CCL2 and precursor B-cell acute lymphoblastic leukemia: Notably, POSTN derived from MSCs is known to promote B-ALL proliferation by activating the integrin-ILK-NF-κB-CCL2 pathway.17 No proteins were enriched by more than 1.5-fold in co-culture media compared to MSC mono-culture (Figure 2E, Table S4) showing that soluble mediators driving ALL-MSC interactions are MSC derived.