RNA interference-mediated simultaneous down-regulation of urokinase-type plasminogen activator receptor and cathepsin B induces caspase-8-mediated apoptosis in SNB19 human glioma cells

The invasive character of gliomas depends on proteolytic cleavage of the surrounding extracellular matrix. Cathepsin B and urokinase-type plasminogen activator receptor (uPAR) together are known to be overexpressed in gliomas and, as such, are attractive targets for gene therapy. In the present study, we used plasmid constructs to induce the RNA interference (RNAi)-mediated down-regulation of uPAR and cathepsin B in SNB19 human glioma cells. We observed that the simultaneous down-regulation of uPAR and cathepsin B induces the up-regulation of proapoptotic genes and initiates a collapse in mitochondrial Delta psi. Cathepsin B and uPAR down-regulated cells showed increases in the expression of activated caspase-8 and DFF40/caspase-activated DNase. Nuclear translocation of AIF and Fas ligand translocation to the cell membrane were also observed. Ki67 and X-linked inhibitor of apoptosis protein levels decreased, thereby indicating apoptosis. These results suggest the involvement of uPAR-cathepsin B complex on the cell surface and its role in maintaining the viability of SNB19 glioma cells. In conclusion, RNAi-mediated down-regulation of uPAR and cathepsin B initiates a partial extrinsic apoptotic cascade accompanied by the nuclear translocation of AIF.