Based on these data, we decided to continue with two co-culture models: first, A-431 and C5120 cells, which can both be efficiently transduced with EGFR-retargeted HAdV5, where there is no apparent effect of the RGD motif; second, MCF-7 and C5120, where tumor cells are preferentially transduced and where the RGD motif contributes considerably to the transduction efficiency. This evidence concerns the gene EGFR and neoplasm.