DDDR-52. Targeting tumour-astrocyte crosstalk for rational identification of novel therapeutic targets for medulloblastoma and atypical teratoid/ rhabdoid tumours

Abstract Atypical Teratoid/Rhabdoid Tumours (ATRT) and Group 3 Medulloblastoma (MB) are aggressive paediatric brain tumours which mostly occur in infants and children. Due to the severity of off-target effects associated with chemo/radiotherapy in young patients, there is increasing consideration of more targeted therapies. Astrocytes have previously been shown to support progression and therapy resistance of other brain tumours; our work aims to elucidate this crosstalk in MB and ATRT to identify novel therapeutic targets amenable for localised delivery to resection cavities. We developed a bespoke 3D model which recapitulates the in vivo scenario, whereby human astrocytes and tumour cells were grown for 7-days in a human brain decellularised extracellular matrix hydrogel. RNA sequencing compared tumour cells from monocultures to those co-cultured with astrocytes. Ubiquitous upregulation of S100A10, SERPINE1, COL1A1, and SOCS3 was observed across the MB cell lines (d283, d341 and d425). For ATRT, common genes including MMP2, NOTCH3, TGFBR2 and GAP43 were upregulated in BT12, BT16 and BT37 cells when cultured with astrocytes. Pathway analyses revealed cancer lines had a more proliferative and invasive phenotype in the presence of astrocytes. Based on RNA-seq analyses, 21 repurposed drugs were screened against MB and ATRT cells. Top ranking compounds included: halofuginone, BB-Cl-amidine, Juglone, and AZD8055. We combined these with potential anti-migratory drugs: Tiplaxtinin, T-5224 and an ANX2T inhibitor and selected synergistic or additive combinations based on bliss synergy scores. For ATRT, a combination of AZD8055 (mTor inhibitor) and Tiplaxtinin (SERPINE1 inhibitor) showed high synergy. 3D migration studies found that T-5224 (FOS inhibitor) and AZD8055 significantly reduced migration of spheroids in vitro for MB cells. Delivery of T-5224 and AZD8055 to a d425 resection model demonstrated tolerability. Similarly, delivery of Tiplaxtinin and AZD8055 conferred tolerability in a BT12 resection model and a survival advantage was indicated in groups treated with AZD8055 alone.