Biology subjects

Jin, X.

Publications and source records attributed to Jin, X..

At least 55 records · Page 3Linked to original sources

bioRxiv2025

HypoxamicroRNA-210 protects against hepatic steatosis by inhibiting CIDEC expression

Background and AimsMetabolic dysfunction-associated steatotic liver disease (MASLD) is a major global health burden. Although hypoxia is known to contribute to MASLD pathogenesis, the role of hypoxia signaling remains poorly defined. We investigated whether HypoxamicroRNA-210 (miR-210), a key hypoxia-inducible microRNA, regulates hepatic lipid metabolism and MASLD development. MethodsSerum miR-210 levels were quantified in MASLD patients and matched controls. Human hepatic spheroids and HepG2 cells were exposed to fatty acids to assess miR-210 induction and lipid accumulation. miR-210 knockout mice were fed a Western diet to evaluate hepatic steatosis and transcriptomic changes using RNA sequencing. RNA pull-down and 3UTR-driven luciferase reporter assays were employed to identify miR-210 targets. Functional effects of miR-210 mimic were examined in knockout mice, db/db mice, and in vitro human hepatic spheroid models. ResultsSerum miR-210 levels were significantly reduced in MASLD patients compared with matched controls. Consistently, human hepatic spheroids did not appropriately increase miR-210 expression in response to fatty acid-induced intracellular hypoxia. This blunted miR-210 response contributed to hepatic lipid accumulation, as loss of miR-210 in a mouse model of MASLD led to increased hepatic lipid deposition and activation of lipid metabolic pathways. We identified CIDEC as a direct miR-210 target mediating its inhibitory effects on hepatic lipid accumulation, and restoring miR-210 expression suppressed CIDEC and reduced hepatic lipid content in knockout mice on a Western diet. Moreover, miR-210 attenuated lipid accumulation in both in vitro human hepatic spheroids and in vivo db/db mice models of MASLD. ConclusionsmiR-210 protects against hepatic steatosis by inhibiting CIDEC expression, suggesting miR-210-CIDEC axis as a promising therapeutic target for reducing hepatic lipid accumulation and preventing MASLD progression. Impact and ImplicationsThis study addresses a critical gap in understanding how hypoxia signaling shapes MASLD and uncovers a novel pathogenic mechanism of hepatic steatosis arising from fatty acids-induced dysregulation of miR-210. Impaired hypoxia responses, via blunted miR-210 induction, contribute to hepatic lipid accumulation through upregulation of CIDEC, a newly identified target of miR-210. These findings establish miR-210 as a novel regulator of hepatic lipid homeostasis and underscore its therapeutic potential. Interventions aimed at restoring miR-210 function in the liver may offer a promising strategy to ameliorate hepatic steatosis and prevent MASLD progression.

molecular biology↗

bioRxiv2025

Context-aware simulation enables systematic optimization of long-read mapping parameters

The performance of long-read mapping is critical yet highly sensitive to parameter choices. We present CycSim, a context-aware simulator that models sequence-context-dependent errors from empirical sequencing data, coupled with a Bayesian optimization framework for systematic parameter tuning. CycSim more accurately reproduces real error profiles than existing simulators, enabling reliable simulation-based optimization. The framework identified parameter configurations that achieved 2.78-fold faster mapping for data from the newly developed Cyclone platform, and consistently improved both mapping efficiency (8.14-32.65% faster) and structural variant calling accuracy (0.75-1.70% higher F1) across ONT, HiFi, and Cyclone datasets, providing a robust and generalizable foundation for analysis-goal-driven parameter refinement.

bioinformatics↗

bioRxiv2025

Early blood-spinal cord barrier stabilization preserves peri-lesional tissue and improves recovery after SCI

Vascular disruption is an early and critical event in spinal cord injury (SCI), but its contribution remains poorly understood. Using novel in vivo two-photon dual-dye imaging, we found simultaneous blood-spinal cord barrier (BSCB) leakage and venous dilation in both the injury epicenter and adjacent transitional segment after cervical SCI in rats. Notably, vascular permeability in the transitional zone preceded axonal and neuronal loss, revealing a therapeutic window. Systemic delivery of ferulic acid-glycol chitosan (FA-GC) nanoparticles, a membrane-sealant, rapidly stabilized the compromised vasculature, reduced neuronal loss in the transitional region, and improved forelimb muscle strength. These findings identified acute vascular leakage beyond the injury epicenter as a driver of secondary pathology and highlight early vascular stabilization as promising therapeutic strategy.

pathology↗

bioRxiv2025

Covalent Reprogramming of Kinase Binders to Modulate Protein Homeostasis

Small molecules that modulate protein abundance through induced proximity have expanded the landscape beyond traditional inhibition. Here, we explore how introducing covalent or latent electrophilic groups into a multi-kinase binder scaffold can reprogram protein homeostasis within the kinase family. Using the broad-spectrum kinase ligand TL13-87 as a template, we synthesized analogs bearing -chloroacetamide, acrylamide, or terminal amine groups. Quantitative proteomics revealed that while most analogs had minimal global impact, MKI-AA uniquely stabilized the mitotic kinase AURKA, a protein often destabilized by ATP-competitive inhibitors. Mechanistic studies showed that MKI-AA acts post-translationally to suppress AURKA ubiquitination and proteasomal degradation. Proteomic mapping of MKI-AA-induced AURKA interactors revealed changes in protein associations upon treatment, providing mechanistic insights into how MKI-AA influences AURKA stability. Intriguingly, adding a short linker to MKI-AA converted it from a stabilizer into a degrader, highlighting how subtle structural variations can invert functional outcomes. These findings demonstrate that electrophilic ligand design can modulate kinase stability and reveal a previously unrecognized mode of covalent proximity-driven protein stabilization.

biochemistry↗

bioRxiv2025

ATHENA: A deep learning-based AI for functional prediction of genomic mutations and synergistic vulnerabilities in prostate cancer

Identifying functional mutations that drive therapy resistance remains a major challenge in prostate cancer. Large-scale sequencing often produces extensive lists of mutations but provides limited insight into which alterations are functionally relevant. To overcome this gap, we developed ATHENA (Attention-based Therapeutic Network Analyzer), a deep learning-based AI framework that predicts the functional impact of genomic mutations and reveals their synergistic vulnerabilities. Integrated with our RNA/DNA-informed variant discovery pipeline OncoVar, ATHENA models nonlinear dependencies among mutations to distinguish driver events from passenger variants. Trained on large multi-cohort datasets and interpreted using SHAP analysis, ATHENA not only stratifies patients by clinical outcomes but also predicts which specific mutations alter tumor behavior and therapy response, enabling direct validation through base editing experiments. Applied to prostate cancer progression models, the OncoVar-ATHENA framework identified stage-specific driver signatures across castration-resistant, AR-variant-driven, and metastatic disease, and uncovered cooperative interactions such as SYVN1-STC2 that promote tumor proliferation. By moving beyond simple mutation identification, ATHENA enables functional prediction of genomic interactions. This approach accelerates the discovery of actionable targets and provides a foundation for rational design of next-generation combination therapies in advanced prostate cancer.

cancer biology↗

bioRxiv2025

The BRCA1- RAD51 Axis Regulates SCAI/REV3 Dependent Replication Fork Maintenance

Replication stress is a key contributor to genomic instability and cancers. BRCA1 has well established roles in protecting stalled forks against degradation. Here we show that BRCA1 has a fork protection-independent role via regulation of RAD51 in a manner that confers dependency on SCAI and REV3. SCAI loss leads to elevated DNA breaks, genomic instability and cell death upon DNA damage. We show that the increased DNA breaks occur in S phase, consistent with fork breakage. BRCA1 drives SLX4-SLX1-ERCC1 mediated DNA break formation in the absence of SCAI and REV3, which are required to maintain integrity of stalled forks for efficient restart. Domain analysis revealed that the increased break signaling seen in the absence of SCAI does not require binding to resection factors like CtIP. Surprisingly, loss of fork reversal factors leads to additive increases in damage signaling and elevated fork shortening in the absence of SCAI/REV3 in a manner that depends on RAD51 activity. We propose that Protexin may be required to replicate through and maintain stalled replication forks at fragile genomic regions. Failure to do so leads to increased DNA breakage and genomic instability.

cell biology↗

bioRxiv2025

Graded Notch Signaling Functions as a Rheostat of Lineage Plasticity and Therapy Resistance in Prostate Cancer

Resistance to androgen receptor (AR)-targeted therapies such as enzalutamide in castration-resistant prostate cancer (CRPC) often arises through lineage plasticity, yet the molecular mechanisms that define this process remain incompletely understood. While previous studies reported that Notch1 and Notch2 exert distinct and sometimes opposing effects in prostate cancer differentiation, the integrated role of Notch pathway activity has not been systematically explored. Here, we identify Notch signaling as a graded Rheostat that governs prostate cancer cell fate transitions. Integrative transcriptomic and functional analyses revealed that intermediate Notch activity maintains a stem-like progenitor state, whereas reduced or elevated signaling drives divergent differentiation trajectories toward luminal or neuroendocrine lineages, respectively. During CRPC progression and enzalutamide resistance, Notch signaling becomes dynamically rewired, peaking in progenitor-like populations that sustain plasticity and survival. Both CRISPR-mediated knockout and pharmacologic inhibition of Notch signaling depleted these progenitor cells and restored enzalutamide sensitivity. These findings demonstrate that the level, rather than the binary presence, of Notch signaling dictates lineage directionality and therapeutic response in CRPC, establishing it as a tunable and actionable driver of resistance.

cancer biology↗

bioRxiv2025

Systematic characterization of cancer-associated SPOP mutants reveals novel and reprogrammable degradative activities

Speckle-type POZ protein (SPOP) functions as the substrate adaptor of the Cullin3-RING ligase (CRL3) complex and is recurrently mutated in multiple cancer types. Among these, F102C and F133L are frequent prostate cancer mutations within the substrate-binding domain, yet their biochemical consequences remain incompletely understood. Using quantitative proteomics, we show that SPOP-F133L, unlike SPOP-F102C, retains degradative activity toward the nuclear basket proteins NUP153 and TPR, indicating substrate-dependent loss-of-function. Moreover, SPOP-F133L induces partial down-regulation of p53 through a CRL-dependent, post-translational mechanism, revealing a potential neo-substrate relationship. Finally, we demonstrate that both SPOP-F102C and SPOP-F133L support targeted protein degradation (TPD) in an engineered cellular system. These findings define the degradative capacities of SPOP mutants and highlight opportunities to repurpose these variants as mutant-selective E3 ligases for therapeutic applications.

biochemistry↗

bioRxiv2025

Single-Cell Multi-Omics Dissects Transcript Isoform and Immune Repertoire Dynamics in Human Immunosenescence

Immunosenescence, a major hallmark of systemic aging, refers to the progressive functional decline of the immune system. This decline not only compromises host defense and immunological memory but also fuels chronic inflammation and tissue degeneration (collectively known as inflammaging). While single-cell RNA sequencing (scRNA-seq) has revealed transcriptomic alterations in immune aging, analyses restricted to transcript abundance fail to capture deeper regulatory layers, such as transcript isoform diversity and the remodeling of immune receptor repertoires. To address this, we present the human peripheral immune single-cell multi-omics atlas that integrates gene expression, transcript isoforms diversity, and immune receptor repertoires. By combining single-cell full-length transcriptome sequencing (scCycloneSEQ), short-read scRNA-seq, and single-cell immune receptor sequencing (scTCR/BCR-seq), we systematically profiled peripheral blood mononuclear cells (PBMCs) from healthy young and elderly donors. Our analyses uncovered extensive age-related remodeling of immune cell composition, functional states, and TCR/BCR diversity. Notably, we identified in CD4 effector memory T cells exhibited widespread differential isoform usage (DIU), 3'UTR length variation, and a marked reshaping of cytotoxic T lymphocyte (CTL) clonotypes--all closely associated with aging-related inflammation and cellular senescence. This multi-omics atlas delineates key molecular features of immunosenescence and provides a high-resolution resource for deciphering the regulatory architecture underlying immune aging.

immunology↗

bioRxiv2025

Complete and haplotype-resolved maps of genomic and epigenetic discordance in monozygotic twins

Telomere-to-telomere (T2T) genome assemblies are indispensable for accurate detection of genetic variation and for resolving complex repetitive regions. Monozygotic (MZ) twin pedigrees provide a powerful model to investigate de novo mutations (DNMs), however, comprehensive, haplotype-resolved analyses of structural variation (SV), allele-specific inheritance in complex regions, and DNA methylation in diploid human genomes remain limited. Here, we generated complete, haplotype-resolved T2T assemblies for two female twins (C33 and C35) from a Han Chinese pedigree by integrating complementary, state-of-the-art sequencing technologies. The resulting T2T-C33 and T2T-C35 assemblies are highly contiguous and complete, with Genome Continuity Inspector (GCI) scores of 74.94 (maternal) and 77.94 (paternal), and consensus quality values (QV) >75 (k = 21). We comprehensively cataloged 62 inter-twin single-nucleotide variants (SNVs), 15 small indels, and identified both shared and private DNMs, revealing nascent genomic divergence between the MZ twins. Focused interrogation of complex regions uncovered pronounced haplotype-specific length polymorphisms and structural heterogeneity within centromeric higher-order repeat (HOR) arrays. Notably, we observed extensive HOR copy-number variation between haplotypes, including a large copy-number difference on maternal chromosome 18, underscoring dynamic HOR array evolution even among genetically identical individuals. Concurrently, genome-wide DNA methylation profiling delineated allele-specific epigenetic variation that may contribute to phenotypic discordance. Together, these high-quality, diploid T2T genomes from a Han Chinese pedigree provide a valuable resource for population-aware genomics and reveal fine-scale, haplotype-specific divergence in MZ twins. Our results advance understanding of repeat dynamics, centromeric architecture, epigenetic variation and the spectrum of human genomic variation at single-base and structural scales.

genomics↗

bioRxiv2025

RUNX1T1-HDAC Reprogramming of the HOX Code Signaling Drives a Targetable Pan-Cancer Lineage Plasticity

Cancer remains a leading cause of death worldwide, with lineage plasticity emerging as a hallmark that drives therapy resistance and tumor progression by enabling cancer cells to alter identity and evade targeted therapies. Although genomic and transcriptomic aberrations correlate with lineage plasticity, the absence of pan-cancer markers to rapidly identify plastic subtypes has limited predictive utility. Homeobox (HOX) genes encode transcription factors that define tissue identity through distinct expression patterns, or HOX codes, in specific lineages. By analyzing multi-omics data, including 39 HOX genes from over 80,000 RNA-seq samples across 114 cancer types, we discovered that HOX code expression robustly represents cancer cell lineages and reveals multiple previously unrecognized lineage-plastic subtypes in prostate cancer, lung cancer, and acute myeloid leukemia (AML), each displaying altered HOX patterns compared to non-plastic subtypes. Differential analysis further identified RUNX1T1 as a novel and consistent marker of plasticity, elevated across all three cancer types and correlating with HOX code and lineage-plastic marker genes. We validated these correlations in bulk and single-cell RNA-seq from extensive preclinical and clinical cohorts and provided direct functional evidence that RUNX1T1 is required for lineage-plastic programs in prostate cancer. Using AI-based modeling, we identified NCOR/HDAC as RUNX1T1 binding partners forming a co-repressor complex that regulates HOX codes and plasticity. Finally, pharmacologic HDAC inhibition selectively suppressed the growth of plastic cells, revealing a novel therapeutic vulnerability. These findings establish ectopic RUNX1T1 as a pan-cancer biomarker and critical mediator of lineage plasticity and identify the RUNX1T1-HDAC complex as a druggable target.

cancer biology↗

bioRxiv2025

Mapping disease critical spatially variable gene programs by integrating spatial transcriptomics with human genetics

Spatial gene expression patterns underlie tissue organization, development, and disease, yet current methods for detecting spatially variable genes (SVGs) lack the flexibility to capture multi-scale structure, ensure robustness across platforms, and integrate with genetic data to assess disease relevance. We present Spacelink, a unified framework that models spatial variability of a gene at both whole-tissue and cell-type resolution using an adaptive mixture of data-driven spatial kernels and summarizes it using an Effective Spatial Variability (ESV) metric. Spacelink achieved up to 3.2x higher detection power over eight existing global SVG and cell-type SVG methods while showing consistently superior FDR control across 34 different simulation settings and also showed superior cross-platform concordance in matched tissue Visium and CosMx datasets. Applied to 3 healthy CosMx human tissues (brain cortex, lymph node, liver), Spacelink revealed that SVGs are highly informative for 113 complex traits and diseases (average GWAS sample size = 340,406). Spacelink showed up to 2.2x higher disease informativeness over competing methods in tissue-relevant complex diseases and traits, conditional on putative non-spatial expression-level confounders. Applied to a mouse organogenesis Stereo-seq atlas (8 developmental stages), Spacelink identified 145 genes with stage-associated ESV within brain independent of mean expression, that are enriched in pathways like Wnt signaling and Rap1 signaling characterizing early and late development, respectively. Integration with in vivo Perturb-seq targeting 35 de novo ASD risk genes revealed that perturbations in excitatory neurons and astrocytes preferentially altered spatially structured downstream gene programs (1.7-2.2x higher average ESV across stages than other cell types), many of which were enriched for polygenic autism GWAS loci. In neurodegeneration, analysis of 32 Visium dorsolateral prefrontal cortex samples spanning Alzheimers disease (AD) pathology stages identified 334 genes with decreasing ESV along amyloid burden (enriched for glycolysis) and 216 genes with decreasing ESV along tau tangle accumulation (enriched for apoptotic pathways). Several AD risk genes (PKM, CLU, GPI) showed conserved reductions in spatial variability with AD pathology in both human and 5xFAD mouse, with PKM linking to a colocalized splicing QTL and amyloid burden QTL variant. These results highlight the utility of Spacelink in decoding spatially variable gene programs that connect tissue architecture to disease genetics.

genomics↗

bioRxiv2025

Endothelial CEPT1 Regulates Hepatic MTTP-Mediated Lipid Metabolism and Impacts Aortic Atherosclerosis

BackgroundThe regulation of hepatic lipid metabolism by vascular endothelial factors remains poorly characterized, despite its relevance to atherosclerosis and steatosis. Microsomal triglyceride transfer protein (MTTP) is essential for hepatic lipid metabolism, but its regulation by endothelial cells has not been previously investigated. ObjectiveThis study examined whether endothelial choline ethanolamine phosphotransferase 1 (CEPT1) modulates hepatic MTTP activity, impacting systemic lipid homeostasis and aortic plaque formation. Methods and ResultsHuman steatotic liver samples exhibited reduced CEPT1 and MTTP protein levels, correlating with diminished lipid exports. In mice, endothelial-specific Cept1 knockdown decreased hepatic MTTP expression, reduced serum triglyceride and cholesterol levels, and markedly attenuated aortic atherosclerosis without evidence of fat malabsorption. In vitro, endothelial CEPT1 silencing suppressed MTTP activity in co-cultured hepatocytes via a paracrine mechanism involving peroxisome proliferator-activated receptor (PPAR) signaling, which was rescued by fenofibrate treatment. Aortic histology confirmed reduced plaque burden and macrophage infiltration in CEPT1-deficient mice. ConclusionsEndothelial CEPT1 critically regulates hepatic MTTP through a paracrine axis, influencing lipid metabolism and atherogenesis. Targeting endothelial CEPT1 may represent a novel therapeutic approach to reduce steatosis and vascular atherosclerosis.

molecular biology↗

bioRxiv2025

PIEZO channels link mechanical forces to uterine contractions in parturition

AbstractMechanical forces are extensively involved in pregnancy and parturition, but their precise roles and mechanisms remain poorly understood. Here, we identify mechanically activated ion channels PIEZO1 and PIEZO2 as key mechanotransducers required for labor progression. Genetic deletion of Piezo1 and Piezo2 in mice resulted in weakened uterine contractions and severe parturition defects. Tissue-specific knockouts revealed that deletion in either the uterus or sensory neurons alone caused modest defects, whereas combined loss significantly impaired labor, demonstrating additive effects. Single-nuclei sequencing showed that loss of PIEZO reduced expression of connexin43 (Gja1), a gap junction protein in uterine smooth muscle cells, suggesting a mechanistic link to impaired contraction. These findings highlight the critical role of PIEZO channels in mechanotransduction during parturition and suggest therapeutic targets for labor dysfunction.

physiology↗

bioRxiv2025

Dorsal Attention Network as a Convergent Hub of Diverse Non-pharmacological Interventions Preserving Functional Gradients and Cognition in Aging

Non-pharmacological interventions (NPIs) in aging neuroscience have largely focused on intervention-specific regional effects, with limited understanding of generalizable network-level mechanisms. Here, adopting a previously unexplored gradient-based perspective of functional brain organization, we analyzed an NPI dataset involving four interventions in older adults (training/control group: n = 112/59). NPIs led to strengthened intra-network functional integration and maintained macroscale gradient architecture. Virtual lesion analyses identified the dorsal attention network (DAN) as a key contributor to gradient maintenance. Critically, enhanced post-intervention DAN connectivity was associated with maintained gradient structure and improved global cognition. These findings establish a unifying framework in which the DAN acts as a convergent hub through which diverse NPIs preserve functional brain organization and attenuate cognitive aging.

neuroscience↗

bioRxiv2025

Integrating 12 Spatial and Single Cell Technologies to Characterise Tumour Neighbourhoods and Cellular Interactions in three Skin Cancer Types

Cutaneous squamous cell carcinoma (cSCC), basal cell carcinoma (BCC), and melanoma - the three major skin cancers - collectively comprise over 70% of all cancer cases. Despite their prevalence, much understanding of cellular interactions in the skin cancer microenvironment is needed, both in the outer skin layer where the cancer originates and at the deeper junctional and dermal layers into which it progresses. To address this gap, we integrated 12 complementary spatial and single-cell technologies to generate orthogonally-validated cell signatures, spatial maps, and interactomes for cSCC, BCC, and melanoma. Through comprehensive comparisons and integrating these spatial methods, we provided practical benchmarking guidelines for experimental design and analysis. By identifying keratinocyte cancer cells and melanomas, we found distinct signatures of these cells compared to non-cancer keratinocytes and melanocytes. Spatial integration of transcriptomics, proteomics and glycomics uncovered cancer niches enriched for cancer initiating cells (melanocytes or keratinocytes) and fibroblast and T-cell (MKFT) clusters, with altered tyrosine and pyrimidine metabolism. Ligand-receptor analysis across >700 cell-type combinations and >1.5 million interactions highlighted key roles for CD44, integrins, and collagens, with CD44-FGF2 emerging as a potential therapeutic target. Consistently, melanoma showed strong MFT interactions, validated by Opal Polaris, RNAScope, Proximal Ligation Assay and two additional single-cell spatial platforms (making a total of 14 technologies). For population-scale generalisation, genetic associations from >500,000 individuals were mapped onto spatial skin tissues, identifying SNPs enriched in domains containing melanocytes and T cells and their ligand-receptor pairs, shedding light on functional mechanisms linking genetic heritability to cells within cancer tissue. We built an interactive multiomics resource for exploring spatially-resolved molecular signatures and cellular crosstalk in skin cancer, available at https://skincanceratlas.com.

cancer biology↗

bioRxiv2025

Expanding the repertoire of chemically induced covalent neoantigens

The ubiquitin-proteasome system generates peptide fragments that are displayed on MHC-I molecules. Recent studies revealed that covalent small molecules can hijack this process, leading to the presentation of hapten-modified peptide fragments, or covalent neoantigens. Here, we report a chemical proteomics platform to systematically investigate this process and harness covalent neoantigens for immune cell recruitment and activation. Using a bioorthogonal cysteine-reactive probe (IA-mTz), we demonstrate that diverse intracellular proteins can be modified, processed, and presented as covalent neoantigens across multiple cell lines. Mass spectrometry confirmed the presence of IA-mTz-modified peptides within the MHC-I immunopeptidome, and structural modeling revealed stable peptide-MHC-I interactions. We further integrated a bioorthogonal strategy that enables immune engagement: IA-mTz-modified cells conjugated with trans-cyclooctene (TCO)-IgG elicited Fc receptor activation in a reporter assay, supporting immune recruitment via antibody-dependent cellular phagocytosis. This approach was extended to additional cysteine-reactive probes and to 2,4-dinitrochlorobenzene (DNCB), a common skin sensitizer, which we show induces covalent neoantigen formation in a cell- and HLA-dependent manner. These findings reveal a previously underappreciated breadth of covalent neoantigen formation and provide a generalizable strategy for immune targeting of covalent neoantigens.

biochemistry↗

bioRxiv2025

HER2; p53 Co-mutated Cancers Show Increased Histone Acetylation and are Sensitive to Neratinib plus Trastuzumab Deruxtecan.

In metastatic breast cancer, HER2-activating mutations often co-occur with TP53 mutations, a combination linked to poor response to neratinib and worse prognosis. To model this clinical challenge, we bred HER2 V777L transgenic mice with two TP53 mutant alleles: TP53 R172H (the murine homolog of human TP53 R175H) and TP53fl/fl, which mimics p53 truncations common in human tumors. TP53 mutations accelerated tumor development and reduced survival in HER2-mutant mice. These co-mutant tumors were resistant to neratinib but remained sensitive to exatecan, the topoisomerase I (TOP1) inhibitor payload in trastuzumab deruxtecan (T-DXd). Mechanistically, TP53 mutant tumors exhibited upregulation of histone acetylation, hypertranscription of DNA repair factors, increased chromatin accessibility, and rendered cells more susceptible to TOP1 inhibitors via G2/M arrest and apoptosis. This vulnerability is dependent on transcriptional activity of TP53 mutations, highlighting a novel strategy to treat HER2;TP53 co-mutant breast cancers using TOP1-targeted therapies. Statement of SignificanceTP53 mutations sensitize HER2-mutant cancers to TOP1 inhibitors via chromatin accessibility and hyper-transcription, supporting combination therapy with neratinib and T-DXd in TP53/HER2 co-mutant breast cancers.

cancer biology↗