A niche that triggers aggressiveness within BRCA1-IRIS overexpressing triple negative tumors is supported by reciprocal interactions with the microenvironment

Abstract

Production of metastasis capable precursors begins within the primary tumor. Here, we define the bidirectional interactions with stromal cells involved in promoting these precursors within BRCA1-IRIS (hereafter IRIS) overexpressing (IRISOE) TNBC tumors. We define an aggressiveness niche, functionally defined as the necrotic/hypoxic core of the tumor, in which metabolically stressed, hypoxic, and inflamed IRISOE TNBC cells secrete higher levels of cytokines, chemokines and growth factors. One cytokine; IL-1β attracts mesenchymal stem cells (MSCs) to the niche and activates them to secrete CXCL1 that entrains IRISOE cells to secrete higher levels of CCL2 and VEGF. CCL2 attracts macrophages (TAMs) to the niche and activates them to secrete S100A8, and VEGF attracts endothelial cells (ECs) and activates them to secrete IL-8. In concert, CXCL1, S100A8 and IL-8 entrain aggressiveness in IRISOE TNBC cells within the niche. Indeed, compared to IRISOE cells alone, tumors developed by co-injecting IRISOE cells admixed with MSCs (10:1) in athymic mice were bigger and more aggressive. They contained more TAMs and ECs, expressed higher-levels of basal, epithelial to mesenchymal transition, and stemness biomarkers, quickly progressed to lymph-node or visceral metastases, and were highly sensitive to the IL-1β inhibitor “Anakinra”. Our findings supported by human data show that breast cancer patients with high-levels of IL-1β, CXCL1, CCL2, S100A8, VEGF, and IL-8 would show worse clinical outcomes. Our findings argue that this cytokine set is a diagnostic biomarker for patients who may benefit from an IRIS inhibitor-based therapy, and is a blue print for translation of approaches to combining that therapy with inhibitors of these bidirectional interactions to overcome TNBC metastasis.

Tumor-Stroma-Inflammation Networks Promote Pro-metastatic Chemokines and Aggressiveness Characteristics in Triple-Negative Breast Cancer

“…Many published studies have described the ability of MSCs and CAFs to promote the metastatic phenotype of TNBC cells (12, 16–18, 21, 23, 26, 65). Yet, they have not directly determined the impact of the pro-inflammatory signals on tumor growth and metastasis when TNBC:stroma interactions are established.…”

“…CXCL8 and CCL5, produced by bone marrow- and adipose-derived MSCs were prime inducers of metastasis in TNBC, acting by elevating the proliferation and invasive properties of the tumor cells, and their resistance to chemotherapy (19, 20, 23, 24, 26, 97–99). Moreover, MSC-derived CCL2 has attracted macrophages to TNBC tumors, activating them to secrete CXCL8, thus leading to an overall increase in tumor-associated macrophages and endothelial cells (21).…”

“…In TNBC, sequencing, serum-profiling and immunohistochemistry studies of small patient cohorts provided initial evidence to relevance of high expression of the two cytokines or of their signaling components to metastasis in TNBC patients (50–53); in parallel, studies in animal models have demonstrated causative tumor-promoting roles for TNFα and IL-1β in TNBC (52, 54–59). TNFα and IL-1β were also connected with pro-malignancy activities of MSCs and CAFs in TNBC (21, 60–65). Specifically with regards to chemokines, we and others have shown that TNFα and IL-1β elevated the expression of CXCL8, CCL2 and CCL5 (or their murine counterparts) by MSCs [(65–69); the degree of increase depended on assay conditions], thus promoting the pro-inflammatory and pro-malignancy phenotype of these stromal cells.…”

Regulation of the Hypoxia-Inducible Factor (HIF) by Pro-Inflammatory Cytokines

“…These alarmin receptors are activated by HIF-1α and strongly induce NF-κB and proinflammatory gene expression which, subsequently, lead to the acquisition of crucial properties of the malignant tissue phenotype [ 91 ]. This includes pro-tumorigenic chemokines CCL2, CCL5, and CXCR1/CXCL8, which are the key initial steps in cell migration in different cell types, including triple-negative breast cancer cells [ 94 , 95 , 96 , 97 , 98 ]. Findings of higher levels of TNF-α plasma levels in various malignancies such as gastrointestinal carcinoma than in controls further support this observation [ 99 , 100 ].…”

Key Factor Regulating Inflammatory Microenvironment, Metastasis, and Resistance in Breast Cancer: Interleukin-1 Signaling

“…CXCL1 enabled IRISOE-TNBC cells to secrete higher levels of CCL2 and VEGF, which recruit and activate TAMs and endothelial cells (ECs), and induce these cells to secrete S100A8/9 and IL-8, respectively. This interaction contributes to the generation of the metastatic precursor of IRISOE-TNBC [100]. Invasive BC cells (MDA-MB-231 cells) activate NF-κB signaling in MSCs by secreting IL-1β, inducing and increasing the production of the same chemokines (CXCL1, 3, 5, 6, 8, and CCL2, 5, etc.)…”