Validation of circulating miRNA biomarkers for predicting lymph node metastasis in gastric cancer

Circulating Exosomal MicroRNA Signature Predicts Peritoneal Metastasis in Patients with Advanced Gastric Cancer

BACKGROUND

Despite a radical operation, about half of gastric cancer (GC) patients with advanced GC experience peritoneal metastasis (PM), and the patients with PM have a poor prognosis. However, because staging laparoscopy was a highly invasive procedure for patients, identification of PM using a liquid biopsy can be useful for patients with GC.

METHODS

This study analyzed two genome-wide miRNA expression profiling datasets (GSE164174 and TCGA). The study prioritized biomarkers in pretreatment plasma specimens from clinical training and validation cohorts of patients with GC. The authors developed an integrated exosomal miRNA panel and established a risk-stratification model, which was combined with the miRNA panel and currently used tumor markers (CEA, CA19-9, CA125, and CA72-4 levels).

RESULTS

The comprehensive discovery effort identified a four-miRNA panel that robustly predicted the metastasis with excellent accuracy in the TCGA dataset (area under the curve [AUC] 0.86). A circulating exosomal miRNA panel was established successfully with remarkable diagnostic accuracy in the clinical training (AUC 0.85) and validation (AUC 0.86) cohorts. Moreover, the predictive accuracy of the panel was significantly superior to that of conventional clinical factors (P < 0.01), and the risk-stratification model was dramatically superior to the panel and currently used clinical factors for predicting PM (AUC 0.94; univariate: odds ratio [OR] 77.00 [P < 0.01]; multivariate OR 57.71 [P = 0.01]).

CONCLUSIONS

The novel risk-stratification model for predicting PM has potential for clinical translation as a liquid biopsy assay for patients with GC. The study findings highlight the potential clinical impact of the model for improved selection and management of patients with GC.

Association of serum and fecal microRNA profiles in cats with gastrointestinal cancer and chronic inflammatory enteropathy

BACKGROUND

Differentiation of gastrointestinal cancer (GIC) from chronic inflammatory enteropathies (CIE) in cats can be challenging and often requires extensive diagnostic testing. MicroRNAs (miRNAs) have promise as non-invasive biomarkers in serum and feces for diagnosis of GIC.

HYPOTHESIS/OBJECTIVES

Cats with GIC will have serum and fecal miRNA profiles that differ significantly from healthy cats and cats with CIE. Identify serum and fecal miRNAs with diagnostic potential for differentiation between cats with GIC and CIE as compared to healthy cats.

ANIMALS

Ten healthy cats, 9 cats with CIE, and 10 cats with GIC; all client-owned.

METHODS

Cats were recruited for an international multicenter observational prospective case-control study. Serum and feces were screened using small RNA sequencing for miRNAs that differed in abundance between cats with GIC and CIE, and healthy cats. Diagnostic biomarker potential of relevant miRNAs from small RNA sequencing and the literature was confirmed using reverse transcription quantitative real-time PCR (RT-qPCR).

RESULTS

Serum miR-223-3p was found to distinguish between cats with GIC and CIE with an area under the curve (AUC) of 0.9 (95% confidence interval [CI], 0.760-1.0), sensitivity of 90% (95% CI, 59.6-99.5%), and specificity of 77.8% (95% CI, 45.3-96.1%). Serum miR-223-3p likewise showed promise in differentiating a subgroup of cats with small cell lymphoma (SCL) from those with CIE. No fecal miRNAs could distinguish between cats with GIC and CIE.

CONCLUSION AND CLINICAL IMPORTANCE

Serum miR-223-3p potentially may serve as a noninvasive diagnostic biomarker of GIC in cats, in addition to providing a much needed tool for the differentiation of CIE and SCL.

Association of fecal and serum microRNA profiles with gastrointestinal cancer and chronic inflammatory enteropathy in dogs

BACKGROUND

Reliable biomarkers to differentiate gastrointestinal cancer (GIC) from chronic inflammatory enteropathy (CIE) in dogs are needed. Fecal and serum microRNAs (miRNAs) have been proposed as diagnostic and prognostic markers of GI disease in humans and dogs.

HYPOTHESIS/OBJECTIVES

Dogs with GIC have fecal and serum miRNA profiles that differ from those of dogs with CIE.

AIMS

(a) identify miRNAs that differentiate GIC from CIE, (b) use high-throughput reverse transcription quantitative real-time PCR (RT-qPCR) to establish fecal and serum miRNA panels to distinguish GIC from CIE in dogs.

ANIMALS

Twenty-four dogs with GIC, 10 dogs with CIE, and 10 healthy dogs, all client-owned.

METHODS

An international multicenter observational prospective case-control study. Small RNA sequencing was used to identify fecal and serum miRNAs, and RT-qPCR was used to establish fecal and serum miRNA panels with the potential to distinguish GIC from CIE.

RESULTS

The best diagnostic performance for distinguishing GIC from CIE was fecal miR-451 (AUC: 0.955, sensitivity: 86.4%, specificity: 100%), miR-223 (AUC: 0.918, sensitivity: 90.9%, specificity: 80%), and miR-27a (AUC: 0.868, sensitivity: 81.8%, specificity: 90%) and serum miR-20b (AUC: 0.905, sensitivity: 90.5%, specificity: 90%), miR-148a-3p (AUC: 0.924, sensitivity: 85.7%, specificity: 90%), and miR-652 (AUC: 0.943, sensitivity: 90.5%, specificity: 90%). Slightly improved diagnostic performance was achieved when combining fecal miR-451 and miR-223 (AUC: 0.973, sensitivity: 95.5%, specificity: 90%).

CONCLUSIONS AND CLINICAL IMPORTANCE

When used as part of a diagnostic RT-qPCR panel, the abovementioned miRNAs have the potential to function as noninvasive biomarkers for the differentiation of GIC and CIE in dogs.

Low Expression of miR-491-3p Is Correlated with Lymph Node Metastasis in Gastric Cancer

Objective

MiR-491-3p, as a tumor suppressor miRNA, was found decreased in many solid tissues. In this study, we aim to investigate miR-491-3p expression in gastric cancer with or without lymph node metastasis (LNM).

Methods

GSE173215 dataset from Gene Expression Omnibus (GEO) was used to measure miRNA expression from tissue samples of gastric cancer patients. Moreover, gastric tumor tissues (non-LNM: n = 78; LNM: n = 68) were obtained to detect the miR-491-3p expression. Receiver operating characteristic (ROC) curve and Kaplan–Meier (KM) survival analysis, as well as Cox regression analysis, were performed to reveal the role of miR-491-3p in diagnosis and prognosis of gastric cancer.

Results

According to GSE173215 datasets (t = −11.25, adjust P value = 1.30E-06) and our clinical results (0.390 ± 0.193 vs. 0.562 ± 0.166, P < 0.005), the gastric cancer patients with LNM showed lower miR-491-3p expression than those without LNM, demonstrating a high diagnostic efficiency (sensitivity: 74.36%; specificity: 69.12%). In addition, both LNM and low miR-491-3p expression were correlated with the poor prognosis of gastric cancer. Furthermore, the LNM patient with low expression of miR-491-3p had the worse prognosis, but the non-LNM patient with high expression of miR-491-3p had the best prognosis. MiR-491-3p expression (HR = 0.003, 95%CI: 3.35E-04∼0.028) and LNM (HR = 2.326, 95%CI: 1.046∼5.173) were independent risk factors for gastric cancer.

Conclusion

Downregulated miR-491-3p expression was found in gastric cancer, being a high diagnostic efficiency and an independent risk factor for gastric cancer, especially in those having LNM.

The seen and the unseen: Molecular classification and image based-analysis of gastrointestinal cancers

Gastrointestinal cancers account for 22.5% of cancer related deaths worldwide and represent circa 20% of all cancers. In the last decades, we have witnessed a shift from histology-based to molecular-based classifications using genomic, epigenomic, and transcriptomic data. The molecular based classification revealed new prognostic markers and may aid the therapy selection. Because of the high-costs to perform a molecular classification, in recent years immunohistochemistry-based surrogate classification were developed which permit the stratification of patients, and in parallel multiple groups developed hematoxylin and eosin whole slide image analysis for sub-classifying these entities. Hence, we are witnessing a return to an image-based classification with the purpose to infer hidden information from routine histology images that would permit to detect the patients that respond to specific therapies and would be able to predict their outcome. In this review paper, we will discuss the current histological, molecular, and immunohistochemical classifications of the most common gastrointestinal cancers, gastric adenocarcinoma, and colorectal adenocarcinoma, and will present key aspects for developing a new artificial intelligence aided image-based classification of these malignancies.

Assessment of the Diagnostic Efficiency of a Liquid Biopsy Assay for Early Detection of Gastric Cancer

IMPORTANCE

Noninvasive detection of early-stage disease is a key strategy for reducing gastric cancer (GC)-associated patient mortality.

OBJECTIVE

To establish a novel, noninvasive, microRNA (miRNA)-based signature for the early detection of GC using a comprehensive biomarker discovery approach with retrospective and prospective validation.

DESIGN, SETTING, AND PARTICIPANTS

This diagnostic study was conducted in 4 phases using publicly available genome sequences and tissue samples from patients at an academic medical center in Japan, and validated with retrospective multicenter cohorts of patients with GC. Three tissue miRNA data sets were used to identify a miRNA signature that discriminated GC vs normal tissues. The robustness of this signature was assessed in serum from 2 retrospective cohorts of patients with GC. A risk-scoring model was derived, then the performance of the miRNA signature was evaluated in a prospective cohort of patients with GC. The robustness of the miRNA signature was compared with current blood-based markers, and a cost-effectiveness analysis of the miRNA signature against the current practice of endoscopy was performed. All clinical samples used for this study were collected and data analyzed between April 1997 and March 2018.

MAIN OUTCOMES AND MEASURES

Assessment of diagnostic efficiency on the basis of area under the curve (AUC), specificity, and sensitivity.

RESULTS

The data sets for the genome-wide expression profiling analysis stage included 598 total patient samples (284 [55.4%] from men; mean [SE] patient age, 65.7 [0.5] years). The resulting 10-miRNA signature was validated in 2 retrospective GC serum cohorts (586 patients; 348 [59.4%] men, mean [SE] age, 66.0 [0.7] years), which led to the establishment of a 5-miRNA signature (AUC, 0.90; 95% CI, 0.85-0.94) that also exhibited high levels of diagnostic performance in patients with stage I disease (AUC, 0.89; 95% CI, 0.83-0.94). A risk-scoring model was derived and the assay was optimized to a minimal number of miRNAs. The performance of the resulting 3-miRNA signature was then validated in a prospective cohort of patients with GC (349 patients; 124 [70.5%] men, median [range] age, 66.0 [0.66] years). The final 3-miRNA signature (miR-18a, miR-181b, and miR-335) exhibited high diagnostic accuracy in all stages of patients (AUC, 0.86; 95% CI 0.83-0.90), including in patients with stage I disease (AUC, 0.85; 95% CI, 0.79-0.91). Furthermore, this miRNA signature was superior to currently used blood markers and outperformed the endoscopic screening in a cost-effectiveness analysis (incremental cost-effectiveness ratio, CNY ¥16162.5 per quality-adjusted life-year [USD $2304.80 per quality-adjusted life-year]).

CONCLUSIONS AND RELEVANCE

These results suggest the potential clinical significance of the 3-miRNA signature as a noninvasive, cost-effective, and facile assay for the early detection of GC.

MiR-21 in the Cancers of the Digestive System and Its Potential Role as a Diagnostic, Predictive, and Therapeutic Biomarker

MicroRNAs (miRNAs) are small non-coding RNAs. They can regulate the expression of their target genes, and thus, their dysregulation significantly contributes to the development of cancer. Growing evidence suggests that miRNAs could be used as cancer biomarkers. As an oncogenic miRNA, the roles of miR-21 as a diagnostic and prognostic biomarker, and its therapeutic applications have been extensively studied. In this review, the roles of miR-21 are first demonstrated via its different molecular networks. Then, a comprehensive review on the potential targets and the current applications as a diagnostic and prognostic cancer biomarker and the therapeutic roles of miR-21 in six different cancers in the digestive system is provided. Lastly, a brief discussion on the challenges for the use of miR-21 as a therapeutic tool for these cancers is added.

miR-30b-5p up-regulation related to the dismal prognosis for patients with renal cell cancer

The diagnosis of renal cell carcinoma (RCC) is often made late since there is no early symptom, which thus results in dismal patient prognosis. As a result, new biomarkers are urgently needed and efforts should be made to identify their functions in predicting RCC prognosis. microRNAs (miRNAs) are a class of small noncoding RNAs that are about 20-22 nucleotides in length, and they have been demonstrated to function as prognostic markers in numerous tumors. This study aimed to assess the role of miR-30b-5p in predicting the prognosis of RCC postoperatively. In this study, RNA was extracted from 284 formalin-fixed and paraffin-embedded kidney cancer tissue samples. After cDNA synthesis, real-time quantitative PCR (RT-qPCR) was adopted for detecting the relative miR-30b-5p level. Then, the Kaplan-Meier method, Cox regression analysis, and the receiver operating characteristic curve analysis were applied in analyzing the miR-30b-5p effect on the prognosis for patients. Our findings indicated that, following adjustment for age, gender, tumor stage, and tumor size, patients with low miR-30b-5p expression had remarkably longer overall survival. Thus, the miR-30b-5p level might be related to RCC prognosis.

Rola miRNA w rozwoju wybranych nowotworów – potencjalne zastosowanie w diagnostyce*

MikroRNA (miRNA) są małymi cząsteczkami kwasu rybonukleinowego, które mimo że nie podlegają procesowi translacji, pełnią ważną funkcję regulacyjną w komórkach eukariotycznych. Ich fizjologiczną funkcją jest utrzymywanie homeostazy komórek. Zaburzona ekspresja miRNA może spowodować rozwój wielu chorób, w tym chorób nowotworowych. Działanie miRNA polega na hamowaniu tworzenia się białek, w tym białek o właściwościach onkogennych i antyonkogennych. Mutacje w miejscach kodowania miRNA mogą prowadzić do nadmiernego lub zmniejszonego wytwarzania wspomnianych białek. Odkrycie miRNA i poznanie ich roli w komórce otworzyło nowe możliwości dla diagnostyki chorób nowotworowych. Zmiany poziomu odpowiednich miRNA, w krwiobiegu lub innych płynach ustrojowych, mogą być markerem diagnostycznym chorób. Diagnostyka onkologiczna mogłaby przebiegać na podstawie badań profilu miRNA pacjenta i porównania go z opracowanymi wcześniej profilami zmian miRNA powiązanymi z występowaniem danego rodzaju choroby nowotworowej. Informacja o zmianach profilu miRNA podstawowych w regulacji ekspresji genów związanych z procesami nowotworzenia, mogłaby się przyczynić do opracowania terapii eksperymentalnych opartych na przywróceniu pierwotnego poziomu miRNA w komórkach, a tym samym, na przywróceniu prawidłowej regulacji ekspresji genów. Coraz nowsze metody wyciszania i włączania ekspresji miRNA mogą w przyszłości zaowocować skutecznymi rozwiązaniami terapeutycznymi.

MicroRNAs: potential biomarkers for diagnosis and prognosis of different cancers

A thorough understanding of the tumor environment and underlying genetic factors helps in the better formulation of cancer management strategies. Availability of efficient diagnostic and prognostic biomarkers facilitates early detection and progression of the disease. MicroRNAs affect different biological processes participating in tumorigenesis through regulation of their target genes. An expanding list of unique RNAs and understanding of their regulatory role has opened up a new field in cancer research. Based on a comprehensive literature search, we identified 728 miRNAs dysregulated in sixteen cancer types namely bladder cancer (BC), breast cancer (BrC), cervical cancer (CC), colorectal cancer (CRC), esophageal cancer (EC), endometrial cancer (EnC), gastric cancer (GC), hepatocellular cancer (HCC), head and neck squamous cell cancer (HNSCC), lung cancer (LC), ovarian cancer (OC), pancreatic cancer (PC), prostate cancer (PrC), renal cell cancer (RCC), skin cancer (SC), and thyroid cancer (TC). Expression of 43 miRNAs was either upregulated or downregulated in six or more of these cancers. Finally, seven miRNAs namely mir-18a, mir-21, mir-143/145, mir-210, mir-218, mir-221, showing maximum dysregulation, either up- or down-regulation in the majority of cancers, were selected for a detailed presentation of their expression and evaluation of their potential as biomarkers in the diagnosis and prognosis of different cancers.

Identifying Small Molecule-miRNA Associations Based on Credible Negative Sample Selection and Random Walk

Recently, many studies have demonstrated that microRNAs (miRNAs) are new small molecule drug targets. Identifying small molecule-miRNA associations (SMiRs) plays an important role in finding new clues for various human disease therapy. Wet experiments can discover credible SMiR associations; however, this is a costly and time-consuming process. Computational models have therefore been developed to uncover possible SMiR associations. In this study, we designed a new SMiR association prediction model, RWNS. RWNS integrates various biological information, credible negative sample selections, and random walk on a triple-layer heterogeneous network into a unified framework. It includes three procedures: similarity computation, negative sample selection, and SMiR association prediction based on random walk on the constructed small molecule-disease-miRNA association network. To evaluate the performance of RWNS, we used leave-one-out cross-validation (LOOCV) and 5-fold cross validation to compare RWNS with two state-of-the-art SMiR association methods, namely, TLHNSMMA and SMiR-NBI. Experimental results showed that RWNS obtained an AUC value of 0.9829 under LOOCV and 0.9916 under 5-fold cross validation on the SM2miR1 dataset, and it obtained an AUC value of 0.8938 under LOOCV and 0.9899 under 5-fold cross validation on the SM2miR2 dataset. More importantly, RWNS successfully captured 9, 17, and 37 SMiR associations validated by experiments among the predicted top 10, 20, and 50 SMiR candidates with the highest scores, respectively. We inferred that enoxacin and decitabine are associated with mir-21 and mir-155, respectively. Therefore, RWNS can be a powerful tool for SMiR association prediction.

MiR-21 Promotes the Invasion and Metastasis of Gastric Cancer Cells by Activating Epithelial-Mesenchymal Transition

BACKGROUND

Gastric cancer (GC) is one of the most common malignant tumors. It is likely to occur in lymph nodes and is prone to distant metastasis in its early stages, which portends a poor prognosis. Previous studies have shown that miRNA-21 was abnormally highly expressed and associated with early metastasis in GC, but the mechanism by which it regulates the invasion and metastasis of GC has not been elucidated.

METHODS

Epithelial-mesenchymal transition (EMT) is an important pathologic basis of tumor invasion and metastasis, and in this study, the relationship between miRNA-21 and EMT in GC invasion and metastasis was investigated using RT-qPCR, Western blot, and wound scratch and transwell assays.

RESULTS

We found that miRNA-21 expression in GC cell lines was higher than in a gastric mucosal epithelial cell line. After transfection with an miRNA-21 mimic, the upregulation of EMT was found to promote migration and invasion of MGC-803 cells. However, the downregulation of EMT was found to accompany the inhibition of invasion and migration of GC cells after downregulation of miRNA-21 expression due to the transfection of an miRNA-21 inhibitor.

CONCLUSIONS

These findings suggest that miRNA-21 might promote the invasion and metastasis of GC by upregulating EMT.

MicroRNA-27a (miR-27a) in Solid Tumors: A Review Based on Mechanisms and Clinical Observations

MicroRNAs (miRNAs) are a family of highly conserved, non-coding single-stranded RNAs transcribed as ~70 nucleotide precursors to an 18–22 nucleotide product (1). miRNAs can silence their homologous target genes at the post-transcriptional level, and these genes have been revealed to play an important role in tumorigenesis, invasion and metastasis (2). MicroRNA-27a (miR-27a), transcripted by miR-27a gene, has proved to implicate with many kinds of solid tumors, showing potential as a useful biomarker or drug target for clinical application. However, even though miR-27a has been reported in many cancers, the mechanism and signal pathways of miR-27 in oncogenesis, invasion, and metastasis are still obscure. Moreover, recent studies show that miR-27a pays an important role in epithelial-mesenchymal-transition, regulating tumor immune response, and chemoresistance. In this review, we summarize the current literature, demonstrate the established link between miR-27a and tumorigenesis, and focus on recently identified mechanisms. The review also aims to demonstrate the potential of miR-27a as a diagnostic and/or prognostic biomarker in solid tumors and to discuss the possibilities of targeted therapy and drug design.

Scenario and future prospects of microRNAs in gastric cancer: A review

Carcinoma of the stomach is one of the major prevalent and principal causes of cancer-related deaths worldwide. Current advancement in technology has improved the understanding of the pathogenesis and pathology of gastric cancers (GC). But, high mortality rates, unfavorable prognosis and lack of clinical predictive biomarkers provide an impetus to investigate novel early diagnostic/prognostic markers and therapeutic targets for GC, which are sufficiently sensitive to GC. Current biomedical investigations have explored several budding GC biomarker by utilizing serum proteins, natural oncogenic genes during improvement in molecular technologies as microarray, and RNA/DNA-Seq. Recently, small non-coding microRNAs (miRNAs) are becoming vital regulators in oncogenesis pathways and can act as handy clinical biomarkers. The newly introduced class of biomarkers is rising as new molecules for cancer diagnosis and prognosis. For better understanding of the gastric carcinogenesis, miRNAs may help to elucidate the mechanisms of tumor growth and can help to discover novel untimely potent markers for early detection of GC. Here in this review, we summarize the recent research studies supporting the utility of miRNAs as novel early diagnostic/prognostic tools and therapeutic targets. Thus, here we introduce potential future treatment strategies for gastrointestinal (GI) cancers, which indicate the practicality and clinical applications of miRNAs in GC.

miR-146a-5p: Expression, regulation, and functions in cancer

Cancer as we know it is actually an umbrella term for over 100 very unique malignancies in various tissues throughout the human body. Each type, and even subtype of cancer, has different genetic, epigenetic, and other cellular events responsible for malignant development and metastasis. Recent work has indicated that microRNAs (miRNAs) play a major role in these processes, sometimes by promoting cancer growth and other times by suppressing tumorigenesis. miRNAs are small, noncoding RNAs that negatively regulate expression of specific target genes. This review goes into an in-depth look at the most recent finding regarding the significance of one particular miRNA, miR-146a-5p, and its involvement in cancer. Target gene validation and pathway analysis have provided mechanistic insight into this miRNA's purpose in assorted tissues. Additionally, this review outlines novel findings that suggest miR-146a-5p may be useful as a noninvasive biomarker and as a targeted therapeutic in several cancers. This article is categorized under: RNA in Disease and Development > RNA in Disease Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs.

Diagnostic utility of epigenetics in breast cancer - A review

Epigenetic alterations are clearly involved in cancer initiation and progression as recent epigenetic studies of genomic DNA, histone modifications and micro-RNA alterations suggest that these are playing an important role in the incidence of breast cancer. Epigenetic information has recently gained the attention of researchers because epigenetic modification of the genome in breast cancer is still an evolving area for researchers. Several active compounds present in foods, poisons, drugs, and industrial chemicals may as a result of epigenetic mechanisms increase or decrease the risk of breast cancer. Epigenetic regulation is critical in normal growth and development and closely conditions the transcriptional potential of genes. Epigenetic mechanisms convey genomic adaption to an environment thereby ultimately contributing towards given phenotype. In addition to the use of epigenetic alterations as a means of screening, epigenetic alterations in a tumor or adjacent tissues or peripheral blood may also help clinicians in determining prognosis and treatment of breast cancer. As we understand specific epigenetic alterations contributing to breast tumorigenesis and prognosis, these discoveries will lead to significant advances for breast cancer treatment, like in therapeutics that target methylation and histone modifications in breast cancer and the newer versions of the drugs are likely to play an important role in future clinical treatment.

microRNA diagnostic panel for Alzheimer's disease and epigenetic trade-off between neurodegeneration and cancer

microRNAs (miRNAs) have been extensively studied as potential biomarkers for Alzheimer's disease (AD). Their profiles have been analyzed in blood, cerebrospinal fluid (CSF) and brain tissue. However, due to the high variability between the reported data, stemming from the lack of methodological standardization and the heterogeneity of AD, the most promising miRNA biomarker candidates have not been selected. Our literature review shows that out of 137 miRNAs found to be altered in AD blood, 36 have been replicated in at least one independent study, and out of 166 miRNAs reported as differential in AD CSF, 13 have been repeatedly found. Only 3 miRNAs have been consistently reported as altered in three analyzed specimens: blood, CSF and the brain (hsa-miR-146a, hsa-miR-125b, hsa-miR-135a). Nonetheless, all 36 repeatedly differential miRNAs in AD blood are promising as components of the diagnostic panel. Given their predicted functions, such miRNA panel may report multiple pathways contributing to AD pathology, enabling the design of personalized therapies. In addition, the analysis revealed that the miRNAs dysregulated in AD overlap highly with miRNAs implicated in cancer. However, the directions of the miRNA changes are usually opposite in cancer and AD, indicative of an epigenetic trade-off between the two diseases.

miR-3607-3p suppresses non-small cell lung cancer (NSCLC) by targeting TGFBR1 and CCNE2

Accumulating evidence indicates that miRNAs can be promising diagnostic and/or prognostic markers for various cancers. In this study, we identified a novel miRNA, miR-3607-3p, and its targets in non-small cell lung cancer (NSCLC). The expression of miR-3607-3p was measured and its correlation with patient prognosis was determined. Ectopic expression in NSCLC cells, xenografts, and metastasis models was used to evaluate the effects of miR-3607-3p on proliferation and migration of NSCLC. Luciferase assay and western blotting were performed to validate the potential targets of miR-3607-3p after preliminary screening by microarray analysis and computer-aided algorithms. We demonstrated that miR-3607-3p was downregulated in NSCLC tissues and that miR-3607-3p might act as an independent predictor for overall survival in NSCLC. Moreover, serum miR-3607-3p may be a novel and stable marker for NSCLC. We found that overexpression of miR-3607-3p inhibited cell proliferation, colony formation, migration and invasion, and hampered the cell cycle of NSCLC cell lines in vitro. Our results suggested that miR-3607-3p directly targets TGFBR1 and CCNE2. In accordance with in vitro studies, we confirmed that miR-3607-3p functions as a potent suppressor miRNA of NSCLC. We showed that miR-3607-3p agomir could reduce tumor growth and inhibit TGFBR1 and CCNE2 protein expression. Taken together, our findings indicate that miR-3607-3p can inhibit NSCLC cell growth and metastasis by targeting TGFBR1 and CCNE2 protein expression, and provide new evidence of miR-3607-3p as a potential non-invasive biomarker and therapeutic target for NSCLC.

MicroRNAs as non-invasive diagnostic biomarkers for gastric cancer: Current insights and future perspectives

Non-invasive diagnostic biomarkers may contribute to an early identification of gastric cancer (GC) and improve the clinical management. Unfortunately, no sensitive and specific screening biomarkers are available yet and the currently available approaches are limited by the nature of the disease. GC is a heterogenic disease with various distinct genetic and epigenetic events that occur during the multifactorial cascade of carcinogenesis. MicroRNAs (miRNAs) are commonly deregulated in gastric mucosa during the Helicobacter pylori infection and in stepwise manner from chronic gastritis, through preneoplastic conditions such as atrophic gastritis and intestinal metaplasia, to early dysplasia and invasive cancer. Identification of miRNAs in blood in 2008 led to a great interest on miRNA-based diagnostic, prognostic biomarkers in GC. In this review, we provide the most recent systematic review on the existing studies related to miRNAs as diagnostic biomarkers for GC. Here, we systematically evaluate 75 studies related to differential expression of circulating miRNAs in GC patients and provide novel view on various heterogenic aspects of the existing data and summarize the methodological differences. Finally, we highlight several important aspects crucial to improve the future translational and clinical research in the field.

Liquid biopsy provides new insights into gastric cancer

Liquid biopsies have great promise for precision medicine as they provide information about primary and metastatic tumors via a minimally invasive method. In gastric cancer patients, a large number of blood-based biomarkers have been reported for their potential role in clinical practice for screening, early diagnosis, prognostic evaluation, recurrence monitoring and therapeutic efficiency follow-up. This current review focuses on blood liquid biopsies' role and their clinical implications in gastric cancer patients, with an emphasis on circulating tumor cells (CTCs), circulating tumor DNA (ctDNA) and circulating non-coding RNAs (ncRNAs). We also provide a brief discussion of the potential and limitations of liquid biopsies use and their future use in the routine clinical care of gastric cancer.

Effects of Yangzheng Sanjie Decoction-containing serum mediated by microRNA-7 on cell proliferation and apoptosis in gastric cancer

Gastric cancer (GC) is one of the most common types of cancer and a leading cause of cancer-associated mortality. MicroRNAs (miRNAs/miRs) are demonstrated to function as oncomiRs or tumor-suppressor-miRs in GC. miR-7 has been identified to be a tumor suppressor of GC by targeting epidermal growth factor receptor (EGFR). In our previous study, Yangzheng Sanjie Decoction (YZSJD), a traditional Chinese formula, was identified to be effective in alleviating the symptoms and even postponing turnover of precancerous lesions. To elucidate the mechanism of YZSJD, the present study evaluated the effects of YZSJD of the GC MKN-45 cell line and investigated the underlying molecular mechanisms using YZSJD-containing serum (YCS). The expression of miR-7 in GC, normal and adjacent tissue samples was examined. The results demonstrated that YCS inhibited proliferation by inducing cell cycle arrest at the S phase, and significantly induced apoptosis compared with the control group. miR-7 was significantly downregulated in GC tissues compared with the matched ones. Using reverse transcription-quantitative polymerase chain reaction and western blot analysis, the expression of miR-7 was inversely associated with EGFR. This indicates that YCS inhibits proliferation and induces apoptosis of GC cells mediated by miR-7 targeting EGFR, which may be one of the mechanisms whereby YZSJD exerts its effects on GC.

Soft-shelled turtle peptide modulates microRNA profile in human gastric cancer AGS cells

Cancer prevention using natural micronutrition on epigenetic mechanisms primarily revolves around plant extracts. However, the role of macronutrition, including animal peptides, on epigenetic modification in cancer has been elusive. In traditional Chinese medicine, the soft-shelled turtle has a long-history of being a functional food that strengthens immunity through unknown mechanisms. The present study aimed to investigate the impact of soft-shelled turtle peptide on microRNA (miRNA) expression in gastric cancer (GC) cells and to analyze the potential anticancer mechanisms for GC. Affymetrix GeneChip miRNA 3.0 Array and quantitative polymerase chain reaction were used to detect the miRNA expression profile in human GC AGS cells treated with the soft-shelled turtle peptide. The results demonstrated that 101 miRNAs (49 upregulated miRNAs and 52 downregulated miRNAs) were significantly differentially expressed in the AGS cells following soft-shelled turtle peptide treatment. Several tumor suppressor miRNAs were upregulated markedly, including miRNA-375, let-7d, miRNA-429, miRNA-148a/148b and miRNA-34a. Pathway analysis indicated that soft-shelled turtle peptide may function with anticancer properties through the Hippo signaling pathway and the forkhead box O signaling pathway. Therefore, these results demonstrated that soft-shelled turtle peptide has the capacity to influence cancer-related pathways through the regulation of miRNA expression in GC cells.

The effect of circulating miR-223 on surveillance of different cancers: a meta-analysis

PURPOSE

Abnormal expression of miR-223 in cancerous tissue has confirmed it as an important player in tumorigenesis of cancers, such as hepatocellular carcinoma, colorectal carcinoma, osteosarcoma, gastric cancer, and chronic lymphocytic leukemia. The present meta-analysis aimed to explore the association between circulating miR-223 and prognosis of cancers.

METHODS

The studies were accessed by an electronic search of multiple databases. RevMan5.3 and STATA14.0 were used to estimate the heterogeneity among studies, pooled effects, and publication bias.

RESULTS

Ten studies with data of 1,002 patients with cancer were included in this meta-analysis. The risk of metastasis from stages 3 to 4 of TNM did not decrease when high versus low circulating expression of miR-223 were compared (pooled odds ratio =0.50, 95% CI: 0.24-1.03). In case of prognosis, the overall survival time was not significantly longer with high circulating miR-223 expression (pooled hazard ratio [HR] =0.64, 95% CI: 0.38-1.11) in all cancer types. However, the overall survival time of chronic lymphocytic leukemia (pooled HR =0.19, 95% CI: 0.07-0.54) increased in subgroup analysis. Moreover, the treatment-free survival of chronic lymphocytic leukemia was significantly increased with high circulating miR-223 expression (pooled HR =0.38, 95% CI: 0.23-0.64).

CONCLUSION

Circulating miR-223 was not an effective biomarker in prognosis surveillance in all cancers but in chronic lymphocytic leukemia.

miR-133b suppresses metastasis by targeting HOXA9 in human colorectal cancer

Functions and mechanisms of microRNA (miRNA) involved in colorectal cancer (CRC) metastasis are largely unknown. Here, a miRNA microarray analysis was performed in CRC primary tissues and metastatic hepatic tissues to disclose crucial miRNA involved in CRC metastasis. MiR-133b was decreased and negatively correlated with metastasis in CRC. Overexpression of miR-133b significantly suppressed metastasis of CRC in vitro and in vivo. HOXA9 was identified as a direct and functional target of miR-133b. In addition, HOXA9 was negatively correlated with miR-133b and promoted CRC malignant progress. Moreover, miR-133b decreased HOXA9 expression, and subsequently downregulated ZEB1 and upregulated E-cadherin expression. Intriguingly, lower miR-133b and higher HOXA9 expression significantly contributed to poorer outcomes in CRC patients. Multivariate analysis indicated that miR-133b was an independent and significant predictor of CRC patient overall survival. In conclusion, we newly determined that miR-133b targeted the HOXA9/ZEB1 pathway to promote tumor metastasis in CRC cells. This axis provided insights into the mechanism underlying miRNA regulation of CRC metastasis and a novel therapeutic target for CRC treatment.

Secreted molecules inducing epithelial-to-mesenchymal transition in cancer development

The epithelial-mesenchymal transition (EMT) is a biologic process that allows a polarized epithelial cell to undergo multiple biochemical changes that enable it to assume a mesenchymal cell phenotype. EMT is involved in embryo development, wound healing, tissue regeneration, organ fibrosis and has also been proposed as the critical mechanism for the acquisition of malignant phenotypes by epithelial cancer cells. These cells have been shown to acquire a mesenchymal phenotype when localized at the invasive front of primary tumours increasing aggressiveness, invasiveness, metastatic potential and resistance to chemotherapy. There is now increasing evidence demonstrating that a crucial role in the development of this process is played by factors secreted by cells of the tumour microenvironment or by the tumour cells themselves. This review summarises the current knowledge of EMT induction in cancer by paracrine or autocrine mechanisms, by exosomes or free proteins and miRNAs.

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.

Identification of circulating microRNA signatures as potential noninvasive biomarkers for prediction and prognosis of lymph node metastasis in gastric cancer

Circulating microRNAs (miRNAs) are emerging as novel noninvasive biomarkers for prediction of lymph node metastasis (LNM) in cancer. The aim of this study was to identify serum miRNA signatures for prediction and prognosis of LNM in gastric cancer (GC). MiSeq sequencing was performed for an initial screening of serum miRNAs in 10 GC patients with LNM, 10 patients without LNM and 10 healthy controls. Reverse transcription quantitative real-time PCR was applied to confirm concentration of candidate miRNAs using a training cohort (n = 279) and a validation cohort (n = 180). We identified a four-miRNA panel (miR-501-3p, miR-143-3p, miR-451a, miR-146a) by multivariate logistic regression model that provided high predictive accuracy for LNM with an area under the receiver operating characteristic curve (AUC) of 0.891 (95% CI, 0.840 to 0.930) in training set. Prospective evaluation of this panel revealed an AUC of 0.822 (95% CI, 0.758 to 0.875, specificity = 87.78%, sensitivity = 63.33%) in validation set. Moreover, Kaplan-Meier analysis showed that LNM patients with low miR-451a and miR-146a levels had worse overall survival (OS) (p < 0.05). In Cox regression analysis, miR-451a was independently associated with OS of LNM (p = 0.028). Our results suggested that use of serum miRNAs seems promising in estimating the probability GC patients harbor LNM and providing prognostic information for LNM.

Profiling of metastatic small intestine neuroendocrine tumors reveals characteristic miRNAs detectable in plasma

Background

Current diagnostic and prognostic blood-based biomarkers for neuroendocrine tumors are limited. MiRNAs have tumor-specific expression patterns, are relatively stable, and can be measured in patient blood specimens. We performed a multi-stage study to identify and validate characteristic circulating miRNAs in patients with metastatic small intestine neuroendocrine tumors, and to assess associations between miRNA levels and survival.

Methods

Using a 742-miRNA panel, we identified candidate miRNAs similarly expressed in 19 small intestine neuroendocrine tumors and matched plasma samples. We refined our panel in an independent cohort of plasma samples from 40 patients with metastatic small intestine NET and 40 controls, and then validated this panel in a second, large cohort of 120 patients with metastatic small intestine NET and 120 independent controls.

Results

miRNA profiling of 19 matched small intestine neuroendocrine tumors and matched plasma samples revealed 31 candidate miRNAs similarly expressed in both tissue and plasma. We evaluated expression of these 31 candidate miRNAs in 40 independent cases and 40 normal controls, and identified 4 miRNAs (miR-21-5p, miR-22-3p, miR-29b-3p, and miR-150-5p) that were differently expressed in cases and controls (p<0.05). We validated these 4 miRNAs in a separate, larger panel of 120 cases and 120 controls. We confirmed that high circulating levels of miR-22-3p (p<0.0001), high levels of miR 21-5p, and low levels of miR-150-5p (p=0.027) were associated with the presence of metastatic small intestine NET. While levels of 29b-3p were lower in cases than in controls in both the initial cohort and the validation cohort, the difference in the validation cohort did not reach statistical significance. We further found that high levels of circulating miR-21-5p, high levels of circulating miR-22-3p and low levels of circulating miR-150-5p were each independently associated with shorter overall survival. A combined analysis using all three markers was highly prognostic for survival (HR 0.47, 95% CI 0.27-0.82).

Conclusions

Our study suggests that elevated circulating levels of miR-21-5p and miR-22-3p and low levels of miR-150-5p are characteristic in patients with metastatic small intestine neuroendocrine tumors, and further suggests that levels of these miRNAs are associated with overall survival. These observations provide the basis for further validation studies, as well as studies to assess the biological function of these miRNAs in small intestine neuroendocrine tumors.

Cell-free microRNAs in blood and other body fluids, as cancer biomarkers

The discovery of cell-free microRNAs (miRNAs) in serum, plasma and other body fluids has yielded an invaluable potential source of non-invasive biomarkers for cancer and other non-malignant diseases. miRNAs in the blood and other body fluids are highly stable in biological samples and are resistant to environmental conditions, such as freezing, thawing or enzymatic degradation, which makes them convenient as potential biomarkers. In addition, they are more easily sampled than tissue miRNAs. Altered levels of cell-free miRNAs have been found in every type of cancer analysed, and increasing evidence indicates that they may participate in carcinogenesis by acting as cell-to-cell signalling molecules. This review summarizes the biological characteristics and mechanisms of release of cell-free miRNAs that make them promising candidates as non-invasive biomarkers of cancer.

Role of miRNAs and their potential to be useful as diagnostic and prognostic biomarkers in gastric cancer

Alterations in epigenetic control of gene expression play an important role in many diseases, including gastric cancer. Many studies have identified a large number of upregulated oncogenic miRNAs and downregulated tumour-suppressor miRNAs in this type of cancer. In this review, we provide an overview of the role of miRNAs, pointing to their potential to be useful as diagnostic and/or prognostic biomarkers in gastric cancer. Moreover, we discuss the influence of polymorphisms and epigenetic modifications on miRNA activity.

MiR-203 inhibits tumor invasion and metastasis in gastric cancer by ATM

Gastric cancer is one of the most common malignancies in the world. A number of miRNAs are aberrantly expressed during the progression of gastric cancer. In this study, we aimed to investigate the role of miR-203 in the invasion and metastasis of gastric cancer and the potential mechanism of the effect of miR-203 on the tumor progression of gastric cancer. Our results showed that miR-203 was significantly downregulated in gastric cancer tissues and cells, while ataxia telangiectasia mutated kinase (ATM) was upregulated in gastric cancer tissues and cells and was directly regulated by miR-203. Ectopic overexpression of miR-203 inhibited the colony formation, migration, and invasion of gastric cancer cells. In addition, miR-203 overexpression significantly suppressed the protein level of Snail and obviously promoted the protein level of E-cadherin in gastric cancer cells. ATM knockdown phenocopied the effect of miR-203 overexpression. These results suggested that miR-203 suppressed the migration and invasion of gastric cancer through regulating the level of ATM-mediated-Snail and E-cadherin. MiR-203 might be a novel therapeutic strategy for the treatment of gastric cancer.

Potential biomarker panels in overall breast cancer management: advancements by multilevel diagnostics

Breast cancer (BC) prevalence has reached an epidemic scale with half a million deaths annually. Current deficits in BC management include predictive and preventive approaches, optimized screening programs, individualized patient profiling, highly sensitive detection technologies for more precise diagnostics and therapy monitoring, individualized prediction and effective treatment of BC metastatic disease. To advance BC management, paradigm shift from delayed to predictive, preventive and personalized medical services is essential. Corresponding step forwards requires innovative multilevel diagnostics procuring specific panels of validated biomarkers. Here, we discuss current instrumental advancements including genomics, proteomics, epigenetics, miRNA, metabolomics, circulating tumor cells and cancer stem cells with a focus on biomarker discovery and multilevel diagnostic panels. A list of the recommended biomarker candidates is provided.

Circulating microRNA-203 predicts metastases, early recurrence, and poor prognosis in human gastric cancer

BACKGROUND

Metastasis is a major cause of death in patients with gastric cancer (GC). MicroRNAs (miRNAs) relating to the epithelial-mesenchymal transition (EMT) control GC progression and metastasis. The aim of this study was to evaluate serum EMT-associated miRNAs for metastatic and prognostic noninvasive biomarkers in GC.

METHODS

In the first step of this study (preliminary experiments), we selected candidate miRNAs associated with metastasis by analyzing the expression of the miR-200 family (miR-200a, miR-200b, miR-200c, miR-141, and miR-429) and miR-203 in serum samples from stage I (n = 12) and stage IV (n = 12) GC patients. The second phase involved the independent validation of candidate miRNAs in serum specimens from 130 patients with GC and 22 controls.

RESULTS

Based on the preliminary experiments, miR-203 was selected as the candidate serum miRNA that was most closely associated with metastasis. Validation analysis revealed that serum miR-203 levels were significantly lower in stage IV than stage I-III GC patients. Serum miR-203 expression was significantly lower in GC patients with a higher T stage, vessel invasion, and lymph node, peritoneal, and distant metastases. Low expression of serum miR-203 was significantly associated with poor disease-free and overall survival. Multivariate analysis revealed that low serum miR-203 expression was an independent predictive marker for lymph node, peritoneal, and distant metastases and a poor prognosis in patients with GC.

CONCLUSIONS

Serum miR-203 has the potential to serve as a noninvasive biomarker for prognosis and to predict metastasis in patients with GC.

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.

Prognostic and diagnostic potential of miR-146a in oesophageal squamous cell carcinoma

BACKGROUND

Accumulating evidence indicates that dysregulated microRNA-146a (miR-146a) is involved in tumour genesis and cancer progression. We aimed to evaluate its expression level and the potential for the diagnosis and prognosis in oesophageal squamous cell cancer (ESCC).

METHODS

We examined miR-146a expression in 62 pairs of ESCC cancerous and matched paracancerous tissue, 115 formalin-fixed paraffin-embedded (FFPE) tissue samples and serum samples from 154 ESCC patients and 154 healthy volunteers using quantitative reverse transcription-PCR (qRT-PCR). Kaplan-Meier method, Cox regression and receiver-operating characteristic (ROC) curve analysis were applied to analyse its prognostic and diagnostic value.

RESULTS

MicroRNA-146a expression level was significantly decreased in ESCC tissue compared with paracancerous tissue (P<0.001). Its regulation level was negatively associated with T factor and TNM stage. Kaplan-Meier curve revealed that its downregulation level predicted worse overall survival (OS) and progression-free survival (PFS). Both univariate and multivariate analyses identified miR-146a expression as independent prognostic factor for OS and PFS. Serum miR-146a was significantly reduced in ESCC patients than in healthy controls (P<0.001). Area under the curve ROC value, sensitivity and specificity for this marker were 0.863 ± 0.033, 85.7% and 68.6% in the Discovery Group, and 0.891 ± 0.027, 82.1% and 83.3% in the Validation Group.

CONCLUSIONS

MicroRNA-146a is significantly reduced in cancerous tissue and serum samples of ESCC patients. It is an ideal biomarker for the prognosis and diagnosis of ESCC.

Metastatic breast cancer: the potential of miRNA for diagnosis and treatment monitoring

Breast cancer affects approximately 12 % women worldwide and results in 14 % of all cancer-related fatalities. Breast cancer is commonly categorized into one of four main subtypes (luminal A, luminal B, human epidermal growth factor receptor 2 (HER2) positive and basal), indicating molecular characteristics and informing treatment regimes. The most severe form of breast cancer is metastasis, when the tumour spreads from the breast tissue to other parts of the body. Significantly, the primary tumour subtype affects rates and sites of metastasis. Currently, up to 5 % of patients present with incurable metastasis, with an additional 10–15 % of patients going on to develop metastasis within 3 years of diagnosis. MicroRNAs (miRNAs) are short 21–25 long nucleotides that have been shown to significantly affect gene expression. Currently, >2000 miRNAs have been identified and significantly, specific miRNAs have been found associated with diseases states. Importantly, miRNAs are found circulating in the blood, presenting an opportunity to use these circulating disease-related miRNAs as biomarkers. Clearly, the identification of circulating miRNA specific to metastatic breast cancer presents a unique opportunity for early disease identification and for monitoring disease burden. Currently however, few groups have identified miRNA associated with metastatic breast cancer. Here, we review the literature surrounding the identification of metastatic miRNA in breast cancer patients, highlighting key areas where miRNA biomarker discovery could be beneficial, identifying key concepts, recognizing critical areas requiring further research and discussing potential problems.

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.

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.

Circulating MicroRNAs as Biomarkers and Mediators of Cell-Cell Communication in Cancer

The realization of personalized medicine for cancer will rely not only on the development of new therapies, but on biomarkers that direct these therapies to the right patient. MicroRNA expression profiles in the primary tumor have been shown to differ between cancer patients and healthy individuals, suggesting they might make useful biomarkers. However, examination of microRNA expression in the primary tumor requires an invasive biopsy procedure. More recently, microRNAs have been shown to be released from the primary tumor into the circulation where they can be utilized as non-invasive biomarkers to diagnose patients, predict prognosis, or indicate therapeutic response. This review provides an overview of the current use of circulating microRNAs as biomarkers as well as recent findings on their role in regulating cell signaling interactions in the tumor microenvironment.

Circulating microRNAs and long non-coding RNAs in gastric cancer diagnosis: An update and review

Gastric cancer (GC) is the fourth most common cancer and the third leading cause of cancer mortality worldwide. MicroRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are the most popular non-coding RNAs in cancer research. To date, the roles of miRNAs and lncRNAs have been extensively studied in GC, suggesting that miRNAs and lncRNAs represent a vital component of tumor biology. Furthermore, circulating miRNAs and lncRNAs are found to be dysregulated in patients with GC compared with healthy individuals. Circulating miRNAs and lncRNAs may function as promising biomarkers to improve the early detection of GC. Multiple possibilities for miRNA secretion have been elucidated, including active secretion by microvesicles, exosomes, apoptotic bodies, high-density lipoproteins and protein complexes as well as passive leakage from cells. However, the mechanism underlying lncRNA secretion and the functions of circulating miRNAs and lncRNAs have not been fully illuminated. Concurrently, to standardize results of global investigations of circulating miRNAs and lncRNAs biomarker studies, several recommendations for pre-analytic considerations are put forward. In this review, we summarize the known circulating miRNAs and lncRNAs for GC diagnosis. The possible mechanism of miRNA and lncRNA secretion as well as methodologies for identification of circulating miRNAs and lncRNAs are also discussed. The topics covered here highlight new insights into GC diagnosis and screening.

Analysis of Deregulated microRNAs and Their Target Genes in Gastric Cancer

BACKGROUND

MicroRNAs (miRNAs) are widely studied non-coding RNAs that modulate gene expression. MiRNAs are deregulated in different tumors including gastric cancer (GC) and have potential diagnostic and prognostic implications. The aim of our study was to determine miRNA profile in GC tissues, followed by evaluation of deregulated miRNAs in plasma of GC patients. Using available databases and bioinformatics methods we also aimed to evaluate potential target genes of confirmed differentially expressed miRNA and validate these findings in GC tissues.

METHODS

The study included 51 GC patients and 51 controls. Initially, we screened miRNA expression profile in 13 tissue samples of GC and 12 normal gastric tissues with TaqMan low density array (TLDA). In the second stage, differentially expressed miRNAs were validated in a replication cohort using qRT-PCR in tissue and plasma samples. Subsequently, we analyzed potential target genes of deregulated miRNAs using bioinformatics approach, determined their expression in GC tissues and performed correlation analysis with targeting miRNAs.

RESULTS

Profiling with TLDA revealed 15 deregulated miRNAs in GC tissues compared to normal gastric mucosa. Replication analysis confirmed that miR-148a-3p, miR-204-5p, miR-223-3p and miR-375 were consistently deregulated in GC tissues. Analysis of GC patients' plasma samples showed significant down-regulation of miR-148a-3p, miR-375 and up-regulation of miR-223-3p compared to healthy subjects. Further, using bioinformatic tools we identified targets of replicated miRNAs and performed disease-associated gene enrichment analysis. Ultimately, we evaluated potential target gene BCL2 and DNMT3B expression by qRT-PCR in GC tissue, which correlated with targeting miRNA expression.

CONCLUSIONS

Our study revealed miRNA profile in GC tissues and showed that miR-148a-3p, miR-223-3p and miR-375 are deregulated in GC plasma samples, but these circulating miRNAs showed relatively weak diagnostic performance as sole biomarkers. Target gene analysis demonstrated that BCL2 and DNMT3B expression in GC tissue correlated with their targeting miRNA expression.

High-Throughput Sequencing of miRNAs Reveals a Tissue Signature in Gastric Cancer and Suggests Novel Potential Biomarkers

Gastric cancer has a high incidence and mortality rate worldwide; however, the use of biomarkers for its clinical diagnosis remains limited. The microRNAs (miRNAs) are biomarkers with the potential to identify the risk and prognosis as well as therapeutic targets. We performed the ultradeep miRnomes sequencing of gastric adenocarcinoma and gastric antrum without tumor samples. We observed that a small set of those samples were responsible for approximately 80% of the total miRNAs expression, which might represent a miRNA tissue signature. Additionally, we identified seven miRNAs exhibiting significant differences, and, of these, hsa-miR-135b and hsa-miR-29c were able to discriminate antrum without tumor from gastric cancer regardless of the histological type. These findings were validated by quantitative real-time polymerase chain reaction. The results revealed that hsa-miR-135b and hsa-miR-29c are potential gastric adenocarcinoma occurrence biomarkers with the ability to identify individuals at a higher risk of developing this cancer, and could even be used as therapeutic targets to allow individualized clinical management.

Cancer type-specific epigenetic changes: gastric cancer

Gastric cancer (GC) remains a major cause of mortality despite declining rate in the world. Epigenetic alterations contribute significantly to the development and progression of gastric tumors. Epigenetic refers to the number of modifications of the chromatin structure that affect gene expression without altering the primary sequence of DNA, and these changes lead to transcriptional activation or silencing of the gene. Over the years, the study of epigenetic processes has increased, and novel therapeutic approaches have emerged. This chapter summarizes the main epigenomic mechanisms described recently involved in gastric carcinogenesis, focusing on the roles that aberrant DNA methylation, histone modifications (histone acetylation and methylation), and miRNAs (oncogenic and tumor suppressor function of miRNA) play in the onset and progression of gastric tumors. Clinical implications of these epigenetic alterations in GC are also discussed.

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.