RESUMEN
Human tissue kallikrein-binding protein (Kallistatin, KAL), a secretory protein that participates in the regulation of multiple signaling pathways by binding to the extracellular receptor, however, at present has not been reported about the intracellular activity, and whether it has the similar biological activity with extracellular activity. Here we constructed no signal peptide KAL (NSK) into the adeno-associated virus vector to explore the intracellular activity of KAL. Both the endothelial cell and lung cancer cells could express KAL, but not secreted after rAAV2-NSK transfection. The proliferation and migration of human umbilical vein endothelial cells (HUVECs) were inhibited, but the apoptosis rate was not affected. The proliferation rates, mobility and tubule formation of all the three tested lung cancer cells, such as NCI-H446, NCI-H460 and A549, were inhibited to different extents. This cellular study not only confirmed the intracellular activity, but also suggested it may serve as a kind of "balance factor" in multi-targeted controlling, which may provide a new train of thoughts to explain the regulatory contradiction in PI3K-Akt signaling pathways by KAL.