Clinicopathologic and prognostic significance of SATB1 in cutaneous malignant melanoma

Immunohistochemical Expression of SATB2 in Malignant Melanomas

Accurate diagnosis of cancer of unknown primary (CUP) poses a significant daily challenge for pathologists, necessitating reliable immunohistochemical (IHC) markers. SATB2 is a transcription factor primarily expressed in colorectal neoplasms. This study investigates the IHC expression of SATB2 in malignant melanomas (MM). Using tissue microarrays (TMAs) from Aalborg University Hospital, Denmark, comprising 56 primary and 12 metastatic MMs, we evaluated SATB2 expression through H-scores. We found that 48% of MM cases expressed SATB2, predominantly with weak to moderate staining intensity. Although no significant difference was observed between primary and metastatic MMs, a higher median H-score was noted in metastatic lesions. The results highlight the potential diagnostic pitfall of SATB2 expression in MM and underline the need for careful interpretation.

SATB1, senescence and senescence-related diseases

Aging leads to an accumulation of cellular mutations and damage, increasing the risk of senescence, apoptosis, and malignant transformation. Cellular senescence, which is pivotal in aging, acts as both a guard against cellular transformation and as a check against cancer progression. It is marked by stable cell cycle arrest, widespread macromolecular changes, a pro-inflammatory profile, and altered gene expression. However, it remains to be determined whether these differing subsets of senescent cells result from unique intrinsic programs or are influenced by their environmental contexts. Multiple transcription regulators and chromatin modifiers contribute to these alterations. Special AT-rich sequence-binding protein 1 (SATB1) stands out as a crucial regulator in this process, orchestrating gene expression by structuring chromatin into loop domains and anchoring DNA elements. This review provides an overview of cellular senescence and delves into the role of SATB1 in senescence-related diseases. It highlights SATB1's potential in developing antiaging and anticancer strategies, potentially contributing to improved quality of life and addressing aging-related diseases.

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.

Identification and External Validation of a Transcription Factor-Related Prognostic Signature in Pediatric Neuroblastoma

Background

Neuroblastoma is a common solid tumor originating from the sympathetic nervous system, commonly found in children, and it is one of the leading causes of tumor-related deaths in children. In addition to pathological features, molecular-level features, such as how much gene expression is present and the mutational profile, may provide useful information for the precise treatment of neuroblastoma. Transcription factors (TFs) play an important regulatory role in all aspects of cellular life activities. But there are currently no studies on transcription factor-based biomarkers of neuroblastoma prognosis, and this study is much needed.

Methods

We downloaded RNA transcriptome data and clinical data from the TARGET database to construct a prognostic model. The prognostic model was constructed by using univariate Cox analysis, LASSO, and multivariate Cox regression. We divided the patients into low-risk and high-risk groups using the median value of the risk score as the cut-off. Then, we validated the prognostic model with the dataset GSE49710.

Results

We constructed a prognostic model consisting of eight genes (SATB1, ZNF564, SOX14, EN1, IKZF2, SLC2A4RG, FOXJ2, and ZNF521). Patients in the high-risk group had a lower survival rate than those in the low-risk group. The area under the 3-year ROC curve of the model reached 0.825, suggesting a good predictive efficacy. We performed target gene prediction for the eight transcription factors in the model using six online databases and found that TUT1 may be a target gene for transcription factor EN1 and is associated with immune infiltration.

Conclusion

This prognostic model consisting of eight transcription factor-associated genes demonstrated reliable predictive efficacy. This prediction model may provide new potential targets for the treatment of neuroblastoma and personalized monitoring of neuroblastoma patients with high and low risk.

SATB1-mediated chromatin landscape in T cells

The regulatory circuits that define developmental decisions of thymocytes are still incompletely resolved. SATB1 protein is predominantly expressed at the CD4⁺CD8⁺cell stage exerting its broad transcription regulation potential with both activatory and repressive roles. A series of post-translational modifications and the presence of potential SATB1 protein isoforms indicate the complexity of its regulatory potential. The most apparent mechanism of its involvement in gene expression regulation is via the orchestration of long-range chromatin loops between genes and their regulatory elements. Multiple SATB1 perturbations in mice uncovered a link to autoimmune diseases while clinical investigations on cancer research uncovered that SATB1 has a promoting role in several types of cancer and can be used as a prognostic biomarker. SATB1 is a multivalent tissue-specific factor with a broad and yet undetermined regulatory potential. Future investigations on this protein could further uncover T cell-specific regulatory pathways and link them to (patho)physiology.

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.

Identification of prognostic mRNAs in metastatic cutaneous melanoma

Cutaneous melanoma is the most common cause of skin cancer-related deaths worldwide. There is an urgent need to identify prognostic biomarkers to facilitate decision-making for treatment of metastatic cutaneous melanoma. Gene expression microarrays and RNA-seq technology have recently improved or changed current prognostic and therapeutic strategies for several cancers. However, according to the current melanoma staging system, prognosis is almost entirely dependent on clinicopathological features. To identify novel prognostic biomarkers, we investigated gene expression and clinical data for patients with cutaneous melanoma from three cohorts of The Cancer Genome Atlas and Gene Expression Omnibus. Kaplan-Meier survival analysis using median values of each gene as cutoff value revealed that nine genes (ABCC3, CAPS2, CCR6, CDCA8, CLU, DPF1, PTK2B, SATB1, and SYNE1) were statistically significant prognostic biomarkers of metastatic cutaneous melanoma in all three independent cohorts. Low expression of two genes (CDCA8 and DPF1) and high expression of seven genes (ABCC3, CAPS2, CCR6, CLU, PTK2B, SATB1, and SYNE) were significantly associated with positive metastatic cutaneous melanoma prognoses. In conclusion, we suggest nine novel prognostic biomarkers for cutaneous metastatic melanoma.

SATB1 and PTEN expression patterns in biopsy proven kidney diseases

BACKGROUND

In present study we investigated expression pattern of the special tissue markers. SATB1 and PTEN to evaluate possible influence in pathophysiology and development of various biopsy proven kidney diseases.

METHODS

The 32 kidney biopsy samples were analysed using light, immunofluorescence and electron microscopy. There were 19 samples in proliferative and 13 samples in non- proliferative group of renal diseases. As control group, 9 specimens of healthy kidney tissue taken after surgery of kidney tumour were used. SATB1 and PTEN markers were used for immunofluorescence staining. Analysed tissue structures were glomeruli, proximal convoluted tubules (PCT) and distal convoluted tubules (DCT). The number of SATB1 and PTEN cells were calculated and the data compared between kidney structures, disease groups and control specimens.

RESULTS

Both markers were positive in all investigated kidney structures, with expression generally, more prominent in tubular epithelial cells than in glomeruli, with the highest staining intensity rate as well as highest rate of both markers in DCT of proliferative diseases group (SATB1 64.5 %, PTEN 52 %). There was statistically significant difference in SATB1 expression in all tissue structures of interest in proliferative as well as non- proliferative group compared to control group (p < 0.01-p < 0.0001). PTEN expression were found significantly decreased in PCT of both disease groups in regard to control (PTEN 25.3 % and 23.8 % vs. 41.1 % (p < 0.01 and p < 0.001 respectively).

CONCLUSION

SATB1 and PTEN could be considered as markers influenced in kidney disease development. SATB1/PTEN expression should be further investigated as useful markers of kidney disease activity as well as potential therapeutic target.

Human p21-activated kinase 5 (PAK5) expression and potential mechanisms in relevant cancers: Basic and clinical perspectives for molecular cancer therapeutics

An oncogenic role, p21-activated kinase 5 (PAK5), has proven as a significant mediator for many cellular progression, which is expressed highly in human organs such as lung, liver, kidney, blood vessels endothelial cells and inflammatory cells. PAK5 was primitively detected in the cerebrum and accelerated the filopodia formation in neurocytes. It can reverse the effect of Rho and adjust its activity to mediate maintenance and development of nerve axon by binding with Cdc42-GTP. Moreover, PAK5 has been suggested to mediate protean, multitudinous and inscrutable functions in cancer. Currently, many researches indicated that PAK5 was dysregulated in ovarian cancer, cervical cancer, melanoma, osteosarcoma, renal carcinoma, breast cancer, gastric cancer and so on, which was involved in cell proliferation, apoptosis, migration and invasion. This review focuses the latest knowledge on the structure, expression, signalling pathway of PAK5, emphasizing its function in cancer.

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.

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.

New susceptibility loci for cutaneous melanoma risk and progression revealed using a porcine model

Despite major advances, it is estimated that a large part of melanoma predisposing genes remains to be discovered. Animal models of spontaneous diseases are valuable tools and experimental crosses can be used to identify and fine-map new susceptibility loci associated with melanoma. We performed a Genome-Wide Association Study (GWAS) of melanoma occurrence and progression (clinical ulceration and presence of metastasis) in a porcine model of spontaneous melanoma, the MeLiM pig. Five loci on chromosomes 2, 5, 7, 8 and 16 showed genome-wide significant associations (p < 5 × 10^–6) with either one of these phenotypes. Suggestive associations (p < 5 × 10^–5) were also found at 16 additional loci. Moreover, comparison of the porcine results to those reported by human melanoma GWAS indicated shared association signals notably at CDKAL1 and TERT loci but also nearby CCND1, FTO, PLA2G6 and TMEM38B-RAD23B loci. Extensive search of the literature revealed a potential key role of genes at the identified porcine loci in tumor invasion (DST, PLEKHA5, CBY1, LIMK2 and ETV5) and immune response modulation (ETV5, HERC3 and DICER1) of the progression phenotypes. These biological processes are consistent with the clinico-pathological features of MeLiM tumors and can open new routes for future melanoma research in humans.

SNF5 deficiency induces apoptosis resistance by repressing SATB1 expression in Sézary syndrome

SNF5, is a core member of the SWI/SNF chromatin remodeling complex. It's deficiency leads to multiple types of aggressive cancer. Sézary syndrome, a leukemic variant of cutaneous T-cell lymphoma, is characterized by its resistance to apoptosis. Although the cause of apoptosis resistance is still poorly understood, recent evidence has revealed the importance of SATB1 in the apoptosis resistance of Sézary syndrome. In this study, we show that SNF5 is an upstream regulator of SATB1 in several conditions and that both are deficient in Sézary cells. Additionally, SNF5 not only controls the expression of SATB1, but also utilizes SATB1 to recruit itself to specific sites. Overexpression of SNF5 induces SATB1 expression and partially reverse apoptosis resistance phenotype in Sézary cells. These results suggest that both SNF5 and SATB1 may regulate apoptosis-related genes in Sézary syndrome. Thus, targeting SWI/SNF complex may represent a promising approach for Sézary syndrome therapy.

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.

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.

Analysis of cellular and molecular antitumor effects upon inhibition of SATB1 in glioblastoma cells

Background

The Special AT-rich Sequence Binding Protein 1 (SATB1) regulates the expression of many genes by acting as a global chromatin organizer. While in many tumor entities SATB1 overexpression has been observed and connected to pro-tumorigenic processes, somewhat contradictory evidence exists in brain tumors with regard to SATB1 overexpression in glioblastoma and its association with poorer prognosis and tumor progression. On the functional side, initial data indicate that SATB1 may be involved in several tumor cell-relevant processes.

Methods

For the detailed analysis of the functional relevance and possible therapeutic potential of SATB1 inhibition, we employ transient siRNA-mediated knockdown and comprehensively analyze the cellular and molecular role of SATB1 in glioblastoma.

Results

In various cell lines with different SATB1 expression levels, a SATB1 gene dose-dependent inhibition of anchorage-dependent and –independent proliferation is observed. This is due to cell cycle-inhibitory and pro-apoptotic effects of SATB1 knockdown. Molecular analyses reveal SATB1 knockdown effects on multiple important (proto-) oncogenes, including Myc, Bcl-2, Pim-1, EGFR, β-catenin and Survivin. Molecules involved in cell cycle, EMT and cell adhesion are affected as well. The putative therapeutic relevance of SATB1 inhibition is further supported in an in vivo tumor xenograft mouse model, where the treatment with polymeric nanoparticles containing SATB1-specific siRNAs exerts antitumor effects.

Conclusion

Our results demonstrate that SATB1 may represent a promising target molecule in glioblastoma therapy whose inhibition or knockdown affects multiple crucial pathways.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-3006-6) contains supplementary material, which is available to authorized users.

Special AT-rich Sequence-binding Protein 1 (SATB1) Functions as an Accessory Factor in Base Excision Repair

Base excision repair is initiated by DNA glycosylases that recognize specific altered bases. DNA glycosylases for oxidized bases carry both a glycosylase activity that removes the faulty base and an apyrimidinic/apurinic lyase activity that introduces a single-strand DNA incision. In particular, the CUT domains within the CUX1 and CUX2 proteins were recently shown to interact with the 8-oxoguanine (8-oxoG) DNA glycosylase and stimulate its enzymatic activities. SATB1, which contains two CUT domains, was originally characterized as a T cell-specific genome organizer whose aberrant overexpression in breast cancer can promote tumor progression. Here we investigated the involvement of SATB1 in DNA repair. SATB1 knockdown caused a delay in DNA repair following exposure to H₂O₂, an increase in OGG1-sensitive oxidized bases within genomic DNA, and a decrease in 8-oxoG cleavage activity in cell extracts. In parallel, we observed an increase in phospho-CHK1 and γ-H2AX levels and a decrease in DNA synthesis. Conversely, ectopic expression of SATB1 accelerated DNA repair and reduced the levels of oxidized bases in genomic DNA. Moreover, an enhanced GFP-SATB1 fusion protein was rapidly recruited to laser microirradiation-induced DNA damage. Using purified proteins, we showed that SATB1 interacts directly with OGG1, increases its binding to 8-oxoG-containing DNA, promotes Schiff base formation, and stimulates its glycosylase and apyrimidinic/apurinic lyase enzymatic activities. Structure/function analysis demonstrated that CUT domains, but not the homeodomain, are responsible for the stimulation of OGG1. Together, these results identify another CUT domain protein that functions both as a transcription factor and an accessory factor in base excision repair.

SATB1 promotes prostate cancer metastasis by the regulation of epithelial-mesenchymal transition

Special AT-rich sequence binding protein 1 (SATB1) plays important role in the regulation of chromatin structure and gene expression. Recent studies have indicated oncogenic role of SATB1. However, the function of SATB1 in prostate cancer progression and metastasis remains unclear. In this study SATB1 expression vector or siRNA was employed to modulate the expression level of SATB1 in prostate cancer cells and xenograft tumor in nude mouse model. Immunohistochemical analysis was performed on clinical prostate cancer samples. Silencing SATB1 inhibited the growth of DU-145 cells subcutaneous tumor in nude mice, while SATB1 overexpression promoted the growth of LNCaP cells subcutaneous tumor in nude mice. Immunohistochemical and Western blot analysis of the xenografts showed that silencing SATB1 led to decreased expression of vimentin and MMP2 and increased expression of E-cadherin, while SATB1 overexpression led to increased expression of vimentin and MMP2 and decreased expression of E-cadherin. Furthermore, SATB1, vimentin and MMP2 expression was increased significantly while E-cadherin expression was reduced significantly in clinical samples of prostate carcinoma with metastasis compared to prostate carcinoma without metastasis and benign prostate hyperplasia. Taken together, these findings suggest that the modulation of epithelial-mesenchymal transition by SATB1 may contribute to prostate cancer metastasis.

Downregulation of SATB1 increases the invasiveness of Jurkat cell via activation of the WNT/β-catenin signaling pathway in vitro

Special AT-rich sequence-binding protein-1 (SATB1) is critical for genome organizer that reprograms chromatin organization and transcription profiles, and associated with tumor growth and metastasis in several cancer types. Many studies suggest that SATB1 overexpression is an indicator of poor prognosis in various cancers, such as breast cancer, malignant cutaneous melanoma, and liver cancer. However, their expression patterns and function values for adult T cell leukemia (ATL) are still largely unknown. The aim of this study is to examine the levels of SATB1 in ATL and to explore its function and mechanisms in Jurkat cell line. Here, we reported that SATB1 expressions were decreased in ATL cells (p < 0.001) compared with normal controls. Knockdown of SATB1 expression significantly enhanced invasion of Jurkat cell in vitro. Furthermore, knockdown of SATB1 gene enhances β-catenin nuclear accumulation and transcriptional activity and thus may increase the invasiveness of Jurkat cell through the activation of Wnt/β-catenin signaling pathway in vitro.

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.

Expression of SATB1 and HER2 in breast cancer and the correlations with clinicopathologic characteristics

Background

Special AT-rich sequence binding protein 1 (SATB1) is found acting as a “genome organizer” that functions as a landing platform to regulate tissue-specific gene ex-pression. In breast cancer cell lines it has been proven that SATB1 could upregulate the expression of the HER2. In this paper, the relevance of SATB1 and HER2 expression was assessed in human breast cancer tissues, and their influence on tumor histological grade and patients’ survival was explored.

Methods

Using immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH), 169 patients with breast cancer were assessed for SATB1 expression, HER2 amplification and hormone-receptor (HR) expression. The effects of SATB1 expression on HER2 and HR expression as well as their association with clinicopathologic characteristics were further analyzed by statistical evaluation.

Results

SATB1 expression was correlated with HER2 expression in breast cancer(r = 0.191; p = 0.013). SATB1, HER2 and SATB1/HER2 co-expression was negatively correlated with HR expression (r = −0.228, p = 0.003; r = −0.338, p = 0.000; r = −0.527, p = 0.000, respectively). SATB1 and HER2 single positive and their co-expression were all significantly correlated with higher histological grade (r = 0.239, p = 0.002; r = 0.160, p = 0.038; r = 0.306, p = 0.003, respectively). Multivariate cox regression analyses showed that SATB1 and HER2 were independent risk factors for breast cancer patients, while HR was a protective factor for patients’ survival. Comparing to SATB1 or HER2 single positive expression, SATB1/HER2 co-expression tended to have even worse prognosis.

Conclusions

SATB1 and HER2 performed a synergistic effect in breast cancer. Their expression correlated with poorly differentiated breast cancer and indicated an unfavorable prognosis.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1400555050159723.

Nicotinamide induces apoptosis of F9 mouse teratocarcinoma stem cells by downregulation of SATB1 expression

The aim of this study was to decide whether nicotinamide (NA) could induce apoptosis of F9 mouse teratocarcinoma stem cells (MF9) by downregulation of special AT-rich sequence binding protein 1 (SATB1) expression. We used different concentrations of NA (0, 1.5, 2, and 2.5 mmol/L) to treat MF9 cells and analyze SATB1 expression by RT-qPCR and Western blotting; in addition, the cell proliferation was detected in a microplate reader with Cell Counting Kit-8 (CCK-8), and the cell cycle and apoptosis were analyzed using flow cytometry. We found that the expression of SATB1 was decreased significantly in NA-treated groups than in the control group, and its expression level was inversely related to the NA concentration. In addition, CCK-8 analysis showed that NA significantly inhibited the proliferation of MF9 cells, and flow cytometry showed that NA blocked MF9 cells to G1 phase and significantly promoted apoptosis in any treated groups. To confirm the results, we constructed small interference RNA (siRNA) targeting at mouse SATB1 and transferred into MF9 cells. The results indicated that the expression of SATB1 in both mRNA and protein levels was significantly decreased after cells transferred with siRNA sequence for 48 h, the proliferation of MF9 cells was significantly inhibited, and most of MF9 cells were blocked at G1 phase, and the apoptosis rate was increased obviously. The results showed that NA could inhibit the proliferation and induce apoptosis of MF9 cells. These findings might be used as an efficient candidate for teratocarcinoma therapy.

SATB1 Promotes Pancreatic Cancer Growth and Invasion Depending on MYC Activation

BACKGROUND

SATB1 plays an important role in human malignant progression, inducing cancer cell proliferation and metastasis by regulating downstream gene expressions. However, little is known about the underlying mechanisms in which SATB1 promotes pancreatic cancer tumorigenesis.

AIMS

To investigate SATB1 expression levels and its biological functions in promoting pancreatic cancer growth and invasion.

METHODS

SATB1 expression levels were detected in seven human pancreatic cancer cell lines and 16 pairs of normal pancreatic/pancreatic cancer tissues using RT-PCR and western blot. SW1990 or Capan-1 cells stably knockdown (shRNA) or transiently knockdown (siRNA) SATB1 cells, and PANC-1 stably overexpressing SATB1 cells were investigated with MTT, EdU assay, flow cytometry, and transwell invasion assay for cell proliferation and invasion activity. The binding of SATB1 to MYC promoter region was examined using reporter assay. Expression of SATB1 in 68 pancreatic cancer samples was studied by immunohistochemical staining and scoring.

RESULTS

SATB1 was overexpressed in pancreatic cancer tissues samples, showing strong correlation with pancreatic cancer invasion depth and tumor staging. SATB1 induced MYC mRNA and protein expression; promoted pancreatic cancer cell growth; increased cell population in S phase; and enhanced pancreatic cancer cell invasion in vitro. On the other hand, SATB1 knockdown showed opposite effects. Furthermore, MYC blocking in SATB1-overexpressing cells attenuated the promotion of pancreatic cancer cell growth and invasion. Our data also indicated that SATB1 bound to specific promoter region of MYC.

CONCLUSIONS

SATB1 is overexpressed in pancreatic cancer, promoting cancer cell proliferation and invasion through the activation of MYC.

Overexpression of Special AT-Rich Sequence-Binding Protein 1 in Endometrial Cancer: A Clinicopathologic Study

Objective

Special AT-rich sequence-binding protein 1 (SATB1), as a genome organizer, serves important functions in tumor progression and metastasis. The SATB1 is overexpressed in various malignant tumors. However, the expression and prognostic value of SATB1 in endometrial cancer remain unknown. The aim of this study was to explore the prognostic values of SATB1 expression in endometrial cancer.

Methods/Materials

We investigated the expression of SATB1 in 172 untreated endometrial cancer tissues and 25 normal endometrial tissues through immunohistochemical staining. We also analyzed the association of SATB1 level with clinicopathologic parameters and determined its prognostic significance.

Result

Special AT-rich sequence-binding protein 1 was expressed in 78 (45.3%) of the 172 endometrial cancer samples, but not in the normal endometrial samples. The positive expression of SATB1 was associated with clinicopathologic factors, such as International Federation of Gynecology and Obstetrics stage, histological grade, myometrial invasion depth, lymph node metastasis, vascular/lymphatic invasion, and recurrence. The patients with positive SATB1 expression had worse overall survival and disease-free survival rates than the patients with negative SATB1 expression (P< 0.001 for both). Multivariate Cox analysis indicated that SATB1 was an independent parameter for overall survival (hazards ratio, 2.928; 95% confidence interval, 1.072–7.994;P= 0.036) and disease-free survival (hazards ratio, 2.825; 95% confidence interval, 1.111–7.181;P= 0.029).

Conclusions

Results showed that SATB1 may be involved in tumor development and progression in endometrial cancer, may serve as a promising biomarker for predicting the prognosis of endometrial cancer patients, and thus may act as a novel target for treating endometrial carcinoma.

Expression of special AT-rich sequence-binding protein 1 is an independent prognostic factor in cutaneous T-cell lymphoma

Cutaneous T-cell lymphoma (CTCL) is a group of slowly progressive, lymphoproliferative disorders characterized by localization of neoplastic T lymphocytes to the skin. The most common type of CTCL is mycosis fungoides which has a mild clinical course with slow and long progression. The rate of progression is generally slow and takes many years but often remains unpredictable. Special AT-rich sequence-binding protein-1 (SATB1) is a global chromatin organizer which controls gene expression by folding and remodeling chromatin, but which also regulates the level of histone methylation and acetylation, important in differentiation and apoptosis. The aim of the present study was to determine if SATB1 may be considered a prognostic and predictive factor of CTCL. The results showed that moderate and high expression of SATB1 correlate with significantly better prognosis of CTCL patients. Moreover, we showed that downregulation of SATB1 in Jurkat cells caused their resistance to activation-induced cell death. In conclusion, SATB1 expression appears to be a strong candidate as a prognostic factor confirming the inner heterogeneous features of CTCLs.

Prognostic and treatment predictive significance of SATB1 and SATB2 expression in pancreatic and periampullary adenocarcinoma

BACKGROUND

Pancreatic cancer and other pancreaticobiliary type periampullary adenocarcinomas have a dismal prognosis even after resection and neoadjuvant chemotherapy. Intestinal type periampullary adenocarcinomas generally have a better prognosis, but little is known on optimal neoadjuvant and adjuvant treatment. New prognostic and treatment predictive biomarkers are needed for improved treatment stratification of patients with both types of periampullary adenocarcinoma. Expression of the Special AT-rich sequence-binding protein 1 (SATB1) has been demonstrated to confer a worse prognosis in several tumour types, whereas its close homologue SATB2 is a proposed diagnostic and favourable prognostic marker for colorectal cancer. The prognostic value of SATB1 and SATB2 expression in periampullary adenocarcinoma has not yet been described.

METHODS

Immunohistochemical expression of SATB1 and SATB2 was analysed in tissue microarrays with primary tumours and a subset of paired lymph node metastases from 175 patients operated with pancreaticoduodenectomy for periampullary adenocarcinoma. Kaplan-Meier and Cox regression analysis were applied to explore the impact of SATB1 and SATB2 expression on recurrence free survival (RFS) and overall survival (OS).

RESULTS

Positive expression of SATB1 was denoted in 16/106 primary pancreatobiliary type tumours and 11/65 metastases, and in 15/63 primary intestinal type tumours and 4/26 metastases, respectively. Expression of SATB1 was an independent predictor of a significantly shorter RFS and OS in pancreatobiliary type, but not in intestinal type adenocarcinomas. Moreover, SATB1 expression predicted an improved response to adjuvant chemotherapy in both tumour types. SATB2-expression was seen in 3/107 pancreatobiliary type primary tumours, and in 8/61 intestinal type primary tumours. The small number of cases with positive SATB2 expression did not allow for any firm conclusions on its prognostic value.

CONCLUSIONS

These findings demonstrate the potential utility of SATB1 as a prognostic and predictive biomarker for chemotherapy response in both intestinal type and pancreatobiliary type periampullary adenocarcinomas, including pancreatic cancer.

Increased expressions of SATB1 and S100A4 are associated with poor prognosis in human colorectal carcinoma

This study was designed to explore the correlation between expressions of SATB1 and S100A4 and their relationships to the clinicopathologic parameters of colorectal carcinoma (CRC). Expressions of SATB1 and S100A4 were evaluated by immunohistochemistry in a cohort of 131 primary CRC patients undergone surgical resection from 2005 to 2007. SATB1 and S100A4 were positively expressed in 48.9% and 54.2% of CRC cases, respectively. SATB1 and S100A4 expressions in tumor tissues were significantly higher than those in the corresponding normal tissues. A positive correlation was observed between SATB1 and S100A4. Moreover, the levels of SATB1 and S100A4 were both significantly associated with invasion, lymph node status, and TNM stage of CRC, whereas S100A4 expression was also correlated with distant metastasis. Multivariate analysis revealed that SATB1 expression was an independent prognostic indicator for poor survival of CRC. Further survival analysis indicated that co-expression of SATB1 and S100A4 suggested a worse 5-year overall survival rate in CRC patients. Thus, combined analysis of SATB1 and S100A4 expressions may be valuable in determining the development and progression of CRC. Co-expression of SATB1 and S100A4 is an unfavorable prognostic indicator and may be useful in the follow-up of patients with CRC.

A time course-dependent metastatic gene expression signature predicts outcome in human metastatic melanomas

BACKGROUND

The prognosis of patients with metastatic melanomas is extremely heterogeneous. Therefore, identifying high-risk subgroups by using innovative prediction models would help to improve selection of appropriate management options.

METHODS

In this study, two datasets (GSE7929 and GSE7956) of mRNA expression microarray in an animal melanoma model were normalized by frozen Robust Multi-Array Analysis and then combined by the distance-weighted discrimination method to identify time course-dependent metastasis-related gene signatures by Biometric Research Branch-ArrayTools (BRB)-ArrayTools. Then two datasets (GSE8401 and GSE19234) of clinical melanoma samples with relevant clinical and survival data were used to validate the prognosis signature.

RESULTS

A novel 192-gene set that varies significantly in parallel with the increasing of metastatic potentials was identified in the animal melanoma model. Further, this gene signature was validated to correlate with poor prognosis of human metastatic melanomas but not of primary melanomas in two independent datasets. Furthermore, multivariate Cox proportional hazards regression analyses demonstrated that the prognostic value of the 192-gene set is independent of the TNM stage and has higher areas under the receiver operating characteristic curve than stage information in both validation datasets.

CONCLUSION

Our findings suggest that a time course-dependent metastasis-related gene expression signature is useful in predicting survival of malignant melanomas and might be useful in informing treatment decisions for these patients.

Expression of SATB1 promotes the growth and metastasis of colorectal cancer

Special AT-rich sequence-binding protein-1 (SATB1) has been identified as a genome organizer that reprograms chromatin organization and transcription profiles. SATB1 promotes tumor growth and metastasis in breast cancer and is associated with poor prognosis in several cancer types. The association between SATB1 and colorectal cancer (CRC) has not been studied intensively. Therefore, this study aimed to investigate the effect of SATB1 on CRC growth and metastasis in vitro and in vivo and its correlation with overall survival and clinicopathological factors in CRC patients. Stable SATB1 knockdown and SATB1-overexpressing cell lines were established. SATB1 knockdown decreased cell growth, colony formation, migration, and invasion and increased apoptosis in CRC cells in vitro (p<0.05), whereas SATB1 overexpression had the opposite effect. SATB1 overexpression increased tumor growth and metastasis to lung and liver in vivo by using xenograft animal models (p<0.05). Thus, SATB1 promoted an aggressive CRC phenotype in vitro and in vivo. Immunohistochemical analysis of 560 CRC specimens showed that SATB1 expression was significantly higher in CRC tissues than in matched non-tumor mucosa (p<0.001). In addition, SATB1 expression was significantly higher in patients with poorly differentiated tumors, higher invasion depth, distant metastasis, and advanced TNM stage. SATB1-positive patients had a poorer prognosis than SATB1-negative patients, and SATB1 was identified as an independent prognostic factor for CRC (p = 0.009). Strikingly, we also evaluated SATB2 expression in CRC and found that SATB2 was more abundantly expressed in non-cancerous mucosa compared to colorectal cancer tissues (p<0.001). However, SATB2 expression had no influence on prognosis of CRC patients (p = 0.836). SATB1 expression was significantly associated with shorter survival time either in SATB2-positive patients or in SATB2-negative patients (p<0.001). In conclusion, our findings indicated an important role for SATB1 in CRC tumorigenesis and metastasis. Therefore, SATB1 may represent an important prognostic biomarker and therapeutic target for CRC.

Overexpression of SATB1 is associated with biologic behavior in human renal cell carcinoma

Special AT-rich sequence-binding protein-1 (SATB1) has been reported to be aberrantly expressed in various cancers and correlated with the malignant behavior of cancer cells. However, the function of SATB1 in RCC remains unclear. With the combination of immunohistochemistry, western blotting, immunofluorescence, qRT-PCR, and cell proliferation, migration and invasion assays, we found that levels of SATB1 mRNA and protein were dramatically increased in human ccRCC tissues (P<0.001 for both), and upregulation of SATB1 was significantly associated with depth of invasion (P<0.001), lymph node status (P = 0.001) and TNM stage (P = 0.009). SATB1 knockdown inhibited the proliferation, migration and invasion of 786-O cells, whereas SATB1 overexpression promoted the growth and aggressive phenotype of ACHN cells in vitro. Furthermore, SATB1 expression was positively correlated with ZEB2 expression (P = 0.013), and inversely linked to levels of SATB2 and E-cadherin (P = 0.005 and P<0.001, respectively) in ccRCC tissues. Our data provide a basis for the concept that overexpression of SATB1 may play a critical role in the acquisition of an aggressive phenotype for RCC cells through EMT, providing new insights into the significance of SATB1 in invasion and metastasis of ccRCC, which may contribute to fully elucidating the exact mechanism of development and progression of RCC.

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.

The haplotype of three polymorphisms in the SATB1 promoter region impacts survival in breast cancer patients

Special AT-rich sequence binding protein 1 (SATB1) has regulatory effects on gene expression and appears to play an important role in tumor progression. The present study screened the promoter region of the SATB1 gene for polymorphisms, evaluated the corresponding haplotypes regarding alterations in promoter activity in vitro and analyzed the impact of these haplotypes on the clinical course of breast cancer patients. A cohort of 241 female Caucasian breast cancer patients who had been treated was enrolled in this retrospective analysis. The median follow-up time was 93 months (range, 4–155 months). PCR products from DNA of 10 healthy, unrelated volunteers were analyzed to identify new polymorphisms within the promoter region. Genotyping was conducted using restriction fragment length polymorphism and pyrosequencing. PCR constructs with the respective alleles from the four most frequent haplotypes were cloned into the vector pGEM^®-T Easy and then transferred into the luc2-containing reporter vector pGl 4.10^® for transfection of HEK293 cells. The pGl 4.73^® vector, containing hRluc, was used for normalizing the transfection rates. Sequencing the region -3807 to -2828 bp upstream of ATG from ten healthy blood donors, three single nucleotide polymorphisms consisting of base exchanges were identified: -3600T>C, -3363A>G and -2984C>T. The SATB1 -3600T/-3363A/-2984C haplotype had lower promoter activity than all other constructs in vitro and exhibited a significant association with nodal status (P<0.05). Kaplan-Meier survival analysis revealed significantly improved overall survival for homozygous SATB1 -3600T/-3363A/-2984C haplotype carriers compared with heterozygous carriers or the other haplotypes (P=0.033). The SATB1 -3600T/-3363A/-2984C haplotype is associated with lower promoter activity and appears to impact upon survival in breast cancer patients.

Tissue prognostic biomarkers in primary cutaneous melanoma

Cutaneous melanoma (CM) causes the greatest number of skin cancer-related deaths worldwide. Predicting CM prognosis is important to determine the need for further investigation, counseling of patients, to guide appropriate management (particularly the need for postoperative adjuvant therapy), and for assignment of risk status in groups of patients entering clinical trials. Since recurrence rate is largely independent from stages defined by morphological and morphometric criteria, there is a strong need for identification of additional robust prognostic factors to support decision-making processes. Most data on prognostic biomarkers in melanoma have been evaluated in tumor tissue samples by conventional morphology and immunohistochemistry (IHC) as well as DNA and RNA analyses. In the present review, we critically summarize main high-quality studies investigating IHC-based protein biomarkers of melanoma outcome according to Reporting Recommendations for Tumor Marker Prognostic Studies (REMARK)-derived criteria. Pathways have been classified and conveyed in the "biologic road" previously described by Hanahan and Weinberg. Data derived from genomic and transcriptomic technologies have been critically reviewed to better understand if any of investigated proteins or gene signatures should be incorporated into clinical practice or still remain a field of melanoma research. Despite a wide body of research, no molecular prognostic biomarker has yet been translated into clinical practice. Conventional tissue biomarkers, such as Breslow thickness, ulceration, mitotic rate and lymph node positivity, remain the backbone prognostic indicators in melanoma.

Inhibition of SATB1 by shRNA suppresses the proliferation of cutaneous malignant melanoma

Overexpression of special AT-rich sequence binding protein 1 (SATB1), a global genome organizer, as a predictor of poor prognosis in cutaneous malignant melanoma (CMM) attracted great interest in previous research. In this article, upregulated SATB1 was observed in three melanoma cell lines and in eight CMM tissues. After downregulating SATB1 by RNAi, proliferation of A375 was suppressed in vitro and in vivo. In summary, the proliferation of CMM could be related closely to the SATB1 gene. Interference of this gene may be a promising method for CMM therapy.

Role of special AT rich sequence binding protein 1 in digestive system neoplasms

Special AT rich sequence binding protein 1 (SATB1) is a unique global regulatory factor. Epigenetic modifications and dynamic changes in chromatin organization mediated by SATB1 have recently been shown to play an important role in regulating cancer-promoting genes. The role of SATB1 in promoting metastasis was discovered in breast carcinoma cells in 2008. In recent years, high expression of SATB1 has been found in digestive system neoplasms including oral cancer, stomach cancer, liver cancer, gallbladder cancer and colorectal cancer. SATB1 is related closely to proliferation, invasion and metastasis of tumor cells. Digestive system neoplasms are the most common malignant tumor in China, and control of cancer metastasis has been the research focus. A better understanding of the role of SATB1 will contribute to the diagnosis, treatment and prognosis evaluation in malignant tumors. In this review, we will summarize recent progress in understanding the role of SATB1 in digestive system neoplasms.

Plakoglobin represses SATB1 expression and decreases in vitro proliferation, migration and invasion

Plakoglobin (γ-catenin) is a homolog of β-catenin with dual adhesive and signaling functions. Plakoglobin participates in cell-cell adhesion as a component of the adherens junction and desmosomes whereas its signaling function is mediated by its interactions with various intracellular protein partners. To determine the role of plakoglobin during tumorigenesis and metastasis, we expressed plakoglobin in the human tongue squamous cell carcinoma (SCC9) cells and compared the mRNA profiles of parental SCC9 cells and their plakoglobin-expressing transfectants (SCC9-PG). We observed that the mRNA levels of SATB1, the oncogenic chromatin remodeling factor, were decreased approximately 3-fold in SCC9-PG cells compared to parental SCC9 cells. Here, we showed that plakoglobin decreased levels of SATB1 mRNA and protein in SCC9-PG cells and that plakoglobin and p53 associated with the SATB1 promoter. Plakoglobin expression also resulted in decreased SATB1 promoter activity. These results were confirmed following plakoglobin expression in the very low plakoglobin expressing and invasive mammary carcinoma cell line MDA-MB-231 cells (MDA-231-PG). In addition, knockdown of endogenous plakoglobin in the non-invasive mammary carcinoma MCF-7 cells (MCF-7-shPG) resulted in increased SATB1 mRNA and protein. Plakoglobin expression also resulted in increased mRNA and protein levels of the metastasis suppressor Nm23-H1, a SATB1 target gene. Furthermore, the levels of various SATB1 target genes involved in tumorigenesis and metastasis were altered in MCF-7-shPG cells relative to parental MCF-7 cells. Finally, plakoglobin expression resulted in decreased in vitro proliferation, migration and invasion in different carcinoma cell lines. Together with the results of our previous studies, the data suggests that plakoglobin suppresses tumorigenesis and metastasis through the regulation of genes involved in these processes.

Over-expression of the special AT rich sequence binding protein 1 (SATB1) promotes the progression of nasopharyngeal carcinoma: association with EBV LMP-1 expression

BACKGROUND

Special AT rich sequence binding protein 1 (SATB1) plays a crucial role in the biology of various types of human cancer. However, the role of SATB1 in human nasopharyngeal carcinoma (NPC) remains unknown. In the present study, we sought to investigate the contribution of aberrant SATB1 expression in the progression of NPC and its association with the Epstein Barr virus (EBV)-encoded latent membrane protein 1 (LMP-1).

METHODS

Immunohistochemical analysis was performed to detect SATB1 and LMP-1 protein in clinical samples, and the association of SATB1 protein expression with patient clinicopathological characteristics and LMP-1 expression were analyzed. SATB1 expression profiles were evaluated in well-differentiated NPC cell line CNE1, poorly-differentiated CNE2Z, undifferentiated C666-1 and immortalized nasopharyngeal epithelia NP-69 cells using quantitative RT-PCR, western blotting and fluorescent staining. After inhibition the SATB1 expression by using SATB1 specific small interfering RNA in these cell lines, the change of cell proliferation was investigated by western blotting analysis of PCNA (proliferating cell nuclear antigen) expression and CCK-8 assay, and the cell migration was assessed by Transwell migration assay. Finally, the expressions of SATB1 and PCNA were examined in CNE1 cells that forced LMP-1 expression by fluorescent staining and RT-PCR.

RESULTS

Immunohistochemical analysis revealed that SATB1 protein expression was elevated in NPC tissues compared to benign nasopharyngeal tissues (P = 0.005). Moreover, high levels of SATB1 protein expression were positively correlated with clinical stage (P = 0.025), the status of lymph node metastasis (N classification) (P = 0.018), distant metastasis (M classification) (P = 0.041) and LMP-1 expression status (r = 2.35, P < 0.01) in NPC patients. In vitro experiments demonstrated that an inverse relationship between SATB1 expression and NPC differentiation status, with SATB1 weakly expressed in NP-69 cells and CNE1 cells, and significant increasingly expressed in CNE-2Z and C666-1 cells. Targeted knockdown of SATB1 expression obviously attenuated the proliferation and migration of highly SATB1-expressing CNE2Z and C666-1 cells, but not NP-69 and CNE1 cells. Interestingly, forced LMP-1 expression in CNE1 cells led to a surprisingly increasing SATB1 expression and nuclear location, companying with an up-regulated PCNA expression.

CONCLUSIONS

Our results reveal that EBV LMP-1-mediated over-expression of SATB1 is associated with NPC progression, suggesting SATB1 may represent a promising biomarker and therapeutic target for NPC.

Expression and biological roles of SATB1 in human bladder cancer

Special AT-rich sequence-binding protein-1 (SATB1) has been recently reported to be overexpressed in various cancers and associate with the malignant behavior of cancer cells. However, the expression and potential roles of SATB1 in bladder cancer remains unclear. In the present study, SATB1 expression was analyzed in 85 archived bladder cancer specimens using immunohistochemistry and the correlations between SATB1 expression and clinicopathological parameters were evaluated. To further explore the biological functions of SATB1 in bladder cancer, siRNA knockdown was performed in 5637 and T24 bladder cancer cell lines. We then carried out CCK8 assay and examined cisplatin-induced apoptosis to address the roles of SATB1 in proliferation and apoptosis. We found that SATB1 was overexpressed in 33 of 85 (38.8 %) bladder cancer specimens. SATB1 overexpression associated with tumor grade (p = 0.002) and tumor stage (p = 0.027). SATB1 depletion in 5637 and T24 cells decreased cell proliferation while upregulating cisplatin-induced apoptosis. Further study demonstrated that SATB1 knockdown decreased cyclin D1 and cyclin E expression and upregulated caspase3 cleavage. In conclusion, SATB1 is overexpressed in bladder cancer and regulates malignant cell growth and apoptosis, which makes SATB1 a therapeutic target candidate for bladder cancer.

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.

SATB1 is overexpressed in metastatic prostate cancer and promotes prostate cancer cell growth and invasion

Background

Special AT-rich sequence binding protein 1 (SATB1) is a nuclear factor that functions as the global chromatin organizer to regulate chromatin structure and gene expression gene expression. SATB1 has been shown to be abnormally expressed in various types of cancer. However, the expression and role of SATB1 in prostate cancer remain unclear.

Methods

120 cases of prostatic carcinoma and 60 cases of benign prostate hyperplasia were analyzed for SATB1 expression by immunohistochemistry. LNCaP, DU-145, and PC3 prostate cancer cells were examined for SATB1 expression by Western blot analysis. Cell proliferation and invasion was evaluated by CCK8 and transwell invasion assay, respectively.

Results

SATB1 staining was stronger in prostatic carcinomas with metastasis than in those without metastasis, but was absent in benign prostate hyperplasia. Furthermore, SATB1 expression was positively correlated with bone metastasis and the Gleason score. SATB1 overexpression promoted the proliferation and invasion of LNCaP cells while SATB1 knockdown inhibited the proliferation and invasion of DU-145 cells.

Conclusions

These findings provide novel insight into oncogenic role of SATB1 in prostate cancer, suggesting that SATB1 is a promising biomarker and therapeutic target for prostate 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.

Identification of special AT-rich sequence binding protein 1 as a novel tumor antigen recognized by CD8+ T cells: implication for cancer immunotherapy

BACKGROUND

A large number of human tumor-associated antigens that are recognized by CD8(+) T cells in a human leukocyte antigen class I (HLA-I)-restricted fashion have been identified. Special AT-rich sequence binding protein 1 (SATB1) is highly expressed in many types of human cancers as part of their neoplastic phenotype, and up-regulation of SATB1 expression is essential for tumor survival and metastasis, thus this protein may serve as a rational target for cancer vaccines.

METHODOLOGY/PRINCIPAL FINDINGS

Twelve SATB1-derived peptides were predicted by an immuno-informatics approach based on the HLA-A*02 binding motif. These peptides were examined for their ability to induce peptide-specific T cell responses in peripheral blood mononuclear cells (PBMCs) obtained from HLA-A*02(+) healthy donors and/or HLA-A*02(+) cancer patients. The recognition of HLA-A*02(+) SATB1-expressing cancer cells was also tested. Among the twelve SATB1-derived peptides, SATB1(565-574) frequently induced peptide-specific T cell responses in PBMCs from both healthy donors and cancer patients. Importantly, SATB1(565-574)-specific T cells recognized and killed HLA-A*02(+) SATB1(+) cancer cells in an HLA-I-restricted manner.

CONCLUSIONS/SIGNIFICANCE

We have identified a novel HLA-A*02-restricted SATB1-derived peptide epitope recognized by CD8(+) T cells, which, in turn, recognizes and kills HLA-A*02(+) SATB1(+) tumor cells. The SATB1-derived epitope identified may be used as a diagnostic marker as well as an immune target for development of cancer vaccines.