| dc.description.abstract | Cancer is one of the leading causes of death globally, but thanks to innovations in treatments, such as development of immunotherapy, deaths caused by cancer have decreased. However, tumor cells can evade antitumor responses of immune cells. To prevent and treat tumors that evade the immune system, knowledge about different immune escape mechanisms is required. A potential, newly discovered evasion mechanism could be elevated expression of neolacto-series glycosphingolipids (nsGSLs). nsGSLs are present on the cell membrane of many cell types and nsGSL levels are regulated by signal peptide peptidase like 3 (SPPL3), as it has been shown that nsGSL levels are elevated in HAP1 SPPL3-/- cells. Recently, it was revealed that elevated nsGSL levels on tumor cells cause a decreased cytotoxicity of CD8 cytotoxic T cells. Yet, it was unknown whether elevated nsGSL levels on tumor cells have an effect on the antitumor response of other immune cells, such as γδ T cells and natural killer (NK) cells. This project therefore aimed to explore effects of elevated nsGSL levels on the antitumor function of γδ T cells and NK cells. To study effects on γδ T cells, γδ T cells were cocultured with HAP1 cells with elevated, normal, and absent nsGSL levels and by flow cytometry the killing capacity of γδ T cells was measured. This revealed no effect of elevated nsGSL levels on the killing capacity of γδ T cells. To assess an effect of genetic loss of SPPL3 on NK cells, NALM6 SPPL3-/- cells were created by genome editing. The killing capacity of NK cells cocultured with NALM6 SPPL3-/- cells compared to wild-type (WT) cells varied depending on the NK cell donor. NK cell activation, as assessed by the percentage of CD107a positive and TNF positive NK cells, was decreased for NK cells cocultured with NALM6 SPPL3-/- cells compared to cells cocultured with WT cells. Finally, to study whether the accessibility of defined NK cell receptor ligands is possibly involved in the diminished activation of NK cells, the effect of genetic loss of SPPL3 on the accessibility of CD112, B7H6, UBLP1, CD48, HLA-E, and ICAM-1 was assessed. Decreased accessibility of UBLP1, CD48, HLA-E, and ICAM-1, but not of CD122 and B7H6 was observed in NALM6 SPPL3-/- cells compared to WT cells. Overall, this study shows that the effect of genetic loss of nsGSL regulator SPPL3 on antitumor responses varies per immune cell, as it diminishes NK cell activation, but does not affect the killing capacity of γδ T cells. | |
| dc.subject | This report shows that the effect of genetic loss of nsGSL regulator SPPL3 on antitumor responses varies per immune cell, as it diminishes NK cell activation, but does not affect the killing capacity of γδ T cells. In addition, decreased accessibility of NK cell receptor ligands UBLP1, CD48, HLA-E, and ICAM-1, but not of CD122 and B7H6 was observed in NALM6 SPPL3-/- cells compared to WT cells. | |
