Exploring the interplay between immune cells and tumors Insights into antigen presentation and tumor immune evasion

In this thesis, we generated a panel of HAP1 cells, which are knockout for different proteins of the antigen presentation pathway, that can be used to investigate human leukocyte antigen class I (HLA-I; major histocompatibility complex I, MHC-I) mediated antigen presentation. This panel was used to investigate the presentation of a TAP-independent peptide by TAP-deficient tumors and healthy, TAP-proficient tissues. We found that healthy tissues were also able to present TAP-independent peptides, which underlines the need of thorough validation before clinical targeting of such antigens. Furthermore, we elaborated on proteasome generated spliced-peptides by tumors and their potential for a role in immunotherapy. We concluded that their role will be minimal. We switched to HLA-independent immune activation by first focusing on in vitro expansion of γδ T cells. These and other innate immune cells were assessed for their anti-tumor immune responses towards tumors lacking the protease SPPL3, which results in upregulation of neolacto-series glycosphingolipids (nsGSLs) on tumor cells. Anti-tumor responses by innate immune cells against SPPL3-negative tumor cells was reduced, either through nsGSL-dependent or nsGSL-independent regulation by SPPL3. Altogether, we showed that tumors benefit from nsGSLs in order to escape from anti-tumor responses in vitro and potentially benefit from nsGSL overexpression during tumor growth in vivo.