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

Abstract

SummaryMany tumor cells have elevated levels of hydrolytic and proteolytic enzymes, presumably to aid in key processes such as angiogenesis, cancer cell invasion, and metastasis. Since the activities of these enzymes are often regulated by post-translational mechanisms, their functional roles in cancer progression are difficult to study using traditional genomic and proteomic methods. Thus, methods that allow for the direct monitoring of enzyme activity in a physiologically relevant environment are required to better understand the roles of specific players in the complex process of tumorigenesis. This review highlights advances in the field of activity-based proteomics, which uses small molecules known as activity-based probes (ABPs) that covalently bind to the catalytic site of target enzymes. We discuss the application of ABPs to cancer biology, specifically to the discovery of tumor biomarkers, the screening of enzyme inhibitors, and the imaging of enzymes implicated in cancer.

Chemical genetic strategy for targeting protein kinases based on covalent complementarity

“…For example, fluorescently labeled versions of the inhibitors could be used to quantitatively probe the occupancy of kinase active sites to determine the percent activity required for signaling events (25,26,(43)(44)(45). This strategy may also be useful for studying the properties of pseudokinases, for which there is no good readout of active site occupancy.…”

Novel Matrix Metalloproteinase Inhibitor [18F]Marimastat-Aryltrifluoroborate as a Probe for In vivo Positron Emission Tomography Imaging in Cancer

“…Hence, cancer-specific small molecule 18 F-labeled radiotracers are urgently needed. Rapid on-site production of bioactive specific molecular imaging agents is hampered by 18 F labeling methodologies that traditionally have relied on C-F bond formation under conditions that are generally incompatible with biomolecule stability, such as scrupulously dry organic solvents at 70°C to 140°C. Overcoming these obstacles is plagued by relatively time-consuming multistep syntheses that are further complicated by side reactions requiring extensive purification.…”

“…Overcoming these obstacles is plagued by relatively time-consuming multistep syntheses that are further complicated by side reactions requiring extensive purification. Coupled with the short half-life of 18 F (110 min), these problems reduce specific activity and the imaging time window. Recently, Ting and colleagues (2) used arylboronate precursors to capture aqueous [ 18 F]fluoride in the form of an aryltrifluoroborate (ArBF 3 ) for 18 F-labeling in a rapid, one-step synthesis under acidic aqueous conditions at room temperature.…”

“…Coupled with the short half-life of 18 F (110 min), these problems reduce specific activity and the imaging time window. Recently, Ting and colleagues (2) used arylboronate precursors to capture aqueous [ 18 F]fluoride in the form of an aryltrifluoroborate (ArBF 3 ) for 18 F-labeling in a rapid, one-step synthesis under acidic aqueous conditions at room temperature. Indeed, the [ 18 F]aryltrifluoroborate was stable in vivo because no [ 18 F]fluoride accumulation was detected in bone, a highly fluorophilic tissue (3).…”

“…Indeed, the [ 18 F]aryltrifluoroborate was stable in vivo because no [ 18 F]fluoride accumulation was detected in bone, a highly fluorophilic tissue (3). Such chemistries have the potential to fast-track the introduction of 18 F-labeled bioconjugates in "kit" form 7 for diagnostic imaging in humans. To validate this novel labeling method for cancer imaging, we hypothesized that an optimal target would be highly expressed in many tumors, show discrimination between different cancer stages, and be targeted by nanomolar inhibitor drugs with clinically demonstrated safety.…”