American Association for Cancer Research
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Supplementary Figure 2 from Tumoral Immune Suppression by Macrophages Expressing Fibroblast Activation Protein-α and Heme Oxygenase-1

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journal contribution
posted on 2023-04-03, 22:47 authored by James N. Arnold, Lukasz Magiera, Matthew Kraman, Douglas T. Fearon

PDF file - 18K, Assessment of peripheral blood chimerism of the bone marrow chimeric mice.



The depletion of tumor stromal cells that are marked by their expression of the membrane protein fibroblast activation protein-α (FAP) overcomes immune suppression and allows an anticancer cell immune response to control tumor growth. In subcutaneous tumors established with immunogenic Lewis lung carcinoma cells expressing ovalbumin (LL2/OVA), the FAP+ population is comprised of CD45+ and CD45− cells. In the present study, we further characterize the tumoral FAP+/CD45+ population as a minor subpopulation of F4/80hi/CCR2+/CD206+ M2 macrophages. Using bone marrow chimeric mice in which the primate diphtheria toxin receptor is restricted either to the FAP+/CD45+ or to the FAP+/CD45− subset, we demonstrate by conditionally depleting each subset that both independently contribute to the immune-suppressive tumor microenvironment. A basis for the function of the FAP+/CD45+ subset is shown to be the immune inhibitory enzyme, heme oxygenase-1 (HO-1). The FAP+/CD45+ cells are the major tumoral source of HO-1, and an inhibitor of HO-1, Sn mesoporphyrin, causes the same extent of immune-dependent arrest of LL2/OVA tumor growth as does the depletion of these cells. Because this observation of immune suppression by HO-1 expressed by the FAP+/CD45+ stromal cell is replicated in a transplanted model of pancreatic ductal adenocarcinoma, we conclude that pharmacologically targeting this enzyme may improve cancer immunotherapy. Cancer Immunol Res; 2(2); 121–6. ©2013 AACR.

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