Proteomic profiling of small extracellular vesicles (EVs), released by chronic myeloid leukemia cells K562

ABSTRACT: Chronic and acute myeloid leukemia (CML/AML) evade immune surveillance and induce immunosuppression, largely by upregulating Foxp3+ regulatory T cells (Treg). However, mechanisms that drive Treg in myeloid leukemias are largely unknown. Here, we show that leukemic (CML- and AML-derived) extracellular vesicles (EVs) drive human Treg, by de novo induction of Treg and by upregulating suppressive phenotype and activity of Treg. Rab27a-mediated EVs secretion contributed to Treg expansion, activity, and leukemic engraftment in vivo in a mouse model of CML-like disease. Leukemic EVs downregulated mTOR-S6 and upregulated STAT5 signaling in T cells, to upregulate Foxp3 and Treg activity, as well as evoked significant transcriptomic changes in Treg. By using high resolution 23-color spectral flow cytometry we identified 2 distinct, highly suppressive subsets of Treg expanded by leukemic EVs, characterized by elevated expression of tumor Treg markers CCR8, CCR4, TIGIT, CD39, CD30, TNFR2 and IL21R. Finally, we identified 4 1BBL/TNFSF9 protein in leukemic EVs. Deficiency of 4-1BBL in leukemic cells and EVs resulted in lower expression of CD30, TNFR2 and LAG-3 on Treg and thus weaker effector phenotype. Collectively, our data pinpoint leukemic extracellular vesicles as a significant factor that drives regulatory T cells and immunosuppression in myeloid leukemias. Our results suggest that targeting of Rab27a and EVs secretion may be a viable therapeutic option in myeloid leukemias, whereas detection of 4 1BBL containing EVs could be used as an early biomarker of immunosuppression and leukemia development/relapse

INSTRUMENT(S): LTQ Orbitrap Velos, Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Bone Marrow

SUBMITTER: Dominik Cysewski  

LAB HEAD: Katarzyna Piwocka

PROVIDER: PXD027240 | Pride | 2022-02-16

REPOSITORIES: Pride