ERBB2 and cancer: Incorporation of the FMDV2 derived, αvβ6 integrin targeted A20 peptide into the HI loop of the fiber knob of the Ad5NULL platform has been shown to facilitate tumor-restricted transduction and transgene expression in an immunocompromised mouse xenograft model.44,55 Similarly, DARPins for cancer-overexpressed receptors, such as HER2/neu, have also been demonstrated to facilitate cancer-specific delivery for AAV.56