Immunotherapy offers significant promise for the improvement of cancer therapy for multiple different cancers, including Diffuse Intrinsic Pontine Glioma (DIPG). DIPG carries the worst prognosis of any childhood brain cancer. Immune responses induced by immunotherapy rely on T cell responses to cancer cells due to peptide expression of immunogenic peptides on Human Leukocyte Antigen (HLA) molecules. Immunotherapies try to induce the expression of peptides which will induce robust T cell response to cancer antigens. Previous studies with Histone Deacetylase Inhibitors (HDACi) have shown upregulation of cancer antigens as well as HLA molecules on an RNA level in DIPG. These drugs are also being tested in clinical trials for DIPG. As such, a preliminary proteomics study into the effect of three different HDACi; Panobinostat, Pracinostat and Romidepsin on the proteome of DIPG cells was conducted. DIPG17 cells were treated with an IC10 dose in triplicate. After samples were processed using an S-trap protocol, samples were initially run on DDA and DIA mode the Orbitrap Fusion. All searches were conducted using PEAKS X Pro. Initial DDA search identified 3447 proteins, which increased to 8998 with High pH fractionation of samples, both of which were used to create a spectral library for DIA analysis which identified 6425 proteins. Pathway analysis of all significantly modulated proteins following DMSO control showed enrichment of HDACs, histone-acetyl transferases, DNA methylation and PRC2 complex activity. After treatment with Pracinostat and Romidepsin, there was upregulation of the cancer antigen TP53 and its biochemical pathway. Each HDACi enriched different pathways and had substantial effects on the antigen presentation pathway. These results suggest that treatment with HDACi increase HLA-B and cancer antigen expression. This may also offer new potential combinational therapies against DIPG. Further experimentation will be conducted into the effect of all three HDACi on the DIPG immunopeptidome.