Functional Role of miRNAs in the Progression of Breast Ductal Carcinoma in Situ

Association of microRNA-21 expression with breast cancer subtypes and its potential as an early biomarker

Breast cancer has become the most diagnosed cancer worldwide in 2020 with high morbidity and mortality rates. The alarming increase in breast cancer incidence has sprung many researchers to focus on developing novel screening tests to identify early breast cancer which will allow clinicians to provide timely and effective treatments. With much evidence supporting the notion that the deregulation of miRNAs (a class of non-coding RNA) greatly contributes to cancer initiation and progression, the promising role of miRNAs as cancer biomarkers is gaining traction in the research world. Among the upregulated miRNAs identified in breast carcinogenesis, miR-21 was shown to be significantly expressed in breast cancer tissues and bodily fluids of breast cancer patients. Therein, this review paper aims to provide an overview of breast cancer, the role and significance of miR-21 in breast cancer pathogenesis, and its potential as a breast cancer biomarker. The paper also discusses the current types of tumor biomarkers and their limitations, the presence of miR-21 in extracellular vesicles and plasma, screening methods available for miRNA detection along with some challenges faced in developing diagnostic miR-21 testing for breast cancer to provide readers with a comprehensive outlook based on using miR-21 in clinical settings.

miR-145, miR-205 and miR-451: potential tumor suppressors involved in the progression of in situ to invasive carcinoma of the breast

BACKGROUND

MicroRNAs (miRNAs) control diverse biologic processes during tumor progression. This study was conducted to identify miRNAs that are implicated in progression of in situ to invasive breast cancer (IBC) and to evaluate their association with clinicopathological features of ductal carcinoma in situ (DCIS).

METHODS

We performed miRNA microarray analyses to find differentially expressed miRNAs between DCIS and IBC in a test set, and validated expression levels of selected miRNAs using a different set of tumors. Finally, we evaluated the relationship between clinicopathological features and the expression of selected miRNAs in DCIS samples.

RESULTS

We found that miR-145-5p, miR-205-5p and miR-451a are significantly down-regulated in IBC compared to DCIS in the whole group, and in the estrogen receptor (ER)-positive and ER-negative subgroups. In a validation set, miR-145, miR-205, and miR-451 also showed lower expression levels in IBC than in DCIS, irrespective of ER status. Moreover, their expression levels were significantly lower in the invasive component compared to the in situ component within same tumors. MiR-145, miR-205 and miR-451 commonly showed lower expression levels in DCIS with positive HER2 status and high Ki-67 proliferation index. Especially, miR-145 and miR-205 showed lower expression levels in DCIS with microinvasion, compared to pure DCIS. In addition, lower miR-205 expression level was associated with high nuclear grade, comedo type necrosis, and hormone receptor negativity.

CONCLUSIONS

Our study showed that miR-145, miR-205 and miR-451 expression decreased in IBC compared to DCIS, and their expression levels were low in DCIS with high-risk features for progression, implying their contributions in the progression of DCIS to invasive carcinoma as tumor suppressors.

Insights Into Exosomal Non-Coding RNAs Sorting Mechanism and Clinical Application

Exosomes are natural nanoscale bilayer phospholipid vesicles that can be secreted by almost all types of cells and are detected in almost all types of body fluids. Exosomes are effective mediators of cell–cell signaling communication because of their ability to carry and transfer a variety of bioactive molecules, including non-coding RNAs. Non-coding RNAs have also been found to exert strong effects on a variety of biological processes, including tumorigenesis. Many researchers have established that exosomes encapsulate bioactive non-coding RNAs that alter the biological phenotype of specific target cells in an autocrine or a paracrine manner. However, the mechanism by which the producer cells package non-coding RNAs into exosomes is not well understood. This review focuses on the current research on exosomal non-coding RNAs, including the biogenesis of exosomes, the possible mechanism of sorting non-coding RNAs, their biological functions, and their potential for clinical application in the future.

Pathological features of 11,337 patients with primary ductal carcinoma in situ (DCIS) and subsequent events: results from the UK Sloane Project

Background

The Sloane audit compares screen-detected ductal carcinoma in situ (DCIS) pathology with subsequent management and outcomes.

Methods

This was a national, prospective cohort study of DCIS diagnosed during 2003–2012.

Results

Among 11,337 patients, 7204 (64%) had high-grade DCIS. Over time, the proportion of high-grade disease increased (from 60 to 65%), low-grade DCIS decreased (from 10 to 6%) and mean size increased (from 21.4 to 24.1 mm). Mastectomy was more common for high-grade (36%) than for low-grade DCIS (15%). Few (6%) patients treated with breast-conserving surgery (BCS) had a surgical margin <1 mm. Of the 9191 women diagnosed in England (median follow-up 9.4 years), 7% developed DCIS or invasive malignancy in the ipsilateral and 5% in the contralateral breast. The commonest ipsilateral event was invasive carcinoma (n = 413), median time 62 months, followed by DCIS (n = 225), at median 37 months. Radiotherapy (RT) was most protective against recurrence for high-grade DCIS (3.2% for high-grade DCIS with RT compared to 6.9% without, compared with 2.3 and 3.0%, respectively, for low/intermediate-grade DCIS). Ipsilateral DCIS events lessened after 5 years, while the risk of ipsilateral invasive cancer remained consistent to beyond 10 years.

Conclusion

DCIS pathology informs patient management and highlights the need for prolonged follow-up of screen-detected DCIS.

Identification of genes and miRNA associated with idiopathic recurrent pregnancy loss: an exploratory data mining study

BACKGROUND

Recurrent pregnancy loss (RPL) is a significant adverse pregnancy complication, with an incompletely understood pathology. While many entities were proposed to elucidate the pathogenic basis of RPL, only few were significant enough to warrant investigation in all affected couples.. The aim of this study was to provide novel insights into the biological characteristics and related pathways of differentially expressed miRNA (DEMs) and genes (DEGs), in RPL, and construct a molecular miRNAs-mRNAs network.

METHODS

miRNAs and gene expression data were collected, and a number of DEMs and (DEGs) were obtained, and regulatory co-expression network were constructed. Function and enrichment analyses of DEMs were conducted using DIANA-miRPath. DEGs were screened, and were used in generation of protein-protein interaction (PPI) network, using STRING online database. Modularity analysis, and pathway identification operations were used in identifying graph clusters and associated pathways. DEGs were also used for further gene ontology (GO) analysis, followed by analysis of KEGG pathway.

RESULTS

A total of 34 DEMs were identified, and were found to be highly enriched in TGF-β signaling pathway, Fatty acid metabolism and TNF signaling pathway. Hub miRNAs were selected and were found to be involved in several functional pathways including progesterone-mediated oocyte maturation and Thyroid hormone signaling pathway. Five dysregulated feedback loops involving miRNA and TFs were identified and characterized. Most notably, PPI network analysis identified hub-bottleneck protein panel. These appear to offer potential candidate biomarker pattern for RPL diagnosis and treatment.

CONCLUSIONS

The present study provides novel insights into the molecular mechanisms underlying RPL.

Breast Ductal Carcinoma in Situ: Precursor to Invasive Breast Cancer

This Editorial introduces this month's special Breast Ductal Carcinoma in Situ Theme Issue, a series of reviews intended to highlight the relationship of ductal carcinoma in situ as a precursor to breast cancer and emphasize the need for appropriate treatment in hopes of minimizing the progression to invasive disease.

Comparing MicroRNA Profilings of Purified HER-2-Negative and HER-2-Positive Cells Validates miR-362-5p/Sema3A as Characteristic Molecular Change in Triple-Negative Breast Cancers

Background

HER-2 is a key molecule serving as the therapeutic target, prognostic biomarker, and classification marker in breast cancer. Accurate microRNA profilings had not been conducted in purified tumor cells of HER-2-negative and HER-2-positive tissue specimens obtained from breast cancer patients.

Methods

(i) Differential expression microRNA discovery using laser capture microdissection- (LCM-) assisted specimen preparation and microRNA array chips on HER-2 overexpressing and triple-negative breast carcinoma (TNBC) subtype tissues, (ii) differential expression microRNA validation by quantitative real-time PCR, and (iii) independent validation on tissue microarray.

Results

Five microRNAs (miR-20a-5p, miR-221-3p, miR-362-5p, miR-502-3p, and miR-222-3p) were screened and validated as upregulated microRNAs in TNBC cells comparing to HER-2 overexpressing cells using a microRNA array (5 cases in each group) and quantitative real-time PCR (20 cases in each group). The expression difference of miR-362-5p had the most significant statistical significance (p = 0.0016) among the five microRNAs. The expression of miR-362-5p and its target gene Sema3A was further analyzed using in situ hybridization (ISH) and immunohistochemistry on standard tissue sections (n = 150). 70.8% of HER-2-negative cells showed moderate expression of miR-362-5p whereas 20.4% HER-2-negative cells correlated with strong expression of miR-362-5p (p < 0.0001). The proportion of patients with moderate/strong miR-362-5p expression in luminal, HER-2 overexpressing, and TNBC subtypes were 53.2%, 22.2%, and 74.3%, respectively (p = 0.0002). High miR-362-5p expressers had shorter overall survival in the univariate analysis (p = 0.046). There was a significant negative correlation between miR-362-5p and Sema3A expression (p < 0.0001). The patients with negative/weak Sema3A protein expression had poorer prognosis than those with moderate (HR: 3.723, p = 0.021) or strong (HR: 3.966, p = 0.013) Sema3A protein expression in the multivariate analysis.

Conclusions

miR-362-5p/Sema3A might provide a promising therapeutic pathway and represents a candidate therapeutic target of the TNBC subtype.

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

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