Molecular Imaging and Biology

, Volume 16, Issue 2, pp 224–234

A Titratable Two-Step Transcriptional Amplification Strategy for Targeted Gene Therapy Based on Ligand-Induced Intramolecular Folding of a Mutant Human Estrogen Receptor

Authors

  • Ian Y. Chen
    • Department of Medicine, Division of Cardiovascular Medicine, Stanford University School of MedicineStanford University
  • Ramasamy Paulmurugan
    • Department of Radiology, Molecular Imaging Program at Stanford (MIPS), Stanford University School of MedicineStanford University
  • Carsten H. Nielsen
    • Cluster for Molecular Imaging, Department of Clinical Physiology, Nuclear Medicine and PET, RigshospitaletUniversity of Copenhagen
  • David S. Wang
    • Department of Radiology, Molecular Imaging Program at Stanford (MIPS), Stanford University School of MedicineStanford University
  • Vinca Chow
    • Department of AnesthesiologyBrigham and Women’s Hospital
  • Robert C. Robbins
    • Department of Cardiothoracic Surgery, Stanford University School of MedicineStanford University
    • Department of Radiology, Molecular Imaging Program at Stanford (MIPS), Stanford University School of MedicineStanford University
    • The Bio-X Program, Stanford University School of MedicineStanford University
    • Department of BioengineeringStanford University
    • Department of Material Science and EngineeringStanford University
Research Article

DOI: 10.1007/s11307-013-0673-4

Cite this article as:
Chen, I.Y., Paulmurugan, R., Nielsen, C.H. et al. Mol Imaging Biol (2014) 16: 224. doi:10.1007/s11307-013-0673-4

Abstract

Purpose

The efficacy and safety of cardiac gene therapy depend critically on the level and the distribution of therapeutic gene expression following vector administration. We aimed to develop a titratable two-step transcriptional amplification (tTSTA) vector strategy, which allows modulation of transcriptionally targeted gene expression in the myocardium.

Procedures

We constructed a tTSTA plasmid vector (pcTnT-tTSTA-fluc), which uses the cardiac troponin T (cTnT) promoter to drive the expression of the recombinant transcriptional activator GAL4-mER(LBD)-VP2, whose ability to transactivate the downstream firefly luciferase reporter gene (fluc) depends on the binding of its mutant estrogen receptor (ERG521T) ligand binding domain (LBD) to an ER ligand such as raloxifene. Mice underwent either intramyocardial or hydrodynamic tail vein (HTV) injection of pcTnT-tTSTA-fluc, followed by differential modulation of fluc expression with varying doses of intraperitoneal raloxifene prior to bioluminescence imaging to assess the kinetics of myocardial or hepatic fluc expression.

Results

Intramyocardial injection of pcTnT-tTSTA-fluc followed by titration with intraperitoneal raloxifene led to up to tenfold induction of myocardial fluc expression. HTV injection of pcTnT-tTSTA-fluc led to negligible long-term hepatic fluc expression, regardless of the raloxifene dose given.

Conclusions

The tTSTA vector strategy can effectively modulate transgene expression in a tissue-specific manner. Further refinement of this strategy should help maximize the benefit-to-risk ratio of cardiac gene therapy.

Key words

Gene therapyDrug-regulated gene expressionTranscriptional amplificationTranscriptional targetingIntramolecular foldingBioluminescence imaging

Copyright information

© World Molecular Imaging Society 2013