Abstract PS4-04-14: Evaluation of TNBC-PDX Models for Personalized Medicine

Abstract Background: Triple-negative breast cancer (TNBC) is known to be highly heterogeneous compared to other subtypes. Establishing reliable preclinical models is essential for personalized treatment strategies, such as selecting effective drugs for each patient. Patient-derived xenograft (PDX) models, created by transplanting patient tumors into immunodeficient nude mice, are considered to more accurately replicate tumor diversity and drug responses. This study aimed to evaluate the retention of clinically relevant biomarkers in TNBC-PDX models. Methods: With approval from the Kobe University Institutional Review Board (Approval number: B200006), tumor tissues were collected from TNBC patients who met the inclusion criteria and provided informed consent. The tissues were implanted into nude mice to establish TNBC-PDX models. Expression of key biomarkers—EGFR, AR, CK5/6, HER2, and Trop-2—was assessed in both the original patient tumors and corresponding PDX tumors using immunohistochemistry. Results: EGFR and Trop-2 expression was retained in all models. However, AR expression was not preserved. CK5/6 and HER2 showed variable expression across cases. Conclusion: TNBC-PDX models are promising tools for drug evaluation in personalized medicine. However, since some biomarkers, such as AR and CK5/6, may not be consistently retained, prior validation of biomarker expression is essential for accurate therapeutic evaluation. Citation Format: S. Inoue, M. Miki, M. Yamamoto, H. Tanino, T. Kunihisa, S. Inubushi. Evaluation of TNBC-PDX Models for Personalized Medicine [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS4-04-14.