Rapid Visualization of Deeply Located Tumors in Vivo by Intravenous Administration of a γ-Glutamyltranspeptidase-Activated Fluorescent Probe

We previously showed that spraying the fluorescent probe gGlu-HMRG (γ-glutamyl hydroxymethyl rhodamine green) can visualize even tiny tumors on the mesentery and peritoneal wall of tumor-bearing mice. However, during surgery, repeated spraying is necessary to detect tumors located deep within organs. Here, we examine whether deeply located tumors can be stained by intravenous administration of this probe. In mice bearing subcutaneous tumors, intravenous administration of gGlu-HMRG resulted in a rapid and specific increase of fluorescence in the tumor, which was visible to the naked eye within 5 min, and the maximum fluorescence intensity ratio of tumor to normal tissue (T/N = 4.3) was reached at 30 min. In mice bearing lung tumors, the T/N ratio reached approximately 20 at 30 min after administration, and deeply located tumors were clearly visualized. These results suggest that intravenous administration of gGlu-HMRG may be a useful technique in fluorescence-guided surgery of tumors.