Cloning and functional characterization of recombinant equine P-selectin

Holothurian glycosaminoglycan inhibits metastasis via inhibition of P-selectin in B16F10 melanoma cells

P-selectin-mediated tumor cell adhesion to platelets is a well-established stage in the process of tumor metastasis. Through computerized structural analysis, we found a marine-derived polysaccharide, holothurian glycosaminoglycan (hGAG), behaved as a ligand-competitive inhibitor of P-selectin, indicating its potential to disrupt the binding of P-selectin to cell surface receptor and activation of downstream regulators of tumor cell migration. Our experimental data demonstrated that hGAG significantly inhibited P-selectin-mediated adhesion of tumor cells to platelets and tumor cell migration in vitro and reduced subsequent pulmonary metastasis in vivo. Furthermore, abrogation of the P-selectin-mediated adhesion of tumor cells led to down-regulation of protein levels of integrins, FAK and MMP-2/9 in B16F10 cells, which is a crucial molecular mechanism of hGAG to inhibit tumor metastasis. In conclusion, hGAG has emerged as a novel anti-cancer agent via blocking P-selectin-mediated malignant events of tumor metastasis.

Clinical application of dendritic cells and interleukin-2 and tools to study activated T cells in horses--first results and implications for quality control

Dendritic cells (DCs) are antigen-presenting cells, which are well known for their capacity to stimulate immunity. The ex vivo generation of myeloid DC from monocytes has facilitated the development of DC-vaccination protocols which have been extensively evaluated in tumour immunology and are regarded by some as a gold mine for clinical research. However, there is a considerable amount of work required to overcome the potential risks associated with such therapy. It is therefore mandatory to characterize the system to be applied and to study the reactions, particularly at the level of T cell responses. The first objective of the current study was to test if tumour lysates loaded autologous DC or recombinant human IL-2 are well tolerated in horses and performed an exploratory phase I study on equine sarcoids and squamous cell carcinomas. We consequently intended to establish a robust protocol for the magnetic separation of monocytes such as in use in human clinical studies. Finally we intended to address the limits in the reagents to study equine T cell based immune reactions, and analysed markers for CD25 and FoxP3. The data showed that local application of DC or IL-2 did not cause side effects. Additionally our data show that a polyclonal approach to detect antigens such as CD25 might be successful, where mAbs are not available. Our data also demonstrate that the mAb FJK16s, which has been used successfully in rodents, humans, and dogs, can also be applied in horses. We finally wish to share our concerns regarding quality control for clinical studies and encourage multi-central studies such as in human medicine to ensure that progress along established standards is made for the benefit of veterinary medicine.

Characterization of equine P-selectin glycoprotein ligand-1 by using a specific monoclonal antibody

P-selectin glycoprotein ligand (PSGL-1) is a widely distributed adhesion molecule that plays a critical role in regulating lymphocyte homing and leukocyte trafficking during inflammation. The lack of specific reagents for equine PSGL-1 (ePSGL-1) has prevented mechanistic studies regarding its function and regulation in the horse. We synthesized a ePSGL-1 peptide to generate a monoclonal antibody (mAb), ePL1. Using flow cytometry and Western blot, we showed that ePL1 binds specifically to ePSGL-1 in transfected mammalian cells. We also demonstrated that ePL1 binds to equine leukocytes and recognized a protein with molecular weight 165 and 280kDa under reducing and non-reducing condition, respectively, likely corresponding to ePSGL-1. Seventy percent of equine monocytes bound by both ePL1 and HECA-452, an antibody defining sLex-like carbohydrate epitope. Both ePL1 and HECA-452 recognized ePSGL-1 protein precipitated by equine P-selectin-IgG chimera. Neuraminidase treatment increased ePL1 binding and the molecular weight of ePSGL-1, O-sialoglycoprotein endopeptidase digestion and tyrosine mutation abolished ePL1 staining and recognition. The ePL1 specific binding epitope appears to be the polypeptide backbone of ePSGL-1 in the presence of tyrosine but the process is independent of sialylation modification. In conclusion, we provide evidence that this antibody can be used for cell surface staining and immune-blot analyses.