Diagnostic Relevance of microRNAs in Other Body Fluids Including Urine, Feces, and Saliva

Role of salivary miRNAs in the diagnosis of gastrointestinal disorders: a mini-review of available evidence

MiRNAs are short, non-coding RNA molecules, which are involved in the regulation of gene expression and which play an important role in various biological processes, including inflammation and cell cycle regulation. The possibility of detecting their extracellular expression, within body fluids, represented the main background for their potential use as non-invasive biomarkers of various diseases. Salivary miRNAs particularly gained interest recently due to the facile collection of stimulated/unstimulated saliva and their stability among healthy subjects. Furthermore, miRNAs seem to represent biomarker candidates of gastrointestinal disorders, with miRNA-based therapeutics showing great potential in those conditions. This review aimed to highlight available evidence on the role of salivary miRNAs in different gastrointestinal conditions. Most salivary-based miRNA studies available in the literature that focused on pathologies of the gastrointestinal tract have so far been conducted on pancreatic cancer patients and delivered reliable results. A few studies also showed the diagnostic utility of salivary miRNAs in conditions such as esophagitis, esophageal cancer, colorectal cancer, or inflammatory bowel disease. Moreover, several authors showed that salivary miRNAs may confidently be used as biomarkers of gastric cancer, but the use of salivary miRNA candidates in gastric inflammation and pre-malignant lesions, essential stages of Correa's cascade, is still put into question. On the other hand, besides miRNAs, other salivary omics have shown biomarker potential in gastro-intestinal conditions. The limited available data suggest that salivary miRNAs may represent reliable biomarker candidates for gastrointestinal conditions. However, their diagnostic potential requires validation through future research, performed on larger cohorts.

Current and future applications of biomarkers in samples collected through minimally invasive methods for cancer medicine and population-based research

Despite advances in cancer medicine and research, invasive and potentially risky procedures such as biopsies, venous blood tests, imaging, colonoscopy, and pap smear tests are still primarily used for screening, staging, and assessing response to therapy. The development and interdisciplinary use of biomarkers from urine, feces, saliva, scent, and capillary blood collected with minimally invasive methods represents a potential opportunity for integration with biomarker analysis for cancers, both in clinical practice (e.g., in screening, treatment, and disease monitoring, and improved quality of life for patients) and population-based research (e.g., in epidemiology/public health, studies of social and environmental determinants, and evolutionary medicine). In this article, we review the scientific rationale, benefits, challenges, and potential opportunities for measuring cancer-related biomarkers in samples collected through minimally invasive methods.

Liquid biopsy for the assessment of adrenal cancer heterogeneity: where do we stand?

Almost 10 years have passed since the first attempts of liquid biopsy aimed at the characterisation of tumor cells present in the bloodstream from a regular sample of peripheral blood were performed. Liquid biopsy has been used to characterise tumor heterogeneity in various types of solid tumors including adrenocortical carcinoma. The development of molecular biology, genetics, and methodological advances such as digital PCR and next-generation sequencing allowed us to use besides circulating tumor cells a variety of circulating cell-free nucleic acids, DNAs, RNAs and microRNAs secreted by tumors into blood and other body fluids as specific molecular markers. These markers are used for diagnosis, to check tumor development, selecting efficient therapies, therapy monitoring and even possess prognostic power. In adrenocortical carcinoma, there are some studies reporting analysis of circulating tumor cells, circulating cell free DNA and microRNAs for assessing tumor heterogeneity. Among microRNAs, hsa-miR-483-5p seems to be the most important player. Combined with other microRNAs like hsa-miR-195, their expression correlates with recurrence-free survival. Most studies support the applicability of liquid biopsy for assessing temporal tumor heterogeneity (i.e. tumor progression) in adrenocortical cancer. In this mini-review, the available findings of liquid biopsy for assessing tumor heterogeneity in adrenocortical cancer are presented.

Aberrant Non-Coding RNA Expressed in Gastric Cancer and Its Diagnostic Value

Gastric cancer (GC) is one of the digestive tract malignancies with high invasion and mortality rates. Recent studies have reported that non-coding RNAs (ncRNAs) seem to play a crucial part in many tumors. Due to their high stability, ncRNAs may used as novel biomarkers to predict the occurrence and prognosis of GC. Here, we measured miRNA, lncRNA and cirRNA expression profiles of GC patients by using microarray and RNA-sequencing data from tissue samples. The diagnosis prediction model based on the ncRNA signatures and clinical features was evaluated by circulating and tissue validation and ROC analysis. Nine miRNAs and eight lncRNAs were obtained from the microarray analysis. Six miRNAs (miR-550a-5p, miRNA-936, miR-1306-3p, miR-3185, miR-6083, miR-6792-3p) and three lncRNAs (lnc-MB21D1-3:5, lnc-PSCA-4:2 and lnc-ABCC5-2:1) were abnormally expressed in circulating and tissue samples compared with normal control (NC), which was closely related to clinical pathology and survival time of GC patients; circRNA sequencing and qRT-PCR revealed four circRNAs (circASHL2, circCCDC9, circNHSL1 and cirMLLT10) were abnormally expressed in GC tissues and parts of them were negative relationship with their predicted binding miRNAs. These ncRNAs might act as promising molecular markers for the diagnosis and prognosis of gastric cancer.

Saliva RNA Biomarkers of Gastrointestinal Dysfunction in Children With Autism and Neurodevelopmental Disorders: Potential Implications for Precision Medicine

Gastrointestinal (GI) disorders are common in children with neurodevelopmental disorders such as autism spectrum disorder (ASD). A limited understanding of the biologic factors that predispose this population to GI disorders has prevented development of individualized therapies to address this important medical issue. The goal of the current study was to determine if elements of the salivary micro-transcriptome could provide insight into the biologic perturbations unique to children with ASD-related GI disturbance. This cohort study included 898 children (ages 18-73 months) with ASD, non-ASD developmental delay (DD), or typical development (TD). The saliva micro-transcriptome of each child was assessed with RNA-seq. Outputs were aligned to microbial and human databases. A Kruskal Wallis analysis of variance (ANOVA) was used to compare levels of 1821 micro-transcriptome features across neurodevelopmental status (ASD, DD, or TD) and GI presence or absence. An ANOVA was also used to compare micro-transcriptome levels among GI sub-groups (constipation, reflux, food intolerance, other GI condition, no GI condition), and to identify RNAs that differed among children taking three common GI medications (probiotics, reflux medication, or laxatives). Relationships between features identified in ANOVA testing were examined for associations with scores on the Autism Diagnostic Observation Schedule, 2nd Edition (ADOS-2) and the Vineland Adaptive Behavior Scales. GI disturbance rates were higher among children with ASD than peers with TD but were similar to those with DD. Five piwi-interacting RNAs and three microbial RNAs displayed an interaction between developmental status and GI disturbance. Fifty-seven salivary RNAs differed between GI sub-groups-with microRNA differences between food intolerance and reflux groups being most common. Twelve microRNAs displayed an effect of GI disturbance and showed association with GI medication uses and measures of behavior. These 12 microRNAs displayed enrichment for 13 physiologic pathways, including metabolism/digestion long-term depression, and neurobiology of addiction. This study identifies salivary micro-transcriptome features with differential expression among children with ASD-related GI disturbance. A subset of the RNAs displays relationships with treatment modality and are associated with autistic behaviors. The pathobiologic targets of the micro-transcriptome markers may serve as targets for individualized therapeutic interventions aimed at easing pain and behavioral difficulties seen in ASD-related GI disturbance.

Genome-wide study of salivary miRNAs identifies miR-423-5p as promising diagnostic and prognostic biomarker in oral squamous cell carcinoma

Survival rates of oral squamous cell carcinoma (OSCC) remained substantially unchanged over the last decades; thus, additional prognostic tools are strongly needed. Salivary miRNAs have emerged as excellent non-invasive cancer biomarker candidates, but their association with OSCC prognosis has not been investigated yet. In this study, we analyzed global salivary miRNA expression in OSCC patients and healthy controls, with the aim to define its diagnostic and prognostic potential.

Methods: Saliva was collected from patients with newly diagnosed untreated primary OSCC and healthy controls. Global profiling of salivary miRNAs was carried out through a microarray approach, while signature validation was performed by quantitative real-time PCR (RT-qPCR). A stringent statistical approach for microarray and RT-qPCR data normalization was applied. The diagnostic performance of miRNAs and their correlation with OSCC prognosis were comprehensively analyzed.

Results: In total, 25 miRNAs emerged as differentially expressed between OSCC patients and healthy controls and, among them, seven were significantly associated with disease-free survival (DFS). miR-106b-5p, miR-423-5p and miR-193b-3p were expressed at high levels in saliva of OSCC patients and their combination displays the best diagnostic performance (ROC - AUC = 0.98). Moreover, high expression of miR-423-5p was an independent predictor of poor DFS, when included in multivariate survival analysis with the number of positive lymph nodes - the only significant clinical prognosticator. Finally, we observed a significant decrease in miR-423-5p expression in matched post-operative saliva samples, suggesting its potential cancer-specific origin.

Conclusion: Salivary miRNAs identified in our cohort of patients show to be accurate in OSCC detection and to effectively stratify patients according to their likelihood of relapse. These results, if validated in an independent set of patients, could be particularly promising for screening/follow-up of high-risk populations and useful for preoperative prognostic assessment.

Future Directions in Diagnosis, Prognosis and Disease Monitoring of Adrenocortical Carcinoma: Novel Non-Invasive Biomarkers

Adrenocortical carcinoma (ACC) is a rare endocrine malignancy with frequent metastatic spread and poor prognosis. The disease can occur at any age with unexpected biological behavior. Recent genome-wide studies of ACC have contributed to our understanding of the disease, but diagnosis of ACC remains a challenge, even for multidisciplinary expert teams. Patients with ACC are frequently diagnosed in advanced stages and have limited therapeutic options. Therefore, for earlier diagnosis and better clinical management of adrenocortical carcinoma, specific, sensitive, and minimal invasive markers are urgently needed. Over several decades, great efforts have been made in discovering novel and reliable diagnostic and prognostic biomarkers including microRNAs, steroid profilings, circulating tumor cells, circulating tumor DNAs and radiomics. In this review, we will summarize these novel noninvasive biomarkers and analyze their values for diagnosis, predicting prognosis, and disease monitoring. Current problems and possible future application of these non-invasive biomarkers will also be discussed.

Pathogenetic Role and Clinical Implications of Regulatory RNAs in Biliary Tract Cancer

Biliary tract cancer (BTC) is characterised by poor prognosis and low overall survival in patients. This is generally due to minimal understanding of its pathogenesis, late diagnosis and limited therapeutics in preventing or treating BTC patients. Non-coding RNA (ncRNA) are small RNAs (mRNA) that are not translated to proteins. ncRNAs were considered to be of no importance in the genome, but recent studies have shown they play essential roles in biology and oncology such as transcriptional repression and degradation, thus regulating mRNA transcriptomes. This has led to investigations into the role of ncRNAs in the pathogenesis of BTC, and their clinical implications. In this review, the mechanisms of action of ncRNA are discussed and the role of microRNAs in BTC is summarised. The scope of this review will be limited to miRNA as they have been shown to play the most significant roles in BTC progression. There is huge potential in miRNA-based biomarkers and therapeutics in BTC, but more studies, research and technological advancements are required before it can be translated into clinical practice for patients.

Redox regulation of microRNAs in endometriosis-associated pain

Endometriosis is a chronic, painful condition with unknown etiology. A differential expression of microRNAs in the endometriotic tissues from women with endometriosis with pain compared to those without suggested a plausible role for miRNA or epigenetic mechanisms in the etiology of endometriotic pain. The peritoneal milieu is involved in maintenance of endometriotic lesion and nociception. We recently showed the mechanistic role for oxidized-lipoproteins (ox-LDLs) present in peritoneal fluid (PF) in endometriosis and pain. We explored the possibility of ox-LDLs modulating the expression of miRNAs in a manner similar to PF from women with endometriosis. Expression levels of miRNAs and their predicted nociceptive and inflammatory targets were determined in PF and ox-LDL treated human endometrial cell-lines. Samples from IRB-approved and consented patients with and without endometriosis or pain were used. These were compared to endometrial cell-lines treated with various forms of oxidized-lipoproteins. RNA (including miRNAs) were isolated from treated endometrial cells and expression levels were determined using commercial miRNome arrays. Cell lysates were used in immunoblotting for inflammatory proteins using a protein array. Twenty miRNAs including isoforms of miR-29, miR-181 and let-7 were mutually differentially expressed in cells treated with PF from endometriosis patients with pain and those treated with ox-LDL components. The ox-LDLs and endo-PF treatment also produced significant overexpression of microRNA predicted target genes nerve growth factor, interleukin-6 and prostaglandin E synthase and overexpression of their downstream protein targets Mip1α and MCP1. This study showed similarities between miRNA regulation in PF from endometriotic women and ox-LDLs present in abundance in the PF of these women. Key miRNAs responsible for targeting nociceptive and inflammatory molecules were downregulated in the presence of ox-LDLs and endo-PF, thus playing a role in the etiology of endometriotic pain. These redox-sensitive miRNAs can be of potential use as targets in the treatment of endometriosis-associated pain.

miR-146a suppresses STAT3/VEGF pathways and reduces apoptosis through IL-6 signaling in primary human retinal microvascular endothelial cells in high glucose conditions

microRNA (miRNA) play critical roles in the pathological processes of diabetic retinopathy, including inflammatory responses, insulin signaling, and angiogenesis. In addition to their regulatory functions on gene expression, miRNA is considered as a potential therapeutic target, as well as a diagnostic marker for many diseases. Our understanding on the pathological mechanisms underlying diabetic retinopathy is still incomplete and additional investigations are required to develop novel therapeutic strategies. The aim of this study was to investigate our hypothesis that miR-146a plays a role in suppressing pro-inflammatory pathways, involving STAT3 and VEGF, through regulating IL-6 signaling to reduce apoptosis of human retinal endothelial cells (REC) in high glucose conditions. Human REC were cultured in normal (5mM) glucose or high glucose medium (25mM) for 3days. We performed transfections on REC with miRNA mimics (hsa-miR-146a-5p). Overexpression of miR-146a reduced IL-6 levels, STAT3 phosphorylation, and VEGF levels in REC cultured in high glucose. Cellular apoptosis was decreased in REC overexpressing miR-146a, as demonstrated by the inhibition of DNA fragmentation. More importantly, we demonstrated that the regulatory role of miR-146a on STAT3/VEGF and apoptosis was mediated by IL-6 receptor signaling in REC. Overall, we report that miR-146a suppressed IL-6 signaling, leading to reduced levels of STAT3 and VEGF in REC in high glucose conditions, leading to decreased apoptosis. The outcome suggests that miR-146a is a potential molecular target for inhibiting inflammation and apoptosis in the diabetic retina through the suppression of the IL-6-mediated STAT3/VEGF pathway.

Serum microRNA profiling in patients with glioblastoma: a survival analysis

Because circulating microRNAs (miRNAs) have drawn a great deal of attention as promising novel cancer diagnostics and prognostic biomarkers, we sought to identify serum miRNAs significantly associated with outcome in glioblastoma patients. To do this, we performed global miRNA profiling in serum samples from 106 primary glioblastoma patients. The study subjects were randomly divided into two sets: set one (n = 40) and set two (n = 66). Using a Cox regression model, 3 serum miRNAs (miR-106a-5p, miR-182, and miR-145-5p) and 5 serum miRNAs (miR-222-3p, miR-182, miR-20a-5p, miR-106a-5p, and miR-145-5p) were identified significantly associated with 2-year patient overall survival and disease-free survival (P < 0.05) in both sets and the combined set. We then created the miRNA risk scores to assess the total impact of the significant serum miRNAs on survival. The high risk scores were associated with poor patient survival (overall survival: HR = 1.92, 95% CI: 1.19, 10.23, and disease-free survival: HR = 2.03, 95%CI: 1.24, 4.28), and were independent of other clinicopathological factors. Our results suggest that serum miRNAs could serve as prognostic predictors of glioblastoma.

The Emerging Role of miRNAs and Their Clinical Implication in Biliary Tract Cancer

Biliary tract cancers are aggressive malignancies that include gallbladder cancer and tumors of intra- and extrahepatic ducts and have a poor prognosis. Surgical resection remains the main curative therapy. Nevertheless, numerous patients experience recurrence even after radical surgery. This scenario drives the research to identify biliary tract cancer biomarkers despite the limited progress that has been made. Recently, a large number of studies have demonstrated that deregulated expression of microRNAs is closely associated with cancer development and progression. In this review, we highlight the role and importance of microRNAs in biliary tract cancers with an emphasis on utilizing circulating microRNAs as potential biomarkers. Additionally, we report several single-nucleotide polymorphisms in microRNA genes that are associated with the susceptibility of biliary tract tumors.

The Potential Use of Salivary miRNAs as Promising Biomarkers for Detection of Cancer: A Meta-Analysis

BACKGROUND

Accumulating evidence has demonstrated that microRNAs (miRNAs) could serve as promising molecular biomarkers for cancer detection. This study aims to systematically assess the diagnostic performance of salivary miRNAs in detection of cancer through a comprehensive meta-analysis.

METHODS

Eligible studies were identified using PubMed and other computerized databases up to October 31, 2015, supplemented by a manual search of references from retrieved articles. The pooled sensitivity, specificity, and other measurements of accuracy of salivary miRNAs in the diagnosis of cancer were analyzed using the bivariate binomial mixed model.

RESULTS

Seventeen studies from 8 articles with 694 subjects were included in this meta-analysis. All studies have a relatively high score of quality assessment. The overall sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) of salivary miRNAs in detection of cancer were 0.77 (95% confidence intervals [CI]: 0.69-0.84), 0.77 (95%CI: 0.65-0.88), 3.37 (95%CI: 2.26-5.02), 0.29 (95%CI: 0.23-0.38), and 11.41 (95%CI: 7.35-17.73), respectively. The AUC was 0.84 (95%CI: 0.80-0.87). Moreover, both whole saliva and saliva supernatant could be used as sources of clinical specimens for miRNAs detection.

CONCLUSIONS

Our meta-analysis demonstrated that salivary miRNAs may serve as potential noninvasive biomarkers for cancer detection. The findings need to be confirmed with further research before it can be applied in the clinic.

Are circulating microRNAs peripheral biomarkers for Alzheimer's disease?

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by memory loss, multiple cognitive abnormalities and intellectual impairments. Currently, there are no drugs or agents that can delay and/or prevent the progression of disease in elderly individuals, and there are no peripheral biomarkers that can detect AD early in its pathogenesis. Research has focused on identifying biomarkers for AD so that treatment can be begun as soon as possible in order to restrict or prevent intellectual impairments, memory loss, and other cognitive abnormalities that are associated with the disease. One such potential biomarker is microRNAs that are found in circulatory biofluids, such as blood and blood components, serum and plasma. Blood and blood components are primary sources where miRNAs are released in either cell-free form and then bind to protein components, or are in an encapsulated form with microvesicle particles. Exosomal miRNAs are known to be stable in biofluids and can be detected by high throughput techniques, like microarray and RNA sequencing. In AD brain, enriched miRNAs encapsulated with exosomes crosses the blood brain barrier and secreted in the CSF and blood circulations. This review summarizes recent studies that have identified miRNAs in the blood, serum, plasma, exosomes, cerebral spinal fluids, and extracellular fluids as potential biomarkers of AD. Recent research has revealed only six miRNAs - miR-9, miR-125b, miR-146a, miR-181c, let-7g-5p, and miR-191-5p - that were reported by multiple investigators. Some studies analyzed the diagnostic potential of these six miRNAs through receiver operating curve analysis which indicates the significant area-under-curve values in different biofluid samples. miR-191-5p was found to have the maximum area-under-curve value (0.95) only in plasma and serum samples while smaller area-under-curve values were found for miR-125, miR-181c, miR-191-5p, miR-146a, and miR-9. This article shortlisted the promising miRNA candidates and discussed their diagnostic properties and cellular functions in order to search for potential biomarker for AD.