A 2-Mb sequence-ready contig map and a novel immunoglobulin superfamily gene IGSF4 in the LOH region of chromosome 11q23.2

Short-stalk isoforms of CADM1 and CADM2 trigger neuropathogenic measles virus-mediated membrane fusion by interacting with the viral hemagglutinin

Measles virus (MeV), an enveloped RNA virus in the family Paramyxoviridae, usually causes acute febrile illness with skin rash, but in rare cases persists in the brain, causing a progressive neurological disorder, subacute sclerosing panencephalitis (SSPE). MeV bears two envelope glycoproteins, the hemagglutinin (H) and fusion (F) proteins. The H protein possesses a head domain that initially mediates receptor binding and a stalk domain that subsequently transmits the fusion-triggering signal to the F protein. We have recently shown that cell adhesion molecule 1 (CADM1, also known as IGSF4A, Necl-2, SynCAM1) and CADM2 (also known as IGSF4D, Necl-3, SynCAM2) are host factors enabling cell-cell membrane fusion mediated by hyperfusogenic F proteins of neuropathogenic MeVs as well as MeV spread between neurons lacking the known receptors. CADM1 and CADM2 interact in cis with the H protein on the same cell membrane, triggering hyperfusogenic F protein-mediated membrane fusion. Multiple isoforms of CADM1 and CADM2 containing various lengths of their stalk regions are generated by alternative splicing. Here we show that only short-stalk isoforms of CADM1 and CADM2 predominantly expressed in the brain induce hyperfusogenic F protein-mediated membrane fusion. While the known receptors interact in trans with the H protein through its head domain, these isoforms can interact in cis even with the H protein lacking the head domain and trigger membrane fusion, presumably through its stalk domain. Thus, our results unveil a new mechanism of viral fusion triggering by host factors. Importance Measles, an acute febrile illness with skin rash, is still an important cause of childhood morbidity and mortality worldwide. Measles virus (MeV), the causative agent of measles, may also cause a progressive neurological disorder, subacute sclerosing panencephalitis (SSPE), several years after acute infection. The disease is fatal, and no effective therapy is available. Recently, we have reported that cell adhesion molecule 1 (CADM1) and CADM2 are host factors enabling MeV cell-to-cell spread in neurons. These molecules interact in cis with the MeV attachment protein on the same cell membrane, triggering the fusion protein and causing membrane fusion. CADM1 and CADM2 are known to exist in multiple splice isoforms. In this study, we report that their short-stalk isoforms can induce membrane fusion by interacting in cis with the viral attachment protein independently of its receptor-binding head domain. This finding may have important implications for cis-acting fusion triggering by host factors.

CADM1 and SPC25 Gene Mutations in Lung Cancer Patients With Idiopathic Pulmonary Fibrosis

Introduction

To investigate the genomic profiles of patients with lung cancer with idiopathic pulmonary fibrosis (IPF-LC), mechanism of carcinogenesis, and potential therapeutic targets.

Methods

We analyzed 29 matched, surgically resected, cancerous and noncancerous lung tissues (19 IPF-LC and 10 non–IPF-LC) by whole-exome sequencing and bioinformatics analysis and established a medical-engineering collaboration with the Department of Engineering of the Tokyo University of Science.

Results

In IPF-LC, CADM1 and SPC25 were mutated at a frequency of 47% (9 of 19) and 53% (10 of 19), respectively. Approximately one-third of the IPF-LC cases (7 of 19; 36%) had both mutations. Pathway analysis revealed that these two genes are involved in transforming growth factor-β1 signaling. CADM1 and SPC25 gene mutations decreased the expression of CADM1 and increased that of SPC25 revealing transforming growth factor-β1–induced epithelial-to-mesenchymal transition and cell proliferation in lung cancer cells. Furthermore, treatment with paclitaxel and DNMT1 inhibitor suppressed SPC25 expression.

Conclusions

CADM1 and SPC25 gene mutations may be novel diagnostic markers and therapeutic targets for IPF-LC.

Identification of rare variants in CADM1 in patients with anorexia nervosa

As a polygenic psychiatric disorder, the genetics of anorexia nervosa (AN) remains largely unexplored. Recently a large GWAS meta-analysis identified a significant SNP (rs6589488) as associated with AN. We suggested that rs6589488 might have gotten its association as being in linkage disequilibrium with unknown variants or functional intronic variants. In a selective cohort containing 51 patients diagnosed with restrictive subtype AN, we screened the whole coding region of the CADM1gene by Sanger sequencing and further investigated if these variants are associated with specific outcome. Only 13 single nucleotide polymorphisms, including 2 missense variants, 2 synonymous variants, 2 variants located at 5'-UTR and 7 intronic variants, including rs6589488, were identified in our AN cohort. The 2 missense variants, p.Val5Leu and p.Asp285Glu were not predicted to be deleterious. In conclusion, the intronic initial variant appears to be not associated with causative coding variant in the vicinity. If CADM1 is not the AN predisposition factor, the causative variant probably lies within 1 Mb of CADM1. Interestingly, among the 7 closest genes to CADM1, the nicotinamide N-methyltransferase (NNMT) gene is known to be associated with obesity. We suggest that the intronic variant in CADM1 could be in linkage disequilibrium with other causative variants located in NNMT.

Identification of markers associated with estimated breeding value and horn colour in Hungarian Grey cattle

OBJECTIVE

This study was conducted to estimate effect of single nucleotide polymorphisms (SNP) on the estimated breeding value of Hungarian Grey (HG) bulls and to find markers associated with horn colour.

METHODS

Genotypes 136 HG animals were determined on Geneseek high-density Bovine SNP 150K BeadChip. A multi-locus mixed-model was applied for statistical analyses.

RESULTS

Six SNPs were identified to be associated (-log10P>10) with green and white horn. These loci are located on chromosome 1, 3, 9, 18, and 25. Seven loci (on chromosome 1, 3, 6, 9, 10, 28) showed considerable association (-log10P>10) with the estimated breeding value.

CONCLUSION

Analysis provides markers for further research of horn colour and supplies markers to achieve more effective selection work regarding estimated breeding value of HG.

Comparison of SynCAM1/CADM1 PDZ interactions with MUPP1 using mammalian and bacterial pull-down systems

BACKGROUND

Synaptic cell adhesion molecule 1 (SynCAM1) also known as cell adhesion molecule 1 (CADM1) is a transmembrane cell adhesion protein that operates in a variety of physiological and pathological cellular contexts, and its interaction with the PDZ signalling protein MUPP1 have been previously implicated in autism spectrum disorder (ASD).

METHODS

We used in vitro pull-down systems based on the bacterial and mammalian extracts to study SynCAM1/CADM1 PDZ interactions with MUPP1 at various conditions.

RESULTS

So far, the investigated interaction of SynCAM1/CADM1 with MUPP1 has been mostly attributed to an unspecified region of MUPP1 PDZ domains 1-5 or exclusively to domain 2, using a yeast two-hybrid system. We also confirmed the single interaction of native synaptosomal CADM1 with PDZ domain 2. However, in this work, using recombinant proteins overexpressed in bacteria, we found an in vitro pull-down conditions in which all first five domains and, to a much lesser extent, MUPP1 domains 7 and 11 significantly interacted with the whole C-terminal domain of SynCAM1/CADM1. These PDZ interactions were confirmed by a pull-down assay using the last seven amino acids of the SynCAM1/CADM1 PDZ motif and using two fusion partners. Multiple interactions were additionally replicated using the continuous N-terminal MUPP1 protein fragment, which included first five PDZ domains, containing either intact or mutated domain 2.

CONCLUSIONS

We hypothesize that multiple interactions might exist in vivo, representing transient low-affinity interactions or alternative binding sites on MUPP1 when domain 2 is occupied or occluded by the interaction with other ligands. This newly identified interactions extend the potential genetic mutations, possibly affecting SynCAM1/CADM1/MUPP1 function. Possible reasons for the absence of some of the identified CADM1 PDZ interactions in mammalian extracts are discussed.

Comparative expression of cell adhesion molecule1 (CADM1) in the testes of experimental mice and some farm animals

Cell adhesion molecule1 (CADM1) is a member of the immunoglobulin superfamily (IGSF) that has been found in mammalian testis and plays a substantial role in cell-to-cell interaction via either hemophilic (between spermatogenic cells) or heterophilic (between spermatogenic and somatic Sertoli cells) binding. The present study investigated the immunohistochemical localization of CADM1 in the testes of adult mice (Mus musculus), as well as sexually mature bull (Bos taurus), camel (Camelus dromedarius), and donkey (Equus asinus), using immunohistochemical techniques. The results revealed that CADM1 expression was observed in the spermatogonia and early spermatocytes as well as elongated spermatids in the mice testes; however, in the bull testis, its expression was restricted to the elongated spermatids. This expression was found in some of the early spermatocytes and elongated spermatids of the rutting camel testis but only found in the elongated spermatids of the non-rutting camel testis. Interestingly, CADM1 expression was detected in the spermatogonia, early spermatocytes, and elongated spermatids of the donkey testis. On the other hand, there was no expression of CADM1 observed in the Sertoli or interstitial cells. In conclusion, the expression of CADM1 during spermatogenesis differed among species and between rutting and non-rutting camel. Accordingly, this study emphasized the crucial role of CADM1 in the process of spermatogenesis and how it is related to sexual activity in both experimental and farm animals.

Downregulating SynCAM and MPP6 expression is associated with ovarian cancer progression

Synaptic cell adhesion molecules (SynCAMs) are single transmembrane proteins that belong to the immunoglobulin superfamily of cell adhesion molecules. In the present study, a decrease in SynCAM levels in ovarian tumor tissues compared with normal tissues is reported; the downregulation was accompanied by the grade malignancy. The observations suggested that SynCAM may be essential for important novel functions in ovarian cancer. Further experiments showed that low SynCAM expression inhibited membrane palmitoylated protein 6 (MPP6) expression, a member of the palmitoylated membrane protein subfamily of peripheral membrane-associated guanylate kinases. In addition, low levels of MPP6 in ovarian tumor tissues correlated with shorter patient survival. A SynCAM-regulated pathway may provide molecular targets for the treatment of ovarian cancer and novel biomarkers to be used in clinical diagnosis.

Negative feedback loop of bone resorption by NFATc1-dependent induction of Cadm1

Trimethylation of histone H3 lysine 4 and lysine 27 (H3K4me3 and H3K27me3) at gene promoter regions critically regulates gene expression. Key developmental genes tend to exhibit changes in histone modification patterns from the H3K4me3/H3K27me3 bivalent pattern to the H3K4me3 monovalent pattern. Using comprehensive chromatin immunoprecipitation followed by sequencing in bone marrow-derived macrophages (BMMs) and mature osteoclasts, we found that cell surface adhesion molecule 1 (Cadm1) is a direct target of nuclear factor of activated T cells 1 (NFATc1) and exhibits a bivalent histone pattern in BMMs and a monovalent pattern in osteoclasts. Cadm1 expression was upregulated in BMMs by receptor activator of nuclear factor kappa B ligand (RANKL), and blocked by a calcineurin/NFATc1 inhibitor, FK506. Cadm1-deficient mice exhibited significantly reduced bone mass compared with wild-type mice, which was due to the increased osteoclast differentiation, survival and bone-resorbing activity in Cadm1-deficient osteoclasts. These results suggest that Cadm1 is a direct target of NFATc1, which is induced by RANKL through epigenetic modification, and regulates osteoclastic bone resorption in a negative feedback manner.

Mast cells in asthma--state of the art

Mast cells (MCs) play a central role in tissue homoeostasis, sensing the local environment through numerous innate cell surface receptors. This enables them to respond rapidly to perceived tissue insults with a view to initiating a co-ordinated programme of inflammation and repair. However, when the tissue insult is chronic, the ongoing release of multiple pro-inflammatory mediators, proteases, cytokines and chemokines leads to tissue damage and remodelling. In asthma, there is strong evidence of ongoing MC activation, and their mediators and cell-cell signals are capable of regulating many facets of asthma pathophysiology. This article reviews the evidence behind this.

CADM1/TSLC1 Identifies HTLV-1-Infected Cells and Determines Their Susceptibility to CTL-Mediated Lysis

Human T cell lymphotropic virus-1 (HTLV-1) primarily infects CD4⁺ T cells, causing inflammatory disorders or a T cell malignancy in 5% to 10% of carriers. The cytotoxic T lymphocyte (CTL) response is a key factor that controls the viral load and thus the risk of disease. The ability to detect the viral protein Tax in primary cells has made it possible to estimate the rate at which Tax-expressing infected cells are eliminated by CTLs in persistently infected people. However, most HTLV-1-infected cells are Tax^–at a given time, and their immunophenotype is poorly defined. Here, we aimed to identify a cell-surface molecule expressed by both Tax⁺ and Tax^–HTLV-1-infected cells and use it to analyse the CTL response in fresh peripheral blood mononuclear cells. Cell adhesion molecule 1 (CADM1/TSLC1) was the best single marker of HTLV-1 infection, identifying HTLV-1-infected cells with greater sensitivity and specificity than CD25, CCR4 or ICAM-1. CADM1⁺CD4⁺ T cells carried a median of 65% of proviral copies in peripheral blood. In a cohort of 23 individuals, we quantified the rate of CTL-mediated killing of Tax⁺ and Tax⁻CADM1⁺ cells. We show that CADM1 expression is associated with enhanced susceptibility of infected cells to CTL lysis: despite the immunodominance of Tax in the CTL response, Tax⁺CADM1^– cells were inefficiently lysed by CTLs. Upregulation of the CADM1 ligand CRTAM on CD8⁺ T cells correlated with efficient lysis of infected cells. Tax^–CADM1⁺ cells were lysed at a very low rate by autologous CTLs, however, were efficiently killed when loaded with exogenous peptide antigen. High expression of CADM1 on most HTLV-1-infected cells in the face of enhanced CTL counterselection implies that CADM1 confers a strong benefit on the virus.

Human T cell lymphotropic virus-1 (HTLV-1) infects white blood cells (CD4⁺ T cells) for the lifetime of the host. The immune response limits viral spread, and people with a weak immune response have a high risk of developing an aggressive blood cancer, or a condition involving irreversible spinal cord damage. Virus and host are engaged in a constant battle: virus proteins drive the host cell to divide or infect new cells. We know that the viral protein Tax is an important target of the immune response, and cells which produce Tax are killed quickly. Infected cells which do not produce Tax are difficult to detect, so we have no idea how quickly they are killed. In this paper we show that most infected cells have a host protein ‘CADM1’ on their surface. We measured killing of CADM1 cells and saw that Tax⁺CADM1⁺ cells are the only infected cells which are strongly targeted by the immune response. We also found that infected cells which did not have CADM1 on the surface escaped killing, showing that CADM1 aids in immune control of HTLV-1. These findings are an important step forward in our understanding of cellular turnover and immune control in chronic infection.

Genetic variants in Cell Adhesion Molecule 1 (CADM1): a validation study of a novel endothelial cell venous thrombosis risk factor

INTRODUCTION

In a protein C deficient family, we recently identified a candidate gene, CADM1, which interacted with protein C deficiency in increasing the risk of venous thrombosis (VT). This study aimed to determine whether CADM1 variants also interact with protein C pathway abnormalities in increasing VT risk outside this family.

MATERIALS AND METHODS

We genotyped over 300 CADM1 variants in the population-based MEGA case-control study. We compared VT risks between cases with low protein C activity (n=194), low protein S levels (n=23), high factor VIII activity (n=165) or factor V Leiden carriers (n=580), and all 4004 controls. Positive associations were repeated in all 3496 cases and 4004 controls.

RESULTS

We found 22 variants which were associated with VT in one of the protein C pathway risk groups. After mutual adjustment, six variants remained associated with VT. The strongest evidence was found for rs220842 and rs11608105. For rs220842, the odds ratio (OR) for VT was 3.2 (95% CI 1.2-9.0) for cases with high factor VIII activity compared with controls. In addition, this variant was associated with an increased risk of VT in the overall study population (OR: 1.5, 95% CI 1.0-2.2). The other variant, rs11608105, was not associated with VT in the overall study population (OR: 1.0, 95% CI 0.8-1.1), but showed a strong effect on VT risk (OR: 21, 95% CI 5.1-88) when combined with low protein C or S levels.

CONCLUSIONS

In a population-based association study, we confirm a role for CADM1 variants in increasing the risk of VT by interaction with protein C pathway abnormalities.

CADM1 controls actin cytoskeleton assembly and regulates extracellular matrix adhesion in human mast cells

CADM1 is a major receptor for the adhesion of mast cells (MCs) to fibroblasts, human airway smooth muscle cells (HASMCs) and neurons. It also regulates E-cadherin and alpha6beta4 integrin in other cell types. Here we investigated a role for CADM1 in MC adhesion to both cells and extracellular matrix (ECM). Downregulation of CADM1 in the human MC line HMC-1 resulted not only in reduced adhesion to HASMCs, but also reduced adhesion to their ECM. Time-course studies in the presence of EDTA to inhibit integrins demonstrated that CADM1 provided fast initial adhesion to HASMCs and assisted with slower adhesion to ECM. CADM1 downregulation, but not antibody-dependent CADM1 inhibition, reduced MC adhesion to ECM, suggesting indirect regulation of ECM adhesion. To investigate potential mechanisms, phosphotyrosine signalling and polymerisation of actin filaments, essential for integrin-mediated adhesion, were examined. Modulation of CADM1 expression positively correlated with surface KIT levels and polymerisation of cortical F-actin in HMC-1 cells. It also influenced phosphotyrosine signalling and KIT tyrosine autophosphorylation. CADM1 accounted for 46% of surface KIT levels and 31% of F-actin in HMC-1 cells. CADM1 downregulation resulted in elongation of cortical actin filaments in both HMC-1 cells and human lung MCs and increased cell rigidity of HMC-1 cells. Collectively these data suggest that CADM1 is a key adhesion receptor, which regulates MC net adhesion, both directly through CADM1-dependent adhesion, and indirectly through the regulation of other adhesion receptors. The latter is likely to occur via docking of KIT and polymerisation of cortical F-actin. Here we propose a stepwise model of adhesion with CADM1 as a driving force for net MC adhesion.

SynCAM, a novel putative tumor suppressor, suppresses growth and invasiveness of glioblastoma

SynCAM, also named by TSLC1, SgIGSF and IGSF4, was identified as a neural tissue-specific immunoglobulin-like cell-cell adhesion molecule. However, the role of SynCAM in tumorigenesis remains elusive. We aimed to clarify its epigenetic regulation and biological functions in glioblastoma. SynCAM was silenced in 72 % (5/7) glioblastoma cell lines. A significant downregulation was also detected in paired glioblastoma tumors compared with adjacent non-cancerous tissues. In contrast, SynCAM was readily expressed in various normal adult brain tissues. Ectopic expression of SynCAM in the silenced cancer cell line T98G significantly reduced colony formation and cell proliferation, induced cell cycle arrests and repressed cell invasive ability. Nude mice were subcutaneously injected into the flank with T98G cells and treated with normal saline, pcDNA3.1 (vector) or pcDNA3.1-SynCAM, respectively. Treatment with pcDNA3.1-SynCAM retarded growth in the xenografts, which contributed to a 58 % decrease in tumor volume compared to controls. In conclusion, our results suggest that SynCAM suppressions growth of glioblastoma and may serve as a novel functional tumor-suppressor gene.

Transforming growth factor-β1 (TGF-β1) regulates cell junction restructuring via Smad-mediated repression and clathrin-mediated endocytosis of nectin-like molecule 2 (Necl-2)

Nectin-like molecule-2 (Necl-2), a junction molecule, is exclusively expressed by spermatogenic cells. It mediates homophilic interaction between germ cells and heterophilic interaction between Sertoli and germ cells. Knockout studies have shown that loss of Necl-2 causes male infertility, suggesting Necl-2-based cell adhesion is crucial for spermatogenesis. Transforming growth factor-βs (TGF-βs) are crucial for regulating cell junction restructuring that are required for spermatogenesis. In the present study, we aim to investigate the mechanism on how TGF-β1 regulates Necl-2 expression to achieve timely junction restructuring in the seminiferous epithelium during spermatogenesis. We have demonstrated that TGF-β1 reduces Necl-2 mRNA and protein levels at both transcriptional and post-translational levels. Using inhibitor and clathrin shRNA, we have revealed that TGF-β1 induces Necl-2 protein degradation via clathrin-dependent endocytosis. Endocytosis assays further confirmed that TGF-β1 accelerates the internalization of Necl-2 protein to cytosol. Immunofluorescence staining also revealed that TGF-β1 effectively removes Necl-2 from cell-cell interface. In addition, TGF-β1 reduces Necl-2 mRNA via down-regulating Necl-2 promoter activity. Mutational studies coupled with knockdown experiments have shown that TGF-β1-induced Necl-2 repression requires activation of Smad proteins. EMSA and ChIP assays further confirmed that TGF-β1 promotes the binding of Smad proteins onto MyoD and CCAATa motifs in vitro and in vivo. Taken together, TGF-β1 is a potent cytokine that provides an effective mechanism in controlling Necl-2 expression in the testis via Smad-dependent gene repression and clathrin-mediated endocytosis.

Interaction of Necl-4/CADM4 with ErbB3 and integrin α6 β4 and inhibition of ErbB2/ErbB3 signaling and hemidesmosome disassembly

Nectin-like molecule 4 (Necl-4)/CADM4, a transmembrane cell-cell adhesion molecule with three Ig-like domains, was shown to serve as a tumor suppressor, but its mode of action has not been elucidated. In this study, we showed that Necl-4 interacted in cis with ErbB3 through their extracellular regions, recruited PTPN13 and inhibited the heregulin-induced activation of the ErbB2/ErbB3 signaling. In addition, we extended our previous finding that Necl-4 interacts in cis with integrin α6 β4 through their extracellular regions and found that Necl-4 inhibited the phorbol ester-induced disassembly of hemidesmosomes. These results indicate that Necl-4 serves as a tumor suppressor by inhibiting the ErbB2/ErbB3 signaling and hemidesmosome disassembly.

Reduction of the ST6 β-galactosamide α-2,6-sialyltransferase 1 (ST6GAL1)-catalyzed sialylation of nectin-like molecule 2/cell adhesion molecule 1 and enhancement of ErbB2/ErbB3 signaling by microRNA-199a

Nectin-like molecule 2 (Necl-2)/cell adhesion molecule 1 (CADM1) is shown to be down-regulated by the promoter hypermethylation and/or loss of heterozygosity at chromosome 11q23.2 in many types of cancers, including lung and breast cancers, and is proposed to serve as a tumor suppressor. However, the incidence of these epigenetic and genetic abnormalities of Necl-2 is 30-60% in these cancers, and other mechanisms for the suppression of Necl-2 are presumed to be present. We previously showed that Necl-2 interacts in cis with ErbB3 and suppresses the heregulin (HRG)-induced ErbB2/ErbB3 signaling for cell movement and death. We studied here the relationship between Necl-2 and microRNA-199a (miR-199a) that is up-regulated or down-regulated in a variety of cancers. miR-199a did not directly target the Necl-2 mRNA or affect its mRNA level in human lung cancer A549 cells and human embryonic kidney HEK293 cells. Necl-2 was at least sialylated by the sialyltransferase ST6 β-galactosamide α-2,6-sialyltransferase 1 (ST6GAL1). miR-199a targeted ST6GAL1 and reduced both the sialylation and the protein level of Necl-2. In addition, miR-199a enhanced the HRG-induced ErbB2/ErbB3 signaling. These results indicate that the suppressive role of Necl-2 in the HRG-induced ErbB2/ErbB3 signaling is regulated by miR-199a at least through the reduction of the ST6GAL1-catalyzed sialylation of Necl-2 and/or through the reduction of the protein level of Necl-2 presumably by the protein degradation.

CADM1 is expressed as multiple alternatively spliced functional and dysfunctional isoforms in human mast cells

Cell adhesion molecule 1 (CADM1) is implicated in the pathogenesis of several diseases and is responsible for adhesion and survival of mast cells (MCs). Differential expression of CADM1 isoforms was found in different species. We previously cloned SP4, SP1, SP6 and a dysfunctional isoform from human lung MCs (HLMCs) and the MC line HMC-1. The aim of this study was to identify all isoforms expressed in human MCs. The functional isoforms SP4, SP1, SP6 and SP3, with alternative splicing between exons 7/11, were detected in human MCs by RT-PCR. Two dysfunctional isoforms with alternative splicing of cryptic exons A and B between exons 1/2, leading to premature termination of translation, were found in ∼40% of MC specimens. Sequencing of genomic DNA showed that splicing of cryptic exon B did not result from specific SNPs within this exon or its putative splice branch point. Highly glycosylated CADM1 (∼105 kDa) was detected by western blotting, but an extracellular domain (∼95 kDa) was found only in the culture medium from HLMCs, but not HMC-1 cells, indicating differential protein expression. Transfection of SP1 and SP6, but not SP4, reduced adhesion of HMC-1 cells to human lung fibroblasts but not airway smooth muscle cells. Hence, dysfunctional and functional CADM1 isoforms are found in human MCs. The longer SP1 and SP6 were most evident in differentiated HLMCs and displayed differential adhesion compared to SP4. These multiple isoforms are likely to contribute to MC function in both health and disease.

Biomarker discovery in non-small cell lung cancer: integrating gene expression profiling, meta-analysis, and tissue microarray validation

PURPOSE

Global gene expression profiling has been widely used in lung cancer research to identify clinically relevant molecular subtypes as well as to predict prognosis and therapy response. So far, the value of these multigene signatures in clinical practice is unclear, and the biologic importance of individual genes is difficult to assess, as the published signatures virtually do not overlap.

EXPERIMENTAL DESIGN

Here, we describe a novel single institute cohort, including 196 non-small lung cancers (NSCLC) with clinical information and long-term follow-up. Gene expression array data were used as a training set to screen for single genes with prognostic impact. The top 450 probe sets identified using a univariate Cox regression model (significance level P < 0.01) were tested in a meta-analysis including five publicly available independent lung cancer cohorts (n = 860).

RESULTS

The meta-analysis revealed 14 genes that were significantly associated with survival (P < 0.001) with a false discovery rate <1%. The prognostic impact of one of these genes, the cell adhesion molecule 1 (CADM1), was confirmed by use of immunohistochemistry on tissue microarrays from 2 independent NSCLC cohorts, altogether including 617 NSCLC samples. Low CADM1 protein expression was significantly associated with shorter survival, with particular influence in the adenocarcinoma patient subgroup.

CONCLUSIONS

Using a novel NSCLC cohort together with a meta-analysis validation approach, we have identified a set of single genes with independent prognostic impact. One of these genes, CADM1, was further established as an immunohistochemical marker with a potential application in clinical diagnostics.

CADM1 isoforms differentially regulate human mast cell survival and homotypic adhesion

Cell adhesion molecule 1 (CADM1), expressed by human lung mast cells (HLMCs), mediates their adhesion to airway smooth muscle (ASM), and contributes to ASM-dependent HLMC proliferation and survival. CADM1 is expressed in alternatively spliced isoforms, but those present in HLMCs and their function are not known. We cloned three functional and one cryptic non-functional isoform with alternative splicing between exons 7/11 and 1/2, respectively, from HLMCs and human MC lines (HMC-1 and LAD2). Differentiated HLMCs and LAD2 cells expressed the functional isoform SP4 containing exons 7/8/11 (~80% of clones), as well as SP1 (exons 7/8/9/11) and a novel SP6 (exons 7/8/9/10/11). In contrast, immature HMC-1 cells expressed only functional SP4. SP4 overexpression in HMC-1 cells and HLMCs augmented homotypic adhesion to a greater extent than SP1 in various conditions. In contrast, CADM1 downregulation abolished homotypic adhesion, indicating that CADM1 is the sole receptor mediating mast cell aggregation. CADM1-mediated adhesion was enhanced by the presence of cell survival factors. SP1 overexpression in HMC-1 cells compromised survival compared to SP4 overexpression or control. CADM1 downregulation resulted in reduced viability and decreased expression of the pro-survival protein Mcl-1_L, but not Blc-2 or Bcl-X_L, and increased caspase-3/7 activity in both HMC-1 cells and HLMCs. This coincided with decreased basal Kit levels in HLMCs. In summary, human MCs express multiple CADM1 isoforms which exhibit differential regulation of survival and homotypic adhesion. The most highly expressed SP4 isoform is likely to contribute to MC aggregation and longevity in mastocytosis, and augment the pathophysiology of allergic diseases.

The transmembrane domain of CEACAM1-4S is a determinant of anchorage independent growth and tumorigenicity

CEACAM1 is a multifunctional Ig-like cell adhesion molecule expressed by epithelial cells in many organs. CEACAM1-4L and CEACAM1-4S, two isoforms produced by differential splicing, are predominant in rat liver. Previous work has shown that downregulation of both isoforms occurs in rat hepatocellular carcinomas. Here, we have isolated an anchorage dependent clone, designated 253T-NT that does not express detectable levels of CEACAM1. Stable transfection of 253-NT cells with a wild type CEACAM1-4S expression vector induced an anchorage independent growth in vitro and a tumorigenic phenotype in vivo. These phenotypes were used as quantifiable end points to examine the functionality of the CEACAM1-4S transmembrane domain. Examination of the CEACAM1 transmembrane domain showed N-terminal GXXXG dimerization sequences and C-terminal tyrosine residues shown in related studies to stabilize transmembrane domain helix-helix interactions. To examine the effects of transmembrane domain mutations, 253-NT cells were transfected with transmembrane domain mutants carrying glycine to leucine or tyrosine to valine substitutions. Results showed that mutation of transmembrane tyrosine residues greatly enhanced growth in vitro and in vivo. Mutation of transmembrane dimerization motifs, in contrast, significantly reduced anchorage independent growth and tumorigenicity. 253-NT cells expressing CEACAM1-4S with both glycine to leucine and tyrosine to valine mutations displayed the growth-enhanced phenotype of tyrosine mutants. The dramatic effect of transmembrane domain mutations constitutes strong evidence that the transmembrane domain is an important determinant of CEACAM1-4S functionality and most likely by other proteins with transmembrane domains containing dimerization sequences and/or C-terminal tyrosine residues.

Interaction of nectin-like molecule 2 with integrin alpha6beta4 and inhibition of disassembly of integrin alpha6beta4 from hemidesmosomes

In normal epithelial cells, integrin α(6)β(4) is abundantly expressed and forms hemidesmosomes, which is a cellular structure that mediates cell-extracellular matrix binding. In many types of cancer cells, integrin α(6)β(4) is up-regulated, laminin is cleaved, and hemidesmosomes are disrupted, eventually causing an enhancement of cancer cell movement and facilitation of their invasion. We previously showed that the immunoglobulin-like cell adhesion molecule Necl-2 (Nectin-like molecule 2), known as a tumor suppressor, inhibits cancer cell movement by suppressing the ErbB3/ErbB2 signaling. We show here that Necl-2 interacts in cis with integrin α(6)β(4). The binding of Necl-2 with integrin β(4) was mediated by its extracellular region. In human colorectal adenocarcinoma Caco-2 cells, integrin α(6)β(4) was localized at hemidesmosomes. Small interfering RNA-mediated suppression of Necl-2 expression enhanced the phorbol ester-induced disruption of the integrin α(6)β(4) complex at hemidesmosomes, whereas expression of Necl-2 suppressed the disruption of this structure. These results indicate that tumor-suppressive functions of Necl-2 are mediated by the stabilization of the hemidesmosome structure in addition to the inhibition of the ErbB3/ErbB2 signaling.

The synaptic cell adhesion molecule, SynCAM1, mediates astrocyte-to-astrocyte and astrocyte-to-GnRH neuron adhesiveness in the mouse hypothalamus

We previously identified synaptic cell adhesion molecule 1 (SynCAM1) as a component of a genetic network involved in the hypothalamic control of female puberty. Although it is well established that SynCAM1 is a synaptic adhesion molecule, its contribution to hypothalamic function is unknown. Here we show that, in addition to the expected neuronal localization illustrated by its presence in GnRH neurons, SynCAM1 is expressed in hypothalamic astrocytes. Cell adhesion assays indicated that SynCAM is recognized by both GnRH neurons and astrocytes as an adhesive partner and promotes cell-cell adhesiveness via homophilic, extracellular domain-mediated interactions. Alternative splicing of the SynCAM1 primary mRNA transcript yields four mRNAs encoding membrane-spanning SynCAM1 isoforms. Variants 1 and 4 are predicted to be both N and O glycosylated. Hypothalamic astrocytes and GnRH-producing GT1-7 cells express mainly isoform 4 mRNA, and sequential N- and O-deglycosylation of proteins extracted from these cells yields progressively smaller SynCAM1 species, indicating that isoform 4 is the predominant SynCAM1 variant expressed in astrocytes and GT1-7 cells. Neither cell type expresses the products of two other SynCAM genes (SynCAM2 and SynCAM3), suggesting that SynCAM-mediated astrocyte-astrocyte and astrocyte-GnRH neuron adhesiveness is mostly mediated by SynCAM1 homophilic interactions. When erbB4 receptor function is disrupted in astrocytes, via transgenic expression of a dominant-negative erbB4 receptor form, SynCAM1-mediated adhesiveness is severely compromised. Conversely, SynCAM1 adhesive behavior is rapidly, but transiently, enhanced in astrocytes by ligand-dependent activation of erbB4 receptors, suggesting that erbB4-mediated events affecting SynCAM1 function contribute to regulate astrocyte adhesive communication.

The connections between neural crest development and neuroblastoma

Neuroblastoma (NB), the most common extracranial solid tumor in childhood, is an extremely heterogeneous disease both biologically and clinically. Although significant progress has been made in identifying molecular and genetic markers for NB, this disease remains an enigmatic challenge. Since NB is thought to be an embryonal tumor that is derived from precursor cells of the peripheral (sympathetic) nervous system, understanding the development of normal sympathetic nervous system may highlight abnormal events that contribute to NB initiation. Therefore, this review focuses on the development of the peripheral trunk neural crest, the current understanding of how developmental factors may contribute to NB and on recent advances in the identification of important genetic lesions and signaling pathways involved in NB tumorigenesis and metastasis. Finally, we discuss how future advances in identification of molecular alterations in NB may lead to more effective, less toxic therapies, and improve the prognosis for NB patients.

Cadm1 expression and function in the mouse lens

PURPOSE

The immunoglobulin superfamily member Cadm1 is a single-pass, type 1 membrane protein that mediates calcium-independent, cell-cell adhesion. Cadm1 has been implicated in tumor formation and synaptogenesis. A recent analysis of mouse lens cell membranes identified Cadm1 as a major constituent of the fiber cell membrane proteome. Here the authors examined the expression and function of Cadm1 in the mouse lens.

METHODS

Cadm1 expression was analyzed by Western blotting and immunofluorescence. The morphology of individual wild-type and Cadm1-null lens cells was visualized by confocal microscopy.

RESULTS

Cadm1 was present in epithelial and superficial fiber cells as a heavily glycosylated protein with an apparent molecular mass of ≈80 kDa. Analysis of proteins extracted from various strata of the lens indicated that Cadm1 was degraded during fiber cell differentiation, at approximately the same time as the lens organelles, an observation confirmed by confocal microscopy. In epithelial cells, Cadm1 was enriched in basolateral membranes, whereas, in fiber cells, expression was restricted to the lateral membranes. Lenses from Cadm1-null mice were of normal size and transparency. The three-dimensional morphology of the cells in the epithelial layer was unaltered in the absence of Cadm1. However, in contrast to wild-type lens fiber cells, Cadm1-null fiber cells had an irregular, highly undulating morphology.

CONCLUSIONS

Cadm1 is an abundant component of the lens fiber cell membrane. Although not essential for lens transparency, Cadm1 has an indispensable role in establishing and maintaining the characteristic three-dimensional architecture of the lens fiber cell mass.

Localisation of RA175 (Cadm1), a cell adhesion molecule of the immunoglobulin superfamily, in the mouse testis, and analysis of male infertility in the RA175-deficient mouse

RA175, a member of the immunoglobulin superfamily, plays an important role in cell adhesion, and RA175 gene-deficient mice (RA175(-/-) ) show oligoastheno-teratozoospermia. To understand the function of RA175, location in the testis and the morphological features of its spermatogenic cells in RA175(-/-) mice were investigated. Immunohistochemical studies revealed that RA175 immunoreactivity was observed on the cell surface of the spermatogenic cells at specific stages. A strong reaction was detected from type A spermatogonia to pachytene spermatocytes at stage IV and from step 6 to step 16 spermatids during spermatogenesis. From pachytene spermatocytes at stage VI to step 4 spermatids, the reaction was not detected by the enzyme-labelled antibody method and was faintly detected by the indirect immunofluorescence method. Abnormal vacuoles in the seminiferous epithelium, showing exfoliation of germ cells, and ultrastructural abnormality of the elongate spermatids were revealed in the RA175(-/-) testes. Other members of the immunoglobulin superfamily such as basigin, nectin-2 and nectin-3, which have an important role in spermatogenesis, were immunohistochemically detected in the RA175(-/-) testis. These observations indicate a unique expression pattern of RA175 in the testis and provide clues regarding the mechanism of male infertility in the testis.

Synaptic cell adhesion molecule SynCAM 1 is a target for polysialylation in postnatal mouse brain

Among the large set of cell surface glycan structures, the carbohydrate polymer polysialic acid (polySia) plays an important role in vertebrate brain development and synaptic plasticity. The main carrier of polySia in the nervous system is the neural cell adhesion molecule NCAM. As polySia with chain lengths of more than 40 sialic acid residues was still observed in brain of newborn Ncam(-/-) mice, we performed a glycoproteomics approach to identify the underlying protein scaffolds. Affinity purification of polysialylated molecules from Ncam(-/-) brain followed by peptide mass fingerprinting led to the identification of the synaptic cell adhesion molecule SynCAM 1 as a so far unknown polySia carrier. SynCAM 1 belongs to the Ig superfamily and is a powerful inducer of synapse formation. Importantly, the appearance of polysialylated SynCAM 1 was not restricted to the Ncam(-/-) background but was found to the same extent in perinatal brain of WT mice. PolySia was located on N-glycans of the first Ig domain, which is known to be involved in homo- and heterophilic SynCAM 1 interactions. Both polysialyltransferases, ST8SiaII and ST8SiaIV, were able to polysialylate SynCAM 1 in vitro, and polysialylation of SynCAM 1 completely abolished homophilic binding. Analysis of serial sections of perinatal Ncam(-/-) brain revealed that polySia-SynCAM 1 is expressed exclusively by NG2 cells, a multifunctional glia population that can receive glutamatergic input via unique neuron-NG2 cell synapses. Our findings sug-gest that polySia may act as a dynamic modulator of SynCAM 1 functions during integration of NG2 cells into neural networks.

CADM1 interacts with Tiam1 and promotes invasive phenotype of human T-cell leukemia virus type I-transformed cells and adult T-cell leukemia cells

CADM1 encodes a multifunctional immunoglobulin-like cell adhesion molecule whose cytoplasmic domain contains a type II PSD95/Dlg/ZO-1 (PDZ)-binding motif (BM) for associating with other intracellular proteins. Although CADM1 lacks expression in T lymphocytes of healthy individuals, it is overexpressed in adult T-cell leukemia-lymphoma (ATL) cells. It has been suggested that the expression of CADM1 protein promotes infiltration of leukemic cells into various organs and tissues, which is one of the frequent clinical manifestations of ATL. Amino acid sequence alignment revealed that Tiam1 (T-lymphoma invasion and metastasis 1), a Rac-specific guanine nucleotide exchange factor, has a type II PDZ domain similar to those of membrane-associated guanylate kinase homologs (MAGUKs) that are known to bind to the PDZ-BM of CADM1. In this study, we demonstrated that the cytoplasmic domain of CADM1 directly interacted with the PDZ domain of Tiam1 and induced formation of lamellipodia through Rac activation in HTLV-I-transformed cell lines as well as ATL cell lines. Our results indicate that Tiam1 integrates signals from CADM1 to regulate the actin cytoskeleton through Rac activation, which may lead to tissue infiltration of leukemic cells in ATL patients.

Silencing of ErbB3/ErbB2 signaling by immunoglobulin-like Necl-2

ErbB2 and ErbB3, members of the EGF receptor/ErbB family, form a heterodimer upon binding of a ligand, inducing the activation of Rac small G protein and Akt protein kinase for cell movement and survival, respectively. The enhanced ErbB3/ErbB2 signaling causes tumorigenesis, invasion, and metastasis. We found here that the ErbB3/ErbB2 signaling is regulated by immunoglobulin-like Necl-2, which is down-regulated in various cancer cells and serves as a tumor suppressor. The extracellular region of ErbB3, but not ErbB2, interacted in cis with that of Necl-2. This interaction reduced the ligand-induced, ErbB2-catalyzed tyrosine phosphorylation of ErbB3 and inhibited the consequent ErbB3-mediated activation of Rac and Akt, resulting in the inhibition of cancer cell movement and survival. These inhibitory effects of Necl-2 were mediated by the protein-tyrosine phosphatase PTPN13 which interacted with the cytoplasmic tail of Necl-2. We describe here this novel mechanism for silencing of the ErbB3/ErbB2 signaling by Necl-2.

Role of the spermatogenic-Sertoli cell interaction through cell adhesion molecule-1 (CADM1) in spermatogenesis

Endocrine and local secretory factors have long been known to be required for spermatogenesis. Evidence has been accumulating in recent years indicating that direct contact between spermatogenic and Sertoli cells is also required for spermatogenesis. Cell adhesion molecules of various types have been found in the mammalian testis that are expressed in spermatogenic and/or Sertoli cells and involved in homophilic and/or heterophilic binding. We have cloned a novel cell adhesion molecule, cell adhesion molecule-1 (CADM1), also known as immunoglobulin superfamily 4A or spermatogenic immunoglobulin superfamily, from the mouse testis. CADM1 belongs to the immunoglobulin superfamily and is composed of three immunoglobulin-like domains, a transmembrane domain, and a short intracellular domain. In the seminiferous epithelium, CADM1 is expressed in intermediate spermatogonia through to early pachytene spermatocytes as well as in elongating spermatids--but not in round spermatids, mature spermatozoa, or Sertoli cells. One of the heterophilic binding partners of CADM1 has proven to be a poliovirus receptor, another member of the immunoglobulin superfamily that is expressed in Sertoli cells. Knockout mice for CADM1 develop male infertility due to defective spermatogenesis. These findings suggest that cell adhesion molecules between spermatogenic and Sertoli cells play essential roles in spermatogenesis.

Expression and clinical significance of TSLC1 and DAL-1/4.1B in pancreatic cancer

AIM: To investigate the expression and clinicopathological significance of TSLC1 and DAL-1/4.1B proteins in pancreatic cancer.

METHODS: Immunohistochemical S-P method was used to measure the protein expression of TSLC1 and DAL-1/4.1B in 9 cases of normal pancreatic tissues, 11 cases of pancreatitis tissues and 42 cases of pancreatic cancer tissues, respectively.

RESULTS: The positive expression rates of TSLC1 and DAL-1/4.1B in pancreatic carcinoma were significantly lower than those in normal pancreatic tissues and pancreatitis tissues respectively (30.95% vs 77.78%, 81.82%; 28.57% vs 66.67%, 81.82%, P< 0.05 or 0.01). The expression levels of TSLC1 and DAL-1/4.1B in pancreatic cancer showed a significant correlation with the differentiation degree, lymph node metastasis and TNM staging (P < 0.05, respectively), but not with the gender, age, location or pathological typing. In 42 cases of pancreatic carcinoma, a significantly positive correlation was found between the expression of TSLC1 and DAL-1/4.1B proteins (r_s = 0.489, P < 0.01).

CONCLUSION: Down-regulated expression of TSLC1 and DAL-1/4.1B exist in pancreatic cancer, which are involved in the pathogenesis, development and metastasis of pancreatic cancer through TSLC1- DAL-1/4.1B cascade.

CADM1 is a strong neuroblastoma candidate gene that maps within a 3.72 Mb critical region of loss on 11q23

Background

Recurrent loss of part of the long arm of chromosome 11 is a well established hallmark of a subtype of aggressive neuroblastomas. Despite intensive mapping efforts to localize the culprit 11q tumour suppressor gene, this search has been unsuccessful thus far as no sufficiently small critical region could be delineated for selection of candidate genes.

Methods

To refine the critical region of 11q loss, the chromosome 11 status of 100 primary neuroblastoma tumours and 29 cell lines was analyzed using a BAC array containing a chromosome 11 tiling path. For the genes mapping within our refined region of loss, meta-analysis on published neuroblastoma mRNA gene expression datasets was performed for candidate gene selection. The DNA methylation status of the resulting candidate gene was determined using re-expression experiments by treatment of neuroblastoma cells with the demethylating agent 5-aza-2'-deoxycytidine and bisulphite sequencing.

Results

Two small critical regions of loss within 11q23 at chromosomal band 11q23.1-q23.2 (1.79 Mb) and 11q23.2-q23.3 (3.72 Mb) were identified. In a first step towards further selection of candidate neuroblastoma tumour suppressor genes, we performed a meta-analysis on published expression profiles of 692 neuroblastoma tumours. Integration of the resulting candidate gene list with expression data of neuroblastoma progenitor cells pinpointed CADM1 as a compelling candidate gene. Meta-analysis indicated that CADM1 expression has prognostic significance and differential expression for the gene was noted in unfavourable neuroblastoma versus normal neuroblasts. Methylation analysis provided no evidence for a two-hit mechanism in 11q deleted cell lines.

Conclusion

Our study puts CADM1 forward as a strong candidate neuroblastoma suppressor gene. Further functional studies are warranted to elucidate the role of CADM1 in neuroblastoma development and to investigate the possibility of CADM1 haploinsufficiency in neuroblastoma.

Genetic polymorphisms of matrix metalloproteinases in lung, breast and colorectal cancer

The matrix metalloproteinases (MMPs) can degrade various components of the extracellular matrix and are implicated in the development and progression of cancer. There is evidence suggesting an association of MMP gene polymorphisms with cancer susceptibility and/or metastasis. This paper reviews the findings on several single nucleotide polymorphisms in the collagenase, stromelysin and gelatinase genes in lung cancer, breast cancer and colorectal cancer.

Nectin-like proteins mediate axon Schwann cell interactions along the internode and are essential for myelination

Axon-glial interactions are critical for the induction of myelination and the domain organization of myelinated fibers. Although molecular complexes that mediate these interactions in the nodal region are known, their counterparts along the internode are poorly defined. We report that neurons and Schwann cells express distinct sets of nectin-like (Necl) proteins: axons highly express Necl-1 and -2, whereas Schwann cells express Necl-4 and lower amounts of Necl-2. These proteins are strikingly localized to the internode, where Necl-1 and -2 on the axon are directly apposed by Necl-4 on the Schwann cell; all three proteins are also enriched at Schmidt-Lanterman incisures. Binding experiments demonstrate that the Necl proteins preferentially mediate heterophilic rather than homophilic interactions. In particular, Necl-1 on axons binds specifically to Necl-4 on Schwann cells. Knockdown of Necl-4 by short hairpin RNA inhibits Schwann cell differentiation and subsequent myelination in cocultures. These results demonstrate a key role for Necl-4 in initiating peripheral nervous system myelination and implicate the Necl proteins as mediators of axo-glial interactions along the internode.

Tumor suppressor in lung cancer-1 as a novel ameloblast adhesion molecule and its downregulation in ameloblastoma

Tumor suppressor in lung cancer-1 (TSLC1) is an intercellular adhesion molecule of the immunoglobulin superfamily. There is little information regarding the developmental expression profiles. In an attempt to clarify the distribution of TSLC1 proteins in mouse embryos tissue by immunohistochemistry, it was found that the TSLC1-specific signals were detected in the tooth germ as early as bud stage. The signals of TSLC1 were in the enamel epithelium at the cap stage, and became restricted to ameloblasts during the transition to and throughout the bell stage. In contrast, the signals for E-cadherin, which is important in odontogenesis, were distributed in all the components of the ectoderm-derived germ at any stage. In addition, E-cadherin preferred to locate on the basal membrane of ameloblasts, whereas TSLC1 preferred the lateral. And in further contrast, all the ameloblastomas examined were positive for E-cadherin (18/18) whereas all but one was negative for TSLC1 (1/18). These results indicate that TSLC1 is a novel interameloblast adhesion molecule that may be downregulated during ameloblastic tumorigenesis.

Expression and localization of the cell adhesion molecule SgIGSF during regeneration of the olfactory epithelium in mice

Spermatogenic immunoglobulin superfamily (SgIGSF) is a cell adhesion molecule originally discovered in mouse testis. SgIGSF is expressed not only in spermatogenic cells but also in lung and liver epithelial cells and in neurons and glia of the central and peripheral nervous systems. In the present study, we examined the expression and localization of SgIGSF in mouse olfactory epithelium before and after transection of the olfactory nerves, by RT-PCR, Western blotting and immunohistochemistry. In normal olfactory mucosa, SgIGSF showed 100 kDa in molecular weight, which was identical with that in the lung but different from that in the brain. SgIGSF was expressed on the membrane of all olfactory, sustentacular and basal cells, but more abundantly in the apical portions of the olfactory epithelium where the dendrites of olfactory cells are in contact with sustentacular cells. After olfactory nerve transection, mature olfactory cells disappeared in 4 days but were regenerated around 7–15 days by proliferation and differentiation of basal cells into mature olfactory cells through the step of immature olfactory cells. During this period, both the mRNA and protein for SgIGSF showed a transient increase, with peak levels at 7 days and 11 days, respectively, after the transection. Immunohistochemistry showed that the enriched immunoreactivity for SgIGSF at 7–11 days was localized primarily to the membrane of immature olfactory cells. These results suggested that, during regeneration of the olfactory epithelium, the adhesion molecule SgIGSF plays physiological roles in differentiation, migration, and maturation of immature olfactory cells.

Expression and DNA methylation patterns of Tslc1 and Dal-1 genes in hepatocellular carcinomas induced by N-nitrosodiethylamine in rats

To assess the involvement of the TSLC cascade in hepatocarcinogenesis, we investigated the expression and DNA methylation patterns of the genes Tslc1 and Dal-1 in hepatocellular carcinomas (HCC) induced using N-nitrosodiethylamine (DEN) in rats. Six-week-old male F344 rats received a single intraperitoneal injection of DEN at a dose of 10 mg/kg body weight, followed by combined treatment with partial hepatectomy and colchicine to induce cell-cycle disturbance and a selection procedure consisting of 2-acetylaminofluorene and carbon tetrachloride. Total RNA was extracted from 10 HCC, and the expression levels of Tslc1 and Dal-1 were measured using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis. Three of 10 HCC showed reduced expression of Tslc1, compared with normal liver tissues, but no changes in the expression level of Dal-1 were found. For DNA methylation analysis, bisulfite sequencing was performed. The 5' upstream region of Tslc1 was methylated in the three HCC in which its expression was reduced, but was unmethylated in normal liver tissue. Western blot analysis also revealed reduced expression of Tslc1 protein in the three HCC. These results suggest that alterations to the TSLC cascade might have a role in hepatocarcinogenesis using DEN in rats.

Heterophilic binding of the adhesion molecules poliovirus receptor and immunoglobulin superfamily 4A in the interaction between mouse spermatogenic and Sertoli cells

The cell adhesion protein immunoglobulin superfamily 4A (IGSF4A) is expressed on the surfaces of spermatogenic cells in the mouse testis. During spermatogenesis, IGSF4A is considered to bind to the surface of Sertoli cells in a heterophilic manner. To identify this unknown partner of IGSF4A, we generated rat monoclonal antibodies against the membrane proteins of mouse Sertoli cells grown in primary culture. Using these monoclonal antibodies, we isolated a clone that immunostained Sertoli cells and reacted with the product of immunoprecipitation of the homogenate of mouse testis with anti-IGSF4A antibody. Subsequently, to identify the Sertoli cell membrane protein that is recognized by this monoclonal antibody, we performed expression cloning of a cDNA library from the mouse testis. As a result, we identified poliovirus receptor (PVR), which is another IGSF-type cell adhesion molecule, as the binding partner of IGSF4A. The antibodies raised against PVR and IGSF4A immunoprecipitated both antigens in the homogenate of mouse testis. Immunoreactivity for PVR was present in Sertoli cells but not in spermatogenic cells at all stages of spermatogenesis. Overexpression of PVR in TM4, a mouse Sertoli cell line, increased more than three-fold its capacity to adhere to Tera-2, which is a human cell line that expresses IGSF4A. These findings suggest that the heterophilic binding of PVR to IGSF4A is responsible, at least in part, for the interaction between Sertoli and spermatogenic cells during mouse spermatogenesis.

Aberrant DNA methylation of the 5' upstream region of Tslc1 gene in hamster pancreatic tumors

To determine if the Tslc1 gene is involved in pancreatic carcinogenesis, the expression level of Tslc1 and the DNA methylation status of its 5' upstream region were investigated in pancreatic duct adenocarcinomas (PDAs) induced in hamsters by N-nitrosobis(2-oxopropyl)amine (BOP). Female Syrian golden hamsters received 70 mg/kg of BOP followed by repeated exposure to an augmentation pressure regimen consisting of a choline-deficient diet combined with ethionine-methionione-BOP injection. Total RNA was extracted from 11 PDAs and the level of Tslc1 expression was measured in each by real-time quantitative reverse transcription (RT)-polymerase chain reaction (PCR). The expression level of Tslc1 was significantly reduced in PDAs (p < 0.05) compared with normal pancreatic tissues. In order to assess the DNA methylation status of the 5' upstream region of Tslc1, bisulfite sequencing was performed. Although this region was unmethylated in normal pancreatic tissue, it was highly methylated in four PDAs, correlating with reduced Tslc1 expression. These results suggest that a reduction in the expression of Tslc1 due to aberrant DNA methylation might be involved in the development of PDAs induced in hamsters by BOP.

Reduced expression of the Tslc1 gene and its aberrant DNA methylation in rat lung tumors

TSLC1 gene inactivation due to promoter methylation has been reported in several human cancers. Here, we investigated the expression of the Tslc1 gene and its methylation pattern in lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine (BHP). Six-week-old male Wistar rats were given 2000 ppm BHP in their drinking water for 12 weeks and maintained without further treatment until they were sacrificed at 25 weeks. Total RNA was extracted from a total of 11 lung adenocarcinomas and their Tslc1 gene expressions were analyzed by real-time quantitative reverse transcription-polymerase chain reaction. Tslc1 expression was significantly reduced in the lung adenocarcinomas compared with three normal lung tissues (p < 0.05). Bisulfite sequence analysis of four lung adenocarcinomas and two normal lung tissues revealed that the 5' upstream region of the Tslc1 gene was highly methylated in the four lung adenocarcinomas, but unmethylated in the two normal lung tissues. These results suggest that aberrant Tslc1 gene methylation may be involved in BHP-induced development of lung adenocarcinomas in rats.

Hypermethylation of the TSLC1/IGSF4 promoter is associated with tobacco smoking and a poor prognosis in primary nonsmall cell lung carcinoma

BACKGROUND

The tumor suppressor gene TSLC1/IGSF4 on chromosomal region 11q23 is frequently inactivated by promoter methylation in various cancers, including nonsmall cell lung carcinoma (NSCLC). Several studies have demonstrated that the hypermethylation of the CpG islands of genes, including tumor suppressors, is associated with exposure to tobacco smoke. The purpose of this study was to investigate the possible association of TSLC1/IGSF4 methylation with tobacco smoking as well as with the clinical characteristics of tumors using a large number of primary NSCLC.

METHODS

The promoter methylation of TSLC1/IGSF4 was analyzed in 103 primary NSCLC. TSLC1/IGSF4 expression was examined by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry, whereas its methylation status was determined by bisulfite single-strand conformation polymorphism (SSCP) coupled with bisulfite sequencing.

RESULTS

The TSLC1/IGSF4 promoter was methylated in 45 (44%) of 103 primary NSCLC. Methylation was observed in all histologic subtypes of NSCLC, including adenocarcinoma (29 of 68, 43%), squamous cell carcinoma (14 of 26, 54%), adenosquamous carcinoma (1 of 2, 50%), and large cell carcinoma (1 of 7, 14%). The incidence of methylation in tumors was significantly higher in male patients than in female patients (P = .027). The TSLC1/IGSF4 methylation was preferentially observed in heavy smokers (smoking index > or = 800) (P = .0054). Furthermore, in smokers the methylation was significantly associated with pack-years smoked (P = .034) and cigarettes per day (P = .021). The TSLC1/IGSF4 methylation was also significantly associated with a shorter disease-free survival (P = .049), providing an independent prognostic factor (P = .038) in adenocarcinoma patients.

CONCLUSIONS

TSLC1/IGSF4 methylation is associated with tobacco smoking and could be an indicator of poor prognosis.