Radiation Drives the Evolution of Orthotopic Xenografts Initiated from Glioblastoma Stem-like Cells.

A consequence of the intratumor heterogeneity (ITH) of glioblastoma (GBM) is the susceptibility to treatment-driven evolution. To determine the potential of radiotherapy to influence GBM evolution, we used orthotopic xenografts initiated from CD133+ GBM stem-like cells (GSC). Toward this end, orthotopic xenografts grown in nude mice were exposed to a fractionated radiation protocol, which resulted in a significant increase in animal survival. Brain tumors from control and irradiated mice were then collected at morbidity and compared in terms of growth pattern, clonal diversity, and genomic architecture. In mice that received fractionated radiation, tumors were less invasive, with more clearly demarcated borders and tumor core hypercellularity as compared with controls, suggesting a fundamental change in tumor biology. Viral integration site analysis indicated a reduction in clonal diversity in the irradiated tumors, implying a decrease in ITH. Changes in clonal diversity were not detected after irradiation of GSCs in vitro, suggesting that the radiation-induced reduction in ITH was dependent on the brain microenvironment. Whole-exome sequencing revealed differences in mutation patterns between control and irradiated tumors, which included modifications in the presence and clonality of driver mutations associated with GBM. Moreover, changes in the distribution of mutations as a function of subpopulation size between control and irradiated tumors were consistent with subclone expansion and contraction, that is, subpopulation evolution. Taken together, these results indicate that radiation drives the evolution of the GSC-initiated orthotopic xenografts and suggest that radiation-driven evolution may have therapeutic implications for recurrent GBM. SIGNIFICANCE: Radiation drives the evolution of glioblastoma orthotopic xenografts; when translated to the clinic, this may have therapeutic implications for recurrent tumors.

UVB-Induced Tumor Heterogeneity Diminishes Immune Response in Melanoma.

Although clonal neo-antigen burden is associated with improved response to immune therapy, the functional basis for this remains unclear. Here we study this question in a novel controlled mouse melanoma model that enables us to explore the effects of intra-tumor heterogeneity (ITH) on tumor aggressiveness and immunity independent of tumor mutational burden. Induction of UVB-derived mutations yields highly aggressive tumors with decreased anti-tumor activity. However, single-cell-derived tumors with reduced ITH are swiftly rejected. Their rejection is accompanied by increased T cell reactivity and a less suppressive microenvironment. Using phylogenetic analyses and mixing experiments of single-cell clones, we dissect two characteristics of ITH: the number of clones forming the tumor and their clonal diversity. Our analysis of melanoma patient tumor data recapitulates our results in terms of overall survival and response to immune checkpoint therapy. These findings highlight the importance of clonal mutations in robust immune surveillance and the need to quantify patient ITH to determine the response to checkpoint blockade.

Identification of low variability textural features for heterogeneity quantification of 18F-FDG PET/CT imaging / Identificación de texturas de baja variabilidad para la cuantificación de la heterogeneidad en imagen 18F-FDG PET/TC

Objective. To identify those textural features that are insensitive to both technical and biological factors in order to standardise heterogeneity studies on 18F-FDG PET imaging. Materials and methods. Two different studies were performed. First, nineteen series from a cylindrical phantom filled with different 18F-FDG activity concentration were acquired and reconstructed using three different protocols. Seventy-two texture features were calculated inside a circular region of interest. The variability of each feature was obtained. Second, the data for 15 patients showing non-pathological liver were acquired. Anatomical and physiological features such as patient's weight, height, body mass index, metabolic active volume, blood glucose level, SUV and SUV standard deviation were also recorded. A liver covering region of interest was delineated and low variability textural features calculated in each patient. Finally, a multivariate Spearman's correlation analysis between biological factors and texture features was performed. Results. Only eight texture features analysed show small variability (<5%) with activity concentration and reconstruction protocol making them suitable for heterogeneity quantification. On the other hand, there is a high statistically significant correlation between MAV and entropy (P<0.05). Entropy feature is, indeed, correlated (P<0.05) with all patient parameters, except body mass index. Conclusions. The textural features that are correlated with neither technical nor biological factors are run percentage, short-zone emphasis and intensity, making them suitable for quantifying functional changes or classifying patients. Other textural features are correlated with technical and biological factors and are, therefore, a source of errors if used for this purpose (AU)

Objetivo. Identificar las texturas que son independientes de los factores técnicos y biológicos en imagen PET con 18F-FDG con el fin de estandarizar la heterogeneidad en imagen PET. Material y métodos. Se realizaron 2 estudios. En primer lugar, se estudió la variabilidad de 72 parámetros texturales en una región de interés circular en el interior de un maniquí cilíndrico, con 19 concentraciones de actividad y 3 protocolos de reconstrucción diferentes. A continuación, se estudió una población de 15 pacientes sin captaciones hepáticas. De cada paciente se registraron el peso, altura, índice de masa corporal, volumen metabólico activo, niveles de glucosa en sangre, SUV y desviación estándar de SUV. Se obtuvieron las texturas de baja variabilidad de una región de interés centrada en hígado. Finalmente, se realizó un análisis de correlación multivariado de Spearman entre los factores biológicos y los parámetros texturales. Resultados. Solo 8 parámetros texturales muestran baja variabilidad (<5%) con la concentración de actividad y el protocolo de reconstrucción, haciéndolos adecuados para cuantificar la heterogeneidad de la región captante. Por otro lado, existe una correlación estadísticamente significativa entre el volumen metabólico activo y la entropía (p<0,05). La entropía está, además, correlacionada con los demás parámetros, excepto el índice de masa corporal. Conclusiones. Las únicas texturas que no están correlacionadas con ninguno de los parámetros anatómicos o fisiológicos son run percentage, short-zone emphasis e intensidad, siendo estas las más adecuadas para realizar análisis cuantitativos de heterogeneidades mediante parámetros de textura. Otras texturas están relacionadas con factores técnicos y biológicos y, por tanto, constituyen una fuente de errores cuando se utilizan para este fin (AU)

The intra-tumor heterogeneity of cell signaling factors in breast cancer: p4E-BP1 and peIF4E are diffusely expressed and are real potential targets

Breast cancers and most malignant tumors are composed of heterogeneous tumor cells both at genetic and morphological levels; intra-tumor heterogeneity can be one underlying cause of therapeutic resistance. Classical studies have focused on analyses of the relationship between primary tumors and metastatic dissemination, and on subclone evolution. However, it should be noted that tumor heterogeneity at the level of protein expression (proteomics) has not been yet studied in depth. The differences in protein expression also can play an important role in elucidating the relationship between intra-tumor heterogeneity and resistance to systemic therapy. In fact, in human tumors there is not always a homogeneous expression of many of the crucial factors involved in cell signaling, such as pMAPK, pAKt, pMTOR, even with constitutive oncogenic alterations upstream, such as HER2, PI3 K. Conversely, two of these factors, peIF4E and p4E-BP1, which are downstream, and control protein translation, show a diffuse and strong protein expression. In summary, most of cell signaling factors show a heterogeneous expression, regardless of oncogenic alterations. Tissue heterogeneity could be driven by local factors, including hypoxia. The fact that the phosphorylation of crucial proteins such as 4E-BP1 and eIF4E is observed homogeneously throughout most tumors and are druggable opens the chance to get real potential targets in cancer therapy (AU)

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[The effect of ionizing radiation and physical loading on the molecular heterogeneity of nucleoside phosphate kinases in liver subcellular fractions]. / Vliianie ioniziruiushchei radiatsii i fizicheskoi nagruzki na molekuliarnuiu geterogennost' nukleozidfosfatkinaz v subkletochnykh fraktsiiakh pecheni.

The different molecular forms of nucleoside-monophosphate kinases (KF 2.7.4.4) and nucleoside-diphosphate kinases (KF 1.7.4.6) which are responsible for the final steps of pyrimidine nucleotide synthesis were determined in mitochondrial rat hepatic supernatant under condition of combined influence of X-ray and maximum physical exercises (running up to complete exhaustion). The maximum activity of investigated nucleosidediphosphate kinases were observed in intact animals in that fractions which were eluted with tris-HCl buffer solution (0.075 and 1.0 M, pH 7.4). X-ray radiation and physical exercises caused the deviation of chromatographic data of maximal enzymatic activities. The drastic lowering of investigated enzymes was observed after X-ray irradiation and maximum physical exhaustion. This fact is in favour for the suppression of the final steps of primidine nucleotides synthesis under explored conditions of experimental investigations.