Lung gene expression in a rhesus allergic asthma model correlates with physiologic parameters of disease and exhibits common and distinct pathways with human asthma and a mouse asthma model.

Experimental nonhuman primate models of asthma exhibit multiple features that are characteristic of an eosinophilic/T helper 2 (Th2)-high asthma subtype, characterized by the increased expression of Th2 cytokines and responsive genes, in humans. Here, we determine the molecular pathways that are present in a house dust mite-induced rhesus asthma model by analyzing the genomewide lung gene expression profile of the rhesus model and comparing it with that of human Th2-high asthma. We find that a prespecified human Th2 inflammation gene set from human Th2-high asthma is also present in rhesus asthma and that the expression of the genes comprising this gene set is positively correlated in human and rhesus asthma. In addition, as in human Th2-high asthma, the Th2 gene set correlates with physiologic markers of allergic inflammation and disease in rhesus asthma. Comparison of lung gene expression profiles from human Th2-high asthma, the rhesus asthma model, and a common mouse asthma model indicates that genes associated with Th2 inflammation are shared by all three species. However, some pathophysiologic aspects of human asthma (ie, subepithelial fibrosis, angiogenesis, neural biology, and immune host defense biology) are better represented in the gene expression profile of the rhesus model than in the mouse model. Further study of the rhesus asthma model may yield novel insights into the pathogenesis of human Th2-high asthma.

Cooperation of cytokine signaling with chimeric transcription factors in leukemogenesis: PML-retinoic acid receptor alpha blocks growth factor-mediated differentiation.

We utilized a mouse model of acute promyelocytic leukemia (APL) to investigate how aberrant activation of cytokine signaling pathways interacts with chimeric transcription factors to generate acute myeloid leukemia. Expression in mice of the APL-associated fusion, PML-RARA, initially has only modest effects on myelopoiesis. Whereas treatment of control animals with interleukin-3 (IL-3) resulted in expanded myelopoiesis without a block in differentiation, PML-RARA abrogated differentiation that normally characterizes the response to IL-3. Retroviral transduction of bone marrow with an IL-3-expressing retrovirus revealed that IL-3 and promyelocytic leukemia-retinoic acid receptor alpha (PML-RARalpha) combined to generate a lethal leukemia-like syndrome in <21 days. We also observed that a constitutively activated mutant IL-3 receptor, beta(c)V449E, cooperated with PML-RARalpha in leukemogenesis, whereas a different activated mutant, beta(c)I374N, did not. Analysis of additional mutations introduced into beta(c)V449E showed that, although tyrosine phosphorylation of beta(c) is necessary for cooperation, the Src homology 2 domain-containing transforming protein binding site is dispensable. Our results indicate that chimeric transcription factors can block the differentiative effects of growth factors. This combination can be potently leukemogenic, but the particular manner in which these types of mutations interact determines the ability of such combinations to generate acute myeloid leukemia.

Identification of IgG(1) variants with increased affinity to FcγRIIIa and unaltered affinity to FcγRI and FcRn: comparison of soluble receptor-based and cell-based binding assays.

Clinical response to the anti-CD20 antibody rituximab has been demonstrated to correlate with the polymorphism in the FcγRIIIa receptor where patients homozygous for the higher affinity V158 allotype showed a better response rate. This finding suggests that engineering of anti-CD20 for increased FcγRIIIa affinity could result in improved clinical outcome. To identify variants with increased affinity to FcγRIIIa, we developed quantitative assays using soluble receptors as well as engineered cell lines expressing FcγRI or FcγRIIIa on the cell surface. We assayed a set of anti-CD20 IgG(1) variants that had identical Fab regions, but alterations in the Fc regions, in both the soluble receptor-based and cell-based FcγRIIIa binding assays. We obtained similar relative binding affinity increases and assay precisions. The increase in affinity for FcγRIIIa correlated with the increase in activity in the antibody-dependent cellular cytotoxicity assay. These variants had unaltered FcγRI binding. In addition to Fcγ receptors, IgG also binds to FcRn, the receptor responsible for the long circulating half-life of IgG. The mutations in the anti-CD20 variants were previously found not to affect FcRn binding in the soluble receptor-based assays; consequently, we used anti-Her2 variants with different binding affinities to FcRn to study FcRn binding assays. We generated a cell line expressing FcRn on the cell surface to measure IgG binding and obtained similar ranking of these anti-Her2 variants in the cell-based and the soluble receptor-based FcRn binding assays. In conclusion, both the soluble receptor-based and cell-based binding assays can be used to identify IgG(1) variants with increased affinity to FcγRIIIa and unaltered affinity to FcγRI and FcRn.

De novo proteomic sequencing of a monoclonal antibody raised against OX40 ligand.

De novo sequencing of a full-length monoclonal antibody raised against OX40 ligand is described. Using a combination of overlapping complementary proteolytic and chemical digestions, with analysis by mass spectrometry and Edman degradation, both the heavy and light chains were fully sequenced. Particular attention was paid to those modifications that could be susceptible to degradation in the complementarity determining region and Fc region. An overview of the protocol is described, and suggestions for improvements to aid in such sequencing projects in the future are discussed.

CCAAT/Enhancer binding proteins repress the leukemic phenotype of acute myeloid leukemia.

CCAAT/enhancer binding proteins (C/EBPs) are a family of factors that regulate cell growth and differentiation. These factors, particularly C/EBPalpha and C/EBPepsilon, have important roles in normal myelopoiesis. In addition, loss of C/EBP activity appears to have a role in the pathogenesis of myeloid disorders including acute myeloid leukemia (AML). Acute promyelocytic leukemia (APL) is a subtype of AML in which a role for C/EBPs has been postulated. In almost all cases of APL, a promyelocytic leukemia-retinoic acid receptor alpha (PML-RARalpha) fusion protein is expressed as a result of a t(15;17)(q22;q12) chromosomal translocation. PML-RARalpha inhibits expression of C/EBPepsilon, whereas all-trans retinoic acid (tRA), a differentiating agent to which APL is particularly susceptible, induces C/EBPepsilon expression. PML-RARalpha may also inhibit C/EBPalpha activity. Thus, the effects of PML-RARalpha on C/EBPs may contribute to both the development of leukemia and the unique sensitivity of APL to tRA. We tested the hypothesis that increasing the activity of C/EBPs would revert the leukemic phenotype. C/EBPalpha and C/EBPepsilon were introduced into the FDC-P1 myeloid cell line and into leukemic cells from PML-RARA transgenic mice. C/EBP factors suppressed growth and induced partial differentiation in vitro. In vivo, enhanced expression of C/EBPs prolonged survival. By using a tamoxifen-responsive version of C/EBPepsilon, we observed that C/EBPepsilon could mimic the effect of tRA, driving neutrophilic differentiation in leukemic animals. Our results support the hypothesis that induction of C/EBP activity is a critical effect of tRA in APL. Furthermore, our findings suggest that targeted modulation of C/EBP activities could provide a new approach to therapy of AML.