Comparison of the E3 and L3 regions for arming oncolytic adenoviruses to achieve a high level of tumor-specific transgene expression

Robinson, Michael J.; Ge, Ying; Ko, Derek; Yendluri, S; Laflamme, Genevieve; Hawkins, LK; Jooss, Karin

doi:10.1038/sj.cgt.7701093

Cited by 13 publications

(13 citation statements)

References 37 publications

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“…During the protein translation process, the 2A peptide self-cleaves, leading to initial cleavage of the two proteins, and the furin cleavage sequence enables endogenous furin cleavage of residual amino acids derived from the 2A cleavage sequence from the C terminus of the first protein located downstream of the promoter. Armed dlE102 vectors were constructed by inserting the 2A-furin transgene expression cassette either upstream (DMFL) or downstream (DLFM) of the MAV-1 L3 gene; this gene is homologous to the human Ad5 23K protease gene that is reported to be a suitable insertion site for achieving a high level of transgene expression when transgenes are linked to viral genes by a splice acceptor sequence (51) (Fig. 3).…”

Section: Resultsmentioning

confidence: 99%

“…The MAV-1 L3 gene is homologous to the human Ad5 23K gene that is expressed late during virus infection following DNA replication (51). Insertion of the transgene expression cassette downstream of L3 (DLFM) had no effect on virus growth and allowed a high level of transgene expression, both in vitro and in vivo, that was dependent on virus replication.…”

Section: Discussionmentioning

confidence: 99%

“…Most adenoviral vector arming strategies involve gene replacement (27) or the use of splice acceptor sequences to link transgenes to endogenous viral genes (30,51). Both of these approaches require detailed knowledge of viral gene functions and transcription maps, neither of which has been fully defined for the MAV-1 genome.…”

Section: Discussionmentioning

confidence: 99%

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Novel Immunocompetent Murine Tumor Model for Evaluation of Conditionally Replication-Competent (Oncolytic) Murine Adenoviral Vectors

Robinson

et al. 2009

J Virol

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Oncolytic adenoviral vectors that express immunostimulatory transgenes are currently being evaluated in clinic. Preclinical testing of these vectors has thus far been limited to immunodeficient xenograft tumor models since human adenoviruses do not replicate effectively in murine tumor cells. The effect of the immunostimulatory transgene on overall virus potency can therefore not be readily assessed in these models. Here, a model is described that allows the effective testing of mouse armed oncolytic adenovirus (MAV) vectors in immunocompetent syngeneic tumor models. These studies demonstrate that the MAV vectors have a high level of cytotoxicity in a wide range of murine tumor cells. The murine oncolytic viruses were successfully armed with murine granulocyte-macrophage colony-stimulating factor (mGM-CSF) by a novel method which resulted in vectors with a high level of tumor-specific transgene expression. The mGM-CSF-armed MAV vectors showed an improved level of antitumor potency and induced a systemic antitumor immune response that was greater than that induced by unarmed parental vectors in immunocompetent syngeneic tumor models. Thus, the oncolytic MAV-1 system described here provides a murine homolog model for the testing of murine armed oncolytic adenovirus vectors in immunocompetent animals. The model allows evaluation of the impact of virus replication and the host immune response on overall virus potency and enables the generation of translational data that will be important for guiding the clinical development of these viruses.Oncolytic adenoviral vectors are currently being developed for the treatment of various cancers (1, 5, 33). The preclinical characterization of oncolytic adenoviral vectors has so far been restricted to immunodeficient xenograft tumor models (29, 31, 49) because human adenoviruses do not replicate efficiently in murine tumor cells (15,22,55). While these immunodeficient animal models can demonstrate effective replication in and destruction of human tumors by adenovirus type 5 (Ad5)-based vectors, the viruses do not replicate in mouse tissues and the models thus cannot assess the complete safety and efficacy profile of the vectors in normal tissue, nor do they permit evaluation of the impact of an active immune system on overall vector potency. In contrast, the effect of virus replication and the immune response could be evaluated in an immunocompetent syngeneic tumor model, which is especially important when such viruses are armed with immunomodulatory transgenes to increase their potency. In this report, we describe the use of a species-specific mouse armed oncolytic adenovirus type 1 (MAV-1) vector that can replicate in murine cells (25) as a murine virus homolog to the human oncolytic adenoviruses. MAV-1 is a 31-kb double-stranded DNA virus that has a genomic structure and organization comparable to those of human Ad5 (37, 59), and it has previously been used in an in vivo experimental model to study adenovirus replication in an immunocompetent host (36,40

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Novel Immunocompetent Murine Tumor Model for Evaluation of Conditionally Replication-Competent (Oncolytic) Murine Adenoviral Vectors

Robinson

et al. 2009

J Virol

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“…After the hexon significantly affected viral replication, but downstream the 23K gene showed the highest levels of transgene expression when compared to E3-19K or E3-14.7K replacements. Linking transgene expression to the L3 transcripts, which are abundant at the late phase, achieved high levels of transgene expression without affecting viral growth in a non-deleted adenoviral backbone [48].…”

Section: Transgene Location Affects Expression Levels and Fitness Of mentioning

confidence: 99%

Effect of Transgene Location, Transcriptional Control Elements and Transgene Features in Armed Oncolytic Adenoviruses

Farrera-Sal

Fillat

Alemany

2020

Cancers

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Clinical results with oncolytic adenoviruses (OAds) used as antitumor monotherapies show limited efficacy. To increase OAd potency, transgenes have been inserted into their genome, a strategy known as "arming OAds". Here, we review different parameters that affect the outcome of armed OAds. Recombinant adenovirus used in gene therapy and vaccination have been the basis for the design of armed OAds. Hence, early region 1 (E1) and early region 3 (E3) have been the most commonly used transgene insertion sites, along with partially or complete E3 deletions. Besides transgene location and orientation, transcriptional control elements, transgene function, either virocentric or immunocentric, and even the codons encoding it, greatly impact on transgene levels and virus fitness.

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“…Thus, additional insertion sites within E3 may be possible 32. Finally, transgenes have also been expressed from the L3 region of the genome 33. This strategy, described by Robinson et al , also relied on a splice acceptor sequence but retained all viral genes.…”

Section: Placement Of Transgenesmentioning

confidence: 99%

Armed replicating adenoviruses for cancer virotherapy

Cody

Douglas

2009

Cancer Gene Ther

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Conditionally replicating adenoviruses (CRAds) have many advantages as agents for cancer virotherapy and have been safely used in human clinical trials. However, replicating adenoviruses have been limited in their ability to eliminate tumors by oncolysis. Thus, the efficacy of these agents must be improved. To this end, CRAds have been engineered to express therapeutic transgenes that exert antitumor effects independent of direct viral oncolysis. These transgenes can be expressed under native gene control elements, in which case placement within the genome determines the expression profile, or they can be controlled by exogenous promoters. The therapeutic transgenes used to arm replicating adenoviruses can be broadly classified into three groups. There are those that mediate killing of the infected cell, those that modulate the tumor microenvironment and those with immunomodulatory functions. Overall, the studies to date in animal models have shown that arming a CRAd with a rationally chosen therapeutic transgene can improve its antitumor efficacy over that of an unarmed CRAd. However, a number of obstacles must be overcome before the full potential of armed CRAds can be realized in the human clinical context. Hence, strategies are being developed to permit intravenous delivery to disseminated cancer cells, overcome the immune response and enable in vivo monitoring of the biodistribution and activity of armed CRAds.

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Comparison of the E3 and L3 regions for arming oncolytic adenoviruses to achieve a high level of tumor-specific transgene expression

Cited by 13 publications

References 37 publications

Novel Immunocompetent Murine Tumor Model for Evaluation of Conditionally Replication-Competent (Oncolytic) Murine Adenoviral Vectors

Novel Immunocompetent Murine Tumor Model for Evaluation of Conditionally Replication-Competent (Oncolytic) Murine Adenoviral Vectors

Effect of Transgene Location, Transcriptional Control Elements and Transgene Features in Armed Oncolytic Adenoviruses

Armed replicating adenoviruses for cancer virotherapy

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