Abstract 5712: Nutrient scarcity confers breast cancer brain metastasis sensitivity to serine synthesis pathway inhibition

The metabolic milieu of the brain is severely deprived of nutrients, including the amino acids serine and its catabolite glycine. The metabolic rewiring required for tumor cells to survive in the nutrient-limited environment of the brain and the metabolic vulnerabilities this confers are poorly understood. Here we demonstrate that cell-intrinsic de novo serine synthesis is a major determinant of triple-negative breast cancer (TNBC) brain metastasis. Whole proteome comparison of TNBC cells that differ in their capacity to colonize the brain reveals that 3-phosphoglycerate dehydrogenase (PHGDH), which catalyzes the rate-limiting step of glucose-derived serine synthesis, is the most significantly upregulated protein in cells that efficiently metastasize to the brain. Expression of catalytically active PHGDH in a non-brain trophic cell line promoted brain metastasis. Furthermore, genetic silencing or pharmacological inhibition of PHGDH attenuated brain metastasis burden in mice. These findings indicate that nutrient availability determines serine synthesis pathway dependence in brain metastasis, and suggest that PHGDH inhibitors may be useful in the treatment of patients with cancers that have spread to the brain

Limited Environmental Serine and Glycine Confer Brain Metastasis Sensitivity to PHGDH Inhibition

A hallmark of metastasis is the adaptation of tumor cells to new environments. Metabolic constraints imposed by the serine and glycine-limited brain environment restrict metastatic tumor growth. How brain metastases overcome these growth-prohibitive conditions is poorly understood. Here, we demonstrate that 3-phosphoglycerate dehydrogenase (PHGDH), which catalyzes the rate-limiting step of glucose-derived serine synthesis, is a major determinant of brain metastasis in multiple human cancer types and preclinical models. Enhanced serine synthesis proved important for nucleotide production and cell proliferation in highly aggressive brain metastatic cells. In vivo, genetic suppression and pharmacologic inhibition of PHGDH attenuated brain metastasis, but not extracranial tumor growth, and improved overall survival in mice. These results reveal that extracellular amino acid availability determines serine synthesis pathway dependence, and suggest that PHGDH inhibitors may be useful in the treatment of brain metastasis. SIGNIFICANCE: Using proteomics, metabolomics, and multiple brain metastasis models, we demonstrate that the nutrient-limited environment of the brain potentiates brain metastasis susceptibility to serine synthesis inhibition. These findings underscore the importance of studying cancer metabolism in physiologically relevant contexts, and provide a rationale for using PHGDH inhibitors to treat brain metastasis