Organoid-based modeling of platinum resistance identifies KRT17 as both a response mediator and biomarker for targeted therapy in ovarian cancer

Variable platinum responses drive high mortality in high-grade serous ovarian cancer (HGSOC), but to date, there is no molecular approach to define resistance levels for clinical decision-making. Here, we developed the organoid drug resistance assay (ODR-test) with patient-derived organoids from our ovarian cancer biobank and found that all HGSOC patients develop molecular resistance under exposure to carboplatin, although with varying clinical implications. Sustained phenotypic reprogramming and cellular plasticity under carboplatin pressure emerged as a conserved mechanism irrespective of the basal resistance level. Transcriptional and proteomic analyses revealed changes in cell adhesion and differentiation in post-platinum lines as adaptive responses that drive the increase in resistance. We identified Keratin 17 (KRT17) as a mediator of developing platinum resistance and validated its function by CRISPR/Cas9 and overexpression. Additionally, we found that KRT17 expression status (K-score) is a significant negative prognostic histopathological biomarker in a large cohort (N=384) of advanced HGSOC patients. In organoids, increased KRT17 levels enhanced sensitivity to PI3K/Akt inhibitors Alpelisib and Afuresertib, highlighting the potential of KRT17 as a stratification biomarker for targeted therapies.