Bernhard B. Singer

CEACAM1 inhibits Toll-like receptor 2-triggered antibacterial responses of human pulmonary epithelial cells.

Although Moraxella catarrhalis and Neisseria meningitidis are important human pathogens, they often colonize the human respiratory tract without causing overt clinical symptoms. Both pathogens express structurally unrelated proteins that share the ability to stimulate the adhesion molecule CEACAM1 expressed on human cells. Here we demonstrate that the interaction of CEACAM1 with ubiquitous surface protein A1 expressed on M. catarrhalis or with opacity-associated proteins on N. meningitidis resulted in reduced Toll-like receptor 2–initiated transcription factor NF-κB–dependent inflammatory responses of primary pulmonary epithelial cells. These inhibitory effects were mediated by tyrosine phosphorylation of the immunoreceptor tyrosine-based inhibitory motif of CEACAM1 and by recruitment of the phosphatase SHP-1, which negatively regulated Toll-like receptor 2–dependent activation of the phosphatidylinositol 3-OH kinase–Akt kinase pathway. Our results identify a CEACAM1-dependent immune-evasion strategy.

Moraxella catarrhalis is internalized in respiratory epithelial cells by a trigger-like mechanism and initiates a TLR2- and partly NOD1-dependent inflammatory immune response

Moraxella catarrhalis is an important pathogen in patients with chronic obstructive lung disease (COPD). While M. catarrhalis has been categorized as an extracellular bacterium so far, the potential to invade human respiratory epithelium has not yet been explored. Our results obtained by electron and confocal microscopy demonstrated a considerable potential of M. catarrhalis to invade bronchial epithelial (BEAS‐2B) cells, type II pneumocytes (A549) and primary small airway epithelial cells (SAEC). Moraxella invasion was dependent on cellular microfilament as well as on bacterial viability, and characterized by macropinocytosis leading to the formation of lamellipodia and engulfment of the invading organism into macropinosomes, thus indicating a trigger‐like uptake mechanism. In addition, the cells examined expressed TLR2 as well as NOD1, a recently found cytosolic protein implicated in the intracellular recognition of bacterial cell wall components. Importantly, inhibition of TLR2 or NOD1 expression by RNAi significantly reduced the M. catarrhalis‐induced IL‐8 secretion. The role of TLR2 and NOD1 was further confirmed by overexpression assays in HEK293 cells. Overall, M. catarrhalis may employ lung epithelial cell invasion to colonize and to infect the respiratory tract, nonetheless, the bacteria are recognized by cell surface TLR2 and the intracellular surveillance molecule NOD1.

CD30-mediated cell cycle arrest associated with induced expression of p21(CIP1/WAF1) in the anaplastic large cell lymphoma cell line Karpas 299.

One of the major characteristics of anaplastic large cell lymphomas (ALCL) is the expression of the Ki-1/CD30 antigen. While the receptor mediates NF-κB-activation in Hodgkins lymphomas, some data suggest the CD30-mediated apoptosis of other CD30-expressing cells. We were able to demonstrate that activation of CD30 leads to different effects regarding cell proliferation of the ALCL-derived cell lines Karpas 299 and JB6. Western and Northern blotting analysis revealed that CD30-induced growth inhibition of Karpas 299 cells correlated with a strong upregulation of the cell cycle inhibitor p21CIP1/WAF1. We found a non activating point mutation at codon 273 in exon 8 of the p53 gene in Karpas 299 cells which indicates an p53-independent mechanism for induced p21 expression. Abundant p21 protein expression resulted in hypophosphorylation of the retinoblastoma protein (Rb) and inhibition of the proliferating cell nuclear antigen (PCNA). CD30-stimulated cells showed no indications of apoptotic cell death, like genomic DNA fragmentation or cleavage of the caspase-3 target protein poly (ADP-ribose) polymerase (PARP). Our results indicate that CD30 is able to mediate an p21-associated cell cycle arrest in ALCL with possible implications for prognosis and clinical treatment.

CEACAM1 (CD66a) mediates delay of spontaneous and fas ligand-induced apoptosis in granulocytes

Granulocytes form the first and fastest line of defense against pathogenic infections. Their survival is limited by apoptosis, a process that is critical for the resolution of inflammation. Pro‐apoptotic and pro‐inflammatory cytokines, as well as several receptors, can alter the lifespan of granulocytes. Here we report that the carcinoembryonic antigen‐related cell adhesion molecule 1 (CEACAM1, CD66a) is involved in the regulation of granulocyte survival. Until now CEACAM1 is described to control cell proliferation, cell migration, tumor growth, angiogenesis and diverse leukocyte functions. However, very little is known about its role in granulocytes. We found that CEACAM1 expression in resting rat granulocytes is significantly higher than in other leukocyte subtypes. Stimulation led to a strongly increased CEACAM1 cell surface expression and to release of soluble CEACAM1. DNA fragmentation assays and annexin V staining revealed that binding of CEACAM1‐specific antibodies, Fab fragments and soluble CEACAM1‐Fc constructs to cell surface‐expressed CEACAM1 causes a delay of spontaneous and Fas ligand (CD95L)‐induced apoptosis. Tyrosine phosphorylation of CEACAM1‐L, its association with SHP‐1, the activation of Erk1/2 and caspase‐3 appeared to be crucial for the CEACAM1‐mediated anti‐apoptotic effect. These findings provide evidence that CEACAM1 influences the resolution of inflammation by prolonging the survival of rat granulocytes.

Deregulation of the CEACAM Expression Pattern Causes Undifferentiated Cell Growth in Human Lung Adenocarcinoma Cells

CEACAM1, CEA/CEACAM5, and CEACAM6 are cell adhesion molecules (CAMs) of the carcinoembryonic antigen (CEA) family that have been shown to be deregulated in lung cancer and in up to 50% of all human cancers. However, little is known about the functional impact of these molecules on undifferentiated cell growth and tumor progression. Here we demonstrate that cell surface expression of CEACAM1 on confluent A549 human lung adenocarcinoma cells plays a critical role in differentiated, contact-inhibited cell growth. Interestingly, CEACAM1-L, but not CEACAM1-S, negatively regulates proliferation via its ITIM domain, while in proliferating cells no CEACAM expression is detectable. Furthermore, we show for the first time that CEACAM6 acts as an inducer of cellular proliferation in A549 cells, likely by interfering with the contact-inhibiting signal triggered by CEACAM1-4L, leading to undifferentiated anchorage-independent cell growth. We also found that A549 cells expressed significant amounts of non-membrane anchored variants of CEACAM5 and CEACAM6, representing a putative source for the increased CEACAM5/6 serum levels frequently found in lung cancer patients. Taken together, our data suggest that post-confluent contact inhibition is established and maintained by CEACAM1-4L, but disturbances of CEACAM1 signalling by CEACAM1-4S and other CEACAMs lead to undifferentiated cell growth and malignant transformation.

Functional capacities of human IgM memory B cells in early inflammatory responses and secondary germinal center reactions

Significance Human IgM+IgD+CD27+ B lymphocytes represent a large subpopulation of the human B-cell pool, but their generation is debated and their immunological functions are poorly understood. This work shows that these lymphocytes possess typical memory B-cell expression patterns, enabling them to differentiate rapidly into plasma cells upon restimulation. Moreover, we reveal unique features of these IgM memory B cells, their potential to reenter germinal center reactions, and their specific interaction with immunomodulatory neutrophils in early inflammatory responses. Thus, key characteristics and functions of a major human B-cell subset are elucidated. The generation and functions of human peripheral blood (PB) IgM+IgD+CD27+ B lymphocytes with somatically mutated IgV genes are controversially discussed. We determined their differential gene expression to naive B cells and to IgM-only and IgG+ memory B cells. This analysis revealed a high similarity of IgM+(IgD+)CD27+ and IgG+ memory B cells but also pointed at distinct functional capacities of both subsets. In vitro analyses revealed a tendency of activated IgM+IgD+CD27+ B cells to migrate to B-cell follicles and undergo germinal center (GC) B-cell differentiation, whereas activated IgG+ memory B cells preferentially showed a plasma cell (PC) fate. This observation was supported by reverse regulation of B-cell lymphoma 6 and PR domain containing 1 and differential BTB and CNC homology 1, basic leucine zipper transcription factor 2 expression. Moreover, IgM+IgD+CD27+ B lymphocytes preferentially responded to neutrophil-derived cytokines. Costimulation with catecholamines, carcinoembryonic antigen cell adhesion molecule 8 (CEACAM8), and IFN-γ caused differentiation of IgM+IgD+CD27+ B cells into PCs, induced class switching to IgG2, and was reproducible in cocultures with neutrophils. In conclusion, this study substantiates memory B-cell characteristics of human IgM+IgD+CD27+ B cells in that they share typical memory B-cell transcription patterns with IgG+ post-GC B cells and show a faster and more vigorous restimulation potential, a hallmark of immune memory. Moreover, this work reveals a functional plasticity of human IgM memory B cells by showing their propensity to undergo secondary GC reactions upon reactivation, but also by their special role in early inflammation via interaction with immunomodulatory neutrophils.

Contrast-enhanced transrectal ultrasound (CE-TRUS) with cadence-contrast pulse sequence (CPS) technology for the identification of prostate cancer.

OBJECTIVES Various imaging modalities, such as magnetic resonance imaging (MRI), have been assessed with regard to their value in the detection of prostate cancer (CaP). However, there is a need for less time-consuming and more cost effective procedures in urology. In order to determine the ability of contrast-enhanced transrectal ultrasound (CE-TRUS) to identify CaP, we investigated patients scheduled for radical prostatectomy for CaP and radical cystoprostatectomy for bladder cancer. MATERIAL AND METHODS Between May and August 2008, 35 consecutive patients with CaP and muscle-invasive bladder carcinoma were prospectively enrolled in this single center study. All patients underwent B-mode TRUS and CE-TRUS (Sequoia 512 unit with an endocavity probe EV8C4, 8 MHz; Siemens, Erlangen, Germany) by one investigator blinded to any clinical data before radical surgery. Contrast-enhanced images were obtained after intravenous infusion of a bolus (2.4 ml) of the contrast agent SonoVue (Bracco, Milan, Italy). Ultrasound findings (CE-TRUS and B-mode TRUS) were correlated with step-section histology. RESULTS On a per-patient basis, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for detecting CaP with CE-TRUS were 71.0%, 50.0%, 91.7%, and 18.2%, respectively. In comparison with B-mode TRUS (sensitivity 45.2%, specificity 75.0%, PPV 93.3%, and NPV 18.0%), CE-TRUS performed significantly better (P=0.004, McNemar test). On a per-prostate-lobe basis sensitivity, specificity, PPV, and NPV were 69.0%, 33.3%, 83.3%, and 18.2%. CONCLUSION CE-TRUS detected prostate cancer with a modest sensitivity and a high PPV in a selected patient cohort. Future randomized-controlled multicenter studies are needed to further validate the value of CE-TRUS in the detection of CaP. Based on our results, CE-TRUS may not be recommended as a routine procedure in the diagnosis of CaP at present.

Homophilic adhesion and CEACAM1-S regulate dimerization of CEACAM1-L and recruitment of SHP-2 and c-Src

The monomer/dimer equilibrium of adhesion molecule CEACAM1-L is regulated by binding between opposing membranes, which in turn controls cytoplasmic enzyme binding and signaling (see also in this issue the accompanying paper by Klaile et al.).

Helicobacter pylori adhesin HopQ engages in a virulence-enhancing interaction with human CEACAMs

Helicobacter pylori specifically colonizes the human gastric epithelium and is the major causative agent for ulcer disease and gastric cancer development. Here, we identify members of the carcinoembryonic antigen-related cell adhesion molecule (CEACAM) family as receptors of H. pylori and show that HopQ is the surface-exposed adhesin that specifically binds human CEACAM1, CEACAM3, CEACAM5 and CEACAM6. HopQ–CEACAM binding is glycan-independent and targeted to the N-domain. H. pylori binding induces CEACAM1-mediated signalling, and the HopQ–CEACAM1 interaction enables translocation of the virulence factor CagA into host cells and enhances the release of pro-inflammatory mediators such as interleukin-8. Based on the crystal structure of HopQ, we found that a β-hairpin insertion (HopQ-ID) in HopQs extracellular 3+4 helix bundle domain is important for CEACAM binding. A peptide derived from this domain competitively inhibits HopQ-mediated activation of the Cag virulence pathway, as genetic or antibody-mediated abrogation of the HopQ function shows. Together, our data suggest the HopQ–CEACAM1 interaction to be a potentially promising novel therapeutic target to combat H. pylori-associated diseases.

CEACAM1: A Novel Urinary Marker for Bladder Cancer Detection

BACKGROUND Carcinoembryonic antigen-related cell adhesion molecule 1 (biliary glycoprotein; CEACAM1) is expressed in normal bladder urothelium and in angiogenically activated endothelial cells, where it exhibits proangiogenic properties. OBJECTIVE The aim of this study was to evaluate the value of urinary CEACAM1 for detection of urothelial carcinoma of the bladder (UCB). DESIGN, SETTING, AND PARTICIPANTS This prospective study included 175 patients. MEASUREMENTS Immunohistochemistry for CEACAM1 was performed on UCB sections of 10 patients. Enzyme-linked immunosorbent assay (ELISA) for CEACAM1 was performed on urine specimens of healthy volunteers (n=30), patients with benign prostatic hyperplasia (BPH; n=5), severe cystitis (n=5), non-muscle-invasive UCB (n=72), muscle-invasive UCB (n=21), or past history of UCB without evidence of disease (n=42). Western blot analysis was performed on a subgroup of these subjects (n=53). RESULTS AND LIMITATIONS CEACAM1 immunostaining in normal urothelium disappears in noninvasive UCB but appears in endothelial cells of adjacent vessels. Western blotting revealed presence of CEACAM1 in the urine of no healthy volunteers, of 76% of noninvasive UCB patients, and of 100% of invasive UCB patients. ELISA analysis confirmed that urinary CEACAM1 levels were significantly higher in UCB patients compared with control subjects (median: 207 ng/ml vs 0 ng/ml; p<0.001). The area under the curve for UCB detection was 0.870 (95% confidence interval [CI]: 0.810-0.931). In multivariable logistic regression analyses that adjusted for the effects of age and gender, higher CEACAM1 levels were associated with cancer presence (hazard ratio [HR]: 2.89; 95% CI: 2.01-4.15; p<0.001) and muscle-invasive cancer (HR: 5.53; 95% CI: 1.68-18.24; p=0.005). The cut-off level of 110 ng/ml yielded sensitivity of 74% and specificity of 95% for detecting UCB. Sensitivity was 88% for detecting high-grade UCB and 100% for detecting invasive-stage UCB. Larger studies are necessary to establish the diagnostic and prognostic roles of this highly promising novel marker in UCB. CONCLUSIONS Urinary CEACAM1 levels discriminate UCB patients from non-UCB subjects. Moreover, urinary levels of CEACAM1 increased with advancing stage and grade.