Mechanisms underlying differential expression of interleukin-8 in breast cancer cells

Chemokine receptors and their ligands in breast cancer: The key roles in progression and metastasis

Chemokines and their receptors are a family of chemotactic cytokines with important functions in the immune response in both health and disease. Their known physiological roles such as the regulation of leukocyte trafficking and the development of immune organs generated great interest when it was found that they were also related to the control of early and late inflammatory stages in the tumor microenvironment. In fact, in breast cancer, an imbalance in the synthesis of chemokines and/or in the expression of their receptors was attributed to be involved in the regulation of disease progression, including invasion and metastasis. Research in this area is progressing rapidly and the development of new agents based on chemokine and chemokine receptor antagonists are emerging as attractive alternative strategies. This chapter provides a snapshot of the different functions reported for chemokines and their receptors with respect to the potential to regulate breast cancer progression.

Neutrophil-activating secretome characterizes palbociclib-induced senescence of breast cancer cells

Senescent cells have a profound impact on the surrounding microenvironment through the secretion of numerous bioactive molecules and inflammatory factors. The induction of therapy-induced senescence by anticancer drugs is known, but how senescent tumor cells influence the tumor immune landscape, particularly neutrophil activity, is still unclear. In this study, we investigate the induction of cellular senescence in breast cancer cells and the subsequent immunomodulatory effects on neutrophils using the CDK4/6 inhibitor palbociclib, which is approved for the treatment of breast cancer and is under intense investigation for additional malignancies. Our research demonstrates that palbociclib induces a reversible form of senescence endowed with an inflammatory secretome capable of recruiting and activating neutrophils, in part through the action of interleukin-8 and acute-phase serum amyloid A1. The activation of neutrophils is accompanied by the release of neutrophil extracellular trap and the phagocytic removal of senescent tumor cells. These findings may be relevant for the success of cancer therapy as neutrophils, and neutrophil-driven inflammation can differently affect tumor progression. Our results reveal that neutrophils, as already demonstrated for macrophages and natural killer cells, can be recruited and engaged by senescent tumor cells to participate in their clearance. Understanding the interplay between senescent cells and neutrophils may lead to innovative strategies to cope with chronic or tumor-associated inflammation.

Therapeutic Peptide RF16 Derived from CXCL8 Inhibits MDA-MB-231 Cell Invasion and Metastasis

Interleukin (IL)-8 plays a vital role in regulating inflammation and breast cancer formation by activating CXCR1/2. We previously designed an antagonist peptide, (RF16), to inhibits the activation of downstream signaling pathways by competing with IL-8 in binding to CXCR1/2, thereby inhibiting IL-8-induced chemoattractant monocyte binding. To evaluate the effect of the RF16 peptide on breast cancer progression, triple-negative MDA-MB-231 and ER-positive MCF-7 breast cancer cells were used to investigate whether RF16 can inhibit the IL-8-induced breast cancer metastasis. Using growth, proliferation, and invasiveness assays, the results revealed that RF16 reduced cell proliferation, migration, and invasiveness in MDA-MB-231 cells. The RF16 peptide also regulated the protein and mRNA expressions of epithelial-mesenchymal transition (EMT) markers in IL-8-stimulated MDA-MB-231 cells. It also inhibited downstream IL-8 signaling and the IL-8-induced inflammatory response via the mitogen-activated protein kinase (MAPK) and Phosphoinositide 3-kinase (PI3K) pathways. In the xenograft tumor mouse model, RF16 synergistically reinforces the antitumor efficacy of docetaxel by improving mouse survival and retarding tumor growth. Our results indicate that RF16 significantly inhibited IL-8-stimulated cell growth, migration, and invasion in MDA-MB-231 breast cancer cells by blocking the activation of p38 and AKT cascades. It indicated that the RF16 peptide may serve as a new supplementary drug for breast cancer.

Anti-cancer therapeutic strategies based on HGF/MET, EpCAM, and tumor-stromal cross talk

As an intelligent disease, tumors apply several pathways to evade the immune system. It can use alternative routes to bypass intracellular signaling pathways, such as nuclear factor-κB (NF-κB), Wnt, and mitogen-activated protein (MAP)/phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR). Therefore, these mechanisms lead to therapeutic resistance in cancer. Also, these pathways play important roles in the proliferation, survival, migration, and invasion of cells. In most cancers, these signaling pathways are overactivated, caused by mutation, overexpression, etc. Since numerous molecules share these signaling pathways, the identification of key molecules is crucial to achieve favorable consequences in cancer therapy. One of the key molecules is the mesenchymal-epithelial transition factor (MET; c-Met) and its ligand hepatocyte growth factor (HGF). Another molecule is the epithelial cell adhesion molecule (EpCAM), which its binding is hemophilic. Although both of them are involved in many physiologic processes (especially in embryonic stages), in some cancers, they are overexpressed on epithelial cells. Since they share intracellular pathways, targeting them simultaneously may inhibit substitute pathways that tumor uses to evade the immune system and resistant to therapeutic agents.

A chemokine regulatory loop induces cholesterol synthesis in lung-colonizing triple-negative breast cancer cells to fuel metastatic growth

Triple-negative breast cancer (TNBC) has a high propensity for organ-specific metastasis. However, the underlying mechanisms are not well understood. Here we show that the primary TNBC tumor-derived C-X-C motif chemokines 1/2/8 (CXCL1/2/8) stimulate lung-resident fibroblasts to produce the C-C motif chemokines 2/7 (CCL2/7), which, in turn, activate cholesterol synthesis in lung-colonizing TNBC cells and induce angiogenesis at lung metastatic sites. Inhibiting cholesterol synthesis in lung-colonizing breast tumor cells by pulmonary administration of simvastatin-carrying HER3-targeting nanoparticles reduces angiogenesis and growth of lung metastases in a syngeneic TNBC mouse model. Our findings reveal a novel, chemokine-regulated mechanism for the cholesterol synthesis pathway and a critical role of metastatic site-specific cholesterol synthesis in the pulmonary tropism of TNBC metastasis. The study has implications for the unresolved epidemiological observation that use of cholesterol-lowering drugs has no effect on breast cancer incidence but can unexpectedly reduce breast cancer mortality, suggesting interventions of cholesterol synthesis in lung metastases as an effective treatment to improve survival in individuals with TNBC.

An updated review on the role of the CXCL8-CXCR1/2 axis in the progression and metastasis of breast cancer

Chronic inflammation is a major factor in tumor growth and progression. Cancer cells secrete C-X-C chemokine ligand 8 (CXCL8) along with its receptor C-X-C chemokine receptor 1 (CXCR1) and chemokine receptor 2 (CXCR2). It plays a significant role in the activation and trafficking of inflammatory mediators, tumor proliferation and interferes in breast cancer development by controlling cell adhesion, proliferation, migration, and metastasis. This axis also plays a significant role in driving different cancers and melanomas, including breast cancer progression, by controlling stem cell masses. Few small-molecule CXCR1/2 inhibitors and CXCL8 releasing inhibitors have been identified in the past two decades that bind these receptors in their inactive forms and blocks their signaling as well as the biological activities associated with inflammation. Inhibitors of certain inflammatory molecules are projected to be more efficient in different inflammatory diseases. Preclinical trials indicate that patients may be benefitted from combined treatment with targeted drugs, chemotherapies, and immunotherapies. Thus, targeting the CXCL8-CXCR1/2 signaling axis in breast cancer could be a promising approach for its therapeutics. This review examines the roles of the CXCL8-CXCR1/2 signaling axis and how it is implicated in the tumor microenvironment in breast cancer. In addition, we also discuss the potential role of the CXCL8-CXCR1/2 axis in targeted therapeutics for breast cancer.

Heregulin Drives Endocrine Resistance by Altering IL-8 Expression in ER-Positive Breast Cancer

Sustained HER2/HER3 signaling due to the overproduction of the HER3 ligand heregulin (HRG) is proposed as a key contributor to endocrine resistance in estrogen receptor-positive (ER+) breast cancer. The molecular mechanisms linking HER2 transactivation by HRG-bound HER3 to the acquisition of a hormone-independent phenotype in ER+ breast cancer is, however, largely unknown. Here, we explored the possibility that autocrine HRG signaling drives cytokine-related endocrine resistance in ER+ breast cancer cells. We used human cytokine antibody arrays to semi-quantitatively measure the expression level of 60 cytokines and growth factors in the extracellular milieu of MCF-7 cells engineered to overexpress full-length HRGβ2 (MCF-7/HRG cells). Interleukin-8 (IL-8), a chemokine closely linked to ER inaction, emerged as one the most differentially expressed cytokines. Cytokine profiling using structural deletion mutants lacking both the N-terminus and the cytoplasmic-transmembrane region of HRGβ2-which is not secreted and cannot transactivate HER2-or lacking a nuclear localization signal at the N-terminus-which cannot localize at the nucleus but is actively secreted and transactivates HER2-revealed that the HRG-driven activation of IL-8 expression in ER+ cells required HRG secretion and transactivation of HER2 but not HRG nuclear localization. The functional blockade of IL-8 with a specific antibody inversely regulated ERα-driven transcriptional activation in endocrine-sensitive MCF-7 cells and endocrine-resistant MCF-7/HRG cells. Overall, these findings suggest that IL-8 participates in the HRG-driven endocrine resistance program in ER+/HER2- breast cancer and might illuminate a potential clinical setting for IL8- or CXCR1/2-neutralizing antibodies.

Prognostic Value of CXCR2 in Breast Cancer

The tumor microenvironment appears essential in cancer progression and chemokines are mediators of the communication between cancer cells and stromal cells. We have previously shown that the ligands of the chemokine receptor CXCR2 were expressed at higher levels in triple-negative breast cancers (TNBC). Our hypothesis was that CXCR2 expression could also be altered in breast cancer. Here, we have analyzed the potential role of CXCR2 in breast cancer in a retrospective cohort of 105 breast cancer patients. Expression of CXCR2, CD11b (a marker of granulocytes) and CD66b (a marker of neutrophils) was analyzed by immunohistochemistry on tumor samples. We demonstrated that CXCR2 stained mainly stromal cells and in particular neutrophils. CXCR2, CD11b and CD66b expression were correlated with high grade breast cancers. Moreover, TNBC displayed a higher expression of CXCR2, CD11b and CD66b than hormone receptor positive or Her2 positive tumors. High levels of CXCR2 and CD11b, but not CD66b, were associated with a higher infiltration of T lymphocytes and B lymphocytes. We also observed a correlation between CXCR2 and AP-1 activity. In univariate analyses, CXCR2, but not CD11b or CD66b, was associated with a lower risk of relapse; CXCR2 remained significant in multivariate analysis. Our data suggest that CXCR2 is a stromal marker of TNBC. However, higher levels of CXCR2 predicted a lower risk of relapse.

IL-8 and MCP-1/CCL2 regulate proteolytic activity in triple negative inflammatory breast cancer a mechanism that might be modulated by Src and Erk1/2

Inflammatory breast cancer (IBC) is a highly metastatic and lethal breast cancer. As many as 25-30% of IBCs are triple negative (TN) and associated with low survival rates and poor prognosis. We found that the microenvironment of IBC is characterized by high infiltration of tumor associated macrophages (TAMs) and by over-expression of the cysteine protease cathepsin B (CTSB). TAMs in IBC secrete high levels of the cytokines interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1/CCL2) compared to non-IBC patients. Herein, we tested the roles of IL-8 and MCP-1/CCL2 in modulating proteolytic activity and invasiveness of TN-non-IBC as compared to TN-IBC and addressed the underlying molecular mechanism(s) for both cytokines. Quantitative real time PCR results showed that IL-8 and MCP-1/CCL2 were significantly overexpressed in tissues of TN-IBCs. IL-8 and MCP-1/CCL2 induced CTSB expression and activity of the p-Src and p-Erk1/2 signaling pathways relevant for invasion and metastasis in TN-non-IBC, HCC70 cells and TN-IBC, SUM149 cells. Dasatinib, an inhibitor of p-Src, and U0126, an inhibitor of p-Erk1/2, down-regulated invasion and expression of CTSB by HCC70 and SUM149 cells, a mechanism that is reversed by IL-8 and MCP-1/CCL2. Our study shows that targeting the cytokines IL-8 and MCP-1/CCL2 and associated signaling molecules may represent a promising therapeutic strategy in TN-IBC patients.

The health status alters the pituitary function and reproduction of mice in a Cxcr2-dependent manner

This study explores the effects of microbiota on reproductive function of Cxcr2 knockout animals. Cxcr2 is involved in the control of pituitary action and the subsequent development of mammary gland, uterus and ovary.

Microbiota and chronic infections can affect not only immune status, but also the overall physiology of animals. Here, we report that chronic infections dramatically modify the phenotype of Cxcr2 KO mice, impairing in particular, their reproduction ability. We show that exposure of Cxcr2 KO females to multiple types of chronic infections prevents their ability to cycle, reduces the development of the mammary gland and alters the morphology of the uterus due to an impairment of ovary function. Mammary gland and ovary transplantation demonstrated that the hormonal contexture was playing a crucial role in this phenomenon. This was further evidenced by alterations to circulating levels of sex steroid and pituitary hormones. By analyzing at the molecular level the mechanisms of pituitary dysfunction, we showed that in the absence of Cxcr2, bystander infections affect leukocyte migration, adhesion, and function, as well as ion transport, synaptic function behavior, and reproduction pathways. Taken together, these data reveal that a chemokine receptor plays a direct role in pituitary function and reproduction in the context of chronic infections.

Combined Effects of Eicosapentaenoic Acid and Adipocyte Renin-Angiotensin System Inhibition on Breast Cancer Cell Inflammation and Migration

Obesity is a major risk factor for breast cancer (BC). Obesity-related metabolic alterations such as inflammation and overactivation of the adipose renin–angiotensin system (RAS) may contribute to the progression of BC. Clinically used antihypertensive drugs such as angiotensin-converting enzyme inhibitors (ACE-I) and dietary bioactive components such as eicosapentaenoic acid (EPA) are known for their anti-inflammatory and adipose RAS blocking properties. However, whether EPA enhances the protective effects of ACE-I in lessening adipocyte inflammation on BC cells has not been studied. We hypothesized that combined EPA and ACE-I would attenuate BC cell inflammation and migration possibly via adipose RAS inhibition. To test our hypothesis, we examined the (i) direct effects of an ACE-I (captopril (CAP)) or EPA, individually and combined, on MCF-7 and MDA-MB-231 human BC cells, and the (ii) effects of conditioned medium (CM) from human adipocytes pretreated with the abovementioned agents on BC cells. We demonstrated that CM from adipocytes pretreated with EPA with or without captopril (but not direct treatments of BC cells) significantly reduced proinflammatory cytokines expression in both BC cell lines. Additionally, cell migration was reduced in MDA-MB-231 cells in response to both direct and CM-mediated CAP and/or EPA treatments. In summary, our study provides a significant insight into added benefits of combining anti-inflammatory EPA and antihypertensive ACE-I to attenuate the effects of adipocytes on breast cancer cell migration and inflammation.

Blockade of the Complement C5a/C5aR1 Axis Impairs Lung Cancer Bone Metastasis by CXCL16-mediated Effects

RATIONALE

C5aR1 (CD88), a receptor for complement anaphylatoxin C5a, is a potent immune mediator. Its impact on malignant growth and dissemination of non-small cell lung cancer cells is poorly understood.

OBJECTIVES

To investigate the contribution of the C5a/C5aR1 axis to the malignant phenotype of non-small cell lung cancer cells, particularly in skeletal colonization, a preferential lung metastasis site.

METHODS

Association between C5aR1 expression and clinical outcome was assessed in silico and validated by immunohistochemistry. Functional significance was evaluated by lentiviral gene silencing and ligand l-aptamer inhibition in in vivo models of lung cancer bone metastasis. In vitro functional assays for signaling, migration, invasion, metalloprotease activity, and osteoclastogenesis were also performed.

MEASUREMENTS AND MAIN RESULTS

High levels of C5aR1 in human lung tumors were significantly associated with shorter recurrence-free survival, overall survival, and bone metastasis. Silencing of C5aR1 in lung cancer cells led to a substantial reduction in skeletal metastatic burden and osteolysis in in vivo models. Furthermore, metalloproteolytic, migratory, and invasive tumor cell activities were modulated in vitro by C5aR1 stimulation or gene silencing. l-Aptamer blockade or C5aR1 silencing significantly reduced the osseous metastatic activity of lung cancer cells in vivo. This effect was associated with decreased osteoclastogenic activity in vitro and was rescued by the exogenous addition of the chemokine CXCL16.

CONCLUSIONS

Disruption of C5aR1 signaling in lung cancer cells abrogates their tumor-associated osteoclastogenic activity, impairing osseous colonization. This study unveils the role played by the C5a/C5aR1 axis in lung cancer dissemination and supports its potential use as a novel therapeutic target.

Anti-tumor properties of methoxylated analogues of resveratrol in malignant MCF-7 but not in non-tumorigenic MCF-10A mammary epithelial cell lines

Resveratrol is a plant-derived polyphenol that is known for its anti-inflammatory and anti-tumorigenic properties in in vitro and in vivo models. Recent studies show that some resveratrol analogues might be more potent anti-tumor agents, which may partly be attributed to their ability to activate the aryl hydrocarbon receptor (AHR). Here, the anti-tumorigenic properties of resveratrol and structural analogues oxyresveratrol, pinostilbene, pterostilbene and tetramethoxystilbene (TMS) were studied in vitro, using in the malignant human MCF-7 breast cancer cell line and non-tumorigenic breast epithelial cell line MCF-10A. Cell viability and migration assays showed that methoxylated analogues of resveratrol are more potent anti-tumorigenic compounds than resveratrol and its hydroxylated analogue oxyresveratrol, with 2,3',4,5'-tetramethoxy-trans-stilbene (TMS) being the most potent compound. TMS decreased MCF-7 tumor cell viability with 50% at 3.6 μM and inhibited migration with 37.5 ± 14.8% at 3 μM. In addition, TMS activated the AHR more potently (EC50 in a reporter gene assay 2.0 μM) and induced AHR-mediated induction of cytochrome P450 1A1 (CYP1A1) activity (EC50 value of 0.7 μM) more than resveratrol and the other analogues tested. Cell cycle analysis showed that TMS induced a shift in cell cycle status from the G1 to the G2/M phase causing a cell cycle arrest in the MCF-7 cells, while no effect of TMS was observed in the non-tumorigenic MCF-10A mammary epithelial cell line. Gene expression analysis showed that 3 μM TMS increased gene expression of CYP1A1 (289-fold), CYP1B1 (5-fold) and Nqo1 (2-fold), and decreased gene expression of IL-8 (3-fold) in MCF-7 cells. In MCF-10A cells, 10 μM TMS also increased gene expression of CYP1A1 (5-fold) and CYP1B1 (2-fold), but decreased gene expression of Nqo1 (1.4-fold) in contrast to MCF-7 cells. TMS displays more potent anti-tumorigenic properties and activates the AHR more effectively than resveratrol. In addition, this is the first study to show that TMS, but not resveratrol, selectively inhibits the cell cycle of breast tumor cells and not the non-tumorigenic cells. Our study provides more insight in the anti-tumor properties of the methoxylated analogues of resveratrol in breast cells in vitro.

Interleukin-8 Activates Breast Cancer-Associated Adipocytes and Promotes Their Angiogenesis- and Tumorigenesis-Promoting Effects

Increasing evidence supports the critical role of active stromal adipocytes in breast cancer development and spread. However, the mediators and the mechanisms of action are still elusive. We show here that cancer-associated adipocytes (CAAs) isolated from 10 invasive breast carcinomas are proinflammatory and exhibit active phenotypes, including higher proliferative, invasive, and migratory capacities compared to their adjacent tumor-counterpart adipocytes (TCAs). Furthermore, all CAAs secreted higher level of interleukin-8 (IL-8), which is critical in mediating the paracrine procarcinogenic effects of these cells. Importantly, ectopic expression of IL-8 in TCA cells activated them and enhanced their procarcinogenic effects both in vitro, in a STAT3-dependent manner, and in vivo In contrast, inhibition of the IL-8 signaling using specific short hairpin RNA, anti-IL-8 antibody, or reparixin suppressed the active features of CAAs, including their non-cell-autonomous tumor-promoting activities both on breast luminal cells and in orthotopic tumor xenografts in mice. IL-8 played also an important role in enhancing the proangiogenic effects of breast adipocytes. These results provide clear indication that IL-8 plays key roles in the activation of breast CAAs and acts as a major mediator for their paracrine protumorigenic effects. Thus, targeting CAAs by inhibiting the IL-8 pathway could have great therapeutic value.

Smart Hydrogel Microfluidics for Single-Cell Multiplexed Secretomic Analysis with High Sensitivity

Secreted proteins determine a range of cellular functionalities correlated with human health and disease progression. Because of cell heterogeneity, it is essential to measure low abundant protein secretions from individual cells to determine single-cell activities. In this study, an integrated platform consisting of smart hydrogel immunosensors for the sensitive detection of single-cell secretions is developed. A single cell and smart hydrogel microparticles are encapsulated within a droplet. After incubation, target secreted proteins from the cell are captured in the smart hydrogel particle for immunoassay. The temperature-induced volume phase transition of the hydrogel biosensor allows the concentration of analytes within the gel matrix to increase, enabling high-sensitivity measurements. Distinct heterogeneity for live cell secretions is determined from 6000 cells within 1 h. This method is tested for low abundant essential secretions, such as interleukin-6, interleukin-8, and monocyte chemoattractant protein-1 secretions of both suspended cells (HL60) and adherent cells (MCF7 and MDA-MB-231). This platform is highly flexible and can be used to simultaneously measure a wide range of clinically relevant cellular secretions; it thus represents a novel tool for precise biological assays.

Orientin inhibits invasion by suppressing MMP-9 and IL-8 expression via the PKCα/ ERK/AP-1/STAT3-mediated signaling pathways in TPA-treated MCF-7 breast cancer cells

BACKGROUND

Orientin (luteolin 8-C-β-D-glucopyranoside), a glycosyl dietary flavonoid, has therapeutic effects such as anti-inflammation and antiadipogenesis. However, there is little known about the antimigratory and anti-invasive effects of orientin. Thus, we demonstrate the anti-invasive effects of orientin compared with well-known anticancer flavonoid, luteolin and luteolin 8-C-β-fucopyranoside (LU8C-FP).

PURPOSE

We investigated whether orientin would inhibit the migration and invasion of 12-O-tetradecanoyl phorbol-13-acetate (TPA) induced MCF-7 breast cancer cells.

METHODS

We investigated the anti-invasive mechanism of orientin by using wound-healing assay, Matrigel invasion assay, gelatin zymography, qRT-PCR, ELISA, western blotting, nuclear, membrane and cytosolic fractionations, and immunofluorescence staining in MCF-7 cell line.

RESULTS

We demonstrated the antimigratory and anti-invasive effects of orientin in TPA-treated MCF-7 cells. TPA-induced membrane translocation of protein kinase C alpha (PKCα), phosphorylation of extracellular signal regulated kinase (ERK), and nuclear translocations of activator protein-1 (AP-1) and signal transducer and activator of transcription 3 (STAT3) were downregulated by orientin. In addition, orientin also inhibited matrix metalloproteinase-9 (MMP-9) and interleukin-8 (IL-8) expression.

CONCLUSION

Orientin inhibits migratory and invasive responses by suppressing MMP-9 and IL-8 expression through mitigation of TPA-induced PKCα and ERK activation, as well as the nuclear translocation of AP-1 and STAT3. Therefore, orientin prevents tumor invasion and could be applied as a possible therapeutic agent for the treatment of cancer metastasis.

Proteasome inhibition induces IKK-dependent interleukin-8 expression in triple negative breast cancer cells: Opportunity for combination therapy

Triple negative breast cancer (TNBC) cells express increased levels of the pro-inflammatory and pro-angiogenic chemokine interleukin-8 (IL-8, CXCL8), which promotes their proliferation and migration. Because TNBC patients are unresponsive to current targeted therapies, new therapeutic strategies are urgently needed. While proteasome inhibition by bortezomib (BZ) or carfilzomib (CZ) has been effective in treating hematological malignancies, it has been less effective in solid tumors, including TNBC, but the mechanisms are incompletely understood. Here we report that proteasome inhibition significantly increases expression of IL-8, and its receptors CXCR1 and CXCR2, in TNBC cells. Suppression or neutralization of the BZ-induced IL-8 potentiates the BZ cytotoxic and anti-proliferative effect in TNBC cells. The IL-8 expression induced by proteasome inhibition in TNBC cells is mediated by IκB kinase (IKK), increased nuclear accumulation of p65 NFκB, and by IKK-dependent p65 recruitment to IL-8 promoter. Importantly, inhibition of IKK activity significantly decreases proliferation, migration, and invasion of BZ-treated TNBC cells. These data provide the first evidence demonstrating that proteasome inhibition increases the IL-8 signaling in TNBC cells, and suggesting that IKK inhibitors may increase effectiveness of proteasome inhibitors in treating TNBC.

Serglycin promotes breast cancer cell aggressiveness: Induction of epithelial to mesenchymal transition, proteolytic activity and IL-8 signaling

Serglycin is an intracellular proteoglycan that is expressed and constitutively secreted by numerous malignant cells, especially prominent in the highly-invasive, triple-negative MDA-MB-231 breast carcinoma cells. Notably, de novo expression of serglycin in low aggressive estrogen receptor α (ERα)-positive MCF7 breast cancer cells promotes an aggressive phenotype. In this study, we discovered that serglycin promoted epithelial to mesenchymal transition (EMT) in MCF7 cells as shown by increased expression of mesenchymal markers vimentin, fibronectin and EMT-related transcription factor Snail2. These phenotypic traits were also associated with the development of drug resistance toward various chemotherapy agents and induction of their proteolytic potential as shown by the increased expression of matrix metalloproteinases, including MMP-1, MMP-2, MMP-9, MT1-MMP and up-regulation of urokinase-type plasminogen activator. Knockdown of serglycin markedly reduced the expression of these proteolytic enzymes in MDA-MB-231 cells. In addition, serglycin expression was closely linked to a pro-inflammatory gene signature including the chemokine IL-8 in ERα-negative breast cancer cells and tumors. Notably, serglycin regulated the secretion of IL-8 in breast cancer cells independently of their ERα status and promoted their proliferation, migration and invasion by triggering IL-8/CXCR2 downstream signaling cascades including PI3K, Src and Rac activation. Thus, serglycin promotes the establishment of a pro-inflammatory milieu in breast cancer cells that evokes an invasive mesenchymal phenotype via autocrine activation of IL-8/CXCR2 signaling axis.

Let-7b inhibits cancer-promoting effects of breast cancer-associated fibroblasts through IL-8 repression

Cancer-associated fibroblasts (CAFs) are major players in the development and spread of breast carcinomas through non-cell-autonomous signaling. These paracrine effects are under the control of several genes and microRNAs. We present here clear evidence that let-7b, a tumor suppressor microRNA, plays key roles in the persistent activation of breast stromal fibroblasts and their functional interplay with cancer cells. We have first shown that let-7b is down-regulated in CAFs as compared to their corresponding normal adjacent fibroblasts, and transient specific let-7b inhibition permanently activated breast fibroblasts through induction of the IL-6-related positive feedback loop. More importantly, let-7b-deficient cells promoted the epithelial-to-mesenchymal transition process in breast cancer cells in an IL-8-dependent manner, and also enhanced orthotopic tumor growth in vivo. On the other hand, overexpression of let-7b by mimic permanently suppressed breast myofibroblasts through blocking the positive feedback loop, which inhibited their paracrine pro-carcinogenic effects. Furthermore, we have shown that let-7b negatively controls IL-8, which showed higher expression in the majority of CAF cells as compared to their adjacent normal counterparts, indicating that IL-8 plays a major role in the carcinoma/stroma cross-talk. These findings support targeting active stromal fibroblasts through restoration of let-7b/IL-8 expression as a therapeutic option for breast carcinomas.

Sorafenib improves alkylating therapy by blocking induced inflammation, invasion and angiogenesis in breast cancer cells

Molecular targeted compounds are emerging as a strategy to improve classical chemotherapy. Herein, we describe that using low dose of the multikinase inhibitor sorafenib improves cyclophosphamide antitumor activity by inhibiting angiogenesis, metastasis and promoting tumor healing in MDA-MB231 xenografts and the 4T1-12B syngeneic breast cancer metastasis model. Mechanistic studies in MDA-MB231 cells revealed that alkylation upregulates inflammatory genes/proteins such as COX-2, IL8, CXCL2 and MMP1 in a MEK1/2-ERK1/2-dependent manner. These proteins enrich the secretome of cancer cells, stimulating cell invasion and angiogenesis via autocrine and paracrine mechanisms. Sorafenib inhibits MEK1/2-ERK1/2 pathway thereby decreasing inflammatory genes and mitigating cell invasion and angiogenesis at basal and alkylation-induced conditions whereas NRF2 and ER stress pathways involved in alkylation survival are not affected. In non-invasive/non-angiogenic breast cancer cells (SKBR3 and MCF7), alkylation did not elicit inflammatory responses with the only sorafenib effect being ERK1/2-independent ROS-dependent cytotoxicity when using higher drug concentrations. In summary, our data show that alkylating agents may elicit inflammatory responses that seems to contribute to malignant progression in specific breast cancer cells. Identifying and targeting drivers of this phenotype may offer opportunities to optimize combined drug regimens between classical chemotherapeutics and targeted agents.

Sohlh2 suppresses epithelial to mesenchymal transition in breast cancer via downregulation of IL-8

Breast cancer is one of the deadliest cancers worldwide due to its strong metastasis to other organs. Metastasis of breast cancer involves a complex set of events, including epithelial-mesenchymal transition (EMT) that increases invasiveness of the tumor cells. We previously identified sohlh2 is a tumor suppressor in the pathogenesis of ovarian cancer. However, the functions of sohlh2 in breast cancer cell migration and invasion remain unknown. Here we report a novel sohlh2/IL-8 signaling pathway in the invasive breast cancer. We observed sohlh2 expression was downregulated in the metastatic breast cancer. Ectopic sohlh2 expression in breast cancer cells reduced EMT and inhibited cell migration and invasion in vitro, and metastasis in vivo. Moreover, the depletion of sohlh2 induced the opposite effects to ectopic sohlh2 expression. RNA-Seq data from a sohlh2 knockdown breast cancer cell line showed that after sohlh2 depletion, the mRNA level of interleukin 8 (IL-8) was significantly increased in these cancer cells, which consequently increased secretion of IL-8 protein. Using chromatin immunoprecipitation and reporter assays, we demonstrated that sohlh2 bound to IL-8 promoter and repressed its activities. The enhanced migration and invasion in sohlh2 -ablated MCF-7 cells were blocked by knockdown of IL-8 expression, while exogenous IL-8 neutralized the anti-migratory and invasive activities of sohlh2 in MDA-MB-231cells. Overall, these results demonstrate that sohlh2 functions as a tumor metastasis suppressor via suppressing IL-8 expression in breast cancer.

Combination Therapies Targeting HDAC and IKK in Solid Tumors

The rationale for developing histone deacetylase (HDAC) inhibitors (HDACi) as anticancer agents was based on their ability to induce apoptosis and cell cycle arrest in cancer cells. However, while HDACi have been remarkably effective in the treatment of hematological malignancies, clinical studies with HDACi as single agents in solid cancers have been disappointing. Recent studies have shown that, in addition to inducing apoptosis in cancer cells, class I HDACi induce IκB kinase (IKK)-dependent expression of proinflammatory chemokines, such as interleukin-8 (IL8; CXCL8), resulting in the increased proliferation of tumor cells, and limiting the effectiveness of HDACi in solid tumors. Here, we discuss the mechanisms responsible for HDACi-induced CXCL8 expression, and opportunities for combination therapies targeting HDACs and IKK in solid tumors.

Stimulation of transient receptor potential M3 (TRPM3) channels increases interleukin-8 gene promoter activity involving AP-1 and extracellular signal-regulated protein kinase

Stimulation of Ca²⁺ permeable TRPM3 (transient receptor potential melastatin-3) channels with the steroid ligand pregnenolone sulfate activates stimulus-responsive transcription factors, including the transcription factor AP-1 (activator protein-1). As part of a search for AP-1-regulated target genes we analyzed the gene encoding interleukin-8 (IL-8) in HEK293 cells expressing TRPM3 channels. Here, we show that stimulation of TRPM3 channels activated transcription of an IL-8 promoter-controlled reporter gene that was embedded into the chromatin of the cells. Mutational analysis of the IL-8 promoter revealed that the AP-1 binding site of the IL-8 promoter was essential to connect TRPM3 stimulation with the transcription of the IL-8 gene. Genetic experiments revealed that the basic region leucine zipper proteins c-Jun and ATF2 and the ternary complex factor Elk-1 are essential to couple TRPM3 channel stimulation with the IL-8 gene. Moreover, we identified extracellular signal-regulated protein kinase (ERK1/2) as signal transducer connecting TRPM3 stimulation with enhanced transcription of the IL-8 gene. Furthermore, we show that stimulation of TRPC6 (transient receptor potential canonical-6) channels with its ligand hyperforin also increased IL-8 promoter activity, involving the AP-1 binding site within the IL-8 gene, suggesting that activation of IL-8 gene transcription may be a common theme following TRP channel stimulation.

A Chip for Estrogen Receptor Action: Detection of Biomarkers Released by MCF-7 Cells through Estrogenic and Anti-Estrogenic Effects

The fluorescence-based multi-analyte chip platform for the analysis of estrogenic and anti-estrogenic substances is a new in vitro tool for the high throughput screening of environmental samples. In contrast to existing tools, the chip investigates the complex action of xenoestrogens in a human cell model by characterizing protein expression. It allows for the quantification of 10 proteins secreted by MCF-7 cells, representing various biological and pathological endpoints of endocrine action and distinguishing between estrogen- and anti-estrogen-dependent secretion of proteins. Distinct protein secretion patterns of the cancer cell line after exposure to known estrogen receptor agonists ß-estradiol, bisphenol A, genistein, and nonylphenol as well as antagonists fulvestrant and tamoxifen demonstrate the potential of the chip. Stimulation of cells with Interleukin-1ß shifts concentrations of low abundant biomarkers towards the working range of the chip. In the non-stimulated cell culture, Matrix Metalloproteinase 9 (MMP-9) and Vascular Endothelial Growth Factor (VEGF) show differences upon treatment with antagonists and agonists of the estrogen receptor. In stimulated MCF-7 cells challenged with receptor agonists secretion of Monocyte Chemoattractant Protein (MCP-1), Interleukin-6 (IL-6), Rantes, and Interleukin-8 (IL-8) significantly decreases. In parallel, the proliferating effect of endocrine-disrupting substances in MCF-7 cells is assessed in a proliferation assay based on resazurin. Using ethanol as a solvent for test substances increases the background of proliferation and secretion experiments, while using dimethyl sulfoxide (DMSO) does not show any adverse effects. The role of the selected biomarkers in different physiological processes such as cell development, reproduction, cancer, and metabolic syndrome makes the chip an excellent tool for either indicating endocrine-disrupting effects in food and environmental samples, or for screening the effect of xenoestrogens on a cellular and molecular level.

Downregulation of transgelin blocks interleukin-8 utilization and suppresses vasculogenic mimicry in breast cancer cells

Vasculogenic mimicry (VM) is a non-classical mechanism recently described in many tumors, whereby cancer cells, rather than endothelial cells, form blood vessels. Transgelin is an actin-binding protein that has been implicated in multiple stages of cancer development. In this study, we investigated the role of transgelin in VM and assessed its effect on the expression of endothelial and angiogenesis-related genes during VM in MDA-MB-231 breast cancer cells. We confirmed the ability of MDA-MB-231 cells to undergo VM through a tube formation assay. Flow cytometry analysis revealed an increase in the expression of the endothelial-related markers VE-cadherin and CD34 in cells that underwent VM, compared with those growing in a monolayer, which was confirmed by immunocytochemistry. We employed siRNA to silence transgelin, and knockdown efficiency was determined by western blot analyses. Downregulation of transgelin suppressed cell proliferation and tube formation, but increased IL-8 levels in Matrigel cultures. RT-PCR analyses revealed that the expression of IL-8, VE-cadherin, and CD34 was unaffected by transgelin knockdown, indicating that increased IL-8 expression was not due to enhanced transcriptional activity. More importantly, the inhibition of IL-8/CXCR2 signaling also resulted in suppression of VM with increased IL-8 levels, confirming that increased IL-8 levels after transgelin knockdown was due to inhibition of IL-8 uptake. Our findings indicate that transgelin regulates VM by enhancing IL uptake. These observations are relevant to the future development of efficient antivascular agents. Impact statement Vasculogenic mimicry (VM) is an angiogenic-independent mechanism of blood vessel formation whereby aggressive tumor cells undergo formation of capillary-like structures. Thus, interventions aimed at angiogenesis might not target the entire tumor vasculature. A more holistic approach is therefore needed in the development of improved antivascular agents. Transgelin, an actin-binding protein, has been associated with multiple stages of cancer development such as proliferation, migration and invasion, but little is known about its role in vasculogenic mimicry. We present here, an additional mechanism by which transgelin promotes malignancy by way of its association with the occurrence of VM. Although transgelin knockdown did not affect the transcript levels of most of the angiogenesis-related genes in this study, it was associated with the inhibition of the uptake of IL-8, accompanied by suppressed VM, indicating that transgelin is required for VM. These observations are relevant to the future development of efficient antivascular agents.

IL-1β produced by aggressive breast cancer cells is one of the factors that dictate their interactions with mesenchymal stem cells through chemokine production

The aim of this work was to understand whether the nature of breast cancer cells could modify the nature of the dialog of mesenchymal stem cells (MSCs) with cancer cells. By treating MSCs with the conditioned medium of metastatic Estrogen-receptor (ER)-negative MDA-MB-231, or non-metastatic ER-positive MCF-7 breast cancer cells, we observed that a number of chemokines were produced at higher levels by MSCs treated with MDA-MB-231 conditioned medium (CM). MDA-MB-231 cells were able to induce NF-κB signaling in MSC cells. This was shown by the use of a NF-kB chemical inhibitor or an IκB dominant negative mutant, nuclear translocation of p65 and induction of NF-κB signature. Our results suggest that MDA-MB-231 cells exert their effects on MSCs through the secretion of IL-1β, that activates MSCs and induces the same chemokines as the MDA-MB-231CM. In addition, inhibition of IL-1β secretion in the MDA-MB-231 cells reduces the induced production of a panel of chemokines by MSCs, as well the motility of MDA-MB-231 cells. Our data suggest that aggressive breast cancer cells secrete IL-1β, which increases the production of chemokines by MSCs.

High incidence of triple negative breast cancers following pregnancy and an associated gene expression signature

Breast cancer risk increases transiently in the period following pregnancy; pregnancy-associated breast cancers (PABC) are more aggressive than cases diagnosed in nulliparous women. We have previously reported that in the normal human breast pregnancy results in the upregulation of a number of inflammation related genes, suggesting a pro-tumorigenic environment as well as downregulation of ESR1 (ERα) and ERBB2 (HER2) and upregulation of ESR2 (ERβ), suggesting a protective effect. In this study, we aimed to investigate the possibility of differential regulation of the same gene set modulated in the normal breast, in human breast tumors following pregnancy. Gene expression was measured by real-time PCR on tumor regions isolated by laser capture microdissection from paraffin sections. Immunohistochemistry was performed on tissue microarrays (TMA) for protein expression. Hierarchical clustering was performed using the average linkage method to determine coordinate expression of sets of genes. We find that breast cancers detected within 10 years following pregnancy display a different gene expression pattern than those detected in nulliparous breast cancer patients. The gene expression difference is mainly attributable to a triple negative (TNBC) subgroup found to be more frequent in PABCs up to 10 years following a pregnancy. We also show that protein and mRNA expression levels correlate in half of the proteins tested by TMA. Despite the fact that this is a small study of 53 patients, we identified a gene expression signature that is differentially expressed in pregnancy-associated TNBC.

Iroquois homeobox 2 suppresses cellular motility and chemokine expression in breast cancer cells

Background

Disseminated tumor cells (DTCs) can be detected using ultrasensitive immunocytochemical assays and their presence in the bone marrow can predict the subsequent occurrence of overt metastasis formation and metastatic relapse. Using expression profiling on early stage primary breast tumors, low IRX2 expression was previously shown to be associated with the presence of DTCs in the bone marrow, suggesting a possible role of IRX2 in the early steps of metastasis formation. The purpose of this study is to gain insights into the significance of IRX2 protein function in the progression of breast cancer.

Methods

To assess the physiological relevance of IRX2 in breast cancer, we evaluated IRX2 expression in a large breast cancer cohort (n = 1992). Additionally, constitutive IRX2 over expression was established in BT-549 and Hs578T breast cancer cell lines. Subsequently we analyzed whether IRX2 overexpression effects chemokine secretion and cellular motility of these cells.

Results

Low IRX2 mRNA expression was found to correlate with high tumor grade, positive lymph node status, negative hormone receptor status, and basal type of primary breast tumors. Also in cell lines low IRX2 expression was associated with mainly basal breast cancer cell lines. The functional studies show that overexpression of the IRX2 transcription factor in basal cell lines suppressed secretion of the pro-metastatic chemokines and inhibited cellular motility but did not influence cell proliferation.

Conclusion

Our results imply that the IRX2 transcription factor might represent a novel metastasis associated protein that acts as a negative regulator of cellular motility and as a repressor of chemokine expression. Loss of IRX2 expression could therefore contribute to early hematogenous dissemination of breast cancer by sustaining chemokine secretion and enabling mobilization of tumor cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1907-4) contains supplementary material, which is available to authorized users.

IL-8 signaling is up-regulated in alcoholic hepatitis and DDC fed mice with Mallory Denk Bodies (MDBs) present

Chemokines and their receptors are involved in oncogenesis and in tumor progression, invasion, and metastasis. Various chemokines also promote cell proliferation and resistance to apoptosis of stressed cells. The chemokine CXCL8, also known as interleukin-8 (IL-8), is a proinflammatory molecule that has functions within the tumor microenvironment. Deregulation of IL-8 signaling is shown to play pivotal roles in tumorigenesis and progression. Mallory-Denk Bodies (MDBs) are prevalent in various liver diseases including alcoholic hepatitis (AH) and are formed in mice livers by feeding DDC. By comparing AH livers where MDBs had formed with normal livers, there were significant changes of IL-8 signaling by RNA sequencing (RNA-Seq) analyses. Real-time PCR analysis of CXCR2 further shows a 6-fold up-regulation in AH livers and a 26-fold up-regulation in the livers of DDC re-fed mice. IL-8 mRNA was also significantly up-regulated in AH livers and DDC re-fed mice livers. This indicates that CXCR2 and IL-8 may be crucial for liver MDB formation. MDB containing balloon hepatocytes in AH livers had increased intensity of staining of the cytoplasm for both CXCR2 and IL-8. Overexpression of IL-8 leads to an increase of the mitogen activated protein kinase (MAPK) cascade and exacerbates the inflammatory cycle. These observations constitute a demonstration of the altered regulation of IL-8 signaling in the livers of AH and mice fed DDC where MDBs formed, providing further insight into the mechanism of MDB formation mediated by IL-8 signaling in AH.

ATM regulation of IL-8 links oxidative stress to cancer cell migration and invasion

Ataxia-telangiectasia mutated (ATM) protein kinase regulates the DNA damage response (DDR) and is associated with cancer suppression. Here we report a cancer-promoting role for ATM. ATM depletion in metastatic cancer cells reduced cell migration and invasion. Transcription analyses identified a gene network, including the chemokine IL-8, regulated by ATM. IL-8 expression required ATM and was regulated by oxidative stress. IL-8 was validated as an ATM target by its ability to rescue cell migration and invasion defects in ATM-depleted cells. Finally, ATM-depletion in human breast cancer cells reduced lung tumors in a mouse xenograft model and clinical data validated IL-8 in lung metastasis. These findings provide insights into how ATM activation by oxidative stress regulates IL-8 to sustain cell migration and invasion in cancer cells to promote metastatic potential. Thus, in addition to well-established roles in tumor suppression, these findings identify a role for ATM in tumor progression.

Targeting the MUC1-C oncoprotein inhibits self-renewal capacity of breast cancer cells

The capacity of breast cancer cells to form mammospheres in non-adherent serum-free culture is used as a functional characteristic of the self-renewing stem-like cell population. The present studies demonstrate that silencing expression of the MUC1-C oncoprotein inhibits growth of luminal MCF-7 and HER2-overexpressing SKBR3 breast cancer cells as mammospheres. We also show that triple-negative MDA-MB-468 breast cancer cells are dependent on MUC1-C for growth as mammospheres and tumor xenografts. Similar results were obtained when MUC1-C function was inhibited by expression of a MUC1-C(CQC→AQA) mutant. Moreover, treatment with the MUC1-C inhibitor GO-203, a cell penetrating peptide that binds to the MUC1-C cytoplasmic domain and blocks MUC1-C function, confirmed the importance of this target for self-renewal. The mechanistic basis for these findings is supported by the demonstration that MUC1-C activates NF-κB, occupies the IL-8 promoter with NF-κB, and induces IL-8 transcription. MUC1-C also induces NF-κB-dependent expression of the IL-8 receptor, CXCR1. In concert with these results, targeting MUC1-C with GO-203 suppresses IL-8/CXCR1 expression and disrupts the formation of established mammospheres. Our findings indicate that MUC1-C contributes to the self-renewal of breast cancer cells by activating the NF-κB→IL-8/CXCR1 pathway and that targeting MUC1-C represents a potential approach for the treatment of this population.

Characterization of buffalo interleukin 8 (IL-8) and its expression in endometritis

River buffalo (Bubalus bubalis bubalis) with a population over 135 million heads is an important livestock. Interleukin 8 (IL-8) is a member of the chemokine family and is an important chemoattractant for neutrophils associated with a wide variety of inflammatory diseases such as endometritis. Tissue samples from the mammary gland, uterus and ovary were obtained from river buffalo (Mediterranean type) with and without endometritis. Bacteriological examination showed the presence of both gram positive and negative in all buffalo with endometritis. RNA extraction and complementary DNA (cDNA) synthesis were conducted from all tissues. Specific primer for IL8 full coding regions was designed using known cDNA sequences of Bubalus bubalis, Genbank accession number AY952930.1. IL-8 gene expression was investigated in buffalo tissues. Expression of IL-8 in buffalo with endometritis was found to increase significantly over buffalo without endometritis only in the uterus (P = 0.0159). PCR products from uterus tissues (target organs) of buffalo with and without endometritis, were purified and sequenced. No polymorphic sites were detected in the investigated samples. IL-8 cDNA nucleotide sequences of buffalo with and without endometritis were 100% identical (accession number JX413057). Buffalo IL8 cDNAs were compared with corresponding sequences of member of subfamily Bovinae (buffalo and cattle) and subfamily Caprinae (sheep and goat). IL-8 species specific differences were identified.

PKCη promotes senescence induced by oxidative stress and chemotherapy

Senescence is characterized by permanent cell-cycle arrest despite continued viability and metabolic activity, in conjunction with the secretion of a complex mixture of extracellular proteins and soluble factors known as the senescence-associated secretory phenotype (SASP). Cellular senescence has been shown to prevent the proliferation of potentially tumorigenic cells, and is thus generally considered a tumor suppressive process. However, some SASP components may act as pro-tumorigenic mediators on premalignant cells in the microenvironment. A limited number of studies indicated that protein kinase C (PKC) has a role in senescence, with different isoforms having opposing effects. It is therefore important to elucidate the functional role of specific PKCs in senescence. Here we show that PKCη, an epithelial specific and anti-apoptotic kinase, promotes senescence induced by oxidative stress and DNA damage. We further demonstrate that PKCη promotes senescence through its ability to upregulate the expression of the cell cycle inhibitors p21^Cip1 and p27^Kip1 and enhance transcription and secretion of interleukin-6 (IL-6). Moreover, we demonstrate that PKCη creates a positive loop for reinforcing senescence by increasing the transcription of both IL-6 and IL-6 receptor, whereas the expression of IL-8 is specifically suppressed by PKCη. Thus, the presence/absence of PKCη modulates major components of SASP. Furthermore, we show that the human polymorphic variant of PKCη, 374I, that exhibits higher kinase activity in comparison to WT-374V, is also more effective in IL-6 secretion, p21^Cip1 expression and the promotion of senescence, further supporting a role for PKCη in senescence. As there is now considerable interest in senescence activation/elimination to control tumor progression, it is first crucial to reveal the molecular regulators of senescence. This will improve our ability to develop new strategies to harness senescence as a potential cancer therapy in the future.

Berberine hydrochloride IL-8 dependently inhibits invasion and IL-8-independently promotes cell apoptosis in MDA-MB-231 cells

Breast cancer, the leading cause of cancer-related mortality worldwide in females, has high metastastic and recurrence rates. The aim of the present study was to evaluate the anti-metastatic and anticancer in situ effect of berberine hydrochloride (BER) in MDA-MB-231 cells. BER dose-dependently inhibited proliferation and the IL-8 secretion of MDA-MB-231 cells. Additional experiments revealed that the inactivation of PI3K, JAK2, NF-κB and AP-1 by BER contributed to the decreased IL-8 secretion. BER abrogated cell invasion induced by IL-8 accompanied with the downregulation of the gene expression of MMP-2, EGF, E-cadherin, bFGF and fibronectin. In addition, BER reduced cell motility but induced G2/M arrest and cell apoptosis in an IL-8‑independent manner. BER modulated multiple signaling pathway molecules involved in the regulation of cell apoptosis, including activation of p38 MAPK and JNK and deactivation of JAK2, p85 PI3K, Akt and NF-κB. The enhanced cell apoptosis induced by BER was eliminated by inhibitors of p38 MAPK and JNK but was strengthened by activator of p38 MAPK. Thus, BER inhibited cell metastasis partly through the IL-8 mediated pathway while it induced G2/M arrest and promoted cell apoptosis through the IL-8 independent pathway. Apoptosis induced by BER was mediated by crosstalks of various pathways including activation of p38 MAPK and JNK pathways and inactivation of Jak2/PI3K/NF-κB/AP-1 pathways. The results suggested that BER may be an efficient and safe drug candidate for treating highly metastatic breast cancer.

Chromatin remodeling protein SMAR1 regulates NF-κB dependent Interleukin-8 transcription in breast cancer

Interleukin-8 (IL-8) is a pleiotropic chemokine involved in metastasis and angiogenesis of breast tumors. The expression of IL-8 is deregulated in metastatic breast carcinomas owing to aberrant NF-κB activity, which is known to positively regulate IL-8 transcription. Earlier, we have shown that tumor suppressor SMAR1 suppresses NF-κB transcriptional activity by modulating IκBα function. Here, we show that NF-κB target gene IL-8, is a direct transcriptional target of SMAR1. Using chromatin immunoprecipitation and reporter assays, we demonstrate that SMAR1 binds to IL-8 promoter MAR (matrix attachment region) and recruits HDAC1 dependent co-repressor complex. Further, we also show that SMAR1 antagonizes p300-mediated acetylation of RelA/p65, a post-translational modification indispensable for IL-8 transactivation. Thus, we decipher a new role of SMAR1 in NF-κB dependent transcriptional regulation of pro-angiogenic chemokine IL-8.

PAD2 overexpression in transgenic mice promotes spontaneous skin neoplasia

Peptidylarginine deiminase 2 (PAD2/PADI2) has been implicated in various inflammatory diseases and, more recently, cancer. The goal of this study was to test the hypothesis that PAD2 promotes oncogenesis using a transgenic mouse model. We found that about 37% of transgenic mice overexpressing human FLAG-PAD2 downstream of the MMTV-LTR promoter develop spontaneous neoplastic skin lesions. Molecular and histopathologic analyses of the resulting lesions find that they contain increased levels of markers for invasion, inflammation, and epithelial-to-mesenchymal transition (EMT) and that a subset of the lesions progress to invasive squamous cell carcinoma (SCC). We then stably overexpressed FLAG-PAD2 in the human SCC cell line, A431, and found that the PAD2-overexpressing cells were more tumorigenic in vitro and also contained elevated levels of markers for inflammation and EMT. Collectively, these studies provide the first genetic evidence that PAD2 functions as an oncogene and suggest that PAD2 may promote tumor progression by enhancing inflammation within the tumor microenvironment.

The role of inflammation in inflammatory breast cancer

Inflammatory breast cancer (IBC) is the most aggressive form of breast cancer. Despite extensive study, whether inflammation contributes to the tumorigenicity or aggressiveness of IBC remains largely unknown. In this chapter, we will review the potential role played by inflammation in IBC based on the results of in vitro, in vivo, and patient studies. Current evidence suggests that several major inflammatory signaling pathways are constitutively active in IBC and breast cancer. Among them, the NF-κB, COX-2, and JAK/STAT signaling systems seem to play a major role in the tumorigenesis of IBC. Inflammatory molecules such as interleukin-6, tumor necrosis factor alpha (TNF-α), and gamma interferon have been shown to contribute to malignant transformation in preclinical studies of IBC, while transforming growth factor-β, interleukins 8 and 1β, as well as TNF-α appear to play a role in proliferation, survival, epithelial-mesenchymal transition, invasion, and metastasis. In this chapter, we also describe work thus far involving inhibitors of inflammation in the development of prevention and treatment strategies for IBC.

Interleukin-8 in breast cancer progression

Interleukin-8 (IL-8) is a chemokine that has an autocrine and/or paracrine tumor-promoting role and significant potential as a prognostic and/or predictive cancer biomarker. In breast cancer, which is mostly determined by expression of estrogen receptor (ER) and human epidermal growth factor receptor 2 (HER2), IL-8 could play a specific role. IL-8 is highly expressed in ER- breast cancers, but it increases invasiveness and metastatic potential of both ER- and ER+ breast cancer cells. It is also highly expressed in HER2+ breast cancers. Because of the complex crosstalk between these receptors and IL-8, its role is mainly determined by delicate balance in their signaling pathways. Therefore, the main point of this review was to analyze the possible influence of IL-8 in breast cancer progression related to its interaction with ER and HER2 and the consequent therapeutic implications of these relations.

Unraveling regulatory programs for NF-kappaB, p53 and microRNAs in head and neck squamous cell carcinoma

In head and neck squamous cell carcinoma (HNSCC), mutations of p53 usually coexist with aberrant activation of NF-kappaB (NF-κB), other transcription factors and microRNAs, which promote tumor pathogenesis. However, how these factors and microRNAs interact to globally modulate gene expression and mediate oncogenesis is not fully understood. We devised a novel bioinformatics method to uncover interactive relationships between transcription factors or microRNAs and genes. This approach is based on matrix decomposition modeling under the joint constraints of sparseness and regulator-target connectivity, and able to integrate gene expression profiling and binding data of regulators. We employed this method to infer the gene regulatory networks in HNSCC. We found that the majority of the predicted p53 targets overlapped with those for NF-κB, suggesting that the two transcription factors exert a concerted modulation on regulatory programs in tumor cells. We further investigated the interrelationships of p53 and NF-κB with five additional transcription factors, AP1, CEBPB, EGR1, SP1 and STAT3, and microRNAs mir21 and mir34ac. The resulting gene networks indicate that interactions among NF-κB, p53, and the two miRNAs likely regulate progression of HNSCC. We experimentally validated our findings by determining expression of the predicted NF-κB and p53 target genes by siRNA knock down, and by examining p53 binding activity on promoters of predicted target genes in the tumor cell lines. Our results elucidating the cross-regulations among NF-κB, p53, and microRNAs provide insights into the complex regulatory mechanisms underlying HNSCC, and shows an efficient approach to inferring gene regulatory programs in biological complex systems.

The role of calcium, NF-κB and NFAT in the regulation of CXCL8 and IL-6 expression in Jurkat T-cells

T-cells play an important role in host immunity against invading pathogens. Determining the underlying regulatory mechanisms will provide a better understanding of T-cell-derived immune responses. In this study, we have shown the differential regulation of IL-6 and CXCL8 by NF-κB and NFAT in Jurkat T-cells, in response to PMA, heat killed Escherichia coli and calcium. CXCL8 was closely associated with the activation pattern of NFAT, while IL-6 expression was associated with NF-κB. Furthermore, increasing the intracellular Ca(2+) concentration by calcium ionophore treatment of the cells resulted in NFAT induction without affecting the NF-κB activity. Interestingly, NF-κB activation by heat killed E. coli, as well as CXCL8 and IL-6 expression was significantly suppressed following addition of the calcium ionophore. This indicates that calcium plays an important role in regulating protein trafficking and T-cell signalling, and the subsequent inflammatory gene expression infers an involvement of NFAT in CXCL8 regulation.Understanding these regulatory patterns provide clarification of conditions that involve altered intracellular signalling leading to T-cell-derived cytokine expression.

Luteolin 8-C-β-fucopyranoside inhibits invasion and suppresses TPA-induced MMP-9 and IL-8 via ERK/AP-1 and ERK/NF-κB signaling in MCF-7 breast cancer cells

Matrix metalloproteinase 9 (MMP-9) and interleukin-8 (IL-8) play major roles in tumor progression and invasion of breast cancer cells. The present study was undertaken to investigate the inhibitory mechanism of cell invasion by luteolin 8-C-β-fucopyranoside (named as LU8C-FP), a C-glycosylflavone, in human breast cancer cells. We investigated whether LU8C-FP would inhibit MMP-9 activation and IL-8 expression in 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated MCF-7 breast cancer cells. LU8C-FP suppressed TPA-induced MMP-9 and IL-8 secretion and mRNA expression via inhibition of the MAPK signaling pathway and down-regulation of nuclear AP-1 and NF-κB. TPA-induced phosphorylation of ERK 1/2 was suppressed by LU8C-FP, whereas JNK and p38 MAPK phosphorylation were unaffected. In addition, LU8C-FP blocked the ERK 1/2 pathways following expression of MMP-9 and IL-8. These results suggest LU8C-FP may function to suppress invasion of breast cancer cells through the ERK/AP-1 and ERK/NF-κB signaling cascades.

Matrix metalloproteinase 8 (collagenase 2) induces the expression of interleukins 6 and 8 in breast cancer cells

Matrix metalloproteinase 8 (MMP-8) is a tumor-suppressive protease that cleaves numerous substrates, including matrix proteins and chemokines. In particular, MMP-8 proteolytically activates IL-8 and, thereby, regulates neutrophil chemotaxis in vivo. We explored the effects of expression of either a WT or catalytically inactive (E198A) mutant version of MMP-8 in human breast cancer cell lines. Analysis of serum-free conditioned media from three breast cancer cell lines (MCF-7, SK-BR-3, and MDA-MB-231) expressing WT MMP-8 revealed elevated levels of IL-6 and IL-8. This increase was mirrored at the mRNA level and was dependent on MMP-8 catalytic activity. However, sustained expression of WT MMP-8 by breast cancer cells was non-permissive for long-term growth, as shown by reduced colony formation compared with cells expressing either control vector or E198A mutant MMP-8. In long-term culture of transfected MDA-MB-231 cells, expression of WT but not E198A mutant MMP-8 was lost, with IL-6 and IL-8 levels returning to base line. Rare clonal isolates of MDA-MB-231 cells expressing WT MMP-8 were generated, and these showed constitutively high levels of IL-6 and IL-8, although production of the interleukins was no longer dependent upon MMP-8 activity. These studies support a causal connection between MMP-8 activity and the IL-6/IL-8 network, with an acute response to MMP-8 involving induction of the proinflammatory mediators, which may in part serve to compensate for the deleterious effects of MMP-8 on breast cancer cell growth. This axis may be relevant to the recognized ability of MMP-8 to orchestrate the innate immune system in inflammation in vivo.

EpCAM modulates NF-κB signaling and interleukin-8 expression in breast cancer

The epithelial cell adhesion molecule (EpCAM) is a 40-kD type I transmembrane protein that is overexpressed in human epithelial cancers and is currently the target of molecular therapy based on its overexpression at the cell surface. Recently, we and others have shown a role for EpCAM in cell signaling and carcinogenesis, and EpCAM expression seems to promote breast cancer invasion. Interleukin-8 (IL-8/CXCL-8) is an inflammatory cytokine that has recently been shown to modulate breast cancer invasion and angiogenesis. In preliminary experiments, we identified a correlation between EpCAM and IL-8 expression in primary human breast cancers. Specific ablation of EpCAM in breast cancer cell lines results in decreased IL-8 expression, and IL-8 contributes to EpCAM-dependent breast cancer invasion. Specific ablation of EpCAM is also associated with decreased NF-κB transcription factor activity, decreased phosphorylation of the NF-κB family member RELA, and increased IκBα protein expression. EpCAM modulates IL-8 expression at baseline, and following IL-1β stimulation, which is known to be a potent inducer of NF-κB in breast cancer. In functional rescue experiments, specific ablation of RELA or forced expression of the NF-κB inhibitor protein IκBα prevented EpCAM-dependent rescue of IL-8 promoter activity. These studies show for the first time that EpCAM can modulate NF-κB transcription factor activity and IL-8 expression in breast cancer and confirm the role of EpCAM signaling in modulating breast cancer invasion. Further study is required to define the molecular mechanism(s) of EpCAM signaling in breast cancer and to direct the rational development of molecular therapies targeting EpCAM.

Blimp1 activation by AP-1 in human lung cancer cells promotes a migratory phenotype and is inhibited by the lysyl oxidase propeptide

B lymphocyte-induced maturation protein 1 (Blimp1) is a master regulator of B cell differentiation, and controls migration of primordial germ cells. Recently we observed aberrant Blimp1 expression in breast cancer cells resulting from an NF-κB RelB to Ras signaling pathway. In order to address the question of whether the unexpected expression of Blimp1 is seen in other epithelial-derived tumors, we selected lung cancers as they are frequently driven by Ras signaling. Blimp1 was detected in all five lung cancer cell lines examined and shown to promote lung cancer cell migration and invasion. Interrogation of microarray datasets demonstrated elevated BLIMP1 RNA expression in lung adenocarcinoma, pancreatic ductal carcinomas, head and neck tumors as well as in glioblastomas. Involvement of Ras and its downstream kinase c-Raf was confirmed using mutant and siRNA strategies. We next addressed the issue of mechanism of Blimp1 activation in lung cancer. Using knockdown and ectopic expression, the role of the Activator Protein (AP)-1 family of transcription factors was demonstrated. Further, chromatin immunoprecipitation assays confirmed binding to identified AP-1 elements in the BLIMP1 promoter of ectopically expressed c-Jun and of endogenous AP-1 subunits following serum stimulation. The propeptide domain of lysyl oxidase (LOX-PP) was identified as a tumor suppressor, with ability to reduce Ras signaling in lung cancer cells. LOX-PP reduced expression of Blimp1 by binding to c-Raf and inhibiting activation of AP-1, thereby attenuating the migratory phenotype of lung cancer cells. Thus, Blimp1 is a mediator of Ras/Raf/AP-1 signaling that promotes cell migration, and is repressed by LOX-PP in lung cancer.