A standardized patient-derived glioblastoma organoid platform for evaluating radiotherapy efficacy and overcoming resistance.

Patient-derived glioblastoma (GBM) organoids (GBOs) maintain characteristics of their original tumors; however, they have not been widely applied to systematically assess therapy responses at scale or elucidate mechanisms underlying treatment resistance. Here, we develop a standardized reaggregated GBO (rGBO) platform for scalable, quantitative evaluation of radiation responses across 48 patients with GBM. Radiation responses in rGBOs correlate with the survival duration of corresponding patients treated with standard-of-care radiotherapy. Transcriptomic analyses identify gene signatures associated with radiosensitivity and radioresistance. Connectivity mapping with perturbational datasets identifies a panel of compounds with potential for reducing radioresistant and enhancing radiosensitive signatures. Subsequent testing demonstrates that inhibitors of bromodomain and extraterminal (BET) family proteins enhance radiotherapy efficacy in GBO and xenograft models by downregulating the radioresistant signature. Together, our study highlights the potential of rGBOs for standardizing therapeutic screening, evaluating patient-specific responses, identifying associated molecular features, and developing strategies to overcome treatment resistance.