Cathepsin cysteine proteases are effectors of invasive growth and angiogenesis during multistage tumorigenesis

Abstract

Tumors develop through successive stages characterized by changes in gene expression and protein function. Gene expression profiling of pancreatic islet tumors in a mouse model of cancer revealed upregulation of cathepsin cysteine proteases. Cathepsin activity was assessed using chemical probes allowing biochemical and in vivo imaging, revealing increased activity associated with the angiogenic vasculature and invasive fronts of carcinomas, and differential expression in immune, endothelial, and cancer cells. A broad-spectrum cysteine cathepsin inhibitor was used to pharmacologically knock out cathepsin function at different stages of tumorigenesis, impairing angiogenic switching in progenitor lesions, as well as tumor growth, vascularity, and invasiveness. Cysteine cathepsins are also upregulated during HPV16-induced cervical carcinogenesis, further encouraging consideration of this protease family as a therapeutic target in human cancers.

Design of cell-permeable, fluorescent activity-based probes for the lysosomal cysteine protease asparaginyl endopeptidase (AEP)/legumain

“…These tools will prove useful for monitoring legumain activity in living cells and have the potential to be applied to in vivo imaging studies of legumain function as demonstrated for the papain family cathepsins [18]. We believe these reagents will prove to be valuable tools for future studies of legumain function Profiling subsite specificity of endogenous legumain using positional scanning combinatorial libraries of peptide AOMKs.…”

Application of activity-based probes to the study of enzymes involved in cancer progression

“…The cathepsin-specific ABP DCG-04 has been applied to the evaluation of cathepsin inhibitors in RIP1-TAG2 transgenic mice, a mouse model of pancreatic cancer [42,43]. In these studies, inhibitors were injected into mice, and normal and tumor tissue samples were collected and analyzed for residual cathepsin activity.…”

“…In these studies, inhibitors were injected into mice, and normal and tumor tissue samples were collected and analyzed for residual cathepsin activity. The inhibition of these proteases by the cathepsinspecific inhibitor JPM-OEt resulted in a reduction in invasion, angiogenesis, and tumor growth [43]. Importantly, fluorescently-labeled DCG-04 enabled the biochemical identification and monitoring of the cysteine cathepsins during tumorigenesis in these mice.…”

“…In contrast, ABPs covalently bind to active enzymes, thus permitting assignment of imaging signals to specific enzymes [13,14]. In fact, a number of ABPs that target cysteine proteases have been used to image enzyme activity in tumor cells both in vitro and in vivo [43,48,49].…”

“…A fluorescently-tagged DCG-04 analog has been used to image cysteine cathepsin activity during tumorigenesis in RIP1-TAG2 transgenic mice [43]. In this study, the ABP was administered systemically by intravenous injection into a mouse.…”