The detection of rare and unstable biomarkers is frequently obscured by uninformative proteins. This hindrance represents a major obstacle in current biomarker-discovery efforts. Disease-specific expression profiles of ubiquitinated substrates can provide a diagnostic tool for detecting abnormal conditions. Additionally, identifying changes in proteasomes composition can reveal disease-specific interactions with regulatory proteins. These reagents are superior to other proteomic methods because they eliminate uninformative proteins, and selectively isolate biomarkers.

There is a significant unmet need for deploying rapid in vitro assays that can provide diagnostic, prognostic and therapeutic guidelines for cancer and other aberrant cellular conditions. However, the conspicuous absence of useful diagnostic assays arises from the difficulty in identifying informative biomarkers that can guide the analysis of tissue, blood and other patient-derived materials. Biomarkers generally represent low abundance regulatory molecules (including proteins, lipids, and nucleic acids), that can provide an indication of the cellular condition. The ubiquitin/proteasome system of protein degradation is implicated in diverse cellular functions, and plays a central role in controlling the stability of key protein regulators of cell growth and survival. We have developed tools to specifically interrogate this pathway, and to identify changes in the pattern of abundance of ubiquitinated proteins and proteasomes. These affinity reagents permit very rapid isolation of proteins that are attached to ubiquitin, as well as catalytically active proteins. Both species of proteins have a high likelihood of revealing changes in expression pattern of important cellular proteins. We reported that the activity of this pathway is strongly increased in primary breast cancer tissue, and numerous protein factors are expressed at high levels. Given the strong activation of this proteolytic pathway in other cancers, CellXplore’s proven technologies can be readily adapted to provide an efficient platform for biomarker discovery.