Elsevier

Academic Radiology

Volume 9, Issue 2, Supplement, February 2002, Pages S314-S315
Academic Radiology

Session 3
Molecular Imaging of MMP Expression and Therapeutic MMP Inhibition

https://doi.org/10.1016/S1076-6332(03)80214-3Get rights and content

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Rationale and Objectives

Matrix metalloproteinase (MMP), a family of proteolytic enzymes, are critically involved in tumor progression and angiogenesis (1). A number of MMP-inhibitors have been developed as cytostatic and antiangiogenic agents. Direct imaging of enzyme activity has only recently been proposed using near infrared fluorescence (NIRF) imaging and enzyme-sensitive optical probes (2). The purpose of this study was to: (a) develop an imaging approach to visualize matrix metalloproteinase-2 (MMP-2) activity

Materials and Methods

An MMP-2 sensitive NIRF-probe was designed by coupling multiple fluorochromes to a long circulating graft copolymer via an MMP-specific peptide sequence. The selectivity of the probe was tested against a panel of MMP's in vitro. Inhibition studies were performed using different amounts of a clinical MMP-inhibitor (AG3340 (prinomastat), Aguron/Pfizer, San Diego, CA). Animal tumor models were established using an MMP-2 positive (human fibrosarcoma, HT1080) and an MMP-2 negative tumor cell line

Results

Each assembled probe contained on average 12 cleavable fluorochromes, which resulted in an efficient quenching in its native state. In vitro, a strong and dose dependent increase of fluorescence was detected after dequenching of the probe with the purified enzyme (up to 8.5-fold). Tested against a panel of MMP's the probe revealed a high selectivity for MMP-2 while other MMP's (MMP-1, MMP-7, MMP-8 and MMP-9) activated the probe less efficiently. Activation of the probe was inhibited in a dose

Conclusion

Our data show the feasibility of imaging MMP-2 enzyme activity in vivo using new near-infrared optical imaging technology and “smart” MMP-sensitive probes. Moreover, imaging of therapeutic protease inhibition is feasible using this approach. Therefore, this is a powerful tool not only to evaluate molecular expression patterns of proteases but also to monitor novel anti-cancer therapies in vivo.

Acknowledgements

The authors would like to thank Agouron Pharmaceuticals and Pfizer for providing prinomastat, and R. Feeley, S. Gregory, and D. Shalinsky (Department of Research Pharmacology) for helpful discussions and critical review of the manuscript of the original manuscript.

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Supported in part by NIH CA088365 and a RSNA seed grant. C.B. supported by the Deutsche Forschungsgemeinschaft.

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