ESR1-Stabilizing Long Noncoding RNA TMPO-AS1 Promotes Hormone-Refractory Breast Cancer Progression

Liquid biopsy using non-coding RNAs and extracellular vesicles for breast cancer management

This article examines liquid biopsy using non-coding RNAs and extracellular vesicles in detail. Liquid biopsy is emerging as a prominent non-invasive diagnostic tool in the treatment of breast cancer. We will elucidate the roles of these molecules in early detection, monitoring treatment effectiveness, and prognostic assessment of breast cancer. Additionally, the clinical significance of these molecules will be discussed. We aim to delve into the distinct characteristics of these molecules and their possible roles in breast cancer management, with an anticipation of their contribution to future diagnostic and therapeutic advancements.

Non-coding RNAs and estrogen receptor signaling in breast cancer: Nanotechnology-based therapeutic approaches

This review investigates the regulatory role of non-coding RNAs (ncRNAs) in estrogen receptor (ER) signaling pathways, particularly in the context of breast cancer therapy, with an emphasis on the emerging potential of nanotechnology for drug delivery. The information was obtained from reputable databases, including PubMed, Elsevier, Springer, Wiley, Taylor, and Francis, which contain past and present research. Breast cancer remains the most prevalent cancer among women worldwide, and ER signaling mechanisms heavily influence its progression. Treatment options have traditionally encompassed surgery, chemotherapy, radiation therapy, targeted therapy, and hormone therapy. In recent decades, nanomedicine has emerged as a promising approach to breast cancer treatment. By passively targeting tumor cells and reducing toxicity, nanodrugs can overcome the challenges of conventional chemotherapy. Additionally, nanocarriers can stimulate tumor cells, enhancing treatment efficacy. Recent advancements in nanomedicine offer promising approaches for targeted cancer therapy, potentially overcoming the limitations of conventional treatments. This review explores the interactions between long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) with ER pathways, their impact on breast cancer progression, and how these interactions can be leveraged to enhance therapeutic efficacy through nanotechnology-based drug delivery systems.

Long Non-Coding RNAs, Nuclear Receptors and Their Cross-Talks in Cancer-Implications and Perspectives

Long non-coding RNAs (lncRNAs) play key roles in various epigenetic and post-transcriptional events in the cell, thereby significantly influencing cellular processes including gene expression, development and diseases such as cancer. Nuclear receptors (NRs) are a family of ligand-regulated transcription factors that typically regulate transcription of genes involved in a broad spectrum of cellular processes, immune responses and in many diseases including cancer. Owing to their many overlapping roles as modulators of gene expression, the paths traversed by lncRNA and NR-mediated signaling often cross each other; these lncRNA-NR cross-talks are being increasingly recognized as important players in many cellular processes and diseases such as cancer. Here, we review the individual roles of lncRNAs and NRs, especially growth factor modulated receptors such as androgen receptors (ARs), in various types of cancers and how the cross-talks between lncRNAs and NRs are involved in cancer progression and metastasis. We discuss the challenges involved in characterizing lncRNA-NR associations and how to overcome them. Furthering our understanding of the mechanisms of lncRNA-NR associations is crucial to realizing their potential as prognostic features, diagnostic biomarkers and therapeutic targets in cancer biology.

Long non-coding RNA SOX2OT in tamoxifen-resistant breast cancer

Hormone receptor (HR)-positive breast cancer can become aggressive after developing hormone-treatment resistance. This study elucidated the role of long non-coding RNA (lncRNA) SOX2OT in tamoxifen-resistant (TAMR) breast cancer and its potential interplay with the tumor microenvironment (TME). TAMR breast cancer cell lines TAMR-V and TAMR-H were compared with the luminal type A cell line (MCF-7). LncRNA expression was assessed via next-generation sequencing, RNA extraction, lncRNA profiling, and quantitative RT-qPCR. SOX2OT overexpression effects on cell proliferation, migration, and invasion were evaluated using various assays. SOX2OT was consistently downregulated in TAMR cell lines and TAMR breast cancer tissue. Overexpression of SOX2OT in TAMR cells increased cell proliferation and cell invasion. However, SOX2OT overexpression did not significantly alter SOX2 levels, suggesting an independent interaction within TAMR cells. Kaplan-Meier plot analysis revealed an inverse relationship between SOX2OT expression and prognosis in luminal A and B breast cancers. Our findings highlight the potential role of SOX2OT in TAMR breast cancer progression. The downregulation of SOX2OT in TAMR breast cancer indicates its involvement in resistance mechanisms. Further studies should explore the intricate interactions between SOX2OT, SOX2, and TME in breast cancer subtypes.

Therapeutic significance of long noncoding RNAs in estrogen receptor-positive breast cancer

About 70% of cases of breast cancer are compromised by Estrogen-positive breast cancer. Through its regulation of several processes, including cell proliferation, cell cycle progression, and apoptosis, Estrogen signaling plays a pivotal role in the genesis and progression of this particular kind of breast cancer. One of the best treatment strategies for treating Estrogen-positive breast cancer is blocking Estrogen signaling. However, patients' treatment failure is mainly caused by the emergence of resistance and metastases, necessitating the development of novel therapeutic targets. Numerous studies have shown long noncoding RNAs (lncRNAs) to play a role in Estrogen-mediated carcinogenesis. These lncRNAs interact with co-regulators and the Estrogen signaling cascade components, primarily due to Estrogen activation. Vimentin and E-cadherin are examples of epithelial-to-mesenchymal transition markers, and they regulate genes involved in cell cycle progression, such as Cyclins, to affect the growth, proliferation, and metastasis of Estrogen-positive breast cancer. Furthermore, a few of these lncRNAs contribute to developing resistance to chemotherapy, making them more desirable targets for enhancing results. Thus, to shed light on the creation of fresh approaches for treating this cancer, this review attempts to compile recently conducted studies on the relationship between lncRNAs and the advancement of Estrogen-positive breast cancer.

Deciphering the oncogenic landscape: Unveiling the molecular machinery and clinical significance of LncRNA TMPO-AS1 in human cancers

The in-depth exploration of long non-coding RNAs (lncRNAs) reveals their pivotal and diverse roles in various disorders, particularly cancer. Within this intricate landscape, thymopoietin-antisense RNA-1 (TMPO-AS1) emerges as a noteworthy instigator of oncogenesis in humans. This exhaustive review seeks to intricately unravel the present understanding of TMPO-AS1, emphasizing its molecular foundations and highlighting its clinical applications in the realm of cancer research. TMPO-AS1 consistently exhibits heightened expression across a spectrum of cancer types, encompassing lung, colorectal, breast, cervical, bladder, pancreatic, hepatocellular, gastric, ovarian, and osteosarcoma. Elevated levels of TMPO-AS1 are intricately linked to unfavorable prognoses, accompanied by distinctive clinical and pathological characteristics. Functionally, TMPO-AS1 showcases its prowess in enhancing cancer cell migration, invasion, proliferation, and orchestrating epithelial-mesenchymal transition (EMT) through a myriad of molecular mechanisms. These mechanisms entail intricate interactions with proteins, microRNAs, and intricate signaling pathways. Furthermore, TMPO-AS1 is intricately involved in regulating critical cellular processes, including apoptosis and the cell cycle. The mounting evidence converges towards the potential of TMPO-AS1 serving as a diagnostic and prognostic biomarker, further entwined with its potential role in influencing chemoresistance in cancer. This potential is underscored by its consistent associations with clinical outcomes and treatment responses. This comprehensive investigation not only consolidates our existing knowledge of TMPO-AS1's multifaceted roles but also sheds illuminating insights on its profound significance in the intricate landscape of cancer biology, paving the way for potential applications in clinical practice.

Neat1 lncRNA organizes the inflammatory gene expressions in the dorsal root ganglion in neuropathic pain caused by nerve injury

Primary sensory neurons regulate inflammatory processes in innervated regions through neuro-immune communication. However, how their immune-modulating functions are regulated in concert remains largely unknown. Here, we show that Neat1 long non-coding RNA (lncRNA) organizes the proinflammatory gene expressions in the dorsal root ganglion (DRG) in chronic intractable neuropathic pain in rats. Neat1 was abundantly expressed in the DRG and was upregulated after peripheral nerve injury. Neat1 overexpression in primary sensory neurons caused mechanical and thermal hypersensitivity, whereas its knockdown alleviated neuropathic pain. Bioinformatics analysis of comprehensive transcriptome changes indicated the inflammatory response was the most relevant function of genes upregulated through Neat1. Consistent with this, upregulation of proinflammatory genes in the DRG following nerve injury was suppressed by Neat1 knockdown. Expression changes of these proinflammatory genes were regulated through Neat1-mRNA interaction-dependent and -independent mechanisms. Notably, Neat1 increased proinflammatory genes by stabilizing its interacting mRNAs in neuropathic pain. Finally, Neat1 in primary sensory neurons contributed to spinal inflammatory processes that mediated peripheral neuropathic pain. These findings demonstrate that Neat1 lncRNA is a key regulator of neuro-immune communication in neuropathic pain.

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.

Bisphenol A interferes with lncRNA Fhadlos2 and RUNX3 association in adolescent mouse ovary

Bisphenol A (BPA) has a number of adverse effects on the reproductive development of females. In particular, the mechanism of disruption of ovarian development in adolescent mice is still unclear. Based on transcriptome sequencing results, a differentially expressed lncRNA, Fhad1os2, was detected in the ovaries of BPA-exposed pubertal mice. In our study, the lncRNA Fhad1os2, localized in the ovarian granulosa cell cytoplasm, could regulate the proliferation of mouse ovarian granulosa cells. Mechanistically, the results of RNA pull-down experiments as well as mass spectrometry analysis showed that ERα, an interfering signaling molecule of BPA, could directly bind lncRNA Fhad1os2 and decrease the transcription of lncRNA Fhad1os2 in response to the estrogen-like effect of BPA. BPA exposure also caused abnormal lncRNA Fhad1os2 pulldown protein-related signaling pathways in the ovaries of adolescent mice. Furthermore, lncRNA Fhad1os2 interacted with RUNX3, a transcription factor related to follicle development and hormone synthesis. As a negative regulator, lncRNA Fhad1os2 transactivated the expression of Runx3, which in turn induced RUNX3 to positively regulate aromatase (Cyp19a1) expression in mouse ovarian granulosa cells and promote estrogen synthesis. In conclusion, our study indicates that BPA exposure interferes with ERα-regulated lncRNA Fhad1os2 interactions with RUNX3 in pubertal mice, affecting estrogen synthesis in mouse granulosa cells and contributing to premature ovarian maturation in pubertal mice.

Non-Coding RNAs Modulating Estrogen Signaling and Response to Endocrine Therapy in Breast Cancer

The largest part of human DNA is transcribed into RNA that does not code for proteins. These non-coding RNAs (ncRNAs) are key regulators of protein-coding gene expression and have been shown to play important roles in health, disease and therapy response. Today, endocrine therapy of ERα-positive breast cancer (BC) is a successful treatment approach, but resistance to this therapy is a major clinical problem. Therefore, a deeper understanding of resistance mechanisms is important to overcome this resistance. An increasing amount of evidence demonstrate that ncRNAs affect the response to endocrine therapy. Thus, ncRNAs are considered versatile biomarkers to predict or monitor therapy response. In this review article, we intend to give a summary and update on the effects of microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) on estrogen signaling in BC cells, this pathway being the target of endocrine therapy, and their role in therapy resistance. For this purpose, we reviewed articles on these topics listed in the PubMed database. Finally, we provide an assessment regarding the clinical use of these ncRNA types, particularly their circulating forms, as predictive BC biomarkers and their potential role as therapy targets to overcome endocrine resistance.

In Silico and Experimental Analyses of Long Non-coding RNA TMPO-AS1 Expression in Iranian Patients with Gastric Cancer

Background: In recent decades, many long non-coding RNAs (lncRNAs) have been reported to play a prominent role in tumorigenesis and the progression of human cancers, including gastric cancer (GC), a leading cause of cancer death in Iranian men and women. Studies have demonstrated that thymopoietin antisense transcript 1 (TMPO-AS1) was upregulated in different cancers by acting as an oncogenic lncRNA. Objectives: This study aimed to evaluate the expression of lncRNA TMPO-AS1 in Iranian patients with GC. Methods: In order to conduct the present study, 40 gastric tumor samples and 40 marginal noncancerous counterparts were collected. The characteristics of patients’ samples were recorded, and the TMPO-AS1 expression levels were evaluated by qRT-PCR analysis. The Cancer Genome Atlas (TCGA) data for TMPO-AS1 were used and analyzed through GEPIA and TANRIC online tools. Receiver operating characteristic (ROC) curve analysis was used to estimate the diagnostic value. Student t-test, one-way ANOVA, and chi-square test were accomplished via SPSS software. Results: Our data demonstrated that TMPO-AS1 was overexpressed in cancerous tissues compared to adjacent nonmalignant ones (P = 0.0076). None of the demographic and clinicopathological data were associated with TMPO-AS1 expression levels. The TCGA data demonstrated that TMPO-AS1 was upregulated in GC tissues in comparison to adjacent nonmalignant ones (P = 0.001). ROC curve analysis suggested that TMPO-AS1 expression levels could discriminate GC tumor tissues from normal ones (AUC = 0.699, P = 0.001). Conclusions: Altogether, in our study, we demonstrated that lncRNA TMPO-AS1 may be considered a biomarker in Iranian patients with GC. However, further investigations are required to confirm the potential application of this lncRNA in diagnosis, prognosis, and therapeutic applications of GC.

Metformin and long non-coding RNAs in breast cancer

Breast cancer (BC) is the second most common cancer and cause of death in women. In recent years many studies investigated the association of long non-coding RNAs (lncRNAs), as novel genetic factors, on BC risk, survival, clinical and pathological features. Recent studies also investigated the roles of metformin treatment as the firstline treatment for type 2 diabetes (T2D) played in lncRNAs expression/regulation or BC incidence, outcome, mortality and survival, separately. This comprehensive study aimed to review lncRNAs associated with BC features and identify metformin-regulated lncRNAs and their mechanisms of action on BC or other types of cancers. Finally, metformin affects BC by regulating five BC-associated lncRNAs including GAS5, HOTAIR, MALAT1, and H19, by several molecular mechanisms have been described in this review. In addition, metformin action on other types of cancers by regulating ten lncRNAs including AC006160.1, Loc100506691, lncRNA-AF085935, SNHG7, HULC, UCA1, H19, MALAT1, AFAP1-AS1, AC026904.1 is described.

Recent Clinical Advances on Long Non-Coding RNAs in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a more aggressive type of breast cancer due to its heterogeneity and complex molecular mechanisms. TNBC has a high risk for metastasis, and it is difficult to manage clinical conditions of the patients. Various investigations are being conducted to overcome these challenges using RNA, DNA, and proteins for early diagnosis and treatment. Recently, long non-coding RNAs (lncRNAs) have emerged as a novel target to treat the multistep process of TNBC. LncRNAs regulate epigenetic expression levels, cell proliferation and apoptosis, and tumour invasiveness and metastasis. Thus, lncRNA-based early diagnosis and treatment options could be helpful, especially for patients with severe TNBC. lncRNAs are expressed in a highly specific manner in cells and tissues and are involved in TNBC progression and development. lncRNAs could be used as sensitive and specific targets for diagnosis, treatment, and monitoring of patients with TNBC. Therefore, the exploration of novel diagnostic and prognostic biomarkers is of extreme importance. Here, we discuss the molecular advances on lncRNA regulation of TNBC and lncRNA-based early diagnosis, treatment, and drug resistance.

Dual Function of CCAT2 in Regulating Luminal Subtype of Breast Cancer Depending on the Subcellular Distribution

Breast cancer is the most common cancer in women around the world. Emerging evidence has indicated the important roles that non-coding RNAs play in regulating tumor development and progression in breast cancer. Herein, we found a dual function of long non-coding RNA (LncRNA) CCAT2 in the luminal subtype of breast cancer, depending on its subcellular distribution. CCAT2 showed an overall downregulation in the tumor tissues from luminal breast cancer patients. Transient overexpression of CCAT2 in the luminal subtype of breast cancer cell MCF-7 or T47D significantly suppressed cell proliferation in vitro and inhibited tumor growth in vivo. Gene expression analysis of cancer stem cell markers including OCT4, NANOG, h-TERT, SOX2 and KLF4; flow cytometry analysis of breast cancer stem cell population, and mammosphere formation assay demonstrated inhibition of cancer cell stemness with transient transfection of CCAT2 in which exogenous CCAT2 mainly distributed in the cytoplasm and regulated miR-221-p27 signaling via RNA sequence interaction. However, overexpression of CCAT2 in MCF-7 cells through pMX retroviral nuclear expression vector accumulated CCAT2 in the nucleus, leading to upregulation of OCT4-PG1, a pseudogene of stem gene OCT4, thereby promoting the cancer cell stemness. In conclusion, the current study, for the first time, revealed a dual function of lncRNA CCAT2 as a tumor suppressor or oncogene depending upon its subcellular distribution. It also demonstrated the regulatory mechanism of cytoplasmic CCAT2 in suppressing tumorigenesis in the luminal subtype of breast cancer.

Functional Relationships between Long Non-Coding RNAs and Estrogen Receptor Alpha: A New Frontier in Hormone-Responsive Breast Cancer Management

In the complex and articulated machinery of the human genome, less than 2% of the transcriptome encodes for proteins, while at least 75% is actively transcribed into non-coding RNAs (ncRNAs). Among the non-coding transcripts, those ≥200 nucleotides long (lncRNAs) are receiving growing attention for their involvement in human diseases, particularly cancer. Genomic studies have revealed the multiplicity of processes, including neoplastic transformation and tumor progression, in which lncRNAs are involved by regulating gene expression at epigenetic, transcriptional, and post-transcriptional levels by mechanism(s) that still need to be clarified. In breast cancer, several lncRNAs were identified and demonstrated to have either oncogenic or tumor-suppressive roles. The functional understanding of the mechanisms of lncRNA action in this disease could represent a potential for translational applications, as these molecules may serve as novel biomarkers of clinical use and potential therapeutic targets. This review highlights the relationship between lncRNAs and the principal hallmark of the luminal breast cancer phenotype, estrogen receptor α (ERα), providing an overview of new potential ways to inhibit estrogenic signaling via this nuclear receptor toward escaping resistance to endocrine therapy.

A long non-coding RNA with important roles in the carcinogenesis

Long non-coding RNAs are demonstrated to contribute to carcinogenesis. TMPO Antisense RNA 1 (TMPO-AS1) is an example of lncRNAs with crucial roles in this process. This lncRNA serves as a sponge for miR-320a, miR-383-5p, miR-329-3p, miR-126, miR-329, miR-199a-5p, miR-577, miR-4731-5p, miR-140-5p, miR-1179, miR-143-3p, miR-326, miR-383-5p, let-7c-5p, let-7g-5p, miR-199a-5p, miR-200c, miR-204-3p, miR-126-5p, miR-383-5p, miR-498, miR-143-3p, miR-98-5p, miR-140 and miR-143. It can also affect activity of PI3K/Akt/mTOR pathway. The current review summarizes the role of TMPO-AS1 in the carcinogenesis and assessment of its potential as a marker for certain types of cancers.

Estrogen-Inducible LncRNA BNAT1 Functions as a Modulator for Estrogen Receptor Signaling in Endocrine-Resistant Breast Cancer Cells

Recent advances in RNA studies have revealed that functional long noncoding RNAs (lncRNAs) contribute to the biology of cancers. In breast cancer, estrogen receptor α (ERα) is an essential transcription factor that primarily promotes the growth of luminal-type cancer, although only a small number of lncRNAs are identified as direct ERα targets and modulators for ERα signaling. In this study, we performed RNA-sequencing for ER-positive breast cancer cells and identified a novel estrogen-inducible antisense RNA in the COL18A1 promoter region, named breast cancer natural antisense transcript 1 (BNAT1). In clinicopathological study, BNAT1 may have clinical relevance as a potential diagnostic factor for prognoses of ER-positive breast cancer patients based on an in situ hybridization study for breast cancer specimens. siRNA-mediated BNAT1 silencing significantly inhibited the in vitro and in vivo growth of tamoxifen-resistant ER-positive breast cancer cells. Notably, BNAT1 silencing repressed cell cycle progression whereas it promoted apoptosis. Microarray analysis revealed that BNAT1 silencing in estrogen-sensitive breast cancer cells repressed estrogen signaling. We showed that BNAT1 knockdown decreased ERα expression and repressed ERα transactivation. RNA immunoprecipitation showed that BNAT1 physically binds to ERα protein. In summary, BNAT1 would play a critical role in the biology of ER-positive breast cancer by modulating ERα-dependent transcription regulation. We consider that BNAT1 could be a potential molecular target for diagnostic and therapeutic options targeting luminal-type and endocrine-resistant breast cancer.

Molecular Mechanisms of Anti-Estrogen Therapy Resistance and Novel Targeted Therapies

Breast cancer (BC) is the most commonly diagnosed cancer in women, constituting one-third of all cancers in women, and it is the second leading cause of cancer-related deaths in the United States. Anti-estrogen therapies, such as selective estrogen receptor modulators, significantly improve survival in estrogen receptor-positive (ER+) BC patients, which represents about 70% of cases. However, about 60% of patients inevitably experience intrinsic or acquired resistance to anti-estrogen therapies, representing a major clinical problem that leads to relapse, metastasis, and patient deaths. The resistance mechanisms involve mutations of the direct targets of anti-estrogen therapies, compensatory survival pathways, as well as alterations in the expression of non-coding RNAs (e.g., microRNA) that regulate the activity of survival and signaling pathways. Although cyclin-dependent kinase 4/6 and phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) inhibitors have significantly improved survival, the efficacy of these therapies alone and in combination with anti-estrogen therapy for advanced ER+ BC, are not curative in advanced and metastatic disease. Therefore, understanding the molecular mechanisms causing treatment resistance is critical for developing highly effective therapies and improving patient survival. This review focuses on the key mechanisms that contribute to anti-estrogen therapy resistance and potential new treatment strategies alone and in combination with anti-estrogen drugs to improve the survival of BC patients.

In vitro breast cancer models for studying mechanisms of resistance to endocrine therapy

The development of endocrine resistance is a common reason for the failure of endocrine therapies in hormone receptor-positive breast cancer. This review provides an overview of the different types of in vitro models that have been developed as tools for studying endocrine resistance. In vitro models include cell lines that have been rendered endocrine-resistant by ex vivo treatment; cell lines with de novo resistance mechanisms, including genetic alterations; three-dimensional (3D) spheroid, co-culture, and mammosphere techniques; and patient-derived organoid models. In each case, the key discoveries, different analysis strategies that are suitable, and strengths and weaknesses are discussed. Certain recently developed methodologies that can be used to further characterize the biological changes involved in endocrine resistance are then emphasized, along with a commentary on the types of research outcomes that using these techniques can support. Finally, a discussion anticipates how these recent developments will shape future trends in the field. We hope this overview will serve as a useful resource for investigators that are interested in understanding and testing hypotheses related to mechanisms of endocrine therapy resistance.

The Mechanisms of lncRNA-Mediated Multidrug Resistance and the Clinical Application Prospects of lncRNAs in Breast Cancer

Simple Summary

Multidrug resistance (MDR) is a major cause of breast cancer (BC) chemotherapy failure. Long noncoding RNAs (lncRNAs) have been shown closely related to the chemoresistance of BC. In this work, the mechanisms of lncRNA-mediated MDR in BC were elaborated from eight sections, including apoptosis, autophagy, DNA repair, cell cycle, drug efflux, epithelial-mesenchymal transition, epigenetic modification and the tumor microenvironment. Additionally, we also discuss the clinical significance of lncRNAs, which may be biomarkers for diagnosis, therapy and prognosis.

Abstract

Breast cancer (BC) is a highly heterogeneous disease and presents a great threat to female health worldwide. Chemotherapy is one of the predominant strategies for the treatment of BC; however, multidrug resistance (MDR) has seriously affected or hindered the effect of chemotherapy. Recently, a growing number of studies have indicated that lncRNAs play vital and varied roles in BC chemoresistance, including apoptosis, autophagy, DNA repair, cell cycle, drug efflux, epithelial-mesenchymal transition (EMT), epigenetic modification and the tumor microenvironment (TME). Although thousands of lncRNAs have been implicated in the chemoresistance of BC, a systematic review of their regulatory mechanisms remains to be performed. In this review, we systematically summarized the mechanisms of MDR and the functions of lncRNAs mediated in the chemoresistance of BC from the latest literature. These findings significantly enhance the current understanding of lncRNAs and suggest that they may be promising prognostic biomarkers for BC patients receiving chemotherapy, as well as therapeutic targets to prevent or reverse chemoresistance.

Molecular and cellular functions of long non-coding RNAs in prostate and breast cancer

Long noncoding RNAs (lncRNAs) are defined as noncoding RNA transcripts with a length greater than 200 nucleotides. Research over the last decade has made great strides in our understanding of lncRNAs, especially in the biology of their role in cancer. In this article, we will briefly discuss the biogenesis and characteristics of lncRNAs, then review their molecular and cellular functions in cancer by using prostate and breast cancer as examples. LncRNAs are abundant, diverse, and evolutionarily, less conserved than protein-coding genes. They are often expressed in a tumor and cell-specific manner. As a key epigenetic factor, lncRNAs can use a wide variety of molecular mechanisms to regulate gene expression at each step of the genetic information flow pathway. LncRNAs display widespread effects on cell behavior, tumor growth, and metastasis. They act intracellularly and extracellularly in an autocrine, paracrine and endocrine fashion. Increased understanding of lncRNA's role in cancer has facilitated the development of novel biomarkers for cancer diagnosis, led to greater understanding of cancer prognosis, enabled better prediction of therapeutic responses, and promoted identification of potential targets for cancer therapy.

Using immune-related lncRNAs to construct novel biomarkers and investigate the immune landscape of breast cancer

Background

The role of immune-related long noncoding RNAs (irlncRNAs) in breast cancer (BRCA) is still unclear. Recently, studies have performed analyses based on the expression of irlncRNAs, however, in the present study, we used a novel method that did not require the specific expression levels of lncRNAs of BRCA patients.

Methods

We downloaded transcriptome and clinical data of BRCA patients from The Cancer Genome Atlas (TCGA), obtained immune genes from the Immport database, and extracted immune genes and lncRNAs for correlation analysis. Then, the differential expression of irlncRNA pairs (IRLPs) was determined and the prognostic signature was established by the IRLPs. The immune cell abundance of the TCGA-BRCA cohort was downloaded from the Tumor IMmune Estimation Resource (TIMER) database, and the relationship between the risk score of the IRLP signature and immune cell abundance was analyzed. Finally, we explored the relationship between risk scores and drug sensitivity based on the R package pRRophetic.

Results

Univariate cox regression results showed that 33 IRLPs had significant effects on the overall survival (OS) of BRCA patients. Then 22 IRLPs were obtained via lasso regression for further analysis. Multivariate regression analysis obtained 12 IRLPs to establish the IRLP prognostic signature. The model showed that this IRLP signature could act as a prognostic biomarker for BRCA patients. Kaplan-Meier (KM) survival analysis indicated that low-risk patients of IRLP’s signature had a better OS (P<0.001). Advanced status BRCA patients may have higher risk scores, and univariate and multivariate cox regression analyses showed that risk scores were independent prognostic factors of clinical features (P<0.001). The results of the relationship between risk scores and immune infiltration showed that M1 macrophages were higher in the low-risk group (P=0.00015), while M2 macrophages were higher in the high-risk group (P=0.0015). The high-risk group had a greater sensitivity to chemotherapeutic agents such as cisplatin, docetaxel, doxorubicin, and gemcitabine.

Conclusions

In present study, we used a novel method that did not require the specific expression levels of lncRNAs of BRCA patients, which can be used as a novel model for predicting the prognosis of BRCA patients.

Long non-coding RNA TMPO-AS1 facilitates the progression of colorectal cancer cells via sponging miR-98-5p to upregulate BCAT1 expression

BACKGROUND AND AIM

Colorectal cancer, as a common malignant carcinoma in the gastrointestinal tract, has a high mortality globally. However, the specific molecular mechanisms of long non-coding RNA (lncRNA) thymopoietin antisense transcript 1 (TMPO-AS1) in colorectal cancer were unclear.

METHODS

We tested the expression level of TMPO-AS1 via qRT-PCR in colorectal cancer cells, while the protein levels of branched chain amino acid transaminase 1 (BCAT1) and the stemness-related proteins were evaluated by western blot analysis. Colony formation, EdU staining, TUNEL, flow cytometry, and sphere formation assays were to assess the biological behaviors of colorectal cancer cells. Then, luciferase reporter, RIP, and RNA pull down assay were applied for confirming the combination between microRNA-98-5p (miR-98-5p) and TMPO-AS1/BCAT1.

RESULTS

TMPO-AS1 was aberrantly expressed at high levels in colorectal cancer cells. Silenced TMPO-AS1 restrained cell proliferation and stemness and promoted apoptosis oppositely, while overexpressing TMPO-AS1 exerted the adverse effects. Furthermore, miR-98-5p was proven to a target of TMPO-AS1 inhibit cell progression in colorectal cancer. Additionally, BCAT1 was proved to enhance cell progression as the target of miR-98-5p, and it offset the effect of silenced TMPO-AS1 on colorectal cancer cells.

CONCLUSION

TMPO-AS1 promotes the progression of colorectal cancer cells via sponging miR-98-5p to upregulate BCAT1 expression.

Analysis of the estrogen receptor-associated lncRNA landscape identifies a role for ERLC1 in breast cancer progression

Estrogen receptor alpha (ERα) plays a vital role in the development of normal breast tissue and in breast cancer. By cross-analyzing The Cancer Genome Atlas (TCGA) database, ERα-regulated long noncoding RNA 1 (ERLC1) was identified as a long noncoding RNA exhibiting a strong association with ERα signaling and high specificity of expression in breast tissue. ERLC1 was transcriptionally activated by ERα, and ERLC1 stabilized the ESR1 transcript by sequestering miR-129 and tethering FXR1 to maintain a positive feedback loop that potentiated ERα signaling. ERLC1 was elevated in tamoxifen-resistant breast cancer cells, where ERLC1 depletion restored sensitivity to tamoxifen and increased the efficacy of palbociclib or fulvestrant therapy. Collectively, these data warrant further investigation of ERLC1 as a modulator of therapeutic response and potential therapeutic target in ER+ breast cancer.

Long non-coding RNA TMPO-AS1 promotes cell proliferation, migration, invasion and epithelial-to-mesenchymal transition in gallbladder carcinoma by regulating the microRNA-1179/E2F2 axis

Gallbladder carcinoma (GBC), which is a common tumor of the biliary system, poses a serious threat to human life and health. The present study aimed to investigate the molecular mechanism of the long non-coding (lnc)RNA thymopoietin antisense transcript 1 (TMPO-AS1)/microRNA (miRNA/miR)-1179/E2F transcription factor 2 (E2F2) axis in GBC. The viability, proliferation, migration, invasion and epithelial-to-mesenchymal transition (EMT) of GBC cell lines were assessed via the Cell Counting Kit-8, colony formation, Transwell migration and invasion, immunofluorescence and western blot assays. In the present study, lncRNA TMPO-AS1 was significantly upregulated in clinical GBC tissues and cell lines, and was highly expressed in stage III+IV patients with GBC compared with stage I+II patients with GBC. In addition, the overall survival rate of patients with low TMPO-AS1 expression levels was higher than those with high TMPO-AS1 expression levels. Furthermore, TMPO-AS1 knockdown inhibited the viability, proliferation, migration, invasion and EMT of GBC cell lines. In addition, miR-1179 expression was downregulated in clinical GBC tissues and cell lines, and negatively correlated with TMPO-AS1 expression. The results revealed that miR-1179 is a target of TMPO-AS1, which was confirmed via the dual-luciferase reporter assay and RNA pull-down analysis. Overexpression of miR-1179 inhibited the viability, proliferation, migration, invasion and EMT of GBC cell lines. Furthermore, E2F2 was verified as a direct target of miR-1179 by binding to its 3'-untranslated region. E2F2 expression was significantly upregulated in clinical GBC tissues and cell lines, and negatively correlated with miR-1179 expression. Notably, E2F2 knockdown partially hindered the effects of TMPO-AS1/miR-1179 on the proliferation and metastasis of GBC cell lines. Taken together, the results of the present study suggest that TMPO-AS1 potentially plays a tumor-promoting role in the occurrence and development of GBC, which may be achieved by regulating the miR-1179/E2F2 axis.

Long Intergenic Noncoding RNA OIN1 Promotes Ovarian Cancer Growth by Modulating Apoptosis-Related Gene Expression

Patients with advanced ovarian cancer usually exhibit high mortality rates, thus more efficient therapeutic strategies are expected to be developed. Recent transcriptomic studies revealed that long intergenic noncoding RNAs (lincRNAs) can be a new class of molecular targets for cancer management, because lincRNAs likely exert tissue-specific activities compared with protein-coding genes or other noncoding RNAs. We here show that an unannotated lincRNA originated from chromosome 10q21 and designated as ovarian cancer long intergenic noncoding RNA 1 (OIN1), is often overexpressed in ovarian cancer tissues compared with normal ovaries as analyzed by RNA sequencing. OIN1 silencing by specific siRNAs significantly exerted proliferation inhibition and enhanced apoptosis in ovarian cancer cells. Notably, RNA sequencing showed that OIN1 expression was negatively correlated with the expression of apoptosis-related genes ras association domain family member 5 (RASSF5) and adenosine A1 receptor (ADORA1), which were upregulated by OIN1 knockdown in ovarian cancer cells. OIN1-specifc siRNA injection was effective to suppress in vivo tumor growth of ovarian cancer cells inoculated in immunodeficient mice. Taken together, OIN1 could function as a tumor-promoting lincRNA in ovarian cancer through modulating apoptosis and will be a potential molecular target for ovarian cancer management.

lncRNA and breast cancer: Progress from identifying mechanisms to challenges and opportunities of clinical treatment

Breast cancer is a malignant tumor that has a high mortality rate and mostly occurs in women. Although significant progress has been made in the implementation of personalized treatment strategies for molecular subtypes in breast cancer, the therapeutic response is often not satisfactory. Studies have reported that long non-coding RNAs (lncRNAs) are abnormally expressed in breast cancer and closely related to the occurrence and development of breast cancer. In addition, the high tissue and cell-type specificity makes lncRNAs particularly attractive as diagnostic biomarkers, prognostic factors, and specific therapeutic targets. Therefore, an in-depth understanding of the regulatory mechanisms of lncRNAs in breast cancer is essential for developing new treatment strategies. In this review, we systematically elucidate the general characteristics, potential mechanisms, and targeted therapy of lncRNAs and discuss the emerging functions of lncRNAs in breast cancer. Additionally, we also highlight the advantages and challenges of using lncRNAs as biomarkers for diagnosis or therapeutic targets for drug resistance in breast cancer and present future perspectives in clinical practice.

From Micro to Long: Non-Coding RNAs in Tamoxifen Resistance of Breast Cancer Cells

Breast cancer is the most commonly diagnosed cancer and the leading cause of cancer mortality among women. Two thirds of patients are classified as hormone receptor positive, based on expression of estrogen receptor alpha (ERα), the main driver of breast cancer cell proliferation, and/or progesterone receptor, which is regulated by ERα. Despite presenting the best prognosis, these tumors can recur when patients acquire resistance to treatment by aromatase inhibitors or antiestrogen such as tamoxifen (Tam). The mechanisms that are involved in Tam resistance are complex and involve multiple signaling pathways. Recently, roles for microRNAs and lncRNAs in controlling ER expression and/or tamoxifen action have been described, but the underlying mechanisms are still little explored. In this review, we will discuss the current state of knowledge on the roles of microRNAs and lncRNAs in the main mechanisms of tamoxifen resistance in hormone receptor positive breast cancer. In the future, this knowledge can be used to identify patients at a greater risk of relapse due to the expression patterns of ncRNAs that impact response to Tam, in order to guide their treatment more efficiently and possibly to design therapeutic strategies to bypass mechanisms of resistance.

The Role of Sex-specific Long Non-coding RNAs in Cancer Prevention and Therapy

The functions of a large number of non-coding genes in human DNA have yet to be accurately identified. Long non-coding RNA (lncRNA) measuring 10 kb or less in length regulates transcription or post-transcriptional events. The lncRNAs have attracted increased attention of researchers in recent years. In this review, we summarize the recently published lncRNAs which are known to influence cancer development and progression. We also discuss recent studies investigating tumor-specific lncRNA expression. These lncRNAs provide very useful information that allows prediction of the degree of malignancy and a survival rate in cancer patients as clinically relevant biomarkers. Because symptoms and progression of cancer differ from onset to death between males and females, it is important to consider the gender of the patient when diagnosing cancer and predicting the progression. Considering the importance of gender difference, we also examine the influence of sex hormones involved in the expression and regulation of lncRNAs as biomarkers. Many of the lncRNAs examined in this review have been studied in cancers occurring in the female or male reproductive organs, but the association between lncRNAs and sex hormones has also been reported in common organs such as the lung, renal and colon. Although lncRNAs have not yet been widely used as definitive cancer indicators, recent studies have demonstrated the potential role of lncRNAs as biomarkers and therapeutic targets reflecting sex-specificity in a number of different cancers.

The Emerging Role of Thymopoietin-Antisense RNA 1 as Long Noncoding RNA in the Pathogenesis of Human Cancers

Long noncoding RNAs (lncRNAs) play essential roles in the occurrence and development of multiple human cancers. An accumulating body of researches have investigated thymopoietin antisense RNA 1 (TMPO-AS1) as a newly discovered lncRNA, which functions as an oncogenic lncRNA that is upregulated in various human malignancies and associated with poor prognosis. Many studies have detected abnormally high expression levels of TMPO-AS1 in multiple cancers, such as lung cancer, breast cancer, colorectal cancer (CRC), hepatocellular carcinoma, CRC, gastric cancer, ovarian cancer, thyroid cancer, esophageal cancer, Wilms tumor, cervical cancer, retinoblastoma, bladder cancer, osteosarcoma, and prostate cancer. TMPO-AS1 has been subsequently demonstrated to play a pivotal role in tumorigenesis and progression. The aberrantly expressed TMPO-AS1 acts as a competing endogenous RNA (ceRNA) that inhibits miRNA expression, thus activating the expression of downstream oncogenes. This study comprehensively summarizes the aberrant expressions of TMPO-AS1 as reported in the current literature and explains the relevant biological regulation mechanisms in carcinogenesis and tumor progression. Corresponding studies have indicated that TMPO-AS1 has a potential value as a promising biomarker or a target for cancer therapy.

The regulation of RNA metabolism in hormone signaling and breast cancer

As the most frequent women's cancer, breast cancer causes the second most cancer-related death in women worldwide. Majority of the breast cancers are hormone receptor-positive and commonly treated by hormone therapy. Thus, the expression levels of hormone receptors signaling pathways are pivotal in the development and therapy of breast cancer. The expression of hormone receptors signaling pathways is not only regulated at the transcription level but also at the post-transcription level by both proteins and RNAs. In addition to that, the function of hormone receptors can also be regulated by RNAs. In this review, we summarize the roles of RNAs in hormone receptor-positive breast cancer. We introduce how mRNA stability and protein function of genes in hormone receptors signaling pathways are regulated by RNA-binding proteins, miRNAs, and lncRNAs. We believe these proteins and RNAs can be potential therapeutic targets of breast cancer.

Endocrine resistance and epigenetic reprogramming in estrogen receptor positive breast cancer

Despite the enormous advances during the last three decades, breast cancer continues to be the most frequent type of cancer as well as one of the most frequent cancer-related causes of death in women. Therapeutic management of patients with hormone receptor-positive breast cancer becomes very often a challenge, since de novo or acquired resistance deprives a significant percentage of the patients from the clinical benefit of the well-tolerated hormone therapy. Several molecular mechanisms are implicated in resistance to endocrine therapy, including changes in hormone receptor signaling, activation of parallel signaling pathways, modifications of cell cycle regulators, activation of different transcription factors as well as changes in stem cells activity. In addition, a growing number of studies supports the pivotal role of epigenetic changes not only in the initiation and progression of breast cancer, but also in resistance to endocrine therapy. These changes refer to DNA methylation, histone post-translational modifications as well as to ncRNAs alterations. In this review, we provide an overview of epigenetic mechanisms underlying the endocrine resistance focusing exclusively on breast cancer patients.

Long noncoding RNA (lncRNA) EIF3J-DT induces chemoresistance of gastric cancer via autophagy activation

Chemotherapy is currently the main treatment for unresectable or advanced postoperative gastric cancers. However, its efficacy is negatively affected by the occurrence of chemoresistance, which severely affects patient prognosis. Recently, dysregulation in autophagy has been suggested as a potential mechanism for chemoresistence, and long noncoding RNA (lncRNA) also shows its regulatory role in cancer drug resistance. Using RNA sequencing, we found that lncRNA EIF3J-DT was highly expressed in drug-resistant gastric cancer cells. In-vitro and in-vivo experiments showed that EIF3J-DT activated autophagy and induced drug resistance in gastric cancer cells by targeting ATG14. Bioinformatics and experimental results showed that EIF3J-DT regulated the expression of ATG14 through direct binding to enhance stabilization of ATG14 mRNA and via blocking the degradation of ATG14 mRNA through competitively binding with microRNA (miRNA) MIR188-3p. Therefore, EIF3J-DT increased the expression of ATG14, contributing to activation of autophagy and chemoresistance. Furthermore, it was confirmed that EIF3J-DT and ATG14 were highly expressed in gastric cancer patients resistant to chemotherapy, and this was closely associated with patient prognosis. In conclusion, EIF3J-DT is involved in the regulation of autophagy and chemoresistance in gastric cancer cells by targeting ATG14. It may be a suitable new target for enhancing chemosensitivity and improving prognosis.Abbreviations: 3-MA: 3-methyladenine; 5-Fu: 5-fluorouracil; ATG: autophagy related; C-CASP3: cleaved caspase 3; C-CASP7: cleaved caspase 7; C-PARP: cleaved PARP; CQ: chloroquine; CR: complete response; DIG: digoxigenin; ESR1: estrogen receptor 1; FBS: fetal bovine serum; FISH: fluorescence in situ hybridization; IHC: immunohistochemistry; ISH: in situ hybridization; lncRNA: long noncoding RNA; miRNA: microRNA; MUT: mutant; NC: negative control; OXA: oxaliplatin; PBS: phosphate-buffered saline; PD: progressive disease; PFA: paraformaldehyde; PR: partial response; qPCR: quantitative polymerase chain reaction; RAPA: rapamycin; SD: stable disease; TEM: transmission electron microscopy; WT: wild type.

The Long Non-coding RNA TMPO-AS1 Promotes Bladder Cancer Growth and Progression via OTUB1-Induced E2F1 Deubiquitination

Background: Increasing evidence indicates that long non-coding RNAs (lncRNAs) play crucial roles in cancer tumorigenesis and progression. TMPO antisense RNA 1 (TMPO-AS1) has been found to be involved in several cancers by acting as a competing endogenous RNA. However, the potential roles of TMPO-AS1 in bladder cancer (BC) and the potential interactions with proteins remain poorly understood.

Methods: The expression of the lncRNA TMPO-AS1 was evaluated via bioinformatic analysis and further validated by quantitative real-time PCR (qRT-PCR). Loss- and gain-of-function assays were performed to determine the biological functions of TMPO-AS1 in BC cell proliferation, migration, and invasion. Moreover, chromatin immunoprecipitation, Western blotting, and fluorescence in situ hybridization, as well as RNA pull-down, RNA immunoprecipitation, and luciferase reporter assays, were conducted to explore the upstream and downstream molecules interacting with TMPO-AS1.

Results: TMPO-AS1 is upregulated in BC. Functional experiments demonstrated that TMPO-AS1 promotes cell proliferation, migration, and invasion in BC and inhibits cell apoptosis in vivo and in vitro. Mechanically, E2F1 is responsible for TMPO-AS1 upregulation. Additionally, TMPO-AS1 facilitates the interaction of E2F1 with OTU domain-containing ubiquitin aldehyde binding 1 (OTUB1), leading to E2F1 deubiquitination and stabilization; therefore, TMPO-AS1 promotes BC malignant phenotypes. Furthermore, rescue experiments showed that TMPO-AS1 promotes BC growth in an E2F1-dependent manner.

Conclusions: Our study is the first to uncover the novel TMPO-AS1/E2F1 positive regulatory loop important for the promotion of BC malignant behaviors. The TMPO-AS1/E2F1 loop should be considered in the quest for new BC therapeutic options.

Down-Regulation of TMPO-AS1 Induces Apoptosis in Lung Carcinoma Cells by Regulating miR-143-3p/CDK1 Axis

Evidence has shown that long non-coding RNAs (lncRNA) play pivotal roles in cancer promotion as well as suppression. But the molecular mechanism of lncRNA TMPO antisense transcript 1 (TMPO-AS1) in lung cancer (LC) remains unclear. This study mainly investigated the effect of TMPO-AS1 in LC treatment. TMPO-AS1 was tested by Kaplan-Meier method. Quantitative real time polymerase chain reaction (qRT-PCR) was employed to assess the expressions of TMPO-AS1, miR-143-3p, and CDK1 respectively in LC tissues and cell lines. TMPO-AS1, miR-143-3p and CDK1 expressions in LC cells were regulated through cell transfection, followed by MTT for cell viability detection. Besides, dual-luciferase reporter assays were performed to verify the interrelated microRNA of TMPO-AS1 and the target of miR-143-3p. Western blot experiments were used to examine the expressions of apoptosis-related proteins, and flow cytometry tested the cell apoptosis in treated cells. TMPO-AS1 and CDK1 were overexpressed in LC tissues and cells, while miR-143-3p level was suppressed. The decrease of TMPO-AS1 led to the increase of miR-143-3p, which further resulted in the reduction of CDK1. Down-regulating TMPO-AS1 reduced LC cell viability, motivated cell apoptosis, as well as promoted the expressions of Bcl and CCND1 and restrained Caspase-3 level, but all these consequences were abrogated by miR-143-3p inhibitor. Simultaneously, siCDK1 could reverse the anti-apoptosis and pro-activity functions of miR-143-3p inhibitor in LC cells. Down-regulation of TMPO-AS1 has the effects of pro-apoptosis in LC by manipulating miR-143-3p/CDK1, which is hopeful to be a novel therapy for LC patients.

TMPO-AS1, a Novel E2F1-Regulated lncRNA, Contributes to the Proliferation of Lung Adenocarcinoma Cells via Modulating miR-326/SOX12 Axis

Background

TMPO-AS1, an antisense lncRNA located at human chromosome 12p23.1, has been identified as an oncogene involved in cell proliferation in various cancers, including LUAD. In this study, we aimed to explore the novel molecular mechanism of TMPO-AS1 underlying LUAD growth.

Materials and Methods

The transcription levels of TMPO-AS1, miR-326, and SOX12 in LUAD tissues and cell lines were detected by quantitative real-time PCR (qRT-PCR). The cell proliferation ability was evaluatect 3d by cell counting kit-8 (CCK-8) assay. Cell cycle and apoptosis analysis was assessed by flow cytometry. The target relationship among TMPO-AS1, miR-326, and SOX12 and promoter activity of TMPO-AS1 was measured using dual-luciferase reporter assay. The protein levels of SOX12 in LUAD cells were determined by Western blot. ChIP-qPCR assay was performed to validate the direct binding between E2F1 and TMPO-AS1 promoter.

Results

TMPO-AS1 was up-regulated in LUAD tissues as well as cell lines. Boosted TMPO-AS1 expression was positively correlated with poor prognosis and pathological stage in LUAD. Down-regulation of TMPO-AS1 could restrain the proliferation of LUAD cells through arresting the cell cycle at G0/G1 phase and inducing apoptosis in vitro. Mechanically, we demonstrated that TMPO-AS1 could modulate the proliferation of LUAD cells through increasing SOX12 expression level via sponging miR-326 in accordance with bioinformatics analysis and experimental validation. Furthermore, we identified that TMPO-AS1 could be activated by E2F transcription factor 1 (E2F1) as a novel target gene.

Conclusion

TMPO-AS1 can modulate LUAD cell proliferation through E2F1/miR-326/SOX12 pathway.

Long Non-coding RNAs Involved in Metabolic Alterations in Breast and Prostate Cancers

Breast and prostate cancers are the most prevalent cancers in females and males, respectively. These cancers exhibit sex hormone dependence and thus, hormonal therapies are used to treat these cancers. However, acquired resistance to hormone therapies is a major clinical problem. In addition, certain portions of these cancers initially exhibit hormone-independence due to the absence of sex hormone receptors. Therefore, precise and profound understanding of the cancer pathophysiology is required to develop novel clinical strategies against breast and prostate cancers. Metabolic reprogramming is currently recognized as one of the hallmarks of cancer, as exemplified by the alteration of glucose metabolism, oxidative phosphorylation, and lipid metabolism. Dysregulation of metabolic enzymes and their regulators such as kinases, transcription factors, and other signaling molecules contributes to metabolic alteration in cancer. Moreover, accumulating lines of evidence reveal that long non-coding RNAs (lncRNAs) regulate cancer development and progression by modulating metabolism. Understanding the mechanism and function of lncRNAs associated with cancer-specific metabolic alteration will therefore provide new knowledge for cancer diagnosis and treatment. This review provides an overview of recent studies regarding the role of lncRNAs in metabolism in breast and prostate cancers, with a focus on both sex hormone-dependent and -independent pathways.

Managing therapeutic resistance in breast cancer: from the lncRNAs perspective

Breast cancer (BC) is the most common female malignancy and the second leading cause of cancer-related death worldwide. In spite of significant advances in clinical management, the mortality of BC continues to increase due to the frequent occurrence of treatment resistance. Intensive studies have been conducted to elucidate the molecular mechanisms underlying BC therapeutic resistance, including increased drug efflux, altered drug targets, activated bypass signaling pathways, maintenance of cancer stemness, and deregulated immune response. Emerging evidence suggests that long noncoding RNAs (lncRNAs) are intimately involved in BC therapy resistance through multiple modes of action. Therefore, an in-depth understanding of the implication of lncRNAs in resistance to clinical therapies may improve the clinical outcome of BC patients. Here, we highlight the role and underlying mechanisms of lncRNAs in regulating BC treatment resistance with an emphasis on lncRNAs-mediated resistance in different clinical scenarios, and discuss the potential of lncRNAs as novel biomarkers or therapeutic targets to improve BC therapy response.

Perspectives on the Role of Non-Coding RNAs in the Regulation of Expression and Function of the Estrogen Receptor

Estrogen receptors (ERs) comprise several nuclear and membrane-bound receptors with different tissue-specific functions. ERα and ERβ are two nuclear members of this family, whereas G protein-coupled estrogen receptor (GPER), ER-X, and Gq-coupled membrane estrogen receptor (Gq-mER) are membrane-bound G protein-coupled proteins. ERα participates in the development and function of several body organs such as the reproductive system, brain, heart and musculoskeletal systems. ERβ has a highly tissue-specific expression pattern, particularly in the female reproductive system, and exerts tumor-suppressive roles in some tissues. Recent studies have revealed functional links between both nuclear and membrane-bound ERs and non-coding RNAs. Several oncogenic lncRNAs and miRNAs have been shown to exert their effects through the modulation of the expression of ERs. Moreover, treatment with estradiol has been shown to alter the malignant behavior of cancer cells through functional axes composed of non-coding RNAs and ERs. The interaction between ERs and non-coding RNAs has functional relevance in several human pathologies associated with estrogen regulation, such as cancers, intervertebral disc degeneration, coronary heart disease and diabetes. In the current review, we summarize scientific literature on the role of miRNAs and lncRNAs on ER-associated signaling and related disorders.

Long Non-Coding RNAs in Drug Resistance of Breast Cancer

Breast cancer (BC) is the most common cancer and the leading cause of death in women. Advances in early diagnosis and therapeutic strategies have decreased the mortality of BC and improved the prognosis of patients to some extent. However, the development of drug resistance has limited the success rate of systemic therapies. Long non-coding RNAs (lncRNAs) are involved in drug resistance in BC via various mechanisms, which contribute to a complex regulatory network. In this review, we summarize the latest findings on the mechanisms underlying drug resistance modulated by lncRNAs in BC. In addition, we discuss the potential clinical applications of lncRNAs as targeted molecular therapy against drug resistance in BC.

Propofol suppresses hypoxia-induced esophageal cancer cell migration, invasion, and EMT through regulating lncRNA TMPO-AS1/miR-498 axis

Background

Propofol has been reported to be related to the migration, invasion, and epithelial‐mesenchymal transition (EMT) of esophageal cancer (EC) cells. However, the detailed mechanism has not yet been fully reported. The purpose of this research was to elucidate the function of long non‐coding RNA TMPO antisense RNA 1 (lncRNA TMPO‐AS1) and microRNA‐498 (miR‐498) in propofol‐regulated EC.

Methods

Transwell assay was performed to assess cell migratory and invasive abilities. Western blot assay was employed to determine the levels of EMT markers and hypoxia inducible factor‐1 (HIF‐1α). Quantitative real‐time polymerase chain reaction (qRT‐PCR) was carried out to detect the levels of TMPO‐AS1 and miR‐498. Moreover, the interaction between TMPO‐AS1 and miR‐498 was predicted by starBase, and then confirmed by the dual‐luciferase reporter assay and RNA immunoprecipitation (RIP) assay.

Results

Propofol suppressed hypoxia‐induced EC cell migration, invasion, and EMT. Both TMPO‐AS1 overexpression and miR‐498 knockdown weakened the effect of propofol on hypoxia‐induced EC cell progression. Interestingly, TMPO‐AS1 targeted miR‐498 and suppressed miR‐498 expression. TMPO‐AS1 regulated EC cell progression via downregulating miR‐498 expression.

Conclusions

Collectively, our findings demonstrated that propofol inhibited hypoxia‐induced EC cell mobility through modulation of the TMPO‐AS1/miR‐498 axis, providing a theoretical basis for the treatment of EC.

Emerging roles of long non-coding RNAs in breast cancer biology and management

Breast cancer is the most common cancer in women with the highest mortality among this gender. Despite treatment strategies including surgery, hormone therapy and targeted therapy have recently advanced, innovative biomarkers are needed for the early detection, treatment and prognosis. An increasing number of non-coding RNAs (ncRNAs) have shown great potential as crucial players in different stages of the breast cancer tumorigenesis, influencing cell death, metabolism, epithelial-mesenchymal transition (EMT), metastasis and drug resistance. Long non-coding RNAs (lncRNAs), specifically, are a class of RNA transcripts with a length greater than 200 nucleotides, which have also been shown to exerts oncogenic or tumour suppressive roles in the pathogenesis of breast cancer. LncRNAs are implicated in different molecular mechanisms by regulating gene expressions and functions at transcriptional, translational, and post-translational levels. Here, we aim to briefly discuss the latest existing body of knowledge regarding the key functions and the molecular mechanisms of some of the most relevant lncRNAs in the pathogenesis, treatment and prognosis of breast cancer.

Proliferation-associated long noncoding RNA, TMPO-AS1, is a potential therapeutic target for triple-negative breast cancer

Triple‐negative breast cancer (TNBC) is an aggressive subtype of breast cancer compared with luminal or epidermal growth factor receptor 2 subtypes, thus effective therapeutic options for TNBC are yet to be developed. Nowadays, oncogenic long noncoding RNAs (lncRNAs) are applied to cancer management as a new class of therapeutic targets. We previously showed that thymopoietin antisense transcript 1 (TMPO‐AS1) is a proliferation‐associated lncRNA that contributes to hormone‐dependent breast cancer progression by stabilizing estrogen receptor‐α mRNA. We here showed that TMPO‐AS1 is abundantly expressed in basal‐like breast cancer subtype based on the transcriptomic data in The Cancer Genome Atlas as well as in TNBC cell lines and patient‐derived cells. Small interfering RNA‐based loss‐of‐function analyses showed that TMPO‐AS1 knockdown substantially represses the proliferation and migration of TNBC cells. Expression microarray analysis showed that TMPO‐AS1 alters gene signatures related to transforming growth factor‐β signaling in addition to proliferative E2F signaling pathways. TMPO‐AS1‐targeted siRNA treatment through engineered drug delivery systems using cancer‐targeted polyion complex micelle or nanoball technology significantly impaired the in vivo growth of primary and metastatic TNBC xenograft tumors. Our findings suggest that TMPO‐AS1 plays a key role in TNBC pathophysiology and could be a potential therapeutic target for TNBC.

Long Noncoding RNAs Involved in the Endocrine Therapy Resistance of Breast Cancer

Long noncoding RNAs (lncRNAs) are defined as RNAs longer than 200 nucleotides that do not encode proteins. Recent studies have demonstrated that numerous lncRNAs are expressed in humans and play key roles in the development of various types of cancers. Intriguingly, some lncRNAs have been demonstrated to be involved in endocrine therapy resistance for breast cancer through their own mechanisms, suggesting that lncRNAs could be promising new biomarkers and therapeutic targets of breast cancer. Here, we summarize the functions and mechanisms of lncRNAs related to the endocrine therapy resistance of breast cancer.

PSF Promotes ER-Positive Breast Cancer Progression via Posttranscriptional Regulation of ESR1 and SCFD2

Endocrine therapy is standard treatment for estrogen receptor (ER)-positive breast cancer, yet long-term treatment often causes acquired resistance, which results in recurrence and metastasis. Recent studies have revealed that RNA-binding proteins (RBP) are involved in tumorigenesis. Here, we demonstrate that PSF/SFPQ is an RBP that potentially predicts poor prognosis of patients with ER-positive breast cancer by posttranscriptionally regulating ERα (ESR1) mRNA expression. Strong PSF immunoreactivity correlated with shorter overall survival in patients with ER-positive breast cancer. PSF was predominantly expressed in a model of tamoxifen-resistant breast cancer cells, and depletion of PSF attenuated proliferation of cultured cells and xenografted tumors. PSF expression was significantly associated with estrogen signaling. PSF siRNA downregulated ESR1 mRNA by inhibiting nuclear export of the RNA. Integrative analyses of microarray and RNA immunoprecipitation sequencing also identified SCFD2, TRA2B, and ASPM as targets of PSF. Among the PSF targets, SCFD2 was a poor prognostic indicator of breast cancer and SCFD2 knockdown significantly suppressed breast cancer cell proliferation. Collectively, this study shows that PSF plays a pathophysiologic role in ER-positive breast cancer by posttranscriptionally regulating expression of its target genes such as ESR1 and SCFD2. Overall, PSF and SCFD2 could be potential diagnostic and therapeutic targets for primary and hormone-refractory breast cancers. SIGNIFICANCE: This study defines oncogenic roles of RNA-binding protein PSF, which exhibits posttranscriptional regulation in ER-positive breast cancer.

RNA-binding protein NONO promotes breast cancer proliferation by post-transcriptional regulation of SKP2 and E2F8

The majority of breast cancers are primarily hormone‐sensitive and can be managed by endocrine therapy, although therapy‐resistant or hormone‐refractory cancers need alternative treatments. Recently, increasing attention is being paid to RNA‐binding proteins (RBP) in cancer pathophysiology. The precise role of RBP in breast cancer, however, remains to be clarified. We herein show that an RBP non‐POU domain‐containing octamer binding (NONO) plays a critical role in the pathophysiology of breast cancers regardless of their hormone dependency. Clinicopathological and immunohistochemical study of 127 breast cancer cases showed that NONO is a significant independent prognostic factor for breast cancer patients. Notably, siRNA‐mediated NONO knockdown substantially repressed the proliferation of both hormone‐sensitive MCF‐7 and hormone‐refractory MB‐MDA‐231 breast cancer cells. Integrative analysis combined with expression microarray and RIP‐sequencing (RNA immunoprecipitation‐sequencing) showed that NONO post‐transcriptionally regulates the expression of cell proliferation‐related genes by binding to their mRNAs, as exemplified by S‐phase‐associated kinase 2 and E2F transcription factor 8. Overall, these results suggest that NONO is a key regulator for breast cancer proliferation through the pre‐mRNA splicing of cell proliferation‐related genes and could be a potential new diagnostic and therapeutic target for advanced disease.