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Purpose: The reoperation rate for breast-conserving surgery is as high as 15–30% due to residual tumor in the surgical cavity after surgery. In vivo tumor-targeted optical molecular imaging may serve as a red-flag technique to improve intraoperative surgical margin assessment and to reduce reoperation rates. Cysteine cathepsins are overexpressed in most solid tumor types, including breast cancer. We developed a cathepsin-targeted, quenched fluorescent activity-based probe, VGT-309, and evaluated whether it could be used for tumor detection and image-guided surgery in syngeneic tumor-bearing mice. Methods: Binding specificity of the developed probe was evaluated in vitro. Next, fluorescent imaging in BALB/c mice bearing a murine breast tumor was performed at different time points after VGT-309 administration. Biodistribution of VGT-309 after 24 h in tumor-bearing mice was compared to control mice. Image-guided surgery was performed at multiple time points tumors with different clinical fluorescent camera systems and followed by ex vivo analysis. Results: The probe was specifically activated by cathepsins X, B/L, and S. Fluorescent imaging revealed an increased tumor-to-background contrast over time up to 15.1 24 h post probe injection. In addition, VGT-309 delineated tumor tissue during image-guided surgery with different optical fluorescent imaging camera systems. Conclusion: These results indicate that optical fluorescent molecular imaging using the cathepsin-targeted probe, VGT-309, may improve intraoperative tumor detection, which could translate to more complete tumor resection when coupled with commercially available surgical tools and techniques.
Suurs, F. V., Qiu, S. Q., Yim, J. J., Schröder, C. P., Timmer-Bosscha, H., Bensen, E. S., … van Dam, G. M. (2020). Fluorescent image-guided surgery in breast cancer by intravenous application of a quenched fluorescence activity-based probe for cysteine cathepsins in a syngeneic mouse model. EJNMMI Research, 10(1). https://doi.org/10.1186/s13550-020-00688-0