O1 Elevated expression level of capillary morphogenesis gene 2 in pancreatic ductal adenocarcinoma cell is associated with distant metastasis and poor prognosis

Introduction Emerging evidence revealed the active role played by capillary morphogenesis gene 2 (CMG2) during the disease progression and metastasis of some cancers. It was shown that CMG2 was increased in pancreatic tumours in our previous research. The current study further validated this finding for the expression of CMG2 in pancreatic cancer and also dissected its clinical implication. Method Immunochemical staining of CMG2 was performed on a pancreatic cancer tissue microarray (PA2081, Biomax, n = 104). Clinical relevance of CMG2 was analysed in TCGA pancreatic cancer cohort and gene array data (GSE71729) using ANOVA and Kaplan-Meier analyses. Influence of CMG2 on adhesion to a mesothelial cell monolayer was determined using both Mia-PaCa-2 and PANC-1 cell lines with CMG2 knockdown. Result CMG2 is increased significantly in pancreatic ductal adenomas, P < 0.001 compared with adjacent non-tumour tissues. Higher levels of CMG2 were also revealed in the distant metastases of pancreatic cancer, P < 0.001 compared with both primary tumuors and distant metastasis. Elevated expression CMG2 protein in pancreatic cancers was also observed on the tissue microarray. Patients with higher CMG2 expression tumours had shorter overall survival (median = 15.8 months), P < 0.001 compared with those patients with lower CMG2 expressing tumours (median = 30.4 months). Knockdown of the CMG2 significantly decreased the number of cells which adhere to the mesothelial cells (P < 0.001). Conclusion Elevated CMG2 expression in pancreatic ductal adenocarcinomas is associated with distant metastasis and shorter survival which requires further investigation to shed light on its therapeutic potential. Take-home Message Elevated CMG2 expression in pancreatic ductal adenocarcinomas is associated with distant metastasis and shorter survival.

Binding of the von Willebrand Factor A Domain of Capillary Morphogenesis Protein 2 to Anthrax Protective Antigen Vaccine Reduces Immunogenicity in Mice

ABSTRACT Protective antigen (PA) is a component of anthrax toxin that can elicit toxin-neutralizing antibody responses. PA is also the major antigen in the current vaccine to prevent anthrax, but stability problems with recombinant proteins have complicated the development of new vaccines containing recombinant PA. The relationship between antigen physical stability and immunogenicity is poorly understood, but there are theoretical reasons to think that this parameter can affect immune responses. We investigated the immunogenicity of anthrax PA, in the presence and absence of the soluble von Willebrand factor A domain of the human form of receptor capillary morphogenesis protein 2 (sCMG2), to elicit antibodies to PA in BALB/c mice. Prior studies showed that sCMG2 stabilizes the 83-kDa PA structure to pH, chemical denaturants, temperature, and proteolysis and slows the hydrogen-deuterium exchange rate of histidine residues far from the binding interface. In contrast to a vaccine containing PA without adjuvant, we found that mice immunized with PA in stable complex with sCMG2 showed markedly reduced antibody responses to PA, including toxin-neutralizing antibodies and antibodies to domain 4, which correlated with fewer toxin-neutralizing antibodies. In contrast, mice immunized with PA in concert with a nonbinding mutant of sCMG2 (D50A) showed anti-PA antibody responses similar to those observed with PA alone. Our results suggest that addition of sCMG2 to a PA vaccine formulation is likely to result in a significantly diminished immune response, but we discuss the multitude of factors that could contribute to reduced immunogenicity. IMPORTANCE The anthrax toxin PA is the major immunogen in the current anthrax vaccine (anthrax vaccine adsorbed). Improving the anthrax vaccine for avoidance of a cold chain necessitates improvements in the thermodynamic stability of PA. We address how stabilizing PA using sCMG2 affects PA immunogenicity in BALB/c mice. Although the stability of PA is increased by binding to sCMG2, PA immunogenicity is decreased. This study emphasizes that, while binding of a ligand retains or improves conformational stability without affecting the native sequence, epitope recognition or processing may be affected, abrogating an effective immune response.

Capillary Morphogenesis gene 2 mediates multiple pathways of growth factor-induced angiogenesis by regulating endothelial cell chemotaxis

Pathological angiogenesis contributes to diseases as varied as cancer and corneal neovascularization. The vascular endothelial growth factor (VEGF) - VEGF receptor 2 (KDR/VEGFR2) axis has been the major target for treating pathological angiogenesis. However, VEGF-targeted therapies exhibit reduced efficacy over time, indicating that new therapeutic strategies are needed. Therefore, identifying new targets that mediate angiogenesis is of great importance. Here, we report that one of the anthrax toxin receptors, capillary morphogenesis gene 2 (ANTXR2/CMG2), plays an important role in mediating angiogenesis induced by both bFGF and VEGF. Inhibiting physiological ligand binding to CMG2 results in significant reduction of corneal neovascularization, endothelial tube formation and cell migration. We also report the novel finding that CMG2 mediates angiogenesis by regulating the direction of endothelial chemotactic migration without affecting overall cell motility.

A canstatin-derived peptide provides insight into the role of Capillary Morphogenesis Gene 2 in angiogenic regulation and matrix uptake

Capillary Morphogenesis Gene 2 protein (CMG2) is a transmembrane, integrin-like receptor and the primary receptor for the anthrax toxin. In addition to its role as an anthrax toxin receptor, CMG2 has been repeatedly shown to play a role in angiogenic processes. However, the molecular mechanism mediating observed CMG2-related angiogenic effects has not been fully elucidated. Previous studies have found that CMG2 binds type IV collagen (Col-IV), a key component of the vascular basement membrane, as well as other ECM proteins. Currently, no link has been made between these CMG2-ECM interactions and angiogenesis; however, ECM fragments are known to play a role in regulating angiogenesis. Here, we further characterize the CMG2-Col-IV interaction and explore the effect of this interaction on angiogenesis. Using a peptide array, we observed that CMG2 preferentially binds peptide fragments of the NC1 (non-collagenous domain 1) domains of Col-IV. These domains are also known as the fragments arresten (from the α1 chain) and canstatin (from the α2 chain) and have documented antiangiogenic properties. A second peptide array was probed to map a putative binding epitope. A top hit from the initial array, a canstatin-derived peptide, binds to the CMG2 ligand-binding von Willebrand factor A (vWA) domain with sub-micromolar affinity (peptide S16, Kd = 400 ± 200 nM). This peptide competes with anthrax protective antigen (PA) for CMG2 binding, and does not bind CMG2 in the presence of EDTA. Together these data suggest that, like PA, S16 interacts with CMG2 at the metal-ion dependent adhesion site (MIDAS) of its vWA domain. We demonstrate that CMG2 specifically mediates endocytic uptake of S16, since CMG2-/- endothelial cells show markedly reduced S16 uptake, without reducing total endocytosis. Furthermore, we show that S16 reduces endothelial migration but not cell proliferation. Taken together, our data demonstrate that a Col IV-derived anti-angiogenic peptide acts via CMG2, suggesting a possible link between CMG2-Col IV interactions and angiogenesis.