Molecular cloning of the cDNA for a growth factor-inducible gene with strong homology to S-100, a calcium-binding protein

The Role of S100A6 in Human Diseases: Molecular Mechanisms and Therapeutic Potential

S100A6, also known as calcyclin, is a low-molecular-weight Ca2+-binding protein from the S100 family that contains two EF-hands. S100A6 is expressed in a variety of mammalian cells and tissues. It is also expressed in lung, colorectal, pancreatic, and liver cancers, as well as other cancers such as melanoma. S100A6 has many molecular functions related to cell proliferation, the cell cycle, cell differentiation, and the cytoskeleton. It is not only involved in tumor invasion, proliferation, and migration, but also the pathogenesis of other non-neoplastic diseases. In this review, we focus on the molecular mechanisms and potential therapeutic targets of S100A6 in tumors, nervous system diseases, leukemia, endometriosis, cardiovascular disease, osteoarthritis, and other related diseases.

S100A6 Protein-Expression and Function in Norm and Pathology

S100A6, also known as calcyclin, is a calcium-binding protein belonging to the S100 protein family. It was first identified and purified more than 30 years ago. Initial structural studies, focused mostly on the mode and affinity of Ca²⁺ binding and resolution of the resultant conformational changes, were soon complemented by research on its expression, localization and identification of binding partners. With time, the use of biophysical methods helped to resolve the structure and versatility of S100A6 complexes with some of its ligands. Meanwhile, it became clear that S100A6 expression was altered in various pathological states and correlated with the stage/progression of many diseases, including cancers, indicative of its important, and possibly causative, role in some of these diseases. This, in turn, prompted researchers to look for the mechanism of S100A6 action and to identify the intermediary signaling pathways and effectors. After all these years, our knowledge on various aspects of S100A6 biology is robust but still incomplete. The list of S100A6 ligands is growing all the time, as is our understanding of the physiological importance of these interactions. The present review summarizes available data concerning S100A6 expression/localization, interaction with intracellular and extracellular targets, involvement in Ca²⁺-dependent cellular processes and association with various pathologies.

S100A6 as a Constituent and Potential Marker of Adult and Cancer Stem Cells

Adult or tissue stem cells are present in various tissues of the organism where they reside in a specific environment called the niche. Owing to their ability to generate a progeny that can proliferate and differentiate into specialized cell types, adult stem cells constitute a source of new cells necessary for tissue maintenance and/or regeneration. Under normal conditions they divide with a frequency matching the pace of tissue renewal but, following tissue damage, they can migrate to the site of injury and expand/divide intensively to facilitate tissue repair. For this reason much hope is being placed on the use of adult stem cells in regenerative therapies, including tissue engineering. Identification and characterization of tissue stem cells has been a laborious process due to their scarcity and lack of universal markers. Nonetheless, recent studies, employing various types of transcriptomic analyses, revealed some common trends in gene expression pattern among stem cells derived from different tissues, suggesting the importance of certain genes/proteins for the unique properties of these cells. S100A6, a small calcium binding protein, has been recognized as an important factor influencing cell proliferation and differentiation. Accumulating results show that S100A6 is a constituent of adult stem cells and, in some cases, may even be considered as their marker. Thus, in this review we summarize literature data concerning the presence of S100A6 in adult and cancer stem cells and speculate on its potential role and usefulness as a marker of these cells.

Identification and Biochemical Characterization of High Mobility Group Protein 20A as a Novel Ca2+/S100A6 Target

During screening of protein-protein interactions, using human protein arrays carrying 19,676 recombinant glutathione s-transferase (GST)-fused human proteins, we identified the high-mobility protein group 20A (HMG20A) as a novel S100A6 binding partner. We confirmed the Ca²⁺-dependent interaction of HMG20A with S100A6 by the protein array method, biotinylated S100A6 overlay, and GST-pulldown assay in vitro and in transfected COS-7 cells. Co-immunoprecipitation of S100A6 with HMG20A from HeLa cells in a Ca²⁺-dependent manner revealed the physiological relevance of the S100A6/HMG20A interaction. In addition, HMG20A has the ability to interact with S100A1, S100A2, and S100B in a Ca²⁺-dependent manner, but not with S100A4, A11, A12, and calmodulin. S100A6 binding experiments using various HMG20A mutants revealed that Ca²⁺/S100A6 interacts with the C-terminal region (residues 311–342) of HMG20A with stoichiometric binding (HMG20A:S100A6 dimer = 1:1). This was confirmed by the fact that a GST-HMG20A mutant lacking the S100A6 binding region (residues 311–347, HMG20A-ΔC) failed to interact with endogenous S100A6 in transfected COS-7 cells, unlike wild-type HMG20A. Taken together, these results identify, for the first time, HMG20A as a target of Ca²⁺/S100 proteins, and may suggest a novel linkage between Ca²⁺/S100 protein signaling and HMG20A function, including in the regulation of neural differentiation.

Blocking the interface region amongst S100A6 and RAGE V domain via S100B protein

The Ca²⁺-mediated S100 family protein S100A6 has a crucial task in various intracellular and extracellular activities thereby demonstrating a possible involvement in the advancement and development of malignant tumors. S100A6 has been found to associate with receptor for advanced glycation end products, RAGE, through its extracellular extension. This extension is famously identified as a prominent receptor for many S100 family associates. Additionally, S100A6 binds to S100B protein and forms a heterodimer. Thus, we consider the S100B protein to be a prospective drug molecule to obstruct the interacting regions amongst S100A6 and RAGE V domain. We applied the NMR spectroscopy method to locate the binding area amid the S100A6m (mutant S100A6, cysteine at 3rd position of S100A6 is replaced with serine, C3S) and S100B proteins. The ¹H-¹⁵N HSQC NMR titrations revealed the probable requisite dynamics of S100A6m and S100B interfaces. Utilizing data from the NMR titrations as input parameters, we ran the HADDOCK program and created a S100A6m-S100B heterodimer complex. The obtained complex was then superimposed with the reported complex of S100A6m-RAGE V domain. This superimposition displayed the possibility of S100B to be a potential antagonist that can block the interface area of the S100A6m and the RAGE V domain. Moreover, an in vitro cancer model using SW480 cells in water-soluble tetrazolium-1 assay (WST-1) showed a noticeable change in the cell proliferation as an effect of these proteins. Our study indicates the possibility to develop a S100B-like competitor that could play a key role in the treatment of S100- and RAGE-mediated human diseases.

Lysozyme as the anti-proliferative agent to block the interaction between S100A6 and the RAGE V domain

In this report, using NMR and molecular modeling, we have studied the structure of lysozyme-S100A6 complex and the influence of tranilast [N-(3, 4-dimethoxycinnamoyl) anthranilic acid], an antiallergic drug which binds to lysozyme, on lysozyme-S100A6 and S100A6-RAGE complex formation and, finally, on cell proliferation. We have found that tranilast may block the S100A6-lysozyme interaction and enhance binding of S100A6 to RAGE. Using WST1 assay, we have found that lysozyme, most probably by blocking the interaction between S100A6 and RAGE, inhibits cell proliferation while tranilast may reverse this effect by binding to lysozyme. In conclusion, studies presented in this work, describing the protein-protein/-drug interactions, are of great importance for designing new therapies to treat diseases associated with cell proliferation such as cancers.

Interaction of S100A6 with Target Proteins In Vitro and in Living Cells

S100A6 is a member of the EF-hand Ca²⁺-binding protein family, which plays important roles in a wide variety of Ca²⁺ signaling in the cells, as well as in pathophysiological conditions. Herein, we describe analytical protocols for evaluating the interaction of S100A6 with multiple target proteins in vitro, including biotinylated S100A6 overlay, glutathione-S-transferase (GST)-precipitation, surface plasmon resonance, and a GST-precipitation assay in living cells. These methods will elucidate the detailed molecular mechanisms of S100A6/target interactions and further improve our understanding of the physiological significance of S100A6-mediated Ca²⁺ signaling. Moreover, they may be used to evaluate other physical S100/target interactions.

Distinct prognostic roles of S100 mRNA expression in gastric cancer

BACKGROUND

The S100 protein family is implicated in tumor invasion and metastasis, but its prognostic roles in gastric cancer (GC) has not been elucidated.

MATERIALS AND METHODS

In the current study, Kaplan-Meier plotter (KM plotter) database integrated the expression data and survival information of 1065 GC patients were downloaded from the Gene Expression Omnibus (GEO) (GSE22377, GSE14210 and GSE51105) that published by the three major cancer centers (Berlin, Bethesda and Melbourne). Then this database was used to explore the prognostic values of mRNA expression of each individual S100 in GC patients. We further assessed the prognostic value of S100 in different Lauren classifications, clinicopathological features and clinical treatment of gastric cancer.

RESULTS

Expression of 12 members of the S100 family correlated with overall survival (OS) for all GC patients. Increased expression of S100A3, S100A5, S100A7, S100A7A, S100A11, S100A13, S100Z and S100 G were found to be strongly associated with worse survival, while S100A8, S100A9, S100B and S100 P were correlated with better prognosis in all GC patients. Further assessment of prognostic values of S100 in gastric cancer with different clinical features indicated that different S100 members may interact with different signaling pathways and exerted different functions in gastric cancer development.

CONCLUSIONS

Although the results should be further testified in clinical studies, our findings offer new insights into the contribution of S100 members to GC progression and might promote development of S100 targeted reagents for treating GC.

S100A6 protein: functional roles

S100A6 protein belongs to the A group of the S100 protein family of Ca2+-binding proteins. It is expressed in a limited number of cell types in adult normal tissues and in several tumor cell types. As an intracellular protein, S100A6 has been implicated in the regulation of several cellular functions, such as proliferation, apoptosis, the cytoskeleton dynamics, and the cellular response to different stress factors. S100A6 can be secreted/released by certain cell types which points to extracellular effects of the protein. RAGE (receptor for advanced glycation endproducts) and integrin β1 transduce some extracellular S100A6's effects. Dosage of serum S100A6 might aid in diagnosis in oncology.

Identification and characterization of a centrosomal protein, FOR20 as a novel S100A6 target

S100A6 is a Ca²⁺-signal transducer that interacts with numerous proteins and regulates their biochemical functions. Here we identified a centrosomal protein, FOR20 (FOP-related protein of 20 kDa) as a novel S100A6 target by screening protein microarrays carrying 19,676 recombinant GST-fused human proteins. Binding experiments revealed that S100A6 interacts with the N-terminal region (residues 1-30) of FOR20 in a Ca²⁺-dependent manner in vitro and in living cells. Several S100 proteins including S100A1, A2, A4, A11, B also exhibited Ca²⁺-dependent interactions with FOR20 as well as S100A6. We found that two distantly related centrosomal proteins, FOP and OFD1, also possess N-terminal regions with a significant sequence similarity to the putative S100A6-binding site (residues 1-30) in FOR20 and are capable of binding to S100A6 in a Ca²⁺-dependent manner. Taken together, these results may indicate that S100A6 interacts with FOR20 and related centrosomal proteins through a conserved N-terminal domain, suggesting a novel Ca²⁺-dependent regulation of centrosomal function.

Distinct prognostic values of S100 mRNA expression in breast cancer

S100 family genes encode low molecular weight, acidic-Ca²⁺ binding proteins implicating in a wide spectrum of biological processes. S100 family contains at least 20 members, most of which are frequently dysregulated in human malignancies including breast cancer. However, the prognostic roles of each individual S100, especially the mRNA level, in breast cancer patients remain elusive. In the current study, we used "The Kaplan-Meier plotter" (KM plotter) database to investigate the prognostic values of S100 mRNA expression in breast cancer. Our results indicated that high mRNA expression of S100A8, S100A9, S100A11 and S100P were found to be significantly correlated to worse outcome, while S100A1 and S100A6 were associated with better prognosis in all breast cancer patients. We further assessed the prognostic value of S100 in different intrinsic subtypes and clinicopathological features of breast cancer. The associated results will elucidate the role of S100 in breast cancer and may further lead the research to explore the S100-targeting reagents for treating breast cancer patients.

S100A6 promotes cell proliferation in human nasopharyngeal carcinoma via the p38/MAPK signaling pathway

An elevated level of S100A6 is associated with poor outcomes of many tumor types, but, how S100A6 contributes to nasopharyngeal carcinoma (NPC) progression remains unknown. Here, we investigated the expression and prognostic significance of S100A6 in NPC and explored the molecular mechanisms under-lying the role of S100A6 in NPC development. The results showed that S100A6 was markedly up-regulated in NPC tissues and cell lines compared to paired peritumoral normal tissues and a normal nasopharyngeal epithelial cell line, respectively. In tissues from 92 NPC patients, high S100A6 expression was associated with advanced N stage, locoregional failure and disease progression and was predictive of poor locoregional recurrence-free survival (LRRFS, P = 0.001) and progression-free survival (PFS, P = 0.001). Multivariate analysis showed that S100A6 is an independent prognostic factor for LRRFS and PFS. Silencing S100A6 using siRNA or shRNA significantly suppressed NPC cell proliferation, colony formation and p38/mitogen-activated protein kinase (MAPK) activity in vitro and inhibited tumor growth in a xenograft mouse model of NPC. In contrast, overexpressing S100A6 via plasmid transfection resulted in increased NPC cell proliferation and p38/MAPK activation. S100A6-induced proliferation was abolished by a p38 inhibitor. In summary, S100A6 may be a new prognostic marker of NPC and may promote NPC development via the activation of p38/MAPK signaling pathways. These findings suggest S100A6/p38/MAPK signaling as a potential therapeutic target for NPC. © 2016 Wiley Periodicals, Inc.

Imaging mass spectrometry for accessing molecular changes during burn wound healing

The spatiotemporal analysis of the proteomic profile during human wound healing is a critical investigative step that can establish the complex interplay of molecular events that comprise the local response to burn injury. Partial-thickness wound samples with adjacent "normal" skin were collected from twenty-one patients with burn wounds and examined across a time spectrum ranging from the acute injury period at 3, 6, 11 days to the later hypertrophic scar period at 7 and 15 months. The techniques used for histology-directed tissue analyses highlighted inflammatory protein markers at the early time points after injury with diminished expression as burn wounds progressed into the proliferative phase. The datasets show the usefulness of MALDI MS and imaging mass spectrometry as discovery approaches to identify and map the cutaneous molecular sequence that is activated in response to the unique systemic inflammatory response following burn trauma. This information has the potential to define the unique factors that predispose human burn victims to disfiguring hypertrophic scar formation.

S100A6 Regulates Endothelial Cell Cycle Progression by Attenuating Antiproliferative Signal Transducers and Activators of Transcription 1 Signaling

OBJECTIVE

S100A6, a member of the S100 protein family, has been described as relevant for cell cycle entry and progression in endothelial cells. The molecular mechanism conferring S100A6's proliferative actions, however, remained elusive.

APPROACH AND RESULTS

Originating from the clinically relevant observation of enhanced S100A6 protein expression in proliferating endothelial cells in remodeling coronary and carotid arteries, our study unveiled S100A6 as a suppressor of antiproliferative signal transducers and activators of transcription 1 signaling. Discovery of the molecular liaison was enabled by combining gene expression time series analysis with bioinformatic pathway modeling in S100A6-silenced human endothelial cells stimulated with vascular endothelial growth factor A. This unbiased approach led to successful identification and experimental validation of interferon-inducible transmembrane protein 1 and protein inhibitors of activated signal transducers and activators of transcription as key components of the link between S100A6 and signal transducers and activators of transcription 1.

CONCLUSIONS

Given the important role of coordinated endothelial cell cycle activity for integrity and reconstitution of the inner lining of arterial blood vessels in health and disease, signal transducers and activators of transcription 1 suppression by S100A6 may represent a promising therapeutic target to facilitate reendothelialization in damaged vessels.

High-level S100A6 promotes metastasis and predicts the outcome of T1-T2 stage in clear cell renal cell carcinoma

S100A6 (calcyclin), functions in cell cycle progression and differentiation, has been reported to promote the tumorigenesis and malignancy of many types of cancers. Clear cell renal cell carcinoma (ccRCC) is the most common subtype of RCC, lacking both promising prognostic markers and effective therapeutic targets. In our previous study, we have found the elevated S100A6 in the ccRCC tumor tissues, and the differentially expressed genes determined by microarray analysis were found to be strongly related to tumor metastasis after S100A6 knockdown and overexpression in the ccRCC cell line 786-O. The mRNA expression of S100A6 detected by RT-PCR in 6 cell lines and 174 tumor tissues, including 58 metastatic ccRCC and 116 clinicopathological features paired non-metastatic ccRCC (1:2), indicated S100A6 was elevated in the metastatic cells and tumor tissues. The protein expression was consistent with mRNA expression. The biological function of S100A6 in promoting metastasis was determined through overexpression and knockdown of S100A6 in the ccRCC cell lines 786-O, caki-1, and ACHN. In the scratch wound migration assay as well as migration and invasion assays, S100A6 knockdown significantly suppressed the migratory and invasive abilities of tumor cells, whereas overexpression enhanced the malignancy. Further research with the follow-up data of 129 ccRCC patients were analyzed by the Cox regression and survival analysis. The expression of S100A6 was up-regulated in metastatic ccRCC cells. In the metastatic tumor tissues, the expression of S100A6 was also higher than in the non-metastatic tissues. High S100A6 expression might be crucial to promote metastasis in ccRCC by enhancing the ability of tumor cells migration and invasion. In addition, the quantitative mRNA expression of S100A6 in the tumor tissues was an independent risk factor and might be used as a prognostic marker for the metastatic risk of the localized T1-T2 stage ccRCC.

S100A6 expression in cutaneous smooth muscle neoplasms

The S100A6 protein is expressed in a variety of tissues and distinct staining patterns in S100A6 immunohistochemistry may be useful in the differential diagnosis of difficult lesions. We evaluated the staining pattern of the S100A6 antibody in 22 cases each of pilar leiomyoma (LM), angioleiomyoma (ALM), and cutaneous leiomyosarcoma (LMS). S100A6 labeled both the nucleus and cytoplasm of myocytes in positive cases. About 64% of LM and 86% ALM had positive staining to the S100A6 antibody but predominantly in a weak staining pattern. In contrast, 95% of the LMS exhibited moderate to strong staining with the S100A6 antibody. The difference in the frequency of positive cases was statistically significant in the LM vs LMS comparison (p = 0.025), but we found intensity of staining to be of greatest practical utility. Analysis between the groups taking in to consideration differences in intensity of staining using the nonparametric rank sum (Mann-Whitney U test) demonstrated that there was a statistically significant difference between LM and LMS and between ALM and LMS. Weak or absent S100A6 staining supports a diagnosis of LM, whereas strong positive staining supports a diagnosis of LMS.

Effect of S100A6 over-expression on β-catenin in endometriosis

AIM

S100A6 is over-expressed in several human tumors, including pancreatic carcinoma, malignant fibrous histiocytoma, breast, colon, and gastric carcinoma, but little is known about the role of S100A6 in endometriosis. The aim of the present study was to investigate the effect of S100A6 over-expression on β-catenin in endometrial stromal cells.

METHODS

Endometrial stromal cells were transfected with an hS100A6-expressing recombinant lentivirus construct. The expression of β-catenin was assessed using western blot and reverse transcription-polymerase chain reaction.

RESULTS

S100A6 over-expression promoted β-catenin expression at the RNA and protein levels, in endometrial stromal cells.

CONCLUSIONS

S100A6 induces expression of β-catenin in endometrial stromal cells.

S100A6 expression in keratinocytes and its impact on epidermal differentiation

S100A6 is a calcium binding protein expressed in many types of epithelia including epidermis. S100A6 is a binding partner of a number of proteins engaged in cytoskeletal organization, cell cycle control, stress response or apoptosis. So far the effect of its overexpression or knock-down on cell physiology has been studied only at the cellular level. Here, we used an in vitro model of differentiating epidermis to study the role of S100A6 at the tissue level and in the context of tissue differentiation. First of all we have shown that S100A6 mRNA level diminished several fold during primary keratinocyte differentiation and investigated the epigenetic and transcriptional mechanisms involved in this tight expression control. Using bisulfite treatment, luciferase assay and chromatin immunoprecipitation we found that changes in S100A6 expression were DNA methylation independent but could be orchestrated by epidermal specific factors: the ΔNp63 transcription factor and retinoic acid. To investigate if the drop-down in S100A6 expression is indeed critical for keratinocyte differentiation we developed HaCaT cells with stable S100A6 knock-down or overexpression and tested them in 2- and 3-dimensional (organotypic) culture conditions. S100A6 overexpressing cells exhibited accelerated proliferation, enhanced adhesion properties and suppressed loricrin expression - features typical for undifferentiated keratinocytes. In organotypic culture these cells formed thicker epidermis with more Ki67 positive cells, keratin 10 expression spatially limited to the uppermost cell layers and non-detectable loricrin expression. Together, results obtained in both culture models proved that increased S100A6 content in keratinocytes dramatically changed the pace and extent of epidermal differentiation.

S100A6 (calcyclin) is a novel marker of neural stem cells and astrocyte precursors in the subgranular zone of the adult mouse hippocampus

S100A6 (calcyclin), an EF-hand calcium binding protein, is considered to play various roles in the brain, for example, cell proliferation and differentiation, calcium homeostasis, and neuronal degeneration. In addition to some limbic nuclei, S100A6 is distributed in the rostral migratory stream, one of the major neurogenic niches of the adult brain. However, the potential involvement of S100A6 in adult neurogenesis remains unclear. In this study, we aimed to elucidate the role of S100A6 in the other major neurogenic niche, the subgranular zone of the dentate gyrus in the adult mouse hippocampus. Immunofluorescent multiple labeling showed that S100A6 was highly expressed in neural stem cells labeled by sex determining region Y-box 2, brain lipid-binding protein protein and glial fibrillary acidic protein. S100A6+ cells often extended a long process typical of radial glial morphology. In addition, S100A6 was found in some S100β+ astrocyte lineage cells. Interestingly, proliferating cell nuclear antigen was detected in a fraction of S100A6+/S100β+ cells. These cells were considered to be lineage-restricted astrocyte precursors maintaining mitotic potential. On the other hand, S100A6 was rarely seen in neural lineage cells labeled by T-box brain protein 2, doublecortin, calretinin and calbindin D28K. Cell fate-tracing experiment using BrdU showed that the majority of newly generated immature astrocytes were immunoreactive for S100A6, while mature astrocytes lacked S100A6 immunoreactivity. Administration of S100 protein inhibitor, trifluoperazine, caused a reduction in production of S100β+ astrocyte lineage cells, but had no impact on neurogenesis. Overall, our data provide the first evidence that S100A6 is a specific marker of neural stem cells and astrocyte precursors, and may be especially important for generation of astrocytes in the adult hippocampus.

Aberrant expression of S100A6 and matrix metalloproteinase 9, but not S100A2, S100A4, and S100A7, is associated with epidermal carcinogenesis

BACKGROUND

S100 proteins belong to a family of calcium-binding proteins that regulate cell proliferation and differentiation. Despite our growing knowledge about the biology of S100 proteins in some human cancers, little is known about the expression of S100 family members in epidermal tumors and their clinical significance.

OBJECTIVE

To determine the expression of S100A2, S100A4, S100A6, S100A7, as well as matrix metalloproteinases 9 (MMP9) in a spectrum of epidermal tumors with benign and malignant characteristics.

METHODS

Immunohistological staining was performed for S100A2, S100A4, S100A6, S100A7, and MMP9 in 101 cases of various types of epidermal tumors, viz., squamous cell carcinoma (SCC), Bowen's disease (BD), actinic keratosis (AK), basal cell carcinoma (BCC), keratoacanthoma (KA), and seborrheic keratosis (SK). Thirteen specimens of normal skin (NS) served as control.

RESULTS

S100A2, S100A6, and S100A7 positive immunostaining was variably observed in different epidermal tumors. S100A4 staining was not observed in any epidermal tumors, but was clearly visible in dendritic cells. MMP9 immunostaining was positive only in 22/26 (84.62%) of SCC and 2/15 (13.33%) of BD cases. Expression of S100A2, S100A6, and S100A7 was increased in tumor cells compared to NS. However, only S100A6 expression was significantly associated with malignant transformation of epidermal tumors. Moreover, S100A6 expression was correlated with MMP9 expression in metastatic SCC.

CONCLUSIONS

Epidermal tumors show increased expression of S100A2 and S100A7 proteins. S100A4 may be a useful and distinct marker for epidermal dendritic cells. Expression of S100A6 and MMP9 in combination is associated with the development of SCC.

The S100A6 calcium-binding protein regulates endothelial cell-cycle progression and senescence

Endothelial cells regulate many aspects of vascular physiology, including vasculogenesis and angiogenesis. The S100 family of calcium-binding proteins regulates many aspects of cell function but their roles in vascular physiology are less well understood. Herein, we investigated the expression and function of S100-related family members in endothelial cells. Analysis of total endothelial mRNAs using a human gene chip array revealed significant gene expression of the S100 calcium-binding protein family members S100A6, S100A10, S100A11 and S100A13. We then examined the expression and functional properties of the major S100 family member, S100A6, in vascular endothelial cells. Comparison of primary and transformed human cells revealed significant differences in S100A6 protein levels in these cells. In primary human endothelial cells, S100A6 was present in both the nucleus and the cytoplasm. To assess the function of endothelial S100A6, we depleted protein levels using RNA interference and this caused increased cell-cycle arrest in the G2/M phase under different conditions. S100A6 depletion caused a decrease in both cyclin-dependent kinase 1 (CDK1) and phospho-CDK1 levels, which are essential for eukaryote cell-cycle progression. S100A6 depletion also decreased expression of CDK1, cyclin A1 (CCNA1) and cyclin B (CCNB1) genes with effects on cell-cycle progression. Depletion of endothelial S100A6 levels also elevated β-galactosidase expression, which is an important hallmark of cellular senescence and exit from the mammalian cell cycle. We thus propose that S100A6 has an important role in regulating endothelial commitment to, and progression through, the cell cycle.

Immunohistochemical Characterization of S100A6 in the Murine Ovary

S100 proteins comprise a large family of Ca(2+)-binding proteins and exhibit a variety of intra- and extracellular functions. Despite our growing knowledge about the biology of S100 proteins in some tissues such as brain and smooth muscle, little is known about S100 proteins in the normal mammalian reproductive tissue. In the present study, we investigated the distribution pattern of S100A6 (alternatively named calcyclin) in the murine ovary by immunohistochemical study using specific antibody. S100A6 was localized substantially in the cytoplasm of luteal cells, with concomitant expression of S100A11, another S100 protein, but not in the other type of cells such as oocytes, follicle epithelial cells (granulosa cells), and cells of stroma including theca interna cells in the murine ovary. S100A6-immunoreactive corpora lutea (CLs) were divided into two types: homogeneously and heterogeneously stained CLs, and possibly they may represent differentiating and mature CL, respectively. Our regression analysis revealed that expression level of S100A6 positively correlated with that of cytochrome P450 11A, a steroidogenic enzyme in the heterogeously stained CL. These results suggested that S100A6 may contribute to differentiation of steroidogenic activity of luteal cells in a synergistic manner with S100A11 by facilitating some shared functions.

S100A6 overexpression is associated with poor prognosis and is epigenetically up-regulated in gastric cancer

S100A6 has been implicated in a variety of biological functions as well as tumorigenesis. In this study, we investigated the expression status of S100A6 in relation to the clinicopathological features and prognosis of patients with gastric cancer and further explored a possible association of its expression with epigenetic regulation. S100A6 expression was remarkably increased in 67.5% of gastric cancer tissues as compared with matched noncancerous tissues. Statistical analysis demonstrated a clear correlation between high S100A6 expression and various clinicopathological features, such as depth of wall invasion, positive lymph node involvement, liver metastasis, vascular invasion, and tumor-node metastasis stage (P < 0.05 in all cases), as well as revealed that S100A6 is an independent prognostic predictor (P = 0.026) significantly related to poor prognosis (P = 0.0004). Further exploration found an inverse relationship between S100A6 expression and the methylation status of the seventh and eighth CpG sites in the promoter/first exon and the second to fifth sites in the second exon/second intron. In addition, the level of histone H3 acetylation was found to be significantly higher in S100A6-expressing cancer cells. After 5-azacytidine or trichostatin A treatment, S100A6 expression was clearly increased in S100A6 low-expressing cells. In conclusion, our results suggested that S100A6 plays an important role in the progression of gastric cancer, affecting patient prognosis, and is up-regulated by epigenetic regulation.

Immunohistochemical expression of S100A6 in cellular neurothekeoma: clinicopathologic and immunohistochemical analysis of 31 cases

Neurothekeoma is a term introduced by Gallager and Helwig describing a superficial tumor of purported nerve sheath derivation, with cellular and myxoid types. Recently, it has been suggested that the cellular type does not have nerve sheath differentiation. This subtype represents an uncommon neoplasm and sometimes can be problematic to diagnose because it can be easily mistaken for melanoma. We studied the immunohistochemical features of 31 cases of cellular neurothekeomas to evaluate their immunoprofile. Immunohistochemical studies were performed in all 31 cases with formalin-fixed paraffin-embedded tissue sections with antibodies against S100 protein, S100A6, and melanoma antigen recognized by T-cells (MART-1). In addition, 8 cases were evaluated for HMB-45 antigen, keratin (with a pankeratin cocktail), epithelial membrane (EMA), and smooth muscle antigen (SMA). The lesions were from 8 men and 23 women aged 6-64 years (mean 35 years). Four tumors were located on the nose; 4 scalp; 4 finger; 3 thigh; 2 shoulder; 2 wrist; 2 hand; and 1 each on pelvis, cheek, toe, chest, eyebrow, forearm, penis, axilla, mouth, and leg. All tumors were positive for S100A6 (100%) and negative for cytokeratin, HMB-45 antigen, MART-1, and EMA (100%); 29 cases were negative for S100 protein (93.5%; the 2 positive cases had only scattered cells labeled), and only 2 cases were focally positive for SMA (7.5%). Therefore, the combination of strong immunoreactivity for S100A6, in nested dermal spindle cell proliferations, and lack of S100 protein or keratin, supports a diagnosis of cellular neurothekeoma.

Up-regulation of RAGE and S100A6 in rats exposed to cigarette smoke

Cigarette smoke has been widely investigated in terms of epidemiology and pathological endpoints in relation to human lung diseases and animal study. In this study we exposed Wistar rats to cigarette smoke at concentrations of 20% and 60% to explore potential molecular mechanisms at the protein level. Exposures were conducted twice a day, 5 days a week for 43 weeks. As a major metabolite of nicotine in cigarette, cotinine level in rat urine was determined by HPLC-MS. A dose-dependent analysis indicated that cotinine may be used as an exposure marker of cigarette smoke. Expression of receptor for advanced glycation endproducts (RAGE), an immunoglobulin super family that triggers the intracellular signal cascade reaction leading to inflammation and its ligand S100A6 (calgranulin) in bronchial epithelial cells and lung tissues of rats, were found to be positive correlated with cotinine levels, indicating that RAGE and S100A6 may be attributable to inflammation and oxidative damage caused by cigarette smoke.

Inhibition of cancer cell proliferation by designed peptide amphiphiles

HOX genes encode conserved transcription factors that control the morphological diversification along the anteroposterior body axis. HOX proteins bind to DNA through a highly conserved 60 amino acid sequence called the homeodomain, and greater DNA binding specificity and stability are achieved when it forms complexes with cofactors such as PBX and MEIS in humans. In particular, HOX proteins from paralog groups 1-8, interact with PBX proteins via a specific and highly conserved hydrophobic six amino acid sequence localized in the N-terminal region of HOX. In several oncogenic transformations, deregulated HOX gene expression has been observed, indicating an involvement of these transcriptional regulators in carcinogenesis and metastasis. Inhibition of the HOX-PBX interaction could be a strategy to control the abnormal proliferation of these cancer cells. In this study we describe a small designed peptide amphiphile (PA) which self-assembles into micelles and shows inhibition of T3M4 pancreatic cancer cells, K562 leukemia cells and MJT1 melanoma cells while non-cancerous fibroblast NIH 3T3 cells are less affected. This molecule contains three critical regions: a 9-amino-acid sequence designed to disrupt HOX/PBX/DNA complex formation, a 16-amino-acid sequence to deliver the peptide into the cell and a 16-carbon-acyl chain which we show leads to the molecule's self-assembly and significantly enhances the effectiveness of the molecule to slow cell proliferation.

S100-annexin complexes--biology of conditional association

S100 proteins and annexins both constitute groups of Ca2+-binding proteins, each of which comprises more than 10 members. S100 proteins are small, dimeric, EF-hand-type Ca2+-binding proteins that exert both intracellular and extracellular functions. Within the cells, S100 proteins regulate various reactions, including phosphorylation, in response to changes in the intracellular Ca2+ concentration. Although S100 proteins are known to be associated with many diseases, exact pathological contributions have not been proven in detail. Annexins are non-EF-hand-type Ca2+-binding proteins that exhibit Ca2+-dependent binding to phospholipids and membranes in various tissues. Annexins bring different membranes into proximity and assist them to fuse, and therefore are believed to play a role in membrane trafficking and organization. Several S100 proteins and annexins are known to interact with each other in either a Ca2+-dependent or Ca2+-independent manner, and form complexes that exhibit biological activities. This review focuses on the interaction between S100 proteins and annexins, and the possible biological roles of these complexes. Recent studies have shown that S100-annexin complexes have a role in the differentiation of gonad cells and neurological disorders, such as depression. These complexes regulate the organization of membranes and vesicles, and thereby may participate in the appropriate disposition of membrane-associated proteins, including ion channels and/or receptors.

Peripheral blood B lymphocytes derived from patients with idiopathic pulmonary arterial hypertension express a different RNA pattern compared with healthy controls: a cross sectional study

BACKGROUND

Idiopathic pulmonary arterial hypertension (IPAH) is a progressive and still incurable disease. Research of IPAH-pathogenesis is complicated by the lack of a direct access to the involved tissue, the human pulmonary vasculature. Various auto-antibodies have been described in the blood of patients with IPAH. The purpose of the present work was therefore to comparatively analyze peripheral blood B lymphocyte RNA expression characteristics in IPAH and healthy controls.

METHODS

Patients were diagnosed having IPAH according to WHO (mean pulmonary arterial pressure > or = 25 mmHg, pulmonary capillary occlusion pressure < or = 15 mmHg, absence of another explaining disease). Peripheral blood B-lymphocytes of patients and controls were immediately separated by density gradient centrifugation and magnetic beads for CD19. RNA was thereafter extracted and analyzed by the use of a high sensitivity gene chip (Affymetrix HG-U133-Plus2) able to analyze 47000 transcripts and variants of human genes. The array data were analyzed by two different softwares, and up-and down-regulations were defined as at least 1.3 fold with standard deviations smaller than fold-changes.

RESULTS

Highly purified B-cells of 5 patients with IPAH (mean pulmonary artery pressure 51 +/- 13 mmHg) and 5 controls were analyzed. Using the two different analyzing methods we found 225 respectively 128 transcripts which were up-regulated (1.3-30.7 fold) in IPAH compared with healthy controls. Combining both methods, there were 33 overlapping up-regulated transcripts and no down-regulated B-cell transcripts.

CONCLUSION

Patients with IPAH have a distinct RNA expression profile of their peripheral blood B-lymphocytes compared to healthy controls with some clearly up-regulated genes. Our finding suggests that in IPAH patients B cells are activated.

Expression of S100A6 protein in a broad spectrum of cutaneous tumors using tissue microarrays

BACKGROUND

S100A6, a calcium-binding protein in the S100 family, has been observed in melanocytic nevi, neural tumors, fibrohistiocytic tumors and is overexpressed in melanoma. Previous studies reported S100A6 expression in atypical fibroxanthomas (AFX) but not in a small number of desmoplastic melanomas (DM). Limited data on S100A6 expression in cutaneous epithelial tumors exists in the literature. The goal of this study was to determine the specificity and sensitivity of S100A6 protein in a spectrum of cutaneous mesenchymal or epithelial tumors.

METHODS

Tissue microarrays of cutaneous epithelial neoplasms, mesenchymal neoplasms, DM and malignant peripheral nerve sheath tumors (MPNST) were stained with S100A6 antibody.

RESULTS

Eleven basal cell carcinomas (BCC) failed to express S100A6, whereas all 10 squamous cell carcinomas (SCC) expressed S100A6. Four of seven microcystic adnexal carcinomas (MAC) stained for S100A6. Tumors with duct differentiation variously expressed S100A6 protein, with two hidradenomas showing the strongest staining. Malignant spindle cell tumors, with the exception of 13 of 30 MPNST, had a high incidence of S100A6 positivity.

CONCLUSIONS

S100A6 expression may distinguish SCC from BCC, MAC from BCC and hidradenoma from other adnexal tumors. S100A6 expression favors DM over MPNST but overlap limits its diagnostic use.

Radon-induced proteomic profile of lung tissue in rats

The aim of this study was to investigate the differential expression of proteins in lung of rats following long-term exposure to radon. The total proteins of lung tissue from Wistar rats exposed to radon for cumulative doses up to 100, 200, or 400 WLM (working level months) were isolated by two-dimensional electrophoresis (2-DE) and analyzed with ImageMaster 2D Platinum software. Comparison of the 2-DE images between the control and radon-exposed groups resulted in 14 upregulated and 9 downregulated protein spots, of which 15 were identified by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) or matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry (MALDI-TOF/TOF-MS). The simultaneous up-expressions of RAGE and S100A6 indicated that both proteins might be applied as biomarkers for lung injury induced by long-term radon exposure.

Upregulated expression of S100A6 in human gastric cancer

OBJECTIVE

The expression of S100A6 (calcyclin), a member of the S100 calcium binding protein family, is elevated in a number of malignant tumors, but there have been few reports about its expression in gastric cancer. The aim of this study was to investigate its expression regulations in human gastric cancer and noncancerous mucosa, and the response to chemotherapeutic drugs in the gastric cancer cell line.

MATERIALS AND METHODS

In one matched gastric cancer sample pair, the serial analysis of gene expression (SAGE) experiment was conducted to compare the gene expression profiles between cancerous and adjacent tissues. To detect the expression regulations among more cancerous tissues, microarrays were carried out and real-time RT-PCR was conducted to validate the results. At the protein level, Western blot and tissue microarray (TMA) examination were further used to verify S100A6 expression. The regulation detection of S100A6 with flurouracil and doxorubicin at the mRNA and protein level was performed in the SGC7901 cell line.

RESULTS

With the SAGE strategy, five times more S100A6 tags were identified in cancer tissues than in normal tissues. With the cDNA microarray, S100A6 was found to be significantly upregulated in 21 of 42 (50%) nonselective gastric cancers. In 10 other paired samples, the upregulation of S100A6 was consolidated with RT-PCR and Western blot analysis as well. A total of 14 endoscopy-sectioned gastric noncancerous lesions and corresponding normal gastric mucosa were also applied to profile the gene expression; both cDNA microarray and RT-PCR demonstrated no significant alterations of S100A6 at the mRNA level. TMA examination showed that 34 of 52 (65.4%) cancer samples were positively stained, while only 17 of 80 (21.3%) noncancerous lesions were positively detected and all nine normal mucosae were detected to be negative. An in vitro experiment showed that in the gastric cell line SGC-7901, S100A6 mRNA was detected to be upregulated from 24 to 72 h after treatment with 5 mg/L 5-flurouracil or 0.3 mg/L doxorubicin, and there were two wave upregulations of the S100A6 protein.

CONCLUSION

The observed regulated expression of S100A6 suggests that it is associated with gastric cancer tumorigenesis and quantitation of S100A6 is a promising tool for diagnosis of gastric cancer.

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.

Binding and functional characteristics of two E-box motifs within the S100A6 (calcyclin) gene promoter

S100A6 (calcyclin) is a small calcium-binding protein of the S100 family often associated with cancer and metastasis. We have previously shown that the E-box sequence at position -283/-278 of the S100A6 gene promoter interacts with USF transcription factor and contributes to promoter transcriptional activity. We now present evidence that a second E-box motif at position -593/-588 of the promoter also binds USF and that the USF1/USF2 heterodimer is the prevailing dimeric form of the transcription factor bound. Using the chromatin immunoprecipitation assay (ChIP), we show that USF is bound in vivo to the E-box regulatory element(s). Depletion of the endogenous USF pool by means of a decoy oligonucleotide evokes a severe inhibition of S100A6 gene promoter activity. Furthermore, we show that S100A6 gene promoter activity can be stimulated by palmitate and that mutation of the -283/-278 E-box sequence completely blocks this stimulation.

Calcium Homeostasis in Human Placenta: Role of Calcium‐Handling Proteins

The human placenta is a transitory organ, representing during pregnancy the unique connection between the mother and her fetus. The syncytiotrophoblast represents the specialized unit in the placenta that is directly involved in fetal nutrition, mainly involving essential nutrients, such as lipids, amino acids, and calcium. This ion is of particular interest since it is actively transported by the placenta throughout pregnancy and is associated with many roles during intrauterine life. At term, the human fetus has accumulated about 25-30 g of calcium. This transfer allows adequate fetal growth and development, since calcium is vital for fetal skeleton mineralization and many cellular functions, such as signal transduction, neurotransmitter release, and cellular growth. Thus, there are many proteins involved in calcium homeostasis in the human placenta.

Promoter hyper-methylation of calcium binding proteins S100A6 and S100A2 in human prostate cancer

BACKGROUND

S100A6 and S100A2 are members of the S100 family of calcium binding proteins, which are down regulated in prostate cancer, however the molecular mechanism(s) underlying their loss of expression is unknown.

METHODS

The promoter and exon 1 region of the S100A6 and S100A2 genes was sequenced in bisulfite modified DNA from non-malignant, benign prostatic hyperplasia (BPH), malignant and metastatic prostate tissues and in cell lines. Immunohistochemistry was performed to correlate S100A2 expression with methylation status.

RESULTS

S100A6 methylation was absent or occurred at isolated sites in 14/14 cases of non-malignant epithelium and 5/5 cases of BPH tissues, whereas methylation was seen in 14/27 (52%) cases of prostatic cancer (P<0.0001), 2/2 cases of metastatic cancer and in the CWR22 prostatic cancer xenograft. Critical CpG sites within the S100A2 promoter were methylated in LNCaP, LNCaP-LN3, and CWR22 cells but not in Du145, PC3 or BPH45 cells. In tissues, S100A2 methylation was seen in 32/34 (94%) cases of adenocarcinoma and 5/5 cases of metastatic cancer. However, S100A2 methylation was also seen in 9/12 (75%) cases of non-malignant tissues and in 5/5 cases of BPH. Immunostaining, showed absent S100A2 expression all 41 cases of prostatic cancer, whereas staining was seen in the basal cells of non-malignant epithelium.

CONCLUSIONS

Loss of S100A6 and S100A2 proteins is frequent in human prostatic cancer. A major mechanism underlying the loss of S100A6 expression appears to involve promoter hyper-methylation. However, mechanisms other than methylation of the known promoter are involved in silencing S100A2 in the prostate.

The Ankrd2, Cdkn1c and Calcyclin Genes are Under the Control of MyoD During Myogenic Differentiation

Skeletal muscle development requires the coordinated expression of numerous transcription factors to control the specification of the muscle fate in mesodermal cells and the differentiation of the committed myoblasts into functional contractile fibers. The bHLH transcription factor MyoD plays a key role in these processes, since its forced expression is sufficient to induce the myogenesis in a variety of non-muscle cells in culture. Consistent with this observation, the majority of skeletal muscle genes require MyoD to activate their own transcription. In order to identify novel MyoD-target genes we generated C2C12 MyoD-silenced clones, and used a muscle-specific cDNA microarray to study the induced modifications of the transcriptional profile. Gene expression was analyzed at three different stages in differentiating MyoD(-)C2C12 myoblasts. These microarray data sets identified many additional uncharacterized downstream MyoD transcripts that may play important functions in muscle cell differentiation. Among these genes, we concentrated our study on the cell cycle regulators Cdkn1c and calcyclin and on the muscle-specific putative myogenic regulator Ankrd2. Bioinformatic and functional studies on the promoters of these genes clarified their dependence on MyoD activity. Clues of other regulatory mechanisms that might interact with the principal bHLH transcription factor have been revealed by the unexpected up-regulation in MyoD(-) cells of these novel (and other) target transcripts, at the differentiation stage in which MyoD became normally down-regulated.

Expression of S100A2 and S100A6 in thyroid carcinomas

AIMS

S100 calcium-binding proteins are known to play multiple roles in carcinoma development. In this study, we focused on two kinds of these proteins, S100A2 and S100A6, and investigated their expression in thyroid neoplasms.

METHODS AND RESULTS

We investigated S100A2 and S100A6 expression in 141 thyroid neoplasms by immunohistochemistry. S100A2 was not expressed in normal follicles or follicular tumours, with one exception. Although 89.5% of papillary carcinoma were positive for S100A2, the expression was heterogeneous except in two cases. In anaplastic carcinoma, 78.5% of cases expressed S100A2 diffusely, while the remaining cases were negative. In normal follicles, S100A6 expression was always low, while 8.3% of follicular adenomas and 39.5% of follicular carcinomas showed increased expression. In papillary carcinomas, S100A6 expression was increased in 75% of cases, but in anaplastic carcinomas it was decreased, with only 14.3% showing high expression.

CONCLUSIONS

The expression patterns of S100A2 and S100A6 in thyroid neoplasms are unique compared with those of other carcinomas, suggesting that: (i) S100A2 and S100A6 contribute to certain events in papillary carcinoma progression, and (ii) S100A2 expression is one of the biological characteristics of anaplastic carcinoma.

Calcyclin (S100A6) expression is stimulated by agents evoking oxidative stress via the antioxidant response element

Calcyclin (S100A6) is a cell-specific, calcium binding protein of the S100 family whose expression is augmented in many types of cancer. By means of luciferase activity assays, RT-PCR and Northern blot hybridization, we established that transcription of S100A6 gene is increased by agents known to evoke oxidative stress. Mutation of the antioxidant response element (ARE) located at position -290/-281 of the calcyclin gene promoter, and overlapping the E-box sequence recognized by the upstream stimulatory factor (USF), led to inhibition of calcyclin gene promoter activity stimulated by cadmium ions. Electrophoretic mobility shift assays (EMSA) with the -302/-260 calcyclin gene promoter fragment revealed, apart from USF binding, the presence of another protein complex (N) shown by competitive EMSA to be bound to ARE. DNA affinity chromatography followed by Western blot showed the binding of Nrf2 transcription factor to the immobilized calcyclin gene promoter fragment and concomitant appearance of complex N in EMSA of the eluted fractions. The results indicate that agents evoking oxidative stress activate calcyclin gene via the ARE sequence in its promoter.

S100A6 (Calcyclin) is a prostate basal cell marker absent in prostate cancer and its precursors

S100A6 (Calcyclin) is a calcium-binding protein that has been implicated in a variety of biological functions as well as tumorigenesis. The aim of our study was to investigate the involvement of S100A6 during prostate cancer development and progression. Using immunohistochemistry, the expression of S100A6 was examined in benign (n=66), premalignant (n=10), malignant (n=66) and metastatic prostate (n=5) tissues arranged in a tissue-microarray or whole sections as well as in prostate cancer cell lines. The S100A6 immunostaining pattern in tissues was compared with that of cytokeratin 5 (a basal cell marker) and 18 (a benign luminal cell marker). In all cases of benign epithelium, intense S100A6 expression was seen in the basal cell layer with absent staining in luminal cells. In all cases of prostatic adenocarcinoma (matched), metastatic lesions and 3/10 high-grade prostatic intraepithelial neoplasia lesions, an absence of S100A6 was seen. Western blotting and RT–PCR analysis of cell lines showed S100A6 expression to be absent in LNCaP, LNCaP-LN3 and LNCaP-Pro5 but present in Du145, PC3, PC-3M and PC-3M-LN4. LNCaP cells treated with 5-Azacytidine, caused re-expression of S100A6 mRNA. Sequencing of bisulphite modified DNA showed CpG methylation within the S100A6 promoter region and exon 1 of LNCaP, LNCaP-LN3 and LNCaP-Pro5 cell lines but not in Du145 cells. Our data suggest that loss of S100A6 protein expression is common in prostate cancer development and may occur at an early stage. The mechanism of loss of expression may involve hypermethylation of CpG sites. The finding of intense S100A6 expression in the basal cells of benign glands but loss of expression in cancer could be useful as a novel diagnostic marker for prostate cancer.

Serial Analysis of Gene Expression in Neurofibromatosis Type 2–Associated Vestibular Schwannoma

HYPOTHESIS

The genesis, morphology, and growth characteristics of vestibular schwannomas are determined by genetic alterations which vary gene transcript expression and this transcript expression can be qualitatively and quantitatively evaluated using the SAGE technique. By use of such technique, gene products with tumorigenic potential may be identified, providing insight and targets for future study.

BACKGROUND

Serial analysis of gene expression (SAGE) is a powerful new technique that allows detailed qualitative and quantitative evaluation of cellular gene transcript expression. Tissue in limited quantity (5 x 10 to 2 x 10 cells) may be analyzed by a modified version of SAGE called microSAGE. Application of SAGE or microSAGE to study vestibular schwannoma gene expression has not been previously reported.

METHODS

Fresh, vestibular schwannoma specimen from an individual with the diagnosis of neurofibromatosis type 2 was attained intraoperatively and maintained in a sealed container at -80degreesC until the time of analysis. The tissue was processed according to the microSAGE protocol, using 180 mg of vestibular schwannoma as starting material.

RESULTS

The protocol resulted in the generation and sequencing of a tag library involving 458 tags representing 277 different gene products, including many transcripts known to be expressed in vestibular schwannomas. Several gene products with tumorigenic potential were identified.

CONCLUSIONS

These data demonstrate that microSAGE is a useful technique to study vestibular schwannoma gene expression. Future studies will include building more comprehensive libraries and comparing libraries from various vestibular schwannoma phenotypes to identify useful diagnostic or prognostic markers, and targets for therapeutic intervention.

Annexin 11 is required for midbody formation and completion of the terminal phase of cytokinesis

Annexins are Ca(2+)-binding, membrane-fusogenic proteins with diverse but poorly understood functions. Here, we show that during cell cycle progression annexin 11 translocates from the nucleus to the spindle poles in metaphase and to the spindle midzone in anaphase. Annexin 11 is recruited to the midbody in late telophase, where it forms part of the detergent-resistant matrix that also contains CHO1. To investigate the significance of these observations, we used RNA interference to deplete cells of annexin 11. A combination of confocal and video time-lapse microscopy revealed that cells lacking annexin 11 fail to establish a functional midbody. Instead, daughter cells remain connected by intercellular bridges that contain bundled microtubules and cytoplasmic organelles but exclude normal midbody components such as MKLP1 and Aurora B. Annexin 11-depleted cells failed to complete cytokinesis and died by apoptosis. These findings demonstrate an essential role for annexin 11 in the terminal phase of cytokinesis.

Involvement of NF-kappaB in the regulation of S100A6 gene expression in human hepatoblastoma cell line HepG2

S100A6 (calcyclin) is an acidic calcium binding protein with two EF-hand motifs and overexpressed in several tumors including intrahepatic carcinoma. TNFalpha, a strong NF-kappaB activator required for hepatocyte proliferation during liver regeneration, triggered the expression of S100A6 mRNA in human hepatoblastoma cell line HepG2. Transient expression of NF-kappaB (p65) increased S100A6 promoter activity and expression of inhibitor of NF-kappaB (IkappaBalpha) decreased TNFalpha-induced S100A6 promoter activity. To confirm the involvement of NF-kappaB in S100A6 promoter activation, we analyzed serially deleted promoter constructs of the S100A6 gene by luciferase reporter assay and found a NF-kappaB-responsive DNA fragment at the position between -584 and -361. Electrophoretic mobility shift assays showed that TNFalpha induced p65 binding to a potential NF-kappaB binding site at -460/-451. Furthermore, treatment of cells with CAPE (caffeic acid phenethyl ester), a specific NF-kappaB (p65) inhibitor, decreased NF-kappaB binding and promoter activity. These results suggest that NF-kappaB transcription factor contributes to the activation of S100A6 gene expression in response to TNFalpha in HepG2 cells.

Calcium-regulated interaction of Sgt1 with S100A6 (calcyclin) and other S100 proteins

S100A6 (calcyclin), a small calcium-binding protein from the S100 family, interacts with several target proteins in a calcium-regulated manner. One target is Calcyclin-Binding Protein/Siah-1-Interacting Protein (CacyBP/SIP), a component of a novel pathway of beta-catenin ubiquitination. A recently discovered yeast homolog of CacyBP/SIP, Sgt1, associates with Skp1 and regulates its function in the Skp1/Cullin1/F-box complex ubiquitin ligase and in kinetochore complexes. S100A6-binding domain of CacyBP/SIP is in its C-terminal region, where the homology between CacyBP/SIP and Sgt1 is the greatest. Therefore, we hypothesized that Sgt1, through its C-terminal region, interacts with S100A6. We tested this hypothesis by performing affinity chromatography and chemical cross-linking experiments. Our results showed that Sgt1 binds to S100A6 in a calcium-regulated manner and that the S100A6-binding domain in Sgt1 is comprised of 71 C-terminal residues. Moreover, S100A6 does not influence Skp1-Sgt1 binding, a result suggesting that separate Sgt1 domains are responsible for interactions with S100A6 and Skp1. Sgt1 binds not only to S100A6 but also to S100B and S100P, other members of the S100 family. The interaction between S100A6 and Sgt1 is likely to be physiologically relevant because both proteins were co-immunoprecipitated from HEp-2 cell line extract using monoclonal anti-S100A6 antibody. Phosphorylation of the S100A6-binding domain of Sgt1 by casein kinase II was inhibited by S100A6, a result suggesting that the role of S100A6 binding is to regulate the phosphorylation of Sgt1. These findings suggest that protein ubiquitination via Sgt1-dependent pathway can be regulated by S100 proteins.

Identification of a putative calcium-binding protein as a dioxin-responsive gene in zebrafish and rainbow trout

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD, dioxin) is a widespread environmental contaminant that causes multiple effects in vertebrates. TCDD elicits its toxicity through aryl hydrocarbon receptor (AhR)-mediated modulation of gene regulation, increasing intracellular free calcium, and inducing calcium-mediated apoptosis in cell culture. Two TCDD-responsive cDNAs, which encode putative calcium-binding proteins, have been isolated from zebrafish and rainbow trout. The zebrafish and rainbow trout sequences are 88% similar to each other at the amino acid level and are orthologs of the human S100A4 calcium-binding protein. In zebrafish liver cell culture, treatment with TCDD increases S100A4a mRNA abundance. In juvenile rainbow trout, S100A4 mRNA was constitutively expressed in the heart, kidney, intestine, and spleen, but not in the liver. Exposure to TCDD significantly increased rainbow trout S100A4 mRNA abundance in the rainbow trout kidney. Taken together, these findings demonstrate in zebrafish and rainbow trout that dioxin increases expression of this EF-hand calcium-binding protein gene in a tissue-dependent fashion. However, demonstration that the encoded S100A4 proteins actually bind calcium and play a role in dioxin toxicity will require further study.

Calcyclin (S100A6) regulates pulmonary fibroblast proliferation, morphology, and cytoskeletal organization in vitro

Calcyclin (S100A6) is a member of the S100A family of calcium binding proteins. While the precise function of calcyclin is unknown, calcyclin expression is associated with cell proliferation and calcyclin is expressed in several types of cancer phenotypes. In the present study, the functional role of calcyclin was further elucidated in pulmonary fibroblasts. Antisense S100A6 RNA expression inhibited serum and mechanical strain-induced fibroblast proliferation. This attenuated proliferative response was accompanied by a flattened, spread cell morphology, and disruption of tropomyosin labeled microfilaments. Changes in cytoskeletal organization did not correspond with a decrease in tropomyosin levels. These observations suggest a role for calcyclin in modulating calcium dependent signaling events that regulate progression through the cell cycle. J. Cell. Biochem. 88: 848-854, 2003.

S100A6 overexpression within astrocytes associated with impaired axons from both ALS mouse model and human patients

Astrogliosis is one of the earliest pathological changes observed in neurodegenerative diseases in general and in amyotrophic lateral sclerosis (ALS) in particular. ALS is characterized by selective degeneration of motoneurons. There are 2 forms of the disease: sporadic ALS (SALS), comprising 90%-95% of cases, and familial ALS (FALS), comprising 5%-10% of cases. FALS is an age-dependent autosomal dominant disorder in which mutations in the homodimeric enzyme Cu/ Zn superoxide dismutase 1 (SOD1) is linked to the disease. The animal model for this disease is a transgenic mouse expressing the mutated human SOD1(G93A) gene. Here we show by immunohistochemistry and double immunofluorescence that astrocytes located near impaired axons of motoneurons that were selectively programmed to die overexpressed S100A6, a Ca2+/Zn2+ binding protein able to translocate into the nucleus. Transgenic mice overexpressing the mutated human SOD1 gene and patients suffering from SALS showed this selective astrocytic S100A6 expression. For instance, the pyramidal tract could be macroscopically detected on S100A6-labeled spinal cord and brainstem sections from SALS patients. Transgenic mice overexpressing the non-mutated SOD1 gene did not overexpress S100A6, although glial fibrillary associated protein astrogliosis was seen. Although these results do not give any clue about the beneficial or detrimental role played by S100A6, its induction may be assumed to appropriately serve some function(s).