Proteomic detection of changes in protein synthesis induced by NGX6 transfected in human nasopharyngeal carcinoma cells

Genome-wide association study in thoroughbred horses naturally infected with cyathostomins

Cyathostomins are considered one of the most important parasites of horses. A group of horses within a herd can be responsible for eliminating the majority of parasite eggs. This phenotype might be explained by genetic factors. This study aimed to identify genomic regions associated with fecal egg count (FEC) and hematological parameters by performing a genomic-wide association study (GWAS) in Thoroughbred horses naturally infected with cyathostomins. Packed cell volume (PCV), differential leukocyte, and FEC were determined from 90 horses. All animals were genotyped using the Illumina Equine 70 K BeadChip panel containing 65,157 SNP markers. The five genomic windows that have explained the highest percentage of the additive genetic variance of a specific trait (top 5) were further explored to identify candidate genes. A total of 33, 21, 30, 21, and 19 genes were identified for FEC, PCV, eosinophils, neutrophils, and lymphocyte count, respectively. The top 5 marker regions explained 2.86, 2.56, 2.73, 2.33, and 2.37% of the additive genetic variation of FEC, PCV, eosinophils, neutrophils, and lymphocytes count, respectively. This is the first study correlating phenotypic horse health traits to GWAS analysis, which may be used for animal breeding activities, reducing losses due to parasite infections.

Functional analysis of tumor-derived immunoglobulin lambda and its interacting proteins in cervical cancer

BACKGROUND

Immunoglobulin lambda (Igλ) has been reported to be expressed in many normal and tumor tissues and cells. However, the function and clinical significance of tumor-derived Igλ remain unclear.

METHODS

The differential expressions of Immunoglobulin Lambda Constants (IGLCs) in cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC) were examined with The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx), and Human Protein Atlas (HPA) databases. The effects of IGLCs on patient clinical phenotypes and prognosis were explored via bioinformatics analyses based on the TCGA databases. We used the bioinformatics analyses based on the TCGA and GTEx databases to elucidate the correlations among IGLC expressions, immunomodulator expressions, tumor stemness, and infiltration scores of tumor infiltrating immune cells. Co-immunoprecipitation (Co-IP) and silver staining combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to obtain potential tumor-derived Igλ-interacting proteins. Functional annotation of candidate proteins identified by LC-MS/MS was performed in Database for Annotation, Visualization and Integrated Discovery (DAVID). The bioinformatics analyses of 7 IGLCs in CESC and normal cervical tissues were performed based on TCGA, GTEx, and Gene Expression Profiling Interactive Analysis 2 (GEPIA2) databases. Protein-protein interaction (PPI) network was analyzed based on tumor-derived Igλ-interacting proteins in Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database. Immunohistochemistry (IHC) was used to validate the expressions of IGLCs in CESC.

RESULTS

We found that the expressions of the majority of IGLCs (IGLC1, IGLC2, IGLC3, IGLC4, IGLC5, IGLC6, and IGLC7) were upregulated in CESC tissues, compared with those in normal cervical tissues. The expressions of IGLC5 and IGLC7 had significant difference in different pathologic metastasis (M), one of tumor, node, and metastasis (TNM) staging system, categories of CESC. Except for disease-free interval (DFI), 4 IGLC (IGLC1, IGLC2, IGLC3, and IGLC7) expression levels were positively associated with patient overall survival (OS), disease-specific survival (DSS), and progression-free interval (PFI) respectively in CESC tissues. 5 IGLC (IGLC1, IGLC2, IGLC3, IGLC6, and IGLC7) expressions were positively correlated with the expressions of a majority of immunomodulators respectively in CESC tissues. Tumor stemness was negatively correlated with the expressions of 4 IGLCs (IGLC1, IGLC2, IGLC3, and IGLC7) respectively in CESC tissues. Except for IGLC4, IGLC5, and IGLC7, 4 IGLC (IGLC1, IGLC2, IGLC3, and IGLC6) expressions were positively correlated with infiltration scores of 6 tumor-infiltrating immune cells (B cell, T cell CD4, T cell CD8, neutrophil, macrophage, and DC). After analyses of the above bioinformatics data of tumor-derived Igλ, Co-IP and LC-MS/MS were used to confirm that 4 proteins (RPL7, RPS3, H1-5, and H1-6) might interact with tumor-derived Igλ in cervical cancer cells. Functional analyses of these candidate proteins showed that they interacted with many proteins and were involved in various cellular biological processes. Finally, IHC was used to further confirm the above bioinformatics results, it was indicated that the expression level of Igλ in cervical adenocarcinoma and cervical squamous cell carcinoma was higher than that in normal cervical tissue.

CONCLUSION

This study comprehensively investigated the functions of tumor-derived Igλ and its interacting proteins based on bioinformatics analysis and the potential value of Igλ as a prognostic and therapeutic marker for CESC, providing new direction and evidence for CESC therapy.

Alkaline ceramidase catalyzes the hydrolysis of ceramides via a catalytic mechanism shared by Zn2+-dependent amidases

Human alkaline ceramidase 3 (ACER3) is one of three alkaline ceramidases (ACERs) that catalyze the conversion of ceramide to sphingosine. ACERs are members of the CREST superfamily of integral-membrane hydrolases. All CREST members conserve a set of three Histidine, one Aspartate, and one Serine residue. Although the structure of ACER3 was recently reported, catalytic roles for these residues have not been biochemically tested. Here, we use ACER3 as a prototype enzyme to gain insight into this unique class of enzymes. Recombinant ACER3 was expressed in yeast mutant cells that lack endogenous ceramidase activity, and microsomes were used for biochemical characterization. Six-point mutants of the conserved CREST motif were developed that form a Zn-binding active site based on a recent crystal structure of human ACER3. Five point mutants completely lost their activity, with the exception of S77A, which showed a 600-fold decrease compared with the wild-type enzyme. The activity of S77C mutant was pH sensitive, with neutral pH partially recovering ACER3 activity. This suggested a role for S77 in stabilizing the oxyanion of the transition state. Together, these data indicate that ACER3 is a Zn2+-dependent amidase that catalyzes hydrolysis of ceramides via a similar mechanism to other soluble Zn-based amidases. Consistent with this notion, ACER3 was specifically inhibited by trichostatin A, a strong zinc chelator.

Current insights into the expression and functions of tumor-derived immunoglobulins

Numerous studies have reported expressions of immunoglobulins (Igs) in many human tumor tissues and cells. Tumor-derived Igs have displayed multiple significant functions which are different from classical Igs produced by B lymphocytes and plasma cells. This review will concentrate on major progress in expressions, functions, and mechanisms of tumor-derived Igs, similarities and differences between tumor-derived Igs and B-cell-derived Igs. We also discuss the future research directions of tumor-derived Igs, including their structural characteristics, physicochemical properties, mechanisms for rearrangement and expression regulation, signaling pathways involved, and clinical applications.

Identification of Liver Epithelial Cell-derived Ig Expression in μ chain-deficient mice

Growing evidence indicates that B cells are not the only source of immunoglobulin (Ig). To investigate this discovery further, we used μMT mice, which have a disruption of the first transmembrane exon of the μ heavy chain and do not express the membrane form of IgM. These mice lack mature B cells and thus serve as a good model to explore Ig expression by liver epithelial cells. We found that Ig heavy chains (μ, δ, γ and α) and light chains (κ and λ) were expressed in sorted liver epithelial cells of μMT mice. Surprisingly, each heavy chain class showed its respective variable region sequence characteristics in their variable region, instead of sharing the same VDJ usage, which suggests that class switching does not occur in liver epithelial cells. Moreover, the γ and α chains, but not the μ and δ chains, showed mutations in the variable region, thus indicating that different classes of Ig have different activities. Our findings support the concept that non-B cells, liver epithelial cells here, can produce different classes of Ig.

Epithelial cells are a source of natural IgM that contribute to innate immune responses

Currently, natural IgM antibodies are considered to be the constitutively secreted products of B-1 cells in mice and humans. In this study, we found that mouse epithelial cells, including liver epithelial cells and small intestinal epithelial cells (IECs), could express IgM that also showed natural antibody activity. Moreover, similar to the B-1 cell-derived natural IgM that can be upregulated by TLR9 agonists (mimicking bacterial infection), the expression of epithelial cell-derived natural IgM could also be significantly increased by TLR9 signaling. More importantly, the epithelial cell-derived IgM was polyreactive, and it could recognize single-stranded DNA (ssDNA), double-stranded DNA (dsDNA), lipopolysaccharide (LPS), and insulin with low affinity; additionally, TLR9 agonists could enhance it in a MyD88-dependent manner. Furthermore, epithelial cell-derived IgM could bind various bacteria; therefore, it could be involved in anti-infection responses. Together, these results highlight the fact that epithelial cells are an important source of natural IgM, in addition to that produced by B-1 cells, and IgM contributes to the innate immune responses in local tissues, further demonstrating that the epithelium is a first line of defense in the protection against invading microbes.

Prognostic value and characterization of the ovarian cancer-specific antigen CA166-9

COC166-9 is an ovarian cancer-specific monoclonal antibody, and COC166-9-based immunotherapy has been shown to possess killing effects against ovarian cancer cells in vitro and in vivo. However the antigen recognized by COC166-9 (COC166-9-Ag, CA166-9) has not been identified and the clinical significance of CA166-9 expression remains unknown. We found that CA166-9 was positive in 53.1% of ovarian cancer tissues. Expression of CA166-9 was strongly correlated with the cancer recurrence (P<0.001). Patients with positive CA166-9 had substantially shorter overall survival (P=0.026) and disease-free survival (P=0.002). CA166-9 was also shown to be an independent predictive factor for overall survival (HR=2.454, P=0.016) and disease-free survival (HR=2.331, P=0.021). We identified CA166-9 as human immunoglobulin γ-1 heavy chain constant region (IGHG1). Purified IGHG1 promoted proliferation, migration, and invasion of CA166-9-negative ovarian cancer HOC1A cells, whereas it had minimal effects on the phenotypes of CA166-9-positive ovarian cancer CAOV-3 cells. In addition, overexpression of IGHG1 enhanced migration of ovarian cancer cells. On the contrary, COC166-9 inhibited proliferation, migration, and invasion of CAOV-3 cells, but had no effects on HOC1A cells. Therefore, IGHG1 similarly to CA166-9, could play an important role in ovarian cancer development and may serve as a potential prognostic marker and a therapeutical target for ovarian cancer.

NGX6a is degraded through a proteasome-dependent pathway without ubiquitination mediated by ezrin, a cytoskeleton-membrane linker

Our previous study demonstrated that the NGX6b gene acts as a suppressor in the invasion and migration of nasopharyngeal carcinoma (NPC). Recently, we identified the novel isoform NGX6a, which is longer than NGX6b. In this study, we first found that NGX6a was degraded in NPC cells and that this degradation was mediated by ezrin, a linker between membrane proteins and the cytoskeleton. Specific siRNAs against ezrin increase the protein level of NGX6a in these cells. During degradation, NGX6a is not ubiquitinated but is degraded through a proteasome-dependent pathway. The distribution pattern of ezrin was negatively associated with NGX6a in an immunochemistry analysis of a nasopharyngeal carcinoma tissue microarray and fetus multiple organ tissues and Western blot analysis in nasopharyngeal and NPC cell lines, suggesting that ezrin and NGX6a are associated and are involved in the progression and invasion of NPC. By mapping the interacting binding sites, the seven-transmembrane domain of NGX6a was found to be the critical region for the degradation of NGX6a, and the amino terminus of ezrin is required for the induction of NGX6a degradation. The knockdown of ezrin or transfection of the NGX6a mutant CO, which has an EGF-like domain and a transmembrane 1 domain, resulted in no degradation, significantly reducing the ability of invasion and migration of NPC cells. This study provides a novel molecular mechanism for the low expression of NGX6a in NPC cells and an important molecular event in the process of invasion and metastasis of nasopharyngeal carcinoma cells.

Spontaneous production of immunoglobulin M in human epithelial cancer cells

It is well known that B-1 B cells are the main cell type that is responsible for the production of natural immunoglobulin M (IgM) and can respond to infection by increasing IgM secretion. However, we unexpectedly found that some epithelial cells also can express rearranged IgM transcript that has natural IgM characteristics, such as germline-encoded and restricted rearrangement patterns. Here we studied IgM expression in human non-B cells and found that IgM was frequently expressed by many human epithelial cancer cells as well as non-cancer epithelial cells. Moreover, CD79A and CD79B, two molecules that are physically linked to membranous IgM on the surface of B cells to form the B cell antigen receptor complex, were also expressed on the cell surface of epithelial cancer cells and co-located with IgM. Like the natural IgM, the epithelial cancer cell-derived IgM recognized a series of microbial antigens, such as single-stranded DNA, double-stranded DNA, lipopolysaccharide, and the HEp-2 cell antigen. More important, stimulation of the toll-like receptor 9 (TLR9), which mimics bacterial infection, substantially increased the secretion of IgM in human epithelial cancer cells. These findings indicate that human epithelial cancer cells as well as non-cancer epithelial cells can spontaneously produce IgM with natural antibody activity.

Heterogeneity of aberrant immunoglobulin expression in cancer cells

Accumulating evidence has shown that immunoglobulin (Ig) is 'unexpectedly' expressed by epithelial cancer cells and that it can promote tumor growth. The main purpose of this study was to explore the components of the cancerous Ig and its possible function. The presence of cancerous Ig in the Golgi apparatus was confirmed by immunofluorescence, indirectly suggesting that the cancerous Ig was processed and packaged in cancer cells. Western blot analysis and ELISA results indicated that cancer cells produced membrane Ig and secreted Ig into the supernatant fraction. The cancerous Ig consists of an α heavy chain and a κ light chain. Finally, by analyzing the Ig components pulled down by protein A beads, the cancerous Ig was found to be structurally distinct from normal Ig. The cancerous Ig was truncated or aberrant. Although the underlying mechanism that causes the abnormalities has not been determined, our current discoveries strengthen our previous findings and promise fruitful future explorations.

CREST--a large and diverse superfamily of putative transmembrane hydrolases

Background

A number of membrane-spanning proteins possess enzymatic activity and catalyze important reactions involving proteins, lipids or other substrates located within or near lipid bilayers. Alkaline ceramidases are seven-transmembrane proteins that hydrolyze the amide bond in ceramide to form sphingosine. Recently, a group of putative transmembrane receptors called progestin and adipoQ receptors (PAQRs) were found to be distantly related to alkaline ceramidases, raising the possibility that they may also function as membrane enzymes.

Results

Using sensitive similarity search methods, we identified statistically significant sequence similarities among several transmembrane protein families including alkaline ceramidases and PAQRs. They were unified into a large and diverse superfamily of putative membrane-bound hydrolases called CREST (alkaline ceramidase, PAQR receptor, Per1, SID-1 and TMEM8). The CREST superfamily embraces a plethora of cellular functions and biochemical activities, including putative lipid-modifying enzymes such as ceramidases and the Per1 family of putative phospholipases involved in lipid remodeling of GPI-anchored proteins, putative hormone receptors, bacterial hemolysins, the TMEM8 family of putative tumor suppressors, and the SID-1 family of putative double-stranded RNA transporters involved in RNA interference. Extensive similarity searches and clustering analysis also revealed several groups of proteins with unknown function in the CREST superfamily. Members of the CREST superfamily share seven predicted core transmembrane segments with several conserved sequence motifs.

Conclusions

Universal conservation of a set of histidine and aspartate residues across all groups in the CREST superfamily, coupled with independent discoveries of hydrolase activities in alkaline ceramidases and the Per1 family as well as results from previous mutational studies of Per1, suggests that the majority of CREST members are metal-dependent hydrolases.

Reviewers

This article was reviewed by Kira S. Markarova, Igor B. Zhulin and Rob Knight.

The presence of IGHG1 in human pancreatic carcinomas is associated with immune evasion mechanisms

OBJECTIVES

To investigate the expression of Igγ-1 chain C region (IGHG1) in human pancreatic carcinomas and determine the biological function of IGHG1 expression in immune evasion mechanisms.

METHODS

Comparative proteomic analysis was used to detect the differential expression of IGHG1 in human pancreatic cancer tissues versus adjacent noncancerous tissues, followed by confirmatory tests including quantitative real-time reverse transcription-polymerase chain reaction, Western blot analysis, immunohistochemistry, and immunofluorescence. A murine pancreatic tumor model was established by transplantation of IGHG1-overexpressing Panc02 cells. The cytotoxic responses of natural killer (NK) cells were assessed with a lactate dehydrogenase release assay.

RESULTS

Igγ-1 chain C region was found to be present in human pancreatic cancer tissues but nearly absent or expressed lower in adjacent noncancerous tissues. In the murine pancreatic tumor model, the tumor growth was significantly accelerated from day 12 to 20 after tumor injection, and the survival time of animals was decreased. Blockage of IGHG1 led to retarded tumor growth and improved survival. The cytotoxicity assay revealed that IGHG1 downregulated the cytotoxic activity of NK cells through inhibition of antibody-dependent cellular cytotoxicity function.

CONCLUSIONS

The presence of IGHG1 in pancreatic cancer cells might constitute an important element responsible for tumor cell proliferation and immune evasion mechanisms.

LMP1-augmented kappa intron enhancer activity contributes to upregulation expression of Ig kappa light chain via NF-kappaB and AP-1 pathways in nasopharyngeal carcinoma cells

BACKGROUND

Expression of kappa gene is under the control of distinct cis-regulatory elements, including the kappa intron enhancer (iE kappa) and the kappa 3' enhancer (3'E kappa). The active enhancers and expression of immunoglobulin is generally considered to be restricted to B lymphocytes. However, accumulating evidence indicated that epithelial cancer cells, including nasopharyngeal carcinoma (NPC) cell lines, express immunoglobulins. The mechanisms underlying the expression of Igs in nonlymphoid cells remain unknown. On the basis of our previous finding that expression of kappa light chain in NPC cells can be upregulated by EBV-encoded latent membrane protein 1(LMP1) through the activation of NF-kappaB and AP-1 signaling pathways, we thus use NPC cells as model to further explore the molecular mechanisms of nonlymphoid cells expressing Ig kappa.

RESULTS

In this study, luciferase reporter plasmid containing human wild-type iE kappa, and its derivative plasmids containing mutant binding sites for transcription factor NF-kappaB or AP-1 were constructed. Luciferase reporter assays demonstrate iE kappa is active in Ig kappa-expressing NPC cells and LMP1 expression can upregulate the activity of iE kappa in NPC cells. Mutation of the NF-kappaB or AP-1 site within and downstream the iE kappa, inhibition of the NF-kappaB and AP-1 pathways by their respective chemical inhibitor Bay11-7082 and SP600125 as well as stable or transient expression of dominant-negative mutant of I kappaB alpha (DNMI kappaB alpha) or of c-Jun (TAM67) indicate that both sites are functional and LMP1-enhanced iE kappa activity is partly regulated by these two sites. Gel shift assays show that LMP1 promotes NF-kappaB subunits p52 and p65 as well as AP-1 family members c-Jun and c-Fos binding to the kappa NF-kappaB and the kappa AP-1 motifs in vitro, respectively. Both chemical inhibitors and dominant negative mutants targeting for NF-kappaB and AP-1 pathways can attenuate the LMP1-enhanced bindings. Co-IP assays using nuclear extracts from HNE2-LMP1 cells reveal that p52 and p65, c-Jun and c-Fos proteins interact with each other at endogenous levels. ChIP assays further demonstrate p52 and p65 binding to the kappaB motif as well as c-Jun and c-Fos binding to the AP-1 motif of Ig kappa gene in vivo.

CONCLUSION

These results suggest that human iE kappa is active in Ig kappa-expressing NPC cells and LMP1-stimulated NF-kappaB and AP-1 activation results in an augmenting activation of the iE kappa. LMP1 promotes the interactions of heterodimeric NF-kappaB (p52/p65) and heterodimeric AP-1 (c-Jun/c-Fos) transcription factors with the human iE kappa enhancer region are important for the upregulation of kappa light chain in LMP1-positive nasopharyngeal carcinoma cells.

The polymorphisms on Igkappa gene are related to susceptibility of breast cancer and gastric cancer

The phenomenon of immunoglobulin (Ig) expression in cancer cells has been discovered recently; the Ig protein expressed and secreted in cancer cells was found to be in favor of tumor growth. Two single-nucleotide polymorphism (SNP) loci rs232230 (5658C/G) and rs232228 (3635T/C) were identified on Igkappa gene previously, and we have demonstrated that they were associated with nasopharyngeal carcinoma susceptibility. In the present study, we further performed the study focused on these two SNPs in gastric and breast cancer, trying to demonstrate the association between the genotypes of the two SNPs and the susceptibility of gastric cancer and breast cancer. Our results suggested that the 5658-G allele and 3635-C allele were risk factors for both gastric cancer (odds ratio [OR]: 1.64 and 1.67, respectively) and breast cancer (OR: 1.94 and 1.56, respectively). Further, we also identified that they were related to other risk factors, including Helicobacter pylori (Hp) infection in gastric cancer and age in breast cancer.

Immunoglobulin expression in non-lymphoid lineage and neoplastic cells

It has traditionally been believed that the production of immunoglobulin (Ig) molecules is restricted to B lineage cells. However, immunoglobulin genes and proteins have been recently found in a variety of types of cancer cells, as well as some proliferating epithelial cells and neurons. The immunoglobulin molecules expressed by these cells consist predominantly of IgG, IgM, and IgA, and the light chains expressed are mainly kappa chains. Recombination activating genes 1 and 2, which are required for V(D)J recombination, are also expressed in these cells. Knowledge about the function of these non-lymphoid cell-derived immunoglobulins is limited. Preliminary data suggests that Ig secreted by epithelial cancer cells has some unidentified capacity to promote the growth and survival of tumor cells. As immunoglobulins are known to have a wide spectrum of important functions, the discovery of non-lymphoid cells and cancers that produce immunoglobulin calls for in-depth investigation of the functional and pathological significance of this previously unrecognized phenomenon.

Serum protein profiling to identify high-risk neuroblastoma: preclinical relevance of blood-based biomarkers

INTRODUCTION

Development of early detection assays for advanced stage neuroblastoma (NB) remains elusive. We have previously shown that serum protein profiling technologies can differentiate healthy from NB children. As various sources of patient related bias exist in serum proteins, we hypothesized a well controlled animal model may provide a better method to identify tumor blood-based markers during NB progression.

METHODS

Tumors were induced in the left kidneys of nude mice by the injection of cultured human NB cells (10(6)). Sera were collected from control and tumor-bearing mice at 2, 4, and 6 wk. Albumin-depleted sera were subjected to comparative proteomic profiling using 2D gel electrophoresis. Paired samples at each time point were analyzed and differentially expressed serum proteins were identified by mass spectrometry. Additionally, sera proteomic analysis from children with Stage IV NB and healthy controls were performed.

RESULTS

Overexpression of five mouse serum proteins [alpha(1)-acid glycoprotein, alpha(1)-antitrypsin, alpha(2)-macroglobulin, serum amyloid P-component, and serum amyloid A) were found only in NB-bearing mice. Changes in protein abundance were found to increase 2.5-fold (P < or = 0.05) between 2-, 4-, and 6-wk old mice. Underexpression of immunoglobulin kappa chain constant region was observed in the sera of tumor bearing mice compared with controls (2.5-fold, P < or = 0.05). Among NB patients, alpha(1)-acid glycoprotein, apolipoprotein A-IV, haptoglobin, and serum amyloid A were found to be up-regulated.

CONCLUSIONS

We identified distinct acute phase proteins that show up-regulation in both an animal tumor model and high-risk NB patients. As these serum proteins have been recognized as markers of tumor progression and prognosis in human malignancies, the validation of these polypeptides may enable serum proteomic profiling to become a valuable tool for identifying high-risk NB.

Expression and secretion of immunoglobulin alpha heavy chain with diverse VDJ recombinations by human epithelial cancer cells

Generally, only B lymphocytes express immunoglobulin. Recently, we found the expression of Ig alpha heavy chain in human epithelial cancer cells unexpectedly. We first detected Ig VDJ-Calpha and Ialpha-Calpha transcripts in multiple cancer cell lines. Further, the configuration of the Ig heavy chain genomic locus was analyzed in human cancer cells. We found that cancer cells have the recombination VDJ region, but bear Ig Salpha region in germline configuration, which is different from Ig expression pattern in B cells. And human epithelial cancers possess the essential effectors including RAG-1 and RAG-2, but not activation induced cytidine deaminase (AID) protein. These provide further proofs for Ig alpha expression. In addition, we found that human cancer cells not only express the protein of Ig alpha chain, but also secrete the protein in secretory IgA (SIgA) pattern. Importantly, diverse CDR3 recombinations were found in human cancer cells of different epithelial origin. Since IgA is the key immunoglobulin which contributes to local immunity of mucous membrane, the aberrant expression of Ig alpha heavy chain might increase our further comprehension to development and immunity of cancers.

Upregulated expression of kappa light chain by Epstein-Barr virus encoded latent membrane protein 1 in nasopharyngeal carcinoma cells via NF-kappaB and AP-1 pathways

B lymphocytes are generally considered to be the only source of immunoglobulins. However, increasing evidence revealed that some human epithelial cancer cell lines, including nasopharyngeal carcinoma (NPC) cell lines, expressed immunoglobulins. Moreover, we previously found that expression of kappa light chain in NPC cells could be upregulated by EBV-encoded latent membrane protein 1 (LMP1). Here, Western blot and flow cytometric analysis of intracellular kappa staining indicated that upregulation of the expression of kappa was inhibited by using LMP1-targeted DNAzyme and that Bay11-7082 and SP600125, inhibitors of JNK and NF-kappaB, respectively, inhibited LMP1-augmented kappa light chain expression in NPC cells. LMP1-positive NPC cells expressing the dominant-negative mutant of IkappaBalpha (DNMIkappaBalpha) or of c-Jun (TAM67) exhibited significantly decreasing kappa production compared with their parental cells. These results suggest that LMP1 elevated kappa light chain through activation of the NF-kappaB and AP-1 signaling pathways. The present study provided some hints of possible mechanisms by which human cancer cells of epithelial origin produced immunoglobulins.

A functional single nucleotide polymorphism site detected in nasopharyngeal carcinoma-associated transforming gene Tx

Tx is a transforming gene cloned from a nasopharyngeal carcinoma (NPC) cell line CNE2. Sequence analysis revealed that Tx encoded an aberrant immunoglobulin kappa light chain, which is abnormally expressed in epithelial tumor cells and plays an important role in nasopharyngeal carcinogenesis. Bioinformatic analysis confirmed the presence of a single nucleotide polymorphism (SNP) site in the Tx gene as matched to the Cancer Genome Anatomy Project SNP clusters database, which predicted 8 candidate SNP sites. Distribution of the confirmed SNP site in the genomes of healthy individuals and NPC patients was analyzed by denaturing high performance liquid chromatography. Heteroduplex genotype (GC/CG) occurred in NPC patients with a frequency significantly higher (52.44%) than that detected in healthy individuals (33.75%). In contrast, homoduplex genotype (GG) was less frequent in NPC patients (31.70%) than in normal individuals (56.25%), suggesting that heteroduplex genotype of Tx gene might be a risk factor for NPC.

Expression of immunoglobulin kappa light chain constant region in abnormal human cervical epithelial cells

Although it is generally believed that, under normal conditions, the only source of immunoglobulin is mature B lymphocytes, we recently found several epithelium-derived carcinoma cell lines also express immunolglobulin-like protein. We extended our study to biopsy samples of human cervical tissues with various epithelial lesions. By in situ hybridization, we only detected a low level of mRNA for the immunoglobulin kappa light chain constant region in epithelia with cervicitis. However, in epithelia with dysplasia and carcinoma, the expression of mRNA for the kappa constant region was markedly increased. There was no significant difference in the level of mRNA for the kappa constant region between epithelial dysplasia and carcinoma. The aberrant expression of immunoglobulin kappa light chain constant region in dysplastic and cancerous cervical epithelial cells may serve as a marker for malignant cell transformation.

Identification of tissue-specific genes in nasopharyngeal epithelial tissue and differentially expressed genes in nasopharyngeal carcinoma by suppression subtractive hybridization and cDNA microarray

Suppression subtractive hybridization (SSH) was performed for isolation of tissue-specific genes in nasopharyngeal epithelial tissue, by use of cDNAs from human adult nasopharyngeal epithelial tissue as tester and mixed cDNAs from esophagus, lung, liver, heart, stomach, spleen, skeletal muscle, kidney, and skin as drivers. Fourteen differentially expressed genes in nasopharyngeal epithelial tissue were obtained. Among these genes, LPLUNC1 and SPLUNC1 were confirmed to be specifically expressed in nasopharyngeal epithelial tissue and the trachea. A novel transcript of SPLUNC1, which we designate NASG, was found. We also combined SSH and cDNA microarray hybridization to identify genes whose expressions were altered in nasopharyngeal carcinoma (NPC). We used NPC cell line HNE1 and primary human embryo nasopharyngeal epithelial cells in one SSH experiment, and NPC biopsies and normal adult nasopharyngeal epithelial tissue in another. Some 1,200 SSH inserts from four subtractive cDNA libraries were arrayed onto nylon membranes by use of robotic printing. Differential gene expression was verified by hybridizing of the membranes with radioactively labeled first-strand cDNA from NPC cell line HNE1, primary human embryo nasopharyngeal epithelial cells, NPC biopsies, and normal adult nasopharyngeal epithelial tissue. Seventeen differentially expressed genes in NPC were obtained. Among these genes, we identified SPLUNC1 and LPLUNC1 to be down-expressed in NPC biopsies (34/48, 33/48).

Expression of tumor related genes NGX6, NAG-7, BRD7 in gastric and colorectal cancer

AIM: NGX6, NAG-7 and BRD7 genes are tumor related genes, which have been newly cloned by positional candidate cloning strategy. This study was designed to investigate the expression levels of NGX6, NAG-7 and BRD7 genes in human gastric and colorectal cancer tissues, and their corresponding normal tissues, and to investigate whether these genes play a role in the pathogenesis of gastric and colorectal cancers.

METHODS: Reverse transcription-polymerase chain reaction (RT-PCR), dot hybridization and Northern blot analysis were used to compare the expression levels of NGX6, NAG-7 and BRD7 genes in 34 gastric cancer tissues and 34 colorectal cancer tissues with their corresponding normal tissues of the same patients, respectively.

RESULTS: Among the 34 colorectal cancer specimens and the 34 gastric cancer specimens, the expression of NGX6 in 25 colorectal cancer tissues was absent or very weak (73.5%) by RT-PCR analysis. The down-regulation rate of NGX6 in colorectal cancer tissues was significantly higher than that in corresponding normal tissues (26.5%,9/34) (P < 0.005). Moreover, the down-regulation of NGX6 was significantly correlated with lymph node and/or distance metastases. Patients with lymph node and/or distance metastasis had much higher down-regulation rate of NGX6 than patients without metastases (93.8% vs 55.6%, P < 0.05). However no correlation was found between the expression of NGX6 and pathologic type of colorectal cancer in this study, and also the expression of NGX6 did not display any difference between gastric cancer and corresponding normal tissues (58.8% vs 70.6%, P > 0.25). Dot hybridization and Northern blot analysis confirmed the results of RT-PCR. Furthermore, NAG-7 and BRD7 mRNA was not up- or down-regulated in gastric and colorectal cancers compared with their corresponding normal tissues in our study.

CONCLUSION: The down-regulation of NGX6 may be closely associated with tumorigenesis and metastasis of colorectal carcinoma. However, it may not contribute to the development and progression of gastric carcinoma. In addition, the expression levels of NAG-7, and BRD7 did not alter in gastric and colorectal cancers. This seems to suggest that NAG-7 and BRD7 genes may not play a role in gastric and colorectal carcinogenesis.

Proteomic analysis of differential protein expression in human nasopharyngeal carcinoma cells induced by NAG7 transfection

Nasopharyngeal carcinoma (NPC) is a commonly occurring tumor in southern China and south east Asia. A genetic factor has now been recognized to be associated with this cancer. A new gene, named NAG7, was cloned from the common minimal deletion region in 3p25.3-26.3. In order to investigate the function of NAG7 gene, proteomic methods were used to find and identify the differential proteins and expected to elucidate the mechanism of NAG7. The NAG7 eukaryotic expression vector was constructed and transfected into NPC cell line HNE1 with liposome. Twenty-two differential protein spots in transfected cells were found significant and reproducible using high-resolution two-dimensional electrophoresis. Nine proteins that were up-regulated and seven proteins that were down-regulated were identified by matrix assisted laser desorption/ionization time of flight mass spectrometry and database analysis. These proteins included growth arrest specific protein, DNA binding protein, caspase 6, pinch protein and ras-related protein rab-36, which are involved in cell cycling, transcription regulation, signaling pathways and apoptosis. NAG7 may exert its functions by mediating differential expression of these proteins.