Using Human Neural Stem Cells to Create Genetically Accurate Models of PLGG, Developing PLGG Models Using Patient-Derived Tumor Tissue, Dual mTOR/NOTCH inhibition as a Therapeutic Strategy for PLGG

This award is made up of three distinct projects including:

      • Using human neural stem cells to create genetically accurate models of LGG. We have shown that we can take normal human brain cells and introduce into these cells the genetic changes that we find in LGG. Although we can model three of the six subtypes of LGG, the cells do not grow for enough time to allow us to use them for drug screen. The lack of long-term growth suggests that we need to refine our models. As a proof of principle, we did create a model that has activation of a common driver in PLGA (the MAP kinase pathway), and we found that the drug trametinib, which is currently in clinical trials for pediatric LGG, can suppress the growth of our engineered cells. This result shows that our models behave as we hoped, validating our approach. The next step is to combine the known drivers of LGG with suppression of epigenetic modifiers that were recently demonstrated to be the end-result of cellular senescence. We hypothesize that this approach will allow our normal cells to tolerate the drivers of pediatric LGG – thereby creating a panel of genetically accurate human cells that will allow us to find new drugs to help children with LGG.
      • Models of pediatric LGG which grow robustly and allow the study of tumor biology and drug testing are desperately needed. In prior work from multiple groups, including our own, tumor- derived cells have stop growing over time, limiting our ability to study them. We are currently trying to bypass these limitations using genetic methods, i.e. knocking down tumor suppressor genes and/or introducing oncogenes that facilitate the growth of these tumors. An alternative approach that we are currently developing with our collaborators is known as conditionally reprogrammed cells (CRC) using specific culture conditions previously applied to study many epithelial cancers, which we are now applying to cells derived from primary pediatric LGG with promising initial results. There has been great success in growing fastidious cells using CRC, and we anticipate that this approach will allow us for the first time to grow primary LGG cells in culture.
      • Recent studies in our laboratory suggest that in addition to BRAF, other signaling pathways are operational in LGG and other low-grade gliomas in children. We have already identified mTOR and NOTCH as frequently active in these tumors, and these pathways may represent additional therapeutic targets in aggressive tumors. We are currently dissecting in detail the status of the NOTCH and mTOR pathways and their relation to BRAF in tumors. We will determine the mTOR and p16INK4a expression in a COG cohort of low grade glioma tumors as part of a comprehensive COG biology study. We have previously demonstrated efficacy of mTOR and NOTCH monotherapy in LGG, and now we propose to test combination therapy in LGG models in vitro and in vivo to find if they can synergistically stop the growth of LGG cell lines.

These three projects will develop new models and test better therapies for patients with LGG.