Dysregulated expression of dicer and drosha in breast cancer

The 3' UTR polymorphisms rs3742330 in DICER1 and rs10719 in DROSHA genes are not associated with primary open-angle and angle-closure glaucoma: As case-control study

AIM

In a retrospective and exploratory case-control study, we examined the genetic association of two common polymorphisms in the 3' untranslated region (UTR) of DICER1 (rs3742330) and DROSHA (rs10719) genes in primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG), and its related clinical phenotypes in a Saudi cohort.

METHODS

DNA genotyping was performed using TaqMan real-time PCR assays in 500 participants, including 152 POAG, 102 PACG, and 246 non-glaucomatous controls. Statistical analyses were performed to examine the association(s).

RESULTS

Allele and genotype frequency of rs3742330 and rs10719 did not vary significantly in POAG and PACG compared to controls. No significant deviation was observed from Hardy-Weinberg Equilibrium (p > 0.05). Gender stratification revealed no significant allelic/genotype association with glaucoma types. Also, these polymorphisms showed no significant genotype effect on clinical markers such as intraocular pressure, cup/disc ratio, and the number of antiglaucoma medications. Logistic regression showed no effect of age, sex, rs3742330, and rs10719 genotypes on the risk of disease outcome. We also examined a combined allelic effect of rs3742330 (A>G) and rs10719 (A>G). However, none of the allelic combinations significantly affected POAG and PACG.

CONCLUSIONS

The 3' UTR polymorphisms rs3742330 and rs10719 of DICER1 and DROSHA genes are not associated with POAG and PACG or its related glaucoma indices in this Middle-Eastern cohort of Saudi Arab ethnicity. However, there is a need to validate the results on a broader population and other ethnicities.

The diagnostic, prognostic role and molecular mechanism of miR-328 in human cancer

MicroRNA are non-coding small RNAs that bind to their target mRNA and cause mRNA degradation or translation inhibition. MiRNA dysregulation is linked to a variety of human cancers and has a role in the genesis and development of cancer pathology. MiR-328 has been reported to be involved in various human cancers. And miR-328 is considered a key regulator in human cancer. It participates in biological processes such as proliferation, apoptosis, invasion, migration, and EMT. The present review will combine the basic and clinical studies to find that miR-328 promotes tumorigenesis and metastasis in human cancer. And we will describe the diagnostic, prognostic, and therapeutic value of miR-328 in various human cancers.

Association of DROSHA rs6877842, rs642321 and rs10719 polymorphisms with increased susceptibility to breast cancer: A case-control study with genotype and haplotype analysis

BACKGROUND

Multiple lines of evidence suggest that single nucleotide polymorphisms (SNPs) in genes encoding components of the microRNA processing machinery may underlie susceptibility to various human diseases, including cancer.

OBJECTIVE

The present study aimed to investigate whether rs6877842, rs642321 and rs10719 SNPs of DROSHA, a key component of the miRNA biogenesis pathway, are associated with increased risk of breast cancer.

METHODS

A total of 100 patients diagnosed with breast cancer and 100 healthy women were included. Following extraction of DNA, genotyping was performed by tetra primer- amplification refractory mutation system-PCR (T-ARMS-PCR) technique. Under the co-dominant, dominant and recessive inheritance models, the association between DROSHA SNPs and breast cancer risk was determined by logistic regression analysis. The association of DROSHA SNPs with patients' clinicopathological parameters was assessed. Also, haplotype analysis was performed to evaluate the combined effect of DROSHA SNPs on breast cancer risk.

RESULTS

We observed a statistically significant association between DROSHA rs642321 polymorphism and breast cancer susceptibility (P < 0.05). Under the dominant inheritance model, DROSHA rs642321 polymorphism was significantly associated with increased risk of breast cancer (OR: 6.091; 95% CI: 3.291-11.26; P = 0.0001). Our findings demonstrated that DROSHA rs642321 T allele can contribute to the development of breast cancer (OR: 3.125; 95% CI: 1.984-4.923; P = 0.0001). We also found that GTC and GTT haplotypes conferred significant risk for breast cancer (OR: 2.367; 95% CI: 1.453-3.856; P = 0.0001 and OR: 7.944; 95% CI: 2.073-30.43; P = 0.0001, respectively).

CONCLUSIONS

These results provide the first evidence that DROSHA rs642321 polymorphism is associated with increased risk of breast cancer. However, further studies are needed to firmly validate these findings.

MicroRNA expression profiling of endocrine sensitive and resistant breast cancer cell lines

Background

Methods

Results

Conclusions

•

Around 50–60% of microRNAs were significantly differentially expressed between ER- and ER + breast cancer cell lines.

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Transfection of miR-200c-3p mimic into ER -ve cells induced MET and reduced cell motility.

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Transfecting of miR-449a inhibitor into ER -ve cells reduced cell invasion but did not induce EMT.

APE1 controls DICER1 expression in NSCLC through miR-33a and miR-130b

Increasing evidence suggests different, not completely understood roles of microRNA biogenesis in the development and progression of lung cancer. The overexpression of the DNA repair protein apurinic/apyrimidinic endodeoxyribonuclease 1 (APE1) is an important cause of poor chemotherapeutic response in lung cancer and its involvement in onco-miRNAs biogenesis has been recently described. Whether APE1 regulates miRNAs acting as prognostic biomarkers of lung cancer has not been investigated, yet. In this study, we analyzed miRNAs differential expression upon APE1 depletion in the A549 lung cancer cell line using high-throughput methods. We defined a signature of 13 miRNAs that strongly correlate with APE1 expression in human lung cancer: miR-1246, miR-4488, miR-24, miR-183, miR-660, miR-130b, miR-543, miR-200c, miR-376c, miR-218, miR-146a, miR-92b and miR-33a. Functional enrichment analysis of this signature revealed its biological relevance in cancer cell proliferation and survival. We validated DICER1 as a direct functional target of the APE1-regulated miRNA-33a-5p and miR-130b-3p. Importantly, IHC analyses of different human tumors confirmed a negative correlation existing between APE1 and Dicer1 protein levels. DICER1 downregulation represents a prognostic marker of cancer development but the mechanisms at the basis of this phenomenon are still completely unknown. Our findings, suggesting that APE1 modulates DICER1 expression via miR-33a and miR-130b, reveal new mechanistic insights on DICER1 regulation, which are of relevance in lung cancer chemoresistance and cancer invasiveness.

Exosomes in breast cancer management. Where do we stand? A literature review

BACKGROUND

Exosomes constitute cellular molecular fingertips that participate in intercellular communication both in health and disease states. Hence, exosomes emerge as critical mediators of cancer development and progression, as well as potential biomarkers and novel therapeutic targets.

OBJECTIVE

To review literature data regarding applications of circulating exosomes in breast cancer management.

METHODS

This is a literature review of relevant published studies until April 2020 in PubMed and Google Scholar databases. Original papers in the English language concerning exosome related studies were included.

RESULTS

Exosomes represent molecular miniatures of their parent cells. Several homeostatic mechanisms control exosomal secretion and synthesis. Exosomal exchange among cells creates an intricate intercellular crosstalk orchestrating almost every tissue process, as well as carcinogenesis. Available data highlight exosomes as major mediators of cancer development and progression. The secretion of specific exosomal molecules, particularly miRNAs, correlates with the underlying processes and can be used as a means of tumor detection and prognostic assessment.

CONCLUSIONS

Exosomal miRNAs expression profiles and levels closely relate to cancer extent, type and prognosis. Deep comprehension of such correlations and systematization of experimental outcomes will offer a novel approach in cancer detection and management. This article is protected by copyright. All rights reserved.

Towards Understanding the Pathogenicity of DROSHA Mutations in Oncohematology

Myelodysplastic syndrome (MDS) refers to a heterogeneous group of closely related clonal hematopoietic disorders, which are characterized by accumulation of somatic mutations. The acquired mutation burden is suggested to define the pathway and consequent phenotype of the pathology. Recent studies have called attention to the role of miRNA biogenesis genes in MDS progression; in particular, the mutational pressure of the DROSHA gene was determined. Therefore, this highlights the importance of studying the impact of all collected missense mutations found within the DROSHA gene in oncohematology that might affect the functionality of the protein. In this study, the selected mutations were extensively examined by computational screening, and the most deleterious were subjected to a further molecular dynamic simulation in order to uncover the molecular mechanism of the structural damage to the protein altering its biological function. The most significant effect was found for variants I625K, L1047S, and H1170D, presumably affecting the endonuclease activity of DROSHA. Such alterations arisen during MDS progression should be taken into consideration as evoking certain clinical traits in the malignifying clonal evolution.

Micro-RNA: The darkhorse of cancer

The discovery of micro RNAs (miRNA) in cancer has opened up new vistas for researchers in recent years. Micro RNAs area set of small, endogenous, highly conserved, non-coding RNAs that control the expression of about 30% genes at post-transcriptional levels. Typically, microRNAs impede the translation and stability of messenger RNAs (mRNA), control genes associated with cellular processes namely inflammation, cell cycle regulation, stress response, differentiation, apoptosis, and migration. Compelling findings revealed that miRNA mutations or disruption correspond to diverse human cancers and suggest that miRNAs can function as tumor suppressors or oncogenes. Here we summarize the literature on these master regulators in clinical settings from last three decades as both abrupt cancer therapeutics and as an approach to sensitize tumors to chemotherapy. This review highlights (I) the prevailing perception of miRNA genomics, biogenesis, as well as function; (II) the significant advancements in regulatory mechanisms in the expression of carcinogenic genes; and (III) explains, how miRNA is utilized as a diagnostic and prognostic biomarker for the disease stage indicating survival as well as therapeutic targets in cancer.

Therapeutic Targeting of MicroRNAs in the Tumor Microenvironment

The tumor-microenvironment (TME) is an amalgamation of various factors derived from malignant cells and infiltrating host cells, including cells of the immune system. One of the important factors of the TME is microRNAs (miRs) that regulate target gene expression at a post transcriptional level. MiRs have been found to be dysregulated in tumor as well as in stromal cells and they emerged as important regulators of tumorigenesis. In fact, miRs regulate almost all hallmarks of cancer, thus making them attractive tools and targets for novel anti-tumoral treatment strategies. Tumor to stroma cell cross-propagation of miRs to regulate protumoral functions has been a salient feature of the TME. MiRs can either act as tumor suppressors or oncogenes (oncomiRs) and both miR mimics as well as miR inhibitors (antimiRs) have been used in preclinical trials to alter cancer and stromal cell phenotypes. Owing to their cascading ability to regulate upstream target genes and their chemical nature, which allows specific pharmacological targeting, miRs are attractive targets for anti-tumor therapy. In this review, we cover a recent update on our understanding of dysregulated miRs in the TME and provide an overview of how these miRs are involved in current cancer-therapeutic approaches from bench to bedside.

Evaluation of the clinical significance of RNase III enzyme DROSHA in pediatrics acute lymphocytic leukemia

Acute lymphocytic leukemia (ALL) is one of the subtypes of leukemia; it is one of the leading causes of malignancy and morbidity and childhood mortality. This study examined the dysregulation of DROSHA and its clinical implications in ALL. In the case-control investigation, we have included 140 samples, consisting of 70 peripheral whole blood samples diagnosed with ALL and 70 age and sex-matched healthy children, to assess the level of expression of DROSHA mRNA between two groups. Quantitative Real-Time PCR was used to establish the level of DROSHA gene expression in the patients and controls. The results revealed that DROSHA was overexpressed in patients compared with controls (p < 0.001). There were no major differences between DROSHA expression and demographic factors and clinicopathological parameters (p > 0.001). The finding of the study revealed that DROSHA expression in ALL patients is significantly up-regulated; which is suggesting that may be served as a critical role in the pathogenesis of ALL. Also, DROSHA will possibly be utilized as a novel therapeutic target for ALL patients within the future.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

MicroRNAs Involved in Carcinogenesis, Prognosis, Therapeutic Resistance and Applications in Human Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is the most aggressive, prevalent, and distinct subtype of breast cancer characterized by high recurrence rates and poor clinical prognosis, devoid of both predictive markers and potential therapeutic targets. MicroRNAs (miRNA/miR) are a family of small, endogenous, non-coding, single-stranded regulatory RNAs that bind to the 3′-untranslated region (3′-UTR) complementary sequences and downregulate the translation of target mRNAs as post-transcriptional regulators. Dysregulation miRNAs are involved in broad spectrum cellular processes of TNBC, exerting their function as oncogenes or tumor suppressors depending on their cellular target involved in tumor initiation, promotion, malignant conversion, and metastasis. In this review, we emphasize on masses of miRNAs that act as oncogenes or tumor suppressors involved in epithelial–mesenchymal transition (EMT), maintenance of stemness, tumor invasion and metastasis, cell proliferation, and apoptosis. We also discuss miRNAs as the targets or as the regulators of dysregulation epigenetic modulation in the carcinogenesis process of TNBC. Furthermore, we show that miRNAs used as potential classification, prognostic, chemotherapy and radiotherapy resistance markers in TNBC. Finally, we present the perspective on miRNA therapeutics with mimics or antagonists, and focus on the challenges of miRNA therapy. This study offers an insight into the role of miRNA in pathology progression of TNBC.

MicroRNAs Contribute to Breast Cancer Invasiveness

Cancer statistics in 2018 highlight an 8.6 million incidence in female cancers, and 4.2 million cancer deaths globally. Moreover, breast cancer is the most frequent malignancy in females and twenty percent of these develop metastasis. This provides only a small chance for successful therapy, and identification of new molecular markers for the diagnosis and prognostic prediction of metastatic disease and development of innovative therapeutic molecules are therefore urgently required. Differentially expressed microRNAs (miRNAs) in cancers cause multiple changes in the expression of the tumorigenesis-promoting genes which have mostly been investigated in breast cancers. Herein, we summarize recent data on breast cancer-specific miRNA expression profiles and their participation in regulating invasive processes, in association with changes in cytoskeletal structure, cell-cell adhesion junctions, cancer cell-extracellular matrix interactions, tumor microenvironments, epithelial-to-mesenchymal transitions and cancer cell stem abilities. We then focused on the epigenetic regulation of individual miRNAs and their modified interactions with other regulatory genes, and reviewed the function of miRNA isoforms and exosome-mediated miRNA transfer in cancer invasiveness. Although research into miRNA’s function in cancer is still ongoing, results herein contribute to improved metastatic cancer management.

Amplification of hsa-miR-191/425 locus promotes breast cancer proliferation and metastasis by targeting DICER1

The dysregulation of micro RNAs (miRNAs) is a crucial characteristic of human cancers. Herein, we observed frequent amplification of the MIR191/425 locus in breast cancer, which is correlated with poor survival outcome. We demonstrated that the miR-191/425 cluster binds the 3' untranslated region of the DICER1 transcript and posttranscriptionally represses DICER1 expression, thereby impairing global miRNAs biogenesis. Functionally, the forced expression of miR-191 or miR-425 stimulated the proliferation, survival, migration and invasion of breast cancer cells, whereas the inhibition of miR-191 or miR-425 suppressed these oncogenic behaviors of breast cancer cells, in a manner dependent on miR-191/425-mediated downregulation of DICER1. Furthermore, the miR-191/425 cluster promoted breast tumor growth, invasion and metastasis in vivo. The let-7 family of miRNAs was downregulated upon forced expression of miR-191 or miR-425, with a corresponding increase in the levels of let-7 target, high-mobility group AT-hook 2 (HMGA2). The forced expression of let-7 partially abrogated the miR-191/425-mediated oncogenic effects in breast cancer cells, suggestive of let-7 as a downstream effector of the miR-191/425-DICER1 axis. Collectively, we proposed that the inhibition of global miRNA processing, through miR-191/425-mediated downregulation of DICER1, promotes breast cancer progression.

Impaired microRNA processing by DICER1 downregulation endows thyroid cancer with increased aggressiveness

The global downregulation of microRNAs (miRNAs) is emerging as a common hallmark of cancer. However, the mechanisms underlying this phenomenon are not well known. We identified that the oncogenic miR-146b-5p attenuates miRNA biosynthesis by targeting DICER1 and reducing its expression. DICER1 overexpression inhibited all the miR-146b-induced aggressive phenotypes in thyroid cells. Systemic injection of an anti-miR-146b in mice with orthotopic thyroid tumors suppressed tumor growth and recovered DICER1 levels. Notably, DICER1 downregulation promoted proliferation, migration, invasion, and epithelial-mesenchymal transition through miRNA downregulation. Our analysis of The Cancer Genome Atlas revealed a general decrease in DICER1 expression in thyroid cancer that was associated with a worse clinical outcome. Administration of the small-molecule enoxacin to promote DICER1 complex activity reduced tumor aggressiveness both in vitro and in vivo. Overall, our data confirm DICER1 as a tumor suppressor and show that oncogenic miR-146b contributes to its downregulation. Moreover, our results highlight a potential therapeutic application of RNA-based therapies including miRNA inhibitors and restoration of the biogenesis machinery, which may provide treatments for thyroid and other cancers.

Impaired expression of Drosha in breast cancer

BACKGROUND

Impaired miRNAs processing pathway is one interesting scenario for global downregulation of the miRNAome in various types of malignancy. We previously reported that DGCR8 and Dicer genes dysregulated in patients with breast cancer.

OBJECTIVE

To evaluate the expression pattern of Drosha in patients with breast cancer.

METHODS

We evaluated the mRNA expression level of Drosha in 70 fresh breast carcinomas and adjacent non-neoplastic tissue using quantitative real-time PCR and assessed the possible correlation between its expression and clinicopathological parameters.

RESULTS

Our results revealed that mRNA expression level of Drosha was decreased in tumors when compared to adjacent non-neoplastic tissue. However, this difference is not statistically significant (P > 0.05). Downregulation of Drosha is related to older age at diagnosis, higher histological grade, higher tumor size and metastasis. However, there was no significant correlation between Drosha expression level and clinicopathological parameters (P > 0.05). We found that Drosha expression negatively correlated with DGCR8 (P = 0.043), whereas dysregulated expression levels of Drosha and Dicer are positively correlated with to each other (P < 0.0001).

CONCLUSION

This study provides evidence that the expression of Drosha is impaired in breast cancer. However, the molecular basis of observed expression pattern have remained inexplicable and should be further investigated.

microRNA Expression in Ethnic Specific Early Stage Breast Cancer: an Integration and Comparative Analysis

Breast cancer (BC) has a higher incidence in young Lebanese woman as compared to the West. We assessed the microRNA (miRNA) microarray profile of tissues derived from Lebanese patients with early BC and performed mRNA-miRNA integration analysis. 173 miRNAs were significantly dysregulated in 45 BC versus 17 normal adjacent breast tissues, including 74 with a fold change more than two of which 17 were never reported before in cancer. Integration analysis of mRNA-miRNA microarray data revealed a potential role of 51 dysregulated miRNA regulating 719 tumor suppressive or oncogenic mRNA associated with increased proliferation and decreased migration and invasion. We then performed a comparative miRNA microarray profile analysis of BC tissue between these 45 Lebanese and 197 matched American BC patients. Notably, Lebanese BC patients had 21 exclusively dysregulated miRNA (e.g. miR-31, 362-3p, and 663) and 4 miRNA with different expression manner compared to American patients (e.g. miR-1288-star and 324-3p). Some of these differences could reflect variation in patient age at diagnosis or ethnic variation affecting miRNA epigenetic regulation or sequence of miRNA precursors. Our data provide a basis for genetic/epigenetic investigations to explore the role of miRNA in early stage BC in young women, including ethnic specific differences.

miRNA biogenesis-associated RNase III nucleases Drosha and Dicer are upregulated in colorectal adenocarcinoma

Drosha and Dicer are important regulators of microRNA (miRNA) biogenesis, and it has been suggested that their aberrant regulation may cause colorectal cancer (CRC). The aim of the present study was to evaluate the mRNA expression levels of these two important RNase III nucleases and their association with clinical features in CRC specimens from South Korean patients. The expression levels of Drosha and Dicer mRNA were investigated in 77 CRC tissues and adjacent histologically non-neoplastic tissues using the quantitative polymerase chain reaction. The expression levels of Drosha and Dicer mRNA were identified to be upregulated in CRC. Neither the Drosha nor the Dicer mRNA expression level was associated with any clinical parameter, including sex, age, TNM stage, body mass index and carcinoembryonic antigen titer in patients with CRC. Furthermore, the expression levels of Drosha and Dicer mRNA were not associated with each other. The miRNA biogenesis-associated RNase III nucleases Drosha and Dicer are significantly upregulated in CRC, suggesting their importance in the pathobiology of colorectal carcinogenesis.

RNA interference of Dicer-1 and Argonaute-1 increasing the sensitivity of Aphis gossypii Glover (Hemiptera: Aphididae) to plant allelochemical

Plant allelochemicals are a group of important defensive agents of plants, which have been documented to be deleterious to insect herbivores. In the present study, we found that the expression level of Dicer-1 was significantly increased when Aphis gossypii adults fed on plant allelochemicals (tannic acid and gossypol) incorporated artificial diets. Consider that miRNAs play great regulatory roles in various biological processes, this suggested that miRNAs may be related to the regulation of enzymes involved in metabolism of plant allelochemicals in A. gossypii. To further reveal the roles of miRNAs in the response of A. gossypii against plant allelochemicals, both Dicer-1 and Argonaute-1, an important component of the RNA-induced silencing complex (RISC) in miRNA pathway, were silenced using systemic RNA interference (RNAi). The results indicated that silence of Dicer-1 reduced the expression of miRNAs, and resulted in a high mortality of A. gossypii when fed on both tannic acid and gossypol. The silencing of Argonaute-1 resulted in the mortality of A. gossypii by the treatment of tannic acid significantly increased compared with control, however, the sensitivity of A. gossypii to gossypol was not significantly changed. It suggested that miRNAs play potential regulatory roles in the response of A. gossypii to plant allelochemicals. These results should be useful to understand the molecular mechanisms of the cotton aphid adaption to plant allelochemicals.

DROSHA rs642321 Polymorphism Influence Susceptibility to Childhood Acute Lymphoblastic Leukemia: A Preliminary Report

Introduction:

It has been well known that the microRNA biogenesis is involved in the pathogenesis of various diseases. We investigated the possible association between DROSHA rs642321 variant and risk of acute lymphocytic leukemia (ALL).

Materials and Methods:

We genotyped 75 children diagnosed with ALL and 115 age- and sex-matched children with no history of cancer of any type (as the control group) by the tetra amplification refractory mutation system-polymerase chain reaction.

Results:

We found that DROSHA rs642321 C > T variant significantly decreased the risk of ALL in codominant (TT vs. CC: odds ratio [OR] = 0.33, 95% confidence interval [CI] = 0.14–0.80, P = 0.020) and dominant (TT + CT vs. CC: OR = 0.51, 95% CI = 0.27–0.94, P = 0.037) inheritance model tested. The rs642321 T allele was associated with protective against ALL (OR = 0.58, 95% CI = 0.38–0.88, P = 0.011) in comparison with C allele.

Conclusion:

The study findings revealed that DROSHA rs642321 variant decreased the risk of pediatrics ALL in an Iranian population. Larger sample sizes with different ethnicities are needed to validate our findings.

Tamoxifen differentially regulates miR-29b-1 and miR-29a expression depending on endocrine-sensitivity in breast cancer cells

Endocrine-resistance develops in ∼40% of breast cancer patients after tamoxifen (TAM) therapy. Although microRNAs are dysregulated in breast cancer, their contribution to endocrine-resistance is not yet understood. Previous microarray analysis identified miR-29a and miR-29b-1 as repressed by TAM in MCF-7 endocrine-sensitive breast cancer cells but stimulated by TAM in LY2 endocrine-resistant breast cancer cells. Here we examined the mechanism for the differential regulation of these miRs by TAM in MCF-7 versus TAM-resistant LY2 and LCC9 breast cancer cells and the functional role of these microRNAs in these cells. Knockdown studies revealed that ERα is responsible for TAM regulation of miR-29b-1/a transcription. We also demonstrated that transient overexpression of miR-29b-1/a decreased MCF-7, LCC9, and LY2 proliferation and inhibited LY2 cell migration and colony formation but did not sensitize LCC9 or LY2 cells to TAM. Furthermore, TAM reduced DICER1 mRNA and protein in LY2 cells, a known target of miR-29. Supporting this observation, anti-miR-29b-1 or anti-miR-29a inhibited the suppression of DICER by 4-OHT. These results suggest miR-29b-1/a has tumor suppressor activity in TAM-resistant cells and does not appear to play a role in mediating TAM resistance.

Argonaute 2 Expression Correlates with a Luminal B Breast Cancer Subtype and Induces Estrogen Receptor Alpha Isoform Variation

Estrogen receptor alpha (ERα) signaling pathways are frequently disrupted in breast cancer and contribute to disease progression. ERα signaling is multifaceted and many ERα regulators have been identified including transcription factors and growth factor pathways. More recently, microRNAs (miRNAs) are shown to deregulate ERα activity in breast carcinomas, with alterations in both ERα and miRNA expression correlating to cancer progression. In this study, we show that a high expression of Argonaute 2 (AGO2), a translation regulatory protein and mediator of miRNA function, correlates with the luminal B breast cancer subtype. We further demonstrate that a high expression of AGO2 in ERα+ tumors correlates with a poor clinical outcome. MCF-7 breast cancer cells overexpressing AGO2 (MCF7-AGO2) altered ERα downstream signaling and selective ERα variant expression. Enhanced ERα-36, a 36 kDa ERα isoform, protein and gene expression was observed in vitro. Through quantitative polymerase chain reaction (qPCR), we demonstrate decreased basal expression of the full-length ERα and progesterone receptor genes, in addition to loss of estrogen stimulated gene expression in vitro. Despite the loss, MCF-7-AGO2 cells demonstrated increased estrogen stimulated tumorigenesis in vivo. Together with our clinical findings on AGO2 expression and the luminal B subtype, we suggest that AGO2 is a regulator of altered ERα signaling in breast tumors.

Dicer Elicits Paclitaxel Chemosensitization and Suppresses Cancer Stemness in Breast Cancer by Repressing AXL

Paclitaxel is a standard-of-care chemotherapy for breast cancer, despite the increasing recognition of its poor effectiveness in the treatment of patients with advanced disease. Here, we report that adenovirus-type 5 E1A-mediated elevation of the miRNA-processing enzyme Dicer is sufficient to enhance paclitaxel sensitization and reduce cancer stem-like cell properties in this setting. Elevating Dicer expression increased levels of the AXL kinase targeting miRNA miR-494, thereby repressing AXL expression to increase paclitaxel sensitivity. We found that Dicer expression was regulated at the transcription level by E1A, through activation of an MAPK14/CEBPα pathway. Our findings define a mechanism of E1A-mediated chemosensitization for paclitaxel, which is based upon the suppression of breast cancer stem-like cells, with potential implications for the diagnosis and treatment of breast cancer patients. Cancer Res; 76(13); 3916-28. ©2016 AACR.

Prognostic significance of Dicer expression in hepatocellular carcinoma

Dicer is a RNaseIII endonuclease of the microRNA processing pathway, which is implicated in carcinogenesis of various types of human cancer. The present study assessed the expression level of Dicer in hepatocellular carcinoma (HCC) tissue to evaluate its association with HCC tumorigenesis. A low expression of Dicer was significantly associated with a shorter postoperative survival time of patients with HCC, which was assessed using the log-rank test with Kaplan-Meier survival analysis. Multivariate analysis identified that Dicer expression was an independent predictor for HCC outcome (relative risk, 0.660; 95% confidence interval, 0.506–0.861; P=0.002). A functional assay demonstrated that Dicer overexpression inhibited the proliferation and promoted the apoptosis of HCC cells. In addition, a Transwell assay revealed that Dicer markedly inhibited the migration and invasion of HCC cells. The present findings indicate that Dicer expression modified the outcomes of HCC patients by inhibiting proliferation, promoting apoptosis and inhibiting metastasis of HCC cells.

Regulation of the T-box transcription factor Tbx3 by the tumour suppressor microRNA-206 in breast cancer

BACKGROUND

The Tbx3 transcription factor is over-expressed in breast cancer, where it has been implicated in proliferation, migration and regulation of the cancer stem cell population. The mechanisms that regulate Tbx3 expression in cancer have not been fully explored. In this study, we demonstrate that Tbx3 is repressed by the tumour suppressor miR-206 in breast cancer cells.

METHODS

Bioinformatics prediction programmes and luciferase reporter assays were used to demonstrate that miR-206 negatively regulates Tbx3. We examined the impact of miR-206 on Tbx3 expression in breast cancer cells using miR-206 mimic and inhibitor. Gene/protein expression was examined by quantitative reverse-transcription-PCR and immunoblotting. The effects of miR-206 and Tbx3 on apoptosis, proliferation, invasion and cancer stem cell population was investigated by cell-death detection, colony formation, 3D-Matrigel and tumorsphere assays.

RESULTS

In this study, we examined the regulation of Tbx3 by miR-206. We demonstrate that Tbx3 is directly repressed by miR-206, and that this repression of Tbx3 is necessary for miR-206 to inhibit breast tumour cell proliferation and invasion, and decrease the cancer stem cell population. Moreover, Tbx3 and miR-206 expression are inversely correlated in human breast cancer. Kaplan-Meier analysis indicates that patients exhibiting a combination of high Tbx3 and low miR-206 expression have a lower probability of survival when compared with patients with low Tbx3 and high miR-206 expression. These studies uncover a novel mechanism of Tbx3 regulation and identify a new target of the tumour suppressor miR-206.

CONCLUSIONS

The present study identified Tbx3 as a novel target of tumour suppressor miR-206 and characterised the miR-206/Tbx3 signalling pathway, which is involved in proliferation, invasion and maintenance of the cancer stem cell population in breast cancer cells. Our results suggest that restoration of miR-206 in Tbx3-positive breast cancer could be exploited for therapeutic benefit.

Dysregulation of microRNA biogenesis machinery in cancer

MicroRNAs (miRNAs) are integral to the gene regulatory network. A single miRNA is capable of controlling the expression of hundreds of protein coding genes and modulate a wide spectrum of biological functions, such as proliferation, differentiation, stress responses, DNA repair, cell adhesion, motility, inflammation, cell survival, senescence and apoptosis, all of which are fundamental to tumorigenesis. Overexpression, genetic amplification, and gain-of-function mutation of oncogenic miRNAs ("onco-miRs") as well as genetic deletion and loss-of-function mutation of tumor suppressor miRNAs ("suppressor-miRs") are linked to human cancer. In addition to the dysregulation of a specific onco-miR or suppressor-miRs, changes in global miRNA levels resulting from a defective miRNA biogenesis pathway play a role in tumorigenesis. The function of individual onco-miRs and suppressor-miRs and their target genes in cancer has been described in many different articles elsewhere. In this review, we primarily focus on the recent development regarding the dysregulation of the miRNA biogenesis pathway and its contribution to cancer.

MicroRNAs: New Biomarkers for Diagnosis, Prognosis, Therapy Prediction and Therapeutic Tools for Breast Cancer

Dysregulation of microRNAs (miRNAs) is involved in the initiation and progression of several human cancers, including breast cancer (BC), as strong evidence has been found that miRNAs can act as oncogenes or tumor suppressor genes. This review presents the state of the art on the role of miRNAs in the diagnosis, prognosis, and therapy of BC. Based on the results obtained in the last decade, some miRNAs are emerging as biomarkers of BC for diagnosis (i.e., miR-9, miR-10b, and miR-17-5p), prognosis (i.e., miR-148a and miR-335), and prediction of therapeutic outcomes (i.e., miR-30c, miR-187, and miR-339-5p) and have important roles in the control of BC hallmark functions such as invasion, metastasis, proliferation, resting death, apoptosis, and genomic instability. Other miRNAs are of interest as new, easily accessible, affordable, non-invasive tools for the personalized management of patients with BC because they are circulating in body fluids (e.g., miR-155 and miR-210). In particular, circulating multiple miRNA profiles are showing better diagnostic and prognostic performance as well as better sensitivity than individual miRNAs in BC. New miRNA-based drugs are also promising therapy for BC (e.g., miR-9, miR-21, miR34a, miR145, and miR150), and other miRNAs are showing a fundamental role in modulation of the response to other non-miRNA treatments, being able to increase their efficacy (e.g., miR-21, miR34a, miR195, miR200c, and miR203 in combination with chemotherapy).

Dysregulated expression of Dicer in invasive ductal breast carcinoma

Several lines of evidence suggest that the global down-regulation of the microRNAome (miRNAome) involved in pathogenesis of various malignancies. Impaired microRNAs processing pathway is one possible mechanism for global down-regulation of the miRNAome. Dicer is a key enzyme in miRNA processing pathway, and dysregulation of its expression has been suggested as a possible cause of miRNAome alterations observed in various cancers. However, Dicer mRNA expression in invasive ductal breast carcinoma (IDC) has not been investigated in depth. Therefore, this study aimed to evaluate the mRNA expression of Dicer in IDC and also to assess the correlation of its expression with clinicopathological parameters including age, histological grade, tumor size and lymph node metastasis. We investigated the expression of the Dicer in seventy fresh invasive ductal breast carcinomas and matched adjacent non-neoplastic tissue by quantitative real-time PCR using validated reference genes. In addition, the possible impact of clinicopathological characteristics on Dicer expression levels was analyzed. Our results showed that Dicer mRNA expression is down-regulated in slightly more than half (51.43 %) of the tumor specimens when compared to adjacent non-neoplastic tissue. Comparison of the Dicer expression level between tumor and matched adjacent non-neoplastic tissue showed that there is no statistical significant differences between them (P = 0.425). We also found that Dicer mRNA expression in IDC samples was not correlated with clinicopathological features. In conclusion, our findings provide additional evidence to support the hypothesis that Dicer expression down-regulated in breast cancer. This study suggested that the decreased expression of Dicer may be potential underlying mechanism in pathogenesis of IDC.

MicroRNA biogenesis pathways in cancer

MicroRNAs (miRNAs) are critical regulators of gene expression. Amplification and overexpression of individual 'oncomiRs' or genetic loss of tumour suppressor miRNAs are associated with human cancer and are sufficient to drive tumorigenesis in mouse models. Furthermore, global miRNA depletion caused by genetic and epigenetic alterations in components of the miRNA biogenesis machinery is oncogenic. This, together with the recent identification of novel miRNA regulatory factors and pathways, highlights the importance of miRNA dysregulation in cancer.

Roles of microRNA-140 in stem cell-associated early stage breast cancer

An increasing body of evidence supports a stepwise model for progression of breast cancer from ductal carcinoma in situ (DCIS) to invasive ductal carcinoma (IDC). Due to the high level of DCIS heterogeneity, we cannot currently predict which patients are at highest risk for disease recurrence or progression. The mechanisms of progression are still largely unknown, however cancer stem cell populations in DCIS lesions may serve as malignant precursor cells intimately involved in progression. While genetic and epigenetic alterations found in DCIS are often shared by IDC, mRNA and miRNA expression profiles are significantly altered. Therapeutic targeting of cancer stem cell pathways and differentially expressed miRNA could have significant clinical benefit. As tumor grade increases, miRNA-140 is progressively downregulated. miR-140 plays an important tumor suppressive role in the Wnt, SOX2 and SOX9 stem cell regulator pathways. Downregulation of miR-140 removes inhibition of these pathways, leading to higher cancer stem cell populations and breast cancer progression. miR-140 downregulation is mediated through both an estrogen response element in the miR-140 promoter region and differential methylation of CpG islands. These mechanisms are novel targets for epigenetic therapy to activate tumor suppressor signaling via miR-140. Additionally, we briefly explored the emerging role of exosomes in mediating intercellular miR-140 signaling. The purpose of this review is to examine the cancer stem cell signaling pathways involved in breast cancer progression, and the role of dysregulation of miR-140 in regulating DCIS to IDC transition.

The expression of Dicer and Drosha in matched normal tissues, tumours and lymph node metastases in triple negative breast cancer

Background

Breast cancer is the most common malignancy in women world-wide. Triple negative breast cancer (TNBC) is a highly aggressive subtype that lacks expression of hormone receptors for estrogen, progesterone and human epidermal growth factor 2; and is associated with a high propensity for metastatic spread. Several studies have identified critical roles for microRNAs in breast cancer, but the role of two critical enzymes involved in microRNA biogenesis, Dicer and Drosha, is not well understood, particularly with respect to metastatic progression in this subtype.

Methods

We examined the expression of Dicer and Drosha in a series of invasive 35 TNBCs with matched normal adjacent tissues (n = 18) and lymph node metastases (n = 15) using semi-quantitative real time RT-PCR. The relationship of their expression with clinical features including age at diagnosis, lymph node positivity and tumour size was analysed.

Results

We report that Dicer was significantly decreased while Drosha was significantly increased in tumours when compared to normal adjacent tissues. While there was no difference in Drosha expression in lymph node metastases when compared to the primary tumour, Dicer was significantly increased. There was no correlation between the expression of either Dicer or Drosha to age at diagnosis, lymph node positivity and tumour size.

Conclusions

In conclusion, Dicer and Drosha are dysregulated in TNBC and matched lymph node metastases however, the clinical relevance of this is still not known. The altered expression of Dicer and Drosha may serve as markers for disrupted miRNA biogenesis in TNBC.

MicroRNAs and anticancer drugs

MicroRNAs (miRNAs) are a class of small, non-coding, and endogenous RNA molecules, which are evolutionarily conserved but play a significant role in regulation of protein-coding gene expression at posttranscriptional and translational levels. Strikingly, a single miRNA is able to trigger hundreds of putative target genes by incomplete or complete complementary binding to their 3' untranslated regions. Given their appearance in almost all types of tissues, miRNAs have been demonstrated to be intensively involved in normal and pathological processes of human cells. Aside from the role as invaluable biomarkers in indication of tumorigenesis and tumor progression, numerous studies have revealed the potential of miRNAs as novel targets of anticancer drugs in cancer therapy. In this review article, we focus on the summary of the latest publications on the topic of miRNA and anticancer drugs, and expect to shed light on understanding the molecular mechanisms of chemoresistance involving miRNA regulation. These pieces of evidence will eventually provide insight into the development of novel and more efficacious anticancer drugs in the future.

Complexity in regulation of microRNA machinery components in invasive breast carcinoma

Altered expression of microRNA (miRNA) machinery components may play an important role in breast cancer progression. The objective of the current study was to evaluate Drosha, the DiGeorge syndrome critical region gene 8 (DGCR8), Dicer, and Argonaute 2 (AGO2) mRNA expression in invasive breast carcinoma (IBC) and to assess the value of clinical parameters on their expression. By using quantitative real-time PCR, we examined the expression of the four miRNA machinery components in 52 breast tumor tissues which are diagnosed as invasive ductal carcinoma and adjacent non-neoplastic tissues. In the present study, decreased mRNA expression levels of major miRNA machinery components were observed in IBC. The altered mRNA expression levels of DGCR8 and AGO2 are positively correlated with to each other. This study revealed for the first time that expression alterations of DGCR8 are significantly associated with estrogen receptor and Ki-67 status in IBC. Moreover, AGO2 mRNA expression level was significantly correlated with N stage. These results provided evidences that down-regulated the four miRNA machinery components may play an important role in breast pathobiology and that DGCR8 and AGO2 might be associated with important clinical factors.

Prognostic significance of deregulated dicer expression in breast cancer

BACKGROUND

Dicer, an RNase III-type endonuclease, is the key enzyme involved in RNA interference and microRNA pathways. Aberrant expression of Dicer is reported in several human cancers. Our aim was to assess the prognostic role of Dicer in breast cancer.

METHODS

The entire series comprised 666 invasive breast cancers (IBCs), 480 DCIS cases (397 associated with IBC and 83 pure DCIS) and 305 lymph node metastases. Cytoplasmic Dicer expression by immunohistochemistry was scored as negative (no staining) and positive (weak, moderate or strong staining).

RESULTS

Dicer staining was assessable in 446 IBC, 128 DCIS and 101 lymph node metastases. Expression of Dicer was observed in 33% (145/446) of IBCs, 34% (44/128) of DCIS and 57% (58/101) of lymph node metastases. Dicer expression was increased in nodal metastases compared to primary tumours (p<0.001); and was associated with ER negativity (p<0.001), HER2 positivity (p<0.001), high Ki67 labeling index (p<0.001) and expression of basal-like biomarkers (p = 0.002). Dicer positivity was more frequent in the HER2 overexpressing (p<0.001) and basal-like (p = 0.002) subtypes compared to luminal A subtype. Dicer expression was associated with reduced overall survival (OS) on univariate analysis (p = 0.058) and remained an independent predictor of OS on multivariate analysis (HR 2.84, 95% CI 1.43-5.62, p = 0.003), with nodal status (HR 2.61, 95% CI 1.18-5.80, p = 0.018) and PR (HR 0.28, 95% CI 0.13-0.59, p = 0.001). Further, moderate or strong expression of Dicer was associated with improved disease-free survival in the HER2-overexpressing subtype compared to negative or weak expression (p = 0.038).

CONCLUSION

Deregulated Dicer expression is associated with aggressive tumour characteristics and is an independent prognostic factor for OS. Our findings suggest that Dicer is an important prognostic marker in breast cancer and that its prognostic role may be subtype specific.

Silencing Dicer expression enhances cellular proliferative and invasive capacities in human tongue squamous cell carcinoma

microRNAs (miRNAs) are aberrantly expressed in cancer. An enzyme essential for miRNA processing is Dicer, whose expression is deregulated in diverse types of cancer and correlates with tumor progression. However, whether the regulation of Dicer expression affects tongue squamous cell carcinoma is unknown. In the present study, we investigated how silencing the expression of Dicer alters cell proliferation, cell cycle patterns, and cell migration and invasion in the Tca-8113 tongue squamous cell carcinoma cell line. Dicer expression levels were determined using quantitative PCR and western blot analysis in normal oral gingival epithelial cells and in two tongue squamous cell carcinoma lines, Tca-8113 and UM-1. Tca-8113 cells were transfected with Dicer siRNA or a negative control siRNA. Cell proliferation was determined using the MTT assay and the cell cycle was examined using flow cytometry. Cell migration and invasion changes were evaluated using wound-healing, adherence and Transwell assays. Dicer was expressed at lower levels in the tongue squamous cell carcinoma cell lines Tca-8113 and UM-1 compared to normal gingival epithelial cells, and less Dicer was expressed in UM-1 cells compared to Tca-8113 cells. Notably, Tca-8113 cells transfected with Dicer siRNA had significantly higher proliferative and invasive abilities than cells transfected with the negative control siRNA or non-transfected cells. Silencing Dicer may promote the progression of tongue squamous cell carcinoma. Dicer could serve a promising biomarker and a potential therapeutic target for tongue squamous cell carcinoma.

Genetic variants in RAN, DICER and HIWI of microRNA biogenesis genes and risk of cervical carcinoma in a Chinese population

OBJECTIVE

Recent evidence indicates that dysregulation of microRNA (miRNA) biogenesis is implicated in cancer development and progression. Based on the important role of miRNA biogenesis genes in carcinogenesis, we hypothesized that genetic variations of the miRNA biogenesis genes may modulate susceptibility to cervical cancer.

METHODS

We identified three single nucleotide polymorphisms (SNPs) located in the 3'-untranslated regions (3'-UTR) of of miRNA biogenesis key genes (rs1057035 in DICER, rs3803012 in RAN and rs10773771 in HIWI) and genotyped these SNPs in a case-control study of 1,486 cervical cancer cases and 1,549 cancer-free controls in Chinese women.

RESULTS

Logistic regression analyses showed that no significant associations were observed between the three SNPs and cervical cancer risk [rs3803012 in RAN AG/GG vs. AA adjusted OR =1.104, 95% confidence interval (CI): 0.859-1.419; rs1057035 in DICER CT/CC vs. TT adjusted OR =0.962, 95% CI: 0.805-1.149; rs10773771 in HIWI CT/CC vs. TT adjusted OR =0.963, 95% CI: 0.826-1.122].

CONCLUSIONS

The findings did not suggest that genetic variants in the 3'-UTR of RAN, DICER and HIWI of miRNA biogenesis genes were associated with the risk of cervical cancer in this Chinese population.

miRNA dysregulation in breast cancer

miRNAs have emerged, in the last decade, as key players in the carcinogenic process, with many candidates identified as playing important roles in many aspects of tumor development, growth, metastasis, and drug resistance. More recently, polymorphisms in miRNAs themselves or in their binding sites in target genes have been identified to incur increased risk of breast cancer in certain populations. In addition, epigenetic regulation and differential expression of processing enzymes has been shown to contribute to the aberrant expression of miRNAs in breast cancer. This review focuses on the area of miRNA dysregulation in breast cancer through both genetic and epigenetic mechanisms, and the impact of this dysregulation on breast cancer risk and resistance to therapies.

Control of metastatic progression by microRNA regulatory networks

Aberrant microRNA (miRNA) expression is a defining feature of human malignancy. Specific miRNAs have been identified as promoters or suppressors of metastatic progression. miRNAs control metastasis through divergent or convergent regulation of metastatic gene pathways. Some miRNA regulatory networks govern cell-autonomous cancer phenotypes, whereas others modulate the cell-extrinsic composition of the metastatic microenvironment. The use of small RNAs as probes into the molecular and cellular underpinnings of metastasis holds promise for the identification of candidate genes for potential therapeutic intervention.

Genome-wide and species-wide in silico screening for intragenic MicroRNAs in human, mouse and chicken

MicroRNAs (miRNAs) are non-coding RNAs (ncRNAs) involved in regulation of gene expression. Intragenic miRNAs, especially those exhibiting a high degree of evolutionary conservation, have been shown to be coordinately regulated and/or expressed with their host genes, either with synergistic or antagonistic correlation patterns. However, the degree of cross-species conservation of miRNA/host gene co-location is not known and co-expression information is incomplete and fragmented among several studies. Using the genomic resources (miRBase and Ensembl) we performed a genome-wide in silico screening (GWISS) for miRNA/host gene pairs in three well-annotated vertebrate species: human, mouse, and chicken. Approximately half of currently annotated miRNA genes resided within host genes: 53.0% (849/1,600) in human, 48.8% (418/855) in mouse, and 42.0% (210/499) in chicken, which we present in a central publicly available Catalog of intragenic miRNAs (http://www.integratomics-time.com/miR-host/catalog). The miRNA genes resided within either protein-coding or ncRNA genes, which include long intergenic ncRNAs (lincRNAs) and small nucleolar RNAs (snoRNAs). Twenty-seven miRNA genes were found to be located within the same host genes in all three species and the data integration from literature and databases showed that most (26/27) have been found to be co-expressed. Particularly interesting are miRNA genes located within genes encoding for miRNA silencing machinery (DGCR8, DICER1, and SND1 in human and Cnot3, Gdcr8, Eif4e, Tnrc6b, and Xpo5 in mouse). We furthermore discuss a potential for phenotype misattribution of miRNA host gene polymorphism or gene modification studies due to possible collateral effects on miRNAs hosted within them. In conclusion, the catalog of intragenic miRNAs and identified 27 miRNA/host gene pairs with cross-species conserved co-location, co-expression, and potential co-regulation, provide excellent candidates for further functional annotation of intragenic miRNAs in health and disease.

The microRNA-200 family targets multiple non-small cell lung cancer prognostic markers in H1299 cells and BEAS-2B cells

Lung cancer remains the leading cause of cancer-related mortality for both men and women. Tumor recurrence and metastasis is the major cause of lung cancer treatment failure and death. The microRNA‑200 (miR-200) family is a powerful regulator of the epithelial-mesenchymal transition (EMT) process, which is essential in tumor metastasis. Nevertheless, miR-200 family target genes that promote metastasis in non-small cell lung cancer (NSCLC) remain largely unknown. Here, we sought to investigate whether the microRNA-200 family regulates our previously identified NSCLC prognostic marker genes associated with metastasis, as potential molecular targets. Novel miRNA targets were predicted using bioinformatics tools based on correlation analyses of miRNA and mRNA expression in 57 squamous cell lung cancer tumor samples. The predicted target genes were validated with quantitative RT-PCR assays and western blot analysis following re-expression of miR-200a, -200b and -200c in the metastatic NSCLC H1299 cell line. The results show that restoring miR-200a or miR-200c in H1299 cells induces downregulation of DLC1, ATRX and HFE. Reinforced miR-200b expression results in downregulation of DLC1, HNRNPA3 and HFE. Additionally, miR-200 family downregulates HNRNPR3, HFE and ATRX in BEAS-2B immortalized lung epithelial cells in quantitative RT-PCR and western blot assays. The miR-200 family and these potential targets are functionally involved in canonical pathways of immune response, molecular mechanisms of cancer, metastasis signaling, cell-cell communication, proliferation and DNA repair in Ingenuity pathway analysis (IPA). These results indicate that re-expression of miR-200 downregulates our previously identified NSCLC prognostic biomarkers in metastatic NSCLC cells. These results provide new insights into miR-200 regulation in lung cancer metastasis and consequent clinical outcome, and may provide a potential basis for innovative therapeutic approaches for the treatment of this deadly disease.

Altered expression of the miRNA processing endoribonuclease Dicer has prognostic significance in human cancers

Several studies have implicated miRNAs in the initiation and progression of human cancers. Examining the biogenesis pathways that generate these important regulatory molecules has revealed new mechanisms for tumor development. Altered expression of the endoribonuclease Dicer in many tumors has given new hope to unraveling the complex relationship between miRNA processing and cancer. This may provide further insight into mechanisms for targeting multiple genes that are critical for the malignant phenotype of several cancers. The evaluated article demonstrates that Dicer is transcriptionally regulated by Sox4 and reduced levels of this transcription factor consequently leads to a reduction in expression, and therefore deregulation of cancer-related miRNAs in melanoma. Reduced Dicer expression in malignant melanoma is an independent predictor of poor survival. In this review, we assess the prognostic significance of Dicer expression in different tumor types.

The microRNA maturation regulator Drosha is an independent predictor of outcome in breast cancer patients

Drosha is a protein that plays a key role in the biogenesis of microRNAs which are well known to be deranged in human breast cancer (BC). The purpose of the current study was to assess the biological and prognostic value of Drosha protein expression in BC. Drosha protein expression was assessed immunohistochemically in two sets of BC: (1) full-face sections of selected BC series with distinct stages of tumour progression (Normal parenchymal cells, ductal carcinoma in situ (DCIS), primary invasive BC and nodal metastases) to evaluate its differential expression, (2) tissue microarray comprising a large and well-characterised series of unselected clinically annotated invasive BC to investigate its correlation with clinicopathological features and patient outcome. A gradual loss of Drosha cytoplasmic expression was observed along tumour progression from DCIS, to invasive and to metastatic cancer cells. In invasive BC, loss of Drosha cytoplasmic expression was associated with BRCA1 and ER expression and with shorter BC specific survival (BCSS), disease free interval (DFI) and distant metastasis free interval (DMFI). This correlation was maintained in ER negative, HER2 negative, triple negative and LN negative cases. Moreover, loss of cytoplasmic Drosha was predictive of better response to chemotherapy and endocrine therapy. This study provides evidence that Drosha protein potentially plays an important role in BC progression and assessment of its expression provides an independent predictor of patient outcome. These observations provide further evidence that alterations in miRNA regulation influence tumour behaviour.

Induction of differentiation-specific miRNAs in TPA-induced myeloid leukemia cells through MEK/ERK activation

Cellular microRNAs (miRNAs) are pivotal regulators involved in various biological processes through the post-transcriptional regulation of gene expression. Signaling pathways are extensively activated during 12-O-Tetradecanoylphorbol-13-acetate (TPA)-induced differentiation of human leukemia cells, but the modulation of miRNA expression and processing in this context has yet to be fully explored. In this study, we comprehensively analyzed 10 miRNAs that are consistently upregulated during TPA-induced differentiation of various leukemia cell lines by employing microarray technology. The upregulation of these miRNAs was further verified by quantitative RT-PCR, and, markedly, a subset of the miRNAs was found to be induced via the MEK/ERK signaling pathway using TPA and specific pharmacological inhibitors. Moreover, immunoblotting and quantitative RT-PCR analysis demonstrated that the expression levels of key miRNA processing machineries (i.e., Drosha, Dicer, Ago1 and Ago2) were not induced in this context, but the transcription of the miRNA products was triggered by MEK/ERK activation. Therefore, we identified the unique miRNAs that respond to TPA treatment in leukemia cells and demonstrated the essential role of the MEK/ERK signaling pathway in the induction of these miRNA transcripts.

miR-18a promotes malignant progression by impairing microRNA biogenesis in nasopharyngeal carcinoma

Dysregulation of microRNA (miRNA) biogenesis is implicated in cancer development and progression. Dicer and Drosha are established regulators of miRNA biogenesis. In this study, we used a miRNA array to evaluate the miRNA expression profiles in nasopharyngeal carcinoma (NPC) samples. The significance analysis of microarrays showed a global downregulation of miRNA expression in NPC samples compared with normal nasopharyngeal epithelial tissues. Notably, miR-18a, a member of the oncogenic miR-17-92 cluster, was upregulated in the NPC samples and cell lines. Clinical parameter studies showed that higher levels of miR-18a correlated with NPC advanced stage, lymph node metastasis, Epstein-Barr virus infection and a higher death rate from NPC, indicating oncogenic roles in NPC development. The expression levels of miR-18a and Dicer1 were inversely related in NPC tissues. Further studies demonstrated that miR-18a negatively regulated Dicer1 by binding to the 3' untranslated regions of Dicer1. In vitro and in vivo biological function assays showed that miR-18a promoted the growth, migration and invasion of NPC cells by regulating Dicer1 expression, which caused the global downregulation of miRNA expression levels including miR-200 family and miR-143. Furthermore, we found that the epithelial mesenchymal transition marker E-cadherin and the oncogene K-Ras were aberrantly expressed after miR-18a transduction, and these alterations were directly induced by downregulation of the miR-200 family and miR-143. Collectively, our findings indicate that miR-18a plays an oncogenic role in the development of NPC by widespread downregulation of the miRNome and could be a potential therapeutic target for NPC.

Loss of Dicer expression is associated with breast cancer progression and recurrence

Dicer is a protein that plays a pivotal role in the final steps of the microRNA (miRNA) processing pathway, to produce mature miRNAs from their precursor molecules. The purpose of the current study was to assess the biological and prognostic value of Dicer protein expression in breast cancer (BC). Dicer protein expression was assessed immunohistochemically in two sets of BC: (1) full-face sections of selected BC series with distinct stages of tumour progression (normal, in situ (DCIS), primary invasive BC and nodal metastases) to evaluate its differential expression. (2) Tissue microarray comprising a large and well-characterised series of unselected clinically annotated invasive BC (n = 1,174) to investigate its correlation with clinicopathological features and patient outcome. A gradual loss of Dicer protein expression was observed in malignant compared to normal breast tissues, with the loss being the least in DCIS and most prominent in metastatic malignant cells. In invasive BC, loss of Dicer expression was associated with features of aggressive behaviour including higher histological grade, loss of hormone receptor and BRCA1 protein expression and with shorter disease-free survival (DFS). Dicer expression was an independent predictor of recurrence in the aggressive HER2-positive subgroup. Moreover, loss of Dicer was predictive of better response to chemotherapy and to endocrine therapy. This study provides evidence that Dicer protein plays a role in human BC progression and behaviour, and assessment of its expression could provide prognostic information in BC including the HER2-positive class.