ID #807  Harnessing programmed cell death and metabolic vulnerabilities to enhance therapy in medulloblastoma

Abstract

Medulloblastoma (MB) is the most common malignant paediatric brain tumour and comprises four molecular subgroups with distinct biological and clinical characteristics. Although survival outcomes have improved for some patients, current multimodal therapies, including surgery, craniospinal irradiation, and intensive chemotherapy remain highly toxic and frequently cause severe long-term neurocognitive side effects. There is therefore a critical need for more effective and less harmful treatment strategies, particularly for high-risk MYC-driven disease.

Anti-apoptotic members of the BCL-2 family, including BCL-XL and MCL-1, are commonly dysregulated in MB and contribute to tumour cell survival and therapeutic resistance. BH3 mimetics are small-molecule inhibitors that selectively antagonise these pro-survival proteins, enabling BAK/BAX activation and induction of intrinsic mitochondrial apoptotic cell death. In parallel, altered tumour metabolism represents an emerging vulnerability in cancer. Dihydroorotate dehydrogenase (DHODH), catalyses a key step in de novo pyrimidine synthesis and is upregulated in rapidly proliferating tumour cells. DHODH inhibitors such as BAY-2402234 exploit this metabolic dependency.

Here, we investigated the therapeutic potential of combining BH3 mimetics with the standard-of-care chemotherapeutic cyclophosphamide or the DHODH inhibitor BAY-2402234 in MYC-driven MB cell lines in vitro. In D425 and D283 MB cells, the BCL-XL inhibitor A1331852 or the MCL-1 inhibitor S63845 significantly enhanced tumour cell death when combined with cyclophosphamide or BAY-2402234. Increased apoptotic signalling was confirmed by elevated cleavage of caspase-3 and PARP-1. Combined treatments with BAY-2402234 and BH3-mimetics was highly synergistic, as confirmed by BLISS synergy assays.

Genetic deletion of the pro-apoptotic effectors BAK and BAX conferred resistance to BH3 mimetic induced apoptosis, confirming on-target engagement of mitochondrial cell death pathways. In contrast, loss of BAK/BAX did not protect cells from BAY-2402234–mediated cytotoxicity, suggesting additional apoptosis-independent mechanisms. Mechanistically, BAY-2402234 induced S-phase cell cycle arrest, whereas cyclophosphamide triggered G2/M-phase arrest.

Finally, we explored ferroptosis as an additional programmed cell death vulnerability. The ferroptosis inducers erastin and RSL3 demonstrated cooperative killing when combined with either BCL-XL or MCL-1 inhibition. Together, these findings support a novel combination treatment paradigm integrating BH3-mimetics with chemotherapy, metabolic inhibition, or ferroptosis induction, and highlight programmed cell death-based strategies as promising therapeutic avenues for medulloblastoma.