Self-assembling protein platform for direct quantification of circulating microRNAs in serum with total internal reflection fluorescence microscopy

Circulating microRNAs in cancer: Hope or hype?

Circulating miRNAs are a novel class of stable, minimally invasive disease biomarkers that are considered to be valuable in diagnosis, prognosis and treatment response monitoring. Unlike intracellular miRNAs, circulating miRNAs are released from their producer cells and, based on their targeted functions, they may shuttle in and out of circulation. Their discovery has opened up new avenues for clinical realms and led to a quest for targeted biomarkers. Subsequently, as more cell-free miRNAs are being discovered, their expression is expected to provide precise information regarding disease progression and treatment outcomes, thereby fostering personalized therapeutic strategies. The significance of circulating miRNAs capitalizes on the fact that they are highly stable in body fluids and their expression levels can be detected by common techniques such as qPCR and microarray. However, discrepancies have started to emerge in terms of their reliability and their response under physiological and pathological conditions. Functional studies are still pending, which may determine whether circulating miRNAs play a role as a central component or just as an auxiliary tuner. Also, the distinct clinical signatures that they display have never been subjected to an extensive critical review and experimental validation. As a consequence, the applicability of circulating miRNAs remains a matter of deliberation, despite many intriguing perspectives about their competency. In this review, we highlight some ambiguous issues with the application of circulating miRNAs, which may warrant an immediate consideration. We propose that the circulating miRNA domain needs to be reevaluated to authenticate their specific role and to probe whether they actually carry any clinical weightage.

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 miRNAs: roles in cancer diagnosis, prognosis and therapy

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

Circulating miRNAs in cancer: from detection to therapy

Since the discovery of circulating microRNAs (miRNAs) in body fluids, an increasing number of studies have focused on their potential as non-invasive biomarkers and as therapeutic targets or tools for many diseases, particularly for cancers. Because of their stability, miRNAs are easily detectable in body fluids. Extracellular miRNAs have potential as biomarkers for the prediction and prognosis of cancer. Moreover, they also enable communication between cells within the tumor microenvironment, thereby influencing tumorigenesis. In this review, we summarize the progresses made over the past decade regarding circulating miRNAs, from the development of detection methods to their clinical application as biomarkers and therapeutic tools for cancer. We also discuss the advantages and limitations of different detection methods and the pathways of circulating miRNAs in cell-cell communication, in addition to their clinical pharmacokinetics and toxicity in human organs. Finally, we highlight the potential of circulating miRNAs in clinical applications for cancer.

Role of microRNAs in schistosomes and schistosomiasis

Schistosomes, a class of parasitic trematode worms, cause schistosomiasis. Accumulating evidence suggests that microRNAs (miRNAs)-small, non-coding RNAs that are known to play critical regulatory roles in many organisms-may be involved in schistosome development and sexual maturation, as well as the pathogenesis of schistosomiasis. Schistosoma miRNAs, such as Bantam and miR-10, may be involved in the pathological processes of schistosomiasis, and recent studies suggest that schistosome-specific miRNAs (e.g., Bantam, miR-3479-3p) in the bloodstream of a final host could be used as biomarkers for schistosomiasis diagnosis. Furthermore, aberrant miRNAs, such as miR-223 and miR-454, can be produced by a host in response to schistosome infection, and these miRNAs may contribute to the pathogenesis of schistosomiasis-associated liver injury. Here, we summarize recent progress evaluating the relationship between schistosome miRNAs and schistosomiasis and discuss how these miRNAs can mediate the pathogenesis of schistosomiasis and be used as biomarkers for schistosomiasis diagnosis.

Direct quantification of circulating miRNAs in different stages of nasopharyngeal cancerous serum samples in single molecule level with total internal reflection fluorescence microscopy

MicroRNAs (miRNAs) are small noncoding RNAs that regulate human gene expression at the post-transcriptional level. Growing evidence indicates that the expression profile of miRNAs is highly correlated with the occurrence of human diseases including cancers. Playing important roles in complex gene regulation processes, the aberrant expression pattern of various miRNAs is implicated in different types and even stages of cancer. Besides localizing in cells, many of these miRNAs are found circulating around the body in a wide variety of fluids such as urine, serum and saliva. Surprisingly, these extracellular circulating miRNAs are highly stable and resistant to degradation, and therefore, are considered as promising biomarkers for early cancer diagnostic via noninvasive extraction from body fluids. Unfortunately, the abundance of these small RNAs is ultralow in the body fluids, making it challenging to quantify them in complex sample matrixes. Establishing a sensitive, specific yet simple assay for an accurate quantification of circulating miRNAs is therefore desirable. Our group previously reported a sensitive and specific detection assay of miRNAs in single molecule level with the aid of total internal reflection fluorescence microscopy. In this work, we advanced the assay to differentiate the expression of a nasopharyngeal carcinoma (NPC) up-regulator hsa-mir-205 (mir-205) in serum collected from patients of different stages of NPC. To overcome the background matrix interference in serum, a locked nucleic acid-modified molecular beacon (LNA/MB) was applied as the detection probe to hybridize, capture and detect target mir-205 in serum matrix with enhanced sensitivity and specificity. A detection limit of 500 fM was achieved. The as-developed method was capable of differentiating NPC stages by the level of mir-205 quantified in serum with only 10 μL of serum and the whole assay can be completed in 1 h. The experimental results agreed well with those previously reported whereas the quantity of miR-205 determined by our assay was found comparable to that of quantitative reverse transcription polymerase chain reaction (qRT-PCR), supporting that this assay can be served as a promising noninvasive detection tool for early NPC diagnosis, monitoring and staging.