Staphylococcal nuclease domain-containing protein 1 as a potential tissue marker for prostate cancer

Tudor-SN exacerbates pathological vascular remodeling by promoting the polyubiquitination of PTEN via NEDD4-1

BACKGROUND

Dysregulation of vascular homeostasis can induce cardiovascular diseases and increase global mortality rates. Although lineage tracing studies have confirmed the pivotal role of modulated vascular smooth muscle cells (VSMCs) in the progression of pathological vascular remodeling, the underlying mechanisms are still unclear.

METHODS

The expression of Tudor-SN was determined in VSMCs of artery stenosis, PDGF-BB-treated VSMCs and atherosclerotic plaque. Loss- and gain-of-function approaches were used to explore the role of Tudor-SN in the modulation of VSMCs phenotype both in vivo and in vitro.

RESULTS

In this study, we demonstrate that Tudor-SN expression is significantly elevated in injury-induced arteries, atherosclerotic plaques, and PDGF-BB-stimulated VSMCs. Tudor-SN deficiency attenuates, but overexpression aggravates the synthetic phenotypic switching of VSMCs and pathological vascular remodeling. Loss of Tudor-SN also reduces atherosclerotic plaque formation and increases plaque stability. Mechanistically, PTEN, the major regulator of the MAPK and PI3K-AKT signaling pathways, plays a vital role in Tudor-SN-mediated regulation on proliferation and migration of VSMCs. Tudor-SN facilitates the polyubiquitination and degradation of PTEN via NEDD4-1, thus exacerbating vascular remodeling under pathological conditions. BpV (HOpic), a specific inhibitor of PTEN, not only counteracts the protective effect of Tudor-SN deficiency on proliferation and migration of VSMCs, but also abrogates the negative effect of carotid artery injury-induced vascular remodeling in mice.

CONCLUSIONS

Our findings reveal that Tudor-SN deficiency significantly ameliorated pathological vascular remodeling by reducing NEDD4-1-dependent PTEN polyubiquitination, suggesting that Tudor-SN may be a novel target for preventing vascular diseases.

Androgen receptor modulatory miR-1271-5p can promote hormone sensitive prostate cancer cell growth

In most patients with advanced prostate cancer treated with hormonal therapy, androgen independence eventually emerges, leading to death. Androgen receptor signalling remains an important prostate cancer driver, even in the advanced disease stage. MicroRNAs (miRs), non-coding RNAs that regulate gene expression by inhibiting translation and/or promoting degradation of target mRNAs, can act as tumour suppressors or "oncomiRs" and modulate tumour growth. Because of their stability in tissues and in circulation, and their specificity, microRNAs have emerged as potential biomarkers, as well as therapeutic targets in cancer. We identified miR-1271-5p as an androgen receptor modulatory microRNA and we show it can promote hormone sensitive prostate cancer cell growth. Inhibition or overexpression of miR-1271-5p levels affects prostate cancer cell growth, apoptosis and expression of both androgen receptor target genes and other genes that are likely direct targets, dependent on androgen receptor status, and tumour stage. We conclude that miR-1271-5p has the potential to drive progression of hormone-dependent disease and that the use of specific inhibitors of miR-1271-5p may have therapeutic potential in prostate cancer.

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.

SND1 binds to ERG and promotes tumor growth in genetic mouse models of prostate cancer

SND1 and MTDH are known to promote cancer and therapy resistance, but their mechanisms and interactions with other oncogenes remain unclear. Here, we show that oncoprotein ERG interacts with SND1/MTDH complex through SND1's Tudor domain. ERG, an ETS-domain transcription factor, is overexpressed in many prostate cancers. Knocking down SND1 in human prostate epithelial cells, especially those overexpressing ERG, negatively impacts cell proliferation. Transcriptional analysis shows substantial overlap in genes regulated by ERG and SND1. Mechanistically, we show that ERG promotes nuclear localization of SND1/MTDH. Forced nuclear localization of SND1 prominently increases its growth promoting function irrespective of ERG expression. In mice, prostate-specific Snd1 deletion reduces cancer growth and tumor burden in a prostate cancer model (PB-Cre/Ptenflox/flox/ERG mice), Moreover, we find a significant overlap between prostate transcriptional signatures of ERG and SND1. These findings highlight SND1's crucial role in prostate tumorigenesis, suggesting SND1 as a potential therapeutic target in prostate cancer.

Unique Spectrum of Activating BRAF Alterations in Prostate Cancer

PURPOSE

Alterations in BRAF have been reported in 3% to 5% of prostate cancer, although further characterization is lacking. Here, we describe the nature of BRAF alterations in prostate cancer using a large cohort from commercially available tissue and liquid biopsies subjected to comprehensive genomic profiling (CGP).

EXPERIMENTAL DESIGN

Tissue and liquid biopsies from patients with prostate cancer were profiled using FoundationOne CDx and FoundationOne Liquid CDx CGP assays, respectively. Tissue biopsies from non-prostate cancer types were used for comparison (n = 275,151). Genetic ancestry was predicted using a single-nucleotide polymorphism (SNP) based approach.

RESULTS

Among 15,864 tissue biopsies, BRAF-activating alterations were detected in 520 cases (3.3%). The majority (463 samples, 2.9%) harbored class II alterations, including BRAF rearrangements (243 samples, 1.5%), K601E (101 samples, 0.6%), and G469A (58 samples, 0.4%). BRAF-altered prostate cancers were enriched for CDK12 mutations (OR, 1.87; 9.2% vs. 5.2%; P = 0.018), but depleted in TMPRSS2 fusions (OR, 0.25; 11% vs. 32%; P < 0.0001), PTEN alterations (OR, 0.47; 17% vs. 31%; P < 0.0001), and APC alterations (OR, 0.48; 4.4% vs. 8.9%; P = 0.018) relative to BRAF wild-type (WT) disease. Compared with patients of European ancestry, BRAF alterations were more common in tumors from patients of African ancestry (5.1% vs. 2.9%, P < 0.0001) and Asian ancestry (6.0% vs. 2.9%, P < 0.001).

CONCLUSIONS

Activating BRAF alterations were detected in approximately 3% of prostate cancers, and most were class II mutations and rearrangements; BRAF V600 mutations were exceedingly rare. These findings suggest that BRAF activation in prostate cancer is unique from other cancers and supports further clinical investigation of therapeutics targeting the mitogen-activated protein kinase (MAPK) pathway.

Research Progress in Function and Regulation of E3 Ubiquitin Ligase SMURF1

Smad ubiquitylation regulatory factor 1 (Smurf1) is an important homologous member of E6-AP C-terminus type E3 ubiquitin ligase. Initially, Smurf1 was reportedly involved in the negative regulation of the bone morphogenesis protein (BMP) pathway. After further research, several studies have confirmed that Smurf1 is widely involved in various biological processes, such as bone homeostasis regulation, cell migration, apoptosis, and planar cell polarity. At the same time, recent studies have provided a deeper understanding of the regulatory mechanisms of Smurf1's expression, activity, and substrate selectivity. In our review, a brief summary of recent important biological functions and regulatory mechanisms of E3 ubiquitin ligase Smurf1 is proposed.

High intratumoral plasma cells content in primary prostate cancer defines a subset of tumors with potential susceptibility to immune-based treatments

BACKGROUND

Data on advanced prostate cancer (PCa) suggest more prior systemic therapies might reduce tumor immune responsiveness. In treatment-naïve primary PCa, recent work correlated intratumoral plasma cell content with enhanced tumor immune-responsiveness. We sought to identify features of localized PCa at a high risk of recurrence following local treatment with high plasma cell content to help focus future immune-based neoadjuvant trials.

METHODS

We performed retrospective analyses of molecular profiles from three independent cohorts of over 1300 prostate tumors. We used Wilcoxon Rank Sum to compare molecular pathways between tumors with high and low intratumoral plasma cell content and multivariable Cox proportional hazards regression analyses to assess metastasis-free survival.

RESULTS

We validated an expression-based signature for intratumoral plasma cell content in 113 primary prostate tumors with both RNA-expression data and digital image quantification of CD138+ cells (plasma cell marker) based on immunohistochemisty. The signature showed castration-resistant tumors (n = 101) with more prior systemic therapies contained lower plasma cell content. In high-grade primary PCa, tumors with high plasma cell content were associated with increased predicted response to immunotherapy and decreased response to androgen-deprivation therapy. Master regulator analyses identified upregulated transcription factors implicated in immune (e.g. SKAP1, IL-16, and HCLS1), and B-cell activity (e.g. VAV1, SP140, and FLI-1) in plasma cell-high tumors. Master regulators overactivated in tumors with low plasma cell content were associated with shorter metastasis-free survival following radical prostatectomy.

CONCLUSIONS

Markers of plasma cell activity might be leveraged to augment clinical trial targeting and selection and better understand the potential for immune-based treatments in patients with PCa at a high risk of recurrence following local treatment.

N-Glycosylation on Asn50 of SND1 Is Required for Glioma U87 Cell Proliferation and Metastasis

Staphylococcal nuclease domain-containing protein 1 (SND1) is an evolutionarily conserved multidomain protein, which has gained attention recently due to its positive regulation in several cancer progression and metastatic spread. However, the specific contribution of SND1 glycosylation in glioma remains uncertain. In the current study, we confirmed that SND1 was highly expressed in human glioma. Using site-directed mutagenesis, we created four predicted N-glycosylation site mutants for SND1 and provided the first evidence that SND1 undergoes N-glycosylation on its Asn50, Asn168, Asn283, and Asn416 residues in human glioma U87 cells. In addition, we found that removing the N-glycans on the Asn50 site destabilized SND1 and led to its endoplasmic reticulum-associated degradation. Furthermore, destabilized SND1 inhibits the glioma cell proliferation and metastasis. Collectively, our results reveal that N-glycosylation at Asn50 is essential for SND1 folding and trafficking, thus essential for the glioma process, providing new insights for SND1 as a potential disease biomarker for glioma.

MEK inhibitor sensitivity in BRAF fusion-driven prostate cancer

PURPOSE

The identification of subpopulations harboring druggable targets has become a major step forward in the subclassification of solid tumors into small groups suitable for specific therapies. BRAF fusions represent a paradigm of uncommon and targetable oncogenic events and have been widely correlated to the development of specific malignancies. However, they are only present in a limited frequency across most common tumor types. At this regard, we performed a genomic screening aimed to identifying rare variants associated to advanced prostate cancer development.

METHODS

Tumoral tissue genomic screening of 41 patients developing advanced prostate cancer was performed at our center as part of the GETHI XX study. The project, sponsored by the Spanish Collaborative Group in Rare Cancers (GETHI), aims to analyze the molecular background of rare tumors and to discover unfrequent molecular variants in common tumors.

RESULTS

Here we present the clinical outcome and an in-deep molecular analysis performed in a case harboring a SND1-BRAF fusion gene. The identification of such rearrangement in a patient refractory to standard therapies led to the administration of trametinib (MEK inhibitor). Despite unsensitive to standard therapies, the patient achieved a dramatic response to trametinib. A comprehensive study of the tumor demonstrated this event to be a trunk alteration with higher expression of MEK in areas of tumor invasion.

CONCLUSIONS

Our study describes the patient-driven discovery of the first BRAF fusion-driven prostate cancer effectively treated with trametinib. Consequently, MAPK pathway activation could define a new subtype of prostate cancer susceptible to a tailored management.

Inhibition of RNA Binding in SND1 Increases the Levels of miR-1-3p and Sensitizes Cancer Cells to Navitoclax

Simple Summary

Despite of decades of intensive research, several cancer types, for example aggressive colon cancers, are still difficult to treat, and life expectancy is low. Since cancer cells are often resilient and tolerate chemical stresses such as cancer drugs efficiently, they have been difficult to treat. Therefore, combined treatment methods that target cancer cells’ stress tolerance may enhance the treatment outcome. Here we have shown that certain cancer drugs are more effective in colon cancer cells when the expression of a protein called SND1, implicated in regulation of stress responses, is prevented in those cells. We also found that a drug compound called suramin binds to a certain “pocket” of an SND1 protein, and this prevents the interaction of SND1 and certain small RNA molecules, called microRNAs. This block of SND1-microRNA interaction reduces the resilience of colon cancer cells and thus sensitizes them to cancer treatment.

Abstract

SND1 is an RNA-binding protein overexpressed in large variety of cancers. SND1 has been proposed to enhance stress tolerance in cancer cells, but the molecular mechanisms are still poorly understood. We analyzed the expression of 372 miRNAs in the colon carcinoma cell line and show that SND1 silencing increases the expression levels of several tumor suppressor miRNAs. Furthermore, SND1 knockdown showed synergetic effects with cancer drugs through MEK-ERK and Bcl-2 family-related apoptotic pathways. To explore whether the SND1-mediated RNA binding/degradation is responsible for the observed effect, we developed a screening assay to identify small molecules that inhibit the RNA-binding function of SND1. The screen identified P2X purinoreceptor antagonists as the most potent inhibitors. Validation confirmed that the best hit, suramin, inhibits the RNA binding ability of SND1. The binding characteristics and mode of suramin to SND1 were characterized biophysically and by molecular docking that identified positively charged binding cavities in Staphylococcus nuclease domains. Importantly, suramin-mediated inhibition of RNA binding increased the expression of miR-1-3p, and enhanced sensitivity of cancer cells to Bcl-2 inhibitor navitoclax treatment. Taken together, we demonstrate as proof-of-concept a mechanism and an inhibitor compound for SND1 regulation of the survival of cancer cells through tumor suppressor miRNAs.

The Emerging Roles of circSMARCA5 in Cancer

Circular RNAs have a unique covalent closed-loop structure, which is mainly formed by the reverse splicing of exons from a precursor mRNA. With the development of key technologies such as high-throughput sequencing and the advancement of bioinformatics in recent years, our understanding of circular RNAs has become increasingly more detailed, and their abnormal expression in a variety of cancers has attracted increasing attention. Studies have shown that circSNARCA5 not only plays a crucial role in the occurrence and development of cancer but may also serve as a reliable indicator for tumor screening or a good marker for evaluating cancer prognosis. Nevertheless, there are no reviews focusing on the relationship between circSMARCA5 and cancer. Therefore, we will first explain the main biological characteristics of circSMARCA5, such as biogenesis and biological effects. Then, the focus will be on its role and significance in cancer. Finally, we will summarize the known information on circSMARCA5 in cancer and discuss future research prospects.

Nucleases as molecular targets for cancer diagnosis

Early cancer diagnosis is a crucial element to improved treatment options and survival. Great research efforts have been made in the search for better performing cancer diagnostic biomarkers. However, the quest continues as novel biomarkers with high accuracy for an early diagnosis remain an unmet clinical need. Nucleases, which are enzymes capable of cleaving nucleic acids, have been long considered as potential cancer biomarkers. The implications of nucleases are key for biological functions, their presence in different cellular counterparts and catalytic activity led the enthusiasm towards investigating the role of nucleases as promising cancer biomarkers. However, the most essential feature of these proteins, which is their enzymatic activity, has not been fully exploited. This review discusses nucleases interrogated as cancer biomarkers, providing a glimpse of their physiological roles. Moreover, it highlights the potential of harnessing the enzymatic activity of cancer-associated nucleases as a novel diagnostic biomarker using nucleic acid probes as substrates.

Discovery of Klf2 interactors in mouse embryonic stem cells by immunoprecipitation-mass spectrometry utilizing exogenously expressed bait

Krüppel-like factor 2 (Klf2) is a DNA-binding transcription factor that regulates embryonic stem cell-specific gene expression. Transcription cofactors such as p300 acetyltransferase and Erk kinases interact with Klf2, providing an additional layer of transcription regulation in embryonic stem cells. To carry out a thorough survey of the Klf2 interactome in embryonic stem cells and identify novel transcription cofactors, we designed a modified immunoprecipitation-mass spectrometry (IP-MS) method. In this method, recombinant Klf2, expressed and purified from Sf9 insect cells instead of ectopically expressed in cells, was used as bait. Using this modified IP-MS method, we discovered nine Klf2-interacting proteins, including the previously reported Crebbp and p300. These proteins showed at least an 8-fold increase in signal intensity in Klf2 pull-downs compared with controls, with P-values <0.010. Among the identified Klf2-binding proteins confirmed using our IP-MS workflow was Snd1, which we found to interact directly with Klf2 and function as a transcriptional coactivator of Klf2 to drive the Oct4 gene expression. Collectively, our IP-MS protocol may offer a useful tool for identifying novel transcription cofactors in stem cells.

miRNA-296-5p functions as a potential tumor suppressor in human osteosarcoma by targeting SND1

Background:

The pathogenesis of osteosarcoma (OS) is still unclear, and it is still necessary to find new targets and drugs for anti-OS. This study aimed to investigate the role and mechanism of the anti-OS effects of miR-296-5p.

Methods:

We measured the expression of miR-296-5p in human OS cell lines and tissues. The effect of miR-296-5p and its target gene staphylococcal nuclease and tudor domain containing 1 on proliferation, migration, and invasion of human OS lines was examined. The Student's t test was used for statistical analysis.

Results:

We found that microRNA (miR)-296-5p was significantly downregulated in OS cell lines and tissues (control vs. OS, 1.802 ± 0.313 vs. 0.618 ± 0.235, t = 6.402, P < 0.01). Overexpression of miR-296-5p suppressed proliferation, migration, and invasion of OA cells. SND1 was identified as a target of miR-296-5p by bioinformatic analysis and dual-luciferase reporter assay. Overexpression of SND1 abrogated the effects induced by miR-296-5p upregulation (miRNA-296-5p vs. miRNA-296-5p + SND1, 0.294 ± 0.159 vs. 2.300 ± 0.277, t = 12.68, P = 0.003).

Conclusion:

Our study indicates that miR-296-5p may function as a tumor suppressor by targeting SND1 in OS.

Discovery and Proof-of-Concept Study of Nuclease Activity as a Novel Biomarker for Breast Cancer Tumors

Simple Summary

A diagnostic biomarker for the detection of breast cancer remains an unmet clinical need despite decades of intensive research efforts. Herein, we describe, for the first time, the use of nuclease activity as a biomarker to discriminate between healthy and cancer biopsy samples. We have identified a panel of three nucleic acid probes able to target nucleases derived from breast cancer tumors with high sensitivity and specificity. These results are in good agreement with histopathological analysis as the diagnostic gold standard. Moreover, these findings support nuclease activity as a potential adjacent diagnostic tool and shed light on the use of nuclease activity as a detection biomarker in breast cancer.

Abstract

Breast cancer is one of the most common pathologies diagnosed in the clinical practice. Despite major advancements in diagnostic approaches, there is no widely accepted biomarker in the clinical practice that can diagnose breast malignancy. Confirmatory diagnosis still relies on the pathological assessment of tissue biopsies by expert pathologists. Thus, there is an unmet need for new types of biomarkers and novel platform technologies that can be easily and robustly integrated into the clinic and that can assist pathologists. Herein, we show that nuclease activity associated to malignant tumors can be used as a novel biomarker in breast cancer, which can be detected via specific degradation of nucleic acid probes. In this study we have identified a set of three chemically modified nucleic acid probes that can diagnose malignancy in biopsy samples with high accuracy (89%), sensitivity (82%) and specificity (94%). This work represents a breakthrough for the potential clinical use of nuclease activity as biomarker, which can be detected via nucleic acids probes, for the clinical diagnosis of malignancy in breast tissue biopsies. This platform technology could be readily implemented into the clinic as adjunct to histopathological diagnostic.

Circ SMARCA5 Inhibited Tumor Metastasis by Interacting with SND1 and Downregulating the YWHAB Gene in Cervical Cancer

Cervical cancer is one of the diseases that seriously endanger women's health. Circular RNA plays an important role in regulating the occurrence and development of cervical cancer. Here, we investigated the mechanisms of circ SMARCA5 in the development of cervical cancer. Quantitative reverse transcriptase polymerase chain reaction (RT-qPCR) results showed that the expression of SMARCA5 was downregulated in cervical cancer tissues and cell lines. Then we found that overexpression of SMARCA5 inhibited proliferation and invasion, but promoted apoptosis in cervical cancer cells. These were detected by Cell Counting Kit-8, Transwell, and Annexin V-fluorescein isothiocyanate/propidium iodide detection kit, respectively, and the expression of the apoptosis-related proteins was determined by western blotting. Then we predicted that SMARCA5 combined with Staphylococcal nuclease domain-containing 1 (SND1) by starBase, and verified by RNA pull-down assay. To further reveal the molecular mechanisms of SMARCA5 in the progression of cervical cancer, the interaction protein of SND1 was predicted by STRING, and the interaction was verified by co-immunoprecipitation assay. Then, the effects of SND1 or YWHAB on the development of cervical cancer were detected by the gain and loss function test, and we found that knockdown of SND1 or YWHAB reversed the effects of SMARCA5 short interfering RNA on proliferation, invasion, and apoptosis of cervical cancer cells. Overexpression of SMARCA5 inhibited cervical cancer metastasis in vivo. Our results showed that overexpression of circ SMARCA5 inhibits the binding of SND1 to YWHAB, and inhibits the proliferation and invasion, but promotes apoptosis in cervical cancer cells, thus inhibiting the metastasis of cervical cancer.

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.

SND1 facilitates the invasion and migration of cervical cancer cells by Smurf1-mediated degradation of FOXA2

Staphylococcal nuclease domain-containing protein 1 (SND1) is known to be involved in the progression of a variety of human cancers. However, the role of SND1 in cervical cancer remains unclear. Here, we found that the expression of SND1 in cervical cancer tissue was higher than that in normal cervical tissue. Importantly, high SND1 expression was closely associated with tumorigenic phenotype and shorter survival among cervical cancer patients. Functional assays demonstrated that SND1 knockdown inhibited the migration and invasion capabilities of cervical cancer cells in vitro. Additionally, a xenograft assay showed that silencing SND1 in cervical cancer cells suppressed lung metastasis in vivo. Further investigation revealed that knockdown of SND1 inhibited epithelial-to-mesenchymal transition (EMT) of cervical cancer cells by enhancing FOXA2 expression. Moreover, the pro-metastasis effect of SND1 in cervical cancer was at least in part dependent on FOXA2 inhibition. Mechanistically, we found that SND1-induced FOXA2 ubiquitination resulted in degradation, mediated by the E3 ligase enzyme Smurf1. In summary, SND1 plays a crucial role in cervical cancer metastasis, and we provide evidence that SND1 may serve as a prognostic and therapeutic target in cervical cancer.

Posttranscriptional Inhibition of Protein Tyrosine Phosphatase Nonreceptor Type 23 by Staphylococcal Nuclease and Tudor Domain Containing 1: Implications for Hepatocellular Carcinoma

Oncoprotein staphylococcal nuclease and tudor domain containing 1 (SND1) regulates gene expression at a posttranscriptional level in multiple cancers, including hepatocellular carcinoma (HCC). Staphylococcal nuclease (SN) domains of SND1 function as a ribonuclease (RNase), and the tudor domain facilitates protein–oligonucleotide interaction. In the present study, we aimed to identify RNA interactome of SND1 to obtain enhanced insights into gene regulation by SND1. RNA interactome was identified by immunoprecipitation (IP) of RNA using anti‐SND1 antibody from human HCC cells followed by RNA immunoprecipitation sequencing (RIP‐Seq). Among RNA species that showed more than 10‐fold enrichment over the control, we focused on the tumor suppressor protein tyrosine phosphatase nonreceptor type 23 (PTPN23) because its regulation by SND1 and its role in HCC are not known. PTPN23 levels were down‐regulated in human HCC cells versus normal hepatocytes and in human HCC tissues versus normal adjacent liver, as revealed by immunohistochemistry. In human HCC cells, knocking down SND1 increased and overexpression of SND1 decreased PTPN23 protein. RNA binding and degradation assays revealed that SND1 binds to and degrades the 3′‐untranslated region (UTR) of PTPN23 messenger RNA (mRNA). Tetracycline‐inducible PTPN23 overexpression in human HCC cells resulted in significant inhibition in proliferation, migration, and invasion and in vivo tumorigenesis. PTPN23 induction caused inhibition in activation of tyrosine‐protein kinase Met (c‐Met), epidermal growth factor receptor (EGFR), Src, and focal adhesion kinase (FAK), suggesting that, as a putative phosphatase, PTPN23 inhibits activation of these oncogenic kinases. Conclusion: PTPN23 is a novel target of SND1, and our findings identify PTPN23 as a unique tumor suppressor for HCC. PTPN23 might function as a homeostatic regulator of multiple kinases, restraining their activation.

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.

Channeling of newly synthesized fatty acids to cholesterol esterification limits triglyceride synthesis in SND1-overexpressing hepatoma cells

SND1 is a putative oncoprotein whose molecular function remains unclear. Its overexpression in hepatocellular carcinoma impairs cholesterol homeostasis due to the altered activation of the sterol regulatory element-binding protein (SREBP) 2, which results in the accumulation of cellular cholesteryl esters (CE). In this work, we explored whether high cholesterol synthesis and esterification originates changes in glycerolipid metabolism that might affect cell growth, given that acetyl-coenzyme A is required for cholesterogenesis and fatty acids (FA) are the substrates of acyl-coenzyme A:cholesterol acyltransferase (ACAT). SND1-overexpressing hepatoma cells show low triglyceride (TG) synthesis, but phospholipid biosynthesis or cell growth is not affected. Limited TG synthesis is not due to low acetyl-coenzyme A or NADPH availability. We demonstrate that the main factor limiting TG synthesis is the utilization of FAs for cholesterol esterification. These metabolic adaptations are linked to high Scd1 expression, needed for the de novo production of oleic acid, the main FA used by ACAT. We conclude that high cholesterogenesis due to SND1 overexpression might determine the channeling of FAs to CEs.

Promise and Implementation of Proteomic Prostate Cancer Biomarkers

Prostate cancer is one of the most commonly diagnosed malignancy and the fifth leading cause of cancer mortality in men. Despite the broad use of prostate-specific antigen test that resulted in an increase in number of diagnosed cases, disease management needs to be improved. Proteomic biomarkers alone and or in combination with clinical and pathological risk calculators are expected to improve on decreasing the unnecessary biopsies, stratify low risk patients, and predict response to treatment. To this end, significant efforts have been undertaken to identify novel biomarkers that can accurately discriminate between indolent and aggressive cancer forms and indicate those men at high risk for developing prostate cancer that require immediate treatment. In the era of “big data” and “personalized medicine” proteomics-based biomarkers hold great promise to provide clinically applicable tools, as proteins regulate all biological functions, and integrate genomic information with the environmental impact. In this review article, we aim to provide a critical assessment of the current proteomics-based biomarkers for prostate cancer and their actual clinical applicability. For that purpose, a systematic review of the literature published within the last 10 years was performed using the Web of Science Database. We specifically discuss the potential and prospects of use for diagnostic, prognostic and predictive proteomics-based biomarkers, including both body fluid- and tissue-based markers.

miR-361-5p inhibits glioma migration and invasion by targeting SND1

Background

Downregulation of miR-361-5p contributes to epithelial–mesenchymal transition of glioma cells. However, the relevance of miR-361-5p to migration and invasion of gliomas remains unknown.

Materials and methods

The relationship between miR-361-5p and SND1 expression was analyzed in 120 human gliomas and 8 glioma cell lines by in situ hybridization, immunohistochemistry, and Western blot. Dual-luciferase reporter assay was used to identify SND1 as a target of miR-361-5p. The mechanisms through which miR-361-5p inhibits glioma cell migration and invasion were studied by in vitro assays.

Results

miR-361-5p expression was significantly downregulated in glioma tissues and glioma cell lines, and was inversely correlated with glioma grades. However, SND1 expression was positively correlated with glioma grades and inversely correlated with miR-361-5p expression. miR-361-5p overexpression suppressed glioma cell migration and invasion through targeting SND1 and subsequently decreasing MMP-2 expression. In glioma cell lines, SND1 overexpression could partly reverse the antitumor effects of miR-361-5p.

Conclusion

The findings provide evidence that miR-361-5p directly targets SND1 to degradation and then reduces MMP-2 gene transcription, thus inhibiting glioma migration and invasion. miR-361-5p is an important tumor suppressor and a novel diagnostic biomarker of glioma, and miR-361-5p and SND1 are potential therapeutic candidates for malignant gliomas.

Tudor staphylococcal nuclease is a structure-specific ribonuclease that degrades RNA at unstructured regions during microRNA decay

Tudor staphylococcal nuclease (TSN) is an evolutionarily conserved ribonuclease in eukaryotes that is composed of five staphylococcal nuclease-like domains (SN1-SN5) and a Tudor domain. TSN degrades hyper-edited double-stranded RNA, including primary miRNA precursors containing multiple I•U and U•I pairs, and mature miRNA during miRNA decay. However, how TSN binds and degrades its RNA substrates remains unclear. Here, we show that the C. elegans TSN (cTSN) is a monomeric Ca²⁺-dependent ribonuclease, cleaving RNA chains at the 5'-side of the phosphodiester linkage to produce degraded fragments with 5'-hydroxyl and 3'-phosphate ends. cTSN degrades single-stranded RNA and double-stranded RNA containing mismatched base pairs, but is not restricted to those containing multiple I•U and U•I pairs. cTSN has at least two catalytic active sites located in the SN1 and SN3 domains, since mutations of the putative Ca²⁺-binding residues in these two domains strongly impaired its ribonuclease activity. We further show by small-angle X-ray scattering that rice osTSN has a flexible two-lobed structure with open to closed conformations, indicating that TSN may change its conformation upon RNA binding. We conclude that TSN is a structure-specific ribonuclease targeting not only single-stranded RNA, but also unstructured regions of double-stranded RNA. This study provides the molecular basis for how TSN cooperates with RNA editing to eliminate duplex RNA in cell defense, and how TSN selects and degrades RNA during microRNA decay.

MAPK activation and HRAS mutation identified in pituitary spindle cell oncocytoma

Pituitary spindle cell oncocytoma (SCO) is an uncommon primary pituitary neoplasm that presents with mass effect on adjacent neurovascular structures, similar to non-hormone-producing pituitary adenomas. To determine the molecular etiology of SCO, we performed exome sequencing on four SCO cases, with matched normal controls, to assess somatic mutations and copy number alterations. Our analysis revealed a low mutation rate and a copy-neutral profile, consistent with the low-grade nature of this tumor. However, we identified a co-occurring somatic HRAS (p.Q61R) activating point mutation and MEN1 frameshift mutation (p.L117fs) present in a primary and recurrent tumor from one patient. Other SCOs demonstrated mutations in SND1 and FAT1, which are associated with MAPK pathway activation. Immunohistochemistry across the SCO cohort demonstrated robust MAPK activity in all cases (n=4), as evidenced by strong phospho-ERK staining, while phospho-AKT levels suggested only basal levels of PI3K pathway activation. Taken together, this identifies the MAPK signaling pathway as a novel therapeutic target for spindle cell oncocytoma, which may offer a powerful adjunct for aggressive tumors refractory to surgical resection.

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.

Tudor-SN protein expression in colorectal cancer and its association with clinical characteristics

Objectives

Tudor-SN protein (SND1) is known to be up-regulated in some types of human malignancies and functions as an oncogene. The objective of our study was to investigate the expression and prognostic value of SND1 in human colorectal cancer (CRC).

Methods

Real-time PCR and western blot were performed to examine the SND1 expression in human CRC and their corresponding non-cancerous colon tissues from 42 patients. Its clinical significance was evaluated by analyzing its expression with multiple pathological characters of CRC patients. Finally, a Kaplan-Meier survival curve was derived for SND1 gene expression among these CRC patients.

Results

We found a significantly increased expression of SND1 mRNA and protein in tissue samples of CRC when compared to those in the paired normal adjacent colon tissues. High SND1 expression was positively correlated with higher tumor grades, aggressive N1+N2 nodal status and poor differentiation. Additionally, the overall survival rate in CRC patients with higher expression of SND1 was significantly shorter than that with lower SND1 expression.

Conclusion

Our findings suggested that SND1 might act as an important agent in the CRC carcinogenesis and predicted worse outcomes. The high expression of SND1 could be used as a novel predictive and prognostic marker of CRC.

miR-320a functions as a suppressor for gliomas by targeting SND1 and β-catenin, and predicts the prognosis of patients

miR-320a downexpression contributes to tumorigenesis in several human cancers. However, the relevance of miR-320a to prognosis, proliferation and invasion in gliomas remains unclear. In this study, we demonstrated that miR-320a expression was decreased in human glioma tissues and cell lines. Moreover, miR-320a expression was inversely correlated with glioma grades and Ki-67 index, but positively correlated with patients’ survival. Contrarily, SND1 and β-catenin expressions were positively correlated with glioma grades and Ki-67 index, but inversely correlated with miR-320a expression and patients’ survival. Furthermore, two subgroups with distinct prognoses in our glioma patients of different grade, IDH status, age and KPS were identified according to expression of miR-320a, SND1 or β-catenin. Cox regression showed that miR-320a and SND1 were independent predictors and β-catenin was an auxiliary predictor for patients’ survival. miR-320a overexpression suppressed the G1/S phase transition, proliferation, migration and invasion of glioblastoma cells. Mechanistically, we validated SND1 and β-catenin as direct targets of miR-320a, and found that miR-320a overexpression increased SND1-inhibited tumor suppressor p21^WAF1 and decreased Smad2, Smad4, MMP2, MMP7 and cyclinD1, the pivotal downstream effectors of SND1 or β-catenin. Our findings demonstrate the potential values of miR-320a, SND1 and β-catenin as prognostic biomarkers and therapeutic candidates for malignant gliomas.

The long noncoding RNA SPRIGHTLY acts as an intranuclear organizing hub for pre-mRNA molecules

Molecular mechanisms by which long noncoding RNA (lncRNA) molecules may influence cancerous condition are poorly understood. The aberrant expression of SPRIGHTLY lncRNA, encoded within the drosophila gene homolog Sprouty-4 intron, is correlated with a variety of cancers, including human melanomas. We demonstrate by SHAPE-seq and dChIRP that SPRIGHTLY RNA secondary structure has a core pseudoknotted domain. This lncRNA interacts with the intronic regions of six pre-mRNAs: SOX5, SMYD3, SND1, MEOX2, DCTN6, and RASAL2, all of which have cancer-related functions. Hemizygous knockout of SPRIGHTLY by CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 in melanoma cells significantly decreases SPRIGHTLY lncRNA levels, simultaneously decreases the levels of its interacting pre-mRNA molecules, and decreases anchorage-independent growth rate of cells and the rate of in vivo tumor growth in mouse xenografts. These results provide the first demonstration of an lncRNA's three-dimensional coordinating role in facilitating cancer-related gene expression in human melanomas.

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.

[EXPRESSION OF PLAKIN FAMILY IN UROTHELIAL CARCINOMA OF THE UPPER URINARY TRACT]

(Objective) To determine whether the plakin family proteins periplakin, desmoplakin, plectin, and envoplakin could be markers of urothelial carcinoma of the upper urinary tract. (Materials and methods) Fifty-seven surgical specimens were obtained from patients with urothelial carcinoma of the upper urinary tract, who were admitted to the Jikei University Hospital between April 2000 and December 2005. The expression of plakin family proteins in cancerous and normal tissues was investigated using immunohistochemistry, and its association with clinicopathological parameters was analyzed. (Results) The expression of periplakin, envoplakin, and desmoplakin was significantly lower in cancerous tissue than in normal urothelium (P < 0.0001, P < 0.0001, and P < 0.0001, respectively). Strong desmoplakin expression in cancerous tissue was significantly associated with poor cancer-specific survival and overall survival (P = 0.023 and P = 0.034, respectively, compared with cancerous tissue with slight or less desmoplakin expression). Furthermore, strong plectin expression was significantly associated with poor metastasis-free survival (P = 0.034, compared with cancerous tissue with slight or less plectin expression). (Conclusion) Plakin family, particularly desmoplakin was suggested to be a prognostic marker of urothelial carcinoma of the upper urinary tract.

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 staphylococcal nuclease drives chemoresistance of non-small cell lung carcinoma cells by regulating S100A11

Lung cancer is the leading cause of cancer-related deaths worldwide. Non-small cell lung cancer (NSCLC), the major lung cancer subtype, is characterized by high resistance to chemotherapy. Here we demonstrate that Tudor staphylococcal nuclease (SND1 or TSN) is overexpressed in NSCLC cell lines and tissues, and is important for maintaining NSCLC chemoresistance. Downregulation of TSN by RNAi in NSCLC cells led to strong potentiation of cell death in response to cisplatin. Silencing of TSN was accompanied by a significant decrease in S100A11 expression at both mRNA and protein level. Downregulation of S100A11 by RNAi resulted in enhanced sensitivity of NSCLC cells to cisplatin, oxaliplatin and 5-fluouracil. AACOCF₃, a phospholipase A₂ (PLA₂) inhibitor, strongly abrogated chemosensitization upon silencing of S100A11 suggesting that PLA₂ inhibition by S100A11 governs the chemoresistance of NSCLC. Moreover, silencing of S100A11 stimulated mitochondrial superoxide production, which was decreased by AACOCF₃, as well as N-acetyl-L-cysteine, which also mimicked the effect of PLA₂ inhibitor on NSCLC chemosensitization upon S100A11 silencing. Thus, we present the novel TSN-S100A11-PLA₂ axis regulating superoxide-dependent apoptosis, triggered by platinum-based chemotherapeutic agents in NSCLC that may be targeted by innovative cancer therapies.

Staphylococcal Nuclease and Tudor Domain Containing 1 (SND1 Protein) Promotes Hepatocarcinogenesis by Inhibiting Monoglyceride Lipase (MGLL)

Staphylococcal nuclease and tudor domain containing 1 (SND1) is overexpressed in multiple cancers, including hepatocellular carcinoma (HCC), and functions as an oncogene. This study was carried out to identify novel SND1-interacting proteins to better understand its molecular mechanism of action. SND1-interacting proteins were identified by a modified yeast two-hybrid assay. Protein-protein interaction was confirmed by co-immunoprecipitation analysis. Monoglyceride lipase (MGLL) expression was analyzed by quantitative RT-PCR, Western blot, and immunohistochemistry. MGLL-overexpressing clones were analyzed for cell proliferation and cell cycle analysis and in vivo tumorigenesis in nude mice. MGLL was identified as an SND1-interacting protein. Interaction of SND1 with MGLL resulted in ubiquitination and proteosomal degradation of MGLL. MGLL expression was detected in normal human hepatocytes and mouse liver, although it was undetected in human HCC cell lines. An inverse correlation between SND1 and MGLL levels was identified in a human HCC tissue microarray as well as in the TCGA database. Forced overexpression of MGLL in human HCC cells resulted in marked inhibition in cell proliferation with a significant delay in cell cycle progression and a marked decrease in tumor growth in nude mouse xenograft assays. MGLL overexpression inhibited Akt activation that is independent of enzymatic activity of MGLL and overexpression of a constitutively active Akt rescued cells from inhibition of proliferation and restored normal cell cycle progression. This study unravels a novel mechanism of SND1 function and identifies MGLL as a unique tumor suppressor for HCC. MGLL might function as a homeostatic regulator of Akt restraining its activation.

Tudor-SN Interacts with Piwi Antagonistically in Regulating Spermatogenesis but Synergistically in Silencing Transposons in Drosophila

Piwi proteins associate with piRNAs and functions in epigenetic programming, post-transcriptional regulation, transposon silencing, and germline development. However, it is not known whether the diverse functions of these proteins are molecularly separable. Here we report that Piwi interacts with Tudor-SN (Tudor staphylococcal nuclease, TSN) antagonistically in regulating spermatogenesis but synergistically in silencing transposons. However, it is not required for piRNA biogenesis. TSN is known to participate in diverse molecular functions such as RNAi, degradation of hyper-edited miRNAs, and spliceosome assembly. We show that TSN colocalizes with Piwi in primordial germ cells (PGCs) and embryonic somatic cells. In adult ovaries and testes, TSN is ubiquitously expressed and enriched in the cytoplasm of both germline and somatic cells. The tsn mutants display a higher mitotic index of spermatogonia, accumulation of spermatocytes, defects in meiotic cytokinesis, a decreased number of spermatids, and eventually reduced male fertility. Germline-specific TSN-expression analysis demonstrates that this function is germline-dependent. Different from other known Piwi interters, TSN represses Piwi expression at both protein and mRNA levels. Furthermore, reducing piwi expression in the germline rescues tsn mutant phenotype in a dosage-dependent manner, demonstrating that Piwi and TSN interact antagonistically in germ cells to regulate spermatogenesis. However, the tsn deficiency has little, if any, impact on piRNA biogenesis but displays a synergistic effect with piwi mutants in transposon de-silencing. Our results reveal the biological function of TSN and its contrasting modes of interaction with Piwi in spermatogenesis, transposon silencing, and piRNA biogenesis.

Piwi proteins bind to a large class of small noncoding RNAs called Piwi-interacting RNAs (piRNAs). These proteins have emerged as major players in germline development, stem cell self-renewal, transposon silencing, and gene regulation. However, it is not known whether these functions of Piwi proteins represent separate molecular mechanisms. Furthermore, although multiple Piwi interactors have been identified, including Tudor-domain-containing proteins, none of them regulates Piwi expression or interacts with Piwi antagonistically, or only impact on a subset of Piwi functions. Here we show that Drosophila Piwi interacts with a special Tudor-domain-containing protein called Tudor-SN (Tudor staphylococcal nuclease, TSN). TSN is drastically different from the known Piwi interactors because it represses Piwi mRNA and protein expression and interacts with Piwi antagonistically in spermatogenesis but synergistically in transposon silencing. However, this interaction is not required for piRNA biogenesis. Our study represents the first demonstration that different functions of Piwi are mediated by different molecular mechanisms. In addition, this is the first in vivo study that reveals the biological function of TSN protein in an organism.

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

The NF-κB-inducible Staphylococcal nuclease and tudor domain-containing 1 gene (SND1) encodes a coactivator involved in inflammatory responses and tumorigenesis. While SND1 is known to interact with certain transcription factors and activate client gene expression, no comprehensive mapping of SND1 target genes has been reported. Here, we have approached this question by performing ChIP-chip assays on human hepatoma HepG2 cells and analyzing SND1 binding modulation by proinflammatory TNFα. We show that SND1 binds 645 gene promoters in control cells and 281 additional genes in TNFα-treated cells. Transcription factor binding site analysis of bound probes identified motifs for established partners and for novel transcription factors including HSF, ATF, STAT3, MEIS1/AHOXA9, E2F and p300/CREB. Major target genes were involved in gene expression and RNA metabolism regulation, as well as development and cellular metabolism. We confirmed SND1 binding to 21 previously unrecognized genes, including a set of glycerolipid genes. Knocking-down experiments revealed that SND1 deficiency compromises the glycerolipid gene reprogramming and lipid phenotypic responses to TNFα. Overall, our findings uncover an unexpected large set of potential SND1 target genes and partners and reveal SND1 to be a determinant downstream effector of TNFα that contributes to support glycerophospholipid homeostasis in human hepatocellular carcinoma during inflammation.

Common Oncogene Mutations and Novel SND1-BRAF Transcript Fusion in Lung Adenocarcinoma from Never Smokers

Lung adenocarcinomas from never smokers account for approximately 15 to 20% of all lung cancers and these tumors often carry genetic alterations that are responsive to targeted therapy. Here we examined mutation status in 10 oncogenes among 89 lung adenocarcinomas from never smokers. We also screened for oncogene fusion transcripts in 20 of the 89 tumors by RNA-Seq. In total, 62 tumors had mutations in at least one of the 10 oncogenes, including EGFR (49 cases, 55%), K-ras (5 cases, 6%), BRAF (4 cases, 5%), PIK3CA (3 cases, 3%), and ERBB2 (4 cases, 5%). In addition to ALK fusions identified by IHC/FISH in four cases, two previously known fusions involving EZR- ROS1 and KIF5B-RET were identified by RNA-Seq as well as a third novel fusion transcript that was formed between exons 1–9 of SND1 and exons 2 to 3′ end of BRAF. This in-frame fusion was observed in 3/89 tested tumors and 2/64 additional never smoker lung adenocarcinoma samples. Ectopic expression of SND1-BRAF in H1299 cells increased phosphorylation levels of MEK/ERK, cell proliferation, and spheroid formation compared to parental mock-transfected control. Jointly, our results suggest a potential role of the novel BRAF fusion in lung cancer development and therapy.

Circadian disruption-induced microRNAome deregulation in rat mammary gland tissues

Breast cancer is the most common malignancy affecting women worldwide, and evidence is mounting that circadian-disruption-induced breast cancer is a warranted concern. Although studies on the role of epigenetics have provided valuable insights, and although epigenetics has been increasingly recognized in the etiology of breast cancer, relatively few studies have investigated the epigenetic link between circadian disruption (CD) and breast cancer. Using a proven photoperiod-shifting paradigm, differing degrees of CD, various tissue-extraction time points, and Illumina sequencing, we investigated the effect of CD on miRNA expression in the mammary tissues of a rodent model system. To our knowledge, our results are the first to illustrate CD-induced changes in miRNA expressions in mammary tissues. Furthermore, it is likely that these miRNA expression changes exhibit varying time frames of plasticity linked to both the degree of CD and length of reentrainment, and that the expression changes are influenced by the light and dark phases of the 24-hour circadian cycle. Of the differentially expressed miRNAs identified in the present study, all but one have been linked to breast cancer, and many have predicted circadian-relevant targets that play a role in breast cancer development. Based on the analysis of protein levels in the same tissues, we also propose that the initiation and development of CD-induced breast cancer may be linked to an interconnected web of increased NF-κB activity and increased levels of Tudor-SN, STAT3, and BCL6, with aberrant CD-induced downregulation of miR-127 and miR-146b potentially contributing to this dynamic. This study provides direct evidence that CD induces changes in miRNA levels in mammary tissues with potentially malignant consequences, thus indicating that the role of miRNAs in CD-induced breast cancer should not be dismissed.

The promoter of cell growth- and RNA protection-associated SND1 gene is activated by endoplasmic reticulum stress in human hepatoma cells

Background

Staphyloccocal nuclease domain-containing protein 1 (SND1) is involved in the regulation of gene expression and RNA protection. While numerous studies have established that SND1 protein expression is modulated by cellular stresses associated with tumor growth, hypoxia, inflammation, heat-shock and oxidative conditions, little is known about the factors responsible for SND1 expression. Here, we have approached this question by analyzing the transcriptional response of human SND1 gene to pharmacological endoplasmic reticulum (ER) stress in liver cancer cells.

Results

We provide first evidence that SND1 promoter activity is increased in human liver cancer cells upon exposure to thapsigargin or tunicamycin or by ectopic expression of ATF6, a crucial transcription factor in the unfolded protein response triggered by ER stress. Deletion analysis of the 5’-flanking region of SND1 promoter identified maximal activation in fragment (-934, +221), which contains most of the predicted ER stress response elements in proximal promoter. Quantitative real-time PCR revealed a near 3 fold increase in SND1 mRNA expression by either of the stress-inducers; whereas SND1 protein was maximally upregulated (3.4-fold) in cells exposed to tunicamycin, a protein glycosylation inhibitor.

Conclusion

Promoter activity of the cell growth- and RNA-protection associated SND1 gene is up-regulated by ER stress in human hepatoma cells.

Role of the staphylococcal nuclease and tudor domain containing 1 in oncogenesis (review)

The staphylococcal nuclease and tudor domain containing 1 (SND1) is a multifunctional protein overexpressed in breast, prostate, colorectal and hepatocellular carcinomas and malignant glioma. Molecular studies have revealed the multifaceted activities of SND1 involved in regulating gene expression at transcriptional as well as post-transcriptional levels. Early studies identified SND1 as a transcriptional co-activator. SND1 is also a component of RNA-induced silencing complex (RISC) thus mediating RNAi function, a regulator of mRNA splicing, editing and stability, and plays a role in maintenance of cell viability. Such diverse actions allow the SND1 to modulate a complex array of molecular networks, thereby promoting carcinogenesis. Here, we describe the crucial role of SND1 in cancer development and progression, and highlight SND1 as a potential target for therapeutic intervention.

Suppression of miR-184 in malignant gliomas upregulates SND1 and promotes tumor aggressiveness

BACKGROUND

Malignant glioma is an aggressive cancer requiring new therapeutic targets. MicroRNAs (miRNAs) regulate gene expression post transcriptionally and are implicated in cancer development and progression. Deregulated expressions of several miRNAs, specifically hsa-miR-184, correlate with glioma development.

METHODS

Bioinformatic approaches were used to identify potential miR-184-regulated target genes involved in malignant glioma progression. This strategy identified a multifunctional nuclease, SND1, known to be overexpressed in multiple cancers, including breast, colon, and hepatocellular carcinoma, as a putative direct miR-184 target gene. SND1 levels were evaluated in patient tumor samples and human-derived cell lines. We analyzed invasion and signaling in vitro through SND1 gain-of-function and loss-of-function. An orthotopic xenograft model with primary glioma cells demonstrated a role of miR-184/SND1 in glioma pathogenesis in vivo.

RESULTS

SND1 is highly expressed in human glioma tissue and inversely correlated with miR-184 expression. Transfection of glioma cells with a miR-184 mimic inhibited invasion, suppressed colony formation, and reduced anchorage-independent growth in soft agar. Similar phenotypes were evident when SND1 was knocked down with siRNA. Additionally, knockdown (KD) of SND1 induced senescence and improved the chemoresistant properties of malignant glioma cells. In an orthotopic xenograft model, KD of SND1 or transfection with a miR-184 mimic induced a less invasive tumor phenotype and significantly improved survival of tumor bearing mice.

CONCLUSIONS

Our study is the first to show a novel regulatory role of SND1, a direct target of miR-184, in glioma progression, suggesting that the miR-184/SND1 axis may be a useful diagnostic and therapeutic tool for malignant glioma.

Whole transcriptome sequencing reveals extensive unspliced mRNA in metastatic castration-resistant prostate cancer

Men with metastatic prostate cancer who are treated with androgen deprivation therapies (ADT) usually relapse within 2 to 3 years with disease that is termed castration-resistant prostate cancer (CRPC). To identify the mechanism that drives these advanced tumors, paired-end RNA-sequencing (RNA-seq) was performed on a panel of CRPC bone marrow biopsy specimens. From this genome-wide approach, mutations were found in a series of genes with prostate cancer relevance, including AR, NCOR1, KDM3A, KDM4A, CHD1, SETD5, SETD7, INPP4B, RASGRP3, RASA1, TP53BP1, and CDH1, and a novel SND1:BRAF gene fusion. Among the most highly expressed transcripts were 10 noncoding RNAs (ncRNAs), including MALAT1 and PABPC1, which are involved in RNA processing. Notably, a high percentage of sequence reads mapped to introns, which were determined to be the result of incomplete splicing at canonical splice junctions. Using quantitative PCR (qPCR), a series of genes (AR, KLK2, KLK3, STEAP2, CPSF6, and CDK19) were confirmed to have a greater proportion of unspliced RNA in CRPC specimens than in normal prostate epithelium, untreated primary prostate cancer, and cultured prostate cancer cells. This inefficient coupling of transcription and mRNA splicing suggests an overall increase in transcription or defect in splicing.

IMPLICATIONS

Inefficient splicing in advanced prostate cancer provides a selective advantage through effects on microRNA networks but may render tumors vulnerable to agents that suppress rate-limiting steps in splicing.

The transcriptional co-activator SND1 is a novel regulator of alternative splicing in prostate cancer cells

Splicing abnormalities have profound impact in human cancer. Several splicing factors, including SAM68, have pro-oncogenic functions, and their increased expression often correlates with human cancer development and progression. Herein, we have identified using mass spectrometry proteins that interact with endogenous SAM68 in prostate cancer (PCa) cells. Among other interesting proteins, we have characterized the interaction of SAM68 with SND1, a transcriptional co-activator that binds spliceosome components, thus coupling transcription and splicing. We found that both SAM68 and SND1 are upregulated in PCa cells with respect to benign prostate cells. Upregulation of SND1 exerts a synergic effect with SAM68 on exon v5 inclusion in the CD44 mRNA. The effect of SND1 on CD44 splicing required SAM68, as it was compromised after knockdown of this protein or mutation of the SAM68-binding sites in the CD44 pre-mRNA. More generally, we found that SND1 promotes the inclusion of CD44 variable exons by recruiting SAM68 and spliceosomal components on CD44 pre-mRNA. Inclusion of the variable exons in CD44 correlates with increased proliferation, motility and invasiveness of cancer cells. Strikingly, we found that knockdown of SND1, or SAM68, reduced proliferation and migration of PCa cells. Thus, our findings strongly suggest that SND1 is a novel regulator of alternative splicing that promotes PCa cell growth and survival.

Staphylococcal nuclease domain containing-1 (SND1) promotes migration and invasion via angiotensin II type 1 receptor (AT1R) and TGFβ signaling

Staphylococcal nuclease domain containing-1 (SND1) is overexpressed in human hepatocellular carcinoma (HCC) patients and promotes tumorigenesis by human HCC cells. We now document that SND1 increases angiotensin II type 1 receptor (AT1R) levels by increasing AT1R mRNA stability. This results in activation of ERK, Smad2 and subsequently the TGFβ signaling pathway, promoting epithelial-mesenchymal transition (EMT) and migration and invasion by human HCC cells. A positive correlation was observed between SND1 and AT1R expression levels in human HCC patients. Small molecule inhibitors of SND1, alone or in combination with AT1R blockers, might be an effective therapeutic strategy for late-stage aggressive HCC.