Hochschulschrift:
Dissertation, Universitätsmedizin der Universität Greifswald, 2024
Anmerkungen:
Literaturverzeichnis: Seite 33-39. - Literaturangaben
Text deutsch, Publikationen englisch
Beschreibung:
LLGL1
In this work, various factors that may influence self-renewal of myeloid leukemia stem cells (LSCs) were investigated. The focus was primarily on polarity regulators of the scribble polarity complex family and proteins that regulate signaling pathways involved in leukemic stem cell self-renewal. Investigation of the different scribble complex members identified LLGL1 as a vulnerability in acute myeloid leukemia (AML). Inactivation of LLGL1 in leukemic cells showed decreased proliferative capacity in vitro and delayed leukemia development in vivo. Moreover, genetic inactivation of Llgl1 in the murine FLT3-ITD driven leukemia mouse model resulted in the loss of stem cell-associated gene expression and induced a leukemic phenotype characterized primarily by GMP-like cells. Overexpression of HoxA9 restored the original aggressive AML phenotype. These data demonstrate that LLGL1 appears to play a functional role in proliferative capacity as well as in maintaining the undifferentiated cell phenotype in AML. The conventional (“straight”) FLT3-ITD-knockin mouse model is characterized by a myeloproliferative phenotype associated with enlargement of the spleen, increased granulocyte and monocyte populations, and a reduction in lymphoid. Interestingly, the crossing of homozygous FLT3ITD/ITD mice with different Cre recombinases (Mx1-Cre, Scl-CreERT, LysM-Cre, retroviral Cre-Expression) showed (without the presence of another conditional allele) the development of an aggressive and morphologically immature AML phenotype. In addition, a polyclonal expansion of progenitor cells resulting from the activation of Myc-dependent gene expression programs and a differentiation blockade was observed. The activated Cre recombinase excises a residual neomycin resistance cassette in the inserted FLT3-ITD target vector and its loss may contribute to the observed leukemia phenotype. Chromosome translocations occurring in AML can lead to oncogenic fusions with aberrant epigenetic and transcriptional functions. Direct therapeutic targeting of these fusion proteins in leukemias has not yet been achieved. Through global proteome analyses in murine LSCs, calcium-dependent cellular functions as well as phospholipase C (PLC)-dependent signaling pathways were found, as potential vulnerabilities in AML1-ETO (AE) driven leukemias. The PLC family member PLCG1 could be found as most highly expressed in AE-transformed leukemia, which can be induced by an intergenic regulatory DNA element. Genetic inactivation of PLCG1 in human and murine AE-transformed AML inhibits self-renewal capacity and proliferation of LSCs in vitro and leukemia maintenance in vivo. Pharmacological inhibition of calcium-dependent signaling pathways downstream of PLCG1 in AE-transformed cells resulted in a reduction of leukemia burden in an AE-induced leukemia mouse model. Our results demonstrated that PLCG1-dependent Ca2+ signaling is a critical pathway for the maintenance and self-renewal of AE-mutated leukemia stem cells, thus providing a potential therapeutic target for AE-driven LSCs.