The first CRAds were based on the partial deletion of the E1B sequence (E1B-55K) (Fig. 3c).48 As viral genome replication can be completed without E1B-55K in most tumor cells, as they lack p53, E1B-55K-deleted Ads only undergo genome amplification and subsequent lysis in a patient’s tumor cells, leaving non-tumor cells unaffected. This evidence concerns the gene TP53 and neoplasm.