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Paramyxoviruses for Tumor-targeted Immunomodulation: Design and Evaluation Ex Vivo
Published on: January 7, 2019
Optimisation of replication-selective oncolytic adenoviral mutants in combination with chemotherapeutics
1Centre for Molecular Oncology and Imaging, Institute of Cancer, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK. g.hallden@qmul.ac.uk
Abstract:
Replication-selective oncolytic adenoviruses are promising anti-tumour therapeutic agents that have been proven safe in hundreds of patients. While clinical efficacy was limited with the viral mutants alone, outcomes were improved in combination with chemotherapeutics. To further increase efficacy of viral-based therapies it is necessary to explore the cellular mechanisms responsible for enhanced tumour elimination in combination with cytotoxic drugs and to develop mutants with higher potency. To this end we generated a set of novel adenoviral mutants with deletions of the anti-apoptotic E1B19K-gene and the pRb-binding E1ACR2-region. Mutants with the E1B19K deletion significantly increased tumour cell killing in combination with cytotoxic drugs including gemcitabine, 5-fluorouracil (5-FU), docetaxel and mitoxantrone through enhancement of drug-induced apoptosis but did not sensitise normal cells to drugs. The double-deleted AdDeltaDelta (DeltaE1ACR2 and DeltaE1B19K) mutant had high cell killing activity in prostate and pancreatic carcinoma models. Replication was similar to the parental Ad5 and DeltaCR2 viruses in all tumour cells and was attenuated in normal cells. In combination with chemotherapeutics AdDeltaDelta synergistically enhanced cell death in all tested cancer cell lines and in prostate and pancreatic xenografts in vivo. These data suggest that the AdDeltaDelta mutant is a candidate for targeting of solid tumours specifically in combination with cytotoxic factors. Our findings imply that less toxic doses than currently practised in the clinic could efficiently target adenocarcinomas when combined with the AdDeltaDelta mutant.
Insights
Novel oncolytic adenoviruses, engineered with specific gene deletions, enhance cancer cell killing when combined with chemotherapy. This dual therapy shows promise for treating solid tumors, potentially allowing for reduced chemotherapy doses.
Area of Science:
- Oncology
- Virology
- Gene Therapy
Background:
- Replication-selective oncolytic adenoviruses show promise as anti-tumor agents, with improved efficacy when combined with chemotherapeutics.
- Further development requires understanding cellular mechanisms of enhanced tumor elimination and creating more potent viral mutants.
Purpose of the Study:
- To generate and evaluate novel adenoviral mutants with deletions in anti-apoptotic (E1B19K) and pRb-binding (E1ACR2) genes.
- To assess the efficacy of these mutants, particularly a double-deleted mutant (AdDeltaDelta), in combination with cytotoxic drugs against solid tumors.
Main Methods:
- Generation of adenoviral mutants with E1B19K gene deletion and/or E1ACR2 region deletion.
- Evaluation of tumor cell killing in vitro and in vivo (prostate and pancreatic carcinoma models) with and without chemotherapeutics (gemcitabine, 5-FU, docetaxel, mitoxantrone).
- Assessment of viral replication in tumor and normal cells.
Main Results:
- E1B19K-deleted mutants enhanced drug-induced apoptosis and tumor cell killing without sensitizing normal cells.
- The AdDeltaDelta mutant demonstrated high cell killing activity and synergistic enhancement of cell death with chemotherapeutics in vitro and in vivo.
- AdDeltaDelta showed similar replication to parental viruses in tumor cells but was attenuated in normal cells.
Conclusions:
- The AdDeltaDelta mutant shows significant potential as a therapeutic agent for solid tumors, especially when used in combination with cytotoxic chemotherapy.
- This combination therapy may allow for the use of lower, less toxic doses of chemotherapy in clinical settings.
- AdDeltaDelta represents a promising candidate for enhancing oncolytic virotherapy efficacy against adenocarcinomas.
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