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Metabolic rewiring of macrophages by CpG potentiates clearance of cancer cells and overcomes tumor-expressed CD47−mediated ‘don’t-eat-me’ signal


Macrophages enforce antitumor immunity by engulfing and killing tumor cells. Although these functions are determined by a balance of stimulatory and inhibitory signals, the role of macrophage metabolism is unknown. Here, we study the capacity of macrophages to circumvent inhibitory activity mediated by CD47 on cancer cells. We show that stimulation with a CpG oligodeoxynucleotide, a Toll-like receptor 9 agonist, evokes changes in the central carbon metabolism of macrophages that enable antitumor activity, including engulfment of CD47+ cancer cells. CpG activation engenders a metabolic state that requires fatty acid oxidation and shunting of tricarboxylic acid cycle intermediates for de novo lipid biosynthesis. This integration of metabolic inputs is underpinned by carnitine palmitoyltransferase 1A and adenosine tri-phosphate citrate lyase, which, together, impart macrophages with antitumor potential capable of overcoming inhibitory CD47 on cancer cells. Our findings identify central carbon metabolism to be a novel determinant and potential therapeutic target for stimulating antitumor activity by macrophages.

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The data and code that support the findings of this study are available within the paper and its Supplementary Information files and are available from the corresponding author upon reasonable request.

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We would like to thank all members of the Beatty laboratory for helpful suggestions, and B. Keith, A. Rustgi, A. Minn, T. Ridky and K. Wellen for their scientific critiques. We thank J. Benci and O. Kawalekar for their assistance with CRISPR/Cas9 and Seahorse experiments; M. Stone for her assistance with immunohistochemistry; A. Rech for manuscript review; K. Foskett for sharing his Seahorse bioanalyzer; J. Scholler and A. Posey for assistance with lentivirus production and the Molecular Biology and Molecular Pathology and Imaging Cores of the Penn Center supported by a Molecular Studies in Digestive and Liver Diseases grant (P30-DK050306) from the National Institutes of Health. This work was supported by grants from the NIH (R01 CA197916 to G.L.B., R03 HD092630 to N.W.S., and F30 CA196124 to M.L), and the Seed Grant Program from the American Medical Association Foundation (M. Liu).

Author information

Experiments and data analysis were performed by M.L., R.S.O., S.T., K.G., N.W.S. and G.L.B. Tumor cell culture and injection and tumor growth studies were performed by M.L. and K.G. immunofluorescence by M.L. Immunohistochemistry was performed by M.L. Flow cytometry was performed by M.L. In vitro and in vivo phagocytosis assays were performed by M.L. Detection of cytokines by cytokine bead array was done by M.L. BODIPY-C16 labeling experiments were performed by M.L. and R.S.O. Membrane fluidity assay was performed by M.L. Seahorse assays were performed by M.L. and R.S.O. 13C metabolite tracing was done by M.L. and R.S.O. R.S.O., S.T. and N.W.S. provided experimental advice. M.L. and G.L.B designed the study. M.L. and G.L.B. prepared and wrote the manuscript and all authors edited and approved the final manuscript.

Competing interests

The authors declare no competing interests.

Correspondence to Gregory L. Beatty.

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Fig. 1: Macrophage activation via TLR agonists, but not disruption of CD47, induces antitumor activity in a model of pancreatic cancer.
Fig. 2: CpG induces antitumor activity in vivo.
Fig. 3: CpG-induced antitumor activity requires macrophages.
Fig. 4: CpG stimulates macrophage antitumor activity in vitro and in vivo that is independent of the anti-phagocytic signal CD47 expressed on PDAC cells.
Fig. 5: CpG evokes metabolic changes in macrophages without polarization to M1 or M2.
Fig. 6: Fatty acid oxidation induced by CpG is essential for macrophage antitumor activity.
Fig. 7: Metabolic rewiring of TCA cycle supports the oxidative phenotype and antitumor activity of CpG-activated macrophages.