Extracellular vesicles associated microRNAs: Their biology and clinical significance as biomarkers in gastrointestinal cancers

Abstract

Gastrointestinal (GI) cancers, including colorectal, gastric, esophageal, pancreatic, and liver, are associated with high mortality and morbidity rates worldwide. One of the underlying reasons for the poor survival outcomes in patients with these malignancies is late disease detection, typically when the tumor has already advanced and potentially spread to distant organs. Increasing evidence indicates that earlier detection of these cancers is associated with improved survival outcomes and, in some cases, allows curative treatments. Consequently, there is a growing interest in the development of molecular biomarkers that offer promise for screening, diagnosis, treatment selection, response assessment, and predicting the prognosis of these cancers. Extracellular vesicles (EVs) are membranous vesicles released from cells containing a repertoire of biological molecules, including nucleic acids, proteins, lipids, and carbohydrates. MicroRNAs (miRNAs) are the most extensively studied non-coding RNAs, and the deregulation of miRNA levels is a feature of cancer cells. EVs miRNAs can serve as messengers for facilitating interactions between tumor cells and the cellular milieu, including immune cells, endothelial cells, and other tumor cells. Furthermore, recent years have witnessed considerable technological advances that have permitted in-depth sequence profiling of these small non-coding RNAs within EVs for their development as promising cancer biomarkers -particularly non-invasive, liquid biopsy markers in various cancers, including GI cancers. Herein, we summarize and discuss the roles of EV-associated miRNAs as they play a seminal role in GI cancer progression, as well as their promising translational and clinical potential as cancer biomarkers as we usher into the area of precision oncology.

Keywords: Biomarker; Extracellular vesicles; Gastrointestinal cancers; MiRNA; Technology.

Figure 1:

Extracellular vesicle (EVs) formation, classification, and cargo. EVs exhibit a size range from 30 to 10,000 nm. EV formation: the early endosomes originate from the inward budding of the cell’s plasma membrane (PM) and subsequently mature into late endosomes. These late endosomes harbor a variety of intraluminal vesicles, and this specific type of late endosome is characterized as a multivesicular body (MVB). MVB has different subtypes; one subtype fuses with lysosomes, facilitating the degradation of their contents. Another subtype involves the outward budding of the cell’s PM into the extracellular space, releasing vesicles. EV classification: EVs can be categorized based on size, biogenesis, and content. Small EVs, ranging from 30nm to 150nm, encompass ectosomes (marked by CD4 and CD9), arrestin domain-containing protein 1-mediated microvesicles (ARMMs, marked by ARRDC1, VPS4, and TSG101), and exosomes (marked by CD63). Medium-size EVs, in the size range of 100nm to 5,000nm, can be further subdivided into apoptotic vesicles (marked by phosphatidylserine) and microvesicles (marked by selectins, integrins, and annexins). Large oncosomes, with sizes ranging from 1,000nm to 10,000nm, can be identified by markers ARF6 and CK18. EVs cargo: EVs carry various molecules, including nucleic acids, proteins, lipids, etc. They play essential roles in cellular communication. ARRDC1: arrestin domain containing 1, VPS4: vacuolar protein sorting 4 homolog A, TSG101: tumor susceptibility 101, ARF6: ADP-ribosylation factor 6, and CK18: Cytokeratin 18.

Figure 2:

Overview of the potential of EV-miRNAs to serve as cancer prevention, screening, diagnostic, prognostic, personalized therapeutic, and treatment monitoring biomarkers in patients with GI cancers. A). Enhance immune responses and prevent tumor development via EV-miRNAs-loaded cancer vaccines; B). Distinguish the health, low-risk, and high-risk individuals for early cancer detection; C). Track drug efficacy to enhance individualized therapy; D). Inform treatment decisions through prognostic insights.

Figure 3:

The role of EV-miRNAs in mediating interactions between tumor cells and other cell types within the tumor microenvironment and circulatory system modulating malignant behaviors of cancer cells. Schematic representation of the tumor microenvironment (TME), which comprises immune cells, blood vessels, fibroblasts, and extracellular matrix components, among others; EV-miRNAs mediate crosstalk between tumor cells, stromal and normal cells within the tumor microenvironment. EV-miRNAs are also involved in the crosstalk listed in the figure, including EV-miR-126, -25-3p, -135b-5p, -29a, -21-5p, -934, and -200a, among others; EV-miRNAs regulate tumor cells malignant behaviors, impacting tumor migration, growth, invasion, angiogenesis, and their responses to immune therapy and chemotherapy. The figure also highlights the key pathways involved in this process. CELF2: CUGBP ELAV-like family number 2; WWOX: WW domain-containing oxidoreductase; EMT: Epithelial-Mesenchymal Transition; KLF2: Krüppel-like factor 2; KLF4: Krüppel-like factor 4; FOXO1: forkhead box protein O1; FGF1: fibroblast growth factor 1; Grhl2: Grainyhead-like 2; ZEB1: Zinc finger E-box-binding homeobox; PD-L1: programmed-death ligand 1; ROS: reactive oxygen species.

Figure 4:

Currently used methodologies for miRNA detection. The schematic diagram illustrates a range of EV-miRNA detection techniques, including qRT-PCR, droplet-based digital PCR, biosensors, isothermal amplification, nanomaterials, and next-generation sequencing (NGS).