Synergistic activation by p38MAPK and glucocorticoid signaling mediates induction of M2-like tumor-associated macrophages expressing the novel CD20 homolog MS4A8A Astrid Schmieder 1 *, Kai Schledzewski 1 *, Julia Michel 1 , Jan P. Tuckermann 2 , Lydia Tome 1 , Carsten Sticht 3 , Cleopatra Gkaniatsou 1 , Jan P. Nicolay 1 , Alexandra Demory 1 , Jo ¨rg Faulhaber 1 , Julia Kzhyshkowska 1 , Cyrill Ge ´raud 1 and Sergij Goerdt 1 1 Department of Dermatology, Venereology and Allergology, University Medical Center and Medical Faculty Mannheim, University of Heidelberg, and Center of Excellence in Dermatology, Mannheim, Germany 2 Leibniz Institute for Age Research, Fritz-Lipmann-Institute, Jena, Germany 3 Center for Medical Research, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany Tumor-associated macrophages (TAMs) represent alternatively activated (M2) macrophages that support tumor growth. Previously, we have described a special LYVE-1 1 M2 TAM subset in vitro and in vivo; gene profiling of this TAM subset identified MS4A8A as a novel TAM molecule expressed in vivo by TAM in mammary carcinoma and malignant melanoma. In vitro, Ms4a8a mRNA and MS4A8A protein expression was strongly induced in bone marrow-derived macrophages (BMDMs) by combining M2 mediators (IL-4, glucocorticoids) and tumor-conditioned media (TCM). Admixture of MS4A8A 1 TCM/IL-4/GC- treated BMDM significantly enhanced the tumor growth rate of subcutaneously transplanted TS/A mammary carcinomas. Upon forced overexpression of MS4A8A, Raw 264.7 macrophage-like cells displayed a special gene signature. Admixture of these MS4A8A 1 Raw 264.7 cells also significantly enhanced the tumor growth rate of subcutaneously transplanted mammary carcinomas. To identify the signaling pathways involved in synergistic induction of MS4A8A, the major signaling cascades with known functions in TAM were analyzed. Although inhibitors of NF-jB activation and of the MAPK JNK and ERK did not show relevant effects, the p38a/b MAPK inhibitor SB203580 strongly and highly significantly (p > 0.001) inhibited MS4A8A expression on mRNA and protein level. In addition, MS4A8A expression was restricted in M2 BMDM from mice with defective GC receptor (GR) dimerization indicating that classical GR gene regulation is mandatory for MS4A8A induction. In conclusion, expression of MS4A8A within the complex signal integration during macrophage immune responses may act to fine tune gene regulation. Furthermore, MS4A8A 1 TAM may serve as a novel cellular target for selective cancer therapy. Tumor-associated macrophages (TAMs) are a heterogeneous population of macrophages that represent a prominent com- ponent of stromal leukocytes in most malignant tumors. TAMs have been recognized as key regulators of the link between inflammation and cancer. 1 TAMs support tumor growth and affect the clinical outcome of cancer patients. 2–4 In most tumors analyzed, TAMs have been described to represent special subsets of alternatively activated (M2) mac- rophages. 5 In contrast to classically activated (M1) macro- phages that are proinflammatory macrophages with a high production of reactive nitrogen, oxygen intermediates, proin- flammatory cytokines and a strong microbicidal and tumori- cidal activity, M2 macrophages are induced by Th2 cytokines such as IL-4, IL-13 and IL-10 as well as by anti-inflammatory mediators such as glucocorticoids (GC). 6–8 M2 macrophages are characterized by upregulation of endocytotic receptors such as stabilin-1, CD163 and macrophage mannose receptor and are responsible for termination of inflammatory reactions and for inducing healing processes supporting angiogenesis, immunosuppression and tissue repair. 9–11 M2-like TAMs show altered NF-jB 12 signaling and express a specific molec- ular repertoire, e.g., TNF-a, IL-1b, IL-6 and IL-10. Proof of principle has been presented that M2-like TAMs may be reprogramed into M1 macrophages as a novel therapeutic approach in cancer. 13,14 MS4A8A is a member of the newly defined MS4A/CD20 family of proteins characterized by four transmembrane regions. This family comprises about 26 members in human and mouse. 15 The functions of many MS4A family members Key words: tumor-associated macrophages, tumor immunity, p38- MAPK pathway, MS4A family Additional Supporting Information may be found in the online version of this article. *A.S. and K.S. contributed equally to this work Grant sponsor: Deutsche Forschungsgemeinschaft (Project B12, Project B1); Grant numbers: SFB405, SFB-TR23 DOI: 10.1002/ijc.25657 History: Received 11 Jun 2010; Accepted 25 Aug 2010; Online 7 Sep 2010 Correspondence to: Dr. Astrid Schmieder, Department of Dermatology, Venereology and Allergology, Medical Faculty Mannheim, University of Heidelberg, Theodor-Kutzer Ufer 1-3, 68167 Mannheim, Germany, Tel: +49 621 383 2048, Fax: þ49-621-383-3815, E-mail: astrid.schmieder@umm.de Tumor Immunology Int. J. Cancer: 129, 122–132 (2011) V C 2010 UICC International Journal of Cancer IJC