Down-regulation of miR-92 in human plasma is a novel marker for acute leukemia patients

Circulating MiR-16-5p and MiR-19b-3p as Two Novel Potential Biomarkers to Indicate Progression of Gastric Cancer

Gastric cancer (GC) is the second most common cancer in China and the second leading cause of cancer-related death in the world. Identifying circulating biomarkers is helpful to improve theranostics of gastric cancer. Herein, we are for the first time to report miR-16-5p and miR-19b-3p were identified to be the novel potential plasma biomarkers to detect gastric cancer. Differentially expressed miRNAs were initially screened out by genome-wide miRNA profiling microarrays between 16 plasma samples of gastric cancer and 18 matched normal controls, and then were quantified and validated by quantitative reverse transcription-PCR method between 155 gastric cancer cases and 111 normal controls. Additionally, 30 plasma samples from precancerous lesions and 18 paired samples from gastric cancer patients with gastrectomy were further detected. Results showed that based on two normalization methods, miR-16-5p and miR-19b-3p in plasma were found to be capable of distinguishing normal population from GC cases with different TNM stages and differentiation grades, particularly including the early cancer cases (P<0.05). And the two miRNAs were down-regulated in GC cases (FC<0.5). Especially, the down-regulation degree was correlated with the progression of the GC cases from the early stage to the advanced stage (0.2< r_s<0.3, P<0.01). And the same weak down-regulation of the two biomarkers as the early GC occurred initially in the precancerous diseases (P<0.05). The corresponding performance of the two miRNAs to detect GC in ROC analysis gradually performed better with the disease progression from the earlier stages or lower grades to the advanced stages (TNM Ⅳ stage: AUC=0.832 for miR-16-5p; TNM Ⅲ stage: AUC=0.822 for miR-19b-3p) or high grade (Poorly differentiated: AUC=0.801, 0.791 respectively for miR-16-5p and miR-19b-3p). Additionally, miR-19b-3p remained down-regulated in patient plasma within 9 days after gastrectomy. In conclusion, miR-19b-3p and miR-16-5p maybe prospective biomarkers to detect gastric cancer and indicate its progression, and thus may own great potential in applications such as early screening and progression evaluation of gastric cancer in the near future.

Modulation of miRNAs in Pulmonary Hypertension

MicroRNAs (miRNAs) have emerged as a new class of posttranscriptional regulators of many cardiac and vascular diseases. They are a class of small, noncoding RNAs that contributes crucial roles typically through binding of the 3′-untranslated region of mRNA. A single miRNA may influence several signaling pathways associated with cardiac remodeling by targeting multiple genes. Pulmonary hypertension (PH) is a rare disorder characterized by progressive obliteration of pulmonary (micro) vasculature that results in elevated vascular resistance, leading to right ventricular hypertrophy (RVH) and RV failure. The pathology of PH involves vascular cell remodeling including pulmonary arterial endothelial cell (PAEC) dysfunction and pulmonary arterial smooth muscle cell (PASMC) proliferation. There is no cure for this disease. Thus, novel intervention pathways that govern PH induced RVH may result in new treatment modalities. Current therapies are limited to reverse the vascular remodeling. Recent studies have demonstrated the roles of various miRNAs in the pathogenesis of PH and pulmonary disorders. This review provides an overview of recent discoveries on the role of miRNAs in the pathogenesis of PH and discusses the potential for miRNAs as therapeutic targets and biomarkers of PH at clinical setting.

Plasma circulating-microRNA profiles are useful for assessing prognosis in patients with cytogenetically normal myelodysplastic syndromes

Myelodysplastic syndromes are a heterogeneous group of clonal bone marrow hematopoietic stem cell disorders characterized by ineffective hematopoiesis and peripheral cytopenias. Chromosomal abnormalities and gene mutations have been shown to have essential roles in pathogenesis and correlate with prognosis. Molecular markers, however, are not integrated into currently used prognostic systems. The goal of this study is to identify plasma microRNAs useful for classification and risk stratification of myelodysplastic syndromes. We applied a novel, high-throughput digital quantification technology (NanoString) to profile microRNA expression in plasma samples of 72 patients with myelodysplastic syndromes and 12 healthy individuals. We correlated these results with overall survival. In patients with myelodysplastic syndromes associated with a diploid karyotype, we identified and validated a 7-microRNA signature as an independent predictor of survival with a predictive power of 75% accuracy (P=0.008), better than those of the International Prognostic Scoring Systems and the MD Anderson Prognostic Lower Risk Prognostic Model. We also identified differentially expressed plasma microRNAs in patients with myelodysplastic syndromes versus healthy individuals and between patients with myelodysplastic syndromes associated with different cytogenetic features. These results validate the utility of circulating-microRNA levels as noninvasive biomarkers that can inform the management of patients with myelodysplastic syndromes. Our findings also shed light on interactions of gene regulation pathways that are likely involved in the pathogenesis of myelodysplastic syndromes.

Antidiabetic drug metformin inhibits esophageal adenocarcinoma cell proliferation in vitro and in vivo

Esophageal carcinoma is the eighth most common cancer worldwide and the sixth leading cause of cancer-related deaths, with one of the worst prognoses of any form of cancer. Treatment with the anti-diabetic drug metformin has been associated with reduced cancer incidence in patients with type 2 diabetes. This study therefore evaluated the effects of metformin on the proliferation, in vitro and in vivo, of human esophageal adenocarcinoma cells, as well as the microRNAs associated with the antitumor effects of metformin. Metformin inhibited the proliferation of the esophageal adenocarcinoma cell lines OE19, OE33, SK-GT4 and OACM 5.1C, blocking the G0 to G1 transition in the cell cycle. This was accompanied by strong reductions in G1 cyclins, especially cyclin D1, cyclin-dependent kinase (Cdk)4, and Cdk6, and decreases in retinoblastoma protein phosphorylation. In addition, metformin reduced the phosphorylation of epidermal growth factor receptor and insulin-like growth factor and insulin-like growth factor-1 receptor, as well as angiogenesis-related proteins, such as vascular endothelial growth factor, tissue inhibitor of metalloproteinases (TIMP)-1, and TIMP-2. Metformin also markedly altered microRNA expression. Treatment with metformin of athymic nude mice bearing xenograft tumors reduced tumor proliferation. These findings suggest that metformin may have clinical use in the treatment of esophageal adenocarcinoma.

Downregulation of serum miR-17 and miR-106b levels in gastric cancer and benign gastric diseases

Altered microRNA (miRNA) associated with gastric cancer (GC) development and miR-17 and miR-106b were differentially expressed in GC tissues. This study detected serum levels of miR-17 and miR-106b expression in GC, benign gastric disease (BGD) and healthy controls to assess them as tumor markers for GC. Serum samples from 40 GC, 32 BGD (10 gastric ulcer, 14 gastric polyps, and 8 gastric ulcer with polyps) and 36 healthy individuals were subjected to quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis of miR-17 and miR-106b expression. The data showed that the serum levels of miR-17 and miR-106b were significantly reduced in healthy individuals and BGD patients compared to GC patients. There was a significant association of miR-17 and miR-106b expression with age, but not with other clinicopathological features, such as gender, tumor differentiation, stage and lymphatic metastasis. Further analysis showed that, in discriminating GC patients from healthy controls, miR-17 could yield a receiver-operating characteristic (ROC) area under the curve (AUC) of 0.879 with 80.6% sensitivity and 87.5% specificity and miR-106b could yield an AUC of 0.856 with 75.0% sensitivity and 92.5% specificity. The combined AUC of miR-17 and miR-106b was 0.913 with 83.3% sensitivity and 87.5% specificity. Collectively, these data suggest that detection of serum miR-17 and miR-106b levels should be further evaluated as novel non-invasive biomarkers in early GC detection and surveillance of disease progression.

Circulating MicroRNAs: Methodological Aspects in Detection of These Biomarkers

MicroRNAs (miRNAs) are evolutionarily conserved small non-coding RNAs that regulate expression of protein-coding genes involved in important biological processes and (patho)physiological states. Circulating miRNAs are protected against degradation, indicating their relevant biological functions. Many studies have demonstrated an association of the specific profile of circulating miRNAs with a wide range of cancers as well as non-malignant diseases. These findings demonstrate the implication of circulating miRNAs in the pathogenesis of diseases and their potential as non-invasive disease biomarkers. However, methods for measurement of circulating miRNAs have critical technical hotspots, resulting in a discrepancy of the reported results and difficult definition of consensus disease biomarkers that may be implicated in clinical use. Here, we review functions of circulating miRNAs and their aberrant expression in particular diseases. Further, we discuss methodological aspects of their detection and quantification as well as our experience with the methods.

Circulating microRNA as Biomarkers in Hematological Malignancies

Hematopoiesis is a highly regulated process controlled by a complex network of molecular mechanisms that simultaneously regulate differentiation, proliferation, and apoptosis of hematopoietic stem cells. Aberrant microRNA (miRNA) expression could affect normal hematopoiesis, leading to the development of hematological malignancies. Hematologic cancers, which are caused by malignant transformation of cells of the bone marrow and the lymphatic system, are usually divided into three major groups: leukemias, lymphomas, and monoclonal gammopathies. Hematologic malignancies are highly aggressive diseases with high morbidity and mortality. For these reasons, early and easily obtainable markers for diagnosis, risk stratification, and follow-up are essential for improvement of outcome and survival of these patients. Recent studies have provided new insights about the diagnostic value of expression patterns of miRNAs in serum/plasma in these diseases. While the use of circulating miRNAs is only at the experimental level, it appears to have a great potential. This chapter deals with the use of circulating miRNAs as minimally invasive biomarkers in hematologic malignancies.

MicroRNAs as biomarkers in pituitary tumors

The use of extracellular microRNAs (miRNAs) as circulating biomarkers is currently leading to relevant advances in the diagnosis and assessment of prognosis of several diseases. Specific miRNAs have also been shown to play a role in the pathophysiology of many neoplastic and non-neoplastic diseases. A number of studies have demonstrated that miRNAs show differential expression in various tumors, such as in the prostate, ovary, lung, breast, brain, and pituitary. Recent findings have built connections between miRNAs that are deregulated within the tumor and their presence in peripheral blood. MiRNAs have been shown to be stable in the blood where they are present in either free and/or uncomplexed form, as well as packed in microvesicles, exosomes, and apoptotic bodies, or bound to different proteins. Because the pituitary is a highly vascularized organ that releases hormones into the circulation, miRNAs would be useful biomarkers for the diagnosis of pituitary tumors, as well as for predicting or detecting recurrence after surgery. Here we review the biological significance of miRNAs in pituitary tumors and the potential value of circulating miRNAs as biomarkers.

miR-638 regulates differentiation and proliferation in leukemic cells by targeting cyclin-dependent kinase 2

MicroRNAs have been extensively studied as regulators of hematopoiesis and leukemogenesis. We identified miR-638 as a novel regulator in myeloid differentiation and proliferation of leukemic cells. We found that miR-638 was developmentally up-regulated in cells of myeloid but not lymphoid lineage. Furthermore, significant miR-638 down-regulation was observed in primary acute myeloid leukemia (AML) blasts, whereas miR-638 expression was dramatically up-regulated in primary AML blasts and leukemic cell lines undergoing forced myeloid differentiation. These observations suggest that miR-638 might play a role in myeloid differentiation, and its dysregulation may contribute to leukemogenesis. Indeed, ectopic expression of miR-638 promoted phorbol 12-myristate 13-acetate- or all-trans-retinoic acid-induced differentiation of leukemic cell lines and primary AML blasts, whereas miR-638 inhibition caused an opposite phenotype. Consistently, miR-638 overexpression induced G1 cell cycle arrest and reduced colony formation in soft agar. Cyclin-dependent kinase 2 (CDK2) was found to be a target gene of miR-638. CDK2 inhibition phenotypically mimicked the overexpression of miR-638. Moreover, forced expression of CDK2 restored the proliferation and the colony-forming ability inhibited by miR-638. Our data suggest that miR-638 regulates proliferation and myeloid differentiation by targeting CDK2 and may serve as a novel target for leukemia therapy or marker for AML diagnosis and prognosis.

microRNAs: a new class of breast cancer biomarkers

MicroRNAs (miRNAs) are regulatory molecules known to be aberrantly expressed in cancer and contribute to numerous aspects of tumor biology including the initiation, growth and spread of the tumor. With such diverse roles, it is becoming apparent that some may also provide valuable information which may be of use in a clinical setting, demonstrating the potential to act as both screening tools for the stratification of high-risk patients, while informing the treatment decision-making process. There is mounting evidence to suggest that some miRNAs may even provide assistance in the diagnosis of patients with breast cancer. In addition, miRNAs may themselves be considered therapeutic targets, with inhibition or reintroduction of a particular miRNA capable of inducing a response in vivo. This review focuses on miRNAs that have prognostic, diagnostic or predictive potential in breast cancer as well as the possible challenges in the translation of such observations to the clinic.

Cell-free microRNAs as cancer biomarkers: the odyssey of miRNAs through body fluids

Cell-free microRNAs (cfmiRNAs), also known as extracellular or secretory microRNAs, are an emerging class of miRNAs that are released or secreted by cells. These miRNAs are transferred through various body fluids. A growing body of research has recently revealed that cancer cells also secrete their distinctive cfmiRNAs to the extracellular environment highlighting the contribution of cfmiRNAs to cancer progression. CfmiRNAs show high stability in the body fluids. Three pathways have been proposed for their entry into the body fluids: passive release from broken, injured and dead cells; active secretion through microvesicles; and active secretion via microvesicle-free protein-dependent route. Active pathways seem to play leading roles in the delivery of miRNAs. Detection of cfmiRNAs is of particular relevance to their translation into the clinic. Much effort has been devoted to the development of highly sensitive and efficient approaches for detection purposes. Nevertheless, some barriers such as finding a unique internal control for all cancer types remain to be bypassed. This review aims to provide an insight into the promises represented by cfmiRNAs as cancer biomarkers and describes advances made in the identification of numerous types of extracellular miRNAs that have potential for use in the diagnosis of a variety of cancers.

Association of plasma MiR-17-92 with dyslipidemia in patients with coronary artery disease

Circulating microRNAs (miRNAs) have already been proposed as sensitive and informative biomarkers for the diagnosis of multiple diseases. We investigated the miRNA expression patterns in plasma samples of patients with coronary artery disease (CAD) and explored the potential functions of certain miRNAs.Deep sequencing analysis was performed to determine the miRNA expression profiles using RNA samples isolated from 20 healthy subjects and 20 patients with CAD. Quantitative reverse transcription polymerase chain reaction was applied to confirm the differential expression of the miR-17-92 cluster in 81 patients and 50 healthy volunteers. The association between the miR-17-92 cluster and clinical characteristics of patients with CAD were analyzed using SPSS16.0, SPSS Inc, Chicago, IL.Hundreds of miRNAs were detected and most members from the miR-17-92 cluster and its paralogs, including miR-18a, miR-92a, miR-106b, and miR-17, exhibited differential expression in the plasma of patients with CAD compared with controls. Moreover, these miRNAs were found widely related to the blood lipids in the patients with CAD, as miR-17 was positively correlated with total cholesterol, low-density lipoprotein cholesterol, and apolipoprotein B, while miR-92a was found positively related to high-density lipoprotein cholesterol (HDL-C) but negatively related to lipoprotein-a. Additionally, miR-106b was positively related to HDL-C and apolipoprotein A-I.Taken together with existing evidence from mechanistic studies, the current results of our study support a relationship between the miR-17-92 family and lipid metabolism, which merits further study.

U6 is not a suitable endogenous control for the quantification of circulating microRNAs

Recently, microRNAs have been detected in serum and plasma, and circulating microRNA (miRNA) profiles have now been associated with many diseases such as cancers and heart disease, as well as altered physiological states. Because of their stability and disease resistance, circulation miRNAs appear to be an ideal material for biomarkers of diseases and physiological states in blood. However, the lack of a suitable internal reference gene (internal reference miRNA) has hampered research and application of circulating miRNAs. Currently, U6 and miR-16 are the most common endogenous controls in the research of miRNAs in tissues and cells. We performed microarray-based serum miRNA profiling on the serum of 20 nasopharyngeal carcinoma patients and 20 controls to detect the expressions of U6 and miRNAs. Profiling was followed by real-time quantitative Polymerase Chain Reaction (qPCR) in 80 patients (20 each with gastric cancer, nasopharyngeal carcinoma, colorectal cancer, and breast cancer) and 30 non-cancerous controls. qPCR was also performed to detect miRNAs in serum with repeated freezing and thawing. The results of microarray showed that with the exception of U6, Ct values of miR-16, miR-24, miR-142-3p, miR-19b and miR-192 in serum samples of nasopharyngeal carcinoma were greater than control samples. The results of 110 cases showed large fluctuations in U6 expression. The difference between the greatest and the least levels of expression was 3.29 for delta Ct values, and 1.23 for miR-16. The expressions of U6, miR-16 and miR-24 in serum subjected to different freeze-thaw cycles showed that U6 expression gradually decreased after 1, 2, and 4 cycles of freezing and thawing, while the expression of miR-16 and miR-24 remained relatively stable. Collectively, our results suggested that U6 is unsuitable as an internal reference gene in the research of circulating miRNAs.

Selective miRNA expression profile in chronic myeloid leukemia K562 cell-derived exosomes

BACKGROUND

Chronic myeloid leukemia (CML) is a myeloproliferative disorder of hematopoietic stem cell scarrying the Philadelphia (Ph) chromosome and an oncogenic BCR-ABL1 fusion gene. The tyrosine kinase inhibitor (TKI) of BCR-ABL1 kinase is a treatment of choice for control of CML.

OBJECTIVE

Recent studies have demonstrated that miRNAs within exosomes from cancer cells play crucial roles in initiation and progression. This study was performed to assess miRNAs within exosomes of K562 cells.

METHODS

miRNA microarray analysis of K562 cells and K562 cell-derived exosomes was conducted with the 6th generation miRCURYTM LNA Array (v.16.0). Gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were also carried out. GO terms and signaling pathways were categorized into 66 classes (including homophilic cell adhesion, negative regulation of apoptotic process, cell adhesion) and 26 signaling pathways (such as Wnt).

RESULTS

In exosomes, 49 miRNAs were up regulated as compared to K562 cells, and two of them were further confirmed by quantitative real-time PCR. There are differentially expressed miRNAs between K562 cell derived-exosomes and K562 cells.

CONCLUSION

Selectively expressed miRNAs in exosomes may promote the development of CML via effects on interactions (e.g. adhesion) of CML cells with their microenvironment.

Expression profiling of serum microRNA-101 in HBV-associated chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma

MicroRNAs (miRNAs) represent a class of evolutionarily conserved, non-coding small RNAs (18-25 nt) that have emerged as master regulators of several biological processes. Recently, circulating miRNAs have also been reported to be promising biomarkers for various pathological conditions. In the present study, we report the comparative expression profiling of microRNA-101 (miR-101) in serum and tissue samples from chronic hepatitis B (CHB), HBV-associated liver cirrhosis (HBV-LC), and HBV-associated hepatocellular carcinoma (HBV-HCC) patients and healthy controls. The serum miR-101 levels were found to be significantly downregulated in the HBV-HCC patients compared with the HBV-LC patients (P<0.001), CHB patients (P<0.001) and healthy controls but were upregulated in the HBV-LC patients compared with the CHB patients (P<0.001) and healthy controls (P<0.001). Consistent with the serum data, the expression of miR-101 was also upregulated and downregulated in the HBV-LC and HBV-HCC tissue samples, respectively. A receiver operating characteristic (ROC) analysis of serum miR-101 yielded an area under the ROC curve (AUC) of 0.976 with 95.5% sensitivity and 90.2% specificity when differentiating between HBV-HCC and HBV-LC. Our results suggest that the serum miR-101 level can serve as a potential non-invasive biomarker to differentiate HBV-HCC from HBV-LC.

MicroRNAs in Cancer Biology and Therapy: Current Status and Perspectives

The study of a class of small non-coding RNA molecules, named microRNAs (miRNAs), has advanced our understanding of many of the fundamental processes of cancer biology and the molecular mechanisms underlying tumor initiation and progression. MiRNA research has become more and more attractive as evidence is emerging that miRNAs likely play important regulatory roles virtually in all essential bioprocesses. Looking at this field over the past decade it becomes evident that our understanding of miRNAs remains rather incomplete. As research continues to reveal the mechanisms underlying cancer therapy efficacy, it is clear that miRNAs contribute to responses to drug therapy and are themselves modified by drug therapy. One important area for miRNA research is to understand the functions of miRNAs and the relevant signaling pathways in the initiation, progression and drug-resistance of tumors to be able to design novel, effective targeted therapeutics that directly target pathologically essential miRNAs and/or their target genes. Another area of increasing importance is the use of miRNA signatures in the diagnosis and prognosis of various types of cancers. As the study of non-coding RNAs is increasingly more popular and important, it is without doubt that the next several years of miRNA research will provide more fascinating results.

Circulating miR-192 in liver fluke-associated cholangiocarcinoma patients: a prospective prognostic indicator

BACKGROUND

This study aimed to investigate the miR-192 levels in patients' sera of liver fluke-associated cholangiocarcinoma (CCA) for a prospective prognostic indicator.

METHODS

MicroRNA polymerase chain reaction (PCR) array was performed using pooled serum samples from 11 CCA patients and nine healthy subjects. Selected miRNAs were verified for the differential levels in both sera and tumor tissues (of patients and Opisthorchis viverrini (Ov)-induced CCA model) using TaqMan miRNA expression assay.

RESULTS

Our results demonstrated that miR-192 was significantly higher in the serum of CCA patients than that in healthy subjects giving a sensitivity of 74% and specificity of 72% (area under the curve [AUC] = 0.803; 95% confidence interval [CI], 0.708-0.897, P < 0.0001). Serum miR-192 examined in Ov infected subjects and subjects with periductal fibrosis were increased but not statistically significantly when compared with healthy subjects. High levels of serum miR-192 were significantly correlated with lymph node metastasis (P = 0.047) and shorter survival compared with individuals with low levels of serum miR-192 (hazard ratio [HR] 2.076, 95% CI 1.004-4.291, P = 0.049). We also found that the expression levels of miR-192 appeared to be elevated in both CCA tissues of patients and in Ov-induced CCA tissues of a hamster model.

CONCLUSIONS

This finding indicates that elevated levels of miR-192 may be involved in CCA genesis and have a potential utility as a noninvasive prognostic indicator for CCA patients.

Tumor surveillance by circulating microRNAs: a hypothesis

A growing body of experimental evidence supports the diagnostic relevance of circulating microRNAs in various diseases including cancer. The biological relevance of circulating microRNAs is, however, largely unknown, particularly in healthy individuals. Here, we propose a hypothesis based on the relative abundance of microRNAs with predominant tumor suppressor activity in the blood of healthy individuals. According to our hypothesis, certain sets of circulating microRNAs might function as a tumor surveillance mechanism exerting continuous inhibition on tumor formation. The microRNA-mediated tumor surveillance might complement cancer immune surveillance.

The role of circulating microRNA-126 (miR-126): a novel biomarker for screening prediabetes and newly diagnosed type 2 diabetes mellitus

Recent studies suggested an association of endothelial microRNA-126 (miR-126) with type 2 diabetes mellitus (T2DM). In the current study, we examined whether circulating miR-126 is associated with T2DM and pre-diabetic syndrome. The study included 82 subjects with impaired glucose tolerance (IGT), 75 subjects with impaired fasting glucose (IFG), 160 patients with newly diagnosed T2DM, and 138 healthy individuals. Quantitative polymerase chain reaction (qPCR) was used to examine serum miR-126. Serum miR-126 was significantly lower in IGT/IFG subjects and T2DM patients than in healthy controls (p < 0.05). After six months of treatment (diet control and exercise in IGT/IFG subjects, insulin plus diet control and exercise in T2DM patients), serum miR-126 increased significantly (p < 0.05). An analysis based on serum miR-126 in the sample revealed a significantly higher odds ratio (OR) for the subjects with the lowest 1/3 of serum miR-126 for T2DM (OR: 3.500, 95% confidence interval: 1.901–6.445, p < 0.05) than subjects within the highest 1/3 of serum miR-126. Such an association was still apparent after adjusting for other major risk factors. The area under the curve (AUC) for the receiver-operating characteristic (ROC) analysis was 0.792 (95% confidence interval: 0.707–0.877, p < 0.001). These results encourage the use of serum miR-126 as a biomarker for pre-diabetes and diabetes mellitus, as well as therapeutic response.

MicroRNAs in brain metastases: potential role as diagnostics and therapeutics

Brain metastases remain a daunting adversary that negatively impact patient survival. Metastatic brain tumors affect up to 45% of all cancer patients with systemic cancer and account for ~20% of all cancer-related deaths. A complex network of non-coding RNA molecules, microRNAs (miRNAs), regulate tumor metastasis. The brain micro-environment modulates metastatic tumor growth; however, defining the precise genetic events that promote metastasis in the brain niche represents an important, unresolved problem. Understanding these events will reveal disease-based targets and offer effective strategies to treat brain metastases. Effective therapeutic strategies based upon the biology of brain metastases represent an urgent, unmet need with immediate potential for clinical impact. Studies have demonstrated the ability of miRNAs to distinguish normal from cancerous cells, primary from secondary brain tumors, and correctly categorize metastatic brain tumor tissue of origin based solely on miRNA profiles. Interestingly, manipulation of miRNAs has proven effective in cancer treatment. With the promise of reduced toxicity, increased efficacy and individually directed personalized anti-cancer therapy, using miRNA in the treatment of metastatic brain tumors may prove very useful and improve patient outcome. In this review, we focus on the potential of miRNAs as diagnostic and therapeutic targets for the treatment of metastatic brain lesions.

Serum microRNA levels in patients with Crohn's disease during induction therapy by infliximab

BACKGROUND AND AIM

microRNAs (miRNAs) have been suggested to be candidates for biomarkers in various diseases including Crohn's disease (CD). To identify possible biomarkers predictive of the therapeutic effect of infliximab in CD, we investigated serum miRNA levels during the induction therapy by the medication.

METHODS

Nineteen CD patients who were applied to the induction therapy by infliximab were enrolled. Serum samples for miRNA analyses were obtained at weeks 0 and 6, and the therapeutic efficacy by infliximab was assessed according to the Crohn's disease activity index value at week 14. Exploratory miRNA profiling by low-density array was initially performed in three patients. The levels of candidate miRNA were subsequently determined by real-time polymerase chain reaction (PCR) assays in the remaining 16 patients. The miRNA levels during the induction therapy were compared between the two groups classified by the clinical response to infliximab at week 14.

RESULTS

Low-density array analysis identified 14 miRNAs that showed twofold or more altered expression during the induction therapy by infliximab. Subsequent analysis by real-time PCR demonstrated significantly increased levels of five miRNAs (let-7d, let-7e, miR-28-5p, miR-221, and miR-224) at week 6 when compared with those at week 0 (P < 0.05 each). In addition, miRNA levels of let-7d and let-7e were significantly increased in the group of patients who achieved clinical remission by infliximab (P = 0.001 and P = 0.002, respectively).

CONCLUSION

let-7d and let-7e might be possible therapeutic biomarkers in patients with CD, who are treated by infliximab.

MicroRNAs as biomarkers in leukemia

Current diagnostic and prognostic markers still exhibit biological limitation and seeking novel molecular biomarkers is crucial for early clinical diagnosis and in the development of novel strategies for leukemia therapy. Emerging evidence showed that dysregulated microRNAs (miRNAs) play important roles in cancer including leukemia. In this review, we summarized recent progress on the role of miRNAs in leukemia, mainly focusing on recent findings that suggest the potential of miRNAs as biomarkers for diagnosis and prognosis. Notably, the circulating miRNAs were also discussed for the fact that they can be detected in body fluids, and thus represent a novel source of promising biomarkers that may be applied to clinical settings.

Expression profiling of leukemia patients: key lessons and future directions

Gene expression profiling (GEP) is a well-established indispensable tool used to study hematologic malignancies, including leukemias. Here, we summarize the insights into the molecular basis of leukemias obtained by means of GEP, focusing especially on acute myeloid leukemia (AML), one of the first diseases to be extensively studied by GEP. Profiling mRNA and microRNA expression are discussed in view of their applicability to class prediction, class discovery, and comparison, as well as outcome prediction, and special attention is paid to the recent advances in our understanding of the role of alternative RNA splicing in AML. In addition to microarray-based GEP approaches, over the last few years RNA sequencing based on next-generation sequencing technology is gaining wider recognition as an advanced tool for transcriptome profiling. Therefore, the advantages of RNA sequencing-based GEP and its current and potential implications in AML are discussed. Finally, we also highlight recent efforts to integrate already available and newly acquired omics data sets so that a more precise understanding of AML biology and clinical behavior can be achieved, which ultimately will contribute to further refine leukemia management.

Short, terminally modified 2'-OMe RNAs as inhibitors of microRNA

We applied 14-mer 2'-OMe RNAs as inhibitors of selected micro RNAs. To improve their properties, we introduced a trimethoxystilbene residue at the 5'-terminus and three 2'-fluoro-2'-deoxynucleotides at the 3'-terminus to obtain potent inhibitors, whose mismatch discrimination is substantially better than that of typically applied >18-mers.

Tumor-associated circulating microRNAs as biomarkers of cancer

MicroRNAs (miRNAs), the 17- to 25-nucleotide long noncoding RNAs that modulate the expression of mRNAs and proteins, have emerged as critical players in cancer initiation and progression processes. Deregulation of tissue miRNA expression levels associated with specific genetic alterations has been demonstrated in cancer, where miRNAs function either as oncogenes or as tumor-suppressor genes and are shed from cancer cells into circulation. The present review summarizes and evaluates recent advances in our understanding of the characteristics of tumor tissue miRNAs, circulating miRNAs, and the stability of miRNAs in tissues and their varying expression profiles in circulating tumor cells, and body fluids including blood plasma. These advances in knowledge have led to intense efforts towards discovery and validation of differentially expressing tumor-associated miRNAs as biomarkers and therapeutic targets of cancer. The development of tumor-specific miRNA signatures as cancer biomarkers detectable in malignant cells and body fluids should help with early detection and more effective therapeutic intervention for individual patients.

Inhibition of microRNA miR-92a induces apoptosis and inhibits cell proliferation in human acute promyelocytic leukemia through modulation of p63 expression

MicroRNAs (miRNAs) are endogenous non-coding RNAs, 19-25 nucleotides in length involved in post-transcriptional regulation of gene expression of great majority of the human protein coding genes. Different aspects of cellular activities like cell growth, proliferation, and differentiation are regulated by miRNAs through their interaction with particular RNA species. In many tumors up or down-regulation of different miRNAs has been reported. Human miR-17-92 gene cluster is located on 13q31.3, rooming several miRNAs including miR-17-5p, miR-17-3p, miR-18, miR-19a, miR-20a and miR-92a. Amplification or overexpression of this cluster has been reported in acute myeloid leukemia, acute lymphoblastic leukemia and several other cancer types. Here, we performed inhibition of miR-92a in an acute promyelocytic leukemia (APL) cell line (HL-60) using locked nucleic acid (LNA) antagomir. In different time points after LNA-anti-miR92a transfection, MTT assay and annexin/propidium iodide staining were performed. These assessments indicate that miR-92a inhibition can extensively decrease the viability of these cells which is mainly due to induction of apoptosis. Western blot analysis of p63 protein also revealed that miR-92a inhibition resulted in p63 expression, hence activation of cellular pathways which are normally controlled by p63 protein are retrieved. These findings could open up a path to the miRNAs based therapeutic approach for treatment of APL.

MicroRNAs as potential biomarkers in diseases and toxicology

MiRNAs (microRNAs) are single-stranded non-coding RNAs of approximately 21-23 nucleotides in length whose main function is to inhibit gene expression by interfering with mRNA processes. MicroRNAs suppress gene expression by affecting mRNA (messenger RNAs) stability, targeting the mRNA for degradation, or both. In this review, we have examined how microRNA expression could be altered following exposure to chemicals and how they could represent appropriate tissue and more interestingly circulating biomarkers. Among the key questions before using the microRNA for evaluation of risk toxicity, it remains still to clarify how they could be causally involved in the adverse effects and how stable their changes are.

MicroRNA-378 functions as an onco-miR in nasopharyngeal carcinoma by repressing TOB2 expression

Increasing evidence indicates that microRNAs (miRNAs) has been implicated in the progression and metastasis of numerous cancers. In particular, abnormal expression of miR-378 has been observed in various cancers and is associated with cell survival, migration, invasion, angio-genesis and tumor growth. Our previous studies have shown that miR-378 was decreased in nasopharyngeal carcinoma (NPC) plasma and was negatively correlated with NPC progression. However, the tissue expression of miR-378 and its biological function remained unknown in NPC. In this study, we report for the first time that expression level of miR-378 was commonly upregulated in both NPC tissues and NPC cell lines compared to normal healthy nasopharyngeal epithelial samples and human nasopharyngeal epithelial cell lines (NP69), respectively, and was opposite to the reported results in plasma. Functional studies showed that upregulation of miR-378 dramatically promoted cell proliferation, colony formation, migration and invasion in vitro, as well as tumor growth in vivo. Bioinformatics analyses were performed to predict the target genes of miR-378, and the following mechanistic investigations revealed that miR-378 overexpression was able to downregulate the expression of transducer of ERBB2 (TOB2), a potential tumor suppressor, and miR-378 silencing enhanced TOB2 expression. In clinical specimens, TOB2 was widely repressed in tumor tissues accompanied by miR-378 overexpression. Taken together, this study indicates that miR-378 regulates TOB2 and may function as an onco-miR in NPC progression, providing a potential target for gene therapy of NPC.

Inhibition of microRNA miR-92a induces apoptosis and necrosis in human acute promyelocytic leukemia

BACKGROUND

MicroRNAs (miRNAs) are endogenous non-coding RNAs, 19-25 nucleotides in length, involved in post-transcriptional regulation of gene expression in a considerable majority of mRNAs. Different aspects of cellular activities like cell growth, proliferation, and differentiation are regulated by miRNAs through their regulatory effects on particular RNA species. In many tumors, up- or down-regulation of different miRNAs has been reported. In acute myeloid leukemia, up-regulation of miR-92a has been reported in human in-vitro studies.

MATERIALS AND METHODS

We performed inhibition of miR-92a in an acute promyelocytic leukemia cell line (HL-60), using locked nucleic acid (LNA) Antagomir. At different time points after LNA-anti-miR92a transfection, qRT-Real-Time-polymerase chain reaction (PCR) and Annexin-V/Propidium Iodide staining were performed and the data was analyzed using the Kruskal-Wallis and Mann-Whitney tests.

RESULTS

The assessment of the apoptosis and necrosis indicates that miR-92a inhibition can decrease the viable HL-60 cells and this is at least partially due to induction of apoptosis.

CONCLUSION

These findings suggest the inhibition of miR-92a as a novel approach for treatment of Acute Promyelocytic Leukemia (APL).

Circulating microRNAs as biomarkers of acute stroke

MicroRNAs have been identified as key regulators of gene expression and thus their potential in disease diagnostics, prognosis and therapy is being actively pursued. Deregulation of microRNAs in cerebral pathogenesis has been reported to a limited extent in both animal models and human. Due to the complexity of the pathology, identifying stroke specific microRNAs has been a challenge. This study shows that microRNA profiles reflect not only the temporal progression of stroke but also the specific etiologies. A panel of 32 microRNAs, which could differentiate stroke etiologies during acute phase was identified and verified using a customized TaqMan Low Density Array (TLDA). Furthermore we also found 5 microRNAs, miR-125b-2*, -27a*, -422a, -488 and -627 to be consistently altered in acute stroke irrespective of age or severity or confounding metabolic complications. Differential expression of these 5 microRNAs was also observed in rat stroke models. Hence, their specificity to the stroke pathology emphasizes the possibility of developing these microRNAs into accurate and useful tools for diagnosis of stroke.

Noninvasive micromarkers

BACKGROUND

The recent revolutionary advances made in genome-wide sequencing technology have transformed biology and molecular diagnostics, allowing new sRNA (small RNA) classes to be discovered as potential disease-specific biological indicators. Cell-free microRNAs (miRNAs) have been shown to exist stably in a wide spectrum of body fluids and their expression profiles have been shown to reflect an assortment of physiological conditions, underscoring the utility of this new class of molecules to function as noninvasive biomarkers of disease.

CONTENT

We summarize information on the known mechanisms of miRNA protection and release into extracellular space and compile the current literature on extracellular miRNAs that have been investigated as biomarkers of 20 different cancers, 11 organ damage conditions and 10 diverse disease states. We also discuss the various strategies involved in the miRNA biomarker discovery workflow and provide a critical opinion on the impediments faced by this advancing field that need to be overcome in the laboratory.

SUMMARY

The field of miRNA-centered diagnostics is still in its infancy, and basic questions with regard to the exact role of miRNAs in the pathophysiology of diseases, and the mechanisms of their release from affected cells into biological fluids are yet to be completely understood. Nevertheless, these noninvasive micromarkers have immense potential in translational medicine not only for use in monitoring the efficacy and safety of therapeutic regimens but also to guide the diagnosis of diseases, to determine the risk of developing diseases or conditions, and more importantly, to inform treatment options.

In silico prediction and in vivo validation of Daphnia pulex microRNAs

Daphnia pulex, the crustacean with the first sequenced genome, is an important organism that has been widely used in ecological and toxicological research. MicroRNAs (miRNAs) are 21–25 nucleotide small non-coding RNAs that are involved in a myriad of physiological processes. In this research, we predicted 75 D. pulex miRNAs by sequence homology and secondary structure identification from the full genome sequence. Fourteen predicted miRNAs were selected for quantitative real time polymerase chain reaction (RT-PCR) validation. Out of these, eight (mir-8, mir-9, mir-12, mir-92, mir-100, mir-133, mir-153 and mir-283) were successfully amplified and validated. Next, expression levels were quantified at three different life stages (days 4, 8 and 12 of age) using U6 spliceosomal RNA as a reference gene. The expression of mir-8, mir-9, mir-12, mir-92 and mir-100 significantly differed across time suggesting these microRNAs might play a critical role during D. pulex development. This is the first study to identify and validate miRNAs in D. pulex, which is an important first step in further studies that evaluate their roles in development and response to environmental and ecological stimuli.

[Role of tumor-derived secretary small RNAs in EBV related lymphoma]

EB virus (EBV) is associated with heterogeneous lymphomas. In these lymphomas EBV+ lymphoma cells are embedded in non-neoplastic bystanders: B and T cells, macrophages. Without these bystander cells, the lymphoma cells are incapable of being engrafted in immunodeficient mice. In this context, the bystanders are tumor-supportive "inflammatory niche". Recently, EBV-infected cells produce exosomes that contain EBV specifically encoded miRNAs (EBV-miRNAs). Accordingly, we hypothesized that exosomal EBV-miRNAs might redirect tumor surrounding immune cells from tumor reactive into tumor-supportive "inflammatory niche". The EBV-miRNAs in the exosome secreted from EBV positive lymphoma cells significantly influenced on monocyte/macrophage Mo/Mf in inducing CD69, IL-10, and TNF, suggesting that EBV-miRNAs might polarize Mo/Mf into tumor associated Mf (TAM). EBV-miRNAs were required to develop lymphoproliferative disease (LPD) in vivo mouse model. Moreover, when Mfs were depleted by clodronate liposome, EBV positive tumor cells disappeared. These results suggest that lymphoma-derived secretary EBV-miRNAs regulate Mo/Mf to support the lymphoma survival or development. Most importantly, exosomal EBV-miRNAs derived from the lymphoma cells were transferred to Mf in human EBV+ lymphoma samples, which showed correlation with prognosis.

Circulating microRNAs as Promising Tumor Biomarkers

microRNAs (miRNAs) are small, nonprotein-coding RNAs that function as posttranscriptional regulators of target genes. miRNAs are involved in multiple cell differentiation, proliferation, and apoptosis processes that are closely related to tumorigenesis. Circulating miRNAs are promising cancer biomarkers under development with great translational potential in personalized medicine. Here, we describe the origin and function of circulating miRNAs and compare the current new high-throughput technology applied to miRNA quantitation. The latest publications on circulating miRNAs were summarized, indicating that miRNAs are potential biomarkers of diagnosis, prognosis, and treatment response of major cancer types including prostate, breast, lung, colorectal, and hematological cancers. We addressed the strengths and limitations of applying circulating miRNAs in clinical laboratory and several issues associated with the accurate measurement of circulating miRNAs.

Identification and validation of miRNAs as endogenous controls for RQ-PCR in blood specimens for breast cancer studies

Introduction

A prerequisite to accurate interpretation of RQ-PCR data is robust data normalization. A commonly used method is to compare the cycle threshold (C_T) of target miRNAs with those of a stably expressed endogenous (EC) miRNA(s) from the same sample. Despite the large number of studies reporting miRNA expression patterns, comparatively few appropriate ECs have been reported thus far. The purpose of this study was to identify stably expressed miRNAs with which to normalize RQ-PCR data derived from human blood specimens.

Methods

MiRNA profiling of approximately 380 miRNAs was performed on RNA derived from blood specimens from 10 women with breast cancer and 10 matched controls. Analysis of mean expression values across the dataset (GME) identified stably expressed candidates. Additional candidates were selected from the literature and analyzed by the geNorm algorithm. Further validation of three candidate ECs by RQ-PCR was performed in a larger cohort (n = 40 cancer, n = 20 control) was performed, including analysis by geNorm and NormFinder algorithms.

Results

Microarray screening identified 10 candidate ECs with expression patterns closest to the global mean. Geometric averaging of candidate ECs from the literature using geNorm identified miR-425 as the most stably expressed miRNA. MiR-425 and miR-16 were the best combination, achieving the lowest V-value of 0.185. Further validation by RQ-PCR confirmed that miR-16 and miR-425 were the most stably expressed ECs overall. Their combined use to normalize expression data enabled the detection of altered target miRNA expression that reliably differentiated between cancers and controls in human blood specimens.

Conclusion

This study identified that the combined use of 2 miRNAs, (miR-16 and miR-425) to normalize RQ-PCR data generated more reliable results than using either miRNA alone, or use of U6. Further investigation into suitable ECs for use in miRNA RQ-PCR studies is warranted.

Assessment of operability of patients with pulmonary arterial hypertension associated with congenital heart disease

Pulmonary arterial hypertension (PAH) is a common complication of congenital heart disease, and is now predominantly among patients with uncorrected left-to-right shunts. A growing population is characterized by persistent or recurrent PAH after surgical or interventional correction of left-to-right shunts; the latter having a worse prognosis than other forms of PAH associated with congenital heart disease. New treatments for PAH have been shown to be effective in improving PAH exercise capacity and hemodynamics, raising the hope for making previously inoperable congenital heart defects operable and shifting the framework for the assessment of operability. This review focuses on current methods for assessing operability in PAH associated with congenital heart disease, and the possibility of "treat-and-repair" vs. "repair-and-treat" strategies for patients with inoperable or borderline PAH.

'Caged' peptide nucleic acids activated by red light in a singlet oxygen mediated process

Common 'caged' nucleic acid binders, which can be applied for temporal and spatial control of gene expression, are activated by high energy light (<450 nm). The light of this type is damaging to cells and is strongly absorbed by cellular components. Therefore, shifting the triggering light to the visible region (>550 nm) is highly desirable. Herein we report on a cyclic peptide nucleic acid (PNA), whose backbone contains a 9,10-dialkoxy-substituted anthracene linker. The sequence of this compound was selected to be complementary to a representative microRNA (miR-92). We demonstrated that the cyclic PNA does not bind complementary nucleic acids and is, correspondingly, 'caged'. Its uncaging can be conducted by its exposure to red light (635 nm) in the presence of pyropheophorbide-a. The latter process is mediated by singlet oxygen ((1)O2), which cleaves the 9,10-dialcoxyanthracene linker within the PNA with formation of a linear PNA, an efficient binder of the complementary ribonucleic acid. This is the first example of a red light-activated, 'caged' peptide nucleic acid.

Urinary exosomal microRNAs in incipient diabetic nephropathy

MicroRNAs (miRNAs), a class of small non-protein-encoding RNAs, regulate gene expression via suppression of target mRNAs. MiRNAs are present in body fluids in a remarkable stable form as packaged in microvesicles of endocytic origin, named exosomes. In the present study, we have assessed miRNA expression in urinary exosomes from type 1 diabetic patients with and without incipient diabetic nephropathy. Results showed that miR-130a and miR-145 were enriched, while miR-155 and miR-424 reduced in urinary exosomes from patients with microalbuminuria. Similarly, in an animal model of early experimental diabetic nephropathy, urinary exosomal miR-145 levels were increased and this was paralleled by miR-145 overexpression within the glomeruli. Exposure of cultured mesangial cells to high glucose increased miR-145 content in both mesangial cells and mesangial cells-derived exosomes, providing a potential mechanism for diabetes-induced miR-145 overexpression. In conclusion, urinary exosomal miRNA content is altered in type 1 diabetic patients with incipient diabetic nephropathy and miR-145 may represent a novel candidate biomarker/player in the complication.

Host serum miR-223 is a potential new biomarker for Schistosoma japonicum infection and the response to chemotherapy

BACKGROUND

Numerous studies have shown that aberrant microRNA (miRNA) expression is associated with the pathogenesis and progression of various human diseases. Hence, serum miRNAs are considered to be potential biomarkers for the diagnosis of human diseases. This study examined whether several miRNAs known to be commonly deregulated in liver diseases are deregulated in the serum of hosts with hepatic schistosomiasis, and thus whether they could serve as potential markers for detection of schistosome infection and evaluation of the effectiveness of chemotherapy.

METHODS

We analyzed the serum levels of six selected candidate miRNA molecules (miR-146b, miR-122, miR-223, miR-199a-5p, miR-199a-3p, miR-34a) from mice, rabbits, buffalos and humans infected with Schistosoma japonicum using qPCR. We evaluated liver pathology by determining the hydroxyproline content in liver tissues. Primary resident liver cells were isolated to quantify the expression level of deregulated miRNAs. Bioinformatics analyses were also conducted to assess the potential function of miR-223.

RESULTS

Using a mouse model of Schistosoma japonicum infection, we found that the expression level of serum miR-223 was significantly elevated after infection, but returned to near normal levels after the treatment with praziquantel (PZQ). Importantly, the level of serum miR-223 reflected the extent of liver pathology post-infection. We validated the elevated level of the circulating miR-223 in serum samples of other host species including rabbits, buffalos and humans. In addition, our results showed that miR-223 was primarily located in the Kupffer cells, but its expression levels were significantly up-regulated in hepatocytes, hepatic stellate cells and Kupffer cells after infection. Bioinformatics analyses revealed a potential functional role of miR-223 in transcription regulator activity, transcription factor activity and DNA binding.

CONCLUSIONS

This study suggested that the circulating miR-223 could serve as a potential new biomarker for the detection of schistosome infection and the assessment of the response to chemotherapy.

Up-regulation of circulating miR-20a is correlated with hepatitis C virus-mediated liver disease progression

Chronic hepatitis C virus (HCV) infection is one of the major causes of liver fibrosis and liver transplantation in the United States. Circulating microRNAs (miRNAs) in the blood are emerging as biomarkers for pathological conditions. In the present study we performed a systematic screening approach to identify up-regulated miRNAs in the plasma/serum of HCV-infected patients with different stages of hepatic histological disease severity. We initially screened serum samples of HCV-infected patients with fibrosis and compared them with sera of healthy volunteers using serum miRNA array profiling and identified a group of modulated miRNAs. Subsequent study demonstrated that miR-20a and miR-92a in HCV-infected fibrosis patients sera were significantly up-regulated when compared with that of healthy volunteers or non-HCV-associated liver disease. We have also observed an increase of plasma miR-20a and miR-92a in acute and chronic HCV-infected patients as compared to that of healthy volunteers. However, there was no correlation between the plasma/serum levels of any of these miRNAs with HCV viral loads. We next investigated longitudinal plasma samples from HCV-infected patients. Our results suggested that miR-20a and miR-92a remained unaltered in HCV-infected patients who progressed from acute to chronic infection. On the other hand, miR-92a expression was reduced in acute to resolved individuals. These data provide evidence that plasma/serum levels of miR-20a and miR-92a have potential as sensitive and cost-effective biomarkers for early detection of HCV infection.

CONCLUSION

Circulating miR-20a may serve as a potential for predictive biomarker in HCV-mediated fibrosis.

Characterization of microRNA expression profiles and the discovery of novel microRNAs involved in cancer during human embryonic development

MicroRNAs (miRNAs), approximately 22-nucleotide non-coding RNA molecules, regulate a variety of pivotal physiological or pathological processes, including embryonic development and tumorigenesis. To obtain comprehensive expression profiles of miRNAs in human embryos, we characterized miRNA expression in weeks 4-6 of human embryonic development using miRNA microarrays and identified 50 human-embryo-specific miRNAs (HES-miRNAs). Furthermore, we selected three non-conserved or primate-specific miRNAs, hsa-miR-638, -720, and -1280, and examined their expression levels in various normal and tumor tissues. The results show that expression of most miRNAs is extremely low during early human embryonic development. In addition, the expression of some non-conserved or primate-specific miRNAs is significantly different between tumor and the corresponding normal tissue samples, suggesting that the miRNAs are closely related to the pathological processes of various tumors. This study presents the first comprehensive overview of miRNA expression during human embryonic development and offers immediate evidence of the relationship between human early embryonic development and tumorigenesis.

Sweating the small stuff: microRNAs and genetic changes define pancreatic cancer

MicroRNAs (miRNAs) are 18- to 22-nucleotide-long, single-stranded, noncoding RNAs that regulate important biological processes including differentiation, proliferation, and response to cellular stressors such as hypoxia, nutrient depletion, and traversion of the cell cycle by controlling protein expression within the cell. Many investigators have profiled cancer tissue and serum miRNAs to identify potential therapeutic targets, understand the pathways involved in tumorigenesis, and identify diagnostic tumor signatures. In the setting of pancreatic cancer, obtaining pancreatic tissue is invasive and impractical for early diagnosis. Several groups have profiled miRNAs that are present in the blood as a means to diagnose tumor progression and predict prognosis/survival or drug resistance. Several miRNA signatures found in pancreatic tissue and the peripheral blood, as well as the pathways that are associated with pancreatic cancer, are reviewed here in detail. Three miRNA biomarkers (miR-21, miR-155, and miR-200) have been repetitively identified in both pancreatic cancer tissue and patients' blood. Those miRNAs regulate and are regulated by the central genetic and epigenetic changes observed in pancreatic cancer including p53, transforming growth factor β, p16(INK4A), BRCA1/2, and Kras. These miRNAs are involved in DNA repair, cell cycle, and cell invasion and also play important roles in promoting metastases.