Biology subjects

Foo, S.

Publications and source records attributed to Foo, S..

At least 19 recordsLinked to original sources

bioRxiv2026

Development of a tryptophan-based dual selection system reveals the spatial organization of S-layer assembly during cytokinesis in Sulfolobus acidocaldarius

Sulfolobus acidocaldarius is a thermoacidophilic archaeon used as a model system for studying fundamental cellular processes and for emerging biotechnological applications. However, the limited availability of selectable markers restricts advanced genetic manipulation in this organism. Here, we report the development of a tryptophan auxotrophy-based selection system in S. acidocaldarius. A {Delta}trpBA mutant was constructed in the {Delta}pyrE background strain using a classical pop-in/pop-out recombination strategy. The resulting mutant exhibited little growth defects in rich medium, likely due to exogenous tryptophan supplied by complex nutrients, but failed to grow in a newly developed defined Brock-based amino acid dropout medium lacking tryptophan. Exploiting both uracil and tryptophan auxotrophies, we achieved dual-plasmid co-transformation and co-expression of the surface layer proteins and a dominant-negative mutant of the AAA-ATPase Vps4, revealing that the accumulation of surface layer lattice forming protein SlaA at the midzone of division-arrested cells together with its membrane anchor SlaB. Together, these results provide evidence for spatial regulation of S-layer assembly during archaeal cytokinesis while expanding the genetic toolkit available for S. acidocaldarius. ImportanceSulfolobus acidocaldarius is a key archaeal model organism for studying cellular processes shared with more complex life and is increasingly used for biotechnological applications. Here, we establish tryptophan auxotrophy as a new selectable marker in S. acidocaldarius, expanding the range of genetic selection systems available in this organism. By developing a defined Brock-based dropout medium, we enable stringent amino acid auxotrophy selection and precise control over nutrient composition. This system can be combined with existing uracil-based selection to support dual auxotrophy workflows, enabling co-transformation, simultaneous expression of multiple proteins, and more sophisticated genetic manipulation strategies. Using both markers, we show that S-layer proteins are localised to the division bridge in cytokinesis-arrested cells. This exemplifies ways in which the expanding molecular genetic tool kit available for Sulfolobus acidocaldarius is furthering our understanding of archaeal cell biology.

Molecular Biology↗

bioRxiv2026

Bridging the lipid divide: archaeal ESCRT-III binds phosphoinositol and polarises the cytokinetic membrane

All cells remodel their membranes to divide. The highly conserved ESCRT-III system forms contractile polymers which, through direct interactions with membrane lipids, remodel membranes across the tree of life. In exploring how ESCRT-III divides the chemically and structurally unique archaeal membrane, we reveal that the homologue CdvB1 is required for the establishment of a distinct membrane domain within the division bridge of Sulfolobus acidocaldarius, associated with an accumulation of membrane-spanning inositol phosphate lipids. We show that CdvB1 associates with phosphoinositides in vitro and that this interaction aids cytokinesis in vivo. Together, we suggest that although eukaryotes inherited their membrane lipids from bacteria during eukaryogenesis, key features of the ESCRT-III:membrane interface that allow these polymers to bind, organise, and remodel eukaryotic membranes, may originate in archaea.

cell biology↗

bioRxiv2026

Intratumoural oncolytic HSV-1 reshapes the local and systemic immune landscape through CD8+ T cell reprogramming

Most oncolytic viruses are delivered by intratumoural injection, and local administration can induce regression of both injected and distant tumours in mice and patients. However, the mechanisms by which local viral infection reprograms systemic immunity remain poorly understood. Here we show that intratumoural RP1, an oncolytic HSV-1 encoding GM-CSF and GALV-GP-R-, drives regression of injected and uninjected murine melanoma tumours and prolongs survival. RP1 elicits coordinated CD4 and CD8 T cell infiltration accompanied by local cytokine remodelling, reshaping the immune landscape at both tumour sites. Leveraging the Timer of Cell Kinetics and Activity (Tocky) system and Kaede photoconvertible protein technology, we resolve the temporal dynamics of CD8 T cell responses following local virotherapy and identify two systemically induced, virus-driven CD8 T cell populations distinguished by TCR engagement kinetics: antigen-engaged Timer-positive viral-induced precursors (VIPs) and Timer-negative KLRG1 viral-induced terminal effectors (VITEs). Single-cell transcriptomic and pseudotime analyses reveal divergent differentiation trajectories; VIPs exhibit sustained antigen engagement within the tumour microenvironment (TME), a transcriptional programme associated with self-renewal, and preferential homing to draining lymph nodes. A VIP-associated gene signature correlates with clinical response to RP1 plus PD-1 blockade in the IGNYTE trial of RP1 and nivolumab in PD-1-refractory melanoma and is independently associated with response to immune checkpoint inhibitor (ICI) therapy in melanoma. These findings establish a mechanistic link between local oncolytic virotherapy, systemic CD8 T cell reprogramming, and durable regression of distant lesions in patients.

cancer biology↗

bioRxiv2026

Preclinical efficacy of a systemically-administered, second-generation STING agonist that promotes antitumour immunity in combination with radiotherapy

As potent triggers of innate immunity, STING agonists hold promise as active immunotherapeutic agents for cancer treatment. Second-generation STING agonists, suitable for systemic delivery, are being investigated in preclinical research and have entered clinical trials. Here, the novel synthetic STING agonist, BI-1703880 (STINGa), which was designed for intravenous delivery, was investigated for anti-tumour and immunological effects. We show that STINGa activates the STING pathway and results in a transient and dose-dependent upregulation and secretion of interferons and proinflammatory cytokines in vitro and in vivo. We show that intravenous administration of repeated dosing with low-dose STINGa is well tolerated. We report that radiotherapy (RT) and STING agonism synergizes to generate innate immune cell and CD8+ T cell responses that control tumour growth. Anti-tumour activity induced by combined RT / STINGa was reduced in mice lacking a functional immune system. RT / STINGa combination treatment also initiated development of protective immune memory. RT / STINGa upregulated PD-L1, PD-1 and CTLA-4 in the tumour microenvironment. Our findings show that combining RT / STINGa with immune checkpoint inhibitors further increases therapeutic benefit. Our data confirm STING as a therapeutic target in cancer and support the clinical development of BI-1703880 STING agonist, thereby suggesting radiotherapy as a potential combination for enhancing anti-tumour efficacy.

cancer biology↗

bioRxiv2026

Addition of chemotherapy to radiotherapy promotes progenitor-exhausted CD8⁺ T-cell clonal dominance in head and neck cancer

Concomitant chemoradiotherapy (CRT) is a standard-of-care for unresectable locally-advanced head and neck squamous cell carcinoma (LA-SCCHN), but its immune effects, particularly compared to radiotherapy (RT) alone, remain unclear. Using syngeneic murine models, we integrated Nr4a3-Tocky reporter analysis with single-cell transcriptomics and T-cell receptor clonotyping comprehensively to profile intratumoural CD8 T-cells following RT/CRT. We show that CRT uniquely drives robust antigen-specific clonal expansion and biases differentiation toward progenitor (or precursor) exhausted (TPEX) phenotypes, while RT favours terminal exhaustion (TEX). Single-cell analyses reveal CRT-induced clonal dominance within TPEX subsets, suggesting the potential for enhanced immune reinvigoration. In peripheral blood mononuclear cells (PBMCs) from patients treated with CRT, high levels of TEX cells were found early and at 3 months post-treatment, with delayed peripheral TPEX expansion at 3 months, indicating phased progenitor recovery. These findings demonstrate distinct immunological remodelling by CRT versus RT and underscore the critical importance of treatment timing for optimising combination immunotherapy strategies in LA-SCCHN.

cancer biology↗

bioRxiv2026

Temporal Mechanisms of T-Cell Fate Decisions under Immune Checkpoint Blockade Resolved by CanonicalTockySeq

In cancer immunotherapy, T-cell functional states change dynamically, and no single marker or gene fully defines them. Static molecular profiles may therefore be insufficient to resolve these states. Capturing signalling history together with ongoing activity could provide a temporal framework for their dissection. Here, we developed CanonicalTockySeq, which integrates a molecular clock of T-cell receptor (TCR) signalling based on the Fluorescent Timer reporter Nr4a3-Tocky (Timer-of-cell-kinetics-and-activity) with scRNA-seq to establish an experimentally anchored temporal reference. Using landmark Tocky fractions as biological ground truths, CanonicalTockySeq constructs a transcriptomic manifold in canonical space with conical geometry. In a murine melanoma model treated with combination anti-PD-L1 and anti-CTLA-4, this framework separates temporal progression (geodesic angle) from signalling strength (radial intensity), enabling time-resolved analysis of gene-expression programmes at single-cell resolution. Application to scRNA-seq data from patients with melanoma further identifies distinct temporal programmes associated with clinical response. These analyses indicate that effective combination immunotherapy is associated with decreased persistence of antigen engagement, suppression of exhaustion-associated TCR signalling programmes, and maintenance of progenitor-like features linked to durable antitumour responses. Collectively, our findings identify temporal-state control as a key component of immunotherapy outcome and establish CanonicalTockySeq as a framework for resolving T-cell response states in vivo.

immunology↗

bioRxiv2025

Fibrillar adhesions are the primary integrin complexes shaped by matrix topography

Mechanisms of matrix topography recognition are poorly understood. Here, we show that 5{beta}1-integrin mediated fibrillar adhesions serve this function. While on planar substrates, their formation requires fibronectin secretion, tensins, and actomyosin contractility, these requirements are bypassed on nanotopographical features. While focal adhesions avoid these features, fibrillar adhesions rapidly align along pre-existing fibrous cell-derived matrix or electrospun nanofibers where they can then template fibronectin fibrils. Topography-induced fibrillar adhesions depend primarily on 5{beta}1-integrin clustering and disassemble upon cortical stiffening driven by myosin-II overactivation or increased membrane tension. We propose a generic theoretical model where the adhesion receptor favours the membrane and substrate planes to be tilted relative to each other. This model matches experimental observations of preferential 5{beta}1-integrin clustering along nanofibers and concave edges of large negative curvature along micro-ridges. These findings establish fibrillar adhesions as primary adhesion complexes that form independently of focal adhesions in response to matrix topography.

cell biology↗

bioRxiv2025

Adaptation of eukaryotic membrane homeostasis to species-specific cellular lipid landscapes

The physicochemical properties of biological membranes must be maintained within a range compatible with cellular physiology. In the face of external perturbations, membrane lipid homeostasis mechanisms sense and control membrane features. How such mechanisms evolve to function in organisms with different cellular lipid make-up is unknown. Here, we address this fundamental question by exploiting the natural divergence in membrane lipid composition between the related fission yeasts S. pombe and S. japonicus. Using lipidomics and transcriptomics, we show that the activity of the membrane-bound transcriptional activator Mga2, which regulates the {Delta}-9 desaturase Ole1 expression, is set to sense distinct levels of membrane unsaturation in the two species. Through retro-engineering and physiological experiments, we identify an evolutionary divergent but functionally constrained element within the juxtamembrane region of Mga2, which fine-tunes its performance to species-specific lipid composition. Our experiments indicate that high baseline expression of ole1, set by cis-regulatory elements in its upstream non-coding region, has redefined the dynamic range of Mga2 activation in S. pombe, supporting high lipidome unsaturation. Our work explores an "experiment of nature" to highlight the broad principles underlying the organisation and evolution of membrane homeostasis, which should be applicable to other genetic networks supporting cellular homeostatic processes.

cell biology↗

bioRxiv2025

The mechanism of cell cycle dependent proteasome-mediated CdvB degradation in Sulfolobus acidocaldarius

Protein degradation helps order events in the cell division cycle in eukaryotes, bacteria and archaea. This process is best understood in eukaryotes, where chromosome segregation and mitotic exit are triggered by APC/C and ubiquitin-regulated proteasome-dependent degradation of Securin and Cyclin B, respectively. Recent findings show that the archaeal proteasome also targets cellular substrates, including CdvB, for degradation in a cell cycle-dependent manner in Sulfolobus acidocaldarius - one of the closest experimentally tractable archaeal relatives of eukaryotes. Here, using CdvB as a model target protein to explore the mechanism of cyclic protein degradation, we identify the C-terminal broken winged helix of CdvB, which was previously shown to bind CdvA, as a domain that is sufficient to render a fusion protein unstable as cells transit from division phase to G1 phase. In parallel, we show that the rate of CdvB degradation accelerates during division, in part due to a cell cycle-dependent increase in the expression of the proteasome-activating nucleotidase (PAN), under the control of a cyclically expressed novel transcription factor, "CCTF1" (saci_0800), that can repress PAN expression. Taken together, our findings reveal the mechanisms by which archaea, despite lacking CDK/cyclin or APC/C proteins, regulate proteasome-mediated degradation to order events during cell division.

cell biology↗

bioRxiv2025

Temporal and spatial coordination of DNA segregation and cell division in an archaeon.

Cells must coordinate DNA segregation with cytokinesis to ensure that each daughter cell inherits a complete genome. Here, we explore how DNA segregation and division are mechanistically coupled in archaeal relatives of eukaryotes, which lack CDK/Cyclins. Using live cell imaging we first describe the series of sequential changes in DNA organisation that accompany cell division in Sulfolobus, which computational modelling shows likely aid genome segregation. Through a perturbation analysis we identify a regulatory checkpoint which ensures that the compaction of the genome into two spatially segregated nucleoids only occurs once cells have assembly a division ring - which also defines the axis of DNA segregation. Finally, we show that DNA compaction and segregation depends, in part, on a ParA homologue, SegA, and its partner SegB, whose absence leads to bridging DNA. Taken together, these data show how regulatory checkpoints like those operating in eukaryotes aid high-fidelity division in an archaeon.

cell biology↗

bioRxiv2025

The mechanics of a continuous self-assembling surface-layer aids cell division in an archaeon

The surface layer or "S-layer" is a planar lattice of glycosylated proteins that coats a wide range of archaea and bacteria instead of a classical cell wall or capsular polysaccharides, insulating them from the extracellular space and providing the cell membrane with physical support. Although the S-layers role as a mechanical support for the membrane might be expected to hinder cell division, we show that in rapidly dividing Sulfolobus acidocaldarius cells, the S-layer protein SlaA self-assembles into flexible lattice that helps flattens the cytokinetic furrow to accelerate ESCRT-III dependent cell division - a role that is especially important under conditions of mechanical stress. Taken together, these results generated using mutational analysis, live and fixed cellular imaging, along with electron cryomicroscopy, define the rules governing S-layer self-assembly and show how the mechanical properties of flexible lattice coats can enhance membrane functions to both physically support a cell and help to drive ESCRT-III dependent cell division. Significance statementThe bounding membrane of a cell must be protected from environmental insults. In many bacteria and archaea that lack a cell wall, this is achieved by an enveloping S-layer. By virtue of its rigid, planar structure, the S-layer is also expected to act as a barrier to the cell shape changes required for cytokinesis. In this study of the S-layer lattice in the archaeon Sulfolobus acidocaldarius however, we demonstrate a role for this self-assembling mechanical support in re-shaping the cytokinetic furrow as an aid to ESCRT-III-mediated division. In showing how mechanically active and passive structures can work together to give rise to mechanically stable cells that can divide, this reconciles what seems like a trade-off between resilience and flexibility.

molecular biology↗

bioRxiv2025

A temperature sensitive mutant screen reveals translational stress-induced cell cycle regulation in a thermophilic archaeon

The homology of the archaeal and eukaryotic ribosome provides one of the key pieces of evidence that underpins the idea that eukaryotes acquired their core information processing machinery from archaea. Since this discovery, reverse genetics has been used to study the functions of many archaeal proteins with eukaryotic homologues. Yet, our general understanding of archaeal growth and division remains unclear, in part because of difficulties of carrying out unbiased genetic screens in archaea. Here, by overcoming several technical hurdles we have used a screen of temperature sensitive mutants in Sulfolobus acidocaldarius to identify core regulators of cell growth and division. First, flow cytometry was used to define DNA content, identifying a set of mutants defective in cell cycle progression at elevated growth temperatures. Using genome sequencing and plasmid rescue, we then identified a point mutation in the large ribosomal subunit that inhibits translation and prevents entry into division following a shift to the restrictive temperature. This study reveals a link between translation and cell cycle control, and opens up the future possibility of using forward genetic screens in archaea to further our understanding of the similarities and differences in the cell biology of archaea, bacteria and eukaryotes. Significance statementO_LICurrent knowledge of archaeal cell biology is limited by the lack of forward genetics. C_LIO_LIWhole genome sequencing and plasmid rescue identifies causative mutation in a temperature sensitive mutant strain. C_LIO_LIA mutation in a ribosomal subunit blocks translation to prevent entry into division. C_LI

cell biology↗

bioRxiv2024

PBRM1 directs PBAF to pericentromeres and protects centromere integrity

The specialised structure of the centromere is critical for effective chromosome segregation, but its repetitive nature makes it vulnerable to rearrangements. Centromere fragility can drive tumorigenesis, but protective mechanisms preventing fragility are still not fully understood. The PBAF chromatin remodelling complex is frequently misregulated in cancer, but its role in cancer is still not fully characterized. Here, we identify PBAF as a protector of centromere and pericentromere structure with profound consequences for genome stability. A conserved feature of isogenic cell lines lacking PBRM1, a subunit of PBAF, is compromised centromere and pericentromere integrity. PBAF is present at these regions, and the binding pattern changes when PBRM1 is absent. PBRM1 loss creates a dependence on the spindle assembly checkpoint, which represents a therapeutic vulnerability. Importantly, we find that even in the absence of any perturbations, PBRM1 loss leads to centromere fragility, thus identifying a new player in centromere protection.

molecular biology↗

bioRxiv2024

Combination of oncolytic Maraba virus with immune checkpoint blockade overcomes therapy resistance in an immunologically cold model of advanced melanoma with dysfunctional T cell receptor signalling.

BackgroundOver the past decade, cancer immunotherapies have revolutionised the treatment of melanoma; however, responses vary across patient populations. Recently, baseline tumour size has been identified as an independent prognostic factor for overall survival in melanoma patients receiving immune checkpoint inhibitors (ICIs). MG1 is a novel oncolytic agent with broad tumour tropism that has recently entered early phase clinical trials. The aim of this study was to characterise T cell responses in human and mouse melanoma models following MG1 treatment and to establish if features of the tumour immune microenvironment (TIME) at two distinct tumour burdens would impact the efficacy of oncolytic virotherapy. MethodsHuman 3D in vitro priming assays were performed to measure anti-tumour and anti-viral T cell responses following MG1 infection. TCR sequencing, T2 killing assay, and peptide recall assays were used to assess the evolution of the TCR repertoire, and measure specific T cell responses, respectively. In vivo, subcutaneous 4434 melanomas were characterised using RNAseq, immunohistochemistry (IHC), and flow cytometry. The effectiveness of intra-tumoural MG1 was assessed in advancing 4434 tumours and the generation of anti-tumour and anti-viral T cells measured by splenocyte recall assays. Finally, combination MG1 and -PD-1 therapy was investigated in advanced 4434 tumours. ResultsMG1 effectively primed functional cytotoxic T cells (CTLs) against tumour associated antigens (TAA) as well as virus-derived peptides, as assessed using peptide recall and T2 killing assays, respectively. TCR sequencing revealed that MG1-primed CTL comprised larger clusters of similar CDR3 amino acid sequences compared to controls. In vivo testing of MG1 demonstrated that MG1 monotherapy was highly effective at treating early disease, resulting in 90% cures; however, the efficacy of MG1 reduced as the disease burden (local tumour size) increased, and the addition of -PD-1 was required to overcome resistance in more advanced disease. Differential gene expression profiles revealed that increased tumour burden was associated with an immunologically colder TIME. Furthermore, analysis of TCR signalling in advancing tumours demonstrated a different dynamic of TCR engagement compared to smaller tumours, in particular a shift in antigen recognition by CD4+ cells, from conventional to regulatory subset. ConclusionCombination of MG1 with PD-1 overcomes therapy resistance in an immunologically cold model of advanced melanoma.

cancer biology↗

bioRxiv2023

PARP inhibitors enhance reovirus-mediated cell killing through the death-inducing signaling complex (DISC) with an associated NF-kappa B-regulated immune response.

Oncolytic Reovirus type 3 Dearing (RT3D), is a naturally occurring double-stranded (ds) RNA virus that is under development as an oncolytic immunotherapy We used an unbiased high-throughput cytotoxicity screen of different targeted therapeutic agents with the aim of identifying potential drug-viral sensitizers to enhance RT3D tumour killing. Talazoparib, a clinical poly(ADP)-ribose polymerase 1 (PARP-1) inhibitor, was identified as a top hit and found to cause profound sensitisation to RT3D. This effect was not seen with other classes of oncolytic virus and was not mediated by enhanced viral replication or PARP inhibitor-related effects on the DNA damage response. RT3D interacts with retinoic acid-induced gene-1 (RIG-I) and activates PARP-1, with consequent PARylation of components of the extrinsic apoptosis pathway. Pharmacological and genetic inhibition of PARP-1 abrogates this PARylation and increases levels of extrinsic apoptosis, NF-kB signalling and pro-inflammatory cell death. Direct interaction between PARP-1 and RIG-I following RT3D/talazoparib treatment is a key factor in activating downstream signaling pathways that lead to IFN-{beta} and TNF-/TRAIL production which, in turn, amplify the therapeutic effect through positive feedback. Critically, it was possible to phenocopy the effect of RT3D through the use of non-viral ds-RNA therapy and RIG-I agonism. In in vivo studies, we demonstrated profound combinatorial efficacy of RT3D and talazoparib in human A375 melanoma in immunodeficient mice. More impressively, in immunocompetent mouse models of 4434 murine melanoma, we achieved 100% tumour control and protection from subsequent tumour rechallenge with the combination regimen. Correlative immunophenotyping confirmed significant innate and adaptive immune activation with the combination of RT3D and PARP inhibition. Taken together, these data provide a clear line of sight to clinical translation of combined regimens of PARP inhibition or ds-RNA agonism, with either viral or non-viral agents, in tumour types beyond the relatively narrow confines of current licensed indications for PARP inhibition.

cancer biology↗

bioRxiv2023

A mitochondrial quality control mechanism reverses the phagosome maturation arrest caused by Mycobacterium tuberculosis

Phagosome maturation arrest (PMA) imposed by Mycobacterium tuberculosis (Mtb) is a classic tool that helps Mtb evade macrophage anti-bacterial responses. The exclusion of RAB7, a small GTPase, from Mtb-phagosomes causes PMA. Here, we report an unexpected mechanism that triggers crosstalk between the mitochondrial quality control (MQC) and the phagosome maturation pathways that reverses the PMA. CRISPR-mediated p62/SQSTM1 depletion (p62KD) does not appear to impact mitochondrial quality. The p62KD cells are restrictive to Mtb growth, triggered by an increasingly oxidative environment and increased lysosomal targeting. The lysosomal targeting of Mtb is facilitated by enhanced TOM20+ mitochondria-derived vesicles (MDVs) biogenesis, a key MQC mechanism. In p62KD cells, TOM20+-MDVs biogenesis is MIRO1/MIRO2-dependent and gets delivered to lysosomes for degradation in a RAB7-dependent manner. Upon infection in p62KD cells, TOM20+-MDVs get extensively targeted to Mtb-phagosomes, inadvertently facilitating RAB7 recruitment, PMA reversal and lysosomal targeting of Mtb; the phenotype also replicated in p62/SQSTM1 knockout cells. Triggering MQC collapse in p62KDcells further diminishes Mtb survival, signifying cooperation between redox- and lysosome-mediated mechanisms. The MQC-anti-bacterial pathway crosstalk could be exploited for host-directed anti-tuberculosis therapies.

microbiology↗

bioRxiv2023

Sculpting the tumour microenvironment by combining radiotherapy and ATR inhibition for curative-intent anti-PD-L1- and anti-NKG2A-based adjuvant immunotherapy

Despite some success in other cancer types, the results of combining radiotherapy/chemoradiotherapy and immune checkpoint blockade have been disappointing in patients with locally advanced head and neck squamous cell carcinoma (HNSCC). For such a potentially radiocurable disease, there remains an imperative to explore novel combination approaches. Here, we show that combining ATR inhibition with radiotherapy (ATRi/RT) increases the frequency of highly activated NKG2A/PD-1 double-positive T cells in patients and in animal models of HNSCC. Addition of dual anti-NKG2A and anti-PD-1/-PD-L1 blockade to ATRi/RT in the adjuvant, post-radiotherapy setting induces a robust antitumour immune response in HNSCC preclinical models. Efficacy of the combination regimen relies on CD40/CD40L costimulatory-mediated infiltration of activated/proliferative/memory CD8 and CD4 conventional T cells with persistent or new T cell receptor (TCR) signalling, respectively, as defined by tracking of T cell dynamics. In this favourable therapeutic context, TCR sequencing shows increased richness of the TCR repertoire and the emergence of numerous and large TCR clusters that share antigen specificity in response to full combination therapy. Collectively, our data point towards promising combination approaches for future clinical testing in HNSCC.

immunology↗

bioRxiv2022

CDK4/6 inhibition and dsRNA sensor agonism co-operate to enhance anti-cancer effects through ER stress and immune modulation of tumour cells

Cytoplasmic pattern recognition receptors (PRRs) for double-stranded RNA (RIG-I/MDA5) are key mediators of anti-viral responses. PRR agonists, such as dsRNA oncolytic Reovirus type 3 Dearing (Rt3D), potently activate RNA sensors. We used an unbiased cytotoxicity screen to reveal synergistic drug-virotherapy combinations and found potent effects of Rt3D combined with the CDK4/6 inhibitor, palbociclib. The combination augmented oncolytic virus-induced endoplasmic reticulum (ER) stress/unfolded protein response (UPR) and the expression and activation/signaling of RNA sensors. Combined Rt3D-palbociclib treatment potently increased interferon production and signaling, and knockdown studies implicated key UPR proteins and the RNA sensor, RIG-I, as essential to the phenotype observed. Further experiments, using canonical RIG-I agonists and an ER stress inducer, thapsigargin, confirmed cross-talk between RNA sensing and ER stress pathways that augmented cancer cell death and interferon production. Combined Rt3D-palbociclib also increased innate immune activation within tumour cells and IFN-induced HLA expression. Analysis of the immunopeptidome revealed changes to HLA-captured peptides with Rt3D-palbociclib, including altered expression of peptides from cancer/testis antigens (CTA) and endogenous retroviral elements (ERVs). Our findings highlight cross-talk between UPR signaling and RNA-mediated PRR activation as a means of enhancing anti-cancer efficacy with potential pro-immunogenic consequences. This has implications for future clinical development of PRR agonists and oncolytic viruses, and broadens the therapeutic remit of CDK4/6 inhibitors to include roles as both ER stress and dsRNA PRR sensitizers.

cancer biology↗