Abstract
Problem
Currently, surgical excision of tumors is dependent on the surgeon's ability to differentiate tumor from normal tissue using non-quantifiable criteria such as tumor location, texture, color, relationship to surrounding structures etc. Under these circumstances, the ability to detect/treat micro-metastases and residual tumors in real time is limited.
Methods
We have developed a more objective means of visualizing tumor markers utilizing a novel strategy for selectively delivering molecules to cancer cells using activatable cell-penetrating peptides (ACPPs), in which the fluorescently labeled cell-penetrating peptide (CPP) is coupled via a cleavable linker to a peptide that inhibits the uptake of the CPP. Upon exposure to proteases secreted by tumor, especially matrix-metalloproteinases, the linker is cleaved, dissociating the inhibitory peptide and allowing the CPP to bind to and enter tumor cells.
Results
We injected Cy5-labeled ACPP into transgenic mice with spontaneous tumors as well as mice xenografted with human cancer cell lines (including sarcoma and carcinoma derived from larynx, breast and prostate). All tumors retain the Cy5 label to a greater extent than normal tissues. Furthermore, xenografts derived from cancer cell lines that were stably transfected with GFP or RFP show colocalization of the FP marker with the Cy5-labeled ACPPs. Finally, in the same mouse models, tumors excised using ACPP guided molecular imaging showed improved completeness of tumor removal as quantified by Alu PCR.
Conclusion
We have developed a novel method for molecular imaging of tumors in vivo using ACPPs. Using this technique, we were able to improve completeness of tumor excision in murine models.
Significance
This technique will help to improve complete resection of tumor at the time of surgery, thereby reducing patient morbidity in terms of total time under anesthesia and residual tumor as well as reducing operating room costs.
Support
K08 EB008122 from NIH-NIBIB to Quyen Nguyen. Era of Hope Innovator Award from Department of Defense to Roger Tsien.
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