Visualization of Cathepsin Activity Using ProSense 680 Agent from Well to Cell to Animal

Cathepsins are proteases, detected at basal levels in all living cells (Turk et. al., 2001), that are known to play an important role in several physiological processes such as lysosomal protein degradation, antigen presentation and apoptosis. However, cathepsins are also associated with pathological conditions and diseases such as cancer, osteoporosis and bronchial asthma (Turk et. al., 2001; Zavasnik-Bergant & Turk, 2006; Vasiljeva et. al., 2007). In cancer in particular, there is a significant increase in lysosomal cathepsins at the mRNA and protein level, and these proteases have shown considerable potential as biomarkers for tumor progression and metastasis. As cathepsin activity is regulated by posttranslational intracellular processing (Katunuma, 2010), requiring the diverse functions of a living cell, cathepsins may also serve as biomarkers of tumor cell viability. In summary, their well-established role in tumor development, progression and metastasis (Mohamed & Sloane, 2006; Conus & Simon, 2010) makes cathepsins attractive targets for visualization and characterization of viable tumor cells. In vitro and in vivo Imaging a p p l i c a t i o n n o t e