PKN1 and glioblastoma: As we did not detect significant changes in the invasiveness-related proteases in U87 cells, we believe that the MSC- and DBK-induced migration is related to the changes in intracellular calcium transients, through a mechanism described by Seifert and Sontheimer62.The intracellular calcium ion transients in GBM cells in vitro induced the formation of small bleb-like protrusions at the plasma membrane, which stimulated an amoeboid phenotype of cell migration that was unrelated to proteolytic activity and ECM degradation63.