Implication of Soluble Forms of Cell Adhesion Molecules in Infectious Disease and Tumor: Insights from Transgenic Animal Models.

Cell adhesion molecules (CAMs) are surface ligands, usually glycoproteins, which mediate cell-to-cell adhesion. They play a critical role in maintaining tissue integrity and mediating migration of cells, and some of them also act as viral receptors. It has been known that soluble forms of the viral receptors bind to the surface glycoproteins of the viruses and neutralize them, resulting in inhibition of the viral entry into cells. Nectin-1 is one of important CAMs belonging to immunoglobulin superfamily and herpesvirus entry mediator (HVEM) is a member of the tumor necrosis factor (TNF) receptor family. Both CAMs also act as alphaherpesvirus receptor. Transgenic mice expressing the soluble form of nectin-1 or HVEM showed almost complete resistance against the alphaherpesviruses. As another CAM, sialic acid-binding immunoglobulin-like lectins (Siglecs) that recognize sialic acids are also known as an immunoglobulin superfamily member. Siglecs play an important role in the regulation of immune cell functions in infectious diseases, inflammation, neurodegeneration, autoimmune diseases and cancer. Siglec-9 is one of Siglecs and capsular polysaccharide (CPS) of group B Streptococcus (GBS) binds to Siglec-9 on neutrophils, leading to suppress host immune response and provide a survival advantage to the pathogen. In addition, Siglec-9 also binds to tumor-produced mucins such as MUC1 to lead negative immunomodulation. Transgenic mice expressing the soluble form of Siglec-9 showed significant resistance against GBS infection and remarkable suppression of MUC1 expressing tumor proliferation. This review describes recent developments in the understanding of the potency of soluble forms of CAMs in the transgenic mice and discusses potential therapeutic interventions that may alter the outcomes of certain diseases.

RNA and protein expression of herpesvirus entry mediator (HVEM) is associated with molecular markers, immunity-related pathways and relapse-free survival of patients with AML.

Immune checkpoint molecules are highly relevant as potential prognostic markers and therapeutic targets in malignant diseases. HVEM belongs to the TNF receptor family and provides stimulatory as well as inhibitory signals depending on the ligand. Abnormal HVEM expression has been described in various malignancies, but the role in AML is unknown. Here we report extensive data on HVEM surface protein expression analyzed by flow cytometry on bone marrow leukemic cells of 169 AML patients at diagnosis. An independent cohort of 512 AML patients was analyzed for HVEM mRNA expression in bone marrow samples by Affymetrix microarrays. Consistently for both cohorts and methods, we show that HVEM was differentially expressed and that expression levels were associated with defined genetic markers. HVEM expression was lower in cases with FLT3-ITD (p = 0.001, p < 0.001), with mutations in NPM1 (p = 0.001, p < 0.001) or with the combination of NPM1 mutation and FLT3 wild type (p = 0.049, p = 0.050), while a biallelic mutation in CEBPA correlated positively with higher HVEM expression (p = 0.015, p < 0.001). In a differential gene expression analysis, we found 13 genes including HOXA9, MEIS1 and MN1 that were closely associated with HVEM expression. Besides, four gene sets closely linked to immunity were enriched in HVEM (high) samples. Finally, high expression of HVEM was associated with a trend toward longer relapse-free survival. The results of this study provide new information on the potential significance of HVEM in AML.

Significant involvement of herpesvirus entry mediator in human esophageal squamous cell carcinoma.

BACKGROUND: Herpesvirus entry mediator (HVEM) is known to regulate immune response and to be expressed in several human malignancies. However, to the authors's knowledge, the precise role of HVEM in human cancer biology remains unknown. The objective of the current study was to clarify the clinical significance of HVEM in human esophageal squamous cell carcinoma as well as its in vivo functions. METHODS: HVEM expression was evaluated in 103 patients with esophageal squamous cell carcinoma to explore its clinical relevance and prognostic value. The functions of HVEM in tumors were analyzed in vitro and in vivo using the small interfering RNA (siRNA) silencing technique. RESULTS: HVEM expression was found to be significantly correlated with depth of tumor invasion and lymph node metastasis. Furthermore, it was found to be inversely correlated with tumor-infiltrating CD4(+) , CD8(+) , and CD45RO(+) lymphocytes. It is important to note that HVEM status was identified as an independent prognostic marker. HVEM gene silencing significantly inhibited cancer cell proliferation in vitro and cancer growth in vivo. This antitumor effect was associated with reduced cell proliferation activity. The effect was also correlated with the induction of CD8(+) cells and upregulation of local immune response. CONCLUSIONS: HVEM plays a critical role in both tumor progression and the evasion of host antitumor immune responses, possibly through direct and indirect mechanisms. Therefore, HVEM may be a promising therapeutic target for human esophageal cancer.

Herpesvirus entry mediator (HVEM) attenuates signals mediated by the lymphotoxin ß receptor (LTßR) in human cells stimulated by the shared ligand LIGHT.

Signals mediated by members of the tumor necrosis factor receptor superfamily modulate a network of diverse processes including initiation of inflammatory responses and altering cell fate between pathways favoring survival and death. Although such pathways have been well-described for the TNF-α receptor, less is known about signaling induced by the TNF superfamily member LIGHT and how it is differentially altered by expression of its two receptors LTßR and HVEM in the same cell. We used cell lines with different relative expression of HVEM and LTßR to show that LIGHT-induced signals mediated by these receptors were associated with altered TRAF2 stability and RelA nuclear translocation. Production of the inflammatory chemokine CXCL10 was primarily mediated by LTßR. Higher expression of HVEM was associated with cell survival, while unopposed LTßR signaling favored pathways leading to apoptosis. Importantly, restoring HVEM expression in cells with low endogenous expression recapitulated the phenotype of cells with higher endogenous expression. Together, our data provide evidence that relative expression of HVEM and LTßR modulates canonical NF-κB and pro-apoptotic signals stimulated by LIGHT.