MYC Overexpressing Multiple Myeloma Are Dependent on GLS1

Introduction. MYC alterations trigger transition from monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) to multiple myeloma (MM). They also represent secondary genomic events inducing tumor progression. MYC localization to the nucleus and the short life of the protein are key factors that limit its direct targeting. To overcome these issues, we sought to determine the top genomic dependencies in MYC overexpressing MM by analyzing large-scale knockdown screening, followed by functional validations. Methods. We performed in silico analyses from the Dependency Map (Achilles 2.4.3) together with CCLE (Affymetrix U133+2 expression array), CLUE (Connectivity Map) and MM patient datasets (Chng et al. 2007, Gutierrez et al. 2010, MMRF RG Dataset), to look for gene dependencies and differentially expressed pathways in MYC OE cancer cell lines and MM patient samples. We generated an isogenic model of MYC OE in U266 MM cell line by using EF1A-C-MYC lentiviral vector, and performed RNA sequencing, a quantitative proteomic analysis by Tandem Mass Tag mass spectrometry (TMT-MS) and a drug screening with ~2000 compounds. To further investigate dependency on glutamine metabolism in MYC OE cell lines, we treated them with GLS1 inhibitor CB-839 and siRNA targeting GLS1 in several cell lines with various MYC expressions and in our isogenic model. Results. By analyzing correlations between MYC expression and gene ATARiS scores corresponding to the effect of over 9000 knockdowns in 236 cell lines, we identified specific vulnerabilities of MYC overexpressing cells for the genes involved in glutamine metabolism and cell cycle pathways. Top dependencies were observed with MYC binding protein MAX (r = -0.51, p Conclusion. By using a combination of different datasets and models, we characterized the main dependencies in MYC overexpressing MM. Glutamine metabolism and cell cycle emerged as strong dependencies by using therapeutic inhibitors. Altogether, our results demonstrate that MYC OE MM cells are dependent on glutamine metabolism and cell cycle, and these findings can potentially lead to development of new therapeutic approaches in MM patients. Disclosures Leleu: Oncopeptide: Honoraria; Sanofi: Honoraria; Takeda: Honoraria; Carsgen: Honoraria; Incyte: Honoraria; Novartis: Honoraria; Karyopharm: Honoraria; Amgen: Honoraria; Celgene: Honoraria; Janssen: Honoraria; BMS: Honoraria; Merck: Honoraria. Facon: Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees. Manier: Amgen: Research Funding; Celgene: Research Funding; Janssen: Research Funding.