TMET-39. DUAL TARGETING OF MAP KINASE SIGNALING AND METABOLISM IS A THERAPEUTIC VULNERABILITY IN PEDIATRIC DIFFUSE MIDLINE GLIOMAS

Abstract Metabolic reprogramming in pediatric diffuse midline glioma is driven by gene expression changes induced by the hallmark histone mutation H3K27M, which results in aberrantly permissive activation of oncogenic signaling pathways. Previous studies of diffuse midline glioma with altered H3K27 (DMG-H3K27a) have shown that the RAS pathway, specifically through its downstream kinase, extracellular-signal-related kinase 5 (ERK5), is critical for tumor growth. However, there remains a knowledge gap in identifying effectors of ERK signaling and their roles in DMG-H3K27a. Leveraging several patient multi-omic datasets, we identified a unique relationship between ERK5 and brain tumor glycolysis. We establish that ERK5 is a critical regulator of cell proliferation and glycolysis in DMG-H3K27a, where ERK5 knockdown leads to decreases in glycolysis and increases in mitochondrial metabolism. We demonstrate through loss of function and overexpression studies that ERK5 mediates glycolysis through regulation of glycolytic enzyme Phosphofructo-2-Kinase/Fructose-2,6-Biphosphatase 3 (PFKFB3). PFKFB3 is a protein that catalyzes the synthesis or degradation of fructose-2,6-bisphosphate (F2,6BP). Furthermore, we establish a novel mechanism, in which ERK5 mediates PFKFB3 expression via activation of MEF2A, an oncogenic transcription factor. DMG-H3K27a cells are sensitive to the loss or inhibition of PFKFB3 both in vitro and in orthotopic mouse models. However, monotherapy is ineffective in heterogenous diseases such as gliomas, including DMG-H3K27a. To combat this, we show multi-targeted therapy against the ERK5-PFKFB3 axis is synergistic in vitro and in vivo. Multi-targeted drug therapy against the ERK5-PFKFB3 axis, such as with small-molecule inhibitors, may represent a promising therapeutic approach in patients with pediatric diffuse midline glioma. Moreover, we have identified resistance to our dual therapy using several systems biology approaches, which we are currently investigating and validating. Collectively, our study defines a novel, targetable axis in DMG-H3K27a and highlights the importance of tumor cell metabolism in defining therapeutic vulnerabilities.