Abstract 2309: Unlocking the proteome of metastatic prostate cancer circulating tumor cells

In recent years, liquid biopsies have emerged to provide improved insights on the current disease state of a patient, but they generally rely on a small number of protein markers from immunofluorescent staining or cell-free DNA, which provides limited information especially around drug targets. As more targeted and immune therapies enter the market, selecting the optimal drug target could improve patient outcomes drastically. One way to achieve this goal is to generate multi-omic datasets from the cancer cells in circulation, known as circulating tumor cells (CTCs). In this study, Astrin Biosciences’ patented isolation technology was used to enrich CTCs with high purity from the blood of metastatic castration resistant prostate cancer (mCRPC) patients. The enriched CTCs and a patient matched control sample consisting primarily of white blood cells were divided such that RNA and protein could be interrogated from the same patient. Label free unbiased mass spectrometry was used to identify proteins and marks the first time a global proteomic assessment has been performed in CTCs from cancer patients. Initial analysis identified over 1,500 peptides corresponding to greater than 500 proteins with increased epithelial cell markers in the CTC-enriched sample and increased WBC markers in the control sample. Hallmarks of androgen response and detection of the androgen receptor were also identified in the CTC proteome. In addition to the proteome, RNA sequencing will also be performed to generate a multi-omic platform to detect cancer signaling mechanisms and biomarkers. Overall, this study was designed to show the feasibility of obtaining multi-omic data from a liquid biopsy and future studies will provide more insight into the clinical utility of such data. As we analyze more patients, we plan to compare the protein and RNA signatures across mCRPC patients and eventually be able to map patient outcomes and correlate them with drug response with the overall goal to improve treatment selection and patient outcomes. Citation Format: Justin M. Drake, Zoi Sychev, Alec Horrmann, Kaylee J. Smith, Catalina Galeano-Garces, Ali Arafa, Nicholas Heller, Mahdi Ahmadi, Jiarong Hong, Megan Ludwig, Justin Hwang, Emmanuel S. Antonarakis, Jayant Parthasarathy. Unlocking the proteome of metastatic prostate cancer circulating tumor cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 1