Dystroglycan expression is reduced during prostate tumorigenesis and is regulated by androgens in prostate cancer cells

LINC01140 Hinders the Development of Breast Cancer Through Targeting miR-200b-3p to Downregulate DMD

Long non-coding RNAs (lncRNAs) are frequently reported to be involved in breast cancer (BC) oncogenicity. The goal of this study was to probe lncRNA LINC01140's role and action mechanism in BC. Relative LINC01140, miR-200b-3p, and dystrophin (DMD) levels were determined using quantitative real-time polymerase chain reaction (qRT-PCR). DMD protein levels in BC cells were quantified using Western blotting, and the targeting relationships were validated by luciferase reporter assays and RNA immunoprecipitation experiments. The proliferative potential of the cells was evaluated using CCK-8 and colony formation tests, while the migratory and invasive abilities of the cells were assessed using scratch and transwell assays. Apoptosis was assessed by flow cytometry. Nude mouse models have been established to allow the examination of tumor growth in vivo. Pronounced downregulation of LINC01140 and DMD, as well as upregulation of miR-200b-3p, was observed in BC. LINC01140 binds directly to miR-200b-3p to downregulate DMD expression. Ectopic LINC01140 expression not only limited tumor growth in vivo but also diminished the proliferation, migration, and invasion abilities of BC cells in vitro, however, it induced apoptosis in BC cells. Elevated miR-200b-3p expression stimulated the tumorigenic potential of BC cells and attenuated the suppressive effect of LINC01140 or DMD overexpression on BC cell malignancy, whereas DMD overexpression restricted the tumorigenic potential of BC cells. Overall, LINC01140 prevents BC development via the miR-200b-3p-DMD axis. These findings support the latent potential and usefulness of the LINC01140-miR-200b-3p-DMD network as a target for BC therapy.

Involvement of abnormal dystroglycan expression and matriglycan levels in cancer pathogenesis

Dystroglycan (DG) is a glycoprotein composed of two subunits that remain non-covalently bound at the plasma membrane: α-DG, which is extracellular and heavily O-mannosyl glycosylated, and β-DG, an integral transmembrane polypeptide. α-DG is involved in the maintenance of tissue integrity and function in the adult, providing an O-glycosylation-dependent link for cells to their extracellular matrix. β-DG in turn contacts the cytoskeleton via dystrophin and participates in a variety of pathways transmitting extracellular signals to the nucleus. Increasing evidence exists of a pivotal role of DG in the modulation of normal cellular proliferation. In this context, deficiencies in DG glycosylation levels, in particular those affecting the so-called matriglycan structure, have been found in an ample variety of human tumors and cancer-derived cell lines. This occurs together with an underexpression of the DAG1 mRNA and/or its α-DG (core) polypeptide product or, more frequently, with a downregulation of β-DG protein levels. These changes are in general accompanied in tumor cells by a low expression of genes involved in the last steps of the α-DG O-mannosyl glycosylation pathway, namely POMT1/2, POMGNT2, CRPPA, B4GAT1 and LARGE1/2. On the other hand, a series of other genes acting earlier in this pathway are overexpressed in tumor cells, namely DOLK, DPM1/2/3, POMGNT1, B3GALNT2, POMK and FKTN, hence exerting instead a pro-oncogenic role. Finally, downregulation of β-DG, altered β-DG processing and/or impaired β-DG nuclear levels are increasingly found in human tumors and cell lines. It follows that DG itself, particular genes/proteins involved in its glycosylation and/or their interactors in the cell could be useful as biomarkers of certain types of human cancer, and/or as molecular targets of new therapies addressing these neoplasms.

Biosynthetic Mechanisms and Biological Significance of Glycerol Phosphate-Containing Glycan in Mammals

Bacteria contain glycerol phosphate (GroP)-containing glycans, which are important constituents of cell-surface glycopolymers such as the teichoic acids of Gram-positive bacterial cell walls. These glycopolymers comprising GroP play crucial roles in bacterial physiology and virulence. Recently, the first identification of a GroP-containing glycan in mammals was reported as a variant form of O-mannosyl glycan on α-dystroglycan (α-DG). However, the biological significance of such GroP modification remains largely unknown. In this review, we provide an overview of this new discovery of GroP-containing glycan in mammals and then outline the recent progress in elucidating the biosynthetic mechanisms of GroP-containing glycans on α-DG. In addition, we discuss the potential biological role of GroP modification along with the challenges and prospects for further research. The progress in this newly identified glycan modification will provide insights into the phylogenetic implications of glycan.

PCYT2 synthesizes CDP-glycerol in mammals and reduced PCYT2 enhances the expression of functionally glycosylated α-dystroglycan

α-Dystroglycan (α-DG) is a highly glycosylated cell-surface protein. Defective O-mannosyl glycan on α-DG is associated with muscular dystrophies and cancer. In the biosynthetic pathway of the O-mannosyl glycan, fukutin (FKTN) and fukutin-related protein (FKRP) transfer ribitol phosphate (RboP). Previously, we reported that FKTN and FKRP can also transfer glycerol phosphate (GroP) from CDP-glycerol (CDP-Gro) and showed the inhibitory effects of CDP-Gro on functional glycan synthesis by preventing glycan elongation in vitro. However, whether mammalian cells have CDP-Gro or associated synthetic machinery has not been elucidated. Therefore, the function of CDP-Gro in mammals is largely unknown. Here, we reveal that cultured human cells and mouse tissues contain CDP-Gro using liquid chromatography tandem-mass spectrometry (LC-MS/MS). By performing the enzyme activity assay of candidate recombinant proteins, we found that ethanolamine-phosphate cytidylyltransferase (PCYT2), the key enzyme in de novo phosphatidylethanolamine biosynthesis, has CDP-Gro synthetic activity from glycerol-3-phosphate (Gro3P) and CTP. In addition, knockdown of PCYT2 dramatically reduced cellular CDP-Gro. These results indicate that PCYT2 is a CDP-Gro synthase in mammals. Furthermore, we found that the expression of functionally glycosylated α-DG is increased by reducing PCYT2 expression. Our results suggest an important role for CDP-Gro in the regulation of α-DG function in mammals.

High LARGE1 Expression May Predict Benefit from Adjuvant Chemotherapy in Resected Non-Small-Cell Lung Cancer

Background

LARGE1 plays a pivotal role in glycosylation of alpha-Dystroglycan (α-DG) and is aberrantly downregulated in cell lines originating from epithelium-derived cancers including lung cancer. However, the expression of LARGE1 and its clinical significance in NSCLC are not clear.

Materials and Methods

The data were collected from the TCGA database to investigate LARGE1 expression in stage I–III NSCLC and explore its associations with clinicopathological parameters and overall survival of patients. The prognostic role of LARGE1 was examined in subgroups according to clinical features and treatments. The results were validated in external cohorts from the NCBI GEO database. Gene Set Enrichment Analysis (GSEA) was performed to investigate the potential molecular mechanisms during LARGE1 alteration in NSCLC.

Results

LARGE1 was aberrantly downregulated in NSCLC compared with adjacent tissues and normal lung tissues and in tumors with advanced stage compared with early stage. There was only a trend of association between high LARGE1 with OS in multivariate analysis. Surprisingly, high LARGE1 was significantly associated with improved OS in a subgroup of the patients with adjuvant chemotherapy (ACT) and a significant interaction between LARGE1 expression and ACT was found. Improved OS after ACT was also found in patients with high LARGE1 compared to those with low LARGE1. When combining LARGE1 expression and ACT, compared with patients with non-ACT, HR of low LARGE1/ACT was 0.592 (95% CI=0.432–0.813, P=0.0012), and HR of high LARGE1/ACT was 0.124 (95% CI=0.031–0.505, P=0.0036). The results were verified in two external cohorts from the GEO database. GSEA indicated that LARGE1 might downregulate cell cycle pathway to improve ACT sensitivity and subsequently the prognosis in NSCLC.

Conclusion

High LARGE1 can be used to identify the patients with resected stage I–III NSCLC most likely to benefit from adjuvant chemotherapy.

Nintedanib treatment delays prostate dorsolateral lobe cancer progression in the TRAMP model: contribution to the epithelial-stromal interaction balance

Prostate cancer (PCa) progression mechanism has been linked to epithelial proliferation, tumor invasion ability, and growth factors. Nintedanib (BIBF 1120) has been reported as being FGF and VEGF pathway inhibitors, exhibiting antitumor activity. Thus, the objective herein was to characterize the early Nintedanib treatment effects on the structure and molecules involved in the basal membrane, the extracellular matrix (ECM) maintenance, in addition to the angiogenesis and mitogenic processes at different grades of prostatic tumor development in TRAMP mice. Therefore, 45 male TRAMP mice were divided into control groups: 8-week-old mice (TC8), 12-week-old mice (TC12), and 16-week-old mice (TC16); and treated groups with 10 mg/kg/day Nintedanib dose for 4 weeks. The treated groups were euthanized at 12 (TN12) and 16 (TN16) weeks of age. Samples from the dorsolateral lobe were collected and processed for light microscopy, immunohistochemistry, Western blotting, and microvessel density analysis. The results showed that early Nintedanib treatment led to an increase of healthy epithelium frequency and a reduction of LGPIN and a maximum vascularization density in the TN12 group. Also, treatment led to a well-differentiated adenocarcinoma decrease and an α and β dystroglycan and also laminin 1 increase in the TN16 group. IGFR1 decreased in the TN16 group. To conclude, early Nintedanib treatment led to a reduction in cancer severity, interfering in both ECM compounds and angiogenesis process to then contribute to a balance, not only in the prostatic epithelium and stroma, but also in the epithelial-stromal interaction during PCa progression.

The glycosyltransferase LARGE2 is repressed by Snail and ZEB1 in prostate cancer

Reductions in both expression of the dystroglycan core protein and functional glycosylation of the α-dystroglycan (αDG) subunit have been reported in a number of cancers and may contribute to disease progression. In the case of prostate cancer, one mechanism that contributes to αDG hypoglycosylation is transcriptional down-regulation of LARGE2 (GYLTY1B), a glycosyltransferase that produces the functional (laminin-binding) glycan on αDG, but the mechanism(s) underlying reduction of LARGE2 mRNA remain unclear. Here, we show that αDG hypoglycosylation is associated with epithelial-to-mesenchymal transition (EMT)-like status. We examined immunoreactivity for both functionally-glycosylated αDG and E-cadherin by flow cytometry and the relative expression of ZEB1 mRNA and the αDG glycosyltransferase LARGE2 mRNA in prostate and other cancer cell lines by quantitative RT-PCR. To study the role of ZEB1 and other transcription factors in the regulation of LARGE2, we employed overexpression and knockdown approaches. Snail- or ZEB1-driven EMT caused αDG hypoglycosylation by repressing expression of the LARGE2 mRNA, with both ZEB1-dependent and -independent mechanisms contributing to Snail-mediated LARGE2 repression. To examine the direct regulation of LARGE2 by Snail and ZEB1 we employed luciferase reporter and chromatin immunoprecipitation assays. Snail and ZEB1 were found to bind directly to the LARGE2 promoter, specifically to E/Z-box clusters. Furthermore, analysis of gene expression profiles of clinical samples in The Cancer Genome Atlas reveals negative correlation of LARGE2 and ZEB1 expression in various cancers. Collectively, our results suggest that LARGE2 is negatively regulated by Snail and/or ZEB1, revealing a mechanistic basis for αDG hypoglycosylation during prostate cancer progression and metastasis.

Correlation of deregulated like-acetylglucosaminyl transferase and aberrant α-dystroglycan expression with human tongue cancer metastasis

PURPOSE

The present study examined the correlation of α-dystroglycan (α-DG) expression and like-acetylglucosaminyl transferase (LARGE) with metastasis of human tongue cancer.

MATERIALS AND METHODS

Fifty human tongue cancer tissues and 2 tongue squamous cell carcinoma cell lines (CAL27 and SCC4) were involved. Immunohistochemistry was used to detect the expression of α-DG and LARGE. Methylation-specific polymerase chain reaction was performed to assess the methylation status of the LARGE gene promoter. CAL27 and SCC4 cells were transfected with exogenous LARGE and treated with 5-aza-2'-deoxycytidine (Aza-dC), respectively. Glycol sites of α-DG were detected by western blotting. In addition, the laminin overlay assay, cell adhesion assay, and invasion assay were performed.

RESULTS

Immunohistochemical results showed that decreased expression of VIA4-1 and IIH6 (antibodies that recognize the glycol sites of α-DG) were correlated with the lymph node metastasis of tongue cancer (n = 50; P = .016 and .025, respectively). Decreased LARGE expression and hypermethylation of the LARGE gene promoter were correlated with lymph node metastasis and α-DG glycosylation in human tongue cancer (n = 50; P = .043 and .015 respectively). In addition, LARGE overexpression and Aza-dC treatment actively led to restoration of functional α-DG expression, elevation of laminin binding, and decrease of migratory ability in cancer cells.

CONCLUSION

The results suggested that absent α-DG expression and LARGE deregulation were closely associated with nodal metastasis of tongue cancer. Aberrant α-DG expression and glycosylation were attributed at least in part to the abnormal epigenetic modification of LARGE, especially the hypermethylation of its promoter.

Nuclear targeting of dystroglycan promotes the expression of androgen regulated transcription factors in prostate cancer

Dystroglycan is frequently lost in adenocarcinoma, but the mechanisms and consequences are poorly understood. We report an analysis of β-dystroglycan in prostate cancer in human tissue samples and in LNCaP cells in vitro. There is progressive loss of β-dystroglycan immunoreactivity from basal and lateral surfaces of prostate epithelia which correlates significantly with increasing Gleason grade. In about half of matched bone metastases there is significant dystroglycan re-expression. In tumour tissue and in LNCaP cells there is also a tyrosine phosphorylation-dependent translocation of β-dystroglycan to the nucleus. Analysis of gene expression data by microarray, reveals that nuclear targeting of β-dystroglycan in LNCaP cells alters the transcription of relatively few genes, the most unregulated being the transcription factor ETV1. These data suggest that proteolysis, tyrosine phosphorylation and translocation of dystroglycan to the nucleus resulting in altered gene transcription could be important mechanisms in the progression of prostate cancer.

VHL-dependent regulation of a β-dystroglycan glycoform and glycogene expression in renal cancer

Identification of novel biomarkers and targets in renal cell carcinoma (RCC) remains a priority and one cellular compartment that is a rich potential source of such molecules is the plasma membrane. A shotgun proteomic analysis of cell surface proteins enriched by cell surface biotinylation and avidin affinity chromatography was explored using the UMRC2- renal cancer cell line, which lacks von Hippel-Lindau (VHL) tumour suppressor gene function, to determine whether proteins of interest could be detected. Of the 814 proteins identified ~22% were plasma membrane or membrane-associated, including several with known associations with cancer. This included β-dystroglycan, the transmembrane subunit of the DAG1 gene product. VHL-dependent changes in the form of β-dystroglycan were detected in UMRC2-/+VHL transfectants. Deglycosylation experiments showed that this was due to differential sialylation. Analysis of normal kidney cortex and conventional RCC tissues showed that a similar change also occurred in vivo. Investigation of the expression of genes involved in glycosylation in UMRC2-/+VHL cells using a focussed microarray highlighted a number of enzymes involved in sialylation; upregulation of bifunctional UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) was validated in UMRC2- cells compared with their +VHL counterparts and also found in conventional RCC tissue. These results implicate VHL in the regulation of glycosylation and raise interesting questions regarding the extent and importance of such changes in RCC.

Dystroglycan function is a novel determinant of tumor growth and behavior in prostate cancer

BACKGROUND

Dystroglycan is a ubiquitously expressed cell adhesion molecule frequently found to be altered or reduced in adenocarcinomas, however the mechanisms or consequences of dystroglycan loss have not been studied extensively.

METHODS

We examined the consequence of overexpression or RNAi depletion of dystroglycan on properties of in vitro growth migration and invasion of LNCaP, PC3, and DU145 prostate cancer cell lines.

RESULTS

Using LNCaP cells we observed cell density-dependent changes in β-dystroglycan with the appearance of several lower molecular weight species ranging in size from 43 to 26 kDa. The bands of 31 and 26 kDa were attributed to proteolysis, whereas bands between 43 and 38 kDa were a consequence of mis-glycosylation. The localization of β-dystroglycan in LNCaP colonies in culture also varied, cells with a mesenchymal appearance at the periphery of the colony had more pronounced membrane localization of dystroglycan. Whereas some cells demonstrated nuclear dystroglycan. Increased dystroglycan levels were inhibitory to growth in soft agar but promoted Matrigel invasion, whereas reduced dystroglycan levels promoted growth in soft agar but inhibited invasion. Similar results were also obtained for PC3 and DU145 cells.

CONCLUSIONS

This study suggests that changes in β-dystroglycan distribution within the cell and/or the loss of dystroglycan during tumorigenesis, through a combination of proteolysis and altered glycosylation, leads to an increased ability to grow in an anchorage independent manner, however dystroglycan may need to be re-expressed for cell invasion and metastasis to occur.

Loss of LARGE2 disrupts functional glycosylation of α-dystroglycan in prostate cancer

Dystroglycan (DG) is a cell surface receptor for extracellular matrix proteins and is involved in cell polarity, matrix organization, and mechanical stability of tissues. Previous studies documented loss of DG protein expression and glycosylation in a variety of cancer types, but the underlying mechanisms and the functional consequences with respect to cancer progression remain unclear. Here, we show that the level of expression of the βDG subunit as well as the glycosylation status of the αDG subunit inversely correlate with the Gleason scores of prostate cancers; furthermore, we show that the functional glycosylation of αDG is substantially reduced in prostate cancer metastases. Additionally, we demonstrate that LARGE2 (GYLTL1B), a gene not previously implicated in cancer, regulates functional αDG glycosylation in prostate cancer cell lines; knockdown of LARGE2 resulted in hypoglycosylation of αDG and loss of its ability to bind laminin-111 while overexpression restored ligand binding and diminished growth and migration of an aggressive prostate cancer cell line. Finally, our analysis of LARGE2 expression in human cancer specimens reveals that LARGE2 is significantly down-regulated in the context of prostate cancer, and that its reduction correlates with disease progression. Our results describe a novel molecular mechanism to account for the commonly observed hypoglycosylation of αDG in prostate cancer.

Increased expression of CD133 is a strong predictor of poor outcome in stage I colorectal cancer patients

OBJECTIVE

Stage I colorectal carcinomas display a highly variable behavior which is not accurately predicted by the available prognostic markers. CD133 is considered a useful marker to identify the so-called cancer stem cells in colorectal cancers (CRCs) and its expression has been shown to have prognostic significance in CRC patients. This study aimed to verify whether immunohistochemical evaluation of CD133 might correlate with the progression risk of stage I CRC patients.

MATERIAL AND METHODS

Expression levels of the CD133 molecule were analyzed and compared in two series of stage I surgically resected CRC patients showing disease progression and death for the disease and patients with no evidence of disease progression after at least 6 years after surgery.

RESULTS

A positive staining for CD133 was detected in 52% of the cases with poor prognosis and only in 9% of the group with good prognosis, and this difference was highly significant (p < 0.001). A significant correlation was detected between CD133 expression and histological parameters, such as tumor budding, vascular invasion, and presence of lymph node micrometastases but not tumor grading, gender, and age. Disease-free survival and cancer-specific survival of CD133 negative tumors were significantly longer compared to positive cases. In multivariate analyses, CD133 staining confirmed to be a predictor of shorter survival independent from vascular invasion but not from lymph nodes micrometastases.

CONCLUSIONS

These findings demonstrate that CD133 immunostaining is a useful predictor of high risk progression in stage I CRC patients and might help to identify patients eligible for adjuvant chemotherapy.

Increased expression of CD133 and reduced dystroglycan expression are strong predictors of poor outcome in colon cancer patients

Background

Expression levels of CD133, a cancer stem cell marker, and of the α-subunit of the dystroglycan (α-DG) complex, have been previously reported to be altered in colorectal cancers.

Methods

Expression levels of CD133 and α-DG were assessed by immunohistochemistry in a series of colon cancers and their prognostic significance was evaluated.

Results

Scattered cells positive for CD133 were rarely detected at the bases of the crypts in normal colonic mucosa while in cancer cells the median percentage of positive cells was 5% (range 0–80). A significant correlation was observed with pT parameter and tumor stage but not with tumor grade and N status. Recurrence and death from disease were significantly more frequent in CD133-high expressing tumors and Kaplan-Meier curves showed a significant separation between high vs low expressor groups for both disease-free (p = 0.002) and overall (p = 0.008) survival.

Expression of α-DG was reduced in a significant fraction of tumors but low α-DG staining did not correlate with any of the classical clinical-pathological parameters. Recurrence and death from the disease were significantly more frequent in α-DG-low expressing tumors and Kaplan-Meier curves showed a significant separation between high vs low expressor tumors for both disease-free (p = 0.02) and overall (p = 0.02) survival. Increased expression of CD133, but not loss of α-DG, confirmed to be an independent prognostic parameters at a multivariate analysis associated with an increased risk of recurrence (RR = 2.4; p = 0.002) and death (RR = 2.3; p = 0.003).

Conclusions

Loss of α-DG and increased CD133 expression are frequent events in human colon cancer and evaluation of CD133 expression could help to identify high-risk colon cancer patients.

The tumor suppressor HINT1 regulates MITF and β-catenin transcriptional activity in melanoma cells

Histidine triad nucleotide-binding protein 1 (HINT1) is a haploinsufficient tumor suppressor gene that inhibits the Wnt/β-catenin pathway in colon cancer cells and Microphthalmia-associated transcription factor (MITF) activity in human mast cells. MITF and β-catenin play a central role in melanocyte and melanoma cell survival, and this study aimed to investigate the effects of HINT1 on the MITF and β-catenin pathways in malignant melanoma cells. We found that HINT1 inhibits MITF and β-catenin transcriptional activity, and both proteins can be co-immunoprecipitated with an anti-HINT1-specific antibody in melanoma cell lines. Stable, constitutive overexpression of the HINT1 protein in human melanoma cells significantly impaired cell proliferation in vitro and tumorigenesis in vivo. These effects were associated with a decreased expression of cyclin D1 and BCL2, well known MITF and β-catenin transcription targets, respectively. We also demonstrated that BCL2 and cyclin D1 can partially rescue the HINT1-driven phenotype. Moreover, we found in ChIP assays that HINT1 binds the chromatin at MITF and β-catenin sites in BCL2 and cyclin D1 promoters, respectively, and that mSIN3a and HDAC1, well known transcriptional repressors, can be co-immunoprecipitated with an anti-HINT1-specific antibody. These findings support the tumor suppressor activity of HINT1 gene in melanoma cells by promoting the formation of non-functional complexes with oncogenic transcription factors like MITF and β-catenin.

Steroid hormone receptors, matrix metalloproteinases, insulin-like growth factor, and dystroglycans interactions in prostatic diseases in the elderly men

OBJECTIVES

The aim of this study was to evaluate the reactivity of steroid hormone receptors (SHRs), dystroglycans (DGs), matrix metalloproteinases (MMPs), insulin-like growth factor receptor (IGFR-1), and laminin (Lam) in both prostatic stromal and epithelial compartments showing different diseases in elderly men.

METHODS

Sixty prostatic samples were obtained from 60- to 90-year-old patients (mean 63 years) with and without prostatic lesions from Hospital of the School of Medicine, State University of Campinas (UNICAMP). The Samples were divided into standard (no lesions); high grade prostatic intraepithelial neoplasia (HGPIN); prostatic cancer (PC); and benign prostatic hyperplasia (BPH) groups. The samples were submitted to immunohistochemistry and Western blotting analyses. Research Ethics Committee of the School of Medicine, University of Campinas/UNICAMP (number 0094.0.146.000-08).

RESULTS

The results showed increased IGFR-1 and MMPs protein levels in the PC and HGPIN groups. Decreased αDG and βDG protein levels were verified in the PC and HGPIN groups. Androgen receptor (AR) reactivity was similar among all groups. Estrogen receptor α (Erα) immunoreactivity was more intense in the epithelium in the PC and HGPIN groups. Estrogen receptor β (ERβ) immunoreactivity was weak in the epithelium of the HGPIN and PC groups.

CONCLUSIONS

To conclude, there was an association among IGFR-1, MMPs, and SHRs, indicating IGFR-1 as a target molecule in prostate therapy, considering the IGF proliferative properties. Also, the distinct SHRs reactivities in the lesions in both prostatic compartments indicated different paracrine signals and pointed out the importance of estrogenic pathways in the activation of these disorders.

Microfabricated electrochemical cell-based biosensors for analysis of living cells in vitro

Cellular biochemical parameters can be used to reveal the physiological and functional information of various cells. Due to demonstrated high accuracy and non-invasiveness, electrochemical detection methods have been used for cell-based investigation. When combined with improved biosensor design and advanced measurement systems, the on-line biochemical analysis of living cells in vitro has been applied for biological mechanism study, drug screening and even environmental monitoring. In recent decades, new types of miniaturized electrochemical biosensor are emerging with the development of microfabrication technology. This review aims to give an overview of the microfabricated electrochemical cell-based biosensors, such as microelectrode arrays (MEA), the electric cell-substrate impedance sensing (ECIS) technique, and the light addressable potentiometric sensor (LAPS). The details in their working principles, measurement systems, and applications in cell monitoring are covered. Driven by the need for high throughput and multi-parameter detection proposed by biomedicine, the development trends of electrochemical cell-based biosensors are also introduced, including newly developed integrated biosensors, and the application of nanotechnology and microfluidic technology.

Fer kinase regulates cell migration through α-dystroglycan glycosylation

This is the first report on the role of Fer kinase in down-regulating the expression of laminin-binding glycans that suppress cell migration. The data show a novel biochemical interaction between glycan-based adhesion and cell migration, mediated by a tyrosine kinase.

Glycans of α-dystroglycan (α-DG), which is expressed at the epithelial cell–basement membrane (BM) interface, play an essential role in epithelium development and tissue organization. Laminin-binding glycans on α-DG expressed on cancer cells suppress tumor progression by attenuating tumor cell migration from the BM. However, mechanisms controlling laminin-binding glycan expression are not known. Here, we used small interfering RNA (siRNA) library screening and identified Fer kinase, a non–receptor-type tyrosine kinase, as a key regulator of laminin-binding glycan expression. Fer overexpression decreased laminin-binding glycan expression, whereas siRNA-mediated down-regulation of Fer kinase increased glycan expression on breast and prostate cancer cell lines. Loss of Fer kinase function via siRNA or mutagenesis increased transcription levels of glycosyltransferases, including protein O-mannosyltransferase 1, β3-N-acetylglucosaminyltransferase 1, and like-acetylglucosaminyltransferase that are required to synthesize laminin-binding glycans. Consistently, inhibition of Fer expression decreased cell migration in the presence of laminin fragment. Fer kinase regulated STAT3 phosphorylation and consequent activation, whereas knockdown of STAT3 increased laminin-binding glycan expression on cancer cells. These results indicate that the Fer pathway negatively controls expression of genes required to synthesize laminin-binding glycans, thus impairing BM attachment and increasing tumor cell migration.

Relative quantitation of proteins in expressed prostatic secretion with a stable isotope labeled secretome standard

Expressed prostatic secretion (EPS) is a proximal fluid directly derived from the prostate and, in the case of prostate cancer (PCa), is hypothesized to contain a repertoire of cancer-relevant proteins. Quantitative analysis of the EPS proteome may enable identification of proteins with utility for PCa diagnosis and prognosis. The present investigation demonstrates selective quantitation of proteins in EPS samples from PCa patients using a stable isotope labeled proteome standard (SILAP) generated through the selective harvest of the "secretome" from the PC3 prostate cancer cell line grown in stable isotope labeled cell culture medium. This stable isotope labeled secretome was digested with trypsin and equivalently added to each EPS digest, after which the resultant mixtures were analyzed by liquid chromatography-tandem mass spectrometry for peptide identification and quantification. Relative quantification of endogenous EPS peptides was accomplished by comparison of reconstructed mass chromatograms to those of the chemically identical SILAP peptides. A total of 86 proteins were quantified from 263 peptides in all of the EPS samples, 38 of which were found to be relevant to PCa. This work demonstrates the feasibility of using a SILAP secretome standard to simultaneously quantify many PCa-relevant proteins in EPS samples.

Periacinar retraction clefting in nonneoplastic and neoplastic prostatic glands: artifact or molecular involvement

A space between neoplastic acini and prostatic stroma is not rare and studies have interpreted this as an artifact, considering the absence of endothelial cells indicating vascular invasion. Thus, the aims of this work were to characterize and correlate the occurrence and extent of retraction clefting with the reactivities of α and β dystroglycan (αDG, βDG), laminin, matrix metalloproteinase 2 (MMP-2), p63, insulin-like growth factor 1(IGF-1), vimentin, and fibroblast growth factor 2 (FGF-2). The study was based on nonneoplastic and neoplastic prostatic tissues obtained from necropsies and retropubic radical prostatectomies. The results showed that periacinar retraction clefting was significantly more frequent in prostatic carcinoma samples than in normal prostatic acini. Most of the neoplastic acini (72.0%) showed retraction clefting of more than 50% of circumference, which were significantly more frequent in Gleason score 7 and 6. Decreased collagen and reticular and elastic fibers were verified in the stroma around neoplastic acini. Weak and discontinuous αDG, βDG, and laminin immunoreactivities and intensified MMP-2, vimentin, IGF-1 and FGF-2 immunoreactivities were verified in the neoplastic acini; p63 immunoreactivity was negative in all carcinomas. Thus, these findings showed that the lack of epithelial basal cells, DGs, and laminin and increased MMP-2, IGF-1, and FGF-7 could be considered important pathways in periacinar retraction occurrence. This study demonstrated the origin of and the biological mechanisms responsible for periacinar retraction clefting in prostatic carcinoma.

Identification of Endothelin-1 and NR4A2 as CD133-regulated genes in colon cancer cells

Several in vitro assays have been proposed to identify cancer stem cells (CSCs), including immunophenotyping, sphere assay and side population (SP) assay. CD133 antigen has been proposed as a CSC marker in colon cancer (CC). However, no functional data are available to date and conflicting results have been reported regarding its role as true CSC marker. Here we set out to identify a molecular signature associated with potential CSC. CD133(+) cells isolated from the CaCo-2 CC cell line were analysed by microarray molecular profiling compared to CD133(-) counterparts. Various differentially expressed genes were identified and the most relevant transcripts found to be over-expressed in CD133(+) cells were evaluated by quantitative RT-PCR in the CD133(+) fractions isolated from several CC cell lines. In the attempt to find a correlation between putative CSCs, isolated by means of CD133 immunophenotyping and the SP approach, we demonstrated a significant enrichment of CD133(+) cells within the SP fraction of CC cells, and comparison of the gene expression profiles revealed that Endothelin-1 (END-1) and nuclear receptor subfamily 4, group A, member 2 (NR4A2) transcripts are highly expressed in both CD133(+) and SP fractions of CC cells. Moreover, depletion of CD133 by siRNA induced a significant attenuation of END-1 and NR4A2 expression levels in CaCo-2 cells, while expression of all three molecules decreased during sodium butyrate-induced differentiation. In conclusion, we have identified a molecular signature associated with potential CSCs and showed for the first time the existence of a functional relationship between CD133, END-1 and NR4A2 expression in colon cancer cells.

Reduced glycosylation of α-dystroglycans on carcinoma cells contributes to formation of highly infiltrative histological patterns in prostate cancer

BACKGROUND

α-Dystroglycan (DG) carries glycan chains that bind to laminin and thus function in homeostasis of not only skeletal muscle but also of various epithelial cells. Loss of glycosylation has been suggested to play important roles in tumor development, particularly in detachment and migration of carcinoma cells. We previously reported that glycosylation of α-DG, but not levels of α-DG core protein itself, is reduced in prostate carcinoma. In this study, we investigate the association between reduction of laminin-binding glycans on α-DG and the degree of tumor cell differentiation and/or infiltrative properties, as assessed by the Gleason grading system.

METHODS

Immunohistochemical analysis of 146 biopsy specimens of prostate adenocarcinoma with various Gleason scores was carried out employing IIH6 and 6C1 antibodies, which recognize laminin-binding glycans on α-DG and α-DG core proteins, respectively. Double immunofluorescence staining was performed to evaluate colocalization of α-DG and laminin, and to determine which types of epithelial cells express laminin-binding glycans on α-DG.

RESULTS

Reduction of α-DG glycosylation, rather than loss of α-DG core protein, was correlated with higher Gleason patterns. Reduction was most conspicuous at the interface between carcinoma cells and the basement membrane. In addition, in non-neoplastic prostate glands, laminin-binding glycans were expressed predominantly on the basolateral surface of basal cells.

CONCLUSIONS

Reduced expression of laminin-binding glycans on α-DG may contribute to formation of highly infiltrative behavior of prostate carcinoma cells. Substantial reduction of laminin-binding glycans in carcinoma tissue could be partly ascribed to disappearance of pre-existing basal cells.

Dystroglycan is associated with tumor progression and patient survival in gastric cancer

Previous reports had indicated that there was a possible correlation of dystroglycan (DG) with biological behavior of cancer cells and cancer patients' survival. However, the role of DG expression in gastric cancer was rarely studied. In this study, α-DG and β-DG expression were determined by immunohistochemistry in specimens of primary cancer, metastatic lymph node, distal metastatic lesion, and their normal counterpart tissues in 20 gastric cancer patients. Correlations between α-DG and β-DG expression and prognosis were retrospectively analyzed. Our results found that positive expression of α-DG in normal mucosa, paired primary tumor, metastatic lymph node and distal metastatic site was detected in 95%, 70%, 25%, and 5% specimens, individually. Regarding β-DG,it was 70%, 55%, 10%, and 10%, individually. Patients who had lower α-DG expression in tumors than in normal counterparts showed poor survival (p = 0.002), whereas such a correlation was not found in the case of β-DG (p = 0.079). Difference of α-DG between primary tumor and its normal counterparts was an independent prognostic factor in gastric cancer with distal metastasis. This study showed DG expression was gradually reduced during tumor progression. Different expression of α-DG, but not β-DG, between primary tumor and normal specimen, correlated with patient survival, implicating a potential marker for gastric cancer prognosis.

Loss of nuclear p27(kip1) and α-dystroglycan is a frequent event and is a strong predictor of poor outcome in renal cell carcinoma

Expression levels of p27(kip1) , a negative regulator of the G1 phase of the cell cycle, and 8-hydroxydeoxyguanosine (8-OHdG), a marker of oxidative DNA damage, were assessed by immunostaining in a series of renal cell carcinomas (RCCs) and their prognostic significance was evaluated. Expression of p27(kip1) as well as of the α-subunit of the dystroglycan (DG) complex, previously reported to be altered in RCC, was also evaluated by western blot analysis. Nuclear expression of p27(kip1) was reduced in a significant fraction of tumors and low p27(kip1) staining correlated with higher tumor grade (P < 0.01). Recurrence and death from clear cell RCCs were significantly more frequent in p27(kip1) -low expressing tumors and Kaplan-Meier curves showed a significant separation between high vs low expressor groups for both disease-free (P = 0.011) and overall (P = 0.002) survival. Low nuclear expression of p27(kip1) as well as loss of α-DG were confirmed to be independent prognostic parameters at a multivariate analysis and the simultaneous loss of both molecules defined a "high-risk" group of patients with increased risk of recurrence (RR = 28.7; P = 0.01) and death (RR = 12.9; P = 0.03). No significant correlation with clinical or pathological parameters was found for 8-OHdG staining. Western blot analyses suggested a post-translational mechanism for the loss of α-DG expression and demonstrated that cytoplasmic dislocation of the protein contributes to the loss of active nuclear p27(kip1) . Loss of nuclear p27(kip1) is a frequent event in human RCCs and is a powerful predictor of poor outcome which, in combination with low DG expression, could help to identify high-risk patients with clear cell RCC.

Expression of alpha-dystroglycan correlates with tumour grade and predicts survival in oral squamous cell carcinoma

AIMS

Dystroglycan (DG) is a non-integrin adhesion molecule connecting the extracellular matrix to the actin cytoskeleton. Decreased expression of DG has been reported in several human cancers and related to tumour aggressiveness.

METHODS

Expression of the alpha-DG subunit was evaluated by immunostaining in a series of oral squamous cell carcinoma (OSCC) and its relation with traditional prognostic indicators and with the clinical outcome of the patients was evaluated.

RESULTS

Alpha-DG expression was easily detected in normal epithelium with a mean percentage of positive cells >80% but was undetectable in a significant fraction (59%) of OSCC. Loss of alpha-DG staining correlated with higher tumour grade (p = 0.04) and stage (p = 0.01), with nodal involvement (p = 0.001) and with an increased risk of recurrence (p = 0.002) and death (p = 0.004) in a univariate analysis, but it was not confirmed as an independent predictor of clinical outcome in a multivariate analysis.

CONCLUSIONS

Loss of alpha-DG expression, which corresponds to loss of a functional DG complex, is a frequent event in human OSCC. Further studies are warranted on the role of this molecule in the entire multistep process of oral squamous tumorigenesis.

Post-translational modulation of CD133 expression during sodium butyrate-induced differentiation of HT29 human colon cancer cells: implications for its detection

The CD133 molecule has been proposed as a surface marker of cancer stem cells in several human malignancies, including colon cancers. The function and the mechanisms regulating CD133 expression remain unknown. The HT29 human colon cancer cells undergo differentiation following treatment with various agents and represent a useful in vitro model of colon differentiation. This study evaluated the behavior of CD133 during sodium butyrate-induced differentiation of HT29 cells. Treatment with sodium butyrate induced a progressive decrease of CD133 expression, as assessed by flow cytometry using the AC133 monoclonal antibody. Indeed, expression of CD133, which was about 47% in untreated control cells, gradually decreased down to about 3% after 72 h in a time- and dose-dependent manner. No relationship was observed between CD133 protein evaluated by flow cytometry and mRNA expression level, and no changes were detected in the methylation status of the CD133 gene promoter during HT29 differentiation. Moreover, the expression of the CD133 protein, evaluated by Western blot analysis using a specific anti-CD133 antibody directed against the C-terminal intracytoplasmic region of human CD133 protein, did not correlate with flow cytometry results. Different results were also obtained using the two antibodies to analyze the expression of the CD133 molecule in human colon cancers. These findings demonstrate that membrane expression of the CD133 stem cell marker might undergo a complex regulation during differentiation of colon cells and suggest that HT29 cells are a useful in vitro model to study the mechanisms involved in this regulation which likely occurs at a post-transcriptional level.

Dystroglycan is not required for maintenance of the luminal epithelial basement membrane or cell polarity in the mouse prostate

BACKGROUND

Dystroglycan is a cell-surface receptor for extracellular matrix proteins including laminins and perlecan. Prior studies have shown its involvement in assembly and/or maintenance of basement membrane structures, cell polarity and tissue morphogenesis; and its expression is often reduced in prostate and other cancers. However, the role of dystroglycan in normal epithelial tissues such as the prostate is unclear.

METHODS

To investigate this, we disrupted dystroglycan expression in the prostate via a conditional gene targeting strategy utilizing Cre recombinase expressed in luminal prostate epithelial cells.

RESULTS

Contrary to expectations, deletion of dystroglycan in luminal epithelial cells resulted in no discernable phenotype as judged by histology, basement membrane ultrastructure, localization of dystroglycan ligands, cell polarity or regenerative capacity of the prostate following castration. Dystroglycan expression remains in keratin-5-positive basal cells located in the proximal ducts where dystroglycan expression is elevated in regenerating prostates.

CONCLUSIONS

Our results show that dystroglycan in luminal epithelial cells is not required for the maintenance of basement membranes, cell polarity or prostate regeneration. However, it is possible that persistent dystroglycan expression in the basal cell compartment may support these or other functions.

A tumor suppressor function of laminin-binding alpha-dystroglycan

Interaction of epithelial cells with basement membrane (BM) is mediated by cell-adhesion molecules, which regulate cell proliferation, motility, and differentiation by integrating signals from extracellular matrix and soluble factors. alpha-Dystroglycan (alpha-DG) is one of the most important adhesion molecules in epithelial cell-BM interaction. alpha-DG serves as the cell surface receptor for several major BM proteins, including laminin, perlecan, and agrin. The laminin G-like domain in all these proteins binds to a unique glycan structure, so-called laminin-binding glycan, attached to alpha-DG with high affinity. Formation of the laminin-binding glycan is required for the BM assembly, and loss or deficiency of the glycan causes muscular dystrophy. We studied the role of this alpha-DG-specific glycan modification in tumor development, and identified a tumor suppressor function of the laminin-binding alpha-DG. In this chapter, we describe methods used to isolate the cell populations from human prostate cancer cell line PC3 and characterize their potentials in tumor formation and metastasis in vitro and in vivo.

Increments of alpha-dystroglycan expression in liver metastasis correlate with poor survival in gastric cancer

BACKGROUND

Dystroglycan (DG) is a recently focused adhesion molecule with possible roles in cancer development and progression. We investigated correlations between alpha-DG expression and prognosis in gastric carcinoma with liver metastasis.

METHODS

For 40 patients with gastric adenocarcinoma and liver-only metastasis, alpha-DG expression was determined by immunohistochemistry in paraffin-embedded surgical specimens of resected stomach tumor, resected liver metastasis, and their normal counterpart tissues. Correlations between alpha-DG expression and prognosis were retrospectively analyzed.

RESULTS

alpha-DG expression was higher in primary gastric cancer (P = 0.006) and lower in liver metastasis (P = 0.002) than in each normal counterpart. In primary stomach cancer, patients who had lower alpha-DG expression in tumors than in normal counterparts showed poor overall survival (OS) (P = 0.028). In contrast, in the liver, patients who had higher alpha-DG expression in tumors than in normal counterparts showed poor OS (P = 0.022). Also, higher alpha-DG expression in liver metastasis than in stomach tumors led to poor recurrence-free survival (P = 0.023) and OS (P = 0.056).

CONCLUSIONS

This approach may be used to further understanding of the pathogenesis of liver metastasis from gastric cancer. Further studies are warranted to reveal the mechanisms of alpha-DG dysregulation in liver metastasis.

Identification of Sp1 and GC-boxes as transcriptional regulators of mouse Dag1 gene promoter

Dystroglycan is a widely expressed adhesion complex that anchors cells to the basement membrane and is involved in embryonic development and differentiation. Dystroglycan expression is frequently reduced in human dystrophies and malignancies, and its molecular functions are not completely understood. Several posttranslational mechanisms have been identified that regulate dystroglycan expression and/or function, while little is known about how expression of the corresponding Dag1 gene is regulated. This study aimed to clone the Dag1 gene promoter and to characterize its regulatory elements. Analysis of the mouse Dag1 gene 5'-flanking region revealed a TATA and CAAT box-lacking promoter including a GC-rich region. Transfection studies with serially deleted promoter constructs allowed us to identify a minimal promoter region containing three Specificity protein 1 (Sp1) sites and an E-box. Sp1 binding was confirmed by chromatin immunoprecipitation assay, and Sp1 downregulation reduced dystroglycan expression in muscle cells. Treatment with 5-aza-2'-deoxycytidine and/or the histone deacetylase inhibitor trichostatin A increased Dag1 mRNA expression levels in myoblasts, and methylation decreased promoter activity in vitro. Furthermore, Dag1 gene promoter methylation was reduced while its expression increased during differentiation of C(2)C(12) myoblast cells in myotubes. In conclusion, for the first time we have characterized the activity of the mouse Dag1 gene promoter, confirming a complex regulation by Sp1 transcription factor, DNA methylation, and histone acetylation, which might be relevant for a better understanding of the physiopathology of the dystroglycan complex.

Tumor suppressor function of laminin-binding alpha-dystroglycan requires a distinct beta3-N-acetylglucosaminyltransferase

Alpha-dystroglycan (alpha-DG) represents a highly glycosylated cell surface molecule that is expressed in the epithelial cell-basement membrane (BM) interface and plays an essential role in epithelium development and tissue organization. The alpha-DG-mediated epithelial cell-BM interaction is often impaired in invasive carcinomas, yet roles and underlying mechanisms of such an impaired interaction in tumor progression remain unclear. We report here a suppressor function of laminin-binding glycans on alpha-DG in tumor progression. In aggressive prostate and breast carcinoma cell lines, laminin-binding glycans are dramatically decreased, although the amount of alpha-DG and beta-dystroglycan is maintained. The decrease of laminin-binding glycans and consequent increased cell migration were associated with the decreased expression of beta3-N-acetylglucosaminyltransferase-1 (beta3GnT1). Forced expression of beta3GnT1 in aggressive cancer cells restored the laminin-binding glycans and decreased tumor formation. beta3GnT1 was found to be required for laminin-binding glycan synthesis through formation of a complex with LARGE, thus regulating the function of LARGE. Interaction of the laminin-binding glycans with laminin and other adhesive molecules in BM attenuates tumor cell migratory potential by antagonizing ERK/AKT phosphorylation induced by the components in the ECM. These results identify a previously undescribed role of carbohydrate-dependent cell-BM interaction in tumor suppression and its control by beta3GnT1 and LARGE.

Expression of beta-dystroglycan is reduced or absent in many human carcinomas

AIMS

Dystroglycan is an important structural and signalling protein that is expressed in most human cells. alpha-Dystroglycan has been investigated and found to be reduced in human cancers, but there is only one published study on the expression of beta-dystroglycan in human cancer and that was only on small numbers of breast and prostatic cancers. The aim was to conduct a comprehensive immunohistochemical survey of the expression of beta-dystroglycan in normal human tissues and common cancers.

METHODS AND RESULTS

Triplicate tissue microarrays of 681 samples of normal human tissues and common cancers were stained using an antibody directed against the cytoplasmic component of beta-dystroglycan. beta-Dystroglycan was strongly expressed at the intercellular junctions and basement membranes of all normal human epithelia. Expression of beta-dystroglycan was absent or markedly reduced in 100% of oesophageal adenocarcinomas, 97% of colonic cancers, 100% of transitional cell carcinomas of the urothelium and 94% of breast cancers. In the breast cancers, the only tumours that showed any retention of beta-dystroglycan expression were small low-grade oestrogen receptor-positive tumours. The only cancers that showed retention of beta-dystroglycan expression were cutaneous basal cell carcinomas.

CONCLUSIONS

There is loss or marked reduction of beta-dystroglycan expression (by immunohistochemistry) in the vast majority of human cancers surveyed. Since beta-dystroglycan is postulated to have a tumour suppressor effect, this loss may have important functional significance.

Aberrant expression of beta-dystroglycan may be due to processing by matrix metalloproteinases-2 and -9 in oral squamous cell carcinoma

Dystroglycan (DG), a non-integrin adhesion molecule, is formed by two subunits, alpha- and beta-DG, which bind to extracellular matrix molecules and cytoskeleton. DG expression is frequently reduced in human cancers and has been related to tumor grade and aggressiveness. The exact proteolytic processing of beta-DG remains largely unknown. In this study, we investigated the correlation of beta-DG degradation with invasiveness in oral squamous cell carcinoma (OSCC) and its possible processing by matrix metalloproteinases (MMP). Immunohistochemical staining was used to assess beta-DG expression in 60 cases of OSCC. The effects of the MMP inhibitor 1,10-phenanthroline on tumour cell invasion and beta-DG degradation were investigated using in vitro invasion assays and immunoblot analysis. Co-immunoprecipitation and N-terminal sequencing were performed to determine the possible cleavage site of beta-DG by MMP. The alpha- and beta-DG expression was reduced or lost in OSCC. In four cell lines studied (SCC-4, SCC-9, SCC-15 and SCC-25), Western blot revealed a 30kDa fragment of beta-dystroglycan (beta-DG30) in addition to beta-DG itself. beta-DG degradation was almost abolished using 1,10-phenanthroline and there was a significant decrease in tumor cell invasion. The N-terminal sequence of beta-DG30 was detected as Ile-Asn-Thr-Asn, or Ile-Val-Thr-Gln. We conclude that beta-DG degradation may play a role both in OSCC invasion and metastasis. MMP activity seems to be one mechanism for beta-DG processing into beta-DG30.

Processing and secretion of the N-terminal domain of alpha-dystroglycan in cell culture media

Alpha-dystroglycan (alpha-DG) plays a crucial role in maintaining the stability of muscle cell membrane. Although it has been shown that the N-terminal domain of alpha-DG (alpha-DG-N) is cleaved by a proprotein convertase, its physiological significance remains unclear. We show here that native alpha-DG-N is secreted by a wide variety of cultured cells into the culture media. The secreted alpha-DG-N was both N- and O-glycosylated. Finally, a small amount of alpha-DG-N was detectable in the normal human serum. These observations indicate that the cleavage of alpha-DG-N is a widespread event and suggest that the secreted alpha-DG-N might be transported via systemic circulation in vivo.