CNSC-68. SEX DIFFERENCES IN GLYCINE BIOSYNTHESIS DRIVE RESPONSES TO COMBINED NUTRIENT DEPRIVATION AND PHARMACOLOGICAL INHIBITION IN PEDIATRIC HGG

Abstract In children and adults, high-grade gliomas (HGGs) are the most common and deadly primary brain malignancies. Generally, male HGGs occur at higher incidence and demonstrate more rapid proliferation, resulting in shorter overall male survival. Obscurity of molecular mechanisms driving this phenomenon prevents implementation of clinically effective treatments. Recently, a positive correlation between HGG cellular proliferation and metabolic reprogramming toward glycine biosynthesis was identified. By analyzing pediatric and adult HGG patient data, we discovered significantly worse outcomes unique to pediatric males bearing upregulation of serine and glycine biosynthesis transcripts. Previously, we have identified differential flux of glucose into serine and glycine biosynthesis drives sex differences in lung cancer. Therefore, we sought to confirm and target this paradigm in our NF1-/- DNp53 model of HGG. By performing metabolic tracing with [13C]-labeled glucose in male and female cells, we identified higher enrichment of [13C]-labeled serine and glycine in male cells relative to female cells. Through Western blotting, we identify male-specific upregulation of serine and glycine biosynthetic pathway enzymes in transformed cells, supporting our labelling results. Next, we sought to determine if inhibition of de-novo serine and glycine biosynthesis was similarly sex-biased. Utilizing serine-and-glycine-deprived media conditions, we identified a male-biased decrease in proliferation following pharmacological inhibition of de-novo serine and glycine biosynthesis. More precisely, in the absence of exogenous glycine, we discovered that inhibition of de-novo synthesis of glycine from serine drove male-specific decreases in proliferation. Additionally, we identified that transformed female cell robustness against inhibition of glycine biosynthesis is driven by the uptake of exogenous nucleotide precursors. These data confirm that sex differences in de-novo glycine biosynthesis drive sex differences in HGG cellular proliferation. As well, our work suggests that dietary restriction of serine and glycine, in-combination with pharmacological inhibition of de-novo glycine biosynthesis, represents a novel treatment paradigm.