Cathepsin B and uPAR Knockdown Inhibits Tumor-induced Angiogenesis by Modulating VEGF Expression in Glioma

Angiogenesis, which is the process of sprouting of new blood vessels from pre-existing vessels, is vital for tumor progression. Proteolytic remodeling of extracellular matrix is a key event in vessel sprouting during angiogenesis. Urokinase plasminogen activator receptor (uPAR) and cathepsin B are both known to be overexpressed and implicated in tumor angiogenesis. In the present study, we observed that knockdown of uPAR and cathepsin B using puPAR (pU), pCathepsin B (pC), and a bicistronic construct of uPAR and cathepsin B (pCU) caused significant inhibition of angiogenesis by disrupting the JAK/STAT pathway-dependent expression of VEGF. Further, transcriptional suppression of uPAR and cathepsin B inhibited tumor-induced migration, and proliferation of endothelial cells and decreased tumor-promoted expression of VEGFR-2, Rac1, gp91(phox), cyclin D1, Cdk4, and p-Rb in HMEC. Furthermore, U251 and SNB19 xenograft tissue sections from nude mice treated with pCU showed reduced expression of VEGF and CD31, which is a blood vessel visualization marker. Overall, results revealed that knockdown of uPAR and cathepsin B inhibited tumor-induced angiogenesis by disrupting the JAK/STAT pathway-dependent expression of VEGF. These data provide new insight in characterizing the pathways involved in the angiogenic cascade and for the identification of novel target proteins for use in therapeutic intervention for gliomas.