The murine EGFR+ HNSCC tumor cell line MOC2, established from a carcinogen-induced oral SCC in a C57BL/6 mouse (30 (link)), was purchased from Kerafast, Inc. The cell line was authenticated by STR (short tandem repeat) and was free of pathogens. Purified fusion toxins were analyzed using 4–12% SDS-PAGE gels. The gels were stained with Gel Code Blue Staining Reagent (Thermo Fisher Scientific, Inc.) and mounted with DryEase Mini Cellophane (Thermo Fisher Scientific, Inc.). Western blot analysis was performed as previously described (31 (link)). Briefly, proteins (~1 µg in 15 µl per sample) were separated on 4–12% SDS-PAGE gels and transferred onto nitrocellulose membranes (Thermo Fisher Scientific, Inc.). The membranes were blocked with 5% blotting grade blocker non-fat dry milk (Bio-Rad Laboratories, Inc.) in 1X PBS, 0.02% Tween 20 for 1 h with shaking and washed once with 1X PBS, pH 7.4, 0.2% Tween 20 at room temperature with shaking. The three EGF fusion toxins were detected using mouse anti-DT, mouse anti-human EGF, or mouse anti-human IL2 primary antibodies (1:1,000) and rat anti-mouse IgG-HRP as the secondary antibody (1:4,000). The proteins were detected using the TMB (Tetramethylbenzidine) membrane peroxidase substrate (SeraCare; LGC Clinical diagnostics). The antibodies used in the present study are listed in Table SI.