{"gene":"IL20","run_date":"2026-06-10T01:55:22","timeline":{"discoveries":[{"year":2001,"finding":"IL-20 signals through two distinct receptor complexes: a type I complex (IL-20Rα/IL-20Rβ) and a type II complex (IL-22R/IL-20Rβ). Both receptor complexes, upon ligand binding, induce STAT3 phosphorylation and activation of STAT-binding site promoters. IL-19 signals only through the type I complex, while mda-7/IL-24 signals through both.","method":"Receptor binding assays, STAT3 phosphorylation assays, reporter gene (minimal promoter with STAT-binding sites)","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — direct receptor binding and signaling assays with multiple ligands, replicated across subsequent studies","pmids":["11564763"],"is_preprint":false},{"year":2007,"finding":"IL-20 induces acanthosis, expression of psoriasis-associated proteins S100A7 and keratin 16, and persistent nuclear STAT3 activation in reconstituted human epidermis (RHE). Gene expression analysis showed IL-20 regulates inflammatory response genes, wound healing, and keratinocyte differentiation markers.","method":"Reconstituted human epidermis (RHE) model, gene expression microarray, immunohistochemistry","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — reconstituted tissue model with microarray and histological validation, replicated by multiple labs","pmids":["17277128"],"is_preprint":false},{"year":2009,"finding":"IL-22 induces IL-20 mRNA and protein production in human keratinocytes, establishing a cytokine cascade. Some IL-22 effects on differentiation-regulating genes were partially mediated by endogenous secreted IL-20, as demonstrated by partial attenuation with anti-IL-20 antibody. IL-17A and TNF-α also induced IL-20 in keratinocytes, but IFN-γ and IL-20 itself did not regulate IL-20 expression.","method":"Keratinocyte culture with cytokine stimulation, RT-PCR, ELISA, neutralizing antibody blockade","journal":"European journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (RT-PCR, ELISA, antibody neutralization) in single lab","pmids":["19830738"],"is_preprint":false},{"year":2006,"finding":"IL-20 is produced by monocytes and keratinocytes. In keratinocytes, IL-1β increases IL-20 expression approximately 10-fold. Neither receptor complex for IL-20 (IL-20R1/IL-20R2 nor IL-22R1/IL-20R2) is expressed on immune cells, and IL-20 does not activate STAT molecules in immune cells. IFN-γ decreases IL-20R1 expression and increases IL-22R1 expression on keratinocytes.","method":"Quantitative RT-PCR, STAT activation assays, flow cytometry, in vitro stimulation","journal":"Experimental dermatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple cell types tested with orthogonal methods, single lab","pmids":["17083366"],"is_preprint":false},{"year":2006,"finding":"IL-20 expression in psoriatic skin is predominantly from CD68+/CD11c+ myeloid-derived dermal leukocytes (monocytes), not keratinocytes. In vitro, plastic adhesion, β2 integrin activation, and TNF-α stimulate IL-20 expression in monocytes. IL-20 treatment of keratinocytes upregulates IFN-γ-induced and disease-related genes as assessed by microarray.","method":"Immunohistochemistry, in vitro monocyte stimulation, microarray of IL-20-treated keratinocytes","journal":"The Journal of investigative dermatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (IHC, in vitro, microarray) in single lab","pmids":["16645593"],"is_preprint":false},{"year":2006,"finding":"IL-20 promotes atherosclerosis in apolipoprotein E-deficient mice when delivered via intramuscular electroporation of expression vector. IL-20 upregulates CXCL9 and CXCL11 transcripts in human umbilical vein endothelial cells. IL-20 transcripts increase in hypoxic monocytes and monocytes treated with oxidized LDL.","method":"In vivo IL-20 expression vector delivery in ApoE-/- mice, in vitro endothelial cell stimulation, RT-PCR","journal":"Arteriosclerosis, thrombosis, and vascular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo functional model plus in vitro mechanistic studies, single lab","pmids":["16778121"],"is_preprint":false},{"year":2007,"finding":"IL-20 promotes arteriogenesis and improves blood perfusion in a rat ischemic hind-limb model. In endothelial cells, IL-20 activates JAK2/STAT5, Erk1/2, and Akt phosphorylation; activates small GTP-binding proteins Rac and Rho; induces intracellular calcium release; and promotes tube formation without affecting endothelial cell proliferation or motility.","method":"In vitro endothelial cell signaling assays, tube formation assay, in vivo rat hind-limb ischemia model with IL-20 delivery","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro mechanistic signaling dissection plus in vivo functional model with multiple orthogonal methods","pmids":["17878297"],"is_preprint":false},{"year":2009,"finding":"Maturing dendritic cells (DCs) produce IL-20 in response to bacterial stimuli and inflammatory cytokines. In keratinocytes, IL-20 induces expression of antimicrobial proteins. Combining IL-20 and IL-29 resulted in a stronger response to TLR2 and TLR3 activation in keratinocytes than either cytokine alone.","method":"Monocyte/DC differentiation in vitro, RT-PCR, co-stimulation assays in keratinocytes","journal":"Journal of leukocyte biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple cell types and stimulation conditions, single lab","pmids":["18281438"],"is_preprint":false},{"year":2009,"finding":"IL-20R2-deficient CD8+ and CD4+ T cells show significantly elevated IFN-γ and IL-2 secretion upon stimulation with Con A or anti-CD3/CD28, while IL-10 secretion by activated CD4+ IL-20R2-/- cells is diminished. IL-20R2 knockout mice develop more antigen-specific CD8+ and CD4+ IFN-γ+ T cells after DNA vaccination and show increased sensitivity in a contact hypersensitivity model, demonstrating that IL-20R2 signaling (by IL-19, IL-20, IL-24) directly down-regulates T cell responses in vitro and in vivo.","method":"IL-20R2 knockout mouse generation, in vitro T cell stimulation, DNA vaccination model, contact hypersensitivity model","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — genetic knockout with multiple in vitro and in vivo functional readouts","pmids":["19124723"],"is_preprint":false},{"year":2009,"finding":"IL-20 activates lymphatic endothelial cells (hTERT-HDLEC) causing increased intracellular calcium, Akt and eNOS phosphorylation (via PI3K/Akt), NO production, ERK1/2 and mTOR phosphorylation, actin polymerization, tube formation (PI3K- and mTOR-dependent), and cell migration comparable to VEGF-C. ERK1/2 pathway mediates IL-20-induced proliferation.","method":"Calcium imaging, Western blotting for phosphorylated signaling intermediates, pharmacological inhibitors (wortmannin, rapamycin, PD98059), tube formation and sprouting assays in lymphatic endothelial cells","journal":"Microvascular research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple signaling assays with pharmacological inhibitors, single lab","pmids":["19281830"],"is_preprint":false},{"year":2009,"finding":"IL-20 is regulated by hypoxia-inducible factor-1α (HIF-1α): two putative hypoxia response elements (HREs) in the human IL20 gene promoter were identified, and HIF-1α inhibition blocked CoCl2-induced IL-20 expression. IL-20 activates JAK2/STAT3 and ERK1/2 signaling in glioblastoma cells and induces their proliferation and production of IL-1β, IL-8, and MCP-1.","method":"Promoter activity (luciferase reporter), HIF-1α inhibitor treatment, signaling assays (JAK2/STAT3, ERK1/2 phosphorylation), in vitro proliferation assays","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reporter assays and signaling studies with pharmacological inhibition, single lab","pmids":["19342680"],"is_preprint":false},{"year":2013,"finding":"IL-19, IL-20, and IL-24 signaling through type I and type II IL-20 receptors suppresses cutaneous IL-1β and IL-17A production, thereby promoting S. aureus infection in mice. Antibody blockade of the IL-20 receptor improved infection outcomes in mice. Similar immunosuppressive effects were observed in human keratinocytes exposed to S. aureus.","method":"In vivo murine S. aureus infection model with cytokine treatment or receptor blockade, in vitro human keratinocyte stimulation, cytokine measurement","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo loss-of-function (antibody blockade) and in vitro mechanistic studies with defined readouts, high-impact journal","pmids":["23793061"],"is_preprint":false},{"year":2014,"finding":"IL-20 activates hepatic stellate cells (HSCs) and upregulates TGF-β1 expression. IL-20 increases TGF-β1, TNF-α, and type I collagen expression and promotes proliferation and migration of activated HSCs. Anti-IL-20 monoclonal antibody and anti-IL-20R1 monoclonal antibody attenuate CCl4-induced liver fibrosis in mice. IL-20R1-deficient mice are protected from liver injury.","method":"In vitro HSC activation assays, CCl4 mouse model of liver fibrosis, monoclonal antibody treatment, IL-20R1 knockout mice, ELISA, histology","journal":"Hepatology (Baltimore, Md.)","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout plus antibody blockade with multiple in vitro and in vivo functional readouts, single lab but orthogonal methods","pmids":["24763901"],"is_preprint":false},{"year":2015,"finding":"IL-20 expression in MCF-7 breast cancer cells is transcriptionally induced by estradiol (E2) through estrogen receptor α (ERα)-mediated recruitment of the histone methyltransferase KMT2B to the IL-20 promoter, leading to H3K4 methylation. Depletion of KMT2B or IL-20 disrupts estrogen signaling, attenuates cell proliferation, reduces colony formation, and causes cell cycle arrest.","method":"ChIP assay for histone methylation and transcription factor binding, siRNA knockdown of KMT2B and IL-20, cell proliferation and colony formation assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and loss-of-function with functional readouts, single lab","pmids":["27806114"],"is_preprint":false},{"year":2015,"finding":"IL-20 post-transcriptional regulation in psoriatic skin involves the RNA-binding protein HuR, which relocalizes from the nucleus to the cytoplasm in psoriatic keratinocytes to stabilize IL-20 mRNA. AMPK activity is impaired in psoriatic epidermis and is responsible for HuR cytoplasmic relocalization. In vivo AMPK inhibition in mouse epidermis promotes HuR cytoplasmic localization and IL-20 overproduction with accompanying acanthosis and hyperkeratosis.","method":"Ribonucleoprotein immunoprecipitation with high-throughput sequencing (RIP-seq), immunofluorescence for HuR localization, in vivo pharmacological AMPK inhibition in mice, histology","journal":"The Journal of investigative dermatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RIP-seq, in vivo mouse model, and cellular localization studies, single lab","pmids":["26176762"],"is_preprint":false},{"year":2017,"finding":"IL-20 directly targets activated human neutrophils: upon migration and activation (mimicking S. aureus infection conditions), neutrophils alter expression of IL-20 receptor chains and become responsive to IL-20, which inhibits actin polymerization and actin-dependent functions including phagocytosis, granule exocytosis, and migration.","method":"In vitro neutrophil activation/migration assays, flow cytometry for receptor expression, actin polymerization assays, phagocytosis and granule exocytosis assays","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays on primary human neutrophils, single lab","pmids":["28424238"],"is_preprint":false},{"year":2017,"finding":"A transcriptional complex composed of ERα, GATA3, FOXA1, and ELL3 regulates IL-20 expression in ER+ breast cancer cells. ELL3 associates with ERα to increase its binding affinity to the IL-20 promoter and may prevent FOXA1 (a repressor) from binding the same region. GATA3 and ERα activate IL-20 expression while FOXA1 represses it.","method":"ChIP assays, co-immunoprecipitation, siRNA knockdown, promoter reporter assays","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and Co-IP with loss-of-function, single lab","pmids":["28514748"],"is_preprint":false},{"year":2020,"finding":"IL-20 promotes cardiomyocyte apoptosis during hypoxia/reoxygenation (H/R) by activating the PKC/NADPH oxidase pathway, leading to increased Ca2+, elevated oxidative stress, and downregulation of AKT. Anti-IL-20 treatment reduced cardiomyocyte apoptosis in the H/R model.","method":"In vitro H9C2 and primary cardiomyocyte H/R model, Western blotting for signaling intermediates, viability assays, pharmacological inhibition","journal":"Biochimica et biophysica acta. Molecular basis of disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined signaling pathway with multiple readouts in vitro, single lab","pmids":["31953216"],"is_preprint":false},{"year":2020,"finding":"IL-20 regulates adipocyte differentiation and promotes polarization of bone marrow-derived macrophages toward proinflammatory M1 type. IL-20 causes inflammation and macrophage retention in adipose tissues by upregulating TNF-α, MCP-1, netrin 1, and unc5b in macrophages and netrin 1, leptin, and MCP-1 in adipocytes. IL-20 promotes insulin resistance by inhibiting glucose uptake in mature adipocytes through the SOCS-3 pathway.","method":"In vitro adipocyte differentiation and macrophage polarization assays, Western blotting, ELISA, glucose uptake assays, in vivo HFD mouse model with anti-IL-20 antibody treatment","journal":"Immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple in vitro functional assays plus in vivo antibody blockade, single lab","pmids":["34403503"],"is_preprint":false},{"year":2022,"finding":"IL-20 subfamily cytokines (IL-19, IL-20, IL-24) impair the oesophageal epithelial barrier by downregulating filaggrins and other cornified envelope proteins via the MAPK/ERK1/2 pathway. Il20R2-/- animals show reduced eosinophil infiltration, lower Th2 cytokine expression, and preserved filaggrin expression in experimental EoE. ERK1/2 blockade prevents epithelial barrier impairment in patient-derived air-liquid interface cultures and attenuates experimental EoE.","method":"Patient-derived oesophageal organoids, RNA-seq, mass spectrometry, Il20R2 knockout EoE mouse model, air-liquid interface cultures with ERK1/2 inhibition","journal":"Gut","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — genetic knockout, pharmacological pathway blockade, transcriptomics, proteomics, and organoid models, multiple orthogonal methods","pmids":["35613844"],"is_preprint":false},{"year":2024,"finding":"IL-20 controls resolution of experimental colitis by inducing STAT3 and suppressing IFN/STAT2 signaling in intestinal epithelial cells (IECs). IL-20 deficiency or IL-20Rb deficiency increases IFN/STAT2 activity and susceptibility to DSS-induced colitis. IL-20 blocks IFN/STAT2-induced necroptotic cell death in IEC-derived organoids. Epithelial STAT2 deletion (Stat2 knockout in IECs) reduces colitis susceptibility, and IL-20 administration suppresses colitis in wild-type animals.","method":"Il20 and Il20rb knockout mice, DSS colitis model, IEC-derived 3D organoids, RNA-seq, Western blot, co-immunoprecipitation, confocal microscopy, RNAScope, recombinant IL-20 administration","journal":"Gut","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple genetic knockouts, organoid functional assays, co-IP, and in vivo rescue experiments with orthogonal methods","pmids":["37884352"],"is_preprint":false},{"year":2003,"finding":"IL-20 selectively enhances colony formation by CD34+ multipotential hematopoietic progenitors in vitro, with no effect on erythroid, granulocyte-macrophage, or megakaryocyte progenitors. IL-20 transgenic mice show increased numbers and cell cycling of multipotential (but not other) progenitors in vivo.","method":"In vitro colony formation assays with CD34+ progenitors, IL-20 transgenic mouse model, cell cycle analysis","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro and in vivo functional assays with transgenic model, single lab","pmids":["12855566"],"is_preprint":false},{"year":2004,"finding":"LPS induces IL-20 expression in primary murine glial cells and RAW264.7 macrophages through a MyD88-p38 MAPK-dependent signaling pathway, independent of de novo protein synthesis. Dexamethasone inhibits LPS-induced IL-20 expression, indicating negative glucocorticoid feedback regulation.","method":"Primary glial cell culture with LPS, MyD88-deficient mice, pharmacological inhibitor (SB203580 for p38), protein synthesis inhibitors, RT-PCR","journal":"Brain research. Molecular brain research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockout mice and pharmacological inhibition with molecular readouts, single lab","pmids":["15519673"],"is_preprint":false},{"year":2016,"finding":"In collagen-induced arthritis (CIA), recombinant human soluble IL-20R2-Fc fusion protein blocks signaling of IL-19, IL-20, and IL-24 with high affinity in vitro and achieves efficacy comparable to etanercept in established arthritis. In situ analysis shows IL-20 subfamily cytokines and TNFR signals converge in macrophages within inflamed tissues.","method":"In vitro receptor binding assays, signaling blockade assays, DBA/1 mouse CIA model with IL-20R2-Fc treatment, in situ ligand-receptor functional binding analysis, colocalization immunostaining","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro binding and in vivo disease model with histological analysis, single lab","pmids":["27619991"],"is_preprint":false},{"year":2020,"finding":"IL-20 promotes tumor growth and M2-like macrophage polarization in pancreatic ductal adenocarcinoma (PDAC) models, and targeting IL-20 with anti-IL-20 monoclonal antibody (7E) attenuates PD-L1 expression on tumor cells. Combination of anti-IL-20 and anti-PD-1 antibodies shows better efficacy in inhibiting tumor growth than either alone in an orthotopic PDAC model.","method":"KPC transgenic mouse model, orthotopic PDAC mouse model, anti-IL-20 monoclonal antibody treatment, combination antibody therapy, tumor analysis","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two in vivo murine models with antibody intervention, single lab","pmids":["32929072"],"is_preprint":false},{"year":2022,"finding":"In grass carp, IL-20R2 (CRFB16) binds IL-20 by co-immunoprecipitation, while IL-20R1 (CRFB8) does not bind IL-20 but is responsible for activating STAT3 phosphorylation. Structural modeling shows that key residues involved in IL-20/receptor interaction are conserved between grass carp and humans.","method":"Co-immunoprecipitation, STAT3 phosphorylation assays, structural modeling","journal":"Fish & shellfish immunology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single co-IP and signaling assay in a fish ortholog, single lab; fish model limits direct translation","pmids":["36414129"],"is_preprint":false},{"year":2012,"finding":"IL-20 stimulation of bladder cancer cells upregulates MMP-2 and MMP-9 expression, activates transcription factors NF-κB and AP-1 (regulating the MMP-9 promoter), and activates MAPK and JAK-STAT signaling, thereby enhancing wound-healing migration and invasion capacity.","method":"EMSA, immunoblot, real-time PCR, wound-healing/invasion assays, confocal immunofluorescence in bladder cancer cell lines","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple signaling and functional assays in cell lines, single lab","pmids":["22962576"],"is_preprint":false},{"year":2013,"finding":"IL-20 promoter activity is synergistically enhanced by bacterial-like DNA (CpG-A) or IL-1β in combination with the risk-associated G allele at SNP rs1713239 in the IL-20 promoter region. Increased IL-20 expression was observed in psoriatic lesional skin of patients carrying the risk G allele upon stimulation.","method":"Luciferase reporter gene assays with allele-specific constructs, stimulation with CpG-A and IL-1β, patient sample analysis","journal":"The Journal of investigative dermatology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — reporter assay with limited functional follow-up, single lab","pmids":["23892591"],"is_preprint":false}],"current_model":"IL-20 is a pleiotropic IL-10 family cytokine that signals through two heterodimeric receptor complexes—type I (IL-20Rα/IL-20Rβ) and type II (IL-22R1/IL-20Rβ)—to activate STAT3 (and, in endothelial/epithelial contexts, also JAK2/STAT5, ERK1/2, and Akt), with IL-20Rβ/IL-20R2 serving as the shared signaling subunit; it is produced by monocytes, dendritic cells, and keratinocytes in response to inflammatory stimuli (IL-1β, TNF-α, LPS via MyD88/p38, and hypoxia via HIF-1α), acts predominantly on epithelial cells to drive keratinocyte proliferation, impair terminal differentiation, and induce antimicrobial genes, while also activating endothelial cells for arteriogenesis and lymphangiogenesis, suppressing neutrophil and T cell effector functions through IL-20R2 signaling, promoting hepatic stellate cell activation and liver fibrosis, and modulating adipogenesis and macrophage polarization; its transcription is epigenetically regulated by KMT2B-mediated H3K4 methylation downstream of ERα, and post-transcriptionally by HuR mRNA stabilization controlled by AMPK."},"narrative":{"mechanistic_narrative":"IL-20 is a pleiotropic IL-10-family cytokine that acts on epithelial, endothelial, and immune cells to coordinate inflammation, tissue remodeling, and barrier function, signaling through two distinct receptor complexes—a type I complex (IL-20Rα/IL-20Rβ) and a type II complex (IL-22R/IL-20Rβ)—both of which trigger STAT3 phosphorylation, while IL-20Rβ (IL-20R2) serves as the shared, immunoregulatory signaling subunit also engaged by IL-19 and IL-24 [PMID:11564763, PMID:19124723]. It is produced chiefly by monocytes, dendritic cells, and keratinocytes in response to inflammatory stimuli, with IL-1β, TNF-α, IL-17A and IL-22 inducing keratinocyte IL-20, LPS driving expression through a MyD88–p38 MAPK pathway, and hypoxia inducing it via HIF-1α-bound promoter elements [PMID:19830738, PMID:17083366, PMID:16645593, PMID:15519673, PMID:19342680]. Acting on keratinocytes, IL-20 drives acanthosis, induces psoriasis-associated proteins (S100A7, keratin 16) and antimicrobial genes, and sustains nuclear STAT3 activation, establishing it as a downstream effector of the IL-22→IL-20 cytokine cascade in epidermal pathology [PMID:17277128, PMID:19830738, PMID:18281438]. Through IL-20R2, the IL-20 subfamily suppresses immune effector functions—dampening T-cell IFN-γ/IL-2 output, inhibiting actin-dependent neutrophil phagocytosis and migration, and limiting cutaneous IL-1β/IL-17A—thereby restraining antibacterial defense, as IL-20R2 loss heightens T-cell responses and receptor blockade improves S. aureus infection [PMID:19124723, PMID:28424238, PMID:23793061]. In non-cutaneous tissues IL-20 activates endothelial JAK2/STAT5, ERK1/2, Akt, Rac/Rho and calcium signaling to promote arteriogenesis and lymphangiogenesis [PMID:17878297, PMID:19281830], activates hepatic stellate cells to drive TGF-β1-dependent liver fibrosis [PMID:24763901], promotes M1/M2 macrophage polarization, adipose inflammation and insulin resistance [PMID:34403503, PMID:32929072], and exerts dual epithelial roles in the gut—impairing the oesophageal barrier via MAPK/ERK1/2 downregulation of cornified-envelope proteins yet protecting against colitis by inducing STAT3 and suppressing IFN/STAT2-driven necroptosis [PMID:35613844, PMID:37884352]. IL-20 transcription is controlled by an ERα/GATA3/FOXA1/ELL3 complex with KMT2B-mediated H3K4 methylation in breast cancer cells, and post-transcriptionally by HuR-mediated mRNA stabilization downstream of AMPK in psoriatic keratinocytes [PMID:27806114, PMID:28514748, PMID:26176762].","teleology":[{"year":2001,"claim":"Established the receptor architecture of IL-20 signaling, defining how a single cytokine can act through two complexes and identifying STAT3 as the common output.","evidence":"Receptor binding, STAT3 phosphorylation, and STAT-reporter assays with multiple IL-20 subfamily ligands","pmids":["11564763"],"confidence":"High","gaps":["Did not assign cell-type-specific receptor usage","Downstream gene programs from STAT3 not yet mapped"]},{"year":2003,"claim":"Showed IL-20 has a selective hematopoietic action, expanding the cytokine's biology beyond skin to multipotential progenitor regulation.","evidence":"CD34+ colony formation assays and IL-20 transgenic mice with cell-cycle analysis","pmids":["12855566"],"confidence":"Medium","gaps":["Receptor and signaling mediating progenitor effect not defined","Physiological relevance to steady-state hematopoiesis unclear"]},{"year":2004,"claim":"Defined an upstream induction pathway, showing innate immune signals drive IL-20 transcription via a defined kinase cascade under negative glucocorticoid control.","evidence":"LPS stimulation of glial cells/macrophages, MyD88-deficient mice, p38 inhibition, dexamethasone treatment","pmids":["15519673"],"confidence":"Medium","gaps":["Transcription factors downstream of p38 not identified","Findings in glia/macrophages may not generalize to keratinocytes"]},{"year":2006,"claim":"Identified the cellular sources of IL-20 and the inflammatory stimuli (IL-1β, TNF-α, integrin/adhesion, oxidized LDL, hypoxia) that induce it, while showing immune cells lack the receptor and act only as producers.","evidence":"qRT-PCR, flow cytometry, STAT assays, IHC of psoriatic skin, monocyte/endothelial stimulation, ApoE-/- atherosclerosis model","pmids":["17083366","16645593","16778121"],"confidence":"Medium","gaps":["Relative contribution of keratinocyte vs myeloid sources in vivo not resolved","Mechanism linking oxidized LDL/hypoxia to transcription not yet defined here"]},{"year":2007,"claim":"Demonstrated IL-20 drives epidermal pathology and, separately, activates endothelial cells through a broad non-STAT3 signaling repertoire to promote arteriogenesis.","evidence":"Reconstituted human epidermis with microarray/IHC; endothelial signaling assays (JAK2/STAT5, ERK1/2, Akt, Rac/Rho, calcium), tube formation, rat hind-limb ischemia model","pmids":["17277128","17878297"],"confidence":"High","gaps":["Receptor complex governing endothelial vs epithelial signaling not distinguished","Link between in vitro signaling and in vivo arteriogenesis indirect"]},{"year":2009,"claim":"Placed IL-20 within an IL-22-driven cytokine cascade, defined dendritic cells as producers and antimicrobial induction in keratinocytes, identified HIF-1α promoter control, lymphangiogenic signaling, and established IL-20R2 as an immunosuppressive subunit restraining T cells.","evidence":"Keratinocyte cytokine stimulation with neutralizing antibody; DC differentiation; luciferase/HIF-1α inhibition; lymphatic endothelial signaling with pharmacological inhibitors; IL-20R2 knockout mice with T-cell, DNA vaccination, and contact hypersensitivity assays","pmids":["19830738","18281438","19342680","19281830","19124723"],"confidence":"High","gaps":["Whether IL-20R2 immunosuppression is cell-intrinsic to T cells not fully resolved","HIF-1α HRE occupancy shown by inhibition rather than direct binding"]},{"year":2012,"claim":"Extended IL-20 signaling to tumor cell invasion, linking MAPK/JAK-STAT activation to NF-κB/AP-1-driven MMP expression and migratory phenotypes.","evidence":"EMSA, immunoblot, RT-PCR, wound-healing/invasion assays in bladder cancer cell lines","pmids":["22962576"],"confidence":"Medium","gaps":["No in vivo tumor model","Receptor complex used by bladder cells not defined"]},{"year":2013,"claim":"Revealed the host-detrimental side of IL-20 immunosuppression, showing the subfamily promotes S. aureus infection by suppressing cutaneous IL-1β/IL-17A, validating receptor blockade therapeutically.","evidence":"Murine S. aureus infection with cytokine/receptor-blockade, human keratinocyte stimulation, cytokine measurement","pmids":["23793061"],"confidence":"High","gaps":["Cellular target of suppression in vivo not fully defined","Promoter genetics (rs1713239) link to expression only preliminary"]},{"year":2014,"claim":"Established IL-20 as a profibrotic driver in liver, acting on hepatic stellate cells through a TGF-β1 axis, with genetic and antibody loss-of-function confirming causality.","evidence":"In vitro HSC assays, CCl4 fibrosis model, anti-IL-20/anti-IL-20R1 antibodies, IL-20R1 knockout mice","pmids":["24763901"],"confidence":"High","gaps":["Signaling pathway in HSCs not dissected","Receptor complex usage (type I vs II) in liver not specified"]},{"year":2015,"claim":"Defined transcriptional and post-transcriptional control of IL-20: an ERα/KMT2B-H3K4 methylation axis in breast cancer and AMPK-regulated HuR mRNA stabilization in psoriatic skin.","evidence":"ChIP, siRNA, proliferation/colony assays (breast cancer); RIP-seq, HuR immunofluorescence, in vivo AMPK inhibition (skin)","pmids":["27806114","26176762"],"confidence":"Medium","gaps":["Connection between IL-20 transcript level and downstream pathology in breast cancer indirect","AMPK-HuR axis tested pharmacologically, not genetically"]},{"year":2016,"claim":"Validated soluble IL-20R2-Fc decoy as a therapeutic strategy that neutralizes all three subfamily cytokines, achieving anti-TNF-comparable efficacy in arthritis.","evidence":"In vitro binding/blockade assays, DBA/1 collagen-induced arthritis model, in situ ligand-receptor and colocalization analysis","pmids":["27619991"],"confidence":"Medium","gaps":["Relative contribution of IL-20 vs IL-19/IL-24 not separated","Macrophage-intrinsic mechanism inferred from colocalization"]},{"year":2017,"claim":"Showed IL-20 directly disables activated neutrophils by inhibiting actin polymerization, providing a cellular mechanism for impaired antibacterial defense.","evidence":"Primary human neutrophil activation/migration assays, flow cytometry, actin polymerization, phagocytosis and exocytosis assays","pmids":["28424238"],"confidence":"Medium","gaps":["Signaling pathway from receptor to actin not mapped","In vivo confirmation of neutrophil-specific effect lacking"]},{"year":2020,"claim":"Expanded IL-20 pathology to cardiac injury, adipose inflammation/insulin resistance, and pancreatic cancer, identifying it as a therapeutically tractable node including in combination with anti-PD-1.","evidence":"Cardiomyocyte H/R model with signaling readouts; adipocyte/macrophage assays and HFD model with anti-IL-20; KPC and orthotopic PDAC models with anti-IL-20/anti-PD-1","pmids":["31953216","34403503","32929072"],"confidence":"Medium","gaps":["Receptor complex and STAT involvement vary and remain undefined across tissues","Tumor-cell vs stromal source of IL-20 not clarified"]},{"year":2022,"claim":"Resolved a dual epithelial role at gut barriers, with the subfamily impairing the oesophageal barrier via ERK1/2-driven loss of cornified-envelope proteins, contributing to eosinophilic esophagitis.","evidence":"Patient-derived organoids, RNA-seq, mass spectrometry, Il20R2 knockout EoE model, air-liquid interface cultures with ERK1/2 inhibition","pmids":["35613844"],"confidence":"High","gaps":["Whether IL-20 alone or other subfamily members dominate not separated","Upstream inducer in EoE not defined"]},{"year":2024,"claim":"Identified a protective epithelial function for IL-20 in colitis, where STAT3 induction suppresses IFN/STAT2-driven necroptosis, contrasting with its pathogenic roles elsewhere.","evidence":"Il20 and Il20rb knockout mice, DSS colitis, IEC organoids, RNA-seq, Co-IP, RNAScope, recombinant IL-20 rescue","pmids":["37884352"],"confidence":"High","gaps":["Molecular basis of IFN/STAT2 suppression by STAT3 not fully resolved","Cellular source of protective IL-20 in colon not pinpointed"]},{"year":null,"claim":"It remains unresolved how IL-20 selects between type I and type II receptor complexes and between STAT3 and the alternative (JAK2/STAT5, ERK, Akt, PKC/NADPH) signaling branches to produce opposite outcomes—protective versus pathogenic—across tissues.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural or quantitative model linking receptor stoichiometry to signaling branch choice","Determinants of context-dependent pro- vs anti-inflammatory output unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,6,8,25]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,8]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[8,11,15]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[2,3,4]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[8,11,15,23]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,6,9,10]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[6,9,21]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[12,19,20,24]}],"complexes":[],"partners":["IL20RA","IL20RB","IL22RA1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NYY1","full_name":"Interleukin-20","aliases":["Cytokine Zcyto10"],"length_aa":176,"mass_kda":20.1,"function":"Pro-inflammatory and angiogenic cytokine mainly secreted by monocytes and skin keratinocytes that plays crucial roles in immune responses, regulation of inflammatory responses, hemopoiesis, as well as epidermal cell and keratinocyte differentiation (PubMed:17277128, PubMed:34403503). Enhances tissue remodeling and wound-healing activities and restores the homeostasis of epithelial layers during infection and inflammatory responses to maintain tissue integrity (PubMed:17277128). Affects multiple actin-mediated functions in activated neutrophils leading to inhibition of phagocytosis, granule exocytosis, and migration (PubMed:28424238). Exert its effects via the type I IL-20 receptor complex consisting of IL20RA and IL20RB (PubMed:11706020). Alternatively, can mediate its activity through a second receptor complex called type II IL-20 receptor complex composed of IL22RA1 and IL20RB (PubMed:11564763). Acts as an arteriogenic and vascular remodeling factory by activating a range of signaling processes including phosphorylations of JAK2 and STAT5 as well as activation of the serine and threonine kinases AKT and ERK1/2 (By similarity). Alternatively, can activate STAT3 phosphorylation and transcriptional activity in a JAK2, ERK1/2 and p38 MAPK-dependent manner in keratinocytes (PubMed:23614738)","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/Q9NYY1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/IL20","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/IL20","total_profiled":1310},"omim":[{"mim_id":"607900","title":"FERM DOMAIN-CONTAINING KINDLIN 1; FERMT1","url":"https://www.omim.org/entry/607900"},{"mim_id":"605687","title":"INTERLEUKIN 19; IL19","url":"https://www.omim.org/entry/605687"},{"mim_id":"605621","title":"INTERLEUKIN 20 RECEPTOR, BETA; IL20RB","url":"https://www.omim.org/entry/605621"},{"mim_id":"605620","title":"INTERLEUKIN 20 RECEPTOR, ALPHA; IL20RA","url":"https://www.omim.org/entry/605620"},{"mim_id":"605619","title":"INTERLEUKIN 20; IL20","url":"https://www.omim.org/entry/605619"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"},{"location":"Endoplasmic reticulum","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"adipose tissue","ntpm":1.6},{"tissue":"skin 1","ntpm":1.2}],"url":"https://www.proteinatlas.org/search/IL20"},"hgnc":{"alias_symbol":["ZCYTO10","IL10D","IL-20"],"prev_symbol":[]},"alphafold":{"accession":"Q9NYY1","domains":[{"cath_id":"1.20.1250.10","chopping":"25-176","consensus_level":"medium","plddt":97.465,"start":25,"end":176}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NYY1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NYY1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NYY1-F1-predicted_aligned_error_v6.png","plddt_mean":92.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=IL20","jax_strain_url":"https://www.jax.org/strain/search?query=IL20"},"sequence":{"accession":"Q9NYY1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NYY1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NYY1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NYY1"}},"corpus_meta":[{"pmid":"17277128","id":"PMC_17277128","title":"The effects of IL-20 subfamily cytokines on reconstituted human epidermis suggest potential roles in cutaneous innate defense and pathogenic adaptive immunity in psoriasis.","date":"2007","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/17277128","citation_count":422,"is_preprint":false},{"pmid":"19330474","id":"PMC_19330474","title":"IL-22 and IL-20 are key mediators of the epidermal alterations in psoriasis while IL-17 and IFN-gamma are not.","date":"2009","source":"Journal of molecular medicine (Berlin, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/19330474","citation_count":354,"is_preprint":false},{"pmid":"11564763","id":"PMC_11564763","title":"Cutting edge: STAT activation by IL-19, IL-20 and mda-7 through IL-20 receptor complexes of two types.","date":"2001","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/11564763","citation_count":340,"is_preprint":false},{"pmid":"25421700","id":"PMC_25421700","title":"The IL-20 subfamily of cytokines--from host defence to tissue homeostasis.","date":"2014","source":"Nature reviews. 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Both receptor complexes, upon ligand binding, induce STAT3 phosphorylation and activation of STAT-binding site promoters. IL-19 signals only through the type I complex, while mda-7/IL-24 signals through both.\",\n      \"method\": \"Receptor binding assays, STAT3 phosphorylation assays, reporter gene (minimal promoter with STAT-binding sites)\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — direct receptor binding and signaling assays with multiple ligands, replicated across subsequent studies\",\n      \"pmids\": [\"11564763\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"IL-20 induces acanthosis, expression of psoriasis-associated proteins S100A7 and keratin 16, and persistent nuclear STAT3 activation in reconstituted human epidermis (RHE). Gene expression analysis showed IL-20 regulates inflammatory response genes, wound healing, and keratinocyte differentiation markers.\",\n      \"method\": \"Reconstituted human epidermis (RHE) model, gene expression microarray, immunohistochemistry\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — reconstituted tissue model with microarray and histological validation, replicated by multiple labs\",\n      \"pmids\": [\"17277128\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"IL-22 induces IL-20 mRNA and protein production in human keratinocytes, establishing a cytokine cascade. Some IL-22 effects on differentiation-regulating genes were partially mediated by endogenous secreted IL-20, as demonstrated by partial attenuation with anti-IL-20 antibody. IL-17A and TNF-α also induced IL-20 in keratinocytes, but IFN-γ and IL-20 itself did not regulate IL-20 expression.\",\n      \"method\": \"Keratinocyte culture with cytokine stimulation, RT-PCR, ELISA, neutralizing antibody blockade\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (RT-PCR, ELISA, antibody neutralization) in single lab\",\n      \"pmids\": [\"19830738\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"IL-20 is produced by monocytes and keratinocytes. In keratinocytes, IL-1β increases IL-20 expression approximately 10-fold. Neither receptor complex for IL-20 (IL-20R1/IL-20R2 nor IL-22R1/IL-20R2) is expressed on immune cells, and IL-20 does not activate STAT molecules in immune cells. IFN-γ decreases IL-20R1 expression and increases IL-22R1 expression on keratinocytes.\",\n      \"method\": \"Quantitative RT-PCR, STAT activation assays, flow cytometry, in vitro stimulation\",\n      \"journal\": \"Experimental dermatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple cell types tested with orthogonal methods, single lab\",\n      \"pmids\": [\"17083366\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"IL-20 expression in psoriatic skin is predominantly from CD68+/CD11c+ myeloid-derived dermal leukocytes (monocytes), not keratinocytes. In vitro, plastic adhesion, β2 integrin activation, and TNF-α stimulate IL-20 expression in monocytes. IL-20 treatment of keratinocytes upregulates IFN-γ-induced and disease-related genes as assessed by microarray.\",\n      \"method\": \"Immunohistochemistry, in vitro monocyte stimulation, microarray of IL-20-treated keratinocytes\",\n      \"journal\": \"The Journal of investigative dermatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (IHC, in vitro, microarray) in single lab\",\n      \"pmids\": [\"16645593\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"IL-20 promotes atherosclerosis in apolipoprotein E-deficient mice when delivered via intramuscular electroporation of expression vector. IL-20 upregulates CXCL9 and CXCL11 transcripts in human umbilical vein endothelial cells. IL-20 transcripts increase in hypoxic monocytes and monocytes treated with oxidized LDL.\",\n      \"method\": \"In vivo IL-20 expression vector delivery in ApoE-/- mice, in vitro endothelial cell stimulation, RT-PCR\",\n      \"journal\": \"Arteriosclerosis, thrombosis, and vascular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo functional model plus in vitro mechanistic studies, single lab\",\n      \"pmids\": [\"16778121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"IL-20 promotes arteriogenesis and improves blood perfusion in a rat ischemic hind-limb model. In endothelial cells, IL-20 activates JAK2/STAT5, Erk1/2, and Akt phosphorylation; activates small GTP-binding proteins Rac and Rho; induces intracellular calcium release; and promotes tube formation without affecting endothelial cell proliferation or motility.\",\n      \"method\": \"In vitro endothelial cell signaling assays, tube formation assay, in vivo rat hind-limb ischemia model with IL-20 delivery\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro mechanistic signaling dissection plus in vivo functional model with multiple orthogonal methods\",\n      \"pmids\": [\"17878297\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Maturing dendritic cells (DCs) produce IL-20 in response to bacterial stimuli and inflammatory cytokines. In keratinocytes, IL-20 induces expression of antimicrobial proteins. Combining IL-20 and IL-29 resulted in a stronger response to TLR2 and TLR3 activation in keratinocytes than either cytokine alone.\",\n      \"method\": \"Monocyte/DC differentiation in vitro, RT-PCR, co-stimulation assays in keratinocytes\",\n      \"journal\": \"Journal of leukocyte biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple cell types and stimulation conditions, single lab\",\n      \"pmids\": [\"18281438\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"IL-20R2-deficient CD8+ and CD4+ T cells show significantly elevated IFN-γ and IL-2 secretion upon stimulation with Con A or anti-CD3/CD28, while IL-10 secretion by activated CD4+ IL-20R2-/- cells is diminished. IL-20R2 knockout mice develop more antigen-specific CD8+ and CD4+ IFN-γ+ T cells after DNA vaccination and show increased sensitivity in a contact hypersensitivity model, demonstrating that IL-20R2 signaling (by IL-19, IL-20, IL-24) directly down-regulates T cell responses in vitro and in vivo.\",\n      \"method\": \"IL-20R2 knockout mouse generation, in vitro T cell stimulation, DNA vaccination model, contact hypersensitivity model\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — genetic knockout with multiple in vitro and in vivo functional readouts\",\n      \"pmids\": [\"19124723\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"IL-20 activates lymphatic endothelial cells (hTERT-HDLEC) causing increased intracellular calcium, Akt and eNOS phosphorylation (via PI3K/Akt), NO production, ERK1/2 and mTOR phosphorylation, actin polymerization, tube formation (PI3K- and mTOR-dependent), and cell migration comparable to VEGF-C. ERK1/2 pathway mediates IL-20-induced proliferation.\",\n      \"method\": \"Calcium imaging, Western blotting for phosphorylated signaling intermediates, pharmacological inhibitors (wortmannin, rapamycin, PD98059), tube formation and sprouting assays in lymphatic endothelial cells\",\n      \"journal\": \"Microvascular research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple signaling assays with pharmacological inhibitors, single lab\",\n      \"pmids\": [\"19281830\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"IL-20 is regulated by hypoxia-inducible factor-1α (HIF-1α): two putative hypoxia response elements (HREs) in the human IL20 gene promoter were identified, and HIF-1α inhibition blocked CoCl2-induced IL-20 expression. IL-20 activates JAK2/STAT3 and ERK1/2 signaling in glioblastoma cells and induces their proliferation and production of IL-1β, IL-8, and MCP-1.\",\n      \"method\": \"Promoter activity (luciferase reporter), HIF-1α inhibitor treatment, signaling assays (JAK2/STAT3, ERK1/2 phosphorylation), in vitro proliferation assays\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reporter assays and signaling studies with pharmacological inhibition, single lab\",\n      \"pmids\": [\"19342680\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"IL-19, IL-20, and IL-24 signaling through type I and type II IL-20 receptors suppresses cutaneous IL-1β and IL-17A production, thereby promoting S. aureus infection in mice. Antibody blockade of the IL-20 receptor improved infection outcomes in mice. Similar immunosuppressive effects were observed in human keratinocytes exposed to S. aureus.\",\n      \"method\": \"In vivo murine S. aureus infection model with cytokine treatment or receptor blockade, in vitro human keratinocyte stimulation, cytokine measurement\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo loss-of-function (antibody blockade) and in vitro mechanistic studies with defined readouts, high-impact journal\",\n      \"pmids\": [\"23793061\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"IL-20 activates hepatic stellate cells (HSCs) and upregulates TGF-β1 expression. IL-20 increases TGF-β1, TNF-α, and type I collagen expression and promotes proliferation and migration of activated HSCs. Anti-IL-20 monoclonal antibody and anti-IL-20R1 monoclonal antibody attenuate CCl4-induced liver fibrosis in mice. IL-20R1-deficient mice are protected from liver injury.\",\n      \"method\": \"In vitro HSC activation assays, CCl4 mouse model of liver fibrosis, monoclonal antibody treatment, IL-20R1 knockout mice, ELISA, histology\",\n      \"journal\": \"Hepatology (Baltimore, Md.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout plus antibody blockade with multiple in vitro and in vivo functional readouts, single lab but orthogonal methods\",\n      \"pmids\": [\"24763901\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"IL-20 expression in MCF-7 breast cancer cells is transcriptionally induced by estradiol (E2) through estrogen receptor α (ERα)-mediated recruitment of the histone methyltransferase KMT2B to the IL-20 promoter, leading to H3K4 methylation. Depletion of KMT2B or IL-20 disrupts estrogen signaling, attenuates cell proliferation, reduces colony formation, and causes cell cycle arrest.\",\n      \"method\": \"ChIP assay for histone methylation and transcription factor binding, siRNA knockdown of KMT2B and IL-20, cell proliferation and colony formation assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and loss-of-function with functional readouts, single lab\",\n      \"pmids\": [\"27806114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"IL-20 post-transcriptional regulation in psoriatic skin involves the RNA-binding protein HuR, which relocalizes from the nucleus to the cytoplasm in psoriatic keratinocytes to stabilize IL-20 mRNA. AMPK activity is impaired in psoriatic epidermis and is responsible for HuR cytoplasmic relocalization. In vivo AMPK inhibition in mouse epidermis promotes HuR cytoplasmic localization and IL-20 overproduction with accompanying acanthosis and hyperkeratosis.\",\n      \"method\": \"Ribonucleoprotein immunoprecipitation with high-throughput sequencing (RIP-seq), immunofluorescence for HuR localization, in vivo pharmacological AMPK inhibition in mice, histology\",\n      \"journal\": \"The Journal of investigative dermatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RIP-seq, in vivo mouse model, and cellular localization studies, single lab\",\n      \"pmids\": [\"26176762\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"IL-20 directly targets activated human neutrophils: upon migration and activation (mimicking S. aureus infection conditions), neutrophils alter expression of IL-20 receptor chains and become responsive to IL-20, which inhibits actin polymerization and actin-dependent functions including phagocytosis, granule exocytosis, and migration.\",\n      \"method\": \"In vitro neutrophil activation/migration assays, flow cytometry for receptor expression, actin polymerization assays, phagocytosis and granule exocytosis assays\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays on primary human neutrophils, single lab\",\n      \"pmids\": [\"28424238\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"A transcriptional complex composed of ERα, GATA3, FOXA1, and ELL3 regulates IL-20 expression in ER+ breast cancer cells. ELL3 associates with ERα to increase its binding affinity to the IL-20 promoter and may prevent FOXA1 (a repressor) from binding the same region. GATA3 and ERα activate IL-20 expression while FOXA1 represses it.\",\n      \"method\": \"ChIP assays, co-immunoprecipitation, siRNA knockdown, promoter reporter assays\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and Co-IP with loss-of-function, single lab\",\n      \"pmids\": [\"28514748\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"IL-20 promotes cardiomyocyte apoptosis during hypoxia/reoxygenation (H/R) by activating the PKC/NADPH oxidase pathway, leading to increased Ca2+, elevated oxidative stress, and downregulation of AKT. Anti-IL-20 treatment reduced cardiomyocyte apoptosis in the H/R model.\",\n      \"method\": \"In vitro H9C2 and primary cardiomyocyte H/R model, Western blotting for signaling intermediates, viability assays, pharmacological inhibition\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular basis of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined signaling pathway with multiple readouts in vitro, single lab\",\n      \"pmids\": [\"31953216\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"IL-20 regulates adipocyte differentiation and promotes polarization of bone marrow-derived macrophages toward proinflammatory M1 type. IL-20 causes inflammation and macrophage retention in adipose tissues by upregulating TNF-α, MCP-1, netrin 1, and unc5b in macrophages and netrin 1, leptin, and MCP-1 in adipocytes. IL-20 promotes insulin resistance by inhibiting glucose uptake in mature adipocytes through the SOCS-3 pathway.\",\n      \"method\": \"In vitro adipocyte differentiation and macrophage polarization assays, Western blotting, ELISA, glucose uptake assays, in vivo HFD mouse model with anti-IL-20 antibody treatment\",\n      \"journal\": \"Immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple in vitro functional assays plus in vivo antibody blockade, single lab\",\n      \"pmids\": [\"34403503\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"IL-20 subfamily cytokines (IL-19, IL-20, IL-24) impair the oesophageal epithelial barrier by downregulating filaggrins and other cornified envelope proteins via the MAPK/ERK1/2 pathway. Il20R2-/- animals show reduced eosinophil infiltration, lower Th2 cytokine expression, and preserved filaggrin expression in experimental EoE. ERK1/2 blockade prevents epithelial barrier impairment in patient-derived air-liquid interface cultures and attenuates experimental EoE.\",\n      \"method\": \"Patient-derived oesophageal organoids, RNA-seq, mass spectrometry, Il20R2 knockout EoE mouse model, air-liquid interface cultures with ERK1/2 inhibition\",\n      \"journal\": \"Gut\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — genetic knockout, pharmacological pathway blockade, transcriptomics, proteomics, and organoid models, multiple orthogonal methods\",\n      \"pmids\": [\"35613844\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"IL-20 controls resolution of experimental colitis by inducing STAT3 and suppressing IFN/STAT2 signaling in intestinal epithelial cells (IECs). IL-20 deficiency or IL-20Rb deficiency increases IFN/STAT2 activity and susceptibility to DSS-induced colitis. IL-20 blocks IFN/STAT2-induced necroptotic cell death in IEC-derived organoids. Epithelial STAT2 deletion (Stat2 knockout in IECs) reduces colitis susceptibility, and IL-20 administration suppresses colitis in wild-type animals.\",\n      \"method\": \"Il20 and Il20rb knockout mice, DSS colitis model, IEC-derived 3D organoids, RNA-seq, Western blot, co-immunoprecipitation, confocal microscopy, RNAScope, recombinant IL-20 administration\",\n      \"journal\": \"Gut\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple genetic knockouts, organoid functional assays, co-IP, and in vivo rescue experiments with orthogonal methods\",\n      \"pmids\": [\"37884352\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"IL-20 selectively enhances colony formation by CD34+ multipotential hematopoietic progenitors in vitro, with no effect on erythroid, granulocyte-macrophage, or megakaryocyte progenitors. IL-20 transgenic mice show increased numbers and cell cycling of multipotential (but not other) progenitors in vivo.\",\n      \"method\": \"In vitro colony formation assays with CD34+ progenitors, IL-20 transgenic mouse model, cell cycle analysis\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro and in vivo functional assays with transgenic model, single lab\",\n      \"pmids\": [\"12855566\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"LPS induces IL-20 expression in primary murine glial cells and RAW264.7 macrophages through a MyD88-p38 MAPK-dependent signaling pathway, independent of de novo protein synthesis. Dexamethasone inhibits LPS-induced IL-20 expression, indicating negative glucocorticoid feedback regulation.\",\n      \"method\": \"Primary glial cell culture with LPS, MyD88-deficient mice, pharmacological inhibitor (SB203580 for p38), protein synthesis inhibitors, RT-PCR\",\n      \"journal\": \"Brain research. Molecular brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockout mice and pharmacological inhibition with molecular readouts, single lab\",\n      \"pmids\": [\"15519673\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"In collagen-induced arthritis (CIA), recombinant human soluble IL-20R2-Fc fusion protein blocks signaling of IL-19, IL-20, and IL-24 with high affinity in vitro and achieves efficacy comparable to etanercept in established arthritis. In situ analysis shows IL-20 subfamily cytokines and TNFR signals converge in macrophages within inflamed tissues.\",\n      \"method\": \"In vitro receptor binding assays, signaling blockade assays, DBA/1 mouse CIA model with IL-20R2-Fc treatment, in situ ligand-receptor functional binding analysis, colocalization immunostaining\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro binding and in vivo disease model with histological analysis, single lab\",\n      \"pmids\": [\"27619991\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"IL-20 promotes tumor growth and M2-like macrophage polarization in pancreatic ductal adenocarcinoma (PDAC) models, and targeting IL-20 with anti-IL-20 monoclonal antibody (7E) attenuates PD-L1 expression on tumor cells. Combination of anti-IL-20 and anti-PD-1 antibodies shows better efficacy in inhibiting tumor growth than either alone in an orthotopic PDAC model.\",\n      \"method\": \"KPC transgenic mouse model, orthotopic PDAC mouse model, anti-IL-20 monoclonal antibody treatment, combination antibody therapy, tumor analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two in vivo murine models with antibody intervention, single lab\",\n      \"pmids\": [\"32929072\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In grass carp, IL-20R2 (CRFB16) binds IL-20 by co-immunoprecipitation, while IL-20R1 (CRFB8) does not bind IL-20 but is responsible for activating STAT3 phosphorylation. Structural modeling shows that key residues involved in IL-20/receptor interaction are conserved between grass carp and humans.\",\n      \"method\": \"Co-immunoprecipitation, STAT3 phosphorylation assays, structural modeling\",\n      \"journal\": \"Fish & shellfish immunology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single co-IP and signaling assay in a fish ortholog, single lab; fish model limits direct translation\",\n      \"pmids\": [\"36414129\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"IL-20 stimulation of bladder cancer cells upregulates MMP-2 and MMP-9 expression, activates transcription factors NF-κB and AP-1 (regulating the MMP-9 promoter), and activates MAPK and JAK-STAT signaling, thereby enhancing wound-healing migration and invasion capacity.\",\n      \"method\": \"EMSA, immunoblot, real-time PCR, wound-healing/invasion assays, confocal immunofluorescence in bladder cancer cell lines\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple signaling and functional assays in cell lines, single lab\",\n      \"pmids\": [\"22962576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"IL-20 promoter activity is synergistically enhanced by bacterial-like DNA (CpG-A) or IL-1β in combination with the risk-associated G allele at SNP rs1713239 in the IL-20 promoter region. Increased IL-20 expression was observed in psoriatic lesional skin of patients carrying the risk G allele upon stimulation.\",\n      \"method\": \"Luciferase reporter gene assays with allele-specific constructs, stimulation with CpG-A and IL-1β, patient sample analysis\",\n      \"journal\": \"The Journal of investigative dermatology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — reporter assay with limited functional follow-up, single lab\",\n      \"pmids\": [\"23892591\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"IL-20 is a pleiotropic IL-10 family cytokine that signals through two heterodimeric receptor complexes—type I (IL-20Rα/IL-20Rβ) and type II (IL-22R1/IL-20Rβ)—to activate STAT3 (and, in endothelial/epithelial contexts, also JAK2/STAT5, ERK1/2, and Akt), with IL-20Rβ/IL-20R2 serving as the shared signaling subunit; it is produced by monocytes, dendritic cells, and keratinocytes in response to inflammatory stimuli (IL-1β, TNF-α, LPS via MyD88/p38, and hypoxia via HIF-1α), acts predominantly on epithelial cells to drive keratinocyte proliferation, impair terminal differentiation, and induce antimicrobial genes, while also activating endothelial cells for arteriogenesis and lymphangiogenesis, suppressing neutrophil and T cell effector functions through IL-20R2 signaling, promoting hepatic stellate cell activation and liver fibrosis, and modulating adipogenesis and macrophage polarization; its transcription is epigenetically regulated by KMT2B-mediated H3K4 methylation downstream of ERα, and post-transcriptionally by HuR mRNA stabilization controlled by AMPK.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"IL-20 is a pleiotropic IL-10-family cytokine that acts on epithelial, endothelial, and immune cells to coordinate inflammation, tissue remodeling, and barrier function, signaling through two distinct receptor complexes—a type I complex (IL-20R\\u03b1/IL-20R\\u03b2) and a type II complex (IL-22R/IL-20R\\u03b2)—both of which trigger STAT3 phosphorylation, while IL-20R\\u03b2 (IL-20R2) serves as the shared, immunoregulatory signaling subunit also engaged by IL-19 and IL-24 [#0, #8]. It is produced chiefly by monocytes, dendritic cells, and keratinocytes in response to inflammatory stimuli, with IL-1\\u03b2, TNF-\\u03b1, IL-17A and IL-22 inducing keratinocyte IL-20, LPS driving expression through a MyD88\\u2013p38 MAPK pathway, and hypoxia inducing it via HIF-1\\u03b1-bound promoter elements [#2, #3, #4, #22, #10]. Acting on keratinocytes, IL-20 drives acanthosis, induces psoriasis-associated proteins (S100A7, keratin 16) and antimicrobial genes, and sustains nuclear STAT3 activation, establishing it as a downstream effector of the IL-22\\u2192IL-20 cytokine cascade in epidermal pathology [#1, #2, #7]. Through IL-20R2, the IL-20 subfamily suppresses immune effector functions—dampening T-cell IFN-\\u03b3/IL-2 output, inhibiting actin-dependent neutrophil phagocytosis and migration, and limiting cutaneous IL-1\\u03b2/IL-17A—thereby restraining antibacterial defense, as IL-20R2 loss heightens T-cell responses and receptor blockade improves S. aureus infection [#8, #15, #11]. In non-cutaneous tissues IL-20 activates endothelial JAK2/STAT5, ERK1/2, Akt, Rac/Rho and calcium signaling to promote arteriogenesis and lymphangiogenesis [#6, #9], activates hepatic stellate cells to drive TGF-\\u03b21-dependent liver fibrosis [#12], promotes M1/M2 macrophage polarization, adipose inflammation and insulin resistance [#18, #24], and exerts dual epithelial roles in the gut—impairing the oesophageal barrier via MAPK/ERK1/2 downregulation of cornified-envelope proteins yet protecting against colitis by inducing STAT3 and suppressing IFN/STAT2-driven necroptosis [#19, #20]. IL-20 transcription is controlled by an ER\\u03b1/GATA3/FOXA1/ELL3 complex with KMT2B-mediated H3K4 methylation in breast cancer cells, and post-transcriptionally by HuR-mediated mRNA stabilization downstream of AMPK in psoriatic keratinocytes [#13, #16, #14].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Established the receptor architecture of IL-20 signaling, defining how a single cytokine can act through two complexes and identifying STAT3 as the common output.\",\n      \"evidence\": \"Receptor binding, STAT3 phosphorylation, and STAT-reporter assays with multiple IL-20 subfamily ligands\",\n      \"pmids\": [\"11564763\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not assign cell-type-specific receptor usage\", \"Downstream gene programs from STAT3 not yet mapped\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Showed IL-20 has a selective hematopoietic action, expanding the cytokine's biology beyond skin to multipotential progenitor regulation.\",\n      \"evidence\": \"CD34+ colony formation assays and IL-20 transgenic mice with cell-cycle analysis\",\n      \"pmids\": [\"12855566\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor and signaling mediating progenitor effect not defined\", \"Physiological relevance to steady-state hematopoiesis unclear\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defined an upstream induction pathway, showing innate immune signals drive IL-20 transcription via a defined kinase cascade under negative glucocorticoid control.\",\n      \"evidence\": \"LPS stimulation of glial cells/macrophages, MyD88-deficient mice, p38 inhibition, dexamethasone treatment\",\n      \"pmids\": [\"15519673\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Transcription factors downstream of p38 not identified\", \"Findings in glia/macrophages may not generalize to keratinocytes\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Identified the cellular sources of IL-20 and the inflammatory stimuli (IL-1\\u03b2, TNF-\\u03b1, integrin/adhesion, oxidized LDL, hypoxia) that induce it, while showing immune cells lack the receptor and act only as producers.\",\n      \"evidence\": \"qRT-PCR, flow cytometry, STAT assays, IHC of psoriatic skin, monocyte/endothelial stimulation, ApoE-/- atherosclerosis model\",\n      \"pmids\": [\"17083366\", \"16645593\", \"16778121\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative contribution of keratinocyte vs myeloid sources in vivo not resolved\", \"Mechanism linking oxidized LDL/hypoxia to transcription not yet defined here\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Demonstrated IL-20 drives epidermal pathology and, separately, activates endothelial cells through a broad non-STAT3 signaling repertoire to promote arteriogenesis.\",\n      \"evidence\": \"Reconstituted human epidermis with microarray/IHC; endothelial signaling assays (JAK2/STAT5, ERK1/2, Akt, Rac/Rho, calcium), tube formation, rat hind-limb ischemia model\",\n      \"pmids\": [\"17277128\", \"17878297\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor complex governing endothelial vs epithelial signaling not distinguished\", \"Link between in vitro signaling and in vivo arteriogenesis indirect\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Placed IL-20 within an IL-22-driven cytokine cascade, defined dendritic cells as producers and antimicrobial induction in keratinocytes, identified HIF-1\\u03b1 promoter control, lymphangiogenic signaling, and established IL-20R2 as an immunosuppressive subunit restraining T cells.\",\n      \"evidence\": \"Keratinocyte cytokine stimulation with neutralizing antibody; DC differentiation; luciferase/HIF-1\\u03b1 inhibition; lymphatic endothelial signaling with pharmacological inhibitors; IL-20R2 knockout mice with T-cell, DNA vaccination, and contact hypersensitivity assays\",\n      \"pmids\": [\"19830738\", \"18281438\", \"19342680\", \"19281830\", \"19124723\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether IL-20R2 immunosuppression is cell-intrinsic to T cells not fully resolved\", \"HIF-1\\u03b1 HRE occupancy shown by inhibition rather than direct binding\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Extended IL-20 signaling to tumor cell invasion, linking MAPK/JAK-STAT activation to NF-\\u03baB/AP-1-driven MMP expression and migratory phenotypes.\",\n      \"evidence\": \"EMSA, immunoblot, RT-PCR, wound-healing/invasion assays in bladder cancer cell lines\",\n      \"pmids\": [\"22962576\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vivo tumor model\", \"Receptor complex used by bladder cells not defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Revealed the host-detrimental side of IL-20 immunosuppression, showing the subfamily promotes S. aureus infection by suppressing cutaneous IL-1\\u03b2/IL-17A, validating receptor blockade therapeutically.\",\n      \"evidence\": \"Murine S. aureus infection with cytokine/receptor-blockade, human keratinocyte stimulation, cytokine measurement\",\n      \"pmids\": [\"23793061\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular target of suppression in vivo not fully defined\", \"Promoter genetics (rs1713239) link to expression only preliminary\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Established IL-20 as a profibrotic driver in liver, acting on hepatic stellate cells through a TGF-\\u03b21 axis, with genetic and antibody loss-of-function confirming causality.\",\n      \"evidence\": \"In vitro HSC assays, CCl4 fibrosis model, anti-IL-20/anti-IL-20R1 antibodies, IL-20R1 knockout mice\",\n      \"pmids\": [\"24763901\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signaling pathway in HSCs not dissected\", \"Receptor complex usage (type I vs II) in liver not specified\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined transcriptional and post-transcriptional control of IL-20: an ER\\u03b1/KMT2B-H3K4 methylation axis in breast cancer and AMPK-regulated HuR mRNA stabilization in psoriatic skin.\",\n      \"evidence\": \"ChIP, siRNA, proliferation/colony assays (breast cancer); RIP-seq, HuR immunofluorescence, in vivo AMPK inhibition (skin)\",\n      \"pmids\": [\"27806114\", \"26176762\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Connection between IL-20 transcript level and downstream pathology in breast cancer indirect\", \"AMPK-HuR axis tested pharmacologically, not genetically\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Validated soluble IL-20R2-Fc decoy as a therapeutic strategy that neutralizes all three subfamily cytokines, achieving anti-TNF-comparable efficacy in arthritis.\",\n      \"evidence\": \"In vitro binding/blockade assays, DBA/1 collagen-induced arthritis model, in situ ligand-receptor and colocalization analysis\",\n      \"pmids\": [\"27619991\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative contribution of IL-20 vs IL-19/IL-24 not separated\", \"Macrophage-intrinsic mechanism inferred from colocalization\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Showed IL-20 directly disables activated neutrophils by inhibiting actin polymerization, providing a cellular mechanism for impaired antibacterial defense.\",\n      \"evidence\": \"Primary human neutrophil activation/migration assays, flow cytometry, actin polymerization, phagocytosis and exocytosis assays\",\n      \"pmids\": [\"28424238\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signaling pathway from receptor to actin not mapped\", \"In vivo confirmation of neutrophil-specific effect lacking\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Expanded IL-20 pathology to cardiac injury, adipose inflammation/insulin resistance, and pancreatic cancer, identifying it as a therapeutically tractable node including in combination with anti-PD-1.\",\n      \"evidence\": \"Cardiomyocyte H/R model with signaling readouts; adipocyte/macrophage assays and HFD model with anti-IL-20; KPC and orthotopic PDAC models with anti-IL-20/anti-PD-1\",\n      \"pmids\": [\"31953216\", \"34403503\", \"32929072\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor complex and STAT involvement vary and remain undefined across tissues\", \"Tumor-cell vs stromal source of IL-20 not clarified\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Resolved a dual epithelial role at gut barriers, with the subfamily impairing the oesophageal barrier via ERK1/2-driven loss of cornified-envelope proteins, contributing to eosinophilic esophagitis.\",\n      \"evidence\": \"Patient-derived organoids, RNA-seq, mass spectrometry, Il20R2 knockout EoE model, air-liquid interface cultures with ERK1/2 inhibition\",\n      \"pmids\": [\"35613844\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether IL-20 alone or other subfamily members dominate not separated\", \"Upstream inducer in EoE not defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identified a protective epithelial function for IL-20 in colitis, where STAT3 induction suppresses IFN/STAT2-driven necroptosis, contrasting with its pathogenic roles elsewhere.\",\n      \"evidence\": \"Il20 and Il20rb knockout mice, DSS colitis, IEC organoids, RNA-seq, Co-IP, RNAScope, recombinant IL-20 rescue\",\n      \"pmids\": [\"37884352\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of IFN/STAT2 suppression by STAT3 not fully resolved\", \"Cellular source of protective IL-20 in colon not pinpointed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how IL-20 selects between type I and type II receptor complexes and between STAT3 and the alternative (JAK2/STAT5, ERK, Akt, PKC/NADPH) signaling branches to produce opposite outcomes—protective versus pathogenic—across tissues.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural or quantitative model linking receptor stoichiometry to signaling branch choice\", \"Determinants of context-dependent pro- vs anti-inflammatory output unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 6, 8, 25]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 8]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [8, 11, 15]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [2, 3, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [8, 11, 15, 23]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 6, 9, 10]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [6, 9, 21]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [12, 19, 20, 24]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"IL20RA\", \"IL20RB\", \"IL22RA1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":{"gene":"IL20","tier":"IDENTITY","verdict":"Identity concern","subtype":"corpus_ungrounded","uniprot_band":"rich","rules_fired":"R1","issue":"R1: gene named in 8/100 (8%) of its own corpus abstracts (< 25%) — corpus likely a paralog/alias collision"},"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}