Figure 5.

Cell death induction of Db-scTRAIL proteins in vitro. The bioactivity of Db-Glyco-scTRAIL-FAVSGAA (left), Db10-Glyco-scTRAIL-FAVSGAA (middle) and Db-Glyco-scTRAIL-FAVSGIA (right, filled circles) was assayed in vitro in presence of the apoptosis sensitizer bortezomib (Brt) on Colo205 (upper, 250 ng/ml Brt), HT1080 (middle, 10 ng/ml Brt) and HCT116 (lower, 5 ng/ml Brt) tumor cells. Db-scTRAIL-95L8 served as a reference (filled squares). After 16 hours of incubation, crystal violet staining was performed. In order to demonstrate EGFR-dependent increase of the bioactivity, the binding of the fusion proteins was competed by blocking with 70 nM cetuximab (open symbols), resulting in abolished EGFR targeting and thus lower bioactivity. Mean ± SD (n = 3).