Abstract 699: Dynamic adaptation and heterogeneity in tumor patient-derived organoids: Insights into cancer evolution and drug resistance.

Abstract Tumor plasticity and cellular heterogeneity have long been recognized as major contributors to the limited success of cancer therapies, underscoring the need for more physiologically relevant preclinical models. Patient-derived organoids (PDOs) offer a three-dimensional, heterogeneous platform that better reflects tumor complexity compared to traditional cell lines or animal models. Their adoption in drug development pipelines and avatar clinical trials has grown significantly in recent years. In this study, tumor PDOs were characterized using single-cell RNA sequencing, whole-exome sequencing, and sub-lethal therapeutic exposure to assess intra- and inter-patient heterogeneity and adaptive dynamics. PDOs from different donors exhibited patient-specific transcriptional signatures while retaining stem-like features. Mutational landscapes evolved over time, with variants being retained, lost, or acquired relative to the original tissue. Notably, subpopulations persisted through treatment and gave rise to distinct clonal cultures with unique transcriptional profiles upon drug withdrawal. These findings confirm that tumor PDOs preserve cellular heterogeneity and exhibit dynamic adaptability, making them powerful tools for investigating cancer evolution, drug resistance, and mutation dynamics. Inter-patient variability highlights the need for personalized therapeutic strategies, while intra-patient heterogeneity positions PDOs as ideal models for studying complex cellular interactions and mechanisms of pharmacological persistence. Citation Format: Javier Frias Aldeguer, Jasmin Pourfarzad, Alessandro Gregory, Farzin Pourfarzad, Rene Overmeer, Robert G. Vries, Sylvia F. Boj. Dynamic adaptation and heterogeneity in tumor patient-derived organoids: Insights into cancer evolution and drug resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 699.