Human breast cancer cells educate macrophages toward the M2 activation status

Abstract

IntroductionThe immune system plays a major role in cancer progression. In solid tumors, 5-40 % of the tumor mass consists of tumor-associated macrophages (TAMs) and there is usually a correlation between the number of TAMs and poor prognosis, depending on the tumor type. TAMs usually resemble M2 macrophages. Unlike M1-macrophages which have pro-inflammatory and anti-cancer functions, M2-macrophages are immunosuppressive, contribute to the matrix-remodeling, and hence favor tumor growth. The role of TAMs is not fully understood in breast cancer progression.MethodsMacrophage infiltration (CD68) and activation status (HLA-DRIIα, CD163) were evaluated in a large cohort of human primary breast tumors (562 tissue microarray samples), by immunohistochemistry and scored by automated image analysis algorithms. Survival between groups was compared using the Kaplan-Meier life-table method and a Cox multivariate proportional hazards model. Macrophage education by breast cancer cells was assessed by ex vivo differentiation of peripheral blood mononuclear cells (PBMCs) in the presence or absence of breast cancer cell conditioned media (MDA-MB231, MCF-7 or T47D cell lines) and M1 or M2 inducing cytokines (respectively IFN-γ, IL-4 and IL-10). Obtained macrophages were analyzed by flow cytometry (CD14, CD16, CD64, CD86, CD200R and CD163), ELISA (IL-6, IL-8, IL-10, monocyte colony stimulating factor M-CSF) and zymography (matrix metalloproteinase 9, MMP-9).ResultsClinically, we found that high numbers of CD163+ M2-macrophages were strongly associated with fast proliferation, poor differentiation, estrogen receptor negativity and histological ductal type (p<0.001) in the studied cohort of human primary breast tumors. We demonstrated ex vivo that breast cancer cell-secreted factors modulate macrophage differentiation toward the M2 phenotype. Furthermore, the more aggressive mesenchymal-like cell line MDA-MB231, which secretes high levels of M-CSF, skews macrophages toward the more immunosuppressive M2c subtype.ConclusionsThis study demonstrates that human breast cancer cells influence macrophage differentiation and that TAM differentiation status correlates with recurrence free survival, thus further emphasizing that TAMs can similarly affect therapy efficacy and patient outcome.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-015-0621-0) contains supplementary material, which is available to authorized users.

Basal‐like breast cancer engages tumor‐supportive macrophages via secreted factors induced by extracellular S100A4

“…We showed that upon S100A4 stimulation, basal‐like BCCs secrete factors that trigger monocyte‐to‐macrophage differentiation and polarization. This is in line with previous studies demonstrating that basal‐like/TNBC, compared to luminal BC, have superior abilities to recruit macrophages (Espinoza et al ., 2016; Sousa et al ., 2015), modulate their polarization, and stimulate protumorigenic functions (Hollmen et al ., 2015; Sousa et al ., 2015; Stewart et al ., 2012; Su et al ., 2014). The current study adds to the previous knowledge by revealing a strong potentiating influence of S100A4, which is expressed at elevated levels in basal‐like/TNBC as also reported previously (Egeland et al ., 2017).…”

Elevated expression of chemokine C-C ligand 2 in stroma is associated with recurrent basal-like breast cancers

“…55 To clearly determine the relevance of CCL2 expression and macrophage recruitment and activity in triple-negative breast cancer, it would be necessary to perform immunostaining for markers identifying these macrophage subtypes, including M1-and M2-like cells, and compare their expression patterns with a panmacrophage marker. [55][56][57] These studies are beyond the scope of this manuscript but are of interest in the future. In summary, our studies demonstrate an association between poor outcome in basal-like breast cancer and CCL2 expression in the stroma.…”

Small cell lung cancer: Recruitment of macrophages by circulating tumor cells

“…Other cytokines found in supernatants of the two CTC cell lines but not in HEK293 and possibly involved in monocyte-macrophage differentiation comprise IL-4, IL-5, pentraxin-3 (PTX-3) and VEGF. [68][69][70] Recruitment of macrophages may be less important during intravasation where the nearby tumor supports proinvasive factors but of significant advantage at the site of extravasation to enhance degradation of tissue components and to provide protection from immune defense. 71 CHI3L1 was reported to promote macrophage recruitment and angiogenesis in colorectal cancer.…”