Glioblastoma (GBM) is the most common brain tumor malignancy in adults that is characterized by unique
niches termed pseudo-palisading necrosis. These hypoxic regions are a defining feature of the disease which
promote chemoresistance, radioresistance, and ultimately drive disease progression. Understanding the
generation and sustainment of these regions is critical to understanding how to effectively treat the disease.
Multi-omics analysis of human GBM patients reveals that the creatine transporter, Slc6a8 is specifically
expressed by tumor cells in hypoxic and necrotic regions. Surrounding these regions are tumor-associated
myeloid cells (TAMCs), which are the most abundant infiltrating immune cell in GBM. Surprisingly, the TAMCs
that surround the hypoxic pseudo-palisading regions express the enzymes necessary to produce creatine.
Therefore, we hypothesize that TAMC-derived creatine promotes the generation of the pseudo-palisading
necrotic niche in GBM, and that this metabolic crosstalk promotes both GBM fitness and therapy resistance.
Previous work has identified that the hypoxic pseudo-palisading niche contains glioma stem cells (GSC),
which are generated by the hypoxic stress within these regions. Furthermore, Slc6a8 is directly regulated by
hypoxia, suggesting creatine uptake exerts a role on GSC phenotypes. Thus, the first aim of this proposal is to
examine how creatine transport influences GSC phenotypes in both human and mouse models of GBM. In this
aim, we will also utilize inducible models of GBM that recapitulate the genetic and pathologic features of human
GBM to determine if Slc6a8 is necessary for the formation of the hypoxic pseudo-palisading niche in tumors.
Our preliminary data indicate that TAMCs isolated from both mice and humans with GBM are proficient
producers of creatine. Furthermore, we found that this metabolic phenotype is specific to the tumor
microenvironment (TME) and is induced by extracellular lactate. Thus, the second aim of this proposal will
examine how the ablation of creatine biosynthesis by TAMCs controls tumor growth and progression in mouse
models of GBM. This aim will also determine how lactate induces the creatine biosynthetic phenotype of TAMCs
The third aim of this proposal is to examine if a clinically relevant inhibitor of creatine transport influences
GBM growth. We will test how this inhibitor works in the context of chemo and radiotherapy to determine how
creatine uptake influences GBM recurrence. To establish translatable value from this work, we will generate
tumor samples and patient-derived xenografts from patients, screen them for expression of creatine metabolic
genes, then assess sensitivity to creatine metabolic inhibitory therapy. The results of this aim will identify if
blocking TAMC-to-tumor metabolic communication is a feasible strategy for GBM therapy.