ABSTRACT
Gene-modified replication-competent adenoviruses (Ads) are emerging as a promising new modality for the treatment of cancer. We have previously shown that E1B 19kDa and E1B 55kDa gene deleted Ad (Ad-deltaE1B19/55) exhibits improved tumor-specific replication and cell lysis, leading to potent anti-tumor effect. As an additional effort to increase cancer cell-selectivity of replicating adenovirus, we have first generated eleven E1A-mutant Ads (Ad-mt#1~#11) with deletion or substitution in retinoblastoma (Rb) binding sites of E1A. Of these viruses, Ad-mt#7 demonstrated significantly improved cytopathic effect (CPE) and viral replication in a cancer cell-specific manner. To further increase the cancer cell-specific killing effect of Ad-mt#7, both E1B 19kDa and E1B 55kDa genes were deleted, resulting in an Ad-deltaE1Bmt7. As assessed using CPE assay, MTT assay, and immunoblot analysis for Ad fiber expression, Ad-deltaE1Bmt7 exerted markedly enhanced cancer cell-specific killing effect as well as viral replication in comparison to either Ad-mt#7 or Ad-deltaE1B19/55. Furthermore, the growth of established human cervical carcinoma in nude mice was significantly suppressed by intratumoral injection of Ad-deltaE1Bmt7. In summary, we have developed an oncolytic adenovirus with significantly improved therapeutic profiles for cancer treatment.