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Absence of NKG2D ligands defines leukaemia stem cells and mediates their immune evasion.

ABSTRACT: Patients with acute myeloid leukaemia (AML) often achieve remission after therapy, but subsequently die of relapse1 that is driven by chemotherapy-resistant leukaemic stem cells (LSCs)2,3. LSCs are defined by their capacity to initiate leukaemia in immunocompromised mice4. However, this precludes analyses of their interaction with lymphocytes as components of anti-tumour immunity5, which LSCs must escape to induce cancer. Here we demonstrate that stemness and immune evasion are closely intertwined in AML. Using xenografts of human AML as well as syngeneic mouse models of leukaemia, we show that ligands of the danger detector NKG2D-a critical mediator of anti-tumour immunity by cytotoxic lymphocytes, such as NK cells6-9-are generally expressed on bulk AML cells but not on LSCs. AML cells with LSC properties can be isolated by their lack of expression of NKG2D ligands (NKG2DLs) in both CD34-expressing and non-CD34-expressing cases of AML. AML cells that express NKG2DLs are cleared by NK cells, whereas NKG2DL-negative leukaemic cells isolated from the same individual escape cell killing by NK cells. These NKG2DL-negative AML cells show an immature morphology, display molecular and functional stemness characteristics, and can initiate serially re-transplantable leukaemia and survive chemotherapy in patient-derived xenotransplant models. Mechanistically, poly-ADP-ribose polymerase 1 (PARP1) represses expression of NKG2DLs. Genetic or pharmacologic inhibition of PARP1 induces NKG2DLs on the LSC surface but not on healthy or pre-leukaemic cells. Treatment with PARP1 inhibitors, followed by transfer of polyclonal NK cells, suppresses leukaemogenesis in patient-derived xenotransplant models. In summary, our data link the LSC concept to immune escape and provide a strong rationale for targeting therapy-resistant LSCs by PARP1 inhibition, which renders them amenable to control by NK cells in vivo.

SUBMITTER: Paczulla AM

PROVIDER: S-EPMC6934414 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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Absence of NKG2D ligands defines leukaemia stem cells and mediates their immune evasion.

Paczulla Anna M AM Rothfelder Kathrin K Raffel Simon S Konantz Martina M Steinbacher Julia J Wang Hui H Tandler Claudia C Mbarga Marcelle M Schaefer Thorsten T Falcone Mattia M Nievergall Eva E Dörfel Daniela D Hanns Pauline P Passweg Jakob R JR Lutz Christoph C Schwaller Juerg J Zeiser Robert R Blazar Bruce R BR Caligiuri Michael A MA Dirnhofer Stephan S Lundberg Pontus P Kanz Lothar L Quintanilla-Martinez Leticia L Steinle Alexander A Trumpp Andreas A Salih Helmut R HR Lengerke Claudia C

Nature 20190717 7768

Patients with acute myeloid leukaemia (AML) often achieve remission after therapy, but subsequently die of relapse1 that is driven by chemotherapy-resistant leukaemic stem cells (LSCs)2,3. LSCs are defined by their capacity to initiate leukaemia in immunocompromised mice4. However, this precludes analyses of their interaction with lymphocytes as components of anti-tumour immunity5, which LSCs must escape to induce cancer. Here we demonstrate that stemn ...[more]

PMID: 31316209

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Project description:Patients with acute myeloid leukaemia (AML) often achieve remission yet subsequently die of disease relapse, which is commonly driven by chemotherapy-resistant leukaemic stem cells (LSCs). LSCs are defined by their capacity to initiate leukaemia in immuno-compromised mice. This precludes an analysis of their interaction with lymphocytes as components of anti-tumour immunity, which LSCs must escape in order to induce cancer7. Here we propose that stemness and immune evasion are closely intertwined in human AML. Using human AML xenograft and syngeneic mouse leukemia models, we show that ligands of the danger detector NKG2D, a critical mediator of anti-tumour immunity by cytotoxic lymphocytes such as natural killer (NK) cells, are generally expressed on bulk AML cells but not on LSCs. Functional LSCs can be isolated by their lack of NKG2D ligand (NKG2DL) expression, even in human AMLs not expressing the conventional LSC marker CD34. NKG2DL expressing AML cells are cleared by NK cells while NKG2DLneg leukaemic cells isolated from the same individuals escape NK cell killing. These NKG2DLneg AML cells show an immature morphology, display molecular and functional stemness characteristics, can initiate serially re-transplantable leukaemia and survive chemotherapy in patient-derived xenotransplants (PDX). Mechanistically, poly-ADP-ribose polymerase 1 (PARP1) negatively regulates NKG2DL and PARP1 inhibition (PARPi) induces NKG2DL surface expression in LSCs. Consequently, co-treatment with PARPi and NK cells suppresses leukaemogenesis in PDX models. Low expression of surface NKG2DL as well as high PARP1 expression are associated with inferior clinical outcome in patients with AML. In summary, our data link the concept of LSCs to immune escape and indicate absence of immunostimulatory NKG2DL as a novel method to identify LSCs across genetic AML subtypes. Moreover, we provide a strong rationale for targeting therapy resistant LSCs by PARP1 inhibition rendering them amenable to NK cell control in vivo.

Dataset Information

Absence of NKG2D ligands defines leukaemia stem cells and mediates their immune evasion.

Publications

Absence of NKG2D ligands defines leukaemia stem cells and mediates their immune evasion.

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