MicroRNAs as Molecular Targets for Cancer Therapy: On the Modulation of MicroRNA Expression

MicroRNAs as behind-the-scenes molecules in breast cancer metastasis and their therapeutic role through novel microRNA-based delivery strategies

Breast cancer is the primary cause of cancer-related death and the most frequent malignancy among women in Western countries. Although there have been advancements in combination treatments and targeted therapies for the metastatic diseases management, metastatic breast cancer is still the second most common cause of cancer-related deaths among U.S. women. The routes of metastasis encompass invasion, intravasation, circulation, extravasation, infiltration into a remote location to establish a metastatic niche, and the formation of micro-metastases in a new environment. Each of these processes is regulated by changes in gene expression. MicroRNAs (miRNAs) are widely expressed by a variety of organisms and have a key role in cell activities including suppressing or promoting cancer through regulating various pathways. Target gene expression is post-transcriptionally regulated by miRNAs, which contribute to the development, spread, and metastasis of breast cancer. In this study, we comprehensively discussed the role of miRNAs as predictors of breast cancer metastasis, their correlation with the spread of the disease to certain organs, and their potential application as targets for breast cancer treatment. We also provided molecular mechanisms of miRNAs in the progression of breast cancer, as well as current challenges in miRNA-based therapeutic approaches. Furthermore, as one of the primary issues with the treatment of solid malignancies is the efficient delivery of miRNAs, we examined a number of cutting-edge carriers for miRNA-based therapies and CRISPR/Cas9 as a targeted therapy for breast cancer.

miRNAs: Potential as Biomarkers and Therapeutic Targets for Cancer

MicroRNAs (miRNAs) are single-stranded, non-coding RNA molecules that regulate gene expression post-transcriptionally by binding to messenger RNAs. miRNAs are important regulators of gene expression, and their dysregulation is implicated in many human and canine diseases. Most cancers tested to date have been shown to express altered miRNA levels, which indicates their potential importance in the oncogenic process. Based on this evidence, numerous miRNAs have been suggested as potential cancer biomarkers for both diagnosis and prognosis. miRNA-based therapies have also been tested in different cancers and have provided measurable clinical benefits to patients. In addition, understanding miRNA biogenesis and regulatory mechanisms in cancer can provide important knowledge about resistance to chemotherapies, leading to more personalized cancer treatment. In this review, we comprehensively summarized the importance of miRNA in human and canine cancer research. We discussed the current state of development and potential for the miRNA as both a diagnostic marker and a therapeutic target.

Targeting miRNAs and Other Non-Coding RNAs as a Therapeutic Approach: An Update

Since the discovery of the first microRNAs (miRNAs, miRs), the understanding of miRNA biology has expanded substantially. miRNAs are involved and described as master regulators of the major hallmarks of cancer, including cell differentiation, proliferation, survival, the cell cycle, invasion, and metastasis. Experimental data indicate that cancer phenotypes can be modified by targeting miRNA expression, and because miRNAs act as tumor suppressors or oncogenes (oncomiRs), they have emerged as attractive tools and, more importantly, as a new class of targets for drug development in cancer therapeutics. With the use of miRNA mimics or molecules targeting miRNAs (i.e., small-molecule inhibitors such as anti-miRS), these therapeutics have shown promise in preclinical settings. Some miRNA-targeted therapeutics have been extended to clinical development, such as the mimic of miRNA-34 for treating cancer. Here, we discuss insights into the role of miRNAs and other non-coding RNAs in tumorigenesis and resistance and summarize some recent successful systemic delivery approaches and recent developments in miRNAs as targets for anticancer drug development. Furthermore, we provide a comprehensive overview of mimics and inhibitors that are in clinical trials and finally a list of clinical trials based on miRNAs.

The various role of microRNAs in breast cancer angiogenesis, with a special focus on novel miRNA-based delivery strategies

After skin malignancy, breast cancer is the most widely recognized cancer detected in women in the United States. Breast cancer (BCa) can happen in all kinds of people, but it's much more common in women. One in four cases of cancer and one in six deaths due to cancer are related to breast cancer. Angiogenesis is an essential factor in the growth of tumors and metastases in various malignancies. An expanded level of angiogenesis is related to diminished endurance in BCa patients. This function assumes a fundamental part inside the human body, from the beginning phases of life to dangerous malignancy. Various factors, referred to as angiogenic factors, work to make a new capillary. Expanding proof demonstrates that angiogenesis is managed by microRNAs (miRNAs), which are small non-coding RNA with 19-25 nucleotides. MiRNA is a post-transcriptional regulator of gene expression that controls many critical biological processes. Endothelial miRNAs, referred to as angiomiRs, are probably concerned with tumor improvement and angiogenesis via regulation of pro-and anti-angiogenic factors. In this article, we reviewed therapeutic functions of miRNAs in BCa angiogenesis, several novel delivery carriers for miRNA-based therapeutics, as well as CRISPR/Cas9 as a targeted therapy in breast cancer.

Visualization of microRNA-21 Dynamics in Neuroblastoma Using Magnetic Resonance Imaging Based on a microRNA-21-Responsive Reporter Gene

Background

MicroRNAs (miRs) have been shown to be closely associated with the occurrence and development of tumors and to have potential as diagnostic and therapeutic targets. The detection of miRs by noninvasive imaging technology is crucial for deeply understanding their biological functions. Our aim was to develop a novel miR-21-responsive gene reporter system for magnetic resonance imaging (MRI) visualization of the miR-21 dynamics in neuroblastoma.

Methods

The reporter gene ferritin heavy chain (FTH1) was modified by the addition of 3 copies of the sequence completely complementary to miR-21 (3xC_miR-21) to its 3’-untranslated region (3’ UTR) and transduced into SK-N-SH cells to obtain SK-N-SH/FTH1-3xC_miR-21 cells. Then, the antagomiR-21 was delivered into cells by graphene oxide functionalized with polyethylene glycol and dendrimer. Before and after antagomiR-21 delivery, FTH1 expression, MRI contrast and intracellular iron uptake were assayed in vitro and in vivo.

Results

In the SK-N-SH/FTH1-3xC_miR-21 cells, FTH1 expression was in an “off” state due to the combination of intratumoral miR-21 with the 3’ UTR of the reporter gene. AntagomiR-21 delivered into the cells bound to miR-21 and thereby released it from the 3’ UTR of the reporter gene, thus “switching on” FTH1 expression in a dose-dependent manner. This phenomenon resulted in intracellular iron accumulation and allowed MRI detection in vitro and in vivo.

Conclusion

MRI based on the miR-21-responsive gene reporter may be a potential method for visualization of the endogenous miR-21 activity in neuroblastoma and its response to gene therapy.

New biomarkers in peripheral blood of patients with ovarian cancer: high expression levels of miR-16-5p, miR-17-5p, and miR-638

OBJECTIVES

Ovarian cancer is one of the most fatal gynecologic malignities. miR-16-5p, miR-17-5p, and miR-638 genes were found to have been associated with ovarian cancer in accordance with the data obtained from the previous microarray research performed by Tuncer et al. (J Ovarian Res 13(1):99, 2020). The expression levels of these miRNAs in the peripheral blood samples of 142 ovarian cancer patients, and 97 healthy controls were investigated for performing the validation, and to identify whether these genes were the possible biomarkers to be used in the early diagnosis of high-risk ovarian cancer patients, and in the prognosis of patients.

METHODS

The miRNA expression analysis was performed using the miRNA-specific cDNA synthesis, and real-time PCR methods following the RNA isolation from the peripheral blood lymphocytes.

RESULTS

miR-16-5p, miR-17-5p, and miR-638 miRNA gene expression levels were found to have twofold higher expression levels in patient groups compared with the gene expression levels in healthy controls, and were statistically significant (p < 0.05). In addition, the comparison of the miRNA expression levels with the clinical data of patients showed that there was a significant difference with smoking history and the increased expression level of miR-17-5 (p: 0.007). There was a significant difference between the increased expression level of miR-638 with the locally advanced stage, and abdominal/pelvic metastatic patients (p: 0.03).

CONCLUSIONS

The obtained data suggest that miR-16-5p, miR-17-5p, and miR-638 molecules might be the noninvasive biomarkers in identifying the ovarian cancer. However, the investigation and monitoring of the changeability of these biomarkers in benign ovarian diseases, and during the treatment must be performed in future studies for identifying the accurate diagnostic, and prognostic features of miRNAs.

MiR-200c-based metabolic modulation in glioblastoma cells as a strategy to overcome tumor chemoresistance

Glioblastoma (GB) is the most aggressive and common form of primary brain tumor characterized by fast proliferation, high invasion, and resistance to current standard treatment. The average survival rate post-diagnosis is 14.6 months, despite the aggressive standard post-surgery radiotherapy concomitant with chemotherapy with temozolomide (TMZ). Currently, efforts are being endowed to develop new and more efficient therapeutic approaches capable to overcome chemoresistance, inhibit tumor progression and improve overall patient survival rate. Abnormal microRNA (miRNA) expression has been correlated with chemoresistance, proliferation and resistance to apoptosis, which result from their master regulatory role of gene expression. Altered cell metabolism, favoring glycolysis, was identified as an emerging cancer hallmark and has been described in GB, thus offering a new target for innovative GB therapies. In this work, we hypothesized that a gene therapy-based strategy consisting of the overexpression of a miRNA downregulated in GB and predicted to target crucial metabolic enzymes might promote a shift of GB cell metabolism, decreasing the glycolytic dependence of tumor cells and contributing to their sensitization to chemotherapy with TMZ. The increase of miR-200c levels in DBTRG cells resulted in downregulation of mRNA of enzymes involved in bioenergetics pathways and impaired cell metabolism and mobility. Additionally, miR-200c overexpression prior to DBTRG cell exposure to TMZ resulted in cell cycle arrest. Overall, our results show that miR-200c overexpression could offer a way to overcome chemoresistance developed by GB cells in response to current standard chemotherapy, providing an improvement to current GB standard treatment, with benefit for patient outcome.

The role of single nucleotide polymorphisms of miRNAs 100 and 146a as prognostic factors for prostate cancer

INTRODUCTION

Prostate cancer has a high incidence in men and is the second cause of cancer death among americans male. microRNA (miR) is becoming a potential new prognostic factor for prostate cancer. Single nucleotide polymorphisms (SNPs) are common polymorphisms, characterized by a single exchange of nitrogen based in the DNA. This polymorphism is present in the miRs, altering their function.

OBJECTIVE

To evaluate the role of SNP rs1834306 of miR100 and rs2910164 of miR146a in the development and prognosis of prostate cancer.

METHODS

One hundred patients diagnosed with prostate cancer and 68 controls were selected. The identification of SNP was rated by quantitative polymerase chain reaction from blood samples, and the analysis was performed within the presence of SNP and the prognostic variables.

RESULTS

In the SNP rs1834306 (miR100), a smaller presence of the polymorphic homozygous genotype was identified in patients with PSA >10 ng/mL, (P=0.03); when evaluating only the presence of the polymorphic allele G (P=0.09) it was compared to the presence of the wild type allele A. Among the patients with prostate cancer, SNP rs2910164 (miR146A), the polymorphic allele was more frequent in patients with a Gleason score ⩾7 than in patients with a Gleason score <7, (P=0.043). In patients with prostate cancer, miR100 was overexpressed in those with pT3 staging compared to pT2 and among those who had biochemical recurrence (P = 0.004 and P = 0.011, respectively).

CONCLUSIONS

SNP of miR146a acts as a poor prognostic factor (Gleason ⩾7), and the SNP of miR100 is linked to better prognostic data (PSA <10). MiR100 was overexpressed in prostate cancer with worse prognostic factors.

MicroRNAs Involved in Inflammatory Breast Cancer: Oncogene and Tumor Suppressors with Possible Targets

Inflammatory breast cancer (IBC) as a rare and highly aggressive type of breast cancer displays phenotypic characteristics. To date, the IBC-associated molecular mechanisms are entirely unknown. In addition, there is an urgent need to identify the new biomarkers involved in the diagnosis and therapeutic purposes of IBC. MicroRNAs, a category of short noncoding RNAs, are capable of controlling the post-transcriptional expression of genes and thus can act as diagnostic predictive tools. In this review, we addressed the status of oncogenic and tumor suppressor miRNA-mediated IBC in current studies. Furthermore, based on their targets, their involvement in cancer progression, angiogenesis, metastasis, and apoptosis were determined.

miRNAs and radiotherapy response in prostate cancer

BACKGROUND

Gaining insight into microRNAs (miRNAs) and genes that regulate the therapeutic response of cancer diseases in general and prostate cancer (PCa) in particular is an important issue in current molecular biomedicine and allows the discovery of predictive miRNA targets.

OBJECTIVES

The aim of this study was to analyze the available data on the influence of radiotherapy (RT) on miRNA expression and on miRNA involved in radiotherapy response in PCa.

MATERIALS AND METHODS

The data used in this review were extracted from research papers and the DIANA, STRING, and other databases with a special focus on the mechanisms of radiotherapy PCa response and the miRNA involved and associated genes.

RESULTS AND DISCUSSION

A search for miRNA prognostic and therapeutic effectiveness markers should rely on both the data of recent experimental studies on the influence of RT on miRNA expression and miRNAs involved in regulation of radiosensitivity in PCa and on bioinformatics resources. miRNA panels and genes targeted by them and involved in radioresponse regulation highlighted by meta-analysis and cross-analysis of the data in the present review have.

CONCLUSION

Selected miRNA and gene panel has good potential as prognostic and radiotherapy effectiveness markers for PCa and, moreover, as radiotherapy effectiveness markers in other types of cancer, as the proposed model is not specific to PCa, which opens up opportunities for the development of a universal diagnostic system (or several intersecting systems) for oncology radiotherapy in general.

MiR-130a-3p blocks Wnt signaling cascade in the triple-negative breast cancer by targeting the key players at multiple points

OBJECTIVES

Aberrant Wnt signaling cascade is a hallmark of the triple-negative breast cancer (TNBC) that is linked with the increased proliferation, invasion, and poor overall survival. many genes are post-transcriptionally regulated by microRNAs (miRNAs) therefore; it is indisputable that the dysregulation of the miRNAs is an explanation for the aberrant signaling cascades. Thus, the present study was conducted to find the putative miRNA targeting the key players of Wnt/β -catenin cascade in the TNBC.

METHODS

The miR-130a-3p was found as a potential regulator of the Wnt signaling cascade by applying several bioinformatic algorithms. Quantitative real-time PCR (qRT-PCR) was used to analyze the expression levels of miR-130a-3p and Wnt cascade genes in the TNBC cells. Afterward, TNBC cells were transiently transfected with the miR-130a-3p to investigate its effects on the expression of Wnt cascade genes. Subsequently, MTT, soft agar colony formation, scratch, transwell cell migration, and transwell cell invasion assays were used to determine the behavior of the TNBC cells in response to miR-130a-3p restoration.

RESULTS

Results of the qRT-PCR showed downregulation of miR-130a-3p and upregulation of the Wnt cascade genes in the TNBC cells compared to the normal cells. Transient overexpression of miR-130a-3p decreased the expression levels of Wnt cascade genes significantly in the TNBC cells. Moreover, following the miR-130a-3p overexpression, the proliferation, anchorage-independent growth, and migration of the TNBC cells were reduced.

CONCLUSION

Overall, our findings provided an evidence for the significant role of miR-130a-3p in the regulation of Wnt/β-catenin cascade, and also introduced the miR-130a-3p as a new therapeutic target for the patients with TNBC.

MIR-520f Regulated Itch Expression and Promoted Cell Proliferation in Human Melanoma Cells

Accumulating evidence suggests that abnormal expression and dysfunction of microRNA is involved in development of cancers. However, the function of miR-520f especially in human melanoma remains elusive. In the current study, the underlying function of miR-520f in human melanoma was investigated. Our study demonstrated that the miR-520f level in human melanoma cell lines and clinical tissues was increased. Overexpression of miR-520f promoted cell proliferation by using the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide assay, colony formation, anchorage-independent growth assay, and 5-bromo-2-deoxyuridine assays. Furthermore, we revealed that miR-520f could interact with circular RNA Itchy E3 ubiquitin protein ligase (ITCH) 3'-untranslated region and suppress ITCH expression in human melanoma cells. The inhibitory effect of miR-520f-in could be partially restored by knockdown of ITCH in human melanoma cells. In summary, this study provides novel insights into miR-520f act as a crucial role in the regulation of human melanoma cell growth via regulating ITCH, which might be a potential biomarker and therapeutic target of human melanoma.

In silico drug repositioning based on drug-miRNA associations

Drug repositioning has become a prevailing tactic as this strategy is efficient, economical and low risk for drug discovery. Meanwhile, recent studies have confirmed that small-molecule drugs can modulate the expression of disease-related miRNAs, which indicates that miRNAs are promising therapeutic targets for complex diseases. In this study, we put forward and verified the hypothesis that drugs with similar miRNA profiles may share similar therapeutic properties. Furthermore, a comprehensive drug–drug interaction network was constructed based on curated drug-miRNA associations. Through random network comparison, topological structure analysis and network module extraction, we found that the closely linked drugs in the network tend to treat the same diseases. Additionally, the curated drug–disease relationships (from the CTD) and random walk with restarts algorithm were utilized on the drug–drug interaction network to identify the potential drugs for a given disease. Both internal validation (leave-one-out cross-validation) and external validation (independent drug–disease data set from the ChEMBL) demonstrated the effectiveness of the proposed approach. Finally, by integrating drug-miRNA and miRNA-disease information, we also explain the modes of action of drugs in the view of miRNA regulation. In summary, our work could determine novel and credible drug indications and offer novel insights and valuable perspectives for drug repositioning.

MicroRNA delivery mediated by PEGylated polyethylenimine for prostate cancer therapy

A microRNA (miRNA) nanomedicine PEG-PEI/miR-221/222 was synthesized based on PEGylated polyethylenimine PEG-PEI and used to transfect prostate cancer cells (PC-3) in vitro. Gel retardation assay confirmed the formation of nanomedicine, of which the zeta potential and particle size were determined by dynamic light scattering. Its cytotoxicity was analyzed by CCK-8 assay-while its transfection efficiency was analyzed by flow cytometry. Cell uptake and intracellular distribution of nanoparticles were evaluated using laser confocal microscopy. RT-PCR and western-blot assays were conducted to verify the regulation of SIRT1 target gene. We found that the properties of the nanocomplexes of miRNA and PEG-PEI depended on N/P ratios. At higher N/P ratio, accompanied by higher zeta potential and higher cytotoxicity, PEG-PEI is needed to completely condense the miRNA into small particles with uniform size distribution. Under an N/P ratio of 20, high transfection efficiency and low carrier cytotoxicity were obtained simultaneously in PC-3 cells in vitro. Consequently, the SIRT1 expression was up-regulated due to the nanoparticle-delivered miR-221/222, which resulted in effective inhibition of PC-3 cells. Our study revealed the PEG-PEI/miR-221/222 nanomedicine as a prospective alternative for treatment of advanced prostate cancer and also lays a foundation for future in vivo investigation.

miR-204-5p and miR-3065-5p exert antitumor effects on melanoma cells

MicroRNA (miR)-204-5p was previously identified to be downregulated in melanoma compared with melanocytic nevi. This observation prompted a functional study on miR-204-5p and the newly-identified miR-3065-5p, two miRNAs suggested to be tumor-suppressive oncomiRs. Application of miR-204-5p mimics or inhibitors resulted in a decrease or increase, respectively, in melanoma cell proliferation and colony formation. miR-204-5p mimics hindered invasion, whereas miR-204-5p inhibitors stimulated cancer cell migration. Modulation of miR-3065-5p led to a decrease in melanoma cell proliferation, altered cell cycle distribution and increased expression levels of its target genes HIPK1 and ITGA1, possibly due to functional modifications identified in these cells. miR-204-5p and miR-3065-5p demonstrated antitumor capacities that may need to be taken into account in the development of melanoma treatment approaches.

Non-viral based miR delivery and recent developments

miRNAs are promising therapeutic targets or tools for the treatment of numerous diseases, with most prominently, cancer. The inherent capacity of these short nucleic acids to regulate multiple cancer-related pathways simultaneously has prompted strong research on understanding miR functions and their potential use for therapeutic purposes. A key determinant of miR therapeutics' potential for treatment is their delivery. Viral and non-viral vectors attempt to address the major limitations associated with miR delivery, but several hurdles have been identified. Here, we present an overview on the general limitations of miR delivery, and the delivery strategies exploited to overcome them. We provide an introduction on the advantages and disadvantages of viral and non-viral vectors, and we go into detail to analyze the most prominently used non-viral systems. We provide with an update on the most recent research on this topic and we describe the mechanism and limitations of the lipid-, polymer- and inorganic material- based miR delivery systems.

Targeted delivery of miRNA-204-5p by PEGylated polymer nanoparticles for colon cancer therapy

AIM

miRNAs have been recognized for their potential in cancer therapeutics, and multiple miRNAs were suggested to affect target genes expression. To overcome limitations of free synthetic miRNAs, such as easily degraded in biofluids and limited in cellular uptake, novel miRNAs delivery systems need to be developed.

MATERIALS & METHODS

Using surface-functionalizing technique, poly(D,L-lactide-co-glycolide)/poly(L-lactide)-block-poly(ethylene glycol)-folate polymer nanoparticle (PLGA/PLA-PEG-FA) loaded with miR-204-5p (FA-NPs-miR-204) was developed. The therapeutic efficacy of FA-NPs-miR-204 was evaluated in the Luc-HT-29 xenograft tumor model in vivo.

RESULTS

FA-NPs-miR-204 could be taken up by HT-29  and HCT-116 cells efficiently, resulting in significant inhibitory effect on cell proliferation and promotive effect on cell apoptosis. In vivo study showed that FA-NPs-miR-204 could exert tumor suppressive function in Luc-HT-29 xenograft model.

CONCLUSION

Our study demonstrates a convenient miRNA delivery system that targets tumor tissue and exerts tumor suppressive function, thus demonstrating a potential new therapeutic option for colon cancer.

Identification of associations between small molecule drugs and miRNAs based on functional similarity

MicroRNAs (miRNAs) are a class of small non-coding RNA molecules that regulate gene expression at post-transcriptional level. Increasing evidences show aberrant expression of miRNAs in varieties of diseases. Targeting the dysregulated miRNAs with small molecule drugs has become a novel therapy for many human diseases, especially cancer. Here, we proposed a novel computational approach to identify associations between small molecules and miRNAs based on functional similarity of differentially expressed genes. At the significance level of p < 0.01, we constructed the small molecule and miRNA functional similarity network involving 111 small molecules and 20 miRNAs. Moreover, we also predicted associations between drugs and diseases through integrating our identified small molecule-miRNA associations with experimentally validated disease related miRNAs. As a result, we identified 2265 associations between FDA approved drugs and diseases, in which ~35% associations have been validated by comprehensive literature reviews. For breast cancer, we identified 19 potential drugs, in which 12 drugs were supported by previous studies. In addition, we performed survival analysis for the patients from TCGA and GEO database, which indicated that the associated miRNAs of 4 drugs might be good prognosis markers in breast cancer. Collectively, this study proposed a novel approach to predict small molecule and miRNA associations based on functional similarity, which may pave a new way for miRNA-targeted therapy and drug repositioning.

Role of micro-RNAs in drug resistance of multiple myeloma

While novel therapeutic approaches have profoundly improved survival of multiple myeloma (MM) patients, drug resistance and treatment refractoriness still persists. This obstacle highly demands thorough investigation into the root and underlying molecular mechanisms to develop more effective strategies. The advent of micro-RNAs (miRNAs) in the study of cancer biology and pathogenesis in recent years has revolutionized therapy in this field and particularly opened new windows to further understanding of tumor drug resistance. However; in spite of the fact that miRNAs involvement in MM pathogenesis and progression has been substantially evidenced, miRNA investigation in MM drug resistance is still in its infancy. Our knowledge of the potential role of miRNAs in MM drug resistance comes from few recent reports confirming that some miRNAs including miR-137/197, miR-21 and miR-221/222 could negatively modulate drug sensitivity of MM cells. Further continuous researches are required to exploit miRNAs to elucidate the critical mechanisms controlling drug resistance in MM. In this review, we will highlight the most recent observations on the role of miRNAs in MM drug resistance. Moreover, approaches and insights into clinical application of miRNAs to overcome MM drug resistance will be discussed.

DNA-Methyltransferase 1 Induces Dedifferentiation of Pancreatic Cancer Cells through Silencing of Krüppel-Like Factor 4 Expression

Purpose: The dismal prognosis of pancreatic cancer has been linked to poor tumor differentiation. However, molecular basis of pancreatic cancer differentiation and potential therapeutic value of the underlying molecules remain unknown. We investigated the mechanistic underexpression of Krüppel-like factor 4 (KLF4) in pancreatic cancer and defined a novel epigenetic pathway of its activation for pancreatic cancer differentiation and treatment.Experimental Design: Expressions of KLF4 and DNMT1 in pancreatic cancer tissues were determined by IHC and the genetic and epigenetic alterations of KLF4 in and KLF4's impact on differentiation of pancreatic cancer were examined using molecular biology techniques. The function of dietary 3,3'-diindolylmethane (DIM) on miR-152/DNMT1/KLF4 signaling in pancreatic cancer was evaluated using both cell culture and animal models.Results: Overexpression of DNMT1 and promoter hypermethylation contributed to decreased KLF4 expression in and associated with poor differentiation of pancreatic cancer. Manipulation of KLF4 expression significantly affected differentiation marker expressions in pancreatic cancer cells. DIM treatment significantly induced miR-152 expression, which blocked DNMT1 protein expression and its binding to KLF4 promoter region, and consequently reduced promoter DNA methylation and activated KLF4 expression in pancreatic cancer cells. In addition, DIM treatment caused significant inhibition of cell growth in vitro and tumorigenesis in animal models of pancreatic cancer.Conclusions: This is the first demonstration that dysregulated KLF4 expression associates with poor differentiation of pancreatic cancer. Epigenetic activation of miR-152/DNMT1/KLF4 signaling pathway by dietary DIM causes differentiation and significant growth inhibition of pancreatic cancer cells, highlighting its translational implications for pancreatic and other cancers. Clin Cancer Res; 23(18); 5585-97. ©2017 AACR.

MicroRNA-7641 is a regulator of ribosomal proteins and a promising targeting factor to improve the efficacy of cancer therapy

Many diseases, including myocardial infarction, autoimmune disease, viral diseases, neurodegenerative diseases, and cancers, are frequently diagnosed with aberrant expression of microRNAs (miRNAs) and their allied pathways. This indicates the crucial role of miRNAs in maintaining biological and physiological processes. miR-7641 is a miRNA whose role in disease has not been fully investigated. In the present study, we investigated the expression pattern of miR-7641 and its target genes in different cancer cells, as well as in clinical cancer patients. Our data confirmed RPS16 and TNFSF10 as two direct targets of miR-7641, while gene expression study showed that a group of genes are also deregulated by miR-7641, including many ribosomal proteins that are frequently co-expressed with RPS16 in breast cancer. Direct inhibition of miR-7641 using a locked nucleic acid upregulated the expression of its target genes, sensitized cancer cells, and enhanced the efficiency of therapeutic agents such as doxorubicin. In addition, inhibition of miR-7641 boosted doxorubicin-mediated apoptosis of cancer cells via upregulation of apoptotic molecules Caspase 9 (CAS9) and poly ADP ribose polymerase (PARP) and downregulation of anti-apoptotic molecule BCL2. Thus, miR-7641 might be a clinically important cancer biomarker. Inhibition of miR-7641 expression could be an efficient treatment strategy for clinical patients.

miR-629-3p may serve as a novel biomarker and potential therapeutic target for lung metastases of triple-negative breast cancer

Background

Different breast cancer subtypes show distinct tropisms for sites of metastasis. Notably, the lung is the most common site for the first distant recurrence in triple-negative breast cancer (TNBC). The identification of novel biomarkers for lung metastasis is of great importance to improving the outcome of TNBC. In this study, we sought to identify a microRNA (miRNA)-based biomarker and therapeutic target for lung metastasis of TNBC.

Methods

A total of 669 patients without de novo stage IV TNBC were recruited for this study. miRNA profiling was conducted in the discovery cohort. Diagnostic accuracy and prognostic values of candidate miRNAs were evaluated in the training and validation cohorts, respectively. The biological functions of candidate miRNAs, as well as potential targets, were further evaluated through bioinformatic analysis as well as by performing in vitro and in vivo assays.

Results

In the discovery set, we found that miR-629-3p was specifically upregulated in both metastatic foci (fold change 144.16, P < 0.0001) and primary tumors (fold change 74.37, P = 0.004) in patients with lung metastases. In the training set, the ROC curve showed that miR-629-3p yielded high diagnostic accuracy in discriminating patients with lung metastasis from patients without recurrence (AUC 0.865, 95% CI 0.800–0.930, P < 0.0001). Although miR-629-3p predicted poor overall survival and disease-free survival in the validation set, it failed to show significance after multivariate analysis. Notably, logistic regression analyses confirmed that miR-629-3p was an independent risk factor for lung metastasis (OR 4.1, 95% CI 2.5–6.6, P < 0.001). Inhibition of miR-629-3p drastically attenuated the viability and migration of TNBC cells, and it markedly suppressed lung metastasis in vivo. Furthermore, we identified the leukemia inhibitory factor receptor (LIFR), a well-known metastatic suppressive gene, to be a direct target of miR-629-3p.

Conclusions

miR-629-3p may serve as a novel biomarker and potential therapeutic target for lung metastases of TNBC mediated via LIFR.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-017-0865-y) contains supplementary material, which is available to authorized users.

Downregulation of miR-429 contributes to the development of drug resistance in epithelial ovarian cancer by targeting ZEB1

Drug resistance is an obstacle to the treatment of epithelial ovarian cancer. Recently, research has suggested that miRNAs (microRNAs) are involved in cancer development, and speculation has been made about their possible involvement in drug resistance. Thus, we attempted to identify selected miRNAs involved in the development of chemo-resistance in epithelial ovarian cancer. Using miRNA profiles of a panel of cisplatin-resistant (SKOV3/DDP) cells, we validated data using quantitative real time-PCR (QRT-PCR), and studied the effects of miR-429 on cancer cell chemo-sensitivity, using gain- and loss-of-function studies. Data show that SKOV3/DDP expressed less miR-429 compared with parental SKOV3 cells and lower miR-429 expression conferred shorter overall survival (OS) and less progression-free survival (PFS) than the patients with more miR-429 expression (P < 0.01). Upregulation of miR-429 increases cisplatin sensitivity in epithelial ovarian cancer cells. Studies have confirmed that the zinc finger E-box binding homeobox1 (ZEB1) is a direct and functional target of miR-429 and that over-expression of miR-429 reduces autophagy-related protein anti-ATG7, anti-LC3A/B (P < 0.05). Thus, overexpression of miR-429 may suppress ZEB1, and may be a potential sensitizer to cisplatin treatment that may have therapeutic implications.

What Is New in the miRNA World Regarding Osteosarcoma and Chondrosarcoma?

Despite the availability of multimodal and aggressive therapies, currently patients with skeletal sarcomas, including osteosarcoma and chondrosarcoma, often have a poor prognosis. In recent decades, advances in sequencing technology have revealed the presence of RNAs without coding potential known as non-coding RNAs (ncRNAs), which provides evidence that protein-coding genes account for only a small percentage of the entire genome. This has suggested the influence of ncRNAs during development, apoptosis and cell proliferation. The discovery of microRNAs (miRNAs) in 1993 underscored the importance of these molecules in pathological diseases such as cancer. Increasing interest in this field has allowed researchers to study the role of miRNAs in cancer progression. Regarding skeletal sarcomas, the research surrounding which miRNAs are involved in the tumourigenesis of osteosarcoma and chondrosarcoma has rapidly gained traction, including the identification of which miRNAs act as tumour suppressors and which act as oncogenes. In this review, we will summarize what is new regarding the roles of miRNAs in chondrosarcoma as well as the latest discoveries of identified miRNAs in osteosarcoma.

Micro RNA 34a and Let-7a Expression in Human Breast Cancers is Associated with Apoptotic Expression Genes

Breast cancer is the most common cause of cancer-related death among women in the whole world. MiR- 34a and let-7a are well known tumor suppressors that participate in the regulation of apoptosis, invasion and other cellular functions. In this study, expression of miR-34a, let-7a and apoptosis pathway genes such as Bcl-2, Caspase-3 and P53 were evaluated using quantitative real-time PCR in 45 paired samples of normal margin and tumor tissue collected from breast cancer patient at advanced stage (3-4). MiR-34a, let-7a, caspase-3 and P53 expression are reduced and Bcl-2 expression is increased within tumoral tissues in comparison with normal margin tissues. P53 expression directly or indirectly was correlated with miR-34a, let-7a, Bcl-2 and caspase-3 expression. In This study we found that MiR-34a and let-7a expression are reduced in the tumoral tissues. Down- regulation of these two molecules correlated with expression of genes associated with apoptosis. These results suggest that due to the correlation of miR-34a and let-7a with apoptotic and anti-apoptotic pathways these molecules could participate as regulators in advanced clinical stages of breast cancer and should be considered as markers for diagnosis, prognostic assessment and targeted therapy.

miR-205 promotes epithelial-mesenchymal transition by targeting AKT signaling in endometrial cancer cells

AIM

AKT signaling regulates multiple biological processes and expresses in various cancers. miR-205 plays complex roles in tumorigenesis and tumor progression by acting either as a tumor suppressor or an oncogene depending on the tumor type. Here we describe the molecular mechanism of miR-205 regulating epithelial-mesenchymal transition by activation of AKT signaling in endometrial cancer cells HEC-50B and HEC-1-A.

MATERIAL AND METHODS

The proliferation of HEC-50B cells transfected with miR-205 mimic was assessed by WST-1 assay. The migration and invasion were evaluated by BD transwell migration and matrigel invasion assays. The EMT markers were detected by Western blot.

RESULTS

We found that miR-205 increased the proliferation in HEC-50B cells. The migration and invasion of HEC-50B cells and HEC-1-A cells were enhanced by miR-205. When HEC-50B cells and HEC-1-A cells were treated with anti-miR-205 inhibitor, the migration and invasion were decreased as compared with the negative control. The overexpression of miR-205 inhibited E-cadherin expression and promoted Snail expression by activation of AKT and downregulation of glycogen synthase kinase 3β. However, after the HEC-50B cells and HEC-1-A cells were treated with anti-miR-205 inhibitor, E-cadherin expression was increased and Snail protein level was decreased by inhibition of AKT expression.

CONCLUSION

Our data strongly suggest that miR-205 plays an important role in endometrial cancer migration and invasion by targeting the AKT pathway. Our data highlight miR-205 as a potential molecular target for endometrial cancer treatment.

miR-671-5p inhibits epithelial-to-mesenchymal transition by downregulating FOXM1 expression in breast cancer

MicroRNA (miRNA) dysfunction is associated with a variety of human diseases, including cancer. Our previous study showed that miR-671-5p was deregulated throughout breast cancer progression. Here, we report for the first time that miR-671-5p is a tumor-suppressor miRNA in breast tumorigenesis. We found that expression of miR-671-5p was decreased significantly in invasive ductal carcinoma (IDC) compared to normal in microdissected formalin-fixed, paraffin-embedded (FFPE) tissues. Forkhead Box M1 (FOXM1), an oncogenic transcription factor, was predicted as one of the direct targets of miR-671-5p, which was subsequently confirmed by luciferase assays. Forced expression of miR-671-5p in breast cancer cell lines downregulated FOXM1 expression, and attenuated the proliferation and invasion in breast cancer cell lines. Notably, overexpression of miR-671-5p resulted in a shift from epithelial-to-mesenchymal transition (EMT) to mesenchymal-to-epithelial transition (MET) phenotypes in MDA-MB-231 breast cancer cells and induced S-phase arrest. Moreover, miR-671-5p sensitized breast cancer cells to cisplatin, 5-fluorouracil (5-FU) and epirubicin exposure. Host cell reactivation (HCR) assays showed that miR-671-5p reduces DNA repair capability in post-drug exposed breast cancer cells. cDNA microarray data revealed that differentially expressed genes when miR-671-5p was transfected are associated with cell proliferation, invasion, cell cycle, and EMT. These data indicate that miR-671-5p functions as a tumor suppressor miRNA in breast cancer by directly targeting FOXM1. Hence, miR-671-5p may serve as a novel therapeutic target for breast cancer management.

Let‑7 miRNAs sensitize breast cancer stem cells to radiation‑induced repression through inhibition of the cyclin D1/Akt1/Wnt1 signaling pathway

The tumor-suppressive let-7 family of microRNAs (miRNAs) has been previously identified to induce cell apoptosis, proliferation‑inhibition and suppression of the self‑renewal capacities of cancer stem cells (CSCs). However, let‑7‑mediated sensitization of tumors to radiation treatment remains to be investigated fully in triple negative breast cancer (TNBC), of which the clinical treatment is challenging. The inhibitory effect of let‑7 miRNAs on the self‑renewal ability of CSCs from TNBC was investigated. It was identified that radiation inhibited the self‑renewal ability of TNBC stem cells by inhibiting cyclin D1 and protein kinase B (Akt1) phosphorylation. Let‑7d stimulates radiation‑induced tumor repression, exerting synergistic effects with radiotherapy on stem cell renewal. Through western blotting, immunofluorescence and a luciferase assay, it was identified that reduced cyclin D1/Akt1/wingless type MMTV integration site family member 1 (Wnt1) signaling activity accounts for the let‑7‑induced radiation sensitization. Let‑7 directly inhibits cyclin D1 expression, resulting in low phosphorylation of Akt1, which is critical for the let‑7‑induced inhibition of mammosphere numbers. The let‑7d‑induced Akt1 inhibition contributed to tumor repression, with similar results to those obtained with Akt inhibitors. Furthermore, it was identified that the inhibition of Wnt1 is critical for the functioning of let‑7d, and that addition of recombinant Wnt1 abolished the effects of let‑7d on sensitization to radiotherapy. Let‑7d is suggested to be a promising therapeutic agent in the treatment of TNBC by targeting CSCs and sensitizing tumors to radiotherapy via inhibition of cyclin D1/Akt1/Wnt1 signaling.

An Amphiphilic Peptide Induces Apoptosis Through the miR29b-p53 Pathway in Cancer Cells

Peptides have been in the limelight, as therapeutic agents for cancer treatment through various applications due to their high target selectivity and exceptional ability to penetrate the cell membrane. Recent studies have revealed that synthesized peptides bind to hairpin structures of RNA that affect their activities such as changing the efficacy of microRNA maturation. MicroRNA-mediated p53 activation by the microRNA-29 (miR29) family is one of the most important regulatory pathways in cancer therapeutics. By targeting the suppressors of p53, a tumor suppressor protein, miR29 induces apoptosis of cancer cells through p53 stabilization. Here, we identify a novel synthesized amphiphilic peptide, LK-L1C/K6W/L8C, which enhances expression of miR29b and promotes p53 activity. In the presence of LK-L1C/K6W/L8C, pre-miR29b preferentially forms a complex with the Dicer protein through interaction of LK-L1C/K6W/L8C with the terminal loop region of pre-miR29b, leading to an increase in Dicer processing. Furthermore, LK-L1C/K6W/L8C stimulates apoptosis by improving p53 stability in miR29-inducible HeLa and MCF7 cells. Collectively, our study shows that a peptide can directly influence the miR29b-mediated p53 activation pathway in cancer cells. Therefore, our findings provide the basis for a new, potentially promising peptide-based drug for cancer therapy.

Chemical modifications in the seed region of miRNAs 221/222 increase the silencing performances in gastrointestinal stromal tumor cells

Most GastroIntestinal Stromal Tumors (GISTs) are characterized by KIT gene overexpression, which in turn is regulated by levels of microRNA 221 and microRNA 222. GISTs can also be distinguished by their miRNAs expression profile in which miRNAs 221/222 result reduced in comparison with GI normal tissues. In this paper, to restore normal miRNAs levels and to improve the silencing performances of miRNAs 221/222, new miRNA mimics in which guide strands are modified by Phosphorothioate (PS) and/or 2'-O-methyl RNA (2'-OMe) inside and outside the seed region, were synthesized and tested in GIST48 cells. We evaluated the positional effect of the chemical modifications on the miRNAs silencing activity, compared to natural and several commercial miRNA mimics. Our results show that chemically modified miRNAs 221/222 with alternating 2'-OMe-PS and natural nucleotides in the seed region are effective inhibitors of KIT gene expression and exhibit increased stability in rat plasma. Besides, their transfection in GIST 48 cells showed significant effects on different cellular processes in which KIT plays a functional role for tumor development (such as migration, cell proliferation, and apoptosis). Therefore, modified miRNAs 221/222 may provide an alternative therapeutic option for GIST treatment also aimed to overcome drug resistance concerns.

Inflamma-miRs in Aging and Breast Cancer: Are They Reliable Players?

Human aging is characterized by chronic low-grade inflammation known as “inflammaging.” Persistent low-level inflammation also plays a key role in all stages of breast cancer since “inflammaging” is the potential link between cancer and aging through NF-kB pathways highly influenced by specific miRs. Micro-RNAs (miRNAs) are small non-coding RNAs that negatively regulate gene expression at a posttranscriptional level. Inflamma-miRs have been implicated in the regulation of immune and inflammatory responses. Their abnormal expression contributes to the chronic pro-inflammatory status documented in normal aging and major age-related diseases (ARDs), inflammaging being a significant mortality risk factor in both cases. Nevertheless, the correct diagnosis of inflammaging is difficult to make and its hidden contribution to negative health outcomes remains unknown. This methodological work flow was aimed at defining crucial unanswered questions about inflammaging that can be used to clarify aging-related miRNAs in serum and cell lines as well as their targets, thus confirming their role in aging and breast cancer tumorigenesis. Moreover, we aim to highlight the links between the pro-inflammatory mechanism underlying the cancer and aging processes and the precise function of certain miRNAs in cellular senescence (CS). In addition, miRNAs and cancer genes represent the basis for new therapeutic findings indicating that both cancer and ARDs genes are possible candidates involved in CS and vice versa. Our goal is to obtain a focused review that could facilitate future approaches in the investigation of the mechanisms by which miRNAs control the aging process by acting as efficient ARDs inflammatory biomarkers. An understanding of the sources and modulation of inflamma-miRs along with the identification of their specific target genes could enhance their therapeutic potential.

Microtargeting cancer metabolism: opening new therapeutic windows based on lipid metabolism

Metabolic reprogramming has emerged as a hallmark of cancer. MicroRNAs are noncoding RNAs that posttranscriptionally repress the expression of target mRNAs implicated in multiple physiological processes, including apoptosis, differentiation, and cancer. MicroRNAs can affect entire biological pathways, making them good candidates for therapeutic intervention compared with classical single target approaches. Moreover, microRNAs may become more relevant in the fine-tuning adaptation to stress situations, such as oncogenic events, hypoxia, nutrient deprivation, and oxidative stress. Furthermore, artificial microRNAs can be designed to modulate the expression of multiple targets of a specific pathway. In this review, we describe the metabolic reprogramming associated to cancer, with a special interest in the altered lipid metabolism. Next, we describe specific features of microRNAs that make them relevant to target cancer cell metabolism. Finally, in an attempt to open new therapeutic windows, we emphasize two exciting scenarios for microRNA-mediated intervention that need to be further explored: 1) the cooperation between FA biosynthesis (lipogenesis) and FA oxidation as complementary partners for the survival of cancer cells; and 2) the regulation of the intracellular lipid content modulating both lipid storage into lipid droplets, and lipid mobilization through lipolysis and/or lipophagy.

Down regulation of miR-202 modulates Mxd1 and Sin3A repressor complexes to induce apoptosis of pancreatic cancer cells

Aberrant regulation of microRNA expression in pancreatic cancers has been shown to play an important role in its inherent poor prognosis and malignant potential. MicroRNAs have also been shown to inhibit translation of genes by targeting the 3'-untranslated region (3-UTR) of mRNAs resulting in the inhibition of translation and often destruction of the mRNA. In the present study we investigated the role of the microRNA miR-202 in the apoptotic pathways of pancreatic cancer cells. The adamantyl-related molecule, 3-Cl-AHPC down-regulated expression of miR-202 and miR-578 resulting in the increased expression of mRNA and protein expression of their target genes, Max dimerization protein 1 (Mxd1/Mad1) and the Sin3A associated protein 18 (SAP18). Overexpression of pre-miR-202 led to diminished levels of Mxd1 and blocked the 3-Cl-AHPC-mediated increase in Mxd1 mRNA expression. The addition of the microRNA inhibitor 2'-O-methylated miR-202 enhanced the 3-Cl-AHPC-mediated increase of Mxd1 mRNA levels as well as 3-CI-AHPC-mediated apoptosis. We found increased Mxd1 bound to the Sin3A repressor protein complex through its increased binding with HDAC-2 and subsequently enhanced transcriptional repression in cells as evidenced by increased HDAC activity. Mxd1 also repressed human telomerase reverse transcriptase (hTERT) mRNA expression through its increased binding to the hTERT promoter site and resulted in decreased telomerase activity in cells. Our results demonstrate that down regulation of miR-202 increased the expression of its target Mxd1, followed by Mxd1 recruitment to the Sin3A repressor complex and through its dimerization with Max, and increased repression of Myc-Max target proteins.

Manipulating miRNA Expression: A Novel Approach for Colon Cancer Prevention and Chemotherapy

Small non-coding RNA has been implicated in the control of various cellular processes such as proliferation, apoptosis, and differentiation. About 50% of the miRNA genes are positioned in cancer-associated genomic regions. Several studies have shown that miRNA expression is deregulated in cancer and modulating their expression has reversed the cancer phenotype. Therefore, mechanisms to modulate microRNA (miRNA) activity have provided a novel opportunity for cancer prevention and therapy. In addition, a common cause for development of colorectal cancers is environmental and lifestyle factors. One such factor, diet has been shown to modulate miRNA expression in colorectal cancer patients. In this chapter, we will summarize the work demonstrating that miRNAs are novel promising drug targets for cancer chemoprevention and therapy. Improved delivery, increased stability and enhanced regulation of off-target effects will overcome the current challenges of this exciting approach in the field of cancer prevention and therapy.

MiR-200b expression in breast cancer: a prognostic marker and act on cell proliferation and apoptosis by targeting Sp1

MicroRNAs (miRNAs) have been identified as important post-transcriptional regulators involved in various biological and pathological processes of cells. In the present study, we investigated the roles and mechanisms of miR-200b in human breast cancer (BC). MiR-200b expression was carried out by qRT-PCR in human BC cell lines and clinical samples and the prognostic potential of miR-200b expression was further evaluated. In vitro, effects of miR-200b on BC cell proliferation, apoptosis and cell cycle distribution were tested by CCK-8 kit, flow cytometric analysis respectively. Luciferase assay and Western blot analysis were performed to validate the potential targets of miR-200b after the preliminary screening by employing open access software. We found that miR-200b was significantly down-regulated in both BC tissues and cell lines. The low expression of miR-200b was correlated with late TNM stage, negative oestrogen receptor and positive HER-2 status. Multivariate analysis showed that miR-200b expression was an independent prognostic predictor for BC patients. Integrated analysis identified Sp1 as a direct and functional target of miR-200b. Knockdown of Sp1 inhibited cell proliferation, induce apoptosis and act on cell cycle resembling that of miR-200b high expression. Our data demonstrates that miR-200b has potential to serve as prognostic biomarker and tumour suppressor for BC patients. As a direct and functional target of miR-200b, Sp1 and miR-200b both could be an exciting target for BC treatment strategy.

Advances in miRNA-Mediated Mucin Regulation

MicroRNAs (miRNAs) are an important class of small non-coding RNAs that direct post-transcriptional gene regulation by different mechanisms. Mounting evidences from numerous studies in the last decade have unraveled that deregulated miRNAs, and their cognate target expressions are strongly implicated in the carcinogenesis. Recent advances have highlighted miRNA-mediated regulation of mucins that have critical role in inflammation and cancer biology. The aberrant expression and differential glycosylation of mucins cause tumorigenesis, metastasis, chemoresistance and poor outcome of cancer patients, thus recognizing them as attractive therapeutic targets. Though current mucin-based therapies (antibodies, vaccines, immunotherapy, peptide inhibitors) have shown preclinical utility but only a handful promise for clinical transferability. In this context, understanding miRNA-mediated modulation of multiple mucin(s) expression and function gives a new hope for future anti-tumor therapeutics. Herein, we reviewed miRNA biogenesis, mechanism of action, and their role in tumor development. Further, we provide an overview of miRNA-mediated mucin regulation and their application as anticancer therapeutics.

miR-638 mediated regulation of BRCA1 affects DNA repair and sensitivity to UV and cisplatin in triple-negative breast cancer

Introduction

Triple-negative breast cancer (TNBC) represents 15 to 20% of all types of breast cancer; however, it accounts for a large number of metastatic cases and deaths, and there is still no effective treatment. The deregulation of microRNAs (miRNAs) in breast cancer has been widely reported. We previously identified that miR-638 was one of the most deregulated miRNAs in breast cancer progression. Bioinformatics analysis revealed that miR-638 directly targets BRCA1. The aim of this study was to investigate the role of miR-638 in breast cancer prognosis and treatment.

Methods

Formalin-fixed, paraffin-embedded (FFPE) breast cancer samples were microdissected into normal epithelial and invasive ductal carcinoma (IDC) cells, and total RNA was isolated. Several breast cancer cell lines were used for the functional analysis. miR-638 target genes were identified by TARGETSCAN-VERT 6.2 and miRanda. The expression of miR-638 and its target genes was analyzed by real-time qRT-PCR and Western blotting. Dual-luciferase reporter assay was employed to confirm the specificity of miR-638 target genes. The biological function of miR-638 was analyzed by MTT chemosensitivity, matrigel invasion and host cell reactivation assays.

Results

The expression of miR-638 was decreased in IDC tissue samples compared to their adjacent normal controls. The decreased miR-638 expression was more prevalent in non-TNBC compared with TNBC cases. miR-638 expression was significantly downregulated in breast cancer cell lines compared to the immortalized MCF-10A epithelial cells. BRCA1 was predicted as one of the direct targets of miR-638, which was subsequently confirmed by dual-luciferase reporter assay. Forced expression of miR-638 resulted in a significantly reduced proliferation rate as well as decreased invasive ability in TNBC cells. Furthermore, miR-638 overexpression increased sensitivity to DNA-damaging agents, ultraviolet (UV) and cisplatin, but not to 5-fluorouracil (5-FU) and epirubicin exposure in TNBC cells. Host cell reactivation assays showed that miR-638 reduced DNA repair capability in post UV/cisplatin-exposed TNBC cells. The reduced proliferation, invasive ability, and DNA repair capabilities are associated with downregulated BRCA1 expression.

Conclusions

Our findings suggest that miR-638 plays an important role in TNBC progression via BRCA1 deregulation. Therefore, miR-638 might serve as a potential prognostic biomarker and therapeutic target for breast cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-014-0435-5) contains supplementary material, which is available to authorized users.

Clinicopathological and prognostic implications of the miR-200 family in patients with epithelial ovarian cancer

The aim of the present study was to investigate the association of the expression of members in the miR-200 family with clinicopathological characteristics and their impacts on overall survival in patients with epithelial ovarian cancer (EOC). Expression levels of members in the miR-200 family, including miR-200a, miR-200b, miR-200c, miR-141, and miR-429, were detected by using miRNA qRT-PCR and in situ hybridization. Associations of their expression with clinicopathological factors and overall survival were statistically evaluated. Among five members in the miR-200 family, the expression levels of miR-200a, miR-200b and miR-200c were significantly higher in EOC tissues than those in normal surface ovarian epithelium tissues, in line with the findings ofin situ hybridization analysis. In addition, tumors with high miR-200a and miR-200 bexpressionwere both more likely to have advanced stage (both P=0.006) and higher grade (P=0.01 and 0.02), whilehighmiR-200 cexpression was onlysignificantly associated with advanced stage disease (P=0.01). Moreover, univariate analysis showed that the patients with high miR-200a, miR-200b and miR-200c expression all correlated with shorter overall survival in EOC patients (all P<0.001). Multivariate statistical analysis further identified miR-200a, miR-200b and miR-200c asindependent prognostic factorsfor EOC (all P=0.01). In conclusion, these findings suggest that miR-200a, miR-200b and miR-200c overexpression may promote the aggressive tumor progression and be recognized as reliable markers to predict the survival in patients with EOCs. The three miRNAs could be attractive therapeutic targets in patients with advanced-stage EOCs.