Diffuse midline glioma (DMG) is a highly aggressive and untreatable pediatric cancer primarily arising in the pontine brainstem region, necessitating the development of representative models for treatment advance. Here we developed an FGF4-driven human brainstem organoid model, which we used to genetically engineer H3.3K27M-altered DMG. We demonstrated that brainstem pontine glial specification is critical for DMG tumorigenesis, yielding infiltrative tumors that recapitulate patient-representative intratumoral heterogeneity. Prolonged GD2 chimeric antigen receptor (CAR) T cell treatment mirrored clinical outcomes and revealed extensive transcriptional heterogeneity, from which both potent effector and dysfunctional CAR T cell populations could be identified. Furthermore, incorporation of myeloid cells generated DMG-specific microglia that reduced treatment efficacy and revealed CAR T cell functional states most vulnerable to microglia-mediated immunosuppression. Thus, we present a representative DMG model offering a months-long experimental window in vitro, which we leveraged to delineate CAR T cell functionality and microglial impact, aiding therapy development for this devastating disease.

Radiotherapy plus cisplatin (chemoradiation) is standard treatment for women with locoregionally advanced cervical cancer. Both radiotherapy and cisplatin induce DNA single and double-strand breaks (SSBs and DSBs). These double-strand breaks can be repaired via two major DNA repair pathways: Classical Non-Homologous End-Joining (cNHEJ) and Homologous Recombination. Besides inducing DNA breaks, cisplatin also disrupts the cNHEJ pathway. Patients contra-indicated for cisplatin are treated with radiotherapy plus hyperthermia (thermoradiation). Hyperthermia inhibits the HR pathway. The aim of our study is to enhance chemoradiation or thermoradiation by adding PARP1-inhibition, which disrupts both the SSB repair and the Alternative NHEJ DSB repair pathway. This was studied in cervical cancer cell lines (SiHa, HeLa, C33A and CaSki) treated with hyperthermia (42 °C) ± ionizing radiation (2–6 Gy) ± cisplatin (0.3–0.5 µM) ± PARP1-inhibitor (olaparib, 4.0–5.0 µM). Clonogenic assays were performed to measure cell reproductive death. DSBs were analyzed by γ-H2AX staining and cell death by live cell imaging. Both chemoradiation and thermoradiation resulted in lower survival fractions and increased unrepaired DSBs when combined with a PARP1-inhibitor. A quadruple modality, including ionizing radiation, hyperthermia, cisplatin and PARP1-i, was not more effective than either triple modality. However, both chemoradiation and thermoradiation benefit significantly from additional treatment with PARP1-i.