Small EVs-Associated DNA as Complementary Biomarker to Circulating Tumor DNA in Plasma of Metastatic Colorectal Cancer Patients

Stoichiometric constraints for detection of EV-borne biomarkers in blood

Stochiometric issues, encompassing both the quantity and heterogeneity of extracellular vesicles (EVs) derived from tumour or other tissues in blood, pose important challenges across various stages of biomarker discovery and detection, affecting the integrity of data, introducing losses and artifacts during blood processing, EV purification and analysis. These challenges shape the diagnostic utility of EVs especially within the framework of established and emerging methodologies. By addressing these challenges, we aim to delineate crucial parameters and requirements for tumour-specific EV detection, or more precisely, for tumour identification via EV based assays. Our endeavour involves a comprehensive examination of the layers that mask or confound the traceability of EV markers such as nucleic acids and proteins, and focus on 'low prevalence-low concentration' scenario. Finally, we evaluate the advantages versus limitations of single-particle analysers over more conventional bulk assays, suggesting that the combined use of both to capture and interpret the EV signals, in particular the EV surface displayed proteins, may ultimately provide quantitative information on their absolute abundance and distribution.

The detection, biological function, and liquid biopsy application of extracellular vesicle-associated DNA

Cell-derived extracellular vesicles (EVs), which carry diverse biomolecules such as nucleic acids, proteins, metabolites, and lipids reflecting their cell of origin, are released under both physiological and pathological conditions. EVs have been demonstrated to mediate cell-to-cell communication and serve as biomarkers. EV-associated DNA (EV-DNA) comprises genomic and mitochondrial DNA (i.e., gDNA and mtDNA) fragments. Some studies have revealed that EV-DNA can represent the full nuclear genome and mitochondrial genome of parental cells. Furthermore, DNA fragments loaded into EVs are stable and can be transferred to recipient cells to regulate their biological functions. In this review, we summarized and discussed EV-DNA research advances with an emphasis on EV-DNA detection at the population-EV and single-EV levels, gene transfer-associated biological functions, and clinical applications as biomarkers for disease liquid biopsy. We hope that this review will provide potential directions or guidance for future EV-DNA investigations.

Characterization and proteomic analysis of plasma-derived small extracellular vesicles in locally advanced rectal cancer patients

BACKGROUND

Neoadjuvant chemoradiotherapy (nCRT) stands as a pivotal therapeutic approach for locally advanced rectal cancer (LARC), yet the absence of a reliable biomarker to forecast its efficacy remains a challenge. Thus, this study aimed to assess whether the proteomic compositions of small extracellular vesicles (sEVs) might offer predictive insights into nCRT response among patients with LARC, while also delving into the proteomic alterations within sEVs post nCRT.

METHODS

Plasma samples were obtained from LARC patients both pre- and post-nCRT. Plasma-derived sEVs were isolated utilizing the TIO2-based method, followed by LC-MS/MS-based proteomic analysis. Subsequently, pathway enrichment analysis was performed to the Differentially Expressed Proteins (DEPs). Additionally, ROC curves were generated to evaluate the predictive potential of sEV proteins in determining nCRT response. Public databases were interrogated to identify sEV protein-associated genes that are correlated with the response to nCRT in LARC.

RESULTS

A total of 16 patients were enrolled. Among them, 8 patients achieved a pathological complete response (good responders, GR), while the remaining 8 did not achieve a complete response (poor responders, PR). Our analysis of pretreatment plasma-derived sEVs revealed 67 significantly up-regulated DEPs and 9 significantly down-regulated DEPs. Notably, PROC (AUC: 0.922), F7 (AUC: 0.953) and AZU1 (AUC: 0.906) demonstrated high AUC values and significant differences (P value < 0.05) in discriminating between GR and PR patients. Furthermore, a signature consisting of 5 sEV protein-associated genes (S100A6, ENO1, MIF, PRDX6 and MYL6) was capable of predicting the response to nCRT, yielding an AUC of 0.621(95% CI: 0.454-0.788). Besides, this 5-sEV protein-associated gene signature enabled stratification of patients into low- and high-risk group, with the low-risk group demonstrating a longer overall survival in the testing set (P = 0.048). Moreover, our investigation identified 11 significantly up-regulated DEPs and 31 significantly down-regulated DEPs when comparing pre- and post-nCRT proteomic profiles. GO analysis unveiled enrichment in the regulation of phospholipase A2 activity.

CONCLUSIONS

Differential expression of sEV proteins distinguishes between GR and PR patients and holds promise as predictive markers for nCRT response and prognosis in patients with LARC. Furthermore, our findings highlight substantial alterations in sEV protein composition following nCRT.

Liquid biopsy in colorectal cancer: Onward and upward

Colorectal cancer (CRC) remains a leading cause of cancer-related deaths worldwide. In recent years, liquid biopsy has emerged as one of the most interesting areas of research in oncology, leading to innovative trials and practical changes in all aspects of CRC management. RNAs and cell free DNA (cfDNA) methylation are emerging as promising biomarkers for early diagnosis. Post-surgical circulating tumour DNA (ctDNA) can aid in evaluating minimal residual disease and personalising adjuvant treatment. In rectal cancer, ctDNA could improve response assessment to neoadjuvant therapy and risk stratification, especially in the era of organ-preservation trials. In the advanced setting, ctDNA analysis offers the opportunity to monitor treatment response and identify driver and resistance mutations more comprehensively than traditional tissue analysis, providing prognostic and predictive information. The aim of this review is to provide a detailed overview of the clinical applications and future perspectives of liquid biopsy in CRC.

Scalable purification of extracellular vesicles with high yield and purity using multimodal flowthrough chromatography

Extracellular vesicles (EVs) are cell derived membranous nanoparticles. EVs are important mediators of cell-cell communication via the transfer of bioactive content and as such they are being investigated for disease diagnostics as biomarkers and for potential therapeutic cargo delivery to recipient cells. However, existing methods for isolating EVs from biological samples suffer from challenges related to co-isolation of unwanted materials such as proteins, nucleic acids, and lipoproteins. In the pursuit of improved EV isolation techniques, we introduce multimodal flowthrough chromatography (MFC) as a scalable alternative to size exclusion chromatography (SEC). The use of MFC offers significant advantages for purifying EVs, resulting in enhanced yields and increased purity with respect to protein and nucleic acid co-isolates from conditioned 3D cell culture media. Compared to SEC, significantly higher EV yields with similar purity and preserved functionality were also obtained with MFC in 2D cell cultures. Additionally, MFC yielded EVs from serum with comparable purity to SEC and similar apolipoprotein B content. Overall, MFC presents an advancement in EV purification yielding EVs with high recovery, purity, and functionality, and offers an accessible improvement to researchers currently employing SEC.

Recent Advances in the Study of Extracellular Vesicles in Colorectal Cancer

There has been significant progress in the study of extracellular vesicles (EVs) since the 2017 American Gastroenterological Association-sponsored Freston Conference "Extracellular Vesicles: Biology, Translation and Clinical Application in GI Disorders." The burgeoning interest in this field stems from the increasing recognition that EVs represent an understudied form of cell-to-cell communication and contain cargo replete with biomarkers and therapeutic targets. This short review will highlight recent advances in the field, with an emphasis on colorectal cancer. After a brief introduction to secreted particles, we will describe how our laboratory became interested in EVs, which led to refined methods of isolation and identification of 2 secreted nanoparticles. We will then summarize the cargo found in small EVs released from colorectal cancer cells and other cells in the tumor microenvironment, as well as those found in the circulation of patients with colorectal cancer. Finally, we will consider the continuing challenges and future opportunities in this rapidly evolving field.

Feasibility of Leukemia-Derived Exosome Enrichment and Co-isolated dsDNA Sequencing in Acute Myeloid Leukemia Patients: A Proof of Concept for New Leukemia Biomarkers Detection

Simple Summary

The present pilot study aimed at investigating the feasibility of a leukemia-derived exosome enrichment approach followed by exosomal dsDNA target re-sequencing for adult Acute Myeloid Leukemias (AML) marker detection. To our knowledge, this is the first time that a proof-of-concept combining a leukemia-derived exosome enrichment strategy based on a commercial CE-IVD kit and next-generation sequencing was applied in a cohort of adult AML patients. The reported approach is easy, quick and user friendly and gives the possibility of obtaining a good quantity of exosomal dsDNA (composed of exosomal cargo and surrounding DNA) suitable for further analysis. The time-effective procedure opens up future effective clinical applications. This pilot study presents the potential of a proof-of-concept based on exosome analysis to be applied in clinical practice, as well as the feasibility of this kind of investigations using a certified kit, avoiding many additional analyses. It may encourage further studies regarding extracellular vesicles in myeloid neoplasia.

Abstract

Exosomes are extracellular vesicles playing a pivotal role in the intercellular communication. They shuttle different cargoes, including nucleic acids from their cell of origin. For this reason, they have been studied as carriers of tumor markers in different liquid biopsy approaches, in particular for solid tumors. Few data are available concerning exosomes as markers of myeloid neoplasia. To better understand their real potential and the best approach to investigate leukemic exosomes, we present the results of a pilot feasibility study evaluating the application of next-generation sequencing analysis of dsDNA derived from exosomes isolated in 14 adult patients affected by acute myeloid leukemias. In particular, leukemia-derived exosome fractions have been analyzed. The concentration of dsDNA co-extracted with exosomes and the number and types of mutations detected were considered and compared with ones identified in the Bone Marrow (BM) and Peripheral Blood (PB) cells. Exosomal DNA concentration, both considering the cargo and the DNA surrounding the lipid membrane resulted in a linear correlation with leukemic burden. Moreover, exosomal DNA mutation status presented 86.5% of homology with BM and 75% with PB. The results of this pilot study confirmed the feasibility of a leukemia-derived exosome enrichment approach followed by exosomal dsDNA NGS analysis for AML biomarker detection. These data point to the use of liquid biopsy in myeloid neoplasia for the detection of active leukemic cells resident in the BM via a painless procedure.

New Perspectives on the Importance of Cell-Free DNA Biology

Body fluids are constantly replenished with a population of genetically diverse cell-free DNA (cfDNA) fragments, representing a vast reservoir of information reflecting real-time changes in the host and metagenome. As many body fluids can be collected non-invasively in a one-off and serial fashion, this reservoir can be tapped to develop assays for the diagnosis, prognosis, and monitoring of wide-ranging pathologies, such as solid tumors, fetal genetic abnormalities, rejected organ transplants, infections, and potentially many others. The translation of cfDNA research into useful clinical tests is gaining momentum, with recent progress being driven by rapidly evolving preanalytical and analytical procedures, integrated bioinformatics, and machine learning algorithms. Yet, despite these spectacular advances, cfDNA remains a very challenging analyte due to its immense heterogeneity and fluctuation in vivo. It is increasingly recognized that high-fidelity reconstruction of the information stored in cfDNA, and in turn the development of tests that are fit for clinical roll-out, requires a much deeper understanding of both the physico-chemical features of cfDNA and the biological, physiological, lifestyle, and environmental factors that modulate it. This is a daunting task, but with significant upsides. In this review we showed how expanded knowledge on cfDNA biology and faithful reverse-engineering of cfDNA samples promises to (i) augment the sensitivity and specificity of existing cfDNA assays; (ii) expand the repertoire of disease-specific cfDNA markers, thereby leading to the development of increasingly powerful assays; (iii) reshape personal molecular medicine; and (iv) have an unprecedented impact on genetics research.

Advances in the analysis of single extracellular vesicles: A critical review

There is an ever-growing need for new cancer diagnostic approaches that provide earlier diagnosis as well as richer diagnostic, prognostic, and resistance information. Extracellular vesicles (EVs) recovered from a liquid biopsy have paradigm-shifting potential to offer earlier and more complete diagnostic information in the form of a minimally invasive liquid biopsy. However, much remains unknown about EVs, and current analytical approaches are unable to provide precise information about the contents and source of EVs. New approaches have emerged to analyze EVs at the single particle level, providing the opportunity to study biogenesis, correlate markers for higher specificity, and connect EV cargo with the source or destination. In this critical review we describe and analyze methods for single EV analysis that have emerged over the last five years. In addition, we note that current methods are limited in their adoption due to cost and complexity and we offer opportunities for the research community to address this challenge.