The CD40 molecule, a member of the TNF receptor gene family, has been intensively studied with respect to regulation of B cell proliferation and survival. Although CD40 is also expressed on carcinoma ...cell lines, information concerning the biological function of CD40 on cells of epithelial origin is limited. In this study we detected constitutive CD40 on human breast carcinoma cell lines and an increase in CD40 expression following treatment with cytokines IL-1alpha and IFN-gamma. CD40 ligation was also found to increase MHC II expression in cells pretreated with IFN-gamma. In contrast to normal B cells, where CD40 signaling provides a potent survival signal, we observed that CD40 ligation in breast carcinoma cells results in growth inhibition and enhanced susceptibility to Fas-mediated apoptosis. Enhanced apoptosis appears to be attributable, at least in part, to an up-regulation of Fas expression caused by CD40 ligation. These results suggest a potentially important role for CD40 in breast tumor biology.
Abstract
This work reports a new method to improve our recent demonstration of zinc oxide (ZnO) nanoparticles (NPs) selectively killing certain human cancer cells, achieved by incorporating Fe ions ...into the NPs. Thoroughly characterized cationic ZnO NPs (∼6 nm) doped with Fe ions (Zn1-x
Fe
x
O, x = 0-0.15) were used in this work, applied at a concentration of 24 μg/ml. Cytotoxicity studies using flow cytometry on Jurkat leukemic cancer cells show cell viability drops from about 43% for undoped ZnO NPs to 15% for ZnO NPs doped with 7.5% Fe. However, the trend reverses and cell viability increases with higher Fe concentrations. The non-immortalized human T cells are markedly more resistant to Fe-doped ZnO NPs than cancerous T cells, confirming that Fe-doped samples still maintain selective toxicity to cancer cells. Pure iron oxide samples displayed no appreciable toxicity. Reactive oxygen species generated with NP introduction to cells increased with increasing Fe up to 7.5% and decreased for >7.5% doping.
Long-range chromosomal interactions bring distal regulatory elements and promoters together to regulate gene expression in biological processes. By performing promoter capture Hi-C (PCHi-C) on human ...embryonic stem cell-derived cardiomyocytes (hESC-CMs), we show that such promoter interactions are a key mechanism by which enhancers contact their target genes after hESC-CM differentiation from hESCs. We also show that the promoter interactome of hESC-CMs is associated with expression quantitative trait loci (eQTLs) in cardiac left ventricular tissue; captures the dynamic process of genome reorganisation after hESC-CM differentiation; overlaps genome-wide association study (GWAS) regions associated with heart rate; and identifies new candidate genes in such regions. These findings indicate that regulatory elements in hESC-CMs identified by our approach control gene expression involved in ventricular conduction and rhythm of the heart. The study of promoter interactions in other hESC-derived cell types may be of utility in functional investigation of GWAS-associated regions.
CD40 ligand is an important immunoregulatory protein expressed by T cells. This protein exists as two isoforms, a membrane glycoprotein and a truncated soluble form. Here we demonstrate that membrane ...and soluble CD40L (sCD40L) are differentially regulated depending upon the activation stimulus. In T cell receptor activated cells, both membrane and sCD40L proteins are expressed and CD28 costimulation further increases their expression. The dissection of TCR generated signals into calcium and PKC-dependent pathways demonstrates that calcium is sufficient to induce membrane CD40L yet insufficient for sCD40L. In contrast, sCD40L is preferentially induced by PKC. Moreover, sCD40L production is blocked by Zn
2+-dependent metalloproteinase inhibitors while membrane CD40L is concurrently increased. This profile suggests the potential involvement of the ADAM-10 protease which was subsequently shown to cleave membrane CD40L to generate sCD40L. Given the role of sCD40L in numerous disease pathologies and its ability to activate proximal and distal immune responses, the regulated cleavage of CD40L may likely contribute to disease mechanisms.
In the original version of the Article, the gene symbol for tissue factor pathway inhibitor was inadvertently given as 'TFP1' instead of 'TFPI'. This has now been corrected in both the PDF and HTML ...versions of the Article.
CD40L expression is well recognized to be of critical importance in initiation of the immune response. Because cAMP mediates actions of bronchodilators commonly used in asthma, the effects of cAMP in ...regulating the immune response are of major importance. Cyclic AMP was found to either inhibit or markedly increase CD40L expression dependent upon the mechanisms of T cell activation. Cyclic AMP inhibited CD40L expression induced by TCR activation. In contrast, cAMP enhanced CD40L induced by CD2-mediated T cell activation or by calcium-dependent mechanisms. While neither CD28 costimulation nor exogenous IL-2 or IL-4 prevented cAMP inhibition in TCR activated cells, addition of calcium ionophore to TCR activation prevented any inhibitory effects and caused cAMP to increase CD40L expression. Actions of cAMP to increase CD40L expression appeared independent of PKC and were not a reflection of generalized cellular activation since neither CD25 nor CD69 expression was affected. The markedly contrasting actions of cAMP to decrease or increase CD40L expression, an important control point in the immune response, could be relevant to actions of commonly used medications including bronchodilators.
We report that the novel anthracycline analog, 13-deoxy, 5-iminodoxorubicin (DIDOX), represents a potentially new class of immunosuppressive agents. DIDOX has been structurally modified from the ...parent compound, doxorubicin, to remove the carbonyl group at carbon-13 and the quinone moiety at carbon-5 since these structures likely mediate the cardiotoxic side effects of this family of chemotherapeutic drugs. Our studies demonstrate that DIDOX inhibits T cell proliferation and the expression of the T cell activation molecules, CD25 and CD40L. DIDOX also inhibits the production of the pro-inflammatory cytokine, TNF-α and IL-2. Studies using animal models demonstrate that DIDOX inhibits the inflammation accompanying contact hypersensitivity reactions and possesses reduced cardiotoxicity compared to doxorubicin. These findings indicate that DIDOX has important immunosuppressive activities that may warrant the development of this new and improved anthracycline for the treatment of T cell-mediated inflammatory diseases.
Expression of Pim-1, an oncogenic serine/threonine kinase, is highly regulated at the transcriptional, posttranscriptional, and posttranslational levels. Here, we report that expression of Pim-1 ...kinase is additionally regulated at the translational level. Pim-1 protein expression did not increase in Hut-78 lymphocytes in response to PMA1/ionomycin stimulation despite approximately 20-fold increases in mRNA levels, suggesting that translation was repressed. Sequence analysis of the 5'-untranslated region (UTR) indicated a long (400 nucleotide), 76% G + C-rich region, characteristics known to inhibit translation. Deletion of the 5'-UTR of pim-1 increased translation of the Pim-1 protein approximately 10-fold in vitro in reticulocyte lysates and approximately 1.6-fold in vivo in NIH-3T3 cells. When full-length 5'-UTR-containing pim-1 cDNA constructs were transfected into NIH-3T3 cells overexpressing eukaryotic translation initiation factor 4E (eIF-4E), approximately 6-fold higher levels of Pim-1 protein were produced, as compared to that produced in control NIH-3T3 cells. Moreover, eIF-4E overexpression had little effect in the absence of the 5'-UTR, suggesting that it relieved 5'-UTR-mediated inhibition of Pim-1 expression.
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