Contribution of tumor heterogeneity in a new animal model of CNS tumors

From bedside to bench: New insights in epilepsy-associated tumors based on recent classification updates and animal models on brain tumor networks

Low-grade neuroepithelial tumors (LGNTs), particularly those with glioneuronal histology, are highly associated with pharmacoresistant epilepsy. Increasing research focused on these neoplastic lesions did not translate into drug discovery; and anticonvulsant or antitumor therapies are not available yet. During the last years, animal modeling has improved, thereby leading to the possibility of generating brain tumors in mice mimicking crucial genetic, molecular and immunohistological features. Among them, intraventricular in utero electroporation (IUE) has been proven to be a valuable tool for the generation of animal models for LGNTs allowing endogenous tumor growth within the mouse brain parenchyma. Epileptogenicity is mostly determined by the slow-growing patterns of these tumors, thus mirroring intrinsic interactions between tumor cells and surrounding neurons is crucial to investigate the mechanisms underlying convulsive activity. In this review, we provide an updated classification of the human LGNT and summarize the most recent data from human and animal models, with a focus on the crosstalk between brain tumors and neuronal function.

Pediatric low-grade glioma models: advances and ongoing challenges

Pediatric low-grade gliomas represent the most common childhood brain tumor class. While often curable, some tumors fail to respond and even successful treatments can have life-long side effects. Many clinical trials are underway for pediatric low-grade gliomas. However, these trials are expensive and challenging to organize due to the heterogeneity of patients and subtypes. Advances in sequencing technologies are helping to mitigate this by revealing the molecular landscapes of mutations in pediatric low-grade glioma. Functionalizing these mutations in the form of preclinical models is the next step in both understanding the disease mechanisms as well as for testing therapeutics. However, such models are often more difficult to generate due to their less proliferative nature, and the heterogeneity of tumor microenvironments, cell(s)-of-origin, and genetic alterations. In this review, we discuss the molecular and genetic alterations and the various preclinical models generated for the different types of pediatric low-grade gliomas. We examined the different preclinical models for pediatric low-grade gliomas, summarizing the scientific advances made to the field and therapeutic implications. We also discuss the advantages and limitations of the various models. This review highlights the importance of preclinical models for pediatric low-grade gliomas while noting the challenges and future directions of these models to improve therapeutic outcomes of pediatric low-grade gliomas.

Advances in glioma models using in vivo electroporation to highjack neurodevelopmental processes

Glioma is the most prevalent type of neurological malignancies. Despite decades of efforts in neurosurgery, chemotherapy and radiation therapy, glioma remains one of the most treatment-resistant brain tumors with unfavorable outcomes. Recent progresses in genomic and epigenetic profiling have revealed new concepts of genetic events involved in the etiology of gliomas in humans, meanwhile, revolutionary technologies in gene editing and delivery allows to code these genetic "events" in animals to genetically engineer glioma models. This approach models the initiation and progression of gliomas in a natural microenvironment with an intact immune system and facilitates probing therapeutic strategies. In this review, we focus on recent advances in in vivo electroporation-based glioma modeling and outline the established genetically engineered glioma models (GEGMs).

Pediatric Glioma Models Provide Insights into Tumor Development and Future Therapeutic Strategies

In depth study of pediatric gliomas has been hampered due to difficulties in accessing patient tissue and a lack of clinically representative tumor models. Over the last decade, however, profiling of carefully curated cohorts of pediatric tumors has identified genetic drivers that molecularly segregate pediatric gliomas from adult gliomas. This information has inspired the development of a new set of powerful in vitro and in vivo tumor models that can aid in identifying pediatric-specific oncogenic mechanisms and tumor microenvironment interactions. Single-cell analyses of both human tumors and these newly developed models have revealed that pediatric gliomas arise from spatiotemporally discrete neural progenitor populations in which developmental programs have become dysregulated. Pediatric high-grade gliomas also harbor distinct sets of co-segregating genetic and epigenetic alterations, often accompanied by unique features within the tumor microenvironment. The development of these novel tools and data resources has led to insights into the biology and heterogeneity of these tumors, including identification of distinctive sets of driver mutations, developmentally restricted cells of origin, recognizable patterns of tumor progression, characteristic immune environments, and tumor hijacking of normal microenvironmental and neural programs. As concerted efforts have broadened our understanding of these tumors, new therapeutic vulnerabilities have been identified, and for the first time, promising new strategies are being evaluated in the preclinical and clinical settings. Even so, dedicated and sustained collaborative efforts are necessary to refine our knowledge and bring these new strategies into general clinical use. In this review, we will discuss the range of currently available glioma models, the way in which they have each contributed to recent developments in the field, their benefits and drawbacks for addressing specific research questions, and their future utility in advancing biological understanding and treatment of pediatric glioma.

Rat and Mouse Brain Tumor Models for Experimental Neuro-Oncology Research

Rodent brain tumor models have been useful for developing effective therapies for glioblastomas (GBMs). In this review, we first discuss the 3 most commonly used rat brain tumor models, the C6, 9L, and F98 gliomas, which are all induced by repeated injections of nitrosourea to adult rats. The C6 glioma arose in an outbred Wistar rat and its potential to evoke an alloimmune response is a serious limitation. The 9L gliosarcoma arose in a Fischer rat and is strongly immunogenic, which must be taken into consideration when using it for therapy studies. The F98 glioma may be the best of the 3 but it does not fully recapitulate human GBMs because it is weakly immunogenic. Next, we discuss a number of mouse models. The first are human patient-derived xenograft gliomas in immunodeficient mice. These have failed to reproduce the tumor-host interactions and microenvironment of human GBMs. Genetically engineered mouse models recapitulate the molecular alterations of GBMs in an immunocompetent environment and “humanized” mouse models repopulate with human immune cells. While the latter are rarely isogenic, expensive to produce, and challenging to use, they represent an important advance. The advantages and limitations of each of these brain tumor models are discussed. This information will assist investigators in selecting the most appropriate model for the specific focus of their research.

Multicolor strategies for investigating clonal expansion and tissue plasticity

Understanding the generation of complexity in living organisms requires the use of lineage tracing tools at a multicellular scale. In this review, we describe the different multicolor strategies focusing on mouse models expressing several fluorescent reporter proteins, generated by classical (MADM, Brainbow and its multiple derivatives) or acute (StarTrack, CLoNe, MAGIC Markers, iOn, viral vectors) transgenesis. After detailing the multi-reporter genetic strategies that serve as a basis for the establishment of these multicolor mouse models, we briefly mention other animal and cellular models (zebrafish, chicken, drosophila, iPSC) that also rely on these constructs. Then, we highlight practical applications of multicolor mouse models to better understand organogenesis at single progenitor scale (clonal analyses) in the brain and briefly in several other tissues (intestine, skin, vascular, hematopoietic and immune systems). In addition, we detail the critical contribution of multicolor fate mapping strategies in apprehending the fine cellular choreography underlying tissue morphogenesis in several models with a particular focus on brain cytoarchitecture in health and diseases. Finally, we present the latest technological advances in multichannel and in-depth imaging, and automated analyses that enable to better exploit the large amount of data generated from multicolored tissues.

Diffusion Kurtosis Imaging Reflects GFAP, TopoIIα, and MGMT Expression in Astrocytomas

Objective

Preliminary study of magnetic resonance (MR) diffusion kurtosis imaging (DKI) assessing the pathological glial fibrillary acidic protein (GFAP), TopoIIα, and O 6-methylguanine-DNA methyltransferase (MGMT) expression in astrocytomas.

Materials and Methods

This study was approved by the local ethics committee, and informed consent was obtained from all participants. Sixty-six cases with pathologically proven astrocytomas were enrolled in this study; of which, 34 were high grade and remaining 32 were low grade. They patients underwent conventional MRI head scan, DKI scan, and enhanced scan under the same conditions. Fractional anisotropy (FA) and mean kurtosis (MK) calculated from DKI, as well as GFAP, TopoIIα, and MGMT expression level were compared prospectively between high and low-grade astrocytomas. Spearman rank correlation analysis was used for comparing values of DKI and GFAP, TopoIIα, and MGMT expression level in the two groups.

Results

The MK values were significantly higher in high-grade astrocytomas than those in low-grade astrocytomas (P < 0.05); FA values demonstrated no significant difference between the two groups (P = 0.331). GFAP expression level was significantly lower in high-grade astrocytomas than in low-grade astrocytomas (P < 0.05). Topo-IIα expression level were significantly higher in high-grade astrocytomas than in low-grade astrocytomas (P < 0.05). There was no significant difference in MGMT expression level between the two groups (P = 0.679). MK values were negatively correlated with the expression of GFAP (r = -0.836; P = 0.03), however, they were positively correlated with the expression of Topo-IIα (r = 0.896; P = 0.01). FA values were not correlated with the expression of GFAP (r = 0.366; P = 0.05), Topo-IIα (r = -0.562; P = 0.05), and MGMT (r = -0.153; P = 0.10).

Conclusion

MK, the DKI parameter values of astrocytomas, was significantly correlated to the expression of GFAP and TopoIIα. To a certain extent, applying DKI may provide the biological behavior of tumor cell differentiation, proliferation activity, invasion and metastasis, and can guide individual treatment.

In Vivo and Ex Vivo Pediatric Brain Tumor Models: An Overview

After leukemia, tumors of the brain and spine are the second most common form of cancer in children. Despite advances in treatment, brain tumors remain a leading cause of death in pediatric cancer patients and survivors often suffer from life-long consequences of side effects of therapy. The 5-year survival rates, however, vary widely by tumor type, ranging from over 90% in more benign tumors to as low as 20% in the most aggressive forms such as glioblastoma. Even within historically defined tumor types such as medulloblastoma, molecular analysis identified biologically heterogeneous subgroups each with different genetic alterations, age of onset and prognosis. Besides molecularly driven patient stratification to tailor disease risk to therapy intensity, such a diversity demonstrates the need for more precise and disease-relevant pediatric brain cancer models for research and drug development. Here we give an overview of currently available in vitro and in vivo pediatric brain tumor models and discuss the opportunities that new technologies such as 3D cultures and organoids that can bridge limitations posed by the simplicity of monolayer cultures and the complexity of in vivo models, bring to accommodate better precision in drug development for pediatric brain tumors.

Radiomic prediction models for the level of Ki-67 and p53 in glioma

OBJECTIVE

To identify glioma radiomic features associated with proliferation-related Ki-67 antigen and cellular tumour antigen p53 levels, common immunohistochemical markers for differentiating benign from malignant tumours, and to generate radiomic prediction models.

METHODS

Patients with glioma, who were scanned before therapy using standard brain magnetic resonance imaging (MRI) protocols on T1 and T2 weighted imaging, were included. For each patient, regions-of-interest (ROI) were drawn based on tumour and peritumoral areas (5/10/15/20 mm), and features were identified using feature calculations, and used to create and assess logistic regression models for Ki-67 and p53 levels.

RESULTS

A total of 92 patients were included. The best area under the curve (AUC) for the Ki-67 model was 0.773 for T2 weighted imaging in solid glioma (sensitivity, 0.818; specificity, 0.833), followed by a less reliable AUC of 0.773 (sensitivity, 0.727; specificity 0.667) in 20-mm peritumoral areas. The highest AUC for the p53 model was 0.709 (sensitivity, 1; specificity, 0.4) for T2 weighted imaging in 10-mm peritumoral areas.

CONCLUSION

Using T2-weighted imaging, the prediction model for Ki-67 level in solid glioma tissue was better than the p53 model. The 20-mm and 10-mm peritumoral areas in the Ki-67 and p53 model, respectively, showed predictive effects, suggesting value in further research into areas without conventional MRI features.

Glial cell type-specific gene expression in the mouse cerebrum using the piggyBac system and in utero electroporation

Glial cells such as astrocytes and oligodendrocytes play crucial roles in the central nervous system. To investigate the molecular mechanisms underlying the development and the biological functions of glial cells, simple and rapid techniques for glial cell-specific genetic manipulation in the mouse cerebrum would be valuable. Here we uncovered that the Gfa2 promoter is suitable for selective gene expression in astrocytes when used with the piggyBac system and in utero electroporation. In contrast, the Blbp promoter, which has been used to induce astrocyte-specific gene expression in transgenic mice, did not result in astrocyte-specific gene expression. We also identified the Plp1 and Mbp promoters could be used with the piggyBac system and in utero electroporation to induce selective gene expression in oligodendrocytes. Furthermore, using our technique, neuron-astrocyte or neuron-oligodendrocyte interactions can be visualized by labeling neurons, astrocytes and oligodendrocytes differentially. Our study provides a fundamental basis for specific transgene expression in astrocytes and/or oligodendrocytes in the mouse cerebrum.

Histone-Mutant Glioma: Molecular Mechanisms, Preclinical Models, and Implications for Therapy

Pediatric high-grade glioma (pHGG) is the leading cause of cancer death in children. Despite histologic similarities, it has recently become apparent that this disease is molecularly distinct from its adult counterpart. Specific hallmark oncogenic histone mutations within pediatric malignant gliomas divide these tumors into subgroups with different neuroanatomic and chronologic predilections. In this review, we will summarize the characteristic molecular alterations of pediatric high-grade gliomas, with a focus on how preclinical models of these alterations have furthered our understanding of their oncogenicity as well as their potential impact on developing targeted therapies for this devastating disease.

Diffusion Kurtosis Imaging Reflects Glial Fibrillary Acidic Protein (GFAP), Topo IIα, and O⁶-Methylguanine-DNA Methyltransferase (MGMT) Expression in Astrocytomas

BACKGROUND Astrocytomas are the most common primary brain neoplasms. Biological indicators of astrocytomas can reflect its biological characteristics. The aim of this study was to assess the expression of the pathological glial fibrillary acidic protein (GFAP) Topo IIα and O⁶-methylguanine-DNA methyltransferase (MGMT) in astrocytomas using magnetic resonance (MR) diffusion kurtosis imaging (DKI) to evaluate the biological characteristics of astrocytomas. MATERIAL AND METHODS Sixty-six patients with pathologically proven astrocytomas were enrolled in this study. All patients underwent conventional MRI head scanning, DKI scanning, and enhanced scanning under the same conditions. Spearman's rank correlation analysis and Bonferroni correction were used to compare the values of DKI and the expression levels of GFAP, Topo IIα, and MGMT between the 2 groups. RESULTS Mean kurtosis (MK) values were negatively correlated with the expression of GFAP (r=-0.836; P=0.03). However, these were positively correlated with the expression of Topo IIα (r=0.896; P=0.01). Moreover, fractional anisotropy (FA) values were not correlated with the expression of GFAP (r=0.366; P=0.05), Topo IIα (r=-0.562; P=0.05), or MGMT (r=-0.153; P=0.10). CONCLUSIONS MK was significantly associated with the expression of GFAP and Topo IIα. To a certain extent, applying DKI may show the biological behavior of tumor cell differentiation, proliferation activity, invasion, and metastasis, and guide individual treatment.

Spontaneous development of intratumoral heterogeneity in a transposon-induced mouse model of glioma

Glioma is the most common form of malignant brain cancer in adults. The Sleeping Beauty (SB) transposon‐based glioma mouse model allows for effective in vivo analysis of candidate genes. In the present study, we developed a transposon vector that encodes the triple combination of platelet‐derived growth factor subunit A (PDGFA), and shRNAs against Nf1 and Trp53 (shNf1/shp53). Initiation and progression of glioma in the brain were monitored by expression of a fluorescent protein. Transduction of the vector into neural progenitor and stem cells (NPC) in the subventricular zone (SVZ) of the neonatal brain induced proliferation of oligodendrocyte precursor cells, and promoted formation of highly penetrant malignant gliomas within 2‐4 months. Cells isolated from the tumors were capable of forming secondary tumors. Two transposon vectors, encoding either PDGFA or shNf1/shp53 were co‐electroporated into NPC. Cells expressing PDGFA or shNf1/shp53 were labeled with unique fluorescent proteins allowing visualization of the spatial distribution of cells with different genetic alterations within the same tumor. Tumor cells located at the center of tumors expressed PDGFA at higher levels than those located at the periphery, indicating that intratumoral heterogeneity in PDGFA expression levels spontaneously developed within the same tumor. Tumor cells comprising the palisading necrosis strongly expressed PDGFA, suggesting that PDGFA signaling is involved in hypoxic responses in glioma. The transposon vectors developed are compatible with any genetically engineered mouse model, providing a useful tool for the functional analysis of candidate genes in glioma.

H3.3K27M Cooperates with Trp53 Loss and PDGFRA Gain in Mouse Embryonic Neural Progenitor Cells to Induce Invasive High-Grade Gliomas

Gain-of-function mutations in histone 3 (H3) variants are found in a substantial proportion of pediatric high-grade gliomas (pHGG), often in association with TP53 loss and platelet-derived growth factor receptor alpha (PDGFRA) amplification. Here, we describe a somatic mouse model wherein H3.3^K27M and Trp53 loss alone are sufficient for neoplastic transformation if introduced in utero. H3.3^K27M-driven lesions are clonal, H3K27me3 depleted, Olig2 positive, highly proliferative, and diffusely spreading, thus recapitulating hallmark molecular and histopathological features of pHGG. Addition of wild-type PDGFRA decreases latency and increases tumor invasion, while ATRX knockdown is associated with more circumscribed tumors. H3.3^K27M-tumor cells serially engraft in recipient mice, and preliminary drug screening reveals mutation-specific vulnerabilities. Overall, we provide a faithful H3.3^K27M-pHGG model which enables insights into oncohistone pathogenesis and investigation of future therapies.

Epilepsy-Associated KCNQ2 Channels Regulate Multiple Intrinsic Properties of Layer 2/3 Pyramidal Neurons

KCNQ2 potassium channels are critical for normal brain function, as both loss-of-function and gain-of-function KCNQ2 variants can lead to various forms of neonatal epilepsy. Despite recent progress, the full spectrum of consequences as a result of KCNQ2 dysfunction in neocortical pyramidal neurons is still unknown. Here, we report that conditional ablation of Kcnq2 from mouse neocortex leads to hyperexcitability of layer 2/3 (L2/3) pyramidal neurons, exhibiting an increased input resistance and action potential frequency, as well as a reduced medium afterhyperpolarization (mAHP), a conductance partly mediated by KCNQ2 channels. Importantly, we show that introducing the KCNQ2 loss-of-function variant KCNQ2I205V into L2/3 pyramidal neurons using in utero electroporation also results in a hyperexcitable phenotype similar to the conditional knock-out. KCNQ2I205V has a right-shifted conductance-to-voltage relationship, suggesting loss of KCNQ2 channel activity at subthreshold membrane potentials is sufficient to drive large changes in L2/3 pyramidal neuronal excitability even in the presence of an intact mAHP. We also found that the changes in excitability following Kcnq2 ablation are accompanied by alterations at action potential properties, including action potential amplitude in Kcnq2-null neurons. Importantly, partial inhibition of Nav1.6 channels was sufficient to counteract the hyperexcitability of Kcnq2-null neurons. Therefore, our work shows that loss of KCNQ2 channels alters the intrinsic neuronal excitability and action potential properties of L2/3 pyramidal neurons, and identifies Nav1.6 as a new potential molecular target to reduce excitability in patients with KCNQ2 encephalopathy.

SIGNIFICANCE STATEMENT

KCNQ2 channels are critical for the development of normal brain function, as KCNQ2 variants could lead to epileptic encephalopathy. However, the role of KCNQ2 channels in regulating the properties of neocortical neurons is largely unexplored. Here, we find that Kcnq2 ablation or loss-of-function at subthreshold membrane potentials leads to increased neuronal excitability of neocortical layer 2/3 (L2/3) pyramidal neurons. We also demonstrate that Kcnq2 ablation unexpectedly leads to a larger action potential amplitude. Importantly, we propose the Nav1.6 channel as a new molecular target for patients with KCNQ2 encephalopathy, as partial inhibition of these channels counteracts the increased L2/3 pyramidal neuron hyperexcitability of Kcnq2-null neurons.

Minute amounts of hamartin wildtype rescue the emergence of tuber-like lesions in conditional Tsc1 ablated mice

Tuberous sclerosis (TSC) is a phacomatosis associated with highly differentiated malformations including tubers in the brain. Those are composed of large dysplastic neurons and 'giant cells'. Cortical tubers are frequent causes of chronic seizures and resemble neuropathologically focal cortical dysplasias (FCD) type IIb. Patients with FCDIIb, however, lack additional stigmata of TSC. Mutations and allelic variants of the TSC1 gene have been observed in patients with tubers as well as FCDIIb. Those include hamartin(R692X) and hamartin(R786X), stop mutants frequent in TSC patients and hamartin(H732Y) frequent in FCDIIb. Expression of these variants in cell culture led to aberrant distribution of corresponding proteins. We here scrutinized morphological and structural effects of these TSC1 variants by intraventricular in utero electroporation (IUE), genetically mimicking the discrete focal character and a somatic postzygotic mosaicism of the lesion, focusing on the gene dosage required for tuber-like lesions to emerge in Tsc1(flox/flox) mice. Expression of only hamartin(R692X) as well as hamartin(R786X) led to a 2-fold enlargement of neurons with high pS6 immunoreactivity, stressing their in vivo pathogenic potential. Co-electroporation of the different aberrant alleles and varying amounts of wildtype TSC1 surprisingly revealed already minimal amounts of functional hamartin to be sufficient for phenotype rescue. This result strongly calls for further studies to unravel new mechanisms for substantial silencing of the second allele in cortical tubers, as proposed by Knudson's '2-hit hypothesis'. The rescuing effects may provide a promising basis for gene therapies aiming at reconstituting hamartin expression in tubers.

Overview of Transgenic Glioblastoma and Oligoastrocytoma CNS Models and Their Utility in Drug Discovery

Many animal models have been developed to investigate the sources of central nervous system (CNS) tumor heterogeneity. Reviewed in this unit is a recently developed CNS tumor model using the piggyBac transposon system delivered by in utero electroporation, in which sources of tumor heterogeneity can be conveniently studied. Their applications for studying CNS tumors and drug discovery are also reviewed. © 2016 by John Wiley & Sons, Inc.

Tracking and transforming neocortical progenitors by CRISPR/Cas9 gene targeting and piggyBac transposase lineage labeling

The ability to induce targeted mutations in somatic cells in developing organisms and then track the fates of those cells is a powerful approach both for studying neural development and for modeling human disease. The CRISPR/Cas9 system allows for such targeted mutagenesis, and we therefore tested it in combination with a piggyBac transposase lineage labeling system to track the development of neocortical neural progenitors with targeted mutations in genes linked to neurodevelopmental disruptions and tumor formation. We show that sgRNAs designed to target PTEN successfully decreased PTEN expression, and led to neuronal hypertrophy and altered neuronal excitability. Targeting NF1, by contrast, caused increased astrocytogenesis at the expense of neurogenesis, and combined targeting of three tumor suppressors (PTEN, NF1 and P53) resulted in formation of glioblastoma tumors. Our results demonstrate that CRISPR/Cas9 combined with piggyBac transposase lineage labeling can produce unique models of neurodevelopmental disruption and tumors caused by somatic mutation in neural progenitors.

Ets Factors Regulate Neural Stem Cell Depletion and Gliogenesis in Ras Pathway Glioma

As the list of putative driver mutations in glioma grows, we are just beginning to elucidate the effects of dysregulated developmental signaling pathways on the transformation of neural cells. We have employed a postnatal, mosaic, autochthonous glioma model that captures the first hours and days of gliomagenesis in more resolution than conventional genetically engineered mouse models of cancer. We provide evidence that disruption of the Nf1-Ras pathway in the ventricular zone at multiple signaling nodes uniformly results in rapid neural stem cell depletion, progenitor hyperproliferation, and gliogenic lineage restriction. Abolishing Ets subfamily activity, which is upregulated downstream of Ras, rescues these phenotypes and blocks glioma initiation. Thus, the Nf1-Ras-Ets axis might be one of the select molecular pathways that are perturbed for initiation and maintenance in glioma.

Pathological bases for a robust application of cancer molecular classification

Any robust classification system depends on its purpose and must refer to accepted standards, its strength relying on predictive values and a careful consideration of known factors that can affect its reliability. In this context, a molecular classification of human cancer must refer to the current gold standard (histological classification) and try to improve it with key prognosticators for metastatic potential, staging and grading. Although organ-specific examples have been published based on proteomics, transcriptomics and genomics evaluations, the most popular approach uses gene expression analysis as a direct correlate of cellular differentiation, which represents the key feature of the histological classification. RNA is a labile molecule that varies significantly according with the preservation protocol, its transcription reflect the adaptation of the tumor cells to the microenvironment, it can be passed through mechanisms of intercellular transference of genetic information (exosomes), and it is exposed to epigenetic modifications. More robust classifications should be based on stable molecules, at the genetic level represented by DNA to improve reliability, and its analysis must deal with the concept of intratumoral heterogeneity, which is at the origin of tumor progression and is the byproduct of the selection process during the clonal expansion and progression of neoplasms. The simultaneous analysis of multiple DNA targets and next generation sequencing offer the best practical approach for an analytical genomic classification of tumors.