P04.08.A PATIENT-DERIVED ORGANOIDS FOR MODELING AND CHARACTERIZING PEDIATRIC BRAIN TUMORS

Abstract

Abstract BACKGROUND Central nervous system (CNS) tumors are the most common solid tumors in the pediatric population and the leading cause of death among childhood cancers. They present common features related to the development and produce symptoms based on their location, rate of tumor growth and age of the child. Tumors of embryonal origin, such as medulloblastoma or primitive neuroectodermal tumor, have a higher incidence in younger patients, whereas older ones tend to present tumors of glial origin. Most of CNS-embryonal tumors are highly malignant and consequently leading to poor prognoses. Despite the understanding of their underlying molecular landscape that has helped in clinical advances to improve life expectancies of the patients, there is still an emerging need to minimize morbidity and manage the long-term therapy effects. MATERIAL AND METHODS Human samples were collected according to protocols approved by the institutional review board with written consent. Patient-Derived Organoids (PDOs) and Patient-Derived Xenograft Organoids (PDXOs) were obtained using scalpels by chopping in small pieces the tumor tissue and were grown in PDOs medium. PDOs and PDXOs were analyzed through DNA methylation, immunostainings, sc-RNA sequencing and orthotopic nude mice engraftment. Therapeutic regimens were adapted according to patients’ treatment protocols depending on the tumor of origin. RESULTS Developing new models to better understand the complexity and heterogeneity of pediatric tumors and to test personalized treatment strategies remains a clinical challenge. We tried to answer this medical need with PDOs and PDXOs established through the direct in vitro culture of different kinds of primary tumors (ependymoma EPN, medulloblastoma MB and low-grade glial tumors) and MB patient derived xenograft (PDX)-derived tumors. We have developed a method that recapitulates mutational profiles, histological features, and cellular heterogeneity of the corresponding parental tumors. We have obtained promising results from the DNA methylation profile analysis, nowadays used for an accurate routine CNS tumors diagnosis. Through this new model, we confirmed the action of clinically used therapeutic regimens, i.e., for EPN with ZFTA-RELA fusion and G3 MB-derived PDOs. PDOs were subjected to the same treatment the patients underwent and responded similarly to the patients. CONCLUSION We found a suitable in vitro culture condition to generate and maintain PDOs from different kinds of pediatric brain tumors. Their reliability has been proved by different analyses, confirming they still resemble the parental tumors. Through this new model, we confirmed the action of clinically used therapeutic regimens, suggesting its potential at the translation level as a reliable tool for testing personalized medicine, drug screening and development of newer and more specific therapeutic strategies.