Exosomes as a Source of Biomarkers for Gastrointestinal Cancers

SIMPLE SUMMARY: Exosomes are small (40–160 nanometer) extracellular vesicles with significant roles in cancer development and progression. Exosomes are abundantly produced by cancer cells, carry tumor-specific content, such as DNA, RNA, and proteins, and have the potential to serve as biomarkers and therapeutic targets. Since exosomes are present in various biofluids, such as blood, saliva, urine, and peritoneal fluid, they render themselves as a great platform for the development of liquid biopsies. This review offers a comprehensive summary of diagnostic, prognostic, and predictive exosomal biomarkers in colorectal and gastric cancers. We also discuss the challenges and limitations of exosomes in clinical application and future prospects. ABSTRACT: Exosomes are small, lipid-bilayer bound extracellular vesicles of 40–160 nanometers in size that carry important information for intercellular communication. Exosomes are produced more by tumor cells than normal cells and carry tumor-specific content, such as DNA, RNA, and proteins, which have been implicated in tumorigenesis, tumor progression, and treatment response. Due to the critical role of exosomes in cancer development and progression, they can be exploited to develop specific biomarkers and therapeutic targets. Since exosomes are present in various biofluids, such as blood, saliva, urine, and peritoneal fluid, they are ideally suited to be developed as liquid biopsy tools for early diagnosis, molecular profiling, disease surveillance, and treatment response monitoring. In the past decade, numerous studies have been published about the functional significance of exosomes in a wide variety of cancers, with a particular focus on exosome-derived RNAs and proteins as biomarkers. In this review, utilizing human studies on exosomes, we highlight their potential as diagnostic, prognostic, and predictive biomarkers in gastrointestinal cancers.