Blast - T cell - interaction in pediatric acute myeloid leukemia

Rothämel, Paula (2022): Blast - T cell - interaction in pediatric acute myeloid leukemia. Dissertation, LMU München: Medizinische Fakultät

Abstract

While accounting for only approximately 15 % of pediatric leukemia, patients with acute myeloid leukemia (AML) have still a worse prognosis than the average of pediatric cancers. Over the last decades, immunotherapy has developed from a promising therapeutic option to a robust clinical reality for treating cancer patients. AML has been excluded from this development. Here, the possible interaction of pediatric AML with the immune system is investigated. Therefore, this work analyzed bmT cells (T cells in the bone marrow), AML blasts, NK and NKT cells within bone marrow samples of 29 pediatric AML patients and 9 healthy bone marrow (BM) donors for protein expression by flow cytometry, for RNA expression by RNA-sequencing and for chromatin accessibility by ATAC-sequencing. Firstly, bmT cell phenotype was altered in AML compared to healthy BM donors. Concerning the T cell maturation stages, there was a shift towards a more mature phenotype in AML patients detectable in contrast to healthy BM donors. This was shown at protein level in flow cytometry, but also in RNA-seq within the scope of reduced IL21R and upregulated Perforin 1 and Granzyme B expression by CD8+ bmT cells in AML patients. Moreover, bmT cells of AML patients showed overexpression of several co-inhibitory and co-stimulatory molecules at protein level in comparison to healthy BM donors. Here, TIM-3 and PD-1 are worthy of special mention being consistently overexpressed on all T cell subsets (CD3+, CD4+ and CD8+ bmT cells). On CD8+ bmT cells also LAG-3 expression was upregulated, both at protein and RNA level. Secondly, to investigate, whether the observed alterations in phenotype of physiologic immune cells (T cells, NK and NKT cells) were linked to blast phenotype, we analyzed two common axes of interaction between antigen presenting cells and immune cells in the context of AML. Here, CD226 expression on bmT cells, NK and NKT cells was shown to be negatively correlated with CD112 expression on AML blasts. This might indicate that the described alterations are rather caused by a direct or indirect blast-T cell-interaction also in sense of immunoescape strategies than the results of an adaptive response to the tumor microenvironment. Thirdly, CD134 expression on CD8+ bmT cells at initial diagnosis was shown to be of potential prognostic relevance in context of AML relapse, even after multiple testing correction. In RNA-seq this could be reaffirmed. In order to better describe the functionality of a bmT cell population we developed the so-called exhaustion indices. Those indices describe the relation of the co-inhibitory and co-stimulatory marker expression on bmT cells and were evaluated for prognostic relevance concerning “future relapse”. A high CD134/PD-1 index of CD8+ bmT cells was shown to be a potential negative prognostic marker concerning AML relapse, whereas a high ICOS/TIM-3 index of CD3+ bmT cells was correlated with increased relapse-free survival. Even with the limitation in mind of a small sample size and lack of a validation cohort, the results are indicative for an immune-interaction of pediatric AML blasts. Finally, targets for synthetic immunotherapy were investigated. Considering co- and single-expression values on AML blasts, as well as expression levels on leukemic stem cells CD33 and CLL1 were shown to be the best suited target antigens in context of combinatorial CAR-T cell therapies (synNotch-CAR, Tandem-CAR). However, prospective clinical trials will have to confirm clinical relevance.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Themengebiete: 600 Technik, Medizin, angewandte Wissenschaften ; 600 Technik, Medizin, angewandte Wissenschaften > 610 Medizin und Gesundheit
• Fakultäten: Medizinische Fakultät
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 22. Dezember 2022
• 1. Bericht­erstatter:in: Feuchtinger, Tobias