CA9 and neoplasm: Compared to levels of CAIX expression in control tumors, which increased significantly as tumors grew from 300 to 600 mm3, and declined as tumors became more vascularized, tumors from mice administered sunitinib demonstrated significantly higher levels of CAIX expression early during tumor progression, and levels remained consistently elevated at larger volumes (Figure 2a,c), consistent with increased hypoxia resulting from diminished vasculature.