Institutional creator:

Instytut Biologii Doświadczalnej im. Marcelego Nenckiego PAN ; Uniwersytet Warszawski

Contributor:

Piwocka, Katarzyna (1970– ) : Supervisor ; Kozłowska, Ewa : Assistant supervisor

Publisher:

Nencki Institute of Experimental Biology PAS

Place of publishing:

Warsaw

Description:

175, [1] pages : illustrations ; 30 cm ; Afiliation of auxiliary supervisor: University of Warsaw ; Bibliography ; Summary in Polish

Degree grantor:

Instytut Biologii Doświadczalnej im. Marcelego Nenckiego PAN

Type of object:

Thesis

Abstract:

Chronic and acute myeloid leukemia (CML/AML) constitute cancers that arise in the bone marrow, due to malignant transformation (by oncogenic mutations such as BCR-ABL1, FLT3-ITD and others) of myeloid progenitor cells. As myeloid leukemias develop, they expand outside the bone marrow and engraft other tissues, such as the spleen or blood. Development and expansion of myeloid leukemias has been recently shown to be significantly facilitated by immunosuppression - a state when anti-tumor immunity is attenuated and dysfunctional. Immunosuppression is largely established by suppressive cell subsets of the immune system, such as regulatory T cells (Tregs) - a type of T cells that express transcription factor Foxp3 and perform tolerogenic/suppressive function. Tregs have been shown to be upregulated in blood and bone marrow of patients with myeloid leukemias. However, as this has only recently been described, mechanisms that drive expansion and suppressive activity of Tregs in leukemias remain largely unexplored. This thesis has aimed at dissecting modulation of Tregs by leukemic extracellular vesicles (EVs) - small, lipid bilayer-enclosed structures released outside cells as mediators of intercellular communication. As EVs have been demonstrated to modulate non-immune components of the leukemic bone marrow niche and have been shown to interact with Tregs in solid tumors, they might also constitute drivers of Foxp3+ regulatory T cells in myeloid leukemias. Using ex vivo cultures of murine and human Tregs with EVs released by CML and AML cell lines, leukemic EVs were shown to upregulate suppressive phenotype and activity of Tregs, as well as level of Foxp3. Leukemic EVs also induced Foxp3 expression in non-regulatory, conventional T cells. Leukemic EVs have upregulated phosphorylation of STAT5 and downregulated mTOR-S6 signaling in T cells to promote Treg induction, activity and stability. RNA-sequencing has revealed significant remodeling of Treg transcriptome by leukemic EVs, upregulated expression of tumor Treg genes and several transcription factors engaged in this regulation. Furthermore, 23-color spectral flow cytometry and unsupervised clustering tools have revealed 2 subsets of human effector Tregs (eTreg) expanded by leukemic EVs - CD30+CCR8hiTNFR2hi eTreg1 and CD39+TIGIThi eTreg2. Mass spectrometric analysis of leukemic EVs' proteome revealed presence of TNF superfamily protein 4-1BBL, which was engaged in modulation of expression of effector molecules (CD30, TNFR2, LAG-3) on Tregs. Finally, in a developed immunocompetent mouse model of CML-like disease, influence of EVs on Tregs and leukemic progression was validated by development of leukemia by Rab27a deficient cells, with attenuated secretion of EVs. Rab27a deficient leukemia has exhibited reduced engraftment in animals, whereas Tregs were less abundant and exhibited a less activated, less suppressive phenotype than in wild type counterparts. Altogether, data presented in this thesis pin-point extracellular vesicles, released by chronic and acute myeloid leukemia cells, as significant modulators of regulatory T cells - their induction, suppressive phenotype, function and effector subsets. In vivo, in a mouse model of leukemia-like disease, Rab27a-mediated secretion of EVs was shown to modulate Tregs and leukemic engraftment. Therefore, EVs and EVs-Tregs interaction may be evaluated as potential therapeutic targets in myeloid neoplasms

Detailed Resource Type:

PhD Dissertations

Resource Identifier:

oai:rcin.org.pl:235646

Source:

IBD PAN, call no. 19941

Language:

eng

Language of abstract:

pol

Digitizing institution:

Nencki Institute of Experimental Biology of the Polish Academy of Sciences

Original in:

Library of the Nencki Institute of Experimental Biology PAS

Access:

Open