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Wang W, Guo X, Li YM, Wang XY, Yang XJ, Wang YF, Wang TY. Enhanced transgene expression using cis-acting elements combined with the EF1 promoter in a mammalian expression system. Eur J Pharm Sci 2018; 123:539-545. [DOI: 10.1016/j.ejps.2018.08.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 07/12/2018] [Accepted: 08/11/2018] [Indexed: 10/28/2022]
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Hofacre A, Yagiz K, Mendoza D, Lopez Espinoza F, Munday AW, Burrascano C, Singer O, Gruber HE, Jolly DJ, Lin AH. Efficient Therapeutic Protein Expression Using Retroviral Replicating Vector with 2A Peptide in Cancer Models. Hum Gene Ther 2018; 29:437-451. [PMID: 29216761 DOI: 10.1089/hum.2017.205] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Toca 511, a retroviral replicating vector (RRV), uses an internal ribosomal entry site (IRES) to express an optimized yeast cytosine deaminase (yCD2), which converts 5-fluorocytosine to 5-fluorouracil. This configuration is genetically stable in both preclinical mouse models and human clinical trials. However, the use of IRES (∼600 bp) restricts choices of therapeutic transgenes due to limits in RRV genome size. This study replaced IRES with 2A peptides derived from picornaviruses with or without a GSG linker. The data show that GSG-linked 2A (g2A) peptide resulted in higher polyprotein separation efficiency than non-GSG linked 2A peptide. The study also shows that RRV can tolerate insertion of two separate 2A peptides to allow expression of two transgenes without compromising the assembly and function of the virus in addition to insertion of a single 2A peptide to confirm genetic stability with yCD2, green fluorescent protein, and HSV-1 thymidine kinase. In a parallel comparison of the RRV-IRES-yCD2 and RRV-g2A-yCD2 configurations, the study shows the yCD2 protein expressed from RRV-g2A-yCD2 has higher activity, resulting in a higher survival benefit in an intracranial tumor mouse model. These data enable a wider range of potential product candidates that could be developed using the RRV platform.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Amy H Lin
- Tocagen, Inc. , San Diego, California
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Lin AH, Twitty CG, Burnett R, Hofacre A, Mitchell LA, Espinoza FL, Gruber HE, Jolly DJ. Retroviral Replicating Vector Delivery of miR-PDL1 Inhibits Immune Checkpoint PDL1 and Enhances Immune Responses In Vitro. MOLECULAR THERAPY. NUCLEIC ACIDS 2016; 6:221-232. [PMID: 28325288 PMCID: PMC5363416 DOI: 10.1016/j.omtn.2016.11.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 11/15/2016] [Accepted: 11/16/2016] [Indexed: 01/03/2023]
Abstract
Tumor cells express a number of immunosuppressive molecules that can suppress anti-tumor immune responses. Efficient delivery of small interfering RNAs to treat a wide range of diseases including cancers remains a challenge. Retroviral replicating vectors (RRV) can be used to stably and selectively introduce genetic material into cancer cells. Here, we designed RRV to express shRNA (RRV-shPDL1) or microRNA30-derived shRNA (RRV-miRPDL1) using Pol II or Pol III promoters to downregulate PDL1 in human cancer cells. We also designed RRV expressing cytosine deaminase (yCD2) and miRPDL1 for potential combinatorial therapy. Among various configurations tested, we showed that RRV-miRPDL1 vectors with Pol II or Pol III promoter replicated efficiently and exhibited sustained downregulation of PDL1 protein expression by more than 75% in human cancer cell lines with high expression of PDL1. Immunologic effects of RRV-miRPDL1 were assessed by a trans-suppression lymphocyte assay. In vitro data showed downregulation of PDL1+ tumor cells restored activation of CD8+ T cells and bio-equivalency compared to anti-PDL1 antibody treatment. These results suggest RRV-miRPDL1 may be an alternative therapeutic approach to enhance anti-tumor immunity by overcoming PDL1-induced immune suppression from within cancer cells and this approach may also be applicable to other cancer targets.
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Affiliation(s)
- Amy H Lin
- Tocagen Inc., 3030 Bunker Hill Street, Suite 230, San Diego, CA 92109, USA
| | | | - Ryan Burnett
- Tocagen Inc., 3030 Bunker Hill Street, Suite 230, San Diego, CA 92109, USA
| | - Andrew Hofacre
- Tocagen Inc., 3030 Bunker Hill Street, Suite 230, San Diego, CA 92109, USA
| | - Leah A Mitchell
- Tocagen Inc., 3030 Bunker Hill Street, Suite 230, San Diego, CA 92109, USA
| | | | - Harry E Gruber
- Tocagen Inc., 3030 Bunker Hill Street, Suite 230, San Diego, CA 92109, USA
| | - Douglas J Jolly
- Tocagen Inc., 3030 Bunker Hill Street, Suite 230, San Diego, CA 92109, USA.
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