{"gene":"KREMEN2","run_date":"2026-04-28T18:30:27","timeline":{"discoveries":[{"year":2003,"finding":"Kremen2 (Krm2) acts as a switch that converts Dkk2 from an activator into an inhibitor of Wnt/LRP6 signaling; co-transfection of Krm2 with Dkk2 in HEK293 cells blocks Dkk2-mediated LRP6 activation and enhances inhibition of Wnt/Frizzled signaling. The interaction between Krm2 and Dkks is mediated by the second cysteine-rich domain of Dkks. Krm2 also co-operates with Dkk4 (but not Dkk3) to inhibit Wnt signaling, and epistasis in Xenopus embryos confirms cooperative Wnt inhibition.","method":"Transfection/co-transfection in HEK293 cells with luciferase reporters, Xenopus embryo microinjection (genetic epistasis), domain-mapping experiments","journal":"Gene","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (cell reporter assays, Xenopus epistasis, domain mapping) in a well-cited foundational study","pmids":["12527209"],"is_preprint":false},{"year":2010,"finding":"Osteoblast-specific overexpression of Krm2 in transgenic mice (Col1a1-Krm2) causes severe osteoporosis with impaired osteoblast maturation, decreased canonical Wnt signaling, and reduced Opg production; Krm2-knockout mice show high bone mass with a >3-fold increase in bone formation, establishing Krm2 as a negative regulator of bone formation acting through the Dkk1/Krm/Lrp5/6 ternary complex.","method":"Transgenic mouse overexpression (Col1a1-Krm2), Krm2 knockout mice, histomorphometry, primary osteoblast differentiation assays, Wnt signaling reporter assays","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 — complementary gain- and loss-of-function mouse models with cell-autonomous phenotype validation","pmids":["20436912"],"is_preprint":false},{"year":2014,"finding":"Osteoblast-specific overexpression of Krm2 impairs fracture healing more severely than Lrp5 deficiency; Col1a1-Krm2 callus shows decreased active β-catenin and reduced Smpd3 expression, placing Krm2-mediated Wnt inhibition upstream of β-catenin activity during bone repair.","method":"Transgenic mouse fracture healing model (flexible/semi-rigid fixation), microarray gene expression analysis, immunohistochemistry for active β-catenin","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo model with molecular readouts, but mechanistic depth limited to pathway marker measurement","pmids":["25061805"],"is_preprint":false},{"year":2021,"finding":"Knockdown of Krm2 in gastric cancer cells suppresses cell survival, induces apoptosis and G2/M cell cycle arrest, inhibits migration in vitro, and reduces tumorigenesis in xenografts; mechanistically, Krm2 knockdown suppresses the PI3K/Akt signaling pathway.","method":"shRNA knockdown, colony formation, apoptosis assay, cell cycle analysis, migration assay, xenograft mouse model, Western blot for PI3K/Akt pathway components","journal":"Frontiers in oncology","confidence":"Medium","confidence_rationale":"Tier 2 — KD with defined cellular phenotypes and pathway readout, but no direct binding or reconstitution data linking Krm2 to PI3K/Akt","pmids":["33489867"],"is_preprint":false},{"year":2023,"finding":"Kremen2 physically interacts with SOCS3 to prevent SOCS3-mediated ubiquitination and proteasomal degradation of EGFR, thereby maintaining EGFR protein levels and sustaining activation of PI3K-AKT and JAK2-STAT3 signaling pathways in NSCLC cells.","method":"Co-immunoprecipitation, Western blot, immunofluorescence co-localization, ubiquitination assay, KO/KD cell lines, xenograft and metastatic mouse models","journal":"Journal of experimental & clinical cancer research","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP establishing Kremen2–SOCS3 interaction, ubiquitination assay mechanistically linking the interaction to EGFR stability, validated in vivo","pmids":["37270563"],"is_preprint":false},{"year":2024,"finding":"In SMARCB1-deficient cancers, loss of SMARCB1-containing SWI/SNF complexes (which normally recruit H3K27me3/EZH2 to repress KREMEN2) leads to CBP/p300-mediated H3K27ac at the KREMEN2 locus and transcriptional upregulation of KREMEN2, which cooperates with the SMARCA1 chromatin remodeling complex. Simultaneous CBP/p300 inhibition represses KREMEN2 expression and triggers apoptosis via KREMEN1 monomerization (loss of KREMEN1–KREMEN2 interaction suppresses anti-apoptotic signaling).","method":"Dual siRNA paralog-pair screen, ChIP for H3K27me3/H3K27ac, CBP/p300 dual inhibitor treatment, KREMEN2 overexpression/knockdown, xenograft models, Co-IP for KREMEN1–KREMEN2 interaction","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods (ChIP, Co-IP, pharmacologic inhibition, genetic KD, xenografts) in a single rigorous study with mechanistic resolution","pmids":["38839769"],"is_preprint":false},{"year":2024,"finding":"FTO (m6A demethylase) negatively regulates KREMEN2 mRNA stability in high-grade serous ovarian cancer; m6A marks at the 3′ and 5′ UTRs of KREMEN2 mRNA are recognized and stabilized by the reader IGF2BP1 (but not IGF2BP2 or IGF2BP3), thereby promoting KREMEN2-dependent tumor growth.","method":"Methylated RNA immunoprecipitation qPCR (MeRIP-qPCR), RNA immunoprecipitation (RIP), FTO overexpression, IGF2BP1/2/3 RIP, in vitro and in vivo tumor growth assays","journal":"Laboratory investigation","confidence":"Medium","confidence_rationale":"Tier 2 — MeRIP-qPCR and RIP directly map m6A sites and reader identity; functional consequence shown in vitro and in vivo, single lab","pmids":["38615731"],"is_preprint":false},{"year":2025,"finding":"KRM2 physically interacts with and positively regulates ATF2 protein levels in renal cell carcinoma; KRM2 knockdown reduces ATF2 expression (confirmed by co-immunoprecipitation and cycloheximide chase), and ATF2 knockdown reverses the cancer-promoting and ferroptosis-inhibiting effects of KRM2.","method":"Co-immunoprecipitation, cycloheximide pulse-chase assay, gene expression microarray, KRM2/ATF2 KD cell lines, xenograft mouse model, ferroptosis indicator assays","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP and chase assay establish direct interaction and protein stabilization; epistasis via ATF2 KD, single lab","pmids":["40057259"],"is_preprint":false},{"year":2025,"finding":"In cBAF-deficient cancers (SMARCA4/SMARCA2-deficient and SS18-SSX fusion cancers), transcriptional upregulation of KREMEN2 (due to loss of cBAF repression) confers dependence on CBP/p300; simultaneous inhibition of CBP/p300 represses KREMEN2 expression, triggering KREMEN1-mediated apoptosis and suppressing xenograft growth.","method":"CBP/p300 dual inhibitor treatment, KREMEN2 expression analysis, xenograft models, genetic knockdown of KREMEN2, apoptosis assays","journal":"Cancer research communications","confidence":"Medium","confidence_rationale":"Tier 2 — extends prior SMARCB1 findings to broader cBAF subcomplex deficiencies; single lab replication with in vivo validation","pmids":["39625239"],"is_preprint":false}],"current_model":"KREMEN2 is a transmembrane receptor that (1) acts as a co-receptor modulating Dkk-family ligands to form ternary complexes with LRP5/6 and inhibit Wnt/β-catenin signaling; (2) interacts with SOCS3 to protect EGFR from ubiquitin-mediated degradation, thereby activating PI3K-AKT and JAK2-STAT3 pathways; (3) physically interacts with KREMEN1, with heterodimer disruption triggering apoptosis; (4) interacts with ATF2 to promote its stability and suppress ferroptosis; and (5) is transcriptionally regulated by the SWI/SNF–EZH2 axis and post-transcriptionally stabilized via m6A modification read by IGF2BP1, collectively defining roles in bone homeostasis, Wnt signaling, and oncogenic signaling across multiple cancer types."},"narrative":{"teleology":[{"year":2003,"claim":"Establishing that KREMEN2 functions as a co-receptor that switches Dkk2 from a Wnt activator to a Wnt inhibitor resolved how Dkk ligand context determines signaling outcome at the LRP5/6 receptor.","evidence":"Co-transfection luciferase reporter assays in HEK293 cells plus Xenopus embryo epistasis experiments with domain mapping","pmids":["12527209"],"confidence":"High","gaps":["Structural basis of the Krm2–Dkk–LRP6 ternary complex not determined","Relative contribution of Krm2 versus Krm1 to Dkk-mediated Wnt inhibition unclear","Endogenous stoichiometry and tissue-level relevance not addressed"]},{"year":2010,"claim":"Complementary transgenic overexpression and knockout mouse models demonstrated that KREMEN2 is a physiological negative regulator of bone formation acting through Dkk1/Krm/Lrp5/6-dependent Wnt inhibition in osteoblasts.","evidence":"Col1a1-Krm2 transgenic mice (severe osteoporosis) and Krm2-knockout mice (high bone mass), with histomorphometry and primary osteoblast assays","pmids":["20436912"],"confidence":"High","gaps":["Whether KREMEN2 has bone-cell-extrinsic effects (e.g., on osteoclasts) not tested","Functional redundancy with KREMEN1 in bone not delineated"]},{"year":2014,"claim":"Showing that Krm2 overexpression impaired fracture healing more severely than Lrp5 loss positioned KREMEN2-mediated Wnt inhibition as a rate-limiting step in bone repair upstream of β-catenin activation.","evidence":"Transgenic mouse fracture model with semi-rigid/flexible fixation, immunohistochemistry for active β-catenin, microarray","pmids":["25061805"],"confidence":"Medium","gaps":["Direct comparison between Krm2 and Lrp5 mutants is confounded by different genetic backgrounds","Downstream effector Smpd3 linkage is correlative"]},{"year":2021,"claim":"Demonstrating that KREMEN2 knockdown suppresses gastric cancer cell survival and PI3K/Akt signaling revealed a Wnt-independent oncogenic function, raising the question of how a Wnt inhibitory co-receptor promotes tumor growth.","evidence":"shRNA knockdown in gastric cancer cell lines, xenograft models, Western blot for PI3K/Akt pathway components","pmids":["33489867"],"confidence":"Medium","gaps":["No direct binding partner linking KREMEN2 to PI3K/Akt was identified","Whether the gastric cancer role requires Wnt pathway engagement untested"]},{"year":2023,"claim":"Identifying SOCS3 as a direct KREMEN2-binding partner that bridges KREMEN2 to EGFR stability provided the first mechanistic explanation for KREMEN2's Wnt-independent oncogenic activity via PI3K-AKT and JAK2-STAT3 signaling.","evidence":"Reciprocal Co-IP, ubiquitination assay, EGFR protein-level rescue, xenograft and metastatic mouse models in NSCLC cells","pmids":["37270563"],"confidence":"High","gaps":["Whether KREMEN2–SOCS3 interaction occurs outside NSCLC contexts unknown","Domain on KREMEN2 responsible for SOCS3 binding not mapped","Relationship between KREMEN2's Wnt co-receptor and EGFR-stabilizing functions not addressed"]},{"year":2024,"claim":"Revealing that SWI/SNF (SMARCB1/cBAF) complexes recruit EZH2-mediated H3K27me3 to repress KREMEN2, and that KREMEN2 upregulation in SWI/SNF-deficient cancers creates a CBP/p300-dependent vulnerability, established a chromatin-level mechanism controlling KREMEN2 expression and linked KREMEN1–KREMEN2 heterodimerization to anti-apoptotic signaling.","evidence":"ChIP for H3K27me3/H3K27ac, CBP/p300 dual inhibitor, Co-IP for KREMEN1–KREMEN2, dual siRNA screen, xenografts in SMARCB1-deficient and cBAF-deficient cancers","pmids":["38839769","39625239"],"confidence":"High","gaps":["How KREMEN1–KREMEN2 heterodimer delivers an anti-apoptotic signal mechanistically unknown","Whether KREMEN2 upregulation is sufficient or merely necessary for the CBP/p300 vulnerability not fully resolved","Applicability beyond SWI/SNF-deficient cancer subtypes untested"]},{"year":2024,"claim":"Demonstrating that m6A modifications on KREMEN2 mRNA are stabilized by the reader IGF2BP1 (countered by FTO demethylation) revealed a post-transcriptional regulatory layer controlling KREMEN2 abundance in high-grade serous ovarian cancer.","evidence":"MeRIP-qPCR, RNA immunoprecipitation with IGF2BP1/2/3, FTO overexpression, tumor growth assays","pmids":["38615731"],"confidence":"Medium","gaps":["Specific m6A site(s) and their individual contributions not resolved at nucleotide resolution","Whether IGF2BP1-dependent stabilization operates in non-ovarian contexts unknown"]},{"year":2025,"claim":"Identification of ATF2 as a direct KREMEN2-binding partner whose protein stability is maintained by KREMEN2 uncovered a ferroptosis-suppressive axis in renal cell carcinoma, adding a third Wnt-independent effector mechanism.","evidence":"Co-IP, cycloheximide pulse-chase, ATF2 epistasis knockdown, ferroptosis indicator assays, xenograft model","pmids":["40057259"],"confidence":"Medium","gaps":["Mechanism by which KREMEN2 stabilizes ATF2 (e.g., blocking specific E3 ligase) not identified","Whether ATF2 stabilization is specific to renal cell carcinoma not tested","Relationship between ATF2 stabilization and KREMEN2's other signaling outputs unexplored"]},{"year":null,"claim":"A unified structural and signaling model explaining how KREMEN2 coordinates its Wnt co-receptor function with its Wnt-independent oncogenic activities (EGFR/SOCS3, ATF2, KREMEN1 heterodimerization) remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of KREMEN2 alone or in complex exists","Whether distinct KREMEN2 domains separately mediate Wnt-dependent and Wnt-independent functions is untested","In vivo genetic evidence connecting KREMEN2's oncogenic roles to patient outcomes is lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,4]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,1]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,4]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,3,4]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[5,8]}],"complexes":["Dkk–Krm–LRP5/6 ternary complex","KREMEN1–KREMEN2 heterodimer"],"partners":["DKK1","DKK2","LRP6","SOCS3","KREMEN1","ATF2","IGF2BP1"],"other_free_text":[]},"mechanistic_narrative":"KREMEN2 is a transmembrane co-receptor that modulates Wnt/β-catenin signaling, bone homeostasis, and oncogenic survival pathways. It forms ternary complexes with Dickkopf (Dkk) family ligands and LRP5/6, converting Dkk2 from a Wnt activator to a Wnt inhibitor and cooperating with Dkk1/Dkk4 to suppress canonical Wnt signaling; genetic gain- and loss-of-function in mice establish KREMEN2 as a physiological negative regulator of osteoblast-mediated bone formation [PMID:12527209, PMID:20436912]. Beyond Wnt modulation, KREMEN2 sustains EGFR protein stability by binding SOCS3 and blocking SOCS3-mediated EGFR ubiquitination, thereby activating PI3K-AKT and JAK2-STAT3 signaling in NSCLC, and independently stabilizes ATF2 to suppress ferroptosis in renal cell carcinoma [PMID:37270563, PMID:40057259]. KREMEN2 expression is epigenetically controlled by the SWI/SNF–EZH2 axis: in cBAF/SMARCB1-deficient cancers, loss of H3K27me3 repression and gain of CBP/p300-dependent H3K27ac upregulate KREMEN2, whose heterodimerization with KREMEN1 provides a pro-survival signal that is abolished by CBP/p300 inhibition [PMID:38839769, PMID:39625239]."},"prefetch_data":{"uniprot":{"accession":"Q8NCW0","full_name":"Kremen protein 2","aliases":["Dickkopf receptor 2","Kringle domain-containing transmembrane protein 2","Kringle-containing protein marking the eye and the nose"],"length_aa":462,"mass_kda":48.8,"function":"Receptor for Dickkopf proteins. Cooperates with DKK1/2 to inhibit Wnt/beta-catenin signaling by promoting the endocytosis of Wnt receptors LRP5 and LRP6. Plays a role in limb development; attenuates Wnt signaling in the developing limb to allow normal limb patterning and can also negatively regulate bone formation","subcellular_location":"Membrane","url":"https://www.uniprot.org/uniprotkb/Q8NCW0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KREMEN2","classification":"Not Classified","n_dependent_lines":47,"n_total_lines":1208,"dependency_fraction":0.03890728476821192},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/KREMEN2","total_profiled":1310},"omim":[{"mim_id":"609899","title":"KRINGLE DOMAIN-CONTAINING TRANSMEMBRANE PROTEIN 2; KREMEN2","url":"https://www.omim.org/entry/609899"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"retina","ntpm":3.8},{"tissue":"skin 1","ntpm":7.5}],"url":"https://www.proteinatlas.org/search/KREMEN2"},"hgnc":{"alias_symbol":["MGC10791","KRM2"],"prev_symbol":[]},"alphafold":{"accession":"Q8NCW0","domains":[{"cath_id":"2.40.20.10","chopping":"46-119","consensus_level":"medium","plddt":93.8389,"start":46,"end":119},{"cath_id":"-","chopping":"125-214","consensus_level":"high","plddt":94.2994,"start":125,"end":214},{"cath_id":"2.60.120.290","chopping":"221-327","consensus_level":"high","plddt":94.7375,"start":221,"end":327}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NCW0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NCW0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NCW0-F1-predicted_aligned_error_v6.png","plddt_mean":76.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KREMEN2","jax_strain_url":"https://www.jax.org/strain/search?query=KREMEN2"},"sequence":{"accession":"Q8NCW0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8NCW0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8NCW0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NCW0"}},"corpus_meta":[{"pmid":"12527209","id":"PMC_12527209","title":"Kremen2 modulates Dickkopf2 activity during Wnt/LRP6 signaling.","date":"2003","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/12527209","citation_count":266,"is_preprint":false},{"pmid":"20436912","id":"PMC_20436912","title":"Negative regulation of bone formation by the transmembrane Wnt antagonist Kremen-2.","date":"2010","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/20436912","citation_count":52,"is_preprint":false},{"pmid":"25061805","id":"PMC_25061805","title":"Osteoblast-specific Krm2 overexpression and Lrp5 deficiency have different effects on fracture healing in mice.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25061805","citation_count":19,"is_preprint":false},{"pmid":"37270563","id":"PMC_37270563","title":"Kremen2 drives the progression of non-small cell lung cancer by preventing SOCS3-mediated degradation of EGFR.","date":"2023","source":"Journal of experimental & clinical cancer research : CR","url":"https://pubmed.ncbi.nlm.nih.gov/37270563","citation_count":16,"is_preprint":false},{"pmid":"38839769","id":"PMC_38839769","title":"Targeting dependency on a paralog pair of CBP/p300 against de-repression of KREMEN2 in SMARCB1-deficient cancers.","date":"2024","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/38839769","citation_count":11,"is_preprint":false},{"pmid":"33489867","id":"PMC_33489867","title":"Knockdown of Kremen2 Inhibits Tumor Growth and Migration in Gastric Cancer.","date":"2021","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/33489867","citation_count":10,"is_preprint":false},{"pmid":"28487939","id":"PMC_28487939","title":"Identification of novel genes associated with fracture healing in osteoporosis induced by Krm2 overexpression or Lrp5 deficiency.","date":"2017","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/28487939","citation_count":8,"is_preprint":false},{"pmid":"38615731","id":"PMC_38615731","title":"N6-Methyladenosine-Modified KREMEN2 Promotes Tumorigenesis and Malignant Progression of High-Grade Serous Ovarian Cancer.","date":"2024","source":"Laboratory investigation; a journal of technical methods and pathology","url":"https://pubmed.ncbi.nlm.nih.gov/38615731","citation_count":7,"is_preprint":false},{"pmid":"40057259","id":"PMC_40057259","title":"KRM2 promotes renal cell carcinoma progression and inhibits ferroptosis by interacting with ATF2.","date":"2025","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/40057259","citation_count":1,"is_preprint":false},{"pmid":"39625239","id":"PMC_39625239","title":"Efficacy of CBP/p300 Dual Inhibitors against Derepression of KREMEN2 in cBAF-Deficient Cancers.","date":"2025","source":"Cancer research communications","url":"https://pubmed.ncbi.nlm.nih.gov/39625239","citation_count":1,"is_preprint":false},{"pmid":"41472941","id":"PMC_41472941","title":"Kremen2 Promotes Colorectal Cancer Progression by Activating the EGFR/JAK2/STAT3 Signaling Pathway.","date":"2026","source":"Iranian journal of biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/41472941","citation_count":0,"is_preprint":false},{"pmid":"40638942","id":"PMC_40638942","title":"KREMEN2 promotes the proliferation and the metastasis through activating PI3K/AKT/mTOR signaling pathway in non-small cell lung cancer.","date":"2025","source":"Biochemistry and cell biology = Biochimie et biologie cellulaire","url":"https://pubmed.ncbi.nlm.nih.gov/40638942","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8060,"output_tokens":2703,"usd":0.032363},"stage2":{"model":"claude-opus-4-6","input_tokens":6028,"output_tokens":2779,"usd":0.149423},"total_usd":0.181786,"stage1_batch_id":"msgbatch_01Mgbec4vM6c9vXht7JVJzss","stage2_batch_id":"msgbatch_01JkuuH5RB2BdJNsgnhjbC6s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2003,\n      \"finding\": \"Kremen2 (Krm2) acts as a switch that converts Dkk2 from an activator into an inhibitor of Wnt/LRP6 signaling; co-transfection of Krm2 with Dkk2 in HEK293 cells blocks Dkk2-mediated LRP6 activation and enhances inhibition of Wnt/Frizzled signaling. The interaction between Krm2 and Dkks is mediated by the second cysteine-rich domain of Dkks. Krm2 also co-operates with Dkk4 (but not Dkk3) to inhibit Wnt signaling, and epistasis in Xenopus embryos confirms cooperative Wnt inhibition.\",\n      \"method\": \"Transfection/co-transfection in HEK293 cells with luciferase reporters, Xenopus embryo microinjection (genetic epistasis), domain-mapping experiments\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (cell reporter assays, Xenopus epistasis, domain mapping) in a well-cited foundational study\",\n      \"pmids\": [\"12527209\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Osteoblast-specific overexpression of Krm2 in transgenic mice (Col1a1-Krm2) causes severe osteoporosis with impaired osteoblast maturation, decreased canonical Wnt signaling, and reduced Opg production; Krm2-knockout mice show high bone mass with a >3-fold increase in bone formation, establishing Krm2 as a negative regulator of bone formation acting through the Dkk1/Krm/Lrp5/6 ternary complex.\",\n      \"method\": \"Transgenic mouse overexpression (Col1a1-Krm2), Krm2 knockout mice, histomorphometry, primary osteoblast differentiation assays, Wnt signaling reporter assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — complementary gain- and loss-of-function mouse models with cell-autonomous phenotype validation\",\n      \"pmids\": [\"20436912\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Osteoblast-specific overexpression of Krm2 impairs fracture healing more severely than Lrp5 deficiency; Col1a1-Krm2 callus shows decreased active β-catenin and reduced Smpd3 expression, placing Krm2-mediated Wnt inhibition upstream of β-catenin activity during bone repair.\",\n      \"method\": \"Transgenic mouse fracture healing model (flexible/semi-rigid fixation), microarray gene expression analysis, immunohistochemistry for active β-catenin\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo model with molecular readouts, but mechanistic depth limited to pathway marker measurement\",\n      \"pmids\": [\"25061805\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Knockdown of Krm2 in gastric cancer cells suppresses cell survival, induces apoptosis and G2/M cell cycle arrest, inhibits migration in vitro, and reduces tumorigenesis in xenografts; mechanistically, Krm2 knockdown suppresses the PI3K/Akt signaling pathway.\",\n      \"method\": \"shRNA knockdown, colony formation, apoptosis assay, cell cycle analysis, migration assay, xenograft mouse model, Western blot for PI3K/Akt pathway components\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KD with defined cellular phenotypes and pathway readout, but no direct binding or reconstitution data linking Krm2 to PI3K/Akt\",\n      \"pmids\": [\"33489867\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Kremen2 physically interacts with SOCS3 to prevent SOCS3-mediated ubiquitination and proteasomal degradation of EGFR, thereby maintaining EGFR protein levels and sustaining activation of PI3K-AKT and JAK2-STAT3 signaling pathways in NSCLC cells.\",\n      \"method\": \"Co-immunoprecipitation, Western blot, immunofluorescence co-localization, ubiquitination assay, KO/KD cell lines, xenograft and metastatic mouse models\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP establishing Kremen2–SOCS3 interaction, ubiquitination assay mechanistically linking the interaction to EGFR stability, validated in vivo\",\n      \"pmids\": [\"37270563\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"In SMARCB1-deficient cancers, loss of SMARCB1-containing SWI/SNF complexes (which normally recruit H3K27me3/EZH2 to repress KREMEN2) leads to CBP/p300-mediated H3K27ac at the KREMEN2 locus and transcriptional upregulation of KREMEN2, which cooperates with the SMARCA1 chromatin remodeling complex. Simultaneous CBP/p300 inhibition represses KREMEN2 expression and triggers apoptosis via KREMEN1 monomerization (loss of KREMEN1–KREMEN2 interaction suppresses anti-apoptotic signaling).\",\n      \"method\": \"Dual siRNA paralog-pair screen, ChIP for H3K27me3/H3K27ac, CBP/p300 dual inhibitor treatment, KREMEN2 overexpression/knockdown, xenograft models, Co-IP for KREMEN1–KREMEN2 interaction\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods (ChIP, Co-IP, pharmacologic inhibition, genetic KD, xenografts) in a single rigorous study with mechanistic resolution\",\n      \"pmids\": [\"38839769\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"FTO (m6A demethylase) negatively regulates KREMEN2 mRNA stability in high-grade serous ovarian cancer; m6A marks at the 3′ and 5′ UTRs of KREMEN2 mRNA are recognized and stabilized by the reader IGF2BP1 (but not IGF2BP2 or IGF2BP3), thereby promoting KREMEN2-dependent tumor growth.\",\n      \"method\": \"Methylated RNA immunoprecipitation qPCR (MeRIP-qPCR), RNA immunoprecipitation (RIP), FTO overexpression, IGF2BP1/2/3 RIP, in vitro and in vivo tumor growth assays\",\n      \"journal\": \"Laboratory investigation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — MeRIP-qPCR and RIP directly map m6A sites and reader identity; functional consequence shown in vitro and in vivo, single lab\",\n      \"pmids\": [\"38615731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"KRM2 physically interacts with and positively regulates ATF2 protein levels in renal cell carcinoma; KRM2 knockdown reduces ATF2 expression (confirmed by co-immunoprecipitation and cycloheximide chase), and ATF2 knockdown reverses the cancer-promoting and ferroptosis-inhibiting effects of KRM2.\",\n      \"method\": \"Co-immunoprecipitation, cycloheximide pulse-chase assay, gene expression microarray, KRM2/ATF2 KD cell lines, xenograft mouse model, ferroptosis indicator assays\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP and chase assay establish direct interaction and protein stabilization; epistasis via ATF2 KD, single lab\",\n      \"pmids\": [\"40057259\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In cBAF-deficient cancers (SMARCA4/SMARCA2-deficient and SS18-SSX fusion cancers), transcriptional upregulation of KREMEN2 (due to loss of cBAF repression) confers dependence on CBP/p300; simultaneous inhibition of CBP/p300 represses KREMEN2 expression, triggering KREMEN1-mediated apoptosis and suppressing xenograft growth.\",\n      \"method\": \"CBP/p300 dual inhibitor treatment, KREMEN2 expression analysis, xenograft models, genetic knockdown of KREMEN2, apoptosis assays\",\n      \"journal\": \"Cancer research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — extends prior SMARCB1 findings to broader cBAF subcomplex deficiencies; single lab replication with in vivo validation\",\n      \"pmids\": [\"39625239\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KREMEN2 is a transmembrane receptor that (1) acts as a co-receptor modulating Dkk-family ligands to form ternary complexes with LRP5/6 and inhibit Wnt/β-catenin signaling; (2) interacts with SOCS3 to protect EGFR from ubiquitin-mediated degradation, thereby activating PI3K-AKT and JAK2-STAT3 pathways; (3) physically interacts with KREMEN1, with heterodimer disruption triggering apoptosis; (4) interacts with ATF2 to promote its stability and suppress ferroptosis; and (5) is transcriptionally regulated by the SWI/SNF–EZH2 axis and post-transcriptionally stabilized via m6A modification read by IGF2BP1, collectively defining roles in bone homeostasis, Wnt signaling, and oncogenic signaling across multiple cancer types.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"KREMEN2 is a transmembrane co-receptor that modulates Wnt/β-catenin signaling, bone homeostasis, and oncogenic survival pathways. It forms ternary complexes with Dickkopf (Dkk) family ligands and LRP5/6, converting Dkk2 from a Wnt activator to a Wnt inhibitor and cooperating with Dkk1/Dkk4 to suppress canonical Wnt signaling; genetic gain- and loss-of-function in mice establish KREMEN2 as a physiological negative regulator of osteoblast-mediated bone formation [PMID:12527209, PMID:20436912]. Beyond Wnt modulation, KREMEN2 sustains EGFR protein stability by binding SOCS3 and blocking SOCS3-mediated EGFR ubiquitination, thereby activating PI3K-AKT and JAK2-STAT3 signaling in NSCLC, and independently stabilizes ATF2 to suppress ferroptosis in renal cell carcinoma [PMID:37270563, PMID:40057259]. KREMEN2 expression is epigenetically controlled by the SWI/SNF–EZH2 axis: in cBAF/SMARCB1-deficient cancers, loss of H3K27me3 repression and gain of CBP/p300-dependent H3K27ac upregulate KREMEN2, whose heterodimerization with KREMEN1 provides a pro-survival signal that is abolished by CBP/p300 inhibition [PMID:38839769, PMID:39625239].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Establishing that KREMEN2 functions as a co-receptor that switches Dkk2 from a Wnt activator to a Wnt inhibitor resolved how Dkk ligand context determines signaling outcome at the LRP5/6 receptor.\",\n      \"evidence\": \"Co-transfection luciferase reporter assays in HEK293 cells plus Xenopus embryo epistasis experiments with domain mapping\",\n      \"pmids\": [\"12527209\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of the Krm2–Dkk–LRP6 ternary complex not determined\",\n        \"Relative contribution of Krm2 versus Krm1 to Dkk-mediated Wnt inhibition unclear\",\n        \"Endogenous stoichiometry and tissue-level relevance not addressed\"\n      ]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Complementary transgenic overexpression and knockout mouse models demonstrated that KREMEN2 is a physiological negative regulator of bone formation acting through Dkk1/Krm/Lrp5/6-dependent Wnt inhibition in osteoblasts.\",\n      \"evidence\": \"Col1a1-Krm2 transgenic mice (severe osteoporosis) and Krm2-knockout mice (high bone mass), with histomorphometry and primary osteoblast assays\",\n      \"pmids\": [\"20436912\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether KREMEN2 has bone-cell-extrinsic effects (e.g., on osteoclasts) not tested\",\n        \"Functional redundancy with KREMEN1 in bone not delineated\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showing that Krm2 overexpression impaired fracture healing more severely than Lrp5 loss positioned KREMEN2-mediated Wnt inhibition as a rate-limiting step in bone repair upstream of β-catenin activation.\",\n      \"evidence\": \"Transgenic mouse fracture model with semi-rigid/flexible fixation, immunohistochemistry for active β-catenin, microarray\",\n      \"pmids\": [\"25061805\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct comparison between Krm2 and Lrp5 mutants is confounded by different genetic backgrounds\",\n        \"Downstream effector Smpd3 linkage is correlative\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrating that KREMEN2 knockdown suppresses gastric cancer cell survival and PI3K/Akt signaling revealed a Wnt-independent oncogenic function, raising the question of how a Wnt inhibitory co-receptor promotes tumor growth.\",\n      \"evidence\": \"shRNA knockdown in gastric cancer cell lines, xenograft models, Western blot for PI3K/Akt pathway components\",\n      \"pmids\": [\"33489867\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No direct binding partner linking KREMEN2 to PI3K/Akt was identified\",\n        \"Whether the gastric cancer role requires Wnt pathway engagement untested\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identifying SOCS3 as a direct KREMEN2-binding partner that bridges KREMEN2 to EGFR stability provided the first mechanistic explanation for KREMEN2's Wnt-independent oncogenic activity via PI3K-AKT and JAK2-STAT3 signaling.\",\n      \"evidence\": \"Reciprocal Co-IP, ubiquitination assay, EGFR protein-level rescue, xenograft and metastatic mouse models in NSCLC cells\",\n      \"pmids\": [\"37270563\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether KREMEN2–SOCS3 interaction occurs outside NSCLC contexts unknown\",\n        \"Domain on KREMEN2 responsible for SOCS3 binding not mapped\",\n        \"Relationship between KREMEN2's Wnt co-receptor and EGFR-stabilizing functions not addressed\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revealing that SWI/SNF (SMARCB1/cBAF) complexes recruit EZH2-mediated H3K27me3 to repress KREMEN2, and that KREMEN2 upregulation in SWI/SNF-deficient cancers creates a CBP/p300-dependent vulnerability, established a chromatin-level mechanism controlling KREMEN2 expression and linked KREMEN1–KREMEN2 heterodimerization to anti-apoptotic signaling.\",\n      \"evidence\": \"ChIP for H3K27me3/H3K27ac, CBP/p300 dual inhibitor, Co-IP for KREMEN1–KREMEN2, dual siRNA screen, xenografts in SMARCB1-deficient and cBAF-deficient cancers\",\n      \"pmids\": [\"38839769\", \"39625239\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How KREMEN1–KREMEN2 heterodimer delivers an anti-apoptotic signal mechanistically unknown\",\n        \"Whether KREMEN2 upregulation is sufficient or merely necessary for the CBP/p300 vulnerability not fully resolved\",\n        \"Applicability beyond SWI/SNF-deficient cancer subtypes untested\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrating that m6A modifications on KREMEN2 mRNA are stabilized by the reader IGF2BP1 (countered by FTO demethylation) revealed a post-transcriptional regulatory layer controlling KREMEN2 abundance in high-grade serous ovarian cancer.\",\n      \"evidence\": \"MeRIP-qPCR, RNA immunoprecipitation with IGF2BP1/2/3, FTO overexpression, tumor growth assays\",\n      \"pmids\": [\"38615731\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Specific m6A site(s) and their individual contributions not resolved at nucleotide resolution\",\n        \"Whether IGF2BP1-dependent stabilization operates in non-ovarian contexts unknown\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identification of ATF2 as a direct KREMEN2-binding partner whose protein stability is maintained by KREMEN2 uncovered a ferroptosis-suppressive axis in renal cell carcinoma, adding a third Wnt-independent effector mechanism.\",\n      \"evidence\": \"Co-IP, cycloheximide pulse-chase, ATF2 epistasis knockdown, ferroptosis indicator assays, xenograft model\",\n      \"pmids\": [\"40057259\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which KREMEN2 stabilizes ATF2 (e.g., blocking specific E3 ligase) not identified\",\n        \"Whether ATF2 stabilization is specific to renal cell carcinoma not tested\",\n        \"Relationship between ATF2 stabilization and KREMEN2's other signaling outputs unexplored\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A unified structural and signaling model explaining how KREMEN2 coordinates its Wnt co-receptor function with its Wnt-independent oncogenic activities (EGFR/SOCS3, ATF2, KREMEN1 heterodimerization) remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No high-resolution structure of KREMEN2 alone or in complex exists\",\n        \"Whether distinct KREMEN2 domains separately mediate Wnt-dependent and Wnt-independent functions is untested\",\n        \"In vivo genetic evidence connecting KREMEN2's oncogenic roles to patient outcomes is lacking\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 4]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0016055\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 3, 4]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [5, 8]}\n    ],\n    \"complexes\": [\n      \"Dkk–Krm–LRP5/6 ternary complex\",\n      \"KREMEN1–KREMEN2 heterodimer\"\n    ],\n    \"partners\": [\n      \"DKK1\",\n      \"DKK2\",\n      \"LRP6\",\n      \"SOCS3\",\n      \"KREMEN1\",\n      \"ATF2\",\n      \"IGF2BP1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}