Abstract
IntroductionBreast cancer progression is promoted by stromal cells that populate the tumors, including cancer-associated fibroblasts (CAFs) and mesenchymal stem/stromal cells (MSCs). The activities of CAFs and MSCs in breast cancer are integrated within an intimate inflammatory tumor microenvironment (TME) that includes high levels of tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β). Here, we identified the impact of TNF-α and IL-1β on the inflammatory phenotype of CAFs and MSCs by determining the expression of inflammatory chemokines that are well-characterized as pro-tumorigenic in breast cancer: CCL2 (MCP-1), CXCL8 (IL-8) and CCL5 (RANTES).MethodsChemokine expression was determined in breast cancer patient-derived CAFs by ELISA and in patient biopsies by immunohistochemistry. Chemokine levels were determined by ELISA in (1) human bone marrow-derived MSCs stimulated by tumor conditioned media (Tumor CM) of breast tumor cells (MDA-MB-231 and MCF-7) at the end of MSC-to-CAF-conversion process; (2) Tumor CM-derived CAFs, patient CAFs and MSCs stimulated by TNF-α (and IL-1β). The roles of AP-1 and NF-κB in chemokine secretion were analyzed by Western blotting and by siRNAs to c-Jun and p65, respectively. Migration of monocytic cells was determined in modified Boyden chambers.ResultsTNF-α (and IL-1β) induced the release of CCL2, CXCL8 and CCL5 by MSCs and CAFs generated by prolonged stimulation of MSCs with Tumor CM of MDA-MB-231 and MCF-7 cells. Patient-derived CAFs expressed CCL2 and CXCL8, and secreted CCL5 following TNF-α (and IL-1β) stimulation. CCL2 was expressed in CAFs residing in proximity to breast tumor cells in biopsies of patients diagnosed with invasive ductal carcinoma. CCL2 release by TNF-α-stimulated MSCs was mediated by TNF-RI and TNF-RII, through the NF-κB but not via the AP-1 pathway. Exposure of MSCs to TNF-α led to potent CCL2-induced migration of monocytic cells, a process that may yield pro-cancerous myeloid infiltrates in breast tumors.ConclusionsOur novel results emphasize the important roles of inflammation-stroma interactions in breast cancer, and suggest that NF-κB may be a potential target for inhibition in tumor-adjacent stromal cells, enabling improved tumor control in inflammation-driven malignancies.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-015-0080-7) contains supplementary material, which is available to authorized users.
Highlights
Breast cancer progression is promoted by stromal cells that populate the tumors, including cancer-associated fibroblasts (CAFs) and mesenchymal stem/stromal cells (MSCs)
We began this study by determining the influence of such tumor-derived factors on the inflammatory traits of CAFs generated by MSCs exposed to Tumor conditioned medium (CM), using the expression of the inflammatory/ pro-malignancy chemokines CCL2, CXCL8 and CCL5 as readouts
Tumor CM of MDA-MB-231 cells has increased the release of CCL2 and CXCL8 but not of CCL5 (Figure 1A), while Tumor CM of MCF-7 cells did not promote the release of CXCL8 and CCL5 by the Tumor CM-generated CAFs (Figure 1B2,B3) and downregulated the expression of CCL2 by the cells (Figure 1B1)
Summary
Breast cancer progression is promoted by stromal cells that populate the tumors, including cancer-associated fibroblasts (CAFs) and mesenchymal stem/stromal cells (MSCs). The activities of CAFs and MSCs in breast cancer are integrated within an intimate inflammatory tumor microenvironment (TME) that includes high levels of tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β). Recent studies demonstrated that breast tumors are populated by myofibroblasts that express pro-cancerous functions [1,2,3,4], known as cancer-. Major causative pro-tumoral roles were attributed to IL-1β in breast cancer via angiogenesis and matrix-remodeling activities [30,31,32,33,34,35,36,37]. Overall, based on recent studies addressing the roles of TNF-α and IL-1β in malignancy, both cytokines are considered potential targets for therapy in cancer [32,38,39,40]
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