MODL-06. USING HYDROGEL MODELS TO RECAPITULATE THE TUMOUR-IMMUNE MICROENVIRONMENT OF AGGRESSIVE GROUP 4 MEDULLOBLASTOMA TUMOURS

Abstract BACKGROUND Medulloblastoma is the most common malignant childhood brain-tumour, predominantly affecting children between the ages of one and nine. It is divided into four molecular subgroups amongst which, Group 3 (G3) and Group 4 (G4) subgroups have the worst prognosis. Subgroups possess distinct extracellular-matrix (ECM) and tumour immune microenvironments (TIME) directly influencing therapy-response and metastasis. Current models of medulloblastoma fail to precisely recreate the complex, subgroup-specific TIME and do not mimic intricate immune-tumour heterotypic signalling facilitating immune-evasion. Here we use a HyStem-hydrogel which forms a hyaluronan-rich environment mimicking the natural brain architecture. This overcomes several limitations of current MB models, allowing customisation of subgroup matching of ECM components, adjustable ECM-stiffness and co-culturing of immune cells. METHODS HyStem-hydrogels were co-assembled with ECM components (with/without laminin) and G4 medulloblastoma cell line CHLA-01-MED. Hydrogels were imaged every three-days using an EVOS M7000 system and assessed for cell-viability with PrestoBlue every seven days. Co-culture laminin-supplemented HyStem hydrogels were established with M1-like or M2-like resting/activated macrophages and their growth tracked in the same manner. On day twenty-eight, hydrogels were fixed and stained for markers of cellular proliferation (Ki-67), ECM (laminin, vitronectin) and macrophage markers. Media from hydrogel co-cultures was collected and ELISAs permofmed to assess cytokine production. RESULTS Hydrogels with/without laminin both remained viable and stable for 28 days. Laminin-supplemented hydrogels displayed a mixed laminar-nodular phenotype which mirrored the heterogenous nature of G4 patient-tumours. Co-culture of CHLA-01-MED cells with activated-macrophages led to cytokine production and altered growth patterns. CONCLUSION We show that HyStem hydrogels recapitulate biologically relevant behaviour of aggressive G4-MB tumours in vitro and represent a promising model for G4-tumours. Future research will involve inclusion of additional brain relevant cells/ECM components and comparisons to a fully customisable peptide-amphiphile hydrogel.