MicroRNA-21 targets the tumor suppressor gene tropomyosin 1 (TPM1)

Non-coding RNA as mediators in microenvironment–breast cancer cell communication

The tumor microenvironment has a critical role in the survival and decision of the cancer cells. These include support by enhanced angiogenesis, and metastasis or adaptation of dormancy. This article discusses methods by which the microenvironment sustains the tumor. This process is important as it will identify avenues of drug targets. Non-coding RNAs (ncRNAs) are evolving as key mediators in the interaction between the cancer cells and the microenvironment. Thus, the question is how to develop methods to effectively block the effects of the ncRNA and/or to introduce them to prevent metastasis, dormancy or to reverse dormancy. We focused on the advantages of using mesenchymal stem cells (MSCs) for RNA delivery. MSCs can be available as "off-the-shelf" cells. Thus far, MSCs are shown to be safe when transplanted across allogeneic barriers. We discussed the various methods by which MSCs can interact with cancer cells to deliver ncRNA or antagomirs. We also include the advances and possible confounds of using these methods. Overall, this review article provides a potential method by which MSCs can be used for effective delivery of nucleic acid to treat cancer.

Novel evidence for an oncogenic role of microRNA-21 in colitis-associated colorectal cancer

OBJECTIVE

miR-21 was found to be overexpressed in the colon tissues and serum of patients with UC and colorectal cancer (CRC); however, the exact roles of miR-21 in colitis-associated CRC remain unclear. The aim of our study was to investigate the biological mechanisms of miR-21 in colitis-associated colon cancer (CAC).

DESIGN

miR-21 expression was examined in the tumours of 62 patients with CRC from China and 37 colitis-associated neoplastic tissues from Japan and Austria. The biological functions of miR-21 were studied using a series of in vitro, in vivo and clinical approaches.

RESULTS

miR-21 levels were markedly upregulated in the tumours of 62 patients with CRC, 22 patients with CAC, and in a mouse model of CAC. Following azoxymethane and dextran sulfate sodium intervention, miR-21-knockout mice showed reduced expression of proinflammatory and procarcinogenic cytokines (interleukin (IL) 6, IL-23, IL-17A and IL-21) and a decrease in the size and number of tumours compared with the control mouse group. The absence of miR-21 resulted in the reduced expression of Ki67 and the attenuated proliferation of tumour cells with a simultaneous increase in E-cadherin and decrease in β-catenin and SOX9 in the tumours of CAC mice. Furthermore, the absence of miR-21 increased the expression of its target gene PDCD4 and subsequently modulated nuclear factor (NF)-κB activation. Meanwhile, miR-21 loss reduced STAT3 and Bcl-2 activation, causing an increase in the apoptosis of tumour cells in CAC mice.

CONCLUSIONS

These observations provide novel evidence for miR-21 blockade to be a key strategy in reducing CAC.

Emerging role of microRNA-21 in cancer

MicroRNAs (miRs) are a class of single-stranded RNA molecules of 15-27 nucleotides in length that regulate gene expression at the post-translational level. miR-21 is one of the earliest identified cancer-promoting 'oncomiRs', targeting numerous tumor suppressor genes associated with proliferation, apoptosis and invasion. The regulation of miR-21 and its role in carcinogenesis have been extensively investigated. Recent studies have focused on the diagnostic and prognostic value of miR-21 as well as its implication in the drug resistance of human malignancies. The further use of miR-21 as a biomarker and target for cancer treatments is likely to improve the outcome for patients with cancer. The present review highlights recent findings associated with the importance of miR-21 in hematological and non-hematological malignancies.

Expression of micrornas in molecular genetic breast cancer subtypes

BACKGROUND

It is shown that each type of human malignancies has a unique set of expressed miRNAs, and tumor-specific miRNAs in biological tissues of a patient are stable. The aim of this study was to determine the differences in the expression of miRNAs in tumor tissue of invasive breast carcinoma compared to normal tissue, as well as to analyze the variable expression of miRNAs in molecular genetic subtypes of breast cancer.

METHODS

We determined differences in mRNA expression in 35 biopsies of tumor tissue of various molecular genetic subtypes of breast cancer and 35 biopsies of adjacent conventionally normal breast tissue by RT-PCR in real time. We assessed the expression levels of miRNA-21, 221, 222, 155, 205, 20a , 125b and 200a.

RESULTS

A significant increase in the level of expression of the oncogenic miRNA-20a (p=0.000141) and miRNA-221 (p=0.037777) in the triple negative cancer in comparison with the luminal A and luminal B/HER2/neu-negative breast cancer subtypes was established. Assessment of significance of the results was conducted using ROC analysis. For miRNA-221 AUC value was 0.772, for miRNA-20a AUC value was 0.949. The obtained results suggest the possibility of using the levels of miRNA-21, 155, 205, 125b expression in tumor tissue to assess a malignant potential of a breast carcinoma. The levels of expression of oncogenic miRNA-221 and miRNA-20a are increased in TNBC compared with luminal A and luminal B/HER2/neu-negative breast cancer subtypes, supporting the characteristic of TNBC as the most aggressive subtype of breast cancer. MiRNA-20a is a marker of TNBC compared with luminal subtypes of breast cancer.

MICRO ABSTRACT

To identify markers for breast cancer with triple-negative phenotype, we evaluated expression levels of siRNA-21, 221, 222, 155, 205, 20a, 125b, 200a and 146b in the tumor tissue of 35 patients by RT-PCR. AUC value equal to 0.949 in the ROC-analysis allows us to recommend the miRNA-20a as a marker of triple negative breast cancer to differentiate it from the luminal subtypes.

Prognostic role of microRNA-21 expression in gliomas: a meta-analysis

MicroRNA-21 (miRNA-21) has recently been shown to be a promising prognostic tumor biomarker. However, few studies have not supported this idea and have shown inconsistent data. Thus, we conducted a meta-analysis to elucidate the predictive value of miRNA-21 in gliomas. The relevant studies were identified by performing online search in PubMed, EMBASE and Web of Science databases up to Apr 2016. This meta-analysis study included seven eligible studies, consisting of 1121 gliomas and 533 glioblastoma multiforme (GBM) patients. Heterogeneity between studies was assessed using Egger's and Begg's test. Hazard ratios (HRs) with 95 % confidence intervals (CIs) for overall survival (OS), which compared the expression levels of miRNA-21 in patients with gliomas, were extracted and estimated. Our analysis revealed that the high expression of miRNA-21 is associated with the worse OS in gliomas. Further subgroup analysis indicated that increased expression of miRNA-21 was also associated with OS in GBM patients. Moreover, we observed a correlation between miRNA-21 expression and the World Health Organization defined gliomas grading system (WHO grade). Besides, high miRNA-21 expression was significantly correlated with lowered OS both in the Asian group and non-Asian group. In the cut-off subgroup analysis, both mean cut off value and median cut off value were significantly associated with OS. The expression level of miRNA-21 was not high in low KPS (Karnofsky score) group. miRNA-21 appears to be a promising biomarker for predicting the progression of patients with gliomas or GBM. However, due to the limited sample size, further prospective or retrospective multi-center well designed studies with adequate sample size should be conducted to verify its definite prognostic value.

MicroRNA-21 Increases Proliferation and Cisplatin Sensitivity of Osteosarcoma-Derived Cells

Osteosarcoma is the most common primary bone tumor and poor prognosis for osteosarcoma patients is mainly due to chemotherapy resistance. MicroRNAs are important to maintain pathophysiological mechanisms of cancer and influence cell sensitivity to chemotherapy. In this study, we tested the functions of microRNA-21 for malignant features as well as for drug resistance of osteosarcoma. We used Northern blot to measure microRNA-21 levels in osteosarcoma-derived cell lines. MicroRNA-21 activity was modulated by either expressing a sponge to decrease its activity in an osteosarcoma-derived cell line expressing high levels of microRNA-21 or by introducing pri-microRNA-21 in a cell line with low endogenous levels. Cell migration was determined in a scratch assay and cell proliferation was measured by performing growth curve analysis. Sensitivity of the cells towards chemotherapeutics was investigated by performing cell viability assays and calculating the IC50 values. While cell migration was unaffected by modulated microRNA-21 levels, microRNA-21 inhibition slowed proliferation and exogenously expressed microRNA-21 promoted this process. Modulated microRNA-21 activity failed to effect sensitivity of osteosarcoma-derived cell lines to doxorubicin or methotrexate. Contrarily, reduction of microRNA-21 activity resulted in enhanced resistance towards cisplatin while ectopic expression of microRNA-21 showed the opposite effect. Increased microRNA-21 levels repressed the expression of Sprouty2 and ectopic expression of Sprouty2 was able to largely rescue the observed effects of microRNA-21 in osteosarcoma. In summary, our data indicate that in osteosarcoma microRNA-21 expression is an important component for regulation of cell proliferation and for determining sensitivity to cisplatin.

MicroRNAs in glioblastoma multiforme pathogenesis and therapeutics

Glioblastoma multiforme (GBM) is the most common and lethal cancer of the adult brain, remaining incurable with a median survival time of only 15 months. In an effort to identify new targets for GBM diagnostics and therapeutics, recent studies have focused on molecular phenotyping of GBM subtypes. This has resulted in mounting interest in microRNAs (miRNAs) due to their regulatory capacities in both normal development and in pathological conditions such as cancer. miRNAs have a wide range of targets, allowing them to modulate many pathways critical to cancer progression, including proliferation, cell death, metastasis, angiogenesis, and drug resistance. This review explores our current understanding of miRNAs that are differentially modulated and pathologically involved in GBM as well as the current state of miRNA-based therapeutics. As the role of miRNAs in GBM becomes more well understood and novel delivery methods are developed and optimized, miRNA-based therapies could provide a critical step forward in cancer treatment.

MicroRNAs in extracellular vesicles: potential cancer biomarkers

Extracellular vesicles (EV) are small membrane-bound structures that are secreted by various cell types, including tumor cells. Recent studies have shown that EVs are important for cell-to-cell communication, locally and distantly; horizontally transferring DNA, mRNA, microRNA (miRNA), proteins and lipids. In the context of cancer biology, tumor-derived EVs are capable of modifying the microenvironment, promoting tumor progression, immune evasion, angiogenesis and metastasis. miRNAs contained within EVs are functionally associated with cancer progression, metastasis and aggressive tumor phenotypes. These factors, along with their stability in bodily fluids, have led to extensive investigations on the potential role of circulating EV-derived miRNAs as tumor biomarkers. In this review, we summarize the current understanding of circulating EV miRNAs in human cancer, and discuss their clinical utility and challenges in functioning as biomarkers.

Tissue microRNA-21 expression predicted recurrence and poor survival in patients with colorectal cancer - a meta-analysis

OBJECTIVE

MicroRNA-21 (miR-21) has been shown to play an important role in cancer prognosis. We performed a meta-analysis to evaluate the prognostic effect of miR-21 from tissues and serum on survival of the patients with colorectal cancer (CRC).

METHODS

Relevant studies were identified by searching PubMed, Embase, and Cochrane Library. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) of total and subgroup analyses, for overall survival (OS) and disease-free survival (DFS), were calculated to investigate the association between miR-21 expression and CRC prognosis.

RESULTS

Our analysis included eleven studies (3,669 subjects). In addition, four studies explored the association between miR-21 and DFS, and ten studies focused on the prognostic value of miR-21 for OS. Our results indicated that increased miR-21 expression of tissues predicted both poor DFS and OS in patients with CRC (DFS: HR =1.59, 95% CI =1.20-2.10; OS: HR =1.53, 95% CI =1.23-1.90). Consistent results were observed among colon cancer and quantitative real-time polymerase chain reaction subgroups.

CONCLUSION

Meta-analysis indicated that miR-21 predicted recurrence and poor survival in patients with CRC. miR-21 may be more suitable to predict cancer prognosis in colon cancer patients.

Targeting oncomiRNAs and mimicking tumor suppressor miRNAs: Νew trends in the development of miRNA therapeutic strategies in oncology (Review)

MicroRNA (miRNA or miR) therapeutics in cancer are based on targeting or mimicking miRNAs involved in cancer onset, progression, angiogenesis, epithelial-mesenchymal transition and metastasis. Several studies conclusively have demonstrated that miRNAs are deeply involved in tumor onset and progression, either behaving as tumor-promoting miRNAs (oncomiRNAs and metastamiRNAs) or as tumor suppressor miRNAs. This review focuses on the most promising examples potentially leading to the development of anticancer, miRNA-based therapeutic protocols. The inhibition of miRNA activity can be readily achieved by the use of miRNA inhibitors and oligomers, including RNA, DNA and DNA analogues (miRNA antisense therapy), small molecule inhibitors, miRNA sponges or through miRNA masking. On the contrary, the enhancement of miRNA function (miRNA replacement therapy) can be achieved by the use of modified miRNA mimetics, such as plasmid or lentiviral vectors carrying miRNA sequences. Combination strategies have been recently developed based on the observation that i) the combined administration of different antagomiR molecules induces greater antitumor effects and ii) some anti-miR molecules can sensitize drug-resistant tumor cell lines to therapeutic drugs. In this review, we discuss two additional issues: i) the combination of miRNA replacement therapy with drug administration and ii) the combination of antagomiR and miRNA replacement therapy. One of the solid results emerging from different independent studies is that miRNA replacement therapy can enhance the antitumor effects of the antitumor drugs. The second important conclusion of the reviewed studies is that the combination of anti-miRNA and miRNA replacement strategies may lead to excellent results, in terms of antitumor effects.

A Tumor-specific MicroRNA Recognition System Facilitates the Accurate Targeting to Tumor Cells by Magnetic Nanoparticles

Targeted therapy for cancer is a research area of great interest, and magnetic nanoparticles (MNPs) show great potential as targeted carriers for therapeutics. One important class of cancer biomarkers is microRNAs (miRNAs), which play a significant role in tumor initiation and progression. In this study, a cascade recognition system containing multiple plasmids, including a Tet activator, a lacI repressor gene driven by the TetOn promoter, and a reporter gene repressed by the lacI repressor and influenced by multiple endogenous miRNAs, was used to recognize cells that display miRNA signals that are characteristic of cancer. For this purpose, three types of signal miRNAs with high proliferation and metastasis abilities were chosen (miR-21, miR-145, and miR-9). The response of this system to the human breast cancer MCF-7 cell line was 3.2-fold higher than that to the human breast epithelial HBL100 cell line and almost 7.5-fold higher than that to human embryonic kidney HEK293T cells. In combination with polyethyleneimine-modified MNPs, this recognition system targeted the tumor location in situ in an animal model, and an ~42% repression of tumor growth was achieved. Our study provides a new combination of magnetic nanocarrier and gene therapy based on miRNAs that are active in vivo, which has potential for use in future cancer therapies.

Tiny giants of gene regulation: experimental strategies for microRNA functional studies

The discovery over two decades ago of short regulatory microRNAs (miRNAs) has led to the inception of a vast biomedical research field dedicated to understanding these powerful orchestrators of gene expression. Here we aim to provide a comprehensive overview of the methods and techniques underpinning the experimental pipeline employed for exploratory miRNA studies in animals. Some of the greatest challenges in this field have been uncovering the identity of miRNA-target interactions and deciphering their significance with regard to particular physiological or pathological processes. These endeavors relied almost exclusively on the development of powerful research tools encompassing novel bioinformatics pipelines, high-throughput target identification platforms, and functional target validation methodologies. Thus, in an unparalleled manner, the biomedical technology revolution unceasingly enhanced and refined our ability to dissect miRNA regulatory networks and understand their roles in vivo in the context of cells and organisms. Recurring motifs of target recognition have led to the creation of a large number of multifactorial bioinformatics analysis platforms, which have proved instrumental in guiding experimental miRNA studies. Subsequently, the need for discovery of miRNA-target binding events in vivo drove the emergence of a slew of high-throughput multiplex strategies, which now provide a viable prospect for elucidating genome-wide miRNA-target binding maps in a variety of cell types and tissues. Finally, deciphering the functional relevance of miRNA post-transcriptional gene silencing under physiological conditions, prompted the evolution of a host of technologies enabling systemic manipulation of miRNA homeostasis as well as high-precision interference with their direct, endogenous targets. For further resources related to this article, please visit the WIREs website.

New Concepts in Cancer Biomarkers: Circulating miRNAs in Liquid Biopsies

The effective and efficient management of cancer patients relies upon early diagnosis and/or the monitoring of treatment, something that is often difficult to achieve using standard tissue biopsy techniques. Biological fluids such as blood hold great possibilities as a source of non-invasive cancer biomarkers that can act as surrogate markers to biopsy-based sampling. The non-invasive nature of these “liquid biopsies” ultimately means that cancer detection may be earlier and that the ability to monitor disease progression and/or treatment response represents a paradigm shift in the treatment of cancer patients. Below, we review one of the most promising classes of circulating cancer biomarkers: microRNAs (miRNAs). In particular, we will consider their history, the controversy surrounding their origin and biology, and, most importantly, the hurdles that remain to be overcome if they are really to become part of future clinical practice.

Expression of tropomyosin 2 gene isoforms in human breast cancer cell lines

In humans, four tropomyosin genes (TPM1, TPM2, TPM3, and TPM4) are known to produce a multitude of isoforms via alternate splicing and/or using alternate promoters. Expression of tropomyosin has been shown to be modulated at both the transcription and the translational levels. Tropomyosins are known to make up some of the stress fibers of human epithelial cells and differences in their expression has been demonstrated in malignant breast epithelial cell lines compared to 'normal' breast cell lines. We have recently reported the expression of four novel TPM1 isoforms (TPM1λ, TPM1µ, TPM1ν, and TPM1ξ) from human malignant tumor breast cell lines that are not expressed in adult and fetal cardiac tissue. Also, we evaluated their expression in relation to the stress fiber formation. In this study, nine malignant breast epithelial cell lines and three 'normal' breast cell lines were examined for stress fiber formation and expression of tropomyosin 2 (TPM2) isoform-specific RNAs and proteins. Stress fiber formation was assessed by immunofluorescence using Leica AF6000 Deconvolution microscope. Stress fiber formation was strong (++++) in the 'normal' cell lines and varied among the malignant cell lines (negative to +++). No new TPM2 gene RNA isoforms were identified, and TPM2β was the most frequently expressed TPM2 RNA and protein isoform. Stress fiber formation positively correlated with TPM2β RNA or protein expression at high, statistically significant degrees. Previously, we had shown that TPM1δ and TPM1λ positively and inversely, respectively, correlated with stress fiber formation. The most powerful predictor of stress fiber formation was the combination of TPM2β RNA, TPM1δ RNA, and the inverse of TPM1λ RNA expression. Our results suggest that the increased expression of TPM1λ and the decreased expression of TPM1δ RNA and TPM2β may lead to decreased stress fiber formation and malignant transformation in human breast epithelial cells.

Considering Exosomal miR-21 as a Biomarker for Cancer

Cancer is a fatal human disease. Early diagnosis of cancer is the most effective method to prevent cancer development and to achieve higher survival rates for patients. Many traditional diagnostic methods for cancer are still not sufficient for early, more convenient and accurate, and noninvasive diagnosis. Recently, the use of microRNAs (miRNAs), such as exosomal microRNA-21(miR-21), as potential biomarkers was widely reported. This initial systematic review analyzes the potential role of exosomal miR-21 as a general biomarker for cancers. A total of 10 studies involving 318 patients and 215 healthy controls have covered 10 types of cancers. The sensitivity and specificity of pooled studies were 75% (0.70–0.80) and 85% (0.81–0.91), with their 95% confidence intervals (CIs), while the area under the summary receiver operating characteristic curve (AUC) was 0.93. Additionally, we examined and evaluated almost all other issues about biomarkers, including cutoff points, internal controls and detection methods, from the literature. This initial meta-analysis indicates that exosomal miR-21 has a strong potential to be used as a universal biomarker to identify cancers, although as a general biomarker the case number for each cancer type is small. Based on the literature, a combination of miRNA panels and other cancer antigens, as well as a selection of appropriate internal controls, has the potential to serve as a more sensitive and accurate cancer diagnosis tool. Additional information on miR-21 would further support its use as a biomarker in cancer.

Relevance of miR-21 in regulation of tumor suppressor gene PTEN in human cervical cancer cells

BACKGROUND

Expression of the microRNA miR-21 has been found to be altered in almost all types of cancers and it has been classified as an oncogenic microRNA or oncomir. Due to the critical functions of its target proteins in various signaling pathways, miR-21 is an attractive target for genetic and pharmacological modulation in various cancers. Cervical cancer is the second most common cause of death from cancer in women worldwide and persistent HPV infection is the main etiologic agent. This malignancy merits special attention for the development of new treatment strategies. In the present study we analyze the role of miR-21 in cervical cancer cells.

METHODS

To identify the downstream cellular target genes of upstream miR-21, we silenced endogenous miR-21 expression in a cervical intraepithelial neoplasia-derived cell lines using siRNAs. The effect of miR-21 on gene expression was assessed in cervical cancer cells transfected with the siRNA expression plasmid pSIMIR21. We identified the tumor suppressor gene PTEN as a target of miR-21 and determined the mechanism of its regulation throughout reporter construct plasmids. Using this model, we analyzed the expression of miR-21 and PTEN as well as functional effects such as autophagy and apoptosis induction.

RESULTS

In SiHa cells, there was an inverse correlation between miR-21 expression and PTEN mRNA level as well as PTEN protein expression in cervical cancer cells. Transfection with the pSIMIR21 plasmid increased luciferase reporter activity in construct plasmids containing the PTEN-3'-UTR microRNA response elements MRE21-1 and MRE21-2. The role of miR-21 in cell proliferation was also analyzed in SiHa and HeLa cells transfected with the pSIMIR21 plasmid, and tumor cells exhibited markedly reduced cell proliferation along with autophagy and apoptosis induction.

CONCLUSIONS

We conclude that miR-21 post-transcriptionally down-regulates the expression of PTEN to promote cell proliferation and cervical cancer cell survival. Therefore, it may be a potential therapeutic target in gene therapy for cervical cancer.

miRNA-21 as a novel therapeutic target in lung cancer

Lung cancer is a leading cause of cancer death, and late diagnosis is one of the most important reasons for the high mortality rate. microRNAs (miRNAs) are key players in gene regulation and therefore in tumorigenesis. As far as lung carcinogenesis is concerned, miRNAs open novel fields in biomarker research, in diagnosis, and in therapy. In this review we focus on miR-21 in lung cancer and especially on how miR-21 is involved 1) as a biomarker in response or resistance to therapy or 2) as a therapeutic target.

MicroRNA-206, let-7a and microRNA-21 pathways involved in the anti-angiogenesis effects of the interval exercise training and hormone therapy in breast cancer

AIMS

MicroRNAs (miRNAs) are the targeting signal-transduction pathways that can mediate tumorigenesis via their down and/or up-regulation. For example, miR-21 and miR-206 can effect on the tumor angiogenesis as an oncomir and a tumor suppressor, respectively.

MATERIALS AND METHODS

The present study is aimed to investigate the effects of the interval exercise training in combination with tamoxifen and/or letrozole on miR-21, miR-206 and let-7 as well as their underlying pathways in regard to tumor angiogenesis in sixty four mice with breast tumor. ELISA, immunohistochemistry, qRT-PCR assays were performed accomplish the study.

KEY FINDINGS

The results showed that the tumor size was significantly declined in the exercise training, tamoxifen and letrozole groups compared to tumor group. Mir-206 and let-7 were up-regulated, and mir-21 expression was down-regulated in the exercise training compared to tumor group. Exercise training decreased the expression of ER-α, HIF-α, VEGF, CD31 and Ki67 in tumor tissue. The combination tamoxifen and/or letrozole with the exercise training could down-regulate the expression of ERα, miR-21, HIF-1α, TNF-α, CD31, Ki67 and VEGF, and up-regulate the expression of miR-206, PDCD-4, let-7 and IL-10 that led to reducing the angiogenesis and tumor growth.

SIGNIFICANCE

Our results showed that miR-21, miR-206 and let-7a pathways may involve in the anti-angiogenesis effects of the interval exercise training with hormone therapy in mice model of breast tumor.

An update on sputum MicroRNAs in lung cancer diagnosis

Lung cancer is one of the leading cause of cancer mortality in the world. It is well known that genetic damages could result in lung tumor genesis. Despite years of research, the survival rate of the patients has not been markedly improved. According to lack of high sensitivity and specificity in diagnostic tests, just about 15-20% of lung cancer cases are discovered prior to progression of the disease. In last decade, sputum biomarkers have been developed for early detection/diagnosis of lung cancer. MicroRNAs are a class of small endogenous noncoding RNAs, which act as post-transcriptional regulators. Some specific miRNAs can have multifunctions in lung development and their aberrant expression could induce lung tumor genesis. The differences in miRNAs between the normal and cancerous lung lead to emerging of a novel type of biomarkers, which can be helpful in screening of high risk individuals, diagnosis of lung cancer as well as its therapy.

microRNA-449a functions as a tumor suppressor in neuroblastoma through inducing cell differentiation and cell cycle arrest

microRNA-449a (miR-449a) has been identified to function as a tumor suppressor in several types of cancers. However, the role of miR-449a in neuroblastoma has not been intensively investigated. We recently found that the overexpression of miR-449a significantly induces neuroblastoma cell differentiation, suggesting its potential tumor suppressor function in neuroblastoma. In this study, we further investigated the mechanisms underlying the tumor suppressive function of miR-449a in neuroblastoma. We observed that miR-449a inhibits neuroblastoma cell survival and growth through 2 mechanisms--inducing cell differentiation and cell cycle arrest. Our comprehensive investigations on the dissection of the target genes of miR-449a revealed that 3 novel targets- MFAP4, PKP4 and TSEN15 -play important roles in mediating its differentiation-inducing function. In addition, we further found that its function in inducing cell cycle arrest involves down-regulating its direct targets CDK6 and LEF1. To determine the clinical significance of the miR-449a-mediated tumor suppressive mechanism, we examined the correlation between the expression of these 5 target genes in neuroblastoma tumor specimens and the survival of neuroblastoma patients. Remarkably, we noted that high tumor expression levels of all the 3 miR-449a target genes involved in regulating cell differentiation, but not the target genes involved in regulating cell cycle, are significantly correlated with poor survival of neuroblastoma patients. These results suggest the critical role of the differentiation-inducing function of miR-449a in determining neuroblastoma progression. Overall, our study provides the first comprehensive characterization of the tumor-suppressive function of miR-449a in neuroblastoma, and reveals the potential clinical significance of the miR-449a-mediated tumor suppressive pathway in neuroblastoma prognosis.

MicroRNA-21 expression and its pathogenetic significance in cutaneous melanoma

Identification of prognostic biomarkers is timely for melanoma as clinicians seek ways to stratify patients for molecular therapy. MicroRNAs are promising as tissue biomarkers because they can be assayed directly from formalin-fixed paraffin-embedded clinical samples. We previously reported that microRNA-21 (miR-21) was strongly expressed in melanoma relative to naevi and now sought to further assess the significance of this by assessing its relationship with its putative target, PTEN. Clinical melanoma samples were analysed by immunohistochemical analysis for PTEN, stem-loop qRT-PCR for miR-21 and PCR for BRAF/NRAS mutation status. Cell lines were investigated for the effect of anti-miR-21 on PTEN. A total of 81 clinical melanocytic tumour samples were investigated, with uniformly high PTEN expression in the nucleus and cytoplasm of naevi and with preferential loss of PTEN expression in the nucleus of melanoma cells. miR-21 expression was inversely associated with nuclear PTEN expression but not with cytoplasmic PTEN expression. An anti-miR-21 preferentially altered nuclear PTEN in melanoma cell lines. The presence of a BRAF or NRAS mutation had no significant effect on miR-21 expression. These data suggest miR-21 may exert an oncogenic effect in melanoma by favouring redistribution of PTEN to the nucleus.

Study of microRNAs-21/221 as potential breast cancer biomarkers in Egyptian women

microRNAs (miRNAs) play an important role in cancer prognosis. They are small molecules, approximately 17-25 nucleotides in length, and their high stability in human serum supports their use as novel diagnostic biomarkers of cancer and other pathological conditions. In this study, we analyzed the expression patterns of miR-21 and miR-221 in the serum from a total of 100 Egyptian female subjects with breast cancer, fibroadenoma, and healthy control subjects. Using microarray-based expression profiling followed by real-time polymerase chain reaction validation, we compared the levels of the two circulating miRNAs in the serum of patients with breast cancer (n=50), fibroadenoma (n=25), and healthy controls (n=25). The miRNA SNORD68 was chosen as the housekeeping endogenous control. We found that the serum levels of miR-21 and miR-221 were significantly overexpressed in breast cancer patients compared to normal controls and fibroadenoma patients. Receiver Operating Characteristic (ROC) curve analysis revealed that miR-21 has greater potential in discriminating between breast cancer patients and the control group, while miR-221 has greater potential in discriminating between breast cancer and fibroadenoma patients. Classification models using k-Nearest Neighbor (kNN), Naïve Bayes (NB), and Random Forests (RF) were developed using expression levels of both miR-21 and miR-221. Best classification performance was achieved by NB Classification models, reaching 91% of correct classification. Furthermore, relative miR-221 expression was associated with histological tumor grades. Therefore, it may be concluded that both miR-21 and miR-221 can be used to differentiate between breast cancer patients and healthy controls, but that the diagnostic accuracy of serum miR-21 is superior to miR-221 for breast cancer prediction. miR-221 has more diagnostic power in discriminating between breast cancer and fibroadenoma patients. The overexpression of miR-221 has been associated with the breast cancer grade. We also demonstrated that the combined expression of miR-21 and miR-221can be successfully applied as breast cancer biomarkers.

MicroRNAs: promising biomarkers for diagnosis and therapeutic targets in human colorectal cancer metastasis

Colorectal cancer (CRC) is the third most common cancer and the fourth most common cause of cancer-related death worldwide. Distant metastasis is a major cause of mortality in CRC. MicroRNAs (miRNAs) are small non-coding RNA molecules involved in the post-transcriptional and translational regulation of gene expression. Many miRNAs are aberrantly expressed in cancer and influence tumor progression. Accumulating studies suggest that multiple miRNAs are actively involved in the CRC metastasis process. Thus, we aim to introduce the role of miRNAs in multi-steps of CRC metastasis, including cancer cell invasion, intravasation, circulation, extravasation, colonization, angiogenesis, and epithelial-mesenchymal transition (EMT). Moreover, we suggest the potential application of miRNAs as biomarkers for CRC patients with metastasis. [BMB Reports 2015; 48(4): 217-222]

Non-coding RNAs in Mammary Gland Development and Disease

Non-coding RNAs (ncRNAs) are untranslated RNA molecules that function to regulate the expression of numerous genes and associated biochemical pathways and cellular functions. NcRNAs include small interfering RNAs (siRNAs), microRNAs (miRNAs), PIWI-interacting RNAs (piRNAs), small nucleolar RNAs (snoRNAs) and long non-coding RNAs (lncRNAs). They participate in the regulation of all developmental processes and are frequently aberrantly expressed or functionally defective in disease. This Chapter will focus on the role of ncRNAs, in particular miRNAs and lncRNAs, in mammary gland development and disease.

miR-203 promotes proliferation, migration and invasion by degrading SIK1 in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDA) is among the most lethal human cancers and it is insensitive to many chemotherapeutic drugs. The molecular basis of pancreatic cancer remains to be elucidated. Investigations into the molecular mechanism involved in the development and progression as well as drug resistance of the disease may be useful to understand the pathogenesis and progression of the disease and offer new targets for effective therapies. In the present study, we showed that salt-inducible kinase 1 (SIK1) was downregulated and loss of SIK1 was associated with gemcitabine resistance in pancreatic cancer. In pancreatic cancer cells, SIK1 inhibited proliferation, migration and invasion. An analysis of potential microRNA target sites was performed using the prediction algorithms, miRanda, TargetScan and PicTar. The three algorithms predicted that miR-203 is capable of targeting 3'UTR of SIK1. Subsequent experiments confirmed the prediction. In addition, the results showed that miR-203 promotes proliferation, migration and invasion in pancreatic cancer cells, whereas the restoration of SIK1 abrogated the regulation of pre-miR‑203-mediated proliferation, migration and invasion.

MicroRNAs in diffuse large B-cell lymphoma

The aberrant expression of microRNAs (miRs) has a significant impact on the biological characteristics of lymphocytes, and is important in the pathogenesis of diffuse large B-cell lymphoma (DLBCL). It has been demonstrated, using miR profiling and detecting distinct miR signatures, that certain miRs may accurately distinguish different subtypes and prognostic classifications of DLBCL, as well as distinguish DLBCL from other more indolent lymphomas, including follicular lymphoma. miRs are excellent biomarkers for cancer diagnosis and prognosis. In DLBCL, specific miR expression profiles in the tissues of patients are associated with prognosis and clinical outcome. Over the past decade, there has been substantial investigation concerning the pathogenetic, diagnostic and prognostic roles of miRs in DLBCL. The aim of the present review is to describe the aberrant expression of miRs in DLBCL, and the functions, potential clinical use and possible therapeutic targets of miRs in this disease.

Canine Mammary Carcinomas: A Comparative Analysis of Altered Gene Expression

Breast cancer represents the second most frequent neoplasm in humans and sexually intact female dogs after lung and skin cancers, respectively. Many similar features in human and dog cancers including, spontaneous development, clinical presentation, tumor heterogeneity, disease progression and response to conventional therapies have supported development of this comparative model as an alternative to mice. The highly conserved similarities between canine and human genomes are also key to this comparative analysis, especially when compared to the murine genome. Studies with canine mammary tumor (CMT) models have shown a strong genetic correlation with their human counterparts, particularly in terms of altered expression profiles of cell cycle regulatory genes, tumor suppressor and oncogenes and also a large group of non-coding RNAs or microRNAs (miRNAs). Because CMTs are considered predictive intermediate models for human breast cancer, similarities in genetic alterations and cancer predisposition between humans and dogs have raised further interest. Many cancer-associated genetic defects critical to mammary tumor development and oncogenic determinants of metastasis have been reported and appear to be similar in both species. Comparative analysis of deregulated gene sets or cancer signaling pathways has shown that a significant proportion of orthologous genes are comparably up- or down-regulated in both human and dog breast tumors. Particularly, a group of cell cycle regulators called cyclin-dependent kinase inhibitors (CKIs) acting as potent tumor suppressors are frequently defective in CMTs. Interestingly, comparative analysis of coding sequences has also shown that these genes are highly conserved in mammals in terms of their evolutionary divergence from a common ancestor. Moreover, co-deletion and/or homozygous loss of the INK4A/ARF/INK4B (CDKN2A/B) locus, encoding three members of the CKI tumor suppressor gene families (p16/INK4A, p14ARF and p15/INK4B), in many human and dog cancers including mammary carcinomas, suggested their important conserved genetic order and localization in orthologous chromosomal regions. miRNAs, as powerful post-transcriptional regulators of most of the cancer-associated genes, have not been well evaluated to date in animal cancer models. Comprehensive expression profiles of miRNAs in CMTs have revealed their altered regulation showing a strong correlation with those found in human breast cancers. These genetic correlations between human and dog mammary cancers will greatly advance our understanding of regulatory mechanisms involving many critical cancer-associated genes that promote neoplasia and contribute to the promising development of future therapeutics.

MicroRNA-205 increases the sensitivity of docetaxel in breast cancer

Chemotherapy has been widely used in breast cancer therapy, but the efficacy of chemotherapy is intimately associated with the sensitivity of therapeutic drugs to breast cancer. Docetaxel is a first-line chemotherapeutic drug in breast cancer treatment, but further improvement to its efficacy has thus far proved difficult. microRNAs (miRs) are a class of endogenous, small, non-coding RNAs, which regulate gene expression at the post-transcriptional level. miR-205, a regulator of HER-3, is reported to be a tumor suppressor in breast cancer. In the present study, the reintroduction of miR-205 is shown to inhibit cell proliferation and clonogenic potential, and increase the sensitivity of MCF-7 and MDA-MB-231 cells to docetaxel. miR-205 also shows a synergistic effect with docetaxel in vivo. The present study provides a novel strategy to increase the sensitivity to docetaxel in breast cancer patients.

Relevance of Rabbit VX2 Tumor Model for Studies on Human Hepatocellular Carcinoma: A MicroRNA-Based Study

MicroRNAs are small (~22 nt), noncoding RNA molecules that have critical cellular functions in proliferation, differentiation, angiogenesis and apoptosis. miRNA expression profiling has been used to create signatures of solid tumors and, in many cases, it has been shown to correlate with the severity of the disease. The rabbit VX2 tumor model has been used widely to study a number of human cancers. Our objective in this study is to generate an miRNA signature of the VX2 tumor and to identify miRNAs that are highly expressed in this aggressive tumor. In this study, we performed miRNA profiling of the rabbit VX2 tumor using a microarray that has probes for 1292 unique miRNAs. Their expression in tumor samples was quantified and analyzed. We found that 35 miRNAs were significantly up-regulated in the VX2 tumor. Among these, 13 human miRNAs and eight members of the let-7 family were previously identified in cancers. In addition, we show that the expression of three miRNAs (miR-923, miR-1275, and miR-1308) is novel for the rabbit VX2 tumor, and their expression was not previously shown to be associated with any type of cancer. For the first time, we show the miRNA signature profile for a solid tumor in a rabbit model. miRNAs highly expressed in the VX2 tumor may serve as novel candidates for molecular biomarkers and as potential drug targets.

A multi-targeted approach to suppress tumor-promoting inflammation

Cancers harbor significant genetic heterogeneity and patterns of relapse following many therapies are due to evolved resistance to treatment. While efforts have been made to combine targeted therapies, significant levels of toxicity have stymied efforts to effectively treat cancer with multi-drug combinations using currently approved therapeutics. We discuss the relationship between tumor-promoting inflammation and cancer as part of a larger effort to develop a broad-spectrum therapeutic approach aimed at a wide range of targets to address this heterogeneity. Specifically, macrophage migration inhibitory factor, cyclooxygenase-2, transcription factor nuclear factor-κB, tumor necrosis factor alpha, inducible nitric oxide synthase, protein kinase B, and CXC chemokines are reviewed as important antiinflammatory targets while curcumin, resveratrol, epigallocatechin gallate, genistein, lycopene, and anthocyanins are reviewed as low-cost, low toxicity means by which these targets might all be reached simultaneously. Future translational work will need to assess the resulting synergies of rationally designed antiinflammatory mixtures (employing low-toxicity constituents), and then combine this with similar approaches targeting the most important pathways across the range of cancer hallmark phenotypes.

Role of deregulated microRNAs in non-small cell lung cancer progression using fresh-frozen and formalin-fixed, paraffin-embedded samples

Non-small cell lung cancer (NSCLC) is responsible for the highest number of cancer-associated mortalities worldwide, and the five-year survival rate is <15% following the initial diagnosis. MicroRNAs (miRNAs) serve important functions in a number of human diseases, including cancer. The present study investigated the expression status, clinical relevance and functional role of miRNA in NSCLC. miRNA expression profiling was performed in lung adenocarcinoma and adjacent unaffected lung tissues using 47 groups of fresh-frozen (FF) and 45 of formalin-fixed, paraffin-embedded (FFPE) samples from 11 pulmonary bulla. miR-21, -30e, -363 and -623 were further examined for differential expression in two independent cohorts. Other miRNAs, including miR-5100 and miR-650, were upregulated, while miR-10a and -26b were downregulated in FF NSCLC tissues. The associations between these miRNAs and their clinicopathological features were also investigated. miR-363, -10a and -145 were associated with lymph node status (P=0.002, 0.005 and 0.007, respectively) and miR-650 and -145 were associated with differentiation (P=0.01 and 0.05, respectively). No associations were identified for the other miRNAs examined. In the FFPE NSCLC samples, miR-30e-5p correlated with the differentiation of the tissue (P=0.011). The present study indicates that these miRNAs may be appropriate candidates for molecular diagnostic and prognostic markers in NSCLC.

Role of Calprotectin as a Modulator of the IL27-Mediated Proinflammatory Effect on Endothelial Cells

An underlying endothelial dysfunction plays a fundamental role in the pathogenesis of cardiovascular events and is the central feature of atherosclerosis. The protein-based communication between leukocytes and inflamed endothelial cells leading to diapedesis has been largely investigated and several key players such as IL6, TNFα, or the damage associated molecular pattern molecule (DAMP) calprotectin are now well identified. However, regarding cytokine IL27, the controversial current knowledge about its inflammatory role and the involved regulatory elements requires clarification. Therefore, we examined the inflammatory impact of IL27 on primary endothelial cells and the potentially modulatory effect of calprotectin on both transcriptome and proteome levels. A qPCR-based screening demonstrated high IL27-mediated gene expression of IL7, IL15, CXCL10, and CXCL11. Calprotectin time-dependent downregulatory effects were observed on IL27-induced IL15 and CXCL10 gene expression. A mass spectrometry-based approach of IL27 ± calprotectin cell stimulation enlightened a calprotectin modulatory role in the expression of 28 proteins, mostly involved in the mechanism of leukocyte transmigration. Furthermore, we showed evidence for STAT1 involvement in this process. Our findings provide new evidence about the IL27-dependent proinflammatory signaling which may be under the control of calprotectin and highlight the need for further investigations on molecules which might have antiatherosclerotic functions.

Aurora-A promotes chemoresistance in hepatocelluar carcinoma by targeting NF-kappaB/microRNA-21/PTEN signaling pathway

Hepatocellular carcinoma (HCC) is highly resistant to chemotherapy. Previously, we have shown that Aurora-A mRNA is upregulated in HCC cells or tissues and silencing of Aurora-A using small interfering RNA (siRNA) decreases growth and enhances apoptosis in HCC cells. However, the clinical significance of Aurora-A protein expression in HCC and association between Aurora-A expression and HCC chemoresistance is unclear. Here, we showed that Aurora-A protein is upregulated in HCC tissues and significantly correlated with recurrence-free and overall survival of patients and multivariate analysis indicated that immunostaining of Aurora-A will be an independent prognostic factor for patients. Silencing of Aurora-A significantly increased the chemosensitivity of HCC cells both in vitro and in vivo, while overexpression of Aurora-A induced the opposite effects. Furthermore, overexpression of Aurora-A reduces chemotherapy-induced apoptosis by promoting microRNA-21 expression, which negatively regulates PTEN and then inhibits caspase-3-mediated apoptosis induction. Mechanically, we demonstrated that Aurora-A promotes expression of nuclear Ikappaβ-alpha (Iκβα) protein and enhances NF-kappa B (NF-κB) activity, thus promotes the transcription of miR-21. This study first reported the involvement of Aurora-A/NF-κB/miR-21/PTEN/Akt signaling axis in chemoresistance of HCC cells, suggesting that targeting this signaling pathway would be helpful as a therapeutic strategy for the reversal of chemoresistance in HCC.

Systemic Delivery of Anti-miRNA for Suppression of Triple Negative Breast Cancer Utilizing RNA Nanotechnology

MicroRNAs play important roles in regulating the gene expression and life cycle of cancer cells. In particular, miR-21, an oncogenic miRNA is a major player involved in tumor initiation, progression, invasion and metastasis in several cancers, including triple negative breast cancer (TNBC). However, delivery of therapeutic miRNA or anti-miRNA specifically into cancer cells in vivo without collateral damage to healthy cells remains challenging. We report here the application of RNA nanotechnology for specific and efficient delivery of anti-miR-21 to block the growth of TNBC in orthotopic mouse models. The 15 nm therapeutic RNA nanoparticles contains the 58-nucleotide (nt) phi29 pRNA-3WJ as a core, a 8-nt sequence complementary to the seed region of miR-21, and a 39-nt epidermal growth factor receptor (EGFR) targeting aptamer for internalizing RNA nanoparticles into cancer cells via receptor mediated endocytosis. The RNase resistant and thermodynamically stable RNA nanoparticles remained intact after systemic injection into mice and strongly bound to tumors with little or no accumulation in healthy organs 8 h postinjection, and subsequently repressed tumor growth at low doses. The observed specific cancer targeting and tumor regression is a result of several key attributes of RNA nanoparticles: anionic charge which disallows nonspecific passage across negatively charged cell membrane; "active" targeting using RNA aptamers which increases the homing of RNA nanoparticles to cancer cells; nanoscale size and shape which avoids rapid renal clearance and engulfment by lung macrophages and liver Kupffer cells; favorable biodistribution profiles with little accumulation in healthy organs, which minimizes nonspecific side effects; and favorable pharmacokinetic profiles with extended in vivo half-life. The results demonstrate the clinical potentials of RNA nanotechnology based platform to deliver miRNA based therapeutics for cancer treatment.

Therapies targeting cancer stem cells: Current trends and future challenges

Traditional therapies against cancer, chemo- and radiotherapy, have multiple limitations that lead to treatment failure and cancer recurrence. These limitations are related to systemic and local toxicity, while treatment failure and cancer relapse are due to drug resistance and self-renewal, properties of a small population of tumor cells called cancer stem cells (CSCs). These cells are involved in cancer initiation, maintenance, metastasis and recurrence. Therefore, in order to develop efficient treatments that can induce a long-lasting clinical response preventing tumor relapse it is important to develop drugs that can specifically target and eliminate CSCs. Recent identification of surface markers and understanding of molecular feature associated with CSC phenotype helped with the design of effective treatments. In this review we discuss targeting surface biomarkers, signaling pathways that regulate CSCs self-renewal and differentiation, drug-efflux pumps involved in apoptosis resistance, microenvironmental signals that sustain CSCs growth, manipulation of miRNA expression, and induction of CSCs apoptosis and differentiation, with specific aim to hamper CSCs regeneration and cancer relapse. Some of these agents are under evaluation in preclinical and clinical studies, most of them for using in combination with traditional therapies. The combined therapy using conventional anticancer drugs with CSCs-targeting agents, may offer a promising strategy for management and eradication of different types of cancers.

MicroRNAs in breast cancer: oncogene and tumor suppressors with clinical potential

MicroRNAs (miRs) are small single-stranded RNA molecules, which function as key negative regulators of post-transcriptional modulation in almost all biological processes. Abnormal expression of microRNAs has been observed in various types of cancer including breast cancer. Great efforts have been made to identify an association between microRNA expression profiles and breast cancer, and to understand the functional role and molecular mechanism of aberrant-expressed microRNAs. As research progressed, 'oncogenic microRNAs' and 'tumor suppressive microRNAs' became a focus of interest. The potential of candidate microRNAs from both intercellular (tissue) and extracellular (serum) sources for clinical diagnosis and prognosis was revealed, and treatments involving microRNA achieved some amazing curative effects in cancer disease models. In this review, advances from the most recent studies of microRNAs in one of the most common cancers, breast cancer, are highlighted, especially the functions of specifically selected microRNAs. We also assess the potential value of these microRNAs as diagnostic and prognostic markers, and discuss the possible development of microRNA-based therapies.

Helicobacter pylori and microRNAs: Relation with innate immunity and progression of preneoplastic conditions

The accepted paradigm for intestinal-type gastric cancer pathogenesis is a multistep progression from chronic gastritis induced by Helicobacter pylori (H. pylori) to gastric atrophy, intestinal metaplasia, dysplasia and ultimately gastric cancer. The genetic and molecular mechanisms underlying disease progression are still not completely understood as only a fraction of colonized individuals ever develop neoplasia suggesting that bacterial, host and environmental factors are involved. MicroRNAs are noncoding RNAs that may influence H. pylori-related pathology through the regulation of the transcription and expression of various genes, playing an important role in inflammation, cell proliferation, apoptosis and differentiation. Indeed, H. pylori have been shown to modify microRNA expression in the gastric mucosa and microRNAs are involved in the immune host response to the bacteria and in the regulation of the inflammatory response. MicroRNAs have a key role in the regulation of inflammatory pathways and H. pylori may influence inflammation-mediated gastric carcinogenesis possibly through DNA methylation and epigenetic silencing of tumor suppressor microRNAs. Furthermore, microRNAs influenced by H. pylori also have been found to be involved in cell cycle regulation, apoptosis and epithelial-mesenchymal transition. Altogether, microRNAs seem to have an important role in the progression from gastritis to preneoplastic conditions and neoplastic lesions and since each microRNA can control the expression of hundreds to thousands of genes, knowledge of microRNAs target genes and their functions are of paramount importance. In this article we present a comprehensive review about the role of microRNAs in H. pylori gastric carcinogenesis, identifying the microRNAs downregulated and upregulated in the infection and clarifying their biological role in the link between immune host response, inflammation, DNA methylation and gastric carcinogenesis.

miR-21 synergizes with BMP9 in osteogenic differentiation by activating the BMP9/Smad signaling pathway in murine multilineage cells

Bone morphogenetic proteins (BMPs), particularly BMP9, have been shown to promote the osteogenic differentiation of murine multilineage cells (MMCs) and to promote bone formation in bone diseases; however, the mechanisms involved remain poorly understood. MicroRNAs (miRNAs or miRs) have been proven to regulate mesenchymal stem cell (MSC) differentiation. In this study, we identified a novel mechanism that unravels the functional axis of a key miRNA (miR-21) which contributes to BMP9-induced osteogenic differentiation. We screened differentially expressed miRNAs in MMCs during BMP9-induced osteogenic differentiation and found that miR-21 was significantly upregulated by BMP9 during the osteogenesis of MMCs. Furthermore, miR-21 was confirmed to promote the osteogenic differentiation of the MMCs by suppressing Smad7, which negatively regulates the osteogenic differentiation of MMCs. The upregulation of miR-21 may promote the osteogenic differentiation of MMCs in synergy with BMP9. The findings of our study revealed a novel function of miR-21, and suggest that the overexpression of miR-21 contributes to bone formation by promoting BMP9-induced osteogenic differentiation. Our data may provide a molecular basis for the development of novel therapeutic strategies to treat bone diseases, such as osteoporosis and other inflammatory bone diseases.

miRNA oligonucleotide and sponge for miRNA-21 inhibition mediated by PEI-PLL in breast cancer therapy

MicroRNA-21 (miR-21) inhibition is a promising biological strategy for breast cancer therapy. However its application is limited by the lack of efficient miRNA inhibitor delivery systems. As a cationic polymer transfection material for nucleic acids, the poly (l-lysine)-modified polyethylenimine (PEI-PLL) copolymer combines the high transfection efficiency of polyethylenimine (PEI) and the good biodegradability of polyllysine (PLL). In this work, PEI-PLL was successfully synthesized and confirmed to transfect plasmid and oligonucleotide more effectively than PEI in MCF-7 cells (human breast cancer cells). In this regard, two kinds of miR-21 inhibitors, miR-21 sponge plasmid DNA (Sponge) and anti-miR-21 oligonucleotide (AMO), were transported into MCF-7 cells by PEI-PLL respectively. The miR-21 expression and the cellular physiology were determined post transfection. Compared with the negative control, PEI-PLL/Sponge or PEI-PLL/AMO groups exhibited lower miR-21 expression and cell viability. The anti-tumor mechanism of PEI-PLL/miR-21 inhibitors was further studied by cell cycle and western blot analyses. The results indicated that the miR-21 inhibition could induce the cell cycle arrest in G1 phase, upregulate the expression of Programmed Cell Death Protein 4 (PDCD4) and thus active the caspase-3 apoptosis pathway. Interestingly, the PEI-PLL/Sponge and PEI-PLL/AMO also sensitized the MCF-7 cells to anti-tumor drugs, doxorubicin (DOX) and cisplatin (CDDP). These results demonstrated that PEI-PLL/Sponge and PEI-PLL/AMO complexes would be two novel and promising gene delivery systems for breast cancer gene therapy based on miR-21 inhibition.

STATEMENT OF SIGNIFICANCE

This work was a combination of the high transfection efficiency of polyethylenimine (PEI), the good biodegradability of polyllysine (PLL) and the breast cancer-killing effect of miR-21 inhibitors. The poly (l-lysine)-modified polyethylenimine (PEI-PLL) copolymer was employed as the vector of miR-21 sponge plasmid DNA (Sponge) or anti-miR-21 oligonucleotide (AMO). PEI-PLL showed more transfection efficiency and lower cytotoxicity in human breast cancer cells than PEI. Moreover, the breast cancer cells exhibited significantly lower miR-21 expression and cell viability post transfection with sponge or AMO. Interestingly, the PEI-PLL/miR-21 inhibitor complexes also sensitized the cancer cells to anti-cancer chemotherapy drugs, doxorubicin (DOX) and cisplatin (CDDP). This synergistic effect provides a good application prospect of co-delivery miR-21 inhibitors and chemical drugs in breast cancer therapy.

Cell-Free miR-27a, a Potential Diagnostic and Prognostic Biomarker for Gastric Cancer

MicroRNAs (miRNAs) have been demonstrated to play an important role in carcinogenesis. Previous studies revealed that miRNAs are present in human plasma in a remarkably stable form that is protected from endogenous RNase activity. In this study, we measured the plasma expression levels of three miRNAs (miR-21, miR-27a, and miR-155) to investigate the usefulness of miRNAs for gastric cancer detection. We initially examined plasma miRNA expression levels in a screening cohort consisting of 15 patients with gastric cancer and 15 healthy controls from Korean population, using TaqMan quantitative real-time polymerase chain reaction. We observed that the expression level of miR-27a was significantly higher in patients with gastric cancer than in healthy controls, whereas the miR-21 and miR-155a expression levels were not significantly higher in the patients with gastric cancer. Therefore, we further validated the miR-27a expression level in 73 paired gastric cancer tissues and in a validation plasma cohort from 35 patients with gastric cancer and 35 healthy controls. In both the gastric cancer tissues and the validation plasma cohort, the miR-27a expression levels were significantly higher in patients with gastric cancer. Receiver-operator characteristic (ROC) analysis of the validation cohort, revealed an area under the ROC curve value of 0.70 with 75% sensitivity and 56% specificity in discriminating gastric cancer. Thus, the miR-27a expression level in plasma could be a useful biomarker for the diagnosis and/or prognosis of gastric cancer.

Therapeutic Targeting of microRNAs in Cancer: Future Perspectives

Preclinical Research The discovery of microRNAs (miRNAs) and their link with cancer has opened a new era in cancer therapeutics. Approximately, 18 - 24 nucleotides long, miRNAs can up-regulate or down-regulate gene expression in many cancer types and are respectively categorized as oncogenes (oncomirs) or tumor suppressors. Expression profiles of miRNAs with biomarker potential can be used for the classification, diagnosis, therapeutic treatment, and prognosis of different cancer types. miRNA mimics and miRNA antagonists are the two main approaches to miRNA-based cancer therapies that respectively inhibit oncomirs or restore the expression of tumor suppressive miRNAs. This review serves to provide some general insight into miRNA biogenesis, cancer related miRNAs, and miRNA therapeutics.