LC3-associated phagocytosis in bone marrow macrophages suppresses acute myeloid leukemia progression through STING activation
Jamie A. Moore, … , Kristian M. Bowles, Stuart A. Rushworth
Jamie A. Moore, … , Kristian M. Bowles, Stuart A. Rushworth
Published January 6, 2022
Citation Information: J Clin Invest. 2022;132(5):e153157. https://doi.org/10.1172/JCI153157.
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Research Article Hematology Oncology

LC3-associated phagocytosis in bone marrow macrophages suppresses acute myeloid leukemia progression through STING activation

Abstract

The bone marrow (BM) microenvironment regulates acute myeloid leukemia (AML) initiation, proliferation, and chemotherapy resistance. Following cancer cell death, a growing body of evidence suggests an important role for remaining apoptotic debris in regulating the immunologic response to and growth of solid tumors. Here, we investigated the role of macrophage LC3–associated phagocytosis (LAP) within the BM microenvironment of AML. Depletion of BM macrophages (BMMs) increased AML growth in vivo. We show that LAP is the predominate method of BMM phagocytosis of dead and dying cells in the AML microenvironment. Targeted inhibition of LAP led to the accumulation of apoptotic cells (ACs) and apoptotic bodies (ABs), resulting in accelerated leukemia growth. Mechanistically, LAP of AML-derived ABs by BMMs resulted in stimulator of IFN genes (STING) pathway activation. We found that AML-derived mitochondrial damage–associated molecular patterns were processed by BMMs via LAP. Moreover, depletion of mitochondrial DNA (mtDNA) in AML-derived ABs showed that it was this mtDNA that was responsible for the induction of STING signaling in BMMs. Phenotypically, we found that STING activation suppressed AML growth through a mechanism related to increased phagocytosis. In summary, we report that macrophage LAP of apoptotic debris in the AML BM microenvironment suppressed tumor growth.

Authors

Jamie A. Moore, Jayna J. Mistry, Charlotte Hellmich, Rebecca H. Horton, Edyta E. Wojtowicz, Aisha Jibril, Matthew Jefferson, Thomas Wileman, Naiara Beraza, Kristian M. Bowles, Stuart A. Rushworth

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Figure 6

AML-derived ABs containing mtDNA activate STING in BMMs via a LAP-dependent mechanism.

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AML-derived ABs containing mtDNA activate STING in BMMs via a LAP-depend...
(A) Primary AML cells were transduced with rLV.EF1.mCherry-Mito9 lentivirus (mCh-AML), and the ABs were isolated (mCh-AB). mCh-ABs were cultured with BMMs from Atg16L1E230+ and Atg16L1E230– mice for 24 hours. (B) mCherry intensity between Atg16L1E230+ and Atg16L1E230– BMMs was analyzed at 4 and 24 hours by confocal microscopy (n = 5). (C) Relative mtDNA levels of MN1 cells and ρ0-generated MN1 cells normalized to DNA levels using TaqMan PCR and Tert and ND3 probes (n = 5). (D). Nonmalignant LSK cells and MN1 cells were stained for MitoTracker Red, and the ABs were isolated before being sorted on the basis of a positive MitoTracker Red signal. ρ0 MN1 cell ABs were also isolated. The ABs were cultured for 24 hours with BMMs from C57/BL6 mice, and RNA was extracted for qPCR analysis. (E) Relative gene expression of Gbp2, Irf7, and Ifit3 in BMMs cultured with sorted mitochondria containing ABs from MN1, LSK, and ρ0 MN1 cells AB (n = 4). (F) Nonmalignant LSK and MN1 cells were stained for MitoTracker Red, and the ABs were isolated before sorting on the basis of a positive MitoTracker Red signal. The ABs were cultured for 24 hours with BMMs from Atg16L1E230– and Atg16L1E230+ mice, and RNA was extracted for qPCR analysis. (G) Relative gene expression of Gbp2, Irf7, and Ifit3 in Atg16L1E230– and Atg16L1E230+ BMMs cultured with sorted mitochondria containing ABs from MN1 and LSK cells (n = 5). Data indicate the mean ± SD. *P < 0.05 and **P < 0.01, by Mann-Whitney U test (B and C) and Kruskal-Wallis test (E and G).