An Organoid-based Functional Precision Medicine Trial in Osteosarcoma: PREMOST

Investigators successfully established a miniaturized system that allows the setup of hundreds of wells and perform assays with minimal manipulation. The adapted geometry used to plate tumor cells in Matrigel, to generate mini-rings around the rim of the wells. This is attained by plating single-cell suspensions obtained from a cell line or a surgical specimen pre-mixed with cold Matrigel in a ring shape around the rim in 96-well plates. Rings can be established using a single-well or multichannel pipette. Cancer cell lines grown in mini-ring format give rise to organized tumor organoids that recapitulate features of the original histology. Treatment protocols and readouts for the mini-ring approach have been optimized. Seeding cells takes place on day 0, 2-3 days are allowed to establish organoids and it is followed by two consecutive daily drug treatments. The assay is flexible and can be easily adapted to single treatments followed by longer incubations, multiple consecutive recurring treatments, multi-drug combinations, or other screening strategies. Assays were implemented to quantify drug response by measuring cell viability after staining of live organoids with specific dyes followed by imaging. The pipeline has been extended to sarcomas: the team characterized organoids established from over 120 sarcoma biopsies, resections, and metastasectomies. Sarcoma organoids showed patient-specific growth characteristics and subtype-specific histopathology. Organoid sensitivity correlated with diagnostic subtype, patient age at diagnosis, lesion type, prior treatment history, and disease trajectory for a subset of the compounds screened. Organoid screening can provide information to facilitate optimal drug selection, avoid ineffective therapies, and mirror patient outcomes in sarcoma.