Oncotarget 2017 Sep 20;8(37):61181-61192. Epub 2017 May 20.
Molecular Imaging Program, Center for Cancer Research, National Cancer Institute, United States National Institutes of Health, Bethesda, Maryland 20892-1088, USA.
Near-infrared (NIR) fluorescent probes are ideal for imaging, because they offer deeper tissue penetration by the light and lower background autofluorescence than fluorophores that emit in the visible range. QSTCy is a newly synthesized, NIR light-emitting probe that is activated by an enzyme commonly overexpressed in tumor cells, human nicotinamide adenine dinucleotide (phosphate): quinone oxidoreductase isozyme 1, known as hNQO1 or DT-diaphorase. The purpose of this study is to compare the sensitivity of detecting peritoneal ovarian cancer metastasis (POCM) with QSTCy and gGlu-HMRG, a green fluorescent probe, upon their surface application. uptake of QSTCy was significantly higher than that of gGlu-HMRG. Using a red fluorescence protein (RFP)-labeled tumor model of POCM, the QSTCy probe provided high sensitivity (96.9%) but modest specificity (61.0%), most likely the result of albumin-probe interactions and non-specific activation in nearby altered but healthy cells. Three types of kinetic maps based on maximum fluorescence signal (MF), wash-in rate (WIR), and area under the curve (AUC) allowed for differentiation of the activated fluorescence signal associated with POCM from the background signal of the small intestine, thereby significantly improving the specificity of QSTCy to 80%, 100%, and 100% for MF, WIR, and AUC, as well yielding a moderate improvement in sensitivity (100% for all approaches) that is comparable to that with gGlu-HMRG, but with the added advantages of NIR fluorescence as the transduction modality. Such a new methodology has the potential to afford identification of cancerous lesions deeper within tissue.