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

High-throughput identification of genotype-specific cancer vulnerabilities in mixtures of barcoded tumor cell lines.

Hundreds of genetically characterized cell lines are available for the discovery of genotype-specific cancer vulnerabilities. However, screening large numbers of compounds against large numbers of cell lines is currently impractical, and such experiments are often difficult to control. Here we report a method called PRISM that allows pooled screening of mixtures of cancer cell lines by labeling each cell line with 24-nucleotide barcodes. PRISM revealed the expected patterns of cell killing seen in conventional (unpooled) assays. In a screen of 102 cell lines across 8,400 compounds, PRISM led to the identification of BRD-7880 as a potent and highly specific inhibitor of aurora kinases B and C. Cell line pools also efficiently formed tumors as xenografts, and PRISM recapitulated the expected pattern of erlotinib sensitivity in vivo

Dorsal Horn Errors in Neuronal Positioning Contribute to Nociceptive Abnormalities in Reelin-Signaling Pathway Mutant Mice

Mutant mice with a deletion of Reelin (Reln), or both lipoprotein receptors, or Disabled-1 (Dab1) exhibit neuronal positioning errors, heat hypersensitivity and mechanical insensitivity. Despite the extensive nociceptive abnormalities, anatomical alterations in the lumbar dorsal horn neurons that participate in Reelin signaling were not yet identified. This thesis will identify these Dab1 and Reelin dorsal horn neurons and characterize their positioning errors associated with the nociceptive abnormalities in Reelin-pathway mutants. In the first study, we found that 70% of Dab1-labeled laminae I-II neurons were glutamatergic as they co-expressed the transcription factor Lmx1b. Dab1-Lmx1b neurons were increased within the IB4 layer and reduced within the lateral reticulated area and lateral spinal nucleus (LSN) of Reln-/- versus Reln+/+ mice. Additionally, Dab1-Lmx1b neurons participated in nociceptive circuits as they expressed Fos following noxious thermal or mechanical stimulation. Importantly, we determined that mispositioned Dab1 neurons that co-expressed Neurokinin-1-receptors contribute specifically to the heat hypersensitivity of dab1-/- mice. The second study asked whether the loss of Reelin laminae I-II neurons contributes to the mechanical insensitivity of dab1-/- mice. We found that 83% of Reelin laminae I-II neurons co-expressed Lmx1b. Although Reelin-Lmx1b and Dab1-Lmx1b neurons were independent populations, together they comprised 37% of laminae I-II glutamatergic neurons. Reelin-Lmx1b neurons sustained similar positioning errors to the Dab1-Lmx1b neurons, that is, with more of these neurons within the IB4 layer and less in the lateral reticulated area and LSN of dab1-/- compared to dab1+/+ mice. The area of laminae I-IIouter was reduced in both Reln and dab1 mutants, but the IB4 layer did not differ between genotypes. We examined the migratory patterns of Reelin and Dab1 neurons and found that they arose from both the early-born (dI5) and late-born (dILB) Lmx1b-expressing populations during embryonic development. When Dab1 was absent, the migration of Reelin and Reelin-Lmx1b neurons were relatively normal whereas without Reelin, Dab1 and Dab1-Lmx1b neurons exhibited clear migratory errors. In combination, we determined that the neuroanatomical abnormalities in Reln-/- and dab1-/- dorsal horn are due to the disruption of the Reelin-Dab1-signaling pathway, and these positioning errors contribute to the nociceptive alterations displayed by the mutant mice

Dorsal Horn Errors in Neuronal Positioning Contribute to Nociceptive Abnormalities in Reelin-Signaling Pathway Mutant Mice

Mutant mice with a deletion of Reelin (Reln), or both lipoprotein receptors, or Disabled-1 (Dab1) exhibit neuronal positioning errors, heat hypersensitivity and mechanical insensitivity. Despite the extensive nociceptive abnormalities, anatomical alterations in the lumbar dorsal horn neurons that participate in Reelin signaling were not yet identified. This thesis will identify these Dab1 and Reelin dorsal horn neurons and characterize their positioning errors associated with the nociceptive abnormalities in Reelin-pathway mutants. In the first study, we found that 70% of Dab1-labeled laminae I-II neurons were glutamatergic as they co-expressed the transcription factor Lmx1b. Dab1-Lmx1b neurons were increased within the IB4 layer and reduced within the lateral reticulated area and lateral spinal nucleus (LSN) of Reln-/- versus Reln+/+ mice. Additionally, Dab1-Lmx1b neurons participated in nociceptive circuits as they expressed Fos following noxious thermal or mechanical stimulation. Importantly, we determined that mispositioned Dab1 neurons that co-expressed Neurokinin-1-receptors contribute specifically to the heat hypersensitivity of dab1-/- mice. The second study asked whether the loss of Reelin laminae I-II neurons contributes to the mechanical insensitivity of dab1-/- mice. We found that 83% of Reelin laminae I-II neurons co-expressed Lmx1b. Although Reelin-Lmx1b and Dab1-Lmx1b neurons were independent populations, together they comprised 37% of laminae I-II glutamatergic neurons. Reelin-Lmx1b neurons sustained similar positioning errors to the Dab1-Lmx1b neurons, that is, with more of these neurons within the IB4 layer and less in the lateral reticulated area and LSN of dab1-/- compared to dab1+/+ mice. The area of laminae I-IIouter was reduced in both Reln and dab1 mutants, but the IB4 layer did not differ between genotypes. We examined the migratory patterns of Reelin and Dab1 neurons and found that they arose from both the early-born (dI5) and late-born (dILB) Lmx1b-expressing populations during embryonic development. When Dab1 was absent, the migration of Reelin and Reelin-Lmx1b neurons were relatively normal whereas without Reelin, Dab1 and Dab1-Lmx1b neurons exhibited clear migratory errors. In combination, we determined that the neuroanatomical abnormalities in Reln-/- and dab1-/- dorsal horn are due to the disruption of the Reelin-Dab1-signaling pathway, and these positioning errors contribute to the nociceptive alterations displayed by the mutant mice

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