Prognostic and Immunological Roles of CES2 in Breast Cancer and Potential Application of CES2-Targeted Fluorescent Probe DDAB in Breast Surgery

Purpose: The expression and function of CES2 in breast cancer (BRCA) has not been fully elucidated. The purpose of this study was to investigate its clinical significance in BRCA. Patients and Methods: Bioinformatics analysis tools and databases, including The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO) databases, SURVIVAL packages, STRING database, Gene Ontology (GO) enrichment, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, Gene set variation analysis (GSVA), and Tumor Immunity Estimation Resource (TIMER), were utilized to measure the expression level and clarify the clinical significance of CES2 in BRCA. In addition, we verified the expression level of CES2 in BRCA at the cellular and tissue levels by Western blot, immunohistochemistry (IHC) and real-time fluorescence quantitative PCR assays. Furthermore, DDAB is the first reported near-infrared fluorescent probe that can be used to monitor CES2 in vivo. We applied the CES2-targeted fluorescent probe DDAB in BRCA for the first time and verified its physicochemical properties and labeling sorting ability by CCK-8, cytofluorimetric imaging, flow cytometry fluorescence detection, and isolated human tumor tissue imaging assays. Results: The expression of CES2 was higher in normal tissues than that in BRCA tissues. Patients with lower CES2 expression in the BRCA T4 stage had a poorer prognosis. Finally, we applied the CES2-targeted fluorescent probe DDAB in BRCA for the first time, which was demonstrated to have good cellular imaging performance with low biological toxicity in BRCA cells and ex vivo human breast tumor tissue models. Conclusion: CES2 can be considered a potential biomarker to predict the prognosis of breast cancer at stage T4 and might contribute to the development of immunological treatment strategies. Meanwhile, CES2 is able to distinguish between breast normal and tumor tissues, the CES2-targeting NIR fluorescent probe DDAB may have potential for surgical applications in BRCA.