PhD Graduate Student Cedars-Sinai Medical Center, United States
Abstract: Pediatric high-grade glioma (pHGG) are among the most lethal cancers in children. Despite the explosion in our understanding of the etiology of these diseases, median survival remains only 12-15 months. Unlike adult glioma, mutations in histone H3.3 including G34R and K27M have been found to occur frequently, observed in around 50% of patients. Due to this prevalence in pHGG, modeling these mutations in vitro and in vivo is important to understand tumor growth as well as treatment efficacy. The complexity of the human brain poses challenges in developing models and studying brain disorders and cancer. The establishment of human induced pluripotent stem cell (hiPSC)-derived in vitro models represents a unique opportunity to investigate these diseases under tightly controlled and personalized experimental setups. Here we have employed hiPSC-derived three-dimensional cortical organoids to model specific brain tumor subtypes by inducing the expression of the corresponding tumor driver genes. hiPSC-cortical organoids were cultured and electroporated, with a panel of DNA plasmids modeling an array of gain of function and loss of function mutations to model adult and pediatric brain tumors. Utilizing a piggyBac (pb) plasmid expressing H3.3 G34R, we were able to successfully generate transgenic cells in the hiPSC-cortical organoids. Successful transduction of organoids was confirmed via fluorescent imaging. Notably, we often observed focal hyperplasia of tranduced cells, which could overgrow the rest of the organoid. After generating the cortical organoids expressing the H3.3 G34R pb plasmids we sought to perform multiple treatment paradigms such as radiation therapy (RT), a treatment arm of the current standard of care therapy, and ADI-PEG20, an arginine deaminase. From preliminary data, we hypothesize that combining RT and ADI-PEG20 will inhibit tumoral cell growth in culture. Through this project, we have established an in vitro human organoid-based cancer modelling system for human brain tumors. Given the relative lack of patient-derived G34R mutant human tumoroids and cell lines, this approach can provide a valuable, renewable model system for high-throughput treatment discovery and validation.
