Abstract 881: Identifying the context of vulnerability to MLN4924 in glioblastoma (GBM)

Abstract

Abstract Neddylation is a post-translational mechanism that marks proteins for degradation through activity of NEDD8 Activating Enzyme (NAE). NAE activates cullin-RING ligases (CRL), which ubiquitylate selected substrates and mark them for proteosomal degradation. MLN4924, or Pevonedistat, targets NAE and inhibits Neddylation and induces apoptosis in sensitive cells. To assess the preferential sensitivity of cell lines to MLN4924, we performed a 10-point drug dose response (DDR) assay on long-term established GBM cell lines. Efficacy of MLN4924 in glioma cell lines was evaluated by measuring cell viability (CellTiterGlo®) and cell cycle progression (flow cytometry with propidium iodide staining). To identify mechanism of differential response to MLN4924 treatment, cell cycle regulatory pathway and DNA damage were also examined by Western blotting. GB1 (IC50 = 0.28 μM) & LN18 (IC50 = 0.19 μM) were established as sensitive and M059K (IC50 = 5.5 μM) & SNU1105 (IC50 = 20.9 μM) as non-sensitive cell lines based on the IC50 values. Flow cytometry analysis of DNA content revealed significant arrest of cells in G2/M even at low doses of 100 nM of MLN4924 preferentially in GB1 and LN18. This was consistent with an increase in CRL substrates p21, p27 and WEE1 in GB1 and LN18 possibly contributing to the G2/M arrest. While CDT1 accumulation was observed starting at 2h post MLN4924 treatment in sensitive cell lines, it took upto 8h for CDT1 accumulation in the non-sensitive cell lines. Increases in CDT1 induced re-replication causing massive arrest in G2/M phase lead to increased DNA damage, validated by higher expression of γH2AX in the sensitive cell lines. Additionally, we also investigated the efficacy of MLN4924 against orthotopic glioma PDX models in vitro and in vivo to validate our findings. In a cohort of glioblastoma PDX models we discovered that GBM PDX models with lower Neddylation gene set enrichment score (GBM116, GBM59, SF7300) were markedly more vulnerable to MLN4924 than GBM PDX models with higher Neddylation gene set enrichment score (GBM91 and GBM102) in vitro and in vivo. Orthotopic PDX models of selected GBM revealed survival prolongation of GBM116, but minimal survival benefit to GBM102 tumors. Validation of the predictive markers of vulnerability to MLN4924 in additional PDX models will set the stage for prospective clinical trials of MLN4924 in glioblastoma patients. Citation Format: Leena Chaudhuri, Rita L. Bybee, Lauren K. Hartman, Sen Peng, Darren Finlay, Kristiina Vuori, Michael E. Berens, Harshil D. Dhruv. Identifying the context of vulnerability to MLN4924 in glioblastoma (GBM) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 881.