Abstract 1940: EpCAM and L1CAM expression signatures in circulating tumor cells of advanced colorectal cancer

Abstract Background: Colorectal cancer (CRC) is the third most common deadliest cancer among both men and women in the United States. Hence, to improve CRC clinical management, there is an unmet need for affordable and personalized approaches, such as non-invasive blood tests that analyze circulating tumor cells (CTCs). However, there is limited data about the expression of markers associated with epithelial-mesenchymal transition (EMT) of CTCs in advanced CRC. In this study, we sought to evaluate EMT markers signatures in CTCs of advanced cases of CRC. Method: Peripheral blood samples (10-20 mL) were collected from five patients with metastatic CRC. CTCs were isolated using the Single-cell CellSelect Slides™ enrichment or in-house protocol, followed by FACS (Fluorescence-Activated Cell Sorting). The following markers were analyzed: Ghost Dye™, CD45, CD133, LGR5, L1CAM, CD326 (EpCAM), CD325 (CDH2), CD274 (PD-L1), CD87 (VIM), and Cytokeratin-7/-8. FACS data analysis was done in FlowJo and plugins needed. Results: The average age of diagnosis was 51.6 years. At the time of blood collection, all CRC patients had stage IV disease and were progressing. Self-organizing map clustering and dimensionality reduction algorithm analysis of 10, 197 sorted CD45 negative living cells showed that LGR5 was the least expressed marker. The highest expression of CD133 was associated with highest expression of either EpCAM or L1CAM, which were both inversely correlated with LGR5. Co-expression of EpCAM and L1CAM were negatively associated with CD133, but positively associated with LGR5. EpCAM and L1CAM expression had significant association with CDH2, VIM, Cytokeratin-7/-8 and PD-L1. Conclusion: In advanced CRC, the mutually exclusive expression of EpCAM and L1CAM in the presence of CD133, and absence of LGR5 could be linked to increased plasticity leading to EMT, and increased risk of metastasis and recurrence. In addition, it is important to consider other markers alongside EpCAM for the identification of CTCs in advanced CRC. Citation Format: Gabriela Felix, Jun Gong, Francesca Aguirre, Lisa Zhou, Rocio Ramirez, Megan P. Hitchins. EpCAM and L1CAM expression signatures in circulating tumor cells of advanced colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1940.