This K08 proposal will complete Dr. Wajd Al-Holou’s training towards his long-term career goal of directing an independent research program that aims to define critical cellular interactions in the tumor microenvironment that drive treatment resistance in glioblastoma (GBM) and ultimately identify therapies targeting mechanisms of resistance. Dr. Al-Holou is an assistant professor in the department of Neurosurgery at the University of Michigan with established success in the field of neurosurgical oncology who completed his clinical training at the University of Michigan and MD Anderson Cancer Center. This proposal builds on Dr. Al-Holou’s previously acquired expertise in tumor biology and the development and analysis of recurrence models in GBM and proposes further training in defining tumor microenvironmental interactions utilizing in vitro and in vivo modeling, cancer genomics and bioinformatics, cancer biology, research ethics, grant writing and biostatistics, by means of investigative research and formal course work. Dr. Maria Castro, an internationally recognized expert on glioma tumor biology and the tumor microenvironment (TME) with a strong record of training scientists, will serve as primary mentor. Dr. Pedro Lowenstein, renowned for his work in vivo modeling and the development of novel therapies for GBM, and Dr. Thomas Wilson, an expert in the utilization of advanced genomics to answer critical biological questions, will serve as co-mentors and have a long track record of mentoring success. The University of Michigan has a rich and collaborative environment, and a strong institutional commitment to its trainees. This 5-year plan includes formal coursework, professional development and progressively independent research, with defined milestones to ensure productivity and a successful transition to independence. GBM is a lethal disease with therapeutic resistance that is driven by marked heterogeneity within the tumor microenvironment. The goal of this research is to elucidate critical TME interactions and cellular crosstalk that drive inherently resistant GBM cells to recur following therapy. We previously identified a rare population of inherently resistant THY1+ tumor cells in treatment naïve tumors that recurred following therapy. These cells show evidence of important cell signaling in the TME, exhibit a mesenchymal and stem-like phenotype, and are co-localize with macrophages in the perivascular niche. We hypothesize that THY1-mediated resistance results from cellular interactions in the TME, especially with macrophages, driving recurrence. To test this hypothesis, we have designed in vitro/in vivo analyses combined with spatial single cell analyses of human GBM to unravel how cell interactions in the TME drive resistance in hopes that inhibiting these interactions will abrogate treatment resistance. In total, this work will provide a foundation upon which Dr. Al-Holou will build a career investigating the intersection of resistan...