Biology subjects

Girard, L.

Publications and source records attributed to Girard, L..

12 recordsLinked to original sources

bioRxiv2026

New histone deposition recruits the DNA methylation maintenance machinery at sites of DNA damage repair

Faithful inheritance of DNA methylation contributes to the memory of epigenetic states and protects against disease. While the mechanisms underlying DNA methylation maintenance at replication forks are well characterized, whether and how DNA methylation is altered or maintained at sites of DNA damage repair is still poorly understood. Here, by exploiting sequencing, imaging and proteomic approaches in mammalian cells exposed to UV radiation, we show that the majority of DNA methylation marks are maintained during UV damage repair and we dissect the molecular machinery involved in DNA methylation control. We detect the recruitment to sites of repair synthesis of the DNMT1 and DNMT3A DNA methylating enzymes, driven by the DNMT1 cofactor UHRF1 and by UV damage repair endonucleases. We also uncover a crosstalk with histone dynamics, whereby newly deposited H3.3 histones at UV damage sites promote the recruitment of DNMT1. Functionally, we reveal the importance of the DNA methylation maintenance machinery for the transcriptional response to UV damage and sustained cell proliferation. This work provides a comprehensive picture of DNA methylation control mechanisms following DNA damage, with important implications for our understanding of human diseases with an altered methylome.

molecular biology↗

bioRxiv2024

A novel and potent MICA/B antibody is therapeutically effective in KRAS LKB1 mutant lung cancer models

Concurrent KRAS LKB1 (STK11, KL) mutant Non-Small Cell Lung Cancers (NSCLC) is particularly difficult to treat and does not respond well to current immune checkpoint blockade (ICB) therapies. This is due to numerous mechanisms including low antigen presentation limiting T cell mediated killing. To activate anti-tumor immunity, we targeted tumor cell - natural killer (NK) cell interactions. We tested whether a novel antibody based therapeutic strategy that predominantly activates natural killer (NK) cells demonstrates efficacy in pre-clinical mouse models of KL NSCLC. NK cells rely on binding of ligands, such as Major Histocompatibility Complex (MHC) class I-related chain A or B (MICA/B), to the activating receptor NKG2D. Importantly MICA and MICB are widely expressed in elevated levels across NSCLC subtypes including KL lung cancers. Proteases with the tumor microenvironment (TME) can cleave these proteins rendering tumor cells less visible to NK cells. We therefore developed a MICA monoclonal antibody, AHA-1031, which utilizes two NK cell activating receptors. AHA1031 prevents ligand shedding without interfering with binding to NKG2D while targeting cancer cells to antibody mediated cell dependent cytotoxicity (ADCC). Our therapeutic novel antibody has significant monotherapy activity in KL cancer models including xenografts of human cell lines and patient derived xenografts. Activating NK cells through MICA/B stabilization and inducing ADCC offers an alternative and potent therapy option in KL tumors. MICA/B are shed across different tumors making this therapeutic strategy universally applicable.

immunology↗

bioRxiv2023

Acquired Cross-resistance in Small Cell Lung Cancer due to Extrachromosomal DNA Amplification of MYC paralogs

Small cell lung cancer (SCLC) presents as a highly chemosensitive malignancy but acquires cross-resistance after relapse. This transformation is nearly inevitable in patients but has been difficult to capture in laboratory models. Here we present a pre-clinical system that recapitulates acquired cross-resistance in SCLC, developed from 51 patient-derived xenografts (PDXs). Each model was tested for in vivo sensitivity to three clinical regimens: cisplatin plus etoposide, olaparib plus temozolomide, and topotecan. These functional profiles captured hallmark clinical features, such as the emergence of treatment-refractory disease after early relapse. Serially derived PDX models from the same patient revealed that cross-resistance was acquired through a MYC amplification on extrachromosomal DNA (ecDNA). Genomic and transcriptional profiles of the full PDX panel revealed that this was not unique to one patient, as MYC paralog amplifications on ecDNAs were recurrent among cross-resistant models derived from patients after relapse. We conclude that ecDNAs with MYC paralogs are recurrent drivers of cross-resistance in SCLC. SIGNIFICANCESCLC is initially chemosensitive, but acquired cross-resistance renders this disease refractory to further treatment and ultimately fatal. The genomic drivers of this transformation are unknown. We use a population of PDX models to discover that amplifications of MYC paralogs on ecDNA are recurrent drivers of acquired cross-resistance in SCLC.

cancer biology↗

bioRxiv2023

ASCL1-ERK1/2 Axis: ASCL1 restrains ERK1/2 via the dual specificity phosphatase DUSP6 to promote survival of a subset of neuroendocrine lung cancers

The transcription factor achaete-scute complex homolog 1 (ASCL1) is a lineage oncogene that is central for the growth and survival of small cell lung cancers (SCLC) and neuroendocrine non-small cell lung cancers (NSCLC-NE) that express it. Targeting ASCL1, or its downstream pathways, remains a challenge. However, a potential clue to overcoming this challenage has been information that SCLC and NSCLC-NE that express ASCL1 exhibit extremely low ERK1/2 activity, and efforts to increase ERK1/2 activity lead to inhibition of SCLC growth and surival. Of course, this is in dramatic contrast to the majority of NSCLCs where high activity of the ERK pathway plays a major role in cancer pathogenesis. A major knowledge gap is defining the mechanism(s) underlying the low ERK1/2 activity in SCLC, determining if ERK1/2 activity and ASCL1 function are inter-related, and if manipulating ERK1/2 activity provides a new therapeutic strategy for SCLC. We first found that expression of ERK signaling and ASCL1 have an inverse relationship in NE lung cancers: knocking down ASCL1 in SCLCs and NE-NSCLCs increased active ERK1/2, while inhibition of residual SCLC/NSCLC-NE ERK1/2 activity with a MEK inhibitor increased ASCL1 expression. To determine the effects of ERK activity on expression of other genes, we obtained RNA-seq from ASCL1-expressing lung tumor cells treated with an ERK pathway MEK inhibitor and identified down-regulated genes (such as SPRY4, ETV5, DUSP6, SPRED1) that potentially could influence SCLC/NSCLC-NE tumor cell survival. This led us to discover that genes regulated by MEK inhibition suppress ERK activation and CHIP-seq demonstrated these are bound by ASCL1. In addition, SPRY4, DUSP6, SPRED1 are known suppressors of the ERK1/2 pathway, while ETV5 regulates DUSP6. Survival of NE lung tumors was inhibited by activation of ERK1/2 and a subset of ASCL1-high NE lung tumors expressed DUSP6. Because the dual specificity phosphatase 6 (DUSP6) is an ERK1/2-selective phosphatase that inactivates these kinases and has a pharmacologic inhibitor, we focused mechanistic studies on DUSP6. These studies showed: Inhibition of DUSP6 increased active ERK1/2, which accumulated in the nucleus; pharmacologic and genetic inhibition of DUSP6 affected proliferation and survival of ASCL1-high NE lung cancers; and that knockout of DUSP6 "cured" some SCLCs while in others resistance rapidly developed indicating a bypass mechanism was activated. Thus, our findings fill this knowledge gap and indicate that combined expression of ASCL1, DUSP6 and low phospho-ERK1/2 identify some neuroendocrine lung cancers for which DUSP6 may be a therapeutic target.

cancer biology↗

bioRxiv2022

Brief report: Reclassifying SCLC-Y as SMARCA4 deficient malignancies - resolving the controversy

IntroductionThe classification of small cell lung cancer (SCLC) into distinct molecular subtypes defined by ASCL1, NEUROD1, POU2F3 or YAP1 expression, paves the way for the development of targeted therapeutics. However, the existence of a distinct YAP1-expressing SCLC subtype remains controversial. Here we have undertaken a detailed molecular and histological characterisation of YAP1 expressing SCLC-Y to understand the biology of this proposed subtype. MethodsThe mutational landscape of human SCLC cell lines was interrogated to identify pathogenic genomic alterations unique to SCLC-Y. Xenograft tumours generated from cell lines representing the molecular subtypes of SCLC (SCLC-A, -N, -P and -Y) were evaluated by a panel of pathologists. Diagnoses were validated by transcriptomic analysis of primary tumour and human cell line datasets. ResultsUnexpectedly, pathogenic mutations in SMARCA4 were identified in six of eight SCLC-Y cell lines and correlated with reduced SMARCA4 mRNA and protein expression. Pathologist evaluations revealed that SMARCA4-deficient SCLC-Y tumours exhibited features consistent with thoracic SMARCA4-deficient undifferentiated tumours (SMARCA4-UT). Similarly, the transcriptional profile SMARCA4-mutant SCLC-Y lines more closely resembled primary SMARCA4-UT, or SMARCA4-deficient non-small cell carcinoma, than SCLC. Combining clinical, pathological, transcriptomic, and genetic data we found little evidence to support a diagnosis of SCLC for any of the YAP1-expressing cell lines originally used to define the SCLC-Y subtype. ConclusionsSCLC-Y cell lines harbour inactivating SMARCA4 mutations and exhibit characteristics consistent with SMARCA4-deficient malignancies rather than SCLC. Our findings suggest that, unlike ASCL1, NEUROD1 and POU2F3, YAP1 is not a subtype defining transcription factor in SCLC.

cancer biology↗

bioRxiv2022

An NMR fingerprint matching approach for the identification and structural re-evaluation of Pseudomonas lipopeptides.

Cyclic lipopeptides (CLiPs) are secondary metabolites secreted by a range of bacterial phyla. CLiPs from Pseudomonas in particular display diverse structural variations in terms of the number of amino acid residues, macrocycle size, amino acid identity and stereochemistry (e.g. D- vs. L-amino acids). Reports detailing the discovery of novel or already characterized CLiPs from new sources appear regularly in literature. Increasingly however, the lack of detailed characterization threatens to cause considerable confusion, especially if configurational heterogeneity is present for one or more amino acids. Using Pseudomonas CLiPs from the Bananamide, Orfamide and Xantholysin groups as test cases, we demonstrate and validate that 1H and 13C NMR chemical shifts of CLiPs are sufficiently sensitive to differentiate between possible diastereomers of a particular sequence even when they only differ in a single D/L configuration. Rapid screening, involving simple comparison of the NMR fingerprint of a newly isolated CLiP with that of a reference CLiP of known stereochemistry, can then be applied to resolve dead-ends in configurational characterization and avoid the much more cumbersome chemical characterization protocols. Even when the stereochemistry of a particular reference CLiP remains to be established, NMR fingerprinting still allows verifying whether a CLiP from a novel source is already present in the reference collection, thus contributing to dereplication. To benefit research involving CLiPs, we have made a publicly available knowledge base at https://www.rhizoclip.be, where we present an overview of published NMR fingerprint data of characterized CLiPs, together with literature data on the originally determined structures. Significance StatementPseudomonas CLiPs, are ubiquitous specialized metabolites, impacting the producers lifestyle and interactions with the (a)biotic environment. Consequently, they generate interest for agricultural and clinical applications. Establishing structure-activity relationships as premise to their development is hindered because full structural characterization including stereochemistry requires labor-intensive analyses, without guarantee for success. Moreover, increasing use of superficial comparison with previously characterized CLiPs introduces or propagates erroneous attributions, clouding further scientific progress. We provide a generally applicable characterization methodology for structural comparison of newly isolated CLiPs to reference compounds with (un)known stereochemistry based on NMR fingerprints. The reference compound database available for the wide scientific community promises to facilitate structural assessment and dereplication of newly isolated CLiPs, and to support genome mining for novel CLiPs.

microbiology↗

bioRxiv2020

Relationship Between Neuroendocrine and Immune Gene Expression in Small Cell Lung Cancer

Small cell lung cancer (SCLC) is classified as a high-grade neuroendocrine (NE) tumor, but a subset of SCLC has been termed "variant" due to the loss of NE characteristics. In this study, we computed NE scores for patient-derived SCLC cell lines and xenografts, as well as human tumors. We aligned NE properties with transcription factor-defined molecular subtypes. Then we investigated the different immune phenotypes associated with high and low NE scores. We found repression of immune response genes as a shared feature between classic SCLC and pulmonary neuroendocrine cells of the healthy lung. With loss of NE fate, variant SCLC tumors regain cell-autonomous immune gene expression and exhibit higher tumor-immune interactions. Pan-cancer analysis revealed this NE lineage-specific immune phenotype in other cancers. Additionally, we observed MHC I re-expression in SCLC upon development of chemoresistance. These findings provide a new framework to guide design of treatment regimens in SCLC.

cancer biology↗

bioRxiv2020

Single-cell analysis of human lung epithelia reveals concomitant expression of the SARS-CoV-2 receptor ACE2 with multiple virus receptors and scavengers in alveolar type II cells

The novel coronavirus SARS-CoV-2 was identified as the causative agent of the ongoing pandemic COVID 19. COVID-19-associated deaths are mainly attributed to severe pneumonia and respiratory failure. Recent work demonstrated that SARS-CoV-2 binds to angiotensin converting enzyme 2 (ACE2) in the lung. To better understand ACE2 abundance and expression patterns in the lung we interrogated our in-house single-cell RNA-sequencing dataset containing 70,085 EPCAM+ lung epithelial cells from paired normal and lung adenocarcinoma tissues. Transcriptomic analysis revealed a diverse repertoire of airway lineages that included alveolar type I and II, bronchioalveolar, club/secretory, quiescent and proliferating basal, ciliated and malignant cells as well as rare populations such as ionocytes. While the fraction of lung epithelial cells expressing ACE2 was low (1.7% overall), alveolar type II (AT2, 2.2% ACE2+) cells exhibited highest levels of ACE2 expression among all cell subsets. Further analysis of the AT2 compartment (n = 27,235 cells) revealed a number of genes co-expressed with ACE2 that are important for lung pathobiology including those associated with chronic obstructive pulmonary disease (COPD; HHIP), pneumonia and infection (FGG and C4BPA) as well as malarial/bacterial (CD36) and viral (DMBT1) scavenging which, for the most part, were increased in smoker versus light or non-smoker cells. Notably, DMBT1 was highly expressed in AT2 cells relative to other lung epithelial subsets and its expression positively correlated with ACE2. We describe a population of ACE2-positive AT2 cells that co-express pathogen (including viral) receptors (e.g. DMBT1) with crucial roles in host defense thus comprising plausible phenotypic targets for treatment of COVID-19.

genomics↗

bioRxiv2020

The hexosamine biosynthesis pathway is a targetable liability in lung cancers with concurrent KRAS and LKB1 mutations.

In non-small cell lung cancer (NSCLC), concurrent mutations in the oncogene KRAS and the tumor suppressor STK11 encoding the kinase LKB1 result in aggressive tumors prone to metastasis but with liabilities arising from reprogrammed metabolism. We previously demonstrated perturbed nitrogen metabolism and addiction to an unconventional pathway of pyrimidine synthesis in KRAS/LKB1 co-mutant (KL) cancer cells. To gain broader insight into metabolic reprogramming in NSCLC, we analyzed tumor metabolomes in a series of genetically engineered mouse models with oncogenic KRAS combined with mutations in LKB1 or p53. Metabolomics and gene expression profiling pointed towards an activation of the hexosamine biosynthesis pathway (HBP), another nitrogen-related metabolic pathway, in both mouse and human KL mutant tumors. KL cells contain high levels of HBP metabolites, higher flux through the HBP pathway and elevated dependence on the HBP enzyme Glutamine-Fructose-6-Phosphate Transaminase 2 (GFPT2). GFPT2 inhibition selectively reduced KL cell growth in culture and xenografts. Our results define a new metabolic vulnerability in KL tumors and provide a rationale for targeting GFPT2 in this aggressive NSCLC subtype.

cancer biology↗

bioRxiv2020

SCLC_CellMiner: Integrated Genomics and Therapeutics Predictors of Small Cell Lung Cancer Cell Lines based on their genomic signatures

Model systems are necessary to understand the biology of SCLC and develop new therapies against this recalcitrant disease. Here we provide the first online resource, CellMiner-SCLC (https://discover.nci.nih.gov/SclcCellMinerCDB) incorporating 118 individual SCLC cell lines and extensive omics and drug sensitivity datasets, including high resolution methylome performed for the purpose of the current study. We demonstrate the reproducibility of the cell lines and genomic data across the CCLE, GDSC, CTRP, NCI and UTSW datasets. We validate the SCLC classification based on four master transcription factors: NEUROD1, ASCL1, POU2F3 and YAP1 (NAPY classification) and show transcription networks connecting each them with their downstream and upstream regulators as well as with the NOTCH and HIPPO pathways and the MYC genes (MYC, MYCL1 and MYCN). We find that each of the 4 subsets express specific surface markers for antibody-targeted therapies. The SCLC-Y cell lines differ from the other subsets by expressing the NOTCH pathway and the antigen-presenting machinery (APM), and responding to mTOR and AKT inhibitors. Our analyses suggest the potential value of NOTCH activators, YAP1 inhibitors and immune checkpoint inhibitors in SCLC-Y tumors that can now be independently validated. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=151 SRC="FIGDIR/small/980623v2_ufig1.gif" ALT="Figure 1"> View larger version (65K): org.highwire.dtl.DTLVardef@10930e7org.highwire.dtl.DTLVardef@699d9corg.highwire.dtl.DTLVardef@1ea773corg.highwire.dtl.DTLVardef@3a1589_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LISCLC-CellMiner provides the most extensive SCLC resource in terms of number of cell lines (118 cell lines), extensive omics data (exome, microarray, RNA-seq, copy number, methylomes and microRNA) and drug sensitivity testing. C_LIO_LIWe find evidence of distinct epigenetic profile of SCLC cell lines (global hypomethylation and histone gene methylation), which is consistent with their plasticity. C_LIO_LITranscriptome analyses demonstrate the coherent transcriptional networks associated with the 4 main genomic subgroups (NEUROD1, ASCL1, POU2F3 & YAP1 = NAPY classification) and their connection with the NOTCH and HIPPO signaling pathways. C_LIO_LISCLC-CellMiner provides a conceptual framework for the selection of therapies for SCLC in a personalized fashion allowing putative biomarkers according molecular classifications and molecular characteristics. C_LIO_LISCLC-Y cell lines differ from the other cancer cell lines; their transcriptome resemble NSCLC cell lines. YAP1 cell lines while being the most resistant to standard of care treatments (etoposide, cisplatin and topotecan) respond to mTOR and AKT inhibitors and present native immune predisposition suggesting sensitivity to immune checkpoint inhibitors. C_LI

cancer biology↗

bioRxiv2019

Stromal Hedgehog pathway activation by IHH suppresses lung adenocarcinoma growth and metastasis by limiting reactive oxygen species

Activation of the Hedgehog (Hh) signaling pathway by mutations within its components drives the growth of several cancers. However, the role of Hh pathway activation in lung cancers has been controversial. We demonstrate that the Hh signaling pathway is activated in lung stroma in a paracrine manner. Genetic deletion of Shh in autochthonous murine lung adenocarcinoma had no effect on survival. Early abrogation of the pathway by an anti-SHH/IHH antibody 5E1 led to significantly worse survival with increased tumor and metastatic burden. Loss of IHH by in vivo CRISPR led to more aggressive tumor growth suggesting that IHH, not SHH, activates the pathway in stroma to drive its tumor suppressive effects - a novel role for IHH in the lung. Tumors from mice treated with 5E1 had decreased blood vessel density and increased reactive oxygen species (ROS). Treatment of KP mice with 5E1 and N-acetylcysteine, as a ROS scavenger, decreased tumor ROS levels, inhibited tumor growth and prolonged mouse survival suggesting that increased ROS levels from stromal Hh pathway inhibition spurred lung tumor growth. Thus, IHH induces stromal Hh pathway activation to suppress tumor growth and metastases, in part, by limiting ROS production.

cancer biology↗

bioRxiv2019

METABOLIC DIVERSITY IN HUMAN NON-SMALL CELL LUNG CANCER CELLS

Intermediary metabolism in cancer cells is regulated by diverse cell-autonomous processes including signal transduction and gene expression patterns arising from specific oncogenotypes and cell lineages. Although it is well established that metabolic reprogramming is a hallmark of cancer, we lack a full view of the diversity of metabolic programs in cancer cells and an unbiased assessment of the associations between metabolic pathway preferences and other cell-autonomous processes. Here we quantified over 100 metabolic features, mostly from 13C enrichment of molecules from central carbon metabolism, in over 80 non-small cell lung cancer (NSCLC) cell lines cultured under identical conditions. Because these cell lines were extensively annotated for oncogenotype, gene expression, protein expression and therapeutic sensitivity, the resulting database enables the user to uncover new relationships between metabolism and these orthogonal processes.

cancer biology↗