The epidermal growth factor (EGF)-related peptides bind the ErbB receptors, inducing the formation of different homo- and heterodimers. Receptor dimerization promotes activation of the intrinsic ...kinase, leading to phosphorylation of specific tyrosines located in the ErbB's cytoplasmic region. These phosphorylated residues serve as docking sites for a variety of signaling molecules whose recruitment stimulates intracellular signaling cascades, which ultimately control diverse genetic programs. Particular ligand-receptor complexes have essential roles in embryonic development as well as in the adult. Finally, ErbB receptors are being pursued as therapeutic targets because aberrant ErbB activity has been observed in many human cancers. In this review, we discuss these data in more detail, illustrating the importance of tightly regulated ErbB signaling throughout life.
Dysregulation of complement activation causes a number of diseases, including paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. These conditions can be treated with ...monoclonal antibodies (mAbs) that bind to the complement component C5 and prevent formation of the membrane attack complex (MAC). While MAC is involved in uncontrolled lysis of erythrocytes in these patients, it is also required for serum bactericidal activity (SBA), i.e. clearance of encapsulated bacteria. Therefore, terminal complement blockage in these patients increases the risk of invasive disease by
more than 1000-fold compared to the general population, despite obligatory vaccination. It is assumed that alternative instead of terminal pathway inhibition reduces the risk of meningococcal disease in vaccinated individuals. To address this, we investigated the SBA with alternative pathway inhibitors. Serum was collected from adults before and after vaccination with a meningococcal serogroup A, C, W, Y capsule conjugate vaccine and tested for meningococcal killing in the presence of factor B and D, C3, C5 and MASP-2 inhibitors. B meningococci were not included in this study since the immune response against protein-based vaccines is more complex. Unsurprisingly, inhibition of C5 abrogated killing of meningococci by all sera. In contrast, both factor B and D inhibitors affected meningococcal killing in sera from individuals with low, but not with high bactericidal anti-capsular titers. While the anti-MASP-2 mAb did not impair SBA, inhibition of C3 impeded meningococcal killing in most, but not in all sera. These data provide evidence that vaccination can provide protection against invasive meningococcal disease in patients treated with alternative pathway inhibitors.
To assess the relative contribution of opsonisation by antibodies, classical and alternative complement pathways to pneumococcal phagocytosis, we analyzed killing of pneumococci by human blood ...leukocytes collected from vaccine-naïve and PCV13-vaccinated subjects. With serotype 4 pneumococci as model, two different physiologic opsonophagocytosis assays based on either hirudin-anticoagulated whole blood or on washed cells from EDTA-anticoagulated blood reconstituted with active serum, were compared. Pneumococcal killing was measured in the presence of inhibitors targeting the complement components C3, C5, MASP-2, factor B or factor D. The two assay formats yielded highly consistent and comparable results. They highlighted the importance of alternative complement pathway activation for efficient opsonophagocytic killing in blood of vaccine-naïve subjects. In contrast, alternative complement pathway inhibition did not affect pneumococcal killing in PCV13-vaccinated individuals. Independent of amplification by the alternative pathway, even low capsule-specific antibody concentrations were sufficient to efficiently trigger classical pathway mediated opsonophagocytosis. In heat-inactivated or C3-inhibited serum, high concentrations of capsule-specific antibodies were required to trigger complement-independent opsonophagocytosis. Our findings suggest that treatment with alternative complement pathway inhibitors will increase susceptibility for invasive pneumococcal infection in non-immune subjects, but it will not impede pneumococcal clearance in vaccinated individuals.
Several diseases caused by the dysregulation of complement activation can be treated with inhibitors of the complement components C5 and/or C3. However, complement is required for serum bactericidal ...activity (SBA) against encapsulated Gram-negative bacteria. Therefore, C3 and C5 inhibition increases the risk of invasive disease, in particular by
As inhibitors against complement components other than C3 and C5 may carry a reduced risk of infection, we compared the effect of inhibitors targeting the terminal pathway (C5), the central complement component C3, the alternative pathway (FB and FD), and the lectin pathway (MASP-2) on SBA against serogroup B meningococci.
Serum from adults was collected before and after vaccination with the meningococcal serogroup B vaccine 4CMenB and tested for meningococcal killing. Since the B capsular polysaccharide is structurally similar to certain human polysaccharides, 4CMenB was designed to elicit antibodies against meningococcal outer membrane proteins.
While only a few pre-vaccination sera showed SBA against the tested B meningococcal isolates, 4CMenB vaccination induced potent complement-activating IgG titers against isolates expressing a matching allele of the bacterial cell surface-exposed factor H-binding protein (fHbp). SBA triggered by these cell surface protein-specific antibodies was blocked by C5 and reduced by C3 inhibition, whereas alternative (factor B and D) and lectin (MASP-2) pathway inhibitors had no effect on the SBA of post-4CMenB vaccination sera.
Compared to the SBA triggered by A,C,W,Y capsule polysaccharide conjugate vaccination, SBA against B meningococci expressing a matching fHbp allele was remarkably resilient against the alternative pathway inhibition.
Aims
Although left ventricular ejection fraction (LVEF) is routinely used to categorize patients with heart failure (HF), whether it predicts outcomes after hospitalization for acute heart failure ...(AHF) is uncertain. Consequently, we assessed the relationship between LVEF and cardiovascular (CV) outcomes in a large, well characterized cohort of patients hospitalized for
AHF.
Methods and results
The 6128 patients from the RELAX‐AHF‐2 trial who had LVEF measured during AHF hospitalization were separated into LVEF quartiles and the relationship between LVEF and a composite of CV mortality and rehospitalization for HF or renal failure through 180 days was assessed. We found progressively lower risk for this composite outcome as LVEF increased (hazard ratio 0.95, 95% confidence interval 0.93–0.98 per 5% LVEF increase, P < 0.001) that was driven predominantly by decreased risk for rehospitalization. The smoothed spline curve depicting risk remained stable as LVEF decreased until reaching approximately 40%, at which point risk increased progressively with further reductions in LVEF. Significant differences between LVEF quartiles for post‐discharge CV risk were seen in patients with an ischaemic aetiology or with a history of HF preceding index hospitalization, but were less robust in patients with non‐ischaemic aetiology and absent in those with de novo
HF.
Conclusion
In patients hospitalized with AHF, CV events over 180 days were more frequent in patients with lower LVEF. This was due predominantly to a significant increase in risk for HF/renal failure rehospitalization but not in either CV or all‐cause mortality. LVEF had greater prognostic value in patients with ischaemic aetiology or pre‐existing
HF.
Defense against
type b (Hib) is dependent on antibodies and complement, which mediate both serum bactericidal activity (SBA) and opsonophagocytosis. Here we evaluated the influence of ...capsule-specific antibodies and complement inhibitors targeting the central component C3, the alternative pathway (AP; fB, fD), the lectin pathway (LP; MASP-2) and the terminal pathway (C5) on both effector functions. Findings may be relevant for the treatment of certain diseases caused by dysregulation of the complement system, where inhibitors of complement factors C3 or C5 are used. Inhibitors against other complement components are being evaluated as potential alternative treatment options that may carry a reduced risk of infection by encapsulated bacteria. Serum and reconstituted blood of healthy adults were tested for bactericidal activity before and after vaccination with the Hib capsule-conjugate vaccine ActHIB. Most sera had bactericidal activity prior to vaccination, but vaccination significantly enhanced SBA titers. Independently of the vaccination status, both C3 and C5 inhibition abrogated SBA, whereas inhibition of the LP had no effect. AP inhibition had a major inhibitory effect on SBA of pre- vaccination serum, but vaccination mitigated this inhibition for all disease isolates tested. Despite this, SBA-mediated killing of some Hib isolates remained retarded. Even for the most serum-resistant isolate, SBA was the dominating defense mechanism in reconstituted whole blood, as addition of blood cells to the serum did not enhance bacterial killing. Limited Fc receptor-mediated opsonophagocytosis was unmasked when bacterial killing by the membrane attack complex was blocked. In the presence of C3 or C5 inhibitors, addition of post-vaccination, but not of pre-vaccination serum to the blood cells triggered opsonophagocytosis, leading to suppression of bacterial multiplication. Taken together, our data indicate that for host defense against Hib, killing by SBA is more efficient than by blood cell opsonophagocytosis. However, additional defense mechanisms, such as bacterial clearance by spleen and liver, may play an important role in preventing Hib-mediated sepsis, in particular for Hib isolates with increased serum-resistance. Results indicate potentially improved safety profile of AP inhibitors over C3 and C5 inhibitors as alternative therapeutic agents in patients with increased susceptibility to Hib infection.
ErbB2 is a receptor tyrosine kinase whose activity in normal cells depends on dimerization with another ligand-binding ErbB receptor. In contrast, amplification of c-erbB2 in tumors results in ...dramatic overexpression and constitutive activation of the receptor. Breast cancer cells overexpressing ErbB2 depend on its activity for proliferation, because treatment of these cells with ErbB2-specific antagonistic antibodies or kinase inhibitors blocks tumor cells in the G1phase of the cell cycle. Intriguingly, loss of ErbB2 signaling is accompanied by a decrease in the phosphotyrosine content of ErbB3. On the basis of these results, it has been proposed that ErbB3 might be a partner for ErbB2 in promoting cellular transformation. To test this hypothesis and directly examine the role of the "kinase dead" ErbB3, we specifically ablated its expression with a designer transcription factor (E3). By infection of ErbB2-overexpressing breast cancer cells with a retrovirus expressing E3, we show that ErbB3 is an essential partner in the transformation process. Loss of functional ErbB2 or ErbB3 has similar effects on cell proliferation and cell cycle regulators. Furthermore, expression of constitutively active protein kinase B rescues the proliferative block induced as a consequence of loss of ErbB2 or ErbB3 signaling. These results demonstrate that ErbB2 overexpression and activity alone are insufficient to promote breast tumor cell division. Furthermore, we identify ErbB3's role, which is to couple active ErbB2 to the phosphatidylinositol 3-kinase/protein kinase B pathway. Thus, the ErbB2/ErbB3 dimer functions as an oncogenic unit to drive breast tumor cell proliferation.
BACKGROUND In acute heart failure (AHF), systolic blood pressure (SBP) is an important clinical variable. This study assessed the association between SBP and short-term and long-term outcomes in a ...large cohort of patients with AHF. METHODS AND RESULTS This is an analysis of 4 randomized controlled trials investigating serelaxin versus placebo in patients admitted with AHF and SBPs from 125 to 180 mm Hg. Outcomes were 180-day all-cause mortality and a composite end point of all-cause mortality, worsening heart failure, or hospital readmission for heart failure the first 14 days. Left ventricular ejection fraction (LVEF) was examined as LVEF<40% and LVEF≥40%. Multivariable Cox regression models were adjusted for known confounders of outcomes in AHF. A total of 10 533 patients with a mean age of 73 (±12) years and a mean SBP of 145 (±7) mm Hg were included. LVEF was assessed in 9863 patients (93%); 4737 patients (45%) had LVEF<40%. Increasing SBP was inversely associated with 180-day mortality (adjusted hazard ratio HR
, 0.93; 95% CI, 0.89-0.98;
=0.008 per 10 mm Hg increase) and with the composite end point (HR
, 0.90; 95% CI, 0.85-0.94;
<0.001 per 10 mm Hg increase). A significant interaction with LVEF was observed, revealing that SBP was not associated with mortality in patients with LVEF≥40% (HR
, 0.98; 95% CI, 0.91-1.04; per 10 mm Hg increase), but was strongly associated with increased mortality in LVEF<40% (HR
, 0.84; 95% CI, 0.77-0.92; per 10 mm Hg increase). CONCLUSIONS Elevated SBP is associated with favorable short-term and long-term outcomes in patients with AHF. In our predefined subgroup analysis, we found that baseline SBP was not associated with mortality in LVEF≥40%, but was strongly associated with mortality in patients with LVEF<40%.
Overexpression of fibroblast growth factor receptor (FGFR) tyrosine kinases has been found in many human breast cancers and has been associated with poor patient prognosis. In order to understand the ...mechanism by which FGFR mediates breast cancer cell proliferation, we used a low molecular weight compound, PD173074, that selectively inhibits FGFR tyrosine kinase activity and autophosphorylation. This potential anticancer agent caused a G1 growth arrest of MDA-MB-415, MDA-MB-453 and SUM 52 breast cancer cells. Our analyses revealed that FGFR signaling links to the cell cycle machinery via D-type cyclins. PD173074-mediated inhibition of FGFR activity caused downregulation of cyclin D1 and cyclin D2 expression, inhibition of cyclin D/cdk4 activity and, as a consequence, reduction of pRB phosphorylation. Retroviral-mediated ectopic expression of cyclin D1 prevented pRB hypophosphorylation and the cell cycle G1 block in PD173074-treated cells, suggesting a central role for D cyclins in proliferation of FGFR-driven breast cancer cells. The repression of FGFR activity caused downregulation of MAPK in MDA-MB-415 and MDA-MB-453 cells. In SUM 52 cells, both MAPK and PI3K signaling pathways were suppressed. In conclusion, results shown here describe a mechanism by which FGFR promotes proliferation of breast cancer cells.
Constitutive expression of Wnt1 and Wnt5a in HC11 mammary cells led to elevated TCF transcriptional activity. Intriguingly, Wnt‐expressing cells also displayed activation of ErbB1 and ...mitogen‐activated protein kinase (MAPK), in contrast to control HC11 cells, which did not. Furthermore, conditioned media harvested from Wnt‐expressing cells stimulated ErbB1 and the MAPK cascade when added to control cells. This process was rapid and could be blocked by an ErbB1 antibody that interferes with ligand binding and by matrix metalloproteinase (MMP) inhibitors. These results suggest that in mammary cells Wnt binding to its receptor, Frizzled (Fz), transactivates ErbB1, probably by MMP‐mediated release of soluble ErbB1 ligands. Importantly, Wnt‐transactivated ErbB1 was responsible for MAPK activation and the increased levels of cyclin D1 present in the Wnt‐expressing HC11 cells. Our finding that Wnts transactivate ErbB1 in addition to stimulating the prototypic β‐catenin/TCF pathway may help to explain why wnt1 is a potent oncogene in the mammary gland.
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