Amlexanox Blocks the Interaction between S100A4 and Epidermal Growth Factor and Inhibits Cell Proliferation

Stanniocalcin 1 promotes lung metastasis of breast cancer by enhancing EGFR-ERK-S100A4 signaling

Lung metastasis is the leading cause of breast cancer-related death. The tumor microenvironment contributes to the metastatic colonization of tumor cells in the lungs. Tumor secretory factors are important mediators for the adaptation of cancer cells to foreign microenvironments. Here, we report that tumor-secreted stanniocalcin 1 (STC1) promotes the pulmonary metastasis of breast cancer by enhancing the invasiveness of tumor cells and promoting angiogenesis and lung fibroblast activation in the metastatic microenvironment. The results show that STC1 modifies the metastatic microenvironment through its autocrine action on breast cancer cells. Specifically, STC1 upregulates the expression of S100 calcium-binding protein A4 (S100A4) by facilitating the phosphorylation of EGFR and ERK signaling in breast cancer cells. S100A4 mediates the effect of STC1 on angiogenesis and lung fibroblasts. Importantly, S100A4 knockdown diminishes STC1-induced lung metastasis of breast cancer. Moreover, activated JNK signaling upregulates STC1 expression in breast cancer cells with lung-tropism. Overall, our findings reveal that STC1 plays important role in breast cancer lung metastasis.

House dust mite-induced endoplasmic reticulum stress mediates MUC5AC hypersecretion via TBK1 in airway epithelium

Purpose: Endoplasmic reticulum (ER) stress regulates mucus hypersecretion, and may activate downstream factors via TBK1 signaling to induce gene expression. However, it remains unclear whether ER stress promotes airway mucus secretion through the TBK1 pathway. We aimed to investigate the role of the TBK1 pathway in the regulation of MUC5AC expression in a mouse model of house dust mite (HDM)-induced allergic asthma. Materials and Methods: Mice with HDM-induced asthma and human bronchial epithelial BEAS-2B cells were treated with amlexanox, an anti-allergy drug (25 μM), or 4-PBA (10 mM). Tissue and cell samples were collected. Tissue samples were stained with hematoxylin and eosin (H&E) or periodic acid Schiff (PAS) to evaluate pathology. Protein expression was analyzed by western blotting and immunofluorescence. Results: Mice exposed to HDM presented ER stress and hypersecretion of mucus Muc5ac from airway epithelial cells (p < 0.001). Similar results were observed in BEAS-2B cells following exposure to HDM. Both in vivo and in vitro studies revealed that HDM-induced ER stress induced MUC5AC overexpression via TBK1 signaling. Amlexanox and 4-PBA markedly reduced mucus production and weakened the TBK1 signal, which mediates MUC5AC hypersecretion. Conclusion: TBK1 plays a pivotal role in HDM-induced ER stress, leading to overproduction of MUC5AC in the asthmatic airway epithelium. The overproduction of MUC5AC can be significantly decreased by inhibiting TBK1 or ER stress using 4-PBA. These findings highlight potential target-specific therapies for patients with chronic allergic asthma.

S100 Proteins in Fatty Liver Disease and Hepatocellular Carcinoma

Non-alcoholic fatty liver disease (NAFLD) is a highly prevalent and slow progressing hepatic pathology characterized by different stages of increasing severity which can ultimately give rise to the development of hepatocellular carcinoma (HCC). Besides drastic lifestyle changes, few drugs are effective to some extent alleviate NAFLD and HCC remains a poorly curable cancer. Among the deregulated molecular mechanisms promoting NAFLD and HCC, several members of the S100 proteins family appear to play an important role in the development of hepatic steatosis, non-alcoholic steatohepatitis (NASH) and HCC. Specific members of this Ca²⁺-binding protein family are indeed significantly overexpressed in either parenchymal or non-parenchymal liver cells, where they exert pleiotropic pathological functions driving NAFLD/NASH to severe stages and/or cancer development. The aberrant activity of S100 specific isoforms has also been reported to drive malignancy in liver cancers. Herein, we discuss the implication of several key members of this family, e.g., S100A4, S100A6, S100A8, S100A9 and S100A11, in NAFLD and HCC, with a particular focus on their intracellular versus extracellular functions in different hepatic cell types. Their clinical relevance as non-invasive diagnostic/prognostic biomarkers for the different stages of NAFLD and HCC, or their pharmacological targeting for therapeutic purpose, is further debated.

The Roles of S100A4 and the EGF/EGFR Signaling Axis in Pulmonary Hypertension with Right Ventricular Hypertrophy

Pulmonary hypertension (PH) is characterized by increased pulmonary arterial pressure caused by the accumulation of mesenchymal-like cells in the pulmonary vasculature. PH can lead to right ventricular hypertrophy (RVH) and, ultimately, heart failure and death. In PH etiology, endothelial-to-mesenchymal transition (EndMT) has emerged as a critical process governing the conversion of endothelial cells into mesenchymal cells, and S100A4, EGF, and EGFR are implicated in EndMT. However, a potential role of S100A4, EGF, and EGFR in PH has to date not been elucidated. We therefore quantified S100A4, EGF, and EGFR in patients suffering from chronic thromboembolic pulmonary hypertension (CTEPH) and idiopathic pulmonary arterial hypertension (iPAH). To determine specificity for unilateral heart disease, the EndMT biomarker signature was further compared between PH patients presenting with RVH and patients suffering from aortic valve stenosis (AVS) with left ventricular hypertrophy. Reduced S100A4 concentrations were found in CTEPH and iPAH patients with RVH. Systemic EGF was increased in CTEPH but not in iPAH, while AVS patients displayed slightly diminished EGF levels. EGFR was downregulated in all patient groups when compared to healthy controls. Longitudinal data analysis revealed no effect of surgical therapies on EndMT markers. Pulmonary thrombo-endarterectomized samples were devoid of S100A4, while S100A4 tissue expression positively correlated with higher grades of Heath–Edwards histopathological lesions of iPAH-derived lung tissue. Histologically, EGFR was not detectable in CTEPH lungs or in iPAH lesions. Together, our data suggest an intricate role for S100A4 and EGF/EGFR in PH with right heart pathology.

Neutralization of S100A4 induces stabilization of atherosclerotic plaques: role of smooth muscle cells

AIMS

During atherosclerosis, smooth muscle cells (SMCs) accumulate in the intima where they switch from a contractile to a synthetic phenotype. From porcine coronary artery, we isolated spindle-shaped (S) SMCs exhibiting features of the contractile phenotype and rhomboid (R) SMCs typical of the synthetic phenotype. S100A4 was identified as a marker of R-SMCs in vitro and intimal SMCs, in pig and man. S100A4 exhibits intra- and extracellular functions. In this study, we investigated the role of extracellular S100A4 in SMC phenotypic transition.

METHODS AND RESULTS

S-SMCs were treated with oligomeric recombinant S100A4 (oS100A4), which induced nuclear factor (NF)-κB activation. Treatment of S-SMCs with oS100A4 in combination with platelet-derived growth factor (PDGF)-BB induced a complete SMC transition towards a pro-inflammatory R-phenotype associated with NF-κB activation, through toll-like receptor-4. RNA sequencing of cells treated with oS100A4/PDGF-BB revealed a strong up-regulation of pro-inflammatory genes and enrichment of transcription factor binding sites essential for SMC phenotypic transition. In a mouse model of established atherosclerosis, neutralization of extracellular S100A4 decreased area of atherosclerotic lesions, necrotic core, and CD68 expression and increased α-smooth muscle actin and smooth muscle myosin heavy chain expression.

CONCLUSION

We suggest that the neutralization of extracellular S100A4 promotes the stabilization of atherosclerotic plaques. Extracellular S100A4 could be a new target to influence the evolution of atherosclerotic plaques.

The potential value of amlexanox in the treatment of cancer: Molecular targets and therapeutic perspectives

Amlexanox (AMX) is an azoxanthone drug used for decades for the treatment of mouth aphthous ulcers and now considered for the treatment of diabetes and obesity. The drug is usually viewed as a dual inhibitor of the non-canonical IκB kinases IKK-ɛ (inhibitor-kappaB kinase epsilon) and TBK1 (TANK-binding kinase 1). But a detailed target profile analysis indicated that AMX binds directly to twelve protein targets, including different enzymes (IKK-ɛ, TBK1, GRK1, GRK5, PDE4B, 5- and 12-lipoxygenases) and non-enzyme proteins (FGF-1, HSP90, S100A4, S100A12, S100A13). AMX has been demonstrated to have marked anticancer effects in multiple models of xenografted tumors in mice, including breast, colon, lung and gastric cancers and in onco-hematological models. The anticancer potency is generally modest but largely enhanced upon combination with cytotoxic (temozolide, docetaxel), targeted (selumetinib) or biotherapeutic agents (anti-PD-1 and anti-CTLA4 antibodies). The multiple targets participate in the anticancer effects, chiefly IKK-ɛ/TBK1 but also S100A proteins and PDE4B. The review presents the molecular basis of the antitumor effects of AMX. The capacity of the drug to block nonsense-mediated mRNA decay (NMD) is also discussed, as well as AMX-induced reduction of cancer-related pain. Altogether, the analysis provides a survey of the anticancer action of AMX, with the implicated protein targets. The use of this well-tolerated drug to treat cancer should be further considered and the design of newer analogues encouraged.

Targeting TANK-binding kinase 1 (TBK1) in cancer

INTRODUCTION

TANK-binding kinase 1 (TBK1) is a Ser/Thr kinase with a central role in coordinating the cellular response to invading pathogens and regulating key inflammatory signaling cascades. While intact TBK1 signaling is required for successful anti-viral signaling, dysregulated TBK1 signaling has been linked to a variety of pathophysiologic conditions, including cancer. Several lines of evidence support a role for TBK1 in cancer pathogenesis, but the specific roles and regulation of TBK1 remain incompletely understood. A key challenge is the diversity of cellular processes that are regulated by TBK1, including inflammation, cell cycle, autophagy, energy homeostasis, and cell death. Nevertheless, evidence from pre-clinical cancer models suggests that targeting TBK1 may be an effective strategy for anti-cancer therapy in specific settings.

AREAS COVERED

This review provides an overview of the roles and regulation of TBK1 with a focus on cancer pathogenesis and drug targeting of TBK1 as an anti-cancer strategy. Relevant literature was derived from a PubMed search encompassing studies from 1999 to 2020.

EXPERT OPINION

TBK1 is emerging as a potential target for anti-cancer therapy. Inhibition of TBK1 alone may be insufficient to restrain the growth of most cancers; hence, combination strategies will likely be necessary. Improved understanding of tumor-intrinsic and tumor-extrinsic TBK1 signaling will inform novel therapeutic strategies.

S100A4 Protein Is Essential for the Development of Mature Microfold Cells in Peyer's Patches

Intestinal microfold cells (M cells) in Peyer's patches are a special subset of epithelial cells that initiate mucosal immune responses through uptake of luminal antigens. Although the cytokine receptor activator of nuclear factor-κB ligand (RANKL) expressed on mesenchymal cells triggers differentiation into M cells, other environmental cues remain unknown. Here, we show that the metastasis-promoting protein S100A4 is required for development of mature M cells. S100A4-producing cells are a heterogenous cell population including lysozyme-expressing dendritic cells and group 3 innate lymphoid cells. We found that in the absence of DOCK8, a Cdc42 activator critical for interstitial leukocyte migration, S100A4-producing cells are reduced in the subepithelial dome, resulting in a maturation defect of M cells. While S100A4 promotes differentiation into mature M cells in organoid culture, genetic inactivation of S100a4 prevents the development of mature M cells in mice. Thus, S100A4 is a key environmental cue that regulates M cell differentiation in collaboration with RANKL.

TBKBP1 and TBK1 form a growth factor signalling axis mediating immunosuppression and tumourigenesis

The kinase TBK1 responds to microbial stimuli and mediates type I interferon (IFN-I) induction. We show that TBK1 is also a central mediator of growth factor signaling; this function relies on a specific adaptor, TBK-binding protein 1 (TBKBP1). TBKBP1 recruits TBK1 to PKCθ via a scaffold protein, Card10, which allows PKCθ to phosphorylate TBK1 at serine-716, a crucial step for TBK1 activation by growth factors but not by innate immune stimuli. While the TBK1/TBKBP1 signaling axis is dispensable for IFN-I induction, it mediates mTORC1 activation and oncogenesis. Lung epithelial cell-conditional deletion of either TBK1 or TBKBP1 inhibits tumorigenesis in a mouse model of lung cancer. In addition to promoting tumor growth, the TBK1/TBKBP1 axis facilitates tumor-mediated immunosuppression by a mechanism involving induction of the checkpoint molecule PD-L1 and stimulation of glycolysis. These findings suggest a PKCθ-TBKBP1-TBK1 growth factor signaling axis mediating both tumor growth and immunosuppression.

The Multifaceted S100A4 Protein in Cancer and Inflammation

The metastasis-promoting S100A4 protein, a member of the S100 family, has recently been discovered as a potent factor implicated in various inflammation-associated diseases. S100A4 is involved in a range of biological functions such as angiogenesis, cell differentiation, apoptosis, motility, and invasion. Moreover, S100A4 is also a potent trigger of inflammatory processes and induces the release of cytokines and growth factors under different pathological conditions.Indeed, the release of S100A4 upon stress and mainly its pro-inflammatory role emerges as the most decisive activity in disease development, such as rheumatoid arthritis (RA), systemic sclerosis (SSc) allergy, psoriasis, and cancer. In the scope of this review, we will focus on the role of S100A4 as a mediator of pro-inflammatory pathways and its associated biological processes involved in the pathogenesis of various human noncommunicable diseases (NCDs) including cancer.

Expression and Roles of S100A4 in Anaplastic Cells of Canine Mammary Carcinomas

S100A4 (metastasin), a member of the S100 protein family, was initially identified in metastatic cells and is well established as a marker of aggressive human cancer. However, expression and roles of S100A4 in canine mammary tumors have not been clarified. In this study, expression of S100A4 was examined immunohistochemically in normal, hyperplastic, and neoplastic mammary glands of dogs. In all normal and benign lesions, S100A4 was restricted to a few stromal fibroblasts and inflammatory cells. However, in 7 of 57 (12%) of the malignant tumors examined, cytoplasmic and nuclear expression of S100A4 was observed in epithelial tumor cells and stromal cells. Particularly, the frequency of S100A4-positive anaplastic carcinomas was high (4/8 cases, 50%). Next, we established a novel cell line, named NV-CML, from a S100A4-positive canine mammary carcinoma. The cultured NV-CML cells and the tumors that developed in the immunodeficient mice after subcutaneous injection of the cells maintained the immunophenotype of the original tumor, including S100A4 expression. Using this cell line, we examined the cellular functions of S100A4 using RNA interference. S100A4 expression level in NV-CML cells transfected with small interfering RNA (siRNA) targeting canine S100A4 (siS100A4) was reduced to about one-fifth of those with negative-control siRNA (siNeg). Cell proliferation in WST-8 assay and cell migration in Boyden chamber assay were significantly decreased in siS100A4-transfected cells compared with siNeg-transfected cells. These findings suggest that S100A4 may be related to progression of canine mammary carcinomas via its influence on cell growth and motility.

Targeting IκappaB kinases for cancer therapy

The inhibitory kappa B kinases (IKKs) and IKK related kinases are crucial regulators of the pro-inflammatory transcription factor, nuclear factor kappa B (NF-κB). The dysregulation in the activities of these kinases has been reported in several cancer types. These kinases are known to regulate survival, proliferation, invasion, angiogenesis, and metastasis of cancer cells. Thus, IKK and IKK related kinases have emerged as an attractive target for the development of cancer therapeutics. Several IKK inhibitors have been developed, few of which have advanced to the clinic. These inhibitors target IKK either directly or indirectly by modulating the activities of other signaling molecules. Some inhibitors suppress IKK activity by disrupting the protein-protein interaction in the IKK complex. The inhibition of IKK has also been shown to enhance the efficacy of conventional chemotherapeutic agents. Because IKK and NF-κB are the key components of innate immunity, suppressing IKK is associated with the risk of immune suppression. Furthermore, IKK inhibitors may hit other signaling molecules and thus may produce off-target effects. Recent studies suggest that multiple cytoplasmic and nuclear proteins distinct from NF-κB and inhibitory κB are also substrates of IKK. In this review, we discuss the utility of IKK inhibitors for cancer therapy. The limitations associated with the intervention of IKK are also discussed.

A signalome screening approach in the autoinflammatory disease TNF receptor associated periodic syndrome (TRAPS) highlights the anti-inflammatory properties of drugs for repurposing

TNF receptor associated periodic syndrome (TRAPS) is an autoinflammatory disease caused by mutations in TNF Receptor 1 (TNFR1). Current therapies for TRAPS are limited and do not target the pro-inflammatory signalling pathways that are central to the disease mechanism. Our aim was to identify drugs for repurposing as anti-inflammatories based on their ability to down-regulate molecules associated with inflammatory signalling pathways that are activated in TRAPS. This was achieved using rigorously optimized, high through-put cell culture and reverse phase protein microarray systems to screen compounds for their effects on the TRAPS-associated inflammatory signalome. 1360 approved, publically available, pharmacologically active substances were investigated for their effects on 40 signalling molecules associated with pro-inflammatory signalling pathways that are constitutively upregulated in TRAPS. The drugs were screened at four 10-fold concentrations on cell lines expressing both wild-type (WT) TNFR1 and TRAPS-associated C33Y mutant TNFR1, or WT TNFR1 alone; signalling molecule levels were then determined in cell lysates by the reverse-phase protein microarray. A novel mathematical methodology was developed to rank the compounds for their ability to reduce the expression of signalling molecules in the C33Y-TNFR1 transfectants towards the level seen in the WT-TNFR1 transfectants. Seven high-ranking drugs were selected and tested by RPPA for effects on the same 40 signalling molecules in lysates of peripheral blood mononuclear cells (PBMCs) from C33Y-TRAPS patients compared to PBMCs from normal controls. The fluoroquinolone antibiotic lomefloxacin, as well as others from this class of compounds, showed the most significant effects on multiple pro-inflammatory signalling pathways that are constitutively activated in TRAPS; lomefloxacin dose-dependently significantly reduced expression of 7/40 signalling molecules across the Jak/Stat, MAPK, NF-κB and PI3K/AKT pathways. This study demonstrates the power of signalome screening for identifying candidates for drug repurposing.