Open access peer-reviewed chapter

Potential Biomarkers for Therapeutic Monitoring and Clinical Outcome in Breast Cancer

Written By

Yuki Yamamoto, Sabrina La Salvia, Sahoo Susmita and Hidetoshi Tahara

Submitted: 03 August 2021 Reviewed: 06 September 2021 Published: 24 November 2021

DOI: 10.5772/intechopen.100311

From the Edited Volume

Breast Cancer - Evolving Challenges and Next Frontiers

Edited by Mani T. Valarmathi

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Non-coding RNAs are a species of RNA that are not translated to proteins. These include transfer RNAs and ribosomal RNAs, microRNAs, transfer RNA-derived fragments, and long non-coding RNA. It is known that expression levels of some non-coding RNAs included microRNAs are altered in cancer cells or tumor tissues. Moreover, expression profiles of such non-coding RNAs correlate between tissues and body fluids. Therefore, several non-coding RNAs are being used as diagnostic/prognosis biomarkers or therapeutic targets in cancer. In this chapter, we review about representative non-coding RNAs and introduce especially microRNA as diagnosis/prognosis biomarkers and therapeutic targets.


  • microRNA
  • isomiR
  • exosome
  • biomarker
  • therapeutics

1. Introduction

Non-coding RNAs (ncRNAs) are generic terms of RNA that are not translated to protein. For example, ribosomal RNA (rRNA) and transfer RNA (tRNA) are included in ncRNAs. In the body, ncRNA does not encode proteins but has important functions.

MicroRNAs (miRNA), one of the ncRNAs, are small non-coding RNAs with an average length of 22 nucleotides. miRNA is transcribed from genomic DNA, the transcribed miRNA is called “primary microRNA (pri-miRNA),” which is long transcripts having stem-loop structures. Pri-miRNA is processed by Drosha and DGCR8 (DiGeorge syndrome critical region 8), one of the microprocessors, to “precursor miRNA (pre-miRNA).” In the next step, there is pre-miRNA transition from nuclei to the cytoplasm through Exportin-5. Cytoplasmic pre-miRNA is processed by Dicer, one of RNaseIII, to double-strand miRNA. The double-strand miRNA binds to AGO (Argonaute) protein and forms RISC (RNA-induced silencing complex). RISC binds 3′ UTR (3′ untranslated region) of target mRNAs, and downregulate gene expression via mRNA cleavage, translational repression, or mRNA degradation (Figure 1) [1]. Recently, it is known that miRNA also binds to 5′ UTR (5′ untranslated region) and CDS (coding sequence) of target mRNAs [2, 3]. miRNAs may have over hundreds of target genes, regulating various biological phenomena. In cancer patients, many miRNAs are aberrantly expressed, caused by chromosomal aberration, epigenetic regulation, and genomic mutation [4, 5, 6]. Therefore, miRNAs with altered expression under pathological conditions are valuable for biomarkers and targets of therapeutics.

Figure 1.

The overview of miRNA biogenesis. miRNA is transcribed from genomic DNA to primary miRNA (pri-miRNA), which is long transcripts having stem-loop structures. Pri-miRNA is processed by Drosha and DGCR8 (DiGeorge syndrome critical region 8), one of the microprocessors, to precursor miRNA (pre-miRNA). After the transition of pre-miRNA from nuclei to the cytoplasm through Exportin-5, cytoplasmic pre-miRNA is processed by TRBP (transactivation response RNA-binding protein) and dicer, one of RNaseIII, to double-strand miRNA. The double-strand miRNA binds to AGO (Argonaute) protein and forms RISC (RNA-induced silencing complex). RISC binds 3′ UTR (3′ untranslated region) of target mRNAs.

Interestingly, recent studies revealed that miRNA sequences have the variation compared with the reference sequences. As miRNAs are called isomiRs, isomiRs are the miRNA variants that have different sequences and/or lengths [7, 8, 9, 10]. These isomiRs are classified as 5′ isomiR, 3′ isomiR, and polymorphic isomiR. isomiRs are generated through the slice site variation by Drosha or Dicer, the nucleotide addition, RNA editing, etc. [11]. Some isomiRs are abnormally expressed in cancer cells caused by chromosomal and/or miRNA processing aberration (Figure 2) [12, 13]. Thus, isomiR is also focused on as novel biomarker for cancer detection.

Figure 2.

The classification and generation of isomiRs. The isomiRs have a different length or sequence with mature miRNAs. These isomiRs are generated by a variation of Drosha or dicer variation. The aberrant processing in 5′ site generates 5′ isomiR. On the other hand, 3′ isomiR is generated by the aberrant processing in 3′ site. Polymorphic isomiR is generated by RNA editing. Navy arrow shows the correct processing site. Magenta and green arrows show the aberrant processing sites for isomiRs, which have a longer length. Orange and blue arrows show the aberrant processing sites for isomiRs, which have a shorter length. The red bar indicates the variati of sequence.

Long non-coding RNA (lncRNA) that is also one of ncRNAs consisting of over 200 nucleotides has multiple functions. LncRNA up- or downregulation has been shown to regulate several biological processes, such as transcription, translation, epigenetic modification, and miRNA expression [14]. It has been shown that lncRNA expressions are altered in various diseases. Therefore, similar to miRNAs, lncRNA has the potential of biomarkers and therapeutics. Moreover, recently it was uncovered that tRNA fragments are functional. Its non-coding RNA is called at tRNA-derived RNA fragment (tRF), and classified as 1-tRF, which is generated from the 3′-end of pre-tRNA, 5′-tRFs, which is generated by the cleavage of 5′ end in D-loop, 3′-tRFs, which is generated by the cleavage of 3′ end in T-loop, and tRNA-derived, stress-induced RNAs (tiRNAs), which is generated by specific cleavage in the anticodon loop. Some tRFs are identified as novel biomarkers for disease diagnosis (Figure 3) [15].

Figure 3.

The classification and various modes of generation of tRFs. tRNA-derived fragments (tRFs) are generated by cleavage of transfer RNA (tRNA). 1-tRFs are cleaved from pre-tRNA. The cleavage of the D-loop generates 5′-tRF. The cleavage of the T-loop generates 3′-tRF. 5′- and 3′-tRNA-derived stress-induced RNAs (tiRNAs) are generated by cleavage of the anticodon loop.


2. Liquid biopsy

A biopsy is a method for disease diagnosis using a part of tissues or cells of the lesion. The tissue specimens are sampled by surgery and the cells derived from the lesion are sampled by fine-needle aspiration. The biopsy is useful for diagnosing diseases and malignancies, because it is possible to observe tissues or cells directly.

Generally, to diagnose breast cancer, inspection, palpation, and mammography are performed at first. Then, if the patients are suspected of tumors, the biopsies using tissue or cells derived from the lesion are performed, resulting in diagnosing breast cancer. However, conventional biopsy, surgery, needle biopsy, fine-needle aspiration, etc., are high invasiveness and have the risk of needle tract seeding. As with other problems, it is also concerned that young women are diagnosed as false positive on mammography, caused by high breast density.

Recently, to solve a problem like this, some researchers focus on “liquid biopsy.” Liquid biopsy is the method for disease diagnosis using body fluid. Body fluids using in the liquid biopsy are mainly blood, but also saliva, urine, and spinal fluid [16, 17]. Because using body fluid like blood, sampling the specimen is capable of low invasiveness and repetitive. These are one of the features and usefulness of liquid biopsy. In the field of cancer research, circulating tumor cells (CTCs) and circulating cell-free DNAs (cfDNAs) are detected and evaluated, resulting in the diagnosis of cancers. However, a recent study uncovered that circulating miRNA in body fluid is reflected in pathology. Many researchers show that specific miRNAs are aberrantly expressed in each disease. More interestingly, some miRNA expressions are altered from an early stage of cancer. Therefore, investigating the alteration of miRNA expression leads to the early diagnosis of cancer.

2.1 Circulating tumor cells (CTCs)

The cancer cells leak to the bloodstream from the primary tumor in the tumor metastasis phase. In the detection of CTCs, cancer cells that are derived from metastatic tumors are directly evaluated. However, detecting CTCs is not easy, because the number of CTCs is too low. To detect and gather CTCs, cell surface markers are recognized by the specific antibodies. Then, evaluating the shape and gene profile of cancer cells results in the diagnosis of malignancy and specific mutation of each tumor. However, the detection in the early stage of cancer is not useful, because the CTCs are detected in the late stage of cancer.

2.2 Cell-free DNAs (cfDNAs)

In the bloodstream, DNA derived from various dead cells containing hematopoietic cells or other cells derived from tissues are circulating. Additionally, it is known that DNA fragments derived from cancer cells are circulating in the bloodstream of cancer patients. These DNA fragments are generated by apoptosis or clearance by immune cells. In the detection of cfDNAs, the tumor-specific somatic mutation is detected, resulting in the diagnosis of cancer. However, the detection of cfDNA derived from cancer cells is not useful for the early diagnosis of cancer, because cfDNAs were derived from the dead cells.

2.3 Non-coding RNAs (ncRNAs)

Recent studies have uncovered that the ncRNAs included miRNAs, tRFs, and other ncRNAs circulate in different body fluids [15, 18]. Generally, circulating RNAs are easily degraded by RNase present in plasma. However, ncRNAs secreted to body fluids via extracellular vesicles like exosomes, or bound to proteins, are resistant to RNase and therefore can be stable in circulation. Exosomes are a type of extracellular vesicles, ranging in size from 50 to 150 nm. Exosomes that are secreted from donor cells circulate in the body fluids and are transferred to target recipient cells. The uptake of exosomes in recipient cells leads to various physiological functions. These functions are caused by ncRNAs and/or proteins contained in exosomes. In this regard, it is thought that exosomes are required for cell-to-cell communications. For example, it is reported that miRNA contained in exosomes secreted from cancer cells, contributing to the metastasis of cancer [19]. Recently, it is thought that exosomes derided from cancer cells educate metastasis site and help the cancer metastasis via the transfer of ncRNA and protein as like this report [20]. Moreover, recent studies uncovered that circulating ncRNA in body fluid is reflected in the pathology. Many researchers show that specific miRNAs are aberrantly expressed in each disease. More interestingly, some miRNA expressions are altered from an early stage of cancer. Therefore, investigating the alteration of miRNA expression leads to the early diagnosis of cancer. In this regard, many researchers focus on the ncRNAs circulating in the body fluids. In particular, miRNAs circulating in the blood are focused on.


3. The method of screening the ncRNAs in the liquid biopsy

In liquid biopsy, there are several methods of screening for the circulating ncRNAs in the body fluids. In the case of using blood, commonly, it is necessary to isolate plasma or serum from blood. Then, RNA purification is performed from plasma or serum. Using purified RNA, the expression profiles of ncRNAs are assessed by real-time PCR or microarray, resulting in the identification of a novel biomarker. Examples are shown below:

3.1 Real-time PCR

In the method using real-time PCR, the specific ncRNA is detected with its primer pair, and the alteration of the ncRNA expression is evaluated. The real-time PCR method is not suited for screening and identification of a novel biomarker, because of using the specific primer pair corresponding to each ncRNAs. On the other hand, this method is available for detecting the already identified ncRNA or the particular ncRNA, because the experimental procedure is easier and the detection sensitivity is more specific than other methods.

3.2 Microarray

In the method using microarray, the alteration of ncRNAs existing on microarray chips is capable of a comprehensive evaluation, because the multiple ncRNAs are detectable at the same time. In the microarray method, the ncRNA expression is detected by the binding between cDNAs synthesized from RNA and probes anchored to the microarray chip. Therefore, the microarray method is not available for unknown ncRNAs.

3.3 Next-generation sequencing (NGS)

In the NGS, the alteration of ncRNA expression is comprehensively evaluated by direct reading the RNA sequence of whole ncRNAs. In this regard, it is possible to identify and compare the expression pattern of ncRNAs like as microarray method. Additionally, it is also possible to identify unknown ncRNAs because of the directly determining ncRNA sequence. Moreover, isomiRs, that many researchers recently focused on, are also detectable. However, experimental procedures and data analyses are more difficult and complex than the other methods, and the experimental cost is also high.


4. microRNA for breast cancer diagnosis

Some miRNAs are altered in the tumor tissue compared with normal tissue. For example, the expression level of miR-21 is increased in various cancers included breast cancer and associated with tumorigenesis. Additionally, some miRNAs have a specific expression level in breast cancers. Recent studies also reported that the expression of some miRNAs is altered by the difference of subtype or stage and with/without the receptors. Furthermore, it is known that some of these miRNAs are circulating in body fluids. Therefore, such miRNAs are available for the biomarkers in liquid biopsy. Specific ncRNAs are described below, and recent reports are summarized in Table 1.

Let-7iUrineDownqRT-PCRDown in breast cancer[21]
miR-15aSerumDownqRT-PCRDown in TNBC[22]
miR-17SerumDownqRT-PCRDown in TNBC[22]
DownqRT-PCRDown in TNBC[22]
miR-19bSerumDownqRT-PCRDown in TNBC[22]
DownqRT-PCRDown in TNBC[22]
miR-92aSerumDownqRT-PCRDown during tumor progression[23]
miR-145PlasmaDownMicroarrayDown in breast cancer[24]
miR-194-5pPlasmaDownNGSDown in brain metastasis[25]
miR-195PlasmaDownNGSDown in metastatic breast cancer[26]
miR-222UrineDownqRT-PCRDown in TNBC[22]
miR-320cUrineDownqRT-PCRDown in TNBC[22]
miR-423UrineDownqRT-PCRDown in breast cancer[21]
miR-622PlasmaDownqRT-PCRDown in breast cancer[27]
miR-660UrineDownqRT-PCRDown in breast cancer[21]
miR-802-5pPlasmaDownNGSDown in brain metastasis[25]
Let-7aSerumUpqRT-PCRUp in TNBC[22]
Let-7eSerumUpqRT-PCRUp in TNBC[22]
miR-16PlasmaUpMicroarrayUp in breast cancer[24]
Up during tumor progression
Up in TNBC
[22, 23, 24, 28]
miR-21-5p (3′ isoRNA)SerumUpNGSUp in breast cancer[29]
miR-23a-3pSerumUpNGSUp in breast cancer[29]
miR-29cSerumUpqRT-PCRUp in early breast cancer[30]
miR-99a-5pPlasmaUpqRT-PCRUp in early breast cancer[31]
miR-142-5pSerumUpNGSUp in luminal A breast cancer and TNBC[32]
Prognostic biomarker (recurrence)
Up in luminal A breast cancer and TNBC
[32, 33]
Up in breast cancer
Prognostic biomarker (drug resistance)
[34, 35]
miR-199aSerumUpqRT-PCRUp in early breast cancer[30]
miR-210PlasmaUpqRT-PCRUp in breast cancer[36]
miR-223-3pPlasmaUpMicroarrayUp during tumor progression[37]
miR-331PlasmaUpNGSUp in metastatic breast cancer[26]
qRT-PCRUp in early breast cancer[21, 30]
miR-451PlasmaUpMicroarrayUp in breast cancer[24]
miR-488SerumUpMicroarrayPrognostic biomarker (recurrence)[38]
miR-576-3pPlasmaUpNGSPrognostic biomarker (recurrence)[33]
miR-1246SerumUpMicroarrayPrognostic biomarker (drug resistance)[35]
miR-1910-3pSerumUpqRT-PCRUp in breast cancer[39]
miR-4433b-5pSerumUpNGSUp in luminal A breast cancer and TNBC[32]
miR-4665-5pPlasmaUpNGSPrognostic biomarker (recurrence)[33]

Table 1.

The alteration of circulating miRNAs in breast cancer.

“Up” indicates upregulation in breast cancer and “Down” indicates downregulation in breast cancer. qRT-PCR, quantitative reverse transcription-polymerase chain reaction; NGS, next-generation sequencing; TNBC, triple-negative breast cancer.

4.1 Circulating miRNAs

Francesca Maria Orlandella and colleagues focused on miR-622 that known to act as a tumor suppressor in several types of cancer. They reported that miR-622 was downregulated in the plasma and tissues of breast cancer patients. Moreover, it was revealed that the expression level of miR-622 correlated with the breast cancer subtypes and the advance of tumor stages. Additionally, miR-622 inhibited the migration of breast cancer cells via targeting NUAK family kinase 1 (NUAK1). In this regard, circulating miR-622 is useful for the biomarker of breast cancer [27].

To identify miRNAs that are useful for the early diagnosis of invasive breast cancers, Mio Yoshikawa and colleagues screened exosomal miRNAs of the plasma by microarray analysis. Using exosomal miRNAs of ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC), five miRNAs, miR-223-3p, miR-130-3p, miR-191-5p, miR-146a, and miR-221-3p, were upregulated in IDC compared with healthy control and DCIS. In this study, they revealed that the expression level of miR-223-3p was correlated between the tissue and plasma exosome. Furthermore, the expression level of miR-223-3p was upregulated according to the advance of tumor stages. In these findings, it is suggested that the expression level of exosomal miR-223-3p reflected the tissue pathogenesis, and the miR-223-3p has the potential as a biomarker for early diagnosing of invasive lesions from DCIS patients in liquid biopsy [37].

4.2 isomiR

Yumiko Koi and colleagues investigated the comprehensive expression profile of ncRNA using the NGS method and focused on the expression level of isomiR. They used the exosomal RNA of serum derived from breast cancer patients. At first, they revealed that 11 circulating small RNAs were upregulated in breast cancer serum compared with healthy controls. Then, 3′-isomiR of miR-21-5p was identified as one of the biomarkers for the diagnosis of breast cancer. Additionally, miR-23a-3p and tRF-Lys-TTT were also identified as biomarkers for the diagnosis of breast cancer. Interestingly, they proposed a discriminant model using the expression levels of these small ncRNAs, and this model was more significantly able to diagnose breast cancer than individual small ncRNA. It was revealed that this model was able to diagnose the stage 0 breast cancer. Moreover, the model also could diagnose the breast cancer irrespective of subtypes. In this regard, the model that included the alteration of isomiR is available for the early diagnosis of breast cancer [29].

4.3 tRFs

As mentioned above, it is clear that tRFs are generated in cancers. Yue Huang and colleagues investigated the expression profile of tRFs in normal breast epithelial cell lines and non-triple negative breast cancer (non-TNBC) cells using RNA sequencing. In further investigation, they revealed that the expression level of tDR-7816 (drives from tRNAGln−CTG−3−1), tDR-5334 (derived from tRNAGly−CCC−5−1), and tDR-4733 (derived from tRNAPhe−GAA−2−1) is altered in the serum of non-TNBC patients compared with healthy controls. It is suggested that these tRFs are useful for the diagnosis of breast cancer [40].

In addition, Jingyi Wang and colleagues explored the expression profiles of tRFs in plasma derived from breast cancer patients. As the result, six tRFs, tRF-Glu-CTC-003, tRF-Gly-CCC-007, tRF-Gly-CCC-008, tRF-Leu-CAA-003, tRF-Ser-TGA-001, and tRF-Ser-TGA-002, were altered in the early stage of breast cancers compared with healthy controls. These six tRFs are also downregulated in the plasma derived from DCIS. Moreover, they also revealed that these tRFs which excluded tRF-Glu-CTC-003 in HER2+ type and tRF-Gly-CCC-008 in luminal type are downregulated in each subtype. In this regard, it is suggested that these tRFs are useful as a novel biomarker for the diagnosis of early-stage breast cancer [41].

4.4 Urinary miRNAs

In the liquid biopsy, urine as the specimens has the advantage of easy and non-invasive collection. Thalia Erbes and colleagues investigated whether miRNAs in serum/plasma that are already identified as the candidates of biomarkers for breast cancer are altered in also urine [42]. The expression level of miR-155 which is known to be upregulated in serum from the breast cancer patients, and useful for the diagnostic biomarker, was upregulated also in urine from the breast cancer patients [42, 43]. Moreover, they revealed that the expression levels of urinary miR-21, miR-125, and miR-451 were also downregulated in the breast cancer patients like serum miRNAs [24, 42, 44, 45]. In the recent study, it is revealed that the expression level of urinary miR-423, miR-424, miR-660, and let-7i was altered in the breast cancer patients compared with healthy controls. Moreover, this study reported that the combination of these miRNA’s alterations more significantly diagnoses the breast cancer than the biomarker using individual miRNA’s alteration [21]. In this regard, urinary miRNAs are useful for the diagnostic and prognosis biomarkers.


5. microRNA for breast cancer therapeutics

As mentioned above, the expression level of various miRNAs is dramatically altered in the development and progression of diseases including the tumors. In this regard, it is thought that the alteration of miRNA expression contributes to the development and progression of several diseases. Moreover, the expression profiles of miRNAs are different in each type of diseases. Then, such miRNAs are available for the therapeutic target of the disease. In cancer research, miRNAs that are over-expressed in tumors are called “oncogenic microRNA (OncomiR)”, and are associated with tumor development and malignancy. On the other hand, miRNAs that are downregulated in tumors are called at “tumor suppressive microRNA (TS-miRNA)” and are contributed to the suppression of tumor progression via targeting genes that are associated with the cancer cell proliferation and survival. It is hoped that miRNA mimics and miRNA inhibitors targeting TS-miRNA or OncomiR are developed as therapeutic drugs. Specific ncRNAs are described below, and recent reports are summarized in Table 2.

miR-429Anti-sense oligonucleotideVHLInhibit the proliferation of HER2+ breast cancer[46]
miR-302binhibitorRUNX2Inhibit the proliferation[47]
miR-532-5pinhibitorRERGInhibit the proliferation and migration[48]
miR-1910-3pinhibitorMTMR3Inhibit proliferation and migration[39]
miR-99amimicFGFR3Inhibit the tumor proliferation and migration[49]
miR-128-3pmimicNEK2Inhibit tumorigenicity and tumor growth of breast cancer stem cells[50]
miR-188-5pmimicRAP2CInduce apoptosis and inhibit the proliferation[51]
miR-299-5pmimicSTK39Inhibit the migration and invasion[52]
miR-342mimicCFL1Inhibit the migration and invasion[53]
miR-424-5pmimicPD-L1Induced apoptosis and cell cycle arrest[54]
miR-590-3pmimicSLUGInhibit the metastasis in TNBCs[55]

Table 2.

The miRNAs as therapeutic targets in breast cancer.

HER2, human epidermal growth factor receptor 2; TNBCs, triple-negative breast cancers.

5.1 miR-22

It is reported that a lot of miRNAs regulate tumor progression and malignancy. Previously, we revealed that miR-22, which induce cellular senescence, suppressed the proliferation of breast tumors. MiR-22 is upregulated during cellular senescence induction. Such miRNAs are called “senescence-associated microRNA (SA-miRNA).” We reported that miR-22 induces cellular senescence via targeting CDK6 and SIRT1. Moreover, it was suggested that miR-22 was the therapeutic target of breast cancer, because miR-22 was downregulated in the breast cancer cells. In an additional investigation, it is reported that the replacement of miR-22 expression repressed the breast tumors through the experiment using the xenograft model mouse model [56].

5.2 miR-155

Jiang and colleagues reported that the expression level of miR-155 was upregulated in breast cancer. Then, they suggested that miR-155 functions as OncomiR, because its target gene is a suppressor of cytokine signaling 1 (SOCS1) known as one of the tumor suppressor genes. This study revealed that the inhibition of the miR-155 expression and function by the antisense oligonucleotide against miR-155 repressed the tumor progression in the investigation using both the breast cancer cells and the xenograft mouse models. In this regard, the inhibition of OncomiR functions is available for the therapeutic targets [57].

5.3 miR-424/503 cluster

It is reported that the miR-424/503 cluster that was coded on X-chromosome was deficient in luminal B breast cancer. It is also clear that the deletion of this locus significantly correlated with the poor prognosis. Therefore, it is suggested that the miR-424/503 cluster functions as TS-miRNA. Moreover, the miR-424/503 cluster targets insulin-like growth factor 1 receptor (IGF1R) and B-cell lymphoma 2 (BCL-2) that contribute to anti-apoptosis. The deletion of this cluster leads to upregulating these gene expressions, resulting in the acquisition of drug resistance [58].

5.4 miR-539

A recent study reported that miR-539 was downregulated in tumor tissues, and it is suggested that miR-539 has the tumor suppressive effects. In the investigation using breast cancer cells, miR-539 mimics repressed the proliferation and migration of cancer cells via targeting epithelial growth factor receptor (EGFR). Additionally, miR-539 also repressed the tumor proliferation [59]. Moreover, it is uncovered that miR-539 was downregulated in TNBC, and miR-539 suppressed the proliferation, invasion, and migration via targeting Laminin subunit alpha 4 (LAMA4) [60].

5.5 miR-142

It is reported that miR-142 is also downregulated in breast tumor tissue compared with normal tissue and suggested that miR-142 functions as TS-miRNA. It is revealed that miR-142 inhibits the expression of the BTB domain and CNC homolog 1 (BACH1), which is associated with the metastasis of breast cancer, resulting in the suppression of the proliferation, invasion, and migration. Moreover, Mansoori and colleagues reported that miR-142 induced apoptosis via targeting estrogen receptor 1 (ESR1) that coded estrogen receptor in the estrogen receptor-positive breast cancer [61, 62].

5.6 miR-34a

miR-34a is the most famous TS-miRNAs that was reported to upregulate in the p53-dependent manner and downregulate in the colorectal cancer patients compared with healthy, and progressed in the development as the nucleic acid drug against cancer. MiR-34a suppressed colorectal cancer progression through the induction of cellular senescence via E2F pathway [63]. In further investigation, it is uncovered that miR-34a downregulates the gene expression via targeting sirtuin 1 (SIRT1), cyclin D1, cyclin-dependent kinase 4/6 (CDK4/6), and MYC [64, 65, 66]. In this regard, the clinical trial of MRX34, the liposomal miR-34a mimic, for various solid tumors included breast cancer was performed in miRNA Therapeutics Inc. Unfortunately, this clinical trial was dropped [67]. However, a recently study reported that miR-34a targets programmed death ligand 1 (PD-L1) in acute myeloid leukemia [68]. Moreover, it is reported that miR-34a expression level is downregulated in TNBC and inversely correlated with PD-L1 expression [69]. Therefore, a novel clinical trial of miR-34a is expected.


6. Conclusions

In this review, we summarized several ncRNAs that are available for the biomarkers diagnosing breast cancer or predicting poor prognosis and the targets of breast cancer therapeutics. The finding and studying of isomiRs or tRFs are leading to the development of highly specific biomarkers, which could lead to early diagnosis of breast cancer. Moreover, it is useful for comparing the alteration of several ncRNA expressions multidimensionally with the comprehensive analysis of the expression profiles of ncRNAs using microarray or NGS method. These approaches and results may lead to highly specific diagnostics of the disease and can correctly predict several different types of breast cancers. In regard to cancer therapeutics, the studies about isomiRs or tRFs may result in the development of novel therapeutic targets for breast cancers. Further research on the ncRNAs will aid to improve the diagnosis and therapeutics of breast cancers.


Conflict of interest

Professor Hidetoshi Tahara is the representative director of a university-originated venture, MiRTeL Co.


  1. 1. Winter J, Jung S, Keller S, Gregory RI, Diederichs S. Many roads to maturity: microRNA biogenesis pathways and their regulation. Nature Cell Biology. 2009;11(3):228-234
  2. 2. Hausser J, Syed AP, Bilen B, Zavolan M. Analysis of CDS-located miRNA target sites suggests that they can effectively inhibit translation. Genome Research. 2013;23(4):604-615
  3. 3. Lee I, Ajay SS, Yook JI, Kim HS, Hong SH, Kim NH, et al. New class of microRNA targets containing simultaneous 5′-UTR and 3′-UTR interaction sites. Genome Research. 2009;19(7):1175-1183
  4. 4. Aure M, Leivonen S-K, Fleischer T, Zhu Q, Overgaard J, Alsner J, et al. Individual and combined effects of DNA methylation and copy number alterations on miRNA expression in breast tumors. Genome Biology. 2013;14(11):R126
  5. 5. Calin GA, Croce CM. MicroRNA signatures in human cancers. Nature Reviews. Cancer. 2006;6(11):857-866
  6. 6. Lu J, Getz G, Miska EA, Alvarez-Saavedra E, Lamb J, Peck D, et al. MicroRNA expression profiles classify human cancers. Nature. 2005;435(7043):834-838
  7. 7. Tan GC, Chan E, Molnar A, Sarkar R, Alexieva D, Isa IM, et al. 5′ isomiR variation is of functional and evolutionary importance. Nucleic Acids Research. 2014;42(14):9424-9435
  8. 8. Morin RD, O’Connor MD, Griffith M, Kuchenbauer F, Delaney A, Prabhu A-L, et al. Application of massively parallel sequencing to microRNA profiling and discovery in human embryonic stem cells. Genome Research. 2008;18(4):610-621
  9. 9. Landgraf P, Rusu M, Sheridan R, Sewer A, Iovino N, Aravin A, et al. A mammalian microRNA expression atlas based on small RNA library sequencing. Cell. 2007;129(7):1401-1414
  10. 10. Kawahara Y, Zinshteyn B, Sethupathy P, Iizasa H, Hatzigeorgiou AG, Nishikura K. Redirection of silencing targets by adenosine-to-inosine editing of miRNAs. Science. 2007;315(5815):1137-1140
  11. 11. Gebert LFR, Macrae IJ. Regulation of microRNA function in animals. Nature Reviews. Molecular Cell Biology. 2019;20(1):21-37
  12. 12. Wang S, Zheng Z, Chen P, Wu M. Tumor classification and biomarker discovery based on the 5′isomiR expression level. BMC Cancer. 2019;19(1):127
  13. 13. Telonis AG, Magee R, Loher P, Chervoneva I, Londin E, Rigoutsos I. Knowledge about the presence or absence of miRNA isoforms (isomiRs) can successfully discriminate amongst 32 TCGA cancer types. Nucleic Acids Research. 2017;45(6):2973-2985
  14. 14. Yao R-W, Wang Y, Chen L-L. Cellular functions of long noncoding RNAs. Nature Cell Biology. 2019;21(5):542-551
  15. 15. Yu M, Lu B, Zhang J, Ding J, Liu P, Lu Y. tRNA-derived RNA fragments in cancer: Current status and future perspectives. Journal of Hematology & Oncology. 2020;13(1):121
  16. 16. Mattox AK, Yan H, Bettegowda C. The potential of cerebrospinal fluid–based liquid biopsy approaches in CNS tumors. Neuro-Oncology. 2019;21(12):1509-1518
  17. 17. Rapado-González Ó, Majem B, Muinelo-Romay L, López-López R, Suarez-Cunqueiro M. Cancer salivary biomarkers for tumours distant to the oral cavity. International Journal of Molecular Sciences. 2016;17(9):1531
  18. 18. Kosaka N, Iguchi H, Ochiya T. Circulating microRNA in body fluid: A new potential biomarker for cancer diagnosis and prognosis. Cancer Science. 2010;101(10):2087-2092
  19. 19. Fong MY, Zhou W, Liu L, Alontaga AY, Chandra M, Ashby J, et al. Breast-cancer-secreted miR-122 reprograms glucose metabolism in premetastatic niche to promote metastasis. Nature Cell Biology. 2015;17(2):183-194
  20. 20. Xu R, Rai A, Chen M, Suwakulsiri W, Greening DW, Simpson RJ. Extracellular vesicles in cancer—Implications for future improvements in cancer care. Nature Reviews. Clinical Oncology. 2018;15(10):617-638
  21. 21. Hirschfeld M, Rücker G, Weiß D, Berner K, Ritter A, Jäger M, et al. Urinary exosomal microRNAs as potential non-invasive biomarkers in breast cancer detection. Molecular Diagnosis & Therapy. 2020;24(2):215-232
  22. 22. Ritter A, Hirschfeld M, Berner K, Rücker G, Jäger M, Weiss D, et al. Circulating non-coding RNA-biomarker potential in neoadjuvant chemotherapy of triple negative breast cancer? International Journal of Oncology. 2020;56(1):47-68
  23. 23. Si H, Sun X, Chen Y, Cao Y, Chen S, Wang H, et al. Circulating microRNA-92a and microRNA-21 as novel minimally invasive biomarkers for primary breast cancer. Journal of Cancer Research and Clinical Oncology. 2013;139(2):223-229
  24. 24. Ng EKO, Li R, Shin VY, Jin HC, Leung CPH, Ma ESK, et al. Circulating microRNAs as specific biomarkers for breast cancer detection. PLoS One. 2013;8(1):e53141
  25. 25. Sereno M, Haskó J, Molnár K, Medina SJ, Reisz Z, Malhó R, et al. Downregulation of circulating miR 802-5p and miR 194-5p and upregulation of brain MEF2C along breast cancer brain metastasization. Molecular Oncology. 2020;14(3):520-538
  26. 26. Mcanena P, Tanriverdi K, Curran C, Gilligan K, Freedman JE, Brown JAL, et al. Circulating microRNAs miR-331 and miR-195 differentiate local luminal a from metastatic breast cancer. BMC Cancer. 2019;19(1):436
  27. 27. Orlandella FM, Mariniello RM, Mirabelli P, De Stefano AE, Iervolino PLC, Lasorsa VA, et al. miR-622 is a novel potential biomarker of breast carcinoma and impairs motility of breast cancer cells through targeting NUAK1 kinase. British Journal of Cancer. 2020;123(3):426-437
  28. 28. Anwar SL, Sari DNI, Kartika AI, Fitria MS, Tanjung DS, Rakhmina D, et al. Upregulation of circulating MiR-21 expression as a potential biomarker for therapeutic monitoring and clinical outcome in breast cancer. Asian Pacific Journal of Cancer Prevention. 2019;20(4):1223-1228
  29. 29. Koi Y, Tsutani Y, Nishiyama Y, Ueda D, Ibuki Y, Sasada S, et al. Predicting the presence of breast cancer using circulating small RNAs, including those in the extracellular vesicles. Cancer Science. 2020;111(6):2104-2115
  30. 30. Zhang L, Xu Y, Jin X, Wang Z, Wu Y, Zhao D, et al. A circulating miRNA signature as a diagnostic biomarker for non-invasive early detection of breast cancer. Breast Cancer Research and Treatment. 2015;154(2):423-434
  31. 31. Garrido-Cano I, Constâncio V, Adam-Artigues A, Lameirinhas A, Simón S, Ortega B, et al. Circulating miR-99a-5p expression in plasma: A potential biomarker for early diagnosis of breast cancer. International Journal of Molecular Sciences. 2020;21(19):7427
  32. 32. Ozawa PMM, Vieira E, Lemos DS, Souza ILM, Zanata SM, Pankievicz VC, et al. Identification of miRNAs enriched in extracellular vesicles derived from serum samples of breast cancer patients. Biomolecules. 2020;10(1):150
  33. 33. Wu H, Wang Q, Zhong H, Li L, Zhang Q, Huang Q, et al. Differentially expressed microRNAs in exosomes of patients with breast cancer revealed by next-generation sequencing. Oncology Reports. 2020;43(1):240-250
  34. 34. Sun Y, Wang M, Lin G, Sun S, Li X, Qi J, et al. Serum microRNA-155 as a potential biomarker to track disease in breast cancer. PLoS One. 2012;7(10):e47003
  35. 35. Zhang Z, Zhang L, Yu G, Sun Z, Wang T, Tian X, et al. Exosomal miR-1246 and miR-155 as predictive and prognostic biomarkers for trastuzumab-based therapy resistance in HER2-positive breast cancer. Cancer Chemotherapy and Pharmacology. 2020;86(6):761-772
  36. 36. Lopes BC, Braga CZ, Ventura FV, De Oliveira JG, Kato-Junior EM, Bordin-Junior NA, et al. miR-210 and miR-152 as biomarkers by liquid biopsy in invasive ductal carcinoma. Journal of Personalized Medicine. 2021;11(1):31
  37. 37. Yoshikawa M, Iinuma H, Umemoto Y, Yanagisawa T, Matsumoto A, Jinno H. Exosome-encapsulated microRNA-223-3p as a minimally invasive biomarker for the early detection of invasive breast cancer. Oncology Letters. 2018;15(6):9584-9592
  38. 38. Masuda T, Shinden Y, Noda M, Ueo H, Hu Q, Yoshikawa Y, et al. Circulating pre-microRNA-488 in peripheral blood is a potential biomarker for predicting recurrence in breast cancer. Anticancer Research. 2018;38(8):4515-4523
  39. 39. Wang B, Mao J-H, Wang B-Y, Wang L-X, Wen H-Y, Xu L-J, et al. Exosomal miR-1910-3p promotes proliferation, metastasis, and autophagy of breast cancer cells by targeting MTMR3 and activating the NF-κB signaling pathway. Cancer Letters. 2020;489:87-99
  40. 40. Huang Y, Ge H, Zheng M, Cui Y, Fu Z, Wu X, et al. Serum tRNA-derived fragments (tRFs) as potential candidates for diagnosis of nontriple negative breast cancer. Journal of Cellular Physiology. 2020;235(3):2809-2824
  41. 41. Wang J, Ma G, Li M, Han X, Xu J, Liang M, et al. Plasma tRNA fragments derived from 5′ ends as novel diagnostic biomarkers for early-stage breast cancer. Molecular Therapy--Nucleic Acids. 2020;21:954-964
  42. 42. Erbes T, Hirschfeld M, Rücker G, Jaeger M, Boas J, Iborra S, et al. Feasibility of urinary microRNA detection in breast cancer patients and its potential as an innovative non-invasive biomarker. BMC Cancer. 2015;15(1):193
  43. 43. Sochor M, Basova P, Pesta M, Dusilkova N, Bartos J, Burda P, et al. Oncogenic MicroRNAs: miR-155, miR-19a, miR-181b, and miR-24 enable monitoring of early breast cancer in serum. BMC Cancer. 2014;14(1):448
  44. 44. Mar-Aguilar F, Mendoza-Ramírez JA, Malagón-Santiago I, Espino-Silva PK, Santuario-Facio SK, Ruiz-Flores P, et al. Serum circulating microRNA profiling for identification of potential breast cancer biomarkers. Disease Markers. 2013;34:259454
  45. 45. Asaga S, Kuo C, Nguyen T, Terpenning M, Giuliano AE, Hoon DS. Direct serum assay for microRNA-21 concentrations in early and advanced breast cancer. Clinical Chemistry. 2011;57(1):84-91
  46. 46. Cava C, Novello C, Martelli C, Lodico A, Ottobrini L, Piccotti F, et al. Theranostic application of miR-429 in HER2+ breast cancer. Theranostics. 2020;10(1):50-61
  47. 47. Ma J, Zhou Z. Downregulation of miR-302b is associated with poor prognosis and tumor progression of breast cancer. Breast Cancer. 2020;27(2):291-298
  48. 48. Huang L, Tang X, Shi X, Su L. miR-532-5p promotes breast cancer proliferation and migration by targeting RERG. Experimental and Therapeutic Medicine. 2020;19(1):400-408
  49. 49. Long X, Shi Y, Ye P, Guo J, Zhou Q, Tang Y. MicroRNA-99a suppresses breast cancer progression by targeting FGFR3. Frontiers in Oncology. 2020;9:1473
  50. 50. Chen Y, Wu N, Liu L, Dong H, Liu X. microRNA-128-3p overexpression inhibits breast cancer stem cell characteristics through suppression of Wnt signalling pathway by down-regulating NEK2. Journal of Cellular and Molecular Medicine. 2020;24(13):7353-7369
  51. 51. Zhu X, Qiu J, Zhang T, Yang Y, Guo S, Li T, et al. MicroRNA-188-5p promotes apoptosis and inhibits cell proliferation of breast cancer cells via the MAPK signaling pathway by targeting Rap2c. Journal of Cellular Physiology. 2020;235(3):2389-2402
  52. 52. Li C, Wang A, Chen Y, Liu Y, Zhang H, Zhou J. MicroRNA-299-5p inhibits cell metastasis in breast cancer by directly targeting serine/threonine kinase 39. Oncology Reports. 2020;43(4):1221-1233
  53. 53. Liu C, Xing H, Luo X, Wang Y. MicroRNA-342 targets Cofilin 1 to suppress the growth, migration and invasion of human breast cancer cells. Archives of Biochemistry and Biophysics. 2020;687:108385
  54. 54. Dastmalchi N, Hosseinpourfeizi MA, Khojasteh SMB, Baradaran B, Safaralizadeh R. Tumor suppressive activity of miR-424-5p in breast cancer cells through targeting PD-L1 and modulating PTEN/PI3K/AKT/mTOR signaling pathway. Life Sciences. 2020;259:118239
  55. 55. Yan M, Ye L, Feng X, Shi R, Sun Z, Li Z, et al. MicroRNA-590-3p inhibits invasion and metastasis in triple-negative breast cancer by targeting Slug. American Journal of Cancer Research. 2020;10(3):965-974
  56. 56. Xu D, Takeshita F, Hino Y, Fukunaga S, Kudo Y, Tamaki A, et al. miR-22 represses cancer progression by inducing cellular senescence. The Journal of Cell Biology. 2011;193(2):409-424
  57. 57. Jiang S, Zhang H-W, Lu M-H, He X-H, Li Y, Gu H, et al. MicroRNA-155 functions as an OncomiR in breast cancer by targeting the suppressor of cytokine signaling 1 gene. Cancer Research. 2010;70(8):3119-3127
  58. 58. Rodriguez-Barrueco R, Nekritz EA, Bertucci F, Yu J, Sanchez-Garcia F, Zeleke TZ, et al. miR-424(322)/503 is a breast cancer tumor suppressor whose loss promotes resistance to chemotherapy. Genes and Development. 2017;31(6):553-566
  59. 59. Guo J, Gong G, Zhang B. miR-539 acts as a tumor suppressor by targeting epidermal growth factor receptor in breast cancer. Scientific Reports. 2018;8(1):2073
  60. 60. Yang Z-X, Zhang B, Wei J, Jiang G-Q, Wu Y-L, Leng B-J, et al. MiR-539 inhibits proliferation and migration of triple-negative breast cancer cells by down-regulating LAMA4 expression. Cancer Cell International. 2018;18(1):16
  61. 61. Mansoori B, Mohammadi A, Ghasabi M, Shirjang S, Dehghan R, Montazeri V, et al. miR-142-3p as tumor suppressor miRNA in the regulation of tumorigenicity, invasion and migration of human breast cancer by targeting Bach-1 expression. Journal of Cellular Physiology. 2019;234(6):9816-9825
  62. 62. Mansoori B, Mohammadi A, Gjerstorff MF, Shirjang S, Asadzadeh Z, Khaze V, et al. miR-142-3p is a tumor suppressor that inhibits estrogen receptor expression in ER-positive breast cancer. Journal of Cellular Physiology. 2019;234(9):16043-16053
  63. 63. Tazawa H, Tsuchiya N, Izumiya M, Nakagama H. Tumor-suppressive miR-34a induces senescence-like growth arrest through modulation of the E2F pathway in human colon cancer cells. Proceedings of the National Academy of Sciences. 2007;104(39):15472-15477
  64. 64. Sun F, Fu H, Liu Q, Tie Y, Zhu J, Xing R, et al. Downregulation of CCND1 and CDK6 by miR-34a induces cell cycle arrest. FEBS Letters. 2008;582(10):1564-1568
  65. 65. Wei JS, Song YK, Durinck S, Chen Q-R, Cheuk ATC, Tsang P, et al. The MYCN oncogene is a direct target of miR-34a. Oncogene. 2008;27(39):5204-5213
  66. 66. Yamakuchi M, Ferlito M, Lowenstein CJ. miR-34a repression of SIRT1 regulates apoptosis. Proceedings of the National Academy of Sciences. 2008;105(36):13421-13426
  67. 67. Hong DS, Kang Y-K, Borad M, Sachdev J, Ejadi S, Lim HY, et al. Phase 1 study of MRX34, a liposomal miR-34a mimic, in patients with advanced solid tumours. British Journal of Cancer. 2020;122(11):1630-1637
  68. 68. Wang X, Li J, Dong K, Lin F, Long M, Ouyang Y, et al. Tumor suppressor miR-34a targets PD-L1 and functions as a potential immunotherapeutic target in acute myeloid leukemia. Cellular Signalling. 2015;27(3):443-452
  69. 69. Huang X, Xie X, Wang H, Xiao X, Yang L, Tian Z, et al. PDL1 And LDHA act as ceRNAs in triple negative breast cancer by regulating miR-34a. Journal of Experimental & Clinical Cancer Research. 2017;36(1):129

Written By

Yuki Yamamoto, Sabrina La Salvia, Sahoo Susmita and Hidetoshi Tahara

Submitted: 03 August 2021 Reviewed: 06 September 2021 Published: 24 November 2021