The autophagy protein Ambra1 regulates gene expression by supporting novel transcriptional complexes

Ambra1 is considered an autophagy and trafficking protein with roles in neurogenesis and cancer cell invasion. Here, we report that Ambra1 also localizes to the nucleus of cancer cells, where it has a novel nuclear scaffolding function that controls gene expression. Using biochemical fractionation and proteomics, we found that Ambra1 binds to multiple classes of proteins in the nucleus, including nuclear pore proteins, adaptor proteins such as FAK and Akap8, chromatin-modifying proteins, and transcriptional regulators like Brg1 and Atf2. We identified biologically important genes, such as Angpt1, Tgfb2, Tgfb3, Itga8, and Itgb7, whose transcription is regulated by Ambra1-scaffolded complexes, likely by altering histone modifications and Atf2 activity. Therefore, in addition to its recognized roles in autophagy and trafficking, Ambra1 scaffolds protein complexes at chromatin, regulating transcriptional signaling in the nucleus. This novel function for Ambra1, and the specific genes impacted, may help to explain the wider role of Ambra1 in cancer cell biology.

Highly Expressed Integrin-α8 Induces Epithelial to Mesenchymal Transition-Like Features in Multiple Myeloma with Early Relapse

Despite recent groundbreaking advances in multiple myeloma (MM) treatment, most MM patients ultimately experience relapse, and the relapse biology is not entirely understood. To define altered gene expression in MM relapse, gene expression profiles were examined and compared among 16 MM patients grouped by 12 months progression-free survival (PFS) after autologous stem cell transplantation. To maximize the difference between prognostic groups, patients at each end of the PFS spectrum (the four with the shortest PFS and four with the longest PFS) were chosen for additional analyses. We discovered that integrin-α8 (ITGA8) is highly expressed in MM patients with early relapse. The integrin family is well known to be involved in MM progression; however, the role of integrin-α8 is largely unknown. We functionally overexpressed integrin-α8 in MM cell lines, and surprisingly, stemness features including HIF1α, VEGF, OCT4, and Nanog, as well as epithelial mesenchymal transition (EMT)-related phenotypes, including N-cadherin, Slug, Snail and CXCR4, were induced. These, consequently, enhanced migration and invasion abilities, which are crucial to MM pathogenesis. Moreover, the gain of integrin-α8 expression mediated drug resistance against melphalan and bortezomib, which are the main therapeutic agents in MM. The cBioPortal genomic database revealed that ITGA8 have significant tendency to co-occur with PDGFRA and PDGFRB and their mRNA expression were up-regulated in ITGA8 overexpressed MM cells. In summary, integrin-α8, which was up-regulated in MM of early relapse, mediates EMT-like phenotype, enhancing migration and invasion; therefore, it could serve as a potential marker of MM relapse and be a new therapeutic target.

Cisplatin at sub-toxic levels mediates integrin switch in lung cancer cells

BACKGROUND

Resistance to chemotherapeutic agents, as well as enhanced metastasis, have been frequently reported in lung cancer.

MATERIALS AND METHODS

Cytotoxicity and proliferative effects of cisplatin on H460 lung cancer cells were evaluated by the MTT assay. Migration capacity was evaluated by the wound healing assay. The number of filopodia per cell were detected by rhodamine-phalloidin staining assay. The changes of protein levels of integrins, and migration-related proteins in response to cisplatin at sub-toxic concentrations were determined by western blotting.

RESULTS

Herein we demonstrate for the first time that exposure to low concentrations of cisplatin results in increase of cell motility with the alteration of integrin expression. Cisplatin-treated cells exhibited a significant increase in the number of filopodia per cell in correlation with enhanced migration. Migration regulatory proteins, namely activated forms of focal-adhesion kinase (FAK) and ATP-dependent tyrosine kinase (AKT), were found to significantly be up-regulated in cisplatin-treated cells in comparison to those of the non-treated control. Active Rho A-GTP and Rac-GTP were found to be increased in accordance with activation of FAK/AKT signals. Furthermore, we found that such migration enhancement may be in part due to the integrin switch mediated by cisplatin treatment. Cisplatin induced a dramatic alteration in the integrin expression pattern by up-regulating integrin α4, αv, β1, and β5 which were previously reported to increase cell motility, while it had no effect on integrin α5, and β3.

CONCLUSION

As the integrin switch is a hallmark of highly aggressive cancer, these findings may provide insights for better understanding of cancer cell adaptation after exposure to cisplatin.

Mesenchymal precursor cells maintain the differentiation and proliferation potentials of breast epithelial cells

INTRODUCTION

Stromal-epithelial interactions play a fundamental role in tissue homeostasis, controlling cell proliferation and differentiation. Not surprisingly, aberrant stromal-epithelial interactions contribute to malignancies. Studies of the cellular and molecular mechanisms underlying these interactions require ex vivo experimental model systems that recapitulate the complexity of human tissue without compromising the differentiation and proliferation potentials of human primary cells.

METHODS

We isolated and characterized human breast epithelial and mesenchymal precursors from reduction mammoplasty tissue and tagged them with lentiviral vectors. We assembled heterotypic co-cultures and compared mesenchymal and epithelial cells to cells in corresponding monocultures by analyzing growth, differentiation potentials, and gene expression profiles.

RESULTS

We show that heterotypic culture of non-immortalized human primary breast epithelial and mesenchymal precursors maintains their proliferation and differentiation potentials and constrains their growth. We further describe the gene expression profiles of stromal and epithelial cells in co-cultures and monocultures and show increased expression of the tumor growth factor beta (TGFβ) family member inhibin beta A (INHBA) in mesenchymal cells grown as co-cultures compared with monocultures. Notably, overexpression of INHBA in mesenchymal cells increases colony formation potential of epithelial cells, suggesting that it contributes to the dynamic reciprocity between breast mesenchymal and epithelial cells.

CONCLUSIONS

The described heterotypic co-culture system will prove useful for further characterization of the molecular mechanisms mediating interactions between human normal or neoplastic breast epithelial cells and the stroma, and will provide a framework to test the relevance of the ever-increasing number of oncogenomic alterations identified in human breast cancer.

Cutting edge: inhaled antigen upregulates retinaldehyde dehydrogenase in lung CD103+ but not plasmacytoid dendritic cells to induce Foxp3 de novo in CD4+ T cells and promote airway tolerance

Dendritic cell (DC)-T cell interactions that underlie inducible/adaptive regulatory T cell generation and airway tolerance are not well understood. In this study, we show that mice lacking CD11c(hi) lung DCs, but containing plasmacytoid DCs (pDCs), fail tolerization with inhaled Ag and cannot support Foxp3 induction in vivo in naive CD4(+) T cells. CD103(+) DCs from tolerized mice efficiently induced Foxp3 in cocultured naive CD4(+) T cells but pDCs and lung macrophages failed to do so. CD103(+) DCs, but not pDCs or lung macrophages, upregulated the expression of retinaldehyde dehydrogenase 2 (aldh1a2), which is key for the production of retinoic acid, a cofactor for TGF-β for Foxp3 induction. Batf3(-/-) mice, selectively lacking CD103(+) DCs, failed tolerization by inhaled Ag. Collectively, our data show that pulmonary tolerance is dependent on CD103(+) DCs, correlating with their ability to upregulate aldh1a2, which can promote Foxp3 expression in T cells.

Systemic flagellin immunization stimulates mucosal CD103+ dendritic cells and drives Foxp3+ regulatory T cell and IgA responses in the mesenteric lymph node

Mucosal immunity is poorly activated after systemic immunization with protein Ags. Nevertheless, induction of mucosal immunity in such a manner would be an attractive and simple way to overcome the intrinsic difficulties in delivering Ag to such sites. Flagellin from Salmonella enterica serovar Typhimurium (FliC) can impact markedly on host immunity, in part via its recognition by TLR5. In this study, we show that systemic immunization with soluble FliC (sFliC) drives distinct immune responses concurrently in the mesenteric lymph nodes (MLN) and the spleen after i.p. and s.c. immunization. In the MLN, but not the spleen, sFliC drives a TLR5-dependent recruitment of CD103(+) dendritic cells (DCs), which correlates with a diminution in CD103(+) DC numbers in the lamina propria. In the MLN, CD103(+) DCs carry Ag and are the major primers of endogenous and transgenic T cell priming. A key consequence of these interactions with CD103(+) DCs in the MLN is an increase in local regulatory T cell differentiation. In parallel, systemic sFliC immunization results in a pronounced switching of FliC-specific B cells to IgA in the MLN but not elsewhere. Loss of TLR5 has more impact on MLN than splenic Ab responses, reflected in an ablation of IgA, but not IgG, serum Ab titers. Therefore, systemic sFliC immunization targets CD103(+) DCs and drives distinct mucosal T and B cell responses. This offers a potential "Trojan horse" approach to modulate mucosal immunity by systemically immunizing with sFliC.

Division of labor between subsets of lymph node dendritic cells determines the specificity of the CD8⁺ T-cell recall response to influenza infection

Cytotoxic T lymphocytes (CTLs) are important targets for vaccines against a wide variety of infections that enter the body via mucosal tissues. To induce effective immunity these vaccines must include the most protective epitopes and elicit rapid recall responses at the site of infection. Although live attenuated viruses are sometimes used to induce cellular immunity against recurrent influenza infections, the mechanisms that determine the magnitude of the response to individual viral components are very poorly defined. Heterosubtypic infections in C57BL/6 mice illustrate an additional level of complexity, when the antigen specificity of the response shifts dramatically between primary and secondary challenge. This model provides a unique opportunity to identify the mechanisms that regulate memory CD8(+) T-cell reactivation in vivo and control the specificity of the recall response by pathogen-specific CTL. We show that multiple factors contribute to the changing pattern of immunodominance during secondary infection, including the location of the memory CD8(+) T cells at the time of reinfection and their ability to directly recognize migratory CD103(+) DCs as they arrive in the lung draining LN.

Denervation dynamically regulates integrin alpha7 signaling pathways and microscopic structures in rats

BACKGROUND

Peripheral nerve injury causes serious problems in orthopedic and plastic surgeries. Cell adhesion molecules such as integrin alpha7 provoke cell binding and signaling pathways within myofibers. Expression profiles of integrin alpha7 signaling pathways and the molecule's microscopic structure were assessed to investigate the long-term dynamic changes in denervated rat skeletal muscle.

METHODS

A denervated rat skeletal muscle model was established by severing the sciatic nerve for 1 week, 2 weeks, 4 weeks, 8 weeks, 12 weeks, 20 weeks, and 26 weeks. Molecular expressions were investigated by mRNA and Western blot. The structural alterations were detected by immunohistochemistry, scanning electron microscopy, and transmission electron microscopy.

RESULTS

The denervated muscle atrophy presented the following dynamic molecular alterations: an initial increase around postdenervation in week (PIW) 8 and then a subsequent decay of integrin alpha7, integrin downstream signaling pathway (Ras or Raf or, ERK1/2), Akt, cleaved caspase-3, fast myosin heavy chain (MHC), beta actin, and RhoA. We demonstrated that the expressions of multiple signaling molecules were highly upregulated at PIW 8 (p<0.01). Scanning electron microscopy findings of the surface textures of myofibers showed more severe damage at PIW 8 and subsequently became smoother. Inner structures of myofibers separated with discontinuity on transmission electron microscopy examinations.

CONCLUSION

Our novel finding showed that time-series alterations of integrin alpha7 signaling molecules and surface microstructures in the long-term denervated rat skeletal muscle are biphasic and coherently dynamic. Persisted p-Akt elevation suggested that denervated muscle may regenerate if reinnervation or other treatment was performed.

BMP-2 and TGF-beta1 differentially control expression of type II procollagen and alpha 10 and alpha 11 integrins in mouse chondrocytes

Bone morphogenetic protein (BMP)-2 and transforming growth factor (TGF)-beta1 are multifunctional cytokines both proposed as stimulants for cartilage repair. Thus it is crucial to closely examine and compare their effects on the expression of key markers of the chondrocyte phenotype, at the gene and protein level. In this study, the expression of alpha 10 and alpha 11 integrin subunits and the IIA/IIB spliced forms of type II procollagen have been monitored for the first time in parallel in the same in vitro model of mouse chondrocyte dedifferentiation/redifferentiation. We demonstrated that TGF-beta1 stimulates the expression of the non-chondrogenic form of type II procollagen, IIA isoform, and of a marker of mesenchymal tissues, i.e. the alpha 11 integrin subunit. On the contrary, BMP-2 stimulates the cartilage-specific form of type II procollagen, IIB isoform, and a specific marker of chondrocytes, i.e. the alpha 10 integrin subunit. Collectively, our results demonstrate that BMP-2 has a better capability than TGF-beta1 to stimulate chondrocyte redifferentiation and reveal that the relative expressions of type IIB to type IIA procollagens and alpha 10 to alpha 11 integrin subunits are good markers to define the differentiation state of chondrocytes. In addition, adenoviral expression of Smad6, an inhibitor of BMP canonical Smad signaling, did not affect expression of total type II procollagen or the ratio of type IIA and type IIB isoforms in mouse chondrocytes exposed to BMP-2. This result strongly suggests that signaling pathways other than Smad proteins are involved in the effect of BMP-2 on type II procollagen expression.

A functionally specialized population of mucosal CD103+ DCs induces Foxp3+ regulatory T cells via a TGF-beta and retinoic acid-dependent mechanism

Foxp3⁺ regulatory T (T reg) cells play a key role in controlling immune pathological re actions. Many develop their regulatory activity in the thymus, but there is also evidence for development of Foxp3⁺ T reg cells from naive precursors in the periphery. Recent studies have shown that transforming growth factor (TGF)-β can promote T reg cell development in culture, but little is known about the cellular and molecular mechanisms that mediate this pathway under more physiological conditions. Here, we show that after antigen activation in the intestine, naive T cells acquire expression of Foxp3. Moreover, we identify a population of CD103⁺ mesenteric lymph node dendritic cells (DCs) that induce the devel opment of Foxp3⁺ T reg cells. Importantly, promotion of T reg cell responses by CD103⁺ DCs is dependent on TGF-β and the dietary metabolite, retinoic acid (RA). These results newly identify RA as a cofactor in T reg cell generation, providing a mechanism via which functionally specialized gut-associated lymphoid tissue DCs can extend the repertoire of T reg cells focused on the intestine.

Maternal allergy influences the proliferation of neonatal T cells expressing CCR4, CXCR5 or CD103

BACKGROUND

Elevated proliferative response to allergen in cord blood mononuclear cells (CBMCs) is related to subsequent allergy development of the neonate and has been suggested as a screening marker for high allergy risk.

OBJECTIVE

To characterize the proliferating cells in CBMCs from a neonatal group influenced by maternal allergy compared with a control group without known allergic heredity.

METHODS

CBMCs were stimulated with bovine beta-lactoglobulin (beta-LG) and proliferation was analysed by radioactive thymidine incorporation and expressed both as the traditional stimulation index (SI) and SI corrected by eliminating non-specific proliferation. After beta-LG combined with endotoxin stimulation, cellular expression of IL-4 and IFN-gamma mRNA was determined by quantitative RT-PCR and adhesion as well as chemokine receptors were analysed by three-colour flow cytometry in proliferating T cells (CD3+ Ki-67+).

RESULTS

The percentage of CCR4+ cells correlated weakly with concurrent IL-4 expression (r(S)=0.5, P<0.05), while CXCR3 correlated strongly with IFN-gamma expression (r(S)=0.83, P<0.001). In the allergy risk group, the percentage of proliferating T cells expressing CCR4 or integrin alphaE (CD103) was significantly reduced compared with the control group, while CXCR5 and the corrected SI were relatively increased (CCR4: P=0.01; integrin alphaE: P=0.03; CXCR5: P=0.04; SI: P=0.04).

CONCLUSION

Our results implied delayed maturation of immune functions involved in cellular migration, cell-cell interaction and immunoregulatory functions in neonates with hereditary allergy risk. The alterations observed in this subject group suggested that the corrected SI as well as proliferation of CCR4+, CXCR5+ or CD103+ T cells in allergen-stimulated CBMCs might serve as early screening markers for allergy risk.

CD103− and CD103+ Bronchial Lymph Node Dendritic Cells Are Specialized in Presenting and Cross-Presenting Innocuous Antigen to CD4+ and CD8+ T Cells

Dendritic cells (DC) are able to capture, process, and present exogenous Ag to CD8(+) T lymphocytes through MHC class I, a process referred to as cross-presentation. In this study, we demonstrate that CD103(+) (CD11c(high)CD11b(low)) and CD103(-) (CD11c(int)CD11b(high)) DC residing in the lung-draining bronchial lymph node (brLN) have evolved to acquire opposing functions in presenting innocuous inhaled Ag. Thus, under tolerogenic conditions, CD103(-) DC are specialized in presenting innocuous Ag to CD4(+) T cells, whereas CD103(+) DC, which do not express CD8alpha, are specialized in presenting Ag exclusively to CD8(+) T cells. In CCR7-deficient but not in plt/plt mice, Ag-carrying CD103(+) DC are largely absent in the brLN, although CD103(+) DC are present in the lung of CCR7-deficient mice. As a consequence, adoptively transferred CD8(+) T cells can be activated under tolerizing conditions in plt/plt but not in CCR7-deficient mice. These data reveal that CD103(+) brLN DC are specialized in cross-presenting innocuous inhaled Ag in vivo. Because these cells are largely absent in CCR7(-/-) mice, our findings strongly suggest that brLN CD103(+) DC are lung-derived and that expression of CCR7 is required for their migration from the lung into its draining lymph node.

Modulation of CD103 expression on human colon carcinoma-specific CTL

Recent results have shown a correlation between survival and frequency of tumor-infiltrating T cells in colorectal cancer patients. However, the mechanisms controlling the ability of human T lymphocytes to infiltrate colon carcinoma remain unclear. Although, it is known that expression of the integrin CD103alpha(E)/beta(7) by intraepithelial lymphocytes controls the retention of lymphocytes in epithelial layers, very little is known about the expression of intestinal homing receptors in human T lymphocytes. In particular, it remains unknown whether expression of CD103/beta(7) by human colon cancer-specific T lymphocytes is controlled by recognition of tumor Ags and is imprinted during T cell priming, facilitating its expression during memory T cell activation. In this study, we demonstrate that expression of CD103/beta(7) in human colon carcinoma-specific CTL is synergistically enhanced by the simultaneous TGF-beta1 stimulation and Ag recognition. These results were confirmed by using a panel of human CTL clones. Finally, we show that priming of naive CD8(+) T cells in the presence of TGF-beta1 ensures up-regulation of CD103/beta(7) in recall responses, at concentrations of TGF-beta1 significantly lower than those required by memory T cells primed in the absence of TGF-beta1. These results indicate a role of TGF-beta1 during T cell priming in modulating expression of CD103/beta(7) and controlling retention of human memory CD8(+) T cells into tumor epithelium.

Induction of tolerance to innocuous inhaled antigen relies on a CCR7-dependent dendritic cell-mediated antigen transport to the bronchial lymph node

Allergic airway diseases such as asthma are caused by a failure of the immune system to induce tolerance against environmental Ags. The underlying molecular and cellular mechanisms that initiate tolerance are only partly understood. In this study, we demonstrated that a CCR7-dependent migration of both CD103+ and CD103- lung dendritic cells (DC) to the bronchial lymph node (brLN) is indispensable for this process. Although inhaled Ag is amply present in the brLN of CCR7-deficient mice, T cells cannot be tolerized because of the impaired migration of Ag-carrying DC and subsequent transport of Ag from the lung to the draining lymph node. Consequently, the repeated inhalation of Ag protects wild-type but not CCR7-deficient mice from developing allergic airway diseases. Thus, the continuous DC-mediated transport of inhaled Ag to the brLN is critical for the induction of tolerance to innocuous Ags.

Great potential of a panel of multiple hMTH1, SPD, ITGA11 and COL11A1 markers for diagnosis of patients with non-small cell lung cancer

Research on molecular mechanisms underlying the carcinogenesis of non-small cell lung cancer (NSCLC) may provide gene targets in critical pathways valuable for improving the efficacy of therapy and survival of patients with NSCLC. However, the molecular markers highly sensitive for the prognosis and treatment evaluation of NSCLC are not yet available. To explore candidates, we conducted an oligonucleotide microarray study with three pairs of NSCLC and normal lung tissue, and determined 8 differentially expressed genes including the Human MutT homologue (hMTH1), Surfactant protein D (SPD), Human hyaluronan binding protein 2 (HABP2), Crystalline-mu (CRYM), Ceruloplasmin (CP), Integrin alpha-11 subunit (ITGA11), Collagen type XI alpha I (COL11A1), and Lung-specific X protein (Lun X). Four lung cancer-related markers MUC-1, hTERT, hnRNP B1, and CK-19 were also incorporated for further analysis. The expression profiles of the twelve genes in seventy pairs of NSCLC tumor and normal lung tissue were then detected quantitatively by using membrane array and quantitative real-time PCR (qRT-PCR). The data of the membrane array and qRT-PCR were compared for consistency and the potential of these mRNA markers in clinical application. The results showed that membrane array and qRT-PCR obtained consistent data for the tested genes in both sensitivity and specificity (correlation coefficient 0.921, p<0.0001). For patients' clinicopathological characteristics, the overexpression of hMTH1, SPD, HABP 2, ITGA11, COL11A1, and CK-19 was significantly correlated with the pathological stage (p<0.05). In addition, the overexpression of hMTH1, SPD, ITGA11, and COL11A1 was correlated with lymph node metastasis and poor prognosis. This is the first report relating SPD to a prognosis marker for NSCLC. Moreover, the combined detection of these four mRNA markers by membrane array had a sensitivity of 89% and a specificity of 84% for NSCLC, significantly higher than these markers had achieved separately. In conclusion, we identified mRNA markers for NSCLC prognosis and therapy evaluation from differentially expressed genes determined by using micro-array. Further studies are needed to collect the data of the mRNA markers used in clinical practice.

Expression of CD103 identifies human regulatory T-cell subsets

BACKGROUND

Analysis of naturally occurring T regulatory CD4+ (nTreg) cells in human diseases is hampered by the lack of specific surface marker. Indeed, the CD25 antigen, which is typically used to identify nTreg cells, is also expressed on activated effector T cells.

OBJECTIVE

We sought to examine whether CD4+ T cells bearing CD103 are suppressor cells, regardless of CD25 coexpression.

METHODS

We first compared freshly isolated tonsillar CD103+ CD25- cells with their CD103- CD25high counterparts for their capacity to suppress T-cell response and their expression of FoxP3 mRNA. Next CD103 was induced on neonatal or adult CD4+ T cells stimulated with allogeneic dendritic cells, and the CD103+ and CD103- fractions were compared as above.

RESULTS

Tonsillar CD4+ CD103+ CD25- T cells displayed comparable suppressive activity and contained similar amounts of FoxP3 mRNA as their CD103- CD25high counterparts. In vitro-generated alloantigen-primed CD103+ cells coexpressed CD25, suppressed T-cell activation, and contained more FoxP3 mRNA than the CD103- CD25+ cells isolated from the same cultures. Finally, neonatal alloreactive cells contained more CD103+ Treg cells than their adult counterparts and, unlike the latter, became hyporesponsive to the priming alloantigens.

CONCLUSIONS

The examination of CD103 and CD25 coexpression allows identification of 3 subsets of human CD4+ nTreg cells, and the detection of CD103 on CD4+ T cells identifies nTreg cells, regardless of CD25 coexpression.

CLINICAL IMPLICATIONS

The greater induction of CD103+ suppressor cells by cord blood should be related to its successful clinical use as an alternative to adult bone marrow transplantation.

Foxp3-expressing CD103+ regulatory T cells accumulate in dendritic cell aggregates of the colonic mucosa in murine transfer colitis

Little is known of the anatomical compartmentalization of colitogenic or regulatory T-cell responses in the murine transfer colitis model. Therefore, we analyzed the putative function of large intestinal dendritic cell (DC) aggregates, to which donor CD4+ T cells selectively home before colitis becomes manifest. The co-stimulatory molecules MHC-II, CD40, CD80, and CD86 were expressed in DC aggregates. IL-23 was primarily absent from DC aggregates at all stages of disease but was expressed at high levels in the severely inflamed lamina propria. Interferon-gamma was up-regulated in the lamina propria during early and advanced disease, whereas in DC aggregates it was detectable to a significant degree only in fully developed colitis. In contrast, Foxp3, a marker of regulatory T cells, was expressed in DC aggregates on T-cell transfer, coinciding with the appearance of CD103+ CD25- T cells in these clusters. Foxp3 was enriched in the CD103+ T-cell fraction isolated from the lamina propria of diseased mice. T-cell grafts depleted of CD103+ T cells generated similar numbers of colonic CD103+ T cells as unfractionated T cells. We conclude that DC aggregates are structures involved in the expansion and/or differentiation of CD103+ CD25- CD4+ Foxp3-expressing regulatory T cells.

Telomerase flies the coop: the telomerase RNA component as a viral-encoded oncogene

Telomerase, the enzyme that elongates our telomeres, is crucial for cancer development based on extensive analyses of human cells, human cancers, and mouse models. New data now suggest that a viral telomerase RNA gene encoded by Marek's disease virus (MDV), an oncogenic herpesvirus of chickens, promotes tumor formation. These findings highlight the importance of telomerase in cancer and raise new questions regarding the mechanisms by which the telomerase RNA component supports tumorigenesis.

A virus-encoded telomerase RNA promotes malignant T cell lymphomagenesis

Telomerase is a ribonucleoprotein complex consisting of two essential core components: a reverse transcriptase and an RNA subunit (telomerase RNA [TR]). Dysregulation of telomerase has been associated with cell immortalization and oncogenesis. Marek's disease herpesvirus (MDV) induces a malignant T cell lymphoma in chickens and harbors in its genome two identical copies of a viral TR (vTR) with 88% sequence identity to chicken TR. MDV mutants lacking both copies of vTR were significantly impaired in their ability to induce T cell lymphomas, although lytic replication in vivo was unaffected. Tumor incidences were reduced by >60% in chickens infected with vTR⁻ viruses compared with animals inoculated with MDV harboring at least one intact copy of vTR. Lymphomas in animals infected with the vTR⁻ viruses were also significantly smaller in size and less disseminated. Constitutive expression of vTR in the chicken fibroblast cell line DF-1 resulted in a phenotype consistent with transformation as indicated by morphological alteration, enhanced anchorage-independent cell growth, cell growth beyond saturation density, and increased expression levels of integrin αv. We concluded that vTR plays a critical role in MDV-induced T cell lymphomagenesis. Furthermore, our results provide the first description of tumor-promoting effects of TR in a natural virus–host infection model.

Integrin alpha 11 is a novel type I interferon stimulated gene

Interferons (IFNs) are a family of cytokines that have many biological functions in the cell, including regulation of cellular growth, differentiation, immunomodulation, and viral replication by inducing a set of interferon stimulated genes (ISGs). Based on their structure and biological activities IFNs are subdivided into two groups: type I IFNs, which includes IFN-alpha and IFN-beta and type II IFNs, represented by IFN-gamma. The aim of this work was to investigate whether integrin alpha 11 (ITGA-11), a novel collagen-binding integrin, is responsive to type I IFN treatment. Our findings indicated that type I IFNs were able to induce the ITGA-11 mRNA levels in T98G cells. Increased levels of ITGA-11 protein were also observed in IFN-treated cells. The in vivo induction of ITGA-11 was detected in spleen and lungs of IFN-treated BALB/c mice. T98G cells infected with Murine encephalomyocarditis virus showed increased levels of ITGA-11 mRNA and protein. We observed that the ITGA-11 promoter has binding sites for transcriptional factors regulated by IFNs and the double-stranded RNA dependent protein kinase (PKR). Therefore we investigated the role of PKR in the induction of ITGA-11 by using a PKR deficient mouse embryo fibroblast cell line (MEFs). PKR(-/-) MEFs treated with IFN did not show increased levels of ITGA-11 protein nor mRNA although that could be promptly detected in wild type MEFs. Taken together our data suggest that ITGA-11 is a new interferon stimulated gene.

The inhibition of tumor cell adhesion on human mesothelial cells (HOMC) by phospholipids in vitro

BACKGROUND AND AIMS

Intraperitoneal tumor cell adhesion to extracellular matrix and to mesothelial cells mediated by integrins is an important step in developing peritoneal carcinosis. In former animal studies, we could demonstrate that intraperitoneal treatment with a new phospholipid (PL) emulsion significantly reduces the amount of peritoneal carcinosis by adhesion prevention. This in vitro study tries to elucidate the influence of phospholipids on cells of the human gastric cancer cell line (NUGC-4) and the human rectal cancer cell line (HRT-18) adhering to mesothelial cells (HOMC) in a monolayer culture in vitro.

MATERIALS AND METHODS

HOMC cells were derived from omentum majus from patients undergoing elective abdominal surgery. Three passages of both cancer cell lines (NUGC-4 and HRT-18) were used. 1x10(5)/100 microl (HRT-18) or 1.2x10(5)/100 microl (NUGC-4) cells, according to forgoing dilution series, were pretreated with different concentrations of phospholipid emulsion (0.05, 0.1, 0.5, 0.75, 1% PL) stained with cell tracker chloromethyl-benzamidodialkylcarbocyanine (CM-DIL) and seeded into each well on the mesothelial monolayer. After 90 min, the number of adherent cells was counted by fluorescence microscopy at 530 and 620 nm. Additionally, flow cytometric analysis of integrin alpha3 and beta1 expression on the tumor cell surface after treatment with phospholipids was completed.

RESULTS

We found a dose dependent effect of phospholipids on both tumor cell lines causing a reduction of cell-cell adhesion. Already low concentrations of phospholipids (PL 0.5) had a significant influence. The mean cell count could be reduced from 234+/-12/mm2 in controls to 124+/-41/mm2 (PL 0.5; NUG-4) and from 295+/-49/mm2 to 169+/-29/mm2 (PL 0.5; HRT-18), respectively. Additionally, the integrin alpha3 and beta1 expression on both cell lines could be reduced.

CONCLUSION

Our results within the scope of published data indicate that adhesion prevention is capable to reduce peritoneal carcinosis.

Human gingival fibroblast integrin subunit expression on titanium implant surfaces

BACKGROUND

Implant surface characteristics have been shown to modify cell behavior and regulate integrin expression. Integrin expression and resultant integrin-mediated cellular activity are essential components of tissue healing and homeostasis. Although both osseous and soft tissue healing around dental implants are critical to clinical success, there is limited information available on the effect of implant surfaces on integrin expression in soft tissues. Therefore, the aim of this study was to examine integrin expression for gingival fibroblasts on titanium surfaces and the influence of titanium surface roughness on integrin expression and cell morphology.

METHODS

Human gingival fibroblasts were cultured on smooth (polished) and rough (sand-blasted acid-etched) titanium surfaces and a cell culture plastic (control) surface. To analyze integrin expression, total RNA was isolated from experimental and control cells, and levels of integrin subunit mRNA were assessed by reverse transcription-polymerase chain reaction (RT-PCR) using primers specific for the alpha2, alpha4, alpha5, alpha(v), and beta1 integrin subunits and aldolase (internal control). PCR products were analyzed by polyacrylamide gel electrophoresis (PAGE), confirmed via DNA sequencing, and quantified using computer-assisted densitometry. The expression of the integrin subunits was analyzed at the protein level using flow cytometry, as well as fluorescence and confocal laser microscopy. Cell morphology was evaluated using scanning electron microscopy (SEM).

RESULTS

Our experiments demonstrated cellular expression of the alpha2, alpha4, alpha5, alpha(v), and beta1 integrin subunits at both mRNA and protein levels on all surfaces. In addition, the alpha4 and beta1 mRNA levels were significantly increased on smooth titanium relative to plastic surfaces (P <.05) with intermediate mRNA levels found on the rough titanium surfaces. The smooth titanium surfaces exhibited a flat monolayer of cells, while rough titanium surfaces showed cells orienting themselves along surface irregularities.

CONCLUSIONS

These results demonstrate the presence of multiple integrin subunits in human gingival fibroblasts grown in contact with titanium implant surfaces and that titanium surface roughness alters cellular morphology but appears to have limited effects on integrin expression. This study provides insight into the complicated cellular and molecular events occurring at the implant surface that may be critical to optimizing the soft tissue interactions with the soft tissue-implant interface.

Elevated Serum Levels of Soluble E-Cadherin in Patients with Primary Sjogren's Syndrome

The aim of this study was to investigate serum levels of soluble E-cadherin (sE-cadherin) in relation to lymphocytic organization and to characterize the expression of E-cadherin and integrin alphaEbeta7/CD103 in salivary gland epithelium of patients with Sjögren's syndrome (SS). Serum levels of sE-cadherin were significantly increased in SS compared to non-SS and nonsignificantly in germinal centre (GC)+ compared to GC- patients. Membrane-bound E-cadherin was detected on the majority of acinar and ductal epithelial cells in both SS and non-SS. alphaEbeta7/CD103-positive cells were found scattered in focal infiltrates and GC, and in small clusters close to ductal and acinar epithelium at an increased level in SS compared to non-SS. Interestingly, E-cadherin-positive cells were detected randomly dispersed in focal lymphocytic infiltrates in 10/21 patients. By double-labelling, the cells with the E-cadherin-positive component were identified as CD68(+) macrophages. Elevated serum levels of sE-cadherin indicate an increased epithelial cell turnover and shedding, and sE-cadherin deserves further analysis as a potential diagnostic tool for SS.

Runx3 regulates integrin alpha E/CD103 and CD4 expression during development of CD4-/CD8+ T cells

During thymic T cell development, immature CD4+CD8+ double-positive (DP) thymocytes develop either into CD4+CD8- Th cells or CD4-CD8+ CTLs. Differentially expressed primary factors inducing the fate of these cell types are still poorly described. The transcription factor Runx3/AML-2 Runx, runt [corrected] dominant factor; AML, acute myeloid leukemia is expressed specifically during the development of CD8 single-positive (SP) thymocytes, where it silences CD4 expression. Deletion of murine Runx3 results in a reduction of CD8 SP T cells and concomitant accumulation of CD4+CD8+ T cells, which cannot down-regulate CD4 expression in the thymus and periphery. In this study we have investigated the role of Runx3 during thymocyte development and CD4 silencing and have identified integrin alpha(E)/CD103 on CD8 SP T cells as a new potential target gene of Runx3. We demonstrate that Runx3 is necessary not only to repress CD4, but also to induce CD103 expression during development of CD8 SP T cells. In addition, transgenic overexpression of Runx3 reduced CD4 expression during development of DP thymocytes, leading to a reduced number of CD4 SP thymocytes and an increased number of CD8 SP thymocytes. This reversal is not caused by redirection of specific MHC class II-restricted cells to the CD8 lineage. Overexpression of Runx3 also up-regulated CD103 expression on a subpopulation of CD4 SP T cells with characteristics of regulatory T cells. Thus, Runx3 is a main regulator of CD4 silencing and CD103 induction and thus contributes to the phenotype of CD8 SP T cells during thymocyte development.

Activation of CD8+ regulatory T cells by human placental trophoblasts

The immunological basis by which a mother tolerates her semi-allogeneic fetus remains poorly understood. Several mechanisms are likely to contribute to this phenomenon including active immune regulation by regulatory T cells. In this article, we report that human placental trophoblasts activate a clonal population of CD8(+) T cells with regulatory function. These cells are not MHC class I restricted, but require costimulation through a member of the carcinoembryonic Ag family present on early gestation trophoblasts. These regulatory T cells express the mucosal markers CD101 and CD103 and display selective usage of the TCR gene Vbeta9. CD8(+) T cells isolated from the peripheral blood of pregnant mothers (16-28 wk) also demonstrate expansions in the same Vbeta family (Vbeta9), signaling a possible role for these cells in preventing fetal rejection in vivo. We have previously characterized a subset of CD8(+) regulatory T cells activated by the combination of the nonclassical class I molecule CD1d and a costimulatory molecule of the carcinoembryonic Ag family present on the intestinal epithelium. These data support the concept that distinct regulatory T cell populations exist at different sites and may be regulated locally by unique restriction elements, costimulatory signals, and Ags.

Immature CD4−CD103+Rat Dendritic Cells Induce Rapid Caspase-Independent Apoptosis-Like Cell Death in Various Tumor and Nontumor Cells and Phagocytose Their Victims

We previously reported the characterization of a MHC class II(low) CD4- CD103+ (CD4-) subset of dendritic cells (DC) in rat spleen that exhibit a Ca2+-, Fas ligand-, TRAIL- and TNF-alpha-independent cytotoxic activity against specific targets in vitro. In this study, we demonstrate that this DC subset was also found in lymph nodes. Freshly extracted and, therefore, immature CD4- DC exhibited a potent cytotoxic activity against a large panel of tumor cell lines as well as primary endothelial cells. The cytotoxic activity of immature CD4- DC required cell-to-cell contact and de novo protein expression. CD4- DC-mediated cell death resembled apoptosis, as evidenced by outer membrane phosphatidylserine exposure and nuclear fragmentation in target cells, but was caspase as well as Fas-associated death domain and receptor-interacting protein independent. Bcl-2 overexpression in target cells did not protect them against DC-mediated cell death. Immature CD4- DC phagocytosed efficiently apoptotic cells in vitro and, therefore, rapidly and specifically engulfed their victims following death induction. Maturation induced a dramatic down-regulation of the killing and phagocytic activities of CD4- DC. In contrast, CD4+ DC were both unable to kill target cells and to phagocytose apoptotic cells in vitro. Taken together, these data indicate that rat immature CD4- CD103+ DC mediate an unusual cytotoxic activity and can use this function to efficiently acquire Ag from live cells.

A role for CD103 in the retention of CD4+CD25+ Treg and control of Leishmania major infection

Endogenous regulatory T cells (T(reg)) play a central role in the control of excessive or misdirected immune responses against self or foreign Ags. To date, virtually no data are available on the nature of the molecules and signals involved in the trafficking and retention of T(reg) in tissues where regulation is required. Here, we show that expression of alpha(E)beta(7) integrin is necessary for the homing of T(reg) at site of Leishmania major infection. The vast majority of T(reg) present in the dermis at steady-state conditions or during L. major infection express the alpha(E) chain (CD103) of alpha(E)beta(7). Genetically susceptible BALB/c mice that lack CD103 become resistant to infection, a phenotype that is associated with a poor capacity of T(reg) to be retained in the infected site. Such susceptible phenotype can be restored when T(reg) from wild-type mice were transferred in CD103(-/-) mice. The central role of CD103 in T(reg) retention was further demonstrated by usage of blocking Abs against CD103 and the transfer of T(reg) purified from CD103(-/-) mice. Our results strongly suggest that this molecule is induced and maintained on T(reg) following or just prior to their arrival in tissues. Furthermore, the expression of CD103 and the subsequent retention of T(reg) in tissues is highly regulated by their exposure to Leishmania Ag and the level of activation of the APCs they encounter. Thus, CD103, by controlling T(reg) retention, can contribute to the outcome of chronic infection by Leishmania.

Peptide-specific CD8 T regulatory cells use IFN-gamma to elaborate TGF-beta-based suppression

We identified a murine peptide-specific CD8 T regulatory cell population able to suppress responding CD4 T cells. Immunization with OVA, poly(I:C), and anti-4-1BB generated a population of SIINFEKL-specific CD8 T regulatory cells that profoundly inhibited peptide-responding CD4 T cells from cellular division. The mechanism of suppression required IFN-gamma, but IFN-gamma alone was not sufficient to suppress the responding CD4 T cells. The data show that CD8 T regulatory cells were unable to suppress unless they engaged IFN-gamma. Furthermore, even in the absence of recall with peptide, the CD8 T regulatory cells suppressed CD4 responses as long as IFN-gamma was present. To examine the effector mechanism of suppression, we showed that neutralizing TGF-beta inhibited suppression because inclusion of anti-TGF-beta rescued the proliferative capacity of the responding cells. TGF-beta-based suppression was dependent completely upon the CD8 T regulatory cells being capable of binding IFN-gamma. This was the case, although peptide recall of primed IFN-gamma (-/-) or IFN-gammaR(-/-) CD8 T cells up-regulated pro-TGF-beta protein as measured by surface latency-associated peptide expression but yet were unable to suppress. Finally, we asked whether the CD8 T regulatory cells were exposed to active TGF-beta in vivo and showed that only wild-type CD8 T regulatory cells expressed the TGF-beta-dependent biomarker CD103, suggesting that latency-associated peptide expression is not always congruent with elaboration of active TGF-beta. These data define a novel mechanism whereby IFN-gamma directly stimulates CD8 T regulatory cells to elaborate TGF-beta-based suppression. Ultimately, this mechanism may permit regulation of pathogenic Th1 responses by CD8 T regulatory cells.

Expression and role of E-cadherin and CD103beta7 (alphaEbeta7 integrin) on cultured mucosal-type mast cells

Mucosal-type mast cells (MMC) in the respiratory and/or gut epithelium play pivotal roles in the development of allergic inflammation and nematode clearance. To determine the role of E-cadherin and alphaEbeta7 integrin in MMC localization to the epithelium, we analyzed the epithelial binding of two types of mouse bone marrow-derived mast cells: S3-BMMC, which developed in medium containing stem cell factor (SCF) plus IL-3, and S39T-BMMC, which developed with SCF, IL-3, IL-9 and TGF-beta1. The latter cells were more similar to mature MMC than the former in terms of mouse mast cell protease (mMCP)-1 expression. FACS analyses revealed that S3-BMMC expressed E-cadherin and beta7 integrin but not alphaE integrin, whereas S39T-BMMC expressed alphaEbeta7 integrin as well as E-cadherin. Mn2+ promoted adhesion of S39T-BMMC to the monolayer of E-cadherin+F9 cells. The adhesion was suppressed significantly by the combined addition of blocking antibodies against integrin alphaE and E-cadherin, whereas either blocking antibody alone failed to do so. S3-BMMC adhesion was suppressed by E-cadherin blocking antibody but not by alphaE blocking antibody. These results suggested that E-cadherin and alphaEbeta7 integrin, which are expressed on MMC-analog S39T-BMMC, play an important role in mast cell-epithelial cell interaction through homophilic as well as heterophilic binding to the epithelial E-cadherin molecule.

Loss of alpha10beta1 integrin expression leads to moderate dysfunction of growth plate chondrocytes

Integrin alpha10beta1 is a collagen-binding integrin expressed on chondrocytes. In order to unravel the role of the alpha10 integrin during development, we generated mice carrying a constitutive deletion of the alpha10 integrin gene. The mutant mice had a normal lifespan and were fertile but developed a growth retardation of the long bones. Analysis of the skeleton revealed defects in the growth plate after birth characterized by a disturbed columnar arrangement of chondrocytes, abnormal chondrocyte shape and reduced chondrocyte proliferation. Electron microscopy of growth plates from newborn mice revealed an increased number of apoptotic chondrocytes and reduced density of the collagen fibrillar network compared to these structures in control mice. These results demonstrate that integrin alpha10beta1 plays a specific role in growth plate morphogenesis and function.

Reduction in adhesiveness to extracellular matrix components, modulation of adhesion molecules and in vivo migration of murine macrophages infected with Toxoplasma gondii

Toxoplasma gondii is an obligate intracellular parasite, able to disseminate into deep tissues and cross biological barriers, reaching immunoprivileged sites such as the brain and retina. In order to investigate whether the parasite uses leukocyte trafficking to disseminate throughout the host, the adhesive potential to extracellular matrix components, the expression of adhesion molecules and the in vivo migration of murine macrophages infected with RH strain of T. gondii were investigated. Cellular adhesion to fibronectin, laminin and collagen IV decreased after 24 h of T. gondii infection. However, the decrease in adhesion of infected macrophages observed at early infection was reversed after 48 h. Moreover, decreased adhesion was dependent on active penetration, since heat-killed parasites were unable to reproduce it. Expression of integrins alphaL, alpha4 and alpha5 chains was downmodulated early postinfection, but a progressive regain of expression was observed after 12 h of infection. Expression of beta2, alphav and alpha4 integrins by peritoneal macrophages at late infection was also gradually reestablished. The assessment of in vivo migration of infected macrophages labeled with the fluorescent dye 5-chloromethylfluorescein diacetate showed a 48-h delay in migration to cervical lymph nodes when compared to LPS pre-stimulated macrophages. Furthermore, cells that migrate to distal lymph nodes were loaded with live parasites. Taken together, these results provide insights about T. gondii escape from the host immune response, placing the macrophage as a "Trojan horse", contributing to parasite dissemination and access to immunoprivileged sites.

The Fibril-associated Collagen IX Provides a Novel Mechanism for Cell Adhesion to Cartilaginous Matrix

Collagen IX is the prototype fibril-associated collagen with interruptions in triple helix. In human cartilage it covers collagen fibrils, but its putative cellular receptors have been unknown. The reverse transcription-PCR analysis of human fetal tissues suggested that based on their distribution all four collagen receptor integrins, namely alpha1beta1, alpha2beta1, alpha10beta1, and alpha11beta1, are possible receptors for collagen IX. Furthermore primary chondrocytes and chondrosarcoma cells express the four integrins simultaneously. Chondrosarcoma cells, as well as Chinese hamster ovary cells transfected to express alpha1beta1, alpha2beta1, or alpha10beta1 integrin as their only collagen receptor, showed fast attachment and spreading on human recombinant collagen IX indicating that it is an effective cell adhesion protein. To further study the recognition of collagen IX we produced recombinant alphaI domains in Escherichia coli. For each of the four alphaI domains, collagen IX was among the best collagenous ligands, making collagen IX exceptional compared with all other collagen subtypes tested so far. Rotary shadowing electron microscopy images of both alpha1I- and alpha2I-collagen IX complexes unveiled only one binding site located in the COL3 domain close to the kink between it and the COL2 domain. The recognition of collagen IX by alpha2I was considered to represent a novel mechanism for two reasons. First, collagen IX has no GFOGER motif, and the identified binding region lacks any similar sequences. Second, the alpha2I domain mutations D219R and H258V, which both decreased binding to collagen I and GFOGER, had very different effects on its binding to collagen IX. D219R had no effect, and H258V prevented type IX binding. Thus, our results indicate that collagen IX has unique cell adhesion properties when compared with other collagens, and it provides a novel mechanism for cell adhesion to cartilaginous matrix.

Correlation between methylation profile of promoter cpg islands of seven metastasis-associated genes and their expression states in six cell lines of liver origin

BACKGROUND & OBJECTIVE

DNA methylation has been regarded as an important epigenetic signature reflecting the transcription state of DNA in cells. This study was to assess the correlation between methylation state of promoter CpG islands of metastasis-associated genes and their expression in 6 liver cell lines, including 5 cancerous.

METHODS

Methylation specific polymerase chain reaction method (MSP) and DNA sequencing verification were used to analyze the methylation state of promoter CpG islands of 7 genes (ASPH, ENO3, ITGA9, LRP6, MTHFD2, OXCT, and SRP72) in 5 liver cancer cell lines (BEL-7402, SMMC-7721, Hep3B, HepG2, and HCCLM3), and 1 immortalized liver cell line (L-02). Expression of 6 genes in this list was assessed by the semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) method.

RESULTS

The methylation state of genes was either unmethylated or heterozygously methylated in these 7 liver cell lines. Except for no expression of OXCT gene was detected by RT-PCR in both HepG2 and HCCLM3 cells where it was heterozygously methylated, there was expression of genes in all the remaining cases.

CONCLUSION

Although expression state of genes in this study supported the general notion that hypermethylation state of promoter CpG islands of genes represents the silenced state of gene transcription, there were exceptions. Therefore, other mechanisms are likely to contribute to the observed expression state of these 7 genes in this study.

Methotrexate markedly reduces the expression of vascular E-selectin, cutaneous lymphocyte-associated antigen and the numbers of mononuclear leucocytes in psoriatic skin

A positive correlation between disease severity and the frequency of cutaneous lymphocyte-associated antigen (CLA)-positive T cells in the blood of untreated patients with psoriasis has been previously observed. A dose-dependent inverse relationship between disease severity and the frequency of circulating CLA(+) T cells in psoriasis patients on methotrexate (MTX) treatment is reported. Circulating T cells from a patient with psoriasis were monitored for CLA expression on a daily basis for 5 weeks. A decrease in the intensity and frequency of CLA(+) mononuclear leucocytes was consistently observed in the blood during the first 3-4 days after each MTX intake, but the CLA expression increased thereafter until the next weekly dose was taken. The MTX treatment of this patient was then discontinued for 16 days, and a marked subjective exacerbation was reported within 9 days, which was confirmed objectively (laser Doppler perfusion imaging) after 11 and 16 days. Biopsies taken 4 days after the last MTX intake showed only a few mononuclear leucocytes in lesional skin, but the exacerbation coincided with a marked increase in CLA expression by mononuclear blood leucocytes, followed by an increase in endothelial E-selectin and a striking influx of CLA(+) mononuclear cells into lesional skin. Conversely, a clinical improvement after the patient resumed the MTX treatment was associated with reduction in CLA expression by mononuclear cells in the blood, downregulation of endothelial E-selectin and an approximate threefold decrease in mononuclear leucocyte infiltration of lesional skin. No MTX-associated changes were detected in the expression of very late antigen-4, vascular cell-adhesion molecule-1 nor the late activation marker CD25. It is concluded that MTX decreases the expression of CLA and E-selectin and that this may be a major mechanism for the therapeutic effect of MTX on psoriatic skin lesions.

Developmentally regulated expression and functional role of alpha7 integrin in the chick embryo

Integrin alpha 7 beta 1 is a specific cellular receptor for laminin. In the present work, we studied the distribution pattern of the alpha 7 subunit by immunofluorescence and immunoprecipitation and the role of the integrin by blocking antibodies in early chick embryos. alpha 7 immunoreactivity was first detectable in the neural plate during neural furrow formation (stage HH5, early neurula, Hamburger & Hamilton 1951) and its expression was upregulated in the neural folds during primary neurulation. The alpha 7 expression domain spanned the entire neural tube by stage HH8 (4 somites), and was then downregulated and confined to the neuroepithelial cells in the germinal region near the lumen and the ventrolateral margins of the neural tube in embryos by the onset of stage HH17 (29 somites). Expression of alpha 7 in the neural tube was transient suggesting that alpha 7 functions during neural tube closure and axon guidance and may not be required for neuronal differentiation or for the maintenance of the differentiated cell types. alpha 7 immunoreactivity was strong in the newly formed epithelial somites, although this expression was restricted only to the myotome in the mature somites. The most intense alpha 7 immunoreactivity was detectable in the paired heart primordia and the endoderm apposing the heart primordia in embryos at stage HH8. In the developing heart, alpha 7 immunoreactivity was: (i) intense in the myocardium; (ii) milder in the endocardial cushions of the ventricle; (iii) intense in the sinus venosus; (iv) distinct in the associated blood vessels; and (v) undetectable in the dorsal mesocardium of embryos at stage HH17. Inhibition of function of alpha 7 by blocking antibodies showed that alpha 7 integrin-laminin signaling may play a critical role in tissue organization of the neural plate and neural tube closure, in tissue morphogenesis of the heart tube but not in the directional migration of pre-cardiac cells, and in somite epithelialization but not in segment formation in presomitic mesoderm. In embryos treated with alpha 7 antibody, the formation of median somites in place of a notochord was intriguing and suggested that alpha 7 integrin-laminin signaling may have played a role in segment re-specification in the mesoderm.

Regulation of CD103 expression by CD8+ T cells responding to renal allografts

CD103 is an integrin with specificity for the epithelial cell-specific ligand, E-cadherin. Recent studies indicate that CD103 expression endows peripheral CD8 cells with a unique capacity to access the epithelial compartments of organ allografts. In the present study we used a nonvascularized mouse renal allograft model to 1) define the mechanisms regulating CD103 expression by graft-infiltrating CD8 effector populations, and 2) identify the cellular compartments in which this occurs. We report that CD8 cells responding to donor alloantigens in host lymphoid compartments do not initially express CD103, but dramatically up-regulate CD103 expression to high levels subsequent to migration to the graft site. CD103+CD8+ cells that infiltrated renal allografts exhibited a classic effector phenotype and were selectively localized to the graft site. CD8 cells expressing low levels of CD103 were also present in lymphoid compartments, but three-color analyses revealed that these are almost exclusively of naive phenotype. Adoptive transfer studies using TCR-transgenic CD8 cells demonstrated that donor-specific CD8 cells rapidly and uniformly up-regulate CD103 expression following entry into the graft site. Donor-specific CD8 cells expressing a dominant negative TGF-beta receptor were highly deficient in CD103 expression following migration to the graft, thereby implicating TGF-beta activity as a dominant controlling factor. The relevance of these data to conventional (vascularized) renal transplantation is confirmed. These data support a model in which TGF-beta activity present locally at the graft site plays a critical role in regulating CD103 expression, and hence the epitheliotropism, of CD8 effector populations that infiltrate renal allografts.

Differential effects of interleukin 12 and interleukin 10 on superantigen-induced expression of cutaneous lymphocyte-associated antigen (CLA) and αEβ7 integrin (CD103) by CD8+ T cells

At both cutaneous and mucosal sites, interleukin (IL)-10, IL-12 and transforming growth factor (TGF)-beta are important regulators of chronic inflammatory disease, where cutaneous lymphocyte-associated antigen (CLA) and alphaE integrin (CD103) may be expressed. Stimulation with streptococcal pyrogenic exotoxin C (SpeC) increased the expression of CD103 by CD8+ but not CD4+ T cells. While adding IL-12 augmented the expression of CLA, superantigen-induced expression of CD103 was markedly suppressed by IL-12, which could be reversed by TGF-beta. Antibodies against TGF-beta inhibited, and a combination of anti-TGF-beta and IL-12 completely abrogated the induced CD103 expression. IL-10 strongly decreased the frequency of CLA+ and although not increasing the frequency of CD103+CD8+ T cells, the amount of CD103 expressed per cell was markedly increased. Thus, the expression of CLA and CD103 may be antagonistically regulated by IL-10 and IL-12 and the balance between these cytokines could influence the T cell migration of inflammatory cells into epithelial tissues.

Regulation of α7 Integrin Expression during Muscle Differentiation

Expression of the laminin-binding alpha7 integrin is tightly regulated during myogenic differentiation, reflecting required functions that range from cell motility to formation of stable myotendinous junctions. However, the exact mechanism controlling alpha7 expression in a tissue- and differentiation-specific manner is poorly understood. This report provides evidence that alpha7 gene expression during muscle differentiation is regulated by the c-Myc transcription factor. In myoblasts, alpha7 is expressed at basal levels, but following conversion to myotubes the expression of the integrin is strongly elevated. The increased alpha7 mRNA and protein levels following myogenic differentiation are inversely correlated with c-Myc expression. Transfection of myoblasts with the c-Myc transcription factor down-regulated alpha7 expression, whereas overexpression of Madmyc, a dominant-negative c-Myc chimera, induced elevated alpha7 expression. Functional analysis with site-specific deletions identified a specific double E-box sequence in the upstream promoter region (-2.0 to -2.6 kb) that is responsible for c-Myc-induced suppression of alpha7 expression. DNA-protein binding assays and supershift analysis revealed that c-Myc forms a complex with this double E-box sequence. Our results suggest that the interaction of c-Myc with this promoter region is an important regulatory element controlling alpha7 integrin expression during muscle development and myotendinous junction formation.

Expression of the integrin subunit alpha8 in murine lung development

The complex interplay between cells and extracellular matrix (ECM) proteins is critical for lung development. Integrins are key modulators of this interaction. The integrin subunit alpha 8 associates with the beta(1)-subunit to form an RGD-binding integrin. We previously showed that, in adult lung, alpha 8 is expressed in contractile interstitial cells and smooth muscle cells and is upregulated in lung injury. To gain insight into the function of alpha 8 during lung development, we examined the spatiotemporal expression of alpha 8 throughout murine lung development. We compared the distribution of alpha 8 with alpha-smooth muscle actin (alpha SMA), fibronectin (alpha 8 ligand), and cytokeratin. alpha 8 co-localized with alpha SMA and fibronectin in the peribronchial and perivascular regions. In all stages, alpha 8 immunoreactivity was detected diffusely in the mesenchyme except for cells surrounding distal, newly forming airways. alpha 8, alpha SMA, and fibronectin co-localized at tips of secondary septae in the alveolar stage. We conclude that alpha 8 is marker for lung mesenchymal cells starting early in development. alpha 8 is also a marker for smooth muscle cells, expressed as early as alpha SMA. Co-localization of alpha 8 with fibronectin suggests a role in branching morphogenesis. Furthermore, alpha 8 may participate in secondary septation by modulating signals from the extracellular matrix to alveolar myofibroblasts.

Compensation for dystrophin-deficiency: ADAM12 overexpression in skeletal muscle results in increased alpha 7 integrin, utrophin and associated glycoproteins

Mouse models for genetic diseases are among the most powerful tools available for developing and testing new treatment strategies. ADAM12 is a disintegrin and metalloprotease, previously demonstrated to significantly alleviate the pathology of mdx mice, a model for Duchenne muscular dystrophy in humans. More specifically ADAM12 appeared to prevent muscle cell necrosis in the mdx mice as evidenced by morphological analysis and by the reduced levels of serum creatine kinase. In the present study we demonstrated that ADAM12 may compensate for the dystrophin deficiency in mdx mice by increasing the expression and redistribution of several components of the muscle cell-adhesion complexes. First, we analyzed transgenic mice that overexpress ADAM12 and found mild myopathic changes and accelerated regeneration following acute injury. We then analyzed changes in gene-expression profiles in mdx/ADAM12 transgenic mice compared with their littermate controls and found only a few genes with an expression change greater than 2-fold between mdx/ADAM12 and mdx. The small changes in gene expression were unexpected, considering the marked improvement of the mdx pathology when ADAM12 is overexpressed, and suggested that significant changes in mdx/ADAM12 muscle might occur post-transcriptionally. Indeed, by immunostaining and immunoblotting we found an approximately 2-fold increase in expression, and distinct extrasynaptic localization, of alpha 7B integrin and utrophin, the functional homolog of dystrophin. The expression of the dystrophin-associated glycoproteins was also increased. In conclusion, these results demonstrate a novel way to alleviate dystrophin deficiency in mice, and may stimulate the development of new approaches to compensate for dystrophin deficiency in animals and humans.

Phenotypic and molecular characterization of CD103+ CD4+ T cells in bronchoalveolar lavage from patients with interstitial lung diseases

BACKGROUND

The integrin CD103 is preferentially expressed on intraepithelial T lymphocytes, and cells expressing this integrin may play a regulatory role in the microenvironment of the epithelial cell layer.

METHODS

The relative number of CD103(+)/CD4(+) T cells in the bronchoalveolar lavage was significantly elevated in all patients diagnosed with interstitial lung diseases compared with patients with other non-fibrotic disorders of the lung.

RESULTS

Analysis by flow cytometry showed that the CD103(+) and the CD103(-) subpopulations were memory T cells based on the high expression of CD45RO(+). However, the CD103(+)/CD4(+) T cells were CD25(low), CD27(-), CD28(low), and CD62L(-), whereas the CD103(-)/CD4(+) T cells expressed CD25 and CD62L and were CD27(high) and CD28(high). In addition, the CD103(+)/CD4(+) T cells expressed significantly higher quantities of VLA-1 and CD101 than did CD103(-)/CD4(+) T cells. Reverse transcriptase polymerase chain reaction analysis of purified CD103(+) and CD103(-) CD4(+) T cells showed production of tumor necrosis factor (TNF) alpha-R-1 (p55), TNF-alpha-R-2 (p75), interferon gamma, interleukin-10, and TNF-alpha mRNA in both subpopulations. No interleukin-4 mRNA was detected in either subpopulation.

CONCLUSIONS

CD103(+)/CD4(+) T cells represent a T-helper 1-like subpopulation in human lungs with a distinct effector phenotype. Despite the lack of CD27 and the low CD25 and CD28 expression, these cells show a high degree of activation. These results suggest that CD103 expressing CD4 T cells in the lung are continuously activated, long-living cells.

Effects of 2,3,7,8-TCDD and PCB 126 on human thymic epithelial cells in vitro

2,3,7,8-Tetrachloro-dibenzo- p-dioxin (TCDD) is a ubiquitously distributed xenobiotic. The adverse effects of TCDD on the mammalian immune system have been studied for decades, but it is still unclear whether TCDD has direct effects on T-lymphocytes or whether it acts via the thymic microenvironment. We have studied the effects of TCDD on primary cultures of human thymic epithelial cells (TEC) focusing on differentiation markers, integrins and adhesion molecules involved in cell-cell and in cell-matrix interactions. TEC were treated with TCDD at concentrations of 0.001, 0.01, 0.1, 1.0 or 10.0 nM or with 100 nM PCB 126 (3,3',4,4',5-pentachlorobiphenyl) for 3 days, and were then analysed by flow cytometry for expression of surface antigens using monoclonal antibodies against Hassall's bodies (TE-8, TE-16) or against surface structures such as CD29, CD49b, CD49e, CD49f, CD51, CD54, CD58, CD61 and CD106. At TCDD concentrations as low as 0.01 nM we found a significant increase in terminally differentiated, TE-16-positive TEC; at a ten-fold greater concentration the number of cells marked with the TE-8 antibody was also increased. With both markers the most pronounced effect (approximately +15%) was observed at 1 nM TCDD. An increase of cells expressing the integrin alpha-chains CD49b, CD49e and CD51 as well as CD54 was observed at concentrations of 0.1 nM TCDD or higher. The proportion of cells expressing CD106 or CD49f decreased significantly upon treatment with TCDD. No effects on the integrin beta-chains CD29 and CD61 could be detected. Overall, PCB 126 induced similar changes to TCDD. In summary, TCDD and a coplanar PCB induced terminal differentiation of human TEC along with changes of integrins and other adhesion molecules. These receptors and their interplay with the extracellular matrix have key functions in the maturation of T-lymphocytes and it is plausible that their alteration would be involved in TCDD-induced immunotoxicity.

T cells of atopic asthmatics preferentially infiltrate into human bronchial xenografts in SCID mice

T cells play an important role in the pathogenesis of bronchial asthma. However, it is not completely known how circulating lymphocytes infiltrate into the airways of asthmatic patients. Because SCID mice are unable to reject xenogenic transplants, many xenotransplant models using various human tissues have been developed. Therefore, to examine the interaction between bronchi and T lymphocytes of asthma, it may be possible to use the human bronchial xenograft and PBMC xenograft in SCID mice. We transplanted human bronchi into the subcutaneum of SCID mice and i.p. injected PBMCs that were obtained from patients with atopic asthma, atopic dermatitis and rheumatoid arthritis, and normal subjects (asthmatic, dermatitis, rheumatic, and normal huPBMC-SCID mice). There was no difference in the percentage of CD3-, CD4-, CD8-, CD25-, CD45RO-, CD103-, and cutaneous lymphocyte Ag-positive cells in PBMCs among the patients with asthma, dermatitis, rheumatoid arthritis, and normal subjects, and CD3-positive cells in peripheral blood of asthmatic, dermatitis, rheumatic, and normal huPBMC-SCID mice. The number of CD3-, CD4-, and CD8-positive cells in the xenografts of asthmatic huPBMC-SCID mice was higher than those of dermatitis, rheumatic, and normal huPBMC-SCID mice. IL-4 mRNA and IL-5 mRNA were significantly higher in the xenografts of asthmatic huPBMC-SCID mice than those in the xenografts of normal huPBMC-SCID mice, but there were no significant differences in the expressions of IL-2 mRNA or IFN-gamma mRNA between them. These findings suggest that T cells, especially Th2-type T cells, of asthmatics preferentially infiltrate into the human bronchi.

Expression of the myeloid-specific leukocyte integrin gene CD11d during macrophage foam cell differentiation and exposure to lipoproteins

The leukocyte integrin gene CD11d is expressed predominantely on subsets of the myelomonocytic lineage (myeloid cells), particularly on macrophage foam cells and splenic red pulp macrophages. Its expression pattern clearly differs from myeloid-specific leukocyte integrins CD11b and CD11c and the leukocyte-specific integrin CD11a. Although the functions of CD11d have not been determined in any detail, its expression in these cell types suggests that it may play a role in the atherosclerotic process. To better understand how this gene is regulated, the steady-state level of CD11d mRNA in differentiating bone marrow CD34+CD38- cells, peripheral blood monocytes, and monocytic cell lines was assessed by Northern blot analysis and RT-PCR and compared with those of CD11a, CD11b, and CD11c. Expression of CD11d occurs early in CD34+CD38- cells, rises, and then decreases, in contrast to the expression of the other leukocyte integrins. Expression of CD11d reappears in peripheral blood monocytes differentiating to macrophage foam cells. Oxidized lipoproteins (OxLDL) and acetylated lipoproteins (AcLDL) failed to upregulate CD11d following differentiation of peripheral blood monocytes or the monocytic cell line HL60. However, when both OxLDL and AcLDL were present during differentiation, CD11d was further upregulated. This suggests that expression of CD11d is coordinately regulated with expression of LDL receptors and the development of the foam cell. Site-directed mutagenesis of the -100 to -20 region of the CD11d promoter revealed transcription factor binding sites essential for expression of this gene. Decoy oligonucleotides to the -100 to -20 region taken up by CD34+CD38- cells block their differentiation into myeloid colonies. This suggests that one or more transcription factors that regulate CD11d also are essential for myeloid differentiation, and that the CD11d promoter may be used as a model gene to identify transcription factors essential for myeloid cell differentiation.

TGF-beta 1 regulates adhesion of mucosal mast cell homologues to laminin-1 through expression of integrin alpha 7

Mucosal mast cells (MMC) or their precursors migrate through the intestinal lamina propria to reside intraepithelially, where expression of mouse mast cell protease-1 indicates the mature phenotype. Alterations in expression of integrins that govern cell adhesion to the extracellular matrix may regulate this process. As the key cytokine mediating differentiation of mouse mast cell protease-1-expressing MMC homologues in vitro, TGF-beta1 was considered a likely candidate for regulation of the integrins that facilitate intraepithelial migration of MMC. Therefore, we examined adhesion of bone marrow-derived mast cells cultured with and without TGF-beta1 to laminin-1, fibronectin, and vitronectin along with expression of integrins likely to regulate this adhesion. Adhesion of PMA-stimulated cultured mast cells to laminin-1 increased from 5.3 +/- 3.6% (mean +/- SEM) in the absence of TGF-beta1 to 58.7 +/- 4.0% (p < 0.05) when cultured mast cells had differentiated into MMC homologues in the presence of TGF-beta1. Increased adhesion of MMC homologues to laminin-1 was also stimulated by FcepsilonRI cross-linking and the calcium ionophore A23187. Expression of the laminin-binding integrin alpha(7) by MMC homologues grown in the presence of TGF-beta1 was demonstrated by RT-PCR and flow cytometry, and preincubation of MMC homologues with the alpha(7)-neutralizing Ab 6A11 inhibited adhesion to laminin-1 by 98% (p < 0.05), demonstrating a novel role for this molecule in adhesion of a hemopoietic cell to laminin-1.

Adhesion of lymphocytes to bladder cancer cells: the role of the alpha(E)beta(7) integrin

The alpha(E)beta(7)integrin (defined by CD103) is expressed by most intra-epithelial lymphocytes (IEL) but by fewer than 2% peripheral blood lymphocytes (PBL). An important ligand for this molecule is the epithelial cell adhesion molecule E-cadherin. Loss of E-cadherin is associated with increased invasion and metastasis in bladder cancer. This study examines the role of the alpha(E)beta(7)-E-cadherin interaction in lymphocyte targeting of bladder cancer cells. Lymphocytes were activated in vitro by mixed lymphocyte reaction (MLR) and CD103 was upregulated by treatment with transforming growth factor beta (TGFbeta). The CD103(+) lymphocytes were used in a flow cytometric adhesion assay with bladder cancer cell lines, differing in expression of E-cadherin and intercellular adhesion molecule-1 (ICAM-1). Antibody blockade was used to confirm the relative importance of CD103 and ICAM-1 to intercellular adhesion. Lymphocytes with upregulated CD103 compared to control lymphocytes showed enhanced adhesion to an E-cadherin expressing bladder cancer cell line ( P=0.0003). This increased adhesion could be abrogated by anti-CD103 adhesion blockade. For ICAM-1 expressing bladder cells, adhesion of lymphocytes could be markedly reduced using anti-ICAM-1 blockade. In conclusion, the upregulation of CD103 by lymphocytes increases adhesion to E-cadherin expressing bladder cancer targets. Loss of E-cadherin in bladder cancer progression may provide a mechanism both for increased invasion and effective immune evasion.

Dendritic cell appearance and differentiation during early and late stages of rat stomach carcinogenesis

Dendritic cell appearance and differentiation during early and late stages of rat stomach carcinogenesis were studied in the pyloric mucosa. Young male rats were given drinking water with or without N-methyl-N'-nitro-N-nitrosoguanidine (MNNG; 100 mg/liter) for 14 days. Use of competitive RT-PCR and northern blotting showed that MNNG exposure induced 3- to 4-fold greater expression of the genes for integrin beta7 and integrin alphaE2 (identical with antigen OX-62, a dendritic cell marker), as well as three cytokines, IL-4, GM-CSF and TNFalpha, in the stomach pyloric mucosa of resistant Buffalo rats compared to sensitive ACI rats. These genes were minimally expressed in control animals. The results confirm the appearance of dendritic cells in the target pyloric mucosa and suggest the possibility that dendritic cell differentiation and maturation are induced by various cytokines, at least in Buffalo rats. Competitive RT-PCR showed expression of integrin alphaE2 and beta7, MHC class II-associated invariant chain (Ii), MHC class II, B7-1, CD28, GM-CSF and TNFalpha genes in all 12 examined stomach adenocarcinomas and adenomas induced in male Lewis and WKY rats with 30 weeks' MNNG exposure, suggesting the presence of dendritic cells in tumors. OX-62 staining and western blotting for OX-62 also confirmed the presence of dendritic cells in tumors. However, the population of dendritic cells in tumors was less than that in the pyloric mucosa after 14 days' MNNG exposure. The present results suggest that immune defense involving dendritic cells is marshaled from the very early initiation stage during rat stomach cancer development, but is downgraded in developed tumors.