Expression analysis of the mouse S100A7/psoriasin gene in skin inflammation and mammary tumorigenesis

Renal tubular S100A7a impairs fatty acid oxidation and exacerbates renal fibrosis via both intracellular and extracellular pathway

A couple of S100 family proteins (S100s) have been reported to exert pro-inflammatory functions in the progression of renal fibrosis. Unlike some S100s which are expressed by both epithelial and stromal inflammatory cells, S100A7 is restricted expressed in epithelium. Persistent S100A7 expression occurs in some invasive carcinomas and is associated with poor prognostic factors. Whereas, whether it is implicated in renal tubular epithelial cell injury and kidney disease remains unexplored. In this study, we demonstrate that S100A7 is highly upregulated in tubular cells of both mouse renal fibrotic lesions and kidney biopsies from patients with chronic kidney disease (CKD). The level of renal S100A7 was associated with both the decline of renal function and the progression of renal fibrosis in CKD patients. Overexpressing S100A7a impaired fatty acid oxidation (FAO) and promoted lipid peroxidation in proximal tubular cells (PTCs). Mechanistically, S100A7a interacts with β-catenin, thereby preventing its ubiquitination and degradation by the β-TrCP-SCF complex, and in turn activated β-catenin signaling, downregulated the expression of PGC-1α. Additionally, S100A7a exacerbated lipid peroxidation via RAGE-p-ERK-NOX2 pathway. Specific deletion of S100a7a in tubular cells enhanced FAO and reduced lipid peroxidation, resulting in improved renal function and alleviation of renal fibrosis induced by unilateral ureteral obstruction and unilateral ischemia-reperfusion injury. Collectively, we delineate a previously unrecognized function of S100A7a in the progression of renal fibrosis.

Identification of a shared gene signature and biological mechanism between diabetic foot ulcers and cutaneous lupus erythemnatosus by transcriptomic analysis

Diabetic foot ulcers (DFU) and cutaneous lupus erythematosus (CLE) are both diseases that can seriously affect a patient's quality of life and generate economic pressure in society. Symptomatically, both DLU and CLE exhibit delayed healing and excessive inflammation; however, there is little evidence to support a molecular and cellular connection between these two diseases. In this study, we investigated potential common characteristics between DFU and CLE at the molecular level to provide new insights into skin diseases and regeneration, and identify potential targets for the development of new therapies. The gene expression profiles of DFU and CLE were obtained from the Gene Expression Omnibus (GEO) database and used for analysis. A total of 41 common differentially expressed genes (DEGs), 16 upregulated genes and 25 downregulated genes, were identified between DFU and CLE. GO and KEGG analysis showed that abnormalities in epidermal cells and the activation of inflammatory factors were both involved in the occurrence and development of DFU and CLE. Protein-protein interaction network (PPI) and sub-module analysis identified enrichment in seven common key genes which is KRT16, S100A7, KRT77, OASL, S100A9, EPGN and SAMD9. Based on these seven key genes, we further identified five miRNAs(has-mir-532-5p, has-mir-324-3p,has-mir-106a-5p,has-mir-20a-5p,has-mir-93-5p) and7 transcription factors including CEBPA, CEBPB, GLI1, EP30D, JUN,SP1, NFE2L2 as potential upstream molecules. Functional immune infiltration assays showed that these genes were related to immune cells. The CIBERSORT algorithm and Pearson method were used to determine the correlations between key genes and immune cells, and reverse key gene-immune cell correlations were found between DFU and CLE. Finally, the DGIbd database demonstrated that Paquinimod and Tasquinimod could be used to target S100A9 and Ribavirin could be used to target OASL. Our findings highlight common gene expression characteristics and signaling pathways between DFU and CLE, indicating a close association between these two diseases. This provides guidance for the development of targeted therapies and mutual interactions.

Comparative analysis of the physical properties of murine and human S100A7: Insight into why zinc piracy is mediated by human but not murine S100A7

S100 proteins are a subfamily of EF-hand calcium-binding proteins found primarily in vertebrate animals. They are distinguished by binding of transition metals and functioning in both the intracellular and extracellular milieu. S100A7 functions in the protection of the skin and mucous membranes and is a biomarker in inflammatory skin disease. A recent study of Neisseria gonorrhoeae infection revealed that human but not murine S100A7 could be used to evade host nutritional immunity. To understand the molecular basis for this difference, we carried out a comparative analysis of the physical and structural properties of human and murine S100A7. The X-ray crystal structure of Ca2+-loaded mouse S100A7 (mS100A7) was determined to 1.69 Å resolution, and Ca2+-induced conformational changes were assessed by NMR. Unlike human S100A7 (hS100A7), which exhibits conformational changes in response to binding of Ca2+, no significant changes in mS100A7 were detected. Dynamic light scattering, circular dichroism, and a competition chelator assay were used to compare the Zn2+ affinity and the effects of ion binding on mS100A7 versus hS100A7. Alignment of their sequences revealed a substantial difference in the C-terminal region, which is an important mediator of protein-protein interactions, suggesting a rationale for the specificity of N. gonorrhoeae for hS100A7. These data, along with more detailed analysis of S100A7 sequence conservation across different species, support the proposal that, although hS100A7 is highly conserved in many mammals, the murine protein is a distinct ortholog. Our results highlight the potential limitations of using mouse models for studying bacterial infections in humans.

RAGE Inhibitors for Targeted Therapy of Cancer: A Comprehensive Review

The receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin family that is overexpressed in several cancers. RAGE is highly expressed in the lung, and its expression increases proportionally at the site of inflammation. This receptor can bind a variety of ligands, including advanced glycation end products, high mobility group box 1, S100 proteins, adhesion molecules, complement components, advanced lipoxidation end products, lipopolysaccharides, and other molecules that mediate cellular responses related to acute and chronic inflammation. RAGE serves as an important node for the initiation and stimulation of cell stress and growth signaling mechanisms that promote carcinogenesis, tumor propagation, and metastatic potential. In this review, we discuss different aspects of RAGE and its prominent ligands implicated in cancer pathogenesis and describe current findings that provide insights into the significant role played by RAGE in cancer. Cancer development can be hindered by inhibiting the interaction of RAGE with its ligands, and this could provide an effective strategy for cancer treatment.

The S100A7 nuclear interactors in autoimmune diseases: a coevolutionary study in mammals

S100A7, a member of the S100A family of Ca²⁺-binding proteins, is considered a key effector in immune response. In particular, S100A7 dysregulation has been associated with several diseases, including autoimmune disorders. At the nuclear level, S100A7 interacts with several protein-binding partners which are involved in transcriptional regulation and DNA repair. By using the BioGRID and GAAD databases, S100A7 nuclear interactors with a putative involvement in autoimmune diseases were retrieved. We selected fatty acid-binding protein 5 (FABP5), autoimmune regulator (AIRE), cystic fibrosis transmembrane conductance regulator (CFTR), chromodomain helicase DNA-binding protein 4 (CHD4), epidermal growth factor receptor (EGFR), estrogen receptor 1 (ESR1), histone deacetylase 2 (HDAC2), v-myc avian myelocytomatosis viral oncogene homolog (MYC), protection of telomeres protein 1 (POT1), telomeric repeat-binding factor (NIMA-interacting) 1 (TERF1), telomeric repeat-binding factor 2 (TERF2), and Zic family member 1 (ZIC1). Linear correlation coefficients between interprotein distances were calculated with MirrorTree. Coevolution clusters were also identified with the use of a recent version of the Blocks in Sequences (BIS2) algorithm implemented in the BIS2Analyzer web server. Analysis of pair positions identified interprotein coevolving clusters between S100A7 and the binding partners CFTR and TERF1. Such findings could guide further analysis to better elucidate the function of S100A7 and its binding partners and to design drugs targeting for these molecules in autoimmune diseases.

S100A7/Ran-binding protein 9 coevolution in mammals

S100A7 has been suggested to interact with Ran-binding protein 9. Both proteins are nowadays considered key effectors in immune response. Functional interaction between proteins is ensured by coevolution. The mechanisms of vertebrate coevolution between S100A7 and RanBP9 remain unclear. Several approaches for studying coevolution have been developed. Protein coevolution was inferred by calculating the linear correlation coefficients between inter-protein distance matrices using Mirrortree. We found an overall moderate correlation value (R = 0.53, p < 1e-06). Moreover, owing to the high conservation of RanBP9 protein among vertebrates, we chose to utilize a recent version of Blocks in Sequences (BIS2) algorithm implemented in BIS2Analyzer webserver. A coevolution cluster was identified between the two proteins (p < 8.10e-05). In conclusion, our coevolutionary analysis suggests that amino acid variations may modulate S100A7/RanBP9 interaction with potential pathogenic effects. Such findings could guide further analysis to better elucidate the function of S100A7 and RanBP9 and to design drugs targeting for these molecules in diseases.

The novel interaction between Neisseria gonorrhoeae TdfJ and human S100A7 allows gonococci to subvert host zinc restriction

Neisseria gonorrhoeae causes the sexually-transmitted infection gonorrhea, a global disease that is difficult to treat and for which there is no vaccine. This pathogen employs an arsenal of conserved outer membrane proteins called TonB-dependent transporters (TdTs) that allow the gonococcus to overcome nutritional immunity, the host strategy of sequestering essential nutrients away from invading bacteria to handicap infectious ability. N. gonorrhoeae produces eight known TdTs, of which four are utilized for acquisition of iron or iron chelates from host-derived proteins or xenosiderophores produced by other bacteria. Of the remaining TdTs, two of them, TdfH and TdfJ, facilitate zinc uptake. TdfH was recently shown to bind Calprotectin, a member of the S100 protein family, and subsequently extract its zinc, which is then internalized by N. gonorrhoeae. Like Calprotectin, other S100s are also capable of binding transition metals such as zinc and copper, and thus have demonstrated growth suppression of numerous other pathogens via metal sequestration. Considering the functional and structural similarities of the TdTs and of the S100s, as well as the upregulation in response to Zn limitation shown by TdfH and TdfJ, we sought to evaluate whether other S100s have the ability to support gonococcal growth by means of zinc acquisition and to frame this growth in the context of the TdTs. We found that both S100A7 and S10012 are utilized by N. gonorrhoeae as a zinc source in a mechanism that depends on the zinc transport system ZnuABC. Moreover, TdfJ binds directly to S100A7, from which it internalizes zinc. This interaction is restricted to the human version of S100A7, and zinc presence in S100A7 is required to fully support gonococcal growth. These studies highlight how gonococci co-opt human nutritional immunity, by presenting a novel interaction between TdfJ and human S100A7 for overcoming host zinc restriction.

Neisseria gonorrhoeae causes the common sexually-transmitted infection gonorrhea. This bacteria’s ability to rapidly acquire antibiotic resistance factors, coupled with the lack of any effective vaccine to prevent infection, has resulted in a disease that poses a global threat and may become untreatable. A group of gonococcal outer membrane proteins called TonB-dependent transporters (TdTs) have been implicated as promising vaccine targets, as they are well-conserved and expressed across gonococcal isolates and play a vital role in allowing the pathogen to acquire essential nutrients during infection of the human host. Here, we describe the conservation and regulation of TdfJ, a gonococcal TdT whose homologues are ubiquitous in the genus Neisseria. We show that TdfJ binds directly to S100A7, a host protein that normally sequesters zinc away from invading pathogens. This novel interaction enables N. gonorrhoeae to strip S100A7 of chelated zinc for its own use. Furthermore, we show that another zinc-binding human protein, S100A12, is also utilized by N. gonorrhoeae as a zinc source by an as-yet-unidentified mechanism. This study provides insight into the functional role of the TdTs during infection and highlights these proteins as promising targets for both vaccine and antimicrobial therapy development.

S100A7 in Psoriasis: Immunodetection and Activation by CRISPR technology

Psoriasis, an inflammatory autoimmune skin disease, is the result of a chronic interaction between hyperproliferative keratinocytes and infiltrating activated immune cells. The mechanisms underlying psoriasis pathogenesis remain largely unknown, although a combination of genetic and environmental factors plays an important role in its development. S100A7 is overexpressed in psoriasis, and there is growing evidence that S100A7 may be involved in the pathogenesis of psoriasis. Since the mechanisms underlying S100A7 regulation and function remain elusive, a better understanding of these mechanisms may be useful to uncover additional treatment approaches for psoriasis. Immunohistology provides invaluable tools for a better understanding of the pathogenetic mechanisms of psoriasis. Here, we describe basic methods for immunofluorescence and immunohistochemistry analysis of S100A7 expression in psoriatic patients as well as in S100A7 CRISPR-activated human keratinocyte cell line.

Evolution and Expression of S100A7 Gene in Vertebrates

The skin is the primary barrier between the internal organs of an organism and the environment, and it provides protection from ultraviolet (UV) radiation. According to the nocturnal bottleneck hypothesis, ungulates might have traversed to the grasslands and were exposed to UV radiation subsequent to the reduction in predation pressure. UV light exposure might have increased the S100A7 expression. In order to test whether the UV radiation is associated with the selection pressure on S100A7, we acquired the complete S100A7 DNA sequences from each of 42 vertebrate species. The results suggested that the evidence of diversifying selection in S100A7 occurred at the end of Mesozoic era, and the site of positive selection was observed in the branch of Artiodactyla (even-toed ungulates). In addition, we found that the transcription level of S100A7 in cashmere goat skin correlates with UV radiation. Our results indicated that S100A7 plays a role in the signaling between the skin genes and UV radiation during evolution.

The evolution of S100A7 in primates: a model of concerted and birth-and-death evolution

The human S100A7 resides in the epidermal differentiation complex (EDC) and has been described as a key effector of innate immunity. In humans, there are five S100A7 genes located in tandem-S100A7A, S100A7P1, S100AL2, S100A7, and S100AP2. The presence of several retroelements in the S100A7A/S100A7P1 and S100A7/S100A7P2 clusters suggests that these genes were originated from a duplication around ~ 35 million years ago, during or after the divergence of Platyrrhini and Catarrhini primates. To test this hypothesis, and taking advantage of the high number of genomic sequences available in the public databases, we retrieved S100A7 gene sequences of 12 primates belonging to the Cercopithecoidea and Hominoidea (Catarrhini species). Our results support the duplication theory, with at least one gene of each cluster being identified in both Cercopithecoidea and Hominoidea species. Moreover, given the presence of an ongoing gene conversion event between S100A7 and S100A7A, a high rate of mutation in S100A7L2 and the presence of pseudogenes, we proposed a model of concerted and birth-and-death evolution to explain the evolution of S100A7 gene family. Indeed, our results suggest that S100A7L2 most likely suffered a neofunctionalization in the Catarrhini group. Being S100A7 a major protein in innate defense, we believe that our findings could open new doors in the study of this gene family in immune system.

Phosphodiesterase 4B plays a role in benzophenone-3-induced phototoxicity in normal human keratinocytes

Benzophenone-3 (BP-3), which is extensively used in organic sunscreen, has phototoxic potential in human skin. Phosphodiesterase 4B (PDE4B) has a well-established role in inflammatory responses in immune cells. Currently, it is unknown if PDE4B is associated with BP-3-induced phototoxicity in normal human keratinocytes (NHKs). We found that BP-3 significantly increased PDE4B expression in ultraviolet B (UVB)-irradiated NHKs. Notably, BP-8, a sunscreen agent that shares the 2-hydroxy-4-methoxyphenyl methanone moiety with BP-3, also upregulated PDE4B expression in NHKs. Upon UVB irradiation, BP-3 upregulated the expression of pro-inflammatory factors, such as prostaglandin endoperoxide synthase 2, tumor necrosis factor α, interleukin 8, and S100A7, and downregulated the level of cornified envelope associated proteins, which are important in the development of the epidermal permeability barrier. The additive effects of UVB-activated BP-3 on the expression of both pro-inflammatory mediators and cornified envelope associated proteins were antagonized by treatment with the PDE4 inhibitor rolipram. The BP-3 and UVB co-stimulation-induced PDE4B upregulation and its association with the upregulation of pro-inflammatory mediators and the downregulation of epidermal differentiation markers were confirmed in a reconstituted three dimensional human epidermis model. Therefore, PDE4B has a role in the mechanism of BP-3-induced phototoxicity.

Interaction with adipocyte stromal cells induces breast cancer malignancy via S100A7 upregulation in breast cancer microenvironment

BACKGROUND

Breast adipocytes play important roles in both the development and function of mammary epithelial cells. Therefore, carcinoma-adipose stromal cell (ASC) interactions have been considered pivotal in supporting tumor growth in breast cancer. In addition, it has been demonstrated that the biological features of cancer-associated adipocytes differ from those of normal ASCs. Therefore, we investigated an interaction between ASCs and carcinoma cell lines to identify genes associated with ASC invasion of carcinoma cells.

METHODS

3T3-L1 ASC-derived conditioned medium (CM) was treated to measure the proliferation rate of breast cancer cells. To further examine the effect of ASCs, breast cancer cells were cocultivated with either primary human or 3T3-L1 ASCs for migration assays, DNA microarrays, quantitative real-time polymerase chain reactions, and Western blotting experiments. Furthermore, immunoreactivity of S100A7, the most upregulated gene in MCF7, after coculture with ASCs was evaluated for 150 breast cancer tissues to statistically analyze its association with clinicopathological parameters.

RESULTS

We first confirmed that ASC-derived CM treatment enhanced the cell proliferation rate of MCF7, T47D, SK-BR-3, and ZR-75-1 cell lines, whereas the migration rate of breast cancer cells was promoted by coculture with ASCs. We identified that a small calcium-binding protein, S100A7, was markedly upregulated (by 5.8-fold) in MCF7 cells after coculture with primary human ASCs. Knockdown of S100A7 significantly suppressed ASC-stimulated cell proliferation and migration rate, indicating a possible involvement of S100A7 in the carcinoma-ASC interaction in breast tumors. Furthermore, strong S100A7 immunoreactivity was detected at the invasive front of adipose stromal tissues compared with that at the intratumoral area. The status of S100A7 was also significantly correlated with adverse pathological parameters, and multivariate analysis revealed that S100A7 could be an independent prognostic marker for a poor relapse-free survival rate. Moreover, induction of oncostatin M was detected in cancer-stimulated ASCs, whereas the downstream S100A7 binding proteins/receptor for advanced glycation endproducts were significantly upregulated in correspondence with S100A7 expression in breast cancer cells after coculture with ASCs.

CONCLUSIONS

The results of our study suggest that paracrine production of cytokines from ASCs stimulates breast carcinoma cell growth via upregulation of S100A7 expression in breast cancer cell lines.

Psoriasin (S100A7) is a novel biomarker for lung squamous cell carcinoma in humans

Objective

Psoriasin (S100A7) plays a role in the malignant potential of several epithelial cancers, and could candidate diagnostic marker or therapeutic target. Nuclear factor kappa B (NF-κB) regulates cancer cell growth and is modulated by phospholipase activity in many cancer cells. In the present study, we first evaluate the involvement of S100A7 in lung squamous cell carcinoma and its clinical usefulness for diagnosis. We then study whether knockdown of S100A7 in lung squamous cell carcinoma cells would reduce cell proliferation and NF-κB activity in vitro and attenuate tumor growth in vivo.

Methods

We examined S100A7 expression in lung squamous cell carcinoma tissues by immunohistology. The human lung squamous cell carcinoma cell line NCI-H520 were transduced with short hairpin RNA targeting S100A7. Quantitative reverse transcriptase-polymerase chain reaction and immunoblotting confirmed knockdown of S100A7 messenger RNA and protein, respectively. Cell proliferation was evaluated by the MTT assay. NF-κB phosphorylation was assayed by western blot. 1 × 10⁶ of NCI-H520/S100A7 knockdown cells were injected into the left flanks of nude mice (aged 6 to 8 weeks). Tumors were followed for 35 days, then removed and stained with hematoxylin and eosin, stained with Ki-67, and analyzed for S100A7 protein expression.

Results

S100A7 protein levels were significantly higher in carcinoma specimens than in nonneoplastic tissues. S100A7 might be a useful marker for diagnosis of lung squamous cell carcinoma. In vitro data showed that inhibition of S100A7 decreased proliferation of NCI-H520 cells. S100A7 knockdown reduced NF-κB phosphorylation and tumor growth in vivo and vivo. Explanted knockdown tumors maintained lower S100A7 levels compared with wild-type, confirmed by immunohistology. Ki-67 staining was more prominent throughout the wild-type tumors compared with knockdown tumors.

Conclusions

Our present results suggest that S100A7 level is a promising tool for diagnosis of lung squamous cell carcinoma. Knockdown of S100A7 suppresses lung cancer growth in part by attenuating NF-κB activity. S100A7 may be a promising therapeutic target for lung squamous cell carcinoma.

Intratumoural inflammation and endocrine resistance in breast cancer

It is becoming clear that inflammation-associated mechanisms can affect progression of breast cancer and modulate responses to treatment. Estrogen receptor alpha (ERα (ESR1)) is the principal biomarker and therapeutic target for endocrine therapies in breast cancer. Over 70% of patients are ESR1-positive at diagnosis and are candidates for endocrine therapy. However, ESR1-positive tumours can become resistant to endocrine therapy. Multiple mechanisms of endocrine resistance have been proposed, including suppression of ESR1. This review discusses the relationship between intratumoural inflammation and endocrine resistance with a particular focus on inflammation-mediated suppression of ESR1.

Knockdown of S100A7 reduces lung squamous cell carcinoma cell growth in vitro and in vivo

OBJECTIVE

S100A7 plays a role in the malignant potential of several epithelial cancers, and could candidate diagnostic marker or therapeutic target. Nuclear factor kappa B (NF-κB) regulates cancer cell growth and is modulated by phospholipase activity in many cancer cells. In the present study, we first evaluate the involvement of S100A7 in lung squamous cell carcinoma and its clinical usefulness for diagnosis. We then study whether knockdown of S100A7 in lung squamous cell carcinoma cells would reduce cell proliferation and NF-κB activity in vitro and attenuate tumor growth in vivo.

METHODS

We examined S100A7 expression in lung squamous cell carcinoma tissues by immunohistology .The human lung squamous cell carcinoma cell line NCI-H520 were transduced with short hairpin RNA targeting S100A7. Quantitative reverse transcriptase-polymerase chain reaction and immunoblotting confirmed knockdown of S100A7 messenger RNA and protein, respectively. Cell proliferation was evaluated by the MTT assay. NF-κB phosphorylation was assayed by western blot. 1×10(6) of NCI-H520/S100A7 knockdown cells were injected into the left flanks of nude mice (aged 6 to 8 weeks). Tumors were followed for 35 days, then removed and stained with hematoxylin and eosin, stained with Ki-67, and analyzed for S100A7 protein expression.

RESULTS

S100A7 protein levels were significantly higher in carcinoma specimens than in nonneoplastic tissues. S100A7 might be a useful marker for diagnosis of lung squamous cell carcinoma. In vitro data showed that inhibition of S100A7 decreased proliferation of NCI-H520 cells. S100A7 knockdown reduced NF-κB phosphorylation and tumor growth in vivo and vivo. Explanted knockdown tumors maintained lower S100A7 levels compared with wild-type, confirmed by immunohistology. Ki-67 staining was more prominent throughout the wild-type tumors compared with knockdown tumors.

CONCLUSIONS

Our present results suggest that S100A7 level is a promising tool for diagnosis of lung squamous cell carcinoma. Knockdown of S100A7 suppresses lung cancer growth in part by attenuating NF-κB activity. S100A7 may be a promising therapeutic target for lung squamous cell carcinoma.

Opposing functions of psoriasin (S100A7) and koebnerisin (S100A15) in epithelial carcinogenesis

The S100 protein family is involved in epithelial cell maturation and inflammation. Some S100 members are dysregulated during carcinogenesis and have been established as tumor markers. Psoriasin (S100A7) and koebnerisin (S100A15) are highly homologous proteins that have been first described in psoriasis, which is characterized by disturbed epidermal maturation and chronic inflammation. Despite their homology, both S100 proteins are distinct in expression and function through different receptors but synergize as chemoattractants and pro-inflammatory 'alarmins' to promote inflammation. Psoriasin and koebnerisin are further regulated with tumor progression in epithelial cancers. In tumor cells, high cytoplasmic expression of psoriasin and koebnerisin may prevent oncogenic activity, whereas their nuclear translocation and extracellular secretion are associated with tumor progression and poor prognosis. The present review outlines these opposing effects of psoriasin and koebnerisin in multifunctional pathways and mechanisms that are known to affect tumor cells ('seeds'), tumor environment ('soil') and tumor cell metastasis ('seeding') thereby influencing epithelial carcinogenesis.

Structural characterization of S100A15 reveals a novel zinc coordination site among S100 proteins and altered surface chemistry with functional implications for receptor binding

Background

S100 proteins are a family of small, EF-hand containing calcium-binding signaling proteins that are implicated in many cancers. While the majority of human S100 proteins share 25-65% sequence similarity, S100A7 and its recently identified paralog, S100A15, display 93% sequence identity. Intriguingly, however, S100A7 and S100A15 serve distinct roles in inflammatory skin disease; S100A7 signals through the receptor for advanced glycation products (RAGE) in a zinc-dependent manner, while S100A15 signals through a yet unidentified G-protein coupled receptor in a zinc-independent manner. Of the seven divergent residues that differentiate S100A7 and S100A15, four cluster in a zinc-binding region and the remaining three localize to a predicted receptor-binding surface.

Results

To investigate the structural and functional consequences of these divergent clusters, we report the X-ray crystal structures of S100A15 and S100A7D24G, a hybrid variant where the zinc ligand Asp24 of S100A7 has been substituted with the glycine of S100A15, to 1.7 Å and 1.6 Å resolution, respectively. Remarkably, despite replacement of the Asp ligand, zinc binding is retained at the S100A15 dimer interface with distorted tetrahedral geometry and a chloride ion serving as an exogenous fourth ligand. Zinc binding was confirmed using anomalous difference maps and solution binding studies that revealed similar affinities of zinc for S100A15 and S100A7. Additionally, the predicted receptor-binding surface on S100A7 is substantially more basic in S100A15 without incurring structural rearrangement.

Conclusions

Here we demonstrate that S100A15 retains the ability to coordinate zinc through incorporation of an exogenous ligand resulting in a unique zinc-binding site among S100 proteins. The altered surface chemistry between S100A7 and S100A15 that localizes to the predicted receptor binding site is likely responsible for the differential recognition of distinct protein targets. Collectively, these data provide novel insight into the structural and functional consequences of the divergent surfaces between S100A7 and S100A15 that may be exploited for targeted therapies.

Emerging avenues linking inflammation and cancer

The role of inflammation in carcinogenesis has been extensively investigated and well documented. Many biochemical processes that are altered during chronic inflammation have been implicated in tumorigenesis. These include shifting cellular redox balance toward oxidative stress; induction of genomic instability; increased DNA damage; stimulation of cell proliferation, metastasis, and angiogenesis; deregulation of cellular epigenetic control of gene expression; and inappropriate epithelial-to-mesenchymal transition. A wide array of proinflammatory cytokines, prostaglandins, nitric oxide, and matricellular proteins are closely involved in premalignant and malignant conversion of cells in a background of chronic inflammation. Inappropriate transcription of genes encoding inflammatory mediators, survival factors, and angiogenic and metastatic proteins is the key molecular event in linking inflammation and cancer. Aberrant cell signaling pathways comprising various kinases and their downstream transcription factors have been identified as the major contributors in abnormal gene expression associated with inflammation-driven carcinogenesis. The posttranscriptional regulation of gene expression by microRNAs also provides the molecular basis for linking inflammation to cancer. This review highlights the multifaceted role of inflammation in carcinogenesis in the context of altered cellular redox signaling.

S100A7 enhances mammary tumorigenesis through upregulation of inflammatory pathways

S100A7/psoriasin, a member of the epidermal differentiation complex, is widely overexpressed in invasive estrogen receptor (ER)α-negative breast cancers. However, it has not been established whether S100A7 contributes to breast cancer growth or metastasis. Here, we report the consequences of its expression on inflammatory pathways that impact breast cancer growth. Overexpression of human S100A7 or its murine homologue mS100a7a15 enhanced cell proliferation and upregulated various proinflammatory molecules in ERα-negative breast cancer cells. To examine in vivo effects, we generated mice with an inducible form of mS100a7a15 (MMTV-mS100a7a15 mice). Orthotopic implantation of MVT-1 breast tumor cells into the mammary glands of these mice enhanced tumor growth and metastasis. Compared with uninduced transgenic control mice, the mammary glands of mice where mS100a7a15 was induced exhibited increased ductal hyperplasia and expression of molecules involved in proliferation, signaling, tissue remodeling, and macrophage recruitment. Furthermore, tumors and lung tissues obtained from these mice showed further increases in prometastatic gene expression and recruitment of tumor-associated macrophages (TAM). Notably, in vivo depletion of TAM inhibited the effects of mS100a7a15 induction on tumor growth and angiogenesis. Furthermore, introduction of soluble hS100A7 or mS100a7a15 enhanced chemotaxis of macrophages via activation of RAGE receptors. In summary, our work used a powerful new model system to show that S100A7 enhances breast tumor growth and metastasis by activating proinflammatory and metastatic pathways.

Nuclear S100A7 is associated with poor prognosis in head and neck cancer

Background

Tissue proteomic analysis of head and neck squamous cell carcinoma (HNSCC) and normal oral mucosa using iTRAQ (isobaric tag for relative and absolute quantitation) labeling and liquid chromatography-mass spectrometry, led to the identification of a panel of biomarkers including S100A7. In the multi-step process of head and neck tumorigenesis, the presence of dysplastic areas in the epithelium is proposed to be associated with a likely progression to cancer; however there are no established biomarkers to predict their potential of malignant transformation. This study aimed to determine the clinical significance of S100A7 overexpression in HNSCC.

Methodology

Immunohistochemical analysis of S100A7 expression in HNSCC (100 cases), oral lesions (166 cases) and 100 histologically normal tissues was carried out and correlated with clinicopathological parameters and disease prognosis over 7 years for HNSCC patients. Overexpression of S100A7 protein was significant in oral lesions (squamous cell hyperplasia/dysplasia) and sustained in HNSCC in comparison with oral normal mucosa (p_trend<0.001). Significant increase in nuclear S100A7 was observed in HNSCC as compared to dysplastic lesions (p = 0.005) and associated with well differentiated squamous cell carcinoma (p = 0.031). Notably, nuclear accumulation of S100A7 also emerged as an independent predictor of reduced disease free survival (p = 0.006, Hazard ratio (HR = 7.6), 95% CI = 1.3−5.1) in multivariate analysis underscoring its relevance as a poor prognosticator of HNSCC patients.

Conclusions

Our study demonstrated nuclear accumulation of S100A7 may serve as predictor of poor prognosis in HNSCC patients. Further, increased nuclear accumulation of S100A7 in HNSCC as compared to dysplastic lesions warrants a large-scale longitudinal study of patients with dysplasia to evaluate its potential as a determinant of increased risk of transformation of oral premalignant lesions.

Structural and functional characterization of a triple mutant form of S100A7 defective for Jab1 binding

S100A7 (psoriasin) is a calcium- and zinc-binding protein implicated in breast cancer. We have shown previously that S100A7 enhances survival mechanisms in breast cells through an interaction with c-jun activation domain binding protein 1 (Jab1), and an engineered S100A7 triple mutant (Asp(56)Gly, Leu(78)Met, and Gln(88)Lys-S100A7(3)) ablates Jab1 binding. We extend these results to include defined breast cancer cell lines and demonstrate a disrupted S100A7(3)/Jab1 phenotype is maintained. To establish the basis for the abrogated Jab1 binding, we have recombinantly produced S100A7(3), demonstrated that it retains the ability to form an exceptionally thermostable dimer, and solved the three dimensional crystal structure to 1.6 A. Despite being positioned at the dimer interface, the Leu(78)Met mutation is easily accommodated and contributes to a methionine-rich pocket formed by Met(12), Met(15), and Met(34). In addition to altering the surface charge, the Gln(88)Lys mutation results in a nearby rotameric shift in Tyr(85), leading to a substantially reorganized surface cavity and may influence zinc binding. The final mutation of Asp(56) to Gly results in the largest structural perturbation shortening helix IV by one full turn. It is noteworthy that position 56 lies in one of two divergent clusters between S100A7 and the functionally distinct yet highly homologous S100A15. The structure of S100A7(3) provides a unique perspective from which to characterize the S100A7-Jab1 interaction and better understand the distinct functions between S100A7, and it is closely related paralog S100A15.

Psoriasin (S100A7), an antimicrobial peptide, is increased in human middle ear cholesteatoma

CONCLUSION

Increased psoriasin in cholesteatoma epithelium may play a role in epithelial inflammatory response and differentiation.

OBJECTIVES

Cholesteatoma is characterized by excessive keratinocyte differentiation leading to inflammation, granulation tissue, and osteolytic activity. Moreover, psoriasin may act as an antimicrobial peptide, stimulate granulocytes, and control keratinocyte differentiation. The purpose of this study was to investigate the differential expression patterns and the localization of psoriasin in cholesteatoma and in normal external auditory canal skin.

MATERIALS AND METHODS

Expression levels of psoriasin mRNA were evaluated by real-time PCR and Western blotting. Cholesteatoma-affected and normal external auditory canal skin samples were immunostained with monoclonal antibody to psoriasin. Localization of immunoreactivity to psoriasin antibody was then compared.

RESULTS

By real-time PCR, expression levels of psoriasin mRNA in cholesteatoma were significantly higher than in normal external auditory canal skin, and this was confirmed by Western blotting. Immunohistochemical staining revealed that psoriasin protein is mainly expressed in the granular layer and in the upper parts of the spinous layer in cholesteatoma epithelium, but that it is expressed in the superficial layer of normal external auditory canal skin.

S100A7-downregulation inhibits epidermal growth factor-induced signaling in breast cancer cells and blocks osteoclast formation

S100A7 is a small calcium binding protein, which has been shown to be differentially expressed in psoriatic skin lesions, as well as in squamous cell tumors of the skin, lung and breast. Although its expression has been correlated to HER+ high-grade tumors and to a high risk of progression, the molecular mechanisms of these S100A7-mediated tumorigenic effects are not well known. Here, we showed for the first time that epidermal growth factor (EGF) induces S100A7 expression in both MCF-7 and MDA-MB-468 cell lines. We also observed a decrease in EGF-directed migration in shRNA-downregulated MDA-MB-468 cell lines. Furthermore, our signaling studies revealed that EGF induced simultaneous EGF receptor phosphorylation at Tyr1173 and HER2 phosphorylation at Tyr1248 in S100A7-downregulated cell lines as compared to the vector-transfected controls. In addition, reduced phosphorylation of Src at tyrosine 416 and p-SHP2 at tyrosine 542 was observed in these downregulated cell lines. Further studies revealed that S100A7-downregulated cells had reduced angiogenesis in vivo based on matrigel plug assays. Our results also showed decreased tumor-induced osteoclastic resorption in an intra-tibial bone injection model involving SCID mice. S100A7-downregulated cells had decreased osteoclast number and size as compared to the vector controls, and this decrease was associated with variations in IL-8 expression in in vitro cell cultures. This is a novel report on the role of S100A7 in EGF-induced signaling in breast cancer cells and in osteoclast formation.

Inactivation of MOXD2 and S100A15A by exon deletion during human evolution

We devised a bioinformatics method for systematic identification of putative human-specific exon-deletion mutations that occurred after the divergence of human and chimpanzee and experimentally verified 2 of the predicted mutations in MOXD2 and S100A15A genes. MOXD2 gene encodes a monooxygenase that is highly conserved in mammals and is mostly expressed in the olfactory epithelium in mouse. The presence of a deletion of the last 2 exons and a polymorphic nonsense mutation in exon 6 suggests that MOXD2 gene is inactive in humans. S100A15A is a member of the S100 family of calcium-binding proteins, the mouse ortholog of which is expressed during epidermal maturation. Human S100A15A gene is likely to be inactive because the start codon-bearing exon is deleted in human. We propose that modification or inactivation of MOXD2 and S100A15A genes have contributed to the loss of certain smell sense in humans and to the development of human skin.

Blockade of RAGE suppresses alloimmune reactions in vitro and delays allograft rejection in murine heart transplantation

The receptor for advanced glycation endproducts (RAGE), a multiligand member of the immunoglobulin superfamily, interacts with proinflammatory AGEs, the products of nonenzymatic glycation and oxidation of proteins; high-mobility group box 1 (HMGB1), also known as amphoterin and S100/calgranulins to amplify inflammation and tissue injury. Previous studies showed that blockade of RAGE suppressed recruitment of proinflammatory mechanisms in murine models. We tested the hypothesis that RAGE contributes to alloimmune responses and report that in vivo, acute rejection of fully allogeneic cardiac allografts in a murine model of heterotopic cardiac transplantation is significantly delayed by pharmacological antagonism of RAGE. In parallel, allogeneic T-cell proliferation in the mixed lymphocyte reaction is, at least in part, RAGE-dependent. These data provide the first insights into key roles for RAGE in allorecognition responses and suggest that antagonism of this receptor may exert beneficial effects in allogeneic organ transplantation.

Pathologies involving the S100 proteins and RAGE

The S100 proteins are exclusively expressed in vertebrates and are the largest subgroup within the superfamily of EF-hand Ca2(+)-binding proteins Generally, S100 proteins are organized as tight homodimers (some as heterodimers). Each subunit is composed of a C-terminal, 'canonical' EF-hand, common to all EF-hand proteins, and a N-terminal, 'pseudo' EF-hand, characteristic of S100 proteins. Upon Ca2(+)-binding, the C-terminal EF-hand undergoes a large conformational change resulting in the exposure of a hydrophobic surface responsible for target binding A unique feature of this protein family is that some members are secreted from cells upon stimulation, exerting cytokine- and chemokine-like extracellular activities via the Receptor for Advanced Glycation Endproducts, RAGE. Recently, larger assemblies of some S100 proteins (hexamers, tetramers, octamers) have been also observed and are suggested to be the active extracellular species required for receptor binding and activation through receptor multimerization Most S100 genes are located in a gene cluster on human chromosome 1q21, a region frequently rearranged in human cancer The functional diversification of S100 proteins is achieved by their specific cell- and tissue-expression patterns, structural variations, different metal ion binding properties (Ca2+, Zn2+ and Cu2+) as well as their ability to form homo-, hetero- and oligomeric assemblies Here, we review the most recent developments focussing on the biological functions of the S100 proteins and we discuss the presently available S100-specific mouse models and their possible use as human disease models In addition, the S100-RAGE interaction and the activation of various cellular pathways will be discussed. Finally, the close association of S100 proteins with cardiomyopathy, cancer, inflammation and brain diseases is summarized as well as their use in diagnosis and their potential as drug targets to improve therapies in the future.

The mouse S100A15 ortholog parallels genomic organization, structure, gene expression, and protein-processing pattern of the human S100A7/A15 subfamily during epidermal maturation

The calcium-binding proteins of the human S100A7/A15 (hS100A7/A15) subfamily are differentially expressed in normal and pathological epidermis. The hS100A7 (psoriasin) and S100A15 reside in a chromosomal cluster of highly similar paralogs. To exploit the power of mouse models for determining functions of gene products, the corresponding S100A7/A15 ortholog was cloned and examined in murine skin. The single mouse S100A15 (mS100A15) gene encodes a protein of 104 amino acids with a predicted molecular weight of 12,870 Da and two EF-hand calcium binding sites. Using gene-specific primers and specific antibodies, expression of mS100A15 in both skin and isolated keratinocytes is confined to differentiating granular and cornified epidermal cells. Immunoblotting of epidermal extracts revealed a series of high molecular weight bands that are also recognized by an antibody for transglutaminase-mediated protein crosslinks. mS100A15 expression is upregulated in cultured keratinocytes induced to differentiate by calcium or phorbol esters. Maximal induction occurs concordantly with expression of late differentiation markers. Induction is enhanced in keratinocytes overexpressing protein kinase Calpha and is dependent on activator protein-1 transcription factors. The regulation, expression pattern and crosslinking of mS100A15 are consistent with the characteristics of the human orthologs, providing a valid surrogate model to study changes in these proteins associated with cutaneous pathologies.