S100A4 antisense oligodeoxynucleotide suppresses invasive potential of neuroblastoma cells

CCAAT/enhancer binding protein β induces motility and invasion of glioblastoma cells through transcriptional regulation of the calcium binding protein S100A4

We have previously shown that decreased expression of CCAAT/enhancer binding protein β (C/EBPβ) inhibits the growth of glioblastoma cells and diminishes their transformation capacity and migration. In agreement with this, we showed that C/EBPβ depletion decreases the mRNA levels of different genes involved in metastasis and invasion. Among these, we found S100 calcium binding protein A4 (S100A4) to be almost undetectable in glioblastoma cells deficient in C/EBPβ. Here, we have evaluated the possible role of S100A4 in the observed effects of C/EBPβ in glioblastoma cells and the mechanism through which S100A4 levels are controlled by C/EBPβ. Our results show that C/EBPβ suppression significantly reduced the levels of S100A4 in murine GL261 and human T98G glioblastoma cells. By employing an S100A4-promoter reporter, we observed a significant induction in the transcriptional activation of the S100A4 gene by C/EBPβ. Furthermore, overexpression of S100A4 in C/EBPβ-depleted glioblastoma cells reverses the enhanced migration and motility induced by this transcription factor. Our data also point to a role of S100A4 in glioblastoma cell invasion and suggest that the C/EBPβ gene controls the invasive potential of GL261 and T98G cells through direct regulation of S100A4. Finally, this study indicates a role of C/EBPβ on the maintenance of the stem cell population present in GL261 glioblastoma cells.

Functional expression, characterization and application of the human S100A4 protein

Preparations utilizing monoclonal antibodies against S100A4 provide useful tools for functional studies to investigate the clinical applications of the human S100A4 protein. In the present study, human S100A4 protein was expressed in Escherichia coli (E. coli) BL21 (DE3), successfully purified by diethylaminoethyl cellulose anion-exchange chromatography and identified by western blot analysis. Soluble S100A4 bioactivity was confirmed by Transwell migration and invasion assays in the human HeLa cell line. Monoclonal antibodies (mAbs) were generated utilizing the standard hybridoma method and were validated by enzyme-linked immunosorbent assay and western blot analysis. The antibody was then used to examine human gastric carcinoma specimens by immunohistochemistry. Recombinant S100A4 was functionally expressed in E. coli and promoted the migration and invasion of HeLa cells. Four hybridoma cell lines, which secreted mAbs specifically against human S100A4 protein, were obtained. One of the four mAbs, namely 2A12D10B2, recognized human S100A4 as indicated by immunohistochemical staining of human gastric carcinoma specimens and recombinant S100A4 was functionally expressed in E. coli. The mAbs of recombinant S100A4 were suitable for detecting S100A4 expression in human tissues and for investigating the subsequent clinical applications of the protein.

Functionally active rat S100A4 from a polymerase chain reaction-synthesized gene expressed in soluble form in Escherichia coli

S100A4 protein is associated with Ca²⁺-dependent regulation of intracellular activities and is significant in the invasion, growth and metastasis of cancer. In order to express rat S100A4 functionally and identify its biological activity following purification, an S100A4 gene fragment was optimized and fully synthesized via overlapping polymerase chain reaction. The gene was inserted into the prokaryotic expression vector, pBV220, with phage λ P_RP_L promoters following confirmation by DNA sequencing. The pBV220-S100A4 plasmid was constructed and transformed into Escherichia coli DH5α. Following temperature induction, rat S100A4 was overexpressed and the protein was observed to be located in the supernatant of the lysates, which was ~30–40% of the total protein within the host. The protein was isolated and purified by metal-chelate affinity chromatography. High purity protein (>98% purity) was obtained and in vitro western blot analysis identified that the recombinant S100A4 was able to bind to the antibody against wild-type S100A4. The bioactivity of the recombinant protein was detected via Transwell migration and invasion assays. The polyclonal antibody of rat S100A4 protein was prepared for rabbit immunization and exhibited similar efficacies when compared with commercial S100A4. Therefore, rat S100A4 was functionally expressed in E. coli; thus, the production of active recombinant S100A4 protein in E. coli may further aid with the investigation and application of S100A4.

S100A4-induced cell motility and metastasis is restricted by the Wnt/β-catenin pathway inhibitor calcimycin in colon cancer cells

Calcimycin restricts Wnt/β-catenin–regulated S100A4 expression, leading to reduced S100A4-mediated cell migration and invasion in colon cancer cells, as well as to inhibition of metastasis formation in xenografted mice.

The calcium-binding protein S100A4 is a central mediator of metastasis formation in colon cancer. S100A4 is a target gene of the Wnt/β-catenin pathway, which is constitutively active in the majority of colon cancers. In this study a high-throughput screen was performed to identify small-molecule compounds targeting the S100A4-promoter activity. In this screen calcimycin was identified as a transcriptional inhibitor of S100A4. In colon cancer cells calcimycin treatment reduced S100A4 mRNA and protein expression in a dose- and time-dependent manner. S100A4-induced cellular processes associated with metastasis formation, such as cell migration and invasion, were inhibited by calcimycin in an S100A4-specific manner. Calcimycin reduced β-catenin mRNA and protein levels despite the expression of Δ45-mutated β-catenin. Consequently, calcimycin inhibited Wnt/β-catenin pathway activity and the expression of prominent β-catenin target genes such as S100A4, cyclin D1, c-myc, and dickkopf-1. Finally, calcimycin treatment of human colon cancer cells inhibited metastasis formation in xenografted immunodeficient mice. Our results demonstrate that targeting the expression of S100A4 with calcimycin provides a functional strategy to restrict cell motility in colon cancer cells. Therefore calcimycin may be useful for studying S100A4 biology, and these studies may serve as a lead for the development of treatments for colon cancer metastasis.

Sustained hypoxia leads to the emergence of cells with enhanced growth, migratory, and promitogenic potentials within the distal pulmonary artery wall

All forms of chronic pulmonary hypertension (PH) are characterized by structural remodeling of the pulmonary artery (PA) media, a process previously attributed solely to changes in the phenotype of resident smooth muscle cells (SMC). However, recent experimental evidence in both systemic and pulmonary circulations suggests that other cell types, including circulating and local progenitors, contribute significantly to this process. The goal of this study was to determine if hypoxia-induced remodeling of distal PA (dPA) media involves the emergence of cells with phenotypic and functional characteristics distinct from those of resident dPA SMC and fibroblasts. In vivo, in contrast to the phenotypically uniform SMC composition of dPA media in control calves, the remodeled dPA media of neonatal calves with severe hypoxia-induced PH comprised cells exhibiting a distinct phenotype, including the expression of hematopoetic (CD45), leukocytic/monocytic (CD11b, CD14), progenitor (cKit), and motility-associated (S100A4) cell markers. Consistent with these in vivo observations, primary cell cultures isolated from dPA media of hypertensive calves yielded not only differentiated SMC, but also smaller, morphologically rhomboidal (thus termed here "R") cells that transiently expressed CD11b, constitutively expressed the mesenchymal cell marker type I procollagen, expressed high mRNA levels of progenitor cell markers cKit, CD34, CD73, as well as for inflammatory mediators, IL-6 and MCP-1, and, with time in culture, gained expression of a myofibroblast marker, alpha-SM-actin. R cells exhibited highly augmented proliferative, migratory, invasive, and potent promitogenic capabilities, which were due, at least in part, to the production of PDGFs, SDF-1/CXCL12, and S100A4. These data suggest that the cellular mechanisms of dPA remodeling include the emergence of cells with phenotypic and functional characteristics markedly distinct from those of resident dPA cells.

Advances in calcium-binding protein S100A4 and digestive neoplasms

S100A4 protein, encoded by S100A4 gene, is a kind of calcium-binding regulatory proteins. Combining with the calcium ions, this protein plays an important role in the progress of tumor growth and metastasis. Recent investigations concluded that there is a relationship between S100A4 protein and tumor invasion or metastasis. This article reviews the biochemical property of this protein and summarizes its action and potential mechanism in digestive tumor progression and metastasis.

Metastasis promoter S100A4 is a potentially valuable molecular target for cancer therapy

The growth, invasion and metastatic spread of cancer have been identified with the deregulation of cell proliferation, altered intercellular and cell-substratum adhesion and enhanced motility and the deposition of disseminated cancer cells at distant sites. The identification of therapeutic targets for cancer is crucial to human welfare. Drug development, molecular modelling and design of effective drugs greatly depend upon the identification of suitable therapeutic targets. Several genetic determinants relating to proliferation and growth, invasion and metastasis have been identified. S100A4 appears to be able to activate and integrate pathways to generate the phenotypic responses that are characteristic of cancer. S100A4 signalling can focus on factors associated with normal and aberrant proliferation, apoptosis and growth, and differentiation. It is able to activate signalling pathways leading to the remodelling of the cell membrane and the extracellular matrix; modulation of cytoskeletal dynamics, acquisition of invasiveness and induction of angiogenesis. Therefore S100A4 is arguably a molecular target of considerable potential possessing a wide ranging biological activity that can alter and regulate the major phenotypic features of cancer. The evolution of an appropriate strategy that permits the identification of therapeutic targets most likely to be effective in the disease process without unduly affecting normal biological processes and function is an incontrovertible imperative. By virtue of its ability to activate interacting and multi-functional signalling systems, S100A4 appears to offer suitable targets for developing new therapeutic procedures. Some effectors of the S100A4-activated pathways might also lend themselves as foci of therapeutic interest.

Dysregulation of matrix metalloproteinases and their tissue inhibitors by S100A4

The S100A4 protein as well as the matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are associated with diseases such as arthritis and cancer. This mini review focuses on in vitro and in vivo studies indicating S100A4 involvement in regulation of MMPs and TIMPs, and the biological and pathobiological consequences of this regulation.