Epithelial cell adhesion molecule expression (CD326) in cancer: a short review.

Epithelial cell adhesion molecule (EpCAM, CD326) is a pleiotropic molecule that potentially offers therapeutic applications in cancer treatment. Initially described as a dominant surface antigen on human colon carcinoma, it is a transmembrane glycoprotein mediating epithelial-specific intercellular cell-adhesion. Recent data suggest that EpCAM is also involved in cell signaling, migration, proliferation and differentiation. Since EpCAM is expressed exclusively in epithelia and epithelial-derived neoplasms, EpCAM can be used as diagnostic marker. Testing for EpCAM is based on morphology and phenotypical staining and can be performed with primary carcinoma tissue and cells harvested from malignant effusions. Stable or highly expressed EpCAM has been detected in most adenocarcinomas and has also been found in metastases, malignant effusions, and cancer stem cells. EpCAM may thus be an ideal tumor antigen candidate to detect circulating and metastasizing cancer cells by microchip technologies. In certain tumor types overexpression was linked to advanced stage of disease and worse overall survival, suggesting EpCAM as a potential prognostic marker. In addition to its diagnostic and prognostic role, EpCAM's broad expression and apparent involvement in tumorigenesis and metastasis point to its potential as a target for immunotherapeutic strategies. The first EpCAM targeting, trifunctional antibody catumaxomab (Removab®) has shown clear clinical benefits in treatment of malignant ascites associated with EpCAM positive carcinomas. Further research and clinical studies should unravel EpCAM's complex role in oncological processes, and expand potential therapeutic applications of EpCAM targeted strategies.

Immunostimulatory properties of CpG-oligonucleotides are enhanced by the use of protamine nanoparticles.

The aim of this paper was to investigate if the immunostimulatory effects of CpG-oligonucleotides (CpG-ODN) can be enhanced by the use of biodegradable protamine nanoparticles (proticles). We analyzed size, surface charge, and morphology of protamine nanoparticles containing CpG-ODN with photon correlation spectroscopy and transmission electron microscopy. Immunostimulatory effects of these nanoparticles on B cells, plasmacytoid dendritic cells (PDC), peripheral blood mononuclear cells, and whole blood were studied. Cytokine production, activation of the cells in terms of upregulation of surface molecules and uptake of nanoparticles were examined. We found that the use of protamine nanoparticles significantly increased (20-fold) CpG-ODN mediated interferon (IFN)-alpha production of PDC. ODN uptake in PDC was only marginally enhanced. CpG-ODN mediated IP-10 production in whole blood was strongly enhanced by the use of nanoparticles. Apart from a slight increase in CpG-ODN-induced interleukin (IL)-6 production in B cells, other parameters like the CpG-mediated activation of B cells and PDC as well as tumor necrosis factor (TNF)-alpha production of PDC remained largely unchanged. The use of control ODN indicated that the protamine nanoparticles themselves have no immunostimulatory properties. These results strongly support the use of particulate delivery systems like biodegradable protamine nanoparticles for the development of CpG-ODN-based therapeutics.

CpG ODN enhance antigen-specific NKT cell activation via plasmacytoid dendritic cells.

Human Valpha24+ Vbeta11+ natural killer T cells (NKT cells) are "natural memory" T cells that detect glycolipid antigens such as alpha-galactosylceramide (alpha-GalCer) presented on CD1d. In the present study we found that highly purified Valpha24+ NKT cells lack TLR9 mRNA, and thus are not sensitive towards stimulation with CpG oligodeoxynucleotides (ODN). Within PBMC, however, CpG ODN synergistically activated NKT cells stimulated with their cognate antigen alpha-GalCer. Depletion of plasmacytoid dendritic cells (PDC) or myeloid dendritic cells (MDC) revealed that both DC subsets were necessary for the synergistic activation of NKT cells by alpha-GalCer and CpG ODN. While PDC were responsible for the stimulation of NKT cells with CpG ODN, MDC but not PDC presented alpha-GalCer via CD1d. Partial activation of NKT cells was mediated by PDC-derived IFN-alpha, whereas full activation of NKT cells as indicated by IFN-gamma production required cell-to-cell contact of PDC and NKT cells in addition to IFN-alpha; OX40 was involved in this interaction. We conclude that CpG-activated PDC enhance alpha-GalCer-specific NKT cell activation, and bias activated NKT cells towards a Th1 phenotype. Our results lead to a novel concept of PDC function: to regulate effector activity of antigen-stimulated T cells in a cell contact-dependent manner without the need of simultaneous presentation of the cognate T cell antigen.

CpG oligonucleotides induce strong humoral but only weak CD4+ T cell responses to protein antigens in rhesus macaques in vivo.

Oligonucleotides containing CpG motifs (CpG ODN) are strong adjuvants for humoral immune responses but data on cellular immune responses in primates are scarce. Rhesus macaque blood contained similar numbers of plasmacytoid dendritic cells and B cells, the key sensors of CpG ODN, as human blood, and these cells were activated by CpG-A and CpG-B in vitro. In vivo, both ODNs induced equal plasma levels of interferon-inducible protein 10 and similarly enhanced antibody responses following i.m. injections of the ODNs, protein antigen, and aluminium hydroxide into rhesus macaques, whereas antigen-specific CD4(+) T cell responses were only slightly increased by CpG ODN.