AU-rich elements (AREs) are RNA elements that enhance the rapid decay of mRNA. The fate of ARE-mRNA is controlled by ARE-binding proteins. HuR, a member of the embryonic lethal abnormal vision (ELAV) family of RNA-binding proteins, is involved in the export and stabilization of ARE-mRNA. In the vast majority of cancer cells, HuR constitutively relocates to the cytoplasm, resulting in the stabilization of ARE-mRNA. Previously, we described that the adenovirus gene product, E4orf6, which is necessary for virus replication, participates in ARE-mRNA export and stabilization. In the present study, we showed the oncolytic potential of E4orf6-deleted adenovirus dl355, which is expected to be replicated selectively in cancer cells. Virus production and cytolytic activity of dl355 were higher in cancer cells than in normal cells. HuR-depletion downregulated dl355 replication, demonstrating that ARE-mRNA stabilization is required for the production of this virus. Tumor growth was inhibited in nude mice by an intratumoral injection of dl355. Furthermore, dl355 had a stronger oncolytic effect than E1B55k-deleted adenovirus. These results indicate that dl355 has potential as an oncolytic adenovirus for a large number of cancers where ARE-mRNA is stabilized.