In mosaic (intermixed tumor–neuron) and assembloid (tumor–organoid juxtaposition) models, the sequential window acquisition of all theoretical mass spectra (SWATH-MS) proteomics revealed that DIPG cells downregulated the expression of extracellular matrix adhesion markers (versican and glypican-1) while increasing the expression of proliferation proteins (Minichromosome Maintenance Complex Component 2 (MCM2) and DNA Polymerase Alpha Subunit 2 (POLA2)), which is indicative of enhanced DNA replication. This evidence concerns the gene POLA2 and neoplasm.