Induced electric fields inhibit breast cancer growth and metastasis by modulating the immune tumor microenvironment

Despite tremendous advances in oncology, metastatic triple-negative breast cancer remains difficult to treat and manage with established therapies. Here, we show in mice with orthotopic triple-negative breast tumors that alternating (100 kHz), and low intensity (<1 mV/cm) induced electric fields (iEFs) significantly reduced primary tumor growth and distant lung metastases. Non-contact iEF treatment can be delivered safely and non-invasively in vivo via a hollow, rectangular solenoid coil. We discovered that iEF treatment enhances anti-tumor immune responses at both the primary breast and secondary lung sites. In addition, iEF reduces immunosuppressive TME by reducing effector CD8+ T cell exhaustion and the infiltration of immunosuppressive immune cells. Furthermore, iEF treatment reduced lung metastasis by increasing CD8+ T cells and reducing immunosuppressive Gr1+ neutrophils in the lung microenvironment. We also observed that iEFs reduced the metastatic potential of cancer cells by inhibiting epithelial-to-mesenchymal transition. By introducing a non-invasive and non-toxic electrotherapeutic for inhibiting metastatic outgrowth and enhancing anti-tumor immune response in vivo, treatment with iEF technology could add to a paradigm-shifting strategy for cancer therapy.

Correction: Activation of the Connective Tissue Growth Factor (CTGF)-Transforming Growth Factor β 1 (TGF-β 1) Axis in Hepatitis C Virus-Expressing Hepatocytes

[This corrects the article DOI: 10.1371/journal.pone.0046526.].

Fibroblast-derived CXCL12 increases vascular permeability in a 3-D microfluidic model independent of extracellular matrix contractility

Cancer-associated fibroblasts (CAFs) play an active role in remodeling the local tumor stroma to support tumor initiation, growth, invasion, metastasis, and therapeutic resistance. The CAF-secreted chemokine, CXCL12, has been directly implicated in the tumorigenic progression of carcinomas, including breast cancer. Using a 3-D in vitro microfluidic-based microtissue model, we demonstrate that stromal CXCL12 secreted by CAFs has a potent effect on increasing the vascular permeability of local blood microvessel analogues through paracrine signaling. Moreover, genetic deletion of fibroblast-specific CXCL12 significantly reduced vessel permeability compared to CXCL12 secreting CAFs within the recapitulated tumor microenvironment (TME). We suspected that fibroblast-mediated extracellular matrix (ECM) remodeling and contraction indirectly accounted for this change in vessel permeability. To this end, we investigated the autocrine effects of CXCL12 on fibroblast contractility and determined that antagonistic blocking of CXCL12 did not have a substantial effect on ECM contraction. Our findings indicate that fibroblast-secreted CXCL12 has a significant role in promoting a leakier endothelium hospitable to angiogenesis and tumor cell intravasation; however, autocrine CXCL12 is not the primary upstream trigger of CAF contractility.

Slit2/Robo1 signaling inhibits small-cell lung cancer by targeting β-catenin signaling in tumor cells and macrophages

Small-cell lung cancer (SCLC) is an aggressive neuroendocrine subtype of lung cancer with poor patient prognosis. However, the mechanisms that regulate SCLC progression and metastasis remain undefined. Here, we show that the expression of the slit guidance ligand 2 (SLIT2) tumor suppressor gene is reduced in SCLC tumors relative to adjacent normal tissue. In addition, the expression of the SLIT2 receptor, roundabout guidance receptor 1 (ROBO1), is upregulated. We find a positive association between SLIT2 expression and the Yes1 associated transcriptional regulator (YAP1)-expressing SCLC subtype (SCLC-Y), which shows a better prognosis. Using genetically engineered SCLC cells, adenovirus gene therapy, and preclinical xenograft models, we show that SLIT2 overexpression or the deletion of ROBO1 restricts tumor growth in vitro and in vivo. Mechanistic studies revealed significant inhibition of myeloid-derived suppressor cells (MDSCs) and M2-like tumor-associated macrophages (TAMs) in the SCLC tumors. In addition, SLIT2 enhances M1-like and phagocytic macrophages. Molecular analysis showed that ROBO1 knockout or SLIT2 overexpression suppresses the transforming growth factor beta 1 (TGF-β1)/β-catenin signaling pathway in both tumor cells and macrophages. Overall, we find that SLIT2 and ROBO1 have contrasting effects on SCLC tumors. SLIT2 suppresses, whereas ROBO1 promotes, SCLC growth by regulating the Tgf-β1/glycogen synthase kinase-3 beta (GSK3)/β-catenin signaling pathway in tumor cells and TAMs. These studies indicate that SLIT2 could be used as a novel therapeutic agent against aggressive SCLC.

Augmentation of Extracellular ATP Synergizes With Chemotherapy in Triple Negative Breast Cancer

Introduction

Breast cancer affects two million patients worldwide every year and is the most common cause of cancer-related death among women. The triple-negative breast cancer (TNBC) sub-type is associated with an especially poor prognosis because currently available therapies fail to induce long-lasting responses. Therefore, there is an urgent need to develop novel therapies that result in durable responses. One universal characteristic of the tumor microenvironment is a markedly elevated concentration of extracellular adenosine triphosphate (eATP). Chemotherapy exposure results in further increases in eATP through its release into the extracellular space of cancer cells via P2RX channels. eATP is degraded by eATPases. Given that eATP is toxic to cancer cells, we hypothesized that augmenting the release of eATP through P2RX channels and inhibiting extracellular ATPases would sensitize TNBC cells to chemotherapy.

Methods

TNBC cell lines MDA-MB 231, Hs 578t and MDA-MB 468 and non-tumorigenic immortal mammary epithelial MCF-10A cells were treated with increasing concentrations the chemotherapeutic agent paclitaxel in the presence of eATPases or specific antagonists of P2RXs with cell viability and eATP content being measured. Additionally, the mRNA, protein and cell surface expressions of the purinergic receptors P2RX4 and P2RX7 were evaluated in all examined cell lines via qRT-PCR, western blot, and flow cytometry analyses, respectively.

Results

In the present study, we observed dose-dependent declines of cell viability and increases in eATP of paclitaxel-treated TNBC cell lines in the presence of inhibitors of eATPases, but not of the MCF-10A cell line. These effects were reversed by specific antagonists of P2RXs. Similar results, as those observed with eATPase inhibitors, were seen with P2RX activators. All examined cell lines expressed both P2RX4 and P2RX7 at the mRNA, protein and cell surface levels.

Conclusion

These results reveal that eATP modulates the chemotherapeutic response in TNBC cell lines, which could be exploited to enhance the efficacy of chemotherapy regimens for TNBC.

Activity of Estrogen Receptor β Agonists in Therapy-Resistant Estrogen Receptor-Positive Breast Cancer

Background

Among women, breast cancer is the leading cause of cancer-related death worldwide. Estrogen receptor α-positive (ERα+) breast cancer accounts for 70% of all breast cancer subtypes. Although ERα+ breast cancer initially responds to estrogen deprivation or blockade, the emergence of resistance compels the use of more aggressive therapies. While ERα is a driver in ERα+ breast cancer, ERβ plays an inhibitory role in several different cancer types. To date, the lack of highly selective ERβ agonists without ERα activity has limited the exploration of ERβ activation as a strategy for ERα+ breast cancer.

Methods

We measured the expression levels of ESR1 and ESR2 genes in immortalized mammary epithelial cells and different breast cancer cell lines. The viability of ERα+ breast cancer cell lines upon treatments with specific ERβ agonists, including OSU-ERb-12 and LY500307, was assessed. The specificity of the ERβ agonists, OSU-ERb-12 and LY500307, was confirmed by reporter assays. The effects of ERβ agonists on cell proliferation, cell cycle, apoptosis, colony formation, cell migration, and expression of tumor suppressor proteins were analyzed. The expression of ESR2 and genes containing ERE-AP1 composite response elements was examined in ERα+ human breast cancer samples to determine the correlation between ESR2 expression and overall survival and that of putative ESR2-regulated genes.

Results

In this study, we demonstrate the efficacy of highly selective ERβ agonists in ERα+ breast cancer cell lines and drug-resistant derivatives. ERβ agonists blocked cell proliferation, migration, and colony formation and induced apoptosis and S and/or G2/M cell-cycle arrest of ERα+ breast cancer cell lines. Also, increases in the expression of the key tumor suppressors FOXO1 and FOXO3a were noted. Importantly, the strong synergy between ERβ agonists and ERα antagonists suggested that the efficacy of ERβ agonists is maximized by combination with ERα blockade. Lastly, ESR2 (ERβ gene) expression was negatively correlated with ESR1 (ERα gene) and CCND1 RNA expression in human metastatic ERα+/HER2- breast cancer samples.

Conclusion

Our results demonstrate that highly selective ERβ agonists attenuate the viability of ERα+ breast cancer cell lines in vitro and suggest that this therapeutic strategy merits further evaluation for ERα+ breast cancer.

Cannabidiol Inhibits Tumorigenesis in Cisplatin-Resistant Non-Small Cell Lung Cancer via TRPV2

Simple Summary

Drug resistance is the key factor contributing to the therapeutic failure of lung cancer and the deaths related to lung cancer. Our study demonstrated that small molecular weight non-psychotropic phytochemical, cannabidiol (CBD), inhibits growth and metastasis of drug-resistant non-small cell lung cancer cells (NSCLC) cells in-vitro and in-vivo. We further discovered that CBD mediates its anti-cancer effects in part via an ion channel receptor, TRPV2, present on lung adenocarcinoma. Moreover, we showed that CBD induces apoptosis of cisplatin-resistant cells by modulating oxidative stress pathways. Overall, these studies indicate that CBD could be used as a promising therapeutic strategy in TRPV2 expressing cisplatin-resistant NSCLC.

Abstract

Chemotherapy forms the backbone of current treatments for many patients with advanced non-small-cell lung cancer (NSCLC). However, the survival rate is low in these patients due to the development of drug resistance, including cisplatin resistance. In this study, we developed a novel strategy to combat the growth of cisplatin-resistant (CR) NSCLC cells. We have shown that treatment with the plant-derived, non-psychotropic small molecular weight molecule, cannabidiol (CBD), significantly induced apoptosis of CR NSCLC cells. In addition, CBD treatment significantly reduced tumor progression and metastasis in a mouse xenograft model and suppressed cancer stem cell properties. Further mechanistic studies demonstrated the ability of CBD to inhibit the growth of CR cell lines by reducing NRF-2 and enhancing the generation of reactive oxygen species (ROS). Moreover, we show that CBD acts through Transient Receptor Potential Vanilloid-2 (TRPV2) to induce apoptosis, where TRPV2 is expressed on human lung adenocarcinoma tumors. High expression of TRPV2 correlates with better overall survival of lung cancer patients. Our findings identify CBD as a novel therapeutic agent targeting TRPV2 to inhibit the growth and metastasis of this aggressive cisplatin-resistant phenotype in NSCLC.

Abstract P4-04-12: Macrophage migration inhibitory factor regulates triple-negative breast cancer progression by enhancing the recruitment of immune suppressive cells

Triple-negative breast cancer (TNBC) accounts for 15-20% of all breast cancers and lacks the expression of estrogen, progesterone, and Her2 receptors. TNBC is a highly aggressive subtype of breast cancer that has been associated with poorer prognosis and worse overall survival rate. Macrophage migration inhibitory factor (MIF) is a multipotent pro-inflammatory cytokine, highly expressed in various cancers and reported to enhance tumor growth and metastasis. However, its role in influencing the anti-tumor immunity is unexplored. We have previously shown that MIF promotes TNBC growth and metastasis. In addition, CPSI-1306 (MIF inhibitor), reduces its oncogenic effects. Here, we have shown that MIF downregulation in human TNBC xenografts correlate with reduced infiltration of myeloid derived suppressor cells (MDSCs). Furthermore, using a MIF knockout mouse model, we detected reduced MDSC population in the tumor microenvironment. In addition, we observed higher recruitment and increased proliferation of CD3+ T cells. Furthermore, we utilized a syngeneic mouse model to study the effect of MIF inhibition on infiltration of different immune cells in-vivo. CPSI-1306 treatment decreased the recruitment of MDSCs in both the tumor and spleen. In addition, CPSI-1306 treatment promotes the infiltration of CD8+ T cells in both the tumor and spleen. However, CPSI-1306 treatment did not influence the recruitment of CD4+ T cells. We further analyzed the expression of various cytokines and chemokines in blood sera of control and CPSI-1306 treated mice groups using a cytokine array kit. We observed that CPSI-1306 treatment group showed reduced levels of GCSF, GMCSF, IL-2 and IL-4 levels compared to vehicle control groups. Overall, our data strongly suggests that small molecular weight MIF inhibitors could be a potential strategy against TNBC.

Citation Format: Manish Charan, Subhadip Das, Sanjay Mishra, Sanjay Varikuti, Abhay R Satoskar, Ramesh K Ganju. Macrophage migration inhibitory factor regulates triple-negative breast cancer progression by enhancing the recruitment of immune suppressive cells [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-04-12.

Abstract P4-04-13: S100a7/rage signaling promotes breast tumorigenesis through modulating tumor-associated macrophages

S100A7 has been shown to be associated with breast cancer growth and metastasis. However, the molecular mechanism through which S100A7 promotes breast tumorigenesis is not completely understood. In this study, we revealed that S100A7 enhanced Stat3-mediated secretion of Serpin-E1 in triple negative breast cancer (TNBC) cell lines. Serpin-E1 has been shown to promote recruitment and polarization toward a pro-tumorigenic phenotype of tumor-associated macrophages through activating the Stat3 pathway. Importantly, we reported that the inhibition of Stat3 led to reduction of S100A7-mediated invasiness of TNBC cells and also significantly decreased the secretion of Serpin-E1 by cancer cells. We also revealed that Stat3 inhibition in TNBC cells or Serpin-E1 neutralization significantly reduced the migration of human monocytes/macrophages by transwell migration assay. We further demonstrate that murine ortholog of S100A7, mS100a7a15 enhanced mammary hyperplasia, tumor growth and metastasis through Stat3 activation. Previously, we reported that S100A7 mediated its tumorigenic effects through RAGE in breast cancer cells. Therefore, we also discovered that combinatorial treatment of Stat3 and RAGE inhibitors in mammary tumor bearing mS100a7a15 overexpression mouse model strongly decreased the tumor burden and enhanced the recruitment of tumor-suppressing M1-macrophages. We also found that combined inhibition of RAGE and Stat3 significantly increased the infiltration of CD4 T cells in the tumor microenvironment (TME). Collectively, these findings suggest S100A7/RAGE signaling pathway could be used as a novel therapeutic target to inhibit breast cancer growth and metastasis through modulating the TME.

Citation Format: Ajeet K Verma, Tasha Wilkie, Sanjay Mishra, Manish Charan, Ramesh K Ganju. S100a7/rage signaling promotes breast tumorigenesis through modulating tumor-associated macrophages [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-04-13.

cPLA2 blockade attenuates S100A7-mediated breast tumorigenicity by inhibiting the immunosuppressive tumor microenvironment

BACKGROUND

Molecular mechanisms underlying inflammation-associated breast tumor growth are poorly studied. S100A7, a pro-inflammatory molecule has been shown to enhance breast cancer growth and metastasis. However, the S100A7-mediated molecular mechanisms in enhancing tumor growth and metastasis are unclear.

METHODS

Human breast cancer tissue and plasma samples were used to analyze the expression of S100A7, cPLA2, and PGE2. S100A7-overexpressing or downregulated human metastatic breast cancer cells were used to evaluate the S100A7-mediated downstream signaling mechanisms. Bi-transgenic mS100a7a15 overexpression, TNBC C3 (1)/Tag transgenic, and humanized patient-derived xenograft mouse models and cPLA2 inhibitor (AACOCF3) were used to investigate the role of S100A7/cPLA2/PGE2 signaling in tumor growth and metastasis. Additionally, CODEX, a highly advanced multiplexed imaging was employed to delineate the effects of S100A7/cPLA2 inhibition on the recruitment of various immune cells.

RESULTS

In this study, we found that S100A7 and cPLA2 are highly expressed and correlate with decreased overall survival in breast cancer patients. Further mechanistic studies revealed that S100A7/RAGE signaling promotes the expression of cPLA2 to mediate its oncogenic effects. Pharmacological inhibition of cPLA2 suppressed S100A7-mediated tumor growth and metastasis in multiple pre-clinical models including transgenic and humanized patient-derived xenograft (PDX) mouse models. The attenuation of cPLA2 signaling reduced S100A7-mediated recruitment of immune-suppressive myeloid cells in the tumor microenvironment (TME). Interestingly, we discovered that the S100A7/cPLA2 axis enhances the immunosuppressive microenvironment by increasing prostaglandin E2 (PGE2). Furthermore, CO-Detection by indEXing (CODEX) imaging-based analyses revealed that cPLA2 inhibition increased the infiltration of activated and proliferating CD4⁺ and CD8⁺ T cells in the TME. In addition, CD163⁺ tumor associated-macrophages were positively associated with S100A7 and cPLA2 expression in malignant breast cancer patients.

CONCLUSIONS

Our study provides new mechanistic insights on the cross-talk between S100A7/cPLA2 in enhancing breast tumor growth and metastasis by generating an immunosuppressive TME that inhibits the infiltration of cytotoxic T cells. Furthermore, our studies indicate that S100A7/cPLA2 could be used as novel prognostic marker and cPLA2 inhibitors as promising drugs against S100A7-overexpressing aggressive breast cancer.

Cancer Treatment: Preclinical & Clinical

The first evidence that cannabinoids may have in vitro and in vivo antineoplastic activity against tumor cell lines and animal tumor models was published in the Journal of the National Cancer Institute nearly 50 years ago. Cannabinoids appear to induce apoptosis in rodent brain tumors by way of direct interaction with the cannabinoid receptor. They may inhibit angiogenesis and tumor cell invasiveness. Despite preclinical findings, attempts to translate the benefits from bench to bedside have been limited. This session provides a review of the basic science supporting the use of cannabinoids in gliomas, paired with the first randomized clinical trial of a cannabis-based therapy for glioblastoma multiforme. Another preclinical presentation reports the effects of cannabinoids on triple-negative breast cancer cell lines and how cannabidiol may affect tumors. The session's second human trial raises concerns about the use of botanical cannabis in patients with advanced cancer receiving immunotherapy suggesting inferior outcomes.

Slit2-Mediated Metabolic Reprogramming in Bone Marrow-Derived Macrophages Enhances Antitumor Immunity

Slit2 exerts antitumor effects in various cancers; however, the underlying mechanism, especially its role in regulating the immune, especially in the bone marrow niche, system is still unknown. Elucidating the behavior of macrophages in tumor progression can potentially improve immunotherapy. Using a spontaneous mammary tumor virus promoter-polyoma middle T antigen (PyMT) breast cancer mouse model, we observed that Slit2 increased the abundance of antitumor M1 macrophage in the bone marrow upon differentiation in vitro. Moreover, myeloablated PyMT mice injected with Slit2-treated bone marrow allografts showed a marked reduction in tumor growth, with enhanced recruitment of M1 macrophage in their tumor stroma. Mechanistic studies revealed that Slit2 significantly enhanced glycolysis and reduced fatty acid oxidation in bone marrow-derived macrophages (BMDMs). Slit2 treatment also altered mitochondrial respiration metabolites in macrophages isolated from healthy human blood that were treated with plasma from breast cancer patients. Overall, this study, for the first time, shows that Slit2 increases BMDM polarization toward antitumor phenotype by modulating immune-metabolism. Furthermore, this study provides evidence that soluble Slit2 could be developed as novel therapeutic strategy to enhance antitumor immune response.

Slit2 Inhibits Breast Cancer Metastasis by Activating M1-Like Phagocytic and Antifibrotic Macrophages

Tumor-associated macrophages (TAM) are heterogeneous in nature and comprise antitumor M1-like (M1-TAM) or pro-tumor M2-like (M2-TAM) TAMs. M2-TAMs are a major component of stroma in breast tumors and enhance metastasis by reducing their phagocytic ability and increasing tumor fibrosis. However, the molecular mechanisms that regulate phenotypic plasticity of TAMs are not well known. Here we report a novel tumor suppressor Slit2 in breast cancer by regulating TAMs in the tumor microenvironment. Slit2 reduced the in vivo growth and metastasis of spontaneous and syngeneic mammary tumor and xenograft breast tumor models. Slit2 increased recruitment of M1-TAMs to the tumor and enhanced the ability of M1-TAMs to phagocytose tumor cells in vitro and in vivo. This Slit2-mediated increase in M1-TAM phagocytosis occurred via suppression of IL6. Slit2 was also shown to diminish fibrosis in breast cancer mouse models by increasing the expression of matrix metalloproteinase 13 in M1-TAMs. Analysis of patient samples showed high Slit2 expression strongly associated with better patient survival and inversely correlated with the abundance of CD163⁺ TAMs. Overall, these studies define the role of Slit2 in inhibiting metastasis by activating M1-TAMs and depleting tumor fibrosis. Furthermore, these findings suggest that Slit2 can be a promising immunotherapeutic agent to redirect TAMs to serve as tumor killers for aggressive and metastatic breast cancers. In addition, Slit2 expression along with CD163⁺ TAMs could be used as an improved prognostic biomarker in patients with breast cancer. SIGNIFICANCE: This study provides evidence that the antitumor effect of Slit2 in breast cancer occurs by activating the phagocytic activity of M1-like tumor-associated macrophages against tumor cells and diminishing fibrosis.

Lipopolysaccharide from the commensal microbiota of the breast enhances cancer growth: role of S100A7 and TLR4

The role of commensal bacterial microbiota in the pathogenesis of human malignancies has been a research field of incomparable progress in recent years. Although breast tissue is commonly assumed to be sterile, recent studies suggest that human breast tissue may contain a bacterial microbiota. In this study, we used an immune‐competent orthotopic breast cancer mouse model to explore the existence of a unique and independent bacterial microbiota in breast tumors. We observed some similarities in breast cancer microbiota with skin; however, breast tumor microbiota was mainly enriched with Gram‐negative bacteria, serving as a primary source of lipopolysaccharide (LPS). In addition, dextran sulfate sodium (DSS) treatment in late‐stage tumor lesions increased LPS levels in the breast tissue environment. We also discovered an increased expression of S100A7 and low level of TLR4 in late‐stage tumors with or without DSS as compared to early‐stage tumor lesions. The treatment of breast cancer cells with LPS increased the expression of S100A7 in breast cancer cells in vitro. Furthermore, S100A7 overexpression downregulated TLR4 and upregulated RAGE expression in breast cancer cells. Analysis of human breast cancer samples also highlighted the inverse correlation between S100A7 and TLR4 expression. Overall, these findings suggest that the commensal microbiota of breast tissue may enhance breast tumor burden through a novel LPS/S100A7/TLR4/RAGE signaling axis.

Racially Disparate Expression of mTOR/ERK-1/2 Allied Proteins in Cancer

Recent studies revealed that ethnic differences in mechanistic target of rapamycin (mTOR) and extracellular signal-regulated kinase (ERK-1/2) signaling pathways might be associated with the development and progression of different human malignancies. The African American (AA) population has an increased rate of cancer incidence and mortality compared to the Caucasian American (CA) population. Although the socioeconomic differences across different ethnic groups contribute to the disparity in developing different cancers, recent scientific evidence indicates the association of molecular and genetic variations in racial disparities of different human malignancies. The mTOR and ERK-1/2 signaling pathways are one of the well-known oncogenic signaling mechanisms that regulate diverse molecular and phenotypic aspects of normal as well as cancer cells in response to different external or internal stimuli. To date, very few studies have been carried out to explore the significance of racial disparity with abnormal mTOR and ERK-1/2 kinase signaling pathways, which may contribute to the development of aggressive human cancers. In this review, we discuss the differential regulation of mTOR and ERK-1/2 kinase signaling pathways across different ethnic groups, especially between AA and CA populations. Notably, we observed that key signaling proteins associated with mTOR and ERK-1/2 pathway including transforming growth factor-beta (TGF-β), Akt, and VEGFR showed racially disparate expression in cancer patients. Overall, this review article encompasses the significance of racially disparate signaling molecules related to mTOR/ERK1/2 and their potential in developing tailor-made anti-cancer therapies.

Contribution of the tumor and obese microenvironment to triple negative breast cancer

The growing burden of obesity and incidence of the aggressive triple negative breast cancer (TNBC) is a challenge, especially amongst vulnerable populations with unmet medical needs and higher mortality from breast cancer. While some mechanisms linking obesity and TNBC have been identified, the complex nature of pathogenesis, in both obesity as well as TNBC poses a real challenge in establishing a causative role of obesity in risk of TNBC. In this review article, we discuss pathological mechanisms identified in the tumor microenvironment (TME) as well as the obese microenvironment (OME), such as inflammation, insulin resistance and survival pathways that contribute to the development and progression of TNBC. Insights into the cross-talk between TME and OME, and their contribution to TNBC development and progression, may pave the way for personalized therapies against TNBC progression, relapse and metastasis.

Directional Migration of Breast Cancer Cells Hindered by Induced Electric Fields May Be Due to Accompanying Alteration of Metabolic Activity

Background: Induced electric fields (iEFs) control directional breast cancer cell migration. While the connection between migration and metabolism is appreciated in the context of cancer and metastasis, effects of iEFs on metabolic pathways especially as they relate to migration, remain unexplored. Materials and Methods: Quantitative cell migration data in the presence and absence of an epidermal growth factor (EGF) gradient in the microfluidic bidirectional microtrack assay was retrospectively analyzed for additional effects of iEFs on cell motility and directionality. Surrogate markers of oxidative phosphorylation (succinate dehydrogenase [SDH] activity) and glycolysis (lactate dehydrogenase activity) were assessed in MDA-MB-231 breast cancer cells and normal MCF10A mammary epithelial cells exposed to iEFs and EGF. Results: Retrospective analysis of migration results suggests that iEFs increase forward cell migration speeds while extending the time cells spend migrating slowly in the reverse direction or remaining stationary. Furthermore, in the presence of EGF, iEFs differentially altered flux through oxidative phosphorylation in MDA-MB-231 cells and glycolysis in MCF10A cells. Conclusions: iEFs interfere with MDA-MB-231 cell migration, potentially, by altering mitochondrial metabolism, observed as an inhibition of SDH activity in the presence of EGF. The energy intensive process of migration in these highly metastatic breast cancer cells may be hindered by iEFs, thus, through hampering of oxidative phosphorylation.

The Roles of Stroma-Derived Chemokine in Different Stages of Cancer Metastases

The intricate interplay between malignant cells and host cellular and non-cellular components play crucial role in different stages of tumor development, progression, and metastases. Tumor and stromal cells communicate to each other through receptors such as integrins and secretion of signaling molecules like growth factors, cytokines, chemokines and inflammatory mediators. Chemokines mediated signaling pathways have emerged as major mechanisms underlying multifaceted roles played by host cells during tumor progression. In response to tumor stimuli, host cells-derived chemokines further activates signaling cascades that support the ability of tumor cells to invade surrounding basement membrane and extra-cellular matrix. The host-derived chemokines act on endothelial cells to increase their permeability and facilitate tumor cells intravasation and extravasation. The tumor cells-host neutrophils interaction within the vasculature initiates chemokines driven recruitment of inflammatory cells that protects circulatory tumor cells from immune attack. Chemokines secreted by tumor cells and stromal immune and non-immune cells within the tumor microenvironment enter the circulation and are responsible for formation of a "pre-metastatic niche" like a "soil" in distant organs whereby circulating tumor cells "seed' and colonize, leading to formation of metastatic foci. Given the importance of host derived chemokines in cancer progression and metastases several drugs like Mogamulizumab, Plerixafor, Repertaxin among others are part of ongoing clinical trial which target chemokines and their receptors against cancer pathogenesis. In this review, we focus on recent advances in understanding the complexity of chemokines network in tumor microenvironment, with an emphasis on chemokines secreted from host cells. We especially summarize the role of host-derived chemokines in different stages of metastases, including invasion, dissemination, migration into the vasculature, and seeding into the pre-metastatic niche. We finally provide a brief description of prospective drugs that target chemokines in different clinical trials against cancer.

Estrogen Receptor Beta (ERβ): A Ligand Activated Tumor Suppressor

Estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ) belong to a superfamily of nuclear receptors called steroid hormone receptors, which, upon binding ligand, dimerize and translocate to the nucleus where they activate or repress the transcription of a large number of genes, thus modulating critical physiologic processes. ERβ has multiple isoforms that show differing association with prognosis. Expression levels of the full length ERβ1 isoform are often lower in aggressive cancers as compared to normal tissue. High ERβ1 expression is associated with improved overall survival in women with breast cancer. The promise of ERβ activation, as a potential targeted therapy, is based on concurrent activation of multiple tumor suppressor pathways with few side effects compared to chemotherapy. Thus, ERβ is a nuclear receptor with broad-spectrum tumor suppressor activity, which could serve as a potential treatment target in a variety of human cancers including breast cancer. Further development of highly selective agonists that lack ERα agonist activity, will be necessary to fully harness the potential of ERβ.

Molecular and Cellular Factors Associated with Racial Disparity in Breast Cancer

Recent studies have demonstrated that racial differences can influence breast cancer incidence and survival rate. African American (AA) women are at two to three fold higher risk for breast cancer than other ethnic groups. AA women with aggressive breast cancers show worse prognoses and higher mortality rates relative to Caucasian (CA) women. Over the last few years, effective treatment strategies have reduced mortality from breast cancer. Unfortunately, the breast cancer mortality rate among AA women remains higher compared to their CA counterparts. The focus of this review is to underscore the racial differences and differential regulation/expression of genetic signatures in CA and AA women with breast cancer. Moreover, immune cell infiltration significantly affects the clinical outcome of breast cancer. Here, we have reviewed recent findings on immune cell recruitment in the tumor microenvironment (TME) and documented its association with breast cancer racial disparity. In addition, we have extensively discussed the role of cytokines, chemokines, and other cell signaling molecules among AA and CA breast cancer patients. Furthermore, we have also reviewed the distinct genetic and epigenetic changes in AA and CA patients. Overall, this review article encompasses various molecular and cellular factors associated with breast cancer disparity that affects mortality and clinical outcome.

Electromagnetic fields alter the motility of metastatic breast cancer cells

Interactions between cells and their environment influence key physiologic processes such as their propensity to migrate. However, directed migration controlled by extrinsically applied electrical signals is poorly understood. Using a novel microfluidic platform, we found that metastatic breast cancer cells sense and respond to the net direction of weak (∼100 µV cm-1), asymmetric, non-contact induced Electric Fields (iEFs). iEFs inhibited EGFR (Epidermal Growth Factor Receptor) activation, prevented formation of actin-rich filopodia, and hindered the motility of EGF-treated breast cancer cells. The directional effects of iEFs were nullified by inhibition of Akt phosphorylation. Moreover, iEFs in combination with Akt inhibitor reduced EGF-promoted motility below the level of untreated controls. These results represent a step towards isolating the coupling mechanism between cell motility and iEFs, provide valuable insights into how iEFs target multiple diverging cancer cell signaling mechanisms, and demonstrate that electrical signals are a fundamental regulator of cancer cell migration.

Abstract 121: S100A9 inhibitor Tasquinimod: A novel strategy to inhibit small cell lung cancer progression and metastasis

Small cell lung cancer (SCLC) treatment is a major clinical challenge at present as it is highly refractory to available drugs. The MDSCs/macrophages are known to help SCLC develop resistant to available therapies. S100A9 (Migration inhibitory factor-related protein 14 (MRP14) is an EF-hand calcium-binding protein that has been involved in cell migration, invasion, proliferation, and tumor metastasis in various type of cancers, however not much is known about its role in SCLC. In this study, we found that S100A9 protein is highly up-regulated in various types of pulmonary neuroendocrine carcinomas (NEC) patient tissues compared to normal using tissue microarrays. We also observed that SCLC patients with higher S100A9 expression have significantly increased numbers of macrophage in the stroma. We have also shown that pre-treatment of the cells with S100A9 inhibitor (Tasquinimod) suppressed in-vitro cell migration, invasion, and colony formation. In addition, we analyzed the efficacy of S100A9 inhibitor against SCLC using in vivo mouse models. S100A9 inhibitor significantly reduces tumor growth and metastasis in SCLC in xenograft mouse models. We further observed that S100A9 inhibitor suppressed myeloid-derived suppressor cells (MDSC) populations and TAMs of the M2-polarized phenotype in SCLC. Moreover, we found myeloid cells sequestered from tumors of treated mice expressed were MI type as they showed higher levels of inducible nitric oxide synthase (iNos), and lower levels of arginase-1. Molecular analysis revealed that Tasquinimod decreases expression of IL6, IL10, and TGF-β1 in the cancer cells which helps inhibit macrophage activation to TAMs. Reduced proliferation and vascularization were observed in the tumors obtained from animals treated with S100A9 inhibitor. We also observed S100A9

inhibitor suppressed osteolytic bone formation in ex-vivo resorption assay. Overall, our studies, for the first time, show that Tasquinimod that targets S100A9 signaling could be used as a novel therapeutic strategy against SCLC.

Citation Format: Salha E. Sassi, Dinesh Ahirwar, Ramesh K. Ganju. S100A9 inhibitor Tasquinimod: A novel strategy to inhibit small cell lung cancer progression and metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 121.

Abstract P5-07-09: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Ahirwar DK, Nasser MW, Shukla RK, Shilo K, Ganju RK. Withdrawn [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-07-09.

Abstract 5870: CPSI-1306: A novel macrophage migration inhibitory factor inhibitor against aggressive breast cancer

Breast cancer is the leading cause of mortality in women, accounting for 23% of all cancer deaths, and one in eight women will develop invasive breast cancer over the course of her life. Although there are therapies available, most tumors develop resistance. In addition, certain types of breast cancers, including high-grade metastatic and triple-negative breast cancer, have limited therapeutic options available. Thus, novel targeted therapeutic strategies are required for prevention of disease progression. Inflammation of breast tumors is a major confounding factor involved in tumor progression and metastasis. Therefore, targeting inflammatory microenvironment could be a major strategy to targets breast tumor progression. Macrophage migration inhibitory factor (MIF) induces severe proinflammatory responses through tautomerase and also functions as a chemokine that mediates the recruitment of inflammatory cells. It has been shown that overexpression of MIF helps in recruiting macrophages to the tumor microenvironment (TME). We are evaluating the clinical efficacy of CPSI-1306, a small-molecular inhibitor of MIF, using in vitro and in vivo assays. Previous reports show that CPSI-1306 specifically inhibits keto-enol tautomerase activity of MIF. In silico analysis of publicly available data showed that higher expression of MIF negatively correlates with breast cancer patient overall, distant metastasis and relapse-free survival. Next, we analyzed the effect of CPSI-1306 on breast cancer in vitro and found that CPSI-1306 significantly induces apoptosis and reduces the viability of metastatic breast cancer MDA-MB 468 and MDA-MB 231 cells in a dose- and time-dependent manner. Mechanistic studies showed that CPSI-1306 induced apoptosis by reducing mitochondrial membrane potential by increasing apoptogenic signals, including apoptosis induction factor (AIF) and Cytochrome-C. Further analysis revealed that CPSI-1306 inhibits activation of cell proliferation marker AKT in metastatic breast cancer cells. We further analyzed the clinical efficacy of CPSI-1306 in vivo, using preclinical MVT-1 mammary tumor orthotopic syngeneic mouse model, and observed that CPSI-1306 significantly reduces tumor growth and metastasis to the lungs. Histologic analysis revealed reduced number of Ki67-positive proliferative cells and CD31-positive blood vessels in CPSI-1306-treated tumors. Our studies revealed that CPSI-1306 could be used as a novel therapeutic agent against aggressive breast cancer.

Citation Format: Subhadip Das, Nabanita Chatterjee, Sanjay Mishra, Dinesh K. Ahirwar, Sanjay Varikuti, Kirti Kaul, Rajni K. Shukla, Abhay R. Satoskar, Ramesh K. Ganju. CPSI-1306: A novel macrophage migration inhibitory factor inhibitor against aggressive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5870.

Novel role of cannabinoid receptor 2 in inhibiting EGF/EGFR and IGF-I/IGF-IR pathways in breast cancer

Breast cancer is the second leading cause of cancer deaths among women. Cannabinoid receptor 2 (CNR2 or CB2) is an integral part of the endocannabinoid system. Although CNR2 is highly expressed in the breast cancer tissues as well as breast cancer cell lines, its functional role in breast tumorigenesis is not well understood. We observed that estrogen receptor-α negative (ERα-) breast cancer cells highly express epidermal growth factor receptor (EGFR) as well as insulin-like growth factor-I receptor (IGF-IR). We also observed IGF-IR upregulation in ERα+ breast cancer cells. In addition, we found that higher CNR2 expression correlates with better recurrence free survival in ERα- and ERα+ breast cancer patients. Therefore, we analyzed the role of CNR2 specific agonist (JWH-015) on EGF and/or IGF-I-induced tumorigenic events in ERα- and ERα+ breast cancers. Our studies showed that CNR2 activation inhibited EGF and IGF-I-induced migration and invasion of ERα+ and ERα- breast cancer cells. At the molecular level, JWH-015 inhibited EGFR and IGF-IR activation and their downstream targets STAT3, AKT, ERK, NF-kB and matrix metalloproteinases (MMPs). In vivo studies showed that JWH-015 significantly reduced breast cancer growth in ERα+ and ERα- breast cancer mouse models. Furthermore, we found that the tumors derived from JWH-015-treated mice showed reduced activation of EGFR and IGF-IR and their downstream targets. In conclusion, we show that CNR2 activation suppresses breast cancer through novel mechanisms by inhibiting EGF/EGFR and IGF-I/IGF-IR signaling axes.

STAT1 gene deficient mice develop accelerated breast cancer growth and metastasis which is reduced by IL-17 blockade

Signal transducer and activator of transcription 1 (STAT1) mediates interferon gamma signaling which activates the expression of various genes related to apoptosis, inflammation, cell cycle and angiogenesis. Several experimental and clinical studies have investigated the role of STAT1 in primary tumor growth in breast cancer; however, its role in tumor metastasis remains to be determined. To determine the role of STAT1 in breast cancer metastasis, we analyzed growth and metastasis in WT or STAT1^−/− mice orthotopically implanted with metastatic 4T1.2 cells. Primary tumor development was faster in STAT1^−/− mice and these mice developed significantly bigger primary tumors and displayed more lung metastasis compared with WT counterparts. STAT1^−/− mice showed elevated Ly6G⁺CD11b⁺ granulocytic MDSC infiltration in their primary tumors and spleens with concomitant upregulation of Mmp9 and Cxcl1 expression in tumors compared with WT counterparts. Blockade of IL-17A in primary tumor-bearing STAT1^−/− mice suppressed accumulation of Ly6G⁺CD11b⁺ cells and markedly reduced lung metastasis. These data show that STAT1 is an important suppressor of primary breast tumor growth and metastasis. Importantly, we found anti-IL-17 treatment can rescue STAT1 deficient animals from developing exacerbated metastasis to the lungs which could be important for immunotherapies for immunocompromised breast cancer patients.

Abstract P6-01-03: N-terminus Slit2 suppresses breast cancer metastasis by inhibiting tumor associated macrophages

This abstract was not presented at the symposium.

TRPV2 is a novel biomarker and therapeutic target in triple negative breast cancer

Transient receptor potential vanilloid type-2 (TRPV2) is an ion channel that is triggered by agonists like cannabidiol (CBD). Triple negative breast cancer (TNBC) is an aggressive disease with limited therapeutic options. Chemotherapy is still the first line for the treatment of TNBC patients; however, TNBC usually gains rapid resistance and unresponsiveness to chemotherapeutic drugs. In this study, we found that TRPV2 protein is highly up-regulated in TNBC tissues compared to normal breast tissues. We also observed that TNBC and estrogen receptor alpha negative (ERβ-) patients with higher TRPV2 expression have significantly higher recurrence free survival compared to patients with lower TRPV2 expression especially those who were treated with chemotherapy. In addition, we showed that TRPV2 overexpression or activation by CBD significantly increased doxorubicin (DOX) uptake and apoptosis in TNBC cells. The induction of DOX uptake was abrogated by TRPV2 blocking or downregulation. In vivo mouse model studies showed that the TNBC tumors derived from CBD+DOX treated mice have significantly reduced weight and increased apoptosis compared to those treated with CBD or DOX alone. Overall, our studies for the first time revealed that TRPV2 might be a good prognostic marker for TNBC and ERβ- breast cancer patient especially for those who are treated with chemotherapy. In addition, TRPV2 activation could be a novel therapeutic strategy to enhance the uptake and efficacy of chemotherapy in TNBC patients.

Fatty acid binding protein 5 promotes metastatic potential of triple negative breast cancer cells through enhancing epidermal growth factor receptor stability

Fatty acid binding protein 5 (FABP5), an intracellular lipid binding protein, has been shown to play a role in various cancers, including breast cancer. However, FABP5 and its role in triple negative breast cancer (TNBC) have not been studied. We show FABP5 protein expression correlates with TNBC, high grade tumors, and worse disease-free survival in a tissue microarray containing 423 breast cancer patient samples. High FABP5 expression significantly correlates with epidermal growth factor receptor (EGFR) expression in these samples. Decreased tumor growth and lung metastasis were observed in FABP5-/- mice othotopically injected with murine breast cancer cells. FABP5 loss in TNBC tumor cells inhibited motility and invasion. Mechanistic studies revealed that FABP5 knockdown in TNBC cells results in decreased EGFR expression and FABP5 is important for EGF-induced metastatic signaling. Loss of FABP5 leads to proteasomal targeting of EGFR. Our studies show that FABP5 has a role in both host and tumor cell during breast cancer progression. These findings suggest that FABP5 mediates its enhanced effect on TNBC metastasis, in part, through EGFR, by inhibiting EGFR proteasomal degradation. These studies show, for the first time, a correlation between FABP5 and EGFR in enhancing TNBC metastasis through a novel mechanism.

Cannabinoid receptor-2 agonist inhibits macrophage induced EMT in non-small cell lung cancer by downregulation of EGFR pathway

JWH-015, a cannabinoid receptor 2 (CB2) agonist has tumor regressive property in various cancer types. However, the underlying mechanism by which it acts in lung cancer is still unknown. Tumor associated macrophage (TAM) intensity has positive correlation with tumor progression. Also, macrophages recruited at the tumor site promote tumor growth by enhancing epithelial to mesenchymal (EMT) progression. In this study, we analyzed the role of JWH-015 on EMT and macrophage infiltration by regulation of EGFR signaling. JWH-015 inhibited EMT in NSCLC cells A549 and also reversed the mesenchymal nature of CALU-1 cells by downregulation of EGFR signaling targets like ERK and STAT3. Also, in vitro co-culture experiments of A549 with M2 polarized macrophages provided evidence that JWH-015 decreased migratory and invasive abilities which was proved by reduced expression of FAK, VCAM1, and MMP2. Furthermore, it decreased macrophage induced EMT in A549 by attenuating the mesenchymal character by downregulating EGFR and its targets. These results were confirmed in an in vivo subcutaneous syngenic mouse model where JWH-015 blocks tumor growth and also inhibits macrophage recruitment and EMT at the tumor site which was regulated by EGFR pathway. Finally, JWH-015 reduced lung tumor lesions in an in vivo tumorigenicity mouse model. These data confer the impact of this cannabinoid on anti-proliferative and anti-tumorigenic effects, thus enhancing our understanding of its therapeutic efficacy in NSCLC. Our findings open new avenues for cannabinoid receptor CB2 agonist-JWH-015 as a novel and potential therapeutic target based on EGFR downregulation mechanisms in NSCLC. © 2016 Wiley Periodicals, Inc.

Cannabinoids as therapeutic agents in cancer: current status and future implications

The pharmacological importance of cannabinoids has been in study for several years. Cannabinoids comprise of (a) the active compounds of the Cannabis sativa plant, (b) endogenous as well as (c) synthetic cannabinoids. Though cannabinoids are clinically used for anti-palliative effects, recent studies open a promising possibility as anti-cancer agents. They have been shown to possess anti-proliferative and anti-angiogenic effects in vitro as well as in vivo in different cancer models. Cannabinoids regulate key cell signaling pathways that are involved in cell survival, invasion, angiogenesis, metastasis, etc. There is more focus on CB1 and CB2, the two cannabinoid receptors which are activated by most of the cannabinoids. In this review article, we will focus on a broad range of cannabinoids, their receptor dependent and receptor independent functional roles against various cancer types with respect to growth, metastasis, energy metabolism, immune environment, stemness and future perspectives in exploring new possible therapeutic opportunities.

Endothelial Robo4 suppresses breast cancer growth and metastasis through regulation of tumor angiogenesis

Targeting tumor angiogenesis is a promising alternative strategy for improvement of breast cancer therapy. Robo4 (roundabout homolog 4) signaling has been shown to protect endothelial integrity during sepsis shock and arthritis, and inhibit Vascular Endothelial Growth Factor (VEGF) signaling during pathological angiogenesis of retinopathy, which indicates that Robo4 might be a potential target for angiogenesis in breast cancer. In this study, we used immune competent Robo4 knockout mouse model to show that endothelial Robo4 is important for suppressing breast cancer growth and metastasis. And this effect does not involve the function of Robo4 on hematopoietic stem cells. Robo4 inhibits breast cancer growth and metastasis by regulating tumor angiogenesis, endothelial leakage and tight junction protein zonula occludens protein-1 (ZO-1) downregulation. Treatment with SecinH3, a small molecule drug which deactivates ARF6 downstream of Robo4, can enhance Robo4 signaling and thus inhibit breast cancer growth and metastasis. SecinH3 mediated its effect by reducing tumor angiogenesis rather than directly affecting cancer cell proliferation. In conclusion, endothelial Robo4 signaling is important for suppressing breast cancer growth and metastasis, and it can be targeted (enhanced) by administrating a small molecular drug.

Abstract 3363: RAGE/S100A7/Stat3-axis enhances breast cancer growth and metastasis via modulating tumor microenvironment

The Receptor for Advanced Glycation Endproducts (RAGE), a multifunctional, multi-ligand receptor, has been shown to play an important role in inflammation. However, not much is known about its role in breast cancer growth and metastasis. In this report, we observed that RAGE expression is upregulated in triple negative breast cancer (TNBC) cell lines, primary tumors and lymph-node metastasis samples. RAGE-/- mice show reduced breast cancer growth. Additionally, blocking RAGE with neutralizing-antibody inhibited lung metastasis in an intracardiac mouse model. Further elucidation of RAGE-mediated mechanisms revealed that RAGE binds to S100A7 and mediates S100A7-induced cell migration, Stat3 and NF-ĸB activation. Our results also indicate that S100A7/RAGE axis-modulates invasion/migration through Stat3 dependent MMP9 activation. In addition, RAGE neutralizing antibody and soluble RAGE inhibited breast cancer progression and metastasis in the inducible mS100a7a15 mouse model system. We demonstrated that RAGE/S100A7 enhanced mammary hyperplasia, tumor growth and metastasis through Stat3 activation. Notably, our studies revealed that RAGE/mS100a7a15 modulates the breast tumor microenvironment through recruitment of phospho-Stat3/MMP9-positive tumor-associated macrophages. Our studies suggest that RAGE expression could be used as a novel biomarker for aggressive/invasive breast cancer, especially TNBC. Collectively, these findings suggest that RAGE/S100A7/Stat3-axis has a novel role in linking inflammation to the development of invasive/aggressive breast cancer including TNBC.

Citation Format: Mohd W. Nasser, Nissar A. Wani, Janani Ravi, Grace A. Amponsah, Dinesh K. Ahirwar, Catherine A. Powell, Mohamad Elbaz, Helong Zhao, Konstantin Shilo, Ramesh K. Ganju. RAGE/S100A7/Stat3-axis enhances breast cancer growth and metastasis via modulating tumor microenvironment. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3363. doi:10.1158/1538-7445.AM2015-3363

Conditioning solid tumor microenvironment through inflammatory chemokines and S100 family proteins

Recently, there has been growing attention to the role of the tumor microenvironment (TME) in cancer growth, metastasis and emergence of chemotherapy resistance. Stromal and tumor cells make up the TME and interact with each other through a complex cross-talk manner. This interaction is facilitated by a variety of growth factors, cytokines, chemokines and S100 proteins. In this review, we focus on chemokines and their cognate receptors in regulating the tumorigenic process. Chemokines are cytokines that have chemotactic potential. Chemokine receptors are expressed on tumor cells and stromal cells. Chemokines and their cognate receptors modulate tumor growth and metastasis in a paracrine and autocrine manner. They play a major role in the modulation of stromal cell recruitment, angiogenic potential, cancer cell proliferation, survival, adhesion, invasion and metastasis to distant sites. In addition, a new class of calcium binding family S100 proteins has been getting attention as they play significant roles in tumor progression and metastasis by modulating TME. Here, we highlight recent developments regarding the inflammatory chemokine/S100 protein systems in the TME. We also focus on how chemokines/S100 proteins, through their role in the TME, modulate cancer cell ability to grow, proliferate, invade and metastasize to different organs. This review highlights the possibility of using the chemokine/chemokine receptor axis as a promising strategy in cancer therapy, the current difficulties in achieving this goal, and how it could be overcome for successful future therapeutic intervention.

Abstract P4-04-07: Breast cancer tissue context determines whether inflammation with bacterial/psoriasin signature is pro- or anti-carcinogenesis

Objective: It is often neglected that breast tissue microbiota and systematic bacterial infection actively and potently influence the development of breast cancer. With reports of both pro-cancer and anti-cancer roles of bacterial inflammation, the actual effect of bacterial inflammation to breast cancer and its mechanism remain unclear and are of our interests.

Rationale: Different from other human tissues, breast tissue microbiota is majorly Gram-negative at both normal and pathological statuses. We discovered that bacterial inflammation in breast tissue has a signature of Psoriasin (S100A7) impact which resembles psoriasis of the skin. However, this Psoriasin mediated inflammation can either promote or inhibit breast cancer development. We hypothesize that different tissue context determines the differential effects of bacterial/Psoriasin inflammation on breast cancer development.

Results: We first verified the presence of commensal Gram-negative microbiota (and LPS) in breast tissues under normal and pathological circumstances using mouse models. We observed that in both normal and cancerous breast tissues, bacterial factors (such as LPS) found in breast triggered secretion of Psoriasin by mammary adenocytes and Psoriasin mediated inflammation. This type of inflammation is featured by macrophage recruitment and ductal infiltration induced by Psoriasin. However, in normal tissues, macrophages matured into M1 type (iNOS positive); whereas in cancerous tissues, macrophages matured into M2 type (Arginase-1 positive). In normal tissues, Psoriasin and M1 caused an unresolved accumulation of inflammation in mammary ducts without lactation, which might lead to accelerated cancer initiation. In tumors, Psoriasin and M2 increased tumor growth and metastasis in immune-competent mammary epithelial specific expression mouse models. This was further confirmed in human patient samples and large cohort bioinformatic analysis. Using human breast cancer cell lines and nude mice, we elucidated that inflammation related Psoriasin upregulation and secretion in cancer cells had differential effects on tumor growth depending on its tissue source. Psoriasin increased cell proliferation and tumor growth in basal-like cancer cells; whereas it decreased cell proliferation and tumor growth in non-basal-like cancer cells. And this difference was mediated through differential regulation of the NF-κB/miR-29b/p53 pathway. in vitro molecular study and in vivo models verified the important role of miR-29b switch in the differential effects of Psoriasin in different tissue types of breast cancer cells.

Conclusion: Bacterial/Psoriasin inflammation differentially influences breast cancer development depending on the tissue context, and it involves the effects on macrophages and cancer cells. Our work provides novel potentials to improving prognosis and targeting inflammation to treat breast cancer in personalized medicine.

Citation Format: Helong Zhao, Mohd W Nasser, Tasha Wilkie, Ramesh K Ganju. Breast cancer tissue context determines whether inflammation with bacterial/psoriasin signature is pro- or anti-carcinogenesis [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-04-07.

Abstract P1-07-35: Fatty acid binding protein 5 promotes metastatic potential of triple negative breast cancer

Triple negative breast cancer (TNBC) is an aggressive subtype of breast cancer that has a poor prognosis for patients, not only due to its aggressive nature, but also due to the lack of effective therapeutic strategies. High mortality is associated with metastasis of the primary TNBC. We analyzed the role of fatty acid binding protein 5 (FABP5), an intracellular fatty acid transport protein, in aggressive breast cancers, especially TNBC. FABP5 expression was analyzed in a tumor microarray (TMA) containing 423 breast cancer patient samples and found that FABP5 expression is associated with tumor grade, triple negative status, and disease-free survival. Next, a mechanistic approach was taken and found that FABP5 knockdown TNBC cell lines express lesser EGFR protein compared to control, and upon EGFR activation express less phospho-FAK and phospho-Pyk2. We found that EGFR was not down regulated at the transcriptional level in FABP5 knockout cells. Further analysis indicated the role for Cbl, an E3 ubiquitin-protein ligase, as a potential mechanistic target for the down-regulation of EGFR protein in FABP5 knockdown cell lines. EGFR is over-expressed in aggressive breast cancers, especially TNBC. Though EGFR is highly expressed in aggressive subtypes of breast cancer, targeted therapeutic strategies have not been successful in clinic. EGFR has been shown to be involved in distant metastasis in aggressive breast cancers. We found a correlation between FABP5 and EGFR expression and metastasis-free survival using publically available datasets from The Cancer Genome Atlas. We next studied the functional consequence of FABP5 knockdown in TNBC cell lines. We showed that EGF-induced FABP5 knockdown cells migrated less compared to control. Additionally, FABP5 knockdown cells were significantly less able to migrate into a wound in response to EGF stimulation. EGF-induced cell attachment of FABP5 knockdown cells is significantly decreased compared to control. Our findings suggest FABP5 modulates metastatic potential of TNBC through alterations in EGFR expression and downstream migratory signaling molecules.

Citation Format: Catherine A Powell, Mohd W Nasser, Jacob C Wochna, Konstantin Shilo, Xiaoli Zhang, Ramesh K Ganju. Fatty acid binding protein 5 promotes metastatic potential of triple negative breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-07-35.

FAAH inhibition enhances anandamide mediated anti-tumorigenic effects in non-small cell lung cancer by downregulating the EGF/EGFR pathway

The endocannabinoid anandamide (AEA), a neurotransmitter was shown to have anti-cancer effects. Fatty acid amide hydrolase (FAAH) metabolizes AEA and decreases its anti-tumorigenic activity. In this study, we have analyzed the role of FAAH inhibition in non-small cell lung cancer (NSCLC). We have shown that FAAH and CB1 receptor which is activated by AEA are expressed in lung adenocarcinoma patient samples and NSCLC cell lines A549 and H460. Since the synthetic analogue of anandamide (Met-F-AEA) did not possess significant anti-tumorigenic effects, we used Met-F-AEA in combination with FAAH inhibitor URB597 which significantly reduced EGF (epidermal growth factor)-induced proliferative and chemotactic activities in vitro when compared to anti-tumorigenic activity of Met-F-AEA alone. Further analysis of signaling mechanisms revealed that Met-F-AEA in combination with URB597 inhibits activation of EGFR and its downstream signaling ERK, AKT and NF-kB. In addition, it inhibited MMP2 secretion and stress fiber formation. We have also shown that the Met-F-AEA in combination with URB597 induces G0/G1 cell cycle arrest by downregulating cyclin D1 and CDK4 expressions, ultimately leading to apoptosis via activation of caspase-9 and PARP. Furthermore, the combination treatment inhibited tumor growth in a xenograft nude mouse model system. Tumors derived from Met-F-AEA and URB597 combination treated mice showed reduced EGFR, AKT and ERK activation and MMP2/MMP9 expressions when compared to Met-F-AEA or URB597 alone. Taken together, these data suggest in EGFR overexpressing NSCLC that the combination of Met-F-AEA with FAAH inhibitor resulted in superior therapeutic response compared to individual compound activity alone.

miR-29b defines the pro-/anti-proliferative effects of S100A7 in breast cancer

INTRODUCTION

S100A7 (Psoriasin) is an inflammatory protein known to be upregulated in breast cancer. However, the role of S100A7 in breast cancer has been elusive, since both pro- and anti-proliferative roles have been reported in different types of breast cancer cells and animal models. To date, the mechanism by which S100A7 differentially regulates breast cancer cell proliferation is still not clear.

METHODS

We used Gene Functional Enrichment Analysis to search for the determining factor of S100A7 differential regulation. We confirmed the factor and elaborated its regulating mechanism using in vitro cell culture. We further verified the findings using xenografts of human breast cancer cells in nude mice.

RESULTS

In the present study, we show that S100A7 significantly upregulates the expression of miR-29b in Estrogen Receptor (ER)-positive breast cancer cells (represented by MCF7), and significantly downregulates miR-29b in ER-negative cells (represented by MDA-MB-231) [Corrected]. The differential regulation of miR-29b by S100A7 in ER-positive and ER-negative breast cancer is supported by the gene expression analysis of TCGA invasive breast cancer dataset. miR-29b transcription is inhibited by NF-κB, and NF-κB activation is differentially regulated by S100A7 in ER-positive and ER-negative breast cancer cells. This further leads to differential regulation of PI3K p85α and CDC42 expression, p53 activation and p53-associated anti-proliferative pathways. Reversing the S100A7-caused changes of miR-29b expression by transfecting exogenous miR-29b or miR-29b-Decoy can inhibit the effects of S100A7 on in vitro cell proliferation and tumor growth in nude mice.

CONCLUSIONS

The distinct modulations of the NF-κB - miR-29b - p53 pathway make S100A7 an oncogene in ER-negative and a cancer-suppressing gene in ER-positive breast cancer cells, with miR-29b being the determining regulatory factor.

Modulation of the tumor microenvironment and inhibition of EGF/EGFR pathway: novel anti-tumor mechanisms of Cannabidiol in breast cancer

The anti-tumor role and mechanisms of Cannabidiol (CBD), a non-psychotropic cannabinoid compound, are not well studied especially in triple-negative breast cancer (TNBC). In the present study, we analyzed CBD's anti-tumorigenic activity against highly aggressive breast cancer cell lines including TNBC subtype. We show here -for the first time-that CBD significantly inhibits epidermal growth factor (EGF)-induced proliferation and chemotaxis of breast cancer cells. Further studies revealed that CBD inhibits EGF-induced activation of EGFR, ERK, AKT and NF-kB signaling pathways as well as MMP2 and MMP9 secretion. In addition, we demonstrated that CBD inhibits tumor growth and metastasis in different mouse model systems. Analysis of molecular mechanisms revealed that CBD significantly inhibits the recruitment of tumor-associated macrophages in primary tumor stroma and secondary lung metastases. Similarly, our in vitro studies showed a significant reduction in the number of migrated RAW 264.7 cells towards the conditioned medium of CBD-treated cancer cells. The conditioned medium of CBD-treated cancer cells also showed lower levels of GM-CSF and CCL3 cytokines which are important for macrophage recruitment and activation. In summary, our study shows -for the first time-that CBD inhibits breast cancer growth and metastasis through novel mechanisms by inhibiting EGF/EGFR signaling and modulating the tumor microenvironment. These results also indicate that CBD can be used as a novel therapeutic option to inhibit growth and metastasis of highly aggressive breast cancer subtypes including TNBC, which currently have limited therapeutic options and are associated with poor prognosis and low survival rates.

RAGE mediates S100A7-induced breast cancer growth and metastasis by modulating the tumor microenvironment

RAGE is a multifunctional receptor implicated in diverse processes including inflammation and cancer. In this study, we report that RAGE expression is upregulated widely in aggressive triple-negative breast cancer (TNBC) cells, both in primary tumors and in lymph node metastases. In evaluating the functional contributions of RAGE in breast cancer, we found that RAGE-deficient mice displayed a reduced propensity for breast tumor growth. In an established model of lung metastasis, systemic blockade by injection of a RAGE neutralizing antibody inhibited metastasis development. Mechanistic investigations revealed that RAGE bound to the proinflammatory ligand S100A7 and mediated its ability to activate ERK, NF-κB, and cell migration. In an S100A7 transgenic mouse model of breast cancer (mS100a7a15 mice), administration of either RAGE neutralizing antibody or soluble RAGE was sufficient to inhibit tumor progression and metastasis. In this model, we found that RAGE/S100A7 conditioned the tumor microenvironment by driving the recruitment of MMP9-positive tumor-associated macrophages. Overall, our results highlight RAGE as a candidate biomarker for TNBCs, and they reveal a functional role for RAGE/S100A7 signaling in linking inflammation to aggressive breast cancer development.

CXCR3 deficiency enhances tumor progression by promoting macrophage M2 polarization in a murine breast cancer model

Tumor associated macrophages play a vital role in determining the outcome of breast cancer. We investigated the contribution of the chemokine receptor CXCR3 to antitumor immune responses using a cxcr3 deficient mouse orthotopically injected with a PyMT breast cancer cell line. We observed that cxcr3 deficient mice displayed increased IL-4 production and M2 polarization in the tumors and spleens compared to WT mice injected with PyMT cells. This was accompanied by larger tumor development in cxcr3(-/-) than in WT mice. Further, tumor-promoting myeloid derived immune cell populations accumulated in higher proportions in the spleens of cxcr3 deficient mice. Interestingly, cxcr3(-/-) macrophages displayed a deficiency in up-regulating inducible nitric oxide synthase after stimulation by either IFN-γ or PyMT supernatants. Stimulation of bone marrow derived macrophages by PyMT supernatants also resulted in greater induction of arginase-1 in cxcr3(-/-) than WT mice. Further, cxcr3(-/-) T cells activated with CD3/CD28 in vitro produced greater amounts of IL-4 and IL-10 than T cells from WT mice. Our data suggests that a greater predisposition of cxcr3 deficient macrophages towards M2 polarization contributes to an enhanced tumor promoting environment in cxcr3 deficient mice. Although CXCR3 is known to be expressed on some macrophages, this is the first report that demonstrates a role for CXCR3 in macrophage polarization and subsequent breast tumor outcomes. Targeting CXCR3 could be a potential therapeutic approach in the management of breast cancer tumors.

C-X-C motif chemokine 12/C-X-C chemokine receptor type 7 signaling regulates breast cancer growth and metastasis by modulating the tumor microenvironment

Introduction

Although C-X-C motif chemokine 12 (CXCL12) has been shown to bind to C-X-C chemokine receptor type 7 (CXCR7), the exact molecular mechanism regulations by CXCL12/CXCR7 axis in breast tumor growth and metastasis are not well understood. CXCR7 expression has been shown to be upregulated during pathological processes such as inflammation and cancer.

Methods

Breast cancer cell lines were genetically silenced or pharmacologically inhibited for CXCR7 and/or its downstream target signal transducer and activator of transcription 3 (STAT3). 4T1 or 4T1 downregulated for CXCR7 and 4T1.2 breast cancer cell lines were injected in mammary gland of BALB/c mice to form tumors, and the molecular pathways regulating tumor growth and metastasis were assessed.

Results

In this study, we observed that CXCL12 enhances CXCR7-mediated breast cancer migration. Furthermore, genetic silencing or pharmacologic inhibition of CXCR7 reduced breast tumor growth and metastasis. Further elucidation of mechanisms revealed that CXCR7 mediates tumor growth and metastasis by activating proinflammatory STAT3 signaling and angiogenic markers. Furthermore, enhanced breast tumorigenicity and invasiveness were associated with macrophage infiltration. CXCR7 recruits tumor-promoting macrophages (M2) to the tumor site through regulation of the macrophage colony-stimulating factor (M-CSF)/macrophage colony-stimulating factor receptor (MCSF-R) signaling pathway. In addition, CXCR7 regulated breast cancer metastasis by enhancing expression of metalloproteinases (MMP-9, MMP-2) and vascular cell-adhesion molecule-1 (VCAM-1). We also observed that CXCR7 is highly expressed in invasive ductal carcinoma (IDC) and metastatic breast tissue in human patient samples. In addition, high CXCR7 expression in tumors correlates with worse prognosis for both overall survival and lung metastasis-free survival in IDC patients.

Conclusion

These observations reveal that CXCR7 enhances breast cancer growth and metastasis via a novel pathway by modulating the tumor microenvironment. These findings identify CXCR7-mediated STAT3 activation and modulation of the tumor microenvironment as novel regulation of breast cancer growth and metastasis. These studies indicate that new strategies using CXCR7 inhibitors could be developed for antimetastatic therapy.

CDK4 deficiency promotes genomic instability and enhances Myc-driven lymphomagenesis

The G1 kinase CDK4 is amplified or overexpressed in some human tumors and promotes tumorigenesis by inhibiting known tumor suppressors. Here, we report that CDK4 deficiency markedly accelerated lymphoma development in the Eμ-Myc transgenic mouse model of B lymphoma and that silencing or loss of CDK4 augmented the tumorigenic potential of Myc-driven mouse and human B cell lymphoma in transplant models. Accelerated disease in CDK4-deficient Eμ-Myc transgenic mice was associated with rampant genomic instability that was provoked by dysregulation of a FOXO1/RAG1/RAG2 pathway. Specifically, CDK4 phosphorylated and inactivated FOXO1, which prevented FOXO1-dependent induction of Rag1 and Rag2 transcription. CDK4-deficient Eμ-Myc B cells had high levels of the active form of FOXO1 and elevated RAG1 and RAG2. Furthermore, overexpression of RAG1 and RAG2 accelerated lymphoma development in a transplant model, with RAG1/2-expressing tumors exhibiting hallmarks of genomic instability. Evaluation of human tumor samples revealed that CDK4 expression was markedly suppressed, while FOXO1 expression was elevated, in several subtypes of human non-Hodgkin B cell lymphoma. Collectively, these findings establish a context-specific tumor suppressor function for CDK4 that prevents genomic instability, which contributes to B cell lymphoma. Furthermore, our data suggest that targeting CDK4 may increase the risk for the development and/or progression of lymphoma.