RESUMEN
Spatial heterogeneity of transcriptional and genetic markers between physically isolated biopsies of a single tumor poses major barriers to the identification of biomarkers and the development of targeted therapies that will be effective against the entire tumor. We analyzed the spatial heterogeneity of multiregional biopsies from 35 patients, using a combination of transcriptomic and genomic profiles. Medulloblastomas (MBs), but not high-grade gliomas (HGGs), demonstrated spatially homogeneous transcriptomes, which allowed for accurate subgrouping of tumors from a single biopsy. Conversely, somatic mutations that affect genes suitable for targeted therapeutics demonstrated high levels of spatial heterogeneity in MB, malignant glioma, and renal cell carcinoma (RCC). Actionable targets found in a single MB biopsy were seldom clonal across the entire tumor, which brings the efficacy of monotherapies against a single target into question. Clinical trials of targeted therapies for MB should first ensure the spatially ubiquitous nature of the target mutation.
Asunto(s)
Neoplasias Cerebelosas/genética , Regulación Neoplásica de la Expresión Génica , Meduloblastoma/genética , Transcriptoma , Adulto , Anciano , Anciano de 80 o más Años , Neoplasias Cerebelosas/patología , Niño , Preescolar , Análisis por Conglomerados , Variaciones en el Número de Copia de ADN , Femenino , Perfilación de la Expresión Génica/métodos , Heterogeneidad Genética , Estudio de Asociación del Genoma Completo , Humanos , Mutación INDEL , Masculino , Meduloblastoma/patología , Persona de Mediana Edad , Mutación , Polimorfismo de Nucleótido Simple , Análisis de Componente Principal , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
The development of targeted anti-cancer therapies through the study of cancer genomes is intended to increase survival rates and decrease treatment-related toxicity. We treated a transposon-driven, functional genomic mouse model of medulloblastoma with 'humanized' in vivo therapy (microneurosurgical tumour resection followed by multi-fractionated, image-guided radiotherapy). Genetic events in recurrent murine medulloblastoma exhibit a very poor overlap with those in matched murine diagnostic samples (<5%). Whole-genome sequencing of 33 pairs of human diagnostic and post-therapy medulloblastomas demonstrated substantial genetic divergence of the dominant clone after therapy (<12% diagnostic events were retained at recurrence). In both mice and humans, the dominant clone at recurrence arose through clonal selection of a pre-existing minor clone present at diagnosis. Targeted therapy is unlikely to be effective in the absence of the target, therefore our results offer a simple, proximal, and remediable explanation for the failure of prior clinical trials of targeted therapy.
Asunto(s)
Neoplasias Cerebelosas/terapia , Células Clonales/efectos de los fármacos , Células Clonales/metabolismo , Meduloblastoma/terapia , Recurrencia Local de Neoplasia/genética , Recurrencia Local de Neoplasia/patología , Selección Genética/efectos de los fármacos , Animales , Neoplasias Cerebelosas/genética , Neoplasias Cerebelosas/patología , Neoplasias Cerebelosas/radioterapia , Neoplasias Cerebelosas/cirugía , Células Clonales/patología , Irradiación Craneoespinal , Análisis Mutacional de ADN , Modelos Animales de Enfermedad , Drosophila melanogaster/citología , Drosophila melanogaster/genética , Femenino , Genoma Humano/genética , Humanos , Masculino , Meduloblastoma/genética , Meduloblastoma/patología , Meduloblastoma/radioterapia , Meduloblastoma/cirugía , Ratones , Terapia Molecular Dirigida/métodos , Recurrencia Local de Neoplasia/terapia , Radioterapia Guiada por Imagen , Transducción de Señal , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
The usefulness of a genetic clock lies in its role to stimulate a sequence of logic reactions for sequential biological circuits. A clock signal is a periodic square wave, its amplitude alternates at a steady frequency between fixed minimal and maximal levels. Transition between the minimum and the maximum is instantaneous for an ideal square wave; however, the function is unrealisable in physical bio-systems. This research develops a new genetic clock generator based on a genetic oscillator, in which, a sine wave generator is adopted as a signal oscillator. It is shown that combination of a genetic oscillator with a toggle switch is able to generate clock signals forming an efficient way to generate a near square wave. In silico study confirms the proposed idea.
