Cancer Research

Colorectal cancer (CRC) brain metastases have a poor prognosis and limited treatment options, including resistance to radiation therapy. Little is known about the molecular and cellular mechanisms that enable CRC tumor cells to adapt to the brain and establish a supportive tumor microenvironment. To address this gap we used spatial transcriptomics to analyze 51 CRC brain metastases. A subset had matched primary colon tumors and longitudinally paired metastatic resections before and after radiation treatment. We identified the critical spatial cellular features of the tumor epithelium and the surrounding tumor microenvironment that support metastatic growth in the brain. CRC brain metastases developed a stromal microenvironment with abundant fibroblasts and tumor-associated macrophages. A fibroblast-macrophage cellular neighborhood promoted angiogenesis, extracellular matrix remodeling, and immune suppression. Tumor cells showed local adaptations. In endothelial-rich regions, they were proliferative whereas in macrophage-rich regions, they were more differentiated and immune evasive. Compared with paired primary tumors, CRC brain metastases showed increased chromosomal instability, with activation of RNA-processing, stress response, and junctional remodeling pathways. After radiation treatment, resistant clones had increased epithelial-mesenchymal transition, while the immunosuppressive stroma remained intact. We identified tumor-derived MIF, GDF15, PRSS3 and SEMA3C ligands and macrophage-derived SPP1 that have the potential to affect multiple cell types in the metastatic niche. These ligand-receptor interactions drive angiogenesis, stromal activation and immune suppression. In a macrophage-tumor-fibroblast co-culture model, knockout of SPP1 in macrophages led to reduced expression of lipid-metabolism related genes and disrupted tumor-promoting interactions. Together, these results indicate that CRC growth in the brain is sustained by a specific cellular organization with immunosuppressive multicellular interactions.

TP53 mutations occur in 80-90% of triple-negative breast cancers (TNBCs) and drive genomic instability and metastatic progression. Poly (ADP-ribose) polymerase (PARP) is critical for DNA repair and replication fork stability. How oncogenic signaling influences PARP function to sustain proliferation during replication stress remains unclear. Mutant p53 (mtp53) R273H associates tightly with chromatin, forms complexes with PARP, and enhances PARP recruitment to replication forks [1-3]. The C-terminal region of mtp53 mediates mtp53-PARP and mtp53-Poly (ADP-ribose) (PAR) interactions that facilitate S phase progression [4, 5]. The PARP inhibitor talazoparib (TAL) combined with the alkylating agent temozolomide (TMZ) produces synergistic cytotoxicity selectively in mtp53, but not wild-type p53 (wtp53), breast cancer cells and organoids. Herein we evaluated the mechanism of mtp53-associated cell death and tested if this could translate to a preclinical xenograft model. We found that TMZ+TAL treatment induced elevated cleaved PARP and {gamma}H2AX and reduced the metastasis-promoting oncoprotein MDMX. In orthotopic xenografts expressing mtp53 R273H, but not wtp53, combination therapy significantly decreased circulating tumor cells (CTCs) and lung metastases. Transcriptomic profiling of tumors from combination treated animals demonstrated downregulation of MDMX, VEGF, and NF-{kappa}B, consistent with the observed suppression of CTCs and lung metastasis, and increased {gamma}H2AX, indicative of replication stress in mtp53 xenografts. Inhibition of metastasis was also observed in mtp53 R273H WHIM25 and p53-undetectable WHIM6 TNBC patient-derived xenografts (PDX). The mtp53 C-terminal domain (347-393) demonstrated a critical tumor promoting function, as CRISPR-mediated deletion impaired replication fork progression, tumor growth, and metastatic dissemination. DNA fiber combing showed that expression of full-length mtp53 R273H, but not C-terminal deleted {Delta}347-393, supported sustained single-stranded DNA gaps (ssGAPs) following Poly (ADP-ribose) glycohydrolase (PARG) inhibition. These findings support that mtp53 uses C-terminal amino acids to exploit PARP to enable replication stress adaptation and that mtp53 is a predictive biomarker for combined PARP inhibitor and DNA damaging therapies targeting TNBC. Significance statementTP53 mutations are the most common genetic alterations in TNBC and a major driver of replication stress and metastasis. This study shows that missense mutant p53 uses C-terminal amino acids to reprogram PARP activity to maintain tumor cell survival under replication stress. We demonstrate that p53 status governs the response to combined PARP inhibitor (PARPi) and DNA-damaging chemotherapy, establishing an additional molecular basis beyond BRCA1 mutations for treating TNBC with PARPi therapy. These findings reveal a previously unrecognized mechanism by which the mutant p53-PARP axis enables replication stress tolerance and drives cancer metastasis. We show mutation of p53 in TNBC provides an additional biomarker-guided framework to improve PARPi therapeutic outcomes.

Cancer cell-autonomous type 1 interferon (IFN-1) production and signaling is frequently activated in response to DNA damage and has been associated with the development of therapy resistance in several cancer types. However, its cell-autonomous role in driving resistance in high-grade serous ovarian cancer (HGSOC), a disease defined by near-universal exposure to genotoxic therapy as frontline treatment, remains unclear. Specifically, whether IFN-1 functions in HGSOC as only a response to genotoxic stress or can independently act in driving resistance phenotypes has not been studied. Utilizing a syngeneic patient-derived model of cisplatin-sensitive (SE) and -resistant (CR) HGSOC, we demonstrate that chronic cisplatin exposure is associated with enrichment of IFN-1 signaling and the interferon-related DNA damage resistance signature (IRDS). Acute cisplatin treatment elicited dynamic, temporal IFN-1 signaling and responses in both sensitive and resistant cells, indicating a conserved stress response in resistant cells. Chronic, low-level exposure to exogenous IFN{beta}, in the absence of a DNA-damaging agent, was sufficient to phenocopy several features of chronic cisplatin driven resistance, including reduced therapeutic sensitivity, cell cycle arrest, and decreased proliferation. Notably, IFN{beta} driven resistance occurred without sustained IRDS or canonical interferon stimulated gene (ISG) induction, revealing alternative mechanisms for IFN-1 mediated therapy resistance. Together, these findings identify IFN{beta} as a functional driver of the development of resistance-associated phenotypes and highlight cell-autonomous IFN-1 signaling as a potential biomarker for resistance and a therapeutic target in platinum-resistant disease.

High-grade serous carcinoma (HGSC) is the most common and aggressive form of ovarian cancer. Advanced HGSCs exhibit pronounced cellular heterogeneity, including a subset of cancer-propagating cells (CPCs, also known as cancer stem cells) that are highly tumorigenic and display stem cell-associated properties such as self-renewal and chemoresistance. In contrast, a substantial fraction of HGSC cells is non-tumorigenic. The role of these non-cancer-propagating cells (non-CPCs) and their relationship to CPCs remain poorly understood. Here, we demonstrate that neoplastic cells expressing the intermediate filament protein keratin 5 (KRT5) represent bona fide CPCs. KRT5 cells form cancer organoids over successive passages, are tumorigenic in serial dilution xenograft assays, and are resistant to the antineoplastic agents, doxorubicin and cisplatin. Single-cell lineage-tracing experiments show that KRT5 CPCs give rise to KRT5- cells. KRT5 and KRT5- populations exhibit distinct gene expression profiles, with KRT5- cells characterized by expression of SPP1, which encodes the secreted factor osteopontin (OPN). Treatment with OPN enhances HGSC organoid growth and chemoresistance, whereas SPP1 knockdown reverses these effects. Together, these findings support a model in which HGSC contains two hierarchically related cell populations: KRT5, OPN-responsive CPCs and KRT5-, non-tumorigenic cells that form a niche producing OPN. Targeting pathways that sustain both stem-like tumor cells and their supportive niche may enable reduced dosing of highly toxic chemotherapeutic agents while enhancing therapeutic efficacy in HGSC.

Compared to immortalized cell lines, patient-derived organoids and other ex vivo models have been shown to better recapitulate patient responses to therapy. High cost and technical complexity have prevented the creation of pan-cancer ex vivo datasets, limiting comprehensive analyses and predictive modeling for ex vivo drug response. We present the Pan-PreClinical (PPC) project: a drug screen atlas of 2.1M experiments across 1,982 ex vivo samples and 3,100 drugs spanning 134 cancer indications tested across 26 studies. We develop a contrastive Bayesian model to harmonize across studies, identifying 303 tissue-specific drug sensitivities and demonstrating drug sensitivities are predictive of clinically-relevant molecular profiles. Integrating established cell line databases reveals systematic biases across 55 cancer subtypes, with cell line screens favoring drugs targeting highly proliferative cells and undervaluing cell-cell communication targets. We leverage PPC to establish an ex vivo foundation model and computational platform for scalable ex vivo cancer biology and predictive oncology.

Histopathologic evaluation remains central to cancer diagnosis and treatment planning, yet the molecular programs underlying distinct tissue morphologies are not routinely accessible in clinical workflows. Spatial transcriptomic/proteomic platforms provide region-specific molecular measurements but are limited by cost, throughput, and scalability. Most computational pathology models rely on either bulk tissue-based gene expression or a focused gene/protein expression-panel prediction, thereby obscuring subregion-specific morpho-molecular relationships and limiting spatial interpretation of a wider gene/protein expression network. This limitation is particularly significant in triple-negative breast cancer (TNBC), which exhibits pronounced spatial heterogeneity across tumor, stroma, and immune compartments. We developed X-SPATIO, a spatially compatible computational pipeline designed to directly link hematoxylin and eosin (H&E) morphology with region-matched mRNA and protein expression. The model was trained on H&E-defined regions of interest paired with spatially-resolved transcriptomic and proteomic data obtained from GeoMx Digital Spatial Profiler. Using a multiple-instance learning approach, X-SPATIO captures morpho-molecular associations, generating spatio-morphologic attention maps that indicate predictive tissue regions. X-SPATIO demonstrated strong performance across biologically relevant spatial biomarkers, achieving area under the curve values ranging [0.79, 0.97]. Attention maps revealed spatial patterns consistent with known biology, indicating alignment between learned features and tissue organization. By integrating spatial molecular ground truth with routine histopathology, X-SPATIO enables cost-effective inference of spatial biomarker expression and establishes a foundation for biologically grounded discovery and precision oncology in TNBC.

BackgroundTumors exhibit substantial cellular and molecular diversity driven by genetic and epigenetic mechanisms. Large-scale profiling efforts have established aberrant DNA methylation as a universal hallmark of cancer. Beyond changes in mean methylation levels, tumor tissues exhibit elevated DNA methylation variability at specific genomic regions within and across tumors. This constitutes a fundamental dimension of cancer epigenomes, reflecting disrupted maintenance of epigenomic states and stochastic drift, which may enable adaptation to the microenvironment, phenotypic plasticity, invasion, disease progression, and treatment resistance. However, the genome-wide organization and functional consequences of DNA methylation variability across cancer types remain incompletely understood. MethodsWe analyzed paired tumor-normal DNA methylation profiles across 16 cancer types to systematically quantify DNA methylation variability. Pan-cancer DNA methylation variability was consistently observed using complementary statistical approaches and multiple modes of data representation. We identified cancer-specific and pan-cancer differentially variable regions and evaluated their associations with genomic features, transcriptional and chromatin regulators, and biological processes. Variability was quantified using three measures per sample: the proportion of intermediately methylated sites (PIM), genome-wide Shannon entropy, and a DNA methylation-based stemness index. Associations with genomic instability, tumor biological features, and clinical outcomes were subsequently assessed. ResultsTumor samples consistently exhibited higher DNA methylation variability than matched normal tissues, reflected by increased dispersion and wider interquartile ranges. Pan-cancer variably methylated regions were depleted in promoters and enriched in open sea regions, in heterochromatic H3K27me3-decorated PRC2-repressed domains, and at enhancers. They preferentially contained motifs for transcription factors involved in developmental regulation. Elevated DNA methylation variability, captured by higher PIM, entropy, and stemness scores, was associated with increased genomic instability manifested by higher aneuploidy, increased DNA break points, a greater fraction of the genome altered, and increased tumor mutational burden, as well as with aggressive tumor features such as lymph node involvement, post-therapy neoplasm events, and elevated hypoxia scores. Importantly, tumors with high DNA methylation variability exhibited significantly worse overall, progression-free, and disease-free survival. ConclusionsDNA methylation variability is a pervasive and clinically relevant feature of tumor epigenomes, reflecting epigenetic and genetic instability, expanded regulatory plasticity, and tumor aggressiveness.

Soft tissue leiomyosarcoma (STLMS) is an aggressive malignancy for which robust molecular subclassification and mechanism-based therapeutic strategies still remain limited. We performed integrative proteogenomic analyses of primary and metastatic STLMS to define subtype-associated molecular programs. Joint analysis of the proteome and phosphoproteome identified 3 biologically distinct subtypes. P1 was characterized by relative genomic stability, low proliferative activity, and enrichment of FGFR2- and PDK-associated signaling. In contrast, P2 and P3 showed greater chromosomal instability and more aggressive clinical behavior, but with distinct molecular features. Notably, P2 was associated with inflammatory and RTK-RAS pathway programs, activation of CDK-AURKA/B-mTOR-ERK kinase networks, IGF1R/PDGFRA alterations, and the poorest outcomes. On the other hand, P3 showed strong cell cycle and DNA repair programs, elevated NCOR1 expression, and increased expression of nonhomologous end joining components, including PARP1. Homologous recombination deficiency analyses distinguished HRD-low P1 from HRD-high P2/P3, and paired analyses suggested increased HRD-related features in metastatic lesions within P3. Immune profiling identified an immune-hot yet potentially suppressive state in P2, marked by higher LGALS9 expression and M2-like macrophage infiltration. To support clinical translation, we developed a tissue microarray-based immunohistochemical classifier that enabled surrogate assignment of proteome-defined subtypes in an independent cohort and showed recurrence-free survival differences across inferred subtypes. These findings together establish a proteogenomic framework for STLMS heterogeneity and nominate subtype-associated biological vulnerabilities for future translational and clinical investigation.

Epigenetic deregulation can alter the expression of cancer-related genes in tumor cells and may promote metastasis by influencing interactions between tumor cells and their immune microenvironment. However, the underlying immune mechanisms remain poorly understood. LSD1 (KDM1A) is a histone demethylase that has been proposed to function as a tumor and metastasis suppressor in breast cancer. Here, using the MMTV-PyMT breast cancer mouse model, we show that natural killer (NK) cells play a critical role in suppressing tumor cell metastasis to the lung, and that ablation of LSD1 leads to increased lung metastasis. This phenotype is accompanied by pronounced upregulation of immune-related genes, including major histocompatibility complex class I (MHC-I) genes, in tumor cells and by extensive remodeling of the tumor immune microenvironment, characterized by reduced abundance and maturation of NK cells. Consistent with these observations, NK cells exhibit reduced cytotoxicity toward Lsd1-null PyMT tumor cells. Notably, NK cell-mediated killing can be restored by disrupting expression of the non-classical MHC-I molecule Qa-1, a ligand for the inhibitory NK receptor CD94/NKG2A, in tumor cells. In transplantation experiments, Lsd1-null PyMT tumor cells formed significantly larger lung metastatic lesions than Lsd1-wildtype tumor cells in SCID mice, which possess functional NK cells, but not in NSG mice that lack NK cells. Collectively, these findings suggest that epigenetic deregulation in LSD1-deficient mammary tumor cells reprograms the tumor immune microenvironment, resulting in impaired NK cell-mediated tumor surveillance and enhanced metastatic progression.

HER2 heterogeneity and reversible phenotypic plasticity play a central role in breast cancer progression and therapeutic resistance, yet how their interaction shapes treatment response remains poorly understood. Experimental and clinical evidence indicates that HER2-positive and HER2-negative tumor cell states can dynamically interconvert, enabling compensatory population shifts that undermine monotherapies targeting a single phenotype. Because stochastic lineage effects, phenotypic switching, and local cell interactions are averaged out in mean-field population-level ODE models, we develop a spatially resolved agent-based model (ABM) that explicitly represents individual-cell dynamics and heterogeneous tumor growth. The model incorporates phenotype-specific proliferation, migration, and death, division-coupled HER2 state transitions, and therapy-induced selective pressures. We consider two therapeutic interventions with complementary mechanisms of action: paclitaxel, which preferentially suppresses HER2-positive proliferation, and Notch inhibition, which targets HER2-negative populations and alters phenotypic composition. Starting from single-cell lineages, we validate the ABM against theoretical predictions from a population-level switching model and against single-cell-derived experimental measurements, demonstrating quantitative agreement with early lineage dynamics and long-term phenotypic equilibria. Simulation results show that monotherapies induce compensatory phenotypic shifts and spatial reorganization that permit tumor persistence. In contrast, combination therapy simultaneously targeting HER2-positive and HER2-negative populations disrupts phenotypic replenishment, fragments spatial structure, and can achieve sustained tumor control across a broad range of treatment strengths. To quantify robustness across heterogeneous tumor parameter regimes, we pair the ABM with an interpretable Random Forest surrogate trained on ensemble simulation data. Using only pre-treatment and early-trajectory features, the surrogate predicts long-term response, identifies growth-rate asymmetries as dominant drivers of resistance, and interpolates across previously unseen parameter combinations within the sampled domain. Together, this integrated mechanistic and data-driven framework clarifies how HER2-mediated plasticity, spatial organization, and competitive growth dynamics shape therapy resistance and provides a scalable approach for predicting and optimizing treatment strategies in HER2-heterogeneous breast cancer. Sample MATLAB code for the agent-based model (ABM) used in this study is available on GitHub.

In approximately half of endometrial carcinoma (EC), PTEN loss-of-function and activating PI3K mutants coexist. Unlike cells with either single mutation, PTEN/PIK3CA coexistent alterations result in elevated membrane phosphatidylinositol (3,4,5)-trisphosphate (PIP3) levels and mTORC1 hyperactivation, rendering PI3K or AKT inhibition ineffective in blocking mTORC1 activity and tumor growth. The bi-steric mTORC1 kinase inhibitor, RMC-6272, suppresses mTORC1 activity and cell growth by reducing protein translation and cell cycle progression. In vivo, RMC-6272, but not PI3K inhibitors, effectively suppressed mTORC1 and growth of EC PDXs with coexistent PTEN/PIK3CA lesions. These findings are consistent with a phase I trial of bi-steric mTORC1 inhibitor RMC-5552, showing anti-tumor activity in patients with EC. PDXs with KRAS co-mutations regrew after RMC-6272 treatment, which was prevented by the addition of the RAS(ON) multi-selective inhibitor RMC-7977. Overall, these data suggest that mTORC1 hyperactivation drives ECs with coexistent PTEN/PIK3CA mutations, explain the limited antitumor activity of PI3K and AKT inhibitors, and support clinical evaluation of mTORC1 inhibitors as potential therapy for EC. SignificanceWe have found the mechanistic consequences of PTEN/PIK3CA co-alterations in endometrial tumors and that these mutations result in a profound hyperactivation of mTORC1 signaling. Single mutant tumors are sensitive to PI3K inhibition but those with both mutations are insensitive to PI3K or AKT inhibition but are exquisitely dependent on mTORC1 kinase. This provides strong preclinical rationale for targeting mTORC1, alone or combined with RAS inhibition (in RAS co-mutant tumors), as an effective therapeutic strategy.

Hormone therapies are frequently used to reduce breast cancer risk in individuals at increased risk for primary or subsequent disease; however, tissue-level responses to these therapies are heterogeneous and incompletely understood. Background parenchymal enhancement (BPE) on breast magnetic resonance imaging (MRI) provides a non-invasive radiologic readout of breast tissue features associated with endocrine responsiveness and cancer risk. Although BPE is associated with hormonal exposure, a subset of patients with BPE do not show a response to preventive endocrine therapy and therefore may remain at increased breast cancer risk. In this study, we integrated single-nucleus RNA sequencing and spatial transcriptomics to define the determinants of endocrine responsiveness in the setting of BPE. We identify hormone-driven epithelial cells with high levels of estrogen signaling and endocrine responsiveness, together with immune-associated epithelial programs characterized by diminished luminal identity and increased expression of immune-modulatory pathways, including major histocompatibility complex (MHC) class II and CD74. Functional organoid assays validate that these epithelial states exhibit differential sensitivity to tamoxifen and demonstrate that inflammatory signals can induce immune-modulatory epithelial programs. Together, our findings identify hormone signaling and immune programs as key determinants of endocrine responsiveness in breast tissue and provide a biological basis for interpreting radiologic markers relevant to cancer prevention.

Melanoma is a highly plastic cancer characterized by distinct cellular phenotypes associated with broadly unique gene expression profiles. TRIM9 is a brain-enriched E3 ubiquitin ligase detected in melanoma, but how TRIM9 expression regulates melanoma phenotype is unknown. Using two metastatic human melanoma cell lines and a mouse melanoma model, we found that TRIM9 promoted melanoma proliferation and altered cell morphology. In cell lines, TRIM9 promoted cellular blebbing and negatively regulated adhesion, secretion, and mesenchymal motility. TRIM9 interacted with VASP in melanoma cells, altering VASP modification, localization, and dynamics. In the absence of TRIM9, cells had an altered actin organization and more focal adhesions, where VASP accumulated and exhibited rapid turnover. We find the alterations in actin architecture and adhesion associated with TRIM9 deletion were coincident with increased motile and contractile mesenchymal behavior in vitro. In vivo loss of TRIM9 in melanoma slowed tumor growth and altered metastasis frequency, size, and destination. Our findings indicate TRIM9 alters the proliferative and morphological phenotypes of metastatic melanoma cells to influence disease progression.

AbstractRecurrent loss-of-function mutations in RUNX1 occur in estrogen receptor-positive (ER+) breast cancers, yet how RUNX1-loss contributes to breast tumorigenesis remains unclear. Here we used genetically engineered mouse models with luminal mammary epithelial cell (MEC)-restricted gene disruption to investigate its role in breast cancer initiation. Loss of RUNX1 alone, or together with RB1, was insufficient to drive tumor formation. In contrast, combined loss of RUNX1 and p53 induced mammary tumors with full penetrance. These tumors contained ER+ cancer cells and exhibited extensive T cell and macrophage infiltration, indicative of an immune hot microenvironment. Mechanistically, RUNX1-deficiency activated interferon signaling in luminal MECs, associated with derepression of RUNX1 target STAT1 and enhanced inflammatory responses. Consistent with these findings, human ER+ breast cancers with low RUNX1 expression displayed elevated immune signatures and poorer patient survival. Together, our results identify RUNX1-loss as a driver of an immune-active subtype of ER+ breast cancer.

Secretory breast carcinoma (SBC) is typically indolent, yet mechanisms underlying aggressiveness and therapeutic resistance to tropomyosin receptor kinase inhibitors (TRKi) remain unclear. Autopsy-based longitudinal multi-organ high-dimensional profiling of metastatic TRKi-resistant SBC demonstrated histopathological heterogeneity, including secretory and squamous components, arising from a shared clonal origin. Integrated genomic and transcriptomic analyses revealed hierarchical transcriptional rewiring consistent with a lineage-plastic state, suggesting a potential link to tumor aggressiveness and therapeutic resistance.

Well-differentiated and dedifferentiated liposarcoma (WDLPS and DDLPS) exhibit markedly different clinical behaviors, with DDLPS showing greater aggressiveness, higher recurrence and metastasis rates, and worse outcomes. Using single-nucleus multiome sequencing, epigenomic profiling, and spatial transcriptomics, we characterized cellular and epigenetic heterogeneity between these subtypes at single-cell and spatial resolution. We found distinct phenotypic states reflecting altered lineage differentiation and plasticity: DDLPS is dominated by early-differentiated progenitor-like cells, sclerotic WDLPS displays broader mesenchymal lineage plasticity, and adipocytic WDLPS contains abundant committed adipocytes. The DDLPS immune microenvironment was dominated by immunosuppressive macrophages, whereas WDLPS harbored more T cells and inflammatory macrophages. Notably, sclerotic WDLPS displayed intermediate cellular and molecular features, suggesting it may represent a distinct WDLPS subtype. Importantly, we identified novel gene regulatory circuits underlying each state, including FABP4/PPARG programs in adipocytic WDLPS, GLI2/TCF7L2/RBPJ/KLF7 programs in sclerotic WDLPS, and KLF7/FOSL2/SP3/GLI2/RBPJ programs in DDLPS. H3K27ac-marked enhancers were enriched near adipocytic marker genes in WDLPS and mesenchymal markers in DDLPS. Together, these findings reveal the cellular heterogeneity of tumor and immune compartments across liposarcoma subtypes and identify regulatory programs driving their differentiation states. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=155 SRC="FIGDIR/small/713651v1_ufig1.gif" ALT="Figure 1"> View larger version (73K): org.highwire.dtl.DTLVardef@1c84ee1org.highwire.dtl.DTLVardef@1b2ad42org.highwire.dtl.DTLVardef@18ce5a6org.highwire.dtl.DTLVardef@138f615_HPS_FORMAT_FIGEXP M_FIG C_FIG

Radiotherapy (RT) transforms tumour tissues into in situ vaccines that trigger antitumor immunity. Immunogenicity depends on how RT is delivered, since heterogeneous RT (spatially fractionated RT, SFRT) elicits more prominent responses than the conventional homogenous one. However, this phenomenon cannot be clinically harnessed, unless the relevant pathways are identified. To gain insights, we developed a hybrid dry-lab/wet-lab approach that integrates systems-level immune phenotypes established by homogenous or heterogenous RT (SFRT) with the transcriptomic profiling of irradiated tumors. By further combining feature extraction with machine-learning, including multilayer perceptron modelling, we ranked predictors of immune infiltration and patient survivability for each RT type. We found that conventional RT induces coordinated upregulation of cytosolic sensors of RNA viruses (OASes and RIG I-like receptors) along with ERV RNAs predominately 400-800 base-pairs long, which might serve as their ligands. For schemes establishing abscopal effects, a coordinated upregulation of the OAS sensors and shared ERV transcripts was observed in both irradiated and distant tumours. Compared to homogenous RT, SFRT triggered earlier and stronger activation of OAS signaling along with NK cell responses. Overall, we show a co-involvement of tumour cell-intrinsic ERVs and their cytosolic RNA sensors in RT-induced antitumor immunity. This key finding could guide mechanistic studies and future precision oncology.

Resistance to cyclin-dependent kinase 4/6 inhibitors remains a major clinical challenge in treating estrogen receptor-positive breast cancer, with no reliable predictive biomarkers currently available for patient selection. To investigate resistance mechanisms, we generated drug-tolerant persisters (DTPs) to abemaciclib and palbociclib in a panel of estrogen receptor-positive breast cancer cell lines. Functional analyses revealed that DTPs showed resistance to CDK4/6 inhibition, maintained G1 arrest, and exhibited increased senescence phenotype. To identify clinically relevant markers of resistance, we compared transcriptomic profiles from DTPs with publicly available gene-expression data from the phase III PEARL trial. Glycoprotein non-metastatic B (GPNMB) emerged as one of the most strongly upregulated transcripts in DTPs, and also was amongst the genes associated with resistance in the PEARL dataset. We further verified that GPNMB overexpression (GPNMB-OE) in sensitive cells conferred resistance to CDK4/6 inhibition, and enhanced migratory capacity. Overexpression of GPNMB drove substantially faster tumor progression and eliminated the growth-inhibitory effect of abemaciclib, which remained highly effective in control tumors. Across all treatment arms, GPNMB-OE tumors failed to respond to CDK4/6 blockade, highlighting a strong resistance phenotype. These results identify GPNMB as a potent promoter of tumor progression and a key mediator of resistance to abemaciclib. Our findings position GPNMB as a potential biomarker and therapeutic target that may help identify patients unlikely to benefit from CDK4/6 inhibition.

Well- and dedifferentiated liposarcomas (WDLPS and DDLPS) are characterized by extensive copy- number alterations rather than recurrent gene-inactivating mutations, obscuring the molecular mechanisms that drive disease progression and, critically, the transition from well-differentiated to the more aggressive dedifferentiated tumor states. Despite marked differences in clinical behavior and prognosis, the regulatory events underlying adipocytic lineage destabilization in DDLPS remain poorly understood. Here, we establish an in vivo model of retroperitoneal liposarcoma in Xenopus tropicalis through early embryonic mosaic perturbation of p53 and Rb pathway components. Combined disruption reproducibly induced retroperitoneal WDLPS development, demonstrating that pathway-level deregulation of the MDM2-p53 and CDK4-Rb axes is sufficient to initiate liposarcoma development in vivo. Strikingly, additional perturbation of transcriptional co-activator ep300 in this context resulted in increased tumor dedifferentiation, yielding lesions composed of spatially coexisting well- and dedifferentiated adipocytic states. In contrast, direct targeted disruption of downstream adipogenic regulators recurrently lost in human DDLPS, including cebpa, g0s2, and dgat2, failed to induce dedifferentiation in the same genetic context in vivo. These findings indicate that dedifferentiation cannot be explained by loss of downstream adipocytic effectors alone but instead reflects destabilization of higher-order regulatory programs governing adipocytic identity. Together, these results establish an in vivo model that closely reflects the clinical situation on a pathway level and provides initial mechanistic insight into how adipocytic differentiation may become destabilized during disease progression. This framework offers a foundation for future studies leveraging higher-order and multi-omic approaches to dissect the molecular processes underlying the WDLPS-to-DDLPS transition.

KRAS is mutated in over 90% of pancreatic ductal adenocarcinomas (PDAC), where hotspot alterations in codons 12, 13, and 61 drive tumor initiation and progression. Although distinct biochemical properties have been described for individual KRAS mutants, whether they generate unique allele-specific signaling programs in PDAC cells remains unresolved. Here, we systematically interrogated the molecular consequences of seven common KRAS mutant variants in reconstituted isogenic, KRAS-deficient PDAC cell lines by integrated transcriptomic, proteomic, and phosphoproteomic profiling. We found that baseline cellular state, rather than allele identity, was the predominant driver of molecular variation. Comparisons with established KRAS reference signatures revealed significant but moderate overlap at the mRNA level and less so at the proteome level. Pathway analyses highlighted interferon response and mitochondrial translation as recurrently altered across alleles, while phosphoproteomic data confirmed robust ERK1/2 activity and suppression of DYRK kinase substrates by mutant KRAS expression. Importantly, no robust allele-specific molecular programs were identified. Together, our study establishes a comprehensive multi-omics resource for KRAS signaling in PDAC and demonstrates that cellular context exerts a stronger influence than allele identity in shaping molecular profiles, with implications for interpreting putative allele-specific signaling dependencies and therapeutic vulnerabilities.