3:00 PM. 32. Targeting Cell-Matrix Induced Chemoresistance With Regorafenib in a 3D Model of Osteosarcoma.Rameshwar Rao, MD PhD1, Michelle Huang, PhD2, Daiyao Zhang, BS2, Carla Huerta-López, PhD2, Christopher Long, BS2, Gisele Aviles Rodriguez2, Esther Mozipo, BS2, Sriya Sagi, MS1, Sarah Heilshorn, PhD2 1Seattle Children's Research Institute, 2Stanford University