Genome organizing function of SATB1 in tumor progression

Proteomic analysis identifies argininosuccinate synthetase 1 and special AT-rich sequence binding protein 1 as reliable markers for the immunohistochemical distinction between WHO types A and B3 thymomas

AIMS

The reliable classification of type A versus type B3 thymomas has prognostic and therapeutic relevance, but can be problematic due to considerably overlapping morphology. No immunohistochemical markers aiding in this distinction have been published so far.

METHODS AND RESULTS

We identified and quantified numerous differentially expressed proteins using an unbiased proteomic screen by mass spectrometry in pooled protein lysates from three type A and three type B3 thymomas. From these, candidates were validated in a larger series of paraffin-embedded type A and B3 thymomas. We identified argininosuccinate synthetase 1 (ASS1) and special AT-rich sequence binding protein 1 (SATB1) as highly discriminatory between 34 type A and 20 type B3 thymomas (94% sensitivity, 98% specificity and 96% accuracy). Although not the focus of this study, the same markers also proved helpful in the diagnosis of type AB (n = 14), B1 (n = 4) and B2 thymomas (n = 10).

CONCLUSIONS

Mutually exclusive epithelial expression of ASS1 in 100% of type B3 thymomas and ectopic nuclear expression of SATB1 in 92% of type A thymomas support the distinction between type A and type B3 thymomas with 94% sensitivity, 98% specificity and 96% accuracy.

A dual function for the chromatin organizer Special A-T rich Binding Protein 1 in B-lineage cells

SATB1 (Special A-T rich Binding protein 1) is a cell type-specific factor that regulates the genetic network in developing T cells and neurons. In T cells, SATB1 is required for lineage commitment, VDJ recombination, development and maturation. Considering that its expression varies during B-cell differentiation, the involvement of SATB1 needs to be clarified in this lineage. Using a KO mouse model in which SATB1 was deleted from the pro-B-cell stage, we examined the consequences of SATB1 deletion in naive and activated B-cell subsets. Our model indicates first, unlike its essential function in T cells, that SATB1 is dispensable for B-cell development and the establishment of a broad IgH repertoire. Second, we show that SATB1 exhibits an ambivalent function in mature B cells, acting sequentially as a positive and negative regulator of Ig gene transcription in naive and activated cells, respectively. Third, our study indicates that the negative regulatory function of SATB1 in B cells extends to the germinal center response, in which this factor limits somatic hypermutation of Ig genes.

CUT homeobox genes: transcriptional regulation of neuronal specification and beyond

CUT homeobox genes represent a captivating gene class fulfilling critical functions in the development and maintenance of multiple cell types across a wide range of organisms. They belong to the larger group of homeobox genes, which encode transcription factors responsible for regulating gene expression patterns during development. CUT homeobox genes exhibit two distinct and conserved DNA binding domains, a homeodomain accompanied by one or more CUT domains. Numerous studies have shown the involvement of CUT homeobox genes in diverse developmental processes such as body axis formation, organogenesis, tissue patterning and neuronal specification. They govern these processes by exerting control over gene expression through their transcriptional regulatory activities, which they accomplish by a combination of classic and unconventional interactions with the DNA. Intriguingly, apart from their roles as transcriptional regulators, they also serve as accessory factors in DNA repair pathways through protein-protein interactions. They are highly conserved across species, highlighting their fundamental importance in developmental biology. Remarkably, evolutionary analysis has revealed that CUT homeobox genes have experienced an extraordinary degree of rearrangements and diversification compared to other classes of homeobox genes, including the emergence of a novel gene family in vertebrates. Investigating the functions and regulatory networks of CUT homeobox genes provides significant understanding into the molecular mechanisms underlying embryonic development and tissue homeostasis. Furthermore, aberrant expression or mutations in CUT homeobox genes have been associated with various human diseases, highlighting their relevance beyond developmental processes. This review will overview the well known roles of CUT homeobox genes in nervous system development, as well as their functions in other tissues across phylogeny.

Overexpression of SATB1 correlates with epithelial-mesenchymal transition and lymphatic metastasis in gastric cancer

BACKGROUND

Gastric cancer (GC) is a malignant tumor with a high mortality rate, and lymphatic metastasis is the main mode of GC metastasis. The nuclear transcriptional regulatory protein SATB1 has been confirmed to be closely related to GC metastasis, but the mechanism has not been elucidated.

METHODS

Epithelial-mesenchymal transition (EMT) is known as the pivotal process of GC metastasis. To evaluate the relationship between SATB1 and EMT in GC metastasis, the immunohistochemical method was used to detect the expression of SATB1, E-cadherin, N-cadherin, Vimentin protein in 52 paraffin-embedded specimens of gastric cancer, and analyze the relationship between their expression and pathological parameters.

RESULTS

Abnormal positive expression of SATB1 protein in paraffin-embedded tumor tissues was positively correlated with local invasion, lymph node metastasis, and TNM staging in gastric cancer. There was a statistically significant difference in the expression of SATB1 between the early stage of gastric cancer (stage I) and the advanced stage (stageII, III, IV). Moreover, SATB1 expression was positively correlated to N-cadherin and Vimentin but negatively to E-cadherin from Stages I to IV.

CONCLUSION

The GC patients with overexpression of SATB1 tended to have advanced stage and lymph node metastasis. SATB1 was positively correlated with EMT in Gastric Cancer.

Chromatin organizer SATB1 controls the cell identity of CD4+ CD8+ double-positive thymocytes by regulating the activity of super-enhancers

CD4⁺ and CD8⁺ double-positive (DP) thymocytes play a crucial role in T cell development in the thymus. DP cells rearrange the T cell receptor gene Tcra to generate T cell receptors with TCRβ. DP cells differentiate into CD4 or CD8 single-positive (SP) thymocytes, regulatory T cells, or invariant nature kill T cells (iNKT) in response to TCR signaling. Chromatin organizer SATB1 is highly expressed in DP cells and is essential in regulating Tcra rearrangement and differentiation of DP cells. Here we explored the mechanism of SATB1 orchestrating gene expression in DP cells. Single-cell RNA sequencing shows that Satb1 deletion changes the cell identity of DP thymocytes and down-regulates genes specifically and highly expressed in DP cells. Super-enhancers regulate the expressions of DP-specific genes, and our Hi-C data show that SATB1 deficiency in thymocytes reduces super-enhancer activity by specifically decreasing interactions among super-enhancers and between super-enhancers and promoters. Our results reveal that SATB1 plays a critical role in thymocyte development to promote the establishment of DP cell identity by globally regulating super-enhancers of DP cells at the chromatin architectural level.

Base excision repair accessory factors in senescence avoidance and resistance to treatments

Cancer cells, in which the RAS and PI3K pathways are activated, produce high levels of reactive oxygen species (ROS), which cause oxidative DNA damage and ultimately cellular senescence. This process has been documented in tissue culture, mouse models, and human pre-cancerous lesions. In this context, cellular senescence functions as a tumour suppressor mechanism. Some rare cancer cells, however, manage to adapt to avoid senescence and continue to proliferate. One well-documented mode of adaptation involves increased production of antioxidants often associated with inactivation of the KEAP1 tumour suppressor gene and the resulting upregulation of the NRF2 transcription factor. In this review, we detail an alternative mode of adaptation to oxidative DNA damage induced by ROS: the increased activity of the base excision repair (BER) pathway, achieved through the enhanced expression of BER enzymes and DNA repair accessory factors. These proteins, exemplified here by the CUT domain proteins CUX1, CUX2, and SATB1, stimulate the activity of BER enzymes. The ensued accelerated repair of oxidative DNA damage enables cancer cells to avoid senescence despite high ROS levels. As a by-product of this adaptation, these cancer cells exhibit increased resistance to genotoxic treatments including ionizing radiation, temozolomide, and cisplatin. Moreover, considering the intrinsic error rate associated with DNA repair and translesion synthesis, the elevated number of oxidative DNA lesions caused by high ROS leads to the accumulation of mutations in the cancer cell population, thereby contributing to tumour heterogeneity and eventually to the acquisition of resistance, a major obstacle to clinical treatment.

3D Genome Organization as an Epigenetic Determinant of Transcription Regulation in T Cells

In the heart of innate and adaptive immunity lies the proper spatiotemporal development of several immune cell lineages. Multiple studies have highlighted the necessity of epigenetic and transcriptional regulation in cell lineage specification. This mode of regulation is mediated by transcription factors and chromatin remodelers, controlling developmentally essential gene sets. The core of transcription and epigenetic regulation is formulated by different epigenetic modifications determining gene expression. Apart from “classic” epigenetic modifications, 3D chromatin architecture is also purported to exert fundamental roles in gene regulation. Chromatin conformation both facilitates cell-specific factor binding at specified regions and is in turn modified as such, acting synergistically. The interplay between global and tissue-specific protein factors dictates the epigenetic landscape of T and innate lymphoid cell (ILC) lineages. The expression of global genome organizers such as CTCF, YY1, and the cohesin complexes, closely cooperate with tissue-specific factors to exert cell type-specific gene regulation. Special AT-rich binding protein 1 (SATB1) is an important tissue-specific genome organizer and regulator controlling both long- and short-range chromatin interactions. Recent indications point to SATB1’s cooperation with the aforementioned factors, linking global to tissue-specific gene regulation. Changes in 3D genome organization are of vital importance for proper cell development and function, while disruption of this mechanism can lead to severe immuno-developmental defects. Newly emerging data have inextricably linked chromatin architecture deregulation to tissue-specific pathophysiological phenotypes. The combination of these findings may shed light on the mechanisms behind pathological conditions.

Special AT-Rich Sequence-Binding Protein 1 Supports Survival and Maturation of Naive B Cells Stimulated by B Cell Receptors

Epigenetic mechanisms underpin the elaborate activities of essential transcription factors in lymphocyte development. Special AT-rich sequence-binding protein 1 (SATB1) is a chromatin remodeler that orchestrates the spatial and temporal actions of transcription factors. Previous studies have revealed the significance of SATB1 in T cell lineage. However, whether and how SATB1 controls B cell lineage development is yet to be clarified. In this study, we show that SATB1 is an important factor during splenic B cell maturation. By analyzing SATB1/Tomato reporter mice, we determined the dynamic fluctuation of SATB1 expression in the B cell lineage. Although SATB1 expression decreased to minimal levels during B cell differentiation in the bone marrow, it resurged markedly in naive B cells in the spleen. The expression was dramatically downregulated upon Ag-induced activation. Splenic naive B cells were subdivided into two categories, namely SATB1^high and SATB1^-/low, according to their SATB1 expression levels. SATB1^high naive B cells were less susceptible to death and greater proliferative than were SATB1^-/low cells during incubation with an anti-IgM Ab. Additionally, SATB1^high cells tended to induce the expression of MHC class II, CD86, and CD83. Accordingly, naive B cells from B lineage-specific SATB1 conditional knockout mice were more susceptible to apoptosis than that in the control group upon anti-IgM Ab stimulation in vitro. Furthermore, conditional knockout mice were less capable of producing Ag-specific B cells after immunization. Collectively, our findings suggest that SATB1 expression increases in naive B cells and plays an important role in their survival and maturation.

Prognostic Significance of TLR2, SMAD3 and Localization-dependent SATB1 in Stage I and II Non-Small-Cell Lung Cancer Patients

This study aimed to explore the prognostic value of SATB1, SMAD3, and TLR2 expression in non-small-cell lung carcinoma patients with clinical stages I-II. To investigate, we evaluated immunohistochemical staining to each of these markers using tissue sections from 69 patients from our cohort and gene expression data for The Cancer Genome Atlas (TCGA) cohort. We found that, in our cohort, high expression levels of nuclear SATB1ⁿ and SMAD3 were independent prognostic markers for better overall survival (OS) in NSCLC patients. Interestingly, expression of cytoplasmic SATB1^c exhibited a significant but inverse association with survival rate, and it was an independent predictor of unfavorable prognosis. Likewise, TLR2 was a negative outcome biomarker for NSCLC even when adjusting for covariates. Importantly, stratification of NSCLCs with respect to combined expression of the three biomarkers allowed us to identify subgroups of patients with the greatest difference in duration of survival. Specifically, expression profile of SATB1^n-high/SMAD3^high/TLR2^low was associated with the best OS, and it was superior to each single protein alone in predicting patient prognosis. Furthermore, based on the TCGA dataset, we found that overexpression of SATB1 mRNA was significantly associated with better OS, whereas high mRNA levels of SMAD3 and TLR2 with poor OS. In conclusion, the present study identified a set of proteins that may play a significant role in predicting prognosis of NSCLC patients with clinical stages I-II.

CUT Domain Proteins in DNA Repair and Cancer

Simple Summary

Genetic integrity is ensured by complex groups of proteins involved in DNA repair. In particular, base damage is repaired by enzymes of the base excision repair pathway. Recent studies have revealed that some transcription factors can function as accessory factors that stimulate the enzymatic activities of these DNA repair enzymes. It is well known that defects in DNA repair mechanisms cause the accumulation of changes in DNA, called mutations, that increase the possibility that cells become tumorigenic. Paradoxically, once they have emerged certain cancer cells are acutely dependent on the heightened activities of base excision repair enzymes because their metabolism generates highly reactive molecules that cause multiple types of damage to bases. In this context, the function of accessory factors becomes essential to cancer cell survival. As a by-product of this adaptation, cancer cells become more resistant to therapies that cause DNA damage, such as chemotherapy and radiation.

Abstract

Recent studies revealed that CUT domains function as accessory factors that accelerate DNA repair by stimulating the enzymatic activities of the base excision repair enzymes OGG1, APE1, and DNA pol β. Strikingly, the role of CUT domain proteins in DNA repair is exploited by cancer cells to facilitate their survival. Cancer cells in which the RAS pathway is activated produce an excess of reactive oxygen species (ROS) which, if not counterbalanced by increased production of antioxidants, causes sustained oxidative DNA damage and, ultimately, cell senescence. These cancer cells can adapt by increasing their capacity to repair oxidative DNA damage in part through elevated expression of CUT domain proteins such as CUX1, CUX2, or SATB1. In particular, CUX1 overexpression was shown to cooperate with RAS in the formation of mammary and lung tumors in mice. Conversely, knockdown of CUX1, CUX2, or SATB1 was found to be synthetic lethal in cancer cells exhibiting high ROS levels as a consequence of activating mutations in KRAS, HRAS, BRAF, or EGFR. Importantly, as a byproduct of their adaptation, cancer cells that overexpress CUT domain proteins exhibit increased resistance to genotoxic treatments such as ionizing radiation, temozolomide, and cisplatin.

Role of Satb1 and Satb2 Transcription Factors in the Glutamate Receptors Expression and Ca2+ Signaling in the Cortical Neurons In Vitro

Transcription factors Satb1 and Satb2 are involved in the processes of cortex development and maturation of neurons. Alterations in the expression of their target genes can lead to neurodegenerative processes. Molecular and cellular mechanisms of regulation of neurotransmission by these transcription factors remain poorly understood. In this study, we have shown that transcription factors Satb1 and Satb2 participate in the regulation of genes encoding the NMDA-, AMPA-, and KA- receptor subunits and the inhibitory GABA(A) receptor. Deletion of gene for either Satb1 or Satb2 homologous factors induces the expression of genes encoding the NMDA receptor subunits, thereby leading to higher amplitudes of Ca²⁺-signals in neurons derived from the Satb1-deficient (Satb1^fl/+ * Nex^Cre/+) and Satb1-null mice (Satb1^fl/fl * Nex^Cre/+) in response to the selective agonist reducing the EC50 for the NMDA receptor. Simultaneously, there is an increase in the expression of the Gria2 gene, encoding the AMPA receptor subunit, thus decreasing the Ca²⁺-signals of neurons in response to the treatment with a selective agonist (5-Fluorowillardiine (FW)). The Satb1 deletion increases the sensitivity of the KA receptor to the agonist (domoic acid), in the cortical neurons of the Satb1-deficient mice but decreases it in the Satb1-null mice. At the same time, the Satb2 deletion decreases Ca²⁺-signals and the sensitivity of the KA receptor to the agonist in neurons from the Satb1-null and the Satb1-deficient mice. The Satb1 deletion affects the development of the inhibitory system of neurotransmission resulting in the suppression of the neuron maturation process and switching the GABAergic responses from excitatory to inhibitory, while the Satb2 deletion has a similar effect only in the Satb1-null mice. We show that the Satb1 and Satb2 transcription factors are involved in the regulation of the transmission of excitatory signals and inhibition of the neuronal network in the cortical cell culture.

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.

Enhanced affinity of racemic phosphorothioate DNA with transcription factor SATB1 arising from diastereomer-specific hydrogen bonds and hydrophobic contacts

Phosphorothioate modification is commonly introduced into therapeutic oligonucleotides, typically as a racemic mixture in which either of the two non-bridging phosphate oxygens is replaced by sulfur, which frequently increases affinities with proteins. Here, we used isothermal titration calorimetry and X-ray crystallography to investigate the thermodynamic and structural properties of the interaction between the primary DNA-binding domain (CUTr1) of transcription factor SATB1 and dodecamer DNAs with racemic phosphorothioate modifications at the six sites known to contact CUTr1 directly. For both the modified and unmodified DNAs, the binding reactions were enthalpy-driven at a moderate salt concentration (50 mM NaCl), while being entropy-driven at higher salt concentrations with reduced affinities. The phosphorothioate modifications lowered this susceptibility to salt, resulting in a significantly enhanced affinity at a higher salt concentration (200 mM NaCl), although only some DNA molecular species remained interacting with CUTr1. This was explained by unequal populations of the two diastereomers in the crystal structure of the complex of CUTr1 and the phosphorothioate-modified DNA. The preferred diastereomer formed more hydrogen bonds with the oxygen atoms and/or more hydrophobic contacts with the sulfur atoms than the other, revealing the origins of the enhanced affinity.

SATB1 as oncogenic driver and potential therapeutic target in head & neck squamous cell carcinoma (HNSCC)

The Special AT-rich sequence binding protein 1 (SATB1) is a genome organizer protein that controls gene expression of numerous genes by regulating chromatin architecture and targeting chromatin-remodeling/-modifying enzymes onto specific chromatin regions. SATB1 is overexpressed in various tumors. In head and neck squamous cell carcinoma (HNSCC), SATB1 upregulation is correlated with TNM classification, metastasis, poor prognosis and reduced overall survival. In this paper, we comprehensively analyze cellular and molecular effects of SATB1 in a large set of primary cell lines from primary HNSCC or metastases, using RNAi-mediated knockdown in vitro and, therapeutically, in tumor xenograft mouse models in vivo. In a series of 15 cell lines, major differences in SATB1 levels are observed. In various 2-D and 3-D assays, growth inhibition upon efficient siRNA-mediated SATB1 knockdown depends on the cell line rather than initial SATB1 levels. Inhibitory effects are found to be based on cell cycle deceleration, apoptosis induction, decreased HER3 and Heregulin A&B expression, and effects on EMT genes. In vivo, systemic treatment of tumor xenograft-bearing mice with siRNAs formulated in polymeric nanoparticles inhibits tumor growth of two HNSCC xenograft models, resulting from therapeutic SATB1 reduction and concomitant decrease of proliferation and induction of apoptosis. In conclusion, SATB1 represents a promising target in HNSCC, affecting crucial cellular processes and molecular pathways.

SATB1 establishes ameloblast cell polarity and regulates directional amelogenin secretion for enamel formation

BACKGROUND

Polarity is necessary for epithelial cells to perform distinct functions at their apical and basal surfaces. Oral epithelial cell-derived ameloblasts at secretory stage (SABs) synthesize large amounts of enamel matrix proteins (EMPs), largely amelogenins. EMPs are unidirectionally secreted into the enamel space through their apical cytoplasmic protrusions, or Tomes' processes (TPs), to guide the enamel formation. Little is known about the transcriptional regulation underlying the establishment of cell polarity and unidirectional secretion of SABs.

RESULTS

The higher-order chromatin architecture of eukaryotic genome plays important roles in cell- and stage-specific transcriptional programming. A genome organizer, special AT-rich sequence-binding protein 1 (SATB1), was discovered to be significantly upregulated in ameloblasts compared to oral epithelial cells using a whole-transcript microarray analysis. The Satb1-/- mice possessed deformed ameloblasts and a thin layer of hypomineralized and non-prismatic enamel. Remarkably, Satb1-/- ameloblasts at the secretory stage lost many morphological characteristics found at the apical surface of wild-type (wt) SABs, including the loss of Tomes' processes, defective inter-ameloblastic adhesion, and filamentous actin architecture. As expected, the secretory function of Satb1-/- SABs was compromised as amelogenins were largely retained in cells. We found the expression of epidermal growth factor receptor pathway substrate 8 (Eps8), a known regulator for actin filament assembly and small intestinal epithelial cytoplasmic protrusion formation, to be SATB1 dependent. In contrast to wt SABs, EPS8 could not be detected at the apical surface of Satb1-/- SABs. Eps8 expression was greatly reduced in small intestinal epithelial cells in Satb1-/- mice as well, displaying defective intestinal microvilli.

CONCLUSIONS

Our data show that SATB1 is essential for establishing secretory ameloblast cell polarity and for EMP secretion. In line with the deformed apical architecture, amelogenin transport to the apical secretory front and secretion into enamel space were impeded in Satb1-/- SABs resulting in a massive cytoplasmic accumulation of amelogenins and a thin layer of hypomineralized enamel. Our studies strongly suggest that SATB1-dependent Eps8 expression plays a critical role in cytoplasmic protrusion formation in both SABs and in small intestines. This study demonstrates the role of SATB1 in the regulation of amelogenesis and the potential application of SATB1 in ameloblast/enamel regeneration.

MiR-191-5p inhibits lung adenocarcinoma by repressing SATB1 to inhibit Wnt pathway

Background

To investigate the function of miR‐191‐5p in lung adenocarcinoma and its possible mechanism.

Methods

QRT‐PCR was adopted for the detection of the expression levels of miR‐191‐5p and SATB1 (HGNC: 10541). The effects of miR‐191‐5p and SATB1 on cell proliferation and migration were examined through the CCK‐8 and Transwell assays. Subsequently, the binding relationships between miR‐191‐5p and SATB1 were confirmed by dual‐luciferase reporter gene assay. Finally, the potential mechanisms of action of miR‐191‐5p were explored through a serious of in vivo and in vitro experiments.

Results

Lung adenocarcinoma patients had a notably lower expression level of miR‐191‐5p than controls, patients with metastasis had a lower level than those without metastasis, and the level in patients with lung adenocarcinoma in stage III‐IV was lower than that in patients with lung adenocarcinoma in stage I‐II. Overexpression of miR‐191‐5p repressed the migration and proliferation of lung cancer A549/H1650 cells. According to the reporter gene assay, miR‐191‐5p could bind to SATB1. Besides, SATB1 was significantly overexpressed in cancer tissues of patients with lung adenocarcinoma, and SATB1 overexpression accelerated the migration and proliferation of A549/H1650 cells and reversed inhibition on cell migration and proliferation by miR‐191‐5p.

Conclusion

Overexpression of miR‐191‐5p is capable of blocking the migration and proliferation of lung cancer cells, and its mechanism may be through targeting SATB1 thus downregulating Wnt signaling.

Assessment of the Utility of Gene Positioning Biomarkers in the Stratification of Prostate Cancers

There is a pressing need for additional clinical biomarkers to predict the aggressiveness of individual cancers. Here, we examine the potential usefulness of spatial genome organization as a prognostic tool for prostate cancer. Using fluorescence in situ hybridization on formalin-fixed, paraffin embedded human prostate tissue specimens, we compared the nuclear positions of four genes between clinically relevant subgroups of prostate tissues. We find that directional repositioning of SP100 and TGFB3 gene loci stratifies prostate cancers of differing Gleason scores. A more peripheral position of SP100 and TGFB3 in the nucleus, compared to benign tissues, is associated with low Gleason score cancers, whereas more internal positioning correlates with higher Gleason scores. Conversely, LMNA is more internally positioned in many non-metastatic prostate cancers, while its position is indistinguishable from benign tissue in metastatic cancer. The false positive rates were relatively low, whereas, the false negative rates of single or combinations of genes were high, limiting the clinical utility of this assay in its current form. Nevertheless, our findings of subtype-specific gene positioning patterns in prostate cancer provides proof-of-concept for the potential usefulness of spatial gene positioning for prognostic applications, and encourage further exploration of spatial gene positioning patterns to identify novel clinically relevant molecular biomarkers, which may aid treatment decisions for cancer patients.

HER2, NF-κB, and SATB1 Expression Patterns in Gastric Cancer and Their Correlation with Clinical and Pathological Parameters

Gastric cancer (GC) is currently recognized as one of the most common and fatal tumor worldwide. The identification of novel biomarkers in relation to clinical information as well as extending the knowledge on a multiple crosstalk between various oncogenic pathways implicated in GC carcinogenesis seems pivotal to limit the disease-associated mortality. Therefore, we assessed the expression of HER2, NF-κB, and SATB1 in a total of 104 gastric adenocarcinomas and 30 normal gastric samples and correlated the expression patterns with each other and with some clinicopathological variables. Protein expression was examined by immunohistochemistry (IHC) on tissue microarrays (TMAs), and fluorescence in situ hybridization (FISH) was employed to detect HER2 amplification. In the studied group, HER2 and SATB1 were found to be overexpressed in gastric cancer tissue in comparison to normal gastric mucosa. The expression status of the former protein was seen to differ according to some clinicopathological features, but without statistical significance, whereas the expression of the latter was not importantly associated with any of them. In turn, the NF-κB protein level was significantly related to the presence of lymph node metastasis. HER2 expression was not significantly correlated with that of other proteins, but a positive correlation was found between the expression of SATB1 and NF-κB. Further studies with a larger group of patients combined with in vitro mechanistic experiments are required to fully elucidate the role and relationship of HER2, NF-κB, and SATB1 expression in gastric cancer progression. However, to the best of our knowledge, this study is the first look at a simultaneous evaluation of these three markers in the samples of gastric cancer patients.

HOXC13-AS-miR-122-5p-SATB1-C-Myc feedback loop promotes migration, invasion and EMT process in glioma

Purpose

Differentially expressed long non-coding ribonucleic acids (lncRNAs) have been reported as a key factor of glioma carcinogenesis, but the underlying mechanism involved is still unknown.

Materials and methods

In the present study, lncRNA HOXC13 antisense RNA (HOXC13-AS) was identified as a potential oncogene in glioma, and Western blotting, wound healing and Transwell assays were carried out to explore the effects of HOXC13-AS on the epithelial-mesenchymal transition (EMT) process as well as the migration and invasion of glioma cells.

Results

A further mechanistic study showed that HOXC13-AS sponged miR-122-5p to indirectly regulate SATB1 expression and affect the EMT process via the Wnt/β-catenin pathway. Meanwhile, the promoter activity was significantly increased via c-Myc, a key factor of the Wnt/β-catenin pathway, thus forming a positive HOXC13-AS-miR-122-5p-SATB1-c-Myc feedback loop to drive the malignant behavior in glioma.

Discussion

This study evidences the constitutive HOXC13-AS-miR-122-5p-SATB1-c-Myc feedback loop and provides a potential therapeutic target for glioma treatment.

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.

Transcriptomic analysis of human IL-7 receptor alpha low and high effector memory CD8+ T cells reveals an age-associated signature linked to influenza vaccine response in older adults

Here, we investigated the relationship of the age‐associated expansion of IL‐7 receptor alpha low (IL‐7Rα^low) effector memory (EM) CD8⁺ T cells with the global transcriptomic profile of peripheral blood cells in humans. We found 231 aging signature genes of IL‐7Rα^low EM CD8⁺ T cells that corresponded to 15% of the age‐associated genes (231/1,497) reported by a meta‐analysis study on human peripheral whole blood from approximately 15,000 individuals, having high correlation with chronological age. These aging signature genes were the target genes of several transcription factors including MYC, SATB1, and BATF, which also belonged to the 231 genes, supporting the upstream regulatory role of these transcription factors in altering the gene expression profile of peripheral blood cells with aging. We validated the differential expression of these transcription factors between IL‐7Rα^low and ^high EM CD8⁺ T cells as well as in peripheral blood mononuclear cells (PBMCs) of young and older adults. Finally, we found a significant association with influenza vaccine responses in older adults, suggesting the possible biological significance of the aging signature genes of IL‐7Rα^low EM CD8⁺ T cells. The results of our study support the relationship of the expansion of IL‐7Rα^low EM CD8⁺ T cells with the age‐associated changes in the gene expression profile of peripheral blood cells and its possible biological implications.

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

Background

The 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.

Methods

A 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.

Results

Compared 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).

Conclusion

These results showed that expression of SATB1 may have an effect on the disease progression and survival outcome of cervical cancer.

SATB family chromatin organizers as master regulators of tumor progression

SATB (Special AT-rich binding protein) family proteins have emerged as key regulators that integrate higher-order chromatin organization with the regulation of gene expression. Studies over the past decade have elucidated the specific roles of SATB1 and SATB2, two closely related members of this family, in cancer progression. SATB family chromatin organizers play diverse and important roles in regulating the dynamic equilibrium of apoptosis, cell invasion, metastasis, proliferation, angiogenesis, and immune modulation. This review highlights cellular and molecular events governed by SATB1 influencing the structural organization of chromatin and interacting with several co-activators and co-repressors of transcription towards tumor progression. SATB1 expression across tumor cell types generates cellular and molecular heterogeneity culminating in tumor relapse and metastasis. SATB1 exhibits dynamic expression within intratumoral cell types regulated by the tumor microenvironment, which culminates towards tumor progression. Recent studies suggested that cell-specific expression of SATB1 across tumor recruited dendritic cells (DC), cytotoxic T lymphocytes (CTL), T regulatory cells (Tregs) and tumor epithelial cells along with tumor microenvironment act as primary determinants of tumor progression and tumor inflammation. In contrast, SATB2 is differentially expressed in an array of cancer types and is involved in tumorigenesis. Survival analysis for patients across an array of cancer types correlated with expression of SATB family chromatin organizers suggested tissue-specific expression of SATB1 and SATB2 contributing to disease prognosis. In this context, it is pertinent to understand molecular players, cellular pathways, genetic and epigenetic mechanisms governed by cell types within tumors regulated by SATB proteins. We propose that patient survival analysis based on the expression profile of SATB chromatin organizers would facilitate their unequivocal establishment as prognostic markers and therapeutic targets for cancer therapy.

Cancer-associated fibroblasts promote progression and gemcitabine resistance via the SDF-1/SATB-1 pathway in pancreatic cancer

Cancer-associated fibroblasts (CAFs), a dominant component of the pancreatic tumor microenvironment, are mainly considered as promotors of malignant progression, but the underlying molecular mechanism remains unclear. Here, we show that SDF-1 secreted by CAFs stimulates malignant progression and gemcitabine resistance in pancreatic cancer, partially owing to paracrine induction of SATB-1 in pancreatic cancer cells. CAF-secreted SDF-1 upregulated the expression of SATB-1 in pancreatic cancer cells, which contributed to the maintenance of CAF properties, forming a reciprocal feedback loop. SATB-1 was verified to be overexpressed in human pancreatic cancer tissues and cell lines by quantitative real-time PCR, western blot, and immunohistochemical staining, which correlated with tumor progression and clinical prognosis in pancreatic cancer patients. We found that SATB-1 knockdown inhibited proliferation, migration, and invasion in SW1990 and PANC-1 cells in vitro, whereas overexpression of SATB-1 in Capan-2 and BxPC-3 cells had the opposite effect. Immunofluorescence staining showed that conditioned medium from SW1990 cells expressing SATB-1 maintained the local supportive function of CAFs. Furthermore, downregulation of SATB-1 inhibited tumor growth in mouse xenograft models. In addition, we found that overexpression of SATB-1 in pancreatic cancer cells participated in the process of gemcitabine resistance. Finally, we investigated the clinical correlations between SDF-1 and SATB-1 in human pancreatic cancer specimens. In summary, these findings demonstrated that the SDF-1/CXCR4/SATB-1 axis may be a potential new target of clinical interventions for pancreatic cancer patients.

Expression of p16 and SATB1 in Invasive Ductal Breast Cancer - A Preliminary Study

BACKGROUND/AIM

An impaired cell-cycle control and genetic material organization are crucial elements of carcinogenesis. p16 is a tumor suppressor protein which decelerates promotion of the cells from G₁ to S phase, whereas special AT-rich sequence-binding protein 1 (SATB1) is a nuclear matrix protein that binds to specific regions of the DNA and ensures its proper organization and function. Increased levels of both markers are observed in various types of cancers. The aim of this study was to investigate the expression of p16 and SATB1 proteins in regard to expression of the Ki-67 antigen and available clinicopathological data (i.a. receptor status, staging and grading).

MATERIALS AND METHODS

The study was performed on 130 samples of archived invasive ductal breast cancers. Immunohistochemical reactions were performed on freshly prepared tissue microarrays and subsequently scanned by a histologic scanner. Reactions were evaluated separately in the cytoplasm (p16c, SATB1c) and nucleus (p16n, SATB1n, Ki-67) with use of a quantification software under researcher supervision.

RESULTS

Expression was observed for Ki-67 in 100%, p16c in 90%, p16n in 89.2%, SATB1c in 98.5% and SATB1n in 87.7% of cancer cases. Statistical analysis showed strong positive correlations: p16c vs. p16n and SATB1c vs. SATB1n (p<0.001 for both) and weak positive correlations: p16c vs. SATB1c and p16c vs. SATB1n (p=0.008, p=0.027; respectively). Expression of p16n was stronger in G₁ vs. G₂ (p=0.034) while Ki-67 expression was stronger in cases with negative progesterone receptor status (p=0.011). All other analyzed associations were statistically insignificant.

CONCLUSION

A weak association between immunohistochemical expression of p16 and SATB1 indicated limited possibility of their independent usage. Further studies concerning determination of a wider panel of proteins controlling cell cycle should be considered.

EGFR aptamer-conjugated liposome-polycation-DNA complex for targeted delivery of SATB1 small interfering RNA to choriocarcinoma cells

Choriocarcinoma is a highly aggressive and vascular cancer. The main treatment for choriocarcinoma is the chemotherapy associated with severe side effects. Therefore, the development of novel strategies to eliminate choriocarcinoma is crucial for increasing the health of women. SATB1 (special AT-rich sequence binding protein 1) participates in tissue-specific gene expression and higher-order chromatin organization, and could promote cancer progression and invasion. For the first time, we hereby demonstrated that the expression of SATB1 was increased by 19 folds in choriocarcinoma cells compared with the normal chorionic cell line, and inhibition of SATB1 expression could markedly inhibit the proliferation of choriocarcinoma cells. Then we developed the gene drug delivery system EGFR-LPDS (epidermal growth factor receptor aptamer-conjugated liposome-polycation-DNA complex loaded with SATB1 siRNA) to increase the delivery and therapeutic effect of SATB1 siRNA against choriocarcinoma cells. The results showed that EGFR-LPDS could specifically target choriocarcinoma cells, resulting in significant inhibition of SATB1 expression, growth inhibitory effect and apoptosis in EGFR over-expressing choriocarcinoma cells in vitro. Notably, EGFR-LPDS could inhibit the expression of SATB1 in choriocarcinoma xenograft in mice, and exhibited the best therapeutic efficacy against mice bearing choriocarcinoma xenograft compared with other controls. Notably, EGFR-LPDS achieved a striking tumor weight inhibitory rate of 81.4%. This is the first report of the therapeutic efficacy of SATB1 siRNA towards choriocarcinoma, and the increased SATB1 siRNA delivery by nanoparticles to choriocarcinoma cells using EGFR aptamers. Thus, EGFR-LPDS represents an up-and coming approach for choriocarcinoma therapy. Considering that there are still limited treatment strategies for choriocarcinoma therapy, patients with choriocarcinoma may be beneficial from this gene therapy.

PAK5 promotes the migration and invasion of cervical cancer cells by phosphorylating SATB1

p21-activated kinase 5 (PAK5) is involved in several oncogenic signaling pathways and its amplification or overexpression has been found in various types of cancer; however, the pathophysiologic role of PAK5 in cervical cancer (CC) remains elusive. This study aims to elucidate the effects of PAK5 on CC metastasis and its specific regulation mechanism. We performed western blotting and immunohistochemistry (IHC) analysis and found that the expression levels of PAK5 were significantly upregulated in CC cells and tissues. In addition, statistical analysis via IHC showed that increased PAK5 significantly correlated with CC progression. Mn²⁺-Phos-tag SDS-PAGE, western blotting, immunofluorescence and dual luciferase reporter assays were utilized to determine the involvement of SATB1 in PAK5-mediated epithelial-mesenchymal transition (EMT). We found that PAK5-mediated special AT-rich binding protein-1 (SATB1) phosphorylation on Ser47 initiated EMT cascade and promoted migration and invasion of CC cells. Furthermore, overexpression of PAK5 induced lung metastasis of CC cells in xenograft modes. Taken together, we conclude that PAK5 is a novel prognostic indicator and plays an important role in the CC metastasis.

Expression of p16 and SATB1 in Invasive Ductal Breast Cancer - A Preliminary Study

BACKGROUND/AIM

An impaired cell-cycle control and genetic material organization are crucial elements of carcinogenesis. p16 is a tumor suppressor protein which decelerates promotion of the cells from G₁ to S phase, whereas special AT-rich sequence-binding protein 1 (SATB1) is a nuclear matrix protein that binds to specific regions of the DNA and ensures its proper organization and function. Increased levels of both markers are observed in various types of cancers. The aim of this study was to investigate the expression of p16 and SATB1 proteins in regard to expression of the Ki-67 antigen and available clinicopathological data (i.a. receptor status, staging and grading).

MATERIALS AND METHODS

The study was performed on 130 samples of archived invasive ductal breast cancers. Immunohistochemical reactions were performed on freshly prepared tissue microarrays and subsequently scanned by a histologic scanner. Reactions were evaluated separately in the cytoplasm (p16c, SATB1c) and nucleus (p16n, SATB1n, Ki-67) with use of a quantification software under researcher supervision.

RESULTS

Expression was observed for Ki-67 in 100%, p16c in 90%, p16n in 89.2%, SATB1c in 98.5% and SATB1n in 87.7% of cancer cases. Statistical analysis showed strong positive correlations: p16c vs. p16n and SATB1c vs. SATB1n (p<0.001 for both) and weak positive correlations: p16c vs. SATB1c and p16c vs. SATB1n (p=0.008, p=0.027; respectively). Expression of p16n was stronger in G₁ vs. G₂ (p=0.034) while Ki-67 expression was stronger in cases with negative progesterone receptor status (p=0.011). All other analyzed associations were statistically insignificant.

CONCLUSION

A weak association between immunohistochemical expression of p16 and SATB1 indicated limited possibility of their independent usage. Further studies concerning determination of a wider panel of proteins controlling cell cycle should be considered.

Prognostic and Clinicopathological Significance of SATB1 in Colorectal Cancer: A Meta-Analysis

Background: A large number of studies have reported the aberrant expression of special AT-rich sequence binding protein 1 (SATB1) in colorectal cancer (CRC). However, the role of SATB1 in CRC is still controversial. Therefore, we performed this meta-analysis to elucidate the prognostic and clinical value of SATB1 in CRC patients.

Methods: We searched Web of Science, EMBASE and PubMed entirely in January 2018 to identify related articles. Pooled Hazard ratio (HR) was adopted to evaluate the prognostic value of SATB1 in CRC and odd ratio (OR) was used to assess the clinicopathological significance of SATB1 in CRC.

Results: Ten eligible studies containing 7 on prognosis and 9 on clinicopathological characteristics were finally included in the present meta-analysis. Results revealed that patients with high expression of SATB1 tended to have shorter overall survival (OS) (pooled HR: 1.64, 95% CI: 1.04–2.57). Besides, we also discovered that the expression of SATB1 was associated with histologic grade (OR = 1.88, 95% CI: 1.06–3.34), distant metastasis (OR = 1.43, 95% CI: 1.11–1.85) and lymph node metastasis (OR = 1.50, 95% CI: 1.03–2.19).

Conclusion: Broadly speaking, our meta-analysis demonstrated that high expression level of SATB1 was related to poor prognosis in CRC patients.

Prognostic significance of SATB1 in gastrointestinal cancer: a meta-analysis and literature review

Background

The special AT-rich sequence-binding proteins 1 (SATB1) is a major regulator involved in cell differentiation. It has been shown that SATB1 acts as an oncogenic regulator. The clinical and prognostic significance of SATB1 in gastrointestinal cancer remains controversial. The purpose of this study is to conduct a systematic review and meta-analysis to elucidate the impact of SATB1 in gastrointestinal cancer.

Results

A total of 3174 gastrointestinal cancer patients from 15 studies were included. The correlation between SATB1 expression and OS or RFS was investigated in 12 and 5 studies respectively. The results of meta-analysis showed that SATB1 overexpression is inversely correlated with OS (combined HR: 1.79, p = 0.0003) and RFS (combined HR: 2.46, p < 0.0001). In subgroup analysis, SATB1 expression is significantly correlated with poor prognosis in gastrointestinal cancer in Asian population. SATB1 expression is associated with stage, invasion depth, lymph node metastasis and distant metastasis.

Methodology

Published studies with data on overall survival (OS) and/or relapse free survival (RFS) and SATB1 expression were searched from Cochrane Library, PubMed and Embase (up to Dec 30, 2016). The outcome measurement is hazard ratio (HR) for OS or RFS related with SATB1 expression. Two reviewers independently screened the literatures, extracted the data and performed meta-analysis using RevMan 5.3.0 software. The combined HRs were calculated by fixed- or random-effect models.

Conclusions

The results of this meta-analysis suggest that SATB1 overexpression is related to advanced stage, lymph node metastasis and distant metastasis. SATB1 overexpression is a marker indicating poor prognosis in gastrointestinal cancer.

SATB1 overexpression correlates with gastrointestinal neoplasms invasion and metastasis: a meta-analysis for Chinese population

Background

Gastrointestinal neoplasm (GIN) is the most common neoplasm in China. The global chromatin organizer SATB1 (special AT-rich sequence binding protein 1) is aberrantly expressed in multiple human neoplasms. We conducted this meta-analysis to investigate whether the invasion and metastasis of GIN correlates with SATB1 levels in tumor tissues in Chinese patients.

Materials and Methods

Eligible studies were identified through multiple search strategies in the databases PubMed, Embase, Medline, CNKI, and WANFANG, and the relevant clinicopathological data were extracted. Data were pooled using the Mantel-Haenszel fixed-effects or DerSimonian-Laid random-effects model.

Results

Fourteen studies consisting of 1622 patients were included. There were 3, 3, and 8 studies that evaluated esophageal, gastric, and colorectal cancers, respectively. The overall mean percentage of patients with elevated SATB1 levels was 47.84%. Among patients with GIN, SATB1 overexpression was associated with depth of invasion (T stage: RR 1.27, 95% CI 1.18–1.36, P = 0.000), regional lymph node metastasis (N stage: RR 1.51, 95% CI 1.22–1.87, P = 0.000), and distant metastasis (M stage: RR 2.54, 95% CI 1.46–4.41, P = 0.001). The tumor type most closely linked with invasion and metastasis in GIN was gastric cancer (RR for T stage: 1.64, RR for N stage: 1.68, RR for M stage: 3.15).

Conclusions

invasion and metastasis of GIN in Chinese patients correlates with SATB1 overexpression in tumor tissues, most profoundly in gastric cancer.

Beyond cell-cell adhesion: Plakoglobin and the regulation of tumorigenesis and metastasis

Plakoglobin (also known as? -catenin) is a member of the Armadillo family of proteins and a paralog of β -catenin. Plakoglobin is a component of both the adherens junctions and desmosomes, and therefore plays a vital role in the regulation of cell-cell adhesion. Similar to β -catenin, plakoglobin is capable of participating in cell signaling in addition to its role in cell-cell adhesion. In this context, β -catenin has a well-documented oncogenic potential as a component of the Wnt signaling pathway. In contrast, while some studies have suggested a tumor promoting activity of plakoglobin in a cell/malignancy specific context, it generally acts as a tumor/metastasis suppressor. How plakoglobin acts as a growth/metastasis inhibitory protein has remained, until recently, unclear. Recent evidence suggests that plakoglobin may suppress tumorigenesis and metastasis by multiple mechanisms, including the suppression of oncogenic signaling, interactions with various proteins involved in tumorigenesis and metastasis, and the regulation of the expression of genes involved in these processes. This review is primarily focused on various mechanisms by which plakoglobin may inhibit tumorigenesis and metastasis.

Into the Fourth Dimension: Dysregulation of Genome Architecture in Aging and Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by synapse dysfunction and cognitive impairment. Understanding the development and progression of AD is challenging, as the disease is highly complex and multifactorial. Both environmental and genetic factors play a role in AD pathogenesis, highlighted by observations of complex DNA modifications at the single gene level, and by new evidence that also implicates changes in genome architecture in AD patients. The four-dimensional structure of chromatin in space and time is essential for context-dependent regulation of gene expression in post-mitotic neurons. Dysregulation of epigenetic processes have been observed in the aging brain and in patients with AD, though there is not yet agreement on the impact of these changes on transcription. New evidence shows that proteins involved in genome organization have altered expression and localization in the AD brain, suggesting that the genomic landscape may play a critical role in the development of AD. This review discusses the role of the chromatin organizers and epigenetic modifiers in post-mitotic cells, the aging brain, and in the development and progression of AD. How these new insights can be used to help determine disease risk and inform treatment strategies will also be discussed.

SATB1 and bladder cancer: Is there a functional link?

PURPOSE

SATB1, a global genome organizer, has been shown to play a role in the development and progression of some solid tumors, but its role in bladder cancer is undetermined. Moreover, there is conflicting data about the role of SATB1 in other tumors. This study was initiated to assess a potential role for SATB1 with the hypothesis that SATB1 acts as a tumor promoter in bladder cancer.

MATERIALS AND METHODS

We evaluated SATB1 expression in bladder cancer cell lines (HTB-5, HTB-9) and compared them to a benign urothelial cell line (UROtsa). Short-hairpin RNA was used to silence SATB1 in multiple cell lines, and cell death and cell proliferation were assessed using multiple assays.

RESULTS

SATB1 expression was increased significantly in all cancer cell lines compared to benign urothelial cells. SATB1 expression was knocked down by short-hairpin RNA and functional outcomes, including cell number, cell-cycle arrest, cell viability, and apoptosis after cisplatin treatment, were measured. Surprisingly, knockdown of SATB1 in 2 high-grade cancer cell lines showed opposing functional roles. Compared to the non-silencing control, HTB-5 cells, showed decreased cellular proliferation and increased sensitivity to cisplatin, whereas HTB-9 cells, showed increased cell numbers and increased resistance to cisplatin.

CONCLUSION

We conclude that our results in bladder cancer are consistent with the conflicting data reported in other cancers, and that SATB1 might have different roles in cancer dependent on genetic background and stage of the cancer.

Elevated expression of SATB1 is involved in pancreatic tumorigenesis and is associated with poor patient survival

Special AT-rich sequence-binding protein 1 (SATB1) is a master chromatin organizer which has been reported to be implicated in tumor progression in breast and lung cancer. However, its functions in pancreatic tumorigenesis have yet to be elucidated. In the present study, the involvement of SATB1 in pancreatic cancer development was investigated in human BxPC-3 pancreatic adenocarcinoma cells. Short hairpin (sh)RNA was used to stably downregulate SATB1 expression, and functional assays, including cell proliferation, colony formation, soft agar and migration assays, were performed in vitro. In addition, a mouse pancreatic cancer xenograft model was created to examine the tumor-promoting properties of SATB1 in vivo. The present findings demonstrated that stable knockdown of SATB1 expression inhibited the proliferation, colony formation, anchorage-independent growth and suppressed the migratory capabilities of BxPC-3 cells in vitro. In addition, SATB1 downregulation significantly inhibited tumor growth in xenografted mice in vivo. Furthermore, SATB1 was revealed to be upregulated in human pancreatic cancer tissue samples compared with matched non-cancerous adjacent tissues, and high SATB1 expression was associated with poor patient survival. Overall, the present study demonstrated that SATB1 promoted the proliferation of pancreatic cancer cells in vitro. In addition, SATB1 expression was revealed to be upregulated in human pancreatic cancer tissues and its upregulation was associated with poor patient survival. Therefore, SATB1 may have potential as a novel prognostic biomarker and therapeutic target for the treatment of patients with pancreatic cancer.

High expression of special AT-rich sequence binding protein-1 predicts esophageal squamous cell carcinoma relapse and poor prognosis

Previous studies of the roles of special AT-rich sequence binding protein-1 (SATB1) in the development and progression of cancer have suggested that SATB1 promotes cancer cell metastasis. The aim of the present study is to evaluate the role of SATB1 in the progression and prognosis of esophageal squamous cell carcinoma (ESCC). ESCC tissues were collected from 102 patients and SATB1 mRNA expression was measured by reverse transcription-quantitative polymerase chain reaction. The association between expression of SATB1 mRNA with clinicopathological features and prognosis was assessed, and the prognosis of ESCC was evaluated using Kaplan-Meier survival curves. In the 102 ESCC tissues, SATB1 mRNA expression correlated with the clinical tumor node metastasis stage (P<0.05), but not with any other clinicopathological features (including age, gender, tumor differentiation grade, adjuvant radio/chemotherapy, or the consumption of alcohol and use of cigarettes) (P>0.05). The disease-free survival (DFS) and overall survival (OS) of patients with high SATB1 expression was decreased compared with those with low SATB1 expression. The present study indicated that SATB1 mRNA expression was associated with the postoperative recurrent and poor prognosis in ESCC. SATB1 may be a novel marker for predicting the recurrent and worse prognosis of ESCC.

Inhibition of prostate cancer cell growth in vivo with short hairpin RNA targeting SATB1

Despite previous advances, the treatment options for prostate cancer remain limited. For the purposes of gene knockdown, the utility of RNA interference has been demonstrated and is considered to have therapeutic potential. In the present study, a short hairpin RNA (shRNA) was used to assess the effect of special AT-rich sequence binding protein (SATB1) downregulation on the growth and metastatic potential of prostate cancer in xenograft nude mice. A plasmid carrying shRNA targeting SATB1, pSilencer-SATB1-shRNA, was successfully engineered. Using this plasmid, significant downregulation of SATB1 mRNA and protein expression in the DU145 prostate cancer cells was observed. pSilencer-SATB1-shRNA was demonstrated to be markedly efficacious against prostate cancer xenografts in nude mice. These results may lead to a novel method of improving gene therapy efficacy against prostate cancer via regulating the function of SATB1.

SATB1 plays an oncogenic role in esophageal cancer by up-regulation of FN1 and PDGFRB

Esophageal cancer is a highly aggressive malignancy with very poor overall prognosis. Given the strong clinical relevance of SATB1 in esophagus cancer and other cancers suggested by previous studies, the exact function of SATB1 in esophagus cancer development is still unknown. Here we showed that the knockdown of SATB1 in esophageal cancer cell lines diminished the cell proliferation, survival and invasion. Whole genome transcriptome analysis of SATB1 knockdown cells revealed the different gene expression profiles between TE-1 cells and MDA-MB-231 cells. Network analysis and functional experiments further identified FN1 and PDGFRB to be key downstream genes regulated by SATB1 in esophageal cancer cells. Importantly, FN1 and PDGFRB were found to be highly expressed in human esophageal cancer. In summary, we provided the first molecular evidence that SATB1 played an oncogenic role in esophageal cancer by up-regulation of FN1 and PDGFRB.

Molecular profiling of locally-advanced rectal adenocarcinoma using microRNA expression (Review)

Treatment for locally-advanced rectal cancer (LARC) typically consists of neoadjuvant chemoradiation followed by total mesorectal excision. Recently, there has been growing interest in non-operative management for patients who are medically-inoperable or wish to avoid surgical morbidity and permanent colostomy. Approximately 50% of patients who receive pre-operative neoadjuvant chemoradiation develop some degree of pathologic response. Approximately 10-20% of patients are found to have a complete pathologic response, a finding which has frequently been shown to predict better clinical outcomes, including local-regional control, distant metastasis and survival. Many recent studies have evaluated the role of molecular biomarkers in predicting response to neoadjuvant therapy. MicroRNAs (miRNAs) are an emerging class of biomarkers that have the potential to predict which patients are most likely to benefit from pre-operative therapy and from a selective surgical approach. Here, we review the published literature on microRNAs as prognostic and predictive biomarkers in rectal cancer after pre-operative therapy. In the future, the development of prospectively validated miRNA signatures will allow clinical implementation of miRNAs as prognostic and predictive signatures in LARC.

The Molecular Revolution in Cutaneous Biology: Chromosomal Territories, Higher-Order Chromatin Remodeling, and the Control of Gene Expression in Keratinocytes

Three-dimensional organization of transcription in the nucleus and mechanisms controlling the global chromatin folding, including spatial interactions between the genes, noncoding genome elements, and epigenetic and transcription machinery, are essential for establishing lineage-specific gene expression programs during cell differentiation. Spatial chromatin interactions in the nucleus involving gene promoters and distal regulatory elements are currently considered major forces that drive cell differentiation and genome evolution in general, and such interactions are substantially reorganized during many pathological conditions. During terminal differentiation of the epidermal keratinocytes, the nucleus undergoes programmed transformation from highly active status, associated with execution of the genetic program of epidermal barrier formation, to a fully inactive condition and finally becomes a part of the keratinized cells of the cornified epidermal layer. This transition is accompanied by marked remodeling of the three-dimensional nuclear organization and microanatomy, including changes in the spatial arrangement of lineage-specific genes, nuclear bodies, and heterochromatin. This mini-review highlights the important landmarks in the accumulation of our current knowledge on three-dimensional organization of the nucleus, spatial arrangement of the genes, and their distal regulatory elements, and it provides an update on the mechanisms that control higher-order chromatin remodeling in the context of epidermal keratinocyte differentiation in the skin.

Special AT-rich sequence binding protein 1 promotes tumor growth and metastasis of esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma is one of the most aggressive malignancies worldwide. Special AT-rich sequence binding protein 1 is a nuclear matrix attachment region binding protein which participates in higher order chromatin organization and tissue-specific gene expression. However, the role of special AT-rich sequence binding protein 1 in esophageal squamous cell carcinoma remains unknown. In this study, western blot and quantitative real-time polymerase chain reaction analysis were performed to identify differentially expressed special AT-rich sequence binding protein 1 in a series of esophageal squamous cell carcinoma tissue samples. The effects of special AT-rich sequence binding protein 1 silencing by two short-hairpin RNAs on cell proliferation, migration, and invasion were assessed by the CCK-8 assay and transwell assays in esophageal squamous cell carcinoma in vitro. Special AT-rich sequence binding protein 1 was significantly upregulated in esophageal squamous cell carcinoma tissue samples and cell lines. Silencing of special AT-rich sequence binding protein 1 inhibited the proliferation of KYSE450 and EC9706 cells which have a relatively high level of special AT-rich sequence binding protein 1, and the ability of migration and invasion of KYSE450 and EC9706 cells was distinctly suppressed. Special AT-rich sequence binding protein 1 could be a potential target for the treatment of esophageal squamous cell carcinoma and inhibition of special AT-rich sequence binding protein 1 may provide a new strategy for the prevention of esophageal squamous cell carcinoma invasion and metastasis.

Effect of SATB1 silencing on the proliferation, invasion and apoptosis of TE-1 esophageal cancer cells

The aim of the present study was to investigate the effect of special AT-rich sequence-binding protein-1 (SATB1)-targeted small interfering RNA (siRNA) on the proliferation, invasion and apoptosis of TE-1 human esophageal cancer cells. SATB1 has been correlated with the metastasis and poor prognosis of colon and breast cancer, but the role of SATB1 in esophageal cancer remains unknown. Therefore, the present study constructed and transfected SATB1-siRNA into TE-1 cells in order to knockdown the expression of the SATB1 gene. Western blot analysis, a cell counting kit, transwell chamber assays and flow cytometry were used to assess the effect of SATB1-siRNA on the proliferation, invasion and apoptosis of cells. The results demonstrated that the expression of the SATB1 gene was efficiently knocked down by SATB1-siRNA, and that SATB1-siRNA inhibited the proliferation, invasion and apoptosis of TE-1 cells. Therefore, it was concluded that the SATB1 gene is important in the pathogenesis of human esophageal cancer, and may present a novel therapeutic target for esophageal cancer.

SATB1 promotes epithelial-mesenchymal transition and metastasis in prostate cancer

Special AT-rich sequence-binding protein-1 (SATB1) is associated with cancer progression and poor clinical outcome. The present study aims to evaluate whether SATB1 affects the biological behaviors of prostate cancer (PCa), and furthermore, to elucidate whether this effect works through the epithelial-mesenchymal transition (EMT) pathway. Firstly, the expression of SATB1 was investigated in a series of PCa tissues as well as in a panel of PCa cell lines. Cell proliferation, migration and invasion were evaluated in SATB1 knockdown and overexpressed PCa cell lines by MTT and Transwell assays. The results showed that the expression of SATB1 was markedly upregulated in PCa tissues and all PCa cell lines (P<0.001). Ectopic expression of SATB1 promoted PCa cell proliferation and migration. Knockdown of SATB1 repressed the ability of cell proliferation and migration of PCa cells. In addition, inhibition of SATB1 could reverse the EMT processes through upregulation of E-cadherin and downregulation of vimentin. The present study provided evidence that SATB1 may act as a potential therapeutic target in PCa patients.

RHS6-mediated chromosomal looping and nuclear substructure binding is required for Th2 cytokine gene expression

Subset-specific gene expression is a critical feature of CD4 T cell differentiation. Th2 cells express Th2 cytokine genes including Il4, Il5, and Il13 and mediate the immune response against helminths. The expression of Th2 cytokine genes is regulated by Rad50 hypersensitive site 6 (RHS6) in the Th2 locus control region; however, the molecular mechanisms of RHS6 action at the chromatin level are poorly understood. Here, we demonstrate that RHS6 is crucial for chromosomal interactions and nuclear substructure binding of the Th2 cytokine locus. RHS6-deficient cells had a marked reduction in chromatin remodeling and in intrachromosomal interactions at the Th2 locus. Deficiency of RHS6-binding transcription factors GATA3, SATB1, and IRF4 also caused a great reduction in chromatin remodeling and long-range chromosomal interactions involving the Th2 locus. RHS6 deficiency abrogated association of the Th2 locus with the nuclear substructure and RNA polymerase II. Therefore, RHS6 serves as a crucial cis-acting hub for coordinate regulation of Th2 cytokine genes by forming chromosomal loops and binding to a nuclear substructure.