Action of spontaneously produced beta interferon in differentiation of embryonal carcinoma cells through an autoinduction mechanism

Antitumor effect of recombinant human interferon-β adenovirus on esophageal squamous cell cancer in vitro

Interferon (IFN)-β has efficient antitumor effect both in vitro and in vivo, but its clinical implication is limited by short half-life and systemic toxicities. Gene therapy could be the choice to avoid the defects. Adenovirus vector containing human IFN-β gene was transfected into esophageal squamous cell carcinoma KYSE150 cells. Expression of human (h)IFN-β was detected by reverse transcription polymerase chain reaction and immunocytochemistry in KYSE150 cells. Cell growth and clonogenic assays, and flow cytometry were used to observe the antiproliferation effect and apoptosis on tumor cells, respectively. Reverse transcription polymerase chain reaction and immunocytochemistry showed obvious hIFN-β expression in KYSE150 cells after transfection and the tumor cell proliferation was obviously inhibited through cell proliferation and clonogenic assays. Flow cytometry analysis showed 27.3% cell apoptosis in adenovirus vector containing human IFN-β gene transfection group compared with 1.12% in empty vector control group. These findings indicate that hIFN-β gene mediated by recombinant adenovirus may have antitumor activity against human esophageal carcinoma cell by inducing apoptosis in vitro.

Cancer gene therapy using mesenchymal stem cells expressing interferon-beta in a mouse prostate cancer lung metastasis model

Cell-based therapy for cancer is a promising new field. Among cell types that can be used for this purpose, mesenchymal stem cells (MSCs) appear to hold great advantage for reasons including easier propagation in culture, possible genetic modification to express therapeutic proteins and preferential homing to sites of cancer growth upon in vivo transfer. The present study evaluated the potential of genetically modified MSC, constitutively expressing interferon (IFN)-beta, in an immunocompetent mouse model of prostate cancer lung metastasis. A recombinant adeno-associated virus (rAAV) encoding mouse IFN-beta was constructed and initially tested in vitro for high-level expression and bioactivity of the transgenic protein. MSCs were transduced by the rAAV-IFN-beta or green fluorescent protein ex vivo and used as cellular vehicles to target lung metastasis of TRAMP-C2 prostate cancer cells in a therapy model. Cohorts of mice were killed on days 30 and 75 to determine the effect of therapy by measurement of tumor volume, histology, immunohistochemistry, enzyme-linked immunosorbent assay and flow cytometry. Results indicated a significant reduction in tumor volume in lungs following IFN-beta-expressing MSC therapy. Immunohistochemistry of the lung demonstrated increased tumor cell apoptosis and decreased tumor cell proliferation and blood vessel counts. A significant increase in the natural kill cell activity was observed following IFN-beta therapy correlating the antitumor effect. Systemic level of IFN-beta was not significantly elevated from this targeted cell therapy. These data demonstrate the potential of MSC-based IFN-beta therapy for prostate cancer lung metastasis.

Differential growth of IFN-beta-engineered tumor cells in nude and IFN receptor-null mice

The purpose of this study was to investigate the therapeutic potential of interferon-beta (IFN-beta) against tumors that resist its antiproliferative effects. Mouse fibrosarcoma cells (UV-2237m-P) and their counterparts, transfected with either IFN-beta cDNA (UV-2237m-IFN-beta) or its control vector (UV-2237m-neo), were used in the study. UV-2237m-IFN-beta cells, still expressing functional IFN receptors, were resistant to the antiproliferative effects of IFN-beta. UV-2237m-P and UV-2237m-neo cells produced progressive tumors in both nude and IFN receptor-null nude (IFNAR-/-nude) mice. In contrast, growth of UV-2237m-IFN-beta cells was significantly delayed in nude mice. UV-2237m-IFN-beta tumors from nude mice contained fewer microvessels, fewer proliferating cells, and more apoptotic cells than did UV-2237m-P and UV-2237m-neo tumors. They expressed high levels of inducible nitric oxide synthase (iNOS) and were densely infiltrated by macrophages. Incubation with macrophages from nude mice, but not those from IFNAR-/- nude mice or iNOS-null/nude mice, led to more significant killing of UV-2237m-IFN-beta cells than that of control cells, which was blocked by iNOS inhibitor N-methylarginine. Similarly, more UV-2237m-IFN-beta cells were killed when they were incubated with spleen lymphocytes from nude mice. These data indicate that IFN-beta can inhibit growth of IFN-beta-resistant tumors by T cell-independent host-mediated mechanisms, including the role of macrophages, natural killer (NK) cells, and iNOS activity.

Inducible nitric oxide synthase activity is essential for inhibition of prostatic tumor growth by interferon-beta gene therapy

We have previously reported that adenoviral vector-mediated interferon (IFN)-beta gene therapy inhibits orthotopic growth of human prostate cancer cells in nude mice. The purpose of this study was to determine efficacy and mechanisms of this therapy in immune-competent mice. TRAMP-C2Re3 mouse prostate cancer cells infected with 100 multiplicity of infection (MOI) of adenoviral vector encoding for mouse IFN-beta (AdmIFN-beta), but not AdE/1 (a control adenoviral vector), produced approximately 60 ng/10(5) cells/24 h of IFN-beta. The tumorigenicity of AdmIFN-beta-transduced cells was dramatically reduced in the prostates of C57BL/6 mice. A single intratumoral injection of 2 x 10(9) PFU (plaque-forming unit) of AdmIFN-beta inhibited tumor growth by 70% and prolonged survival of tumor-bearing mice. Intriguingly, this AdmIFN-beta therapy did not alter the growth of tumors in inducible nitric oxide synthase (iNOS)-null C57BL/6 mice. Immunohistochemical analysis revealed that treatment of tumors with AdmIFN-beta in wild-type C57BL/6 mice led to increased iNOS expression, decreased microvessel density, decreased cell proliferation, and increased apoptosis. Furthermore, quantitative reverse-transcriptional PCR analysis showed that AdmIFN-beta therapy, in C57BL/6 but not the iNOS-null counterparts, reduced levels of the mRNAs for angiopoietin, basic fibroblast growth factor, matrix metalloproteinase-9, transforming growth factor-beta1, vascular endothelial growth factor (VEGF)-A, and VEGF-B, as well as the antiapoptotic molecule endothelin-1. These data indicated that IFN-beta gene therapy could be effective alternative for the treatment of locally advanced prostate cancer and suggest an obligatory role of NO in IFN-beta antitumoral effects in vivo.

Intrapulmonary IFN-beta gene therapy using an adenoviral vector is highly effective in a murine orthotopic model of bronchogenic adenocarcinoma of the lung

Given previous work showing that an adenoviral vector expressing IFN-beta (Ad.IFNbeta) was highly effective in eradicating i.p. mesothelioma tumors, the antitumor efficacy of this agent was evaluated in an orthotopic model of bronchogenic adenocarcinoma of the lung. These transgenic mice have a conditionally expressed, oncogenic K-rasG12D allele that can be activated by intratracheal administration of an adenovirus expressing Cre recombinase (Ad.Cre). K-rasG12D mutant mice were given Ad.Cre intranasally to activate the oncogene. Mice were then given 10(9) plaque-forming units of a control vector (Ad.LacZ) or Ad.IFNbeta intranasally 3 and 4 weeks later, a time when lung tumors had been established. Cells derived from K-ras-mutated lung tumors were also grown in the flanks of mice to study mechanisms of therapeutic responses. In two separate experiments, untreated tumor-bearing mice all died by day 57 (median survival, 49 days). Ad.LacZ-treated mice all died by day 71 (median survival, 65 days). In contrast, 90% to 100% of mice treated with Ad.IFNbeta were long-term survivors (>120 days; P < 0.001). In addition, immunity to re-challenge with tumor cells was induced. In vitro and flank tumor studies showed that Ad.IFNbeta induced direct tumor cell killing and that depleting natural killer or CD8+ T cells, but not CD4+ T cells, with antibodies attenuated the effect of Ad.IFNbeta. These studies, showing remarkable antitumor activity in this orthotopic lung cancer model, provide strong preclinical support for a trial of Ad.IFNbeta to treat human non-small cell lung cancer.

Long-lasting RNAi activity in mammalian neurons

The effect of RNA interference (RNAi) induced by synthetic small interfering RNAs (siRNAs) on proliferating mammalian cells appears to last for approximately 3-7 days after its induction. Here we show that the RNAi activity induced by a synthetic 21-nucleotide siRNA duplex in postmitotic neurons, mouse primary hippocampal neurons and neurons that differentiated from mouse embryonal carcinoma P19 cells persists for at least 3 weeks, suggesting long-lasting RNAi activity in mammalian neurons. In addition, we also show that an apoptotic (or antiviral) pathway triggered by long dsRNAs is generated during neuronal differentiation of P19 cells, by which the sequence-specific RNAi activity involving long dsRNA appears to be masked.

Adenovirus-mediated interferon-beta gene therapy suppresses growth and metastasis of human prostate cancer in nude mice

The purpose of this study was to determine the effects of interferon-beta (IFN-beta) gene transfer on the growth of PC3MM2 human prostate cancer cells in nude mice. Intralesional delivery of an adenoviral vector encoding murine IFN-beta (AdIFN-beta), but not a vector encoding bacterial beta-galactosidase (AdLacZ), suppressed PC3MM2 tumors in a dose-dependent manner. At the highest dose (2x10(9) plaque-forming units, PFU), a single injection of AdIFN-beta (but not AdLacZ) suppressed orthotopic PC3MM2 tumors and development of metastasis by 80%, and eradicated the tumors in 20% of mice. Immunohistochemical staining showed that AdIFN-beta-treated tumors contained fewer microvessels, fewer proliferating cells, and more apoptotic cells than did the control tumors. Compared with controls, tumors injected with AdIFN-beta expressed higher levels of IFN-beta and inducible nitric oxide synthase (iNOS) and lower levels of basic fibroblast growth factor (bFGF) and transforming growth factor beta1 (TGF-beta1). In vitro analysis indicated that expression of bFGF and TGF-beta1 in PC3MM2 cells could be suppressed by the nitric oxide donor sodium nitroprusside. These data suggest that intratumoral delivery of the IFN-beta gene with adenoviral vectors could be an effective therapy for prostate cancer and that tumor suppression by AdIFN-beta correlated with up-regulation of iNOS and down-regulation of angiogenesis.

Dimerization of the interferon type I receptor IFNaR2-2 is sufficient for induction of interferon effector genes but not for full antiviral activity

We constructed chimeric receptors wherein the extracellular domain of the erythropoietin receptor (EpoR) was fused to the transmembrane and intracellular domains of the interferon (IFN) type I receptor subunits, IFNaR1 or IFNaR2-2. Transfection into 2fTGH and Tyk2-deficient 11,1 cells showed that EpoR/IFNaR2-2 alone was able to transduce a signal upon stimulation with erythropoietin (Epo), as judged by induction of the interferon type I-inducible 6-16 promoter. In contrast, protection against infection with encephalomyocarditis virus or vesicular stomatitis virus was reduced or absent, respectively. To further investigate the role of IFNaR1 in the induction of an antiviral state, we analyzed the Epo- versus IFNalpha-induced transcription of a set of genes, involved in antiviral protection. Up to 24 h after stimulation with Epo or IFNalpha, comparable transcription of the p56, dsRNA-dependent protein kinase, 2'-5'A synthetase, and MxA genes was seen. However, at later time points, only in the case of Epo induction, a sharp decrease of mRNA levels was observed. Western blotting analysis of dsRNA-dependent protein kinase showed a similar pattern at the protein level. Taken together, our results imply a role for IFNaR1 in the induction of sustained mRNA and protein levels that are likely required for optimal antiviral activity.

Characterization of a soluble ternary complex formed between human interferon-beta-1a and its receptor chains

The extracellular portions of the chains that comprise the human type I interferon receptor, IFNAR1 and IFNAR2, have been expressed and purified as recombinant soluble His-tagged proteins, and their interactions with each other and with human interferon-beta-1a (IFN-beta-1a) were studied by gel filtration and by cross-linking. By gel filtration, no stable binary complexes between IFN-beta-1a and IFNAR1, or between IFNAR1 and IFNAR2 were detected. However, a stable binary complex formed between IFN-beta-1a and IFNAR2. Analysis of binary complex formation using various molar excesses of IFN-beta-1a and IFNAR2 indicated that the complex had a 1:1 stoichiometry, and reducing SDS-PAGE of the binary complex treated with the cross-linking reagent dissucinimidyl glutarate (DSG) indicated that the major cross-linked species had an apparent Mr consistent with the sum of its two individual components. Gel filtration of a mixture of IFNAR1 and the IFN-beta-1a/IFNAR2 complex indicated that the three proteins formed a stable ternary complex. Analysis of ternary complex formation using various molar excesses of IFNAR1 and the IFN-beta-1a/IFNAR2 complex indicated that the ternary complex had a 1:1:1 stoichiometry, and reducing SDS-PAGE of the ternary complex treated with DSG indicated that the major cross-linked species had an apparent Mr consistent with the sum of its three individual components. We conclude that the ternary complex forms by the sequential association of IFN-beta-1a with IFNAR2, followed by the association of IFNAR1 with the preformed binary complex. The ability to produce the IFN-beta-1a/IFNAR2 and IFN-beta-1a/IFNAR1/IFNAR2 complexes make them attractive candidates for X-ray crystallography studies aimed at determining the molecular interactions between IFN-beta-1a and its receptor.

Expression of interferon-beta is associated with growth arrest of murine and human epidermal cells

The cytokine interferon-beta is a regulator of cell replication and function, including invasion and induction of angiogenesis. The goal of this study was to determine whether the expression of interferon-beta by cells in the epidermis correlated with terminal differentiation. In situ hybridization analysis and immunohistochemical staining of formalin-fixed, paraffin-embedded specimens of normal human and murine epidermis and human and murine skin tumors of epithelial origin revealed that only differentiated, nondividing cells of the epidermis expressed interferon-beta protein. Keratinocyte cultures established from the epidermis of 3 d old mice were maintained under conditions permitting continuous cell division or induction of differentiation. Continuously dividing cells did not produce interferon-beta whereas nondividing differentiated cells expressing keratin 1 did. Growth-arrested, undifferentiated keratinocytes also expressed interferon-beta protein. Neutralizing interferon-beta in the culture medium inhibited differentiation, but the addition of exogenous interferon-beta did not stimulate differentiation. These data indicate that interferon-beta is produced by growth-arrested, terminally differentiated keratinocytes.

Constitutive expression of interferon beta in differentiated epithelial cells exposed to environmental stimuli

The body's first line of defense against external challenge are the epithelial cells that line the skin and the respiratory, digestive, and genitourinary tracts. Inasmuch as interferon-beta (IFN-beta) participates in host defense against viral, bacterial, and parasitic infections and tumors, we hypothesized that this secreted protein is expressed in various murine epithelial cell types that line portals of entry to the body. We used immunohistochemistry and in situ hybridization techniques to measure IFN-beta expression in the various epithelial cell types and in internal murine organs sheltered from environmental stimuli. The epithelial cell types lining the skin, digestive tract, urinary tract, reproductive tract, and upper respiratory tract constitutively expressed IFN-beta. Specifically, all differentiated epithelial cells at risk of environmental exposure expressed IFN-beta (protein and mRNA) with the exception of the ciliated epithelial cells lining the lower respiratory tract. Epithelial cells of internal organs that are not directly exposed to external pathogens did not express IFN-beta.

Differences in activity between alpha and beta type I interferons explored by mutational analysis

Type I interferon (IFN) subtypes alpha and beta share a common multicomponent, cell surface receptor and elicit a similar range of biological responses, including antiviral, antiproliferative, and immunomodulatory activities. However, alpha and beta IFNs exhibit key differences in several biological properties. For example, IFN-beta, but not IFN-alpha, induces the association of tyrosine-phosphorylated receptor components ifnar1 and ifnar2, and has activity in cells lacking the IFN receptor-associated, Janus kinase tyk2. To define the structural basis for these functional differences we produced human IFN-beta with point mutations and compared them to wild-type IFN-beta in assays that distinguish alpha and beta IFN subtypes. IFN-beta mutants with charged residues (N86K, N86E, or Y92D) introduced at two positions in the C helix lost the ability to induce the association of tyrosine-phosphorylated receptor chains and had reduced activity on tyk2-deficient cells. The combination of negatively charged residues N86E and Y92D (homologous with IFN-alpha8) increased the cross-species activity of the mutant IFN-betas on bovine cells to a level comparable to that of human IFN-alphas. In contrast, point mutations in the AB loop and D helix had no significant effect on these subtype-specific activities. A subset of these latter mutations did, however, reduce activity in a manner analogous to IFN-alpha mutations. The effects of these mutations on IFN-beta activity are discussed in the context of a family of related ligands acting through a common receptor and signaling pathway.

Differential constitutive expression of interferon genes in early mouse embryos

Recent evidence suggests that several processes during mammalian embryogenesis may be regulated by IFNs or IFN-like molecules. With the use of MAPPing, the simultaneous presence of transcripts homologous to IFN-alpha, IFN-beta, IRF-1, and IRF-2 was examined in mouse embryos and in embryonal carcinoma (EC) P19 cells, which are equivalent to epiblast cells of the early postimplantation blastocysts. Transcripts for IFN-alpha, but not for IFN-beta, were detected as maternal transcripts in the ovulated oocyte and persisted over early embryogenesis. IRF-1 transcripts appeared only after the first cell cleavage in the two-cell stage embryo. IRF-2 transcripts were analyzed only in EC P19 cells and were found in both undifferentiated (D-) and differentiated (D+) cells. The IFN-alpha transcripts present in (D-) P19 cells were cloned and the partial cDNA sequences determined. Mu IFN-alpha A and a new Mu IFN-alpha species (Mu IFN-alpha 12) were isolated from (D-) P19 cells. The presence of constitutive IFN-alpha transcripts in early mouse embryos suggests a role for these molecules during embryogenesis.

Basal and interferon-induced 2',5'-oligoadenylate synthetase activity in human placental trophoblast and trophoblast-derived malignant cell lines

Human placental trophoblasts produce interferon (tro-IFNs) when stimulated with viral inducers. Since the antiviral and cellular functions of IFNs are partly mediated by the 2',5'-oligoadenylate synthetase (2-5A synthetase) pathway, the aim of the present study was to determine the basal and IFN-induced levels of 2-5A synthetase in villous trophoblast cultures. A considerable basal level of 2-5A synthetase was observed in syncytiotrophoblast cultures from both first and third trimester. In contrast no basal activity was detectable in placental fibroblast- and trophoblast-derived malignant cell lines (Far, FEG-3, and BeWo). Stimulation with tro-IFN-beta, -alpha and leucocyte-IFN (leu-IFN)-alpha increased the enzyme activity in first and third trimester human syncytiotrophoblast cultures. Treatment with recombinant-IFN (rec-IFN)-gamma significantly enhanced 2-5A synthetase activity in first trimester syncytiotrophoblast, but had no effect on third trimester syncytiotrophoblast. Tro-IFN-beta, -alpha and leu-IFN-alpha induced high levels of 2-5A synthetase activity in placental fibroblast, BeWo and FEG-3 cell-lines, whereas rec-IFN-gamma treatment did not induce 2-5A synthetase activity in any of these cells. No detectable 2-5A synthetase activity was found in the Far cell line. The capability of cells deriving from the fetoplacental unit to raise an antiviral response by the induction of 2-5A synthetase may be important in defending the fetus against viral infection from the mother. Furthermore 2-5A synthetase in cells of the fetoplacental unit may play a role in their normal growth and development.

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.

Binding properties of newly identified Xenopus proteins containing dsRNA-binding motifs

BACKGROUND

Although most RNA-binding proteins recognize a complex set of structural motifs in their RNA target, the double-stranded (ds) RNA-binding proteins are limited to interactions with double helices. Recently, it has been discovered that some dsRNA-binding proteins share regions of amino-acid similarity known as dsRNA-binding motifs.

RESULTS

A Xenopus ovary cDNA expression library was screened with radiolabeled dsRNA to identify previously uncharacterized dsRNA-binding proteins. The analysis of an incomplete cDNA identified during the screen led to the discovery of two longer cDNAs of related sequence. The proteins encoded by these cDNAs each contained two dsRNA-binding motifs, in glycine. The nucleic-acid-binding properties of a fusion protein containing the two dsRNA-binding motifs and the auxiliary domain were analyzed using a gel mobility shift assay. The fusion protein bound dsRNA of a variety of different sequences, and exhibited a preference for binding to dsRNA and RNA-DNA hybrids over other nucleic acids. Appropriate mRNAs, corresponding to each cDNA, were detected in polyadenylated RNA isolated from Xenopus stage VI oocytes, but translation of one of the mRNAs appeared to be masked until meiotic maturation.

CONCLUSION

dsRNA-binding motifs are often found in proteins that bind dsRNA, and our results show that they can be associated with auxiliary domains rich in arginine and glycine. These motifs can confer very tight binding to dsRNA. Binding can also occur to RNA-DNA hybrids, suggesting recognition of some aspect of the A-form helical structure that is adopted by both dsRNA and RNA-DNA hybrids.