Identification of a novel ligand-receptor pair constitutively activated by ras oncogenes

Analysis of the key ligand receptor CADM1_CADM1 in the regulation of thyroid cancer based on scRNA-seq and bulk RNA-seq data

INTRODUCTION

Advanced papillary thyroid cancer (PTC) has a poor prognosis, 60~70% of which become radio iodine refractory (RAI-R), but the molecular markers that assess PTC progress to advanced PTC remain unclear. Meanwhile, current targeted therapies are badly effective due to drug resistance and adverse side effects. Ligand-receptor pairs (L/R pairs) play an important role in the interactions between tumor cells and other cells in the tumor microenvironment (TME). Nowadays, therapies targeting ligand-receptor pairs in the TME are advancing rapidly in the treatment of advanced cancers. However, therapies targeting L/R pairs applied to advanced PTC remains challenging because of limited knowledge about L/R pairs in PTC.

METHODS

We screened the critical L/R pair: CADM1-CADM1 using 65311 single-cell RNA sequencing (scRNA-seq) samples from 7 patients in different stage of PTC and bulk RNA-seq datasets containing data from 487 tumor samples and 58 para-carcinoma samples. Moreover, the expression levels of CADM1-CADM1 was assessed by quantitative real time polymerase chain reaction (qRT-PCR) and the function was analyzed using Transwell immigration assay.

RESULTS

We found that CADM1_CADM1 could be regarded as a biomarker representing a good prognosis of PTC. In addition, the high expression of CADM1_CADM1 can strongly increase the sensitivity of many targeted drugs, which can alleviate drug resistance. And the results of qRT-PCR showed us that the expression of CADM1_CADM1 in PTC was down-regulated and overexpression of CADM1 could suppresses tumor cell invasion migration.

CONCLUSION

Our study identified that CADM1_CADM1 played an essential role in the progression of PTC for the first time and our findings provide a new potential prognostic and therapeutic ligand-receptor pair for advanced PTC.

Insights into the Mechanisms of Action of MDA-7/IL-24: A Ubiquitous Cancer-Suppressing Protein

Melanoma differentiation associated gene-7/interleukin-24 (MDA-7/IL-24), a secreted protein of the IL-10 family, was first identified more than two decades ago as a novel gene differentially expressed in terminally differentiating human metastatic melanoma cells. MDA-7/IL-24 functions as a potent tumor suppressor exerting a diverse array of functions including the inhibition of tumor growth, invasion, angiogenesis, and metastasis, and induction of potent "bystander" antitumor activity and synergy with conventional cancer therapeutics. MDA-7/IL-24 induces cancer-specific cell death through apoptosis or toxic autophagy, which was initially established in vitro and in preclinical animal models in vivo and later in a Phase I clinical trial in patients with advanced cancers. This review summarizes the history and our current understanding of the molecular/biological mechanisms of MDA-7/IL-24 action rendering it a potent cancer suppressor.

Intravesical High Dose BCG Tokyo and Low Dose BCG Tokyo with GMCSF+IFN α Induce Systemic Immunity in a Murine Orthotopic Bladder Cancer Model

This study evaluates a short therapy schedule for bladder cancer using BCG Tokyo. BCG Tokyo was evaluated in vitro using bone marrow derived dendritic cells, neutrophils, RAW macrophages and the murine bladder cancer cell line, MB49PSA, and compared to other BCG strains. BCG Tokyo > BCG TICE at inducing cytokine production. In vivo, high dose (1 × 10⁷ colony forming units (cfu)) and low dose (1 × 10⁶ cfu) BCG Tokyo with and without cytokine genes (GMCSF + IFNα) were evaluated in C57BL/6J mice (n = 12–16 per group) with orthotopically implanted MB49PSA cells. Mice were treated with four instillations of cytokine gene therapy and BCG therapy. Both high dose BCG alone and low dose BCG combined with cytokine gene therapy were similarly effective. In the second part the responsive groups, mice (n = 27) were monitored by urinary PSA analysis for a further 7 weeks after therapy cessation. More mice were cured at day 84 than at day 42 confirming activation of the immune system. Cured mice resisted the re-challenge with subcutaneous tumors unlike naïve, age matched mice. Antigen specific T cells recognizing BCG, HY and PSA were identified. Thus, fewer intravesical instillations, with high dose BCG Tokyo or low dose BCG Tokyo with GMCSF + IFNα gene therapy, can induce effective systemic immunity.

The Interleukin-10 Family of Cytokines and Their Role in the CNS

Resident cells of the central nervous system (CNS) play an important role in detecting insults and initiating protective or sometimes detrimental host immunity. At peripheral sites, immune responses follow a biphasic course with the rapid, but transient, production of inflammatory mediators giving way to the delayed release of factors that promote resolution and repair. Within the CNS, it is well known that glial cells contribute to the onset and progression of neuroinflammation, but it is only now becoming apparent that microglia and astrocytes also play an important role in producing and responding to immunosuppressive factors that serve to limit the detrimental effects of such responses. Interleukin-10 (IL-10) is generally considered to be the quintessential immunosuppressive cytokine, and its ability to resolve inflammation and promote wound repair at peripheral sites is well documented. In the present review article, we discuss the evidence for the production of IL-10 by glia, and describe the ability of CNS cells, including microglia and astrocytes, to respond to this suppressive factor. Furthermore, we review the literature for the expression of other members of the IL-10 cytokine family, IL-19, IL-20, IL-22 and IL-24, within the brain, and discuss the evidence of a role for these poorly understood cytokines in the regulation of infectious and sterile neuroinflammation. In concert, the available data indicate that glia can produce IL-10 and the related cytokines IL-19 and IL-24 in a delayed manner, and these cytokines can limit glial inflammatory responses and/or provide protection against CNS insult. However, the roles of other IL-10 family members within the CNS remain unclear, with IL-20 appearing to act as a pro-inflammatory factor, while IL-22 may play a protective role in some instances and a detrimental role in others, perhaps reflecting the pleiotropic nature of this cytokine family. What is clear is that our current understanding of the role of IL-10 and related cytokines within the CNS is limited at best, and further research is required to define the actions of this understudied family in inflammatory brain disorders.

Functional Detection of TNF Receptor Family Members by Affinity-Labeled Ligands

Aberrant expression of TNF family of cytokines has been linked to human diseases, and biologics targeting their signaling have become the best selling drugs globally. However, functional detection with labeled ligands for accurate detection of TNFR family of receptor-expressing target tissues or cell types remains to be developed. Here we show that TNF receptor family members are heat-stable and can be recognized both in vitro and in vivo by their ligands labeled with alkaline phosphatase. Such an approach may be used in lieu of antibodies for the identification of the cell types involved in receptor signaling during disease onset and progression.

A Broad Blockade of Signaling from the IL-20 Family of Cytokines Potently Attenuates Collagen-Induced Arthritis

Two heterodimeric receptors consisting of either IL-20R1 or IL-22R1 in complex with a common β receptor subunit IL-20R2 are shared by three of the IL-20 family of cytokines: IL-19, IL-20, and IL-24. These proinflammatory cytokines have been implicated in the pathogenesis of some autoimmune diseases, including rheumatoid arthritis (RA), psoriasis, and atopic dermatitis. Although mAbs against IL-19 and IL-20 have each been shown to modulate disease severity of collagen-induced arthritis in animal models, and anti-IL-20 therapeutic Ab has exhibited some efficacy in the treatment of RA in clinical trials, benefits for a complete blockade of these functionally redundant cytokines remain to be explored. In this report, we show that recombinant human soluble IL-20R2-Fc fusion protein binds to IL-19, IL-20, and IL-24 with similar high affinity and blocks their signaling in vitro. In DBA/1 mouse collagen-induced arthritis model, recombinant human IL-20R2-Fc exhibits comparable efficacy as TNF blocker etanercept in the treatment of established arthritis, whereas the combined use of both biologics manifests little synergistic therapeutic effects. In situ ligand-receptor functional binding analysis shows that a large amount of immune infiltrates expressing high levels of TNFR and IL-20 subfamily cytokines congregate within the inflamed disease tissues. Colocalization experiments reveal that signals from IL-20R2 and TNF transduction pathways seem to converge in macrophages and function in tandem in orchestrating the pathogenesis of RA. Elucidation of this interaction provides a better understanding of cytokine cross-talk in RA and a rationale for more effective biologic therapies that target IL-20R2 instead of individual cytokines from IL-20 family.

Alternative splicing directs two IL-20R2 isoforms and is responsible for the incomplete gene knockout via the exon I ablation

Two heterodimeric receptors consisting of interleukin (IL)-20R2 are shared by three of the IL-20 family of cytokines, IL-19, IL-20 and IL-24. Along with IL-22, these cytokines are downstream effectors of IL-23 and have been implicated in keratinocyte functions and the pathogenesis of psoriasis. Surprisingly, whereas knocking out either the IL-23 or IL-22 gene abolished imiquimod-induced psoriatic phenotypes in mice, similar attempt for IL-20R2 had little effect. Here, we report that the apparent disparity may result from a new IL-20R2 isoform encoded by an alternatively spliced transcript which survived the previous attempt for IL-20R2 gene knockout via the exon I deletion.

Molecular targets and signaling pathways regulated by interleukin (IL)-24 in mediating its antitumor activities

Cancer remains a major health issue in the world and the effectiveness of current therapies is limited resulting in disease recurrence and resistance to therapy. Therefore to overcome disease recurrence and have improved treatment efficacy there is a continued effort to develop and test new anticancer drugs that are natural or synthetic - (conventional chemotherapeutics, small molecule inhibitors) and biologic (antibody, tumor suppressor genes, oligonucleotide) product. In parallel, efforts for identifying molecular targets and signaling pathways to which cancer cells are "addicted" are underway. By inhibiting critical signaling pathways that is crucial for cancer cell survival, it is expected that the cancer cells will undergo a withdrawal symptom akin to "de-addiction" resulting in cell death. Thus, the key for having an improved and greater control on tumor growth and metastasis is to develop a therapeutic that is able to kill tumor cells efficiently by modulating critical signaling pathways on which cancer cells rely for their survival.Currently several small molecule inhibitors targeted towards unique molecular signaling pathways have been developed and tested in the clinic. Few of these inhibitors have shown efficacy while others have failed. Thus, targeting a single molecule or pathway may be insufficient to completely block cancer cell proliferation and survival. It is therefore important to identify and test an anticancer drug that can inhibit multiple signaling pathways in a cancer cell, control growth of both primary and metastatic tumors and is safe.One biologic agent that has the characteristics of serving as a potent anticancer drug is interleukin (IL)-24. IL-24 suppresses multiple signaling pathways in a broad-spectrum of human cancer cells leading to tumor cell death, inhibition of tumor angiogenesis and metastasis. Additionally, combining IL-24 with other therapies demonstrated additive to synergistic antitumor activity. Clinical testing of IL-24 as a gene-based therapeutic for the treatment of solid tumors demonstrated that IL-24 is efficacious and is safe. The unique features of IL-24 support its further development as an anticancer drug for cancer treatment.In this review we summarize the current understanding on the molecular targets and signaling pathways regulated by IL-24 in mediating its anticancer activity.

IL-24 transgenic mice: in vivo evidence of overlapping functions for IL-20, IL-22, and IL-24 in the epidermis

IL-20 and IL-24 share two different heterodimeric receptors consisting of either IL-20R1 or IL-22R1 and a common IL-20R2 subunit, whereas IL-22 signals through IL-22R1/IL-10R2. However, until now, only IL-20 and IL-22 have been proven to play important roles in vivo in the epidermis where all four receptor subunits are expressed. In this study, we show that IL-24 transgenic mice manifest many similar phenotypes to that of IL-20 and IL-22, including neonatal lethality, epidermal hyperplasia, and abnormality in keratinocyte differentiation. These results support a largely redundant role in epidermal functions for IL-20, IL-22, and IL-24, which seem to be IL-22R1 dependent. Moreover, we show that IL-24 transgenic mice exhibit infiltrating macrophages in the dermis with concomitant increases in MCP-1 production from both keratinocytes in the epidermis and immune infiltrates in the adjacent dermal layer below. Furthermore, we demonstrate that the homodimeric IL-20R2 soluble receptor is a potent blocker for IL-24 and can be used to further dissect the crosstalk among the IL-20 family of cytokines in normal development as well as in autoimmune diseases.

The p38 MAPK regulates IL-24 expression by stabilization of the 3' UTR of IL-24 mRNA

Background

IL-24 (melanoma differentiation-associated gene-7 (mda-7)), a member of the IL-10 cytokine family, possesses the properties of a classical cytokine as well as tumor suppressor effects. The exact role of IL-24 in the immune system has not been defined but studies have indicated a role for IL-24 in inflammatory conditions such as psoriasis. The tumor suppressor effects of IL-24 include inhibition of angiogenesis, sensitization to chemotherapy, and p38 mitogen-activated protein kinase (MAPK)-mediated apoptosis. Current knowledge on the regulation of IL-24 expression is sparse. Previous studies have suggested that mRNA stabilization is of major importance to IL-24 expression. Yet, the mechanisms responsible for the regulation of IL-24 mRNA stability remain unidentified. As p38 MAPK is known to regulate gene expression by interfering with mRNA degradation we examined the role of p38 MAPK in the regulation of IL-24 gene expression in cultured normal human keratinocytes.

Methodology/Principal Findings

In the present study we show that anisomycin- and IL-1β- induced IL-24 expression is strongly dependent on p38 MAPK activation. Studies of IL-24 mRNA stability in anisomycin-treated keratinocytes reveal that the p38 MAPK inhibitor SB 202190 accelerates IL-24 mRNA decay suggesting p38 MAPK to regulate IL-24 expression by mRNA-stabilizing mechanisms. The insertion of the 3′ untranslated region (UTR) of IL-24 mRNA in a tet-off reporter construct induces degradation of the reporter mRNA. The observed mRNA degradation is markedly reduced when a constitutively active mutant of MAPK kinase 6 (MKK6), which selectively activates p38 MAPK, is co-expressed.

Conclusions/Significance

Taken together, we here report p38 MAPK as a regulator of IL-24 expression and determine interference with destabilization mediated by the 3′ UTR of IL-24 mRNA as mode of action. As discussed in the present work these findings have important implications for our understanding of IL-24 as a tumor suppressor protein as well as an immune modulating cytokine.

Automated fluorescent differential display for cancer gene profiling

Since its invention in 1992, differential display (DD) has become the most commonly used technique for identifying differentially expressed genes because of its many advantages over competing technologies such as DNA microarray, serial analysis of gene expression (SAGE), and subtractive hybridization. A large number of these publications have been in the field of cancer, specifically on p53 target genes. Despite the great impact of the method on biomedical research, there had been a lack of automation of DD technology to increase its throughput and accuracy for systematic gene expression analysis. Many previous DD work has taken a "shotgun" approach of identifying one gene at a time, with a limited number of polymerase chain reactions (PCRs) set up manually, giving DD a low-tech and low-throughput image. We have optimized the DD process with a platform that incorporates fluorescent digital readout, automated liquid handling, and large-format gels capable of running entire 96-well plates. The resulting streamlined fluorescent DD (FDD) technology offers an unprecedented accuracy, sensitivity, and throughput in comprehensive and quantitative analysis of gene expression. These major improvements will allow researchers to find differentially expressed genes of interest, both known and novel, quickly and easily.

IL-24: a classic cytokine and/or a potential cure for cancer?

IL-24, a member of the IL-10 family of cytokines, is produced by monocytes and Th2 cells. Interestingly, immune cells do not appear to express specific IL-24 receptor chains (IL-20R1/IL-20R2 and IL-22R/IL-20R2), it is therefore unlikely that IL-24 has classical immune-modulating properties. Skin, on the other hand, seems to represent a major target tissue for IL-24 and related cytokines such as IL-19, -20, and -22. However, the initial interest in IL-24 did not arise from its physiological signalling properties through its cognate receptors but rather because of its tentative ability to selectively kill different cancer cells. In an attempt to further investigate the signalling events underlying the IL-24-induced cancer cell death, we found that melanoma cell lines did not react in the expected and previously described way. Using several different forms and delivery modes of IL-24, we were unable to detect any apoptosis-inducing properties of this cytokine in melanoma cells. In the present ‘Point of view’ we will briefly summarizse these findings and put them in context of published reports stating that IL-24 might be a long sought after treatment for several types of cancer.

Interleukin-24 induces expression of beta4 integrin but suppresses anchorage-independent growth of rat mammary tumor cells by a mechanism that is independent of beta4

Wistar-Furth rats develop multiple mammary adenocarcinomas following initiation with methylnitrosourea, whereas Copenhagen rats are resistant to the development of mammary tumors. We have previously isolated cell lines from tumors induced in resistant Copenhagen x Wistar-Furth F(1) rats by infusion of a retrovirus harboring v-Ha-ras directly into the main mammary ducts. Some of the cell lines were able to grow in soft agar, but a significant number did not display anchorage-independent growth. Here, we compared by microarray analysis genes that are differentially expressed in these cell lines. The expression of interleukin-24 (IL-24) and beta(4) integrin was highly correlated with the inability of cells to grow in soft agar. Ectopic expression of IL-24 in anchorage-independent cells inhibited their growth in monolayer culture, in soft agar, and in nude mice in vivo and inhibited their ability to migrate and invade in in vitro assays. Furthermore, growth suppression by IL-24 was associated with the transcriptional up-regulation of p27(Kip1) via the activation of Stat3. We showed, for the first time, that beta(4) integrin is a downstream target of IL-24. However, beta(4) does not play a direct role in regulating the proliferative capacity of rat mammary tumor cells. Our results show that IL-24 suppresses the growth of rat mammary carcinoma cells and may play a role in the resistance of Copenhagen rats to mammary carcinogenesis.

Protein arginine methyltransferases: Evolution and assessment of their pharmacological and therapeutic potential

Protein arginine N-methylation is a post-translational modification whose influence on cell function is becoming widely appreciated. Protein arginine methyltransferases (PRMT) catalyze the methylation of terminal nitrogen atoms of guanidinium side chains within arginine residues of proteins. Recently, several new members of the PRMT family have been cloned and their catalytic function determined. In this report, we present a review and phylogenetic analysis of the PRMT found so far in genomes. PRMT are found in nearly all groups of eukaryotes. Many human PRMT originated early in eukaryote evolution. Homologs of PRMT1 and PRMT5 are found in nearly every eukaryote studied. The gene structure of PRMT vary: most introns appear to be inserted randomly into the open reading frame. The change in catalytic specificity of some PRMT occurred with changes in the arginine binding pocket within the active site. Because of the high degree of conservation of sequence among the family throughout evolution, creation of specific PRMT inhibitors in pathogenic organisms may be difficult, but could be very effective if developed. Furthermore, because of the intricate involvement of several PRMT in cellular physiology, their inhibition may be fraught with unwanted side effects. Nevertheless, development of pharmaceutical agents to control PRMT functions could lead to significant new targets.

mda-7/IL-24: multifunctional cancer-specific apoptosis-inducing cytokine

"Differentiation therapy" provides a unique and potentially effective, less toxic treatment paradigm for cancer. Moreover, combining "differentiation therapy" with molecular approaches presents an unparalleled opportunity to identify and clone genes mediating cancer growth control, differentiation, senescence, and programmed cell death (apoptosis). Subtraction hybridization applied to human melanoma cells induced to terminally differentiate by treatment with fibroblast interferon (IFN-beta) plus mezerein (MEZ) permitted cloning of melanoma differentiation associated (mda) genes. Founded on its novel properties, one particular mda gene, mda-7, now classified as a member of the interleukin (IL)-10 gene family (IL-24) because of conserved structure, chromosomal location, and cytokine-like properties has become the focus of attention of multiple laboratories. When administered by transfection or adenovirus-transduction into a spectrum of tumor cell types, melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) induces apoptosis, whereas no toxicity is apparent in normal cells. mda-7/IL-24 displays potent "bystander antitumor" activity and also has the capacity to enhance radiation lethality, to induce immune-regulatory activities, and to inhibit tumor angiogenesis. Based on these remarkable attributes and effective antitumor therapy in animal models, this cytokine has taken the important step of entering the clinic. In a Phase I clinical trial, intratumoral injections of adenovirus-administered mda-7/IL-24 (Ad.mda-7) was safe, elicited tumor-regulatory and immune-activating processes, and provided clinically significant activity. This review highlights our current understanding of the diverse activities and properties of this novel cytokine, with potential to become a prominent gene therapy for cancer.

Cytokine and tumor cell apoptosis inducing activity of mda-7/IL-24

Melanoma Differentiation Associated gene-7 (mda-7)/IL-24 has shown potent tumor cell apoptosis inducing capacity in multiple cancers, making it a strong candidate for use as a human cancer gene therapeutic. Several independent studies have currently documented and confirmed mda-7/IL-24's cytokine nature including presence of a canonical secretory signal peptide, processing and secretion of the molecule by cells and it's binding to specific interleukin receptors on the cell surface. Receptor binding has been shown to activate the JAK/STAT signal transduction pathway with concomitant stimulation of STAT 1 and 3 transactivators. The physiological role(s) of this molecule in modulating immune responses, as a member of the IL-10 family of cytokines, is not well documented and most current information pertains to its apparently restricted expression patterns in specific cell types with immunomodulatory activity. On the other hand, several additional signal transduction pathways were modulated when cells overexpress mda-7/IL-24, not all of which are necessarily downstream of mda-7/IL-24 induced JAK/STAT activation. A summary of the current status of information is presented to provide a perspective for the cytokine-related properties of mda-7/IL-24 in correlation to its tumor cell apoptosis inducing activity. Moreover, new evidence has surfaced pointing toward apoptosis induction via mechanisms independent of cytokine activity-related JAK/STAT activation.

Endo180 binds to the C-terminal region of type I collagen

Type I collagen is a fibril-forming heterotrimer composed of two alpha1 and one alpha2 chains and plays a crucial role in cell-matrix adhesion and cell differentiation. Through a comprehensive differential display screening of oncogenic ras target genes, we have shown that the alpha1 chain of type I collagen (col1a1) is markedly down-regulated by the ras oncogene through the mitogen-activated protein kinase pathway. Although ras-transformed cells are no longer able to produce and secrete endogenous collagen, they can still adhere to exogenous collagen, suggesting that the cells express a collagen binding factor(s) on the cell surface. When the region of col1a1 encompassing the C-terminal glycine repeat and C-prodomain (amino acids 1000-1453) was affinity-labeled with human placental alkaline phosphatase, the secreted trimeric fusion protein could bind to the surface of Ras-transformed cells. Using biochemical purification followed by matrix-assisted laser desorption/ionization mass spectrometry analysis, we identified this collagen binding factor as Endo180 (uPARAP, CD280), a member of the mannose receptor family. Ectopic expression of Endo180 in CosE5 cells followed by in situ staining and quantitative binding assays confirmed that Endo180 indeed recognizes and binds to placental alkaline phosphatase. The interaction between Endo180 and the C-terminal region of type I collagen appears to play an important role in cell-matrix adhesion.

Interleukin-24 and its receptors

Interleukin 24 (IL-24) is a new member of the IL-10 family of cytokines and it signals through two heterodimeric receptors: IL-20R1/IL-20R2 and IL-22R1/IL-20R2. Upon binding to its receptors, IL-24 induces rapid activation of Stat-1 and Stat-3 transcription factors, which appear to play a role in cell survival and proliferation. Under physiological conditions, the major sources of IL-24 are the activated monocytes and T helper 2 cells, whereas the major IL-24 target tissues, based on the receptor expression pattern, are non-haematopoietic in origin, and include skin, lung and reproductive tissues. Structurally and functionally, IL-24 is highly conserved across species. This review highlights our current knowledge of IL-24 as a cytokine, with much less emphasis placed on the non-receptor-mediated functions (a subject of several reviews) focused on in much of the earlier literature on IL-24. The potential roles of IL-24 as part of a complex cytokine network in wound healing, psoriasis and cancer are discussed.

Conservation of the genomic structure and receptor-mediated signaling between human and rat IL-24

IL-24/MDA-7 is a new member of the IL-10 family of cytokines, which signals through two heterodimeric receptor complexes (IL-20R1/IL-20R2 and IL-22R/IL-20R2). Previously, we identified a rat gene named mob-5, which encodes a secreted protein that shares a high degree of homology with human IL-24. Expression of mob-5 and its putative cell surface receptors was shown to be upregulated by oncogenic ras. Here we show that not only do rat mob-5 and human IL-24 share a strikingly similar genomic structure but also that the rat MOB-5 protein can bind to and signal through the human IL-24 receptors. Like human IL-24, binding of the rat MOB-5 protein to the human IL-24 receptors leads to activation of the JAK/STAT pathway, which in turn supports receptor-dependent survival and proliferation of Ba/F3 cells. Furthermore, using human colon cancer cell lines with somatic knockout of either the mutant or the wild-type k-ras allele, we demonstrate that the human IL-24 receptors also are upregulated by oncogenic ras. Taken together, these results provide strong experimental evidence that MOB-5 is indeed the rat homolog of human IL-24.

Interleukin 24 is induced by the RET/PTC3 oncoprotein and is an autocrine growth factor for epithelial cells

Thyroid cancers, like hematological malignancies, are commonly associated with chromosomal translocations leading to the formation of fusion proteins. Through altered signaling by fusion proteins, cell death and survival pathways are disrupted and the physiological balance of cell-cell communication may be lost. A consequence of this disruption is the release of factors by stressed cells that alert the host. One type of host response is leukocytic infiltration that may develop into chronic inflammation or autoimmune disease. Although inflammation can be associated with neoplastic tissue, the mechanism driving this process is largely unknown. Therefore, to address the mechanism of cancer inflammation we investigated the effects of an oncogene in a murine model system. A comprehensive genetic analysis revealed several soluble factors that were induced by RET/papillary thyroid carcinoma (PTC)3 gene expression including several proinflammatory cytokines, chemokines and immunologically relevant costimulatory molecules. Following a large genetic screen using RP3-expressing thyroid cells, we identified a highly abundant transcript and later identified it as interleukin 24 (Il24), a cytokine with diverse tumor suppressor and inflammatory activities. We show that RET/PTC3 induces Il24 expression in rat thyrocytes and that this expression is dependent on the signaling properties of its tyrosine kinase. Likewise, RET/PTC3 induces large amounts of Il24 following expression in murine thyrocytes, but its expression is dramatically reduced in poorly differentiated carcinomas, a finding that parallels the loss of RET/PTC3 expression. Consistent with its behavior as a tumor suppressor, the loss of Il24 coincided with the loss of RET/PTC3 in poorly differentiated mouse tumors. A functional role of Il24 in the autocrine growth/survival of RET/PTC3-expressing thyroid cells was identified helping to support its role in cellular transformation. These data suggest that the induction of Il24 by oncogenes may support tumor growth at the early stages of cancer.

Interleukin-10 and related cytokines and receptors

The Class 2 alpha-helical cytokines consist of interleukin-10 (IL-10), IL-19, IL-20, IL-22, IL-24 (Mda-7), and IL-26, interferons (IFN-alpha, -beta, -epsilon, -kappa, -omega, -delta, -tau, and -gamma) and interferon-like molecules (limitin, IL-28A, IL-28B, and IL-29). The interaction of these cytokines with their specific receptor molecules initiates a broad and varied array of signals that induce cellular antiviral states, modulate inflammatory responses, inhibit or stimulate cell growth, produce or inhibit apoptosis, and affect many immune mechanisms. The information derived from crystal structures and molecular evolution has led to progress in the analysis of the molecular mechanisms initiating their biological activities. These cytokines have significant roles in a variety of pathophysiological processes as well as in regulation of the immune system. Further investigation of these critical intercellular signaling molecules will provide important information to enable these proteins to be used more extensively in therapy for a variety of diseases.

MDA-7/IL-24 is a unique cytokine–tumor suppressor in the IL-10 Family

The melanoma differentiation associated gene-7 (mda-7) cDNA was isolated by virtue of being induced during melanoma differentiation. Initial gene transfer studies convincingly demonstrated potent antitumor effects of mda-7. Further studies showed that the mechanism of antitumor activity was due to induction of apoptosis. Most striking was the tumor-selective killing by mda-7 gene transfer--normal cells were unaffected by Adenoviral delivery of mda-7 (Ad-mda7). A variety of molecules implicated in apoptosis and intracellular signaling are regulated by Ad-mda7 transduction. Different apoptosis effector proteins are regulated in different tumor types, suggesting that Ad-mda7 may regulate various signaling pathways. mda-7 encodes a secreted protein, MDA-7, which has now been designated as IL-24, and is a novel member of the IL-10 cytokine family. MDA-7/IL-24 protein is actively secreted from cells after mda-7 gene transfer. In human peripheral blood mononuclear cells (PBMC), STAT3 activation by MDA-7/IL-24 is followed by elaboration of secondary Th1 cytokines, demonstrating that MDA-7/IL-24 is a pro-Th1 cytokine. Furthermore, MDA-7/IL-24 is antagonized by the prototypic Th2 cytokine IL-10. MDA-7/IL-24 protein is endogenously expressed in cultured NK and B-cells and is also expressed in dendritic cells in tissues. MDA-7/IL-24 protein is expressed in nevi and melanoma primary tumors, to varying degrees, but is rarely expressed in malignant melanoma or other human tumors evaluated. Indeed, loss of MDA-7/IL-24 protein expression correlates strongly with melanoma tumor invasion and disease progression. The "bystander" effects proposed for MDA-7/IL-24 protein include immune stimulation, antiangiogenesis and receptor-mediated cytotoxicity. Thus, mda-7 is a unique multifunctional cytokine in the IL-10 family and may have potent antitumor utility in a clinical setting.

Mda-7/IL-24 induces apoptosis of diverse cancer cell lines through JAK/STAT-independent pathways

Experimental evidence documents that the MDA-7/IL-24 protein (an IL-10 family cytokine) binds to IL-20 and IL-22 receptor complexes resulting in the activation of JAK/STAT signaling pathways. Recent published reports utilizing human blood derived primary lymphocytes have provided additional confirmatory evidence relating to the cytokine properties of this molecule. A notable attribute of mda-7/IL-24 is its cancer cell-specific apoptosis inducing capacity, which currently remains incompletely understood. Treatment with distinctive tyrosine kinase inhibitors (Genistein and AG18) or a JAK-selective inhibitor (AG490) did not prevent Ad.mda-7 induced apoptosis in diverse cell lines. In addition, there is no apparent correlation between patterns of expression of IL-20R1, IL-20R2, and IL-22R mRNA and susceptibility to Ad.mda-7 in different cell lines. Furthermore, Ad.mda-7 is able to induce killing in STAT/JAK deficient cells. In contrast, treatment with the p38(MAPK) selective inhibitor SB203580, partially inhibited apoptosis induced by Ad.mda-7 in different cell lines. These results demonstrate for the first time that signaling events leading to susceptibility to Ad.mda-7 induced apoptosis, might be tyrosine kinase independent and can thus be distinguished from its cytokine function related properties mediated by the IL-20/IL-22 receptor complexes that require JAK/STAT kinase activity.

Restoring apoptosis as a strategy for cancer gene therapy: focus on p53 and mda-7

Understanding the molecular and genetic determinants of cancer will provide unique opportunities for developing rational and effective therapies. Malignant cells are frequently resistant to chemotherapy and radiation induced programmed cell death (apoptosis). This resistance can occur by mutations in the tumor suppressor gene p53. Strategies designed to replace this defective tumor suppressor protein, as well as forced expression of a novel cancer specific apoptosis inducing gene, melanoma differentiation associated gene-7 (mda-7), offer promise for restoring apoptosis in tumor cells. Conditional-replicating viruses that selectively induce cytolysis in tumor cells provides an additional means of targeting cancer cells for destruction. Although these approaches represent works in progress, future refinements will in all likelihood result in the next generation of cancer therapies.

IL-20: a new target for the treatment of inflammatory skin disease

The discovery of dramatic pro-inflammatory effects of IL-20 on skin highlighted a novel regulatory pathway in cutaneous inflammation. Specific receptor complexes for IL-20 are induced on keratinocytes and transmit potent signals via the signal transducer and activator of transcription-3. In response to IL-20, keratinocytes proliferate and express pro-inflammatory genes including TNF-alpha, which leads to activation of NF-kappaB. Recently, two related cytokines, IL-19 and IL-24, have been shown to trigger the IL-20 receptor, and a second receptor complex has also been found to respond to IL-20 and IL-24. IL-20 signalling appears to be a prominent component of cutaneous inflammation, but the extent to which inflammatory processes rely upon it is unknown. Nonetheless, the prevalence of diseases involving pathological cutaneous inflammation makes the identification of safe and effective anti-inflammatory therapies for the skin a priority. Detailed understanding of the signal transduction pathways by which the skin responds to IL-20 and related factors may make it possible to develop new pharmaceutical agents to selectively suppress cutaneous inflammation.

Melanoma differentiation associated gene-7, mda-7/IL-24, selectively induces growth suppression, apoptosis and radiosensitization in malignant gliomas in a p53-independent manner

Malignant gliomas are extremely aggressive cancers currently lacking effective treatment modalities. Gene therapy represents a promising approach for this disease. A requisite component for improving gene-based therapies of brain cancer includes tumor suppressor genes that exhibit cancer constrained inhibitory activity. Subtraction hybridization identified melanoma differentiation associated gene-7 (mda-7) as a gene associated with melanoma cell growth, differentiation and progression. Ectopic expression of mda-7 by means of a replication-incompetent adenovirus (Ad), Ad.mda-7, induces growth suppression and apoptosis selectively in diverse human cancers, without producing any apparent harmful effect in normal cells. We presently demonstrate that Ad.mda-7 induces growth inhibition and apoptosis in malignant human gliomas expressing both mutant and wild-type p53, and these effects correlate with an elevation in expression of members of the growth arrest and DNA damage (GADD) gene family. In contrast, infection with a recombinant Ad expressing wild-type p53, Ad.wtp53, specifically affects mutant p53 expressing gliomas. When tested in early passage normal and immortal human fetal astrocytes, growth inhibition resulting from infection with Ad.mda-7 or Ad.wtp53 is significantly less than in malignant gliomas and no toxicity is evident in these normal cells. Moreover, infection of gliomas with Ad.mda-7 or treatment with purified GST-MDA-7 protein sensitizes both wild-type and mutant p53 expressing tumor cells to the growth inhibitory and antisurvival effects of ionizing radiation, and this response correlates with increased expression of specific members of the GADD gene family. Since heterogeneity in p53 expression is common in evolving gliomas, the present findings suggest that Ad.mda-7 may, in many instances, prove more beneficial for the gene-based therapy of malignant gliomas than administration of wild-type p53.

MDA-7/IL-24: novel cancer growth suppressing and apoptosis inducing cytokine

The melanoma differentiation-associated gene-7 (mda-7) was cloned by subtraction hybridization as a molecule whose expression is elevated in terminally differentiated human melanoma cells. Current information based on structural and sequence homology, has led to the recognition of MDA-7 as an IL-10 family cytokine member and its renaming as IL-24. Northern blot analysis revealed mda-7/IL-24 expression in human tissues associated with the immune system such as spleen, thymus, peripheral blood leukocytes and normal melanocytes. The MDA-7/IL-24 mouse counterpart, FISP, appears to be a Th2-specific protein and the rat counterpart, C49A/MOB-5, is associated with wound healing and is also induced as a consequence of ras-transformation. A notable property of MDA-7/IL-24 is its ability to induce apoptosis in a large spectrum of human cancer derived cell lines, in mouse xenografts and upon intratumoral injection in human tumors (phase I clinical trials). Various aspects of this intriguing molecule including its cytokine and anti-tumoral effects are described and discussed.

The identification of novel wound-healing genes through differential display

Effective methods to identify novel genes in complicated dynamic tissue processes are needed in molecular biology research. Traditional techniques primarily target known genes and are inefficient in the pursuit of unknown genes. Here we describe the use of a modified differential display polymerase chain reaction (DD-PCR) protocol for the identification of genes differentially expressed in wound healing. Full-thickness dorsal wounds were made on 35 adult rats, followed by wound harvest at 12 hours, 24 hours, 3 days, 5 days, 7 days, 10 days, and 14 days after injury. Modified DD-PCR was performed and gene fragments displaying definite changes during wound healing were cloned and sequenced. Gene fragments from DD-PCR were compared with available gene bank database sequences. Specific primer PCR was used to confirm DD-PCR expression patterns. As a result, over 1000 gene fragments were amplified by DD-PCR, 35 of which demonstrated distinct differences during repair. Cloning and sequencing of 13 of these gene fragments revealed that some were homologous to several characterized genes with previously unsuspected roles in repair, whereas others were completely novel genes with no known function. Specific primer PCR further confirmed expression of six of these 13 gene fragments. Only one of the 13 cloned fragments, later identified as interleukin-1beta, had well-recognized associations with tissue injury. Other fragments corresponded to various genes involved in cellular processes such as differentiation, proliferation, exocytosis, and myofibril assembly. No prior studies have linked them to wound healing. We have demonstrated that modified DD-PCR can be used to effectively identify novel genes differentially expressed during repair. Because DD-PCR allows for the simultaneous amplification of multiple arbitrary transcripts, it is a powerful genetic screening tool for complicated dynamic tissue processes, particularly when multiple, limited-sized samples are involved.

mda-7 (IL-24) Mediates selective apoptosis in human melanoma cells by inducing the coordinated overexpression of the GADD family of genes by means of p38 MAPK

Subtraction hybridization identified melanoma differentiation-associated gene-7 (mda-7) as a gene induced during terminal differentiation in human melanoma cells. On the basis of structure, chromosomal localization and cytokine-like properties, mda-7 is classified as IL-24. Administration of mda-7/IL-24 by means of a replication-incompetent adenovirus (Ad.mda-7) induces apoptosis selectively in diverse human cancer cells without inducing harmful effects in normal fibroblast or epithelial cells. The present studies investigated the mechanism underlying this differential apoptotic effect. Infection of melanoma cells, but not normal immortal melanocytes, with Ad.mda-7 induced a time- and dose-dependent increase in expression, mRNA and protein, of a family of growth arrest and DNA damage (GADD)-inducible genes, which correlated with induction of apoptosis. Among the members of the GADD family of genes, GADD153, GADD45 alpha, and GADD34 displayed marked, and GADD45 gamma showed minimal induction. Treatment of melanoma cells with SB203580, a selective inhibitor of the p38 mitogen-activated protein kinase (MAPK) pathway, effectively inhibited Ad.mda-7-induced apoptosis. Additional support for an involvement of the p38 MAPK pathway in Ad.mda-7-mediated apoptosis was documented by using an adenovirus expressing a dominant negative mutant of p38 MAPK. Infection with Ad.mda-7 increased the phosphorylation of p38 MAPK and heat shock protein 27 in melanoma cells but not in normal immortal melanocytes. In addition, SB203580 effectively inhibited Ad.mda-7-mediated induction of the GADD family of genes in a time- and dose-dependent manner, and it effectively blocked Ad.mda-7-mediated down-regulation of the antiapoptotic protein BCL-2. Inhibition of GADD genes by an antisense approach either alone or in combination also effectively blocked Ad.mda-7-induced apoptosis in melanoma cells. These results support the hypothesis that Ad.mda-7 mediates induction of the GADD family of genes by means of the p38 MAPK pathway, thereby resulting in the selective induction of apoptosis in human melanoma cells.

The conserved helix C region in the superfamily of interferon-gamma /interleukin-10-related cytokines corresponds to a high-affinity binding site for the HSP70 chaperone DnaK

HSP70 chaperones mediate protein folding by ATP-dependent interaction with short linear peptide segments that are exposed on unfolded proteins. The mode of action of the Escherichia coli homolog DnaK is representative of all HSP70 chaperones, including the endoplasmic reticulum variant BiP/GRP78. DnaK has been shown to be effective in assisting refolding of a wide variety of prokaryotic and eukaryotic proteins, including the alpha-helical homodimeric secretory cytokine interferon-gamma (IFN-gamma). We screened solid-phase peptide libraries from human and mouse IFN-gamma to identify DnaK-binding sites. Conserved DnaK-binding sites were identified in the N-terminal half of helix B and in the C-terminal half of helix C, both of which are located at the IFN-gamma dimer interface. Soluble peptides derived from helices B and C bound DnaK with high affinity in competition assays. No DnaK-binding sites were found in the loops connecting the alpha-helices. The helix C DnaK-binding site appears to be conserved in most members of the superfamily of interleukin (IL)-10-related cytokines that comprises, apart from IL-10 and IFN-gamma, a series of recently discovered small secretory proteins, including IL-19, IL-20, IL-22/IL-TIF, IL-24/MDA-7 (melanoma differentiation-associated gene), IL-26/AK155, and a number of viral IL-10 homologs. These cytokines belong to a relatively small group of homodimeric proteins with highly interdigitated interfaces that exhibit the strongly hydrophobic character of the interior core of a single-chain folded domain. We propose that binding of DnaK to helix C in the superfamily of IL-10-related cytokines may constitute the hallmark of a novel conserved regulatory mechanism in which HSP70-like chaperones assist in the formation of a hydrophobic dimeric "folding" interface.

The protein product of the tumor suppressor gene, melanoma differentiation-associated gene 7, exhibits immunostimulatory activity and is designated IL-24

The melanoma differentiation-associated gene 7 (mda-7) has been studied primarily in the context of its tumor suppressor activity. Although mda-7 has been designated as IL-24 based on its gene location in the IL-10 locus and its mRNA expression in leukocytes, no functional evidence supporting this cytokine designation exists. To further characterize MDA-7/IL-24 expression patterns in the human immune system, MDA-7/IL-24 protein levels were examined in human PBMC. MDA-7/IL-24 was detected in PHA- and LPS-stimulated whole PBMC lysate by Western blot and in PHA-activated CD56 and CD19 subsets by immunohistochemistry. The biological function of MDA-7/IL-24, secreted from Ad-MDA7-transfected HEK 293 cells, was assessed by examining the effect of MDA-7/IL-24 on the cytokine secretion profile of PBMC. Within 48 h MDA-7/IL-24 induced secretion of high levels of IL-6, TNF-alpha, and IFN-gamma and low levels of IL-1beta, IL-12, and GM-CSF from human PBMC as measured by ELISA. The MDA-7/IL-24-mediated induction of these Th1-type cytokines was inhibited by the addition of IL-10 to the PBMC cultures, suggesting that these two related protein family members may provide antagonistic functions. Therefore, because human blood leukocytes can be stimulated to produce MDA-7/IL-24, as well as respond to MDA-7/IL-24 by expressing secondary cytokines, MDA-7/IL-24 has the expression profile and major functional attributes that justify its designation as an IL.

The family of IL-10-related cytokines and their receptors: related, but to what extent?

Five novel cytokines (IL-19, IL-20, IL-22 (IL-TIF), IL-24 (human MDA-7, mouse FISP, rat C49A/Mob-5), and IL-26 (AK155)) demonstrating limited primary sequence identity and probable structural homology to IL-10 have been identified. These cellular cytokines, as well as several cytokines encoded in viral genomes (viral cytokines), form a family of IL-10-related cytokines or the IL-10 family. These cytokines share not only homology but also receptor subunits and perhaps activities. Receptors for these cytokines belong to the class II cytokine receptor family. The receptors are IL-10R2 (CRF2-4), IL-22R1 (CRF2-9), IL-22BP (CRF2-10), IL-20R1 (CRF2-8) and IL-20R2 (CRF2-11). Biological activities of these cytokines, receptor utilization and signaling, as well as expression patterns for cytokines and their receptors are summarized. Although data indicate that these cytokines are involved in regulation of inflammatory and immune responses, their major functions remain to be discovered.

Interleukin 24 (MDA-7/MOB-5) signals through two heterodimeric receptors, IL-22R1/IL-20R2 and IL-20R1/IL-20R2

Interleukin 24 (IL-24) encodes a secreted protein that exhibits significant homology to the interleukin 10 (IL-10) family of cytokines. Here we show that the human IL-24 is secreted by activated peripheral blood mononuclear cells and is the ligand for two heterodimeric receptors, IL-22R1/IL-20R2 and IL-20R1/IL-20R2. The latter is also the receptor for IL-20. COS cells transfected with either IL-24 receptor heterodimers bind the ligand with similar saturation kinetics. IL-24 binding to either its endogenous receptors on human keratinocytes or to ectopically expressed receptors on baby hamster kidney cells leads to activation of the signal transducers and activators of transcription. Taken together, these results provide compelling evidence for IL-24 being the fourth member of IL-10 family of cytokines to which their specific receptors have been identified.

The interleukin-10 family of cytokines

A family of interleukin-10 (IL-10)-related cytokines has emerged, comprising a series of herpesviral and poxviral members and several cellular sequence paralogs, including IL-19, IL-20, IL-22 [IL-10-related T-cell-derived inducible factor (IL-TIF)], IL-24 [melanoma differentiation-associated antigen 7 (MDA-7)] and IL-26 (AK155). Although the predicted helical structure of these homodimeric molecules is conserved, certain receptor-binding residues are variable and define the interaction with specific heterodimers of different type-2 cytokine receptors. This leads, through the activation of signal transducer and activator of transcription (STAT) factors, to diverse biological effects. For example, whereas IL-10 is a well-studied pleiotropic immunosuppressive and immunostimulatory cytokine, IL-22/IL-TIF mediates acute-phase response signals in hepatocytes and IL-20 induces the hyperproliferation of keratinocytes, which has been proposed as a pathogenic mechanism of psoriasis.

The cancer growth suppressing gene mda-7 induces apoptosis selectively in human melanoma cells

Human melanoma cells growth arrest irreversibly, lose tumorigenic potential and terminally differentiate after treatment with a combination of fibroblast interferon (IFN-beta) and the protein kinase C activator mezerein (MEZ). Applying subtraction hybridization to this model differentiation system permitted cloning of melanoma differentiation associated gene-7, mda-7. Expression of mda-7 inversely correlates with melanoma development and progression, with elevated expression in normal melanocytes and nevi and increasingly reduced expression in radial growth phase, vertical growth phase and metastatic melanoma. When expressed by means of a replication incompetent adenovirus (Ad.mda-7) growth of melanoma, but not normal early passage or immortal human melanocytes, is dramatically suppressed and cells undergo programmed cell death (apoptosis). Infection of metastatic melanoma cells with Ad.mda-7 results in an increase in cells in the G(2)/M phase of the cell cycle and changes in the ratio of pro-apoptotic (BAX, BAK) to anti-apoptotic (BCL-2, BCL-XL) proteins. Ad.mda-7 infection results in a temporal increase in mda-7 mRNA and intracellular MDA-7 protein in most of the melanocyte/melanoma cell lines and secretion of MDA-7 protein is readily detected following Ad.mda-7 infection of both melanocytes and melanoma cells. The present studies document a differential response of melanocytes versus melanoma cells to ectopic expression of mda-7 and support future applications of mda-7 for the gene-based therapy of metastatic melanoma.

Genomic structure, chromosomal localization and expression profile of a novel melanoma differentiation associated (mda-7) gene with cancer specific growth suppressing and apoptosis inducing properties

Abnormalities in cellular differentiation are frequent occurrences in human cancers. Treatment of human melanoma cells with recombinant fibroblast interferon (IFN-beta) and the protein kinase C activator mezerein (MEZ) results in an irreversible loss in growth potential, suppression of tumorigenic properties and induction of terminal cell differentiation. Subtraction hybridization identified melanoma differentiation associated gene-7 (mda-7), as a gene induced during these physiological changes in human melanoma cells. Ectopic expression of mda-7 by means of a replication defective adenovirus results in growth suppression and induction of apoptosis in a broad spectrum of additional cancers, including melanoma, glioblastoma multiforme, osteosarcoma and carcinomas of the breast, cervix, colon, lung, nasopharynx and prostate. In contrast, no apparent harmful effects occur when mda-7 is expressed in normal epithelial or fibroblast cells. Human clones of mda-7 were isolated and its organization resolved in terms of intron/exon structure and chromosomal localization. Hu-mda-7 encompasses seven exons and six introns and encodes a protein with a predicted size of 23.8 kDa, consisting of 206 amino acids. Hu-mda-7 mRNA is stably expressed in the thymus, spleen and peripheral blood leukocytes. De novo mda-7 mRNA expression is also detected in human melanocytes and expression is inducible in cells of melanocyte/melanoma lineage and in certain normal and cancer cell types following treatment with a combination of IFN-beta plus MEZ. Mda-7 expression is also induced during megakaryocyte differentiation induced in human hematopoietic cells by treatment with TPA (12-O-tetradecanoyl phorbol-13-acetate). In contrast, de novo expression of mda-7 is not detected nor is it inducible by IFN-beta+MEZ in a spectrum of additional normal and cancer cells. No correlation was observed between induction of mda-7 mRNA expression and growth suppression following treatment with IFN-beta+MEZ and induction of endogenous mda-7 mRNA by combination treatment did not result in significant intracellular MDA-7 protein. Radiation hybrid mapping assigned the mda-7 gene to human chromosome 1q, at 1q 32.2 to 1q41, an area containing a cluster of genes associated with the IL-10 family of cytokines. Mda-7 represents a differentiation, growth and apoptosis associated gene with potential utility for the gene-based therapy of diverse human cancers.

Cutting edge: STAT activation by IL-19, IL-20 and mda-7 through IL-20 receptor complexes of two types

IL-10-related cytokines include IL-20 and IL-22, which induce, respectively, keratinocyte proliferation and acute phase production by hepatocytes, as well as IL-19, melanoma differentiation-associated gene 7, and AK155, three cytokines for which no activity nor receptor complex has been described thus far. Here, we show that mda-7 and IL-19 bind to the previously described IL-20R complex, composed by cytokine receptor family 2-8/IL-20Ralpha and DIRS1/IL-20Rbeta (type I IL-20R). In addition, mda-7 and IL-20, but not IL-19, bind to another receptor complex, composed by IL-22R and DIRS1/IL20Rbeta (type II IL-20R). In both cases, binding of the ligands results in STAT3 phosphorylation and activation of a minimal promoter including STAT-binding sites. Taken together, these results demonstrate that: 1) IL-20 induces STAT activation through IL-20R complexes of two types; 2) mda-7 and IL-20 redundantly signal through both complexes; and 3) IL-19 signals only through the type I IL-20R complex.

Interleukin-10 and the interleukin-10 receptor

Interleukin-10 (IL-10), first recognized for its ability to inhibit activation and effector function of T cells, monocytes, and macrophages, is a multifunctional cytokine with diverse effects on most hemopoietic cell types. The principal routine function of IL-10 appears to be to limit and ultimately terminate inflammatory responses. In addition to these activities, IL-10 regulates growth and/or differentiation of B cells, NK cells, cytotoxic and helper T cells, mast cells, granulocytes, dendritic cells, keratinocytes, and endothelial cells. IL-10 plays a key role in differentiation and function of a newly appreciated type of T cell, the T regulatory cell, which may figure prominently in control of immune responses and tolerance in vivo. Uniquely among hemopoietic cytokines, IL-10 has closely related homologs in several virus genomes, which testify to its crucial role in regulating immune and inflammatory responses. This review highlights findings that have advanced our understanding of IL-10 and its receptor, as well as its in vivo function in health and disease.

Cytokines: IL-20 - a new effector in skin inflammation

The newly discovered cytokine interleukin-20 (IL-20) is structurally related to IL-10, yet it appears to be an autocrine factor for keratinocytes that regulates their participation in inflammation.

Differential display analysis of gene expression altered by ras oncogene

The goal of the signal transduction pathways, such as those controlled by Ras, is in large part to ensure highly stringent regulation of the target genes in the nucleus, which are collectively responsible for the signal output, or phenotypes, of the cell. Understanding of the Ras effect ultimately requires the identification of these downstream target genes. Reverse genetic approaches would trace back the pathways by which they are regulated by Ras. While newer methods such as DNA microarray are emerging, differential display has allowed the identification of a greater number of differentially expressed genes than have been cloned by all the other methods combined, based on Medline search. Much of this success has been attributed to its simplicity (RT-PCR and DNA-sequencing gel) and versatility (compare more than two RNAs for both up- and downregulated genes). It has become obvious that finding the genes by either differential display or DNA microarray is only the first step toward the understanding of biological problems under investigation. It is hoped that finding the right genes through careful experimental designs, such as outlined here, will narrow down the number of relevant genes and increase the odds for solving the puzzles of nature, such as ras.

Cutting edge: FISP (IL-4-induced secreted protein), a novel cytokine-like molecule secreted by Th2 cells

Th cell subsets, namely Th1 and Th2 cells, play an important role in mounting an immune response against invading pathogens. Several genes are selectively up-regulated during differentiation and effector phases of Th subsets. In this study, we report the identification of a novel cytokine-like molecule designated FISP (IL-4-induced secreted protein), which is selectively expressed and secreted by Th2 cells. Detectable levels of FISP are observed only 3 days after initiation of Th2 differentiation. Expression of FISP in developing Th cells requires at least two signals: TCR signaling involving protein kinase C activation and STAT6-dependent IL-4R signaling.

Interleukin-10 and the Interleukin-10 Receptor

Interleukin-10 (IL-10), first recognized for its ability to inhibit activation and effector function of T cells, monocytes, and macrophages, is a multifunctional cytokine with diverse effects on most hemopoietic cell types. The principal routine function of IL-10 appears to be to limit and ultimately terminate inflammatory responses. In addition to these activities, IL-10 regulates growth and/or differentiation of B cells, NK cells, cytotoxic and helper T cells, mast cells, granulocytes, dendritic cells, keratinocytes, and endothelial cells. IL-10 plays a key role in differentiation and function of a newly appreciated type of T cell, the T regulatory cell, which may figure prominently in control of immune responses and tolerance in vivo. Uniquely among hemopoietic cytokines, IL-10 has closely related homologs in several virus genomes, which testify to its crucial role in regulating immune and inflammatory responses. This review highlights findings that have advanced our understanding of IL-10 and its receptor, as well as its in vivo function in health and disease.

Identification of the functional interleukin-22 (IL-22) receptor complex: the IL-10R2 chain (IL-10Rbeta ) is a common chain of both the IL-10 and IL-22 (IL-10-related T cell-derived inducible factor, IL-TIF) receptor complexes

Interleukin-10 (IL-10)-related T cell-derived inducible factor (IL-TIF; provisionally designated IL-22) is a cytokine with limited homology to IL-10. We report here the identification of a functional IL-TIF receptor complex that consists of two receptor chains, the orphan CRF2-9 and IL-10R2, the second chain of the IL-10 receptor complex. Expression of the CRF2-9 chain in monkey COS cells renders them sensitive to IL-TIF. However, in hamster cells both chains, CRF2-9 and IL-10R2, must be expressed to assemble the functional IL-TIF receptor complex. The CRF2-9 chain (or the IL-TIF-R1 chain) is responsible for Stat recruitment. Substitution of the CRF2-9 intracellular domain with the IFN-gammaR1 intracellular domain changes the pattern of IL-TIF-induced Stat activation. The CRF2-9 gene is expressed in normal liver and kidney, suggesting a possible role for IL-TIF in regulating gene expression in these tissues. Each chain, CRF2-9 and IL-10R2, is capable of binding IL-TIF independently and can be cross-linked to the radiolabeled IL-TIF. However, binding of IL-TIF to the receptor complex is greater than binding to either receptor chain alone. Sharing of the common IL-10R2 chain between the IL-10 and IL-TIF receptor complexes is the first such case for receptor complexes with chains belonging to the class II cytokine receptor family, establishing a novel paradigm for IL-10-related ligands similar to the shared use of the gamma common chain (gamma(c)) by several cytokines, including IL-2, IL-4, IL-7, IL-9, and IL-15.