Structure of the osteopontin gene and its promoter

Immunoregulatory Roles of Osteopontin in Diseases

Osteopontin (OPN) is a multifunctional protein that plays a pivotal role in the immune system. It is involved in various biological processes, including cell adhesion, migration and survival. The study of the immunomodulatory effects of OPN is of paramount importance due to its potential therapeutic applications. A comprehensive understanding of how OPN regulates the immune response could pave the way for the development of novel treatments for a multitude of diseases, including autoimmune disorders, infectious diseases and cancer. Therefore, in the following paper, we provide a systematic overview of OPN and its immunoregulatory roles in various diseases, laying the foundation for the development of OPN-based therapies in the future.

Identification of significant genes in non-small cell lung cancer by bioinformatics analyses

Background

Lung cancer is the most malignant cancer featured with undesirable prognosis. It is urgent to identify novel biomarkers to improve both diagnosis and prognosis. The purpose of the study was to identify significant genes involved in lung cancer through bioinformatic methods and reveal potential underlying mechanisms.

Methods

Three datasets GSE19188, GSE27262, GSE118375, containing 122 lung cancer and 96 normal tissues, were available from GEO database. GEO2R and Venn diagram online software were applied to pick out differentially expressed genes (DEGs). Next, we used the Database for Annotation, Visualization and Integrated Discovery (DAVID) to analyze Kyoto Encyclopedia of Gene and Genome (KEGG) pathway and gene ontology (GO) enrichment, followed by protein-protein interaction (PPI) of these DEGs visualized by cytoscape. The MCODE plug-in was performed to construct a module complex of DEGs. In addition, Kaplan-Meier analysis was implemented for analysis of overall survival. To further validate the expression of these genes, Gene Expression Profiling Interactive Analysis (GEPIA) was used.

Results

A total of 149 DEGs were identified, including 127 downregulated genes and 22 upregulated genes. KEGG analysis revealed that the DEGs were mainly enriched in ECM-receptor interaction, Vascular smooth muscle contraction, and PPAR signaling pathway. GO analysis of DEGs showed that significant functional enrichment of angiogenesis, cell adhesion, and vasculogenesis. 13 genes were selected as hub genes based on MCODE, and 11 of 13 genes had a significance. The results of GEPIA were consistent with survival analysis. Furthermore, reanalysis of these genes found they were significantly enriched in ECM-receptor interaction and PI3K-Akt signaling pathway.

Conclusions

We have identified several key genes, which could be potential diagnostic and prognostic biomarker as well as therapy targets.

Secreted Phosphoprotein 1 Promoter Genetic Variants Are Associated with the Response to Pegylated Interferon α Plus Ribavirin Combination Therapy in Egyptian Patients with Chronic Hepatitis C Virus Infection

Background/Aims

The T-helper 1 (TH1) immune reaction is essential for the eradication of hepatitis C virus (HCV) during pegylated interferon α (PEG-IFN-α)- and ribavirin (RBV)-based therapy in chronic HCV patients. Secreted phosphoprotein 1 (SPP1) was shown to be a crucial cytokine for the initiation of a TH1 immune response. We aimed to investigate whether SPP1 single nucleotide polymorphisms (SNPs) may influence sustained virological response (SVR) rates.

Methods

Two SNPs in the promoter region of SPP1 at the −443 C>T and −1748 G>A loci were genotyped in 100 patients with chronic HCV genotype 4 infection using a TaqMan SNP genotyping assay.

Results

Sixty-seven patients achieved a SVR, and 33 patients showed no SVR. Patients carrying the T/T genotype at the −443 locus showed a significantly higher SVR rate than those carrying the C/T or C/C genotype (83.67% vs 50.98%, p<0.001). At the −1748 locus, the SVR rate was significantly higher in patients with the G/G genotype than in those with the A/A genotype (88.89% vs 52.63%, p=0.028) and in patients with the G/A genotype than in those with the A/A genotype (85.29% vs 52.63%, p=0.001).

Conclusions

SPP1 SNPs at −443 C>T and −1748 G>A loci may be useful markers for predicting the response to PEG-IFN-α-2b plus RBV therapy in Egyptian patients with chronic HCV genotype 4 infection.

Osteopontin is a promoter for hepatocellular carcinoma metastasis: a summary of 10 years of studies

In this review, we summarize the novel findings from our series of studies on the leading metastasis-related gene, osteopontin (OPN). In our previous gene expression profiling study, OPN was identified as one of the leading genes associated with the metastasis of hepatocellular carcinoma (HCC). We focused on OPN to evaluate its prognostic values and important roles in HCC metastasis. A retrospective study of large cohorts of HCC patients demonstrated that plasma OPN level was one of the leading independent prognostic factors for HCC patients, even in the early stage of HCC, and could serve as a surrogate serologic biomarker for monitoring the treatment response and tumor recurrence after HCC resection. Using both in vitro and in vivo investigations, we found that OPN has an important role in metastasis and tumor growth of HCC and is an attractive potential therapeutic target for combating HCC metastasis. We also found that OPN⁺ HCC cells have much more amplifications at chromosomal regions, and promoter polymorphisms are important in the regulation of OPN expression and tumor growth and lung metastasis of HCC.

Myxovirus resistance, osteopontin and suppressor of cytokine signaling 3 polymorphisms predict hepatitis C virus therapy response in an admixed patient population: comparison with IL28B

OBJECTIVES

Suppressor of cytokine signaling 3, myxovirus resistance protein and osteopontin gene polymorphisms may influence the therapeutic response in patients with chronic hepatitis C, and an association with IL28 might increase the power to predict sustained virologic response. Our aims were to evaluate the association between myxovirus resistance protein, osteopontin and suppressor of cytokine signaling 3 gene polymorphisms in combination with IL28B and to assess the therapy response in hepatitis C patients treated with pegylated-interferon plus ribavirin.

METHOD

Myxovirus resistance protein, osteopontin, suppressor of cytokine signaling 3 and IL28B polymorphisms were analyzed by PCR-restriction fragment length polymorphism, direct sequencing and real-time PCR. Ancestry was determined using genetic markers.

RESULTS

We analyzed 181 individuals, including 52 who were sustained virologic responders. The protective genotype frequencies among the sustained virologic response group were as follows: the G/G suppressor of cytokine signaling 3 (rs4969170) (62.2%); T/T osteopontin (rs2853744) (60%); T/T osteopontin (rs11730582) (64.3%); and the G/T myxovirus resistance protein (rs2071430) genotype (54%). The patients who had ≥3 of the protective genotypes from the myxovirus resistance protein, the suppressor of cytokine signaling 3 and osteopontin had a greater than 90% probability of achieving a sustained response (p<0.0001). The C/C IL28B genotype was present in 58.8% of the subjects in this group. The sustained virological response rates increased to 85.7% and 91.7% by analyzing C/C IL28B with the T/T osteopontin genotype at rs11730582 and the G/G suppressor of cytokine signaling 3 genotype, respectively. Genetic ancestry analysis revealed an admixed population.

CONCLUSION

Hepatitis C genotype 1 patients who were responders to interferon-based therapy had a high frequency of multiple protective polymorphisms in the myxovirus resistance protein, osteopontin and suppressor of cytokine signaling 3 genes. The combined analysis of the suppressor of cytokine signaling 3 and IL28B genotypes more effectively predicted sustained virologic response than IL28B analysis alone.

Osteopontin promoter polymorphisms at locus -443 significantly affect the metastasis and prognosis of human hepatocellular carcinoma

Osteopontin (OPN) plays a crucial role in hepatocellular carcinoma (HCC) metastasis. However, little is known about the impact of OPN polymorphisms on cancer progression. In this study, we first identified the single nucleotide polymorphisms (SNPs) in the OPN promoter region by direct sequencing in 30 HCCs, and then evaluated the prognostic values of the selected ones in two large cohorts of 826 HCC patients. The identified SNPs were functionally analyzed using in vitro and in vivo assays and their correlations with OPN levels were also evaluated. Only SNP at locus -443 and their related haplotypes (Ht2: -1748A/-616G/-443T/-155* [*indicates base deletion]; Ht3: -1748A/-616G/-443C/-155*) were significantly associated with overall survival (OS) and time to recurrence (TTR). The patients with the -443TT/TC genotype or Ht2 had a shorter OS and TTR compared with those with -443CC genotype or Ht3. This was further confirmed in the validation cohort. Moreover, this correlation remained significant in patients with small HCCs (≤5 cm). Multivariate analyses indicated that the prognostic performance of the -443 genotypes (OS, P=0.031; TTR, P=0.005) and their related haplotypes (OS, P=0.002; TTR, P=0.001) was independent of other clinicopathological factors. The Ht2 and -443TT genotype could significantly increase the promoter transcriptional activity and expression level of OPN compared with the Ht3 or -443CC genotype, and lead to an obvious increase in both in vitro invasion and in vivo tumor growth and lung metastasis of HCC cells (P<0.05).

CONCLUSION

The genetic variation at locus -443 of the OPN promoter plays important roles in the regulation of OPN expression and cancer progression of HCCs, which is a novel determinant and target for HCC metastasis and prognosis.

Osteopontin gene polymorphisms as predictors for the efficacy of interferon therapy in chronic hepatitis C Egyptian patients with genotype 4

This study aimed to determine the relationship between osteopontin gene polymorphisms and its protein level and the efficacy of interferon-based therapies in Hepatitis C virus (HCV) patients. Hundreds HCV patients genotype 4, treated with pegylated interferon alfa-2b plus ribavirin and 60 healthy subjects were enrolled. All individuals were subjected to clinical and laboratory parameters, including hepatitis markers and HCV quantitation by real-time polymerase chain reaction. Single nucleotide polymorphisms (SNPs) of osteopontin (OPN) gene (nucleotide -155, -443 and -1748) were analysed by direct sequencing in addition to estimation of serum level of OPN. SNP at -443 (C/C versus C/T, T/T) was found to represent predictors for treatment response by univariate logistic regression analysis. OPN serum level was independent predictors for treatment response by both univariate and multivariate logistic regression analysis. SNP at nucleotide -443 and serum OPN protein levels could be used as useful markers to predict the efficacy of treatment.

AP-1 inhibits expression of MMP-2/9 and its effects on rat smooth muscle cells

BACKGROUND

We designed AP-1 small interfering RNA (siRNA) to study the relationship between AP-1 expression and matrix metalloproteinase (MMP)-2 activation.

METHODS

To suppress the expression of AP-1 gene, we used RNA interference to silence the AP-1 gene post-transcriptionally in rat smooth muscle cells. Effects of AP-1 siRNA on mRNA expression of AP-1 were examined using reverse transcriptase polymerase chain reaction (RT-PCR). Phosphorylation levels of c-Jun, c-Fos, and the activity of AP-1 were determined by Western blotting and AP-1 DNA-binding activity assay. To observe the expression of SM alpha-actin and downstream genes of AP-1, we simultaneously examined the activity of cell matrix metal proteinases and the migration ability of smooth muscle cells using a modified Boyden-chamber assay. Effects of AP-1 siRNA on rat vascular smooth muscle cells (VSMC) in vitro were evaluated using cell cycle analysis, MTT-tests, BrdU-ELISA and immunofluorescence.

RESULTS

AP-1 siRNA decreased not only AP-1 mRNA and AP-1 binding activity, but also c-Jun and c-Fos phosphorylation levels and the expression levels of urokinase-type plasminogen (u-PA), MMPs, TGF-beta1 and bFGF in VSMCs. The AP-1 siRNA also significantly inhibited PDGF/IL-1-induced MMP-2 and MMP-9 gelatinolytic activity in VSMCs. The invasion and migration of VSMC were also induced greatly.

CONCLUSIONS

AP-1 inhibited expression of MMP-2/9 and AP-1 siRNA was able to effectively inhibit the proliferation, migration and de-differentiation of rat smooth muscle cells.

Osteopontin: regulation in tumor metastasis

Osteopontin is a secreted phosphoprotein that has been implicated as an important mediator of tumor metastasis and has been investigated for use as a biomarker for advanced disease and as a potential therapeutic target in the regulation of cancer metastasis. The OPN DNA sequence is highly conserved and the protein contains several important functional domains including alpha(v)beta integrin and CD44 binding sites. High levels of OPN expression correlate with tumor invasion, progression or metastasis in multiple cancer. Studies demonstrate that osteopontin mediates the molecular mechanisms which determine metastatic spread, such as prevention of apoptosis, extracellular matrix proteolysis and remodeling, cell migration, evasion of host-immune cells and neovascularization. Transcriptional regulation of OPN is complex and involves multiple pathways, including AP-1, Myc, v-Src, Runx/CBF, TGF-B/BMPs/Smad/Hox, and Wnt/ss-catenin/APC/GSK-3ss/Tcf-4. The current state of knowledge of OPN biology suggests that it is an attractive target for therapeutic modulation of metastatic disease.

Breast cancer metastasis suppressor 1 (BRMS1) inhibits osteopontin transcription by abrogating NF-kappaB activation

Background

Osteopontin (OPN), a secreted phosphoglycoprotein, has been strongly associated with tumor progression and aggressive cancers. MDA-MB-435 cells secrete very high levels of OPN. However metastasis-suppressed MDA-MB-435 cells, which were transfected with breast cancer metastasis suppressor 1 (BRMS1), expressed significantly less OPN. BRMS1 is a member of mSin3-HDAC transcription co-repressor complex and has been shown to suppress the metastasis of breast cancer and melanoma cells in animal models. Hence we hypothesized that BRMS1 regulates OPN expression.

Results

The search for a BRMS1-regulated site on the OPN promoter, using luciferase reporter assays of the promoter deletions, identified a novel NF-κB site (OPN/NF-κB). Electrophoretic mobility shift assays and chromatin immunoprecipitations (ChIP) confirmed this site to be an NF-κB-binding site. We also show a role of HDAC3 in suppression of OPN via OPN/NF-κB.

Conclusion

Our results show that BRMS1 regulates OPN transcription by abrogating NF-κB activation. Thus, we identify OPN, a tumor-metastasis activator, as a crucial downstream target of BRMS1. Suppression of OPN may be one of the possible underlying mechanisms of BRMS1-dependent suppression of tumor metastasis.

The role of Osteopontin in tumor metastasis

Osteopontin (OPN) is a glyco-phosphoprotein that is expressed and secreted by numerous human cancers. OPN functions in cell adhesion, chemotaxis, macrophage-directed interleukin-10 (IL-10) suppression, stress-dependent angiogenesis, prevention of apoptosis, and anchorage-independent growth of tumor cells by regulating cell-matrix interactions and cellular signaling through binding with integrin and CD44 receptors. While constitutive expression of OPN exists in several cell types, induced expression has been detected in T-lymphocytes, epidermal cells, bone cells, macrophages, and tumor cells in remodeling processes such as inflammation, ischemia-reperfusion, bone resorption, and tumor progression. Recently, substantial evidence has linked OPN with the regulation of metastatic spread by tumor cells. However, the molecular mechanisms that define the role of OPN in tumor metastasis are incompletely understood. Transcriptional regulators that contribute to the induction of OPN expression have received significant attention as potential modulators of the OPN-mediated metastatic phenotype. The following review will discuss the molecular structure of OPN, the evidence for its functional role in tumor cell metastasis, the downstream signals that activate invasive mechanisms, and the recent reports concerning regulation of OPN transcription.

Genetic polymorphims in promoter region of osteopontin gene may be a marker reflecting hepatitis activity in chronic hepatitis C patients

BACKGROUND AND AIMS

Osteopontin, an extracellular matrix protein with RGD motif, is shown to be a cytokine essential for Th1 immune response initiation. Genetic polymorphisms in the osteopontin gene (OPN) determine the magnitude of immunity against rickettsial infection in mice. Similar polymorphisms, if present also in human beings, might affect hepatitis activity in those infected with HCV.

METHODS

Blood was collected from 176 patients with chronic hepatitis C. SNPs in the promoter region of OPN were analyzed in 20 patients by direct sequencing of DNA fragments amplified by PCR and in 156 patients by Invader assay. Ninety-five patients compatible to evaluation criteria were classified into three groups depending on maximal serum ALT levels during the observation periods at least for 2 years as follows; lower than 30IU/L (low-activity group), between 30 and 80IU/L with no hepatoprotective treatment (medium-activity group), and higher than 80IU/L irrespective of hepatoprotective treatment (high-activity group).

RESULTS

There were 16, 19, and 60 patients in the low-, medium-, and high-activity groups, respectively. Four SNPs (nt -155, -443, -616, and -1748) were detected in the promoter region of OPN. Among them, the SNP at nt -443 (C or T) was a novel one and showed an association with hepatitis activity in our patients: T/T homozygosity was found in 2 (13%), 8 (42%), and 25 (44%), and C/T heterozygosity in 12 (75%), 8 (42%), and 23 (40%), in the low-, medium-, and high-activity groups, respectively. The other 3 SNPs already known showed linkage disequilibrium with D(') and r(2) greater than 0.937 to each other without correlation to disease activity.

CONCLUSIONS

OPN promoter region SNP at nt -433 may be a useful marker reflecting hepatitis activity in chronic hepatitis C patients.

The first intron of the human osteopontin gene contains a C/EBP-beta-responsive enhancer

The osteopontin (OPN) protein is found expressed at high level in several processes including fibrotic evolution of organ injuries, tumorigenesis, and immune response. The molecular mechanisms that underly overexpression, especially at the transcriptional level, have been only partially clarified. Therefore, this study was undertaken in search for additional DNA elements in the regulatory regions of the OPN gene and cognate transcription factors. Our results on the region upstream of the transcription start site confirmed that essential elements are located within the first 100 bp. Analysis of the sequence that includes the first untranslated exon and first intron revealed that it could enhance the promoter activity. Experiments of transfection of constructs containing different fragments of this sequence showed that most of the enhancer activity was confined in the terminal 30-bp tract of the first intron, although it was not functioning in a myofibroblast cell line. DNA/protein binding assays and cotransfection experiments showed that the C/EBP-beta transcription factor was able to bind a recognition sequence in this 30-bp segment. We found a bi-allelic sequence polymorphism at +245 in the first intron, which did not show a significant functional effect, but is a useful tool for future association studies.

Stimulation of osteopontin mRNA expression in HL-60 cells is independent of differentiation

12-O-Tetradecanoylphorbol 13-acetate (TPA) induces HL-60 cells to differentiate along the monocyte/macrophage pathway and stimulates expression of the extracellular adhesion protein osteopontin (OPN). In this study, the mechanism of TPA-mediated OPN mRNA expression and its relationship to differentiation were investigated. The induction of OPN mRNA by TPA was dose dependently inhibited by staurosporine (0.4-10.0 nM) and chelerythrine (0.1-5.0 microM), indicating that OPN expression requires PKC activation. Furthermore, the mitogen-activated protein kinase kinase (MAPKK) inhibitor, PD 098059 (1.0-10.0 microM), inhibited the effect of TPA in a dose-dependent fashion. Cycloheximide (10 microg/ml) ablated the induction of OPN mRNA by TPA. To determine if OPN mRNA expression was associated with a particular differentiational pathway, HL-60 cells were treated with RA, 9-cis-RA, calcitriol, or sodium butyrate. None of these agents stimulated OPN mRNA. Treatment with TPA subsequent to a 120-h pretreatment with retinoic acid (RA), 9-cis-RA, or calcitriol resulted in a potentiation of the induction of OPN mRNA. These results support a role for protein kinase C (PKC) in promoting OPN expression because each of these agents increased PKC levels. An hOPN promoter/reporter construct was responsive to TPA, indicating that this effect is at the level of transcription. Thus, TPA-stimulated transcription of the OPN gene apparently occurs via a PKC/MAPK-dependent mechanism that is independent of that associated with differentiation and is not dependent on the maturational state of these cells.