Extracellular Vesicle Heterogeneity: Subpopulations, Isolation Techniques, and Diverse Functions in Cancer Progression

Abstract

Cells release membrane enclosed nano-sized vesicles termed extracellular vesicles (EVs) that function as mediators of intercellular communication by transferring biological information between cells. Tumor-derived EVs have emerged as important mediators in cancer development and progression, mainly through transfer of their bioactive content which can include oncoproteins, oncogenes, chemokine receptors, as well as soluble factors, transcripts of proteins and miRNAs involved in angiogenesis or inflammation. This transfer has been shown to influence the metastatic behavior of primary tumors. Moreover, tumor-derived EVs have been shown to influence distant cellular niches, establishing favorable microenvironments that support growth of disseminated cancer cells upon their arrival at these pre-metastatic niches. It is generally accepted that cells release a number of major EV populations with distinct biophysical properties and biological functions. Exosomes, microvesicles, and apoptotic bodies are EV populations most widely studied and characterized. They are discriminated based primarily on their intracellular origin. However, increasing evidence suggests that even within these EV populations various subpopulations may exist. This heterogeneity introduces an extra level of complexity in the study of EV biology and function. For example, EV subpopulations could have unique roles in the intricate biological processes underlying cancer biology. Here, we discuss current knowledge regarding the role of subpopulations of EVs in cancer development and progression and highlight the relevance of EV heterogeneity. The position of tetraspanins and integrins therein will be highlighted. Since addressing EV heterogeneity has become essential for the EV field, current and novel techniques for isolating EV subpopulations will also be discussed. Further dissection of EV heterogeneity will advance our understanding of the critical roles of EVs in health and disease.

Engineering State‐of‐the‐Art Plasmonic Nanomaterials for SERS‐Based Clinical Liquid Biopsy Applications

“…EVs can be classified into two major subclasses: exosomes (30-100 nm in diameter) which are formed by the inward budding of the endosomal membrane during maturation of multivesicular endosome, and microvesicles (50-10 000 nm in diameter) that are shed from the plasma membrane surface via outward budding. [97,120] However, sensitive and specific detection of tumor-derived EVs is difficult due to the i) abundant background presence of EVs secreted from non neoplastic cells as well as other nonvesicular materials, [1b,98] and ii) inherent EV heterogeneity in biophysical characteristic and composition. EVs can also be used to track inflammatory responses, as well as stromal and other systemic changes (which are not derivable from CTCs or circulating tumor NAs).…”

“…[96] EVs are of interest for diagnostic and prognostic applications as they contain various molecules (e.g., NAs and proteins) derived directly from secreted cells. [97] Furthermore, the current lack of a standardized EV isolation and analysis workflow makes the clinical translation of EVs even challenging. [2] Additionally, EVs can be easily sampled as they are present in various body fluids (e.g., blood and urine).…”

Extracellular vesicles, news about their role in immune cells: physiology, pathology and diseases

“…However, EVs derived from immune cells can also reinforce cancer progression [49,[53][54][55] (Fig. Moreover, the EVs of cancer cell origin move to the proximity of neighbouring vessels, thus inducing stimulation of angiogenesis (red of the vessel system over the pink background to the right) [46]. [18][19][20].…”

“…3). EVs of cancer origin penetrate within vessels (bottom, light green background), where they induce the intra-lumenal assembly of pre-metastatic cell niches [45][46][47], destined to develop into metastases. In contrast, EVs released from unaffected cancer cells reinforce the adjacent fibroblast (green) and cancer (yellow) cells, distributed over the central golden background.…”

“…Among biomarkers, some correspond to whole EVs, known to be released from particular cancer cells [45][46][47]; others are based on EV surface proteins, such as tetraspanins and 14-3-3ζ [3,60] or on miRNAs, such as miR-301a-3p and many others, abundant in the lumen of cancer EVs [46,48]. Important for these studies is the identification of biomarkers, useful for the strategy of medical action.…”