PIMREG and central nervous system cancer: Some lysosomal cathepsin proteases are released into the cytoplasmand translocate into the nucleus and are implicated in mechanismsof nucleocytoplasmic shuttling.19−23 Intracellular localization of cathepsins involved in nuclear importand export (CatB, CatK, CatL, and CatS)19 were examined in U87 glioma cells 15 min after treatment with buffercontrol, IgG control, or DX3 by confocal fluorescence microscopy.IgG control did not impact localization of these cathepsins, but DX3caused a marked shift of CatB signal into the nucleus (Figure 3A, Figure S1A,B).