Abstract 2140: Delineating a functional link between a phosphoserine aminotransferase (PSAT1)-associated gene signature and EGFR-mutant NSCLC

Abstract

Abstract Phosphoserine aminotransferase 1 (PSAT1) catalyzes the second enzymatic step within the serine synthetic pathway and its expression is elevated in numerous human cancers, such as NSCLC. While PSAT1 suppression decreases SSP activity and cell proliferation, non-canonical activities have recently been suggested that may contribute to its pro-tumorigenic function, as is seen with other metabolic enzymes such as pyruvate kinase. Thus, we conducted a genome wide expression screen to uncover potential unknown cellular processes impacted by PSAT1 and to identify a PSAT1-associated gene signature that might inform patient outcomes in NSCLC. Loss of PSAT1 in EGFR-mutant PC9 lung cancer cells led to 491 differentially expressed genes (279-down; 212-up). KEGG and gene ontology analysis identified biological pathways such as metabolic processes, cell cycle regulation, cell adhesion, and cell motility. Transcript analysis confirmed inhibitory effects on the Rb/E2F1 and β-catenin pathways as well as expression of effectors on the actin cytoskeleton upon loss of PSAT1. Importantly, these could be rescued by PSAT1 restoration, including the loss of F-actin stress fibers as observed with phalloidin staining. Lastly, a bioinformatics approach utilizing transcriptomic data from human lung cancer patients was used to define genes altered between EGFR-mutant lung cancers and normal lung and that were differentially expressed in our PSAT1 depletion RNA-seq study. From this, we identified a PSAT1-associated gene signature that was then used to assign risk survival scores to these NSCLC patients. Subsequent, Kaplan Meier analysis demonstrated the prognostic ability of this gene signature for both relapse free and overall survival in EGFR-mutant NSCLC but was unable to predict risk groups in other NSCLC subtypes. Together, transcriptomic analysis under PSAT1 silencing identified its impact on various biological processes, including actin cytoskeleton rearrangement, and led to identification of a gene signature that has predictive ability towards survival outcomes in EGFR-mutant lung cancer. Citation Format: Rumeysa Biyik-Sit, Brian F. Clem. Delineating a functional link between a phosphoserine aminotransferase (PSAT1)-associated gene signature and EGFR-mutant NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2140.