Figure 3.

EGFR and EGFRvIII expressed on U87MG cell lines were affinity labelled with [¹²⁵I]-EG₂ in the absence and presence of 100-fold excess unlabelled EG₂ (A, left). The resulting bands were competed for by unlabelled sdAb and corresponded to the expected molecular weight as confirmed by Western blot (A, right). IC₅₀ values were calculated by fitting [¹²⁵I]-EG₂ cell binding data to a one-site competition model using non-linear regression. For monovalent EG₂ binding to EGFR on the surface of U87MG.wtEGFR cells, the average IC₅₀ was 7.04 ± 2.67 × 10⁻⁸ M (B). Similarly, the average IC₅₀ on U87MG.EGFRvIII cells was 5.98 ± 0.12 × 10⁻⁸ M (C).