ATRT-01. PARP INHIBITION AS A THERAPEUTIC TARGET IN ATRT

Atypical teratoid rhabdoid tumors (ATRTs) are highly aggressive pediatric brain tumors with poor survival. The available treatments rely on toxic chemotherapy and radiotherapy, which alone can cause poor outcomes for young patients. Poly (ADP-ribose) polymerases (PARP), multifunctional enzymes which play an important role in DNA damage repair and genome stability have emerged as a new target in cancer therapy. An FDA approved drug screen revealed that Rucaparib, a PARP inhibitor, is important for ATRT cell growth.In this study we investigated the effect of Rucaparib treatment in ATRT. Using MTS and colony formation assays we found that Rucaparib treatment decreased ATRT cell growth and inhibited clonogenic potential of ATRT cells. Flow cytometry and Western blot analysis showed that Rucaparib treatment led to cell cycle arrest and apoptosis. Moreover, Rucaparib treatment led to DNA damage accumulation as seen by increased expression of yH2AX by immunofluorescence. In vivo, Rucaparib treatment significantly decreased tumor growth and prolonged survival in orthotopic mouse models. Furthermore, Immunohistochemistry revealed an increased number of P53 and Caspase3positive cells in the Rucaparib treatment group, confirming the induction of apoptosis in vivo. Furthermore, Rucaparib pretreatment sensitizes ATRT cells to radiation and significantly increased survival of xenograft-bearing mice. Thus, we demonstrated that Rucaparib has potential to be a new therapeutic strategy for ATRT as shown by its ability to decrease ATRT tumor growth both in vitro and in vivo.