Locus Summary

Gene:MIRLET7E; microRNA let-7e
Aliases: LET7E, let-7e, MIRNLET7E, hsa-let-7e
Summary:microRNAs (miRNAs) are short (20-24 nt) non-coding RNAs that are involved in post-transcriptional regulation of gene expression in multicellular organisms by affecting both the stability and translation of mRNAs. miRNAs are transcribed by RNA polymerase II as part of capped and polyadenylated primary transcripts (pri-miRNAs) that can be either protein-coding or non-coding. The primary transcript is cleaved by the Drosha ribonuclease III enzyme to produce an approximately 70-nt stem-loop precursor miRNA (pre-miRNA), which is further cleaved by the cytoplasmic Dicer ribonuclease to generate the mature miRNA and antisense miRNA star (miRNA*) products. The mature miRNA is incorporated into a RNA-induced silencing complex (RISC), which recognizes target mRNAs through imperfect base pairing with the miRNA and most commonly results in translational inhibition or destabilization of the target mRNA. The RefSeq represents the predicted microRNA stem-loop. [provided by RefSeq, Sep 2009]
Databases:miRBase, OMIM, HGNC, Ensembl, GeneCard, Gene
Source:NCBIAccessed: 30 August, 2019

Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 30 August 2019 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

Tag cloud generated 30 August, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (11)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

MicroRNA Function

Numbers shown below represent number of publications held in OncomiRDB database for Oncogenic and Tumor-Suppressive MicroRNAs.

TissueTarget Gene(s)Regulator(s)MIRLET7E Function in CancerEffect
breast (1)
-breast cancer (1)
CCND1 (1)
KDM5B (1)
inhibit cell cycle progression (1)
tumor-suppressive (1)
nerve (1)
-neuroblastoma (1)
MYCN (1)
inhibit cell proliferation (1)
inhibit clonogenic growth (1)
tumor-suppressive (1)

Source: OncomiRDB Wang D. et al. Bioinformatics 2014, 30(15):2237-2238.

Latest Publications: MIRLET7E (cancer-related)

Xu P, Xia T, Ling Y, Chen B
MiRNAs with prognostic significance in multiple myeloma: A systemic review and meta-analysis.
Medicine (Baltimore). 2019; 98(33):e16711 [PubMed] Related Publications
BACKGROUND: Multiple myeloma (MM) is a clonal plasma cell malignancy associated with hypercalcemia, bone lesions, and renal failure. The prognostic significance of the mutation of miRNAs, one kind of small noncoding RNA molecules that can modulate gene expression, should be confirmed in non-Hodgkin lymphomas (NHL). This study aimed to identify the prognostic value of miRNAs in patients with MM.
METHODS: A meta-analysis was performed to estimate the pooled hazard ratios and their corresponding 95% confidence intervals for the associations between levels of miRNA expression (predictive factors) and outcomes in patients with MM. We systematically searched the PubMed, Web of Science, and China National Knowledge Infrastructure databases (final search conducted January 1, 2018) to identify eligible studies. Eligible studies were included by certain inclusion and exclusion criteria, whose quality was assessed by Newcastle-Ottawa Scale.
RESULTS: After performing the literature search and review, 10 relevant studies, including 1214 cases, were identified. The results of our meta-analysis revealed that upregulated miR-92a level and downregulated miR-16, miR-25, miR-744, miR-15a, let-7e, and miR-19b expression were associated with poor prognosis in MM.
CONCLUSIONS: This study identified miRNAs could serve as potential prognostic biomarkers in MM. Given the limited research available, the clinical application of these findings has yet to be verified.

Khodadadi Kohlan A, Saidijam M, Amini R, et al.
Induction of let-7e gene expression attenuates oncogenic phenotype in HCT-116 colorectal cancer cells through targeting of DCLK1 regulation.
Life Sci. 2019; 228:221-227 [PubMed] Related Publications
AIMS: MicroRNAs (miRNAs) are small noncoding RNAs that negatively control gene expression at the translational level. There are compelling evidences indicating that the expression of let-7e is downregulated in various cancers, however, the role of let-7e in colorectal cancer (CRC) and its mechanism has been remained unknown. Here, we investigated the potential role of let-7e in regulating CRC cells phenotypes.
MAIN METHODS: Let-7e and DCLK1 siRNA were transfected in HCT-116 cells. Colony formation assay, scratch test, Annexin V/PI flow cytometry, and sphere formation assay were performed to examine the cell proliferation, migration, apoptosis, and stemness, respectively. The expression of let-7e, epithelial-mesenchymal transition (EMT)-related genes, Doublecortin like kinase protein 1 (DCLK1), and cancer stem cells (CSCs) were assessed using RT-qPCR while the protein level of DCLK1 was determined by western blotting.
KEY FINDINGS: Overexpression of let-7e effectively inhibited cell proliferation, suppressed migration, reduced sphere formation, and precluded EMT process as well as stemness factors. Furthermore, let-7e suppressed DCLK1 expression. Additionally, we found that the expression of let-7e was negatively correlated with DCLK1 expression in CRC cells.
SIGNIFICANCE: Let-7e plays an important role as tumor suppressor miRNA in CRC probably through inhibition of DCLK1 expression.

Park Y, Kim J
Regulation of IL-6 signaling by miR-125a and let-7e in endothelial cells controls vasculogenic mimicry formation of breast cancer cells.
BMB Rep. 2019; 52(3):214-219 [PubMed] Free Access to Full Article Related Publications
The role of tumor-proximal factors in tumor plasticity during chemoresistance and metastasis following chemotherapy is well studied. However, the role of endothelial cell (EC) derived paracrine factors in tumor plasticity, their effect on chemotherapeutic outcome, and the mechanism by which these paracrine factors modulate the tumor microenvironment are not well understood. In this study, we report a novel mechanism by which endothelial miR-125a and let-7e-mediated regulation of interleukin-6 (IL-6) signaling can manipulate vasculogenic mimicry (VM) formation of MDA-MB-231 breast cancer cells. We found that endothelial IL-6 levels were significantly higher in response to cisplatin treatment, whereas levels of IL-6 upon cisplatin exposure remained unchanged in MDA-MB-231 breast cancer cells. We additionally found an inverse correlation between IL-6 and miR-125a/let-7e expression levels in cisplatin treated ECs. Interestingly, IL-6, IL-6 receptor (IL-6R), and signal transducer and activator of transcription 3 (STAT3) genes in the IL-6 pathway are closely regulated by miR-125a and let-7e, which directly target its 3' untranslated region. Functional analyses revealed that endothelial miR-125a and let-7e inhibit IL-6-induced adhesion of monocytes to ECs. Furthermore, conditioned medium from cisplatin treated ECs induced a significantly higher formation of VM in MDA-MB-231 breast cancer cells as compared to that from intact ECs; this effect of cisplatin treatment was abrogated by concurrent overexpression of miR-125a and let-7e. Overall, this study reveals a novel EC-tumor cell crosstalk mediated by the endothelial miR-125a/let-7e-IL-6 signaling axis, which might improve chemosensitivity and provide potential therapeutic targets for the treatment of cancer. [BMB Reports 2019; 52(3): 214-219].

Ding C, Yu H, Shi C, et al.
MiR-let-7e inhibits invasion and magration and regulates HMGB1 expression in papillary thyroid carcinoma.
Biomed Pharmacother. 2019; 110:528-536 [PubMed] Related Publications
Thyroid cancer keeps rapidly increasing worldwide and the most frequent type is papillary thyroid carcinoma (PTC). MicroRNAs (miRNAs) are proved dysregulated in many types of malignancies, including thyroid cancer. Although miR-let-7e has been implicated in several types of cancer regulation, relatively little is known about the function of miR-let-7e in PTC. In this study, we showed that the overexpression of miR-let-7e or knockdown of high mobility group box 1 (HMGB1) inhibited cell migration and invasion. MiR-let-7e downregulates HMGB1 expression by directly targeting the HMGB1 3'-UTR. Furthermore, HMGB1 reintroduction reversed the anti-proliferation, anti-migration, and anti-invasion roles of miR-let-7e. miR-let-7e might function as a tumor suppressor in papillary thyroid carcinoma through HMGB1. Therefore, our study demonstrates that miR-let-7e plays an important role in papillary thyroid carcinoma progression and might represent a new potential therapeutic target for treatment.

Campayo M, Navarro A, Benítez JC, et al.
miR-21, miR-99b and miR-375 combination as predictive response signature for preoperative chemoradiotherapy in rectal cancer.
PLoS One. 2018; 13(11):e0206542 [PubMed] Free Access to Full Article Related Publications
INTRODUCTION: Preoperative chemoradiotherapy (CRT) is a standard treatment for locally advanced rectal cancer patients. Despite the benefits of CRT, its use in non-responder patients can be associated with increased toxicities and surgical resection delay. The identification of CRT response biomarkers, such as microRNAs, could improve the management of these patients. We have studied the microRNA expression in pretreatment endoscopy biopsies from rectal cancer patients treated with CRT to identify potential microRNAs able to predict CRT response and clinical outcome of these patients.
MATERIAL AND METHODS: RNA from pretreatment endoscopy biopsies from 96 rectal cancer patients treated with preoperative CRT were studied. Pathological response was graded according to the tumor regression grade (TRG) Dworak classification. In the screening phase, 377 miRNAs were studied in 12 patients with extreme responses (TRG0-1 vs TRG4). The potential role as predictive biomarkers for CRT response, disease-free survival (DFS) and overall survival (OS) of the miRNAs identified in the screening phase were validated in the whole cohort.
RESULTS: In the screening phase, an 8-miRNAs CRT-response signature was identified: let-7b, let-7e, miR-21, miR-99b, miR-183, miR-328, miR-375 and miR-483-5p. In the validation phase, miR-21, miR-99b and miR-375 emerged as CRT response-related miRNAs while miR-328 and let-7e emerged as prognostic markers for DFS and OS. Interestingly, ROC curve analysis showed that the combination of miR-21, miR-99b and miR-375 had the best capacity to distinguish patients with maximum response (TRG4) from others.
CONCLUSIONS: miR-21, miR-99b and miR-375 could add valuable information for individualizing treatment in locally advanced rectal cancer patients.

Oztemur Islakoglu Y, Noyan S, Aydos A, Gur Dedeoglu B
Meta-microRNA Biomarker Signatures to Classify Breast Cancer Subtypes.
OMICS. 2018; 22(11):709-716 [PubMed] Related Publications
Breast cancer is one of the leading causes of morbidity and mortality that is in need of novel diagnostics and therapeutics. Meta-analysis of microarray data offers promise to combine studies and provide more robust results. We report here a molecular classification of pathological subtypes (estrogen receptor [ER], progesterone receptor [PR], and Human Epidermal Growth Factor Receptor 2 [HER2]) of breast cancers with microRNA (miRNA)-dependent signatures. A ranking-based meta-analysis approach was applied to eight independent microarray data sets and meta-miRNA lists were obtained that are specific to each breast cancer subtype. The comparison of the lists with miRCancer and the PhenomiR 2.0 databases pointed out nine prominent miRNAs: let-7b-5p, let-7c-5p, let-7e-5p, miR-130a-3p, miR-30a-5p, miR-92a-1-5p, miR-211-5p, miR-500a-3p, and miR-516b-3p. Further analysis conducted with the TCGA data showed that these miRNAs can differentiate tumors from normal samples as well as discriminate the molecular subtypes of breast cancer. According to the PAM50 classification, three of these miRNAs (let-7b-5p, let-7c-5p, and miR-30a-5p) downregulated significantly, whereas miR-130a-3p, miR-92a-1-5p, miR-211-5p, and miR-500a-3p upregulated in tumors from the luminal A to the basal-like subtypes. When the prominent meta-miRNAs and their targets were analyzed, they appeared to be taking part in important signaling pathways in cancer such as the PI3K-Akt signaling and the p53 signaling pathways. Furthermore, the regulatory genes, which are key players for ER, PR, and ErBb signaling pathways, were found to be under control of several meta-miRNAs. These meta-miRNAs and the genes they are regulating offer new promise for future translational research and potential targets for precision medicine diagnostics.

Zamora-Contreras AM, Alvarez-Salas LM
Let-7 miRNA Precursors Co-express with LIN28B in Cervical Cells.
Microrna. 2018; 7(1):62-71 [PubMed] Related Publications
BACKGROUND: The let-7 microRNAs (miRNAs) are frequently dysregulated in carcinogenic processes, including cervical cancer. LIN28 proteins regulate let-7 biogenesis by binding to conserved sequences within the pre-miRNA structure. Nevertheless, recent research has shown that some let-7 miRNAs may escape LIN28 regulation.
OBJECTIVE: Correlate pre-let-7 miRNAs and LIN28B levels in cervical cell lines with different malignancy and HPV content.
METHODS: Pre-let-7 levels were determined by RTqPCR. LIN28B and other let-7 targets were analyzed by immunoblot. In silico tools were used to correlate let-7 and LIN28B expression and to analyze prelet- 7 sequences and structures.
RESULTS: Lin28B protein was detected in all tested cell lines although it was more expressed in tumor cell lines. High levels of pre-let-7c/f-1 and pre-miR-98 were present in almost all cell lines regardless malignancy and LIN28B expression. Pre-let-7g/i were mainly expressed in tumor cell lines, pre-let-7e and pre-let-7-a3 were absent in all cell lines and pre-let-7a-2 showed indistinct expression. LIN28B showed positive correlation with pre-let-7i/g/f-1 and pre-miR-98 in tumor cell lines, suggesting escape from regulation. Sequence alignment and analysis of pre-let-7 miRNAs showed distinctive structural features within the preE region that may influence the ideal pre-let-7 structuring for LIN28B interaction. Short preE-stems were present in pre-let-7 that may escape LIN28B regulation, but long preEstems were mostly associated with high-level pre-let-7 miRNAs.
CONCLUSION: The observed differences of pre-let-7 levels in cervical cell lines may be the result of alternative preE structuring affecting interaction with LIN28B thus resulting in differential let-7 regulation.

Gozé C, Reynes C, Forestier L, et al.
Pilot Study of Whole Blood MicroRNAs as Potential Tools for Diffuse Low-Grade Gliomas Detection.
Cell Mol Neurobiol. 2018; 38(3):715-725 [PubMed] Related Publications
Earlier diagnosis and longitudinal monitoring of diffuse low-grade gliomas (DLGG) increase overall survival by maximizing surgery efficacy and optimizing time for an adjuvant treatment when resection is incomplete. Presently, only imaging permits the non-invasive detection and monitoring of DLGG, but it lacks sensitivity. Measure of circulating microRNAs levels could represent a non-invasive alternative. We hypothesized that slow-growing DLGG induce overtime a systemic reaction impacting blood cells microRNA profiles, while the intact blood-brain barrier restricts the passage of tumor microRNAs into bloodstream. In 15 DLGG patients and 15 healthy controls, expression levels of 758 microRNAs were measured by the TaqMan OpenArray RT-qPCR platform, on preoperative whole blood, containing both cell-free and blood cells microRNAs. Normalized data were computed by a Student t test with a p value threshold allowing a 10% rate of false positive. Statistical analysis retained fifteen microRNAs, all overexpressed in patients. MiR-20a, miR-106a, miR-20b, and miR-93 belong to clusters genetically related. As miR-223 and miR-let7e, they target the transcription factor STAT3. MicroRNA expression levels were not correlated to preoperative tumor volume. A signature composed of miR-93, miR-590-3p, and miR-454 enabled to nearly perfectly separate patients from controls. Our study performed on a homogeneous cohort was designed accordingly to DLGG particularities and provided the first microRNAs signature proposal. Functional convergence on STAT3 and overexpression of miR-223, factors respectively involved in myeloid-derived suppressor cells and granulocytes, argued for a systemic peripheral response. Overexpressed microRNAs and tumor volume were uncorrelated, making a tumor origin elusive.

Shi W, Zhang Z, Yang B, et al.
Overexpression of microRNA let-7 correlates with disease progression and poor prognosis in hepatocellular carcinoma.
Medicine (Baltimore). 2017; 96(32):e7764 [PubMed] Free Access to Full Article Related Publications
The aim of the study was to explore the clinical significance of let-7 expression in hepatocellular carcinoma (HCC).A PCR array was conducted to screen for let-7 expression in early-stage HCC. Next, the deregulation of let-7 was confirmed by quantitative real-time RT-PCR (qRT-PCR) in another set of liver tissues, including normal control (NC), chronic hepatitis (CH), liver cirrhosis (LC), HCC, and adjacent nontumor (NT) tissues. In addition, as the potential target mRNA of let-7, alpha 2(I) collagen (COL1A2) mRNA was also quantified in the above liver tissues. Finally, an association study comparing let-7 and COL1A2 and their clinical significance in HCC was conducted.PCR array analysis revealed that the expression levels of let-7a/7b/7c were significantly downregulated in early-stage HCC compared to those in NT tissues. As compared to NC samples, qRT-PCR further confirmed that let-7a/7b/7c/7e were significantly upregulated in CH, LC, and NT tissues, while there were no significant differences in expression between the HCC and NC groups. Although COL1A2 may be the target mRNA of let-7, only let-7c expression was inversely correlated with COL1A2 mRNA expression in CH tissues. In HCC tissues, levels of let-7a/7b/7c/7e were positively correlated with that of COL1A2 mRNA. The clinical significance study revealed that elevated let-7a expression was significantly correlated with serosal and vein invasion, while elevated let-7c expression was significantly correlated with vein invasion and advanced TNM stage. Elevated let-7e expression was significantly correlated with vein invasion in HCC. Significantly shorter postoperative overall survival was observed in HCC patients with high let-7c expression.The results suggest that aberrant expression of let-7a/7b/7c/7e occurs in benign liver diseases and HCC. The upregulation of let-7 expression is associated with the progression and poor prognosis of HCC, and further mechanistic studies are warranted.

Shan Y, Liu Y, Zhao L, et al.
MicroRNA-33a and let-7e inhibit human colorectal cancer progression by targeting ST8SIA1.
Int J Biochem Cell Biol. 2017; 90:48-58 [PubMed] Related Publications
Colorectal cancer (CRC) is one of the leading causes of cancer mortality worldwide. Aberrant sialylation is crucially involved in the progression of various types of cancer. MicroRNAs (miRNAs) have been broadly studied in cancer. MicroRNA-33a (miR-33a) and Has-let-7e (let-7e) are non-coding RNA that can reduce cell motility and viability in cancer. In this study, miR-33a and let-7e levels were confirmed to be significantly down-regulated in CRC samples (n=32) and drug resistant cell line (HCT-8/5-FU) compared with those in the matched adjacent tissues and drug sensitivity cell line (HCT-8). ST8SIA1 was highly expressed in CRC tissues and HCT-8/5-FU cells, which was negatively correlated with miR-33a/let-7e expression. Luciferase reporter assays confirmed that both miR-33a and let-7e bound to the 3'-untranslated (3'-UTR) region of ST8SIA1. Inhibiting miR-33a/let-7e expression in CRC cells increased endogenous ST8SIA1 mRNA and protein levels. MiR-33a/let-7e knockdown promoted chemoresistance, proliferation, invasion, angiogenesis in vitro, and tumor growth in vivo. Whereas, ectopic expression of miR-33a/let-7e suppressed chemoresistance, proliferation, invasion and angiogenesis in CRC cell lines. ST8SIA1 knockdown mimicked the tumor suppressive effect of miR-33a/let-7e on CRC cells, while restoration of ST8SIA1 abolished the tumor suppressive effect of miR-33a/let-7e on CRC cells. Taken together, altered expression of miR-33a/let-7e was correlated with ST8SIA1 level, which might contribute to CRC progression. The miR-33a/let-7e-ST8SIA1 axis could be a therapeutic target for CRC patients.

Fedorko M, Juracek J, Stanik M, et al.
Detection of let-7 miRNAs in urine supernatant as potential diagnostic approach in non-metastatic clear-cell renal cell carcinoma.
Biochem Med (Zagreb). 2017; 27(2):411-417 [PubMed] Free Access to Full Article Related Publications
INTRODUCTION: Urinary microRNAs (miRNAs) are emerging as a clinically useful tool for early and non-invasive detection of various types of cancer. The aim of this study was to evaluate whether let-7 family miRNAs differ in their urinary concentrations between renal cell carcinoma (RCC) cases and healthy controls.
MATERIALS AND METHODS: In the case-control study, 69 non-metastatic clear-cell RCC patients and 36 gender/age-matched healthy controls were prospectively enrolled. Total RNA was purified from cell-free supernatant of the 105 first morning urine specimens. Let-7 family miRNAs were determined in cell-free supernatant using quantitative miRNA real-time reverse-transcription PCR and absolute quantification approach.
RESULTS: Concentrations of all let-7 miRNAs (let-7a, let-7b, let-7c, let-7d, let-7e and let-7g) were significantly higher in urine samples obtained from RCC patients compared to healthy controls (P < 0.001; P < 0.001; P = 0.005; P = 0.006; P = 0.015 and P = 0.002, respectively). Subsequent ROC analysis has shown that let-7a concentration possesses good ability to differentiate between cases and controls with area under curve being 0.8307 (sensitivity 71%, specificity 81%).
CONCLUSIONS: We have shown that let-7 miRNAs are abundant in the urine samples of patients with clear-cell RCC, and out of six let-7 family members, let-7a outperforms the others and presents promising non-invasive biomarker for the detection of RCC.

Ma J, Zhan Y, Xu Z, et al.
ZEB1 induced miR-99b/let-7e/miR-125a cluster promotes invasion and metastasis in esophageal squamous cell carcinoma.
Cancer Lett. 2017; 398:37-45 [PubMed] Related Publications
Esophageal squamous cell carcinoma (ESCC) is one of the most common digestive tumors in Asia. Recent researches demonstrate that miRNAs are involved in the development of ESCC. In this study, we identified a miRNA cluster, termed miR-99b/let-7e/miR-125a as pro-metastasis oncomir. Overexpression of this miRNA cluster promoted ESCC cell migration and invasion in vitro and induced an experimental metastasis in vivo. ZEB1 was discovered to bind to the promoter region of miR-99b/let-7e/miR-125a cluster and regulate the expression of miRNAs at transcriptional level. Knockdown of ZEB1 resulted in a decrease of both mature and primary miRNAs. Further research revealed AT-rich interaction domain 3A (ARID3A) as a direct target of miR-99b/let-7e/miR-125a cluster. Reduced ARID3A phenocopied miR-99b/let-7e/miR-125a overexpression, and elevated ARID3A counteracted the pro-metastasis effect of miR-99b/let-7e/miR-125a. Moreover, ARID3A was downregulated by ZEB1 in a miR-99b/let-7e/miR-125a dependent manner. Collectively, our study sheds light on the essential role of miR-99b/let-7e/miR-125a cluster in tumor metastasis.

Xiao M, Cai J, Cai L, et al.
Let-7e sensitizes epithelial ovarian cancer to cisplatin through repressing DNA double strand break repair.
J Ovarian Res. 2017; 10(1):24 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Resistance to platinum-based chemotherapy remains a great challenge for ovarian cancer treatment. The human let-7 family contains 13 members located on nine different chromosomes, and most members have been implicated in the modulation of drug sensitivity in cancers. Our previous study showed that deregulation of let-7e in epithelial ovarian cancer (EOC) promoted the development of resistance to cisplatin. In the present study, we aimed to investigate the underlying mechanism and further evaluate the clinical value of let-7e in predicting chemo-response and prognosis in EOC.
RESULTS: In situ hybridization assays revealed a significantly decreased expression of let-7e in chemo-resistant EOC tissues compared with chemo-sensitive cases. Transfection with let-7e agomir sensitized EOC cells to cisplatin, down-regulated BRCA1 and Rad51 expression, and repressed the repair of cisplatin-induced DNA double strand break, while let-7e inhibitor exerted the opposite effects. In human EOC tissues, BRCA1 and Rad51 levels were increased in the chemo-resistant group compared with the sensitive group and were negatively correlated with let-7e. Low let-7e and high Rad51 were significantly associated with poor progression-free survival and overall survival and multivariate regression analyses showed that let-7e was an independent predictor for overall survival and chemotherapy response in EOC. Receiver operating characteristic analysis indicated that let-7e level was highly predictive of resistance to platinum-taxane chemotherapy with an area under the curve of 0.826.
CONCLUSIONS: In EOC, low let-7e leads to activation of BRCA1 and Rad51 expression and subsequent enhancement of DSB repair, which in turn results in cisplatin-resistance. Let-7e is a potential predictor for survival and chemo-response in EOC and re-expression of let-7e might be an effective strategy for overcoming chemo-resistance.

Wu YF, Xu Q, He CY, et al.
Association of Polymorphisms in three pri-miRNAs that Target Pepsinogen C with the Risk and Prognosis of Gastric Cancer.
Sci Rep. 2017; 7:39528 [PubMed] Free Access to Full Article Related Publications
We aimed to explore the associations of polymorphisms in three microRNAs (miRNAs) (let-7e rs8111742, miR-365b rs121224 and miR-4795 rs1002765) that target PGC with the risk and prognosis of gastric cancer/atrophic gastritis. Sequenom's MassArray was used to genotype the miRNA polymorphisms in 724 gastric cancer cases, 862 atrophic gastritis cases and 862 controls in a Chinese population. We found that let-7e rs8111742 and miR-4795 rs1002765 were associated with the risk of gastric cancer in the H. pylori-positive subgroup. MiR-365b rs121224 was associated with the risk of intestinal-type gastric cancer in the alcohol consumption subgroup. Intestinal-type gastric cancer patients at Borrmann stages III-IV who carry the miR-365b rs121224 GG genotype had better prognosis compared with those who carry the CG or CC genotypes. MiR-365b rs121224 was associated with Lauren typing and TNM staging, in which the distribution of GG genotype carriers in intestinal-type gastric cancer and the TNM stage I-II subgroup was higher than that of CG or CC genotypes, which contrasted with the distribution in diffuse-type gastric cancer or TNM III-IV groups. These findings suggested that the polymorphisms in these miRNAs might be biomarkers for gastric cancer risk and prognosis, especially for populations infected with Helicobacter pylori or who consume alcohol.

Kim H, Yang JM, Jin Y, et al.
MicroRNA expression profiles and clinicopathological implications in lung adenocarcinoma according to EGFR, KRAS, and ALK status.
Oncotarget. 2017; 8(5):8484-8498 [PubMed] Free Access to Full Article Related Publications
Lung adenocarcinoma has distinctive clinicopathological features that are related to specific genetic alterations, including EGFR and KRAS mutations and ALK rearrangement. MicroRNAs are small non-coding RNAs that post-transcriptionally regulate many important biological processes and influence cancer phenotypes. This study retrospectively investigated microRNA expression profiles, and their clinicopathological implications, in lung adenocarcinoma according to genetic status (EGFR, KRAS, ALK, and triple negative). A total of 72 surgically resected lung adenocarcinoma specimens (19 EGFR-mutated, 17 KRAS-mutated, 16 ALK-rearranged, and 20 triple negative cancers) were screened for 23 microRNAs using quantitative real-time reverse transcriptase polymerase chain reaction. We then evaluated the associations between the microRNA expressions and the cancers' genetic and clinicopathological features. Eight microRNAs were associated with clinicopathological features, such as male sex and ever-smoker status (high miR-373-3p, miR-1343-3p, miR-138-1-3p, and miR-764; low miR-27b-3p) and vascular invasion (high miR-27b-3p; low miR-1343-3p and miR-764). Clustering and discriminant analyses revealed that the microRNA expression patterns in the ALK group were different from those in the EGFR and KRAS groups. Five microRNAs (high miR-1343-3p; low miR-671-3p, miR-103a-3p, let-7e, and miR-342-3p) were especially distinctive in the ALK group, compared to the EGFR and KRAS groups. Moreover, a significant association was observed between ALK-rearrangement, decreased miR-342-3p expression, and immunohistochemical loss of E-cadherin. Therefore, microRNA expression profiles appear to have distinctive clinicopathological implications in ALK-rearranged lung adenocarcinoma. Furthermore, the association of ALK rearrangement, decreased miR-342-3p expression, and E-cadherin loss might indicate that miR-342-3p is involved in the ALK-associated phenotypes and epithelial-mesenchymal transition.

Tomsic J, Fultz R, Liyanarachchi S, et al.
Variants in microRNA genes in familial papillary thyroid carcinoma.
Oncotarget. 2017; 8(4):6475-6482 [PubMed] Free Access to Full Article Related Publications
Papillary Thyroid Carcinoma (PTC) displays one of the highest familiality scores of all cancers as measured by case-control studies, yet only a handful of genes have been implicated until now. Variants in microRNAs have been associated with the risk of several cancers including PTC but the magnitude of this involvement is unclear. This study was designed to test to what extent genomic variants in microRNAs contribute to PTC risk. We used SOLiD technology to sequence 321 genomic regions encoding 427 miRNAs in one affected individual from each of 80 PTC families. After excluding variants with frequency ≥ 1% in 1000 Genomes Phase 1 (n = 1092) we detected 1978 variants. After further functional filtering steps 25 variants in pre-miRs remained. Co-segregation was observed for six out of 16 tested miRNA variants with PTC in the families, namely let-7e, miR-181b, miR-135a, miR-15b, miR-320, and miR-484. Expression of miR-135a and miR-181b was tested in normal thyroid and tumor tissue from patients that carry the variants and a decrease in expression was observed. In vitro assays were applied to measure the effect of the variants on microRNAs' maturation. Four out of six variants were tested. Only the let-7e and miR-181b variants showed an effect on processing leading to lower levels of mature miRNA. These two variants were not detected in 1170 sporadic PTC cases nor in 1404 controls. Taken together, our data show that high penetrance germline sequence variants of miRNAs potentially predispose to a fraction of all PTC but are not common.

Gong W, Zheng J, Liu X, et al.
Knockdown of NEAT1 restrained the malignant progression of glioma stem cells by activating microRNA let-7e.
Oncotarget. 2016; 7(38):62208-62223 [PubMed] Free Access to Full Article Related Publications
Nuclear paraspeckle assembly transcript 1 (NEAT1), a long non-coding RNA, promotes oncogenesis in various tumors, including human gliomas. Herein, we studied the expression and function of NEAT1 in glioma stem cells (GSCs). Quantitative real-time PCR demonstrated that NEAT1 was upregulated in GSCs. NEAT1 knockdown inhibited GSC cell proliferation, migration and invasion and promoted GSC apoptosis. A potential binding region between NEAT1 and microRNA let-7e was confirmed by dual-luciferase assays. Upregulation of NEAT1 reduced the expression of let-7e, and there was reciprocal repression between NEAT1 and let-7e in an Argonaute 2-dependent manner. Let-7e expression was lower expression in glioblastoma tissues and GSCs than in normal brain tissues and cells. Restoration of let-7e suppressed tumor function by inhibiting proliferation, migration and invasion while promoting apoptosis in GSCs. NEAT1 knockdown and let-7e overexpression both reduced NRAS protein expression. NRAS was identified as a direct target of let-7e and promoted oncogenesis in GSCs. As NEAT1 promoted oncogenesis by downregulating let-7e expression, both of these genes could be considered for application in glioma therapy.

Xu Q, Wu YF, Li Y, et al.
SNP-SNP interactions of three new pri-miRNAs with the target gene PGC and multidimensional analysis of H. pylori in the gastric cancer/atrophic gastritis risk in a Chinese population.
Oncotarget. 2016; 7(17):23700-14 [PubMed] Free Access to Full Article Related Publications
Gastric cancer (GC) is a multistep complex disease involving multiple genes, and gene-gene interactions have a greater effect than a single gene in determining cancer susceptibility. This study aimed to explore the interaction of the let-7e rs8111742, miR-365b rs121224, and miR-4795 rs1002765 single nucleotide polymorphisms (SNPs) with SNPs of the predicted target gene PGC and Helicobacter pylori status in GC and atrophic gastritis (AG) risk. Three miRNA SNPs and seven PGC SNPs were detected in 2448 cases using the Sequenom MassArray platform. Two pairwise combinations of miRNA and PGC SNPs were associated with increased AG risk (let-7e rs8111742 - PGC rs6458238 and miR-4795 rs1002765 - PGC rs9471643). Singly, miR-365b rs121224 and PGC rs6912200 had no effect individually but in combination they demonstrated an epistatic interaction associated with AG risk. Similarly, let-7e rs8111742 and miR-4795 rs1002765 SNPs interacted with H. pylori infection to increase GC risk (rs8111742: Pinteraction = 0.024; rs1002765: Pinteraction = 0.031, respectively). A three-dimensional interaction analysis found miR-4795 rs1002765, PGC rs9471643, and H. pylori infection positively interacted to increase AG risk (Pinteraction = 0.027). Also, let-7e rs8111742, PGC rs6458238, and H. pylori infection positively interacted to increase GC risk (Pinteraction = 0.036). Furthermore, both of these three-dimensional interactions had a dosage-effect correspondence (Ptrend < 0.001) and were verified by MDR. In conclusion, the miRNAs SNPs (let-7e rs8111742 and miR-4795 rs1002765) might have more superior efficiency when combined with PGC SNPs and/or H. pylori for GC or AG risk than a single SNP on its own.

Calura E, Bisognin A, Manzoni M, et al.
Disentangling the microRNA regulatory milieu in multiple myeloma: integrative genomics analysis outlines mixed miRNA-TF circuits and pathway-derived networks modulated in t(4;14) patients.
Oncotarget. 2016; 7(3):2367-78 [PubMed] Free Access to Full Article Related Publications
The identification of overexpressed miRNAs in multiple myeloma (MM) has progressively added a further level of complexity to MM biology. miRNA and gene expression profiles of two large representative MM datasets, available from retrospective and prospective series and encompassing a total of 249 patients at diagnosis, were analyzed by means of in silico integrative genomics methods, based on MAGIA2 and Micrographite computational procedures. We first identified relevant miRNA/transcription factors/target gene regulation circuits in the disease and linked them to biological processes. Members of the miR-99b/let-7e/miR-125a cluster, or of its paralog, upregulated in t(4;14), were connected with the specific transcription factors PBX1 and CEBPA and several target genes. These results were validated in two additional independent plasma cell tumor datasets. Then, we reconstructed a non-redundant miRNA-gene regulatory network in MM, linking miRNAs, such as let-7g, miR-19a, mirR-20a, mir-21, miR-29 family, miR-34 family, miR-125b, miR-155, miR-221 to pathways associated with MM subtypes, in particular the ErbB, the Hippo, and the Acute myeloid leukemia associated pathways.

Aragon Han P, Weng CH, Khawaja HT, et al.
MicroRNA Expression and Association with Clinicopathologic Features in Papillary Thyroid Cancer: A Systematic Review.
Thyroid. 2015; 25(12):1322-9 [PubMed] Related Publications
BACKGROUND: Studies have suggested that microRNAs (miR) may be useful prognostic markers and are associated with aggressive clinicopathologic features in papillary thyroid cancer (PTC). This systematic review examined associations between miRs and aggressive clinicopathologic features in PTC.
METHODS: A literature search was performed within the PubMed, Embase, Cochrane, Web of Science, and Scopus databases for papers published prior to November 24, 2014. The search was performed by combining the concepts "thyroid tumor" with "microRNA" and by using "and" as the Boolean operator. Upon retrieval of candidate studies, full-text publications were reviewed in their entirety and selected if they examined the prognostic significance between miR expression and established aggressive clinicopathologic features of PTC.
RESULTS: Fifteen studies from 13 unique groups that included 807 patients were reviewed. Most of the studies were retrospective, and none included patients who had undergone routine central lymph node dissection. Expression levels of miRs-21, -34b, -130b, -135b, -146b, -151, -181b, -199b-5p, -221, -222, -451, -623, -1271, -2861, and let-7e showed significant association with at least one aggressive feature, such as large tumor size, extrathyroidal extension, multifocality, lymphovascular invasion, lymph node metastases, distant metastasis, advanced American Joint Cancer Committee stage, and presence of the BRAF(V600E) mutation. Herein we summarize the literature with regard to these associations.
CONCLUSION: Further studies are needed to investigate whether miRs are independent predictors of aggressive clinicopathologic features before it can be recommended that miR expression levels should be incorporated into the management algorithm for patients with PTC. A well-designed prospective study is needed to assess these potential associations.

Fontemaggi G, Bellissimo T, Donzelli S, et al.
Identification of post-transcriptional regulatory networks during myeloblast-to-monocyte differentiation transition.
RNA Biol. 2015; 12(7):690-700 [PubMed] Free Access to Full Article Related Publications
Treatment of leukemia cells with 1,25-dihydroxyvitamin D3 may overcome their differentiation block and lead to the transition from myeloblasts to monocytes. To identify microRNA-mRNA networks relevant for myeloid differentiation, we profiled the expression of mRNAs and microRNAs associated to the low- and high-density ribosomal fractions in leukemic cells and in their differentiated monocytic counterpart. Intersection between mRNAs shifted across the fractions after treatment with putative target genes of modulated microRNAs showed a series of molecular networks relevant for the monocyte cell fate determination, as for example the post-transcriptional regulation of the Polo-like kinase 1 (PLK1) by miR-22-3p and let-7e-5p.

Chiam K, Wang T, Watson DI, et al.
Circulating Serum Exosomal miRNAs As Potential Biomarkers for Esophageal Adenocarcinoma.
J Gastrointest Surg. 2015; 19(7):1208-15 [PubMed] Related Publications
BACKGROUND: The poor prognosis and rising incidence of esophageal adenocarcinoma highlight the need for improved detection methods. The potential for circulating microRNAs (miRNAs) as biomarkers in other cancers has been shown, but circulating miRNAs have not been well characterized in esophageal adenocarcinoma. We investigated whether circulating exosomal miRNAs have potential to discriminate individuals with esophageal adenocarcinoma from healthy controls and non-dysplastic Barrett's esophagus.
METHODS: Seven hundred fifty-eight miRNAs were profiled in serum circulating exosomes from a cohort of 19 healthy controls, 10 individuals with Barrett's esophagus, and 18 individuals with locally advanced esophageal adenocarcinoma. MiRNA expression was assessed using all possible permutations of miRNA ratios per individual. Four hundred eight miRNA ratios were differentially expressed in individuals with cancer compared to controls and Barrett's esophagus (Mann-Whitney U test, P < 0.05). The 179/408 ratios discriminated esophageal adenocarcinoma from healthy controls and Barrett's esophagus (linear regression, P < 0.05; area under receiver operating characteristic (ROC) > 0.7, P < 0.05). A multi-biomarker panel (RNU6-1/miR-16-5p, miR-25-3p/miR-320a, let-7e-5p/miR-15b-5p, miR-30a-5p/miR-324-5p, miR-17-5p/miR-194-5p) demonstrated enhanced specificity and sensitivity (area under ROC = 0.99, 95% CI 0.96-1.0) over single miRNA ratios to distinguish esophageal adenocarcinoma from controls and Barrett's esophagus.
CONCLUSIONS: This study highlights the potential for serum exosomal miRNAs as biomarkers for the detection of esophageal adenocarcinoma.

Tsai CH, Lin LT, Wang CY, et al.
Over-expression of cofilin-1 suppressed growth and invasion of cancer cells is associated with up-regulation of let-7 microRNA.
Biochim Biophys Acta. 2015; 1852(5):851-61 [PubMed] Related Publications
Cofilin-1, a non-muscle isoform of actin regulatory protein that belongs to the actin-depolymerizing factor (ADF)/cofilin family is known to affect cancer development. Previously, we found that over-expression of cofilin-1 suppressed the growth and invasion of human non-small cell lung cancer (NSCLC) cells in vitro. In this study, we further investigated whether over-expression of cofilin-1 can suppress tumor growth in vivo, and performed a microRNA array analysis to better understand whether specific microRNA would be involved in this event. The results showed that over-expression of cofilin-1 suppressed NSCLC tumor growth using the xenograft tumor model with the non-invasive reporter gene imaging modalities. Additionally, cell motility and invasion were significantly suppressed by over-expressed cofilin-1, and down-regulation of matrix metalloproteinase (MMPs) -1 and -3 was concomitantly detected. According to the microRNA array analysis, the let-7 family, particularly let-7b and let-7e, were apparently up-regulated among 248 microRNAs that were affected after over-expression of cofilin-1 up to 7 days. Knockdown of let-7b or let-7e using chemical locked nucleic acid (LNA) could recover the growth rate and the invasion of cofilin-1 over-expressing cells. Next, the expression of c-myc, LIN28 and Twist-1 proteins known to regulate let-7 were analyzed in cofilin-1 over-expressing cells, and Twist-1 was significantly suppressed under this condition. Up-regulation of let-7 microRNA by over-expressed cofilin-1 could be eliminated by co-transfected Twist-1 cDNA. Taken together, current data suggest that let-7 microRNA would be involved in over-expression of cofilin-1 mediated tumor suppression in vitro and in vivo.

Lv J, Xia K, Xu P, et al.
miRNA expression patterns in chemoresistant breast cancer tissues.
Biomed Pharmacother. 2014; 68(8):935-42 [PubMed] Related Publications
BACKGROUND/AIMS: Breast cancer chemoresistance is a major obstacle to the successful treatment of patients. miRNAs perform critical roles in biological processes, including tumorigenesis and chemoresistance. However, little clinical data are available regarding the relationship between miRNA expression patterns and breast cancer chemoresistance.
METHODS: We created a doxorubicin-resistant MCF-7 (MCF-/Adr) cell line using a pulse-selection method; then verified the resistance of the MCF-7/Adr cell line to doxorubicin by using the methyl thiazolyl tetrazolium (MTT) assay, terminal deoxyribonucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) staining, and Intracellular doxorubicin accumulation assay. Then, we performed qRT-PCR to detect the expression patterns of 14 selected miRNAs (which are related to breast cancer resistance) in both cell lines. Subsequently, we performed a bioinformatics analysis, including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, to determine the putative functions of 13 differentially expressed miRNA-targeted genes. Finally, we tested the expression levels of these 13 miRNAs in 10 chemotherapy non-responder breast cancer tissues and 29 responder tissues. All statistical analyses were performed by a two-tailed Student's t-test, and a P value less than 0.05 was considered statistically significant.
RESULTS: The results of the MTT assay showed that the MCF-7/Adr cell line was significantly more resistant to doxorubicin compared to the MCF-7 cells The results of the TUNEL assay indicated that doxorubicin induced an increase in the number apoptotic cells in the MCF-7 group. Additionally, the accumulation of doxorubicin was higher in MCF-7 cells compared to MCF-7/Adr cells, which was consistent with the MTT and TUNEL results. The qRT-PCR results demonstrated that compared to the parental MCF-7 cell line, miR-200a, miR-141, miR-200c, miR-31, miR-429, and miR-196b were over-expressed, and let-7e, miR-576-3p, miR-125b-1, miR-370, miR-145, miR-765, and miR-760 were significantly down-regulated in MCF-7/Adr cells. The GO analysis results revealed that the predicted target genes of these 14 miRNAs primarily regulated protein binding, zinc ion binding, DNA binding, and transcription factor activity. The KEGG data demonstrated that these target genes are mainly involved in the MAPK signaling pathway, regulation of the actin cytoskeleton, cytokine-cytokine receptor interaction, and other signaling pathways. Compared to the breast cancer tissues from chemotherapy responders, 10 miRNAs were identified to be dysregulated in the chemoresistant breast cancer tissues. Three of these miRNAs were up-regulated (miR-141, miR-200c, and miR-31), and 7 were down-regulated (let-7e, miR-576-3p, miR-125b-1, miR-370, miR-145, miR-765, and miR-760).
CONCLUSION: In this study, we identified 10 dysregulated miRNAs in both breast cancer cells and chemoresistant tissues, which might be biomarkers for the prognosis of breast cancer chemoresistance. Our study contributes to a comprehensive understanding of prognostic biomarkers during clinical treatment, and we hypothesize that the miRNA signatures of drug-resistant carcinoma tissues could be useful for developing new strategies for targeted therapies in patients with chemoresistant breast cancer.

Kiss O, Tőkés AM, Spisák S, et al.
Breast- and salivary gland-derived adenoid cystic carcinomas: potential post-transcriptional divergencies. A pilot study based on miRNA expression profiling of four cases and review of the potential relevance of the findings.
Pathol Oncol Res. 2015; 21(1):29-44 [PubMed] Related Publications
Adenoid cystic carcinoma (ACC) is a malignant tumor of the salivary glands but identical tumors can also arise from the breast. Despite their similar histomorphological appearance the salivary gland- and the breast-derived forms differ in their clinical features: while ACC of the salivary glands (sACC) have an aggressive clinical course, the breast-derived form (bACC) shows a very favourable clinical outcome. To date no exact molecular alterations have yet been identified which would explain the diverse clinical features of the ACCs of different origin. In our pilot experiment we investigated the post-transcriptional features of ACC cases by performing microRNA-profiling on 2-2 bACC and sACC tissues and on 1-1 normal breast and salivary gland tissue. By comparing the microRNA-profiles of the investigated samples we identified microRNAs which were expressed differently in bACC and sACC cases according to their normal controls: 7 microRNAs were overexpressed in sACC cases and downexpressed in bACC tumors (let-7b, let-7c, miR-17, miR-20a, miR-24, miR-195, miR-768-3) while 9 microRNAs were downexpressed in sACC cases and overexpressed in bACC tissues (let-7e, miR-23b, miR-27b, miR-193b, miR-320a, miR-320c, miR-768-5p, miR-1280 and miR-1826) relative to their controls. We also identified 8 microRNAs which were only expressed in sACCs and one microRNA (miR-1234) which was only absent in sACC cases. By target predictor online databases potential targets of the these microRNAs were detected to identify genes that may play central role in the diverse clinical outcome of bACC and sACC cases.

Zhu WY, Luo B, An JY, et al.
Differential expression of miR-125a-5p and let-7e predicts the progression and prognosis of non-small cell lung cancer.
Cancer Invest. 2014; 32(8):394-401 [PubMed] Related Publications
Aberrant expression of various microRNAs (miRNA) has shown diagnostic and prognostic significance in non-small cell lung cancer (NSCLC). qRT-PCR analysis confirmed altered expression of miR-125a-5p, let-7e, miR-30a, miR-30e and miR-30e-3p in 70 paired tissue and serum samples from NSCLC patients. The reduced expression of miR-125a-5p, let-7e and miR-30e was strongly associated with NSCLC dedifferentiation. The lost expression of miR-125a-5p and let-7e was associated with shorter overall survival and let-7e was an independent prognostic factor for NSCLC patients. These five miRNA expressions should be further evaluated as biomarkers for the early detection and prognosis of NSCLC patients.

Ferreira AF, Moura LG, Tojal I, et al.
ApoptomiRs expression modulated by BCR-ABL is linked to CML progression and imatinib resistance.
Blood Cells Mol Dis. 2014 Jun-Aug; 53(1-2):47-55 [PubMed] Related Publications
BACKGROUND: Chronic myeloid leukemia (CML) is a myeloproliferative disease characterized by the presence of Philadelphia chromosome (Ph) leading to expression of a BCR-ABL1 fusion oncogene. The BCR-ABL protein has a constitutive tyrosine kinase activity which is responsible for CML pathogenesis by promoting cell apoptosis resistance; however, the cellular and molecular mechanisms associated with BCR-ABL expression and apoptosis impairment in CML leukemic cells have not been fully elucidated.
METHODS: This study evaluated apoptomiRs and their predicted apoptotic genes in BCR-ABL(+) cells from patients in different phases of CML treated with tyrosine kinase inhibitor (TKI) according to their imatinib (IM) response by qPCR. Phosphotyrosine and c-ABL expressions in HL-60.BCR-ABL cells treated with TKI were done by Western blot.
RESULTS: We found that dasatinib (DAS) modulated miR-let-7d, miR-let-7e, miR-15a, miR-16, miR-21, miR-130a and miR-142-3p expressions while IM modulated miR-15a and miR-130a levels. miR-16, miR-130a and miR-145 expressions were modulated by nilotinib (NIL). We observed higher miR-15a, miR-130b and miR-145; and lower miR-16, miR-26a and miR-146a expressions in CML-CP in comparison with controls. CML-AP patients showed low miR-let-7d, miR-15a, miR-16, miR-29c, miR-142-3p, miR-145, and miR-146a levels in comparison with CML-CP. We noted that the miR-26a, miR-29c, miR-130b and miR-146a expressions were downregulated in IM resistant patients in comparison with IM responsive patients.
CONCLUSIONS: This study showed the modulation of apoptomiRs by BCR-ABL kinase activity and the deregulation of apoptomiRs and their predicted apoptotic target genes in different CML phases and after treatment with TK inhibitors. ApoptomiRs may be involved in the BCR-ABL(+) cell apoptosis regulation.

Aure MR, Leivonen SK, Fleischer T, et al.
Individual and combined effects of DNA methylation and copy number alterations on miRNA expression in breast tumors.
Genome Biol. 2013; 14(11):R126 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The global effect of copy number and epigenetic alterations on miRNA expression in cancer is poorly understood. In the present study, we integrate genome-wide DNA methylation, copy number and miRNA expression and identify genetic mechanisms underlying miRNA dysregulation in breast cancer.
RESULTS: We identify 70 miRNAs whose expression was associated with alterations in copy number or methylation, or both. Among these, five miRNA families are represented. Interestingly, the members of these families are encoded on different chromosomes and are complementarily altered by gain or hypomethylation across the patients. In an independent breast cancer cohort of 123 patients, 41 of the 70 miRNAs were confirmed with respect to aberration pattern and association to expression. In vitro functional experiments were performed in breast cancer cell lines with miRNA mimics to evaluate the phenotype of the replicated miRNAs. let-7e-3p, which in tumors is found associated with hypermethylation, is shown to induce apoptosis and reduce cell viability, and low let-7e-3p expression is associated with poorer prognosis. The overexpression of three other miRNAs associated with copy number gain, miR-21-3p, miR-148b-3p and miR-151a-5p, increases proliferation of breast cancer cell lines. In addition, miR-151a-5p enhances the levels of phosphorylated AKT protein.
CONCLUSIONS: Our data provide novel evidence of the mechanisms behind miRNA dysregulation in breast cancer. The study contributes to the understanding of how methylation and copy number alterations influence miRNA expression, emphasizing miRNA functionality through redundant encoding, and suggests novel miRNAs important in breast cancer.

Kubiczkova L, Kryukov F, Slaby O, et al.
Circulating serum microRNAs as novel diagnostic and prognostic biomarkers for multiple myeloma and monoclonal gammopathy of undetermined significance.
Haematologica. 2014; 99(3):511-8 [PubMed] Free Access to Full Article Related Publications
Multiple myeloma still remains incurable in the majority of cases prompting a further search for new and better prognostic markers. Emerging evidence has suggested that circulating microRNAs can serve as minimally invasive biomarkers for multiple myeloma and monoclonal gammopathy of undetermined significance. In this study, a global analysis of serum microRNAs by TaqMan Low Density Arrays was performed, followed by quantitative real-time PCR. The analyses revealed five deregulated microRNAs: miR-744, miR-130a, miR-34a, let-7d and let-7e in monoclonal gammopathy of undetermined significance, newly diagnosed and relapsed multiple myeloma when compared to healthy donors. Multivariate logistical regression analysis showed that a combination of miR-34a and let-7e can distinguish multiple myeloma from healthy donors with a sensitivity of 80.6% and a specificity of 86.7%, and monoclonal gammopathy of undetermined significance from healthy donors with a sensitivity of 91.1% and a specificity of 96.7%. Furthermore, lower levels of miR-744 and let-7e were associated with shorter overall survival and remission of myeloma patients. One-year mortality rates for miR-744 and let-7e were 41.9% and 34.6% for the 'low' expression and 3.3% and 3.9% for the 'high' expression groups, respectively. Median time of remission for both miR-744 and let-7e was approximately 11 months for the 'low' expression and approximately 47 months for the 'high' expression groups of myeloma patients These data demonstrate that expression patterns of circulating microRNAs are altered in multiple myeloma and monoclonal gammopathy of undetermined significance and miR-744 with let-7e are associated with survival of myeloma patients.

Peng C, Wang M, Shen Y, et al.
Reconstruction and analysis of transcription factor-miRNA co-regulatory feed-forward loops in human cancers using filter-wrapper feature selection.
PLoS One. 2013; 8(10):e78197 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: As one of the most common types of co-regulatory motifs, feed-forward loops (FFLs) control many cell functions and play an important role in human cancers. Therefore, it is crucial to reconstruct and analyze cancer-related FFLs that are controlled by transcription factor (TF) and microRNA (miRNA) simultaneously, in order to find out how miRNAs and TFs cooperate with each other in cancer cells and how they contribute to carcinogenesis. Current FFL studies rely on predicted regulation information and therefore suffer the false positive issue in prediction results. More critically, FFLs generated by existing approaches cannot represent the dynamic and conditional regulation relationship under different experimental conditions.
METHODOLOGY/PRINCIPAL FINDINGS: In this study, we proposed a novel filter-wrapper feature selection method to accurately identify co-regulatory mechanism by incorporating prior information from predicted regulatory interactions with parallel miRNA/mRNA expression datasets. By applying this method, we reconstructed 208 and 110 TF-miRNA co-regulatory FFLs from human pan-cancer and prostate datasets, respectively. Further analysis of these cancer-related FFLs showed that the top-ranking TF STAT3 and miRNA hsa-let-7e are key regulators implicated in human cancers, which have regulated targets significantly enriched in cellular process regulations and signaling pathways that are involved in carcinogenesis.
CONCLUSIONS/SIGNIFICANCE: In this study, we introduced an efficient computational approach to reconstruct co-regulatory FFLs by accurately identifying gene co-regulatory interactions. The strength of the proposed feature selection method lies in the fact it can precisely filter out false positives in predicted regulatory interactions by quantitatively modeling the complex co-regulation of target genes mediated by TFs and miRNAs simultaneously. Moreover, the proposed feature selection method can be generally applied to other gene regulation studies using parallel expression data with respect to different biological contexts.

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Cite this page: Cotterill SJ. MicroRNA let-7e, Cancer Genetics Web: http://www.cancer-genetics.org/MIRLET7E.htm Accessed:

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