|M.Sc Student||Melchers Micol Marie|
|Subject||The Effect of the IDH1-R132H Mutation on the|
Immunopeptidome in Cancer Cells
|Department||Department of Biology||Supervisor||Professor Arie Admon|
|Full Thesis text|
Isocitrate-dehydrogenase isoform 1 (IDH1) is a key cellular metabolic enzyme that functions to convert isocitrate into α-Ketoglutarate (αKG) with production of NADPH. This enzyme is essential for a number of cellular processes, including the Krebs cycle, demethylation, and collagen synthesis, among others. IDH1 is often mutated in diffuse gliomas, as well as in other solid and hematopoietic tumors. The most frequent IDH1 mutation, occurring in 90% of the IDH1 mutated tumors, is the replacement of arginine in position 132 with histidine (IDH1-R132H). This somatic point mutation leads to aberrant enzymatic activity, resulting in the reduction of αKG to D-2-hydroxyglutarate (2-HG). The resulting cellular metabolic changes lead to impaired demethylases activity, and thus, epigenetic alterations. Lacking effective treatments, IDH1-R132H mutated glioma patients face lower survival rates, albeit associated with a somewhat better prognosis compared to the wild type IDH1 glioma patients. Therefore, attempts were made to exploit the IDH1-R132H mutation to find mutation-specific epitopes presented by HLA molecules of the cancer cells suitable for peptide-based cancer vaccines. Furthermore, investigating the IDH1-R132H mutation can shed light on its impact on the antigen presentation machinery. In this work, we used immunoaffinity purification of the HLA molecules and LC-MS/MS-based peptidomics and proteomics to examine how this mutation effects both antigen presentation machinery and the presentation of HLA peptides. We utilized for these studies sarcoma cell lines and tissue samples from a transgenic mouse model expressing the human HLA molecules, which are knocked-out for murine MHC molecules. Our results indicate that the IDH1-R132H mutation results in downregulation of the antigen presentation machinery and subsequently antigen presentation itself. We hypothesize that the observed HLA downregulation may be an escape mechanism of mutation-positive cancer cells from immune surveillance. Furthermore, we identified two HLA peptides, presented on the IDH1-R132H cells only, that may serve as potential candidates for immunotherapeutic vaccines. Further investigation pursuing the mutation’s impact will provide insight into the mechanisms behind the immune responses in IDH1-R132H-positive tumor patients and may lead to better and more specific immunotherapeutic strategies for these patients.