EP4 receptor promotes invadopodia and invasion in human breast cancer

A phase I dose-escalation and expansion study of RMX1002, a selective E-type prostanoid receptor 4 antagonist, as monotherapy and in combination with anti-PD-1 antibody in advanced solid tumors

RMX1002 (grapiprant) is a selective E-type prostanoid receptor 4 (EP4) antagonist and a promising candidate for cancer therapy, potentially enhancing anti-tumor immune responses. This study aimed to evaluate the safety, pharmacokinetics, pharmacodynamics, and efficacy of RMX1002 as monotherapy and in combination with anti-PD-1 antibody toripalimab for advanced solid tumors. This multicenter, phase I trial enrolled patients with histologically or cytologically confirmed advanced solid tumors. This study included three phases: Ia (dose-escalation of RMX1002 monotherapy from 200 to 650 mg BID), Ib (dose-escalation from 500 to 650 mg BID in combination with toripalimab), and Ic (dose-expansion of 500 mg BID with toripalimab). Safety, pharmacokinetics, pharmacodynamics, and efficacy were assessed. A total of 45 patients were enrolled (17 in phase Ia, 12 in phase Ib, and 16 in phase Ic). No dose-limiting toxicity was reported, and the MTD was not reached. Overall, 21 patients experienced RMX1002-related adverse events with CTCAE grade ≥ 3. Pharmacokinetics revealed rapid absorption of RMX1002 with the maximum concentration (Cmax) reached within 2 to 5 h, and dose-dependent increases in Cmax and area under the concentration-time curve. The increase in urinary metabolite of PGE2 suggested the inhibition of EP4 signaling pathway. The best response was stable disease, reported in 64.7%, 28.6%, and 18.8% of patients in phase Ia, Ib, and Ic, respectively. RMX1002 was well tolerated and showed a best response of stable disease. RMX1002 500 mg BID with toripalimab 240 mg every 3 weeks is the recommended dose for future trials.

Acquired resistance to jadomycin B in human triple-negative breast cancer cells is associated with increased cyclooxygenase-2 expression

Jadomycin B, produced by the soil bacterium Streptomyces venezuelae ISP5230, induces cytotoxicity in human breast cancer cells in vitro and has antitumoral effects in animal models. In models of multidrug-resistant, triple-negative breast cancer, jadomycin B has shown promise as it is not a substrate of ABCB1 and ABCG2 drug efflux transporters. The generation of reactive oxygen species and inhibition of topoisomerases are potential mechanisms of jadomycin B-mediated DNA damage and apoptosis. However, the mechanisms of jadomycin B's anticancer activity have not been fully elucidated. By gradually exposing MDA-MB-231 triple-negative human breast cancer cells to jadomycin B, we hypothesized that resistance could be selected to further understand jadomycin B's pharmacological mechanisms. A 3-fold increase in the jadomycin B IC50 was observed in MDA-MB-231 cells exposed to increasing jadomycin B concentrations (0-3 μM) over 7 months, herein 231-JB cells. The 231-JB cells were cross-resistant to jadomycin F and S but not to the comparator drugs mitoxantrone, doxorubicin, and SN-38. The 231-JB cells did not have increased mRNA expression of topoisomerase-2 nor ABCB1 and ABCG2. Cyclooxygenase-2 (COX-2) increased by 25-fold, but expression of prostaglandin E2 receptor 4 did not significantly change. Cotreatment with celecoxib (15-45 μM), a COX-2 inhibitor, resensitized the 231-JB cells to jadomycin B (IC50 = 1.41 ± 0.24 to 0.75 ± 0.31 μM vs 2.28 ± 0.54 with 0 μM celecoxib). To our knowledge, this work represents the first report of the involvement of COX-2 in jadomycin B activity in vitro, proving to be an exciting new target for the exploration of jadomycin B anticancer activity. SIGNIFICANCE STATEMENT: Cyclooxygenase-2 (COX-2), the rate-limiting enzyme in prostaglandin production, is associated with procancer signaling. COX-2, ABCB1, and ABCG2 overexpression are typically correlated in cancer, contributing to chemotherapy resistance. We observed increased COX-2, but not ABCG2 or ABCB1, expression in 231-JB cells. This indicates that jadomycin B triggers a distinct resistance mechanism. The COX-2 inhibitor celecoxib reversed jadomycin B resistance in 231-JB cells. As such, 231-JB cells represent an important model for COX-2 signaling in breast cancer and jadomycin B mechanism of action.

Molecular and Cellular Machinery of Lymphatic Metastasis in Breast Cancer

Breast cancer is one of the most common malignant tumours in women worldwide. A primary route for breast cancer cells to disseminate is through regional lymphatic vessels and nodes. Cancer cell-induced lymphangiogenesis plays a crucial role in lymphatic metastasis and is associated with poor survival of breast cancer. Advances in molecular biology have led to the identification of biomarkers associated with lymphangiogenesis and lymphatic metastasis, including lymphatic vessel endothelial cell (LVEC) markers and tumour microenvironment markers, such as vascular endothelial growth factor receptor 3 (VEGFR3), podoplanin (PDPN), and lymphatic endothelial hyaluronan receptor-1 (LYVE1). LVEC molecular markers play a profound role in both the formation of new lymphatic vessels and the invasive expansion of primary tumour. Abnormal expression of LVEC markers may contribute to lymphatic vessel disease and/or metastasis of cancer cells through the lymphatic system. These molecular markers may present a potential for targeted therapies and precision diagnostics for managing lymphatic metastasis in breast cancer. This review aims to provide a comprehensive summary of the current understanding of the molecular and cellular machinery underlying lymphatic metastasis in breast cancer, with a particular focus on the lymphangiogenic markers and their role in the lymphatic dissemination.

Remodeling the immune microenvironment for gastric cancer therapy through antagonism of prostaglandin E2 receptor 4

Gastric cancer is highly prevalent among digestive tract tumors. Due to the intricate nature of the gastric cancer immune microenvironment, there is currently no effective treatment available for advanced gastric cancer. However, there is promising potential for immunotherapy targeting the prostaglandin E2 receptor subtype 4 (EP4) in gastric cancer. In our previous study, we identified a novel small molecule EP4 receptor antagonist called YY001. Treatment with YY001 alone demonstrated a significant reduction in gastric cancer growth and inhibited tumor metastasis to the lungs in a mouse model. Furthermore, administration of YY001 stimulated a robust immune response within the tumor microenvironment, characterized by increased infiltration of antigen-presenting cells, T cells, and M1 macrophages. Additionally, our research revealed that YY001 exhibited remarkable synergistic effects when combined with the PD-1 antibody and the clinically targeted drug apatinib, rather than fluorouracil. These findings suggest that YY001 holds great promise as a potential therapeutic strategy for gastric cancer, whether used as a standalone treatment or in combination with other drugs.

Depletion of BATF in CAR-T cells enhances antitumor activity by inducing resistance against exhaustion and formation of central memory cells

Chimeric antigen receptor (CAR) T cell therapy has limited efficacy against solid tumors, and one major challenge is T cell exhaustion. To address this challenge, we performed a candidate gene screen using a hypofunction CAR-T cell model and found that depletion of basic leucine zipper ATF-like transcription factor (BATF) improved the antitumor performance of CAR-T cells. In different types of CAR-T cells and mouse OT-1 cells, loss of BATF endows T cells with improved resistance to exhaustion and superior tumor eradication efficacy. Mechanistically, we found that BATF binds to and up-regulates a subset of exhaustion-related genes in human CAR-T cells. BATF regulates the expression of genes involved in development of effector and memory T cells, and knocking out BATF shifts the population toward a more central memory subset. We demonstrate that BATF is a key factor limiting CAR-T cell function and that its depletion enhances the antitumor activity of CAR-T cells against solid tumors.

The Prostaglandin E2 Pathway and Breast Cancer Stem Cells: Evidence of Increased Signaling and Potential Targeting

Culprits of cancer development, metastasis, and drug resistance, cancer stem cells (CSCs) are characterized by specific markers, active developmental signaling pathways, metabolic plasticity, increased motility, invasiveness, and epithelial-mesenchymal transition. In breast cancer, these cells are often more prominent in aggressive disease, are amplified in drug-resistant tumors, and contribute to recurrence. For breast cancer, two distinct CSC populations exist and are typically defined by CD44+/CD24- cell surface marker expression or increased aldehyde dehydrogenase (ALDH) activity. These CSC populations share many of the same properties but also exhibit signaling pathways that are more active in CD44+/CD24- or ALDH+ populations. Understanding these CSC populations and their shared or specific signaling pathways may lead to the development of novel therapeutic strategies that will improve breast cancer patient outcomes. Herein, we review the current evidence and assess published patient tumor datasets of sorted breast CSC populations for evidence of heightened prostaglandin E2 (PGE₂) signaling and activity in these breast CSC populations. PGE₂ is a biologically active lipid mediator and in cancer PGE₂ promotes tumor progression and poor patient prognosis. Overall, the data suggests that PGE₂ signaling is important in propagating breast CSCs by enhancing inherent tumor-initiating capacities. Development of anti-PGE₂ signaling therapeutics may be beneficial in inhibiting tumor growth and limiting breast CSC populations.

Photodynamic Priming Improves the Anti-Migratory Activity of Prostaglandin E Receptor 4 Antagonist in Cancer Cells In Vitro

The combination of photodynamic agents and biological inhibitors is rapidly gaining attention for its promise and approval in treating advanced cancer. The activity of photodynamic treatment is mainly governed by the formation of reactive oxygen species upon light activation of photosensitizers. Exposure to reactive oxygen species above a threshold dose can induce cellular damage and cancer cell death, while the surviving cancer cells are "photodynamically primed", or sensitized, to respond better to other drugs and biological treatments. Here, we report a new combination regimen of photodynamic priming (PDP) and prostaglandin E2 receptor 4 (EP4) inhibition that reduces the migration and invasion of two human ovarian cancer cell lines (OVCAR-5 and CAOV3) in vitro. PDP is achieved by red light activation of the FDA-approved photosensitizer, benzoporphyrin derivative (BPD), or a chemical conjugate composed of the BPD linked to cetuximab, an anti-epithelial growth factor receptor (EGFR) antibody. Immunoblotting data identify co-inhibition of EGFR, cAMP-response element binding protein (CREB), and extracellular signal-regulated kinase 1/2 (ERK1/2) as key in the signaling cascades modulated by the combination of EGFR-targeted PDP and EP4 inhibition. This study provides valuable insights into the development of a molecular-targeted photochemical strategy to improve the anti-metastatic effects of EP4 receptor antagonists.

A Novel Invadopodia-Specific Marker for Invasive and Pro-Metastatic Cancer Stem Cells

Introduction

Stem-like cancer cells or cancer stem cells (CSCs) may comprise a phenotypically and functionally heterogeneous subset of cells, whereas the molecular markers reflecting this CSC hierarchy remain elusive. The glycolytic enzyme alpha-enolase (ENO1) present on the surface of malignant tumor cells has been identified as a metastasis-promoting factor through its function of activating plasminogen. The expression pattern of surface ENO1 (sENO1) concerning cell-to-cell or CSC heterogeneity and its functional roles await further investigation.

Methods

The cell-to-cell expression heterogeneity of sENO1 was profiled in malignant cells from different types of cancers using flow cytometry. The subcellular localization of sENO1 and its functional roles in the invadopodia formation and cancer cell invasiveness were investigated using a series of imaging, molecular, and in vitro and in vivo functional studies.

Results

We showed here that ENO1 is specifically localized to the invadopodial surface of a significant subset (11.1%-63.9%) of CSCs in human gastric and prostate adenocarcinomas. sENO1⁺ CSCs have stronger mesenchymal properties than their sENO1^- counterparts. The subsequent functional studies confirmed the remarkable pro-invasive and pro-metastatic capacities of sENO1⁺ CSCs. Mechanistically, inhibiting the surface localization of ENO1 by downregulating caveolin-1 expression compromised invadopodia biogenesis, proteolysis, and CSC invasiveness.

Conclusions

Our study identified the specific expression of ENO1 on the invadopodial surface of a subset of highly invasive and pro-metastatic CSCs. sENO1 may provide a diagnostically and/or therapeutically exploitable target to improve the outcome of patients with aggressive and metastatic cancers.

Tissue remodeling by invadosomes

One of the strategies used by cells to degrade and remodel the extracellular matrix (ECM) is based on invadosomes, actin-based force-producing cell–ECM contacts that function in adhesion and migration and are characterized by their capacity to mediate pericellular proteolysis of ECM components. Invadosomes found in normal cells are called podosomes, whereas invadosomes of invading cancer cells are named invadopodia. Despite their broad involvement in cell migration and in protease-dependent ECM remodeling and their detection in living organisms and in fresh tumor tissue specimens, the specific composition and dynamic behavior of podosomes and invadopodia and their functional relevance in vivo remain poorly understood. Here, we discuss recent findings that underline commonalities and peculiarities of podosome and invadopodia in terms of organization and function and propose an updated definition of these cellular protrusions, which are increasingly relevant in patho-physiological tissue remodeling.

Hold on or Cut? Integrin- and MMP-Mediated Cell-Matrix Interactions in the Tumor Microenvironment

The tumor microenvironment (TME) has become the focus of interest in cancer research and treatment. It includes the extracellular matrix (ECM) and ECM-modifying enzymes that are secreted by cancer and neighboring cells. The ECM serves both to anchor the tumor cells embedded in it and as a means of communication between the various cellular and non-cellular components of the TME. The cells of the TME modify their surrounding cancer-characteristic ECM. This in turn provides feedback to them via cellular receptors, thereby regulating, together with cytokines and exosomes, differentiation processes as well as tumor progression and spread. Matrix remodeling is accomplished by altering the repertoire of ECM components and by biophysical changes in stiffness and tension caused by ECM-crosslinking and ECM-degrading enzymes, in particular matrix metalloproteinases (MMPs). These can degrade ECM barriers or, by partial proteolysis, release soluble ECM fragments called matrikines, which influence cells inside and outside the TME. This review examines the changes in the ECM of the TME and the interaction between cells and the ECM, with a particular focus on MMPs.

Molecular Complexity of Lymphovascular Invasion: The Role of Cell Migration in Breast Cancer as a Prototype

Lymphovascular invasion (LVI) is associated with poor outcome in breast cancer (BC); however, its underlying mechanisms remain ill-defined. LVI in BC develops through complex molecular pathways involving not only the interplay with the surrounding microenvironment along with endothelial cells lining the lymphovascular spaces but also changes in the malignant epithelial cells with the acquisition of more invasive and migration abilities. In this review, we focus on the key features that enable tumour cell detachment from the primary niche, their migration and interaction with the surrounding microenvironment as well as the crosstalk with the vascular endothelial cells, which eventually lead to intravasation of tumour cells and LVI. Intravascular tumour cell survival and migration, their distant site extravasation, stromal invasion and growth are part of the metastatic cascade. Cancer cell migration commences with loss of tumour cells' cohesion initiating the invasion and migration processes which are usually accompanied by the accumulation of specific cellular and molecular changes that enable tumour cells to overcome the blockades of the extracellular matrix, spread into surrounding tissues and interact with stromal cells and immune cells. Thereafter, tumour cells migrate further via interacting with lymphovascular endothelial cells to penetrate the vessel wall leading ultimately to intravasation of cancer cells. Exploring the potential factors influencing cell migration in LVI can help in understanding the underlying mechanisms of LVI to identify targeted therapy in BC.

Eicosanoids in Cancer: Prostaglandin E2 Receptor 4 in Cancer Therapeutics and Immunotherapy

The cyclooxygenase-2 (COX-2) enzyme is frequently overexpressed in epithelial malignancies including those of the breast, prostate, lung, kidney, ovary, and liver and elevated expression is associated with worse outcomes. COX-2 catalyzes the metabolism of arachidonic acid to prostaglandins. The COX-2 product prostaglandin E2 (PGE2) binds to four G-protein-coupled EP receptors designated EP1-EP4. EP4 is commonly upregulated in cancer and supports cell proliferation, migration, invasion, and metastasis through activation of multiple signaling pathways including ERK, cAMP/PKA, PI3K/AKT, and NF-κB. EP4 antagonists inhibit metastasis in preclinical models. Cancer stem cells, that underlie therapy resistance and disease relapse, are driven by the expression of EP4. Resistance to several chemotherapies is reversed in the presence of EP4 antagonists. In addition to tumor cell-autonomous roles of EP4, many EP4-positive host cells play a role in tumor behavior. Endothelial cell-EP4 supports tumor angiogenesis and lymphangiogenesis. Natural Killer (NK) cells are critical to the mechanism by which systemically administered EP4 antagonists inhibit metastasis. PGE2 acts on EP4 expressed on the NK cell to inhibit tumor target cell killing, cytokine production, and chemotactic activity. Myeloid-derived suppressor cells (MDSCs), that inhibit the development of cytotoxic T cells, are induced by PGE2 acting on myeloid-expressed EP2 and EP4 receptors. Inhibition of MDSC-EP4 leads to maturation of effector T cells and suppresses the induction of T regulatory cells. A number of EP4 antagonists have proven useful in dissecting these mechanisms. There is growing evidence that EP4 antagonism, particularly in combination with either chemotherapy, endocrine therapy, or immune-based therapies, should be investigated further as a promising novel approach to cancer therapy. Several EP4 antagonists have now progressed to early phase clinical trials and we eagerly await the results of those studies.

Reciprocal interaction of HOTAIR and SP1 together enhance the ability of Xiaoji decoction and gefitinib to inhibit EP4 expression

ETHNOPHARMACOLOGICAL RELEVANCE

The Chinese herbal prescription Xiaoji decoction (XJD) has long been used for cancer treatment. However, the molecular mechanisms underlying the effects of this medicine, particularly to enhance the efficiency of EGFR-TKI in the treatment of lung cancer have not been well elucidated.

MATERIALS AND METHODS

Cell viability and cell cycle distribution were detected by MTT assay and flow cytometry, respectively. The phosphorylation of ERK1/2 and protein levels of SP1 and EP4 were determined by Western blot. The expression of the HOX transcript antisense RNA (HOTAIR) was measured by qRT-PCR. Transient transfection experiments were used to overexpress the HOTAIR, SP1 and EP4 genes. The interaction between HOTAIR and SP1 were further examined via RNA immunoprecipitation (RIP) assay. A tumor xenograft model was used to confirm the in vitro findings.

RESULTS

We showed that XJD inhibited growth and induced cell arrest of human non-small cell lung cancer (NSCLC) cells. We also found that XJD increased the phosphorylation of ERK1/2 and inhibited levels of HOTAIR and SP1, EP4 proteins, which were blocked by inhibitor of MEK/ERK. There was reciprocal interaction between HOTAIR and SP1. Silencing of HOTAIR reduced EP4 protein levels and repressed the growth of NSCLC cells, while overexpression of HOTAIR and SP1 overcame XJD-reduced EP4 protein expression. Additionally, excessive expressed EP4 reversed the effect of XJD on cell growth. Importantly, there was synergy of XJD with another cancer treatment drug, EGFR-TKI gefitinib, in this process. We also found that XJD inhibited tumor growth in a xenograft nude mice model.

CONCLUSIONS

Our results show that XJD inhibits NSCLC cell growth via ERK1/2-mediated reciprocal repression of HOTAIR and SP1 protein expression, followed by reduced EP4 gene expression. XJD and gefitinib exhibit synergy in this process. The in vitro and in vivo study provides a novel mechanism by which XJD enhances the growth inhibitory effect of gefitinib in gefitinib-resistant NSCLC cells.

Desmoglein 1 Regulates Invadopodia by Suppressing EGFR/Erk Signaling in an Erbin-Dependent Manner

Loss of the desmosomal cell-cell adhesion molecule, Desmoglein 1 (Dsg1), has been reported as an indicator of poor prognosis in head and neck squamous cell carcinomas (HNSCC) overexpressing epidermal growth factor receptor (EGFR). It has been well established that EGFR signaling promotes the formation of invadopodia, actin-based protrusions formed by cancer cells to facilitate invasion and metastasis, by activating pathways leading to actin polymerization and ultimately matrix degradation. We previously showed that Dsg1 downregulates EGFR/Erk signaling by interacting with the ErbB2-binding protein Erbin (ErbB2 Interacting Protein) to promote keratinocyte differentiation. Here, we provide evidence that restoring Dsg1 expression in cells derived from HNSCC suppresses invasion by decreasing the number of invadopodia and matrix degradation. Moreover, Dsg1 requires Erbin to downregulate EGFR/Erk signaling and to fully suppress invadopodia formation. Our findings indicate a novel role for Dsg1 in the regulation of invadopodia signaling and provide potential new targets for development of therapies to prevent invadopodia formation and therefore cancer invasion and metastasis. IMPLICATIONS: Our work exposes a new pathway by which a desmosomal cadherin called Dsg1, which is lost early in head and neck cancer progression, suppresses cancer cell invadopodia formation by scaffolding ErbB2 Interacting Protein and consequent attenuation of EGF/Erk signaling.

ECM Cross-Linking Regulates Invadopodia Dynamics

Invadopodia are membrane protrusions dynamically assembled by invasive cancer cells in contact with the extracellular matrix (ECM). Invadopodia are enriched by the structural proteins actin and cortactin as well as metalloproteases such as MT1-MMP, whose function is to degrade the surrounding ECM. During metastasis, invadopodia are necessary for cancer cell intravasation and extravasation. Although signaling pathways involved in the assembly and function of invadopodia are well studied, few studies address invadopodia dynamics and how the cell-ECM interactions contribute to cell invasion. Using iterative analysis based on time-lapse microscopy and mathematical modeling of invasive cancer cells, we found that cells oscillate between invadopodia presence and cell stasis-termed the "invadopodia state"-and invadopodia absence during cell translocation-termed the "migration state." Our data suggest that β1-integrin-ECM binding and ECM cross-linking control the duration of each of the two states. By changing the concentration of cross-linkers in two-dimensional and three-dimensional cultures, we generate an ECM in which 0-0.92 of total lysine residues are cross-linked. Using an ECM with a range of cross-linking degrees, we demonstrate that the dynamics of invadopodia-related functions have a biphasic relationship to ECM cross-linking. At intermediate levels of ECM cross-linking (0.39), cells exhibit rapid invadopodia protrusion-retraction cycles and rapid calcium spikes, which lead to more frequent MT1-MMP delivery, causing maximal invadopodia-mediated ECM degradation. In contrast, both extremely high or low levels of cross-linking lead to slower invadopodia-related dynamics and lower ECM degradation. Additionally, β1-integrin inhibition modifies the dynamics of invadopodia-related functions as well as the length of time cells spend in either of the states. Collectively, these data suggest that β1-integrin-ECM binding nonlinearly translates small physical differences in the extracellular environment to differences in the dynamics of cancer cell behaviors. Understanding the conditions under which invadopodia can be reduced by subtle environment-targeting treatments may lead to combination therapies for preventing metastatic spread.

miR-182 suppresses invadopodia formation and metastasis in non-small cell lung cancer by targeting cortactin gene

Background

Metastasis is the leading cause of cancer mortality and is a major hurdle for lung cancer treatment. Invadopodia, which are cancer-specific protrusive structures, play a crucial role in the metastatic cascade through degradation of the basement membrane and surrounding stroma. Cortactin, a critical component of invadopodia, frequently used as an invadopodia marker, a universally important player in invadopodia function, and is frequently overexpressed in cancer, but the exact mechanism of regulation is not yet fully understood.

Methods

The expression level of CTTN in human non-small cell lung cancer (NSCLC) tissues was detected by qRT-PCR. Cell migration, invasion and invadopodia formation were assessed in vitro by wound-healing, transwell assay and immunofluorescence, respectively. The dual-luciferase reporter assay was used to identify the direct target of miR-182.

Results

Hepatocyte growth factor (HGF) and phorbol 12,13-dibutyrate (PDBu) can induce CTTN expression, motility, and invasion ability, as well as invadopodia formation in non-small cell lung cancer (NSCLC). Moreover, miR-182 suppressed metastasis and invadopodia formation by targeting CTTN in NSCLC. Our qRT-PCR results showed that CTTN expression was inversely correlated with miR-182 expression that suppressed invadopodia formation via suppression of the Cdc42/N-WASP pathway. Furthermore, miR-182 negatively regulated invadopodia function, and suppressed extracellular matrix(ECM) degradation in lung cancer cells by inhibiting cortactin.

Conclusion

Collectively, our results demonstrated that miR-182 targeted CTTN gene in NSCLC and suppressed lung cancer invadopodia formation, and thus suppressed lung cancer metastasis. This suggests a therapeutic application of miR-182 in NSCLC.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0824-1) contains supplementary material, which is available to authorized users.

Discovery of an Experimental Model of Unicuspid Aortic Valve

Background

The epithelial growth factor receptor family of tyrosine kinases modulates embryonic formation of semilunar valves. We hypothesized that mice heterozygous for a dominant loss‐of‐function mutation in epithelial growth factor receptor, which are Egfr^Vel/+ mice, would develop anomalous aortic valves, valve dysfunction, and valvular cardiomyopathy.

Methods and Results

Aortic valves from Egfr^Vel/+ mice and control mice were examined by light microscopy at 2.5 to 4 months of age. Additional Egfr^Vel/+ and control mice underwent echocardiography at 2.5, 4.5, 8, and 12 months of age, followed by histologic examination. In young mice, microscopy revealed anatomic anomalies in 79% of Egfr^Vel/+ aortic valves, which resembled human unicuspid aortic valves. Anomalies were not observed in control mice. At 12 months of age, histologic architecture was grossly distorted in Egfr^Vel/+ aortic valves. Echocardiography detected moderate or severe aortic regurgitation, or aortic stenosis was present in 38% of Egfr^Vel/+ mice at 2.5 months of age (N=24) and in 74% by 8 months of age. Left ventricular enlargement, hypertrophy, and reversion to a fetal myocardial gene expression program occurred in Egfr^Vel/+ mice with aortic valve dysfunction, but not in Egfr^Vel/+ mice with near‐normal aortic valve function. Myocardial fibrosis was minimal or absent in all groups.

Conclusions

A new mouse model uniquely recapitulates salient functional, structural, and histologic features of human unicuspid aortic valve disease, which are phenotypically distinct from other forms of congenital aortic valve disease. The new model may be useful for elucidating mechanisms by which congenitally anomalous aortic valves become critically dysfunctional.

EP4 as a Therapeutic Target for Aggressive Human Breast Cancer

G-protein-coupled receptors (GPCRs, also called seven-transmembrane or heptahelical receptors) are a superfamily of cell surface receptor proteins that bind to many extracellular ligands and transmit signals to an intracellular guanine nucleotide-binding protein (G-protein). When a ligand binds, the receptor activates the attached G-protein by causing the exchange of Guanosine-5′-triphosphate (GTP) for guanosine diphosphate (GDP). They play a major role in many physiological functions, as well as in the pathology of many diseases, including cancer progression and metastasis. Only a few GPCR members have been exploited as targets for developing drugs with therapeutic benefit in cancer. Present review briefly summarizes the signaling pathways utilized by the EP (prostaglandin E receptor) family of GPCR, their physiological and pathological roles in carcinogenesis, with special emphasis on the roles of EP4 in breast cancer progression. We make a case for EP4 as a promising newer therapeutic target for treating breast cancer. We show that an aberrant over-expression of cyclooxygenase (COX)-2, which is an inflammation-associated enzyme, occurring in 40–50% of breast cancer patients leads to tumor progression and metastasis due to multiple cellular events resulting from an increased prostaglandin (PG) E2 production in the tumor milieu. They include inactivation of host anti-tumor immune cells, such as Natural Killer (NK) and T cells, increased immuno-suppressor function of tumor-associated macrophages, promotion of tumor cell migration, invasiveness and tumor-associated angiogenesis, due to upregulation of multiple angiogenic factors including Vascular Endothelial Growth Factor (VEGF)-A, increased lymphangiogenesis (due to upregulation of VEGF-C/D), and a stimulation of stem-like cell (SLC) phenotype in cancer cells. All of these events were primarily mediated by activation of the Prostaglandin (PG) E receptor EP4 on tumor or host cells. We show that selective EP4 antagonists (EP4A) could mitigate all of these events tested with cells in vitro as well as in vivo in syngeneic COX-2 expressing mammary cancer bearing mice or immune-deficient mice bearing COX-2 over-expressing human breast cancer xenografts. We suggest that EP4A can avoid thrombo-embolic side effects of long term use of COX-2 inhibitors by sparing cardio-protective roles of PGI2 via IP receptor activation or PGE2 via EP3 receptor activation. Furthermore, we identified two COX-2/EP4 induced oncogenic and SLC-stimulating microRNAs—miR526b and miR655, one of which (miR655) appears to be a potential blood biomarker in breast cancer patients for monitoring SLC-ablative therapies, such as with EP4A. We suggest that EP4A will likely produce the highest benefit in aggressive breast cancers, such as COX-2 expressing triple-negative breast cancers, when combined with other newer agents, such as inhibitors of programmed cell death (PD)-1 or PD-L1.

Knockdown delta-5-desaturase in breast cancer cells that overexpress COX-2 results in inhibition of growth, migration and invasion via a dihomo-γ-linolenic acid peroxidation dependent mechanism

BACKGROUND

Cyclooxygenase-2 (COX-2), the inducible COX form, is a bi-functional membrane-bound enzyme that typically metabolizes arachidonic acid (downstream ω-6 fatty acid) to form 2-series of prostaglandins known to be involved in cancer development. Overexpression of COX-2 has been found in a majority of breast carcinomas, and has also been associated with increased severity and the development of the metastasis. Our lab recently demonstrated that COX-2 can also metabolize dihomo-γ-linolenic acid (DGLA, a precursor of ω-6 arachidonic acid) to produce an anti-cancer byproduct, 8-hydroxyoctanoic acid (8-HOA) that can inhibit growth and migration of colon and pancreatic cancer cells. We thus tested whether our strategy of knocking down delta-5-desaturase (D5D, the key enzyme that converts DGLA to arachidonic acid) in breast cancer cells overexpressing COX-2 can also be used to promote 8-HOA formation, thereby suppressing cancer growth, migration, and invasion.

METHODS

SiRNA and shRNA transfection were used to knock down D5D expression in MDA-MB 231 and 4 T1 cells (human and mouse breast cancer cell lines expressing high COX-2, respectively). Colony formation assay, FITC Annexin V/PI double staining, wound healing and transwell assay were used to assess the effect of our strategy on inhibition of cancer growth, migration, and invasion. GC/MS was used to measure endogenous 8-HOA, and western blotting was performed to evaluate the altered key protein expressions upon the treatments.

RESULTS

We demonstrated that D5D knockdown licenses DGLA to inhibit growth of breast cancer cells via promoting formation of 8-HOA that can inhibit histone deacetylase and activate cell apoptotic proteins, such as procaspase 9 and PARP. Our strategy can also significantly inhibit cancer migration and invasion, associated with altered expression of MMP-2/- 9, E-cadherin, vimentin and snail. In addition, D5D knockdown and DGLA supplementation greatly enhanced the efficacy of 5-fluorouracil on breast cancer growth and migration.

CONCLUSIONS

Consistent to our previous studies on colon and pancreatic cancer, here we demonstrate again that the high level of COX-2 in breast cancer cells can be capitalized on inhibiting cancer growth and migration. The outcome of this translational research could guide us to develop new anti-cancer strategy and/or to improve current chemotherapy for breast cancer treatment.

Platelet "first responders" in wound response, cancer, and metastasis

Platelets serve as "first responders" during normal wounding and homeostasis. Arising from bone marrow stem cell lineage megakaryocytes, anucleate platelets can influence inflammation and immune regulation. Biophysically, platelets are optimized due to size and discoid morphology to distribute near vessel walls, monitor vascular integrity, and initiate quick responses to vascular lesions. Adhesion receptors linked to a highly reactive filopodia-generating cytoskeleton maximizes their vascular surface contact allowing rapid response capabilities. Functionally, platelets normally initiate rapid clotting, vasoconstriction, inflammation, and wound biology that leads to sterilization, tissue repair, and resolution. Platelets also are among the first to sense, phagocytize, decorate, or react to pathogens in the circulation. These platelet first responder properties are commandeered during chronic inflammation, cancer progression, and metastasis. Leaky or inflammatory reaction blood vessel genesis during carcinogenesis provides opportunities for platelet invasion into tumors. Cancer is thought of as a non-healing or chronic wound that can be actively aided by platelet mitogenic properties to stimulate tumor growth. This growth ultimately outstrips circulatory support leads to angiogenesis and intravasation of tumor cells into the blood stream. Circulating tumor cells reengage additional platelets, which facilitates tumor cell adhesion, arrest and extravasation, and metastasis. This process, along with the hypercoagulable states associated with malignancy, is amplified by IL6 production in tumors that stimulate liver thrombopoietin production and elevates circulating platelet numbers by thrombopoiesis in the bone marrow. These complex interactions and the "first responder" role of platelets during diverse physiologic stresses provide a useful therapeutic target that deserves further exploration.