Imagerie Moléculaire

Hervé Trillaud, Chrit Moonen

Laboratory for Molecular and Functional Imaging: from Physiology to Therapy

CNRS/ University Victor Segalen Bordeaux Bordeaux, France

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

Seeing genes in action

Molecular Imaging: Spatio-temporal mapping of gene expression and its physiological consequences

PET/SPECT

MRI

Optics

Ultrasound

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

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

Luciferase geneCMV promotor

+ luciferin

Mapping transgene expression in gene therapy: adding a spy

Cancer cells overexpressing luciferaseCancer cells overexpressing luciferase

Photon emissionLowik et al

Leiden, The Netherlands

Optical Imaging

Metastases of luciferase overexpressingcancer cells

i.p. luciferin

CCD Camera

intensifier screen

photonemission

Imageanalysis

0

500

1000

1500

2000

0 5 10 15 20 25 30

days

Photoncounting

Experimental bone metastasis 20 days after intra-cardiac injection (3x106 cells)

Day 20 Day 34Day 30Day 27Day 23

Paclitaxel15 mg/kg, iv, q.d.

Days 20-24

Vehicle

B

A

Lassota et al., Novartis

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

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

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

Imaging transgene expression: MRI

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

Weissleder et al., Nature Med. 6, 2000Tumor expressing transferrin receptor

Control (no transferrin receptor)

Parametric T2* map(color overlay proportional to T2*)

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

Target specific part MAB (fragments) Peptides Aptamers (short DNA/RNA

strings)

Linkage

Contrast agent (multiple) Gd Iron particle

Specific contrast agent design for MRI

Imaging of the HER-2/neu receptor with MRI

Artemov et al. Cancer Research, 2003

Non-HER expressingTumor line

HER expressingTumor line

In vitro In vivo

Melanoma Angiogenesis: Detection With v3 Integrin-Targeted Paramagnetic

Nanoparticles

Time course after injectionof target specific contrast agent

Wickline, Lanza et al St Louis

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

Prostate cancer: improved diagnostics using cell labeling:

Detection of metastases in Detection of metastases in lymph nodes using lymph nodes using USPIOUSPIO

(Sinerem, Combidex)(Sinerem, Combidex)

????

Harisinghani, Barentsz et al. NEJM 2003

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

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

Target specific part MAB (fragments) Peptides Aptamers (short DNA/RNA

strings)

Linkage

Contrast agent (multiple) Gd Iron particle

Drugs

Combined MR contrast agents for imaging/therapy

D

4x

ControlDXR-NP

Rejection of Mouse Melanoma 7d after -Targeted Doxorubicin Nanoparticles

Tumor Tumor

Inflammatory cells

0

25

50

75

100

0

25

50

75

100

Targeted DXR Control

rejection viable

Wickline, Lanza et al St Louis

MRI guided FUS for spatio-temporal control of gene expression under control of a heat sensitive

promoter

f zx

FUS heating with automatic feedback MR temperature control

Guilhon et al, J. Gene Med, J. Mol. Imag. 2003

Fully automatic tempcontrol in focal point:SD of 0.58 °C

Analysis of GFP gene Expression using Confocal Microscope

1 cm

Transmission Image Fluorescence Image

Heated region

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

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/differentiation in vivo for gene therapy purposes?

Transplantation of cells by intravascular injection (renal artery, rat): Bos et al. Radiology, 2004

referenceDay 2 after stem cell inj

Day 4 after stem cell inj Day 7 after stem cell inj Day 7 after stem cell injEx vivo

<1hr after stem cell inj

Transplantation of 5x106 cells by intravascular injection (portal vein): Bos et al. Radiology, 2004

reference Day 2 (CCl4) <1hr after stem cell inj

Day 4 post stem cell Day 8 post stem cell Day 12 post stem cell

Summary (1)Summary (1)

Molecular imaging allows :

the non-invasive spatio-temporal evaluation of gene

expression

the non-invasive characterization of disease processes on

the molecular levelmolecular level in vivo

the use of image biomarkers for therapy assessment

the further evaluation of animal modelsanimal models for human disease

the rapid development of new treatmentnew treatment strategies such

as gene and (stem) cell-based therapies

Summary (2)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

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