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A mutual activation loop between breast cancer cells and myeloid-derived suppressor cells facilitates spontaneous metastasis through IL-6 trans-signaling in a murine model

Cited 106 time in Web of Science Cited 108 time in Scopus
Authors

Oh, Keunhee; Lee, Ok-Young; Shon, Suh Youn; Nam, Onyou; Ryu, Po Mee; Seo, Myung Won; Lee, Dong-Sup

Issue Date
2013-09-10
Publisher
BioMed Central Ltd.
Citation
Breast Cancer Research Vol.15, pp.1-16
Keywords
Myeloid-derived suppressor cell (MDSC)Breast cancer cellMetastasisIL-6 trans-signaling
Abstract
Introduction : Tumor cell interactions with the microenvironment, especially those of bone-marrow-derived myeloid cells, are important in various aspects of tumor metastasis. Myeloid-derived suppressor cells (MDSCs) have been suggested to constitute tumor-favoring microenvironments. In this study, we elucidated a novel mechanism by which the MDSCs can mediate spontaneous distant metastasis of breast cancer cells.

Methods : Murine breast cancer cells, 4T1 and EMT6, were orthotopically grafted into the mammary fat pads of syngeneic BALB/c mice. CD11b+Gr-1+ MDSCs in the spleen, liver, lung and primary tumor mass were analyzed. To evaluate the role of MDSCs in the distant metastasis, MDSCs were depleted or reconstituted in tumor-bearing mice. To evaluate whether MDSCs in the metastasizing tumor microenvironment affect breast cancer cell behavior, MDSCs and cancer cells were co-cultivated. To investigate the role of MDSCs in in vivo metastasis, we blocked the interactions between MDSCs and cancer cells.

Results : Using a murine breast cancer cell model, we showed that murine breast cancer cells with high IL-6 expression recruited more MDSCs and that the metastasizing capacity of cancer cells paralleled MDSC recruitment in tumor-bearing mice. Metastasizing, but not non-metastasizing, tumor-derived factors induced MDSCs to increase IL-6 production and full activation of recruited MDSCs occurred in the primary tumor site and metastatic organ in the vicinity of metastasizing cancer cells, but not in lymphoid organs. In addition, tumor-expanded MDSCs expressed Adam-family proteases, which facilitated shedding of IL-6 receptor, thereby contributing to breast cancer cell invasiveness and distant metastasis through IL-6 trans-signaling. The critical role of IL-6 trans-signaling was confirmed in both the afferent and efferent pathways of metastasis.

Conclusion : In this study, we showed that metastasizing cancer cells induced higher MDSCs infiltration and prompted them to secret exaggerated IL-6 as well as soluble IL-6Rα, which, in turn, triggered a persistent increase of pSTAT3 in tumor cells. This potential tumor-MDSC axis involving IL-6 trans-signaling directly affected breast cancer cell aggressiveness, leading to spontaneous metastasis.
ISSN
1465-5411
Language
English
URI
https://hdl.handle.net/10371/91317
DOI
https://doi.org/10.1186/bcr3473
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