MicroRNAs in body fluids as biomarkers for non-small cell lung cancer: a systematic review

A novel circulating miRNA-based signature for the early diagnosis and prognosis prediction of non-small-cell lung cancer

BACKGROUND

Non-small-cell lung cancer (NSCLC) is a significant public health issue worldwide. The aim of our study was to develop a serum miRNA-based molecular signature for the early detection and prognosis prediction of NSCLC.

METHODS

The significantly altered circulating miRNAs were profiled in GSE24709. The top ten upregulated miRNAs were miR-432, miR-942, miR-29c-5p, miR-601, miR-613, miR-520d-3p, miR-1261, miR-132-5p, miR-302b, and miR-154-5p, while the top ten downregulated miRNAs were miR-562, miR-18b, miR-9-3p, miR-154-3p, miR-20b, miR-18a, miR-487a, miR-20a, miR-103, and miR-144. Then, the top four upregulated serum miRNAs (miR-432, miR-942, miR-29c-5p, and miR-601) were validated by real-time quantitative PCR. The clinical significance of two candidate serum miRNAs, miR-942 and miR-601, was further explored.

RESULTS

Our results showed that the expression levels of serum miR-942 and serum miR-601 were significantly upregulated in NSCLC. In addition, serum miR-942 and serum miR-601 showed better performance than CEA, CYFRA21-1, and SCCA for early diagnosis of NSCLC. Combining serum miR-942 and serum miR-601 enhanced the efficacy of detecting early-stage NSCLC. Moreover, high serum miR-942 and serum miR-601 were both associated with adverse clinical variables and poor survival. The NSCLC patients with simultaneously high serum miR-942 and serum miR-601 suffered worst clinical outcome, while those with simultaneously low serum miR-942 and serum miR-601 had most favorable outcome. The multivariate analysis showed that serum miR-942 and serum miR-601 were independent prognostic factors for NSCLC.

CONCLUSIONS

Taken together, serum miR-942 and serum miR-601 might serve as a promising molecular signature for the early detection and prognosis prediction of NSCLC.

Radiation-Induced Normal Tissue Damage: Oxidative Stress and Epigenetic Mechanisms

Radiotherapy (RT) is currently one of the leading treatments for various cancers; however, it may cause damage to healthy tissue, with both short-term and long-term side effects. Severe radiation-induced normal tissue damage (RINTD) frequently has a significant influence on the progress of RT and the survival and prognosis of patients. The redox system has been shown to play an important role in the early and late effects of RINTD. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are the main sources of RINTD. The free radicals produced by irradiation can upregulate several enzymes including nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase), lipoxygenases (LOXs), nitric oxide synthase (NOS), and cyclooxygenases (COXs). These enzymes are expressed in distinct ways in various cells, tissues, and organs and participate in the RINTD process through different regulatory mechanisms. In recent years, several studies have demonstrated that epigenetic modulators play an important role in the RINTD process. Epigenetic modifications primarily contain noncoding RNA regulation, histone modifications, and DNA methylation. In this article, we will review the role of oxidative stress and epigenetic mechanisms in radiation damage, and explore possible prophylactic and therapeutic strategies for RINTD.

Serum miR-223: A Validated Biomarker for Detection of Early-Stage Non-Small Cell Lung Cancer

BACKGROUND

The published circulating miRNA signatures proposed for early-stage non-small cell lung cancer (NSCLC) detection are inconsistent and difficult to replicate. Reproducibility and validation of an miRNA simple signature of NSCLC are prerequisites for translation to clinical application.

METHODS

The serum level of miR-223 and miR-29c, emerging from published studies, respectively, as a highly sensitive and a highly specific biomarker of early-stage NSCLC, was measured with droplet digital PCR (ddPCR) technique in an Italian cohort of 75 patients with stage I-II NSCLC and 111 tumor-free controls. By ROC curve analysis we evaluated the miR-223 and miR-29c performance in discerning NSCLC cases from healthy controls.

RESULTS

Reproducibility and robust measurability of the two miRNAs using ddPCR were documented. In a training set (40 stage I-II NSCLCs and 56 controls), miR-223 and miR-29c, respectively, showed an AUC of 0.753 [95% confidence interval (CI), 0.655-0.836] and 0.632 (95% CI, 0.527-0.729) in identifying NSCLC. Combination of miR-223 with miR-29c yielded an AUC of 0.750, not improved over that of miR-223 alone. Furthermore, in an independent blind set (35 stage I-II NSCLCs and 55 controls), we validated serum miR-223 as an effective biomarker of stage I-II NSCLC (AUC = 0.808; 95% CI, 0.712-0.884), confirming the miR-223 diagnostic performance reported by others in Chinese cohorts.

CONCLUSIONS

Using ddPCR technology, miR-223 was externally validated as a reproducible, effective serum biomarker of early-stage NSCLC in ethnically different subjects. Combination with miR-29c did not improve the miR-223 diagnostic performance.

IMPACT

Serum miR-223 determination may be proposed as a tool for refining NSCLC risk stratification, independent of smoking habit and age.

Comparison of value of biomarkers in diagnosing lung cancer: An overview of systematic reviews protocol

BACKGROUND

In both sexes combined, lung cancer is the most commonly diagnosed cancer and the leading cause of cancer death. Furthermore, the incidence rate is increasing in many countries. Many lung cancer patients have a poor prognosis because they are usually diagnosed at an advanced stage. Therefore, there is an urgent need to develop effective methods for early diagnosis of lung cancer. Some systematic reviews have evaluated the value of biomarkers for diagnosing lung cancer. However, it remains unclear which biomarker has superior performance for early and accurate detection of lung cancer. This overview aims to assess the methodological and reporting quality of available systematic reviews and to find an optimal biomarker for diagnosing lung cancer.

METHODS

We searched PubMed, Embase.com, the Cochrane Library of Systematic Reviews, and Web of Science to identify relevant systematic reviews including randomized controlled trials, cross-sectional studies, case-control studies, or cohort studies that reported the value of biomarkers for diagnosing lung cancer. The methodological quality will be assessed using AMASAR-2 checklist, and the reporting quality will be assessed using PRISMA-DTA checklist. Bubble plot will be generated to map the biomarkers, methodological and reporting quality. The pairwise meta-analysis and indirect comparisons will be performed using STATA 13.0.

RESULTS

The results of this study will be published in a peer-reviewed journal CONCLUSION:: This overview will provide comprehensive evidence of different biomarkers for the diagnosis of lung cancer.

ETHICS AND DISSEMINATION

Ethics approval and patient consent are not required as this study is an overview based on published systematic reviews.

Circulating MicroRNA Biomarkers for Lung Cancer Detection in East Asian Populations

BACKGROUND

Lung cancer (LC) is the leading cause of cancer-related death in Eastern Asia. The prognosis of LC highly depends on tumor stages and early detection could substantially reduce LC mortality. Accumulating evidence suggested that circulating miRNAs in plasma or serum may have applications in early LC detection. We thus conducted a systematic literature review on the diagnostic value of miRNAs markers for LC in East Asian populations.

METHODS

PubMed and ISI Web of Knowledge were searched to retrieve relevant articles published up to 17 September 2018. Information on study design, population characteristics, investigated miRNAs and diagnostic accuracy (including sensitivity, specificity and area under the curve (AUC)) were independently extracted by two reviewers.

RESULTS

Overall, 46 studies that evaluated a total of 88 miRNA markers for LC diagnosis in East Asian populations were identified. Sixteen of the 46 studies have incorporated individual miRNA markers as panels (with 2⁻20 markers). Three promising miRNA panels with ≥90% sensitivity and ≥90% specificity were discovered, two of which were externally validated. Diagnostic performance of circulating miRNAs in East Asian populations was comparable to previously summarized performance in Western populations. Forty-four miRNAs were reported in both populations. No major differences in diagnostic performance by ethnicity of the same miRNA was observed.

CONCLUSIONS

Circulating miRNAs or miRNA panels, possibly in combination with other promising molecular markers including epigenetic and genetic markers, may be promising candidates for noninvasive LC early detection. However, large studies with samples collected prospectively in true screening settings are required to validate the promising markers or marker panels.

Circulating microRNA biomarkers for lung cancer detection in Western populations

Lung cancer (LC) is a leading cause of cancer-related death in the Western world. Patients with LC usually have poor prognosis due to the difficulties in detecting tumors at early stages. Multiple studies have shown that circulating miRNAs might be promising biomarkers for early detection of LC. We aimed to provide an overview of published studies on circulating miRNA markers for early detection of LC and to summarize their diagnostic performance in Western populations. A systematic literature search was performed in PubMed and ISI Web of Knowledge to find relevant studies published up to 11 August 2017. Information on study design, population characteristics, miRNA markers, and diagnostic accuracy (including sensitivity, specificity, and AUC) were independently extracted by two reviewers. Overall, 17 studies evaluating 35 circulating miRNA markers and 19 miRNA panels in serum or plasma were included. The median sensitivity (range) and specificity (range) were, respectively, 78.4% (51.7%-100%) and 78.7% (42.9%-93.5%) for individual miRNAs, and 83.0% (64.0%-100%) and 84.9% (71.0%-100%) for miRNA panels. Most studies incorporated individual miRNA markers as panels (with 2-34 markers), with multiple miRNA-based panels generally outperforming individual markers. Two promising miRNA panels were discovered and verified in prospective cohorts. Of note, both studies exclusively applied miRNA ratios when building up panels. In conclusion, circulating miRNAs may bear potential for noninvasive LC screening, but large studies conducted in screening or longitudinal settings are needed to validate the promising results and optimize the marker panels.

miR-126/VCAM-1 regulation by naringin suppresses cell growth of human non-small cell lung cancer

Certain studies have indicated that naringin possesses various pharmacological activities including anti-aging, anti-oxidation, anticancer, cardiovascular and cerebrovascular disease prevention, in addition to anti-hepatic effects. The present study explores the anticancer effect of naringin on human small cell lung cancer H69AR cells. Cell growth and apoptosis rates of H69AR cells were measured by MTT or flow cytometry, which demonstrated naringin suppressed cell growth and induced apoptosis of H69AR cells. MicroRNA (miR)-126 expression and levels of phosphorylated protein kinase B (AKT), mechanistic target of rapamycin (mTOR), nuclear factor (NF)-κB and vascular cell adhesion molecule 1 (VCAM-1) proteins were detected by quantitative polymerase chain reaction and western blotting. It was identified that naringin increased miR-126 expression and suppressed the phosphorylation of AKT, mTOR, NF-κB and VCAM-1 proteins in H69AR cells. Suppression of miR-126 expression reduced the anticancer effects of naringin on H69AR cells, reversed the naringin-induced reduction of phosphoinositide 3-kinase/AKT/mTOR, and suppressed VCAM-1 protein levels. However, close of miR-126 expression did not affect the levels of NF-κB protein in H69AR cells. In summary, naringin exhibits its anti-cancer effect by suppressing cell growth of small cell lung cancer cells through miR-126/VCAM-1 signaling pathway.

Clinically Correlated MicroRNAs in the Diagnosis of Non-Small Cell Lung Cancer: A Systematic Review and Meta-Analysis

(1) Background. Non-small cell lung cancer (NSCLC) has a high mortality rate. MiRNAs have been found to be diagnostic biomarkers for NSCLC. However, controversial results exist. We conducted this meta-analysis to evaluate the diagnostic value of miRNAs for NSCLC. (2) Methods. Databases and reference lists were searched. Pooled sensitivity (SEN), specificity (SPE), and area under the curve (AUC) were applied to examine the general diagnostic efficacy, and subgroup analysis was also performed. (3) Results. Pooled SEN, SPE, and AUC were 85%, 88%, and 0.93, respectively, for 71 studies. Multiple miRNAs (AUC: 0.96) obtained higher diagnostic value than single miRNA (AUC: 0.86), and the same result was found for Caucasian population (AUC: 0.97) when compared with Asian (AUC: 0.91) and Caucasian/African population (AUC: 0.92). MiRNA had higher diagnostic efficacy when participants contained both smokers and nonsmokers (AUC is 0.95 for imbalanced group and 0.91 for balanced group) than when containing only smokers (AUC: 0.90). Meanwhile, AUC was 0.91 for both miR-21 and miR-210. (4) Conclusions. Multiple miRNAs such as miR-21 and miR-210 could be used as diagnostic tools for NSCLC, especially for the Caucasian and nonsmoking NSCLC.

The clinical value of miR-193a-3p in non-small cell lung cancer and its potential molecular mechanism explored in silico using RNA-sequencing and microarray data

miR‐193a‐3p is a tumor‐related miRNA playing an essential role in tumorigenesis and progression of non‐small cell lung cancer (NSCLC). The objective of the present study was to investigate the relationship between miR‐193a‐3p expression and clinical value and to further explore the potential signaling of miR‐193a‐3p in the carcinogenesis of NSCLC. RNA‐sequencing and microarray data were collected from the databases GEO, ArrayExpress and The Cancer Genome Atlas (TCGA). Furthermore, in silico assessments were performed to analyze the prospective pathways and networks of the target genes of miR‐193a‐3p. In total, 453 cases of NSCLC patients and 476 normal controls were included in blood samples, while 920 cases of NSCLC patients and 406 normal controls were included in tissue samples. The pooled positive likelihood ratio, the pooled negative likelihood ratio and the pooled diagnostic odds ratio were calculated to reflect the diagnostic value of miR‐193a‐3p in blood and tissue samples. Moreover, the areas under the curve of the summary receiver operating characteristic curve of blood and tissue were 0.64 and 0.79, respectively. In addition, we found a lower level of miR‐193a in NSCLC tissues than in non‐cancerous controls based on TCGA. A gene ontology (GO) enrichment analysis demonstrated that miR‐193a‐3p could be related to key signaling pathways in NSCLC. Also, several vital pathways were illustrated by KEGG. Lower expression of miR‐193a‐3p in tissue samples of NSCLC may be associated with tumorigenesis and be a predictor of deterioration of NSCLC patients, and pathway analysis revealed crucial signaling pathways correlated with the incidence and progress of NSCLC.

Systematic review and critique of circulating miRNAs as biomarkers of stage I-II non-small cell lung cancer

Selected circulating microRNAs (miRNAs) have been suggested for non-invasive screening of non-small cell lung cancer (NSCLC), however the numerous proposed miRNA signatures are inconsistent. Aiming to identify miRNAs suitable specifically for stage I-II NSCLC screening in serum/plasma samples, we searched the databases "Pubmed", "Medline", "Scopus", "Embase" and "WOS" and systematically reviewed the publications reporting quantitative data on the efficacy [sensitivity, specificity and/or area under the curve (AUC)] of circulating miRNAs as biomarkers of NSCLC stage I and/or II. The 20 studies fulfilling the search criteria included 1110 NSCLC patients and 1009 controls, and were of medium quality according to Quality Assessment of Diagnostic Accuracy Studies checklist. In these studies, the patient cohorts as well as the control groups were heterogeneous for demographics and clinicopathological characteristics; moreover, numerous pre-analytical and analytical variables likely influenced miRNA determinations, and potential bias of hemolysis was often underestimated. We identified four circulating miRNAs scarcely influenced by hemolysis, each featuring high sensitivity (> 80%) and AUC (> 0.80) as biomarkers of stage I-II NSCLC: miR-223, miR-20a, miR-448 and miR-145; four other miRNAs showed high specificity (> 90%): miR-628-3p, miR-29c, miR-210 and miR-1244. In a model of two-step screening for stage I-II NSCLC using first the above panel of serum miRNAs with high sensitivity and high AUC, and subsequently the panel with high specificity, the estimated overall sensitivity is 91.6% and overall specificity is 93.4%. These and other circulating miRNAs suggested for stage I-II NSCLC screening require validation in multiple independent studies before they can be proposed for clinical application.

Changes in miRNA in the lung and whole blood after whole thorax irradiation in rats

We used a rat model of whole thorax x-ray irradiation to profile the microRNA (miRNA) in lung and blood up to 4 weeks after radiation. MiRNA from normal and irradiated Wistar rat lungs and whole blood were analyzed by next-generation sequencing and the changes by radiation were identified by differential deRNA-seq 1, 2, 3 and 4 weeks after irradiation. The average total reads/library was 2,703,137 with a mean of 88% mapping to the rat genome. Detailed profiles of 100 of the most abundant miRNA in rat blood and lung are described. We identified upregulation of 4 miRNA, miR-144-5p, miR-144-3p, miR-142-5p and miR-19a-3p in rat blood 2 weeks after radiation that have not previously been shown to be altered after radiation to the lung. Ingenuity Pathway Analysis identified signaling of inflammatory response pathways. These findings will support development of early detection methods, as well as mechanism(s) of injury and mitigation in patients after radiotherapy or radiological accidents.

The Pursuit of Noninvasive Diagnosis of Lung Cancer

The noninvasive diagnosis of lung cancer remains a formidable challenge. Although tissue diagnosis will remain the gold standard for the foreseeable future, questions pertaining to the risks and costs associated with invasive diagnostic procedures are of prime relevance. This review addresses new modalities for improving the noninvasive evaluation of suspicious lung nodules. Ultimately, the goal is to translate early diagnosis into early treatment. We discuss how biomarkers could assist in distinguishing benign from malignant nodules and aggressive from indolent tumors. The field of biomarkers is rapidly expanding and progressing, and efforts are well underway to apply molecular diagnostics to address the shortcomings of current lung cancer diagnostic tools.

Mechanism and biological role of Dnmt2 in Nucleic Acid Methylation

A group of homologous nucleic acid modification enzymes called Dnmt2, Trdmt1, Pmt1, DnmA, and Ehmet in different model organisms catalyze the transfer of a methyl group from the cofactor S-adenosyl-methionine (SAM) to the carbon-5 of cytosine residues. Originally considered as DNA MTases, these enzymes were shown to be tRNA methyltransferases about a decade ago. Between the presumed involvement in DNA modification-related epigenetics, and the recent foray into the RNA modification field, significant progress has characterized Dnmt2-related research. Here, we review this progress in its diverse facets including molecular evolution, structural biology, biochemistry, chemical biology, cell biology and epigenetics.

Serum level of microRNA-147 as diagnostic biomarker in human non-small cell lung cancer

Objectives In this study, we intended to examine the gene expression level and the clinical significance of microRNA-147 (miR-147) in cancer tissues and sera of patients with non-small cell lung cancer (NSCLC). Methods Quantitative real-time PCR (qRT-PCR) was used to investigate the expression levels of miR-147 in 32 paired NSCLC tissues and their adjacent normal lung tissues, sera of 122 control and 87 NSCLC patients. The correlation of serum miR-147 expression level with clinicopathological characteristics, and the prognosis of NSCLC patients was statistically evaluated. Results MiR-147 was significantly down-regulated in NSCLC tissues than in paired adjacent normal tissues, and in sera of NSCLC patients than in sera of control patients. In addition, serum miR-147 was markedly down-regulated in advanced NSCLC patients and the patients with lymph node metastasis (LNM). Low serum miR-147 expression level was found to be significantly correlated with tumor, lymph node, metastasis stage, LNM, and tumor size. Statistical analysis showed that patients with low serum miR-147 had much worse overall survival, and low serum miR-147 expression level was an independent prognostic factor for poor prognosis for NSCLC. Conclusion Low serum miR-147 expression level may be a useful biomarker for patients with NSCLC.

miR-Test: a blood test for lung cancer early detection

Lung cancer is the leading cause of cancer death worldwide. Low-dose computed tomography screening (LDCT) was recently shown to anticipate the time of diagnosis, thus reducing lung cancer mortality. However, concerns persist about the feasibility and costs of large-scale LDCT programs. Such concerns may be addressed by clearly defining the target "high-risk" population that needs to be screened by LDCT. We recently identified a serum microRNA signature (the miR-Test) that could identify the optimal target population. Here, we performed a large-scale validation study of the miR-Test in high-risk individuals (n = 1115) enrolled in the Continuous Observation of Smoking Subjects (COSMOS) lung cancer screening program. The overall accuracy, sensitivity, and specificity of the miR-Test are 74.9% (95% confidence interval [CI] = 72.2% to 77.6%), 77.8% (95% CI = 64.2% to 91.4%), and 74.8% (95% CI = 72.1% to 77.5%), respectively; the area under the curve is 0.85 (95% CI = 0.78 to 0.92). These results argue that the miR-Test might represent a useful tool for lung cancer screening in high-risk individuals.

Clinical use of microRNAs as potential non-invasive biomarkers for detecting non-small cell lung cancer: a meta-analysis

Emerging studies have revealed that microRNA (miRNA) in body fluid may serve as a potential biomarker to detect non-small cell lung cancer (NSCLC). However, the diagnostic accuracy of miRNA for NSCLC detection is still under debate because there is inconsistency in previous studies. Hence, we conducted this meta-analysis to comprehensively evaluate the diagnostic performance of miRNA. A systematic literature search was performed to retrieve relevant articles in PubMed and other databases, and STATA 12.0 (StataCorp, College Station, TX, USA) was used to calculate the pooled parameters. A total of 28 articles involving 2121 NSCLC patients and 1582 healthy controls were included in this meta-analysis. The overall pooled sensitivity and specificity of miRNA were 0.75 and 0.79, respectively. The pooled positive likelihood ratio was 3.6, negative likelihood ratio was 0.32 and diagnostic odds ratio was 12. The area under the curve (AUC) was 0.84. Subgroup and meta-regression analyses established that miRNA assays were more accurate in Caucasian populations (AUC of 0.86, sensitivity of 0.79 and specificity of 0.82, respectively) than in Asian populations (AUC, sensitivity and specificity of 0.83, 0.72 and 0.80, respectively). In addition, the multiple miRNA assays (AUC of 0.89, sensitivity of 0.83 and specificity of 0.82, respectively) showed a higher accuracy than single miRNA assays (AUC, sensitivity and specificity of 0.81, 0.77 and 0.71, respectively) in NSCLC detection. Subgroup analyses based on specimen types suggested that blood-based miRNA (AUC of 0.86, sensitivity of 0.78 and specificity of 0.80, respectively) may have a higher diagnostic accuracy as biomarkers than sputum-based miRNA (AUC of 0.81, sensitivity of 0.69 and specificity of 0.80, respectively). In conclusion, miRNA may serve as a potential biomarker in NSCLS detection, especially the multiple miRNA from blood, with a relatively high diagnostic accuracy.

MicroRNA expression profiling in PBMCs: a potential diagnostic biomarker of chronic hepatitis C

The expression levels of miR-16, miR-193b, miR-199a, miR-222, and miR-324 in PBMCs were significantly higher in CHC patients compared with healthy controls and significantly different between CHC patients with HCV genotype 1 (GT-1) and non-genotype-1 (non-GT-1). Multivariate logistic regression analysis also showed that patients with high expression levels of the six target miRNAs had an approximately 7.202-fold risk of CHC compared with those with low expression levels of the target miRNAs. We concluded that the expression levels of miR-16, miR-193b, miR-199a, miR-222, and miR-324 target miRNAs in PBMCs of CHC may act as significant risk biomarkers for the development of CHC.

Diagnostic value of microRNA-21 in the diagnosis of lung cancer: evidence from a meta-analysis involving 11 studies

Molecular biomarkers that can be detected in easily accessible body fluids have been proposed as non-invasive, cost-effective, and useful tools for cancer diagnosis. Recently, extensive research has explored the involvement of the aberrant expression of microRNA-21 (miRNA-21, miR-21) in lung cancer. Inconsistent results, however, have prevented its widespread use in diagnosis. In light of this situation, our meta-analysis aimed to systematically determine whether aberrant miR-21 expression can distinguish patients with lung cancer from cancer-free controls with a high level of diagnostic accuracy. A comprehensive literature search for relevant studies published before December 23, 2013 was conducted in the MEDLINE, EMBASE, the Cochrane Library, and three Chinese databases. The pooled sensitivity, specificity and other parameters were used to assess the overall performance of miR-21-based assays. Statistical analysis was conducted using the STATA 11.0 software. Eleven research articles involving 676 patients with lung cancer and 529 healthy controls were considered eligible for inclusion in the present meta-analysis. The following summary parameters were calculated from all the included studies: sensitivity of 0.66 (95 % confidence interval [CI]: 0.57-0.74), specificity of 0.82 (95 % CI: 0.74-0.88), positive likelihood ratio (PLR) of 3.70 (95 % CI: 2.50-5.60), negative likelihood ratio (NLR) of 0.42 (95 % CI: 0.32-0.54); diagnostic odds ratio (DOR) of 9.00 (95 % CI: 5.00-16.00), and area under the curve (AUC) of 0.81 (95 % CI: 0.77-0.84). In addition, we added two pre-specified covariates (ethnicity and specimen types) to the bivariate model to assess their impact on the diagnostic value of miR-21 for lung cancer. Similar results were also observed in subgroup analyses, indicating a relatively low level of accuracy. The current meta-analysis indicates that a single miR-21 may not be sufficient to identify lung cancer and that more miRNAs should be used to detect lung carcinoma.

Methodological challenges in utilizing miRNAs as circulating biomarkers

MicroRNAs (miRNAs) have emerged as important regulators in the post-transcriptional control of gene expression. The discovery of their presence not only in tissues but also in extratissular fluids, including blood, urine and cerebro-spinal fluid, together with their changes in expression in various pathological conditions, has implicated these extracellular miRNAs as informative biomarkers of disease. However, exploiting miRNAs in this capacity requires methodological rigour. Here, we report several key procedural aspects of miRNA isolation from plasma and serum, as exemplified by research in cardiovascular and pulmonary diseases. We also highlight the advantages and disadvantages of various profiling methods to determine the expression levels of plasma- and serum-derived miRNAs. Attention to such methodological details is critical, as circulating miRNAs become diagnostic tools for various human diseases.