The Role of MAPKs in B Cell Receptor-Induced Down-Regulation of Egr-1 in Immature B Lymphoma Cells

Cross-linking of the B cell receptor (BCR) on the immature B lymphoma cell line BKS-2 induces growth inhibition and apoptosis accompanied by rapid down-regulation of the immediate-early gene egr-1. In these lymphoma cells, egr-1 is expressed constitutively and has a prosurvival role, as Egr-1-specific antisense oligonucleotides or expression of a dominant-negative inhibitor of Egr-1 also prevented the growth of BKS-2 cells. Moreover, enhancement of Egr-1 protein with phorbol 12-myristate 13-acetate or an egr-1 expression vector rescued BKS-2 cells from BCR signal-induced growth inhibition. Nuclear run-on and mRNA stability assays indicated that BCR-derived signals act at the transcriptional level to reduce egr-1 expression. Inhibitors of ERK and JNK (but not of p38 MAPK) reduced egr-1 expression at the protein level. Transcriptional regulation appears to have a role because egr-1 promoter-driven luciferase expression was reduced by ERK and JNK inhibitors. Promoter truncation experiments suggested that several serum response elements are required for MAPK-mediated egr-1 expression. Our study suggests that BCR signals reduce egr-1 expression by inhibiting activation of ERK and JNK. Unlike ERK and JNK, p38 MAPK reduces constitutive expression of egr-1. Unlike the immature B lymphoma cells, normal immature B cells did not exhibit constitutive MAPK activation. BCR-induced MAPK activation was modest and transient with a small increase in egr-1 expression in normal immature B cells consistent with their inability to proliferate in response to BCR cross-linking

Tumor-Stromal Interactions Influence Radiation Sensitivity in Epithelial- versus Mesenchymal-Like Prostate Cancer Cells

HS-27a human bone stromal cells, in 2D or 3D coultures, induced cellular plasticity in human prostate cancer ARCaPE and ARCaPM cells in an EMT model. Cocultured ARCaPE or ARCaPM cells with HS-27a, developed increased colony forming capacity and growth advantage, with ARCaPE exhibiting the most significant increases in presence of bone or prostate stroma cells. Prostate (Pt-N or Pt-C) or bone (HS-27a) stromal cells induced significant resistance to radiation treatment in ARCaPE cells compared to ARCaPM cells. However pretreatment with anti-E-cadherin antibody (SHEP8-7) or anti-alpha v integrin blocking antibody (CNT095) significantly decreased stromal cell-induced radiation resistance in both ARCaPE- and ARCaPM-cocultured cells. Taken together the data suggest that mesenchymal-like cancer cells reverting to epithelial-like cells in the bone microenvironment through interaction with bone marrow stromal cells and reexpress E-cadherin. These cell adhesion molecules such as E-cadherin and integrin alpha v in cancer cells induce cell survival signals and mediate resistance to cancer treatments such as radiation

Toll-like receptor expression and responsiveness of distinct murine splenic and mucosal B-cell subsets.

Toll-like receptors (TLRs) are pattern recognition receptors that recognize pathogen associated molecular patterns and trigger innate immunity leading to initiation of adaptive immunity. TLR-mediated activation of dendritic cells (DCs) is known to be a critical event in the initiation of cellular and humoral immune responses. Recent work however suggests that B cells also express TLRs, and that they can be activated via TLR ligands. However, whether such B cell activation occurs only on memory B cells, or whether it can also occur on truly naïve B cells remains controversial. Furthermore, the expression and functional relevance of TLRs on distinct subsets of B cells, which are known to play differential roles in humoral responses is not known.In this study, we investigated the expression pattern of different TLRs in distinct subsets of murine B cells (naïve, memory, follicular, marginal zone, B-1 and peyer's patch). In contrast to the reported restricted expression pattern of TLRs in human peripheral blood naïve B cells, murine splenic naïve B cells express a variety of TLRs with the exception of TLR5 and 8. Consistent with this relatively broad expression pattern, murine naive B cells proliferate and secrete antibody to a variety of TLR agonists in vitro, in the absence of B-cell receptor cross-linking. In addition, we observed subtle differences in the antibody secretion pattern of follicular, marginal zone, B-1 and peyer's patch B-cell subsets.Thus various B cell subsets, including truly naïve B cells, express multiple TLRs, and signaling via such TLRs results in their robust proliferation and antibody secretion, even in the absence of dendritic cell activation, or T-cell help

B Cell Tolerance in Health and Disease

B lymphocyte receptors are generated randomly during the bone marrow developmental phase of B cells. Hence, the B cell repertoire consists of both self and foreign antigen specificities necessitating specific tolerance mechanisms to eliminate self-reactive B cells. This review summarizes the major mechanisms of B cell tolerance, which include clonal deletion, anergy and receptor editing. In the bone marrow presentation of antigen in membrane bound form is more effective than soluble form and the role of dendritic cells in this process is discussed. Toll like receptor derived signals affect activation of B cells by certain ligands such as nucleic acids and have been shown to play crucial roles in the development of autoimmunity in several animal models. In the periphery availability of BAFF, a B cell survival factor plays a critical role in the survival of self-reactive B cells. Antibodies against BAFF have been found to be effective therapeutic agents in lupus like autoimmune diseases. Recent developments are targeting anergy to control the growth of chronic lymphocytic leukemia cells

Fungal endophytes from two orchid species pointer towards organ specificity

Fungal endophytes may influence plant communities by altering the host's fitness either positively or negatively. Little is known, however, about their host/organ specificity, life style and role in plantfungus symbiosis under varying environmental conditions. We compared the leaf and root endophyte assemblages of two orchids (Bulbophyllum neilgherrense and Pholidota pallida) from natural forests and greenhouse conditions. Xylariaceae species were consistently associated with leaf and root tissues, while Guignardia and Pestalotiopsis were found predominantly in the leaf tissues of both orchids. Correspondence analysis of the endophyte assemblages showed that the endophytes exhibited distinct organ but little host specificity. More endophytes were shared by the two different orchids growing in the same location when compared to endophyte assemblages of a single orchid from different locations. Considering the influence of endophytes in shaping the host's community, diverse habitats must be screened vigorously to address questions regarding the role of endophytes in hostendophyte interactions. Rostlinná společenstva mohou být ovlivněna působením houbových endofytů, které se odráží ve změnách fitness jejich hostitelů, ať už pozitivních či negativních. Avšak málo je známo o hostitelské či orgánové specificitě endofytů, jejich životním stylu a roli v symbiotickém vztahu s rostlinou při růz-ných podmínkách prostředí. Autoři srovnávali společenstva listových a kořenových endofytů dvou orchidejí (Bulbophyllum neilgherrense a Pholidota pallida), rostoucích v přirozených lesích a sklení-kových podmínkách. Druhy z čeledi Xylariaceae byly pevně spjaty s listovými i kořenovými pletivy, zatímco druhy rodů Guignardia a Pestalotiopsis jsou nacházeny převážně v listových pletivech obou orchidejí. Korespondenční analýza společenstev endofytů ukázala, že tyto houby vykazují zřetelnou orgánovou specificitu, ale nízkou specificitu hostitelskou. Vice společných endofytů měly dvě různé orchideje rostoucí na společné lokalitě ve srovnání se společenstvy endofytů jednotlivých rostlin z různých lokalit. Vzhledem k vlivu endofytů na utváření společenstev svých hostitelů bude ještě potřebný důsledný průzkum různých substrátů pro ozřejmení role endofytů v interakcích s jejich hostiteli

A heat map summary of TLR expression and responsiveness to different TLR ligands by distinct murine B cell subsets.

<p>The values for TLR expression profile, proliferation and antibody secretion in response to various TLR ligands by different B-cell subsets shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000863#pone-0000863-g001" target="_blank">Figures 1</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000863#pone-0000863-g002" target="_blank"></a><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000863#pone-0000863-g003" target="_blank">3</a> were plotted on a log scale, and represented as a heat map. For TLR expression, blue represents an 1 fold increase relative to β-actin, green represents 2 fold increase, yellow represents 3 fold increase, red represents 4 fold increase and dark brown represents ≥5 fold increase. For proliferation, blue represents an 1 fold increase relative to unstimulated medium controls, green represents 2 fold increase, yellow represents 3 fold increase, red represents 4 fold increase and dark brown represents 5 fold increase. For antibody secretion, blue represents an 1 fold increase relative to unstimulated medium controls, green represents 2 fold increase, yellow represents 3 fold increase, red represents 4 fold increase and dark brown represents 5 fold increase.</p

TLR-induced B-cell differentiation and immunoglobulin secretion of murine B-cell subsets.

<p>A, FACS sorted follicular B-cells (CD19⁺ B220⁺CD23⁺CD21⁻) were cultured in vitro with various TLR ligands as indicated for 5 days and antibody profile of culture supernatants measured by ELISA as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000863#s2" target="_blank">Materials and Methods</a>. B-D, FACS sorted marginal zone, B-1 and peyer's patch B-cells (CD19⁺ B220⁺CD23⁻CD21⁺ for marginal zone B, CD19⁺B220⁺CD23⁻for peritoneal B-1 B and CD19⁺B220⁺ for peyer's patch B cells) were cultured in vitro with various TLR ligands as indicated for 5 days and antibody secretion measured by ELISA as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000863#s2" target="_blank">Materials and Methods</a>.</p

TLR expression profile of murine B-cell subsets.

<p>Real-time PCR profile of TLR expression in FACS sorted follicular B-cells (CD19⁺ B220⁺CD23⁺CD21⁻, panel A), marginal Zone B (CD19⁺ B220⁺CD23⁻CD21⁺, panel B), peritoneal B-1 (CD19⁺B220⁺CD23⁻, panel C) and peyer's patch B cells (CD19⁺B220⁺, panel D) as indicated with β-actin as loading control. CD11c+ dendritic cells were used as a positive control (panel E). Values represent the ratio of the TLR to β-actin.</p