SP1 is required for basal activation and chromatin accessibility of CD151 promoter in liver cancer cells

LncSUMO1P3 exacerbates malignant behaviors of esophageal squamous cell carcinoma cells via miR-486-5p/PHF8/CD151

Background

Esophageal squamous cell carcinoma (ESCC) is a malignancy usually associated with smoking or alcohol consumption. The involvement of long noncoding RNAs (lncRNAs) in the regulation of tumor development and metastasis through molecular mechanisms has been unveiled by accumulating evidence. However, the function of lncRNA SUMO1 Pseudogene 3 (lncSUMO1P3) essential to ESCC development remains obscure.

Methods

Reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) and Western blot (WB) analysis were done to measure RNA and protein levels. Functional assays were carried out to examine the changes in ESCC cell phenotype. Supported by bioinformatics analysis, mechanism assays were done for assessment of putative interactions among different genes.

Results

LlncSUMO1P3 was aberrantly up-regulated in ESCC cell lines, and lncSUMO1P3 deficiency could hamper cell proliferation, migration and invasion as well as epithelial-mesenchymaltransition (EMT) in ESCC while lncSUMO1P3 overexpression led to the opposite consequences. LncSUMO1P3 could competitively bind to microRNA-486-5p (miR-486-5p) or PHD finger protein 8 (PHF8) to modulate CD151 expression. CD151 was also verified to regulate ESCC cell biological behaviors.

Conclusion

Our study revealed that lncSUMO1P3, up-regulated in ESCC cells, could sponge miR-486-5p and recruit PHF8 to up-regulate CD151, thus influencing the malignant behaviors of ESCC cells.

Site specific hypermethylation of CpGs in Connexin genes 30, 26 and 43 in different grades of glioma and attenuated levels of their mRNAs

AIM

Gliomas, the intracranial tumours are considered the deadliest malignancies. The gap junctional Connexins (Cxs) that maintain cellular homeostasis perform a unique function in glial tumour suppression. However, the differential methylation patterns of Cxs were not revealed in glioma so far. The current study attempts to categorise promoter methylation of Cx30 and Cx26 and intron methylation of Cx43 in different grades of human glioma.

MATERIALS AND METHODS

About 85 glioma patients with pathologically confirmed grades and 15 control brain tissues were recruited in the study. Bisulphite-PCR-Single Stranded Conformation analysis(SSCA), Bisulphite sequencing and MeDIP-qPCR were carried out to assess methylation status and Cx mRNA levels were also analysed to evaluate the effect of methylation.

RESULTS

We found that promoter CpG islands(CpGs) reside in Sp1 and Ap2 sites of Cx30 and 26 were hypermethylated in high grades (HG) of glioma rather than low grades. The input % of both was significantly increased (p < 0.03) in progressive grades. Interestingly, Cx43 could exhibit a significant increase (p < 0.05) in input % only in grade IV. While, Cx30 and 26 mRNAs were downregulated according to their methylation status in progressive fashion with grades, Cx43 was downregulated irrespective of intron methylation.

CONCLUSION

Thus, we suggest that the sites and extent of methylation of Cxs (30 and 26 but not in 43) are found to be altered. In different grades of glioma can provide better appreciation of the grade of the patient and might help in strategies based on epigenetic approaches.

Identification of a TGF-β-miR-195 positive feedback loop in hepatocytes and its deregulation in hepatoma cells

Resistance to TGF-β-induced growth repression is prevalent in various cancer cells, but the underlying mechanisms remain unclear. In this study, we showed that activation of TGF-β signaling caused Sma- and Mad-related family (Smad) 2 and Smad3 to bind directly to the promoter region of miR-195, and then activated miR-195 transcription in normal hepatocytes. Conversely, miR-195 inhibited the expression of Smad7 by binding to its 3'-UTR, thereby strengthening TGF-β-Smad signaling. These data identify a novel TGF-β-miR-195 positive regulatory circuitry in normal hepatocytes. Further investigation revealed that HDAC1, a histone deacetylase that was abnormally overexpressed in hepatocellular carcinoma, could bind to the miR-195 promoter via Smad3 and cause hypoacetylation in the histones associated with the miR-195 promoter in hepatoma cells. This resulted in transcriptional repression of miR-195 and, subsequently, disruption of the TGF-β-miR-195 regulatory loop and evasion of TGF-β-mediated growth inhibition. Moreover, silencing HDAC1 in hepatoma cells restored TGF-β-mediated growth suppression, but this effect was attenuated if miR-195 expression decreased. These findings suggest that HDAC1-induced miR-195 down-regulation is an important mechanism for tumor cells to resist the cytostatic activity of TGF-β, and highlight the importance of TGF-β-Smad2/3-miR-195-Smad7 circuitry in preventing uncontrolled cell proliferation.-Wang, R., Fu, T., You, K., Li, S., Zhao, N., Yang, J., Zhuang, S.-M. Identification of a TGF-β-miR-195 positive feedback loop in hepatocytes and its deregulation in hepatoma cells.

SP and KLF Transcription Factors in Digestive Physiology and Diseases

Specificity proteins (SPs) and Krüppel-like factors (KLFs) belong to the family of transcription factors that contain conserved zinc finger domains involved in binding to target DNA sequences. Many of these proteins are expressed in different tissues and have distinct tissue-specific activities and functions. Studies have shown that SPs and KLFs regulate not only physiological processes such as growth, development, differentiation, proliferation, and embryogenesis, but pathogenesis of many diseases, including cancer and inflammatory disorders. Consistently, these proteins have been shown to regulate normal functions and pathobiology in the digestive system. We review recent findings on the tissue- and organ-specific functions of SPs and KLFs in the digestive system including the oral cavity, esophagus, stomach, small and large intestines, pancreas, and liver. We provide a list of agents under development to target these proteins.

Sp1-mediated ectopic expression of T-cell lymphoma invasion and metastasis 2 in hepatocellular carcinoma

T-cell lymphoma invasion and metastasis 2 (TIAM2) is a neuron-specific protein that has been found ectopically expressed in hepatocellular carcinoma (HCC). Results from clinical specimens and cellular and animal models have shown that the short form of TIAM2 (TIAM2S) functions as an oncogene in the tumorigenesis of liver cancer. However, the regulation of TIAM2S ectopic expression in HCC cells remains largely unknown. This study aimed to identify the mechanism underlying the ectopic expression of TIAM2S in liver cancer cells. In this report, we provide evidence illustrating that Sp1 binds directly to the GC box located in the TIAM2S core promoter. We further demonstrated that overexpression of Sp1 in HepaRG cells promotes endogenous TIAM2S mRNA and protein expressions, and knockdown of Sp1 in 2 HCC cell lines, HepG2 and PLC/PRF/5, led to a substantial reduction in TIAM2S mRNA and protein in these cells. Of 60 paired HCC samples, 70% showed a significant increase (from 1.1- to 3.6-fold) in Sp1 protein expression in the tumor cells. The elevated Sp1 expression was highly correlated with both TIAM2S mRNA and protein expressions in these samples. Together, these results illustrate that Sp1 positively controls TIAM2S transcription and that Sp1-mediated transcriptional activation is essential for TIAM2S ectopic expression in liver cancer cells.

Identification of Critical Elements for Regulation of Inorganic Pyrophosphatase (PPA1) in MCF7 Breast Cancer Cells

Cytosolic inorganic pyrophosphatase plays an important role in the cellular metabolism by hydrolyzing inorganic pyrophosphate (PPi) formed as a by-product of various metabolic reactions. Inorganic pyrophosphatases are known to be associated with important functions related to the growth and development of various organisms. In humans, the expression of inorganic pyrophosphatase (PPA1) is deregulated in different types of cancer and is involved in the migration and invasion of gastric cancer cells and proliferation of ovarian cancer cells. However, the transcriptional regulation of the gene encoding PPA1 is poorly understood. To gain insights into PPA1 gene regulation, a 1217 bp of its 5'-flanking region was cloned and analyzed. The 5'-deletion analysis of the promoter revealed a 266 bp proximal promoter region exhibit most of the transcriptional activity and upon sequence analysis, three putative Sp1 binding sites were found to be present in this region. Binding of Sp1 to the PPA1 promoter was confirmed by Electrophoretic mobility shift assay (EMSA) and Chromatin immunoprecipitation (ChIP) assay. Importance of these binding sites was verified by site-directed mutagenesis and overexpression of Sp1 transactivates PPA1 promoter activity, upregulates protein expression and increases chromatin accessibility. p300 binds to the PPA1 promoter and stimulates Sp1 induced promoter activity. Trichostatin A (TSA), a histone deacetylase (HDAC) inhibitor induces PPA1 promoter activity and protein expression and HAT activity of p300 was important in regulation of PPA1 expression. These results demonstrated that PPA1 is positively regulated by Sp1 and p300 coactivates Sp1 induced PPA1 promoter activity and histone acetylation/deacetylation may contribute to a local chromatin remodeling across the PPA1 promoter. Further, knockdown of PPA1 decreased colony formation and viability of MCF7 cells.

Analysis of transcriptional factors and regulation networks in laryngeal squamous cell carcinoma patients with lymph node metastasis

The present study was to identify and quantitate differentially expressed proteins in laryngeal squamous cell carcinoma (LSCC) tissues with or without lymph node metastasis and to explore transcriptional factors and regulation networks associated with the process. Tissue specimens were taken from 20 patients with LSCC, including 10 cases of LSCC without metastasis LSCC (N0) and 10 cases of LSCC with metastasis LSCC (Nx). Among the 643 unique proteins identified by using iTRAQ labeling and quantitative proteomic technology, 389 proteins showed an abundance change in LSCC (Nx) as compared to LSCC (N0). Cytoskeleton remodeling, cell adhesion, and immune response activation were found to be the main processes in LSCC metastasis. The construction of transcription regulation networks identified key transcription regulators for lymph node metastasis of LSCC, including Sp1, c-myc, and p53, which may affect LSCC metastasis through the epithelial-mesenchymal transition. Furthermore, our results suggest that ubiquitination may be a critical factor in the networks. The present study provides insights into transcriptional factors and regulation networks involved in LSCC metastasis, which may lead to new strategies for treatment of LSCC metastasis.

SP1 plays a pivotal role for basal activity of TIGAR promoter in liver cancer cell lines

TIGAR expression resulted in down-regulation of glycolysis, reduction of intracellular levels of reactive oxygen species, and protection from apoptosis. Despite biological importance, its promoter has not yet been characterized. In this study, we characterized that transcription factor SP1 plays a pivotal role for basal activity of TIGAR promoter. By 5'RACE, the transcription start site was identified locating at 134 bp upstream of the translation initiation site. Different portions of 5'-flanking and 5'-untranslated regions were fused to a luciferase reporter gene to create reporter plasmids, and constructs were transiently transfected into HepG2, Bel-7402, and Smmc-7721 cell lines for luciferase analysis. A minimal region -56/-4 bearing a SP1-binding site was characterized and plays a vital role. Data from electrophoretic mobility shift assay and chromatin immunoprecipitation showed that SP1 can interact with the SP1-binding site within TIGAR promoter in vitro and in vivo. Conclusively, SPl is indispensable for basal activity of TIGAR promoter.

NF-kappaB P50/P65 hetero-dimer mediates differential regulation of CD166/ALCAM expression via interaction with micoRNA-9 after serum deprivation, providing evidence for a novel negative auto-regulatory loop

CD166/ALCAM plays an important role in tumor aggression and progression as well as protecting cancer cells against apoptosis and autophagy. However, the mechanism by which pro-cell death signals control CD166 expression remains unclear. Here we show that following serum deprivation (SD), upregulation of CD166 protein is shorter than that of CD166 mRNA. Molecular analysis revealed both CD166 and miR-9-1 as two novel NF-κB target genes in hepatoma cells. In vivo activation and translocation of the NF-κB P50/P65 hetero-dimer into the nucleus following the phosphorylation and accompanied degradation of its inhibitor, IκBα, contributes to efficient transcription of both genes following SD. We show that following serum starvation, delayed up-regulation of miR-9 represses translation of CD166 protein through its target sites in the 3'-UTR of CD166 mRNA. We also propose that miR-9 promotes cell migration largely due to inhibition of CD166. Collectively, the study elucidates a novel negative auto-regulatory loop in which NF-κB mediates differential regulation of CD166 after SD.

SP1 acts as a key factor, contributes to upregulation of ADAM23 expression under serum deprivation

ADAM23 modulates many cellular functions, alteration of expression causes a number of tumor types; however, the mechanisms controlling ADAM23 expression remain unknown. Here we have identified a SP1 binding site (-202/-190) that binds SP1 at the proximal promoter of human ADAM23 gene; furthermore, serum deprivation enhances open chromatin accessibility and help expose the SP1 binding site; finally, SP1 binding recruits RNA polymerase II, which in turn results in upregulation of endogenous ADAM23 expression. Therefore, the present study delineates the fundamental elements of a core promoter structure that will be helpful for future studies of the regulation of ADAM23 gene.

The role of Sp1 and Sp3 in normal and cancer cell biology

Sp1 and Sp3 are transcription factors expressed in all mammalian cells. These factors are involved in regulating the transcriptional activity of genes implicated in most cellular processes. Dysregulation of Sp1 and Sp3 is observed in many cancers and diseases. Due to the amino acid sequence similarity of the DNA binding domains, Sp1 and Sp3 recognize and associate with the same DNA element with similar affinity. However, others and our laboratory demonstrated that these two factors possess different properties and exert different functional roles. Both Sp1 and Sp3 can interact with and recruit a large number of proteins including the transcription initiation complex, histone modifying enzymes and chromatin remodeling complexes, which strongly suggest that Sp1 and Sp3 are important transcription factors in the remodeling chromatin and the regulation of gene expression. In this review, the role of Sp1 and Sp3 in normal and cancer cell biology and the multiple mechanisms deciding the functional roles of Sp1 and Sp3 will be presented.