## 4 Studies of the Molecular Profiling of EVs as Potential Biomarkers
### Lipidome Profiling Analysis of EVs in Multiple Cancers
These authors identified a decrease in PC/PE ratios in EVs relative to LIM1215 parent cells [172] (Table 1). Moreover, a lipid composition study of EVs and cells of their origin and between \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Cancer Type** & **Biomarker** & **Sample** & **Authors** \\ \hline \multirow{4}{*}{Prostate Cancer} & Glucoronate; increased creatinine, glucuronate, & \multirow{4}{*}{Urine and plasma-derived EVs} & \multirow{4}{*}{[5]} \\  & pantothenic acid, 4-pyridoxide acid in urina; lysine, & & \\  & kynureine, threonine, tryptophan, cylindite in plasma & & \\ \hline \multirow{4}{*}{Prostate Cancer} & Increased CHOL, sphingolipids and glycerophospholipids, & \multirow{4}{*}{_In vitro_: PC-3, RWPE1, and NB26 cell lines} & \multirow{4}{*}{[74]} \\  & decreased glycerolipids and prenolic lipids & & \\  & Increased glycerophospholipids and sphingolipids & & \\  & Colorectal Cancer & Increased glycerophospholipids, SM, CHOL, and PS & \\  & Breast Cancer & Increased levels of CHOL and SM, decreased levels of PC & \\  & Glioblastoma and & Increased SM and ceramides in glioblastoma than & \\  & hepatocellular carcinoma & & \\  & & & \\  & & \\  & & & \\  & & \\  & & & \\  & & \\  & & & \\ \end{tabular}
\end{table} 
Table 2: Summary of the lipids and other metabolites identified in EVs with potential as biomarkers of different cancers. EVs derived from high and low metastasis triple negative breast cancer (TNBC) cell lines, D3H2 LN and D3H1, showed an increase in the levels of CHOL, SM, and a decrease in the levels of PC in their EVs. In addition, EVs derived from D3H2 LN were enriched in unsaturated diacylglycerols (DGs) compared with EVs from D3H1 [173] (Table 2). Moreover, studies performed on glioblastoma, hepatocellular carcinoma, and human bone marrow-derived mesenchymal stem cells (MSCs) have shown high abundance of SM and ceramides in EVs released by glioblastoma cells (U87), while opposite results were reported for EVs secreted by hepatocellular carcinoma cells (Huh7). PS was only slightly enriched in EVs released by all three cell lines, while the PC and PI content were higher in cells than in EVs [174] (Table 2). On another note, several lipid species present in EVs released from ovarian cancer cells (SKOV-3) differ when compared to those from ovarian surface epithelial cells (HOSEPiC). In particular, EVs from HOSEPiC cells were more abundant in PS, PI, PE, and phosphatidylglycerol (PG), while EVs secreted from SKOV-3 cells presented higher content in lysophosphatidylinositol (LPI), lysophosphatidylLysserine (LPS), lysophosphatidylinositol (LPG), lysophosphatidylcholine (LPC) [175] (Table 2). Lysophospholipids (LPLs) consist of lyso-glycerophospholipids and lysosphingolipids, which are implicated in important functional roles, e.g., through intracellular G protein-coupled receptor (GPCR)-mediated signaling. Although a comprehensive understanding of LPL levels and their distribution patterns is lacking, several studies have revealed that LPLs are associated with the development, progression, and metastasis of cancers, as in ovarian cancer [181]. On this note, analysis of the urine exosome lipid repertoire in patients with renal carcinoma suggested that lysophospholipids represent the most present lipid class than in healthy control cells [182]. Prostate cancer patients' urine exosomes (PCa) revealed up to nine differentially expressed lipid species, including lactosylceramide, with the highest patient/control ratio [176] (Table 2). To date, only a few studies have investigated the lipid composition of EVs in biofluids, due to difficulties in lipid isolation from these vesicles. There are increasing updates on the EVs' lipid composition, functionality, and potential use as biomarkers.