1 expression is not directly regulated by E₂, DHT, 3β-adiol, or dithiothreitol despite high NAT1 and ESR1 expression in luminal A breast cancer cells, suggesting that ESR1, XBP1, and NAT1 expression may share a common transcriptional network arising from the luminal epithelium associated with better survival in breast cancer. Clusters of high-expression genes, including NAT1, in breast tumors might serve as potential targets for novel therapeutic drug development.

Bioinformatics-based identification of miR-542-5p as a predictive biomarker in breast cancer therapy

Background

Tamoxifen is the first-line hormone therapy for estrogen receptor alpha positive (ERα+) breast cancer. However, about 40% of patients with ERα + breast cancer who receive tamoxifen therapy eventually develop resistance resulting in a poor prognosis. The aim of this study was to mine available data sets in the Gene Expression Omnibus (GEO) database, including in vitro (cell lines) and in vivo (tissue samples), and to identify all miRNAs associated with tamoxifen resistance (TamR) in breast cancer. Secondly, this study aimed to predict the key gene regulatory networks of newly found TamR-related miRNAs and evaluate the potential role of the miRNAs and targets as potential prognosis biomarkers for breast cancer patients.

Result

Microarray data sets from two different studies were used from the GEO database: 1. GSE66607: miRNA of MCF-7 TamR cells; 2. GSE37405: TamR tissues. Differentially expressed microRNAs (miRNAs) were identified in both data sets and 5 differentially expressed miRNAs were found to overlap between the two data sets. Profiles of GSE37405 and data from the Kaplan-Meier Plotter Database (KMPD) along with Gene Expression Profiling Interactive Analysis (GEPIA) were used to reveal the relationship between these 5 miRNAs and overall survival. The results showed that has-miR-542-5p was the only miRNA associated with overall survival of ERα + breast cancer patients who received adjuvant tamoxifen. Targets of has-miR-542-5p were predicted by miRanda and TargetScan, and the mRNA expression of the three 3 target gene, Tyrosine 3-Monooxygenase/Tryptophan 5-Monooxygenase Activation Protein Beta (YWHAB), Lymphocyte Antigen 9 (LY9), and Secreted Frizzled Related Protein 1 (SFRP1) were associated with overall survival in 2 different databases. Copy-number alterations (CNAs) of SFRP1 confer survival disadvantage to breast cancer patients and alter the mRNA expression of SFRP1 in cBioPortal database.

Conclusion

This study indicates that miRNA has-miR-542-5p is associated with TamR and can predict prognosis of breast cancer patients. Furthermore, has-miR-542-5p may be acting through a mechanism involving the target genes YWHAB, LY9, and SFRP1. Overall, has-miR-542-5p is a predictive biomarker and potential target for therapy of breast cancer patients.

Electronic supplementary material

The online version of this article (10.1186/s41065-018-0055-7) contains supplementary material, which is available to authorized users.

Non coding RNA analysis in fibrolamellar hepatocellular carcinoma

Fibrolamellar hepatocellular carcinoma (FLC) is a rare primary liver cancer found in adolescents and young adults without underlying liver disease. A deletion of ~400 kD has been found in one copy of chromosome 19 in the tumor tissue of all patients tested. This produces a fusion of the genes DNAJB1 and PRKACA which, in turn, produces a chimeric transcript and protein. Transcriptomic analysis of the tumor has shown upregulation of various oncologically relevant pathways, including EGF/ErbB, Aurora Kinase A, pak21 and wnt. To explore other factors that may contribute to oncogenesis, we examined the microRNA (miRNA) and long non-coding RNA (lncRNA) expression in FLC. The non-coding RNA expression profile in tumor tissue samples is distinctly different from the adjacent normal liver and from other liver tumors. Furthermore, miRZip knock down or over expression of certain miRNAs led to changes in the levels of coding genes that recapitulated changes observed in FLC, suggesting mechanistically that the changes in the cellular levels of miRNA are not merely correlative. Thus, in addition to serving as diagnostic tools for FLC, non-coding RNAs may serve as therapeutic targets.

Identification of miRNAs as biomarkers for acquired endocrine resistance in breast cancer

Therapies targeting estrogen receptor α (ERα) including tamoxifen, a selective estrogen receptor modulator (SERM) and aromatase inhibitors (AI), e.g., letrozole, have proven successful in reducing the death rate for breast cancer patients whose initial tumors express ERα. However, about 40% of patients develop acquired resistance to these endocrine treatments. There is a critical need to develop sensitive circulating biomarkers that accurately identify signaling pathways altered in breast cancer patients resistant to endocrine therapies. Serum miRNAs have the potential to serve as biomarkers of the progression of endocrine-resistant breast cancer due to their cancer-specific expression and stability. Exosomal transfer of miRNAs has been implicated in metastasis and endocrine-resistance. This review focuses on miRNAs in breast tumors and in serum, including exosomes, from breast cancer patients that are associated with resistance to tamoxifen since it is best-studied.

miR-1271 inhibits ERα expression and confers letrozole resistance in breast cancer

Attenuation of estrogen receptor α (ERα) expression via unknown mechanism(s) is a hallmark of endocrine-resistant breast cancer (BCa) progression. Here, we report that miR-1271 was significantly down-regulated in letrozole-resistant BCa tissues and in letrozole-resistant BCa cells. miR-1271 directly targeted the chromatin of DNA damage-inducible transcript 3 (DDIT3) gene. miR-1271 expression level was inversely correlated to DDIT3 mRNA level in BCa biopsies. Form a mechanistic standpoint, reintroduction of exogenous miR-1271 could effectively restore ERα level via inhibiting DDIT3 expression, thereby potentiating letrozole sensitivity in BCa cells. Moreover, DDIT3 deregulation promoted letrozole-resistance by acting as a potent corepressor of ESR1 transcription. Taken together, we have identified that disruption of the miR-1271/DDIT3/ERα cascade plays a causative role in the pathogenesis of letrozole resistance in BCa.

The miR-29 transcriptome in endocrine-sensitive and resistant breast cancer cells

Aberrant microRNA expression contributes to breast cancer progression and endocrine resistance. We reported that although tamoxifen stimulated miR-29b-1/a transcription in tamoxifen (TAM)-resistant breast cancer cells, ectopic expression of miR-29b-1/a did not drive TAM-resistance in MCF-7 breast cancer cells. However, miR-29b-1/a overexpression significantly repressed TAM-resistant LCC9 cell proliferation, suggesting that miR-29b-1/a is not mediating TAM resistance but acts as a tumor suppressor in TAM-resistant cells. The target genes mediating this tumor suppressor activity were unknown. Here, we identify miR-29b-1 and miR-29a target transcripts in both MCF-7 and LCC9 cells. We find that miR-29b-1 and miR-29a regulate common and unique transcripts in each cell line. The cell-specific and common downregulated genes were characterized using the MetaCore Gene Ontology (GO) enrichment analysis algorithm. LCC9-sepecific miR-29b-1/a-regulated GO processes include oxidative phosphorylation, ATP metabolism, and apoptosis. Extracellular flux analysis of cells transfected with anti- or pre- miR-29a confirmed that miR-29a inhibits mitochondrial bioenergetics in LCC9 cells. qPCR,luciferase reporter assays, and western blot also verified the ATP synthase subunit genes ATP5G1 and ATPIF1 as bone fide miR29b-1/a targets. Our results suggest that miR-29 repression of TAM-resistant breast cancer cell proliferation is mediated in part through repression of genes important in mitochondrial bioenergetics.

The lncRNA n340790 accelerates carcinogenesis of thyroid cancer by regulating miR-1254

Long non-coding RNAs (lncRNAs) have been recently reported to be dysregulated and play a critical role in the progression of thyroid cancer. Here, we found that the lncRNA n340790 was highly expressed in human thyroid cancer tissues and was strongly correlated with the clinical characteristics of patients. There was a good prognostic value of n340790 for thyroid cancer. In vitro overexpression of n340790 promoted the development of thyroid cancer, while silencing n340790 inhibited this process. Additionally, n340790 accelerated the growth of thyroid cancer tumor in vivo. Furthermore, we discovered that n340790 could act as an endogenous sponge by directly binding to miR-1254 and downregulating miR-1254 expression. In addition, miR-1254 could inhibit the stimulatory effect of n340790 on the growth and invasion of thyroid cancer cells. In conclusion, n340790 promoted the development process of malignant thyroid cancer by regulating miR-1254, and targeting n340790 may be a promising strategy as a thyroid cancer therapy.

Mechanisms of resistance to selective estrogen receptor down-regulator in metastatic breast cancer

Based on the prominent role estrogen receptor (ER) plays in breast cancer, endocrine therapy has been developed to block the ER pathway and has shown great effectiveness. Fulvestrant, the first selective ER down-regulator (SERD), was demonstrated to completely suppress ERα and notably efficient. However, resistance to fulvestrant occurs, either intrinsic or acquired during the treatment. Several potential mechanisms inducing fulvestrant resistance have been proposed, composed of activated ERα-independent compensatory growth factor signaling, stimulated downstream kinases, altered cell cycle mediators, etcetera. Experimentally, combinations of fulvestrant with targeted treatments were reported to eliminate the resistance and improve the effect of fulvestrant. Meanwhile, some clinical trials associated with the targeted combination therapies are in progress. This review focuses on the underlying mechanisms that contribute to fulvestrant resistance in ER-positive breast cancer and provides an overview of combined fulvestrant with targeted agents to shed light on optimal therapies for patients with ER-positive breast cancer.