Growth of Triple-Negative Breast Cancer Cells Relies upon Coordinate Autocrine Expression of the Proinflammatory Cytokines IL-6 and IL-8

Breast cancer is a leading cause of cancer-related death, and it is important to understand pathways that drive the disease to devise effective therapeutic strategies. Our results show that Toll-like receptor 4 (TLR4) drives breast cancer cell growth differentially based on the presence of TP53, a tumor suppressor. TP53 is mutationally inactivated in most types of cancer and is mutated in 30-50% of diagnosed breast tumors. We demonstrate that TLR4 activation inhibits growth of TP53 wild-type cells, but promotes growth of TP53 mutant breast cancer cells by regulating proliferation. This differential effect is mediated by changes in tumor cell cytokine secretion. Whereas TLR4 activation in TP53 mutant breast cancer cells increases secretion of progrowth cytokines, TLR4 activation in TP53 wild-type breast cancer cells increases type I IFN (IFN-γ) secretion, which is both necessary and sufficient for mediating TLR4-induced growth inhibition. This study identifies a novel dichotomous role for TLR4 as a growth regulator and a modulator of tumor microenvironment in breast tumors. These results have translational relevance, demonstrating that TP53 mutant breast tumor growth can be suppressed by pharmacologic TLR4 inhibition, whereas TLR4 inhibitors may in fact promote growth of TP53 wild-type tumors. Furthermore, using data generated by The Cancer Genome Atlas consortium, we demonstrate that the effect of TP53 mutational status on TLR4 activity may extend to ovarian, colon, and lung cancers, among others, suggesting that the viability of TLR4 as a therapeutic target depends on TP53 status in many different tumor types.reast cancer has one of the highest incidence rates of cancer in women worldwide, with more than 1.5 million women diagnosed with the disease in 2012. Owing to its high incidence, breast cancer is also one of the leading causes of cancer-related deaths, with 40,000 women predicted to die of the disease in 2014 in the US alone. The diagnosis and treatment of breast cancer has been significantly improved by the identification of three major subtypes of the disease based on receptor expression: estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-positive, and triple-negative [tumors lacking ER, progesterone receptor (PR), and HER2]. Of these subtypes, ER-positive breast cancer accounts for 70-80% of all diagnosed breast tumors.ER-positive breast cancer is largely responsive to endocrine therapy; however, intrinsic or acquired resistance occurs in onethird of cases and contributes significantly to breast cancerassociated mortality. Therefore, identifying therapeutic targets to prevent ER-positive breast cancer mortality is a major focus of scientific investigation. ER-positive breast tumors with a high mutation load are associated with poor patient survival, and a high mutation load likely affects the response to endocrine therapy (1). Because known drivers of endocrine resistance (e.g., PR negativity and HER2 amplification) are not enriched in this subset, the identification of no...

Section: Tlr4 Inhibits Breast Cancer Cell Proliferation In a Tp53-depsupporting

confidence: 91%

TLR4 has a TP53-dependent dual role in regulating breast cancer cell growth

Haricharan

Brown

2015

“…Interleukin 6 (IL-6) and IL-8 have been shown to regulate BCSC survival and self-renewal (6,31,(34)(35)(36)(37)(38). Treatment of MDA-MB-231, SUM-159, or SUM-149 TNBC cells with paclitaxel induced IL-8 mRNA expression on day 4 (Fig.…”

Section: /Prmentioning

confidence: 99%

Hypoxia-inducible factors are required for chemotherapy resistance of breast cancer stem cells

Samanta¹,

Gilkes²,

Chaturvedi³

et al. 2014

434

396

Triple negative breast cancers (TNBCs) are defined by the lack of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 expression, and are treated with cytotoxic chemotherapy such as paclitaxel or gemcitabine, with a durable response rate of less than 20%. TNBCs are enriched for the basal subtype gene expression profile and the presence of breast cancer stem cells, which are endowed with self-renewing and tumor-initiating properties and resistance to chemotherapy. Hypoxia-inducible factors (HIFs) and their target gene products are highly active in TNBCs. Here, we demonstrate that HIF expression and transcriptional activity are induced by treatment of MDA-MB-231, SUM-149, and SUM-159, which are human TNBC cell lines, as well as MCF-7, which is an ER + /PR + breast cancer line, with paclitaxel or gemcitabine. Chemotherapy-induced HIF activity enriched the breast cancer stem cell population through interleukin-6 and interleukin-8 signaling and increased expression of multidrug resistance 1. Coadministration of HIF inhibitors overcame the resistance of breast cancer stem cells to paclitaxel or gemcitabine, both in vitro and in vivo, leading to tumor eradication. Increased expression of HIF-1α or HIF target genes in breast cancer biopsies was associated with decreased overall survival, particularly in patients with basal subtype tumors and those treated with chemotherapy alone. Based on these results, clinical trials are warranted to test whether treatment of patients with TNBC with a combination of cytotoxic chemotherapy and HIF inhibitors will improve patient survival.digoxin | mammary fat pad implantation | tumor relapse

“…IL-8 and IL-6 are two additional biomarkers of disease progression identified in high NOS2 expressing ER − breast tumors (4) and triple negative breast cancer patients (30). Herein, we show IFN-γ induced the mRNA expression of IL-6 that was abated by NOS2 inhibition via AG.…”

Section: Discussionmentioning

confidence: 68%

Tumor microenvironment-based feed-forward regulation of NOS2 in breast cancer progression

Heinecke¹,

Ridnour²,

Cheng³

et al. 2014

153

147

Inflammation is widely recognized as an inducer of cancer progression. The inflammation-associated enzyme, inducible nitric oxide synthase (NOS2), has emerged as a candidate oncogene in estrogen receptor (ER)-negative breast cancer, and its increased expression is associated with disease aggressiveness and poor survival. Although these observations implicate NOS2 as an attractive therapeutic target, the mechanisms of both NOS2 induction in tumors and nitric oxide (NO)-driven cancer progression are not fully understood. To enhance our mechanistic understanding of NOS2 induction in tumors and its role in tumor biology, we used stimulants of NOS2 expression in ER − and ER + breast cancer cells and examined downstream NO-dependent effects. Herein, we show that up-regulation of NOS2 occurs in response to hypoxia, serum withdrawal, IFN-γ, and exogenous NO, consistent with a feed-forward regulation of NO production by the tumor microenvironment in breast cancer biology. Moreover, we found that key indicators of an aggressive cancer phenotype including increased S100 calcium binding protein A8, IL-6, IL-8, and tissue inhibitor matrix metalloproteinase-1 are up-regulated by these NOS2 stimulants, whereas inhibition of NOS2 in MDA-MB-231 breast cancer cells suppressed these markers. Moreover, NO altered cellular migration and chemoresistance of MDA-MB-231 cells to Taxol. Most notably, MDA-MB-231 tumor xenographs and cell metastases from the fat pad to the brain were significantly suppressed by NOS2 inhibition in nude mice. In summary, these results link elevated NOS2 to signals from the tumor microenvironment that arise with cancer progression and show that NO production regulates chemoresistance and metastasis of breast cancer cells.I nflammation is a major component of the tumor microenvironment and a driving force in cancer initiation, promotion, and progression (1-3). Epithelial cancers express markers of inflammation that promote disease progression and drug resistance through evasion of cell death pathways and increased tumor metastasis. Rapid cancer growth leads to tumor hypoxia and nutrient deprivation, which promotes chronic inflammatory feed-forward signaling and selection of resistant tumors that are clinically challenging and sometimes untreatable.Several proinflammatory proteins such as COX2, NF-κB, IL-6, IL-8, S100 calcium binding protein A8 (S100A8), and VEGF are markers of chronic inflammation in the tumor microenvironment. In addition, these proinflammatory mediators directly correlate with inducible nitric oxide synthase (NOS2), which is an emerging biomarker of aggressive tumors that predicts poor survival in patients with elevated tumor NOS2 expression (4-8). These and other clinical studies warrant an improved mechanistic understanding of intratumoral NOS2 regulation and endogenous NO production, which may be therapeutically beneficial.Toward this end, our laboratory and others have used NO donors to study NO signaling in cancer. However, intratumoral NOS2 induction by components of the tumor microenv...