{"gene":"HOXB7","run_date":"2026-04-28T18:06:53","timeline":{"discoveries":[{"year":1996,"finding":"HOXB7 directly transactivates the basic fibroblast growth factor (bFGF) gene through one of five putative homeodomain binding sites in its promoter, driving melanoma cell proliferation; antisense oligomers targeting HOXB7 mRNA abolished bFGF expression and inhibited cell proliferation.","method":"Band shift assay, cotransfection/reporter assay, antisense oligomer knockdown","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 — in vitro DNA binding assay plus cotransfection reporter assay plus loss-of-function antisense, multiple orthogonal methods in single study","pmids":["8756643"],"is_preprint":false},{"year":2001,"finding":"HOXB7 upregulates multiple pro-angiogenic factors (VEGF, GROα/MGSA, IL-8, angiopoietin-2) and MMP-9 while abrogating angiopoietin-1, driving a tumor-associated angiogenic switch in breast cancer cells and promoting vascularized tumor formation in vivo.","method":"Gene expression profiling, retroviral transduction, in vitro coculture angiogenesis assay, xenograft in nude mice with CD31/CD34 immunostaining","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 — clean gain-of-function with defined cellular and in vivo phenotype, single lab","pmids":["11522651"],"is_preprint":false},{"year":2006,"finding":"Overexpression of HOXB7 in epithelial cells induces epithelial-mesenchymal transition (EMT), upregulates bFGF, activates Ras and RhoA GTPases, increases phospho-ERK1/2 (MAPK), and promotes migration, invasion, and vascularized tumor formation; effects reversed by FGF receptor and Ras-MAPK inhibitors and by HOXB7-specific siRNA.","method":"Stable transfection/overexpression in MCF10A and MDCK cells, siRNA knockdown, Ras/RhoA activity assays, Western blot, xenograft in mice, pharmacologic inhibition","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods including gain-of-function, loss-of-function siRNA, pharmacologic rescue, and in vivo validation","pmids":["17018609"],"is_preprint":false},{"year":2007,"finding":"HOXB7 physically interacts with the DNA-dependent protein kinase holoenzyme components Ku70, Ku80, and DNA-PKcs, and with PARP, identified by GST pull-down/affinity chromatography and confirmed by co-immunoprecipitation; HOXB7 expression enhances non-homologous end joining (NHEJ) DNA double-strand break repair in vitro and in vivo, conferring radiation resistance.","method":"GST pull-down, co-immunoprecipitation, NHEJ repair assay in vitro and in vivo, siRNA knockdown","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 1–2 — reciprocal co-IP confirming GST pull-down partners, functional NHEJ assay with rescue experiment","pmids":["17308091"],"is_preprint":false},{"year":1999,"finding":"HOXB7 physically interacts with the coactivator CBP (CREB-binding protein) both in vitro and in vivo; this interaction requires the HOXB7 N-terminal domain and two C-terminal CBP domains, and enhances HOXB7 transactivation potential; histone deacetylase inhibition (trichostatin A) further augments HOXB7 transcriptional activity.","method":"Co-immunoprecipitation in vivo, GST pull-down in vitro, deletion/domain mapping, transient transfection reporter assay","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro and in vivo binding confirmed with domain mapping and functional reporter assay","pmids":["10435624"],"is_preprint":false},{"year":1999,"finding":"IκB-α physically interacts with HOXB7 via its ankyrin repeats and C-terminal domain (binding HOXB7 N-terminal domain) and markedly increases HOXB7-dependent transcription from a homeodomain consensus reporter, revealing IκB-α as a positive co-regulator of homeodomain protein transcriptional activity.","method":"In vitro binding assay, co-immunoprecipitation, transient transfection reporter assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal binding and functional reporter, single lab","pmids":["10026139"],"is_preprint":false},{"year":2001,"finding":"Mutations in the Pbx-binding pentapeptide motif or the DNA-binding homeodomain abolish HOXB7's ability to inhibit G-CSF-induced myeloid differentiation; mutations at casein kinase II phosphorylation sites or deletion of the C-terminal glutamate-rich region or N-terminal 14 aa actually enhance differentiation, defining functional regions of HOXB7.","method":"Site-directed mutagenesis, stable retroviral transduction of 32D myeloid cells, G-CSF differentiation assay","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 1 — mutagenesis with defined cellular differentiation phenotype, single lab","pmids":["11290787"],"is_preprint":false},{"year":2011,"finding":"HOXB7 directly binds the EGFR promoter to enhance its transcription (demonstrated by ChIP and luciferase assay), rendering MCF-7 cells resistant to tamoxifen through cross-talk between EGFR signaling and ERα; HOXB7 is itself an ERα-responsive gene and its expression progressively increases with long-term tamoxifen treatment.","method":"ChIP, luciferase reporter assay, long-term tamoxifen treatment model, siRNA knockdown","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 — direct promoter binding by ChIP validated with luciferase assay, mechanistic link to resistance established","pmids":["21690342"],"is_preprint":false},{"year":2014,"finding":"HOXB7 directly binds and activates the TGFβ2 promoter (shown by luciferase and ChIP assays), upregulating TGFβ/SMAD3 signaling to promote breast cancer cell migration, invasion, and lung metastasis; HOXB7 also induces M2 tumor-associated macrophage recruitment via TGFβ2.","method":"Luciferase reporter assay, ChIP, TGFβ2 siRNA/pharmacologic inhibition, xenograft lung metastasis model, MMTV transgenic mice","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 1–2 — direct promoter binding by ChIP plus luciferase validation, functional rescue with TGFβ2 knockdown/inhibition, in vivo metastasis model","pmids":["25542862"],"is_preprint":false},{"year":2015,"finding":"HOXB7 physically interacts with ERα (demonstrated by ChIP and co-immunoprecipitation); the HOXB7-ERα complex enhances transcription of multiple ERα target genes including HER2; MYC (stabilized by EGFR-HER2 signaling phosphorylation) inhibits miR-196a transcription, relieving repression of HOXB7 to form a MYC-HOXB7-HER2 positive feedback loop in tamoxifen-resistant breast cancer.","method":"ChIP, co-immunoprecipitation, luciferase reporter assay, MYC small-molecule inhibitors, xenograft regression","journal":"Cancer discovery","confidence":"High","confidence_rationale":"Tier 1–2 — reciprocal ChIP and co-IP, pharmacologic rescue in vivo, multiple orthogonal methods","pmids":["26180042"],"is_preprint":false},{"year":2012,"finding":"PARP-1 physically interacts with HOXB7 via the HOXB7 homeodomain and PARP-1 first zinc finger domain; PARP-1 poly(ADP-ribosyl)ates HOXB7, primarily on the C-terminal glutamate-rich tail, reducing HOXB7 transcriptional activity; deletion of the Glu-rich tail abolishes ADP-ribosylation and renders HOXB7 more transcriptionally active.","method":"Co-immunoprecipitation, GST pull-down, ADP-ribosylation assay, deletion mutagenesis, luciferase reporter assay","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 — in vitro biochemical assay plus mutagenesis plus functional reporter, multiple orthogonal methods","pmids":["22844406"],"is_preprint":false},{"year":2003,"finding":"The HOXB7 promoter is regulated by direct binding of NF-Y, YY1, Sp1/Sp3, and USF-1 transcription factors; site-specific mutagenesis of their binding sites reduced HOXB7 promoter activity by 55–78%.","method":"Electrophoretic mobility shift assay (EMSA), cell transfection, site-directed mutagenesis, reporter assay","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 1–2 — EMSA plus functional mutagenesis in cell transfection, single lab","pmids":["12697323"],"is_preprint":false},{"year":2013,"finding":"HOXB7 forms a dimer with PBX2 that acts as a positive transcriptional regulator of oncogenic miR-221 and miR-222; disruption of HOXB7/PBX2 dimers (by HXR9 peptide) reduces miR-221/222 transcription and elevates c-FOS expression, leading to melanoma cell death.","method":"HXR9 peptide (HOX/PBX dimerization antagonist), luciferase reporter, ChIP, cell death assays in melanoma cell lines","journal":"International journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacologic disruption of complex with functional downstream pathway readout, single lab","pmids":["23400877"],"is_preprint":false},{"year":2008,"finding":"Oncogenic HOXB7 activity in breast cancer cells requires TALE cofactors; HOXB7 increases expression of Pbx2 and Prep1 while decreasing Pbx1; a dominant-negative Pbx1 mutant (Pbx1NT) sequesters Prep1 in the cytoplasm, reducing tumorigenic properties of HOXB7-transduced cells and increasing apoptosis, p16, and p53.","method":"Retroviral transduction, dominant-negative mutant, in vitro and in vivo tumor assays, Western blot","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 — dominant-negative epistasis with in vivo validation, single lab","pmids":["18378073"],"is_preprint":false},{"year":1999,"finding":"Enforced HOXB7 expression in human hematopoietic stem/progenitor cells (HSCs/HPCs) promotes self-renewal and proliferation of primitive HPCs and putative HSCs, and specifically expands granulo-monocytic progenitors with sustained proliferation, suggesting a role in myeloid-biased progenitor expansion.","method":"Retroviral transduction of purified human peripheral blood HPCs, HPP-CFC assay, LTC-IC assay, clonogenic assay, liquid suspension culture","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 — clean gain-of-function with defined proliferative and differentiation phenotype readouts, single lab","pmids":["10208421"],"is_preprint":false},{"year":1998,"finding":"Hoxb7 expression in mammary epithelial cells is regulated by the extracellular matrix (ECM): culturing on a basement membrane induces Hoxb7 downregulation, indicating ECM-dependent transcriptional control of HOXB7 in the mammary gland.","method":"RT-PCR, cell culture on basement membrane vs. inert substratum (polyHEMA), comparison of mouse mammary epithelial cell lines","journal":"Journal of cellular biochemistry","confidence":"Low","confidence_rationale":"Tier 3 — single method (RT-PCR/culture condition), no molecular mechanism identified, single lab","pmids":["9620166"],"is_preprint":false},{"year":2010,"finding":"miR-196a directly represses HOXB7 mRNA and protein levels; reduced miR-196a in melanoma cells leads to elevated HOXB7, which induces Ets-1 activity via bFGF upregulation, ultimately driving BMP4 overexpression and enhanced melanoma cell migration.","method":"miR-196a mimic/inhibitor transfection, Western blot, reporter assay (implied), functional migration assay","journal":"Cellular and molecular life sciences","confidence":"Medium","confidence_rationale":"Tier 2 — gain and loss of miRNA function with ordered pathway validation, single lab","pmids":["20480203"],"is_preprint":false},{"year":2015,"finding":"During mesenchymal stromal cell (MSC) aging, miR-196a upregulation inversely correlates with HOXB7 expression; forced HOXB7 expression reduces senescence, improves proliferation and osteogenesis, and dramatically increases autocrine bFGF secretion, placing HOXB7 as a master regulator downstream of miR-196a in MSC aging.","method":"miR-196a overexpression, lentiviral HOXB7 overexpression, proliferation/senescence/osteogenesis assays, bFGF ELISA, in vivo skeletal aging model in mice","journal":"Stem cells","confidence":"Medium","confidence_rationale":"Tier 2 — multiple functional assays with in vivo validation, single lab","pmids":["25428821"],"is_preprint":false},{"year":2017,"finding":"HOXB7 localizes to cell membrane protrusions in migrating pancreatic cancer cells; HOXB7 knockdown reduces protrusions and decreases ERK1/2 phosphorylation without altering active Rho GTPase levels; HOXB7-driven ERK1/2 activation selectively stimulates JNK and HSP27 phosphorylation to promote cell motility and invasiveness.","method":"Immunocytochemistry (subcellular localization), siRNA knockdown, rescue construct, Western blot for phospho-ERK1/2/JNK/HSP27, motility and invasion assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — localization tied to functional consequence, loss-of-function with rescue, pathway specificity demonstrated, single lab","pmids":["28912272"],"is_preprint":false},{"year":2019,"finding":"HOXB7 interacts with Ku70, Ku80, and DNA-PKcs (confirmed by GST pull-down and co-immunoprecipitation) in esophageal squamous cell carcinoma cells; HOXB7 knockdown reduces expression of these DNA repair proteins, sensitizes cells to cisplatin, and causes S-phase arrest; the HXR9 peptide (HOXB7/PBX dimerization antagonist) synergistically enhances cisplatin sensitivity.","method":"GST pull-down, co-immunoprecipitation, immunofluorescent colocalization, siRNA knockdown, CCK8 assay, flow cytometry, in vivo tumor model","journal":"Thoracic cancer","confidence":"Medium","confidence_rationale":"Tier 2 — confirmed protein interactions with functional cisplatin sensitivity readout, replicates prior Ku70/80/DNA-PKcs binding finding","pmids":["31568655"],"is_preprint":false},{"year":2015,"finding":"Genome-wide ChIP-seq identified 1,504 HOXB7 chromatin binding sites in BT-474 breast cancer cells; 17 sites validated by ChIP-qPCR across multiple cell lines; direct HOXB7 target genes identified near binding sites include CTNND2 and SCGB1D2.","method":"ChIP-seq, ChIP-qPCR validation, gene expression analysis","journal":"International journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 — genome-wide ChIP-seq with qPCR validation, multi-cell-line confirmation, single lab","pmids":["26014856"],"is_preprint":false},{"year":2018,"finding":"HOXB7 upregulates LIN28B (a pluripotency factor and cancer gene) as a direct transcriptional target, sustaining cancer stem cell expansion; HOXB7 overexpression enhances reprogramming to iPSCs with efficiency comparable to LIN28B or c-MYC.","method":"ChIP (implied for direct target), gene expression profiling, iPSC reprogramming assay, stem cell marker analysis, siRNA knockdown","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 — direct target identification with functional reprogramming validation, single lab","pmids":["29576613"],"is_preprint":false},{"year":2000,"finding":"Overexpression of HOXB7 in multipotent C3H10T1/2 cells increases proliferation 3.5-fold and induces smooth muscle cell (SMC) differentiation (upregulating calponin and SM22α by 3–4-fold) without promoting osteogenic or chondrogenic lineages; HOXB7 expression was detected in human atherosclerotic plaques.","method":"Retroviral overexpression, semi-quantitative RT-PCR for SMC markers, cell morphology analysis, proliferation assay","journal":"Journal of cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — gain-of-function with lineage-specific marker readout, single lab","pmids":["10842316"],"is_preprint":false},{"year":1998,"finding":"Cis-acting regulatory elements within 3.5 kb upstream of Hoxb-7 cooperate to establish anterior-posterior restricted expression; deletion analysis identifies at least three control elements including one that confers Hox-like A-P expression boundaries in an orientation- and promoter-dependent manner in transgenic mice.","method":"Transgenic mouse reporter (lacZ), deletion analysis, in vivo expression analysis","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo transgenic deletion analysis with defined spatial expression phenotype, single lab","pmids":["8104144"],"is_preprint":false},{"year":1998,"finding":"In mice, Hoxb7 homozygous knockout causes first and second rib defects (12% penetrance); Hoxa7/Hoxb7 double knockouts show higher penetrance and increased expressivity of upper thoracic rib defects, demonstrating functional redundancy between paralogous Hox genes in axial skeletal patterning.","method":"Gene targeting/knockout in mice (Hoxa7-/- and Hoxb7-/-), skeletal analysis of double mutants","journal":"Mechanisms of development","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined skeletal phenotype, genetic epistasis via double mutant, replicated in two paralog knockouts","pmids":["9784603"],"is_preprint":false},{"year":2014,"finding":"TUG1 lncRNA, induced by p53, recruits PRC2 to the HOXB7 promoter; ChIP assays show EZH2 binds the HOXB7 locus and H3K27 trimethylation silences HOXB7 expression; TUG1 knockdown upregulates HOXB7, which in turn activates AKT and MAPK pathways to promote NSCLC proliferation.","method":"ChIP assay (EZH2 and H3K27me3 at HOXB7 promoter), luciferase assay (p53 binding to TUG1 promoter), siRNA knockdown, in vitro and in vivo proliferation assays","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP demonstrates direct epigenetic regulation of HOXB7 locus, functional downstream pathway validated, single lab","pmids":["24853421"],"is_preprint":false},{"year":1998,"finding":"Synergistic activation of the Purkinje cell-specific pcp-2(L7) gene promoter is achieved by co-expression of HoxB7 and HoxA5 acting on the L7ATE element; in contrast, En-2 represses the same promoter, demonstrating combinatorial homeodomain protein control of a neuron-specific gene.","method":"Cotransfection reporter assay in vitro, RT-PCR to confirm expression in cerebellar Purkinje cells","journal":"Journal of neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 — functional reporter assay with defined combinatorial transcriptional outcome, single lab","pmids":["9740027"],"is_preprint":false},{"year":2017,"finding":"HOXB7 knockdown in gastric cancer cells inhibits invasion and migration while activating HOXB7 overexpression promotes these phenotypes via downregulation of PTEN and activation of phospho-Akt signaling.","method":"siRNA knockdown, cDNA overexpression, Matrigel invasion and wound healing assays, Western blot for phospho-Akt and PTEN","journal":"Journal of gastroenterology and hepatology","confidence":"Low","confidence_rationale":"Tier 3 — Western blot pathway readout with knockdown/overexpression, no direct binding or promoter evidence, single lab","pmids":["26968988"],"is_preprint":false},{"year":2018,"finding":"HOXB7 knockdown in cutaneous squamous cell carcinoma cells inhibits Wnt/β-catenin pathway activation; co-immunoprecipitation demonstrates that endogenous HOXB7 physically binds β-catenin, linking HOXB7 to Wnt signaling in CSCC.","method":"Co-immunoprecipitation, siRNA knockdown, Western blot for Wnt pathway components, xenograft tumor model","journal":"American journal of physiology. Cell physiology","confidence":"Low","confidence_rationale":"Tier 3 — single co-IP for HOXB7/β-catenin interaction with downstream pathway readout, single lab","pmids":["30067384"],"is_preprint":false}],"current_model":"HOXB7 is a homeodomain transcription factor that directly binds specific promoter elements to transactivate target genes including bFGF, EGFR, and TGFβ2; it interacts with cofactors CBP (enhancing transactivation), IκB-α (co-activating), PBX2/PREP1 TALE proteins (required for oncogenic activity), and ERα (co-activating ER target genes including HER2); its activity is negatively regulated by PARP-1-mediated poly(ADP-ribosyl)ation of its C-terminal glutamate-rich tail; HOXB7 also directly interacts with DNA repair proteins Ku70, Ku80, and DNA-PKcs to enhance non-homologous end joining; at the cellular level, HOXB7 promotes EMT, angiogenesis, stem cell expansion (via LIN28B), myeloid progenitor self-renewal, and smooth muscle differentiation, while its own expression is epigenetically silenced by EZH2/PRC2-mediated H3K27 trimethylation and post-transcriptionally repressed by miR-196a/b."},"narrative":{"teleology":[{"year":1996,"claim":"Establishing that HOXB7 is a direct transcriptional activator of the bFGF gene resolved how a homeodomain protein could drive melanoma cell proliferation through a specific growth factor target.","evidence":"Band shift assay demonstrating direct DNA binding to bFGF promoter, cotransfection reporter assay, and antisense oligomer knockdown abolishing bFGF expression in melanoma cells","pmids":["8756643"],"confidence":"High","gaps":["Identity of additional direct HOXB7 target genes beyond bFGF was unknown","Whether bFGF is the sole mediator of HOXB7-driven proliferation was untested","Genome-wide binding profile not yet determined"]},{"year":1998,"claim":"Knockout studies in mice established that Hoxb7 has a developmental role in axial skeletal patterning, with functional redundancy with its paralog Hoxa7, grounding HOXB7 in classical Hox gene biology.","evidence":"Hoxb7-/- mice showing rib defects at 12% penetrance; Hoxa7/Hoxb7 double knockouts with increased penetrance and expressivity","pmids":["9784603"],"confidence":"High","gaps":["Low penetrance of single knockout leaves open whether additional paralogs compensate","No hematopoietic or oncogenic phenotype assessed in knockout mice"]},{"year":1999,"claim":"Discovery that CBP and IκB-α serve as HOXB7 cofactors established how HOXB7 transactivation is amplified, revealing that its activity depends on chromatin-modifying and signaling-associated coactivators.","evidence":"Co-immunoprecipitation and GST pull-down for CBP and IκB-α interactions; domain mapping; reporter assays showing enhanced transcriptional activity","pmids":["10435624","10026139"],"confidence":"High","gaps":["Whether CBP and IκB-α cooperate on the same promoters was not tested","Endogenous target gene regulation by these cofactors was not shown","IκB-α co-activation mechanism (non-NF-κB) remained unexplained"]},{"year":1999,"claim":"Demonstrating that HOXB7 expands primitive hematopoietic progenitors and promotes myeloid-biased self-renewal placed HOXB7 as a regulator of stem/progenitor cell fate decisions beyond solid tissues.","evidence":"Retroviral transduction of purified human HPCs with HPP-CFC and LTC-IC assays showing expanded myeloid progenitors","pmids":["10208421"],"confidence":"Medium","gaps":["Direct transcriptional targets mediating progenitor expansion were unknown","In vivo repopulation assays were not performed","Mechanism distinguishing self-renewal from differentiation block was unclear"]},{"year":2001,"claim":"Structure-function mutagenesis revealed that HOXB7's Pbx-binding pentapeptide and homeodomain are essential for blocking myeloid differentiation, while the C-terminal glutamate-rich region restrains its activity, defining functional domain architecture.","evidence":"Site-directed mutagenesis of HOXB7 domains in 32D myeloid cells with G-CSF differentiation assay","pmids":["11290787"],"confidence":"Medium","gaps":["Biochemical basis for C-terminal auto-inhibition was not resolved","Endogenous target genes mediating differentiation block were not identified"]},{"year":2001,"claim":"Showing that HOXB7 orchestrates a pro-angiogenic transcriptional program (VEGF, IL-8, angiopoietin-2) while suppressing angiopoietin-1 extended its role from single-target transactivation to coordinated regulation of tumor vascularization.","evidence":"Retroviral HOXB7 overexpression in breast cancer cells with gene expression profiling, in vitro angiogenesis coculture, and vascularized xenografts","pmids":["11522651"],"confidence":"Medium","gaps":["Direct vs. indirect transcriptional control of angiogenic targets was not distinguished","Whether bFGF mediates all angiogenic effects was untested"]},{"year":2006,"claim":"Establishing that HOXB7 induces EMT through bFGF-dependent Ras-MAPK activation resolved the signaling cascade linking a homeodomain transcription factor to mesenchymal transformation and invasion.","evidence":"HOXB7 overexpression in MCF10A/MDCK cells with pharmacologic FGF receptor and Ras-MAPK inhibitors reversing EMT; siRNA rescue; xenograft validation","pmids":["17018609"],"confidence":"High","gaps":["Whether HOXB7 activates EMT transcription factors (Snail, Twist) directly was unknown","Contribution of non-bFGF targets to EMT was not tested"]},{"year":2007,"claim":"Discovery that HOXB7 physically associates with the Ku70/Ku80/DNA-PKcs complex and enhances NHEJ revealed an unexpected non-transcriptional function in DNA double-strand break repair.","evidence":"GST pull-down and reciprocal co-immunoprecipitation identifying Ku70, Ku80, DNA-PKcs as partners; NHEJ repair assay in vitro and in vivo; siRNA knockdown","pmids":["17308091"],"confidence":"High","gaps":["Whether HOXB7 stimulates DNA-PKcs kinase activity or merely scaffolds the complex was unclear","Relative contribution of transcriptional vs. non-transcriptional mechanisms to radiation resistance was not separated"]},{"year":2008,"claim":"Showing that TALE cofactors PBX2/PREP1 are required for HOXB7 oncogenic activity established that HOXB7 does not act as a monomer in cancer but depends on heterodimeric cofactor complexes.","evidence":"Dominant-negative Pbx1 mutant sequestering Prep1 in cytoplasm and ablating HOXB7-driven tumorigenesis in vitro and in vivo","pmids":["18378073"],"confidence":"Medium","gaps":["Genome-wide identification of PBX2/HOXB7-co-occupied sites was not performed","Whether PBX2 selectivity over PBX1 reflects differential expression or binding affinity was unknown"]},{"year":2012,"claim":"Identifying PARP-1-mediated poly(ADP-ribosyl)ation of the HOXB7 C-terminal glutamate-rich tail as a negative regulatory mechanism explained the earlier observation that this tail restrains HOXB7 transcriptional activity.","evidence":"Co-IP, GST pull-down, in vitro ADP-ribosylation assay, deletion mutagenesis removing Glu-rich tail, luciferase reporter","pmids":["22844406"],"confidence":"High","gaps":["Whether PARP-1 regulation of HOXB7 occurs in physiological contexts (not just overexpression) was untested","Specific ADP-ribosylation sites on HOXB7 were not mapped at residue level"]},{"year":2011,"claim":"Demonstrating that HOXB7 directly binds the EGFR promoter to drive tamoxifen resistance revealed a second major direct transcriptional target and linked HOXB7 to endocrine therapy failure.","evidence":"ChIP and luciferase reporter assay in MCF-7 cells; long-term tamoxifen treatment model; siRNA knockdown restoring sensitivity","pmids":["21690342"],"confidence":"High","gaps":["Whether HOXB7 binds EGFR promoter as monomer or with PBX cofactors was not determined","Patient stratification by HOXB7 levels for tamoxifen response was not clinically validated"]},{"year":2014,"claim":"Identifying TGFβ2 as a direct HOXB7 target driving metastasis and M2 macrophage recruitment expanded HOXB7's role to tumor microenvironment remodeling beyond cell-autonomous effects.","evidence":"ChIP and luciferase validation at TGFβ2 promoter; TGFβ2 siRNA/inhibitor rescue; MMTV transgenic and xenograft lung metastasis models","pmids":["25542862"],"confidence":"High","gaps":["Whether HOXB7 directly transcribes macrophage chemoattractants beyond TGFβ2 was unknown","Contribution of TGFβ2-independent HOXB7 targets to metastasis was not quantified"]},{"year":2014,"claim":"Revealing that EZH2/PRC2-mediated H3K27me3 silences the HOXB7 locus (recruited by TUG1 lncRNA) established an epigenetic layer controlling HOXB7 expression upstream of its transcriptional and post-transcriptional regulators.","evidence":"ChIP assay showing EZH2 occupancy and H3K27me3 at HOXB7 promoter; TUG1 knockdown derepressing HOXB7; downstream AKT/MAPK activation in NSCLC","pmids":["24853421"],"confidence":"Medium","gaps":["Direct RNA-protein interaction between TUG1 and PRC2 at the HOXB7 locus was not demonstrated by RIP or CHART","Whether PRC2 regulation of HOXB7 is tissue-specific was not tested"]},{"year":2015,"claim":"Mapping 1,504 genome-wide HOXB7 binding sites by ChIP-seq provided the first unbiased view of HOXB7's chromatin occupancy, validating known targets and identifying new ones including CTNND2 and SCGB1D2.","evidence":"ChIP-seq in BT-474 cells with ChIP-qPCR validation across multiple breast cancer cell lines","pmids":["26014856"],"confidence":"Medium","gaps":["Functional validation of most binding sites was not performed","Cofactor co-occupancy (PBX2, ERα) at these sites was not assessed"]},{"year":2015,"claim":"Elucidation of the MYC–miR-196a–HOXB7–ERα–HER2 positive feedback loop explained how HOXB7 sustains tamoxifen resistance through physical interaction with ERα and co-activation of HER2 transcription.","evidence":"Reciprocal ChIP and co-IP for HOXB7-ERα; MYC inhibitor disrupting the loop; xenograft regression","pmids":["26180042"],"confidence":"High","gaps":["Structural basis of HOXB7-ERα interaction was not determined","Whether this feedback loop operates in other ER+ cancers beyond breast was untested"]},{"year":2018,"claim":"Identification of LIN28B as a direct HOXB7 transcriptional target linked HOXB7 to cancer stemness and cellular reprogramming, explaining its capacity to expand stem cell populations.","evidence":"HOXB7 overexpression driving LIN28B upregulation and iPSC reprogramming at efficiency comparable to LIN28B or c-MYC","pmids":["29576613"],"confidence":"Medium","gaps":["ChIP evidence for direct HOXB7 binding at LIN28B promoter was implied but not explicitly shown with full controls","Whether let-7 miRNA repression downstream of LIN28B mediates HOXB7's stemness effects was not tested"]},{"year":2019,"claim":"Replication of HOXB7–Ku70/Ku80/DNA-PKcs interaction in esophageal cancer cells and demonstration that disrupting HOXB7/PBX dimers sensitizes tumors to cisplatin reinforced the DNA repair function and established therapeutic relevance of targeting HOXB7 cofactor interactions.","evidence":"GST pull-down and co-IP confirming prior interaction findings; HXR9 peptide synergizing with cisplatin in vitro and in vivo","pmids":["31568655"],"confidence":"Medium","gaps":["Whether HOXB7 enhances repair of cisplatin-induced interstrand crosslinks specifically via NHEJ or other pathways was unclear","HXR9 peptide targets multiple HOX-PBX dimers, not HOXB7-specific"]},{"year":null,"claim":"The structural basis of HOXB7 interactions with ERα, DNA-PKcs, and PBX2, and the genome-wide identification of cofactor-dependent versus cofactor-independent HOXB7 target genes, remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No crystal or cryo-EM structure of HOXB7 in complex with any partner","Genome-wide cofactor co-occupancy studies (e.g., PBX2/ERα ChIP-seq) have not been performed alongside HOXB7 ChIP-seq","Relative contributions of transcriptional vs. non-transcriptional (NHEJ) functions to in vivo phenotypes are not separated"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[0,7,8,20]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,4,7,8,9,10,21]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[4,7,9,20]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[18]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,4,7,8,9,21]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[3,19]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,7,9,25]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[24]}],"complexes":["HOXB7-PBX2-PREP1","HOXB7-ERα","Ku70/Ku80/DNA-PKcs"],"partners":["CBP","PBX2","PREP1","ESR1","XRCC6","XRCC5","PRKDC","PARP1"],"other_free_text":[]},"mechanistic_narrative":"HOXB7 is a homeodomain transcription factor that drives cell proliferation, epithelial-mesenchymal transition, angiogenesis, DNA repair, and stem/progenitor cell expansion across multiple tissue contexts. It directly transactivates target gene promoters including bFGF, EGFR, TGFβ2, and LIN28B, acting through TALE cofactors PBX2/PREP1 and the coactivator CBP, while its transcriptional output is negatively regulated by PARP-1-mediated poly(ADP-ribosyl)ation of its C-terminal glutamate-rich tail [PMID:8756643, PMID:17018609, PMID:25542862, PMID:29576613, PMID:10435624, PMID:18378073, PMID:22844406]. Beyond transcriptional regulation, HOXB7 physically interacts with the Ku70/Ku80/DNA-PKcs complex to enhance non-homologous end joining, conferring resistance to DNA-damaging agents [PMID:17308091, PMID:31568655]. HOXB7 cooperates with ERα as a transcriptional co-activator at ER target genes including HER2, establishing a MYC–HOXB7–HER2 positive feedback loop that drives tamoxifen resistance in breast cancer, while its own expression is epigenetically silenced by EZH2/PRC2-mediated H3K27 trimethylation and post-transcriptionally repressed by miR-196a [PMID:26180042, PMID:21690342, PMID:24853421, PMID:20480203]."},"prefetch_data":{"uniprot":{"accession":"P09629","full_name":"Homeobox protein Hox-B7","aliases":["Homeobox protein HHO.C1","Homeobox protein Hox-2C"],"length_aa":217,"mass_kda":24.0,"function":"Sequence-specific transcription factor which is part of a developmental regulatory system that provides cells with specific positional identities on the anterior-posterior 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Hox2.3 homeobox-containing gene: regulation in differentiating pluripotent stem cells and expression pattern in embryos.","date":"1987","source":"Differentiation; research in biological diversity","url":"https://pubmed.ncbi.nlm.nih.gov/2892751","citation_count":25,"is_preprint":false},{"pmid":"2895022","id":"PMC_2895022","title":"A zebrafish homologue of the murine Hox-2.1 gene.","date":"1988","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/2895022","citation_count":25,"is_preprint":false},{"pmid":"30067384","id":"PMC_30067384","title":"Specific knockdown of HOXB7 inhibits cutaneous squamous cell carcinoma cell migration and invasion while inducing apoptosis via the Wnt/β-catenin signaling pathway.","date":"2018","source":"American journal of physiology. 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development","url":"https://pubmed.ncbi.nlm.nih.gov/1677811","citation_count":22,"is_preprint":false},{"pmid":"9740027","id":"PMC_9740027","title":"Regulation of a Purkinje cell-specific promoter by homeodomain proteins: repression by engrailed-2 vs. synergistic activation by Hoxa5 and Hoxb7.","date":"1998","source":"Journal of neurobiology","url":"https://pubmed.ncbi.nlm.nih.gov/9740027","citation_count":21,"is_preprint":false},{"pmid":"26307396","id":"PMC_26307396","title":"Upregulation of HOXB7 promotes the tumorigenesis and progression of gastric cancer and correlates with clinical characteristics.","date":"2015","source":"Tumour biology : the journal of the International Society for Oncodevelopmental Biology and Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/26307396","citation_count":20,"is_preprint":false},{"pmid":"22879911","id":"PMC_22879911","title":"Detection of IGF2BP3, HOXB7, and NEK2 mRNA expression in brush cytology specimens as a new diagnostic tool in patients with biliary strictures.","date":"2012","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/22879911","citation_count":20,"is_preprint":false},{"pmid":"8601038","id":"PMC_8601038","title":"Differential effects of retinoic acid and a retinoid antagonist on the spatial distribution of the homeoprotein Hoxb-7 in vertebrate embryos.","date":"1995","source":"Developmental dynamics : an official publication of the American Association of Anatomists","url":"https://pubmed.ncbi.nlm.nih.gov/8601038","citation_count":19,"is_preprint":false},{"pmid":"26135503","id":"PMC_26135503","title":"HOXB7-S3 inhibits the proliferation and invasion of MCF-7 human breast cancer cells.","date":"2015","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/26135503","citation_count":18,"is_preprint":false},{"pmid":"30951946","id":"PMC_30951946","title":"MicroRNA-384 is lowly expressed in human prostate cancer cells and has anti-tumor functions by acting on 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cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro DNA binding assay plus cotransfection reporter assay plus loss-of-function antisense, multiple orthogonal methods in single study\",\n      \"pmids\": [\"8756643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"HOXB7 upregulates multiple pro-angiogenic factors (VEGF, GROα/MGSA, IL-8, angiopoietin-2) and MMP-9 while abrogating angiopoietin-1, driving a tumor-associated angiogenic switch in breast cancer cells and promoting vascularized tumor formation in vivo.\",\n      \"method\": \"Gene expression profiling, retroviral transduction, in vitro coculture angiogenesis assay, xenograft in nude mice with CD31/CD34 immunostaining\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean gain-of-function with defined cellular and in vivo phenotype, single lab\",\n      \"pmids\": [\"11522651\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Overexpression of HOXB7 in epithelial cells induces epithelial-mesenchymal transition (EMT), upregulates bFGF, activates Ras and RhoA GTPases, increases phospho-ERK1/2 (MAPK), and promotes migration, invasion, and vascularized tumor formation; effects reversed by FGF receptor and Ras-MAPK inhibitors and by HOXB7-specific siRNA.\",\n      \"method\": \"Stable transfection/overexpression in MCF10A and MDCK cells, siRNA knockdown, Ras/RhoA activity assays, Western blot, xenograft in mice, pharmacologic inhibition\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods including gain-of-function, loss-of-function siRNA, pharmacologic rescue, and in vivo validation\",\n      \"pmids\": [\"17018609\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"HOXB7 physically interacts with the DNA-dependent protein kinase holoenzyme components Ku70, Ku80, and DNA-PKcs, and with PARP, identified by GST pull-down/affinity chromatography and confirmed by co-immunoprecipitation; HOXB7 expression enhances non-homologous end joining (NHEJ) DNA double-strand break repair in vitro and in vivo, conferring radiation resistance.\",\n      \"method\": \"GST pull-down, co-immunoprecipitation, NHEJ repair assay in vitro and in vivo, siRNA knockdown\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — reciprocal co-IP confirming GST pull-down partners, functional NHEJ assay with rescue experiment\",\n      \"pmids\": [\"17308091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"HOXB7 physically interacts with the coactivator CBP (CREB-binding protein) both in vitro and in vivo; this interaction requires the HOXB7 N-terminal domain and two C-terminal CBP domains, and enhances HOXB7 transactivation potential; histone deacetylase inhibition (trichostatin A) further augments HOXB7 transcriptional activity.\",\n      \"method\": \"Co-immunoprecipitation in vivo, GST pull-down in vitro, deletion/domain mapping, transient transfection reporter assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro and in vivo binding confirmed with domain mapping and functional reporter assay\",\n      \"pmids\": [\"10435624\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"IκB-α physically interacts with HOXB7 via its ankyrin repeats and C-terminal domain (binding HOXB7 N-terminal domain) and markedly increases HOXB7-dependent transcription from a homeodomain consensus reporter, revealing IκB-α as a positive co-regulator of homeodomain protein transcriptional activity.\",\n      \"method\": \"In vitro binding assay, co-immunoprecipitation, transient transfection reporter assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal binding and functional reporter, single lab\",\n      \"pmids\": [\"10026139\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Mutations in the Pbx-binding pentapeptide motif or the DNA-binding homeodomain abolish HOXB7's ability to inhibit G-CSF-induced myeloid differentiation; mutations at casein kinase II phosphorylation sites or deletion of the C-terminal glutamate-rich region or N-terminal 14 aa actually enhance differentiation, defining functional regions of HOXB7.\",\n      \"method\": \"Site-directed mutagenesis, stable retroviral transduction of 32D myeloid cells, G-CSF differentiation assay\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis with defined cellular differentiation phenotype, single lab\",\n      \"pmids\": [\"11290787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"HOXB7 directly binds the EGFR promoter to enhance its transcription (demonstrated by ChIP and luciferase assay), rendering MCF-7 cells resistant to tamoxifen through cross-talk between EGFR signaling and ERα; HOXB7 is itself an ERα-responsive gene and its expression progressively increases with long-term tamoxifen treatment.\",\n      \"method\": \"ChIP, luciferase reporter assay, long-term tamoxifen treatment model, siRNA knockdown\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct promoter binding by ChIP validated with luciferase assay, mechanistic link to resistance established\",\n      \"pmids\": [\"21690342\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"HOXB7 directly binds and activates the TGFβ2 promoter (shown by luciferase and ChIP assays), upregulating TGFβ/SMAD3 signaling to promote breast cancer cell migration, invasion, and lung metastasis; HOXB7 also induces M2 tumor-associated macrophage recruitment via TGFβ2.\",\n      \"method\": \"Luciferase reporter assay, ChIP, TGFβ2 siRNA/pharmacologic inhibition, xenograft lung metastasis model, MMTV transgenic mice\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct promoter binding by ChIP plus luciferase validation, functional rescue with TGFβ2 knockdown/inhibition, in vivo metastasis model\",\n      \"pmids\": [\"25542862\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"HOXB7 physically interacts with ERα (demonstrated by ChIP and co-immunoprecipitation); the HOXB7-ERα complex enhances transcription of multiple ERα target genes including HER2; MYC (stabilized by EGFR-HER2 signaling phosphorylation) inhibits miR-196a transcription, relieving repression of HOXB7 to form a MYC-HOXB7-HER2 positive feedback loop in tamoxifen-resistant breast cancer.\",\n      \"method\": \"ChIP, co-immunoprecipitation, luciferase reporter assay, MYC small-molecule inhibitors, xenograft regression\",\n      \"journal\": \"Cancer discovery\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — reciprocal ChIP and co-IP, pharmacologic rescue in vivo, multiple orthogonal methods\",\n      \"pmids\": [\"26180042\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PARP-1 physically interacts with HOXB7 via the HOXB7 homeodomain and PARP-1 first zinc finger domain; PARP-1 poly(ADP-ribosyl)ates HOXB7, primarily on the C-terminal glutamate-rich tail, reducing HOXB7 transcriptional activity; deletion of the Glu-rich tail abolishes ADP-ribosylation and renders HOXB7 more transcriptionally active.\",\n      \"method\": \"Co-immunoprecipitation, GST pull-down, ADP-ribosylation assay, deletion mutagenesis, luciferase reporter assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro biochemical assay plus mutagenesis plus functional reporter, multiple orthogonal methods\",\n      \"pmids\": [\"22844406\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The HOXB7 promoter is regulated by direct binding of NF-Y, YY1, Sp1/Sp3, and USF-1 transcription factors; site-specific mutagenesis of their binding sites reduced HOXB7 promoter activity by 55–78%.\",\n      \"method\": \"Electrophoretic mobility shift assay (EMSA), cell transfection, site-directed mutagenesis, reporter assay\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 — EMSA plus functional mutagenesis in cell transfection, single lab\",\n      \"pmids\": [\"12697323\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"HOXB7 forms a dimer with PBX2 that acts as a positive transcriptional regulator of oncogenic miR-221 and miR-222; disruption of HOXB7/PBX2 dimers (by HXR9 peptide) reduces miR-221/222 transcription and elevates c-FOS expression, leading to melanoma cell death.\",\n      \"method\": \"HXR9 peptide (HOX/PBX dimerization antagonist), luciferase reporter, ChIP, cell death assays in melanoma cell lines\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacologic disruption of complex with functional downstream pathway readout, single lab\",\n      \"pmids\": [\"23400877\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Oncogenic HOXB7 activity in breast cancer cells requires TALE cofactors; HOXB7 increases expression of Pbx2 and Prep1 while decreasing Pbx1; a dominant-negative Pbx1 mutant (Pbx1NT) sequesters Prep1 in the cytoplasm, reducing tumorigenic properties of HOXB7-transduced cells and increasing apoptosis, p16, and p53.\",\n      \"method\": \"Retroviral transduction, dominant-negative mutant, in vitro and in vivo tumor assays, Western blot\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — dominant-negative epistasis with in vivo validation, single lab\",\n      \"pmids\": [\"18378073\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Enforced HOXB7 expression in human hematopoietic stem/progenitor cells (HSCs/HPCs) promotes self-renewal and proliferation of primitive HPCs and putative HSCs, and specifically expands granulo-monocytic progenitors with sustained proliferation, suggesting a role in myeloid-biased progenitor expansion.\",\n      \"method\": \"Retroviral transduction of purified human peripheral blood HPCs, HPP-CFC assay, LTC-IC assay, clonogenic assay, liquid suspension culture\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean gain-of-function with defined proliferative and differentiation phenotype readouts, single lab\",\n      \"pmids\": [\"10208421\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Hoxb7 expression in mammary epithelial cells is regulated by the extracellular matrix (ECM): culturing on a basement membrane induces Hoxb7 downregulation, indicating ECM-dependent transcriptional control of HOXB7 in the mammary gland.\",\n      \"method\": \"RT-PCR, cell culture on basement membrane vs. inert substratum (polyHEMA), comparison of mouse mammary epithelial cell lines\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single method (RT-PCR/culture condition), no molecular mechanism identified, single lab\",\n      \"pmids\": [\"9620166\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"miR-196a directly represses HOXB7 mRNA and protein levels; reduced miR-196a in melanoma cells leads to elevated HOXB7, which induces Ets-1 activity via bFGF upregulation, ultimately driving BMP4 overexpression and enhanced melanoma cell migration.\",\n      \"method\": \"miR-196a mimic/inhibitor transfection, Western blot, reporter assay (implied), functional migration assay\",\n      \"journal\": \"Cellular and molecular life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — gain and loss of miRNA function with ordered pathway validation, single lab\",\n      \"pmids\": [\"20480203\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"During mesenchymal stromal cell (MSC) aging, miR-196a upregulation inversely correlates with HOXB7 expression; forced HOXB7 expression reduces senescence, improves proliferation and osteogenesis, and dramatically increases autocrine bFGF secretion, placing HOXB7 as a master regulator downstream of miR-196a in MSC aging.\",\n      \"method\": \"miR-196a overexpression, lentiviral HOXB7 overexpression, proliferation/senescence/osteogenesis assays, bFGF ELISA, in vivo skeletal aging model in mice\",\n      \"journal\": \"Stem cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple functional assays with in vivo validation, single lab\",\n      \"pmids\": [\"25428821\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"HOXB7 localizes to cell membrane protrusions in migrating pancreatic cancer cells; HOXB7 knockdown reduces protrusions and decreases ERK1/2 phosphorylation without altering active Rho GTPase levels; HOXB7-driven ERK1/2 activation selectively stimulates JNK and HSP27 phosphorylation to promote cell motility and invasiveness.\",\n      \"method\": \"Immunocytochemistry (subcellular localization), siRNA knockdown, rescue construct, Western blot for phospho-ERK1/2/JNK/HSP27, motility and invasion assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — localization tied to functional consequence, loss-of-function with rescue, pathway specificity demonstrated, single lab\",\n      \"pmids\": [\"28912272\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HOXB7 interacts with Ku70, Ku80, and DNA-PKcs (confirmed by GST pull-down and co-immunoprecipitation) in esophageal squamous cell carcinoma cells; HOXB7 knockdown reduces expression of these DNA repair proteins, sensitizes cells to cisplatin, and causes S-phase arrest; the HXR9 peptide (HOXB7/PBX dimerization antagonist) synergistically enhances cisplatin sensitivity.\",\n      \"method\": \"GST pull-down, co-immunoprecipitation, immunofluorescent colocalization, siRNA knockdown, CCK8 assay, flow cytometry, in vivo tumor model\",\n      \"journal\": \"Thoracic cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — confirmed protein interactions with functional cisplatin sensitivity readout, replicates prior Ku70/80/DNA-PKcs binding finding\",\n      \"pmids\": [\"31568655\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Genome-wide ChIP-seq identified 1,504 HOXB7 chromatin binding sites in BT-474 breast cancer cells; 17 sites validated by ChIP-qPCR across multiple cell lines; direct HOXB7 target genes identified near binding sites include CTNND2 and SCGB1D2.\",\n      \"method\": \"ChIP-seq, ChIP-qPCR validation, gene expression analysis\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genome-wide ChIP-seq with qPCR validation, multi-cell-line confirmation, single lab\",\n      \"pmids\": [\"26014856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"HOXB7 upregulates LIN28B (a pluripotency factor and cancer gene) as a direct transcriptional target, sustaining cancer stem cell expansion; HOXB7 overexpression enhances reprogramming to iPSCs with efficiency comparable to LIN28B or c-MYC.\",\n      \"method\": \"ChIP (implied for direct target), gene expression profiling, iPSC reprogramming assay, stem cell marker analysis, siRNA knockdown\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct target identification with functional reprogramming validation, single lab\",\n      \"pmids\": [\"29576613\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Overexpression of HOXB7 in multipotent C3H10T1/2 cells increases proliferation 3.5-fold and induces smooth muscle cell (SMC) differentiation (upregulating calponin and SM22α by 3–4-fold) without promoting osteogenic or chondrogenic lineages; HOXB7 expression was detected in human atherosclerotic plaques.\",\n      \"method\": \"Retroviral overexpression, semi-quantitative RT-PCR for SMC markers, cell morphology analysis, proliferation assay\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — gain-of-function with lineage-specific marker readout, single lab\",\n      \"pmids\": [\"10842316\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Cis-acting regulatory elements within 3.5 kb upstream of Hoxb-7 cooperate to establish anterior-posterior restricted expression; deletion analysis identifies at least three control elements including one that confers Hox-like A-P expression boundaries in an orientation- and promoter-dependent manner in transgenic mice.\",\n      \"method\": \"Transgenic mouse reporter (lacZ), deletion analysis, in vivo expression analysis\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo transgenic deletion analysis with defined spatial expression phenotype, single lab\",\n      \"pmids\": [\"8104144\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"In mice, Hoxb7 homozygous knockout causes first and second rib defects (12% penetrance); Hoxa7/Hoxb7 double knockouts show higher penetrance and increased expressivity of upper thoracic rib defects, demonstrating functional redundancy between paralogous Hox genes in axial skeletal patterning.\",\n      \"method\": \"Gene targeting/knockout in mice (Hoxa7-/- and Hoxb7-/-), skeletal analysis of double mutants\",\n      \"journal\": \"Mechanisms of development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined skeletal phenotype, genetic epistasis via double mutant, replicated in two paralog knockouts\",\n      \"pmids\": [\"9784603\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TUG1 lncRNA, induced by p53, recruits PRC2 to the HOXB7 promoter; ChIP assays show EZH2 binds the HOXB7 locus and H3K27 trimethylation silences HOXB7 expression; TUG1 knockdown upregulates HOXB7, which in turn activates AKT and MAPK pathways to promote NSCLC proliferation.\",\n      \"method\": \"ChIP assay (EZH2 and H3K27me3 at HOXB7 promoter), luciferase assay (p53 binding to TUG1 promoter), siRNA knockdown, in vitro and in vivo proliferation assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP demonstrates direct epigenetic regulation of HOXB7 locus, functional downstream pathway validated, single lab\",\n      \"pmids\": [\"24853421\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Synergistic activation of the Purkinje cell-specific pcp-2(L7) gene promoter is achieved by co-expression of HoxB7 and HoxA5 acting on the L7ATE element; in contrast, En-2 represses the same promoter, demonstrating combinatorial homeodomain protein control of a neuron-specific gene.\",\n      \"method\": \"Cotransfection reporter assay in vitro, RT-PCR to confirm expression in cerebellar Purkinje cells\",\n      \"journal\": \"Journal of neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional reporter assay with defined combinatorial transcriptional outcome, single lab\",\n      \"pmids\": [\"9740027\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"HOXB7 knockdown in gastric cancer cells inhibits invasion and migration while activating HOXB7 overexpression promotes these phenotypes via downregulation of PTEN and activation of phospho-Akt signaling.\",\n      \"method\": \"siRNA knockdown, cDNA overexpression, Matrigel invasion and wound healing assays, Western blot for phospho-Akt and PTEN\",\n      \"journal\": \"Journal of gastroenterology and hepatology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — Western blot pathway readout with knockdown/overexpression, no direct binding or promoter evidence, single lab\",\n      \"pmids\": [\"26968988\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"HOXB7 knockdown in cutaneous squamous cell carcinoma cells inhibits Wnt/β-catenin pathway activation; co-immunoprecipitation demonstrates that endogenous HOXB7 physically binds β-catenin, linking HOXB7 to Wnt signaling in CSCC.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, Western blot for Wnt pathway components, xenograft tumor model\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single co-IP for HOXB7/β-catenin interaction with downstream pathway readout, single lab\",\n      \"pmids\": [\"30067384\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HOXB7 is a homeodomain transcription factor that directly binds specific promoter elements to transactivate target genes including bFGF, EGFR, and TGFβ2; it interacts with cofactors CBP (enhancing transactivation), IκB-α (co-activating), PBX2/PREP1 TALE proteins (required for oncogenic activity), and ERα (co-activating ER target genes including HER2); its activity is negatively regulated by PARP-1-mediated poly(ADP-ribosyl)ation of its C-terminal glutamate-rich tail; HOXB7 also directly interacts with DNA repair proteins Ku70, Ku80, and DNA-PKcs to enhance non-homologous end joining; at the cellular level, HOXB7 promotes EMT, angiogenesis, stem cell expansion (via LIN28B), myeloid progenitor self-renewal, and smooth muscle differentiation, while its own expression is epigenetically silenced by EZH2/PRC2-mediated H3K27 trimethylation and post-transcriptionally repressed by miR-196a/b.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"HOXB7 is a homeodomain transcription factor that drives cell proliferation, epithelial-mesenchymal transition, angiogenesis, DNA repair, and stem/progenitor cell expansion across multiple tissue contexts. It directly transactivates target gene promoters including bFGF, EGFR, TGFβ2, and LIN28B, acting through TALE cofactors PBX2/PREP1 and the coactivator CBP, while its transcriptional output is negatively regulated by PARP-1-mediated poly(ADP-ribosyl)ation of its C-terminal glutamate-rich tail [PMID:8756643, PMID:17018609, PMID:25542862, PMID:29576613, PMID:10435624, PMID:18378073, PMID:22844406]. Beyond transcriptional regulation, HOXB7 physically interacts with the Ku70/Ku80/DNA-PKcs complex to enhance non-homologous end joining, conferring resistance to DNA-damaging agents [PMID:17308091, PMID:31568655]. HOXB7 cooperates with ERα as a transcriptional co-activator at ER target genes including HER2, establishing a MYC–HOXB7–HER2 positive feedback loop that drives tamoxifen resistance in breast cancer, while its own expression is epigenetically silenced by EZH2/PRC2-mediated H3K27 trimethylation and post-transcriptionally repressed by miR-196a [PMID:26180042, PMID:21690342, PMID:24853421, PMID:20480203].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Establishing that HOXB7 is a direct transcriptional activator of the bFGF gene resolved how a homeodomain protein could drive melanoma cell proliferation through a specific growth factor target.\",\n      \"evidence\": \"Band shift assay demonstrating direct DNA binding to bFGF promoter, cotransfection reporter assay, and antisense oligomer knockdown abolishing bFGF expression in melanoma cells\",\n      \"pmids\": [\"8756643\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of additional direct HOXB7 target genes beyond bFGF was unknown\", \"Whether bFGF is the sole mediator of HOXB7-driven proliferation was untested\", \"Genome-wide binding profile not yet determined\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Knockout studies in mice established that Hoxb7 has a developmental role in axial skeletal patterning, with functional redundancy with its paralog Hoxa7, grounding HOXB7 in classical Hox gene biology.\",\n      \"evidence\": \"Hoxb7-/- mice showing rib defects at 12% penetrance; Hoxa7/Hoxb7 double knockouts with increased penetrance and expressivity\",\n      \"pmids\": [\"9784603\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Low penetrance of single knockout leaves open whether additional paralogs compensate\", \"No hematopoietic or oncogenic phenotype assessed in knockout mice\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Discovery that CBP and IκB-α serve as HOXB7 cofactors established how HOXB7 transactivation is amplified, revealing that its activity depends on chromatin-modifying and signaling-associated coactivators.\",\n      \"evidence\": \"Co-immunoprecipitation and GST pull-down for CBP and IκB-α interactions; domain mapping; reporter assays showing enhanced transcriptional activity\",\n      \"pmids\": [\"10435624\", \"10026139\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CBP and IκB-α cooperate on the same promoters was not tested\", \"Endogenous target gene regulation by these cofactors was not shown\", \"IκB-α co-activation mechanism (non-NF-κB) remained unexplained\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Demonstrating that HOXB7 expands primitive hematopoietic progenitors and promotes myeloid-biased self-renewal placed HOXB7 as a regulator of stem/progenitor cell fate decisions beyond solid tissues.\",\n      \"evidence\": \"Retroviral transduction of purified human HPCs with HPP-CFC and LTC-IC assays showing expanded myeloid progenitors\",\n      \"pmids\": [\"10208421\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct transcriptional targets mediating progenitor expansion were unknown\", \"In vivo repopulation assays were not performed\", \"Mechanism distinguishing self-renewal from differentiation block was unclear\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Structure-function mutagenesis revealed that HOXB7's Pbx-binding pentapeptide and homeodomain are essential for blocking myeloid differentiation, while the C-terminal glutamate-rich region restrains its activity, defining functional domain architecture.\",\n      \"evidence\": \"Site-directed mutagenesis of HOXB7 domains in 32D myeloid cells with G-CSF differentiation assay\",\n      \"pmids\": [\"11290787\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Biochemical basis for C-terminal auto-inhibition was not resolved\", \"Endogenous target genes mediating differentiation block were not identified\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Showing that HOXB7 orchestrates a pro-angiogenic transcriptional program (VEGF, IL-8, angiopoietin-2) while suppressing angiopoietin-1 extended its role from single-target transactivation to coordinated regulation of tumor vascularization.\",\n      \"evidence\": \"Retroviral HOXB7 overexpression in breast cancer cells with gene expression profiling, in vitro angiogenesis coculture, and vascularized xenografts\",\n      \"pmids\": [\"11522651\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs. indirect transcriptional control of angiogenic targets was not distinguished\", \"Whether bFGF mediates all angiogenic effects was untested\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Establishing that HOXB7 induces EMT through bFGF-dependent Ras-MAPK activation resolved the signaling cascade linking a homeodomain transcription factor to mesenchymal transformation and invasion.\",\n      \"evidence\": \"HOXB7 overexpression in MCF10A/MDCK cells with pharmacologic FGF receptor and Ras-MAPK inhibitors reversing EMT; siRNA rescue; xenograft validation\",\n      \"pmids\": [\"17018609\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether HOXB7 activates EMT transcription factors (Snail, Twist) directly was unknown\", \"Contribution of non-bFGF targets to EMT was not tested\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Discovery that HOXB7 physically associates with the Ku70/Ku80/DNA-PKcs complex and enhances NHEJ revealed an unexpected non-transcriptional function in DNA double-strand break repair.\",\n      \"evidence\": \"GST pull-down and reciprocal co-immunoprecipitation identifying Ku70, Ku80, DNA-PKcs as partners; NHEJ repair assay in vitro and in vivo; siRNA knockdown\",\n      \"pmids\": [\"17308091\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether HOXB7 stimulates DNA-PKcs kinase activity or merely scaffolds the complex was unclear\", \"Relative contribution of transcriptional vs. non-transcriptional mechanisms to radiation resistance was not separated\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Showing that TALE cofactors PBX2/PREP1 are required for HOXB7 oncogenic activity established that HOXB7 does not act as a monomer in cancer but depends on heterodimeric cofactor complexes.\",\n      \"evidence\": \"Dominant-negative Pbx1 mutant sequestering Prep1 in cytoplasm and ablating HOXB7-driven tumorigenesis in vitro and in vivo\",\n      \"pmids\": [\"18378073\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Genome-wide identification of PBX2/HOXB7-co-occupied sites was not performed\", \"Whether PBX2 selectivity over PBX1 reflects differential expression or binding affinity was unknown\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identifying PARP-1-mediated poly(ADP-ribosyl)ation of the HOXB7 C-terminal glutamate-rich tail as a negative regulatory mechanism explained the earlier observation that this tail restrains HOXB7 transcriptional activity.\",\n      \"evidence\": \"Co-IP, GST pull-down, in vitro ADP-ribosylation assay, deletion mutagenesis removing Glu-rich tail, luciferase reporter\",\n      \"pmids\": [\"22844406\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PARP-1 regulation of HOXB7 occurs in physiological contexts (not just overexpression) was untested\", \"Specific ADP-ribosylation sites on HOXB7 were not mapped at residue level\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstrating that HOXB7 directly binds the EGFR promoter to drive tamoxifen resistance revealed a second major direct transcriptional target and linked HOXB7 to endocrine therapy failure.\",\n      \"evidence\": \"ChIP and luciferase reporter assay in MCF-7 cells; long-term tamoxifen treatment model; siRNA knockdown restoring sensitivity\",\n      \"pmids\": [\"21690342\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether HOXB7 binds EGFR promoter as monomer or with PBX cofactors was not determined\", \"Patient stratification by HOXB7 levels for tamoxifen response was not clinically validated\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identifying TGFβ2 as a direct HOXB7 target driving metastasis and M2 macrophage recruitment expanded HOXB7's role to tumor microenvironment remodeling beyond cell-autonomous effects.\",\n      \"evidence\": \"ChIP and luciferase validation at TGFβ2 promoter; TGFβ2 siRNA/inhibitor rescue; MMTV transgenic and xenograft lung metastasis models\",\n      \"pmids\": [\"25542862\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether HOXB7 directly transcribes macrophage chemoattractants beyond TGFβ2 was unknown\", \"Contribution of TGFβ2-independent HOXB7 targets to metastasis was not quantified\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Revealing that EZH2/PRC2-mediated H3K27me3 silences the HOXB7 locus (recruited by TUG1 lncRNA) established an epigenetic layer controlling HOXB7 expression upstream of its transcriptional and post-transcriptional regulators.\",\n      \"evidence\": \"ChIP assay showing EZH2 occupancy and H3K27me3 at HOXB7 promoter; TUG1 knockdown derepressing HOXB7; downstream AKT/MAPK activation in NSCLC\",\n      \"pmids\": [\"24853421\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct RNA-protein interaction between TUG1 and PRC2 at the HOXB7 locus was not demonstrated by RIP or CHART\", \"Whether PRC2 regulation of HOXB7 is tissue-specific was not tested\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Mapping 1,504 genome-wide HOXB7 binding sites by ChIP-seq provided the first unbiased view of HOXB7's chromatin occupancy, validating known targets and identifying new ones including CTNND2 and SCGB1D2.\",\n      \"evidence\": \"ChIP-seq in BT-474 cells with ChIP-qPCR validation across multiple breast cancer cell lines\",\n      \"pmids\": [\"26014856\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional validation of most binding sites was not performed\", \"Cofactor co-occupancy (PBX2, ERα) at these sites was not assessed\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Elucidation of the MYC–miR-196a–HOXB7–ERα–HER2 positive feedback loop explained how HOXB7 sustains tamoxifen resistance through physical interaction with ERα and co-activation of HER2 transcription.\",\n      \"evidence\": \"Reciprocal ChIP and co-IP for HOXB7-ERα; MYC inhibitor disrupting the loop; xenograft regression\",\n      \"pmids\": [\"26180042\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of HOXB7-ERα interaction was not determined\", \"Whether this feedback loop operates in other ER+ cancers beyond breast was untested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identification of LIN28B as a direct HOXB7 transcriptional target linked HOXB7 to cancer stemness and cellular reprogramming, explaining its capacity to expand stem cell populations.\",\n      \"evidence\": \"HOXB7 overexpression driving LIN28B upregulation and iPSC reprogramming at efficiency comparable to LIN28B or c-MYC\",\n      \"pmids\": [\"29576613\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"ChIP evidence for direct HOXB7 binding at LIN28B promoter was implied but not explicitly shown with full controls\", \"Whether let-7 miRNA repression downstream of LIN28B mediates HOXB7's stemness effects was not tested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Replication of HOXB7–Ku70/Ku80/DNA-PKcs interaction in esophageal cancer cells and demonstration that disrupting HOXB7/PBX dimers sensitizes tumors to cisplatin reinforced the DNA repair function and established therapeutic relevance of targeting HOXB7 cofactor interactions.\",\n      \"evidence\": \"GST pull-down and co-IP confirming prior interaction findings; HXR9 peptide synergizing with cisplatin in vitro and in vivo\",\n      \"pmids\": [\"31568655\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether HOXB7 enhances repair of cisplatin-induced interstrand crosslinks specifically via NHEJ or other pathways was unclear\", \"HXR9 peptide targets multiple HOX-PBX dimers, not HOXB7-specific\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis of HOXB7 interactions with ERα, DNA-PKcs, and PBX2, and the genome-wide identification of cofactor-dependent versus cofactor-independent HOXB7 target genes, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No crystal or cryo-EM structure of HOXB7 in complex with any partner\", \"Genome-wide cofactor co-occupancy studies (e.g., PBX2/ERα ChIP-seq) have not been performed alongside HOXB7 ChIP-seq\", \"Relative contributions of transcriptional vs. non-transcriptional (NHEJ) functions to in vivo phenotypes are not separated\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [0, 7, 8, 20]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 4, 7, 8, 9, 10, 21]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [4, 7, 9, 20]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [18]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 4, 7, 8, 9, 21]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [3, 19]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 7, 9, 25]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [24]}\n    ],\n    \"complexes\": [\n      \"HOXB7-PBX2-PREP1\",\n      \"HOXB7-ERα\",\n      \"Ku70/Ku80/DNA-PKcs\"\n    ],\n    \"partners\": [\n      \"CBP\",\n      \"PBX2\",\n      \"PREP1\",\n      \"ESR1\",\n      \"XRCC6\",\n      \"XRCC5\",\n      \"PRKDC\",\n      \"PARP1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}