DNAR-13. SONIDEGIB AND GANT61 INDUCE DNA DAMAGE IN PEDIATRIC SONIC HEDGEHOG MEDULLOBLASTOMA

Abstract

Abstract Medulloblastoma is the most common malignant brain tumor in children, accounting for 20-25% of all pediatric brain tumors. The current standard of care includes both craniospinal and focal radiation therapy which leads to long term consequences in the pediatric population such as bone and tissue hypoplasia, decreased neurocognitive functioning, as well as an increased risk for secondary radiation induced cancers. Thus, there is a need for novel approaches to radiation therapy that can effectively target and kill tumor cells while minimizing radiation toxicity in healthy tissue in the pediatric patient population. The dysregulation and constitutive activation of the Sonic Hedgehog (SHH) signaling pathway accounts for ~30% of all medulloblastomas. In addition to playing a role in tumorigenesis, the SHH pathway is known to play a role in the radiation sensitivity and risk of tumor recurrence. We hypothesize that inhibiting the SHH pathway at Smoothened (Smo) or Gli1 will increase DNA damage, resulting in increased cell killing following radiation therapy. We found that treatment of medulloblastoma cells with the drug Sonidegib or GANT61 decreased the expression of the respective targets Smo and Gli1. Both drugs also significantly decreased expression of FANCD2, a DNA damage repair gene essential for homologous recombination. Pretreatment with Sonidegib or GANT61 resulted functionally with decreased tumor cell viability and self-renewal following radiation. These data suggest that Smo and Gli1 inhibition are promising targets for increasing the radiation sensitivity of pediatric SHH medulloblastoma.