GREM1 and glioblastoma: Analysis of GREM1 expression on the surface of BC cell EVs by immuno-electron microscopy using a GREM1 antibody confirmed higher expression of GREM1 on BT-549 EVs compared to MCF7 EVs and, interestingly, lower expression on glioblastoma U87MG-derived EVs compared to the former two (Fig. 4A).