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INTRODUCTION: Small Cell Lung Cancer (SCLC) can be classified into transcriptional subtypes with distinct degrees of neuroendocrine (NE) differentiation. Recent evidence supports plasticity among subtypes with a bias toward adoption of low-NE states during disease progression or upon acquired chemotherapy resistance. Here, we identify a role for SMARCA4, the catalytic subunit of the SWI/SNF complex, as a regulator of subtype shift in SCLC. METHODS: ATACseq and RNAseq experiments were performed in SCLC cells after pharmacological inhibition of SMARCA4. DNA binding of SMARCA4 was characterized by ChIPseq in high-NE SCLC patient derived xenografts (PDXs). Enrichment analyses were applied to transcriptomic data. Combination of FHD-286 and afatinib was tested in vitro and in a set of chemo-resistant SCLC PDXs in vivo. RESULTS: SMARCA4 expression positively correlates with that of NE genes in both SCLC cell lines and patient tumors. Pharmacological inhibition of SMARCA4 with FHD-286 induces the loss of NE features and downregulates neuroendocrine and neuronal signaling pathways while activating non-NE factors. SMARCA4 binds to gene loci encoding NE-lineage transcription factors ASCL1 and NEUROD1 and alters chromatin accessibility, enhancing NE programs. Enrichment analysis applied to high-confidence SMARCA4 targets confirmed neuron related pathways as the top GO Biological processes regulated by SMARCA4 in SCLC. In parallel, SMARCA4 also controls REST, a known suppressor of the NE phenotype, by regulating SRRM4-dependent REST transcript splicing. Furthermore, SMARCA4 inhibition drives ERBB pathway activation in SCLC, rendering SCLC tumors sensitive to afatinib. CONCLUSIONS: This study nominates SMARCA4 as a key regulator of the NE state plasticity and defines a novel therapeutic strategy for SCLC.
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ADN Helicasas , Neoplasias Pulmonares , Proteínas Nucleares , Carcinoma Pulmonar de Células Pequeñas , Factores de Transcripción , Humanos , Carcinoma Pulmonar de Células Pequeñas/genética , Carcinoma Pulmonar de Células Pequeñas/metabolismo , Carcinoma Pulmonar de Células Pequeñas/patología , Carcinoma Pulmonar de Células Pequeñas/tratamiento farmacológico , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patología , Neoplasias Pulmonares/tratamiento farmacológico , ADN Helicasas/genética , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Línea Celular Tumoral , Animales , Ratones , Regulación Neoplásica de la Expresión Génica , Proteínas RepresorasRESUMEN
Transposable elements (TEs) are abundant in the human genome, and they provide the sources for genetic and functional diversity. The regulation of TEs expression and their functional consequences in physiological conditions and cancer development remain to be fully elucidated. Previous studies suggested TEs are repressed by DNA methylation and chromatin modifications. The effect of 3D chromatin topology on TE regulation remains elusive. Here, by integrating transcriptome and 3D genome architecture studies, we showed that haploinsufficient loss of NIPBL selectively activates alternative promoters at the long terminal repeats (LTRs) of the TE subclasses. This activation occurs through the reorganization of topologically associating domain (TAD) hierarchical structures and recruitment of proximal enhancers. These observations indicate that TAD hierarchy restricts transcriptional activation of LTRs that already possess open chromatin features. In cancer, perturbation of the hierarchical chromatin topology can lead to co-option of LTRs as functional alternative promoters in a context-dependent manner and drive aberrant transcriptional activation of novel oncogenes and other divergent transcripts. These data uncovered a new layer of regulatory mechanism of TE expression beyond DNA and chromatin modification in human genome. They also posit the TAD hierarchy dysregulation as a novel mechanism for alternative promoter-mediated oncogene activation and transcriptional diversity in cancer, which may be exploited therapeutically.
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Neuroendocrine (NE) transformation is a mechanism of resistance to targeted therapy in lung and prostate adenocarcinomas leading to poor prognosis. Up to date, even if patients at high risk of transformation can be identified by the occurrence of Tumor Protein P53 (TP53) and Retinoblastoma Transcriptional Corepressor 1 (RB1) mutations in their tumors, no therapeutic strategies are available to prevent or delay histological transformation. Upregulation of the cell cycle kinase Cell Division Cycle 7 (CDC7) occurred in tumors during the initial steps of NE transformation, already after TP53/RB1 co-inactivation, leading to induced sensitivity to the CDC7 inhibitor simurosertib. CDC7 inhibition suppressed NE transdifferentiation and extended response to targeted therapy in in vivo models of NE transformation by inducing the proteasome-mediated degradation of the MYC Proto-Oncogen (MYC), implicated in stemness and histological transformation. Ectopic overexpression of a degradation-resistant MYC isoform reestablished the NE transformation phenotype observed on targeted therapy, even in the presence of simurosertib. CDC7 inhibition also markedly extended response to standard cytotoxics (cisplatin, irinotecan) in lung and prostate small cell carcinoma models. These results nominate CDC7 inhibition as a therapeutic strategy to constrain lineage plasticity, as well as to effectively treat NE tumors de novo or after transformation. As simurosertib clinical efficacy trials are ongoing, this concept could be readily translated for patients at risk of transformation.
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Proteínas de Ciclo Celular , Neoplasias Pulmonares , Neoplasias de la Próstata , Proteínas Proto-Oncogénicas c-myc , Humanos , Masculino , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Neoplasias de la Próstata/genética , Neoplasias de la Próstata/patología , Neoplasias de la Próstata/metabolismo , Neoplasias de la Próstata/tratamiento farmacológico , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/patología , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/tratamiento farmacológico , Proteínas Proto-Oncogénicas c-myc/genética , Proteínas Proto-Oncogénicas c-myc/metabolismo , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/metabolismo , Línea Celular Tumoral , Proteínas Serina-Treonina Quinasas/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/metabolismo , Ratones , Animales , Tumores Neuroendocrinos/genética , Tumores Neuroendocrinos/patología , Tumores Neuroendocrinos/metabolismo , Tumores Neuroendocrinos/tratamiento farmacológico , Proteolisis/efectos de los fármacos , Proteínas de Unión a Retinoblastoma/genética , Proteínas de Unión a Retinoblastoma/metabolismo , Ubiquitina-Proteína LigasasRESUMEN
The identification of cell-type-specific 3D chromatin interactions between regulatory elements can help to decipher gene regulation and to interpret the function of disease-associated non-coding variants. However, current chromosome conformation capture (3C) technologies are unable to resolve interactions at this resolution when only small numbers of cells are available as input. We therefore present ChromaFold, a deep learning model that predicts 3D contact maps and regulatory interactions from single-cell ATAC sequencing (scATAC-seq) data alone. ChromaFold uses pseudobulk chromatin accessibility, co-accessibility profiles across metacells, and predicted CTCF motif tracks as input features and employs a lightweight architecture to enable training on standard GPUs. Once trained on paired scATAC-seq and Hi-C data in human cell lines and tissues, ChromaFold can accurately predict both the 3D contact map and peak-level interactions across diverse human and mouse test cell types. In benchmarking against a recent deep learning method that uses bulk ATAC-seq, DNA sequence, and CTCF ChIP-seq to make cell-type-specific predictions, ChromaFold yields superior prediction performance when including CTCF ChIP-seq data as an input and comparable performance without. Finally, fine-tuning ChromaFold on paired scATAC-seq and Hi-C in a complex tissue enables deconvolution of chromatin interactions across cell subpopulations. ChromaFold thus achieves state-of-the-art prediction of 3D contact maps and regulatory interactions using scATAC-seq alone as input data, enabling accurate inference of cell-type-specific interactions in settings where 3C-based assays are infeasible.
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In lung and prostate adenocarcinomas, neuroendocrine (NE) transformation to an aggressive derivative resembling small cell lung cancer (SCLC) is associated with poor prognosis. We previously described dependency of SCLC on the nuclear transporter exportin 1. Here, we explored the role of exportin 1 in NE transformation. We observed up-regulated exportin 1 in lung and prostate pretransformation adenocarcinomas. Exportin 1 was up-regulated after genetic inactivation of TP53 and RB1 in lung and prostate adenocarcinoma cell lines, accompanied by increased sensitivity to the exportin 1 inhibitor selinexor in vitro. Exportin 1 inhibition prevented NE transformation in different TP53/RB1-inactivated prostate adenocarcinoma xenograft models that acquire NE features upon treatment with the aromatase inhibitor enzalutamide and extended response to the EGFR inhibitor osimertinib in a lung cancer transformation patient-derived xenograft (PDX) model exhibiting combined adenocarcinoma/SCLC histology. Ectopic SOX2 expression restored the enzalutamide-promoted NE phenotype on adenocarcinoma-to-NE transformation xenograft models despite selinexor treatment. Selinexor sensitized NE-transformed lung and prostate small cell carcinoma PDXs to standard cytotoxics. Together, these data nominate exportin 1 inhibition as a potential therapeutic target to constrain lineage plasticity and prevent or treat NE transformation in lung and prostate adenocarcinoma.
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Adenocarcinoma , Neoplasias Pulmonares , Neoplasias de la Próstata , Factores de Transcripción SOXB1 , Carcinoma Pulmonar de Células Pequeñas , Humanos , Masculino , Adenocarcinoma/patología , Regulación hacia Abajo , Neoplasias Pulmonares/patología , Neoplasias de la Próstata/tratamiento farmacológico , Neoplasias de la Próstata/patología , Carcinoma Pulmonar de Células Pequeñas/genética , Factores de Transcripción SOXB1/genética , Factores de Transcripción SOXB1/metabolismo , Animales , Proteína Exportina 1RESUMEN
INTRODUCTION: SCLC is a highly aggressive neuroendocrine tumor that is characterized by early acquired therapeutic resistance and modest benefit from immune checkpoint blockade (ICB). Repression of the major histocompatibility complex class I (MHC-I) represents a key mechanism driving resistance to T cell-based immunotherapies. METHODS: We evaluated the role of the lysine-specific demethylase 1 (LSD1) as a determinant of MHC-I expression, functional antigen presentation, and immune activation in SCLC in vitro and in vivo through evaluation of both human SCLC cell lines and immunocompetent mouse models. RESULTS: We found that targeted inhibition of LSD1 in SCLC restores MHC-I cell surface expression and transcriptionally activates genes encoding the antigen presentation pathway. LSD1 inhibition further activates interferon signaling, induces tumor-intrinsic immunogenicity, and sensitizes SCLC cells to MHC-I-restricted T cell cytolysis. Combination of LSD1 inhibitor with ICB augments the antitumor immune response in refractory SCLC models. Together, these data define a role for LSD1 as a potent regulator of MHC-I antigen presentation and provide rationale for combinatory use of LSD1 inhibitors with ICB to improve therapeutic response in SCLC. CONCLUSIONS: Epigenetic silencing of MHC-I in SCLC contributes to its poor response to ICB. Our study identifies a previously uncharacterized role for LSD1 as a regulator of MHC-I antigen presentation in SCLC. LSD1 inhibition enables MHC-I-restricted T cell cytolysis, induces immune activation, and augments the antitumor immune response to ICB in SCLC.
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Presentación de Antígeno , Antígenos de Histocompatibilidad Clase I , Histona Demetilasas , Neoplasias Pulmonares , Carcinoma Pulmonar de Células Pequeñas , Animales , Antígenos de Neoplasias , Antígeno B7-H1 , Genes MHC Clase I , Antígenos de Histocompatibilidad Clase I/genética , Histona Demetilasas/genética , Histona Demetilasas/metabolismo , Humanos , Neoplasias Pulmonares/patología , Ratones , Carcinoma Pulmonar de Células Pequeñas/patologíaRESUMEN
Small cell lung cancer (SCLC) is an aggressive malignancy characterized by early metastasis and extreme lethality. The backbone of SCLC treatment over the past several decades has been platinum-based doublet chemotherapy, with the recent addition of immunotherapy providing modest benefits in a subset of patients. However, nearly all patients treated with systemic therapy quickly develop resistant disease, and there is an absence of effective therapies for recurrent and progressive disease. Here we conducted CRISPR-Cas9 screens using a druggable genome library in multiple SCLC cell lines representing distinct molecular subtypes. This screen nominated exportin-1, encoded by XPO1, as a therapeutic target. XPO1 was highly and ubiquitously expressed in SCLC relative to other lung cancer histologies and other tumor types. XPO1 knockout enhanced chemosensitivity, and exportin-1 inhibition demonstrated synergy with both first- and second-line chemotherapy. The small molecule exportin-1 inhibitor selinexor in combination with cisplatin or irinotecan dramatically inhibited tumor growth in chemonaïve and chemorelapsed SCLC patient-derived xenografts, respectively. Together these data identify exportin-1 as a promising therapeutic target in SCLC, with the potential to markedly augment the efficacy of cytotoxic agents commonly used in treating this disease. SIGNIFICANCE: CRISPR-Cas9 screening nominates exportin-1 as a therapeutic target in SCLC, and exportin-1 inhibition enhances chemotherapy efficacy in patient-derived xenografts, providing a novel therapeutic opportunity in this disease.
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Carioferinas/metabolismo , Neoplasias Pulmonares/tratamiento farmacológico , Receptores Citoplasmáticos y Nucleares/metabolismo , Carcinoma Pulmonar de Células Pequeñas/tratamiento farmacológico , Animales , Línea Celular Tumoral , Humanos , Neoplasias Pulmonares/patología , Ratones , Carcinoma Pulmonar de Células Pequeñas/patología , Proteína Exportina 1RESUMEN
Small cell lung cancers (SCLCs) have high mutational burden but are relatively unresponsive to immune checkpoint blockade (ICB). Using SCLC models, we demonstrate that inhibition of WEE1, a G2/M checkpoint regulator induced by DNA damage, activates the STING-TBK1-IRF3 pathway, which increases type I interferons (IFN-α and IFN-ß) and pro-inflammatory chemokines (CXCL10 and CCL5), facilitating an immune response via CD8+ cytotoxic T cell infiltration. We further show that WEE1 inhibition concomitantly activates the STAT1 pathway, increasing IFN-γ and PD-L1 expression. Consistent with these findings, combined WEE1 inhibition (AZD1775) and PD-L1 blockade causes remarkable tumor regression, activation of type I and II interferon pathways, and infiltration of cytotoxic T cells in multiple immunocompetent SCLC genetically engineered mouse models, including an aggressive model with stabilized MYC. Our study demonstrates cell-autonomous and immune-stimulating activity of WEE1 inhibition in SCLC models. Combined inhibition of WEE1 plus PD-L1 blockade represents a promising immunotherapeutic approach in SCLC.
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Protocolos de Quimioterapia Combinada Antineoplásica , Antígeno B7-H1 , Proteínas de Ciclo Celular , Neoplasias Pulmonares , Proteínas de la Membrana , Proteínas Tirosina Quinasas , Factor de Transcripción STAT1 , Carcinoma Pulmonar de Células Pequeñas , Animales , Protocolos de Quimioterapia Combinada Antineoplásica/farmacología , Antígeno B7-H1/antagonistas & inhibidores , Antígeno B7-H1/inmunología , Proteínas de Ciclo Celular/antagonistas & inhibidores , Proteínas de Ciclo Celular/metabolismo , Línea Celular Tumoral , Sinergismo Farmacológico , Inhibidores de Puntos de Control Inmunológico/farmacología , Neoplasias Pulmonares/tratamiento farmacológico , Neoplasias Pulmonares/inmunología , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patología , Proteínas de la Membrana/metabolismo , Ratones , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Tirosina Quinasas/antagonistas & inhibidores , Proteínas Tirosina Quinasas/metabolismo , Factor de Transcripción STAT1/metabolismo , Carcinoma Pulmonar de Células Pequeñas/tratamiento farmacológico , Carcinoma Pulmonar de Células Pequeñas/inmunología , Carcinoma Pulmonar de Células Pequeñas/metabolismo , Carcinoma Pulmonar de Células Pequeñas/patologíaRESUMEN
BACKGROUND: Lineage plasticity, the ability to transdifferentiate among distinct phenotypic identities, facilitates therapeutic resistance in cancer. In lung adenocarcinomas (LUADs), this phenomenon includes small cell and squamous cell (LUSC) histologic transformation in the context of acquired resistance to targeted inhibition of driver mutations. LUAD-to-LUSC transdifferentiation, occurring in up to 9% of EGFR-mutant patients relapsed on osimertinib, is associated with notably poor prognosis. We hypothesized that multi-parameter profiling of the components of mixed histology (LUAD/LUSC) tumors could provide insight into factors licensing lineage plasticity between these histologies. METHODS: We performed genomic, epigenomics, transcriptomics and protein analyses of microdissected LUAD and LUSC components from mixed histology tumors, pre-/post-transformation tumors and reference non-transformed LUAD and LUSC samples. We validated our findings through genetic manipulation of preclinical models in vitro and in vivo and performed patient-derived xenograft (PDX) treatments to validate potential therapeutic targets in a LUAD PDX model acquiring LUSC features after osimertinib treatment. RESULTS: Our data suggest that LUSC transdifferentiation is primarily driven by transcriptional reprogramming rather than mutational events. We observed consistent relative upregulation of PI3K/AKT, MYC and PRC2 pathway genes. Concurrent activation of PI3K/AKT and MYC induced squamous features in EGFR-mutant LUAD preclinical models. Pharmacologic inhibition of EZH1/2 in combination with osimertinib prevented relapse with squamous-features in an EGFR-mutant patient-derived xenograft model, and inhibition of EZH1/2 or PI3K/AKT signaling re-sensitized resistant squamous-like tumors to osimertinib. CONCLUSIONS: Our findings provide the first comprehensive molecular characterization of LUSC transdifferentiation, suggesting putative drivers and potential therapeutic targets to constrain or prevent lineage plasticity.
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Adenocarcinoma del Pulmón/patología , Carcinoma de Pulmón de Células no Pequeñas/patología , Carcinoma de Células Escamosas/patología , Proteínas Proto-Oncogénicas c-akt/metabolismo , Proteínas Proto-Oncogénicas c-myc/metabolismo , Adenocarcinoma del Pulmón/genética , Adenocarcinoma del Pulmón/metabolismo , Animales , Carcinoma de Pulmón de Células no Pequeñas/genética , Carcinoma de Pulmón de Células no Pequeñas/metabolismo , Carcinoma de Células Escamosas/genética , Carcinoma de Células Escamosas/metabolismo , Transdiferenciación Celular , Humanos , Ratones Endogámicos NOD , Fosfatidilinositol 3-Quinasas/genética , Fosfatidilinositol 3-Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-akt/genética , Proteínas Proto-Oncogénicas c-myc/genética , Transducción de Señal , TranscriptomaRESUMEN
Lineage plasticity is implicated in treatment resistance in multiple cancers. In lung adenocarcinomas (LUAD) amenable to targeted therapy, transformation to small cell lung cancer (SCLC) is a recognized resistance mechanism. Defining molecular mechanisms of neuroendocrine (NE) transformation in lung cancer has been limited by a paucity of pre/posttransformation clinical samples. Detailed genomic, epigenomic, transcriptomic, and protein characterization of combined LUAD/SCLC tumors, as well as pre/posttransformation samples, supports that NE transformation is primarily driven by transcriptional reprogramming rather than mutational events. We identify genomic contexts in which NE transformation is favored, including frequent loss of the 3p chromosome arm. We observed enhanced expression of genes involved in the PRC2 complex and PI3K/AKT and NOTCH pathways. Pharmacologic inhibition of the PI3K/AKT pathway delayed tumor growth and NE transformation in an EGFR-mutant patient-derived xenograft model. Our findings define a novel landscape of potential drivers and therapeutic vulnerabilities of NE transformation in lung cancer. SIGNIFICANCE: The difficulty in collection of transformation samples has precluded the performance of molecular analyses, and thus little is known about the lineage plasticity mechanisms leading to LUAD-to-SCLC transformation. Here, we describe biological pathways dysregulated upon transformation and identify potential predictors and potential therapeutic vulnerabilities of NE transformation in the lung. See related commentary by Meador and Lovly, p. 2962. This article is highlighted in the In This Issue feature, p. 2945.