{"gene":"ITIH1","run_date":"2026-04-28T18:06:54","timeline":{"discoveries":[{"year":1987,"finding":"ITIH1 (heavy chain H1 of inter-alpha-trypsin inhibitor) was characterized by cDNA cloning, establishing that human ITI is a multipolypeptide complex composed of distinct heavy chains (H1, H2) and a light chain synthesized from separate mRNAs, with the H1 chain (~90–95 kDa) expressed exclusively in liver. The deduced H1 amino acid sequence revealed potential calcium-binding sites and regions homologous to thiol-proteinase inhibitor reactive sites.","method":"cDNA cloning, RNA blot analysis, cell-free translation of hybrid-selected mRNA, partial amino acid sequencing of purified protein","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — direct cDNA sequencing plus protein sequence confirmation; foundational structural characterization","pmids":["2446322"],"is_preprint":false},{"year":1987,"finding":"cDNA library screening with anti-ITI antibodies resolved ITI into three distinct protein components; cDNA groups 2 and 3 (corresponding to heavy chains including H1) are distantly related to each other but unrelated to the bikunin/UTI light-chain component, confirming ITI is a multi-component complex rather than a single-chain protein.","method":"cDNA expression library screening, partial amino acid sequencing of purified serum ITI, sequence comparison","journal":"Biological chemistry Hoppe-Seyler","confidence":"High","confidence_rationale":"Tier 1 — independent cDNA cloning and protein sequencing; replicated the multichain finding of Salier et al. 1987","pmids":["3663330"],"is_preprint":false},{"year":1989,"finding":"ITI was shown to consist of two distinct proteins (225 kDa inter-alpha-TI containing heavy chains H1 [65 kDa] and H2 [70 kDa], and 125 kDa pre-alpha-TI containing H3 [90 kDa]), all sharing a single identical trypsin-inhibitory light chain (bikunin, 30 kDa). The multiple polypeptide chains within each complex are assembled by a glycan linkage (sensitive to trifluoromethanesulfonic acid and hyaluronidase), not by peptide bonds.","method":"Biochemical fractionation, SDS-PAGE, agarose gel electrophoresis, chemical denaturation, trifluoromethanesulfonic acid treatment, hyaluronidase digestion","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstitution-level biochemistry with multiple orthogonal chemical dissection methods; highly cited foundational paper","pmids":["2476436"],"is_preprint":false},{"year":1989,"finding":"ITIH1 and ITIH3 genes are co-localized to chromosome 3p21.1–21.2, while ITIH2 maps to chromosome 10p15 and the light-chain (bikunin/AMBP) gene to chromosome 9q32–33. This established that inter-alpha-trypsin inhibitor is encoded by at least four genes on three different chromosomes.","method":"In situ hybridization chromosomal localization, Northern analysis, cell-free translation of hybrid-selected poly(A)+ RNA","journal":"European journal of biochemistry","confidence":"High","confidence_rationale":"Tier 2 — direct cytogenetic mapping with multiple probe validation; highly replicated","pmids":["2465147"],"is_preprint":false},{"year":1993,"finding":"The heavy chains of ITI, including HC1 (the ITIH1 gene product), were identified as the serum-derived hyaluronan-associated proteins (SHAP) that become covalently linked to hyaluronan synthesized by fibroblasts. The HA-binding domain was mapped to the C-terminal half of HC1, which contains an amphipathic alpha-helix structure. Amino acid sequence of SHAP peptides showed essentially 100% identity with HC1 (human).","method":"Protein sequencing of HA-lyase-released peptides and V8 protease fragments, SDS-PAGE, Western blot with anti-ITI antibodies, bovine and human serum incubation with exogenous HA","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — direct protein sequencing and biochemical domain mapping; highly cited foundational paper","pmids":["7504674"],"is_preprint":false},{"year":1994,"finding":"A chondroitin sulphate chain covalently cross-links all three polypeptide chains of ITI (bikunin, H1, and H2) via a protein-glycosaminoglycan-protein cross-link. Thermolysin digestion and mass spectrometry of the glycosaminoglycan-containing fragment confirmed the covalent assembly.","method":"Thermolysin digestion, ion-exchange chromatography, peptide sequencing, mass spectrometry","journal":"European journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1 — direct chemical characterization by MS and sequencing of the cross-linking glycan fragment","pmids":["7513643"],"is_preprint":false},{"year":1995,"finding":"The C-terminal Asp residue of ITIH1 (HC1) is esterified to the C6-hydroxyl of an internal N-acetylglucosamine residue within the hyaluronan chain, establishing the precise covalent linkage chemistry between ITIH1 and hyaluronan. Equivalent linkages were identified for HC2 and HC3 at their respective C-terminal Asp residues.","method":"Thermolysin digestion of SHAP·HA complex from synovial fluid, CsCl gradient centrifugation, chondroitinase AC II digestion, reverse-phase HPLC, protein N-terminal sequencing, electrospray ionization MS, CID-MS/MS","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — MS/MS structural characterization with protein sequencing; provides atomic-level linkage chemistry","pmids":["7592891"],"is_preprint":false},{"year":1997,"finding":"The null allele ITIH1*Q0iwate results from deletion of a single nucleotide in the codon for Lys87, causing a frameshift and a premature termination codon that truncates the ITIH1 protein at amino acid 128, producing a non-functional truncated protein.","method":"SSCP analysis, direct DNA sequencing of genomic ITIH1","journal":"The Japanese journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 — direct sequencing of a naturally occurring loss-of-function allele","pmids":["9290263"],"is_preprint":false},{"year":2006,"finding":"TSG-6 forms covalent complexes with the heavy chains (HCs) of ITI including HC1/ITIH1, and these TSG-6·HC complexes cause release of free bikunin from the ITI complex. Free bikunin, but not HC-associated bikunin, functions as a relevant tissue kallikrein inhibitor in airway secretions, demonstrating that TSG-6-mediated heavy-chain transfer modulates the antiprotease activity of the ITI system.","method":"Immunoprecipitation from bronchoalveolar lavage fluid, in vitro reconstitution with purified components, primary cultures of human airway epithelial cells, TNF-α/IL-1β induction experiments","journal":"American journal of respiratory cell and molecular biology","confidence":"High","confidence_rationale":"Tier 1–2 — reconstitution with purified components plus immunoprecipitation from physiological fluid and cell culture","pmids":["16873769"],"is_preprint":false},{"year":2007,"finding":"Pentraxin 3 (PTX3) directly interacts with the heavy chains of ITI (including HC1/ITIH1) but not with bikunin, and this interaction is mediated by the N-terminal domain of PTX3. The PTX3–HC interaction is required for organizing hyaluronan in the cumulus oophorus extracellular matrix, as shown by rescue of the Ptx3-knockout phenotype in vitro; a monoclonal antibody blocking PTX3/ITI-HC interaction also prevents HA matrix formation.","method":"Coimmunoprecipitation from cumulus matrix extracts, solid-phase binding assay with purified proteins, recombinant PTX3 domain mapping, in vitro culture of Ptx3-/- cumulus cell-oocyte complexes, blocking antibody experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — direct binding assay with purified proteins, reciprocal Co-IP, genetic rescue, and functional antibody blockade","pmids":["17675295"],"is_preprint":false},{"year":2008,"finding":"ITIH1 (along with other ITIH family members) is expressed in multiple normal tissues and is frequently downregulated in multiple human solid tumors including breast, colon, and lung cancer, consistent with a role as a putative tumor suppressor. ITIH proteins contribute to ECM stability through covalent linkage to hyaluronan.","method":"cDNA dot blot (Cancer Profiling Array), semiquantitative RT-PCR, immunohistochemistry on tissue microarray","journal":"BMC cancer","confidence":"Low","confidence_rationale":"Tier 3 — expression analysis without direct mechanistic experimental manipulation of ITIH1","pmids":["18226209"],"is_preprint":false},{"year":2022,"finding":"KDM5C (a lysine demethylase) epigenetically silences ITIH1 transcription by regulating H3K4me1 modification at the ITIH1 promoter in liver hepatocellular carcinoma (LIHC) cells. KDM5C knockdown increases ITIH1 expression; subsequent ITIH1 knockdown rescues malignant behaviors and restores PI3K/AKT signaling activity, placing ITIH1 downstream of KDM5C as a suppressor of PI3K/AKT pathway activation.","method":"siRNA knockdown of KDM5C, ChIP for H3K4me1 at ITIH1 promoter, Western blot for PI3K/AKT signaling components, xenograft tumor model, double-knockdown epistasis (KDM5C KD + ITIH1 KD)","journal":"The Kaohsiung journal of medical sciences","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP-based epigenetic mechanism plus genetic epistasis via double knockdown","pmids":["35080113"],"is_preprint":false},{"year":2024,"finding":"ITIH1 functions as a secreted ligand of integrin α5β1, antagonizing fibronectin binding to this receptor and thereby inhibiting focal adhesion kinase (FAK) signaling to suppress HCC progression. TGF-β promotes liquid-phase separation of the m6A writer METTL3, reducing ITIH1 mRNA stability via m6A modification. Recombinant ITIH1 (r-ITIH1) protein inhibits HCC in mouse models, patient-derived organoids, and patient-derived xenografts, and synergizes with TGF-β inhibitors.","method":"Co-IP/binding assays for ITIH1–integrin α5β1 interaction, fibronectin competition assays, FAK phosphorylation measurement, METTL3 phase-separation imaging, m6A-seq/MeRIP for ITIH1 mRNA, in vivo mouse HCC model, patient-derived organoids and xenografts, recombinant protein administration","journal":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods including binding assays, signaling readouts, m6A mapping, and multiple preclinical models","pmids":["39234824"],"is_preprint":false},{"year":2024,"finding":"ITIH1 suppresses renal cell carcinoma (RCC) progression by inhibiting the NF-κB signaling pathway. ITIH1 knockdown in RCC cells increased phospho-NF-κB, decreased IκB, increased IKK, Cyclin D1, PCNA, and α-SMA, and enhanced cell proliferation and invasion; these effects were reversed by the NF-κB inhibitor JSH-23, placing ITIH1 upstream of NF-κB as a negative regulator.","method":"siRNA knockdown and overexpression of ITIH1 in RCC cell lines, Western blotting for NF-κB pathway components, proliferation and invasion assays, pharmacological rescue with JSH-23","journal":"Experimental and therapeutic medicine","confidence":"Medium","confidence_rationale":"Tier 2–3 — KD/OE with defined pathway readouts and pharmacological epistasis, single lab","pmids":["39091412"],"is_preprint":false}],"current_model":"ITIH1 encodes the heavy chain H1 of the inter-alpha-trypsin inhibitor complex, a liver-secreted plasma glycoprotein assembled by a chondroitin sulphate glycan cross-link joining H1, H2, and bikunin; ITIH1 is covalently transferred to hyaluronan via esterification of its C-terminal Asp to an N-acetylglucosamine residue in the HA chain, a process facilitated by TSG-6 and coupled to PTX3 binding through the ITI heavy-chain component to organize extracellular matrix; as a secreted protein ITIH1 acts as an integrin α5β1 ligand that antagonizes fibronectin and suppresses FAK signaling, while its transcription is epigenetically silenced by KDM5C via H3K4me1 modification and post-transcriptionally by TGF-β-driven METTL3 m6A modification, with loss of ITIH1 activating NF-κB and PI3K/AKT pathways to promote tumor progression in liver and renal cancers."},"narrative":{"teleology":[{"year":1987,"claim":"Resolving the long-standing question of whether ITI is a single polypeptide or a multi-component complex, cDNA cloning demonstrated that ITIH1 is a distinct heavy chain encoded by its own mRNA and expressed exclusively in liver, establishing the multi-gene architecture of the ITI system.","evidence":"cDNA cloning, RNA blot, cell-free translation, partial amino acid sequencing from two independent groups","pmids":["2446322","3663330"],"confidence":"High","gaps":["No functional assay for isolated H1 chain","Post-translational assembly mechanism unknown"]},{"year":1989,"claim":"The molecular basis of ITI assembly was established: H1 and H2 are joined to bikunin not by peptide bonds but via a glycosaminoglycan (chondroitin sulfate) cross-link, explaining the unusual multi-chain architecture and sensitivity to hyaluronidase/chemical deglycosylation.","evidence":"SDS-PAGE, trifluoromethanesulfonic acid treatment, hyaluronidase digestion of purified plasma ITI","pmids":["2476436"],"confidence":"High","gaps":["Precise chemical nature of the glycan–protein bond not yet resolved","Assembly pathway in hepatocytes unknown"]},{"year":1993,"claim":"The extracellular function of ITIH1 was reframed when its gene product was identified as the serum-derived hyaluronan-associated protein (SHAP), demonstrating that HC1 is covalently transferred from ITI to hyaluronan chains, with the HA-binding determinant mapped to the C-terminal half of the protein.","evidence":"Protein sequencing of HA-lyase-released peptides, Western blot with anti-ITI antibodies, in vitro incubation of serum with exogenous HA","pmids":["7504674"],"confidence":"High","gaps":["Enzyme or catalyst mediating the transfer not identified","Structural basis of C-terminal HA binding unresolved"]},{"year":1995,"claim":"The atomic-level linkage chemistry was defined: the C-terminal Asp of HC1/ITIH1 forms an ester bond to the C6-hydroxyl of an internal GlcNAc residue in the hyaluronan chain, providing the precise covalent mechanism for HA cross-linking.","evidence":"ESI-MS/MS and CID-MS/MS of thermolysin-digested SHAP·HA complex from human synovial fluid","pmids":["7592891"],"confidence":"High","gaps":["Transferase catalyzing the ester bond formation not yet identified","Reversibility and turnover of the linkage unknown"]},{"year":2006,"claim":"TSG-6 was identified as the catalyst that forms covalent intermediates with ITI heavy chains including HC1, driving their transfer to HA and simultaneously releasing free bikunin as an active serine protease inhibitor, connecting ITIH1 metabolism to airway antiprotease defense.","evidence":"Immunoprecipitation from bronchoalveolar lavage fluid, in vitro reconstitution with purified TSG-6/ITI, primary human airway epithelial cells with TNF-α/IL-1β stimulation","pmids":["16873769"],"confidence":"High","gaps":["Catalytic mechanism of TSG-6 in transesterification not structurally resolved","Whether TSG-6 is the sole catalyst in all tissues unknown"]},{"year":2007,"claim":"PTX3 was shown to directly bind ITI heavy chains (including HC1) through its N-terminal domain, and this interaction is required for organizing hyaluronan matrices in the cumulus oophorus, as demonstrated by rescue of the Ptx3-knockout matrix-assembly defect and blockade by an anti-PTX3 antibody.","evidence":"Co-IP from cumulus matrix, solid-phase binding with purified proteins, PTX3 domain mapping, Ptx3−/− cumulus culture rescue, blocking antibody","pmids":["17675295"],"confidence":"High","gaps":["Stoichiometry of the PTX3–HC1 complex on HA not determined","Whether PTX3 interaction is required for HA stabilization beyond cumulus matrix unknown"]},{"year":2022,"claim":"Epigenetic regulation of ITIH1 was established: KDM5C silences ITIH1 transcription by demethylating H3K4me1 at its promoter in HCC cells, and double-knockdown epistasis showed that ITIH1 loss downstream of KDM5C reactivates PI3K/AKT signaling and restores malignant behavior.","evidence":"siRNA KD of KDM5C, ChIP for H3K4me1 at ITIH1 promoter, KDM5C/ITIH1 double KD epistasis, xenograft tumor model","pmids":["35080113"],"confidence":"Medium","gaps":["Whether KDM5C is recruited to ITIH1 promoter by a specific transcription factor is unknown","Single-lab finding; independent replication needed","Direct protein-level readout of ITIH1 secretion after KDM5C manipulation not shown"]},{"year":2024,"claim":"ITIH1 was shown to function as a secreted integrin α5β1 ligand that competes with fibronectin to suppress FAK signaling in HCC, while TGF-β promotes METTL3 phase separation to m6A-modify ITIH1 mRNA and reduce its stability, providing a unified post-transcriptional and signaling mechanism for ITIH1 tumor suppression.","evidence":"Co-IP/binding assays for ITIH1–integrin α5β1, fibronectin competition, FAK phosphorylation, m6A-seq/MeRIP, METTL3 phase-separation imaging, in vivo HCC model, patient-derived organoids and xenografts, recombinant ITIH1 treatment","pmids":["39234824"],"confidence":"High","gaps":["Structural basis of ITIH1–integrin α5β1 binding versus the established HA-ester function not reconciled","Whether integrin antagonism is independent of HA binding unknown"]},{"year":2024,"claim":"ITIH1 was independently shown to suppress RCC progression via negative regulation of NF-κB signaling, with pharmacological rescue by the NF-κB inhibitor JSH-23 confirming pathway epistasis.","evidence":"siRNA KD and overexpression in RCC cell lines, Western blot for NF-κB pathway, proliferation/invasion assays, JSH-23 pharmacological rescue","pmids":["39091412"],"confidence":"Medium","gaps":["Mechanism by which a secreted protein inhibits intracellular NF-κB not defined","No in vivo model provided","Relationship between NF-κB suppression and integrin/FAK pathway unclear"]},{"year":null,"claim":"Key unresolved questions include the structural basis for ITIH1's dual roles in HA cross-linking and integrin antagonism, how secreted ITIH1 accesses intracellular NF-κB signaling, and whether the tumor-suppressive function operates through the same C-terminal domain responsible for HA esterification.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of ITIH1 or ITIH1–HA complex","No genetic loss-of-function animal model for ITIH1","Relationship between HA stabilization and tumor-suppressive signaling unexplored"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[8,12,13]},{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[4,6,12]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,4,6,12]},{"term_id":"GO:0031012","term_label":"extracellular matrix","supporting_discovery_ids":[4,6,9]}],"pathway":[{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[4,6,9]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[12,13]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[11,12,13]}],"complexes":["Inter-alpha-trypsin inhibitor (ITI; H1-H2-bikunin)","SHAP·HA complex"],"partners":["ITIH2","AMBP","TNFAIP6","PTX3","ITGA5","ITGB1","METTL3","KDM5C"],"other_free_text":[]},"mechanistic_narrative":"ITIH1 encodes heavy chain H1 of the inter-alpha-trypsin inhibitor (ITI) complex, a liver-expressed secreted glycoprotein that is assembled with heavy chain H2 and bikunin via a chondroitin sulfate cross-link and functions primarily in extracellular matrix organization through covalent transfer to hyaluronan [PMID:2476436, PMID:7592891]. The C-terminal Asp of ITIH1 is esterified to an internal N-acetylglucosamine of hyaluronan chains, a transfer catalyzed by TSG-6, which also liberates free bikunin as an active serine protease inhibitor; pentraxin 3 (PTX3) binds the ITI heavy chains to cooperatively organize hyaluronan matrices essential for processes such as cumulus oophorus expansion [PMID:7592891, PMID:16873769, PMID:17675295]. As a secreted protein, ITIH1 also acts as an integrin α5β1 ligand that competes with fibronectin to suppress FAK signaling, and its expression is negatively regulated both epigenetically by KDM5C-mediated H3K4me1 demethylation and post-transcriptionally by TGF-β-driven METTL3 m6A modification, with loss of ITIH1 activating NF-κB and PI3K/AKT pathways to promote hepatocellular and renal cell carcinoma progression [PMID:39234824, PMID:35080113, PMID:39091412]."},"prefetch_data":{"uniprot":{"accession":"P19827","full_name":"Inter-alpha-trypsin inhibitor heavy chain H1","aliases":["Inter-alpha-trypsin inhibitor complex component III","Serum-derived hyaluronan-associated protein","SHAP"],"length_aa":911,"mass_kda":101.4,"function":"May act as a carrier of hyaluronan in serum or as a binding protein between hyaluronan and other matrix protein, including those on cell surfaces in tissues to regulate the localization, synthesis and degradation of hyaluronan which are essential to cells undergoing biological processes Contains a potential peptide which could stimulate a broad spectrum of phagocytotic cells","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/P19827/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ITIH1","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ITIH1","total_profiled":1310},"omim":[{"mim_id":"600564","title":"INTER-ALPHA-TRYPSIN INHIBITOR, HEAVY CHAIN 4; ITIH4","url":"https://www.omim.org/entry/600564"},{"mim_id":"176870","title":"ALPHA-1 MICROGLOBULIN/BIKUNIN PRECURSOR; AMBP","url":"https://www.omim.org/entry/176870"},{"mim_id":"147270","title":"INTER-ALPHA-TRYPSIN INHIBITOR, HEAVY CHAIN 1; ITIH1","url":"https://www.omim.org/entry/147270"},{"mim_id":"146650","title":"INTER-ALPHA-TRYPSIN INHIBITOR, HEAVY CHAIN 3; ITIH3","url":"https://www.omim.org/entry/146650"},{"mim_id":"146640","title":"INTER-ALPHA-TRYPSIN INHIBITOR, HEAVY CHAIN 2; ITIH2","url":"https://www.omim.org/entry/146640"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"liver","ntpm":1407.7}],"url":"https://www.proteinatlas.org/search/ITIH1"},"hgnc":{"alias_symbol":["H1P","IATIH","ITIH"],"prev_symbol":[]},"alphafold":{"accession":"P19827","domains":[{"cath_id":"2.60.40","chopping":"52-264_605-626","consensus_level":"medium","plddt":93.8402,"start":52,"end":626},{"cath_id":"2.60.40","chopping":"270-286_481-573","consensus_level":"medium","plddt":95.4991,"start":270,"end":573},{"cath_id":"3.40.50.410","chopping":"292-477","consensus_level":"high","plddt":96.8712,"start":292,"end":477},{"cath_id":"-","chopping":"668-906","consensus_level":"high","plddt":81.7419,"start":668,"end":906}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P19827","model_url":"https://alphafold.ebi.ac.uk/files/AF-P19827-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P19827-F1-predicted_aligned_error_v6.png","plddt_mean":87.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ITIH1","jax_strain_url":"https://www.jax.org/strain/search?query=ITIH1"},"sequence":{"accession":"P19827","fasta_url":"https://rest.uniprot.org/uniprotkb/P19827.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P19827/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P19827"}},"corpus_meta":[{"pmid":"18226209","id":"PMC_18226209","title":"Frequent 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liver.","date":"2014","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/25037231","citation_count":203,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"28675934","id":"PMC_28675934","title":"Characterization of the Extracellular Matrix of Normal and Diseased Tissues Using Proteomics.","date":"2017","source":"Journal of proteome research","url":"https://pubmed.ncbi.nlm.nih.gov/28675934","citation_count":185,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"2476436","id":"PMC_2476436","title":"Analysis of inter-alpha-trypsin inhibitor and a novel trypsin inhibitor, pre-alpha-trypsin inhibitor, from human plasma. Polypeptide chain stoichiometry and assembly by glycan.","date":"1989","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/2476436","citation_count":183,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"25173105","id":"PMC_25173105","title":"Common variants near ABCA1, AFAP1 and GMDS confer risk of primary open-angle glaucoma.","date":"2014","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/25173105","citation_count":179,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"7592891","id":"PMC_7592891","title":"Evidence for the covalent binding of SHAP, heavy chains of inter-alpha-trypsin inhibitor, to hyaluronan.","date":"1995","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/7592891","citation_count":158,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"7504674","id":"PMC_7504674","title":"A serum-derived hyaluronan-associated protein (SHAP) is the heavy chain of the inter alpha-trypsin inhibitor.","date":"1993","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/7504674","citation_count":157,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"14760718","id":"PMC_14760718","title":"Screening for N-glycosylated proteins by liquid chromatography mass spectrometry.","date":"2004","source":"Proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/14760718","citation_count":156,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"23533145","id":"PMC_23533145","title":"In-depth proteomic analyses of exosomes isolated from expressed prostatic secretions in urine.","date":"2013","source":"Proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/23533145","citation_count":138,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"17675295","id":"PMC_17675295","title":"PTX3 interacts with inter-alpha-trypsin inhibitor: implications for hyaluronan organization and cumulus oophorus expansion.","date":"2007","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17675295","citation_count":129,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"23376485","id":"PMC_23376485","title":"Proteomic analysis of podocyte exosome-enriched fraction from normal human urine.","date":"2013","source":"Journal of proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/23376485","citation_count":126,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"2465147","id":"PMC_2465147","title":"Human plasma inter-alpha-trypsin inhibitor is encoded by four genes on three chromosomes.","date":"1989","source":"European journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/2465147","citation_count":95,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"2446322","id":"PMC_2446322","title":"Isolation and characterization of cDNAs encoding the heavy chain of human inter-alpha-trypsin inhibitor (I alpha TI): unambiguous evidence for multipolypeptide chain structure of I alpha TI.","date":"1987","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/2446322","citation_count":93,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"22516433","id":"PMC_22516433","title":"Proteomic analysis of microvesicles from plasma of healthy donors reveals high individual variability.","date":"2012","source":"Journal of proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/22516433","citation_count":81,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"7513643","id":"PMC_7513643","title":"Chondroitin sulphate covalently cross-links the three polypeptide chains of inter-alpha-trypsin inhibitor.","date":"1994","source":"European journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/7513643","citation_count":71,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"3663330","id":"PMC_3663330","title":"cDNA cloning of human inter-alpha-trypsin inhibitor discloses three different proteins.","date":"1987","source":"Biological chemistry Hoppe-Seyler","url":"https://pubmed.ncbi.nlm.nih.gov/3663330","citation_count":70,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"16873769","id":"PMC_16873769","title":"TSG-6 potentiates the antitissue kallikrein activity of inter-alpha-inhibitor through bikunin release.","date":"2006","source":"American journal of respiratory cell and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16873769","citation_count":65,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"31273033","id":"PMC_31273033","title":"Extracellular Hsp90α and clusterin synergistically promote breast cancer epithelial-to-mesenchymal transition and metastasis via LRP1.","date":"2019","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/31273033","citation_count":64,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10968,"output_tokens":1471,"usd":0.027484},"stage2":{"model":"claude-opus-4-6","input_tokens":4756,"output_tokens":1869,"usd":0.105758},"total_usd":0.372427,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":24292,"output_tokens":5049,"usd":0.074305},"round2_rules_fired":"R3","round2_stage2":{"model":"claude-opus-4-6","input_tokens":7649,"output_tokens":2867,"usd":0.16488}},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2008,\n      \"finding\": \"ITIH1, as a member of the inter-alpha-trypsin inhibitor heavy chain family, contributes to extracellular matrix stability through covalent linkage to hyaluronan; ITIH genes are frequently downregulated in multiple human solid tumors, suggesting a tumor suppressive role in ECM maintenance.\",\n      \"method\": \"cDNA dot blot analysis (Cancer Profiling Array), semiquantitative RT-PCR, immunohistochemistry across 13 tumor entities\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — systematic expression analysis across multiple tumor types with IHC validation; mechanistic role inferred from known ECM-hyaluronan covalent linkage function, not directly demonstrated for ITIH1 alone in this paper\",\n      \"pmids\": [\"18226209\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"KDM5C (lysine demethylase 5C) epigenetically represses ITIH1 transcription by regulating H3K4me1 modification at the ITIH1 promoter, leading to ITIH1 transcriptional inactivation; silencing ITIH1 downstream of KDM5C activates PI3K/AKT signaling to promote liver hepatocellular carcinoma progression.\",\n      \"method\": \"KDM5C knockdown in LIHC cell lines, chromatin modification analysis (H3K4me1 at ITIH1 promoter), siRNA-mediated ITIH1 silencing, PI3K/AKT pathway activity assays, xenograft tumor model\",\n      \"journal\": \"The Kaohsiung journal of medical sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (epigenetic mark mapping, KD rescue experiments, pathway assays) but single lab\",\n      \"pmids\": [\"35080113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"ITIH1 acts as a secreted ligand of integrin α5β1 to antagonize fibronectin binding, thereby inhibiting focal adhesion kinase (FAK) signaling and suppressing HCC progression; TGF-β promotes liquid phase separation of METTL3, which reduces ITIH1 mRNA stability via m6A modification, thus decreasing ITIH1 levels and unleashing HCC progression.\",\n      \"method\": \"Recombinant ITIH1 protein binding assays with integrin α5β1, FAK signaling pathway analysis, METTL3 liquid phase separation assay, m6A mRNA stability assays, mouse model, patient-derived organoids, patient-derived xenografts, synergy with TGF-β inhibitor\",\n      \"journal\": \"Advanced science (Weinheim, Baden-Wurttemberg, Germany)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — reconstituted receptor-ligand interaction, multiple in vivo models, mechanistic pathway (m6A/METTL3 → ITIH1 mRNA stability → integrin α5β1/FAK) supported by orthogonal methods\",\n      \"pmids\": [\"39234824\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"ITIH1 suppresses renal cell carcinoma (RCC) progression by inhibiting the NF-κB signaling pathway; ITIH1 knockdown increases phosphorylation of NF-κB, decreases IκB protein, and increases IKK, Cyclin D1, PCNA, and α-SMA, promoting RCC cell proliferation and invasion, while ITIH1 overexpression inhibits these processes.\",\n      \"method\": \"siRNA-mediated ITIH1 knockdown and ITIH1 overexpression in RCC cell lines, Western blotting for NF-κB pathway components, proliferation and invasion assays, NF-κB inhibitor (JSH-23) rescue experiment\",\n      \"journal\": \"Experimental and therapeutic medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KD/OE with defined pathway readout and pharmacological rescue, single lab\",\n      \"pmids\": [\"39091412\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"A null allele of ITIH1 (ITIH1*Q0iwate) results from deletion of a single nucleotide in the codon for Lys87, causing a frameshift and premature termination at amino acid 128, producing a truncated non-functional ITIH1 protein.\",\n      \"method\": \"Single-strand conformation polymorphism (SSCP) analysis and direct DNA sequencing of ITIH1 gene\",\n      \"journal\": \"The Japanese journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct molecular characterization of mutation with sequencing confirmation\",\n      \"pmids\": [\"9290263\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ITIH1 is a secreted extracellular matrix protein that covalently links to hyaluronan to stabilize the ECM, acts as a ligand for integrin α5β1 to antagonize fibronectin and suppress FAK signaling, inhibits NF-κB signaling to restrain tumor cell proliferation and invasion, and is itself regulated at the transcriptional level by KDM5C-mediated H3K4me1 demethylation and post-transcriptionally by TGF-β-driven METTL3 liquid-phase separation that reduces ITIH1 mRNA stability via m6A modification.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll classify each paper, then extract discoveries only from KEEP papers.\n\n**Classification:**\n\n- [1] KEEP — about ITIH gene family including ITIH1, ECM/hyaluronan function\n- [2] EXCLUDE — about ITIH4, not ITIH1\n- [3] EXCLUDE — about ITIH5, not ITIH1\n- [4] EXCLUDE — GWAS association study, no mechanism\n- [5] EXCLUDE — ITIH4, not ITIH1\n- [6] KEEP — about ITIH1 specifically, KDM5C epigenetic regulation\n- [7] EXCLUDE — Cdk5/p25 kinase study; \"H1P\" is a histone-derived peptide substrate, not ITIH1\n- [8] KEEP — RFLP in ITIH1 gene (structural/null allele data)\n- [9] KEEP — ITIH1 as ligand of integrin α5β1, mechanism\n- [10] KEEP — ITIH1 polymorphism/genetics\n- [11] KEEP — ITIH1 protein polymorphism linkage\n- [12] KEEP — ITIH1 RFLP\n- [13] KEEP — ITIH1 in gastric cancer, siRNA KD functional assay\n- [14] KEEP — ITIH1 in RCC, NF-κB mechanism\n- [15] KEEP — ITIH1*Q0iwate null allele, frameshift\n- [16] KEEP — ITIH1 expression in hepatic stellate cells\n- [17] EXCLUDE — focuses on ITIH3/ITIH4, not ITIH1\n- [18] EXCLUDE — ITIH1 only mentioned as differentially expressed, no mechanism\n- [19] EXCLUDE — genome engineering paper, H1p is a Pol III promoter\n\n**gene2pubmed additional papers:**\n- PMID:25056061 EXCLUDE — GWAS, no ITIH1 mechanism\n- PMID:12477932 EXCLUDE — cDNA collection\n- PMID:23974872 EXCLUDE — GWAS\n- PMID:12754519 EXCLUDE — glycoproteomics methods\n- PMID:21926972 EXCLUDE — GWAS\n- PMID:26496610 EXCLUDE — general interactome\n- PMID:33961781 EXCLUDE — general interactome\n- PMID:14718574 EXCLUDE — plasma proteome\n- PMID:21873635 EXCLUDE — GO annotation\n- PMID:15489334 EXCLUDE — cDNA collection\n- PMID:16344560 EXCLUDE — promoter analysis\n- PMID:15174051 EXCLUDE — serum interactome proteomics\n- PMID:19416921 EXCLUDE — GWAS\n- PMID:25037231 EXCLUDE — ECM proteomics, no ITIH1 mechanism\n- PMID:28675934 EXCLUDE — ECM proteomics methods\n- PMID:2476436 KEEP — biochemical characterization of ITI chains, heavy chain assembly via glycan\n- PMID:7592891 KEEP — SHAP/HC1 covalent binding to hyaluronan, C-terminal Asp esterified to HA\n- PMID:7504674 KEEP — SHAP identified as ITI heavy chain HC1, HA-binding domain mapping\n- PMID:14760718 EXCLUDE — glycoproteomics\n- PMID:23533145 EXCLUDE — prostate exosome proteomics\n- PMID:17675295 KEEP — PTX3 interacts with ITI heavy chains, HC-specific interaction, cumulus matrix\n- PMID:23376485 EXCLUDE — podocyte exosome proteomics\n- PMID:2465147 KEEP — chromosomal localization, multi-gene structure of ITI\n- PMID:2446322 KEEP — cDNA characterization, calcium-binding sites, multipolypeptide structure\n- PMID:22516433 EXCLUDE — plasma microvesicle proteomics\n- PMID:7513643 KEEP — chondroitin sulphate covalently cross-links ITI chains including H1\n- PMID:3663330 KEEP — cDNA cloning, three distinct proteins\n- PMID:16873769 KEEP — TSG-6/HC complex formation, bikunin release, antiprotease function\n- PMID:31273033 EXCLUDE — about eHsp90α/clusterin, not ITIH1\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1987,\n      \"finding\": \"ITIH1 (heavy chain H1 of inter-alpha-trypsin inhibitor) was characterized by cDNA cloning, establishing that human ITI is a multipolypeptide complex composed of distinct heavy chains (H1, H2) and a light chain synthesized from separate mRNAs, with the H1 chain (~90–95 kDa) expressed exclusively in liver. The deduced H1 amino acid sequence revealed potential calcium-binding sites and regions homologous to thiol-proteinase inhibitor reactive sites.\",\n      \"method\": \"cDNA cloning, RNA blot analysis, cell-free translation of hybrid-selected mRNA, partial amino acid sequencing of purified protein\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct cDNA sequencing plus protein sequence confirmation; foundational structural characterization\",\n      \"pmids\": [\"2446322\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"cDNA library screening with anti-ITI antibodies resolved ITI into three distinct protein components; cDNA groups 2 and 3 (corresponding to heavy chains including H1) are distantly related to each other but unrelated to the bikunin/UTI light-chain component, confirming ITI is a multi-component complex rather than a single-chain protein.\",\n      \"method\": \"cDNA expression library screening, partial amino acid sequencing of purified serum ITI, sequence comparison\",\n      \"journal\": \"Biological chemistry Hoppe-Seyler\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — independent cDNA cloning and protein sequencing; replicated the multichain finding of Salier et al. 1987\",\n      \"pmids\": [\"3663330\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1989,\n      \"finding\": \"ITI was shown to consist of two distinct proteins (225 kDa inter-alpha-TI containing heavy chains H1 [65 kDa] and H2 [70 kDa], and 125 kDa pre-alpha-TI containing H3 [90 kDa]), all sharing a single identical trypsin-inhibitory light chain (bikunin, 30 kDa). The multiple polypeptide chains within each complex are assembled by a glycan linkage (sensitive to trifluoromethanesulfonic acid and hyaluronidase), not by peptide bonds.\",\n      \"method\": \"Biochemical fractionation, SDS-PAGE, agarose gel electrophoresis, chemical denaturation, trifluoromethanesulfonic acid treatment, hyaluronidase digestion\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution-level biochemistry with multiple orthogonal chemical dissection methods; highly cited foundational paper\",\n      \"pmids\": [\"2476436\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1989,\n      \"finding\": \"ITIH1 and ITIH3 genes are co-localized to chromosome 3p21.1–21.2, while ITIH2 maps to chromosome 10p15 and the light-chain (bikunin/AMBP) gene to chromosome 9q32–33. This established that inter-alpha-trypsin inhibitor is encoded by at least four genes on three different chromosomes.\",\n      \"method\": \"In situ hybridization chromosomal localization, Northern analysis, cell-free translation of hybrid-selected poly(A)+ RNA\",\n      \"journal\": \"European journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct cytogenetic mapping with multiple probe validation; highly replicated\",\n      \"pmids\": [\"2465147\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"The heavy chains of ITI, including HC1 (the ITIH1 gene product), were identified as the serum-derived hyaluronan-associated proteins (SHAP) that become covalently linked to hyaluronan synthesized by fibroblasts. The HA-binding domain was mapped to the C-terminal half of HC1, which contains an amphipathic alpha-helix structure. Amino acid sequence of SHAP peptides showed essentially 100% identity with HC1 (human).\",\n      \"method\": \"Protein sequencing of HA-lyase-released peptides and V8 protease fragments, SDS-PAGE, Western blot with anti-ITI antibodies, bovine and human serum incubation with exogenous HA\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct protein sequencing and biochemical domain mapping; highly cited foundational paper\",\n      \"pmids\": [\"7504674\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"A chondroitin sulphate chain covalently cross-links all three polypeptide chains of ITI (bikunin, H1, and H2) via a protein-glycosaminoglycan-protein cross-link. Thermolysin digestion and mass spectrometry of the glycosaminoglycan-containing fragment confirmed the covalent assembly.\",\n      \"method\": \"Thermolysin digestion, ion-exchange chromatography, peptide sequencing, mass spectrometry\",\n      \"journal\": \"European journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct chemical characterization by MS and sequencing of the cross-linking glycan fragment\",\n      \"pmids\": [\"7513643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The C-terminal Asp residue of ITIH1 (HC1) is esterified to the C6-hydroxyl of an internal N-acetylglucosamine residue within the hyaluronan chain, establishing the precise covalent linkage chemistry between ITIH1 and hyaluronan. Equivalent linkages were identified for HC2 and HC3 at their respective C-terminal Asp residues.\",\n      \"method\": \"Thermolysin digestion of SHAP·HA complex from synovial fluid, CsCl gradient centrifugation, chondroitinase AC II digestion, reverse-phase HPLC, protein N-terminal sequencing, electrospray ionization MS, CID-MS/MS\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — MS/MS structural characterization with protein sequencing; provides atomic-level linkage chemistry\",\n      \"pmids\": [\"7592891\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"The null allele ITIH1*Q0iwate results from deletion of a single nucleotide in the codon for Lys87, causing a frameshift and a premature termination codon that truncates the ITIH1 protein at amino acid 128, producing a non-functional truncated protein.\",\n      \"method\": \"SSCP analysis, direct DNA sequencing of genomic ITIH1\",\n      \"journal\": \"The Japanese journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct sequencing of a naturally occurring loss-of-function allele\",\n      \"pmids\": [\"9290263\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"TSG-6 forms covalent complexes with the heavy chains (HCs) of ITI including HC1/ITIH1, and these TSG-6·HC complexes cause release of free bikunin from the ITI complex. Free bikunin, but not HC-associated bikunin, functions as a relevant tissue kallikrein inhibitor in airway secretions, demonstrating that TSG-6-mediated heavy-chain transfer modulates the antiprotease activity of the ITI system.\",\n      \"method\": \"Immunoprecipitation from bronchoalveolar lavage fluid, in vitro reconstitution with purified components, primary cultures of human airway epithelial cells, TNF-α/IL-1β induction experiments\",\n      \"journal\": \"American journal of respiratory cell and molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — reconstitution with purified components plus immunoprecipitation from physiological fluid and cell culture\",\n      \"pmids\": [\"16873769\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Pentraxin 3 (PTX3) directly interacts with the heavy chains of ITI (including HC1/ITIH1) but not with bikunin, and this interaction is mediated by the N-terminal domain of PTX3. The PTX3–HC interaction is required for organizing hyaluronan in the cumulus oophorus extracellular matrix, as shown by rescue of the Ptx3-knockout phenotype in vitro; a monoclonal antibody blocking PTX3/ITI-HC interaction also prevents HA matrix formation.\",\n      \"method\": \"Coimmunoprecipitation from cumulus matrix extracts, solid-phase binding assay with purified proteins, recombinant PTX3 domain mapping, in vitro culture of Ptx3-/- cumulus cell-oocyte complexes, blocking antibody experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct binding assay with purified proteins, reciprocal Co-IP, genetic rescue, and functional antibody blockade\",\n      \"pmids\": [\"17675295\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"ITIH1 (along with other ITIH family members) is expressed in multiple normal tissues and is frequently downregulated in multiple human solid tumors including breast, colon, and lung cancer, consistent with a role as a putative tumor suppressor. ITIH proteins contribute to ECM stability through covalent linkage to hyaluronan.\",\n      \"method\": \"cDNA dot blot (Cancer Profiling Array), semiquantitative RT-PCR, immunohistochemistry on tissue microarray\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — expression analysis without direct mechanistic experimental manipulation of ITIH1\",\n      \"pmids\": [\"18226209\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"KDM5C (a lysine demethylase) epigenetically silences ITIH1 transcription by regulating H3K4me1 modification at the ITIH1 promoter in liver hepatocellular carcinoma (LIHC) cells. KDM5C knockdown increases ITIH1 expression; subsequent ITIH1 knockdown rescues malignant behaviors and restores PI3K/AKT signaling activity, placing ITIH1 downstream of KDM5C as a suppressor of PI3K/AKT pathway activation.\",\n      \"method\": \"siRNA knockdown of KDM5C, ChIP for H3K4me1 at ITIH1 promoter, Western blot for PI3K/AKT signaling components, xenograft tumor model, double-knockdown epistasis (KDM5C KD + ITIH1 KD)\",\n      \"journal\": \"The Kaohsiung journal of medical sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP-based epigenetic mechanism plus genetic epistasis via double knockdown\",\n      \"pmids\": [\"35080113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"ITIH1 functions as a secreted ligand of integrin α5β1, antagonizing fibronectin binding to this receptor and thereby inhibiting focal adhesion kinase (FAK) signaling to suppress HCC progression. TGF-β promotes liquid-phase separation of the m6A writer METTL3, reducing ITIH1 mRNA stability via m6A modification. Recombinant ITIH1 (r-ITIH1) protein inhibits HCC in mouse models, patient-derived organoids, and patient-derived xenografts, and synergizes with TGF-β inhibitors.\",\n      \"method\": \"Co-IP/binding assays for ITIH1–integrin α5β1 interaction, fibronectin competition assays, FAK phosphorylation measurement, METTL3 phase-separation imaging, m6A-seq/MeRIP for ITIH1 mRNA, in vivo mouse HCC model, patient-derived organoids and xenografts, recombinant protein administration\",\n      \"journal\": \"Advanced science (Weinheim, Baden-Wurttemberg, Germany)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods including binding assays, signaling readouts, m6A mapping, and multiple preclinical models\",\n      \"pmids\": [\"39234824\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"ITIH1 suppresses renal cell carcinoma (RCC) progression by inhibiting the NF-κB signaling pathway. ITIH1 knockdown in RCC cells increased phospho-NF-κB, decreased IκB, increased IKK, Cyclin D1, PCNA, and α-SMA, and enhanced cell proliferation and invasion; these effects were reversed by the NF-κB inhibitor JSH-23, placing ITIH1 upstream of NF-κB as a negative regulator.\",\n      \"method\": \"siRNA knockdown and overexpression of ITIH1 in RCC cell lines, Western blotting for NF-κB pathway components, proliferation and invasion assays, pharmacological rescue with JSH-23\",\n      \"journal\": \"Experimental and therapeutic medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — KD/OE with defined pathway readouts and pharmacological epistasis, single lab\",\n      \"pmids\": [\"39091412\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ITIH1 encodes the heavy chain H1 of the inter-alpha-trypsin inhibitor complex, a liver-secreted plasma glycoprotein assembled by a chondroitin sulphate glycan cross-link joining H1, H2, and bikunin; ITIH1 is covalently transferred to hyaluronan via esterification of its C-terminal Asp to an N-acetylglucosamine residue in the HA chain, a process facilitated by TSG-6 and coupled to PTX3 binding through the ITI heavy-chain component to organize extracellular matrix; as a secreted protein ITIH1 acts as an integrin α5β1 ligand that antagonizes fibronectin and suppresses FAK signaling, while its transcription is epigenetically silenced by KDM5C via H3K4me1 modification and post-transcriptionally by TGF-β-driven METTL3 m6A modification, with loss of ITIH1 activating NF-κB and PI3K/AKT pathways to promote tumor progression in liver and renal cancers.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ITIH1 is a secreted extracellular matrix glycoprotein that stabilizes the ECM through covalent linkage to hyaluronan and functions as a tumor suppressor in multiple solid tumor types [PMID:18226209]. ITIH1 acts as a ligand for integrin α5β1, antagonizing fibronectin binding and thereby inhibiting focal adhesion kinase (FAK) signaling to suppress hepatocellular carcinoma progression; its expression is post-transcriptionally downregulated by TGF-β-driven METTL3 liquid-phase separation, which reduces ITIH1 mRNA stability via m6A modification [PMID:39234824]. ITIH1 also restrains tumor cell proliferation and invasion through inhibition of the NF-κB signaling pathway [PMID:39091412], and its transcription is epigenetically repressed by KDM5C-mediated H3K4me1 demethylation at the ITIH1 promoter, with ITIH1 silencing activating PI3K/AKT signaling in liver cancer [PMID:35080113].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Identification of a natural null allele (ITIH1*Q0iwate) established that ITIH1 can be rendered non-functional by a single-nucleotide deletion causing a frameshift and premature termination, providing the first molecular-genetic characterization of ITIH1 loss-of-function.\",\n      \"evidence\": \"SSCP analysis and direct sequencing of the ITIH1 gene in human subjects\",\n      \"pmids\": [\"9290263\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Phenotypic consequences of homozygous ITIH1 null status in carriers were not characterized\",\n        \"No functional assay confirmed loss of ECM activity for the truncated protein\"\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Systematic expression profiling across 13 tumor types revealed frequent ITIH1 downregulation in solid tumors, linking its ECM-stabilizing hyaluronan-binding function to a candidate tumor suppressive role.\",\n      \"evidence\": \"cDNA dot blot (Cancer Profiling Array), RT-PCR, and immunohistochemistry across multiple tumor entities\",\n      \"pmids\": [\"18226209\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Tumor-suppressive function was inferred from expression loss rather than demonstrated by functional reconstitution\",\n        \"ITIH1-specific hyaluronan covalent linkage was not directly assayed in this study\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"The question of how ITIH1 is epigenetically silenced was addressed by showing that KDM5C demethylates H3K4me1 at the ITIH1 promoter, repressing ITIH1 transcription and activating PI3K/AKT signaling in hepatocellular carcinoma.\",\n      \"evidence\": \"KDM5C knockdown with H3K4me1 chromatin analysis at ITIH1 promoter, siRNA-mediated ITIH1 silencing, PI3K/AKT pathway assays, and xenograft models in LIHC cell lines\",\n      \"pmids\": [\"35080113\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single-lab study; independent replication is lacking\",\n        \"Whether KDM5C-ITIH1 axis operates in tumor types beyond HCC is unknown\",\n        \"Direct ChIP-seq for KDM5C occupancy at the ITIH1 promoter was not shown\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Two key mechanistic questions — the receptor through which ITIH1 signals and the post-transcriptional mechanism controlling its levels — were resolved: ITIH1 binds integrin α5β1 to antagonize fibronectin and inhibit FAK signaling, while TGF-β induces METTL3 liquid-phase separation to destabilize ITIH1 mRNA via m6A modification.\",\n      \"evidence\": \"Recombinant protein binding assays with integrin α5β1, FAK pathway analysis, METTL3 phase separation and m6A assays, patient-derived organoids, xenografts, and TGF-β inhibitor synergy in mouse models\",\n      \"pmids\": [\"39234824\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of ITIH1–integrin α5β1 interaction is unresolved\",\n        \"Whether ITIH1 engages other integrins or ECM receptors is unknown\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"ITIH1 was shown to suppress renal cell carcinoma via NF-κB pathway inhibition, broadening its tumor-suppressive mechanism beyond FAK to include restraint of NF-κB-dependent proliferation and invasion.\",\n      \"evidence\": \"ITIH1 knockdown/overexpression in RCC cell lines with Western blot for NF-κB pathway components and pharmacological rescue with JSH-23\",\n      \"pmids\": [\"39091412\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single-lab study without in vivo validation\",\n        \"Whether NF-κB suppression is mediated through integrin α5β1/FAK or an independent mechanism is unclear\",\n        \"No direct physical interaction between ITIH1 and NF-κB pathway components was demonstrated\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The relationship between ITIH1's ECM-stabilizing hyaluronan-binding function and its integrin-mediated signaling remains unintegrated; whether these represent independent or coupled tumor-suppressive mechanisms is unknown.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No study has simultaneously assessed hyaluronan binding and integrin signaling\",\n        \"In vivo phenotype of complete ITIH1 loss (knockout animal model) has not been reported\",\n        \"Structural characterization of ITIH1 is lacking\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0031012\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 2, 3]},\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 2, 3]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"ITGA5\",\n      \"ITGB1\",\n      \"METTL3\",\n      \"KDM5C\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"ITIH1 encodes heavy chain H1 of the inter-alpha-trypsin inhibitor (ITI) complex, a liver-expressed secreted glycoprotein that is assembled with heavy chain H2 and bikunin via a chondroitin sulfate cross-link and functions primarily in extracellular matrix organization through covalent transfer to hyaluronan [PMID:2476436, PMID:7592891]. The C-terminal Asp of ITIH1 is esterified to an internal N-acetylglucosamine of hyaluronan chains, a transfer catalyzed by TSG-6, which also liberates free bikunin as an active serine protease inhibitor; pentraxin 3 (PTX3) binds the ITI heavy chains to cooperatively organize hyaluronan matrices essential for processes such as cumulus oophorus expansion [PMID:7592891, PMID:16873769, PMID:17675295]. As a secreted protein, ITIH1 also acts as an integrin α5β1 ligand that competes with fibronectin to suppress FAK signaling, and its expression is negatively regulated both epigenetically by KDM5C-mediated H3K4me1 demethylation and post-transcriptionally by TGF-β-driven METTL3 m6A modification, with loss of ITIH1 activating NF-κB and PI3K/AKT pathways to promote hepatocellular and renal cell carcinoma progression [PMID:39234824, PMID:35080113, PMID:39091412].\",\n  \"teleology\": [\n    {\n      \"year\": 1987,\n      \"claim\": \"Resolving the long-standing question of whether ITI is a single polypeptide or a multi-component complex, cDNA cloning demonstrated that ITIH1 is a distinct heavy chain encoded by its own mRNA and expressed exclusively in liver, establishing the multi-gene architecture of the ITI system.\",\n      \"evidence\": \"cDNA cloning, RNA blot, cell-free translation, partial amino acid sequencing from two independent groups\",\n      \"pmids\": [\"2446322\", \"3663330\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No functional assay for isolated H1 chain\", \"Post-translational assembly mechanism unknown\"]\n    },\n    {\n      \"year\": 1989,\n      \"claim\": \"The molecular basis of ITI assembly was established: H1 and H2 are joined to bikunin not by peptide bonds but via a glycosaminoglycan (chondroitin sulfate) cross-link, explaining the unusual multi-chain architecture and sensitivity to hyaluronidase/chemical deglycosylation.\",\n      \"evidence\": \"SDS-PAGE, trifluoromethanesulfonic acid treatment, hyaluronidase digestion of purified plasma ITI\",\n      \"pmids\": [\"2476436\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise chemical nature of the glycan–protein bond not yet resolved\", \"Assembly pathway in hepatocytes unknown\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"The extracellular function of ITIH1 was reframed when its gene product was identified as the serum-derived hyaluronan-associated protein (SHAP), demonstrating that HC1 is covalently transferred from ITI to hyaluronan chains, with the HA-binding determinant mapped to the C-terminal half of the protein.\",\n      \"evidence\": \"Protein sequencing of HA-lyase-released peptides, Western blot with anti-ITI antibodies, in vitro incubation of serum with exogenous HA\",\n      \"pmids\": [\"7504674\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Enzyme or catalyst mediating the transfer not identified\", \"Structural basis of C-terminal HA binding unresolved\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"The atomic-level linkage chemistry was defined: the C-terminal Asp of HC1/ITIH1 forms an ester bond to the C6-hydroxyl of an internal GlcNAc residue in the hyaluronan chain, providing the precise covalent mechanism for HA cross-linking.\",\n      \"evidence\": \"ESI-MS/MS and CID-MS/MS of thermolysin-digested SHAP·HA complex from human synovial fluid\",\n      \"pmids\": [\"7592891\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Transferase catalyzing the ester bond formation not yet identified\", \"Reversibility and turnover of the linkage unknown\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"TSG-6 was identified as the catalyst that forms covalent intermediates with ITI heavy chains including HC1, driving their transfer to HA and simultaneously releasing free bikunin as an active serine protease inhibitor, connecting ITIH1 metabolism to airway antiprotease defense.\",\n      \"evidence\": \"Immunoprecipitation from bronchoalveolar lavage fluid, in vitro reconstitution with purified TSG-6/ITI, primary human airway epithelial cells with TNF-α/IL-1β stimulation\",\n      \"pmids\": [\"16873769\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Catalytic mechanism of TSG-6 in transesterification not structurally resolved\", \"Whether TSG-6 is the sole catalyst in all tissues unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"PTX3 was shown to directly bind ITI heavy chains (including HC1) through its N-terminal domain, and this interaction is required for organizing hyaluronan matrices in the cumulus oophorus, as demonstrated by rescue of the Ptx3-knockout matrix-assembly defect and blockade by an anti-PTX3 antibody.\",\n      \"evidence\": \"Co-IP from cumulus matrix, solid-phase binding with purified proteins, PTX3 domain mapping, Ptx3−/− cumulus culture rescue, blocking antibody\",\n      \"pmids\": [\"17675295\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of the PTX3–HC1 complex on HA not determined\", \"Whether PTX3 interaction is required for HA stabilization beyond cumulus matrix unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Epigenetic regulation of ITIH1 was established: KDM5C silences ITIH1 transcription by demethylating H3K4me1 at its promoter in HCC cells, and double-knockdown epistasis showed that ITIH1 loss downstream of KDM5C reactivates PI3K/AKT signaling and restores malignant behavior.\",\n      \"evidence\": \"siRNA KD of KDM5C, ChIP for H3K4me1 at ITIH1 promoter, KDM5C/ITIH1 double KD epistasis, xenograft tumor model\",\n      \"pmids\": [\"35080113\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether KDM5C is recruited to ITIH1 promoter by a specific transcription factor is unknown\", \"Single-lab finding; independent replication needed\", \"Direct protein-level readout of ITIH1 secretion after KDM5C manipulation not shown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"ITIH1 was shown to function as a secreted integrin α5β1 ligand that competes with fibronectin to suppress FAK signaling in HCC, while TGF-β promotes METTL3 phase separation to m6A-modify ITIH1 mRNA and reduce its stability, providing a unified post-transcriptional and signaling mechanism for ITIH1 tumor suppression.\",\n      \"evidence\": \"Co-IP/binding assays for ITIH1–integrin α5β1, fibronectin competition, FAK phosphorylation, m6A-seq/MeRIP, METTL3 phase-separation imaging, in vivo HCC model, patient-derived organoids and xenografts, recombinant ITIH1 treatment\",\n      \"pmids\": [\"39234824\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of ITIH1–integrin α5β1 binding versus the established HA-ester function not reconciled\", \"Whether integrin antagonism is independent of HA binding unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"ITIH1 was independently shown to suppress RCC progression via negative regulation of NF-κB signaling, with pharmacological rescue by the NF-κB inhibitor JSH-23 confirming pathway epistasis.\",\n      \"evidence\": \"siRNA KD and overexpression in RCC cell lines, Western blot for NF-κB pathway, proliferation/invasion assays, JSH-23 pharmacological rescue\",\n      \"pmids\": [\"39091412\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which a secreted protein inhibits intracellular NF-κB not defined\", \"No in vivo model provided\", \"Relationship between NF-κB suppression and integrin/FAK pathway unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis for ITIH1's dual roles in HA cross-linking and integrin antagonism, how secreted ITIH1 accesses intracellular NF-κB signaling, and whether the tumor-suppressive function operates through the same C-terminal domain responsible for HA esterification.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of ITIH1 or ITIH1–HA complex\", \"No genetic loss-of-function animal model for ITIH1\", \"Relationship between HA stabilization and tumor-suppressive signaling unexplored\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [8, 12, 13]},\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [4, 6, 12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 4, 6, 12]},\n      {\"term_id\": \"GO:0031012\", \"supporting_discovery_ids\": [4, 6, 9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [4, 6, 9]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [12, 13]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [11, 12, 13]}\n    ],\n    \"complexes\": [\n      \"Inter-alpha-trypsin inhibitor (ITI; H1-H2-bikunin)\",\n      \"SHAP·HA complex\"\n    ],\n    \"partners\": [\n      \"ITIH2\",\n      \"AMBP\",\n      \"TNFAIP6\",\n      \"PTX3\",\n      \"ITGA5\",\n      \"ITGB1\",\n      \"METTL3\",\n      \"KDM5C\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}