S100A4 and leukemia: A CCK-8 assay was performed to observe the survival of leukemia cells in the absence of S100A4. As shown in Fig. 5e, similar to our previous data, more cells survived after treatment with BM-MSC-exos, and there was a significant difference in cell viability between the BM-MSC-exo-treated group and the group without BM-MSC-exos treatment.