A Lipidomic Approach to Identify Potential Biomarkers in Exosomes From Melanoma Cells With Different Metastatic Potential.

Simona Lobasso,Francesco Mannavola,Patrizia Lopalco,Francesco Silvestris,Paola Tanzarella,Angela Corcelli,Chiara Ingrosso,Claudia Felici,Marco Tucci

doi:10.3389/fphys.2021.748895

Abstract

Melanoma, one of the most lethal cutaneous cancers, is characterized by its ability to metastasize to other distant sites, such as the bone. Melanoma cells revealed a variable in vitro propensity to be attracted toward bone fragments, and melanoma-derived exosomes play a role in regulating the osteotropism of these cells. We have here investigated the lipid profiles of melanoma cell lines (LCP and SK-Mel28) characterized by different metastatic propensities to colonize the bone. We have purified exosomes from cell supernatants by ultracentrifugation, and their lipid composition has been compared to identify potential lipid biomarkers for different migration and invasiveness of melanoma cells. Matrix-assisted laser desorption ionization-time-of-flight/mass spectrometry (MALDI-TOF/MS) lipid analysis has been performed on very small amounts of intact parental cells and exosomes by skipping lipid extraction and separation steps. Statistical analysis has been applied to MALDI mass spectra in order to discover significant differences in lipid profiles. Our results clearly show more saturated and shorter fatty acid tails in poorly metastatic (LCP) cells compared with highly metastatic (SK-Mel28) cells, particularly for some species of phosphatidylinositol. Sphingomyelin, lysophosphatidylcholine, and phosphatidic acid were enriched in exosome membranes compared to parental cells. In addition, we have clearly detected a peculiar phospholipid bis(monoacylglycero)phosphate as a specific lipid marker of exosomes. MALDI-TOF/MS lipid profiles of exosomes derived from the poorly and highly metastatic cells were not significantly different.

Highlights

Living cells release lipid bilayer vesicles into the extracellular fluid, i.e., extracellular vesicles (EVs), which aroused great interest in the scientific community in the last 10 years due to their important role in complex intercellular communication.Extracellular vesicles are released by cells of most living organisms and are different in origin, size, and composition
Total lipids of LCP and SK-Mel28 cells were extracted by the classical extraction method and analyzed by both MALDI-TOF/MS and coupled thin-layer chromatography (TLC) and MALDI-TOF/MS
A pre-chromatographic separation of different lipid classes by TLC, followed by MALDI-TOF/MS analysis of individual lipid bands, offers the opportunity to identify minor components as well, whose signals were barely distinguishable from the noise in the total lipid profiles

Summary

Introduction

Extracellular vesicles are released by cells of most living organisms (animals, bacteria, and plants) and are different in origin, size, and composition They are grouped in microvesicles, apoptotic bodies, and exosomes. Endocytosis from the plasma membrane leads to the formation of an early endosome in the cytosol, and the inward budding of the endosomal membrane fills its lumen with intraluminal vesicles, which mature in late endosome, termed as multivesicular body (MVB). Their fusion with the plasma membrane allows for the release of intraluminal vesicles into the extracellular space while their different origin determines variation in lipid bilayer membrane. Their common feature, is that they carry a pool of functional biomolecules (including DNA, RNAs, proteins, and lipids) (Record et al, 2014; Isola et al, 2016; Kalluri, 2016; Kalra et al, 2016; Skotland et al, 2017; Kalluri and LeBleu, 2020)

Objectives

Methods

Results

Conclusion