EXTH-15. RADIATION-INDUCED LATE MALIGNANT MENINGIOMA TRANSFORMATION: CDK 4/6 INHIBITOR THERAPY

Abstract

Meningiomas are the most common primary brain tumor reported in the United States each year and account for approximately 30% of primary neoplasms. Though in most cases the etiology of meningiomas is unclear, prior exposure to radiation is responsible for a subset of meningiomas. Some have speculated that there may be a relationship between pretreatment characteristics and radiotherapy parameters in the development of radiation-induced meningiomas (RIM). Compared with their sporadic counterparts, currently, the clinical treatment involves is similar with radiation used as a first line therapy. Novel therapeutic agents being investigated in the treatment of these tumors, rely on the direct or cell cycle-mediated induction of DNA damage to promote cellular apoptosis. Our pre-clinical data showed that disruption of p16INK4a-Cdk4-Rb (retinoblastoma) pathways plays a significant role in the development of RIM in Rb+ low-gradelow-grade meningioma cells. These observations highlight the critical role of the p16INK4a-Cdk4-Rb pathway in RIM and suggest that targeting this pathway might be a promising strategy to improve the therapeutic efficacy among RIM patients. Pretreatment characteristics and radiotherapy parameters which may influence the time interval for development of radiation-induced Rb+ meningiomas (RIM) were identified. Our results also demonstrated that CDK 4/6 Inhibitor, significantly suppresses radiation induced malignant transformation and prolonged survival in a cell-free, slice culture model and xenograft model of meningioma. Success of the proposed therapeutic strategies in both in vitro and in vivo models may form the basis for future research.