Abstract 5313: Real-time video imaging of protease expression in vivo

Abstract

Abstract Most new drug candidates generated during in vitro screening turn out to be invalid after time-consuming and costly testing in animal models. Therefore, there is an urgent need for development of noninvasive, real-time, sensitive, and cost-effective tools with high throughput for monitoring and early detection of drug efficacy in vivo. Proteases are known as exceptionally critical signaling proteins that are involved in numerous processes such as cancers. Considerable efforts have been made to identify the role of certain proteases in given biological processes and to screen specific molecules that can regulate protease expression. Most experimental methods are based on the use of protease reporters or molecular beacons. Moreover, they are limited to in vitro applications. To date, protease-activatable probes have already emerged as powerful tools for in vivo imaging because of their potential to offer high specificity and lower background. However, current activatable probes strive to image protease activity and effects in real-time. Although major improvements have been made, such as the conjugation of macromolecules to improve in vivo stability, these probes still suffer in sensitivity and specificity. In addition, conventional protease activatable probes typically take about 24 hours to activate fully, impeding real-time imaging and high throughput in in vivo applications. Here, we report a simple methodology to improve real-time imaging of protease activity by in vivo activatable probes by balancing competing needs for stability and sensitivity in applications where there are high target-to-background signal ratios. We demonstrate the first true real-time in vivo video imaging of extracellular protease expression using an ultrafast-acting and extended-use activatable probe. This simple, one-step technique is capable of boosting fluorescent signals upon target protease cleavage as early as 30 minutes from injection in a small animal model and is able to sustain the strong fluorescent signal up to 24 hours. Using this method, we video imaged the expression and inhibition of matrix metalloproteinases (MMPs) in a MMPs-positive SCC-7 tumor-bearing mouse model. The current platform can be universally applied to any target protease of interest with a known peptide substrate and is adaptable to a wide range of real-time imaging applications with high throughputs such as for in vivo drug screening, examinations of the therapeutic efficacy of drugs, and monitoring of disease onset and development in animal models. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5313. doi:10.1158/1538-7445.AM2011-5313