Allen Choi
Research Mentor: George WANG
Mentor Department: Pathology-MCTP, Medicine
Author(s): George Wang
Session: Session 1 (9:00 AM – 9:50 AM)
Presentation Type: Poster 128
Abstract
TMPRESS:ERG gene fusion is found in 50% of prostate cancer patients, resulting in Androgen Receptor (AR) signaling pathway disruption and chromatin structural change, making ERG an important driver of genes for prostate cancer tumor development. Despite its significant role in driving oncogenesis, ERG has long been regarded as a difficult target due to lack of enzymatic pockets or canonical ligand-binding cavities, making this incompatible with high-affinity small-molecules who prefer deep, enclosed pockets. Here, we established that the ERG structure contains a N-terminal pointed (PNT) domain, which serves as a docking site for signaling molecules, driving ERG’s role in prostate cancer. A doxycycline-inducible shRNA system in TMPRSS2:ERG-positive VCaP cells displayed that ERG protein levels were significantly reduced in VCaP-shERG cells, which corresponded to higher apoptotic cancer cell levels and growth inhibition, which translated to the dependency of cancer cells on ERG demonstrated in vivo. As a result of these findings, differential scanning fluorimetry was performed to determine the small molecules which bound to the PNT domain, yielding PBITE-1, a PMT-domain ligand that inhibits ERG function in prostate cancer cells. NMR chemical-shift perturbation mapping and molecular docking demonstrated that two ?-helixes and adjacent flexible loop structural features within PNT domain creates a PBITE-1 responsive surface, creating stable ligand-binding pocket. We demonstrated PBITE-1’s functional implication on ERG-driven tumor proliferation using cell viability analysis on ERG+ and ERG- cell lines, where only ERG+ cell lines were shown to be affected by the treatment. Furthermore, the flow-cytometry analysis revealed the induced apoptotic response in PBITE-1 treated ERG+ cell lines. In mouse organoid models, treatment with PBITE-1 resulted in dose-dependent inhibition of cell proliferation. These findings support ERG PNT domain as a directly targetable therapeutic target, for future ERG-directed inhibitors and targeted protein degraders development.
