RESUMO
Primary central nervous system (CNS) histiocytic sarcoma is a rare hematolymphoid malignancy with features of mature histiocytes and carries a poor prognosis. We describe a unique case in which a 50-year-old woman presented with recurrent acute brainstem syndrome, area postrema syndrome, and myelitis with corresponding magnetic resonance imaging (MRI) lesions meeting diagnostic criteria for seronegative neuromyelitis optica spectrum disorder (NMOSD). Despite initial improvement with steroids and plasma exchange, she experienced recurrent symptoms over 10 months referable to new and persistently enhancing lesions. At autopsy, neuropathology revealed a diffusely infiltrative primary CNS histiocytic sarcoma. This case represents a rare clinicoradiologic mimic of NMOSD, underscoring the importance of evaluation for infiltrative diseases in cases of atypical seronegative NMOSD.
Assuntos
Neoplasias do Sistema Nervoso Central , Sarcoma Histiocítico , Área Postrema , Diagnóstico Diferencial , Feminino , Sarcoma Histiocítico/diagnóstico , Humanos , Imageamento por Ressonância Magnética , Pessoa de Meia-Idade , Neuromielite Óptica/diagnóstico por imagemRESUMO
ASH1L histone methyltransferase plays a crucial role in the pathogenesis of different diseases, including acute leukemia. While ASH1L represents an attractive drug target, developing ASH1L inhibitors is challenging, as the catalytic SET domain adapts an inactive conformation with autoinhibitory loop blocking the access to the active site. Here, by applying fragment-based screening followed by medicinal chemistry and a structure-based design, we developed first-in-class small molecule inhibitors of the ASH1L SET domain. The crystal structures of ASH1L-inhibitor complexes reveal compound binding to the autoinhibitory loop region in the SET domain. When tested in MLL leukemia models, our lead compound, AS-99, blocks cell proliferation, induces apoptosis and differentiation, downregulates MLL fusion target genes, and reduces the leukemia burden in vivo. This work validates the ASH1L SET domain as a druggable target and provides a chemical probe to further study the biological functions of ASH1L as well as to develop therapeutic agents.
Assuntos
Antineoplásicos/farmacologia , Proteínas de Ligação a DNA/antagonistas & inibidores , Inibidores Enzimáticos/farmacologia , Histona-Lisina N-Metiltransferase/antagonistas & inibidores , Leucemia/tratamento farmacológico , Leucemia/enzimologia , Animais , Antineoplásicos/química , Domínio Catalítico/efeitos dos fármacos , Domínio Catalítico/genética , Linhagem Celular Tumoral , Transformação Celular Neoplásica/efeitos dos fármacos , Transformação Celular Neoplásica/genética , Cristalografia por Raios X , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/genética , Desenho de Fármacos , Descoberta de Drogas , Inibidores Enzimáticos/química , Feminino , Histona-Lisina N-Metiltransferase/química , Histona-Lisina N-Metiltransferase/genética , Humanos , Leucemia/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Modelos Moleculares , Proteína de Leucina Linfoide-Mieloide/genética , Oncogenes , Domínios Proteicos , Proteínas Recombinantes de Fusão/genéticaRESUMO
The nuclear receptor-binding SET domain (NSD) family of histone methyltransferases is associated with various malignancies, including aggressive acute leukemia with NUP98-NSD1 translocation. While NSD proteins represent attractive drug targets, their catalytic SET domains exist in autoinhibited conformation, presenting notable challenges for inhibitor development. Here, we employed a fragment-based screening strategy followed by chemical optimization, which resulted in the development of the first-in-class irreversible small-molecule inhibitors of the nuclear receptor-binding SET domain protein 1 (NSD1) SET domain. The crystal structure of NSD1 in complex with covalently bound ligand reveals a conformational change in the autoinhibitory loop of the SET domain and formation of a channel-like pocket suitable for targeting with small molecules. Our covalent lead-compound BT5-demonstrates on-target activity in NUP98-NSD1 leukemia cells, including inhibition of histone H3 lysine 36 dimethylation and downregulation of target genes, and impaired colony formation in an NUP98-NSD1 patient sample. This study will facilitate the development of the next generation of potent and selective inhibitors of the NSD histone methyltransferases.
Assuntos
Antineoplásicos/farmacologia , Inibidores Enzimáticos/farmacologia , Regulação Leucêmica da Expressão Gênica , Histona-Lisina N-Metiltransferase/antagonistas & inibidores , Leucócitos/efeitos dos fármacos , Complexo de Proteínas Formadoras de Poros Nucleares/genética , Proteínas de Fusão Oncogênica/antagonistas & inibidores , Antineoplásicos/síntese química , Sítios de Ligação , Inibidores Enzimáticos/síntese química , Histona-Lisina N-Metiltransferase/genética , Histona-Lisina N-Metiltransferase/metabolismo , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Humanos , Cinética , Leucemia/tratamento farmacológico , Leucemia/enzimologia , Leucemia/genética , Leucemia/patologia , Leucócitos/enzimologia , Leucócitos/patologia , Modelos Moleculares , Proteína Meis1/genética , Proteína Meis1/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Proteínas de Fusão Oncogênica/genética , Proteínas de Fusão Oncogênica/metabolismo , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Transdução de Sinais , Especificidade por Substrato , Células Tumorais CultivadasRESUMO
Malignant tumors of the central nervous system (CNS) cause substantial morbidity and mortality, yet efforts to optimize chemo- and radiotherapy have largely failed to improve dismal prognoses. Over the past decade, RNA sequencing (RNA-seq) has emerged as a powerful tool to comprehensively characterize the transcriptome of CNS tumor cells in one high-throughput step, leading to improved understanding of CNS tumor biology and suggesting new routes for targeted therapies. RNA-seq has been instrumental in improving the diagnostic classification of brain tumors, characterizing oncogenic fusion genes, and shedding light on intratumor heterogeneity. Currently, RNA-seq is beginning to be incorporated into regular neuro-oncology practice in the form of precision neuro-oncology programs, which use information from tumor sequencing to guide implementation of personalized targeted therapies. These programs show great promise in improving patient outcomes for tumors where single agent trials have been ineffective. As RNA-seq is a relatively new technique, many further applications yielding new advances in CNS tumor research and management are expected in the coming years.
Assuntos
Oncologia , Neoplasias do Sistema Nervoso/genética , Análise de Sequência de RNA/métodos , Regulação Neoplásica da Expressão Gênica , HumanosRESUMO
We show here that computer game players can build high-quality crystal structures. Introduction of a new feature into the computer game Foldit allows players to build and real-space refine structures into electron density maps. To assess the usefulness of this feature, we held a crystallographic model-building competition between trained crystallographers, undergraduate students, Foldit players and automatic model-building algorithms. After removal of disordered residues, a team of Foldit players achieved the most accurate structure. Analysing the target protein of the competition, YPL067C, uncovered a new family of histidine triad proteins apparently involved in the prevention of amyloid toxicity. From this study, we conclude that crystallographers can utilize crowdsourcing to interpret electron density information and to produce structure solutions of the highest quality.
Assuntos
Crowdsourcing/métodos , Cristalografia/métodos , Currículo , Modelos Químicos , Software , Hidrolases/química , Hidrolases/classificação , Conformação ProteicaRESUMO
Methylation at histone 3, lysine 36 (H3K36) is a conserved epigenetic mark regulating gene transcription, alternative splicing and DNA repair. Genes encoding H3K36 methyltransferases (KMTases) are commonly overexpressed, mutated or involved in chromosomal translocations in cancer. Molecular biology studies have demonstrated that H3K36 KMTases regulate oncogenic transcriptional programs. Structural studies of the catalytic SET domain of H3K36 KMTases have revealed intriguing opportunities for design of small molecule inhibitors. Nevertheless, potent inhibitors for most H3K36 KMTases have not yet been developed, underlining the challenges associated with this target class. As we now have strong evidence linking H3K36 KMTases to cancer, drug development efforts are predicted to yield novel compounds in the near future.
Assuntos
Antineoplásicos/farmacologia , Inibidores Enzimáticos/farmacologia , Metiltransferases/antagonistas & inibidores , Neoplasias/tratamento farmacológico , Bibliotecas de Moléculas Pequenas/farmacologia , Antineoplásicos/síntese química , Antineoplásicos/química , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Humanos , Metiltransferases/genética , Metiltransferases/metabolismo , Neoplasias/metabolismo , Bibliotecas de Moléculas Pequenas/síntese química , Bibliotecas de Moléculas Pequenas/químicaRESUMO
ASH1L (absent, small, or homeotic-like 1) is a histone methyltransferase (HMTase) involved in gene activation that is overexpressed in multiple forms of cancer. Previous studies of ASH1L's catalytic SET domain identified an autoinhibitory loop that blocks access of histone substrate to the enzyme active site. Here, we used both nuclear magnetic resonance and X-ray crystallography to identify conformational dynamics in the ASH1L autoinhibitory loop. Using site-directed mutagenesis, we found that point mutations in the autoinhibitory loop that perturb the structure of the SET domain result in decreased enzyme activity, indicating that the autoinhibitory loop is not a simple gate to the active site but is rather a key feature critical to ASH1L function. We also identified a second loop in the SET-I subdomain of ASH1L that experiences conformational dynamics, and we trapped two different conformations of this loop using crystallographic studies. Mutation of the SET-I loop led to a large decrease in ASH1L enzymatic activity in addition to a significant conformational change in the SET-I loop, demonstrating the importance of the structure and dynamics of the SET-I loop to ASH1L function. Furthermore, we found that three C-terminal chromatin-interacting domains greatly enhance ASH1L enzymatic activity and that ASH1L requires native nucleosome substrate for robust activity. Our study illuminates the role of concerted conformational dynamics in ASH1L function and identifies structural features important for ASH1L enzymatic activity.