Mechanisms of endocrine resistance in breast cancer: an overview of the proposed roles of noncoding RNA

DNA Damage Responses in Tumors Are Not Proliferative Stimuli, but Rather They Are DNA Repair Actions Requiring Supportive Medical Care

BACKGROUND

In tumors, somatic mutagenesis presumably drives the DNA damage response (DDR) via altered regulatory pathways, increasing genomic instability and proliferative activity. These considerations led to the standard therapeutic strategy against cancer: the disruption of mutation-activated DNA repair pathways of tumors.

PURPOSE

Justifying that cancer cells are not enemies to be killed, but rather that they are ill human cells which have the remnants of physiologic regulatory pathways.

RESULTS

1. Genomic instability and cancer development may be originated from a flaw in estrogen signaling rather than excessive estrogen signaling; 2. Healthy cells with genomic instability exhibit somatic mutations, helping DNA restitution; 3. Somatic mutations in tumor cells aim for the restoration of DNA damage, rather than further genomic derangement; 4. In tumors, estrogen signaling drives the pathways of DNA stabilization, leading to apoptotic death; 5. In peritumoral cellular infiltration, the genomic damage of the tumor induces inflammatory cytokine secretion and increased estrogen synthesis. In the inflammatory cells, an increased growth factor receptor (GFR) signaling confers the unliganded activation of estrogen receptors (ERs); 6. In breast cancer cells responsive to genotoxic therapy, constitutive mutations help the upregulation of estrogen signaling and consequential apoptosis. In breast tumors non-responsive to genotoxic therapy, the possibilities for ER activation via either liganded or unliganded pathways are exhausted, leading to farther genomic instability and unrestrained proliferation.

CONCLUSIONS

Understanding the real character and behavior of human tumors at the molecular level suggests that we should learn the genome repairing methods of tumors and follow them by supportive therapy, rather than provoking additional genomic damages.

Establishment of a prognostic risk prediction model incorporating disulfidptosis-related lncRNA for patients with prostate cancer

PURPOSE

Prostate cancer (PCa) is one of the major tumor diseases that threaten men's health globally, and biochemical recurrence significantly impacts its prognosis. Disulfidptosis, a recently discovered cell death mechanism triggered by intracellular disulfide accumulation leading to membrane rupture, is a new area of research in the context of PCa. Currently, its impact on PCa remains largely unexplored. This study aims to investigate the correlation between long non-coding RNAs (lncRNAs) associated with disulfidptosis and the prognosis of PCa, seeking potential connections between the two.

METHODS

Transcriptomic data for a PCa cohort were obtained from the Cancer Genome Atlas database. Disulfidptosis-related lncRNAs (DDRLs) were identified through differential expression and Pearson correlation analysis. DDRLs associated with biochemical recurrence-free survival (BRFS) were precisely identified using univariate Cox and LASSO regression, resulting in the development of a risk score model. Clinical factors linked to BRFS were determined through both univariate and multivariate Cox analyses. A prognostic nomogram combined the risk score with key clinical variables. Model performance was assessed using Receiver Operating Characteristic (ROC) curves, Decision Curve Analysis (DCA), and calibration curves. The functional impact of a critical DDRL was substantiated through assays involving CCK8, invasion, migration, and cell cloning. Additionally, immunohistochemical (IHC) staining for the disulfidptosis-related protein SLC7A11 was conducted.

RESULTS

The prognostic signature included AC026401.3, SNHG4, SNHG25, and U73166.1 as key components. The derived risk score from these signatures stood as one of the independent prognostic factor for PCa patients, correlating with poorer BRFS in the high-risk group. By combining the risk score with clinical variables, a practical nomogram was created, accurately predicting BRFS of PCa patients. Notably, silencing AC026401.3 significantly hindered PCa cell proliferation, invasion, migration, and colony formation. IHC staining revealed elevated expression of the dithiosulfatide-related protein SLC7A11 in tumor tissue.

CONCLUSIONS

A novel prognostic signature for PCa DDRLs, possessing commendable predictive power, has been constructed, simultaneously providing potential therapeutic targets associated with disulfidptosis, among which AC026401.3 has been validated in vitro and demonstrated inhibition of PCa tumorigenesis after its silencing.

Genomic Alterations Associated with Estrogen Receptor Pathway Activity in Metastatic Breast Cancer Have a Differential Impact on Downstream ER Signaling

Mutations in the estrogen receptor gene (ESR1), its transcriptional regulators, and the mitogen-activated protein kinase (MAPK) pathway are enriched in patients with endocrine-resistant metastatic breast cancer (MBC). Here, we integrated whole genome sequencing with RNA sequencing data from the same samples of 101 ER-positive/HER2-negative MBC patients who underwent a tumor biopsy prior to the start of a new line of treatment for MBC (CPCT-02 study, NCT01855477) to analyze the downstream effects of DNA alterations previously linked to endocrine resistance, thereby gaining a better understanding of the associated mechanisms. Hierarchical clustering was performed using expression of ESR1 target genes. Genomic alterations at the DNA level, gene expression levels, and last administered therapy were compared between the identified clusters. Hierarchical clustering revealed two distinct clusters, one of which was characterized by increased expression of ESR1 and its target genes. Samples in this cluster were significantly enriched for mutations in ESR1 and amplifications in FGFR1 and TSPYL. Patients in the other cluster showed relatively lower expression levels of ESR1 and its target genes, comparable to ER-negative samples, and more often received endocrine therapy as their last treatment before biopsy. Genes in the MAPK-pathway, including NF1, and ESR1 transcriptional regulators were evenly distributed. In conclusion, RNA sequencing identified a subgroup of patients with clear expression of ESR1 and its downstream targets, probably still benefiting from ER-targeting agents. The lower ER expression in the other subgroup might be partially explained by ER activity still being blocked by recently administered endocrine treatment, indicating that biopsy timing relative to endocrine treatment needs to be considered when interpreting transcriptomic data.

Combinatorial treatments of tamoxifen and SM6Met, an extract from Cyclopia subternata Vogel, are superior to either treatment alone in MCF-7 cells

Synergistic drug combinations are not only popular in antibiotic, anti-microbial, immune disease (i.e., AIDS) and viral infection studies, but has also gained traction in the field of cancer research as a multi-targeted approach. It has the potential to lower the doses needed of standard of care (SOC) therapeutic agents, whilst maintaining an effective therapeutic level. Lower dosages could ameliorate the fundamental problems such as drug resistance and metastasis associated with current SOC therapies. In the current study, we show that the combination of SM6Met with (2)-4-hydroxytamoxifen (4-OH-Tam, the active metabolite of tamoxifen) produces a strong synergistic effect in terms of inhibiting MCF7 ER-positive (ER⁺) breast cancer cell proliferation and that a 20 times lower dose of 4-OH-Tam in combination with SM6Met is required to produce the same inhibitory effect on cell proliferation as 4-OH-Tam on its own. Cell cycle analyses of the best combination ratios of SM6Met and 4-OH-Tam also suggests that the combination results in increased accumulation of cells in the S-phase and in the apoptotic phase. Moreover, the best combination ratio (20:1) of SM6Met with 4-OH-Tam displayed greater anti-metastatic potential in terms of inhibiting ER⁺ breast cancer cell migration, invasion, and colony formation than the SOC therapy alone, suggesting that SM6Met together with 4-OH-Tam could be a viable drug combination for not only delaying resistance and ameliorating the negative side-effects associated with current SOC therapies, like tamoxifen, but could also provide a novel, more affordable therapeutic alternative for treating or preventing ER⁺ breast cancer metastasis.

Ginsenoside Rh2 Regulates the CFAP20DC-AS1/MicroRNA-3614-3p/BBX and TNFAIP3 Axis to Induce Apoptosis in Breast Cancer Cells

While a number of coding genes have explained the anticancer activity of ginsenoside Rh2, little is known about noncoding RNAs. This study was performed to elucidate the regulatory activity of long noncoding RNA (lncRNA) CFAP20DC-AS1, which is known to be downregulated by Rh2. MiR-3614-3p, which potentially binds CFAP20DC-AS1, was screened using the LncBase Predicted program, and the binding was verified by assaying the luciferase activity of a luciferase/lncRNA recombinant plasmid construct. The competitive endogenous RNA (ceRNA) relationship of the two RNAs was further validated by quantitative PCR after deregulation of each RNA using siRNA. The effect of miRNA and target genes on the MCF-7 cancer cell growth was determined by monitoring proliferation and apoptosis in the presence of Rh2 after deregulating the corresponding gene. The miRNA decreased the luciferase activity of the luciferase/CFAP20DC-AS1 fusion vector, confirming the binding. SiRNA-based deregulation of CFAP20DC-AS1 attenuated the expression of miR-3614-3p and vice versa. In contrast to CFAP20DC-AS1, miR-3614-3p was upregulated by Rh2, inhibiting proliferation but stimulating apoptosis of the MCF-7 cells. Target genes of miR-3614-3p, BBX and TNFAIP3, were downregulated by Rh2 and the miRNA but upregulated by the lncRNA. Rh2 inhibits CFAP20DC-AS1, which obscures the association of the lncRNA with miR-3614-3p, resulting in the suppression of oncogenic BBX and TNFAIP3. Taken together, the Rh2/CFAP20DC-AS1/miR-3614-3p/target gene axis contributes to the antiproliferation activity of Rh2 in cancer cells.

Noncoding RNAs related to the hedgehog pathway in cancer: clinical implications and future perspectives

Cancer is a type of malignant affliction threatening human health worldwide; however, the molecular mechanism of cancer pathogenesis remains to be elusive. The oncogenic hedgehog (Hh) pathway is a highly evolutionarily conserved signaling pathway in which the hedgehog-Patched complex is internalized to cellular lysosomes for degradation, resulting in the release of Smoothened inhibition and producing downstream intracellular signals. Noncoding RNAs (ncRNAs) with diversified regulatory functions have the potency of controlling cellular processes. Compelling evidence reveals that Hh pathway, ncRNAs, or their crosstalk play complicated roles in the initiation, metastasis, apoptosis and drug resistance of cancer, allowing ncRNAs related to the Hh pathway to serve as clinical biomarkers for targeted cancer therapy. In this review, we attempt to depict the multiple patterns of ncRNAs in the progression of malignant tumors via interactions with the Hh crucial elements in order to better understand the complex regulatory mechanism, and focus on Hh associated ncRNA therapeutics aimed at boosting their application in the clinical setting.

Exploring the Mechanism of Baicalin Intervention in Breast Cancer Based on MicroRNA Microarrays and Bioinformatics Strategies

Objective

To explore the mechanism of baicalin intervention in breast cancer based on microRNA microarrays.

Methods

The inhibitory rate of baicalin intervention in MCF-7 breast cancer cells was determined by MTT. Then, the miRNA microarrays were used to validate the key microRNAs. After that, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to validate microRNA, hsa-miR-15a, hsa-miR-100, hsa-miR-16, and hsa-miR-7t. Finally, the potential targets of these key microRNAs are predicted by miRWalk, and DAVID was utilized for gene ontology (GO) enrichment analysis and pathway enrichment analysis.

Results

Baicalin may inhibit the proliferation of MCF-7 cells in a dose-dependent and time-dependent manner. The concentration of baicalin 150 μmol/L was determined for the subsequent miRNA chip research. A total of 92 upregulated microRNAs and 35 downregulated microRNAs were obtained. The upregulated miRNAs include hsa-miR-6799-5p, hsa-miR-6126, hsa-miR-4792, hsa-miR-6848-5p, hsa-miR-3197, hsa-miR-6779-5p, and hsa-miR -654-5p. The downregulated miRNAs include hsa-miR-3911, hsa-miR-504-5p, hsa-miR-30a-3p, hsa-miR-193b-3p, and hsa-miR-181b-5p. Then, differentially expressed miRNA was verified by qRT-PCR. The results showed that the expression of hsa-miR-15a, hsa-miR-100, hsa-miR-16, and hsa-let-7c was upregulated (P < 0.05), which was consistent with the results of the miRNA microarray. The enrichment analysis showed that baicalin might regulate the DNA-templated proliferation, DNA-templated transcription, p53 signaling pathway, etc., of MCF-7 breast cancer cells through miRNA.

Conclusion

Baicalin inhibits the proliferation of breast cancer cells. It may achieve antitumor effects through regulating microRNAs so as to affect the DNA replication (such as cellular response to DNA damage stimulus and DNA binding), RNA transcription (such as regulation of transcription, DNA-templated, transcription from RNA polymerase II promoter, and transcription factor binding), protein synthesis (such as mRNA binding, Golgi apparatus, and protein complex), endocytosis, pathways in cancer, p53 signaling pathway, and so on.

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.

Biological Activity Evaluation and In Silico Studies of Polyprenylated Benzophenones from Garcinia celebica

This study aimed to isolate polyprenylated benzophenones from the rootbark of Garcinia celebica and assess their activities in vitro and in silico. The antioxidant activity was evaluated by the DPPH, ABTS, and FRAP methods. The cytotoxicity was evaluated against HeLa, MCF-7, A549, and B16 cancer cell lines. The antiplasmodial activity was performed against the chloroquine-sensitive Plasmodium falciparum strain 3D7. Molecular docking was analyzed on alpha-estrogen receptor (3ERT) and P. falciparum lactate dehydrogenase enzyme (1CET). The prediction of ADMET for the compounds was also studied. For the first time, (-)-cycloxanthochymol, isoxanthochymol, and xanthochymol were isolated from the root bark of Garcinia celebica. The antioxidant and cytotoxicity evaluation showed that all benzophenones exhibited antioxidant activity compared to gallic acid and quercetin as positive controls and also exhibited strong activity against HeLa, MCF-7, A549, and B16 cell lines compared to cisplatin as the positive control. The antiplasmodial evaluation showed that isoxanthochymol exhibited activity against the chloroquine-sensitive P. falciparum strain 3D7. In addition, the in silico molecular docking study supported in vitro activities. The ADMET analysis also indicated the isolated benzophenones are potential oral drug candidates.

Prolactin and endocrine therapy resistance in breast cancer: The next potential hope for breast cancer treatment

Breast cancer, a hormone‐dependent tumour, generally includes four molecular subtypes (luminal A, luminal B, HER2 enriched and triple‐negative) based on oestrogen receptor, progesterone receptor and human epidermal growth factor receptor‐2. Multiple hormones in the body regulate the development of breast cancer. Endocrine therapy is one of the primary treatments for hormone‐receptor‐positive breast cancer, but endocrine resistance is the primary clinical cause of treatment failure. Prolactin (PRL) is a protein hormone secreted by the pituitary gland, mainly promoting mammary gland growth, stimulating and maintaining lactation. Previous studies suggest that high PRL levels can increase the risk of invasive breast cancer in women. The expression levels of PRL and PRLR in breast cancer cells and breast cancer tissues are elevated in most ER⁺ and ER⁻ tumours. PRL activates downstream signalling pathways and affects endocrine therapy resistance by combining with prolactin receptor (PRLR). In this review, we illustrated and summarized the correlations between endocrine therapy resistance in breast cancer and PRL, as well as the pathophysiological mechanisms and clinical practices. The study on PRL and its receptor would help explore reversing endocrine therapy‐resistance for breast cancer.

lncExplore: a database of pan-cancer analysis and systematic functional annotation for lncRNAs from RNA-sequencing data

Over the past few years, with the rapid growth of deep-sequencing technology and the development of computational prediction algorithms, a large number of long non-coding RNAs (lncRNAs) have been identified in various types of human cancers. Therefore, it has become critical to determine how to properly annotate the potential function of lncRNAs from RNA-sequencing (RNA-seq) data and arrange the robust information and analysis into a useful system readily accessible by biological and clinical researchers. In order to produce a collective interpretation of lncRNA functions, it is necessary to integrate different types of data regarding the important functional diversity and regulatory role of these lncRNAs. In this study, we utilized transcriptomic sequencing data to systematically observe and identify lncRNAs and their potential functions from 5034 The Cancer Genome Atlas RNA-seq datasets covering 24 cancers. Then, we constructed the 'lncExplore' database that was developed to comprehensively integrate various types of genomic annotation data for collective interpretation. The distinctive features in our lncExplore database include (i) novel lncRNAs verified by both coding potential and translation efficiency score, (ii) pan-cancer analysis for studying the significantly aberrant expression across 24 human cancers, (iii) genomic annotation of lncRNAs, such as cis-regulatory information and gene ontology, (iv) observation of the regulatory roles as enhancer RNAs and competing endogenous RNAs and (v) the findings of the potential lncRNA biomarkers for the user-interested cancers by integrating clinical information and disease specificity score. The lncExplore database is to our knowledge the first public lncRNA annotation database providing cancer-specific lncRNA expression profiles for not only known but also novel lncRNAs, enhancer RNAs annotation and clinical analysis based on pan-cancer analysis. lncExplore provides a more complete pathway to highly efficient, novel and more comprehensive translation of laboratory discoveries into the clinical context and will assist in reinterpreting the biological regulatory function of lncRNAs in cancer research. Database URL http://lncexplore.bmi.nycu.edu.tw.

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.

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.

Regulation of aromatase expression: Potential therapeutic insight into breast cancer treatment

Estrogen signaling has been implicated in hormone-dependent breast cancer which constitutes >75% of breast cancer diagnosis and other malignancies. Aromatase, the key enzyme involved in the synthesis of estrogen, is often dysregulated in breast cancers. This has led to the administration of aromatase-inhibitors (AIs), commonly used for hormone-dependent breast cancers. Unfortunately, the increasing development of acquired resistance to the current AIs and modulators of estrogen receptors, following initial disease steadiness, has posed a serious clinical challenge in breast cancer treatment. In this review we highlight historical and recent advances on the transcriptional and post-translational regulation of aromatase in both physiological and pathological contexts. We also discuss the different drug combinations targeting various tumor promoting cell signaling pathways currently being developed and tested both in laboratory settings and in the clinic.

LncRNA-42060 Regulates Tamoxifen Sensitivity and Tumor Development via Regulating the miR-204-5p/SOX4 Axis in Canine Mammary Gland Tumor Cells

Tamoxifen is the drug of choice for endocrine therapy of breast cancer. Its clinical use is limited by the development of drug resistance. There is increasing evidence that long non-coding RNAs (lncRNAs) are associated with tumor drug resistance. Therefore, we established two TAM-resistant cell lines, CHMp^TAM and CHMm^TAM. The different expression levels of lncRNA and miRNA in CHMm^TAM and CHMm were screened by RNA sequencing, and the lncRNA-miRNA interactions were analyzed. LncRNA ENSCAFG42060 (lnc-42060) was found to be significantly upregulated in drug-resistant cells and tumor tissues. Further functional validation revealed that the knockdown of lnc-42060 inhibited proliferation, migration, clone formation, restoration of TAM sensitivity, and reduction of stem cell formation in drug-resistant cells, whereas overexpression of lnc-4206 showed opposite results. Bioinformatics and dual-luciferase reporter gene assays confirmed that lnc-42060 could act as a sponge for miR-204-5p, further regulating SOX4 expression activity and thus influencing tumor cell progression. In conclusion, we screened lncRNAs and miRNAs associated with TAM resistance in canine mammary gland tumor cells for the first time. lnc-42060 served as a novel marker that may be used as an important biomarker for future diagnosis and treatment.

MALAT1 Promotes Tumorigenesis and Increases Cellular Sensitivity to Herceptin in HER2-positive Breast Cancer

BACKGROUND

The function of MALAT1, a kind of long non-coding RNAs (lncRNA), in HER2-positive breast cancer remains largely unexplored. Therefore, there is a need investigate the effect of MALAT1 on tumor development in HER2-positive breast cancer.

OBJECTIVES

We detected MALAT1 expression in HER2-positive breast cancer cells and tissues and analyzed the effects of MALAT1 on cell proliferation in HER2-positive breast cancer cell lines (BT-474 and SKBR3).

METHODS

A mouse xenograft model was established for detecting the function of MALAT1 in HER2-positive breast cancer.

RESULTS & DISCUSSION

As a result, MALAT1 was remarkably up-regulated in HER2-positive breast cancer both in cells and tissues. In addition, the silence of MALAT1 inhibited the proliferation of HER2-positive breast cancer cells both in vitro and in vivo. Furthermore, the knockdown of MALAT1 by shRNA down-regulated DNMT1, DNMT3a, and DNMT3b, while up-regulated BRCA1 and PTEN in HER2-positive breast cancer both in cell lines and mouse xenograft models.

CONCLUSION

In short, MALAT1 might be a potential biomarker and therapeutic target for HER2-positive breast cancer therapy.

MAGI1, a Scaffold Protein with Tumor Suppressive and Vascular Functions

MAGI1 is a cytoplasmic scaffolding protein initially identified as a component of cell-to-cell contacts stabilizing cadherin-mediated cell–cell adhesion in epithelial and endothelial cells. Clinical-pathological and experimental evidence indicates that MAGI1 expression is decreased in some inflammatory diseases, and also in several cancers, including hepatocellular carcinoma, colorectal, cervical, breast, brain, and gastric cancers and appears to act as a tumor suppressor, modulating the activity of oncogenic pathways such as the PI3K/AKT and the Wnt/β-catenin pathways. Genomic mutations and other mechanisms such as mechanical stress or inflammation have been described to regulate MAGI1 expression. Intriguingly, in breast and colorectal cancers, MAGI1 expression is induced by non-steroidal anti-inflammatory drugs (NSAIDs), suggesting a role in mediating the tumor suppressive activity of NSAIDs. More recently, MAGI1 was found to localize at mature focal adhesion and to regulate integrin-mediated adhesion and signaling in endothelial cells. Here, we review MAGI1′s role as scaffolding protein, recent developments in the understanding of MAGI1 function as tumor suppressor gene, its role in endothelial cells and its implication in cancer and vascular biology. We also discuss outstanding questions about its regulation and potential translational implications in oncology.

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.

[Patients treated with palbociclib and endocrine therapy for metastatic breast cancer: Can we predict the occurrence of severe early hematological toxicity?]

INTRODUCTION

The addition of palbociclib to endocrine therapy has been shown to improve progression free survival in hormone receptor positive metastatic breast cancer patients. This cyclin CDK4/6 inhibitor could expose patients to a grade 3-4 hematological toxicity, leading to treatment discontinuation or treatment interruption that is potentially associated with a lack of efficiency. The aim of this study was to identify predictive factors of severe early hematotoxicity (ESHT).

METHODS

This retrospective cohort study included patients who started palbociclib in the Institut Sainte Catherine between December 1, 2016 and January 1, 2019 for the treatment of metastatic breast cancer. Individual data and hematological toxicity were collected from electronic medical records. ESHT was defined as the occurrence, during the first 3 cycles, of grade 4 or grade 3 hematological toxicity requiring palbociclib dose reduction.

RESULTS

In total, 181 patients (180 females) were included; median age was 67 years. Forty-six patients (25.4%) experienced an ESHT. Predictive factors of ESHT in multivariate analysis were a performance status (PS) of 2 or more (P=0.024) and an history of radiotherapy of bone metastasis in the previous year (P=0.003). Before palbociclib initiation, a neutrophil count below 3.37g/L was predictive of ESHT with a sensibility of 76% and a specificity of 71%.

CONCLUSIONS

ECOG PS, bone radiotherapy within the year and low baseline neutrophils count are associated with ESHT in palbociclib-treated metastatic breast cancer patients. These elements could be useful for a careful monitoring leading to adapted therapy.

Identification of novel cell glycolysis related gene signature predicting survival in patients with breast cancer

One of the most frequently identified tumors and a contributing cause of death in women is breast cancer (BC). Many biomarkers associated with survival and prognosis were identified in previous studies through database mining. Nevertheless, the predictive capabilities of single-gene biomarkers are not accurate enough. Genetic signatures can be an enhanced prediction method. This research analyzed data from The Cancer Genome Atlas (TCGA) for the detection of a new genetic signature to predict BC prognosis. Profiling of mRNA expression was carried out in samples of patients with TCGA BC (n = 1222). Gene set enrichment research has been undertaken to classify gene sets that vary greatly between BC tissues and normal tissues. Cox models for additive hazards regression were used to classify genes that were strongly linked to overall survival. A subsequent Cox regression multivariate analysis was used to construct a predictive risk parameter model. Kaplan–Meier survival predictions and log-rank validation have been used to verify the value of risk prediction parameters. Seven genes (PGK1, CACNA1H, IL13RA1, SDC1, AK3, NUP43, SDC3) correlated with glycolysis were shown to be strongly linked to overall survival. Depending on the 7-gene-signature, 1222 BC patients were classified into subgroups of high/low-risk. Certain variables have not impaired the prognostic potential of the seven-gene signature. A seven-gene signature correlated with cellular glycolysis was developed to predict the survival of BC patients. The results include insight into cellular glycolysis mechanisms and the detection of patients with poor BC prognosis.

CDK4/6 Inhibitor Treatments in Patients with Hormone Receptor Positive, Her2 Negative Advanced Breast Cancer: Potential Molecular Mechanisms, Clinical Implications and Future Perspectives

Hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer is the most common breast cancer subtype, and endocrine therapy (ET) remains its therapeutic backbone. Although anti-estrogen therapies are usually effective initially, approximately 50% of HR+ patients develop resistance to ET within their lifetime, ultimately leading to disease recurrence and limited clinical benefit. The recent addition of cyclin-dependent kinase 4 (CDK4) and CDK6 inhibitors (palbociclib, ribociclib, abemaciclib) to ET have remarkably improved the outcome of patients with HR+ advanced breast cancer (ABC) compared with anti-estrogens alone, by targeting the cell-cycle machinery and overcoming some aspects of endocrine resistance. However, which patients are the better candidates for these drugs, which are the main characteristics for a better selection of patients or if there are predictive biomarkers of response, is still unknown. In this review we reported the mechanism of action of CDK4/6 inhibitors as well as their potential mechanism of resistance, their implications in clinical practice and the forthcoming strategies to enhance their efficacy in improving survival and quality of life of patients affected with HR+, HER2-, ABC.

A Competing Endogenous RNA Network Reveals Novel lncRNA, miRNA and mRNA Biomarkers With Diagnostic and Prognostic Value for Early Breast Cancer

Background:

This study aims to reveal early breast cancer (BC) specific competing endogenous RNA (ceRNA) network through the expression profiles of microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and mRNAs.

Methods:

Based on The Cancer Genome Atlas (TCGA), we obtained the differentially expressed mRNAs, miRNAs, and lncRNAs (DEmRNAs, DEmiRNAs and DElncRNAs) between early BC and normal samples. The lncRNA–miRNA–mRNA interaction network was constructed using Cytoscape. Functional enrichment were performed using GeneCoDis3. The expression of selected genes were validated by qRT-PCR. Based on the published dataset, we validated the result of TCGA integration analysis. The diagnostic and prognostic value of candidate genes was evaluated by ROC curve analysis and survival analysis, respectively.

Results:

Totally, 1207 DEmRNAs, 194 DElncRNAs and 37 DEmiRNAs were obtained. Functional enrichment analysis results showed that all of DEmRNAs were enriched in pathway of cytokine-cytokine receptor interaction, PPAR signaling pathway and pathways in cancer. The DEmRNA-DEmiRNA-DElncRNA interaction network in early BC was consisted of 23 DEmiRNAs, 95 DElncRNAs and 309 DEmRNAs. Among ceRNA network, IL-6-hsa-miR-182-5p-ADAMTS9-AS1 interactions, LIFR-hsa-miR-21-5p-ADAMTS9-AS1 interactions and MMP1/MMP11-hsa-miR-145-5p-CDKN2B-AS1 interactions were speculated to involve in the development of early BC. The qRT-PCR results were consistent with our integrated analysis. Except for ADAMTS9-AS1 and CDKN2B-AS1, expression of the others results in the Gene Expression Omnibus (GEO) dataset were generally consistent with TCGA integrated analysis. The area under curve (AUC) of the ADAMTS9-AS1, CDKN2B-AS1, IL-6, MMP11, hsa-miR-145-5p and hsa-miR-182-5p were 0.947, 0.862, 0.842, 0.993, 0.960 and 0.944, and the specificity and sensitivity of the 6 biomarkers were 83.4% and 95.6%, 72.2% and 90.3%, 80.1% and 74.3%, 96.2% and 96.5%, 90.1% and 92.3%, and 88.7% and 90.4%, respectively. In addition, IL-6 had potential prognostic value for early BC.

Conclusion:

These findings may provide novel insights into the lncRNA-miRNA-mRNA network and uncover potential therapeutic targets in early BC.

Comprehensive Transcriptomic Analysis Reveals Dysregulated Competing Endogenous RNA Network in Endocrine Resistant Breast Cancer Cells

Background

Tamoxifen and fulvestrant, both approved for endocrine therapy, have remarkably increased the prognosis of hormone receptor-positive breast cancer patients. However, acquired resistance to endocrine therapy greatly reduces its clinical efficacy. Accumulating evidence suggests a pivotal role of non-coding RNAs (ncRNAs) in breast cancer endocrine resistance, but the specific functions of ncRNAs in tamoxifen and fulvestrant resistance remain largely unknown.

Methods

Microarray analysis was performed for endocrine therapy sensitive (MCF-7), tamoxifen-resistant (LCC2), and dual tamoxifen and fulvestrant-resistant (LCC9) breast cancer cells. Gene ontology and pathway analysis were conducted for functional prediction of the unannotated differentially expressed ncRNAs. Competing endogenous RNA regulatory networks were constructed.

Results

We discovered a total of 3,129 long non-coding RNAs (lncRNAs), 13,556 circular RNAs (circRNAs), 132 microRNAs, and 3358 mRNAs that were significantly differentially expressed. We constructed co-expression networks for lncRNA-mRNA, circRNA-mRNA, and microRNA-mRNA. In addition, we established lncRNA-microRNA-mRNA and circRNA-microRNA-mRNA regulatory networks to depict ncRNA crosstalk and transcriptomic regulation of endocrine resistance.

Conclusions

Our study delineates a comprehensive profiling of ncRNAs in tamoxifen and fulvestrant resistant breast cancer cells, which enriches our understanding of endocrine resistance and sheds new light on identifying novel endocrine resistance biomarkers and potential therapeutic targets to overcome endocrine resistance.

Activating transcription factor-2 (ATF2) is a key determinant of resistance to endocrine treatment in an in vitro model of breast cancer

BACKGROUND

Activating transcription factor-2 (ATF2), a member of the leucine zipper family of DNA binding proteins, has been implicated as a tumour suppressor in breast cancer. However, its exact role in breast cancer endocrine resistance is still unclear. We have previously shown that silencing of ATF2 leads to a loss in the growth-inhibitory effects of tamoxifen in the oestrogen receptor (ER)-positive, tamoxifen-sensitive MCF7 cell line and highlighted that this multi-faceted transcription factor is key to the effects of tamoxifen in an endocrine sensitive model. In this work, we explored further the in vitro role of ATF2 in defining the resistance to endocrine treatment.

MATERIALS AND METHODS

We knocked down ATF2 in TAMR, LCC2 and LCC9 tamoxifen-resistant breast cancer cell lines as well as the parental tamoxifen sensitive MCF7 cell line and investigated the effects on growth, colony formation and cell migration. We also performed a microarray gene expression profiling (Illumina Human HT12_v4) to explore alterations in gene expression between MCF7 and TAMRs after ATF2 silencing and confirmed gene expression changes by quantitative RT-PCR.

RESULTS

By silencing ATF2, we observed a significant growth reduction of TAMR, LCC2 and LCC9 with no such effect observed with the parental MCF7 cells. ATF2 silencing was also associated with a significant inhibition of TAMR, LCC2 and LCC9 cell migration and colony formation. Interestingly, knockdown of ATF2 enhanced the levels of ER and ER-regulated genes, TFF1, GREB1, NCOA3 and PGR, in TAMR cells both at RNA and protein levels. Microarray gene expression identified a number of genes known to mediate tamoxifen resistance, to be differentially regulated by ATF2 in TAMR in relation to the parental MCF7 cells. Moreover, differential pathway analysis confirmed enhanced ER activity after ATF2 knockdown in TAMR cells.

CONCLUSION

These data demonstrate that ATF2 silencing may overcome endocrine resistance and highlights further the dual role of this transcription factor that can mediate endocrine sensitivity and resistance by modulating ER expression and activity.

Genome-wide analysis of therapeutic response uncovers molecular pathways governing tamoxifen resistance in ER+ breast cancer

Background

Prioritization of breast cancer patients based on the risk of resistance to tamoxifen plays a significant role in personalized therapeutic planning and improving disease course and outcomes.

Methods

In this work, we demonstrate that a genome-wide pathway-centric computational framework elucidates molecular pathways as markers of tamoxifen resistance in ER+ breast cancer patients. In particular, we associated activity levels of molecular pathways with a wide spectrum of response to tamoxifen, which defined markers of tamoxifen resistance in patients with ER+ breast cancer.

Findings

We identified five biological pathways as markers of tamoxifen failure and demonstrated their ability to predict the risk of tamoxifen resistance in two independent patient cohorts (Test cohort1: log-rank p-value = 0.02, adjusted HR = 3.11; Test cohort2: log-rank p-value = 0.01, adjusted HR = 4.24). We have shown that these pathways are not markers of aggressiveness and outperform known markers of tamoxifen response. Furthermore, for adoption into clinic, we derived a list of pathway read-out genes and their associated scoring system, which assigns a risk of tamoxifen resistance for new incoming patients.

Interpretation

We propose that the identified pathways and their read-out genes can be utilized to prioritize patients who would benefit from tamoxifen treatment and patients at risk of tamoxifen resistance that should be offered alternative regimens.

Funding

This work was supported by the Rutgers SHP Dean's research grant, Rutgers start-up funds, Libyan Ministry of Higher Education and Scientific Research, and Katrina Kehlet Graduate Award from The NJ Chapter of the Healthcare Information Management Systems Society.

Long non-coding RNA MAFG-AS1 knockdown blocks malignant progression in breast cancer cells by inactivating JAK2/STAT3 signaling pathway via MAFG-AS1/miR-3196/TFAP2A axis

BACKGROUND

Breast cancer is still a leading threat to women's lives. Long non-coding RNAs (lncRNA) associated with cancer progression are getting attention. The objective of this study was to investigate the role of lncRNA MAFG-antisense 1 (MAFG-AS1) and mechanisms of action in breast cancer.

METHODS

The expression of MAFG-AS1, microRNA-3196 (miR-3196) and transcription factor AP-2 alpha (TFAP2A) was detected by quantitative real-time polymerase chain reaction (qRT-PCR). The cell proliferation was assessed by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay. The number of colonies was observed through colony formation assay. The protein levels of Cyclin D1, Ki67, Bcl-2 associated X protein (Bax), B-cell lymphoma2 (Bcl-2), Hexokinase II (HK2), lactate dehydrogenase A (LDHA), TFAP2A, Janus kinase 2 (JAK2), phosphorylated-JAK2 (p-JAK2), signal transducer and activator of transcription 3 (STAT3), and phosphorylated-STAT3 were quantified by western blot. The cell apoptosis was monitored using flow cytometry. The glycolysis progression was evaluated according to glucose consumption and lactate production. The relationship between miR-3196 and MAFG-AS1 or TFAP2A was predicted by the online tool starBase and verified by the dual-luciferase reporter assay. The role of MAFG-AS1 in vivo was determined by the tumor formation assay in nude mice.

RESULTS

MAFG-AS1 was highly expressed in tumor tissues and cells. MAFG-AS1 knockdown restrained proliferation, colony formation, and glycolysis but promoted apoptosis of breast cancer cells. MiR-3196 was a target of MAFG-AS1, and its inhibition reversed the role of MAFG-AS1 knockdown. TFAP2A was a target of miR-3196, and its overexpression abolished the effects of miR-3196 reintroduction. MAFG-AS1 knockdown suppressed the activity of the JAK2/STAT3 signaling pathway. Moreover, MAFG-AS1 knockdown reduced tumor growth in vivo.

CONCLUSION

MAFG-AS1 knockdown attenuated breast cancer progression in vitro and in vivo through activation of the JAK2/STAT3 signaling pathway by the MAFG-AS1/miR-3196/TFAP2A regulatory axis.

Notch1 in Cancer Therapy: Possible Clinical Implications and Challenges

The Notch family consists of four highly conserved transmembrane receptors. The release of the active intracellular domain requires the enzymatic activity of γ-secretase. Notch is involved in embryonic development and in many physiologic processes of normal cells, in which it regulates growth, apoptosis, and differentiation. Notch1, a member of the Notch family, is implicated in many types of cancer, including breast cancer (especially triple-negative breast cancer), leukemias, brain tumors, and many others. Notch1 is tightly connected to many signaling pathways that are therapeutically involved in tumorigenesis. Together, they impact apoptosis, proliferation, chemosensitivity, immune response, and the population of cancer stem cells. Notch1 inhibition can be achieved through various and diverse methods, the most common of which are the γ-secretase inhibitors, which produce a pan-Notch inhibition, or the use of Notch1 short interference RNA or Notch1 monoclonal antibodies, which produce a more specific blockade. Downregulation of Notch1 can be used alone or in combination with chemotherapy, which can achieve a synergistic effect and a decrease in chemoresistance. Targeting Notch1 in cancers that harbor high expression levels of Notch1 offers an addition to therapeutic strategies recruited for managing cancer. Considering available evidence, Notch1 offers a legitimate target that might be incorporated in future strategies for combating cancer. In this review, the possible clinical applications of Notch1 inhibition and the obstacles that hinder its clinical application are discussed. SIGNIFICANCE STATEMENT: Notch1 plays an important role in different types of cancer. Numerous approaches of Notch1 inhibition possess potential benefits in the management of various clinical aspects of cancer. The application of different Notch1 inhibition modalities faces many challenges.

MDM2 inhibition in combination with endocrine therapy and CDK4/6 inhibition for the treatment of ER-positive breast cancer

Background

Resistance to endocrine therapy is a major clinical challenge in the management of oestrogen receptor (ER)-positive breast cancer. In this setting, p53 is frequently wildtype and its activity may be suppressed via upregulation of its key regulator MDM2. This underlies our rationale to evaluate MDM2 inhibition as a therapeutic strategy in treatment-resistant ER-positive breast cancer.

Methods

We used the MDM2 inhibitor NVP-CGM097 to treat in vitro and in vivo models alone and in combination with fulvestrant or palbociclib. We perform cell viability, cell cycle, apoptosis and senescence assays to evaluate anti-tumour effects in p53 wildtype and p53 mutant ER-positive cell lines (MCF-7, ZR75-1, T-47D) and MCF-7 lines resistant to endocrine therapy and to CDK4/6 inhibition. We further assess the drug effects in patient-derived xenograft (PDX) models of endocrine-sensitive and endocrine-resistant ER-positive breast cancer.

Results

We demonstrate that MDM2 inhibition results in cell cycle arrest and increased apoptosis in p53-wildtype in vitro and in vivo breast cancer models, leading to potent anti-tumour activity. We find that endocrine therapy or CDK4/6 inhibition synergises with MDM2 inhibition but does not further enhance apoptosis. Instead, combination treatments result in profound regulation of cell cycle-related transcriptional programmes, with synergy achieved through increased antagonism of cell cycle progression. Combination therapy pushes cell lines resistant to fulvestrant or palbociclib to become senescent and significantly reduces tumour growth in a fulvestrant-resistant patient-derived xenograft model.

Conclusions

We conclude that MDM2 inhibitors in combination with ER degraders or CDK4/6 inhibitors represent a rational strategy for treating advanced, endocrine-resistant ER-positive breast cancer, operating through synergistic activation of cell cycle co-regulatory programmes.

Compensatory Estrogen Signal Is Capable of DNA Repair in Antiestrogen-Responsive Cancer Cells via Activating Mutations

Cancer cells are embarrassed human cells exhibiting the remnants of same mechanisms for DNA stabilization like patients have in their healthy cells. Antiestrogens target the liganded activation of ERs, which is the principal means of genomic regulation in both patients and their tumors. The artificial blockade of liganded ER activation is an emergency situation promoting strong compensatory actions even in cancer cells. When tumor cells are capable of an appropriate upregulation of ER signaling resulting in DNA repair, a tumor response may be detected. In contrast, when ER signaling is completely inhibited, tumor cells show unrestrained proliferation, and tumor growth may be observed. The laboratory investigations of genomic mechanisms in antiestrogen-responsive and antiestrogen-unresponsive tumor cells have considerably enhanced our knowledge regarding the principal regulatory capacity of estrogen signaling. In antiestrogen-responsive tumor cells, a compensatory increased expression and liganded activation of estrogen receptors (ERs) result in an apoptotic death. Conversely, in antiestrogen resistant tumors exhibiting a complete blockade of liganded ER activation, a compensatory effort for unliganded ER activation is characteristic, conferred by the increased expression and activity of growth factor receptors. However, even extreme unliganded ER activation is incapable of DNA restoration when the liganded ER activation is completely blocked. Researchers mistakenly suspect even today that in tumors growing under antiestrogen treatment, the increased unliganded activation of estrogen receptor via activating mutations is an aggressive survival technique, whilst it is a compensatory effort against the blockade of liganded ER activation. The capacity of liganded ERs for genome modification in emergency states provides possibilities for estrogen/ER use in medical practice including cancer cure.

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.

Dissecting miRNA facilitated physiology and function in human breast cancer for therapeutic intervention

MicroRNAs (miRNAs) are key epigenomic regulators of biological processes in animals and plants. These small non coding RNAs form a complex networks that regulate cellular function and development. MiRNAs prevent translation by either inactivation or inducing degradation of mRNA, a major concern in post-transcriptional gene regulation. Aberrant regulation of gene expression by miRNAs is frequently observed in cancer. Overexpression of various 'oncomiRs' and silencing of tumor suppressor miRNAs are associated with various types of human cancers, although overall downregulation of miRNA expression is reported as a hallmark of cancer. Modulations of the total pool of cellular miRNA by alteration in genetic and epigenetic factors associated with the biogenesis of miRNA machinery. It also depends on the availability of cellular miRNAs from its store in the organelles which affect tumor development and cancer progression. Here, we have dissected the roles and pathways of various miRNAs during normal cellular and molecular functions as well as during breast cancer progression. Recent research works and prevailing views implicate that there are two major types of miRNAs; (i) intracellular miRNAs and (ii) extracellular miRNAs. Concept, that the functions of intracellular miRNAs are driven by cellular organelles in mammalian cells. Extracellular miRNAs function in cell-cell communication in extracellular spaces and distance cells through circulation. A detailed understanding of organelle driven miRNA function and the precise role of extracellular miRNAs, pre- and post-therapeutic implications of miRNAs in this scenario would open several avenues for further understanding of miRNA function and can be better exploited for the treatment of breast cancers.

miR-622 is a novel potential biomarker of breast carcinoma and impairs motility of breast cancer cells through targeting NUAK1 kinase

BACKGROUND

Aberrant expression of microRNAs (miR) has been proposed as non-invasive biomarkers for breast cancers. The aim of this study was to analyse the miR-622 level in the plasma and in tissues of breast cancer patients and to explore the role of miR-622 and its target, the NUAK1 kinase, in this context.

METHODS

miR-622 expression was analysed in plasma and in tissues samples of breast cancer patients by q-RT-PCR. Bioinformatics programs, luciferase assay, public dataset analysis and functional experiments were used to uncover the role of miR-622 and its target in breast cancer cells.

RESULTS

miR-622 is downregulated in plasma and in tissues of breast cancer patients respect to healthy controls and its downregulation is significantly associated with advanced grade and high Ki67 level. Modulation of miR-622 affects the motility phenotype of breast cancer cells. NUAK1 kinase is a functional target of miR-622, it is associated with poor clinical outcomes of breast cancer patients and is inversely correlated with miR-622 level.

CONCLUSIONS

miR-622/NUAK1 axis is deregulated in breast cancer patients and affects the motility phenotype of breast cancer cells. Importantly, miR-622 and NUAK1 hold promises as biomarkers and as targets for breast cancers.

microRNA-Dependent Modulation of Genes Contributes to ESR1's Effect on ERα Positive Breast Cancer

Background: Dysregulation of ESR1 accounts for endocrine therapy resistance and metastasis of ERα positive breast cancer. However, the underlying molecular mechanism of ESR1 in ERα positive breast cancer remains insufficiency. Notably, to date, a comprehensive miRNA-mRNA regulatory network involved in modulation of ESR1 in development and progression of ERα positive breast cancer is still not established. Methods: Microarray miRNA and mRNA expression profiling from GEO database were used to obtained significant DE-miRNAs and DE-mRNAs in ERα positive breast cancer. Functional enrichment analysis was conducted by Enrichr database. STRING database was utilized to construct protein-protein interaction network, after which hub genes were identified through Cytoscape. Kaplan-Meier plotter was introduced to perform survival analysis. The relationship between ESR1-miRNA or miRNA-target gene pairs were experimentally validated. Results: 74 DE-miRNAs, including 19 upregulated and 55 downregulated miRNAs, and 830 DE-mRNAs, including 359 upregulated and 471 downregulated mRNAs, in ERα positive breast cancer were identified. Potential DE-mRNAs were statistically enriched in several cancer-associated pathways, such as cell cycle and pathway in cancer. Fifty-one hub genes with node degree more than 10 were screened. Twenty-seven of 51 hub genes had significant prognostic values in ERα positive breast cancer. Based on the 27 hub genes, a miRNA-hub gene network, containing 26 miRNAs, was established. Seven of 26 miRNAs were found to possess prognostic predictive roles for patients with ERα positive breast cancer by combination of TCGA and METABRIC data. Intriguingly, ESR1 positively correlated and regulated the 7 miRNAs and the 7 miRNAs inversely correlated and modulated their corresponding downstream targets in MCF-7 and T47D cells, supporting the accuracy of in silico analysis. The relationship between ESR1-miRNA, miRNA-mRNA, or ESR1-mRNA pairs was validated in clinical ERα positive breast cancer. Conclusions: In total, the current findings from this work add substantially to the understanding of ESR1's molecular regulatory mechanism in ERα positive breast cancer.

The Effect of (E)-1-(4'-aminophenyl)-3-phenylprop-2-en-1-one on MicroRNA-18a, Dicer1, and MMP-9 Expressions against DMBA-Induced Breast Cancer

BACKGROUND

Most of breast cancer patients are estrogen receptor alpha-positive and have high resistance and side effect of chemotherapeutic drug. Therefore, discovering an effective anticancer agent is needed. This research explored the effect of (E)-1-(4'-aminophenyl)-3-phenylprop-2-en-1-one (APE) on miR-18a, Dicer1, and MMP-9 expressions.

METHODS

Twenty four female Sprague-Dawley rats were invetigated in this study. The rats were divided into 6 groups of 4. G1 was considered as normal rat. G2, G3, T1, T2, and T3 were given DMBA 20 mg/kgBW twice a week for 5 weeks to induce mammary cancer. After being affiliated with cancer, G2 was given vehicle and G3 was treated with tamoxifen. T1, T2, and T3 were treated with APE intraperitoneally everyday for 21 days at doses of 5, 15, and 45 mg/kgBW/day, respectively. Blood plasma was collected to measure miR-18a expression using qRT-PCR. Mammary tissues were also collected to determine Dicer1 and MMP-9 expressions by using  immunohistochemistry.

RESULTS

The results showed significant down-regulation of miR-18a relative expression and up-regulation of Dicer1 expression in G3 and T1 compared to G2 (P<0.05). MMP-9 expression has significant decrease in T1 compared to G2 (P<0.05).

CONCLUSION

APE can decrease miR-18a and MMP-9 expressions and increase Dicer1 expression in rat mammary cancer. Therefore, this compound could be a candidate of novel anticancer.

Identification and Analysis of Estrogen Receptor α Promoting Tamoxifen Resistance-Related lncRNAs

70-75% breast cancer patients are estrogen receptor alpha positive (ERα+), and the antiestrogen drug tamoxifen has been used for the past three decades. However, in 20-30% of these patients, tamoxifen therapy fails due to intrinsic or acquired resistance. A previous study has showed ERα signaling still exerts significant roles in the development of tamoxifen resistance and several lncRNAs have been demonstrated important roles in tamoxifen resistance. But ERα directly regulated and tamoxifen resistance related lncRNAs remain to be discovered. We reanalyze the published ERα chromatin immunoprecipitation-seq (ChIP-seq) and RNA-seq data of tamoxifen-sensitive (MCF-7/WT) and tamoxifen-resistant (MCF-7/TamR) breast cancer cells. We demonstrate that there are differential ERα recruitment events and the differentials may alert the expression profile in MCF-7/WT and MCF-7/TamR cells. Furthermore, we make an overlap of the ERα binding lncRNAs and differentially expressed lncRNAs and get 49 ERα positively regulated lncRNAs. Among these lncRNAs, the expression levels of AC117383.1, AC144450.1, RP11-15H20.6, and ATXN1-AS1 are negatively correlated with the survival probability of breast cancer patients and ELOVL2-AS1, PCOLCE-AS1, ITGA9-AS1, and FLNB-AS1 are positively correlated. These lncRNAs may be potential diagnosis or prognosis markers of tamoxifen resistance.

TCRP1 induces tamoxifen resistance by promoting the activation of SGK1 in MCF‑7 cells

Tamoxifen is widely used as a highly effective drug for treating estrogen‑receptor (ER) alpha‑positive breast cancer. However, tamoxifen resistance developed during cancer treatment remains a significant challenge. Tongue cancer resistance‑related protein1 (TCRP1), which is recognized as a novel drug target, is related to chemo‑resistance in human cancers, moreover, it is often overexpressed in various cancer cells, such as in lung cancer, breast cancer, and tongue cancer. However, the effects of TCRP1 on tamoxifen‑resistant breast cancer cells and tissues are far from clear. The present study revealed that TCRP1 induced tamoxifen resistance in breast cancer cells. Western blotting, quantitative real‑time polymerase chain reaction (RT‑PCR) and immunohistochemical staining were performed to detect the expression level of TCRP1 in vivo and in vitro between primary breast cancer tissues and tamoxifen‑resistant breast cancer tissues. The data revealed that the expression of TCRP1 was upregulated in the tamoxifen‑resistant breast cancer tissues and human breast cancer cell line, MCF‑7. Further study revealed that knocking down TCRP1 inhibited the growth of MCF‑7 cells with tamoxifen‑resistance (MCF7‑R cells) and induced cell apoptosis. Moreover, TCRP1 promoted serum‑ and glucocorticoid‑inducible kinase 1 (SGK1) activation via phosphorylation of phosphoinositide‑dependent kinase 1 (PDK1) in MCF7‑R cells. In addition, it was also observed that knocking down TCRP1 inhibited tumorigenesis of MCF‑7 cells in nude mice. In conclusion, these data indicated that TCRP1 could induce tamoxifen resistance by regulating the PDK1/SGK1 signaling pathway. Thus, TCRP1 could be explored as a promising candidate for treating tamoxifen‑resistant breast cancer in the future.

The LncRNA HOTAIRM1 Promotes Tamoxifen Resistance by Mediating HOXA1 Expression in ER+ Breast Cancer Cells

Breast cancer is one of the most commonly diagnosed cancers in women worldwide. Approximately 40% of patients with breast cancer acquire endocrine resistance following therapy with tamoxifen. Many explanations for the development of endocrine resistance have been put forward, one of them being the dysregulation of long non-coding RNAs (lncRNAs). The lncRNA HOTAIRM1, known to be involved in myelopoiesis as well as transcriptional regulation of the HOXA genes in embryonic stem cells, is also expressed in breast cancer cells. This study explored the molecular mechanisms of HOTAIRM1 involved in acquired tamoxifen resistance. We showed that HOTAIRM1 and HOXA1 are concurrently up-regulated in tamoxifen-resistant MCF7 (TAMR) cells. Knockdown of HOTAIRM1 down-regulated HOXA1 expression and restored sensitivity to tamoxifen. In addition, the knockdown of HOXA1 showed similar effects, suggesting that the HOTAIRM1/HOXA1 axis regulates tamoxifen resistance. Furthermore, we showed that HOTAIRM1 directly interacts with EZH2 and prevents the PRC2 complex from binding and depositing H3K27me3 on the putative promoter of HOXA1. Together, our findings suggest that HOXA1 and its neighboring lncRNA, HOTAIRM1, might serve as potential therapeutic targets for ER+ breast cancer patients who have acquired tamoxifen resistance.

Linc01638 Promotes Tumorigenesis in HER2+ Breast Cancer

Background

Long non‐coding RNAs play crucial roles in various biological activities and diseases. The role of long intergenic non‐coding RNA01638 (linc01638) in breast cancer, espe-cially in HER2-positive breast cancer, remains largely unknown.

Objective

To investigate the effect of linc01638 on tumorigenesis in HER2-positive breast cancer.

Methods

We first used qRT-PCR to detect linc01638 expression in HER2-positive breast cancer cells and tissues. Then we analyzed the effects of linc01638 expression in HER2-positive breast cancer cells through cell apoptosis assay, cell proliferation assay, colony formation assay, and cell invasion assay. We conducted mouse xenograft model to further confirm the role of linc01638 in HER2-positive breast cancer. Moreover, we used Western blot and IHC analysis to access the effect of linc01638 on DNMTs, BRCA1 and PTEN expressions in transplanted tumors.

Results

Linc01638 was found to be remarkably overexpressed in HER2-positive breast cancer cells and tissues. Suppression of linc01638 enhanced cell apoptosis, as well as inhibited the growth and in-vasiveness of HER2-positive breast cancer cells in vitro and tumor progression and metastasis in vivo. Furthermore, inhibition of linc01638 by shRNA attenuated expression of DNMT1, DNMT3a, and DNMT3b, and promoted expression of BRCA1 and PTEN in HER2-positive breast cancer cells and mouse xenograft models.

Conclusion

Linc01638 might be a promising biomarker and therapeutic target for treatment of HER2-positive breast cancer.

Shikonin and 4-hydroxytamoxifen synergistically inhibit the proliferation of breast cancer cells through activating apoptosis signaling pathway in vitro and in vivo

Background

Tamoxifen (TAM) is a cell type-specific anti-estrogen and is applied to improve the survival of patients with estrogen receptor positive (ER +) breast cancer. However, long-term TAM use can induce serious drug resistance, leading to breast cancer recurrence and death in patients. Further, it is almost useless among patients with estrogen receptor negative (ER −) breast cancer. Shikonin (SK) is a natural product broadly explored in cancer therapy. Some studies have demonstrated the combined treatment of SK and clinical anticancer drugs including TAM on various tumors. However, the combined effect of SK and 4-hydroxytamoxifen (4-OHT) on ER- breast cancer is not known. The current study aimed to assess the combination effects of SK and 4-OHT on human breast cancer cells, MCF-7 (ER +) and MDA-MB-435S (ER −), in vitro and in vivo and to investigate the underlying mechanisms.

Methods

CCK-8 assays and flow cytometry were conducted to determine the cell viability and apoptotic profiles of human breast cancer cell lines (MCF-7 and MDA-MB-435S) treated with SK, 4-OHT, and the combination. ROS and JC-1 assays were used to determine ROS level and mitochondrial membrane potential. Western blot analysis was performed to investigate proteins that are associated with apoptosis. Haematoxylin & Eosin (HE) staining was used to detect the tumor and kidney morphology of mice. TUNEL and immunohistochemical staining were performed to detect Ki67 expression level and cell apoptotic profile in tumor tissues.

Results

SK and 4-OHT synergistically inhibited MCF-7 and MDA-MB-435S cell proliferation and promoted apoptosis by reducing mitochondrial membrane potential and increasing the intracellular ROS level. The combination of SK and 4-OHT activated the mitochondrial-dependent apoptosis and the death receptor pathways, significantly regulating the PI3K/AKT/Caspase 9 signaling pathway. Compared with SK and 4-OHT alone, the combination of SK and 4-OHT could better inhibit tumor growth in mice.

Conclusion

The combination of SK and 4-OHT shows highly efficient anticancer effects on breast cancer therapy. SK may be a promising candidate as an adjuvant to 4-OHT for breast cancer treatments, especially for ER- breast cancer.

A novel tumour suppressor lncRNA F630028O10Rik inhibits lung cancer angiogenesis by regulating miR-223-3p

Lung cancer is the world's leading cause of cancer‐related morbidity and mortality despite advances in surgery, chemotherapy and immunotherapy; thus, there is an urgent need to find new molecules to develop novel treatment strategies. Although ncRNAs were found to account for 98% transcripts, the number of lncRNAs with distinct function in lung cancer is extremely limited. We previously demonstrated that Plasmodium infection inhibits tumour growth and metastasis, but the exact mechanisms involved have not been fully understood. In this study, we carried out RNA sequencing (RNA‐Seq) of tumour tissues isolated from LLC tumour‐bearing mice treated with either Plasmodium yoelli (Py)‐infected red blood cells or uninfected red blood cells. We found that F630028O10Rik (abbreviated as F63) is a novel lncRNA that was significantly up‐regulated in tumours isolated from mice treated with Py‐infected red blood cells compared to the control. By using gene silencing technique, F63 was found to inhibit both tumour Vascular Endothelial Growth Factor A (VEGFA) secretion and endothelial cells clone formation, migration, invasion and tube formation. Injection of cholesterol‐modified siRNA‐F63 into mice tumour tissues produced a significant increase in tumour volume, blood vessel formation and angiogenesis 17 days after injection. We further showed that inhibiting miR‐223‐3p results in the down‐regulation of VEGFA and VEGFR2 which are vital molecules for angiogenesis. These results reveal that F63 inhibit tumour growth and progression by modulating tumour angiogenesis suggesting F63 can be a novel lncRNA with great potential as a candidate molecule for gene therapy in lung cancer.

Increased Expression of Gankyrin and Stemness Factor Oct-4 are Associated with Unfavorable Clinical Outcomes and Poor Benefit of Tamoxifen in Breast Carcinoma Patients

Tamoxifen is the most important treatment component in estrogen receptor positive (ER+) breast carcinoma patients. Tamoxifen resistance incidence presents an important obstacle in clinical treatment. Mechanisms underlying tamoxifen refractory are not completely understood. Although elevated expression of Gankyrin (P28GANK) and stem cell markers Nanog, Oct-4 and Sox-2 have been reported in breast carcinoma, their role in tamoxifen resistance progression has not been explored. In the present study, P28GANK and stem cell markers Nanog, Oct-4 and Sox-2 expression were evaluated using quantitative RT-PCR and immunohistochemical technology in 72 breast carcinoma patients who received tamoxifen as adjuvant anti-hormone treatment. Expression data were correlated with the clinical outcome and survival of patients. Data analysis showed that P28GANK, Oct-4 and Sox-2 transcripts were significantly overexpressed in tamoxifen resistance patients. Immunohistochemical staining indicated that protein expression of P28GANK and Oct-4 were also significantly higher in tamoxifen resistance patients. We have shown a positive correlation between mRNA and protein expression of P28GANK, Oct-4 and Sox-2. Multivariate logistic regression analysis indicated that P28GANK (P = 0.002) and Oct-4 (P = 0.013) overexpression could be negative independent factors of disease outcome. Additionally, in the whole study group, multivariate Cox regression analysis revealed that high expression of P28GANK and Oct-4 remained significant and unfavorable predictive factors for patients' survival. These findings suggest that Gankyrin and Oct-4 overexpression could promote tamoxifen refractory in breast cancer patients. More studies are warranted to clarify the predictive role of these potential biomarkers for patients who don't benefit from tamoxifen treatment and their possible application as prognostic markers in ER⁺ tamoxifen-treated breast carcinoma patients.

The Effect of Coenzyme Q10 Supplementation on Vascular Endothelial Growth Factor and Serum Levels of Interleukin 6 and 8 in Women with Breast Cancer: A Double-Blind, Placebo-Controlled, Randomized Clinical Trial

Background

To better evaluate the efficacy of CoQ10 on the inflammatory markers in breast cancer patients, we conducted a clinical study of patients with breast cancer undergoing tamoxifen therapy. CoQ10 serves as an antioxidant and inhibits oxidation caused by reactive oxygen species. The aim of the current study was to assess the effect of coenzyme Q10 supplementation on serum levels of interleukin 6, 8, and vascular endothelial growth factor (VEGF) in patients with breast cancer undergoing tamoxifen therapy by a double-blind, placebo-controlled, randomized clinical trial.

Methods

In the study, 30 breast cancer patients and 29 healthy subjects were randomized into four groups. Two groups of intervention received 100 mg CoQ10, and two control groups took placebo once a day for 2 months. Blood draws were obtained at baseline and at the end of the study. Serum levels of IL-6, IL-8 and VEGF were analyzed using ELISA kits.

Results

The data of the 59 participants were analyzed. Supplementation with CoQ10 demonstrated a significant decrease in IL-8 and IL-6 serum levels compared to placebo (P< 0.05). Although the downward trend was evident, CoQ10 supplementation did not reveal any significant effect on serum VEGF concentration. The group of patients who received supplements showed the most reduction in serum levels of cytokines among other groups.

Conclusion

CoQ10 supplementation could be effective in ameliorating inflammatory cytokine levels, thereby reducing the consequences of inflammation caused by breast cancer. To generalize the results, larger and longer intervention studies with higher safe doses are needed and should take account of possible costs and harms as well as benefits (registration number: IRCT2015042021874N1).

Hormonal Therapy Resistance and Breast Cancer: Involvement of Adipocytes and Leptin

Obesity, a recognized risk factor for breast cancer in postmenopausal women, is associated with higher mortality rates regardless of menopausal status, which could in part be explained by therapeutic escape. Indeed, adipose microenvironment has been described to influence the efficiency of chemo- and hormonal therapies. Residual cancer stem cells could also have a key role in this process. To understand the mechanisms involved in the reduced efficacy of hormonal therapy on breast cancer cells in the presence of adipose secretome, human adipose stem cells (hMAD cell line) differentiated into mature adipocytes were co-cultured with mammary breast cancer cells and treated with hormonal therapies (tamoxifen, fulvestrant). Proliferation and apoptosis were measured (fluorescence test, impedancemetry, cytometry) and the gene expression profile was evaluated. Cancer stem cells were isolated from mammospheres made from MCF-7. The impact of chemo- and hormonal therapies and leptin was evaluated in this population. hMAD-differentiated mature adipocytes and their secretions were able to increase mammary cancer cell proliferation and to suppress the antiproliferative effect of tamoxifen, confirming previous data and validating our model. Apoptosis and cell cycle did not seem to be involved in this process. The evaluation of gene expression profiles suggested that STAT3 could be a possible target. On the contrary, leptin did not seem to be involved. The study of isolated cancer stem cells revealed that their proliferation was stimulated in the presence of anticancer therapies (tamoxifen, fulvestrant, doxorubicine) and leptin. Our study confirmed the role of adipocytes and their secretome, but above all, the role of communication between adipose and cancer cells in interfering with the efficiency of hormonal therapy. Among the pathophysiological mechanisms involved, leptin does not seem to interfere with the estrogenic pathway but seems to promote the proliferation of cancer stem cells.

Mitochondrial fragmentation, elevated mitochondrial superoxide and respiratory supercomplexes disassembly is connected with the tamoxifen-resistant phenotype of breast cancer cells

Tamoxifen resistance remains a clinical obstacle in the treatment of hormone sensitive breast cancer. It has been reported that tamoxifen is able to target respiratory complex I within mitochondria. Therefore, we established two tamoxifen-resistant cell lines, MCF7 Tam5R and T47D Tam5R resistant to 5 μM tamoxifen and investigated whether tamoxifen-resistant cells exhibit mitochondrial changes which could help them survive the treatment. The function of mitochondria in this experimental model was evaluated in detail by studying i) the composition and activity of mitochondrial respiratory complexes; ii) respiration and glycolytic status; iii) mitochondrial distribution, dynamics and reactive oxygen species production. We show that Tam5R cells exhibit a significant decrease in mitochondrial respiration, low abundance of assembled mitochondrial respiratory supercomplexes, a more fragmented mitochondrial network connected with DRP1 Ser637 phosphorylation, higher glycolysis and sensitivity to 2-deoxyglucose. Tam5R cells also produce significantly higher levels of mitochondrial superoxide but at the same time increase their antioxidant defense (CAT, SOD2) through upregulation of SIRT3 and show phosphorylation of AMPK at Ser 485/491. Importantly, MCF7 ρ0 cells lacking functional mitochondria exhibit a markedly higher resistance to tamoxifen, supporting the role of mitochondria in tamoxifen resistance. We propose that reduced mitochondrial function and higher level of reactive oxygen species within mitochondria in concert with metabolic adaptations contribute to the phenotype of tamoxifen resistance.

Identification of an eight-lncRNA prognostic model for breast cancer using WGCNA network analysis and a Cox‑proportional hazards model based on L1-penalized estimation

An ever‑increasing number of long noncoding (lnc)RNAs has been identified in breast cancer. The present study aimed to establish an lncRNA signature for predicting survival in breast cancer. RNA expression profiling was performed using microarray gene expression data from the National Center for Biotechnology Information Gene Expression Omnibus, followed by the identification of breast cancer‑related preserved modules using weighted gene co‑expression network (WGCNA) network analysis. From the lncRNAs identified in these preserved modules, prognostic lncRNAs were selected using univariate Cox regression analysis in combination with the L1‑penalized (LASSO) Cox‑proportional Hazards (Cox‑PH) model. A risk score based on these prognostic lncRNAs was calculated and used for risk stratification. Differentially expressed RNAs (DERs) in breast cancer were identified using MetaDE. Gene Set Enrichment Analysis pathway enrichment analysis was conducted for these prognostic lncRNAs and the DERs related to the lncRNAs in the preserved modules. A total of five preserved modules comprising 73 lncRNAs were mined. An eight‑lncRNA signature (IGHA1, IGHGP, IGKV2‑28, IGLL3P, IGLV3‑10, AZGP1P1, LINC00472 and SLC16A6P1) was identified using the LASSO Cox‑PH model. Risk score based on these eight lncRNAs could classify breast cancer patients into two groups with significantly different survival times. The eight‑lncRNA signature was validated using three independent cohorts. These prognostic lncRNAs were significantly associated with the cell adhesion molecules pathway, JAK‑signal transducer and activator of transcription 5A pathway, and erbb pathway and are potentially involved in regulating angiotensin II receptor type 1, neuropeptide Y receptor Y1, KISS1 receptor, and C‑C motif chemokine ligand 5. The developed eight‑lncRNA signature may have clinical implications for predicting prognosis in breast cancer. Overall, this study provided possible molecular targets for the development of novel therapies against breast cancer.

Improvement of the anti-proliferative activity of the peptide ERα17p in MCF-7 breast cancer cells using nanodiamonds

Nanodiamonds (NDs) are emerging delivery systems with biomedical applications and interesting perspectives in oncology. Their use has been proposed to assist the internalization of anticancer drugs and to decrease administered drug doses. The pro-apoptotic peptide ERα17p, which is issued from the hinge/N-terminus parts of the AF2 region of the human estrogen receptor α (ERα), is active at a concentration of 10μM on breast cancer cells and particularly on those cancer cells that are ERα-positive. We have synthesized ND@ERα17p conjugates by physisorption of the cationic peptide ERα17p on the surface of anionic NDs. Resulting ND@ERα17p suspensions were characterized by far-UV electronic circular dichroism (ECD), dynamic light scattering (DLS) and zetametry. We then tested the anti-proliferative action of ND@ERα17p on ERα-positive MCF-7 breast carcinoma cells. ND@ERα17p allowed a decrease of the active concentration to 0.1nM (ND@ERα17p), revealing unambiguously that NDs could be used to improve the anti-proliferative action of this peptide. This preliminary study proposes a novel approach for enhancing the apoptotic action displayed by ERα17p, in the context of breast cancer.

Overcoming Tamoxifen Resistance by Regulation of Del-1 in Breast Cancer

BACKGROUND

Hormone receptor-positive breast cancer accounts for nearly two-thirds of breast cancer cases; it ultimately acquires resistance during endocrine treatment and becomes more aggressive. This study evaluated the role of developmental endothelial locus (Del)-1 in tamoxifen-resistant (TAM-R) breast cancer.

METHODS

Del-1 expression in recurrent TAM-R breast cancer tissue was evaluated and compared to that in the original tumor tissue from the same patients. Del-1 expression was also evaluated in TAM-R cells by quantitative real-time PCR, western blotting, and enzyme-linked immunosorbent assay. The effects of Del-1 knockdown on the proliferation, migration, and invasion of TAM-R cells was assessed with wound-healing and Matrigel transwell assays.

RESULTS

Del-1 was more highly expressed in recurrent breast cancer as compared to the original tumor tissues before initiation of endocrine treatment. Del-1 mRNA was upregulated in TAM-R and small interfering RNA-mediated knockdown of Del-1 suppressed the migration and proliferation of TAM-R cells while partly restoring TAM sensitivity. And the TAM resistance was recovered by knockdown of Del-1.

CONCLUSIONS

TAM-R breast cancer is characterized by Del-1 overexpression and tumor progression can be inhibited by Del-1 depletion, which restores TAM sensitivity. Thus, therapeutic strategies that target Del-1 may be effective for the treatment of hormone-resistant breast cancer.