Epitope recognition of antibodies that define the sialomucin, endolyn (CD164), a negative regulator of haematopoiesis

The stem cell revolution: on the role of CD164 as a human stem cell marker

Accurately defining hierarchical relationships between human stem cells and their progeny, and using this knowledge for new cellular therapies, will undoubtedly lead to further successful treatments for life threatening and chronic diseases, which represent substantial burdens on patient quality of life and to healthcare systems globally. Clinical translation relies in part on appropriate biomarker, in vitro manipulation and transplantation strategies. CD164 has recently been cited as an important biomarker for enriching both human haematopoietic and skeletal stem cells, yet a thorough description of extant human CD164 monoclonal antibody (Mab) characteristics, which are critical for identifying and purifying these stem cells, was not discussed in these articles. Here, we highlight earlier but crucial research describing these relevant characteristics, including the differing human CD164 Mab avidities and their binding sites on the human CD164 sialomucin, which importantly may affect subsequent stem cell function and fate.

Structural and functional diversity of neutrophil glycosylation in innate immunity and related disorders

The granulated neutrophils are abundant innate immune cells that utilize bioactive glycoproteins packed in cytosolic granules to fight pathogenic infections, but the neutrophil glycobiology remains poorly understood. Facilitated by technological advances in glycoimmunology, systems glycobiology and glycoanalytics, a considerable body of literature reporting on novel aspects of neutrophil glycosylation has accumulated. Herein, we summarize the building knowledge of the structural and functional diversity displayed by N- and O-linked glycoproteins spatiotemporally expressed and sequentially brought-into-action across the diverse neutrophil life stages during bone marrow maturation, movements to, from and within the blood circulation and microbicidal processes at the inflammatory sites in peripheral tissues. It transpires that neutrophils abundantly decorate their granule glycoproteins including neutrophil elastase, myeloperoxidase and cathepsin G with peculiar glyco-signatures not commonly reported in other areas of human glycobiology such as hyper-truncated chitobiose core- and paucimannosidic-type N-glycans and monoantennary complex-type N-glycans. Sialyl Lewis^x, Lewis^x, poly-N-acetyllactosamine extensions and core 1-/2-type O-glycans are also common neutrophil glyco-signatures. Granule-specific glycosylation is another fascinating yet not fully understood feature of neutrophils. Recent literature suggests that unconventional biosynthetic pathways and functions underpin these prominent neutrophil-associated glyco-phenotypes. The impact of glycosylation on key neutrophil effector functions including extravasation, degranulation, phagocytosis and formation of neutrophil extracellular traps during normal physiological conditions and in innate immune-related diseases is discussed. We also highlight new technologies that are expected to further advance neutrophil glycobiology and briefly discuss the untapped diagnostic and therapeutic potential of neutrophil glycosylation that could open avenues to combat the increasingly prevalent innate immune disorders.

Loss and gain of N-linked glycosylation sequons due to single-nucleotide variation in cancer

Despite availability of sequence site-specific information resulting from years of sequencing and sequence feature curation, there have been few efforts to integrate and annotate this information. In this study, we update the number of human N-linked glycosylation sequons (NLGs), and we investigate cancer-relatedness of glycosylation-impacting somatic nonsynonymous single-nucleotide variation (nsSNV) by mapping human NLGs to cancer variation data and reporting the expected loss or gain of glycosylation sequon. We find 75.8% of all human proteins have at least one NLG for a total of 59,341 unique NLGs (includes predicted and experimentally validated). Only 27.4% of all NLGs are experimentally validated sites on 4,412 glycoproteins. With respect to cancer, 8,895 somatic-only nsSNVs abolish NLGs in 5,204 proteins and 12,939 somatic-only nsSNVs create NLGs in 7,356 proteins in cancer samples. nsSNVs causing loss of 24 NLGs on 23 glycoproteins and nsSNVs creating 41 NLGs on 40 glycoproteins are identified in three or more cancers. Of all identified cancer somatic variants causing potential loss or gain of glycosylation, only 36 have previously known disease associations. Although this work is computational, it builds on existing genomics and glycobiology research to promote identification and rank potential cancer nsSNV biomarkers for experimental validation.

Overexpression of CD164 in oral cavity squamous cell carcinoma predicts a favourable prognosis

The aim of the present study was to investigate the association between cluster of differentiation (CD) 164 expression with clinicopathological parameters and prognosis among patients with oral cavity squamous cell carcinoma (OSCC). The present study retrospectively reviewed 70 patients with OSCC who underwent curative primary surgery. A number of patients subsequently received postoperative chemoradiotherapy although the specimens were not exposed to radiation or chemotherapy prior to anti-CD164 antibody immunohistochemical staining. CD164 overexpression was arbitrarily defined as exhibiting an H-score of ≥120. Univariate and multivariate analyses were performed for sex, age, American Joint Committee on Cancer stage, tumour location, histological grade, surgical margin and H-score. The 5-year overall survival rate was 54.4% and the median follow-up time was 46 months for surviving patients. Univariate analyses revealed that a low overall survival rate was associated with advanced-stage disease (P<0.001), buccogingival tumour location (P=0.038) and a CD164 H-score of <120 (P=0.016). Multivariate Cox's regression analyses revealed that poor overall survival rate was associated with advanced-stage disease (P=0.001) and a CD164 H-score of <120 (P=0.04). CD164 overexpression in OSCC was associated with favourable survival rate. Thus, CD164 expression may be a clinically useful predictor of prognosis in patients with OSCC.

Protective Effects of Chronic Intermittent Hypobaric Hypoxia Pretreatment against Aplastic Anemia through Improving the Adhesiveness and Stress of Mesenchymal Stem Cells in Rats

Aplastic anemia (AA) is a common malignant blood disease, and chronic intermittent hypobaric hypoxia (CIHH) has a beneficial effect against different diseases. The aim of the present study was to investigate the protective effect of CIHH against AA and underlying mechanisms. 5-Fluorouracil and busulfan treatment induced AA model in rats with reduction of hematological parameters and bone marrow tissue injury and decrease of the colony numbers of progenitor cells. CIHH pretreatment significantly reduced the incidence rate of AA and alleviated above symptoms in AA model. The adhesive molecules of bone marrow mesenchymal stem cells (BMMSCs) in AA model, VLA-4, VCAM-1, and ICAM-1 were upregulated, and those of CD162 and CD164 were downregulated by CIHH pretreatment. The expressions of HIF-1α and NF-κB in BMMSCs were also decreased through CIHH pretreatment. Overall, the results demonstrated for the first time that CIHH has an anti-AA effect through improving the adhesiveness and stress of mesenchymal stem cells in rats. CIHH could be a promising and effective therapy for AA.

CD164 regulates proliferation and apoptosis by targeting PTEN in human glioma

Cluster of differentiation 164 (CD164), a sialomucin, has been demonstrated to be involved in the regulation of proliferation, apoptosis, adhesion and differentiation in multiple cancers. CD164 is regarded to be a potential promotor of tumor growth. However, the involvement of CD164 in human glioma proliferation and apoptosis remains unknown. The aim of the present study was to investigate the expression and oncogenic function of CD164 in normal human astrocytes (NHA) and glioma cells in vitro and in vivo. The results of the present study demonstrated that CD164 mRNA and protein levels were significantly increased in human glioma cell lines and tissue samples. CD164 overexpression promoted the proliferation of NHA in vitro, and its tumorigenic effect was confirmed in a murine xenograft model. Knockdown of CD164 inhibited cell proliferation and promoted apoptosis of the U87 human glioma cell line in vitro and in vivo. In addition, knockdown of CD164 was demonstrated to upregulate the Bax/Bcl2 ratio and phosphatase and tensin homolog (PTEN) expression, reduce protein kinase B (AKT) phosphorylation and promote the expression of p53 in U87 cells. The results suggest that CD164 expression may have affected the proliferation and apoptosis of human glioma cells via the PTEN/phosphoinositide 3-kinase/AKT pathway, and may therefore present a potential target for the diagnosis and treatment of glioma.

Regulation of myoblast motility and fusion by the CXCR4-associated sialomucin, CD164

Myoblast fusion is fundamental to the development and regeneration of skeletal muscle. To fuse, myoblasts undergo cell-cell recognition and adhesion and merger of membranes between apposing cells. Cell migration must occur in advance of these events to bring myoblasts into proximity, but the factors that regulate myoblast motility are not fully understood. CD164 is a cell surface sialomucin that is targeted to endosomes and lysosomes via its intracellular region. In hematopoietic progenitor cells, CD164 forms complexes with the motility-stimulating chemokine receptor, CXCR4, in response to the CXCR4 ligand, CXCL12/SDF-1 (Forde, S., Tye, B. J., Newey, S. E., Roubelakis, M., Smythe, J., McGuckin, C. P., Pettengell, R., and Watt, S. M. (2007) Blood 109, 1825-1833). We have previously shown that CD164 stimulates myotube formation in vitro. We report here that CD164 is associated with CXCR4 in C2C12 myoblasts. Cells in which CD164 levels are increased or decreased via overexpression or RNA interference-mediated knockdown, respectively, show enhanced or reduced myotube formation and cell migration, the latter both basally and in response to CXCL12/SDF-1. Furthermore, expression of CD164 cytoplasmic tail mutants that alter the endosome/lysosome targeting sequence and, consequently, the subcellular localization in myoblasts, reveals a similar correlation between cell motility and myotube formation. Finally, Cd164 mRNA is expressed in the dorsal somite (the early myogenic compartment of the mouse embryo) and in premuscle masses. Taken together, these results suggest that CD164 is a regulator of myoblast motility and that this property contributes to its ability to promote myoblast fusion into myotubes.

The Drosophila ortholog of the endolysosomal membrane protein, endolyn, regulates cell proliferation

Endolyn (CD164) is a sialomucin that regulates the proliferation, adhesion, and migration of human haematopoietic stem and progenitor cells. This molecule is predominately localized in endocytotic compartments, where it may contribute to endolysosomal biogenesis and trafficking. In order to more closely define the function of endolyn from an evolutionary view-point, we first analyzed endolyn orthologs in species ranging from insects, fish, and birds to mammals. The predicted molecular structures of the endolyn orthologs from these species are well conserved, particularly with respect to significant O-linked glycosylation of the extracellular domain, and the high degree of amino acid similarities within their transmembrane and cytoplasmic domains, with the latter possessing the lysosomal target signal, YXXphi. Focusing on Drosophila, our studies showed that the subcellular distribution of endolyn in non-polarized Drosophila S2 cells resembles that of its human counterpart in hematopoietic cells, with its predominant localization being within intracellular vesicles, while a small fraction occurs on the cell surface. Both Y --> A and L --> A mutations in the YHTL motif perturbed the normal subcellular distribution of Drosophila endolyn. Interestingly, embryonic and early larval development was often arrested in endolyn-deficient Drosophila mutants. This may partly be due to the role of endolyn in regulating cell proliferation, since knock-down of endolyn expression in S2 cells resulted in up to 50% inhibition of cell growth, with a proportion of cells undergoing apoptosis. Taken together, these results demonstrate that endolyn is an evolutionarily conserved sialomucin fundamentally involved in cell proliferation in both the human and Drosophila melanogaster.

Endolyn (CD164) modulates the CXCL12-mediated migration of umbilical cord blood CD133+ cells

Hematopoietic stem cell/hematopoietic progenitor cell (HSC/HPC) homing to specific microenvironmental niches involves interactions between multiple receptor ligand pairs. Although CXCL12/CXCR4 plays a central role in these events, CXCR4 regulators that provide the specificity for such cells to lodge and be retained in particular niches are poorly defined. Here, we provide evidence that the sialomucin endolyn (CD164), an adhesion receptor that regulates the adhesion of CD34+ cells to bone marrow stroma and the recruitment of CD34+CD38(lo/-) cells into cycle, associates with CXCR4. The class II 103B2 monoclonal antibody, which binds the CD164 N-linked glycan-dependent epitope or CD164 knockdown by RNA interference, significantly inhibits the migration of CD133+ HPCs toward CXCL12 in vitro. On presentation of CXCL12 on fibronectin, CD164 associates with CXCR4, an interaction that temporally follows the association of CXCR4 with the integrins VLA-4 and VLA-5. This coincides with PKC-zeta and Akt signaling through the CXCR4 receptor, which was disrupted on the loss of CD164 though MAPK signaling was unaffected. We therefore demonstrate a novel association among 3 distinct families of cell-surface receptors that regulate cell migratory responses and identify a new role for CD164. We propose that this lends specificity to the homing and lodgment of these cells within the bone marrow niche.