MicroRNAs (miRNAs), a class of post-transcriptional gene expression regulators, have recently been detected in human body fluids, including peripheral blood plasma as extracellular nuclease resistant ...entities. However, the origin and function of extracellular circulating miRNA remain essentially unknown. Here, we confirmed that circulating mature miRNA in contrast to mRNA or snRNA is strikingly stable in blood plasma and cell culture media. Furthermore, we found that most miRNA in plasma and cell culture media completely passed through 0.22 µm filters but remained in the supernatant after ultracentrifugation at 110 000g indicating the non-vesicular origin of the extracellular miRNA. Furthermore, western blot immunoassay revealed that extracellular miRNA ultrafiltrated together with the 96 kDa Ago2 protein, a part of RNA-induced silencing complex. Moreover, miRNAs in both blood plasma and cell culture media co-immunoprecipited with anti-Ago2 antibody in a detergent free environment. This is the first study to show that extracellular miRNAs are predominantly exosomes/microvesicles free and are associated with Ago proteins. We hypothesize that extracellular miRNAs are in the most part by-products of dead cells that remain in extracellular space due to the high stability of the Ago2 protein and Ago2-miRNA complex. Nevertheless, our data does not reject the possibility that some miRNAs can be associated with exosomes.
Studies of miRNA association with Argonaute (AGO) proteins in mammalian cells have indicated lack of bias toward particular AGO. However, to our knowledge, the use of quantitative methods for ...studying miRNA association with different AGOs has not been reported so far. In this work we compared the total miRNA content in AGO1 and AGO2 immunoprecipitates obtained from MCF7 adenocarcinoma cells using TaqMan Low Density miRNA Arrays and successfully verified selected miRNAs with qPCR. For most of the miRNA species AGO1 and AGO2 profiles were well correlated, however, some miRNAs demonstrated consistent biases toward one of the Argonautes. Furthermore, miRNAs which were predominantly AGO2-associated derived mostly from sense strands of the corresponding pre-miRNAs while the majority of AGO1 biased miRNAs originated from antisense strands of the pre-miRNAs. Additionally, we show that circulating miRNA in human blood plasma can be immunoprecipitated with both AGO1 and AGO2 antibody. However, unlike in cell lysates, AGO1 and AGO2 associated miRNA profiles in plasma did not correlate, indicating that many cell types contribute to circulating miRNA (given that expression of AGO proteins is tissue specific). Furthermore, AGO-specific miRNA profiles in blood cells differed significantly from miRNAs profiles in plasma indicating that most circulating miRNAs are likely to derive from non-blood cells. Since circulating miRNAs hold great promise as biomarkers for numerous cancers and other diseases, we hypothesize that AGO-specific miRNA profiles might add an additional dimension to circulating miRNA-based diagnostics.
Colorectal cancer (CRC) is one of the most commonly diagnosed cancers. Circulating microRNAs (miRNAs) have been suggested as potentially promising markers for early detection of CRC. We aimed to ...identify and evaluate a panel of miRNAs that might be suitable for CRC early detection.
MiRNAs were profiled by TaqMan MicroRNA Array and screened for differential expression in 5 pools of plasma samples of CRC patients (N = 50) and 5 pools of neoplasm-free controls (N = 50). Additional miRNAs were selected from a literature review. Identified candidates were evaluated in independent validation samples with respect to discrimination of CRC patients (N = 80) or advanced adenoma patients (N = 50) and neoplasm-free controls (N = 194). Diagnostic performance of the panel of miRNAs was assessed by multiple logistic regression, using bootstrap analysis to correct for over-optimism.
Five miRNAs identified to be differentially expressed from TaqMan MicroRNA Array (miR-29a, -106b, -133a, -342-3p, -532-3p), and seven miRNAs reported to be differentially expressed in the literature (miR-18a, -20a, -21, -92a, -143, -145, -181b) were selected for validation. Nine of the twelve miRNAs (miR-18a, -20a, -21, -29a, -92a, -106b, -133a, -143, -145) were found to be differentially expressed in CRC patients and controls in the validation samples. The optimism-corrected area under the curve was 0.745 (95% confidence interval: 0.708-0.846). None of the selected miRNAs showed significant differential expression between advanced adenoma patients and neoplasm-free controls.
The identified panel of miRNAs could be of potential use in the development of a multi-marker blood based test for early detection of CRC.
The study underscores the high potential of plasma miRNAs for the improvement of current offers of non-invasive CRC screening.
Tobacco smoking is responsible for substantial morbidity and mortality worldwide, in particular through cardiovascular, pulmonary, and malignant pathology. CpG methylation might plausibly play a role ...in a variety of smoking-related phenomena, as suggested by candidate gene promoter or global methylation studies. Arrays allowing hypothesis-free searches on a scale resembling genome-wide studies of SNPs have become available only very recently. Methylation extents in peripheral-blood DNA were assessed at 27,578 sites in more than 14,000 gene promoter regions in 177 current smokers, former smokers, and those who had never smoked, with the use of the Illumina HumanMethylation 27K BeadChip. This revealed a single locus, cg03636183, located in F2RL3, with genome-wide significance for lower methylation in smokers (p = 2.68 × 10−31). This was similarly significant in 316 independent replication samples analyzed by mass spectrometry and Sequenom EpiTyper (p = 6.33 × 10−34). Our results, which were based on a rigorous replication approach, show that the gene coding for a potential drug target of cardiovascular importance features altered methylation patterns in smokers. To date, this gene had not attracted attention in the literature on smoking.
Multiple studies have investigated global DNA methylation profiles and gene-specific DNA methylation in blood-based DNA to develop powerful screening markers for cancer. This systematic review ...summarizes the current evidence on methylation studies that investigated methylation level of blood-derived DNA of breast cancer (BC) patients in comparison to healthy controls by conducting a systematic literature review in PubMed and Web of Science. Essential results, such as methylation levels of BC cases and healthy controls,
values, and odds ratios, were extracted from these studies by two investigators independently. Overall, 45 publications met the inclusion criteria for this review. DNA from whole blood, as well as cell-free DNA (cfDNA) from serum or plasma, was used in these studies. The most common method used for measuring global DNA methylation was the investigation of repetitive elements as surrogates and the application of array-based genome-wide methylation analysis. For measuring gene-specific methylation level, methylation-specific PCR and pyrosequencing were the most frequently used methods. Epigenome-wide blood DNA hypomethylation in BC patients were reported in several studies; however, the evidence is still not conclusive. The most frequently investigated gene in whole blood was
, which was found more frequently methylated in patients compared to controls.
was the most widely investigated gene in cfDNA of serum or plasma, which was also found more frequently methylated in patients compared to controls. Several of the eligible studies reported the associations of global hypomethylation and increased BC risk. Studies investigated associations between gene-specific methylation and BC risk, while got heterogeneous results. But two studies reported that hypermethylation of
gene was associated with increased BC risk, which suggest the potential use of this gene for BC risk stratification. Overall, our review suggests the possibility of using blood-based DNA methylation marker as promising marker for BC risk stratification, as several studies found associations between certain methylation level in blood and BC risk. However, so far, the evidence is still quite limited. Optimal markers are yet to be developed and promising results needed to be validated in prospective study cohorts and tested in large screening populations.
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.
What's new?
Metastasis is the major cause of death for colorectal cancer (CRC) patients. Prognostic markers that are constantly measurable using liquid biopsies could facilitate the earlier prediction of relapse events and metastasis formation. In a prospective study cohort of 543 colorectal cancer patients, the authors evaluated the role of circulating miRNAs as potential prognostic markers for CRC with a specific focus on miRNAs known to be involved in tumor progression and metastasis formation. MiR‐122 and several members of the miR‐200 family were identified as prognostic markers, suggesting their potential use in the development of a multi‐marker blood test for CRC prognosis.
Triple-negative breast cancers (TNBC) are associated with high risk of early tumor recurrence and poor outcome. Common prognostic biomarkers give very restricted predictive information of tumor ...recurrences in TNBC. Human serum contains stably expressed microRNAs (miRNAs), which have been discovered to predict prognosis in patients with cancer. The purpose of this study was to identify circulating biomarkers able to predict clinical outcome in TNBC.
We performed genome-wide serum miRNA expression and real-time PCR analyses to investigate the ability of miRNAs in predicting tumor relapse in serum samples from 60 primary TNBC. Patients were divided into training and testing cohorts.
By Cox regression analysis, we identified a four-miRNA signature (miR-18b, miR-103, miR-107, and miR-652) that predicted tumor relapse and overall survival. This miRNA signature was further validated in an independent cohort of 70 TNBC. A high-risk signature score was developed and significantly associated with tumor recurrence and reduced survival. Multivariate Cox regression models indicated that the risk score based on the four-miRNA signature was an independent prognostic classifier of patients with TNBC.
This signature may serve as a minimally invasive predictor of tumor relapse and overall survival for patients with TNBC. This prediction model may ultimately lead to better treatment options for patients with TNBC.
In a recent genome-wide study, cytosine bases in the F2RL3 gene, which codes for a protein relevant for cardiovascular physiology, were discovered to be hypomethylated in smokers. We aimed to ...determine the clinical importance of methylation at the F2RL3 locus.
In the KAROLA prospective cohort study, 1206 participants of inpatient cardiovascular rehabilitation programmes after experiencing an acute coronary syndrome, myocardial infarction, or coronary intervention were recruited in two clinics in Germany. Active follow-up was conducted over 8 years. Methylation at loci in F2RL3 was characterized by Sequenom matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Associations of methylation and smoking with secondary cardiovascular events, and cause-specific and all-cause mortality were examined by multiple Cox's regression estimating confounder-controlled hazard ratios. A total of 49 non-fatal myocardial infarctions, 41 non-fatal strokes, 64 cardiovascular deaths, and 50 deaths due to other causes were observed. In Cox's models controlling for established prognostic factors, F2RL3 methylation was strongly associated with mortality. Adjusted hazard ratios (95% confidence intervals) for death from cardiovascular, non-cardiovascular, or any cause were 2.32 (0.97-5.58), 5.16 (1.81-14.7), and 3.19 (1.64-6.21) in subjects in the lowest quartile of methylation in comparison to the highest quartile. In contrast, no association was seen with the combined secondary event outcome. The strong association of smoking with all outcomes was markedly attenuated when F2RL3 was included in the regression models.
The results seem to indicate methylation in F2RL3 to be a potential mediator of the detrimental impact of smoking and to be strongly related to mortality among patients with stable coronary heart disease. Multidisciplinary research efforts are needed to unravel prognostic, preventive, and therapeutic potentials of these pronounced associations.
In recent years, circulating miRNAs have attracted a great deal of attention as promising novel markers for various diseases. Here, we investigated their potential to serve as minimally invasive, ...early detection markers for breast cancer in blood plasma. We profiled miRNAs extracted from the plasma of early stage breast cancer patients (taken at the time‐point of diagnosis) and healthy control individuals using TaqMan low‐density arrays (TLDA). Selected candidates identified in the initial screen were further validated in an extended study cohort of 207 individuals including 127 sporadic breast cancer cases and 80 healthy controls via RT‐qPCR. Four miRNAs (miR‐148b, miR‐376c, miR‐409‐3p and miR‐801) were shown to be significantly upregulated in the plasma of breast cancer patients. ROC curve analysis showed that the combination of only three miRNAs (miR‐148b, miR‐409‐3p and miR‐801) had an equal discriminatory power between breast cancer cases and healthy controls as all four miRNAs together (AUC = 0.69). In conclusion, the identified miRNAs might be of potential use in the development of a multimarker blood‐based test to complement and improve early detection of breast cancer. Such a multimarker blood test might for instance provide a prescreening tool, especially for younger women, to facilitate decisions about which individuals to recommend for further diagnostic tests.
What's new?
Circulating microRNAs (miRNAs) have distinct expression profiles in cancer and are unusually stable in plasma, making them potentially useful for early cancer detection. Here, using the largest plasma sample size for miRNA profiling of breast cancer to date, four circulating miRNAs were found to be more abundant in breast cancer patients compared with healthy individuals. The identified miRNAs could be used to develop a multi‐marker blood‐based test to complement existing early breast cancer detection strategies.
The use of circulating tumor cells (CTC) as a prognostic marker in metastatic breast cancer (MBC) has been well established. However, their efficacy and accuracy are still under scrutiny mainly ...because of methods of their enrichment and identification. We hypothesized that circulating miRNAs can predict the CTC status of patients with MBC, and tested for the same. Furthermore, we aimed at establishing a panel of circulating miRNAs capable of differentiating MBC cases from healthy controls.
Circulating miRNAs from plasma of CTC-positive and CTC-negative patients with MBC, and healthy controls, were profiled by TaqMan Human MicroRNA arrays. Candidates from the initial screen were validated in an extended cohort of 269 individuals (61 CTC-positive, 72 CTC-negative, 60 CTC-low MBC cases, and 76 controls).
CTC-positive had significantly higher levels of miR-141, miR-200a, miR-200b, miR-200c, miR-203, miR-210, miR-375, and miR-801 than CTC-negative MBC and controls (P < 0.00001), whereas miR-768-3p was present in lower amounts in MBC cases (P < 0.05). miR-200b was singled out as the best marker for distinguishing CTC-positive from CTC-negative patients (AUC 0.88). We identified combinations of miRNAs for differentiating MBC cases from controls (AUC 0.95 for CTC-positive; AUC 0.78 for CTC-negative). Combinations of miRNAs and miR-200b alone were found to be promising prognostic marker for progression-free and overall survival.
This is the first study to document the capacity of circulating miRNAs to indicate CTC status and their potential as prognostic markers in patients with MBC.
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