Profiling of promoter occupancy by the SND1 transcriptional coactivator identifies downstream glycerolipid metabolic genes involved in TNFα response in human hepatoma cells

Dynamic regulation of pancreatic β cell function and gene expression by the SND1 coregulator in vitro

The pancreatic β cell synthesizes, packages, and secretes insulin in response to glucose-stimulation to maintain blood glucose homeostasis. Under diabetic conditions, a subset of β cells fail and lose expression of key transcription factors (TFs) required for insulin secretion. Among these TFs is Pancreatic and duodenal homeobox 1 (PDX1), which recruits a unique subset of transcriptional coregulators to modulate its activity. Here we describe a novel interacting partner of PDX1, the Staphylococcal Nuclease and Tudor domain-containing protein (SND1), which has been shown to facilitate protein-protein interactions and transcriptional control through diverse mechanisms in a variety of tissues. PDX1:SND1 interactions were confirmed in rodent β cell lines, mouse islets, and human islets. Utilizing CRISPR-Cas9 gene editing technology, we deleted Snd1 from the mouse β cell lines, which revealed numerous differentially expressed genes linked to insulin secretion and cell proliferation, including limited expression of Glp1r. We observed Snd1 deficient β cell lines had reduced cell expansion rates, GLP1R protein levels, and limited cAMP accumulation under stimulatory conditions, and further show that acute ablation of Snd1 impaired insulin secretion in rodent and human β cell lines. Lastly, we discovered that PDX1:SND1 interactions were profoundly reduced in human β cells from donors with type 2 diabetes (T2D). These observations suggest the PDX1:SND1 complex formation is critical for controlling a subset of genes important for β cell function and is targeted in diabetes pathogenesis.

Improved β-cell function leads to improved glucose tolerance in a transgenic mouse expressing lipoprotein lipase in adipocytes

Lipoprotein lipase (LPL) hydrolyzes the triglyceride core of lipoproteins and also functions as a bridge, allowing for lipoprotein and cholesterol uptake. Transgenic mice expressing LPL in adipose tissue under the control of the adiponectin promoter (AdipoQ-LPL) have improved glucose metabolism when challenged with a high fat diet. Here, we studied the transcriptional response of the adipose tissue of these mice to acute high fat diet exposure. Gene set enrichment analysis (GSEA) provided mechanistic insight into the improved metabolic phenotype of AdipoQ-LPL mice. First, the cholesterol homeostasis pathway, which is controlled by the SREBP2 transcription factor, is repressed in gonadal adipose tissue AdipoQ-LPL mice. Furthermore, we identified SND1 as a link between SREBP2 and CCL19, an inflammatory chemokine that is reduced in AdipoQ-LPL mice. Second, GSEA identified a signature for pancreatic β-cells in adipose tissue of AdipoQ-LPL mice, an unexpected finding. We explored whether β-cell function is improved in AdipoQ-LPL mice and found that the first phase of insulin secretion is increased in mice challenged with high fat diet. In summary, we identify two different mechanisms for the improved metabolic phenotype of AdipoQ-LPL mice. One involves improved adipose tissue function and the other involves adipose tissue-pancreatic β-cell crosstalk.

Integrated proteogenomic characterization of urothelial carcinoma of the bladder

Background

Urothelial carcinoma (UC) is the most common pathological type of bladder cancer, a malignant tumor. However, an integrated multi-omics analysis of the Chinese UC patient cohort is lacking.

Methods

We performed an integrated multi-omics analysis, including whole-exome sequencing, RNA-seq, proteomic, and phosphoproteomic analysis of 116 Chinese UC patients, comprising 45 non-muscle-invasive bladder cancer patients (NMIBCs) and 71 muscle-invasive bladder cancer patients (MIBCs).

Result

Proteogenomic integration analysis indicated that SND1 and CDK5 amplifications on chromosome 7q were associated with the activation of STAT3, which was relevant to tumor proliferation. Chromosome 5p gain in NMIBC patients was a high-risk factor, through modulating actin cytoskeleton implicating in tumor cells invasion. Phosphoproteomic analysis of tumors and morphologically normal human urothelium produced UC-associated activated kinases, including CDK1 and PRKDC. Proteomic analysis identified three groups, U-I, U-II, and U-III, reflecting distinct clinical prognosis and molecular signatures. Immune subtypes of UC tumors revealed a complex immune landscape and suggested the amplification of TRAF2 related to the increased expression of PD-L1. Additionally, increased GARS, related to subtype U-II, was validated to promote pentose phosphate pathway by inhibiting activities of PGK1 and PKM2.

Conclusions

This study provides a valuable resource for researchers and clinicians to further identify molecular pathogenesis and therapeutic opportunities in urothelial carcinoma of the bladder.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13045-022-01291-7.

Mitochondrion-Localized SND1 Promotes Mitophagy and Liver Cancer Progression Through PGAM5

Staphylococcal nuclease domain-containing protein 1 (SND1) is an evolutionarily conserved multifunctional protein that functions mainly in the nucleus and cytoplasm. However, whether SND1 regulates cellular activity through mitochondrial-related functions remains unclear. Herein, we demonstrate that SND1 is localized to mitochondria to promote phosphoglycerate mutase 5 (PGAM5)-mediated mitophagy. We find that SND1 is present in mitochondria based on mass spectrometry data and verified this phenomenon in different liver cancer cell types by performing organelle subcellular isolation. Specifically, The N-terminal amino acids 1-63 of SND1 serve as a mitochondrial targeting sequence (MTS), and the translocase of outer membrane 70 (TOM 70) promotes the import of SND1 into mitochondria. By immunoprecipitation-mass spectrometry (IP-MS), we find that SND1 interacts with PGAM5 in mitochondria and is crucial for the binding of PGAM5 to dynamin-related protein 1 (DRP1). Importantly, we demonstrate that PGAM5 and SND1-MTS are required for SND1-mediated mitophagy under FCCP and glucose deprivation treatment as well as for SND1-mediated cell proliferation and tumor growth both in vitro and in vivo. Aberrant expression of SND1 and PGAM5 predicts poor outcomes in hepatocellular carcinoma (HCC) patients. Taken together, these findings establish a previously unappreciated role of SND1 and the association of mitochondrion-localized SND1 with PGAM5 in mitophagy and tumor progression.

Impact of hepatocyte-specific deletion of staphylococcal nuclease and tudor domain containing 1 (SND1) on liver insulin resistance and acute liver failure of mice

Although our previous research shows an ameliorated high-fat diet (HFD)-induced hepatic steatosis and insulin resistance in global SND1 transgenic mice, the involvement of SND1 loss-of-function in hepatic metabolism remains elusive. Herein, we aim to explore the potential impact of hepatocyte-specific SND1 deletion on insulin-resistant mice. As SND1 is reported to be linked to inflammatory response, the pathobiological feature of acute liver failure (ALF) is also investigated. Hence, we construct the conditional liver knockout (LKO) mice of SND1 for the first time. Under the condition of HFD, the absence of hepatic SND1 affects the weight of white adipose tissue, but not the gross morphology, body weight, cholesterol level, liver weight, and hepatic steatosis of mice. Furthermore, we fail to observe significant differences in either HFD-induced insulin resistance or lipopolysaccharide/D-galactosamine-induced (LPS/D-GaIN) ALF between LKO and wild type (WT) mice in terms of inflammation and tissue damage. Compared with negative controls, there is no differential SND1 expression in various species of sample with insulin resistance or ALF, based on several gene expression omnibus datasets, including GSE23343, GSE160646, GSE120243, GSE48794, GSE13271, GSE151268, GSE62026, GSE120652, and GSE38941. Enrichment result of SND1-binding partners or related genes indicates a sequence of issues related to RNA or lipid metabolism, but not glucose homeostasis or hepatic failure. Overall, hepatic SND1 is insufficient to alter the phenotypes of hepatic insulin resistance and acute liver failure in mice. The SND1 in various organs is likely to cooperate in regulating glucose homeostasis by affecting the expression of lipid metabolism-related RNA transcripts during stress.

Long non-coding RNAs as the critical regulators of doxorubicin resistance in tumor cells

Resistance against conventional chemotherapeutic agents is one of the main reasons for tumor relapse and poor clinical outcomes in cancer patients. Various mechanisms are associated with drug resistance, including drug efflux, cell cycle, DNA repair and apoptosis. Doxorubicin (DOX) is a widely used first-line anti-cancer drug that functions as a DNA topoisomerase II inhibitor. However, DOX resistance has emerged as a large hurdle in efficient tumor therapy. Furthermore, despite its wide clinical application, DOX is a double-edged sword: it can damage normal tissues and affect the quality of patients’ lives during and after treatment. It is essential to clarify the molecular basis of DOX resistance to support the development of novel therapeutic modalities with fewer and/or lower-impact side effects in cancer patients. Long non-coding RNAs (lncRNAs) have critical roles in the drug resistance of various tumors. In this review, we summarize the state of knowledge on all the lncRNAs associated with DOX resistance. The majority are involved in promoting DOX resistance. This review paves the way to introducing an lncRNA panel marker for the prediction of the DOX response and clinical outcomes for cancer patients.

The Role of the PRMT5-SND1 Axis in Hepatocellular Carcinoma

Arginine methylation is an essential post-translational modification (PTM) deposited by protein arginine methyltransferases (PRMTs) and recognized by Tudor domain-containing proteins. Of the nine mammalian PRMTs, PRMT5 is the primary enzyme responsible for the deposition of symmetric arginine methylation marks in cells. The staphylococcal nuclease and Tudor domain-containing 1 (SND1) effector protein is a key reader of the marks deposited by PRMT5. Both PRMT5 and SND1 are broadly expressed and their deregulation is reported to be associated with a range of disease phenotypes, including cancer. Hepatocellular carcinoma (HCC) is an example of a cancer type that often displays elevated PRMT5 and SND1 levels, and there is evidence that hyperactivation of this axis is oncogenic. Importantly, this pathway can be tempered with small-molecule inhibitors that target PRMT5, offering a therapeutic node for cancer, such as HCC, that display high PRMT5–SND1 axis activity. Here we summarize the known activities of this writer–reader pair, with a focus on their biological roles in HCC. This will help establish a foundation for treating HCC with PRMT5 inhibitors and also identify potential biomarkers that could predict sensitivity to this type of therapy.

Genetic variants in m6A modification genes are associated with colorectal cancer risk

The N6-methyladenosine (m6A) modification plays important regulatory roles in gene expression, cancer occurrence and metastasis. Herein, we aimed to explore the association between genetic variants in m6A modification genes and susceptibility to colorectal cancer. We used logistic regression models to investigate the associations between candidate single-nucleotide polymorphisms (SNPs) in 20 m6A modification genes and colorectal cancer risk. The false discovery rate (FDR) method was used for multiple comparisons. Dual luciferase assays and RNA m6A quantifications were applied to assess transcriptional activity and measure m6A levels, respectively. We found that SND1 rs118049207 was significantly associated with colorectal cancer risk in a Nanjing population (odds ratio (OR) = 1.69, 95% confidence interval (95% CI) = 1.31-2.18, P = 6.51 × 10-6). This finding was further replicated in an independent Beijing population (OR = 1.36, 95% CI = 1.04-1.79, P = 2.41 × 10-2) and in a combined analysis (OR = 1.52, 95% CI = 1.27-1.84, P = 8.75 × 10-6). Stratification and interaction analyses showed that SND1 rs118049207 multiplicatively interacted with the sex and drinking status of the patients to enhance their colorectal cancer risk (P = 1.56 × 10-3 and 1.41 × 10-2, respectively). Furthermore, rs118049207 served as an intronic enhancer on SND1 driven by DMRT3. SND1 mRNA expression was markedly increased in colorectal tumour tissues compared with adjacent normal tissues. The colorimetric m6A quantification strategy revealed that SND1 could alter m6A levels in colorectal cancer cell lines. Our findings indicated that genetic variants in m6A modification genes might be promising predictors of colorectal cancer risk.

The novel chromatin architectural regulator SND1 promotes glioma proliferation and invasion and predicts the prognosis of patients

BACKGROUND

Upregulation of staphylococcal nuclease domain-containing protein 1 (SND1) is a common phenomenon in different human malignant tissues. However, little information is available on the underlying mechanisms through which SND1 affects glioma cell proliferation and invasion.

METHODS

SND1, Ras homolog family member A (RhoA), and marker of proliferation Ki-67 (MKI67) were analyzed in 187 gliomas by immunostaining. The correlation between those markers and patients' prognoses was assessed using the Kaplan-Meier estimator. Gene Ontology, chromatin immunoprecipitation, electrophoretic mobility shift assay, and chromosome conformation capture were applied to identify SND1-activated target genes. We also used MTT, colony formation, transwell and orthotopic implantation assays to investigate SND1 function in glioma cell proliferative and invasive activity.

RESULTS

We identified SND1 and RhoA as independent predictors of poor prognosis in glioma patients. SND1 knockdown significantly suppressed the proliferation and invasion of glioma cells. Mechanistically, we discovered that SND1 facilitated malignant glioma phenotypes by epigenetically inducing chromatin topological interaction, which activated downstream RhoA transcription. RhoA sequentially regulated expression of CCND1, CCNE1, CDK4, and CDKN1B and accelerated G1/S phase transition in glioma cell proliferation.

CONCLUSIONS

Our findings identify SND1 as a novel chromatin architectural modifier and promising prognostic indicator for glioma classification and treatment.

Linc00668 Promotes Invasion and Stem Cell-Like Properties of Breast Cancer Cells by Interaction With SND1

Long non-coding RNAs (lncRNAs) are reported to be involved in breast cancer progression. Herein, we observed that the expression of Linc00668 was increased in breast cancer compared to normal tissue. The patients with high Linc00668 expression exhibited an association with a higher metastatic risk. We demonstrated that forced expression of Linc00668 enhanced, whereas depletion of Linc00668 diminished invasion and self-renewal of breast cancer cells as well as resistance to doxorubicin (Dox). Further mechanistic studies revealed that Linc00668 associated with staphylococcal nuclease domain-containing 1 (SND1) and regulated the expression of downstream genes. Linc00668 depletion led to reduced expression of the downstream target of SND1 and further attenuated the self-renewal capacity of breast cancer cells. Our observations suggest that Linc00668 promotes metastasis, and chemotherapeutic resistance in breast cancer by interacting with SND1. Therefore, Linc00668 may serve as a potential therapeutic modulator in breast cancer treatment.

Simvastatin Evokes An Unpredicted Antagonism For Tamoxifen In MCF-7 Breast Cancer Cells

Purpose

Tamoxifen (TAM) is a non-steroidal antiestrogen drug, used in the prevention and treatment of all stages of hormone-responsive breast cancer. Simvastatin (SIM) is a lipid-lowering agent and has been shown to inhibit cancer cell growth. The study aimed to investigate the effect of the combination of TAM and SIM in the treatment of estrogen receptor positive (ER+) breast cancer cell line, MCF-7, and in mice-bearing Ehrlich solid tumors.

Methods

MCF-7 cells were treated with different concentrations of TAM or/and SIM for 72 hours and the effects of the combination treatment on cytotoxicity, oxidative stress markers, apoptosis, angiogenesis, and metastasis were investigated using different techniques. In addition, tumor volume, oxidative markers, and inflammatory markers of the combined therapy were explored in mice bearing solid EAC tumors.

Results

The results showed that treatment of MCF-7 cells with the combination of 10 µM TAM, and 2 µM SIM significantly inhibited the increase in oxidative stress markers, LDH, and NF-kB induced by TAM. In addition, there was a significant decrease in the total apoptotic ratio, caspase-3 activity, and glucose uptake, while there was a non-significant change in Bax/bcl-2 ratio compared to the TAM-treated group. Using the isobologram equation, the drug interaction was antagonistic with combination index, CI=1.18. On the other hand, the combination regimen decreased VEGF, and matrix metalloproteinases, MMP 2&9 compared to TAM-treated cells. Additionally, in vivo, the combination regimen resulted in a non-significant decrease in the tumor volume, decreased oxidative markers, and the protein expression of TNF-α, and NF-κB compared to the TAM treated group.

Conclusion

Although the combination regimen of TAM and SIM showed an antagonistic drug interaction in MCF-7 breast cancer, it displayed favorable antiangiogenic, anti-metastatic, and anti-inflammatory effects.

Lipidomic data uncover extensive heterogeneity in phosphatidylcholine structural variants in HepG2 cells

The data contain information related to the research article entitled “Profiling of promoter occupancy by the SND1 transcriptional coactivator identifies downstream glycerolipid metabolic genes involved in TNFα response in human hepatoma cells” (DOI: 10.1093/nar/gkv858). In the article alluded to, we reported that tumor necrosis factor alpha (TNFα) increases notably the cellular content of the major glycerolipid phosphatidylcholine (PC). Here, accompanying lipidomic data determine the PC structural variants that have been identified in human hepatoma HepG2 cells and those whose relative abundance is modified by TNFα. We used ultrahigh performance liquid chromatography (UHPLC) coupled to electrospray ionization (ESI) tandem mass spectrometry (MS/MS)-based lipidomic profiling to analyze lipid extracts of control and TNFα-treated HepG2 cells. The identity of PC individual species was elucidated using the values of the retention time and molecular weight in addition to the fragmentation patterns. MS data were then processed and analyzed for the characterization of statistically significant differences in detected structural variants. We have annotated the dataset of PC species that characterize HepG2 cells' phenotype, both under normal and pro-inflammatory conditions.

Insights Into SND1 Oncogene Promoter Regulation

The staphylococcal nuclease and Tudor domain containing 1 gene (SND1), also known as Tudor-SN, TSN or p100, encodes an evolutionarily conserved protein with invariant domain composition. SND1 contains four repeated staphylococcal nuclease domains and a single Tudor domain, which confer it endonuclease activity and extraordinary capacity for interacting with nucleic acids, individual proteins and protein complexes. Originally described as a transcriptional coactivator, SND1 plays fundamental roles in the regulation of gene expression, including RNA splicing, interference, stability, and editing, as well as in the regulation of protein and lipid homeostasis. Recently, SND1 has gained attention as a potential disease biomarker due to its positive correlation with cancer progression and metastatic spread. Such functional diversity of SND1 marks this gene as interesting for further analysis in relation with the multiple levels of regulation of SND1 protein production. In this review, we summarize the SND1 genomic region and promoter architecture, the set of transcription factors that can bind the proximal promoter, and the evidence supporting transactivation of SND1 promoter by a number of signal transduction pathways operating in different cell types and conditions. Unraveling the mechanisms responsible for SND1 promoter regulation is of utmost interest to decipher the SND1 contribution in the realm of both normal and abnormal physiology.

A Computational Approach to Identify Novel Potential Precursor miRNAs and their Targets from Hepatocellular Carcinoma Cells

Background:

Recent advances in next-generation sequencing technology allow highthroughput RNA-Sequencing to be widely applied in studying coding and non-coding RNA profiling in cells. RNA-Seq data usually contains functional transcriptomic and other small and larger non-coding (nc) RNA sequences. </P><P> Objective: MicroRNAs (miRNAs), a small nc-RNA act as epigenetic markers and the expression of their target genes and pathways that regulate Hepatocellular Carcinoma (HCC), a primary malignancy of the liver. The unreported potential novel miRNAs targeting HCC pathways can be identified from the sequenced data.

Methods:

In this study, we performed a computational identification of novel putative miRNAs and their targets from publicly available high-throughput sequencing Fastq data of human HCC cells HepG2, NorHep and SKHep1, retrieved from NCBI-SRA.

Results:

Totally, 572 unique known precursor miRNAs and 1062 unique novel miRNAs were identified from HepG2, Nor and SKHep1 HCC cell lines. Interestingly, 140 novel miRNAs were predicted to be extensively involved in targeting genes of HCC related pathways such as apoptosis, cell signaling, cell division, cell-cycle arrest, GPCR, MAPK cascade, TOR signaling, TNFSF11 signaling and liver development.

Conclusion:

The predicted novel miRNAs reported in the paper might have a vital role in regulating the molecular mechanism of HCC and thus, further studies on these miRNAs will provide significant clues for researchers into the complex biological process of liver cancer.

Global Tudor-SN transgenic mice are protected from obesity-induced hepatic steatosis and insulin resistance

In the current study, we explored the impact of Tudor-staphylococcal nuclease (SN) on obesity induced by a high-fat diet (HFD) in mice, because the functional involvement of Tudor-SN in lipid metabolism in vivo is unknown. HFD-transgenic (Tg) mice exhibited reductions in hepatic steatosis and systemic insulin resistance. There was no difference in hepatic lipid accumulation between chow-fed wild-type (WT) and chow-fed Tg mice; consistently, no difference in activation of the lipogenic pathway was detected. Overactivation of hepatic nuclear sterol regulatory element-binding protein (nSrebp2)-2, the central regulator of cholesterol metabolic proteins, was observed in HFD-Tg livers along with improved cholesterol homeostasis, but no such changes were observed in HFD-WT livers. Consistent results were observed in vitro in α-mouse liver 12 cells treated with palmitate mimicking the HFD state. In addition, global gene analysis indicated that various downstream targets of nSrebp2, were up-regulated in HFD-Tg livers. Moreover, HFD-WT mice displayed islet hypertrophy and suppression of glucose-induced insulin secretion from islets, whereas HFD-Tg mice had normal pancreatic islets. This finding suggests that the improved pancreatic metabolism of HFD-Tg mice is related to the systemic effect of insulin resistance, not to the autonomous influence of pancreatic cells. Tudor-SN is likely to be a key regulator for ameliorating HFD-induced hepatic steatosis and systemic insulin resistance in vivo.-Wang, X., Xin, L., Duan, Z., Zuo, Z., Wang, Y., Ren, Y., Zhang, W., Sun, X., Liu, X., Ge, L., Yang, X., Yao, Z., Yang, J. Global Tudor-SN transgenic mice are protected from obesity-induced hepatic steatosis and insulin resistance.

SND1 acts upstream of SLUG to regulate the epithelial-mesenchymal transition (EMT) in SKOV3 cells

Staphylococcal nuclease domain-containing protein 1 (SND1) has been reported as an oncoprotein in a variety of cancers involving multiple processes, including proliferation, angiogenesis, and metastasis. However, the mechanisms underlying metastasis remain largely unknown. Herein, by using the ovarian cancer cell line SKOV3, which has high metastasis ability, we showed that loss-of-function of SND1 dramatically suppressed the invasion and migration of SKOV3 cells. We then performed gene expression profiles and further verified (by use of quantitative PCR and Western blot analysis) that loss-of-function of SND1 resulted in up-regulation of epithelial markers, such as epithelial cadherin and claudin 1, and down-regulation of mesenchymal markers, including neural cadherin and vimentin. Moreover, we illustrated that SLUG, a key transcription factor implicated in epithelial-mesenchymal transition and metastasis, acts as an essential effector of the SND1-promoted epithelial-mesenchymal transition process via regulating N-CAD and VIM expression (or E-CAD and CLDN1). The underlying molecular mechanisms illustrated that SND1 regulates the gene transcriptional activation of SLUG by increasing chromatin accessibility through the recruitment of the acetyltransferases GCN5 and CBP/p300 to the SLUG promoter proximal region. Overall, SND1 was identified as a novel upstream regulator of SLUG, which plays important roles in regulating the E-CAD/N-CAD expression switch.-Xin, L., Zhao, R., Lei, J., Song, J., Yu, L., Gao, R., Ha, C., Ren, Y., Liu, X., Liu, Y., Yao, Z., Yang, J. SND1 acts upstream of SLUG to regulate the epithelial-mesenchymal transition (EMT) in SKOV3 cells.

The multifaceted oncogene SND1 in cancer: focus on hepatocellular carcinoma

Staphylococcal nuclease and tudor domain containing 1 (SND1) is a protein that regulates a complex array of functions. It controls gene expression through transcriptional activation, mRNA degradation, mRNA stabilization, ubiquitination and alternative splicing. More than two decades of research has accumulated evidence of the role of SND1 as an oncogene in various cancers. It is a promoter of cancer hallmarks like proliferation, invasion, migration, angiogenesis and metastasis. In addition to these functions, it has a role in lipid metabolism, inflammation and stress response. The participation of SND1 in such varied functions makes it distinct from most oncogenes that are relatively more focused in their role. This becomes important in the case of hepatocellular carcinoma (HCC) since in addition to typical cancer drivers, factors like lipid metabolism deregulation and chronic inflammation can predispose hepatocytes to HCC. The objective of this review is to provide a summary of the current knowledge available on SND1, specifically in relation to HCC and to shed light on its prospect as a therapeutic target.

SREBP-2-driven transcriptional activation of human SND1 oncogene

Upregulation of Staphylococcal nuclease and tudor domain containing 1 (SND1) is linked to cancer progression and metastatic spread. Increasing evidence indicates that SND1 plays a role in lipid homeostasis. Recently, it has been shown that SND1-overexpressing hepatocellular carcinoma cells present an increased de novo cholesterol synthesis and cholesteryl ester accumulation. Here we reveal that SND1 oncogene is a novel target for SREBPs. Exposure of HepG2 cells to the cholesterol-lowering drug simvastatin or to a lipoprotein-deficient medium triggers SREBP-2 activation and increases SND1 promoter activity and transcript levels. Similar increases in SND1 promoter activity and mRNA are mimicked by overexpressing nuclear SREBP-2 through expression vector transfection. Conversely, SREBP-2 suppression with specific siRNA or the addition of cholesterol/25-hydroxycholesterol to cell culture medium reduces transcriptional activity of SND1 promoter and SND1 mRNA abundance. Chromatin immunoprecipitation assays and site-directed mutagenesis show that SREBP-2 binds to the SND1 proximal promoter in a region containing one SRE and one E-box motif which are critical for maximal transcriptional activity under basal conditions. SREBP-1, in contrast, binds exclusively to the SRE element. Remarkably, while ectopic expression of SREBP-1c or -1a reduces SND1 promoter activity, knocking-down of SREBP-1 enhances SND1 mRNA and protein levels but failed to affect SND1 promoter activity. These findings reveal that SREBP-2 and SREBP-1 bind to specific sites in SND1 promoter and regulate SND1 transcription in opposite ways; it is induced by SREBP-2 activating conditions and repressed by SREBP-1 overexpression. We anticipate the contribution of a SREBPs/SND1 pathway to lipid metabolism reprogramming of human hepatoma cells.

Identification of tissue damage, extracellular matrix remodeling and bacterial challenge as common mechanisms associated with high-risk cutaneous squamous cell carcinomas

In this study we used a genetic extracellular matrix (ECM) disease to identify mechanisms associated with aggressive behavior of cutaneous squamous cell carcinoma (cSCC). cSCC is one of the most common malignancies and usually has a good prognosis. However, some cSCCs recur or metastasize and cause significant morbidity and mortality. Known factors that are associated with aggressiveness of cSCCs include tumor grading, size, localization and microinvasive behavior. To investigate molecular mechanisms that influence biologic behavior we used global proteomic and histologic analyses of formalin-fixed paraffin-embedded tissue of primary human cSCCs. We compared three groups: non-recurring, non-metastasizing low-risk sporadic cSCCs; metastasizing sporadic cSCCs; and cSCCs from patients with recessive dystrophic epidermolysis bullosa (RDEB). RDEB is a genetic skin blistering and ECM disease caused by collagen VII deficiency. Patients commonly suffer from high-risk early onset cSCCs that frequently metastasize. The results indicate that different processes are associated with formation of RDEB cSCCs compared to sporadic cSCCs. Sporadic cSCCs show signs of UV damage, whereas RDEB cSCCs have higher mutational rates and display tissue damage, inflammation and subsequent remodeling of the dermal ECM as tumor initiating factors. Interestingly the two high-risk groups - high-risk metastasizing sporadic cSCCs and RDEB cSCCs - are both associated with tissue damage and ECM remodeling in gene-ontology enrichment and Search Tool for the Retrieval of Interacting Genes/Proteins analyses. In situ histologic analyses validate these results. The high-risk cSCCs also show signatures of enhanced bacterial challenge. Histologic analyses confirm correlation of bacterial colonization with worse prognosis. Collectively, this unbiased study - performed directly on human patient material - reveals that common microenvironmental alterations linked to ECM remodeling and increased bacterial challenges are denominators of high-risk cSCCs. The proteins identified here could serve as potential diagnostic markers and therapeutic targets in high-risk cSCCs.

Oncogenic Role of SND1 in Development and Progression of Hepatocellular Carcinoma

SND1, a subunit of the miRNA regulatory complex RISC, has been implicated as an oncogene in hepatocellular carcinoma (HCC). In this study, we show that hepatocyte-specific SND1 transgenic mice (Alb/SND1 mice) develop spontaneous HCC with partial penetrance and exhibit more highly aggressive HCC induced by chemical carcinogenesis. Livers from Alb/SND1 mice exhibited a relative increase in inflammatory markers and spheroid-generating tumor-initiating cells (TIC). Mechanistic investigations defined roles for Akt and NF-κB signaling pathways in promoting TIC formation in Alb/SND1 mice. In human xenograft models of subcutaneous or orthotopic HCC, administration of the selective SND1 inhibitor 3', 5'-deoxythymidine bisphosphate (pdTp), inhibited tumor formation without effects on body weight or liver function. Our work establishes an oncogenic role for SND1 in promoting TIC formation and highlights pdTp as a highly selective SND1 inhibitor as a candidate therapeutic lead to treat advanced HCC. Cancer Res; 77(12); 3306-16. ©2017 AACR.

Tudor staphylococcal nuclease: biochemistry and functions

Tudor staphylococcal nuclease (TSN, also known as Tudor-SN, SND1 or p100) is an evolutionarily conserved protein with invariant domain composition, represented by tandem repeat of staphylococcal nuclease domains and a tudor domain. Conservation along significant evolutionary distance, from protozoa to plants and animals, suggests important physiological functions for TSN. It is known that TSN is critically involved in virtually all pathways of gene expression, ranging from transcription to RNA silencing. Owing to its high protein-protein binding affinity coexistent with enzymatic activity, TSN can exert its biochemical function by acting as both a scaffolding molecule of large multiprotein complexes and/or as a nuclease. TSN is indispensible for normal development and stress resistance, whereas its increased expression is closely associated with various types of cancer. Thus, TSN is an attractive target for anti-cancer therapy and a potent tumor marker. Considering ever increasing interest to further understand a multitude of TSN-mediated processes and a mechanistic role of TSN in these processes, here we took an attempt to summarize and update the available information about this intriguing multifunctional protein.

Tudor-SN Regulates Milk Synthesis and Proliferation of Bovine Mammary Epithelial Cells

Tudor staphylococcal nuclease (Tudor-SN) is a highly conserved and ubiquitously expressed multifunctional protein, related to multiple and diverse cell type- and species-specific cellular processes. Studies have shown that Tudor-SN is mainly expressed in secretory cells, however knowledge of its role is limited. In our previous work, we found that the protein level of Tudor-SN was upregulated in the nucleus of bovine mammary epithelial cells (BMEC). In this study, we assessed the role of Tudor-SN in milk synthesis and cell proliferation of BMEC. We exploited gene overexpression and silencing methods, and found that Tudor-SN positively regulates milk synthesis and proliferation via Stat5a activation. Both amino acids (methionine) and estrogen triggered NFκB1 to bind to the gene promoters of Tudor-SN and Stat5a, and this enhanced the protein level and nuclear localization of Tudor-SN and p-Stat5a. Taken together, these results suggest the key role of Tudor-SN in the transcriptional regulation of milk synthesis and proliferation of BMEC under the stimulation of amino acids and hormones.