Special AT-rich Binding Protein 1 Expression Research Articles

SATB1 protein is associated with the epithelial‑mesenchymal transition process in non‑small cell lung cancers.

Lung cancer is one of the most frequently diagnosed neoplasms and the leading cause of cancer-related mortality worldwide. Its predominant subtype is non-small cell lung cancer (NSCLC), which accounts for over 80% of the cases. Surprisingly, the majority of lung cancer-related deaths are caused not by a primary tumour itself, but by its metastasis to distant organs. Therefore, it becomes especially important to identify the factors involved in lung cancer metastatic spread. Special AT-rich binding protein 1 (SATB1) is a nuclear matrix protein that mediates chromatin looping and plays the role of global transcriptional regulator. During the past decade, it has received much attention as a factor promoting tumour invasion. In breast, colorectal and prostate cancers, SATB1 has been shown to influence the epithelial-mesenchymal transition (EMT) process, which is thought to be crucial for cancer metastasis. The aim of this study was to analyse the possible correlations between the expression of SATB1 and major EMT-associated proteins in NSCLC clinical samples. Additionally, the impact of EMT induction in NSCLC cell lines on SATB1 mRNA expression was also investigated. Immunohistochemistry was used to assess the expression of SATB1, SNAIL, SLUG, Twist1, E-cadherin, and N-cadherin in 242 lung cancer clinical samples. EMT was induced by TGF-β1 treatment in the A549 and NCI-H1703 lung cancer cell lines. Changes in gene expression profiles were analyzed using real-time PCR and Droplet Digital PCR. SATB1 expression was positively correlated with the expression of SNAIL (R=0.129; P=0.045), SLUG (R=0.449; P<0.0001), and Twist1 (R=0.264; P<0.0001). Moreover, SATB1 expression significantly increased after in vitro EMT induction in A549 and NCI-H1703 cell lines. The results obtained may point to the role of SATB1 as one of the regulators of EMT in NSCLC.

The Role of SATB1 in Tumour Progression and Metastasis.

Carcinogenesis is a long-drawn, multistep process, in which metastatic spread is an unequivocal hallmark of a poor prognosis. The progression and dissemination of epithelial cancers is commonly thought to rely on the epidermal-mesenchymal transition (EMT) process. During EMT, epithelial cells lose their junctions and apical-basal polarity, and they acquire a mesenchymal phenotype with its migratory and invasive capabilities. One of the proteins involved in cancer progression and EMT may be SATB1 (Special AT-Rich Binding Protein 1)—a chromatin organiser and a global transcriptional regulator. SATB1 organizes chromatin into spatial loops, providing a “docking site” necessary for the binding of further transcription factors and chromatin modifying enzymes. SATB1 has the ability to regulate whole sets of genes, even those located on distant chromosomes. SATB1 was found to be overexpressed in numerous malignancies, including lymphomas, breast, colorectal, prostate, liver, bladder and ovarian cancers. In the solid tumours, an elevated SATB1 level was observed to be associated with an aggressive phenotype, presence of lymph node, distant metastases, and a poor prognosis. In this review, we briefly describe the prognostic significance of SATB1 expression in most common human cancers, and analyse its impact on EMT and metastasis.

Divergent SATB1 expression across human life span and tissue compartments.

Special AT‐rich binding protein‐1 (SATB1) is a global chromatin organizer capable of activating or repressing gene transcription in mice and humans. The role of SATB1 is pivotal for T‐cell development, with SATB1‐knockout mice being neonatally lethal, although the exact mechanism is unknown. Moreover, SATB1 is dysregulated in T‐cell lymphoma and proposed to suppress transcription of the Pdcd1 gene, encoding the immune checkpoint programmed cell death protein 1 (PD‐1). Thus, SATB1 expression in T‐cell subsets across different tissue compartments in humans is of potential importance for targeting PD‐1. Here, we comprehensively analyzed SATB1 expression across different human tissues and immune compartments by flow cytometry and correlated this with PD‐1 expression. We investigated SATB1 protein levels in pediatric and adult donors and assessed expression dynamics of this chromatin organizer across different immune cell subsets in human organs, as well as in antigen‐specific T cells directed against acute and chronic viral infections. Our data demonstrate that SATB1 expression in humans is the highest in T‐cell progenitors in the thymus, and then becomes downregulated in mature T cells in the periphery. Importantly, SATB1 expression in peripheral mature T cells is not static and follows fine‐tuned expression dynamics, which appear to be tissue‐ and antigen‐dependent. Furthermore, SATB1 expression negatively correlates with PD‐1 expression in virus‐specific CD8+ T cells. Our study has implications for understanding the role of SATB1 in human health and disease and suggests an approach for modulating PD‐1 in T cells, highly relevant to human malignancies or chronic viral infections.

The expression of special AT-rich binding protein 1 in cervical cancer and its clinical significance.

BackgroundThe oncogenic potential of special AT-rich binding protein 1 (SATB1) has been reported in various types of cancer, but its function in cervical cancer remains not fully investigated. This study aimed to investigate the effect of SATB1 mRNA expression on tumor progression and outcomes in the cervical cancer patients.MethodsA total of 33 cervical cancer patients treated in our hospital from September 2012 to December 2015 were included. The mRNA expression level of STAB1 in cervical cancer tissue was determined by real-time PCR, and the patients were divided into dichotomous groups based on their SATB1 expression level. Clinical characteristics, recurrence, and survival outcomes were compared between groups.ResultsCompared with the SATB1-low group, the SATB1-high group had significantly advanced International Federation of Gynecology and Obstetrics (FIGO) stages (P=0.037) and histologic grade (P=0.036). Kaplan–Meier analysis showed that SATB1-high group had a worse overall survival (P=0.078, marginal significant). In the subgroup analysis of pathological types, adenocarcinomas group (n=8) had a significantly higher SATB1 expression level as compared with the squamous cell carcinomas (n=18) and adenosquamous carcinomas (n=7) groups (both P<0.05). Cervical squamous cell carcinomas patients with a high-expression SATB1 (n=8) had more advanced FIGO stages (P=0.015) and histologic grades (P=0.060, marginal significant) as well as a higher (P=0.069, marginal significant) incidence of lymphatic metastasis than those with a low expression of SATB1 (n=10).ConclusionThese results showed that expression of SATB1 may have an effect on the disease progression and survival outcome of cervical cancer.

SATB1 3'-UTR and lncRNA-UCA1 competitively bind to miR-495-3p and together regulate the proliferation and invasion of gastric cancer.

High expression of special AT-rich-binding protein 1 (SATB1) correlates with the advanced TNM stage and short overall and recurrence-free survival of gastric cancer (GC). A bioinformatic analysis revealed that SATB1 3'-untranslated region (3'-UTR) and long noncoding RNA UCA1 (lncRNA-UCA1) might competitively bind to microRNA-495-3p (miR-495-3p). Interestingly, lncRNA-UCA1 is also an important contributor to GC. The current study aimed to demonstrate the potential interaction among SATB1/miR-495-3p/lncRNA-UCA1 network and their effects on GC proliferation and invasion. The expression in GC and paracancerous normal tissues were assessed using real-time polymerase chain reaction and Western blot analysis. Luciferase reporter, RNA pull-down, and transfection assays were performed to determine the interaction among SATB1/miR-495-3p/lncRNA-UCA1 network in GC cells. GC proliferation and invasion were evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, transwell invasion, and colony formation assays. Results showed higher expression of SATB1 and lncRNA-UCA1 but lower miR-495-3p expression in GC than in the normal tissues. In luciferase reporter assay, miR-495-3p bound to three seed sequences in SATB1 3'-UTR but only one in lncRNA-UCA1. SATB1 knockdown increased the combination of miR-495-3p with lncRNA-UCA1 but decreased lncRNA-UCA1 expression. Decreased lncRNA-UCA1 was also observed with the mimics increased miR-495-3p. These data suggested that SATB1 3'-UTR functions as a competing endogenous RNA of miR-495-3p and positively regulates lncRNA-UCA1. LncRNA-UCA1 knockdown only decreased SATB1 expression in MKN-45 cells but not in BGC-823 cells, which suggested that the regulatory effect of lncRNA-UCA1 on SATB1 by sponging miR-495-3p is cell-dependent. This study further identified that SATB1/miR-495-3p/lncRNA-UCA1 network is implicated in GC proliferation and invasion. The current study firstly revealed that SATB1 interacts with miR-495-3p/lncRNA-UCA1 network, whereby enhancing GC proliferation and invasion.

Abstract 1552: SATB1 is a novel prognostic factor in esophageal cancer patients and promotes migration and invasion of esophageal cancer cells

Abstract Introduction: Esophageal squamous cell carcinoma (ESCC) is a highly aggressive malignancy with extremely poor overall survival. There is no available molecular marker in clinical application until now. SATB1(special AT-rich binding protein 1) tether genomic DNA in nucleolus and hold three-dimensional structure of genomic DNA. We evaluated SATB1 expression using clinical samples from patients of ESCC and analyzed the association with clinicopathological factors and prognosis to identify novel prognostic marker in ESCC. In addition, we investigated the function of SATB1 using ESCC cells. We focused on matrix metalloproteinase protein (MMP3), which has a SATB1 binding site in its upstream. Materials and Methods: We accumulated 71 samples of ESCC patients who underwent primary tumor resection. The relative expression levels of SATB1 were obtained by normalizing the amount of SATB1 mRNA with respect to GAPDH mRNA as an endogenous control for each sample. We divided 71 ESCC samples into 2 groups, which are SATB1 low expression group (n=35) and SATB1 high expression group (n=36) according to the median of SATB1 expression level, and performed the comparison between two groups. In order to elucidate biological significance, we generated SATB1 overexpression stable transfectants in KYSE150, and performed migration and invasion assays. Next, we knockdowned SATB1 expression of KYSE410, which are ESCC lines, using SATB1 siRNA and evaluated the capability of migration and invasion. Moreover, to validate whether SATB1 altered MMP3 genomic locus, we analyzed comparative genomic hybridization (CGH) array obtained from 54 esophageal cancer samples. We examined MMP3 expression in SATB1 overexpression cells using qRT-PCR. Result: The SATB1 high expression group showed greater tumor depth than the low expression group (P=0.003). In the overall survival curve, patients in the SATB1 high expression group had a significant poorer prognosis than those in the SATB1 low expression group (P=0.013). Multivariate analysis showed that the level of SATB1 expression was an independent prognostic predictor (OR; 1.56, 95%CI; 1.04 - 2.44, P = 0.043). SATB1 transfectants significantly increased the capability of migration and invasion compared to mock (P&amp;lt;0.05). KYSE410 cells transfected with SATB1 siRNA significantly decreased the capability of migration and invasion compared to control cells (P&amp;lt;0.05). Genomic alterations in SATB1 locus were strongly correlated with those in MMP3 locus (P&amp;lt;0.0001, ρ=0.5156). Overexpression of SATB1 showed the elevated MMP3 level compared to mock (P&amp;lt;0.05). Conclusion: We indicated that SATB1 is novel prognostic factor in ESCC and that SATB1 promote migration and invasion of ESCC cells. SATB1 may be a promising new candidate for targeted therapies for ESCC. Citation Format: Yusuke Tsuruda, Ryunosuke Kogo, Shuhei Ito, Akihiro Kitagawa, Atsushi Fujii, Shotaro Kuramitsu, Dai Simizu, Yosuke Kuroda, Hidetoshi Eguchi, Tkaaki Masuda, Shoji Natsugoe, Masaki Mori, Koshi Mimori. SATB1 is a novel prognostic factor in esophageal cancer patients and promotes migration and invasion of esophageal cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1552.

SATB1 Level Correlates with Ki-67 Expression and Is a Positive Prognostic Factor in Non-small Cell Lung Carcinoma.

Non-small cell lung carcinomas (NSCLCs), mainly adenocarcinoma (AC) and squamous cell carcinoma (LSCC), account for about 80% of all lung cancer cases. One of the proteins involved in NSCLC progression may be special AT-rich binding protein 1 (SATB1), a potent transcriptional regulator, able to control the expression of whole sets of genes simultaneously. SATB1 has been found to be associated with aggressive phenotype and poor prognosis in numerous malignancies, including breast, colon, ovary and prostate cancer. However, its role in NSCLC is still not fully understood. The aim of this study was to investigate the expression of SATB1 protein and mRNA in NSCLC and non-malignant lung tissue (NMLT) samples, as well as to determine possible relationships of SATB1 expression with both the expression of Ki-67 and the clinicopathological data of the patients. The study was performed on 277 NSCLC (158 AC, 119 LSCC) and 20 NMLT samples. We observed increased SATB1 immunoreactivity in NSCLC when compared to NMLT, and in LSCC when compared to AC cases. We also noted that an elevated SATB1 immunoreactivity was associated with a poor degree of AC differentiation, whereas in LSCC, an inverse relationship was observed. Our analyses revealed that the expression of SATB1 positively correlated with Ki-67 index in NSCLC and LSCC, but not in AC cases. Finally, we found that high SATB1 expression was associated with a better overall survival of patients with NSCLC. SATB1 plays diverse roles in different NSCLC subtypes, and its expression may have a prognostic significance for patients with these tumours.

Hepatic SATB1 induces paracrine activation of hepatic stellate cells and is upregulated by HBx.

Chronic hepatitis B virus (HBV) infection is a major cause of chronic liver diseases, but its involvement in hepatic fibrogenesis remains unclear. Special AT-rich binding protein 1 (SATB1) has been implicated in reprogramming chromatin organization and transcription profiles in many cancers and non-cancer-related conditions. We found that hepatic SATB1 expression was significantly up-regulated in fibrotic tissues from chronic hepatitis B virus (HBV)-infected patients and HBV transgenic (HBV-Tg) mouse model. Knockdown of SATB1 in the liver significantly alleviated CCl4-induced fibrosis in HBV-Tg mouse model. Moreover, we suggested HBV encoded x protein (HBx) induced SATB1 expression through activation of JNK and ERK pathways. Enforced expression of SATB1 in hepatocytes promoted the activation and proliferation of hepatic stellate cells (HSCs) by secretion of connective tissue growth factor (CTGF), Interleukin-6 (IL-6) and platelet derived growth factor-A (PDGF-AA). Our findings demonstrated that HBx upregulated hepatic SATB1 which exerted pro-fibrotic effects by paracrine activation of stellate cells in HBV-related fibrosis.

Regulation of SATB1 during thymocyte development by TCR signaling.

T lymphocyte development and differentiation is a multi-step process that begins in the thymus and completed in the periphery. Sequential development of thymocytes is dependent on T cell receptor (TCR) signaling and an array of transcription factors. In this study we show that special AT-rich binding protein 1 (SATB1), a T lineage-enriched chromatin organizer and regulator, is induced in response to TCR signaling during early thymocyte development. SATB1 expression profile coincides with T lineage commitment and upregulation of SATB1 correlates with positive selection of thymocytes. CD4 thymocytes exhibit a characteristic bimodal expression pattern that corresponds to immature and mature CD4 thymocytes. We also demonstrate that GATA3, the key transcriptional regulator of αβ T cells positively regulates SATB1 expression in thymocytes suggesting an important role for SATB1 during T cell development.

SATB1 Mediates Long-Range Chromatin Interactions: A Dual Regulator of Anti-Apoptotic BCL2 and Pro-Apoptotic NOXA Genes.

Aberrant expression of special AT-rich binding protein 1 (SATB1), a global genomic organizer, has been associated with various cancers, which raises the question of how higher-order chromatin structure contributes to carcinogenesis. Disruption of apoptosis is one of the hallmarks of cancer. We previously demonstrated that SATB1 mediated specific long-range chromosomal interactions between the mbr enhancer located within 3’-UTR of the BCL2 gene and the promoter to regulate BCL2 expression during early apoptosis. In the present study, we used chromosome conformation capture (3C) assays and molecular analyses to further investigate the function of the SATB1-mediated higher-order chromatin structure in co-regulation of the anti-apoptotic BCL2 gene and the pro-apoptotic NOXA gene located 3.4Mb downstream on Chromosome 18. We demonstrated that the mbr enhancer spatially juxtaposed the promoters of BCL2 and NOXA genes through SATB1-mediated chromatin-loop in Jurkat cells. Decreased SATB1 levels switched the mbr-BCL2 loop to mbr-NOXA loop, and thus changed expression of these two genes. The SATB1-mediated dynamic switch of the chromatin loop structures was essential for the cooperative expression of the BCL2 and NOXA genes in apoptosis. Notably, the role of SATB1 was specific, since inhibition of SATB1 degradation by caspase-6 inhibitor or caspase-6-resistant SATB1 mutant reversed expression of BCL-2 and NOXA in response to apoptotic stimulation. This study reveals the critical role of SATB1-organized higher-order chromatin structure in regulating the dynamic equilibrium of apoptosis-controlling genes with antagonistic functions and suggests that aberrant SATB1 expression might contribute to cancer development by disrupting the co-regulated genes in apoptosis pathways.

Abstract 2043: SATB1 (special AT-rich binding protein 1) as a putative therapeutic target in colorectal cancer

Abstract The Special AT-rich Binding Protein 1 (SATB1) is a global chromatin organizer that regulates the expression of a large number of genes in direct and indirect manners. By functioning as a “landing platform” for chromatin remodeling enzymes, SATB1 targets chromatin remodeling complexes to DNA at the base of chromatin loops. Thus, SATB1 influences the expression of multiple genes in an epigenetic manner. In several human cancers, SATB1 overexpression has been described and connected to carcinogenesis. Furthermore, the expression of SATB1 correlates with tumor progression and is associated with poor prognosis. Colorectal cancer is one of the most common causes for cancer-related deaths worldwide. Although methods of diagnosis and treatment have improved over the last few decades, the tumor stage at diagnosis is still the most important prognostic marker and the overall survival of patients with advanced colorectal cancer is still poor due to the high risk of metastasis. Therefore, it is critical to determine potential targets for new therapeutic strategies. In this study, we have analyzed the function of SATB1 in primary and in established colorectal cancer cell lines and determined the therapeutic relevance of SATB1-specific gene knockdown approaches by RNA interference (RNAi). In CRC cells, an RNAi-mediated knockdown of the SATB1 was achieved by transient or by stable transfection with specific siRNAs or shRNAs-encoding plasmids, each leading to markedly reduced SATB1 mRNA and protein levels. SATB1 knockdown caused an inhibition of proliferation, a deceleration of cell cycle progression and pro-apoptotic effects. Further analyses revealed effects of SATB1 on multiple signaling pathways influencing e.g. EMT, apoptosis and ErbB receptor expression. The functional relevance of SATB1 (knockdown) was also determined in vivo in an s.c. tumor xenograft model in athymic nude mice, using stable LS174T knockdown cells. Notably, a marked inhibition of tumor growth was observed. Beyond stable established cell lines, studies were extended towards primary colorectal carcinoma cells. Transient siRNA-mediated SATB1 knockdown led to antiproliferative and proapoptotic effects in primary cell lines with different SATB1 expression levels. The therapeutic potential of SATB1 inhibition was further explored in vivo in mice bearing s.c. xenografts. For the induction of therapeutic RNAi in vivo, mice were treated with polymeric nanoparticles containing siRNAs, i.e., polyethylenimine (PEI)/siRNA-complexes. Notably, a marked inhibition of tumor growth was observed in the siRNA treatment group, indicating profound therapeutic effects of SATB1 knockdown in primary colorectal cancer cells. Taken together, these results indicate an important and complex role of SATB1 in the tumorigenesis of colorectal cancer, and establish SATB1 inhibition or siRNA-mediated knockdown as a promising target for pharmacological intervention. Citation Format: Anja Frömberg, Michael Rabe, Michael Linnebacher, Achim M. Aigner. SATB1 (special AT-rich binding protein 1) as a putative therapeutic target in colorectal cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2043. doi:10.1158/1538-7445.AM2015-2043

Multiple effects of the special AT-rich binding protein 1 (SATB1) in colon carcinoma.

SATB1 (special AT-rich binding protein 1) is a global chromatin organizer regulating the expression of a large number of genes. Overexpression has been found in various solid tumors and positively correlated with prognostic and clinicopathological properties. In colorectal cancer (CRC), SATB1 overexpression and its correlation with poor differentiation, invasive depth, TNM (tumor, nodes, metastases) stage and prognosis have been demonstrated. However, more detailed studies on the SATB1 functions in CRC are warranted. In this article, we comprehensively analyze the cellular and molecular role of SATB1 in CRC cell lines with different SATB1 expression levels by using RNAi-mediated knockdown. Using siRNAs with different knockdown efficacies, we demonstrate antiproliferative, cell cycle-inhibitory and proapoptotic effects of SATB1 knockdown in a SATB1 gene dose-dependent manner. Tumor growth inhibition is confirmed in vivo in a subcutaneous tumor xenograft mouse model using stable knockdown cells. The in-depth analysis of cellular effects reveals increased activities of caspases-3, -7, -8, -9 and other mediators of apoptotic pathways. Similarly, the analysis of E- and N-cadherin, slug, twist, β-catenin and MMP7 indicates SATB1 effects on epithelial-mesenchymal transition (EMT) and matrix breakdown. Our results also establish SATB1 effects on receptor tyrosine kinases and (proto-)oncogenes such as HER receptors and Pim-1. Taken together, this suggests a more complex molecular interplay between tumor-promoting and possible inhibitory effects in CRC by affecting multiple pathways and molecules involved in proliferation, cell cycle, EMT, invasion and cell survival.

SATB1 collaborates with loss of p16 in cellular transformation.

Tumor progression is associated with invasiveness and metastatic potential. The special AT-rich binding protein 1 (SATB1) has been identified as a key factor in the progression of breast cancer cells to a malignant phenotype and is associated with progression of human tumors. In normal development, SATB1 coordinates gene expression of progenitor cells by functioning as a genome organizer. In contrast to progenitor and tumor cells, SATB1 expression in nontransformed cells is not compatible with proliferation. Here we show that SATB1 expression in mouse embryonic fibroblasts induces cell cycle arrest and senescence that is associated with elevated p16 protein levels. Deletion of p16 overcomes the SATB1-induced senescence. We further provide evidence for an interaction of SATB1 with the retinoblastoma (RB)/E2F pathway downstream of p16. A combined deletion of the RB proteins, RB, p107 and p130 (triple-mutant; TM), prevents SATB1-induced G1 arrest, which is restored upon the reintroduction of RB into SATB1-expressing TM fibroblasts. SATB1 interacts with the E2F/RB complex and regulates the cyclin E promoter in an E2F-dependent manner. These findings demonstrate that p16 and the RB/E2F pathway are critical for SATB1-induced cell cycle arrest. In the absence of p16, SATB1 causes anchorage-independent growth and invasive phenotype in fibroblasts. Our data illustrate that p16 mutations collaborate with the oncogenic activity of SATB1. Consistent with our finding, a literature survey shows that deletion of p16 is generally associated with SATB1 expressing human cell lines and tumors.

Immunohistochemical detection of SATB1 is independent of thyroid cancer differentiation

The association of special AT-rich binding protein 1 (SATB1) with a poor prognosis in various cancers has been reported. However, this association is controversial. SATB1 expression in aggressive types of thyroid cancer has not been reported to date. Retrospective. SATB1 expression was immunohistochemically investigated in 35 papillary thyroid cancers, one follicular thyroid cancer, six poorly differentiated thyroid cancers, and two anaplastic thyroid cancers. SATB1 expression was observed in none of two anaplastic thyroid cancers, one of six poorly differentiated thyroid cancers, and nine of 36 well-differentiated thyroid cancers. SATB1 expression was not significantly associated with any high-risk group-related clinicopathologic factors in well-differentiated thyroid cancer. Survival was not associated with SATB1 expression. SATB1 expression is independent of thyroid cancer differentiation, as well as high-risk-related factors. SATB1 may not play a role in the aggressiveness of thyroid cancer.

Silencing SATB1 inhibits proliferation of human osteosarcoma U2OS cells

It has been shown that over-expression of Special AT-rich binding protein 1 (SATB1) in breast cancer predicts a poor prognosis. This study was aimed at investigating the effects of silencing SATB1 on mesenchymal derived human osteosarcoma U2OS cells and the underlying mechanisms. The expressions of SATB1 and the related genes in the cells were detected by qRT-PCR and/or Western Blotting. SATB1 silencing was achieved by stable transfection with the vectors expressing small hairpin RNA versus SATB1. Cell proliferation was detected in a microplate reader with Cell Counting Kit-8 and the cell cycle was analyzed by flow cytometry using a cell cycle detection kit. The study found that SATB1 was particularly over-expressed in human osteosarcoma U2OS. Silencing SATB1 inhibited the proliferation of U2OS. It was found that inhibition of cell proliferation resulted from cell cycle arrest due to down-regulated expression of CFGF and JunB. The over-expression of SATB1 is responsible for abnormal proliferation of mesenchymal derived human Osteosatcoma U2OS cells, indicating that silencing SATB1 expression in the cells might be developed as an efficient osteosarcoma therapy. CTGF and JunB were involved in SATB1-mediated proliferation of U2OS cells.

Loss of Special AT-Rich Binding Protein 1 Expression is a Marker of Poor Survival in Lung Cancer

Lung cancer is the leading cause of cancer-related mortality and requires more effective molecular markers of prognosis and therapeutic responsiveness. Special AT-rich binding protein 1 (SATB1) is a global genome organizer that recruits chromatin remodeling proteins to epigenetically regulate hundreds of genes in a tissue-specific manner. Initial studies suggest that SATB1 overexpression is a predictor of poor prognosis in breast cancer, but the prognostic significance of SATB1 expression has not been evaluated in lung cancer. A cohort of 257 lung cancers was evaluated by immunohistochemistry. Epigenetic silencing of SATB1 was examined in cell lines by 5-Aza 2-deoxycytidine and trichostatin A treatment, and chromatin immunoprecipitation. Significant loss of SATB1 expression was found in squamous preinvasive lesions (p < 0.04) and in non-small cell lung cancers (p < 0.001) compared with matched normal bronchial epithelium. Loss of SATB1 independently predicted poor cancer-specific survival in squamous cell carcinomas (SCCs; hazard ratio: 2.06, 95% confidence interval: 1.2-3.7, p = 0.016). Treatment of lung cancer cell lines with the histone deacetylase inhibitor trichostatin A resulted in up-regulation of SATB1. SATB1 was associated with a decrease in the active chromatin mark acetylated histone H3K9 and an increase in the repressive polycomb mark trimethylated H3K27 in a SCC cell line relative to a normal bronchial epithelial cell line. This is the first study showing that SATB1 expression is lost in early preinvasive squamous lesions and that loss of SATB1 is associated with poor prognosis in lung SCC. We hypothesize that the SATB1 gene is epigenetically silenced through histone modifications.

Loss of expression of the chromatin remodelling protein SATB1 in lung cancer is an independent prognostic marker

Lung cancer is the leading cause of cancer-related mortality and requires more effective molecular markers of prognosis and therapeutic responsiveness. Special AT-rich binding protein 1 (SATB1) is a global genome organiser that recruits chromatin remodelling proteins to epigenetically regulate hundreds of genes in a tissue-specific manner. SATB1 overexpression is a powerful predictor of poor prognosis in breast cancer, but the significance of SATB1 expression has not been previously evaluated in lung cancer. In a cohort of 285 primary lung cancers, significant loss of SATB1 expression was found in squamous preinvasive lesions ( p p p p = 0.016). Loss of SATB1 was also significantly associated with poor cancer-specific survival in small cell lung cancers (SCLC; HR 14.48, 95%CI 1.3–164.0, p = 0.03), however further investigation of a larger sample is warranted. Treatment of lung cancer cell lines A549 and H520 with the histone deacetylase inhibitor Trichostatin A resulted in up-regulation of SATB1. SATB1 was associated with a decrease in the active chromatin mark acetylated histone H3K9 and an increase in the repressive polycomb mark, trimethylated H3K27 in the SCC cell line NCI-H520 relative to the normal bronchial epithelial cell line NL20. This is the first study showing that SATB1 expression is lost in early preinvasive squamous lesions in the lung and that loss of SATB1 is associated with poor prognosis in lung SCC. Loss of SATB1 expression may be a result of epigenetic silencing caused by histone modifications.

Expression of SATB1 and heparanase in gastric cancer and its relationship to clinicopathologic features

The purpose of this study was to investigate the expression of special AT-rich binding protein 1 (SATB1) and heparanase in human gastric cancer as well as its relationship to the clinicopathologic factors. Specimens from 102 patients who underwent radical gastrectomy between 2000 and 2002 were studied by immunohistochemistry for SATB1 and heparanase expression. SATB1 and heparanase were positively expressed in 48.0% and 51.0% of gastric cancer cases, respectively. The expression of SATB1 and heparanase was significantly correlated with the depth of invasion, tumor-node-metastatsis (TNM) stage, lymph node metastasis, whereas SATB1 expression was also significantly correlated with distant metastasis. Patients with SATB1-negative expression and heparanase-negative expression had higher survival rates than those with SATB1-positive or heparanase-positive expression. Moreover, a positive correlation was found between SATB1 and heparanase. In multivariable analysis, SATB1 expression was also identified as an independent prognostic indicator for gastric cancer. Our results suggest that combined analysis of SATB1 and heparanase expression may have significant value in determining invasion and metastasis of gastric cancer and assessing prognosis in patients with gastric cancer.

Nuclear Matrix Binding Regulates SATB1-mediated Transcriptional Repression

Special AT-rich binding protein 1 (SATB1) originally was identified as a protein that bound to the nuclear matrix attachment regions (MARs) of the immunoglobulin heavy chain intronic enhancer. Subsequently, SATB1 was shown to repress many genes expressed in the thymus, including interleukin-2 receptor alpha, c-myc, and those encoded by mouse mammary tumor virus (MMTV), a glucocorticoid-responsive retrovirus. SATB1 binds to MARs within the MMTV provirus to repress transcription. To address the role of the nuclear matrix in SATB1-mediated repression, a series of SATB1 deletion constructs was used to determine protein localization. Wild-type SATB1 localized to the soluble nuclear, chromatin, and nuclear matrix fractions. Mutants lacking amino acids 224-278 had a greatly diminished localization to the nuclear matrix, suggesting the presence of a nuclear matrix targeting sequence (NMTS). Transient transfection experiments showed that NMTS fusions to green fluorescent protein or LexA relocalized these proteins to the nuclear matrix. Difficulties with previous assay systems prompted us to develop retroviral vectors to assess effects of different SATB1 domains on expression of MMTV proviruses or integrated reporter genes. SATB1 overexpression repressed MMTV transcription in the presence and absence of functional glucocorticoid receptor. Repression was alleviated by deletion of the NMTS, which did not affect DNA binding, or by deletion of the MAR-binding domain. Our studies indicate that both nuclear matrix association and DNA binding are required for optimal SATB1-mediated repression of the integrated MMTV promoter and may allow insulation from cellular regulatory elements.