Imagerie Mol

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• Imagerie Moléculaire
• Hervé Trillaud, Chrit Moonen
• Laboratory for Molecular and Functional Imaging
• from Physiology to Therapy
• CNRS/ University Victor Segalen Bordeaux
• Bordeaux, France

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Gene expression profile
List of 210 genes with highest differences in
expression profile between Prostate Cancer and
Benign Prosthetic Hyperplasia
Down regulation
Up regulation
Luo et al, Cancer Res, 2001
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Seeing genes in action

• Molecular Imaging Spatio-temporal mapping of
  gene expression and its physiological
  consequences
• PET/SPECT
• MRI
• Optics
• Ultrasound

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Outline

• Improved diagnostics for (individualized) therapy
• Seeing genes in action(trans)gene expression
• Seeing drugs in action
• Biomarkers
• Therapy guided by Molecular Imaging
• Combined diagnostic/therapeutic contrast agents
• Local drug delivery
• Spatio-temporal control of transgene expression
• Stem cell therapy
• Conclusion/Challenges ahead

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Outline

• Improved diagnostics for (individualized) therapy
• Seeing genes in action(trans)gene expression
• Seeing drugs in action
• Biomarkers
• Therapy guided by Molecular Imaging
• Combined diagnostic/therapeutic contrast agents
• Local drug delivery
• Spatio-temporal control of transgene expression
• Stem cell therapy
• Conclusion/Challenges ahead

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Mapping transgene expression in gene therapy
adding a spy Cancer cells overexpressing
luciferase
Luciferase gene
CMV promotor
luciferin
Lowik et al Leiden, The Netherlands
Photon emission
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Optical Imaging
photon emission
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Experimental bone metastasis 20 days after
intra-cardiac injection (3x106 cells)
A
Vehicle
Day 20
Day 34
Day 30
Day 27
Day 23
B
Paclitaxel 15 mg/kg, iv, q.d. Days 20-24
Lassota et al., Novartis
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Optical Imaging

• Very powerful tool for rapid evaluation of drug
  efficacy
• Limited clinical use because of light
  penetration/scattering problems
• seeing drugs in action using molecular imaging

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Mapping gene expression MRI

• As compared to PET and optical methods, MRI
  requires a higher concentration of contrast agent
• Need a spy with amplification of contrast

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Imaging gene expression MRIAmplification
required
MR contrast agent is a weak relaxation agent
until galactosidase has cleaved the galactose
unit inner sphere of Gd3 becomes available to
water 
Fluorescence image
MRI
Xenopus Laevis embryos Galactosidase Green
Fluorescent Protein mRNA injection on right.
Meade et al. Nature Biotech 2000
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Imaging transgene expression MRI

• Co-expression of transferrin receptor, probed
  with super-paramagnetic particles

Parametric DT2 map (color overlay proportional
to DT2)
Control (no transferrin receptor)
Tumor expressing transferrin receptor
Weissleder et al., Nature Med. 6, 2000
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Expression of endogenous genes of special
interest in cancer

• General for almost all tumors
• Angiogenesis (VEGF receptor, Integrins)
• Proteases (Cathepsin, Matrix MetalloProtease)
• Apoptosis (Annexin V)
• Specific
• HER2/neu (overexpressed in 25 of breast cancers)
• P53
• Need for specific contrast agent

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Specific contrast agent design for MRI

• Target specific part
• MAB (fragments)
• Peptides
• Aptamers (short DNA/RNA strings)
• Linkage
• Contrast agent (multiple)
• Gd
• Iron particle

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Imaging of the HER-2/neu receptor with MRI
In vitro
In vivo
Non-HER expressing Tumor line
HER expressing Tumor line
Artemov et al. Cancer Research, 2003
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Melanoma Angiogenesis Detection With avb3
Integrin-Targeted Paramagnetic Nanoparticles
Time course after injection of target specific
contrast agent
Wickline, Lanza et al St Louis
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Imaging biomarkers for cancer diagnosis and
treatment

• Identification of unique signatures related to
  gene expression
• Early diagnosis and detection of metastases (PET
  FDG)
• Assessment of drug response
• Helpful in therapeutic decision stratification
• Major field of impact for MRI
• Perfusion changes in validation of angiogenesis
  drugs
• Diffusion changes in drug response
• Choline metabolism
• Thermal dose assessment in tumor ablation
• Macrophage activity

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Prostate cancer improved diagnostics using
cell labeling
?
Detection of metastases in lymph nodes using
USPIO (Sinerem, Combidex)

Harisinghani, Barentsz et al. NEJM 2003
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Outline

• Improved diagnostics for (individualized) therapy
• Seeing genes in action(trans)gene expression
• Seeing drugs in action
• Biomarkers
• Therapy guided by Molecular Imaging
• Combined diagnostic/therapeutic contrast agents
• Local drug delivery
• Spatio-temporal control of transgene expression
• Stem cell therapy
• Conclusion/Challenges ahead

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Combined diagnostic/therapeutic contrast
agents/drugs

• Radio-labelled drugs for detection (PET, SPECT)
  and radio-therapy
• Specific contrast agent used subsequently for
  (pro)drug delivery
• Modular contrast agents for MRI, US

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Combined MR contrast agents for imaging/therapy

• Target specific part
• MAB (fragments)
• Peptides
• Aptamers (short DNA/RNA strings)
• Linkage
• Contrast agent (multiple)
• Gd
• Iron particle
• Drugs

D
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Rejection of Mouse Melanoma 7d after
anb3-Targeted Doxorubicin Nanoparticles
Tumor
Tumor
4x
Inflammatory cells
Control
rejection
viable
anb3-DXR-NP
Wickline, Lanza et al St Louis
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MRI guided FUS for spatio-temporal control of
gene expression under control of a heat sensitive
promoter

• FUS heating with automatic feedback MR
  temperature control

Fully automatic temp control in focal point SD
of 0.58 C
Guilhon et al, J. Gene Med, J. Mol. Imag. 2003
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Analysis of GFP gene Expression using Confocal
Microscope
1 cm
Heated region
Transmission Image
Fluorescence Image
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Outline

• Improved diagnostics for (individualized) therapy
• Seeing genes in action(trans)gene expression
• Seeing drugs in action
• Biomarkers
• Therapy guided by Molecular Imaging
• Combined diagnostic/therapeutic contrast agents
• Local drug delivery
• Spatio-temporal control of transgene expression
• Stem cell therapy
• Conclusion/Challenges ahead

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Issues in imaging research of stem cells

• When and how do stem cells migrate to their
  target tissue?
• When and how do stem cells differentiate in vivo?
• What is the timeframe of stem cell multiplication
  and functional recovery at the target site?
• Can we influence stem cell behavior/differentiatio
  n in vivo for gene therapy purposes?

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Transplantation of cells by intravascular
injection (renal artery, rat) Bos et al.
Radiology, 2004
reference
Day 2 after stem cell inj
lt1hr after stem cell inj
Day 7 after stem cell inj
Day 7 after stem cell inj Ex vivo
Day 4 after stem cell inj
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Transplantation of 5x106 cells by intravascular
injection (portal vein) Bos et al. Radiology,
2004
reference
Day 2 (CCl4)
lt1hr after stem cell inj
Day 4 post stem cell
Day 8 post stem cell
Day 12 post stem cell
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Summary (1)

• Molecular imaging allows
• the non-invasive spatio-temporal evaluation of
  gene expression
• the non-invasive characterization of disease
  processes on the molecular level in vivo
• the use of image biomarkers for therapy
  assessment
• the further evaluation of animal models for human
  disease
• the rapid development of new treatment strategies
  such as gene and (stem) cell-based therapies

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Summary (2)

• Molecular imaging will lead to
• a need for specialists understanding molecular
  biology, imaging and chemistry
• blurring between diagnostics and treatment
• a new look at clinical imaging instruments with
  combined technologies MRI/(focused)ultrasound
  PET/CT MRI/PET
• a large role for optical Molecular Imaging of
  mice
• a paradigm shift in health care towards early
  molecular diagnostics and image guided molecular
  therapy

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Ackowledgment

• Many thanks for contributions and discussions
• Andreas Jacobs Ralph Weissleder Tobias
  Schäffter
• Alan Koretsky Chris Bakker
  Simon Cherry
• Nicolas Grenier Kullervo Hynynen Tom
  Meade
• Bertrand Tavitian Peter Lassota
  Silvio Aime
• Clemens Lowik Ronald Blasberg Sam
  Wickline
• Arend Heerschap Jim Basilion Dimitri
  Artemov
• Zaver Bhujwalla Jelle Barentsz Robert
  Muller
• Mark Bednarski King Li Michal Neeman
• Jeff Bulte Joe Frank
  Hervé Trillaud