Prostate Cancer Patient-Derived Organoids (PDOs) as Functional Avatars for Antisense Oligonucleotide (ASO)-Based...

Patient-derived tumor organoids (PDOs) closely preserve the cellular heterogeneity, histopathology, and molecular features of the original tumors, making them powerful preclinical models. Antisense oligonucleotides (ASOs) are an emerging class of precision medicines that modulate gene expression at the RNA level with high target specificity, yet their application in organoid systems remains underexplored. Here, we adapted previously described protocols to establish a biobank of prostate cancer (PC) PDOs, achieving a high initial growth success rate (>90%). Histological and molecular analyses confirmed the preservation of key tumor features. Using these models, we assessed several ASOs, with particular emphasis on OGX-427 (Apatorsen), an ASO targeting heat shock protein 27 (HSP27) that has been evaluated in phase I/II clinical trials. While OGX-427 effectively suppressed HSP27 expression and inhibited cell growth in 2D cultures, its efficacy was markedly limited in 3D organoids, likely due to extracellular matrix and structural barriers. Removing Matrigel and applying single-cell transfection overcame these barriers, achieving efficient ASO uptake, significant target protein downregulation, and robust, dose-dependent inhibition of organoid growth. These findings underscore the utility of PDOs for evaluating ASO-based therapies and their potential to accelerate precision oncology strategies for PC and other malignancies.