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.

Grant Number: 1R21CA297629-01A1
NIH Institute/Center: NIH
Principal Investigator: Hamid Band