VEGFA and glioblastoma: However, the abnormal vasculature in GBM is immature and inefficient to deliver enough oxygen and nutrients to tumor cells, and hypoxic conditions upregulate the expression of vascular endothelial growth factors, which further promotes aggressive and immature angiogenesis and leads to worse hypoxia.[23,24] A recent animal study also confirmed the correlation between 18F-FMISO uptake and blood flow, blood volume, and the metabolic rate of oxygen,[25] which could explain why nCBV, nCBF, and Vp had a higher correlation with the uptake of 18F-FMISO than other parameters.