RESUMO
We have engineered a human adenovirus, ONYX-411, that selectively replicates in human tumor cells, but not normal cells, depending upon the status of their retinoblastoma tumor suppressor protein (pRB) pathway. Early and late viral gene expression as well as DNA replication were significantly reduced in a functional pRB-pathway-dependent manner, resulting in a restricted replication profile similar to that of nonreplicating adenoviruses in normal cells both in vitro and in vivo. In contrast, the viral life cycle and tumor cell killing activity of ONYX-411 was comparable to that of wild-type adenovirus following infection of human tumor cells in vitro as well as after systemic administration in tumor-bearing animals.
Assuntos
Adenovírus Humanos/genética , Proteínas de Ciclo Celular , Ciclo Celular/genética , Proteínas de Ligação a DNA , Vetores Genéticos/genética , Neoplasias Experimentais/terapia , Fatores de Transcrição/genética , Replicação Viral/genética , Proteínas E1A de Adenovirus/genética , Proteínas E1A de Adenovirus/metabolismo , Adenovírus Humanos/patogenicidade , Animais , Antineoplásicos , Replicação do DNA , DNA Viral/genética , Vírus Defeituosos , Fatores de Transcrição E2F , Fibroblastos/fisiologia , Regulação Viral da Expressão Gênica/genética , Humanos , Camundongos , Camundongos Knockout , Neoplasias Experimentais/patologia , Regiões Promotoras Genéticas , Proteína do Retinoblastoma/genética , Proteína do Retinoblastoma/metabolismo , Taxa de Sobrevida , Transplante Heterólogo , Células Tumorais Cultivadas/patologiaRESUMO
ONYX-015 has been used successfully in the clinic as a cancer therapeutic in combination with chemotherapy. The combination of ONYX-015 and chemotherapy appears to be more efficacious than either regimen alone. In this study, we try to enhance this combination by "arming" ONYX-015 with a therapeutic transgene, an approach more commonly used with nonreplicating viruses in the context of gene therapy. We chose the prodrug converting enzyme carboxylesterase (CE), which converts the camptothecin derivative CPT-11 (irinotecan) to the much more potent chemotherapeutic SN-38. The transgene was introduced into three distinct positions in the E3 region of the adenovirus genome to allow either early or late expression during the virus life cycle. We demonstrate that each of these ONYX-015-based adenoviruses expresses an active CE enzyme that can efficiently convert CPT-11 to SN-38. Furthermore, the cytotoxicity of CE-expressing viruses, but not control viruses, is enhanced significantly in the presence of the prodrug. Finally, we demonstrate that we can achieve transgene expression and activity in vivo in a human tumor xenograft model, and that treatment with a CE-expressing virus in combination with CPT-11 enhances survival of tumor-bearing mice. These results indicate that the addition of a prodrug converting enzyme may be a feasible approach to additionally enhance the efficacy of replicating adenoviruses as cancer therapeutics.