Abstract 434: Characterizing the role of serine metabolism in pediatric sarcomas

Sarcomas represent a diverse group of malignancies with unique molecular and pathological characteristics. In order to improve sarcoma treatment, a better understanding of the alterations associated with specific sarcoma subtypes is critically important. Renewed interest in the altered metabolic properties of cancer cells has led to an exploration of targeting metabolic dependencies as a novel therapeutic strategy. Metabolism of the amino acid serine is frequently altered in cancer, supporting a number of critical biological processes, including protein, lipid, and nucleotide synthesis, and redox balance. The first, rate-limiting step in the serine synthesis pathway is catalyzed by the enzyme 3-phosphoglycerate dehydrogenase (PHGDH), which is overexpressed in several cancers. Previous work has shown that PHGDH loss or inhibition is selectively toxic to cancer cells with high PHGDH expression or increased flux through the serine synthesis pathway. In this study, we have characterized the dependency of pediatric sarcomas on serine metabolism by examining expression of PHGDH in Ewing sarcoma and rhabdomyosarcoma cell lines, and evaluating the effects of PHGDH inhibition and serine deprivation on cellular proliferation and bioenergetic properties. We show that PHGDH is highly expressed in pediatric sarcoma cell lines, and that PHGDH knockdown resulted in decreased proliferation, especially under conditions of serine limitation. Moreover, pharmacological inhibition of PHGDH resulted in a dose-dependent decrease in proliferation and mitochondrial bioenergetic function. Furthermore, individual sarcoma cell lines were differentially sensitive to serine deprivation, indicating that some sarcoma cells may depend on extracellular serine in addition to de novo serine synthesis. Our findings suggest that the dependency of pediatric sarcomas on serine metabolism should be further investigated in order to identify vulnerabilities that could be targeted for potential therapeutic benefit. Citation Format: Sameer Issaq, Ria Kidner, Jason Rohde, Matthew Boxer, Lee Helman. Characterizing the role of serine metabolism in pediatric sarcomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 434. doi:10.1158/1538-7445.AM2017-434