Equal Pro-inflammatory Profiles of CCLs, CXCLs, and Matrix Metalloproteinases in the Extracellular Microenvironment In Vivo in Human Dense Breast Tissue and Breast Cancer

Abstract

The inflammatory microenvironment affects breast cancer progression. Proteins that govern the inflammatory response are secreted into the extracellular space, but this compartment still needs to be characterized in human breast tissues in vivo. Dense breast tissue is a major risk factor for breast cancer by yet unknown mechanisms and no non-toxic prevention for these patients exists. Here, we used the minimal invasive technique of microdialysis for sampling of extracellular proteins in live tissues in situ in breast cancers of women before surgery and in healthy women having dense or non-dense breast tissue on mammography. Proteins were profiled using a proximity extension assay. Out of the 32 proteins assessed, 26 exhibited similar profiles in breast cancers and dense breast tissues; CCL-4, -7, -8, -11, -15, -16, -22, -23, and -25, CXCL-5, -8, -9, -16 as well as sIL-6R, IL-18, vascular endothelial growth factor, TGF-α, fibroblast growth factor 19, matrix metalloproteinase (MMP)-1, -2, -3, and urokinase-type plasminogen activator were all increased, whereas CCL-3, CX3CL1, hepatocyte growth factor, and MMP-9 were unaltered in the two tissues. CCL-19 and -24, CXCL-1 and -10, and IL-6 were increased in dense breast tissue only, whereas IL-18BP was increased in breast cancer only. Our results provide novel insights in the inflammatory microenvironment in human breast cancer in situ and define potential novel therapeutic targets. Additionally, we show previously unrecognized similarities of the pro-inflammatory microenvironment in dense breast tissue and breast cancer in vivo suggesting that anti-inflammatory breast cancer prevention trials for women with dense breast tissue may be feasible.

The effects of flaxseed and tamoxifen on the inflammatory microenvironment in normal breast tissue and in breast cancer

“…This corroborates an in vivo study of inflammatory mediators in the microenvironment in healthy postmenopausal women were we found significant associations between reduced IL-1Ra/IL-1β ratio, increased levels of IL-6, IL-8, VEGF and CCL2 in breast tissue with extremely high MD compared to breast tissue with low MD (34). We have also shown that out of 32 pro-inflammatory mediators assessed, 26 proteins exhibited similar profiles in breast cancer and dense breast tissue suggesting a pro-inflammatory microenvironment as a possible initiator of malignant transformation in dense breast tissue (35).…”

“…MMP-9 has been associated with poor outcome in breast cancer patients but some experimental models have shown anti-tumoral effects on xenografts in mice (195,196,198,199). Furthermore, in a previous study by our group, no elevated levels of MMP-9 were measured in human breast cancers compared to adjacent normal breast tissue in vivo, whereas other MMPs were significantly elevated in breast cancer compared to adjacent normal breast tissue (35). This underlines the importance of studying the inflammatory mediators in their bioactive compartment.…”

“…In mouse models MMP-8 has shown to suppress metastasis and, intriguingly, MMP-9 has been associated with tumor regression and anti-angiogenic activity in some, but not all, experimental models (197)(198)(199). Furthermore, MMP-9 was not elevated in a study by our group of human breast cancer compared to adjacent normal breast tissue in vivo, although MMP-1,-2,-3 were significantly elevated (35).…”

“…In our study we investigated apparently normal breast tissue, and thus the levels of IL-1β and other inflammatory mediators may not be as upregulated as in a more inflammatory environment. These differences in expression of inflammatory mediators are to some extent illustrated by one of our previous studies that showed that 23 of 32 inflammatory proteins were significantly increased in breast cancer compared to adjacent normal breast tissue (35). Hence, the possibility to detect any significant changes in inflammatory mediators in normal breast tissue may to some extent be limited.…”

“…However, we have shown that postmenopausal women with extremely high MD have a more pro-inflammatory microenvironment compared to women with low MD which could contribute to a higher risk of developing breast cancer (34). Furthermore, we have also compared postmenopausal women with dense breast tissue to women with breast cancer and found that 26 of 32 inflammatory mediators showed similar profile (35). There is limited knowledge of the association between MD and survival in women diagnosed with breast cancer.…”