Abstract
Simple SummaryThe screening methods and therapeutic strategies for gastrointestinal cancer (GIC) have improved, but mortality in GIC patients remains high. Early detection and precise evaluation of GIC are required to further improve treatment outcomes in GIC patients. MicroRNAs (miRNAs), which do not encode proteins, have attracted attention as biomarkers of various diseases. Since the first report revealing the strong correlation between miRNAs and cancer in 2002, numerous studies have illustrated the changes in the expression and the biological and oncological effects of miRNAs in GIC. Furthermore, miRNAs circulating in the blood are reported to be associated with GIC status. These miRNAs are thought to be useful as noninvasive biomarkers because of their stability in blood. Herein, we discuss the potential of miRNAs as noninvasive biomarkers for each type of GIC on the basis of previous reports and describe perspectives for their future application.Gastrointestinal cancer (GIC) is a common disease and is considered to be the leading cause of cancer-related death worldwide; thus, new diagnostic and therapeutic strategies for GIC are urgently required. Noncoding RNAs (ncRNAs) are functional RNAs that are transcribed from the genome but do not encode proteins. MicroRNAs (miRNAs) are short ncRNAs that are reported to function as both oncogenes and tumor suppressors. Moreover, several miRNA-based drugs are currently proceeding to clinical trials for various diseases, including cancer. In recent years, the stability of circulating miRNAs in blood has been demonstrated. This is of interest because these miRNAs could be potential noninvasive biomarkers of cancer. In this review, we focus on circulating miRNAs associated with GIC and discuss their potential as novel biomarkers.
Highlights
Cancer is the third leading cause of death globally, and almost 9.6 million cancerrelated deaths worldwide were reported in 2018
We focus on circulating miRNAs in gastrointestinal cancer (GIC) and provide an overview of the role of circulating miRNAs, discussing their biological functions and their potential as tumor markers and therapeutic targets
The results revealed that miR-1246 expression was significantly increased and miR-106b expression significantly decreased in each cohort
Summary
Cancer is the third leading cause of death globally, and almost 9.6 million cancerrelated deaths worldwide were reported in 2018. Multivesicular endosomes (MVBs) containing many ILVs fuse with the cell plasma membrane, and ILVs are released into the extracellular space as exosomes [30] Via this process, miRNAs are sorted into exosomes and are called exosomal miRNAs. microvesicles (MVs) are spontaneously generated from cells by direct budding and contain mature miRNAs and AGO2-bound miRNAs with other molecules, including several types of proteins [31,32]. Montecalvo et al [40] reported that DCs transferred cellular signals to neighbor DCs via exosomal miRNAs, and these miRNAs functioned as a means of communication and post-transcriptional regulation between DCs. Regarding other biological effects, Thomou et al [41] revealed that adipose tissue releases circulating exosomal miRNAs, which regulate gene expression in distant liver tissue. Circulating miRNAs have important roles in cellular communication and induce biological effects in several situations
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