Lipooligosaccharide Structures of Invasive and Carrier Isolates of Neisseria meningitidis Are Correlated with Pathogenicity and Carriage.

The degree of phosphorylation and phosphoethanolaminylation of lipid A on neisserial lipooligosaccharide (LOS), a major cell-surface antigen, can be correlated with inflammatory potential and the ability to induce immune tolerance in vitro. On the oligosaccharide of the LOS, the presence of phosphoethanolamine and sialic acid substituents can be correlated with in vitro serum resistance. In this study, we analyzed the structure of the LOS from 40 invasive isolates and 25 isolates from carriers of Neisseria meningitidis without disease. Invasive strains were classified as groups 1-3 that caused meningitis, septicemia without meningitis, and septicemia with meningitis, respectively. Intact LOS was analyzed by high resolution matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Prominent peaks for lipid A fragment ions with three phosphates and one phosphoethanolamine were detected in all LOS analyzed. LOS from groups 2 and 3 had less abundant ions for highly phosphorylated lipid A forms and induced less TNF-α in THP-1 monocytic cells compared with LOS from group 1. Lipid A from all invasive strains was hexaacylated, whereas lipid A of 6/25 carrier strains was pentaacylated. There were fewer O-acetyl groups and more phosphoethanolamine and sialic acid substitutions on the oligosaccharide from invasive compared with carrier isolates. Bioinformatic and genomic analysis of LOS biosynthetic genes indicated significant skewing to specific alleles, dependent on the disease outcome. Our results suggest that variable LOS structures have multifaceted effects on homeostatic innate immune responses that have critical impact on the pathophysiology of meningococcal infections.

Loss of p53 and MCT-1 overexpression synergistically promote chromosome instability and tumorigenicity.

MCT-1 oncoprotein accelerates p53 degradation by means of the ubiquitin-dependent proteolysis. Our present data show that induction of MCT-1 increases chromosomal translocations and deregulated G(2)-M checkpoint in response to chemotherapeutic genotoxin. Remarkably, increases in chromosome copy number, multinucleation, and cytokinesis failure are also promoted while MCT-1 is induced in p53-deficient cells. In such a circumstance, the Ras-mitogen-activated protein kinase/extracellular signal-regulated kinase kinase-mitogen-activated protein kinase signaling activity and the expression of metastatic molecules are amplified. Given a p53-silencing background, MCT-1 malignantly transforms normal breast epithelial cells that are satisfactory for stimulating cell migration/adhesion and tumorigenesis. Detailed analyses of MCT-1 oncogenicity in H1299 p53-null lung cancer cells have shown that ectopically expressed MCT-1 advances xenograft tumorigenicity and angiogenesis, which cannot be completely suppressed by induction of p53. MCT-1 counteracts mutually with p53 at transcriptional levels. Clinical validations confirm that MCT-1 mRNA levels are differentially enriched in comparison between human lung cancer and nontumorigenic tissues. The levels of p53 mRNA are comparatively reduced in a subset of cancer specimens, which highly present MCT-1 mRNA. Our results indicate that synergistic promotions of chromosomal imbalances and oncogenic potency as a result of MCT-1 expression and p53 loss play important roles in tumor development.