A functional drug-screening platform built on patient-derived glioblastoma organoids predicted individual patient responses to temozolomide more accurately than the standard MGMT promoter methylation biomarker, and identified lazertinib as a candidate therapy for temozolomide-resistant tumors, according to a study published June 12, 2026 in Cell Reports Medicine. The findings, from researchers at Korea Advanced Institute of Science and Technology (KAIST) and Chungnam National University Hospital, both in Daejeon, South Korea, suggest that functional ex vivo testing of glioblastoma organoids drug response could offer a more reliable path to personalized treatment selection than current molecular biomarkers alone.
Glioblastoma remains the most lethal primary brain tumor in adults, with median survival under 15 months despite surgery, radiation, and temozolomide chemotherapy. The disease's extreme inter-patient heterogeneity means that treatment response varies substantially, yet clinical decision-making still relies heavily on MGMT promoter methylation status — a biomarker with well-documented concordance limitations. A subset of patients with methylated MGMT promoters fail to respond to temozolomide, while some unmethylated patients respond, reflecting the multiple resistance mechanisms that a single epigenetic marker cannot capture.
The central argument of this study is that directly measuring how a patient's own tumor cells respond to drugs in a three-dimensional culture system captures the functional output of all resistance mechanisms simultaneously — genetic, epigenetic, and structural — without requiring each pathway to be identified individually. This positions the glioblastoma organoids drug response platform as a potential clinical decision-support tool rather than simply a research model.
The GBO drug sensitivity testing platform
The research team collected fresh surgical tumor specimens from 55 patients (59 samples, including four recurrent cases) and established glioblastoma-derived organoid (GBO) lines using a serum-free, three-dimensional sphere culture system without exogenous growth factors or extracellular matrix scaffolding. Thirty-six GBO lines were successfully established, representing a 61.0% success rate. Eighteen lines were included in the primary drug sensitivity and clinical correlation analysis.
To confirm that the organoids faithfully represented the original tumors, the team performed whole-exome sequencing on five GBO lines and matched parental tumors, demonstrating high concordance in somatic mutation profiles. RNA sequencing on seven lines confirmed preservation of GBM molecular subtypes. Histological analysis using GFAP, SOX2, and OLIG2 immunohistochemistry validated that GBOs recapitulated the cellular architecture of the parental tissue. Orthotopic transplantation of GBO lines into immunodeficient mice confirmed tumor-forming capacity and histological features consistent with glioblastoma in vivo.
Predicting temozolomide resistance
The platform's clinical validation rested on correlating GBO drug sensitivity testing (GBO-DST) results — measured by IC₅₀ and area under the curve (AUC) — with actual patient outcomes across 18 patients with confirmed progression and survival endpoints.
GBO-DST demonstrated 100% concordance with clinical response to temozolomide across this cohort. MGMT promoter methylation status showed concordance of 77.8%, with a subset of patients where methylation status and clinical outcome diverged while GBO-DST remained concordant. Patients whose organoids showed low IC₅₀ values for temozolomide — indicating sensitivity — had statistically significantly longer progression-free survival and overall survival in Kaplan-Meier analyses (p < 0.05) compared with patients whose GBOs showed temozolomide resistance. The correlation held across both newly diagnosed and recurrent GBM samples.
The mechanistic basis for this superior predictive accuracy became apparent through transcriptomic analysis. RNA sequencing and KEGG/GO pathway enrichment in TMZ-resistant versus TMZ-sensitive GBOs identified upregulation of DNA damage repair pathways, activation of EGFR and receptor tyrosine kinase signaling, and downregulation of apoptotic pathways in resistant lines. Upregulation of axonogenesis and cell adhesion genes — including PTPRZ1, L1CAM, NCAM1, MAPT, and GPM6A — was also detected. In one recurrent GBO line (GBO-019), epigenetic re-expression of MGMT despite promoter methylation was identified as an acquired resistance mechanism, illustrating exactly the class of failure that methylation status alone cannot detect.