Poster Presentation 28th Annual Lorne Proteomics Symposium 2023

Proinflammatory cytokines improve the HLA ligandome landscape of Diffuse Midline Glioma (#178)

Fatemeh shamekhi 1 2 , Dongbin Jin 1 , Terry C.C. Lim Kam Sian 1 3 , Liesl Bramberger 1 , Nicole Chew 2 , Claire Sun 2 , Ron Firestein 2 , Pouya Faridi 1 3
  1. School of Clinical Sciences, Department of Medicine, Monash University, Clayton, Victoria, Australia
  2. VPCC-Next Generation Precision Medicine Centre for Cancer Research , Hudson Institute of Medical Research, Clayton, Victoria, Australia
  3. Monash Proteomics and Metabolomics Facility, Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia

Diffuse midline glioma (DMG) carries the worst prognosis of all paediatric brain tumours and is one of the leading causes of cancer-related death in children. Immunotherapy can introduce significant promise for cancer therapy. Presentation of immunogenic tumour antigens on Human Leukocyte Antigen (HLA) molecules is critical for the immune surveillance against tumours. Patients diagnosed with immunologically “cold” tumours usually have low levels of expression of HLA-peptide complexes in the tumour surface, leading to an immunosuppressive tumour microenvironment and immune evasion.  Proinflammatory cytokines are involved in a “hot” tumour microenvironment encouraging immune infiltrate and have shown upregulating effect of cancer antigens along with HLA molecules. In this study, we studied the effect of two main pro-inflammatory cytokine on a) the expression level of HLA class I and II b) diversifying the HLA-bound peptides present on patient-derived DIPG-cell lines. From the 17 cell lines we studied, HLA-I expression increases by two-fold by IFN-g and 1.1-fold by TNF-a. For HLA-II, we found different patterns in different cell lines. Then by using immunopeptidomics techniques, we studied the immunopeptidome of SU-DIPG17 cell lines in the presence and absence of pro-inflammatory cytokines. In total we identified 3206 HLA-I and HLA-II bound peptides. 81 peptides were derived from known cancer-specific or associated antigens such as GPNMB and NPM. We also found IFN treatment increased the abundance of peptides present by HLA-B by 1.7-fold. However, the abundance of peptides present by HLA-A and C were less altered after IFN treatment. The results suggest that IFN-γ and TNF-α induce the expression of HLA-I and HLA-II proteins and the diversity of DMG immunopeptidome. However, IFN had a more significant effect on both aspects in both FACS and immunopeptidomics assessments. This result suggests that proinflammatory cytokines treatment enhances antigen processing leading to the presentation of novel T-cell antigens.