In the tumor environment, the linker was selectivelycleaved, thereby exposing LMWP to target GBM cells.120 Besides, in the approach above designed by Gao and co-workers,the anionic E8 was used to hinder the cationic property of R8 throughan MMP-2 sensitive linker, which further exposed R8 CPP in the tumorsite, circumventing their poor selectivity and improving their penetratingproperties.125. The gene discussed is MMP2; the disease is glioblastoma.