We first explored the basal expression level of miR-145-5p and miR-5096 in HMEC and U87 cells, in homotypic cultures. We observed that miR-145-5p was almost exclusively expressed in HMEC and could not be detected at a significant level in U87 (Figure 1A). In contrast, miR-5096 was mainly expressed in U87 and poorly detected in HMEC (Figure 1B). We subsequently labelled U87 with the cell tracker DiL-C18 , and co-cultured these cells with HMEC before flow cytometry sorting. As an additional control, the expression levels of these miRs were measured in U87 and HMEC, sorted immediately after being mixed, and were similar to that measured in cells cultured separately, i.e. miR-145-5p and miR-5096 remained poorly detected in U87 and HMEC, respectively (not shown). After 12 hours of co-culture, mir145-5p expression level was increased in both U87 (by 40%) and HMEC (by 20%) (Figure 1A). At the same time, miR-5096 expression level was significantly increased in HMEC while decreased by 20% in U87 (Figure 1B). These observations led us to explore miR exchanges between these two cell types.