The SRCR/SID region of DMBT1 defines a complex multi-allele system representing the major basis for its variability in cancer

Proteogenomic insights into the biology and treatment of pancreatic ductal adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease with poor prognosis. Proteogenomic characterization and integrative proteomic analysis provide a functional context to annotate genomic abnormalities with prognostic value.

METHODS

We performed an integrated multi-omics analysis, including whole-exome sequencing, RNA-seq, proteomic, and phosphoproteomic analysis of 217 PDAC tumors with paired non-tumor adjacent tissues. In vivo functional experiments were performed to further illustrate the biological events related to PDAC tumorigenesis and progression.

RESULTS

A comprehensive proteogenomic landscape revealed that TP53 mutations upregulated the CDK4-mediated cell proliferation process and led to poor prognosis in younger patients. Integrative multi-omics analysis illustrated the proteomic and phosphoproteomic alteration led by genomic alterations such as KRAS mutations and ADAM9 amplification of PDAC tumorigenesis. Proteogenomic analysis combined with in vivo experiments revealed that the higher amplification frequency of ADAM9 (8p11.22) could drive PDAC metastasis, though downregulating adhesion junction and upregulating WNT signaling pathway. Proteome-based stratification of PDAC revealed three subtypes (S-I, S-II, and S-III) related to different clinical and molecular features. Immune clustering defined a metabolic tumor subset that harbored FH amplicons led to better prognosis. Functional experiments revealed the role of FH in altering tumor glycolysis and in impacting PDAC tumor microenvironments. Experiments utilizing both in vivo and in vitro assay proved that loss of HOGA1 promoted the tumor growth via activating LARP7-CDK1 pathway.

CONCLUSIONS

This proteogenomic dataset provided a valuable resource for researchers and clinicians seeking for better understanding and treatment of PDAC.

High temperature requirement A1 in cancer: biomarker and therapeutic target

As the life expectancy of the population increases worldwide, cancer is becoming a substantial public health problem. Considering its recurrence and mortality rates, most cancer cases are difficult to cure. In recent decades, a large number of studies have been carried out on different cancer types; unfortunately, tumor incidence and mortality have not been effectively improved. At present, early diagnostic biomarkers and accurate therapeutic strategies for cancer are lacking. High temperature requirement A1 (HtrA1) is a trypsin-fold serine protease that is also a chymotrypsin-like protease family member originally discovered in bacteria and later discovered in mammalian systems. HtrA1 gene expression is decreased in diverse cancers, and it may play a role as a tumor suppressor for promoting the death of tumor cells. This work aimed to examine the role of HtrA1 as a cell type-specific diagnostic biomarker or as an internal and external regulatory factor of diverse cancers. The findings of this study will facilitate the development of HtrA1 as a therapeutic target.

Salivary Scavenger and Agglutinin (SALSA) Is Expressed in Mucosal Epithelial Cells and Decreased in Bronchial Epithelium of Asthmatic Horses

The Salivary Scavenger and Agglutinin (SALSA) protein is an innate immune protein with various alleged functions, including the regulation of inflammation and tissue remodeling. Transcriptomic studies of severe equine asthma (SEA) showed downregulation of the gene encoding SALSA in bronchial epithelium of asthmatic compared to non-asthmatic horses. This study aimed to characterize expression of SALSA in equine tissues by immunohistochemistry (IHC), corroborate potential differences in epithelial gene expression between asthmatic and non-asthmatic horses, and assess the structure of equine SALSA. An antibody against SALSA was validated through immunoprecipitation followed by mass spectrometry and Western blotting to recognize the equine protein. This antibody was applied to tissue microarrays (TMAs) containing 22 tissues each from four horses. A quantitative PCR assay was designed to compare gene expression for SALSA between six asthmatic and six non-asthmatic horses, before and after an asthmatic challenge, using cDNA from endoscopic bronchial biopsies as source material. The SALSA gene from bronchial cDNA samples of 10 horses, was amplified and sequenced, and translated to characterize the protein structure. Immunostaining for SALSA was detected in the mucosal surfaces of the trachea, bronchi, bronchioles, stomach, small intestine and bladder, in pancreatic and salivary gland ducts, and in uterine gland epithelium. Staining was strongest in the duodenum, and the intercalated ducts and Demilune cells of the salivary gland. SALSA was concentrated in the apical regions of the epithelial cell cytoplasm, suggestive of a secreted protein. Gene expression was significantly lower (p = 0.031) in asthmatic compared to non-asthmatic horses. Equine SALSA consisted of three to five scavenger receptor cysteine-rich (SRCR) domains, two CUB (C1r/C1s, uegf, bmp-1) domains and one Zona Pellucida domain. These domains mediate the binding of ligands involved in innate immunity. Varying numbers of SRCR domains were identified in different horses, indicating different isoforms. In summary, equine SALSA has a predilection for mucosal sites, has multiple isoforms, and has decreased expression in asthmatic horses, suggesting alterations in innate immunity in equine asthma.

Long non-coding RNA CRNDE promotes gallbladder carcinoma carcinogenesis and as a scaffold of DMBT1 and C-IAP1 complexes to activating PI3K-AKT pathway

Deleted in malignant brain tumors 1 (DMBT1) is deleted during cancer progression and as a potential tumor-suppressor gene in various types of cancer. However, its role in Gallbladder cancer remains poorly understood. DMBT1 has low-expression and deletion of copy number were detected in normal tissues and GBC cancer tissues by qRT-PCR. Knockdown of DMBT1 increased migration and invasion and overexpressed DMBT1 impaired migration and invasion in GBC cells. We also evaluated the molecular mechanism of DMBT1 by RNA sequencing and GSEA analysis. RNA-Pulldown and RIP assay authenticated CRNDE can specified binding with DMBT1 and c-IAP1. Downregulation of DMBT1 resulted in significant change of gene expression (at least 2-fold) in PI3K-AKT pathway, increased expression of MMP-9, JUK-1, ERK and AKT, activating PI3K-AKT pathway lead to GBC carcinogenesis.We for the first time reported, DMBT1 as a prognosis biomarker, is low-expressed in GBC tumors, and CRNDE act as a scaffold to recruit the DMBT1 and c-IAP1, promotes the PI3K-AKT pathway. Our study reveals DMBT1 may be an important contributor to GBC cancer development.

Increased expression of deleted in malignant brain tumors (DMBT1) gene in precancerous gastric lesions: Findings from human and animal studies

Helicobacter pylori infection triggers a cascade of inflammatory stages that may lead to the appearance of non-atrophic gastritis, multifocal atrophic, intestinal metaplasia, dysplasia, and cancer. Deleted in malignant brain tumors 1 (DMBT1) belongs to the group of secreted scavenger receptor cysteine-rich proteins and is considered to be involved in host defense by binding to pathogens. Initial studies showed its deletion and loss of expression in a variety of tumors but the role of this gene in tumor development is not completely understood. Here, we examined the role of DMBT1 in gastric precancerous lesions in Caucasian, African American and Hispanic individuals as well as in the development of gastric pathology in a mouse model of H. pylori infection. We found that in 3 different populations, mucosal DMBT1 expression was significantly increased (2.5 fold) in individuals with dysplasia compared to multifocal atrophic gastritis without intestinal metaplasia; the increase was also observed in individuals with advanced gastritis and positive H. pylori infection. In our animal model, H. pylori infection of Dmbt1-/- mice resulted in significantly higher levels of gastritis, more extensive mucous metaplasia and reduced Il33 expression levels in the gastric mucosa compared to H. pylori-infected wild type mice. Our data in the animal model suggest that in response to H. pylori infection DMBT1 may mediate mucosal protection reducing the risk of developing gastric precancerous lesions. However, the increased expression in human gastric precancerous lesions points to a more complex role of DMBT1 in gastric carcinogenesis.

Human DMBT1-Derived Cell-Penetrating Peptides for Intracellular siRNA Delivery

Small interfering RNA (siRNA) is a promising molecule for gene therapy, but its therapeutic administration remains problematic. Among the recently proposed vectors, cell-penetrating peptides show great promise in in vivo trials for siRNA delivery. Human protein DMBT1 (deleted in malignant brain tumor 1) is a pattern recognition molecule that interacts with polyanions and recognizes and aggregates bacteria. Taking advantage of these properties, we investigated whether specific synthetic DMBT1-derived peptides could be used to formulate nanoparticles for siRNA administration. Using an electrophoretic mobility shift assay and UV spectra, we identified two DMBT1 peptides that could encapsulate the siRNA with a self- and co-assembly mechanism. The complexes were stable for at least 2 hr in the presence of either fetal bovine serum (FBS) or RNase A, with peptide-dependent time span protection. ζ-potential, circular dichroism, dynamic light scattering, and transmission electron microscopy revealed negatively charged nanoparticles with an average diameter of 10–800 nm, depending on the reaction conditions, and a spherical or rice-shaped morphology, depending on the peptide and β-helix conformation. We successfully transfected human MCF7 cells with fluorescein isothiocyanate (FITC)-DMBT1-peptide-Cy3-siRNA complexes. Finally, DMBT1 peptides encapsulating an siRNA targeting a fluorescent reporter gene showed efficient gene silencing in MCF7-recombinant cells. These results lay the foundation for a new research line to exploit DMBT1-peptide nanocomplexes for therapeutic siRNA delivery.

The scavenging capacity of DMBT1 is impaired by germline deletions

The Scavenger Receptor Cysteine-Rich (SRCR) proteins are an archaic group of proteins characterized by the presence of multiple SRCR domains. They are membrane-bound or secreted proteins, which are generally related to host defense systems in animals. Deleted in Malignant Brain Tumors 1 (DMBT1) is a SRCR protein which is secreted in mucosal fluids and involved in host defense by pathogen binding by its SRCR domains. Genetic polymorphism within DMBT1 leads to DMBT1-alleles giving rise to polypeptides with interindividually different numbers of SRCR domains, ranging from 8 SRCR domains (encoded by 6 kb DMBT1 variant) to 13 SRCR domains (encoded by the 8 kb DMBT1 variant). In the present study, we have investigated whether reduction from 13 to 8 amino-terminal SRCR domains leads to reduction of bacterial binding. The 6 kb variant bound ~20–45% less bacteria compared to the 8 kb variant. These results support the hypothesis that genetic variation in DMBT1 may influence microbial defense.

DMBT1 expression in biliary carcinogenesis with correlation of clinicopathological data

AIMS

Deleted in malignant brain tumours 1 (DMBT1) exerts functions in the regulation of epithelial differentiation and inflammation and has been proposed as a tumour suppressor. Because chronic inflammation is a hallmark of cholangiocarcinogenesis, the aim of this study was to investigate the expression of DMBT1 in biliary tract cancer (BTC) and to correlate this expression with clinicopathological data.

METHODS AND RESULTS

The expression of DMBT1 protein was examined immunohistochemically in 157 BTC patients [41 intrahepatic (ICC), 60 extrahepatic cholangiocarcinomas (ECC) and 56 adenocarcinomas of the gallbladder (GBAC)]. Additionally, 56 samples of high-grade biliary intraepithelial neoplasia (BilIN 3) and 92 corresponding samples of histological non-neoplastic biliary tract tissues were included. DMBT1 expression was increased significantly in BilIN 3 compared to normal tissue (P < 0.0001) and BTC (P < 0.0001). BTC showed no significant difference in DMBT1 expression compared to non-neoplastic biliary tissue (P = 0.315). Absent DMBT1 expression in non-neoplastic biliary tissue of BTC patients was associated with poorer survival (P = 0.027). DMBT1 expression was correlated significantly with patients' age (P < 0.001).

CONCLUSION

DMBT1 is expressed differently in cholangiocarcinogenesis and poorer patients' survival rates are associated with absent DMBT1 expression in non-neoplastic biliary tissue, suggesting a tumour-suppressive role of DMBT1 in early cholangiocarcinogenesis.

Salivary agglutinin is the major component in human saliva that modulates the lectin pathway of the complement system

Saliva interacts with blood after mucosal damage or leakage of gingival crevicular fluid. Surface-adsorbed salivary agglutinin (SAG) activates the lectin pathway (LP) of the complement system via mannose-binding lectin, while SAG in solution inhibits complement activation. In the present study we investigated if, next to SAG, whole and glandular saliva itself and other salivary glycoproteins activate or inhibit the LP. Complement activation was measured by detecting C4 deposition on microtiter plates coated with saliva or purified proteins. Complement inhibition was measured after incubating serum with saliva or proteins in microtiter plates coated with mannan, an LP activator. Adsorbed whole, sublingual and submandibular saliva showed LP-dependent complement activation. Blood group secretors, but not non-secretors, activated the LP. Saliva of both secretors and non-secretors inhibited C4 deposition on mannan. After depletion of SAG, saliva no longer inhibited the LP. Other salivary proteins, including amylase, MUC5B and histatin 2, did not activate or inhibit the LP. Surface-adsorbed whole saliva and glandular saliva samples activate the LP of complement, depending on the presence of SAG and the secretor status of the donor. In solution, saliva inhibits the LP, depending on the presence of SAG, but independent of the secretor status.

SALSA: A Regulator of the Early Steps of Complement Activation on Mucosal Surfaces

Complement is present mainly in blood. However, following mechanical damage or inflammation, serous exudates enter the mucosal surfaces. Here, the complement proteins interact with other endogenous molecules to keep microbes from entering the parenteral tissues. One of the mucosal proteins known to interact with the early complement components of both the classical and the lectin pathway is the salivary scavenger and agglutinin (SALSA). SALSA is also known as deleted in malignant brain tumors 1 and gp340. It is found both attached to the epithelium and secreted into the surrounding fluids of most mucosal surfaces. SALSA has been shown to bind directly to C1q, mannose-binding lectin, and the ficolins. Through these interactions SALSA regulates activation of the complement system. In addition, SALSA interacts with surfactant proteins A and D, secretory IgA, and lactoferrin. Ulcerative colitis and Crohn's disease are examples of diseases, where complement activation in mucosal tissues may occur. This review describes the latest advances in our understanding of how the early complement components interact with the SALSA molecule. Furthermore, we discuss how these interactions may affect disease propagation on mucosal surfaces in immunological and inflammatory diseases.

Dmbt1 does not affect a Western style diet-induced liver damage in mice

In the last three decades the prevalence of non-alcoholic fatty liver disease has markedly increased. Results from epidemiologic studies indicate that not only a general overnutrition but rather a diet rich in sugar, fat and cholesterol (= Western style diet) maybe a risk factor for the development of non-alcoholic fatty liver disease. Concerning liver diseases, it is known that Deleted in malignant brain tumors 1 is amongst others related to liver injury and repair. In addition Deleted in malignant brain tumors 1 seems to play a role in regard to the maintenance of the intestinal homeostasis and the regulation of food intake. Starting from this background the aim of the present study was to investigate if Dmbt1 plays a role in Western style diet-induced non-alcoholic steatohepatitis in mice. Dmbt1^+/+ and Dmbt1^−/− mice were fed a Western style diet or control diet ad libitum for 12 weeks. Both Western style diet fed groups gained significant more weight than the controls and developed a mild non-alcoholic steatohepatitis. The presence/absence of functional Deleted in malignant brain tumors 1 had no effect on parameters like food intake, weight gain, fasting glucose, and liver damage. These results suggest that Deleted in malignant brain tumors 1 plays a minor part on the development of a diet-induced liver damage in mice.

Deleted in malignant brain tumor 1 is secreted in the oviduct and involved in the mechanism of fertilization in equine and porcine species

Oviductal environment affects preparation of gametes for fertilization, fertilization itself, and subsequent embryonic development. The aim of this study was to evaluate the effect of oviductal fluid and the possible involvement of deleted in malignant brain tumor 1 (DMBT1) on IVF in porcine and equine species that represent divergent IVF models. We first performed IVF after pre-incubation of oocytes with or without oviductal fluid supplemented or not with antibodies directed against DMBT1. We showed that oviductal fluid induces an increase in the monospermic fertilization rate and that this effect is canceled by the addition of antibodies, in both porcine and equine species. Moreover, pre-incubation of oocytes with recombinant DMBT1 induces an increase in the monospermic fertilization rate in the pig, confirming an involvement of DMBT1 in the fertilization process. The presence of DMBT1 in the oviduct at different stages of the estrus cycle was shown by western blot and confirmed by immunohistochemical analysis of ampulla and isthmus regions. The presence of DMBT1 in cumulus–oocyte complexes was shown by western blot analysis, and the localization of DMBT1 in the zona pellucida and cytoplasm of equine and porcine oocytes was observed using immunofluorescence analysis and confocal microscopy. Moreover, we showed an interaction between DMBT1 and porcine spermatozoa using surface plasmon resonance studies. Finally, a bioinformatic and phylogenetic analysis allowed us to identify the DMBT1 protein as well as a DMBT1-like protein in several mammals. Our results strongly suggest an important role of DMBT1 in the process of fertilization.

High DMBT1 concentrations in breast milk correlate with increased risk of infection in preterm and term neonates

Background

Human milk contains immune molecules involved in the protection of newborns against infections. We analyzed the concentration of Deleted in Malignant Brain Tumors 1 (DMBT1), a protein with functions in innate immunity, in breast milk.

Methods

DMBT1 was detected in breast milk by Western blotting and its concentration was quantified by ELISA in 95 breast milk samples collected from mothers of preterm and term neonates during the first four weeks after delivery. Possible effects of maternal or neonatal parameters were analyzed by different statistical tests.

Results

The mean DMBT1 concentration (± standard error of the mean) in the tested milk samples was 2.48 ± 0.26 μg/mL (range: 0.112 μg/mL to 17.984 μg/mL) and represented 0.0087% of the total protein content. The comparison between the newborns with infection and the newborns without infection revealed significantly higher DMBT1 concentrations in breast milk in the group with infection (6.72 ± 2.53 μg/mL versus 2.20 ± 0.35 μg/mL (P = 0.031)). Neither maternal nor neonatal parameters showed a correlation with the milk DMBT1 levels.

Conclusions

DMBT1 is a component of breast milk after birth and is up-regulated in the breast milk from mothers with newborns suffering from neonatal infection. Thus, breast milk DMBT1 may be part of the innate immunity similar to secretory IgA.

Deleted in malignant brain tumors-1 protein (DMBT1): a pattern recognition receptor with multiple binding sites

Deleted in Malignant Brain Tumors-1 protein (DMBT1), salivary agglutinin (DMBT1(SAG)), and lung glycoprotein-340 (DMBT1(GP340)) are three names for glycoproteins encoded by the same DMBT1 gene. All these proteins belong to the scavenger receptor cysteine-rich (SRCR) superfamily of proteins: a superfamily of secreted or membrane-bound proteins with SRCR domains that are highly conserved down to sponges, the most ancient metazoa. In addition to SRCR domains, all DMBT1s contain two CUB domains and one zona pellucida domain. The SRCR domains play a role in the function of DMBT1s, which is the binding of a broad range of pathogens including cariogenic streptococci, Helicobacter pylori and HIV. Mucosal defense proteins like IgA, surfactant proteins and lactoferrin also bind to DMBT1s through their SRCR domains. The binding motif on the SRCR domains comprises an 11-mer peptide in which a few amino acids are essential for binding (GRVEVLYRGSW). Adjacent to each individual SRCR domain are glycosylation domains, where the attached carbohydrate chains play a role in the binding of influenza A virus and Helicobacter pylori. The composition of the carbohydrate chains is not only donor specific, but also varies between different organs. These data demonstrate a role for DMBT1s as pattern recognition molecules containing various peptide and carbohydrate binding motifs.

Identification of a DMBT1 polymorphism associated with increased breast cancer risk and decreased promoter activity

According to present estimations, the unfavorable combination of alleles with low penetrance but high prevalence in the population might account for the major part of hereditary breast cancer risk. Deleted in Malignant Brain Tumors 1 (DMBT1) has been proposed as a tumor suppressor for breast cancer and other cancer types. Genomewide mapping in mice further identified Dmbt1 as a potential modulator of breast cancer risk. Here, we report the association of two frequent and linked single-nucleotide polymorphisms (SNPs) with increased breast cancer risk in women above the age of 60 years: DMBT1 c.-93C>T, rs2981745, located in the DMBT1 promoter; and DMBT1 c.124A>C, p.Thr42Pro, rs11523871(odds ratio [OR]=1.66, 95% confidence interval [CI]=1.21-2.29, P=0.0017; and OR=1.66; 95% CI=1.21-2.28, P=0.0016, respectively), based on 1,195 BRCA1/2 mutation-negative German breast cancer families and 1,466 unrelated German controls. Promoter studies in breast cancer cells demonstrate that the risk-increasing DMBT1 -93T allele displays significantly decreased promoter activity compared to the DMBT1 -93C allele, resulting in a loss of promoter activity. The data suggest that DMBT1 polymorphisms in the 5'-region are associated with increased breast cancer risk. In accordance with previous results, these data link decreased DMBT1 levels to breast cancer risk.

Secreted cyclophilin A, a peptidylprolyl cis-trans isomerase, mediates matrix assembly of hensin, a protein implicated in epithelial differentiation

Hensin is a rabbit ortholog of DMBT1, a multifunctional, multidomain protein implicated in the regulation of epithelial differentiation, innate immunity, and tumorigenesis. Hensin in the extracellular matrix (ECM) induced morphological changes characteristic of terminal differentiation in a clonal cell line (clone C) of rabbit kidney intercalated cells. Although hensin is secreted in monomeric and various oligomeric forms, only the polymerized ECM form is able to induce these phenotypic changes. Here we report that hensin secretion and matrix assembly were inhibited by the peptidylprolyl cis-trans isomerase (PPIase) inhibitors cyclosporin A (CsA) and a derivative of cyclosporin A with modifications in the d-Ser side chain (Cs9) but not by the calcineurin pathway inhibitor FK506. PPIase inhibition led to failure of hensin polymerization in the medium and ECM, plus the loss of apical cytoskeleton, apical microvilli, and the columnar epithelial shape of clone C cells. Cyclophilin A was produced and secreted into the media to a much greater extent than cyclophilins B and C. Our results also identified the direct CsA-sensitive interaction of cyclophilin A with hensin, suggesting that cyclophilin A is the PPIase that mediates the polymerization and matrix assembly of hensin. These results are significant because this is the first time a direct role of peptidylprolyl cis-trans isomerase activity has been implicated in the process of epithelial differentiation.

Salivary agglutinin/glycoprotein-340/DMBT1: a single molecule with variable composition and with different functions in infection, inflammation and cancer

Salivary agglutinin (SAG), lung glycoprotein-340 (gp-340) and Deleted in Malignant Brain Tumours 1 (DMBT1) are three names for identical proteins encoded by the dmbt1 gene. DMBT1/SAG/gp-340 belongs to the scavenger receptor cysteine-rich (SRCR) superfamily of proteins, a superfamily of secreted or membrane-bound proteins with SRCR domains that are highly conserved down to sponges, the most ancient metazoa. On the one hand, DMBT1 may represent an innate defence factor acting as a pattern recognition molecule. It interacts with a broad range of pathogens, including cariogenic streptococci and Helicobacter pylori, influenza viruses and HIV, but also with mucosal defence proteins, such as IgA, surfactant proteins and MUC5B. Stimulation of alveolar macrophage migration, suppression of neutrophil oxidative burst and activation of the complement cascade point further to an important role in the regulation of inflammatory responses. On the other hand, DMBT1 has been demonstrated to play a role in epithelial and stem cell differentiation. Inactivation of the gene coding for this protein may lead to disturbed differentiation, possibly resulting in tumour formation. These data strongly point to a role for DMBT1 as a molecule linking innate immune processes with regenerative processes.

DMBT1 confers mucosal protection in vivo and a deletion variant is associated with Crohn's disease

BACKGROUND & AIMS

Impaired mucosal defense plays an important role in the pathogenesis of Crohn's disease (CD), one of the main subtypes of inflammatory bowel disease (IBD). Deleted in malignant brain tumors 1 (DMBT1) is a secreted scavenger receptor cysteine-rich protein with predominant expression in the intestine and has been proposed to exert possible functions in regenerative processes and pathogen defense. Here, we aimed at analyzing the role of DMBT1 in IBD.

METHODS

We studied DMBT1 expression in IBD and normal tissues by quantitative reverse transcription-polymerase chain reaction, immunohistochemistry, and mRNA in situ hybridization. Genetic polymorphisms within DMBT1 were analyzed in an Italian IBD case-control sample. Dmbt1(-/-) mice were generated, characterized, and analyzed for their susceptibility to dextran sulfate sodium-induced colitis.

RESULTS

DMBT1 levels correlate with disease activity in inflamed IBD tissues. A highly significant fraction of the patients with IBD displayed up-regulation of DMBT1 specifically in the intestinal epithelial surface cells and Paneth cells. A deletion allele of DMBT1 with a reduced number of scavenger receptor cysteine-rich domain coding exons is associated with an increased risk of CD (P = .00056; odds ratio, 1.75) but not for ulcerative colitis. Dmbt1(-/-) mice display enhanced susceptibility to dextran sulfate sodium-induced colitis and elevated Tnf, Il6, and Nod2 expression levels during inflammation.

CONCLUSIONS

DMBT1 may play a role in intestinal mucosal protection and prevention of inflammation. Impaired DMBT1 function may contribute to the pathogenesis of CD.

Regulation of DMBT1 via NOD2 and TLR4 in intestinal epithelial cells modulates bacterial recognition and invasion

Mucosal epithelial cell layers are constantly exposed to a complex resident microflora. Deleted in malignant brain tumors 1 (DMBT1) belongs to the group of secreted scavenger receptor cysteine-rich proteins and is considered to be involved in host defense by pathogen binding. This report describes the regulation and function of DMBT1 in intestinal epithelial cells, which form the primary immunological barrier for invading pathogens. We report that intestinal epithelial cells up-regulate DMBT1 upon proinflammatory stimuli (e.g., TNF-alpha, LPS). We demonstrate that DMBT1 is a target gene for the intracellular pathogen receptor NOD2 via NF-kappaB activation. DMBT1 is strongly up-regulated in the inflamed intestinal mucosa of Crohn's disease patients with wild-type, but not with mutant NOD2. We show that DMBT1 inhibits cytoinvasion of Salmonella enterica and LPS- and muramyl dipeptide-induced NF-kappaB activation and cytokine secretion in vitro. Thus, DMBT1 may play an important role in the first line of mucosal defense conferring immune exclusion of bacterial cell wall components. Dysregulated intestinal DMBT1 expression due to mutations in the NOD2/CARD15 gene may be part of the complex pathophysiology of barrier dysfunction in Crohn's disease.

Genetic mapping in mice identifies DMBT1 as a candidate modifier of mammary tumors and breast cancer risk

Low-penetrance breast cancer susceptibility alleles seem to play a significant role in breast cancer risk but are difficult to identify in human cohorts. A genetic screen of 176 N2 backcross progeny of two Trp53(+/-) strains, BALB/c and C57BL/6, which differ in their susceptibility to mammary tumors, identified a modifier of mammary tumor susceptibility in an approximately 25-Mb interval on mouse chromosome 7 (designated SuprMam1). Relative to heterozygotes, homozygosity for BALB/c alleles of SuprMam1 significantly decreased mammary tumor latency from 70.7 to 61.1 weeks and increased risk twofold (P = 0.002). Dmbt1 (deleted in malignant brain tumors 1) was identified as a candidate modifier gene within the SuprMam1 interval because it was differentially expressed in mammary tissues from BALB/c-Trp53(+/-) and C57BL/6-Trp53(+/-) mice. Dmbt1 mRNA and protein was reduced in mammary glands of the susceptible BALB/c mice. Immunohistochemical staining demonstrated that DMBT1 protein expression was also significantly reduced in normal breast tissue from women with breast cancer (staining score, 1.8; n = 46) compared with cancer-free controls (staining score, 3.9; n = 53; P < 0.0001). These experiments demonstrate the use of Trp53(+/-) mice as a sensitized background to screen for low-penetrance modifiers of cancer. The results identify a novel mammary tumor susceptibility locus in mice and support a role for DMBT1 in suppression of mammary tumors in both mice and women.

Innate immunity glycoprotein gp-340 variants may modulate human susceptibility to dental caries

Background

Bacterial adhesion is an important determinant of colonization and infection, including dental caries. The salivary scavenger receptor cysteine-rich glycoprotein gp-340, which mediates adhesion of Streptococcus mutans (implicated in caries), harbours three major size variants, designated gp-340 I to III, each specific to an individual saliva. Here we have examined the association of the gp-340 I to III polymorphisms with caries experience and adhesion of S. mutans.

Methods

A case-referent study was performed in 12-year-old Swedish children with high (n = 19) or low (n = 19) caries experiences. We measured the gp-340 I to III saliva phenotypes and correlated those with multiple outcome measures for caries experience and saliva adhesion of S. mutans using the partial least squares (PLS) multivariate projection technique. In addition, we used traditional statistics and 2-year caries increment to verify the established PLS associations, and bacterial adhesion to purified gp-340 I to III proteins to support possible mechanisms.

Results

All except one subject were typed as gp-340 I to III (10, 23 and 4, respectively). The gp-340 I phenotype correlated positively with caries experience (VIP = 1.37) and saliva adhesion of S. mutans Ingbritt (VIP = 1.47). The gp-340 II and III phenotypes tended to behave in the opposite way. Moreover, the gp-340 I phenotype tended to show an increased 2-year caries increment compared to phenotypes II/III. Purified gp-340 I protein mediated markedly higher adhesion of S. mutans strains Ingbritt and NG8 and Lactococcus lactis expressing AgI/II adhesins (SpaP or PAc) compared to gp-340 II and III proteins. In addition, the gp-340 I protein appeared over represented in subjects positive for Db, an allelic acidic PRP variant associated with caries, and subjects positive for both gp-340 I and Db tended to experience more caries than those negative for both proteins.

Conclusion

Gp-340 I behaves as a caries susceptibility protein.

Variant size- and glycoforms of the scavenger receptor cysteine-rich protein gp-340 with differential bacterial aggregation

Glycoprotein gp-340 aggregates bacteria in saliva as part of innate defence at mucosal surfaces. We have detected size- and glycoforms of gp-340 between human saliva samples (n = 7) and lung gp-340 from a proteinosis patient using antibodies and lectins in Western blots and ELISA measurements. Western blots of saliva samples, and of gp-340 purified, from the seven donors using a gp-340 specific antibody distinguished four gp-340 size variants, designated I to IV (n = 2,2,2 and 1). While saliva gp-340 variants I to III had single bands of increasing sizes, variant IV and lung gp-340 had double bands. Purified I to IV proteins all revealed a N-terminal sequence TGGWIP upon Edman degradation. Moreover, purified gp-340 from the seven donors and lung gp-340 shared N-glycans, sialylated Galbeta1-3GalNAc and (poly)lactosamine structures. However, the larger size gp-340 grouping II/III (n = 4) and smaller size grouping I/IV correlated with a secretor, Se(+), and a non secretor, Se(-), dependent glycoform of gp-340, respectively (p = 0.03). The Se(+) glycoforms contained ABH, Le(b), Le(y) and polylactosamine structures, while the Se(-) glycoforms lacked ABH antigens but expressed Le(a), Le(x) and lactosamine structures. By contrast, lung gp-340 completely lacked ABH, Le(a/b), Le(x/y) or sLe(x) structures. Gp-340 and secretor typing of saliva from additional donors (n = 29) showed gp-340 glycoforms I to IV for 6, 16, 4 and 0 donors, respectively, and 3 non-typeable donors, and verified that gp-340 glycoforms I and II/III correlate with Se(-) and Se(+) phenotypes, respectively (p < 0.0001). The glycoforms of saliva and lung gp-340 mediated differential aggregation of Le(b)- (Helicobacter pylori), sialylpolylactosamine- (Streptococcus suis) or sialic acid- (Streptococcus mutans) binding bacteria. In conclusion, variant size- and glycoforms of gp-340 are expressed by different individuals and may modulate the biological properties of gp-340 pertinent to health and disease.

Serine proteases HTRA1 and HTRA3 are down-regulated with increasing grades of human endometrial cancer

OBJECTIVE

The high temperature requirement factor A (HTRA) family consists of serine proteases with domains homologous to those of bacterial HTRA. Four human HTRA members have been described: HTRA1-4. HTRA1 and HTRA3 share a high degree of domain homologies and may therefore share a functional similarity. HTRA1 mRNA and protein is reported to be down-regulated in SV40-transformed cells, a malignant melanoma cell line, ovarian tumors, and ovarian cancer cell lines, suggesting a progressive loss of HTRA1 and the protein in cancer. This raises the possibility that HTRA3 may likewise be involved in cancer. This study examined the expression of mRNA and protein levels of HTRA1 and HTRA3 in human endometrial cancer (EC).

METHODS

Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis was performed in normal endometrium (n = 4) and in three grades of EC (n = 5 for each EC grade). Immunohistochemistry was used to determine the protein expression and the cellular localization of HTRA1 and HTRA3 in normal endometrium tissue (n = 6) and in three grades of EC (n = 8-10 for each EC grade).

RESULTS

RT-PCR analysis showed a significant reduction of HTRA1 and HTRA3 mRNA in endometrial cancer compared to normal endometrium. HTRA1 and HTRA3 protein showed a similar pattern of expression in EC tissue. Positive immunostaining, scored semiquantitatively, revealed a significant decrease of HTRA1 and 3 protein expression with increasing grades of EC.

CONCLUSION

These data suggest that HTRA1 and HTRA3 mRNA and protein levels decrease with increasing grades of EC.

Molecular characterization of the porcine deleted in malignant brain tumors 1 gene (DMBT1)

The human gene deleted in malignant brain tumors 1 (DMBT1) is considered to play a role in tumorigenesis and pathogen defense. It encodes a protein with multiple scavenger receptor cysteine-rich (SRCR) domains, which are involved in recognition and binding of a broad spectrum of bacterial pathogens. The SRCR domains are encoded by highly homologous repetitive exons, whose number in humans may vary from 8 to 13 due to genetic polymorphism. Here, we characterized the porcine DMBT1 gene on the mRNA and genomic level. We assembled a 4.5 kb porcine DMBT1 cDNA sequence from RT-PCR amplified seminal vesicle RNA. The porcine DMBT1 cDNA contains an open reading frame of 4050 nt. The transcript gives rise to a putative polypeptide of 1349 amino acids with a calculated mass of 147.9 kDa. Compared to human DMBT1, it contains only four N-terminal SRCR domains. Northern blotting revealed transcripts of approximately 4.7 kb in size in the tissues analyzed. Analysis of ESTs suggested the existence of secreted and transmembrane variants. The porcine DMBT1 gene spans about 54 kb on chromosome 14q28-q29. In contrast to the characterized cDNA, the genomic BAC clone only contained 3 exons coding for N-terminal SRCR domains. In different mammalian DMBT1 orthologs large interspecific differences in the number of SRCR exons and utilization of the transmembrane exon exist. Our data suggest that the porcine DMBT1 gene may share with the human DMBT1 gene additional intraspecific variations in the number of SRCR-coding exons.

Generation of a vector system facilitating cloning of DMBT1 variants and recombinant expression of functional full-length DMBT1

Deleted in malignant brain tumours 1 (DMBT1) codes for a approximately 340kDa glycoprotein with highly repetitive scavenger receptor cysteine-rich (SRCR) domains. DMBT1 was implicated in cancer, defence against viral and bacterial infections, and differentiation of epithelial cells. Recombinant expression and purification of DMBT1 is an essential step for systematic standardized functional research and towards the evaluation of its therapeutical potential. So far, DMBT1 is obtained from natural sources such as bronchioalveolar lavage or saliva, resulting in time consuming sample collection, low yields, and protein preparations which may substantially vary due to differential processing and genetic polymorphism, all of which impedes functional research on DMBT1. Cloning of DMBT1 cDNAs is hampered because of the size and the 13 highly homologous SRCR exons. In this study, we report on the setup of a vector system that facilitates cloning of DMBT1 variants. We demonstrate applicability of the vector system by expression of the largest DMBT1 variant in a tetracycline-inducible mammalian expression system using the Chinese hamster ovary cell line. Yields up to 30 mg rDMBT1 per litre of cell culture supernatant could be achieved with an optimized production procedure. By harnessing the specific bacteria-binding property of DMBT1 we established an affinity purification procedure which allows the isolation of more than 3 mg rDMBT1 with a purity of about 95%. Although the glycosylation moieties of rDMBT1 are different from DMBT1(SAG) isolated from saliva, we demonstrate that rDMBT1 is functionally active in aggregating Gram-positive and Gram-negative bacteria and binding to C1q and lactoferrin, which represent two known endogenous DMBT1 ligands.

Decreased Replication Ability of E1-Deleted Adenoviruses Correlates with Increased Brain Tumor Malignancy

E1 region replacement adenoviruses are replication defective and are propagated in cells providing adenovirus E1A and E1B proteins. Although they are being developed for antitumor therapies, the proliferative behaviors of these viruses in normal brain tissues or in brain tumors are unknown. To address this, freshly cultured cells from normal human brain and common brain tumors (astrocytomas and meningiomas) were infected using wild-type species C adenoviruses and adenoviruses missing E1A (H5dl312) or E1A plus E1B (H5dl434). Viral DNA replication, late viral protein expression, and production of infectious progeny were characterized. Wild-type adenoviruses grew efficiently in normal brain and brain tumor cells. In comparison, E1-deleted adenovirus DNA replication was delayed and lower in cells derived from normal brain tissues, meningiomas, and low-grade astrocytomas. However, in contrast, E1-deleted adenovirus DNA replication did not occur or was extremely low in cells derived from malignancy grade III and IV astrocytic tumors. Because wild-type adenoviruses infected and replicated in all cells, the malignancy grade-based differential E1-deleted adenovirus DNA replication was not explained by differential virus uptake. Infectious H5dl312 and H5dl434 production correlated with viral DNA replication. Compared with a 5-day average for wild-type infections, advanced cytopathology was noted approximately 4 weeks after H5dl312 or H5dl434 infection of meningioma, astrocytoma, and normal brain cells. Cytopathology was not observed after H5dl312 or H5dl434 infection of glioblastoma, anaplastic astrocytoma, and gliosarcoma cells. Because of this tumor grade-based differential growth, the E1-deleted adenoviruses may represent novel tools for studies of brain tumor malignancy.

Salivary agglutinin/DMBT1SAG expression is up-regulated in the presence of salivary gland tumors

Salivary agglutinin (SAG) is encoded by the gene Deleted in Malignant Brain Tumors 1 (DMBT1) and represents the salivary variant of DMBT1 (DMBT1(SAG)). While SAG is a bona fide anti-caries factor, DMBT1 was proposed as a candidate tumor-suppressor for brain, digestive tract, and lung cancer. Though DMBT1(SAG) is expressed in the salivary glands, its expression in salivary gland tumors is unknown. Here we analyzed DMBT1(SAG) expression in 20 salivary gland tumors and 14 tumor-flanking tissues by immunohistochemistry. DMBT1(SAG) in salivary gland tumors resembles the changes of expression levels known from DMBT1 in tumors in other cancer types. Particularly, DMBT1(SAG) was up-regulated in 10/14 tumor-flanking tissues, and a strong staining of the luminal content in the tumor and/or the tumor-flanking tissue was observed in 14/20 cases. This suggests that, in addition to its role in caries defense, SAG may serve as a potential tumor indicator and/or tumor suppressor in salivary gland tissue.

DMBT1 expression is down-regulated in breast cancer

Background

We studied the expression of DMBT1 (deleted in malignant brain tumor 1), a putative tumor suppressor gene, in normal, proliferative, and malignant breast epithelium and its possible relation to cell cycle.

Methods

Sections from 17 benign lesions and 55 carcinomas were immunostained with anti DMBT1 antibody (DMBTh12) and sections from 36 samples, were double-stained also with anti MCM5, one of the 6 pre-replicative complex proteins with cell proliferation-licensing functions. DMBT1 gene expression at mRNA level was assessed by RT-PCR in frozen tissues samples from 39 patients.

Results

Normal glands and hyperplastic epithelium in benign lesions displayed a luminal polarized DMBTh12 immunoreactivity. Normal and hyperplastic epithelium adjacent to carcinomas showed a loss of polarization, with immunostaining present in basal and perinuclear cytoplasmic compartments. DMBT1 protein expression was down-regulated in the cancerous lesions compared to the normal and/or hyperplastic epithelium adjacent to carcinomas (3/55 positive carcinomas versus 33/42 positive normal/hyperplastic epithelia; p = 0.0001). In 72% of cases RT-PCR confirmed immunohistochemical results. Most of normal and hyperplastic mammary cells positive with DMBTh12 were also MCM5-positive.

Conclusions

The redistribution and up-regulation of DMBT1 in normal and hyperplastic tissues flanking malignant tumours and its down-regulation in carcinomas suggests a potential role in breast cancer. Moreover, the concomitant expression of DMTB1 and MCM5 suggests its possible association with the cell-cycle regulation.

Carcinogen inducibility in vivo and down-regulation of DMBT1 during breast carcinogenesis

Deleted in malignant brain tumors 1 (DMBT1) has been proposed as a candidate tumor suppressor for brain and epithelial cancer. Initial studies suggested loss of expression rather than mutation as the predominant mode of DMBT1 inactivation. However, in situ studies in lung cancer demonstrated highly sophisticated changes of DMBT1 expression and localization, pointing to a chronological order of events. Here we report on the investigation of DMBT1 in breast cancer in order to test whether these principles might also be attributable to other tumor types. Comprehensive mutational analyses did not uncover unambiguous inactivating DMBT1 mutations in breast cancer. Expression analyses in the human and mouse mammary glands pointed to the necessity of DMBT1 induction. While age-dependent and hormonal effects could be ruled out, 9 of 10 mice showed induction of Dmbt1 expression after administration of the carcinogen 7,12-dimethybenz(alpha)anthracene prior to the onset of tumorigenesis or other histopathological changes. DMBT1 displayed significant up-regulation in human tumor-flanking tissues compared to in normal breast tissues (P < 0.05). However, the breast tumor cells displayed a switch from lumenal secretion to secretion to the extracellular matrix and a significant down-regulation compared to that in matched normal flanking tissues (P < 0.01). We concluded that loss of expression also is the predominant mode of DMBT1 inactivation in breast cancer. The dynamic behavior of DMBT1 in lung carcinoma is fully reflected in breast cancer, which suggests that this behavior might be common to tumor types arising from monolayered epithelia.

Detection of gene amplification and deletion in high-grade gliomas using a genome DNA microarray (GenoSensor Array 300)

Glioblastoma is a rapidly growing tumor that accounts for more than 50% of all primary gliomas. Amplification of oncogenes and deletion of tumor suppressor genes frequently affects tumor progression. Thus, the goal of this study was to conduct a comprehensive analysis of gene aberrations of individual glioblastomas. A genome DNA microarray (GenoSensor Array 300), spotted with 287 target genes, was used to analyze resected tissue from 11 different high-grade gliomas. The average number of gene aberrations was 9.0 per case (WHO grade III) and 13.3 per case (WHO grade IV). EGFR was the most frequent amplified gene in this series (4 of 11 cases), and high-level amplification was also detected for EGFR, SAS/CDK4, and AKT1. A high frequency of deleted genes was observed in 6 of 11 cases (54.5%), including FGFR2, MTAP, and DMBT1. The detected gene aberrations were matched to the classical primary glioblastoma pathway in five of nine cases. We conclude that the GenoSensor Array 300 genomic DNA microarray is a useful method for the comprehensive identification of amplified and deleted genes in glioblastoma.

Frequent downregulation of DMBT1 and galectin-3 in epithelial skin cancer

DMBT1 and galectin-3 are potential interacting proteins with presumably complex roles in tumorigenesis. While at present a variety of mechanisms are discussed for DMBT1 and its participation in cancer, galectin-3 is commonly known to exert tumor-promoting effects. However, in vitro studies in a rodent system have suggested that DMBT1/galectin-3 interaction in the ECM triggers epithelial differentiation, which would point to tumor-suppressive properties. To improve the understanding of DMBT1/galectin-3 action in cancer, we carried out studies in skin cancer of different origins. Mutational analyses of DMBT1 identified a missense mutation in 1 of 13 melanoma cell lines. It led to an exchange of an evolutionary conserved proline residue for serine and located within the second CUB domain of DMBT1. Immunohistochemical analyses demonstrated absence of DMBT1/galectin-3 expression from melanocytes but induction of DMBT1 expression in 1 of 8 nevi and 1 of 11 melanomas and of galectin-3 expression in 3 of 8 nevi and 4 of 8 melanomas. These data suggest that DMBT1 and galectin-3 are unlikely to act as classical tumor suppressors in melanomas. DMBT1 and galectin-3 appear to be secreted to the ECM by epithelial cells within the epidermis and the hair follicle. Compared to the flanking normal epidermis, skin tumors of epithelial origin frequently displayed downregulation of DMBT1 (18 of 19 cases) and galectin-3 (12 of 12 cases). Thus, loss of DMBT1/galectin-3 expression may play a role in the genesis of epithelial skin cancer. This would support the view that galectin-3 can exert tumor-suppressive effects in certain scenarios, and DMBT1/galectin-3-mediated differentiation represents a candidate mechanism for this effect.

DMBT1, a regulator of mucosal homeostasis through the linking of mucosal defense and regeneration?

DMBT1 (deleted in malignant brain tumor 1), which encodes a large scavenger receptor cysteine rich (SRCR) B protein, has been proposed to be a tumor suppressor gene, due to the high frequency of its homozygous deletion and the lack of expression in a variety of cancers. However, studies on its physiological functions and its relationship with tumorigenesis are still at an initial stage. Two mucosal defense-related molecules, gp-340 and salivary agglutinin, have been identified to be alternatively spliced products of DMBT1, which suggests that DMBT1 is a pattern recognition receptor in innate immunity. Meanwhile, results from immunohistochemical staining and studies at the cellular level, began to associate DMBT1 with a proliferation to differentiation switching process in gastrointestinal epithelial cells. Together with its up-regulation in inflammation, these findings suggest that DMBT1 might be a local regulator of homeostasis, possibly through linking mucosal inflammation to the modulation of epithelial regeneration, and whose abnormality is a frequent cause of malignancy.