BIOL-09. PROTEOMIC ANALYSES REVEAL THAT CO-CULTURE OF DIFFUSE INTRINSIC PONTINE GLIOME (DIPG) WITH CORTICAL ORGANOIDS ALTERS CELL ADHESION, DNA SYNTHESIS AND REPLICATION, AND DENDRITIC GROWTH SIGNALLING

Diffuse Intrinsic Pontine Gliomas (DIPGs) are deadly brain cancers in children for which there is currently no effective treatment. In part, this can be attributed to preclinical models that lack essential elements of the in vivo tissue environment, resulting in treatments that appear promising preclinically, but fail to result in effective cures. Recently developed co-culture models combining stem cell-derived brain organoids with brain cancer cells provide tissue dimensionality and a human-relevant tissue-like microenvironment. As these models are technically challenging and time consuming it is imperative to establish whether interaction with the organoid influences DIPG biology and thus warrants their use. To address this question, we cultured DIPG cells with GFP-expressing cortical organoids. We created “mosaic” co-cultures enriched for tumour cell-neuronal cell interactions, where disaggregated spheroids and organoids were mixed and allowed to reform, versus “assembloid” co-cultures enriched for tumour cell-tumour cell interactions, where preformed tumour spheroids and organoids were combined. Sequential window acquisition of all theoretical mass spectra (SWATH-MS) was used to analyse the proteomes of DIPG fractions isolated by flow-assisted cell sorting. Control proteomes from DIPG spheroids were compared with DIPG cells isolated from mosaic and assembloid co-cultures. This revealed that tumour cell adhesion was reduced, and DNA synthesis and replication were increased, in DIPG cells under either co-culture condition. By contrast, the mosaic co-culture was alone associated with pathways implicated in dendrite growth. We propose that co-culture with brain organoids is a valuable tool to parse the contribution of the brain microenvironment to DIPG tumour biology.