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Cancer Res. 2013 Jan 15;73(2):855-64. doi: 10.1158/0008-5472.CAN-12-2969. Epub 2012 Nov 27.

Real-time in vivo molecular detection of primary tumors and metastases with ratiometric activatable cell-penetrating peptides.

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Department of Pharmacology, Division of Head and Neck Surgery, Howard Hughes Medical Institute, University of California at San Diego, La Jolla, California 92093, USA.


Management of metastatic disease is integral to cancer treatment. Evaluation of metastases often requires surgical removal of all anatomically susceptible lymph nodes for ex vivo pathologic examination. We report a family of novel ratiometric activatable cell-penetrating peptides, which contain Cy5 as far red fluorescent donor and Cy7 as near-infrared fluorescent acceptor. Cy5 is quenched in favor of Cy7 re-emission until the intervening linker is cut by tumor-associated matrix metalloproteinases-2 and 9 (MMP2,9) or elastases. Such cleavage increases the Cy5:Cy7 emission ratio 40-fold and triggers tissue retention of the Cy5-containing fragment. This ratiometric increase provides an accelerated and quantifiable metric to identify primary tumors and metastases to liver and lymph nodes with increased sensitivity and specificity. This technique represents a significant advance over existing nonratiometric protease sensors and sentinel lymph node detection methods, which give no information about cancer invasion.

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