Co-targeting IGF-1R and Glutaminase in Ewing Sarcoma - PROJECT SUMMARY Aberrant activation of receptor tyrosine kinases (RTK) drives or enables tumorigenesis, metastasis, and therapeutic resistance across cancers but RTK targeting is only successful in few of these. IGF-1R provides a key oncogenic axis in Ewing Sarcoma (EWS), the second most common malignant bone tumor of children and young adults with a 5-year survival rate of only 39% once metastasized. Yet, clinical trials showed limited responses to IGF-1R inhibitors in EWS. An essential cancer hallmark is the metabolic rewiring with enhanced accumulation of glucose and its aerobic glycolysis (the Warburg effect). This helps reallocate glucose-derived metabolites for macromolecular synthetic needs of proliferative tumor cells and away from use in bioenergetics. Increased glucose uptake (using FDG-PET scanning) is a mark of EWS patient tumors and correlates with worse outcomes. Yet, knockdown (KD) of the EWS driver oncogene EWS-FLI1 led to enhanced glucose uptake and glycolysis, suggesting other molecular pathways counter the EWS-FLI1 effect to inhibit glycolysis. We identified EHD1, a member of the EPS15-Homology Domain-containing (EHD) protein family, as a required element of the EWS tumorigenesis and metastasis. Mechanistically, EHD1 promoted the intracellular traffic of IGF-1R to elevate its cell surface expression and signaling. Our new data demonstrate that EHD1 overexpression upregulates glucose uptake, essential for glycolysis, in an IGF-1R dependent manner. Metabolomics analyses demonstrated that EHD1-KO, which genetically mimics IGF-1R inhibition, in EWS cell models led to a switch to glutamine- dependent maintenance of TCA cycle, in the process of glutamine anaplerosis. Glutaminase 1 (GLS) or GLS2 convert glutamine to glutamate for entry into metabolic pathways. GLS is universally pro-oncogenic while GLS2 is context dependent. We found that EWS cells only express GLS. GLS inhibition is untested in EWS but effective in other cancer models. GLS inhibitor CB-839 (Telaglenastat) was found safe in phase 1 trials and is in phase 2 trials in prostate cancer (NCT04824937). We found CB-839 to inhibit EWS cell proliferation and migration at nanomolar IC50s, and to be synergistic with Linsitinib, an IGF-1R inhibitor in advanced clinical trials. We hypothesize that a metabolic switch to glutamine dependence sustains EWS tumorigenesis and metastasis in the face of IGF-1R inhibition, and thus concurrent targeting of IGF-1R and GLS will provide an effective targeted therapy approach for EWS. We propose complementary genetic and pharmacologic studies using cell line and Patient-derived xenograft (PDX)-derived tumor organoid models of EWS to assess if GLS is a valid therapeutic target in EWS (Aim 1) and if its co-targeting with IGF-1R inhibitors will be additive or synergistic (Aim 2). Our studies evaluate a novel hypothesis, use state of the art and innovative approaches, and explore a co-targeting approach not previously tested. Success of our studies will nominate IGF-1R and GLS inhibitors as a novel and safe combinatorial targeted therapy for EWS. The novel principle of IGF-R plus GLS inhibition may be extendable to other cancers (including NSCLC, breast, and thyroid) with an overactive EHD1-RTK axis.
