A, Expression profiling by qRT-PCR revealed HIF-1α upregulation in WM1617 VEGF-A KD (sh1) xenografts compared to nontarget controls. *, P<0.05. B, Western blotting confirmed HIF-1α upregulation in WM1617 VEGF-A KD (sh1) xenografts compared to nontarget controls. β-actin served as internal loading control. †Four out of five xenograft pairs generated were examined by Western blotting as one xenogaft pair was depleted for histological evaluation, including multilabel IF and fixed paraffin preparation.
C, Proposed model of the adaptive response to VEGF-A inhibition. VEGF-A stimulates vascularization of tumors via angiogenesis. Following VEGF-A inhibition, HIF-1α is increased and, in turn, promotes: 1) VM, an alternative vascularization mechanism; and 2) MSLC enrichment.