Synergistic activation by p38MAPK and glucocorticoid signaling mediates induction of M2‐like tumor‐associated macrophages expressing the novel CD20 homolog MS4A8A

Abstract

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/GCtreated 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.

The CD20 homolog Ms4a8a integrates pro‐ and anti‐inflammatory signals in novel M2‐like macrophages and is expressed in parasite infection

“…2B and C). Tcfec has already been reported to show basal induction by Ms4a8a overexpression in RAW264.7 cells [9] and was shown here to be super-induced by LPS, while Hdc showed basal induction by LPS and super-induction by Ms4a8a. In order to test whether genes coinduced by Ms4a8a and LPS in RAW264.7 cells were similarly regulated in Ms4a8a expressing primary macrophages in vitro and in vivo, LPS/dexa/IL-4-induced Ms4a8a + BMDMs and Ms4a8a + PEMs from mice suffering from late-stage cysticercosis were analyzed by qRT-PCR.…”

“…2A). Gene expression data for groups 1 and 2 have already been published and are publicly accessible and are used here only for control purposes [9]. Among the genes upregulated by Ms4a8a in combination with LPS, statistically significant coinduction of two genes, that is, Hdc and Tcfec, could be confirmed by qRT-PCR (Supporting Information Fig.…”

“…These findings prompted us to study the presence of Ms4a8a in macrophages in parasitic infections, in particular in Trypanosoma congolense and Taenia crassiceps infections in C57BL/6 mouse models, which are characterized by a clear shift from M1 (early stage) to M2 (late stage) predominance [12,15]. Moreover, as we have shown that the induction of Ms4a8a in BMDMs in vitro required M2 mediators and a second, as yet unidentified molecular signal [9], and as there is ample evidence that innate immunity in Trypanosoma and Taenia infections is modulated by Toll-like receptor (TLR) signaling [16][17][18][19], we asked here whether TLR activation in BMDMs provides such a second signal for the induction of Ms4a8a mRNA and protein expression. In addition, we tested whether Ms4a8a might in turn modulate TLR signaling.…”

“…Accordingly, M1 or classically activated macrophages differentiate from monocytes under the predominant influence of pro-inflammatory cytokines such as IFN-γ, IL-12, or TNF-α, while M2, or alternative, macrophage activation was primarily described as a response to Th2 cytokines such as IL-4, IL-13, and IL-10, as well as to anti-inflammatory mediators such as glucocorticoids (GCs) [4][5][6][7]. As these macrophage phenotypes influence the tissue environment, for example, via secretion of active mediators, a solid characterization of macrophages, especially in pathological processes such as cancer or chronic inflammation, is needed to uncover unique key cellular regulators [8].In a previous study, the CD20 homolog Ms4a8a was found to be expressed by M2-like tumor-associated macrophages (TAMs) in murine mammary carcinoma and malignant melanoma [9]. For the induction of Ms4a8a expression in these tumor models, simultaneous treatment of bone marrow derived macrophages (BMDMs) in vitro both by the M2 mediators dexamethasone (dexa)/IL-4 and by tumor-conditioned media (TCM) was necessary, resulting in the activation of the glucocorticoid receptor (GR) and of the p38α/β MAPK signaling pathway.…”

“…These TAMrelated Ms4a8a + macrophages displayed a typical M2 marker profile including mRNA expression of the mannose receptor (Mmr), arginase 1, and CD163, and considerably enhanced the tumor growth rate of subcutaneous transplant tumors when coinjected with TS/A mammary carcinoma cells in mice. Functionally, forced overexpression of Ms4a8a in a macrophage-like cell line induced a special gene signature (Tcfec, Spink5, Sla) involved in immune regulation [9].Since the establishment of the M1/M2 macrophage concept, parasite infections have been the most frequently used model systems for studying alternatively activated macrophages and their functions in vivo [10,11]. Although different parasite models and different organs were analyzed, and although in vivo crosstalk at all levels shapes macrophage function and gene regulation, the expression of M2 marker genes such as Mmr, arginase 1, Ym1, Cdh1, or CD163 remained remarkably consistent in most of these models [12][13][14].…”