KDR and neoplasm: VEGFR-binding assays using U-87 MG cells (known to overexpress VEGFR) revealed a mean Kd value of 44.7 nM for the monomeric form and 0.45 nM for the dimeric form, indicating a nearly 100-fold improvement in U-87 MG tumor–bearing mice, which showed the dimeric probe was over five times greater than that of the monomeric probe across all time points, with statistical significance (p < 0.0001).