{"gene":"MDK","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":1993,"finding":"MDK gene maps to chromosome 11p11.2 by fluorescence in situ hybridization, establishing its chromosomal location.","method":"Fluorescence in situ hybridization (FISH)","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct cytogenetic mapping, single lab, single method","pmids":["8406506"],"is_preprint":false},{"year":1995,"finding":"Human MDK was mapped to chromosome 11p13→p11, and mouse Mdk was mapped to a syntenic region of mouse chromosome 2; a pseudogene of Mdk was mapped to mouse chromosome 11.","method":"Somatic cell hybrid analysis and interspecific backcross analysis","journal":"Cytogenetics and cell genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two complementary mapping methods, single lab","pmids":["7835084"],"is_preprint":false},{"year":1998,"finding":"Mdk knockout mice show altered calretinin expression in hippocampal dentate gyrus granule cell layer and deficits in working memory and increased anxiety, establishing MDK's role in postnatal hippocampal development.","method":"Gene knockout mouse model, immunohistochemistry, Y-maze and elevated plus-maze behavioral tests","journal":"Genes to cells","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cellular and behavioral phenotypes, multiple orthogonal readouts","pmids":["10096022"],"is_preprint":false},{"year":2006,"finding":"MDK overexpression in HeLa cells confers resistance to 5-FU, doxorubicin, and cisplatin; siRNA-mediated MDK knockdown in SNU-638 gastric cancer cells decreases IC50 for all three drugs by 18–44%, establishing MDK as a modulator of multi-drug resistance.","method":"Stable transfection (overexpression), siRNA knockdown, drug cytotoxicity assays (IC50 measurement)","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal gain- and loss-of-function, single lab, two orthogonal approaches","pmids":["16644108"],"is_preprint":false},{"year":2009,"finding":"MDK-deficient (Mdk−/−) mice show delayed Wallerian degeneration and delayed axonal regeneration after sciatic nerve freeze injury, with impaired recovery of motor function, establishing MDK as a required factor for peripheral nerve degeneration and regeneration.","method":"Mdk knockout mouse model, histomorphometry, electromyography, muscle wet weight analysis","journal":"Journal of neuroscience research","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO, multiple orthogonal readouts (histology, EMG, functional recovery)","pmids":["19437545"],"is_preprint":false},{"year":2013,"finding":"A small molecule inhibitor iMDK suppresses endogenous MDK expression, inhibits PI3K pathway activation, and induces apoptosis in MDK-positive lung cancer cells, but not in MDK-negative cells; systemic iMDK inhibits tumor growth in xenograft models, establishing MDK's role in activating the PI3K survival pathway in lung cancer.","method":"Small molecule inhibition (iMDK), cell viability assays, PI3K pathway western blotting, xenograft mouse model, specificity controls with MDK-negative cells","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vitro mechanistic dissection plus in vivo validation with specificity controls","pmids":["23976985"],"is_preprint":false},{"year":2014,"finding":"SP1 binds to the promoter of the MDK gene (confirmed by chromatin immunoprecipitation) and directly transcriptionally upregulates MDK expression; overexpression of MDK in SP1-silenced glioma cells partially rescues SP1 inhibition effects on proliferation in vitro and tumor growth in vivo.","method":"Chromatin immunoprecipitation (ChIP), gene silencing (siRNA), MDK overexpression rescue assays, xenograft mouse model","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — ChIP establishes direct promoter binding, rescue experiment confirms epistasis, single lab with multiple orthogonal methods","pmids":["25428991"],"is_preprint":false},{"year":2014,"finding":"MDK promotes cell migration and proliferation in lacrimal gland cells; recombinant MDK was found in iPSC-conditioned medium and suppresses the p38/JNK pathway and Akt phosphorylation in irradiated lacrimal gland tissue, establishing a role for MDK in radiation injury repair.","method":"iPSC-conditioned medium treatment, western blotting for p38/JNK and Akt phosphorylation, cell migration and proliferation assays, in vivo murine model","journal":"International journal of molecular sciences","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, mechanistic pathway conclusions drawn from conditioned medium not pure recombinant MDK in isolation","pmids":["25314301"],"is_preprint":false},{"year":2018,"finding":"Exosomal miR-9 secreted by NPC cells directly suppresses MDK expression in endothelial cells (confirmed by luciferase reporter assay targeting MDK 3'UTR), and MDK knockdown inhibits endothelial tube formation and migration via PDK/AKT signaling, establishing MDK as a downstream mediator of PI3K/AKT-driven angiogenesis in endothelial cells.","method":"Luciferase 3'UTR reporter assay, western blotting, tube formation assay, migration assay, matrigel plug assay, Phosphorylation Array","journal":"Journal of experimental & clinical cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct target validation by reporter assay plus functional consequence, single lab","pmids":["30001734"],"is_preprint":false},{"year":2019,"finding":"p53 (a key DDR transcription factor) mediates overexpression of MDK, and MDK promotes M2 polarization of microglia to remodel the glioblastoma immunosuppressive microenvironment, establishing MDK as a downstream effector of p53/DDR signaling in shaping the tumor microenvironment.","method":"In vitro and in vivo experiments, western blotting, functional M2 polarization assays, transcriptomic analysis","journal":"EBioMedicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional validation in vivo and in vitro, single lab","pmids":["30773478"],"is_preprint":false},{"year":2020,"finding":"miR-326 targets and inhibits MDK expression, thereby negatively regulating JAK/STAT and MAPK signaling pathways; rescue assays confirmed that MDK re-expression reverses miR-326-mediated attenuation of cardiac hypertrophy in Ang II-treated H9c2 cells and TAC mice.","method":"Luciferase reporter assay (implied target validation), miR-326 overexpression, MDK rescue assays, western blotting for JAK/STAT and MAPK pathways, in vivo TAC model","journal":"European journal of pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct target validation with pathway placement and rescue experiment, single lab","pmids":["31972179"],"is_preprint":false},{"year":2021,"finding":"MDK secreted from ErbB pathway-mutated gallbladder cancer epithelial cells interacts with its receptor LRP1 expressed on tumor-infiltrating macrophages to promote immunosuppressive M2 macrophage differentiation.","method":"Single-cell RNA sequencing, bulk RNA-seq, immunohistochemistry, immunofluorescence, functional experiments (macrophage polarization assays)","journal":"Journal of hepatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional experiments validate scRNA-seq interaction inference, single lab","pmids":["34171432"],"is_preprint":false},{"year":2022,"finding":"IFN-γ upregulates MDK via STAT1 signaling in cancer cell lines; MDK drives EMT activation and cancer metastasis; pharmacological MDK inhibition (iMDK) reverses IFN-γ-activated EMT and abrogates IFN-γ-triggered metastasis across multiple cancer types.","method":"Cell line knockdown/overexpression, western blotting, migration/invasion assays, iMDK inhibitor treatment","journal":"Frontiers in oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — STAT1-MDK pathway established by multiple cancer lines with inhibitor validation, single lab","pmids":["35747815"],"is_preprint":false},{"year":2022,"finding":"MDK enhances glioblastoma stem-like properties by activating Notch1/p-JNK signaling, leading to increased CD133 and Nanog expression, thereby promoting temozolomide resistance; MDK knockdown inhibits tumor growth in xenograft models.","method":"MDK overexpression/knockdown, western blotting for Notch1/p-JNK/CD133/Nanog, xenograft mouse model, in vitro stem cell assays","journal":"American journal of cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pathway placement by western blotting with in vivo validation, single lab","pmids":["36381313"],"is_preprint":false},{"year":2022,"finding":"MDK is a downstream target of IFN-γ/STAT1 in ovarian cancer cells; MDK overexpression promotes proliferation and EMT/metastasis; MDK inhibition (iMDK) reverses IFN-γ-driven EMT and synergistically enhances IFN-γ growth inhibition (combination index <0.1).","method":"Gain-of-function MDK overexpression, iMDK inhibitor, combination index analysis, EMT western blotting, migration/invasion assays","journal":"Biomedicines","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic pathway placement with quantitative drug interaction analysis, single lab","pmids":["36672515"],"is_preprint":false},{"year":2023,"finding":"miR-1275 directly targets MDK as a downstream protein, and MDK initiates PI3K/Akt signaling in breast cancer cells; CRISPR/Cas9 knockout of miR-1275 promotes chemoresistance by increasing cancer stem cell properties via the MDK/AKT axis.","method":"CRISPR/Cas9 gene editing, RT-qPCR, western blotting for PI3K/Akt, cancer stem cell assays","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR-based KO with defined pathway, single lab","pmids":["36594100"],"is_preprint":false},{"year":2024,"finding":"MDK interacts with Syndecan-1 (SDC1) receptor and activates PI3K/AKT and p38 MAPK pathways to promote proliferation, migration, invasion, lymphangiogenesis, and lymph node metastasis of cervical squamous cell carcinoma.","method":"MDK overexpression/knockdown, co-immunoprecipitation (implied interaction with SDC1), western blotting for PI3K/AKT and p38, invasion/migration assays, in vivo lymphangiogenesis assays","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — receptor interaction and pathway activation shown functionally, single lab","pmids":["39040052"],"is_preprint":false},{"year":2024,"finding":"MDK promotes M2 macrophage polarization via MDK-LRP1 interaction; MDK inhibition suppresses M2 polarization in clear cell renal cell carcinoma.","method":"Multiomics analysis, functional M2 polarization assays, MDK inhibition experiments","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional validation of MDK-LRP1 mediated polarization with inhibitor, single lab","pmids":["39107475"],"is_preprint":false},{"year":2024,"finding":"GPC2 promotes prostate cancer cell proliferation, migration, and invasion via MDK-mediated activation of the PI3K/AKT signaling pathway; MDK overexpression rescues the inhibitory effects of GPC2 knockdown on PI3K/AKT signaling and cell behavior.","method":"siRNA knockdown, MDK overexpression rescue assay, western blotting for PI3K/AKT, proliferation/migration/invasion assays","journal":"Functional & integrative genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis established by rescue assay, single lab","pmids":["39014225"],"is_preprint":false},{"year":2024,"finding":"CDK7 promotes MDK expression in irinotecan-resistant colorectal cancer cells; suppression of CDK7 by siRNA or the inhibitor THZ1 significantly reduces MDK expression and re-sensitizes resistant cells to irinotecan, placing MDK downstream of CDK7 in a drug resistance pathway.","method":"Bulk RNA sequencing, siRNA knockdown, CDK7 inhibitor (THZ1), in vivo xenograft experiments, patient tissue analysis","journal":"Life sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNA-seq plus functional genetic and pharmacological validation with in vivo confirmation, single lab","pmids":["39004275"],"is_preprint":false},{"year":2024,"finding":"Syndecan-4 (SDC4) is identified as a receptor for MDK associated with regulatory T cell (Treg) colocalisation in colorectal cancer; MDK-high CRC cells interact with SPP1+ macrophages and stromal cells to establish immunosuppression in the tumor microenvironment.","method":"Spatial transcriptomics, single-cell transcriptome, deep generative model colocalisation analysis, clinical CRC dataset analysis","journal":"EBioMedicine","confidence":"Low","confidence_rationale":"Tier 3 / Weak — receptor identification based on computational/transcriptomic inference without direct biochemical binding validation","pmids":["38614865"],"is_preprint":false},{"year":2024,"finding":"Angelica sinensis polysaccharide (ASP) upregulates MDK expression in adipose-derived stem cells; MDK knockdown abolishes ASP-induced elevation of chondrogenic differentiation markers and PI3K/AKT pathway activity, placing MDK upstream of PI3K/AKT in ASP-induced chondrogenesis.","method":"Transcriptome sequencing, siRNA knockdown, western blotting for PI3K/AKT, chondrogenic differentiation assays (Alcian blue, qRT-PCR)","journal":"Biomedicine & pharmacotherapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pathway placement via genetic knockdown with multiple orthogonal readouts, single lab","pmids":["39191028"],"is_preprint":false},{"year":2024,"finding":"MDK inhibition (iMDK) suppresses the proliferation, migration, and EMT of glioblastoma cells induced by hypoxia; in vivo, hypoxia promotes MDK expression and MDK knockdown reduces these hypoxia-driven malignant behaviors.","method":"MDK knockdown, iMDK inhibitor, CCK8, EdU proliferation assay, wound healing, transwell assay, western blotting for EMT markers","journal":"Biomedicines","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic and pharmacological inhibition with multiple functional readouts, single lab","pmids":["38255198"],"is_preprint":false},{"year":2025,"finding":"EGFRvIII-positive GBM secretes high levels of MDK via the ERK-c-Fos signaling pathway; secreted MDK drives M2 macrophage polarization and CXCL1 secretion via LRP1 receptor on macrophages; blocking MDK signaling in an intracranial glioma model inhibits M2 macrophage polarization and tumor progression.","method":"Western blotting, functional macrophage polarization assays, intracranial glioma mouse model, MDK pathway blockade","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic pathway (ERK-c-Fos-MDK-LRP1) validated in vitro and in vivo, single lab","pmids":["40527884"],"is_preprint":false},{"year":2025,"finding":"MDK interacts directly with c-Myc (demonstrated by microthermometry and co-immunoprecipitation); MDK interaction with c-Myc influences c-Myc ubiquitination and stabilizes it, activating Wnt/β-catenin signaling and EMT, contributing to temozolomide resistance; small molecule ACT001 disrupts the MDK/c-Myc complex, promotes c-Myc degradation, and sensitizes resistant glioma cells to TMZ.","method":"Microthermometry, co-immunoprecipitation, proteomics, western blotting, xenograft and in situ glioma models","journal":"Clinical and translational medicine","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct protein-protein interaction shown by two orthogonal biophysical/biochemical methods plus functional consequence via proteasomal degradation","pmids":["40468625"],"is_preprint":false},{"year":2025,"finding":"Wnt/β-catenin signaling drives MDK upregulation in hepatoblastoma cells; MDK modifies macrophage phenotype toward immunosuppression; MDK inhibition partially reverses macrophage phenotype change, establishing MDK as a Wnt-responsive immunomodulator.","method":"Western blotting, RNA-seq of hepatoblastoma and macrophage cell lines, MDK inhibition experiments, single-cell and spatial transcriptomics","journal":"Journal of hepatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — experimental validation by western blotting and RNA-seq with MDK inhibition, single lab","pmids":["39900120"],"is_preprint":false},{"year":2025,"finding":"MDK binds the SDC4 receptor on beta cells to downregulate Ras signaling, impairing insulin production and secretion, establishing a mechanism for pancreatic cancer-associated new-onset diabetes.","method":"Single-cell RNA sequencing, receptor-ligand interaction analysis, functional beta cell assays (insulin production/secretion)","journal":"Advanced science","confidence":"Low","confidence_rationale":"Tier 3 / Weak — receptor-ligand interaction and downstream pathway inferred from scRNA-seq with some functional validation, single lab","pmids":["40709672"],"is_preprint":false},{"year":2025,"finding":"Remote neuromuscular electrical stimulation (rNMES) upregulates MDK expression in skeletal muscle via the AMPK-ERK axis; circulating MDK reaches wounds and promotes macrophage efferocytosis in a LRP1-dependent manner, accelerating wound healing.","method":"GEO database analysis, in vivo rNMES model, MDK-LRP1 functional assays, macrophage efferocytosis assay","journal":"Journal of biomedical research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct LRP1-dependent mechanistic link established with efferocytosis assay, single lab","pmids":["40441854"],"is_preprint":false},{"year":2025,"finding":"MDK facilitates M2-like macrophage polarization via interaction with LRP1 receptor on macrophages in MASH-HCC; silencing LRP1 in macrophages abolishes MDK-driven M2 polarization and increases cytotoxic cytokine secretion; LRP1-positive macrophages contribute to T cell exhaustion via CXCL16-CXCR6 axis; combining Resmetirom with iMDK synergistically suppresses tumorigenesis in vivo.","method":"scRNA-seq, LRP1 silencing in macrophages, cytokine measurement, in vivo combination therapy model","journal":"Hepatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — LRP1 dependence established by silencing with functional readouts, in vivo validation, single lab","pmids":["41525571"],"is_preprint":false},{"year":2025,"finding":"MDK promotes M2 macrophage polarization and mast cell activation via interaction with the nucleolin (NCL) receptor; MDK knockdown in pancreatic stellate cells reduces PSC activation/fibrosis and suppresses mast cell proliferation and degranulation in chronic pancreatitis; these effects are reversed by recombinant MDK and blocked by NCL neutralization.","method":"scRNA-seq analysis, MDK knockdown in PSCs, co-culture experiments, recombinant MDK rescue, NCL neutralization, in vivo MDK/NCL knockdown, flow cytometry","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — NCL identified as receptor by neutralization experiments, functional rescue confirms MDK-NCL axis, single lab","pmids":["42031197"],"is_preprint":false},{"year":2025,"finding":"Recombinant MDK protein dose-dependently inhibits osteogenic differentiation via the PI3K/AKT signaling pathway and increases expression of inflammatory cytokines (IL-6, TNF-α, IL-1β) via NF-κB signaling; iMDK inhibitor mitigates estrogen deficiency-induced bone loss in ovariectomized mice.","method":"Recombinant MDK protein treatment, transcriptome analysis, western blotting for PI3K/AKT and NF-κB, in vitro osteogenic differentiation assays, ovariectomy mouse model","journal":"Genes & diseases","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — recombinant protein dose-response with transcriptomic and western blot pathway validation plus in vivo model, single lab","pmids":["41674663"],"is_preprint":false},{"year":2025,"finding":"MDK activates the PI3K/AKT pathway in colorectal cancer cells, leading to upregulated AP2A1 expression and promotion of EMT; PI3K inhibitor LY294002 reduces AP2A1 levels and reverses MDK-induced malignant behaviors.","method":"MDK overexpression/knockdown, western blotting for PI3K/AKT/AP2A1/EMT markers, PI3K inhibitor (LY294002), invasion/migration/proliferation assays, xenograft and metastasis mouse models","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis between MDK, PI3K/AKT, and AP2A1 confirmed by inhibitor and genetic approaches with in vivo validation, single lab","pmids":["42073635"],"is_preprint":false},{"year":2025,"finding":"MDK treadmill training upregulates MDK expression and promotes neuronal MDK localization (confirmed by NeuN co-staining); MDK signals through LRP1 receptor to activate PI3K/Akt and upregulate BDNF in neurons; LRP1 siRNA blocks exercise-induced Akt activation, BDNF upregulation, and motor recovery after spinal cord injury.","method":"LRP1 siRNA knockdown in vivo, immunofluorescence co-staining, western blotting for PI3K/Akt/BDNF, in vitro MDK treatment with LRP1 inhibitor (RAP), behavioral analysis (BBB score, gait analysis)","journal":"Neurochemical research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — LRP1-dependent MDK signaling validated by both siRNA and pharmacological blockade with multiple functional readouts, single lab","pmids":["42257999"],"is_preprint":false},{"year":2025,"finding":"MDK attenuates Aβ40 and Aβ42 fibril formation in vitro as demonstrated by Thioflavin T fluorescence assay, circular dichroism, negative stain electron microscopy, and NMR; Mdk knockout in 5xFAD mice increases amyloid plaque formation and microglial activation, establishing MDK as a protective factor counteracting amyloid pathology.","method":"Thioflavin T fluorescence assay, circular dichroism, negative stain electron microscopy, NMR, Mdk/5xFAD double-knockout mouse model, mass spectrometry-based proteomics","journal":"bioRxiv (preprint)","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal in vitro biophysical methods plus genetic mouse model validation, comprehensive proteomics","pmids":["bio_10.1101_2025.03.20.644383"],"is_preprint":true},{"year":2025,"finding":"MDK disrupts melanoma disseminated cancer cell dormancy through an autocrine signal that suppresses the dormancy inducer NR2F1 and alters the p-p38/p-ERK ratio via ALK signaling; dual targeting of MDK (genetic blockade) and NR2F1 (activation) markedly limits metastatic outgrowth and extends survival in mouse models.","method":"MDK genetic blockade, NR2F1 agonist treatment, p-p38/p-ERK ratio analysis, dormancy assays in lymph nodes and visceral tissues, in vivo mouse survival experiments","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic and pharmacological epistasis with functional dormancy and survival readouts, single lab, preprint","pmids":["bio_10.1101_2025.05.27.656365"],"is_preprint":true}],"current_model":"MDK (Midkine) is a secreted heparin-binding growth factor that activates multiple receptors (LRP1, ALK, nucleolin/NCL, syndecan-1/SDC1, syndecan-4/SDC4) to promote cell survival, proliferation, EMT, and drug resistance primarily through PI3K/AKT, MAPK, JAK/STAT, NF-κB, and Notch/JNK signaling cascades; it is transcriptionally regulated by SP1 and STAT1 (downstream of IFN-γ) and by Wnt/β-catenin and p53/DDR pathways, and its extracellular interactions drive macrophage M2 polarization (via LRP1), mast cell activation (via NCL), Treg accumulation, and immune evasion in the tumor microenvironment, while also serving protective roles in peripheral nerve regeneration, hippocampal postnatal development, and amyloid plaque suppression in Alzheimer's disease models."},"narrative":{"mechanistic_narrative":"MDK (Midkine) is a secreted growth factor that signals through cell-surface receptors to activate pro-survival and pro-proliferative cascades, functioning as a context-dependent factor in tissue regeneration, neuronal development, and tumor progression [PMID:23976985, PMID:39040052]. Its dominant downstream output is the PI3K/AKT survival axis: PI3K activation underlies MDK-driven cell survival in lung cancer [PMID:23976985], endothelial angiogenesis [PMID:30001734], cervical carcinoma proliferation and lymphangiogenesis [PMID:39040052], and colorectal EMT via AP2A1 [PMID:42073635], with additional engagement of MAPK/p38, JAK/STAT, Notch1/p-JNK, and NF-κB outputs in different contexts [PMID:31972179, PMID:36381313, PMID:39040052, PMID:41674663]. MDK exerts these effects through several receptors—LRP1, syndecan-1 (SDC1), syndecan-4 (SDC4), nucleolin (NCL), and ALK—engaged in distinct settings [PMID:34171432, PMID:39040052, PMID:38614865, PMID:42031197, PMID:bio_10.1101_2025.05.27.656365]. A recurrent role is reprogramming the tumor microenvironment: MDK secreted by tumor cells engages LRP1 on macrophages to drive immunosuppressive M2 polarization across gallbladder, renal, glioma, and liver cancers [PMID:34171432, PMID:39107475, PMID:40527884, PMID:41525571], and engages NCL to promote mast cell activation [PMID:42031197]. Beyond ligand–receptor signaling, MDK binds c-Myc directly and stabilizes it against ubiquitination to activate Wnt/β-catenin signaling and confer temozolomide resistance in glioma [PMID:40468625]. MDK expression is induced by SP1 [PMID:25428991], IFN-γ/STAT1 [PMID:35747815, PMID:36672515], p53/DDR [PMID:30773478], Wnt/β-catenin [PMID:39900120], and CDK7 [PMID:39004275], and repressed by microRNAs including miR-9, miR-326, miR-1275, and miR-1275 [PMID:30001734, PMID:31972179, PMID:36594100]. In non-malignant tissue, MDK is required for postnatal hippocampal development [PMID:10096022] and peripheral nerve degeneration/regeneration [PMID:19437545], drives LRP1-dependent neurotrophic signaling and BDNF upregulation after spinal cord injury [PMID:42257999], and attenuates Aβ fibril formation, protecting against amyloid pathology [PMID:bio_10.1101_2025.03.20.644383].","teleology":[{"year":1993,"claim":"Establishing the chromosomal location of MDK provided the genomic anchor needed for subsequent functional and comparative studies.","evidence":"FISH mapping to chromosome 11p11.2, refined by somatic cell hybrid and interspecific backcross analysis to mouse synteny","pmids":["8406506","7835084"],"confidence":"Medium","gaps":["Mapping alone gives no functional or mechanistic information","Does not address regulation or protein activity"]},{"year":1998,"claim":"Loss-of-function in mice answered whether MDK has a physiological developmental role, revealing it is required for postnatal hippocampal development and normal behavior.","evidence":"Mdk knockout mouse with immunohistochemistry and behavioral testing (Y-maze, elevated plus-maze)","pmids":["10096022"],"confidence":"High","gaps":["Receptor and signaling pathway mediating the hippocampal phenotype not identified","Cell-autonomous versus secreted action not resolved"]},{"year":2009,"claim":"A second knockout phenotype established MDK as a required factor for peripheral nerve degeneration and regeneration, extending its physiological role beyond development.","evidence":"Mdk knockout mice subjected to sciatic nerve injury with histomorphometry, EMG, and functional recovery readouts","pmids":["19437545"],"confidence":"High","gaps":["Molecular mediators of the regeneration defect not defined","Receptor involvement not tested"]},{"year":2006,"claim":"Reciprocal gain- and loss-of-function tied MDK to drug resistance, a phenotype later recurring across many cancers.","evidence":"Overexpression and siRNA knockdown with IC50 drug cytotoxicity assays in cancer cell lines","pmids":["16644108"],"confidence":"Medium","gaps":["Mechanism linking MDK to multidrug resistance not defined at this stage","No receptor or signaling pathway identified"]},{"year":2013,"claim":"Small-molecule inhibition with specificity controls established the PI3K survival pathway as a core mediator of MDK's pro-tumor function.","evidence":"iMDK inhibitor with PI3K western blotting, viability assays, and xenografts using MDK-negative controls","pmids":["23976985"],"confidence":"High","gaps":["Receptor coupling MDK to PI3K not identified","iMDK acts by suppressing MDK expression rather than blocking ligand binding"]},{"year":2014,"claim":"ChIP-based identification of SP1 as a direct transcriptional activator, with rescue, began defining the regulatory inputs controlling MDK levels.","evidence":"ChIP, siRNA silencing, MDK overexpression rescue, and xenografts in glioma","pmids":["25428991"],"confidence":"High","gaps":["Other transcriptional regulators not addressed here","Downstream MDK signaling in glioma not dissected"]},{"year":2018,"claim":"MicroRNA targeting and reporter validation showed MDK is post-transcriptionally repressed and functions in endothelial angiogenesis via PI3K/AKT.","evidence":"Luciferase 3'UTR reporter (miR-9), tube formation, migration, matrigel plug, and phosphorylation array assays","pmids":["30001734"],"confidence":"Medium","gaps":["Endothelial receptor for MDK not identified","Direct versus paracrine angiogenic action not separated"]},{"year":2019,"claim":"Linking MDK to p53/DDR and showing it drives microglial M2 polarization introduced its role in shaping the immunosuppressive tumor microenvironment.","evidence":"In vitro/in vivo M2 polarization assays, western blotting, and transcriptomics in glioblastoma","pmids":["30773478"],"confidence":"Medium","gaps":["Receptor on microglia not identified in this study","Mechanism of p53-mediated MDK induction not detailed"]},{"year":2021,"claim":"Identification of LRP1 as the macrophage receptor mediating MDK-driven M2 polarization assigned a molecular basis to MDK's immunomodulatory role.","evidence":"scRNA-seq, bulk RNA-seq, immunostaining, and macrophage polarization functional assays in gallbladder cancer","pmids":["34171432"],"confidence":"Medium","gaps":["Direct biochemical MDK-LRP1 binding affinity not measured","Downstream macrophage signaling from LRP1 not fully mapped"]},{"year":2022,"claim":"Multiple studies placed MDK downstream of IFN-γ/STAT1 and Notch1/p-JNK, establishing it as a driver of EMT, metastasis, stemness, and therapy resistance across cancer types.","evidence":"Knockdown/overexpression, iMDK inhibition, EMT/stem-cell markers, combination index analysis, and xenografts in lung, ovarian, and glioblastoma models","pmids":["35747815","36672515","36381313","31972179"],"confidence":"Medium","gaps":["Receptor coupling IFN-γ-induced MDK to EMT not defined","Convergence of multiple pathways onto common effectors unresolved"]},{"year":2024,"claim":"A series of studies expanded MDK's receptor repertoire (SDC1, SDC4, LRP1) and upstream regulators (GPC2, CDK7), consolidating PI3K/AKT as the convergent output across tumor and regenerative contexts.","evidence":"Co-IP (SDC1), rescue assays (GPC2), CDK7 inhibition (THZ1), spatial/single-cell transcriptomics (SDC4-Treg), and macrophage polarization assays across cervical, prostate, colorectal, and renal cancers","pmids":["39040052","39014225","39004275","38614865","39107475","38255198"],"confidence":"Medium","gaps":["Receptor selection in different tissues not mechanistically explained","Some receptor assignments rely on transcriptomic inference without binding validation"]},{"year":2025,"claim":"Direct demonstration that MDK binds and stabilizes c-Myc revealed an intracellular, receptor-independent mechanism activating Wnt/β-catenin and conferring temozolomide resistance.","evidence":"Microthermometry and co-IP for binding, proteomics, ubiquitination/degradation assays, ACT001 disruptor, and glioma models","pmids":["40468625"],"confidence":"High","gaps":["How secreted MDK accesses intracellular c-Myc not resolved","Structural basis of the MDK-c-Myc interaction not determined"]},{"year":2025,"claim":"Functional dissection in non-malignant and immune contexts established LRP1-, NCL-, SDC4-, and ALK-dependent MDK signaling in wound healing, neural repair, mast cell activation, beta-cell dysfunction, and dormancy escape.","evidence":"LRP1 silencing/efferocytosis assays, NCL neutralization, scRNA-seq receptor-ligand inference, ALK-mediated p38/ERK ratio analysis, and in vivo regeneration and metastasis models","pmids":["40441854","42031197","40709672","42257999","40527884","39900120","30001734","42073635","40468625"],"confidence":"Medium","gaps":["Receptor specificity determinants across tissues unresolved","Some receptor-ligand links rest on computational inference"]},{"year":2025,"claim":"Biophysical and genetic evidence established a protective role for MDK in suppressing amyloid pathology, contrasting its pro-tumor functions.","evidence":"Thioflavin T, circular dichroism, electron microscopy, NMR on Aβ fibrils, and Mdk/5xFAD double-knockout mice (preprint)","pmids":["bio_10.1101_2025.03.20.644383"],"confidence":"High","gaps":["Whether the anti-amyloid effect is receptor-dependent not determined","Preprint not yet peer-reviewed"]},{"year":null,"claim":"It remains unresolved what determines MDK's choice among its multiple receptors in a given tissue and how secreted MDK reaches intracellular targets such as c-Myc.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model of receptor selection across LRP1/SDC1/SDC4/NCL/ALK","Mechanism of intracellular access for secreted MDK unknown","Structural basis of receptor and c-Myc binding undetermined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[5,11,16,29]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[33]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[24]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[7,11,27,30]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[5,16,24]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[11,17,23,28,29]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[3,13,24]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2,4,21,32]}],"complexes":[],"partners":["LRP1","SDC1","SDC4","NCL","ALK","MYC","GPC2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P21741","full_name":"Midkine","aliases":["Amphiregulin-associated protein","ARAP","Midgestation and kidney protein","Neurite outgrowth-promoting factor 2","Neurite outgrowth-promoting protein"],"length_aa":143,"mass_kda":15.6,"function":"Secreted protein that functions as a cytokine and growth factor and mediates its signal through cell-surface proteoglycan and non-proteoglycan receptors (PubMed:10212223, PubMed:10772929, PubMed:12084985, PubMed:12122009, PubMed:12573468, PubMed:15466886, PubMed:18469519, PubMed:24458438). Binds cell-surface proteoglycan receptors via their chondroitin sulfate (CS) groups (PubMed:10212223, PubMed:12084985). Thereby regulates many processes like inflammatory response, cell proliferation, cell adhesion, cell growth, cell survival, tissue regeneration, cell differentiation and cell migration (PubMed:10212223, PubMed:10683378, PubMed:10772929, PubMed:12084985, PubMed:12122009, PubMed:12573468, PubMed:15466886, PubMed:22323540, PubMed:24458438). Participates in inflammatory processes by exerting two different activities. Firstly, mediates neutrophils and macrophages recruitment to the sites of inflammation both by direct action by cooperating namely with ITGB2 via LRP1 and by inducing chemokine expression (PubMed:10683378, PubMed:24458438). This inflammation can be accompanied by epithelial cell survival and smooth muscle cell migration after renal and vessel damage, respectively (PubMed:10683378). Secondly, suppresses the development of tolerogenic dendric cells thereby inhibiting the differentiation of regulatory T cells and also promote T cell expansion through NFAT signaling and Th1 cell differentiation (PubMed:22323540). Promotes tissue regeneration after injury or trauma. After heart damage negatively regulates the recruitment of inflammatory cells and mediates cell survival through activation of anti-apoptotic signaling pathways via MAPKs and AKT pathways through the activation of angiogenesis (By similarity). Also facilitates liver regeneration as well as bone repair by recruiting macrophage at trauma site and by promoting cartilage development by facilitating chondrocyte differentiation (By similarity). Plays a role in brain by promoting neural precursor cells survival and growth through interaction with heparan sulfate proteoglycans (By similarity). Binds PTPRZ1 and promotes neuronal migration and embryonic neurons survival (PubMed:10212223). Binds SDC3 or GPC2 and mediates neurite outgrowth and cell adhesion (PubMed:12084985, PubMed:1768439). Binds chondroitin sulfate E and heparin leading to inhibition of neuronal cell adhesion induced by binding with GPC2 (PubMed:12084985). Binds CSPG5 and promotes elongation of oligodendroglial precursor-like cells (By similarity). Also binds ITGA6:ITGB1 complex; this interaction mediates MDK-induced neurite outgrowth (PubMed:15466886, PubMed:1768439). Binds LRP1; promotes neuronal survival (PubMed:10772929). Binds ITGA4:ITGB1 complex; this interaction mediates MDK-induced osteoblast cells migration through PXN phosphorylation (PubMed:15466886). Binds anaplastic lymphoma kinase (ALK) which induces ALK activation and subsequent phosphorylation of the insulin receptor substrate (IRS1), followed by the activation of mitogen-activated protein kinase (MAPK) and PI3-kinase, and the induction of cell proliferation (PubMed:12122009). Promotes epithelial to mesenchymal transition through interaction with NOTCH2 (PubMed:18469519). During arteriogenesis, plays a role in vascular endothelial cell proliferation by inducing VEGFA expression and release which in turn induces nitric oxide synthase expression. Moreover activates vasodilation through nitric oxide synthase activation (By similarity). Negatively regulates bone formation in response to mechanical load by inhibiting Wnt/beta-catenin signaling in osteoblasts (By similarity). In addition plays a role in hippocampal development, working memory, auditory response, early fetal adrenal gland development and the female reproductive system (By similarity)","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/P21741/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MDK","classification":"Not Classified","n_dependent_lines":25,"n_total_lines":1208,"dependency_fraction":0.020695364238410598},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"NPM1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/MDK","total_profiled":1310},"omim":[{"mim_id":"618446","title":"GLYPICAN 2; GPC2","url":"https://www.omim.org/entry/618446"},{"mim_id":"603415","title":"SODIUM VOLTAGE-GATED CHANNEL, ALPHA SUBUNIT 9; SCN9A","url":"https://www.omim.org/entry/603415"},{"mim_id":"162096","title":"MIDKINE; MDK","url":"https://www.omim.org/entry/162096"},{"mim_id":"162095","title":"PLEIOTROPHIN; PTN","url":"https://www.omim.org/entry/162095"},{"mim_id":"156232","title":"MESOMELIC DYSPLASIA, KANTAPUTRA TYPE; MMDK","url":"https://www.omim.org/entry/156232"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"ovary","ntpm":571.9}],"url":"https://www.proteinatlas.org/search/MDK"},"hgnc":{"alias_symbol":["MK","FLJ27379"],"prev_symbol":["NEGF2"]},"alphafold":{"accession":"P21741","domains":[{"cath_id":"2.20.60.10","chopping":"36-74","consensus_level":"medium","plddt":87.2572,"start":36,"end":74},{"cath_id":"-","chopping":"77-124","consensus_level":"high","plddt":83.9219,"start":77,"end":124}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P21741","model_url":"https://alphafold.ebi.ac.uk/files/AF-P21741-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P21741-F1-predicted_aligned_error_v6.png","plddt_mean":72.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MDK","jax_strain_url":"https://www.jax.org/strain/search?query=MDK"},"sequence":{"accession":"P21741","fasta_url":"https://rest.uniprot.org/uniprotkb/P21741.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P21741/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P21741"}},"corpus_meta":[{"pmid":"31801970","id":"PMC_31801970","title":"Midkine 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mapping, single lab, single method\",\n      \"pmids\": [\"8406506\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Human MDK was mapped to chromosome 11p13→p11, and mouse Mdk was mapped to a syntenic region of mouse chromosome 2; a pseudogene of Mdk was mapped to mouse chromosome 11.\",\n      \"method\": \"Somatic cell hybrid analysis and interspecific backcross analysis\",\n      \"journal\": \"Cytogenetics and cell genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two complementary mapping methods, single lab\",\n      \"pmids\": [\"7835084\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Mdk knockout mice show altered calretinin expression in hippocampal dentate gyrus granule cell layer and deficits in working memory and increased anxiety, establishing MDK's role in postnatal hippocampal development.\",\n      \"method\": \"Gene knockout mouse model, immunohistochemistry, Y-maze and elevated plus-maze behavioral tests\",\n      \"journal\": \"Genes to cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cellular and behavioral phenotypes, multiple orthogonal readouts\",\n      \"pmids\": [\"10096022\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"MDK overexpression in HeLa cells confers resistance to 5-FU, doxorubicin, and cisplatin; siRNA-mediated MDK knockdown in SNU-638 gastric cancer cells decreases IC50 for all three drugs by 18–44%, establishing MDK as a modulator of multi-drug resistance.\",\n      \"method\": \"Stable transfection (overexpression), siRNA knockdown, drug cytotoxicity assays (IC50 measurement)\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal gain- and loss-of-function, single lab, two orthogonal approaches\",\n      \"pmids\": [\"16644108\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"MDK-deficient (Mdk−/−) mice show delayed Wallerian degeneration and delayed axonal regeneration after sciatic nerve freeze injury, with impaired recovery of motor function, establishing MDK as a required factor for peripheral nerve degeneration and regeneration.\",\n      \"method\": \"Mdk knockout mouse model, histomorphometry, electromyography, muscle wet weight analysis\",\n      \"journal\": \"Journal of neuroscience research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO, multiple orthogonal readouts (histology, EMG, functional recovery)\",\n      \"pmids\": [\"19437545\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"A small molecule inhibitor iMDK suppresses endogenous MDK expression, inhibits PI3K pathway activation, and induces apoptosis in MDK-positive lung cancer cells, but not in MDK-negative cells; systemic iMDK inhibits tumor growth in xenograft models, establishing MDK's role in activating the PI3K survival pathway in lung cancer.\",\n      \"method\": \"Small molecule inhibition (iMDK), cell viability assays, PI3K pathway western blotting, xenograft mouse model, specificity controls with MDK-negative cells\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vitro mechanistic dissection plus in vivo validation with specificity controls\",\n      \"pmids\": [\"23976985\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"SP1 binds to the promoter of the MDK gene (confirmed by chromatin immunoprecipitation) and directly transcriptionally upregulates MDK expression; overexpression of MDK in SP1-silenced glioma cells partially rescues SP1 inhibition effects on proliferation in vitro and tumor growth in vivo.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), gene silencing (siRNA), MDK overexpression rescue assays, xenograft mouse model\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — ChIP establishes direct promoter binding, rescue experiment confirms epistasis, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"25428991\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"MDK promotes cell migration and proliferation in lacrimal gland cells; recombinant MDK was found in iPSC-conditioned medium and suppresses the p38/JNK pathway and Akt phosphorylation in irradiated lacrimal gland tissue, establishing a role for MDK in radiation injury repair.\",\n      \"method\": \"iPSC-conditioned medium treatment, western blotting for p38/JNK and Akt phosphorylation, cell migration and proliferation assays, in vivo murine model\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, mechanistic pathway conclusions drawn from conditioned medium not pure recombinant MDK in isolation\",\n      \"pmids\": [\"25314301\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Exosomal miR-9 secreted by NPC cells directly suppresses MDK expression in endothelial cells (confirmed by luciferase reporter assay targeting MDK 3'UTR), and MDK knockdown inhibits endothelial tube formation and migration via PDK/AKT signaling, establishing MDK as a downstream mediator of PI3K/AKT-driven angiogenesis in endothelial cells.\",\n      \"method\": \"Luciferase 3'UTR reporter assay, western blotting, tube formation assay, migration assay, matrigel plug assay, Phosphorylation Array\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct target validation by reporter assay plus functional consequence, single lab\",\n      \"pmids\": [\"30001734\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"p53 (a key DDR transcription factor) mediates overexpression of MDK, and MDK promotes M2 polarization of microglia to remodel the glioblastoma immunosuppressive microenvironment, establishing MDK as a downstream effector of p53/DDR signaling in shaping the tumor microenvironment.\",\n      \"method\": \"In vitro and in vivo experiments, western blotting, functional M2 polarization assays, transcriptomic analysis\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional validation in vivo and in vitro, single lab\",\n      \"pmids\": [\"30773478\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"miR-326 targets and inhibits MDK expression, thereby negatively regulating JAK/STAT and MAPK signaling pathways; rescue assays confirmed that MDK re-expression reverses miR-326-mediated attenuation of cardiac hypertrophy in Ang II-treated H9c2 cells and TAC mice.\",\n      \"method\": \"Luciferase reporter assay (implied target validation), miR-326 overexpression, MDK rescue assays, western blotting for JAK/STAT and MAPK pathways, in vivo TAC model\",\n      \"journal\": \"European journal of pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct target validation with pathway placement and rescue experiment, single lab\",\n      \"pmids\": [\"31972179\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MDK secreted from ErbB pathway-mutated gallbladder cancer epithelial cells interacts with its receptor LRP1 expressed on tumor-infiltrating macrophages to promote immunosuppressive M2 macrophage differentiation.\",\n      \"method\": \"Single-cell RNA sequencing, bulk RNA-seq, immunohistochemistry, immunofluorescence, functional experiments (macrophage polarization assays)\",\n      \"journal\": \"Journal of hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional experiments validate scRNA-seq interaction inference, single lab\",\n      \"pmids\": [\"34171432\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"IFN-γ upregulates MDK via STAT1 signaling in cancer cell lines; MDK drives EMT activation and cancer metastasis; pharmacological MDK inhibition (iMDK) reverses IFN-γ-activated EMT and abrogates IFN-γ-triggered metastasis across multiple cancer types.\",\n      \"method\": \"Cell line knockdown/overexpression, western blotting, migration/invasion assays, iMDK inhibitor treatment\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — STAT1-MDK pathway established by multiple cancer lines with inhibitor validation, single lab\",\n      \"pmids\": [\"35747815\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"MDK enhances glioblastoma stem-like properties by activating Notch1/p-JNK signaling, leading to increased CD133 and Nanog expression, thereby promoting temozolomide resistance; MDK knockdown inhibits tumor growth in xenograft models.\",\n      \"method\": \"MDK overexpression/knockdown, western blotting for Notch1/p-JNK/CD133/Nanog, xenograft mouse model, in vitro stem cell assays\",\n      \"journal\": \"American journal of cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pathway placement by western blotting with in vivo validation, single lab\",\n      \"pmids\": [\"36381313\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"MDK is a downstream target of IFN-γ/STAT1 in ovarian cancer cells; MDK overexpression promotes proliferation and EMT/metastasis; MDK inhibition (iMDK) reverses IFN-γ-driven EMT and synergistically enhances IFN-γ growth inhibition (combination index <0.1).\",\n      \"method\": \"Gain-of-function MDK overexpression, iMDK inhibitor, combination index analysis, EMT western blotting, migration/invasion assays\",\n      \"journal\": \"Biomedicines\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic pathway placement with quantitative drug interaction analysis, single lab\",\n      \"pmids\": [\"36672515\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"miR-1275 directly targets MDK as a downstream protein, and MDK initiates PI3K/Akt signaling in breast cancer cells; CRISPR/Cas9 knockout of miR-1275 promotes chemoresistance by increasing cancer stem cell properties via the MDK/AKT axis.\",\n      \"method\": \"CRISPR/Cas9 gene editing, RT-qPCR, western blotting for PI3K/Akt, cancer stem cell assays\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR-based KO with defined pathway, single lab\",\n      \"pmids\": [\"36594100\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MDK interacts with Syndecan-1 (SDC1) receptor and activates PI3K/AKT and p38 MAPK pathways to promote proliferation, migration, invasion, lymphangiogenesis, and lymph node metastasis of cervical squamous cell carcinoma.\",\n      \"method\": \"MDK overexpression/knockdown, co-immunoprecipitation (implied interaction with SDC1), western blotting for PI3K/AKT and p38, invasion/migration assays, in vivo lymphangiogenesis assays\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — receptor interaction and pathway activation shown functionally, single lab\",\n      \"pmids\": [\"39040052\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MDK promotes M2 macrophage polarization via MDK-LRP1 interaction; MDK inhibition suppresses M2 polarization in clear cell renal cell carcinoma.\",\n      \"method\": \"Multiomics analysis, functional M2 polarization assays, MDK inhibition experiments\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional validation of MDK-LRP1 mediated polarization with inhibitor, single lab\",\n      \"pmids\": [\"39107475\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"GPC2 promotes prostate cancer cell proliferation, migration, and invasion via MDK-mediated activation of the PI3K/AKT signaling pathway; MDK overexpression rescues the inhibitory effects of GPC2 knockdown on PI3K/AKT signaling and cell behavior.\",\n      \"method\": \"siRNA knockdown, MDK overexpression rescue assay, western blotting for PI3K/AKT, proliferation/migration/invasion assays\",\n      \"journal\": \"Functional & integrative genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis established by rescue assay, single lab\",\n      \"pmids\": [\"39014225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CDK7 promotes MDK expression in irinotecan-resistant colorectal cancer cells; suppression of CDK7 by siRNA or the inhibitor THZ1 significantly reduces MDK expression and re-sensitizes resistant cells to irinotecan, placing MDK downstream of CDK7 in a drug resistance pathway.\",\n      \"method\": \"Bulk RNA sequencing, siRNA knockdown, CDK7 inhibitor (THZ1), in vivo xenograft experiments, patient tissue analysis\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNA-seq plus functional genetic and pharmacological validation with in vivo confirmation, single lab\",\n      \"pmids\": [\"39004275\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Syndecan-4 (SDC4) is identified as a receptor for MDK associated with regulatory T cell (Treg) colocalisation in colorectal cancer; MDK-high CRC cells interact with SPP1+ macrophages and stromal cells to establish immunosuppression in the tumor microenvironment.\",\n      \"method\": \"Spatial transcriptomics, single-cell transcriptome, deep generative model colocalisation analysis, clinical CRC dataset analysis\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — receptor identification based on computational/transcriptomic inference without direct biochemical binding validation\",\n      \"pmids\": [\"38614865\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Angelica sinensis polysaccharide (ASP) upregulates MDK expression in adipose-derived stem cells; MDK knockdown abolishes ASP-induced elevation of chondrogenic differentiation markers and PI3K/AKT pathway activity, placing MDK upstream of PI3K/AKT in ASP-induced chondrogenesis.\",\n      \"method\": \"Transcriptome sequencing, siRNA knockdown, western blotting for PI3K/AKT, chondrogenic differentiation assays (Alcian blue, qRT-PCR)\",\n      \"journal\": \"Biomedicine & pharmacotherapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pathway placement via genetic knockdown with multiple orthogonal readouts, single lab\",\n      \"pmids\": [\"39191028\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MDK inhibition (iMDK) suppresses the proliferation, migration, and EMT of glioblastoma cells induced by hypoxia; in vivo, hypoxia promotes MDK expression and MDK knockdown reduces these hypoxia-driven malignant behaviors.\",\n      \"method\": \"MDK knockdown, iMDK inhibitor, CCK8, EdU proliferation assay, wound healing, transwell assay, western blotting for EMT markers\",\n      \"journal\": \"Biomedicines\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic and pharmacological inhibition with multiple functional readouts, single lab\",\n      \"pmids\": [\"38255198\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"EGFRvIII-positive GBM secretes high levels of MDK via the ERK-c-Fos signaling pathway; secreted MDK drives M2 macrophage polarization and CXCL1 secretion via LRP1 receptor on macrophages; blocking MDK signaling in an intracranial glioma model inhibits M2 macrophage polarization and tumor progression.\",\n      \"method\": \"Western blotting, functional macrophage polarization assays, intracranial glioma mouse model, MDK pathway blockade\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic pathway (ERK-c-Fos-MDK-LRP1) validated in vitro and in vivo, single lab\",\n      \"pmids\": [\"40527884\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MDK interacts directly with c-Myc (demonstrated by microthermometry and co-immunoprecipitation); MDK interaction with c-Myc influences c-Myc ubiquitination and stabilizes it, activating Wnt/β-catenin signaling and EMT, contributing to temozolomide resistance; small molecule ACT001 disrupts the MDK/c-Myc complex, promotes c-Myc degradation, and sensitizes resistant glioma cells to TMZ.\",\n      \"method\": \"Microthermometry, co-immunoprecipitation, proteomics, western blotting, xenograft and in situ glioma models\",\n      \"journal\": \"Clinical and translational medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct protein-protein interaction shown by two orthogonal biophysical/biochemical methods plus functional consequence via proteasomal degradation\",\n      \"pmids\": [\"40468625\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Wnt/β-catenin signaling drives MDK upregulation in hepatoblastoma cells; MDK modifies macrophage phenotype toward immunosuppression; MDK inhibition partially reverses macrophage phenotype change, establishing MDK as a Wnt-responsive immunomodulator.\",\n      \"method\": \"Western blotting, RNA-seq of hepatoblastoma and macrophage cell lines, MDK inhibition experiments, single-cell and spatial transcriptomics\",\n      \"journal\": \"Journal of hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — experimental validation by western blotting and RNA-seq with MDK inhibition, single lab\",\n      \"pmids\": [\"39900120\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MDK binds the SDC4 receptor on beta cells to downregulate Ras signaling, impairing insulin production and secretion, establishing a mechanism for pancreatic cancer-associated new-onset diabetes.\",\n      \"method\": \"Single-cell RNA sequencing, receptor-ligand interaction analysis, functional beta cell assays (insulin production/secretion)\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — receptor-ligand interaction and downstream pathway inferred from scRNA-seq with some functional validation, single lab\",\n      \"pmids\": [\"40709672\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Remote neuromuscular electrical stimulation (rNMES) upregulates MDK expression in skeletal muscle via the AMPK-ERK axis; circulating MDK reaches wounds and promotes macrophage efferocytosis in a LRP1-dependent manner, accelerating wound healing.\",\n      \"method\": \"GEO database analysis, in vivo rNMES model, MDK-LRP1 functional assays, macrophage efferocytosis assay\",\n      \"journal\": \"Journal of biomedical research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct LRP1-dependent mechanistic link established with efferocytosis assay, single lab\",\n      \"pmids\": [\"40441854\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MDK facilitates M2-like macrophage polarization via interaction with LRP1 receptor on macrophages in MASH-HCC; silencing LRP1 in macrophages abolishes MDK-driven M2 polarization and increases cytotoxic cytokine secretion; LRP1-positive macrophages contribute to T cell exhaustion via CXCL16-CXCR6 axis; combining Resmetirom with iMDK synergistically suppresses tumorigenesis in vivo.\",\n      \"method\": \"scRNA-seq, LRP1 silencing in macrophages, cytokine measurement, in vivo combination therapy model\",\n      \"journal\": \"Hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — LRP1 dependence established by silencing with functional readouts, in vivo validation, single lab\",\n      \"pmids\": [\"41525571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MDK promotes M2 macrophage polarization and mast cell activation via interaction with the nucleolin (NCL) receptor; MDK knockdown in pancreatic stellate cells reduces PSC activation/fibrosis and suppresses mast cell proliferation and degranulation in chronic pancreatitis; these effects are reversed by recombinant MDK and blocked by NCL neutralization.\",\n      \"method\": \"scRNA-seq analysis, MDK knockdown in PSCs, co-culture experiments, recombinant MDK rescue, NCL neutralization, in vivo MDK/NCL knockdown, flow cytometry\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — NCL identified as receptor by neutralization experiments, functional rescue confirms MDK-NCL axis, single lab\",\n      \"pmids\": [\"42031197\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Recombinant MDK protein dose-dependently inhibits osteogenic differentiation via the PI3K/AKT signaling pathway and increases expression of inflammatory cytokines (IL-6, TNF-α, IL-1β) via NF-κB signaling; iMDK inhibitor mitigates estrogen deficiency-induced bone loss in ovariectomized mice.\",\n      \"method\": \"Recombinant MDK protein treatment, transcriptome analysis, western blotting for PI3K/AKT and NF-κB, in vitro osteogenic differentiation assays, ovariectomy mouse model\",\n      \"journal\": \"Genes & diseases\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — recombinant protein dose-response with transcriptomic and western blot pathway validation plus in vivo model, single lab\",\n      \"pmids\": [\"41674663\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MDK activates the PI3K/AKT pathway in colorectal cancer cells, leading to upregulated AP2A1 expression and promotion of EMT; PI3K inhibitor LY294002 reduces AP2A1 levels and reverses MDK-induced malignant behaviors.\",\n      \"method\": \"MDK overexpression/knockdown, western blotting for PI3K/AKT/AP2A1/EMT markers, PI3K inhibitor (LY294002), invasion/migration/proliferation assays, xenograft and metastasis mouse models\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis between MDK, PI3K/AKT, and AP2A1 confirmed by inhibitor and genetic approaches with in vivo validation, single lab\",\n      \"pmids\": [\"42073635\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MDK treadmill training upregulates MDK expression and promotes neuronal MDK localization (confirmed by NeuN co-staining); MDK signals through LRP1 receptor to activate PI3K/Akt and upregulate BDNF in neurons; LRP1 siRNA blocks exercise-induced Akt activation, BDNF upregulation, and motor recovery after spinal cord injury.\",\n      \"method\": \"LRP1 siRNA knockdown in vivo, immunofluorescence co-staining, western blotting for PI3K/Akt/BDNF, in vitro MDK treatment with LRP1 inhibitor (RAP), behavioral analysis (BBB score, gait analysis)\",\n      \"journal\": \"Neurochemical research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — LRP1-dependent MDK signaling validated by both siRNA and pharmacological blockade with multiple functional readouts, single lab\",\n      \"pmids\": [\"42257999\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MDK attenuates Aβ40 and Aβ42 fibril formation in vitro as demonstrated by Thioflavin T fluorescence assay, circular dichroism, negative stain electron microscopy, and NMR; Mdk knockout in 5xFAD mice increases amyloid plaque formation and microglial activation, establishing MDK as a protective factor counteracting amyloid pathology.\",\n      \"method\": \"Thioflavin T fluorescence assay, circular dichroism, negative stain electron microscopy, NMR, Mdk/5xFAD double-knockout mouse model, mass spectrometry-based proteomics\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal in vitro biophysical methods plus genetic mouse model validation, comprehensive proteomics\",\n      \"pmids\": [\"bio_10.1101_2025.03.20.644383\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MDK disrupts melanoma disseminated cancer cell dormancy through an autocrine signal that suppresses the dormancy inducer NR2F1 and alters the p-p38/p-ERK ratio via ALK signaling; dual targeting of MDK (genetic blockade) and NR2F1 (activation) markedly limits metastatic outgrowth and extends survival in mouse models.\",\n      \"method\": \"MDK genetic blockade, NR2F1 agonist treatment, p-p38/p-ERK ratio analysis, dormancy assays in lymph nodes and visceral tissues, in vivo mouse survival experiments\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic and pharmacological epistasis with functional dormancy and survival readouts, single lab, preprint\",\n      \"pmids\": [\"bio_10.1101_2025.05.27.656365\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"MDK (Midkine) is a secreted heparin-binding growth factor that activates multiple receptors (LRP1, ALK, nucleolin/NCL, syndecan-1/SDC1, syndecan-4/SDC4) to promote cell survival, proliferation, EMT, and drug resistance primarily through PI3K/AKT, MAPK, JAK/STAT, NF-κB, and Notch/JNK signaling cascades; it is transcriptionally regulated by SP1 and STAT1 (downstream of IFN-γ) and by Wnt/β-catenin and p53/DDR pathways, and its extracellular interactions drive macrophage M2 polarization (via LRP1), mast cell activation (via NCL), Treg accumulation, and immune evasion in the tumor microenvironment, while also serving protective roles in peripheral nerve regeneration, hippocampal postnatal development, and amyloid plaque suppression in Alzheimer's disease models.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MDK (Midkine) is a secreted growth factor that signals through cell-surface receptors to activate pro-survival and pro-proliferative cascades, functioning as a context-dependent factor in tissue regeneration, neuronal development, and tumor progression [#5, #16]. Its dominant downstream output is the PI3K/AKT survival axis: PI3K activation underlies MDK-driven cell survival in lung cancer [#5], endothelial angiogenesis [#8], cervical carcinoma proliferation and lymphangiogenesis [#16], and colorectal EMT via AP2A1 [#31], with additional engagement of MAPK/p38, JAK/STAT, Notch1/p-JNK, and NF-\\u03baB outputs in different contexts [#10, #13, #16, #30]. MDK exerts these effects through several receptors—LRP1, syndecan-1 (SDC1), syndecan-4 (SDC4), nucleolin (NCL), and ALK—engaged in distinct settings [#11, #16, #20, #29, #34]. A recurrent role is reprogramming the tumor microenvironment: MDK secreted by tumor cells engages LRP1 on macrophages to drive immunosuppressive M2 polarization across gallbladder, renal, glioma, and liver cancers [#11, #17, #23, #28], and engages NCL to promote mast cell activation [#29]. Beyond ligand–receptor signaling, MDK binds c-Myc directly and stabilizes it against ubiquitination to activate Wnt/\\u03b2-catenin signaling and confer temozolomide resistance in glioma [#24]. MDK expression is induced by SP1 [#6], IFN-\\u03b3/STAT1 [#12, #14], p53/DDR [#9], Wnt/\\u03b2-catenin [#25], and CDK7 [#19], and repressed by microRNAs including miR-9, miR-326, miR-1275, and miR-1275 [#8, #10, #15]. In non-malignant tissue, MDK is required for postnatal hippocampal development [#2] and peripheral nerve degeneration/regeneration [#4], drives LRP1-dependent neurotrophic signaling and BDNF upregulation after spinal cord injury [#32], and attenuates A\\u03b2 fibril formation, protecting against amyloid pathology [#33].\",\n  \"teleology\": [\n    {\n      \"year\": 1993,\n      \"claim\": \"Establishing the chromosomal location of MDK provided the genomic anchor needed for subsequent functional and comparative studies.\",\n      \"evidence\": \"FISH mapping to chromosome 11p11.2, refined by somatic cell hybrid and interspecific backcross analysis to mouse synteny\",\n      \"pmids\": [\"8406506\", \"7835084\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mapping alone gives no functional or mechanistic information\", \"Does not address regulation or protein activity\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Loss-of-function in mice answered whether MDK has a physiological developmental role, revealing it is required for postnatal hippocampal development and normal behavior.\",\n      \"evidence\": \"Mdk knockout mouse with immunohistochemistry and behavioral testing (Y-maze, elevated plus-maze)\",\n      \"pmids\": [\"10096022\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor and signaling pathway mediating the hippocampal phenotype not identified\", \"Cell-autonomous versus secreted action not resolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"A second knockout phenotype established MDK as a required factor for peripheral nerve degeneration and regeneration, extending its physiological role beyond development.\",\n      \"evidence\": \"Mdk knockout mice subjected to sciatic nerve injury with histomorphometry, EMG, and functional recovery readouts\",\n      \"pmids\": [\"19437545\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mediators of the regeneration defect not defined\", \"Receptor involvement not tested\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Reciprocal gain- and loss-of-function tied MDK to drug resistance, a phenotype later recurring across many cancers.\",\n      \"evidence\": \"Overexpression and siRNA knockdown with IC50 drug cytotoxicity assays in cancer cell lines\",\n      \"pmids\": [\"16644108\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking MDK to multidrug resistance not defined at this stage\", \"No receptor or signaling pathway identified\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Small-molecule inhibition with specificity controls established the PI3K survival pathway as a core mediator of MDK's pro-tumor function.\",\n      \"evidence\": \"iMDK inhibitor with PI3K western blotting, viability assays, and xenografts using MDK-negative controls\",\n      \"pmids\": [\"23976985\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor coupling MDK to PI3K not identified\", \"iMDK acts by suppressing MDK expression rather than blocking ligand binding\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"ChIP-based identification of SP1 as a direct transcriptional activator, with rescue, began defining the regulatory inputs controlling MDK levels.\",\n      \"evidence\": \"ChIP, siRNA silencing, MDK overexpression rescue, and xenografts in glioma\",\n      \"pmids\": [\"25428991\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Other transcriptional regulators not addressed here\", \"Downstream MDK signaling in glioma not dissected\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"MicroRNA targeting and reporter validation showed MDK is post-transcriptionally repressed and functions in endothelial angiogenesis via PI3K/AKT.\",\n      \"evidence\": \"Luciferase 3'UTR reporter (miR-9), tube formation, migration, matrigel plug, and phosphorylation array assays\",\n      \"pmids\": [\"30001734\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Endothelial receptor for MDK not identified\", \"Direct versus paracrine angiogenic action not separated\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Linking MDK to p53/DDR and showing it drives microglial M2 polarization introduced its role in shaping the immunosuppressive tumor microenvironment.\",\n      \"evidence\": \"In vitro/in vivo M2 polarization assays, western blotting, and transcriptomics in glioblastoma\",\n      \"pmids\": [\"30773478\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor on microglia not identified in this study\", \"Mechanism of p53-mediated MDK induction not detailed\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identification of LRP1 as the macrophage receptor mediating MDK-driven M2 polarization assigned a molecular basis to MDK's immunomodulatory role.\",\n      \"evidence\": \"scRNA-seq, bulk RNA-seq, immunostaining, and macrophage polarization functional assays in gallbladder cancer\",\n      \"pmids\": [\"34171432\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct biochemical MDK-LRP1 binding affinity not measured\", \"Downstream macrophage signaling from LRP1 not fully mapped\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Multiple studies placed MDK downstream of IFN-\\u03b3/STAT1 and Notch1/p-JNK, establishing it as a driver of EMT, metastasis, stemness, and therapy resistance across cancer types.\",\n      \"evidence\": \"Knockdown/overexpression, iMDK inhibition, EMT/stem-cell markers, combination index analysis, and xenografts in lung, ovarian, and glioblastoma models\",\n      \"pmids\": [\"35747815\", \"36672515\", \"36381313\", \"31972179\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor coupling IFN-\\u03b3-induced MDK to EMT not defined\", \"Convergence of multiple pathways onto common effectors unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"A series of studies expanded MDK's receptor repertoire (SDC1, SDC4, LRP1) and upstream regulators (GPC2, CDK7), consolidating PI3K/AKT as the convergent output across tumor and regenerative contexts.\",\n      \"evidence\": \"Co-IP (SDC1), rescue assays (GPC2), CDK7 inhibition (THZ1), spatial/single-cell transcriptomics (SDC4-Treg), and macrophage polarization assays across cervical, prostate, colorectal, and renal cancers\",\n      \"pmids\": [\"39040052\", \"39014225\", \"39004275\", \"38614865\", \"39107475\", \"38255198\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor selection in different tissues not mechanistically explained\", \"Some receptor assignments rely on transcriptomic inference without binding validation\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Direct demonstration that MDK binds and stabilizes c-Myc revealed an intracellular, receptor-independent mechanism activating Wnt/\\u03b2-catenin and conferring temozolomide resistance.\",\n      \"evidence\": \"Microthermometry and co-IP for binding, proteomics, ubiquitination/degradation assays, ACT001 disruptor, and glioma models\",\n      \"pmids\": [\"40468625\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How secreted MDK accesses intracellular c-Myc not resolved\", \"Structural basis of the MDK-c-Myc interaction not determined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Functional dissection in non-malignant and immune contexts established LRP1-, NCL-, SDC4-, and ALK-dependent MDK signaling in wound healing, neural repair, mast cell activation, beta-cell dysfunction, and dormancy escape.\",\n      \"evidence\": \"LRP1 silencing/efferocytosis assays, NCL neutralization, scRNA-seq receptor-ligand inference, ALK-mediated p38/ERK ratio analysis, and in vivo regeneration and metastasis models\",\n      \"pmids\": [\"40441854\", \"42031197\", \"40709672\", \"42257999\", \"40527884\", \"39900120\", \"30001734\", \"42073635\", \"40468625\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor specificity determinants across tissues unresolved\", \"Some receptor-ligand links rest on computational inference\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Biophysical and genetic evidence established a protective role for MDK in suppressing amyloid pathology, contrasting its pro-tumor functions.\",\n      \"evidence\": \"Thioflavin T, circular dichroism, electron microscopy, NMR on A\\u03b2 fibrils, and Mdk/5xFAD double-knockout mice (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.03.20.644383\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the anti-amyloid effect is receptor-dependent not determined\", \"Preprint not yet peer-reviewed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved what determines MDK's choice among its multiple receptors in a given tissue and how secreted MDK reaches intracellular targets such as c-Myc.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model of receptor selection across LRP1/SDC1/SDC4/NCL/ALK\", \"Mechanism of intracellular access for secreted MDK unknown\", \"Structural basis of receptor and c-Myc binding undetermined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [5, 11, 16, 29]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [33]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [24]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [7, 11, 27, 30]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [5, 16, 24]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [11, 17, 23, 28, 29]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [3, 13, 24]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2, 4, 21, 32]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"LRP1\", \"SDC1\", \"SDC4\", \"NCL\", \"ALK\", \"MYC\", \"GPC2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}