Methylation status of TUSC3 is a prognostic factor in ovarian cancer

Intact cell mass spectrometry coupled with machine learning reveals minute changes induced by single gene silencing

Intact (whole) cell MALDI TOF mass spectrometry is a commonly used tool in clinical microbiology for several decades. Recently it was introduced to analysis of eukaryotic cells, including cancer and stem cells. Besides targeted metabolomic and proteomic applications, the intact cell MALDI TOF mass spectrometry provides a sufficient sensitivity and specificity to discriminate cell types, isogenous cell lines or even the metabolic states. This makes the intact cell MALDI TOF mass spectrometry a promising tool for quality control in advanced cell cultures with a potential to reveal batch-to-batch variation, aberrant clones, or unwanted shifts in cell phenotype. However, cellular alterations induced by change in expression of a single gene has not been addressed by intact cell mass spectrometry yet. In this work we used a well-characterized human ovarian cancer cell line SKOV3 with silenced expression of a tumor suppressor candidate 3 gene (TUSC3). TUSC3 is involved in co-translational N-glycosylation of proteins with well-known global impact on cell phenotype. Altogether, this experimental design represents a highly suitable model for optimization of intact cell mass spectrometry and analysis of spectral data. Here we investigated five machine learning algorithms (k-nearest neighbors, decision tree, random forest, partial least squares discrimination, and artificial neural network) and optimized their performance either in pure populations or in two-component mixtures composed of cells with normal or silenced expression of TUSC3. All five algorithms reached accuracy over 90 % and were able to reveal even subtle changes in mass spectra corresponding to alterations of TUSC3 expression. In summary, we demonstrate that spectral fingerprints generated by intact cell MALDI-TOF mass spectrometry coupled to a machine learning classifier can reveal minute changes induced by alteration of a single gene, and therefore contribute to the portfolio of quality control applications in routine cell and tissue cultures.

Health Disparities in Ovarian Cancer: Report From the Ovarian Cancer Evidence Review Conference

Health disparity, defined by the Centers for Disease Control and Prevention (CDC) as "preventable differences in the burden of disease, injury, violence, or opportunities to achieve optimal health that are experienced by socially disadvantaged populations," is seen across multiple diseases. We conducted an evidence review of health disparities and inequities and their mitigation strategies related to ovarian cancer as part of a CDC-sponsored project to develop educational materials for clinicians on the prevention and early diagnosis of gynecologic cancers. Our review found profound disparities in outcomes such as survival, treatment, and stage at diagnosis by factors such as race and ethnicity, insurance, socioeconomic status, and geographic location. We found little direct evidence on mitigation strategies. Studies support equivalent response to equivalent treatment between groups, suggesting that adherence to National Comprehensive Cancer Network guidelines can at least partially mitigate some of the differences.

TUSC3 Methylation in Peripheral Blood Cells as a Biomarker for Diagnosis of Colorectal Cancer

Background

Several case-control studies have suggested that global and loci-specific deoxyribonucleic acid (DNA) methylation in peripheral blood mononuclear cells (PBMCs) of DNA might be potential biomarkers of cancer diagnosis and prognosis. In this study, for the first time, we intended to assess the diagnostic power of the methylation level of tumor suppressor candidate 3 (TUSC3) gene promoter in patients with colorectal cancer (CRC).

Materials and Methods

In the current study, we quantitatively assessed the promoter methylation level of TUSC3 in PBMCs of 70 CRC cases and 75 non-cancerous subjects via methylation quantification of endonuclease-resistant DNA (MethyQESD) method.

Results

The methylation level of the TUSC3 was meaningfully higher in CRC cases than in non-CRC subjects (43.55 ± 21.80% vs. 16.07 ± 13.63%, respectively; P < 0.001). The sensitivity and specificity of this gene for the detection of CRC were 88.6% and 76.0%, respectively. The receiver operating characteristic (ROC) curve examination discovered an area under the curve (AUC) of 0.880, representing a very high accuracy of the TUSC3 methylation marker in distinguishing CRC subjects from healthy individuals. However, there was no substantial diversity in methylation level between various CRC stages (P: 0.088).

Conclusion

For CRC screening, PBMCs are a reliable source for DNA methylation analysis and TUSC3 promoter methylation can be utilized as a hopeful biomarker for early and non-invasive diagnosis of CRC.

TUSC3 inhibits cell proliferation and invasion in cervical squamous cell carcinoma via suppression of the AKT signalling pathway

The decreased expression of tumour suppressor candidate 3 (TUSC3) is associated with proliferation in several types of cancer, leading to an unfavourable prognosis. The present study aimed to assess the cellular and molecular function of TUSC3 in patients with cervical squamous cell carcinoma (CSCC). Levels of mRNA expressions of TUSC3 were analysed in CSCC tissues and six cell lines using qRT-PCR. Immunohistochemistry(IHC) was used to evaluate the protein expression level of TUSC3 in four paired specimens, 220 paraffin-embedded CSCC specimens and 60 cases of normal cervical tissues(NCTs), respectively. Short hairpin RNA interference was employed for TUSC3 knockdown. Cell proliferation, migration and invasion were evaluated using growth curve, MTT assay, wound healing, transwell assay and xenograft tumour model, respectively. The results demonstrated that TUSC3 mRNA and protein expression levels were downregulated in CSCC samples. Multivariate and univariate analyses indicated that TUSC3 was an independent prognostic factor for patients with CSCC. Decreased TUSC3 expression levels were significantly associated with proliferation and an aggressive phenotype of cervical cancer cells both in vitro and in vivo. Moreover, the knockdown of TUSC3 promoted migration and invasion of cancer cells, while the increased expression of TUSC3 exhibited the opposite effects. The downregulation of TUSC3 facilitated proliferation and invasion of CSCC cells through the activation of the AKT signalling pathway. Our data demonstrated that the downregulation of TUSC3 promoted CSCC cell metastasis via the AKT signalling pathway. Therefore, TUSC3 may serve as a novel prognostic marker and potential target for CSCC.

MiR-320d Inhibits Progression of EGFR-Positive Colorectal Cancer by Targeting TUSC3

Background: The mechanism of miR-320d in EGFR-positive colorectal cancer (CRC) has not been fully elucidated. The aim of the present study was to explore the molecular mechanism of miR-320d in CRC.

Methods: The miRNA microarray analysis was conducted to identify differential expressed miRNAs. The expression of miR-320d was validated using quantitative real-time PCR. EGFR-positive CRC cells were transfected with miR-320d mimic and inhibitor, after which cell proliferation, migration, and invasion were assayed. The relationship between miR-320d and TUSC3 was confirmed using bioinformatics and dual-luciferase reporter gene assays. Proteins involved in signaling pathways and the epithelial–mesenchymal transition were detected with Western blot.

Results: We found that the miR-320d expression is associated with tumor size and distant metastasis in colorectal cancer. Overexpression of miR-320d in EGFR-positive HCT-116 and SW480 cells decreased not only the proliferation ability but also the invasion and migration ability. In addition, miR-320d had the ability to inhibit epithelial-to-mesenchymal transition. Luciferase assays revealed that miR-320d directly targets the 3′-UTR of TUSC3. TUSC3 was downregulated by miR-320d at both the protein and mRNA levels in EGFR-positive CRC cell lines.

Conclusion: Generally, our results demonstrated that miR-320d could inhibit the malignant phenotype of EGFR-positive CRC through targeting TUSC3. The miR-320d might be a potential therapeutic target for EGFR-positive CRC.

Two Sisters From Qatar With TUSC3 Genetic Mutation: Psychiatric Considerations

Defects in the tumor suppressor candidate 3 (TUSC3) gene have been identified in individuals with autosomal recessive intellectual disability (ARID). Our report on two sisters from Qatar with a mutation in the TUSC3 gene focuses on the behavioral manifestations and management provided to them. The sisters, daughters of consanguineous parents, exhibited aggressive and impulsive behavior, along with hyperactivity and emotional dysregulation. They also exhibited abnormal sleep and eating patterns. Behavioral therapy and psychotropic medications including aripiprazole 3.75mg, clonidine 0.025mg, and guanfacine 1mg were used for the management of aggressive and agitated behavior. The two girls showed a reduction in aggressive behavior, hyperactivity, impulsivity, and insomnia in response to 2mg daily of guanfacine. Few families around the world were reported to have mutations in the TUSC3 gene resulting in intellectual disability. We describe the first two reported cases of TUSC3 gene mutation in Qatar. We encourage further research to study the effects of TUSC3 gene mutation, its manifestations, and treatment.

TUSC3 induces drug resistance and cellular stemness via Hedgehog signaling pathway in colorectal cancer

Tumor suppressor candidate 3 (TUSC3) is a coding gene responsible for N-glycosylation of many critical proteins. TUSC3 gene plays an oncogenic role in colorectal cancer (CRC), however, the role of TUSC3 in drug resistance of CRC is still unclear. The aim of this study is to investigate the biological function and molecular mechanism of TUSC3 in CRC drug resistance. The expression of TUSC3 in CRC is positively correlated to tumor stage in 90 paired clinical samples, and negatively associated with overall survival and disease-free survival of CRC patients. In vitro, TUSC3 promotes the formation of stemness and induces the drug resistance to 5-fluorouracil and cis-dichlorodiammineplatinum(II) in CRC cells. The tissue microarray assay and bioinformatic analysis indicate that TUSC3 may promote the expression of CD133 and ABCC1 via Hedgehog signaling pathway. Treatment of Hedgehog signaling pathway agonist or inhibitor in TUSC3-silenced or TUSC3-overexpressed cells reverse the effects of TUSC3 in cellular stemness phenotype and drug resistance. Meanwhile, coimmunoprecipitation and immunofluorescence assays indicate a tight relationship between TUSC3 and SMO protein. Our data suggest that TUSC3 promotes the formation of cellular stemness and induces drug resistance via Hedgehog signaling pathway in CRC.

Genome-Wide Identification of Cis-acting Expression QTLs in Large Yellow Croaker

The large yellow croaker is one of the largest marine economic fish in China with the farming yield about 30 tons per year. The genetic selection for growth and disease resistance has been performed in recent years. The identification of trait-associated molecular makers, causative variants, and causative genes is helpful for genetic selection in large yellow croaker. It has been discovered that most of polygenic traits are controlled with multiple genes via regulatory variant, and GWAS-identified loci are enriched in the regulatory variant. Cis-acting eQTL is a widespread regulatory variant that controls the expression of nearby gene. We herein take advantage of RNA-seq and whole genome sequencing technique to identify genome-wide eQTLs in liver tissue for large yellow croaker; a forward selection routine is applied for identification of multiple eQTLs. To fine map causative mutation for each eQTL, a credible set is built to confine causative variants. Totally, 2427 eQTLs have been identified, 69.7% (1,691/2,427) of them are primary eQTL signals, and the remaining are secondary signals, many functional important target genes have been discovered. We highlight several functional pivotal genes including SMC3, TUSC3, TITIN, MCPH1, and MDHC, in which the expression of MCPH1 is regulated by two eQTLs; the distance of these eQTLs from target genes is symmetrically distributed, 25.5% of them are within 1 Mb region from target genes, whereas 74.5% of them are between 1 and 2 Mb regions; most of the identified eQTL has been well resolved, and 19.3 (469/2427) of eQTL have the size of credible set (the number of variants in credible set) less than 50.

Downregulation of microRNA-320a inhibits proliferation and induces apoptosis of retinoblastoma cells via targeting TUSC3

MicroRNA (miR)-320a is specific to vertebrates and has been indicated to serve a role in a number of cancer types, such as gastric, colorectal, pancreatic and ovarian cancer. miR-320a has been reported to be expressed at high levels in retinoblastoma tissues; however its role and mechanism of function in retinoblastoma remain to be elucidated. The aim of the present study was to investigate the role of miR-320a in retinoblastoma cells and the underlying mechanisms. The expression of miR-320a in retinoblastoma cell lines Y79 and WERI-Rb-1, and normal human retinal pigment epithelial cell line ARPE-19 was examined via reverse transcription-quantitative PCR (RT-qPCR). TargetScan bioinformatics analysis and dual-luciferase reporter assay were used to predict and reveal the target gene of miR-320a. Target gene expression was detected via RT-qPCR in retinoblastoma cell lines and ARPE-19 cells. Subsequently, gain- or loss-of-function experiments for miR-320a and tumor suppressor candidate 3 (TUSC3) were performed to study the role of miR-320a/TUSC3 in retinoblastoma cells. Cell viability and apoptosis were assessed via MTT and flow cytometry analysis, respectively. Compared with ARPE-19 cells, miR-320a was prominently expressed in retinoblastoma cell lines. TUSC3 was predicted to be a target gene of miR-320a. Compared with ARPE-19 cells, the expression of TUSC3 in retinoblastoma cell lines was reduced. The results of MTT and flow cytometry analysis revealed that overexpression of TUSC3 reduced the viability of retinoblastoma cells and induced apoptosis. Additional analysis indicated that miR-320a inhibitor enhanced the expression of the target gene TUSC3, thereby inhibiting retinoblastoma cell viability and inducing apoptosis. The effects of miR-320a inhibitor on retinoblastoma cells were inhibited by TUSC3-short hairpin RNA. miR-320a regulated the viability and apoptosis of retinoblastoma cells via targeting TUSC3. Therefore, the present study provided a reference for investigating a potential target for the clinical treatment of retinoblastoma.

Tumour suppressor candidate 3 inhibits biological function and increases endoplasmic reticulum stress of melanoma cells WM451 by regulating AKT/GSK3-β/β-catenin pathway

Melanoma is a highly malignant and is a life-threatening disease with no effective treatment currently. This study aims to evaluate the significance of TUSC3, an endoplasmic reticulum stress (ERS)-inducible gene and explore its relationship with AKT/GSK3-β/β-catenin signalling pathway in melanoma cell WM451. We investigated TUSC3 expression in melanoma cell by qRT-PCR, CCK-8 and clonal formation assays were utilized to evaluate cell proliferation. Wound healing and transwell experiments detected cell migration and invasion. Flow cytometry detected the level of apoptosis. Western blot analysed MMP2, MMP9, p-AKT, p-GSK3-β, β-catenin and AKT, GSK3-β, ERS-related proteins and apoptosis-related proteins in WM451 cells. The results revealed that TUSC3 was remarkably decreased in melanoma cell lines. Overexpression of TUSC3 significantly inhibits melanoma cell WM451 biological functions and promotes expression of ERS-related proteins in WM451 cells, increases ERS in WM451 cells by inhibiting AKT/GSK3-β/β-catenin pathway. These finding suggest that TUSC3 regulates biological functions of melanoma cells WM451 and increases ERS in melanoma cells WM451 via the inhibition of the AKT/GSK3-β/β-catenin signalling pathway. SIGNIFICANCE OF THE STUDY: Melanoma is a highly malignant and is a life-threatening disease with no effective treatment currently. Therefore, studying the molecular mechanism of melanoma occurrence and metastasis is essential for the treatment of melanoma. Meanwhile, mounting studies suggest that TUSC3 is considered to be closely associated with the development of various malignancies. TUSC3 regulates proliferation, migration and epithelial-to-mesenchymal transition, but the molecular mechanism of the tumour suppressor effects of TUSC3 on melanoma cells is not well understood. Our study demonstrates that TUSC3 inhibits biological function of melanoma cells and increases ERS in melanoma cells by inhibiting AKT/GSK3-β/β-catenin pathway. And this is expected to be a new target and method for the treatment of melanoma.

Oligosaccharyltransferase: A Gatekeeper of Health and Tumor Progression

Oligosaccharyltransferase (OST) is a multi-span membrane protein complex that catalyzes the addition of glycans to selected Asn residues within nascent polypeptides in the lumen of the endoplasmic reticulum. This process, termed N-glycosylation, is a fundamental post-translational protein modification that is involved in the quality control, trafficking of proteins, signal transduction, and cell-to-cell communication. Given these crucial roles, N-glycosylation is essential for homeostasis at the systemic and cellular levels, and a deficiency in genes that encode for OST subunits often results in the development of complex genetic disorders. A growing body of evidence has also demonstrated that the expression of OST subunits is cell context-dependent and is frequently altered in malignant cells, thus contributing to tumor cell survival and proliferation. Importantly, a recently developed inhibitor of OST has revealed this enzyme as a potential target for the treatment of incurable drug-resistant tumors. This review summarizes our current knowledge regarding the functions of OST in the light of health and tumor progression, and discusses perspectives on the clinical relevance of inhibiting OST as a tumor treatment.

UHRF1-KAT7-mediated regulation of TUSC3 expression via histone methylation/acetylation is critical for the proliferation of colon cancer cells

The epigenetic factor UHRF1 regulates transcription by modulating DNA methylation and histone modification, and plays critical roles in proliferation, development, and tumorigenesis. Here, we show that Wnt/c-Myc signaling upregulates UHRF1, which in turn downregulates TUSC3, a candidate tumor suppressor gene that is frequently deleted or downregulated in several cancers. We also show that UHRF1-mediated downregulation of TUSC3 is required for the proliferation of colon cancer cells. Furthermore, we demonstrate that UHRF1 suppresses TUSC3 expression by interacting with methylated H3K14 and thereby suppressing the acetylation of H3K14 by the histone acetyltransferase KAT7. Our study provides evidence for the significance of UHRF1-KAT7-mediated regulation of histone methylation/acetylation in the proliferation of tumor cells and in a diverse set of biological processes controlled by Wnt/c-Myc signaling.

TUSC3 as a potential biomarker for prognosis in clear cell renal cell carcinoma

The aim of the present study was to explore the expression levels of tumor suppressor candidate 3 (TUSC3) in human clear cell renal cell carcinoma (ccRCC) and its clinical value. Immunohistochemical staining, western blotting and reverse transcription-quantitative polymerase chain reaction were used to detect TUSC3 expression in paracancerous normal tissues and ccRCC tissues. The tissues were derived from the pathological specimens of 54 patients with ccRCC. Additionally, associations among TUSC3 expression and histological grade and clinicopathological staging of ccRCC were investigated. The results of these comparisons revealed that TUSC3 expression in ccRCC tissues was significantly lower than that in paracancerous tissues (P<0.05). TUSC3 expression in the high differentiation group was higher than that in the median and low differentiation groups (P<0.05). Expression levels of TUSC3 in stage I and II tissues were higher than those in stage III and IV tissues (P<0.05). The expression levels of TUSC3 in the lymph node metastasis group were lower than those in the non-lymph node metastasis group (P<0.05). In conclusion, the expression levels of TUSC3 in human ccRCC tissues were downregulated compared with those found in normal human renal tissue, and TUSC3 may inhibit the progression of ccRCC. Furthermore, the TUSC3 gene may be used as a promising tumor marker for the early diagnosis and prognosis of ccRCC.

Simultaneous miRNA and mRNA transcriptome profiling of glioblastoma samples reveals a novel set of OncomiR candidates and their target genes

Although glioblastomas are common, there remains a need to elucidate the underlying mechanisms behind their initiation and progression and identify molecular pathways for improving treatment. In this study, sixteen fresh-frozen glioblastoma samples and seven samples of healthy brain tissues were analyzed with miRNA and whole transcriptome microarray chips. Candidate miRNAs and mRNAs were selected to validate expression in fifty patient samples in total with the criteria of abundance, relevance and prediction scores. miRNA and target mRNA relationships were assessed by inhibiting selected miRNAs in glioblastoma cells. Functional tests have been conducted in order to see the effects of miRNAs on invasion, migration and apoptosis of GBM cells. Analyses were carried out to determine correlations between selected molecules and clinicopathological features. 1332 genes and 319 miRNAs were found to be dysregulated by the microarrays. The results were combined and analyzed with Transcriptome Analysis Console 3 software and the DAVID online database. Primary differential pathways included Ras, HIF-1, MAPK signaling and cell adhesion. OncomiR candidates 21-5p, 92b-3p, 182-5p and 339-5p for glioblastoma negatively correlated with notable mRNA targets both in tissues and in in vitro experiments. miR-21-5p and miR-339-5p significantly affected migration, invasion and apoptosis of GBM cells in vitro. Significant correlations with overall survival, tumor volume, recurrence and age at diagnosis were discovered. In this article we present valuable integrated microarray analysis of glioblastoma samples regarding miRNA and gene-expression levels. Notable biomarkers and miRNA-mRNA interactions have been identified, some of which correlated with clinicopathological features in our cohort.

Alleviation of endoplasmic reticulum stress by tauroursodeoxycholic acid delays senescence of mouse ovarian surface epithelium

Ovarian surface epithelium (OSE) forms a single layer of mostly cuboidal cells on surface of mammalian ovaries that is inherently exposed to cell stress evoked by tissue damage every ovulation and declines morphologically after menopause. Endoplasmic reticulum (ER) is a principal cell organelle involved in proteosynthesis, but also integrating various stress signals. ER stress evokes a conserved signaling pathway, the unfolded protein response (UPR), leading to cell death or adaptation to stress conditions. In this work, we document that mouse OSE suffers from ER stress during replicative senescence in vitro, develops abnormalities in ER and initiates UPR. Attenuation of ER stress in senescent OSE by tauroursodeoxycholic acid (TUDCA) reconditions ER architecture and leads to delayed onset of senescence. In summary, we show for the first time a mutual molecular link between ER stress response and replicative senescence leading to phenotypic changes of non-malignant ovarian surface epithelium.

Integrated transcriptomic and epigenomic analysis of ovarian cancer reveals epigenetically silenced GULP1

Many epigenetically inactivated genes involved in ovarian cancer (OC) development and progression remain to be identified. In this study we undertook an integrated approach that consisted of identification of genome-wide expression patterns of primary OC samples and normal ovarian surface epithelium along with a pharmacologic unmasking strategy using 3 OC and 3 immortalized normal ovarian epithelial cell lines. Our filtering scheme identified 43 OC specific methylated genes and among the 5 top candidates (GULP1, CLIP4, BAMBI, NT5E, TGFβ2), we performed extended studies of GULP1. In a training set, we identified GULP1 methylation in 21/61 (34%) of cases with 100% specificity. In an independent cohort, the observed methylation was 40% (146/365) in OC, 12.5% (2/16) in borderline tumors, 11% (2/18) in cystadenoma and 0% (0/13) in normal ovarian epithelium samples. GULP1 methylation was associated with clinicopathological parameters such as stage III/IV (p = 0.001), poorly differentiated grade (p = 0.033), residual disease (p < 0.0003), worse overall (p = 0.02) and disease specific survival (p = 0.01). Depletion of GULP1 in OC cells led to increased pro-survival signaling, inducing survival and colony formation, whereas reconstitution of GULP1 negated these effects, suggesting that GULP1 is required for maintaining cellular growth control.

Integrated analysis of genome-wide DNA methylation and gene expression profiles identifies potential novel biomarkers of rectal cancer

DNA methylation was regarded as the promising biomarker for rectal cancer diagnosis. However, the optimal methylation biomarkers with ideal diagnostic performance for rectal cancer are still limited. To identify new molecular markers for rectal cancer, we mapped DNA methylation and transcriptomic profiles in the six rectal cancer and paired normal samples. Further analysis revealed the hypermethylated probes in cancer prone to be located in gene promoter. Meanwhile, transcriptome analysis presented 773 low-expressed and 1,161 over-expressed genes in rectal cancer. Correction analysis identified a panel of 36 genes with an inverse correlation between methylation and gene expression levels, including 10 known colorectal cancer related genes. From the other 26 novel marker genes, GFRA1 and GSTM2 were selected for further analysis on the basis of their biological functions. Further experiment analysis confirmed their methylation and expression status in a larger number (44) of rectal cancer samples, and ROC curves showed higher AUC than SEPT9, which has been used as a biomarker in rectal cancer. Our data suggests that aberrant DNA methylation of contiguous CpG sites in methylation array may be potential diagnostic markers of rectal cancer.

TUSC3: functional duality of a cancer gene

Two decades ago, following a systematic screening of LOH regions on chromosome 8p22, TUSC3 has been identified as a candidate tumor suppressor gene in ovarian, prostate and pancreatic cancers. Since then, a growing body of evidence documented its clinical importance in various other types of cancers, and first initial insights into its molecular function and phenotypic effects have been gained, though the precise role of TUSC3 in different cancers remains unclear. As a part of the oligosaccharyltransferase complex, TUSC3 localizes to the endoplasmic reticulum and functions in final steps of N-glycosylation of proteins, while its loss evokes the unfolded protein response. We are still trying to figure out how this mechanistic function is reconcilable with its varied effects on cancer promotion. In this review, we focus on cancer-related effects of TUSC3 and envisage a possible role of TUSC3 beyond endoplasmic reticulum.

Low levels of tumor suppressor candidate 3 predict poor prognosis of patients with hepatocellular carcinoma

Purpose

The tumor suppressor candidate 3 (TUSC3) has been considered to be closely associated with the occurrence, development and invasion of various malignant tumors. However, the expression of TUSC3 in hepatocellular carcinoma (HCC) tissues remains ambiguous. The purpose of this research was to investigate the expression of TUSC3 in HCC tissues and analyze the relationship between TUSC3 levels and clinicopathological characteristics and prognosis of HCC patients.

Materials and methods

Immunohistochemistry was used to detect the expression of TUSC3 in HCC and the corresponding para-cancerous tissues from 92 samples of HCC patients. mRNA and protein expression levels of TUSC3 were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot assays in 25 paired HCC and corresponding adjacent nontumor tissues. Furthermore, statistical analysis was applied to evaluate the correlation between TUSC3 level and the clinicopathological features and prognosis of HCC patients.

Results

Immunohistochemical assay indicated that the expression of TUSC3 was significantly lower in HCC tissues when compared with the corresponding para-cancerous tissues (χ²=11.512, P=0.001). The analysis of clinicopathological characteristics showed that low expression of TUSC3 in HCC tissues was significantly associated with Edmondson grade, Barcelona Clinic Liver Cancer stage and tumor size (P=0.008, 0.009 and 0.020, respectively). Univariate analysis showed that the expression of TUSC3 was strongly correlated with overall survival (OS) and disease-free survival (DFS) after radical surgery in HCC patients (P<0.001, P<0.001, respectively). Multivariate analysis revealed that the TUSC3 level was an independent risk factor for OS and DFS in HCC patients (P=0.001, P<0.001, respectively). Results of qRT-PCR and Western blot assays indicated that the level of TUSC3 in HCC tissues was significantly lower than that in the corresponding adjacent noncancerous tissues (P<0.01, P<0.001).

Conclusion

The expression of TUSC3 in HCC was significantly downregulated and was correlated with tumor progression and prognosis, which could be used as an independent predictor of prognosis in HCC patients.

Tumor suppressor candidate 3: A novel grading tool and predictor of clinical malignancy in human gliomas

For several years, the cause of autosomal recessive mental retardation has been attributed to the deletion or mutation of a gene named tumor suppressor candidate 3 (TUSC3). Previous research has identified that TUSC3 is a potential tumor suppressor gene in oral epidermoid carcinoma, lung cancer and esophageal cancer. However, to the best of our knowledge, no previously published data has existed on the expression of TUSC3 in gliomas. The present study focused on the expression of TUSC3 in brain gliomas. Additionally, the present study sought to identify he association between TUSC3 expression and the typical clinical and pathological disease manifestations of gliomas. TUSC3 levels were evaluated using a western blot assay and immunohistochemistry on tissue microarray slides. Results indicated a significant decrease in TUSC3 expression in glioma tissues compared with the normal adjacent tissues. Furthermore, TUSC3 expression and World Health Organization grade demonstrated an inverse association in patients with glioma. This revealed that lower levels of TUSC3 in gliomas may be associated with a poorly-differentiated (high grade) tumor and thus a higher malignancy. Through the combination of the results of the present study and future research projects, TUSC3 may be a novel grading tool that assists with evaluating tumor malignancy and consequently a more active therapeutic regimen may be used in patients with glioma.

Racial health disparities in ovarian cancer: not just black and white

Ovarian cancer (OC) is the most lethal gynecological malignancy, which disproportionately affects African American (AA) women. Lack of awareness and socioeconomic factors are considered important players in OC racial health disparity, while at the same time, some recent studies have brought focus on the genetic basis of disparity as well. Differential polymorphisms, mutations and expressions of genes have been reported in OC patients of diverse racial and ethnic backgrounds. Combined, it appears that neither genetic nor the socioeconomic factors alone might explain the observed racially disparate health outcomes among OC patients. Rather, a more logical explanation would be the one that takes into consideration the combination and/or the interplay of these factors, perhaps even including some environmental ones. Hence, in this article, we attempt to review the available information on OC racial health disparity, and provide an overview of socioeconomic, environmental and genetic factors, as well as the epigenetic changes that can act as a liaison between the three. A better understanding of these underlying causes will help further research on effective cancer management among diverse patient population and ultimately narrow health disparity gaps.

TUSC3 induces autophagy in human non-small cell lung cancer cells through Wnt/β-catenin signaling

We investigated the effects of tumor suppressor candidate 3 (TUSC3) on autophagy in human non-small cell lung cancer (NSCLC) cells. A total of 118 NSCLC patients (88 males and 30 females) who underwent surgery at our institute were enrolled in the study. Immunohistochemical analysis revealed that TUSC3 protein expression was lower in NSCLC specimens than adjacent normal tissue. Correspondingly, there was greater methylation of TUSC3 in NSCLC than adjacent normal tissue. After transient transfection of A549 NSCLC cells with constructs designed to up-regulate or down-regulate TUSC3 expression, we analyzed the effects of inhibiting the Wnt pathway (XAV939) and autophagy (chloroquine, CQ) on the behavior of NSCLC cells. We also performed TOP/FOP-Flash reporter assays, MTT assays, Annexin V-FITC/propidium iodide staining, and acridine orange staining to evaluate Wnt/β-catenin signaling, cell proliferation, apoptosis, and autophagy, respectively. Expression of Wnt/β-catenin pathway components and autophagy-related proteins was analyzed using qRT-PCR and Western blotting. We found that TUSC3 inhibited cell proliferation and promoted both apoptosis and autophagy in A549 cells. In addition, TUSC3 increased expression of autophagy-related proteins. It also increased expression of Wnt/β-catenin signaling pathway components and promoted nuclear transfer of β-catenin, resulting in activation of Wnt/β-catenin signaling. TUSC3 thus induces autophagy in human NSCLC cells through activation of the Wnt/β-catenin signaling pathway.

Role of protein glycosylation in cancer metastasis

Although altered glycosylation has been detected in human cancer cells decades ago, only investigations in the last years have enormously increased our knowledge about the details of protein glycosylation and its role in tumour progression. Many proteins, which are heavily glycosylated, i.e. adhesion proteins or proteases, play an important role in cancer metastasis that represents the crucial and frequently life-threatening step in progression of most tumour types. Compared to normal tissue, tumour cells often show altered glycosylation patters with appearance of new tumour-specific antigens. In this review, we give an overview about the role of glycosylation in tumour metastasis, describing recent results about O-glycans, N-glycans and glycosaminoglycans. We show that glycan structures, glycosylated proteins and glycosylation enzymes have influence on different steps of the metastatic process, including epithelial-mesenchymal transition (EMT), migration, invasion/intravasation and extravasation of tumour cells. Regarding the important role of cancer metastasis for patients survival, further knowledge about the consequences of altered glycosylation patterns in tumour cells is needed which might eventually lead to the development of novel therapeutic approaches.

SOX2 regulates multiple malignant processes of breast cancer development through the SOX2/miR-181a-5p, miR-30e-5p/TUSC3 axis

BACKGROUND

High levels of SOX2 protein are correlated with increased dissemination of breast cancer. However, the underlying molecular mechanisms are not fully understood.

METHODS

In this study we investigate the role of SOX2 in breast cancer metastasis using multiple in vitro and in vivo assays including cell culture, shRNA-mediated knockdown, wound healing, colony formation, transwell chamber, xenograft and tail vein injection. Moreover, western blot, immunostaining, microarray and real-time PCR were used to determine the change of protein and miRNA levels. Luciferase assays were also used to evaluate activity which TUSC3 is a target of miR-181a-5p and miR-30e-5p, and the clinical survival relevance was analyzed by Kaplan-Meier analysis.

RESULTS

We identified a novel pathway involving SOX2 regulation of microRNAs to control the proliferation and migration of breast cancer cells. shRNA-mediated knockdown of SOX2 inhibits breast cancer cell expansion and migration. More importantly, we found that these changes are accompanied by significant reduction in the levels of two microRNAs, miR-181a-5p and miR-30e-5p. Overexpression of these two microRNAs leads to reduced protein levels of Tumor Suppressor Candidate 3 (TUSC3) in breast cancer cells; mutations of the potential binding sites in the 3'-UTR of TUSC3 abrogate the inhibitory effects of the microRNAs. We further found that upregulation of TUSC3 expression leads to reduced proliferation and migration of breast cancer cells. In human breast cancer samples the levels of TUSC3 protein are inversely correlated with those of SOX2 protein.

CONCLUSIONS

Taken together, our work reveals a novel SOX2-mediated regulatory axis that plays critical roles in the proliferation, migration and invasiveness of breast cancer cells. Targeting this axis may provide beneficial effect in the treatment of breast cancer.

TUSC3: a novel tumour suppressor gene and its functional implications

The tumour suppressor candidate 3 (TUSC3) gene is located on chromosome region 8p22 and encodes the 34 kD TUSC3 protein, which is a subunit of the oligosaccharyl transferase responsible for the N‐glycosylation of nascent proteins. Known to be related to autosomal recessive mental retardation for several years, TUSC3 has only recently been identified as a potential tumour suppressor gene. Based on the structure and function of TUSC3, specific mechanisms in various diseases have been investigated. Several studies have demonstrated that TUSC3 is an Mg²⁺‐transporter involved in magnesium transport and homeostasis, which is important for learning and memory, embryonic development and testis maturation. Moreover, dysfunction or deletion of TUSC3 exerts its oncological effects as a modulator by inhibiting glycosylation efficiency and consequently inducing endoplasmic reticulum stress and malignant cell transformation. In this study, we summarize the advances in the studies of TUSC3 and comment on the potential roles of TUSC3 in diagnosis and treatment of TUSC3‐related diseases, especially cancer.

Epigenetic basis of cancer health disparities: Looking beyond genetic differences

Despite efforts at various levels, racial health disparities still exist in cancer patients. These inequalities in incidence and/or clinical outcome can only be explained by a multitude of factors, with genetic basis being one of them. Several investigations have provided convincing evidence to support epigenetic regulation of cancer-associated genes, which results in the differential transcriptome and proteome, and may be linked to a pre-disposition of individuals of certain race/ethnicity to early or more aggressive cancers. Recent technological advancements and the ability to quickly analyze whole genome have aided in these efforts, and owing to their relatively easy detection, methylation events are much well-characterized, than the acetylation events, across human populations. The early trend of investigating a pre-determined set of genes for differential epigenetic regulation is paving way for more unbiased screening. This review summarizes our current understanding of the epigenetic events that have been tied to the racial differences in cancer incidence and mortality. A better understanding of the epigenetics of racial diversity holds promise for the design and execution of novel strategies targeting the human epigenome for reducing the disparity gaps.

Effects of RNAi-mediated TUSC3 silencing on radiation-induced autophagy and radiation sensitivity of human lung adenocarcinoma cell line A549 under hypoxic condition

This study examined the effects of RNAi-mediated TUSC3 silencing on radiation-induced autophagy and radiation sensitivity of human lung adenocarcinoma cell line A549 under hypoxic condition. Different CoCl2 concentrations were used to treat A549 cells and establish a CoCl2-induced hypoxic model of A549 cells. MTT and clone formation assays were used to determine the effects of different concentrations of CoCl2 on the growth and proliferation of A549 cells treated by different doses of X-ray irradiation. The siRNA-expressing vector was transfected by liposomes and for silencing of TUSC3. Flow cytometry was used to measure cell cycle changes and apoptosis rate. Real-time quantitative polymerase chain reaction (qRT-PCR) assay was performed to detect the expression of TUSC3 mRNA. Western blotting was applied to detect the changes of TUSC3, LC3, and p62 proteins under different CoCl2 concentrations and after siRNA silencing of TUSC3. The TUSC3 levels in A549 cells increased under hypoxic conditions in a dose-dependent manner (P < 0.05). Hypoxia inhibited the growth and proliferation of A549 cells and promoted apoptosis (P < 0.05). With an increasing dose of X-ray irradiation, A549 cells showed significantly increased growth and proliferation and decreased apoptosis (P < 0.05). After siRNA-TUSC3 was transfected by liposome, the TUSC3 level was substantially inhibited (P < 0.05). Silencing TUSC3 inhibited A549 cell growth and proliferation after radiotherapy under hypoxic condition, promoted apoptosis, increased G0/G1 phase cells, and reduced S phase cells (all P < 0.05). Hypoxia and radiation along with different CoCl2 concentrations could induce cell autophagy, which increased with concentration and dose, while silencing the TUSC3 gene inhibited autophagy (all P < 0.05). RNAi silencing of TUSC3 inhibited growth and proliferation, while enhanced apoptosis and radiation sensitivity of hypoxic A549 lung adenocarcinoma cells.

Quantitative detection of TUSC3 promoter methylation -a potential biomarker for prognosis in lung cancer

Aberrant promoter methylation of tumor relevant genes frequently occurs in early steps of carcinogenesis and during tumor progression. Epigenetic alterations could be used as potential biomarkers for early detection and for prediction of prognosis and therapy response in lung cancer. The present study quantitatively analyzed the methylation status of known and potential gatekeeper and tumor suppressor genes [O-6-methylguanine-DNA methyltransferase (MGMT), Ras association domain family member 1A (RASSF1A), Ras protein activator like 1 (RASAL1), programmed cell death 4 (PDCD4), metastasis suppressor 1 (MTSS1) and tumor suppressor candidate 3 (TUSC3)] in 42 lung cancers and in corresponding non-malignant bronchus and lung tissue using bisulfite-conversion independent methylation-quantification of endonuclease-resistant DNA (MethyQESD). Methylation status was associated with clinical and pathological parameters. No methylation was found in the promoter regions of PDCD4 and MTSS1 of either compartment. MGMT, RASSF1A and RASAL1 showed sporadic (up to 26.2%) promoter methylation. The promoter of TUSC3, however, was frequently methylated in the tumor (59.5%), benign bronchus (67.9%) and alveolar lung (31.0%) tissues from each tumor patient. The methylation status of TUSC3 was significantly associated with smaller tumor size (P=0.008) and a longer overall survival (P=0.013). Pooled blood DNA of healthy individuals did not show any methylation of either gene. Therefore, methylation of TUSC3 shows prognostic and pathobiological relevance in lung cancer. Furthermore, quantitative detection of TUSC3 promoter methylation appears to be a promising tool for early detection and prediction of prognosis in lung cancer. However, additional studies are required to confirm this finding.

TUSC3 suppresses glioblastoma development by inhibiting Akt signaling

Glioblastoma multiform is one of the most common and most aggressive brain tumors in humans. The molecular and cellular mechanisms responsible for the onset and progression of GBM are elusive and controversial. The function of tumor suppressor candidate 3 (TUSC3) has not been previously characterized in GBM. TUSC3 was originally identified as part of an enzyme complex involved in N-glycosylation of proteins, but was recently implicated as a potential tumor suppressor gene in a variety of cancer types. In this study, we demonstrated that the expression levels of TUSC3 were downregulated in both GBM tissues and cells, and also found that overexpression of TUSC3 inhibits GBM cell proliferation and invasion. In addition, the effects of increased levels of methylation on the TUSC3 promoter were responsible for decreased expression of TUSC3 in GBM. Finally, we determined that TUSC3 regulates proliferation and invasion of GBM cells by inhibiting the activity of the Akt signaling pathway.

TUSC3 promotes colorectal cancer progression and epithelial-mesenchymal transition (EMT) through WNT/β-catenin and MAPK signalling

Colorectal cancer (CRC) is one of the most common malignancies and is the second leading cause of cancer death in humans. Tumour suppressor candidate 3 (TUSC3) plays an important role in embryogenesis and metabolism. Deletion of TUSC3 often causes non-syndromic mental retardation. Even though TUSC3 deregulation is frequently observed in epithelial cancers, the function of TUSC3 in CRC has remained unknown. In this study, we observed greater expression of TUSC3 at the mRNA and protein level in clinical colorectal tumour samples compared with paired normal tissues. Gain- and loss-of-function analyses were performed to evaluate the functional significance of TUSC3 in CRC initiation and progression. Immunoblotting, immunofluorescence, and co-immunoprecipitation analyses were used to identify potential pathways with which TUSC3 might be involved. Overexpression of TUSC3 in CRC cells induced epithelial-mesenchymal transition (EMT) in CRC cells, accompanied by down-regulation of the epithelial marker, E-cadherin, and up-regulation of the mesenchymal marker, vimentin. Increased proliferation, migration, and invasion, as well as accelerated xenograft tumour growth, were observed in TUSC3-overexpressing CRC cells, while opposite effects were achieved in TUSC3-silenced cells. In conclusion, our study demonstrated the oncogenic role of TUSC3 in CRC and showed that TUSC3 may be responsible for alternations in the proliferation ability, aggressiveness, and invasive/metastatic potential of CRC through regulating the MAPK, PI3K/Akt, and Wnt/β-catenin signalling pathways.

Decreased TUSC3 Promotes Pancreatic Cancer Proliferation, Invasion and Metastasis

Pancreatic cancer is an aggressive disease with dismal prognosis. It is of paramount importance to understand the underlying etiological mechanisms and identify novel, consistent, and easy-to-apply prognostic factors for precision therapy. TUSC3 (tumor suppressor candidate 3) was identified as a potential tumor suppressor gene and previous study showed TUSC3 is decreased in pancreatic cancer at mRNA level, but its putative tumor suppressor function remains to be verified. In this study, TUSC3 expression was found to be suppressed both at mRNA and protein levels in cell line models as well as in clinical samples; decreased TUSC3 expression was associated with higher pathological TNM staging and poorer outcome. In three pairs of cell lines with different NF-κB activity, TUSC3 expression was found to be reversely correlated with NF-κB activity. TUSC3-silenced pancreatic cancer cell line exhibited enhanced potential of proliferation, migration and invasion. In an orthotopic implanted mice model, TUSC3 silenced cells exhibited more aggressive phenotype with more liver metastasis. In conclusion, the current study shows that decreased immunological TUSC3 staining is a factor prognostic of poor survival in pancreatic cancer patients and decreased TUSC3 promotes pancreatic cancer cell proliferation, invasion and metastasis. The reverse correlation between NF-κB activity and TUSC3 expression may suggest a novel regulation pattern for this molecule.

Racial variation in breast tumor promoter methylation in the Carolina Breast Cancer Study

BACKGROUND

African American (AA) women are diagnosed with more advanced breast cancers and have worse survival than white women, but a comprehensive understanding of the basis for this disparity remains unclear. Analysis of DNA methylation, an epigenetic mechanism that can regulate gene expression, could help to explain racial differences in breast tumor clinical biology and outcomes.

METHODS

DNA methylation was evaluated at 1,287 CpGs in the promoters of cancer-related genes in 517 breast tumors of AA (n = 216) or non-AA (n = 301) cases in the Carolina Breast Cancer Study (CBCS).

RESULTS

Multivariable linear regression analysis of all tumors, controlling for age, menopausal status, stage, intrinsic subtype, and multiple comparisons [false discovery rate (FDR)], identified seven CpG probes that showed significant (adjusted P < 0.05) differential methylation between AAs and non-AAs. Stratified analyses detected an additional four CpG probes differing by race within hormone receptor-negative (HR(-)) tumors. Genes differentially methylated by race included DSC2, KCNK4, GSTM1, AXL, DNAJC15, HBII-52, TUSC3, and TES; the methylation state of several of these genes may be associated with worse survival in AAs. TCGA breast tumor data confirmed the differential methylation by race and negative correlations with expression for most of these genes. Several loci also showed racial differences in methylation in peripheral blood leukocytes (PBL) from CBCS cases, indicating that these variations were not necessarily tumor-specific.

CONCLUSIONS

Racial differences in the methylation of cancer-related genes are detectable in both tumors and PBLs from breast cancer cases.

IMPACT

Epigenetic variation could contribute to differences in breast tumor development and outcomes between AAs and non-AAs.

Tumor suppressor candidate 3 (TUSC3) prevents the epithelial-to-mesenchymal transition and inhibits tumor growth by modulating the endoplasmic reticulum stress response in ovarian cancer cells

Ovarian cancer is one of the most common malignancies in women and contributes greatly to cancer-related deaths. Tumor suppressor candidate 3 (TUSC3) is a putative tumor suppressor gene located at chromosomal region 8p22, which is often lost in epithelial cancers. Epigenetic silencing of TUSC3 has been associated with poor prognosis, and hypermethylation of its promoter provides an independent biomarker of overall and disease-free survival in ovarian cancer patients. TUSC3 is localized to the endoplasmic reticulum in an oligosaccharyl tranferase complex responsible for the N-glycosylation of proteins. However, the precise molecular role of TUSC3 in ovarian cancer remains unclear. In this study, we establish TUSC3 as a novel ovarian cancer tumor suppressor using a xenograft mouse model and demonstrate that loss of TUSC3 alters the molecular response to endoplasmic reticulum stress and induces hallmarks of the epithelial-to-mesenchymal transition in ovarian cancer cells. In summary, we have confirmed the tumor-suppressive function of TUSC3 and identified the possible mechanism driving TUSC3-deficient ovarian cancer cells toward a malignant phenotype.

Global DNA methylation profiling technologies and the ovarian cancer methylome

Cytosine methylation in DNA constitutes an important epigenetic layer of transcriptional and regulatory control in many eukaryotes. Profiling DNA methylation across the genome is critical to understanding the influence of epigenetics in normal biology and disease, such as cancer. Genome-wide analyses such as arrays and next-generation sequencing (NGS) technologies have been used to assess large fractions of the methylome at a single-base-pair resolution. However, the range of DNA methylation profiling techniques can make selecting the appropriate protocol a challenge. This chapter discusses the advantages and disadvantages of various methylome detection approaches to assess which is appropriate for the question at hand. Here, we focus on four prominent genome-wide approaches: whole-genome bisulfite sequencing (WGBS); methyl-binding domain capture sequencing (MBDCap-Seq); reduced-representation-bisulfite-sequencing (RRBS); and Infinium Methylation450 BeadChips (450 K, Illumina). We discuss some of the requirements, merits, and challenges that should be considered when choosing a methylome technology to ensure that it will be informative. In addition, we show how genome-wide methylation detection arrays and high-throughput sequencing have provided immense insight into ovarian cancer-specific methylation signatures that may serve as diagnostic biomarkers or predict patient response to epigenetic therapy.

Genomic alterations on 8p21-p23 are the most frequent genetic events in stage I squamous cell carcinoma of the lung

Genetic alterations in the early stages of cancer have a close correlation with tumor initiation and potentially activate downstream pathways implicated in tumor progression; however, the method of initiation in sporadic neoplasias is largely unknown. In this study, whole-genome microarray-comparative genomic hybridization was performed to identify the early genetic alterations that define the prognosis of patients with stage I squamous cell carcinoma (SCC) of the lung. The most striking finding was the high frequency of copy number losses and hemizygous deletions on chromosome 8p, which occurred in 94.7% (18/19) and 63.2% (12/19) of the cases, respectively, with a delineated minimal common region of 8p21.1-p23.3. More specifically, three loci of homozygous deletions at 8p23.1 were noted in 21.1% (4/19) of the cases. This region contains the following possible target genes, which have previously not been implicated to play a pathogenic role in stage I SCCs: MSRA, MFHAS1, CLDN23, DEFB106A, DEFB105A, LOC441316, FAM90A7P and LOC441318. These findings indicate that genetic alterations on chromosome 8p may be the first step in the initiation of genomic instability in early SCCs, and the newly identified genes in the 8p23.1 chromosomal region might be of interest for the study of the pathophysiology of stage I SCC, as potential targets for therapeutic measures.

X-linked immunodeficiency with magnesium defect, Epstein-Barr virus infection, and neoplasia disease: a combined immune deficiency with magnesium defect

PURPOSE OF REVIEW

To describe the role of the magnesium transporter 1 (MAGT1) in the pathogenesis of 'X-linked immunodeficiency with magnesium defect, Epstein-Barr virus (EBV) infection, and neoplasia' (XMEN) disease and its clinical implications.

RECENT FINDINGS

The magnesium transporter protein MAGT1 participates in the intracellular magnesium ion (Mg) homeostasis and facilitates a transient Mg influx induced by the activation of the T-cell receptor. Loss-of-function mutations in MAGT1 cause an immunodeficiency named 'XMEN syndrome', characterized by CD4 lymphopenia, chronic EBV infection, and EBV-related lymphoproliferative disorders. Patients with XMEN disease have impaired T-cell activation and decreased cytolytic function of natural killer (NK) and CD8 T cells because of decreased expression of the NK stimulatory receptor 'natural-killer group 2, member D' (NKG2D). Patients may have defective specific antibody responses secondary to T cell dysfunction, but B cells have not been shown to be directly affected by mutations in MAGT1.

SUMMARY

XMEN disease has revealed a novel role for free intracellular magnesium in the immune system. Further understanding of the MAGT1 signaling pathway may lead to new diagnostic and therapeutic approaches.

Mesenchymal-like pancreatic cancer cells harbor specific genomic alterations more frequently than their epithelial-like counterparts

The aggressiveness of pancreatic cancer is associated with the acquisition of mesenchymal characteristics by a subset of pancreatic cancer cells. The factors driving the development of this subset are not well understood. In this study, we tested the hypothesis that acquisition of a mesenchymal phenotype occurs selectively in tumor cells that harbor specific enabling genetic alterations. We obtained whole-genome comparative genomic hybridization (CGH) measurements on pancreatic cancer cell lines that have either an epithelial-like (17 cell lines) or a mesenchymal-like (9 cell lines) phenotype in vitro. The total amounts of amplifications and deletions were equivalent between the epithelial and mesenchymal groups, but 20 genes showed a major difference between the groups in prevalence of alterations. All 20 alterations (18 deletions and 2 amplifications) were more prevalent in the mesenchymal group, confirming the advanced nature of this cellular subtype. CDKN2A was altered in more than 50% of both groups, but co-deletions in neighboring genes, and concomitant loss of gene expression, were more prevalent in the mesenchymal group, suggesting that the size of the loss around CDKN2A affects cell phenotype. Whole-genome CGH on 11 primary cancer tissues revealed that the 20 genes were altered at a higher prevalence (up to 55% of the cases for certain genes) than randomly selected sets of 20 genes, with the same direction of alteration as in the cell lines. These findings support the concept that specific genetic alterations enable phenotype plasticity and provide promising candidate genes for further research.

Structural basis of substrate specificity of human oligosaccharyl transferase subunit N33/Tusc3 and its role in regulating protein N-glycosylation

N-linked glycosylation of proteins in the endoplasmic reticulum (ER) is essential in eukaryotes and catalyzed by oligosaccharyl transferase (OST). Human OST is a hetero-oligomer of seven subunits. The subunit N33/Tusc3 is a tumor suppressor candidate, and defects in the subunit N33/Tusc3 are linked with nonsyndromic mental retardation. Here, we show that N33/Tusc3 possesses a membrane-anchored N-terminal thioredoxin domain located in the ER lumen that may form transient mixed disulfide complexes with OST substrates. X-ray structures of complexes between N33/Tusc3 and two different peptides as model substrates reveal a defined peptide-binding groove adjacent to the active site that can accommodate peptides in opposite orientations. Structural and biochemical data show that N33/Tusc3 prefers peptides bearing a hydrophobic residue two residues away from the cysteine forming the mixed disulfide with N33/Tusc3. Our results support a model in which N33/Tusc3 increases glycosylation efficiency for a subset of human glycoproteins by slowing glycoprotein folding.

TUSC3 loss alters the ER stress response and accelerates prostate cancer growth in vivo

Prostate cancer is the most prevalent cancer in males in developed countries. Tumor suppressor candidate 3 (TUSC3) has been identified as a putative tumor suppressor gene in prostate cancer, though its function has not been characterized. TUSC3 shares homologies with the yeast oligosaccharyltransferase (OST) complex subunit Ost3p, suggesting a role in protein glycosylation. We provide evidence that TUSC3 is part of the OST complex and affects N-linked glycosylation in mammalian cells. Loss of TUSC3 expression in DU145 and PC3 prostate cancer cell lines leads to increased proliferation, migration and invasion as well as accelerated xenograft growth in a PTEN negative background. TUSC3 downregulation also affects endoplasmic reticulum (ER) structure and stress response, which results in increased Akt signaling. Together, our findings provide first mechanistic insight in TUSC3 function in prostate carcinogenesis in general and N-glycosylation in particular.

Tumor suppressor candidate TUSC3 expression during rat testis maturation

Analysis of microarray data obtained by comparing gene expression between 2-week-old infant and 7-week-old mature SD rat testes revealed novel targets involved in tumor suppression. Reverse-transcription polymerase chain reaction and Northern blotting indicated that Tusc3 gene expression was upregulated in the normal maturing testis and prostate and other organs such as the cerebrum and ovary. Tumor suppressor candidate 3 protein expression was detected in these same organs at a size of about 40 kDa, in accord with the predicted molecular size. In situ hybridization and immunohistochemistry showed that mRNA and protein localization were prevalent in the testis spermatocytes and interstitial cells such as the Leydig cells, as well as prostate epithelial cells. These data suggest that TUSC3 is deeply involved in spermatogenesis in the testis, inducing sperm differentiation and maturation, and plays a role in normal prostate development and tumor suppression.

van der Zee AG, Wisman GBA, Sidransky D, Hoque MO. Association of promoter methylation of VGF and PGP9.5 with ovarian cancer progression

Purpose

To elucidate the role of biological and clinical impact of aberrant promoter hypermethylation (PH) in ovarian cancer (OC).

Experimental Design

PH of PGP9.5, HIC1, AIM1, APC, PAK3, MGMT, KIF1A, CCNA1, ESR1, SSBP2, GSTP1, FKBP4 and VGF were assessed by quantitative methylation specific PCR (QMSP) in a training set. We selected two genes (VGF and PGP9.5) for further QMSP analysis in a larger independent validation (IV) set with available clinical data. Biologic relevance of VGF gene was also evaluated.

Results

PH frequency for PGP9.5 and VGF were 85% (316/372) and 43% (158/366) respectively in the IV set of samples while no PH was observed in controls. In 372 OC cases with available follow up, PGP9.5 and VGF PH were correlated with better patient survival [Hazard Ratios (HR) for overall survival (OS) were 0.59 (95% Confidence Intervals (CI)  = 0.42–0.84, p = 0.004), and 0.73 (95%CI = 0.55–0.97, p = 0.028) respectively, and for disease specific survival (DSS) were 0.57 (95%CI 0.39–0.82, p = 0.003) and 0.72 (95%CI 0.54–0.96, p = 0.027). In multivariate analysis, VGF PH remained an independent prognostic factor for OS (HR 0.61, 95%CI 0.43–0.86, p<0.005) and DSS (HR 0.58, 95%CI 0.41–0.83, p<0.003). Furthermore, PGP9.5 PH was significantly correlated with lower grade, early stage tumors, and with absence of residual disease. Forced expression of VGF in OC cell lines inhibited cell growth.

Conclusions

Our results indicate that VGF and PGP9.5 PH are potential biomarkers for ovarian carcinoma. Confirmatory cohorts with longitudinal follow-up are required in future studies to define the clinical impact of VGF and PGP9.5 PH before clinical application.