KDR and cancer: PRX177561 reduced the expression of Nestin in vivo indicating that CXCR4 antagonism also reduced the maintenance of the cancer stem cell population as previously demonstrated [40] It was interesting to note that the subcutaneous tumors less susceptible to bevacizumab and sunitinib (i.e., those larger tumors after treatment) expressed higher levels of SDF1α, CXCR4, and angiopoietin 2, after blockade of VEGFR signaling with these two agents.