Characteristics of ovarian cancer detection by a near-infrared fluorescent probe activated by human NAD(P)H: quinone oxidoreductase isozyme 1 (hNQO1)

Abstract

Near-infrared (NIR) fluorescent probes are ideal for in vivo imaging, because they offer deeper tissue penetration by the light and lower background autofluorescence than fluorophores that emit in the visible range. Q3STCy 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 Q3STCy and gGlu-HMRG, a green fluorescent probe, upon their surface application. In vitro uptake of Q3STCy was significantly higher than that of gGlu-HMRG. Using a red fluorescence protein (RFP)-labeled in vivo tumor model of POCM, the Q3STCy 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 Q3STCy 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.

Quinone-based fluorophores for imaging biological processes

“…Compound 17 was recently used for in vivo imaging of ovarian cancer in a mouse model upon activation by hNQO1, enabling the identification of cancerous lesions with minimal interference from tissue autofluorescence. 31 In the context of near-infrared fluorophores, Zhang and Yi recently described two novel probes (23 and 24, Figure 3B) for the detection of NQO1 activity in vitro and in mice. These near-infrared 'turn-on' probes relied on activation by intramolecular charge transfer (ICT) and PeT mechanisms using merocyanine and tricarbocyanine structures.…”

An Activatable Photosensitizer Targeting Human NAD(P)H: Quinone Oxidoreductase 1

“…Rather, its high level has been mainly exploited for diagnostics and alternative therapeutic applications. For example, an array of fluorescent chemosensors have been developed to differentiate cancer cells from healthy cells, and in some instances identify metastases in animal models . Several groups have also developed hNQO1‐bioactivated anticancer agents (e.g., prodrugs) to enhance the cancer selectivity of DNA alkylators or other chemotherapeutic agents .…”

Activatable fluorescent probes in fluorescence-guided surgery: Practical considerations

“…An adequate TBR is only reached after waiting a considerable time for probes in the background to clear, but at the same time, probes bound to the tumor will also begin to clear and produce a lower signal. 21,34 On the other hand, activatable probes remain undetected until they are turned on by specific enzymes or environmental conditions and emit signal, leading to increased contrast and sensitivity: a bright tumor against a dark background (Fig. 1) 35 36.…”