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

Identification of reference miRNAs in plasma useful for the study of oestrogen-responsive miRNAs associated with acquired Protein S deficiency in pregnancy

Background

Accumulating evidence indicate that circulating microRNAs (miRNAs) are useful independent non-invasive biomarkers, with unique miRNA signatures defined for various pathophysiological conditions. However, there are no established universal housekeeping miRNAs for the normalisation of miRNAs in body fluids. We have previously identified an oestrogen-responsive miRNA, miR-494, in regulating the anticoagulant, Protein S, in HuH-7 liver cells. Moreover, increased thrombotic risk associated with elevated circulating oestrogen levels is frequently observed in pregnant women and oral contraceptive users. In order to identify other oestrogen-responsive miRNAs, including miR-494, that may be indicative of increased thrombotic risk in plasma, we used nanoString analysis to identify robust and stable endogenous reference miRNAs for the study of oestrogen-responsive miRNAs in plasma.

Results

We compared the plasma miRNA expression profile of individuals with: (1) Low circulating oestrogens (healthy men and non-pregnant women not taking oral contraceptives), (2) High circulating synthetic oestrogens, (women taking oral contraceptives) and (3) High circulating natural oestrogens (pregnant females >14 weeks gestation). From the nanoString analyses, 11 candidate reference miRNAs which exhibited high counts and not significantly differentially expressed between groups were selected for validation using realtime quantitative polymerase chain reaction (RT-qPCR) and digital droplet PCR (DDPCR) in pooled plasma samples, and the stability of their expression evaluated using NormFinder and BestKeeper algorithms. Four miRNAs (miR-25-5p, miR-188-5p, miR-222-3p and miR-520f) demonstrated detectable stable expression between groups and were further analysed by RT-qPCR in individual plasma samples, where miR-188-5p and miR-222-3p expression were identified as a stable pair of reference genes. The miRNA reference panel consisting of synthetic spike-ins cel-miR-39 and ath-miR159a, and reference miRNAs, miR-188-5p and miR-222-3p was useful in evaluating fold-change of the pregnancy-associated miRNA, miR-141-3p, between groups.

Conclusion

The miRNA reference panel will be useful for normalising qPCR data comparing miRNA expression between men and women, non-pregnant and pregnant females, and the potential effects of endogenous and synthetic oestrogens on plasma miRNA expression.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-017-2636-3) contains supplementary material, which is available to authorized users.

Non-coding RNAs Enabling Prognostic Stratification and Prediction of Therapeutic Response in Colorectal Cancer Patients

Colorectal cancer (CRC) is a heterogeneous disease and current treatment options for patients are associated with a wide range of outcomes and tumor responses. Although the traditional TNM staging system continues to serve as a crucial tool for estimating CRC prognosis and for stratification of treatment choices and long-term survival, it remains limited as it relies on macroscopic features and cases of surgical resection, fails to incorporate new molecular data and information, and cannot perfectly predict the variety of outcomes and responses to treatment associated with tumors of the same stage. Although additional histopathologic features have recently been applied in order to better classify individual tumors, the future might incorporate the use of novel molecular and genetic markers in order to maximize therapeutic outcome and to provide accurate prognosis. Such novel biomarkers, in addition to individual patient tumor phenotyping and other validated genetic markers, could facilitate the prediction of risk of progression in CRC patients and help assess overall survival. Recent findings point to the emerging role of non-protein-coding regions of the genome in their contribution to the progression of cancer and tumor formation. Two major subclasses of non-coding RNAs (ncRNAs), microRNAs and long non-coding RNAs, are often dysregulated in CRC and have demonstrated their diagnostic and prognostic potential as biomarkers. These ncRNAs are promising molecular classifiers and could assist in the stratification of patients into appropriate risk groups to guide therapeutic decisions and their expression patterns could help determine prognosis and predict therapeutic options in CRC.

The role of microRNAs in colorectal liver metastasis: Important participants and potential clinical significances

Colorectal cancer is one of the most common cancers in the world, and liver metastasis is the leading direct cause of cancer-related deaths in colorectal cancer. MicroRNA is involved in tumor metastasis in many aspects; mounting studies have shown that microRNAs play important roles in colorectal liver metastasis. Although lots of reviews about the association between microRNAs and colorectal cancer metastasis have been published, the reviews specifically focusing on microRNAs and colorectal liver metastasis are still lacking in the literature. To address this issue, here, we summarize the underlying mechanisms of microRNAs in colorectal liver metastasis and explore their potential clinical applications in this aspect.

Epigenetics of colorectal cancer: emerging circulating diagnostic and prognostic biomarkers

Colorectal cancer (CRC) is one of the most common cancers worldwide and the second leading cause of cancer-related mortality in western countries. Despite the high incidence, treatment options for advanced CRC remain limited and unsuccessful, resulting in a poor prognosis. Therefore, novel accurate diagnostic, prognostic and predictive biomarkers are clearly and urgently needed to detect advanced colon polyps and early stage CRC and to identify the most effective treatments for specific CRC patients. CRC is known to develop from early premalignant lesions to full blown cancer via a multi-step process involving a series of genetic mutations that accumulate over time. Recent improvement of our understanding of CRC biology and advances in genomic technologies has led to the identification of a variety of epigenetic alterations strongly involved in cancer initiation and progression. Among the epigenetic marks implicated in CRC the most widely studied are the global DNA hypomethylation, the promoter hypermethylation and the miRNAs dysregulations. Many evidence exist that such tumour associated alterations may serve as new potential biomarkers. Moreover, due the non-invasive, objective, and potential reproducible assessment, circulating epigenetic biomarkers have reached increasing attentions in the last few years. In this review, we attempt to analyze the existing most recent literature on the role of circulating DNA methylations and miRNAs alterations in CRC diagnosis and prognosis.

The miR-200 family in ovarian cancer

Ovarian cancer (OC) is the most lethal gynecological malignancy. Its insidious nature, manifesting with little to no symptoms until the disease progresses to metastasis, along with a wide diversity of histological subtypes and corresponding clinical behavior, poses significant therapeutic challenges. The genetic profiling of this aggressive tumor and its subtypes has led to the identification of various molecular markers of prognosis. Among these, the miR-200 family of miRNAs appears to play an important role. The deregulated expression of the miR-200 family members has been detected in a variety of OC studies. The present review examines the potential usefulness of the miR-200 family members as prognostic indicators in ovarian cancer and their impact across different OC publications, with a particular focus on prognostic features, such as disease stage, tumor histology, survival and response to chemotherapy. We present the potential usefulness of the miR-200 family genes as prognostic indicators in OC and highlight the tendency that miR-200 overexpression corresponds with an advanced cancer stage.

Noncoding RNAs in Cancer Diagnosis

The accuracy and efficiency of tumor treatment depends mainly on early and precise diagnosis. Although histopathology is always the gold standard for cancer diagnosis, noninvasive biomarkers represent an opportunity for early detection and molecular staging of cancer. Besides the classical tumor markers, noncoding RNAs (ncRNAs) emerge to be a novel category of biomarker for cancer diagnosis since the dysregulation of ncRNAs is closely associated with the development and progression of human cancers such as liver, lung, breast, gastric, and other kinds of cancers. In this chapter, we will summarize the different types of ncRNAs in the diagnosis of major human cancers. In addition, we will introduce the recent advances in the detection and applications of circulating serum or plasma ncRNAs and non-blood fluid ncRNAs because the noninvasive body fluid-based assays are easy to examine for cancer diagnosis and monitoring.

Biological effects and clinical characteristics of microRNA-106a in human colorectal cancer

MicroRNAs serve important roles in various diseases, particularly cancer. microRNA-106a (miR-106a) exhibits abnormal expression and oncogenic activity in carcinogenesis. The clinical significance of the abnormal expression of miR-106a in colorectal cancer is poorly understood. In the present study, miR-106a expression from colorectal cancer tissues was quantified using the reverse transcription-quantitative polymerase chain reaction. The overexpression or knockdown of miR-106a was performed by transfection with microRNA mimic or inhibitor in human colorectal carcinoma HCT116 cells. The overexpression of miR-106a promoted viability and inhibited apoptosis in colorectal cancer cells. The association between miR-106a expression and clinicopathological factors was analyzed, and it was identified that miR-106a exhibited significantly increased expression in adenocarcinoma tissues compared with in mucinous carcinoma tissues, and the expression of miR-106a was identified to be associated with the depth of invasion and differentiation. The expression of miR-106a in plasma was also determined and it was identified that increased expression of miR-106a, as a characteristic of patients with colorectal cancer, may be distinguished from that of other patients by digitization of the areas under the receiver operating characteristic curves. These data suggested that miR-106a is a potential biomarker in the diagnosis of colorectal carcinoma. However, the underlying molecular mechanism of miR-106a-promoted viability and inhibition of apoptosis requires further investigation.

MicroRNAs: Potential candidates for diagnosis and treatment of colorectal cancer

Colorectal cancer (CRC) is known as the third common cancer worldwide and an important public health problem in different populations. Several genetics and environmental risk factors are involved in the development and progression of CRC including chromosomal abnormalities, epigenetic alterations, and unhealthy lifestyle. Identification of risk factors and biomarkers could lead to a better understanding of molecular pathways involved in CRC pathogenesis. MicroRNAs (miRNAs) are important regulatory molecules which could affect a variety of cellular and molecular targets in CRC. A large number of studies have indicated deregulations of some known tissue-specific miRNAs, for example, miR-21, miR-9, miR-155, miR-17, miR-19, let-7, and miR-24 as well as circulating miRNAs, for example, miR-181b, miR-21, miR-183, let-7g, miR-17, and miR-126, in patients with CRC. In the current review, we focus on the findings of preclinical and clinical studies performed on tissue-specific and circulating miRNAs as diagnostic biomarkers and therapeutic targets for the detection of patients at various stages of CRC.

Circulating microRNA-203 predicts prognosis and metastasis in human colorectal cancer

BACKGROUND AND AIMS

Distant metastasis is a major cause of deaths in patients with colorectal cancer (CRC), which is partly due to lack of robust metastasis-predictive biomarkers. In spite of the important function of microRNA (miR)-203 in cancer metastasis, its clinical significance in CRC metastasis remains unknown. Here, we evaluated the potential role of serum miR-203 as a non-invasive biomarker for CRC metastasis.

METHODS

MiR-203 expression was quantified by quantitative reverse-transcription PCR in 58 pairs of primary CRC (pCRC) and corresponding matched liver metastasis (LM), as well as 186 serum and 154 matched tissue specimens from patients with CRC in cohort 1. Next, we performed validation of miR-203 levels in serum from 144 patients with CRC in an independent cohort (cohort 2). Mouse models of CRC-associated metastases were established to identify the source of circulating miR-203. Expression patterns of miR-203 in tissues were determined by in situ hybridisation.

RESULTS

MiR-203 expression was significantly upregulated in LM compared with matched pCRC tissues. Serum miR-203 levels were significantly upregulated in a stage-dependent manner, and high miR-203 expression was associated with poor survival in patients with CRC in both patient cohorts. Increased miR-203 levels in serum indicated high risk for poor prognosis (HR=2.1), as well as metastasis to lymph nodes (OR=2.5), liver (OR=6.2), peritoneum (OR=7.2) and distant organs (OR=4.4). Serum miR-203 levels were significantly higher in animals with liver or systemic metastasis compared with controls.

CONCLUSIONS

High levels of serum miR-203 associate with poor survival and metastasis, suggesting it to be a promising non-invasive prognostic and metastasis-predictive biomarker in patients with CRC.

Noncoding RNAs in the development, diagnosis, and prognosis of colorectal cancer

More than 90% of the human genome is actively transcribed, but less than 2% of the total genome encodes protein-coding RNA, and thus, noncoding RNA (ncRNA) is a major component of the human transcriptome. Recently, ncRNA was demonstrated to play important roles in multiple biological processes by directly or indirectly interfering with gene expression, and the dysregulation of ncRNA is associated with a variety of diseases, including cancer. In this review, we summarize the function and mechanism of miRNA, long intergenic ncRNA, and some other types of ncRNAs, such as small nucleolar RNA, circular ncRNA, pseudogene RNA, and even protein-coding mRNA, in the progression of colorectal cancer (CRC). We also presented their clinical application in the diagnosis and prognosis of CRC. The summary of the current state of ncRNA in CRC will contribute to our understanding of the complex processes of CRC initiation and development and will help in the discovery of novel biomarkers and therapeutic targets for CRC diagnosis and treatment.

Prognostic Role of the MicroRNA-200 Family in Various Carcinomas: A Systematic Review and Meta-Analysis

Background/Aims. The miRNA-200 (miR-200) family may act as key inhibitors of epithelial-to-mesenchymal transition. However, the potential prognostic value of miR-200s in various human malignancies remains controversial. This meta-analysis analyzed the associations between miR-200 levels and survival outcomes in a variety of tumors. Methods. Eligible published studies were identified by searching the Embase, PubMed, CINAHL, and Google scholar databases. Patient clinical data were pooled, and pooled hazard ratios (HRs) with 95% confidence intervals (95% CI) were used to calculate the strength of this association. Results. The pooled HRs suggested that high tissue expression of miR-200 family members was associated with better survival (overall survival [OS]: HR = 0.70, 95% CI 0.54–0.91; progression-free survival [PFS]: HR = 0.63, 95% CI 0.52–0.76) in thirty-four eligible articles. In contrast, higher expression of circulating miR-200 members was significantly associated with poor clinical outcome (OS, HR = 1.68, 95% CI 1.15–2.46; PFS, HR = 2.62, 95% CI 1.68–4.07). Conclusion. The results from this meta-analysis suggest that miR-200 family members are potential prognostic biomarkers in patients with various carcinomas. To apply these findings in the clinic, large prospective studies are needed to validate the prognostic values of miR-200s in individual cancer types.

miR-141 promotes colon cancer cell proliferation by inhibiting MAP2K4

MicroRNAs (miRNAs or miRs) can function as tumor-suppressor or oncogenic genes. Upregulation of miRNA-141 has been frequently observed in colorectal cancer (CRC) samples. The experimentally observed targets of miR-141 include the tumor-suppressor gene mitogen-activated protein kinase kinase 4 (MAP2K4). The aim of the present study was to investigate the role of miR-141 in the proliferation of colonic cancer. Western blotting, immunohistochemistry and reverse transcription-quantitative polymerase chain reaction were used to detect the expression levels of miR-141 and MAP2K4 in colonic adenocarcinoma (CAC) and adjacent non-cancerous (NC) tissue samples, as well as in human CAC cell lines (HT29, T94 and LS174). MTT assay was used to investigate the proliferation and apoptosis of these three cell lines. The expression levels of miR-141 were significantly upregulated in clinical samples of CAC, compared with adjacent NC tissues. By contrast, MAP2K4 was downregulated in CAC. The in vitro assays demonstrated that overexpression of miR-141 resulted in cell proliferation of CAC by inhibiting MAP2K4 activity. Our study suggests that targeting the miR-141-MAP2K4 signaling pathway may represent a novel approach for the treatment of CRC.

MicroRNA-141 suppresses prostate cancer stem cells and metastasis by targeting a cohort of pro-metastasis genes

MicroRNAs play important roles in regulating tumour development, progression and metastasis. Here we show that one of the miR-200 family members, miR-141, is under-expressed in several prostate cancer (PCa) stem/progenitor cell populations in both xenograft and primary patient tumours. Enforced expression of miR-141 in CD44⁺ and bulk PCa cells inhibits cancer stem cell properties including holoclone and sphere formation, as well as invasion, and suppresses tumour regeneration and metastasis. Moreover, miR-141 expression enforces a strong epithelial phenotype with a partial loss of mesenchymal phenotype. Whole-genome RNA sequencing uncovers novel miR-141-regulated molecular targets in PCa cells including the Rho GTPase family members (for example, CDC42, CDC42EP3, RAC1 and ARPC5) and stem cell molecules CD44 and EZH2, all of which are validated as direct and functionally relevant targets of miR-141. Our results suggest that miR-141 employs multiple mechanisms to obstruct tumour growth and metastasis.

MicroRNAs have important roles in regulating tumor development, progression and metastasis. Here, the authors demonstrate the tumor-suppressive functions of miRNA141 in prostate cancer stem cells mediated by directly targeting CD44, Rho GTPase protein family members, and EZH2.

[The microRNAs as biomarkers: What prospects?]

MicroRNAs are nucleic acids of about twenty nucleotides that regulate about a third of the genome at the post-transcriptional level. Thanks to their different forms of transport, microRNAs are stable and can be detected in biological fluids such as blood, urine, cerebrospinal fluid, or saliva. In addition, the profile of circulating microRNAs is a specific part of the cells in which it is secreted and is modified according to the physiological or pathological conditions of these cells. MicroRNAs therefore appear as biomarkers of interest for many diseases. However, these applications face several challenges because there are currently considerable differences between the sample processing procedures, assay methods, and especially the result standardization strategies. This literature review aims to take stock of the current use of microRNAs as biomarkers mainly in biological fluids and address the perspectives that emerge from the fact that their vesicular circulating forms could be used to assess the state of the cells and the tissues that produce them.

The microRNA-200 family: still much to discover

In the last decade, microRNAs (miRs or miRNAs) became of great interest in cancer research due to their multifunctional and active regulation in a variety of vital cellular processes. In this review, we discuss the miR-200 family, which is composed of five members (miR-141, miR-200a/200b/200c and miR-429). Although being among the best investigated miRNAs in the field, there are still many open issues. Here, we describe the potential role of miR-200 as prognostic and/or predictive biomarker, its influence on motility and cell migration as well as its role in epithelial to mesenchymal transition (EMT) and metastasis formation in different tumour types. Recent studies also demonstrated the influence of miR-200 on drug resistance and described a correlation between miR-200 expression levels and overall survival of patients. Despite intense research in this field, the full role of the miR-200 family in cancer progression and metastasis is not completely understood and seems to differ between different tumour types and different cellular backgrounds. To elucidate these differences further, a finer characterisation of the role of the individual miRNA-200 family members is currently under investigation.

Application of molecular biology of differentiated thyroid cancer for clinical prognostication

Although cancer outcome results from the interplay between genetics and environment, researchers are making a great effort for applying molecular biology in the prognostication of differentiated thyroid cancer (DTC). Nevertheless, role of molecular characterisation in the prognostic setting of DTC is still nebulous. Among the most common and well-characterised genetic alterations related to DTC, including mutations of BRAF and RAS and RET rearrangements, BRAF^V600E is the only mutation showing unequivocal association with clinical outcome. Unfortunately, its accuracy is strongly limited by low specificity. Recently, the introduction of next-generation sequencing techniques led to the identification of TERT promoter and TP53 mutations in DTC. These genetic abnormalities may identify a small subgroup of tumours with highly aggressive behaviour, thus improving specificity of molecular prognostication. Although knowledge of prognostic significance of TP53 mutations is still anecdotal, mutations of the TERT promoter have showed clear association with clinical outcome. Nevertheless, this genetic marker needs to be analysed according to a multigenetic model, as its prognostic effect becomes negligible when present in isolation. Given that any genetic alteration has demonstrated, taken alone, enough specificity, the co-occurrence of driving mutations is emerging as an independent genetic signature of aggressiveness, with possible future application in clinical practice. DTC prognostication may be empowered in the near future by non-tissue molecular prognosticators, including circulating BRAF^V600E and miRNAs. Although promising, use of these markers needs to be refined by the technical sight, and the actual prognostic value is still yet to be validated.

Circulating miR-21-5p and miR-148a-3p as emerging non-invasive biomarkers in thymic epithelial tumors

Thymic epithelial cells give rise to both thymoma and thymic carcinoma. A crucial advance in thymic epithelial tumors (TET) management may derive from the identification of novel molecular biomarkers able to improve diagnosis, prognosis and treatment planning.In a previous study, we identified microRNAs that were differentially expressed in tumor vs normal thymic tissues. Among the microRNAs resulted up-regulated in TET tissues, we evaluated miR-21-5p, miR-148a-3p, miR-141-3p, miR-34b-5p, miR-34c-5p, miR-455-5p as blood plasma circulating non-invasive biomarkers for TET management.We firstly report that the expression levels of specific onco-miRNAs, that we found upregulated in the blood plasma collected from TET patients at surgery, resulted significantly reduced in follow-up samples.This pilot study suggests that circulating miR-21-5p and miR-148a-3p could represent novel non-invasive biomarkers to evaluate the efficacy of therapy and the prognosis of TET.

Downregulation of mir-23b in plasma is associated with poor prognosis in patients with colorectal cancer

MicroRNAs (miRNAs) are short, non-coding RNA molecules that act as regulators of gene expression. Circulating blood miRNAs have potential as cancer biomarkers. The main objective of the present study was to assess the effect of miRNA-23b (miR-23b) expression in plasma on the diagnosis and prognosis of colorectal cancer (CRC). Reverse transcription-quantitative polymerase chain reaction (PCR) was used to measure miR-23b expression levels, and methylation-specific PCR was used to test the promoter methylation status. Subsequently, the expression level of miR-23b in plasma samples was compared between CRC patients and healthy control individuals. The miR-23b expression levels were significantly lower in CRC cells and primary CRC tissues than in nonmalignant colorectal tissues (P<0.001). It was also shown that miR-23b expression is downregulated by promoter methylation and can be restored by demethylation agent treatment. miR-23b was significantly decreased in plasma samples from CRC patients compared with the healthy control individuals (P<0.001). The value of the area under the receiver operating characteristic curve was 0.842 (sensitivity, 84.38%; specificity, 77.08%; 95% confidence interval, 0.763-0.922). Low plasma miR-23b expression was significantly associated with clinical stage, tumor depth, distant metastasis and tumor recurrence. CRC patients with low miR-23b expression in plasma exhibited a shorter recurrence-free survival time and poorer overall survival rate. The present results suggested that the downregulation of miR-23b in the plasma has the potential to be a diagnostic and prognostic biomarker in CRC.

Plasma miR-122 and miR-200 family are prognostic markers in colorectal cancer

Circulating microRNAs (miRNAs) have been proposed as minimally invasive prognostic markers for various types of cancers, including colorectal cancer (CRC), the third most diagnosed cancer worldwide. We aimed to evaluate the levels of circulating miRNAs that might serve as markers for CRC prognosis and survival. We included plasma samples of 543 CRC patients with stage I-IV disease from a population-based study carried out in Germany. After comprehensive evaluation of current literature, 95 miRNAs were selected and measured with Custom TaqMan® Array MicroRNA Cards. Plasma samples of non-metastatic and metastatic colon cancer patients, each group consisting of ten patients with 'good' and ten patients with 'bad' prognosis were screened. Identified candidate miRNAs were further validated by RT-qPCR in the whole study cohort. The association of the miRNA levels with patients' survival and the prognostic subtypes was analyzed with uni- and multivariate logistic regression and Cox proportional hazards regression models. Increased miR-122 levels were associated with a 'bad' prognostic subtype in metastatic CRC (Odds ratio: 1.563, 95% confidence interval (CI): 1.038-2.347) and a shorter relapse-free survival and overall survival for non-metastatic (Hazard ratio (HR): 1.370, 95% CI: 1.028-1.825; HR: 1.353, 95% CI: 1.002-1.828) and metastatic (HR: 1.264, 95% CI: 1.050-1.520; HR: 1.292, 95% CI: 1.078-1.548) CRC patients. Additionally, several members of the miR-200 family showed associations with patients' prognosis and correlations to clinicopathological characteristics. The here identified miRNA markers, miR-122 and the miR-200 family members, could be of use in the development of a multi-marker blood test for CRC prognosis.

From cell biology to immunology: Controlling metastatic progression of cancer via microRNA regulatory networks

Recently, the study of microRNAs has expanded our knowledge of the fundamental processes of cancer biology and the underlying mechanisms behind tumor metastasis. Extensive research in the fields of microRNA and its novel mechanisms of actions against various cancers has more recently led to the trial of a first cancer-targeted microRNA drug, MRX34. Yet, these microRNAs are mostly being studied and clinically trialed solely based on the understanding of their cell biologic effects, thus, neglecting the important immunologic effects that are sometimes opposite of the cell biologic effects. Here, we summarize both the cell biologic and immunologic effects of various microRNAs and discuss the importance of considering both effects before using them in clinical settings. We stress the importance of understanding the miRNA's effect on cancer metastasis from a "systems" perspective before developing a miRNA-targeted therapeutic in treating cancer metastasis.

Circulating MicroRNAs: A Next-Generation Clinical Biomarker for Digestive System Cancers. Int J Mol Sci. 2016;17. [PMID: 27598137 PMCID: PMC5037738 DOI: 10.3390/ijms17091459]

MicroRNAs (miRNAs) are short noncoding RNAs that post-transcriptionally regulate gene expression and play important roles in various physiological and developmental processes such as oncogenic or tumor suppressive regulators. Specific miRNA expression signatures have been identified in a number of human cancers. Cell-free miRNAs have recently been stably detected in plasma and serum (circulating miRNAs), and their presence in blood has attracted the attention of researchers due to their potential as non-invasive biomarkers. Circulating miRNAs have emerged as tumor-associated biomarkers that reflect not only the existence of early-stage tumors, but also the dynamics and status of advanced stage tumors, tumor recurrence, and drug sensitivities. This methodology for liquid biopsy may provide non-invasive and reproductive biomarkers and individualized therapeutic strategies for cancer patients. We herein review the current phase of biological and clinical research on the circulating miRNAs of solid cancers, particularly digestive tract cancers, and discuss future perspectives. The present review may be beneficial for future research on miRNAs used to detect various cancers.

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

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

Recent progress toward the use of circulating microRNAs as clinical biomarkers

MicroRNAs (miRNAs) have been shown to be critical mediators of many cellular and developmental processes and have been implicated in different human diseases. Since the observation of extracellular miRNAs present in various biofluids, much attention and excitement have been garnered toward understanding the functional roles of these circulating extracellular miRNAs and establishing their potential use as noninvasive diagnostic biomarkers. Here, we will review the current state of miRNA biomarkers for many human diseases, including their emerging use in toxicological applications, and discuss the current challenges in the field, with an emphasis on technical issues that often hinder discovery-based miRNA biomarker studies.

Anti-proliferative role and prognostic implication of miR-141 in gastric cancer

Gastric cancer is a prevalent disease causing a high annual death rate worldwide. Recent studies suggest the pivotal regulatory role of microRNAs in gastric cancer and the aberrant expression of microRNA-141 (miR-141) in gastric cancer cells. This study aims to explore the role and possible mechanism of miR-141 in gastric cancer prognosis and cell proliferation. A total of 30 gastric cancer patients were recruited for miR-141 level detection and a follow up of 115 weeks. Human adenocarcinoma cell line AGS was transfected with miR-141 mimic or inhibitor for cell viability, colony formation and cell cycle assays. A gastric cancer mouse model was constructed by implantation of transfected AGS cells. Insulin-like growth factor 1 receptor (IGF1R) was overexpressed in AGS cells to investigate miR-141 mechanism. Results showed that miR-141 was significantly down-regulated in gastric cancer tissue (P < 0.001). The patients with lower miR-141 levels exhibited poorer prognosis. miR-141 inhibited AGS cell viability (P < 0.01), colony formation (P < 0.01) and cell cycle (P < 0.05), and the mice implanted with miR-141 mimic cells showed an obvious smaller tumor size (P < 0.01), suggesting the anti-proliferative role of miR-141. Both the phosphorylated and total IGF1R protein levels were inhibited by miR-141, while IGF1R overexpression reversed the effects of miR-141 in AGS cell proliferation. These results indicate the potential roles of miR-141 as a prognostic factor and as a therapeutic alternative for gastric cancer. Its mechanism may be associated with IGF1R, and further research is necessary for more detail information.

Roles and mechanisms of action of microRNAs in colorectal cancer

MicroRNAs (miRNAs) are a class of endogenous, evolutionarily conserved small non-coding RNAs, which play a vital role in tumour formation, development, metastasis and recurrence by inducing DNA methylation, changing tumor microenvironment and regulating signal pathways such as Wnt/β-catenin, phosphoinositide3-kinase (PI3K), K-RAS, epithelial mesenchymal transitions (EMT) and so on. Recent studies have found that the expression of many miRNAs is dyregulated in colorectal cancer, and they participate in and control the formation and development of colorectal cancer. Thus, understanding the roles and mechanisms of action of miRNAs in colorectal cancer can provide a new avenue for its early diagnosis, clinical staging, treatment and prognosis evaluation.

The Preoperative Peripheral Blood Monocyte Count Is Associated with Liver Metastasis and Overall Survival in Colorectal Cancer Patients. PLoS One. 2016;11:e0157486. [PMID: 27355390 PMCID: PMC4927165 DOI: 10.1371/journal.pone.0157486]

Background

Colorectal cancer (CRC) is the third most common malignancy in males and the second most common in females worldwide. Distant metastases have a strong negative impact on the prognosis of CRC patients. The most common site of CRC metastases is the liver. Both disease progression and metastasis have been related to the patient’s peripheral blood monocyte count. We therefore performed a case-control study to assess the relationship between the preoperative peripheral blood monocyte count and colorectal liver metastases (CRLM).

Methods

Clinical data from 117 patients with colon cancer and 93 with rectal cancer who were admitted to the Chinese People’s Liberation Army General Hospital (Beijing, China) between December 2003 and May 2015 were analysed retrospectively, with the permission of both the patients and the hospital.

Results

Preoperative peripheral blood monocyte counts, the T and N classifications of the primary tumour and its primary site differed significantly between the two groups (P < 0.001, P < 0.001, P = 0.002, P < 0.001), whereas there were no differences in the sex, age, degree of tumour differentiation or largest tumour diameter. Lymph node metastasis and a high preoperative peripheral blood monocyte count were independent risk factors for liver metastasis (OR: 2.178, 95%CI: 1.148~4.134, P = 0.017; OR: 12.422, 95%CI: 5.076~30.398, P < 0.001), although the risk was lower in patients with rectal versus colon cancer (OR: 0.078, 95%CI: 0.020~0.309, P < 0.001). Primary tumour site (P<0.001), degree of tumour differentiation (P = 0.009), T, N and M classifications, TNM staging and preoperative monocyte counts (P<0.001) were associated with the 5-year overall survival (OS) of CRC patients. A preoperative peripheral blood monocyte count > 0.505 × 10⁹ cells/L, high T classification and liver metastasis were independent risk factors for 5-year OS (RR: 2.737, 95% CI: 1.573~ 4.764, P <0.001; RR: 2.687, 95%CI: 1.498~4.820, P = 0.001; RR: 4.928, 95%CI: 2.871~8.457, P < 0.001).

Conclusions

The demonstrated association between preoperative peripheral blood monocyte count and liver metastasis in patients with CRC recommends the former as a useful predictor of postoperative prognosis in CRC patients.

Circulating microRNAs as Prognostic and Predictive Biomarkers in Patients with Colorectal Cancer

MiRNAs are suggested as promising cancer biomarkers. They are stable and extractable from a variety of clinical tissue specimens (fresh frozen or formalin fixed paraffin embedded tissue) and a variety of body fluids (e.g., blood, urine, saliva). However, there are several challenges that need to be solved, considering their potential as biomarkers in cancer, such as lack of consistency between biomarker panels in independent studies due to lack of standardized sample handling and processing, use of inconsistent normalization approaches, and differences in patients populations. Focusing on colorectal cancer (CRC), divergent results regarding circulating miRNAs as prognostic or predictive biomarkers are reported in the literature. In the present review, we summarize the current data on circulating miRNAs as prognostic/predictive biomarkers in patients with localized and metastatic CRC (mCRC).

Systems medicine in colorectal cancer: from a mathematical model toward a new type of clinical trial

Current colorectal cancer (CRC) treatment guidelines are primarily based on clinical features, such as cancer stage and grade. However, outcomes may be improved using molecular treatment guidelines. Potentially useful biomarkers include driver mutations and somatically inherited alterations, signaling proteins (their expression levels and (post) translational modifications), mRNAs, micro‐RNAs and long noncoding RNAs. Moving to an integrated system is potentially very relevant. To implement such an integrated system: we focus on an important region of the signaling network, immediately above the G1‐S restriction point, and discuss the reconstruction of a Molecular Interaction Map and interrogating it with a dynamic mathematical model. Extensive model pretraining achieved satisfactory, validated, performance. The model helps to propose future target combination priorities, and restricts drastically the number of drugs to be finally tested at a cellular, in vivo, and clinical‐trial level. Our model allows for the inclusion of the unique molecular profiles of each individual patient's tumor. While existing clinical guidelines are well established, dynamic modeling may be used for future targeted combination therapies, which may progressively become part of clinical practice within the near future. WIREs Syst Biol Med 2016, 8:314–336. doi: 10.1002/wsbm.1342

This article is categorized under: 1

Biological Mechanisms > Cell Signaling

2

Analytical and Computational Methods > Computational Methods

3

Translational, Genomic, and Systems Medicine > Translational Medicine

Cross Talk between Cancer and Mesenchymal Stem Cells through Extracellular Vesicles Carrying Nucleic Acids

Extracellular vesicles (EVs) are considered to be a novel complex mechanism of cell communication within the tumor microenvironment. EVs may act as vehicles for transcription factors and nucleic acids inducing epigenetic changes in recipient cells. Since tumor EVs may be present in patient biological fluids, it is important to investigate their function and molecular mechanisms of action. It has been shown that tumor cells release EVs, which are capable of regulating cell apoptosis, proliferation, invasion, and epithelial-mesenchymal transition, as well as to suppress activity of immune cells, to enhance angiogenesis, and to prepare a favorable microenvironment for metastasis. On the other hand, EVs derived from stromal cells, such as mesenchymal stem cells (MSCs), may influence the phenotype of tumor cells through reciprocal cross talk greatly influenced by the transcription factors and nucleic acids they carry. In particular, non-coding RNAs (ncRNAs), including microRNAs and long ncRNAs, have recently been identified as the main candidates for the phenotypic changes induced in the recipient cells by EVs. ncRNAs, which are important regulators of mRNA and protein expression, can function either as tumor suppressors or as oncogenes, depending on their targets. Herein, we have attempted to revise actual evidence reported in the literature on the role of EVs in tumor biology with particular regard to the cross talk of ncRNAs between cancer cells and MSCs.

Absolute quantification of cell-free microRNAs in cancer patients

The hypothesis to use microRNAs (miRNAs) circulating in the blood as cancer biomarkers was formulated some years ago based on promising initial results. After some exciting discoveries, however, it became evident that the accurate quantification of cell-free miRNAs was more challenging than expected. Difficulties were linked to the strong impact that many, if not all, pre- and post- analytical variables have on the final results. In this study, we used currently available high-throughput technologies to identify miRNAs present in plasma and serum of patients with breast, colorectal, lung, thyroid and melanoma tumors, and healthy controls. Then, we assessed the absolute level of nine different miRNAs (miR-320a, miR-21-5p, miR-378a-3p, miR-181a-5p, miR-3156-5p, miR-2110, miR-125a-5p, miR-425-5p, miR-766-3p) in 207 samples from healthy controls and cancer patients using droplet digital PCR (ddPCR) technology. We identified miRNAs specifically modulated in one or more cancer types, according to tissue source. The significant reduction of miR-181a-5p levels in breast cancer patients serum was further validated using two independent cohorts, one from Italy (n = 70) and one from US (n = 90), with AUC 0.66 and 0.73 respectively. This study finally powers the use of cell-free miRNAs as cancer biomarkers and propose miR-181a-5p as a diagnostic breast cancer biomarker.

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

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

New Concepts in Cancer Biomarkers: Circulating miRNAs in Liquid Biopsies

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

miR-141 modulates osteoblastic cell proliferation by regulating the target gene of lncRNA H19 and lncRNA H19-derived miR-675

Increasing evidence has reported the significant roles of lncRNA or miRNAs in the biology of various diseases. This study was aimed to elucidate the potential roles of miR-141 and lncRNA H19 and H19-derived miR-675 in regulating osteoblasts proliferation and apoptosis and to explore its potential mechanism. miR-141 mimic or miR-141 inhibitor or siRNA-H19 or miR-675 inhibitor was transfected into human hFOB1.19 cells. The effects or miR-141 expression on H19 or miR-675 expression, on osteoblasts proliferation and apoptosis were analyzed. Moreover, effects of H19 and miR-675 expression on cell proliferation were also analyzed. The results showed that miR-141 was down-regulated in both hFOB1.19 cells and osteosarcoma tissues. The overexpressed miR-141 suppressed H19 and miR-675 expression in hFOB1.19 cells. Besides, miR-141 suppression significantly increased cell viability but this effect was blocked by silencing H19 or miR-675 inhibitor, which is similar to the effects on VEGF and IGF2 expression. Furthermore, miR-141 overexpression induced osteoblasts apoptosis, but decreased the levels of caspase-3 and the Bcl-2/Bax ratio. Taken together, our study revealed that tumor-suppressor miR-141 overexpression suppressed osteoblasts proliferation but induced apoptosis through down-regulating H19 or miR-675 in osteosarcoma. This study may provide theoretical basis for illustrating the interaction between lncRNA and miRNAs in osteosarcoma and for the therapeutic target of miR-141 in osteosarcoma treatment.

MicroRNA-141 and its associated gene FUS modulate proliferation, migration and cisplatin chemosensitivity in neuroblastoma cell lines

In the present study, a novel signaling pathway of microRNA-141 (miR-141)/fused in sarcoma (FUS) was investigated in neuroblastoma (NB). Gene expression of miR-141 was evaluated in 6 NB cell lines. IMR-32 and SH-SY5Y cells were transduced with the miR-141 mimic lentivirus. The effects of miR-141 upregulation on cell proliferation, cell division, migration, chemosensitivity and in vivo explants were evaluated by MTT, cell cycle, wound-healing, cisplatin sensitivity and in vivo tumor growth assays, respectively. The correlation between miR-141 and the FUS gene was evaluated by luciferase assay and qRT-PCR. FUS was also downregulated in IMR-32 and SH-SY5Y cells to evaluate its impact on NB regulation. miR-141 was downregulated in both MYCN- and non-MYCN-amplified NB cell lines. In the IMR-32 and SH-SY5Y cells, lentivirus-induced miR-141 upregulation inhibited cancer proliferation, cell cycle progression, migration and increased cisplatin chemosensitivity in vitro. In addition, miR-141 upregulation reduced the in vivo growth of IMR-32 tumor explants. FUS was found to be inversely regulated by miR-141 in NB. Small interfering RNA (siRNA)-induced FUS downregulation had similar tumor-suppressive effects as miR-141 upregulation on NB cell proliferation, cell cycle progression, migration and cisplatin chemosensitivity. Our data indicate that miR-141 and the FUS gene, which are inversely correlated, play significant functional roles in regulating human NB.

MicroRNAs as growth regulators, their function and biomarker status in colorectal cancer

Gene expression is in part regulated by microRNAs (miRNAs). This review summarizes the current knowledge of miRNAs in colorectal cancer (CRC); their role as growth regulators, the mechanisms that regulate the miRNAs themselves and the potential of miRNAs as biomarkers. Although thousands of tissue samples and bodily fluids from CRC patients have been investigated for biomarker potential of miRNAs (>160 papers presented in a comprehensive tables), none single miRNA nor miRNA expression signatures are in clinical use for this disease. More than 500 miRNA-target pairs have been identified in CRC and we discuss how these regulatory nodes interconnect and affect signaling pathways in CRC progression.

Profiling cell-free and circulating miRNA: a clinical diagnostic tool for different cancers. Tumour Biol. 2016;37:5705-5714. [PMID: 26831657 DOI: 10.1007/s13277-016-4907-3]

Effective cancer management depends on early diagnosis and treatment. There are several microRNAs (miRNAs) which are used for detection of various cancers. Cell-free and circulating miRNAs originate from plasma, either from blood cells or endothelial cells. Cell-free and circulating miRNAs are very much important in the diagnosis and prognosis of cancer therapy. Admittedly, biological knowledge of extracellular miRNAs is still at its preliminary level. Recent discoveries of novel cell-free and circulating miRNAs from the body fluids are now being considered as important biomarkers that may help us in the early diagnosis of any cancer. In the present review, we highlight the biogenesis of miRNAs and their current extracellular pattern, the discovery of circulating miRNA, significant advantages, and different profiling techniques. Finally, we discuss the different circulating miRNAs such as miR-21, miR-20a, miR-155, miR‑221, miR-210, miR-218, miR-200-family, miR-141, miR-122, miR-486-5p, miR‑423-5p, miR-29a, and miR-500 for clinical diagnosis of various cancers. The present review may be beneficial for future researches concerned with miRNAs which are used for detection of various cancers.

The microRNA-200 family: small molecules with novel roles in cancer development, progression and therapy

MicroRNAs (miRNAs) are a large family of small non-coding RNAs that negatively regulate protein-coding gene expression post-transcriptionally via base pairing between the 5′ seed region of a miRNA and the 3′ untranslated region (3′UTR) of a messenger RNA (mRNA). Recent evidence has supported the critical role that miRNAs play in many diseases including cancer. The miR-200 family consisting of 5 members (miR-200a, -200b, -200c, -141, -429) is an emerging miRNA family that has been shown to play crucial roles in cancer initiation and metastasis, and potentially be important for the diagnosis and treatment of cancer. While miR-200s were found to be critically involved in the metastatic colonization to the lungs in mouse mammary xenograft tumor models, a large number of studies demonstrated their strong suppressive effects on cell transformation, cancer cell proliferation, migration, invasion, tumor growth and metastasis. This review aims to discuss research findings about the role of the miR-200 family in cancer initiation, each step of cancer metastatic cascade, cancer diagnosis and treatment. A comprehensive summary of currently validated miR-200 targets is also presented. It is concluded that miR-200 family may serve as novel targets for the therapy of multiple types of cancer.

Circulating cell-free nucleic acids as biomarkers in colorectal cancer screening and diagnosis

Screening methods for the most frequent diagnosed malignant tumor, colorectal cancer (CRC), have limitations. Circulating cell-free DNA (cfDNA) analysis came into focus as a potential screening test for CRC. Detection of epigenetic and genetic alterations of cfDNA as DNA methylation or DNA mutations and related ribonucleic acids may improve cancer detection based on unique, CRC-specific patterns. In this review the authors summarize the CRC-specific nucleic acid biomarkers measured in peripheral blood and their potential as screening markers. Detection of DNA mutation has inadequate sensitivity; however, methylated DNA can be established with higher sensitivity from CRC plasma samples. The ribonucleic acid based miRNA studies represented higher sensitivity for CRC as compared with mRNA studies. Recently, isolation of cfDNA has become automated, highly reproducible and a high throughput method. With automated possible diagnostic tools, a new approach may be available for CRC screening as liquid biopsy.

Blood-based biomarkers for diagnosis, prognosis and treatment of colorectal cancer

The global burden of colorectal cancer (CRC)-associated morbidity and mortality is increasing, in part due to a lack of early detection. Direct structural examination techniques, such as colonoscopy, are invasive and can therefore affect the willingness of patients to participate in screening. Recently, the use of "liquid biopsy" has gained considerable attention as a novel source of biomarkers. Blood-based biomarkers could prove to be practical tools for CRC detection, as the monitoring of biomarkers in biological fluids offers many advantages, including minimal invasiveness and easy accessibility. Biomarkers with high specificity and sensitivity can enable the detection of CRC at an early stage, thereby improving prognosis, prediction of treatment response, and recurrence risk. In this review, we summarize that the biomarkers currently thought to have potential for the early detection and monitoring of CRC, including circulating tumor cells, DNA, RNA and proteins.

Simultaneous Underexpression of let-7a-5p and let-7f-5p microRNAs in Plasma and Stool Samples from Early Stage Colorectal Carcinoma

Colorectal cancer (CRC) is the third most common malignancy and the second most common cause of cancer death worldwide. Early detection of CRC can improve patient survival rates; thus, the identification of noninvasive diagnostic markers is urgently needed. MicroRNAs (miRNAs) have extensive potential to diagnose several diseases, including cancer. In this study, we compared the expression pattern of miRNAs from plasma and stool samples of patients with early stages of CRC (I, II) with that of healthy subjects. We performed miRNA profiling using microarrays on plasma and stool samples of eight patients with CRC and four healthy subjects. Seven miRNAs were found to be underexpressed in both plasma and stool samples of patients with CRC versus healthy subjects. Then, we aimed to verify two out of these seven differentially expressed miRNAs (let-7a-5p and let-7f-5p) by quantitative reverse transcriptase polymerase chain reaction on a larger set of plasma and stool samples of 51 patients with CRC and 26 healthy subjects. We confirmed the results of microarray analysis since their expression was significantly lower in stool and plasma samples of patients with CRC. Moreover, receiver operating characteristic curve analysis demonstrated that fecal let-7f expression levels have significant sensitivity and specificity to distinguish between patients with CRC and healthy subjects. In conclusion, if the results are confirmed in larger series of patients, underexpressed let-7a-5p and let-7f-5p miRNAs in both plasma and stool samples of patients with CRC may serve potentially as noninvasive molecular biomarkers for the early detection of CRC.

Circulating cell-free microRNAs as biomarkers for colorectal cancer

MicroRNAs (miRNAs) are a class of small, endogenous, non-coding, single-stranded RNAs that act as post-transcriptional regulators. Their discovery has provided new avenues for the diagnosis and treatment of cancer. The expression of both oncogenic and tumor suppressor miRNAs can be aberrantly either up- or down-regulated in cancer cells. These miRNAs target mRNAs of genes that either promote or inhibit tumor growth, and are one of several epigenetic factors that control the initiation and progression of colorectal cancer (CRC) and other cancers. Investigations of miRNAs as CRC biomarkers have employed the expression profiling of traditional tissue samples and, more recently, non-invasive samples, such as feces and body fluids, have been analyzed. MiRNAs may also be able to predict responses to chemo- and radiotherapy, and may be manipulated to modify CRC characteristics. We herein discuss the use of circulating miRNAs as possible non-invasive biomarkers of early CRC onset, relapse, or response to treatment. We also discuss the obstacles that currently limit the routine use of epigenetic biomarkers in clinical settings.

Circulating microRNAs: potential biomarkers for common malignancies

MicroRNAs (miRNAs) belong to a class of small noncoding RNAs (ncRNAs), which regulate gene expression at the post-transcriptional level. They are approximately 22 nucleotide sequences in length and have been predicted to control expression of up to 30-60% of all protein-coding genes in mammals. Considering this wide involvement in gene control, aberrant miRNA expression has a strong association with the presence and progression of a disease, hence generating much anticipation in using miRNAs as biomarkers for the diagnosis and prognosis of human cancers. The majority of these miRNAs are intracellular, but recently they have been discovered in bodily fluids. This review will provide an insight into these circulatory miRNA molecules and discuss their potential as cancer biomarkers.

Plasma miR-183 predicts recurrence and prognosis in patients with colorectal cancer

Colorectal cancer (CRC) is one of the most common malignancies worldwide. The prognosis for this cancer is poor, and the development of novel biomarkers, particularly non-invasive surrogate biomarkers, is urgently needed. Recent studies have demonstrated that microRNAs (miRNAs) are stably detectable in the blood and can serve as useful biomarkers for various types of cancer. In this study, the miR-183 expression levels were found to be significantly overexpressed in plasma samples from CRC patients compared with controls, and the postoperative plasma miR-183 levels were significantly reduced compared with the preoperative levels. The value of the area under the receiver operating characteristic (ROC) curve obtained for miR-183 was 0.829, which was higher than those for carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9). High plasma miR-183 expression was significantly associated with lymph node metastasis, distant metastasis, higher pTNM stage (III-IV), and tumor recurrence. CRC patients with elevated miR-183 expression in plasma displayed shorter disease-free survival (DFS) and lower overall survival (OS). More importantly, plasma miR-183 was independently correlated with tumor recurrence and a lower OS. Collectively, our results suggested that the elevated miR-183 in the plasma could be a promising biomarker for predicting the risk of tumor recurrence and poor survival in CRC patients.

Circulating Blood-Borne microRNAs as Biomarkers in Solid Tumors

One of the major challenges in cancer research is the identification of stable biomarkers that could be routinely measured in easily accessible samples. Human blood and other body fluids represent rich sources for the identification of novel biomarkers. It is apparent that the availability of these biomarkers would improve an early detection of asymptomatic disease and the clinical management of cancer. MicroRNAs have been described to be present in various types of body fluids including cell-free serum and plasma. These days, the involvement of microRNAs in molecular pathology of cancer is well established. Moreover, it seems that these molecules could be optimal noninvasive biomarkers owing to their high stability under storage and handling conditions and high sensitivity and specificity in various diseases. To date, more than 100 circulating microRNAs with the potential to serve as novel diagnostic, prognostic, or predictive biomarkers for different types of cancers have been identified, and this number is still increasing. However, there are major discrepancies in the findings by different research groups, and few commonly altered microRNAs have been reported in these studies. Further studies on large cohorts using uniform methodology are warranted to establish the clinical applicability of circulating microRNAs for solid tumors. Here, we summarize the tumor-specific profiles of blood-borne microRNAs and discuss their potential utility for personalized medicine of solid tumors.

MicroRNAs: Clinical Relevance in Colorectal Cancer

Colorectal cancer is one of the most common cancer diagnoses and causes of mortality worldwide. MicroRNAs are a class of small, non-coding regulatory RNAs that have shown strong associations with colorectal cancer. Through the repression of target messenger RNAs, microRNAs modulate many cellular pathways, such as those involved in cell proliferation, apoptosis, and differentiation. The utilization of microRNAs has shown significant promise in the diagnosis and prognosis of colorectal cancer, owing to their unique expression profile associations with cancer types and malignancies. Moreover, microRNA therapeutics with mimics or antagonists show great promise in preclinical studies, which encourages further development of their clinical use for colorectal cancer patients. The unique ability of microRNAs to affect multiple downstream pathways represents a novel approach for cancer therapy. Although still early in its development, we believe that microRNAs can be used in the near future as biomarkers and therapeutic targets for colorectal cancer.