Daniel Portsmouth

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Replicating murine leukaemia virus-based vectors
for cancer gene therapy
Proteins Killing Tumour Cells Leiden, Oct 29th
2007

• Daniel Portsmouth
• RESEARCH INSTITUTE OF VIROLOGY AND BIOMEDICINE,
  VETERINARY UNIVERSITY OF VIENNA, AUSTRIA
• T 43-1-25077-2328, E daniel.portsmouth_at_vu-wien.
  ac.at

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Murine leukaemia virus-based vectors
MLV
RCR
RDR
Replication-competent retroviral vector
Replication-deficient retroviral vector
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Why MLV-based RCRs for cancer therapy ?

• Only transduce dividing cells (cancer selective)
• Stable therapeutic gene expression via proviral
  integration
• No pre-existing immunity in humans
• Small, well characterized genome
• MLV (RDRs) extensively tested in clinical trials,
  no SAEs so far
• No viraemia or presence of virus DNA after
  infection of immunocompetent mice or rhesus
  monkeys
• Spread can be abrogated using AZT

 
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RCR designs
Jespersen et al., Gene (1999)
Logg et al., Human Gene Therapy (2001)
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Influence of vector and host factors

• Replication kinetics and genomic stability
  evaluated in vitro and in s.c. tumours in vivo
• Effect of virus strain, vector design and host
  cell determined

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Influence of RCR design in vitro
Paar et al., J. Virol. (2007)
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Influence of RCR design in vivo
human U87-MG glioma s.c. tumours in nude mice
ACE-GFP
Paar et al., J. Virol. (2007)
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RCRs expressing suicide genes
PNP yCD
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RCRs expressing suicide genes
tumour-restricted replication
U87-MG intracranial glioma
therapeutic efficacy
Wang al., Neurosurg. Focus (2006)
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Targeting RCR vectors

• Transcription
• Colon cancer / B-catenin deregulated cancer (CTP4
  promoter)
• Liver (EIIPa1AT promoter)
• Prostate cancer (probasin promoter) Logg et al.,
  J. Virol. (2002)
• Infection (env, MMPs etc)
• Breast cancer (anti-HER2 antibodies) Tai et al.,
  Human Gene Therapy (2003)
• MMP-expressing cancer (MMP-cleavable blockers)
  Hartl et al., Gene Therapy (2005)

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Transcriptional targeting
MLV U3 (448 bps)
TATA
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Transcriptional targeting
CTP4-regulated replication
EII-Pa1AT-regulated replication
Metzl et al., J. Virol. (2006)
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Summary and Outlook

• Highly promising cancer gene therapy vectors for
  solid tumours
• Can efficiently elicit solid tumour destruction
• Can be transcriptionally targeted to express
  viral and therapeutic genes only in tumour cells
• Envelope can be modified to allow infection
  targeting

• Limitations
• Do not always spread in solid tumours
  (intratumoral barriers ?)
• Therapeutic gene size limited to 1.5 kb
• Potential to cause insertional mutagenesis

• Future Objectives
• Improve RCR intratumoral spread
• Evaluate novel small therapeutic genes
• Integration targeting to benign regions of host
  chromosome

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Acknowledgements
UCLA, California Noriyuki Kasahara Chris Logg

University of Veterinary Sciences,
Vienna Christian Doppler Research Foundation
University of Arhus C, Denmark Finn Skou Pedersen
Walter Günzburg Matthias Paar Christian
Metzl Juraj Hvlaty Daniela Mischek Reinhard Ertl
Ela Knapp Magdalena Pusch
University of Navarra, Spain Gabriela Kramer
Vectura, UK Kai Lipinski
University of Leiden Matthieu Noteborn Claude
Backendorf
Brian Salmons Matthias Renner