bims-pideca Biomed News
on Class IA PI3K signalling in development and cancer
Issue of 2025–12–28
seventeen papers selected by
Ralitsa Radostinova Madsen, MRC-PPU



  1. Cell Syst. 2025 Dec 22. pii: S2405-4712(25)00289-3. [Epub ahead of print] 101456
      The maintenance of cellular homeostasis requires tight regulation of proteome concentration and composition. To achieve this, protein production and elimination must be robustly coordinated. However, the mechanistic basis of this coordination remains unclear. Here, we address this question using quantitative live-cell imaging, computational modeling, transcriptomics, and proteomics approaches. We found that protein decay rates systematically adapt to global alterations of protein synthesis rates. This adaptation is driven by a core passive mechanism supplemented by facultative changes in mechanistic/mammalian target of rapamycin (mTOR) signaling. Passive adaptation hinges on changes in the production rate of the machinery governing protein decay and allows for partial maintenance of the cellular proteome. Sustained changes in mTOR signaling provide an additional layer of adaptation unique to naive pluripotent stem cells, allowing for near-perfect maintenance of proteome composition. Our work unravels the mechanisms protecting the integrity of mammalian proteomes upon variations in protein synthesis rates. A record of this paper's transparent peer review process is included in the supplemental information.
    Keywords:  Bayesian inference; cell proliferation; dynamic SILAC; passive adaptation; proteasome; protein degradation; protein dilution; protein synthesis; protein turnover; proteomics; superstatistical modeling; tandem fluorescent timer
    DOI:  https://doi.org/10.1016/j.cels.2025.101456
  2. bioRxiv. 2025 Dec 19. pii: 2025.12.17.694993. [Epub ahead of print]
      Artery endothelial cells (ECs) arise through different pathways, including differentiation from mesodermal cells (vasculogenesis) or from already established vein or capillary plexus ECs (angiogenesis), the latter being most common during embryonic development and regeneration. Understanding the vein-to-artery (v2a) transition could improve revascularization therapies, but progress is limited by a lack of human models. Here, we develop a human pluripotent stem cell (hPSC) differentiation protocol that models the v2a EC conversion. Comparing v2a and mesoderm-to-artery (m2a) transcriptomes with publicly available single cell RNA sequencing (scRNA-seq) data from human embryos showed they reflected angiogenesis- and vasculogenesis-derived artery ECs, respectively. This reductionist system revealed that VEGF activation alongside PI3K inhibition was sufficient for vein ECs to acquire arterial identity within 48 hours. We model a critical step in vascular development and define the minimal signals required for artery differentiation from veins, providing a framework to promote this conversion in revascularization or therapeutic contexts.
    DOI:  https://doi.org/10.64898/2025.12.17.694993
  3. Structure. 2025 Dec 19. pii: S0969-2126(25)00477-0. [Epub ahead of print]
      The epidermal growth factor receptor (EGFR) was among the first receptor tyrosine kinases (RTKs) shown to be activated by ligand-induced dimerization. Structural studies explain how ligand binding induces the dimerization of EGFR's extracellular region. Unlike other RTKs, EGFR's intracellular tyrosine kinase domain (TKD) is activated allosterically in an asymmetric dimer that is observed crystallographically, but not in cryo-EM studies of intact EGFR. Here, we show that this asymmetric TKD dimer forms only transiently - explaining its lack of definition by cryo-EM. By engineering an asymmetric TKD dimer and studying a TKD-duplicated lung cancer EGFR variant, we show that TKD dimerization increases kinase activity by several hundred-fold. We were also able to stabilize and visualize discrete asymmetric EGFR TKD dimers at high resolution using cryo-EM. Our findings argue that oncogenic mutations activate EGFR primarily by promoting TKD dimerization, and suggest that the transient nature of EGFR TKD dimers may allow biased EGFR signaling.
    Keywords:  cancer; dimerization; epidermal growth factor receptor; growth factor signaling; oncogenic mutation; protein conformation; receptor tyrosine kinases
    DOI:  https://doi.org/10.1016/j.str.2025.11.017
  4. bioRxiv. 2025 Dec 12. pii: 2025.12.09.693285. [Epub ahead of print]
      Cells dynamically regulate chromatin in response to nutrient flux which promotes the transcriptional changes necessary for adaptation. The mechanistic target of rapamycin complex 1 (mTORC1) kinase integrates nutrient signaling with chromatin regulation, yet whether chromatin stability feeds back to mTORC1 activation and stress adaption remains unknown. We previously identified histone H3 at lysine 37 (H3K37) as essential for the response to mTORC1 stress such that mutation of H3K37 to alanine (H3K37A) causes cell death upon mTORC1 inhibition. Herein, we show that H3K37-dependent chromatin stability prevents proteasome-mediated histone degradation, restricts mTORC1 signaling, and safeguards mitochondrial homeostasis during mTORC1 stress. Genetic interaction analyses reveal that H3K37A combined with mutants that destabilize chromatin, including loss of the Set2 H3K36 methyltransferase, Rpd3S histone deacetylase, or multiple histone deposition pathways, causes synthetic lethality when mTORC1 is inhibited. Transcriptome analysis indicates that H3K37A misregulates the mitochondrial transcriptome during mTORC1 stress, which increases mitochondrial reactive oxygen species (ROS) and triggers lethal mitochondrial retrograde signaling. Inactivation of retrograde signaling, or ROS neutralization, rescues viability of H3K37A and chromatin stability mutants during mTORC1 stress. These findings establish chromatin stability as a key safeguard that restrains mTORC1 activity and prevents toxic mitochondrial stress during metabolic adaptation.
    DOI:  https://doi.org/10.64898/2025.12.09.693285
  5. Nat Commun. 2025 Dec 21.
      Growth deceleration before growth termination is a universal feature of growth during development. Transcriptomics analysis reveals that during their two-day period of growth deceleration, wing imaginal discs of Drosophila undergo a progressive metabolic shift from oxidative phosphorylation towards glycolysis. Ultra-sensitive reporters of HIF-1α stability and activity show that imaginal discs become increasingly hypoxic during development in normoxic conditions, suggesting that limiting oxygen supply could underlie growth deceleration. We confirm the expectation that rising levels of HIF-1α dampen TOR signalling activity through transcriptional activation of REDD1. Conversely, excess TOR leads, in a tissue-size-dependent manner, to hypoxia, which boosts HIF-1α levels and activity. Thus, HIF-1α mediates a negative feedback loop whereby TOR signalling triggers hypoxia, which in turn reduces TOR signalling. Abrogation of this feedback by Sima/HIF-1α knockdown leads to cellular stress, which is alleviated by reduced TOR signalling or a modest increase in environmental oxygen. We conclude that Sima/HIF-1α prevents TOR-mediated growth from depleting local oxygen supplies during normal development.
    DOI:  https://doi.org/10.1038/s41467-025-67089-6
  6. bioRxiv. 2025 Dec 13. pii: 2025.12.10.693466. [Epub ahead of print]
      Receptor tyrosine kinase (RTK) fusions are a large class of oncoproteins found in ∼5% of cancers. Key questions remain, however, about how RTK fusions transmit oncogenic signals, including how these largely cytoplasmic proteins activate downstream pathways that originate at the plasma membrane. Fusions are multimeric and can form mesoscale condensates in cancer cells, and condensation has been implicated as an essential mechanism to enable signal transmission from the cytoplasm. However, whether condensates play a causal role, or whether smaller 'diffuse' assemblies are sufficient to transduce signals, has been challenging to establish. Here we apply advanced microscopy, single-cell analysis, and synthetic fusions to determine the principles by which multimerization and condensation drive signaling from cytoplasmic RTK fusions. For EML4-ALK, a prominent fusion that forms condensates, we found poor correlation between condensation and signaling. By contrast, EML4-ALK activity was abundant in the diffuse phase, and the kinetics of diffuse-phase activity aligned more closely with downstream Erk signaling than did kinetics of signaling within condensates. Synthetic RTK fusions showed that cytoplasmic ALK or RET fusion dimers-and even constitutively active monomers-were sufficient to induce strong Ras-Erk signaling despite the absence of condensates, and diffuse fusions were sufficient to transform cells in vitro and in subcutaneous tumor models. A panel of various other cancer-driving RTK fusions showed that low-order multimerization was universal across fusions, whereas mesoscale condensation was rare and did not correlate with signaling. Our results suggest that low-order fusion multimerization is sufficient to drive its phosphorylation, which is necessary and sufficient to trigger downstream oncogenic signaling.
    DOI:  https://doi.org/10.64898/2025.12.10.693466
  7. Orphanet J Rare Dis. 2025 Dec 22. 20(1): 624
       BACKGROUND: Vascular malformations are congenital disorders characterized by abnormal blood and/or lymphatic vessels, often leading to pain, functional impairment, and severe complications. Recent advances in molecular genetics have identified key mutations and signaling pathway aberrations, particularly in the PI3K/AKT/mTOR axis, as critical contributors to the etiology of vascular malformations.
    MAIN BODY: The PI3K/AKT/mTOR axis regulates essential endothelial cell processes, including proliferation, migration, and metabolism. Aberrant activation of this pathway is strongly linked to slow-flow vascular malformations and PIK3CA-related overgrowth spectrum, and increasing evidence also implicates it in fast-flow vascular malformations. These findings underscore the pathway as a promising therapeutic target. This review summarizes current mechanistic insights into PI3K/AKT/mTOR signaling in vascular malformations and examines the therapeutic potential of targeted inhibitors. By integrating results from clinical trials with emerging molecular research, it aims to guide clinical practice while providing future directions for translational investigation.
    CONCLUSION: Recognition of PI3K/AKT/mTOR dysregulation provides a rationale for pathway-directed treatment. Development of selective agents and rational combination strategies-guided by molecular profiling and validated in preclinical and clinical studies-will be essential to enhance efficacy while minimizing resistance and toxicity.
    Keywords:  Alpelisib; PI3K/aKT/mTOR pathway; PIK3CA-related overgrowth spectrum; Sirolimus; Targeted therapy; Vascular malformations
    DOI:  https://doi.org/10.1186/s13023-025-04115-2
  8. Adv Sci (Weinh). 2025 Dec 23. e08648
      The initial invasion of tumors requires a transition from a solid, jammed state to a fluid-like, flocking, unjammed state that enables collective migration. Here, we show that de novo gene transcription is essential for the emergence of flocking in epithelial tissues and identify connexins (Cx) as key mediators of this transition. Using quiescent HaCaT keratinocytes, tumorigenic A431 epidermoid carcinoma cells, primary bronchial epithelial explants, and vocal fold carcinoma (VFC) cells, we find that flocking induction depends on transcriptional programs activated downstream of epidermal growth factor (EGF). EGF stimulation upregulates Cx26 and Cx31 and enhances gap-junctional intercellular communication (GJIC), which is necessary-though not sufficient-to generate the large-scale cell-volume fluctuations and density heterogeneity that accompany unjamming. Sustained signaling through extracellular signal-regulated kinase 1/2 (ERK1/2) and AKT serine/threonine kinase (AKT) downstream of the EGF receptor (EGFR) is required for connexin induction, linking mechanical state transitions to extracellular cues. Pharmacological inhibition and CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats-CRISPR associated protein 9) knockout of connexins block unjamming and collective motility. VFC cells display constitutively elevated connexins and persistent flocking that is highly sensitive to connexin inhibition. Consistently, high Cx26 expression correlates with reduced survival across carcinomas. These findings reveal a transcriptionally controlled, connexin-dependent mechanism that enables tissue fluidization and collective invasion.
    Keywords:  EGFR signaling; collective motility; connexins and fluid exchange; jamming transition; tissue‐level phase transition
    DOI:  https://doi.org/10.1002/advs.202508648
  9. J Immunother Cancer. 2025 Dec 21. pii: e012280. [Epub ahead of print]13(12):
      Multiplex immunofluorescence and immunohistochemistry (mIF/IHC) are increasingly employed antibody-based technologies that use tissue sparingly and facilitate the detection of co-localized or neighboring biomarkers. Specifically, these platforms enable spatial analyses of the tumor microenvironment as well as extended applications, for example, describing normal tissue anatomy, autoimmunity, infectious diseases, etc. mIF/IHC has greatly enhanced biomarker discovery efforts, and a growing number of studies suggest superiority to traditional IHC. Standardization of staining approaches, reporting of image analysis strategies and resultant data is critical for facilitating cross-study comparisons, validation, deployment, and generalization of findings. To address this challenge, The Society for Immunotherapy of Cancer (SITC) previously published two articles providing best practice guidelines for mIF/IHC staining, image analysis, and data sharing. Here, SITC convened stakeholders to develop the third article in the series, a consensus checklist for scientific reporting of mIF/IHC data to support and complement the best practice guidelines. The checklist includes critical components of mIF/IHC applications to be defined within publications such as detailed descriptions of analytical validation; image acquisition, selection, and registration methods; and cell clustering and spatial analysis strategies, amongst others. Such information will help with data reproducibility and comparison across studies towards future drug and assay development.
    Keywords:  Biomarker; Immunotherapy; Pathology; Tumor microenvironment - TME
    DOI:  https://doi.org/10.1136/jitc-2025-012280
  10. Ann Oncol. 2025 Dec 18. pii: S0923-7534(25)06331-8. [Epub ahead of print]
      The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway is frequently activated in many cancers, including prostate cancer where this is often following loss of phosphatase and tensin homolog (PTEN). The CAPItello-281 trial is the first phase III trial to evaluate AKT inhibition added at start of androgen deprivation therapy for metastatic prostate cancer, specifically in combination with abiraterone acetate and prednisone for patients with loss of PTEN in ≥90% of tumor cells on immunohistochemistry staining. Adverse events were common, including hyperglycaemia, diarrhoea and grade 3 rash. Whilst the efficacy in the full trial cohort was modest, post hoc analyses identified significant efficacy in tumors with complete PTEN loss (∼5% of all tumors). Given an increasing number of treatment options for metastatic hormone sensitive prostate cancer, future work could evaluate capivasertib for tumors with greatest sensitivity and in combination with docetaxel, radioligand therapeutics and radiotherapy.
    Keywords:  AKT inhibition; abiraterone acetate; immunohistochemistry; metastatic hormone sensitive prostate cancer; phosphatase and tensin homolog (PTEN)
    DOI:  https://doi.org/10.1016/j.annonc.2025.12.010
  11. bioRxiv. 2025 Dec 11. pii: 2025.12.08.693036. [Epub ahead of print]
       Background: Adults and children with cerebral cavernous malformations (CCMs) are at risk of experiencing lifelong complications such as hemorrhagic strokes, neurological deficits, and epileptic seizures. These complications can severely reduce quality of life. At present, there is no safe or effective therapeutic option for the long-term treatment of CCMs.
    Methods: Using advanced artificial intelligence (AI) and machine learning models, powered by the Benevolent Platform™, we aimed to identify therapeutic drug targets for CCM pathology (e.g., CCM1, CCM2, CCM3). An AI integrative approach utilized various data types from biomedical entities, including diseases, genes, tissues, and biological mechanisms, together with CCM transcriptomic experimental data. High-throughput drug screening of AI-selected FDA-approved medications, analyses of mitochondrial morphology, and studies on pharmacokinetics, pharmacodynamics, and toxicology were conducted in CCM animal models to identify drugs that could potentially be repurposed for the long-term treatment of CCM disease.
    Results: AI predicted the AMPK (AMP-activated protein kinase) and mTOR (mammalian target of rapamycin) pathways as potential therapeutic targets that contribute to CCM pathology. High-content screening validation revealed that the FDA-approved drug metformin, which acts as an AMPK agonist and mTOR inhibitor, can reverse changes in cell-cell junction organization and increase KLF4 expression, a marker for CCM, in human CCM endothelial cells in cultured assays. In addition, pharmacodynamic markers of metformin were observed in CCM mouse models ( Slco1c1-iCreERT2;Krit1 fl/fl ;Pten fl/wt and Slco1c1-iCreERT2;Pdcd10 fl/fl ) including reduced S6 kinase or ribosomal protein phosphorylation, a marker of decrease mTOR signaling, and increased AMPK phosphorylation, a marker of AMPK activation, that corresponded to reduced lesion burden. Pharmacokinetic and toxicological studies in CCM animal models showed that that metformin penetrates the brain and long-term administration has a favorable safety profile. We also demonstrated that brain endothelial cells in chronic CCM mouse models exhibit increased levels of the inflammatory marker VCAM-1, which is associated with altered mitochondrial phenotypes, as observed by immunofluorescence, MITO-tagging, and electron microscopy analysis. Additionally, we discovered that metformin and a potent AMPK activator, PF-06409577, can reverse mitochondrial phenotypic changes in brain endothelial cells and reduce the elevation of VCAM-1 expression associated with chronic CCM disease. Therefore, metformin can provide cytoprotection and may reverse the CCM endothelial phenotype by activating AMPK.
    Conclusions: Predictions using AI technology and high-throughput drug screening, combined with pharmacokinetic, pharmacodynamic, and toxicological studies in CCM animal models, identified metformin as a promising drug candidate for repurposing for the long-term treatment of CCM disease. We propose that metformin enhances metabolic adaptation to brain vascular malformations by activating AMPK, which helps reverse mitochondrial fragmentation in brain endothelial cells.
    Graphical abstract:
    DOI:  https://doi.org/10.64898/2025.12.08.693036
  12. Anal Chem. 2025 Dec 24.
      Mass cytometry can facilitate the study of over 40 protein markers in single cells, making it an ideal technique to investigate complex biological systems. The use of antibodies tagged with metal isotopes as probes makes mass cytometry measurements susceptible to isotopic spillover. In this report, we introduce ccSpill, an instrument-specific matrix built from calibration curves of metal-labeled antibodies and solutions of pure metals that can be applied to single-cell data to remove spillover. ccSpill is unique to each lab, and each set of reporter antibodies and is compatible with isotype-based nonspecific binding (NSB) corrections. We demonstrate that combining ccSpill with NSB corrections is integral to the optimization of sample preparation procedures that involve challenging antibodies and that such a correction identifies and excludes cell artifacts in single-cell analyses. Furthermore, the combined correction demonstrated that low metal ion/antibody ratios are detrimental to capturing features at the edges of single-cell distributions, which are misassigned without a correction. Lastly, by applying the combined correction to phenotypic markers, the identification of cell types was highly enhanced. Combined corrections of spillover and NSB provide a gateway to use mass cytometry unequivocally to characterize rare cells (e.g., senescent), subtypes (e.g., endothelial), or treatment (e.g., rapamycin), which is highly needed in clinical and biomedical research.
    DOI:  https://doi.org/10.1021/acs.analchem.5c05326
  13. Mol Syndromol. 2025 Nov 25.
       Objective: Somatic mosaic activating PIK3CA variants are a well-established cause of segmental overgrowth phenotypes, whereas germline PIK3CA variants are rare and clinically heterogeneous. We report 2 unrelated patients - 1 with a somatic mosaic and 1 with a de novo germline PIK3CA variant - with longitudinal clinical follow-up.
    Case Presentation: Patient 1 carried NM_006218.4:c.1412C>T; p.(Pro471Leu) in the C2 domain and presented with macrocephaly, generalized overgrowth, epilepsy, and structural brain anomalies; mosaicism was supported by an attenuated mutant signal on Sanger sequencing. Patient 2 harbored a de novo NM_006218.4:c.323G>A; p.(Arg108His) in the N-terminal p85-binding region and showed macrocephaly, attention-deficit/hyperactivity disorder, and mitral annular disjunction/mitral valve prolapse with aortic root dilatation.
    Conclusion: These 2 cases illustrate PIK3CA-related phenotypes arising from somatic mosaic and germline contexts and document their clinical course over time. Larger, well-characterized cohorts and complementary functional assays are needed to refine genotype-phenotype relationships, inform clinical care, and evaluate targeted therapies.
    Keywords:  Case report; Exome sequencing; Germline variant; Overgrowth; PIK3CA; Somatic mosaicism
    DOI:  https://doi.org/10.1159/000549757
  14. bioRxiv. 2025 Dec 10. pii: 2025.12.06.692715. [Epub ahead of print]
      Tissues are shaped by extracellular signaling fields which convey information between cells. The cellular composition of tissues, and the extracellular signaling within the tissue, are innately spatially structured. Modern spatialomics data provide unprecedented measurement of ligand and receptor expressivity in situ from tissue sections. Here, we show that by adapting generalizable geospatial statistical models to spatialomics data, we are able to reveal statistically-detailed portraits of morphogenic field interactions within tissues and thereby approach a richer set of biologic questions than is typically pursued. The general methods piloted here can readily be applied to spatialomics data from diverse platforms with no need to alter data collection techniques. Our results demonstrate that the application of spatial statistical modeling to spatialomics data opens many avenues for future experimentation that will be valuable to fundamental biology and to regenerative medicine.
    Highlights: Tissue biology & regenerative medicine requires analysis of tissue morphogen fields and morphogenic interactionsSpatial statistics can be used to model continuous morphogenic interaction fields in tissues from discrete spatialomics data.
    DOI:  https://doi.org/10.64898/2025.12.06.692715
  15. Cell Rep. 2025 Dec 24. pii: S2211-1247(25)01569-4. [Epub ahead of print]45(1): 116797
      Proteins are the most abundant source of amino acids in body fluids. However, the potential contribution of extracellular protein catabolism to the regulation of T cell immunity remains poorly understood. In this study, we show that endocytosed extracellular proteins function as an amino acid source in activated T cells, maintaining mTORC1 activity and sustaining cytokine production following T cell activation. Genetic ablation of Tfe3 impairs the activation-induced upregulation of lysosomal genes and disrupts extracellular protein catabolism, resulting in attenuated mTORC1 signaling and compromised anti-viral and anti-tumor T cell responses. The TFE3-protein-mTORC1 signaling axis demonstrates clinical relevance. CD8+PD-1+ tumor-infiltrating T cells from older patients with lung cancer display reduced lysosomal degradation capacity and impaired cytokine secretion compared to their middle-aged counterparts. This functional defect is rescued by treatment with Vismodegib, a TFE3-inducing drug. Our findings reveal lysosome-mediated extracellular protein catabolism as an important metabolic pathway supporting T cell immunity.
    Keywords:  CP: immunology; CP: metabolism; activated T cells; amino acids; extracellular proteins; lysosomal proteolysis; mTORC1; protein degradation
    DOI:  https://doi.org/10.1016/j.celrep.2025.116797
  16. Nat Commun. 2025 Dec 23.
      Quiescence (reversible cell-cycle arrest) and senescence (irreversible arrest) are challenging to distinguish due to a lack of specific biomarkers, yet both arise simultaneously after chemotherapy. While senescence suppresses tumors by limiting proliferation and recruiting the immune system, quiescent cancer cells evade future therapies and may resume proliferation. Here, we pair time-lapse imaging of cell-cycle dynamics with single-cell RNA sequencing after etoposide treatment to differentiate these states, linking heterogeneous cell-cycle phenotypes to the transcriptomic landscape. We identify diverse senescent types (senotypes) and link them to two arrest pathways - a gradual path arising after a standard mitosis-to-G0 transition, and an alternative direct path driven by a mitotic slip. Using pseudotime trajectory analysis, we find that senescent phenotypes begin to manifest early and gradually along the first trajectory, even in shallow quiescent cells. These data support a model wherein, following chemotherapy, quiescence and senescence exist on a continuum of cell-cycle withdrawal at a transcriptome-wide level.
    DOI:  https://doi.org/10.1038/s41467-025-66836-z
  17. Cell. 2025 Dec 22. pii: S0092-8674(25)01366-2. [Epub ahead of print]
      During chronic stress, cells must support both tissue function and their own survival. Hepatocytes perform metabolic, synthetic, and detoxification roles, but chronic nutrient imbalances can induce hepatocyte death and precipitate metabolic dysfunction-associated steatohepatitis (MASH, formerly NASH). Despite prior work identifying stress-induced drivers of hepatocyte death, chronic stress' functional impact on surviving cells remains unclear. Through cross-species longitudinal single-cell multi-omics, we show that ongoing stress drives prognostic developmental and cancer-associated programs in non-transformed hepatocytes while reducing their mature functional identity. Creating integrative computational methods, we identify and then experimentally validate master regulators perturbing hepatocyte functional balance, increasing proliferation under stress, and directly priming future tumorigenesis. Through geographic regression on human tissue microarray spatial transcriptomics, we uncover spatially structured multicellular communities and signaling interactions shaping stress responses. Our work reveals how cells' early solutions to chronic stress can prime future tumorigenesis and outcomes, unifying diverse modes of cellular dysfunction around core actionable mechanisms.
    Keywords:  chronic stress response; computational methods development; epigenetic priming; genetic perturbation; liver; metabolism; single-cell genomics; tissue memory
    DOI:  https://doi.org/10.1016/j.cell.2025.11.031