Bo Guo

Tissue factor in tumor microenvironment: a systematic review.

The aberrant hemostasis is a common manifestation of cancer, and venous thromboembolism (VTE) is the second leading cause of cancer patients’ mortality. Tissue factor (TF), comprising of a 47-kDa transmembrane protein that presents in subendothelial tissues and leukocytes and a soluble isoform, have distinct roles in the initiation of extrinsic coagulation cascade and thrombosis. Laboratory and clinical evidence showed the deviant expression of TF in several cancer systems and its tumor-promoting effects. TF contributes to myeloid cell recruitment in tumor stroma, thereby remodeling of tumor microenvironment. Additionally, the number of TF-positive-microparticles (TF+MP) from tumor origins correlates with the VTE rates in cancer patients. In this review, we summarize our current understanding of the TF regulation and roles in tumor progression and clinical complications.

C5aR, TNF-α, and FGL2 contribute to coagulation and complement activation in virus-induced fulminant hepatitis

BACKGROUND & AIMSnViral fulminant hepatitis (FH) is a disease with a high mortality rate. Activation of the complement system correlates with the development of FH. However, the key factors mediating complement activation in FH remain elusive.nnnMETHODSnLiver tissues were isolated from FH patients infected by hepatitis B virus (HBV) and from mice infected with murine hepatitis virus strain 3 (MHV-3). Wild type mice were treated with or without antagonists of C5aR or TNF-α, and mice deficient for C5aR (C5aR(-/-)), Fgl2 (Fgl2(-/-)), and Tnfα (Tnfα(-/-)) mice were not treated with the antagonists. C5b-9, C5aR, FGL2, CD31, CD11b, fibrin, TNF-α, and complement C3 cleavage products were detected by immunohistochemistry, immunofluorescence, or ELISA. Sorted liver sinusoidal endothelial cells (LSECs) or myeloid-derived (CD11b(+)) cells were stimulated with C5a, TNF-α or MHV-3 in vitro. The mRNA expressions levels of Fgl2 and Tnfα were determined by qRT-PCR analyses.nnnRESULTSnWe observed that complement activation, coagulation and pro-inflammatory cytokine production were upregulated in the HBV(+) patients with FH. Similar observations were made in the murine FH models. Complement activation and coagulation were significantly reduced in MHV-3 infected mice in the absence of C5aR, Tnfα or Fgl2. The MHV-3 infected C5aR(-/-) mice exhibited reduced numbers of infiltrated inflammatory CD11b(+) cells and a reduced expression of TNF-α and FGL2. Moreover, C5a administration stimulated TNF-α production by CD11b(+) cells, which in turn promoted the expression of FGL2 in CD31(+) LSEC-like cells in vitro. Administration of antagonists against C5aR or TNF-α ameliorated MHV-3-induced FH.nnnCONCLUSIONSnOur results demonstrate that C5aR, TNF-α, and FGL2 form an integral network that contributes to coagulation and complement activation, and suggest that those are potential therapeutic targets in viral FH intervention.

STIM1 Mediates Hypoxia-Driven Hepatocarcinogenesis via Interaction with HIF-1.

Hypoxia and intracellular Ca(2+) transients are fundamental traits of cancer, whereas the route and regulation of Ca(2+) mobilization in hypoxic tumorigenesis are unknown. Here, we show that stromal-interaction molecule 1 (STIM1), an ER Ca(2+) sensor, correlates with elevated hypoxia-inducible factor-1 alpha (HIF-1α) in hypoxic hepatocarcinoma cells (HCCs) and is upregulated during hepatocarcinoma growth. HIF-1 directly controls STIM1 transcription and contributes to store-operated Ca(2+) entry (SOCE). STIM1-mediated SOCE is also required for HIF-1 accumulation in hypoxic HCCs via activation of Ca(2+)/calmodulin-dependent protein kinase II and p300. Administration of YC-1, a HIF-1 inhibitor, or knockdown of HIF1A significantly diminishes hypoxia-enhanced STIM1 and suppresses tumorigenesis. Moreover, ectopic expression of STIM1 or HIF-1α partially reverses impaired growth of tumors treated with YC-1. These results suggest a mutual dependency and regulation of STIM1 and HIF-1 in controlling Ca(2+) mobilization and hypoxic tumor growth and highlight a potential target for early hypoxia-related intervention.

Comprehensive Antibody Epitope Mapping of the Nucleocapsid Protein of Severe Acute Respiratory Syndrome (SARS) Coronavirus: Insight into the Humoral Immunity of SARS

Abstract Background: The epidemic outbreak of severe acute respiratory syndrome (SARS) posed a worldwide threat to public health and economic stability. Although the pandemic has been contained, concerns over its recurrence remain. It is essential to identify specific diagnostic agents and antiviral vaccine candidates to fight this highly contagious disease. Methods: We generated 14 monoclonal antibodies (mAbs) specific to the SARS coronavirus (SARS-CoV) nucleocapsid (N) protein and used these to thoroughly map the N protein antigenic determinants. We identified the immunodominant antigenic sites responsible for the antibodies in sera from SARS patients and antisera from small animals and differentiated the linear from the conformational antibody-combining sites comprising the natural epitopes by use of yeast surface display. Results: We identified 5 conformational and 3 linear epitopes within the entire N protein; 3 conformational and 3 linear epitopes were immunodominant. The antibody responses to the N protein fragments in mammalian sera revealed that 3 regions of the N protein are strong antigenic domains. We expanded the specificity of the N protein epitope and identified 4 novel conformational epitopes (amino acids 1–69, 68–213, 212–341, and 337–422). Conclusion: The antigenic structures identified for the SARS-CoV N protein, the epitope-specific mAbs, and the serum antibody profile in SARS patients have potential use in the clinical diagnosis and understanding of the protective immunity to SARS-CoV.

T lymphocytes maintain structure and function of fibroblastic reticular cells via lymphotoxin (LT)-B

BackgroundAlthough a lot is known about how Fibroblastic Reticular Cells (FRCs) can regulate T lymphocytes (T cells), little is understood about whether or how T cells can regulate FRCs.ResultsThis study shows that the absence of T cells inhibited the secretion of ER-TR7 by splenic FRCs, induced the structural disorder of FRCs, down-regulated the expression of the chemokine ligands CCL21 and CCL19, and weakened the homing ability of T cells to the spleen of nude mice. Transfusion of T cells from BALB/c mice restored the structure and functions of FRCs and recovered them. The expression of lymphotoxin (LT)-B was significantly downregulated in the absence of T cells from nude mice and was recovered after the transfusion of T cells. After the occlusion of the LT-B receptor, the FRCs structure and functions were not restored by transfusion of T cells.ConclusionsThese data reveal that the absence of T cells will subject spleen FRCs to structural and functional abnormality, and weaken the homing ability of T cells to the spleen. These changes are attributed to the T-cell- derived LT-B.

An essential role for C5aR signaling in the optimal induction of a malaria-specific CD4+ T cell response by a whole-killed blood-stage vaccine.

The protective immunity induced by the whole-killed parasite vaccine against malarial blood-stage infection is dependent on the CD4+ T cell response. However, the mechanism underlying this robust CD4+ T cell response elicited by the whole-killed parasite vaccine is still largely unknown. In this study, we observe that immunization with Plasmodium yoelii–parasitized RBC lysate activates complement C5 and generates C5a. However, the protective efficacy against P. yoelii 17XL challenge is considerably reduced, and the malaria-specific CD4+ T cell activation and memory T cell differentiation are largely suppressed in the C5aR-deficient (C5aR−/−) mice. An adoptive transfer assay demonstrates that the reduced protection of C5aR−/− mice is closely associated with the severely impaired CD4+ T cell response. This is further confirmed by the fact that administration of C5aR antagonist significantly reduces the protective efficacy of the immunized B cell–deficient mice. Further study indicates that the defective CD4+ T cell response in C5aR−/− mice is unlikely involved in the expansion of CD4+CD25+Foxp3+ T cells, but strongly linked to a defect in dendritic cell (DC) maturation and the ability to allostimulate CD4+ T cells. These results demonstrate that C5aR signaling is essential for the optimal induction of the malaria-specific CD4+ T cell response by the whole-killed parasite vaccine through modulation of DCs function, which provides us with new clues to design an effective blood-stage subunit vaccine and helps us to understand the mechanism by which the T cell response is regulated by the complement system.

Induction of protective and therapeutic antitumor immunity by a DNA vaccine with C3d as a molecular adjuvant

Although the critical role of complement component C3d as a molecular adjuvant in preventing virus infection is well established, its role in cancer therapies is unclear. In this study, we have engineered a DNA vaccine that expresses extracellular region of murine VEGFR-2 (FLK1(265-2493)) and 3 copies of C3d (C3d3), a component of complement as a molecular adjuvant, designed to increase antitumor immunity. VEGFR-2 has a more restricted expression on endothelial cells and is upregulated once these cells proliferate during angiogenesis in the tumor vasculature. Immunization of mice with vector encoding FLK1(265-2493) alone generated only background levels of anti-VEGFR-2 antibodies and slight inhibitory effect on tumor growth. However, the addition of C3d3 to the vaccine construct significantly augmented the anti-VEGFR-2 humoral immune response and inhibited the tumor growth. The antitumor activity induced by vaccination with vector encoding FLK1(265-2493)-C3d3 fusion protein was also demonstrated via growth inhibition of established tumors following passive transfer of immune serum from vaccinated mice. Our results suggest that vaccination with vector encoding FLK1(265-2493) with C3d3 as a molecular adjuvant induces adaptive humoral activity, which is directed against the murine VEGFR-2 and can significantly inhibit tumor growth, and that administration of C3d as a molecular adjuvant to increase antibodies levels to VEGFR-2 may provide an alternative treatment modality for cancer therapies.

Mapping of binding epitopes of a human decay-accelerating factor monoclonal antibody capable of enhancing rituximab-mediated complement-dependent cytotoxicity

Complement-dependent cytotoxicity (CDC) is thought to be one of the most important mechanisms of action of therapeutic monoclonal antibodies (mAbs). The decay-accelerating factor (DAF) overexpressed in certain tumors limits the CDC effect of the therapeutic anticancer antibodies. The use of DAF blocking antibodies targeted specifically at cancer cells in combination with immunotherapeutic mAbs of cancer may improve the therapeutic effect in cancer patients. In this study, the lysis of Raji cells mediated by CDC was determined after blocking DAF function by anti-DAF polyclonal antibody and 3 mAbs (DG3, DG9, DA11) prepared in our laboratory, respectively, in the presence of the anti-CD20 chimeric mAb rituximab. The binding domains of the three anti-DAF mAbs were identified using yeast surface display technique, and the mimic epitopes of mAb DG3 were screened from a random phage-display nonapeptide library. The results showed that blocking DAF function by anti-DAF polyclonal antibody enhanced complement-mediated killing of Raji cells. Among the 3 mAbs against DAF, only DG3 was found to be able to remarkably enhance the CDC effect of the therapeutic mAb rituximab. DG3 bound to the third short consensus repeat (SCR) of DAF. Binding of DG3 to immobilized DAF was inhibited by mimic epitope peptides screened from the peptide library. Our results suggest that a higher level of DAF expressed by certain tumor cells is significant to abolish the CDC effect of therapeutic anticancer antibodies, and mAbs binding to SCR3 can enhance the complement-mediated killing of Raji cells. It is of significance to identify the DAF epitopes required in inhibiting CDC not only for better understanding of the relationship between the structure and function of DAF, but also for designing and developing anti-DAF mAbs capable of enhancing CDC.

Systemic C3 Modulates CD8+ T Cell Contraction after Listeria monocytogenes Infection

Ag-specific CD8+ T cell contraction (contraction), which occurs after the resolution of infection, is critical for homeostasis of the immune system. Although complement components regulate the primary CD8+ T cell response, there is insufficient evidence supporting their role in regulating contraction and memory. In this study, we show that C3-deficient (C3−/−) mice exhibited significantly less CD8+ T cell contraction than did wild-type mice postinfection with recombinant Listeria monocytogenes expressing OVA. Kinetic analyses also revealed decreased contraction in mice treated with cobra venom factor to deplete C3, which was consistent with the results in C3−/− recipient mice transplanted with bone marrow cells from the same donors as wild-type recipient mice. The phenotypes of memory cells generated by C3−/− mice were not altered compared with those of wild-type mice. Further, C5aR signaling downstream of C3 was not involved in the regulation of contraction. Moreover, the regulation of contraction by C3 may be independent of the duration of antigenic stimulation or the functional avidity of effector CD8+ T cells. However, reduced contraction in C3−/− mice was accompanied by a decrease in the proportion of KLRG-1hi (killer-cell lectin-like receptor G1) CD127lo short-lived effector cells at the peak of the response and correlated with a reduction in the levels of inflammatory cytokines, such as IL-12 and IFN-γ, produced early postinfection. These results provide new insights into the role of systemic C3 in regulating contraction following intracellular bacterial infection and may help to develop vaccines that are more effective.

Cytotoxic chemotherapy reduces T cell trafficking to the spleen by downregulating the expression of C‑C motif chemokine ligand 21 and C‑C motif chemokine ligand 19

T cells serve an important role in the destruction of tumor cells and clearing of foreign pathogens. Previous studies have suggested that the T cell immune response of tumor-bearing patients is significantly lower than that of healthy people, and the principal reason for this is lymphocytopenia, which is caused by repeated cycles of chemotherapy. In addition to lymphocytopenia, the present study revealed that cytotoxic chemotherapy also weakens the homing ability of T cells to the T-cell zone of the spleen, which decreases the possibility of encounters between antigen-specific T cells and dendritic cells presenting the appropriate antigen, thereby weakening the immune response of T cells. These changes are attributed to the lower expression of C-C motif chemokine ligand 21 (CCL21) and C-C motif chemokine ligand 19 (CCL19) in the spleen of secondary lymphoid organs (SLOs). Finally, the present study identified that chemotherapy affects the function and survival of fibroblastic reticular cells in SLOs, which are the main source of CCL21 and CCL19. These observations aid us in further understanding the mechanism that is responsible for the decreased T cell immune response following repeated cycles of chemotherapy.