Purification of Leukemia-Derived Exosomes to Study Microenvironment Modulation

Protocol for isolating leukemia-derived extracellular vesicles from the spleen of preclinical models of leukemia using ultracentrifugation

Here, we present a protocol for the direct isolation of small extracellular vesicles (sEVs) from the spleen of preclinical murine models of leukemia using ultracentrifugation. We describe steps for tissue collection, sample preparation, ultracentrifugation-based isolation, and sEV characterization. This protocol allows for efficient enrichment of both leukemia and its microenvironment-derived sEV (LME-sEV), providing a valuable tool for studying their composition and functional roles. Potential applications include investigating the role of sEV in leukemia progression and identifying biomarkers. For complete details on the use and execution of this protocol, please refer to Gargiulo et al.1.

Extracellular Vesicle Secretion by Leukemia Cells In Vivo Promotes CLL Progression by Hampering Antitumor T-cell Responses

Small extracellular vesicle (sEV, or exosome) communication among cells in the tumor microenvironment has been modeled mainly in cell culture, whereas their relevance in cancer pathogenesis and progression in vivo is less characterized. Here we investigated cancer-microenvironment interactions in vivo using mouse models of chronic lymphocytic leukemia (CLL). sEVs isolated directly from CLL tissue were enriched in specific miRNA and immune-checkpoint ligands. Distinct molecular components of tumor-derived sEVs altered CD8+ T-cell transcriptome, proteome, and metabolome, leading to decreased functions and cell exhaustion ex vivo and in vivo. Using antagomiRs and blocking antibodies, we defined specific cargo-mediated alterations on CD8+ T cells. Abrogating sEV biogenesis by Rab27a/b knockout dramatically delayed CLL pathogenesis. This phenotype was rescued by exogenous leukemic sEV or CD8+ T-cell depletion. Finally, high expression of sEV-related genes correlated with poor outcomes in CLL patients, suggesting sEV profiling as a prognostic tool. In conclusion, sEVs shape the immune microenvironment during CLL progression.

SIGNIFICANCE

sEVs produced in the leukemia microenvironment impair CD8+ T-cell mediated antitumor immune response and are indispensable for leukemia progression in vivo in murine preclinical models. In addition, high expression of sEV-related genes correlated with poor survival and unfavorable clinical parameters in CLL patients. See related commentary by Zhong and Guo, p. 5. This article is highlighted in the In This Issue feature, p. 1.

Small extracellular vesicles: multi-faceted tools for leukemia immune evasion in vivo

Recently, small extracellular vesicles (sEVs) secreted in vivo from chronic lymphocytic leukemia (CLL) preclinical murine models were characterized. Leukemia microenvironment sEV (LME-sEVs) selectively target CD8⁺ T-cells, inducing exhaustion and hampering anti-tumor immune response. Additionally, a sEV-related gene expression correlated with patient treatment-free survival, overall survival and clinical parameters.

Optimizing extracellular vesicles' isolation from chronic lymphocytic leukemia patient plasma and cell line supernatant

In chronic lymphocytic leukemia (CLL) and very likely all cancer types, extracellular vesicles (EVs) are a common mechanism by which intercellular messages are communicated between normal, diseased, and transformed cells. Studies of EVs in CLL and other cancers have great variability and often lack reproducibility. For CLL patient plasma and cell lines, we sought to characterize current approaches used in isolating EV products and understand whether cell culture-conditioned media or complex biological fluids confound results. Utilizing nanoparticle tracking analysis, protein quantification, and electron microscopy, we show that ultracentrifugation with an OptiPrep cushion can effectively minimize contaminants from starting materials including plasma and conditioned media of CLL cell lines grown in EV-depleted complete RPMI media but not grown in the serum-free media AIM V commonly used in CLL experimental work. Moreover, we confirm the benefit of including 25 mM trehalose in PBS during EV isolation steps to reduce EV aggregation, to preserve function for downstream applications and characterization. Furthermore, we report the highest particles/μg EVs were obtained from our CLL cell lines utilizing the CELLine bioreactor flask. Finally, we optimized a proliferation assay that offers a functional evaluation of our EVs with minimal sample requirements.

Diagnostic and Therapeutic Potential of Extracellular Vesicles in B-Cell Malignancies

Extracellular vesicles (EV), comprising microvesicles and exosomes, are particles released by every cell of an organism, found in all biological fluids, and commonly involved in cell-to-cell communication through the transfer of cargo materials such as miRNA, proteins, and immune-related ligands (e.g., FasL and PD-L1). An important characteristic of EV is that their composition, abundance, and roles are tightly related to the parental cells. This translates into a higher release of characteristic pro-tumor EV by cancer cells that leads to harming signals toward healthy microenvironment cells. In line with this, the key role of tumor-derived EV in cancer progression was demonstrated in multiple studies and is considered a hot topic in the field of oncology. Given their characteristics, tumor-derived EV carry important information concerning the state of tumor cells. This can be used to follow the outset, development, and progression of the neoplasia and to evaluate the design of appropriate therapeutic strategies. In keeping with this, the present brief review will focus on B-cell malignancies and how EV can be used as potential biomarkers to follow disease progression and stage. Furthermore, we will explore several proposed strategies aimed at using biologically engineered EV for treatment (e.g., drug delivery mechanisms) as well as for impairing the biogenesis, release, and internalization of cancer-derived EV, with the final objective to disrupt tumor–microenvironment communication.

Imaging intercellular interaction and extracellular vesicle exchange in a co-culture model of chronic lymphocytic leukemia and stromal cells by lattice light-sheet fluorescence microscopy

Recent advances in live cell imaging allow investigating processes that take place over the entire cell volume with unprecedented time and spatial resolution. Here we describe a protocol to study intercellular communication, including extracellular vesicle exchange, between cancer cells and their microenvironment, using lattice light sheet fluorescence microscopy. While the described protocol is intended to study the interactions between chronic lymphocytic leukemia cells and bone marrow stromal cells, many components of it can be applied to study other cancers of hematopoietic or solid tumor origin, as well as to characterize other modalities of intercellular communication.

Feasibility of tumor‑derived exosome enrichment in the onco‑hematology leukemic model of chronic myeloid leukemia

Due to the discovery of their role in intra-cellular communications, exosomes, which carry information specific to the cell of origin, have garnered considerable attention in cancer research. Moreover, there is evidence to suggest the possibility of isolating different exosome sub-populations based on target antigens at the cell surface. Philadelphia chromosome-positive (Ph⁺) chronic myeloid leukemia (CML) is a clonal myeloproliferative neoplasia characterized by the break-point cluster region-proto-oncogene 1 tyrosine-protein kinase (BCR-ABL1) fusion-gene, derived from the t (9;22) translocation. Tyrosine kinase inhibitors (TKIs) target BCR-ABL1 protein and induce major or deep molecular responses in the majority of patients. Despite the fact that several studies have demonstrated the persistence of leukemic cells in the bone marrow niche, even following treatment, TKIs prolong patient survival time and facilitate treatment-free remission. These characteristics render CML a plausible model for investigating the feasibility of tumor-derived exosome fraction enrichment. In the present study, patients in the chronic phase (CP) of CML were treated with TKIs, and the quantification of the BCR-ABL1 exosomal transcript was performed using digital PCR (dPCR). The possibility of tumor-derived exosomes enrichment was confirmed, and for the first time, to the best of our knowledge, the detection of the BCR-ABL1 transcript highlighted the presence of active leukemic cells in patients with CP-CML. According to these findings, tumor-derived exosomes may be considered a novel tool for the identification of active leukemic cells, and for the assessment of innovative monitoring focused on the biological functions of exosomes in CML.

Hematological Malignancy-Derived Small Extracellular Vesicles and Tumor Microenvironment: The Art of Turning Foes into Friends

Small extracellular vesicles (small EVs) are commonly released by all cells, and are found in all body fluids. They are implicated in cell to cell short- and long-distance communication through the transfer of genetic material and proteins, as well as interactions between target cell membrane receptors and ligands anchored on small EV membrane. Beyond their canonical functions in healthy tissues, small EVs are strategically used by tumors to communicate with the cellular microenvironment and to establish a proper niche which would ultimately allow cancer cell proliferation, escape from the immune surveillance, and metastasis formation. In this review, we highlight the effects of hematological malignancy-derived small EVs on immune and stromal cells in the tumor microenvironment.