Lack of glutathione peroxidase-1 exacerbates Abeta-mediated neurotoxicity in cortical neurons

The aetiologies of Alzheimer's disease (AD) are complex and multifactorial. Current therapies are largely ineffective, as the pathophysiological pathways are poorly understood. Observations in AD autopsies, as well as in vivo and in vitro observations in transgenic mice, have implicated oxidative stress as pathogenic in AD. This study used the Glutathione Peroxidase-1 knockout mouse (Gpx1--/--) model to investigate the role of antioxidant disparity in neuropathologies. Cultured neurons from control and Gpx1--/-- embryos were treated with AD-related peptides and the degree of cell loss compared. Results show that antioxidant disparity makes Gpx1--/-- cells more susceptible to Abeta toxicity. Surrogate replacement of Gpx1 with the reactive oxygen species scavenger N-acetyl cysteine and the Gpx1 mimetic ebselen, reverses the Gpx1--/-- increased susceptibility to Abeta toxicity. Such results support a role for oxidative stress in AD-related neuronal loss. This study is the first to report such findings using the Gpx1--/-- model, and supports a role for oxidative stress as one of the contributing factors, in development of AD-like pathologies.

Differential expression and effects of gp130 cytokines and receptors in prostate cancer cells

High levels of circulating interleukin-6 (IL6), and possibly neuroendocrine (NE) differentiation, correlate with advanced prostate cancer (PCa). IL6 has many overlapping biological effects with the related gp130 cytokines LIF and OSM that can be explained by the shared usage of the signalling receptor, gp130. We set out to determine whether LIF and OSM can substitute for IL6 in PCa, particularly in relation to neuroendocrine differentiation. Expression analysis of the gp130 cytokines and receptors by RT-PCR, Southern blotting and immunohistochemistry showed that they are widely expressed in LNCaP, DU145 and PC3 cells, but not in normal prostate epithelial PZ-HPV-7 cells. IL6, but not LIF or OSM inhibited proliferation, induced NE differentiation and tyrosine phosphorylation of STAT3 in LNCaP cells. The data suggests that IL6 has a unique role in the progression of PCa.

Adamts-1 Is Essential for the Development and Function of the Urogenital System1

Successful ovulation and implantation processes play a crucial role in female fertility. Adamts-1, a matrix metalloproteinase with disintegrin and thrombospondin motifs, has been suggested to be regulated by the progesterone receptor in the hormonal pathway leading to ovulation. With the primary aim of investigating the role of Adamts-1 in female fertility, we generated Adamts-1 null mice. Forty-five percent of the newborn Adamts-1 null mice die, with death most likely caused by a kidney malformation that becomes apparent at birth. Surviving female null mice were subfertile, whereas males reproduced normally. Ovulation in null females was impaired because of mature oocytes remaining trapped in ovarian follicles. No uterine phenotype was apparent in Adamts-1 null animals. Embryo implantation occurred normally, the uteri were capable of undergoing decidualization, and no morphological changes were observed. These results demonstrate that a functional Adamts-1 is required for normal ovulation to occur, and hence the Adamts-1 gene plays an important role in female fertility, primarily during the tissue remodeling process of ovulation.

Generation and characterization of recombinant unmodified and phosphorylatable murine IFN-alpha1 in the methylotropic yeast Pichia pastoris

In order to generate reagents to study the murine type I interferon (IFN) system, recombinant murine IFN-alpha1 (rMuIFN-alpha1) protein was expressed in the methylotropic yeast Pichia pastoris. rMuIFN-alpha1 with a phosphate acceptor site engineered at the C-terminus (rMuIFN-alpha1P) to enable radiolabeling by gamma(32)P-ATP and cAMP-dependent protein kinase was also generated. Proteins of 20, 25 (MuIFN-alpha1) and 25.5 (MuIFN-alpha1P), kDa were detected in the yeast growth medium, had type I IFN activity, and were recognized by antimurine L929 cell IFN antibodies. The MuIFN-alpha1 proteins produced in P. pastoris were a mixture of glycosylated and unglycosylated forms, with sugars of approximately 5 kDa added via N-linked glycosylation. The recombinant proteins were highly purified using a single RP-HPLC elution step, and their authenticity was confirmed by amino-terminal amino acid sequencing. The MuIFN-alpha1 and MuIFN-alpha1P protein preparations had specific antiviral activities of 1.3 x 10(7) and 4.7 x 10(6) IU/mg protein, respectively. MuIFN-alpha1P could be radiolabeled to a high specific radioactivity (0.6-2 x 10(8) cpm/microg protein) with gamma(32)P-ATP and cAMP-dependent protein kinase without significantly altering its biologic activity or electrophoretic properties. Binding experiments on COS-7 cells transiently transfected with MuIFNAR-2 and IFNAR-2 demonstrated specific and dose-dependent binding of gamma(32)P-ATP-MuIFN-alpha1P to cell surface type I IFN receptors.

Detailed mapping of the ERG-ETS2 interval of human chromosome 21 and comparison with the region of conserved synteny on mouse chromosome 16

We have carried out a detailed annotation of 550 kb of genomic DNA on human chromosome 21 containing the ERG and ETS2 genes. Comparative genomic analysis between this region and the interval of conserved synteny on mouse chromosome 16 indicated that the order and orientation of the ERG and ETS2 genes were conserved and revealed several regions containing potential conserved noncoding sequences. Four pseudogenes including those for small protein G, laminin receptor, human transposase protein and meningioma-expressed antigen were identified. A potentially novel gene (C21orf24) with alternative mRNA transcripts, consensus splice donor and acceptor sites, but no coding potential nor murine orthologue, was identified and found to be expressed in a range of human cell lines. We have identified four novel splice variants that arise from a previously undescribed 5' exon of the human ERG gene. Comparison of the cDNA sequences enabled us to determine the complete exon-intron structure of the ERG gene. We have also identified the presence of noncoding RNAs in the first and second introns of the ETS2 gene. Our studies have important implications for Down syndrome as this region contains multiple mRNA transcripts, both coding and potentially noncoding, that may play as yet undescribed roles in the pathogenesis of this disorder.

Overexpression of the chromosome 21 transcription factor Ets2 induces neuronal apoptosis

Down syndrome (trisomy 21) neurons display an increased rate of apoptosis in vitro. The genes on chromosome 21 that mediate this increased cell death remain to be elucidated. Here we show that the chromosome 21 transcription factor Ets2, a gene that is overexpressed in Down syndrome, is expressed in neurons, and that moderate overexpression of Ets2 leads to increased apoptosis of primary neuronal cultures from Ets2 tg mice that involves activation of caspase-3. Our data therefore suggest that overexpression of ETS2 may contribute to the increased rate of apoptosis of neurons in Down syndrome.

The chromosome 21 transcription factor ETS2 transactivates the beta-APP promoter: implications for Down syndrome

The gene that codes for beta-amyloid precursor protein (beta-APP), a protein centrally involved in senile plaque formation in Down syndrome (DS) and Alzheimer's disease (AD), is located on chromosome 21. In DS beta-APP expression is three- to fourfold higher than what is expected from the 1.5-fold increased gene load, suggesting that other genes on chromosome 21 directly or indirectly can further up-regulate beta-APP. Here we show that the chromosome 21 transcription factor ETS2 transactivates the beta-APP gene via specific Ets binding sites in the beta-APP promoter and, in this respect, cooperates with the transcription factor complex AP1. We further show that brains and primary neuronal cultures from Ets2 transgenic mice, as well as 3T3 fibroblasts that overexpress ETS2, display molecular abnormalities also seen in DS, such as elevated expression of beta-APP protein, an increase in presenilin-1 and increased beta-amyloid production. We conclude that ETS2 is a transcriptional regulator of beta-APP and that overexpression of ETS2 in DS may play a role in the pathogenesis of the brain abnormalities in DS and possibly AD.

ETS2 overexpression in transgenic models and in Down syndrome predisposes to apoptosis via the p53 pathway

ETS2 is a transcription factor encoded by a gene on human chromosome 21 and alterations in its expression have been implicated in the pathophysiological features of Down syndrome (DS). This study demonstrates that overexpression of ETS2 results in apoptosis. This is shown in a number of circumstances, including ETS2-overexpressing transgenic mice and cell lines and in cells from subjects with DS. Indeed we report for the first time that the ETS2 overexpression transgenic mouse develops a smaller thymus and lymphocyte abnormalities similar to that observed in DS. In all circumstances of ETS2 overexpression, the increased apoptosis correlated with increased p53 and alterations in downstream factors in the p53 pathway. In the human HeLa cancer cell line, transfection with functional p53 enables ETS2 overexpression to induce apoptosis. Furthermore, crossing the ETS2 transgenic mice with p53(-/-) mice genetically rescued the thymic apoptosis phenotype. Therefore, we conclude that overexpression of human chromosome 21-encoded ETS2 induces apoptosis that is dependent on p53. These results have important consequences for understanding DS and oncogenesis and may provide new insights into therapeutic interventions.

Transformation induced by Ewing's sarcoma associated EWS/FLI-1 is suppressed by KRAB/FLI-1

Ewing's sarcoma is a childhood bone tumour with poor prognosis, most commonly associated with a t(11;22)(q24;q12) reciprocal translocation that fuses the EWS and FLI-1 genes, resulting in the production of an aberrant chimeric transcription factor EWS/FLI-1. To elucidate the mechanisms by which EWS/FLI-1 mediates transformation in mouse models, we have generated a murine Ews/Fli-1 fusion protein. We demonstrate that this protein transforms fibroblast cells in vitro similar to human EWS/FLI-1 as demonstrated by serum and anchorage-independent growth, the formation of tumours in nude mice and elevation of the oncogenic marker c-myc. Furthermore, transformation of these cells was inhibited by a specific repressor, KRAB/FLI-1. The KRAB/FLI-1 repressor also suppressed the tumorigenic phenotype of a human Ewing's sarcoma cell line. These findings suggest that the transformed phenotype of Ewing's sarcoma cells can be reversed by using the sequence-specific FLI-1-DNA-binding domain to target a gene repressor domain. The inhibition of EWS/FLI-1 is the first demonstration of the KRAB domain suppressing the action of an ETS factor. This approach provides potential avenues for the elucidation of the biological mechanisms of EWS/FLI-1 oncogenesis and the development of novel therapeutic strategies.

A novel member of the STOMATIN/EPB72/mec-2 family, stomatin-like 2 (STOML2), is ubiquitously expressed and localizes to HSA chromosome 9p13.1

A cDNA encoding a novel second member of the Band7/stomatin-like/SPFH domain family in humans designated stomatin-like 2 (STOML2) has been isolated using the technique of cDNA Representational Difference Analysis. The STOML2 cDNA encoded a 356 amino acid residue polypeptide with a predicted molecular weight of 38.5 kDa. The predicted polypeptide sequence of STOML2 could be delineated into three major domains: an N-terminal alpha-helical region; a domain with significant similarity to a 172 amino acid region of the HSA stomatin polypeptide, composed of an alternating alpha-helical and beta-sheet structure and a C-terminal domain that was mostly alpha-helical. The stomatin-like domain was observed in 51 other proteins with potentially diverse functions. Based on its homology to stomatin, STOML2 was predicted to be cytoplasmically located. However, unlike most of the other proteins containing stomatin-like domains, the predicted STOML2 polypeptide does not contain a transmembrane region although the presence of N-myristoylation sites suggest that it has the potential to be membrane-associated. Northern blot analysis of a panel of poly(A)(+) mRNA from normal human adult tissues showed that a single 1.3-kb mRNA transcript encoding STOML2 was ubiquitously expressed, with relatively higher levels in skeletal muscle and heart compared to other tissues. Comparison of the STOML2 cDNA sequence with human genomic DNA indicated that the gene encoding STOML2 was 3,250 bp long and consisted of ten exons interrupted by nine introns. We have mapped STOML2 to HSA chromosome 9p13.1, a region that is rearranged in some cancers and thought to contain the gene responsible for acromesomelic dysplasia.

Gene targeting of Desrt, a novel ARID class DNA-binding protein, causes growth retardation and abnormal development of reproductive organs

We have cloned and characterized a novel murine DNA-binding protein Desrt, with a motif characteristic of the ARID (A-T rich interaction domain) family of transcription factors. The Desrt gene encodes an 83-kD protein that is shown to bind DNA and is widely expressed in adult tissues. To examine the in vivo function of Desrt, we have generated mice with a targeted mutation in the ARID domain of Desrt. Homozygous mutants have reduced viability, pronounced growth retardation, and a high incidence of abnormalities of the female and male reproductive organs including cryptorchidism. This may thus serve as a model to dissect the mechanisms involved in the development of the reproductive tract including testicular descent. Gene-targeted mice also display a reduction in the thickness of the zona reticularis of the adrenal gland and transient aberrations of the T and B cell compartments of primary lymphoid organs. These data show that this novel DNA-binding protein, Desrt, has a nonredundant function during growth and in the development of the reproductive system.

The soluble murine type I interferon receptor Ifnar-2 is present in serum, is independently regulated, and has both agonistic and antagonistic properties

The ability to modify responses to type I interferons (IFNs) could alter processes such as hematopoiesis and immunity, which involve endogenous IFNs and responses to exogenous IFNs. The data presented here support a significant role for a recently identified soluble isoform of the murine type I IFN receptor, muIfnar-2a, as an efficient regulator of IFN responses. The messenger RNA (mRNA) transcript encoding muIfnar-2a is generally more abundant than that encoding the transmembrane isoform, muIfnar-2c. Furthermore, the ratio of muIfnar-2a:2c transcripts varied from more than 10:1 in the liver and other organs to less than 1:1 in bone-marrow macrophages, indicating independent regulation of the 2 transcripts encoding receptor isoforms and suggesting that the soluble muIfnar-2a levels are biologically relevant in some organs. Western blot analysis showed that soluble muIfnar-2 was present at high levels in murine serum and other biologic fluids and bound type I IFN. Recombinant muIfnar-2a competitively inhibited the activity of both IFNalpha and beta in reporter assays using the L929 cell line and in antiproliferative and antiviral assays using primary cells. Surprisingly, using primary thymocytes from Ifnar-2(-/-) mice, recombinant muIfnar-2a formed a complex with IFN alpha or beta and muIfnar-1 at the cell surface and transmitted an antiproliferative signal. These data indicate potential dual actions of soluble muIfnar-2 and imply that a signal can be transduced through the Ifnar-1 chain of the receptor complex in the absence of the cytoplasmic domain of Ifnar-2. Therefore, our results suggest that soluble Ifnar-2 is an important regulator of endogenous and systemically administered type I IFN.

Type I interferons mediate the lipopolysaccharide induction of macrophage cyclin D2

Lipopolysaccharide (LPS) is a powerful macrophage-activating agent and antimitogen. We recently showed that LPS unexpectedly induces cyclin D2 in macrophages. Since LPS stimulates macrophages to produce autocrine-acting cytokines, we examined whether LPS induction of cyclin D2 was mediated by one such type of cytokine, type I interferons (IFN). We report that bone marrow-derived macrophages (BMM) lacking a component of the type I interferon receptor (IFNAR-1) do not express cyclin D2 mRNA or protein in response to LPS stimulation (0.01-1 microg/ml for 7-30 h). Consistent with this result, addition of anti-IFN-alpha/beta neutralizing antibodies reduced levels of LPS-stimulated cyclin D2 in normal BMM. Furthermore, IFN-alpha alone induced cyclin D2 mRNA and protein in normal BMM. Thus, we have identified a new role for type I IFN in macrophages, namely, as essential mediators of LPS-stimulated cyclin D2 expression.

SOCS1 is a critical inhibitor of interferon gamma signaling and prevents the potentially fatal neonatal actions of this cytokine

Mice lacking suppressor of cytokine signaling-1 (SOCS1) develop a complex fatal neonatal disease. In this study, SOCS1-/- mice were shown to exhibit excessive responses typical of those induced by interferon gamma (IFNgamma), were hyperresponsive to viral infection, and yielded macrophages with an enhanced IFNgamma-dependent capacity to kill L. major parasites. The complex disease in SOCS1-/- mice was prevented by administration of anti-IFNgamma antibodies and did not occur in SOCS1-/- mice also lacking the IFNgamma gene. Although IFNgamma is essential for resistance to a variety of infections, the potential toxic action of IFNgamma, particularly in neonatal mice, appears to require regulation. Our data indicate that SOCS1 is a key modulator of IFNgamma action, allowing the protective effects of this cytokine to occur without the risk of associated pathological responses.

The role of Ets-1 in mast cell granulocyte-macrophage colony-stimulating factor expression and activation

Ets-1 is a transcription factor with restricted expression in lymphocytes, and it has been implicated in the regulation of T cell genes such as TCR alpha, TCR beta, CD4, IL-2, and TNF-alpha. We show in this study that Ets-1 is also expressed in some mast cells constitutively and can be induced in primary mast cells with stimuli that activate mast cells. We also show that Ets-1 plays a role in the regulation of granulocyte-macrophage CSF (GM-CSF), a cytokine expressed by activated mast cells. We have characterized a murine growth factor-independent mast cell line, FMP6-, derived from a factor-dependent cell line, FMP1.6. FMP6- has acquired a distinct connective tissue mast cell-like phenotype, as characterized by the expression of mast cell proteases MMCP-4 and MMCP-6, expression of IL-12, and the down-regulation of IL-4. The parental FMP1.6 cell line displays a mucosal mast cell-like phenotype. FMP6- cells have increased Ets-1 expression and achieve growth-factor independence by the autocrine production of GM-CSF and IL-3. Transient transfection of an Ets-1 expression construct in FMP6- cells results in transactivation of a GM-CSF reporter, while a point mutation in the consensus Ets binding site in the conserved lymphokine element, CLE0, abolishes Ets-1 transactivation. Importantly, antisense Ets-1 demonstrates an ability to repress the activity of the GM-CSF reporter. These data suggest a role for Ets-1 in mast cell growth regulation and activation, and because of the central role of mast cells in inflammatory processes, such as asthma and rheumatoid arthritis, they identify Ets-1 as potentially contributing to the pathophysiology of such diseases.

Mice with a homozygous null mutation for the most abundant glutathione peroxidase, Gpx1, show increased susceptibility to the oxidative stress-inducing agents paraquat and hydrogen peroxide

Glutathione peroxidases have been thought to function in cellular antioxidant defense. However, some recent studies on Gpx1 knockout (-/-) mice have failed to show a role for Gpx1 under conditions of oxidative stress such as hyperbaric oxygen and the exposure of eye lenses to high levels of H2O2. These findings have, unexpectedly, raised the issue of the role of Gpx1, especially under conditions of oxidative stress. Here we demonstrate a role for Gpx1 in protection against oxidative stress by showing that Gpx1 (-/-) mice are highly sensitive to the oxidant paraquat. Lethality was already detected within 24 h in mice exposed to paraquat at 10 mg.kg-1 (approximately (1)/(7) the LD50 of wild-type controls). The effects of paraquat were dose-related. In the 30 mg.kg-1-treated group, 100% of mice died within 5 h, whereas the controls showed no evidence of toxicity. We further demonstrate that paraquat transcriptionally up-regulates Gpx1 in normal cells, reinforcing a role for Gpx1 in protection against paraquat toxicity. Finally, we show that cortical neurons from Gpx1 (-/-) mice are more susceptible to H2O2; 30% of neurons from Gpx1 (-/-) mice were killed when exposed to 65 microM H2O2, whereas the wild-type controls were unaffected. These data establish a function for Gpx1 in protection against some oxidative stressors and in protection of neurons against H2O2. Further, they emphasize the need to elucidate the role of Gpx1 in protection against different oxidative stressors and in different disease states and suggest that Gpx1 (-/-) mice may be valuable for studying the role of H2O2 in neurodegenerative disorders.

Down syndrome and mouse models

The past year has seen major advancements in the characterisation of the Ts65Dn mouse model (which is now known to display many features of Down syndrome). A newer model that is trisomic for the region 21 q22.2--previously called 'Down syndrome' region--has been generated and these mice display behavioural and learning defects. Mutations in the genes Minibrain and SOD1 have been implicated in the development of learning defects in Down syndrome and many new genes from human chromosome 21 are being cloned, which should result in the genesis of other models that phenocopy one or more pathologies of the syndrome.

Animal models in the study of the biological function of genes on human chromosome 21 and their role in the pathophysiology of Down syndrome

Human chromosome 21 is the smallest human autosome and many important genetic/familial disorders map to this chromosome, e.g., familial amyotrophic lateral sclerosis (FALS), Down syndrome, Alzheimer's disease and some cases of Ewings sarcoma. Hence, the identification of genes localised to this chromosome and studies on their normal biological function and their role in disease is gaining momentum. The use of animal models to generate gain- and loss-of-function mutations is an important element of these studies on functionality/pathology and has yielded powerful insights. However, no animal model has yet been generated that exactly models any of the disorders associated with this chromosome. The major utility of the animal models has been to illuminate the biological functions of genes and the causation of pathophysiology of diseases associated with genes on this chromosome.

Cloning and characterization of soluble and transmembrane isoforms of a novel component of the murine type I interferon receptor, IFNAR 2

This report describes the cloning of cDNAs encoding transmembrane and soluble isoforms of a novel chain of the murine type I interferon (IFN) receptor and characterization of its capability to bind ligand and transduce signals. The transmembrane receptor (murine IFNAR 2c) has an extracellular domain of 215 amino acids and an intracellular domain of 250 amino acids, with 48% amino acid and 71% nucleotide identity with human IFNAR 2c. The cDNA for the soluble murine receptor (IFNAR 2a) encodes a 221-amino acid polypeptide identical to the first 210 amino acids of IFNAR 2c plus a novel 11 amino acids. Northern blot analyses show that murine IFNAR 2 is expressed as two transcripts of 4 kilobases encoding the transmembrane isoform and 1.5 kilobases encoding the more abundant soluble isoform. Studies using primary murine cells that lack IFNAR 1 show that IFNAR 2 is expressed, and cells bind type I IFN ligand, but do not transduce signals as detected by electrophoretic mobility shift assays of ISGF3 or GAF complexes binding to their cognate oligonucleotides. These cells show no effects on the ability of IFNgamma to activate these complexes. These studies demonstrate that the IFNAR 2 transmembrane (2c) and soluble (2a) isoforms are conserved between the human and mouse and that IFNAR 2c has intrinsic ligand binding activity, but no intrinsic signal transducing activity as measured in this study.

A type I interferon signaling factor, ISF21, encoded on chromosome 21 is distinct from receptor components and their down-regulation and Is necessary for transcriptional activation of interferon-regulated genes

The type I interferons (IFNs) are a family of cytokines, comprising at least 17 subtypes, which exert pleiotropic actions by interaction with a multi-component cell surface receptor and at least one well characterized signal transduction pathway involving JAK/STAT (Janus kinase/signal transducer and activator of transcription) proteins. In a previous report, we showed that a signaling factor, encoded by a gene located on the distal portion of chromosome 21, distinct from the IFNAR-1 receptor, was necessary for 2'-5'-oligoadenylate synthetase activity and antiviral responses, but not for high affinity ligand binding. In the present studies using hybrid Chinese hamster ovary cell lines containing portions of human chromosome 21, we show that the type I IFN signaling molecule, designated herein as ISF21, is distinct from the second receptor component, IFNAR-2, which is expressed in signaling and non-signaling cell lines. The location of the gene encoding ISF21 is narrowed to a region between the 10;21 and the r21 breakpoints, importantly eliminating the Mx gene located at 21q22.3 (the product of which is involved in IFN-induced antiviral responses) as a candidate for the signaling factor. To characterize the action of this factor in the type I IFN signaling pathway, we show that it acts independently of receptor down-regulation following ligand binding, both of which occur equally in the presence or absence of the factor. In addition, we demonstrate that ISF21 is necessary for transcriptional activation of 2'-5'-oligoadenylate synthetase, 6-16, and guanylate-binding protein gene promoter reporter constructs, which are mediated by several signaling pathways. ISF21 represents a novel factor as the localization to chromosome 21, and the data presented in this study exclude any of the known type I IFN signal-transducing molecules.

Binding of interferon-alpha and -beta to a component of the human type I interferon receptor expressed in simian cells

The type I interferons (IFNs) are a family of homologous cytokines that compete for receptor binding. Past experiments with a cloned human IFN-alpha receptor component (designated herein as HuIFNAR-1) transfected into different cell backgrounds have given contradictory results in terms of binding and signalling after exposure of cells to different human type I IFNs. In order to investigate the binding specificity of human type I IFN subtypes to HuIFNAR-1, a cDNA encoding HuIFNAR-1 was transfected into simian COS cells. HuIFNAR-1 expression in COS cells, which was confirmed by Northern blot analysis, resulted in increased binding of 125I-labelled HuIFN-alpha 2 and -beta. These data support the participation of this receptor component in ligand binding, probably in association with other receptor components.

Endogenous IFN-alpha beta suppresses colony-stimulating factor (CSF)-1-stimulated macrophage DNA synthesis and mediates inhibitory effects of lipopolysaccharide and TNF-alpha

Murine bone marrow-derived macrophages (BMM) are widely used as a suitable model to study the proliferative response to macrophage-CSF or CSF-1. We report here that the amount of DNA synthesis observed in BMM cultures in response to CSF-1 can be masked quite significantly by low levels of IFN-alpha beta produced in the cultures. It was found that Ab to IFN-alpha beta could enhance the proliferative response in CSF-treated BMM that were able to respond to endogenous IFN-alpha beta; however, BMM from mice lacking a component of the type I IFN receptor did not show any enhancement of CSF-1-dependent DNA synthesis on addition of the Ab. While DNA synthesis in CSF-1-stimulated BMM from normal mice was also very sensitive to the inhibitory actions of very low concentrations of added IFN-alpha beta, DNA synthesis in BMM from the "knockout" mice was not, indicating that the type I IFN receptor component containing the null mutation was essential for signal transduction. Previously it was shown that bacterial LPS, TNF-alpha, IFN-gamma, and cAMP could all inhibit CSF-1-stimulated BMM DNA synthesis and proliferation. Using the combined approach of blocking IFN-alpha beta Ab and the IFN receptor "knockout" mice, it was found here that the growth-inhibitory effects of LPS and TNF-alpha are due, to a significant extent, to endogenous IFN-alpha beta, whereas those of IFN-gamma and cAMP occur by a different mechanism. it is proposed that the type I IFN receptor (IFNAR 1) "knockout" mice may be useful in delineating some of the in vivo actions of CSF-1, LPS, TNF-alpha, and possibly other agents.

Endogenous IFN-alpha beta suppresses colony-stimulating factor (CSF)-1-stimulated macrophage DNA synthesis and mediates inhibitory effects of lipopolysaccharide and TNF-alpha

Murine bone marrow-derived macrophages (BMM) are widely used as a suitable model to study the proliferative response to macrophage-CSF or CSF-1. We report here that the amount of DNA synthesis observed in BMM cultures in response to CSF-1 can be masked quite significantly by low levels of IFN-alpha beta produced in the cultures. It was found that Ab to IFN-alpha beta could enhance the proliferative response in CSF-treated BMM that were able to respond to endogenous IFN-alpha beta; however, BMM from mice lacking a component of the type I IFN receptor did not show any enhancement of CSF-1-dependent DNA synthesis on addition of the Ab. While DNA synthesis in CSF-1-stimulated BMM from normal mice was also very sensitive to the inhibitory actions of very low concentrations of added IFN-alpha beta, DNA synthesis in BMM from the "knockout" mice was not, indicating that the type I IFN receptor component containing the null mutation was essential for signal transduction. Previously it was shown that bacterial LPS, TNF-alpha, IFN-gamma, and cAMP could all inhibit CSF-1-stimulated BMM DNA synthesis and proliferation. Using the combined approach of blocking IFN-alpha beta Ab and the IFN receptor "knockout" mice, it was found here that the growth-inhibitory effects of LPS and TNF-alpha are due, to a significant extent, to endogenous IFN-alpha beta, whereas those of IFN-gamma and cAMP occur by a different mechanism. it is proposed that the type I IFN receptor (IFNAR 1) "knockout" mice may be useful in delineating some of the in vivo actions of CSF-1, LPS, TNF-alpha, and possibly other agents.

Aberrant activation of JAK/STAT pathway components in response to G-CSF, interferon-alpha/beta and interferon-gamma in NFS-60 cells

There is evidence that the cellular responses to cytokines, such as granulocyte colony stimulating factor (G-CSF) and interferons, depend on prior activation of components of the JAK/STAT signalling pathway. We report here that the myeloid cell line NFS-60 shows aberrant JAK/STAT signalling yet elicits expected biological responses to G-CSF and interferons-alpha/beta and gamma. Instead of increased phosphorylation of JAK1 and JAK2 in response to G-CSF and interferon-gamma, and JAK1 and Tyk2 in response to interferon-alpha/beta, we observed only an increase of phosphorylation of Tyk2 in response to all of these cytokines in NFS-60 cells. The subset of STAT proteins being activated in response to these cytokines was unusual as well. G-CSF activated STAT3 and STAT5A, whereas interferons activated, in addition to STAT1 and STAT5 other, as yet unidentified, DNA binding proteins. However, NFS-60 cells show normal biological responses to these cytokines, such as proliferation in response to G-CSF, and reduction of proliferation, induction of an anti-viral response and induction of specific genes in response to interferons.

A null mutation in the gene encoding a type I interferon receptor component eliminates antiproliferative and antiviral responses to interferons alpha and beta and alters macrophage responses

To examine the in vivo role(s) of type I interferons (IFNs) and to determine the role of a component of the type I IFN receptor (IFNAR1) in mediating responses to these IFNs, we generated mice with a null mutation (-/-) in the IFNAR1 gene. Despite compelling evidence for modulation of cell proliferation and differentiation by type I IFNs, there were no gross signs of abnormal fetal development or morphological changes in adult IFNAR1-/- mice. However, abnormalities of hemopoietic cells were detected in IFNAR1 -/- mice. Elevated levels of myeloid lineage cells were detected in peripheral blood and bone marrow by staining with Mac-1 and Gr-1 antibodies. Furthermore, bone marrow macrophages from IFNAR1 -/- mice showed abnormal responses to colony-stimulating factor 1 and lipopolysaccharide. IFNAR1 -/- mice were highly susceptible to viral infection: viral titers were undetected 24 hr after infection of IFNAR1 +/+ mice but were extremely high in organs of IFNAR1 -/- mice, demonstrating that the type I IFN system is a major acute antiviral defence. In cell lines derived from IFNAR1 -/- mice, there was no signaling in response to IFN-alpha or -beta as measured by induction of 2'-5' oligoadenylate synthetase, antiviral, or antiproliferative responses. Importantly, these studies demonstrate that type I IFNs function in the development and responses of myeloid lineage cells, particularly macrophages, and that the IFNAR1 receptor component is essential for antiproliferative and antiviral responses to IFN-alpha and -beta.

Human ERG is a proto-oncogene with mitogenic and transforming activity

The ETS related gene, ERG, is one of 20 or more genes belonging to the ETS family of transcription factors. Translocation of the ERG gene t(21;22) results in the chimeric fusion transcript seen in approximately 10% of Ewings sarcomas. In addition, recent studies have shown that a reciprocal translocation t(21;16) of ERG gives rise to two aberrant transcripts seen in some forms of acute myeloid leukaemia. In vitro studies have linked the up regulation of ERG expression with stromal cell independence in erythroleukemic clones and shown that the ERG related genes ETS1 and ETS2 have a mitogenic and transforming activity when overexpressed in NIH3T3 cells. Interestingly ERGB/FLI-1, which is also involved in Ewings sarcoma translocations and shares a very high sequence identify with ERG has been reported to be unable to transform NIH3T3 cells. In this study we investigate the effects of overexpression of ERG on cell proliferation, factor dependence, growth in soft agar and tumorigenesis in nude mice. An ERG expression construct with the human ERG2 cDNA driven by the sheep metallothionein la promoter (sMTERG) was transfected into NIH3T3 cells. Clonal cell lines overexpressing ERG were established. The cell lines became morphologically altered, grew in low serum and serum free media and gave rise to colonies in soft agar suspension. Furthermore, we demonstrate that after subcutaneous injection these clones grow as solid tumors in nude mice. These data demonstrate that c-ERG is a proto-oncogene capable of transforming NIH3T3 cells. Therefore, overexpression or inappropriate expression of ERG may contribute to oncogenesis.

Constitutive and virus-induced interferon production by peripheral blood leukocytes

The production of interferon-alpha (IFN-alpha) by normal human peripheral blood mononuclear cells (PBMNC) was studied using polyclonal antipeptide antibodies designed to react either with all IFN-alpha subtypes or with individual subtypes IFN-alpha 2 or IFN-alpha 4. In this study, we demonstrate the detection of intracellular IFN-alpha in PBMNC using immunofluorescence staining and flow-cytometric analysis. Virtually all cells of the PBMNC population were shown to produce IFN-alpha reactive with all three antisera after stimulation with Sendai virus. The immunofluorescence studies also demonstrated that IFN-alpha is produced by PBMNC in the absence of known viral stimulation but is not secreted in detectable levels. Double-labeling with specific monoclonal antibodies to T and B lymphocytes confirmed that the entire populations of these two cell types produce IFN-alpha, both constitutively and after virus induction. Polymorphonuclear cells (PMNC) isolated from Ficoll-Paque pellets were also shown to contain intracellular IFN-alpha, both before and after virus induction. The finding that all PBMNC produce IFN-alpha constitutively suggests that IFN-alpha may have important regulatory functions in situations other than during overt viral infections.

Decreased natural killer cell activity in endometriosis patients: relationship to disease pathogenesis

A number of reports have measured NK cell activity in patients with endometriosis with varied results. Therefore we have examined the NK activity of PBL from 44 gynecological patients undergoing laparoscopy. This analysis has demonstrated a significant reduction in NK activity only in more severe stages of endometriosis (stages III and IV) relative to patients with milder disease and controls. These data indicate that decreased NK activity is unlikely to be a primary etiological factor in the development of endometriosis but may indicate that decreased NK activity is related to the development of the more frequent and/or larger lesions characteristic of severe endometriosis. These data could indicate potential for immunotherapy of patients with advanced endometriosis by the upregulation of NK activity in vivo.

Immunolocalisation of interferon-alpha in hepatitis C patients and its correlation with response to interferon-alpha therapy

Localised interferon-alpha production was investigated in hepatitis C patients entered into a trial of interferon-alpha-2a therapy. Antibodies capable of reacting specifically with interferon-alpha-2, interferon-alpha-4 or with all interferon-alpha subtypes were used as immunohistochemical and immunofluorescence probes to study interferon-alpha production in liver biopsy tissue, and peripheral blood mononuclear cells prior to and after stimulation with Sendai virus. Measurement of cytoplasmic interferon-alpha, specifically interferon-alpha-2 and interferon-alpha-4, in peripheral blood mononuclear cells isolated from the hepatitis C patients and of total interferon-alpha secreted into culture supernatants by these cells showed interferon-alpha production similar to that of peripheral blood mononuclear cells isolated from normal individuals. Interferon-alpha-positive cells were observed in the infiltrating mononuclear cells of the liver biopsy tissue obtained from 8 of the 14 patients. Lymphocytes, fibroblasts, Kupffer cells, polymorphonuclear cells and monocytes stained positive for interferon-alpha, and specifically interferon-alpha-4, in all of the eight patients. The cytoplasm of hepatocytes also stained weakly positive in three of these patients. Interferon-alpha positive cells showed a good correlation with the degree of histological damage observed in the liver biopsies but not with presence of antibodies towards hepatitis C virus or levels of serum alanine aminotransferase measured prior to interferon-alpha-2a therapy. Interestingly, response to therapy seemed linked to local interferon-alpha production status. Those patients who responded best to therapy displayed no or only low levels of interferon-alpha positive cells in liver biopsy tissue. Thus patients with a lower activation of their endogenous interferon-alpha system may benefit from administration of exogenous interferon-alpha.

Role of interferons in the regulation of cell proliferation, differentiation, and development

There now appears to be evidence to support the view that the type I IFNs are naturally produced negative regulators of growth that also modify cell differentiation. Consistent with this, it appears that the ability to produce and respond to IFN is suppressed in early embryonic development when cell proliferation and differentiation are essential. In the later stages of fetal development, IFN production is de-repressed, and cells show increased sensitivity to IFN, which may be important in regulating cell proliferation and/or differentiation processes or the interaction between fetal and maternal tissues. Interestingly, the IFN system can also be suppressed in disease states such as the development of tumours or in the establishment of a (chronic) viral infection. Therefore, understanding the developmental regulation of the IFN system may be important to understanding and controlling the IFN system in disease. More extensive studies of the developmental stage and tissue-specific expression of type I IFNs and their receptors are necessary, as well as more direct in vivo experiments to further elucidate the role of the IFN system in reproduction and development.

Detection of interferon-alpha expression by PCR in patients with chronic hepatitis C and hepatitis non-A, non-B

The polymerase chain reaction (PCR) was used to examine expression of interferon-alpha (IFN A) genes in general and the expression of messenger RNA (mRNA) encoding the subtypes IFN-alpha-2 and IFN-alpha-4 in blood and liver biopsy samples from patients with chronic hepatitis C or hepatitis non-A, non-B (HC/HNANB) infection entered into a trial of IFN-alpha-2a therapy. Peripheral blood mononuclear cells (PBMC) from healthy controls and HC/HNANB infected patients were studied for their capacity to produce transcripts encoding IFN-alpha after stimulation with Sendai virus. Expression at the level of mRNA for IFN A and the subtypes IFN A2 and A4 was detected in both controls and HC/HNANB infected patients PBMC and no significant difference was seen in expression of IFN A transcripts or level of total IFN-alpha secreted into culture supernatants between controls and patients. Interferon A, and specifically IFN A2 and IFN A4 transcripts were detected in a high proportion of liver biopsies from patients with HC/HNANB infection. The presence of IFN A mRNA (and specifically IFN A2 and IFN A4) showed no correlation to histological improvement nor response to therapy. The use of PCR to detect those IFN A genes that are not expressed, thereby identifying subtypes that may be lacking, could be the key to the choice of IFN-alpha subtypes that are used for effective therapy.

Detection of cells producing murine interferon-alpha using antipeptide antibodies

The purpose of this study was to produce antibodies which could be used to investigate the expression of murine (Mu)IFN-alpha. Rabbits were immunized with a peptide, corresponding to the 15 COOH-terminal amino acids of MuIFN-alpha-1, conjugated to keyhole limpet haemocyanin (KLH), and the resulting antipeptide antibodies were identified by indirect ELISA. Antipeptide antibodies were purified from rabbit immune sera by immunoadsorption to peptide immobilized on nitrocellulose and any remaining antibodies to KLH removed by immunoadsorption to KLH-Sepharose. The characterization of the antipeptide antibodies by ELISA, immunoprecipitation, affinity chromatography and immunofluorescence demonstrated that the antibodies recognize the peptide immunogen and the native IFN-alpha molecule. Using these antibodies for immunofluorescence staining and flow cytometric analyses of stained cells, we have shown that unstimulated murine spleen cells produce IFN-alpha. This finding is in agreement with the recent demonstration of constitutive IFN-alpha production by unstimulated human leucocytes and has important implications for the functions of interferons. The production, characterization and use of antipeptide antibodies as described herein may also have broader application for studies of the expression of other cytokines.

A gene on human chromosome 21 located in the region 21q22.2 to 21q22.3 encodes a factor necessary for signal transduction and antiviral response to type I interferons

The type I interferons (IFNs) are a family of multifunctional cytokines which includes the 15 IFN alpha subtypes and IFN beta. These IFNs compete for binding to cell surface receptors. However, murine cells transfected with a cDNA for a human IFN alpha receptor (IFNAR) developed an antiviral response only to human IFN alpha B, but not to human IFN alpha 2 nor -beta(1). In this study we show, using a panel of CHO-human chromosome 21 hybrid cell lines which all express IFNAR, that only those containing the region 21q22.2 to 21q22.3 transduce signals for IFN responses. Two such hybrid cell lines responded to IFNs alpha 2, -alpha B and -beta by induction of 2'-5' oligoadenylate synthetase and resistance to viral infection. Other hybrid cell lines, that lacked the region 21q22.2-3, failed to transduce signals as above; even though they expressed IFNAR and bound human IFN alpha 2, -alpha B, and -beta. These data demonstrate that a gene(s) located in the region 21q22.2-3 encodes a factor(s) which is necessary for signaling but does not influence ligand binding. This factor is not the cofactor required for IFN gamma signaling which is located in the region 21p to 21q22.1(2).

Structure-function analysis of human IFN-alpha. Mapping of a conformational epitope by homologue scanning

The purpose of this study was to map a conformational epitope of a mAb that binds the IFN subtype alpha 4a. Binding of this mAb, designated I-4-A, to IFN-alpha 4a does not block receptor binding, but does neutralize biologic activity by inhibition of signal transduction. A novel strategy was developed, termed homologue scanning, which uses template-coupled polymerase chain reaction to generate hybrid molecules consisting of part (N-terminus) of the reactive IFN-alpha 4a subtype to locate the epitope, and the remainder of the nonreactive IFN-alpha 14 subtype to provide the overall conformation of an IFN-alpha molecule. Hybrid molecules were expressed as 35S-methionine-labeled proteins and tested for immunoreactivity by Western blotting and antiviral activity by cytopathic effect reduction bioassays. Unless an entire IFN-alpha (hybrid) molecule was formed, immunoreactivity and biologic activity were lost, indicating the importance of the C-terminus for correct folding of IFN-alpha molecules. The epitope for I-4-A was localized to the N-terminal 23 residues of IFN-alpha 4a. Furthermore, the immunoreactivity of IFN-alpha 4a analogues, with alterations in the putative receptor-binding region of IFN-alpha 4a residues 30 to 40 was unaffected, in contrast to the biologic activity that was reduced by several orders of magnitude. Thus, the N-terminal 23 residues of IFN-alpha 4a, which probably are not involved in receptor binding, may be important for other interactions of the receptor-bound ligand. In general terms, the novel approach of homologue scanning, using template-coupled PCR to facilitate the generation of hybrid proteins, will have broad application in the mapping of conformational epitopes of proteins that are members of a homologous family. The ability to identify conformational epitopes will increase our understanding important interactions of proteins with antibodies, receptors, and other macromolecules.

Structure-function analysis of human IFN-alpha. Mapping of a conformational epitope by homologue scanning

The purpose of this study was to map a conformational epitope of a mAb that binds the IFN subtype alpha 4a. Binding of this mAb, designated I-4-A, to IFN-alpha 4a does not block receptor binding, but does neutralize biologic activity by inhibition of signal transduction. A novel strategy was developed, termed homologue scanning, which uses template-coupled polymerase chain reaction to generate hybrid molecules consisting of part (N-terminus) of the reactive IFN-alpha 4a subtype to locate the epitope, and the remainder of the nonreactive IFN-alpha 14 subtype to provide the overall conformation of an IFN-alpha molecule. Hybrid molecules were expressed as 35S-methionine-labeled proteins and tested for immunoreactivity by Western blotting and antiviral activity by cytopathic effect reduction bioassays. Unless an entire IFN-alpha (hybrid) molecule was formed, immunoreactivity and biologic activity were lost, indicating the importance of the C-terminus for correct folding of IFN-alpha molecules. The epitope for I-4-A was localized to the N-terminal 23 residues of IFN-alpha 4a. Furthermore, the immunoreactivity of IFN-alpha 4a analogues, with alterations in the putative receptor-binding region of IFN-alpha 4a residues 30 to 40 was unaffected, in contrast to the biologic activity that was reduced by several orders of magnitude. Thus, the N-terminal 23 residues of IFN-alpha 4a, which probably are not involved in receptor binding, may be important for other interactions of the receptor-bound ligand. In general terms, the novel approach of homologue scanning, using template-coupled PCR to facilitate the generation of hybrid proteins, will have broad application in the mapping of conformational epitopes of proteins that are members of a homologous family. The ability to identify conformational epitopes will increase our understanding important interactions of proteins with antibodies, receptors, and other macromolecules.

Molecular detection of interferon-alpha expression in multiple sclerosis brain

The demonstration of intermittent interferonaemia in patients with multiple sclerosis prompted a molecular analysis of brain tissue for expression of interferon-alpha genes. A sensitive method was developed based on the polymerase chain reaction. Primer sets were used that could amplify all interferons-alpha or two particular subtypes, interferon-alpha 2 and interferon-alpha 4. The procedure was successful in detecting expression of interferons-alpha in brain and non-brain tissues in most patients with multiple sclerosis. However, expression was demonstrable also in a similar proportion of patients with other neural diseases, and patients with other illnesses. The data indicate that there can be constitutive expression of interferons-alpha in brain tissue, but the possibility that this becomes amplified in multiple sclerosis was not revealed by this study.

Expression of large intestinal mucin antigen (LIMA) epitopes in the normal and neoplastic gastrointestinal tract

This study has identified the expression in normal and neoplastic gastrointestinal (GI) tract of epitopes on the colonic mucin LIMA (large intestinal mucin antigen), which are unique markers of normal colonic differentiation. Six anti-LIMA monoclonal antibodies (MAbs) (22D4, 9B5, 2C3, 23B2, 46A2, and 10B3) were studied immunohistochemically in normal GI tract, colorectal adenomas, and colorectal and gastric cancers. All MAbs showed specificities consistent with distinct epitopes, five of which were neuraminidase-resistant and four periodate-sensitive. Each reacted with mucin in 60-100 per cent normal colons--MAbs 10B3 and 23B2 also with small intestinal mucin--but none with gastric mucin. Five MAbs showed crypt and regional gradients in normal colon, MAbs, 22D4, 9B5, and 2C3 showing a hierarchy of reactivities in the crypt. Individual adenomas showed decreasing goblet cell (GC) LIMA expression with increasing size. However, 30 per cent of familial adenomatous polyposis (FAP) patients had generalized background losses of 9B5 and 2C3 GC reactivity, retaining 22D4, whilst 44 per cent of non-FAP patients lost 22D4 GC reactivity, regaining 9B5 and 2C3--evidence for polymorphism of mucin expression. All colorectal cancers expressed LIMA epitopes (frequently weaker than normal), and three MAbs (22D4, 9B5, and 2C3) showed deeper than normal staining in adjacent crypts. Eighty-five per cent of gastric cancers also expressed LIMA epitopes.

Differentiation-associated changes in mucin glycoprotein antigenicity in mucosa adjacent to rare gastrointestinal tract tumours of non-mucosal origin

We have investigated changes in mucin antigenicity and morphology in the perineoplastic mucosa adjacent to rare, predominantly non-mucosal gastrointestinal (GI) tumours. Twenty-nine tumours of small and large intestine, including primary mesenchymal and ectodermal tumours, were examined immunohistochemically using 11 monoclonal antibodies (MAbs) raised against SIMA and LIMA (small and large intestinal mucin antigens). Non-epithelial GI tumours were essentially non-reactive, while adjacent mucosa showed altered mucin expression and morphology, in particular, features of transitional mucosa (TM). Combinations of different SIMA epitopes were detected adjacent to all colorectal tumours, and, similarly, LIMA epitopes adjacent to small intestinal tumours. Specific patterns adjacent to certain tumours may reflect influences of factors produced by individual tumours on mucin composition. Altered antigenicity and morphology in TM thus appear to be reactive changes in response to a wide range of GI tumours, presumably as a consequence of factors secreted by the tumour and/or a host response to the tumour.

Post-transcriptional regulation of interferon-alpha 4 subtype production by lymphoblastoid cells

The constitutive production of interferon-alpha (IFN-alpha) subtypes by the lymphoblastoid cell lines, Namalwa, Daudi and Raji, was investigated using sensitive and semi-quantitative flow cytometric techniques. Further, we sought to determine whether the previously described failure of these cell lines to produce IFN-alpha-4 was a result of the deletion of the IFN A4 gene. Cytoplasmic production of IFN-alpha-2 and IFN-alpha-4 was assessed using IFN-alpha subtype-specific antipeptide antibodies and FITC-labelled secondary antibodies in indirect immunofluorescence-flow cytometry studies. The constitutive production of IFN-alpha-2 was detected in all three cell lines. Significant increases in fluorescence representing increased production of IFN-alpha-2 and possibly other IFN-alpha subtypes were detected after induction by Sendai virus. Approximately 100 per cent of cells in the Namalwa, Daudi and Raji cell populations contained IFN-alpha-2 before and after induction. However, no cells from the same cell populations contained the IFN-alpha-4 subtype. Analysis of genomic DNA isolated from the lymphoblastoid cells using the Polymerase Chain Reaction (PCR) and oligonucleotide primers specific for IFN A2 or IFN A4 confirmed the presence of the genes encoding both IFN-alpha subtypes. Furthermore, using reverse transcriptase-PCR amplification, mRNAs for both IFN-alpha-2 and IFN-alpha-4 were detected. Therefore, in contrast to some leukaemias and derived cell lines where IFN A genes have been deleted, these cell lines of B cell lineage exhibit selective expression of IFN A genes, as a result of altered transcriptional/translational control of IFN-alpha expression.

The adenoma-carcinoma sequence in the colorectum--early appearance of a hierarchy of small intestinal mucin antigen (SIMA) epitopes and correlation with malignant potential

The colorectal adenoma-carcinoma sequence was examined in relation to the ectopic expression of the oncofoetal Small Intestinal Mucin Antigen (SIMA), to the development of morphologic changes in the adenoma and perineoplastic mucosa and to indices of malignant potential. Four anti-SIMA MAbs, which define a novel hierarchy of SIMA epitopes in the normal small intestine and adjacent to colorectal cancers, were used in a retrospective immunohistochemical study of Familial Adenomatous Polyposis (FAP, n = 183) and non-familial (n = 44) adenomas. Inappropriate expression of SIMA epitopes was first detected in mucosa adjacent to minute microadenomas larger than three glands, and with increase in size, in increasing amounts within adenomas themselves, but not with microadenomas smaller than three glands or regions of flat mucosa free of adenomas. SIMA epitope expressed in mucosa adjacent to adenomas preceded changes in perineoplastic morphology, which progressed with adenoma growth to resemble transitional mucosa (TM) adjacent to cancers. Thus, the onset of both SIMA expression and morphological changes in TM were consistent with reactive rather than pre-existing field change phenomena. The previously reported hierarchy of four SIMA epitopes (5C5, 3D4, 4D3, 6C5) was also consistently observed in the adenoma-carcinoma sequence, and applied to (i) the order of epitope detection, (ii) the number of positive adenomas and (iii) extent of staining; (iv) the height in the crypt and (v) distance from the adenoma to which epitopes were expressed in perineoplastic mucosa. These observations are consistent with a progression of changes in mucin composition with adenoma development. The percentage of positive adenomas and reactivity scores for each anti-SIMA MAb correlated with increasing adenoma size, degree of dysplasia and growth pattern. SIMA expression appears to predate the earliest reported oncogene and tumour suppressor gene changes, was persistent and increased throughout adenoma development. SIMA epitopes are thus markers of very early neoplastic change, whose expression correlates with malignant potential and may contribute to the accumulation of changes necessary for tumourigenesis.

Antiproliferative potencies of interferons on melanoma cell lines and xenografts: higher efficacy of interferon beta

BACKGROUND

Human melanomas have shown only limited responsiveness to clinical therapy with interferon (IFN).

PURPOSE

Our aim was to determine the most effective class of IFN for inhibiting growth of melanoma cells and to establish whether variation exists in response of various cell lines to different IFNs.

METHODS

We compared the direct antiproliferative effects of the type I IFN alpha-2b, IFN alpha-4a, and IFN-beta and the type II IFN-gamma on eight melanoma cell lines grown in vitro. We did this comparison by determining the concentration of each IFN that resulted in 50% growth inhibition, using the MTT [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium tetrazolium bromide] dye uptake method. We also tested IFN alpha-2a and IFN-beta for their ability to inhibit the growth of xenografts of the LiBr melanoma cell line in vivo in nude mice. Receptor binding was determined using [35S]methionine-labeled IFN alpha-4a, in competition with unlabeled IFN alpha-2b, IFN alpha-4a, and IFN-beta.

RESULTS

The melanoma cell lines differed markedly in their sensitivity to the IFNs tested: Five were sensitive to low concentrations (less than 30 pM) of IFN-beta, only one was sensitive to similar concentrations of IFN alpha-2b, and none were sensitive to IFN alpha-4a at concentrations up to 920 pM. For all cell lines, the antiproliferative potency of the type I IFNs was IFN-beta greater than IFN alpha-2b greater than IFN alpha-4a. IFN-gamma was less active than IFN-beta on all except one of the cell lines. Similarly, IFN-beta was more potent than IFN alpha-2a in inhibiting the growth of the LiBr xenograft in nude mice. Labeled IFN alpha-4a bound with high specificity in all four melanoma lines tested, and competitive binding experiments showed that the order of binding affinity (IFN-beta greater than IFN alpha-2b greater than IFN alpha-4a) correlated with the order of antiproliferative potency.

CONCLUSION

The finding that melanoma cell lines differ intrinsically in their sensitivity to IFNs may explain differences in clinical response. Our results suggest that IFN-beta may be the most effective IFN in the treatment of melanoma, although confirmation will require clinical trials involving large numbers of patients.

Different interactions of interferon-alpha subtypes at the surface of epithelial and lymphoid cells

The interaction of different interferon (IFN)-alpha subtypes with different cell types was investigated using a unique monoclonal antibody (MAb), I-4-A. This MAb reacts in immunoassays equally with IFN-alpha 2b and IFN-alpha 4a, but does not inhibit the binding of IFN to cell receptors. 125I-labeled I-4-A reacted with IFN-alpha 4a and IFN-alpha 2b bound to receptors on Daudi cells. However, in a "double assay" developed using Daudi cells to measure antiviral and antiproliferative activity, I-4-A neutralized both activities of IFN-alpha 4a, but neither of IFN-alpha 2b. Similarly, in studies on the activation of natural killer (NK) cells, I-4-A neutralized the effect of IFN-alpha 4a but not that of IFN-alpha 2b. In contrast, when cell lines other than lymphoid were studied, e.g., HEp 2 and WISH cells, I-4-A neutralized the antiviral activity of both IFN-alpha subtypes. The neutralization of one IFN-alpha subtype but not another on lymphoid cells suggests a difference either in the receptor-bound form of the subtypes, or in subsequent interactions prerequisite for activation of these cells. Furthermore, the neutralization of a particular IFN subtype, alpha 2b, on epithelial-derived but not lymphoid cells suggests differences in the IFN-receptor complex or the mechanisms of cell activation between these cell types. An implication from these studies is that some IFN-alpha subtypes can exert different functions on lymphoid and epithelial cells.

Validation of the MTT dye assay for enumeration of cells in proliferative and antiproliferative assays

Increasing use is being made of colorimetric assays to quantitate viable cells, e.g., the cellular reduction of the tetrazolium salt, MTT, to formazan by mitochondrial succinate dehydrogenase. We validated this assay for cell proliferation in mixed lymphocyte cultures as compared with 3H-thymidine uptake, and for inhibition of cell proliferation induced by interferon with results compared by direct cell counting. We also found that cells do not, as previously assumed, require functional mitochondria: there were no differences in formazan production by normal cells or respiratory defective cells in which mitochondria had been poisoned by the nucleic acid toxin, ethidium bromide. The high reproducibility of MTT metabolism by lymphoblasts and various cultured cell lines establishes the reliability and versatility of this method for quantitating cell numbers.

Functional analysis of interferon-α subtypes using monoclonal antibodies to interferon-α 4a—subtype reactivity, neutralisation of biological activities and epitope analysis

A panel of monoclonal antibodies (mAb) to a major human interferon-alpha (IFN-alpha) subtype, -alpha 4a, have been produced, characterised and used for studies of structure/function relationships of IFN-alpha subtypes. The mAb were tested for effects on receptor binding of IFN-alpha 4a, reactivity with other major subtypes -alpha 1, -alpha 2b and -alpha 14 by competitive ELISA and western immunoblotting, and for neutralisation of antiviral and antiproliferative activities of the four subtypes. The mAb could be grouped according to reactivity with IFN-alpha subtypes, group I (designated I-4-A) reacted with -alpha 4a and -alpha 2b, group II (I-4-C and I-4-F) reacted with -alpha 4a and -alpha 1, group III (I-4-D), I-4-G and I-4-H) reacted with -alpha 4a only, whereas group IV (I-4-I) reacted with -alpha 4a, -alpha 1 and -alpha 2b. No mAb reacted with IFN-alpha 14. Sequence comparisons of reactive and non-reactive IFN-alpha subtypes, and reactivity patterns with IFN-alpha fragments obtained by Lys-C digestion indicated that the epitopes were located in the N-terminal region (group I), in two regions of the middle of the molecule (group III and IV) and in the C-terminal region (group II). Binding of mAb to any of these four distinct epitopes neutralised the biological activities of IFN-alpha 4a, and in all cases, except I-4-A, inhibited receptor binding. Only the group III mAb bind to an epitope proposed to be in the vicinity of residues 30-40 which are implicated, from in vitro mutagenesis studies, in receptor binding. Binding of mAb to the other 3 epitopes neutralises biological activities by indirect mechanisms. These results emphasise the antigenic diversity between highly homologous IFN-alpha subtypes, which may have a wider functional significance. Individual mAb will have practical applications in the purification and detection of several IFN-alpha subtypes and so facilitate their further characterisation. By virtue of their different mechanisms of neutralisation, this panel of mAb will be useful in further studies of receptor interaction and signal transduction by IFN-alpha, and illustrate principles which are relevant to immunochemical studies of the receptor interactions of other cytokines.

Expression of a novel family of epitopes on small intestinal mucins in colorectal cancers, adjacent and remote mucosa

We describe the production, immunochemical and immunohistochemical characterization of monoclonal antibodies (MAbs) raised against the oncofetal small intestinal mucin antigen (SIMA). Four MAbs, reacting with distinct neuraminidase-sensitive SIMA epitopes, were shown to define a novel differentiation-associated relationship of SIMA epitopes within the normal small intestinal villus. Using Swiss rolls of 15 entire colorectal cancer resections, inappropriate expression of SIMA epitopes was detected in all cancers, in adjacent transitional mucosa and remote morphologically normal mucosa, extending as far as resection margins (73%). SIMA expression, whether preexisting or reactive to the tumor, may predispose to malignant change and tumor recurrence.