Fig. 5.

Sera from anti-EGFR peptide immune mice inhibit the growth and promote the killing of both EGFR and HER2 expressing cells. Cells were incubated with cetuximab (for A431) or trastuzumab (for MDA-MB-453) or with 1:25 dilutions of sera from either Asp or iso-Asp p580 immunized Balb/c mice. Cell proliferation was measured by ³H-thymidine incorporation, and growth inhibition calculated, as described in “Materials and methods”. a Growth inhibition of A431 cells by EGFR p580 immune sera. b Growth inhibition of MDA-MB-453 cells by EGFR p580 immune sera. For ADCC assays, cells were incubated with pre-immune or immune serum followed by incubation with human PBMC. ADCC and % cytotoxicity were calculated as described in “Materials and methods”. c ADCC of EGFR p580 immune sera against A431 cells. d ADCC of EGFR p580 immune serum against MDA-MB-453 cells. Rituximab served as a negative control for both cell lines. Trastuzumab and cetuximab served as positive controls for A431 and MDA-MB-453 cells, respectively. **p < 0.05; ***p < 0.001; NS, not significant; ND, inhibition not detected. Results are representative of three independent experiments