Circulating plasma MiR-141 is a novel biomarker for metastatic colon cancer and predicts poor prognosis

Bioinformatic tools for microRNA dissection

Recently, microRNAs (miRNAs) have emerged as important elements of gene regulatory networks. MiRNAs are endogenous single-stranded non-coding RNAs (∼22-nt long) that regulate gene expression at the post-transcriptional level. Through pairing with mRNA, miRNAs can down-regulate gene expression by inhibiting translation or stimulating mRNA degradation. In some cases they can also up-regulate the expression of a target gene. MiRNAs influence a variety of cellular pathways that range from development to carcinogenesis. The involvement of miRNAs in several human diseases, particularly cancer, makes them potential diagnostic and prognostic biomarkers. Recent technological advances, especially high-throughput sequencing, have led to an exponential growth in the generation of miRNA-related data. A number of bioinformatic tools and databases have been devised to manage this growing body of data. We analyze 129 miRNA tools that are being used in diverse areas of miRNA research, to assist investigators in choosing the most appropriate tools for their needs.

Site-Specific MicroRNA Expression May Lead to Different Subtypes in Ulcerative Colitis

Background and Aim

Ulcerative Colitis (UC) is a type of inflammatory bowel disease, considered as an important disease of gastrointestinal tract having a huge impact on the health of the patient. Prolonged inflammation of colon in UC patients increases the risk of developing colorectal cancer. MiRNA are reported as a connecting link between inflammation and cancer. Differential miRNA expression is reported in Crohn’s disease (CD) patients involving various regions of the gastrointestinal tract. The current study was performed to dissect out the site specific miRNA expression in the colon biopsy samples of UC patients from Northern India.

Methods

Biopsy samples were collected from UC patients and healthy controls from Rectosigmoid Area (RS) and Ascending Colon (AC). MiRNA expression was compared between patients with RS and AC using a microarray platform. Differential expression was further validated by Real Time PCR analysis. Demographic and pathological data of UC -associated CRC patients was collected from the hospital database and analyzed for assessing the site of cancer.

Results

Upon analysis of data generated on a microarray platform and qRT PCR revealed that the expression of six miRNAs hsa-miR-146b-5p, hsa-miR-335-3p, hsa-miR-342-3p, hsa-miR-644b-3p, hsa-miR-491-3p, hsa-miR-4732-3p were downregulated in patients where RS was involved as compared to AC. The expression of hsa-miR-141-3p was upregulated in patients where RS region was involved as compared to AC. Analysis of the registered UC patient’s database from the hospital revealed that the site of CRC was predomimnantly the rectosigmoid region of the colon in most of the cases.

Conclusion

This is the first study to show the differential expression of miRNA involving different sites of colon in UC patients. Taking our data and previous reports into consideration, we propose that differential miRNA expression during UC perhaps contribute in the development of UC-associated CRC at the rectosigmoid area.

MicroRNAs as non-invasive screening biomarkers of colorectal cancer

Colorectal cancer is a major cause of cancer-associated deaths in the world. Early detection would be greatly enhanced if accurate and cost-effective diagnostic biomarkers for this disease were accessible. The development of such a blood test will evidently lower the screening costs in regards of colorectal cancer detection. Lately, it has been suggested that microRNA diagnostic biomarkers are feasible new screening methods for colorectal cancer. This review summarizes the diagnostic potential of circulating microRNA biomarkers in relation with colorectal cancer, as well as current methods to detect them.

Non-coding landscapes of colorectal cancer

For two decades Vogelstein’s model has been the paradigm for describing the sequence of molecular changes within protein-coding genes that would lead to overt colorectal cancer (CRC). This model is now too simplistic in the light of recent studies, which have shown that our genome is pervasively transcribed in RNAs other than mRNAs, denominated non-coding RNAs (ncRNAs). The discovery that mutations in genes encoding these RNAs [i.e., microRNAs (miRNAs), long non-coding RNAs, and circular RNAs] are causally involved in cancer phenotypes has profoundly modified our vision of tumour molecular genetics and pathobiology. By exploiting a wide range of different mechanisms, ncRNAs control fundamental cellular processes, such as proliferation, differentiation, migration, angiogenesis and apoptosis: these data have also confirmed their role as oncogenes or tumor suppressors in cancer development and progression. The existence of a sophisticated RNA-based regulatory system, which dictates the correct functioning of protein-coding networks, has relevant biological and biomedical consequences. Different miRNAs involved in neoplastic and degenerative diseases exhibit potential predictive and prognostic properties. Furthermore, the key roles of ncRNAs make them very attractive targets for innovative therapeutic approaches. Several recent reports have shown that ncRNAs can be secreted by cells into the extracellular environment (i.e., blood and other body fluids): this suggests the existence of extracellular signalling mechanisms, which may be exploited by cells in physiology and pathology. In this review, we will summarize the most relevant issues on the involvement of cellular and extracellular ncRNAs in disease. We will then specifically describe their involvement in CRC pathobiology and their translational applications to CRC diagnosis, prognosis and therapy.

Prognostic Role of MicroRNA-200c-141 Cluster in Various Human Solid Malignant Neoplasms

The miR-200 family has emerged recently as a noticeable marker for predicting cancer prognosis and tumor progression. We aimed to review the evidence of miR-200c-141 genomic cluster as prognostic biomarkers in cancers. The results suggested that high level of miR-200c had no significant impact on OS (HR = 1.14 [0.77-1.69], P = 0.501) and DFS/PFS (HR = 0.72 [0.45-1.14], P = 0.161). Stratified analyses revealed that high miR-200c expression was significantly related to poor OS in serum/plasma (HR = 2.12 [1.62-2.77], P = 0.000) but not in tissues (HR = 0.89 [0.58-1.37], P = 0.599). High miR-200c expression was significantly associated with favorable DFS/PFS in tissues (HR = 0.56 [0.43-0.73], P = 0.000) but worse DFS/PFS in serum/plasma (HR = 1.90 [1.08-3.36], P = 0.027). For miR-141, we found that high miR-141 expression predicted no significant impact on OS (HR = 1.18 [0.74-1.88], P = 0.482) but poor DFS/PFS (HR = 1.11 [1.04-1.20], P = 0.003). Similarly, subgroup analyses showed that high miR-141 expression predicted poor OS in serum/plasma (HR = 4.34 [2.30-8.21], P = 0.000) but not in tissues (HR = 1.00 [0.92-1.09], P = 0.093). High miR-141 expression was significantly associated with worse DFS/PFS in tissues (HR = 1.12 [1.04-1.20], P = 0.002) but not in serum/plasma (HR = 0.90 [0.44-1.83], P = 0.771). Our findings indicated that, compared to their tissue counterparts, the expression level of miR-200c and miR-141 in peripheral blood may be more effective for monitoring cancer prognosis. High miR-141 expression was better at predicting tumor progression than survival for malignant tumors.

MicroRNA expression profiles of bovine milk exosomes in response to Staphylococcus aureus infection

BACKGROUND

Milk exosomes are a rich source of microRNAs (miRNAs) that are protected from degradation. Ingestion of milk and subsequent absorption of miRNAs into recipient cells by endocytosis may play a role in the regulation of neonatal innate and adaptive immunity. In contrast, the miRNA content of milk exosomes may also be indicative of a lactating animal's health; whereby, the presence or absence of specific miRNAs could serve as biomarkers for early detection of bacterial infection that can lead to mastitis. In the present study, we therefore analyzed and compared miRNA expression profiles of milk exosomes from four Holstein cows obtained during mid-lactation prior to and after infection (48 h) of the mammary gland with Staphylococcus aureus.

METHODS

Milk exosomes, purified from control and S. aureus infected cows, were extracted for RNA. Following preparation indexed libraries from both groups the samples were subjected to next generation sequencing.

RESULTS

Next generation sequencing of eight, unpooled small RNA libraries derived from milk exosomes produced about 60.5 million high-quality, bovine-specific sequence reads for comparison of miRNA expression between treatments. Sequence identity analysis showed the miRNAs make up about 13 % of the average RNA content of these exosomes. Although 417 known bovine miRNAs were identified, miRNAs represented the least diverse class of RNA accounting for only 1 % of all unique sequences. The 20 most prevalent unique sequences within this class accounted for about 90 % of the total miRNA-associated reads across samples. Non-annotated, unique reads provided evidence for another 303 previously unknown bovine miRNAs. Expression analyses found 14 known bovine microRNAs significantly differed in frequency between exosomes from infected and control animals.

CONCLUSIONS

Our survey of miRNA expression from uninfected milk exosomes and those produced in response to infection provides new and comprehensive information supporting a role for delivery into milk of specific miRNAs involved in immune response. In particular, bta-miR-142-5p, and -223 are potential biomarkers for early detection of bacterial infection of the mammary gland. Additionally, 22 mammary-expressed genes involved in regulation of host immune processes and response to inflammation were identified as potential binding targets of the differentially expressed miRNAs.

Thrombospondin-1 in a Murine Model of Colorectal Carcinogenesis

Colorectal Cancer (CRC) is one of the late complications observed in patients suffering from inflammatory bowel diseases (IBD). Carcinogenesis is promoted by persistent chronic inflammation occurring in IBD. Understanding the mechanisms involved is essential in order to ameliorate inflammation and prevent CRC. Thrombospondin 1 (TSP-1) is a multidomain glycoprotein with important roles in angiogenesis. The effects of TSP-1 in colonic tumor formation and growth were analyzed in a model of inflammation-induced carcinogenesis. WT and TSP-1 deficient mice (TSP-1^-/-) of the C57BL/6 strain received a single injection of azoxymethane (AOM) and multiple cycles of dextran sodium sulfate (DSS) to induce chronic inflammation-related cancers. Proliferation and angiogenesis were histologically analyzed in tumors. The intestinal transcriptome was also analyzed using a gene microarray approach. When the area containing tumors was compared with the entire colonic area of each mouse, the tumor burden was decreased in AOM/DSS-treated TSP-1^-/- versus wild type (WT) mice. However, these lesions displayed more angiogenesis and proliferation rates when compared with the WT tumors. AOM-DSS treatment of TSP-1^-/- mice resulted in significant deregulation of genes involved in transcription, canonical Wnt signaling, transport, defense response, regulation of epithelial cell proliferation and metabolism. Microarray analyses of these tumors showed down-regulation of 18 microRNAs in TSP-1^-/- tumors. These results contribute new insights on the controversial role of TSP-1 in cancer and offer a better understanding of the genetics and pathogenesis of CRC.

Differential expression of circulating microRNAs according to severity of colorectal neoplasia

There is a need to develop a colorectal cancer (CRC) screening test that is noninvasive, cost effective, and sensitive enough to detect preneoplastic lesions. This case-control study examined the feasibility of using circulating extracellular microRNAs (miRNAs) to differentiate a spectrum of colorectal neoplasia of various severity and hence for early detection of colorectal neoplasia. Archived serum samples of 10 normal controls and 31 cases, including 10 with nonadvanced adenoma, 10 with advanced adenoma, and 11 with CRC, were profiled for circulating miRNAs using next-generation sequencing. Multiple linear regression, adjusting for age, gender, and smoking status, compared controls and the 3 case groups for levels of 175 miRNAs that met stringent criteria for miRNA sequencing analysis. Of the 175 miRNAs, 106 miRNAs were downregulated according to severity of neoplasia and showed a relative decrease in the expression from controls to nonadvanced adenoma to advanced adenoma to CRC (Ptrend < 0.05). Pairwise group comparisons showed that 39 and 80 miRNAs were differentially expressed in the advanced adenoma and CRC groups compared with the controls, respectively. Differences in miRNA levels between the nonadvanced adenoma group and controls were modest. Our study found that expression of many miRNAs in serum was inversely correlated with the severity of colorectal neoplasia, and differential miRNA profiles were apparent in preneoplastic cases with advanced lesions, suggesting circulating miRNAs could serve as potential biomarkers for CRC screening.

Suitability of circulating miRNAs as potential prognostic markers in colorectal cancer

miRNAs are crucial in cellular processes and have been shown to be abnormally expressed in cancer tissue and the circulation. Circulating miRNAs may serve as a novel class of minimally invasive biomarkers for prognosis. Within a first methodologic study, we evaluated the miRNA profile kinetics in the plasma of patients with colorectal cancer after surgical tumor removal to identify potential suitability as prognostic biomarkers. This pilot study is based on the ColoCare Study, a cohort study of newly diagnosed patients with stage I-IV colorectal cancer. Colorectal cancer pre- and postsurgical blood (2-7 days after surgery) and 6 months follow-up blood from 35 patients were examined and candidate miRNAs were investigated in the plasma. miRNA levels were measured by two-step qRT-PCR. Statistical analysis was performed using log-transformed normalized CT values using SAS 9.3. Comparing pre- and postsurgical miRNA levels revealed a statistically significant decrease of nine circulating miRNAs after surgery (miR92a, miR18a, miR320a, miR106a, miR16-2, miR20a, miR223, miR17, and miR143). Analyses of plasma levels over all three time points demonstrated a statistically significant decrease from presurgery to postsurgery and re-increase from postsurgery to the six months follow-up time point of four circulating miRNAs (miR92a, miR320a, miR106a, and miR18a). We were able to show for the first time that in plasma miRNA profiles change within days after colorectal cancer surgery. Our results underscore the role of the investigated miRNAs in colorectal cancer and their potential utility as prognostic biomarkers. See all the articles in this CEBP Focus section, "Biomarkers, Biospecimens, and New Technologies in Molecular Epidemiology."

Serum miRNA expression profile as a prognostic biomarker of stage II/III colorectal adenocarcinoma

We sought to identify a serum miRNA expression profile to improve disease surveillance and to predict post-operative disease recurrence for stage II/III colorectal cancer (CRC) patients. Using the TaqMan Low-Density Array (TLDA), we performed an initial survey to analyze 749 miRNAs in the pooled serum of 20 paired pre- and post-operative CRC patients and 20 matched normal subjects. Using individual RT-qPCR verification in 175 stage II/III CRC patients, we identified that miR-145, miR-106a and miR-17-3p were significantly differentially expressed between pre- and post-operative CRC patients and between pre-operative CRC patients and normal controls (P < 0.0001). The area under the ROC curve (AUC) for the three-miRNA panel was 0.886 (95% CI 0.850-0.921) for discriminating between pre-operative CRC patients and normal subjects and 0.850 (95% CI 0.809-0.891) for discriminating between pre- and post-operative CRC patients. Furthermore, using the Kaplan-Meier method and Cox proportional hazards analysis, we found that miR-17-3p and miR-106a were powerful and independent prognostic indicators and that high levels of these miRNAs were associated with shorter disease-free survival (DFS) (P < 0.0001 for miR-17-3p and P = 0.001 for miR-106a). The present study reveals novel serum-miRNA-based biomarkers for monitoring tumor dynamics as well as for predicting disease recurrence in patients with stage II/III CRC.

Molecular biomarkers in colorectal carcinoma

Colorectal cancer is a tumor with increasing incidence which represents one of the first leading causes of death worldwide. Gene alterations described for colorectal cancer include genome instability (microsatellite and chromosomal instability), CpG islands methylator phenotype, microRNA, histone modification, protein biomarkers, gene mutations (RAS, BRAF, PI3K, TP53, PTEN) and polymorphisms (APC, CTNNB1, DCC). In this article, biomarkers with prognostic value commonly found in colorectal cancer will be reviewed.

Combined assays for serum carcinoembryonic antigen and microRNA-17-3p offer improved diagnostic potential for stage I/II colon cancer

Colorectal cancer is among the leading causes of cancer-related mortality, one of the main reasons for which is the lack of an effective screening method for early-stage disease. The levels of carcinoembryonic antigen (CEA) and microRNA (miR)-17-3p in the serum of 70 patients with stage I/II colon cancer and 70 healthy volunteers were determined, and the diagnostic value of CEA plus miR-17-3p detection for colon cancer was assessed. The levels of CEA were measured by a radioimmunoassay method, and those of miR-17-3p using the reverse transcription-quantitative polymerase chain reaction method. miR-16 was used as the endogenous control, as it displayed high stability, high abundance and low variability in the analyzed serum samples. The receiver operating characteristic (ROC) curve analysis indicated the potential diagnostic value of the two markers and the area under the ROC curve (AUC) for CEA and miR-17-3p was 0.719 (95% CI: 0.658-0.843) and 0.807 (95% CI: 0.748-0.906), respectively. At a threshold of 9.6 ng/ml for CEA, the optimal sensitivity and specificity were 74.6 and 84.3%, respectively, in discriminating colon cancer patients from healthy controls. At a threshold of 2.98 for miR-17-3p, the sensitivity and the specificity were 83.6 and 72.9%, respectively. A combined ROC analysis using CEA and miR-17-3p revealed an AUC of 0.929 (95% CI: 0.834-0.978) with a sensitivity of 96.4% and a specificity of 95.7% in discriminating colon cancer patients from healthy controls. In conclusion, both CEA and miR-17-3p were highly expressed in the serum of our series of colon cancer patients. CEA plus miR-17-3p detection significantly increased the sensitivity and specificity in discriminating stage I/II colon cancer patients from healthy controls. Therefore, combined detection of serum CEA and miR-17-3p levels may have the potential to become a new laboratory method for the early clinical diagnosis of colon cancer.

Circulating miR-200-family micro-RNAs have altered plasma levels in patients with endometriosis and vary with blood collection time

OBJECTIVE

To determine whether circulating micro-RNA (miR) 200a, miR-200b, and miR-141 have altered levels in patients with endometriosis compared with control individuals.

DESIGN

Experimental laboratory study.

SETTING

University.

PATIENT(S)

Patients with endometriosis (n = 61), laparoscopically confirmed endometriosis-free women (n = 35), and self-reported healthy women (n = 30) were included in the study.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Plasma miRNA levels in endometriosis patients and control subjects.

RESULT(S)

We found that the levels of studied miRNAs varied with blood collection time, being lower in the morning than in the evening. When blood collection time was taken into account, the results revealed significantly lower levels of miR-200a and miR-141 in the evening plasma samples of women with endometriosis compared with surgically confirmed disease-free patients. However, the evening-sample levels of all three miRNAs were significantly lower in patients with stage I-II endometriosis than in endometriosis-free control subjects. In cases of stage III-IV endometriosis, only miR-200a levels were significantly lower compared with patients without endometriosis. Circulating miR-200a showed the best discriminative power to differentiate women with endometriosis from patients with similar complaints but without the disease.

CONCLUSION(S)

Our findings suggest that miR-200a and miR-141 have a potential as novel noninvasive biomarkers for endometriosis. In addition, we found that the plasma miR-200a, miR-200b and miR-141 levels vary with blood sampling time, so it is important to take the sample collection time into account when studying miRNAs as biomarkers.

MicroRNAs as potential drug targets for therapeutic intervention in colorectal cancer

INTRODUCTION

MicroRNAs (miRNAs) are small (19 - 22 nucleotide), non-protein-coding RNA segments that function as master regulators of hundreds of genes simultaneously in both normal and malignant cells. In colorectal cancer (CRC) miRNAs are deregulated and have critical roles in initiation and progression of CRC by interacting with various oncogenes and tumor suppressor genes including APC, KRAS and p53, or by modulating downstream signal transduction pathways. Numerous promising miRNAs have emerged as potential drug targets for therapeutic intervention and possible candidates for replacement therapy in CRC.

AREAS COVERED

In this review the authors summarize the available information on miRNAs and their role in CRC. The authors point out specific miRNAs as potential drug targets and those having a significant role in gene activation and gene silencing during the process of CRC development, to highlight their importance as possible therapeutic candidates for the treatment of CRC.

EXPERT OPINION

Targeting miRNAs provides an emerging opportunity to develop effective miRNA-based replacement therapy or antagonists to alter expression in colon cancer patient tumors. However, the biggest challenge is to overcome obstacles associated with pharmacokinetics, delivery and toxicity in order to translate the potential of miRNAs into efficacious anticancer drugs.

Effects of Decitabine on Invasion and Exosomal Expression of miR-200c and miR-141 in Oxaliplatin-Resistant Colorectal Cancer Cells

The effects of decitabine (DAC), a DNA methyltransferase (DNMT) inhibitor, on metastasis and exosomal expression of microRNAs were examined in SW620/OxR cells, a human colorectal cancer (CRC) cell line (SW620) with acquired resistance to oxaliplatin. This cell line shows an invasive phenotype by epithelial-mesenchymal transition. Two CRC cell lines, SW480, derived from primary CRC, and SW620, derived from lymph node metastasis, which were obtained from the same patient, as well as SW620/OxR, were also used in the present study. Cytarabine (Ara-C), a non-DNMT-inhibiting cytidine analog, was used as negative control of DAC. No significant difference was observed in the invasion abilities of SW480 cells treated with DAC or Ara-C. On the other hand, invasion ability was suppressed by treatment with DAC in SW620 and SW620/OxR cells. Up-regulated expression of E-cadherin, microRNA-200c (miR-200c), and miR-141 following DAC treatment indicated the acquisition of epithelial cell-like characteristics in SW620 and SW620/OxR cells. Exosomal expression levels of miR-200c and miR-141 were also up-regulated by DAC treatment in SW620 and SW620/OxR but not in SW480 cells. This increase in exosomal miRNA expression negatively correlated with invasion ability. These results suggest that DNA demethylation treatment caused acquisition of epithelial cell-like characteristics in SW620 and SW620/OxR cells. Furthermore, the observed increased exosomal expression of miR-200c and miR-141 may be an indicator or biomarker candidate for mesenchymal-epithelial transition of CRC cells.

The circulating transcriptome as a source of non-invasive cancer biomarkers: concepts and controversies of non-coding and coding RNA in body fluids

The gold standard for cancer diagnosis remains the histological examination of affected tissue, obtained either by surgical excision, or radiologically guided biopsy. Such procedures however are expensive, not without risk to the patient, and require consistent evaluation by expert pathologists. Consequently, the search for non-invasive tools for the diagnosis and management of cancer has led to great interest in the field of circulating nucleic acids in plasma and serum. An additional benefit of blood-based testing is the ability to carry out screening and repeat sampling on patients undergoing therapy, or monitoring disease progression allowing for the development of a personalized approach to cancer patient management. Despite having been discovered over 60 years ago, the clear clinical potential of circulating nucleic acids, with the notable exception of prenatal diagnostic testing, has yet to translate into the clinic. The recent discovery of non-coding (nc) RNA (in particular micro(mi)RNAs) in the blood has provided fresh impetuous for the field. In this review, we discuss the potential of the circulating transcriptome (coding and ncRNA), as novel cancer biomarkers, 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.

Circulating miR-103 and miR-720 as novel serum biomarkers for patients with colorectal cancer

Circulating microRNAs (miRNAs) have been reported as a biomarker for human malignancies, including colorectal cancer (CRC). The purpose of this study was to identify a novel biomarker for CRC through examination of serum miRNAs from the patients with CRC. Microarray analysis of miRNA expression was performed using paired pre- and post-operative serum from 10 CRC patients. miR-103 and miR-720 decreased significantly in the post-operative serum when compared to pre-operative serum. With an extended scale validation by qRT-PCR (quantitative real-time polymerase chain reaction) in 30 CRC patients, we confirmed that serum miR-103 and miR-720 decreased significantly after surgery (P=0.0004, and P=0.0274, respectively). Next, we examined serum miR-103 and miR-720 levels in 32 non-cancer patients and 84 CRC patients, and we found that expression of these two miRNAs was significantly higher in CRC patients than non-cancer patients. Furthermore, clinical and pathological survey indicated that high expression of miR-103 was significantly associated with histological differentiation grade, and lymphatic invasion and high expression of miR-720 was significantly associated with male gender and lymph node metastasis. Our data suggest that circulating miR-103 and miR-720 show potential as novel serum biomarkers for CRC.

A microRNA molecular modeling extension for prediction of colorectal cancer treatment

Background

Several studies show that the regulatory impact of microRNAs (miRNAs) is an essential contribution to the pathogenesis of colorectal cancer (CRC). The expression levels of diverse miRNAs are associated with specific clinical diagnoses and prognoses of CRC. However, this association reveals very little actionable information with regard to how or whether to treat a CRC patient. To address this problem, we use miRNA expression data along with other molecular information to predict individual response of CRC cell lines and CRC patients.

Methods

A strategy has been developed to join four types of information: molecular, kinetic, genetic and treatment data for prediction of individual treatment response of CRC.

Results

Information on miRNA regulation, including miRNA target regulation and transcriptional regulation of miRNA, in integrated into an in silico molecular model for colon cancer. This molecular model is applied to study responses of seven CRC cell lines from NCI-60 to ten agents targeting signaling pathways. Predictive results of models without and with implemented miRNA information are compared and advantages are shown for the extended model. Finally, the extended model was applied to the data of 22 CRC patients to predict response to treatments of sirolimus and LY294002. The in silico results can also replicate the oncogenic and tumor suppression roles of miRNA on the therapeutic response as reported in the literature.

Conclusions

In summary, the results reveal that detailed molecular events can be combined with individual genetic data, including gene/miRNA expression data, to enhance in silico prediction of therapeutic response of individual CRC tumors. The study demonstrates that miRNA information can be applied as actionable information regarding individual therapeutic response.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1437-0) contains supplementary material, which is available to authorized users.

The potential of plasma miRNAs for diagnosis and risk estimation of colorectal cancer

Circulating microRNAs (miRNAs) were recognized to be potential non-invasive biomarkers for colorectal cancer (CRC) detection and prediction. Meanwhile, the association of the expression of plasma miRNAs with the risk of CRC patients has rarely been analyzed. Therefore, we conducted this study to evaluate the value of plasma miRNAs for CRC diagnosis and risk estimation. Fasting blood samples from 100 CRC patients and 79 cancer-free controls were collected. Plasma miR-106a, miR-20a, miR-27b, miR-92a and miR-29a levels were detected by RT-qPCR. Sensitivity and specificity were employed to evaluate the diagnostic value of miRNAs for CRC. Univariate and multivariate logistic regression were employed to analyze the association between miRNAs expression and CRC risk. As results, miR-106a and miR-20a were elevated in the patients with CRC. The sensitivity of miR-106a was 74.00% and the specificity was 44.40%, while the cutoff value was 2.03. As for miR-20a, the sensitivity was 46.00% and specificity was 73.42% when employed 2.44 as cutoff value. High expression of plasma miR-106a increased CRC risk by 1.80 -fold. Plasma miR-106a and miR-20a may as noninvasive biomarkers for detecting the CRC. High expression of miR-106a associated with CRC risk.

Prospects for Therapeutic Targeting of MicroRNAs in Human Immunological Diseases

MicroRNAs (miRNAs) are endogenous oligoribonucleotides with exciting therapeutic potential. Early studies established a clear role for miRNAs in leukocyte biology. The first miRNA-based therapy, miravirsen, is now in phase 2 clinical trials, making the reality of these therapies undeniable. The capacity for miRNAs to fine-tune inflammatory signaling make them attractive treatment targets for immunological diseases. Nonetheless, the degree of redundancy among miRNAs, coupled with the promiscuity of miRNA binding sites in the transcriptome, require consideration when designing miRNA-directed interventions. Altered miRNA expression occurs across a range of inflammatory conditions, including inflammatory bowel disease, arthritis, and diabetes. However, very few studies successfully treated murine models of immunological diseases with miRNA-based approaches. While discussing recent studies targeting miRNAs to treat immunological conditions, we also reflect on the risks of miRNA targeting and showcase some newer delivery systems that may improve the pharmacological profile of this class of therapeutics.

miR-27 is associated with chemoresistance in esophageal cancer through transformation of normal fibroblasts to cancer-associated fibroblasts

There is increasing evidence that the expression of microRNA (miRNA) in cancer is associated with chemosensitivity but the mechanism of miRNA-induced chemoresistance has not been fully elucidated. The aim of this study was to examine the role of extracellular miRNA in the response to chemotherapy in esophageal cancer. First, serum expression of miRNAs selected by miRNA array was measured by quantitative reverse transcription-polymerase chain reaction in 68 patients with esophageal cancer who received cisplatin-based chemotherapy to examine the relationship between miRNA expression and response to chemotherapy. The serum expression levels of 18 miRNAs were different between responders and non-responders by miRNA array. Of these, high expression levels of miR-27a/b correlated with poor response to chemotherapy in patients with esophageal cancer. Next, in vitro assays were conducted to investigate the mechanism of miRNA-induced chemoresistance. Although transfection of miR-27a/b to cancer cells had no significant impact on chemosensitivity, esophageal cancer cells cultured in supernatant of miR-27a/b-transfected normal fibroblast showed reduced chemosensitivity to cisplatin, compared with cancer cells cultured in supernatant of normal fibroblast. MiR-27a/b-transfected normal fibroblast showed α-smooth muscle actin (α-SMA) expression, a marker of cancer-associated fibroblasts (CAF) and increased production of transforming growth factor-β (TGF-β). Chemosensitivity recovered after administration of neutralizing antibody of TGF-β to the supernatant transfer experiments. Our results indicated that miR-27a/b is involved in resistance to chemotherapy in esophageal cancer, through miR-27a/b-induced transformation of normal fibroblast into CAF.

A Long Non-coding RNA Activated by Transforming Growth Factor-β is an Independent Prognostic Marker of Gastric Cancer

BACKGROUND

A recent study reported that long non-coding RNA activated by TGF-β (lncRNA-ATB) induced epithelial-mesenchymal transition (EMT) through the transforming growth factor-β (TGF-β)/miR-200s/ZEB axis in hepatocellular carcinoma. Herein, we focused on the clinical significance of lncRNA-ATB in gastric cancer (GC) patients.

MATERIALS AND METHODS

Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) was performed to examine expression of lncRNA-ATB, miR-200b, and miR-200c in GC tissues (n = 183). Patients were divided into high and low lncRNA-ATB expression groups using a cutoff of lncRNA-ATB/GAPDH ≥0.60 or <0.60 to determine the clinicopathological significance of lncRNA-ATB in GC. Moreover, we evaluated the expression of TGF-β, lncRNA-ATB, miR-200s, and ZEB1 in GC cell lines by qRT-PCR. GC cell lines were treated by recombinant TGF-β1 or TGF-β receptor inhibitor to examine morphologic changes and genetic alterations, such as lncRNA-ATB, miR-200s, and ZEB1 levels, with respect to the EMT phenotype.

RESULTS

The high lncRNA-ATB group experienced a lower overall survival rate compared with the low lncRNA-ATB group, and multivariate analysis indicated that lncRNA-ATB was an independent prognostic factor (hazard ratio 3.50; 95 % CI 1.73-7.44; p = 0.0004). miR-200c levels were lower and ZEB1 levels were higher in the high lncRNA-ATB group than in the low lncRNA-ATB group. Treatment with TGF-β in GC cell lines resulted in morphological EMT changes, upregulation of lncRNA-ATB and ZEB1, and downregulation of miR-200c and CDH1. SB431542 reduced lncRNA-ATB expression.

CONCLUSION

LncRNA-ATB plays an important role in EMT to promote invasion and metastasis through the TGF-β/miR-200s/ZEB axis, resulting in a poor prognosis in GC. LncRNA-ATB is a novel biomarker of lncRNA, indicative of a poor prognosis in GC patients.

Circulating miRNAs miR-34a and miR-150 associated with colorectal cancer progression

BACKGROUND

Screening for the early detection of colorectal cancer is important to improve patient survival. The aim of this study was to investigate the potential of circulating cell-free miRNAs as biomarkers of CRC, and their efficiency at delineating patients with polyps and benign adenomas from normal and cancer patient groups.

METHODS

The expression of 667 miRNAs was assessed in a discovery set of 48 plasma samples comprising normal, polyp, adenoma, and early and advanced cancer samples. Three miRNAs (miR-34a, miR-150, and miR-923) were further examined in a validation cohort of 97 subjects divided into the same five groups, and in an independent public dataset of 40 CRC samples and paired normal tissues.

RESULTS

High levels of circulating miR-34a and low miR-150 levels distinguished groups of patients with polyps from those with advanced cancer (AUC = 0.904), and low circulating miR-150 levels separated patients with adenomas from those with advanced cancer (AUC = 0.875). In addition, the altered expression of miR-34a and miR-150 in an independent public dataset of forty CRC samples and paired normal tissues was confirmed.

CONCLUSION

We identified two circulating miRNAs capable of distinguishing patient groups with different diseases of the colon from each other, and patients with advanced cancer from benign disease groups.

microRNA-218 expression and its association with the clinicopathological characteristics of patients with cervical cancer

The aim of the present study was to investigate the expression of microRNA-218 (miRNA-218) in the serum and cervical tissue and its association with the clinicopathological features of cervical cancer (CC). The expression of miRNA-218 was detected in the serum and cervical tissue of 112 patients with CC and 50 age-matched hysteromyoma patients via the reverse transcription-quantitative polymerase chain reaction. The clinical data were collected and the association between the expression of miRNA-218 and the clinicopathological characteristics of the patients was analyzed. The expression of miRNA-218 in the cancer group was significantly decreased in the cervical tissue and serum compared with that in the control group (P<0.001). The decreased expression of miRNA-218 was associated with a later International Federation of Gynecology and Obstetrics stage, a more invasive pathological type and lymphatic node metastasis but not with age, age at menarche, menopausal status, number of pregnancies and deliveries, family history of cancer or tumor size. In conclusion, miRNA-218 was found to be downregulated in the cancer tissue and serum of the patients with CC. The decreased expression of miRNA-218 in CC was associated with the invasiveness of the tumor.

The pathological role of microRNAs and inflammation in colon carcinogenesis

Evidence of an association between inflammation, microRNAs (miRNAs) and tumorigenesis has emerged in recent years. Patients with inflammatory bowel disease (IBD) are at an increased risk for colorectal cancer (CRC) development, suggesting that inflammatory mediators play a causative role in colon carcinogenesis. MiRNAs are small (19-22 nucleotides) non-coding RNA molecules that regulate gene expression at the post-transcriptional level by base-pairing to specific messenger RNAs (mRNAs), promoting their degradation or suppressing translation. MiRNAs can act as inflammatory mediators, oncogenes or tumor suppressors in different cellular environments. MiRNAs also serve as biomarkers and therapeutic targets in CRC. The risk of CRC is also influenced by miRNA polymorphisms and binding sites. Their functions as early diagnostic biomarkers or prognostic classifiers has been demonstrated. Here, we reviewed recent findings on miRNAs and inflammation in colon carcinogenesis and discussed the potential for miRNAs and inflammation-related genes as biomarkers and therapeutic targets in CRC.

MicroRNAs as potential biomarkers in cancer: opportunities and challenges

MicroRNAs (miRNAs) are a group of small noncoding RNAs (ncRNAs) that posttranscriptionally regulate gene expression by targeting their corresponding messenger RNAs (mRNAs). Dysregulated miRNAs have been considered as a new type of ‘‘oncomiRs” or ‘‘tumor suppressors,” playing essential roles in cancer initiation and progression. Using genome-wide detection methods, ubiquitously aberrant expression profiles of miRNAs have been identified in a broad array of human cancers, showing great potential as novel diagnostic and prognostic biomarkers of cancer with high specificity and sensitivity. The detectable miRNAs in tissue, blood, and other body fluids with high stability provide an abundant source for miRNA-based biomarkers in human cancers. Despite the fact that an increasing number of potential miRNA biomarkers have been reported, the transition of miRNAs-based biomarkers from bench to bedside still necessitates addressing several challenges. In this review, we will summarize our current understanding of miRNAs as potential biomarkers in human cancers.

Graphene oxide-assisted nucleic acids assays using conjugated polyelectrolytes-based fluorescent signal transduction

In this work, we investigated the interactions between graphene oxide (GO) and conjugated polyelectrolytes (CPEs) with different backbone and side chain structures. By studying the mechanism of fluorescence quenching of CPEs by GO, we find that the charge and the molecular structure of CPEs play important roles for GO-CPEs interactions. Among them, electrostatic interaction, π-π interaction, and cation-π bonding are dominant driving forces. By using a cationic P2, we have developed a sensitive homogeneous sensor for DNA and RNA detection with a detection limit of 50 pM DNA and RNA, which increased the sensitivity by 40-fold as compared to GO-free CPE-based sensors. This GO-assisted CPE sensing strategy is also generic and shows a high potential for biosensor designs based on aptamers, proteins, peptides, and other biological probes.

microRNA-214 enhances the invasion ability of breast cancer cells by targeting p53

Breast cancer (BC) is the foremost cause of cancer-related mortality in women worldwide. An increasing number of studies has confirmed that microRNAs (miRNAs or miRs) play an important role in the development and progression of BC. microRNA-214 (miR-214), a member of the miRNA family, has been demonstrated to function as both a tumor suppressor and oncogene in various types of human cancer. However, the biological function of miR-214 in BC remains unclear. The present study was designed to investigate the potential role of miR-214 in the development and progression of BC. Our results revealed that miR-214 expression was significantly increased in the BC tissues compared with the adjacent benign tissues, and that the upregulation of miR-214 was significantly associated with the invasion ability of the BC cells. Furthermore, p53, which has been reported to be downregulated in BC, was predicted to be the target gene of miR-214 using bioinformatics software programs. Moreover, luciferase reporter vectors were constructed and it was confirmed that p53 is a target of miR-214. Following the transfection of miR-214 into BC cells, we found that the overexpression of miR-214 markedly enhanced cell invasion through the downregulation of p53 expression. By contrast, the overexpression of p53 abrogated the effects of miR-214. In conclusion, this study demonstrates that miR-214 functions as an oncogene in BC, at least partly by promoting cell invasion through the downregulation of p53. Therefore, miR-214 may be a potential therapeutic target for the treatment of BC.

Significance of serum microRNA-21 in diagnosis of hepatocellular carcinoma (HCC): clinical analyses of patients and an HCC rat model

MicroRNAs (miRNAs) are associated with human carcinogenesis and tumor development. Moreover, serum miRNAs can reflect the level of tissue miRNAs and be potential tumor markers. Serum microRNA-21 (miR-21) is overexpressed in many human cancers including hepatocellular carcinoma (HCC). However, how serum miR-21 changes during the HCC formation and whether miR-21 plays a regulatory role in this whole process are unknown. The current study evaluated the prognostic and diagnostic potential of serum miR-21 in HCC patients. Next, we established a HCC rat model and collected the blood and liver tissues at regular time points. AFP from the serum, RNA from the serum and liver tissues were collected and quantified separately. The results revealed that tissue and serum miR-21 was upregulated significantly in the groups of cirrhosis, early and advanced HCC compared with normal and fibrosis groups. The AFP levels were increased in early and advanced HCC compared with other groups. Then, the changes of miR-21 downstream proteins (i.e., programmed cell death 4 [PDCD4] and phosphatase and tensin homolog [PTEN]) in the liver tissues were measured. PDCD4 and PTEN expression was decreased gradually after tumor induction and negatively correlated with miR-21 expression. All these results suggested that serum miR-21 was associated with the prognosis of HCC; the changes in serum miR-21 were earlier and more accurately reflected the pathogenesis of HCC than AFP; therefore, it could be used as an early diagnostic marker for HCC. Our in vivo experiments further confirmed that miR-21 plays an important role in promoting the occurrence and development of HCC by regulating PDCD4 and PTEN.

Analysis of tissue and serum microRNA expression in patients with upper urinary tract urothelial cancer

Introduction

MicroRNAs play an important role in many human malignancies; so far, their expression remains to be studied in upper urinary tract urothelial cancer (UUTUC).

Materials and Methods

The expression of eleven microRNAs (miR-10a, miR-21, miR-96, miR-135, miR-141, miR-182, miR-200b, miR-205, miR-429, miR-520b, miR-1244) formerly shown to be upregulated in urothelial bladder cancer were studied in corresponding normal and cancerous tissue samples of patients undergoing nephroureterectomy for UUTUC. Upregulated microRNAs were then measured in serum samples of patients with UUTUC and patients with non-malignant urological diseases to evaluate their potential as non-invasive biomarkers for UUTUC.

Results

MicroRNA expression allowed differentiation of normal and cancerous tissue: miR-21, miR-96, miR-135, miR-141, miR-182, miR-205, miR-429 and miR-520b were significantly overexpressed. Furthermore, miR-205 was upregulated in poorly differentiated UUTUC. The analysis of circulating RNA in serum demonstrated an increase of miR-141 in patients with UUTUC; receiver operator characteristic analysis demonstrated an area under the curve of 0.726 for miR-141 as a diagnostic biomarker. Furthermore, we observed lower levels of miR-10a and miR-135 in UUTUC patients.

Conclusions

MicroRNA expression is altered in UUTUC. The analysis of circulating miR-141 may be useful to identify patients with UUTUC.

Circulating microRNA testing for the early diagnosis and follow-up of colorectal cancer patients

Early detection of colorectal cancer (CRC) is key for prevention and the ability to impact long-term survival of CRC patients. However, the compliance rate of recommended colonoscopy for the population aged from 50 to 75 years is only 50-75 % in the US. A highly sensitive and specific non-invasive test is needed to enhance CRC management. As for late-stage patients, a non-invasive prognostic biomarker is also critical for improving patient treatment protocols. The discovery that non-coding microRNAs (miRNAs) are stable in body fluids such as plasma, serum and exosomes presents the opportunity to develop novel strategies, taking advantage of circulating miRNAs as early diagnostic biomarkers of CRC. The goal of using circulating miRNA-based prognostic biomarkers for CRC patients has been pursued extensively. In this review, we will try to cover the major recent advancements at the frontier of this research area.

Epigenetics of colorectal cancer

Colorectal cancer (CRC) is one of most common malignancies and a leading cause of cancer related deaths worldwide. Epigenetic change is an important mechanism of colorectal carcinogenesis. Accumulation of epigenetic changes was found in colorectal cancer and other tumors. Aberrant changes in DNA methylation, histone modification, imprinting, and noncoding RNAs were frequently found in human colorectal cancer. Epigenetic changes may serve as a diagnostic, prognostic, and chemo-sensitive marker. It also becomes a cancer preventive or therapeutic target in some circumstances.

A plasma microRNA panel for early detection of colorectal cancer

Colonoscopy remains the standard screening method for detecting colorectal cancer (CRC) at an early stage. However, many people avoid having a colonoscopy because of the fear for its potential complications. Our study aimed to identify plasma microRNAs for preliminarily screening CRC in general population, so that some unnecessary colonoscopies can be avoided. We investigated plasma microRNA expression in three independent cohorts including the discovery (n = 80), training (n = 112), and validation (n = 49) phases recruited at two medical centers. Microarrays were used for screening 723 microRNAs in 80 plasma samples to identify candidate microRNAs. Quantitative reverse-transcriptase PCR was performed on the 161 training and validation plasma samples to evaluate the candidate microRNAs discovered from microarrays. A logistic regression model was constructed based on the training cohort and then verified by using the validation dataset. Area under the receiver operating characteristic curve (AUC) was used to evaluate the diagnostic accuracy. We identified a panel of miR-409-3p, miR-7, and miR-93 that yielded high diagnostic accuracy in discriminating CRC from healthy group (AUC: 0.866 and 0.897 for training and validation dataset, respectively). Moreover, the diagnostic performance of the microRNA panel persisted in nonmetastasis CRC stages (Dukes' A-B, AUC: 0.809 and 0.892 for training and validation dataset, respectively) and in metastasis CRC stages (Dukes' C-D, AUC: 0.917 and 0.865 for training and validation dataset, respectively). In conclusion, our study reveals a plasma microRNA panel that has potential clinical value in early CRC detection and would play a critical role on preliminarily screening CRC in general population.

microRNAs and Colorectal Cancer

Colorectal cancer (CRC) is one of the most common types of human cancer with high cancer-related morbidity and mortality rates. The development and clinical validation of novel therapeutic avenues have improved the clinical outcome, but metastatic CRC still remains an incurable disease in most cases. The interest in discovering novel pathophysiological drivers in CRC is intensively ongoing and the search for novel biomarkers for early diagnosis, for patient's stratification for prognostic purposes or for predicting treatment response are warranted. microRNAs are small RNA molecules that regulate the expression of larger messenger RNA species by different mechanisms with the final consequence to provide a fine tuning tool for global gene expression patterns. First discovered in worms, around 15 years ago it became clear that microRNAs are also existing in humans and that they are widely involved in human carcinogenesis. Within the last years, tremendous progress in the understanding of microRNAs and their role in CRC carcinogenesis has been developed. In this book chapter, several examples of previously identified microRNAs and how they influence colorectal carcinogenesis will be discussed. The information starting at the underlying molecular mechanisms towards clinical applications will be depicted and an overview what great potential these small molecules might carry in future colorectal cancer medicine, will be discussed.

Circulating miRNAs: roles in cancer diagnosis, prognosis and therapy

MicroRNAs (miRNAs) belong to a class of small non-coding RNAs that regulate numerous biological processes by targeting a broad set of messenger RNAs. Recently, miRNAs have been detected in remarkably stable forms in many types of body fluids. A comparison between cancer patients and healthy individuals has clearly shown that certain types of circulating miRNAs are associated with cancer initiation and progression. Research on miRNA-based biomarkers has witnessed phenomenal growth, owing to the non-invasive nature of miRNA-based screening assays and their sensitivity and specificity in detecting cancers. Consequently, a considerable effort has been devoted to identify suitable miRNAs for cancer diagnosis and also decode the information carried by circulating miRNAs. This review highlights the current studies that focus on the identification of circulating miRNA-based diagnostic and prognostic markers, for the most prevalent types of cancer. Additionally, the review also provides an insight into the putative functions of miRNAs, and attempts to delineate the mechanisms through which they are released into the bloodstream. Moreover, methodologies and strategies for identification of circulating miRNAs in cancers are summarized. Finally, potential strategies for circulating miRNA-based cancer therapies are proposed.

miR-224 overexpression is a strong and independent prognosticator of short-term relapse and poor overall survival in colorectal adenocarcinoma

Colorectal adenocarcinoma constitutes the most frequent form of colorectal cancer and a serious cause of cancer-related deaths. The expression of multiple miRNAs, including miR-224, is deregulated in colorectal adenocarcinoma. The aim of this study was the investigation of the prognostic value of miR-224 in colorectal adenocarcinoma. For this purpose, total RNA was isolated from 115 colorectal adenocarcinomas and 66 adjacent non-cancer mucosae. Total RNA (2 µg) was polyadenylated and reverse transcribed. A quantitative PCR method based on SYBR-Green chemistry was developed and applied for the quantification of miR-224 levels, followed by extensive biostatistical analysis. miR-224 levels in malignant colorectal adenocarcinomas ranged between 1.81 and 187.75 RQU (miR-224 copies/1,000 SNORD48 copies) with a median of 34.27, and were significantly elevated, compared to miR-224 levels in adjacent non-cancer mucosae (p<0.001). Enhanced miR-224 expression constitutes a rather strong prognosticator in colorectal adenocarcinoma, predicting short-term relapse and poor overall survival in these patients (p=0.012 and p=0.005, respectively), independent of established clinicopathological parameters. In conclusion, miR-224 is significantly upregulated in malignant colorectal tumors compared to adjacent non-cancer mucosae, and its enhanced expression constitutes an independent predictor of short-term relapse and poor overall survival in colorectal adenocarcinoma patients.

Circulating microRNA biomarker studies: pitfalls and potential solutions

BACKGROUND

Circulating microRNAs have been proposed as disease biomarkers that may aid in risk assessment, diagnosis, prognosis, and monitoring of treatment response. The perceived opportunity has loomed particularly large in neoplastic disease, where alterations in cancer cells are thought to be reflected in the extracellular space as affected cells release upregulated miRNAs or fail to release apparently downregulated species. Despite the promise of miRNA biomarkers, evaluation of the diagnostic specificity and reproducibility of reported markers suggests that realizing this promise remains a work in progress.

CONTENTS

This review examines issues of diagnostic specificity and reproducibility that have afflicted circulating miRNA studies. Surveying the breast cancer literature as an example, few miRNAs are reported consistently. Furthermore, it is posited that the assumptions underlying models of direct contributions of diseased tissue to biofluid miRNA profiles may not hold. Suggestions for improving diagnostic specificity and reliability are provided.

SUMMARY

To maximize the likelihood of return on investment as miRNAs continue to be evaluated as specific and clinically useful markers, a focus is needed on miRNAs found in specific carriers, such as extracellular vesicles. Alternative sampling techniques should be developed, and nonblood biofluids should be considered. Careful optimization and standardization of preanalytical and analytical methods is needed to ensure that future results, positive or negative, are reliable.

Cell-free microRNAs as cancer biomarkers: the odyssey of miRNAs through body fluids. Med Oncol. 2014;31:295. [PMID: 25362261 DOI: 10.1007/s12032-014-0295-y]

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.

An update on microRNAs as colorectal cancer biomarkers: where are we and what's next?

miRNAs are abundant classes of small, endogenous non-coding RNAs, which inhibit the expression of target gene via post-transcriptional regulation. In addition to an important functional role miRNAs play in carcinogenesis, emerging evidence has demonstrated their feasibility as robust cancer biomarkers. In particular, the recent discovery of miRNAs in the body fluids provides an attractive opportunity for the development of non-invasive biomarkers for the diagnosis, prognosis and predictive response to cancer therapy. Colorectal cancer (CRC) is one of the most common cancers worldwide, and accumulating data provides a compelling case for the potential exploitation of miRNAs as CRC-biomarkers. This review summarizes the current state of literature in the field, focusing on the clinical relevance of miRNAs as potential biomarkers for CRC treatment and discussing the forthcoming challenges to further advance this exciting field of 'academic research' into 'bedside clinical care' of patients suffering from CRC.

Regulation of cancer metastasis by cell-free miRNAs

MicroRNAs (miRNAs) are integral molecules in the regulation of numerous physiological cellular processes that have emerged as critical players in cancer initiation and metastatic progression, both by promoting and suppressing metastasis. Recently, cell-free miRNAs shed from cancer cells into circulation have been reported in cancer patients, raising hope for development of novel biomarkers that can be routinely measured in easily accessible samples. In fact, establishing miRNA expression in the circulation likely has advantages over determination in primary tumor tissue, further augmenting the potential applications of miRNA detection in oncological practice. In addition, secretion of miRNAs impacting distant cell signaling or promoting the formation of a niche that sustains a distant tumor microenvironment allows for new treatment approaches to thwart cancer progression.

Deep sequencing of RNA from three different extracellular vesicle (EV) subtypes released from the human LIM1863 colon cancer cell line uncovers distinct miRNA-enrichment signatures

Secreted microRNAs (miRNAs) enclosed within extracellular vesicles (EVs) play a pivotal role in intercellular communication by regulating recipient cell gene expression and affecting target cell function. Here, we report the isolation of three distinct EV subtypes from the human colon carcinoma cell line LIM1863 – shed microvesicles (sMVs) and two exosome populations (immunoaffinity isolated A33-exosomes and EpCAM-exosomes). Deep sequencing of miRNA libraries prepared from parental LIM1863 cells/derived EV subtype RNA yielded 254 miRNA identifications, of which 63 are selectively enriched in the EVs - miR-19a/b-3p, miR-378a/c/d, and miR-577 and members of the let-7 and miR-8 families being the most prominent. Let-7a-3p*, let-7f-1-3p*, miR-451a, miR-574-5p*, miR-4454 and miR-7641 are common to all EV subtypes, and 6 miRNAs (miR-320a/b/c/d, miR-221-3p, and miR-200c-3p) discern LIM1863 exosomes from sMVs; miR-98-5p was selectively represented only in sMVs. Notably, A33-Exos contained the largest number (32) of exclusively-enriched miRNAs; 14 of these miRNAs have not been reported in the context of CRC tissue/biofluid analyses and warrant further examination as potential diagnostic markers of CRC. Surprisingly, miRNA passenger strands (star miRNAs) for miR-3613-3p*, -362-3p*, -625-3p*, -6842-3p* were the dominant strand in A33-Exos, the converse to that observed in parental cells. This finding suggests miRNA biogenesis may be interlinked with endosomal/exosomal processing.

Evaluation and identification of microRNA-106 in the diagnosis of cancer: a meta-analysis

Recently, extensive research has identified the non-invasive and cost-effective biomarker microRNA-106 (miR-106) in cancer detection. However, inconsistent results have prevented its usage in clinical. Therefore, we conducted this meta-analysis aimed to systematically determine diagnostic accuracy of miR-106 in distinguishing patients with cancer from cancer-free controls and further evaluate its value serving as a biomarker in clinical. We conducted a systematically literature search in databases (PubMed, web of science, Embase and the Cochrane Library) collecting relevant articles up to July 22th, 2014. The overall diagnostic accuracy of miR-106 was assessed by the following indexes: sensitivity, specificity, PLR, NLR and DOR. The SROC curve with AUC value was also generated for the assessment. Due to the significant heterogeneity, the random effects approach was chosen in our analysis and meta-regression was performed to explore the potential source of it. We also tested potential presence of publication bias using Deeks' funnel plots test. Stata 12.0 statistical software was used for analysis in the present study. Overall, the 11 studies involving 756 cancer patients and 834 controls were considered eligible in our analysis. The results in our work showed that sensitivity of 0.57 (95% CI: 0.44-0.68) and specificity of 0.85 (95% CI: 0.72-0.92), with the under area AUC value of 0.75 (95% CI: 0.71-0.79) for miR-106 assay. Additionally, the combined PLR, NLR and DOR describing the discriminatory ability were 3.7 (95% CI: 2.2-6.2), 0.51 (95% CI: 0.42-0.62) and 7 (95% CI: 4-12) in the present analysis. The results in our meta-analysis showed that miR-106 had moderate accuracy in identifying cancer patients. Thus, further larger-scale prospective studies are needed to improve the diagnostic efficiency and explore the combination of miR-106 and other biomarkers with more pronounced accuracy.

Upregulation of microRNA 181c expression in gastric cancer tissues and plasma

OBJECTIVE

To test the microRNA-181c (miR-181c) expression in tissues and plasma of gastric cancer (GC) cases, analyze any correlations, and explore the possibility of miR-181c as a potential molecular marker for GC diagnosis.

MATERIALS AND METHODS

Relative miR-181c expression levels in cancers and plasma from 30 GC patients was tested using reverse transcription?real-time fluorescent quantitation PCR and compared to that in samples from 30 gastric ulcer and 30 chronic gastritis patients.

RESULTS

The miR-181c expression level in the GC tissues was significantly higher than that in the gastric ulcer and chronic gastritis tissues (P = 0.000), as was the miR-181c expression level in the GC plasma (P = 0.000). We determined that miR-181c expression in GC plasma was positively correlated to its expression in the GC tissues (P = 0.000).

CONCLUSIONS

The expression of miR-181c is upregulated in GC tissues and plasma, and the miR-181c expression level in GC plasma is positively correlated to that in the corresponding cancer tissues. Plasma miR-181c is possibly a new serological marker for GC diagnosis.

MicroRNA dysregulation as a prognostic biomarker in colorectal cancer

Colorectal cancer (CRC) is one of the most potentially curable cancers, yet it remains the fourth most common overall cause of cancer death worldwide. The identification of robust molecular prognostic biomarkers can refine the conventional tumor–node–metastasis staging system, avoid understaging of tumor, and help pinpoint patients with early-stage CRC who may benefit from aggressive treatments. Recently, epigenetic studies have provided new molecular evidence to better categorize the CRC subtypes and predict clinical outcomes. In this review, we summarize recent findings concerning the prognostic potential of microRNAs (miRNAs) in CRC. We first discuss the prognostic value of three tissue miRNAs (miR-21-5p, miR-29-3p, miR-148-3p) that have been examined in multiple studies. We also summarize the dysregulation of miRNA processing machinery DICER in CRC and its association with risk for mortality. We also reviewe the potential application of miRNA-associated single-nucleotide polymorphisms as prognostic biomarkers for CRC, especially the miRNA-associated polymorphism in the KRAS gene. Last but not least, we discuss the microsatellite instability-related miRNA candidates. Among all these candidates, miR-21-5p is the most promising prognostic marker, yet further prospective validation studies are required before it can go into clinical usage.