HMGB1 and neoplasm: To directly assess the role of Ac-HMGB1 secreted from GemOE tumor cells on induction of CXCR4 on the surface of MSCs, we again exposed early passage MSCs for 24 h to fresh HME medium supplemented or not with recombinant HMGB1 (rHMGB1, 10 μg/ml) that was in vitro acetylated.