EGF and neoplasm: Figure 1A reveals that targeting both receptors simultaneously with EGF4KDEL leads to more potent cell killing than targeting either receptor alone. However, the activity of this agent does not require concomitant overexpression of both EGFR and IL-4R. As shown by Figure 1D, both the EGF and IL-4 ligands can contribute individually to the activity of EGF4KDEL, thus broadening the utility of this agent, allowing it to target tumours expressing varying amounts of EGFR or IL-4R in combination or individually.