Biology subjects

Sun, L.

Publications and source records attributed to Sun, L..

At least 235 records · Page 13Linked to original sources

bioRxiv2023

RIPK3-dependent necroptosis is the primary cause of RIPK1-deficient-induced immunodeficiency.

RIPK1 (receptor-interacting serine/threonine kinase 1) plays a pivotal role in developing the immune system--patients with homozygous loss-of-function mutations of RIPK1 present with immunodeficiency and intestinal inflammation. Here, we reported that RIPK1-deficient rats represented defects of human patients and were certified as a suitable disease model. Knocking out Ripk3 rather than Caspase-8 nearly completely corrected immunodeficiency disorders, developmental defects, and necroptosis in the thymus of RIPK1-deficient rats. However, inflammatory enteritis was still detected in either Ripk1/Ripk3-or Ripk1/Casp-8-double deficient rats and only rescued in Ripk1/Ripk3/Caspase-8-triple deficient rats, suggesting RIPK3 mediated necroptosis and Caspase-8 dependent apoptosis contribute in different part in RIPK1-deficient caused the syndrome. Moreover, RIPK1-deficient rat dermal fibroblasts (RDFs) showed sensitive necroptosis and impaired NF-{kappa}B activation, also reported in RIPK1-deficient human patients. And pharmacological inhibition of NF-{kappa}B activation could sensitize necroptosis of rat cells. Since mutations that damage NF-{kappa}B activation could cause immunodeficiency in human patients, it suggested that aberrantly activated necroptosis play a vital role in certain kinds of primary immunodeficiency syndromes and pharmacological inhibition of necroptosis could be a novel therapeutic strategy for those diseases.

immunology↗

bioRxiv2023

High-throughput screening of functional neo-antigens and their specific TCRs via the Jurkat reporter system combine with droplet microfluidics

T-cell receptor (TCR)-engineered T cells can precisely recognize a broad repertoire of targets derived from both intracellular and surface proteins of tumor cells. TCR-T adoptive cell therapy has shown safety and promising efficacy in solid tumor immunotherapy. However, antigen-specific functional TCR screening is time-consuming and expensive, which limits its application clinically. Here, we developed a novel integrated antigen-TCR screening platform based on droplet microfluidics technology, enabling high-throughput peptide-major histocompatibility complex (pMHC) library-to-TCR library screening with high sensitivity and low background signal. We introduced DNA barcoding technology to label peptide antigen candidate-loaded antigen-presenting cells (APCs) and Jurkat reporter cells to check the specificity of pMHC-TCR candidates. Coupled with the next-generation sequencing pipeline, interpretation of the DNA barcodes and the gene expression level of the Jurkat T-cell activation pathway provided a clear peptide-MHC-TCR recognition relationship. Our proof-of-principle study demonstrates that the platform could achieve unbiased pMHC-TCR library-on-library screening, which is expected to be used in the cross-reactivity and off-target testing of candidate pMHC-TCR libraries in clinical applications.

bioengineering↗

bioRxiv2023

eXclusionarY: Ten years later, where are the sex chromosomes in GWAS?

Ten years ago, a detailed analysis of genome-wide association studies showed that only 33% of the studies included the X chromosome. Multiple recommendations were made to combat eXclusion. Here we re-surveyed the research landscape to determine if these earlier recommendations had been translated. Unfortunately, among the summary statistics reported in 2021 in the NHGRI-EBI GWAS catalog, only 25% provided results for the X chromosome and 3% for the Y chromosome, suggesting that the eXclusion phenomenon documented earlier not only persists but has also expanded into an eXclusionarY problem. Normalizing by physical length of the chromosome, the average number of studies published until 11/29/22 with genome-wide significant findings on the X chromosome is ~1 study/Mb. In contrast, it ranges from ~6 to ~16 studies/Mb for chromosomes 4 and 19, respectively. Compared with the autosomal growth rate of ~0.086 studies/Mb/year over the last decade, studies of the X chromosome grew at less than one-seventh that rate, only ~0.012 studies/Mb/year. Among the studies that reported significant association on the X chromosome, there were extreme heterogeneities in how they analyzed the data and documented the results, suggesting the need for guidelines. Not surprisingly, among the 430 scores sampled from the PolyGenic Score catalog, 0% contained weights for sex chromosomal SNPs. To overcome the dearth of sex chromosome analyses, we provide five sets of recommendations and future directions. Finally, until the sex chromosomes are included in a whole-genome study, instead of GWAS, we propose they be more properly referred to as "AWAS" for "autosome-wide scan".

genetics↗

bioRxiv2023

Elevator Mechanism of Alternating Access in the Escherichia coli Concentrative Nucleoside Transporter NupC

Members of the concentrative nucleoside transporter (CNT) family of proteins mediate uptake of nucleosides into cells driven by a cation gradient, which then enter salvage pathways for nucleic acid synthesis. In humans, they also transport hydrophilic anticancer and antiviral nucleoside analogue drugs into cells and tissues where they exert their pharmacological effects. Escherichia coli CNT NupC (400 residues) is pyrimidine-specific and driven by a proton gradient. We have used computational, biochemical, and biophysical methods to characterize evolutionary relationships, conservation of residues, structural domains, transmembrane helices, and residues involved in nucleoside binding and/or transport activity in NupC compared with those of sodium-driven Vibrio cholerae CNT (vcCNT) and human CNTs (hCNT1-3). As in the crystal structure of vcCNT, NupC appears to contain eight transmembrane-spanning -helices. Wild-type NupC and single-cysteine-containing mutants were tested for transport activity in energized E. coli whole cells and for binding of nucleosides in non-energized native inner membranes using novel cross-polarization magic-angle spinning solid-state nuclear magnetic resonance methods. Wild-type NupC had an apparent affinity of initial rate transport (Kmapp) for [14C]uridine of 22.2 {+/-} 3.7 M and an apparent binding affinity (Kdapp) for [1'-13C]uridine of 1.8-2.6 mM. Mutant S142C retained transport and binding affinities similar to those of the wild type. Mutants G146C and E149C had no transport activity but retained varying degrees of partial binding activity with affinities decreasing in the following order: wild type > S142C > G146C > E149C. Results were explained with respect to a homology model of NupC based on the structure of vcCNT and a hypothetical elevator-type mechanism of alternating access membrane transport in NupC.

molecular biology↗

bioRxiv2023

SCCA1/SERPINB3 promotes suppressive immune environment via STAT-dependent chemokine production, blunting the therapy-induced T cell responses

Radiotherapy is a commonly used cancer treatment; however, patients with high serum squamous cell carcinoma antigen (SCCA1/SERPINB3) are associated with resistance and poor prognosis. Despite being a strong clinical biomarker, the modulation of SERPINB3 in tumor immunity is poorly understood. We investigated the microenvironment of SERPINB3 high tumors through RNAseq of primary cervix tumors and found that SERPINB3 was positively correlated with CXCL1/8, S100A8/A9 and myeloid cell infiltration. Induction of SERPINB3 in vitro resulted in increased CXCL1/8 and S100A8/A9 production, and supernatants from SERPINB3-expressing cultures attracted monocytes and MDSCs. In murine tumors, the orthologue mSerpinB3a promoted MDSC, TAM, and M2 macrophage infiltration contributing to an immunosuppressive phenotype, which was further augmented upon radiation. Radiation-enhanced T cell response was muted in SERPINB3 tumors, whereas Treg expansion was observed. A STAT-dependent mechanism was implicated, whereby inhibiting STAT signaling with ruxolitinib abrogated suppressive chemokine production. Patients with elevated pre-treatment serum SCCA and high pSTAT3 had increased intratumoral CD11b+ myeloid cell compared to patients with low SCCA and pSTAT3 cohort that had overall improved cancer specific survival after radiotherapy. These findings provide a preclinical rationale for targeting STAT signaling in tumors with high SERPINB3 to counteract the immunosuppressive microenvironment and improve response to radiation.

cancer biology↗

bioRxiv2023

USP39 promotes hepatocellular carcinogenesis through regulating alternative splicing in cooperation with SRSF6/HNRNPC

Abnormal alternative splicing (AS) caused by alterations in spliceosomal factors is implicated in cancers. Standard models posit that splice site selection is mainly determined by early spliceosomal U1, U2 snRNPs. Whether and how other mid/late-acting spliceosome components such as USP39 modulate tumorigenic splice site choice remain largely elusive. We observed that hepatocyte-specific knock-in of USP39 promoted hepatocarcinogenesis and potently regulated splice site selection. In human liver cancer cells, USP39 promoted tumor proliferation in a spliceosome-dependent manner. USP39 depletion deregulated hundreds of AS events, including the oncogenic splice-switching of KANK2. Mechanistically, we developed a novel RBP-motif enrichment analysis and found that USP39 modulated exon inclusion/exclusion by interacting with SRSF6/HNRNPC in both humans and mice. Our data represent a paradigm for the control of splice site selection by mid/late-acting spliceosome proteins and their interacting RBPs. USP39 and possibly other mid/late-acting spliceosome proteins may represent potential prognostic biomarkers and targets for cancer therapy. Graphic Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=97 SRC="FIGDIR/small/525324v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@34cbc1org.highwire.dtl.DTLVardef@2d0ee2org.highwire.dtl.DTLVardef@2c4bd6org.highwire.dtl.DTLVardef@26db00_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2023

Amino acid transporter SLC7A5 regulates Paneth cell function to affect the intestinal inflammatory response

The intestine is critical for not only processing and resorbing nutrients but also protecting the organism from the environment. These functions are mainly carried out by the epithelium, which is constantly being self-renewed. Many genes and pathways can influence intestinal epithelial cell proliferation. Among them is mTORC1, whose activation increases cell proliferation. Here, we report the first intestinal epithelial cell-specific knockout ({Delta}IEC) of an amino acid transporter capable of activating mTORC1. We show that the transporter, SLC7A5, is highly expressed in mouse intestinal crypt and Slc7a5{Delta}IEC reduces mTORC1 signaling. Surprisingly, Slc7a5{Delta}IEC mice have increased cell proliferation but reduced secretory cells, particularly mature Paneth cells. scRNA-seq and electron microscopic analyses revealed dedifferentiation of Paneth cells in Slc7a5{Delta}IEC mice, leading to markedly reduced secretory granules with little effect on Paneth cell number. We further show that Slc7a5{Delta}IEC mice are prone to experimental colitis. Thus, SLC7A5 regulates secretory cell differentiation to affect stem cell niche and/or inflammatory response to regulate cell proliferation.

immunology↗

bioRxiv2023

Preclinical Basis of the Efficacy and Pharmacodynamics of Finotonlimab, a Humanized Anti-PD-1 Monoclonal Antibody with Potent Implications for Clinical Benefit

BackgroundThe antibodies of programmed cell death protein 1 (PD-1) and its ligand (PD-L1) have dramatically changed the treatment landscapes for patients with cancer. Clinical uses of PD-1 antibodies have greatly improved the overall survival and durable responses in patients across selected tumor types. MethodsWe describe the preclinical characterization of Finotonlimab, a humanized anti-PD-1 antibody, by head to head comparison with Nivolumab or Pembrolizumab. Herein, we characterized the in vitro and in vivo efficacy, PK, PD and Fc mediated effector function of Finotonlimab. The single-agent anti-tumor activity of Finotonlimab was evaluated using humanized mouse models and a human PBMC reconstituted mouse model. Furthermore, in cynomolgus monkeys, comparative PK measurements confirmed better PK profiles of Finotonlimab than that of Pembrolizumab and Nivolumab. ResultsOur data showed Finotonlimab bind to human PD-1 with significantly high affinity and effectively inhibited its interaction with its ligands, PD-L1 and PD-L2, and thus could effectively stimulate the human T cell functions in vitro and exhibited significant antitumor efficacy in vivo. In addition, Finotonlimab showed minimal impact on Fc receptor dependent effector cell activation, which may contribute to the killing of PD-1+ T cells. In cynomolgus monkeys, Finotonlimab exhibited a non-linear pharmacokinetics (PK) profile in a dose-dependent manner, and approximately 90% of consistent receptor occupancy period was observed at 168 h after a single administration of 1 mg/kg. Following a 13-week successive administration of Finotonlimab, a pharmacodynamics study indicated a sustained mean receptor occupancy of [≥] 93% of PD-1 molecules on circulating T cells in cynomolgus monkeys up to 8 weeks even at 3 mg/kg. ConclusionsTaken together, these preclinical data are encouraging and provide a basis for the efficacy and pharmacodynamics of Finotonlimab in clinical trials.

immunology↗

bioRxiv2023

The mechanosensitive ion channel Piezo1 contributes to ultrasound neuromodulation

Transcranial low-intensity ultrasound is a promising neuromodulation modality, with the advantages of non-invasiveness, deep penetration, and high spatiotemporal accuracy. However, the underlying biological mechanism of ultrasonic neuromodulation remains unclear, hindering the development of efficacious treatments. Here, the well-known Piezo1, was studied through a conditional knockout mouse model as a major molecule for ultrasound neuromodulation ex vivo and in vivo. We showed that Piezo1 knockout in the right motor cortex of mice significantly reduced ultrasound-induced neuronal calcium responses, limb movement and muscle EMG responses. We also detected higher Piezo1 in the central amygdala (CEA) which were found more sensitive to ultrasound stimulation than that of cortex. Knocking out the Piezo1 in CEA neurons showed a significant reduction of response under ultrasound stimulation while knocking out astrocytic Piezo1 showed no obvious changes in neuronal responses. Additionally, we excluded an auditory confound by monitoring auditory cortical activation and using smooth waveform ultrasound with randomized parameters to stimulate P1KO ipsilateral and contralateral regions of the same brain and recording evoked movement in the corresponding limb. Thus, we demonstrate that Piezo1 is functionally expressed in different brain regions, and that it is an important mediator of ultrasound neuromodulation in the brain, laying the ground for further mechanistic studies of ultrasound.

neuroscience↗

bioRxiv2023

Development of Multiomics in situ Pairwise Sequencing (MiP-Seq) for Single-cell Resolution Multidimensional Spatial Omics

Delineating the spatial multiomics landscape will pave the way to understanding the molecular basis of physiology and pathology. However, current spatial omics technology development is still in its infancy. Here, we developed a high-throughput multiomics in situ pairwise sequencing (MiP-Seq) strategy to efficiently decipher multiplexed DNAs, RNAs, proteins, and small biomolecules at subcellular resolution. We delineated dynamic spatial gene profiles in the hypothalamus using MiP-Seq. Moreover, MiP-Seq was unitized to detect tumor gene mutations and allele-specific expression of parental genes and to differentiate sites with and without the m6A RNA modification at specific sites. MiP-Seq was combined with in vivo Ca2+ imaging and Raman imaging to obtain a spatial multiomics atlas correlated to neuronal activity and cellular biochemical fingerprints. Importantly, we proposed a "signal dilution strategy" to resolve the crowded signals that challenge the applicability of in situ sequencing. Together, our method improves spatial multiomics and precision diagnostics and facilitates analyses of cell function in connection with gene profiles.

molecular biology↗

bioRxiv2022

Glyco-engineered pentameric SARS-CoV-2 IgMs show superior activities compared to IgG1 orthologues

Immunoglobulin M (IgM) is the largest antibody isotype with unique features like extensive glycosylation and oligomerization. Major hurdles in characterizing its properties are difficulties in the production of well-defined multimers. Here we report the expression of two SARS-CoV-2 neutralizing monoclonal antibodies in glycoengineered plants. Isotype switch from IgG1 to IgM resulted in the production of pentameric IgMs, comprising of correctly assembled 21 human protein subunits. All four recombinant monoclonal antibodies carried a highly reproducible human-type N-glycosylation profile, with a single dominant N-glycan species at each glycosite. Both pentameric IgMs exhibited increased antigen binding and virus neutralization potency, up to 390-fold, compared to the parental IgG1. Collectively, the results may impact on the future design of vaccines, diagnostics and antibody-based therapies and emphasize the versatile use of plants for the expression of highly complex human proteins with targeted posttranslational modifications.

molecular biology↗

bioRxiv2022

Structural connectome architecture shapes the maturation of cortical morphology from childhood to adolescence

Cortical thinning is an important hallmark of the maturation of brain morphology during childhood and adolescence. However, the connectome-based wiring mechanism that underlies cortical maturation remains unclear. Using neuroimaging, connectome, transcriptome, and computational modeling, we mapped cortical thinning patterns primarily located in lateral frontal and parietal heteromodal nodes during childhood and adolescence, which is structurally constrained by white matter network architecture and is particularly represented using a network-based diffusion model. Furthermore, connectome-based constraints are regionally heterogeneous, with the largest constraints residing in frontoparietal nodes, and are associated with gene expression signatures of microstructural neurodevelopmental events. These results are highly reproducible while using another independent dataset. Our findings advance our understanding of network-level mechanisms and the associated genetic basis that underlies the maturational process of cortical morphology during childhood and adolescence.

neuroscience↗

bioRxiv2022

Fortuitous Somatic Mutations during Antibody Evolution Endow Broad Neutralization against SARS-CoV-2 Omicron Variants

Striking antibody evasion by emerging circulating SARS-CoV-2 variants drives the identification of broadly neutralizing antibodies (bNAbs). However, how a bNAb acquires increased neutralization breadth during antibody evolution is still elusive. Here, we identified a clonally-related antibody family from a convalescent individual. One of the members, XG005, exhibited potent and broad neutralizing activities against SARS-CoV-2 variants, while the other members showed significant reductions in neutralization breadth and potency, especially against the Omicron sublineages. Structural analysis visualizing the XG005-Omicron spike binding interface revealed how crucial somatic mutations endowed XG005 with greater neutralization potency and breadth. A single administration of XG005 with extended half-life, reduced antibody-dependent enhancement (ADE) effect, and increased antibody product quality, exhibited a high therapeutic efficacy in BA.2- and BA.5-challenged mice. Our results provided a natural example to show the importance of somatic hypermutation during antibody evolution for SARS-CoV-2 neutralization breadth and potency.

immunology↗

bioRxiv2022

Dalpiciclib Partially Abrogates ER Signaling Activation Induced by Pyrotinib In HER2+HR+ Breast Cancer

BackgroundRecent evidences from clinical trials (NCT04486911) revealed that the combination of pyrotinib, letrozole and dalpiciclib exerted optimistic therapeutic effect to treat HER2+HR+ breast cancer, however, the underlying molecular mechanism remained further investigation. MethodsThrough the drug sensitivity test, the drug combination efficacy of pyrotinib, tamoxifen and dalpiciclib to BT474 cells were tested. The underlying molecular mechanisms were investigated using immunofluorescence, western blot analysis, immunohistochemical staining and cell cycle analysis. Potential risk factor which may indicate the responsiveness to drug treatment in HER2+/HR+ breast cancer was selected out using RNA-sequence and tested using immunohistochemical staining and in vivo drug susceptibility test. ResultsWe found that pyrotinib combined with dalpiciclib exerted better cytotoxic efficacy than pyrotinib combined with tamoxifen in BT474 cells. Degradation of HER2 could enhance ER nuclear transportation, activating ER signaling pathway in BT474 cells whereas dalpiciclib could partially abrogate this process. This may be the underlying mechanism by which combination of pyrotinib, tamoxifen and dalpiciclib exerted best cytotoxic effect. Furthermore, CALML5 was revealed to be a risk factor in the treatment of HER2+/HR+ breast cancer and the usage of dalpiciclib might overcome this. ConclusionOur study provided evidence that the usage of dalpiciclib in the treatment of HER2+/HR+ breast cancer could partially abrogate the estrogen signaling pathway activation caused by anti-HER2 therapy and revealed that CALML5 could serve as a risk factor in the treatment of HER2+/HR+ breast cancer. FundingThis study was supported by the National Natural Science Foundation of China (#U20A20381, #81872159)

cancer biology↗

bioRxiv2022

Antigen presentation by clonally diverse CXCR5+ B cells to CD4 and CD8 T cells is associated with durable response to immune checkpoint inhibitors.

The mechanism by which ICI (immune checkpoint inhibitor) induce durable antitumor T cell activity remains inadequately defined. Tumors from melanoma patients who responded to ICI or MAPK pathway inhibitors (MAPKi) therapy generally displayed increased T cell infiltration and interferon gamma (IFN{gamma}) pathway activation. Yet, the rate of durable tumor control after ICI is almost twice that of MAPKi. Comparing the transcriptome of cohorts of melanoma patients treated with ICI or MAPKi therapy, we discovered that response to ICI is associated with CXCL13-driven recruitment of CXCR5+ B cells with higher clonal diversity than MAPKi. Higher B cell receptor (BCR) diversity allows presentation of diverse tumor antigens by B cells, resulting in robust increases of IFN{gamma} pathway activity and CXCL13 expression in tumor reactive CD8 T cells after ICI therapy. Accordingly, ICI-treated melanoma patients, but not MAPKi, whose tumors displayed higher BCR diversity and IFN{gamma} pathway score, survived significantly longer than those with either one or none. Thus, response to ICI, but not to MAPKi therapy, induces the recruitment of clonally diverse antigen presenting B cells that activate tumor specific, cytotoxic CD8 T cells to effect a durable antitumor immune response. Our result suggests that enhancing B cells tumor antigen presentation to intratumoral CD8 T cells can increase the rate of long-term response to ICI therapy.

cancer biology↗

bioRxiv2022

The SUMO-interacting Motif in NS2 promotes adaptation of avian influenza virus to mammals

Species differences in the host factor ANP32A/B result in the restriction of avian influenza virus polymerase (vPol) in mammalian cells. Efficient replication of avian influenza viruses in mammalian cells often requires adaptive mutations, such as PB2-E627K, to enable the virus to utilize mammalian ANP32A/B. However, the molecular basis for the productive replication of avian influenza viruses without prior adaptation in mammals remain poorly understood. We show that influenza A virus protein NS2 help to overcome mammalian ANP32A/B-mediated restriction to avian vPol activity by promoting avian vRNP assembly and enhancing mammalian ANP32A/B-vRNP interactions. A conserved SUMO interaction motif (SIM) in NS2 is required for its avian polymerase-enhancing properties. We also demonstrate that disrupting SIM integrity in NS2 impairs avian influenza virus replication and pathogenicity in mammalian hosts, but not in avian hosts. Our results identify NS2 as a cofactor in the adaptation process of avian influenza viruses to mammals.

microbiology↗

bioRxiv2022

Antifungal tolerance and resistance emerge at distinct drug concentrations and rely upon different aneuploid chromosomes

Antifungal drug tolerance is a response distinct from resistance, in which cells grow slowly above the minimum inhibitory drug concentration (MIC). Here we found that the majority (69.2%) of 133 Candida albicans clinical isolates, including standard lab strain SC5314, exhibited temperature-enhanced tolerance at 37{degrees}C and 39{degrees}C, and were not tolerant at 30{degrees}C. Other isolates were either always tolerant (23.3%) or never tolerant (7.5%) at these three temperatures, suggesting that tolerance requires different physiological processes in different isolates. At supra-MIC fluconazole concentrations (8-128 g/ml), tolerant colonies emerged rapidly at a frequency of ~10-3. In liquid passages over a broader range of fluconazole concentrations (0.25-128 g/ml), tolerance emerged rapidly (within one passage) at supra-MIC concentrations. By contrast, resistance appeared at sub-MIC concentrations after 5 or more passages. Of 155 adaptors that evolved higher tolerance, all carried one of several recurrent aneuploid chromosomes, often including chromosome R, alone or in combination with other chromosomes. Furthermore, loss of these recurrent aneuploidies was associated with a loss of acquired tolerance, indicating that specific aneuploidies confer fluconazole tolerance. Thus, genetic background and physiology, and the degree of drug stress (above or below the MIC) influence the evolutionary trajectories and dynamics with which antifungal drug resistance or tolerance emerges. ImportanceAntifungal drug tolerance differs from drug resistance: tolerant cells grow slowly in drug, while resistant cells usually grow well, due to mutations in a few known genes. More than half of Candida albicans clinical isolates have higher tolerance at body temperature than they do at the lower temperatures used for most lab experiments. This implies that different isolates achieve drug tolerance via several cellular processes. When we evolved different strains at a range of high drug concentrations above inhibitory levels, tolerance emerged rapidly and at high frequency (one in 1000 cells) while resistance only appeared later at very low drug concentrations. An extra copy of all or part of chromosome R was associated with tolerance, while point mutations or different aneuploidies were seen with resistance. Thus, genetic background and physiology, temperature, and drug concentration all influence how drug tolerance or resistance evolves.

evolutionary biology↗

bioRxiv2022

Modulating the epigenetic state promotes the reprogramming of transformed cells to pluripotency in a line-specific manner

Somatic cell reprogramming and oncogenic transformation share surprisingly similar features, yet transformed cells are highly resistant to reprogramming. There must be barriers that block transformed cells from reprogramming, but the nature of those barriers is unclear. In this study, we generated a systematic panel of transformed mouse embryonic fibroblasts (MEFs) using a variety of oncogenic transgenes, and discovered transformed cell lines that remain compatible with reprogramming when transfected with Oct4/Sox2/Klf4/Myc. By comparing the reprogramming-capable and incapable transformed lines we identified multiple stages of failure in the reprogramming process. Some transformed lines failed very early, whilst other lines seemed to progress through a normal-looking reprogramming process. Finally, we show that MEK inhibition overcomes one critical reprogramming barrier by indirectly suppressing a hyperactive epigenetic state in some of the transformed cells. This study reveals that the barriers underlying resistance to reprogramming vary between the different transformation methods. Key findingsO_LISomatic cell reprogramming of transformed cells is context-specific C_LIO_LIInhibition of MEK converts some cell lines to reprogramming-capable C_LIO_LITransformed cell lines are characterized by a hyperactive chromatin state C_LIO_LIMEK inhibition indirectly affects chromatin to enable reprogramming C_LI

cell biology↗